Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "sbdwag" <sbdwag@...> wrote:
>
> Im getting ready to order some double sided FR-4 from abcfab and 
have
> a question.
> 
> Right now I do not plan on making very many double sided boards. Its
> more difficult to find single sided pcbs and was wonder how I could
> cover the top side without putting a resist layer on it before I 
etch.
> Is there a cheap paint that I could spray on it and remove after 
etching. 
> 
> Any other advantages or disadvantages to having double sided vs 
single
> sided pcbs when you are only using one side.
> 
> Regards
> Wag
>


As someone else suggested, you could just let the etchant eat the 
copper off the other side, thus preventing short circuits and other 
problems. This will, however, eat up your etchant twice as fast. If 
you don't think it will be a problem, I use Rust-Oleum's 'Painter's 
Touch' oil base spray paint from Home Depot when I etch thin brass, as 
the resist on the side without the toner transfer. Pick a color that's 
a sharp contrast to copper, I'd suggest blue or yellow, so you're sure 
it's all cleaned off. Once your board is done, sprinkle a little 
acetone on the back, just enough to get all the paint 'wet', and wait 
for it to bubble up, then let it dry slightly. If you do it right 
(it's not too hard) you can simply pick up a corner of the paint and 
lift it off in one sheet. You should let it dry for two or three days 
though, otherwise you might wind up with 'semi-wet' paint still stuck 
to the board. If it happens, this can be easily wiped off with acetone 
on a paper towel.

Don't, however, pre-spray boards months before you plan to etch. After 
about two months or so the paint is a bit more difficult to remove, 
especially if you wet it with acetone and don't get it off before it 
dries again. It's still not that bad, you can use a piece of 
hard plastic (break a CD case apart) to scrape it off without damaging 
the copper, or use more acetone or paint remover. Also, it may sound 
like it might work better, but don't use latex paint, once it's cured 
all the way (time depends on brand), you'll need to /sand/ it to get 
it off.