Characterization of interfacial parameters for lifetime modelling in modern optical sensor package assemblies

In this paper, a new possibility to determine the critical energy release rate Gc of interfaces in optical sensor packages is presented. The work focuses on some of the most important materials, such as the silicon-based dies and liquid crystal polymer (LCP) cap materials, bonded with different adhesives. The sample design is optimized to use materials and processes very close to those used in production, reproducing their actual surface properties. The samples could be subjected to static loads using an advanced mixed-mode bending (AMB) test and cyclic loads using a fatigue bending (FB) test. Due to the cyclic loading, conclusions can also be drawn about the fatigue behavior via the Paris law, and the sub-critical strain energy release rate Gth can be determined. A molybdenum substrate that had a SiO2 surface finish was also tested to see if this material could replace the brittle silicon for the tests.