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When electroplating copper my finish is rough and grainy





January 19, 2009

Hello,

I'm working on a research project in which I'm attempting to use plated copper as a heat conductor. Unfortunately, my copper comes out having a grainy appearance with pits and pebbles when viewed under the microscope. This isn't the smooth continuous surface I was hoping for, and I'm afraid it may throw my results.

I would appreciate any advice you can give regarding my process and how I may improve it.

I'm currently using 60g H2SO4, 22.5g CuSO5*5H20, and .02% W/W of 37% HCl. My copper is ultra-pure, oxygen free, and I'm plating with about 10ma cc onto Hastelloy C. The voltage hovers around .3 volts. Everything appears pretty, except the surface finish...

Thanks,

Mike

Mike Fortner
Design engineer - Plano, Texas, USA



First of two simultaneous responses -- January 21, 2009

First, if you want adhesion, you need to use a copper strike solution. Traditionally, this is a cyanide based solution, but there are some proprietary pyrophosphate solutions.

Next, you give amounts, but not the total volume--That is needed for a better answer.

Next, you need a leveler, this can be trace amounts of molasses or thiourea or a huge variety of proprietary additive that serve as levelers and brighteners.

You give an amperage, but not the surface area of the part, so it is meaningless.

Normally, copper is plated at a lower voltage, so plate a part at 1 V, and one at 1.5 V and one at 2V and one at 2.5 V and see which one that you like the best. This will drop your amperage, so adjust it so that you have a reasonable amount, say 2 -3 ma to start. The lower amperage will slow the plate rate down in direct proportion to the amperage ratio. But, you will have a smoother surface.

Next, what are you using for agitation. It is mandatory.

OOps, I now see the . in front of the 3. better written as 0.3 V to avoid future problems. This must be an extremely tiny surface area to have that voltage and that low an amount of amperage. Throws off most calculations. You are in an experimental range.

James Watts
- Navarre, Florida



Second of two simultaneous responses -- January 21, 2009

It is necessary to properly clean and activate the substrate prior to plating. If you are doing this, what is the process cycle?

The result you are getting is typical of acid copper sulfate deposits from a bath without grain refining agents. These materials are generally proprietary and are frequently referred to as brighteners, carriers, make up, etc. Typically, one material is used for make up and one for operation.

You added chloride ion, if you used tap water for the bath make up, from a chlorinated water supply, you may have an excess of chloride ion now.

Some other thoughts: Rectification should be less than 5% AC ripple at operating current and voltage Preferred anodes should be phosphorized copper not oxygen free (oxygen free used for alkaline copper) Solution should be agitated with low pressure air or by mechanical means Anode should be bagged with a pre leached polypro bag Continuous filtration of the solution through a 20 micron or less media preferred

Gene Packman
process supplier - Great Neck, New York


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