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Take a New Look at AOI

Automated optical inspection (AOI) systems represent a prime example of the valuable and effective equipment demanded on today’s assembly floor. The foremost reason is the extraordinarily small component packaging and ever-shrinking PCB size that require the most sophisticated AOI solutions possible to detect flaws and defects during the assembly process.

AOI is well suited for checking tombstones, as shown in Fig. 1. AOI also checks for misaligned or missing components, wrong polarity, wrong part, lifted leads, and lifted lead banks. It also catches marginal opens, which appear to be an open; the assembled joint is barely minimal and certainly not 100 percent.

In many cases, when the AOI operator reviews the quality of a joint using the AOI machine, it can fall in the category of either pass or fail.

Check out our article to get the full scope on AOI. In the meantime, here are some tips and hints to get you more acquainted with AOI.

  • 3D AOI is now used to deal with assembly challenges miniature packing and small PCBs pose.
  • 3D AOI inspects what 2D AOI typically does, but goes much further.
  • For example, it reviews the solder paste at the ends of the leads.
  • Advanced AOI like 2D and 3D use multiple features to detect faults and defects on PCBs, including advanced LED lighting, camera locations, lens resolution, other.
  • The AOI operator plays a major role in determining and assuring defects called out by the AOI machine are either true or false.
  • An experienced AOI programmer assures the right part type is programmed and also that he or she accurately sets up the tolerance or pass code criteria.

Today’s state-of-the-art AOI cameras sport 10 to 12 megapixels with 20 megapixels standing ready, and in the near future they’ll make their entrance onto the assembly floor. Five years ago, AOI featured one to two megapixel cameras. But the big jump in megapixels is providing considerable capability for component feature recognition and a much clearer view.

These extra megapixels hand the AOI operator a highly consistent and crisp picture of extremely small areas on top of components. These viewing advances come at a time when such passives as 0402, 0201 and now 01005 are so small that the human eye can barely see them. But with this large number of pixels, they can be easily spotted.