PC Board Etchant Neutralizer

I never used this method, but this is interesting.

Where did you find or hear about this method? Did you find a product or posting on the internet? Could you share the source of your information? If it was a product could you share the product name, manufacturers name, etc?

Thanks,

It was something I picked up on "Google PC board fabrication"...

On the printout I made, the formula was about page 5 of 21.

I have not tried it as yet, but it looks like 1 part muriatic acid (28% HCl) as found in the hardware store and 2 parts Hydrogen Peroxide (3% H₂O₂) as found in the drug store. Title on this part of the web page is "NEW ETCHANT UPDATE". I would read the article before trying it though. I gather the fumes are a bit wicked.

Bill

Let me try and get the web page.

Lime or soda-ash would be a better less "caustic" choices.

In California, sodium hydroxide (lye) has been taken off the ordinary market. I use it to cure olives, and have had to go to significant effort to obtain it!

I was going to suggest ammonium perchlorate, which I used once many years ago. But I now see it is rocket propellant. Doubtful a good idea, but it works great!

Hi,

as long as we used this etchant we used it until the HCl was exhausted by sipwise adding concentrated (35%) H2O2 that is stabilised with phosphorous acid if etch rate was too low. Then you don't need much neutralisation.

If you want to neutralise considerable amounts of acid then take chalk or marble: CaCO3, this will be decomposed to calcium-chloride and carbon-dioxide. If you don't put in powdery stuff but solid stones the reaction is slow but the bubbling will produce considerable amounts of acidic dust.

Go to the outside and try near the trees you want to burn next winter.

RHABE

Much Thanks Rhabe

So the HCl is what gets depleted. This is a low key operation in that our tank holds about a gallon (<4 liters) of etchant... so if I throw in some chalk, when we are done, I can probably throw the remnants into the sewer?

I kind of wonder what happens to the dissolved Cu. This seems to be the big complaint from the sewage people.

Bill

Hi,

make sure that the chalk is nonporous and not powdered (solid limestone will be best) else foaming and intense bubbling will occur!

If more than 1PCB/month I would join posts 7 A.G.s recommendation to get or build a CNC milling machine.

To get rid of the copper: anti algae is ok but will bring to you maybe problems if swallowing more than a few 100 µg per day. If so you should add zinc to preserve your body chemistry intact.

Better way: get some sodium-sulphide and add slowly until the black precipitate of copper-sulphide stops. Can be done with (H₂S) hydrogen-sulphide too but this is very nasty: very bad smell (the good side) and very very toxic (so the smell prevents most intoxications.) Can be prepared DIY by first burning iron filings with sulphur and then adding muriatic acid that frees the Hydrogen-sulphide as a gas. This has to be made inside a glass or plastic container and immediately let bubbling through the copper solution.

Not really recommended the procedure above unless you like to do chemical experiments.

Cleanest and best and fastest: CNC-milling.

RHABE

The question is, how many PCBs do you need each day or week. A far greener method is to use a CNC machine to make the PCBs, no etching fluid at all needed, just some tiny carbide cutter. Often used by large companies for prototypes and by small flexible companies for all production PCBs. It often faster than the inhouse etching system and FAR FAR faster than when the PCBs are to be sent out for production.....

Either buy or build your own CNC machine, there is of course a CR4 blog on this as well as there being massive amounts of info on the web.

The machine can of course do much much more than just PCBs, so it should not be a "loss" so to say......

Search on YouTube with "CNC PCB", you will get lots of hits. Here are a few examples for you:-

http://www.youtube.com/watch?v=SlGcgQJRncc

http://www.youtube.com/watch?v=yFnHlLIhdl8

http://www.youtube.com/watch?v=oEQsAi_eRAI

http://www.youtube.com/watch?v=VVZONGnSPL4

We had a small CNC PCB mill at work. Very similar to vid's posted. I'm sure a better mill might have worked, but our results on prototype SMC and RF circuit designs were very POOR.

Our designs required:

* SMC = surface mount components, typically 0805 = 80mil.(0.080") x 50mil.(0.050") or smaller

* Traces both sides with plated through vias (soldered copper eyelets did emulate this fairly well)

* 10/10 lead/trace/spacing = 10mil.(0.010") typical width and spacing on IC leads and on copper traces

* 0.062" and 0.031" thick FR4 and special microwave laminates

Our mill was difficult to setup, very slow, frequently broke the fine (10 mil.) bits, and usually left hairline copper shorts. Constant monitoring was needed to stop and reset the machine when the bits broke. In the end, we went back to our local PCB manufacturer for prototypes and actually saved time (man-hours) and money.

If your boards are single sided with through-hole components, the CNC mill could be a good option. If your boards are like ours above, don't waste your time trying to build or use a mill.

Good post, what I now say is NOT criticism. You were fully correct in all of your comments.

To the OP:-

Firstly the machine must be of reasonable quality, that almost goes without say, true for any job!

For ultra fine lands on PCBs, the really tiny bits do break easily if you a) go too deep or b) too fast or c) both!!

I personally would not use a CNC either if the gap between the lands is really really tiny, say less than 0.5 mm as a minimum.

If you can change your design (maybe use more vias for example) to allow bits of 0.5mm or larger to be used, and mill only the copper and very little board at the correct speed, then you should be fine.....copper is soft and high quality PCB material very hard on bits.

How long it takes depends on the complexity of course, and if you have a friendly PCB manufacture a few 100 yards away etc etc....but if a delivery takes days, or longer, then the CNC machine starts to look very attractive!!!

Maybe a company near you can do the milling for a test PCB and then you can judge for yourself better after seeing how long they took and how many bits etc...

