JPH0227144B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applied to a flexible wiring board forming an electric circuit and a method for manufacturing the same. 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. [Summary] The present invention provides a method for manufacturing printed circuit boards for electrical circuits, in which an operation of forming an adhesive layer by transferring it three times or more is performed using a release film coated with an adhesive on one side. and three or more adhesive layers are formed in a laminated structure,
Moreover, the top adhesive layer is maintained in the B-stage state and a release film is attached, so there are no pinholes penetrating both surfaces and it can be attached to other parts. . [Prior Art] A wiring board for electric circuits with a metal layer formed on the surface is manufactured by applying an adhesive made of resin to the metal layer.
It is manufactured by curing this adhesive. If the metal layer is formed on both sides, one side is used for wiring at ground potential, and if the metal layers on both sides are both thin metal foils, it is a flexible board, and the metal layer at ground potential is thick metal. When it is a board, 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, a known technique is to make the insulating layer a multilayer structure so that even if there is a pinhole that penetrates within one layer, there will be no pinhole that penetrates both surfaces. Since this cannot be completely eliminated, it is usually dealt with by introducing a film layer. Therefore, in order to form an insulating layer with a multilayer structure,
The process of applying and curing the adhesive needs to be repeated for each layer, increasing the manufacturing process.
The product naturally has the disadvantage of being expensive. The inventors of the present invention have previously filed an application for a method of manufacturing an electric circuit wiring board that improves this method in Japanese Patent Application No. 772,473/1983. [Problems to be Solved by the Invention] However, the electric circuit board produced by the above-proposed manufacturing method lacks flexibility because all the insulating layers of the multilayer structure are hardened, and furthermore, A request was made for an electrical circuit board that could be attached to parts. 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 the Problems] The first invention of the present invention is a method for manufacturing a flexible electric circuit wiring board, in which the surface of the adhesive layer of a release film coated with an adhesive on one side is A first step of bonding the metal foil and curing the adhesive and removing the release film to form a hardened first adhesive layer on the metal foil; Further, the surface of the adhesive layer of a release film coated with adhesive on one side is bonded to the surface of the cured adhesive, and the release film is removed.
A second step is performed twice, and the surface of the adhesive layer formed in this second step is further bonded with the surface of the adhesive layer of a release film coated with adhesive on one side. The method is characterized by including a third step of holding the agent in a B-stage state and attaching a release film. 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 is this n
It is preferable that the first one or more times of the repeating process involve a step of curing the adhesive, and the adhesive is kept in the B-stage state in the second one or more times. A second invention of the present invention is a flexible electric circuit wiring board, 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 some of the adhesive layers contain 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 5 μm or more and 100 μm.
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. [Function] A release film coated with an adhesive on one side can be produced extremely uniformly in large quantities. Also,
A release film with an adhesive coated on one side is easy to handle, and the process of transferring the adhesive layer of the release film is much faster than the process of uniformly applying a soft adhesive. It is easy to use and requires less man-hours. In addition, B with a release film on the outermost surface.
Since the adhesive in the stage state remains, 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 very difficult to create a thin insulating layer without pinholes through B-stage, so it is usually
It is known that a thickness of 100 μm or more is 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 varnish, pinholes may 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, on the release film, evaporation occurs only in one direction, so we discovered that pinholes do not occur in the thin resin film on the surface 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 Polypropylene film with a thickness of 60 μm as a release film (Alphan film manufactured by Honshu Paper Industries Co., Ltd.)
A flexible epoxy resin is coated to a thickness of 20 μm and dried to obtain a B-stage state. After bonding to Nikko Gould Co., Ltd. (JTC) and curing with heat, 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, the coated surface of the polypropylene film coated with the flexible epoxy resin is further bonded to the resin surface of the copper foil bonded epoxy resin obtained in the second step to a thickness of 20 μm, and separated. A single-sided copper-clad flexible printed circuit board with adhesive and a molding film was obtained (third step). Example 2 A vinyl fluoride film with a thickness of 40 μm as a release film (Tedra Film manufactured by DuPont, USA)
A flexible polyimide resin is coated to a thickness of 15 μm, and this is dried to obtain a B-stage state. The thus obtained B-stage polyimide resin is applied to a rolled copper foil having a thickness of 18 μm. After bonding to a surface (manufactured by Nippon Mining Co., Ltd.) and heating and curing, the vinyl fluoride film is removed (first step). Next, a polyester film with a thickness of 50 μm as a release film is coated with heat-resistant modified nylon resin to a thickness of 20 μm on the cured resin surface of the same foil-laminated polyimide resin obtained in the first step. After the coated surfaces of Lumirror Film (manufactured by Toray Industries, Inc.) are bonded together, the polyester film is removed (second step). Next, the resin surface of the copper foil bonded 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 copper-clad flexible printed circuit board with an adhesive and a release film was obtained. Example 3 A flexible epoxy resin was applied to a 60 μm thick polypropylene film (Toray Film, manufactured by Toray Industries, Inc.) as a release film to a thickness of 10 μm, and this was dried to obtain a B-stage state. 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 epoxy resin in the B stage state coated on the polypropylene film to a thickness of 10 μm is attached to the resin surface of the copper foil laminated epoxy resin obtained in the first step, and heated and cured. This process 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 B-stage epoxy resin coated on the polypropylene film with a thickness of 10 μm are bonded together for mold release. A flexible printed circuit board with film and adhesive on one side of copper was obtained. Example 4 Release film: polypropylene film with a thickness of 40 μm (Alphan Film manufactured by Honshu Paper Industries Co., Ltd.)
Coat epoxy resin to a thickness of 10 μm and dry it to make it into a B-stage state.
It is attached to the treated surface of a 35 μm rolled copper foil (manufactured by Nippon Mining Co., Ltd.), heated and cured, and then the polypropylene film is removed (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 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 single-sided copper-bonded flexible printed circuit board with an adhesive and a release film. [Test Results] The following table shows the results of tests conducted on each of the above examples bonded to a 1 mm thick iron plate and cured by heating. Peel strength and solvent resistance are 2.5mm
Peel off a 35μm wide copper foil in a 90 degree direction,
Shown as a value converted per cm.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, the number of manufacturing steps is small, there are no pinholes, it can be easily used by adhering to other parts after post-processing, and it has excellent post-processability such as low shrinkage. You can get a good substrate.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. Metal foil is bonded to the surface of the adhesive layer of a release film coated with an adhesive on one side, and the adhesive is cured and the release film is removed. A first step of forming a first adhesive layer hardened to The process of bonding the surface of the adhesive layer and removing the release film is
A second step is performed twice, and the surface of the adhesive layer formed in this second step is further bonded with the surface of the adhesive layer of a release film coated with adhesive on one side. A method for manufacturing a flexible electric circuit wiring board, comprising a third step of holding the agent in a B-stage state and attaching a release film. 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 n is 1, and the second step is to maintain the adhesive in the B-stage state.
A method for manufacturing a flexible electric circuit wiring board according to 2. 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 in the remaining one or more times, the adhesive is cured with B. 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 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 in the B stage. 1. A flexible electrical circuit wiring board, which is maintained in a flexible state, and has a release film attached to the surface of its furthest layer. 6. All or part of the adhesive layer contains 1 to 50% by weight of a fibrous inorganic insulating material.
The flexible electric circuit wiring board described in . 7. The flexible electric 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 Each adhesive layer has a thickness of 5 μm or more
The flexible electric circuit wiring board according to claim 5, which has a thickness of 100 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.