LEAD-FREE SOLDER JOINT STRUCTURE AND SOLDER BALL

摘要

Disclosed is a lead-free solder joint structure that can solve a problem involved in a conventional solder used in a flip chip within a semiconductor package. Specifically, the conventional solder is an Sn-Pb solder, for example, having a Pb-5Sn composition. Lead-free solders, which have hitherto been studied, are hard and are likely to form an Sn intermetallic compound and thus are unsuitable for flip chip joint structures within the semiconductor package required to have stress relaxation properties. To solve the problem of the prior art technique, a lead-free solder flip chip joint structure characterized by comprising 0.01 to 0.5% by mass of Ni with the balance consisting of Sn is used as the flip chip joint structure within the semiconductor package using the lead-free solder. 0.3 to 0.9% by mass of Cu and 0.001 to 0.01% by mass of P may be added to this solder composition.