ferric chloride?

[fogwolf]

For those who etch your own boards, where do buy your ferric chloride? I got some in a kit from Small Bear and was lucky enough to find one at a Radio Shack but they don't stock it any more and Small Bear doesn't sell it without a kit. I even called Injectorall directly (the brand Small Bear sends with their PCB etching kits) but they are only wholesale so it was way too expensive. Can't seem to find the stuff from any of the suppliers I order from.

Much appreciated.

[timehawk]

A good alternative I tried yesterday was 2 parts hydrogen peroxide and 1 part multiac acid (forget the exact name) mixed together.  I couldn't find any place to get ferric chloride either.  It etched all the copper away with no problems.

You can get the peroxide at any drug store, and I got the acid at a  local Canadian tire, I think its used to clean cement.

[cheeb]

The radio shack near me always has it, and copper clad board. I'm near one of the good ones.

[The Iron Chef]

I bought the kit from small bear.  Then, I found a fresh gallon at work  . Now I just buy lotsa P n P

[sixstringphil]

I know this doesn't answer your question, but I bought the last bottle my Radio Shack stocked about 2 years ago.  Unless I ordered it, none of the other places around me carried it either. I've also switched to muriatic acid/peroxide because it's so much easier (and CHEAPER) to find.

[Zben3129]

I, too, have switched to muriatic acid and hydrogen peroxide.

Muriatic (Hydrochloric) acid is easy to find at any hardware store, I buy mine 1 gallon at a time for 6 bucks. Try beating that in FeCl.

Also, muriatic acid is clear, so you can watch the progress of your board without having to take it out of the solution. Another plus about muriatic being clear is that it doesn't stain, and ferric stains like CRAZY.

Zach

[fogwolf]

Thanks for the info on the muriatic acid. So does it take about the same amount of time to etch as ferric chloride? Also, what about disposal (being ecologically considerate) - do you add baking soda like ferric chloride? Anything else to consider or know about etching with this versus ferric chloride?

[kurtlives]

I take big 3L jugs of it as I need it from my school's tech room

[timehawk]

It should be safe to pour down the drain with water.  Its used as a cleaner and sometimes in swimming pools.

[Zben3129]

Reguarding pouring down the drain, I wouldn't.

Apart from being bad for the environment, it can also eat your pipes. Pipes can be (and almost always are) made of copper, the same thing you are using the acid to eat off the circuit board.

I have found that the muriatic acid mix works just as fast if not faster than ferric, aswell.

Reguarding the baking soda, what that does is neutralize the acid. However, while that solves for the most part the eating the pipes issue, it still leaves all of the harmful poisons that are made during the etching process. So, if you don't mind polluting  than i guess baking soda might work, though i've never tried it.

I bring mine to the transfer station and give it to the hazardous waste guy.


Zach

P.S. if you do decide to pour the muriatic out down the drain, DO NOT do this in any kind of metal sink, as it will corrode it almost instantly, or take the finish off etc. Put it down a porcelain sink or toilet

[fogwolf]

Wonder if that means by dumping all my solid ferric chloride (post neutralizing) in the garbage means I haven't been 100% safe about it. I understood it that once you neutralized it the solid waste left behind was harmless so I've just been tossing it into the garbage outside. Yikes, how do you find a transfer station and a hazardous waste guy in your area?

[R.G.]

Sorry. I get tired of internet wisdom. The stories just get passed around and get bigger and more interesting as they go. Getting to the facts is always tough.

Whenever you etch a circuit board, you are doing inorganic chemistry. That means, amongst other things, that the processes are simple, have few variants and run to completion based on the available constituents.

When you combine FeCl and Cu in a water bath, you get CuCl (copper chloride), iron, iron oxide (rust) and the water back. Most FeCl baths manage to also evolve some hypochlorous (not hydrochloric) acid; the fumes are irritating, but they are not free chlorine gas. FeCl is a much less active and less aggressive acidic bath than, say, hydrocholoric (muriatic) acid or sulphuric acid. FeCl stains clothes and skin, and makes for irritated eyes. The "poisons" which FeCl evolves are copper chloride. Period. Copper compounds are modestly toxic, but common in the environment. It is impossible to get something like botulina toxin made in the dish. You can only get out combinations of what you started with.

Most sewer pipes in the USA since the 1960s are PVC, which is inert to FeCl and CuCl. Come to think of it, HCl and H2SO4, too. Before that they were often cast iron, about 1/4" thick walls. I have personally placed and fitted cast iron sewer pipe, and it's tough stuff. FeCl in water would have a tough time getting through the layer of organic gook that's already in place inside every sewer pipe that's been in place over a month.

Drinking water pipes are usually copper up to about 1990, then they started changing over to PVC and PEX. It is substantially impossible to get any etchant back into your drinking water supply lines. If you did, the pipes are about 0.050" thick. The copper on a PCB is typically one ounce per square foot, which works out to 0.0014" thick. That is, copper supply lines are on the order of thirty six times as thick as the copper on a PCB. And, being water lines, there is excess water in there that would thin down any etchant that you got in there *even if you could get etchant in there* which you can't.

