JP2012110984A - Drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drilling tool of extremely excellent utility, capable of preventing the sticking of cut chips thereto, while, even if it is of a small-diameter drill, it has a long life up to breakage, with good hole locational accuracy, and capable of achieving realization of a stable hole drilling process.SOLUTION: The drilling tool has: one or a plurality of cutting blades provided at the tip end of a tool body 1 thereof; a plurality of cut chips discharging grooves 2, 3 in a spiral shape provided along the outer periphery of the tool body 1 that extend from the tip end of the tool to the base end side; the plurality of cut chips discharging grooves 2, 3 including one main groove and one or more of sub-grooves; the main groove 2 including the sub-groove 3 provided continuously in a midway of the main groove 2. Helix angles of the main groove 2 and the sub-groove 3 are set at approximately equal angles at a position to the base end side of the tool from a continuously-provided part 4 of both the main groove 2 and sub-groove 3, while the length of the sub-groove 3 is set at 50 to 95% of the length of the main groove 2, with the sub-groove 3 being placed in parallel with the main groove 2 extending from the continuously-provided part 4 to a predetermined position short of the terminal end of the main groove 2.

Description

  The present invention relates to a drilling tool.

  For drilling a printed wiring board (PCB), a drill composed of a body part A having a blade part C and a shank part B as shown in FIG. 1 is used. The size varies depending on the application, but in general, a drill having a diameter of 0.7 mm or less is often used.

  Specifically, as shown in FIG. 2, a spiral chip discharge groove 22 is formed on the outer periphery of the main body 20 on the blade portion C from the drill tip to the base end side. A cutting edge 21 is formed at the intersection ridge line portion between the rake face and the first flank 24 provided at the tip (see, for example, Patent Documents 1 and 2). In the figure, reference numeral 25 denotes a second flank that is connected to the rear side of the first flank 24 in the tool rotation direction, d ′ is the tool diameter, l ′ is the length of the chip discharge groove, and α ′. Is the twist angle.

  In addition, amorphous carbon coatings have been put to practical use as wear-resistant and welding-resistant coatings for non-ferrous work materials such as aluminum alloys, titanium, magnesium, and copper, and drills, end mills, blade-tip-replaceable cutting tips, etc. (See, for example, Patent Document 3).

  By the way, PCB is constructed by bonding copper and glass cloth as an insulating layer impregnated with resin, and recent PCBs have improved heat resistance, bending strength for further reliability improvement. Strengthening and lowering the thermal expansion are demanded, and many have secured high reliability by increasing the mechanical strength of the glass cloth and resin constituting the PCB.

  However, when considered as a work material to be drilled, the PCB having the above-described configuration easily promotes wear of the drill by an increase in mechanical strength, and is accompanied by breakage of the drill during drilling or excessive wear. It is easy to cause deterioration of hole quality such as hole position accuracy.

  On the other hand, with the increase in PCB density, the required hole diameter (drill diameter) is decreasing year by year, and drilling with a diameter of 0.4 mm or less is increasing.

  Further, in the drilling process, in consideration of processing efficiency, it is common to perform drilling by stacking a plurality of PCBs having the same specifications. Specifically, an aluminum plate or a resin-coated aluminum plate whose surface is coated with a resin is placed on the upper surface of a PCB on which a plurality of sheets are stacked to form a hole for drilling. It is common. The aluminum plate with resin is more effective than the aluminum plate in improving the centripetal property and contributes to the improvement of the breakage of the drill. Therefore, it is often used for drilling a small diameter drill having a diameter of 0.4 mm or less.

  In recent years, even for the small-diameter drills for PCBs used for machining PCBs with relatively poor workability as described above, an increase in the number of stacked PCBs for the purpose of reducing machining costs and drilling without breaking the drills. There is a demand for an extended drilling life.

  However, when drilling is performed using an aluminum plate with a resin as a backing plate, the remaining residue of chips is more prominent near the base end portion of the drill blade C than when drilling is performed using an aluminum plate. The higher the viscosity of the resin and the thicker the coated resin, the higher the tendency for the above-mentioned chips to be wound around, making it difficult to achieve the above requirements.

  This is because the chips generated during drilling are usually sucked by the chip suction function attached to the drilling machine and carried out to the specified dust box. However, when using an aluminum plate with resin, drilling is performed. It is considered that the resin softened by the cutting heat at the time is guided to the chip discharge groove together with the chips and discharged, and acts to adhere the drill and the chips in the vicinity of the base end portion of the blade C. It is thought that the remaining amount of chips wound increases by repeating the dawning process.

