JP5112934B2 - Drilling plate and drilling method - Google Patents

Description

  The present invention relates to a punching contact plate used when forming a small-diameter hole in a workpiece, such as a through hole in a printed wiring board, and a punching method using the corresponding plate.

  In this specification and claims, the term “aluminum” is used to include pure aluminum and aluminum alloys. In this specification and claims, the term “plate” is used to include foil.

  In this specification and claims, the term “melt index” means a melt index (melt flow rate) measured at a test temperature of 65 ° C. and a test load of 49 N in accordance with JIS K7210-1999. .

  Conventionally, when drilling through holes in a printed wiring board, multiple printed wiring boards are stacked on the top board, and an aluminum pad is placed on the top surface of the top board. In this state, a method is used in which through holes are formed in all the stacked substrates at once by drilling holes in the substrate for printed wiring by drilling through the corresponding plate from above with a drill. This backing plate is used for the purpose of improving the biting of the drill and preventing the occurrence of damage during processing of the surface of the base plate and the generation of burrs at the periphery of the hole.

  By the way, in recent years, it is required to form a small-diameter hole having a diameter of 0.3 mm or less as the printed wiring board has a higher density. In order to meet such demands, when a drilling process is performed with a small diameter drill having a diameter of 0.3 mm or less using a simple aluminum plate, the drill slides on the surface of the patch plate. In addition to the deterioration of position accuracy, drill breakage frequently occurs, and the inner peripheral surface of the hole is roughened. In addition, the number of stacked printed wiring boards cannot be increased in order to suppress drill breakage. There was a problem that the processing efficiency could not be sufficiently increased.

  Therefore, as a punch plate, a thickness of 0.1 to 3 mm made of a mixture of 20 to 90% by weight of polyethylene glycol having a molecular weight of 10,000 or more and 80 to 10% by weight of a water-soluble lubricant is formed on at least one surface of an aluminum substrate. It has been proposed to use a construction in which a water-soluble lubricant sheet is disposed (see Patent Document 1).

  However, in the technique described in Patent Document 1, the mixture is inferior in film formability, so that it is difficult to form a water-soluble lubricant sheet, and the water-soluble lubricant sheet is easily cracked. There was a problem that the water-soluble lubricant sheet was sticky. Such stickiness makes the hand sticky and difficult to handle when handling the water-soluble lubricant sheet, and blocking tends to occur. When blocking occurs, when a plurality of contact plates are stacked and stored, adjacent contact plates adhere to each other, so that the workability when performing the work of peeling the contact plates one by one at the time of use is greatly reduced. In addition, when peeling the backing plate one by one during use, the lubricant from one of the two adjacent backing plates adheres to the other backing plate and is removed from the water-soluble lubricant sheet. As a result of the unevenness of the thickness and the unevenness of the surface abutting on the base plate side, there was a problem that the drill was broken or the positional accuracy of drilling was lowered.

In order to solve such a problem, at least one surface of an aluminum substrate has 45 to 80% by weight of polyethylene glycol having an average molecular weight of 20,000 to 50,000, 14 to 30% by weight of polyethylene glycol having an average molecular weight of 100,000 or more, trimethylolpropane,. It has been proposed to use a backing plate having a structure in which a lubricating layer having a composition of 5 to 20% by weight and polyvinyl pyrrolidone of 1 to 20% by weight is formed (see Patent Document 2).
JP-A-4-92494 JP 2001-47307 A

  According to the technique disclosed in Patent Document 2, drill breakage can be reduced and the position accuracy of drilling can be improved. In recent years, while further improving the breakage prevention performance of these drills, In the situation where it is strongly demanded to further improve the positional accuracy, the prior art cannot always meet such a requirement.

  The present invention has been made in view of such technical background, and can sufficiently reduce the breakage of the drill, can reduce the inner wall roughness of the hole, and can sufficiently improve the positional accuracy of the hole. An object is to provide a punch plate.

  In order to achieve the above object, the present invention provides the following means.

