Failure Strength Analysis and Young Modulus Assessment of 4H-SiC through a Ball on Ring Test

Imperfections in SiC die can have an impact on their mechanical properties, affecting the target of the high reliability standard, required in power devices intended for automotive applications. In this work the failure strength of 4H-SiC square die of different thicknesses has been determined through a ball-on-ring (BOR) test and compared with previous three-point bending test results. Moreover, an interpretation of the experimental results on the net deflection d-d0 at the center of the die sample, according to a revisited Vitman and Pukh equation, has been reported. This allowed to achieve an assessment of the effective or equivalent Young's modulus of the die, with the BOR equipment on back-grinded 4H-SiC die, thinned up to 110 µm. The BOR provided consistent values for the 180 µm thin samples with the results from the previous the 3-PB test and a value of the equivalent Young's modulus of (391 ±90) GPa for the 110 µm, which is comparable with the theoretical limit measured in 4H-SiC.