  The remaining amount of chips wound varies depending on the processing conditions of the drill speed and feed rate during drilling and the material of the PCB, but as shown in FIG. During the drilling process in which this swarf remains, the swarf (shard lump) leaves the drill as a result of some vibration, etc. It is thought that the hole position accuracy deteriorates and the drill breaks when the drill to be drilled and then the drill to be drilled interferes with the dropped chip lump. FIG. 3B illustrates a chip lump that has fallen on the contact plate.

  Further, for example, in Patent Document 4, in a PCB drill having two cutting edges and two chip discharge grooves, the chip discharge grooves are merged at a position retracted by a predetermined amount from the tip, and behind the merge point. Although a technique for improving rigidity by using a single groove is disclosed, there is no mention of wrapping of chips, and the above requirement cannot be satisfied.

JP-A-56-39807 JP 2006-55915 A JP 2001-341021 A JP 2007-307642 A

  The present invention has been made in view of the current situation as described above, and can prevent wrapping of chips. Even a small-diameter drill having a diameter of 0.7 mm or less, particularly 0.4 mm or less, has a long breakage life and a hole position. It is an object of the present invention to provide a highly practical drilling tool capable of realizing stable drilling with good accuracy.

  The gist of the present invention will be described with reference to the accompanying drawings.

  One or a plurality of cutting edges are provided at the tip of the tool body 1, and a plurality of spiral chip discharge grooves 2 and 3 from the tool tip to the base end side are provided on the outer periphery of the tool body 1, and the plurality of cutting edges are provided. The chip discharge grooves 2 and 3 include a main groove and one or more sub-grooves, and are drilling tools in which the sub-grooves 3 are provided in the middle of the main groove 2. The twist angles of the groove 2 and the sub-groove 3 are set to be substantially equal on the tool base end side from the connecting portion 4 of the main groove 2 and the sub-groove 3, and the groove length of the sub-groove 3 is the main groove 2 to 50% of the groove length, and the auxiliary groove 3 is provided so as to run in parallel with the main groove 2 from the connecting portion 4 to a predetermined position before the end of the main groove 2. The present invention relates to a drilling tool characterized by that.

  Further, one or a plurality of cutting edges are provided at the tip of the tool body 1, and a plurality of spiral chip discharge grooves 2, 3 from the tool tip to the base end side are provided on the outer periphery of the tool body 1, The plurality of chip discharge grooves 2, 3 includes a main groove and one or more sub grooves, and is a drilling tool in which the sub grooves 3 are continuously provided in the middle of the main groove 2, The torsion angles of the main groove 2 and the sub groove 3 are set to be substantially equal on the tool base end side from the connecting portion 4 of the main groove 2 and the sub groove 3, and the groove length of the sub groove 3 is It is set to 70 to 95% of the groove length of the main groove 2, and the auxiliary groove 3 is provided so as to run in parallel with the main groove 2 from the connecting portion 4 to a predetermined position before the end of the main groove 2. The present invention relates to a drilling tool characterized by

  Further, in the drilling tool according to any one of claims 1 and 2, the continuous groove width between the main groove 2 and the sub groove 3 in the continuous portion 4 is the main groove 2 before the continuous installation. The present invention relates to a drilling tool characterized by having a groove width of 1.1 to 1.9 times.

  Further, in the drilling tool according to any one of claims 1 and 2, the continuous groove width between the main groove 2 and the sub groove 3 in the continuous portion 4 is the main groove 2 before the continuous installation. The present invention relates to a drilling tool characterized by being 1.3 to 1.8 times the groove width.

  Further, in the drilling tool according to any one of claims 1 to 4, the start end of the connecting portion 4 is at a position more than twice the tool diameter from the tool tip and 50% of the groove length of the main groove 2. The present invention relates to a drilling tool characterized by being provided at the following positions.

  Further, in the drilling tool according to any one of claims 1 to 5, the main groove 2 in each tool axis perpendicular section including the end points 5 and 6 at the ends of the main groove 2 and the sub groove 3. A first line connecting the cut-up end point 5 and the rotation axis O of the tool and a second line connecting the cut-up end point 6 of the auxiliary groove 3 and the rotation axis O of the tool are viewed in the axial direction of the tool. When projecting onto the same plane perpendicular to the projection plane in FIG. 2, at least one narrow angle γ of the projection plane between the first line and the second line is greater than 90 ° and less than 180 °. The present invention relates to a drilling tool characterized by being.

