Trap Distribution and Along-Surface Discharge Characterization of Aromatic Compound-Modified Silicone Gel

Insulated gate bipolar transistor (IGBT) module is prone to the along-surface discharge at the silicone gel-metal electrode-AlN ceramic substrate, that is, the “triple bonding point,” resulting in insulation breakdown, so it is important to develop high-performance silicone gel. In this article, the composite materials with different contents of 4,4’-dichlorobenzophenone (DCBP) are prepared and their trap distribution and along-surface discharge characteristics are investigated. The results show that the introduction of DCBP reduces the density of deep trap, increases the density of shallow trap and the degree of crosslinking, is more conducive to the detrapping and migration of charge, and accelerates the attenuation of the surface potential of the composite. Under the condition of sinusoidal voltage of 7 kV and frequency of 10 kHz, the composite material can effectively inhibit the development of the along-surface discharge compared with PSG, and the total discharge times are reduced by 65.08%, 48.71%, and 18.27%, respectively. The total discharge range decreases by 69.15%, 62.87%, and 22.88%, and the average discharge range decreases by 25.61%, 27.63%, and 5.64%, respectively. The release of ultraviolet energy during along-surface discharge excites DCBP to a triplet state, promotes the improvement of crosslinking degree and the generation of new re-crosslinking products, prevents the growth of local low-density insulation region, and further inhibits the occurrence of the along-surface discharge, which enhances the insulation performance of the composite.