JPS61252160A - Substrate for flexible electric circuit wiring and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is applied to a flexible wiring board forming an electric circuit and a manufacturing method thereof. In particular, the present invention relates to a wiring board that has a simple manufacturing process, has no pinholes penetrating both surfaces of the insulating layer, and can be easily attached to other components, and a method for manufacturing the same.

〔overview〕

The present invention is a method for manufacturing a printed circuit board for an electric circuit, in which an operation of forming an adhesive layer by transferring the adhesive layer is repeated three or more times using a release film coated with an adhesive on one side. three or more adhesive layers are formed in a laminated structure, and the top adhesive layer is held in a B-stage state and a release film is attached to penetrate through both surfaces. It has no pinholes and can be attached to other parts.

[Conventional technology]

A wiring board for an electric circuit having a metal layer formed on its surface is manufactured by applying an adhesive made of resin to the metal layer and curing the adhesive.

If the metal layer is formed on both sides, one side is used for wiring at ground potential, and if the metal 0 layers on both sides are both thin metal foils, it is a flexible board and the metal layer at ground potential is thick. When it is a metal plate, it becomes a hard circuit board. In this electric circuit board in which metal layers are formed on both sides, if there is a pinhole penetrating the insulating layer, the withstand voltage on both sides becomes small.

To improve this, the insulating layer has a multilayer structure,
Even if there are pinholes that penetrate within one layer, there are known techniques to eliminate pinholes that penetrate both surfaces, but since pinholes cannot be completely eliminated, it is usually necessary to introduce a film layer. This is supported by

Therefore, in order to form a multilayered insulating layer, it is necessary to repeat the adhesive application and curing process for the number of layers, which increases the number of manufacturing steps and makes the product naturally expensive. .

The inventors of the present invention have previously filed a patent application for a method for manufacturing an electric circuit wiring board that improves this method.

[Problem that the invention seeks to solve]

However, the electrical circuit board manufactured by the above-proposed manufacturing method lacks flexibility because all of the insulating layers in the multilayer structure are hardened, and furthermore, consumers have been requesting electrical circuit boards that can be attached to other parts. I was demanded to.

An object of the present invention is to provide a new method of manufacturing a flexible electric circuit wiring board and a board thereof that meet this demand.

[Means for solving problems]

The first invention of the present invention is a method for manufacturing a flexible electric circuit wiring board, in which metal foil is pasted on the surface of the adhesive layer of a release film coated with adhesive on one side, and the adhesive is cured. a first step of forming a hardened first adhesive layer on the metal foil by removing the mold release film; , a second step in which the surfaces of the adhesive layer of a release film coated with an adhesive on one side are bonded together and the release film is removed n times; Further, on the surface of the adhesive layer, the surface of the adhesive layer of a release film coated with adhesive on one side is bonded to maintain the adhesive in a B-stage state, and the release film is attached. The method is characterized in that it includes a third step in which the process is performed.

In this case, n is 1, and it is preferable that the second step involves a step of curing the adhesive, or that the second step involves keeping the adhesive in a B-stage state.

Further, n is 2 or more, and the second step includes a step of curing the adhesive in the first one or more times of the n-time repeating steps, and in the remaining one or more times, the adhesive is cured with B. It is preferable to keep it in a stage state.

A second invention of the present invention is a wiring board for a flexible electric circuit, in which three or more adhesive layers are formed on the surface of a metal foil, and at least one of the adhesive layers in contact with the metal foil is hardened, Among the adhesive layers, at least the layer farthest from the metal foil is maintained in a B-stage state, and a release film is attached to the surface of the farthest layer.

All or part of the adhesive layer contains 1 to 50% by weight of a fibrous inorganic insulating material, and the adhesive constituting each adhesive layer is thermosetting or at least partially contains a thermoplastic material. It is preferable.

The thickness of each adhesive layer is preferably 5 μm or more and 100 μm or less, and the thickness of the metal foil is preferably 9 μm or more and 200 μm or less.

The fibrous inorganic insulating material is preferably fibrous potassium titanate.

Here, curing includes heat curing, curing over time, a method by adding a curing agent, and a curing method by radiation radiation such as an electron beam.

