Guys,
Looking at the issue long term I use 3 types.
Why? Well If I use a 1 next to pin 1 on the silk,
I can easily remove it using "alter"
I use the standard "arc" on packages as well
as the square pin1 (On externals only)
Pad 1 is easy enough to change, but have never had that problem.
For extremely close boards You may need to remove the 1 from
the silk. (many use a square box, which is by standard, better, but
for accel and the non-windowable "alter" the 1 was preferred)
Sometimes the silk outline is hidden.
The use of all three takes the most work, but long term is the most
practical.
I gathered this from the 300 different designer's boards that came
across my desk as a cam guy.
Hope this helps.
Chris Robertson
[log in to unmask]
> Hi Jerry,
>
> I've always used silkscreen markings for SMD pin 1s. In ALL the
> companies I've worked it's always been that way. I've heard the opinion
> of using the padshape (as Harris does) to visualize pin 1s, but I've
> never seen it in practice. With tighter densities you just have to be
> extra careful of moving them around in the end so they make sense to the
> assembly folks, and that they don't get covered up or just plain removed
> by the CAM folk (like when an indicator is over a test point pad/via).
>
> Hope this helps.
>
> Mitch
>
> >
> > > All,
> > >
> > > Do any of you use some kind of pin 1 indicators built
> into your smd
> > pads
> > > ?
> > > For example using a pad with an extra tab or an oblong pad.
> > > Could you please tell me why this is done at your
> company and if you
> > > have had any problems
> > > with fabricators testing these designs ?
> > >
> > > Background:
> > > Yes, we add tabs on pin 1 pads at Harris. We have had
> problems with
> > > some testing houses on fine pitch devices because the offset in
> this pad can
> > > cause the test
> > > probe to not hit the pad properly. We are considering
> alternatives but would
> > > like to hear what
> > > other companies think and do.
> > >
> > >
> > > Regards,
> > >
> > > Jerry Schwartz, CID
> > > IPC Certified Interconnect Designer
> > > "May the Schwartz be with you"
> > >
> > > Jerry Schwartz, CID Designer 3
> > > Harris Corporation GCSD Voice (321)-727-5474
> > > P.O. Box 37, MS 1/9843 Fax (321)-729-5990
> > > Melbourne, FL 32902-0037 Pager (321)-690-9797
> > > mailto:[log in to unmask]
> > > http://harris.com
> > >
> > >
> >
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