Date of Original Version
A novel method for directly testing the adhesion strength of three lead-free solders was developed and compared with conventional methods. The Isotraction Bump Pull method utilizes a combination of favorable qualities of the Cold and Hot Bump Pull tests. Solder bumps were generated onto copper printed circuit board substrates using an in-house-fabricated solder bump-on-demand generator. The method uses polymer epoxy to encapsulate solder bumps under uniform tractions, and tested under tension for pull-off stresses. Maximum pull-off stresses for the novel method are: 18MPa (Sn-3.5Ag), 16MPa (SAC 305) and 22MPa (Sn-0.7Cu) and fall at the low end in the literature comparisons. It is suggested that since the copper substrates used in the current work were untreated, that the lower pull-off stress values resulted. Energy Dispersive X-Ray Spectrometry of the newly created faces after fracture shows that brittle fracture of the Intermetallic Compound layer was the mode of failure.
Turner, G. A., & Meyer, D.M.L. (2018). Lead-Free Solder Pull-Off Stress Comparison of a Novel Bump Pull Method with Conventional Hot/Cold Bump Pull Methods. Research & Development in Material Science, 6(5), 1-8. doi: 10.31031/RDMS.2018.06.000648
Available at: http://dx.doi.org/10.31031/RDMS.2018.06.000648
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