[Lab] Questions: 1) DIY PCB etching and 2) O-scope in lab?

Paul & Andrea Mumby themumbys at gmail.com
Wed Jan 11 13:53:10 EST 2012

Here's my comments:

FeCl3 etchant can be messy, but it's not too bad to etch with in the home
if your careful with it.

HCL+H2O2 etchant can be dangerous to mix if your not careful about it (HCL
can be nasty to get on the skin, where FeCl3 will just stain it, and
irritate it, HCL will cause major chemical burns). Once mixed the etchant
isn't that bad though. It is still a stronger acid than FeCl3, and is very
adept at dissolving proteins (flesh) so not super ideal to get on your
skin, but at least you wouldn't be etching with it at full strength
normally. Also mixing with any kind of Oxidizer (which in some cases H2O2
will act as) will gas off pure Chlorine Gas which is nasty stuff too...
Even the low concentration hardware store Muriatic Acid you would buy would
be strong enough for major chemical burns if not careful.

That said the HCL+H2O2 Etchant is cleaner for the environment, it's
renewable, and it etches a fair bit faster than FeCl3, and it's not as
sensitive to temperature.

I'm personally happy with FeCl3 in my etching, I don't heat it, I have a
fairly cool basement and I etch at ambient temperature (15C-18C) and it
takes me about 30min to etch a 4"x6" single sided PCB using the Toner
Transfer method. I use plastic tupperware containers with a nice seal to
store the etchant in, I drop the board in, seal it up good, and agitate it
by slowly rocking the container back and forth by hand. When done I use a
larger plastic tub to rinse the board off (And heavily dilute any waste
etchant) before rinsing it down the slop sink in my laundry room. I get a
couple dozen boards out of a container of etchant. Then I have to deal with
the fun of disposing of it. (Heavily diluting, and neutralizing with
diluted sodium hydroxide).

Ultimately etching at home requires dangerous chemicals no matter which
method you use. Care needs to be taken in storage, use and disposal to
ensure your safety, and environmental impact.

Another much cleaner and easier option is sending the job out to be done to
a fab shop.

One affordable option is Seeedstudio. They will do boards for a great
price, and are good to deal with. Their basic service will do 5cm x 5cm
PCBs, 2 layers, with silk screen and solder mask. And it's only like $10
for 10 boards, which is $1 per board. Really it's a fantastic price. 10cm x
10cm is only $25 for 10 boards. And you get the nice professional looking
PCBs with holes drilled, solder mask, and silk screen layer on it too...

Hope that helps some.

- Paul

On Wed, Jan 11, 2012 at 12:28 PM, Darcy Whyte <darcy at siteware.com> wrote:

> I've not had boards made by mail yet. What about those boards that just
> have lots of holes? If the circuit is simple that's another way to do it.
> I'm betting someone will come forward with a suggestion of where to get a
> board made. I don't think it's very expensive.
> Another list where people are into circuit boards and stuff is
> OttawaRobotics.org.
> A metal detector is a great project to get kids into making things (and
> electronics).
> On Wed, Jan 11, 2012 at 12:22 PM, <eric.schmidt at rogers.com> wrote:
>> Thanks Darcy;
>> Yes, messy and fraught with the possibility of screwups, but I wanted us
>> to do the "full DIY" process at least once.
>> Who would you suggest for the mail-order route, though? I'm curious about
>> the cost of that option.
>> cheers,
>> Eric
>>   ------------------------------
>> *From:* Darcy Whyte <darcy at siteware.com>
>> *To:* eric.schmidt at rogers.com
>> *Sent:* Wednesday, January 11, 2012 12:08:17 PM
>> *Subject:* Re: [Lab] Questions: 1) DIY PCB etching and 2) O-scope in lab?
>> I noticed an scope in the lab
>> Are you bringing the project to the next modlab?
>>  etching sounds messy
>> Perhaps mail order can solve that one?
>> Or perhaps a DNC machine? Not the best method but it might be easier
>> On Jan 11, 2012 12:01 PM, <eric.schmidt at rogers.com> wrote:
>> So, I've bitten the bullet after lots of lurking on the list, and have
>> initiated our first "dad and kids" electronics project (ok, it'll be vastly
>> "dad with kids looking on")
>> We're going to make this metal detector:
>> http://makeprojects.com/Project/Treasure-Finder/1113/1
>> I'm just wondering how many of you have done PCB etching using the
>> toner-transfer method.
>> After going through a bunch of youtube videos on the etching process,
>> some of them mention the stinkyness/toxicity of the fumes from the acid
>> bath. I bought FeCl3 etchant from Active, but now I'm thinking that maybe
>> HCL+H202 would be better, as described here:
>> http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/
>> Regardless of etchant, though, in mid-winter, doing it in the garage is
>> probably out of the question due to the cold (or is it?) but I assume I
>> have to ventilate the heck out of whatever space we use.
>> any guidance on the etching process?
>> Next question: for this project, you need to tune the reference coil
>> using either an oscilloscope or a frequency-counting multimeter. Does the
>> Lab have either of these? Cuz I don't...
>> thanks in advance for any wisdom.
>> cheers,
>> Eric
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