At 01:12 PM 9/18/01 -0700, Brad Velander wrote:
>Abd ul-Rahman or others,
>         if I read his description correctly he is trying to do a plated
>mounting hole with additional vias within the diameter of the larger pad for
>the plated thru-hole. I am guess that he is trying to make this as a
>component for simple re-use.

Of course. Since Protel does not automatically same-net pads or other 
primitives in contact within a footprint (I can even think of why it should 
not), it will be necessary to manually edit them to assign them the right 
net (if they are pads, the update command will not assign nets to them, I 
forget about other primitives). It is probably better not to use pads but 
use vias instead, as others have suggested, unless one has multiple pads on 
the schematic, or all the pads have the same name.

>         The reasoning that I have heard behind doing this is to make the
>plated through hole more reliable. The reliability is greater when the screw
>may wear away or break the mounting hole plated barrel. The copper top and
>bottom is still connected via the plated vias. This is also a common
>practice in high freq. microwave applications where ground must be
>maintained as ground by repetitive via stitching, every 50 - 100 mils in
>some cases.

Yes, screws can break that hole wall, especially if the PCB is repeatedly 
installed and removed.

I'm a little skeptical about the high-frequency application of this with 
respect to mounting holes, one simply adds the vias as independent 
primitives not as part of a footprint. But a mounting hole on a power 
transistor tab, perhaps one would want to make those vias part of the 
footprint. The copper should be a fill or the like; certainly the holes 
should not overlap and they should have a certain minimum distance between 
them.


[EMAIL PROTECTED]
Abdulrahman Lomax
Easthampton, Massachusetts USA


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