Homebrew PCBs

Hi Adam,

Thank you very much for your feedback.

[snip]

> From what I can see in the picture of your updated anode mounts, 
>it looks ok to me. Get some PVC solvent cement (the smelly stuff 
>used for gluing PVC pluming and irrigation pipes) and drip a 
>little around where the copper anodes meets with the PVC 
>shielding. That way your anodes should not prematurely dissolve 
>at this location and cause them to fall to the bottom of the tank.

Ok, will try to get this.

>Make sure you are using stainless nuts/whashers holding copper 
>posts to the black rectangular plastic frame.

They are all stainless already.

>As for a power supply, I used an old PC power supply with 5V 
>output and a power resistor to change the current. The resistor 
>was made by element wire mounted to a length of wood so I could 
>connect an alligator clip at different positions to change the 
>current. It was extremely crude, but at this stage I only need 
>something that works because I have so many other things to worry 
>about first, such as the getting the chemistry and process 
>working. I'm still working on the more critical PCB processes, so 
>the plating power supply will come some other day.
>
> From memory the power requirements for copper plating are;
>cathode current density 1 to 2 A/dm^2
>I think cell voltage with plating additives I'm using is around 
>700mV at 2A/dm^2. I'll have to confirm this, but I'm sure it was 
>under 1 volt. You definitely don't need a precision constant 
>current source for this type of plating. A voltage source is ok, 
>as the current can change +-%20 without worry. A bit of 
>resistance in the line is enough to take care of current variations.

Thanks for the info about the PC power supply. I will first try to add
diodes in series to the kathode line to raise the overall voltage a
bit so as the regulator can operate better. If this fails, then a
complete redesign of the power supply will be the next step.

Markus

PS: I meanwhile updated the pages with pictures of the first PCB.
Looks like the much too high current created this effect.