[sdiy] Audio circuits and basicelectronics knowledge recommendation.

[rsdio at audiobanshee.com]

Why is hydrochloric acid better than ferric chloride? I've long had the impression that HCl is highly dangerous.

The active agent is the chlorine, which wants to bind with copper more than iron (ferrous) molecules (or hydrogen?). Some chlorine is always released in the process, even though it wants the copper. The ferric chloride does leave behind a lot of iron.


By the way, Chris, lasers aren't bad at cutting PCB copper at all, provided that the setup is designed for it. The LPKF Protolaser S makes fast work of it, but there is a hood that would stop any reflections. Of course, many people cut shiny materials like plexiglass with lasers, so there's always a need to protect against reflections.


On Mar 3, 2016, at 7:30 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
> Don't use ferric chloride.  Use a combination of hydrochloric (or muriatic) acid and a splash of high-strength hydrogen peroxide (25% H2O2 can be bought at most health food stores).  Once you've etched a couple of boards in this solution, it starts to turn emerald green.  I just pour the solution (which I store in a 1-Litre brown bottle) into a pyrex glass dish in my laundry-room basin, then I put on one rubber glove and swish the PCB in the solution until it is etched.  No heaters, no bubbling.  It takes about 3 or 4 minutes of swishing to finish the etching.  It is pretty gentle and doesn't over etch.  I've used the same solution for six years.  I just occasionally add a splash of acid, and every time I add a couple teaspoons of peroxide (which I keep in the second fridge in the laundry room).  Some of the solution sloshes out of the dish and goes down the drain, or sometimes the bottle overflows slightly when refilling it after the etch.  Just flush it with some water from the tap.  It won't hurt your pipes, and it's not particularly noxious at the water treatment plant, especially since only a few teaspoons of it are going down the drain.  It just contains a bit of cupric chloride.
> 
>> From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Chris Juried
>> Sent: Thursday, March 03, 2016 2:50 AM
>> 
>> That's the process I have been using for some time now. I would like to get away from using ferric chloride. 
>>  
>> From: Gordonjcp <gordonjcp at gjcp.net>
>> Sent: Thursday, March 3, 2016 3:17 AM
>> 
>> On Wed, Mar 02, 2016 at 11:37:58PM +0000, Chris Juried wrote:
>> > I would love to get my hands on a laser cuter for prototyping. Any idea what these are running, on the entry level machines?
>> > 
>> 
>> Laser cutters aren't great at making PCBs because copper is shiny.  What you want is a laser *printer*, some press'n'peel and a couple of quid's worth of chemicals in a sealable tub like a Chinese takeaway container.
>>