[1] In a punching plate in which a lubricating layer is formed on at least one surface of an aluminum substrate,
The lubricating layer is
A first lubricating layer comprising polyethylene glycol as a main component;
A second lubricating layer that is disposed between the aluminum substrate and the first lubricating layer and contains polyethylene glycol as a main component;
The number average molecular weight of polyethylene glycol constituting the first lubricating layer is smaller than the number average molecular weight of polyethylene glycol constituting the second lubricating layer,
The punching plate according to claim 1, wherein a melt index of the first lubricating layer is larger than a melt index of the second lubricating layer.

[2] In the punching contact plate in which the lubricating layer is formed on at least one surface of the aluminum substrate,
The lubricating layer is
A first lubricating layer comprising 50% by mass or more of polyethylene glycol having a number average molecular weight of 1000 or more and less than 15000;
A second lubricating layer disposed between the aluminum substrate and the first lubricating layer and containing 50% by mass or more of polyethylene glycol having a number average molecular weight of 50,000 or more and 200,000 or less;
The punching plate according to claim 1, wherein a melt index of the first lubricating layer is larger than a melt index of the second lubricating layer.

  [3] The first lubricating layer includes 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 1,000 to less than 15,000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15,000 to less than 50000, and a number average molecular weight of 50,000 to 200,000. 3. The punching plate according to item 2 above, comprising 5 to 30% by mass of the following polyethylene glycol.

  [4] The second lubricating layer is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 50000 to 200000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 to less than 50000, and a number average molecular weight of 1000 to 15000. 4. The punching patch plate according to 2 or 3 above, comprising 5 to 30% by mass of polyethylene glycol less than 5%.

  [5] The melt index of the first lubricating layer is in a range of 100 to 1000 g / 10 minutes, and the melt index of the second lubricating layer is in a range of 10 to 100 g / 10 minutes, A punching plate according to the item.

[6] In addition to the first lubricating layer and the second lubricating layer, the lubricating layer includes:
Any one of the preceding items 1 to 5, further comprising an intermediate lubricating layer disposed between the first lubricating layer and the second lubricating layer and containing polyethylene glycol as a main component. 2. A punching plate according to 1.

  [7] The punching plate according to any one of items 1 to 6 above is placed on the plurality of stacked substrates for printed wiring, and the holes are drilled from above using a drill in this state. A drilling method characterized by forming holes having a diameter of 0.3 mm or less in a punching plate and a printed wiring board.

  In the invention of [1], both the first lubricating layer and the second lubricating layer contain polyethylene glycol as a main component, and the number average molecular weight of the polyethylene glycol constituting the first lubricating layer constitutes the second lubricating layer. The number average molecular weight of polyethylene glycol is smaller, the melt index of the first lubricating layer is larger than the melt index of the second lubricating layer, and such a first lubricating layer is disposed outside the second lubricating layer. Therefore, when drilling with a drill, the drill enters the first lubricating layer having moderate flexibility and good fluidity while entering the first lubricating layer. Breakage can be sufficiently prevented, and the inner wall roughness of the hole can also be reduced. After that, the drill enters the second lubricating layer having an appropriate hardness and moderately suppressed fluidity, whereby the position accuracy of drilling can be sufficiently improved.

  In the invention of [2], the first lubricating layer contains 50% by mass or more of polyethylene glycol having a number average molecular weight of 1000 or more and less than 15000, and the first lubricating layer contains 50 mass of polyethylene glycol having a number average molecular weight of 50000 or more and 200000 or less. %. The melt index of the first lubricating layer is larger than the melt index of the second lubricating layer, and such a first lubricating layer is disposed outside the second lubricating layer. When drilling with, the drill enters the first lubrication layer with moderate flexibility and good fluidity while entering it, so there is less burden on the drill, and this will prevent breakage of the drill And the roughness of the inner wall of the hole can be reduced. After that, the drill enters the second lubricating layer having an appropriate hardness and moderately suppressed fluidity, whereby the position accuracy of drilling can be sufficiently improved.

  In the invention of [3], the first lubricating layer is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 1000 to less than 15000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 to less than 50000, and a number average molecular weight. Since it is a structure formed by containing 5 to 30% by mass of polyethylene glycol of 50000 or more and 200000 or less, the effect of preventing drill breakage and the effect of reducing the roughness of the inner wall of the hole can be further enhanced.

