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Solder Paste Inspection

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Solder Paste Inspection | 8 June, 2007

What is the general consensus on automated solder paste inspection?

In a previous life, when we implemented AOI equipment, we implemented it at the end of the SMT line; our reasoning was that our screen printers had adequate repeatability for our process, and that the bigger ROI for us was to have the AOI equipment at the end of the line to check placement, value, and polarity of components.

My current company specializes in short run prototype jobs...any where from 1 to 1000 pieces. Any volume, any board. We currently do not have a screen printer, instead pasting both pick/place and hand place jobs by hand. Repeatability is mostly indeterminate due to our processing, but conjecturally is at least good enough to keep rework to a minimum, and provide reliable soldering (at least based upon RMA requests and long-term testing reports from customers).

We've recently begun bidding on a design project for a customer, and one of their questions during the pre-bid survey was whether or not we had paste measurement capabilities. I tend to think that, for short-run prototypes at least, the over-head for 2-d paste inspection isn't cost effective (at least, the capital equipment isn't in my budget right now); but I figured I'd check on industry consensus regarding this process step.

So...what says the community? Required? Not required? Nice to have?

Thanks, ..rob

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Solder Paste Inspection | 8 June, 2007

If you're not doing any fine pitch or BGA's, it's a "nice to have". With manual screen printing any paste height measurement tool you got would likely generate more fails than you could deal with unless you set the parameters so wide that almost anything would get through. If you get into fine pitch or BGA's, you must have a decent screen printed and paste height measurement.

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Solder Paste Inspection | 10 June, 2007

Could you justify a used printer with 2d inspection built in?

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Solder Paste Inspection | 11 June, 2007


I'm trying to. I don't like the manual printing, in works for us with short runs, etc...but, in general, I don't like the non-repeatability of manual printing.

If the right deal comes up, I may be able to justify it. In that case, 2-D inspection would be a secondary requirement for me in searching for a used printer...

thanks ..rob

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Solder Paste Inspection | 11 June, 2007

I would also "nice to have" because of your process. Inspecting solder paste from a 2D point of view manually would not assure you quality if the paste is 75% off pad. Plus hand placing onto solder paste causes it's own set of problems which will conflict with your solder paste inspection. Anyone who has ever actually placed parts on by hand knows what I'm talking about.

If it gets you a customer, buy it, s long as it's cost justified. Growing is growing, but I would tend to agree with Stephen above and buy a screen printer with 2D capability. Then you would have an assured quality print with alignment.

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Solder Paste Inspection

PCB X-Ray Inspection System