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

Food      Living       Outside        Play        Technology       Workshop

Stop using Ferric Chloride etchant! (A better etching solution.)by The Real Elliot on December 12, 2006

Table of Contents

Stop using Ferric Chloride etchant! (A better etching solution.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro:   Stop using Ferric Chloride etchant! (A better etching solution.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1:   Ingredients: The Starter Etchant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 2:   Put the Lime in the Coconut... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 3:   Add PCB and you're Etching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 4:   Chemistry Break . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Step 5:   Save the etchant for next round. You're done. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Step 6:   Alternative (overly-complex) Method: Make Cupric Chloride Faster. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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

Intro:  Stop using Ferric Chloride etchant! (A better etching solution.)Ferric chloride is a traditional home-use circuit board etchant. It's easy enough to come by, and the Ferric by itself is no big environmental problem. However, onceyou've etched a board with it, you're left with a solution with a bunch of copper chloride in it. This dissolved copper is an environmental problem, and you can't just pour itdown the drain (legally) -- you're supposed to take it to a hazardous waste facility. (For instance: How to Dispose of Ferric Chloride in this FAQ. )

Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made inlifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)

I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)

But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.

Step 1: Ingredients: The Starter EtchantFor the starter etchant itself, you only need two ingredients: hydrochloric acid and hydrogen peroxide.

(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)

Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more thanyou'll ever, ever need.

The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.

You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.

As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)

Image Notes1. Not part of etchant, but needed for removing the etch-resist.

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

Step 2: Put the Lime in the Coconut...Measure out two quantities of hydrogen peroxide and pour it into your non-metalic container.

Measure out one quantity of hydrochloric acid and pour it in. ("Do like you oughta, add acid to water" to minimize the chance of an out-of-control exothermic reaction.)

Be careful with the acid. This stuff (at 10 molar) is strong. Mine fumed a bit when I took the cap off. Don't breathe it directly, and be sure you've opened the kitchenwindow.

The starter etchant you've just made, on the other hand, is not so bad -- around 3M HCl with a medium-strong oxidizer. I find it doesn't fume much at room temperaturewhen I'm re-using a batch.

That said, you've got to be very careful to keep it away from metal -- especially your stainless-steel kitchen sink. It'll eat the stainless coating right off. Keep plenty ofwater flowing at all times when you've got any of this (even a drop) near the sink.

Image Notes1. No joke. This stuff is STRONG!

Step 3: Add PCB and you're Etching.Toss the PCB into the solution and it'll take off.

If this is the first time you're using this batch of solution (and I presume it is), it'll etch super-fast. This small board took only 2 minutes. Yikes!

Since I use a deep container, I tend to swirl it around as it etches. This stuff is so active, though, that I'm not sure it's necessary.

Keep the window open for ventilation because the starter solution gives off a little chlorine gas. (The end-etchant gives off much, much less.)

Also, note how the etchant gets greener over time as it eats away the copper. This is good news.

What's happening is that you're dissolving the copper from the board and turning it into cupric chloride. In the long-run, the cupric chloride will be doing most of theetching (instead of requiring disposal). For now, just watch your solution turn light green. Next time you use it, the color will deepen.

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

Image Notes1. Almost done. Only a few traces of copper left.

Step 4: Chemistry Break(Note: I'm an economist, not a chemist. Please leave a comment if you've got any corrections and/or additions to this stuff!)

I stumbled on this idea when I saw this website: Etching with Air Regenerated Acid Cupric Chloride by Adam Sechelle. Cupric chloride can be re-used indefinately bytopping up the acid levels and adding oxygen (bubbled in from the atmosphere). Sounds cheap and environmentally friendly to boot.

The website's got a lot of good chemistry info on cupric chloride etching. His data on etching speeds is great, and his simple titration procedure for maintaining the acidityof the solution is pretty nice.

To make the cupric chloride solution, he dissolves a bunch of copper wire in hydrochloric acid, and mentions maybe using hydrogen peroxide to speed up the oxidation,but doesn't go into detail.

Which got me thinking. You didn't have any cupric chloride yet, but you can make it by dissolving copper. Dissolving copper is the name of the etching game. So we canmake one etchant that makes another etchant that's infinitely re-chargeable. Elegant.

