@Bill,
Yeah, I'm pretty sure we're talking about the same thing (with the exception of my brother's moronic, ham-fisted heat sink mounting story). That picture of nicozeg's is pretty darn good and I don't think it takes much of a leap to "hunch" that the ridges resulting from the laser are significantly larger than the Ra of the remaining die face.
I'm sticking to my original conclusion. Namely that the effective surface area amounts to little more than the "outline" of the letters on such a die until those letters begin working their imprint into the copper. Only then does the peak pressure drop below the yield strength of copper. Granted, we're talking on the order of microns here (perhaps less), so the indentations in the copper should be easily removable via lapping.
If this is indeed the case, one would expect a central spring clip to be slightly more prone to indenting than a pure four-bolt heat sink due to the deflected shape of the baseplate. And in addition to the earlier time aspect I mentioned, there is also the factor of extruding excess TIM before the ridges could indent the copper.
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