Bubbles must cover entire surface of the board. So I must made many
large holes in the tube, something like 1mm diameter whith spaces
about 10mm or less.
You are wright about rates of rise. I made some experiments and large
bubbles rise verry fast and create a huge disturbance in tank. I'm
worry about this. Fast rise means faster etch in bottom area of the
board.
I think about a system to slowly rotate the board. A tiny motor...
Or orizontaly vibrating it...
Adrian
--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> Larger bubbles are supposedly required to get good scrubbing action
at the
> surface of the PCB.
> However, with my small air pump i could not produce enough large
bubbles
> in enough places, so they would rise from a few spots only and
create
> "streaks" on the board that etch much faster.
>
> Since i have the bubbler hose with many tiny bubbles the etching is
more
> even. Still not ideal 'cause large areas take longer - which could
be
> improved with more scrubbing action. Also, the smaller the bubbles
the
> slower they rise, and small bubbles will move around a lot more and
not
> just go straight up in streaks.
>
> With your large air pump i suppose big bubbles are good, if you can
create
> them in enough places so no streaks are visible.
> I reckon a moving air source would make things much easier to get
even,
> maybe a tube with a spiral pattern of many holes, that is rotated
slowly
> by the air in some way would be possible.
>
> ST
>
> On Thu, 22 Dec 2005 06:39:43 +0100, adicont2 <adicont2@y...> wrote:
>
> > I search messages arhive on this subject and no concludent result.
> >
> > Opinions are very diferent: 1mm holes at 2,5 mm space-large
bubbles or
> >
> > aquarium tipe aerator whith millions of little bubles.
> >
> >
> > I have a 200x200x30mm etching tank and I use FeCl. I made a heater
> >
> > from a 4mm PVC hose aranged on entire surface of tank. Something
like
> >
> > this
> >
> > __________
> >
> > __________|
> >
> > |__________
> >
> > __________|
> >
> > |__________
> >
> >
> > The hose is conected to my sower hose, so the temperature is fully
> >
> > ajustable. A simple and safe device...
> >
> > I allso have a very powerfull air pump so I can generate a lot of
air.
> >
> >
> >
> > Adrian
> >
> >
>