JPS589399A - Method of producing metal core 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] The present invention relates to a method for manufacturing a metal core printed wiring board.

Conventionally, insulating substrates such as ceramics have been used as substrates for printed wiring circuits, but recently metal-core printed wiring boards using metal-core substrates have come to be used to improve heat dissipation characteristics. . FIG. 1 is a sectional view showing a conventional manufacturing method of such a metal core printed wiring board. First, a metal substrate 10 to be a core is prepared (FIG. 1A), an insulating coating 11 is formed on its surface (FIG. 1B), and then a printed wiring circuit is formed on this insulating coating (FIG. 1C).

Because the conventional manufacturing method is as described above, it is extremely difficult to form double-sided circuits, and therefore, even if the heat dissipation characteristics are improved, the disadvantage is that it is not possible to achieve a commensurate increase in packaging density. be. In other words, in order to form a double-sided circuit in the conventional example shown in FIG.
It is necessary to provide a rounded wiring in the through-hole to connect the printed wiring circuit on the back side and the printed wiring circuit on the back side, but this requires insulation between the wiring in the through-hole and the metal core, so the process is difficult. There is a problem that not only is this complicated, but also insulation failure is likely to occur in the through-hole portion. Furthermore, the above-mentioned conventional example has the disadvantage that it is difficult to employ a manufacturing process using a continuous elongated body such as rounding, in which the circuit forming process is performed on a metal plate having high rigidity and difficult to transport, and manufacturing costs cannot be reduced. Furthermore, in the conventional example described above, since the circuit forming process is performed on the metal core, there is also a drawback that the selection range of the etching method is limited depending on the type of the metal core and the insulation structure.

The present invention has been made in view of the above-mentioned conventional drawbacks.
The purpose is to provide a method for manufacturing metal-core printed wiring boards, particularly wiring boards for double-sided circuits, at low cost.

The above-mentioned object of the present invention is achieved by the manufacturing method of the present invention, which first forms a printed wiring circuit on a flexible insulating film and then adheres it onto a metal substrate.

The details of the present invention will be explained below with reference to Examples.

FIG. 8 is a rounded sectional view illustrating an embodiment of the manufacturing method of the present invention.

First, as shown in Figure 2, a flexible insulating film is prepared. This flexible insulating film is made of polyethylene,
Polybutadiene, epoxy-impregnated glass cloth, polyind, etc. can be used. Polyind is particularly suitable in terms of heat resistance. The size and thickness of these flexible insulating films can be selected from a very wide range. For example, thin commercial products of about 25 cm are easily available, but such thin films are particularly suitable for reducing thermal resistance. Also, if necessary, these films can be adhered to each other to form a laminated structure. The thickness of these films varies depending on the electrical characteristics of the printed wiring circuit to be formed on it, the required voltage resistance, and the allowable value of thermal resistance in the thickness direction, but typically a range of 5 μm to 60 pm is selected. do.

Next, as shown in FIG. 2B, through holes 21 are formed at predetermined locations in the flexible insulating film by a method such as pressing.

Subsequently, as shown in FIG. 2C, printed wiring circuits n1 through-hole circuits are formed on both sides of the flexible insulating film. As a method for forming a printed wiring circuit and a through-hole circuit on a flexible insulating film, a method similar to the method for forming a conventional flexible printed circuit (FPC) can be adopted. For example, an etched foil method can be used in which a copper foil is pasted on a flexible insulating film such as bolide, followed by circuit printing, and a printed wiring circuit is formed by an etching method. Alternatively, it is of course possible to employ an additive method or a semi-additive method that has been developed relatively recently.

In any of these etching methods, additive methods, and semi-additive methods, conductive treatments such as electroless plating and PvD can also be used together. The material for forming the circuit only needs to be a conductive material, especially silver and copper□
Preferably, gold, aluminum, radium, nickel, tin, lead or alloys thereof or conductive paints are used alone or in combination to make the connections and complete the electrical function of the entire printed wiring circuit. It is preferable to carry out the process-scalable flexible insulating film of the above-mentioned person to C by the 11 assembly line operation in which the flexible insulating film is made into a continuous long body in order to improve the master's ability.

Finally, as shown in the second diagram, a circuit is formed and a flexible insulating film is pasted onto the metal substrate using an insulating adhesive. As materials for the metal substrate, steel, aluminum, iron, or alloys containing these as main components are inexpensive and easily available, and are suitable in terms of workability and heat dissipation. In addition, if an insulating film is formed on all or part of the surface of the metal substrate by screen printing, roll coating, etc. before attaching the flexible insulating film, there will be no problem between the circuit and the metal substrate. It gets hotter by further increasing the insulation properties.

Alternatively, in addition to forming the above-mentioned insulating coating on the metal substrate, an insulating coating may be applied to all or part of the printed wiring circuit on the opposite side by screen printing, roll coating, etc. It can also be formed. Metal substrate (
When aluminum or an alloy thereof is used as the material for the material, all or part of the insulating film can be formed of an anodic oxide film. Appropriate commercially available products such as epoxy resin can be used as the insulating adhesive split pieces.

Although the embodiments in which double-sided circuits are formed have been described above, it is clear that wiring boards with single-sided circuits can also be manufactured by the present invention.

As explained in detail above, the present invention has a structure in which a printed wiring circuit is formed on a flexible insulating film and then this flexible insulating film is attached to a metal substrate. It is easy to adopt a manufacturing process based on this method, and production capacity can be increased. Furthermore, since the printed wiring circuit is completed before being attached to the metal substrate, a wide range of etching methods can be selected regardless of the type of metal substrate or the insulation structure. Furthermore, the method of the present invention has the advantage that printed wiring boards with double-sided circuits can be easily produced.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view for explaining the conventional manufacturing method;
The figure is a sectional view for explaining the process of an embodiment of the present invention. Add...Flexible insulating film, 21...Through hole, n...Printed wiring circuit, 23...Through hole circuit, (capital)...Metal substrate, Cut...Insulating bonding agent. Patent Applicant Sumitomo Electric Industries Co., Ltd. Representative Patent Attorney Hisashi Tamamushi Part 1, Figure 2

Claims (1)

[Claims] After forming a printed wiring circuit on a flexible insulating film,
A method for manufacturing a metal core printed wiring board, which comprises adhering the flexible insulating film onto a metal substrate.