JP7385985B2 - Blade processing equipment and blade processing method - Google Patents

Description

The present invention relates to a technique for processing a blade made of polycrystalline diamond obtained by sintering diamond abrasive grains.

A dicing device that divides a workpiece such as a wafer on which semiconductor devices or electronic components are formed into individual chips includes at least a dicing blade rotated at high speed by a spindle, a worktable on which the workpiece is placed, and a worktable and the blade. X, Y, Z, and θ movement axes are provided to change the relative position with respect to the workpiece, and cutting operations such as cutting and grooving are performed on the workpiece by the operation of these movement axes.

Various types of dicing blades used in such dicing devices have been proposed so far (see, for example, Patent Documents 1 and 2).

Patent Document 1 describes a method in which diamond abrasive grains are fixed to the end face of a metal base material (aluminum flange) by electroforming using electroplating technology, using an alloy of soft metals such as nickel and copper as a binding material. Cast blades are described.

Patent Document 2 describes a diamond blade that is constructed from a base material made up of a plurality of diamond layers, which are formed by sequentially stacking diamond layers having different hardnesses using a chemical vapor deposition (CVD) method.

Japanese Patent Application Publication No. 2005-129741 Japanese Patent Application Publication No. 2010-234597

Incidentally, in recent years, there has been an increasing demand for smaller semiconductor packages and higher integration, and semiconductor chips are becoming thinner. Along with this, extremely thin workpieces with a thickness of 100 μm or less, for example, have become required. Such ultra-thin workpieces are very easy to break, so when dicing ultra-thin workpieces, it is necessary to make the groove width of the cutting groove formed by the dicing blade as narrow as possible. For example, when cutting a workpiece with a thickness of about 100 μm, the blade thickness of the dicing blade needs to be thinner than the thickness of the workpiece, and must be at least 100 μm or less. If cutting is performed using a dicing blade with a blade thickness that is thicker than the thickness of the workpiece, the workpiece may crack before it is cut. For this reason, for example, when grooving a workpiece with a thickness of about 50 μm to a depth of about 30 μm, the width of the groove must of course be 30 μm or less, so the blade thickness of the dicing blade must be adjusted. It is necessary to suppress the thickness to 30 μm or less.

However, conventional dicing blades have the following technical problems and cannot stably and precisely cut extremely thin workpieces.

Furthermore, with brittle materials, it is difficult to avoid cracks that cause cracks. Although ductile materials such as copper, aluminum, organic films, and resins do not crack, they tend to produce burrs, and it is difficult to avoid the occurrence of burrs.

(Crack problem due to inability to adjust protrusion)
First, as shown in FIG. 21, the electroformed blade described in Patent Document 1 has diamond abrasive grains 92 scattered within a bonding material (metal bond) 94, and a diamond abrasive grain 92 having a sharp tip on the surface. The abrasive grains 92 are in a protruding state. At this time, the protruding position and amount of the diamond abrasive grains 92 vary, and it is difficult in principle to control the abrasive grain protrusion with high precision. For this reason, it is not possible to control the depth of cut in one processing unit with high precision. In particular, when cutting an ultra-thin workpiece with a thickness of 100 μm or less, cracks will occur at a certain depth of cut, and the tip of the diamond abrasive grain will cause a fatal cut into the workpiece. Sometimes I put it away. As a result, there is a problem in that the cracks connect with each other, causing more or less chipping.

The cause of such problems lies in the surface morphology of the electroformed blade. That is, as shown in FIG. 21, in the electroformed blade, diamond abrasive grains 92 are bound together by a binder 94, but the surface morphology is such that the diamond abrasive grains 92 are scattered in the binder 94. Existing. Therefore, in the electroformed blade, a reference plane 98 that is the overall average height position exists near the surface of the bonding material 94, and the diamond abrasive grains 92 protrude from the reference plane 98. If the dicing process is continued in this state, not the diamond abrasive grains 92 but the surface portion of the bonding material 94 that binds them will wear out, and the amount of protrusion of the diamond abrasive grains 92 will further increase. For this reason, as described above, it is difficult to accurately control the protruding position and amount of the diamond abrasive grains 92. That is, when the depth of cut changes significantly, cracks occur if the depth of cut exceeds the critical depth of cut (Dc value) of the material, making it impossible to perform ductile mode machining, which is the objective of the present invention.

Particularly in the case of electroformed blades, the diamond abrasive grains 92 that are worn out during cutting fall off as is, and new diamond abrasive grains 92 underneath act next, as the term "self-synthesis" refers to. However, if such falling off of the diamond abrasive grains 92 is allowed, the fallen diamond abrasive grains 92 will get between the blade and the workpiece, and as a result, cracks will be promoted. In processing using a blade on the premise that diamonds will fall off, it is theoretically impossible to prevent the occurrence of cracks.

(Problems that are difficult to sharpen)
In addition, in the case of electroformed blades, even if you try to make the tip of the blade thin and sharp by machining, because diamond abrasive grains are sparsely present, it will be difficult to make it uniformly thin or tapered. However, since the diamond abrasive grains fall off the surface during processing, there is a limit to how sharp the tip of the blade can be.

In other words, in order to manufacture a thin blade, when electroplating is performed, a uniformly thin plate is manufactured, which is then removed from the base material and made into a blade. It is difficult to shape it and make it thinner by processing.

(Heat accumulation problem due to poor thermal conductivity)
In addition, electroformed blades have poor thermal conductivity, and during cutting, heat is likely to accumulate within the blade due to heat generated by frictional resistance with the groove side surface, which may cause the blade to warp.

When an electroformed blade is manufactured using nickel as a binder, as shown in Table 1, the thermal conductivity of nickel is at most about 92 W/m·K. Furthermore, even when copper is used as a binding material, the thermal conductivity is only about 398 W/m・K. If the thermal conductivity of the blade is poor, heat can easily accumulate, causing the blade to warp, and the heat generated during machining can turn the diamond into graphite, so it is necessary to cool the diamond by pouring pure water on it during machining. There are many cases. The thermal conductivity of diamond is 2100 W/m・K, which is an order of magnitude higher than that of nickel or copper.

(Problem of not being able to form cutting edges that are arbitrarily spaced)
On the other hand, the diamond blade described in Patent Document 2 has the following problems.

First of all, since the diamond blade mentioned above is formed by the CVD method, it is a blade made of a very dense film, but as a result, the surface of the diamond blade is almost flat and has arbitrary cuts. It is not possible to form a concave shape or a pocket for removing chips. Furthermore, even if minute irregularities are formed as a result, the size of the grain boundaries cannot be arbitrarily set before film formation. Therefore, the pitch of the unevenness cannot be arbitrarily designed.

(Problem with runout accuracy in blade manufacturing using CVD film formation)
Furthermore, when manufacturing a diamond blade using the CVD method, the thickness distribution of the blade is determined by the film formation distribution. In particular, if there is undulation in the film formation distribution, the undulation cannot be removed. That is, even if an attempt is made to remove the undulations by machining, cracks will appear, making it difficult to form a thin blade. Therefore, it is theoretically difficult to improve the runout accuracy by attaching the spindle flange with high precision and no runout with the reference surfaces aligned with each other.

(Ensuring flatness by joining different materials)
In addition, in order to narrow the groove width of the groove cut by the blade, it is preferable that the outer periphery (tip) of the blade be as thin as possible, but the part that contacts the flange is warped in order to maintain a flat surface that serves as a highly accurate reference. The thickness must be such that it will not occur. However, when manufacturing a blade as an integral part, it is virtually impossible to manufacture the blade as an integral part using a film-forming method when the blade has portions with different thicknesses. Note that if different materials are joined for this purpose, they will deform due to thermal stress and disrupt roundness and flatness, so it is difficult to realize ductile mode machining as in the present invention, which will be described later. It can be difficult. Here, when a workpiece is processed in a state where spiral or streamlined chips are produced during grinding or cutting, this is called ductile mode processing. In other words, ductile mode processing refers to the process in which removal processing proceeds within the plastic deformation region of the workpiece material before it reaches brittle fracture without causing any cracks in the workpiece.

In addition, with a configuration in which a high-hardness diamond chip is embedded in the outer circumference of the blade, the diamond part and the base material part have different thermal expansion and thermal conductivity, so it is difficult to ensure the flatness of the entire blade due to the bimetallic effect, and the height of each part is different. It becomes difficult to align the slightly different tip heights of diamond tips onto the same plane. Furthermore, if the chips are arranged circumferentially, the temperature distribution will not be axially symmetrical and neat, and the flatness will also deteriorate due to thermal stress.

In addition, in order to achieve crack-free ductile mode dicing, it is necessary to groove in extremely localized areas using a thin blade of 0.1 mm or less, or to limit the cutting width. It is not possible to form such thin blades. It is difficult to ensure continuous flatness between the diamond tip and other base metal parts.

Furthermore, although the diamond tip portion has extremely high hardness, the base metal portion may absorb the impact that the diamond tip receives due to the elastic effect of the metal portion of the base material. When machining in ductile mode, it is necessary to continuously make extremely small cuts, but if the base material absorbs this impact, it is no longer possible to perform machining in ductile mode under extremely small cuts. Can not.

From the above, in terms of heat conduction, geometrical flatness and continuity of the plane, and the ability to provide localized effective shearing force without absorbing shock during machining, blades with embedded diamond chips are , becomes a problem.

(With the film formation method, the stress distribution differs depending on the direction of film deposition and blade warping occurs.)
Furthermore, in the above-mentioned diamond blade, compressive stress is formed in the film made of the diamond layer formed by the CVD method, so the way the stress is applied differs as the film is deposited. For this reason, when the film is finally peeled off to form a blade, there is a difference in the way compressive stress is applied on both the left and right sides, resulting in the blade being significantly warped. Even if such warping of the blade is to be corrected, there is no means to correct it, and there is concern that the yield will be reduced due to stress in the film.

Further, in the blade, it is necessary to provide a cutting edge on the outer periphery. The cutting edge requires some kind of continuous irregularities. Even if a sharp blade with no irregularities on the outer periphery is formed, such as a sharp knife, it is possible to make minute cuts in materials such as brittle materials and in some cases ductile materials, while removing chips. In order to solve the problem of the present invention of proceeding with machining, it is impossible to perform substantial cutting without creating minute irregularities on the outer periphery.

(Scriving problem)
Another problem is that, although it is not a problem with the blade itself, even if the blade is manufactured with high precision, the tip is sharp, and the flat state of the blade does not change even under the heat of the cutting process. Even if you can make a blade, how you use that blade is also important. In particular, in the case of scribing, etc., where the blade itself is pressed vertically against the workpiece to create a crack and proceed with the cut, the process clearly utilizes brittle fracture, so it is difficult to use the ductile mode process as in the present invention, which will be described later. cannot be done.

During scribing, the relative speed between the workpiece and blade is set to 0 to prevent them from slipping. In the case of scribing, the blade must rotate freely in order to apply vertical stress to the material, and the bearing or shaft within the blade is pressed vertically downward.

The blade holding part that allows the blade to slide along the workpiece and the blade part that rotates in contact with the workpiece must not be completely fixed. There is no play in the blade, and there is no direct connection to the motor.

For this reason, in conventional scribing blade configurations, the sliding portion between the shaft and the bearing portion is important.

Incidentally, since the present invention does not involve scribing, the motor and blade have a structure in which they are directly connected, and there is no relationship between a shaft and a bearing, and they are assembled in a coaxial configuration with high precision through fitting.

To this end, it is important to match the blade end face with the flange end face directly connected to the motor. That is, the dicing blade requires a reference plane to align with the flange end face.

(Cutting while maintaining a constant depth of cut for the workpiece)
In addition, the removal volume changes greatly as it cuts, and the volume itself removed by one cutting edge changes, and as a result, the predetermined critical cutting depth for removal by one cutting edge cannot be controlled. As a result, the cutting resistance changes greatly during the cutting process, and the unbalance may cause cracks in the workpiece material. In such a case, brittle fracture may also be induced, and ductile mode machining cannot be realized. That is, in order for one cutting edge to maintain a microscopically constant depth of cut with respect to the workpiece, it is necessary to provide a constant depth of cut to the workpiece to ensure a steady state during machining.

Furthermore, if the workpiece is not a flat sample, it may not be possible to fix the workpiece properly. For example, when cutting a cylindrical workpiece as it is, the workpiece moves and not only the depth of cut is not constant, but also the workpiece may vibrate due to cutting.

On the other hand, recently there are also materials that are a mixture of ductile and brittle materials, such as Cu/Low-k materials (materials that are a mixture of copper and low dielectric constant materials). For brittle materials such as low-k materials, the workpiece must be machined within the material's deformation range to avoid brittle fracture. On the other hand, Cu does not crack because it is a ductile material. However, while these materials do not crack, they tend to be highly elongated. These highly ductile materials cling to the blade and create large burrs where the blade exits. Additionally, circular blades often have whisker-like burrs at the top.

Also, with highly ductile materials, there is a problem of the material clinging to the blade if it is dragged by the blade after cutting. If it clings to the blade, it will cause the blade to become clogged faster, and the cutting edge of the blade will be covered with workpiece material, causing a problem that the grinding performance will be significantly reduced.

The present invention has been made in view of these circumstances, and it is an object of the present invention to stably and precisely cut workpieces made of brittle materials in a ductile mode without causing cracks or fractures. It is an object of the present invention to provide a blade processing device and a blade processing method for processing a blade capable of processing a blade.

In order to achieve the above object, the following invention is provided.

A blade processing apparatus according to one aspect of the present invention includes a blade processing means for dressing a tip of a blade made of polycrystalline diamond and driven to rotate by electrical discharge machining.

In the blade processing device according to one aspect of the present invention, it is preferable that the blade is integrally formed into a disk shape, and that the blade processing means generates a continuous cutting edge on the outer circumference of the blade.

Further, in the blade processing apparatus according to one aspect of the present invention, the blade processing means applies a voltage between a processing electrode arranged to face the blade and the blade and the processing electrode to generate an electric discharge. A preferred embodiment includes a voltage applying means for generating a voltage, and a machining liquid supply means for supplying a machining liquid between the blade and the machining electrode.

Further, in the blade machining device according to one aspect of the present invention, it is preferable that the machining liquid supply means supplies ultrapure water as the machining liquid.

Further, in the blade processing device according to one aspect of the present invention, the blade processing means generates a dynamic pressure of the processing fluid between the blade and the processing electrode by rotation of the blade, and moves the processing fluid. Preferably, the blade is dressed while maintaining a constant distance between the blade and the processing electrode using pressure.

Further, in the blade machining method according to one aspect of the present invention, a blade made of polycrystalline diamond and driven to rotate is dressed at the tip of the blade by electrical discharge machining.

Further, the present invention includes the following technical ideas.

A blade processing device according to one aspect of the present invention is a blade processing device that processes a blade integrally formed into a disk shape using polycrystalline diamond obtained by sintering diamond abrasive grains, a rotational drive mechanism for rotating the polycrystalline diamond around the center of the circumference of the polycrystalline diamond; a flat processing electrode disposed opposite to the outer peripheral edge of the polycrystalline diamond; a machining fluid supply means for supplying machining fluid between the rotating polycrystalline diamond and the machining electrode, and applying a voltage between the rotating polycrystalline diamond and the machining electrode. Voltage application means for generating discharge.

The planar processing electrode is not particularly limited as long as it can generate electric discharge between it and the polycrystalline diamond, and for example, a band-shaped electrode, a disc-shaped electrode, etc. can be used. As for the structure of the planar processing electrode, it is desirable to have an electrode structure that causes electric field concentration at the tip of the blade. In the case of a disc-shaped blade, it is possible to create a configuration in which the discharge occurs at only one geometric point, such as by using linear electrodes placed opposite the tip of the arc-shaped blade, or by using disc-shaped electrodes facing the blade. It is preferable to do so.

According to this aspect, while rotating the polycrystalline diamond, an electrical discharge is generated between the polycrystalline diamond and a planar processing electrode placed opposite to the outer peripheral edge of the polycrystalline diamond. Since both truing, which adjusts the shape of the outer peripheral edge of the diamond, and dressing, which forms a cutting edge on the surface of the outer peripheral edge of the polycrystalline diamond, can be performed simultaneously, blade processing can be performed efficiently. More specifically, the discharge gap narrows in areas where the polycrystalline diamond locally protrudes toward the machining electrode, resulting in a stronger electric field than in other areas, and the protruding areas are selected during electrical discharge machining. removed. This selective removal is carried out over the entire circumference of the polycrystalline diamond while the polycrystalline diamond is being rotated, so that the shape of the polycrystalline diamond is also adjusted during dressing.

In addition, the surface of polycrystalline diamond, especially the diamond abrasive grain part, is an insulator because it is a single crystal, but the grain boundary part that connects the diamond abrasive grains contains a small amount of sintering aid. It is also a place where electric field concentration tends to occur because it is relatively conductive and has a geometrically discontinuous shape compared to the diamond abrasive grain part. Therefore, in addition to the electric field being concentrated only at the grain boundary portion, locally high-density electric energy acts on the grain boundary portion. As a result, the erosion action progresses due to the local removal process, resulting in the formation of a sharp cutting edge.

Furthermore, the discharge gap formed between the polycrystalline diamond and the machining electrode becomes fluidly lubricated by the machining fluid supplied from upstream in the rotational direction of the polycrystalline diamond, and the rotation of the polycrystalline diamond causes the machining fluid to move. pressure is occurring in the discharge gap. Since the dynamic pressure of this machining fluid acts to keep the discharge gap constant, electric discharge machining can be performed stably even while the polycrystalline diamond is rotating. This effect of stabilizing electrical discharge machining also contributes to efficient blade machining.

It is also possible to incorporate the blade processing device according to one aspect of the present invention into a dicing device. In this case, the dicing device may be provided with a blade moving mechanism that moves the polycrystalline diamond between the blade processing device and the workpiece processing section. With this configuration, electric discharge machining of the blade can be performed off-line before, during or before machining the workpiece. Alternatively, the processing electrode and the processing liquid supply means may be provided inside a blade cover that surrounds the blade in the workpiece processing section. With this configuration, electric discharge machining can be performed in-process while machining the workpiece with the blade. According to the in-process method, the workpiece is machined using polycrystalline diamond as a blade, with new cutting edges constantly being generated on the surface and always having a well-shaped shape, which improves machining efficiency and It is possible to improve processing accuracy.

However, even when electrical discharge machining is performed offline, the blade is attached to the same rotating axis (spindle) when machining the workpiece with the blade and when machining the blade itself to generate a new cutting edge on the blade. It is desirable that each process be performed while the parts are attached.

If each machining process is performed with blades attached to different rotation axes, even if a new cutting edge is formed on the blade, there will be an error in the attachment of the blade to the rotation axis when the blade is applied to machining the workpiece. arise. This installation error causes eccentricity during rotation, which prevents a constant minute cut from being made to the workpiece, which can sometimes result in fatal cracks in the workpiece. Therefore, the rotational axis on which the blade is attached when machining the workpiece and the rotational axis on which the blade generates a new cutting edge must be the same, that is, each machining process can be performed on the same rotation. desirable.

Further, in the blade machining device according to one aspect of the present invention, a continuous cutting edge is formed at an outer peripheral edge of the polycrystalline diamond due to an electric discharge generated between the polycrystalline diamond and the machining electrode. preferable.

Further, in the blade machining device according to one aspect of the present invention, a grain boundary portion on a surface of an outer peripheral end of the polycrystalline diamond is selectively damaged by electric discharge generated between the polycrystalline diamond and the machining electrode. A preferred embodiment is one in which it is removed.

According to this aspect, it becomes possible to selectively remove the grain boundary portions on the surface of polycrystalline diamond by melting them by electrical discharge machining. Therefore, cutting edges can be generated on the surface of polycrystalline diamond. Even for workpieces made of brittle materials, it is possible to cut stably and accurately in the ductile mode without causing cracks or fractures.

In addition, in polycrystalline diamond that is sintered with diamond abrasive grains spread out, the cutting edges automatically become approximately equally spaced by selectively removing them from the grain boundaries. Further, even if one diamond abrasive grain falls off, the diamond abrasive grain next to it immediately functions as a cutting edge, so that the state of approximately evenly spaced cutting edges is continuously maintained.

On the other hand, when sparse abrasive grains are hardened with a binding material like in conventional grinding wheels, when one abrasive grain falls off, the area around it immediately becomes free of abrasive grains. , only the binding material is used. Therefore, the next abrasive grain will not appear unless the binding material is retreated. From this point of view, when cutting edges are formed by selectively eroding the grain boundaries, there is basically no binding material, and even if it falls off, the side immediately turns into a cutting edge and cuts at approximately constant intervals. The blade is maintained continuously. However, with conventional grinding wheels that remove the binder while retreating to expose the buried abrasive grains, it is in principle impossible to maintain such a continuous cutting edge spacing. For this reason, polycrystalline diamond in which diamond abrasive grains are sintered has a completely different principle in terms of controlling the abrasive grain spacing.

Further, in the blade machining device according to one aspect of the present invention, it is preferable that the machining liquid supply means supplies ultrapure water as the machining liquid.

According to this aspect, the polycrystalline diamond that is the workpiece is also in a state close to a nonconductor, and a large electric field concentration occurs in some grain boundary portions that are electrically conductive. As a result, combined with the electric field concentration effect, electric discharge machining causes selective melting of the grain boundary portions of polycrystalline diamond, contributing to the formation of cutting edges.

Further, in the blade processing device according to one aspect of the present invention, it is preferable that the processing electrode is made of a metal material or a carbon material.

Further, in the blade machining device according to one aspect of the present invention, it is preferable that the machining liquid supply means supplies water in one direction between the drive blade and the machining electrode.

Further, in the blade machining device according to one aspect of the present invention, it is preferable that the cutting edge generating means includes an adjusting means for changing the relative distance between the polycrystalline diamond and the machining electrode.

According to this aspect, the distance between the polycrystalline diamond and the machining electrode (discharge gap) can be maintained appropriately, so that stable electrical discharge machining can be performed.

In particular, when a cutting edge is formed by eroding the grain boundary portion of polycrystalline diamond, since polycrystalline diamond is also a nonconductor, if the discharge gap is set too large, it will hardly be possible to process the cutting edge. Therefore, it is preferable that the discharge gap is extremely small, and by controlling the discharge gap using the adjustment means, stable and efficient discharge machining can be performed.

Further, in the blade processing apparatus according to one aspect of the present invention, it is preferable that the voltage application means apply a voltage whose polarity is alternately reversed between the polycrystalline diamond and the processing electrode.

According to this aspect, the electrode material on the surface of the polycrystalline diamond is applied to the surface of the polycrystalline diamond by performing electric discharge machining on the surface of the polycrystalline diamond while alternating the polarity of the machining voltage between positive and negative. Attachment and detachment are repeated.

In particular, when ultrapure water is used as a machining fluid, ultrapure water is a nonconducting medium, but when some of the electrode material is eluted, the metal ions of the electrode material are integrated into the medium (ultrapure water). It partially penetrates and adheres to polycrystalline diamond, which is a nonconductor. Even on polycrystalline diamond, electric field concentration becomes large, especially at grain boundary areas, making it easier for electrode material to adhere. Thereafter, as the polarity changes, the electrode material attached to the grain boundaries is detached, and the electric field concentration effect on the grain boundaries of polycrystalline diamond produces a selective erosion effect. This enables efficient and local electrical discharge machining. Note that the voltage for alternately reversing the polarity between the polycrystalline diamond and the processing electrode includes a bipolar pulse voltage and an alternating current voltage.

Further, in order to achieve the above object, a blade processing method according to another aspect of the present invention processes a blade integrally formed in a disk shape using polycrystalline diamond obtained by sintering diamond abrasive grains. A blade machining method comprising: rotating the polycrystalline diamond around the center of a circumference of the polycrystalline diamond; and a flat machining electrode disposed opposite to an outer peripheral edge of the polycrystalline diamond. , supplying a machining fluid between the rotating polycrystalline diamond from upstream in the rotational direction of the polycrystalline diamond; and applying a voltage between the rotating polycrystalline diamond and the machining electrode. and a step of applying the voltage to generate a discharge.

According to this aspect, while rotating the polycrystalline diamond, an electrical discharge is generated between the polycrystalline diamond and a planar processing electrode placed opposite to the outer peripheral edge of the polycrystalline diamond. Since both truing, which adjusts the shape of the outer peripheral edge of the diamond, and dressing, which forms a cutting edge on the surface of the outer peripheral edge of the polycrystalline diamond, can be performed simultaneously, blade processing can be performed efficiently.

Further, the present invention includes the following technical ideas.

A dicing device according to one aspect of the present invention is a dicing device for cutting a workpiece, and is configured in a disc shape by polycrystalline diamond formed by sintering diamond abrasive grains, and the polycrystalline diamond is formed by sintering diamond abrasive grains. a dicing blade having a content of 80 vol% or more (hereinafter also simply referred to as "%"); a rotation mechanism for rotating the dicing blade; , a moving mechanism that moves the workpiece relative to the dicing blade.

