Fabrication of highly reliable joint based on Cu@Ni@Sn double-layer powder for high temperature application

Abstract

Abstract A highly reliable three-dimensional network structure joint was fabricated based on Cu@Ni@Sn core-shell powder and transient liquid phase bonding (TLPB) technology for high temperature application. Cu@Ni@Sn joint is characterized by Cu metal particles embedded in the matrix of (Cu,Ni)6Sn5/Ni3Sn4 intermetallics (IMCs), low level of voiding is achieved, they can be reflowed at a low temperatures (<260°C), but reliably working at high temperature up to 415°C. Cu@Ni@Sn double-layer microparticles with different Sn layer and Ni layer thickness were fabricated and compressed as preform used for TLPB joint bonding, the microstructure and phase composition evolution for Cu@Sn and Cu@Ni@Sn system were comparatively studied during reflowing and aging process. Different kinds of interfacial structure designs were made, interfacial microscopic morphology was analyzed and compared under once and twice reflowing soldering process. Results indicated that Sn coating layer was completely consumed to form (Cu,Ni)6Sn5/Ni3Sn4 IMCs, Cu@Ni@Sn bondline have lower void rate and higher shear strength than that of Cu@Sn. The mechanism of Ni coating layer inhibit Cu atom diffusing towards Cu6Sn5 to form Cu3Sn was studied. The high reliable three-dimensional network structure joint based on Cu@Ni@Sn double-layer powder was fabricated for high temperature application.