Heatsink Calculator

Thermal management of semiconductor devices became a formal engineering discipline in the 1950s as the first germanium and silicon power transistors shipped. Early power devices in TO-3 metal cans were screw-mounted directly to chassis; the chassis itself was the heatsink. Extruded aluminum fin-stock heatsinks appeared in the 1960s, and TIM (thermal interface materials) — silicone grease, later graphite pads, and then phase-change materials — evolved alongside to fill microscopic air gaps between mating surfaces.

The thermal-resistance model (R_θ in °C/W, added in series like electrical resistances) was formalized by the Electronic Industries Association (EIA) in the 1970s and remains the primary analytical tool used in datasheets and design guides today. Its elegance: each stage of the path from junction to ambient can be characterized independently (junction-to-case, case-to-sink, sink-to-ambient) and summed, giving a simple additive calculation for the full thermal chain.

Modern high-power electronics — GPUs, EV motor drives, photovoltaic inverters — push heatsinks into active cooling territory. Direct liquid cooling (cold plates bolted to the package lid), vapor chambers (heat pipes with wick+fluid+fin), and even phase-change immersion cooling are now standard for 300+ W applications. The humble fin-stock extrusion persists for everything up to ~50 W continuous dissipation.

Enter the power dissipated, target maximum junction temperature (usually 85°C below T_j,max for reliability margin), ambient air temperature, junction-to-case thermal resistance R_θJC (from datasheet), and case-to-sink resistance R_θCS (TIM — typically 0.1–1 °C/W). The tool returns the required heatsink thermal resistance R_θSA — pick a heatsink with equal or lower rating.

For natural convection in still air, typical finned heatsinks deliver 5–15 °C/W. Add a fan to drop into the 1–5 °C/W range. If R_θSA needed is below 1 °C/W, consider liquid cooling or direct die-cooling techniques. Everything runs client-side; no values leave your browser.