Mechanism of Resistance Microwelding of Insulated Copper Wire to Phosphor Bronze Sheet

Abstract

Resistance microwelding of fine insulated copper wire to phosphor bronze thin sheet without prior removal of insulation is of increasing industrial importance for electrical connections in downsized electronic devices, but the understanding of the process is very limited. Therefore, this work aims to clarify the basic joining mechanism. The effects of main process parameters (welding current, weld time and electrode force) and joint microstructure were investigated by tensile testing, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. A welding mechanism with main process stages (cold wire deformation, insulation melting and displacing, and solid-state bonding) is proposed. It should be pointed out that there is no weld nugget forming at the faying surfaces.