JPS6261392A - Electronic 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 [Field of Application of the Invention] The present invention relates to an electronic circuit board that has been subjected to an insulation sealing process, and more particularly to an electronic circuit board that has been subjected to a potting process after being subjected to a taming coating process.

[Background of the invention]

In recent years, electronic devices and home appliances have become increasingly heavy-weighted, and the printed circuit boards that form the heart of these devices are increasingly required to have higher density packaging and higher reliability. In particular, as a result of the pursuit of high-density packaging, the pattern spacing is becoming narrower and the current that flows also tends to become weaker, so it is necessary to fully consider the effects of moisture absorption on printed circuit boards. In addition, the range of XM usage is wide-ranging and diverse, especially for outdoor equipment such as vending machines and automatic monitoring equipment, as well as home appliances used in environments with a lot of water and humidity, such as washing machines and kitchen equipment. In such cases, sealing technology for moisture-proof insulation is extremely important.

Generally, epoxy resin, 2-urethane resin, and silicone resin are used for moisture-proof insulation treatment of electronic circuit boards.

Coating treatment with a sealing material such as acrylic resin, and so-called potting treatment, in which a substrate is placed in a case or a mold for demolding, and a sealant is poured and hardened until at least the conductive portion is filled, are covered. For products that require a high degree of moisture-proof insulation treatment, in the case of coating, even if the flat part of the board can be coated successfully,
Because the coating film thickness is thinner in parts of thin wires such as lead wires of electronic parts such as ICs and transistors, and on the edges of parts, it is often impossible to prevent leakage current under high humidity conditions.

For this reason, as described in Japanese Patent Publication No. 58-15956, before coating the entire surface, the areas where the allowable leakage current is small are sealed with an insulating material that can be applied thickly, and then the entire surface is coated. Ru. However, the work became extremely complicated and there were problems with productivity. On the other hand, potting, casting, etc. can be expected to have better moisture-proofing and insulation performance than coating, but they are a process to prevent air bubbles from forming from the electronic circuit board when the potting material, such as resin, is cured. In addition, since a rubber-like elastic body is generally used to prevent the problem of wire breakage due to thermal expansion and contraction of electronic circuit boards, there is a problem in adhesiveness with electronic circuit boards and mounted components 8 [Object of the invention] SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic circuit board that has excellent moisture-proof insulation properties and is subjected to insulation sealing treatment that suppresses the generation of bubbles during potting.

[Summary of the invention]

The present invention combines coating treatment and potting treatment to achieve a moisture-proof insulation effect, and
This suppresses the generation of bubbles during the potting process and increases the adhesive strength between the potting material and the electronic circuit board and mounted electronic components. Specifically, in order to prevent bubbles from getting into electronic parts with complex shapes during coating, coating resin or a solution diluted with an organic solvent that is compatible with the coating resin is used. The electronic circuit board is coated once or more than once to form a resin film on the electronic circuit board. Thereafter, the potting material is used to fill the case or mold release mold in which the electronic circuit board is installed, at least until the conductor portion is filled.

Generally, when potting electronic circuit boards, thermoplastic or thermosetting resins with rubber elasticity are often used. Moisture, air, etc. that adhere to the mounted electronic components often form bubbles in the resin. These bubbles have an adverse effect, such as short-circuiting of electronic circuits due to moisture entering from the outside. To prevent the generation of bubbles, the electronic circuit board must be heated during the potting process.
Special treatments such as vacuum degassing, mixing and dispersing an adsorbent in potting resin are required. In the present invention, since a resin film is formed on the electronic circuit board in advance, moisture, air, etc. trapped on or inside the electronic circuit board or mounted components can be prevented from forming bubbles during the potting process. In addition, rubber elastic bodies are generally used as potting materials, but these potting materials have weak adhesion to inorganic materials such as electronic circuit boards, especially lead wires of electronic components. If treatment is applied to increase the adhesive strength between the casting mold and the cast mold, there is a problem that the adhesive strength cannot be easily increased because the ease of releasing the mold from the casting mold decreases and the workability is reduced.1 According to the present invention, the adhesive strength cannot be easily increased. A strong adhesive force can be obtained due to the formation of a resin film. In the present invention, conventionally known potting or casting agents can be used. Specific examples include epoxy resin, urethane resin, and silicone resin.

Polyester resins, acrylic resins, polybutadiene resins, phenol resins, etc. may be used alone or in combination, and may be diluted with organic solvents or monomers depending on the purpose. Furthermore, it may contain dyes, pigments, stabilizers, flame retardants, plasticizers, surfactants, fungicides, adsorbents, and the like. Furthermore, conventionally known coating agents can be used. Specific examples include ABS resin, acrylonitrile-styrene resin, styrene resin, polyethylene, polypropylene ethylene-vinyl acetate copolymer resin,
Polycarbonate, polyamide, acrylic resin, rosin, paraffin, wax, etc. dissolved and diluted with an organic solvent or the monomer itself can be used alone or in a composite system6. Depending on the purpose, dyes, pigments, stabilizers, surfactants,
It may also contain a coupling agent, adsorbent, etc.

