Assessment of selected materials and assembly technologies for power electronics modules with the capability to operate at high temperatures

Wide-band gap semiconductors allow operation of power electronics at considerably higher temperatures than Si-devices. However, a significant improvement of a power module temperature capability is necessary to fully exploit this benefit. For this reason reliability of various ceramic substrates undergoing liquid-liquid thermal shock cycling -50-190°C was tested. Additionally, an impact of the large temperature-span shock cycling on module assembly technologies was studied with focus on Ag-sintering. The benchmarked DUTs were mainly investigated using scanning acoustic microscopy, scanning electron microscopy and laser profilometry. The obtained results were compared with performance of CTE optimized double-side cooled module prototypes. Data presented in this paper extend already published information. For example, the sintered bond of a SiC diode and an AlN/Al substrate was more robust against cycling than the bond of a SiC diode and a Si₃N₄/Cu substrate. On the other hand, Si₃N₄/Cu substrates were significantly more robust than AlN/Al substrates. It was also observed that roughening of Al-metallization can be strongly modified by adding of additional elements. CTE optimized double-side cooled modules were showing high reliability of interconnections; however, a different failure mode - cracking of semiconductor chips was seen.