New Photoetched Upgrade Kit for Robbe U-47 - Units will be ready in about a month.

[safrole]

Jeff is right. If you're

Jeff is right. If you're not doing the actual deck, go with .010 because it's a lot friendlier to details.

Spray etchers (commercial ones) are very expensive. They go to great lengths to ensure even patterns, pressures, etc. For the ones I burn, I use a bubble etcher. It's a bit of overkill, burning seven plates at once with a 1.5 hp regenerative blower. For a guy like you, you can stand there and rock a hot tray of ferric chloride back and forth for a grueling eternity and come out okay. Your real trouble is the exposure. The inconsistencies you see are probably little gooey remainders of resist that was accidentally exposed through the black of your positives. You can try shorter exposures with the same developing time or just develop longer and scrub harder afterward. You always have to scrub vigorously with a vegetable brush or similar. Look for a consistent shine in the exposed brass. Dull areas must be scratched with a razor blade. Not fun at all.

Screen print guys can get away with laser printers and OHP film or better yet vellum just for purpose of making positives. Toner particles all have the same electrical charge going down, so they repel one another and that doesn't promote solid coverage. My laser has a setting for OHP film and then it tries to really cake it on, but it's still not good. That "posi-black" or "toner buddy" stuff is just repackaged clear spraypaint, you can tell by the smell - very distinctive. It also doesn't help much.

I would advise you to cover your brass with clean-lifting blue 3M masking tape, then hand cut your designs with a razor blade and just forego photoresist altogether. Better yet, you can go to a sign shop and get some spray mask sheet which will be in one piece. Then you start with your through-holes, etch until it eats in about half way, then pull it out and wash it off. Cut the detail-only items in and put it back in to finish.

Thinner brass will eliminate your inconsistencies and physical masking can (if the art can be hand cut) solve your film troubles.

Service bureaus will want $50 or so to print your files, and that's only after you convince them the file is perfect and they won't have to mess with it.

[safrole]

Oh, and if you're making

Oh, and if you're making something good for your sub, you can be sure someone else will want it, too. Those people can "chip in" by buying it from you later, it's more than fair. Don't worry about offending me. You as might as well burn 50 as to burn one, after all the trouble you go through.

[rdx*]

Safrole> Do you spray your

[color=#000000]Safrole> Do you spray your photo resist?
If so how do you prepare the brass before?

Do you spray thick or thin?

When I etch I use HCL, H2O2, H2O 1]

[safrole]

Formerly I bubbled all the

Formerly I bubbled all the plates in FeCl2. Now I hire out the etching to a shop that uses FeCl2 in rotary spray machines. I still do prototype work myself, but not the production runs.

Your HCl/H2O2 etching is essentially the same thing, just slower. FeCl2 in water will dissociate to form Fe(OH)3 and HCl. Depending on the strength of your hydrogen peroxide (28%?) you may be forming a bit of perchloric acid, but probably at your specified concentrations the peroxide is just donating oxygen to prolong the activity of the acid. I wouldn't bother with that, since having ferric ions in solution is so much more efficient. They go down to ferrous ions, but turn the copper metal into cuprous ions, which then go into solution. Once the solution starts to slow down, you add muriatic (about 10% by volume) and the ferrous go up to ferric again, and the new cuprous ions also go up to their cupric state, so you're all brand new again.

This is why ferric chloride solution smells like muriatic acid, because it is. Some people use H2O2 to recharge their solution, since it adds no more metal content, but still oxidizes all the ions. You can get 28% from the pool store as clarifier for non-chlorine pools, in case you want to go that route. Be careful because perchlorate gasses are noxious. BTW Vendors who think FeCl2 is not "earth-friendly" are just ignorant or have an angle. You can recharge it with muriatic acid, it doesn't give off nasty gasses, doesn't "go thermal" with uncontrolled exothermic reactions, and is not a poison of groundwater. In fact it's used as a flocculant at water plants, and used to clean arsenic from contaminated soil. It's really what you want to use if your small-time like me. Don't get me wrong, you don't want to drink it or anything, but it is exactly as if you had put some iron nails into a bucket of muriatic acid and let it sit until dissolved. It's as "friendly" as any etchant is going to get.

Don't try to build a spray etcher unless you're only doing small pieces, like 6"x6" or so. The technical headache of making an even spray pattern with multpile nozzles is daunting at best. You can get chemically resistant pumps, plastic full cone spray nozzles, etc, but in the end the bubble etcher is very even and very "low tech". (KISS)

Call me sometime or email me and I'll talk with you about it. I find all the aspects of it very engaging.