--- In
Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
<lcdpublishing@y...> wrote:
> Okay,
>
> I am about to take my first "real" etching tank for a test drive
> today. There are a number of "Firsts" in this for me.
>
> 1) I am working with the powder, according to the directions, I add
> the powder to the water - 1 pound / 1/2 gallon. They caution to add
> it slowly as it could react and bubble up or get very warm. Any
> other worries at this point?
nasty stuff. wear old clothes. mix in a large vessel as splashing
and sizzling can get pretty intense if you over do it. at this point
I suspect AP will sound pretty good :) There is a non-anhydrous form
of FeCl that people have mentioned that doesn't sizzle/splash/heat but
I've never seen it.
>
> 2) I will be using a small fish tank pump and bubbler rocks to
> create a wide spread of bubbles. This will be my first time etching
> with bubbles - I expect that this will speed up the etching process?
yes, speed up some but also make it more uniform. You'll get better
speed up by heating the etchant.
>
> 3) I also have a fish tank heater. I am not sure if I will use this
> or not the first time around. However, I have read the comments " I
> am using a hacked fish tank heater to warm the solution ". This
> creates two questions for me.
>
> 3a) How hot do you need to make the solution?
>
> 3b) Do you really need to modify the heater to obtain the heat
> desired or can you use it without modification?
I use a Top Fin heater. I don't know if it's similar to yours but I
suspect they all come from the same chinese factory. There is a
mechanical stop that prevents much above 100F. You can leave it this
way and it will etch ok - about 12-15 minutes, typical. But, I like
my etchant at about 130F. I've heard of people going up to 160F but I
don't know how my plexiglass tank will take it.
You can remove the mechanical stop but there is a themo safety switch
(I don't know the correct name) that trips off at 110F. It takes
about 10 minutes to reset so I shorted it out (just twisted it) and
use a dimmer to control the temp. I'll someday build a real temp
controller for it.
>
> 4) I suspect if I use any form of metal clip to hang the circuit
> board in the tank, it will probably corrode away and "waste" the
> ferric chloride. So, I am thinking of hanging the circuit boards
> with wire (insulated), is this a good idea?
enamel coated wire is great, I use it all the time.
>
> 5) based on the above descriptions ( and any modifications you folks
> add), how long does etching take using this process? I don't want
> to over etch, and trying to see though that brown solution isn't
> very good. I will of course have to lift out the circuit board to
> check it's progress, but if someone can provide an approximate time
> that would be helpful in that I could detect if something is wrong.
some thoughts (many of which I'm sure you have figured out):
- keep your tank in a larger tub - there will be
splashes and FeCl makes a gawdawful mess.
- wear a rubberized apron (and your worst
old clothes)
- use rubberized gloves
- eye protection (the thought of a splash of FeCl
in the eye gives me the willys)
- make it easy to lift the board out with one hand
for inspection
Have fun and let us know your results
Phil