CN108419432B

CN108419432B - Cover plate, method for manufacturing cover plate, and method for manufacturing flexible circuit board

Info

Publication number: CN108419432B
Application number: CN201780003034.8A
Authority: CN
Inventors: 赤尾悠; 田中秀明; 伊藤保之; 浦充贵; 梅泽荣一
Original assignee: Nippon Mektron KK
Current assignee: Nippon Mektron KK
Priority date: 2016-12-09
Filing date: 2017-08-24
Publication date: 2021-09-07
Anticipated expiration: 2037-08-24
Also published as: CN108419432A; JP6351865B1; TW201822601A; WO2018105176A1; TWI650054B; JPWO2018105176A1

Abstract

The invention provides a cover plate for drilling, a manufacturing method of the cover plate for drilling and a manufacturing method of a flexible circuit board, which can prolong the service life of a drill by inhibiting the damage of the drill and optimize the quality of a through hole after drilling. The cover plate for drilling of the present invention is formed by applying a water-insoluble lubricating layer composed of a lubricating material and a binder to at least one surface of a base material.

Description

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

Technical Field

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

Background

In mass production of Flexible Printed Circuit boards (FPCs), a roll-to-roll method is known as a mass production method. In the first stage of the manufacturing process of a flexible circuit board having a through-hole structure, there are a through-hole drilling process and a through-hole plating process. After that, a resist coating step, a pattern forming step, an etching step, a terminal portion surface treatment step, and the like are performed to produce a flexible printed circuit board.

Among these steps, the through hole drilling step is the first step of manufacturing a flexible circuit board having a through hole structure, and in this step, a drilling method (drilling method) using an NC drilling device having a roll-to-roll transfer function is applied. The NC drilling device can drill holes of about 40 μm in minimum, is equipped with a vertical shaft, and can perform drilling processing by stacking a plurality of copper Clad laminates (FCCL: substrate). The number of stacked copper clad laminates is usually two (two layers), four (four layers), five (five layers), and eight (eight layers).

In addition, the copper clad laminate is a main component constituting the flexible printed circuit board, and has the following structure: an adhesive layer is formed on a film-like insulator base film (e.g., a polyimide film) having a thickness of 12 to 100 μm, and a conductor foil (e.g., a copper foil) having a thickness of about 12 to 50 μm is further bonded to the adhesive layer. The terminal portion or the welded portion is protected by being covered with an insulator. As a material of the insulator, various plastics such as polyimide or Polyester (PET) are used. Copper foil is generally used as the conductor. As the adhesive layer, an epoxy resin-based or acrylic resin-based adhesive is mainly used. Since the flexible printed circuit board can be folded, it is an essential material for a connection portion of a mobile phone, a personal computer, a digital camera, or the like.

As a method for drilling a copper clad laminate, the following method is generally employed: a method of laminating the copper clad laminates and disposing an aluminum foil or the like on the uppermost part of the laminate and drilling the laminate. In recent years, with the increasing demands for reliability and densification of printed wiring board materials, high-quality drilling for improving hole position accuracy, reducing hole wall roughness, and the like has been required, and in order to meet such demands, a drilling method of a drilling cover plate using polyethylene glycol (see, for example, patent document 1), a cover plate containing a water-soluble lubricant as a main component in view of easiness of recycling of an aluminum plate coating, and the like have been proposed and put into practical use. In recent years, in order to improve flexibility and prevent scratches, a pet (polyethylene terephthalate) film having hardness is used in a cover plate for NC drilling of a flexible printed circuit board.

Documents of the prior art

Patent document

Patent document 1: JP-A4-92488

Disclosure of Invention

However, the water-soluble lubricant is sticky and adheres to fingerprints when touched, which deteriorates the workability. In recent years, with the progress toward miniaturization of wiring patterns and reduction in diameter of through holes in order to achieve miniaturization and weight reduction of printed wiring boards, resin components used in PET films have adhered to the wall surfaces of drills, particularly in the progress of miniaturization of wiring patterns and reduction in diameter of through holes

In the following small-diameter machining, the drill may be broken, and in this case, the drill may be broken poorly, the life may be shortened, and the through hole wall surface may have a remarkable unevenness or burr.

