Homebrew PCBs

Stefan Trethan wrote:
> The sad thing is, none of the restrictions is likely to make much  
> difference to terrorists, they'll get it anyway.

Yep. Probably by getting a ticket on the Dover-to-Calais ferry, picking up a 
few bottles of whatever they want from the continent, then coming back on the 
ferry with the stuff hidden under a car seat...

> Maybe you can use lye instead of the sodium carbonate?

Lye? As in sodium hydroxide, the stuff you use to develop PCB photoresist?

Might work, but the real attraction of carbonate is that it's pretty much 
harmless (it's used as a food additive, and sodium bicarbonate, aka 
bicarbonate of soda, is a derivative of carbonate) and produces less froth, 
foam and CO2 than bicarbonate of soda. Plus carbonate is cheaper and better 
for dealing with FeCl spills - it's a powder so it'll soak up FeCl and 
neutralise it at the same time.

IIRC, the trick is to add the carbonate until the solution is slightly 
alkaline, then pour the resulting mess through a coffee filter to catch the 
sludge. Pour the liquid away (it's just water and sodium salts IIRC), and 
dispose of the filter 'in accordance with local laws' so to speak - that ends 
up being covered in fairly pure iron and copper. If you wanted, you could 
(theoretically) split that apart and make up a solid copper/iron lump over 
time, then sell it to a scrap dealer once you've got enough (note how high 
copper prices are these days).

> What does it take to get the required authorisation? Would be interesting  
> finding out...

"I don't know" was the answer I got...

I've just been searching about, seems a few local decorator's supply shops 
still sell the stuff. Guess I'll be spending this Saturday driving around 
looking for somewhere that'll sell me some...

Oh look, \ufffd7 +VAT and P&P (\ufffd8 +VAT) for five litres: 
<http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__Acetone_7.html>... Saves a 
drive round town I guess.

*expects imminent arrival of the Thought Police and Black Helicopter Squad*

> But even if it is not difficult, laws like that will kill of the remaining  
> chemicals shops (which are only just slightly more commonplace than  
> rockinghorse sh** anyway).

I found a neat article on aluminium anodising 
(<http://astro.neutral.org/anodise.shtml>) that mentioned a site called 
TheChemicalShop.com (<http://www.thechemicalshop.com/>, but mute your speakers 
first, at least until you navigate away from the main page - there's a Flash 
video on there, complete with incredibly annoying sound effects and recorded 
speech). Looks like they sell pretty much anything and everything the amateur 
scientist could want, for a price. Ebay seems to be a pretty good source too, 
despite their "NO CHEMICALS!" policy... LOL.

I'll have to dig out my copy of 'Electronic Prototype Construction' (the 
'Kasten book') and read up on CuCl etching baths. Actually, ISTR that book has 
some really 'interesting' (read: dangerous) chemistry listed. Stuff like gold 
plating with cyanide compounds...

*looks*

Oh, here it is. Page 244. Potassium gold cyanide and citric acid...

And more neat stuff - screen printing the component overlay print...
A little hint from page 310 - if you have to solder an IC socket pin on both 
the top and bottom side, use some solder paste to solder the topside, then 
solder the bottom side in the normal way (i.e. solder wire)

Shame it doesn't really cover front panel lettering. So far the only way I've 
found to put legends on black panels is a Letraset rubdown transfer sheet and 
a can of Humbrol spray-on clear-coat. White and aluminium panels are easy - an 
inkjet acetate and a can of 3M Photo-Mount usually works for me. It's the 
black ones that are a pain, and I've just bought a box full of black 'power 
supply' cases (though they're just the right size for USB peripherals and such)...

-- 
Phil.                         |  (\_/)  This is Bunny. Copy and paste Bunny
ygroups@...         | (='.'=) into your signature to help him gain
http://www.philpem.me.uk/     | (")_(") world domination.