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AOI systems

YES we are finally there! Machines that will do visual inspe... - Mar 28, 2001 by SBRgetsitdone  

#5765

AOI systems | 28 March, 2001

YES we are finally there! Machines that will do visual inspection of my PCBs and let me do my work with my eyes closed....almost sounds too good to be true.......

We are at the point of implementing a visual inspection system, but really know little about them. Yes, I have read all the articles about different types of methods and software used for inspection, limitations etc, but what I haven't heard is the experience side of things.

I would appreciate any and all input from users out there, of big and small systems. What are you using? How are your results? what are the good, bad and ugly points? DOES IT REALLY LIVE UP TO THE HYPE?

Phil

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Steve

#5770

AOI systems | 28 March, 2001

Take the leap of faith my friend!! Buy the AOI and watch all of your problems disappear. Okay, so I exaggerated a bit. Let me tell you the real story.

We purchased a CR Technology RTI6500 almost two years ago. We chose the CR Tech unit because it was by far the least expensive, and it provided as much, if not more, features than other systems. The software seemed to be easier to use than others, and setting up new boards can either be accomplished manually, or automatically using CAD data.

Has it done what I purchased it to do? Absolutely. It has saved countless hours in inspection and diagnosis time. The defect data that we collect helps us to improve the SM processes. Setting up new boards is an easy task.

The only downside - I was hoping that once we had a board programmed for inspection, we could turn operation over to operators with minimal training. This hasn't been the case. Component inspections are based off of templates of a known good board. If any of the board charateristics change, like components from a different manufacturer, or different markings, new templates need to be trained. I have yet to see a day go by when we don't need to "massage" at least one of the board setups.

Also, remember that these systems are not perfect. They are only as good as what you instruct them to be. Meaning that there are some instances when defects may still slip through. Each board will also need to be reviewed after inspection for what the system has identified as "false failures".

If you go into this process understanding that you will need a trained tech available for support, then I think you will be pleased with the process.

The benefits by far outweigh the downsides. I would definately recommend AOI.

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CAL

#5772

AOI systems | 28 March, 2001

Phil- A Technology you may want to give serious consideration is the Original Solutions UV-OS-1. No gold PCB's, 100% accurate,and a Money back guarantee - IMPRESSIVE! We did the studies on the Original Solutions Boards and were amazed with the technology. Tomb stones,missing parts, polarity,BGA Shifts,Shorts, X-out boards are a few things the Original solutions technology can handle.

The Technology is sound and Cheap. Contact Mike Feld at Original Solutions 1-866-990-9555 www.original-solutions.com

Cal

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#5773

AOI systems | 28 March, 2001

Steve,

When you say "CAD input", do you mean centroid data ( xy locations ) or generic cad info straight from the layout software. ( so far the machines I have been looking at use centroid)

What are your rates of "false failures" and how do your operators/inspectors know they are false. The idea here is to eliminate the human element as much as possible, and my wicked brain has this image of a inspector sitting after the machine ( still!) and passing everything the machine rejects on the pretense of a "false failure".

Phil

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#5775

AOI systems | 28 March, 2001

Thanks, Cal, I will look into it.

What exactly did you mean by " no gold PCB's " ?

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CAL

#5787

AOI systems | 29 March, 2001

Some AOI manufacturers require you to put in a GOLD PCB. Gold PCB is a perfectly manufactured board - Correct placements, correct polarity, no solder short, a "GOOD" PCB. With the vision limitations of some AOI equipment components that have variations in color can cause false errors. Thus causing down time or false rejects. This is a programming step or false read eliminated with UV-OS.

feel free to call me if you need more info. Cal 610-362-1200 x 272

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#5789

AOI systems | 29 March, 2001

Phil, I have got a couple of CR Technology machines also. We have handed off our "learning" to the operators, but you must have confidence in those people! The must be well trained! The AOI machine will flag the things it feels is "bad" and the operator will need to review these to determine if they are bad or not. Like any other inspection, a good eye is needed!

Larry

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Deon Nungaray

#5790

AOI systems | 29 March, 2001

Hello Phil,

AOI equipment has been around for a number of years. I remember evaluating a machine around 5 years ago. At this time the system was not able to learn right side up or upside down characters. Well, the newer systems have come a long way.

