Ok, I gotta chip in, because there's a need to clarify a few things.
First, glass actually increases in structural strength, under compression, until it reaches a breaking point. Glass however makes a very poor structural material, when it's in tension, and will shear off relatively easily.
Copper acts like a normal material/element. Googling will reveal the force, in psi, to deform it, and it's surprisingly low: copper is a relatively "soft" metal, unlike steel.
The biggest problem with increasing pressure on the CPU die, is that we don't know what the actual surface geometry is, and we only have a poor idea about the direction of the forces applied.
If ya'll just think about it for a second... if you tighten up the 4 surrounding bolts, and given that the block is essentially supported by a center point (the pads are just there for stability), if the baseplate deflects in any way (and it does), what you have is a concave baseplate over a CPU die, and the mounting pressure points are now on the corners of the die.
Now if we're lucky, the baseplate was convex a little bit to start off with, and clamping it down forms a near perfect flat contact, under the clamping pressure.
So in the first scenario, you actually made the TIM joint worse. In the second, you made it perfect. Now ya'll apply Murphy's law here for a second, and realize that the only way to get it right, is by trial and error.
So we remove the springs? The problem with that, is that it becomes infinitely difficult to gauge the applied pressure: a fraction of a turn will make a significant difference.
In designing Radius, I opted to go with springs. Unfortunately, I lacked a little foresight when I ordered them. I've got a set of 4 * 6 lb springs. In retrospect, I would have ordered 9 lb springs, and really, after going over this thread, I would probably have ordered something even stronger.
Note that compressing the springs all the way down, puts them past their limit, and actually damages them, to where they will no longer respond as per specs.
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