On Sat, 02 Dec 2006 22:46:24 +0100, DJ Delorie <
dj@...> wrote:
>> Someone recently posted PICs about using CNC drilled brass for
>> stencils. The holes are of course round but that is not a problem.
> "Plus, I don't have drills small enough for the SMD pads."
>
Some people have so many they sell them. ;-)
>> How much are you going to do? You know you can just bulk-paste a row of
>> pins with a bead over all of them?
> Yeah, I've done that for TQFPs but the next project has an SMD
> connector with the pins underneath, if there's shorts I won't be able
> to see or fix them.
ouch.
> The paste for that is about 11x40 mils, far from
> round. So I want to be very careful about putting the right amount of
> paste in the right place.
> Plus I have a hard time making a bead narrow enough for 0.5mm parts
> without lots of bridges.
Does the connector have air between the pins or is the space filled? I
have found that the flush packages like a QFN actually repell bridges
between pins, those were much easier than they looked.
I'm not sure about this etching business quite frankly. I doubt it will
work well without pro etching equipment you'll see lotsa undercut with the
thick stencils. It might also be extremely tricky to align two sides of TT
precisely enough for the doublesided version you described, since laser
printers have distortion.
Someone here does etch brass sheet for model railroads, i hope he speaks
up.
ST