Estimation of Solder Ball Collapse Height in Semiconductor Packaging Using Theoretical and Solid Modeling Techniques

Semiconductor packages using solder balls as interconnect to the printed circuit board (PCB) are very popular especially in mobile products like smart phones. Recent requirement to make the package much thinner is very challenging. The solder ball collapse height after the solder ball is reflowed on the package substrate metal pad would need to be tightly controlled and aligned with the required height to meet the target overall package thickness. Another challenge is that the package has to be developed in a short period of time. In this study, theoretical and solid modeling techniques were developed to estimate the solder ball collapse height and compared with actual evaluation results. With these, the solder ball collapse height could be quickly estimated to make the package design and development faster avoiding several trial evaluations on different combinations of solder ball size, substrate pad solder mask opening diameter and solder mask thickness. Based on the estimation results, using these techniques showed good agreement with actual solder ball height measurements and have now been successfully used in coming up with final package designs in a fast and cost-effective way.