I recently evaluated a system and I was impressed. Programming basically consisted of X-Y centriod data entry, setting up color parameters, and taking a known good board to teach the system what is acceptable. After that, it was debugging the program with about 10 different populated boards to work all the bugs out. It was pretty straightforward. I would recommend evaluating a few systems and I think you will be impressed.

Some of the drawbacks to most systems are that if a color changes the slightest shade, the machine will give you an error (doing what is supposed to do). Even if it is the same value. These different components of the same value can be programmed in to the library for acceptability parameters for each specific component value.

If you are an OEM or doing turn-key work it will be easier to get a board programmed due to less variance of component manufacturers, styles, and colors. If you are job shop with no control over components it will require a lot more manual intervention and constant debugging. I would recommend looking for a system with a "true color based system". Gray scale based systems have their limitations.

There are many AOI manufacturers out there now days. Find one with a good solid reputation that has been and will be around for a while. These systems can be very expensive so you want the support and most important the UPGRADES when they become available. Most AOI Manufacturers can also perform a cost analysis model for your facility.

Good luck.

Deon Nungaray, Mfg Process Engineer, GMI USA

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Steve

#5796

AOI systems | 29 March, 2001

The CAD data is the centroid data, x,y location. I developed an Excel macro in which we import the data as a text file and convert it to the CR Technology format.

Rates for false failures varies, but is ~10 - 20%. The operators are given an oportunity to review the failed parts. The false failures are simply parts that don't match the template, so they are able to dismiss them. The true failures are assigned a failure code and a rework sheet can be printed out that is routed with the board.

The extra time to review the false failures is minimal. Bottom line is that you can't leave the AOI alone. Whether in-line or off-line, an operator will need to be stationed at the machine.

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genny

#5799

AOI systems | 29 March, 2001

We have been looking into some sort of higher level inspection system as well. But we have been fairly well convinced that X-Ray is far better than AOI. X-Ray is not only good for BGA's, it is also good for any solder related problems. AOI can only inspect what it can see, hidden connections can't be checked. X-ray can catch not soldered, insufficient solder, too much solder, missing components. Any comments

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#5802

AOI systems | 29 March, 2001

Genny, Would you use the X-Ray in addition to AOI? Or would it be in place of? If so, would it pick out wrong value components? Polarity? I never thought of it as a replacement. Seems like you have investigated into this. Do you mind sharing your findings?

Larry

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Peterson

#5806

AOI systems | 29 March, 2001

AOI systems are a LONG way from being practical. You might impress potential customers (if you are a contract manufacturer) But they are basically an over-priced gimmick. Get your processes in line, buy a good 3D paste height checker, verify components and vendors and run the machines! It ain't rocket science!

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#5810

AOI systems | 30 March, 2001

Genny,

Xray systems ( or at least what I have seen ) are a manual based system. That is, you put the board on the machine and look at certain locations that you want to inspect. What we have in mind is an automated system that will catch obvious, non-repeating errors that make up the last 10% of defects on your way to 100% yield. ( random missing parts, short, skews ).

I would hope that by controlling our paste/print and reflow operations, we can maintain high levels solderability.

Phil

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#5811

AOI systems | 30 March, 2001

Genny,

Xray systems ( or at least what I have seen ) are a manual based system. That is, you put the board on the machine and look at certain locations that you want to inspect. What we have in mind is an automated system that will catch obvious, non-repeating errors that make up the last 10% of defects on your way to 100% yield. ( random missing parts, short, skews ).

I would hope that by controlling our paste/print and reflow operations, we can maintain high levels solderability.

Phil

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#5812

AOI systems | 30 March, 2001

Have you had bad experiences?

We have a paste checker on line, and all components are verified at receiving and again when loaded on the machines.

The purpose of AOI ( for us anyway ) is to reduce the time spent after reflow visually checking the boards for defects such as missing parts, shorts and skews. ( I'm not saying we have lots of trouble with this, our yields are around 95% currently ) What we want to eliminate is the human element involved with visual inspection. On a good day, an inspector is only going to catch 85% of the errors, and it goes down from there ( ie Friday afternoons are the worst!)

