JP4541132B2 - Entry board for small-diameter drilling and small-diameter drilling method - Google Patents

Description

  The present invention relates to an entry board used as a backing plate for forming a small-diameter hole in a workpiece, such as a through hole in a printed wiring board, and a small-diameter drilling method using the entry board.

  In this specification, the term “aluminum” includes aluminum alloys in addition to pure aluminum. Further, the term “plate” includes a foil.

  In recent years, with rapid performance enhancement of communication equipment, OA equipment, home appliances, etc., in the printed wiring board responsible for the control center of these equipment, miniaturization, high density, and multilayering of wiring patterns have progressed, There is a demand for smaller through holes and improved positional accuracy.

  Conventionally, in the drilling of through holes in printed wiring boards, in order to increase the processing efficiency, a plurality of printed wiring boards are stacked on the top board, and the aluminum entry is placed on the topmost board. In this state, a method of forming through holes at once in all stacked substrates by drilling through the entry board from above with a drill and drilling the substrate for printed wiring in this state is adopted. ing. Thus, the entry board is used as a backing plate for the purpose of improving the bite of the drill and preventing the damage on the surface of the base plate and the generation of burrs and burrs around the hole periphery.

  However, the diameter of the drill hole is reduced by reducing the diameter of the through hole. However, when drilling with a small diameter drill with a diameter of 0.3 mm or less, especially when an aluminum plate is used for the entry board, the drill is on the surface of the entry board. As a result, the position accuracy of drilling deteriorates, the drill breaks frequently, and the inner peripheral surface of the hole is roughened. There was a problem that the number of stacked sheets could not be increased and the processing efficiency could not be sufficiently increased.

  Accordingly, it has been proposed to use an entry board having a lubricating layer mainly composed of polyethylene glycol on at least one surface of an aluminum substrate. For example, the lubricating layer presented in Patent Document 1 is composed of polyethylene glycol having an average molecular weight of 20,000 to 50,000, polyethylene glycol having an average molecular weight of 100,000 or more, trimethylolpropane, and a partially saponified product of polyvinylpyrrolidone or polyvinyl acetate. It is supposed to be. The lubricating layer presented in Patent Document 2 has three types of polyethylene glycols having an average molecular weight of 1,000 or more and less than 15,000, an average molecular weight of 15,000 or more and less than 50,000, and an average molecular weight of 50,000 or more and 200,000 or less. If necessary, it is made of a resin composition containing an optional component trimethylolpropane. Furthermore, the lubricating layer presented in Patent Document 3 is made of a mixture of polyethylene glycol having an average molecular weight of 3000 or more and less than 10,000, polyethylene glycol having an average molecular weight of 10,000 or more, and trimethylolpropane.

However, in the drilling process using the entry board having these lubricating layers, the melting point of the polyethylene glycol of the lubricating layer is as low as 60 ° C. or less, and the viscosity of the lubricating component melted by the frictional heat associated with the drilling is significantly reduced. The lubrication component with excessive fluidity dissipates from the cutting site and cannot exert a sufficient lubrication action, resulting in frequent breakage of the drill and deterioration of the positional accuracy of the drill, and the lubrication component deposited on the drill. There was a new problem that the printed wiring board was soiled by dripping.
JP 2001-47307 A JP 2004-9193 A JP-T-2004-516149

  In view of the above circumstances, the present invention is capable of exerting a sufficient lubrication effect by spreading the lubricating component of the lubricating layer provided on the entry board to the cutting site by the drill without interruption throughout the small-diameter drilling process. It is an object of the present invention to provide means that can reduce the breakage of the workpiece, improve the positional accuracy of the hole, and avoid contamination of the workpiece due to dripping of the lubricating component.

To achieve the above object, the small-diameter drilling for entry board according to claim 1 of the present invention, the lubricating layer is formed on at least one surface of an aluminum substrate, wherein the lubricating layer has a number average molecular weight of 100 to 1,000 Less than 5 to 30% by mass of polyethylene glycol, 20 to 90% by mass of polyethylene glycol having a number average molecular weight of 10000 or more, and 100 parts by mass of a saponified product of polyvinyl alcohol with respect to 100 parts by mass of trimethylol. It consists of a mixed composition in which 0.5 to 20 parts by mass of propane is mixed .

