etching pcb's

[p.larner]

just wondered if anyone has tried floating a container with the board+ etchant in a heated ultrasonic cleaner?

[liaifat85]

This idea never really crossed my mind. Let's see if else somebody tried.

[Gyro]

The ultrasonic cavitation is going to attack the solder resist and the copper surface being etched equally. I would expect the soft solder resist to start breaking down quite quickly but I've not tried it.

[jpanhalt]

Your success may depend on the etchant you plan to use.  Peroxide/HCl etchants may behave quite differently than ferric chloride.  Which etchant do you plan to use?

[shapirus]

I had this idea, but never tried it, as it was never really required. The H2O2 + citric acid etchant works quite fine as it is, even with little agitation of the solution in the process.

[Gyro]

Your success may depend on the etchant you plan to use.  Peroxide/HCl etchants may behave quite differently than ferric chloride.  Which etchant do you plan to use?

Specified in another of the mess of new threads... https://www.eevblog.com/forum/projects/diy-etching-pcbs/

[jpanhalt]

Thank you for the edification.  Peroxide/HCl is not something I would toss blithely into an ultrasonic.  It is quite reactive, and in my experience attacks photoresist even when cool.  I never tried it with toner. 

[Terry Bites]

Acid in the sizzler, nah.
12% Ebay HPeroxide + HCl drain cleaner in equal volumes.
Works fast even when cold and with only very mild agiatation. Don't take your eyes off the bath or you'll find all your copper gone!
Dilute to taste.

~2 min for a 160mm eurocard!
 

[shapirus]

HCl drain cleaner

Huh? I had no idea it was used as drain cleaner. I wouldn't want any acid in my drain pipes where it could come in contact with metals. Sodium hydroxide is a different story (and it's good at destroying fat, hair and such), and that's what you'll find in your generic "drain cleaner" product. No?

[Jwillis]

HCl drain cleaner

Huh? I had no idea it was used as drain cleaner. I wouldn't want any acid in my drain pipes where it could come in contact with metals. Sodium hydroxide is a different story (and it's good at destroying fat, hair and such), and that's what you'll find in your generic "drain cleaner" product. No?

HCL is Hydrogen Chloride which is a GAS.  An aqueous solution of Hydrogen Chloride (HCl) is Hydrochloric acid or commonly know as Muratic acid. Commonly used to remove calcium and or sodium  deposits (skale) on porcelain and pipes.   

Acid "drain cleaners" are usually Sulfuric acid (H2S04). Which is far more reactive than Hydrochloric acid.

[p.larner]

i find the hydrogen peroxide and acid mix works well but very slow when used a few times,but heating it up in the microwave helps speed it up,hence the original queston as most cleaners are heated,i need to try it in my ultrasonic cleaner and see,need to float a container in the cleaners fluid holding the pcb to be etched tho as i guess the acid mix would eat the stainless cleaner tank.

[MarkT]

HCl gas will corrode your microwave oven, its not a good idea to use gaseous acids indoors at all, but heating them is best done in a fume hood or outdoors.  In an ultrasonic bath it will atomize, gassing you with a mist of acid, not just the gas.

[Jwillis]

When you understand the chemical process then you can adjust the mixture to what ever etching speed works the best for you. There are two processes happening. Hydrogen peroxide is an oxidizer that is very aggressive to metals. The higher the percentage the more reactive it is. Straight HCL acid won't do much to the copper metal but does react to copper oxide aggressively.
So the hydrogen peroxide H²O² makes copper oxide from the metal, but is not soluble. The HCL reacts with the copper oxide to produce copper chloride which is soluble. This description is not perfect but generally correct.
By increasing the ratio of Hydrogen Peroxide to Hydrogen Chloride, the whole etching process speeds up. Or as Terry Bites suggested, increase the H²O² to 30%. Keep in mind that over 70% Hydrogen Peroxide is explosive.70% is used in rocket fuel. So any idea of concentrating H²O² is probably a bad idea.
I use a ratio of 2 H²O² to 1 HCL with a total volume of 750ml for large boards and a reduced volume for smaller boards. With mild agitation the process doesn't take very long. Some people use a 3 to 1 ratio, but I find that to fast and creates a rougher edge to the traces. 

[coppercone2]

you can put ferric chloride in a bag with PCB and test it. I am curious, so far nothing has been said other then maybe the resist wearing out

[Jwillis]

Ultrasonic cleaners would most likely clean the resist off before etching was complete if set to high. All I can say is to give it a try and see what happens. But if the ultrasonic cleaner is just to warm the etchant then you could just put the chemicals in a hot water bath and warm them up before mixing. But the chemical processes heats up anyway. Most of the etching I do only takes a few minutes at room temperature. So how much faster does it need to be? If your etching slows down a lot, then either the ratio is to small (less than 2:1) or the total volume for the size of the copper area is to small. The total volume of H²O² can only react with a finite amount of copper. If the etchant turns a very dark green to almost black during the process, theirs not enough total volume of solution for the amount of copper.

[coppercone2]

there may be a pulse setting etc that helps the process. it would be bomb if you can use that instead of the bubbles