copper electrocrystalization on carbon
- From: Adam S <no@xxxxxxxxxxxxx>
- Date: Wed, 31 Aug 2005 14:21:10 +1000
I am trying to electroplate copper from a solution of sulfuric acid/copper sulfate on to a carbon coated surface. The surface resistivity due to carbon is relatively high, measured at 100 k ohms unit square. After plating for 5 minutes at 1A/dm^2 and observing the surface under a microscope, I can see the deposition of randomly placed sites of copper crystallization. The plating solution used is a commercial bright acid copper plating formulation, but I have observed same effect using a solution of sulfuric acid/copper sulfate without additives.
After the first 30 seconds of electrodeposition the nucleation sites become visible to my microscope. The site density does not greatly increase over time, instead, they continue to grow in size until joining with neighboring clusters and eventually the entire surface will be covered. I have also noticed that solution agitation increases the number of nucleation sites, thus reducing the time to form complete copper coverage.
I would like to know if removing the tendency of electrocrystallization will help speed up coverage of the plating. Is this the cause of slow copper coverage ?
My theory is that once crystals sites are formed they 'rob' copper atoms from depositing to nearby carbon surfaces. There must be more to it than simple surface IR drop, because spacing between crystal sites during initial stages would not occur due to IR drop alone.
Adam .
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