Copper wirebond pull test and reliability characterization with finite element simulation

In this paper, we will compare Cu wire and Au wire behavior during pull test and package reliability test through thermo-mechanical simulation. Relationship between wire pull test and package reliability test, i.e. thermal cycling, is also evaluated in term of die stress underneath the wire bond pad area. A new stress index concept is proposed to characterize the overall die stress level underneath bond pad. Based on this concept, a new method to evaluate Cu pull test limit is established with benchmark to current Au wire standard. The methodology is demonstrated through a Cu wire bonded power package, with the extensive work of process development, reliability test, and stress simulation etc.