Summary for copper plating red spots Discussion
Copper plating red spots are reported on alloy 7025 in a high-efficiency copper cyanide bath, while another alloy, Olin 194, plates without the defect. Deen says the bath is run at about 3-4 oz/gal free cyanide, 4-5 oz/gal copper, pH 13, 65 °C, and 80-200 ASF. In reply, the answerer notes that 80 ASF is very high for traditional rack plating, which is usually closer to 30 ASF, though the setup may use strong agitation. He says he cannot give a definite cause, but suggests the issue may be tied to the alloy difference: 7025 contains about 3% nickel, which could create passive spots or other anomalies under these conditions. He recommends comparing old versus fresh alloy and as-received versus freshly re-machined parts to isolate the source of the red spots.
Q. Hi people, I’m plating copper alloy with copper using a high efficiency copper cyanide bath. Using copper anodes, we control the free cyanide at 3-4 oz/Gal, copper at 4-5 oz/Gal. The pH is around 13 with temp at 65 °C.
The problem is whenever I use copper alloy 7025, red spots can be seen on the surface. But none seen when I use different type copper alloy, e.g., Olin 194. Does anyone experience this situation? The current density range from 80 – 200 ASF.
I would be grateful if someone could explain what is causing this. Thanks.
Deen [surname deleted for privacy by Editor]
– Malaysia
2000
A. Hi Deen. That current density is very high for traditional rack plating, which would probably be more like 30 ASF. I assume you have a fairly fancy agitation system which is propelling plating solution onto the surface to thin down the barrier layer and assure the presence of plenty of copper ions. I mention this because it’s possible that high current density plating exhibits certain anomalies that might not be seen by platers operating at lower current densities.
I can’t answer your question, I can only guess; but Alloy 7025 is quite different from Olin 194. For example, it contains about 3% nickel, and I suppose the nickel could migrate to specific spots on the surface and be passive. You may need to sample old alloy vs. fresh alloy, as received vs. freshly re-machined, etc. Sorry, but I think you have a tough problem on your hands.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
Q. Hello, I am in the need for info re: high purity copper plating over high purity copper piece (101 OFE – Outukumpuo’s best). I need to equal the low oxygen and physical requirements. Thanks, Paul
Paul Olderr
Fermilab (DOE) – Batavia, Illinois
2000
Sorry I can’t be of help here. I am very curious however, why someone would be interested in plating copper over copper?
W. Carl Erickson
– Rome, New York
2000
Hi.
I’m designing line to through [hole?] plate. I’ve some materials but I need more. Can you give me any link to good description on this topic?
Best regards,
Lukasz B.
Electronics – Gdynia, Pomorskie, Poland
2004
adv.: Supplier of Copper Anodes, Nickel Anodes, Bismuth Metal, & Other Metal Products for Industry & The Arts
