Immersion Gold on Copper

Question:

I have a project involving the deposit of gold on a printed circuit board that is “copper finished.” Can this be done with immersion plating? Is there a simple process for doing this? Also, is immersion plating the same as electroless plating? K.A.

Answer:

The direct answer to your first question is yes! You can deposit gold on copper using an immersion process but generally the quality of the deposit is not good.

Strictly speaking, an immersion plating process is not the same as an electroless process. In an immersion process you have a galvanic displacement in which a metal less noble, for example copper or nickel, is displaced by gold. As soon as the copper or nickel surface is no longer exposed, the process stops. A true immersion deposit is limited in thickness and typically does not adhere extremely well to the substrate.

An electroless plating process is essentially an autocatalytic process. In a process of this type the plating process will continue once it has started and as long as the plating bath contains the proper components (metal ions, reducing agents, etc.). In theory, there is no limit to the thickness of metal that can be deposited.

Having said this, you will find discussions in the technical literature as well as the marketing literature in which these two terms are “run together” or interchanged with each other.

Your best bet for more information is to contact one of the vendors listed under Plating Processes, gold, electroless on the Suppliers page at www.pfonline.com or in the 2000 Products Finishing Directory and Technology Guide. Also, Gold Plating Technology by Reid and Goldie, available from Metal Finishing Publications (914-333-2578) discusses gold deposition in great detail.