Reliability Evaluation of SiC Power Module With Sintered Ag Die Attach and Stress-Relaxation Structure

Silicon carbide (SiC) power modules with Ag sinter-bonding die attach were designed on the basis of thermal stress analysis for reliable high-temperature operations. Both the finite-element analysis (FEA) simulations and preliminary experiments confirmed that inserting the direct-bonded-copper (DBC) substrates can effectively reduce the maximum thermal stress in the module. A prototype SiC power module using sintered Ag die attach with a DBC substrate was designed and fabricated. The modules exhibited excellent durability in power cycling between 65 °C and 250 °C up to 20 000 cycles. FEA calculations of cumulative thermal strain and stress distributions adequately predicted the initial cracking position in the specimens after prolonged power cycles, observed by scanning electron microscopy.