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Washing of Misprinted PCBs

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#59668

Washing of Misprinted PCBs | 26 August, 2009

Folks, discovered an issue this morning where solder joints on PCBs that came out of wash system have turned BLUE! Bare pads and test points also contaminated but not as obvious visually. Looks like it could be a chemical reaction between wash solution and flux. Pic attached.

Doesn't seem as if the wrong chemical was used.

Misprinted PCBs are washed in a Miele system using diluted VigonSC and rinsed in DI water (tap water passed through DI resin)

Any ideas? Just wondering if the resin becomes exhausted(i.e. saturated) does the water become contaminated and pick up extra minerals, salts, etc on the way through?

All ideas welcome. Thought I'd seen everything until today.

Attachments:

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#59669

Washing of Misprinted PCBs | 26 August, 2009

O.M.G. ! Its blue pad !

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#59670

Washing of Misprinted PCBs | 26 August, 2009

My understanding is the resin does a one to one ion exchange. And that when it becomes saturated, it does nothing.

edit, and you do mean tap water, not toilet water, right?

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#59676

Washing of Misprinted PCBs | 26 August, 2009

The blue tint could be the result of etching of the tin in your solder connection during cleaning when using a slightly basic cleaning solution. Just about anyone can duplicate this by running a board 7 or 8 times through a cleaner with a saponified cleaning solution.

What is the alloy of the solder connection?

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#59679

Washing of Misprinted PCBs | 27 August, 2009

Alloy is Sn/Pb on a HASL finish. Standard no-clean flux reflowed in Nitrogen.

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#59685

Washing of Misprinted PCBs | 27 August, 2009

SMT-IRL: Run a bare board through your cleaner to confirm our suspicion. Let us know the results, please.

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#59710

Washing of Misprinted PCBs | 28 August, 2009

> O.M.G. ! Its blue pad !

...RE: O.M.G. ! Its blue pad !...

or blue balls, assuming there are BGA's on the assembly

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