Accelerated thermal fatigue test of metallized ceramic substrates for SiC power modules by repeated four-point bending

Maximum tensile stress in the ceramics during thermal cycle test (from -40 to 250°C) of active metal brazing (AMB) substrate was estimated by the finite element method (FEM) analysis, because such a tensile stress is the driving force of Cu plate delamination from the ceramic plate. In order to accelerate thermal fatigue of the AMB substrate, tensile stress 1.5-2.1 times larger than the maximum thermal stress at -40°C was applied to ceramic plate by four-point bending the AMB substrate at 250°C repeatedly at a frequency of 1 Hz. The time to failure by repeated bending of the SÌ
₃
N
₄
-AMB substrate was less than 1/40 of the time to delamination of the Cu plate by the thermal cycling.