Interfacial Reaction and Joint Reliability of Sn-Ag-Cu/OSP-Cu Pad SMT Solder Joint

摘要

The interfacial reactions between Sn3.OAgO.5Cu (in wt%) solder and Cu pad during solder ball attach and SMT reflow at 250℃ with various TALs (time above liquidus) were investigated respectively. A Cu_6Sn_5 IMC layer formed at the interface of solder and Cu substrate in the first reflow of solder ball attach process, and another Cu_6Sn_5 IMC layer formed at the other side of solder joint in the second reflow when the device was mounted onto PCB. However the thickness of the two side IMCs were quite different. The IMC growth kinetics during the two times reflows were discussed. The microstructure variation of bulk solder, and the interfacial status seemed to affect the interfacial behavior. Also, the board level drop tests were performed to evaluate the effect of the interfacial reactions on the reliability of solder joints as a function of reflow time. And the interconnect failure mode was characterized based on IMC growth and Kirkendall voids formation.