What are the differences between digital and analogue x-ray inspection systems?

The fundamental difference is that digital x-ray systems use a digital detector to provide the x-ray image and analogue systems, an analogue detector. In performance terms, digital detectors provide substantially more pixels in the image than analogue detectors and, more importantly, provide a higher level of greyscale sensitivity. The greyscale sensitivity allows better separation in the image of similarly dense material within the sample allowing more subtle variations/faults to be detected. For example, only digital detectors have sufficient greyscale sensitivity to observe ‘champagne’ or ‘interfacial’ voiding within BGA solder joints in addition to the ‘process’ or ‘bulk’ voids that can be seen by analogue and digital systems.

Further information on the different types of voiding that can be seen using digital x-ray inspection systems can be found in the following technical paper presented by Dage at the Proceedings of SMTA International, Chicago, September, 2004 - Digital X-ray Process Control

Dage provides a digital detector, as standard, in all of its x-ray inspection systems. This is the XiDAT detector and is a digital image intensifier providing a 1.3 Mpixel image at 25 frames per second (real time imaging) with a 16-bit greyscale sensitivity. An alternative digital detector that could be used is a CMOS flat panel detector. Further information on the comparison between digital and analogue x-ray inspection for BGA, flip chip and CSP analysis can be found in the following technical paper presented by Dage at the Proceedings of APEX, Anaheim, February 2004 by David Bernard and Steve Ainsworth  – Comparison Between Digital and Analogue X-ray Inspection.