The subject of the invention is to: provided are a cover plate for drilling, a method for manufacturing the cover plate for drilling, and a method for manufacturing a flexible circuit board, wherein the life of a drill is prolonged by suppressing breakage of the drill, and unevenness and burrs on the wall surface of a through hole after drilling are suppressed.

In order to solve the above problems, a cover plate for drilling according to the present invention is characterized in that: the base material is coated on at least one surface with a water-insoluble lubricating layer composed of a lubricating material and a binder, wherein the lubricating material mainly contains polyethylene, the polyethylene has an average particle diameter of 5-7 μm, a molecular weight of 4000-5000 and a melting point of 95-130 ℃.

In the above invention, the lubricant preferably contains polyethylene and polytetrafluoroethylene as main components.

In the above invention, the thickness of the water-insoluble lubricating layer composed of the lubricating material and the binder is preferably 5 μm to 30 μm.

In the above invention, the solid content of the lubricant is preferably 13.0 wt% to 23.1 wt% with respect to the total solid content of the lubricant layer.

In the above invention, examples of applicable substrates include a resin composition film (having a thickness of 125 to 250 μm), a metal film (0.1 to 0.2mm), a phenolic cardboard, and the like.

In order to solve the above problem, a method for manufacturing a cover plate for drilling according to the present invention includes: the lubricant is formed by coating a water-insoluble lubricant layer composed of a lubricant and a binder on at least one surface of a base material and then drying the coated layer, wherein the lubricant comprises polyethylene as a main component, the polyethylene has an average particle diameter of 5-7 μm, a molecular weight of 4000-5000 and a melting point of 95-130 ℃.

In order to solve the above problems, a method for manufacturing a flexible printed circuit board according to the present invention includes: in the through-hole drilling step, a water-insoluble lubricating layer comprising a lubricating material and a binder is applied to at least one surface of a base material to form a drilling cover plate, wherein the lubricating material comprises polyethylene as a main component, the polyethylene has an average particle diameter of 5 to 7 [ mu ] m, a molecular weight of 4000 to 5000, and a melting point of 95 to 130 ℃.

Effects of the invention

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

Drawings

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

Fig. 2(a) is a cross-sectional view showing the laminate after the bottom hole forming process and the through hole forming process, and (b) is a cross-sectional view showing the laminate after the through hole forming process is directly performed without the bottom hole forming process.

Fig. 3(a) and (b) are diagrams illustrating the quality of the through hole, and (c) is a diagram illustrating the wear state of the drill.

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

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

FIG. 6 is a view showing the surface state of the through hole of the cover plate of test No.3 after the drilling.

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

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

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

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

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

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

Fig. 13 is a graph showing the relationship between the number of drilled holes, the breakage rate of the drill, and the quality of the through-hole.

Description of the symbols

5 … drill bit

10 … cover plate

12 … lubricant layer

14、15…PET

16 … bottom hole

17 … through hole

20 … copper clad laminate

30 … PET film

Detailed Description

[ cover plate ]

Hereinafter, a cover plate 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 where a copper clad laminate 20 composed of a plurality of copper clad laminates is coated with a drilling cover sheet 10 of the present invention. The cover plate 10 for drilling of the present invention is composed of a PET film 14 and a water-insoluble lubricant layer 12 formed on the upper surface of the PET film 14. When the drill 5 moves downward, the drill 5 penetrates the lubricant layer 12, the PET film 14, and the copper-clad laminate 20 in this order, and after reaching a predetermined depth, the drill moves upward and is detached from the hole (through hole). In fig. 1, a PET film 30 is formed on the lower surface of the copper-clad laminate 20.

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

The lubricant layer 12 is made of a lubricant and a binder, and the solvent is preferably butyl acetate, ethyl acetate, or toluene. The lubricant is polyethylene, and the average particle diameter thereof is preferably 5 to 7 μm. The binder is preferably isocyanate-modified polybutadiene or retort-modified polybutadiene. The method for mixing these substances is not particularly limited as long as it is a known method used industrially. Specifically, the composition is heated or kneaded using a roll, a kneader, or another kneading device as appropriate to form a uniform mixture.

