Failure mechanisms and mechanical characterization of reactive bonded interfaces

This study presents results of microstructure diagnostics and mechanical strength investigations for reactive bonded components. For this purpose silicon (Si) test specimen were bonded by using commercially available 40 µm thick nickel/aluminum (Ni/Al) NanoFoils{copyright} with a 10 µm thick tin (Sn) solder layer on both sides. Scanning electron (SEM) and high resolution transmission electron microscopy (HRTEM) in combination with energy dispersive X-ray spectroscopy (EDXS) at the bond interface showed the formation of silver-copper-tin (Ag-Cu-Sn) and tin-silver (Sn-Ag) intermetallics within the Sn solder matrix. The hardness and modulus of the solder layer were characterized by Berkovich nanoindentation testing. Results from strength investigations using tensile and micro chevron testing revealed a strong bonding strength of the interface. SEM analyses of the fracture surfaces showed both, cohesive failure through the solder layer and adhesive failure between the silicon substrate and the gold-chrome coating layer.