I make my own pcb boards, and chemical of choice for etching is a very concentrated solution of ferric chloride, I use a pyrex glass dish and a tiny aquarium heater to heat it, I also use a air pump and air stone, to lift the ferric chloride via a pipe, and wash it over the board to be etched.
I have built a small extractor cupboard for fume extraction, It all works great! I am happy, but I got to thinking, how can you measure when the solution needs changing?? and what can you do to extend the life of it.
So far I have come up with the following, all of t is purely at the design stage, so comments welcome.
I figured best way was to measure the conductivity, my thinking goes like this, ferric chloride will start to conduct more as more copper Ions dissolve in the solution, at some point there will be a point that the reaction is too slow to be useful, so measure how much copper is dissolved by how much the solution conducts. First problem I can think of is what electrodes to use! I dont fancy gold, so decided on graphite from a pencil (very thin one), these shouldn't react at all, have a set distance between 2 electrodes, push a current through and measure, my main concern is gasses like chlorine, but if I use very low voltage and current (500mV 10mA), then that shouldnt be a problem, and everything is done in fume cupboard anyway. Pulse the current say every 10 mins for a second or so and measure the strength, then output to a DAC then to a analogue meter.
As too how to rejuvenate the solution I am working on that with my chemistry teacher .
So apart from it being a bit bonkers and pointless what do you think?
I have built a small extractor cupboard for fume extraction, It all works great! I am happy, but I got to thinking, how can you measure when the solution needs changing?? and what can you do to extend the life of it.
So far I have come up with the following, all of t is purely at the design stage, so comments welcome.
I figured best way was to measure the conductivity, my thinking goes like this, ferric chloride will start to conduct more as more copper Ions dissolve in the solution, at some point there will be a point that the reaction is too slow to be useful, so measure how much copper is dissolved by how much the solution conducts. First problem I can think of is what electrodes to use! I dont fancy gold, so decided on graphite from a pencil (very thin one), these shouldn't react at all, have a set distance between 2 electrodes, push a current through and measure, my main concern is gasses like chlorine, but if I use very low voltage and current (500mV 10mA), then that shouldnt be a problem, and everything is done in fume cupboard anyway. Pulse the current say every 10 mins for a second or so and measure the strength, then output to a DAC then to a analogue meter.
As too how to rejuvenate the solution I am working on that with my chemistry teacher .
So apart from it being a bit bonkers and pointless what do you think?