Solder used for flip chip bonding inside a semiconductor package was a Sn-Pb solder such as a Pb-5Sn composition. Lead-free solders which have been studied are hard and easily form intermetallic compounds with Sn, so they were not suitable for a flip chip connection structure inside a semiconductor package, which requires stress relaxation properties. This problem is dissolved by a flip chip connection structure inside a semiconductor package using a lead-free solder which is characterized by consisting essentially of 0.01 - 0.5 mass percent of Ni and a remainder of Sn. 0.3 - 0.9 mass percent of Cu and 0.001 - 0.01 mass percent of P may be added to this solder composition.
