Steve,

I keep hearing some vendors of ceramic SMT capacitor mfg's
say things like keeping a min. space requirement you just
mentioned.

In reality, I see no product follows the min space req
recommended by cap mfg's.  It is a waste of board real
estate.  And cap mfg's are not familiar with SMT
manufacturing process, and they are not sure about the
quality of ceramic cap's that they manufacture.  I had few
experiences of cracked ceramic cap's from mechanical
stress caused by Pick'n Place machine nozzles and chucks,
or sometimes by thermal shocks.  In these instances, the
problem was solved by replacing with a diff brand of cap's or
a diff batch.  Rarely did I have the problem from breaking
boards away from panel.

5mm (0.2") clearance gap recommendation by cap mfg's is
not practical in board design & assembly and I say it is
absurd.

Just my opinion.
Matthew


>>> Steve Collins <[log in to unmask]> December
19, 1997  9:24 am >>>
If the board is scored and uses SM Capacitors check with
your component
vendor. We have had two vendors here in house in the last
couple of months
and both say that the recommended spacing is .200 from
scored edges and the
same for the area around the tabs on routed boards. Like you
I agree that
this is way too much real estate to lose, but this type of
component is are
very susceptible to cracking from thermal stress and
mechanical stresses
more so than SM Resistors.

Steve Collins
PCB Design Supervisor
Antec Network Technologies
----------
> From: JoAnn Amerson <[log in to unmask]>
> To: [log in to unmask]
> Subject: Re: [TN] Design:Component pad
> Date: Friday, December 19, 1997 3:07 AM
>
> > Could someone be kind enough to tell me
> > what is the minimum distance between the
> > edge of pcb and the end of pad on a
> > panelized board ? IPC -std ?
> >
>
> We do not use IPC standards here but we use .040" from
the board edge if
it's
> scored and .020" if it's routed.  I personally feel that's
waaaaay too
much
> real estate to throw away but it wasn't my decision.
Anyone care to help
me
> get this changed?  All help is appreciated.
>
> Happy Holidays!  *<():-)>
>
> JoAnn L. Amerson
> Design Librarian
> Red Lion Controls, Inc.
> E-mail: [log in to unmask]
> Voice: (717) 767-6961 ext 6308
>
>
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