Although mechanical properties of solder have been evaluated by testing of bulk material in tension, applicability of this result is questionable because the in-service solder joints are extremely small. In this study, BGA specimens were made from in-service solder joints and compared with cast specimen from eutectic solder (Sn-37Pb). The mechanical properties were estimated by indentation method. Stress-strain curves were determined by dual indenter method for BGA and cast specimens. The results revealed that mechanical properties of solder joints depended on the size of microstructure. Therefore, when we estimate mechanical properties of in-service solder joints, test specimen should be made from the in-service solder joints itself.