  Moreover, in the drilling tool according to any one of claims 1 to 6, the main groove 2 and the sub-groove 3 are provided as the chip discharge grooves 2 and 3, respectively. This relates to the drilling tool to be used.

  The drilling tool according to any one of claims 1 to 7, wherein an amorphous carbon film is coated as a lubricating film.

  The drilling tool according to any one of claims 1 to 8, wherein the tool diameter is 0.4 mm or less.

  Since the present invention is configured as described above, chips can be prevented from being wound, and even a small-diameter drill having a diameter of 0.7 mm or less, particularly 0.4 mm or less, has a long breakage life and good hole position accuracy and stability. This is a very practical drilling tool that can be used for drilling.

It is a schematic explanatory side view of the drill for PCB. It is an expansion schematic explanatory drawing of a prior art example. (A) The photograph which illustrates the winding remainder of the chip | tip in the base end part vicinity of the blade part C of a drill, (b) The photograph which illustrates the chip lump which fell on the contact plate. It is a schematic explanatory drawing of the blade part of a present Example. It is a schematic explanatory drawing of the cut-off narrow angle of a present Example. It is a general | schematic expanded view which shows the outline | summary of the twist angle of a main groove and a subgroove. It is a general | schematic expanded view which shows the outline | summary of the twist angle of a main groove and a subgroove. It is a general | schematic expanded view which shows the outline | summary of the twist angle of a main groove and a subgroove. It is a general | schematic expanded view which shows the outline | summary of the twist angle of a main groove and a subgroove. It is a table | surface which shows an experimental condition and an experimental result. It is a photograph which shows an experimental result.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  When chips generated at the tip of the tool at the time of drilling are discharged along the chip discharge grooves 2 and 3, chips collide with each other in the connecting portion 4 of the main groove 2 and the sub-groove 3. Since the chips are forcibly scattered (in the tool radial direction) and are difficult to reach the tool base end, the wrapping of chips at the tool base end is prevented.

  In addition, since the main groove 2 and the sub-groove 3 are run side by side after the continuous portion 4, the groove volume is reduced as compared with the case where a plurality of chip discharge grooves are provided independently without being provided continuously. Thus, rigidity can be ensured, and the hole position accuracy can be improved accordingly.

  Further, by making the groove lengths of the main groove 2 and the sub-groove 3 different from each other, the tool base end side (the root portion) that is likely to be a starting point of breakage compared to the case where the groove lengths of the plurality of chip discharge grooves are made the same. ) Makes it possible to ensure rigidity and improve breakage resistance.

  A specific embodiment of the present invention will be described with reference to FIGS.

  In this embodiment, one or a plurality of cutting edges are provided at the tip of the tool body 1, and a plurality of spiral chip discharge grooves 2, 3 from the tool tip to the base end side are provided on the outer periphery of the tool body 1. The plurality of chip discharge grooves 2 and 3 are drilling tools including one main groove and one or more sub-grooves, and the sub-grooves 3 are provided in the middle of the main groove 2. The twist angles of the main groove 2 and the sub-groove 3 are set to be substantially equal at the tool base end side from the connecting portion 4 of the main groove 2 and the sub-groove 3, and the groove of the sub-groove 3 The length is set to 50 to 95% of the groove length of the main groove 2, and the sub-groove 3 runs parallel to the main groove 2 from the connecting portion 4 to a predetermined position before the end of the main groove 2. Is provided.

  In this embodiment, the main groove 2 is a groove having the longest groove length, and the sub-groove 3 is a groove having a shorter groove length than the main groove 2.

  Specifically, in this embodiment, the tool diameter is 0.1 mm, and the main groove 2 and the sub-groove 3 connected to the main groove 2 are provided one by one. Drills with cutting edges that are integrated with the tool body 1 at the intersecting ridge line between the rake face and the tip flank (first flank) of the tool body, and are used for drilling PCBs It is.

  This PCB drilling process is performed by, for example, stacking four PCBs for a semiconductor package (substrate: thickness 0.15 mm / both front and back Cu layers), which are difficult-to-cut materials, as shown in an experimental example to be described later. An aluminum plate with a resin of thickness 0.11 mm is placed as a backing plate, and a 1.5-mm thick paper phenolic material generally used as a discard plate is placed on the lower surface of the PCB so that through holes can be processed. It is done in the arranged state. The thickness of the backing plate is appropriately set in the range of 0.04 to 1.0 mm. Moreover, the thickness of the Cu layer of PCB having a thickness of about 0.1 mm is usually about 2 to 80 μm.

