Lead-Free Solder Inspection with X-Ray

ABSTRACT With the current lead-free policy being sought worldwide, the development of different solder alloy combinations is a critical issue to today's manufacturers. With the transition from traditional tin-lead solder to lead-free chemistries, there comes change in materials as well as processes. Moreover, established inspection tools have to be re-evaluated as to their effectiveness in providing defect detection for these new material combinations. Lead-free solder joints look very different from tin-lead solder joints, resulting in the need to revise verification criteria and re-train QA personnel. Long accepted as a way to inspect quality and process control of Ball Grid Array (BGA) solder joints, X-ray inspection can help the electronics industry in the transition to impeccable lead-free assemblies. X-ray is the only means of detecting internal hidden structures of packages and assemblies, providing insight into a variety of solder defects, such as voiding, poor wetting, opens, delamination, and trace defects. The use of X-ray inspection for defect prevention allows manufacturers to correct problems before they become field failures. With its unique capabilities, X-ray technology will play a crucial role in the inspection of lead-free solder joints. While other inspection modalities such as AOI and SEM allow for views of the perimeter of solder joints, X-ray is the only means of detecting internal defects of packages and assemblies. This paper will show examples of possible defects in solder joints using X-ray inspection systems with microfocus X-ray technique and will also provide an overview of available system configurations specially developed for the needs of solder joint inspection.