Transient liquid-phase infiltration bonding of copper using porous copper interlayer

A transient liquid-phase infiltration process was applied for the bonding of copper using a porous copper interlayer. Porous copper interlayers with porosities ranging from 13.7 to 22.2% and pore sizes ranging from 4.9 to 7.5 mu m were fabricated via sintering of copper paste prepared from a mixture of copper particles and terpineol. Subsequently, molten Sn-Ag-Cu alloy was allowed to infiltrate the porous copper, indicating that the porous copper had an open-cell structure. A copper rod was then bonded to the copper plate through a porous copper interlayer via the infiltration of the Sn-Ag-Cu alloy at 523 K. The microstructure of the bonding layer constituted Cu-Sn intermetallic compounds (IMCs) formed by solid-liquid reaction diffusion and an initial Cu skeleton structure. The maximum shear joint strength of 35 MPa was obtained when the initial bonding interface between the copper rod and the porous interlayer was filled with thin Cu-Sn IMCs. This novel bonding process, using capillary pressure as the driving force, can realise the low-temperature and short-time bonding of copper.