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PCB with stains bleach after flux aqueous wash

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#73491

PCB with stains bleach after flux aqueous wash | 11 February, 2015

we received assembled PCBs with spots that look like a bleach spots all over the PS and CS . The board house said that this is normal due to flux aqueous wash process. Can it cause problems (e.g. corrosion ) in the long run or cause issues when working in extreme temperature environment?

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#73493

PCB with stains bleach after flux aqueous wash | 11 February, 2015

A-610E, 10.7.4 covers solder mask discoloration. Use that for your disposition

In a previous thread, Boardhouse told us "Here are a couple of things that can affect color. * Material color is the major, * Matte green from Enthone would be different in shad than Matte green from Taiyo. * Solder mask is two parts, One the green mask, two the hardner, having to much of one or the other can cause variance in color. * Copper from outer layers can cause color differences, if the outer layer have large copper plains they will look different in color than a board with outer layers that have less copper showing. * Hot air level machines have also been known to change the color of the mask due to the stress of the process. I'm sure there are a few others not listed but these are off the top of my head. [Boardhouse SMTnet]

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#73497

PCB with stains bleach after flux aqueous wash | 12 February, 2015

> A-610E, 10.7.4 covers solder mask discoloration. > Use that for your disposition > > In a previous > thread, Boardhouse told us "Here are a couple of > things that can affect color. * Material color > is the major, * Matte green from Enthone would > be different in shad than Matte green from > Taiyo. * Solder mask is two parts, One the green > mask, two the hardner, having to much of one or > the other can cause variance in color. * Copper > from outer layers can cause color differences, if > the outer layer have large copper plains they > will look different in color than a board with > outer layers that have less copper showing. * > Hot air level machines have also been known to > change the color of the mask due to the stress of > the process. I'm sure there are a few others not > listed but these are off the top of my head. > [Boardhouse SMTnet]

When doing the flux wash, can the washing detergent cause the bleach ?

The major issue, can we use the boards or it can cause damages in the long run like attacking the copper and causing corrosion?

(Tried to upload a picture but received a denial)

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#73498

PCB with stains bleach after flux aqueous wash | 12 February, 2015

Solder mask is intended to protect the traces from the soldering process. That's it.

[Tried to upload a picture. It's broken.]

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#73502

PCB with stains bleach after flux aqueous wash | 12 February, 2015

I remembered something from the TechNet a long time ago about heating the board with a heat gun to see if the white spots disappear. I searched the archives and found this from Bill Kenyon:

Quick identification of solder mask white spots- if it is the white powder fumed silica used to thicken liquid solder masks, you will often see it appear as white spots. If the solder mask is undercured, any cleaning step may strip off part of the green solder mask, exposing the white thickener powder (typical trade name is 'Cab-O-Sil"). Heat the white area with a heat gun. If the residue is the Cab-O-Sil, the heat softened solder mask will allow the Cab-O-Sil to sink back into the green solder mask. If the white spots disappear, problem is insufficient UV cure during solder mask processing.

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#75686

PCB with stains bleach after flux aqueous wash | 9 May, 2016

I wanted to bump this up. I am having the same problems. I cannot convince folks it is a solder mask issue and not our process issue, even though it shows up after wave and wash. I can heat the boards and even send them back through the wave preheaters and they turn green again.

Anybody know of white papers or written documentation regarding under cured solder mask causing the dye to move around? thanks.

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#75753

PCB with stains bleach after flux aqueous wash | 19 May, 2016

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