Study on no-fillet SMT solder joint reliability based on solder joint shape CAD

Four process parameters including, the pad length, the pad width, the stencil thickness and the stand-off, are chosen as four control factors, and by using an L₂₅(5⁶) orthogonal array, the no-fillet chip component solder joints shapes with 25 different process parameters combinations are established. And then all the shape prediction models of the 25 solder joints are built through the Surface Evolver soft, after that, the finite element analysis models are set up by converting the above ones. Afterwards, a non-linear finite element analysis on the no-fillet chip component solder joints under thermal cycles are performed by using ANSYS soft, and the thermal fatigue lifes of them are achieved through Coffin-Manson equation. Finally the variance analysis was performed based on the above lifes figures. The research show that with 95% confidence the stand-off has a significant effect on the reliability of the no-fillet chip component solder joints, whereas the pad length, the pad width and the stencil thickness have little effects on the reliability of the ones.