Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "Len Warner" <yahoo@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, February 19, 2006 9:26 PM
Subject: [Homebrew_PCBs] Re: Photolithography


> 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).

I've heard of people in California doing it that way, as well.

Leon
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