Warning: These reactions uses corrosive acids, gloves should be worn.
Additionally some produce toxic gases and should be performed outside or in a fume hood.
Greetings fellow nerds.
In this video we’re going to show how to make ten etchants for copper printed circuit boards.
Some are better than others but since you, my viewers, are worldwide
you will have to choose which ones you can make with your locally available materials.
I recommend trying a few different ones and finally settling on the one that works best for you.
Now I know there are a lot more etchants out there that I have not listed here
like persulfate and permanganate based etchants but I’ve selected these ones as being the most straightforward to make.
So let’s get started.
First in the peroxide family of etchants is hydrogen peroxide along with an equal amount of concentrated hydrochloric acid.
This etches pretty easily and is the most popular homemade etching solution.
What’s happening is the hydrogen peroxide is oxidizing the copper
and reacting with hydrochloric acid to produce copper chloride.
A disadvantage of this etchant is that it decays and unused etchant loses strength in storage.
But a great thing about this etchant is that it makes useful copper chloride
that can be used as another type of etchant that I’ll detail later on in the video.
The second peroxide family etchant is hydrogen peroxide and sulfuric acid.
This also etches rather quickly and produces less fumes than the hydrochloric acid version.
What’s happening is the hydrogen peroxide is oxidizing the copper and reacting with sulfuric to produce copper sulfate.
Like other peroxide etchants this one also decays in storage and loses strength.
But an advantage of this method is that the copper sulfate can be converted back into sulfuric acid and copper metal.
Making this etchant very easy to recycle.
The third peroxide family etchant is hydrogen peroxide and sodium bisulfate.
Sodium bisulfate is a little easier to get than sulfuric acid as it’s sold as a pH lowering chemical for swimming pools.
It works like the sulfuric acid version and produces a combination of copper sulfate and sodium sulfate.
The downside is that it is extremely slow. And takes hours to do what the other etchants can do in minutes.
Another disadvantage is that unused etchant also decays in storage.
Nonetheless it’s very easy to make. It can also be electrochemically recycled.
Now we start the metal chloride family of etchants and the first and most famous member is ferric chloride.
I already have a separate video on exactly how to make it so i won’t repeat it here.
The chemistry works by oxidizing the copper to copper chloride while the ferric chloride is reduced to ferrous chloride.
A great advantage is it does not decay in storage and unused etchant can last indefinitely in an airtight container.
Recycling is possible but requires extra chemicals and a lot of effort. It might be more straightforward to dispose of it.
The second metal chloride family etchant is copper chloride and hydrochloric acid.
You can simply evaporate or boil down the spent peroxide and hydrochloric acid etchant from earlier
into a highly concentrated solution, or react fresh copper chloride with hydrochloric acid.
The hydrochloric acid is necessary since it reacts with the copper chloride to make tetrachlorocopper ions.
It is these ions that react with copper and comproportionate into dichlorocopper ions.
The great advantage of this etchant is that it can be easily regenerated by bubbling in air.
In fact in storage it not only lasts indefinitely but actually regains strength as it absorbs air.
So it’s even easier to recycle than the sulfuric acid based etchants.
I’ll do a whole video on the chemistry of copper chloride etchants so to keep this video short i’ll stop here
The third metal chloride family etchant is copper sulfate and hydrochloric acid.
This is actually an alternative way to make the tetrachlorocopper ions.
The sulfate ions don’t interfere and the reaction works much the same way.
It can be stored indefinitely and can also be regenerated by air and recycled just as easily.
This is useful for those of you who can’t get hydrogen peroxide to make pure copper chloride.
The next family is the chlorine family of etchants.
So named because they produce chlorine so you have to use these either outside or in a fume hood.
The first is hydrochloric acid and bleach.
It works by reacting with copper and producing copper chloride and sodium chloride.
While not very efficient if you have little else this might be your only choice.
Like i said before this will also produce chlorine gas so be careful.
It also decays in storage so unused etchant loses strength.
This etchant can technically be regenerated and recycled but doing so is so expensive and complicated
that you’d probably be better off starting with one of the metal chloride etchants.
It’s thus more economical to simply dispose of this etchant if you're using it.
The second chlorine family etchant is manganese dioxide and hydrochloric acid.
The manganese dioxide can be obtained from zinc-carbon type batteries.
Whoa, that almost got away from me there.
As you can see the initial burst of chlorine can splatter the chemicals so be careful.
This method works by reacting with copper and producing manganese chloride and copper chloride.
Of course this also makes chlorine as seen earlier.
Like other chlorine etchants it is unstable in storage and will decay.
As with the bleach version recycling is possible but not economical and should simply be disposed of.
The nitrate family of etchants begins with the simplest nitrate source, dilute nitric acid.
This reacts with the copper to produce copper nitrate and nitrogen monoxide.
Nitrogen monoxide is quite toxic so this must be done outside or in a fume hood.
When the etchant stops working it can be boosted with sulfuric acid to reactivate the remaining nitric acid.
After all the nitric acid is depleted the etchant is dead and the copper sulfate can be electrochemically recycled.
Unused etchant can be stored indefinitely without losing strength.
The last etchant is a mixture of a nitrate salt like potassium nitrate and hydrochloric acid.
This is actually a crude version of aqua regia and can even etch gold if you’re so inclined.
The reaction produces copper chloride as well as side products and by products of metal salts,
nitrogen monoxide, chlorine and nitrosyl chloride gases.
This definetely needs to be performed outside or in a fume hood.
The etchant is also unstable in storage and recycling is also not economical.
So there you have it, ten ways to etch copper printed circuit boards.
Now after you’ve depleted your etchants you’ll eventually end up with copper containing chemical waste
that’s horrible for the environment and likely illegal where you live to simply dump down the sink.
But I’ll show methods of recycling, reprocessing and disposal in a later video.
Thanks for watching.
In this video we’re going to chemically process various etchants for safe disposal and recycle or regenerate those that are feasible to do so.
In this video we're going to make ferric chloride. A useful chemical to etch copper clad printed circuit boards.