Homebrew PCBs

leon Heller wrote:
>>> You put the gauge on some PCB and expose it for some time,
>> With the artwork or without?
> 
> Without!

No need to shout! :)

I've spent this afternoon doing a few tests on some cheap Maplin pre-coated 
laminate, with Seno "Develop 110" developer (the one that costs £7 plus VAT 
from Rapid and looks like a bottle of shoe polish). I have a sneaking 
suspicion the boards may have been sitting on a shelf for quite some time as 
they were rather difficult to get even remotely close to step 8 on the step 
gauge. It took half a dozen attempts, and a final exposure time of 960 seconds 
(16 minutes) and a developing time of 60 seconds (it says on the can that it 
only takes 20-30).

My understanding is that my goal is to have a "step held" (the first step 
that's <50% exposed) at step 8. In my case, with positive photoresist, that 
means the first step that's less than 50% clear copper should be step 9.

I think I'm going to liberate a sheet or two of Microtrak or CIF precoated PCB 
laminate from the storage cupboard and see if that works any better. Even if 
it doesn't expose better, it should certainly cut better in the shear...

Hmm. More experimenting required....

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/