Geometric effects of LGA solder joint on board level reliability in 2-pad ceramic LED assembly

In this paper, the effects of newly defined solder geometric factors in a 2-pad LED lighting assembly on the reliability of Land Grid Array solder joints are investigated by adopting the methodology that we derived from our previous work. This has been done by conducting a series of FEM simulations to establish a response surface model for LED package geometric parameters to predict solder joint reliability. It shows that the LED carrier size (A) and solder coverage (SC) are the most influential factors. Decreasing the package size and increasing the solder coverage area can prolong the lifetime. Besides, it shows that the area ratio between two solder joints (AR) also affects the reliability greatly at large carrier size and solder coverage. It is found that in order to minimize the fatigue damage accumulation in the joints, a package design with a small carrier size, large solder coverage and equal pad size is preferable. Given the fact that the effect of SC is marginal in smaller packages, from a cost reduction point of view, intermediate solder coverage level is suggested.