Homebrew PCBs

At 10:15 06/02/19, Leon Heller wrote:
>----- Original Message -----
>From: "patroclus04" <patroclus04@...>
> > I'm thinking on going into photographic methods. I was thinking on
> > getting photosensitive boards, print a mask, and expose it to UV
> > light. Then, as far as I'm concerned, I will have to put in developer,
> > and then etch.<snip>
>
>That's the technique I use, it's very easy. You need to buy or make a UV
>exposure unit, easiest way is to buy a couple of 12" UV tubes and <snip>

Leon, notice the OP appears to be in Spain, not our gloomy northern
latitudes: he may be able to get by with a daylight exposure as long
as the sky is clear so UV is not unduly attenuated.

Simplest way to make an exposure frame is to tape artwork to board
and place in ziplock polythene bag with a thick slab of spongy foam
plastic behind. Squeeze the air out, seal the bag tight (fold end & use
sticky tape seal if you can't get a ziplock bag) then you will have
many minutes while the air pressure clamps your artwork down evenly.

Remember that UV levels will fall off either side of mid-day and vary
with the season, but the exposure latitude of the photoresist is
fairly large so it should not be difficult to learn suitable adjustments
and get repeatable results.

With experience, you can judge the adequacy of the exposure by the
ease and cleanliness of development. You can create a test strip by
sliding a cover slip in stages from an unused area of the board, to
leave a series of steps to judge the minimum usable exposure time
(and the maximum too, if you use scrap board).


Regards, LenW
-- 
   Please trim quotes to minimum for context, then
   reply below, or interleave point-by-point replies.