  In the invention of [4], the second lubricating layer has a number average molecular weight of 50,000 to 200,000 polyethylene glycol 50 to 70% by mass, a number average molecular weight of 15,000 to less than 50000 polyethylene glycol 10 to 30% by mass, and a number average molecular weight. Since it is the structure formed by containing 5 to 30% by mass of polyethylene glycol of 1000 or more and less than 15000, the positional accuracy of drilling can be further improved.

  In the invention of [5], the melt index of the first lubricating layer is in the range of 100 to 1000 g / 10 minutes, and the melt index of the second lubricating layer is in the range of 10 to 100 g / 10 minutes. Further, the effect of reducing the inner wall roughness of the hole and the effect of improving the positional accuracy of the hole can be further enhanced.

  In the invention of [6], since an intermediate lubricating layer containing polyethylene glycol as a main component is disposed between the first lubricating layer and the second lubricating layer, the first lubricating layer and the second lubricating layer In the case of an intermediate lubricating layer having intermediate properties, hardness and fluidity change stepwise due to the presence of the intermediate lubricating layer when the drill enters the lubricating layer from the outside toward the substrate. Therefore, breakage of the drill can be prevented more sufficiently.

  In the invention of [7], when a hole having a diameter of 0.3 mm or less is formed at once on a plurality of stacked printed wiring base plates, the inner wall roughness is small and the hole is excellent in positional accuracy. And breakage of the drill can be sufficiently suppressed.

  FIG. 1 shows an embodiment of a punching plate (1) according to the present invention. This perforating plate (1) is composed of an aluminum substrate (2) having a lubricating layer (3) formed on one side thereof.

  Although it does not specifically limit as said aluminum board | substrate (2), For example, a soft aluminum board, a semi-hard aluminum board, a hard aluminum board etc. are mentioned. Moreover, it is preferable that the thickness of the said aluminum board | substrate (2) is set to 10-200 micrometers. By setting it to 10 μm or more, it is possible to prevent the generation of burrs on the substrate (2), and by setting it to 200 μm or less, it is possible to improve the evacuation of chips generated during production.

  The surface of the aluminum substrate (2) on which the lubricating layer (3) is formed is a water-soluble or water-insoluble undercoat layer (undercoat layer) (in order to improve adhesion to the lubricating layer (3)). 6) is preferably provided (see FIG. 1). Among these, it is particularly preferable that a water-soluble undercoat layer (6) is provided. The constituent material of such a water-soluble undercoat layer is not particularly limited, and examples thereof include a partially saponified product of polyvinyl acetate and a saponified product of polyvinyl alcohol.

The lubricating layer (3) includes at least a first lubricating layer (4) containing polyethylene glycol as a main component and a second lubricating layer (5) containing polyethylene glycol as a main component. The second lubricating layer (5) is disposed between the aluminum substrate (2) and the first lubricating layer (4), and a) polyethylene constituting the first lubricating layer (4) The number average molecular weight of glycol is smaller than the number average molecular weight of polyethylene glycol constituting the second lubricating layer (5). B) The melt index of the composition constituting the first lubricating layer (4) is the second The lubricating layer (5) is configured to satisfy both the conditions a) and b) which are larger than the melt index of the composition constituting the lubricating layer (5).

  Since the first lubricating layer (4) having such a design is arranged outside the second lubricating layer (5), the drill has an appropriate flexibility when drilling with a drill. Since the first lubrication layer (4) having good fluidity is entered while entering, the burden on the drill is small, and thereby breakage of the drill can be sufficiently prevented and the inner wall roughness of the hole can also be reduced. Thereafter, the drill enters the second lubricating layer (5) having an appropriate hardness and moderately suppressed fluidity, and thereby the position accuracy of the drilling can be sufficiently improved.

  Especially, it is preferable that the structure of the said 1st lubricating layer (4) and the said 2nd lubricating layer (5) is the following structures. That is, the first lubricating layer (4) contains 50% by mass or more of polyethylene glycol having a number average molecular weight of 1,000 or more and less than 15,000, and the second lubricating layer (5) is polyethylene glycol having a number average molecular weight of 50,000 or more and 200,000 or less. It is preferable to adopt a configuration containing 50% by mass or more.

