Fuzzy Copper Electroforming

I'm a grad student at the Missouri University, I'm using an acid copper electroplating bath in an attempt to electro-form micro channels. I've been using my bath for about 3 weeks now and it had a very sudden unexplainable change in performance.
I've been using it for about 250 hours thus far and it was working well, not perfectly;

but that, I think, has more to do with the fact that I'm trying to electro-form without using a pulse power supply. I'm getting what appears to be dendritic growth (roundish lumps about 2 mm or smaller in diameter, after plating parts at about 20 ASF for ~15-20 hrs. Is that due to the long plating times? any other suggestion on how to get a thick layer (at least 250 um) that is smooth and uniform?

Anyways, on to my bigger question. I'll just explain what happened and see if anyone has any ideas.

System Description
The bath that I've been using is 10% sulfuric acid, 50ppm HCl, with 0.56% Copper Gleam CLX Start-Up (recommended amount) the bath is about 30 liters. It is a 12" square x 14" deep with 6 anode tubes 3 on one side 3 on the other filled with phosphorized copper nuggets ~18 lbs, nuggets are roughly 1" diameter. The anode tubes are PVC pipe with 1/3 cut out and replace with a screen. The opening of the anode tubes faces away from the cathode.

The cathodes that I have been plating are ~1.5" x 3" 1/8" copper sheet attached by drilling a hole in the top center of the plate, inserting a piece of wire and twisting to secure, the wire is then held in the cathode holder, making sure that the workpiece is under at least 1" of fluid. I generally use jewelry casting wax as a masking material (melts and adheres very well to the copper, and allow one to use a tool to selectively remove wax to control deposition location. I also use 'conductive ink' - basically a solution of silver, carbon and graphite powders in a resin base, it is commonly used for though hole plating of circuit boards.

Attached to this I have a heating and filtering system. The heater is a stainless steel heater (in a PCV housing, I'm going to remove the heater as I don't use it).

Next in the pump line is a 1 micron filter, and a pump (designed for highly corrosive environments). The pump returns the fluid to the tank via a pair of nozzles that are positioned to encourage flow across the work piece (providing agitation with out the hassle of pumping filtered air that will then cause further aerosolization of the working fluids.

Modification Description
As I said earlier, the system seemed to be working mostly fine, until...
I wanted to reposition the fluid return nozzles so that they were aimed to the center of the tank rather than about 1/4 down the tank in an attempt to even out the plating results that I was getting. So I put on my face mask, liquid repellent lab coat and gloves, stuck my fingers of one hand into the bath and adjusted the nozzle spray direction. Then next plate that I plated was drastically different that what I expected!


The Change
So right before I adjusted the nozzle, I had just removed the workpiece from the plater, it looked like all the others, plated but a bit dendriticy (as seen in the first two figures). I rinsed that and put it aside,, adjusted the nozzle and place my work piece into the bath, following the same basic procedure that I have for all the previous pieces.

When I returned to examine the work piece it was covered with a very fine but sharp 'copper fuzz'. The fuzz was completely uniform and very attached to the work piece

This figure show the 'fuzzy copper' growth after 18 hours in the bath.

Next I plated a flat piece of copper to see if it too would turn fuzzy, the following pictures show, the results

This figure shows the two plates side by side, TCV-2.0 was done first TCV-2.1 was done second. The lines on TCV-2.0 are due to the underlying channel structure. TCV-2.1 is 'flat' as it was simply a flat plate

Figure showing the initial flat plate for TCV-2.1.

 
As seen in the above figure, TCV-2.1 grew a long 'tail' spontaneously after ~24 hours in the plating bath.

Christopher, you may be better off shortening your submission - this is too long to take in at one go and not made any easier by having to go outside the website to see the pictures. I know I always ask for process and material details, so perhaps I have met my come-uppance!

Hi, Thanks for the hint, Trevor! We've now reduced the font size, added thumbnail pictures, and presented it in two columns, to try to make it more digestible.

Regards,