Senju Metal Industry Co., Ltd.

Mamoru Kakuishi

Ryuji Ukai

A solder scattering is prevented at the time of reflow and the oxide films formed on the surfaces of solder or electrodes are thoroughly removed. The soldering method according to the present invention contains the steps of: applying solder paste to the electrode on a printed circuit board and mounting an electronic part on the solder paste, volatilizing the residue-free flux contained in the solder paste by heating the printed circuit board in a chamber set to be a vacuum state and approximately 180 degree C. at the time of pre-heating (interval A), removing oxide films formed on the electrode and the like by heating the printed circuit board in the chamber set to be a formic acid atmospheric state and the temperature of approximately 200 degree C. at the time of reducing (interval B), and melting solder powder contained in the solder paste by heating the printed circuit board in the chamber set to be a vacuum state and the temperature of 250 degree C. at the time of main heating (interval C).

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Tochigi, Japan

Mamoru Kakuishi