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I used ammonium persulfate back in the early 70’s for my master’s work in college making communication devices for handicapped. We etched boards that were 18” x 24” for an alternative keyboard using reed switches, plus other boards to scan the keyboard and drive a box that displaced the words on a TV. (I cannot remember the name of the controller. It was a commercial product.) The magnet was attached to a hand held pointer moved by the person using the device. It was sort of a passive “wireless” mouse. The pointer could be molded to the person’s hand shape using RTV, so the “mouse” was even ergonomic.
We built our own etch tank with bubblers out of acrylic. The boards hung vertically with the bubbles going up both sides. I like it because you could watch the progress of the etch through the solution, which was a beautiful blue hue. It was much less messy than ferric chloride and we could get it fairly easily and cheaply then. Now, I don’t know where it is as easily available.
Andrew
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Monday, March 21, 2016 4:36 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Mark-8 'Non-plated through holes' and 2 sided PCBs
Anyone here besides me ever use ammonium persulfate? When I worked in an electronics plan that was what we used to etch our boards. We would put it in a corningware baking pan and put it on a small hotplate to keep it warm. It was fairly quick depending on what concentration you used . it is an oxidixer ,mix with sugar and heat it goes boom!
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, March 20, 2016 2:53 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Mark-8 'Non-plated through holes' and 2 sided PCBs
Where is nitric acid found? Is it practical compared to HCl/H202 or FeCl?
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, March 20, 2016 2:26 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: Mark-8 'Non-plated through holes' and 2 sided PCBs
I do RF PCBs requiring micro strips etc. It must use double sided FR4 boards with consistent permittivity and very accurate trace thicknesses for impedance matching or inductance chokes.
The hackaday technique assures such results repeatably.
All acids must be handled properly, I have 30 years experience with conc. NITRIC and never a problem. HCL is also dangerous, fumes, and can emit large volumes of chlorine if it comes into contact with household ammonia cleaners.
http://www.flinnsci.com/media/396140/acidsafety.pdf
When nitric is etching copper it bubbles a bit and self stirs the mix for cleaner trace edges I have found. Also the fine even bubble generation reveals any improperly cleaned copper areas within a couple seconds. Such areas can lead to longer immersion times which will cause over etching of the properly cleaned areas. In effect it gives me quality control feedback that other etchants don't.
Further, the copper nitrate end product is beneficial to sewer systems for restricting root growth, a fungicide or as a soak for preserving outdoor wooden surfaces.