Keynote
“MECHANICAL MICROSCOPY”: RESOLVING THE MECHANICAL BEHAVIOR AND UNDERLYING MECHANISMS OF MATERIALS WITH HIGH SPATIAL RESOLUTION

In many functional devices such as microelectronic power switches, flexible displays, fuel cells or solar cells a multitude of different materials are combined including semiconductors, dielectric amorphous films, metallic conductors and intermetallic solder joints. Often degradation and failure of such devices is caused by mechanical stresses arising in the different materials during fabrication and/or service. Thus, the mechanical properties of the materials and material systems require not only a quantitative determination but also a thorough understanding of the underlying deformation mechanisms, which is termed as “mechanical microscopy”. Since the involved geometrical and/or microstructural dimensions are small, miniaturized mechanical testing becomes necessary to study the mechanical performance at the relevant length-scale. Several open questions concerning the mechanical properties of the involved materials exists and will be addressed in this overview talk. The focus will be laid on interfaces and their mechanical performance concerning plasticity and fracture [1]. The overview will shed new light on two scientific questions: (1) Do we understand dislocation transmission through grain boundaries in metals? And (2), how prone are interfaces between metallic films and solder joints to failure? The possibilities for materials design but also the limitations of the small scale mechanical testing methods are discussed.

[1] G Dehm, BN Jaya, R Raghavan, C Kirchlechner, Overview on Micro-and Nanomechanical Testing: New Insights in Interface Plasticity and Fracture at Small Length Scales, Acta Materialia 142 (2018), 248-282