JPH03185896A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To contrive to improve the heat dissipation property of a printed wiring board by a method wherein the mixture of a heat-resistant thermoplastic resin powder of a prescribed weight and a high-heat conductivity filler is applied on one surface or both surfaces of a metallic plate by an electrostatic coating method to form an insulating layer, then, a metal foil is lamianted on the surface of the insulating layer. CONSTITUTION:It is necessary that a heat-resistant thermoplastic resin is used in the state of powder and one in the extent of a mean particle diameter of 1 to 100 mum, desirably the extent of a mean particle diameter of 2 to 30mum, can be suitably used. Then, as a high-heat conductivity inorganic filler, various inorganic fillers which are superior in heat conductivity, such as a silicon nitride, an aluminium nitride, a boron nitride and the like, can be used and they may be used singly or mixedly. Among the high-heat conductivity fillers, one of a particle diameter of 1 to 100mum or thereabouts can be suitably used and it is necessary that the usage of the fillers is used in an extent of 50 to 80wt.% to the whole composition containing the heat-resistant thermoplastic resin. In case the usage is less than 50wt.%, the composition is inferior in heat dissipation property and when the usage exceeds 80wt.%, there is a probem that the it is inferior in dispersibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a metal core or metal base printed wiring board having a metal plate, and particularly to a method for manufacturing a printed wiring board with excellent heat dissipation.

(Prior Art and its Problems) In response to the increasing density of electronic devices in recent years, the characteristics required for printed wiring boards to be used are becoming more sophisticated.

One of these required characteristics is a board with excellent heat dissipation properties that can quickly dissipate the heat generated from mounted electronic components. A material with an insulating layer containing a highly thermally conductive filler is used.

However, when forming an insulating layer containing a large amount of highly thermally conductive filler to further improve heat dissipation characteristics, depending on the type of resin used, fluidity during molding may deteriorate, making it difficult to mix uniformly. There have been problems in that it is difficult to uniformly provide the insulating layer on the surface of the metal plate, and that the interlayer adhesive strength with the metal plate is poor.

An object of the present invention is to provide a manufacturing method that uses a heat-resistant thermoplastic resin such as polyether ether ketone or polyphenylene sulfide, and that allows a printed wiring board with excellent heat dissipation properties to be obtained.

(Means for Solving the Problems) The present invention involves applying heat-resistant thermoplastic resin powder mixed with a large amount of highly thermally conductive filler to one or both sides of a metal plate by electrostatic coating to form an insulating layer. It has been discovered that the above problems can be solved by the following.

The printed wiring board manufactured by the present invention has a structure in which an insulating layer is provided on one or both sides of a metal plate, and a metal foil for forming a circuit is laminated on the outermost layer.The metal plate may include aluminum, copper, zinc, It is made of iron, silicon steel, iron-nickel alloy, etc., and usually has a thickness of about 0.2 to 5.0 mm.

This metal plate is preferably subjected to surface treatment, such as chromate treatment, sandblasting, etching, or the like.

Further, the above-mentioned insulating layer is formed of a heat-resistant thermoplastic resin, and this heat-resistant thermoplastic resin has a flow start temperature of 2.
Resins with excellent high frequency properties at temperatures above 00°C can be suitably used. Specific examples include polysulfone, polyphenylene sulfide, polyetheretherketone, thermoplastic fluororesin, polyetherimide, polyethersulfone, polyamideimide, polyphenylene oxide, and the like.

The above-mentioned heat-resistant thermoplastic resin must be used in powder form, and the average particle size is 1 to 100 μm, preferably 2 to 3 μm.
Thicknesses in the range of 0 μm can be suitably used.

Next, as the highly thermally conductive inorganic filler, various inorganic fillers having excellent thermal conductivity, such as silicon nitride, aluminum nitride, and boron nitride, can be used, and they may be used alone or in combination.

