Homebrew PCBs

In a message dated 10/13/2003 4:19:10 PM Central Standard Time, 
pminmo@charter.net writes:
What temperature does Ferric chloride need to be heated too for 
improved etch times?
Phil: 

I have not yet read others' opinions, but I use the nasty stuff (FeCl³) for 
ALL my "one-each" non-PTH work, and HERE's your answer:  Room temperature 
"works", if kinda slowly.  If you heat the stuff before use, 50°C will make it work 
MUCH faster.  I'd be afraid to go OVER that, not so much because it may-well 
then exude noxious fumes, but because it'd melt the adhesive of the resists, 
and then it'd eat EVERYTHING off your blank!

If you MUST use a microwave to warm the etchant, know this:  The stuff is 
VERY electrically-conductive, thus the first few mm. of it work as a "radio-freq. 
shield", so only that first few mm. get hot!  The container will quickly get 
too hot to hold, so, "nuke" it for, say, 15 sec., then stop and "swish" it 
around a bit, and nuke it another 15 sec.  Do this for a total of a minute, until 
you know "what works", and then increase the total time "per the math", if 
necessary.  BE VERY CAREFUL!  If the container breaks open and spills that nasty 
yellow stuff all down your wife's white kitchen-furniture and the insides of 
HER microwave, I don't wanna be in the same State!  

Jan Rowland


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