over plated aerospace boards??

[jrmycooke]

These two pieces were re ran in the same solution and I am not familiar with this visual result. The only variable that was changed is that I scored each part.
Upon closer inspection, it almost appears as if there is thermal staining. Any thoughts.

 

[Geo]

what color is the solution? is it green and what shade? the color can indicate what the base metal could be. it could have some type of bonding agent instead of the normal base metal we are accustomed to. a bonding agent can be something as simple as glue that can be dissolved in hcl. did you try to scrape some of the foil off a piece before AP to see what the base metal looked like?

 

[jrmycooke]

I found this to be odd, plate on both sides??

 

[jrmycooke]

Geo,yes. Treated material no differently than what I would do for a trimmed finger run. Stannous is fresh and verified with a test. This solution presents itself with a negative result for gold, but what you see in the pictures appears to show something opposite. Just a visual observation looks as if the gold had dissolved but left copper behind. Doesn't make sense because color of solution looks neutral.

 

[Geo]

it looks like copper. if you notice where you scored it, it began removing the copper from the score outward.i think it was just the middle of the piece and it just needed more time to completely release.

 

[jrmycooke]

Well that's the weird thing Geo. The pieces you see in the picture went in the bucket as is but with gold on them. When checked, I saw what you see here, tested with Stannous because there is only one place for the gold to go. Test was negative. I am however sometimes seeing a fine black particulate when doing my spray rinse to handle the material that is coming from behind the foils.

 

[Geo]

this is not unusual in AP where some gold has dissolved. its simply cemented back out on the exposed copper.if you can collect a sample of this powder, dissolve it in hcl/Cl and test with stannous chloride.

 

[jrmycooke]

It sure makes me happy to belong to a group of like minded people where we can collaborate on ideas and help troubleshoot problems when they arise. Thank you for your time on this, and everyone else also.

But......... Why would a solution that has already been worked dissolve gold that had not dissolved during the previous run? I would have thought the opposite to be true, a fresh solution is stronger.

 

[Geo]

depends on how much oxygen it has and how much base metal it has to dissolve. a solution that can dissolve gold will dissolve base metal first until a point is reached that the oxygen saturation can effect the gold. this may or may not be whats happening so its better to dissolve the powder in question and test to be sure.

 

[glondor]

Is that a fiber/ plastic type substrate? If so. I did similar parts direct in A/R. Gold was very thick for electronics. Yield by weight was very good.

 

[jrmycooke]

Board was similar to what you speak of, some.smaller pieces seemed to be polymer. How did you handle your copper from an a/r digest?

 

[nickvc]

The truth is if copper is the only contaminant it's not to difficult to remove by decent washing with hot hydrochloric and water rinses, if in doubt just redissolve your powder and that should remove the contaminates.