Abstract: In order to improve the assembly’s reliability of the BGA components, the structure and reliability problems of commonly used aerospace BGA components are analyzed in this paper. A method for the reliability evaluation of the BGA assembly based on the failure physics is proposed. The common failure mechanisms and failure modes are indentified in two aspects. The assembly failure cases are analyzed, as well as the typical characteristics of the structures and the materials of the components. According to the typical failure modes and mechanisms, the appropriate fatigue life model is set up, and the relevant simulation is conducted. According to the Coffin-Manson's fatigue failure physical model and its modified version, the working life and the test life are predicted. Meanwhile, by combining the existing detection equipment and considering the lifetime prediction result, we put forward the reliability evaluation test items, and establish the relevant evaluation process. Based on the existing standard criteria at home & abroad, and the overall consideration of working stress differences among various models and environments, a quantitative criterion for grading the reliability evaluation is proposed in the end.