JP2010274409A - Small diameter drill for machining machinable ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small diameter drill for machining machinable ceramics, having a diameter of 2 mm or less, maintaining sharpness of a tip cutting edge and high hole accuracy of a workpiece and preventing a breakage accident by optimizing the shape and material of the tip cutting edge of the drill and suppressing the progress of wear. <P>SOLUTION: The tip cutting edge of the small diameter drill for drilling a hole with a diameter or 2 mm or less in machinable ceramics, includes a center side cutting edge and a peripheral side cutting edge, and the tip angle of a rotation locus is 120-140° in the center side cutting edge, and 70-100° in the peripheral side cutting edge. The projection length of the peripheral side cutting edge is in a range of 5-30% of the diameter. A helix angle is 25-35°, and the circumferential length of a margin part is in a range of 15-30% of the diameter of the small diameter drill. A space between a preceding margin part connected to a leading edge, and a succeeding margin part connected to a heel, is preferably formed in the cut-off shape of a cylinder part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a small-diameter drill for machining machinable ceramics, and provides a small-diameter drill most suitable for drilling machinable ceramics, particularly a small-diameter drill having a novel shape of the cutting edge of the drill.

  Machinable ceramics that are targeted for drilling with the small-diameter drill of the present invention are ceramics in which mica, zirconia microcrystals, and the like are dispersed in ceramics to provide cleavage or crack resistance. This property allows easy machining of ceramics, which was previously difficult. For this reason, it is used for insulators, protective tubes, substrates, nozzles for chemical equipment, probe cards, etc., taking advantage of the features of ceramics, such as electrical insulation, high thermal conductivity or low thermal conductivity, and corrosion resistance. Yes. For products that take advantage of ease of processing, examples of making prototypes of mass-produced prototypes with machinable ceramics are also known. These machinable ceramics require machining such as drilling, turning, and milling as necessary. The present invention relates to a small-diameter drill that performs drilling with a small diameter of 2 mm or less, preferably 0.5 mm or less, particularly for machinable ceramics used in a probe card for an inspection process of a semiconductor device.

  Hereinafter, as an example in which the drill with the smallest diameter is required, drilling of a probe card will be described as an example. In a semiconductor integrated circuit manufacturing process, when a circuit is completed on a wafer, an energization test is performed before the wafer is separated into individual chips. At this time, an inspection jig called a probe card is used. The probe card uses machinable ceramics as an insulator, and has a large number of perforated small-diameter holes (specifically, a machinable ceramic disc having a diameter of about 12 inches and a diameter of about 0.1 mm). A probe having a needle-like tip is inserted into about 40,000 small-diameter holes.

  Small-diameter drills for drilling machineable ceramics for probe cards currently in use are mainly made of carbide, and no special drills have been used. ing. In the present invention, a drill having a diameter of 2 mm or less is referred to as a small diameter.

  As an example having a feature in the shape of the cutting edge of the drill tip, Patent Document 1 and Patent Document 2 disclose a chamfered blade provided on the outer peripheral side of the cutting blade. These drills have a purpose of preventing the occurrence of dust around the drilled holes and extending their life in drilling high-hardness materials and cast iron, and are provided with negative lands and honing on the cutting edges.

JP 2005-103738 A Japanese Patent Laid-Open No. 7-80714

  The drills described in Patent Documents 1 and 2 have a problem that cutting resistance increases although chipping of the cutting edge and chipping can be prevented by negative land and honing. In particular, the machinable ceramics targeted by the present invention have a small diameter of 2 mm or less, and since the possibility of breakage is high when the cutting resistance is high, it is difficult to apply the known drill.

  Probe cards, one of the main uses of machinable ceramics, are mainly those with a spring mechanism that generates pressure when in contact. Probe diameters and intervals are as high as several tens to hundreds of micrometers. The density is increased, and hundreds to tens of thousands of probes are inserted in one machinable ceramic disk. In the energization test, the probe card is connected to a test device, a voltage is applied to the terminals on the chip to be measured according to the test pattern, the output is measured, and the quality of the chip is determined by comparing with the expected value. At that time, it is necessary to accurately apply the probe to the terminal on the chip, and the accuracy of the hole drilled in the machinable ceramic is very important. For example, the hole accuracy required for machinable ceramics used in recent probe cards is that the hole diameter accuracy is 5 μm or less in the range, the straightness of the holes on the front and back surfaces is 10 μm or less in the range, and the maximum surface roughness Rz on the inner surface Is 1 μm or less, and is managed with very high accuracy. In the near future, the hole diameter accuracy is 2 μm or less in the range, and the straightness of the holes on the front and back surfaces is 5 μm or less in the range, and the performance and accuracy required for the drill are expected to be higher.

  Currently, as the machinable ceramics used for the probe card, those mainly composed of ZrO2-ZrSiO4-SiN are used. The present inventor drilled the machinable ceramic using the conventional general small diameter drill made of cemented carbide for the machinable ceramic, and investigated the damage state of the drill. The cemented carbide small-diameter drill used is a cemented carbide alloy of ultrafine particles, and the drill diameter is 0.12 mm. After drilling machinable ceramics with a conventional general small-diameter drill, we investigated the damage condition of the small-diameter drill, and as a result, the tip of the drill had a jagged wear like a saw blade, resulting in a machined hole. It was found that the hole accuracy decreased as the number increased.

  FIG. 16 shows a model in which the cause of this phenomenon is considered from the relationship between the structure of machinable ceramics and the cutting edge of a drill. FIG. 16 is an explanatory view showing a cutting process of machinable ceramics. In FIG. 16, a machinable ceramic 41 is composed of ceramic crystal grains 42 and ceramic crystal grain boundaries 43, and mica and zirconia microcrystals are dispersed in the ceramic crystal grain boundaries 43. During the cutting process, when the tip end cutting edge 6 composed of the flank 44 of the tip end cutting edge and the rake face 45 of the tip end cutting edge contacts the machinable ceramic 41, the tip end cutting edge 6 and the machinable ceramic 41 Since stress concentrates near the contact point, cracks occur. Here, mica and zirconia microcrystals dispersed in the crystal grain boundaries 43 of the ceramic have a cleavage property and have a property of being easily broken in a specific direction of the crystal. Therefore, the ceramic crystal grains 42 are separated at the boundary of the ceramic crystal grain boundaries 43 due to the stress in the vicinity of the contact point between the tip end cutting edge 6 and the machinable ceramic 41. As a result, the crack remains only a small size, so that a large progression to the inside of the crack is prevented.

  As a result, the machinable ceramic chips 47 are very fine particles, unlike the cutting chips found in general steel materials. Further, the machined surface of the machinable ceramic 41 has a jagged shape because fine particles with different particle sizes are separated from each other. For this reason, the flank 44 of the cutting edge of the drill that comes into contact with the machined surface is subject to jagged wear like a saw blade as shown in FIG. For this reason, the progress of wear of the drill becomes unstable as compared with the case of drilling a general steel material, and the wear of the drill base material tends to progress quickly. An object of the present invention is to propose a drill having a stable and long life for a work material in which such special wear progress occurs.

  Since the drill targeted by the present invention rotates at a high speed at the machining center, wear of the cutting edge of the drill advances due to friction with the machinable ceramics of the work material. In particular, the thermal conductivity of machinable ceramics used in probe cards is extremely low, and the cutting heat generated when cutting is transmitted to the tip and absorbed. Due to these phenomena, wear progresses remarkably from the tip of the small-diameter drill to the outer peripheral side, and in particular, the outer peripheral corner portion of the drill has the fastest cutting speed and is likely to progress. When the wear at the outer peripheral corner progresses and the outer peripheral corner becomes round, as shown in FIG. 6, the wear to the margin where the wear has not progressed until then begins to progress remarkably. As a result, the diameter of the drill in the wear area at the margin is reduced. Then, the hole diameter accuracy opened in the machinable ceramic will be out of the standard value. As described above, from the investigation of the damaged state of the drill, it was found that it is extremely important to suppress the progress of wear of the tip portion in order to maintain the hole accuracy with high accuracy. As the wear of the margin progresses, the guide performance of the outer peripheral corner portion deteriorates, so that the drill becomes unstable cutting and the straightness of the hole is deteriorated. As shown in the following examples, the hole accuracy referred to in the present invention is the hole diameter accuracy on the surface of the workpiece, the straightness in the X direction of the holes on the workpiece surface side and the back surface side, and the Y direction perpendicular to it. The degree of each misalignment.

