Shear behavior of copper column grid array interconnect structure

Considering the significant difference in mechanical properties between the flexible copper column and the solder ball, the shear behavior of the copper column grid array (CuCGA) interconnect was studied by experimental and numerical methods. Results show that the shear curves of CuCGA interconnects presented obviously different new features, comparing with the parabolic shear curve of solder ball in the ball grid array (BGA) interconnect. The shear force linearly increased at first with a larger slope when the shear displacement increased, but it subsequently changed into a smaller slope due to the flexural deformation of Cu solder column and the partial release of stress caused by the increased displacement. The shear curves displayed the same parabolic shape as BGA solder ball in the final stage, and all pull-off fractures occurred in solder/Cu column interface. The curves slopes decreased with the increase of aspect ratio of the Cu column and the decrease of stiffness of Cu soldering column in the first and second stage.