JPS60218899A - 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 printed wiring boards, particularly printed wiring boards having high thermal conductivity.

[Prior art]

Conventionally, wood-grained K, which improves the thermal conductivity of printed wiring boards, has been made of a metal material and coated with an insulating material on the surface, such as a metal substrate, a ceramic substrate, or a resin substrate. These substrates are several tens to hundreds of times more expensive than the widely used glass/epoxy substrates, for example, and about 70 times more expensive for metal substrates, and about 70 times more expensive for ceramic substrates.
It has twice the heat conductivity.

Furthermore, in order to improve heat dissipation, various extreme heat design methods are included, such as attaching a heat sink near the board or electronic components that are heat sources. Although it is suitable for heat dissipation in special fields, such as power transistors and other electronic components that generate extremely large amounts of heat, it is expensive and unsuitable as a general-purpose means for general-purpose boards. .

In addition, the solder resist must not only prevent solder from adhering to the unpolished parts during soldering, but also have moisture-proof, dust-proof, etc. functions, as well as adhesion to insulating substrates, electrical insulation, etc. Insulating materials such as epoxy resin and tutadiene rubber are used as materials having the following characteristics. However, these insulating materials have low thermal conductivity, which impairs the heat dissipation of the insulating substrate, causing heat to accumulate in the mounted electronic components and significantly deteriorating the characteristics of the electronic components. There was this inconvenience.

〔the purpose〕

An object of the present invention is to eliminate the above-mentioned drawbacks, improve the thermal conductivity of a commonly used printed wiring board, and provide an inexpensive printed wiring board with improved heat dissipation.

[Summary]

This object of the present invention is achieved by an improved printed wiring board with high thermal conductivity, which is made of a solder resist in which metal particles having high thermal conductivity wheels are dispersed in an insulating dispersion medium to such an extent as to maintain an insulating state. Ru.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the printed wiring board of the present invention. Reference numeral 1 denotes an insulating substrate made of glass epoxy resin or paper-exposed phenolic resin, and a 2IT conductor, which is used for wiring and/or soldering made of copper foil or the like. 3 is a solder resist containing metal particles 9 having high thermal conductivity, and is coated on the insulating substrate 1. 4 indicates a printed wiring board;
Electronic components 5 are mounted.

To explain the solder resist according to the present invention in detail, FIG. 2 is an enlarged sectional view of a coated portion of the solder resist 3. As shown in FIG. The basic structure consists of an insulating substrate 1, a conductor 2, and a solder resist 3, and the solder resist 3 includes an insulating dispersion 8 of epoxy resin, styrene-modified epoxy resin, f-tadiene rubber, etc., and an insulating state maintained in the insulating dispersion medium. It is composed of dispersed metal particles 9 such as Ag#Cu*AueAt. In the solder resist 3, the metal particles 9 dispersed in the insulating dispersion medium 8 form primary particles and secondary particles, and are electrically connected by being close to or connected in units of several tens of times or less. However, if the mixing ratio of the metal particles 9 is increased, the conductivity will be improved, and if the mixing ratio is decreased to an appropriate ratio, it will become an insulator.

Therefore, the mixing ratio of metal particles 9 to insulating dispersion medium 8 is as follows:
It is determined as appropriate depending on the shape and size of the metal particles 9 and the spacing between the S-connected conductors, but in short, it is determined appropriately at a ratio that can obtain the desired thermal conductivity without impairing the insulation between adjacent conductors. used.

〔effect〕

According to the present invention, since the solder resist coated on the insulating substrate contains metal particles having high thermal conductivity,
Since heat conduction occurs from the entire surface of the insulating substrate, it is significantly improved and has several levels of thermal conductivity compared to conventional printed wiring boards, which rely on convection radiation from the surface of electronic components or heat conduction from lead wires. An improved printed wiring board can be obtained. That is, by providing a heat path from the surface to the solder resist and from the conductor to the solder resist, and because the surface area of the solder resist is usually quite large, heat dissipation performance can be greatly improved.

The solder resist of the printed wiring board according to the present invention can be supplied by means of screen printing method in the same way as the conventional printed wiring board, and thus requires new equipment.

It is possible to make inexpensive printed wiring boards with high thermal conductivity without the need for jigs.

In addition to the above-mentioned effects, the printed wiring board according to the present invention can uniformly apply the heat supply during soldering to the entire surface of the printed wiring board, thereby eliminating soldering defects due to unmelted solder. .

In addition, the areas near low heat-resistant parts are printed wiring boards with a conventional structure to prevent damage to electrical parts due to excessive heating, and the printed wiring boards of the present invention are used only near electrical parts with a larger heat capacity than others. It is also possible to create a height-lit system in combination with

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the printed wiring board of the present invention. FIG. 2 is an enlarged sectional view of the solder resist coating area. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Conductor, 3... Solder resist, 4... Printed wiring board, 5... Electronic component, 6...
...Lead wire, 7...Solder, 8...Insulating dispersion medium,
9...Metal particles. Figure 1 Figure 2

Claims (2)

[Claims] (1) A printed wiring board consisting of an insulating substrate, a conductor for wiring and/or soldering formed on the surface of the insulating substrate, and a solder resist applied to cover part or all of the conductor. A printed wiring board characterized in that the solder resist is composed of an insulating dispersion medium and metal particles dispersed in the insulating dispersion medium to an extent that an insulating state is maintained. (2) The solder resist is composed of an insulating dispersion medium such as epoxy resin or butadiene rubber, and Ag # Cup Au.
The printed wiring board according to claim 1, which contains metal particles having high thermal conductivity such as gAt.