[ method for producing cover plate ]

The cover plate is manufactured through the stirring process, the coating process and the drying process.

First, a mixture was obtained by stirring for 10 minutes using a kneading apparatus so that the ratio of the solid content of the lubricant to the total solid content of the lubricant layer was 13.0 wt% to 23.1 wt%. At this time, the lubricant is dispersed in the solvent.

Then, the stirred mixture was subjected to coating and drying steps using a coating machine (COATER KS-001, manufactured by Xiaolingsha, JP K.K.) to volatilize the solvent in the mixture, thereby obtaining a cover plate having a film thickness of 5 μm to 20 μm.

When the cover plate is manufactured, the coater is set to the following conditions, but the present invention is not limited thereto.

< Condition setting of coating machine >

The line speed was set to 7(m/min), the MR/AR speed was set to 6.5/8.0, the first unwinder was set to 7kg, the dryer was set to 12kg, and the DR was set to 3kg/cm for tension²The winding was set to 1N, and the temperature of the dryer was set to 120 ℃ and 150 ℃. In the coating machine used, the dryer temperature has a first range and a second range, and in the case of implementation, the first range is set to 120 ℃ and the second range is set to 150 ℃. Here, MR is an abbreviation for metering roll, AR is an abbreviation for coating roll, and the speeds of MR, AR are unitless and relative values to the line speed (used)A value specific to the coating machine). In addition, DR is an abbreviation of dancer roll.

The polyethylene used as the lubricant in the cover plate of the present invention may be suitably polyethylene having an average particle diameter of 5 to 7 μm. If the particle diameter is too small, the function of imparting lubricity to the lubricating layer is reduced, while if the particle diameter is too large, the chips are liable to adhere to the drill. The shape of the polyethylene particles may be spherical, square, columnar, needle-shaped, plate-shaped, or irregular, but in the present invention, from the viewpoint of imparting lubricity to the lubricating layer, it is preferable to adopt a spherical particle form, whereby it is possible to impart high lubricity and to prevent chips from adhering to the drill. By setting the average particle diameter of the polyethylene within the above range, the polyethylene protrudes from the surface of the lubricating layer, so that the cover plate has appropriate lubricity.

The polyethylene particles are preferably contained in a mixing ratio of 13.0 wt% to 23.1 wt% with respect to the total solid content (100 wt%) 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. The melting point of the polyethylene is preferably 95 to 130 ℃. If the melting point is too low, the storage stability of the cover sheet is lowered, or the polyethylene itself is melted in the drying step after the lubricant layer is applied, thereby hindering the lubricity of the lubricant layer, whereas if the melting point is too high, the surface unevenness of the lubricant layer becomes remarkable. The melting point can be measured by a conventionally known method, for example, by a Differential Scanning Calorimeter (DSC). The polyethylene preferably has a molecular weight of 4000 to 5000.

[ method for manufacturing Flexible printed Circuit Board ]

As a method for mass production of flexible printed circuit boards by laminating the cover sheet of the present invention on the copper-clad laminate 20, a roll-to-roll method is employed. After a through-hole drilling process, a through-hole plating process, a resist coating process, a pattern exposure process, an etching process, a terminal surface treatment process, and the like, a flexible circuit board is manufactured.

The through hole drilling process is performed using an NC drilling device (not shown) having a roll-to-roll transfer function. The NC drilling device is capable of drilling holes of around 0.1mm, equipped with a vertical shaft. After the cover sheet 10 of the present invention is stacked on the upper side of the copper-clad laminate 20 and the PET film 30 is stacked on the lower side thereof so as to sandwich the copper-clad laminate 20, as shown in fig. 2(b), a drill (not shown) is driven to rotate and moved downward from above the cover sheet 10, thereby forming the through hole 17. In the prior art, the via hole processing is performed after the bottom hole processing (the processing of forming the bottom hole 16) as shown in fig. 2(a) is performed, but in the present invention, the via hole processing may be performed directly on the copper-clad laminate 20 in which the cover sheet 10 of the present invention is laminated without the bottom hole processing. Therefore, since the bottom hole processing step can be omitted, the manufacturing processing time can be shortened, and thus the cost can be reduced.

