TWI438047B - Drilling tools - Google Patents

Description

Drilling tool

The present invention relates to a drilling tool.

For the drilling of a printed circuit board (PCB), a drill having a blade portion A having a blade portion C and a shank portion B as shown in Fig. 1 is used. The size of the drill bit is various depending on the application, but most of the drill bits are used with a diameter of 0.7 mm or less.

Specifically, as shown in FIG. 2, in the blade portion C, a spiral chip discharge groove 22 is formed on the outer periphery of the body 20 from the tip end of the drill toward the base end side, and the inclined surface of the chip discharge groove 22 is provided at the front end. The intersecting ridge portion of the first flank surface is formed with a cutting edge 21 (see, for example, Patent Documents 1 and 2). In addition, in the figure, the figure 25 is a second flank face which is connected to the rear side of the first flank face 24 in the tool rotation direction, d' is the tool diameter, and 1' is the groove length of the chip discharge groove, α' It is a spiral angle.

In addition, a film having abrasion resistance and weldability suitable for non-ferrous materials such as aluminum alloy, titanium, magnesium, and copper is practical for an amorphous carbon film, and is used as a drill or A coating of a cutting tool such as a milling cutter or a blade-replacement type cutter (see, for example, Patent Document 3).

However, the PCB is composed of copper and a glass cloth impregnated with resin as an insulating layer. In recent years, in order to further improve the reliability of the PCB, it is necessary to improve heat resistance, strengthen bending strength, and reduce thermal expansion. Most of them are mechanical strengths for improving the glass cloth or resin used for the construction of the PCB, thereby ensuring high reliability.

However, when considering that the PCB is used as a material to be drilled, the PCB constructed as described above is relatively easy to promote bit wear due to an increase in mechanical strength, and is liable to cause bit breakage or excessive wear in the drilling process. The quality of the hole causing the hole position accuracy or the like is deteriorated.

On the other hand, as the density of the PCB is increased, the required aperture (diameter of the drill) is reduced in diameter year by year, and the drilling process having a diameter of 0.4 mm or less is gradually increased.

In addition, in the drilling processing step, in consideration of the processing efficiency, generally, a plurality of PCBs of the same specification are overlapped and then drilled. Specifically, in general, an aluminum plate which is an abutting plate for improving the centering property of the drill or an aluminum plate with a resin-coated resin whose surface is designed to improve the centering property of the drill is placed on the PCB, and then the drilling process is performed. The aluminum plate with resin is more effective than the aluminum plate for improving the centering property, and in order to contribute to the improvement of the bit breakage, in particular, drilling using a small diameter drill having a diameter of 0.4 mm or less is common.

In recent years, in order to reduce the processing cost, the small-diameter drill for PCB used for the processing of the PCB having poor workability is required to be drilled under the condition that the number of overlapping PCBs is increased and the drill is not broken. It also extends the life of the drill bit.

However, when the aluminum plate with the resin is used as the abutting plate for drilling, when the aluminum plate is used for drilling, the scraps of the chips are clearly generated near the base end portion of the blade portion C of the drill. The higher the viscosity of the resin or the thicker the thickness of the resin to be coated, the higher the tendency of the above-mentioned chips to wrap the debris, so that it is difficult to achieve the above requirements.

The reason is that the chips generated during the drilling process are usually sucked by the chip suction function attached to the drilling machine, and then carried out to the designated garbage bin, but when the aluminum plate with the resin is used, it is formed by the heat of cutting during the drilling process. The softened resin is discharged together with the chips by the guiding of the chip discharge groove, resulting in the adhesion of the drill bit and the chip near the base end portion of the blade portion C. Continuously repeating the drilling process is bound to cause the chip to be attached. The amount of scrap is increased.

The amount of debris attached to the chip is also changed by the number of rotations of the drill during the drilling process or the machining conditions of the feed speed or the material of the PCB, but the obvious chip is produced as shown in Fig. 3(a). The coil is attached with debris, because the chip is attached to the chip during the continuous drilling process due to vibration of a certain factor, etc., causing the chip (chip block) to leave the drill bit, even if the drill has the above suction function but the chip block It is also not sucked so that the chip pieces fall on the abutment plate, and then the drill bit being drilled may cause the hole position accuracy to deteriorate or the bit to be broken due to the interference of the falling chip block. In addition, the chip block dropped on the abutting plate is exemplified in the third (b).

