piclist 2001\03\28\180849a >
Thread: Homemade PCB fabrication
picon face BY : mike@corn2.freeserve.co.uk

On  at , Jinx wrote:

> From:                 Jinx <EraseMEjoecolquittTakeThisOuTspamCLEAR.NET.NZ>
> Subject:              Re: [EE]: Homemade PCB fabrication
> To:                   RemoveMEPICLISTspamBeGonespamRemoveMEMITVMA.MIT.EDU
> > From: Simon
> > I'd like to know how you guys do your PCB at home ?
> > Tell me how
There are less ways to skin a cat, but here's how I do it for double
sided boards.

I use EAGLE pcb program ( http://www.cadsoft.de )
Ferric chloride in a double bath. the inner bath has the ferric and
the outer bath has tap hot water to raise the FeCl temp.

design the board using eagle, but hand route the vias so that
component leads can be used instead, but don't have a top track
going to an IC socket, its difficult to solder to the top of an IC socket
pin ;-)

print out the drawings of the layout
1. the top track, with pads
2 the bottom track with pads ( invert the printout to get the correct
3, the top , just the pads
4, the silk and pads

trim the pads printout to the pcb size.
attach firmly to the board to be etched. then using a .05mm drill in a
pinchuck or, as I do, in a homemade pillar drill built from a cassette
player motor, a pin chuck and some scrap aluminium,  drill out all
the pad holes.

using a very fine grit "wet and dry" abrasive paper remove the burrs
from the pcb, thouroughly de-grease the board with Carbon
Tetrochloride or similar, dont touch the board after cleaning.

Then using a Staedler Lumocolour 313 pen with an "S" nib
( a permenent marker pen used for overhead transparencies,
available in UK at any W H Smiths for about 60p ) draw the pads
around the drilled holes. Then, referring to the relevant printout of
the top or bottom tracks draw in the interconnecting tracks. If you
make an error you can remove the ink with a cotton bud and some
Carbon Tet.

when the tracks are laid out, take a break for a coffee, then re-
check your work for errors and rectify if nessesary.

put about 1/2" of FeCl in the inner bath ( I use a plastic icecream
tub of dimentions about 5" wide x 9" long x 4" high with a resealable
lid) put the inner bath in the outer bath and carefully fill the outer
bath with hot water until the level is sufficient to float the inner tub a
little bit. wait a few mins for the FeCl to raise its temprature to that of
the surrounding water.

Using two plastic PCB guides on the edges of the pcb held in place
with a rubber band , (guides are from an old XT case ) to prevent
the pcb from rubbing the bottom of the bath, place the pcb in the
FeCl and agitate by rocking the inner. within a few seconds you will
see the copper turn pink. carefully remove the board, rinse it in
running water and then visually check that you hav'nt left any
whiskers of resist. replace the pcb in the bath and agitate until the
copper has all gone, then agitate further for about 30 seconds to
ensure the copper is all gone.

wash the pcb in running water, KEEP AWAY from any metal fittings
in the sink, the FeCl in minute quantities will attack the chrome and
wreak havoc with the wifes workplace.
remove the resist with Carbon Tet and burnish with the wet and dry.
all done.. visually check for shorts before building the project using
the printouts of the tracks and silk layers to orientate yourself.
ensure you solder to the top where nessesary for the pseudo vias

with care I can put a track between 0.1 spaced pads without
problems using the mentioned pen. I have also made a PCB for the
AD9850 with its 0.025" spaced pins using this method, but it was a
bugger to do.

hope all this typing was useful to someone.

The usual Caveats apply with regard to FeCl, Carbon Tet, Nicotine,
Caffine etc.

atb Mike W
"Smile" said the Lord, "things could be worse"
so I did, and they were ;-(

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