When drilling a flexible printed circuit board or the like with a drill, the cover sheet of the present invention is disposed on the uppermost layer (drill entry side) of the flexible printed circuit board or the like, and if necessary, a pallet (also referred to as a back up board) is disposed on the lowermost layer, and these sheets are stacked and then drilled. The flexible printed circuit board to be processed is not particularly limited, and may be any of a single-sided circuit board, a double-sided circuit board, and a multilayer circuit board. The flexible printed wiring board may be made of any one of a phenol resin, an epoxy resin, a polyimide resin, a polyester resin, a triazine resin, a fluorine resin, and the like, or may be a fiber-reinforced resin reinforced with glass fibers or the like.

Further, the cover plate of the present invention is less likely to cause lateral slippage even when drilling is performed with a small-diameter drill as described below, and can perform drilling with high positional accuracy (high centering), and therefore, it is not only applicable to drilling with a hole diameter of about 1mm to 6mm, but also applicable to drilling with a small hole diameter, particularly to drilling with a hole diameter of 0.1mm to 0.4mm, more particularly to drilling with a hole diameter of 0.1mm to 0.3mm, and most preferably to drilling with a hole diameter of 0.1mm to 0.2 mm.

[ Performance test 1 of cover plate ]

The following were evaluated on a cover plate containing no lubricant and a cover plate prepared by changing the mixing ratio of the three lubricants, the coating thickness and the drying conditions, and the NC drilling was performed on the cover plate, and the presence or absence of wall surface irregularities, wall surface burrs, interface peeling, plating peeling of the 1 st hole and the 100000 th hole, deformation of the copper foil of the 1 st hole and the 100000 th hole, breakage of the drill (durability of the drill), the degree of adhesion of chips on the drill, the degree of wear of the drill, and the degree of centering (drill position accuracy) were evaluated. A total of nine kinds of cover plates (test plates nos. 1 to 9) were tested, and the evaluation results are shown in table 1 below.

TABLE 1

Next, the evaluation criteria will be described. In the evaluation of the wall surface unevenness, a case having substantially no wall surface unevenness is denoted by ". circleincircle", a case having unevenness but substantially no influence of adhesion of chips to the drill or the like is denoted by ". smallcircle", a case having unevenness but less influence of adhesion of chips to the drill or the like is denoted by ". DELTA", and a case having unevenness and possibly causing poor plating or the like due to influence of adhesion of chips to the drill or the like is denoted by ". times" and cannot be used. For example, the left side of fig. 3(a) shows a state without wall surface irregularities, and the right side shows a state with wall surface irregularities.

In the evaluation of burrs, a "very good" indicates that there is no burr, a "good" indicates that there is some burr but the quality of the through-hole is not affected, a "Δ" indicates that there is burr but the effect on the quality of the through-hole is small, and a "x" indicates that there is burr and the effect on the quality of the through-hole is not small.

In the evaluation of interfacial peeling, no peeling occurred in all of the cover sheets of Nos. 1 to 9, in the evaluation of copper foil deformation, no deformation occurred in all of the cover sheets of Nos. 1 to 9, and in the evaluation of drill breakage, no breakage occurred in all of the cover sheets of Nos. 1 to 9.

< example 1 (test plate No.1) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 1, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 50%. The cover plate had a coating thickness (film thickness) of 20 μm and was formed by drying at 150 ℃ for five minutes after the stirring treatment of polyethylene and binder.

Fig. 4(a) is a view of the 1 st through hole as viewed from above, and fig. 4(b) is a view as viewed from obliquely above. Fig. 4(c) is a view of the 5000 th through hole as viewed from above, and fig. 4(d) is a view as viewed from obliquely above. Fig. 4(e) is a view of the 10000 th through hole as viewed from above, and fig. 4(f) is a view as viewed from obliquely above. Fig. 4(g) is a view of the 100000 th through hole as viewed from above, and fig. 4(h) is a view as viewed from obliquely above.

