TWI650054B - Cover plate, cover manufacturing method and flexible circuit board manufacturing method - Google Patents

Abstract

The present invention provides a drilling processing cover plate, a method for manufacturing a drilling processing cover plate, and a method for manufacturing a flexible circuit board, which are capable of extending the life of the drill bit by suppressing the damage of the drill bit, and optimizing the quality of the through hole after the drilling process; The drilling processing cover is formed by coating a water-insoluble lubricating layer composed of a lubricating material and a binder on at least one surface of the substrate.

Description

Cover plate, cover manufacturing method and flexible circuit board manufacturing method

The present invention relates to an entry sheet, a method of manufacturing the cover, and a method of manufacturing the flexible circuit board.

In the mass production of a Flexible Printed Circuit (FPC), a roll to roll method is known as a mass production method. In the initial stage of the manufacturing process of the flexible wiring board having the through-hole structure, there are a through hole drilling process and a through hole plating process. Thereafter, a flexible circuit board is produced after a resist coating step, a pattern forming step, an etching step, and a terminal portion surface treatment step.

In these processes, the through hole drilling process is an initial process of manufacturing a flexible circuit board having a through hole structure, and in this process, a drilling method using an NC drilling device having a roll-to-roll conveying function is applied (drilling processing methods). The NC drilling apparatus is capable of drilling a hole of at least about 40 μm. The NC drilling apparatus is provided with a main shaft, and is subjected to drilling processing after overlapping a plurality of flexible cupper Clad Laminates (FCCL: substrates). Regarding the number of overlaps of the copper-plated laminate, it is usually two (two layers), four (four layers), five (five), and eight (eight) layers.

Further, the copper-clad laminate constitutes a main component of the flexible printed circuit board, and is formed into a structure in which a film-like insulator "base film" (for example, a polyimide film (for example, a polyimide film) has a thickness of 12 μm to 100 μm. A polyimide film is formed on the polyimide film)), and a conductor foil (for example, a copper foil) having a thickness of about 12 μm to 50 μm is further adhered to the upper portion. The terminal portion or other portions other than the welded portion are covered with an insulator for protection. As the material of the insulator, a plurality of plastics such as polyimine or polyester (PET: Polyethylene Terephthalate) are used. The conductor foil is usually copper foil. The adhesive layer mainly uses an epoxy resin or an acrylic resin adhesive. Since the flexible printed circuit board can be folded, it is an indispensable material in the connection portion of a portable telephone, a personal computer, or a digital camera.

As a method of drilling a copper-plated laminated board, a method of drilling a copper-clad laminate is carried out, and an aluminum foil or the like is placed on the uppermost portion thereof, followed by drilling. In recent years, with the development of the reliability of printed wiring board materials and the development of high density, it is necessary to improve the hole position accuracy or reduce the hole wall roughness and the like, and to cope with such demands. A drilling method for drilling a cover plate using polyethylene glycol (for example, refer to Patent Document 1), or a water-soluble lubrication from the viewpoint of ease of recovery and reuse of an aluminum plate film A cover plate or the like as a main component has been put into practical use. In recent years, in order to improve flexibility and prevent scratches, a PET (Polyethylene Terephthalate) film having hardness has been used for a cover plate for NC drilling of a flexible printed circuit board.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: JP-A-4-92488

However, the water-soluble lubricating material is sticky, and the fingerprint is adhered at the touch, which deteriorates the operability. In addition, in recent years, in order to reduce the size and weight of the printed wiring board, the wiring pattern is refined and the diameter of the through hole is increased. Accordingly, the resin component used in the PET film adheres to the wall surface of the drill. In particular, when the small-diameter processing of 0.1 mm Φ or less is performed, the drill bit is broken. In this case, the drill bit is broken and the life of the drill is shortened, and the unevenness and burr of the wall surface of the through hole are remarkable.

An object of the present invention is to provide a method for manufacturing a hole for drilling a hole, a method for manufacturing a hole for drilling a hole, and a method for producing a cover plate for drilling a hole, which can reduce the life of the drill by suppressing the breakage of the drill bit, thereby suppressing the unevenness and burr of the wall surface of the through hole after the drilling process. A method of manufacturing a flexible circuit board.

In order to solve the above problems, the cover plate for drilling according to the present invention is characterized in that a water-insoluble lubricating layer composed of a lubricating material and a binder is applied to at least one surface of the substrate.

In the above invention, it is preferable that the lubricating material contains polyethylene as a main component, and the polyethylene has an average particle diameter of 5 μm to 7 μm, a molecular weight of 4000 to 5000, and a melting point of 95 ° C to 130 ° C.

