Heatsink Thermal Time Constant Calculator
τ = Rθ·m·c and the full heating curve — how long your heatsink buys before things get hot, for intermittent loads.
Big heatsinks buy TIME as well as temperature: a 2-minute soldering job or a motor's 30-second stall may finish before τ lets things get hot — that's how undersized sinks survive intermittent duty. The lumped model is valid when the metal conducts much faster than it sheds heat (true for chunky aluminium); thin spread-out fins need the full transient curve.
Thermal Time Constant Calculator computes how fast a heatsink/device assembly heats — τ and the full transient curve — free, instant and private in your browser. Designers of intermittent-duty gear: motor drivers, audio amps, spot welders use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Heatsink Thermal Time Constant Calculator
Thermal Time Constant Calculator computes how fast a heatsink/device assembly heats — τ and the full transient curve using the standard engineering relation: τ = Rθ·m·c; T(t) = Ta + P·Rθ·(1 − e^(−t/τ)). Worked live: a 150 g aluminium sink at 5 °C/W has τ ≈ 11 min — a 2-minute soldering-iron-hot burst barely moves it. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Heatsink Thermal Time Constant Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Heatsink Thermal Time Constant Calculator?
- ✓Implements the real formula — τ = Rθ·m·c — with the substitution shown, not a black box
- ✓Built for designers of intermittent-duty gear: motor drivers, audio amps, spot welders
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate thermal time constant?+
How fast a heatsink/device assembly heats — τ and the full transient curve follows τ = Rθ·m·c; T(t) = Ta + P·Rθ·(1 − e^(−t/τ)). For example, a 150 g aluminium sink at 5 °C/W has τ ≈ 11 min — a 2-minute soldering-iron-hot burst barely moves it. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Can an undersized heatsink survive intermittent loads?+
Often, yes — that's the whole point of thermal mass. If the burst is much shorter than τ and the duty cycle lets it cool, the peak temperature stays far below steady state. Compute T(t) at the end of your longest burst rather than the infinite-time value.
When does the lumped (single-τ) model break down?+
When internal conduction is slower than surface loss — thin sprawling fins, plastic housings, or the silicon-to-sink path itself, which has its own much faster τ. For seconds-scale pulses use the device's transient-impedance Zth curve; the heatsink model covers minutes.
Is the Thermal Time Constant Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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