Relationship between dynamic resistance and welding quality during resistance spot welding for micron AuNi₉ wire

Research on dynamic resistance monitoring during micro-gap resistance spot welding for the AuNi₉ wire with a diameter of 200 μm was carried out. The welding time has been experimentally discussed on welding qualities including the welding joints morphology, tensile force, reaction products, reliability check, and failure mode. Then, relationship between the dynamic resistance and welding qualities was experimentally summarized. The favorable welding quality was perfectly corresponded with the extreme value (4.8 mΩ) of dynamic resistance curve when the welding time was 11.5 ms. The welding window was specified as 11.3 to 11.8 ms according to the microstructure analysis (solid solution AuCu with thickness beyond 800 nm) and mechanical test (tensile force beyond 3.0 N). From the perspective of engineering applications, it was determined that the dynamic resistance can be used to monitor the welding quality instead of the different welding parameters for variable materials during parallel micro-gap resistance spot welding.