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Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
Silicate based developers (not sure if they are just sodium silicate or someething slightly different) are MUCH better than NaoH, as they have a much wider margin between 'develop' and 'strip', so temperature is way less critical, and the solution also has a pretty much infinite shelf-life - NaOH needs making fresh each time
Registered Member #142
Joined: Sat Feb 11 2006, 01:19PM
Location:
Posts: 102
This is not to say anything about the suitability of NaOH, but when I saw "Drano" I just had to butt in. Drano has aluminum flakes in it. If you must use hardware store NaOH, get Red Devil brand. It has no Al flakes. But like I said, don't take this as an endorsement of NaOH.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
NaOH isn't as bad as it's made out to be. I have no problems using it if I'm patient, and just slowly add more NaOH until the exposed resist is gone. Obviously it'll strip both exposed and non-exposed resist in a flash if the concentration is too great, so just be careful. I actually rexpose the board after it's etched, and then use NaOH to remove the remaining resist. This might depend more on the quality of your photoresist than your patience however, but once again, I've had no problems with it whenever I'm patient.
mikeselectricstuff wrote ...
NaOH needs making fresh each time
NaOH is completely stable and a solution in water will last forever on the shelf. It's only spent by removing resist.
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
Uzzors wrote ...
NaOH isn't as bad as it's made out to be. I have no problems using it if I'm patient, and just slowly add more NaOH until the exposed resist is gone. Obviously it'll strip both exposed and non-exposed resist in a flash if the concentration is too great, so just be careful. I actually rexpose the board after it's etched, and then use NaOH to remove the remaining resist. This might depend more on the quality of your photoresist than your patience however, but once again, I've had no problems with it whenever I'm patient.
mikeselectricstuff wrote ...
NaOH needs making fresh each time
NaOH is completely stable and a solution in water will last forever on the shelf. It's only spent by removing resist.
Back before I discovered siicate developer I found that a tray of NaOH dev would lose its ability to develop over time (time, not usage) - I have no idea of the chemistry - maybe something to do with the resist it had previously developed or reaction with the plastic tray but it definitely did 'go off' somehow.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
I think you're both right -- aqueous NaOH lasts forever in a sealed bottle, but not in an open tray. Something about taking up CO2 from the air? (sorry, no hypothetical details today) I had no trouble with KOH battery electrolyte solution that sat in a bottle on -my- shelf for 30 years.
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circuit board fabrication
