Shear test evaluation of the mechanical reliability of micro bumps in semiconductors

Abstract

The micro bump is an element for connecting and stacking the silicon die of a semiconductor device, and any damage to the micro bump can greatly influence the reliability of the semiconductor. A shear test and analysis were performed to investigate the effect of the micro bump structure and shear speed on the failure mode, and a structural improvement was proposed. The failure mode and reaction force of the micro bump were measured through shear tests of four micro bump structures with a diameter of 25 mu m at two shear speeds using a bond tester. In addition, a finite element model simulating the shear test was developed using ANSYS and was analyzed under the same conditions as the shear test. It was confirmed that tungsten via has a resistance effect on shear force. Additionally, a structural improvement of the micro bump to resist shear force was suggested by analyzing the passivation thickness and bottom diameter of the micro bumps as design variables.