Determination of mechanical parameters of solder materials using the miniature measuring method "Small Punch Test" and an appropriate FE-simulation

In order to model the aging of SMT (Surface Mount Technology) solder materi als, which is a prerequisite for lifetime predictions of microelectronic jo ints as well as of the microelectronic package as a whole, it is necessary to know the current mechanical parameters of the solder as accurately as po ssible. In fact, the material behavior of solders is strongly affected by a repeate d change of the temperature and the associated thermal loads. Consequently, the current, i.e., "remaining" properties of in-service solders are of spe cial interest. SMT applications use only very small amounts of solder. Ther efore, the Small Punch Test (SPT) can preferably be used to secure material s data. The SPT is essentially a miniature version of a deep-drawing test d uring which a load-deflection curve is obtained. In combination with an FE- simulation the uniaxial stress-strain behavior and the fracture toughness o f the solder material can be determined. It seems worth pointing out that b y virtue of this methodology use of standard size specimens, which are not always available, is avoided a priori.