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Wave Soldering Process Restrictions

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Wave Soldering Process Restrictions | 21 February, 2007

Good Morning Everyone,

I just wanted to get a feel for what other Contract Mnufacturers are doing. Do you allow a production PCB assembly with glued SMT components to be wave processed more than once? (e.g. the first pass did not produce acceptable results so the operator made some adjustments and ran it through again) I am specifically concerned with glass MELF diodes on the wave side.

Opinions would be appreciated.



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Wave Soldering Process Restrictions | 21 February, 2007

Ideally? Never. You risk component break down by re-running the board over the wave machine. In a perfect world, your wave operator would make adjustments after one run, and you'd run another panel over the wave to judge the effectiveness of the adjustments. Besides, the solder presence from the first run may skew your results in the second run.

Functionally, of course, we've done this with regular thru-hole assemblies. I don't glue/wave anything currently; but have in the past. And, of course, we've had to re-run a previously waved board. I'd strongly recommend making it an extreme exception, however.

As to the components...what is your fear? Losing the Melf's over the wave, or their tolerance to the process? Spec sheets will give you the info related to their tolerance to the process. I'm not certain what you'd run into re: losing the parts, memory is hazy as to what I've experienced in the past related to this. I would, initially, expect that you wouldn't lose parts...the glue shouldn't break down, and you've got surface tension on your side.

cheers, ..rob

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Wave Soldering Process Restrictions | 21 February, 2007

Probably not on the whole job, but maybe the 1-5 boards that were used for setup control. Especially MELF's are not super process tolerant. I'd probably allow standard caps and resistors one more time, but I'd need some test data to back it up. I'd run ~25 assemblies through the process 2X and then inspect and test. Touch up and part replacement as well as test fails would drive my final decision.

If this was a "normal" condition with setup, I would either get a new machine, a new operator, or plan on the scrap of the setup assemblies and not mess with it.

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