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Get A Closer Look At AOI

Automated optical inspection (AOI) systems for your PCB inspection are not created equal. Therefore, it’s crucial that you get a better perspective on AOI simply because it plays an increasingly more vital role today. Obviously, some AOI systems currently are older generation at offshore assemblers as well as those in the U. S. Plus, some of the newer ones don’t have all the features and functions that advanced PCB technologies demand.

PCB inspection is taking on greater significance as boards and packaging continue to become increasingly smaller with greater functionality. AOI and its backup associate, x-ray, team up to catch a variety of board assembly problems. But it’s AOI that’s at the forefront of this inspection process.

Fig. 1 -- inspection under orange light[1]AOI takes on a variety of key inspection assignments, like checking out the numbers labeled on passive and active devices and matching them with the database to assure they’re legitimate components, as specified in the BOM. Also, if alternate parts are used, the AOI machine is trained to verify them, regardless of manufacturer, just so long as the device has the same footprint, value, tolerance, voltage, package type, etc.

There is considerably more to know about today’s AOI, and you can get more detail by checking out our article appearing in SMT Magazine.

In the meantime, here are some tips and hints that’ll help you get a better understanding.

  • It’s good to know AOI cannot read a component in white light. However, when it shines an orange light it can read a component’s marking, Fig. 1.
  • The more cameras an AOI system has the better it can catch defects.
  • AOI cameras show be extremely power with high pixel count to assure reading tiny numbers and characters like those on 0201 devices.
  • AOI lighting is crucial. Check to see if your CM or EMS Provider is using conventional light sources or LEDs.
  • Advanced AOI is ideal, but the operator must be competent and understand AOI strengths and how best to subject it to the inspection process.
  • Equally as important is that the AOI operator be trained to verify alternate components.

In short, what’s truly important for OEMs is having a good handle on what’s good and not so good when it comes to AOI technology. There are all kinds of AOI machines available on the market and some are better than others. In reality, it’s the internal algorithms that play the big role in catching most of the defects and differentiate the most effective AOI machines from the least effective. The more powerful the algorithms, the more precise the AOI search is for zeroing in on defects.