Further, for example, Patent Document 4 discloses a PCB drill having two cutting and two chip discharge grooves, and discloses a technique in which each of the chip discharge grooves is merged at a predetermined amount from the front end. The position behind the merging point is one groove, thereby increasing the rigidity, but does not mention the winding of the chips, and thus the above requirements cannot be satisfied.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 56-39807

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2006-55915

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2001-341021

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2007-307642

The present invention has been made in view of the above circumstances, and it is an object of the invention to provide a small-diameter drill having a diameter of 0.7 mm or less, particularly 0.4 mm or less, which can be stabilized even when the diameter is 0.7 mm or less, particularly 0.4 mm or less. Drilling and drilling tools that are extremely practical.

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

In the drilling tool according to the present invention, one or a plurality of cutting edges are provided at the front end of the tool body 1. On the periphery of the tool body 1, a plurality of spiral chip discharge grooves are provided from the front end of the tool toward the base end side, and the plurality of chips are discharged. The groove includes at least one main groove 2a and one sub-groove 2b, and one or a plurality of sub-grooves 2b are formed in the middle of the main groove 2a to form a merged flow, which is characterized by the main groove 2a and The merging portion 6 of the sub-groove 2b is provided with a step 7.

Further, the boring tool according to the first aspect of the invention is characterized in that the step 7 is a groove depth of the main groove 2a and the sub-groove 2b. Differences are formed.

Further, the drilling tool according to the first aspect of the invention is characterized in that the step 7 is 2 μm or more.

Further, the drilling tool according to the second aspect of the invention is characterized in that the step 7 is 2 μm or more.

Further, the drilling tool according to the third aspect of the invention is characterized in that the step 7 is 70% or less of the groove depth of the main groove 2a.

Further, the drilling tool according to the fourth aspect of the invention is characterized in that the step 7 is 70% or less of the groove depth of the main groove 2a.

Further, the boring tool according to any one of the first to sixth aspects of the present invention is characterized in that the main groove 2a or the sub-groove 2b is spiraled. The corners are formed differently on the tool leading end side and the tool base end side, whereby the main groove 2a and the sub-groove 2b are joined together.

The boring tool according to any one of claims 1 to 6, wherein the merging portion 6 is provided at the front end of the tool and has the main groove. The groove 2a has a groove length of 50% or less.

Further, the boring tool according to the seventh aspect of the invention is characterized in that the merging portion 6 is disposed at a groove length of the main groove 2a from the front end of the tool. Below 50% of the location.

Further, the drilling tool according to the invention of claim 8 is characterized in that the drilling tool is coated with a lubricating film.

Further, the boring tool according to the invention of claim 9 is characterized in that the boring tool according to claim 9 is coated with a lubricating film.

Further, the drilling tool according to the invention of claim 10 is characterized in that the lubricating film is made of an amorphous carbon film.

Further, the drilling tool according to the invention of claim 11 is characterized in that the lubricating film is made of an amorphous carbon film.

Further, the drilling tool according to the invention of claim 12 is characterized in that the tool diameter is 0.7 mm or less.

Further, the drilling tool according to the invention of claim 13 is characterized in that the tool diameter is 0.7 mm or less.

Further, the drilling tool according to the invention of claim 12 is characterized in that the tool diameter is 0.4 mm or less.

Further, the drilling tool according to the invention of claim 13 is characterized in that the tool diameter is 0.4 mm or less.

Since the present invention has the above-described configuration, it is possible to prevent the chip from being wound up, and even a small-diameter drill having a diameter of 0.7 mm or less and particularly 0.4 mm or less can be used for a stable drilling process with a long breakage life. Excellent drilling tool.

[Best Embodiment of the Invention]

Hereinafter, the best mode for carrying out the invention will be briefly described on the basis of the drawings.