[Embodiments of the invention]

Embodiments of the present invention will be shown and explained below.The first example is an IC using paper to phenol laminate as an electronic circuit board.
Using a device equipped with transistors, electrolytic capacitors, etc., this was coated, dried and hardened, and then potted. The coating agent and potting agent used are shown in Table 1. The number of samples was 3 for each; the presence or absence of bubbles was conducted, and the presence or absence of malfunction was determined by an operation test after being released for 500 hours in a 70'C 95% RH atmosphere. The test results are shown in Table 1. Maximum coating film thickness is 50
The test was carried out on a product on which a μm-thick film was formed. For comparison, a similar test was conducted on a potting resin that was not coated and had no adsorbent dispersed therein, and the results are also shown in Table 1.

Table 1 Normal in Xo operation test, malfunction in X operation test *MEK
:Methyl ethyl ketone 2nd example, as shown in Figure 1, 50% l-luene of acrylic as a coating agent ~ 0.5 to MEK100 heavy sensitive part
Silane coupling agent (Shin-Etsu Silicone Co., Ltd. KBM)
403) was used to form a coating film (1) with a thickness of 70 μm at the maximum part of a dry-curing machine, and the electronic circuit board was potted with a two-component thermosetting polybutadiene-based polyurethane elastomer (2). was used.

The initial volume resistivity value of this urethane (2) is 1.2×I
QiiΩ-]. 10 pieces of the above electronic circuit board70
An operation test was conducted after being left in a 95% RI-t'# atmosphere for 1000 hours, but no malfunctions were found. In comparison, a two-component type polybutadiene-based polyurethane without coating treatment is coated with 1.2 parts of zeolite-based adsorbent per 100 parts of elastomer, and a silane coupling agent (Shin-Etsu Silicone KBM403).
Electronic circuit board potted without bubbles using a potting agent (initial volume resistivity 1.2 x 1.011 Ω-■) containing O-5 heavy weight dispersion] 0 pieces were heated at 70℃95% as above. Items that malfunctioned as a result of an operation test after being left in a low RHn environment for 1000 hours: 3
There were pieces. In addition, since the latter potting agent contains a zeolide-based inorganic adsorbent dispersed in it, its transparency is much lower than that of the former which does not contain this, making it difficult to locate parts when replacing parts of home appliances, etc. It also has the disadvantage that it is difficult to confirm.

As described above, according to the present invention, it is possible to obtain an electronic circuit board that is extremely reliable and has excellent repairability. [Effects of the Invention] According to the present invention, since a coating treatment and a potting treatment are performed, it is possible to obtain an electronic circuit board with a high moisture-proofing effect and high reliability of electrical insulation, and also to reduce the amount of moisture between the interface between the coating film and the potting agent. Because high adhesive strength can be obtained, this has the effect of reducing moisture infiltration from the adhesive interface compared to directly potting to an electronic circuit board. Furthermore, by coating parts of substrates and electronic components that tend to absorb moisture and air, it is possible to prevent air bubbles from forming in the potting agent from the electronic circuit board during potting and causing malfunctions. can.

[Brief explanation of the drawing]

Fig. 1 shows a partially transparent perspective view of an electronic circuit board coated according to the second example and further subjected to potting treatment.
Potting part), 2... Acrylic coating film, 3... Paper phenol board (printed circuit board), 4
... Electrolytic capacitor, 5... Microcomputer.

Claims (1)

[Claims] 1. In the insulating sealing treatment of an electronic circuit board, the electronic circuit board is coated with a coating agent once or twice or more to form a resin film, and further, a flexible synthetic resin film is formed. An electronic circuit board characterized in that the electronic circuit board is insulated and sealed by casting with resin. 2. In claim 1, the electronic circuit board is equipped with electronic components, and these components are integrally coated once or twice or more and then cast.
An electronic circuit board characterized by: 3. An electronic circuit board according to claim 1 or 2, characterized in that the thickness of the coating resin film applied to the electronic circuit board is 100 μm or less. 4. In the item set forth in claim 1 or 2, the coating agent applied to the electronic circuit board may use resin such as acrylic, epoxy, or urethane alone or in a composite system. An electronic circuit board featuring: 5. In the item set forth in claim 1 or 2, the potting resin applied to the electronic circuit board may be urethane-based, epoxy-based, silicone-based resin, etc. alone or in combination. An electronic circuit board characterized by being used in.