  In this embodiment, a drill (two-edged drill) having two cutting edges and two chip discharge grooves (one main groove and one sub-groove) will be described. The same applies to a single-blade drill provided with a drill or a drill having three or more blades (for example, one having one main groove and two sub-grooves). In this case, a higher centripetal effect can be obtained when a single-blade drill is used, and better machinability can be obtained when a three-blade drill is used.

  Specifically, in the present embodiment, the torsion angles of the main groove 2 and the sub groove 3 are set to substantially equal angles on the tool base end side from the connecting portion 4 of the main groove 2 and the sub groove 3, and The groove length l2 of the sub groove 3 is set to 50 to 95% of the groove length l1 of the main groove. If it is less than 50%, the groove volume from the groove middle part to the base end, which is important for discharging chips to the outside of the substrate, becomes smaller. The difference from the groove length l1 of the main groove 2 becomes small, and it becomes difficult to ensure rigidity at the root portion. In addition, when the groove length l2 of the sub-groove 3 is set to 70% or more of the groove length l1 of the main groove 2, it is possible to realize more stable and long-life drilling because of more stable chip discharge. This has been confirmed by the present inventors. Therefore, the groove length l2 of the sub-groove 3 is more preferably set to 70 to 95% of the groove length l1 of the main groove 2.

  Thereby, the terminal end (cut-up end point 6) of the sub-groove 3 is located on the tool tip side from the terminal end (cut-up end point 5) of the main groove 2, and the sub-groove 3 is the connecting portion 4 ( From the end of the main groove 2 to a predetermined position before the end of the main groove 2 (during section Q in FIG. 4).

  Specifically, the main groove 2 and the sub-groove 3 are continuously provided in the continuous portion 4 so that a part of both overlap, and the two grooves are aligned in a state where the lowest point of each groove is separated by a predetermined distance. Will run. That is, the main groove 2 and the sub-groove 3 are provided so as to run side by side in a state in which a part of the groove shape before the continuous connection is left while a part of the main groove 2 and the secondary groove 3 is overlapped after the connection part 4 (see FIG. 4 (a) to 4 (d) show the blade portion viewed from the side surface at different rotational phases.

  In this embodiment, the continuous groove width W2 between the main groove 2 and the sub groove 3 in the continuous portion 4 (the total groove width in a state where the main groove 2 and the sub groove 3 at the end of the continuous portion partially overlap each other) W2) is continuously provided so as to be 1.1 to 1.9 times the groove width W1 of the main groove 2 before being continuously provided. If it is less than 1.1 times, the groove volume is too small and it is difficult to obtain a smooth chip discharging property. If it is more than 1.9 times, the groove volume is large and it is difficult to ensure the rigidity of the drill. Note that the continuous groove width W2 is set to 1.3 to 1.8 times the groove width W1 of the main groove 2 before continuous connection in consideration of the balance between the properties of chip discharge and rigidity. As a result of intensive studies by the present inventors, it has been obtained as knowledge. In this embodiment, the groove width of the sub-groove 3 is set to be the same as the groove width W1 of the main groove 2. That is, as the continuous groove width W2 approaches two times the groove width W1 of the main groove 2 (sub-groove 3) before continuous connection, the degree of overlap between both becomes smaller.

  Further, in the present embodiment, the connection start point in the connection portion 4 between the main groove 2 and the sub-groove 3 is 50 times the groove length l1 of the main groove 2 at a position more than twice the tool diameter from the tool tip. % Or less. In the present embodiment, the connecting portion 4 between the main groove 2 and the sub-groove 3 is a second portion of the sub-groove 3 that is a distance M2 away from the tool tip from the continuous starting point that is a distance P away from the tool tip in FIG. The range up to the twist angle change point (parallel running start point) is shown. If the continuous start point (starting end of the continuous portion 4) is provided at a position less than twice the tool diameter from the tool tip, it is highly likely that the continuous portion will be polished during re-polishing, and it is difficult to obtain a suitable blade shape. Therefore, if it is provided at a position closer to the base end than 50% of the groove length of the main groove from the tip of the tool, the rigidity deteriorates and the hole position accuracy deteriorates.

