How to run SMT production with low defects

Very short list of strategies: * Accept only products are designed to be manufactured and tested. * Assure components are of the proper form and are solderable. * Make sure your processes are capable and in control. * Provide lots of training for your troops.

Now, understand that accomplishing strategies like that don't happen over-night. So if you want to get tactical, the folk here at SMTnet have a wide range of experience and would most times provide you with suggestions for ideas to consider in solving specific issues, while you're working on the BIG picture.

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My answer will be another question actually:

- Which defect would you like to see disappear first?

(I am not even asking for the second highest defect because when you make the first one disappear, today's list might change anyway)

Erhan

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I would take the following method to start

Which defect is taking the most labor time to fix.

which defect is causing a bottleneck to your production.

Fix the one causing the bottleneck first as it will improve your plant output and profits

Then fix the defect that is taking the most labor time to fix.

Then continue as DaveF mentions.

This method will give you the biggest bang for your buck and you will see measurable results fairly quickly.

Like everything else it all depends on the specific defects in order on how to solve it.

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You can't control what you don't measure.

You have provided very little detail other than post reflow costs are high. What defects are attributed to problems experienced prior to reflow? Are these random or recurring defects? You will need to put each process step and all of its attributes under scrutiny to determine root cause of failures. Once the cause is determined, then you can go about preventing the problem with appropriate actions. You are correct in saying it get more expensive past the reflow stage. Follow the 10X rule to estimate how costly. For example: Cost to place a component is $0.04 per placement. Cost to fine tune placement accuracy(line operator with tweezers) prior to reflow is $0.40 per placement. Cost to rework a placement after reflow is $4.00 Cost to rework a placement after test is $40.00 Cost to rework a placement after Final QA is $400.00 Cost to rework a placement due to Customer Return is $4000.00

Are your post reflow defects from post reflow operations?

I would suggest adopting IPC 9261 (In Process DPMO), track all defects per assembly and location. Using Excel spreadsheet and data sorting you can quickly identify the highest defect rates per defect type, and location. The recurring defects are the ones to solve first. Random events are harder to find out why it happened. Concentrate on the top 2-3 recurring defects and most likely many others will go away once you fix the problem for the top 2-3. Repeat the above general cycle to an acceptable defect rate level.

Do not lump all your defects into a general category across all assemblies. You will end up comparing apples to oranges. Do not use percentages to audit results. Percentages have an insidious way of hiding the bare truth. Express your defect rates in PPM (Parts per Million). The IPC standard referenced earlier will show you how to accomplish your goal of tracking, identifying and concentrating on your pproblems. Good luck and report back to SMTnet on successes, feel free to ask specific questions for individual root cause analysis steps.

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Thanks for your answers

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