High speed pull test characterization of BGA solder joints

The changeover to lead-free solder and components metallization in conjunction with the market transition to portable products is expected to have a strong impact on the reliability of lead-free electronics. For handheld electronic products, particular concern has raised over solder joint fracture induced by drop impact. Existing test methods used to evaluate solder ball attachment, shear and pull test, thus far have not been considered suitable for the evaluation of shock reliability, due to their inability to simulate the high strain rate deformation, which characterizes impact loading. Recently, pull test equipment enabling high speed testing has become commercially available, thus calling for further study to assess its applicability for the measurement of joint strength under dynamic load conditions. In this paper, board level drop test and component level pull test results are reported and compared for different BGA assembly alloys and reflow cycle. Pull testing is performed at different test speed on BGA lead-free solder joints after reflow and after thermal ageing in order to investigate the correlation between failure analysis results and lead-free joints micro structural evolution. High-speed pull testing of solder joints is shown to be a promising test methodology for the evaluation of solder joints brittle fracture resistance. Moreover, high speed pull test results are shown to qualitatively correlate with drop test performance if the failure mode is taken as criterion