Fracture mechanical analysis of cracks in polymer encapsulated metal structures

Cracks inside polymeric packaging materials, which are used for protection and isolation of electronic components, can lead to failure of the whole system. In this presentation, the loading situation of cracks inside the polymer of encapsulated metal structures is analysed. The analysis is based on finite element simulations of thermally induced stresses. In a first approach, a linear elastic material model is assumed in combination with the application of linear elastic fracture concepts. The load of the crack is shown to be influenced by geometrical factors like its own initial form and length. Moreover, the occurrence of delamination in the interface between the metal and polymer can be very important, as it severely influences the crack front inside the polymer. The results of this analysis are compared to experimental observations and show good correlation. It is shown how the model can be improved by the application of a viscoelastic material model for the encapsulation material.