The above-mentioned highly thermally conductive filler can preferably have a particle size of about 1 to 100 μm, and should be used in an amount of 50 to 80% by weight based on the entire composition containing the above-mentioned heat-resistant thermoplastic resin. be.

If the amount used is less than 50% by weight, heat dissipation will be poor, and if the amount used is less than 80% by weight.
There is a problem that dispersibility is poor when the amount exceeds .

In addition to the high thermal conductivity filler, silicon oxide or the like may be added in order to impart low linear expansion coefficient properties. The above-mentioned inorganic filler may be surface-treated with various coupling agents in order to improve its affinity with the resin.

In the method of the present invention, it is necessary to uniformly mix the above-mentioned heat-resistant thermoplastic resin and highly thermally conductive filler, and the mixing method can be carried out using an ordinary mixer.

This mixture is then applied to one or both sides of the metal plate by electrostatic coating. The electrostatic coating method may be a normal electrostatic coating method, and the spraying distance with the metal plate may be adjusted within a range of 5 cm to 1 m, and the coating may be applied under appropriate conditions to achieve a predetermined coating thickness. The thickness of the insulating layer after coating varies depending on the required heat dissipation properties, etc., but is 50 to 300.
The thickness is preferably about μm.

Next, metal foil is laminated on the surface of the insulating layer formed by the above method. As the metal foil, electrolytic copper foil, rolled copper foil, etc. having a thickness of about 10 to 500 μm can be used.

Methods for laminating the metal foils include a method using an adhesive and a method in which the metal foils are laminated and integrated by heating and pressurizing the metal foils to a temperature higher than the melting point of the heat-resistant thermoplastic resin without using an adhesive. According to the present invention, a printed wiring board without surface irregularities, pinholes, voids, etc. can be obtained. Further, if the insulating layers are laminated and integrated while compressing the insulating layers by increasing the pressure by heating and pressing, the insulating layers can be made more uniform.

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

(Example) Aluminum nitride (average particle size 2.5 μm) was used as a highly thermally conductive filler, polyether ether ketone powder was used as a heat-resistant thermoplastic resin powder (melting point 340°C, average particle size 10
, 0 μm).

After mixing the above raw materials with a double cone mixer for 30 minutes so that aluminum nitride accounts for 70% of the total weight, the mixture was mixed on an aluminum plate with a roughened surface (250 m
Electrostatic coating was applied to one side of a sheet (m x 250 mm x 2 mm thick). The thickness of the insulating layer after coating was 250 μm. Then, the obtained laminate was placed in an electric furnace and heat-treated at 370° C. for 10 minutes.

After heat treatment, electrolytic SF+ foil (thickness 35 μm
) and heat pressed for 30 minutes (pressing temperature 370
°C, press pressure 40 Kg/aa).

The obtained substrate (insulating layer thickness: 150 μm) had no surface irregularities and had excellent smoothness, and no pinholes or voids were observed in the insulating layer.

(Effects of the Invention) As described above, the manufacturing method of the present invention prevents the occurrence of surface irregularities and pinholes that tend to occur when the painted surface is uneven or when the coating thickness is large due to the inclusion of a large amount of highly thermally conductive filler. This has the advantage that a metal core or metal base printed wiring board having a metal plate with excellent heat dissipation properties, electrical properties, etc. can be obtained because the insulation layer can be made uniform.

Claims (2)

[Claims] 1. A mixture of 20 to 50% by weight of heat-resistant thermoplastic resin powder and 50 to 80% by weight of highly thermally conductive filler is applied to one or both sides of a metal plate by electrostatic coating to form an insulating layer. A method for manufacturing a printed wiring board, characterized by laminating metal foil on the surface of the layer. 2. A mixture of 20 to 50% by weight of heat-resistant thermoplastic resin powder and 50 to 80% by weight of highly thermally conductive filler is applied to one or both sides of a metal plate by electrostatic coating to form an insulating layer. A method for manufacturing a printed wiring board, which comprises placing a metal foil on the surface of the layer and then applying heat and pressure to compress the insulating layer and integrate the layers.