When the chips generated at the front end portion of the tool are discharged along the chip discharge groove during the drilling process, the chips collide with each other at the joining portion 6 of the main groove 2a and the sub groove b, and further, the main groove 2a is added. The step 7 of the merging portion 6 of the sub-grooves b makes it difficult for the chips to be converge in the merging portion 6 (toward the tool diameter direction) and is difficult to reach the tool base end portion. Therefore, it is possible to prevent the chip from being attached to the tool base end portion.

[Examples]

Embodiments specific to the present invention will be described with reference to Figs. 4 to 10 .

In the drilling tool of this embodiment, one or a plurality of cutting edges are provided at the front end of the tool body 1. On the periphery of the tool body 1, a plurality of spiral chip discharge grooves are provided from the front end of the tool toward the base end side, and the plurality of chips are provided. The discharge groove is composed of at least one main groove 2a and one sub-groove 2b, and one or a plurality of sub-grooves 2b are formed in the middle of the main groove 2a to form a merged flow, which is characterized in that the main groove is The merging portion 6 of 2a and the sub-groove 2b is provided with a step difference 7.

Specifically, the drill of the present embodiment has a tool diameter of 0.075 mm, and is provided with a main groove 2a having a groove length of 1 and a sub groove 2b which merges with the main groove 2a, and a main groove 2b. The intersecting ridge portions of the inclined surface of the groove 2a and the auxiliary groove 2b and the front end flank surface (first flank surface) of the tool body 1 are respectively provided with cutting edges integral with the tool body 1, and the drill is used in Drilling of PCB.

The drilling process of the PCB is, for example, as shown in the following experimental example, in which a hard-to-cut material, that is, a PCB for a semiconductor package (a substrate: a thickness of 0.1 mm/a Cu layer on the front and back sides) is superposed on each other, and is placed thereon. A resin-coated aluminum plate having a thickness of 0.1 mm is used as a contact plate, and in order to enable through-hole processing, a paper phenol material having a thickness of 1.5 mm which is generally used as a discard material is disposed on the lower surface of the PCB, and drilling is performed in this state. . The thickness of the abutment plate is appropriately set in the range of 0.04 to 1.0 mm. Further, the thickness of the Cu layer of the PCB having a thickness of about 0.1 mm is usually about 2 to 80 μm.

Further, in the present embodiment, a drill (two blades) having two cutting edges and two chip discharge grooves (one main groove 2a and one sub groove 2b) will be described, but the form is only The same is true for a one-blade drill having a cutting edge on the main groove side or a drill having three blades or more (for example, a drill having one main groove and two sub-grooves).

More specifically, in the case of the above condition, since the chip is likely to be wound, the tool shown in Fig. 2 is improved in order to solve the problem, and the improved structure is the tool body. 1 coating an amorphous carbon film, providing a first spiral region 3 having a first helix angle α ₁ in the main groove 2a of the drill bit and a tool base end side connected to the first spiral region 3 having a first helix angle α _{1 is} further large in the second spiral region 4 of the second helix angle α ₂ (the helix angle α ₃ of the sub-groove 2b is constant), and the main groove 2a and the sub-groove 2b are merged [refer to Figs. 4 and 5). In addition, Fig. 5(a) to Fig. 5(c) are diagrams of the front end portion of Fig. 4 as seen from various rotation phases. ].

Alternatively, the first spiral region and the second spiral region may be disposed not on the main trench 2a but in the sub trench 2b or on both the main trench 2a and the sub trench 2b. Further, it may be configured such that the spiral angle of the main groove 2a or the sub-groove 2b is gradually changed (curved) toward the base end side of the tool to form a merged flow, and it may be configured to change the main body at the beginning. The helix angles of the grooves 2a and the sub-grooves 2b cause the formation to merge.

