JPH0218986A - Manufacture of flexible printed wiring board - Google Patents

Abstract

PURPOSE:To improve the accuracy of the etching of a polyimide insulating coating, and to shorten the etching time by directly forming the polyimide insulating coating onto a plurality of conductor wirings without using adhesives in the polyimide insulating coating. CONSTITUTION:The unnecessary sections of the conductor layer 5 of a base material composed of a support film layer 1, the conductor layer 5 and an adhesive layer 3 are removed through etching to shape a plurality of conductor wirings 2, the whole surface on the side, on which a plurality of the conductor wirings 2 are formed, is coated with a polyamide acid solution or a polyimide solution to shape a polyimide insulating coating 6, and sections required for connecting a plurality of the conductor wirings 2 are gotten rid of by a polyimide etchant. Consequently, adhesives for bonding the polyimide insulating coating 6 are not used, and the polyimide insulating coating 6 is formed directly onto a plurality of the conductor wirings 2. Accordingly, the accuracy of the etching of the polyimide insulating coating 6 is improved, and the etching time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a flexible printed wiring board having a polyimide insulation coating without using an adhesive.

(Prior Art) In recent years, as electronic devices have become smaller, lighter, and more diverse, flexible printed wiring boards (hereinafter referred to as FPCs), which are thin, lightweight, and highly flexible, have come into widespread use.

As shown in FIGS. 4a-c, the conventional FPC uses a base material in which a conductor layer 5 and a support film 1 are bonded together with an adhesive layer 3 (FIG. 4a), and unnecessary portions of the conductor layer 5 are removed. Etching and removing multiple conductor layers &? Figure 4b to form t2
), an insulating film 7 with an adhesive layer 8 formed thereon, but with windows processed by a mold or a drill formed in the positions corresponding to the parts necessary for connecting the plurality of conductor wirings 2, is overlapped and heated and pressurized. They are laminated and integrated to form a wiring board (Fig. 4C). Furthermore, support film 1 used for FPC
The insulation film 7 is often made of a highly heat-resistant polyimide film, and dimensional changes due to humidity in polyimide, dimensional changes due to pressure during processing, and adhesive stains that occur during press lamination during processing may impede high-density wiring. To become, the fifth
As shown in Figure a%C, polyimide insulation film 7
After a plurality of conductor wirings 2 are laminated and integrated over the entire surface of the wiring board supported on the support film 2 by the adhesive layer 3 (Fig. 5 a, b). , a method of forming a wiring board (FIG. 5C) by etching away polyimide insulating film 7 and adhesive layer 8 at positions corresponding to the parts necessary for connecting a plurality of conductor wirings 2 with a polyimide etching solution is disclosed in Japanese Patent Application Laid-open No. It is shown in Publication No. 113494/1982.

(Problems to be Solved by the Invention) Conventional methods can suppress the decrease in dimensional accuracy of the polyimide film insulation coating and the seepage of the adhesive, but the polyimide etching solution can prevent the polyimide insulation film 7 and the adhesive layer 8 from bonding. had to be removed by etching, resulting in problems such as a decrease in dimensional accuracy due to over-etching and a long etching time.

The present invention provides a method for manufacturing an FPC which has excellent etching accuracy for polyimide insulating coating and can shorten etching time.

(Means for Solving the Problems) In order to improve the etching accuracy of the polyimide insulation coating and shorten the etching time, the present invention does not use the conventional adhesive for bonding the polyimide insulation coating from the FPC. This is a method of manufacturing an FPC in which a polyimide insulating coating 6 is directly formed on a plurality of conductor wirings 2.

That is, as shown in FIG. 1, a photosensitive resin film is laminated on a base material (FIG. 1a) consisting of a support film layer 1, a conductor layer 5, and an adhesive layer 3, and then... It is exposed to light through a film having a negative pattern on which patterns necessary to form jI number of conductor wirings 2 are formed, and the parts that do not form a plurality of conductor wirings 2 are developed and removed. copper i8
In order to form a plurality of conductor wirings 2 by etching and removing unnecessary portions of the conductor layer 5 by spraying a solution or the like (Fig. 1C), after peeling off the remaining photosensitive resin film, a polyamic acid solution or a polyimide solution is added. A polyimide insulation coating 6 is formed by coating the entire surface of the side where the plurality of conductor wirings 2 are formed (Fig. 1d).
Then, a photosensitive resin is applied thereon, exposed and developed using a photosensitive pattern that exposes the parts necessary for connecting the plurality of conductor wirings 2 (Fig. 1e), and the exposed polyimide insulating coating is made of polyimide. An FPC characterized in that it can be removed with an etching solution (FIG. 1 f) and made into an FPC (FIG. 2).
This is the manufacturing method.