  In the present embodiment, when the sub-groove 3 is connected to the middle portion of the main groove 2, the twist angle of the sub-groove 3 or the main groove 2 is changed in the middle. For example, the main groove 2 may have a constant twist angle from the start to the end, and the sub groove 3 may be provided in the middle of the main groove 2 by changing the twist angle of the sub groove 3 in the middle. The corners may be changed in the middle and connected continuously. Specifically, for example, the modes illustrated in FIGS.

  FIGS. 6 and 7 show that the twist angle α of the main groove 2 is constant and the twist angle of the sub-groove 3 is changed from small (β1) → large (β2) → small (β3). is there. Specifically, by changing the initial twist angle β1 of the minor groove 3 to a larger β2 at the first twist angle change point away from the tool tip by a distance M1, the minor groove 3 is brought closer to the major groove 2 so that the minor groove 3 becomes the main groove 3. Immediately after being continuously provided in the groove 2 (FIG. 6) or after intersecting the main groove 2 (FIG. 7), the second twist angle change point at a distance M2 from the tool tip is the same angle as the twist angle α of the main groove 2. Change to β3 and run in parallel. In this case, since the torsion angle α of the main groove is constant, there is an advantage that it is easy to ensure rigidity. 6 and 7, α, β1, and β3 are set to 45 °, and β2 is set to 55 °. Further, the embodiment shown in FIG. 6 is adopted in this embodiment.

  FIGS. 8 and 9 change the torsion angles of the main groove 2 and the sub-groove 3 from small (45 °) to large (55 °), respectively, and both are connected by adjusting the change point of the torsion angles. Is. Specifically, by increasing the twist angle of the sub-groove 3 in the middle, the sub-groove 3 is brought close to the main groove 2 and immediately after the sub-groove 3 is connected to the main groove 2 (FIG. 8) or after crossing the main groove ( 9), the twist angle of the main groove 2 is changed to the same angle as the twist angle of the sub groove 3. In this case, since the torsion angle between the two is changed in the middle, the chip is less likely to be wound, and since the torsion angle is large on the tool base end side, the chip generated at the tip of the tool due to the good pumping action can be reduced. There is an advantage that it can be discharged smoothly. 6-9, the main groove 2 and the subgroove 3 may be reversed. That is, in FIGS. 6 and 7, the torsion angle of the sub-groove 3 may be constant, and the torsion angle of the main groove 2 may be changed from small → large → small. In FIG. 9, by increasing the twist angle of the main groove 2 on the way, the main groove 2 is brought close to the sub-groove 3 and immediately after the main groove 2 is connected to the sub-groove 3 (FIG. 8) or after intersecting the sub-groove (FIG. ), The twist angle of the sub-groove 3 may be changed to the same angle as the twist angle of the main groove 2.

  Further, in the present embodiment, the cut-off end point 5 of the main groove 2 and the rotation axis O of the tool in each cross section perpendicular to the tool axis including the end-up end points 5 and 6 of the main groove 2 and the sub-groove 3 are used. And the second line connecting the cut end point 6 of the sub-groove 3 and the rotation axis O of the tool are projected on the same axis orthogonal projection surface in the axial direction of the tool, Of the narrow angles formed by the first line and the second line on the projection plane, at least one narrow angle γ is greater than 90 ° and equal to or less than 180 °. In other words, in each cross section perpendicular to the tool axis, including the end points 5 and 6 at the ends of the main groove 2 and the sub-groove 3, the respective end points 5 and 6 are connected to the rotation axis O of the tool. Are projected lines that are projected on the same axis orthogonal projection plane in the axial direction of the tool, and include projection lines including the cut-up end points 5 of the main grooves 2 and the cut-up end points 6 of the respective sub grooves 3. Of the narrow angles formed by the projection lines, at least one narrow angle γ is configured to be greater than 90 ° and equal to or less than 180 °.

  Specifically, in this embodiment, one main groove 2 and one sub-groove 3 are provided, and the cut end point 5 and the tool of the tool in the cross section perpendicular to the tool axis including the cut end point 5 of the main groove 2 are provided. A first line connecting the rotation axis O (see FIG. 5B) and the cut-off end point 6 and the rotation axis O of the tool in a cross section perpendicular to the tool axis including the cut-up end point 6 of the auxiliary groove 3 A second line (see FIG. 5A) to be connected is projected onto the same axis perpendicular projection plane in the axial view of the tool, and the narrow angle formed by each of the lines (projection lines) on the axis perpendicular projection plane It is configured such that γ (hereinafter referred to as a cut-off narrow angle; see FIG. 5C) is greater than 90 ° and equal to or less than 180 °.

