PBGA packaging reliability assessments under random vibrations for space applications

In this study, experimental and numerical analyses on the solder joint reliability of plastic ball grid array under harsh random vibration and thermal loadings were presented. The chips were assembled on the daisy chained circuit boards for the test samples preparation, and a half of the samples were processed for underfill to investigate the underfill effects on the solder failures. Two consequential steps of the random vibrations, named as acceptance level and qualification level, were applied. Overall required root mean square (rms) of the power spectrum densities of the steps were 22.48 grms for one minutes and 31.78 grms for two minutes, respectively. A thermal shock test was then performed after the vibration tests. It was found that the samples did not show any solder failure under the test requirements, demonstrating the robustness of the packaging structure for potential space applications. The samples were further tested to induce the failures, and finite element analyses were performed to analyze the sample vibration behaviors and the solder stresses to compare the results with the test data. Finally, a simple analytical calculation for the natural frequency estimations was introduced to overcome the complex finite element modeling efforts.