Theoretical analyses on the shear test

摘要

In board manufacturing the shear test is frequently used to evaluate the quality of the solder joints shortly after the soldering process as well as after thermal cycling. The latter evaluation is in particular applied to leadless ceramic components; a certain load drop is linked to solder degradation in a certain region of the joint which is declared “failed” if the load drop of the shear force reaches a predefined limit. However, there are many uncertainties in this evaluation like component misalignment to the shear tool, excessive voiding of the joint or by a fracture mode away from solder bulk failure. As few is known about these effects from a theoretical viewpoint, FE-studies have been performed to close this gap The analyses comprise studies of size effects, misalignment, and voiding on the shear force response. Additionally, the simulated solder creep response was compared to the measured one to check for the validity of creep laws for SAC solder. For a realistic creep rate range reached in low cycle fatigue, very low shear velocities have to be applied to the joints. A new shear tester was designed with shear velocities down to 1 nm/s to reach this goal.