JPS592396B2 - Manufacturing method for wiring boards using wires in the required wiring pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-density wiring board using insulated wires for the necessary wiring patterns.

Manufacturing methods for printed wiring boards include the subtract method, in which unnecessary copper parts of a copper-clad laminate are dissolved and removed using chemicals to form a wiring pattern, and the wiring is produced by depositing electroless plating on the necessary parts of a non-copper-clad laminate. There are additive methods for forming patterns. In both of these methods, the wiring is formed on a plane, so it is not possible to cross the wiring on the same plane.For crossing wiring, different planes are used and through holes are provided between the plane layers, and the through holes are filled with electroless plating etc. Since interlayer connections are made by metallization, it is difficult to increase the density of wiring patterns. To improve these shortcomings, we have created a high-density wiring board suitable for high-mix, low-volume production by installing an adhesive layer on an insulating substrate and wiring the wires by holding them in the adhesive layer (hereinafter referred to as multi-wire wiring board). (abbreviated as Hitachi Chemical Co., Ltd. product name)).

Multi-wire wiring boards that use wires for such necessary wiring patterns are exposed to heat when wiring them (the wires are attached to the adhesive layer and bonded at the same time) to an insulating substrate such as a thermosetting resin laminate. Insulated wires (wires) covered with heat-resistant resin such as polyimide resin are laid using a numerically controlled wiring machine on a layered or coated thermosetting adhesive that maintains plasticity, and the wiring wires are fixed using a press, etc. A through hole is made across the wire at the end of the wire, the cut end of the wire is exposed on the peripheral wall of the through hole, and an electroless plating metal layer is formed on the inner wall of the through hole to connect to the cut end of the wire.

Multi-wire wiring boards use insulated wires, so they have high insulation even when the wiring intersects or is placed in close parallel, making it suitable for high-density wiring. Adhesives used for multi-wire wiring boards are thermally softened when heated, making it easy to embed wires under pressure, and immediately solidified when air-cooled to fix wires, while hardening when heated and pressurized in the post-process. Rubber-based thermosetting adhesives (for example, adhesive trade name HA-05 manufactured by Hitachi Chemical Co., Ltd.) are used to improve heat resistance, electrical properties, and the like. This adhesive contains a plating catalyst necessary for electroless plating on the inner walls of through holes, etc. The adhesive is not a solution type but is usually laminated onto an insulating substrate in the form of an adhesive sheet containing glass cloth as shown in the drawing. The glass cloth 1 also has the function of preventing the wires from penetrating too deeply and coming into close contact with the circuits on the board when embedding the wires. The adhesive sheet is made by impregnating glass cloth with an adhesive, and then coating the surface to form a layer with a thickness necessary for embedding the wire (140μ or more in solid form) and a thickness necessary for adhering it to the insulating substrate side. It is solid and has a surface 3 of about 50μ). Printed wiring boards are becoming more dense in order to miniaturize and improve the performance of electrical equipment, etc., but the same is true for multi-wire wiring boards, and in order to increase the density, there is a demand for improved insulation properties of adhesive sheets. . The present invention has been made in view of these points, and in a method of manufacturing a wiring board using wires for the necessary wiring pattern, an adhesive layer is used as an adhesive layer in which insulated wires are embedded, and as a reinforcing layer. In addition to the adhesive sheet consisting of a glass cloth and an adhesive layer to the insulating substrate, a glass cloth impregnated with a resin solution that is a mixture of a solid epoxy resin and a liquid epoxy resin at room temperature and dried is used as a reinforcing glass cloth. It is characterized by its use.

The epoxy resin that is night-like at room temperature used in the present invention is a bisphenol type, such as Epicoat 812, 815, 827, 828, 832, 834 manufactured by Ciel Chemical Co., Ltd.
Solid epoxy resins include Epicoat 836, 1001, 1004, 1007, and 1 manufactured by Ciel Chemical.
009 etc.

Among the alicyclic epoxy resins manufactured by Chitsuso Corporation, liquid epoxy resins include Chitsonox X-221, and solid epoxy resins include Chitsonox 313 and 301. Epoxy resins that are liquid at room temperature account for 5 to 50% of all epoxy resins.
Preferably it is 30% by weight.

If the amount of liquid epoxy resin is less than 5% by weight, there is little tendency to improve the insulation resistance after boiling, and if it exceeds 30% by weight, the coated cloth becomes sticky after drying and becomes difficult to handle.

Although tackiness can be reduced by raising the drying temperature and increasing the degree of curing, the working range in which the B-stage condition must be obtained tends to be extremely narrow, and on the other hand, flexibility is lost and folding scratches occur. The amount of epoxy resin impregnated into the reinforcing glass cloth is preferably 15 to 55% by weight (based on the total weight of the resin-impregnated glass cloth).

If the content of epoxy resin in the glass cloth is less than 15% by weight, the ultrasonic heating effect during wiring will be insufficient due to the cavity that remains between the adhesive film and the laminated film, resulting in insufficient embedding of the wire. The peel strength is significantly reduced.

