Date   : Fri, 26 Dec 1997 15:19:35 GMT
From   : Theo Markettos <theomarkettos@...>
Subject: Re: Hard drive part no's.

On Wed, 24 Dec 1997 16:59:10 +0000, viewtronix@... said:

> How much would the double sided coper-clad board cost?  I also need ferric
> chloride, and a UV light source don't I?

I don't know the size of the board you need, but Rapid (01206 751166) sell
100x160mm double sided photo etch PCB for 2.80 pounds.

> These are the steps that I think you need to do to make the circuit board.

If you've never done it before, I suggest doing a little practice first so
you get the hang of things.  A read of the sci.electronics and
alt.comp.hardware.homebuilt FAQs might also be a good place to look for more
detailed insturctions on how to do this.

> 1. Buy double sided copper clad board (obviously!)
>
> 2. Cover both sides of board in photo-resist fluid.

If you buy photo-etch board, you don't need to do this (and it's probably
cheaper if you're only doing a few)

> 3. Cover both sides of board with the negative images of the circuit. How
> do I line both sides up?

One method is to align one side, drill the holes, and then line the other
side using the holes.

> 4. Expose both sides of board to UV light source

You can use sunlight for this, although it's the wrong time of year to start
(and remember that glass mostly filters out UV)

> 5. The uv light should make the photo resist fluid hardened on the places
> where the copper tracks should be, and then the board should be washed, to
> rid it off the unhardened photo-resist fluid.

This may be a different system to how I've done it, but with photoetch board
you need to develop the board in sodium hydroxide (1.25M IIRC) for a few
minutes, then wash it off with water.

> 6. The board should be washed in Ferric Chloride for 5-10 minutes, this
> takes off all of the unwanted copper.

It may take a bit longer than this, depending on the age of the FeCl3
solution and its temperature.

> 7. Wash board again, and the whole thing should be ready, apart from the
> holes in the relative positions on the board, once the holes have been
> made, the board is ready for component assembly.

You also need to go over the board with wire wool to clean off the
photoresist.

> Is this right or just a load of rubbish, that is, as far as I can remember
> a good way to make circuit boards.  

It is good for designs where there isn't very much fine detail, and can
handle double sided designs if you are careful.  It isn't much good for
multilayer designs, or doing things like plated through-holes.

HTH,
Theo

-- 
Theo Markettos
theomarkettos@...