Evaluation of barrier metals of solder bumps for flip-chip interconnection

This paper describes the optimum thickness of barrier metals and the cause of the decrease in the shear strength of 37Pb/63Sn solder bumps for flip-chip interconnection. The authors evaluated the mutual diffusion and the shear strength of solder bumps on barrier metals. From aging test results with the Cu/Ti structure, when the thickness of the Cu film was greater than 10 μm, the shear strength did not change from the initial value. In the Ni/Ti structure, where the Ni film had a thickness of 1.0 μm, the shear strength also did not change from the initial value. In addition, it was confirmed that the decrease in the shear strength is caused by diffusion between Sn and Cu, or Sn and Ni, and oxidization of the barrier metals