Further, the step 7 of the merging portion 6 of the main groove 2a and the sub-groove 2b is formed by the difference in the groove depth of the main groove 2a and the sub-groove 2b for the purpose of the scattering effect of the chips, and thus the main groove 2 The groove depth of the sub-groove 2b and the groove depth of the sub-groove 2b are not limited. Specifically, when the groove depth of the main groove 2a (the depth of the main groove, the deepest distance in the tool radius direction of the main groove 2a) X is formed to be the groove depth of the sub groove 2b (the sub groove depth, the sub When the depth of the tool 2 in the radial direction of the groove 2b is deep, the chips which are to be joined at the merging portion 6 collide with each other and cannot merge, and the chips are scattered in the radial direction. Further, when the groove depth Y of the sub-groove 2b is formed deeper than the groove depth X of the main groove 2a to thereby form the step 7, the sub-groove 2b disappears at the merging portion 6 to cause the chip to collide with the main groove. In the wall of 2a, since the discharge space disappears, the chips will scatter in the radial direction.

Further, in the present embodiment, in order to avoid the risk of breakage caused by the grindstones described in detail below, the groove depth Y of the sub-groove 2b is formed to be shallower than the groove depth X of the main groove 2a. A step 7 is formed [refer to Fig. 6 showing a sectional view of Fig. 5(b) AA].

The step difference 7 is preferably 2 μm or more and 70% or less of the groove depth X of the main groove 2a. When the above-mentioned hysteresis 7 is less than 2 μm, the possibility of producing a grindstone mark on the main groove 2a is high, and the stress is concentrated on the grindstone mark which may become a starting point of the breakage, so that the possibility of breakage becomes high. In addition, the rigidity of the tool will also affect the accuracy of the hole position. In the first embodiment, the step 7 is set to 3 μm (37% of the groove depth X of the main trench 2a), and in the second embodiment, the step 7 is set to 5.2 μm (the groove depth X of the main trench 2a) 64%). Further, when the step 7 is larger than 70% of the groove depth X of the main groove 2a, the sub-groove 2b becomes too shallow, which may hinder the chip discharge with the minimum demand, and thus is not preferable (Fig. 7) Although not shown in the figure, the experimental result of the drill is the break when the step 7 is set to 70% of the groove depth X of the main groove 2a.

In the present application, the joining start point of the main groove 2a and the sub-groove 2b (the position having an O distance from the tool tip) to the joining end point (the position having a P distance from the tool tip) is merged. Department 6. Further, the measurement position of the step 7 in the present application is a position at which the center point of the joining start point and the joining end point of the main groove 2a and the sub-groove 2b is merged (connected).

Further, the position of the base end of the merging portion 6 (the end point of the joining of the main groove 2a and the sub groove 2b) is set to be 50% or less of the groove length 1 of the main groove 2a at the tip end of the tool. The respective helix angles and the connection positions of the first spiral region 3 and the second spiral region 4 are set under the conditions. In this form, the groove is increased in rigidity in a region that is more than 50% of the groove length from the tip end of the tool, and the hole position accuracy is improved. When the merging portion 6 is disposed at a position rearward (base end side) of 50% longer than the groove of the main groove 2a from the tip end of the tool, the groove volume becomes large, resulting in deterioration of the rigidity of the tool, and the hole position The possibility of deterioration in accuracy or loss of damage is increased. In the present embodiment, the position of the base end of the merging portion 6 is set to be located at a position 32% longer than the groove length of the tool tip.

Next, each part will be specifically described.

The drill bit is made of a superhard alloy formed of a hard particle containing WC as a main component and a binder composed mainly of Co. The average particle diameter of the WC particle using the superhard alloy is 0.1 μm to 2 μm. Further, the Co content is a superalloy base material having a weight % of 5 to 15%, and at least the amorphous carbon film is coated on the chip discharge groove of the tool body 1. Since the amorphous carbon film is hard, it is possible to suppress wear of the tool, and it has high lubricity, and it is easy to discharge the chips along the chip discharge groove toward the proximal end side of the tool body 1 to prevent clogging of the chips, so that the chips are less likely to be broken.

Further, in the present embodiment, the lubricating film is an amorphous carbon film formed of a high hardness amorphous carbon (DLC) having a Vickers hardness of 3,000 or more mainly composed of carbon atoms, but as long as Vic When the hardness is 2,000 or more, a film formed by a mixture of a relatively low hardness amorphous carbon (DLC) and another substance (for example, a metal) may be used, and another lubricating film such as a chromium nitride may be used.

