Bondable Copper Substrates with Silver Solid Solution Coatings for High-Power Electronic Applications

Recently, silver solid solution phase with indium, (Ag)-xxIn, has been demonstrated to be one of potential candidates of metallic packaging material for future high-power electronics bonding and interconnection applications due to its great anti-tarnishing property and superior mechanical properties, such as high ductility and high ultimate tensile strength. To further explore and utilize its great potential for electronic packaging applications, the authors have studied the methodology in fabricating silver solid solution thin film layer on copper substrates as its coating layer, using E-beam evaporation deposition. The grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectra (XPS) were used in couple to study the surface composition and thin film quality of the silver-indium solid solution layer on copper substrates. High quality homogenous coating layers with various compositions have been successfully fabricated on copper substrates. It is worthwhile noticing that additional annealing steps are not needed to achieve the homogenous silver-indium solid solution layers. Subsequent solid-state bonding experiments have shown the good bondability of the resulting coating layer of silver-indium solid solution with their cross-sectional optical and scanning electron microscope (SEM) images. Accordingly, the resulting copper substrates with silver-indium solid solution coatings should have a great potential to be used as a highly conductive bondable substrate for high-power electronics and photonics applications.