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Calculates thermal resistance (θja in °C/W), required fin surface area, and forced-air CFM cooling needs for power electronics, LED drivers, and custom PC builds.
Series thermal resistance networks, conduction models, and forced convection curves
Models series thermal resistance from silicon junction to ambient air: θja = θjc (package) + θcs (TIM) + θsa (heat sink).
Pre-configured thermal resistance parameters for TO-220, TO-247 MOSFETs/IGBTs, High-Power LED COBs, and bare silicon dies.
Simulates heat transfer coefficients (h) across 0 LFM (natural convection) to 800+ LFM (high-speed blower fan cooling).
Heat flow behaves like electric current: Temperature difference equals Power (Watts) multiplied by Thermal Resistance (°C/W).
High-performance thermal compound minimizes microscopic air voids, keeping case-to-sink resistance θcs under 0.15°C/W.
Adding a 300 LFM fan increases boundary layer heat transfer, allowing compact heat sinks to dissipate 3x more heat safely.
Everything you need to know about Heat Sink Thermal Resistance & Cooling
Thermal resistance (θ, measured in °C/W) is the measure of a material's resistance to heat flow. It dictates how many degrees Celsius a component's temperature will rise for every watt of power dissipated.
θsa(max) = (Tj(max) - Tambient) / Power - θjc - θcs. If your heat sink has a thermal resistance higher than this value, the semiconductor junction will overheat and fail.
θjc is Junction-to-Case resistance (internal to the transistor). θcs is Case-to-Sink resistance (determined by the thermal paste or pad). θsa is Sink-to-Ambient resistance (determined by heat sink size and airflow).
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Calculates exact cooling fin dimensions (count, height, length, material) needed to maintain junction temperatures safely below Tj(max).
Microscopic air gaps between metal surfaces act as thermal insulators. Thermal paste, pads, or phase-change materials fill these voids, dramatically reducing θcs from ~2.0°C/W down to 0.10°C/W.
Forced airflow increases the convective heat transfer coefficient (h) from ~12 W/m²K in still air up to 60+ W/m²K with high-velocity fans, reducing heat sink thermal resistance by up to 70%.
Copper has nearly double the thermal conductivity of aluminum (390 vs 200 W/m·K), allowing heat to spread faster across the base plate and into the fins, though copper is 3x heavier and more expensive.
Tj(max) is the silicon die operating limit specified on component datasheets (typically 150°C for silicon power MOSFETs, 105°C for LEDs, and 95°C for CPUs). Good engineering practices design for a 20°C to 30°C safety margin.
Yes! Click 'Export CSV' to download complete thermal resistance networks, junction temperatures, and airflow cooling curves, or click 'Snapshot' for chart graphics.
In natural convection, fins spaced too tightly (< 6mm) create boundary layer overlap that chokes buoyant air movement. Forced convection allows much denser fin spacing (< 2mm).
For consumer indoor electronics, 25°C to 30°C is standard. For enclosed power supplies, automotive, or industrial machinery, design for 40°C to 50°C internal enclosure ambient temperatures.
Yes! Proper mounting pressure (typically 40 to 60 PSI) compresses the TIM layer to minimum bond line thickness, ensuring optimal heat transfer into the heat sink.
No software installation is required. The Heat Sink Thermal Resistance & Cooling Designer runs client-side in your web browser using HTML5 Canvas and TypeScript.