Lifetime assessment of soft solder joints on the base of themetallurgical behaviour of Sn₆₂Pb₃₆Ag₂

摘要

The introduction of new packages as well as the ongoingminiaturisation in SMT make the evaluation of the reliability of solderjoints a permanent task. Passive thermal cycling is an important test toevaluate the lifetime of solder joints. However, tin-lead solder behavesviscoplastically. Therefore it is mandatory to take the metallurgicalbehaviour of the solder into account when accelerated tests aredesigned. Two different deformation mechanisms occur, depending on thetemperatures of the test as well as the temperature gradient: grainboundary sliding (GBS) and dislocation climb (DC). Therefore, one is notfree in choosing the parameters of a test cycle because test parameters(temperature ramp, dwell time) have a major influence on the growth ofcracks. Furthermore the stress under service conditions must be takeninto account