----- Original Message -----
From: "Dwight Mattix" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 19, 2005 11:32 AM
Subject: Re: [TN] Delamination at Thermal Via area?
> At 08:47 AM 10/19/2005, Karl Sauter wrote:
> >Dwight,
> >
> >How is heat to get from the device to the thermal via if you don't plate
> >over it?
>
>
> The via is plated, yes?
> The via is connected to the surface copper at the knee of the hole, yes?
> The thermal path is down through the knee of the hole into the via, yes?
> Any plating over the via fill is a small to insignificant part of the total
> % surface copper and therefore a small part of the thermal path into the
> via, no?
>
> Been there, done that, got the T-shirt. It works.
>
Your T-shirt may have shrunk, such that is not fit to wear anymore, or even lost .
. .
The thermal path is thru any material that is thermally conductive . . .
Silver and copper are very conductive both electrically and also thermally . . .
What is the specific thermal conductivity of the copper wall of the hole (remember
that the electroless copper is probably a little less dense than electroplated
copper, and that the thickness of the copper in the hole is going to be less in the
middle of the hole (unless we go for reverse pattern plating etc.))) . . .
What kind of connections are made to internal planes, if any, are there (direct or
thermally relieved) . . .
Where are we actually sinking heat from, and where are we sinking that heat to . . .
Most importantly in the specific question at hand (the one you supposedly got the
T-shirt for), is:
What is the actual thermal conductivity of the "fill" material . . .
What is the thermal conductivity of the overplate material . . .
And most important of all, is the device generating the heat actually in direct (or
proximate) contact (with or without thermal paste) with the overplated via . . .
All of the above have to be resolved before you can really know how much the T-Shirt
shrunk, and whether or not the moths got to it, such that it may not even be fit for
display (or bragging about) anymore (meaning that you may have to go back and take
the training over) . . .
And yes, I understand that the normal conductivity of normal Tin-Lead Solder is only
about 16% of the conductivity of copper (and thats what I got one of my T-shirts
for), although I still can't find anyone to stick his neck out and give a
conductivity number for the newer Lead Free Solders.
This might also be an appropriate time to ask a related question that I have been
trying to get an answer to for years now, and that is this: What is the difference
in conductivity of rolled copper sheet, electroplated copper, and electroless
copper, all of which appear to present different densities, as pretains to the use
of these different types of copper in the manufacture of PC Boards? (the correct
answer gets partial credit towards a replacement T-Shirt).
JaMi
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