A study of high density and reliability BGA package with solder ball lands of oval type

In this paper, we propose the solder ball lands of oval type for the laminated substrate design of BGA. With this design concept, the ball shear strength test was performed for the relative comparison between conventional (spherical) type and a proposed oval type. In the case of oval type pad design, the minimum and average value of solder ball shear were increased relative to circular type pad and its standard deviation value was decreased. Additionally, oval type lands can allow the designers to insert at least 50% more traces between adjacent unit-pitched-solder ball lands than conventional design so that better traceability for this small sized packages can be obtained. The simulation result of solder ball fatigue life with BGA package was covered in this paper.