Thermo-mechanical reliability of high-temperature power modules with metal-ceramic substrates and sintered silver joints

Demands for higher power density and reliability on power electronics systems are driving the need for development of high-temperature packaging solutions. Existing power module packaging technologies that rely on lead-tin or lead-free die-attach solders and alumina direct-bond-copper (DBC) insulated substrates are limited to 125°C junction temperature for reliable module operation. This is because of low-melting temperatures of the solders and low alumina toughness, respectively. Recently, die-attach by silver sintering or the low-temperature joining technique (LTJT), has been shown to significantly improve chip-bonding reliability at higher junction temperatures. Concurrently, direct-bond-aluminum (DBA) substrates with aluminum nitride (AlN) ceramic and DBC substrates using high-toughness silicon nitride (Si3N4) ceramic are shown to be significantly more reliable than alumina DBC substrates, especially over large temperature swings. In this paper, thermal impedance of the power device was measured to characterize the failure of the sample. The robustness of the combination of sintered silver and Si3N4-DBC or AlN-DBA substrates was confirmed.