In the above invention, it is preferred that the lubricating material contains polyethylene and polytetrafluoroethylene as main components.

In the above invention, it is preferable that the water-insoluble lubricating layer composed of the lubricating material and the binder has a thickness of 5 μm to 30 μm.

In the above invention, it is preferred that the ratio of the solid content of the lubricating material to the total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight.

In the above-mentioned invention, as the base material which can be applied, in addition to the resin composition film (having a thickness of 125 μm to 250 μm), a metal thin film (0.1 mm to 0.2 mm) or a phenolic paperboard or the like can be given.

Further, in order to solve the above problems, a method for producing a cover plate for drilling according to the present invention is characterized in that a water-insoluble lubricating layer composed of a lubricating material and a binder is applied to at least one surface of a substrate and dried. And formed.

In the above invention, it is preferable that the lubricating material contains polyethylene as a main component, and the polyethylene has an average particle diameter of 5 μm to 7 μm, a molecular weight of 4000 to 5000, and a melting point of 95 ° C to 130 ° C.

In the above invention, it is preferred that the lubricating material contains polyethylene and polytetrafluoroethylene as main components.

In the above invention, it is preferable that the water-insoluble lubricating layer composed of the lubricating material and the binder has a thickness of 5 μm to 30 μm.

In the above invention, it is preferred that the ratio of the solid content of the lubricating material to the total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight.

In the above-mentioned invention, as the base material which can be applied, in addition to the resin composition film (having a thickness of 125 μm to 250 μm), a metal thin film (0.1 mm to 0.2 mm) or a phenolic paperboard or the like can be given.

Further, in order to solve the above problems, the manufacturing method of the flexible printed circuit board of the present invention is characterized in that in the through hole drilling process, at least one surface of the substrate is coated with a water-insoluble lubricating material composed of a lubricating material and a binder. A layer is formed to form a cover for drilling.

In the above invention, it is preferable that the lubricating material contains polyethylene as a main component, and the polyethylene has an average particle diameter of 5 μm to 7 μm, a molecular weight of 4000 to 5000, and a melting point of 95 ° C to 130 ° C.

In the above invention, it is preferred that the lubricating material contains polyethylene and polytetrafluoroethylene as main components.

In the above invention, it is preferable that the water-insoluble lubricating layer composed of the lubricating material and the binder has a thickness of 5 μm to 30 μm.

In the above invention, it is preferred that the ratio of the solid content of the lubricating material to the total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight.

In the above-mentioned invention, as the base material which can be applied, in addition to the resin composition film (having a thickness of 125 μm to 250 μm), a metal thin film (0.1 mm to 0.2 mm) or a phenolic paperboard or the like can be given.

According to the present invention, by suppressing the damage (demagnetization) of the drill bit, the life of the drill can be prolonged, and the quality of the through hole after the drilling process can be optimized.

5‧‧‧ drill bit

10‧‧‧ Cover

12‧‧‧Lubricating layer

14, 15‧‧‧PET

16‧‧‧Pre-drilling

17‧‧‧through hole

20‧‧‧copper laminate

30‧‧‧PET film

Fig. 1 is a cross-sectional view showing the structure of a cover plate for drilling according to the present invention.

(a) of FIG. 2 shows a cross-sectional view of the laminate after the pre-drilling processing and the through-hole processing, and (b) shows the lamination after directly performing the through-hole processing without omitting the pre-drilling processing. A sectional view of the body.

(a) and (b) in Fig. 3 are diagrams showing the quality of the through holes, and (c) are diagrams showing the wear state of the drill.

Fig. 4 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 1.

Fig. 5 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 2.

Fig. 6 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 3.

Fig. 7 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 4.

Fig. 8 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 5.

Fig. 9 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 6.

Fig. 10 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 7.

Fig. 11 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 8.

Fig. 12 is a view showing the state of the surface of the through hole after the drilling of the cover of Test No. 9.

Figure 13 is a graph showing the relationship between the number of drill holes, the bit breakage rate, and the quality of the through holes.

[cover]

Hereinafter, an entry sheet according to an embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing a state in which the drilling cover 10 of the present invention is applied to a copper-clad laminate 20 composed of a plurality of copper-clad laminates.

The entry sheet 10 for drilling according to the present invention comprises a PET film 14 and a water-insoluble lubricating layer 12 formed on the upper surface of the PET film 14. When the drill 5 is moved downward, the lubricating layer 12, the PET film 14, and the copper-plated laminate 20 are sequentially passed through, and after reaching a predetermined depth, the drill 5 is moved upward and detached from the hole (through hole). In addition, in FIG. 1, a PET film 30 is formed on the lower side surface of the copper-plated laminate 20.

