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

----- Original Message -----
From: "Stuart Wallace" <stuartw@...>
To: <homebrew_pcbs@yahoogroups.com>
Sent: Thursday, July 21, 2005 4:59 PM
Subject: [Homebrew_PCBs] Uneven etching problem


> Hi,
>
>
> Bit of a ramble -- sorry about this...
>
> I've recently developed a bit of a problem with my etching process and
> I'm hoping that someone can give me some suggestions for improvement.
>
> Up to now I've been etching FR2 boards at roughly 10/10 (10 mil tracks,
> 10 mil spaces) with good yield. I've recently moved to FR4 substrate and
> 8/8 rules in order to make a board for a slightly higher-speed design,
> and yield has now dropped to zero. I've uploaded a couple of pictures of
> my latest effort -- they were taken with a camera phone so they may not
> be very useful. I have been experimenting with UV exposure times: the
> top side of the board was exposed for 2 mins 45 secs; the bottom side
> for 2 mins 30 secs. I normally expose for 2 mins 15 seconds but this
> doesn't seem like enough for the FR4 board.

I get boards looking like that when I use old PCB stock. The resist is only
good for six months or so after it has been applied.

Leon



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