JPS5832800B2 - Manufacturing method of printed wiring board with metal core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a printed wiring board with a metal core, and more specifically, a method of forming a conductive circuit by printing wiring processing on a metal core board having through-holes and having an insulated surface. It is related to.

Printed wiring boards with metal cores are usually processed to the final product size because it is necessary to completely insulate the metal core board, and electrolytic plating is used when forming conductive circuits through printed wiring processing. During processing, the electrolytic plating process adheres to the peripheral end surface of the final product, resulting in a short circuit between conductive circuits.

For this reason, in order to prevent electroplating from adhering to the peripheral end surface of the final product, a method has been adopted in which a resist is applied to the peripheral end surface of the final product.

However, this method is inefficient and often fails to completely achieve its purpose due to the difficulty of coating due to the complicated external shape of the resist pinhole final product.

On the other hand, Japanese Patent Laid-Open No. 5339471 discloses an improved method for eliminating the resist coating operation.

This method is a method in which electroplating is performed in a state where outer frames are placed around the final product shape of the metal core substrate at intervals via connecting ribs.

This method attempts to cover the gap between the final product and the outer frame by exposing and curing a photosensitive resin film. If you expose and harden a relatively wide gap or a gap with corners that make a rectangular shape, the photosensitive resin film in the covered area may crack after development.
The corners of the square are often torn, and during electrolytic plating, the electroplating liquid invades the peripheral edge of the final product and the electrolytic plating adheres to the area that should be protected. However, there is still the disadvantage that resist coating work must be carried out on the parts.

Therefore, the present invention has been made in view of these points, and its purpose is to eliminate the work of applying resist to the peripheral edge of the final product, which is performed prior to forming a conductive pattern on an insulating film by electrolytic plating. It's about finding a way.

A detailed explanation will be given below according to the drawings. FIG. 1 shows a plan view of an intermediate process of manufacturing a printed wiring board with a metal core used in a method according to an embodiment of the present invention.

As shown in FIG. 1, there is a metal core substrate 2 with a through hole 1 and a final product shape whose surface is covered with an insulating film (not shown), and around the final product shape of this metal core substrate 2, A predetermined interval 4a is provided by the connecting pieces 3a, 3b, 3c,
This is a printed wiring board 6 with a metal core, which has a frame 5 spaced apart from each other by 4b and 4c.

FIG. 2 shows a plan view of a spacer used in a method according to an embodiment of the present invention, and shows the spacings 4a and 4b of FIG. 1.

Spacers 7a each have a shape that blocks each of the spacers 4c.

7b and 7c.

Next, an example of the manufacturing process of a printed wiring board with a metal core including the process of the present invention will be described in detail with reference to FIGS. 3A to 3G, including the process shown as a plan view in FIG. 1.

3A to 3G are partially enlarged cross-sectional views of the circular chain line portion of the cross section taken along the line AA' in FIG. 1.

First, as shown in Fig. 1, a single flat metal plate with a thickness of 1 to 2 mm is processed by punching, etc., and a metal core substrate 2 that has the shape of the final product and a metal core substrate 2 that has the shape of the final product of the substrate 2 are formed. Connecting piece 3 around the periphery
Predetermined intervals 4a, 4b by a, 3b, 3c
, 4c to form the frame body 5.

Then, a through hole 1 with a diameter of 1 is formed at a desired location on the metal core substrate 2 that affects the shape of the final product.

Next, as shown in FIG. 3A, an insulating film 8 of about 150 μm is formed on the entire surface including the metal core substrate 2 and the outer frame 5 connected by a connecting piece (not shown) by electrodeposition coating. 4c indicates the final product shape. This is the distance between a certain metal core substrate 2 and the outer frame 5.

Next, as shown in FIG. 3B, on the entire surface of the insulating film 8,
Approximately 30 μm of rubber adhesive 9 is applied to improve the adhesion of the copper plating.

Next, as shown in FIG. 3C, a first layer is applied to the entire surface of the adhesive 9.
Electroless copper plating 10 of μ is applied.

Furthermore, as shown in FIG. 3D, the spacer 7c shown in FIG. Close the gap.

At this time, it is preferable that the spacer 7c has the same thickness as the substrate 2.

Next, as shown in FIG. 3E, a photosensitive resin film 11 is attached to the front and back surfaces including the spacer 7c, and a conductive pattern mask is formed by baking a conductive pattern by exposure and development.

Next, as shown in FIG. 3F, the photosensitive resin film 11
A conductive pattern 12 is formed by depositing electrolytic copper plating of approximately 50 μm on the portions not covered by the mask.

Next, as shown in FIG. 3G, the photosensitive resin film 11
Peel off the conductive pattern mask from the spacer 7c.
After removing the connecting piece 3, unnecessary parts of the electroless copper plating 10 are further removed by quick etching, and then the connecting piece 3 is removed.
The parts a, 3b, and 3c are cut, and these parts are covered with an insulating film to complete the process.

As explained above, according to the method of the present invention, by inserting a spacer between the metal core substrate and the frame, the mask of the photosensitive resin film for forming the conductive pattern will not be cracked or torn, and the desired portion will be removed. Since a conductive pattern can be formed only on the electrolytic plate, it is possible to omit the work of applying a resist to prevent electrolytic plating on unnecessary portions (peripheral end surface portion of the final product) before electrolytic plating, which was conventionally performed.

Furthermore, since there is no cracking or tearing of the photosensitive resin film mask, there are benefits such as freedom from repair work.

[Brief explanation of the drawing]

FIG. 1 shows a plan view of an intermediate process of manufacturing a printed wiring board with a metal core used in a method according to an embodiment of the present invention. FIG. 2 shows a plan view of a spacer used in one embodiment of the method of the present invention. 3A to 3G are process cross-sectional views of a manufacturing method according to an embodiment of the present invention, and are partially enlarged cross-sectional views of a circular chain line portion of a cut plane taken along line AA' in FIG. 1. 1...Through hole, 2...Metal core board, 3a. 3b, 3c...Connection piece, 4a+4b+4c
...... Spacing, 5... Frame, 6...
・Printed wiring board with metal core, 7a, 7b, 7c...
...Spacer, 8...Insulating film, 9...
・Adhesive, 10... Electroless copper plating, 11...
...Photosensitive resin film, 12... Conductive pattern.

Claims (1)

[Scope of Claims] 1. Frames are arranged at intervals around the final product shape of a metal core substrate having through holes via connecting pieces, and the surfaces thereof are covered with an insulating film. a step of forming a conductive pattern forming a conductive path on the insulating coating by electrolytic plating, and a step of separating the frame body from the metal core substrate in the shape of a final product by cutting the connecting piece; In the method for manufacturing a printed wiring board with a metal core, which includes the step of applying an insulating film to the cut portion of the metal core substrate in the shape of the final product, prior to the step of forming a conductive pattern by electrolytic plating, the spacing is A method for manufacturing a printed wiring board with a metal core, comprising the step of inserting a spacer into the frame to fill the gap between the final product shape and the frame.