[For production]

A release film coated with an adhesive on one side can be produced extremely uniformly and in large quantities. In addition, the release film with adhesive applied to one side is easy to handle.
The process of transferring the adhesive layer of the release film is much simpler and requires fewer steps than the process of uniformly applying a soft adhesive. Furthermore, since the adhesive in the B-stage state with the release film remains on the outermost surface, there is an advantage that post-processing of this substrate can be easily performed.

Therefore, according to the present invention, a flexible electric circuit wiring board having multiple insulating layers can be manufactured at low cost with a small number of man-hours.

It is known that it is very difficult to create a thin insulating layer without pinholes through the B stage, and therefore a thickness of 100 μm or more is usually required from the viewpoint of reliability. As a result of extensive studies, the inventors of the present invention found that when using a solvent-based FES, pinholes occur due to evaporation shrinkage during the formation of the resin thin film when the solvent is evaporated and dried to produce a B-stage resin thin film. However, they discovered that because evaporation occurs only in one direction on the release film, pinholes do not occur in the resin thin film on the surface that is in contact with the film. Moreover, the shrinkage of the release film due to heating during the formation of the resin thin film is effective in preventing the generation of pinholes, and furthermore, this shrinkage action suppresses curing shrinkage of the substrate after transfer heat curing.

This makes it possible to create a pinhole-free insulating layer using the transfer method, and the effect is ensured by repeating this process three or more times.

When this substrate is subjected to post-processing, it is desirable that the same type of adhesive as that of the substrate be applied to the surface that faces and is to be bonded to the substrate.

[Example 1] A 20 μm thick polypropylene film (Honshu Paper Industries side type Alphan film) was added to the release film having a thickness of 60 μm.
Coat flexible epoxy resin so that it is m,
The B-stage obtained in this way is dried to a B-stage state.
The epoxy resin in a stage state is pasted onto the treated surface of a 35 μm thick electrolytic copper foil (JTC manufactured by Nikko Gould Co., Ltd.), heated and cured, and then the release film is removed (first step).

Next, on the cured resin surface of the copper foil bonded epoxy resin obtained in the first step, the coated surface of the polypropylene film coated with the flexible epoxy resin is further bonded to a thickness of 20 μm. After heating and curing, the polypropylene film was removed (second step).

Next, on the resin surface of the copper foil laminated epoxy resin obtained in the second step, the coated surface of the polypropylene film coated with the flexible epoxy resin is further bonded to a thickness of 20 μm, and separated. A single-sided adhesive-attached flexible printed circuit board with mold film was obtained (third step).

[Example 2] A fluorinated vinyl film (Tedra film manufactured by DuPont, USA) with a thickness of 40 μm as a release film was coated with a 15 μm thick film.
A polyimide resin for flexible use is coated to a thickness of 18 μm and dried to a B-stage state.
After pasting on the treated surface of rolled copper foil (manufactured by Nippon Mining Co., Ltd.) and curing with heat, the vinyl fluoride film is removed (first step).

Next, a release film with a thickness of 50 μm was coated with a heat-resistant modified nylon resin on the cured resin surface of the same foil-laminated polyimide resin obtained in the first step to a thickness of 20 μm.
After bonding the coated surfaces of a μm polyester film (Lumirror Film manufactured by Toshi ■), the polyester film is removed (second step).

Next, the resin surface of the copper foil laminated polyimide-nylon resin obtained in the second step is bonded to the coated surface of the polyester film coated with the heat-resistant modified nylon resin to a thickness of 20 μm. By heating, a single-sided adhesive-attached flexible printed circuit board with a release film was obtained.

[Example 3] Flexible epoxy resin was coated on a 60 μm thick polypropylene film (Torefan film made by Toshi side) as a release film to a thickness of 10 μm, and this was dried to form a B stage. The B-stage epoxy resin obtained in this way was bonded to the treated surface of a 35-μm-thick rolled copper foil (manufactured by Nippon Mining Co., Ltd.), heated and cured, and then the polypropylene film was removed (first step). process).

Next, the resin surface of the copper foil laminated epoxy resin obtained in this first step was coated with the above polypropylene film to a thickness of 10 mm.
The process of bonding the epoxy resin in a B-stage state coated to a thickness of μm and curing by heating is repeated twice (second step).

Next, the resin surface of the copper foil laminated epoxy resin obtained in the second step and the resin surface of the 10 μm thick B-stage epoxy resin coated on the polypropylene film are bonded together for mold release. A single-sided flexible printed circuit board with film and adhesive was obtained.