  That is, the groove lengths l1 and l2 of the main groove 2 and the sub groove 3 are set so that the cut-off narrow angle γ is greater than 90 ° and equal to or less than 180 °. This is derived from the experimental results to be described later. When the cut-off narrow angle γ is within the above range, the hole position accuracy is extremely good. On the other hand, if all of the cut-off narrow angles are 90 ° or less, the chip discharge direction is biased, resulting in unbalanced discharge on the tool base end side, which may cause sudden hole bending. FIG. 5D shows an example of an axis perpendicular projection surface in the case of a drill having three or more blades (for example, one having one main groove and two sub grooves). In the case of three grooves, the cut-off narrowness formed by the projection line (first line) including the cut-up end point 5 of the main groove 2 and the projection line (second line) including the cut-up end point 6 of one sub-groove 3 is formed. If the angle γ is greater than 90 ° and less than or equal to 180 °, it is possible to avoid a deviation in the discharge direction of the chips, and thus a well-balanced discharge is obtained. That is, when there are two or more sub-grooves, there are two or more of the second lines, but the cut-off narrow angle formed by the first line and the plurality of second lines. If at least one of γ is greater than 90 ° and 180 ° or less, deviation in the discharge direction of the chips can be avoided, so that a well-balanced discharge can be obtained.

  The narrow angle γ is expressed by the rotational phase difference (angle difference) between the rising end point 5 of the main groove 2 and the rising end point 6 of the sub-groove 3.

  Further, the tool body 1 is coated with an amorphous carbon film as a lubricating film. That is, in this embodiment, since the groove volume is smaller on the tool base end side (when the web and web taper values are the same) compared to the shape of the conventional two-edged drill, the type, thickness, and overlap of the substrate Depending on the number of sheets, it is difficult to obtain smooth chip discharging performance, which may cause deterioration of inner wall roughness and breakage. However, by covering the amorphous carbon film, it is possible to improve the chip discharging property and to perform highly accurate drilling utilizing the rigid shape.

  Each part will be specifically described.

  In this embodiment, the substrate is made of a cemented carbide made of hard particles mainly composed of WC and a binder mainly composed of Co, and the average particle size of the WC particles of the cemented carbide is 0.00. One having a Co content of 5 to 15% by weight is employed, and at least a chip discharge groove of the tool body 1 is coated with an amorphous carbon film. Since the amorphous carbon film is hard, the wear of the tool is suppressed, and since it has high lubricity, the chips are easily discharged along the chip discharge groove to the base end portion of the tool body 1, and the chips. Prevents clogging and makes it difficult to break.

  In this embodiment, an amorphous carbon film made of high-hardness amorphous carbon (DLC) composed mainly of carbon atoms and having a Vickers hardness of 3000 or more is used as the lubricating film. However, if the Vickers hardness is 2000 or more, a film made of a relatively low hardness amorphous carbon (DLC) or a mixture of DLC and another substance (for example, metal) may be used, or chromium nitride Other lubricating films such as materials may be employed.

  In this example, the amorphous carbon film is formed immediately above the base material. For example, the amorphous carbon film is directly selected from the group 4a, 5a, 6a and Si in the periodic table, or just above the base material. A lower film layer (undercoat film) made of a metal or metalloid composed of two or more elements and having a film thickness of 200 nm or less and 1 nm or more is formed, and the amorphous carbon film is formed on the lower film layer. It is good also as a structure. In addition, the lower coating layer is not limited to the above-described configuration, but one or more elements selected from Group 4a, 5a, 6a and Si of the periodic table and Si and one or more elements selected from nitrogen and carbon You may employ | adopt what consists of a compound with an element.

  In this embodiment, an arc ion plating film forming apparatus is used for forming an amorphous carbon film or an undercoat film. However, a PVD film forming apparatus such as a sputtering method or a laser ablation method may be used. good.

  The present invention was invented as a drill coated with a lubricating film such as an amorphous carbon film used for drilling a non-ferrous work material such as PCB. A cemented carbide alloy composed of hard particles mainly composed of Co and a binder mainly composed of Co is desirable because it is a material having a balance between hardness and toughness.