The thickness of the PET film 14 constituting the cover 10 of the present invention is from 125 μm to 250 μm, and more preferably 125 μm. The thickness (coating thickness) of the water-insoluble lubricating layer composed of the lubricating material and the binder is preferably from 5 μm to 30 μm.

The lubricating layer 12 is composed of a lubricating material and a binder, and as a solvent thereof, butyl acetate, ethyl acetate, and toluene are preferable. The lubricating material is polyethylene, and the average particle diameter thereof is preferably 5 μm to 7 μm. As the binder, isocyanate denaturation polybutadiene or boil denaturation polybutadiene is preferred. The mixing method of these substances is not particularly limited as long as it is a well-known method used industrially. Specifically, the above composition is appropriately heated or heated using a roll, a kneader or other mixing device to form a homogeneous mixture.

[Method of Manufacturing Cover Plate]

The cover plate is produced by a stirring step, a coating step, and a drying step.

First, the mixture was stirred for 10 minutes using a mixing device in such a manner that the ratio of the solid content of the lubricating material to the total solid content of the lubricating layer was from 13.0% by weight to 23.1% by weight. At this time, the lubricating material is in a state of being dispersed in a solvent.

Then, the mixture after stirring was subjected to a coating and drying step using a coating machine (manufactured by Kobayashi Kobayashi Co., Ltd., COATER KS-001) to volatilize the solvent in the mixture to obtain a cover having a film thickness of 5 μm to 20 μm.

When the cover is manufactured, the coater is set to the conditions shown below, but is not limited thereto.

<conditioner setting of coating machine>

The line speed is set to 7 (m/min), the MR/AR speed is set to 6.5/8.0, and for the tension, the first unwinder is set to 7 kg, the dryer is set to 12 kg, and the DR setting is set. It was 3 kg/cm ² , the winding was set to 1 N, and the dryer temperature was set to 120 ° C and 150 ° C. In the coating machine used, the dryer temperature has a first range and a second range, and when implemented, the first range is set to 120 ° C and the second range is set to 150 ° C. Here, MR (metering roll) is an abbreviation of metering roller, AR (applicator roll) is an abbreviation of coating roller, and MR and AR speed are unitless, which is a relative value with respect to linear velocity (coating used) The value that is unique to the machine). In addition, DR (dancer roll) is an abbreviation for elastic adjusting roller.

Further, as the polyethylene used as the lubricating material in the cover of the present invention, polyethylene having an average particle diameter of 5 μm to 7 μm can be suitably used. When the particle diameter is too small, the function of imparting lubricity to the lubricating layer is lowered, and on the other hand, if the particle diameter is too large, the chips are likely to adhere to the drill. Further, the shape of the polyethylene particles may be a spherical shape, a square shape, a cylindrical shape, a needle shape, a plate shape or an indefinite shape. However, in the present invention, from the viewpoint of imparting lubricity to the lubricating layer, it is preferred to use spherical particles. According to the form, it is possible to impart high lubricity and to prevent the chips from adhering to the drill. By setting the average particle diameter of the polyethylene within the above range, the polyethylene is protruded from the surface of the lubricating layer, so that the cover sheet has appropriate lubricity.

It is preferred to contain polyethylene particles in a mixing ratio of from 13.0% by weight to 23.1% by weight based on the total solid content (100% by weight) of the lubricating layer. If the content is too small, the lubricity of the lubricating layer is lowered, and if the content is too large, the chips are likely to adhere to the drill.

Further, the melting point of the polyethylene is preferably from 95 ° C to 130 ° C. If the melting point is too low, the preservability of the cover plate is lowered, or the polyethylene itself is melted in the drying process after the application of the lubricating layer, thereby hindering the lubricity of the lubricating layer, and on the other hand, if the melting point is too high Then, the surface unevenness of the lubricating layer becomes remarkable. Further, regarding the measurement of the melting point, it can be measured using a conventionally known method, for example, using a differential scanning calorimeter (DSC). Further, the molecular weight of the polyethylene is preferably from 4,000 to 5,000.

[Method of Manufacturing Flexible Printed Circuit Board]

As a method of mass-producing a flexible printed circuit on a copper-clad laminate 20 by laminating a cover plate of the present invention, a roll-to-roll method is employed. After passing through the through hole drilling process, the via plating process, the resist coating process, the pattern exposure process, the etching process, the terminal surface treatment process, etc., it is set as the flexible circuit board.

