Package Reliability of the SiC Power Modules in Harsh Environments

Abstract

To evaluate the package reliability of the SiC power modules in harsh environments, the SiC Schottky Barrier Diodes (SBDs) were die bonded to the Si3N4/Cu/Ni(P) substrate with Au-Ge eutectic solder using a vacuum reflow furnace. The Si3N4/Cu/Ni(P) substrates are active metalized copper (AMC). The bonded samples were isothermally aged at 330°C and tested under thermal cycling conditions in the temperature range of −40–300°C in air. During the isothermal aging, cracks of the Ni(P) layer developed, resulting in oxidation of the Cu power path. Decrease in the die bond strength and increase in the electrical resistivity were observed due to the Cu power path oxidation and the growth of the Ni-Ge intermetalic compound (IMC) in the joint. Under the thermal cycling conditions, the metallization of the substrate suffers from serious surface roughness, which greatly degrades the die-attach reliability. The Al electrode was found to seriously exfoliate from the SiC-SBDs due to the thermal stress. After 521 cycles, almost all the Al electrode exfoliated form the anode. Benefit from the excellent mechanical properties of Si3N4, no detachment of the Cu layer was observed from the Si3N4 substrate after 1079 cycles, while the Cu layer detached from the AlN substrate only after 12 cycles.