  If the average particle size of the WC particles is too small, it will be difficult to uniformly disperse the WC particles in the binder, which tends to cause a reduction in the bending strength of the cemented carbide. On the other hand, if the WC particles are too large, the hardness of the cemented carbide decreases. Further, if the Co content is too small, the bending strength of the cemented carbide decreases, and conversely if the Co content is excessively increased, the hardness of the cemented carbide decreases. Therefore, it is desirable to use a cemented carbide having a mean particle size of WC particles of 0.1 μm to 2 μm and a Co content of 5 to 15% by weight as a base material.

  Further, in order to perform a stable drilling process without peeling of a film on a difficult-to-cut material such as PCB, it is desirable to increase the adhesion between the base material and the amorphous carbon film. A metal or a semimetal composed of one or more elements selected from the group 4a, 5a, 6a elements of the periodic table such as Ti, Cr, Ta, and Si and a base metal film is formed directly on the substrate. By forming an amorphous carbon film thereon, the adhesion between the substrate and the amorphous carbon film can be further enhanced. In addition, a compound of one or more elements selected from Group 4a, 5a, 6a and Si of the periodic table and one or more elements selected from nitrogen and carbon is used as a base film directly on the substrate. A film may be formed.

  Since the base film is formed for the purpose of improving the adhesion between the base material and the amorphous carbon film, it is meaningless if it is too thick, and it is desirable to make the film thickness 200 nm or less and 1 nm or more.

  Since the present embodiment is configured as described above, when chips generated at the tip of the tool at the time of drilling are discharged along the chip discharge grooves 2, 3, the connection between the main groove 2 and the sub-groove 3 is performed. Since the chips collide with each other in the installation portion 4, the chips are forcibly scattered (in the tool radial direction) and do not easily reach the tool base end, so that the chips are wound around the tool base end. Will be prevented.

  In addition, since the main groove 2 and the sub-groove 3 are run side by side after the continuous portion 4, the groove volume is reduced as compared with the case where a plurality of chip discharge grooves are provided independently without being provided continuously. Thus, rigidity can be ensured, and the hole position accuracy can be improved accordingly.

  Further, by making the groove lengths of the main groove 2 and the sub-groove 3 different from each other, the tool base end side (the root portion) that is likely to be a starting point of breakage compared to the case where the groove lengths of the plurality of chip discharge grooves are made the same. ) Makes it possible to ensure rigidity and improve breakage resistance.

  Therefore, in this example, even when an aluminum plate with a resin is used as a backing plate, it is difficult to break and the chip discharge performance is remarkably improved, so that the chip can be prevented from being wound and the diameter is 0.7 mm or less. In particular, even a small-diameter drill of 0.4 mm or less is a highly practical drilling tool that has a long breakage life and good hole position accuracy and can realize stable drilling.

  An experimental example supporting the effect of the present embodiment will be described.

  FIG. 10 is a table showing experimental conditions and experimental results in which the hole position accuracy and the remaining winding are evaluated by changing the sub-groove length (and changing the cut-off narrow angle accordingly). The drill used in this experiment had a tool diameter of 0.1 mm and a groove length of the main groove 2 of 1.8 mm. The conventional example is a conventional two-blade, two-groove drill (twist angle of two chip discharge grooves). In each of Experimental Examples 1 to 10, the main groove and the auxiliary groove are connected in the manner shown in FIG. 6, and in Experimental Example 11, the main groove and the auxiliary groove are shown in FIG. And other specifications such as core thickness and tip angle are set to the same value. Each drill is covered with an amorphous carbon film (DLC).

  In this experiment, four PCBs for a semiconductor package, which is a difficult-to-cut material (substrate: thickness 0.15 mm / both front and back Cu layers), are stacked, and an aluminum plate with a resin having a thickness of 0.11 mm is used as a backing plate on the upper surface. A 1.5-mm-thick paper phenolic material generally used as a discarded plate was placed on the lower surface of the PCB so that it could be placed and processed through holes. The number of revolutions of the drill (spindle) was 200 krpm, the feed rate was 1.8 m / min, the ascent rate was 25.4 m / min, and the set hit number was 3,000 hits.

  From FIG. 10, it was confirmed that all of Experimental Examples 1 to 8 and 11 had less winding residue than the conventional example. In particular, as shown in FIG. 11, it was confirmed that Experimental Example 11 was the most favorable with almost no winding residue. This is considered to be because the effect of chip scattering was further increased by changing the twist angle between the two.

