SiC module operational at 200 °C with high power-cycling capability using fatigue-free chip surface packaging technologies

Abstract:
This study demonstrates the successful operation of a silicon carbide (SiC) module with a record-breaking power-cycling capability of over 300,000 cycles for a junction temperature (Tjmax) of 200 °C and temperature swing (DeltaTj) of 135 °C. The obtained lifetime is one order of magnitude longer than the target lifetime for automotive applications. This study focused on fatigue-free chip surface packaging technologies involving the three steps: i) fabrication of a “coefficient of thermal expansion (CTE) matching layer” using the Fe-Ni alloy “Invar” with a CTE value close to that of SiC; ii) use of a sintered copper (Cu) joint; and iii) use of a Cu wire. The CTE matching layer effectively reduces the stress at the interface with the SiC chip as well as forms a strong bond with the Cu wire. This is confirmed experimentally via failure mode observation and analytically via stress–strain numerical simulations. The obtained lifetime result of 334,000 cycles evidences the effectiveness of our fatigue-free design concept.