Bonding Mechanism of Cold Gas-Sprayed Copper Particles Onto Aluminum Nitride Substrates for Power Electronics Packaging

Abstract

This study investigates the bonding mechanisms between cold gas-sprayed (CGS) copper (Cu) particles and aluminum nitride (AlN) substrates. A 300- $\mu $ m-thick Cu coating was successfully deposited and characterized by electron backscatter diffraction (EBSD) techniques revealing microstructural evolution differences between the bulk of the Cu coating and the Cu/AlN interface. The Cu/AlN interface showed finer, homogeneous grains, and the evidence of dynamic recrystallization, while the distal portion of the coating exhibited larger, heterogeneous grains with higher intragranular strains. Image quality (IQ) maps and grain orientation spread analysis confirmed lower strains at the Cu/AlN interface that correlated with smaller microhardness readings suggesting a recrystallization phenomenon. Finite-element simulations of particle impact revealed large plastic deformations, jetting, and a thermal response surpassing the recrystallization temperature of copper. These findings are indicative of a bonding mechanism involving mechanical interlocking and dynamic recrystallization at the Cu/AlN interface. The roughened AlN substrate, with an average surface roughness (Sa) of $0.5~\mu $ m, promoted mechanical interlocking, thus enhancing adhesion. This work provides insights into optimizing CGS for metal coatings on ceramic substrates, particularly in electronic packaging applications, where strong metal-ceramic adhesion is critical for reliable operation in harsh environments.