  Moreover, it has confirmed that all of Experimental Examples 1-8 and 11 had favorable hole position precision compared with the prior art example. Further, in Experimental Examples 2, 4, 6, 7, and 11 in which the minor groove length is 56 to 89% of the main groove length and the cut-off narrow angle is in the range of 106 to 180 °, the hole position accuracy is particularly good. It was confirmed that In Experimental Examples 3, 5, and 8 in which the sub-groove length is in the range of 56 to 89% of the main groove length, the hole position accuracy is better than the conventional example, but the cut-off narrow angle is small. Since it is small, sudden hole bending is caused, and the Max value becomes large (expressed as Max jump in FIG. 10), and there is a possibility that stable hole machining cannot be obtained. In Experimental Example 1, the hole position accuracy is better than that of the conventional example, but the groove length of the main groove 2 and the groove length of the sub groove 3 are the same, and the cut-off narrow angle is small. Due to both factors, Max jump occurs in the same manner, and there is a possibility that stable drilling cannot be obtained.

  In Examples 9 and 10 in which the minor groove length was extremely short, the drill was broken. This is thought to be due to the deterioration of chip discharge.

  From the above, it can be confirmed that the remaining winding of the chips does not depend on the cut-off narrow angle and only affects the hole position accuracy, and both the minor groove length and the cut-off narrow angle are included in the above range. It was confirmed that Experimental Examples 2, 4, 6, 7, and 11 were drilling tools with little winding residue and good hole position accuracy.

DESCRIPTION OF SYMBOLS 1 Tool main body 2 Chip discharge groove 3 Chip discharge groove 4 Connection part 5 Rounding up end point 6 Rounding up end point O Tool axis

Claims (9)

  One or a plurality of cutting edges are provided at the tip of the tool body, and a plurality of spiral chip discharge grooves extending from the tool tip to the base end side are provided on the outer periphery of the tool body. Is a drilling tool including one main groove and one or more sub-grooves, and the sub-grooves are provided in the middle of the main groove, and the twist angles of the main grooves and the sub-grooves are The angle between the main groove and the auxiliary groove is set to be substantially equal on the tool base end side, the groove length of the auxiliary groove is set to 50 to 95% of the groove length of the main groove, and the auxiliary groove is A drilling tool, wherein the drilling tool is provided so as to run in parallel with the main groove from the continuous portion to a predetermined position before the end of the main groove.   One or a plurality of cutting edges are provided at the tip of the tool body, and a plurality of spiral chip discharge grooves extending from the tool tip to the base end side are provided on the outer periphery of the tool body. Is a drilling tool including one main groove and one or more sub-grooves, and the sub-grooves are provided in the middle of the main groove, and the twist angles of the main grooves and the sub-grooves are The tool groove is set at an approximately equal angle on the tool proximal side from the connecting portion of the main groove and the sub groove, and the groove length of the sub groove is set to 70 to 95% of the groove length of the main groove. A drilling tool, wherein the drilling tool is provided so as to run in parallel with the main groove from the continuous portion to a predetermined position before the end of the main groove.   The drilling tool according to any one of claims 1 and 2, wherein the continuous groove width between the main groove and the sub-groove in the continuous portion is 1 of the groove width of the main groove before continuous connection. A drilling tool characterized by being 1 to 1.9 times.   The drilling tool according to any one of claims 1 and 2, wherein the continuous groove width between the main groove and the sub-groove in the continuous portion is 1 of the groove width of the main groove before continuous connection. Drilling tool characterized by being 3 to 1.8 times.   5. The drilling tool according to claim 1, wherein the start end of the continuous portion is at a position that is at least twice the tool diameter from the tool tip and at a position that is 50% or less of the groove length of the main groove. A drilling tool characterized by being provided.   The drilling tool according to any one of claims 1 to 5, wherein the main groove has a rounded end point and a rotation of the tool in a cross section perpendicular to the tool axis, including the rounded end points at the ends of the main groove and the secondary groove. When the first line connecting the axis and the second line connecting the cut end point of the sub-groove and the rotation axis of the tool are projected onto the same axis orthogonal projection plane in the axial view of the tool, A drilling tool characterized in that at least one of the narrow angles formed by the first line and the second line on the projection plane is greater than 90 ° and equal to or less than 180 °.   The drilling tool according to any one of claims 1 to 6, wherein each of the main groove and the sub-groove is provided as the chip discharge groove.   The drilling tool according to any one of claims 1 to 7, wherein an amorphous carbon film is coated as a lubricating film.   The drilling tool according to any one of claims 1 to 8, wherein the tool diameter is 0.4 mm or less.