Experiments and Three-Dimensional Modeling of Delamination in an Encapsulated Microelectronic Package Under Thermal Loading

Interfacial delamination in encapsulated silicon devices has been a great reliability concern in IC packaging. Experimental testing of a transparent quad flat no leads package is carried out with the goal of studying the delamination characteristics and investigating the viability of cohesive zone modeling in simulating delamination patterns and trends. The pattern of initiation and propagation of delamination under thermal loading is the focus of this paper. A microscope is focused on the interface between the pad and the encapsulant to capture the progressive delamination in a package that was molded without a die. When the temperature reaches a critical value, delaminations are observed to initiate and propagate in a certain pattern. The experimental setup is then modeled within the finite element framework, with the failure of the interface described through a cohesive-zone surface interaction approach. With a slight modification to the experimental procedure and through a separate finite element model, the fracture energy of the interface is estimated. It is found that the 3-D numerical model is able to capture the experimentally observed delamination pattern satisfactorily.