Low temperature bonding using microscale Cu particles coated with thin Sn layers at 200 °C

Abstract

Sn-Cu intermetallic compounds (IMCs) consisted joints were achieved by a low temperature solid-state bonding using microscale Cu particles coated with thin Sn layers for high temperature die attach application. The bonding process was conducted at 200 °C for 30 min under an applied pressure of 10 MPa using a thermo-compression bonding system. The formic acid atmosphere was used for reducing the oxide layer on the Sn coating and the Cu substrate during the bonding process. After bonding, the joint showed a microstructure fully comprising Cu-Sn intermetallic compounds matrix with a dispersion of pure Cu particles, and a shear strength equivalent to that of conventional Pb-5Sn solder could be achieved. The results demonstrate that low temperature solid-state bonding using microscale Cu particles coated with thin Sn layers has the potential to fulfill the requirement of die attach application.