Heatsink compounds, also known as thermal interface materials (TIMs), are substances used to improve heat transfer between surfaces in electronic devices and other applications where efficient thermal management is crucial. These compounds fill the microscopic air gaps and irregularities on surfaces that can impede effective heat transfer.

Common types of heatsink compounds include:

1. Thermal paste/grease: Made from silicone with metal oxide particles. Provides good thermal conductivity and is easy to apply.

2. Phase change materials: Soften or melt at specific temperatures, then harden again. Offer good thermal performance and reusability.

3. Thermal epoxies: Two-part adhesives that cure over time. Provide both thermal conduction and mechanical bonding.

4. Thermally conductive pads: Pre-formed pads made from silicone with ceramic or metal particles. Easy to install but less conformable than pastes.

5. Liquid metal-based compounds: Use gallium-based alloys for very high thermal conductivity.

Key properties to consider when selecting a heatsink compound include:

- Thermal conductivity (measured in W/mK)

- Viscosity

- Durability

- Ease of application

- Cost

When applying heatsink compounds, it's important to use a thin, even layer to maximize effectiveness. Excessive amounts can actually reduce thermal performance.

These compounds are widely used in CPUs, GPUs, power electronics, LED lighting, and many other applications where efficient heat dissipation is critical for device performance and longevity.