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

----- Original Message -----
From: "adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, July 01, 2003 11:40 PM
Subject: Re: [Homebrew_PCBs] Pre-coated PCB stock shelf-life


> I can only have experience with negative dry film resists.
> Generally the longer its been on there the more difficult it
> is to remove an invisible residue (scum) left behind on the
> copper surface after developing. They call this "resist lock
> on". I did not notice any change with the stripping and
> exposure between 1 week old boards and 2 years old. The
> residue can be removed with vigorous developing (>35°C &
> lots of brushing), but you run into the chance of damaging
> the exposed resist pattern.
>

Thanks, Adam.

That's something like the problem I got with the old stuff (positive). It
took a lot longer than usual to etch fully, by which time there was a lot of
overetching in other places. I've used brushing as well, on occasions. Just
after I had this problem, I made another PCB with fresh stock and got a
perfect board.

Leon
--
Leon Heller, G1HSM
leon_heller@...
http://www.geocities.com/leon_heller