I’ve built my UV exposure box and tried it out tonight, worked like a charm. It’s more reliable for me than toner transfer, which I could never get consistent results from.
The downside is I have another chemical to deal with, I used [MG Chemicals Positive Developer. It’s diluted 10:1 in a solution of water. It primarily consists of sodium hydroxide (less than 10%, then diluted down to 1%). My research indicates that sodium hydroxide is safe to dispose of down a sink (http://www.wpi.edu/Academics/Depts/Chem … waste.html), and that in it is fact often use as a drain cleaner ([Wikipedia) so it’d stand to reason that I could pour it down a drain.
However, no one comes out and says “pour it down the drain with water” and I don’t want to negatively effect the environment. So currently it is sitting in a container waiting for confirmation that I can just pour it.
Any solid confirmation?](Sodium hydroxide - Wikipedia)](http://www.mgchemicals.com/products/418.html)
It’s OK to pour it down the sink. As you say, it’s used in drain cleaner, and you are only using a dilute solution for developing resist. You can use it many times, of course, until it is exhausted. I mix my own - 12g of NaOH per litre of water (about a teaspoon). It’s so cheap that I only use it once. I only need a small amount for developing a board - I use a small plastic food container for development and agitate it by rocking it for about 30 seconds.
I’ve never been able to get TT to work either. It can be reliable if one uses a laminator, but it means another piece of equipment, and I get very good results with photo-etch. I do my transparencies on an ink-jet printer, using Mega Electronics JetStar film.
This is a useful group:
http://tech.groups.yahoo.com/group/Homebrew_PCBs/
Thanks Leon,
How often do you re-use it? The concentrated solution seemed inexpensive, but if I can re-use it a couple times I will. Is there any down-side to reusing it other than perhaps having it become ineffective and moving the board to a new solution? I would imagine eventually the current batch would just not be effective, and I’d have to change out the solution?
For my test board, I used 30 mL of NaOH concentrate and 300 mL of water, and it developed the board quickly and the solution is still clear. So I imagine it’s good to go for a bit more. I wish the FeCl was as straight-forward, but I’ve read things about Cupric Chloride.
Anyhow,
Thanks for the quick response and link, gives me some reading to do.
I’ve used it 10 times or more.
Ferric chloride can be used indefinitely if you add a little hydrogen peroxide and hydrochloric acid when it gets too slow. It gradually gets replaced by cupric chloride, as the ferric chloride gets rinsed off. I don’t bother; I use it 10 times or more, and then dispose of it.
Thanks again, great info.