Letter 085

Problem with electroforming copper

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I am attempting to electrodeposit a copper layer on a silver coated conductive substrate (wax), resembling a large coin/medallion. It is very important to me to preserve as much of the surface detail as possible, because my next step will be to melt away the wax and use the plated copper as a mold. The diameter of the wax medallions is approximately 6 inches. I am experiencing surface burning, dendritic features, surface "wrinkles", porosity in the areas of low radius curvature, and spontaneous flowering of beads. I must be doing something wrong. Can anyone help me? Thanks for any info or advise.

DMarti

Yes, you are doing something wrong. The preservation of detail you are looking for is not even a challenge for a properly operating process. Compact discs, with their billions of precise dimples, record stampers, wave guides, and a host of super critical items are made by processes similar to yours.

First, talk to a plating chemical supplier, and get a proprietary copper plating bath. Their leveling/brightening agents are the result of decades of development. Then control the temperature as recommended, keep the amperage in a low range, follow their data sheet, and you'll quickly see dramatic improvements. Then go out to some AESF meetings and polish your skills still further.

Ted Mooney, P.E.  finishing.com Brick, NJ

My company also does electroforming on wax shapes (for a totally different application) and it sounds like a bath control problem. Follow the previous advice and tank to a qualified vendor. We are using a product that was developed for rotogravure (printing) but we control to a lower hardness. It is a proprietary bath and I'm sure other vendors have good products too.

Bill Vins microwave & cable assemblies Mesa (what a place-a), Arizona

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