JPH0464307B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is utilized for manufacturing a wiring board forming an electric circuit. In particular, the present invention relates to a method of manufacturing a wiring board that has a simple manufacturing process and has no pinholes penetrating both surfaces of the insulating layer. [Summary] In a method of manufacturing printed circuit boards for electrical circuits, an operation of forming the adhesive layer is performed at least three times by transferring the adhesive layer using a re-keying film coated with adhesive on one side. As a result, three adhesive layers are formed in a laminated structure, and there are no pinholes penetrating both surfaces. [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. [Problems to be solved by the invention] However, in order to form an insulating layer with a multilayer structure, it is necessary to repeat the process of applying and curing the adhesive for the number of layers, which increases the number of manufacturing steps and increases the cost. The product naturally has the disadvantage of being expensive. The present invention improves this and aims to provide a method that can manufacture an electric circuit board including a multilayered insulating layer with a small number of manufacturing steps. [Means for Solving the Problems] The first aspect of the present invention is a method of forming a multilayer insulating layer on a metal foil, and the insulating layer is coated on a RIKEN film with a smooth surface and no pinholes. By forming and transferring on a stage, the smooth pinhole-free surface of the RIKEI film has two or more layers in the multilayer structure of the insulation, forming an insulation layer with excellent electrical insulation properties, especially cross-layer withstand voltage. It is characterized by being The second invention of the present invention is a method for manufacturing an electric circuit wiring board having a multilayer insulating layer with metal layers on both sides. It can be made thinner, which can improve other functions, especially thermal conductivity. Another feature is that if a single-sided metal foil is used as a base material, a single-sided metal-clad metal with good dimensional stability can be produced. The third invention of the present invention is a method for forming a multilayer insulating layer that is strong against external forces that tear it apart, and the method includes mixing a substance that improves the strength of the film, such as whiskers, into one or three of the insulating layers. It is also possible to optionally combine a resin with strong film strength. By making the RIKAY film transparent, visual inspection of the adhesive layer can be made possible. [Function] A film for refilling with an adhesive coated on one side can be produced extremely uniformly in large quantities. In addition, the Rikei film with adhesive coated on one side is easy to handle, and the process of transferring the adhesive layer of the Rikei film is much easier than the process of uniformly applying a soft adhesive. It is easy to use and requires less man-hours. Furthermore, using a transparent film such as RIKEN film has the advantage that the adhesive insulating layer can be easily inspected. Therefore, according to the present invention, an 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, because evaporation occurs only in one direction on RIKEI film, we discovered that pinholes do not occur in the resin thin film on the surface that is in contact with the film.
However, shrinkage of the RIKEN film due to heating during formation of the resin thin film is also effective against the generation of pinholes. Further, it has the effect of suppressing the curing shrinkage of the electrical circuit wiring board after transfer heat curing to a smaller extent. As a result, an insulating layer without pinholes can be created using the transfer method, and the effect is ensured by repeating this three times. [Example 1] A polypropylene film (Toray film made by Toray Industries, Inc.) with a thickness of 60 μm was
Apply flexible epoxy resin to a thickness of 20 μm and dry to bring it to the B stage state (first step). Next, the epoxy resin in the B stage state obtained in the first step is laminated onto the treated surface of a 35 μm thick copper foil and cured by heating (second step). Next, the epoxy resin obtained in the first step is bonded to the resin surface of the copper foil laminated epoxy resin obtained in the second step, and cured by heating (third step). Next, the epoxy resin obtained in the first step was bonded to the resin surface of the copper foil bonded epoxy resin obtained in the third step, and heated and cured to obtain a single-sided copper-clad flexible printed circuit board with an insulating layer of 60 μm. . [Example 2] Rikei Film's 60 μm thick polypropylene film (Alphan Film manufactured by Honshu Paper Industries Co., Ltd.)