Further, in the present embodiment, the amorphous carbon film is formed directly above the substrate, but may be formed, for example, directly above the substrate, and formed from the group 4a, 5a, 6a and Si of the periodic table. a thin film layer (base film) having a thickness of 200 nm or less and 1 nm or more, which is formed of a metal or a semimetal formed of one or more kinds of elements, and then the amorphous carbon is formed on the lower film layer. Membrane. In addition, the lower film layer is not limited to the above-described configuration, and one or two or more elements selected from Groups 4a, 5a, and 6a of the periodic table and Si may be used, and one or more elements selected from nitrogen and carbon may be used. The underlying film layer composed of the compound.

Further, in the present embodiment, the film formation apparatus using the arc ion plating method is used for film formation of the amorphous carbon film or the base film, but PVD formation such as sputtering method or laser ablation coating method may be used. Membrane device.

The first helix angle α ₁ is set at 30° to 45°. The helix angle affects the discharge of the chips and the rigidity of the drill bit. When the helix angle is formed to be large, the chip discharge property can be improved, but conversely, it is related to the decrease in rigidity. When it is configured in the form of a small-diameter drill, the fracture resistance of the drill is not only affected by the rigidity but also susceptible to the chip discharge property. Therefore, the helix angle of the drill having a diameter of 0.7 mm or less, particularly 0.4 mm or less, is preferably set to be larger, and is generally set at 30 to 45 degrees.

In order to further improve the fracture resistance of the drill bit, the inventors of the present invention conducted a repeated study on the rigidity of the drill bit and the spiral angle of the opposite characteristic of the chip discharge property, and found that the aluminum plate was placed on the object to be cut. When a resin aluminum plate is attached, or when there is a large amount of copper foil in the inner and outer layers of the workpiece, if the helix angle is less than 30°, the chip discharge property is deteriorated, and the drill is easily broken. If the helix angle is set to When the ratio is 45°, the increase in chip discharge is caused by the increase in the fracture resistance, but the chip of aluminum or copper is formed to be excessively thin and long, so that the base end of the tool body 1 (chip discharge groove) Part) It is easy to produce chips with attached debris.

In addition, the inventors of the present invention have also found that when a drill having a lubricating film such as an amorphous carbon film is coated, it has an effect of improving fracture resistance as compared with a drill which is not coated. The debris of the chip is obviously generated, and the debris (chip block) of the chip is dropped on the abutting plate, and the falling chip block sometimes interferes with the bit to cause the hole position accuracy to be deteriorated or the drill bit is caused. The fracture life is unstable and causes early damage.

When these factors are taken into consideration, the cutting edge portion of the tip end of the tool for cutting execution is an angle (30°) at a helix angle (the first helix angle α ₁ and the helix angle α _{3 of the} subgroove 2b) is 45° or less. It is preferable to use ~45°) to ensure the chip discharge property while making the generated chips shorter without chipping. Further, the helix angle (the first helix angle α ₁ and the helix angle α _{3 of the} sub-groove 2b) is more preferably set to 30° to 45°. In the present embodiment, the first helix angle α _{1 of the} main groove 2a and the helix angle α ₃ of the sub-groove 2b are set to 38°.

The second helix angle α ₂ is an angle set to be larger than the first helix angle α _{1 by} 5° or more, and is set at 35° to 65°. By forming the second helix angle α ₂ larger than the first helix angle α ₁ , the chip discharge performance on the proximal end side of the chip discharge groove can be increased, and the fracture resistance can be improved.

Further, the effect of coating the amorphous carbon film (lubricating film) is such that the chip discharge direction which is smoothly discharged along the chip discharge groove of the first spiral region 3 set to the first helix angle α ₁ can be forcibly changed. The chip discharge groove which is set to the second spiral region 4 of the second helix angle α ₂ is used to scatter the chips to the outside of the tool body 1 by the synergistic effect with the centrifugal force, and from this point of view, it is also a roll capable of preventing chips. The damage life is longer and stable.

