Homebrew PCBs

On 11/01/14 03:04, Rick Watson wrote:
> On 1/10/2014 12:26 AM, Russell Shaw wrote:
>> Either reduce the exposure time, or better still (i found) is develop the
>> board in weak NaOH stripper. First put the exposed board in a tray of warm
>> water, then add some 10% conc. NaOH while sloshing. Continue sloshing or
>> brushing over with a paint brush for a minute or two. If there's no change,
>> add more NaOH and repeat until the unexposed resist is properly removed,
>> then rinse in water. It gives an excellent result for over-exposed boards.

 > Do you do this after the board has already been developed and dried,
 > then hardened, or is this how you do the initial develop?

It is straight after removing from the exposure light box.

If you've tried developing in the normal developer, then etched the board in 
ferric chloride, and after 15mins found that stubborn copper won't come off due 
to UV leaking through the ink, i have rinsed the board and put it into a tray of 
weak NaOH stripper like i said, got the residual resist removed, then put back 
in the etching tank and ended up with a perfectly saved board.

I usually etch in low-light so that if i needed to do a weak strip, the resist 
is no more exposed than when starting.

I now just develop first-off in weak stripper, because until i fix the printer 
driver in linux that changed and now puts out less ink, all my boards get 
slightly over exposed due to UV getting through the ink.

I've never bothered with a "drying and hardening" step after developing. I just 
rinse the board then put straight in the bubble etcher. 12mins unheated works well.