Metallic members joining method and reflow soldering method

A reflow soldering method in which with a solder intervening between sites to be soldered of metallic members, a resistance heating heater tip is abutted against said metallic members while simultaneously an AC waveform current flows through said heater tip, said sites to be soldered of said metallic members being soldered by making use of Joule heat generated in said heater tip, said method comprising:

• converting an AC voltage of a commercial frequency by a rectifying circuit into a DC voltage;
• converting said DC voltage output from said rectifying circuit by an inverter into a pulsed voltage of a high frequency;
• applying said high-frequency pulsed voltage output from said inverter across a transformer to said heater tip without rectification on a secondary side of said transformer;
• segmenting a current-supplying time for a single soldering into a plurality of unit current-supplying periods and switching said inverter at said high frequency so as to allow an AC waveform current having a set current value to flow through the secondary side of said transformer with one polarity in each odd-numbered unit current-supplying period but with the other polarity in each even-numbered unit current-supplying period;
• the instant that predetermined phenomena or predetermined conditions to halt a regular supply of current occur or are satisfied during said current-supplying time, bringing switching operations of said inverter to a halt to interrupt the regular supply of current;
• and
• providing a switching control of said inverter so as to allow an electric current for erasing residual magnetism to flow through the secondary side of said transformer depending on the elapsed time and polarity in said unit current-supplying period upon said halt of the regular supply of current.