Intel Core i7-9700K, 9900K Confirmed to Use Solder, Not Paste

Ever since Intel switched away from using solder to a thermal interface material on its desktop CPUs, enthusiasts have been asking the company to reverse that decision — and occasionally cracking the integrated heat spreader off the CPU to remove Intel’s thermal interface material (TIM) and substitute their own. Earlier this summer we saw leaked slides implying that the at least some of Intel’s upcoming 9th Generation CPUs will use solder, not paste, but didn’t have confirmation of that decision. New statements from Eurocom, however, have put paid to the rumor.

Overclockers3D contacted the company, which confirmed that at least two chips in the 9th Generation family, the Core i9-9900K and Core i7-9700K will use solder rather than a TIM. The company states:

New Intel i9-9900K and i7-9700K CPUs are coming with gold soldered TIM/IHS to the CPU die. This should help manage the temperatures of the higher-clocked CPUs and will also help with achieving higher overclocked frequencies. Our Sky “C” super-laptops are ready for 9900K /9700K.

That 300MHz gap may not seem like much, but it’s entirely possible the difference is larger than it appears mathematically. CPU power consumption tends to rise linearly with clock, but voltage increases drive power consumption much more sharply. In real-world scenarios, of course, voltage and frequency shift together and simultaneously. Once outside of the “sweet spot” for any given part, the curve bends upwards sharply. The graph below compares power consumption and power consumption for two older Intel CPUs — the Core i7-2600K (Sandy Bridge) and the Core i7-3770K (Ivy Bridge).

But total CPU power consumption is also impacted by temperature, and this is where the use of solder versus thermal paste comes into play. The thermal conductivity of thermal paste, outside of exotic compounds that Intel doesn’t use, is typically measured around 5-10 W/(m*K). Indium, the dominant compound in most CPU solder (for reasons you can read about in an excellent guide to CPU soldering by overclocker Der8auer) has a thermal conductivity of 81.8 W/(m*K).

Because hotter transistors draw more power, using a TIM instead of thermal paste can lead to heat being trapped on the die, which means the transistors in question require more voltage to switch properly at top speed, which means they’ll generate more heat, which means they’ll need more voltage to switch properly at top speed, which means they’ll… you get the picture. There are practical limits to how much we can adjust these issues; the amount of heat that can move out of the CPU is fundamentally limited by the materials used in its construction and CPUs aren’t actually all that great at moving heat out of hot spots in the first place (if they were, hot spot formation wouldn’t be the problem that it is today).

Early data suggests Intel’s new Core i7 and Core i9 chips may have some ability to push above 5GHz, but I wouldn’t buy either chip expecting huge overclocking returns unless you regularly run at least a phase change unit (single-stage freon can take a CPU down to ~-50C). While moving to solder should improve Intel’s temperature and thermals, we expect the company has already tapped most of the chip’s overhead by increasing the maximum boost clock. Also, despite the mention of gold in the Eurocom note, using gold as an alloy for CPU soldering is common. It’s used as a layer between both the CPU die and the solder sheet and then between the solder sheet and the bottom surface of the integrated heat spreader (IHS).

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