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
via.
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'.

regards,

Phil.

-----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
animal.

[EMAIL PROTECTED]
Abdulrahman Lomax
Easthampton, Massachusetts USA

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