塑封电子器件负极端变色原因分析

利用X—RAY光电子能谱仪对125°下，通电15kV，96h后负极一端出现白色物质的塑封电容器进行分析。对比分析性氧化铝结发现，负极一端白色物质为氧化铝富集所致。造成该现象的原因是，环氧塑封料中含有活性氧化铝，由于固化不完全或吸潮导致环氧塑封料中残留水分，残留的水分与活合，在电应力的作用下，有向电源负极迁移的趋势；同时，由于温度效应的存在，塑封树脂软化，加速了水分与活性氧化铝向电源负极迁移的速度，形成了氧化铝在负极端富聚现象，使电容器负极端呈现白色。

Analysis of Negative Extreme Discoloration of Plastic Electronic Devices

X ray photoelectron spectroscopywas used to analyze the white material on plastic capacitor negative terminal, which was appeared at 125°C 15 kV electricity for 96 h. Comparative analysis shows that, the material on negative end wasinduced by alumina enrichment. The reason for this phenomenon is active alumina which was contained in epoxy molding compound electrically migrate to the negative. In- complete curing or moisture absorption leads to residual moisture in epoxy molding compound which combined with alumina promote the migrating. At the same time, plastic resin softening induced by temperature ef- fectaccelerated water and active alumina migratingto the cathode of the power supply, which formed alumina poly phenomenon in the negative extreme rich. That＇s the reason why the capacitor negative terminal appears white.