Jointing interfaces of some kinds of solder on finished boards; immersion gold finished on electroless nickel-phosphorus deposit, was analyzed by SEM, EPMA and TEM. Sn-Ag system solder, expected as highly reliable Pb-free solder because of superior thermal and mechanical properties to other Pb-free solders, formed Ni3Sn4 intermetallic compound and (Cu,Ni)(6)Sn-5 intermetallic compound as reaction layer at the jointed interface of Sn-3.5mass%Ag (Sn-3.5Ag) and Sn-mass%3.5Ag-mass%0.75Cu (Sn-15Ag-0.75Cu), respectively. P-enriched layer was also formed on the Ni-P plated side at each jointing interface, and the thickenss of P-enriched layer for Sn-3.5Ag was thicker than that for Sn-15Ag-0.75Cu. Whereas Sn-Zn system solder, expected as low-melting Pb-free solder because the melting temperature is close to that of the Sn-Pb eutectic solder, formed gamma2(AuZn3) intermetallic compound as reaction layer at the jointing interface of Sn-8.8mass%Zn (Sn-8.8Zn) and Sn-8.0mass%Zn-mass%3.0Bi (Sn-8.0Zn-3.0Bi). P-enriched layer was not observed at each jointing interface. Moreover, Bi crystal was also detected with gamma2(AuZn3) in intermetallic compound layer at the Sn-8.0Zn-3.0Bi jointing interface by TEM.