Good Monday morning,
I won't contribute anything to gold masks and dams, but I do have some
advice regarding stencil aperture modifications. As a producer of laser cut
solder paste masks, we do have some nice software (proprietary of course, it
comes with the LPKF Laser System) that allows easy modifications of
apertures. There are several levels of changes:
1. Making an overall change of all apertures by e.g. 1 mil takes no effort
at all.
2. Making changes to individual D-codes is very easy.
3. Making changes to groups (areas) of apertures is very easy.
4. Making changes to individual apertures (same D-code) is messy. The
problem here is that you have to select individual apertures, which means
touching them, which allows one to move the aperture, to change it or to
forget it. The worst example is changing apertures for specific footprints
to home bases, because you have to select each of them and divide them into
right and left, and upper and lower homebases. Yuk, that's one where one
demands changes in the parts library, or go for the easy solution, don't use
homebases, in stead go for ovals, which falls in category 2.

Thought for the day: when I make a stencil for you, I am part of your
organization. That should mean if it takes you much longer than me to make a
common change, you should ask me to do it. Of course, it also means you
should know some about my processes. (There is probably an abbreviation for
the name of such a clever idea, like TQM or DFM or CS or whatever.)

Regards, Ahne
A-Laser, Inc (503)641-9428.


-----Original Message-----
From:   TechNet [mailto:[log in to unmask]] On Behalf Of Matthias Mansfeld
Subject:        Re: [TN] Stencils for Gold Boards -Reply

On 23 Aug 98 at 17:28, Stephen R. Gregory wrote:

> snip snap
> .....there's no mask, I'll do a 5-mil thick stencil, still do the same
> width reduction, but lengthen the aperture on the toe and heel by
> around 5-10 mils or so, that gives me some volume back that I took
> getting a thinner stencil to reduce the bridging from no damn
> dams...the over printed solder will wick back into the main fillet
> during reflow, and where it counts too, back at the heel. I leave
> the apertures 1:1 for the rest of the 50 mil pitch stuff except for
> the J-leaded parts which I lengthen too, since they need a good deal
> of solder to form their fillets.

Steve, I just wanted to ask, do you use a special CAM software for
this over/undersize black magic or is it much manual work with
D-codes editing and transcoding instead of just pressing the
"undersize button"? The SW I know mostly allows just (semi-)automatic
oversize/undersize for all selected items for which value I ever
needs. (If you dont't like "product placement", reply off-line
please)

Thanks
Matthias
-----------------------------------------------
Matthias Mansfeld Elektronik
* Printed Circuit Board Design and Assembly
Am Langhoelzl 11, D-85540 Haar, GERMANY
Phone: +49-89-4620 0937, Fax: +49-89-4620 0938
E-Mail: [log in to unmask]
Internet: http://home.t-online.de/home/matthias.mansfeld

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