关键词: CBGA, Pb偏析, 晶粒粗化, 蠕变, 位错

Abstract: During the temperature environment test, the solder joint of CBGA assembly appears cracking phenomenon. The view in the industry is that the failure mechanism is due to fatigue damage of solder joint caused by mismatch of thermal expansion coefficient (CTE) between large-size ceramic package and PCB board. The discussion on the failure mechanism of solder joint from the perspective of material microstructure evolution is still less. The phenomenon of solder joint cracking in CBGA assembly solder joints during different cycle temperature impact tests was studied. The microstructure of the solder joints was analyzed by using advanced microscopic analysis instruments such as scanning electron microscope and transmission electron microscope. The microscopic mechanism of solder joint damage was studied from the perspective of grain boundary and crystal phase. The microstructure evolution process of solder joint cracking under different test cycles was studied. The results showed that the microscopic causes of solder joint cracking were related to Pb segregation, grain coarsening and intergranular fracture in eutectic solder, crystal phase dislocation caused by material creep and other factors.

Key words: CBGA, Pb segregation;grain coarsening, creep, dislocation