When the angular difference between the first helix angle α ₁ and the second helix angle α ₂ is less than 5°, the effect of forcibly changing the direction in which the chips are discharged is lowered, and the chips caused by the change in the helix angle are scattered toward the outside of the tool body 1 . The effect will be reduced. Further, when the second helix angle α _{2 is} larger than the first helix angle α ₁ , the rigidity of the base end portion of the tool body 1 is lowered, resulting in deterioration of the fracture resistance.

Further, the angle difference between the first helix angle α ₁ and the second helix angle α ₂ is set to 10° or more, and the total angle of the first helix angle α ₁ and the second helix angle α ₂ is set at 45°. ~60° is better. In the present embodiment, the second helix angle α ₂ is set to 55° which is an angular difference of 17° from the first helix angle α ₁ (38°).

In addition, in order to discharge the chips well, it is preferable to change the second helix angle α ₂ as far as possible on the tool front end side, but generally, the drill bit for the PCB is used after re-polishing the front end after use (re-grinding). Therefore, when the amount of polishing is taken into consideration, the connecting portion 5 of the first spiral region 3 and the second spiral region 4 is set to be 0.2 mm or more from the tip end of the tool and 50% or less of the groove length 1 of the chip discharge groove. The location is better.

In the present embodiment, the change point (joining portion 5) of the first helix angle α ₁ and the second helix angle α ₂ is set at a position (C ₁ ) which is 20.8% from the tip end of the tool.

The present invention is directed to a drill which is coated with a non-ferrous-based material such as a PCB and is coated with a lubricating film such as an amorphous carbon film. However, the substrate is a hard particle containing WC as a main component. A superhard alloy formed of a composite material containing Co as a main component is preferably a material having a balanced hardness and toughness.

If the average particle diameter of the WC particles is too small, it is difficult to uniformly disperse the WC particles in the binder, which tends to cause a decrease in the folding strength of the cemented carbide. On the other hand, if the average particle diameter of the WC particles is too large, the hardness of the superhard alloy may decrease. In addition, if the Co content is too small, the flexural strength of the superhard alloy is lowered, and if the Co content is too large, the hardness of the superhard alloy is lowered. Therefore, the base material is preferably a superhard alloy having an average particle diameter of WC particles of 0.1 μm to 2 μm and a Co content of 5 to 15% by weight.

In addition, it is necessary to further improve the tightness of the substrate and the amorphous carbon film in order to perform stable drilling without peeling off the film for difficult-to-cut materials such as PCB. A metal or a semimetal formed by selecting one or more elements of elements 4a, 5a, and 6a of the periodic table such as Ti, Cr, or Ta, and Si as a base film is formed directly above the substrate, and then The amorphous carbon film is formed on the film, whereby the substrate and the amorphous carbon film can be made more compact. In addition, one or more elements selected from Groups 4a, 5a, 6a and Si of the periodic table and compounds in which one or more elements selected from nitrogen and carbon are selected as a base film can be formed on the substrate. Directly above.

The film formation of the under film is for the purpose of improving the adhesion between the substrate and the amorphous carbon film. If it is too thick, it is meaningless. Therefore, it is preferably a film thickness of 200 nm or less and 1 nm or more.

In the present embodiment, as described above, at least the lubricating film such as the amorphous carbon film is coated on the chip discharge groove to increase the surface lubricity of the chip discharge groove, so that the chips generated by the drilling process are diced. When the cutting angle is increased, the chips become thinner and longer, and the surface lubricity is high, so that the chips can be easily discharged to the base end portion of the tool body 1 (the blade portion C of the first drawing) along the chip discharge groove, and relatively Prevent chip clogging, making it difficult to break the profit.

Further, since the spiral angles α ₁ and α _{3 of the} tip end of the tool are formed to be small, it is possible to prevent the chips from becoming too thin and long, and to make the chips thick and short, which is difficult to be attached to the tool body 1 and, in addition, The blade angle of the cutting edge is ensured to be large, so that it is possible to prevent the cutting edge from being broken and the hole position accuracy can be improved, and the drill bit is not easily broken.

