Thomas McGahee wrote:
>
> Instead of attempting to "float" the board copper-side
> down on the etchant (as mentioned in a previous post),
> attach one or two rubber-suction cups to the back
> of the board and suspend the board a fraction of an inch
> below the surface. In the past I have used suction cups
> attached to plastic shafts (kiddie arrows with the shaft
> cut short) Avoid wooden shafts, as the etchant will
> destroy the wood very quickly.

I use insulated bell wire threaded through 1mm, or whatever, holes in
each corner of the PCB which make cheap and easy to use stand offs.
These are usually drilled out for mounting holes later on.

The upside method is an excellent way of etching boards, no pumps,
aerators, special tanks etc. The etchant stays stagnent all the time
which keeps it clean and the copper residue collects on the bottom, and
because there is no movement means a much "crisper" track outline with
no risk of resist smudging or lifting from the board surface.

It does not pay to have the etchant too hot either, especially if using
etch resist pens (Dalo type), because the heat thins the resist and it
"melts" off the board causing thin or missing traces.

From what I understand, ammonium persulphate has a limited shelf life
once mixed, whereas I have used the same batch of ferric chloride for
years. I get more than 50 hobby sized PCBs from a 1 litre batch.

I use "Brasso" liquid metal polish for cleaning the boards and then give
it a light rub with turpentine finished by a detergent and water rinse
off. If any water beads on the copper after this then it may not etch
properly. This method leaves the copper with a mirror finish and the
solder loves it.

--
Best regards

Tony

mICro's
http://www.picnpoke.com
mailto:sales@picnpoke.com

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]: PIC only [EE]: engineering [OT]: off topic [AD]: advertisements