Thanks for the clarification Phil. Sorry if I misquoted you. That wasn't
my intention. Just to raise a debate. That worked :-)

Does the approach you take differ for SMD or NSMD pads, or is their
little difference for the case you cited below?

Also, as a side issue, what success/spec have you had with PBGA
Via tenting, partial or full? We cannot get full tenting guaranteed by
our manufacturer, in fact the results are quite poor, and I'm still
contemplating whether partial is satisfactory.

At 11:29 AM 6/02/2002 +1100, you wrote:
>Certainly, I believe that there is no need to thermally relieve a via.
>The small length of track from the solder pad to the via will provide the
>thermal relief without needing a relief on the power/ground plane for the
>In the case of a BGA where the power connections are grouped under the
>central area of the device and you want to flood around those connections
>with a surface plane connected to an internal power/ground plane, I would do
>the following;
>Connect the solder ball pads to the surface fill with a thermal relief
>pattern, and connect that fill to the internal plane with un-relieved vias.
>That way, the solderable pads are correctly relieved and the vias have a
>solid, continuous connection.
>Mr Lomax is quite correct in the difference between the vias and the power
>connections. The solder pad for the power connections must be thermally
>relieved. The via is not 'designed' to be soldered to.
>(The only situation where I have known this to be a problem is with
>microwave circuits, where the relief pattern can actually form a resonant LC
>'tank'circuit and cause problems.)
>To quote Mary Sugden, a lot of PB design is actually 'solder joint design'.
>-----Original Message-----
>From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, 5 February 2002 09:41
>To: Protel EDA Forum
>Subject: Re: [PEDA] Thermal relief
>At 08:34 AM 2/5/2002 +1100, Colin Weber wrote:
> >I was talking with another designer, Phil Dutton, and he also recommended
> >the Power Connections Relieved.
> >"Make sure that your Power connections are relieved, or they will cool
> >down faster than the rest of the device, inducing stresses."
>That is "Power Connections." We've been talking about vias. Different
>Abdulrahman Lomax
>Easthampton, Massachusetts USA


Colin Weber

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