Homebrew PCBs

----- Original Message ----- 
From: "Adam Seychell" <a_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, June 05, 2008 9:53 AM
Subject: Re: [Homebrew_PCBs] Out-of-date pre-coated boards


> Leon wrote:
>> I've just noticed something that might be useful to other people using
>> pre-coated boards.
>>
>> I was using up some rather old off-cuts while I waited for some new 
>> material
>> to arrive, without much success. The new material arrived this morning 
>> and I
>> noticed that the faint yellow pattern on the resist after UV exposure was
>> much more noticeable than it had been on the old stock.
>>
>
> They could be a different brand/formula photoresist. could you explain
> what problems you had ? Is it negative or positive resist ?
> Was it a exposure, developing issue, or copper residue problem. The only
> problem I've experienced with aged resists (>2 years) is a stubborn
> residual invisible film left behind on the copper surface after
> developing. It requires rigorous developing to remove it, and etching to
> remove the rest.

The actual material was Fotoboard 2 (positive resist). The main problem 
(with my standard exposure) was incomplete removal of the resist during 
development. I could probably have got over the problem with more separation 
between the tracks and rubbing the board during development, but I wanted to 
use 10/10 mil tracks. It was easier to dump it and order some fresh boards. 
I've had the problem before.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller