Manifold decomposition processes of silicone vapor and electrical contact failure

Adsorbed silicone vapor on contact surfaces decomposes typically to SiO₂ by elevated temperature due to discharge or Joule heating. However, even if temperature is lower than decomposition temperature, weak decomposition is induced in very complex states. Namely, silicone molecule has an equilibrium reaction from linear molecular structure to ring structure, or its reverse reaction in the room temperature. Furthermore, in the oxidation process, as the molecular changes various structures and causes imperfect decomposition, and various types of compounds occur. In the present paper, electrical condition of load and occurrence of the failure due to silicone vapor contamination were discussed with practical examples. And it was clarified that various high polymer silicone compounds including liquid are formed by their polymerization in the decomposing process. Furthermore, a mechanism of formation of carbon from the silicon vapor under this process is also discussed.