Archive of the former Yahoo!Groups mailing list: Homebrew PCBs
Subject: A Fast PCB Etching Strategy
From: ic_sizzle@...
Date: 2016-11-08
Hi there,
Newbie here.
I use FeCl etchant, poured into a (genuine, high-heat) Pyrex baking dish which I heat on an single burner electric stove.
Not very much etchant is actually required, maybe 1/2 cup? I do the heating outside, as when the etchant bath is up to temperature, it fumes. I use a hand-held (pistol type) ExeTech IR digital pyrometer (or an el-cheapo HF model) to measure the bath temperature, (which off-hand at the moment I don't remember the etching temperature?) In any case when it fumes, the acid bath is ready for etching.
Ferric Chloride (FeCl) etchant acid works great and ∗∗FAST∗∗ when hot, but there is additional little trick that speeds things up even more, and that I learned on the InterNet. Unfortunately I have forgotten the innovative fellow's name who shared his awesome technique with his fellow nettizens and me.
Wearing nitril gloves (Harbor Freight, 50 pairs for $8), the fellow immerses the to be etched PCB into the hot bath, then using a sponge sopping up hot acid, wipes the copper away on the PCB. This method removes copper so quickly, that it is mind blowing. In something like 20 ~ 45 seconds the PCB is done!! The neato thing about this, is that the acid does not have sufficient time to under-errode thin-trace resist. Really small traces can be reliably etched using this method.
After the PCB is fully etched, squeeze the acid out of the sponge, put into plastic bag for future use, pour the acid into a 'used-acid' container for future re-use (my experience is around 4 ~ 5 times and then discard). Move the etched PCB into a 5 gallon bucket filled with cold water, while still wearing the nitril gloves for removing all of the etchant.
Another technique the same fellow described, but which I have not used, involved pouring a small quantity of hot acid into double ZipLock plastic bags (previously 'breaking' the corners of the PCB to prevent bag puncturing), zip the bags shut, and then squeegying the bags until the PCBs are fully etched. Remove the PCB, zip the bags shut, throw out the bags.
I use the PCB-in-a-Box toner transfer + the green 'foils'. I have cooked up a double-sided method, that is accomplished with toner-transfer, but it is a bit involved, however, the key, is that the side to side registration works because, well there are easy to match optical alignment targets.
In any case
Cheers
ic_sizzle