In one aspect of the present invention, it is preferable that the dicing blade makes a cut in the work while rotating in a down-cut direction.

Note that the down-cut direction refers to a direction of rotation in which the cutting edge of the dicing blade cuts into the surface of the work when the work is moved relative to the dicing blade.

Further, in one aspect of the present invention, a cutting edge (microcutting edge) consisting of a recess formed on the surface of the polycrystalline diamond is continuously provided along the circumferential direction on the outer periphery of the dicing blade. Preferably.

Because it is composed of polycrystalline diamond, it is completely different from conventional diamond electrodeposited materials, which are electrodeposited with a softer binder than diamond.

In the case of conventional electrodeposited diamond, the diamond protrudes because the bonding material recedes compared to the diamond, and as a result, the protrusion of the diamond abrasive grains becomes larger with respect to the average level line. As a result, the depth of cut becomes excessive in the abrasive grain portion with a large amount of protrusion, which exceeds the critical depth of cut unique to the material and causes cracks.

In contrast, in the case of the present invention, the dicing blade is mostly made of diamond, and the recessed portion surrounded by diamonds serves as the cutting edge. Therefore, no protruding abrasive grains are formed because the surroundings recede. As a result, the depth of cut is not excessive, and the recesses act as cutting edges. The flat reference surface is a diamond surface, and since there are concave portions here and there, the concave portions are basically used as cutting edges for machining.

In this way, the diamond abrasive grains predominately exist in the whole, and the sintering aid that diffuses and remains between them causes the cutting edge to be formed within the diamond abrasive grains. It becomes a cutting edge in the dented area. Further, the content of diamond abrasive grains at this time will be described later, but only when the content of diamond abrasive grains is 80% or more does the empty portion act as a cutting edge. When the content decreases, the concave part is not formed on the outer edge formed by diamond abrasive grains, so the concave and convex parts become almost the same, or the convex part becomes dominant and becomes relatively protruding. The cutting edge cannot provide a stable depth of cut below a certain level without causing fatal cracks to the workpiece.

Further, a major feature of the blade according to the present invention is that it is made of sintered diamond. Sintered diamond is manufactured by placing diamonds with uniform particle sizes in advance, adding a small amount of sintering aid, and using high temperature and high pressure. The sintering aid diffuses into the diamond abrasive grains, resulting in the diamonds being firmly bonded together.

With electroplated or electroformed blades, the diamonds do not bond together. This method hardens the diamond abrasive grains by hardening them with the surrounding metal.

In the case of sintering, the sintering aid diffuses into the diamond, thereby firmly bonding the diamond particles together. The properties of diamond can be utilized by bonding diamond particles together. In terms of rigidity, hardness, heat conduction, etc., the higher the diamond content, the more physical properties that are close to those of diamond can be utilized. This is done by bonding the diamonds together.

Compared to other manufacturing methods such as electroforming blades, the diamonds are baked at high temperatures and pressures, which allows the diamonds to bond together. Examples of such sintered diamonds include Compax Diamond (trademark) manufactured by GE Corporation. Compax diamond is made of single crystal particles that are bonded together using a sintering aid.

In terms of diamond content, natural diamonds and artificial diamonds naturally have a high diamond content and exist as strong diamonds. When these single-crystal diamonds fall off, they tend to crack along their cleavage surfaces. For example, if all the blades are made of single-crystal diamond, even if they are formed into a disk shape, if there is a cleavage in a certain direction, the blade may break into two from the cleavage. When diamond wears out as processing progresses, there is also the problem that the wear depends on the surface orientation along the cleavage surface.

In the case of single-crystal diamond, it is not possible to strictly control the wear process within the material, such as the unit of wear during the diamond wear process.

On the other hand, similarly, members manufactured by vapor phase growth using CVD, such as DLC (diamond-like carbon), are also polycrystalline, but the size of crystal grain boundaries cannot be precisely controlled. Therefore, even when abrasion occurs from grain boundaries, it is not possible to set how uniformly the abrasion occurs, and it is not possible to strictly control the crystal units and grain boundary units that wear out and fall off during processing. Therefore, large defects may sometimes occur, or excessive stress may be applied to some defects, causing large cracks.

On the other hand, PCD (Polycrystalline Diamond), in which fine diamond particles are fired at high temperature and high pressure, is considered to be polycrystalline diamond like DLC, but its crystal structure is completely different. In PCD, in which fine particles are fired together, the diamond fine particles themselves are single crystals, and are completely crystalline with extremely high hardness. In PCD, in order to bond the single crystals together, a sintering aid is mixed in to bond the single crystals together. At this time, the orientation of the bonded portions is not perfectly aligned, so the bond as a whole becomes a polycrystalline body rather than a single crystal. Therefore, there is no dependence on crystal orientation during the wear process, and the material has a constant high strength in any direction.

From the above, in the case of PCD, all structures are polycrystalline because they are not perfect single crystals, but they are polycrystalline bodies in which minute single crystals of uniform size are densely aggregated.

With this configuration, during the wear process during machining, the initial state can be maintained with high accuracy in terms of the state of the outer peripheral cutting edge and the pitch unit control of the outer peripheral cutting edge. In the process of wear due to dicing, rather than the single crystals themselves cracking, the parts that connect the single crystals are relatively weak in terms of hardness and strength, so the bonds break at the grain boundaries and fall off. I will do it.

In PCD, when forming cutting edges, the cutting edges are worn along the grain boundaries between single crystals, so evenly spaced cutting edges are naturally set. All the unevenness created in this way becomes a cutting edge. In addition, between the naturally uneven cutting edges that exist at regular intervals, there are also uneven cutting edges due to grain boundaries of particles, and because they are all composed of diamond, they exist as cutting edges.

As described above, the blade according to the present invention is particularly effective when combined with the PCD configuration and the disk shape. Cutting edges exist on the outer periphery of the disk, and they reach the processing point by acting on the processing point in sequence. The cutting edge is not constantly at the machining point during machining, but only contributes to machining with its polar arc while rotating, so the cutting edge is not overheated because machining and cooling are repeated. As a result, diamond does not react thermochemically and contributes stably to processing.

Next, the formation of equally spaced cutting edges is an essential element for ductile mode dicing, which is a subject of the present invention described later. In other words, in ductile mode dicing, as will be described later, the depth of cut that a single cutting edge makes into the material is important, and the depth of cut that a single cutting edge makes into the workpiece is determined by the "cutting edge spacing around the outer circumference of the blade." is related to the necessary elements. The relationship between the critical cutting depth that one blade gives to the workpiece at this point and the cutting edge spacing will be described later, but in order to specify the critical cutting depth of one blade, it is essential to set a stable cutting edge spacing. . In order to accurately set the cutting edge spacing, PCD, which is made by sintering and bonding single crystal abrasive grains with uniform grain sizes, is suitable.

As a supplementary note, in the "formation of equally spaced cutting edges" of the present invention, a blade in which diamond abrasive grains are arranged in the PCD material of the present invention and a diamond abrasive grain arrangement in other general cases are shown. This section describes the differences from conventional blades.

In electroformed blades, the content of abrasive grains is low. Also in Japanese Unexamined Patent Publication No. 2010-005778, the content of diamond abrasive grains in the abrasive grain layer is about 10%. Therefore, it is unlikely that the abrasive grain content will be set to exceed 70%. Therefore, each abrasive grain exists sparsely. Although the abrasive grains are arranged somewhat uniformly, the distance between the abrasive grains is large in order to ensure sufficient protrusion of each abrasive grain.

Patent No. 3308246 describes a dicing blade for cutting rare earth magnets, which is said to be formed from a composite sintered body of diamond and/or CBN. The content of diamond or CBN is 1 to 70 vol%, more preferably 5 to 50%. If the diamond content exceeds 70%, there will be no problem with warping or bending, but it will become weaker against impact and more likely to break.

Patent No. 4714453 also discloses a tool for cutting and grooving composite materials such as ceramics, metals, and glass. In a tool made by firing diamond, it is stated that 3.5 to 60 vol% of abrasive grains are contained in the fired pair. The technical problem here is that even if the bond material has a high modulus of elasticity and high hardness, it has a high ability to retain the abrasive grains, and with the configuration described, it is possible to always maintain sufficient protrusion of the abrasive grains. It is stated that by maintaining sufficient "protrusion of abrasive grains", it is possible to effectively maintain self-sharpening edges and enable high-speed machining.

Considering the conventional examples as described above, neither the electroformed blade nor the polycrystalline diamond blade does not cover the gaps between abrasive grains. Furthermore, there is no concept of using the gaps between spread abrasive grains as cutting edges. In the present invention, in order to process in the ductile mode, the critical depth of cut given by one cutting edge is important, as will be explained later in the mathematical formula, and in order to keep the depth of cut below a certain level, the interval between the cutting edges becomes important. Furthermore, instead of creating large isolated abrasive grains that stick out, the cutting edges are spread with diamonds and the recessed areas are used to form evenly spaced cutting edges.

FIGS. 22A and 22B schematically show the abrasive grain spacing depending on the diamond abrasive grain content. In order to form a cutting edge that does not cause excessive cutting with a constant abrasive grain spacing, it is necessary to spread the diamonds closely together and to roughen the diamond by continuously removing some of the abrasive grains. . For this purpose, a diamond abrasive grain content of at least 70% or more is required to cover the entire surface. Then some of the diamonds must be removed. If sintering is performed with a diamond abrasive grain content of 80% or more, it is possible to form a state in which diamonds are spread out with at least spatial gaps as shown in FIG. 22A, and from there, by roughening while removing the abrasive grains themselves, , it becomes possible to form a blade with naturally evenly spaced cutting edges. In addition, all the unevenness created in this way acts as a cutting edge.

From the above, in order to form equally spaced cutting edges, it is necessary to use a material that is densely covered with abrasive grains and then fired at high temperature and high pressure.

Note that when the content of diamond abrasive grains is 70% or less as shown in FIG. 22B, it becomes difficult to arbitrarily form equally spaced cutting edges. This is because if the content is less than 70%, there will inevitably be areas where diamond abrasive grains are rich and areas where they are not, and areas where diamond abrasive grains are sparse will be cut due to the presence of isolated abrasive grains. This is because the gap between the blades may become large. If the spacing between the cutting edges is large, or if there are sparse areas, such as one diamond abrasive grain protruding too much, it will not be possible to set the exact amount of protrusion, and this may cause fatal cracks to the workpiece. This will give the depth of cut.

In the patent No. 4714453 mentioned above, in order to solve the problem of performing high-speed machining with sufficient protrusion of the abrasive grains, it is preferable that the content of diamond abrasive grains is 70% or less. However, in the present invention, it is a problem to perform crack-free dicing in ductile mode. Therefore, in order to make the concavities between the abrasive grains act as cutting edges and to maintain a constant spacing between the cutting edges, the diamond content should be at least 70%, ideally 80%. It is desirable that there be at least one.

Further, the blade in this case is not simply a sharp blade like a cutter. In other words, the tip is made with a sharp blade, and it is not cut using a scissor-like principle. It is necessary to remove the workpiece and make grooves while cutting. It is necessary to continuously eject the chips while cutting the next blade into the material, and to do so continuously. Therefore, it is not enough just to have a sharp tip; instead, a fine cutting edge is required.

In the case of such a structure in which diamonds are densely packed, a constant spacing between the cutting edges is formed not only by the grain boundaries but also by the natural roughness of the outer circumference. Examples of specific spacing between cutting edges will be shown later, but the diamond grain size and the spacing between cutting edges may be completely different sizes.

In cases where the cutting edge spacing differs from the diamond grain size, the concept of cutting edges differs from that of ordinary electroformed blades. That is, in conventional blades, diamonds exist embedded in a binder, so individual diamonds exist independently from each other, and therefore, the size of the cutting edge is the same as the diamond particle size. That is, one diamond forms one cutting edge. In this configuration, the unit of self-generating edge is each diamond, which corresponds to each cutting edge. The unit of cutting edge and the unit of self-generating edge do not change. For example, if it is necessary to catch the workpiece to some extent, the cutting edge must be made larger because the depth of cut is required, but since the abrasive grains themselves fall off with self-generating blades, the units of self-generating blades also become larger. As a result, the lifespan becomes extremely short.

From the above, in conventional electroformed blades, etc., the fact that the size of the abrasive grains and the size of the cutting edge are the same is a constraint for maintaining the state of the cutting edge.

In contrast, in the case of the blade using sintered diamond of the present invention, small diamonds are bonded together. A cutting edge larger than the diamond particles is formed on the outer periphery of a sintered diamond blade formed by bonding diamonds together. Compared to the unit of a cutting edge, the grain size of each abrasive grain, diamond, that makes up the sintered body is very small, about 1μ.

When using the blade according to the present invention, individual diamonds fall off during machining, but the entire cutting edge does not fall off. Also, when the blade falls off, the abrasive grains that make up one cutting edge do not fall off like in the case of electroformed blades, but instead some diamonds are missing and fall off in the part where the diamonds are bonded together. Become.

As a result, in the process of self-sharpening, in the case of the present invention, the diamond peels off due to wear in an area smaller than the size of the cutting edge, and the size of the cutting edge itself does not change significantly. Within one cutting edge, dicing progresses with extremely small parts peeling off. As a result, the size of the cutting edge itself does not change, and on the other hand, the entire cutting edge does not become dull due to wear. While small and partially self-growing, the maximum depth of cut per cutting edge is kept within a certain level. As a result, it is possible to sustain ductile mode machining and achieve stable sharpness.

Another way to look at it is that in the case of a dresser in which the abrasive grains are solidified by electrodeposition with a conventional binding material such as nickel, when one abrasive grain falls off, the part where it fell off becomes a hole. , the cutting edge disappears, and the workability corresponding to that part disappears. Therefore, in order to maintain workability and make it easier for the next cutting edge to protrude, the design must be such that the bonding material wears out quickly so that the next abrasive grain can protrude.

In contrast, in the configuration of the present invention, the part where the diamond is missing becomes a small dent, and the dent part also exists as a minute cutting edge within the larger cutting edge as an area surrounded by other diamond abrasive grains. It constitutes minute roughness that causes it to bite into the workpiece. In other words, the concept of self-generation is completely different from the conventional structure in that the diamond missing part becomes the next cutting edge.

The concept of the cutting edge, the spacing, and the critical depth of cut that one cutting edge can cut into is based on the setting conditions in dicing, such as setting a constant blade depth of cut with a blade that requires a cutting edge on the outer periphery, and setting that depth of cut. It is necessary to feed the workpiece at a feed rate commensurate with the workpiece. Therefore, a device that operates the blade at a constant feed along the surface shape at a constant depth of cut is required. If the workpiece is flat, it is necessary to set a constant depth of cut parallel to the surface of the workpiece to be machined and relatively feed the blade.

Next, by rotating the disc-shaped blade, the cutting edge at the outer edge of each removes the workpiece at the processing point, and then cuts through the air, allowing the blade to cool naturally. . In particular, since only a small portion of the workpiece comes into contact with the workpiece, most of it is cooled in the open air.

In the case of cutting, etc., the cutting edge is constantly in contact with the workpiece, and the cutting edge part becomes heated due to friction, and even diamond can wear away thermochemically. By cutting into the workpiece with the shaped blade upright, it is possible to largely avoid abrasion of the diamond due to thermal effects.

Further, in one aspect of the present invention, it is preferable that the polycrystalline diamond is obtained by sintering the diamond abrasive grains using a soft metal sintering aid.

Using a soft metal as a sintering aid makes the blade conductive. If the blade is not conductive, it is difficult to accurately estimate the outer diameter of the outer peripheral edge of the blade, and furthermore, considering installation errors caused by attachment to the spindle, it is difficult to accurately estimate the position of the blade tip relative to the workpiece.

Therefore, a conductive blade is used, and electrical continuity is established between the conductive blade and a chuck plate that chucks the reference flat substrate, and conduction is established when the conductive blade contacts the chuck plate. The relative heights of the blade and chuck plate can be found.

Further, in one aspect of the present invention, it is preferable that the recess is formed by abrasion or dressing treatment of the polycrystalline diamond.

Moreover, in one aspect of the present invention, it is preferable that the average particle diameter of the diamond abrasive grains is 25 μm or less.

Here, the above-mentioned patent number 3308246 describes a diamond blade for cutting rare earth magnets, but it is preferable that the diamond content is 1 to 70 vol% and the average diamond particle size is 1 to 100 μm. There is. Further, in Example 1, the average particle size of diamond is 150 μm. The purpose of this is to reduce bending and warping and improve the wear resistance of the core metal.

Furthermore, in the blade of Patent No. 3,892,204, an average diamond particle size of 10 to 100 μm is effective, but an average particle size of 40 to 100 μm is more desirable.

JP-A No. 2003-326466 describes a blade for dicing ceramics, glass, resins, and metals, and states that the average particle size is preferably 0.1 μm to 300 μm.

Thus, in conventional blades, a relatively large diamond grain size is appropriate.

In the present invention, the average particle size of the diamond abrasive grains, together with the diamond content, must be 25 μm or less.

When the diameter is 25 μm or more, the area ratio in which the diamonds are in contact with each other is significantly reduced, and although some of the diamonds are connected by sintering, the majority of the diamonds are left empty without the sintering aid.

Unless the width of the blade is such that at least two to three fine particles are present in the thickness direction, a strong blade in which the abrasive grains are interconnected cannot be formed. If it is composed of fine particles of 25 μm or more, the thickness must be at least 50 μm or more in the thickness direction. However, if a blade is thicker than 50 μm in the thickness direction, the maximum cutting depth of one blade will be larger than the Dc value of 0.1 μm in SiC, for example, due to the linearity of the existing cutting edge. Therefore, there is a possibility that ductile mode machining will not be possible to a small extent, making ideal ductile mode machining difficult and, in principle, increasing the probability of brittle fracture. This point will be explained in detail later.

Therefore, it is desirable that the diamond particle size is 25 μm or less. However, as for the minimum particle size, currently trials are being carried out on fine diamonds with a diameter of about 0.3 to 0.5 μm, but it is unclear how ultra-fine diamonds with smaller diameters can be used.

Further, in one aspect of the present invention, the outer peripheral part of the dicing blade is preferably configured to be thinner than the inner part of the outer peripheral part, and the thickness of the outer peripheral part of the dicing blade is preferably 50 μm or less. More preferred.

Here, the outer peripheral portion of the dicing blade refers to the width of the portion that penetrates into the workpiece. In the case of ductile mode dicing, the part that enters the workpiece may break the workpiece if the blade width is larger than the workpiece thickness. This will be explained in detail later.

Further, in one aspect of the present invention, the rotation mechanism is provided with a metal flange surface perpendicular to a rotation axis for rotating the dicing blade, and the dicing blade has a reference plane portion on one side, and It is preferable that the reference plane portion be fixed to the rotating shaft with the reference plane portion in contact with the flange surface. In this aspect, it is more preferable that the reference plane part of the dicing blade has an annular shape centered on the rotation axis.

A dicing device according to another aspect of the present invention is a dicing device for cutting a workpiece, and is configured in a disk shape by polycrystalline diamond formed by sintering diamond abrasive grains, and the polycrystalline diamond is formed by sintering diamond abrasive grains. a dicing blade having a grain content of 80 vol% or more; a rotation mechanism for rotating the dicing blade; and a dicing blade that provides a certain depth of cut into the workpiece and provides fine particles to the dicing blade. A moving mechanism that moves the workpiece relative to the dicing blade.

A dicing method according to still another aspect of the present invention is a dicing method for cutting a workpiece, wherein the polycrystalline diamond is formed into a disk shape by sintering diamond abrasive grains, and the polycrystalline diamond is formed by the diamond abrasive grains. A step of giving a constant depth of cut to the work while rotating a dicing blade having an abrasive content of 80 vol% or more, and a step of giving a constant depth of cut to the work by the dicing blade, The method includes a step of moving the workpiece relatively to the dicing blade.

In yet another aspect of the present invention, it is preferable that the dicing blade cuts into the workpiece while rotating in a down-cut direction.

In still another aspect of the present invention, the outer periphery of the dicing blade is provided with recesses (microcutting edges) formed on the surface of the polycrystalline diamond continuously along the circumferential direction. is preferred.

In yet another aspect of the present invention, it is preferable that the polycrystalline diamond is obtained by sintering the diamond abrasive grains using a soft metal sintering aid.

Moreover, in yet another aspect of the present invention, it is preferable that the average particle diameter of the diamond abrasive grains is 25 μm or less.

In still another aspect of the present invention, it is preferable that the outer peripheral part of the dicing blade is thinner than the inner part of the outer peripheral part, and the thickness of the outer peripheral part of the dicing blade is 50 μm or less. It is more preferable.

In still another aspect of the present invention, a metal flange surface is provided that is perpendicular to a rotation axis for rotating the dicing blade, and the dicing blade has a reference plane part on one side, and the dicing blade has a reference plane part on one side. It is preferable that the rotating shaft be fixed to the rotating shaft while being in contact with the flange surface. In this aspect, it is more preferable that the reference plane part of the dicing blade has an annular shape centered on the rotation axis.

According to the blade processing device, the blade processing method, and the dicing device of the present invention, even a workpiece made of a brittle material can be cut with the cutting depth of the dicing blade set to less than the critical cutting depth of the workpiece. This makes it possible to process a blade that can stably and accurately cut in the ductile mode without generating cracks or fractures.

Perspective view showing the appearance of the dicing device Front view of dicing blade Side sectional view showing the AA cross section in Figure 2 Enlarged cross-sectional view showing an example of the configuration of the cutting edge part Enlarged cross-sectional view showing another example of the configuration of the cutting edge part An enlarged cross-sectional view showing yet another example of the configuration of the cutting edge part Schematic diagram showing the state near the surface of polycrystalline diamond Diagram showing the state of the workpiece surface when grooving is performed using a blade with a diamond abrasive particle diameter of 50 μm, and an example of cracks occurring. Cross-sectional view showing the dicing blade attached to the spindle Diagram showing the results of comparative experiment 1 (silicon grooving) (this embodiment) Diagram showing the results of comparative experiment 1 (silicon grooving) (conventional technology) Diagram showing the results of comparative experiment 2 (sapphire grooving) (this embodiment) Diagram showing the results of comparative experiment 2 (sapphire grooving) (conventional technology) Diagram showing the results of comparative experiment 3 (for blade thickness 20 μm) Diagram showing the results of comparative experiment 3 (in case of blade thickness 50 μm) Diagram showing the results of comparative experiment 3 (for blade thickness of 70 μm) Diagram showing the results of comparative experiment 4 (work surface) Diagram showing the results of comparative experiment 4 (workpiece cross section) Diagram showing the results of comparative experiment 5 (work surface) Diagram showing the results of comparative experiment 5 (workpiece cross section) Diagram showing the results of comparative experiment 6 (this embodiment) Diagram showing the results of comparative experiment 6 (prior art) An explanatory diagram schematically showing how dicing is performed using a blade having a cutting edge with a tapered type on both sides. Diagram showing how burrs and chipping occur Explanatory diagram for geometrically calculating the maximum cutting depth when machining by moving the blade in parallel Diagram showing the results of measuring the outer peripheral edge of the blade with a roughness meter Diagram showing the results of measuring the outer peripheral edge of the blade with a roughness meter Diagram showing the surface condition of the outer peripheral edge of the blade (side surface of the blade tip) Diagram showing the surface condition of the outer peripheral edge of the blade (blade tip) Schematic diagram showing how the blade tip cuts into the workpiece material Explanatory diagram used to explain blade thickness Explanatory diagram used to explain the thickness of the blade (when the thickness of the blade is greater than the thickness of the workpiece) Explanatory diagram used to explain the thickness of the blade (when the thickness of the blade is smaller than the thickness of the workpiece) Schematic diagram showing the surface of an electroformed blade Schematic diagram showing the abrasive spacing depending on the diamond abrasive grain content (when the abrasive grain content is 80% or more) Schematic diagram showing the abrasive spacing depending on the diamond abrasive grain content (when the abrasive grain content is 70% or less) Cross-sectional view of the outer peripheral edge of the blade when the cutting edge is formed using a fiber laser (50 μm holes at 100 μm intervals) Front view of particle supply mechanism Side view of particle supply mechanism Schematic diagram showing a configuration example of a blade processing device according to the first embodiment A schematic diagram showing a configuration example of a blade processing device according to a second embodiment Schematic diagram showing a configuration example of a blade processing device according to a third embodiment Schematic diagram showing a configuration example of a blade processing device according to a fourth embodiment Schematic diagram showing how it would look when applied to a conventional electroformed blade Schematic diagram showing how diamond abrasive grains are applied to sintered polycrystalline diamond

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a dicing apparatus and a dicing method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the appearance of a dicing device. As shown in FIG. 1, the dicing apparatus 10 has a load port 12 for transferring a cassette containing a plurality of workpieces W to/from an external device, and a suction section 14, and a conveyor for transporting the workpieces W to each part of the apparatus. It is composed of a means 16, an imaging means 18 for taking an image of the surface of the workpiece W, a processing section 20, a spinner 22 for cleaning and drying the workpiece W after processing, a controller 24 for controlling the operation of each part of the apparatus, and the like. ing.

