With its 9th generation Core processor family, Intel introduced STIM (soldered thermal interface material) to transfer heat between the processor die and the metal integrated heatspreader (IHS), as opposed to fluid thermal pastes. Enthusiasts prefer soldered IHS for their superior heat-transfer characteristics. It was known since the series launch that STIM will be restricted to the unlocked "K" SKUs, such as the i9-9900K and i7-9700K, while locked SKUs would retain thermal pastes. PC enthusiast @momomo_us (Twitter handle) de-lidded a Core i5-9400F sample to confirm this.The Core i5-9400F was de-lidded (its IHS removed) and placed next to a de-lidded i5-9600K, showing you TIM residue surrounding the i5-9400F die, and solder fragments on that of the i5-9600K. Interestingly, the i5-9600K die looks visibly larger than the i5-9400F, despite both being 6-core processors with 9 MB L3 cache. This isn't because the latter lacks an iGPU (not physically anyway). The i5-9400F die appears to be roughly as big as the 6-core "Coffee Lake" die used in 8th generation Core 6-core processors, while the i5-9600K appears to be carved out of the 8-core "Coffee Lake" die by disabling two CPU cores. The iGPU is physically present on the i5-9400F, but disabled.