Turns out that hydrochloric/peroxide is a common home-brew etchant (and I've re-re-invented the wheel, again) but I guess that people got so used to throwing awaytheir "spent" etchant that they don't think about re-using it. The whole point of this instructable is that you don't throw it away, but use the dissolved copper forevermore asyour long-run etchant.

Here's what's going on chemically:

Before there's much copper dissolved in the solution, Cu + 2 HCl + H2 O2 -> CuCl2 + 2H2 O is the dominant net reaction. That is, the extra oxygen in solution from the

peroxide is oxidizing the copper metal, in presence of the acid, to make copper (II) chloride. That's our starter etchant. The resulting CuCl2 shoud be a nice emerald

green color.

After you've dissolved a lot of copper into the solution, and used up all the peroxide, the copper chloride does most of the etching for you: CuCl2 + Cu -> 2 CuCl. That's

the end etchant.

Eventually you etch so much that you convert all the CuCl2 into CuCl, which doesn't dissolve copper (and is a yucky brown color). As long as you've got enough acid inthe solution, you can simply add more oxygen to re-oxidize the copper(I), making more copper(II) chloride and water: 2 CuCl + 2 HCl + O -> 2 CuCl2 + H2 O. And then

you can etch again.

Bottom Line:

Two things to maintain: CuCl2 levels and acid levels.

CuCl2 : After all the peroxide is used up, and the solution starts turning brownish, you'll have to add oxygen to regenerate the solution again: toss in a few more capfuls of

peroxide or bubble air through the solution or swirl it around vigorously, or just pour it into an open container and wait. It's easy to tell when you're ready to etch again,because the solution turns green.

It's also impossible to add too much oxygen by adding air, so bubble/swirl to your heart's content. If you're using peroxide to add oxygen, be sparing -- a little goes a longway, and it's mostly water so you're diluting your etchant by adding it.

Acid: Note that HCl is being consumed in the starter etchant and the regeneration reactions. So we're going to have to add a bit more acid as time goes by. If you noticethat it's harder to re-green your brown etchant, it's probably time to start thinking acid.

I've tried the titration described on Adam's site a couple times, and it's pretty easy but requires an accurate scale and pure lye (back to the hardware store...). It's easierto just toss in a capful of acid every few batches of boards, which seems to do the trick for me.

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

Step 5: Save the etchant for next round. You're done.Once you're done etching, pour the etchant back into your storage bottle, rinse off the board, flux, drill, populate, and solder.

Some final notes here:

1) You can make quite a bit of this stuff very easily, and since you're re-using it, there's no real reason to skimp; put plenty of etchant in your "tank." When you use toolittle FeCl etchant, for instance, it can get saturated with copper and slow down which can result in long etching times and pitting or undercutting or worse. When I'metching a board with copper chloride, I'll pour a couple extra inches of solution into the container. It's reusable anyway, and the extra exposure to oxygen just regeneratesit. Live large.

2) Don't make too much. As you keep re-using the solution, you're going to need to add a little more acid and a little more peroxide every once in a while. If you've got a750 milliliter container, start out with less than 500 milliliters of solution. Give yourself some room to grow over time. After all, the main point is to avoid having to disposethe copper in spent etchant.

3) If you've got too much volume of etchant (it will happen eventually) you can evaporate out the extra water by putting it in a shallow (non-metallic) pan or beaker orwhatever and letting it sit for a while. This concentrates the copper in solution, giving you a stronger etchant. It'll also re-oxidize some of the copper for you, a bonus.Remember when you're adding the peroxide that you're actually adding 97% water.

4) The linked website suggests that the acid levels in the etchant are not critical as long as there's some acid in solution to do the CuCl2 regeneration. The amount of

CuCl2 (vs CuCl) present is easy to diagnose by the color of the solution. Add oxygen to re-green, and add a bit of acid if that's not working. Worst case is that you may

have to wait a few more minutes per etch with a sub-optimal bath. This isn't rocket surgery.

5) I do have an aquarium pump ($6 at fish store) that I've used to re-activate my solution. Sometimes I'd leave it on for a few hours while I'm at work if I've been etching alot. But lately I've been lazy/impatient and tossed in a couple capfuls of peroxide. Both seem to work just fine.