On the other hand, if the resin content exceeds 55% by weight, the excess resin will deteriorate the flexibility of the glass cloth and cause folding scratches. Furthermore, a slipping phenomenon occurs between the adhesive film and the resin layer, reducing wiring accuracy when embedding the wire. If the amount of epoxy resin impregnated into the glass cloth is relatively small, the adhesion of copper plating inside the through holes will be sufficient due to the action of the plating catalyst (for example, palladium-based PEC-8) contained in the adhesive layer (HA-05). However, if the epoxy resin content increases or the activity of the copper plating solution is insufficient, plating adhesion defects may occur, so a plating catalyst may also be included in the epoxy resin for impregnation.

Comparative Example 1 Adhesive HA-05 (manufactured by Hitachi Chemical Co., Ltd.) was applied to a 40μ polypropylene film (biaxially oriented film manufactured by Toray Industries, Ltd.) to a thickness of 140μ and 50μ after drying. A reinforcing glass cloth (959/A) was inserted between the adhesive films, and the adhesive sheets were bonded together using a pressure roll at 130°C.

Comparative Example 2 In Comparative Example 1, an adhesive sheet was prepared using glass cloth that had been impregnated with adhesive HA-05 and dried.

The content of HA-05 is 40% by weight. Comparative Example 3 In Comparative Example 2, a methyl ethyl ketone solution of an epoxy resin was used in place of the adhesive HA-05.

The epoxy resin was prepared by dissolving and mixing 3 parts of dicyandiamide as a curing agent in 100 parts by weight of Epikote 1001 (manufactured by Shell Chemical Co., Ltd., melting point: 64-74°C). In addition, as a plating catalyst, Ca
t#10 (metsuki catalyst manufactured by Hitachi Chemical Co., Ltd.) was added and mixed in an amount of 15% by weight based on the resin content.

The content of epoxy resin in the glass cloth was 40%. Comparative Example 4 Epicoat 100 was used as the epoxy resin in Comparative Example 3.
4 (melting point 96-104 fat C) was used.

Comparative Example 5 In Comparative Example 3, the amount of K in Epicote 1001 was changed to Epicote 828, which is liquid at room temperature, and the content in the glass cloth was changed to 10% by weight.

In Example 1 and Comparative Example 5, the content of epoxy resin in the glass cloth was 40% by weight.

Example 2 In Example 1, the content in the glass cloth was 20% by weight.

Example 3 In Example 1, the ratio of Epicote 1001 and 828 (
weight) was made 85:15.

Example 4 In Example 1, Epicote 1004 was used instead of Epicote 1001.

The adhesive sheet made in this way was heated at 175℃ and 25k.
Cured for 30 minutes in a 9/(-d press, then 16
It was cured for 2 hours with hot air at 0°C.

The following table shows the results of measuring the water absorption rate of the thus obtained adhesive sheet when it was treated in hot water at 70° C. for 5 hours and the insulation resistance (according to JIS-C-6481) under normal conditions and after 2 hours of boiling. In addition, the uncured adhesive sheet was bonded to an insulating substrate, a wire was ultrasonically bonded onto it, and the variation in peel strength when the wire was peeled off was determined, and the results are shown in the table below.

As explained above, by using the epoxy resin-impregnated glass cloth of the present invention, the insulation resistance of the adhesive sheet after moisture absorption can be increased about 10 times.

It has also become possible to stably produce adhesive sheets with good wire wiring properties.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of the adhesive sheet. Explanation of symbols, 1...Glass cloth for reinforcement, 2.
...Adhesive layer in which the wire is embedded, 3...
...Adhesive layer that is bonded to the insulating substrate.

Claims (1)

[Claims] 1. An adhesive layer is formed on an insulating substrate, an insulated wire is placed on the adhesive layer and bonded at the same time to form a wiring pattern, a through hole is made across the insulated wire, and a through hole is formed inside the through hole. In the manufacturing method of wiring boards using wires for the necessary wiring pattern, the adhesive layer is the adhesive layer in which the insulated wires are embedded, the reinforcing glass cloth, and the adhesive with the insulating substrate. Necessary wiring characterized in that the reinforcing glass cloth is a glass cloth impregnated with a resin solution obtained by mixing a solid epoxy resin with an epoxy resin that is liquid at room temperature and dried. A method of manufacturing wiring boards using wire in the pattern. 2 Epoxy resin that is liquid at room temperature accounts for 5% of all epoxy resins.
Claim 1 characterized in that the amount is 30% by weight.
A method of manufacturing a wiring board using wire for the required wiring pattern described in Section 1. 3 Epoxy resin impregnation rate of reinforcing glass cloth is 15%
55%. A method of manufacturing a wiring board using wire for a necessary wiring pattern according to claim 1 or 2, wherein the wiring pattern is 55%.