Failure Analysis of Printed Circuit Board Solder Joint under Thermal Shock

Investigating the failure mechanism of solder joints under different temperature conditions is significant to ensure the service life of a printed circuit board (PCB). In this research, the stress and strain distribution of a PCB solder joint was evaluated by high- and low-temperature thermal shock tests. The cross-section of the solder joint after thermal shock testing was measured using a 3D stereoscopic microscope and SEM equipped with EDS. The microstructure of the lead-free solder joint and the phase of the intermetallic compound (IMC) layer were studied by XRD. The working state of the PCB solder joint under thermal shock was simulated and analyzed by the finite element method. The results show that thermal shock has a great effect on the reliability of solder joints. The location of the actual crack is consistent with the maximum stress-strain concentration area of the simulated solder joint. The brittle Cu6Sn5 and Cu3Sn phases at the interface accelerate the failure of solder joints. Limiting the growth of Cu6Sn5 and Cu3Sn phases can improve the reliability of solder joints to a certain extent.

Automated summary

Investigating the failure mechanism of solder joints under different temperature conditions is crucial for ensuring the longevity of printed circuit boards (PCBs). This research utilized high- and low-temperature thermal shock tests to evaluate the stress and strain distribution of a PCB solder joint. The cross-section of the solder joint after thermal shock testing was examined through a 3D stereoscopic microscope and SEM with EDS. The microstructure and intermetallic compound (IMC) phase of the lead-free solder joint were also studied using XRD. Additionally, the finite element method was employed to simulate and analyze the behavior of the PCB solder joint under thermal shock. The findings demonstrate that thermal shock significantly impacts the reliability of solder joints, with actual cracks occurring in the area of maximum stress and strain concentration in the simulated solder joint. The brittle Cu6Sn5 and Cu3Sn phases at the interface accelerate the failure of solder joints, while limiting their growth can enhance solder joint reliability to some extent.