热冲击条件下倒装焊点失效的有限元模拟

Finite Element Simulation of Failure of Flip Chip Solder Joint under Thermal Shock

PBGA封装体由数种热膨胀系数不同的材料组成,在热循环过程中易由于封装材料间的热失配导致倒装焊点失效。建立了PBGA封装体的二维模型,利用ANSYS有限元模拟软件对-55-125℃热冲击条件下PBGA倒装焊点的应力、应变及累积塑性应变能进行了分析。结果表明：热冲击结束后,在边角焊点与PBC板、FR-4板界面的应力应变及累积塑性应变能最大。边角焊点为最易失效的焊点。

PBGA package is composed of several kinds of materials with different thermal expansion coefficients, and the flip chip joint is easy to fail due to thermal mismatch between encapsulation materials during thermal cycling. The two-dimensional model of PBGA package was established, and the stress, strain and cumulative strain energy under the thermal shock load from-55 ℃ to 125 ℃ were analyzed by using ANSYS finite element software. The results show that after the thermal shock, the stress, strain and cumulative plastic strain at the interfaces between the corner welding point, the PBC plate and the FR-4 plate are maximum. The corner welding joints are the most easily invalid solder joint.