Characterization of Cu-Sn-In system in Pb-free TLP Bonding

SILVANA SOMMADOSSI

Valencia

Conferencia; 4th International Conference on Materials Science & Nanotechnology. Future Materials 2023, October 23- 27, 2023, Valencia, Spain; 2023

This work present the results obtained from experimental and theoretical studies made on the ternary Cu-In-Sn system in the context of Pb-free Transient Liquid Phase Bonding (TLPB) for application in electronics. The TLPB involves melting, dissolution, saturation, reaction (in some cases) and homogenization. This joining technology is used from structural to electronics applications. One goal of TLPB is to get thin joints which can withstand high temperatures and stresses by a proper filler material and manufacturing parameters selection, including dissimilar materials bonding. Since there are still some discrepancies regarding the nature of the Cu-In-Sn intermetallic phases (IP), the phase identification, crystallography, microstructure and phase transformation kinetics during the diffusion-reaction process occurring at the interfaces of Cu/In-Sn/Cu joints should be deeply understanding in order to get the optimal manufacturing parameters, i. e. filler material composition and thickness, time, temperature, pressure and atmosphere. The results showed the formation of two IP layers, Cu-poor and the Cu-rich, which grow by diffusion and reaction control process, respectively. The Cu-poor layer consists in η-phase (Cu5Sn6/Cu2In) with a duplex morphology of large and small grains. While the Cu-rich layer presents a fine microstructure of a mixture of ζ-Cu10Sn3 and Tau-phase (Cu11In2Sn4/Cu16In3Sn) when the filler material is close to eutectic composition. If the filler Sn content increases, the ε-Cu3Sn appears. While, if filler material Sn content decreases, the δ-Cu7In3 forms. The Cu-rich layer is quite attractive because of its fast kinetic, high thermal stability and good mechanical behavior.