Abstract
The interconnected solder joints within automotive electronic components are the most vulnerable parts of the structure, and their reliability is crucial for the development of new energy vehicles. This study focuses on automotive ADAS (Advanced Driver Assistance System) devices, analyzing the failure behavior of internal BGA (Ball Grid Array) lead-free solder joints under thermal shock conditions.Through thermal shock testing from −40℃ to 95℃, it was observed that microcracks first appeared in the upper intermetallic compound (IMC) layer of corner solder joints after 1600 cycles. As the number of thermal shock cycles increased, the net-like β-Sn phase in the solder joints gradually transformed into block and dot-like structures. Due to the relatively weak strength between the IMC layer and the Ag-Sn compound region, cracks typically propagated along the boundaries of these areas. Recrystallization occurred in the interface between the solder joint and the upper pad, with the proportion of high-angle grain boundaries increasing from 10.74% to 72.43%. The crack propagation mode changed from initial intergranular to transgranular fracture. Throughout the thermal shock test, the upper IMC layer remained thicker than the lower one, with the lower IMC layer thickness showing a minimum point at 750 cycles.The average thrust force between the solder joints and the substrate decreased more rapidly with thermal shock cycles, indicating that non-solder mask defined pads are more effective in improving structural strength.
Published Version
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