Quantitative reliability analysis of flip–chip packages under thermal–cyclic loading and in consideration of parameter uncertainties

To study the quantitative reliability of electronic packages, a finite element analysis with the assumption that certain geometric parameters are random variables is carried out for a flip–chip package. The equivalent plastic strain range of the package subject to thermal–cyclic loading is obtained, and the fatigue life of the package is determined based on a modified Coffin-Manson equation. Both quantities obtained are random variables owing to the randomness or uncertainties of geometric parameters. It is found that, among different geometric parameters, the size of the solder bump affects the random fatigue life of the package the most. In the second phase of the study, a modified Coffin-Manson equation with random nature is considered. This can be achieved by assuming some parameters in the equation to be random variables. It also reflects a certain kind of uncertainty of the material property. Through mathematical derivation and numerical illustration, it is shown that the predicted fatigue lives may have different mean values and different variations, and the difference may be significant. The present study indicates that both random geometric configuration and random life prediction rule may cause the fatigue life of the package to have scattered distribution as those observed from experiments.