[sdiy] PCB etching (in the UK)

[Ken MacBeth]

Paul- I've got a nice RS UV exposure box that you can have to get you started, I'll send it to you via Business Post...if you want it! I develop large home made pcbs in a large developing tray (photographic for 20"x16" prints. On the cooker I have a glass/pyrex pan which allows you to bring the water up to a temperature so that when the FC crystals are added everything works quickly. I adgitate the tray with the PCB being etched, continuously. When I feel the chemical has to be heated up, I 'boil' the chemical again. It does not take me long to do a large board this way. Understanding missus- yes, I'm divourced, I know. Chemical, in my case, go everywhere, so you do have to watch that. Oh yeah, the sodium hydroxide used to develop the image is bought cheaper as 'drain-cleaner' in your hardware store. Go canny with this stuff- you only need tiny amounts. The boards that Rapid (cheapest) are supplying instruct you that they are now twice as sensitive to Sodium Hydroxide than b!
 efore. One can get a bit prissy about rubber gloves, lab coats etc. I've never bothered with that. I knock out excellent demo boards though! But some of my clothes, especially footware do look a bit of a state...
Regards, Ken- still thinking on ideas.


Neil Johnson <nej22 at hermes.cam.ac.uk> wrote:
Hi Paul,

> I've decided its time to invest in some PCB etching gear.
> I need a UV box and would like a bubble etch tank.

You'll also need bags of spare time, and a very understanding missus!! I
used to make my own boards, and have a heated bubble-etch tank (bought
from Farnell) in storage, as well as a bottle of ferric chloride
(available most places), and a UV box (from Maplin).

You will also need a PCB drill and a selection of drill bits. If you're
careful, buy tungsten-carbide drills, as they will keep their edge longer,
but (a) they are more expensive than HSS, and (b) they are more brittle,
so have a greater tendency to break.

You will also need a selection of plastic trays to develop and wash the
boards, a lab coat to protect yourself from splashes of etchant,
protective goggles to protect your eyes (you do not want ferric chloride
in your eyes...it hurts...) and some rubber gloves to protect your
hands (ferric chloride stains your hands, making you look like a heavy
smoker!)

Once your board is developed and etched, you then have to drill all those
holes. Unless you want lung disorders, wear a face mask to stop the
fibre-glass dust being breathed in, and/or a vacuum cleaner to suck up the
dust.

As you may have gathered, I used to make my own boards, but now prefer to
spend my time designing and building, rather than drilling more bloody
little holes ("tedium" doesn't even begin to describe how dull a job it
is). I know PCB Pool are not cheap, but when you consider how much effort
goes into making a PCB, I would rather spend that time designing a better
circuit, or improving the layout, than slaving over a bubbling vat of
fuming ferric chloride, or coughing up fibre-glass dust.

> Can anyone recomend any particular brand? and also where to get them (in
> the UK)

Rapid Electronics sell most of what you'll need, including precoated UV
PCB material. If I were mad enough to start out again I'd look at:

34-0760 Heated bubble-etch tank £200.00
34-0695 PCB Production kit C £204.75

For larger boards you might need the larger UV box 34-0705 (priced at
£207.30).

Assuming that you'll be using CAD to design your boards, I had excellent
results printing to thin tracing paper in a laser printer, rather than
clear film as the toner sticks better and gives more solid blacks and
better definition. Remember to arrange it so the toner side is closest to
the PCB, otherwise you get smudgy edges.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk http://www.cl.cam.ac.uk/~nej22
---- IEE Cambridge Branch: http://www.iee-cambridge.org.uk ----




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