The processing section 20 is provided with two air-bearing spindles 28 that are arranged opposite to each other and have a built-in high-frequency motor with a blade 26 attached to the tip. Then, index feed in the Y direction and incision feed in the Z direction are performed. Further, the work table 30 on which the work W is placed by suction is configured to be rotatable around an axis in the Z direction, and is configured to be ground and fed in the X direction in the figure by the movement of the X table 32. There is.

The work table 30 includes a porous chuck (porous body) that vacuum-chucks the work W using negative pressure. The workpiece W placed on the worktable 30 is held and fixed in a vacuum suction state by a porous chuck (not shown). As a result, the workpiece W, which is a flat sample, is uniformly attracted to the entire surface while being flattened by the porous chuck. Therefore, even if shear stress is applied to the workpiece W during dicing, the workpiece W will not be misaligned.

This workpiece holding method that vacuum-chucks the entire workpiece allows the blade to constantly give the workpiece a constant depth of cut.

For example, if the workpiece is a sample that cannot be straightened into a flat plate, it is difficult to define the reference plane of the workpiece surface, and therefore it is difficult to set the cutting depth of the blade from that reference plane. Become. If it is not possible to set a constant depth of cut of the blade into the workpiece, it is also impossible to set the critical depth of cut at which one cutting edge constantly makes a stable cut, making stable ductile mode dicing difficult.

If the workpiece is straightened into a flat plate, the reference plane of the workpiece surface can be defined and the blade cutting depth can be set from the reference plane, so the critical cutting depth per cutting edge can be set and stable. ductile mode dicing becomes possible.

Note that it is not necessary to use vacuum suction, and the entire surface of the hard substrate may be adhered. If the surface of even a thin substrate can be defined based on the surface firmly bonded over the entire surface, stable ductile mode dicing becomes possible.

FIG. 2 is a front view of the dicing blade. FIG. 3 is a side sectional view taken along the line AA in FIG. 2.

As shown in FIGS. 2 and 3, the dicing blade (hereinafter simply referred to as "blade") 26 of the present embodiment is a ring-shaped blade, and the center part thereof is for attaching to the spindle 28 of the dicing apparatus 10. A mounting hole 38 is bored.

The blade 26 is made of sintered diamond and has a disk or ring shape, and if it has a concentric configuration, the temperature distribution will be axially symmetrical. If the same material has an axially symmetrical temperature distribution, shear stress associated with Poisson's ratio will not act in the radial direction. Therefore, the outer peripheral edge maintains an ideal circular shape, and since the outer peripheral edge remains on the same plane, the rotation acts on the workpiece in a straight line.

The blade 26 is integrally formed into a disk shape using polycrystalline diamond (PCD) formed by sintering diamond abrasive grains. This polycrystalline diamond has a diamond abrasive grain content (diamond content) of 80% or more, and each diamond abrasive grain is bonded to each other by a sintering aid (for example, cobalt, etc.).

The outer circumferential portion of the blade 26 is the portion that cuts into the workpiece W, and is provided with a cutting edge portion 40 that is thinner than the inner portion. The cutting edge 40 has a cutting edge (micro cutting edge) consisting of minute depressions formed on the surface of the polycrystalline diamond along the circumferential direction of the blade outer peripheral end (outer peripheral edge) 26a at a micro pitch (e.g. 10 μm) and are formed continuously.

In this embodiment, the thickness of the cutting edge portion 40 (blade thickness) is configured to be at least thinner than the thickness of the workpiece W. For example, when cutting a work W of 100 μm, the thickness of the cutting edge 40 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.

The cross-sectional shape of the cutting edge 40 may be tapered so that the thickness gradually decreases toward the outside (toward the tip end), or it may be formed straight with a uniform thickness.

4A to 4C are enlarged cross-sectional views showing examples of the configuration of the cutting blade portion 40. FIG. Note that FIGS. 4A to 4C correspond to an enlarged portion of section B in FIG. 3.

The cutting blade 40A shown in FIG. 4A is a one-side tapered type (one-sided V type) in which only one side surface is processed obliquely into a tapered shape. The cutting edge 40A has, for example, a thickness T ₁ of 10 μm at the outer circumferential end, which is formed thinnest, and a taper angle θ ₁ of a tapered portion of one side surface of 20 degrees. Note that the thickness of the inner portion of the blade 26 (excluding the annular portion 36 described later) is 1 mm (the same applies to FIGS. 4B and 4C).

The cutting edge portion 40B shown in FIG. 4B is of a both-side tapered type (both V-type) in which side surfaces on both sides are processed obliquely into a tapered shape. The cutting edge portion 40B has, for example, a thickness T ₂ of 10 μm at the outer circumferential end where it is formed thinnest, and a taper angle θ ₂ of the tapered portions of both side surfaces is 15 degrees. .

The cutting edge 40C shown in FIG. 4C is of a straight type (parallel type) in which side surfaces on both sides are machined straight and parallel. The cutting edge portion 40C has, for example, a thickness T ₃ of 50 μm at the thinnest straight tip portion. Note that the inner side portion (center side portion) of the straight tip portion is tapered on one side, and the taper angle θ ₃ is 20 degrees.

FIG. 5 is a schematic diagram schematically showing the state near the surface of polycrystalline diamond. As shown in FIG. 5, the polycrystalline diamond 80 is in a state in which diamond abrasive grains (diamond particles) 82 are bonded to each other at high density due to the sintering aid 86. On the surface of this polycrystalline diamond 80, a cutting edge (microcutting edge) 84 consisting of a minute depression (recess) is formed. This recess 84 is formed by selectively wearing away a sintering aid 86 such as cobalt by mechanically processing the polycrystalline diamond 80. Since the polycrystalline diamond 80 has a high abrasive grain density, the dents formed where the sintering aid 86 is worn are minute pocket-like, and there are no sharp diamond abrasive grains protruding like in an electroformed blade ( (See Figure 21). Therefore, the depression formed on the surface of the polycrystalline diamond 80 functions as a pocket for transporting chips generated when cutting the workpiece W, and also functions as a cutting edge 84 that makes a cut into the workpiece W. . This improves the evacuation of chips and makes it possible to control the cutting depth of the blade 26 into the workpiece W with high precision.

Here, the blade 26 of this embodiment will be explained in more detail.

As shown in FIG. 5, the blade 26 of this embodiment is integrally formed of polycrystalline diamond 80 formed by sintering diamond abrasive grains 82 using a sintering aid 86. Therefore, although a very small amount of sintering aid 86 exists in the gaps between polycrystalline diamonds 80, the sintering aid is also diffused into the diamond abrasive grains themselves, and in reality, the diamonds are firmly bonded to each other. It becomes a form. This sintering aid 86 is made of cobalt, nickel, or the like, and has a lower hardness than diamond. Therefore, although the diamonds bond together, the strength of the sintering aid-rich portions is slightly weaker than that of single-crystal diamond. When processing the workpiece W, these portions are worn and worn down, resulting in a moderate depression with respect to the surface (reference plane) of the polycrystalline diamond 80. Furthermore, by subjecting the polycrystalline diamond 80 to abrasion treatment, depressions are formed on the surface of the polycrystalline diamond 80 from which the sintering aid has been removed. In addition, by sharpening with a GC (Green Carborundum) sharpening stone, or in some cases by cutting the hard and brittle cemented carbide, in addition to the sintering aid, some diamonds may be missing. , moderate roughness is formed on the outer periphery of polycrystalline diamond. By making the roughness of this outer peripheral part larger than the diamond grain size, minute diamond abrasive grains are missing within one cutting edge, making it difficult for the cutting edge to wear out.

The depressions formed on the surface of polycrystalline diamond 80 work advantageously for processing in ductile mode. That is, as described above, this recess functions as a pocket for discharging chips generated when cutting the workpiece W, and also functions as a cutting edge 84 that makes a cut into the workpiece W. Therefore, the amount of cut into the workpiece W is naturally limited to a predetermined range, and a fatal cut will not be made.

Further, since the blade 26 of this embodiment is integrally formed with polycrystalline diamond 80, the number, pitch, and width of the recesses formed on the surface of polycrystalline diamond 80 can be arbitrarily adjusted. becomes possible.

That is, the polycrystalline diamond 80 constituting the blade 26 of this embodiment has diamond abrasive grains 82 bonded to each other using a sintering aid 86. Therefore, the sintering aid 86 exists between the diamond abrasive grains 82 that are bonded to each other, and a grain boundary exists. Since this grain boundary portion corresponds to a recess, by setting the grain size (average particle size) of the diamond abrasive grains 82, the pitch and number of recesses are automatically determined. In addition, by using the sintering aid 86 made of soft metal, it is possible to selectively form the dents, and it is also possible to selectively wear out the sintering aid 86. Also, the roughness can be adjusted by setting the abrasion treatment and dressing treatment while rotating the blade 26. That is, the pitch, width, depth, and number of the cutting edges 84, which are concavities formed on the surface of the polycrystalline diamond 80, are adjusted by the pitch of the grain boundaries formed by selecting the grain size of the diamond abrasive grains 82. It becomes possible to do so. The pitch, width, depth, and number of the cutting edges 84 play an important role in machining in the ductile mode.

As described above, according to the present embodiment, by appropriately adjusting parameters with good controllability such as selection of the grain size of the diamond abrasive grains 82, abrasion treatment, and dressing treatment, a desired cut can be made precisely along the grain boundaries of the crystal. The spacing of the blades 84 can be achieved. Further, on the outer circumferential portion of the blade 26, cutting edges 84 made of recesses formed on the surface of the polycrystalline diamond 80 can be arranged in a straight line along the circumferential direction.

Here, for comparison, there is a similar wheel made of sintered diamond abrasive grains that is used for scribing, but to avoid confusion with a scribing wheel, we will mention the differences.

A wheel used for scribing is disclosed in, for example, Japanese Patent Laid-Open No. 2012-030992. The above document discloses a wheel made of sintered diamond and having an annular blade having a cutting edge on the outer periphery. Scribing and the dicing of the present invention are both technologies for dividing materials and are often considered to be in the same category, but their processing principles and specific configurations are completely different depending on the processing principles.

First, as a decisive difference between the above-mentioned document and the present invention, scribing in the above-mentioned document refers to scribing lines (vertical cracks) on the surface of a substrate formed of a brittle material, as described in paragraph [0020] of the above-mentioned document. ), and vertical cracks extending in the vertical direction are generated by scribing (see paragraph [0022] of the above document). Cut using this crack.

On the other hand, the present invention has a completely different principle as a processing method for shearing away material without causing cracks or chipping. Specifically, the blade itself rotates at high speed and acts almost horizontally on the workpiece surface to remove the workpiece, so no stress is applied to the workpiece in the vertical direction. In addition, the depth of cut is kept within the deformation range of the material and the depth of cut is such that no cracks will occur, resulting in a crack-free surface after processing. From the above, the processing principles are completely different.

In light of the above differences in processing principles, specific differences in blade specifications are listed below.

・(Point of cutting edge vertical angle)
Scribing only creates cracks within the material, so it hardly penetrates into the material. Since only the ridgeline of the cutting edge acts, the angle of the cutting edge is usually an obtuse angle (see paragraph [0070] of the above document). It is completely unthinkable to make the angle less than 20 degrees, let alone an acute angle, considering damage caused by torsion.

On the other hand, dicing penetrates into the material and removes the penetrated part, so the cutting edge is straight, or at most the apex angle of the cutting edge is V-shaped to take into account buckling due to dicing resistance in the direction of blade movement. To some extent. The maximum apex angle is less than 20 degrees.

In addition, if the apex angle is more than 20 degrees, the cross section after cutting will be oblique and the cross-sectional area will increase.In addition, in terms of the processing mechanism, the blade tip grinds on the side of the blade rather than the cutting element. The volume will increase. As a result, the efficiency of machining decreases and sometimes machining does not proceed. In the case of dicing, a cutting edge is formed on the outer periphery of the blade, and while the cutting edge at the tip efficiently cuts, the side surface of the blade improves lubricity with the workpiece, reducing the amount of grinding and creating a mirror finish. That is required. If the amount of grinding on the side surface of the blade increases, the amount of grinding on the side surface will inevitably increase, and the cross section after cutting will not be mirror-finished. Therefore, for dicing, a straight shape is most desirable, but at the very least it is best to have an extremely small V-shape to the extent that the blade does not buckle, and at most 20 degrees or less.

・(Material composition)
In scribing, if the direction of movement changes while the wheel is in contact with the workpiece (biting), the cutting edge may break due to torsional stress. Therefore, even if the same diamond sintered body is used, the weight percentage of diamond is set at 65% to 75%. As a result, not only wear resistance and impact resistance but also torsional strength properties are improved. When the weight percentage of diamond is 75% or more, the hardness of the wheel itself increases, but the torsional strength decreases. Therefore, the diamond content is set relatively low.

In contrast, in dicing, the blade rotates at high speed and moves in a straight line while removing a fixed amount of material. Therefore, no torsional stress is applied. On the other hand, if the diamond content is low, the apparent hardness will decrease when cutting, and the workpiece will recover elastically due to the reaction force from the workpiece and within the time it takes for the cutting edge of the blade to cut. It may not be possible to maintain a predetermined depth of cut. Therefore, in the case of dicing, the hardness of the blade is sufficiently large compared to the hardness of the workpiece so that the workpiece can continue cutting at a predetermined depth without rebounding. In order for machining to proceed in the deformation range of the material in ductile mode without allowing elastic recovery during the cutting edge action time during machining, a surface hardness equivalent to that of single crystal diamond (about 10,000 on the Knoop hardness) is required. A hardness of approximately 8000 is required. As a result, the diamond content must be 80% or more. However, when the diamond content exceeds 98%, the proportion of the sintering aid decreases dramatically, which weakens the bonding force between the diamonds and reduces the toughness of the blade itself, making it brittle and easily chipped. Therefore, the diamond content must be 80% or more, and from a practical point of view, it is preferably 98% or less.

From the above, even though the PCD used in the scribing wheel and the PCD used in the dicing blade of the present invention are the same material, their processing principles are completely different. The diamond content will be completely different.

・(Wheel structure and reference plane point)
Additionally, the wheel structure is different. The scribing wheel has a holder, and the holder is an element that rotatably holds the scribing wheel. Since the holder mainly includes a pin and a support frame, the pin portion (shaft portion) does not rotate. The inner diameter of the wheel acts as a bearing, and it rotates by rubbing against the shaft (pin), forming vertical scribing lines (vertical cracks) on the surface of the material.

In contrast, in the blade according to the present invention, the blade is coaxially attached to a rotating spindle. The spindle and blade rotate together at high speed. The blade must be installed perpendicular to the spindle axis, and vibration due to rotation must be eliminated.

Therefore, a reference plane exists in the blade. The reference surface present on the blade is fixed by being brought into contact with the reference end surface of a flange that is vertically attached to the spindle in advance. This ensures the perpendicularity of the blade to the spindle rotation axis. Only when this perpendicularity is ensured will the cutting edge formed on the outer periphery act in a straight line on the workpiece as the blade rotates.

Further, the reference surface in the case of scribing is a cylindrical surface parallel to the axis of the disc blade, and is defined on the premise that the blade is pressed vertically. However, in the blade according to the present invention, the reference plane of the blade is the side end surface (disk surface) of the blade that faces the flange of the spindle, as described above. By setting the reference plane of the blade to the side surface (disc surface) of the blade, the blade rotates with high precision while being balanced with respect to the blade center. Therefore, even when the blade is rotating at high speed, the cutting edge formed at the tip of the blade acts accurately at a predetermined height position defined by a constant radius position with respect to the center of the blade. The cutting edge acts horizontally on the workpiece surface and removes it, without applying any vertical stress to the workpiece. Therefore, even if the workpiece is a brittle material, no cracks will be caused by stress perpendicular to the workpiece surface.

・(Processing principle)
The decisive difference between scribing and dicing according to the present invention is whether the process is performed by creating cracks in the vertical direction or whether the process is performed without generating any cracks.

・(Role of groove on peripheral blade)
Also, in scribing, a scribing line is applied only to the surface by pressing it with the vertical stress of the scriber. In the case of scribing, the role of the grooves on the peripheral blade is to generate cracks perpendicular to the material while the protruding part of the cutting edge of the wheel contacts (bites into) the brittle material substrate (see paragraph [0114 of the above literature). ]reference). That is, the groove is such that a scribing line can be formed in the portion other than the groove to the extent that it bites into the material and causes a vertical crack. Therefore, rather than the grooves, it is important how the peaks between the grooves bite into the material.

On the other hand, in the case of dicing, the recess provided at the outer peripheral end plays the role of a cutting edge. The portion between the recesses forms an outer peripheral contour, and is set so that the cutting edge provided therebetween has a critical cutting depth that does not cause cracks to the workpiece surface. Therefore, in the case of dicing, it is necessary to form cutting edges.

In addition, in the case of scribing, the groove depth is formed to the extent that it provides the amount of biting to create a scribing line, but in the case of dicing, the depth of the groove is formed to the extent that the depth of the groove is sufficient to create a scribing line. must be removed by polishing. Therefore, the tip of the blade must completely penetrate into the workpiece, while no swinging of the blade is allowed, and the cutting edge must operate perpendicularly to the surface of the workpiece deep into the material.

In the case of the blade according to the present invention, the cutting edge has concave portions spaced at regular intervals at the outer peripheral end. As will be shown later, the interval between the cutting edges may be determined as long as the critical cutting depth provided by one cutting edge does not cause cracks. For this purpose, it is necessary to keep the cutting edge spacing appropriate.

In addition, the direction of the cutting edge of the scribing wheel is changed by 90 degrees while the scribing hole is in contact with the brittle material, and this is called the caster effect.

With a dicing blade, the direction of the cutting edge cannot be changed by 90 degrees because the blade is deep inside the material. For example, if you use a dicing blade with a straight shape or an apex angle of 20 degrees or less and change the cutting edge while making contact, the blade will break.

In the case of polycrystalline diamond 80 sintered using a sintering aid 86 made of a soft metal, abrasion treatment or dressing treatment is the most suitable method for forming dents on its surface. Not exclusively. For example, when a sintering aid such as cobalt or nickel is used, it is also possible to form depressions on the surface of the polycrystalline diamond 80 by chemically dissolving it partially through acid-based etching.

On the other hand, in conventional electroformed blades, the diamond abrasive grains themselves play the role of the cutting edge, but in order to adjust the pitch and width of the cutting edge, it is necessary to initially disperse the diamond abrasive grains to It is technically difficult to do so because it has no choice but to rely on In other words, it involves many ambiguities such as the dispersion of diamond abrasive grains, and cannot be substantially controlled. Further, even if there are parts where the diamond abrasive grains are insufficiently dispersed and aggregated, or parts where the diamond abrasive grains are too dispersed and sparse, it is difficult to arbitrarily adjust this. As described above, with conventional electroformed blades, it is impossible to control the arrangement of cutting edges.

In addition, in conventional electroformed blades, there is no way to artificially arrange micron-order diamond abrasive grains one by one in the current technology, and it is almost impossible to efficiently arrange the cutting edges in a straight line. It's impossible. In addition, with conventional electroformed blades that have a mixture of dense and sparse cutting edges and cannot practically control the arrangement of the cutting edges, it is difficult to control the amount of cut into the workpiece W, and in principle, the ductile Mode processing cannot be performed.

Further, the blade according to the present invention uses polycrystalline diamond formed by sintering diamond. Polycrystalline diamond does not become polycrystalline diamond even if metal powder is added to the diamond and normal sintering is performed. Sintering is required under high temperature and pressure. Details are as shown in paragraph [0194] described later.

Therefore, it is completely different from ordinary diamond particles hardened with a metal powder binder, such as the one described in JP-A-6-91437.

Furthermore, as described in JP-A-5-144937, even if diamonds are simply sintered with some kind of binder, it cannot be said that the diamonds are bonded to each other, so they are different from polycrystalline diamonds. distinguished as a thing.

Here, polycrystalline diamond refers to one in which the sintering aid serves as a medium, the sintering aid diffuses into the diamond particles, and the diamonds bond together to form a single diamond crystal. Therefore, it is distinguished from a simple sintered body of diamond solidified with metal powder.

In the blade 26 of this embodiment, the average particle diameter of the diamond abrasive grains contained in the polycrystalline diamond is preferably 25 μm or less (more preferably 10 μm or less, still more preferably 5 μm or less).

According to the experimental results conducted by the present inventor, when the average particle diameter of diamond abrasive grains was 50 μm, cracks occurred when the wafer material was SiC and the wafer was diced with a cutting depth of 0.1 mm. This is probably due to the diamond falling off. When sintering with a diamond average particle diameter of 50 μm or more, the area where the diamond particles adhere to each other becomes smaller, and larger particles are bonded together in a localized area. Therefore, due to the composition of the material, it has a drawback of being extremely weak in impact resistance and prone to chipping. When diamonds fall off in units of 50 μm or more due to localized impact, a very large cutting edge is formed as a result of this falling off. In that case, a cutting depth greater than a predetermined critical cutting depth will be applied as an isolated cutting edge, and as a result, the probability of chipping or cracking will be extremely high. In addition, if a diamond of about 50 μm falls off, not only will the remaining cutting edge become larger, but the dropped diamond abrasive grains themselves may become entangled between the workpiece and the blade, causing further cracks. . No results have been obtained in which such cracks occur regularly in the case of fine particles of 25 μm or less.

Figure 6 shows the appearance of the workpiece surface when grooving was performed using a blade with diamond abrasive grains having an average particle size of 50 μm, and shows an example where cracks have occurred.

In addition, Table 2 shows the results of evaluating the incidence of cracking or chipping when grooving was performed using blades with diamond abrasive grains having average particle diameters of 50 μm, 25 μm, 10 μm, 5 μm, 1 μm, and 0.5 μm. show. The evaluation results show that the incidence of cracking or chipping increases in the order of A, B, C, and D. Other conditions are as follows.

・Standard evaluation conditions: SiC substrate (4H) (hexagonal crystal)
・Spindle rotation speed: 20000rpm
・Feeding speed: 1mm/s
・ Cutting depth: 100μm
・Evaluation guideline: Evaluate based on whether or not there is chipping of 10μm or more. (Ideally, there should be no chipping at all.)

In addition, cracks occurred in sapphire at a cut depth of 0.2 μm. Similar cracks occurred in quartz and silicon as well.

Furthermore, when the average particle size of the diamond abrasive grains is 50 μm, it is difficult to reduce the blade thickness (thickness at the outer peripheral edge of the blade) to 50 μm or less, and when manufacturing the blade 26, the blade 26 is chipped at the outer peripheral portion. There are many. Also, even if you try to make a blade with a blade thickness of 100μm (0.1mm), there will be parts with large voids, and even the slightest impact may cause it to break, so it is difficult to realistically make a blade stably. was difficult.

On the other hand, when the average particle diameter of diamond abrasive grains is 25 μm, 5 μm, 1 μm, or 0.5 μm, the same cutting is performed on brittle materials such as SiC, sapphire, quartz, and silicon as when the average particle diameter is 50 μm. However, no cracks occurred. In other words, in these brittle materials, if the average particle diameter of diamond abrasive grains is 50 μm, cracks will occur at submicron-order cuts, and if diamond abrasive grains with a larger average particle diameter are used, cracks will inevitably occur at the cuts. becomes larger, leading to fatal cracks. On the other hand, when diamond abrasive grains with an average particle diameter of 25 μm or less (more preferably 10 μm or less, still more preferably 5 μm or less) are used, the cutting depth can be kept small and the cutting depth can be controlled with high precision. becomes possible.

The general processing conditions for this experiment were a blade outer diameter of 50.8 mm, a wafer size of 2 inches, a grooving depth of 10 μm, a spindle rotation speed of 20,000 rpm, and a table feed rate of 5 mm/s.

