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I bought one of those etching tanks from Circuit Specialist ET20 and it recommends I use no less than 2 Liters of etchant. That's about 1/2 gallon which is over-kill for the size board I am doing. I would even say that this tank is over-kill but I have it and want to try to use it. One site recommended a 3:1 water to acid ratio I was wondering if that sounds right.
the etching tank you purchased contains an aquarium heater, which will get too hot and break if if the liquid level is under the heating element. Therefore this releatively high amount of etching solution is recommended.
The heater will become red hot heating the glass cylinder too. Causing movement of the etching solution by any means will break the cylinder at the point between "cool" and "hot".
Not using the heater the etching process takes a long time at room temperature. At 10degC it won't etch at all. (or just within a week or so).
The tank should be equipped with an air distribution frame at the bottom. This is very important for the mechanical work during etching. (The already etched copper has to be washed away by water movement to accelerate the process.)
The mixture should be 200g on 1l of water. Using 250g accelerates etching, but burries the risk of a crystallized etching solution at the tank buttum if the temperature of the solution rises above +55degC, which it does around the heater.
If cyrstallization occurs the only way to dissolve the concrete hard stuff is adding a little amount of water and lots of developer (natriumpersulfate). Do that outdoors because those two chemicals react procucing tremendeous heat and poisonous gases.
the etching tank you purchased contains an aquarium heater, which will get too hot and break if if the liquid level is under the heating element. Therefore this releatively high amount of etching solution is recommended.
The heater will become red hot heating the glass cylinder too. Causing movement of the etching solution by any means will break the cylinder at the point between "cool" and "hot".
Not using the heater the etching process takes a long time at room temperature. At 10degC it won't etch at all. (or just within a week or so).
The tank should be equipped with an air distribution frame at the bottom. This is very important for the mechanical work during etching. (The already etched copper has to be washed away by water movement to accelerate the process.)
The mixture should be 200g on 1l of water. Using 250g accelerates etching, but burries the risk of a crystallized etching solution at the tank buttum if the temperature of the solution rises above +55degC, which it does around the heater.
If cyrstallization occurs the only way to dissolve the concrete hard stuff is adding a little amount of water and lots of developer (natriumpersulfate). Do that outdoors because those two chemicals react producing tremendeous heat and poisonous gases.
I use a small (6" x 4") disposable plastic container, the sort they sell for freezing stuff. I then put 2 heaped teaspoons of Ammonium Persulphate in and add boiling water (¾" deep). The AP quickly dissolves and I float the board on the surface of the solution, copper side down. I manage this be placing a loop of masking tape on the back of the board. Five minutes later the board is complete. I throw the used liquid in the pool.
Hans,
What chemical reaction causes heat and poisonous gasses? Ammonium Persulphate + Sodium (Natrium) Persulphate shouldn't react at all.
Mike, Hans may have meant sodium hydroxide, which is one of the developers for photoresist. That would react with ammonium persulfate. It would also act to dissolve crystalline precipitates from the persulfate.
the etching tank you purchased contains an aquarium heater, which will get too hot and break if if the liquid level is under the heating element. Therefore this releatively high amount of etching solution is recommended.
The heater will become red hot heating the glass cylinder too. Causing movement of the etching solution by any means will break the cylinder at the point between "cool" and "hot".
Not using the heater the etching process takes a long time at room temperature. At 10degC it won't etch at all. (or just within a week or so).
The tank should be equipped with an air distribution frame at the bottom. This is very important for the mechanical work during etching. (The already etched copper has to be washed away by water movement to accelerate the process.)
The mixture should be 200g on 1l of water. Using 250g accelerates etching, but burries the risk of a crystallized etching solution at the tank buttum if the temperature of the solution rises above +55degC, which it does around the heater.
If cyrstallization occurs the only way to dissolve the concrete hard stuff is adding a little amount of water and lots of developer (natriumpersulfate). Do that outdoors because those two chemicals react producing tremendeous heat and poisonous gases.
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