Patent ID: 8083121
Filing Date: 2011-12-27
Classification: B23K,H05K,Y02P

Abstract:
1. A soldering method for soldering a first electrode having a solder portion to a second electrode by melting under heat the solder portion of the first electrode, the method comprising steps of: (a) coating a soldering paste on at least one of the solder portion of the first electrode and the second electrode, the soldering paste comprising liquid basis formed of resin component, an activator for removing oxide film produced on surfaces of the solder portion, and a flake-like shaped metal powder including a core metal and a surface metal covering a surface of the core metal, wherein the solder portion wets and spreads along the surface metal when the solder portion is fluidized, and the core metal includes tin or tin-based alloy, and the surface metal includes silver; (b) positioning the first electrode and the second electrode so that the soldering paste coated in the step (a) is disposed between the solder portion of the first electrode and the second electrode; (c) letting molten solder come in contact with the second electrode by melting the solder portion under heat and wetting and spreading the molten solder along surfaces of the metal powder included in the soldering paste by guiding the molten solder; and (d) solidifying the molten solder after the step (c), thereby forming a soldered portion which connects the first electrode to the second electrode, wherein: in the step (a), an amount of the flake-like shaped metal powder in the soldering paste is 1-20 vol %, in the step (c), the surface of the core metal is exposed at a portion of the metal powder which is not in contact with the molten solder, while the surface metal is taken into the core metal by dissolution, and in the step (d), the soldered portion is formed by the solder portion and most of the metal powder included in the soldering paste for coating in the step (a).