Fabrication of Highly Reliable Joint Based on Cu/Ni/Sn Double-Layer Powder for High Temperature Application

Abstract

A highly reliable three-dimensional network structure joint was fabricated based on Cu/Ni/Sn powder with double-layer coatings and transient liquid phase bonding (TLPB) technology for high temperature application. The Cu/Ni/Sn joint is characterized by Cu metal particles embedded in the matrix of (Cu,Ni)6Sn5/Ni3Sn4 intermetallic compounds (IMCs), with a low void ratio, and can be reflowed at low temperatures (<260°C), but it can reliably work at a high temperature up to 415°C. Cu/Ni/Sn double-layer powders with different Sn layer and Ni layer thickness were was fabricated and compressed as preform used for TLPB joint bonding. The microstructure and phase composition evolution for Cu/Sn and Cu/Ni/Sn systems during reflow and aging were comparatively studied. Two kinds of interfacial structure designs were made, and corresponding interfacial microscopic morphology was analyzed and compared under once and twice reflow soldering processes. The results indicated that the Sn-coating layer was completely consumed to form (Cu,Ni)6Sn5/Ni3Sn4 IMCs, and the Cu/Ni/Sn joint had a lower void ratio and a higher shear strength than those of Cu/Sn. The mechanism of the Ni-coating layer inhibiting phase transformation was studied. The high reliable three-dimensional network structure joint based on Cu/Ni/Sn double-layer powder was fabricated for high temperature application.