H2O2 + HCl + H20 + Cu = AWESOME!
Ok, I’m not a chemist. In school, I was a bit of a chemistry nerd, but, I’ve forgotten everything. However, as stated in my previous post, I’m not excited about the trace results from milling PCBs. So, etchant is in order. But, who wants to use ferric chloride to etch PCBs? The stuff is nasty and has to be disposed in a controlled environment. So, what is the solution? GOOGLE TO THE RESCUE!
I ran across this Instructible: http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!–A-better-etc/.
It describes how to make a reusable and renewable etchant, cupric chloride. A trip to Walmart by Julie for hydrogen peroxide and a trip to the hardware store for hydrochloric acid is really all it takes, if you have enough other stuff saved at home. (Chugs, you can show this to Pam to illustrate the importance of holding onto things). I had a couple of unused plastic paint trays for mixing and used an old glass for measuring.
I used a 2:1 ratio for making the etchant, H2O2 to HCl. I detected no fumes from this process, but chlorine gas while etching is quite possible, so this should be done in a well ventilated area, i.e. outside for me.
After mixing, throw in some copper clad and let it work. Hey, looky there. It works! WHOA, Sharpie works as a resist (as well as super glue remnants from gluing to the fixture). Neat, it’s green! In other words, this works. I had a bath of baking soda water to neutralize the boards when they came out (sweet, I love bubbled).
To make a long story short, I made two batches — the second was observed by Cat, who apparently, also loves bubbles. She screamed in joy, every time I made some for her to see :) The peroxide bottle was only $.88, so the rest of the peroxide went away so I could store the resulting etchant. It doesn’t allow light to enter, keeping the etchant pristine, and is easily sharpied with skull and crossbone symbols, and ominous words such as, ETCHANT and POISON!
From here on out, I’ll be drilling and milling the boards on the CNC. However, traces will be done with etchant. Sharpies will be used to secure up the vias, so no etchant eats copper away. This process will be documented later, once I’m ready. I hope to design some kind of oxygenation-agitator to go in the etch tank. Perhaps, this will connect to my Nitrox bottles at home to increase the oxygen concentration, keeping my etchant pristine for longer.