Cedric Sez
Saturday, January 17, 2009
Since I have clearly shown my ignorance on the finer details of how electricity behaves, I decided some time spent with the writings of Cedric Green were in order!
Instead of dwelling on all the laws and math, I read looking for clues to use in my empirical approach.
“Note that very small test plates can give a very misleading idea of how larger plates will behave, because the current intensity could be so great that grounds will be lifted and the bite will be irregular and results discouraging. So trials on small plates must be at lower voltage and current than you need use for larger plates.” ... I guess that plates of 4 square inches qualify as small test plates.
“....with 6 cm. (2.5") between plate and grid.” ... 2 inches is probably a good place to be located.
“The galv-etch process is unforgiving about carelessly grounded or ill-treated plates.” ... at some point I may have to introduce a different photo resist system as a variable.
“If the ground shows signs of breaking up, then the amperage must be reduced.” ... well, my ground clearly breaks up under certain conditions.
“The use of a very low amperage and voltage is advisable only if one is using a fragile resist on a very small plate.” ... small plate sounds familiar.
I got small plates.
I am lifting the resist (grounds)
I am using the recommended distance
I need to reduce the current flowing.
Unless I hear a really nifty suggestion, I think I am heading to a set of experiments that:
1. holds distance at 2 inches
2. varies current (by using the current controlled function of my power supply) from .05 to .25 amps.
3. comprehends the fact that the etch depth is going to be proportional to the amperage so time is going to have to be introduced in some clever way. I’ll probably run to 1 hour and measure etch depth and quality of etch and then continue until failure and record that info as well.
It would seem from Cedric Green’s notes that when I reduced voltage, I should have seen a change in amperage. I did not see that happen as amperage was constant. That little detail bothers me but I will press on with the path described.
