Power supply to induction coil is controlled by controlling temperature closed-loop temperature controller nearby welding head. Use a closed-loop temperature controller allows a uniform heat input welding head, eliminate production scrap or rework. By using this method and device, the present invention Chrysler has increased its throughput in 60% ~ 90%. In this invented optical pyrometer sensory from the welding head emitted radiation. A controller of input, and provide a condition of the signal, the power output power control. This controller can be programmed to control around a specific set point to need corresponding soldering temperature base alloy. And closed-loop control soldering process visualization technology changes not sensitive. In addition, flux drying stove no longer soldering process is required.