Study of cu wire crack under thermal cycling test

Copper wire is increasingly used in microelectronics because of its low cost, higher stiffness and better electrical and mechanical properties. However, there are some potential concerns on both wire neck crack and wedge bond crack under thermal cycling test (TCT). It is important to understand failure mechanism of Cu wire crack so that approach can be made for improvement to avoid Cu wire crack. In this study, simulations are conducted to investigate effects of delamination and epoxy molding compound (EMC) CTE on both Cu wire neck crack and wedge bond crack. Reducing CTE mismatch between EMC and LF/Cu wire can help reduce both wire cracks, while delamination can trigger Cu wedge bond crack but can lower risk of Cu wire neck crack. Therefore, appropriate molding compound with proper CTE to match CTE of LF and Cu wire as possible and keep delamination free can be used to avoid both Cu wire neck crack and wedge bond crack concerns.