Homebrew PCBs

--- 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