  Further, the first lubricating layer (4) is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 1000 to less than 15000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 to less than 50000, and a number average molecular weight of 50000. It is particularly preferable that the composition contains 5 to 30% by mass of polyethylene glycol of 200000 or less, and in this case, breakage of the drill during drilling can be more sufficiently prevented, and the inner wall of the hole Roughness can be sufficiently reduced.

  The second lubricating layer (5) is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 50000 to 200000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 to less than 50000, and a number average molecular weight of 1000. It is particularly preferable that the composition contains 5 to 30% by mass of polyethylene glycol of less than 15000, and in this case, the position accuracy of drilling can be further improved.

  The thickness of the first lubricating layer (4) is preferably 10 to 100 μm. When it is 10 μm or more, it is possible to sufficiently ensure the effect of preventing drill breakage and reducing the inner wall roughness of the hole, and when it is 100 μm or less, it is possible to effectively prevent the lubricating layer component from being wound around the drill bit.

  The thickness of the second lubricating layer (5) is preferably 10 to 100 μm. When it is 10 μm or more, it is possible to sufficiently ensure the effect of improving the positional accuracy of drilling, and when it is 100 μm or less, it is possible to effectively prevent the lubricating layer component from being wound around the drill bit.

  Therefore, the thickness of the lubricating layer (3) is preferably 20 to 200 μm.

  In this invention, the melt index (MI) of the composition constituting the first lubricating layer (4) is in the range of 100 to 1000 g / 10 min, and the melt of the composition constituting the second lubricating layer (5) The index (MI) is preferably in the range of 10 to 100 g / 10 minutes. When the configuration satisfies such a condition, the various effects (the drill breakage prevention effect, the hole inner wall roughness reduction effect, and the hole positioning accuracy improvement effect) can be further enhanced.

  In addition, as the lubricating layer (3), an intermediate lubricating layer containing polyethylene glycol as a main component is further disposed between the first lubricating layer (4) and the second lubricating layer (5). A configuration may be adopted. When this intermediate lubricating layer has an intermediate property between the first lubricating layer and the second lubricating layer, when the drill enters the lubricating layer (3) from the outside toward the substrate (2). Further, since the hardness and fluidity can be changed stepwise due to the presence of the intermediate lubricating layer, breakage of the drill can be more sufficiently prevented.

  In addition, in the composition which comprises the said 1st lubrication layer (4), in the range which does not inhibit the effect of this invention, you may contain other polyethylene glycols from which a number average molecular weight range differs in addition to various additives. .

  Similarly, as long as the effect of the present invention is not impaired, the composition constituting the second lubricating layer (5) may contain other additives such as various other polyethylene glycols having different number average molecular weight ranges. good.

  Although it does not specifically limit as a manufacturing method of the punching plate (1) of this invention, For example, the following methods can be illustrated.

That is, the second lubricating layer forming composition is applied on the aluminum substrate (2) by a roll method, a curtain coating method or the like to form the second lubricating layer (5), and then the first lubricating layer is further formed thereon. A method of forming the first lubricating layer (4) by applying the forming composition by a roll method or a curtain coating method,
The composition for forming the second lubricating layer is formed into a sheet shape by a press method, a roll method, a T-die extrusion method, etc., and this is overlaid on the aluminum substrate (2) and heated and pressed with a press or a roll. After forming the lubricating layer (5), the first lubricating layer-forming composition formed into a sheet shape by a press method, a roll method, a T-die extrusion method, or the like is further stacked thereon with a press or roll. A method of forming the first lubricating layer (4) by heating and pressing;
The second lubricating layer forming composition is formed into a sheet by a press method, a roll method, a T-die extrusion method, etc., and this is adhered to the aluminum substrate (2) with an adhesive. (1) A method of adhering a composition for forming a lubricating layer formed into a sheet shape by a press method, a roll method, a T-die extrusion method, or the like,
After forming the second lubricating layer (5) by printing the second lubricating layer-forming composition on the aluminum substrate (2) and drying, the first lubricating layer-forming composition is further formed thereon. Examples include a method of forming the first lubricating layer (4) by printing and drying.

