JPH07336026A - Manufacture of flexible printed circuit board with cover lay film - Google Patents

Abstract

PURPOSE:To provide a simple method for manufacturing a flexible printed circuit board with a cover lay film having excellent flexibility and dimensional stability. CONSTITUTION:A method for manufacturing a flexible printed circuit board with a cover lay film comprises the steps of removing a metal foil 3 of a residual area part after the foil 3 is formed with a circuit only on an area part of 1/2 or less of the board adhered with the foil 3 to a base film 1 via adhesive 2, coating the film with the adhesive, then forming the foil of the board adhered with the foil only in the area of 1/2 or less with the circuit, then covering the board with the film 2 with the adhesive 2 on the circuit bending the board from its center, and thermally press-bonding it.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing a flexible printed wiring board.

[0002]

2. Description of the Related Art As is well known, a flexible printed wiring board is a base material formed by bonding an insulating material usually called a flexible base film such as a polyimide film and a copper foil with an adhesive agent. For the wiring, the copper foil part necessary for wiring is left and other parts are removed by etching, and in order to protect the wiring part, except for the conductor part necessary for connection, apply an adhesive to the resist ink or the same base film as the base material. It is manufactured by a manufacturing method in which the applied cover lay film is covered and the exposed conductor part is plated on a necessary part.

[0003]

However, when the resist ink is used for protecting the wiring, the process is simple, but the flexibility is insufficient, and it is difficult to apply it to applications requiring folding endurance. In addition, if a cover lay film that applies an adhesive to a base film in a separate process is used, it is excellent in flexibility, but the process such as positioning and thermocompression bonding by a press becomes complicated, and further, the base material and the cover lay film are used. However, there is a problem in that dimensional changes are large after heating and pasting with a press or the like due to the difference in heat history received by each, since they are manufactured in different steps.

When the adhesive for a flexible printed wiring board disclosed in Japanese Patent Laid-Open No. 3-181580 is applied to the manufacturing method of the present invention, the adhesive cures when the base film and the metal foil are adhered. Since the metal foil does not have adhesiveness after etching, it cannot be manufactured. The present invention has been made to solve the above-mentioned problems, and provides a method for manufacturing a flexible printed wiring board with a coverlay film, which is excellent in flexibility and dimensional stability, and is easy to manufacture. is there.

[0005]

Means for Solving the Problems The inventors of the present invention have earnestly studied a method for producing a flexible printed wiring board with a coverlay film capable of achieving the above-mentioned object, and as a result, when the substrate is processed into a circuit, the wiring portion is covered with a metal foil. Collect it on one side of the metal foil, keep it at half of the metal foil, remove the remaining metal foil by etching to expose the adhesive side, bend it and cover the wiring part with the adhesive, flexible printing with cover lay film It has been found that when a wiring board is manufactured, the coverlay film portion can be manufactured in the same step as that of the substrate, so that the steps are simple and the problems such as dimensional stability can be solved. Furthermore, there are restrictions on the type of adhesive to enable the above manufacturing method. That is, even if the base film and the metal foil are once adhered and the adhesive is not deteriorated even after the etching process, the above manufacturing method cannot be established unless the adhesive has adhesiveness. As an adhesive having such characteristics, the inventors have found that the epoxy-modified acrylic adhesive disclosed in Japanese Patent Application No. 5-246124 previously filed by the present inventors can be applied to this production method.

According to the present invention, only a half or less of the area of a flexible printed board having a metal foil adhered to a base film via an adhesive is processed into a circuit, and the metal foil in the remaining area is removed, or After applying the adhesive to the base film, the metal foil of the flexible printed circuit board is adhered with the metal foil only in an area of 1/2 or less, the metal foil is processed into a circuit, and then the substrate is bent from the center to form a base film with an adhesive on the circuit. The present invention relates to a method for manufacturing a flexible printed wiring board with a cover lay film, which is covered with a sheet and heated and pressed. The base film used in the present invention is not particularly limited, and for example, Kapton (Toray
Polyimide films such as Deupon), apical (manufactured by Kanegafuchi Chemical), and PET films such as lumirror (manufactured by Toray) and dia foil (manufactured by Dia foil Hoechst) are used.
As shown in FIG. 2, the adhesive 2 is evenly applied onto the base film 1, dried, and then bonded to the metal foil 3.
There is no limitation on the bonding method, and it is manufactured by a laminating method of continuously bonding with a heating roll or a pressing method of heating and pressing with a hot plate.

In this way, the obtained metal foil on the substrate is processed into a circuit by etching according to the wiring. At this time, the wiring portion of the metal foil 3 is concentrated on one side (the left side portion in FIG. 2) from the center, and the other half (the right side portion in FIG. 2) is entirely removed by etching to remove the adhesive 2 Show the side of. Instead of removing the remaining half by etching, after applying an adhesive to the base film,
A method of processing a circuit of the metal foil of the flexible printed board to which the metal foil is adhered only in the area of 2 or less may be used. Then, the surface of the adhesive is perforated, and as shown in FIG. 1, it is bent to cover the metal foil 3 of the wiring portion with the adhesive 2 and heat-pressed.

