Homebrew PCBs

On 16 Dec 2010, at 00:10, Simao Cardoso wrote:

> Simon Gornall wrote:
> 
> > 
> > Do you have a reference for that current calculation, Simao ?
> 
> > Now admittedly, this is for a DC plating environment, not a
> > reverse-pulsed one, but my reading of the pulse-plating literature
> > implied that pulse-plating *let* you increase the current (to get
> > things done faster, which board-houses like). It didn't *require* you
> > to increase the current. I could be wrong, of course :)
> 
> No. Just current densities i saw at various patents and papers. Like for
> DC 1A per dm.sq max for chemistries without additives 75min time. Or
> 3A/dm.sq with additives and true phosphoric anodes 25min. Time also
> depends on the copper thick you wish, these are for 25micrometer or 1mil
> deposit IIRC.
> 
> Your 144 is 12x12 inch on a square foot and you must be using ASF values
> (amps per square foot) for the current density. There are ~9.3dm.sq in a
> foot.sq, so 20asf are ~2.1A/dm², thats a nice value for DC, 35minutes is
> fast enough, but it should fall in the need-additives-category... 
> 
> The patents and papers i follow for this chemistry say 4 to 6 A/dm.sq
> direct pulse. With 100A i could burn 200x300mm (~100in.sq) boards dark
> brown at 8.3A/dm.sq or 77.2asf on 10minutes for 1mil deposit :D 
> (if reverse pulses could replace additives) 
> 
Ok, so if I'm only planning on being able to plate a 160x100mm board, or 1.6dm^2, using your figures that comes to a range of 6.4A -> 9.6A in the forward direction, and 19.2A->28.8A in the reverse direction. That's still (just) within the design I have, although I might add a few more CAT4101's in the reverse direction. I'd prefer to run them at 700mA each max rather than 1A.

Simon

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