The support film l used in the present invention may be a polyimide film or a polyester film, and a polyimide film with excellent heat resistance is preferred. Copper or aluminum can be used as the conductor layer 5, and conventionally used epoxy resin, acrylic resin, or polyimide resin can be used as the adhesive layer 2. When using a polyimide resin for this adhesive layer 2, it is preferable to use a resin that has a lower etching rate than the polyimide insulation coating 6. In this case, the polyimide should be coated with at least 1% of a three-dimensional crosslinking component such as bismaleimide or Evokin resin. Use the one obtained by adding.

The polyimide insulating coating 6 can be made of condensed polyimide, and it is preferable to use polyamic acid, which is a prepolymer of polyimide, because the etching rate can be controlled by the heating temperature and time performed after coating and before etching. At this time, it is more preferable that the imidization rate of the polyimide insulating coating 6 is 25 to 75% because the etching rate is high.

What is the enoting capacity of polyimide? At night, solutions containing basic compounds such as quaternary ammonium such as tetramethylammonium hydroxide, hydrazine, and ethylenediamine, amines, or hydroxides of alkali metals such as sodium, potassium, and lithium are used. Can be used.

(Function) The FPC manufacturing method of the present invention, in which the polyimide insulation coating 6 is directly formed on the plurality of conductor wirings 2 without using an adhesive for bonding the polyimide insulation coating, improves the etching accuracy of the polyimide insulation coating. It is possible to improve the etching time and shorten the etching time.

Example I 20 g of 4,4°-diminodiphenyl ether (hereinafter referred to as DDE) to 230 g of N-methyl-2-pyrrolidone
was added and stirred until DDE was completely dissolved. The solution was cooled to below 5°C, and while maintaining this temperature, 21.8 g of pyromellitic dianhydride was added little by little to react. After that, the temperature of the solution was raised to 80° C., and the solution was heated for 3 hours to prepare a polyimide solution.

For testing purposes, we omitted the process of laminating a dry film on the copper foil of a commercially available polyimide film with copper foil to form a copper etching resist and removing unnecessary tJA fR to form a circuit. The polyimide solution is applied to the entire surface of the copper foil of the film, and 1
It was dried with hot air at 80°C for 10 minutes. The imidization rate at this time was about 55%.

A photosensitive resin OMR-83 (Tokyo Ohka Co., Ltd., trade name) was coated on the entire surface, and after heating and drying at 80°C for 10 minutes, the pattern shown in Figure 3 was exposed and developed. Ta. The exposed polyimide insulation coating was etched at 50°C for 10 minutes with a mixed solution of ethylenediamine and hydrazine (with a weight ratio of 3 parts ethylene diamine to 7 parts hydrazine), and after washing with water, the resist was peeled off and a test piece was prepared. did.

The test pieces thus obtained were examined for perforation, amount of adhesive seeping out, minimum perforation for spacing, minimum perforation for diameter, perforation for accuracy, and soldering heat resistance.

The holes in the coverlay are the amount of adhesive seeping out, the minimum holes are the spacing, the minimum holes are the diameter, and the holes are the accuracy using the test pattern shown in Figure 3. The amount of adhesive seeping out was determined by measuring the width 21 of the adhesive staining on the exposed copper foil in the pattern of 12 square holes 10 mm x 10 mm, and the minimum hole size was 13 square holes 5 III 11 x 5111.
The minimum spacing between adjacent pattern portions remaining without overetching of the coverlay was measured. The minimum hole diameter is 14 square holes 3ffiI11 x 311Im
, 15 square holes IIIm x 1 mIm, 16 square holes 0.5
mnx0.5mm, 17 square holes Q, 3mmx0.3I,
Using the square hole 0.1 m + * Xo, l ms of No. 18 and the square hole 0゜05 mm x 0.05 mm of No. 19, find out to what diameter the hole can be drilled within a 10% error range for the negative pattern diameter. It was measured. In addition, the accuracy of hole making is determined by using a pattern part in which 20 round holes (diameter 5III11) are arranged at 101 intervals. It was measured. After this measurement, the solder heat resistance was determined by floating the sample in a solder bath at a predetermined temperature for a certain period of time, and checking for peeling of the coverlay film. These results are shown in Table 1.

Example 2 10.8 g of p-phenylenediamine was added to 230 g of N-methyl-2-pyrrolidone, stirred until p-phenylenediamine was completely dissolved, and the solution was cooled to 5° C. or lower and maintained at this temperature. Then, 29.4 g of 3.3', 4.4'-biphenyltetracarboxylic dianhydride was added little by little to react. After the entire amount had been added, the temperature of the solution was raised to 80°C and cooked for 4 hours. And polyimide? It was made into a liquid. Using this solution, the etching conditions were set to 70°C.
A test piece was prepared in the same manner as in Example 1, except that the time was 10 minutes.As in Example 1, the perforation is the amount of adhesive seeping out of the part, the minimum perforation is the interval, and the minimum perforation is the diameter. , Anaki investigated accuracy and soldering heat resistance.

