Identification of traction-separation parameters by means of peel testing and in situ confocal microscopy

Delamination owed to environmental stress is a relevant concern in the field of microelectronics packaging. This study is focused on the adhesion of a photosensitive insulator to inorganic passivation layers and metal caps. Peel testing has been combined with confocal laser scanning microscopy to image the bent shape of the peeled layer in situ. Elastic plastic beam theory and finite element analysis have been used to identify a cohesive traction-separation law matching both the work of separation and the peel arm profile. The results indicate that the actual adhesion energy amounts to similar to 30% of the external work, whereas the rest is dissipated by plasticity. Being the latter related to the curvature of the peel arm during delamination, these results confirm the relevance of in situ imaging in the field of microelectronics reliability.