The adhesive used in the present invention comprises (A) acrylonitrile 18 to 40% by weight, glycidyl methacrylate 2 to 6% by weight as a functional group monomer, and the balance ethyl acrylate, butyl acrylate or a mixture thereof. Epoxy-modified acrylic elastomer having a Tg of −10 ° C. or more and a weight average molecular weight of 800,000 or more, (B) alkyl-modified phenol resin, (C) epoxy resin and (D).
It is preferable to use a composition comprising an imidazole curing agent. The compounding amount of the epoxy modified acrylic elastomer is preferably 60 to 80% by weight. If the compounding amount is small,
A good adhesive force cannot be obtained during bending and adhesion after circuit processing. On the contrary, if the compounding amount is large, the heat resistance of the adhesive decreases and swelling occurs during soldering work.

When an acrylic elastomer having a carboxylic acid or a hydroxyl group is used as the functional group monomer, the adhesiveness after circuit processing and the chemical resistance during etching cannot be achieved at the same time. The composition of the epoxy-modified acrylic elastomer is adjusted by copolymerizing ethyl acrylate, butyl acrylate, and acrylonitrile so that Tg becomes -10 ° C or higher. If the Tg is less than -10 ° C, the tackiness of the adhesive is too large and the workability is significantly reduced. Tg
Is preferably -10 to 10 ° C. The weight average molecular weight must be 800,000 or more. If it is less than 800,000, the flowability of the adhesive will be too great and control will not be possible.

The amount of acrylonitrile used for this is 18
-40% by weight. If it is less than 18% by weight, the chemical resistance is poor and it cannot withstand various processing steps, and if it exceeds 40% by weight, it tends to gel during polymerization of the acrylic elastomer and the life of the resulting acrylic elastomer is extremely shortened. The amount of glycidyl methacrylate used as the functional group monomer is a copolymerization ratio of 2 to 6% by weight. If it is less than 2% by weight, good adhesion cannot be obtained, and 6
When the content exceeds the weight%, the elastomer is easily gelled, which is not preferable. When a mixture of ethyl acrylate and butyl acrylate is used as the balance, the ratio is determined in consideration of the Tg of the resulting copolymer.

For the alkyl-modified phenol resin, epoxy resin and imidazole type curing agent, a total of 20
-40% by weight. The amount of each compounded is not particularly limited, but is determined in consideration of workability by adhesive tack and heat resistance of the adhesive. Solvents for dissolving these components into an adhesive solution include methyl ethyl ketone (MEK), dimethylformamide (DMF),
Organic solvents such as toluene and methyl cellosolve are preferable,
One or a mixture of these is used,
It is not limited to these. As described above,
A flexible printed wiring board with a coverlay film can be suitably manufactured.

[0012]

EXAMPLES Examples of the present invention will now be described, but the present invention is not limited thereto. Example 1 By weight, 29.25 parts of ethyl acrylate, 39.25 parts of butyl acrylate, 30 parts of acrylonitrile and 3 parts of glycidyl methacrylate were polymerized by a pearl polymerization method to obtain Tg of -6.9 ° C and a weight average molecular weight of 900,000. 134 parts by weight of acrylic elastomer, Hitanol 2400
(Alkylphenol resin, manufactured by Hitachi Chemical Co., Ltd.) 24
28 parts by weight, EPPN-201 (phenol novolac type epoxy resin, manufactured by Nippon Kayaku Co., Ltd.) and 2PZ-
0.8 parts by weight of CNS (1-cyanoethyl-2phenylimidazolium trimellitate, manufactured by Shikoku Kasei Co., Ltd.) was dissolved in 7.1 parts by weight of DMF in advance, and then dissolved in 800 parts by weight of MEK. An adhesive was prepared.

Next, the above adhesive solution was added to a thickness of 25 μm.
Kapton film (manufactured by Toray-Dupont Co., Ltd.) so that the thickness after drying is 35 μm, and dried at 120 ° C. for 10 minutes.
Co., Ltd.) The temperature of the roughened surface is 150 using a hot press.
A flexible printed board was produced by pressure bonding under the conditions of a temperature of 20 ° C., a pressure of 20 kg / cm ² , and a heating time of 30 minutes. After that, as shown in FIG. 2, the copper foil 3 is etched to form a circuit on the substrate by ½ or less, and the remaining copper foil is completely removed by etching to expose the surface of the adhesive 2. I got a plate. The part where all the copper foil is removed is punched with a punch press, bent from the center, and the hole is aligned with the predetermined position of the wiring part.
The temperature of 170 ° C, pressure of 30 kg / cm ² , heating time of 3
The flexible printed wiring board with the coverlay film having the structure shown in FIG. 1 was obtained by pressure bonding with a hot press under the condition of 0 minutes.

