[SI-LIST] Re: Flooded Vias vs Thermal Relief
- From: Jack Olson <pcbjack@xxxxxxxxx>
- To: Shawn Arnold <shawn@xxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 19 Mar 2010 09:55:28 -0500
Thanks Shawn, that was an important point.
I didn't consider that before I wrote, but I've seen little pieces of
(almost) isolated planes hanging on by a single spoke or two. flooded
vias would join them up nicely!
Thanks everyone else, too!
stunned but enlighted,
Jack
.
On Fri, Mar 19, 2010 at 9:35 AM, Shawn Arnold <
shawn@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hi Steve,
>
> The big deal with thermals is the lack of copper for return path on higher
> density devices and via patterns, the ring and spokes eat away the Cu that
> the traces run over. His question pertained only to vias not thru-hole
> devices. The impedance effect is minimal but the return path and Swiss
> cheesing of the planes is significant when with a single button click he
> can
> turn on thermals for manual design review and direct connects for Gerber
> generation.
>
> Shawn
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of steve weir
> Sent: Friday, March 19, 2010 7:14 AM
> To: Jack Olson
> Cc: SI-LIST
> Subject: [SI-LIST] Re: Flooded Vias vs Thermal Relief
>
> Jack, I would demand that anyone promoting such an idea back it up with
> real numbers. The back of my envelope shows that for reasonable thermal
> ties the difference between solid and tied is about 24pH for a via pair,
> or the equivalent of less than 2mils Z axis.
>
> Steve.
>
> Jack Olson wrote:
> > Greetings,
> > I am being instructed to flood all vias instead of using thermal relief,
> to
> > get a "better" connection to planes. I've typically used thermal reliefs
> > simply because they are easier to see in checking or design reviews (but
> its
> > only one mouse click for me to change them so I'm not really
> complaining).
> >
> > but it got me thinking.....
> >
> > Have any test results ever showed that spokes have a significant
> impedance
> > or anything that can change circuit performance?
> > (and I'm referring to 12mil plated through-hole vias on boards 100MHz
> max)
> >
> > I don't remember anyone ever talking about that.
> >
> > surfin' the learnin' curve,
> > Jack
> >
> >
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>
> --
> Steve Weir
> IPBLOX, LLC
> 150 N. Center St. #211
> Reno, NV 89501
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