The results are shown in Table 1.

Example 3 20g of DDE was added to 290g of P-chlorophenol,
The solution was stirred until DDE was completely dissolved, heated to 130°C while blowing nitrogen gas, and heated to 3, 3°, 4°C.
．． 4″-Biphenyltetracarboxylic dianhydride 29.4
g was added little by little to react, and after the entire amount had been added,
The temperature of the solution was raised to 160°C and reacted for 1 hour, the temperature of the solution was cooled to 60°C, the supply of nitrogen gas was stopped, and the water was reduced to 0.
．． 5g was added and reacted at 60°C for 4 hours to obtain a polyimide solution. Using this polyimide solution, the etching solution was 4% potassium hydroxide and the etching conditions were 80'.
CT: A test piece was prepared in the same manner as in Example 1, except that the time was 10 minutes, and in the same manner as in Example 1, the perforation is the amount of adhesive seeping out in the area, the minimum perforation is the interval, and the minimum perforation is the The accuracy and soldering heat resistance of the diameter and hole were examined.

The results are shown in Table 1.

Comparative Example 1 An adhesive-backed polyimide film LF-0110 (DuPont, trade name) with a window made with a mold was prepared without polyimide etching without using a polyimide film.
A test piece was prepared in the same manner as in Example 1, except that it was heated and pressurized under the conditions of ℃ and 30 kg/CIA.
The amount of adhesive seeping out of the hole, the minimum hole spacing, the minimum hole diameter, the precision of the hole, and the soldering heat resistance were investigated.

The results are shown in Table 1.

Comparative Example 2 Polyimide film with adhesive LF-0110 (DuPont, trade name) was heated at 190°C without using polyimide solution.
A test piece was prepared in the same manner as in Example 1, except that heat and pressure was applied at 30 kg/cI11 and polyimide etching was performed at 70°C for 30 minutes. The amount of seepage, minimum hole spacing, minimum hole diameter, hole hole accuracy, and solder heat resistance were investigated.

The results are shown in Table 1.

Table 1 (Effects of the Invention) As explained above, an FPC was manufactured in which a polyimide insulation coating was directly formed on a plurality of conductor wirings without using an adhesive for bonding the polyimide insulation coating of the present invention. The method improves the etching accuracy of polyimide insulation coatings and reduces the etching time. Furthermore, since no adhesive is used to bond the polyimide insulation coating, there is no adhesive seepage, the area of the connection portion can be secured, and an FPC with excellent connection reliability can be manufactured.

[Brief explanation of the drawing]

1a-r are cross-sectional views for explaining the manufacturing process of an FPC according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a wiring board manufactured according to an embodiment of the present invention, and FIG. FIG. 4a is a top view showing the etching pattern of the polyimide insulation coating used for testing the examples and comparative examples of the present invention;
-c and Fig. 5a''-c are cross-sectional views for explaining the manufacturing process of a conventional example. Support film 2. Plural conductor wiring adhesive layers 5. Four-layer polyimide insulation coating insulation film 8. Adhesion Agent layer (a) (b) (c) (d) Fig. 1 12 square holes 10 cods x 10 ff 13 square holes 5 ff Hole 0.3H a) (b) (c) (a) (b) (c)

Claims (2)

[Claims] 1. The support film layer (1), the plurality of conductor wirings (2), the adhesive layer (3) for bonding the support film layer (1) and the plurality of conductor wirings (2), and the surface of the plurality of conductor wirings (2). A method for manufacturing a flexible printed wiring board comprising an insulating layer (4) that insulates parts other than those necessary for connection, a base material comprising a support film layer (1), a conductor layer (5) and an adhesive layer (3). A plurality of conductor wirings (2) are formed by etching away unnecessary portions of the conductor layer (5), and a polyamic acid solution or a polyimide solution is applied to the entire surface of the side on which the plurality of conductor wirings (2) are formed. forming an insulating coating (6);
A method for manufacturing a flexible printed wiring board, characterized in that a portion necessary for connecting a plurality of conductor wirings (2) is removed using a polyimide etching solution. 2. In the step of etching away the polyimide insulation coating (6) to expose the portion necessary for connecting the plurality of conductor wirings (2), the imidization rate of the polyimide insulation coating (6) is 25 to 75%. The method for manufacturing a flexible printed wiring board according to claim 1.