IN-SITU EXPERIMENTAL CHARACTERIZATION OF INTERFACIAL TOUGHNESS OF ALUMINUM THIN FILMS ON POLYIMIDE SUBSTRATES

Interfacial delamination embodies a major issue as concerns the mechanical reliability of metal-on polymer thin films. The interfacial toughness of a metal/polymer material system is a relevant constraint when dealing with the design of electronic devices, which feature stacks of several dissimilar materials. This evidence provides the motivations for the experimental measurement of metal/polymer adhesion. In this study, the interfacial delamination of Aluminum thin films on Polyimide substrates has been investigated combining in-situ light microscopy with a miniaturized 90 degrees peel test setup. Being peel forces in the mN range, dedicated clamps have been designed in order to avoid the use of conventional sliding fixtures meanwhile ensuring proper 90 degrees peel geometry when testing samples on a uniaxial tensile stage. Peel tests revealed a very sharp delamination front, with no evidences of interface heterogeneities. In-situ imaging allowed to interpret the trend of the force/displacement curve. Meaningful data for the computation of the fracture energy (similar to 90 J/m(2)) were clearly distinguished from data affected by undesired dissipation phenomena competing with delamination, such as plastic deformation of the Aluminum film.