Compression creep of 63Sn37Pb solder balls Original Research Article

Using a constant load compression test, the creep deformation of 63Sn37Pb solder balls was studied in the load range 0.5–2 N and in the temperature range 25–150 °C. There was no steady-state creep due to continuous changes in the contact area, which resulted in a decrease in the contact stress. Assuming that the compression velocity was proportional to the uniaxial strain rate and the contact stress was proportional to the uniaxial stress for a contact radius less than 0.3 of the ball diameter, a power law relationship was developed between the compression velocity and the contact area for constant load compression creep during quasi-steady-state creep. The finite element method was used to simulate compression creep of the solder ball with a power law relation between uniaxial stress and strain. The simulation results showed that the nominal stress exponent obtained from compression creep was 0.61 of the stress exponent obtained from uniaxial creep. Using this relationship, we obtained a stress exponent of 1.93–4.21 and activation energy of 47.9–72.6 kJ mol–1 for the compression creep of 63Sn37Pb solder balls.