The adhesive force of the coverlay film is 1.5 kgf
/ Cm, and there was no abnormality when floated on a solder bath at 280 ° C. In addition, the dimensional change of the wiring portion before and after the pressure bonding of the coverlay film was 0.05%, which was extremely excellent. Furthermore,
Since the coverlay film was manufactured in the same step as the substrate, a separate step of manufacturing the coverlay film could be omitted, and workability was greatly improved.

Example 2 The adhesive used in Example 1 was applied to a Kapton film having a thickness of 25 μm so that the film thickness after drying would be 35 μm.
It is dried at 20 ° C. for 10 minutes, and a roughened electrolytic copper foil surface having a thickness of 35 μm is applied only to a half area of the adhesive surface of the film using a hot press to a temperature of 150 ° C. and a pressure of 20 kg / cm ^2. ,
A flexible printed wiring board with a coverlay film was obtained in the same manner as in Example 1 except that the flexible printed board was pressure-bonded under the heating time of 30 minutes. The adhesive force of the coverlay film was 1.3 kgf / cm, and there was no abnormality when floated in a solder bath at 280 ° C. In addition, the dimensional change of the wiring portion before and after the pressure bonding of the coverlay film was 0.06%, which was extremely excellent.

Comparative Example 1 Teisan Resin HTR-700 (acrylic elastomer, manufactured by Teikoku Chemical Industry Co., Ltd.) 83 parts by weight, Teisan Resin WS-023B (acrylic elastomer, manufactured by Teikoku Chemical Industry Co., Ltd.) 37 parts by weight, Hitanol 2410 (Alkylphenol resin, manufactured by Hitachi Chemical Co., Ltd.) 37 parts by weight, B
63 parts by weight of REN-S (novolac type brominated epoxy resin, manufactured by Nippon Kayaku Co., Ltd.) and 1.5 parts by weight of 2PZ-CNS (1-cyanoethyl-2phenylimidazolium trimellitate, manufactured by Shikoku Kasei Co., Ltd.) DMF13.
A composition comprising 15 parts by weight of a solution dissolved in 5 parts by weight,
A coverlay film was prepared in the same manner as in Example 1 of the present invention using an adhesive (described in Example 1 of JP-A-3-181580) dissolved in 860 parts by weight of a mixed solvent of MEK: toluene = 1: 1. We produced a flexible printed wiring board. However, the cover lay film does not adhere to the wiring board,
It was peeled off when floated on a solder bath at 280 ° C.

Comparative Example 2 The adhesive described in Example 1 was applied to a Kapton film having a thickness of 25 μm so that the film thickness after drying would be 35 μm,
It was dried at 120 ° C. for 10 minutes and then at 150 ° C. for 30 minutes to prepare a coverlay film. This is applied to the circuit processed surface of the flexible printed circuit board that was manufactured in a separate process as usual.
A flexible printed wiring board with a cover lay film was obtained by pressure bonding with a hot press under the conditions of a temperature of 170 ° C., a pressure of 30 kg / cm ² , and a heating time of 30 minutes. The adhesive force of the coverlay film was 1.8 kgf / cm, and there was no abnormality when floated in a solder bath at 280 ° C., but the dimensional change rate was as large as 0.2%, which caused problems. Moreover, since the cover lay film and the flexible printed circuit board are manufactured in separate steps, workability is lowered.

[0018]

INDUSTRIAL APPLICABILITY The flexible printed wiring board with a coverlay film obtained by the present invention has excellent dimensional stability because the coverlay film and the substrate are manufactured in the same process. Further, the present invention can significantly reduce the manufacturing time as compared with the conventional manufacturing method. Furthermore, the epoxy-modified acrylic adhesive used in the present invention has high heat resistance and excellent adhesive strength even after each step.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flexible printed wiring board with a coverlay film manufactured by the present invention.

FIG. 2 is a cross-sectional view of a flexible printed circuit board after circuit processing according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Base film, 2 ... Adhesive, 3 ... Metal foil

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H05K 1/03 D 7511-4E 3/00 Z 3/38 E 7511-4E

Claims (2)

[Claims] 1. A metal foil is adhered to a base film via an adhesive agent, and only a half or less area of the flexible printed board is processed into a circuit, and then the metal foil of the remaining area is removed, or the base film is removed. 1/2 after applying adhesive to
The following is characterized in that the metal foil of a flexible printed circuit board to which a metal foil is adhered only in the area below is processed into a circuit, then the board is bent from the center, the circuit is covered with an adhesive-attached base film, and heat-pressed. Manufacturing method of flexible printed wiring board with coverlay film. 2. The adhesive is (A) acrylonitrile 18
A copolymer obtained by copolymerizing 40% by weight to 2 to 6% by weight of glycidyl methacrylate as a functional group monomer and the balance of ethyl acrylate, butyl acrylate or a mixture thereof, and having a Tg of -10 ° C or higher. The coverlay according to claim 1, which is a composition comprising an epoxy-modified acrylic elastomer having a weight average molecular weight of 800,000 or more, (B) an alkyl-modified phenol resin, (C) an epoxy resin, and (D) an imidazole-based curing agent. Manufacturing method of flexible printed wiring board with film.