A method for manufacturing the blade 26 configured as described above is to place fine diamond powder on a base mainly composed of tungsten carbide and place it in a mold. Next, a solvent metal (sintering aid) such as cobalt is added into this mold as a sintering aid. Next, it is fired and sintered under a high pressure of 5 GPa or higher and a high temperature atmosphere of 1300°C or higher. This causes the diamond abrasive grains to bond directly to each other, forming a very strong diamond ingot. In this way, for example, a cylindrical ingot with a diameter of 60 mm, a sintered diamond layer (polycrystalline diamond) of 0.5 mm, and a tungsten carbide layer of 3 mm can be obtained. Examples of polycrystalline diamond formed on tungsten carbide include DA200 manufactured by Sumitomo Electric Hardmetal. The blade 26 of this embodiment can be obtained by taking out only the polycrystalline diamond and subjecting the blade base material to a peripheral abrasion treatment or dressing treatment into a predetermined shape. The diamond surface of the cylindrical ingot (excluding the cutting edge 40) is polished to a surface roughness (arithmetic mean roughness) by performing scaif polishing (scaif, polishing disk) to form a reference surface to eliminate runout during rotation. (Ra) It is preferable to process it into a mirror surface of about 0.1 μm.

Here, the abrasion treatment and dressing treatment in the above manufacturing method can be performed under the following conditions.

The wear treatment includes the following conditions.

・Blade rotation speed: 10000rpm
・Feeding speed: 5mm/s
・ Workpiece processing target: Quartz glass (glass material)
- Processing time: 30 minutes - Due to the above processing, the cobalt sintering aid of about 1 to 2 μm was removed and a depression was formed. Furthermore, by applying a thin layer of very thin etching solution (weakly acidic) and processing in a dry environment without supplying pure water, the dents became even deeper.

The following conditions may be used as the dressing treatment (wear treatment).

・Blade rotation speed: 10000rpm
・Feeding speed: 5mm/s
・ Workpiece processing target: GC600 dressing grindstone (70mm□)
(GC600 means #600 grain size of silicon carbide abrasive material. Particle size is based on Japan Industrial Standards (JIS) R6001)
- Processing time: 15 minutes - Even in this process, the cobalt sintering aid was slightly removed and depressions were formed.

In addition, it is preferable that the roughness of the blade outer peripheral end and the blade side surface of the blade outer peripheral portion be changed. Specifically, the outer peripheral edge of the blade corresponds to a cutting edge, and the cutting edge interval is adjusted along grain boundaries by wear treatment. In particular, the outer peripheral edge of the blade is machined a little roughly because it cuts into the workpiece material and removes a certain amount of material.

On the other hand, the blade side surface is not actively removed, but only needs to be rough enough to scrape out the groove side surface when it comes into contact with the groove side surface of the workpiece material. In addition, if there is a protrusion on the side surface of the blade, it will induce cracks on the side surface of the groove, so while machining can be done without forming a protrusion, the area of contact with the side surface of the groove should be reduced to minimize friction. It is necessary to reduce the heat generated by Therefore, it is preferable to roughen the side surfaces finely.

Conventional electroformed blades are manufactured by hardening the abrasive grains with plating, so the abrasive grains are distributed in the same way over the entire surface.As a result, the shape of the abrasive grains attached to the outer edge of the blade and the blade side surface is different. I couldn't make a big difference. In other words, it was not possible to obviously change the roughness situation between the outer circumferential edge of the blade, which cuts the workpiece, and the side surface part, which rubs against the workpiece and scrapes the blade minutely.

In the case of the blade according to the present invention, most of the blade is made of diamond, and can be molded from that state. For example, in the case of the blade according to the present invention, diamond lapping or the like may be performed to roughen the side surface. By roughening the surface with minute diamonds (particle size 1 μm to 150 μm), it is possible to form a roughness with Ra of about 0.1 μm to 20 μm, for example.

On the other hand, the outer peripheral part of the blade, unlike the side part of the blade, needs to be cut while processing the workpiece, and therefore, unlike the side part, it is better to give it a roughness as a cutting edge. Such roughness can be formed on the outer periphery using, for example, a pulsed laser.

When forming a cutting edge with a pulsed laser, the following conditions are preferably used.

Laser oscillation device: Fiber laser manufactured by IPG, USA: YLR-150-1500-QCW
Feeding table: JK702
Wavelength: 1060nm
Output: 250W
Pulse width: 0.2msec
Focal position 0.1mm
Blade rotation speed 2.8rpm
Gas: High purity nitrogen gas 0.1L/min
Hole diameter 50μm
Blade material: Sumitomo Electric DA150 (diamond particle size 5μm)
Outer diameter 50.8mm
With such a pulsed fiber laser, as shown in FIG. 23, continuous semicircular sharp cutting edges with a diameter of 0.05 mm can be formed on the outer peripheral edge of the blade at a pitch of 0.1 mm. In this cutting edge formation, the diamond grain size is 5 μm, but one cutting edge itself can be a 50 μm cutting edge. Furthermore, if they are formed at equal intervals, the apparent interval becomes smaller by increasing the rotation speed, making it possible to perform ductile mode dicing. (Example: When the spindle rotation speed is 10,000 rpm or more) With fiber lasers, cutting edges can be formed with various hole diameters, from about 5 μm to 1 mm. However, depending on the laser beam diameter, it is usually possible to open a gap of about 5 μm to 200 μm.

Rather than forming notches in a material made by solidifying diamonds using electroplating, such as by electroforming, the material is made of sintered diamond, and a series of small notches are formed on the outer edge of the disc. , each notch acts as a cutting edge.

JP-A No. 2005-129741 describes a method of forming a notch on the outer periphery of a blade manufactured by electroforming, but the notch in this case has a chip evacuation function and prevents clogging. A notch is provided as a function, but not as a cutting edge. When manufactured using the electroforming method, diamonds are not necessarily present at the edge of the notch, but are present together with the binder, so the binder wears away during processing, so the diamond acts as a cutting edge as a material. It's not a thing.

On the other hand, when the blade is made of polycrystalline diamond, the tip of the cutting edge formed on the outer periphery acts as a cutting edge. In addition, since the diameter of the diamond abrasive grains is small at 5 μm compared to the size of the cutting edge, which is 50 μm, it is possible for one diamond abrasive grain to chip off and grow small within the cutting edge. Become. In the conventional electroforming grinding wheel, the diamond abrasive grains act as cutting edges, so the size of the cutting edge and the self-growth unit are the same size, but in the case of the present invention, an arbitrary cutting edge cannot be formed. This allows you to change the size of the cutting edge and the unit in which diamonds grow naturally, and as a result, it is possible to maintain sharpness for a long time.

Furthermore, by increasing the roughness of the outer peripheral edge of the blade compared to the roughness of the side surface of the blade, it is possible to make a mirror finish while cutting with the outer peripheral edge of the blade while cutting the workpiece with a fine rough surface on the blade side. I can do it. Conventionally, with blades made by electroforming, it was difficult to change the roughness of the outer peripheral edge and the roughness of the side surface independently, and it was virtually impossible to do so, but by using sintered diamond as in the present invention, In addition, it is possible to form equally spaced cutting edges on the outer peripheral edge, and to make the blade side surface a finely roughened surface. As a result, while ensuring sharpness on the outer periphery and cutting efficiently, it is possible to perform mirror finishing completely independently on the side of the workpiece.

In addition, in a configuration in which high-hardness diamond chips are embedded one by one only on the outer periphery of the blade (for example, as disclosed in Japanese Patent Application Laid-Open No. 7-276137), the cutting edges may be formed at equal intervals, but they are formed in a single disc-like shape. Because it is not made of PCD, as mentioned above, it applies localized effective shear force to the workpiece without absorbing heat conduction, geometric flatness, continuity of plane, or impact from machining. It is clear that the blade is completely different from the blade according to the present invention in that the blade is processed in a ductile mode.

The spacing between the cutting edges and the surface roughness of the side surfaces are adjusted as appropriate depending on the material to be processed.

FIG. 7 is a cross-sectional view showing the blade 26 attached to the spindle 28. As shown in FIG. 7, the spindle 28 is rotatably supported by a spindle body 44 containing a motor (not shown) (high-frequency motor) and the spindle body 44, with its tip protruding from the spindle body 44. It is mainly composed of a spindle shaft 46 disposed at.

The hub flange 48 is a member interposed between the spindle shaft 46 and the blade 26, and is provided with a tapered mounting hole 48a and a cylindrical protrusion 48b. The hub flange 48 is provided with a flange surface 48c that serves as a reference surface for determining the perpendicularity of the blade 26 with respect to the spindle shaft 46 (rotation shaft). A blade reference surface 36a of the blade 26 is brought into contact with this flange surface 48c, as will be described later.

The blade 26 is provided with an annular portion (contact area) 36 formed thicker on the inner side of the cutting edge portion 40 on one end surface (see FIGS. 2 and 3). A blade reference surface 36a is formed in this annular portion 36, with which the flange surface 48c of the hub flange 48 comes into contact. The blade reference surface 36a is preferably provided at a higher position than other positions on the end face where the annular portion 36 is formed, thereby facilitating flatness. Further, the thickness of the annular portion 36 constituting the blade reference surface 36a needs to be sufficiently thicker than the cutting edge portion 40 provided on the outer circumference of the blade.

The outer peripheral part of the blade must have a narrow cutting width to prevent brittle fracture on the material surface during cutting, and its thickness must be 50 μm or less.

However, if the entire blade is manufactured to a thickness of 50 μm or less, including the blade reference surface while maintaining the same thickness at the outer periphery of the blade, processing distortion during processing during the process of creating a flat blade becomes a major problem. In particular, if the entire blade is made to have a thickness of about 50 μm, the blade will warp to one side due to the balance of strain on both sides of the blade. If the blade is even slightly warped, the outer peripheral edge is very thin, so a very small stress will cause the blade to buckle toward the originally warped side, making it unusable.

Therefore, the thickness of the portion forming the blade reference surface must not be such that even if processing strain remains on the blade surface, the strain will cause warping. The thickness of the reference surface portion of the blade should be at least 0.25 mm, preferably 0.5 mm or more, to the extent that warping due to processing strain does not occur in a disk with a diameter of about 50 mm. If the blade reference surface portion does not have this thickness, it will not be possible to maintain a flat surface as the blade reference surface. If the plane cannot be maintained, it will be difficult to cause the outer peripheral edge of the blade to act on the workpiece in a straight line.

From the above, the blade 26 of this embodiment needs to satisfy the following conditions.

That is, since the blade reference surface 36a must maintain a flat surface even if the machining strain on both sides of the blade 26 is unbalanced, the thickness of the reference surface portion must be at least 0.3 mm or more.

On the other hand, the outer peripheral edge of the blade must be processed in an extremely small area in order to avoid inducing cracks in the material. For this purpose, the thickness of the cutting edge 40 provided on the outer circumference of the blade needs to be 50 μm or less.

In other words, for example, when looking at a blade with a diameter of 50 mm as a whole, it is necessary to manufacture everything in one piece to maintain flatness, and while the inner circumference of the blade must be made thicker to maintain flatness, the outer circumference of the blade must be made thicker to maintain flatness. It has to be thin.

Incidentally, as a method for achieving flatness, mirror finishing such as scaife polishing can be used.

To attach the blade 26, first, the tapered spindle shaft 46 is fitted into the mounting hole 48a of the hub flange 48, and then the hub flange 48 is positioned on the spindle shaft 46 using a fixing means (not shown). Fix it. Next, with the mounting hole 38 of the blade 26 fitted into the protrusion 48b of the hub flange 48, the blade 26 is attached to the hub flange 48 by screwing the blade nut 52 into the threaded portion formed at the tip of the protrusion 48b. Position and fix.

When the blade 26 is attached to the spindle shaft 46 via the hub flange 48 in this way, the perpendicularity of the blade 26 to the spindle shaft 46 is determined by the flatness of the flange surface 48c of the hub flange 48 and the blade reference surface 36a of the blade 26. It is determined by the flatness and the mounting accuracy of overlapping the two. For this reason, the flange surface (a surface perpendicular to the rotational axis) 48c of the hub flange 48 and the blade reference surface 36a of the blade 26 that contacts this flange surface 48c are flattened by, for example, mirror polishing, and are It is preferable that the verticality is formed with high accuracy. As a result, when the blade 26 is attached to the spindle shaft 46 via the hub flange 48, the blade 26 is positioned and fixed in a state where the flange surface 48c and the blade reference surface 36a are in contact with each other. Accuracy can be perpendicular.

Furthermore, since the accuracy of the center position of the blade 26 is determined by the fitting accuracy between the mounting hole 38 of the blade 26 and the protrusion 48b of the hub flange 48, the inner circumferential surface of the mounting hole 38 and the outer circumference of the protrusion 48b By increasing the machining accuracy of the surfaces, these coaxialities can be ensured, and good mounting accuracy can be achieved.

As a result, in addition to the accuracy of the blade itself, high accuracy of attachment to the spindle shaft 46 is ensured, so that highly accurate cutting can be achieved.

That is, in order to process in the ductile mode, not only must the thickness of the cutting edge 40 of the blade 26 be made thin, but also the cutting edge 40 must be rotated in a direction perpendicular to the rotational axis (spindle axis 46) of the blade 26. Although highly accurate mounting is required so that it can act on a substantially straight line, this required accuracy can be fully satisfied.

In this embodiment, the hub flange 48 that pivotally supports the blade 26 and the spindle shaft 46 are made of stainless steel (for example, SUS304, SUS304 is stainless steel based on Japan Industrial Standards (JIS), hereinafter the stainless steel in the present invention refers to Japanese Industrial Standards). (based on industrial standards). On the other hand, the blade 26 is integrally formed of polycrystalline diamond 80 as described above. That is, the blade reference surface 36a is supported by a metal reference surface. According to such a configuration, even if the cutting edge portion 40 on the outer circumference of the blade becomes hot due to cutting, or even if there is heat on the spindle shaft 46 side, the heat is first uniformly transmitted to the inside of the blade 26. That is, the blade 26 is made of polycrystalline diamond 80, which has extremely high thermal conductivity, whereas the hub flange 48 and spindle shaft 46, which pivotally support the blade 26, have significantly higher thermal conductivity than polycrystalline diamond 80. Constructed of low-strength stainless steel. Therefore, the heat generated in these is transmitted in the circumferential direction along the blade 26, and is immediately uniformized in the circumferential direction of the blade 26, resulting in a radial temperature distribution. Only the diamond part transmits heat quickly, and the stainless steel spindle shaft 46 and hub flange 48 have a cross-sectional area that makes it difficult for heat to be transmitted and there are few contact areas, so as a result, the diamond part makes the heat even more uniform. In this uniform state, thermal equilibrium is ensured.

Furthermore, since there is no member that inhibits thermal expansion and no bimetal effect at the outer circumferential portion of the blade, the outer circumferential portion of the blade 26 can maintain good roundness and flatness. As a result, the cutting edge 84 provided at the outer peripheral end of the blade acts on the workpiece W in a straight line.

Although the present embodiment shows a configuration in which the blade 26 is attached to the spindle shaft 46 via the hub flange 48, a configuration in which the blade 26 is directly attached to the spindle shaft 46 may also be used, and similar effects can be obtained. be able to.

Next, a dicing method using the blade 26 of this embodiment will be explained. This dicing method can stably and accurately cut brittle materials such as silicon, sapphire, SiC (silicon carbide), and glass while plastically deforming them without causing brittle fractures such as cracks or chipping. It's a method.

First, the work W is taken out from a cassette placed on the load port 12 and placed on the work table 30 by the transport means 16. The surface of the workpiece W placed on the worktable 30 is imaged by the imaging means 18, and the position of the line to be diced on the workpiece W and the position of the blade 26 are determined in each of X, Y, and θ (not shown). The work table 30 can be adjusted and matched by the moving axis. When the alignment is completed and dicing is started, the spindle 28 starts rotating, and the spindle 28 lowers in the Z direction to a predetermined height by the amount by which the blade 26 cuts or grooves the workpiece W, and the blade 26 increases the speed. Rotate. In this state, the work W is processed and fed in the X direction shown in FIG. 1 by a moving shaft (not shown) together with the work table 30 relative to the blade position, and the blade 26 attached to the tip of the spindle is lowered to a predetermined height. Dicing is performed.

At this time, the cutting depth (cutting amount) of the blade 26 into the workpiece W is set. By rotating the blade 26, which requires a large number of cutting edges on the outer periphery, at high speed, one cutting edge (micro cutting edge) 84 must be set to be less than or equal to the critical cutting depth (Dc value). This critical depth of cut is the maximum depth of cut that allows cutting in a ductile mode by plastic deformation without causing brittle fracture of the brittle material.

Here, Table 3 shows the relationship between the workpiece material and the critical depth of cut per blade that does not cause cracks.

As can be seen from Table 3, when the workpiece material is silicon, for example, the critical cutting depth is 0.15 μm, so the cutting depth of the blade 26 into the workpiece W is set to 0.15 μm or less. If the depth of cut exceeds 0.15 μm, cracks will inevitably occur in the workpiece material.

Furthermore, among the workpiece materials shown in Table 3, silicon has the smallest critical cutting depth (0.15 μm), indicating that it is easier to break than other materials. From this, for most materials, if the cutting depth is 0.15 μm or less, ductile mode machining is possible, which in principle allows machining to proceed within the deformation range of the material without generating cracks.

Further, the circumferential speed of the blade 26 with respect to the workpiece W (blade circumferential speed) is set to be sufficiently larger than the relative feed rate of the blade 26 with respect to the workpiece W (processing feed rate). For example, when the rotation speed of the blade 26 is 20,000 rpm and the outer diameter of the blade 26 is 50.8 mm, the relative feed speed of the blade 26 is set to 10 mm/s with respect to the rotation speed of the blade 26 of 53.17 m/s.

Note that the cutting depth and rotation speed of the blade 26, and the relative feed speed of the blade 26 with respect to the workpiece W are controlled by the controller 24 shown in FIG.

The dicing process in such a ductile mode is repeatedly performed with each cutting depth set to be equal to or less than the critical cutting depth until the groove depth of the cutting line reaches the final cutting depth.

When the dicing process along one cutting line for the workpiece W is completed, the blade 26 is index-fed and positioned to the next cutting line to be processed next, and the blade 26 is index-fed and positioned to the next cutting line to be processed next, and the blade 26 is diced along the cutting line by the same processing procedure as described above. Dicing processing is performed.

By repeating the dicing process, when all the dicing processes along a predetermined number of cutting lines are completed, the workpiece W is rotated 90 degrees together with the work table 30, and the above-mentioned cutting line is The dicing process is performed along a cutting line perpendicular to the direction.

In this way, when all the dicing processes along all the cutting lines are completed, the workpiece W is cut and divided into a large number of chips.

Here, in order to verify the effects of the present invention, the results of grooving a workpiece using the blade 26 of this embodiment and a conventional electroforming blade in the dicing method described above will be described.

[Comparative experiment 1] (Silicon wafer)
As the blade 26 of this embodiment, a double-sided tapered type (both V-type) was used. On the other hand, as a conventional electroformed blade, a blade thickness of 50 μm (#600) was used. Other conditions are as follows.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu)
・Blade rotation speed: 20000rpm
・Workpiece feed speed (processing feed speed): 10mm/s
・Cutting depth: 30μm
・Work: Silicon wafer (thickness 780μm)
The results of Comparative Experiment 1 are shown in FIGS. 8A and 8B. Note that FIGS. 8A and 8B show the state of the workpiece surface after grooving.

As shown in FIG. 8A, when the blade 26 of this embodiment was used, cutting grooves could be formed on the workpiece without causing any cracks.

On the other hand, as shown in FIG. 8B, when the conventional electroforming blade was used, minute cracks were generated on the workpiece surface. Cracks also appeared on the bottom of the cut groove.

In this way, when the blade 26 of this embodiment is used, it is possible to stably and accurately cut in the ductile mode without generating cracks, compared to when using a conventional electroformed blade. I confirmed that it can be done.

[Comparative experiment 2] (sapphire wafer)
Next, a comparative experiment was conducted using the same blade as in Comparative Experiment 1 under the following conditions.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu)
・Blade rotation speed: 20000rpm
・Workpiece feed speed (processing feed speed): 10mm/s
・Cutting depth: 50μm
・Work: Sapphire wafer (thickness 200μm)
The results of Comparative Experiment 2 are shown in FIGS. 9A and 9B. Note that FIGS. 9A and 9B show the state of the workpiece surface after grooving, and FIG. 9A shows the case when the blade 26 of this embodiment is used, and FIG. 9B shows the case when the conventional electroforming blade is used. It is.

As is clear from FIGS. 9A and 9B, it was confirmed that even when the workpiece was changed to a sapphire wafer, the same results as in Comparative Experiment 1, which targeted silicon wafers, were obtained.

[Comparative experiment 3] (SiC wafer)
Next, a comparative experiment was conducted using a straight blade under the following conditions. The blade thickness was 20 μm, 50 μm, and 70 μm.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu)
・Blade rotation speed: 20000rpm
・Workpiece feed speed (processing feed speed): 2mm/s
・Cutting depth: 200μm
・Workpiece: 4H-SiC wafer Si surface (thickness 330μm)
10A to 10C show the state of the workpiece surface after grooving by the blade 26 of this embodiment, in which FIG. 10A shows when the blade thickness is 20 μm, FIG. 10B shows when the blade thickness is 50 μm, FIG. 10C shows a case where the blade thickness is 70 μm.

Ideally, the blade thickness should be 50 μm or less, but in the case of SiC, with a blade thickness of 70 μm, there were small cracks, but no significant cracks.

[Comparative experiment 4] (Cemented carbide)
Next, a comparative experiment was conducted under the following conditions using a straight blade as before. The blade thickness was 20 μm.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu, AD20T is the device model number)
・Blade rotation speed: 10000rpm
・Workpiece feed speed (processing feed speed): 1mm/s
・Cutting depth: 40μm
・Work: Carbide WC (WC: tungsten carbide)
11A and 11B show the workpiece surface (FIG. 11A) and cross section (FIG. 11B) after grooving by the blade 26 of this embodiment. As shown in the figure, it is shown that ideal ductile mode processing can be performed even on hard materials such as cemented carbide.

[Comparative Experiment 5] (Polycarbonate)
Next, a comparative experiment was conducted under the following conditions using a straight blade as before. The blade thickness was 50 μm.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu)
・Blade rotation speed: 20000rpm
・Workpiece feed speed (processing feed speed): 1mm/s
・Cutting depth: 500μm (full cut)
- Workpiece: Polycarbonate FIGS. 12A and 12B show the surface of the workpiece after grooving by the blade 26 of this embodiment and the cross section of the workpiece, respectively. As shown in FIG. 12A, a sharp cutting line is observed when viewed from the work surface. As shown in FIG. 12B, it can be seen that a mirror-like cut surface was obtained when compared with the conventional electroformed blade.

[Comparative experiment 6] (CFRP: carbon-fiber-reinforced plastic)
Next, a comparative experiment was conducted under the following conditions using a straight blade as before. The blade thickness was 50 μm.

・Equipment: Blade dicing device AD20T (manufactured by Tokyo Seimitsu)
・Blade rotation speed: 20000rpm
・Workpiece feed speed (processing feed speed): 1mm/s
・Cutting depth: 500μm (full cut)
・Work: CFRP
The results of Comparative Experiment 6 are shown in FIGS. 13A and 13B. Note that FIGS. 13A and 13B show the cross-section of the workpiece after grooving, and FIG. 13A shows the case where the blade 26 of this embodiment is used, and FIG. 13B shows the case where the conventional electroforming blade is used. It is.

Compared to conventional electroforming blades, electroforming blades tear off each fiber one by one, making it impossible to observe a clean cross section of the fibers, but with the blade according to the present invention, individual fibers are sharp without being entangled and torn. It is possible to obtain a cut surface with a fiber end surface.

This result shows that in the case of the blade according to the present invention, a continuous cutting edge is formed, each recessed portion serves as a cutting edge, and the diamonds are bonded to each other. Therefore, with an electroformed blade, when the cutting edge cuts a single fiber, the impact is absorbed by the soft binding material, and the cutting edge does not act sharply, but the blade according to the present invention uses the shear stress of the diamond to This is because the cutting edge acts sharply without absorbing instantaneous impact.

Next, we will explain why practical dicing is possible even when cutting is performed in ductile mode with the cutting depth of the blade 26 on the workpiece W being equal to or less than the critical cutting depth (Dc value). do.

For example, consider a case where a workpiece W made of a silicon wafer is cut using a blade 26 having an outer diameter of 50 mm. It is assumed that cutting edges (microcutting edges) along the grain boundaries are provided along the circumferential direction at a pitch of about 10 μm at the outer peripheral end of the blade. In this case, since the outer circumferential length of the blade is 157 mm (157000 μm), approximately 15700 cutting edges are formed on the outer circumference.

