Quote:One of the prominent parts of Intel’s announcement this week for the new 9th Generation core processors was that both the overclockable consumer processors and the new high-end desktop processors all feature a soldered thermal interface material (STIM) between the silicon die and the heatspreader. This is a vast improvement over the previous thermal interface material due to the solder's superior ability to conduct thermal energy away from the silicon die. As part of the announcement, Intel also engaged in some extreme overclocking at its launch event using Liquid Nitrogen as an effective coolant, and some overclocking world champions.

Choosing A Thermal Interface Material (TIM)

With the desktop processors we use today, they are built from a silicon die (the smart bit), a package substrate (the green bit), a heatspreader (the silver bit), and a material that helps transfer heat from the silicon die to the heatspreader. The quality of the binding between the silicon die and the heatspreader using this thermal interface material is a key component in the processors ability to remove the heat generated from using it.

Traditionally there are two different types of thermal material: a heat conductive paste, or a bonded metal. Both have positives and negatives.

Full reading: https://www.anandtech.com/show/13465/intels-push-to-enthusiasts-soldered-cpus-and-69-ghz-overclocks