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New PCB etchant




 
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Author Topic: New PCB etchant  (Read 4291 times)
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VE3ELQ
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« on: January 29, 2019, 09:52:19 AM »

Since the early 60s I've made many PC boards and always used Ferric Chloride etchant despite its many downsides. The other day I stumbled across an article for an alternative home brew etchant using the readily available low cost chemicals Hydrogen Peroxide (Walmart) and Muriatic acid (Home Depot) in a 2:1 ratio.  So yesterday I mixed up a batch and etched a PCB. The results were amazing. It perfectly etched the board in about 3 minutes at room temperature no less.  This is about 5 times faster and 5 times cheaper than FC with no heating and its easy to get.  Check it out, it works fantastic. John KA1TDQ are you reading this ??

https://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

73s  Nigel
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KA0HCP
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« Reply #1 on: January 29, 2019, 04:18:09 PM »

Vinegar, table salt, H2O2 (Hydrogen Peroxide) (drugstore strength).

Salt and H2O2 are consumed in the reaction.  As the reaction slows simply add more salt and H2O2.   Flush down drain.   Use fresh H2O2, as it does age and lose strength.  Concentrated H2O2 (for faster action or economy) can be found at hair supply stores, as it is used for bleaching hair.


Works great, less chance of burning holes in clothing or carpet with Hydrochloric acid, HCl (Muriatic Acid), and no disposal issues.

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« Reply #2 on: January 29, 2019, 05:04:53 PM »

-HEAVILY EDITED-

Dragging out my college chemistry, I think this is the reaction, with corrections to above.

Cu + H2O2 + NaCl + CH3COOH  =>  CuCl + H20 + O-- (combines with Hydrogen from Vinegar as water) + CH3COONa + H+ (combines with free Oxygen to water).

- Salt, NaCl is consumed
- Vinegar, Acetic acid is consumed splitting off Hydrogen+
- Hydrogen Peroxide is split to water and Oxygen--
- products: Copper Chloride in solution (blue/green) and Sodium Acetate (clear) in resulting aqueous solution.

-Suggestion: Exact quantities are not critical, but roughly use equal parts Peroxide and Vinegar (if same concentration), dump in table salt to excess to saturate solution and have undissolved available to dissolve and react.  Stir or agitate gently.  As reaction slows add equal parts vinegar and peroxide, add salt as necessary to keep solution saturated.

Warming will speed reaction.  Per chemistry rule of thumb, increasing temperature 10C/21F degrees will roughly double reaction rate.

Safety:  Put Peroxide in container first, then Vinegar, then Salt.  Always pour "Acid Into Water"!!!

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VE3ELQ
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« Reply #3 on: January 29, 2019, 06:47:23 PM »

Vinegar, table salt, H2O2 (Hydrogen Peroxide) (drugstore strength).

Bill thanks for that.
I did see that article also, and some others, and was planning to try that as experiment #2.  But I was so impressed with the results of the first batch that I see no reason to try the vinegar method.  Yes acid need to be treated with respect as does Ferric Chloride.  It will certainly eat your shorts.   Smiley

73s  Nigel
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« Reply #4 on: January 30, 2019, 10:21:00 AM »


The vinegar + salt thing is used for rust removal... the reaction product is HCL.
Aka "Muriatic Acid"...

There's another compound, I can't recall the name at the moment, white powder, dissolves clear
and results in a fast etch with the result being copper sulfate, and being reversable with the addition of
some HCL, iirc.  Mmmm... "something persulfate"??

                               _-_-
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VE3ELQ
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« Reply #5 on: January 30, 2019, 12:26:56 PM »



There's another compound, I can't recall the name at the moment, white powder, dissolves clear
and results in a fast etch with the result being copper sulfate, and being reversable with the addition of
some HCL, iirc.  Mmmm... "something persulfate"??

                               _-_-

That's probably Ammonium Persulfate your referring to. Its quite expensive up here, much more $ than FC so never tried it or anything else but FC, until now.

Totally impressed with Hydrogen Peroxide and Muriatic acid 2:1 really works well and cheap.

73s  Nigel
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SM6OID
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« Reply #6 on: January 30, 2019, 02:11:26 PM »

Hi!

Since early 80's and up until, maybe 15 years ago, I used Hydrogen Peroxide (35% strength) and Muriatic acid when making PCB's. The problem is that nowadays I cant get Hydrogen Peroxide in any decent strength.
Simply because the reactive properties, making it suitable for making explosions...
When I started to use it, I was probably 15 o 16 years old, it was NO problem what so ever to get the chemicals.

Anyway, it was a very nice etching solution, Ferric Chloride was a pain to use. 
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« Reply #7 on: February 07, 2019, 01:07:28 PM »

Today I tried to etch a PC board using some leftover previous mix about a week old stored in a plastic bottle. After 15 minutes in the solution it failed to do anything to the copper, no apparent reaction at all.  So I mixed up a small fresh batch which worked perfectly etching the PCB in about 3.5 minutes. Seems the older mix had somehow neutralized itself and was useless. Dont understand why but from now on will mix it fresh when needed. Just a FYI.

73s Nigel
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« Reply #8 on: February 08, 2019, 11:00:54 AM »

If you want near explosive grade hydrogen peroxide the easiest, best and probably most local place for it is your local indoor nursery... Aka Hydroponic Shop.

It is used to disinfect water used in hydroponic solutions. As it destroys chlorine and chloramines in the water it gives the benefit of adding an oxygen molecule giving the water 'super oxegenated' status.

IOW, it eats everything organic in the water (in theory).

I get 30 pct H2O2 locally from California Hydroponics.


Beware, the stores that cater to '100 percent organics' may not carry it.  This is because idiots will pour it straight into their organic solution.  This eats all the nutrients.

Proper method is to fill an open bucket, add H2O2 and let it sit a couple days.  Then pump to a new bucket and mix with solution.


--Shane
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