As can be seen from table 1, the cover plate of test plate No.1 had substantially no wall surface irregularities up to the 5000 th hole (see fig. 4(b) and (d)), and the results were good with respect to the presence or absence of through-hole plating delamination, the degree of adhesion of chips to the drill, and the degree of wear of the drill.

< example 2 (test plate No.2) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 2, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 33%. The cover plate had a coating thickness (film thickness) of 10 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 5(a) is a view of the 1 st through hole as viewed from above, and fig. 5(b) is a view as viewed from obliquely above. Fig. 5(c) is a view of the 5000 th through hole as viewed from above, and fig. 5(d) is a view as viewed from obliquely above. Fig. 5(e) is a view of the 10000 th through hole as viewed from above, and fig. 5(f) is a view as viewed from obliquely above. Fig. 5(g) is a view of the 100000 th through hole as viewed from above, and fig. 5(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the cover plate of test plate No.2 showed slight unevenness of the wall surface up to the 10000 th well (see FIGS. 5(b), (d), and (f)). The results were basically good with respect to the presence or absence of peeling of the through-hole plating layer and the degree of centering. The degree of adhesion of chips to the drill bit was slightly higher than that in example 1, but the influence on the quality of the through-hole was small. With respect to the degree of wear of the drill bit, wear occurs to a certain extent but not yet to the extent that replacement is performed.

< example 3 (test plate No.3) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 3, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 33%. The cover plate had a coating thickness (film thickness) of 20 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 6(a) is a view of the 1 st through hole as viewed from above, and fig. 6(b) is a view as viewed from obliquely above. Fig. 6(c) is a view of the 5000 th through hole as viewed from above, and fig. 6(d) is a view as viewed from obliquely above. Fig. 6(e) is a view of the 10000 th through hole as viewed from above, and fig. 6(f) is a view as viewed from obliquely above. Fig. 6(g) is a view of the 100000 th through hole as viewed from above, and fig. 6(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the cover plate of test plate No.3 showed slight unevenness of the wall surface up to the 10000 th well (see FIGS. 6(b), (d), and (f)). The results of the presence or absence of the through-hole plating layer peeling, the degree of adhesion of chips to the drill, the degree of wear of the drill, and the degree of centering were basically good.

< example 4 (test plate No.4) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 4, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 50%. The cover plate had a coating thickness (film thickness) of 10 μm and was formed by drying at 120 ℃ for two minutes and further at 150 ℃ for three minutes after the stirring treatment of polyethylene and binder.

Fig. 7(a) is a view of the 1 st through hole as viewed from above, and fig. 7(b) is a view as viewed from obliquely above. Fig. 7(c) is a view of the 5000 th through hole as viewed from above, and fig. 7(d) is a view as viewed from obliquely above. Fig. 7(e) is a view of the 10000 th through hole as viewed from above, and fig. 7(f) is a view as viewed from obliquely above. Fig. 7(g) is a view of the 100000 th through hole as viewed from above, and fig. 7(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the lid plate of test plate No.4 showed almost no wall surface irregularities up to the 10000 th well, and showed slight wall surface irregularities in the 100000 th well (see FIGS. 7(b), (d), (f) and (h)). The burr is slightly present but has less impact on via quality. In addition, the presence or absence of the through-hole plating layer peeling was somewhat noticeable, but to a lesser extent, the through-hole quality was affected.