Further, the invention of claim 2 is configured such that the saponification degree of the saponified product of polyvinyl alcohol in the lubricating layer of the entry board for drilling a small diameter of claim 1 is 15 to 90 mol%.

Furthermore, the invention of claim 3 is configured such that the thickness of the lubricating layer in the entry board for small-diameter drilling according to any of claims 1 or 2 is 10 to 100 μm.

According to a fourth aspect of the present invention, an undercoat layer containing a saponified polyvinyl alcohol is interposed between the aluminum substrate and the lubricating layer in the small-diameter hole entry board according to any one of the first to third aspects. Is adopted.

On the other hand, a small-diameter drilling method according to a fifth aspect of the present invention is such that the entry board according to any one of the first to fourth aspects is arranged on a plurality of stacked substrates for printed wiring. In this state, a hole having a diameter of 0.3 mm or less is formed in the entry board and the printed wiring board from above using a drill.

According to the first aspect of the present invention, the lubricating layer of the small-bore hole entry board is mixed with polyethylene glycol having a melting point of 60 ° C. or less and saponified polyvinyl alcohol having a melting point of 180 to 190 ° C. together with trimethylolpropane. Therefore, at the time of drilling using the entry board, even if it is melted by frictional heat of cutting, it retains a certain degree of viscosity and does not become excessively fluid. It can be supplied from end to end and can exhibit a stable lubricating action. Therefore, by using this entry board, the breakage frequency of the drill is greatly reduced, the positional accuracy of the hole is improved, and contamination of the workpiece due to dripping of the lubricating component from the drill is also avoided. Further, since the ratio of each component constituting the lubricating layer of the entry board is set within a specific range, the effects such as reduction of the breakage frequency of the drill, improvement of the position accuracy of the hole, prevention of dripping of the lubricating component, etc. Is more reliably exhibited, and the film strength, uniformity, water solubility and the like of the lubricating layer are improved.

According to the invention of claim 2 , since the saponification degree of the polyvinyl alcohol contained in the lubricating layer of the entry board is in a specific range, a uniform lubricating layer can be formed by good compatibility with polyethylene glycol and lubrication. Since sufficient water solubility is imparted to the component, the lubricating component adhering to the printed wiring board after drilling or drill can be easily removed by washing with water.

According to invention of Claim 3 , since the said lubricating layer has thickness of a specific range, while being able to exhibit sufficient lubricity, favorable coating property can be ensured and the fall of productivity can be avoided.

According to the invention of claim 4 , in addition to preventing the lubricating layer from peeling and cracking by the undercoat layer interposed between the aluminum substrate and the lubricating layer, the polyvinyl alcohol ken constituting the undercoat layer is prevented. Since the chemical compound is mixed in the lubricating component during drilling and suppresses the decrease in the viscosity of the lubricating component due to frictional heat of cutting, good lubrication is obtained and the dripping of the lubricating component from the drill is less likely to occur. .

According to the small-diameter drilling method according to the invention of claim 5 , when forming a small-diameter hole having a diameter of 0.3 mm or less at once for a plurality of stacked printed wiring base plates, breakage of the drill is prevented. It is hard to occur, and the hole position accuracy can be set high.

  FIG. 1 shows an embodiment of an entry board for small-diameter drilling according to the present invention. The entry board 1 has a lubricating layer 4 formed on one surface of an aluminum substrate 2 with an undercoat layer 3 interposed therebetween.

  As the aluminum substrate 2 of the entry board 1, for example, a thickness 0.1 made of JIS A1100-H18 material, JIS A1N30-H18 material, JIS A1050-H18 material, JIS A3003-H18 material, JIS A3004-H18 material, etc. A single aluminum plate of about 0.25 mm or a soft aluminum plate having a Vickers hardness (Hv) of 20 to 50 and a thickness of 5 to 100 μm and a Vickers hardness (Hv) of 50 to 140 and a thickness of 30 to 200 μm What stuck together the aluminum plate is used suitably. In the case of using the latter laminated with the soft and hard aluminum plate, the lubricating layer 4 is formed on the surface of the soft aluminum plate via the undercoat layer 3.