The through hole drilling process is performed using an NC drilling device (not shown) having a roll-to-roll conveying function. The NC drilling device is capable of drilling a hole of about 0.1 mm and is provided with a spindle. The cover sheet 10 of the present invention is placed on the upper side of the copper-plated laminate 20 and the PET film 30 is placed on the lower side so as to sandwich the copper-plated laminate 20, as shown in (b) of FIG. The driving drill (not shown) is rotated, and the drill is moved downward from above the cover 10 to form the through hole 17.

In the prior art, the through hole processing is performed after the pre-drill processing (the process of forming the pre-drill 16) as shown in (a) of FIG. 2 is performed, but in the present invention, for the lamination In the copper-plated laminate 20 of the cover 10 of the present invention, the through-hole processing can be directly performed by omitting the pre-drilling processing. because Since the pre-drilling processing step can be omitted, the manufacturing processing time can be shortened, and thus cost reduction can be achieved.

When the flexible printed circuit board or the like is drilled using a drill, the cover of the present invention is placed on the uppermost layer of the flexible printed circuit board or the like (the drill entering side), and the pallet is placed on the lowermost layer as needed (also called For the back up board, the boards are overlapped and drilled. The processed flexible printed circuit board is not particularly limited and may be any one of a single-sided circuit board, a double-sided circuit board, and a multilayer circuit board. In addition, the material of the flexible printed circuit board may be a phenol resin, an epoxy resin, a polyimide resin, a polyester resin, or a triazine resin. Any one of a resin, a fluororesin, and the like, or a fiber-reinforced resin obtained by reinforcing these resins with glass fibers or the like.

Further, according to the cover plate of the present invention, even when drilling with a small-diameter drill as described below, lateral sliding rarely occurs, and drilling with high positional accuracy (high centripetality) can be performed, so that it is used for Drilling processing with a hole diameter of about 1mm~6mm can be suitably used for drilling with small apertures, especially for drilling with a hole diameter of 0.1mm~0.4mm, and it is more suitable for use with a hole diameter of 0.1. Drilling with mm~0.3mm is most suitable for drilling with a hole diameter of 0.1mm~0.2mm.

[Performance test of cover plate 1]

In the following, the cover plate not containing the lubricating material, and the cover plate made by changing the mixing ratio, coating thickness, and drying conditions of the three lubricating materials are subjected to NC drilling processing, for the first hole, the 5000th hole, and the 10000th. The presence or absence of the wall surface of the 100,000th hole, the presence or absence of the wall burr, the presence or absence of the interface peeling, the presence or absence of the peeling of the through hole of the first hole and the 100,000th hole, and the passage of the first hole and the 100,000th hole Hole copper foil The presence or absence of deformation, the presence or absence of breakage of the drill (durability of the drill), the degree of adhesion of the chips on the drill, the degree of wear of the drill, and the centripetality (drilling position accuracy) were evaluated.

A total of nine kinds of cover plates (test plates No. 1 to No. 9) were tested, and the evaluation results are shown in Table 1 below.

Next, the criteria for evaluation will be described.

In the evaluation of the wall surface unevenness, the wall surface unevenness is substantially indicated by "◎", and the unevenness is observed, but the influence of the drill is affected by the "○", and the unevenness is observed. "△" indicates that there is unevenness and the plating may be caused by adhesion to the drill or the like, which may cause plating failure or the like, and the use of "X" is indicated. For example, the diagram on the left side of (a) in FIG. 3 shows a state in which there is no wall surface unevenness, and the diagram on the right side shows a state in which the wall surface is uneven.

In the evaluation of burrs, the absence of burrs is indicated by "◎", and some burrs are used, but the quality of the through holes is not indicated by "○". If there is burr but the influence on the quality of the through holes is small, "△" is used. Indicates that there is a burr and the influence on the quality of the through hole is not small represented by "x".

In the evaluation of the interface peeling, none of the cover sheets of No. 1 to No. 9 were peeled off, and in the evaluation of the deformation of the copper foil, all the cover sheets of No. 1 to No. 9 were not deformed, and the drill was broken. In the evaluation, none of the covers of No. 1 to No. 9 were damaged.

<Example 1 (Test Plate No. 1)>

As a lubricating material constituting the cover plate according to the first embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) was used, and isocyanate-denatured polybutadiene (isocyanate denaturation) was used as a binder. Polybutadiene) (trade name: TP-1001, manufactured by Nippon Soda Co., Ltd.), and the content of the lubricating material is 50%. The cover sheet had a coating thickness (film thickness) of 20 μm and was formed by drying at 150 ° C for five minutes after being subjected to agitation treatment with polyethylene and a binder.