6) The environmental benefit of etching with copper over ferric lies mostly in not having to dispose of the copper that comes off your boards every few times you etch.When and if you do end up with too much copper etchant, please treat it like the hazardous waste that it is -- look into your local hazardous chemical disposal options.There's no getting around the fact that copper salts are (for instance) poisonous to fish even in very dilute concentrations.

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

Image Notes1. Pretty green color means it's working. This is just from the one etching session.2. Really deep green is what you get after re-using the same 500 ml of etchant for months. Note: You probably shouldn't store etchant in food containers. I've sincelabelled this container "poisonous" and "etchant." Keep out of reach of children.

Step 6: Alternative (overly-complex) Method: Make Cupric Chloride Faster.When I originally started trying to make Cupric Chloride etchant, I hadn't thought of just using the regular procedure of etching to get there. So I deliberately dissolved abunch of copper from a wire.

I don't think it's a particularly good idea, but here's how I got to the end-stage etchant faster.

I mixed the acid/peroxide 1:1 instead of 1:2. The idea was to have a bunch of acid leftover for later regeneration. I don't think it's a good idea, and I wouldn't do it again.1:2 is probably better, and results in more copper in solution faster with less fuming.

To control the fumes, I used the patent-pending (just kidding) Two-Pint-Glass Fume-Containment-Apparatus. Pour in the peroxide, add the copper, then put one glass ontop of the other. Pour the acid down through a small gap between the two glasses and re-seal. Voila. No fumes. (See video. I think I did it with water as an example.)

I also kick-started the formation of cupric chloride by first making copper oxide, which turns to cupric chloride just in the presence of acid alone. This isn't necessary at all,but it was fun. Heat up a coil of copper wire on the stove to red-hot and you get a flakey coating of copper oxide.

Otherwise, it's basically the previous procedure, so just see the pics for notes. I wouldn't recommend it anyway. The less copper you dissolve, the less copper needs tobe (eventually?) disposed of, and the acid/peroxide etchant is plenty easy to use.

The two-cup technique is cute. I still recommend it.

Image Notes1. About this much wire. Didn't end up all dissolving anyway.

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

Image Notes1. Red hot on stove. Let it cool!

Image Notes1. Closeup of copper oxides on the wire after cooling. They're cracked b/c I re-bent the wire. Save the flakes.

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

Image Notes1. Doubled pint glasses to contain fumes

Image Notes1. Peroxide and wire first. Slide acid down between the two cups. See videodemo.

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

Image Notes1. The endpoint. All the copper in solution is spent.

Image Notes1. Capful of peroxide and it's green again.

Image Notes1. Groovy test pattern.

Image Notes1. Almost there...

Image Notes1. Done.

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

Image Notes1. Acetone bled through the paper towel and stained my countertop. Usesomething waterproof. It does come clean eventually, but the scrubbing sucks.

Image Notes1. Plenty of headroom!

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

Related Instructables

Etching a circuitwith toilet bowlcleaner byRapidMustang

1by none631

PCB EtchingSolution -Cupric Chlorideby vkoudymov

Sponge + FerricChlorideMethod -- EtchPCBs in OneMinute! byTechShopJim

HCL - EtchedAluminumCircuit Boardsby penguinjak

(easily) etchimages incopper by prank

Comments

50 comments Add Comment view all 480 comments

 kavesman1 says:  Jun 13, 2012. 12:58 AM  REPLYIve done a little research into this etchant,and i wanted to share the info i found. Most of the commerical pcb machine pdf ive seen that are setup for thissolution state that there a balance that needs to be maintained. Here are the stats on the etchant solution : Hydrogen Peroxide – 0.16 gal. of 35% H2O2,Hydrochloric Acid - 0.32 gal. of 30% HCl, and Water - 0.36 gal. for specific gravity control.

These are the Amounts to make 1 Gallon. It also said that the best rate of etching is when the concentration of dissolved copper in the solution is between125-175 grams per liter. The specific gravity range of 1.2393 to 1.3303 (28o Be to 36o Be) are when those concentrations are maintained.And the pH isabout 1 +/-.

