JPS5858838B2 - 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 having a metal core, and more specifically, a resist for a conductive circuit is formed on a metal core substrate having through-holes and whose surface has been subjected to an opacity treatment. It is about the method.

Conventionally, printed wiring boards are made by laminating and bonding metal foil onto a base material such as natural or synthetic fiber, paper, cloth, glass fiber paper, cloth, etc. bonded with an insulating resin as an insulating substrate. A method is used in which wiring is formed by removing non-designated metal foil by chemical treatment, or wiring is added by chemical plating or the like.

However, this type of wiring board has inherent limitations in terms of bending strength and the like due to the nature of the substrate used.

Therefore, when this type of printed wiring board is mounted with heavy electrical components, it is not suitable for practical use because it causes a large amount of deflection or damage.

The present invention aims to improve this, and its structure uses a metal core as a factor to support bending strength, an insulating layer is formed on the surface of the core, and a conductive circuit layer is further provided by printed wiring processing.

That is, the mechanical strength of the printed wiring board is achieved by the metal core.

Printed wiring boards having a metal core had to be used in the final product shape as a processed size due to the need to insulate the metal core over the entire surface.

However, when printing resist patterns to form conductive circuits through printed wiring processing, when working with commonly used photosensitive resin films or custom-made dry photopolymer films, the dry photopolymer film comes out around the edges of the product. The parts that popped out due to exposure and curing were scattered during handling and adhered to the inside of the product, leading to wiring defects.

In addition, in order to prevent this scattering, if the dry photopolymer film is cut smaller than the product, it will waste space on the product. At times, it may be considered to dissolve and remove it, but in either case this would hinder the improvement of packaging density.

According to such a method, it is not possible to cover the end face of the product with a dry photopolymer film, which causes the inconvenience that plating is deposited on the periphery during plating work for forming circuits.

In order to avoid this, a method of applying a resist as a correction work has been considered, but this work is inefficient and unsatisfactory from both a practical and economical point of view.

The present invention has been made in view of these points, and when baking a resist pattern to form a conductive circuit by printed wiring processing on a metal core substrate having through holes and having an insulated surface, A photosensitive resin film is pasted on the periphery of the final product shape of the metal core board, with external frames arranged at intervals via connecting ribs, and conductive circuit resist is formed through circuit baking and development using light exposure. By forming this, it is possible to prevent the dry photopolymer film from scattering around the peripheral edge of the product and to prevent plating from adhering to the edge of the product (eliminating the need for resist coating).

This will be further explained with reference to the drawings.

FIG. 1 shows the final product shape of a metal core substrate having through holes and whose surface is insulated, where 1 is a through hole.

FIG. 2 shows the method of the present invention and has a through hole,
When pattern-baking a resist pattern for forming a conductive circuit by printed wiring processing on a metal core substrate whose surface has been insulated, a gap of 4 is applied to the periphery of the final product shape 20 of the metal core substrate via connecting ribs 3. With the external frame 5 placed at the same position, a photosensitive resin film 6 is attached to the entire flat surface by baking the circuit so that at least the peripheral edge of the external frame 5 becomes an unexposed area 7, and then developing it to form a conductive circuit. This is used to form a resist for use.

According to the present invention, by providing an unexposed portion on the peripheral edge of the outer frame, the dry photopolymer film can be melted and the problem of skipping can be eliminated.

In addition, a dry photopolymer film is exposed and cured around the periphery of the final product and on the inner part of the outer frame facing the product shape.
By covering the gap between the product and the outer frame, it is possible to prevent plating from adhering to the edges of the product.

Next, the manufacturing process of a printed wiring board having a metal core, including the process of the present invention, will be explained step by step.

■ 1.0mm to 2mm thick metal core board at required locations. The state shown in FIG. 2 is obtained in which the through holes of the orrtjn are raised and an external frame of a constant width is arranged around the final product shape with several connecting ribs at intervals of 0.2 to 10 mm.

■ Form an insulating layer of approximately 150μ over the entire surface by electrodeposition coating.

(2) To improve the adhesion of the plated copper over the entire surface, apply a 20-30μ thick adhesive containing a sensitizer, mainly a rubber type.

■ Panel copper plating is applied over the entire surface using chemical copper plating of several microns and electrolytic copper plating of approximately 10 microns.

■ Form a circuit pattern resist by pasting a photosensitive dry film, baking the circuit, and developing it.

■ Form a conductive circuit using 30μ electrolytic copper plating and electrolytic solder plating.

■ Peel off the resist and remove unnecessary parts of the panel copper plating by etching.

■ Cut the connecting ribs and apply epoxy resin to the cut surfaces.

In the present invention, the connecting ribs 3 are used to support the external frame 5 in the final shape 2, and the minimum necessary number is used.

The interval 4 is a gap provided between the final product and the outer frame, and is a gap provided between the final product and the outer frame, and is used to ensure that the insulating layer is sufficiently formed on the end surface of the final product in the step of forming an insulating layer by electrodeposition coating, which is performed in the first stage of the present invention. In order to enable the insulating layer to be formed and coated with a uniform thickness over the entire surface, and also to enable the conductive circuit layer to be formed in a uniform thickness by electroplating performed at a later stage of the present invention. Therefore, the interval is 0.2rran ~ 10mm
The degree is appropriate.

As explained above, according to the present invention, the peripheral edge of the outer frame is made into an unexposed area to prevent the dry photopolymer film from curing, prevent scattering during pattern development, and harden the gap between the product and the outer frame. By covering with a dry photopolymer film, there is no need to apply resist to the product end face, completely solving the problem of preventing partial plating from adhering to the product. Since it also acts as a guide during case work, work efficiency is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the final product shape of a metal core substrate having through holes, and Fig. 2 shows the method of the present invention. FIG. 3 is a plan view showing a state in which the Explanation of symbols, 1...Through hole, 2...Final product shape of metal core board, 3...Connecting riff, 4... Spacing,
5... Outer frame.

Claims (1)

[Claims] 1 When baking a pattern of resist when forming a conductive circuit by printed wiring processing on a metal core board with through holes and an insulated surface, a connecting circle riff is placed around the final product shape of the metal core board. A metal core characterized by comprising a step of pasting a photosensitive resin film with an outer frame arranged at intervals through the metal core, baking the circuit by exposure to light, and forming a resist for a conductive circuit through development. A method for manufacturing a printed wiring board having the following.