(a) of FIG. 4 is a view of the first through hole as viewed from above, and (b) of FIG. 4 is a view of the first through hole viewed obliquely from above. (c) of FIG. 4 is a view of the 5000th through hole viewed from above, and (d) of FIG. 4 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 4 is a view of the 10000th through hole viewed from above, and (f) of FIG. 4 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 4 is a view of the 100,000th through hole viewed from above, and (h) in Fig. 4 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1, it is understood that the cover plate of the test plate No. 1 has substantially no wall surface unevenness until the 5,000th hole (refer to (b), (d) in Fig. 4), and the presence or absence of peeling of the through-hole plating layer on the drill bit The degree of adhesion of the chips and the degree of wear of the drills were all good.

<Example 2 (test plate No. 2)>

As a lubricating material constituting the cover plate according to the second embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) is used, and isocyanate-modified polybutadiene (trade name) is used as a binder. : TP-1001, manufactured by Nippon Soda Co., Ltd., so that the content of the lubricating material is 33%. The cover sheet had a coating thickness (film thickness) of 10 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 5 is a view of the first through hole viewed from above, and (b) of FIG. 5 is a view of the first through hole viewed obliquely from above. (c) of FIG. 5 is a view of the 5000th through hole viewed from above, and (d) of FIG. 5 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 5 is a view of the 10000th through hole viewed from above, and (f) of FIG. 5 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 5 is a view of the 100,000th through hole as viewed from above, and (h) in Fig. 5 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 2 can see a slight wall unevenness until the 10000th hole (see (b), (d), (f) in Fig. 5). Regarding the presence or absence of the peeling of the via plating and the centripetality, the results were basically good. The degree of adhesion of the chips on the drill bit is slightly increased as compared with the first embodiment, but to the extent that the influence on the quality of the through hole is small. Regarding the degree of wear of the drill bit, how much wear occurs but has not yet been replaced.

<Example 3 (test plate No. 3)>

As a lubricating material constituting the cover plate according to the third embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) is used, and isocyanate-modified polybutadiene (trade name) is used as a binder. : TP-1001, manufactured by Nippon Soda Co., Ltd., so that the content of the lubricating material is 33%. The cover sheet had a coating thickness (film thickness) of 20 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 6 is a view of the first through hole as viewed from above, and (b) of FIG. 6 is a view of the first through hole viewed obliquely from above. (c) of FIG. 6 is a view of the 5000th through hole viewed from above, and (d) of FIG. 6 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 6 is a view of the 10000th through hole viewed from above, and (f) of FIG. 6 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 6 is a view of the 100,000th through hole as viewed from above, and (h) in Fig. 6 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 3 can see a slight wall unevenness until the 10000th hole (see (b), (d), (f) in Fig. 6). Regarding the presence or absence of peeling of the via plating, the degree of adhesion of the chips on the drill, the degree of wear of the drill, and the centripetality, the results were basically good.

<Example 4 (Test Plate No. 4)>

As a lubricating material constituting the cover plate according to the fourth embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) was used, and isocyanate-modified polybutadiene (trade name) was used as a binder. : TP-1001, manufactured by Nippon Soda Co., Ltd., so that the content of the lubricating material is 50%. The cover sheet had a coating thickness (film thickness) of 10 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 7 is a view of the first through hole viewed from above, and (b) of FIG. 7 is a view of the first through hole viewed obliquely from above. (c) of FIG. 7 is a view of the 5000th through hole viewed from above, and (d) of FIG. 7 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 7 is a view of the 10000th through hole viewed from above, and (f) of FIG. 7 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 7 is a view of the 100,000th through hole as viewed from above, and (h) in Fig. 7 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 4 does not substantially see the wall surface unevenness until the 10000th hole, and the wall surface unevenness is slightly seen in the 100,000th hole (refer to (b), (d in Fig. 7). ), (f), (h)). The burrs are slightly present, but have less impact on the quality of the vias. In addition, as for the presence or absence of the peeling of the through-hole plating, some peeling can be seen, but the degree is such that the influence on the quality of the through-hole is small.

