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Immersion Gold Plating -- Can it be done without Nickel plating?

In my case, I only want to have a thin layer of Au to cover on Cu to prevent Cu oxidation. To do so, somebody has told me I have to do electroless plating Ni first, and then immersion Au. I don't understand the purpose of Ni plating. Can I go directly doing immersion Au? Another question, what's the difference of electroless Au and immersion Au in terms of coating quality, and process?

Karen Yan
student - Singapore
2007

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The problem with a "thin layer to cover" is that the gold will diffuse into the copper, faster at higher temperatures. Immersion processes rely on the difference in the electrochemical activity of the substrate and the coating to provide the reduction capacity to deposit the coating. Once the substrate has received a very thin coating there is no more "battery" left to power a thicker coating. Electroless processes would actually be better called autocatalytic processes--the thickness just continues to build as time goes on.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007