Hi,
That's close to a quick estimate i came up with:
70/0.4 in 1 second. So in 2 seconds that's 350 degrees C.
70/0.5 comes out to 280 degrees C in 2 seconds.
That's counting the metal as 1 gram of copper. I'd have to check the actual size of the package, it's been a while.
Yes i figured the die was too small to think about too, and that the contact area was a pretty good heat conductor so there was no lag in the response of the die to package metal full conduction. If there is a lag, which there might be a little, the die is even hotter.