Degradation characteristics and Ni3Sn4 IMC growth by a thermal shock test in SAC305 solder joints of MLCCs applied in automotive electronics

Abstract

In this study, the degradation characteristics in MLCCs SAC305 lead-free solder joints were verified by thermal shock testing (from -40A degrees C to 125A degrees C). The thermal stress distribution in the solder joints was simulated utilizing ANSYS 13.0 and the thermal stress concentration was verified between the Ni plating layer and Cu electrode. After the test, the degradation of the mechanical characteristics was compared by conducting shear tests. The shear force decreased by 21.1% after 1200 cycles in C1608. In the case of C1005, the shear force decreased by 21.3% after 1000 cycles. The Ni3Sn4 IMCs were confirmed at the starting point at the shear fracture surface through ingredient analysis after the thermal shock test. Also, by observation of the cross-sections before and after the test, cracks were verified after thermal shock at the 1400th cycle. The cracks formed between the Ni plating layer and the solder joint. After the 1800th cycle, the Ni3Sn4 IMC thickness in C1608 grew to 8 mu m. In C1005, the IMC thickness increased to 9 mu m. Therefore, the Ni3Sn4 IMC growth affected the degradation and reliability reduction characteristics in the MLCC SAC305 lead-free solder joints. In the future, research aimed at preventing Ni3Sn4 IMCs should be carried out.