Thermal Management

Heatsink Thermal Stack Calculator

Keeping power electronics cool requires managing the thermal resistance path from the Junction to the Ambient air.

This calculator sums the resistance of the Component Case ($R_{\theta JC}$), Thermal Interface Material ($R_{\theta CS}$), and Heatsink ($R_{\theta SA}$) to predict the final Chip Die Temperature ($T_J$).

Power & Environment

Conditions
W
°C
°C
°C
Safe Limit: 110 °C

Thermal Stack

Resistance
°C/W
°C/W
°C/W

Analysis Result

Output
Chip Die Temp (TJ)
— °C
Enter Power
Total RθJA — °C/W
Temp Rise (ΔT) — °C
Sink TIM Device Heat Source (Tj)

Formulas Explained

Analyze Mode (Find TJ)

TJ = Ta + Pd × (RJC + RCS + RSA)

Calculates final temp based on selected heatsink.

Size Mode (Find RSA)

RSA = ((Tsafe – Ta) / Pd) – RJC – RCS

Calculates max allowed heatsink resistance.

Safe Limit

Tsafe = Tj,max – Margin

Derates the component max temp for reliability.

Thermal Resistance (Rθ)

Unit: °C/W

Measures temperature rise per Watt of power.

How to Use

Optimize your thermal design in 3 steps.

1

Choose Mode

Select Analyze Chip Die Temp to check an existing heatsink, or Size Heatsink to find out what heatsink you need.

2

Define Constraints

Enter the Power, Ambient Temp, and your desired Safety Margin (e.g., 40°C below max).

3

Build Stackup

Fill in the resistances for the Device (RJC) and Paste (RCS). The tool will calculate the result instantly.