High resolution and fast throughput-time X-ray computed tomography for semiconductor packaging applications

The recent applications of 3D X-ray computed tomography (CT) in microelectronic packages, including nondestructive failure analysis, defect monitoring in solder joints and Cu vias, and progressive reliability study of solder voids, electron migration induced void nucleation in solder joints, and void evolution in Cu vias are reviewed. The high resolution and non-destructive 3D X-ray CT data has proven to be highly valuable in package assembly process development, quality control and reliability risk assessment; however, the field of view of current lab-scale 3D X-ray CT technology is limited to about 1-2mm² localized area at micron level resolution, due to its low brightness and nonparallel X-ray beam resulting in long data acquisition time. Synchrotron X-ray sources, on the other hand, can provide large area collimated beams with high brightness, which allows imaging within 3-20 minutes an entire 3D package, including Si, underfill, multiple levels of solder joints, and dielectric layers, Cu vias as well as through holes in multiple substrates. The limitation of current 3D X-ray CT techniques as well as directions for next generation 3D X-ray CT techniques provided by the synchrotron X-ray study of 3D packages are discussed in this paper.