JPS6260286A - 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] 〔Technical field〕 The present invention relates to a printed wiring board.

[Background technology]

Recently, as miniaturization has progressed, electronic components have been mounted on printed wiring boards at a higher density. When electronic components are mounted with high density, a large amount of heat is locally generated by the electronic components. Therefore, there is a need for printed wiring boards to absorb this heat efficiently and to quickly radiate the absorbed heat. However, conventional printed wiring boards have
There has been a need for a printed wiring board with good heat dissipation properties as there is no one that can adequately respond to this problem.[Object of the Invention] The purpose is to provide

[Disclosure of the invention]

In order to achieve the above object, the gist of the present invention is a printed wiring board in which an electric path is formed on the front surface of a metal substrate with heat dissipation fins formed on the back surface through an insulating layer.

An embodiment of this will be explained in detail below based on the accompanying drawings.

As shown in FIG. 1, in this printed wiring board, an electric path 3 is formed on the surface of a substrate 1 made of a metal such as aluminum or its alloy, with an insulating layer 2 interposed therebetween. Heat dissipation fins 4 are formed on the back surface of the substrate 1. Since the substrate 1 is made of metal such as aluminum or its alloy, it has good thermal conductivity. Therefore, heat generated by electronic components mounted on this printed wiring board can be efficiently absorbed. Moreover, on the back side of the board 1, there are heat dissipation fins 4.
... is formed, increasing the heat dissipation area. Therefore, the absorbed heat can be quickly radiated to the outside.

Because of the above, this printed wiring board is
It has extremely good heat dissipation.

Note that another structure for improving the heat dissipation of the printed wiring board is as shown in FIG. 2. That is, as shown in the figure, a metal heat radiation block 13 having heat radiation fins 12 is attached to the back surface of a metal substrate 11 of a separately prepared printed wiring board 10 using machine screws 14, 1.4, etc. . In the figure, 15 is an insulating layer and 16 is an electric path. However, if you do it like this,
Metal substrate 11 and heat dissipation block 13 of printed wiring board 10
At the mating surface 17, heat transfer is poor and sufficient heat dissipation cannot be obtained. In addition, printed wiring board 10
This work is necessary because it is necessary to fix the heat dissipation block 13 with the machine screws 14, 14, etc. In contrast, the printed wiring board according to the present invention does not have the above-mentioned mating surface, has good thermal conductivity, and does not require any work to fix the printed wiring board, which saves time and effort.

Next, various examples of methods for forming the insulating layer will be shown.

As a first example, an adhesive made of an inorganic or organic insulating material is applied to the surface of a metal substrate such as aluminum,
There is a method of forming an insulating layer made of adhesive. As a second example, a metal oxide layer such as alumite with a thickness of 5 to 20 mm is formed on the surface or the entire surface of a metal substrate such as aluminum by anodization, and a position on the surface of the metal oxide layer that is on the substrate surface is formed. There is a method in which the adhesive is applied to the substrate to form an insulating layer consisting of a metal oxide layer and an adhesive layer. In this way, the thickness of the insulating layer can be increased and the adhesion between the substrate and the adhesive layer can be improved. Moreover, since the chemical resistance can be improved, the substrate will not be corroded by the etching solution used when forming the electric circuit. As a third example, a metal oxide layer such as alumite having a thickness of 5 to 20 Inn is formed on the surface or the entire surface of a metal substrate such as aluminum by anodic oxidation. Thereafter, a paint such as an acrylic resin paint, an acrylic melamine resin paint, an epoxy resin paint, or an epoxy acrylic resin paint is electrodeposited on the surface of this metal oxide layer (at least the portion on the substrate surface). Furthermore, there is a method in which the adhesive is applied to a position corresponding to the surface of the substrate on the surface of the paint layer to form an insulating layer consisting of a metal oxide layer, a paint layer, and an adhesive layer.

In the second and third examples, a filler made of a metal oxide such as alumina may be mixed into the adhesive. In this way, the thermal conductivity and adhesive properties of the adhesive can be improved. As described above, there are various methods for forming the insulating layer, but the method is not limited to these.

The formation of the electric path may be performed by a so-called full additive method in which a resist layer is provided on the surface of the insulating layer except for the portion where the electric path is formed, electroless plating is performed, and then the resist layer is removed. , perform electroless plating on the entire surface of the insulating layer to form a thin conductor layer, and provide a resist layer on the surface of this thin conductor layer except for the part where the electric path is formed,
It may also be performed by a so-called semi-additive method in which the resist layer is removed by electroplating, and then unnecessary portions of the thin conductive layer are etched away.

Alternatively, a conductive paste of gold, silver, copper, etc. may be used and printed on the surface of the insulating layer, or a metal foil may be pasted on the surface of the insulating layer to eliminate the need for this metal foil. It may also be carried out by a so-called subtractive method in which a portion is removed by etching.

The printed wiring board according to the present invention is not limited to the above embodiments. The material of the substrate is not limited to aluminum or its alloy, but may be other metals such as nickel or copper. The insulating layer is not particularly limited either, but one with high electrical insulation and good thermal conductivity is preferred.

〔Effect of the invention〕

As seen above, the printed wiring board according to the present invention has extremely excellent heat dissipation properties because the electrical circuit is formed on the surface of the metal substrate with heat dissipation fins formed on the back surface via an insulating layer. There is. Because of its good heat dissipation, electronic components can be mounted in high density, which allows printed wiring boards to be made smaller. The printed wiring board according to the present invention is a printed wiring board for hybrid IC and L E
It can be used for high energy density printed wiring boards such as D multi-layer printed wiring boards, and has great utility value in the field of electronic devices aiming for miniaturization.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a printed wiring board according to the present invention, and FIG. 2 is a cross-sectional view of a comparative example of a printed wiring board. 1... Metal substrate 2... Insulating layer 3... Electric circuit 4
... Heat dissipation fin agent Patent attorney Takehiko Matsumoto Figure 1 Figure 2

Claims (8)

[Claims] (1) A printed wiring board in which an electric path is formed on the front surface of a metal substrate with heat dissipation fins formed on the back surface through an insulating layer. (2) The printed wiring board according to claim 1, wherein the insulating layer comprises an adhesive layer applied to the surface of the substrate. (3) Claim 1 in which the insulating layer consists of a metal oxide layer formed on at least the substrate surface by anodic oxidation, and an adhesive layer coated on the surface of the metal oxide layer at a position on the substrate surface. Printed wiring board as described in section. (4) The insulating layer includes a metal oxide layer formed on at least the substrate surface by anodic oxidation, a paint layer electrodeposited on the surface of this metal oxide layer at least on the substrate surface, and a surface of this paint layer. The printed wiring board according to claim 1, comprising an adhesive layer applied to at least a position corresponding to the surface of the substrate. (5) The printed wiring board according to any one of claims 1 to 4, wherein the electric path is formed by a fully additive method. (6) The printed wiring board according to any one of claims 1 to 4, wherein the electric path is formed by a semi-additive method. (7) The printed wiring board according to any one of claims 1 to 4, wherein the electrical path is formed by printing a conductive paste on an insulating layer. (8) The printed wiring board according to any one of claims 1 to 4, wherein the electric path is formed by a subtractive method.