JPS60246695A - 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 video tape recorders.

2. Description of the Prior Art Structure and its Problems With the rapid advancement of electronic equipment, the demand for printed wiring boards is increasing.

Various methods have been used to manufacture printed wiring boards, but the mainstream is called the etched foil method.
This method uses a so-called copper-clad laminate in which copper foil is bonded to paper phenol or glass epoxy/substrate, and removes unnecessary copper foil by etching.

However, since this method involves a large amount of material loss and is intended to save resources, an alternative manufacturing method called the additive method has recently been attracting attention.

This additive method uses an insulating substrate such as paper phenol or glass epoxy that does not have a copper foil attached as a starting material, and uses electroless plating technology to directly form the necessary circuit-like conductor layer on this surface. Various manufacturing processes have been developed as such additive methods.

One such method is the manufacturing method shown in FIGS. 1A-CV'c.

Immediately after coating the adhesive 2 on the main surface of an insulating substrate 1 such as paper phenol by screen printing as shown in Figure 1A, copper is applied to the surface of the adhesive 2 as shown in Figure 2BK. A metal powder 3 such as powder is spread and pressed to heat and harden the adhesive 2, and then, as shown in FIG. This is a method of making printed wiring boards by depositing 4. The work environment is difficult because metal powder is handled, but printed wiring boards using this method require complicated processes and are extremely difficult to evenly adhere the metal powder to the adhesive layer. Since a conductive metal layer is deposited by electroless plating on a surface where a large amount of excess copper powder layer was present, the adhesive strength of the layer decreases, and furthermore, the surface condition is quite uneven, giving an unsightly appearance. There were inconveniences such as solder droplets being scattered during soldering work.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for manufacturing a printed wiring board that has a relatively simple manufacturing process, a good surface condition, and extremely excellent adhesion of the conductor layer.

Structure of the Invention In the printed wiring board according to the present invention, fine metal powder is mixed into a synthetic resin on at least the entire surface of an insulating substrate.

Using the dispersed conductive paste, apply it to the desired wiring circuit diagram shape, remove the surface resin layer of the spun conductive paste, and then apply an electroless plating method to form a conductive metal layer on the exposed metal fine powder layer. It was precipitated.

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

FIGS. 2A to 2C show the manufacturing process of a printed wiring board in one embodiment of the present invention.

In FIG. 2, 6 is an insulating substrate, 6 is a conductive adhesive layer,
6a(d) fine metal powder; 7 is a conductive metal layer;

The manufacturing method of the printed wiring board of this embodiment constructed as described above will be described in detail below.

First, as shown in FIG. 2, the insulating substrate 5 is made of a synthetic resin substrate such as a paper phenol base material or a glass epoxy base material, or an insulating substrate 6 made of a ceramic such as alumina. Using a so-called conductive paste made by dispersing and mixing fine metal powder such as fine metal powder into an epoxy resin or acrylic resin, it is applied to the desired wiring circuit diagram shape using a screen printing method and cured by heating. As a result, a conductive adhesive layer 〇 was formed. .

In this case, the metal fine powder 6a used for the conductive benist is
The metal is not limited to the above-mentioned copper or silver, but any metal may be used as long as it has good conductivity and can serve as a catalyst nucleus for electroless plating in the next step.

In addition, these metal fine powders 6a preferably have a particle size as small as possible and an irregular shape, and are mixed and dispersed in an epoxy resin, acrylic resin, or polyimide resin at a weight ratio of 50 to 86%. A conductive paste was prepared by this method.

Next, as shown in FIG. 2B, the fixed conductive adhesive layer 6
Only the resin present in the surface layer of the metal powder layer 6a is removed to expose a part of the metal fine powder layer 6a to the surface. In this step, plasma treatment is particularly performed and oxygen gas is supplied in a vacuum (ITorr). It was found that when this method was used to ash the resin content, the surface condition became densely roughened.

In this example, resin-like electrolytic copper powder (particle size 5 to 1
0μ) in an epoxy resin containing imidazole as a hardening agent at a weight ratio of approximately 70%.

The conductive adhesive 1i6 is formed into a desired wiring (b) circuit shape using the dispersed conductive paste, and then plasma treatment is performed to ash the epoxy resin layer covering the surface of the conductive adhesive layer 6. By removing the adhesive layer, an adhesive layer was formed in which the copper fine powder layer was densely exposed on the surface.

Then, a circuit conductor layer is formed by depositing a conductive metal layer 7 on the surface of this conductive adhesive layer 6 by electroless plating, but in this example, copper plating is performed as electroless plating to coat copper. A conductive metal layer 7 was formed by immersing the steel in an electroless steel plating solution consisting of an alkaline solution of a complex salt and formalin to deposit a steel having a ratio of 30 to 36/1.

In addition, in this electroless plating process, by forming through holes in the insulating substrate in advance, performing an activation treatment, and then performing electroless plating, it is possible to create a printed wiring board with so-called slot hole conductivity. .

Effects of the Invention As is clear from the above explanation, the printed wiring board according to the present invention is coated on the main surface of an insulating substrate in the shape of a wiring circuit diagram using a conductive paste in which fine metal powder is mixed and dispersed in a synthetic resin. By this, a conductive adhesive layer is formed, and the surface resin of this adhesive layer is removed by plasma treatment to expose the metal fine powder layer, and then a conductive metal layer is formed on the surface by electroless plating. It was made through a process of

Therefore, the printed wiring board according to the present invention has the same conductivity as the conventional example. The process of forming the conductive adhesive layer is simplified, and the workability is improved without damaging the working environment due to metal powder. Moreover, the surface of the conductive adhesive layer formed by plasma treatment is extremely dense. There was no excess metal powder layer with a roughened surface and no adhesive layer, and the adhesiveness with the conductive metal layer formed by electroless plating was significantly improved.

[Brief explanation of the drawing]

FIGS. 1A to 1C are process diagrams for manufacturing a conventional printed wiring board, and FIGS. 2A to 2C are process diagrams showing a method for manufacturing a printed wiring board according to an embodiment of the present invention. 5... Insulating substrate, 6... Conductive adhesive layer, 6a...
...Metal fine powder, 7 ・ Conductive metal 'i! . Name of agent: Patent attorney Toshio Nakaya and 1 other person 1st
Figure 2

Claims (1)

[Claims] (1) Apply a conductive paste prepared by mixing and dispersing fine gold powder into a synthetic resin onto at least one surface of an insulating substrate in the desired wiring circuit shape, and apply a surface resin layer of the fixed conductive paste. A method for manufacturing a printed wiring board, comprising depositing a conductive metal layer by electroless plating on the metal fine powder layer exposed by removal. (Kon) Claim 1 characterized in that the surface resin layer of the fixed conductive paste is removed by plasma treatment.
A method for manufacturing a printed wiring board as described in Section 1.