Yes, gold plated areas turn orange in color and can be remove by dipping them in microetch for a few seconds.
Lourdes
>>> Bruce Stacy <[log in to unmask]> 02/18 8:42 AM >>>
How do yo know they are Cu stains on electrolytic Au? What color are they?
Does the gold turn orange in color? Need more info.
Bruce Stacy
Lourdes Mertens <[log in to unmask]> on 02/18/99 08:55:31 AM
Please respond to "\"TechNet E-Mail Forum.\" <[log in to unmask]>,
Lourdes Mertens" <[log in to unmask]>
To: [log in to unmask]
cc: (bcc: Bruce Stacy/ECSDOMAIN)
Subject: Re: [TN] Immersion Gold contaminated with Copper
How would you explain copper stains on electrolytic gold ( hard or soft)
after it's been immersed in an amine based resist stripper at 140 F for
about 15 minutes. The panels are copper, solder plated and selectively gold
plated before resist strip.
Lourdes Mertens
>>> "<Rudy Sedlak>" <[log in to unmask]> 02/17 8:51 PM >>>
In a message dated 2/17/99 4:14:33 PM Pacific Standard Time,
[log in to unmask] writes:
<<
enough time) When I dropped a nickel/Iron component into the bath it
immediately plated with the copper.
Perhaps one of the
plating gurus can explain the likelihood of electroless copper plating
onto
gold. >>
You are confusing electroless and immersion plating.
When you plate electroless, something in the bath, called a reducing agent
causes the metal to plate out, this can be Formaldehyde, or Sodium
Hypophophite, or many others.
When you immersion plate, the substrate dissolves, and this causes the
metal
in solution to plate. One of the classic examples is putting a nail (iron)
into an acidic Copper salt (like Copper Sulfate) solution. This is what
happened when you did your experiment. The fact that there was Nickle in
the
Iron was incidental to what happened.
It is difficult to explain clearly, but there are rules about what metal
can
immersion plate on to another, and roughly speaking, in order for a metal
to
immersion plate on to another metal, the metal in solution must be more
"noble", or less readily oxidized, than the substrate. This is why Gold
can
immersion plate on to Copper, but Copper cannot immersion plate on to
Gold....
I'm tired, I am gonna stop now...
Rudy Sedlak
RD Chemical Company
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