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Stain on PCB from reflow oven

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#61621

Stain on PCB from reflow oven | 15 April, 2010

We found stains on the boards come out of reflow oven. The board itself color changed to yellowish from white . We understand discolor soldermask due to high temperature. This can be acceptable by our customer not the stains. The stains look like watermark. We think it is flux. It can’t be cleaned off with alcohol. What are these marks? Please advice. Thanks.

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#61624

Stain on PCB from reflow oven | 16 April, 2010

Your picture is not very useful in conveying the stains. Could the stains be a delamination of the board?

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#61627

Stain on PCB from reflow oven | 16 April, 2010

Looks like a simple variance in the solder mask discoloring.

Shawn

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#61628

Stain on PCB from reflow oven | 16 April, 2010

We have asked the supplier use whiter soldermask taking more heat. We also asked the board supplier to double coat board with soldermask. All these tries failed. We are wondering if the stains are flux contamination.

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#61630

Stain on PCB from reflow oven | 16 April, 2010

White solder mask does have a tendency to yellow within the lead free environment. so double coating will not help any. I due believe the flux is a factor in the yellowing but due to the color is the main reason.

Find out what brand of S/M mask they are using. this looks like EKIRESIN PSR-550B WH-65 the only other option you have is have your board house run a couple sample boards with Taiyo PSR-4000 white or some other Solder mask mfg's white.

The Bright whites hold up better than the duller white colors.

Dave - whats with always jumping to De-lamination? this board showed no signs of delam. (Its not always a board shop issue).

Regards, Boardhouse

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#61631

Stain on PCB from reflow oven | 16 April, 2010

Have you tried running a few bare boards through the oven? If there is no flux on them and you still get the "stains" then I think you can eliminate the flux as the cuprit.

And I've been told that white is the second most difficult solder mask colour for a boardshop to make. Black being the worst due to contrast issues when lining up layers.

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#61632

Stain on PCB from reflow oven | 16 April, 2010

It could be the flux condensed in the oven. We plan to clean the vent and filter next week. Then we see if help. I just want to see if anybody has same problem in experience. Soldermask supplier told us the same white soldermask always change to a little burning color. Espacially lead free require high temperature. We just don't understand why it looks like stain. It should be whole borad changing color. Let me know any thoughts

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#61636

Stain on PCB from reflow oven | 16 April, 2010

If you are trying for a nice reflective surface you will get a white with better spectral reflection if you paint with an appropriate formula after the board is soldered.

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reflow oven profiler

Reflow Oven