The ORP range for the best etching is between 500-600mv, and the sensor must be platinum tip type.Any lower,and the etch rate suffers.Any higher, andthere might be a release of clorine gas from the etchant.And the best temp to maintain the etch rate is 130*F for PCV or 160*F for polypropylene sprayequipment.

There is also the Free Acid Level.This is a measure of the HCL in the etchant.To little and the etchant takes too long.Too much,and there is a risk ofundercut...or lateral etching. The specs on that is to maintain a 1-2N HCL level.

I also read somewhere that 1 gallon of etchant can hold 16oz of etched copper in solution before it starts to get overloaded. But,you can possibly doElectrolysis to recover the copper that is in the etchant.

Hope this info helps.

 abend says:  Jun 21, 2012. 12:44 PM  REPLYI gave this a shot using 30% H2O2 from a hydroponic store and HCl straight out of the bottle. The resulting solution etches about two square inches ofboard in about 3 seconds. I assume the commercial solution would be a bit slower, thanks to the water, but still pretty fast.

Unfortunately, it gets warm as it does this. If you keep etching boards in it fast enough, you can get it hot enough to boil itself, which makes a mess anddrives enough of the oxygen out that it no longer etches boards. I controlled the temperature by dropping an ice cube in every once in a while.

Gloves and goggles are a must, a fume hood would be good too.

 kavesman1 says:  Jun 22, 2012. 2:51 AM  REPLYJust read another doc on that.Since most commercial makers are using a spray setup,that would naturally cool the etchant and add the O2 back intoit. And they also have a regen electrolysis system that sometimes has a cooling loop built into it. Guess that would keep the temps in the acceptablerange.

I'm looking into getting a atomizing sprayer nozzle to see if that could help in keeping the temps down and adding the O2 back into the etchant toimprove the etching.

 Witchunter says:  Jun 19, 2012. 3:24 PM  REPLYWill 18% HCl acid work? I couldn't find anything else at the store...

 kavesman1 says:  Jun 22, 2012. 2:33 AM  REPLYI think either home depot or lowe's sells muratic acid in the pool supply area that has a concentration of 31% HCI.

 AaronM04 says:  Apr 28, 2012. 4:24 PM  REPLYI've had problems reusing the solution -- long etch times. Would it help to have an ORP (oxidation-reduction potential) meter? Would the kind used foraquariums and pools be useful for this? (they're ~$30) If not, what kind is useful?

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

 ddipschmitt says:  May 21, 2012. 10:13 AM  REPLYI use a fish tank heater and a bubbler and my average etch time is 35 min.I found I had really long etch times until I added the bubbler. Even with a temp of about 110 F it would take hours. When I built the bubbler I startedgetting good results consistently.

P.S.Try putting a penny in some solution, it's pretty strange.

 mattgilbert says:  May 19, 2012. 10:42 AM  REPLYI don't know what an ORP is, but I had the same problem until I started using an aquarium aerator. One time I had a lot of boards in a batch, and thesolution did get dark and slow, but just leaving the aerator on for a while after the boards where taken out cleared it up nicely.

 Sam Grove says:  May 11, 2012. 8:13 PM  REPLYExcept for the solder pads, the resist makes a good conformal coating for copper trace.

You can scratch through the coating on pads with your soldering iron tip and add solder or just use alcohol and a cotton swab to clear the pads.

 pcooper2 says:  May 11, 2012. 10:40 AM  REPLYTIP: Store the unused muriatic acid bottle outdoors in a shaded, ventilated area. They never seal quite right after opening, and the acid fumes will corrode allmetal in the area. You'll be sorry if you stored it in your garage or workshop near your tool chest!

I have an old ceramic toilet tank and lid in my back yard for this purpose. The tank lid sits on the ground, I put the acid bottle on it, then put the tank upsidedown on top as a cover. The flush hole and bolt holes provide some ventilation and the ceramic tank protects the plastic bottle from deterioration due tosunlight.

