In order to investigate the evolution of intermetallic compounds （IMC） in micro solder joints

this study focused on the IMC evolution in Sn-Ag-Cu （SAC） and Sn-Ag-Cu-Bi-Ni （SAC-BiNi） solder joints under dif- ferent soldering process during reflow. The effect of soldering process parameters

including soldering temperature

reflow time

and cooling condition

on the morphology and IMC grain size was investigated systemically by deep- etching method and Electron Microscope （SEM） observation. Experimental results indicated that soldering temper- ature had remarkable influence on the morphology of IMCs which may lead to different IMC growth behaviors. IMCs formed at higher soldering temperature showed facet-like appearance. The grain size of IMCs increased quickly when the bulk solder was in molten state. Cooling rate had limited effect on the IMCs but significant influence on the microstructure of the bulk solder.