  Further, the sharpness of the cutting edge of the tip portion is lost, so that the cutting resistance increases and the drill suddenly breaks. In the case of a probe card that is mainly used at present, the current mainstream of the probe card is a machineable ceramic disc having a diameter of about 12 inches, and a small-diameter drilling process of about 40,000 holes is performed on the disc. . When considering the life of a conventional general drill, drilling 200 to 500 holes with a single drill and replacing it with a new one. However, one of the problems with conventional drills is that breakage occurs in machinable ceramics suddenly before the end of the drill life as described above. Not only are the materials of machinable ceramics that cost 10,000 yen wasted, but also the processing man-hours are wasted.

  Therefore, more specifically showing the purpose of the present invention, by optimizing the tip cutting edge of the drill with the shape and material to suppress the progress of wear of the drill, while maintaining the sharpness of the tip cutting edge, The aim is to provide a small-diameter drill for machining ceramics that maintains the hole accuracy of the workpiece with high accuracy and prevents breakage accidents.

  As a result of examining the drill base material, the shape of the tip cutting edge optimal for wear resistance, and the material of the hard coating on the tip cutting edge as a drill that drills small diameters in machinable ceramics etc. It was born. That is, the present invention is a small-diameter drill for drilling a small diameter of 2 mm or less in machinable ceramics, and the cutting edge of the small-diameter drill is composed of a center-side cutting edge and an outer peripheral-side cutting edge. The angle of the tip angle on the rotation locus viewed from the direction perpendicular to the axis of the center is 120 ° to 140 ° of the tip angle of the center side cutting edge, and 70 ° to 100 ° of the tip angle of the outer peripheral side cutting edge. A small diameter drill for machining ceramics, characterized in that the projected length of the outer peripheral cutting edge in the drill radial direction is in the range of 5% to 30% of the diameter.

  Other inventions of the present invention, in addition to the conditions of the tip angle of the center side cutting edge and the outer peripheral side cutting edge and the projection length of the outer peripheral side cutting edge in the radial direction of the drill, This is an optimized shape of the margin when viewed in a cross section perpendicular to the tool axis. That is, another invention of the present invention is a small diameter drill for drilling a small diameter of 2 mm or less in machinable ceramics, and the cutting edge of the small diameter drill is composed of a center side cutting edge and an outer peripheral side cutting edge. The angle of the tip angle in the rotation locus viewed from the direction perpendicular to the axis of the drill is such that the tip angle of the center side cutting edge is 120 ° to 140 °, and the tip angle of the outer peripheral side cutting edge is The projection length of the outer peripheral cutting edge in the radial direction of the drill is in the range of 5% to 30% of the diameter, the twist angle of the small diameter drill is 25 ° to 35 °, and the leading of the small diameter drill It has a leading margin part connected to the edge and a rear margin part connected to the heel, and the circumferential length of the margin part when viewed in a cross section perpendicular to the tool axis other than the cutting edge at the tip is the small diameter 15% to 30% of the diameter of the drill Is enclosed between the said preceding margin portion of the rear margin is small drill machinable ceramics processing, characterized in that a shape of the cylindrical portion has been removed. In this specification, the circumferential length of the margin portion indicates the margin width in other words.

  In the small-diameter drill for machining machinable ceramics of the present invention, it is desirable that the base material of the drill is a cemented carbide and is formed by a tip cutting edge coated with a hard film. The hard coating is, for example, diamond, diamond-like carbon (hereinafter DLC), or a nitride, carbide, or carbonitride composed of one or more elements selected from aluminum, titanium, chromium, and silicon as a metal element. Carbonic nitride is recommended. Specifically, diamond, DLC, CrSiN, TiSiN, AlCrSiN, and TiAlN hard coatings are recommended.

  In the small-diameter drill for machining machinable ceramics according to the present invention, it is desirable that at least the base material of the cutting edge of the drill is made of either cubic boron nitride (CBN) or polycrystalline diamond.

ADVANTAGE OF THE INVENTION According to this invention, in the drilling process using the small diameter drill to machinable ceramics, it becomes possible to suppress significantly the wear progress of an outer periphery corner part.
According to the present invention, it is possible to propose a drill that can maintain a stable and high hole accuracy over a long period of time even in small-diameter drilling for machinable ceramics.
Further, in particular, the base material of the drill is a cemented carbide and the tip part cutting edge coated with a hard coating is used, or at least the base part of the tip part cutting edge of the drill is cubic boron nitride (CBN) or polycrystalline diamond If it forms by either of these, in addition to the effect which suppresses the abrasion progress of the outer periphery corner part by the shape of a front-end | tip part cutting edge, the sharpness of a front-end | tip part cutting edge is ensured. Particularly, the use of the machinable ceramics to which the drill of the present invention is applied is most suitable for drilling a probe card used in the manufacturing process of a semiconductor integrated circuit.

It is the front view seen from the perpendicular direction with respect to the axial center of the small diameter drill for machining ceramics which is one Example of this invention. It is an enlarged view of the drill part of FIG. The left view when FIG. 1 is rotated 90 degrees in the rotation direction of a drill is shown. It is a figure showing the rotation locus | trajectory of FIG. It is a schematic diagram showing the wear form of the flank wear of the conventional general small diameter drill. It is a schematic diagram showing the wear mode of margin wear of the conventional general small diameter drill. It is a figure showing the comparison of the chisel edge length by the difference of the angle of a tip angle, (a) shows a thing with a big tip angle and a short chisel edge length, (b) shows a thing with a small tip angle and a long chisel edge length. Show. It is an enlarged view of the drill part which has the front margin part and the back margin part of the small diameter drill for machining ceramics which is another example of this invention. It is a figure showing the AA sectional view of Drawing 8 of the small diameter drill for machinable ceramics which is other examples of the present invention. It is explanatory drawing which shows the maximum wear width of the conventional general small diameter drill. It is explanatory drawing which shows the maximum margin wear width of the conventional common small diameter drill. It is explanatory drawing which shows the center side maximum wear width and outer periphery side maximum wear width of the example of this invention. It is explanatory drawing which shows the maximum margin wear width of the example of this invention. It is a schematic explanatory drawing which shows the drilling of the workpiece material of an Example. It is explanatory drawing which shows the measuring method of straightness. It is explanatory drawing which shows the cutting process of machinable ceramics. It is explanatory drawing which shows the cutting process of machinable ceramics when the sharpness of a front-end | tip part cutting blade is lost.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a front view of a small-diameter drill for machining ceramics that is an embodiment of the present invention. FIG. 2 is an enlarged view of the drill portion 1 of FIG. 1, and the tip end cutting edge 6 of the drill is composed of a center side cutting edge 8 and an outer peripheral side cutting edge 9. FIG. 3 shows a left side view when FIG. 1 is rotated 90 ° in the rotation direction of the drill. FIG. 4 is a diagram illustrating the rotation trajectory of FIG. FIG. 5 is a schematic diagram showing a wear form of flank wear of a conventional general small diameter drill. FIG. 6 is a schematic view showing a wear form of margin wear of a conventional general small diameter drill. FIG. 7 is a diagram showing a comparison of the chisel edge length 20 according to the difference in the angle of the tip angle. FIG. 7A shows a case where the tip angle is large and the chisel edge 19 is short, and FIG. Show things. FIG. 8 is an enlarged view of a drill portion 1 having a leading margin portion 22 and a rear margin portion 24 of a small diameter drill for machining machinable ceramics which is another example of the present invention. FIG. 9 is a diagram showing a cross-sectional view taken along the line AA of FIG.

