Brad
You are correct as usual, but may have overlooked one aspect.
If this is a mounting hole(where there can multiple installation and
removals of the screws),
it could break the barrel of the via. Not to bad for a double sided pcb, but
terrible for a
multilayer. If the inner layers are planes connected to different screw
terminals, scrap the board.
I use this a lot on switch mode power supplies.
Bob Fearon
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.
> 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.
> I have similar structures in my library but they do not work as
> fluidly as I would like so I have waiting for other responses to find out if
> there is a better way myself.
>
> Brad Velander,
> Lead PCB Designer,
> Norsat International Inc.,
> #300 - 4401 Still Creek Dr.,
> Burnaby, B.C., V5C 6G9.
> Tel. (604) 292-9089 direct
> Fax (604) 292-9010
> website www.norsat.com
>
> > -----Original Message-----
> > From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]]
> > Sent: Tuesday, September 18, 2001 3:52 PM
> > To: Protel EDA Forum
> > Subject: Re: [PEDA] Pad with multiple holes surrounding it.
> >
> >
> > At 02:22 PM 9/18/01 -0500, Ted Tontis wrote:
> > >I believe he is trying to put supporting holes around the
> > top of the PTH.
> >
> > I'd like to know what a "supporting hole" is, since holes
> > remove physical
> > support.
> >
> > Holes placed for additional ground connection would be likely
> > to make only
> > a negligible contribution under most circumstances; the pad,
> > if it goes to
> > a ground plane or copper pour, should be made direct-connect
> > unless it is
> > to be soldered. Holes surrounding a central hole going to a plane may
> > remove connection to the inner hole unless they are direct-connect.
> >
> > A .125 hole direct-connect to a ground plane is equivalent to a trace
> > almost a half-inch wide for a distance of perhaps 30 mils at most.
> >
> <SNIP>
> >
> > [EMAIL PROTECTED]
> > Abdulrahman Lomax
> > Easthampton, Massachusetts USA
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