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

----- Original Message -----
From: "patroclus04" <patroclus04@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, February 19, 2006 8:51 PM
Subject: [Homebrew_PCBs] Re: Photolithography


>
> Thank you, I think I get the point. Just have two questions about.
>
> "and put the
> board and transparency on the glass. I then put a heavy book on top of the
> board to ensure it is pressed down. "
>
> I can't see what you say... Sorry. as this may sound stupid.. but..I
> put the PCB on top of glass?? the glass on top?? If you put a heavy
> book on top, how can UV light expose the board??

The glass is above the tubes. The transparency is touching the glass, the
PCB is on top of the transparency, and the book is on top of the board.
Plastic foam would be better, as a pressure pad, but makes the construction
more difficult. Vacuum is even better, and is used by PCB manufacturers.

>
> the other question is regarding to UV light. I don't know where to get
> these kind of lamps... I heard of some people usinf fluorescent lights
> with fair results.. but I suppose it is not enough. I would like to
> build one of those boxes you guys talk about. I suppose it will also
> be usefull to erase EVPROMs..

Suitable UV lamps are available from suppliers like Farnell and RS. The
frequency used for EPROM erasure is different (shorter wavelength). EPROMs
aren't used any more.

Leon

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