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Old 17th Jul 2017, 11:40 pm   #19
Oldcodger
Octode
 
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 1,134
Default Re: UV Dry Film PCB technique - experiences to date.

David - feedback - it might seem laborious, but I've got the transition from Express to photodraw down to an art now.
I looked at the jetstar sheets I got and couldn't any difference in which side to print on, so guessed- yep - I got it wrong, but fortunately on the non porous side, the ink just sponged off. Latest print on to the other side is brilliant .
I've split the A4 sheets into two A5 ones and printed a test piece ( to determine optimum exposure time ), with the two PCB i intend to make.
I notice the "warming up " time for the tubes- so I think I'll just set my timer to max ( min is approx 36 secs , so max should be 11 times that using a 470k pot on a 555 timer circuit) ,for a warm up time, then I've got a test mask of 4x periods, so I'll start with 30 (nominal ) seconds and work up. Like Doctors & Legal Guys, I'll just practice- and as one jovial solicitor said- "one day we''ll get it right".
Far cry from ye olde days . I remember making kids a XYLAPHONE from a PE/PW design. Keyboard was printed in the mag( which some one has posted to me - another project in the future for grandson) . I simply photo copied the
keyboard layout, traced it onto a PCB ,then bribed SWIMBO a new bottle of nail varnish for giving my board a coat or two of her least favourite clear/nearly clear stuff. I then cut out the keys with a sharp nail, added the electronic circuit with a Dalo( or felt tip pen -I can't remember which), and etched.
For history, years ago, some one came out with a nail varnish pen, along the lines of a fine felt tip pen. Swimbo pointed it out to me ,as it might be great for making PCB, but alas ,we never found one on sale.
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