Jack Olson wrote:
>
> I found it...
> The article was published in "Surface Mount Technology" September 1993
> by Jeffrey G. Holmes, Motorola, Phoenix, AZ
>
> It was only three pages, I scanned 'em into this address:
>
> http://www.geocities.com/Heartland/Hills/5131/thermal.htm
> <http://www.geocities.com/Heartland/Hills/5131/thermal.htm>

Thanks ...

In fact, this cross checks fairly well.

Given in the article:
Ta = 27C
Tj = 150C max.
A  = 15 sq.cm. = .0015 sq.meters
h  = 23 worst case still air,
     28 best case still air

Q = 23 * (150 - 27) * 0.0015 = 4.24W
Q = 28 * (150 - 27) * 0.0015 = 5.17W

The article states about 5W max still air.
Not bad.  Not bad at all.