what do you think is the best chemical to use for pcb etching?

 

HYDROFLORIC ACID!!!! :shock:

No just kidding. That stuff is extremely nasty and requires a bunch of control measures and PPE (Personal Protective Equipment).

I use Ferric Chloride and I like it because it is cheap, widely available at a lot of electronics stores, and is somewhat docile to the home electronics buff. I haven't had any problems associated with the Ferric Chloride. It etches nicely at a warm temperature and produces some good resulting PCB's. It is also reusable to a point. I haven't reached a point where my old ferric chloride wont etch, so I don't know what the life-span is.

 

i use ferric chloride aswell. was just wondering if anyone used something which lasts longer/etches faster etc

 

Alright, I did a little bit of research at MG Chemicals, who produces the three common copper etching solutions.
Website here:
http://www.mgchemicals.com/products/410.html

Some simple facts about the etching solutions:
1. Ferric Chloride
A. Stated as providing a more consistent etch than Ammonium Persulfate
B. Stated as etching twice as fast than Ammonium Persulfate
C. Roughly 10-20 minute etching time.
D. Will not remove most etch resist inks.

2. Ammonium Persulfate
A. Translucent liquid allows the user to see the progress of the etching process.
B. Roughly 30 minute etching time.
C. No flash point stated on MSDS, so it is not directly flammable.
D. May remove some etch resist inks. Must use a compatible etch resist pen.

3. Sodium Persulphate
A. Flash point at 180 deg F. FLAMMABLE!
B. The solution is shock sensitive
C. Solution decomposes when heated.
D. Cleaner solution, allows increased visibility during etching.
E. Will not remove most etch resist ink.
F. Must be stored in a ventilated container due to gasseous nature.

So it looks like Ferric Chloride is the most common, most stable, Most docile and consistent etchant solution.

 

I use Sodium Persulphate and have good luck. I use a toner transfer method, and tuch up with a sharpe, but the etch will sometime eat though the marker. put hot water in a ziplock bag and mix in chemical, and swish.
Very clean chemical.

Have fun

 

hcl + h2o2 + h2o

 

i used ammonium persulphate, it's quite clean, but once you heat it with water it starts to decompose...kind of expensive seeing i have little money to spend.

Ferric Chloride is quite good as you can use over and over if you run electricity through the used etchant. (electrolysis) the copper simply builds up over the terminals and the etchant regains it's corrosive form again.

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I haven't ever performed the electrolysis on Ferric Chloride. What kind of voltage and amperage do you use to perform this? Any special procedures?

Thsi process would be extremely helpful, considering most regulations wont allow you to dispose the Ferric Chloride down the sewer due to the copper content. The regulations that I have read instruct to remove the copper, add baking soda in order to even out the PH level to around 7, and then flush into the sewer.

Thanks for the great idea!

 

but then if it was corrosive again you wudnt need 2 get rid of it down the sewer

 

Good point. ops:

 

no i mean that you can use it over and over again, and keep on etching boards with the same etchant!

Seeing that copper has an atomic positive charge, the copper will build up on the negative terminal.(like charges repel, different charges atract.)
I dont know what voltages are needed but, the amount of current doesn't really matter if you have all the time in the world. I'm guessing any where like 12v and over.

honestly though, i have never tried it myself, but theoretically it seems correct. (well to me)

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Yeah, but isn't the anode going to corrode? I seem to recall I used ferric chloride to electrically etch (on purpose) even a stainless steel spoon once.

Now you can definitely use the board itself as an anode, and get really fast etch times. As the traces form, they'll become isolated from the anode connection and stop this effect in places one by one. Moreover, the point where you'd electrically connect the power supply is very difficult to protect from corrosion unless it's totally out of the solution.

 

I know that it is corrosive even in its weak used up form, but platinum doesn't react with it. The reaction of corrosion occurs because the FeCl exchanges elcetrons with the steel to form a chemical bond. (rust)

But if we place a charge on the terminals, the FeCl will be repelled but the copper will be attracted to the terminals. Then you have FeCl just sitting in the tank. As soon as you switch off the power, the FeCl starts eating the copper coating on the terminal.

Switching the power back on would reverse this reaction.

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