Characteristics and aging of PCB embedded power electronics
The decrease of battery prices makes the electrification of the power train an irresistible development. Also the introduction of a 48 V on-board grid is decided to supply large auxiliaries. For such applications cost is always an important factor. PCB embedded power electronics offers improvements compared to power electronics bonded and soldered on Al2O3 as dielectric material. These improvements are a reduction of height, lightweight construction, cost efficiency of the applied materials and a reduction of the parasitic inductance. Sinter layers offer an increase of the melting temperature from 220 to 935 °C, compared to solder, and the thermal resistance between semiconductor and cooling water is low due to a thin dielectric layer of 150 mm and the heat spreading inside the copper leadframe, together with PCB materials having a thermal conductivity of 1.5 W/mK. A thermal resistance of 0.5 K/W per IGBT can be achieved. This paper describes the challenges of the production process, the 5 mm copper metallization of the semiconductor and the sinter process. Production failures were detected by curve tracer measurements, lock-in thermography and cross sections. The application potential of the embedding technology is demonstrated by measurements of the thermal impedance and temperature dependent partial discharge measurements. The effect of aging of PCB material by thermal cycling on the partial discharge behavior could be demonstrated. First results of an ongoing power cycling measurement are described as well. Finally the aspect of new PCB material without glass-fiber enforcement offering higher thermal conductivity and higher glass-transition-temperature is shown.