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AOI False Calls

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AOI False Calls | 20 February, 2013

I am getting a lot of false calls on our AOI(YTV F1)on low contrast part markings like brown-on-yellow tantalum capacitors and etched oscillators, and on lead banks where the pcb has the part outlined in silkscreen. We are contract and cannot change any design features, so if there is a way to reduce or eliminate these in AOI programming, it would be appreciated.

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AOI False Calls | 20 February, 2013

You should have a number of lighting options to deal with the low contrast lettering. Low angle, B/W, reverse color. etc... If I am reading you right, you might have your bridge inspector too far out on the lead banks, that it is seeing the silkscreen as a bridge. Maybe narrow your window a bit, right down to the base of the toe fillet, as far from the silkscreen as feasible. Touchy area, as a bridge could escape if you are too narrow in your window. Contract Mfg is truly a different can of worms at times!

If I missed the intention of your post, sorry! 'hege

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AOI False Calls | 27 February, 2013

For yellow colored tantalum caps, try using Fusion light (P5. For pre process use green filter. Let me know if that works for you. I've had the best results with this setting.

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AOI False Calls | 28 February, 2013

If your silkscreen is too close to the toes of your leads, you can bring the lead bank inspection box in a little bit to compensate. I haven't had many issues with tantalum caps. I inspect those under white light with no filter just fine, but then you are dealing with another vendor. Try different light sources with different filtering to see what works best. The disadvantage to multiple light sources is it adds time to your inspection, at least on the M1. The F1, if I'm not mistaken, has the ability to do single pass inspection (Oh if I could do it over again). If it's a contrast issue, this should fix it; however, if your markings are not consistent, nothing will help. This is the issue with the etching on the crystals. Even if you get good contrast, you are dealing with inconsistent font. About the only thing you can do is lower your pass score to an acceptable level, or do a presence/absence inspection. Solder inspection on the top can works great for this, but you run the risk of having the wrong crystal installed. Do you do any functional testing on this product? If so, then this should alleviate any fears of wrong placements (aside from the rework involved of course).

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Solder Paste Inspection