Strength of solid-state silver bonding between copper

In this Project, we designed and set up an experiment to measure the bonding strength. Silver (Ag) layer is used as a bonding medium between copper (Cu). The upper Cu is called Cu chip and the lower Cu is Cu substrate. Both Copper (Cu) and silver (Ag) are ductile metal with very excellent electrical and thermal conductivity. Samples with structure of Cu/Ag/Cu are manufactured using solid-state bonding process at 300°C. The Cu substrates are electroplated with 50μm Ag layer. The Cu chip and substrate are held and pressed together with 1000 psi static pressure. This is a solid-state process without any molten phase involved. Scanning electron microscopy (SEM) is used to examine the quality of Ag joints, the Cu-Ag interfaces, and the microstructure. Its images demonstrate that Cu chip is well bonded to the Ag layer on Cu substrate. Six samples went through shear test to determine the joint strength. They all pass the MIL-STD-883G standard.