How does heat sink compound (thermal paste) work?

Thermal paste, also known as heat sink compound or thermal interface material (TIM), is a substance used to improve the thermal conductivity and transfer of heat between two surfaces, typically the CPU (central processing unit) or GPU (graphics processing unit) and the heat sink.

When a CPU or GPU operates, it generates heat due to the electrical resistance in the transistors and other components. To prevent the device from overheating, a heat sink is used to dissipate this heat away from the chip. However, there are microscopic imperfections on both the chip's surface and the heat sink's base that can create tiny air gaps between them. Air is a poor conductor of heat, so these gaps can reduce the efficiency of heat transfer.

Here's how thermal paste works to overcome this problem:

• Filling in imperfections: Thermal paste is a viscous material with high thermal conductivity. When applied, it fills in the microscopic imperfections on the surfaces of the CPU/GPU and the heat sink. This ensures that there is maximum contact between the two surfaces, minimizing the number of air gaps.
• Enhancing thermal conductivity: The thermal paste is designed to have a much higher thermal conductivity than air. By creating a continuous layer of thermal paste between the chip and the heat sink, it allows heat to flow more easily from the CPU/GPU to the heat sink.
• Eliminating air pockets: Air pockets can act as insulators, hindering the heat transfer process. The thermal paste helps to eliminate these pockets, promoting a more efficient transfer of heat.
• Compensation for surface irregularities: Even if the surfaces of the CPU/GPU and the heat sink appear smooth, they often have microscopic irregularities. Thermal paste, being a malleable material, can conform to these irregularities, further improving the contact area and heat transfer efficiency.

For more information, check out "Repairing & Avoiding Electronic Faults with Thermal Paste".