Electronics Assembly Knowledge, Vision & Wisdom
Should We Invest in 3D Optical Inspection?
Should We Invest in 3D Optical Inspection?
We are correcting many solder defects. The search for defects is taking too long. Should we go with a 3D AOI system to save inspection time? The Assembly Brothers, Jim Hall and Phil Zarrow, share their experiences and insight.
Board Talk
Board Talk is presented by ITM Consulting

Phil Zarrow
Phil Zarrow, ITM Consulting
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.


Jim Hall
Jim Hall, ITM Consulting
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

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Transcript
Phil
Welcome to the Board Talk. This is Phil Zarrow and Jim Hall, the Assembly Brothers. Pick and Place. And we're here to answer your SMT and through-hole process related questions and thoughts. Jim, what's today's inquiry?

Jim
It comes from P.S. We are forced to correct many solder defects on the PCB bottom side - SMD glue side. The inspection and search for defects is taking too long. Our soldering waves are not new. We have tried several times to prevent these defects, but with the old equipment, we are limited. Would you suggest we investigate a 3D AOI system to save inspection time, any other suggestions?

Phil
The answer to the question is, sure go ahead and investigate, there are lots of great end of year deals or beginning of year deals whenever you are listening to this. But that's not the real answer to your problem because as better as automated optical inspection is getting, it's not value added - you may find the errors, but why don't you do something to prevent the errors from happening in the first place.

And I would say from what you described here, you're using kind of an antiquated methodology. The minute I see glue side I get the heebie-jeebies. And the fact that we're doing wave soldering here and everything else, so the first thing I'll offer is I would made an adjustment either to your designs and/or to your methodology. I would try to get away from the methodology you're using now in terms of wave soldering.

Jim
A 3D AOI system is not an inexpensive piece of hardware. You're going to spend significant money.  Why not buy a new solder wave or selective soldering system so that you don't create defects. The point is, that's what reliability, productivity and all those good things that should be driving our profit and effectiveness of our enterprise, and you know, finding defects faster we then can fix them is really not particularly spending big money to do so.

You know if you had nothing else and it was just a change in a procedure, that's one thing, but to look at a very expensive piece of gear - it will find the problem, but it's not going to rectify the problem.  

It also surprises me that you're having these defects, they are hard to find on waves. I think defects when wave soldering are easy to find.

Phil
So bottom line is you need to move into the 21st century here and you really want to look into getting double sided reflow, get rid of the glue, sell that glue machine on Ebay, get the money, use it towards getting a selective soldering machine.  

Or a good wave machine, again if you're stuck with surface mount on both sides, look at the pallets, but the better way is selective. Pallets are good, they can work, but it depends on your layout and they can add to your little demons. 

Jim
If you want to spend money on inspection, spend it on an x-ray machine so that you can look into the barrels of holes or underneath components and so forth, where more and more of your joints are going to be.  

Phil
So however you're going to solder on those boards, or whatever you do --  

Jim
Don't solder like my brother.  

Phil
Please don't solder like my brother.

Comments
We have 2D benchtop & 3D in-line AOI and are getting ready to purchase a SPI/AOI combo machine. It will take several years to create an AOI policy and learn how create efficient, effective programs. Our learning curve was 3-4 years. Once you have AOI you need to decide what and how to collect, analyze, and act on the data and that is where the real power of AOI lies. PDCA continuous improvement. AOI is not the holy grail. Do not expect overnight turn around results. Harness the power of AOI and your process will get better and that is what you really want.
Tim Swanson, NEMO Manufacturing
Further clarification is required here. I think what the Brothers are saying is to drop the glue process, and get a selective solder machine for the PTH parts, not the bottomside SMT parts currently being glued. Then paste and reflow both sides of the board for the SMT parts, assemble the PTH parts and use the Selective Solder machine to solder those. You would need to analyze your CCA designs as to whether you can do a double-sided SMT reflow based on the size of the parts. But perhaps there is a happy compromise where perhaps 95% of the SMT parts can be successfully soldered followed by Selective solder, followed by a short manual process.
Richard Stadem, Analog Technologies Corp.
If you are going to apply 3D AOI simply as an optical faultfinder, there is really not much value added with this. However, in a kind of smart factory, where recognized defects are used as a means to correct production flaws right when they were made, by placement equipment or paste printer, you can realize a good ROI with such a machine. Especially in conjunction with an SPI system which feeds back positioning data to the printer for immediate process correction, to provide accurate solder printing. Maybe this solution is for the company not financially appropriate, then a careful review of the basic process equipment, the oven, and the methodology as you suggested, is a very good first step to a solution. Just talking about aspects of electronics manufacturing in the 21st century.
Gerhard B. Wolski
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