(Georgia Institute of Technology, 2020-08-06)
Mohan, Kashyap
To address the demand for higher electrification and efficiency in automobiles and aviation, there is an increasing focus on developing new power electronics packaging technologies which can enable the wide-bandgap devices to operate at their full potential. In particular, new die-attach interconnection materials are needed with thermal stability at temperatures greater than 250°C, superior thermal and electrical conductivities for higher thermal dissipation and power handling. In this thesis, low-temperature, low-pressure sintering of nanoporous copper (Cu) films to form all-Cu die-attach joints is proposed as the next-generation die-attach technology capable of addressing the above-mentioned challenges. To realize the above objectives, two research tasks were identified and demonstrated. In the first task, fabrication o nanoporous Cu by chemical dealloying of amorphous Cu alloy ribbons and electroplated Cu-Zn films was explored. Fundamental relationships between the Cu-Zn electroplating parameters, composition of the electroplated films, morphology of the dealloyed films, and residual Zn after dealloying were established. Based on the results, guidelines were also framed for large-scale fabrication of nanoporous Cu films. In the second task, the effect of the sintering temperatures and sintering atmospheres on the sintering kinetics of nanoporous Cu film was explored, followed by the development of assembly parameters to enable good metallurgical bonding between nanoporous Cu and Cu metallizations. The initial assembly trials gave promising results and Cu-Cu joints with shear strengths>40MPa were achieved.