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High Conductivity Acid Copper Electroforming

2005

I am interested in using acid copper electroforming to build high power transformers. The designs are such that standard fabrication techniques would be difficult. The plate must be very high conductivity, on the order of 100% IACS and approximately 1mm thick. As I understand it, standard acid copper formulations give a lower conductivity (~75% IACS) plate due to the codeposition of impurities from the brighteners, levelers, etc.

For this reason I am considering using an additive free high throw bath consisting of 80g/L CuSO4-5H20, 200g/L H2SO4, 15-50ppm Cl @ ~20A/sq ft. I have read of pulse reverse being used in an additive free bath to increase throwing power and also to control surface roughness (leveling) while providing a deposit of 101% IACS for particle accelerator components. The most important factor is conductivity, I would guess that excessive surface roughness would lead to voids/discontinuities forming in a thick layer like this. I would appreciate any comments or thoughts on this bath chemistry and the use of PR for this application. Any references that cover the specifics of this type of process (no organics, high throw, acid copper with PR) would be great.

I also have some simple questions about anodes, why are high phosphorus anodes required? What is the reason why C110 (.04% O), or oxygen free materials (C101/102) can not work? Will C122 work (0.02%P)? I ask because of the high cost of C812 (0.04-0.06%P) anode material. Also it seems reasonable that some of this phosphorus would end up being co-deposited which would lower conductivity dramatically. I have built some simple test plating cells that used C110 as anode material for plating ~10mil layers DC, seemed to work ok.

Thank you for your consideration.

Eric Prigge
Electrical Engineer - Huntington Beach, CA US

It would prove useful to do a literature search with 'Jack Dini' as the author. Jack has published a number of papers on high tech copper electroforming. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

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