Strain Rate Dependence on Nanoindentation Responses of Interfacial Intermetallic Compounds in Electronic Solder Joints with Cu and Ag Substrates

This study evaluated mechanical behavior of the intermetallic compounds (IMCs) formed at the interfaces between potential Pb-free solders (Sn-Ag-Cu and Sn-Zn) and the wires of Cu and Ag under different loading rates. Compared to Ag based IMCs, Cu based IMCs were harder and stiffer, but less strain rate sensitive. The morphology of the indent impression was found depending on the ratio of the modulus to hardness, and the crystal structure of the IMCs.