Hydrochloric and sulphuric acids EAT clothes, skin, and eyes and do it quickly. They are vividly dangerous to handle, all on their own. Add to that hydrogen peroxide, which is a stronger oxidizer than chlorine in equal concentrations and you get something that you really ought to think twice about. The result of HCL eating copper is... yep, water and CuCl. All you're sidestepping is the iron. Same "poison" as FeCl turns out. And the rest of that aggressive acid in the bath. Sulphuric/peroxide gives water, H2SO4, an assortment of the lesser H2S's, and CuS, copper sulphate. And the rest of that aggressive acid in the bath.

There is a real advantage to clear baths if you don't have standardized baths and good timing, in that you can see when the copper's gone. You can get the same advantage with ammonium persulphate, which is less aggressive and dangerous to handle than the strong acid baths.

NONE of these etching baths is particularly good for you. But FeCl is less dangerous to handle and store than the strong acid concoctions.

Remember that when you accidentally splash.

[chassit]

Wonder if that means by dumping all my solid ferric chloride (post neutralizing) in the garbage means I haven't been 100% safe about it. I understood it that once you neutralized it the solid waste left behind was harmless so I've just been tossing it into the garbage outside. Yikes, how do you find a transfer station and a hazardous waste guy in your area?

Heavy metals including Cu leach out very easily from land fills. But is still far better than pouring down the sink. Where I work, we have copper and acid disposal services. I would talk to local college chemistry and environmental science departments about hazardous waste. If it isn't much they may even take it for you (you may be more likely to get away with this if you contact a grad student in the department). At the very least every one of these departments has a chemical safety officer who can point you in the right direction.

[Zben3129]

Hydrochloric and sulphuric acids EAT clothes, skin, and eyes and do it quickly. They are vividly dangerous to handle, all on their own. Add to that hydrogen peroxide, which is a stronger oxidizer than chlorine in equal concentrations and you get something that you really ought to think twice about. The result of HCL eating copper is... yep, water and CuCl. All you're sidestepping is the iron. Same "poison" as FeCl turns out. And the rest of that aggressive acid in the bath. Sulphuric/peroxide gives water, H2SO4, an assortment of the lesser H2S's, and CuS, copper sulphate. And the rest of that aggressive acid in the bath.

While hydrochloric acid will eat clothes, skin, and blind you almost instantly in high concentrations, the storebought products will not to do this (aslong as you don't soak in it for hours).  I work with chemicals a lot, and HCl can be nearly harmless, or deadly in minutes, depending on the concentration. When I work with 0.1M (around store bought concentration) hydrochloric acid, I do so at a counter, and get it on my hands, and wash them off after. When I work with 40% HCl, I use a fume hood / protective gloves / sealing goggles / mask etc, as simply breathing this stuff can essentially dissolve your lungs. If you dunk your hand in storebought muriatic acid (HCl), and then take it out and rinse it off, the effects are going to be minor itching/stinging on any open wounds you have, and a slight chance of some itching on your hand. The rumors everyone hears of Hydrochloric being the all-dissolving acid are far from true in this case. In terms of eyes, this stuff is still dangerous to get in your eyes, so take caution (not that FeCl is good in your eyes either).

As for drinking this stuff (little kids, pets, etc.), HIGHLY DANGEROUS!!! MAKE SURE IT IS IN A SAFE PLACE. Again, same goes for FeCl, except a clear bottle of liquid may be confusable for a child, whereas a bottle of black liquid doesn't resemble a common drink.


Zach

[R.G.]

While hydrochloric acid will eat clothes, skin, and blind you almost instantly in high concentrations, the storebought products will not to do this (aslong as you don't soak in it for hours). 

That's good to know. I don't follow the concentrations of the store-bought stuff. I simply have the strong acids marked on my list of "Rattlesnakes in that bottle". I do remember that the HCl from some pool supply places can get pretty stout. The variant used for cleaning concrete at HD is likely to not be as dangerous.

Of course, sufficient dilution will cut down the damage; works with nearly anything dangerous except plutonium and polonium dust... 

I work with chemicals a lot, and HCl can be nearly harmless, or deadly in minutes, depending on the concentration.

It is, after all, what we produce in our stomachs to digest food. 

The details do matter.

The rumors everyone hears of Hydrochloric being the all-dissolving acid are far from true in this case. In terms of eyes, this stuff is still dangerous to get in your eyes, so take caution (not that FeCl is good in your eyes either).

After risking my vision throughout most of my misspent youth, I found that Harbor Freight sells a full-face shield for under $15, and after kicking myself solidly in the pants for a while bought two.  Felt downright stupid for being so reckless for so long.

As for drinking this stuff (little kids, pets, etc.), HIGHLY DANGEROUS!!! MAKE SURE IT IS IN A SAFE PLACE. Again, same goes for FeCl, except a clear bottle of liquid may be confusable for a child, whereas a bottle of black liquid doesn't resemble a common drink.

Well, there's Coca-Cola.

[Zben3129]

I work with chemicals a lot, and HCl can be nearly harmless, or deadly in minutes, depending on the concentration.

It is, after all, what we produce in our stomachs to digest food. 

Crazy that whats already in there will kill you if you drink it   

As for drinking this stuff (little kids, pets, etc.), HIGHLY DANGEROUS!!! MAKE SURE IT IS IN A SAFE PLACE. Again, same goes for FeCl, except a clear bottle of liquid may be confusable for a child, whereas a bottle of black liquid doesn't resemble a common drink.

Well, there's Coca-Cola.

Ah yes of course, how did I forget Coke! Though if I opened a bottle of FeCl and it hissed like soda and was bubbling I would run away    Time to go grab a pepsi!



Zach