  In the small-diameter drill for machining machinable ceramics of the present invention, as shown in FIG. 1, a drill part 1 having a diameter D and a neck part 2 constitute a neck length 3 and are connected to a shank part 4. The drill portion 1 is provided with a groove 7 for discharging chips. As shown in FIGS. 2 and 4, the tip end cutting edge 6 of the drill is composed of a center side cutting edge 8 and an outer peripheral side cutting edge 9.

  Machinable ceramics used as work materials are ceramics in which mica or zirconia microcrystals are dispersed in ceramics. The machined surface generated during cutting is a surface having a jagged shape such that fine particles are peeled off. FIG. 5 is a schematic diagram showing the wear pattern of the flank wear of a conventional general small diameter drill. The flank 44 of the tip of the conventional general drill has a saw blade as shown in FIG. Such jagged flank wear 17 occurs. FIG. 6 is a schematic diagram showing a wear form of margin wear 18 of a conventional general small-diameter drill, and margin wear 18 of the form shown in FIG. Furthermore, since machinable ceramics have low thermal conductivity, heat hardly accumulates in the chips and heat is accumulated at the tip 5 of the drill. As a result, the flank wear 17 easily progresses at the tip 5 of the drill, and the wear of the outer peripheral corner portion 10 with the fastest cutting speed progresses. As shown in FIG. There is a problem that the diameter becomes small and the hole diameter accuracy deviates from the standard value. Furthermore, when the flank wear 17 of the tip end cutting edge 6 proceeds as shown in FIG. 6, the sharpness of the tip end cutting edge 6 is greatly lost. FIG. 17 is an explanatory view showing the cutting process of the machinable ceramic when the sharpness of the tip end cutting edge is lost. As shown in FIG. 17, when the sharpness of the tip end cutting edge 6 is lost, the contact area between the tip end cutting edge 46 and the machinable ceramic 41 where the sharpness is lost increases. As a result, the stress applied to the contact area between the tip end cutting edge 46 and the machinable ceramics 41 whose sharpness has been lost during cutting is dispersed. Then, there are a plurality of crack propagation directions, and the cutting process of the machinable ceramics is different from the cutting process of the tip end cutting edge 6 when it is sharp. As a result, there arises a problem that the drill breaks due to the deterioration of the degree of positional deviation in the X direction of the machining hole and the Y direction perpendicular thereto or an increase in cutting resistance. Such a state is likely to occur especially as the wear progresses at the tip 5, so it is important to suppress the wear progress. Therefore, it is desirable for the small diameter drill for machining machinable ceramics to have the shape of the tip portion 5 as in the present invention that suppresses the progress of wear and ensures sharpness and biting property.

  The small-diameter drill for machining machinable ceramics according to the present invention is a small-diameter drill for drilling small-diameter holes with a diameter of 2 mm or less in machinable ceramics. As shown in FIGS. The center side cutting edge 8 and the outer peripheral side cutting edge 9 are configured, and the angle of the tip angle in the rotation locus viewed from the direction perpendicular to the axis of the drill is the tip angle 14 of the center side cutting edge. 120 ° to 140 °, the tip angle 15 of the outer peripheral cutting edge is 70 ° to 100 °, and the projection length 16 of the outer peripheral cutting edge 9 in the radial direction of the drill is in the range of 5% to 30% of the diameter D. It is characterized by being.

  The small-diameter drill for machining machinable ceramics according to the present invention is provided such that the tip angle 14 of the center-side cutting edge is 120 ° to 140 ° as shown in FIG. As a result, when drilling the machinable ceramics, the tip portion 5 sufficiently bites the work material, and the tip portion 5 can be cut straight with respect to the work material. When the tip angle 14 of the center-side cutting edge is less than 120 °, the rigidity of the tip portion 5 is lowered, and it is easily affected by cutting heat generated when drilling a machinable ceramic having low thermal conductivity. For this reason, the cutting heat cannot be released from the distal end portion 5 and wear easily proceeds. Further, when the tip angle 14 of the center side cutting edge is less than 120 °, a manufacturing problem occurs. FIG. 7 is a diagram showing a comparison of chisel edge lengths depending on a difference in tip angle. For example, as shown in FIGS. 7A and 7B, the small tip angle in FIG. 7B is smaller in the chisel edge 19 of the tip 5 than the one having a large tip angle in FIG. It will be long. In other words, the chisel edge 19 becomes long as shown in FIG. In other words, the length 21 of the projected cutting edge of the tip 5 of the drill is shortened when projected onto a flat surface, and the biting property to the work material is lowered, resulting in a problem that the straightness of the processed hole is deteriorated. In addition, when the tip angle 14 of the center-side cutting edge exceeds 140 °, the tip portion 5 becomes difficult to bite against the work material, so that the tip portion 5 becomes unstable and the straightness of the machining hole is reduced. . The tip angle 14 of the center side cutting edge is more preferably in the range of 125 ° to 135 °. These things became clear from the Example shown below.

  The small diameter drill for machining machinable ceramics according to the present invention is provided with a tip angle 15 of the outer peripheral cutting edge of 70 ° to 100 ° as shown in FIG. As a result, the angle formed by the outer peripheral cutting edge 9 and the leading edge 12 becomes larger than when the outer peripheral cutting edge 9 is not provided, and the progress of wear of the outer peripheral corner portion 10 can be suppressed. High-precision drilling.

  In the case of a conventional general drill, if the tip angle of the tip end cutting edge 6 is reduced, the angle formed by the tip end cutting edge 6 and the leading edge 12 is increased, thereby increasing the rigidity of the outer peripheral corner portion 10 and the outer peripheral corner portion. Although the wear resistance of No. 10 is improved, as shown in FIG. 7B, the length 21 of the projected cutting edge of the drill tip 5 is shortened when projected onto a flat surface, and the biting property to the work material is reduced. The straightness of the hole is worsened by lowering. On the other hand, when the tip angle of the tip end cutting edge 6 is increased, the sharpness of the tip end cutting edge 6 is improved, but since the angle formed by the tip end cutting edge 6 and the leading edge 12 is reduced, the outer corner portion 10 Rigidity decreases and wear progresses faster. Therefore, in the present invention, in order to improve both the sharpness and the wear resistance, a center side cutting edge 8 and an outer peripheral side cutting edge 9 are provided on the tip end cutting edge 6 of the drill, and a tip angle 15 of the outer peripheral side cutting edge is provided. Is provided in the range of 70 ° to 100 °.

  When the tip angle 15 of the outer peripheral cutting edge is less than 70 °, the guide performance of the outer peripheral corner portion 10 is improved when drilling, but the angle of the corner portion 11 formed by the center cutting edge 8 and the outer peripheral cutting edge 9 is improved. As a result, the possibility of occurrence of chipping and chipping increases, and the wear of the corner portion 11 becomes easy to progress, so that the drilling accuracy is deteriorated. The appropriate range of the tip angle 15 of the outer peripheral cutting edge is also clarified from the following examples. Further, when the tip angle 15 of the outer peripheral cutting edge exceeds 100 °, the angle of the outer peripheral corner portion 10 becomes smaller, and the cutting heat generated when drilling machining machinable ceramics having low thermal conductivity is reduced. The corner part 10 cannot be escaped and wear progresses, and the outer corner part 10 becomes round. As a result, the margin wear 18 progresses, and the diameter of the tip portion 5 is likely to be reduced. As a result, the diameter of the processed hole is reduced, and the guide performance of the outer peripheral corner portion 10 is lowered, so that the drill becomes unstable. Therefore, high-precision drilling over a long time becomes difficult. Preferably, the tip angle 15 of the outer peripheral cutting edge is in the range of 80 ° to 90 °. In this case, the guide performance of the outer peripheral corner portion 10 is stabilized, the margin wear 18 is suppressed, and the tip angle 15 is increased for a long time. Accurate drilling is possible.

