Preparation of silver nanosheets used for low temperature bonding

A simple electroless deposition method of fabricating silver nanosheets which is a promising replacement for a high-temperature lead-rich solder used for electronics has been reported. This substrate free deposition method can solve the surface coating problem of the nanostructured silver. By controlling the deposition time, the silver nanosheets with a length of 2μm and a width ranging from 10nm to 20nm have been selected due to its relative large surface area and high uniformity. The relatively high surface energy of nanostructured silver results in a melting point depression. About 1 μm high Cu micro cones are used to bond with the silver nanosheets. After room temperature bonding with the assistance of a constant pressure of 10kPa, the bonded sample was put in the oven to be heated to accumulate the diffusion between the two metals. More crystal information of the silver nanosheets has also been provided by X-ray diffraction analysis (XRD) and transmission electron microscope analysis (TEM) respectively. As silver has high electrical and thermal conductivities, this silver nanosheets has potential applications as conducting interconnectors and tracks in printed circuit boards.