Liquid Metal vs Thermal Paste for CPUs: Conductivity Data, Compatibility, and Long-Term Behavior
Thermal paste transfers heat through microscopic contact between the CPU IHS and heatsink base. Liquid metal, which is conductive and stays liquid at room temperature, fills those microscopic gaps more completely. The conductivity advantage is large on paper; whether it translates to useful temperature reduction depends on which component is the actual thermal bottleneck.
Thermal Conductivity Comparison
Thermal conductivity is measured in watts per meter-kelvin (W/m·K). Higher values indicate faster heat transfer through a given thickness of material. The gap between standard paste and liquid metal is significant—roughly an order of magnitude—but the practical temperature delta depends on layer thickness and contact surface area.
| Product | Type | Conductivity (W/m·K) | Electrically Conductive |
|---|---|---|---|
| Thermal Grizzly Conductonaut | Liquid metal (GaInSn alloy) | 73 | Yes |
| Thermal Grizzly Conductonaut Extreme | Liquid metal | 82 | Yes |
| Thermal Grizzly Kryonaut Extreme | Paste (carbon micro-particles) | 14.2 | No |
| Thermal Grizzly Kryonaut | Paste | 12.5 | No |
| Noctua NT-H2 | Paste | 8.9 | No |
| Arctic MX-6 | Paste (carbon-based) | 8.5 | No |
| Generic white paste (stock) | Paste (zinc oxide) | 3–4 | No |
The 73 W/m·K of Conductonaut vs. the 12.5 W/m·K of Kryonaut represents a 5.8x conductivity difference. However, at typical application thicknesses of 0.05–0.1 mm, the actual contribution of the interface layer to total thermal resistance is only a fraction of the total path from die to heatsink fins. The IHS copper, the heatsink base, and the contact flatness between them dominate. On a CPU with a large, flat IHS and a well-lapped heatsink, the paste layer’s contribution may be 1–3 degrees Celsius; liquid metal saves most of that, yielding perhaps 1–5 degrees Celsius at the package level.
Where liquid metal produces larger real-world gains—sometimes 10–20 degrees Celsius—is in delidded configurations where it is applied between the bare CPU die and the IHS copper underside. The die is far smaller than the IHS, concentrating heat flux across a tiny area. Stock solder between the die and IHS on Intel processors is often porous or incompletely bonded, adding 5–15 degrees Celsius of interface resistance that liquid metal eliminates entirely.
Compatibility Constraints
Gallium-based liquid metals (GaInSn and similar alloys) react with aluminum through a galvanic corrosion process. Gallium dissolves the aluminum oxide passivation layer and then alloys with the base aluminum, progressively degrading the heatsink contact surface. This reaction begins within hours of contact and is irreversible. The result is pitting on the heatsink base and eventual structural degradation at the contact surface.
Compatible heatsink base materials include nickel-plated copper, bare copper, and nickel. Virtually all premium air coolers and AIO water blocks use copper bases, making them compatible. However, some low-cost and mid-tier coolers use aluminum bases that may appear copper-colored due to anodizing or surface finish. Before applying liquid metal, verify the base material: copper is non-magnetic, aluminum is; a magnet test distinguishes them. Nickel-plated copper bases are the safest choice because the nickel barrier prevents any aluminum-gallium interaction even if the plating is thin.
AMD Ryzen CPUs with an IHS have copper IHS tops, so liquid metal between the IHS and heatsink is aluminum-safe. Intel CPUs in LGA sockets have aluminum-topped IHS on budget models; higher-end SKUs (i9, i7) use copper IHS. Check the specific SKU before applying liquid metal directly to the top of an Intel IHS.
Long-Term Behavior
Gallium-based liquid metals do not dry out or pump-out over time the way paste compounds can. Traditional thermal pastes can experience pump-out—displacement from the interface under repeated thermal cycling—after two to five years, leading to gradual temperature increases. Liquid metal, being liquid at room temperature (melting point of GaInSn eutectic alloys is approximately −19 degrees Celsius), remains fluid throughout the operating range and does not pump out in the traditional sense.
The long-term concern with liquid metal is migration. The liquid can slowly creep along microscopic surface irregularities over months to years, potentially reaching the edge of the IHS or heatsink base. In delidded configurations without a containment mechanism, this can expose the liquid to the motherboard surface. Products like Thermal Grizzly’s Conductonaut Extreme include a containment ring design intended to prevent edge migration on delidded Intel CPUs. In standard (non-delidded) desktop configurations, the clamped interface between a flat heatsink base and flat IHS provides adequate mechanical containment for indefinite service life under normal use conditions.
Reapplication intervals for premium paste compounds are typically three to five years depending on thermal cycling frequency. Liquid metal, absent a containment failure, does not require scheduled reapplication and is considered a one-time application in standard configurations.