Somebody on another forum asked why we used the amount of paste that we do and not the grain sized that other manufacturers use. While I have put some emphasis here on the importance of proper contact & pressure I would also like to add some to the application debate.
I am not one to second guess my competitors application recommendations but when doing an in house study on grease failure I observed that when a compound is compressed it spreads in a perfect circle with a smooth line at the edge.
It does reach a point where there is not enough compound to push the grease out evenly, it then forms little extensions that fold back in or join with other little extensions to form little pockets of air and is what I call an Air mixing Zone.
This is observed as a halo of radial lighter and darker areas that I have outlined below.
The darker areas contain little air pockets that expand under heat and pressure and causes early failure of the mount and can in just a few weeks temps can rise 3-4 C under stress.
I can not say this works for all compounds but I have yet not seen one that does not exhibit it, thick or thin.
The example below was a competition compound used by some in this results thread. I took 2 Glass slides a copper simulated IHS. I applied an approximate "grain of rice" and then clamped the simulated IHS between the 2 slides with 4 binder clips (approximately 50-60lbs) I then placed it in an oven @ 100C for a couple of hours to stress it a bit. Most of these compounds are rated 150C or higher so this was at the lower range of what you commonly see in a stress test like this and not overdone by any means.
You can see in the second illustration where a few of the air bubbles have expanded, pushed aside the grease. If I had done a more extensive test these bubbles would continue to expand and migrate to join with other bubbles for a rather spectacular failure as noted on our website.
With ICD the amount prescribed is intended to spread just enough so it does not enter the Air Mixing Zone
in the span of contact area. In the early giveaways I had the users on several forums spread with varying amounts and methods and the near universal consensus was the "pea" method for best performance which I then refined down to the 5.0-5.5 mm bead with subsequent testing to our final application instructions.