Patent ID: 7604152

Claim:
An electronic device for which a printed circuit board is used that is manufactured by a method for manufacturing a lead-free printed circuit board for electronic devices with a substrate to which a plurality of electronic parts having connection terminals with different metal compositions are connected by soldering, wherein: a plurality of solder pastes comprising solder components with different compositions are used; said plurality of solder pastes comprising solder components with different compositions comprise a solder paste having a Sn—Bi solder component without Ag, and a solder paste having a Sn—Bi—Ag solder component; when said electronic parts are connected by soldering to said substrate, a solder paste having a solder component with a different composition is used for each of the metal compositions for the connection terminals of electronic parts; when Ag is present at connection terminals of an electronic part to be connected by soldering, said solder paste having a Sn—Bi solder component without Ag is applied only to the substrate electrodes corresponding to the connection terminals with Ag thereat, and when Ag is absent at connection terminals of an electronic part to be connected by soldering, said solder paste having a Sn—Bi—Ag solder component is applied only to the substrate electrodes corresponding to the connection terminals without Ag thereat; and wherein, in said case in which Ag is present at connection terminals of an electronic part to be connected by soldering, said connection terminals with Ag thereat have a metal composition of Sn-3Ag-0.5Cu, and in said case in which Ag is absent at connection terminals of an electronic part to be connected by soldering, said connection terminals without Ag thereat have a metal composition of Sn-3Bi.