  Further, the drilling using the punching plate (1) of the present invention is performed as follows, for example. That is, a plurality of printed wiring base plates are stacked on a top plate, and the perforating plate (1) of the present invention is arranged on the upper surface of the uppermost base plate with the lubricating layer side facing up. In this state, a hole having a diameter of 0.3 mm or less is formed on the punching plate and the printed wiring board from above using a drill. In this drilling method, drilling is performed using the punching plate (1) of the present invention, so that breakage of the drill can be reduced and the positional accuracy of the holes can be improved. Moreover, since breakage of the drill can be suppressed in this way, it is possible to increase the number of stacked printed wiring boards, thereby increasing the productivity of the printed wiring board. Examples of the printed wiring board include a copper clad laminate and a multilayer board.

  In the embodiment, the lubricating layer (3) is formed on one side of the aluminum substrate (2). However, the lubricating layer (3) is not particularly limited to such a configuration, and is formed on both sides of the aluminum substrate (2). You may employ | adopt the structure in which the lubricating layer (3) provided with the said characteristic was formed.

  Moreover, in the said embodiment, although the lubrication layer (3) was formed through the undercoat layer (6) on the single side | surface of the board | substrates made from aluminum (2), it is not specifically limited to such a structure, For example, A configuration formed directly on one surface of the aluminum substrate (2) may be employed.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
On one side of a 70 μm thick aluminum substrate made of JIS A3004-H18 material, a mixture of 70 parts by mass of polyvinyl alcohol with a saponification degree of 80 mol% and 30 parts by mass of polyvinyl alcohol with a saponification degree of 73.5 mol%, An undercoat layer was formed by coating to a thickness of 3 μm. Next, on this undercoat layer, a roll coating method is applied to a mixed composition comprising 55 parts by mass of polyethylene glycol having a number average molecular weight of 200,000, 25 parts by mass of polyethylene glycol having a number average molecular weight of 20,000, and 20 parts by mass of polyethylene glycol having a number average molecular weight of 10,000. To form a second lubricating layer having a thickness of 15 μm, and further, on this second lubricating layer, 60 parts by mass of polyethylene glycol having a number average molecular weight of 10,000, 20 parts by mass of polyethylene glycol having a number average molecular weight of 30,000, and A mixed composition composed of 20 parts by mass of polyethylene glycol having a number average molecular weight of 100,000 was applied by a roll coating method to form a first lubricating layer having a thickness of 15 μm, thereby producing a punching plate.

  The melt index of the mixed composition forming the second lubricating layer was 20 g / 10 minutes, and the melt index of the mixed composition forming the first lubricating layer was 200 g / 10 minutes.

<Examples 2 to 5>
Except that the second lubricating layer was formed using the mixed composition having the composition shown in Table 1, and the first lubricating layer was formed using the mixed composition having the composition shown in Table 1, the same as in Example 1. A punching plate was prepared.

<Comparative Examples 1 and 2>
On one side of a 70 μm thick aluminum substrate made of JIS A3004-H18 material, a mixture of 70 parts by mass of polyvinyl alcohol with a saponification degree of 80 mol% and 30 parts by mass of polyvinyl alcohol with a saponification degree of 73.5 mol%, An undercoat layer was formed by coating to a thickness of 3 μm. Next, a single-layer lubricating layer having a thickness of 30 μm is formed on the undercoat layer by applying the mixed composition having the composition shown in Table 1 by a roll coating method, and a punching plate is formed. Produced.

  Various evaluations were performed based on the following evaluation methods for each punching plate obtained as described above. These results are shown in Table 2.

<Drill breaking prevention evaluation method>
The drilling of 5000 hits was performed on 100 drills, the number of breaks in 100 was examined, and evaluated based on the following criteria.
(Criteria)
“◎”: The number of breaks in 100 is 0 “O”: The number of breaks in 100 is 1 “Δ”: The number of breaks in 100 is 2 to 4 “x”: Breaks in 100 Number is 5 or more.