< example 5 (test plate No.5) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 5, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 50%. The cover plate had a coating thickness (film thickness) of 20 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 8(a) is a view of the 1 st through hole as viewed from above, and fig. 8(b) is a view as viewed from obliquely above. Fig. 8(c) is a view of the 5000 th through hole as viewed from above, and fig. 8(d) is a view as viewed from obliquely above. Fig. 8(e) is a view of the 10000 th through hole as viewed from above, and fig. 8(f) is a view as viewed from obliquely above. Fig. 8(g) is a view of the 100000 th through hole as viewed from above, and fig. 8(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the lid plate of test plate No.5 showed almost no wall surface irregularities until the 5000 th well, and showed slight wall surface irregularities in the 10000 nd well and the 100000 th well (see FIGS. 8(b), (d), (f) and (h)). The results were basically good with respect to the presence or absence of the peeling of the through-hole plating layer. The degree of adhesion of chips to the drill bit was slightly higher than that in example 1, but the influence on the quality of the through-hole was small. With respect to the degree of wear of the drill bit, wear occurs to a certain extent but not yet to the extent that replacement is performed.

< example 6 (test plate No.6) >

Polyethylene (trade name: ZJ-24FA, manufactured by Fujiu shellac, JP K.K.) was used as a lubricant constituting the cover plate of example 6, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Cauda corporation) was used as a binder for mixing, so that the content of polyethylene (lubricant) was 33%. The cover plate had a coating thickness (film thickness) of 10 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 9(a) is a view of the 1 st through hole as viewed from above, and fig. 9(b) is a view as viewed from obliquely above. Fig. 9(c) is a view of the 5000 th through hole as viewed from above, and fig. 9(d) is a view as viewed from obliquely above. Fig. 9(e) is a view of the 10000 th through hole as viewed from above, and fig. 9(f) is a view as viewed from obliquely above. Fig. 9(g) is a view of the 100000 th through hole as viewed from above, and fig. 9(h) is a view as viewed from obliquely above.

Referring to table 1, it can be seen that the cover plate of test plate No.6 had slight wall surface irregularities in the 5000 th well and had almost no wall surface irregularities in the 10000 th well (see fig. 9(b), (d), (f) and (h)). The results were basically good with respect to the presence or absence of the peeling of the through-hole plating layer. In addition, the burr can be slightly seen, but to a lesser extent, the quality of the through-hole. The degree of adhesion of chips to the drill bit was slightly higher than that in example 1, but the influence on the quality of the through-hole was small.

< example 7 (test plate No.7) >

Polyethylene (trade name: XD-448 (microcrystalline wax), manufactured by Fujiu shellac, JP K.K.) was used as a lubricant constituting the cover plate of example 7, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Co., Ltd.) was used as a binder, so that the content of the lubricant was 33%. The cover plate had a coating thickness (film thickness) of 10 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 10(a) is a view of the 1 st through hole as viewed from above, and fig. 10(b) is a view as viewed from obliquely above. Fig. 10(c) is a view of the 5000 th through hole as viewed from above, and fig. 10(d) is a view as viewed from obliquely above. Fig. 10(e) is a view of the 10000 th through hole as viewed from above, and fig. 10(f) is a view as viewed from obliquely above. Fig. 10(g) is a view of the 100000 th through hole as viewed from above, and fig. 10(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the lid plate of test plate No.7 showed slight wall surface irregularities in the 5000 th well, and almost no wall surface irregularities in the 10000 nd well and the 100000 th well (see FIGS. 10(b), (d), (f) and (h)). The burr is slightly present but to a lesser extent affects the via quality. The presence or absence of peeling of the through-hole plating layer was somewhat noticeable, but was of such a degree that the quality of the through-hole was less affected. As for the deformation of the through-hole copper foil, the deformed portions were sporadically visible in the 10000 th hole, but the influence on the quality of the through-hole was small. The degree of adhesion of chips to the drill bit was slightly higher than that in example 1, but the influence on the quality of the through-hole was small. With respect to the degree of wear of the drill bit, wear occurs to a certain extent but not yet to the extent that replacement is performed.

< example 8 (test plate No.9) >

Polyethylene (trade name: ZJ-22, manufactured by Fujiu shellac of JP K Co., Ltd.) was used as a lubricant constituting the cover plate of example 8, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Kabushiki Kaisha) was used as a binder, so that the content ratio of the lubricant was 33%. The cover plate had a coating thickness (film thickness) of 30 μm, and was formed by drying at 120 ℃ for two minutes and further drying at 150 ℃ for three minutes after the agitation treatment of polyethylene and a binder.