  The undercoat layer 3 is made of polyvinyl alcohol having a saponification degree of 15 to 90 mol% and a polymerization degree of about 100 to 800, and has a thickness of about 0.1 to 5.0 μm.

  The lubricating layer 4 is made of a mixed composition containing polyethylene glycol having a number average molecular weight of 100 or more and less than 1000, polyethylene glycol having a number average molecular weight of 10,000 or more, a saponified product of polyvinyl alcohol, and trimethylolpropane. It is set to about 100 μm.

  For example, when through holes are drilled in a printed wiring board using this entry board 1, first, a plurality of printed wiring boards are stacked on the top board, and the entry board 1 is placed on the uppermost stack. Is arranged so that the lubricating layer 4 side faces upward. In this state, a hole is drilled from above the entry board 1 to reach the slab by means of a drill from above, and through holes are formed all at once in all the printed wiring boards stacked in a single drilling operation.

  In such a drilling process, holes are made through the entry board 1 arranged at the top in a state where the printed wiring boards are stacked, so that the through holes of each printed wiring board have burrs and burrs on the edge. The post-processing of these base plates is facilitated, and damage caused by burrs and burrs on the metal layer of the printed wiring manufactured from these base plates is prevented. In addition, the number of base plates to be stacked at the time of one punching process can be increased, and the productivity of the printed wiring board can be increased.

  In addition, when this entry board 1 is used, even when a hole having a small diameter of 0.3 mm or less is formed, a good lubricating action by the lubricating layer 4 is continuously exhibited until the end of processing, so that the drill is entered. It does not skid on the board surface, the drilling position accuracy is increased, drill breakage is reduced, and the inner peripheral surface of the hole is prevented from being roughened. It is difficult to avoid contamination of the base plate due to the dripping. This is because the lubricating component of the lubricating layer 4 has the above-described composition, so that the viscosity does not decrease so much even when it is melted by frictional heat during processing, and the dissipation due to excessive fluidity of the lubricating component is prevented. This is because the lubrication component is continuously supplied to the cutting site by the drill, and the stable and good lubricating action is maintained.

  Moreover, in this entry board 1, since the lubricating component constituting the lubricating layer 4 is excellent in solubility in water, the lubricating component adhering to the printed wiring board can be easily removed by washing with water. Become.

  Here, the saponification product of polyvinyl alcohol used for the lubricating layer 4 of the entry board 1 functions to improve the heat resistance of the entire lubricating layer and to suppress the deterioration of the lubricating property due to frictional heat during drilling. That is, the melting point of two types of polyethylene glycols having different number average molecular weights used for the lubricating layer 4 is 60 ° C. or less, whereas the melting point of the saponified polyvinyl alcohol is 180 to 190 ° C. In the lubricating layer, the viscosity of the lubricating component melted by the frictional heat at the time of drilling does not drop so much, and dissipation due to excessive fluidity of the lubricating component is prevented.

  Such a saponified product of polyvinyl alcohol preferably has a saponification degree of 15 to 90 mol%. If the degree of saponification is too low, the water-solubility is inferior, so that the lubricating component adhering after drilling cannot be easily removed by washing with water. On the other hand, if the degree of saponification is too high, the lubricity is lowered and the compatibility with polyethylene glycol is deteriorated, so that it is difficult to form a uniform lubricating layer.

  The blended amount of the saponified polyvinyl alcohol occupies 5 to 50% by mass of the saponified polyvinyl alcohol and the two types of polyethylene glycol having different number average molecular weights as the base composition. A range is preferred. When the blending amount is less than 5% by mass of the base composition, the effect of improving the heat resistance is not sufficiently exhibited. Conversely, when it exceeds 50% by mass, compatibility with polyethylene glycol cannot be obtained, and the lubricating layer 4 As a result, the production efficiency of the entry board is lowered due to a decrease in the coating quality.

  On the other hand, polyethylene glycol having a number average molecular weight of 100 or more and less than 1000 used in the lubricating layer 4 improves lubricity and water solubility of the lubricating layer, and is a phase between the saponified polyvinyl alcohol and polyethylene glycol having a number average molecular weight of 10,000 or more. It functions to improve solubility. The blending amount of the low molecular weight polyethylene glycol is preferably in the range occupying 5 to 30% by mass of the base composition. If the amount is less than 5% by mass, the above functions are insufficient. 4 will be sticky.

