On Thu, 29 Jan 1998 15:27:02 +0000, you wrote:

>At 08:01 29/01/98 +1100, you wrote:
>>At the end of the day, nothing beats photoetching. Use your laser to print
>>the artwork on a transparency and expose it to UV light, develop it and
>>etch it. Simple.
>>
>>Adios,
>>LarZ
>>
>
>If you do this make sure the toner side of the transparency is next to the
>copper. You can get some light where you dont want it otherwise. This is
>more of an issue when doing double sided boards. I have had more success
>however doing the following.
>
>Print out your layout using normal paper on your laser printer.
I use tracing paper - very good toner adhesion, cheap and translucent
enough to UV. I often do PCBS with 10 thou tracks no problem.
You need the heavy stuff - 90gsm or more - the thin stuff crinkles too
much.
>Develop in NaOH or whatever.

Forget NaOH - it's horrible, temp sensitive,  the solution doesn't
last long, and you need to get the strength right to get a sensible
dev time without over-developing. The ONLY good thing about it is it's
cheap. 
 I use a silicate based developer from Mega Electronics - it is almost
impossible to over-develop with this stuff, so you can use
it really strong, development taking about 10 secs, but leaving it for
30 secs won't over-develop. Solution lasts until you use it all up,
i.e. very long shelf-life, and you can just top it up when it gets
slow. It comes as a concentrate, so a bottle lasts a long long time.


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