JPS60214594A - Method of producing printed circuit board - 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 Field of the Invention The present invention relates to a method for manufacturing printed wiring boards used in general electronic equipment such as televisions and video tape recorders.

2. Description of the Related Art Structures of Conventional Examples and Their Problems In recent years, with the widespread use of electronic equipment, the demand for printed wiring boards has increased rapidly.

Printed wiring boards have traditionally been considered an essential component in the configuration of electronic circuits, and recently there has been an extremely strong demand for smaller, higher density, and lower cost electronic circuits, and a variety of printed wiring boards are being used to meet these demands. It's starting to get worse.

Generally speaking, there are two main methods for manufacturing printed wiring boards. One of these is the etched foil method, which uses a copper-clad laminate such as paper phenol as a starting material and dissolves unnecessary portions of the copper foil by etching.

On the other hand, the other method is called the additive method, in which the starting material is a laminate made of paper phenol, etc., which does not fully adhere to the copper, and selectively conductive coating is applied mainly to the required areas of the surface using electroless plating technology. This is a method of forming a metal layer.

However, in the former method, the copper foil must be dissolved and removed by etching, resulting in significant loss of material, and a disadvantage peculiar to the deep etching method is that the conductor width of the circuit conductor layer cannot be reduced by deep etching.

7 (6) by interfering with fine wiring.

The latter method is shown in Figures 1A-D.
As shown in FIG. 1A, this method involves coating the surface of an insulating substrate 1 with a synthetic resin such as a copolymer resin of acrylonitrile and butadiene that can be eluted by chemical treatment. The adhesive layer 2 is formed, and then, as shown in FIG. 1B, the adhesive layer is etched in a chromium etching-sulfuric acid mixture or a potassium permanganate solution.

By dissolving the butadiene present in the adhesive, roughening the surface, and performing an activation treatment, the entire activation layer 3 is formed as shown in Figure 1C. Anti-electrostatic full 11i' plating on the surface in reverse wiring diagram shape.
<After the entire IE resist film 4 is formed, electroless copper plating is performed on the entire conductive metal layer 6 made of copper as shown in the first diagram.
was formed.

However, in printed wiring boards manufactured using this method, it is technically important to uniformly and precisely roughen the surface condition of the adhesive layer and to improve the adhesion of the conductive metal layer formed thereon. This is a key point, and because the control technology for surface treatment is insufficient, the adhesive strength of the circuit conductor layer varies widely.

During the soldering process, defects such as the circuit conductor layer blistering or peeling from the adhesive layer occurred.

In addition, this method requires the use of a strongly oxidizing solution such as a chromic acid mixture or potassium permanganate to roughen the surface of the adhesive layer, and sufficient consideration must be taken to prevent pollution. However, a large amount of equipment had to be installed in the waste liquid treatment equipment.

OBJECTS OF THE INVENTION The purpose of the present invention is to improve the manufacturing method of printed wiring boards by an additive method and to make the surface of the adhesive layer non-polluting.

An object of the present invention is to provide a method for manufacturing a printed wiring board whose surface is roughened by a processing technique and a circuit conductor layer can be formed on the surface with extremely good adhesion.

Structure of the Invention In order to achieve the above object, the present invention provides a printed wiring board in which an insulating resin layer mixed and dispersed with an inorganic filler is formed on at least one surface of an insulating substrate, and the insulating resin layer After roughening the surface layer q (- to expose part of the p15 substance 7 filler), a conductive metal layer in the form of a wiring circuit is formed on this surface. 1 = is created.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 2M to 2D show the manufacturing process of a printed wiring board in an embodiment of the present invention.

In Fig. 2 M to D, 6 is an insulating substrate, 7 is an adhesive layer,
7a is an inorganic filler, 8 is an active (I-Rohi layer).

9 is an insulating resist layer, and 10 is a conductive metal layer.

Regarding the printed wiring board configured as shown below, 61
,・The manufacturing process will be explained in detail based on examples.

First, as shown in FIG. 2A, an inorganic filler 7 is applied to the surface of an insulating substrate 10 made of a synthetic resin substrate such as paper phenol, paper epoxy, or glass epoxy, or a metal plate.
As a, fine powders of alumina, calcium carbonate, silica, carbon, etc. are mixed and dispersed in thermosetting resins such as epoxy resins, acrylic resins, and phenolic resins to form a paste, which can be processed using screen printing methods, etc. The insulating resin layer 7 was formed by applying the resin to a thickness of 30 to 60 μm and curing it by heating.

