Thermal management is based on thermal resistance concepts. The total thermal resistance from junction to ambient (Rth(j-a)) is the sum of: junction-to-case (Rth(j-c)), case-to-sink (Rth(c-s)), and sink-to-ambient (Rth(s-a)). MacMic IGBT modules specify Rth(j-c) in datasheets. For reliable operation, junction temperature (Tj) must be kept below maximum rating (typically 150°C or 175°C) under worst-case conditions. Calculate Tj using: Tj = Ta + Ploss × Rth(j-a), where Ta is ambient temperature and Ploss is total power dissipation.

Select heat sinks based on required thermal resistance (Rth(s-a)) calculated from power dissipation and temperature rise limits. For natural convection, typical Rth(s-a) ranges from 0.5 to 5°C/W depending on size. Forced air cooling can achieve 0.1 to 0.5°C/W. Consider: (1) Thermal resistance vs. airflow curves; (2) Physical dimensions and mounting compatibility; (3) Fin density and orientation for airflow; (4) Material (aluminum is standard, copper for high performance). MacMic T1A and H1A packages are compatible with industry-standard heat sink mounting patterns.

Thermal interface materials (TIM) fill microscopic air gaps between module and heat sink, reducing contact thermal resistance (Rth(c-s)). Options include: (1) Thermal grease - Best performance (0.1-0.3°C-cm²/W) but messy application; (2) Thermal pads - Easier assembly, moderate performance (0.3-0.8°C-cm²/W); (3) Phase change materials - Combine good performance with easy application. For MacMic modules, apply thin uniform layer (0.1-0.2mm) of high-quality TIM with thermal conductivity >3 W/mK. Proper application can reduce Rth(c-s) to 0.05-0.1°C/W.

Calculate total power losses to size thermal management: Ptotal = Pconduction + Pswitching. Conduction loss: Pcond = Vce(sat) × Ic × duty cycle. Use Vce(sat) from datasheet at actual operating temperature (typically 1.5x room temperature value at 125°C). Switching loss: Psw = (Eon + Eoff) × fsw, where Eon/Eoff are switching energies per pulse and fsw is switching frequency. For HN series at 50KHz, switching losses dominate. For 6TC series at 10KHz, conduction losses are typically 60-70% of total.

Implement temperature monitoring for protection and thermal management: (1) NTC thermistors - Built into many IGBT modules, provide case temperature measurement; (2) Thermocouples - Direct measurement of heat sink or module case temperature; (3) IR cameras - Useful for prototype validation and hotspot identification. Set temperature thresholds: Warning at 80-90% of Tj_max, shutdown at 95% of Tj_max. For MacMic modules with 150°C Tj_max, recommend case temperature limits of 100-110°C for long-term reliability.

Different applications have unique thermal requirements. For HN series high-frequency welding/induction: Switching losses dominate at 50KHz - focus on minimizing switching energy through gate drive optimization and ensure adequate heat sinking for high-frequency operation. For 6TC series motor drives: Conduction losses are primary concern - optimize for low Vce(sat) and ensure continuous operation thermal design. For intermittent duty applications (welding): Consider thermal capacitance of heat sink for short overload periods. For continuous duty (pumps/fans): Design for steady-state thermal conditions with margin.