Thermal Resistance Basics

Understanding thermal resistance is critical for IGBT module design. The total thermal resistance from junction to ambient includes Rth(j-c) from junction to case, Rth(c-s) from case to heatsink, and Rth(s-a) from heatsink to ambient. Each component must be carefully selected to maintain junction temperature below limits.

Heatsink Selection

Select heatsink based on required thermal resistance calculated from power losses and temperature rise. Natural convection heatsinks are suitable for low power, while forced air or liquid cooling may be needed for high power applications. Always include safety margin for worst-case conditions.

Thermal Interface Materials

Thermal interface materials (TIM) fill microscopic air gaps between module and heatsink. Options include thermal grease, phase change materials, and thermal pads. Proper application is essential for achieving specified thermal performance.