[SI-LIST] Re: Advantages & Disadvantages of Flooding Vias??
- From: Richard Jungert <r_jungert@xxxxxxxxxxx>
- To: <manatoshgbaidya@xxxxxxxxx>, steve weir <weirsi@xxxxxxxxxx>, si list freelist <si-list@xxxxxxxxxxxxx>
- Date: Mon, 2 Mar 2009 07:19:05 -0800
Manatosh.
One of the things you could do is use 2oz. copper. With 2 oz. copper you will
have to make all your spacing checks with min 0.010" clearance. Because of the
density of the board your doing this may or may not work, or you may be too far
along to try this but 2 oz. copper but its great for thermal dissapation. 1.5
oz copper is also available last time I talked to fabricators.
From your message I think your making a thermal path.
If your building a thermal path, one thing I have done in the past is settup
special vias for thermal dissapation. These special types of vias don't have
thermal spokes and drill holes can be much larger to facilitate a good copper
fill.
Having problems with the board warping you may want to think about how well
balanced the copper routing is distributed from top to bottom layers. Too much
copper on the top layers and then very few routes or planes on the bottom
layers with cause your board to warp towards the layers with excessive copper.
Try to distribute your routing and copper planes evenly from top to bottom of
your design. Another thing one can do is ask your fabricator to add thieving on
layers where copper is sparse. From my experience the fabricator will do this
as an added bonus. Always put this request in your fab notes and your on your
way.
Balance is always a good thing when designing boards and circuits.
Good luck.
Richard Jungert
http://www.rjungert.com
170 board designs
3D EM Simulations to 50Ghz with Sonnet
S parameter evaluations
2 US patents
> Date: Sun, 1 Mar 2009 22:09:47 -0800
> From: weirsi@xxxxxxxxxx
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Advantages & Disadvantages of Flooding Vias??
>
> Thermal ties are appropriate when you want to limit the heat sinking,
> such as with a TH component lead, where excessive heatsinking will make
> reliable soldering and desoldering difficult to impossible. Continuous
> pads are the norm for stitch vias.
>
> Typical thermal ties cover a minimum of 180 degrees arc. For instance
> if your antipads are 0.035" 0.015" ties would cover 185 degrees arc at
> the outside of the antipad. Are you sure that thermals insert too much
> resistance? If they do, I would be concerned about the current carrying
> capacity of the via barrels.
>
> Steve
> ManatoshGBaidya@xxxxxxxxx wrote:
> > Hi Gentleman,
> >
> > Good Morning.
> > I am working on a dense Aerospace Cockpit Control Board and I want to
> > Flood all of my Vias as Vias Connecting to the Respective planes (Power
> > & Gnd) is not having good connectivity through the Thermal Spokes.
> > Flooding vias will help me gaining the required copper area for the
> > Circuit.
> > Via size used is .015 Inch Drill\.025 Inch Pad.
> > Will this create any problem in the Component Assembling Process as some
> > of the heat may pass through the planes and thus PCB may undergo Bow &
> > Twist or expansion of the PCB.
> >
> > Please put your expertise thoughts on it.
> >
> > Thank you,
> > Regards,
> > Manatosh
> >
> >
> >
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> --
> Steve Weir
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