Quantitative reliability analysis of electronic packages in consideration of variability of model parameters

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 maximum strain 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 derived are random variables owing to the randomness of geometric parameters. It is found that, among the different geometric parameters, the size of the solder bump affects the random fatigue life of the package the most. It may cause the fatigue life to have a coefficient of variation of 10.65% under the assumption that the solder diameter is a random variable uniformly distributed between 0.27 mm and 0.33 mm. In the second phase of the study, a modified Coffin-Manson equation with a certain random nature is considered. This can be achieved by assuming some parameters in the equation to be random variables. 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. It is concluded that both random geometric configuration and random life prediction rule may cause the fatigue life of the package to have distribution following a specific probability density function as those obtained from experiments.