X-Ray Inspection: New Capabilities and Methodology for PCBA Analysis

Le résumé fourni par la source

ABSTRACT The continuous miniaturization trends results in always denser PCBAs (Printed Circuit Board Assembly) with increasing solder joint densities. This translates into more and more Surface Mount Area Array or Bottom Termination Components with pitches down to 0.4mm. From an inspection perspective, this technology evolution is setting extreme challenges for assembly quality control or failure analysis, especially when destructive techniques are not desired. This is particularly true when trying to assess COTS (Commercial Off-the-Shelf) boards that often embed the most advanced and densest technologies with little to no information on the PCBA BoM (Bill of Materials) and manufacturing processes used. Fortunately, huge progresses have been done in X-ray inspection technologies these last years, which allows to keeping up with the densification trends and the resulting increase in PCBA complexity. In particular, the use of a movable detector and/or X-ray source within inspection systems has been generalized and permits oblique viewing up to 70° without moving electronic boards during inspections. Oblique angle viewing allows for a much more accurate assessment of the component assembly quality compared to standard 2D topside viewing and the detection of specific subtle defects like Head-on-Pillow (HoP) on BGA (Ball Grid Array) assemblies. Additionally, cracks in solder joints can even now become observable under some conditions thanks to the increased sensitivity and resolution of flat panel detectors as well as the improved efficiency of the last image processing techniques. Last, with laminography capability, an accurate 3D volume dataset of PCBA areas can be obtained with a good spatial resolution which further extends the range of analysis possibilities. This paper will detail through several case studies how X-ray inspection can provide in-house expertise and be used for qualification, failure analysis, technology characterization and even monitoring.

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