High voltage power module packaging insulation endures unipolar electric stress, but its space charge phenomenon has never been paid enough attention. The space charge behavior and trap energy distribution of silicone material for packaging were investigated at various temperatures in this paper. The space charge and isothermal relaxation current of silicone samples were tested at 40, 60, and 80℃ under the applied electrical field from 3 to 15 kV/mm by simultaneous measurement system of space charge and trap energy states. The results show that the space charge accumulation is getting worse with the increase of temperature and applied field. There are charges with the same polarity accumulated near the electrode, which distorts the local electrical field distribution. Furthermore, a modified isothermal relaxation current analysis method based on non-negative least-squares iterative algorithm was proposed, and the depolarized relaxation currents at various temperatures were analyzed to provide the trap energy distribution from 0.8 to 1.2 eV, which was beneficial for understanding the mechanism of space charge behavior. The accumulation of space charges results in local field distortion, and the distorted field can cause partial discharge and insulation failure of packaging. Therefore, it is suggested that the space charge problem should be taken into account at packaging design of high voltage power modules.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |