JPH0618085B2 - Method for producing nonflammable inorganic coating material for electronic parts - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component involving overload or self-heating, that is, a resistor, a film capacitor, a ceramic capacitor,
The present invention relates to a method for producing a nonflammable inorganic coating material for electronic parts used for coils, various heaters, and the like.

Configuration of Conventional Example and Problems Thereof As general coating materials (paints) for electronic parts, mainly organic type, epoxy type, phenol type and silicon type excellent in flame retardancy are known and put into practical use. Among them, the silicon-based material used as a non-combustibility countermeasure coating material for electronic parts has excellent performance in electrical characteristics, heat resistance, water resistance, etc., but lack of resources and odor, smoke generation, It has drawbacks such as the amount of ignition, regulation of solvent, etc. On the other hand, it has to be baked at a high temperature (180 ° C.) for a long time (60 minutes) in the manufacturing process of electronic parts, and has a drawback in mass productivity. There is an urgent need for resolution. For example, the amount of silicon has been reduced to improve the nonflammability level, but the original electrical performance and coating strength deteriorate.

OBJECT OF THE INVENTION The present invention has been made in view of the above points, and enables bake hardening at a constant temperature (about 160 ° C.) for a short time (about 10 minutes), making it nontoxic, odorless, and nonflammable. An object of the present invention is to provide a method for producing a nonflammable inorganic coating material for electronic parts, which exhibits good properties (no flame generation and reduction of smoke generation).

In order to achieve this object, the method for producing an inorganic coating material for electronic parts of the present invention comprises: 100 parts of aqueous colloidal silica having a silica solid content of 1 to 40%; and 1 to 10 parts of ethyl silicate monomer. 1 to 5 parts of a silane coupling agent is added as a binder for hydrolysis, and an inorganic filler is further mixed. First, 1 to 10 parts of ethyl silicate monomer and 1 to 5 parts of silane coupling agent were added as an inorganic binder to 100 parts of aqueous colloidal silica having a silica solid content of 1 to 40% for hydrolysis. The product is in the form of a uniform, transparent varnish. Next, the above varnish is used as a binder component, and silica powder, an inorganic powder such as alumina powder, and an inorganic pigment, if necessary, are mixed to form a thick coating paint, and a uniform completely inorganic liquid for exclusive use in thick coating is mixed. It can be made into a paint as a slurry.

Here, the colloidal silica of the present invention has negatively charged amorphous silica particles dispersed in water to form a colloidal state,
-SiOH groups and -OH ions are present on the surface of the colloidal particles, an electric double layer is formed by the alkali ions, and the particles are stabilized by repulsion between the particles.

The hydrolysis reaction of water molecules in the colloidal silica with ethyl silicate and the silane coupling agent is represented by the following formula.

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH Ethylsilcate silanol RSi (OCH ₃ ) ₃ + 3H ₂ O → RSi (OH) ₃ + 3CH ₃ OH Silane cup Ring agent silanol Silanol, which is a hydrolysis reaction product of both, becomes a medium and becomes compatible.

The reaction mechanism between the colloidal silica and the coupling agent is considered as follows.

In this reaction, colloidal silica is considered to be a kind of silanol, and finally it becomes a hard inorganic coating film of SiO ₂ by dehydration and condensation. Here, in order to increase the density of silanol as much as possible, an organic titanium compound (especially butyl titanate is effective) as a cross-linking agent in (colloidal silica + silane coupling agent) is added in a weight ratio of 0.1 to 0.1.
It is effective to add 1.0%. A coating material obtained by mixing an inorganic filler and, if necessary, an inorganic pigment in such a binder component is dehydrated and condensed by a curing treatment at a baking temperature of 150 ° C. to 170 ° C. for a baking time of 10 to 15 minutes, and harmful gas is also generated. Instead, it becomes a siloxane in the form of a ceramic and forms a dense and thick coating film.

Description of Examples Examples of the present invention will be described below. First, with respect to 100 parts of aqueous colloidal silica (silica solid component 20%), 2 parts of ethyl silicate and 2 parts of silane coupling agent are used.
Part was added as an inorganic binder and hydrolyzed was used as a binder component, and 30 parts of this binder component was mixed with 70 parts of an inorganic filler and 1 part of an inorganic pigment to form a uniform, completely inorganic thick coating composition. Painted.

The above coating material was applied to electronic parts and characteristics were investigated. Here, the electronic component that generates the largest amount of heat is the resistor, and the resistor is used as a typical example of the electronic component because the resistor has a strong requirement in terms of noncombustibility. A metal oxide film resistor having a resistance of 2 W · 22 KΩ was used as the resistor, and a test sample was obtained by curing and drying at 160 ° C. for 15 minutes. The result of the characteristic test is shown below, but it satisfies the standard value sufficiently and is more non-flammable than the conventional silicone-based paint.
Good results were obtained in terms of surface hardness, heat resistance and solvent resistance.

<Test method> Nonflammability: 16 times the rated overload power is applied to the resistor until it is destroyed, and it is checked whether or not a flame is generated at that time. Also, compare the degree of smoke generation.

Solvent resistance: Immersed in trichloroethane and ultrasonically cleaned 1
It is performed for 0 minutes, and the appearance state of the coating film is compared (however, in both cases, the drying condition is 160 ° C. for 15 minutes).

Dryability: Comparative data.

Load life: EIAJ standard (RC-645A) is applied.

Moisture resistance load life: EIAJ standard (RC-645A) is applied.

Humidity characteristics: MIL-STD-202 standard is applied.

Temperature cycle: JIS-C-6402 standard is applied.

Here, the material relating to the production method of the present invention is not limited to the above-mentioned examples, and the silica solid component is 1 to 40%.
1 to 10 parts of ethyl silicate monomer and 1 silane coupling agent to 100 parts of aqueous colloidal silica having
Within the range of up to 5 parts, the intended purpose and effect can be achieved. That is, when the silica solid content of the aqueous colloidal silica is 0% (no silica), colloidal silica cannot be formed, and therefore it is not possible. If it exceeds the limit, gelation of the colloidal solution will start, which is not preferable.
The reason why the ethyl silicate monomer is limited is that the binding force is less than 1 part and the gelation occurs and the coating film cracks when it exceeds 10 parts. The reason for limiting the silane coupling agent is that if it is less than 1 part, it is not effective as a binder, and if it exceeds 5 parts, it gels and cracks in the coating film.

EFFECTS OF THE INVENTION As described above, the inorganic coating material for electronic parts produced by the production method of the present invention can be bake-cured at a low temperature for a short time, so that it is advantageous in terms of mass productivity and energy saving. . Further, when coated on electronic parts, the coating film strength is also hard, it has excellent solvent resistance, and even though it is thickly coated, it does not accompany flame or ignition against overload, and because it has excellent heat resistance, The safety as a covering material for electronic components can be sufficiently ensured. And quality characteristics such as moisture resistance are also good, and no pollution, non-toxic, without using organic solvent,
It is a manufacturing method for providing an odorless completely inorganic coating material for thick coating, and its industriality is extremely great.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Shindo 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In the laboratory (56) Reference JP-A-55-121210 (JP, A)

Claims (1)

[Claims] 1. An ethyl silicate monomer 1 is added to 100 parts of an aqueous colloidal silica having a silica solid content of 1 to 40%.
-10 parts and a silane coupling agent 1-5 parts are added as a binder, it hydrolyzes, and also an inorganic filler is mixed, The manufacturing method of the noncombustible inorganic coating material for electronic parts characterized by the above-mentioned.