Development of heat resistant Pb-free joints by TLPS process of Ag and Sn-Bi-Ag alloy powders

Abstract

TLPS (Transient Liquid Phase Sintering) process is a candidate method of heat-resistant bonding, which makes use of the reaction between low-melting temperature powder of Sn-Bi base alloys and reactive powder of Ag. During heat treatment above the melting temperature of a Sn-Bi base alloy, the molten Sn-Bi reacts rapidly with solid Ag particles, which results in the formation of heat-resistant intermetallic compound (IMC). In this study, the TLPS properties between Sn-17Bi-1Ag (at.%) powder with its liquidus temperature of 200?C and pure Ag powder were investigated. During differential scanning calorimetry (DSC) measurement, an exothermic reaction and an endothermic reaction occurred, which correspond to the formation of the e-Ag3Sn IMC phase and the melting of the Sn-17Bi-1Ag alloy, respectively. After the overall measurement, the obtained reactant consists of the Ag3Sn-IMC and Bi-rich phases, both of which start melting above 250?C, with a small amount of the residual Sn-Bi eutectic phase. These results suggest that the TLPS process can be applied for Pb-free heatresistant bonding.