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

The mechanical behavior of CuCGA 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 to 11.5. 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 between 11.5～16.5. 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.