High-Voltage Stacked Diode Package

Abstract

The Army is moving to a more electric force with a number of high-voltage applications. To support this transition, there have been efforts to develop high voltage (15–30 kV) single-die 4H-silicon carbide (SiC) bipolar switches and diodes. However, packaging these high-voltage devices has proven to be challenging since standard packaging methods cannot withstand the high voltages in a compact form. Therefore, this work aims to develop a compact prototype package with improved size, weight, and power density by stacking diodes. The stacked diode approach allows elimination of almost half of the wirebonds, reduces the board size by 45%, and reduces the package inductance. A module has been designed, fabricated, and tested which is the first 30 kV module reported in the literature to stack two high-voltage diodes in a series configuration. The package has a number of features specific to high-voltage packaging including (1) two fins that extend the perimeter of the package to mitigate shorting, and (2) all the leads were designed with rounded corners to minimize voltage crowding. Hi-pot tests were performed on the unpopulated package and showed the package can withstand 30 kV without breaking down. The completed package with the stacked diodes showed avalanche breakdown occurring at 29 kV. The complete package was then compared to an equivalent discrete diode module and showed a 10X reduction in size. During a clamped-inductive load test the stacked diodes showed lower parasitic capacitance, faster reverse recovery time, and lower turn on energy as compared to the discrete diode packages.