<Evaluation method of inner wall roughness of hole>
The roughness of the inner peripheral wall surface of the hole formed in the lowermost printed wiring board that was punched was observed. That is, after the wiring base plate was solidified with the embedded resin, the cut surface of the hole was observed with a microscope and evaluated based on the following criteria.
(Criteria)
“◎”: The roughness of the inner peripheral wall surface of the hole is less than 3 μm. “O”: The roughness of the inner peripheral wall surface of the hole is less than 3 μm and less than 5 μm. X ”: The roughness of the inner peripheral wall surface of the hole is 10 μm or more.

<Evaluation method of position accuracy for drilling>
4 layers of printed wiring board made of epoxy resin with a total thickness of 0.1 mm, with 12 μm thick copper plates laminated on both sides of a 1.5 mm thick baking sheet, the topmost base plate On top of this, the base plate for drilling in any of Examples 1 to 5 and Comparative Examples 1 and 2 is disposed with the lubricating layer side facing upward, and the corresponding plate is removed from the corresponding plate with a drill having a diameter of 0.1 mm from above. The punching process of 5000 hits reaching the plate was performed. Then, the hole position of 5000 hits was measured with a coordinate measuring machine for each base plate for drilling, and the deviation from the set position was examined and evaluated based on the following criteria.
(Criteria)
“◎”: The average value of the positional deviation of the holes is less than 8 μm “O”: The average value of the positional deviation of the holes is 8 μm or more and less than 11 μm “Δ”: The average value of the positional deviation of the holes is 11 μm or more and less than 14 μm The average value of the positional deviation of the holes is 14 μm or more.

  As is clear from Tables 1 and 2, the punching plate of Examples 1 to 5 of the present invention has very little drill breakage, and the inner wall roughness of the hole is sufficiently reduced. Excellent opening position accuracy.

  On the other hand, the punching contact plate of Comparative Example 1 provided with a single-layer lubricating layer has insufficient drill breakage prevention properties, and the inner wall of the hole is rough. Further, the punching plate of Comparative Example 2 having the same single different lubricating layer was inferior in the positional accuracy of the drilling.

  The punching contact plate of the present invention can be applied to drilling for various workpieces, and is suitably used for punching a printed wiring board.

It is an expanded sectional view of the caulking plate according to one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Drilling plate 2 ... Aluminum board | substrate 3 ... Lubrication layer 4 ... 1st lubrication layer 5 ... 2nd lubrication layer

Claims (6)

In the punching base plate in which the lubricating layer is formed on at least one surface of the aluminum substrate,
The lubricating layer is
A first lubricating layer comprising 50% by mass or more of polyethylene glycol having a number average molecular weight of 1000 or more and less than 15000;
A second lubricating layer disposed between the aluminum substrate and the first lubricating layer and containing 50% by mass or more of polyethylene glycol having a number average molecular weight of 50,000 or more and 200,000 or less;
The punching plate according to claim 1, wherein a melt index of the first lubricating layer is larger than a melt index of the second lubricating layer. The first lubricating layer is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 1000 or more and less than 15000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 or more and less than 50000, and polyethylene having a number average molecular weight of 50,000 or more and 200000 or less. The punching plate according to claim 1 , comprising 5 to 30% by mass of glycol. The second lubricating layer is composed of 50 to 70% by mass of polyethylene glycol having a number average molecular weight of 50000 to 200000, 10 to 30% by mass of polyethylene glycol having a number average molecular weight of 15000 to less than 50000, and polyethylene having a number average molecular weight of 1000 to less than 15000. The perforating plate according to claim 1 or 2 , comprising 5 to 30% by mass of glycol. The melt index of the first lubricating layer ranges from 100 to 1000 g / 10 min, a melt index of the second lubricating layer to any one of claims 1 to 3, in the range of 10 to 100 g / 10 min The punching plate according to the description. In addition to the first lubricating layer and the second lubricating layer, the lubricating layer includes:
The intermediate lubricating layer which is arrange | positioned between this 1st lubricating layer and this 2nd lubricating layer, and contains polyethyleneglycol as a main component is further provided, The any one of Claims 1-4 characterized by the above-mentioned. A punching plate according to the item. The punching plate according to any one of claims 1 to 5 is arranged on a plurality of stacked printed wiring boards, and the drilling is performed from above using a drill in this state. A drilling method comprising forming a hole having a diameter of 0.3 mm or less in a contact plate and a printed wiring board.

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