JPS5953716B2 - Manufacturing method of semi-flexible printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously bonding a prepreg obtained by impregnating or fixing a thermosetting resin powder to a fiber base material and a metal foil without using an adhesive. be.

Conventionally, substrates for flexible printed circuits have been used that are obtained by bonding polyester or polyimide films and metal foil with adhesives, but polyester substrates have poor solder heat resistance, and polyimide substrates tend to absorb moisture. It is expensive and expensive.

These film-based substrates also have poor dimensional stability, so for more advanced uses, so-called semi-flexible printed wiring substrates made of fiber base material are preferred. Fiber-based substrates are generally manufactured by the following two methods.

One is to apply an adhesive to a sheet or/and metal foil obtained by impregnating a fiber base material with a thermosetting resin solution and then drying and curing it, and after removing the solvent in the adhesive in a drying oven, the metal foil is This is a method of thermo-compression bonding the cured sheet and the cured sheet using a press roll. Another method is to overlap prepreg, which is a fiber base material impregnated with thermosetting resin, and metal foil on a heated turn roll, dry the solvent as necessary, and then place the prepreg in a drying oven. In this method, the substrate is manufactured by proceeding with curing.
Since the solvent cannot be completely removed from the substrates obtained by these conventional manufacturing methods, they have a drawback of poor electrical properties after moisture absorption. Furthermore, in the former case, the smoothness of the base material surface is poor, which tends to cause variations in adhesive strength, and in the latter case, the thermosetting resin becomes molten at the heated turn roll, so if a press roll is used, the thermosetting resin Because the resin adheres to the press roll, the prepreg is tensioned and overlaid on the metal foil without using a press roll, so the resulting substrate is likely to be twisted or curled.

In view of these circumstances, the inventors of the present invention conducted intensive studies to improve the drawbacks of conventional semi-flexible printed wiring boards using continuous lamination, and as a result, they arrived at the present invention.

The present invention uses a prepreg that does not substantially contain a solvent so that no solvent remains during lamination, and arranges the prepreg between the metal foil and the releasable film or the metal foil so that no strong tension is applied to the prepreg during lamination. An object of the present invention is to provide a method for producing a semi-flexible printed wiring board, which is characterized by successively three-layer roll press lamination.

The prepreg used in the present invention is a woven or nonwoven fabric made of glass, synthetic resin, paper, carbon, metal, or a mixture of these fibers, and epoxy resin, polyester resin, polyimide resin, or a modified resin based on these resins. It is impregnated or fixed with thermosetting resin powder such as, and contains virtually no solvent before use, so even if the lamination speed is increased, there will be no deterioration in electrical properties due to residual solvent. .

A prepreg that does not substantially contain a solvent is one that has a solvent content of 0.05% or less, and is advantageously manufactured by coating a thermosetting resin powder on a fiber base material and then heating and fixing it. can do. The thermosetting resin has a melting point of 50~
A temperature of 150°C is practically preferable. At temperatures below 50°C, the prepreg becomes sticky and difficult to work with, and the laminating temperature must be lowered, resulting in poor adhesion to the release film or metal foil at the curing temperature. Peeling of the metal foil occurs, which is undesirable.
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In addition, since the temperature at which the resin melts is high at 150°C or higher,
Since the curing reaction also progresses during melting, the adhesive strength with the metal foil decreases. The content of the thermosetting resin is 25 to 85% based on the total weight of the fiber base material and resin. In addition, the release film or metal foil used in the present invention is used to prevent molten resin from adhering to the press roll during lamination, to prevent tension from being applied to the prepreg, and to create a resin surface with a uniform appearance. Plastic films such as polyester and paper coated with silicone or fluorine resin mold release agents, plastic films such as stretched polypropylene, polyester treated with matte, etc. A plastic film, and a metal foil such as aluminum or copper that can be removed by release or etching are used.

Note that the metal foil can also be used as a double-sided copper-clad printed wiring board without being released from the mold. The release film or metal foil used here has the disadvantage that if it is peeled off immediately after press lamination and then cured, the resin surface will not be uniform and liquid remains easily during the processing process, so in the present invention, it is hardened. The releasable film or metal foil cannot be peeled off until then, and is peeled off after curing. Therefore, a light amount of adhesion must be maintained until the curing process. When performing three-layer lamination, a roll laminator with heated rolls is used.

It is preferable to preheat the metal foil, prepreg, release film, or metal foil immediately before the roll laminator in terms of the appearance of the product, improving the adhesive strength of the release film, and increasing the lamination speed. The details of the present invention will be explained in Examples.

Example 1 Epikote #1004 (manufactured by Ciel Chemical Co., Ltd.) 100 parts 2-
A thermosetting resin powder obtained by melting and mixing 0.5 parts of methyl-imidazole (manufactured by Shikoku Kasei Co., Ltd.) and then pulverizing it is sprinkled on a glass cloth with a thickness of 0.1 mm, and then heated and fixed to form a resin-containing powder. A prepreg with a weight of 60% was obtained.

The resin in the prepreg melted at 95°C, and the gelation time at 150°C was 4 minutes. Both sides of a 2 mil polyester film (manufactured by Toray Industries) were coated with KS7O6 manufactured by Shin-Etsu Silicone.
The film was treated with a 0.5% toluene solution to obtain a polyester film with release treatment on both sides.

Next, a 35μ electrolytic copper foil was introduced from the metal roll side of a press roll whose metal roll temperature was set to 120°C and a silicone roll temperature was set to 75°C, and a release-treated polyester release film was introduced from the silicone roll side, and the prepreg was inserted between them. Three-layer lamination was carried out at a speed of 0.3 m/min, the laminated product was rolled up with the copper foil on the outside without tension, and then the roll-shaped laminated product was heated at 100°C for 10 hours and then at 150°C. After heating and curing for 4 hours, the release-treated polyester film was peeled off.
A semi-flexible printed wiring board without twisting was obtained.

The electrical properties of the obtained substrate are shown in Table 1.

Comparative Example 1 After impregnating a glass cloth with a thickness of 0.1 mm with a 60% solution of acetone and 1:1 resin blended in Example 1, it was rolled along a metal roll at 120°C without using a press roll. The 35 μm copper foil was pasted under tension, led to a drying oven, cured at the same time as the solvent dried, wound up into a roll, and further cured at 150° C. for 4 hours to obtain a semi-flexible printed wiring board. .

In this case, tension was applied to the prepreg during lamination, causing the weft of the cloth to become arched, resulting in twisting. The electrical properties of the obtained substrate are shown in Table 1. As described above, according to the present invention, a substrate with a uniform resin surface and no twisting can be obtained, and since there is no residual solvent, semi-flexible printed wiring substrates with excellent electrical properties can be continuously manufactured.

Claims (1)

[Scope of Claims] 1. When bonding a prepreg, which is obtained by impregnating or fixing a thermosetting resin powder to a fiber base material and which does not contain substantially any solvent, and a metal foil, a releasable film or metal is added to the prepreg side. A method for manufacturing a semi-flexible printed wiring board, which comprises successively laminating three layers with foil interposed therebetween and then curing. 2. Claim 1, characterized in that three-layer lamination is performed continuously by interposing a releasable film or metal foil that does not peel off until the thermosetting resin impregnated into the fiber base material is cured. The method for manufacturing the semi-flexible printed wiring board described above.