Part number
The Heat Sink Temperature Calculator is an online tool designed for analyzing heat sink performance in power electronics. It can be used to evaluate LED heat sinks, flat plate heat sinks, aluminum heat sinks, and other thermal solutions. By entering parameters such as heat sink thermal resistance, power dissipation, and maximum ambient temperature, the calculator determines the junction temperature of power components. This tool helps engineers ensure proper thermal management and reliable operation of electronic devices.
| Package | Junction to Case (°C/Watt) | Junction to Air (°C/Watt) |
|---|---|---|
| TO-3 | 5 | 60 |
| TO-39 | 12 | 140 |
| TO-220 | 3 | 62.5 |
| TO-220FB | 3 | 50 |
| TO-223 | 30.6 | 53 |
| TO-252 | 5 | 92 |
| TO-263 | 23.5 | 50 |
| D2PAK | 4 | 35 |
| Heat Sink | Thermal resistance (°C/Watt) |
|---|---|
| 1 sq inch of 1 ounce PCB copper | 43 |
| .5 sq inch of 1 ounce PCB copper | 50 |
| .3 sq inch of 1 ounce PCB copper | 56 |
| Aavid Thermalloy, SMT heat sink: PN:573400D00010 | 14 |
Introduction
To prevent device failure, power components must operate within a specific maximum junction temperature. When designing power electronics, you must consider the device's power dissipation, the ambient environment, and the thermal resistance of the system to ensure the device stays within safe limits.
This tutorial covers the fundamentals of , including how to use a calculator, the underlying thermal theory, and how to select the right heat sink type for your application.
A Heat Sink Calculator is an essential tool for estimating the operating Junction Temperature () of a power electronic component.
Key Inputs Required:
The Junction Temperature is the highest operating temperature of the actual semiconductor chip inside the package. It is almost always higher than the temperature of the case or the heat sink.
Thermal management is often modeled using an electrical circuit analogy (See Ohm's Law for Thermodynamics):
To determine if a heat sink is required (or if a specific heat sink is sufficient), use the following steady-state thermal equation:
Where:
A heat sink is a passive heat exchanger, typically made of metal (aluminum or copper), attached to a device to dissipate heat into the surrounding fluid (usually air).
Heat sinks are categorized by their manufacturing method and fin structure.
The most common and cost-effective type. Aluminum is pushed through a die to create long shapes with straight fins.
Individual fins are bonded to a grooved base plate using thermally conductive epoxy or brazing.
Made by pouring molten metal into a mold (Die casting or Sand casting).
Corrugated sheet metal (copper or aluminum) is brazed onto a base plate.
Sheets of metal stamped into specific shapes.
Selecting the right heat sink involves determining the required Volumetric Thermal Resistance. You must also decide between Natural Convection (passive airflow) and Forced Convection (using a fan).
The table below estimates the required volume of a heat sink based on the airflow available.
Range of Volumetric Thermal Resistance
| Flow Condition | Velocity (m/s) | Volumetric Resistance () |
|---|---|---|
| Natural Convection | ~0 | 500 - 800 |
| Low Flow | 1.0 (200 lfm) | 150 - 250 |
| Moderate Flow | 2.5 (500 lfm) | 80 - 150 |
| High Flow | 5.0 (1000 lfm) | 50 - 80 |
Note: As airflow increases, the efficiency of the heat sink improves, allowing for a smaller heat sink to handle the same thermal load.
This tool calculates the junction temperature of power components using inputs like ambient temperature/thermal resistance values (R1/R2)/and power dissipation. It helps verify if your design stays within safe operating limits for electronics like CPUs/GPUs/power modules.
Thermal Resistance 2 (R2) is optional and used for multi-stage thermal paths. If unsure/leave it blank or input "0". The calculator will automatically focus on R1 (junction-to-case or heatsink resistance) for core calculations.
The preloaded values (e.g./TO-220: 3°C/W junction-to-case) help users quickly reference common electronic packages. Select your component package type from the table to populate the "Thermal Resistance - Junction to Case" field for accurate results.
It works for aluminum/copper/PCB-based heatsinks (e.g./1 sq inch PCB copper = 43°C/W). The tool accounts for material conductivity differences through thermal resistance inputs/making it compatible with folded fin/extruded/cast heatsink designs.
Compare the calculated junction temperature to your component's datasheet limit (e.g./150°C max). If results exceed this value/increase heatsink size/improve airflow/or reduce power dissipation. The "Power" output shows your device's safe operating wattage.
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