  In the small diameter drill for machining machinable ceramics of the present invention, as shown in FIG. 4, the projection length 16 of the outer peripheral cutting edge 9 in the drill radial direction is provided in the range of 5% to 30% of the diameter. As a result, the outer corner portion 10 can be prevented from being worn and processed with improved hole accuracy. When the projected length 16 of the outer peripheral side cutting edge 9 in the radial direction of the drill is less than 5% of the diameter, the effect of suppressing the wear of the outer peripheral corner part 10 of the outer peripheral side cutting edge 9 decreases, and the wear of the outer peripheral corner part 10 progresses. Therefore, there arises a problem that high-precision drilling cannot be maintained for a long time. Moreover, when the projection length 16 of the outer peripheral side cutting edge 9 in the drill radial direction exceeds 30% of the diameter, wear of the tip portion 5 of the drill easily proceeds. As a result, the biting property of the tip 5 is lowered and the drilling accuracy is deteriorated. Preferably, the projection length 16 of the outer peripheral cutting edge 9 in the radial direction of the drill is in the range of 15% to 20% of the diameter. Under these conditions, the progress of wear is suppressed and high accuracy is achieved over a long period of time. Drilling is possible.

  The small diameter drill for machining machinable ceramics according to the present invention has a leading margin 22 connected to the leading edge 12 and a rear margin connected to the heel when viewed in a cross section perpendicular to the tool axis other than the cutting edge 6 at the tip. It is preferable that a shape having a cylindrical deletion portion 23 is provided in which a cylindrical portion is deleted between the leading margin portion 22 and the rear margin portion 24.

  FIG. 8 is an enlarged view of the drill portion of the present invention, FIG. 9 is a cross-sectional view taken along the line AA of FIG. Further, the rotation locus of FIG. 8 of the present invention can be represented by FIG. As shown in FIG. 9, by providing the leading margin portion 22 and the rear margin portion 24, the guide performance of the outer peripheral corner portion 10 can be improved, and the drilling accuracy can be further improved. Here, when the cylindrical portion between the leading margin portion 22 and the rear margin portion 24 is not deleted, that is, in the shape without the cylindrical deleting portion 23, the area where the margin portion contacts the work material is large. Therefore, cutting torque becomes large. Small-diameter drills have low rigidity and are susceptible to cutting torque, so the life may be shortened. Therefore, the circumferential lengths of the leading margin portion 22 and the rear margin portion 24 are set in a range of 15% to 30% of the diameter of the small diameter drill. Preferably, the range of 20% to 25% of the diameter of the small diameter drill is good. If it is less than 15%, the cutting torque can be reduced, but the effect of improving the guide performance of the outer peripheral corner portion 10 is reduced. If it exceeds 30%, the area where the margin portion comes into contact with the work material increases, so that the drilling accuracy increases. However, the cutting torque increases rapidly, so the possibility that the drill breaks increases.

  In the small diameter drill for machining machinable ceramics according to the present invention, it is preferable that the twist angle of the small diameter drill is in a range of 25 ° to 35 °. As a result, it is possible to ensure the chip discharge performance for very fine chips unique to the machinable ceramics while preventing the rigidity of the tip end cutting edge 6 from being lowered. If the angle is less than 25 °, the rigidity of the tip end cutting edge 6 is increased, but the chip dischargeability is reduced, so that the possibility of clogging and breakage during cutting is increased. When the twist angle of the drill is larger than 35 °, the rigidity of the tip end cutting edge 6 is remarkably lowered, and it becomes difficult to maintain the sharpness of the cutting edge.

  In the small-diameter drill for machining machinable ceramics of the present invention, it is desirable that the base material of the drill is a cemented carbide and is formed by a tip cutting edge 6 coated with a hard coating. For example, the hard coating may be diamond, DLC, or a nitride, carbide, carbonitride, carbonitride, or the like composed of one or more elements selected from aluminum, titanium, chromium, and silicon as a metal element. Recommended. Specifically, it is a film of diamond, DLC, CrSiN, TiSiN, AlCrSiN, TiAlN or the like.

In the small-diameter drill for machining machinable ceramics according to the present invention, it is desirable that at least the base material of the cutting edge 6 of the drill is made of either cubic boron nitride (CBN) or polycrystalline diamond. Thereby, the cutting resistance of the drill and the wear of the tip end cutting edge 6 are suppressed, and high-precision drilling over a long period of time becomes possible.
Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto.

In each example shown in the following table, the present invention example, the conventional example, and the comparative example are shown as classifications, and the sample numbers are indicated by consecutive serial numbers for each of the present invention, the conventional example, and the comparative example.
Example 1
Example 1 compared the cutting result with the blade shape which has the outer peripheral side cutting edge which has the shape of this invention with respect to the blade shape which does not have an outer peripheral side cutting edge in the front-end | tip part which is a typical conventional example. Is. In both the present invention example 1 and the conventional example 1, the specifications were unified so that the diameter was 0.12 mm, the neck length was 1.8 mm, the core thickness was 35%, the groove length was 0.6 mm, and the shank diameter was 3 mm. Except for the above specifications, a double-edged drill having a margin 13 and a front-end angle of the center-side cutting edge of 140 ° and a front-end angle of the outer-side cutting edge of the invention example 1 having the outer peripheral cutting edge of 80 °. A tool in which the projection length is 15% (0.018 mm) of the diameter D, the twist angle is 30 °, and the tip angle of the tip end cutting edge is 140 ° in the conventional example 1 having no outer peripheral cutting edge. Each was manufactured and the cutting test was done. In addition, in Invention Example 1 and Conventional Example 1, the base material of the drill is a cemented carbide, and the tip of the drill is subjected to DLC coating as a surface treatment.

As the work material (also referred to as a workpiece), ZrO2-ZrSiO4-SiN based machinable ceramics (width 30 mm, depth 30 mm, thickness 1.7 mm) were used.
For the guide hole drilling, a pilot hole was drilled by a ball end mill, and then a deep hole was drilled by a step process up to a hole depth of 1.8 mm with the drill described above. The cutting conditions at the time of forming the guide hole are a cutting speed of 6.2 m / min, a one-turn feed of 0.005 mm / rev, a step amount of 0.011 mm / time, a processing hole depth of 0.066 mm, and a cooling method using air blow. went. The cutting conditions of the drill were a cutting speed of 6.2 m / min, a one-turn feed of 0.005 mm / rev, a step amount of 0.06 mm / time, a processing hole depth of 1.8 mm, and a cooling method using air blow. The number of drilling operations was set to four rows of one row and 50 holes at a hole interval of 0.27 mm, and 200 holes were made.

As an evaluation method, the wear of the drill was measured at 2500 times using a scanning electron microscope. In the case of a drill that does not have an outer peripheral cutting edge, as shown in FIG. 10, the measurement location is the maximum wear width 25 at the flank 44 of the tip cutting edge, and as shown in FIG. The maximum width of wear when measured in the tool axis direction at the margin 13 was defined as the maximum margin wear width 26.
In the case of a drill having an outer peripheral cutting edge, as shown in FIG. 12, the maximum wear width on the central cutting edge flank and the outer peripheral cutting edge flank is defined as a central maximum wear width 27 and an outer peripheral maximum wear width 28. As shown in FIG. 13, the maximum width of wear when measured in the tool axis direction at the margin 13 was defined as the maximum margin wear width 26.

  A CNC image measuring machine was used to measure the hole diameter accuracy and straightness of the processed holes. As a method for measuring the hole diameter accuracy, the hole 34 to be measured was equally divided into 360 points by image processing, and the hole diameter accuracy was measured by measuring the hole diameter in an approximate circle at the 360 points. The measurement result of the hole diameter accuracy was the difference between the maximum hole diameter and the minimum hole diameter of the hole diameters measured from the 1st to 200th holes.