A 5-gallon plastic paint bucket and lid will work as well, except that the plastic will gradually embrittle with exposure to sunlight and will have to be replacedfrom time to time.

 mnand89 says:  May 9, 2012. 10:01 PM  REPLYHey I am currently doing an experiment with a copper coated silicon wafer and I am observing this problem. So I make a one pot solution of the followingchemicals DI water+ isopropanol+copper (II) chloride+ a polymer solution called Methacryloxy ethyl trimethyl ammonium chloride (METAC)+ copper(I)bromide under inert conditions purged with nitrogen gas. These chemicals are used in a process called Atomic Transfer Radical Polymerization (ATRP). Idunk my wafer coated with copper, gold and chrome and leave the sample in the solution for 2-4 hours. Once I take it out of the solution, the copper layerdisappears. So this has happened twice. I am definitely sure that this mixture is causing the copper to erode away. I have a hypothesis that the copper (I)and (II) salts are causing the oxidation of the elemental copper and it therefore mixes into the solution. Does anyone else have an idea about the chemistrybehind this predicament of mine?

 ckrause3 says:  Apr 28, 2012. 10:29 PM  REPLYThis is the best instructable I've seen on the H2O2/HCL/Cu method. I've been using FeCl2 for years. Using a sponge to wipe across the board to break thesurface tension gives me a completely etched 1/2 oz copper single side board in about 90 seconds. And now I can do it guilt free. I've been using thePulsarPro toner transfer paper for several years - take a tip from me, stop playing with magazine paper and clothes irons and go here: http://www.pcbfx.com

 Electricsrb says:  Feb 22, 2011. 8:25 AM  REPLYMine board took 8h to etch. The solution is perfect I swirl the container around, but it's taken me a loooooong time to fully etch it. Am I doing somethingwrong?

 darkwingz24 says:  Mar 1, 2012. 10:53 AM  REPLYHi,

I have been playing around with this etchant as I have used ferric chloride in the past and it stains and is a pain to dispose of (properly). I mix up thePeroxide (3% Drug store version) and Muriatic acid (Dynamic Paint Products, no %info on bottle). The Muriatic acid definitely fumes when you open thebottle so it's strong.

I mix at 2:1 Peroxide to HCL and it etches the first boards just fine (just a couple minutes). The resulting solution is a light green and after a coupleboards the colour doesn't change much and it pretty much seems to stop etching. I didn't see if it took 8 hours but after 30 min there was still copper.

I too am trying to figure out what may be going wrong. I tried adding more HCL to the bath and it didn't seem to do anything so I added some peroxide tomatch the HCL I added but no result (in the 30 min I had the board in). My etchant never gets that dark green/brown I see in your images. Any advice ortips?

Thanks!

 ptrmail says:  Mar 27, 2012. 1:14 PM  REPLYbe always sure that copper on your board is shiny (does not have an oxidized layer that will protect the copper from etchant)1. i polish it witch some polishing paste, dont forget edges2. clean the result with some alcohol or similiar to remove the paste and any smear (fingerprints), this can protect copper from etching away too, bestthing is to use gloves from this point. dont touch the copper board with your handsif it's polished and clean, its ready to be sprayed with photoresist or for hand drawing ...i do all of this and i dont have problems, i use FeCl3

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

 ecode says:  Mar 8, 2012. 4:01 PM  REPLYI have experienced the exact same thing.  After 24 hours or so it stops etching almost completely.  I believe this is due to all the oxygen leaving thesolution.  You might notice that a new batch it will form bubbles as it out-gasses.

To me the plain HCL and peroxide solution seems useless unless you're just going to use it for one day.  It won't last any time at all in this form.  Youcan't store it in an airtight container because it will explode due to pressure building (a caution many people seem to forget on pages like this).   Youcan't add more peroxide (or acid) to rejuvenate the solution because you're adding mostly water when  you do this so it just makes things worse eachtime you do it.  I can't figure out why people think it's so great.  Maybe they're just using it once or I'm doing something horribly wrong.