First, it is assumed that one cutting edge makes a cut of 0.15 μm so as not to crack the workpiece W, and that the amount removed at one time by the cut is 0.02 μm (20 nm). Note that the critical cutting depth at which cracks do not occur in materials such as SiC, Si, sapphire, and SiO ₂ is usually on the submicron order (for example, about 0.15 μm). In this case, there are 15,700 cutting edges at the outer peripheral edge of the blade, so in principle, machining can proceed by about 0.314 mm (314 μm) per revolution of the blade. If the dicing spindle is set at 10,000 rpm, it rotates 166 times per second. Therefore, the cutting removal distance at the outer peripheral edge of the blade per second is 52.124 mm. For example, when the blade feed rate is 20 mm/s, the speed at which the blade processes and removes the workpiece material in the shearing direction is faster than the speed at which it moves while pushing inside the workpiece material. In other words, when cutting a workpiece material, a minute incision is made to the extent that the workpiece material is not destroyed, and the workpiece material is machined in a horizontal direction perpendicular to the direction of movement of the blade, and the workpiece material is swept away. The blade moves through the removed portion. Therefore, there is no room for cuts of 0.1 μm or more that would cause cracks, so cutting can be performed in the ductile mode processing region based on plastic deformation without causing brittle fracture. In other words, by rotating the blade at high speed and increasing the circumferential speed of the outer peripheral end (tip) of the blade relative to the material to be processed compared to the feed rate of the blade relative to the material to be processed, machining in ductile mode is possible. It becomes possible to do this.

In addition, in practice, it is necessary to allow some leeway to take into account some degree of eccentricity of the blade, and with a blade diameter of φ50.8 mm, machining should be performed at a feed rate of about 10 mm/s while rotating at 20,000 rpm. Otherwise, no cracks will occur in the material.

Next, the results of various studies to realize machining in ductile mode using the blade 26 of this embodiment will be explained.

[About the cross-sectional shape of the cutting edge of the blade]
In this embodiment, the cross-sectional shape of the cutting edge portion 40 provided on the outer periphery of the blade 26 is the double-sided tapered type (both V type) shown in FIG. 4B among the cross-sectional shapes shown in FIGS. 4A to 4C. Preferably used.

FIG. 14 is an explanatory diagram schematically showing a state in which dicing is performed using a blade 26 having a cutting edge portion 40 of a tapered type on both sides. First, the tip 40a provided at an arbitrary position of the cutting edge 40 of the blade 26 is located at the deepest part (lowest part) from the surface of the workpiece W, as shown in parts (A) to (C) in FIG. The workpiece W is ground while gradually moving to point ). Thereafter, as shown from part (C) to part (D) in FIG. 14, the tip 40a of the cutting blade 40 gradually moves from the deepest part of the workpiece W toward the surface part. At this time, a gap S is formed between the side surface of the grinding groove and the side surface of the blade 26.

That is, in the region where the cutting edge portion 40 of the blade 26 cuts inward from the surface of the workpiece W, the upstream side in the blade rotation direction becomes the cutting portion 60 where the workpiece W is ground, while the downstream side thereof becomes the cutting portion 60 where the workpiece W is ground. A discharge section in which a gap S is formed between (the side surface of the cutting edge 40) and the groove side surface, the workpiece W is not ground, and the chips ground by the upstream cutting section 60 are discharged into the groove. It becomes 62.

Generally, burrs and chipping occur when the blade rubs against the side surfaces of the groove when it is removed from the material. For this reason, for example, as shown in FIG. 15, when a straight type blade 90 in which both side surfaces are machined straight and parallel is used, the tip of the blade (cutting edge) enters the inside of the workpiece W and moves outward. The side surface of the blade is constantly in contact with the side surface of the cutting groove until it is removed. Therefore, compared to a double-sided tapered type blade 26, when the blade tip comes out from inside the workpiece W, the sides of the cutting groove and the blade side are more likely to rub against each other, resulting in burrs and chipping (see Figure 15). (See Parts (D) and (E)). Further, when an electroformed blade embedded with diamond abrasive grains is used, the abrasive grains protruding from the side surfaces of the blade scratch the side surfaces of the groove, which tends to promote the occurrence of burrs and chipping on the side surfaces of the groove.

On the other hand, according to the blade 26 having the cutting edge portion 40 of a tapered type on both sides, when the blade 26 comes out from the work W as described above, a gap S is created between the blade side surface and the groove side surface. Therefore, burrs and chipping do not occur. Further, as the chips are discharged, the heat generated during grinding can be discharged together with the chips. This makes it possible to prevent the blade 26 from warping.

That is, the cutting edge portion 40 of the blade 26 cuts into the workpiece W and cuts the workpiece W until it reaches the lowest point, and then the blade 26 passes through the lowest point of the workpiece W and the blade 26 cuts away from the workpiece W. During the extraction process, the blade 26 comes out of the workpiece W with a gap S formed between the blade side surface and the groove side surface, so that it is possible to effectively suppress the occurrence of chipping and the like.

Furthermore, by performing the cutting process as described above, it also contributes to suppressing as much as possible the generation of heat caused by friction caused by contact between the blade side surface and the groove side surface. As a result, an increase in cutting resistance due to a rise in heat can be suppressed, and cutting debris can be prevented from being welded to the blade 26. Moreover, by leaving the cutting waste in the groove while creating the gap S in the process of extracting the blade 26 from the workpiece W, there is an effect of imparting heat to the cutting waste and discharging the heat. These cutting debris can be washed away with subsequent cleaning. Furthermore, since it is possible to suppress the heat generation of the blade 26 and the workpiece W, it is possible to prevent these heat generation without supplying a large amount of water to the blade 26 and the workpiece W. It becomes possible to process.

[Relationship between particle size and content of diamond abrasive grains]
In this embodiment, in order to process in the ductile mode, it is necessary to consider the abrasive grain arrangement in the circumferential direction of the blade 26. The reasons for this are as follows.

First, in order to make a cut of 0.15 μm, it is preferable that the size of the cutting edge (micro cutting edge) used to make the cut is about one digit larger in abrasive grain size and cutting edge spacing. When the cutting edge spacing is three orders of magnitude or more larger, it is difficult to make minute cuts when considering variations in the cutting edge spacing.

Generally, the maximum depth of cut when processing a flat sample by moving a blade with cutting edges set at approximately equal intervals in parallel is calculated geometrically. Based on Figure 16 below, if the hatched area is the chip per blade, the length AC determined by the line connecting the blade center O and a point A on the chip is the maximum cutting depth per blade. The depth is g _max .

In addition, D is the blade diameter, Z is the number of blade cutting edges, N is the number of revolutions per minute of the blade, V _S is the circumferential speed of the blade (πDN), V _W is the feed rate of the workpiece, and S _Z is the number of blades per blade. The feed amount is the feed amount, and a is the depth of cut.

Therefore,

Assuming that the cutting depth g _max is sufficiently smaller than the blade diameter D,

therefore,

Here, by using the cutting edge interval λ instead of the number Z of the blades and substituting Z=πD/λ into equation (1), the maximum depth of cut per blade can be found.

Here, πDN is clearly equal to the blade circumferential speed _VS. That is, in flat plate processing using a blade, the relationship between the cutting edge interval λ and the maximum cutting depth per blade is given by the following equation.

However, g _max : cutting depth per unit cutting edge, λ : cutting edge interval, V _ω : workpiece feed speed, V _s : blade speed, a : blade cutting depth, D : blade diameter.

From this, it can be seen that the spacing between the cutting edges becomes important in order to keep the depth of cut per unit cutting edge below a certain level. The rotational speed of the blade is also important.

According to the relationship shown in this g _max formula, even if V _ω : 40 mm/s, V _s : 26166 mm/s, a: 1 mm, D: 50 mm, and λ: 25 μm, the depth of cut is only about 0.027 μm, The depth of cut is 0.1μm or less. This range is below the critical depth of cut and is therefore within the range of ductile mode machining.

In order to perform ductile mode processing, the above conditions must be met.

Furthermore, as a practical condition, a 2-inch diameter blade (diameter 50 mm) is rotated at 10,000 rpm, the workpiece thickness is 0.5 mm, the workpiece feed rate is 10 mm/s, and the outer circumference of the blade is cut. Assume that the blades are formed at a pitch of 1 mm (V _ω : 10 mm/s, V _s : 157×10 ⁴ mm/s, a: 0.5 mm, D: 50 mm, λ: 1 mm).

Even under these conditions, when substituted into the above equation, the critical depth of cut made by one blade is 0.08 μm, which is still less than 0.1 μm. Therefore, if the blade is not eccentric and ideally all cutting edges act on the removal process of the workpiece, the critical gap between the cutting edges that can be formed on the outer periphery of the blade is 1 mm or less, which is fatal. It becomes possible to proceed with machining without making excessive cuts that would cause cracks.

Note that in SiC, the critical cutting depth that does not cause cracks is approximately 0.1 μm. For other materials such as sapphire, glass, and silicon, the critical cutting depth that does not cause the same crack is approximately 0.2 to 0.5 μm, so if the critical cutting depth is set to 0.1 μm or less, most brittle materials can be processed within the plastic deformation range of the material without causing cracks.

Therefore, it is desirable that the cutting edge spacing around the blade be 1 mm or less.

On the other hand, the cutting edge spacing around the blade is preferably 1 μm or more. If the average cutting edge spacing is 1 μm or less, that is, if the cutting edge spacing is on the order of submicrons, the critical cutting depth amount and the depth unit for material removal will be approximately the same. That is, both of them are on the submicron order, but under such conditions, it is difficult for one cutting edge to actually reach the expected removal amount, and on the contrary, the machining speed rapidly decreases due to the clogging mode.

Under these circumstances, apart from the critical cutting depth of one cutting edge, it is thought that the depth that one cutting edge can remove is unreasonable.

Note that the above idea holds true when the cross-sectional area of the workpiece is constant. That is, the sample is a substantially flat sample, the blade is rotated at high speed, the blade is set to a constant cutting depth with respect to the flat workpiece, and the contents match in terms of the blade cutting the workpiece while sliding it.

It is also important to note that in the above equation, the critical depth of cut given by one cutting edge depends on the interval between the cutting edges. The amount of cut made by one cutting edge affects the distance from the next cutting edge, and if there is a part where the gap between the cutting edges is large, this indicates the possibility of causing a cut crack deeper than the desired critical depth of cut. . Therefore, the cutting edge spacing is an important element, and in order to obtain a stable cutting edge spacing, it is preferable to use a PCD material made of sintered single crystal diamond so that the cutting edge spacing is set naturally from the material composition. It is used.

However, even if the particle size (average particle size) of the diamond abrasive grains is large, if the gaps between the diamond abrasive grains are closely spaced and the actual abrasive grain spacing is on the order of smaller than the grain size, the abrasive grains will be even larger. It becomes possible to suppress and control cuts. In reality, diamond abrasive grains with an ideal particle size of about 1 μm to 5 μm are desirable.

Note that the particle size does not necessarily correspond to the cutting edge spacing. When accurately trued, the spacing between the cutting edges may correspond to the grain size, but when cut and dressed, the spacing between the cutting edges is typically larger than the grain size.

In other words, if the grain boundaries are strictly defined, the gaps on both sides of a single abrasive grain can be interpreted as corresponding to the cutting edge, but in reality, some abrasive grains fall out in clumps and are naturally fixed. It begins to form periodic cutting edges. This allows the cutting edge pitch to be formed by roughening the blade evenly.

FIGS. 17A and 17B show the results of measuring the outer peripheral edge of the blade with a roughness meter. Further, FIGS. 18A and 18B show photographs of the surface condition. Since it is a sintered body, basically all the parts visible on the surface are composed of diamond, which is abrasive grain.

Furthermore, the surface irregularities are formed from diamond grain boundaries, forming a natural, approximately equally spaced irregular shape. Each of these recesses acts as a cutting edge for cutting into the material. As is clear from the figure, this cutting edge pitch has 260 and 263 ridges in the 4 mm range, so it can be seen that the cutting edge pitch is approximately 15 μm pitch. Note that this material is composed of DA200 manufactured by Sumitomo Electric Hardmetal Co., Ltd., and the diameter of the diamond particles is nominally 1 μm. In this way, even though the grain size is small, the cutting edge spacing is larger than that, and as can be seen from the figure, they are formed at approximately equal intervals.

These evenly spaced cutting edges are due to the fact that the blade itself is made of polycrystalline diamond, which is made by sintering single-crystal fine particles.

In this way, the tip of the blade is designed to have large irregularities in order to cut the workpiece, but compared to the tip of the blade, the side surface of the blade has a mirror surface after cutting the workpiece. Grind. For this reason, the tip of the blade is roughly shaped to facilitate cutting, while the side surfaces of the blade are shaped finely.

Note that in conventional electroformed blades, the spacing between diamond abrasive grains is usually much larger than the grain size. This is because the diamond abrasive grains sprinkled sparsely are simply plated, and the plating is completely different.

In contrast, in the blade 26 of this embodiment, the polycrystalline diamond is extremely hard and has high strength because the sintering aid melts into the diamond during sintering and the diamonds are strongly bonded to each other. . Furthermore, polycrystalline diamond has a relatively high diamond content compared to an electroformed blade (see, for example, Japanese Patent Application Laid-Open No. 61-104045), and has relatively high strength compared to an electroformed blade.

In addition, since much of the interior of the blade material is occupied by diamond, it is possible to make the other parts (including the sintering aid) smaller than the diamond volume, and in the case of polycrystalline diamond, Even if the grain size is large, it is possible to make the gap between the diamond abrasive grains substantially on the order of microns.

Furthermore, the concave portions between the diamond abrasive grains play an extremely important role in the present invention. Diamond abrasive grains are extremely hard, but some of the cobalt added as a sintering aid penetrates into the diamond, but some remains between the diamond abrasive grains. This part is a little softer than diamond, so it is easily worn during cutting and becomes slightly concave. In other words, there is a part between the diamonds, and by creating a small cutting edge in the depression between the diamonds, it is possible to obtain a stable cut without making an excessive cut. In addition, the minute cutting edge may act not only in the dents sandwiched between diamonds, but also in dents created by missing diamond particles themselves. This cutting edge interval may be set to an interval that does not exceed the critical depth of cut per blade shown in the above formula.

For example, consider the case where diamond abrasive grains with a grain size of 25 μm are hardened by sintering. For the sake of clarity, it is assumed here that the diamond abrasive grains are cubes with sides of 25 μm. In order to bond diamond abrasive grains to each other, a portion of 1 μm on both sides outside the 25 μm is used as a bonding portion for bonding to another particle. This results in a 27 μm square cube. In that case, the volume percentage occupied by the diamond abrasive grain portion is approximately 78.6%. Therefore, if the diamond content is about 80% or more, even if the diamond abrasive grains have a particle size of 25 μm, the gaps between the diamond abrasive grains, that is, the particle spacing, will actually be about 1 to 2 μm at most, and the dents will be This part becomes the cutting edge (micro-cutting edge) for making cuts. Further, if the particle spacing is about 2 μm, even if particles of that pitch are pushed into the workpiece material at that particle spacing, the displacement of the workpiece material will be more than an order of magnitude smaller than the spacing of the diamond abrasive grains. That is, it is 0.15 μm or less. Furthermore, assuming that cutting edges (micro cutting edges) are formed at a pitch of 25 μm, if the blade diameter is 50 mm, 6280 cutting edges are formed per approximately 157 mm of the total circumference. If the blade were to rotate at 20,000 rpm, 2,093,333 cutting edges could be activated per second.

Let's assume that this one cutting edge makes a cut of 0.15 μm or less, and that 1/5 of that, 0.03 μm, is removed per second. In this way, with 2093333 micro-cutting blades, it would be possible to remove about 62799 μm per second, and theoretically it would be possible to cut about 6 cm per second.

From this point of view, theoretically, even if diamond abrasive grains have a particle size of 25 μm, if the diamond content is 80% or more, the gap between the diamond abrasive grains will be 1 to 2 μm. As a result, it is possible to maintain a stable depth of cut of 0.15 μm without giving an excessive depth of cut.

Furthermore, even if the particle size of the diamond abrasive grains is not 25 μm but smaller, if the diamond content is 80% or more, the critical cutting depth will not be exceeded in terms of cutting depth and material removal, which is a problem. This makes it possible to perform processing in ductile mode without causing cracks.

As mentioned above, in the case of polycrystalline diamond, the diamond abrasive grains (diamond particles) are closely packed, so the diamond content is very high, and each diamond abrasive grain has a cutting edge of the size of the diamond abrasive grain. Acts as.

Furthermore, the distance between the diamond abrasive grains is much smaller than the particle size of the diamond abrasive grains, making it possible to accurately control the depth of cut. As a result, the depth of cut never increases beyond the predetermined originally intended depth of cut, ensuring a constant depth of cut during machining. As a result, it becomes possible to perform cutting in the ductile mode without making mistakes.

It should be noted that with a large particle size of about 25 μm, the content of diamond abrasive grains can be further increased, and some commercially available abrasive grains have a content (diamond content) of about 93%. If this is the case, the proportion of the sintering aid will further decrease, that is, the gaps between the diamond abrasive grains will actually become minute.

However, when using diamond with a large particle size of 25 μm or more, the cutting edge spacing is sufficient for ductile mode machining as mentioned above, but on the other hand, the blade thickness should be 50 μm or less. In some cases, such large abrasive grains cannot be used.

This is because, for example, when manufacturing a blade with a thickness of 40 μm, the cross section of the blade must have at least two or more diamond abrasive grains, but theoretically there would not be two, but 1.6.

[About the blade thickness considering the deformation of the workpiece material]
In order to stably perform ductile mode machining, the depth of cut must be approximately 0.15 μm or less in the depth direction, as described above. In order to make this cut stably, it is also necessary to take into account the thickness direction displacement (longitudinal direction displacement) of the workpiece material, which is taken into account from the cut width.

That is, when cutting is made in a direction parallel to the blade surface (a plane perpendicular to the rotational axis of the blade 26) over a wide range for removal, the accompanying deformation of the workpiece material also spreads in the vertical direction (in the direction of the cutting depth). That is, it is necessary to take into account the Poisson's ratio of the workpiece material and make the cut width to be somewhat finite. This is because if the width of the cut is made extremely large, material deformation due to the influence of Poisson's ratio causes the aftereffects of deformation to extend in the vertical direction as well. This is because the depth of cut exceeding the predetermined critical depth of cut may be made, resulting in cracking of the workpiece W.

Here, we will consider the blade thickness (blade width) that can stably make a cut when considering the influence of Poisson's ratio. Table 4 shows the relationship between Young's modulus and Poisson's ratio of brittle materials.

Here, it is assumed that one cutting edge cuts into the workpiece material. Furthermore, the tip of the thin, straight blade is not arbitrarily sharpened, and when processed normally, the cross-sectional shape is approximately semicircular.

In such a case, for example, if a 0.15 μm incision is made using a rectangular parallelepiped, if the incision is made in parallel with a width of approximately 1 μm, according to Poisson's ratio, there will be an incidental displacement of approximately 0.17 μm in the vertical direction. This will be close to the actual depth of cut. In reality, the influence of Poisson's ratio extends not only to vertical displacement but also to the horizontal direction, so a width of approximately 1 μm can be given as the depth of cut.

However, as shown in Fig. 19, when the approximately semicircular blade tip (blade outer peripheral edge) cuts 0.15 μm into the workpiece material, the width is not uniformly displaced in parallel. Considering the rise of the outer periphery, it is possible to cut into an arcuate width of approximately 5 μm without being affected by Poisson's ratio. That is, Rsinθ=2.5, and R(1-cosθ)=0.15.

Calculating this backwards, the radius of the blade at the tip will be approximately 25 μm, and the apex angle for making the above-mentioned 5 μm wide incision will be approximately 12 degrees.

Therefore, the width of the blade that cuts into the material must be kept within about 50 μm. If it is more than that, each point acts on the material at the same time in a plane, sometimes leading to the induction of minute cracks.

In addition, if the curvature is larger than that, that is, if the blade thickness is about 30 μm, the cutting edge will basically act more locally than in the above situation, so basically the width of the cutting edge will affect the depth of cut. You can cut stably without causing any damage.

Note that the width of the blade is important from the perspective of performing ductile mode machining, but it also has a great deal to do with the buckling strength of the blade alone.

The width of the blade is also limited by the thickness of the workpiece.

Here, the relationship between the width of the blade and the thickness of the workpiece is shown.

The workpiece is generally supported by dicing tape. Since the dicing tape is an elastic body, unlike a hard material such as a workpiece, it is easily displaced in the vertical direction (Z direction) by a small amount of stress. Here, when cutting a workpiece with a blade, the cross-sectional shape of the cut portion in the workpiece, the shaded area shown in FIG. 20A, is important.

When the blade thickness (blade contact area) l is larger than the workpiece thickness h, l>h, the part that the blade contacts (the part that is removed by processing) becomes a horizontally long rectangle, as shown in FIG. 20B. When the cross section to be removed is a horizontally long rectangle, when a distributed load is applied from above, it bends into an arched shape due to deflection, and the maximum displacement of the deflection is as follows. (Actually, it is a deflection of the plate, but it is simply a beam problem and assumed that distributed load is acting.)

In the case of a rectangular beam whose cross section is depth b and height h,

Therefore, the above equation becomes the following.

The maximum deflection is inversely proportional to the cube of the workpiece thickness h and proportional to the fourth power of the blade contact area l at the central portion of the beam.

In particular, at (l/h) ³ , if l/h becomes smaller than 1, the deflection becomes much smaller, and conversely, if l/h becomes larger than 1, the deflection becomes much smaller. becomes larger. From this, cases in which deflection occurs and cases in which it does not occur can be determined depending on the shape of the relative thickness between the blade thickness (blade contact area) l and the workpiece thickness h.

When this blade contact area is larger than the thickness of the workpiece (l>h), the workpiece will deflect within the contact area, but when the workpiece is deflected, vibrations due to the deflection of the workpiece will be caused by intermittent vertical deflection within the plane. occurs, making it impossible to achieve the specified depth of cut. As a result, the blade makes a fatal cut due to the vertical vibration of the workpiece, causing cracks to occur on the workpiece surface.

Therefore, especially in machining using the PCD blade of the present invention, in order to perform crack-free machining, it is necessary to stably and faithfully maintain a predetermined depth of cut. To achieve this, in addition to setting the depth of cut by controlling the cutting edge spacing, it is also necessary to ensure a predetermined depth of cut with high precision by suppressing longitudinal vibrations during machining of the workpiece itself.

For this purpose as well, the blade thickness must be made thinner than the thickness of the target workpiece, as shown in FIG. 20C.

For example, if the workpiece thickness is 50 μm or less, the blade width (thickness) must naturally be 50 μm or less.

In this case, the workpiece does not flex within the contact area. On the other hand, although bending or compressive stress acts within the contact area, the workpiece is a dense continuous body in the lateral direction, and its deformation is restrained by Poisson's ratio. Therefore, the stress applied from the blade acts locally as a reaction force from the work, and as a result, machining at a predetermined depth of cut is possible without cracking.

[Comparison with conventional blades]
In the case of an electroformed blade as disclosed in Patent Document 1, diamonds are dispersed and plating is performed on top of the diamonds, so the diamonds are sparsely present and moreover, they protrude. As a result, the protruding portion may naturally make an excessive cut, inducing brittle fracture. Note that in areas where the bottom and side surfaces of the groove are continuous, the workpiece materials are densely packed together, making it difficult for cracks to form immediately, but cracks and cracks are most likely to occur in areas where the blade comes off. This is the same as the appearance of burrs when the blade exits, and is because the workpiece material is not continuous and has no support.

Further, in the case of the blade of Patent Document 2, since the film is formed by the CVD method, there are no protruding cracks. However, it is impossible to control the arrangement of the cutting edges at the end of the blade, the plane condition and waviness of the side surface of the blade, etc.

Particularly, as far as the side surface of the blade is concerned, the unevenness in film thickness during film formation directly corresponds to the unevenness in the thickness of the blade. Furthermore, since the surface of the film itself is a solid surface, it may come into complete contact with the side surfaces of the material, inducing frictional heat, and may have subtle undulations, which may crack the material.

In contrast, the blade 26 of this embodiment is integrally made of polycrystalline diamond sintered using a soft metal sintering aid, so the blade outer edge and the blade side surface can be subjected to wear treatment. It becomes possible to mold. In particular, since the outer circumferential edge of the blade becomes a cutting edge, as described above, it is also possible to further change the wear treatment conditions in order to obtain a predetermined cutting edge. On the other hand, the first role of the blade side part is to remove chips, but if you take into account the contact with the side of the workpiece, it is possible to stably work the workpiece while making some contact, but not excessively. It is desirable that the sides be roughened to the extent that they are slightly scraped.

In this way, it is not possible in the techniques of any of the cited documents to design the outer circumferential end of the blade and the side surface of the blade to have desired surface conditions depending on the respective conditions, and to manufacture such surfaces.

Note that blades used in scribing are not suitable for machining in ductile mode for the following reasons.

That is, in scribing, the blade itself is not rotated, so minute cutting edges arranged at equal intervals are not required. Furthermore, even if there is a cutting edge, if you use a large cutting edge rather than a microscopic cutting edge that follows the grain boundaries on the micron order, high-speed dicing will crack the material and cannot be used. I can't.

