Analysis and solution of bump deformation failure in Flip chip process

Abstract

In this paper, the root cause and solution of bump deformation failure of memory product in FC(Flip chip) process were studied through experimental and simulation method. After analysis, MUF (Mold under fill) unbalanced flow was proposed to be the real root cause for this type of failure. In order to verificate it, the simulation method was proposed to explain what level of stress did the bump suffer during the mold process. What' more, It was found that all the kinds of products with bump deformation have a larger size of die than those products without bump deformation. So the simulation method was proposed to simulate the MUF flow by different size of die. In order to solve the bump deformation problem, the mold process was optimized. The key parameter which effects the bump deformation was found by DOE. Then the profile was optimized and the result showed that it avoided the bump deformation failure a lot.