What Is Thermal Paste and Why Does It Matter for Your PC?

What Is Thermal Paste?

Thermal paste (also called thermal compound or thermal interface material) is a substance applied between the CPU and its cooler. At a microscopic level, both the CPU lid and the cooler base are not perfectly flat — they have microscopic pits and ridges. Air trapped in these gaps is a very poor conductor of heat. Thermal paste fills these gaps to create direct thermal contact, allowing heat to transfer from the CPU to the cooler far more efficiently.

Types of Thermal Paste

Silicone-based: Most common, electrically non-conductive, easy to apply. Examples: MX-4, Kryonaut Metal-based: Highest conductivity (liquid metal like Conductonaut), but electrically conductive — can short-circuit components if it spreads off the CPU lid Pre-applied pads: Found on many stock coolers; acceptable for stock settings

How Much to Apply

The most common method is a pea-sized dot in the center of the CPU lid. Pressure from the cooler spreads it evenly. Applying too much wastes paste and can cause it to spread off the lid. Applying too little leaves gaps.

When to Replace It

Thermal paste dries out over time and loses effectiveness. Signs of degrading paste:

• CPU temperatures 5–15°C higher than when the system was new
• Thermal throttling on a CPU that previously ran cool
• The system was built 3–5+ years ago and has never had the cooler removed

Reapplying thermal paste (a $7 tube of Arctic MX-4 and 30 minutes) can reduce CPU temperatures by 5–15°C and eliminate throttling entirely. MrGameFix includes thermal paste reapplication guidance in our Remote Hands-On Session service.