基于正交设计的WLCSP柔性无铅焊点随机激励应力应变分析

Stress and strain distribution of lead-free solder joints with compliant layer in wafer level chip scale package under random vibration based on orthogonal design

对晶圆级芯片尺寸封装(wafer level chip scale package,WLCSP)柔性无铅焊点进行了随机振动应力应变有限元分析.以1号柔性层厚度、2号柔性层厚度、上焊盘直径和下焊盘直径4个结构参数作为关键因素,采用正交表设计了16种不同结构参数组合的柔性焊点,获取了16组应力数据并进行了方差分析.结果表明,焊点内最大应力应变随1号柔性层厚度和2号柔性层厚度的增加而减小;在置信度99%时,下焊盘直径和上焊盘直径对应力具有高度显著影响,在置信度95%时,1号柔性层厚度和2号柔性层厚度对应力具有显著影响;各因素对应力影响排序为:下焊盘直径影响最大,其次是上焊盘直径,再次是1号柔性层厚度,最后是2号柔性层厚度.

The 3D finite element analysis models of leadfree solder joint with compliant layer in wafer level chip scale package( WLCSP) were developed. By using ANSYS the finite element analysis of the lead-free solder joints model was performed under random load. 1st compliant layer thickness,2nd compliant layer thickness,die-side and substrate-side pad diameter were selected as four key configuration parameters,by using orthogonal array,the solder joints which have 16 different configuration parameters ' levels combinations were designed. The maximum stress values within lead-free solder joints were obtained. Based on the values of stress the range analysis was performed. The results of study show that the stress and strain decreases with the increase of 1st and 2nd compliant layer thickness. With 99% confidence,the substrate-side pad diameter and die-side pad diameter have significant effect on the stress of solder joint under random vibration load,and with 95% confidence,the 1st compliant layer thickness and the 2nd compliant layer thickness have a certain effect on the stress of solder joint.The substrate-side pad diameter,the die-side pad diameter,the1 st compliant layer thickness and the 2nd compliant layer thickness affect the stress of solder joints in a descending order.