Homebrew PCBs

On Wed, 07 Jun 2006 10:56:54 +0200, Andrew <andrewm1973@...> wrote:

> Ok - yeah - I suppose.  I made my CuCl in a big
> batch to the right concentration/density before
> ever using it - and that took a few days.
> If you go the HCl + H202 route you can etch
> WHILE making it.
> Question for you though.  Is it very aggressive
> on resist and does it undercut much when doing
> it like that ???
> I have found if the acid is very high in my CuCl
> I seem to get more undercut than when it is
> lower.
> Is there a disadvantage to making it as you use
> it ?  Or should I recomend that route to everyone
> that asks me ?

If you use large amounts of HCl and H2O2 it will definitely be more  
agressive. You'll tend to do that because you don't want to add stuff too  
often. But it isn't dramatic if you don't go crazy and make it too strong,  
you can definitely etch boards normally.
If your tank allows it you can start with a lower qantity so there is  
space left for it to grow. You'll also reach higher densities faster.
I started mine "from zero copper" and it worked very well. I had to add  
H2O2 each time for quite a long time, and i still need to regenerate about  
each second or third board now, the density is still way below normal.


> Yeah - If you use it a lot you don't need to
> check it every time.  Mine goes for weeks/months
> without use - so I have to check molarity/density
> almost every time before I use it. (usualy needs
> water)
>

Since i started from zero copper i have yet to reach normal density so i  
didn't add any water yet. A reason for not adding any form of copper was  
that i don't want to have to dispose of it unnecessarily.


> Ah - but I used to do my other etching inside.
> Now there is nasty HCl fumes I have to do it
> outside and wear clothes while etching.
> (maybe I am just moaning at having to wear
> clothes - I dont know)

lol, it would surely draw strange looks if you forgot the clothes while  
etching outside.
I use CuCl inside with no problems. About half a meter to the right is the  
store for thin steel round stock (welding wire, piano wire,..) A meter to  
the left are my two 7k series tek scopes (which i would probably guard  
with my life ;-) ), and so far i haven't seen any corrosion at all that i  
would attribute to it. The key is to keep the HCl molarity as low as  
possible. It will also make it less agressive to OHP pen ink. During  
etching when the bubbler is on some fumes must surely escape, but with the  
lid on most droplets seem to deposit and run back into the tank. I ran it  
closed loop for a while but the droplets would stick the valves of the air  
pump.

> But - still big thumbs up to CuCl.
> ALL you people out there - if you etch
> regularly - use it :D

I only used FeCl before, what a pain with the stain...
Also used HCl/CuCl without a permanent tank for a while, but the mesing  
about with bottles and cleaning and all really wasn't nice. It is great to  
have a tank that doesn't require any preparation or cleaning. I even made  
the PCB holder so it is operated by a lever from the outside, so i don't  
need to touch any "wet" parts or clean them.
Sure one must consider if the effort is worth it, for one board a year it  
wouldn't pay to make a tank.

ST