JPS5826197B2 - Manufacturing method of printed wiring board with metal core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board with a metal core, specifically,
This invention relates to a method for etching the inner wall of a metal core through hole in a printed wiring board with a metal core, the surface of which is laminated with copper foil and provided with through holes.

After drilling a hole in a surface copper-clad laminate with a metal core, in order to connect each pattern on the upper and lower surfaces within the hole without contacting the metal core, or to connect the pattern on one side and the inner wall of the hole. When applying copper plating to the inner wall of the hole, in order to avoid electrical contact between the metal core material and the steel plating on the inner wall of the hole, only the core material inside the hole is etched, and the etched area is coated with an electric layer. Forms an insulating layer.

In other words, to form through-holes in surface copper-clad laminates with metal cores, holes are first drilled to prevent holes from appearing, the metal cores in the holes are etched by 20 to 100 μm, and then electrodeposited using electrophoresis as the principle. An insulating layer is formed using an electrically driven force, and then the entire structure is plated.

When through holes are formed in a wiring board with a metal core, the first
As shown in the figure, the metal core tends to cause flashing inside the laminate, so simply etching parallel to the inner wall of the hole by using the metal plate core as an anode and the other electrode as a cathode in an electrolytic solution will not work. It is not possible to increase the distance to the copper foil, and it is difficult to maintain the thickness of the insulating layer at the corner after electrodeposition, making it impossible to obtain a high breakdown voltage.

In FIG. 1, 1 is a copper foil, 2 is a prepreg whose base material is filled with thermosetting resin, 3 is a metal plate core material, and 4 is a hole formed when a through hole is made.

Furthermore, when etching is performed using the metal plate core material as an anode and the other electrodes as cathodes, there is a problem that the etched metal of the metal plate core material adheres to the copper foil.

In order to etch the corners of the metal plate core material, etching may be carried out in an electrolytic solution using the metal plate core material 3 as an anode and the copper foil 1 as a cathode, but in this case, as shown in FIG. The central part of the inner wall of the through hole in the metal plate core material is not etched, resulting in insufficient adhesion of the electrodeposited resin.

The present invention was made in view of these points, and consists of a metal cored copper cladding in which a metal plate is used as a core material, and a prepreg filled with a thermosetting resin is layered on the surface of the core material, and copper foil is pressed on top of the prepreg. A printed wiring board with a metal core in which through-holes are formed in a laminate, the metal plate core material on the inner wall of the through-hole is etched, an insulating film is formed on that part by electrical driving force, and a chemically plated conductor layer is formed on the inner wall of the through-hole. The manufacturing method is characterized by etching in an electrolytic solution by using the metal plate core material as an anode and the other electrodes as a cathode, and applying a lower potential to the copper foil than the metal plate core material. It is something.

In FIG. 3, 5 is a cathode, and the metal plate core material is an anode.

The copper foil is given a lower potential than the metal plate core material and electrolytically etched in an electrolytic solution such as hydrochloric acid.

By doing this, the structure inside the through-hole will be flattened and the corners of the metal core will be rounded, as shown in FIG.

After this, the insulating resin layer is applied only to the metal core using electrical driving force such as electrodeposition coating or powder coating, and chemical plating is applied to the entire laminate.The structure is as shown in Figure 5. The distance to the plating is kept above a certain value.

In FIG. 5, 6 is an insulating resin layer, and 7 is a chemical plating layer.

Example 1. A double-sided copper-clad laminate with a metal core made of an iron plate between 1 and 2 was subjected to electrolytic etching according to the circuit shown in Figure 3 using dilute hydrochloric acid as the etching electrolyte, and was used as a base coat for automobile exterior painting. The cationic electrodeposition paint used in
m1 electrolytic copper plating of 10 to 50 μm is applied to the entire laminate,
A circuit was formed using through holes.

As a result of a voltage resistance test, it was found to have sufficient voltage resistance at 1 kV for 1 minute or more.

As explained above, in the present invention, in a double-sided copper-clad laminate with a metal core, the corners of the metal core in the hole where burrs are likely to occur can be removed by selectively etching the corners of the metal core in the hole after drilling. We were able to eliminate insulation failure accidents that occurred in the area.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the through-hole part of a printed wiring board with a metal core, Fig. 2 is a sectional view of the through-hole part of the printed wiring board with a metal core etched by the conventional method, and Fig. 3 is a sectional view of the through-hole part of the printed wiring board with a metal core etched by the conventional method. Fig. 4 is a cross-sectional view of a through-hole portion of a printed wiring board with a metal core etched by the method of the present invention, and Fig. 5 is a cross-sectional view of the through-hole portion of a printed wiring board with a metal core etched by the method of the present invention. FIG. Explanation of symbols, 1... Copper foil, 2... Prepreg, 3... Metal plate core material, 4... Paris, 5... - Cathode electrode, 6... Insulating resin layer, 7... Chemical plating layer.

Claims (1)

[Claims] 1 A through hole is formed in a copper-clad laminate with a metal core made by using a metal plate as a core material, stacking a prepreg filled with a thermosetting resin as a base material on the surface and pressing copper foil on top of the prepreg, and forming a through hole in the metal plate on the inner wall of the through hole. The core material is etched and the area is etched,
In the manufacturing method of printed wiring boards with metal cores, in which an insulating film is formed by electrical driving force and a chemically plated conductor layer is formed on the inner wall of the through-hole, the metal plate core material is used as an anode and other electrodes are used as an anode in an electrolytic solution. A method for producing a printed wiring board with a metal core, characterized in that the copper foil serves as a cathode and is etched by applying a potential lower than that of the metal plate core material.