Etching Machine - Current vs Voltage

[cschulte88]

Hello All,

I recently built my own etching machine using plans that I found online. I can switch between 12V and 24V and between AC and DC. I have been pleased with the results but I am looking to be able to fine tune my Amps and Voltage to get the best etch I can. I am looking into voltage dividers and current dividers to building into my unit to control this. I was hoping to get some help from anyone that may know best way to accomplish this. I just ordered a 1k Ohm Pot and a 10k Pot to do some experiments with. I will try to share the results of the testing here. In the mean time if you know anything about what voltage/current settings are best for etching please share! I am using quality stencils and electrolyte solution.

 

[Ken H>]

The current is a function of voltage, AND the concentration of the etching solution, which can to some extent affect the resistance. With the normal etching voltages (18 to 24vdc) and normal etching solution, you will find the current measuring in the mA range. Too much current and the stencil will get too hot.

 

[Callum.D]

You seem to misunderstand some of the concepts of electrics (don't worry, everyone does). Current simply refers to the amount of electrons passing through the circuit per second, one ampere is equal to one coulomb of charge per second (6.24 quintillion electrons per second). The amount of current in a circuit depends entirely on the electromotive force (voltage) applied across the circuit by your supply. The fundamental equation you need to understand is V/R=I, that is that current is equal to the voltage divided by the resistance.

To use a practical analogy, imagine a pipe filled with ping pong balls. By applying a force to at one end of the tube you are able to push the whole stack of balls along, by applying more force the balls are accelerated to a higher speed and more balls will fall out of the end of the tube per second. In this analogy each ball can represent a coulomb of charge and the pushing force you apply represents the electromotive force (voltage). As you can see the more force you apply the more balls move through the tube per second, conversely, in a circuit the more voltage you have across a wire the more current you will get through it. Using this analogy we can also understand resistance as the friction of the ping pong balls against the tube. Imagine you have two tubes, one very tight and dry, the other smooth and lubricated. In the smooth tube you don't have to push very hard at all to achieve a high ping pong ball current, this is because the force that resists the movement of the ping pong balls is very small and so it is very easy to push them through a tube. However in the other, rough tube the ping pong balls have to be pushed very hard to have them move at the same rate because the resisting force is very high. In a circuit the same principles apply according to I=V/R; higher voltage-higher current; higher resistance- lower current.

Its been a while since I took chemistry (I'm majoring in physics and engineering) but according to my understanding, in the context of etching, the relationship is very simple. Basically the more voltage you apply across the electrodes the faster the reaction will occur. As I understand it, the voltage potential between the electrodes shifts the reaction equilibrium causing a reduction/oxidation reaction at each electrode. As Ken H points out a higher concentration of etchant solution will also increase the speed of the reaction since more ions will be moving and reacting at a given time.

Basically, in the end, you are really trying to find out what rate of reaction is the best for your desired results. I'd experiment with trying a bunch of different voltages and enchant concentrations to work out what works best (channel those high school science fair vibes!)

If you need any help with circuitry or something else physics related feel free to reach out to me.