Patent ID: 6915942

Claim:
A method of manufacturing a mount structure having a printed board and an electronic part, which contains Pb in the plating film of a lead, mounted on said printed board by soldering, said method comprising the steps of: a) applying a solder paste which comprise a Sn—Zn based alloy and contains less than 3% of Bi on said printed board, and loading said electronic part on said printed board through said solder paste; b) heating and melting said solder paste applied on said printed board; and c) forcedly cooling down said melted solder paste at a cooling speed in said range of 1.5° C./second to 3.3° C./second in the state where Pb contained in said plating film of said lead of said electronic parts begins to melt into solder paste by melting solder paste, to solidify said melted solder paste.