To solve the connection failure problem of pin A3 of the CCGA-packaged FPGA chip in a certain aerospace product，this paper constructed a "multi-dimensional detection+multi-disciplinary coupling analysis" system and conducted research by combining X-ray detection，SEM analysis，and mechanical and thermal simulation.The results show that the failure is not caused by defects in the chip''s solder column or batch problems in the welding process，but by the dual weak links formed between the solder and the solder mask，and between the copper strip and the solder.Fatigue cracks initiate under the combined action of mechanical loads and temperature cycles，and the large voids distributed at close distances in the solder joint further accelerate the crack propagation，resulting in an occasional defect failure.Based on the failure mechanism，this paper proposes an immediate solution of replacing the spare board，and plans to adopt long-term optimization directions such as inert gas/vacuum welding to reduce the bubble rate and optimize PCB design to enhance mechanical support，providing technical references and feasible process improvement paths for the high-reliability application of aerospace-grade CCGA-packaged devices.