Nanoscale deformation analysis for fracture mechanical evaluation of interface cracks in electronic packages.

J. Keller, M. Schulz, R. Mrossko, B. Wunderle, B. Michel
AMIC Angwandte Micro-Messtechnik GmbH, DE

Keywords: mode mixity, interface cracks, AFM, fracture mechanics, electronic packaging, gray scale correlation, deformation measurement, nanoDAC


The ongoing development of highly integrated electronic packages leads to a steadily increasing number of material interfaces within a package. In combination with increasing harshness (vibration, humidity, temperature) of the system environment the reliability of such packages is often dominated by interface fracture. Therefore interface fracture mechanics is one of the main focuses of electronics reliability research. The determination of fracture mechanical properties of interface cracks is a substantial task for the design for reliability. Without experimental determined fracture mechanical parameters such as the critical energy release rate a reliability forecast based on simulation results cannot be given. The authors present a combined simulative and experimental method for crack tip location determination and crack evaluation of interface specimens. The specimens are loaded in a testing apparatus and images are taken in the vicinity of the crack tip by means of atomic force microscopy (AFM). High resolution images at the interface are taken at different load states during the testing procedure. Then images are analyzed by image correlation techniques and the displacement fields are determined with nm accuracy (nanoDAC method). The results are compared with simulation results to guarantee a correct interpretation of the crack tip displacement field.