Migration of Sintered Nanosilver on Alumina and Aluminum Nitride Substrates at High Temperatures in Dry Air for Electronic Packaging

Joining semiconductor chips at low temperature (below 523 K) by sintering nanosilver paste is emerging as an alternative lead-free solution for power electronic packaging, particularly in high-temperature applications, because of the high melting temperature of silver (1234 K). However, silver is susceptible to migration. In this paper, we study the effects of dc bias, electrode spacing, and temperature on migration of sintered nanosilver on alumina (Al2O3) and aluminum nitride (AlN) substrates. The "lifetime" of silver migration, which is defined as the time at which the leakage current reaches 1 mA, increases with decreasing bias voltage and temperature but with increasing spacing between the nanosilver electrodes. The lifetime of silver migration on the AlN substrate is much longer than that on the Al2O3 substrate. A phenomenological model is proposed to predict well the lifetime of migration of sintered nanosilver on both the AlN and Al2O3 substrates in dry air. The activation energy of silver migration of sintered nanosilver on both Al2O3 and AlN is also obtained and discussed.