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AOI, Quality and SPC

phil

#23616

AOI, Quality and SPC | 3 March, 2003

I am trying to optimise the use of our Automatic Optical Inspection Machines. As the data we collect from the machine is mainly of the attribute type (Pass/fail, Defect1, Defect2, etc), what advice can you provide to improve its use as well as using the data as an SPC tool on the shop floor. (I am trying to devlop an excel SPC tool, do you have any tips, comments or advice to implemet it on the shop floor?)

Sorry for the long questions

Thank you

P

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#23617

AOI, Quality and SPC | 3 March, 2003

Hello phil, The use of AOI systems give us the opportunity to auto-collect defect information much the way you're using them now. AOI systems become extremely effective when the collected data is used to perform some positive change into the process. Ideally, the best way to improve its use is to create an auto-feedback loop that takes the data and makes corrective actions in prior process steps. For actions like this to work, each process step will require a process code, every type of possible defect within that process step will require individual defect codes, and each printed circuit board will require a unique barcode. This will require the good ole' cause and effect diagram to get dusted off and revisited with vigor. One issue that I can't speculate on is whether AOI systems have programmable defect tracking database modules? If they do, you'll want to program these new process and defect codes into the database so you can track defects by process code. If they don't have such modules, I'd recommend following the same steps but using MS Access instead of Excel before you get too far along. Access' database capability will handle more capacity and will be considerably easier to use and get data from than Excel. Create an input interface with input field for bar code number (easily scanned and auto-input to field)and have drop down menus for date, shift, process and defect code selection. Then you'd establish SPC upper and lower control limits and a threshhold limit on individual defects per process step before acting on out of control conditions. Ideally, an auto-flag routine to alert someone would be icing on the cake. This is to track and more effectively use data. Now, how would you adjust a machine or process step based on out of control conditions? Let me know if you require additional assistance. Thanks!

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ROHAN SARKER

#23641

AOI, Quality and SPC | 4 March, 2003

Well very interesting...i think a possible solution can be data acquisition via Matlab and then carrying the necessary operations.Can u give details of your works-----I can then get closer to a possible solution.

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Dave C.

#23644

AOI, Quality and SPC | 4 March, 2003

We have auto-correct funtion on our Panasonic Create CM-301 placement machines but have never turned it on because of a perceived loss of placement time when the camera verifies placement. We look at the first article and correct placemnt if needed. Is anyone using the auto-correct function?

Since this is a closed loop feedback, placement-recognition of placment accuracy-correction-placement-recognition-done. Is this what we want to achieve? Should we let the machine fix itself? Dave C.

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#23646

AOI, Quality and SPC | 4 March, 2003

Hello Rohan, this is starting to date nearly 6 years ago but I will remember everything I can, we used a custom interface to input data and everything was stored in a very large database on a specific server only for quality data, I think we used Oracle. We had custom gurus write the data inquiry and output code for getting reports once the data was gathered. We inspected and input data after reflow, at ICT, and lastly at final test. In addition to my earlier response, we hardcoded defect codes into each process step, so based on the type of defect found, it could only come from a specific process step. Based on where the defect was being entered the system would only allow certain code selections to appear in drop down menus, this was to prevent incorrect entering of data. With the system we had, we were able to track defects per step and create action plans based on reports. Every board must have bar codes and must track specific product rev levels so new data on new product is not confused with same older product. The end result was daily quality meetings where we discussed what products had quality issues the previous day/night, someone would take the action item to investigate, implement resolution and report back to the quality meeting with results. It was a very closed loop process that worked very well and instituted accountability! Let me know if you require additional assistance. Thanks!

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#23648

AOI, Quality and SPC | 4 March, 2003

Hello Dave, I can understand why you might not use the auto-correct function based on the time it takes to perform the operation. I question why there is an auto-correct function in the first place? If I understand the way this works correctly, the machine corrects itself based on looking at the component on the circuit board after placement. So I'm not sure what reference point the machine uses to base it's correction from? What happens if the camera gantry is bad? It's generally not a good idea for a system to test itself. If the system truly does work as intended and you can spare the extra placement/verify time, by all means do it, your goal is to accurately place components. But, when your pulse rate shrinks to a point where you can't afford the time any longer, then what do you do? This is what I recommend, determine that the machine is accurate and repeatable within the manufacturers quality performance specification, if it meets spec then you should not need to use the auto-correct function because the machine is performing as it should according to specification. If it does not meet spec then you have to get the manufacturer involved to fix the issue. Independent testing is a good way to verify machine spec compliance and improve machine performance in the process. Let me know if you require additional assistance. Thanks!

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phil

#23656

AOI, Quality and SPC | 5 March, 2003

Hi, Mike

Thanks for the reply

With your oracle system were you able to perfom SPC analysis? and if possible do you have any Material that may be helpful for me to get my system setup i.e. whether through Excel, Access, Oracle etc.

+ What are your thoughts on Test machines within SMT manufacturing, and at what stage- from your experiance where is the best place to use the AOI to find defects (After reflow, oven bake, Screen Print etc).

Thanks again

Phil

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#23670

AOI, Quality and SPC | 5 March, 2003

Hello Phil, We did use an Oracle relational database with an Access front end to input and query data from the system for reports. We did not perform SPC with the Oracle dB. As the whole data collection process was completely customized, we hadn't implemented automated SPC before they shut the facility down. What we did do though was track daily defects and assign risk priority numbers to large hitters so we could prioritize our efforts and make the resolution and closing procedure more effective. Unfortunately, I do not have any of the specific material that could further assist you in setup, but will investigate a little further because this level of control could be very beneficial to everyone in the industry. With regard to test machines within SMT, not sure what you mean here...? a proto line so to speak for product and process validation before mainstream manufacturing...? If that is what you mean, my comments are proactive for it. You might as well debug the product and process before getting online and causing expensive downtime. This effort requires involvement from designers, material planning, customers for pre-production cost centers, and a host of others. Not even sure if this answer was what you were looking for with test machines...? When you look at integrating AOI in manufacturing with cost versus benefit, the best place to use AOI systems is after reflow, it captures the entire line of defects from each process step. Now if your budget allows multiple AOI purchases, which I highly doubt, ideally you'd want one after each process step, but that's just not realistic. Let me know if you require additional assistance. Thanks!

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phil

#23681

AOI, Quality and SPC | 6 March, 2003

Thanks for the reply Mike, I will look forward to see the end result of your investigation (e-mail people_1@fsmail.net).

Regarding the test machines, I was trying to ask what are the suited/or recommended from your experience, set of test equipment one should implement within a SMT line to inspect defects i.e. AOI, Flying Probe etc.

Again Thank you very much for your help

Kind regards

Phil

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#23689

AOI, Quality and SPC | 6 March, 2003

Hello Phil, sorry for the confusion, because of our level of defect control and tracking at each process step, we did not use AOI systems at the time. We had a manual inspection station after reflow, then ICT and Functional/Final test for each product. The manual inspection after reflow would easily be replaced by an AOI system today. With proper programming and use of some other prior recommendations, you could implement a throrough tracking system and at least start a manual SPC monitoring system. I've just called a few of my contacts for the followup on investigating the Oracle dB and interface for you. I can't speculate on the ICT and Final test solutions that are available from manufacturers today, I'm not that close to them any longer. Let me know if your require additional assistance. Thanks!

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