Fig. 12(a) is a view of the 1 st through hole as viewed from above, and fig. 12(b) is a view as viewed from obliquely above. Fig. 12(c) is a view of the 5000 th through hole as viewed from above, and fig. 12(d) is a view as viewed from obliquely above. Fig. 12(e) is a view of the 10000 th through hole as viewed from above, and fig. 12(f) is a view as viewed from obliquely above. Fig. 12(g) is a view of the 100000 th through hole as viewed from above, and fig. 12(h) is a view as viewed from obliquely above.

As can be seen from Table 1, the cover plate of test plate No.9 showed slight unevenness of the wall surface up to the 10000 th well (see FIGS. 12(b), (d), and (f)). The results were basically good with respect to the presence or absence of through-hole plating delamination, the degree of adhesion of chips to the drill, the degree of wear of the drill, and the degree of centering.

< comparative example 1 (test plate No.8) >

The cover plate according to comparative example 1 was formed using a 250 μm PET film and did not contain a lubricant.

Fig. 11(a) is a view of the 1 st through hole as viewed from above, and fig. 11(b) is a view as viewed from obliquely above. Fig. 11(c) is a view of the 5000 th through hole as viewed from above, and fig. 11(d) is a view as viewed from obliquely above. Fig. 11(e) is a view of the 10000 th through hole as viewed from above, and fig. 11(f) is a view as viewed from obliquely above. Fig. 11(g) is a view of the 100000 th through hole as viewed from above, and fig. 11(h) is a view of the 100000 th through hole as viewed from obliquely above.

Referring to Table 1 and FIG. 11, it is seen that the cover plate of test plate No.8 has wall surface irregularities visible from the 1 st well, and similarly, wall surface irregularities are visible from the 5000 th well, the 10000 th well, and the 100000 th well (see FIGS. 11(b), (d), (f), and (h)). The presence of burrs was confirmed, and the presence or absence of stripping of the through-hole plating layer was confirmed, so that the stripping was seen sporadically, the degree of wear of the drill was high, and the eccentricity of the through-hole was also large.

[ evaluation results and examination ]

The evaluation results of the above-described test items (presence or absence of wall surface unevenness, presence or absence of wall surface burrs, presence or absence of through-hole plating peeling, degree of adhesion of chips on the drill, and degree of wear of the drill) of the cover sheets according to examples 1 to 7 obtained by mixing the lubricant and the binder were examined.

In addition, because the copper foil is basically not deformed, the quality of the through hole can be improved, and the quality of the flexible printed circuit board can be improved. In addition, compared to a cover plate in which the PET film located under the lubricant layer is formed of only the PET film of the related art, the thickness of the PET film can be reduced, and thus the material cost can be reduced.

The wall surface irregularities were good in the results of examples 4 and 5 in the 5000 th well, and good in the results of examples 4, 6 and 7 in the 10000 th well. From this, it was found that, when the content of the lubricant was 50%, the wall surface irregularities could be reduced in the case where the lubricant was ZJ-22. The results of examples 3, 5 and 6 were good in the case of the 10000 th hole, with respect to the presence or absence of peeling of the through-hole plating layer. From this, it was found that when the lubricating material was ZJ-22, the through-hole plating peeling could be reduced when the coating thickness was 20 μm.

The results of examples 1 and 3 were good with respect to the degree of adhesion of chips to the drill. From this, it was found that when the lubricating material was ZJ-22, the degree of adhesion of chips to the drill bit could be reduced when the coating thickness was 20 μm.

[ Performance test 2 of cover plate ]

Next, tests for evaluating the drill breakage rate and drilling quality of the present invention and the conventional cover plate were performed.

Polyethylene (trade name: ZJ-22, manufactured by Fujiumuru, JP) was used as a lubricant constituting the cover plate of the present invention, and isocyanate-modified polybutadiene (trade name: TP-1001, manufactured by Nippon Caoda corporation) was used as a binder, so that the content of the lubricant was 33%. The cover plate had a coating thickness (film thickness) of 5 μm and was formed by drying at 150 ℃ for five minutes after the stirring treatment of polyethylene and binder. The existing cover plates consist of a 250 μm layer of PET and do not contain a lubricating material.