<Example 5 (test plate No. 5)>

As a lubricating material constituting the cover plate according to the fifth embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) was used, and isocyanate-modified polybutadiene was used as a binder (trade name: TP-1001, manufactured by Nippon Soda Co., Ltd., so that the content of the lubricating material is 50%. The cover sheet had a coating thickness (film thickness) of 20 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 8 is a view of the first through hole viewed from above, and (b) of FIG. 8 is a view of the first through hole viewed obliquely from above. (c) of FIG. 8 is a view of the 5000th through hole viewed from above, and (d) of FIG. 8 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 8 is a view of the 10000th through hole viewed from above, and (f) of FIG. 8 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 8 is a view of the 100,000th through hole as viewed from above, and (h) in Fig. 8 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 5 does not substantially see the wall surface irregularities until the 5,000th hole, and the wall surface unevenness is slightly seen in the 10000th hole and the 100,000th hole (refer to FIG. 8 (b), (d), (f), (h)). Regarding the presence or absence of peeling of the via plating, the result was basically good. Regarding the degree of adhesion of the chips on the drill bit, it is slightly more than that of the first embodiment, but the degree is brought about by the quality of the through hole. The extent of the impact is small. Regarding the degree of wear of the drill bit, how much wear occurs but has not yet been replaced.

<Example 6 (test plate No. 6)>

As a lubricating material constituting the cover plate according to the sixth embodiment, polyethylene (trade name: ZJ-24FA, manufactured by JP Co., Ltd.) was used, and isocyanate-modified polybutadiene was used as a binder for mixing. (trade name: TP-1001, manufactured by Nippon Soda Co., Ltd.), and the content ratio of polyethylene (lubricating material) was 33%. The cover sheet had a coating thickness (film thickness) of 10 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 9 is a view of the first through hole as viewed from above, and (b) of FIG. 9 is a view of the first through hole viewed obliquely from above. (c) of FIG. 9 is a view of the 5000th through hole viewed from above, and (d) of FIG. 9 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 9 is a view of the 10000th through hole viewed from above, and (f) of FIG. 9 is a view of the 10000th through hole viewed obliquely from above. (g) in FIG. 9 is a view of the 100,000th through hole viewed from above, and (h) in FIG. 9 is a view of the 100,000th through hole viewed obliquely from above.

Referring to Table 1, it is understood that the cover plate of the test plate No. 6 has a slight unevenness in the wall surface in the 5,000th hole, and the wall surface unevenness is hardly observed in the 10000th hole (refer to (b) and (d) in Fig. 9 , (f), (h)). Regarding the presence or absence of peeling of the via plating, the result was basically good. In addition, the burrs can be seen slightly, but to the extent that the effect on the quality of the through holes is small. The degree of adhesion of the chips on the drill bit is slightly increased as compared with the first embodiment, but to the extent that the influence on the quality of the through hole is small.

<Example 7 (test plate No. 7)>

As a lubricating material constituting the cover plate according to the seventh embodiment, polyethylene (trade name: XD-448 (microcrystalline paraffin), manufactured by JP Co., Ltd.) is used, and isocyanate-modified polybutylene is used as a binder. Diene (trade name: TP-1001, manufactured by Nippon Soda Co., Ltd.), the content of the lubricating material was 33%. The cover sheet had a coating thickness (film thickness) of 10 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 10 is a view of the first through hole viewed from above, and (b) of FIG. 10 is a view of the first through hole viewed obliquely from above. (c) of FIG. 10 is a view of the 5000th through hole viewed from above, and (d) of FIG. 10 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 10 is a view of the 10000th through hole viewed from above, and (f) of FIG. 10 is a view of the 10000th through hole viewed obliquely from above. (g) in FIG. 10 is a view of the 100,000th through hole viewed from above, and (h) in FIG. 10 is a view of the 100,000th through hole viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 7 can slightly see the wall surface irregularities until the 5,000th hole, and the wall surface unevenness is substantially not seen in the 10000th hole and the 100,000th hole (refer to FIG. 10 (b), (d), (f), (h)). The burrs are slightly present, but to the extent that they have a lesser effect on the quality of the through holes. Regarding the presence or absence of the peeling of the through-hole plating, some peeling can be seen, but the extent is such that the influence on the quality of the through-hole is small. Regarding the deformation of the through-hole copper foil, the deformed portion can be seen sporadically in the 10,000th hole, but the degree is such that the influence on the quality of the through-hole is small. The degree of adhesion of the chips on the drill bit is slightly increased as compared with the first embodiment, but to the extent that the influence on the quality of the through hole is small. Regarding the degree of wear of the drill bit, how much wear occurs but has not yet been replaced.

