JPH0349945B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an insulating paint used for coating electronic parts, etc., and particularly to an insulating paint suitable for ceramic capacitors or mica capacitors. [Conventional technology] In recent years, capacitors have become smaller and more sophisticated.
When loading these onto a printed circuit board, an automatic insertion machine is often used to achieve high density and save labor. In this loading method using automatic insertion machine,
Compared to the conventional method of manually inserting a capacitor, this method applies a stronger impact to the capacitor, which often results in chipping of the capacitor leads. Such capacitors usually have an electrically insulating coating, but if a capacitor using a conventional electrically insulating paint is chipped and the capacitor is soldered to a printed circuit board, the heat transmitted from the capacitor lead wires will cause damage to the inside of the capacitor. The solder that fuses the lead wires may start to melt, come out from the chipped part, and travel along the lead wires, causing an accident that may cause the circuit board to shatter. Furthermore, the melted solder may bridge between the electrodes and cause conduction, which may cause an accident in which the capacitor itself is shot. [Object of the Invention] The present invention was developed as a result of research aimed at improving solder heat resistance, which was unsatisfactory with conventional insulating paints.
We found that soldering heat resistance can be improved by using a large amount of fused silica or sintered aluminum silicate, which has an extremely low coefficient of thermal expansion, as a filler in the paint composition. Based on this knowledge, we conducted various studies and developed the present invention. It has come to completion. [Structure of the Invention] The present invention provides an electric insulation coating powder resin composition for dip coating consisting of a thermosetting resin, a filler, and an additive, in which the filler is mainly composed of fused silica powder and/or sintered aluminum silicate powder. The present invention relates to a powder resin composition for electrically insulating coating characterized by the above characteristics, and a paint for electrically insulating coating for dip coating in which a coating agent is blended with this composition. The filler used in the present invention has an extremely low coefficient of thermal expansion, and 50% of the filler components are usually
% (weight %, same hereinafter) or more, preferably 80% or more. Conventionally, the fillers often used in this type of insulating paint are calcium carbonate, crystalline silica, alumina, talc, etc. alone or in combination, but the insulating paint using such fillers is different from the paint of the present invention. In comparison, since the coefficient of thermal expansion is large, when electronic parts such as capacitors are dipped in solder, the paint expands greatly due to heat, making it impossible to suppress elution of solder on molten elements. Various studies were conducted to improve this drawback, and it was discovered that the soldering heat resistance could be improved by using fused silica or sintered aluminum silicate, which has an extremely small coefficient of thermal expansion, as a filler.
The blending ratio of fused silica and sintered aluminum silicate is usually at least 50%, preferably 80% or more of the filler components. If it is less than 50%, the effect of improving soldering heat resistance will be poor. Although the particle size, shape, and particle size distribution of such fused silica and sintered aluminum silicate have a significant effect on the workability and electrical properties of the paint of the present invention in various applications, the present invention of improving solder heat resistance It is not involved in the action and effect of, and is not particularly limited. Next, thermosetting resins include phenolic resins, epoxy resins, silicone resins, melamine resins, etc., and these resins can be used alone or in combination, but the workability, electrical properties, heat resistance,
From the viewpoint of cost, it is particularly preferable to use one or more of solid resol type phenolic resins and solid epoxy resins alone or in combination. Regarding additives, in order to further improve the adhesion between the capacitor body and the paint and to improve the soldering heat resistance, a silane coupling agent, preferably epoxy silane (A-186 manufactured by Union Carbide Co. , A-187, etc.) or a titanium coupling agent (Titanate TTS, manufactured by Ajinomoto Co., Ltd., etc.) in an amount of 1.0 to 0.5% by weight based on the total composition. Other additives include hardening accelerators such as imidazoles and aromatic amines, anti-sagging agents such as finely powdered silica, thickeners such as bentonite, antifoaming agents,
Appropriate amounts of pigments, dyes, etc. can be added. [Effects of the Invention] Since the present invention is constructed as described above, the coating composition of the present invention has excellent soldering heat resistance. For example, a capacitor coated with this coating has excellent soldering heat resistance after being inserted into a printed circuit board. The troubles that occur will be resolved. [Example] The present invention will be described in detail below using Examples and Comparative Examples. However, the present invention is not limited to the examples. Also, the “departments” listed here
All numbers indicate "parts by weight." Table 1 shows the resin compositions used in Examples and Comparative Examples.

[Table] The paint composition shown in Table 1 was mixed with a 3/1 acetone/methanol solvent and additives such as antifoaming agents, thickeners, and pigments in a mixer for 2 hours to prepare a base. . A ceramic capacitor element with a diameter of 4 mm was separately prepared, dip-coated with this paste to a thickness of 1 mm on one side, and baked at 150°C for 1 hour to prepare a sample. In addition, a phenolic resin laminate with a thickness of 0.8 mm was prepared with many 1 mm diameter holes drilled at 1 cm intervals, and 20 capacitors that had been previously painted were inserted into these holes. At the time of insertion, the base of the capacitor lead was intentionally widened to cause chipping, and the laminate was floated in a solder bath kept at 300±5°C for 20 seconds to check for leakage of element solder from the capacitor. The defective incidence rate is shown in Table 2.

[Table] The paint composition of the present invention has less leakage of element solder, indicating that it has excellent solder heat resistance.

Claims (1)

[Scope of Claims] 1. An electrically insulating coating powder resin composition for dip coating comprising a thermosetting resin, a filler and an additive, wherein the filler is mainly composed of fused silica powder and/or sintered aluminum silicate powder. A resin composition for electrical insulation coating as a component. 2. The resin composition for electrical insulation coating according to claim 1, wherein the blending ratio of fused silica powder and/or sintered aluminum silicate powder is 50% by weight or more of the filler components. 3. The resin composition for electrical insulation coating according to claim 1 or 2, wherein the thermosetting resin is a resol-type phenolic resin that is solid at room temperature or a mixture of a resol-type phenolic resin that is solid at room temperature and an epoxy resin. thing. 4. The resin composition for electrical insulation coating according to claim 1, 2, or 3, wherein the additive contains a silane coupling agent and/or a titanium coupling agent. 5 An electrically insulating coating for dip coating consisting of a thermosetting resin, a filler, an additive and a solvent,
A paint for electrical insulation coating in which the filler is mainly composed of fused silica powder and/or sintered aluminum silicate powder. 6. The paint for electrical insulation coating according to claim 5, wherein the blending ratio of fused silica powder and/or sintered aluminum silicate powder is 50% by weight or more of the filler components. 7. The paint for electrical insulation coating according to claim 5 or 6, wherein the thermosetting resin is a resol-type phenolic resin that is solid at room temperature or a mixture of a resol-type phenolic resin that is solid at room temperature and an epoxy resin. 8. The paint for electrical insulation coating according to claim 5, 6 or 7, wherein the additive contains a silane coupling agent and/or a titanium coupling agent.