Further, even if a blade having a minute cutting edge along the grain boundary is used for scribing, the minute cutting edge does not function as a cutting edge that causes cracks in scribing.

Also, scribing presses the blade in the vertical direction. Therefore, stress is applied vertically downward to the shaft passing through the blade, and the blade is configured to slide with respect to the shaft. Since the shaft and blade are not used fixedly, the clearance between the blade and the shaft is low, and since the blade itself does not rotate at high speed, there is no need to provide a reference surface on one side of the blade.

In addition, even if we manufacture a scribing blade with a thin cutting edge of 50 μm or less, especially 30 μm or less, the blade is supported by a thin bearing, and there is no reference surface on one side of the blade with a wide surface to receive it, so the precision against the workpiece is high. Straightness cannot be ensured. As a result, the blade with a thin cutting edge becomes buckled and cannot be used.

[About blade strength]
Next, the relationship between the strength (modulus of elasticity) of the blade material and the strength (modulus of elasticity) of the workpiece material will be described.

In order for the blade to cut a certain amount into the workpiece and continue cutting, the blade material needs to have greater strength than the workpiece material. If the blade material were simply made of a material that is softer than the workpiece material, that is, a material with a small Young's modulus, the workpiece material would If the member has a high modulus of elasticity, the work surface cannot be slightly deformed, and if an attempt is made to forcefully deform it, the blade itself will buckle. As a result, machining does not proceed. Here, the buckling load P of the long column supported at both ends is given by the following equation.

Note that E: Young's modulus, I: second moment of area, and l: length of long column (corresponding to blade diameter).

In the case of a blade with a lower elastic modulus than the workpiece material, if the machining is to proceed while suppressing buckling deformation of the blade, a moment of inertia of area that does not cause buckling deformation is required, and specifically, the blade thickness I have no choice but to make it thicker. However, especially when machining brittle materials, if the blade is thicker than the workpiece, the surface of the workpiece will be deformed and broken. Therefore, the blade thickness must be thinner than the workpiece thickness.

As a result, the blade material must have a higher modulus of elasticity than the workpiece material.

Such a relationship corresponds to the difference between the conventional electroformed blade and the blade 26 of this embodiment. That is, the electroformed blade is bonded with a binding material such as nickel, and is made of a nickel-based material. The Young's modulus of nickel is 219 GPa, while for example SiC is 450 GPa. The diamond abrasive grains electrodeposited on nickel themselves have a strength of 970 GPa, but since they exist individually and independently, they are ultimately controlled by the Young's modulus of nickel. In this case, since the workpiece material is in principle highly elastic, the thickness of the blade must be increased accordingly. As a result, it is necessary to increase the thickness of the electroformed blade to increase the contact area, which leads to cracks and fractures.

On the other hand, in the case of the blade 26 of this embodiment, the Young's modulus of polycrystalline diamond is equivalent to 700 to 800 GPa because the diamonds are bonded to each other. This is almost comparable to the Young's modulus of diamond.

Here, if the elastic modulus of the blade 26 is larger than that of the workpiece W, when the blade 26 makes a cut, the surface on the workpiece W side, not the blade 26, is deformed. It becomes possible to make a cut and process and remove the workpiece W while it remains deformed. Moreover, the blade 26 does not undergo buckling deformation during this process. Therefore, even if the blade 26 is extremely sharp, processing can proceed without buckling.

Table 5 shows the Young's modulus of each material. As is clear from Table 4, polycrystalline diamond (PCD) has a much higher Young's modulus than most materials such as sapphire and SiC. Therefore, it is possible to process even a blade that is thinner than the thickness of the workpiece material.

Next, the relationship between the hardness of the workpiece material and the blade material will be described, and the relationship between the heights is also the same as the elastic modulus described above.

When the hardness of the blade material is lower than the hardness of the workpiece material, for example in the case of an electroformed blade, the diamond is supported by soft copper or nickel. The diamond abrasive grains on the surface have extremely high hardness, but the hardness of the nickel that supports the diamond abrasive grains underneath is extremely low compared to diamond. Therefore, when an impact is applied to the diamond abrasive grain, the nickel underneath absorbs the impact. As a result, in the case of electroformed blades, the hardness of nickel is dominant, so even if the hard diamond abrasive grains collide with the workpiece material and attempt to cut into the workpiece, the bonding material absorbs the impact. As a result, it is difficult to make a predetermined cut. Therefore, in order to proceed with machining, the diamond must be impacted by a blade rotation speed above a certain level. Further, at this time, the impact is momentarily absorbed by the nickel, and the reaction force is applied to the diamond abrasive grains and presses the workpiece material with a large force, resulting in brittle fracture of the workpiece material.

On the other hand, in the case of the blade 26 of this embodiment, polycrystalline diamond has a hardness comparable to that of single crystal diamond, and is much higher in hardness than hard brittle materials such as sapphire and SiC. As a result, even if the cutting edge (micro-cutting edge) consisting of the recesses formed on the surface of polycrystalline diamond acts on the workpiece material, the impact acts locally on the micro-cutting edge, causing the sharp tip to Combined with this, it becomes possible to remove extremely small parts with high precision.

As described above, according to the present embodiment, the blade 26 is integrally formed into a disc-like shape by polycrystalline diamond 80 having a content of 80% or more of diamond abrasive grains 82, and the outer periphery of the blade 26 is A cutting edge portion 40 is provided in which cutting edges (microcutting edges) made of recesses formed on the surface of the diamond 80 are continuously arranged along the circumferential direction. Therefore, compared to conventional electroforming blades, it is possible to control the cutting depth (cutting amount) of the blade 26 into the workpiece W with high precision. Thereby, the workpiece W can be moved relative to the blade 26 while giving the workpiece W a constant depth of cut without making an excessive cut. As a result, it is possible to cut into a workpiece W made of brittle material with the cutting depth of the blade 26 set below the critical cutting depth of the workpiece, thereby preventing the occurrence of cracks or fractures. Therefore, cutting can be performed stably and accurately in ductile mode.

Furthermore, the recesses formed on the surface of the polycrystalline diamond 80 function as pockets for transporting chips generated when processing the workpiece W. This improves the evacuation of chips and makes it possible to discharge the heat generated during machining together with the chips. Furthermore, since the polycrystalline diamond 80 has high thermal conductivity, the heat generated during cutting is not accumulated in the blade 26, which has the effect of preventing an increase in cutting resistance and warping of the blade 26.

Moreover, in the dicing process using the blade 26 of this embodiment, it is preferable that the rotating direction of the blade 26 is a down cutting direction. That is, when moving the workpiece W relative to the blade 26 while making a cut into the workpiece W, as shown in FIG. 14, the rotation direction is such that the cutting edge of the blade 26 cuts into the workpiece surface. It is preferable to perform the dicing process while rotating the blade 26.

Further, in the dicing process using the blade 26 of this embodiment, when the workpiece W is moved relative to the blade 26 while giving the workpiece W a constant cutting depth with the blade 26, fine particles are applied to the blade 26. It is preferable to do this while feeding.

Here, the reason why the above embodiment is preferable will be explained in detail below.

In the case of a disc-shaped blade made of polycrystalline diamond as in this embodiment, depressions are formed at grain boundary portions between diamond particles. The concave portion acts as a cutting edge. Alternatively, a cutting edge is formed by naturally formed unevenness due to roughness, and especially a cutting edge is formed at a concave portion.

The action of the outer peripheral portion of the blade is primarily that of the cutting edge, which cuts into the workpiece and must remove chips while cutting further.

On the other hand, with respect to the side surface of the blade, rather than cutting the workpiece forward, it is important to use the side surface of the blade to smooth the side surface that has already been cut with the tip of the blade. To do this, rather than having the cutting edge actively act on the side surface of the blade, it is necessary to scrape the side surface of the workpiece while smoothly lubricating the side surface of the workpiece and the side of the blade without biting into each other.

An effective method for smoothly lubricating the workpiece side surface and the blade side surface without biting the blade side surface is to apply fine particles to the dicing blade.

In particular, in the groove portion that has just been removed by the blade tip, a new side surface of the workpiece has just appeared, and depending on the workpiece material, a very active surface may appear. The active surface tends to interact with other materials, especially the polycrystalline diamond that is the blade material. In order to prevent this, it is necessary to consider lubrication between the blade side surface and the workpiece material immediately after the blade tip is removed.

Therefore, applying fine particles to the side surface of the blade made of sintered diamond plays a major role in improving the lubrication effect between the blade and the workpiece.

When fine particles are applied to the side surface of a blade made of sintered diamond, the sintered diamond, as mentioned earlier, will cause the dents to form in the grain boundaries and on the uneven surface made up of natural roughness. I have many. Fine particles are taken into the concave portion. When the blade side is rubbed against the workpiece during processing, fine particles that have accumulated in the recesses formed by the polycrystalline diamond fly out and continuously roll between the blade side and the workpiece side. This continuous rolling of fine particles is called the "bearing effect" and prevents the blade from biting the surface of the workpiece, creating a lubricating effect between the blade and the workpiece.

Furthermore, this lubrication effect is not limited to simply preventing the blade from sticking to the workpiece. The bearing effect of fine particles is that the rolling fine particles also have the effect of polishing the side surface of the workpiece.

As the particles roll, the particles rub against the side of the workpiece, polishing the side surface of the workpiece. As a result, the side surface of the workpiece is left with a clean mirror surface without leaving any grinding marks that would be left when simply grinding with fixed abrasive grains. can be formed.

When grooves are formed on both sides of the blade along the rotation, fine particles tend to roll, or a bearing effect appears. For example, in the cross section of the blade in the radial direction, it is preferable to cut a fine V-shaped groove in the side surface of the cross section where the blade enters the workpiece. Then, the particles enter between the V-grooves and roll along the V-grooves as the blade rotates. As a result, particles roll along the V-shaped groove between the workpiece material and the blade, creating a bearing effect. When the rolling effect appears, unlike fixed abrasive grains, individual fine particles change direction to some extent and act randomly, so grinding marks in one direction do not remain, and the side surface of the workpiece material has no polishing effect. Demonstrated. As a result, it is possible to obtain a mirror surface free of grinding marks.

As a method of processing using such fine particles, for example, the fine particles are hardened by pre-firing, and as the fine particles fall off the surface of the blade formed of the hardened fine particles, the spilled fine particles are formed on the side of the blade. You might think of a blade that rolls and creates a mirror finish.

However, in the case of a blade in which rolling fine particles are baked onto the blade surface in advance, as the machining progresses, the blade gradually becomes thinner as the fine particles fall off. That is, it is not possible to form a stable and constant groove width. Furthermore, it becomes difficult to continuously and stably supply fine particles.

In addition, in order for the particles to act continuously, it means that the side surfaces of the blade are continuously worn while supplying the particles, but in such a blade, the concave part that stores the particles is stably configured. It is difficult to do so, and it is also impossible to form the recessed part with diamond, which has a high hardness. Furthermore, it is not possible to provide a blade member itself that is highly rigid and has arbitrary irregularities formed therein.

Furthermore, with such easily peelable materials, the hardness of the blade itself that supports the substrate cannot be ensured, making it difficult to make a constant cut into the workpiece while the fine particles are rolling.

On the other hand, conventional electroformed blades hardened with a binder such as nickel cannot provide this lubrication effect. This is because the electroformed blade has diamonds protruding from the surface of the bonding material in some places. In other words, the surface has a shape in which there are protrusions here and there on a flat surface.

Since the diamond is present in a protruding state, the critical cutting depth of the abrasive grain cannot be controlled as the bonding material forming the reference plane is removed. Therefore, a fatal crack will be caused on the side of the workpiece. Even if fine particles are introduced as in the above embodiment, the side surface of the workpiece may become mirror-finished in some cases even if there is no dent, but even if fine particles are applied to the side surface of the blade to produce a polishing effect. On the other hand, in the case of grinding with a protruding diamond of fixed abrasive grains, grinding marks still remain on the side surface of the workpiece, as well as potential cracks due to the protrusion. The effect of fine particles that create a mirror finish while rolling becomes meaningless when used in combination with a processing phenomenon that causes brittle fracture while causing cracks.

Furthermore, when looking at the blade surface, protruding diamonds are scattered within the flat surface. That is, there is no concave portion where fine particles accumulate on the side surface of the blade.

Even if fine particles were to be stored in the area where the diamond fell out, that is, between the binding materials such as nickel, the hardness of the recesses formed by the metal material such as nickel is lower than that of the material used for the fine particles. Even if the particles escape from the recess, the recess is surrounded by a metal material such as nickel, and not only does the recess not function as a cutting edge, but the part where the particulate escapes is actually cut by the nickel. It only wears out the blade side of the soft metal such as, and on the other hand, it has almost no effect on polishing and removing the workpiece. As a result, the blade itself is only gradually scraped away, and the effect of polishing the workpiece cannot be expected.

When the bonding material of the blade is worn away by fine particles, this means that the blade thickness changes even during processing due to the abrasive removal action of the fine particles on the bonding material. For example, in groove machining, when the groove width is strictly controlled, the blade quickly wears out, making it unusable and meaningless as a blade for machining.

On the other hand, in the case of a blade made of polycrystalline diamond as in this embodiment, the first premise is that it is made of a sintered body of diamond. Further, it is desirable that the diamond content is 80% or more.

The blade is made of polycrystalline diamond, and the fine particles accumulate in the recesses of the sintered body, and when the blade rubs against the workpiece, the fine particles are ejected and roll. Since the periphery of the recess is made of diamond, the fine particles act on the edge of the recess, which is made of diamond, to polish the workpiece.

The recessed areas have a relatively high proportion of sintering aids, which are selectively removed by friction to form the recesses, whereas the non-recessed areas are richer in diamonds and are generally more diamond-rich than the workpiece material. Hardness increases. Therefore, the fine particles coming out of the recessed portion are supported by the high hardness diamond at the edge of the recess, and the fine particles roll and act on the edge made of the high hardness diamond. As a result, polishing pressure is applied to the workpiece, thereby efficiently polishing the workpiece.

In this way, it is possible to achieve both efficient retention of fine particles and the effect of the fine particles rolling on hard diamond.

(Method of supplying fine particles)
The method of supplying the fine particles is not particularly limited as long as the above effects can be obtained, but for example, the following methods (first to third examples) can be preferably employed. .

<First example>
As an example (first example) of a method for supplying fine particles, there is a method in which fine particles contained in a liquid are applied to the blade using a capillary structure on the blade itself.

As the fine particles used, fine particles such as WA white alumina abrasive grains, GC green carborundum abrasive grains, and diamond abrasive grains are preferably used. Fine particles having various particle sizes from approximately 0.01 μm to 10 μm may be used. The particle size and the material of the fine particles used may be appropriately optimized depending on the workpiece material and its purpose. For example, in the case of cutting for the purpose of removing grinding marks on the cut side surface of a PC board or copper board, WA with a grain size of about 1 μm is suitable.

Furthermore, if these fine particles are used as powder as they are, fine particles will be blown away by the wind pressure of the blade rotating at high speed. Therefore, it is preferable to use the fine particles suspended in a liquid. As a suspending solvent, water is the simplest liquid, but in order to efficiently attach fine particles to the blade surface, a suspension in ethanol, IPA, etc. may also be used. Furthermore, a lubricating oil such as wrapping oil may be used. The solvent for suspending the fine particles may be appropriately optimized depending on the characteristics of the workpiece. Even if lapping oil is used, it is supplied only to the blade and not directly to the workpiece.

The liquid containing fine particles supplied to the blade acts only on the cut surface of the workpiece and does not act on the surface of the workpiece. Therefore, from the perspective of the workpiece, the lubricating effect prevents heat generation and does not supply any particular liquid to the workpiece surface. Therefore, it is possible to process workpieces that would normally wet the chip on the surface and damage the device in a wet environment, as if it were dry processing.

It is desirable to apply the liquid just before the blade cuts into the workpiece. The blade is rotating at high speed, and some of it will be blown away by the centrifugal force, so it is desirable to do this just before the blade enters the workpiece.

Note that this does not make any sense at all if what is applied to the blade is a liquid that does not contain fine particles. When applying a liquid that does not contain particulates, the ability to polish the side surface of a cut workpiece basically does not work. Therefore, there is no point in applying a liquid that does not contain fine particles.

In addition, a liquid that does not contain fine particles has a low viscosity, and by including fine particles, the interfacial tension between the fine particles and the liquid acts, increasing the bonding force, and as a result, it becomes possible to increase the overall viscosity. If the viscosity can be increased, even when applied to a blade, the liquid containing particles will not be blown away by the centrifugal force of the blade, and it will be possible to efficiently apply the liquid containing particles to the side or tip of the blade. be.

For example, there is a method of processing while supplying a slurry containing fine particles, but this sometimes wets other parts of the workpiece other than the part to be cut, so it is not recommended to process the workpiece in a strictly dry state. It is not applicable.

Furthermore, when supplying liquid slurry along a workpiece, the slurry needs to have a low viscosity so that it flows along the workpiece rather than sticking to the workpiece. However, in such a case, there is a problem in that when the slurry comes into contact with a blade rotating at high speed, the slurry is blown away. In particular, blades made of polycrystalline diamond have very small recessed areas, and when it comes to effectively capturing particles into the pockets in these areas, the wind pressure and centrifugal force of the blade are dominant, causing the particles to remain on the blade. Sometimes it is difficult.

In contrast, in the method for supplying fine particles in this example, fine particles are suspended in a liquid, and the suspension is applied to the side surface of the blade. The application method uses a capillary structure like a brush to apply the liquid from the solid to the rotating blade solid based on the principle of liquid capillary, and then supplies the liquid to the solid, leaving behind the particulate components contained in the liquid. One possible method is to apply fine particles to the blade.

Even if one attempts to apply fine particles to the blade, it is extremely difficult to coat and adhere solid fine particles to the side surface of the blade, which rotates at high speed.

Therefore, an efficient and good method is to use a liquid, dissolve the fine particles in the liquid to form a suspension, and then apply the fine particles to the blade surface in this state.

First, by dissolving microparticles into a liquid, the viscosity increases and the surface tension increases, making it possible to form a gel. Liquid can enter between the particles and increase surface tension.

By dissolving the fine particles in the liquid in this way, unlike the case where only the liquid is applied to the blade, it becomes possible to have the liquid act reliably on the blade surface as a viscous liquid with high surface tension.

As a method for applying a liquid containing fine particles to the blade surface, for example, a fine particle supply mechanism shown in FIGS. 24 and 25 can be preferably employed. As shown in the figure, the blade 26 is surrounded by a flange cover 100 fixed to the spindle 28 (see FIG. 1), and a liquid supply pipe as a liquid supply means is attached to the flange cover 100. 102, and a capillary structure member 104 that receives a liquid containing particles from the liquid supply pipe 102 and transfers the supplied liquid containing particles to both side surfaces of the blade 26 by capillary action. is installed.

As the capillary structure member 104, a brush-like member, a brush-like member, or a foam member is used. That is, a structural member is used in which small spaces are continuously present in the voids. As shown in FIG. 25, the capillary structure member 104 is slightly bent between the lower end of the liquid supply tube 102 and the circumferential side of the blade 26, and the capillary structure member 104 is bent from both sides so that its tip is along the rotational direction of the blade 26. It is in contact with both peripheral sides of 26. The capillary structure member 104 is formed to have a required width in order to uniformly apply the liquid containing fine particles to the circumferential surface of the blade 26 .

Further, as shown in FIG. 25, a guide member 108 made of a rigid material is provided at the lower end of the liquid supply pipe 102 to guide the tip of the capillary structure member 104 to the circumferential side of the blade 26. As the constituent material of the brush-like member, brush-like member, etc. as the capillary structure member 104, for example, a soft linear member such as a wire made of polyester material or cotton fiber can also be suitably used. If a soft linear member is used, the side surface of the blade 26 will not be excessively damaged even if it comes into contact with the side surface of the blade 26 rotating at high speed.

Even if the capillary structure member 104 uses such a soft linear member, the capillary structure can be formed by guiding the tip of the capillary structure member 104 to the circumferential side of the blade 26 with the guide member 108 made of a rigid material. A blade that rotates at high speed by being able to guide the tip of the capillary structure member 104 made of a soft linear member into contact with the blade 26 without being affected by the gravity of the liquid existing in the gap within the member 104. It becomes possible to reliably supply the liquid containing fine particles to the circumferential side of 26.

As described above, according to the method for supplying fine particles in this example, it is possible to apply the liquid containing fine particles to the side surface of the blade. This allows the blade to touch the capillary structure to which the liquid is to be applied, and uses the interfacial tension between the liquid and the solid to carry the fine particles contained in the liquid to the side surface of the workpiece. I can do it.

In the method of spraying liquid onto a blade rotating at high speed, the liquid is blown away on the blade, and as a result, particles cannot be effectively applied to the blade. By applying the powder to the blade, it is possible to efficiently supply the particles along the side of the blade.

When a liquid containing fine particles is applied to a blade, the liquid adheres to the recessed portions of the blade surface due to the interfacial tension of the liquid. Since the blade rotates vertically and at high speed, some of the liquid adhering to the blade dries, and the heat generated by polishing by the fine particles can be removed by heat of vaporization. Thereby, polishing can be performed without generating excessive heat even during polishing.

Just apply it to the blade, and there is no need to cool the workpiece by pouring water on it. In some cases, it is possible to dry workpieces by applying only a small amount of liquid to the blade.

As a result, it becomes possible to proceed with physical polishing processing by rolling of fine particles more efficiently.

In addition, when the particles escape from the recess, they are sandwiched and rolled between the edge of the recess formed by the diamond particles below and the workpiece, ensuring that the particles rolling into the workpiece do not cut into the workpiece. It is possible to reliably polish the workpiece while giving the same amount of polish.

<Second example>
Another example (second example) of a method for supplying fine particles is to apply gel-like fine particles in advance to a portion of the workpiece where the blade advances.

In this method, highly concentrated fine particles are suspended in a small amount of water in advance and attached in a thin line to the area where the blade moves. As a method of adhesion, it may be applied by extruding with something like a syringe.

<3rd example>
As yet another example (third example) of the method of supplying fine particles, by pasting a thin sheet coated with particles onto a workpiece and cutting the thin sheet, the fine particles on the sheet are naturally drawn in and fed. There is a method in which fine particles are applied between the workpiece and the blade.

In this method, high-density fine particles are applied in advance to a thin sheet. Attach it to the substrate to be cut or grooved.

When processing a predetermined part of a substrate, it is processed together with a thin sheet attached to the surface, and by processing the substrate while processing the thin sheet, the fine particles applied to the thin sheet are processed. While adhering to the blade surface, fine particles are naturally supplied to the blade surface, and it becomes possible to process the substrate while involving the fine particles attached to the blade surface.

(Blade processing equipment)
As described above, the blade 26 of this embodiment is made of polycrystalline diamond (PCD) formed by sintering diamond abrasive grains in order to process the workpiece W in a ductile mode, but In order to stably and accurately cut workpieces made of materials in the ductile mode without causing cracks or fractures, the surface (outer edge) of polycrystalline diamond must be A continuous cutting edge must be formed along the Therefore, it is desirable to process the blade 26 at all times, regularly, or irregularly using a blade processing device that will be described later.

Hereinafter, specific configuration examples (first to fourth embodiments) of the blade processing apparatus according to the present invention will be described. The blade processing device according to any of the embodiments simultaneously performs both truing, which adjusts the shape of the outer peripheral end of the blade, and dressing, which forms a cutting edge by slightly roughening the surface of the outer peripheral end of the blade. Therefore, blade processing can be performed efficiently.

<First embodiment>
FIG. 26 is a schematic diagram showing an example of the configuration of the blade processing device according to the first embodiment. As shown in FIG. 26, the blade processing device 200A according to the first embodiment includes a blade processing section 202 that processes the blade 26. As shown in FIG. This blade processing section 202 is an example of a cutting edge generating means, and while rotating the disc-shaped polycrystalline diamond 26a that constitutes the blade 26, the grain boundary portion of the surface (outer peripheral end) of the polycrystalline diamond 26a is cut. By selectively removing the polycrystalline diamond 26a by electrical discharge machining, a cutting edge is generated on the surface of the polycrystalline diamond 26a while adjusting the shape of the outer peripheral end thereof.

Specifically, the blade machining section 202 applies a voltage between a machining electrode 204 disposed facing the polycrystalline diamond 26a and the disc-shaped polycrystalline diamond 26a and the machining electrode 204 to generate electrical discharge. A power supply unit 206 (voltage application means) that generates a voltage, a nozzle 208 (processing liquid supply means) that injects and supplies machining fluid between the polycrystalline diamond 26a and the machining electrode 204, and a disc-shaped polycrystalline diamond 26a. The blade processing section 202 includes a rotation drive mechanism (not shown) that rotates the blade around the center of its circumference, and a control section (not shown) that controls each part of the blade processing section 202.

