Author Topic: PCB etching, DIY (chemistry mostly)  (Read 2402 times)

Offline afk

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PCB etching, DIY (chemistry mostly)
« on: April 11, 2017, 01:45:02 PM »
Hi guys,

Not so relevant to our usual high voltage stuffs, I'd like to consult you about etching PCB via chemical process (which is cheap!)

Though I'm not really good with chemistry, luckily for PCB etching it is not about organic chemistry (yay).

I am using Copper (II) Chloride solution by using Hydrochloric Acid taking copper directly from the board, with hydrogen peroxide as oxidizer. As you know, CuCl2 takes copper from the board to become Cupric Chloride. This solution can be reusable by bubbling air (oxygen) into the solution with more Hydrochloric Acid, turning CuCl back to CuCl2.

However, the etching speed is really slow. It took me 10 hours to clear up around 9 cm² of copper, which is so darn long. I even had to heat the solution up but it did not speed up much. On the copper tracks that needs removing, it turns dark-colored and it seems that I have to rub them off to speed up the etching (I suspect this is copper oxide that is resulted from copper and peroxide, but it is strange as it isn't solved by acid). It is very time-consuming and inconvenient. Even worse, the longer I leave the PCB in, the chemicals will start to attack the part that I don't want to be removed.

I don't etch PCB much, but I sometimes have to do it, so I need to improve my solution for my future usage. Some DIY sites don't have much information to solve this problem for me; their etching speed doesn't look this long.

Anyone here can help me with this problem?

Offline Mads Barnkob

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Re: PCB etching, DIY (chemistry mostly)
« Reply #1 on: April 11, 2017, 10:36:57 PM »
I only know your problems from using a too thin, saturated or cold Iron(III) chloride / ferric chloride solution.

They are weak acids for copper etching, but they are also relatively harmless, but will colour your clothes for life :) I have a solution that I have been using for years and with the small amount of boards I etch, its still the most cheap way.

I recently bought some Sodium persulfate, but have not yet tried it out.

I will make a thread on toner transfer method and etching later when I have time
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Offline futurist

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Re: PCB etching, DIY (chemistry mostly)
« Reply #2 on: April 12, 2017, 02:12:03 AM »
I etched my PCBs in hydrochloric acid/hydrogen peroxide mixture which went down the drain after each use
Recovery isn't worth the trouble, you probably won't etch that many PCBs and both of the chemicals are cheap as hell

Unfortunately I can't find the ratio I used, but you could experiment with various ones found on the internet
Etching solutions are easy to debug; when I had problems (etching taking too long, copper delaminating, etc.) I would make small dummy boards with lines of various thickness, to avoid ruining real ones

Offline afk

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Re: PCB etching, DIY (chemistry mostly)
« Reply #3 on: April 13, 2017, 07:09:40 AM »
I etched my PCBs in hydrochloric acid/hydrogen peroxide mixture which went down the drain after each use
Recovery isn't worth the trouble, you probably won't etch that many PCBs and both of the chemicals are cheap as hell

Unfortunately I can't find the ratio I used, but you could experiment with various ones found on the internet
Etching solutions are easy to debug; when I had problems (etching taking too long, copper delaminating, etc.) I would make small dummy boards with lines of various thickness, to avoid ruining real ones

I use CuCl2 not for recovery, but mostly to avoid treating the waste by reusing the chemicals again.

You are using HCl and H2O2 like me, and adding CuCl/CuCl2 as the products of etching, it sounds like a good way to destroy your drain system. I don't know about your drain system, but most drainage pipes are made of copper, and this mixture can "etch" your pipe, wearing them down fast.

Copper in CuCl/CuCl2 are also toxic and harmful to the environment; dumping it into your drain or into your garden without treating is bad.

Since there is no dedicated service for treating chemical waste in where I live, I have to take care of everything.

Offline futurist

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Re: PCB etching, DIY (chemistry mostly)
« Reply #4 on: April 13, 2017, 01:56:05 PM »
Don't worry about copper waste, it isn't mercury.. 1 oz PCB has ~300 g/m^2 of copper, so common 10x10 cm PCB has just 3 g of copper - and you don't etch all of it
And as far as I know drain pipes were never made out of copper.. you will more likely damage the plumbing and environment with acidic/caustic drain cleaners than with diluted etching solution

Offline Morvandium

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Re: PCB etching, DIY (chemistry mostly)
« Reply #5 on: July 10, 2020, 11:06:07 PM »
And as far as I know drain pipes were never made out of copper.

Plumbers started using copper drain line (in the US) in the 1930s (plumbers preferred it to much heavier cast-iron), though copper really didn't catch on until the '60s for drain lines.  I've read Chicago required them at least as recently as 2006.  There's 20+feet of copper drain line in my basement (the rest was cast iron, but my repairs are PVC), and it was built in the '70s.

Don't know about other parts of the world.

Offline klugesmith

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Re: PCB etching, DIY (chemistry mostly)
« Reply #6 on: July 10, 2020, 11:35:05 PM »
Copper drains are uncommon in my California experience, except in expensive rain gutter systems.  The associated pipes and fittings (type DWV, even thinner than type M) are easy to get.
https://www.plumbingsupplynow.com/fittings/copper-dwv/

I remember when they stopped selling copper sulfate, for pouring down the drain to kill tree roots in clay drain pipes underground.  Now industrial printed circuit fabricators need to reclaim the copper from used etchant.  On a hobby scale, I think copper from DIY circuit boards is minor, like silver from DIY photo developing once upon a time, and tin-lead solder waste into the garbage can. 

The only etchants I've used for circuit boards are ferric chloride (temperature and agitation are important) and plain salt water with electric current (can even etch stainless steel).
« Last Edit: July 11, 2020, 04:16:51 AM by klugesmith »

Online Twospoons

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Re: PCB etching, DIY (chemistry mostly)
« Reply #7 on: July 11, 2020, 01:35:07 AM »
Last time I used HCl/peroxide it went pretty fast. It does rely on good air contact though.
I've always felt the best results were from warm, fresh, agitated FeCl3. Brushing or spraying work very well.  Obvious downside is the mess - FeCl3 stains everything.
Persulfate is much cleaner, but I felt I got more pinholing with it. Its also slower, and MUST be used hot.

Spent etchant should really be processed to remove the copper - simple enough to electroplate it out.

Offline klugesmith

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Re: PCB etching, DIY (chemistry mostly)
« Reply #8 on: July 11, 2020, 04:18:29 AM »
Sort of off topic, but since we are talking about toxic metals in the drain...

California mines produced roughly 100,000 tons of mercury, starting in 1840's, of which 10% or more ended up in local and Gold Rush river beds.  From which it slowly leaches even today.
https://www.kqed.org/quest/17506/mercury-in-san-francisco-bay
« Last Edit: July 11, 2020, 07:03:52 AM by klugesmith »

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Re: PCB etching, DIY (chemistry mostly)
« Reply #8 on: July 11, 2020, 04:18:29 AM »

 


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