Then, a flexible polyimide resin is applied to a thickness of 5 μm, and this is dried to obtain a B-stage state (first step). Next, the B-stage polyimide resin obtained in the first step is laminated onto the treated surface of a copper foil with a thickness of 18 μm and cured by heating (second step). Next, the polyimide resin obtained in the first step is laminated onto the resin surface of the copper foil laminated polyimide resin obtained in the second step (third step). Next, the resin surfaces of the copper foil laminated polyimide resin obtained in the third step were laminated together and cured by heating to obtain a single-sided copper foil laminated flexible printed circuit board with an insulating layer of 100 μm. [Example 3] Rikei film fluorinated vinyl film with a thickness of 60 μm (Tedra film manufactured by DuPont, USA)
Then, apply epoxy resin to a thickness of 10 μm and dry it to bring it to the B stage state (first step). Next, the epoxy resin in the B-stage state obtained in the first step is laminated onto the treated surface of a 35 μm thick copper foil and cured by heating (second step). Rikei Film's 60μm thick polypropylene film (Alphan Film manufactured by Honshu Paper Industries Co., Ltd.)
Next, a flexible epoxy resin containing 25% potassium titanate fibers is applied to a thickness of 30 μm and dried to bring it to the B stage (third step). Next, the epoxy resin obtained in the third step is laminated onto the resin surface of the copper foil laminated epoxy resin obtained in the second step (fourth step). Next, the resin side of the copper foil laminated epoxy resin obtained in the second step and the resin side of the copper foil laminated epoxy resin obtained in the fourth step are laminated together and heated to harden to form a double-sided copper-clad flexible with an insulating layer of 50 μm. A printed circuit board was obtained. [Example 4] A 50 μm thick polyester film (Lumirror film manufactured by Toray Industries, Inc.) that had been subjected to RIKEI treatment was
Apply epoxy resin to a thickness of 15 μm and dry it to bring it to the B stage state (first step). Next, the epoxy resin in the B-stage state obtained in the first step is laminated onto the treated surface of a 35 μm thick copper foil and cured by heating (second step). Next, the epoxy resin obtained in the first step is bonded to the resin surface of the copper foil laminated epoxy resin obtained in the second step, and cured by heating (third step). Next, the epoxy resin obtained in the first step is laminated onto the resin surface of the copper foil laminated epoxy resin obtained in the third step (fourth step). Next, the resin surface of the copper foil laminated epoxy resin obtained in the fourth step is laminated with the copper foil obtained in the first step (fifth step). Next, the resin side of the copper foil laminated epoxy resin obtained in the fifth step is laminated to the treated side of the 2 mm thick aluminum plate, and the insulation is layered by heating and hardening.
A 60μm aluminum metal base copper clad substrate was obtained. [Example 5] Flexible epoxy resin was applied to a 40 μm thick polypropylene film (Toray Film, manufactured by Toray Industries, Inc.) to a thickness of 10 μm, and dried to bring it to a B-stage state ( first step). Next, apply the epoxy resin obtained in the first step to a thickness of
It is pasted onto the treated surface of 18 μm copper foil and heated to harden (second step). Next, a 50 μm thick polyester film (Lumirror Film, manufactured by Toray Industries, Inc.) was coated with Rikei Film.
Apply and dry 30μm heat-resistant nylon resin (third step). Next, the nylon resin obtained in the third step is heated and bonded to the resin surface of the copper foil laminated epoxy resin obtained in the second step (fourth step). Next, the resin surface of the copper foil laminated epoxy nylon resin obtained in the fourth step and the resin surface of the copper foil laminated epoxy resin obtained in the second step are heated and laminated together to form a double-sided copper clad with an insulating layer of 50 μm. A flexible printed circuit board was obtained. [Example 6] Rikei Film's 60 μm thick polypropylene film (TOREFAN FILM manufactured by Toray Industries, Inc.) is coated with a flexible epoxy resin to a thickness of 15 μm and dried to bring it to the B-stage state. Step 1). Next, the epoxy resin in the B-stage state obtained in the first step is laminated onto the treated surface of a rolled copper foil with a thickness of 35 μm and cured by heating (second step). Next, the B-stage epoxy resin obtained in the first step is laminated onto the treated surface of the 50 μm thick iron foil (third step). Next, the resin surface of the iron foil laminated epoxy resin obtained in the third step is bonded to the epoxy resin in the B stage state obtained in the first step (fourth step). Next, the resin surface of the iron foil-laminated epoxy resin obtained in the fourth step is laminated with the resin surface of the copper foil-laminated epoxy resin obtained in the second step, and heated and cured to form an iron foil-based copper with an insulating layer of 45 μm. A flexible printed circuit board was obtained. Its cross-sectional structure is shown in the figure. [Test Results] The results of tests conducted on each of the above examples are shown in the following table. Peel strength and solvent resistance are values calculated per 1 cm when a 2.5 mm wide copper foil or iron foil is peeled off in a 90 degree direction.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a product with a small number of manufacturing steps and a product that is equivalent to or better than conventional products.