Nozzle 208 is provided upstream of polycrystalline diamond 26a in the rotational direction. By supplying machining liquid from the nozzle 208 while rotating the polycrystalline diamond 26a, the discharge gap between the polycrystalline diamond 26a and the machining electrode 204 is brought into a state of fluid lubrication. The rotation speed for rotating the polycrystalline diamond 26a is, for example, 8000 rpm (rotation per minute).

As the machining liquid, a nearly non-conductive liquid with high resistivity is preferably used, and for example, ultrapure water is suitable. When electrical discharge machining is performed, the polycrystalline diamond 26a that is the workpiece is also in a state close to a nonconductor, and a large electric field concentration occurs in some conductive grain boundary areas (sintering aid). . As a result, combined with the electric field concentration effect, the grain boundary portions of the polycrystalline diamond 26a are selectively melted by electrical discharge machining, contributing to the formation of cutting edges. In particular, when ultrapure water is used as the machining fluid, the machining speed is higher and the electrode wear rate is lower than when oil is used, and the polycrystalline diamond 26a can be electrically discharged with relatively high efficiency.

Here, when discharge oil is used as the machining fluid, some of the diamond abrasive grains turn into pyrolytic carbon and become more easily detached from the polycrystalline diamond 26a. It also leaves a lot to be desired. An object of the present invention is to efficiently perform ductile mode machining by forming cutting edges that are approximately equally spaced. However, when discharge oil is used as a machining fluid, the diamond abrasive grains themselves sometimes become detached to a large extent, inhibiting the formation of equally spaced cutting edges, or even causing the outer peripheral edge of the polycrystalline diamond to become flat. , a cutting edge may not be formed.

Furthermore, when discharge oil is used, it becomes a contaminant, especially for semiconductor workpieces and workpiece materials for electronic components, and changes the characteristics of the materials. In particular, when processing semiconductor materials and electronic component materials, organic components such as discharge oil are difficult to remove even if they adhere to the surface, and organic components and carbon can penetrate inside and affect material properties. I'll end up changing it.

Therefore, when considering the cleanliness of the workpiece surface, it is not possible to use electrical discharge oil as it is, and this becomes a major impediment when applied to electrical discharge machining for the purpose of regenerating the cutting edge of polycrystalline diamond in the present invention. .

The processing electrode 204 is disposed facing the outer circumferential end of the polycrystalline diamond 26a with a gap therebetween. The processing electrode 204 is a planar electrode, and is composed of a band-shaped electrode, a disc-shaped electrode, a wire electrode, or the like. For example, in the case where the processing electrode 204 is configured with a wire electrode, the wire electrode is fed out from a wire supply section (not shown) and wound up in a wire collection section, and the wire electrode is moved between them. Electric discharge machining is performed with the wire electrode facing the polycrystalline diamond 26a that is the workpiece. Note that the planar shape of the machining electrode 204 is not particularly limited as long as it can generate electric discharge between it and the polycrystalline diamond 26a.

Furthermore, it is preferable that the processing electrode 204 is made of a metal electrode or an electrode material (for example, carbon, etc.) that dissolves into the processing liquid and becomes metal ions. As mentioned above, a non-conductive liquid is used as the machining fluid, but in order to further promote localized electrical discharge machining due to electric field concentration, the electrode material of the machining electrode 204 should be replaced with a non-conductive material on the other side (in this example, polycrystalline diamond). In order to attach the electrode material, it is desirable to ionize it, and when it is ionized, it dissolves in a small amount into the processing fluid and becomes attached to the polycrystalline diamond on the other side. Thereafter, a selective erosion effect is produced by the discharge due to the electric field concentration effect.

The distance between the polycrystalline diamond 26a and the machining electrode 204, that is, the discharge gap (distance between the electrodes), is required to be several μm to several tens of μm in order to generate stable discharge. By maintaining such a discharge gap, dielectric breakdown occurs when a voltage is applied between the polycrystalline diamond 26a and the processing electrode 204. The voltage to be applied is, for example, 100V, but of course it can be changed as appropriate depending on the size of the discharge gap, the type and concentration of the machining fluid, etc.

In order to maintain this discharge gap in an appropriate state, it is preferable to provide a discharge gap adjustment means for changing the relative distance between the polycrystalline diamond 26a and the machining electrode 204. The discharge gap adjusting means has an electrode moving means for moving the machining electrode 204, and the discharge gap is adjusted by changing the position of the machining electrode 204 with respect to the polycrystalline diamond 26a using the electrode moving means. The electrode moving means includes, for example, a drive device such as a piezoelectric element, a linear motor, or a motor. Note that instead of the processing electrode 204, the polycrystalline diamond 26a may be moved, or both the processing electrode 204 and the polycrystalline diamond 26a may be moved.

According to the embodiment including the discharge gap adjustment means, the discharge gap can be maintained in an appropriate state, and stable discharge machining can be performed. In addition, although the machining electrode 204 may wear out (wear) due to electrical discharge machining, the discharge gap can be adjusted according to the degree of wear of the machining electrode 204, which improves the machining accuracy of electrical discharge machining. becomes possible. Further, the number of times the processing electrode 204 is replaced can be reduced, and the work and costs associated with replacing the processing electrode 204 can be reduced, and work efficiency can be improved.

Further, in the embodiment including the discharge gap adjustment means, it is more preferable that the embodiment includes a discharge gap detection means for detecting the discharge gap. In this case, the discharge gap adjustment means predetermines the discharge gap by changing the relative distance between the polycrystalline diamond 26a and the machining electrode 204 based on the discharge gap detected by the discharge gap detection means. Adjust to match the set value. As a result, the discharge gap can be automatically adjusted according to the degree of wear (wear and tear) of the machining electrode 204 that occurs during electric discharge machining, thereby increasing machining accuracy and stabilizing electric discharge machining. becomes possible.

As the discharge gap detection means, for example, there is a mode in which it is constituted by an inter-electrode voltage detection means that detects an inter-electrode voltage generated between the polycrystalline diamond 26a and the machining electrode 204. In this case, the discharge gap adjustment means changes the relative distance between the polycrystalline diamond 26a and the machining electrode 204 based on the inter-electrode voltage detected by the discharge gap detection means (inter-electrode voltage detection means). Note that the discharge gap detection means is not limited to the above-mentioned embodiment, and various methods such as optical, magnetic, and electrical methods can be adopted, for example.

In addition, in the blade machining apparatus 200A of the present embodiment, electric discharge machining is performed while rotating the blade 26, so that the machining electrode 204 may be worn out and a portion of the machining electrode 204 may be locally unevenly worn. In this case, as described above, it is preferable to automatically adjust the discharge gap using the discharge gap adjustment means and the discharge gap detection means, but instead of or in addition to this embodiment, the following embodiment may be used. can also be preferably employed.

That is, when the machining electrode 204 is unevenly worn, the electric discharge machining is interrupted and the blade 26 is brought into contact with the surface of the machining electrode 204 while rotating and moving the blade 26 relative to the machining electrode 204. By doing so, the surface of the processing electrode 204 is processed. Thereby, the surface of the processing electrode 204 can be corrected and uneven wear of the processing electrode 204 can be eliminated. According to this aspect, the machining electrode 204 worn out due to electric discharge machining can be regenerated, so that the number of times the machining electrode 204 is replaced can be reduced, and the number of times the machining electrode 204 is replaced can be reduced. Work and costs can be reduced, and work efficiency can be increased.

The power supply section 206 has one electrode terminal connected to the polycrystalline diamond 26a and the other electrode terminal connected to the processing electrode 204, and applies a pulse voltage between the polycrystalline diamond 26a and the processing electrode 204. As for the polarity during electric discharge machining, it is preferable that the polycrystalline diamond 26a side is an anode and the machining electrode 204 side is a cathode. Note that conditions such as the pulse width, pulse interval, and voltage of the pulse voltage applied between the polycrystalline diamond 26a and the machining electrode 204 are such that the electrode is set so as to generate electric discharge between the polycrystalline diamond 26a and the machining electrode 204. It is set appropriately depending on the material, the distance between the electrodes, the type and supply amount of the machining fluid, etc.

Further, it is preferable that the power supply section 206 applies a bipolar pulse voltage or an alternating current voltage in which the polarity between the polycrystalline diamond 26a and the processing electrode 204 is alternately reversed. According to this embodiment, the electrodes on the polycrystalline diamond 26a are machined by electrical discharge machining the grain boundary portions on the surface of the polycrystalline diamond 26a while alternately reversing the polarity between the polycrystalline diamond 26a and the processing electrode 204. The material is repeatedly attached and detached, allowing efficient and local electrical discharge machining.

In the blade machining apparatus 200A configured as described above, after moving the blade 26 to a predetermined position (electrical discharge machining position) before, during or after machining the workpiece W, the blade 26 is rotated while being rotationally driven. While supplying machining liquid between the polycrystalline diamond 26a and the machining electrode 204, a pulse voltage is applied between the polycrystalline diamond 26a and the machining electrode 204 to generate electrical discharge. This causes an electric field to concentrate on the grain boundary portion of the surface (outer peripheral end) of the polycrystalline diamond 26a, causing an erosion action, and the eroded portion acts as a cutting edge. As a result, continuous cutting edges can be generated along the circumferential direction on the surface of the polycrystalline diamond 26a. After that, when processing the workpiece W, the blade 26 is moved to its original position (workpiece processing position), and the blade 26 is rotationally driven to process the workpiece W.

In addition, in this embodiment, as an example, a mode is shown in which the electric discharge machining of the blade 26 is performed offline before, during or after machining the workpiece W, but the present invention is not limited to this. A mode in which electrical discharge machining is performed can also be preferably adopted. According to this aspect, the workpiece W is machined using polycrystalline diamond as the blade 26, with new cutting edges always being generated on the surface and always having a regular shape, thereby improving the processing efficiency and processing. Accuracy can be improved.

Next, the mechanism of shape modification (truing) of the polycrystalline diamond 26a by the blade processing device 200A will be explained.

In the blade processing device 200A, while rotating the disc-shaped polycrystalline diamond 26a around the center of its circumference, machining liquid is supplied from a nozzle 208 provided upstream in the rotation direction of the polycrystalline diamond 26a, and the polycrystalline diamond 26a is The discharge gap between the electrode 204 and the machining electrode 204 is brought into a state of fluid lubrication. When a voltage is applied to the discharge gap by the power supply section 206 in this state, discharge occurs. If the roundness of the polycrystalline diamond 26a is low, the discharge gap fluctuates while the polycrystalline diamond 26a is rotated. In other words, the discharge gap becomes narrower in the portion where the polycrystalline diamond 26a locally protrudes toward the machining electrode 204. Therefore, a stronger electric field is generated between the protruding portion and the machining electrode 204 than other portions, and the protruding portion is selectively removed by electrical discharge machining. This selective removal is performed over the entire circumference of the polycrystalline diamond 26a while the polycrystalline diamond 26a is being rotated, so that the shape of the outer peripheral end of the polycrystalline diamond 26a is adjusted so that the discharge gap is constant. Therefore, the disc-shaped polycrystalline diamond 26a is trued so that its roundness is high.

Next, the mechanism of cutting edge formation (dressing) by the blade processing device 200A will be explained.

First, as a known example related to the present invention, there is a technique for subjecting synthetic diamond to electrical discharge machining, such as that disclosed in Japanese Patent No. 4,451,155.

However, the electric discharge machining in the above known example is completely different from the electric discharge machining that is the object of the present invention. That is, in this known example, conductive diamond formed by the CVD method is used. In the case of diamond formed by the CVD method, the positions of the grain boundaries are determined by the degree of crystal growth, and the size and spacing of the grain boundaries cannot be arbitrarily adjusted. Crystallinity changes greatly depending on the state. If such grain boundaries cannot be uniquely set, the cutting edge formation which is the objective of the present invention will not be achieved.

On the other hand, in the case of the present invention, electrical discharge machining is used to form cutting edges on the surface of polycrystalline diamond. In addition, the cutting edges use grain boundary portions that are present at regular intervals in order to set a constant cutting depth for each cutting edge. In polycrystalline diamond, diamond abrasive grains are densely spread within the space. For example, it is usually desirable that the content of diamond abrasive grains in polycrystalline diamond be 80 vol% or more. Further, in order for the diamond abrasive grains to bond with each other, the content of the diamond abrasive grains must be at least 70 vol% or more.

If the diamond abrasive grains are spread out in this manner, the grain boundaries formed between the diamond abrasive grains are automatically formed at equal intervals. The grain boundaries formed at equal intervals correspond to cutting edge portions, and equally spaced cutting edges are formed for each crystal grain (diamond abrasive grain). With equally spaced cutting edges, the cutting depth of each cutting edge is automatically set within a certain range, ensuring a stable and predetermined depth of cut and preventing fatal cracks in the workpiece. It won't cut like that.

In order to use the grain boundary portion of polycrystalline diamond as a cutting edge, it is important to erode the grain boundary portion relatively deeply compared to the crystal grain portion (diamond abrasive grains). Although the intragranular portion of the crystal grain is a single crystal, the grain boundary portion is discontinuous even if a portion thereof is crystallized, and therefore has poor strength and is easily selectively eroded. By causing an electric field to concentrate on the grain boundaries, the material is selectively eroded and used as a continuous cutting edge assembly with the grain boundaries as cutting edges.

In order to form a continuous cutting edge aggregate, it is important to use polycrystalline diamond, which is obtained by sintering diamond abrasive grains at high temperature and pressure. As a result, grain boundary portions are selectively removed by electrical discharge machining, and a continuous cutting edge assembly is formed by erosion along the grain boundaries.

Further, in order to form a continuous cutting edge assembly for forming a constant cutting edge interval, it is necessary that the cutting edges themselves exist continuously. For this purpose, the cutting edge needs to be a closed loop. If the loop is not closed and breaks midway, the cutting edge that comes after the break will cause a fatal cut. If a closed-loop cutting edge is formed and the cutting edge is rotated on its own axis, the cutting edges at constant intervals will act on the cutting edge infinitely, and each cutting edge will be able to constantly perform machining within a certain cutting depth range. It becomes possible.

The mechanism by which one cutting edge becomes smaller than the critical cutting depth when the cutting edges are spaced at regular intervals has already been explained, and the explanation will be omitted here.

Here, when a dopant is used in conductive diamond formed by the CVD method, there is a problem that electric field concentration is difficult to occur only at the grain boundaries, and cutting edge formation based on the grain boundaries is difficult to proceed. . This does not necessarily mean that it is not suitable to include a dopant, but in order to perform electrical discharge machining by clearly separating the grain boundary portion from the crystal grain portion, the diamond abrasive grain itself must be a dielectric material. The fact that some electrical conductivity remains in the grain boundary portion contributes to selective erosion of the grain boundary portion, which is desirable for forming a cutting edge.

Based on the above, the requirements required of the blade in order to form a continuous cutting edge assembly are listed below. However, the desirable parts are not mandatory requirements.
・Polycrystalline diamond is preferably composed of a sintered body in which diamond abrasive grains are densely spread. It is necessary that the abrasive grains occupy at least 70 vol% or more of the volume.
- As a sintering aid for polycrystalline diamond, it is preferable to use a conductive sintering aid.
- When a conductive sintering aid is used, an electric field concentrates in the grain boundary area where the concentration is particularly high, causing selective consumption and contributing to the formation of cutting edges due to erosion.
・Polycrystalline diamond should not contain too many dopants. In some cases, dopants obscure the boundaries between grain boundaries and grain portions.
・The cutting edge formed at the outer peripheral end of the blade must be a closed loop. In the case of a disc-shaped blade, as the blade rotates, the cutting edges at regular intervals work continuously, and machining progresses stably with a cutting depth within a certain range.
・It is desirable that the blade is disc-shaped and has an integral structure. The uniformity of the base material is important in forming cutting edges at regular intervals, and it is desirable that the base material be a single piece over the entire outer circumference.

Finally, stable electric discharge machining characteristics in the blade machining apparatus 200A will be explained.

Since the blade processing apparatus 200A can perform both truing and dressing of the polycrystalline diamond 26a at the same time, the blade processing can be performed efficiently. In addition, for the following various reasons, the blade machining apparatus 200A can stably perform electrical discharge machining itself, which also contributes to efficient blade machining.

(Reason 1) As a result of processing the disc-shaped polycrystalline diamond 26a while rotating it in the blade processing device 200A, the shape of the outer peripheral end of the polycrystalline diamond 26a is adjusted so that the discharge gap becomes constant. By keeping the discharge gap constant, the electric field generated in the discharge gap is also stabilized, so that electric discharge machining can be performed stably.

(Reason 2) Furthermore, in the blade machining device 200A, the discharge gap is generally in a fluid lubrication state due to the machining fluid supplied from upstream in the rotational direction of the polycrystalline diamond 26a, and the machining fluid moves due to the rotation of the polycrystalline diamond 26a. pressure is occurring in the discharge gap. Therefore, even if a force that causes the discharge gap to fluctuate somewhat is applied due to mechanical vibrations such as rotation of the polycrystalline diamond 26a, the dynamic pressure of the machining fluid acts to keep the discharge gap constant. The dynamic pressure of the machining fluid also acts to suppress the swinging of the polycrystalline diamond 26a with large amplitude and high frequency due to mechanical vibration. As a result, the polycrystalline diamond 26a becomes almost stationary. Therefore, electrical discharge machining can be performed stably even while the polycrystalline diamond 26a is rotating.

(Reason 3) Furthermore, in the blade machining device 200A, the planar machining electrode 204 is placed opposite the disc-shaped polycrystalline diamond 26a, so the machining point where electrical discharge machining is performed is between the polycrystalline diamond 26a and the machining electrode. This is one point on the tangent to 204. By-products generated after electrical discharge machining are smoothly removed from the machining point by the rotation of the crystalline diamond 26a and the new machining fluid continuously supplied from upstream in the rotational direction of the polycrystalline diamond 26a. The flow of machining fluid into and out of the machining point is always constant, and the supplied machining fluid does not stagnate on the way. As a result, the machining point is always kept lubricated with fresh machining fluid, so electrical discharge machining can be performed stably.

(Reason 4) In the case of polycrystalline diamond, unlike single-crystal diamond, there is no crystal orientation. It can be said that all parts of the outer peripheral edge of the polycrystalline diamond 27a have the same mechanical strength and the same physical properties, and that the physical properties such as electrical conductivity are uniform regardless of the crystal orientation. Furthermore, since the diamond abrasive grains are packed so densely in the polycrystalline diamond that the abrasive grains are bonded to each other, the distribution of the diamond abrasive grains in the polycrystalline diamond 26a is uniform, and the outer peripheral edge of the polycrystalline diamond 26a is It can be said that the probability of the existence of diamond abrasive grains is almost the same in any part of the part. In this way, in the blade processing apparatus 200A, the entire polycrystalline diamond 26a to be processed has uniform characteristics. When processing the polycrystalline diamond 26a with the blade processing device 200A while rotating the polycrystalline diamond 26a, no matter which part of the outer circumferential edge of the polycrystalline diamond 26a is located at the processing point during the rotation, there is no change in the material, so there is no electrical discharge. The electric field distribution in the gap becomes constant. In other words, as explained in Reasons 1 to 3 above, in addition to the fact that the external machining environment (size of discharge gap, lubrication state, etc.) at the machining point where electrical discharge machining is performed is constant, The fact that the polycrystalline diamond 26a itself is also materially uniform also contributes to stable electrical discharge machining.

For example, in the case of a conventional electroformed blade, the diamond abrasive grains within the blade are not so dense that the abrasive grains are bonded to each other, but the diamond abrasive grains are dispersed within the metal bonding material. Therefore, the conductivity of the blade changes depending on its location. When processing such an electroformed blade with the blade processing apparatus 200A while rotating, the electric field distribution in the discharge gap is not stable and constantly changes because the material of the electroformed blade to be processed is not uniform. Therefore, a problem arises in that electrical discharge machining cannot be performed stably.

As explained in Reasons 1 to 4, the blade machining device 200A performs electrical discharge machining because the external environment at the machining point is uniform and the material of the polycrystalline diamond 26a to be machined is uniform. It can be done stably.

In summary, according to the blade processing device 200A according to the first embodiment, truing is performed to adjust the shape of the outer peripheral end of the blade, and cutting edges are formed (sharpened) on the surface of the outer peripheral end of the blade, as described below. Since both dressing and dressing can be performed at the same time, blade processing can be performed efficiently.

(Truing)
A planar processing electrode is placed opposite the outer peripheral end of the disc-shaped polycrystalline diamond 26a, and a voltage is applied to the discharge gap while rotating the polycrystalline diamond 26a around the center of its circumference, so that the discharge gap is kept constant. The shape of the outer circumferential end of the polycrystalline diamond 26a is adjusted so that the shape of the polycrystalline diamond 26a becomes . As a result, the roundness of the polycrystalline diamond 26a and the coaxiality between the center of the disc-shaped polycrystalline diamond 26a and the rotation center of the rotation mechanism can be improved.

(dressing)
By supplying machining liquid between the polycrystalline diamond 26a and the machining electrode 204 and applying a voltage between the polycrystalline diamond 26a and the machining electrode 204 to generate electric discharge, the surface of the polycrystalline diamond 26a is Since the electric field concentrates on the grain boundary portion (conductive auxiliary agent) and selectively removes it, a continuous cutting edge can be generated on the surface of the polycrystalline diamond 26a. By using the blade 26 processed by the blade processing device 200A, it is possible to stably and accurately cut a workpiece made of brittle material in a ductile mode without generating cracks or fractures. It becomes possible.

Note that the polycrystalline diamond 26a constituting the blade 26 is not limited to diamond abrasive grains sintered using a conductive sintering aid (for example, nickel or cobalt); The blade processing apparatus 200A can also be applied to blades made of polycrystalline diamond that does not contain any additives. Even in this case, as in the case of applying it to the polycrystalline diamond 26a containing a conductive sintering aid, the electric field concentrates at the grain boundaries on the surface of the polycrystalline diamond and causes an erosion effect, so the polycrystalline diamond It is possible to form a cutting edge on the surface.

<Second embodiment>
FIG. 27 is a schematic diagram showing a configuration example of a blade processing device according to the second embodiment. In addition, in FIG. 27, the same reference numerals are attached to the same components as those in the previous diagram.

As shown in FIG. 27, a blade processing apparatus 200B according to the second embodiment includes a processing tank 210 that stores processing fluid. An electrode holding section 212 is provided inside the processing tank 210, and the counter electrode 204 is held on the upper surface of the electrode holding section 212. Although the method for holding the counter electrode 204 is not particularly limited, the counter electrode 204 is held on the upper surface of the electrode holding portion 212 using, for example, vacuum suction or mechanical means.

The blade 26 is attached to the spindle shaft 46 of the spindle 28 via the hub flange 48 as described above (see FIG. 7). An insulating layer 212 is provided on the outer peripheral surface of the spindle shaft 46 to insulate between the blade side and the spindle body side.

A power supply brush 214 is in contact with the outer peripheral surface of the spindle shaft 46 (on the side closer to the blade than the insulating layer 212), and the power supply brush 214 is connected to an anode terminal of a power supply section (not shown). On the other hand, a power supply terminal 216 is in contact with the side surface of the processing electrode 204, and the power supply terminal 216 is connected to a cathode terminal of a power supply section (not shown). Therefore, the polycrystalline diamond 26a constituting the blade 26 mounted on the spindle shaft 46 is set as an anode through the power supply brush 214, and the processing electrode 204 is set as a cathode through the power supply terminal 216. Note that, similarly to the first embodiment described above, it is preferable that the power supply section applies a bipolar pulse voltage or an alternating current voltage whose polarity is alternately reversed between the polycrystalline diamond 26a and the processing electrode 204.

Further, the blade machining device 200B includes a servo mechanism 218 (discharge gap adjustment means) that controls the distance (discharge gap) between the polycrystalline diamond 26a constituting the blade 26 and the machining electrode 204. The servo mechanism 218 controls the discharge gap by moving the machining electrode 204 relative to the blade 26 so that desired discharge machining is performed during blade machining. As a method for moving the processing electrode 204 relative to the blade 26, for example, only the processing electrode 204 may be moved within the processing tank 210 without changing the position of the processing tank 210, or the processing electrode 204 may be moved relative to the processing tank 210. The processing electrode 204 may be moved integrally with the processing bath 210. Further, the blade 26 may be moved without changing the positions of the processing electrode 204 and the processing tank 210. Further, the blade 26 and the processing electrode 204 may be moved respectively.

Further, the blade processing device 200B includes a nozzle 204 that supplies processing fluid into the processing tank 210. The nozzle 204 opens at a position near the machined part between the polycrystalline diamond 26a and the machined electrode 204, and locally supplies machining liquid to the machined part during electrical discharge machining. This makes it possible to create a flow of machining fluid in the machining area between the polycrystalline diamond 26a and the machining electrode 204, making it possible to perform electrical discharge machining without being affected by impurities generated by electrical discharge machining. .