  Further, the polyethylene glycol having a number average molecular weight of 10,000 or more used for the lubricating layer 4 has a function of increasing the film strength of the lubricating layer 4, but the function is sufficient when the blending amount is less than 20% by mass of the base composition. If the amount exceeds 90% by mass, the lubricating layer 4 becomes hard and brittle. Therefore, the blending amount of the high molecular weight polyethylene glycol is preferably in a range occupying 20 to 90% by mass of the base composition. The upper limit of the number average molecular weight of the high molecular weight polyethylene glycol is about 100,000.

  Trimethylolpropane increases the solubility of the lubricating layer 4 in water, so that the water after the drilling process can be washed with water. Thus, the blending amount of this trimethylolpropane is 0.5 to 20 parts by mass with respect to 100 parts by mass of the base composition composed of two types of polyethylene glycol and saponified polyvinyl alcohol having different number average molecular weights. The range is suitable, and if the amount is too small, the solubility cannot be sufficiently increased. On the other hand, if the amount is too large, the lubricating layer 4 becomes sticky.

  When the thickness of the lubricating layer 4 is less than 10 μm, sufficient lubricity cannot be obtained, and when it exceeds 100 μm, the coating efficiency is lowered and the production efficiency is deteriorated and the material cost is increased.

  The undercoat layer 3 functions to improve the adhesion of the lubricating layer 4 to the aluminum substrate 2 and thereby prevent the lubricating layer 4 from peeling or cracking. Thus, the saponified product of polyvinyl alcohol used for the undercoat layer 3 is mixed into the lubricating component at the time of drilling, and is lubricated by frictional heat of cutting in the same manner as the saponified product of polyvinyl alcohol blended in the lubricating layer 4. It suppresses the decrease in the viscosity of the component, exerts a better lubricating action, and makes it less likely for the lubricating component to sag from the drill. Moreover, since the said undercoat layer 3 and the lubricating layer 4 contain a common component, both layers show high affinity and adhere | attach firmly. Furthermore, since this saponified product of polyvinyl alcohol is water-soluble, there is an advantage that even if a part of the undercoat layer cut by drilling adheres to the workpiece together with the lubricating component, it can be easily removed by washing with water. .

  The entry board for small-diameter drilling according to the present invention has a structure in which a lubricating layer 4 is provided on both surfaces of an aluminum substrate 2, a structure in which the undercoat layer is made of a resin component other than a saponified polyvinyl alcohol, and the lubricating layer 4 is an undercoat layer. 3, which includes any of the structures formed directly on the surface of the aluminum substrate 2 without the interposition 3, and in particular, the undercoat layer 3 made of a saponified polyvinyl alcohol is provided on one surface of the aluminum substrate 2 as in the above embodiment. The one provided with the lubricating layer 4 is most preferable in terms of both performance and cost. In addition, the entry board of the present invention can be applied to small-diameter drilling of various workpieces, but is optimal for drilling of a printed wiring board as in the small-diameter drilling method of the present invention. is there.

Example 1
On one side of a 150 μm thick 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% is An undercoat layer was formed by coating to a thickness of 3 μm. Next, on this undercoat layer, 20 parts by mass of polyethylene glycol having a number average molecular weight of 400, 60 parts by mass of polyethylene glycol having a number average molecular weight of 20000, 20 parts by mass of polyvinyl alcohol having a saponification degree of 80 mol%, and 5 parts by mass of trimethylolpropane. Part of the mixed composition was applied to a thickness of 30 μm to form a lubricating layer, and an entry board for small-diameter drilling was prepared.

Example 2
An entry board for small-diameter drilling was prepared in the same manner as in Example 1 except that the thickness of the lubricating layer was 80 μm.

Example 3
For forming a lubricating layer, 15 parts by mass of polyethylene glycol having a number average molecular weight of 400, 60 parts by mass of polyethylene glycol having a number average molecular weight of 50000, 25 parts by mass of polyvinyl alcohol having a saponification degree of 70 mol%, and 5 parts by mass of trimethylolpropane are mixed. An entry board for small-diameter drilling was prepared in the same manner as in Example 1 except that the composition was used.

