[dorkbotsea-blabber] Soldering station + PCB ?
kevinpurcell at pobox.com
Sun Jun 22 19:37:01 EDT 2008
Use a synthetic sponge for this.
Or use the "etch in a bag" to keep the amount of etchant to a minimum.
You should also be careful about dumping etchant into the swerage
system ... at the very least you should neutralize it with a base. If
you are doing large amounts dispose of the copper-loaded FeCl3 waste
responsibly. It's nasty to wild life (i.e. fish!).
For others remember there are other construction styles that work
very well for one-off or prototyping or RF (or even audio) projects:
"dead bug" style over a copper ground plane for a single point earth.
Components are soldered point to point and suspended above the ground
plane by upside-down ICs or transistors (the dead bugs) or by high
value resistors (think poor insulators!) soldered to the ground
plane. Layout comes from a mix of circuit layout plus earthing/signal
"manhattan style" with square off cuts of PCB glues down onto a
copper ground plane. ICs or transistors can be either dead bug (or
"alive bug" ... but dead bug is usually easier) and components go
from dead bugs to pads or other components.
Both are very popular with radio amateur who still build projects or
even pros who have to build a prototype or a one-off and avoid the
problems and cost of PCB layout/design and getting the layout correct.
73 Kevin N7WIM
On Jun 22, 2008, at 3:42 PM, flight wrote:
> Another tip: I can't recall where I found this but, a good cost-
> technique is to use a sponge. Etching (at the molecular level) is
> near-instantaneous, the long etching times are due to precipitant
> the process. Etchant agitators and bubblers are used to move the
> out of the way so the acid can contact the copper. Problem is, they
> a LOT of etchant. Your average PCB really only needs a few mg of
> acid to be
> etched! A good trick is (assuming you have an etching tray, gloves,
> GOOD AIR CIRCULATION and, of course, some etchant) to pour some
> etchant (I
> use Ferric Chloride since it is more aggressive) into a small
> dish, dip a piece of sponge in it and rub the sponge on your board.
> rubbing action both applies etchant to the board AND moves the
> out of the way. If your etchant is warm and the copper layer of
> your board
> isn't too thick, you can etch a board in 10-15 minutes and only use
> an ounce
> or so of etchant. The only trouble with this technique is you need
> resist to be rather sturdy to resist (heh) the abrasion of the sponge.
> Resist pens wipe right off - use acrylic. Oh yeah - ferric Chloride
> being a Lewis acid, eats cellulose. So don't leave your sponge
> sitting in it
> for long-term storage 'cause it'll turn into a nasty, gritty, goopy
73 DE N7WIM / G8UDP
kevinpurcell at pobox.com
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