According to the blade machining device 200B according to the second embodiment, electrical discharge machining is performed while rotating the blade 26 and immersing the tip portion (outer peripheral end portion) of the blade 26 in the machining fluid stored in the machining tank 210. Therefore, a cutting edge can be efficiently generated on the blade 26 under a stable environment.

<Third embodiment>
FIG. 28 is a schematic diagram showing a configuration example of a blade processing device according to the third embodiment. In addition, in FIG. 28, the same reference numerals are given to the same components as those in the previous diagram.

As shown in FIG. 28, the blade processing device 200C according to the third embodiment has a built-in function as a dicing device, and includes a workpiece processing section 302 that processes the workpiece W and a blade processing section 302 that processes the blade 26. 302.

The workpiece processing section 302 has basically the same configuration as the processing section 20 of the dicing apparatus 10 shown in FIG. That is, the blade 26 is attached to the tip of the spindle 28, and the workpiece W is processed by moving the blade 26 relative to the workpiece W. The blade 26 performs processing by setting a predetermined cut into the workpiece W and then sliding it. By appropriately selecting the rotational speed of the blade 26 and the relative feed rate of the blade 26, one cutting edge is not set to a depth greater than a predetermined cutting depth, and ductile mode machining is performed.

The blade processing section 304 is arranged at a position adjacent to the workpiece processing section 302. The blade 26 is configured to be movable between the workpiece processing section 302 and the blade processing section 304 by a spindle moving mechanism (not shown) while being attached to the tip of the spindle 28 . Note that FIG. 28 shows, as a preferred embodiment, a configuration in which the workpiece processing section 302 and the blade processing section 304 are arranged side by side in order from the upstream side along the relative movement direction of the blade 26 with respect to the workpiece W (left direction in the figure). However, the present invention is not limited thereto, and, for example, the workpiece processing section 302 and the blade processing section 304 may be arranged in parallel in a direction parallel to the rotation axis of the blade 26.

The blade processing section 304 has basically the same configuration as the blade processing device 200A according to the first embodiment, and includes a processing electrode 204, a power supply section 206, and a nozzle 208.

The processing electrode 204 is arranged to face the polycrystalline diamond 26a forming the blade 26 when the blade 26 is moved to the blade processing section 304. Note that the processing electrode 204 is connected to a work table support member 314 via an L-shaped connection member 312, and is configured to be movable integrally with the work table 30.

The power supply unit 206 applies a pulse voltage between the polycrystalline diamond 26a and the processing electrode 204 to generate electric discharge. In FIG. 28, as an example, the power supply unit 206 is configured with a DC power supply, the polycrystalline diamond 26a side is an anode, and the processing electrode 204 side is a cathode. It is also preferable that the section 206 is constituted by an AC power source and the polarity between the polycrystalline diamond 26a and the processing electrode 204 is alternately reversed.

The nozzle 208 injects and supplies machining liquid between the polycrystalline diamond 26a and the machining electrode 204, and as in the first embodiment described above, it is preferable that ultrapure water is used as the machining liquid. be.

According to the blade processing apparatus 200C according to the third embodiment, after the blade 26 is moved from the workpiece processing section 302 to the blade processing section 304, the blade 26 is configured while being rotationally driven in the blade processing section 304. While supplying machining fluid between the polycrystalline diamond 26a and the machining electrode 204, a pulse voltage (or alternating current voltage) is applied between the polycrystalline diamond 26a and the machining electrode 204 to generate electric discharge. As a result, cutting edges are formed at the grain boundaries on the surface (outer peripheral end) of the blade 26, and cutting edges are generated and regenerated at approximately equal intervals for each densely spread diamond abrasive grain.

<Fourth embodiment>
FIG. 29 is a schematic diagram showing a configuration example of a blade processing device according to the fourth embodiment. In addition, in FIG. 29, the same reference numerals are given to the same components as those in the previously shown figures.

As shown in FIG. 29, the blade processing device 200D according to the fourth embodiment has a built-in function as a dicing device, similar to the third embodiment described above, and in particular, in this embodiment, the blade processing device 200D has a built-in function as a dicing device. The section 302 and the blade processing section 304 have an integrated configuration.

Specifically, the blade processing device 200D includes a blade cover (flange cover) 316 that surrounds the blade 26. The blade cover 316 is fixed to the spindle 28 side, and when the blade 26 moves relative to the workpiece W, the flange cover 316 moves together with the blade 26.

A machining electrode 204 is attached to the inside of the blade cover 316 (blade facing surface), and is arranged to face the blade 26 with a gap therebetween.

Furthermore, a nozzle 208 for supplying machining fluid between the blade 26 and the machining electrode 204 is provided inside the blade cover 316.

According to the blade processing apparatus 200D according to the fourth embodiment, when the blade 26 moves relative to the workpiece W when processing the workpiece W, the processing electrode 204 attached inside the blade cover 316 is kept constant with the blade 26. It moves together with the blade 26 while maintaining the interval (discharge gap). Thereby, the surface (outer peripheral end) of the polycrystalline diamond 26a constituting the blade 26 can be subjected to electrical discharge machining while processing the workpiece W. That is, it becomes possible to form the cutting edge of the blade tip and process the workpiece W at the same time, so that efficient machining can be performed.

Here, the characteristic configurations of the blade processing apparatus 200C according to the third embodiment and the blade processing apparatus 200D according to the fourth embodiment are listed below, although some parts overlap with the above description.

(unipolar and bipolar)
Both the blade processing device 200C according to the third embodiment and the blade processing device 200D according to the fourth embodiment employ, as an example, a mode in which the blade side to be processed is used as an anode to promote elution and discharge from the blade surface. However, it is not limited to the mode in which a unipolar pulse voltage is applied, but also the mode in which a bipolar pulse voltage or an alternating current voltage is applied. According to such an embodiment, the process of attaching metal ions to the blade surface and the process of desorbing metal ions proceed alternately, thereby efficiently forming a cutting edge by discharging the grain boundary portion of the surface of polycrystalline diamond, or forming a single metal ion. Cutting edges are formed by partial electrolytic elution. In particular, since the electric field is concentrated at the grain boundaries, adhesion progresses selectively at the grain boundaries compared to other areas, and desorption occurs selectively at the grain boundaries.

(insulation configuration)
Further, as for the configuration for attaching the blade to the spindle, it is desirable that the blade be insulated from the spindle. There are several possible ways to insulate the spindle and the blade. For example, there is a method in which the blade is formed using a coaxial grindstone, the shaft portion is made of ceramics, and the shaft is insulated.

Another method is to insulate the flange for fixing the blade from the blade surface. For example, this method involves alumite treatment of the end surface that supports the blade to eliminate electrical conduction. Note that power may be supplied to the blade by, for example, bringing a simple brush into contact with the shaft.

(Effect of same spindle)
It is desirable that the workpiece machining part and the blade machining part (cutting edge generation/cutting edge regeneration) be performed with the blades being attached to the same spindle. The blade processing apparatus 200C according to the third embodiment and the blade processing apparatus 200D according to the fourth embodiment are both attached to the same spindle 28. If a blade is attached to one spindle for blade processing and then attached to another spindle to process a workpiece, there will almost always be an installation error. As an installation error, for example, if the coaxiality is misaligned, the cutting edge at the tip of the blade will not act on the workpiece at the set cutting edge interval. Since uneven contact occurs depending on the amount of axis misalignment, ductile mode machining, in which all equally spaced cutting edges work stably, cannot be achieved in principle. Cracks occur on the workpiece surface due to the intermittent action of the cutting edge. In addition, there is a considerable problem of runout. In particular, in the case of thin blades, it is important to have the tip of the blade act in a straight line so that the cutting edges are spaced at regular intervals, but if the blade has a certain amount of runout, it will not work in a straight line and will be slightly Since the cutting edges meander, in principle, the cutting edges at regular intervals no longer work constantly, and as a result, ductile mode machining does not proceed. When performing blade machining with the blade machining apparatus 200C according to the third embodiment or the blade machining apparatus 200D according to the fourth embodiment, electric discharge machining is performed by acting on the counter electrode while rotating the blade. Even if there is coaxiality or runout, it is slightly corrected during the cutting edge formation process, improving both coaxiality and runout accuracy. Therefore, there is no problem of installation error.

(Effect of sliding due to constant cutting depth)
In the blade processing apparatus 200C according to the third embodiment and the blade processing apparatus 200D according to the fourth embodiment, the workpiece is processed by making a cut of a constant depth on the blade and sliding the workpiece to maintain the cut depth. This is desirable. As shown in the formula shown above, it becomes possible to set one cutting edge stably so that the depth of cut does not exceed a predetermined depth, and ductile mode machining becomes possible.

(Effects of environment and contamination)
Furthermore, when machining the tip of the blade using the same spindle, it is desirable to set the workpiece machining portion and the blade machining portion at relatively close positions.

In recent years, when processing semiconductor materials such as Si and electronic component materials such as SiC, GaN, and hard glass, the materials used as workpiece materials tend to dislike contamination. That is, if contaminants are present, they will adhere to the surface of the workpiece and penetrate into the material, thereby ruining the properties of the workpiece material itself.

Machine tools use cutting oil, but cutting oil is not used in semiconductors and electronic component materials due to contamination.

Similar to cutting oil, discharge oil and the like often pose problems due to contamination. In the processing of semiconductors and electronic component materials, pure water is usually used for processing. If it is pure water, it will not adversely affect the workpiece in terms of contamination.

(Effect of discharge oil on forming sharp cutting edge)
During electrical discharge machining, electrical discharge oil generates pyrolytic carbon. If this pyrolyzable carbon adheres to the workpiece surface, the workpiece surface will be completely contaminated with carbon. In addition to adhesion of pyrolytic carbon, the heat of electrical discharge machining promotes graphitization of the diamond surface. As a result, the abrasive grains themselves, rather than the grain boundaries, are eroded, and it may become impossible to form sharp cutting edges.

(Effects of using pure water as processing fluid)
It is desirable to use pure water as the machining fluid (discharge fluid). Pure water is a nonconducting liquid, and the blade to be machined is also made of polycrystalline diamond, a material close to a nonconductor. In such a configuration, an extremely large electric field concentration occurs particularly at the grain boundary portion, and only the cutting edge portion is selectively processed due to erosion. This makes it possible to form cutting edges at equal intervals along the diamond abrasive grains.

(Effects of using running water)
In addition, as the processing liquid, it is desirable to use running water in order to exert the effect as a continuous nonconducting liquid. This is because it is necessary to constantly maintain a stable insulation state as a discharge environment. In addition, in order to avoid reusing the liquid once used, it is desirable to make it flow in one pass, for example, at an angle along a slightly inclined electrode.

(Effects of using metal electrodes as electrodes)
Furthermore, it is desirable to use pure water as the machining fluid and to stabilize the environment by flowing water thereon, while the counter electrode is preferably a metal electrode. Normally, when processing with pure water, the pure water part does not conduct electricity if it is a nonconductor, but this can occur locally by using some metal electrodes. That is, a portion of the electrode material dissolves into the pure water to form an electrical path, and as a result, a portion of the electrode material adheres to the surface of the workpiece material, albeit in a very small amount. Next, the attached electrode material remains on the blade surface and is removed by electrical discharge machining. In particular, in order for the electrode material to adhere, the electrode material needs to be metal, and the metal ions move through the pure water and adhere to the opposing blade surfaces. The result of this adhesion is also clear from the analysis results of the workpiece surface.

In each of the embodiments described above, the grain boundary portion on the surface of the polycrystalline diamond 26a is removed by electric discharge machining, but the present invention is not limited to this, and removal may be performed by electrolytic machining. The configuration of the blade machining unit that performs electrolytic machining is basically the same as the configuration of the blade machining unit 202 (see FIG. 26) that performs electrical discharge machining, and detailed description thereof will be omitted here.

Next, we will discuss the mechanism of electrolytic machining, when it is applied to a conventional electroformed blade (a blade using a metal binder made by electroforming) (comparative example) and when it is applied to polycrystalline diamond made by sintering diamond abrasive grains. This will be explained in detail while comparing the case (the present invention).

(When applied to conventional electroformed blades)
When performing electrolytic processing on a conventional electroformed blade, since a metal binder is used in the conventional electroformed blade, there is no electric field concentration as shown in Figure 30, and oxidation on the surface of the electroformed blade is prevented. They proceed simultaneously, and electrolytic elution progresses sparsely overall. Furthermore, unlike a blade made of polycrystalline diamond, an electroformed blade does not have grain boundaries, and the bond material simply recedes and the next diamond abrasive grain comes out.

To explain this mechanism in more detail, in an electroformed blade, the metal binder portion occupies a larger proportion than the diamond abrasive grains, and during elution, the binder portion slowly melts from the rich areas. Furthermore, since diamond abrasive grains are a nonconductor (dielectric material), no current flows near the diamond abrasive grains. Therefore, the binding material remains near the diamond abrasive grains and covers the tips of the diamond abrasive grains. On the other hand, where the distance between diamond abrasive grains is wide, the metal component that is the binder is rich, so this part is slowly eluted. As a result, the area around the diamond abrasive grains swells up and covers the edges of the diamond abrasive grains, while the space between the diamond abrasive grains elutes in an arched shape with large depressions. As a result, sharp cutting edges are less likely to occur.

Furthermore, if such a metal material (binding material) is present on the surface, not only will no electric field be concentrated on the surface, but the electrolyte may be electrolyzed. When the electrolytic solution is electrolyzed, an oxide film covers the surface of the electroforming blade, so electrolytic elution becomes sparse and does not occur uniformly. Furthermore, not only is it impossible to form a sharp edge during the elution process, but by the time the edge is formed, the base of the diamond abrasive grains peels off and the diamond abrasive grains themselves immediately fall off.

Furthermore, when a binding material (ie, binder) is present on the surface, electric field concentration is less likely to occur on the surface. For example, JP-A-6-91437 describes a grinding tool having a structure in which diamond abrasive grains are hardened with a binder. According to the description in paragraph [0017] of JP-A-6-91437, when electrical discharge machining is performed on such a grinding tool, a large amount of energy is applied to the conductive binder near the electrical discharge machining part, causing electrical discharge, and this part is damaged. It is melted and removed. At this time, the diamond fine particles are also melted by the heat of the strong discharge energy. At this time, the fine diamond particles on the surface are successively melted and removed together with the binder.

In particular, dressing is performed by melting and removing cutting/grinding granules within a certain distance range from the electrical discharge machining part, and the dressed surface of the cutting edge is , it becomes a smooth plane parallel to the surface of the electrical discharge machining section.

In the case of the present invention, if a smooth flat surface is obtained after electrical discharge machining, it will have the opposite effect to the purpose of the present invention, which is to dress the surface and regenerate the cutting edge. What is described in Publication No. 6-91437 is a factor that inhibits the present invention.

Furthermore, in the case of JP-A-6-91437, it is thought that melting due to the heat of the binder also promotes melting of the diamond, and in the case of a structure in which diamond abrasive grains are hardened with a binder, that is, in a structure other than polycrystalline diamond. , machining that causes electric field concentration to locally form a cutting edge is not possible.

(When applying diamond abrasive grains to sintered polycrystalline diamond)
Since the surface of polycrystalline diamond obtained by sintering diamond abrasive grains is diamond-rich, electric field concentration occurs in the sintering aid area. Polycrystalline diamond differs from metal-plated grinding wheels in that the diamond abrasive grains are bonded together, but even among the bonded diamond abrasive grains, there are parts that are rich in sintering aid and parts that are not. do.

When polycrystalline diamond is electrolytically processed by electric field elution, the electric field is particularly concentrated in areas rich in sintering aids, as shown in FIG. For example, if Co (cobalt) or Ni (nickel) is used as a sintering aid, an electric field will be concentrated in the part of the diamond abrasive grain where the concentration of the tiny sintering aids Co or Ni is high. Parts are selectively eluted. As a result, penetration and erosion effects along grain boundaries become significant. Its penetrating and erosive action contributes to the formation of sharp cutting edges. In other words, when penetration and erosion occur, grain boundaries are highlighted in the form of deep fissures, and sharp cutting edges are formed. Elution occurs selectively from grain boundaries. Since the diamond abrasive grains are very close to each other, the diamond abrasive grains act deeply to erode the grain boundaries. This erosion effect greatly contributes to the formation of new cutting edges.

Continuously forms sharp edges due to erosion without causing the diamond abrasive grains to fall off quickly. Furthermore, worn diamond abrasive grains on the surface of polycrystalline diamond fall off due to erosion of grain boundaries. Note that after the diamond abrasive grains fall off, the adjacent portions are also diamond abrasive grains, so the intervals between the diamond abrasive grains are still substantially uniform. Forming cutting edges at regular intervals is essential for ductile mode machining.

In addition, when electrolytically machining polycrystalline diamond, a mode in which a voltage is applied to alternately reverse the polarity between the polycrystalline diamond and the processing electrode (i.e., a mode in which an alternating electric field is applied), similar to the case of electrical discharge machining. is preferred. Since diamond abrasive grains are dielectric or nonconducting, elution does not proceed easily even if it is called electric field elution. At that time, by applying a voltage that alternately reverses the polarity between the polycrystalline diamond and the processing electrode, when the polycrystalline diamond side becomes the anode, the sintering aid is electrolytically eluted from the surface of the polycrystalline diamond. While the elution of polycrystalline diamond progresses, when the polycrystalline diamond side becomes a cathode, conductive ions such as metal ions adhere to the surface of the polycrystalline diamond. By repeating adhesion and elution in this manner, electrolytic processing can proceed even on the surface of polycrystalline diamond, which is a dielectric material.

However, even in electrolytic processing, when there is not much difference in the amount of diamond sintering aid eluted between grain boundary areas rich in sintering aids and diamond abrasive grain areas that are not grain boundary areas, the object of the present invention is to does not match. The purpose of the present invention is to generate or regenerate a sharp cutting edge in a blade made of polycrystalline diamond. Therefore, during electrolytic machining, grain boundary areas rich in sintering aids are greatly eroded. Therefore, it is preferable that elution does not progress too much in areas other than the grain boundaries (diamond abrasive grains).

Here, even within polycrystalline diamond, the electric field is particularly concentrated at grain boundary areas where a relatively large amount of sintering aid exists. Therefore, when the surface of polycrystalline diamond becomes a cathode, the electric field concentrates at the grain boundary area where the sintering aid exists, and the conductive ions adhere to the part where the sintering aid is present. adhere to. Attachment and elution of conductive ions are repeated at grain boundary portions where a relatively large amount of sintering aid exists, further promoting selective erosion of the grain boundary portion where a large amount of sintering aid exists.

It is also possible to use various electrolytes as machining fluids. Conventionally, by using discharge oil, pyrolytic carbon adheres to the surface, and when it changes to the anode, it detaches. The diamond surface was processed. On the other hand, further studies by the present inventors have revealed that the surface of polycrystalline diamond can be processed using deionized water, pure water, etc., instead of using carbon-containing discharge oil as the electrolyte.

For example, when deionized water is used as a machining fluid, a small amount of ions are present in the machining fluid, so the electric field concentration that forms near the sintering aid for polycrystalline diamond metal becomes even more pronounced with a small amount of ions. , which greatly contributes to the local erosion effect. As a result, only the grain boundary portion, not the diamond abrasive grain portion, is significantly eroded and processed by elution. Particularly, by combining the aspect of applying an alternating electric field, it becomes possible to suitably erode the material.

Further, in further studies by the present inventors, it was discovered that even when ultrapure water is used as the processing fluid, the sintering aid on the surface of polycrystalline diamond can be selectively eluted by electric field. Originally, when ultrapure water is used as a machining fluid interposed between polycrystalline diamond and a machining electrode, electric field elution should not occur on the surface of polycrystalline diamond because ultrapure water has no conductivity. .

However, electric field elution of polycrystalline diamond has become possible by using a metal electrode as a processing electrode facing the surface of polycrystalline diamond, and in combination with the aspect of applying an alternating electric field described above. The mechanism at this time is not certain, but by using an alternating electric field, the metal of the electrode material becomes metal ions and elutes, which attaches to the opposing polycrystalline diamond surface, and then the attached part elutes. The mechanism by which these materials are processed is becoming clearer.

At this time, the amount of metal ions dissolved is extremely small, and the opposing polycrystalline diamond is also a dielectric, so the electric field is concentrated only in the extremely shallow areas of the polycrystalline diamond where the concentration of the sintering aid is high. As a result, the metal ions dissolved from the opposing processing electrodes form a selective electrical path within the processing fluid (ultra-pure water) and become attached only to the vicinity of the sintering aid. . Next, the metal ions attached only near the sintering aid dissolve out together with the sintering aid, and the grain boundaries of polycrystalline diamond, that is, the areas where a large amount of the sintering aid exists, are selectively removed. Elute.

In this way, when selectively eluting only the grain boundary area on the surface of polycrystalline diamond, that is, the vicinity of the sintering aid, while causing electric field concentration, ultrapure water with extremely low conductivity is used as the processing fluid. In order to create an electrical path in the machining fluid, it is desirable that the machining electrode facing the polycrystalline diamond be made of an electrode material that dissolves into the machining fluid and becomes metal ions. In this embodiment, as an example, a copper-tungsten alloy (Cu-W) is used as the electrode material of the processing electrode, but the material is not limited to this, and for example, copper (Cu), aluminum (Al), nickel (Ni), etc. In addition to the above, any electrode material that can be eluted into metal ions can be suitably used.

Further, in order to elute such an electrode material and selectively adhere to and elute the sintering aid portion on the surface of the polycrystalline diamond, it is desirable to combine it with the mode of applying an alternating electric field described above. By using an electrolytic solution that is difficult to conduct electricity as a machining fluid and repeating adhesion and detachment while causing electric field concentration on polycrystalline diamond, ideal erosion occurs, resulting in the formation of an ideal cutting edge. can do.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above examples, and it goes without saying that various improvements and modifications may be made without departing from the gist of the present invention. It is. Modifications will be described below.

(Modification 1)
In each of the above-described embodiments, a case has been described in which electrical machining (electrical discharge machining or electrolytic machining) is performed on the blade 26 made of polycrystalline diamond 26a. , grindstone, etc.), it is also possible to perform electrical machining (electrical discharge machining or electrolytic machining) with a machining device having the same configuration as the blade machining device, and obtain the same effects as in each of the above-described embodiments. be able to.

(Modification 2)
In each of the embodiments described above, an example was described in which the blade 26 was attached to the horizontally extending main shaft (spindle 28) of the blade processing device. It is applicable even if

DESCRIPTION OF SYMBOLS 10... Dicing device, 20... Processing part, 26... Blade, 26a... Polycrystalline diamond, 28... Spindle, 30... Work table, 36... Annular part, 38... Mounting hole, 40... Cutting edge part, 42... Diamond abrasive grain , 44... Spindle body, 46... Spindle shaft, 48... Hub flange, 80... Polycrystalline diamond, 82... Diamond abrasive grain, 84... Cutting edge (micro cutting edge), 86... Sintering aid, 200... Blade processing device , 202... Blade processing section, 204... Processing electrode, 206... Power supply section, 208... Nozzle, 210... Processing tank, 214... Power supply brush, 216... Power supply terminal

Claims (6)

In order to simultaneously perform truing to adjust the shape of the outer peripheral end of the blade and dressing to form a cutting edge on the surface of the outer peripheral end of the blade for a blade made of polycrystalline diamond and driven to rotate, While rotating the blade, while supplying machining fluid between the blade and the machining electrode, dynamic pressure of the machining fluid was generated in the discharge gap between the blade and the machining electrode by the rotation of the blade. Equipped with a blade machining means for performing electrical discharge machining in the state ,
Blade processing equipment. The blade is integrally configured in a disc shape,
The blade processing means forms the continuous cutting edge on the outer periphery of the blade.
The blade processing device according to claim 1. The blade machining apparatus according to claim 1 or 2 , wherein the machining liquid supply means supplies ultrapure water as the machining liquid. The blade machining means forms the cutting edge by selectively removing a grain boundary portion on the surface of the polycrystalline diamond constituting the blade by the electric discharge machining.
A blade processing device according to any one of claims 1 to 3. In order to simultaneously perform truing to adjust the shape of the outer peripheral end of the blade and dressing to form a cutting edge on the surface of the outer peripheral end of the blade for a blade made of polycrystalline diamond and driven to rotate, While rotating the blade, while supplying machining fluid between the blade and the machining electrode, dynamic pressure of the machining fluid was generated in the discharge gap between the blade and the machining electrode by the rotation of the blade. Perform electrical discharge machining in
Blade processing method. forming the cutting edge by selectively removing a grain boundary portion on the surface of the polycrystalline diamond constituting the blade by the electrical discharge machining;
The blade processing method according to claim 5.

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