引張強さにばらつきを示す微小SACはんだ試験片の初晶Snの形状と分布形態

抄録

The miniature specimens made from Sn-3.0Ag-0.5Cu (SAC) solder tend to show larger variation in the tensile strength than the ordinary size specimen. This means that the comparison of the internal structure between high-strength specimens and low-strength specimens will give valuable information to propose a method for giving high strength to solder joints in electronic equipment. Therefore, in this study, the tensile tests using miniature SAC solder specimens made by casting were conducted. The shape and distribution morphology of primary Tin crystal in the specimen after the tensile test were also investigated, and they were compared between the high-strength specimen and the low-strength specimen. The high-strength specimen had the primary Tin crystals which grow in a direction vertical to tensile direction, while the low-strength specimen had the primary Tin crystals which grow in a direction of about 45 degrees.