Development of low temperature bonding using in-based solders

Abstract

In-based solders were chosen for the low temperature bonding at lower than 180°C Three kinds of bonding types on Au/Cu/Ti/SiO2/Si dies, which were Sn/In and Au/In for Type 1, Au/In and Au/Sn for Type 2, and InSn alloy and InSn alloy for Type 3, were studied expecting that the whole Insolder layer is converted to the mixed intermetallic compound (IMC) phases of In-Cu and In-Au IMCs after bonding below 180°C and annealing at 100-120°C The IMC in the joints were characterized in terms of the microstructure observations and the compositional analysis with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), the phase identification with X-ray Diffraction (XRD) and the re-melting temperature with Differential Scanning Calorimetry (DSC). The phase equilibriums of the joints were examined by thermodynamic calculations to understand the re-melting behavior. As a result, complete bonding consisted of only high melting temperature IMCs, Cu 11In9, Qi2ln, η-Cu6Sn 5, and AuIn2, was successfully made at 120°C followed by annealing at 100°C in Type 3, and at 160°C with annealing for 10hrs or at 180°C without annealing for Type 1, which was confirmed by DSC measurements and explained through thermodynamic calculations. ©2008 IEEE.