| 摘要 |
<p>PROBLEM TO BE SOLVED: To restrain a low-strength and low-melting alloy layer from forming in between a land and a solder layer, so as to ensure full quality and reliability for a soldered joint. SOLUTION: A reflow treatment comprises a heating process of melting solder paste attached to a PCB 3 by heating, and a cooling process of forcibly solidifying the molten solder paste by cooling it down at a cooling rate of 1.5 deg.C/second or higher. An Sn-Zn-Bi alloy containing below 3% Bi is used as the solder paste, and it is preferable that two or more kinds of solder powder be combined and turned into solder paste. Moreover, when a flow treatment is carried out thereafter, a reflow process is performed with the temperature at the soldered joint of an electronic part previously mounted through a reflow treatment being kept at 170 deg.C or below.</p> |