[Example 4] A polypropylene film with a thickness of 10 μm (Alph 1 film manufactured by Honshu Paper Industries Ltd.) was added to a polypropylene film with a thickness of 40 μm as a release film.
The epoxy resin was applied to a thickness of 35 μm and dried to bring it to the B stage state, and the epoxy resin thus obtained in the B stage state was applied to the treated surface of a 35 μm thick rolled copper foil (manufactured by Nippon Kogyo 91). After combining and heating and curing, remove the polypropylene film (first step).

Next, a flexible epoxy resin containing 30% fibrous potassium titanate was coated on a polyethylene film with a thickness of 40 μm as a release film to a thickness of 25 μm, and the resin was dried to bring it into a B-stage state. The surface and the resin surface of the copper foil laminated epoxy resin obtained in the first step are bonded together, heated and cured, and the polyethylene film is removed (second step).

Next, a polypropylene film with a thickness of 40 μm as a release film was coated with a flexible epoxy resin to a thickness of 15 μm, and the resin surface was dried to a B-stage state. The resin surface of the foil-bonded epoxy resin was bonded together to obtain a one-sided body-bonded flexible printed circuit board with an adhesive and a release film.

[Test results]

The following table shows the results of tests conducted on the above-mentioned examples bonded to a 1 m thick iron plate and cured by heating. Peel strength and solvent resistance are values calculated per 1 cm when a 2.5 ts wide copper foil or iron foil is peeled off in a 90 degree direction.

(Hereinafter referred to as the margin of this page) [Effects of the Invention] As explained above, according to the present invention, the number of manufacturing steps is small, there are no pinholes, and the product can be used by easily adhering to other members after post-processing. , and a substrate with good post-processability such as low shrinkage can be obtained.

[Brief explanation of drawings]

The figure is a cross-sectional view of the structure of a substrate obtained by the method described in Example 1.

Claims (11)

[Claims] (1) By pasting metal foil on the surface of the adhesive layer of a release film coated with adhesive on one side, curing the adhesive, and removing the release film,
A first step of forming a hardened first adhesive layer on the metal foil, and a releasing agent in which an adhesive is further applied to one side of the surface of the hardened adhesive formed by this first step. A second step in which the surfaces of the adhesive layer of the film are bonded together and the release film is removed n times, and the surface of the adhesive layer formed in this second step is further bonded to one side. A third step of bonding the surfaces of the adhesive layers of the release film coated with a release agent to maintain the adhesive in a B-stage state and attaching the release film. method for manufacturing substrates for (2) The method for manufacturing a flexible electrical circuit wiring board according to claim (1), wherein n is 1, and the second step includes a step of curing the adhesive. (3) The method for manufacturing a flexible electrical circuit wiring board according to claim (1), wherein n is 1, and the second step is to maintain the adhesive in a B-stage state. (4) n is 2 or more, and the second step involves a step of curing the adhesive in the first one or more times of this n-time repeating step, and a step of curing the adhesive in the remaining one or more times. The method for manufacturing a flexible electrical circuit wiring board according to claim (1), wherein the flexible electrical circuit wiring board is held in a B-stage state. (5) Three or more adhesive layers are formed on the surface of the metal foil, at least the layer in contact with the metal foil is cured, and at least the layer farthest from the metal foil is B. A flexible electrical circuit wiring board that is held in a stage state and has a release film attached to the surface of the farthest layer thereof. (6) The flexible electrical circuit wiring board according to claim (5), wherein all or part of the adhesive layer contains 1 to 50% by weight of a fibrous inorganic insulating material. (7) The flexible electrical circuit wiring board according to claim (5), wherein the adhesive constituting each adhesive layer is thermosetting. (8) The flexible electrical circuit wiring board according to claim (7), wherein at least a portion of the adhesive constituting each adhesive layer contains a thermoplastic material, and the remainder is thermosetting. (9) The thickness of each adhesive layer is 5 μm or more and 100 μm or more.
The flexible electric circuit wiring board according to claim (5), which has a diameter of μm or less. (10) The flexible electric circuit wiring board according to claim (5), wherein the metal foil has a thickness of 9 μm or more and 200 μm or less. (11) The method for manufacturing a flexible electric circuit wiring board according to claim (6), wherein the fibrous inorganic insulating material is fibrous potassium titanate.