Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wave SPC

Hussman

#17708

Wave SPC | 26 September, 2001

What do you folks use for control on your wave solder process? Primarily after wave. I know there are a variety of "wave riders" that will assure proper wave solder parameters, but would like to know what down stream controls some are using.

We are currently using an X-bar and R chart, and I don't like it. I mean, a solder joint is either there or it isn't. We're not measuring the amount of solder on each pad, so there really is no trend that will show we're about to have a solder skip. Plus, we can have multiple skips and still be in control.

This is contract manufacturing so I am limited to board spins, new waves, etc...

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#17716

Wave SPC | 26 September, 2001

Wudduya mean ya can�t replace that ol� John Trieber?

We agree. * Waverider thingies are best used to set-up process and in machine start-up. * Monitoring product characteristics is expensive, gives little information, and is so sloooow. [Plus we turn products before the data becomes meaningful.]

So, we don�t monitor product. We monitor process. [I know, I know. The SPC gods want you to monitor product.] On the back-end, we chart wave temperature, contact time, and pot analysis results.

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John S

#17725

Wave SPC | 27 September, 2001

It seems to depend on your situation. We're an OEM manufacturer and run the same products for extended periods of time. We monitor process indicators such as Dave listed, but we also monitor process defect trends. This is product specific of course. To compensate for that we use p-charts based on the number of defects recorded and the number of defects possible (DPMO). We use the recently published IPC standard on DPMO calculation to come up with the numbers. We've created a nice spreadsheet that does the calculations for it, it just has to be updated for each product you want to characterize. You should be able to find plenty of information on p-charts in a statistics book. Also try Statistical Process Control for Surface Mount Technology by William Messina. At one time there was a paper written by Chrys Shea that had a lot of good info in it.

Hope this helps John

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