The final shape of a solidified solder fillet joint from a reflow process is determined by process parameters and the solder alloy’s physical properties, including surface tension, density, gravity, and wetting angles. This work investigates the influence of surface tension at the solder-atmosphere interface; gravitational effects on the solder, and the influence of wetting angles on the mechanical response of the solder joint when subjected to thermomechanical loads. The predicted optimum fillet shape with minimum fillet area corresponded to the case where the ratio of gravity-to-surface tension forces is almost zero, and wetting angles, θ1 and θ2 being 90 deg. Results from this study suggest that, the influence of gravity on the molten solder geometry is negligible and hence can be assumed to be inconsequential to solder joint reliability issues.

Issue Section:
Technical Papers
Keywords:
reflow soldering, surface tension, wetting, thermomechanical treatment, reliability
Topics:
Solder joints, Solders, Stress, Surface tension, Thermomechanics, Wetting, Geometry, Shapes, Reliability, Finite element analysis
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