Using suitably placed holes as a guide, it is generally not a problem to mill double sided if needed, but a little bit of experience there is import and clean work standards....

Best wishes to all concerned. Interesting blog!!

Andy

I have thought of building an X-Y table run by a couple of stepping motors and a drill press numerically controlled, but that project is way at the back of the stove. Most of what we do is low quantity, and to write the code for the microcontroller would require much more time than doing the board by hand.

I speculate designing one or two designs per year, and probably 10 boards maximum of each design. If things were to get really complex, or I needed say 100 boards, I do have a PCB company about 30 miles away. Biggest problem is that I would have to learn their PC design software.

Catch ya later...

Bill

Why write code, there are several free software packages around that are even used professionally, EMC2 from Sourceforge for example.

There re many more that are under $100......

You only need to make, buy or borrow the hardware and find an old PC or Laptop with a printer port......as most boards are controlled over the printer port, but some use USB and some use serial ports, EMC2 runs on all.....

There are "Instructables" and other web sites showing you how to build such a machine.....there are kits and complete machines or as parts.....take your pick....

Also look at http://www.cnczone.com/forums/

Best wishes.

Hi,

you cannot build as cheap and good as you can buy (used but fine).

We got a lot of similar equipment at www.lasermotion.com and changed in one example the DC-motors to steppers.

Steppers to be selected with minimum 10-fold the torque that is needed to enable accurate micro-step mode.

We never did write our own code, there is so much available for nearly no cost.

(I will have to look what was really used if you are interested.)

below is an example of 50 µm wide 100 µm deep fluidic channels in COC that we milled with this equipment).

RHABE

From http://www.opencircuits.com/Chemical_Etchants

Mixing about 1 part HCl (Which can be found at most hardware stores, also known as Muriatic Acid. Ask for concrete cleaner.) into 2 parts Hydrogen peroxide (normally used for cleaning cuts) you can make a fairly powerful etchant. Use gloves and don't breathe the fumes though. This will etch a 3"x5" board in less than 10 minutes. No need to heat it up. I usually like to drill a small hole through the board on a corner and thread a wire or nylon string through to help agitate / remove the board.

When the board is done etching, the etchant will probably look like green kool-aid, from the copper content in it. This stuff is highly corrosive and will burn skin, which is why you should wear gloves. But it is easy to handle, and fairly easy to dispose of. the etchant is easily deactivated with baking soda. Pour enough baking soda into it slowly (to keep it from boiling and overflowing... remember what happens with baking soda/vinegar? ya...) until it is a solid mass, then leave it in the sun to dry. You should contact your local authorities to find out what you should do with it next. Whatever you do, DO NOT dump the stuff down the drain, it will eat through your pipes just like any of the other etchants.

Alternatively, instead of disposing of the etchant, you can re-use it again and again. In fact, after etching a few boards with this solution, you will have successfully made Acid Cupric Chloride (see below).

Acid Cupric Chloride

Dead simple etchant made from ordinary, store-bought chemicals (hydrochloric acid and hydrogen peroxide). Has the advantage that it can be regenerated by bubbling oxygen/air through it, or by adding more H₂O₂. In addition, it doesn't get used up: the etchant bath simply grows with use (kind of like sourdough starter…) The used etchant also makes a great algecide/pH reducer for your pool (and a whole lot cheaper than that stuff they sell at the pool store).

What you need:

• 38% Hydrochloric Acid, HCl (available at finer hardware stores or pool supply stores as Muriatic Acid)
• 3% Hydrogen Peroxide, H₂O₂ (available from any drug store)
• Plastic or Glass Pans, Jars, and tongs (no metal)

Directions:

1. Mix your HCl and H₂O₂ 1:1 in a non-metalic container, making sure to add the acid slowly to the H₂O₂. DO NOT ADD THE H₂O₂ TO THE ACID!!!
2. After you've masked your board, dip it in the solution and constantly agitate. You should notice a dark green cloud start to come from the board almost immedately which quickly dissapears or turns lighter as it gets further from the surface of the board.
3. Etching should take about 10min depending on the temperature and how well you agitated the etchant. When all of the copper is gone, dip in water to wash off any stray etchant and stop the reaction.
4. When done etching, save used etchant in a non-metalic container and mark clearly its contents.
5. If your etchant has become a dark, murky green color, add a little bit of H₂O₂ or bubble air/O₂ through the solution to regenerate it back to a light, transparent green color.

So why throw the HCl+H₂O₂ out? When used enough times it makes an even better etchant that is even easier to regenerate?

If you must dispose of it, regular household bicarbonate of soda if added slowly will neutralize. However, the copperIII in it makes it a hazardous substance, to be handled by your local hazmat center.

Good post but one significant error, what strength of HP do you need? You need to specify 1% or 5% or whatever.....

In its stronger forms it is not easy to find/buy and can be very dangerous in itself!!!

Andy - you missed it! he did specify 3% H₂O₂.

Thanks, dirty spectacles......

Thanks a bunch Charlie!! You have me convinced!! It just so happens that my etching tank has a bubbler which came with it so I can etch boards and renew the etchant at the same time. I LIKE that idea. Also I have a few gallon jugs around so I have the perfect place to store it when not in use.

Bill

For home/hobby projects I've used Ferric Chloride and Ammonium Persulfate. (AP=Ammonium Perchlorate is the rocket fuel). The heated Persulfate worked better IMHO. This link provides some basic info.

http://www.k9spud.com/wiki/PCB:Etchants

For small amounts (couple quarts a year) of NON-COMMERCIAL disposal, I was told by local authorities (waste disposal & sewage treatment) that you could flush spent etching solution down the toilet. However, this was many years ago in a different location. Please check with your local authorities to determine PROPER disposal methods.