Damage evaluation of lead-free solder joints based on micro-electrical-resistance strain measurement

摘要

The relationship between the micro-electrical-resistance strain and the damage was obtained via the theoretical formula deduction, which provides a theoretical foundation for the feasibility of measuring solder joints' damage based on micro-electrical-resistance strain. Single shear lap creep specimens with a 1 mm~2 cross sectional area between thin copper strips were fabricated using lead-free solder (Sn-3.5Ag) to quantify their micro-electrical-resistance strain with in situ micro-electrical-resistance strain measurement under the shear tensile loading. The results showed that the micro-electrical-resistance strain of the solder joints had two stages at the room temperature. And it increased slowly with an almost linear growth trend at the first stage but increased quickly with an almost exponential growth trend at the second stage. The creep damage curves were very similar with the classic creep damage curve.