[Brief explanation of the drawing]

The figure is a structural sectional view of a substrate obtained by the method described in Example 6.

Claims (1)

[Scope of Claims] 1. A metal foil is pasted onto the surface of the adhesive layer of a re-keying film coated with an adhesive on one side, the adhesive is cured, and the re-keying film is removed, thereby curing into a metal foil. a first step of forming a first adhesive layer; and a first step of forming a first adhesive layer, and an adhesive of a rekeying film in which an adhesive is further applied on one side of the surface of the cured adhesive layer produced by this first step. a second step of forming hardened first and second adhesive layers on the metal foil by laminating the surfaces of the layers, curing the adhesive and removing the adhesive film; Further, on the surface of the cured second adhesive layer manufactured by above, the surface of the adhesive layer of a re-keying film coated with an adhesive on one side is applied, and the adhesive is cured, and the re-keying film is and a third step of forming cured first, second and third adhesive layers on the metal foil by removing. 2. The method for manufacturing an electric circuit wiring board according to claim 1, wherein each of the first, second, and third adhesive layers has a thickness of 10 μm or more and 100 μm or less. 3. The method for manufacturing an electric circuit wiring board according to claim 1, wherein the metal foil has a thickness of 9 μm or more and 200 μm or less. 4. A metal foil is pasted onto the surface of the adhesive layer of a rekeying film coated with an adhesive on one side, the adhesive is cured, and the rekeying film is removed, thereby forming the first adhesive that has hardened into the metal foil. The first step is to form a layer, and the surface of the cured adhesive layer produced by this first step is further laminated with the surface of the adhesive layer of a re-keying film coated with adhesive on one side. a second step of forming cured first and second adhesive layers on the metal foil by curing the adhesive and removing the adhesive film; The surface of the second adhesive layer is laminated with the surface of the adhesive layer of a re-keying film coated with an adhesive on one side, and then the re-keying film is removed, and the adhesive layer from which the re-keying film is removed is a third step of laminating the surface of the above to the surface of a metal body different from the metal foil, and curing the adhesive layer. 5. The method for manufacturing an electric circuit wiring board according to claim 4, wherein the metal body is a metal foil. 6 Claim 4 in which the metal body is a metal substrate
A method for manufacturing an electric circuit wiring board according to 1. 7. The first adhesive is cured on the metal foil by pasting a metal foil on the surface of the adhesive layer of the rekeying film with adhesive applied on one side, curing the adhesive, and removing the rekeying film. a first step of forming a layer; and an adhesive layer of a fibrous inorganic insulating film, which is coated with an adhesive on one side, on the surface of the cured adhesive layer produced by this first step; a second step of forming hardened first and second adhesive layers on the metal foil by attaching the metal foil to the surface of the metal foil, curing the adhesive and removing the adhesive film; The surface of the produced cured second adhesive layer is further laminated with the surface of the adhesive layer of the adhesive film coated on one side with an adhesive via a fibrous inorganic insulating material. a third step of forming hardened first, second and third adhesive layers on the metal foil by curing the metal foil and removing the adhesive film. 8. The method for manufacturing an electric circuit wiring board according to claim 7, wherein the fibrous inorganic insulating material is fibrous potassium titanate.