LEAD FREE SOLDER PASTE, SOLDER JOINING METHOD AND MOUNTING STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide a lead free solder paste, a solder joining method and a mounting structure which can secure reliability after joining without strength degradation in solder junction of copper electrodes. SOLUTION: At least solder particles including Sn/Zn, metal grains 7 made of Cu and the lead free solder paste mixed in flux are used in a solder joining of a copper bump 5 of a electronic parts with a copper terminal 2. By forming a diffusive metal compound layer 9a of Cu and Zn surrounding the metal grain 7 inside melting solder 3' of the junction, a diffusive metal compound layer 9b in a joint interface of the melted solder 3' with the copper terminal 2 and the copper bump 5 is suppressed; the strength degradation is prevented and the reliability after joining is ensured.