Effects of Ceramic Ball-Grid-Array Package's Manufacturing Variations on Solder Joint Reliability

The effects of manufacturing variations on the reliability of solder joints between a ceramic ball grid array (BGA) package and a printed wiring board (PWB) are investigated. Three manufacturing parameters tinder consideration are 1) solder volume, 2) solder height, and 3) solder pad size. To study the manufacturing effects, a solder joint profile model is derived. Then the maximum strain is calculated, and the fatigue life of the solder joint is predicted. The accuracy of the solder profile model is verified by comparing its predicted profiles with experimental results. The fatigue life of a solder joint is estimated by the Coffin-Manson's relation. The calculations show that the manufacturing variations change the joint profile, and subsequently affect the fatigue life. The solder joints formed may have convex, cylindrical and concave profiles. The concave solder joints are preferred, which have long fatigue lives and are less sensitive to the manufacturing variations. For the convex solder joints, their fatigue lives are strongly affected by the joint height variation and by the combined effects of solder volume and pad size.