<Example 8 (test plate No. 9)>

As a lubricating material constituting the cover plate according to the eighth embodiment, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) was used, and isocyanate-modified polybutadiene (trade name) was used as a binder. : TP-1001, manufactured by Nippon Soda Co., Ltd., so that the content of the lubricating material is 33%. The cover sheet had a coating thickness (film thickness) of 30 μm and was formed by drying at 120 ° C for two minutes after being subjected to agitation treatment with polyethylene and a binder, and further drying at 150 ° C for three minutes.

(a) of FIG. 12 is a view of the first through hole viewed from above, and (b) of FIG. 12 is a view of the first through hole viewed obliquely from above. (c) of FIG. 12 is a view of the 5000th through hole viewed from above, and (d) of FIG. 12 is a view of the 5000th through hole viewed obliquely from above. (e) of FIG. 12 is a view of the 10000th through hole viewed from above, and (f) of FIG. 12 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 12 is a view of the 100,000th through hole viewed from above, and (h) in Fig. 12 is a view of the 100,000th through hole viewed obliquely from above.

Referring to Table 1, it can be seen that the cover plate of the test plate No. 9 can see a slight wall unevenness until the 10000th hole (see (b), (d), (f) in Fig. 12). Regarding the presence or absence of peeling of the via plating, the degree of adhesion of the chips on the drill, the degree of wear of the drill, and the centripetality, the results were basically good.

<Comparative Example 1 (test plate No. 8)>

The cover sheet of Comparative Example 1 was formed using a 250 μm PET film and did not contain a lubricating material.

(a) of FIG. 11 is a view of the first through hole viewed from above, and (b) of FIG. 11 is a view of the first through hole viewed obliquely from above. (c) in Fig. 11 is a view of the 5000th through hole viewed from above, (d) in Fig. 11 A diagram of the 5000th through hole is observed from obliquely above. (e) of FIG. 11 is a view of the 10000th through hole viewed from above, and (f) of FIG. 11 is a view of the 10000th through hole viewed obliquely from above. (g) in Fig. 11 is a view of the 100,000th through hole as viewed from above, and (h) in Fig. 11 is a view of the 100,000th through hole as viewed obliquely from above.

Referring to Table 1 and Fig. 11, it can be seen that the cover of the test plate No. 8 can see the wall surface irregularities from the first hole, and similarly, in the 5,000th hole, the 10,000th hole, and the 100,000th hole. The wall surface unevenness is seen (refer to (b), (d), (f), (h) in Fig. 11). It can be confirmed that the burr is present, and the peeling of the plating of the through hole can be seen sporadically, the degree of wear of the drill bit is high, and the amount of eccentricity of the through hole is also large.

[Evaluation Results and Research]

According to the above test items of the cover sheets according to Examples 1 to 7 obtained by mixing the lubricating material and the binder (the presence or absence of wall irregularities, the presence or absence of wall burrs, the presence or absence of peeling of the through-hole plating, the degree of adhesion of the chips on the drill, and The evaluation results of the degree of wear of the drill bit were studied.

In addition, since there is substantially no deformation of the copper foil, the quality of the through hole can be improved, and the quality of the flexible printed circuit board can be improved. Further, since the thickness of the PET film can be made thinner than the cover film composed of the PET film of the prior art in the PET film located under the lubricating layer, the material cost can be reduced.

Regarding the wall unevenness, the results of Examples 4 and 5 were good in the case of the 5,000th hole, and the results of Examples 4, 6, and 7 in the case of the 10000th hole were good. From this, it can be seen that when the lubricating material is ZJ-22, the wall surface unevenness can be reduced when the content ratio of the lubricating material is 50%.

Regarding the presence or absence of peeling of the via plating, the results of Examples 3, 5, and 6 were good at the 10,000th hole. From this, it can be seen that when the lubricating material is ZJ-22, peeling of the via plating can be reduced with a coating thickness of 20 μm.

Regarding the degree of adhesion of the chips on the drill, the results of Examples 1 and 3 were good. From this, it can be seen that when the lubricating material is ZJ-22, the degree of adhesion of the chips on the drill can be reduced with a coating thickness of 20 μm.

[Performance test of cover plate 2]

Next, tests for evaluating the bit breakage rate and the drilling quality of the present invention and the conventional cover were carried out.

As a lubricating material constituting the cover sheet of the present invention, polyethylene (trade name: ZJ-22, manufactured by JP Co., Ltd.) is used, and isocyanate-modified polybutadiene (trade name: TP-) is used as a binder. 1001, manufactured by Nippon Soda Co., Ltd.), the content of the lubricating material is 33%. The cover sheet had a coating thickness (film thickness) of 5 μm and was formed by drying at 150 ° C for five minutes after being subjected to agitation treatment with polyethylene and a binder.