Would we not benefit if that person, instead of checking the whole board, only had to check a few locations that the machine reported back, and verify if they are actually failures? ( accounting for false failures )

In my mind, any process that can be automated to do ( or assist ) a task previously done by a person is a step forward. The biggest issue is ensuring the machine performs as expected.

Phil

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#5813

AOI systems | 30 March, 2001

Sorry, that should have been addressed to Peterson

Phil

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genny

#5816

AOI systems vs. X-ray | 30 March, 2001

We are already using ICT on the PCB, which should catch most missing components, also components installed backwards, or the wrong value(to a point - we do RF so we have lots of very small value caps and inductors which can't be measured), and in some cases, faulty components. To enhance the yield we are seeing from ICT, we have been looking at two additional inspection methods - X-ray, and AOI.

We have had several small builds of a new OEM product that is scheduled to become very high volume(for us). We have had yields ranging from 60-90% first pass test. We looked at the faults we've seen and for us over 90% were things like insufficient solder and not soldered, shorts, misaligned components and rotated components. The rotated components should be picked up by ICT (our CM is still working out a few bugs in the fixture) but the other items should be picked up by X-ray. We were told that X-ray strengths are evaluating solder issues on the board, solder patterns, shapes and volumes. It can also evaluate hidden joints. The fault spectrum(the number of different types of faults) picked up by X-ray is the smallest of the three test types, however the percentage of those faults it finds in most cases is higher than AOI and ICT, and the percentage of faults occurring on our products that fall into the categories for X-ray is quite high for us. Also, whereas ICT requires a fixture, X-ray doesn't, and the programming time is supposed to be about the same for both. The main cost is the actual x-ray equipment. Our CM tried to tell us that the only thing x-ray was really needed for was BGA's of which we aren't using any. However, we have a surface mount SMA connector that you can't see the pin, so AOI would not be able to determine a good connection. It can't be probed from the bottom, so ICT would not work. X-ray is the only thing that can determine if we have a problem before actually hooking up the board and finding no signal going thru.

We were also told that ICT gets stopped by every fault it finds, shorts opens, etc. The board must be reworked and rerun thru the test. Put X-ray in front, and it will catch 90% of opens and shorts. Then ICT time will be much faster as it will primarily need to test only values and functionality of components.

All of this stuff is brand new to me - I had never even heard of ICT 8 months ago. So, very little of this is personal experience, it is what I have been told by my research and talking to people who are supposed to know. If there are errors in my info, please let me know.

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#5818

AOI systems | 30 March, 2001

Phil,

The AOI will do a excellent job doing what you said you are looking for. We justified ours on the same requirements as you stated. Keep in mind that the machine may not "see" everything, there are some hidden joints that you will still need top manually inspect. Ask your sales rep to see a machine in "action" somewhere and talk to the operator running the machine. I have two machines and am going to purchase another two more this year.

Larry

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Peterson

#5822

AOI systems | 30 March, 2001

why not just run some of your money through a wave solder machine and burn it up...same thing as buying AOI machines. Absolutely no ROI...not yet, anyway.

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CAL

#5830

AOI systems | 2 April, 2001

Phil- I just noticed Original Solutions has joined SMTNet. You can find information on the industry list. Cal

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Steve Brown

#5867

AOI systems | 5 April, 2001

I used to work for a company called Intelligent Reasoning Systems Incorporated. http://www.irsinc.com based in Austin Texas. They manufactured two different AOI systems depending on the component packages you wanted to inspect. The good thing about these systems was that they were designed to be able to decide on the article being inspected. After inputting the CAD information, which was basically the component centroids, Circuit refs and part numbers, you just showed it boards. These didn't have to be golden boards, just a couple of boards which had been pasted and reflowed so the machine knew what a missing component looked like, and then ten populated boards. The system was image based so there are no algorithms for engineers to set up and tweak in the event of new parts / vendors. Give them a try, they are the new guys in the business so they have learnt from other peoples mistakes.

Steve.

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Susan Christiansen

#5869

AOI systems | 5 April, 2001

My company is also researching AOI systems and X-ray inspection equipment. Almost all of our assemblies are mixed technology, and contain considerable hand load. Is anyone out there using AOI post solderwave?

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Solder Paste Inspection