Forming High Temperature Solder Interfaces by Low Temperature Fluxless Processing

This paper provides a fundamental study of large area, fluxless bonding with three different solder systems Cu-Sn, Ag-In, and Ag-SnBi, which were pre-deposited in layered structures. The thickness of each individual layer was carefully designed such that, after bonding and annealing at lower temperatures, the final solder interface only had high melting point components and showed higher re-melting points. A systematic bonding study was conducted, and re-melting points and microstructure of the formed solder interface were studied using differential scanning calorimetry (DSC), and scanning electron microsopy (SEM), respectively.