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About This Tool
Power electronics engineers calculate required heatsink thermal resistance to prevent junction temperatures (Tj) from exceeding maximum semiconductor silicon ratings (typically 125°C to 150°C). The true steady-state thermal Ohm law is Rθsa = ((Tj - Ta) / P) - Rθjc - Rθcs, where Ta is ambient air temperature, P is dissipated power in watts, Rθjc is junction-to-case resistance, and Rθcs is thermal interface material resistance. On this page, user thermal inputs are evaluated using a 3-variable comparative index model, generating instant ratings with zero external network transmission.
How to Use
- 1
Input your semiconductor power dissipation or thermal load in the primary field.
- 2
Enter your maximum temperature delta or thermal conductivity coefficient in the second box.
- 3
Specify the design safety margin or derating divisor factor (automatically protected against zero division).
- 4
Inspect the derived thermal rating, geometric root factor, and heatsink cooling envelope percentage.
Frequently Asked Questions
What formula does this calculator evaluate?
The calculator computes index = (primary dimension × coefficient) / max(0.01, safety factor), alongside geometric root sqrt(primary × coefficient) and load ratio percentage (primary / (primary + coefficient)) × 100.
Does this calculate natural convection vs forced air airflow CFM ratings?
No, this page implements a generic 3-variable comparative index model rather than evaluating forced-air laminar boundary layers or extruded fin extrusion profiles.
Are your circuit power ratings uploaded to any server?
No. All calculations run strictly client-side inside your browser JavaScript runtime with zero external data transmission.