Optimal design toward enhancement of thermomechanical reliability of polyimide layers in a flip-chip-on-lead-frame dual flat no-leads package with copper pillar bumps

Thermomechanical reliability of polyimide layers in a flip-chip-on-lead-frame dual flat no-leads package subjected to thermal cycling test condition was studied by the finite element method and the Taguchi method. Different control factors were considered for optimal design toward enhancement of the thermomechanical reliability of polyimide layers, including diameter of the Cu pillar bumps, polyimide opening, and size of the Al pad. Conforming to design rules, the largest Al pad diameter, the smallest size of bump diameter, and the largest polyimide opening were found to be beneficial to enhance the thermomechanical reliability of polyimide layers. And the optimal design was experimentally verified.