Next, as shown in FIG. 2B, this substrate is placed in an oxygen gas atmosphere in a vacuum to generate plasma, thereby incinerating the surface resin layer and partially exposing the inorganic filler 7a, thereby insulating the substrate. The surface of the resin layer 7 is uniformly and precisely roughened. In this case, the plasma treatment selectively incinerates and removes only the organic resin component, and the inorganic filler 7a remains as it is without being removed. The state of surface roughening of the insulating resin layer 7 after plasma treatment is greatly influenced by the shape and particle size of the insulating resin layer 7, as well as the state of dispersion in the resin.

In this example, the particle size of the inorganic filler 7a is about 5 μm.
This silica was mixed and dispersed in a two-component epoxy resin using imidazole as a hardening agent at a weight ratio of 80 to 85% to form a paste, and the entire surface of the insulating substrate 60 was coated by screen printing. Approximately 60 at 160°0
Cured by heating for minutes.

Then, in the vacuum of this substrate i 1 TOrV, oxygen gas -
qB()007 minutes of antiperspirant was supplied and left to stand for about 5 to 10 minutes to remove the resin by ashing.

Then, as shown in Figure 2C, this substrate was
An activation layer 8 consisting of fine particle cores of gold and palladium is formed on the entire surface of the insulating resin layer, which has been roughened by immersion in hydrochloric acid acidic solutions of tin and palladium chloride, respectively, and chemical resistance is further added to this surface. After forming the insulating resist 9 having a reverse wiring diagram shape by screen printing,
This substrate is immersed in an electroless copper plating solution consisting of an alkaline solution of a copper complex salt and formalin, and metal copper is deposited on the surface of the exposed wiring circuit-shaped insulating resin layer 70.
was formed.

In this process, the chemical-resistant insulation resist 9 is required to be resistant to the strong alkalinity of the electroless steel plating bath and to have excellent electrical insulation properties and heat resistance. In this embodiment, an insulating resist that satisfies the required characteristics is made of an epoxy resin or acrylic resin material.

one! However, in this embodiment, before the roughened insulating resin layer 7 is completely formed on both the front and back surfaces of the insulating substrate 6 and the activation treatment is performed, through-holes are formed in the necessary locations of the insulating substrate by molding or drilling. Open it, then perform the activation process,
Through-hole wiring board 7 is formed by forming insulating resist 9 in a reverse wiring diagram shape on both the front and back surfaces of the insulating substrate, and simultaneously forming a conductive metal layer on both the front and back surfaces of the insulating substrate and the inner wall surface of the through hole by electroless copper plating. accomplished.

9.2° In still other implementations of the invention <Ill, the conductive metal layer 10
It has been found that by using a vapor deposition method or a sputtering method instead of the electroless plating method described above as a formation method, the activation treatment step can be omitted and good adhesion of the circuit conductor layer can be obtained.

Effects of the Invention As is clear from the above explanation, the printed wiring board according to the present invention has an insulating resin layer mixed and dispersed with an inorganic filler that will become an adhesive layer formed on the surface of an insulating substrate, and the surface resin layer is processed using plasma technology. It is made by roughening the surface by ashing and removing it using a method, and then forming a conductive metal layer in the shape of a wiring circuit on the surface by electroless plating, vapor deposition, sputtering, etc.

Therefore, it is necessary to perform surface roughening treatment using harmful chemicals, which is a drawback of the conventional additive method, and the roughened surface exhibits an extremely uniform and dense roughened state. It was found that the variation in adhesive strength was small, and the strength was improved by 20 to 30% compared to the conventional additive method.

Furthermore, in the method of the present invention, the range of selection of the insulating resin that forms the adhesive layer is extremely wide, and almost all synthetic resin materials can be used, and many effects not found in conventional methods can be obtained.

[Brief explanation of drawings]

Figures 1A-D are manufacturing process diagrams for conventional printed wiring boards;
Figures M to D are process diagrams showing a method for manufacturing a printed wiring board in an embodiment of the present invention. 6... Insulating substrate, 7... Insulating resin layer,
7a... Inorganic filler, 8... Activation layer 29... Insulating resist layer, 10...
・Conductive metal layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 2

Claims (1)

[Scope of Claims] (1) A step of forming an insulating resin layer containing an inorganic filler mixed and dispersed on at least the whole surface of an insulating substrate, removing a part of the surface resin layer of the insulating resin layer, and forming an inorganic JF filler. A method for manufacturing a printed wiring board, comprising the steps of: roughening the surface by exposing the substrate; and forming a conductive metal layer in the form of a wiring circuit on the insulating substrate. ? ) The surface resin layer of the insulating resin layer is removed by plasma treatment and the surface is roughened, and a conductive metal layer in the form of a wiring circuit is formed by electroless plating. A method for manufacturing printed wiring boards. (3) The method for manufacturing a printed wiring board according to the patent clause 1, characterized in that the conductive metal layer in the form of a wiring circuit is formed using a thin film technique such as vapor deposition or sputtering. Mukun