Nugget shape control in resistance spot welding

In resistance spot welding (RSW) thin workpieces held by two electrodes are joined via solidification of the molten nugget induced by heat generation from electrical resistances in workpieces and at the faying surface. Solidification starts after welding current is turned off, and heat is then transferred through the electrode to the coolant hole. RSW has been used in electronic, optical and medical packaging technologies. For example, micro-resistance spot welding has been used to attach outer shield clips to the plated steel cores of a circuit board during manufacturing of Motorola´s MicroTAC cellular telephones. Small-scale parallel gap welding has been used to join high temperature microelectronic interconnects, and micro-resistance seam welding has been used to hermetically seal plated microelectronic packages. This study theoretically shows that the workpiece surface suffered from the defect of melting if electrode face radius and welding current frequency reduce, and welding current, Curie temperature and magnetic permeability increase.