Debonding failure analysis of overmolded pad array carrier (OMPAC) integrated circuit packages

Recently developed electronic packages called Overmolded Pad Array Chip Carrier (OMPAC) IC packages frequently fail at the interface between the overmold compound and the substrate. In this study, this generic type of structure was evaluated by a combination of experimental and analytical methods. Model specimens representative of OMPAC structures were designed, manufactured and tested to failure. Detailed finite element models of the specimens were developed and analyses conducted to calculate debond stresses. Analytical methods were refined to include the effect of stress singularities. Stress results were averaged over a distance of.010 in. around the stress singularities to capture the intensity of the stress. These results were used in a combined stress failure criterion to calculate interfacial strengths based on macroscopic failure loads. The interfacial strengths were found to approach, but not exceed, those of the bulk overmold compound.