In addition, since the helix angle α ₂ on the proximal end side of the tool is formed to be large, the chip discharge property on the proximal end side of the chip discharge groove 2 can be improved, and the fracture resistance can be improved, and the coating can be made amorphous. The effect of the carbonaceous film (lubricating film) is that the direction in which the chips are discharged smoothly along the chip discharge groove can be forcibly changed, and the effect of multiplying the centrifugal force causes the chips to scatter outside the tool body 1 to prevent chipping. The coil attachment makes the breakage life longer and enables stable drilling.

Further, when the chips generated at the front end portion of the tool are discharged along the chip discharge groove during the drilling process, the chips collide with each other at the joining portion 6 of the main groove 2a and the sub groove 2b, and the main groove is added. The step 7 of the merging portion 6 between the 2a and the sub-groove b is such that the chips are forced to converge in the tool-diameter portion 6 (in the tool diameter direction) and it is difficult to reach the end portion of the tool base. Therefore, it is possible to prevent the chip from being attached to the end portion of the tool base. .

Based on this, the drilling tool of the present embodiment is difficult to be broken even when the aluminum plate with the resin is used as the abutting plate, and the chip discharge property is excellent, and the chip winding can be prevented, even if the diameter is 0.7 mm. In the following, in particular, a small-diameter drill having a diameter of 0.4 mm or less can be used as a drilling tool which is excellent in the fracture life and has excellent hole position accuracy, and can achieve stable drilling processing and is extremely practical.

Next, an experimental example will be described based on the effects of the present embodiment.

Fig. 7 is a graph showing an experimental result of evaluating the accuracy of the hole position when the drill is drilled using the groove depth X in which the main groove 2a is constant and the groove depth Y of the sub groove 2b is changed. The drill used in this experiment has a tool diameter of 0.075 mm and a groove length of 1 (of the main groove) of 1.2 mm. Comparative Example 1 is a drill bit of the previous two blade 2 groove shapes (the spiral angles of the two chip discharge grooves are both In the case of Comparative Example 2 (in the case where the merging portion of the main groove and the sub-groove has no step), and in the first and second embodiments, the helix angles α ₁ and α ₂ of the main groove 2a are 38°, 55°, the helix angle α ₃ of the sub-groove 2b is 38°, and the other is: the core thickness, the front end angle, and the like, and the specifications other than the groove depth Y of the sub-groove 2b are the same value. Further, the groove depths Y of the sub-grooves 2b of the first embodiment and the second embodiment are set to be shallower than the groove depth X of the main grooves 2a. Further, the tool body 1 is covered with an amorphous carbon film (DLC).

In this experiment, a hard-to-cut material, that is, a PCB for semiconductor packaging (substrate: a thickness of 0.1 mm / a Cu layer on both sides of the front and back sides) is superposed, and then a resin-attached aluminum having a thickness of 0.1 mm is placed thereon as an abutting plate. In order to be able to perform through-hole processing, a paper phenol material having a thickness of 1.5 mm which is generally used is disposed as a discarding plate on the lower surface of the above-mentioned PCB. In addition, the number of rotations of the drill (mandrel) was 300 krpm, the feed speed was 1.8 m/min, and the number of strokes was set to 10,000 strokes.

According to Fig. 7 and Fig. 8, it was confirmed that Comparative Example 1 produced a significant chip wrap in the latter half of the experiment, and there was a rubbing trace attached to the entry side of the abutting plate and a drop of the attached chip. Then, it was confirmed that the unevenness was formed on the entry side surface of the contact plate, and the adhesion of the drill was deteriorated, which caused the drill to be easily bent. On the other hand, according to Fig. 7 and Fig. 10, it was confirmed that in the first embodiment and the second embodiment, since the groove is one on the tool base end side, the rigidity of the tool base end side is high, and the above problem does not occur. The drill bit is not easily bent, and it is confirmed that the hole position accuracy is improved when the main groove and the sub groove depth difference (step difference) / the main groove depth is 70% or less. In addition, it was also confirmed that the hole position accuracy was deteriorated when the main groove and the sub groove depth difference (step difference)/main groove depth exceeded 70%. Also. According to the eighth to tenth drawings, it was confirmed that the amount of the chip winding amount was reduced in the order of the comparative example 1, the comparative example 2, and the example, and the amount of the chip winding amount of the second embodiment was confirmed and implemented. Example 1 is equivalent. Therefore, it was confirmed that the curling property can be improved as compared with the prior drill bit according to the present embodiment.