The straightness measurement method will be described with reference to FIGS. FIG. 14 is a schematic explanatory view showing drilling of the work material of the embodiment. FIG. 15 is an explanatory diagram showing a method for measuring straightness. As the measuring method, the origin 30 is the center of the approximate circle obtained at the time of measuring the hole diameter accuracy in the first hole 29 from FIG. Similarly, the center of the approximate circle of the 50th hole 32 was obtained, and a straight line connecting the origin 30 of the first hole 29 and the hole center 33 of the 50th hole was used as the reference axis 31.
The amount of deviation in the direction perpendicular to the reference axis 31 from the theoretical center position 38 (position at every hole interval of 0.27 mm) of the machining hole center 35 to be measured is defined as the X direction deviation amount 36. Measured, and the width of the maximum X-direction deviation amount and the left-side maximum X-direction deviation amount of the right and left X-direction deviation amounts 36 with respect to the theoretical center position 38 is measured in the X direction. The maximum deviation amount width was 39. Further, from the theoretical center position 38 (position at every hole interval of 0.27 mm), the deviation amount of each machining hole center in the direction of the reference axis 31 is measured as the Y-direction deviation quantity 37, and the machining hole center 35 is the theoretical center position. 38, the width between the upper Y-direction deviation maximum value and the lower Y-direction deviation maximum value of the upper and lower Y-direction deviation amounts 37 is defined as the Y-direction deviation maximum width 40. As the measurement results of straightness, the X direction displacement maximum width 39 and the Y direction displacement maximum width 40 when the displacement amounts on the front surface side and back surface side of the first to 200th holes were measured were measured results.

In Example 1, as the evaluation of the wear of the drill after drilling 200 holes and the hole diameter accuracy and straightness of the drilled hole, the maximum margin wear width 26 is measured for the drill wear, and the maximum margin wear width 26 is 5 μm or less. The diameter accuracy was 5 μm or less, and the straightness was 10 μm or less for both the maximum X direction displacement width 39 and the maximum Y displacement width 40.
Table 1 shows the specifications of each sample and the evaluation results of drill wear, hole diameter accuracy, and straightness.

As shown in Table 1, the first margin of the present invention is 3.5 μm with a maximum margin wear width 26 of 5 μm or less, and 4.8 μm with a hole diameter accuracy of 5 μm or less, and the straightness is the maximum width in the X direction deviation 39 and the maximum deviation in the Y direction. Both of them were good, with a large value of 40 μm or less. On the other hand, in the conventional example 1 which does not have the outer peripheral side cutting edge 9, the maximum margin wear width 26 exceeds 9.1 μm over 5 μm, the hole diameter accuracy greatly exceeds 9.4 μm and 5 μm, and the straightness is also in the X direction. The maximum deviation amount width 39 was 12 μm, and the maximum Y-direction deviation amount width 40 was 15 μm, both exceeding 10 μm, which is a straightness range in which both are satisfactory.
From the above results, it is preferable that the small diameter drill for machining machinable ceramics has the outer peripheral side cutting edge 9. When the outer peripheral side cutting edge 9 is not provided, the measurement result of the hole diameter accuracy, the X direction deviation amount It can be seen that the maximum width 39 and the maximum Y-direction deviation amount width 40 are increased. This is because the angle between the leading edge cutting edge 6 and the leading edge 12 in a drill having no outer peripheral cutting edge 9 is such that the outer peripheral cutting edge 9 and the leading edge 12 in a drill having the outer peripheral cutting edge 9 This is because the wear of the outer peripheral corner portion is likely to proceed with a smaller angle than the angle formed by.

(Example 2)
As invention examples 2 to 16 and comparative examples 1 to 6, except that the tip angle of the center side cutting edge was changed respectively, the tip angle of the outer peripheral side cutting edge was set to 80 with a two-edged drill having a margin 13. A tool having the same specifications as in Example 1 was prepared with a projected angle of 15 ° (0.018 mm) of the diameter D and a twist angle of 30 °, and the cutting test was performed. The tip angle of the center-side cutting edge is 140 °, 135 °, 130 °, 125 °, 120 ° in the inventive examples 2-6, the inventive examples 7-11 and the inventive examples 12-16, respectively. In 1, 2, Comparative Examples 3, 4 and Comparative Examples 5 and 6, they were set to 150 ° and 110 °, respectively. The cutting conditions and the work material were the same as in Example 1. Inventive Examples 2 to 6 and Comparative Examples 1 and 2 are made of cemented carbide as the base material of the drill, and DLC coating is applied to the cutting edge of the drill as a surface treatment. Inventive Examples 7 to 11 and In Comparative Examples 3 and 4, the base material of the drill was made of a cemented carbide, and as a surface treatment, a hard coating having a lowermost layer of TiAlN and an uppermost layer of TiSiN was applied to the cutting edge of the drill from the surface of the base material. . Invention Examples 12 to 16 and Comparative Examples 5 and 6 are made of cemented carbide as the base material of the drill, and as a surface treatment, a hard coating of TiAlN as the lowermost layer and AlCrSiN as the uppermost layer is cut from the surface of the base material. The blade was applied. In the notation in the table, the uppermost component is shown.
In Example 2, as the evaluation of the wear of the drill after drilling 200 holes and the hole diameter accuracy and straightness of the drill hole, the center wear maximum width 27 is measured for the drill wear, and the center maximum wear width 27 is 10 μm or less. The hole diameter accuracy is 5 μm or less and the straightness is 10 μm or less for both the maximum X-direction displacement amount width 39 and the maximum Y-direction displacement amount width 40. Table 2 shows the specifications of each sample and the evaluation results of wear, hole diameter accuracy, and straightness of the drill.

  From Table 2, Examples 2 to 16 of the present invention have a center side maximum wear width 27 of 10 μm or less, a hole diameter accuracy measurement result of 5 μm or less, an X-direction displacement maximum width 39 and a Y-direction displacement maximum width 40 of 10 μm or less. ,It was good. Further, in the case of DLC coating, Examples 3 to 5 of the present invention have a center side maximum wear width 27 of 8 μm or less, a hole diameter accuracy measurement result of 3.5 μm or less, a maximum X-direction displacement amount 39 and a maximum Y-direction displacement amount. Large 40 was 9 μm or less, which was particularly good. In the case where the hardest layer is TiAlN and the uppermost layer is TiSiN from the surface of the base material, Examples 8 to 10 of the present invention have a center side maximum wear width 27 of 8 μm or less, and the hole diameter accuracy measurement result is 4.5 μm. Hereinafter, the maximum X-direction deviation amount width 39 and the maximum Y-direction deviation amount width 40 were 9 μm or less, which was particularly favorable. In the case where the lowermost layer is TiAlN and the uppermost layer is AlCrSiN from the surface of the base material, the inventive examples 13 to 15 have a center side maximum wear width 27 of 8 μm or less, and the hole diameter accuracy measurement result is 5 μm or less, The maximum X-direction displacement amount width 39 and the Y-direction displacement amount maximum width 40 were 9 μm or less, which was particularly favorable.

  On the other hand, in Comparative Example 1, the center side maximum wear width 27 at the time of 200 hole cutting was 8.5 μm and 10 μm or less, but the hole diameter accuracy greatly exceeded 5.3 μm and 5 μm, and the straightness was also the amount of deviation in the X direction. The maximum width 39 and the maximum Y-direction displacement amount width 40 were 11 μm. In Comparative Example 2, the center side maximum wear width 27 was 6.3 μm and 10 μm or less at the time of 200-hole cutting, but the hole diameter accuracy exceeded 5.1 μm and 5 μm, and the straightness also had a maximum X-direction deviation amount width 39 of The maximum width 40 of 11 μm and Y-direction displacement amount exceeded 12 μm, which is 10 μm, which is a range of straightness that is good. Similarly, in Comparative Example 3, the center side maximum wear width 27 at the time of 200 hole cutting was 8.7 μm and 10 μm or less, but the hole diameter accuracy greatly exceeded 5.4 μm and 5 μm, and the straightness was also the amount of deviation in the X direction. The maximum width 39 was 12 μm, and the maximum Y direction displacement amount width 40 was 13 μm. In Comparative Example 4, the center-side maximum wear width 27 was 6.5 μm and 10 μm or less at the time of 200-hole cutting, but the hole diameter accuracy greatly exceeded 5.3 μm and 5 μm, and the straightness was also the maximum X-direction deviation amount width 39. In addition, the maximum width 40 in the Y-direction deviation amount was 12 μm, which exceeded 10 μm, which is a range of good straightness. In Comparative Example 5, the center side maximum wear width 27 at the time of 200 hole cutting was 8.7 μm and 10 μm or less, but the hole diameter accuracy greatly exceeded 5.5 μm and 5 μm, and the straightness was also the maximum width in the X direction deviation amount. 39 and the maximum width 40 in the Y direction deviation were 13 μm. In Comparative Example 6, the center side maximum wear width 27 was 6.8 μm and 10 μm or less at the time of 200-hole cutting, but the hole diameter accuracy greatly exceeded 5.4 μm and 5 μm, and the straightness was also the maximum X-direction deviation amount width 39. Was 12 μm, and the maximum width 40 in the Y direction deviation was 13 μm, which exceeded 10 μm, which is a straightness range that is good.

