Analysis of micromorphological evolution of lead-free solder joints under random vibration

Purpose The purpose of this study is to investigate the fatigue failure process of the Sn-3Ag-0.5Cu alloy (SAC305) under vehicle vibration conditions and to analyze the microstructural changes in the material over varying vibration durations. Given that SAC305 is a widely used lead-free solder, examining its reliability in operational environments holds practical significance. Design/methodology/approach In this paper, the solder joints with SAC305 alloy as the material are discussed. The random vibration test of the product-level Ball Grid Array Package chip is carried out with the test parameters in ISO-16750-3. The failure process of the solder joints under actual working conditions is simulated, and the microstructure changes of the solder joints and their influence on the reliability of the materials are explored. Findings The intermetallic compound (IMC) layer of the solder joint has an initial thickness. Within the first 36 h of vibration, this thickness decreases due to changes in the growth mode of the IMCs. After 36 h, however, the thickness of the IMC in the solder joint begins to increase as the duration of vibration extends, leading to a change in the failure mode of the solder joint. Electron Backscatter Diffraction analysis revealed that the IMC of the solder joint precipitated fine grains. Ultimately, the results of the solder joint thrust test indicated that the thrust of the solder joint is more closely correlated with the IMC thickness than with the grain refinement of the IMC layer. Originality/value In this study, the solder joints of SAC305 material have more frequent vibration shocks in the working environment of the on-board chip, and the mechanical damage test caused by random vibration is less than the temperature shock test. It is of practical significance to explore the failure problem of solder joints under mechanical fatigue load.