The evaluation results are shown in fig. 13. Fig. 13 is a graph showing the relationship between the number of drilled holes, the drill breakage (%) and the via hole quality, wherein the horizontal axis represents the number of drilled holes (× 1000) and the vertical axis represents the drill breakage (%) and the via hole quality. The quality of the through hole is a value obtained by comprehensively evaluating the unevenness, plating peeling, deformation, and the like of the wall surface of the through hole, and the quality is improved as the numerical value is larger. The quality of the through-hole is expressed by a numerical value quantified based on a predetermined standard. The "-" line is a curve showing the drill breakage rate (%) of the present cap plate, and the "- □ -" line is a curve showing the through-hole quality of the present cap plate. The line "-" is a curve showing the drill breakage rate (%) of the conventional cap plate (comparative example), and the line "-" is a curve showing the through-hole quality of the conventional cap plate.

[ evaluation results and examination ]

With respect to the drill breakage, in the case of the cover plate of the present invention, breakage of the drill does not occur even if the number of holes exceeds 10000, whereas in the case of the conventional cover plate, the drill breakage rate increases from about when the number of holes exceeds 10000. The quality of the through-hole is slightly different from that of the conventional cover plate in the initial stage, but the quality of both the cover plate and the conventional cover plate is gradually deteriorated as the number of drilled holes increases, and there is almost no difference in the quality.

As described above, according to the cover plate of the present invention, breakage of the drill can be suppressed while maintaining a certain through hole quality, and the life of the drill can be extended.

While one embodiment of the present invention has been described above, various modifications may be made to the present invention.

Claims

1. A cover plate for drilling is characterized in that,

the cover plate for drilling comprises a PET film as a base material and a water-insoluble lubricating layer formed by coating at least one surface of the PET film,

the water-insoluble lubricating layer is composed of a lubricating material and a binder,

the lubricating material takes polyethylene as a main component, the average particle size of the polyethylene is 5-7 mu m, the molecular weight is 4000-5000, and the melting point is 95-130 ℃.

2. The cover plate for drilling according to claim 1,

the lubricating material takes polyethylene and polytetrafluoroethylene as main components.

3. The cover plate for drilling according to claim 1 or 2,

the thickness of the water-insoluble lubricating layer composed of a lubricating material and a binder is 5 to 30 μm.

4. The cover plate for drilling according to claim 1 or 2,

the proportion of the solid content of the lubricating material to the total solid content of the lubricating layer is 13.0 to 23.1 wt%.

5. The cover plate for drilling according to claim 3,

6. A method for manufacturing a cover plate for drilling, characterized in that,

a cover plate for drilling, which is formed by coating a water-insoluble lubricating layer comprising a lubricating material and a binder on at least one surface of a base material and then drying the coated layer, and which comprises a PET film as a base material and a water-insoluble lubricating layer coated on at least one surface of the PET film,

7. The method for manufacturing a cover plate for drilling according to claim 6,

8. The method for manufacturing a cover plate for drilling according to claim 6 or 7,

9. The method for manufacturing a cover plate for drilling according to claim 6 or 7,

10. The method for manufacturing a cover plate for drilling according to claim 8,

11. A method for manufacturing a flexible printed circuit board includes a through hole drilling process,

in the through-hole drilling step, a water-insoluble lubricating layer composed of a lubricating material and a binder is applied to at least one surface of a base material to form a drilling cover plate composed of a PET film as a base material and a water-insoluble lubricating layer applied to at least one surface of the PET film,

12. The manufacturing method of a flexible printed circuit board according to claim 11,

13. The manufacturing method of a flexible printed circuit board according to claim 11 or 12,

14. The manufacturing method of a flexible printed circuit board according to claim 11 or 12,

15. The manufacturing method of a flexible printed circuit board according to claim 13,