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晶圆级芯片尺寸封装(WLCSP)微焊球结构尺寸对其热机械可靠性有重要的影响。通过二维有限元模拟筛选出对WLCSP微焊球及其凸点下金属层(UBM)中热应力影响显著的参数,采用完全因子实验和多因子方差统计分析定量评估各种因子影响的显著性,最后建立三维模型,用子模型技术研究关键尺寸因子对热应力变化的影响。研究发现,焊球半径是影响焊球热应力的最关键尺寸因子,电镀铜开口和铜焊盘厚度对焊球热应力的影响也较显著;钝化层开口和焊球半径是影响UBM热应力的最关键尺寸因子。随着焊球半径增大,焊球热应力减小。
Wafer-scale chip scale package (WLCSP) Micro-solder ball structure size has a significant impact on its thermal mechanical reliability. The parameters influencing the thermal stress in WLCSP micro-solder ball and its under-bump metal layer (UBM) were screened by two-dimensional finite element simulation. The complete factorial experiment and multi-factor analysis of variance were used to quantitatively evaluate the significance of various factors Finally, a three-dimensional model is established, and the effect of the critical dimension factor on the thermal stress is studied by using the sub-model technique. It is found that the solder ball radius is the most critical dimension factor affecting the thermal stress of the solder ball. The effects of the copper plating thickness and copper plating thickness on the thermal stress of the solder ball are also significant. The opening of the passivation layer and the radius of the solder ball are the factors affecting the UBM thermal stress The most critical size factor. As the solder ball radius increases, the solder ball thermal stress decreases.