Homebrew PCBs

On Tue, 18 May 2004 10:40:31 -0000, onenastyviper 
<oneNastyViper@...> wrote:

> Maplins has the hexahydrate, I thought there was two types:
> hexahydrate and another anhydrous one?
> Don't ask me if there is a difference, I haven't studied any chemistry
> but on a website its said to use the hexahydrate not the anhydrous
> one???
> This etching chemistry is complicated...all I want to do is etch
> small circuits in a little tub with the least amount of hassle with
> easy availble and reasonably safe chemicals (ie I don't want to wipe
> out a little part of swinton:-P)
>
> PK


The chemistry is not really complicated, if you want to maintain a good 
etchant
with least cost and no waste it is complicated.
If you only want to make the occassional pcb and don't care if you put in
5cent or 10cent worth of chemicals then you need not regard the chemistry 
much.

I still suggest using CuCl.
A simple and effective etching tank is a tupperware container.
The flat ones work just fine, the PCB need not be vertical and you need
much less etchant than in e.g. a cerial container.
The lid is tight enough to prevent vapor escaping, and also prevents a 
disaster
if you knock the tank over while in storage.
For single-sided pcbs a piece of tape makes a great pcb handle.
For CuCl you only need HCl (Muriatic acid), and H2O2, which is both easy 
to get
hold of.

The procedure when etching is to place the board in the ethant and add a 
small
amount of H2O2. Then it etches, you take the board out, put the etchant 
away,
and reuse next time again only adding a small amount of H2O2.

If one day the etching stops and you see blue sludge on the copper the HCl 
is spent.
add a bit and on it goes again.

That is all the chemistry involved for the occassional PCB.

ST