I think the "end" solution of cupric chloride is the only proper thing that will last.  I'm in the process of trying to make this but it's slow going anddifficult to manage.  What I did was use the same 1 part acid to 2 parts peroxide and then immediately start dissolving a specific amount of copperbased loosely on the formulas on that other page (Adam's stuff; he doesn't say how to do it with peroxide) with a bubbler in the tank.  After a coupleof days I still have a little copper left and my solution is turning brown.  My specific gravity is somewhat low so I'm hoping evaporation will improvethat.  Not sure where to go from here.  I don't know what my acid level is so I don't know if I should wait a while longer and hope it greens up with thebubbler or if I should add more acid (that will reduce my specific gravity even more, not desirable).   The hardest part of this seems to be figuring outif you need more oxygen or if the solution is out of acid because you can't tell from the color of the solution alone.   I wish a simple pH test wouldwork for the acid test, the titration procedure seems like a lot of hassle if you don't have lab equipment.

 vkoudymov says:  Mar 10, 2012. 6:29 PM  REPLYI think the trick to etching using this method is to get the copper concentration up. To do so, you need to get the copper to dissolve. Unfortunately,copper is very poor at dissolving in hydrochloric acid. However, if you can get copper oxide, that'll quickly dissolve/react in hydrochloric acid. I'veput up an instructable on how to do this. Pictured below is the final product (takes about 30 minutes of prep, 5 hours of wait time).

 ecode says:  Mar 11, 2012. 12:18 PM  REPLYYour instructable looks great.  That's definitely the way to go and I will probably use that method to increase my volume and balance myspecific gravity.

Just an update on my original solution.  Once all the solid copper was gone it almost immediately turned green.  I added more acid and didthe titration test.  I'm currently at 3 M acid (perfect) and specific gravity of 1.2 (too much water from my initial peroxide, for sure).

 The Real Elliot says:  Feb 23, 2011. 1:38 PM  REPLY8 minutes is about right. 8 hours, not so much.

What is the concentration of your acid? Is the peroxide fresh?

At this point, there's only two ingredients, so that makes troubleshooting easy....

 conmac863 says:  Feb 1, 2012. 4:52 PM  REPLYI know this is an old post but I have a question.I make the solution and put my copper (2X2 inch piece) in and it goes to town. First piece almost had to throw away because it was in there for about 20minutes and almost etched all the way through. Worked great. I have it in a tupperware type container. Next day I went to etch another piece and nothing....not even a little bubble. I let it sit for several hours and got the tiniest etch on it. Am I not storing the solution correctly or something?Thanks and awesome instructable.

 sarbot says:  Jan 29, 2012. 10:15 AM  REPLYUnfortunately, the formula you are using with "pool acid" or technical grade HCL from hardware stores is still quite heavily contaminated with iron.

It's a well known fact in the industry.

Try using lab grade HCL and see if the iron free HCL works as well - - there may be an exchange principle involving iron in the reaction.

 jaydenr says:  Jan 11, 2011. 12:10 PM  REPLYHelp, my mix just dissolves the copper. My muriatic acid doesn't tell me what percentage the acid solution is, it just says "industrial strength". will this startetching when more copper is dissolved in to it? what can i do?

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

 cincodenada says:  Jan 26, 2012. 11:37 AM  REPLY"Disolving the copper" is what it's supposed to do...that's what etching is: dissolving the unprotected copper from the board.

 TasDev says:  Oct 27, 2011. 12:29 AM  REPLYHere I go exhuming an old article but:

Excellent tips, tried it and etched a few boards with very good results and this could be the answer to my problem of now having to get Ferric Chloride(crystal form) by mail order in my locality.

Just one thing someone may be able to clear up for me though.Adding the peroxide to my HCl which is 280-300g/litre makes the etchant dark brown so there's no way to assess the 'green-ness' of the mix. Tried with 2different concentrations of standard hardware store acid with the same result but the etchant certainly does its job well so my only way of checking its statewould be via specific gravity and ph. No amount of aeration with an air pump and a porous stone makes any difference to the colour or clarity.

Is there iron or some other contaminant in my HCl?(Both the acid and the 6% peroxide appear perfectly clear & clean prior to mixing)

Also did some sample tests in test tubes with the resulting brown colour starting to develop from just a single drop of peroxide in 10ml of HCl.

 silvermoonlyn says:  Jan 20, 2012. 1:25 AM  REPLYMine went a weird rusty brown colour too. It's still working like a charm, but I have to keep checking to see how it's going. It would have been mucheasier if it was clear though. I might try and get some more hydrogen peroxide from a different source and start over. Can someone please tell me how Ishould dispose of this solution?

