Ni3Sn4-composed die bonded interface rapidly formed by ultrasonic-assisted soldering of Sn/Ni solder paste for high-temperature power device packaging

Abstract

The time-consuming of transient-liquid-phase is a big challenge for the die bonding. In this paper, a novel rapid bonding method plus alloying design was proposed to cheaply fabricate SnNi intermetallic joint for high temperature electronic packaging. The ultrasonic effect and the evolution of the joint microstructures, shear strength as a function of Ni content were systemically investigated. The amount of Ni3Sn4 in the joint increased with the addition of Ni, and when the Ni content reached 24wt.%, the joint consisted of nearly sole Ni3Sn4 with a high shear strength of 43.4MPa was achieved. After aging at 300°C for 72h in air, the shear strength of the joint obtained with smaller Ni content solder showed great improvement because of the phase transformation of residual Sn to Ni3Sn4, but for the Sn-24wt.%Ni and Sn-30wt.%Ni, it showed a little decrease due to the grains coarsening of Ni3Sn4. The acoustic cavitation and streaming effects dramatically accelerates the reaction of Ni and Sn during the ultrasonic-assisted soldering. The joint obtained by the Sn-24wt.%Ni solder has the best potential to be applied in the power electronic packaging.