Issue link: https://iconnect007.uberflip.com/i/357479
58 SMT Magazine • August 2014 INtRODuCtION tO INLINE aXI tEChNOLOgy continues aRTIClE each layer by detecting the image signal with strongest contrast; all layers can be reconstruct- ed from one original set of images. Basic algorithms Basic inspection capability for AXI systems includes component and solder joint-level de- fects. Component defects: Missing, misalign- ment, tombstone, billboard, tantalum polarity, skew Solder Joint defects: Insufficient/excess solder, short, open, solder ball, non-wetting, void, lifted lead Bga Ball grid array inspection focuses on the quality of solder joints under a BGA package. The typical problems which may be encoun- tered are opens, shorts, voiding, and head-in- pillow defects (incomplete reflow) of solder balls. BGA Defect Causes Reflow issues • Low temperature: insufficient temperature to completely reflow solder balls and solder paste prevents formation of stable solder joints • High temperature: excessive heat during reflow phase can damage BGA substrate, cause solder sputtering and exhaust solder paste flux or cause solder oxidation which will result in poor solder joints Figure 14: image processing is a vital component for accurate AXi inspection. unprocessed X-ray image (left); with Tri's patented ipi image processing (right). Figure 15: bga HIP defects are signs of incom- plete solder reflow, where the solder ball failed to bond with the printed solder paste. These defects show up as shape deformities on slice images and can lead to premature product failure, although they pass electrical testing without problems.