铜柱长径比对CuCGA互连结构轴向临界压应力的影响

Effect of aspect ratios of Cu column on axial critical compressive stress of CuCGA interconnection structure

借助有限元方法研究Cu CGA互连结构轴向压力载荷下的力学行为.结果表明,直径0.32 mm、长径比5~11.5范围的铜焊柱压曲失稳前会因性能薄弱的钎焊圆角局部区域存在超过钎料极限强度的拉伸应力而引发局部微裂纹;而长径比11.5~16.5范围的铜焊柱则会首先发生屈曲失稳;在综合考虑钎焊圆角局部微裂纹失效和焊柱压曲失稳失效前提下,建立了铜柱长径比和阵列铜焊柱互连结构轴向压力载荷下临界应力的关系方程;轴向临界压应力在长径比5~11.5范围内几乎保持恒定,而在长径比11.5~16.5范围内轴向临界压应力随铜柱长径比λ0增加而降低,规律与描述大柔度杆的欧拉公式相符合.

The mechanical behavior of CuC GA interconnection structure under axial compression load was studied using finite element method. The results showed that tensile stress exceeded tensile strength and microcrack occurred in local area of soldering fillet before buckling instability for soldered Cu column with the diameter of 0. 32 mm and aspect ratio range from 5 to11. 5. Buckling instability first occurred for Cu column with the diameter of 0. 32 mm and aspect ratio range from 11. 5 to 16. 5.The relation equation between aspect ratio of Cu column and the critical stress of soldered Cu column interconnection under axial compressive loading was established based on comprehensive consideration of microcrack failure in soldering fillet and buckling failure. The axial critical compressive stress was nearly constant for aspect ratio of Cu column in the range of 5 ～ 11. 5,while decreased with the increase of Cu column aspect ratio between11. 5 ～ 16. 5. The relationship between axial critical compressive stress and aspect ratio of Cu column was consistent with the Euler formula which is used to describe large flexibility rod.