 rdemar says:  Nov 3, 2011. 9:47 AM  REPLYI'd also question the purity of the peroxide... Something is definitely amiss because I tried it for the first time today and the mixture remained water clearat 1 part HCl and two parts H2O2. The initial etch was just wicked fast - I had to clean the copper off a double-sided octagonal G10 copper clad plate foruse in a quadcopter build, and it mowed ass on it, was a pleasure to watch. The result was one clean fiberglass plate and a beautiful emerald greensolution. NICE. :-)

 aquietinspiration says:  Nov 30, 2011. 12:58 PM  REPLYWhat can I clean the copper plate with before ironing on my design? I have read that you can clean it with acetone and wipe it down with a paper towel butwouldn't that be dangerous since you may be mixing acetone with hydrochloric acid and peroxide??

 lee321987 says:  Jan 11, 2012. 4:34 PM  REPLYScotch Brite pads seem to work pretty good (the hard, green ones).Also, I've read that a very quick dip into etchant cleans it really good. I haven't tried that, but i do know that copper turns pink pretty fast after I put it intoetchant (I think pink means it's REALLY clean).I don't know what would help the toner adhere more though: the extreme clean of an etchant dip, or the added surface area from scuffing....???Anyway... if you do scuff it, MAKE SURE YOU CLEAN THE LEFTOVER DUST really good!

 Orngrimm says:  Jan 3, 2012. 8:54 AM  REPLYI simply rub it with a fine iron-wool-sponge-thing.I rub it till it shines really good.

Also I do the same to remove the toner i used to print the layout to the PCB.

 Pranjal Joshi says:  Dec 24, 2011. 6:38 AM  REPLYthis is quite good than stainy FeCl3...thanx.. i ll try it

 morrison427 says:  Nov 27, 2011. 10:23 AM  REPLYYou can get the initial reaction to start faster if you use a higher strength H2O2 -- like from the beauty store -- but use only a tiny bit. Otherwise it'll outgasboth excess oxygen AND chlorine for a while.

BTDT, got the acid-washed t-shirt.

Jim

 Lectric Wizard says:  Nov 25, 2011. 6:38 AM  REPLYThat should read " electro-plate other projects"

 Lectric Wizard says:  Nov 25, 2011. 6:37 AM  REPLYGREAT IDEA !!! I thought there had to be a simpler way than that used in the other instructable you mentioned. I was wondering if you could use the usedsolution to copper plate other projects ... that would be real recycling !! Thanks for the Instructable !

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

 M2Field says:  Nov 18, 2011. 2:16 PM  REPLYTo reclaim copper from "spent" solution and make the product disposable, just add excess aluminum. Foil, cans, scrap metal...

The aluminum is sacrificed to aluminum chloride and the copper is precipitated out as pure copper powder. Filter out, rinse clean and dry. Recycle at nearly$4 a pound.

Hey! At least the spent etchant is now disposable.

 ipbobcat says:  Nov 16, 2011. 10:09 AM  REPLYI want to etch brass instead of PCBs. Will this technique work with brass as well as copper since it contains zinc, etc.?

 Ninjawulluf says:  Nov 4, 2011. 5:06 AM  REPLYBe careful, those exact ingredient are used to make high explosive Acetone peroxide.http://en.wikipedia.org/wiki/Acetone_peroxide

 rdemar says:  Nov 3, 2011. 9:40 AM  REPLYWowww this is brilliant! I've been into electronic PCB fabrication since I was a teenager and all these many, many years I've basically had a love/haterelationship with Ferric Chloride. I wish I'd known about this from the start, it's fantastic! THANKS!! :-D

 escalix says:  Nov 1, 2011. 1:59 PM  REPLYhi people, i've been reading the article and the comments (seems u know a lot of chemistry) so i think that somebody could help me with my problem please,actually i drop some used ferric chloride over a concrete floor, the floor was never sealed with the expoy resin so i think it may have absorbed it, i didn'tnotice when it happened so it dry completely and now i don't know how to remove it easily. I've tried with some white vinegar and works well, not at 100%,but requires a lot of work; somebody told about the use of oxalic acid but when i ask for it at the store they tell me that is for cleaning marble so i'm not sure ifit will work, any help will be really appreciated, thanks in advance and also i will try to follow this instructable, it's a great option instead of working with ferricchloride.

