Micro-solder Fatigue Life Study Based on Crack Propagation Mechanism for High Reliability FC-CSP

As the size and pitch of flip chip solder joint reducing, and the thickness of the package reduce simultaneously, the solder thermal reliability become more and more critical. In this study, thermal cycling test (TCT) was performed for 3 groups of FC-CSP samples to get the crack initiation and propagation life. FE simulation had been used to get the increment of the solder strain energy density. Base on the experiment and simulation data, new empirical constants of Darveaux model were got for the FC-CSP system. With the modified Darveaux model, the influence of design parameters including packaging geometry size and material properties were compared for FC-CSP solder reliability. For the packaging geometry, substrate thickness should to be considered firstly to increasing the solder fatigue life, then is die thickness. The solder joint standoff showed little influence on the solder fatigue life. For the material properties, the Tg of MUF material should to be higher than high temperature of TCT, which is 150 °C in this study. CTE of MUF material showed the high influential on solder fatigue life. The followed influence rank are CTE of substrate and flexural modulus of MUF material, which have little difference in the influence on solder fatigue life.