Performance depends on system-level factors beyond the heat sink’s inherent Rθ:
- Mounting Pressure: Insufficient pressure leads to high thermal interface resistance.
- TIM Application: Correct amount and even spread are crucial.
- Airflow: Ambient temperature, volume (CFM), direction, and static pressure of the fan. Obstructions in the airflow path.
- Orientation: In natural convection, fins should be vertical to promote chimney-effect airflow. Horizontal fins can trap heat.
- System Layout: Proximity to other heat sources, confined spaces, and inlet/outlet vents.
- Altitude: At high altitudes, air density is lower, reducing convective cooling efficiency.
Always test the heat sink in the final system configuration under worst-case operating conditions.