Homebrew PCBs

twb8899  wrote:
> Adam's comments are correct concerning the use of a sulfuric acid 
> based copper plating system. It will work even better if 
> a "brightner" chemistry is added to the tank. This helps to level out 
> the plating and increase the "throwing power" which is very important 
> when plating in the holes. Do a search on "throwing power" to learn 
> more about this. 
> 
> When plating large flat areas the center of the panel will receive 
> the minimum amount of plating while the edges and corners will get 
> the most. Brightner chemistry helps to level this out and also 
> increase the efficiency through the holes. What is needed is a 1:1 
> thickness ratio between the hole wall and surface thickness and this 
> is almost never achived but you can get very close. 
> 
> The copper anodes should contain a small amount of phosphorus to 
> plate properly in an acid copper tank. These anodes will be 
> marked "CU-PHOS"...

What is the phosphorous for?
I've found that hard-drawn copper shim etches much more difficult
in FeCl than the copper on circuit boards. Why? (i've tried cleaning
any preservatives off first)