  From the above results, the tip angle of the center side cutting edge is preferably in the range of 120 ° to 140 °, and when the tip angle of the center side cutting edge is out of the above range, the hole diameter accuracy is deteriorated, It can be seen that the straightness maximum deviation amount width 39 and the maximum deviation amount width 40 in the Y direction increase. This indicates that the biting on the work material has become unstable and the straightness of the machined hole has deteriorated.

(Example 3)
As the inventive examples 17 to 24 and the comparative examples 7 to 10, except that the tip angle of the outer peripheral cutting edge was changed, respectively, the tip angle of the center cutting edge was set to 130 with a two-edged drill having a margin 13. A tool having the same specifications as in Example 1 was prepared and a cutting test was performed with the projection length of the outer peripheral cutting edge being constant at 15% (0.018 mm) of the diameter D and a twist angle of 30 °. The tip angle of the outer peripheral cutting edge is 70 °, 80 °, 90 °, 100 ° in Invention Examples 17 to 20 and Invention Examples 21 to 24, and in Comparative Examples 5 and 6 and Comparative Examples 7 and 8, respectively. The angles were 60 ° and 110 °. The cutting conditions and the work material were the same as in Example 1. Inventive Examples 17 to 20 and Comparative Examples 7 and 8 were made of cemented carbide as the base material of the drill, and DLC coating was applied to the cutting edge of the drill as a surface treatment. Inventive Examples 21 to 24 and In Comparative Examples 9 and 10, the base material of the cutting edge of the drill was CBN, and the surface treatment was untreated.
In Example 3, as the evaluation of the wear of the drill after drilling 200 holes, the hole diameter accuracy and straightness of the drilled hole, the maximum margin wear width 26 is measured for the drill wear, and the maximum margin wear width 26 is 5 μm or less. The diameter accuracy was 5 μm or less, and the straightness was 10 μm or less for both the maximum X direction displacement width 39 and the maximum Y displacement width 40. Table 3 shows the specifications of each sample and the evaluation results of drill wear, hole diameter accuracy, and straightness.

  According to Table 3, Examples 17 to 24 of the present invention have a maximum margin wear width 26 of 5 μm or less, a hole diameter accuracy of 5 μm or less, and straightness is 10 μm or less for both X-direction displacement maximum width 39 and Y-direction displacement maximum width 40. Met. Further, in the case where the base material of the drill is made of cemented carbide and DLC coating is applied, the maximum margin wear width 26 is 4 μm or less, the hole diameter accuracy is 3.5 μm or less, and the straightness is X Both the maximum direction deviation amount width 39 and the maximum Y direction deviation amount width 40 were 8 μm or less, which was particularly favorable. When the base material of the cutting edge of the drill is CBN and the surface treatment is untreated, the present invention example 22 and the present invention example 23 have a maximum margin wear width 26 of 3.5 μm or less and a hole diameter accuracy of 3.5 μm or less. The straightness was 9 μm or less for both the maximum X-direction displacement amount width 39 and the maximum Y-direction displacement amount width 40, which was particularly good.

  On the other hand, in Comparative Example 7 in which the tip angle of the outer peripheral cutting edge is 60 °, the maximum margin wear width 26 is 5.5 μm, the hole diameter accuracy is 5.2 μm, and the straightness is the X-direction displacement maximum width 39 is 13 μm. The maximum deviation amount width 40 was 12 μm, which exceeded 10 μm, which is a straightness range in which both are good. Further, in Comparative Example 8 in which the tip angle of the outer peripheral cutting edge is 110 °, the maximum margin wear width 26 exceeds 5.3 μm and 5 μm, the hole diameter accuracy is 5.1 μm, and the straightness is the maximum X-direction deviation amount width of 12 μm. The maximum width 40 in the Y-direction deviation amount was 11 μm, which exceeded 10 μm, which is the range of straightness where both are good. Similarly, in Comparative Example 9, the maximum margin wear width 26 is 5.2 μm, the hole diameter accuracy is 5.1 μm, the straightness is the X-direction displacement maximum width 39 is 11 μm, and the Y-direction displacement maximum width 40 is 12 μm. It exceeded 10 μm which is a range of straightness to be good. In Comparative Example 10, the maximum margin wear width 26 exceeds 5.1 μm and 5 μm, the hole diameter accuracy is 5.0 μm, and the straightness is 10 μm in the maximum X-direction displacement 39 and 11 μm in the maximum Y-direction displacement 40 μm. Only the maximum amount of deviation in the Y direction is 40, but it exceeded 10 μm, which is a range of straightness that is good.

  From the above results, the tip angle of the outer peripheral cutting edge is preferably in the range of 70 ° to 100 °. When the tip angle of the outer peripheral cutting edge is out of the above range, the hole diameter accuracy measurement result and It can be seen that the straight X-direction maximum deviation amount width 39 and the Y-direction maximum deviation amount width 40 increase. This is because when the tip angle of the outer peripheral cutting edge is small, the rigidity of the corner portion formed by the center cutting edge 8 and the outer peripheral cutting blade 9 is lowered, and when the tip angle of the outer peripheral cutting edge is large, the rigidity of the outer peripheral corner portion is reduced. Lower. This indicates that wear of the corners and outer peripheral corners is likely to proceed, the drill becomes unstable due to a decrease in guide properties, and the straightness of the processed hole is deteriorated.

Example 4
As the inventive examples 25 to 36 and the comparative examples 11 to 14, the tip angle of the center side cutting edge was changed with a double-edged drill having a margin 13 except that the projected length of the outer peripheral side cutting edge was changed. A tool having the same specifications as in Example 1 was prepared and a cutting test was performed with 130 °, the tip angle of the outer peripheral cutting edge being constant at 80 °, and the twist angle of 30 °. The projected length of the outer peripheral cutting edge is 5% (0.006 mm) of the diameter D, 10% (0.012 mm) of the diameter D, and 15 of the diameter D in the inventive examples 25 to 30 and the inventive examples 31 to 36. % (0.018 mm), 20% of diameter D (0.024 mm), 25% of diameter D (0.030 mm), 30% of diameter D (0.036 mm), Comparative Examples 11, 12 and Comparative Example 13 , 14, respectively, 2% (0.0024 mm) of the diameter D and 35% (0.042 mm) of the diameter D. The cutting conditions and the work material were the same as in Example 1. Inventive Examples 25 to 30 and Comparative Examples 11 and 12 were made of cemented carbide as the base material of the drill, and DLC coating was applied to the cutting edge of the drill as a surface treatment. Inventive Examples 31 to 36 and In Comparative Examples 13 and 14, the base material of the drill was cemented carbide, and the surface treatment was untreated.
In Example 4, as the evaluation of the wear of the drill after drilling 200 holes and the hole diameter accuracy and straightness of the drill hole, the wear of the drill is measured by the outer peripheral maximum wear width 28, and the outer peripheral maximum wear width 28 is 15 μm or less. The hole diameter accuracy is 5 μm or less and the straightness is 10 μm or less for both the maximum X-direction displacement amount width 39 and the maximum Y-direction displacement amount width 40. Table 4 shows the specifications of each sample and the evaluation results of wear, hole diameter accuracy, and straightness of the drill.

