With thermal connections you can visually tell to which plane a via
is connected... don't hardly seem worth it, does it.

Actually, I think the biggest reason we used thermal connections on
vias originally was because the CAD systems were so limited in the
kind of pad stacks which could be defined, especially with regard to
vias.  Prior to CAD systems 99% of the boards designed were only 2 layer.

I had been considering switching to direct connection (I'd have to convince
the engineers that it really is OK... sometimes it like talking to children).
What differences have you noticed?  Performance should be very marginally
better.  Board shop processes should be the same.  Do the board shops call
and ask about them?

In this same vein -- We have traditionaly used anti-pads which are larger
than the positive pads on the outer layers.  I have thought about switching
to an anti-pad just large enough to clear the hole barrel + std clearance.
Any comments/advise?

[log in to unmask]
Don Walker


> This discussion brings up another point....
>
> Does it make sense to use thermal connections on vias?
> Thermals were originally used on thru hole comps to increase
> solderability of the leads, but now that is not necessary for SMT.
> Is there any reason to use them for vias?
> I've been using direct connection to the inner planes.
>
> Tom Kavendek
> Lucent Technologies
> Murray Hill, N.J.
> [log in to unmask]

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