The existing cover is composed of a 250 μm PET layer and does not contain a lubricating material.

The evaluation results are shown in Fig. 13. Figure 13 is a graph showing the relationship between the number of drill holes and the bit breakage rate (%) and the quality of the through hole, wherein the horizontal axis is the number of holes (×1000), and the vertical axis is the bit breakage rate (%) and the through hole. quality.

The through-hole quality is a value obtained by comprehensive evaluation of the unevenness of the wall surface of the through-hole, peeling of the plating layer, and deformation, and the larger the value, the better the quality. In addition, the quality of the through hole is represented by a numerical value quantified according to a predetermined standard. The "-○-" line indicates the curve of the bit breakage rate (%) of the cover of the present invention, and the "-□-" line indicates the curve of the through hole quality of the cover of the present invention. The "-?-" line indicates the curve of the bit breakage rate (%) of the conventional cover (Comparative Example), and the "-X-" line indicates the curve of the through hole quality of the conventional cover.

[Evaluation Results and Research]

Regarding the bit breakage, in the case of the cover of the present invention, the bit breakage does not occur in more than 10,000 holes, and in the case of the conventional cover plate, the bit breakage rate starts to rise from about 10,000 holes.

Regarding the quality of the through hole, the cover plate of the present invention and the conventional cover plate are somewhat different in the initial stage, but as the number of drilled holes increases, the quality of both of them deteriorates slowly, and the quality is substantially the same.

As apparent from the above description, according to the cover of the present invention, it is possible to suppress the breakage of the drill while maintaining a certain quality of the through hole, and it is possible to extend the life of the drill.

Although an embodiment of the present invention has been described above, the present invention can be variously modified in addition to the above.

Claims (12)

A cover plate for drilling processing, characterized in that at least one surface of a substrate is formed by coating a water-insoluble lubricating layer composed of a lubricating material and a binder, and the lubricating material is mainly composed of polyethylene. The average particle diameter of ethylene is 5 μm to 7 μm, the molecular weight is 4000 to 5000, and the melting point is 95 ° C to 130 ° C. The cover plate for drilling according to claim 1, wherein the lubricating material is mainly composed of polyethylene and polytetrafluoroethylene. The cover sheet for drilling according to claim 1, wherein the water-insoluble lubricating layer composed of a lubricating material and a binder has a thickness of 5 μm to 30 μm. The cover sheet for drilling according to any one of claims 1 to 3, wherein a ratio of a solid content of the lubricating material to a total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight. A method for manufacturing a cover plate for drilling, characterized in that a water-insoluble lubricating layer composed of a lubricating material and a binder is coated on at least one surface of a substrate and dried, and the lubricating material is aggregated Ethylene is the main component, and the polyethylene has an average particle diameter of 5 μm to 7 μm, a molecular weight of 4000 to 5000, and a melting point of 95 ° C to 130 ° C. The method for producing a cover plate for drilling according to claim 5, wherein the lubricating material is mainly composed of polyethylene and polytetrafluoroethylene. The method of manufacturing a cover plate for drilling according to claim 5, wherein The water-insoluble lubricating layer composed of a lubricating material and a binder has a thickness of 5 μm to 30 μm. The method for producing a cover sheet for drilling according to any one of claims 5 to 7, wherein a ratio of a solid content of the lubricating material to a total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight. . A manufacturing method of a flexible printed circuit board, comprising: a through hole drilling process, wherein the manufacturing method of the flexible printed circuit board is characterized in that, in the through hole drilling process, coating on at least one surface of the substrate a water-soluble lubricating layer composed of a lubricating material and a binder to form a cover plate for drilling, wherein the lubricating material is mainly composed of polyethylene, and the polyethylene has an average particle diameter of 5 μm to 7 μm and a molecular weight of 4000 to 5000. The melting point is 95 ° C ~ 130 ° C. The method of manufacturing a flexible printed circuit board according to claim 9, wherein the lubricating material is mainly composed of polyethylene and polytetrafluoroethylene. The method of manufacturing a flexible printed circuit board according to claim 9, wherein the water-insoluble lubricating layer composed of a lubricating material and a binder has a thickness of 5 μm to 30 μm. The method of manufacturing a flexible printed circuit board according to any one of claims 9 to 11, wherein a ratio of a solid content of the lubricating material to a total solid content of the lubricating layer is from 13.0% by weight to 23.1% by weight.