JPS60126893A - Method of waterproof treating printed 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 Field of the Invention The present invention relates to a waterproof structure for printed circuit boards used in various types of equipment used in humid environments.

Conventional configurations and their problems For example, when installing an electronic controller in a washing machine, etc., the washing machine is often used in a bathroom, and water may splash and adhere to the surface of the printed circuit board. Because a phenomenon occurs whenever water droplets condense, the surface of the printed circuit board had to be waterproofed.

The conventional waterproof structure of a printed circuit board will be explained below with reference to the drawings.

Conventionally, as shown in Fig. 1, various electronic components 2, etc. are mounted on a printed circuit board 1 made of paper epoxy, etc., and then the printed circuit board 1 is dipped in solvent-based acrylic resin paint, and the printed circuit board 1 and the electronic components 2 are mounted on the printed circuit board 1. A resin coating layer 3 is formed on the surface of the electronic component 2 to perform waterproofing treatment.

However, it is impossible to form a sufficient coating layer on the tip 2' of the lead terminal of the electronic component 2 with just one coat of resin paint, and water may adhere to the tip of the lead terminal 2' of the electronic component 2. , the terminals were bridged, which could cause continuity in places that should not be conductive, causing the device to malfunction.

In order to solve this problem, a method of forming the laminated coating layer 4 by dipping several times as shown in FIG.
There is also a method of forming a partial coating layer 6 on the tip 2' of the lead terminal of the electronic component 2 using a highly viscous resin paint, or a method of applying a casting resin 7 to the case 6 as shown in FIG. Get in,
A botting method has been proposed, in which the printed circuit board 1 on which various electronic components 2 are mounted is immersed to form a resin layer, and some methods have been put into practice.

However, the one in which the laminated coating layer 4 is formed as in the case of FIG. 2 is not suitable for mass production, and there is no guarantee that the tips of the lead terminals of the electronic component 2 can be reliably covered. A method in which a partial resin layer 6 is formed as in the case of FIG. 3 has very poor workability. Furthermore, as shown in FIG. 4, the method in which a resin layer is formed by dipping into the casting resin 7 injected into the case 6 requires a large amount of extra resin, resulting in high costs.

OBJECTS OF THE INVENTION In view of the above-mentioned conventional problems, the present invention provides a waterproofing capability of a printed circuit board that can sufficiently waterproof the necessary parts.

Structure of the Invention In order to achieve the above object, the method for waterproofing a printed circuit board of the present invention involves applying a resin to the surface of a printed circuit board body on which various electronic components are mounted, and applying a resin to the surface of the printed circuit board body on which the lead terminals of the electronic components are attached. A first resin layer is formed by impregnating the cloth with the resin, and a second resin layer is formed by impregnating the cloth with the resin. This means that the ends of the lead terminals of various electronic components can be sufficiently waterproofed.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

First, the printed circuit board 9 on which the electronic parts 8 and the like are inserted is dipped in epoxy resin paint, and then excess resin paint is appropriately drained off.

Next, before the epoxy resin paint adhered to the surface of the printed circuit board 9 hardens, a nonwoven fabric 10 made of polyester or the like is applied to the lead terminals 1 of the discrete electronic components 8, etc.
The epoxy resin paint is held on the surface of the printed circuit board 9 on the side from which the epoxy resin paint 1 protrudes by using its adhesive properties, and then the epoxy resin paint is cured to form the first coating layer 12.

Next, the printed circuit board 9 on which the first coating layer 12 has been formed is dipped in urethane paint to sufficiently impregnate the nonwoven fabric 10 with the urethane paint, and then the urethane paint is appropriately drained. This urethane paint is then cured to form the second coating layer 13.

In this case, the nonwoven fabric 1o is thick enough to cover the lead terminals 11 of the discrete electronic components 8 extending from the printed circuit board 9, and rough enough to be sufficiently impregnated with relatively high viscosity resin paint in a short time. Needless to say, it is better to have the following.

When the waterproof coating layer is formed on the printed circuit board 9 by the above method, the surface of the printed circuit board on the side where the nonwoven fabric 10 is used, that is, the side from which the lead terminals 11 of the discrete electronic component 8 protrude, is fully coated up to the tips of the lead terminals 11. It also makes it possible to form a coating layer reliably, and prevents equipment using this printed circuit board 9 from malfunctioning due to water bridging between the terminals 11 in all four locations where conduction should not occur. It becomes possible to do so.

Effects of the Invention As is clear from the description of the above embodiments, according to the method for waterproofing printed circuit boards of the present invention, lead terminals 75 of various electronic components: Resin is applied to the protruding surface of the printed circuit board using nonwoven fabric. By forming a layer tτ, the lead
This makes it possible to ensure waterproofing at the tip 1 of the terminal.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a printed circuit board that has been waterproofed by applying resin once, which is the conventional waterproofing method for printed circuit boards, and Figure 2 is a cross-sectional view of a printed circuit board that has been waterproofed by applying the same resin several times. Figure 3 is a cross-sectional view of a printed circuit board that has been waterproofed by partially overcoating the same resin.
The figure is a cross-sectional view of a printed circuit board on which a resin layer has been formed by immersing the printed circuit board in a case injected with the same resin, and FIG. FIG. 3 is a cross-sectional view of the substrate. 8...Discrete electronic components, 9...
・Printed circuit board, 10...Nonwoven fabric, 12...
...first resin layer, 13...second resin layer.

Claims (2)

[Claims] (1) A resin is applied to the surface of the printed circuit board body on which various electronic components are mounted, and a cloth with a thickness that allows the lead terminals of the electronic components to rest is provided on top of the resin, and this cloth is impregnated with the resin. A method for waterproofing a printed circuit board, comprising: forming a first resin layer using cloth, and further impregnating the cloth with resin to form a second resin layer. (2) A method for waterproofing a printed circuit board according to claim 1, wherein the cloth is a nonwoven fabric.