On Friday 25 April 2003 15:20, Byron A Jeff wrote:
> Because jumpers aren't the issue. Trying to fabricate a double sided bo=
ard
> is. The task is going to be complicated enough without having to try to=
 get
> two perfectly lined up sizes. Once I get comfortable with the PCB makin=
g
> process then I'll try to tackle double sided boards.

Sure, if you can make a board single-sided, go ahead.  But I've found it=20
almost impossible to layout any circuit I do with just one layer.  But I =
say=20
go ahead and experiment with making a few double-sided via connections on=
 the=20
board.  You can route with top layer set to N/A as far as it will go, the=
n=20
either manually route the vias on the top layer, or turn the top layer ba=
ck=20
on and let it continue.  However, use really large vias just in case.  Fe=
el=20
free to use a 1/4" via if you feel comfortable, and just drill a .025 or=20
whatever hole to fit the connection wire.

Of all the ways I've tried to line up both sides, the best and most relia=
ble=20
I've found is to add a few holes (approx 1/8") at the corners of the boar=
d,=20
make 3 transparencies (I actually use clear inkjet window decals since=20
they're self-stick) -- one for the top, and 2 for the bottom.  Put the bo=
ttom=20
one in place first and drill those corner holes.  Discard that transparen=
cy. =20
Now use the other two and align with the holes you drilled.  You can look=
 up=20
at it thru a line and you'll see the hole-center marks over each other. =20
Adjust until they're perfectly aligned.  Then expose the board, etch, etc=
 and=20
then drill the component holes.  I've tried the fold-into-an envelope met=
hod=20
of aligning the layers, also tried making a pocket out of an L-shaped pie=
ce=20
of scrap PCB with the transparencies pre-stuck and pre-aligned on, but no=
ne=20
gave me as easy and repeatable results as the drill-the-corner-holes meth=
od.

Cheers,
-Neil.

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