  From Table 4, the inventive examples 25 to 36 have an outer peripheral side maximum wear width 28 of 15 μm or less, a hole diameter accuracy of 5 μm or less, and straightness of both the X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40 of 10 μm or less. Met. Further, in the case of DLC coating, Examples 27 and 28 of the present invention were such that the maximum outer wear width 28 was 12 μm or less, the hole diameter accuracy was 3.5 μm or less, the straightness was the maximum X-direction displacement 39 and the Y-direction displacement. Both maximum widths 40 were particularly good at 8 μm or less. In the case of the non-processed example, the present invention examples 33 and 34 are such that the outer peripheral side maximum wear width 28 is 13 μm or less, the hole diameter accuracy is 4 μm or less, and the straightness is both the X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40. It was particularly good at 9 μm or less.

  On the other hand, in Comparative Example 11 in which the projected length of the outer peripheral cutting edge is 2% (0.0024 mm) of the diameter D, the outer peripheral maximum wear width 28 greatly exceeds 17.2 μm and 15 μm, and the hole diameter accuracy is 8.2 μm. The straightness was 14 μm for the maximum width 39 in the X-direction displacement and the maximum width 40 for the Y-direction displacement 13 μm, which exceeded 10 μm, which is a straightness range in which both are good. Further, in Comparative Example 12 in which the projection length 16 of the outer peripheral side cutting edge is 35% (0.042 mm) of the diameter D, the outer peripheral side maximum wear width 28 exceeds 16.4 μm and 15 μm, and the hole diameter accuracy is 5.3 μm, The straightness of the maximum deviation amount width 39 in the X direction and the maximum deviation amount width 40 in the Y direction was 11 μm, both exceeding 10 μm, which is a straightness range in which both are good. Similarly, in Comparative Example 13, the outer peripheral side maximum wear width 28 greatly exceeds 17.9 μm and 15 μm, the hole diameter accuracy is 8.6 μm, the straightness is X direction displacement maximum width 39 is 14 μm, and Y direction displacement maximum width 40. Was over 15 μm and 10 μm, which is a range of straightness in which both are good. Further, in Comparative Example 14, the outer peripheral side maximum wear width 28 exceeds 17.1 μm and 15 μm, the hole diameter accuracy is 6.1 μm, the straightness is X direction displacement maximum width 39 is 12 μm, and Y direction displacement maximum width 40 is 13 μm and both exceeded 10 μm, which is a range of straightness where both are good.

  From the above results, the projected length of the outer peripheral cutting edge is preferably in the range of 5% to 30% of the diameter D. When the projected length of the outer peripheral cutting edge is out of the above range, the hole diameter accuracy is It can be seen that the measurement results and the straight X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40 of the straightness increase. This indicates that when the projected length of the outer peripheral cutting edge is short, the effect of suppressing the wear of the outer peripheral corner portion decreases, and the wear of the outer peripheral corner portion proceeds. In addition, if the projected length of the outer peripheral cutting edge is long, the biting property of the tip portion is lowered, the drilling accuracy is deteriorated, the rigidity of the tip portion is lowered, and wear progresses quickly.

(Example 5)
As Examples 37-39 of the present invention, with a double-edged drill, the tip angle of the center-side cutting edge is 130 °, the twist angle is 30 °, the tip angle of the outer-side cutting edge is 80 °, and the projected length of the outer-side cutting edge Is set to 15% (0.018 mm) of the diameter D, the present invention example 37 includes only the margin 13, the circumferential length (margin width) of the margin portion is set to 20% of the diameter of the drill, and the present invention examples 38 and 39 Has a leading margin portion 22 and a rear margin portion 24, and a cylindrical portion is deleted between the leading margin portion and the rear margin portion. Further, a tool having the same specifications as in Example 1 was prepared, and a cutting test was performed, except that the circumferential length of each marginal portion of Examples 37 to 39 of the present invention was set to 20% of the diameter of the drill. The cutting conditions and the work material were the same as in Example 1. In Examples 37 and 38 of the present invention, the base material of the drill was a cemented carbide, and the cutting edge of the drill was subjected to DLC coating as a surface treatment. In Invention Example 39, the base material of the cutting edge of the drill was CBN, and the surface treatment was untreated.
In Example 5, as the evaluation of the wear of the drill after drilling 200 holes and the hole diameter accuracy and straightness of the drilled hole, the maximum wear width 28 on the outer peripheral side is 15 μm or less, the hole diameter accuracy is 5 μm or less, and the straightness However, both the X-direction deviation maximum width 39 and the Y-direction deviation maximum width 40 were 10 μm or less. Table 5 shows the specifications of each sample and the evaluation results of wear and hole diameter accuracy and straightness of the drill.

Table 5 shows that Examples 37 to 39 of the present invention have a maximum outer wear width 28 of 15 μm or less, a hole diameter accuracy of 5 μm or less, and straightness of both the X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40 of 10 μm or less. It was in the range of and was good. In Invention Example 37, the outer peripheral side maximum wear width 28 was 11.6 μm, the hole diameter accuracy was 3.2 μm, the straightness was X direction displacement maximum width 39 was 8 μm, and Y direction displacement maximum width 40 was 7 μm. In the inventive example 38, the outer peripheral side maximum wear width 28 is 10.8 μm, the hole diameter accuracy is 2.9 μm, the straightness is X direction displacement maximum width 39 is 6 μm, Y direction displacement maximum width 40 is 7 μm, leading margin The drill with the back and rear margins showed better hole diameter accuracy due to improved guideability and stable biting. In addition, the base material of the cutting edge of the drill is CBN, and the surface treatment of the present invention example 39 is an outer peripheral maximum wear width 28 of 9.7 μm, a hole diameter accuracy of 2.7 μm, and a straightness deviating in the X direction. The maximum amount width 39 was 6 μm, and the maximum Y direction displacement amount width 40 was 6 μm. The results were as good as in Example 38 of the present invention, in which the base material was cemented carbide and DLC coating was applied.
From the above results, it is shown that by providing the leading margin portion and the rear margin portion, the guide performance of the outer peripheral corner portion can be improved, and the drilling accuracy is further improved.

(Example 6)
As Examples 40 to 51 of the present invention, the leading margin portion 22 and the trailing margin portion 24 are provided except that the circumferential lengths (margin widths) of the leading margin portion and the trailing margin portion are respectively changed by a double-edged drill. The tip angle of the center side cutting edge is 130 °, the tip angle of the outer periphery side cutting edge is 80 °, the projected length of the outer periphery side cutting edge is 15% (0.018 mm) of the diameter D, and the helix angle is 30 °. A tool having the same specifications as in Example 1 was produced and a cutting test was performed. The circumferential lengths (margin widths) of the leading margin portion and the rear margin portion are the same. In the inventive examples 40 to 45 and the inventive examples 46 to 51, 12%, 15%, 20%, 25 of the diameter of the drill. %, 30%, and 35%. The cutting conditions and the work material were the same as in Example 1. Inventive Examples 40 to 45 are made of cemented carbide as the base material of the drill, and DLC coating is applied to the cutting edge of the drill as a surface treatment. Inventive Examples 46 to 51 are cutting edges of the drill. The base material was polycrystalline diamond, and the surface treatment was untreated.
In Example 6, as an evaluation of the hole diameter accuracy and straightness of 200 holes after processing 200 holes, the hole diameter accuracy is 5 μm or less, and the straightness is 10 μm or less for both the X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40. Was good. Table 6 shows the evaluation results of the specifications, hole diameter accuracy, and straightness of each sample.