1. . . Tool body

2a. . . Main groove

2b. . . Secondary groove

6. . . Confluence

7. . . Step difference

1. . . Long groove

Fig. 1 is a schematic side view showing a drill bit for a PCB.

Fig. 2 is an enlarged schematic explanatory view of a prior art.

Fig. 3(a) is a photograph showing an example of the crumb of the chip near the base end portion of the drill blade portion C, and Fig. 3(b) is a photograph of the chip block dropped on the abutment plate.

Fig. 4 is a schematic explanatory view of the blade portion of the embodiment.

Fig. 5 is an enlarged schematic explanatory view of the front end portion of Fig. 4.

Fig. 6 is a cross-sectional view taken along line A-A of Fig. 5(a).

Figure 7 is a graph showing the results of the experiment.

Fig. 8 is a photograph showing the state of the chip winding of Comparative Example 1 and the abutment plate after the processing.

Fig. 9 is a photograph showing the state of the chip winding of Comparative Example 1.

Fig. 10 is a photograph showing the state of the chip winding of the first embodiment and the abutting plate after the processing.

1. . . Tool body

2a. . . Main groove

2b. . . Secondary groove

6. . . Confluence

7. . . Step difference

α ₁ . . . First helix angle of the main groove

α ₂ . . . Second helix angle of the main groove

α ₃ . . . Helix angle of the secondary groove

Claims (15)

A drilling tool having one or a plurality of cutting edges at a front end of the tool body (1), and a plurality of spiral chip discharge grooves are provided on a periphery of the tool body (1) from a front end of the tool toward a base end side, and the plurality of cutting chips are discharged The groove is composed of at least one main groove (2a) and one sub-groove (2b), and one or a plurality of sub-grooves (2b) are formed in the middle of the main groove (2a) to form a merged flow. The step (7) is provided in the merging portion (6) of the main groove (2a) and the sub-groove (2b), and the step (7) is 2 μm or more. The drilling tool according to claim 1, wherein the step (7) is formed by a difference in groove depth between the main groove (2a) and the sub groove (2b). The drilling tool according to claim 1, wherein the step (7) is 70% or less of a groove depth of the main groove (2a). The drilling tool according to claim 2, wherein the step (7) is 70% or less of a groove depth of the main groove (2a). The drilling tool according to any one of claims 1 to 4, wherein a spiral angle of the main groove (2a) or the sub-groove (2b) is at a tool front end side and a tool base end The sides are formed differently, whereby the main groove (2a) and the sub-groove (2b) are joined together. The boring tool according to any one of claims 1 to 4, wherein the merging portion (6) is provided at a distance of 50% or less from a groove having the main groove (2a) at a tip end of the tool. s position. The drilling tool according to claim 5, wherein the merging portion (6) is disposed at a front end of the tool and has the main groove (2a) The groove is 50% or less in length. The drilling tool according to claim 6, wherein the drilling tool is coated with a lubricating film. The drilling tool according to claim 7, wherein the drilling tool is coated with a lubricating film. The drilling tool according to claim 8, wherein the lubricating film is made of an amorphous carbon film. The drilling tool according to claim 9, wherein the lubricating film is made of an amorphous carbon film. The drilling tool according to claim 10, wherein the tool diameter is 0.7 mm or less. The drilling tool according to claim 11, wherein the tool diameter is 0.7 mm or less. The drilling tool according to claim 10, wherein the tool has a diameter of 0.4 mm or less. The drilling tool according to claim 11, wherein the tool has a diameter of 0.4 mm or less.