Example 4
An entry board for small-diameter drilling was prepared in the same manner as in Example 3 except that the thickness of the lubricating layer was 80 μm.

Example 5
For lubricating layer formation, 15 parts by mass of polyethylene glycol having a number average molecular weight of 800, 60 parts by mass of polyethylene glycol having a number average molecular weight of 20000, 25 parts by mass of polyvinyl alcohol having a saponification degree of 80 mol%, and 5 parts by mass of trimethylolpropane are mixed. An entry board for small-diameter drilling was prepared in the same manner as in Example 1 except that the composition was used.

Comparative Example 1
An undercoat layer having a thickness of 3 μm made of polyvinyl acetate having a saponification degree of 35 mol% was formed on one side of a 150 μm-thick substrate made of JIS A3004-H18 material. Next, on this undercoat layer, a mixed composition of 20 parts by mass of polyethylene glycol having a number average molecular weight of 400, 80 parts by mass of polyethylene glycol having a number average molecular weight of 20000 and 10 parts by mass of trimethylolpropane is adjusted to a thickness of 30 μm. Coating was performed to form a lubricating layer, and an entry board for small-diameter drilling was produced.

Comparative Example 2
An entry board for small-diameter drilling was prepared in the same manner as in Comparative Example 1 except that the thickness of the lubricating layer was 80 μm.

Evaluation test Four sheets of printed wiring board made of epoxy resin having a total thickness of 0.1 mm, in which a copper plate having a thickness of 12 μm is laminated on both sides, are stacked on a baking board made of balinet having a thickness of 1.5 mm. On the base plate, the entry board for small-diameter drilling of any of Examples 1 to 5 and Comparative Examples 1 to 3 is arranged with the lubricating layer side facing upward, and the drill is drilled with a diameter of 0.1 mm from above. A 2000-hit drilling process from the entry board to the steel plate was performed. Then, a hole position of 2000 hits is measured with a coordinate measuring machine for each base plate of the drilling process, and the deviation from the set position is checked, and the lubricant component drips on the uppermost base plate after each drilling process. It was investigated whether there was any. The results are shown in Table 1.

  As is clear from the results in the above table, if the entry boards of Examples 1 to 5 according to the present invention are used, a hole can be formed with very high positional accuracy even in drilling with a very small diameter such as a drill diameter of 0.1 mm. It is possible to prevent contamination due to dripping of the lubricating component during processing. On the other hand, in the same drilling process using the entry boards of Comparative Examples 1 and 2 in which the composition of the lubricating layer is different from that of the present invention, the positional accuracy of the holes to be formed is inferior and the lubricating component being processed It turns out that it is easy to produce the dirt by dripping.

It is an expanded sectional view of the entry board for small diameter drilling processing concerning one embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 ... Entry board for small diameter drilling process 2 ... Aluminum substrate 3 ... Undercoat layer 4 ... Lubrication layer

Claims (5)

A lubricating layer is formed on at least one side of the aluminum substrate,
The lubricating layer is composed of 5 to 30% by mass of polyethylene glycol having a number average molecular weight of 100 or more and less than 1000, 20 to 90% by mass of polyethylene glycol having a number average molecular weight of 10,000 or more, and 5 to 50% by mass of a saponified product of polyvinyl alcohol. An entry board for small-diameter drilling, comprising a mixed composition in which 0.5 to 20 parts by mass of trimethylolpropane is mixed with 100 parts by mass of a base composition . The small diameter drilling for entry board according to claim 1 saponification degree of polyvinyl alcohol saponified is from 15 to 90 mol%. The entry board for small-diameter drilling according to claim 1 or 2 , wherein the lubricating layer has a thickness of 10 to 100 µm. The entry board for small-diameter drilling according to any one of claims 1 to 3 , wherein an undercoat layer containing a saponified product of polyvinyl alcohol is interposed between the aluminum substrate and the lubricating layer. The entry board according to any one of claims 1 to 4 is arranged on the plurality of stacked printed wiring boards, and in this state, the entry board and the printed wiring board are used from above using a drill. A small-diameter drilling method, wherein a hole having a diameter of 0.3 mm or less is formed in a plate.

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