From Table 6, when the base material of the drill is cemented carbide and DLC coating is applied, the inventive examples 41 to 44 have a hole diameter accuracy of 3 μm or less, and the straightness is the maximum X-direction deviation amount width 39 and the Y-direction. The deviation maximum width 40 was both in the range of 8 μm or less, which was good. Furthermore, Examples 42 and 43 of the present invention had particularly good hole diameter accuracy of 3 μm or less, straightness of X-direction displacement maximum width 39 and Y-direction displacement maximum width 40 of 7 μm or less. In Invention Example 40, the hole diameter accuracy was 3.3 μm, the straightness was X direction displacement maximum width 39 and Y direction displacement maximum width 40 was 8 μm. In Invention Example 45, the hole diameter accuracy was 3.0 μm, the straightness was 8 μm in the maximum X-direction deviation amount width 39 and 9 μm in the maximum Y-direction deviation amount width 40. When the base material of the cutting edge of the drill is made of polycrystalline diamond and the surface treatment is not treated, Examples 47 to 50 of the present invention have a hole diameter accuracy of 2 μm or less, and the straightness is a maximum deviation amount width in the X direction 39 and The maximum Y-direction deviation amount width 40 was in the range of 7 μm or less, which was good. Furthermore, Examples 48 and 49 of the present invention had particularly good hole diameter accuracy of 1.5 μm or less, and straightness of X direction displacement maximum width 39 and Y direction displacement maximum width 40 of 7 μm or less. In Invention Example 46, the hole diameter accuracy was 1.7 μm, the straightness was 7 μm in the maximum X-direction deviation amount width 39, and the maximum Y-direction deviation amount width 40 was 8 μm. In Invention Example 51, the hole diameter accuracy was 1.7 μm, and the straightness was such that the X-direction displacement maximum width 39 and the Y-direction displacement maximum width 40 were 8 μm.
From the above results, it is shown that stable machining accuracy can be obtained when the margin width is in the range of 15% to 30%.

(Example 7)
As Examples 52-56 of the present invention, except that the twist angle was changed, a double-edged drill having a leading margin portion 22 and a rear margin portion 24, the tip angle of the center-side cutting edge was 130 °, the outer peripheral side The tip angle of the cutting edge is 80 °, the projected length of the outer cutting edge is 15% (0.018mm) of the diameter D, and the circumferential length (margin width) of the leading and rear margins is the diameter of the drill. A tool having the same specifications as in Example 1 was made as 20%, and a cutting test was performed. The twist angle was set to 20 °, 25 °, 30 °, 35 °, and 40 ° in Examples 52 to 56 of the present invention. The cutting conditions and the work material were the same as in Example 1. In Examples 52 to 56 of the present invention, the base material of the drill was a cemented carbide, and the cutting edge of the drill was subjected to DLC coating as a surface treatment.
In Example 7, as the evaluation of drill wear after drilling 200 holes and the hole diameter accuracy and straightness of the drill hole, the center wear maximum width 27 is measured for drill wear, and the center maximum wear width 27 is 10 μm or less. The hole diameter accuracy was 5 μm or less, and the straightness was 10 μm or less for both the maximum X-direction displacement amount width 39 and the maximum Y-direction displacement amount width 40. Table 7 shows the specifications of each sample and the evaluation results of drill wear, hole diameter accuracy, and straightness.

From Table 7, the invention examples 53 to 55 have a hole diameter accuracy of 3.5 μm or less, a center-side maximum wear width 27 of 8 μm or less, and straightness of X-direction displacement maximum width 39 and Y-direction displacement maximum width 40. Both were in the range of 7 μm or less and were good. In Example 52 of the present invention, the hole diameter accuracy was 3.7 μm, the center-side maximum wear width 27 was 6.4 μm, the straightness was the maximum X-direction deviation amount width 39 was 8 μm, and the maximum Y-direction deviation amount width 40 was 7 μm. . This is because the twist angle is small, the sharpness of the cutting edge of the tip part and the chip dischargeability are reduced, leading to an increase in cutting resistance, and the biting property becomes unstable and the straightness of the machined hole is deteriorated. Show. In Inventive Example 56, the hole diameter accuracy is 3.6 μm, the center-side maximum wear width 27 is 8.3 μm, the straightness is X-direction displacement maximum width 39 is 7 μm, and Y-direction displacement maximum width 40 is 8 μm. there were. This is because when the helix angle is large, the rigidity of the center-side cutting edge decreases and it becomes difficult to maintain the sharpness of the cutting edge. It is thought that the straightness of was deteriorated.
From the above results, it is shown that stable machining accuracy can be obtained when the twist angle is in the range of 25 ° to 35 °.

  In the small diameter drill for machining machinable ceramics according to the present invention, the tip end cutting edge of the small diameter drill is composed of a center side cutting edge and an outer peripheral side cutting edge, and the tip end cutting edge of the drill is optimized by shape and material, By suppressing the progress of wear, the hole accuracy of the workpiece can be maintained with high accuracy while maintaining the sharpness of the cutting edge of the tip, and breakage accidents can also be prevented. The specific application field is suitable for drilling of machinable ceramics used in insulators, protective tubes, substrates, nozzles for chemical devices, probe cards for inspection processes of semiconductor devices, and the like.

DESCRIPTION OF SYMBOLS 1 Drill part 2 Neck part 3 Neck length 4 Shank part 5 Tip part 6 Tip part cutting edge 7 Groove 8 Center side cutting edge 9 Outer peripheral side cutting edge 10 Outer periphery corner part 11 Corner | angular part 12 Leading edge 13 Margin 14 Center side cutting edge Tip angle 15 of the outer peripheral cutting edge 16 Projected length 17 Flank wear 18 Margin wear 19 Chisel edge 20 Chisel edge length 21 Projected cutting edge length 22 Leading margin portion 23 Cylindrical deletion portion 24 Rear margin portion 25 Maximum Wear width 26 Maximum margin wear width 27 Center side maximum wear width 28 Outer peripheral side maximum wear width 29 1st hole 30 Origin 31 Reference shaft 32 50th hole 33 50th hole center 34 Measurement hole 35 to be measured Center of machining hole 36 X direction deviation 37 Y direction deviation 38 Theoretical center position 39 X direction deviation maximum width 40 Y direction deviation maximum width 41 Chip D diameter of Ceramics 42 ceramics grains 43 ceramic grain boundaries 44 tip cutting edge of the flank face 45 tip cutting edge of the rake face 46 sharpness is lost tip cutting edge 47 Machinable Ceramics

Claims (4)

  A small-diameter drill that drills a small diameter of 2 mm or less in machinable ceramics, and the tip cutting edge of the small-diameter drill is composed of a center-side cutting edge and an outer peripheral-side cutting edge, and the axis of the small-diameter drill The angle of the tip angle in the rotation trajectory seen from the vertical direction is such that the tip angle of the center side cutting edge is 120 ° to 140 °, and the tip angle of the outer peripheral side cutting edge is 70 ° to 100 °, A small diameter drill for machining ceramics, characterized in that the projected length of the outer peripheral cutting edge in the drill radial direction is in the range of 5% to 30% of the diameter of the small diameter drill.   A small-diameter drill that drills a small diameter of 2 mm or less in machinable ceramics, and the tip cutting edge of the small-diameter drill is composed of a center-side cutting edge and an outer peripheral-side cutting edge, and the axis of the small-diameter drill The angle of the tip angle in the rotation trajectory seen from the vertical direction is such that the tip angle of the center side cutting edge is 120 ° to 140 °, and the tip angle of the outer peripheral side cutting edge is 70 ° to 100 °, The projected length of the outer peripheral side cutting edge in the radial direction of the drill is in the range of 5% to 30% of the diameter of the small diameter drill, the twist angle of the small diameter drill is 25 ° to 35 °, and the leading edge of the small diameter drill is It has a connected leading margin part and a rear margin part connected to the heel, and the circumferential length of the margin part when viewed in a cross section perpendicular to the tool axis other than the cutting edge of the tip part is that of the small diameter drill. 15% to 30% of the diameter A circumference, machinable ceramics machining diameter drill, characterized in that between the leading margin portion and the rear margin has a shape that a cylindrical portion is removed.   3. The small diameter drill for machining machinable ceramics according to claim 1 or 2, wherein the base material of the drill is a cemented carbide and is formed by a tip cutting edge coated with a hard film.   The machinable ceramic processing according to claim 1 or 2, wherein at least the base material of the cutting edge of the drill is made of either cubic boron nitride (CBN) or polycrystalline diamond. For small diameter drills.

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