 AbbieX says:  Oct 25, 2011. 8:42 PM  REPLYSo, I've etched a couple of things, and the copper came out of solution and is sitting on the bottom of the etchant tank (plastic tupperware container). Ipoured the liquid in a jar for later. What do I do with the blue residue in the bottom of the container?? Thanks, great Instructable!

 williebikes says:  Sep 7, 2011. 5:39 AM  REPLYDo you think I could use an old fish tank as my container for etching? or too big? or will the solution ruin the seals? thanks

 venture electronics says:  Oct 5, 2011. 12:07 PM  REPLYI used an old plastic peanut butter jar Put a prop from a video card on a small motor then hot glue it through the lid and your in buisness. I have doneover 50 boards this way with great success.

 Sparticles says:  Sep 21, 2011. 8:12 AM  REPLYFINALLY! I did it!

Almoast 2 months of trying, I have dozens of failed ones laying here but finally I made a pcb that should work.

My times are extremely long!30 minutes lighting (blacklight)two hours developing (very strong solution of NaSiO4 (google says I should just dip it in there for a couple of seconds.... no)And finally 1,5 to 2 hours etching. (for a small board, so not the 2 minutes like this tutorial the concentration was 23% HCL )

Also it etched unevenly , some parts are nice and some parts I had to scrape off copper and in other parts the traces were beginning to etch away...(next time I will try that printer method)

Don't get me wrong, I'm very pleased that it worked now, but has anyone an Idea what I'm doing wrong?

 venture electronics says:  Oct 5, 2011. 12:05 PM  REPLYThis method of etching is the best. What I did was take a small propellor off a video card and put it on a motor. This will stir the solution and you shouldhave at etch in about a half an hour. The etch always turns out evenly for me. I have tried many other methods and this one seems to work the best. Theonly problem I had was using a shiny paper for the transfer . I did finally find one. (toner method.).

 Sparticles says:  Sep 21, 2011. 8:51 AM  REPLYWhen drilling holes in it, all my copper traces fell off :(

 blinkyblinky says:  Oct 1, 2011. 8:31 PM  REPLYIf I add baking soda, it should neutralize...

It might still be poisonous, though.

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

 3spds says:  Sep 20, 2011. 7:20 PM  REPLYamazing, thank you. be sure you have removed all resist from your board where there are no tracings. when i initially tried this method i was rushed andskimped on exposure time. a nice stark contrast between resist and copper is essential! this method works much, much better than ferric chloride in myexperience. plus, it's way easier to check the status simply by shining a light up from underneath! thank you again for posting this- i'll never go back to thatfoul ochre sludge, except maybe to scare my friends...

cheers,jm

 amortenson says:  Sep 6, 2011. 11:08 PM  REPLYAny idea how I could turn this into usable copper? Was thinking of cuprous oxide photovoltaic panels. I suppose I would need a process to turn the cupricchloride into cuprous oxide and then deposit it on a base material. I was thinking glass.

 snowluck2345 says:  Sep 6, 2011. 6:50 PM  REPLYHow does this work? If I remember correctly HCL will not dissolve copper bercause of the electrochemsitry gotten from a electro pottential chart. I rememberlast year on an AP chem test one of the questions was in regards to why would HCL not dissolve copper, however H2SO4 would. I can't remember myanswer, just that it was right.

 snowluck2345 says:  Sep 6, 2011. 8:07 PM  REPLYI remembered why, Cu is less reactive than H so it is not displaced and no reaction occurs.

 0xCyrusx0 says:  Apr 6, 2011. 1:30 PM  REPLYI'm surprised nobody has mentioned this, considering the intro picture contains hydrogen peroxide, acetone and hydrochloric acid.

Careful not to mix all 3, unless you're attempting to make unstable high explosives (Acetone peroxide http://en.wikipedia.org/wiki/Acetone_peroxide).

It's dangerous enough when you're attempting to make it, I wouldn't want anyone to accidentally make some and dry out the crystals, or store it in acontainer with a screw on top (The crystals will sublime, and recrystalize in the threads on the container. Unscrewing it will break the crystals and detonate.One person on internet forums has died this way).

Besides that, I'll be using this method from now on. I already have the peroxide and acid and acetone from...other projects *Wink*

view all 480 comments