Microstructure and Bonding Properties of Transient Liquid-Phase Bonding using Cu-SnAgCu Molded Sheets By High-Pressure Powder Compression

We propose a bonding technology for transient liquid-phase (TLP) materials using Cu-SnAgCu (SAC) molded sheets, which are a mixture of spherical Cu and SAC particles, for high-temperature die-attach applications. The powder-compressed Cu-SAC molded sheet had a dense internal structure with minimal internal voids and a smooth surface. The Cu-SAC molded sheets were bonded at a bonding temperature of 300°C, bonding time of 20 min, and pressure of 5 MPa under a formic acid atmosphere. The Cu-SAC molded sheet exhibited minimal voids within the sheet and at the bonding interface, and the microstructure between the Cu particles and specimen was composed of intermetallic Cu₃Sn. Consequently, the sheet achieved average shear strength of 50.5 MPa, which is a stable bonding strength under TLP bonding conditions, demonstrating its potential as a high-temperature die-attach material.