[dorkbotsea-blabber] Soldering station + PCB ?

Kevin Purcell 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  
considerations.

<http://www.opencircuits.com/Dead_bug_style>

<http://www.dummies.com/WileyCDA/DummiesArticle/Building-a-Circuit- 
Dead-Bug-Style.id-5881.html>

<http://www.geofex.com/Article_Folders/deadbug/deadbug.htm>

<http://en.wikipedia.org/wiki/Point-to-point_construction>

"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.

<http://www.k8iqy.com/>

<http://www.aoc.nrao.edu/~pharden/hobby/Hobby.shtml>
<http://www.aoc.nrao.edu/~pharden/hobby/HG-MANHAT1.pdf>
<http://www.aoc.nrao.edu/~pharden/hobby/HG-MANHAT2.pdf>

<http://www.k7qo.net/manart.pdf>
<http://home.wanadoo.nl/cmulder/nc20.htm>

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- 
> effective
> technique is to use a sponge. Etching (at the molecular level) is
> near-instantaneous, the long etching times are due to precipitant  
> blocking
> the process. Etchant agitators and bubblers are used to move the  
> precipitate
> out of the way so the acid can contact the copper. Problem is, they  
> require
> 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,  
> goggles,
> GOOD AIR CIRCULATION and, of course, some etchant) to pour some  
> etchant (I
> use Ferric Chloride since it is more aggressive) into a small  
> plastic/glass
> dish, dip a piece of sponge in it and rub the sponge on your board.  
> The
> rubbing action both applies etchant to the board AND moves the  
> precipitant
> 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  
> your
> resist to be rather sturdy to resist (heh) the abrasion of the sponge.
> Resist pens wipe right off - use acrylic. Oh yeah - ferric Chloride  
> (FeCl3),
> 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  
> mess.

-...-
73 DE N7WIM / G8UDP
Kevin Purcell
kevinpurcell at pobox.com





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