36 lines
2.2 KiB
Markdown
36 lines
2.2 KiB
Markdown
# Glossary
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| Name | Meaning | Name | Meaning |
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| ---- | ---- | ---- | ---- |
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| Ambient Temperature Ta | Temperature of Air around IC | Junction Temperature Tj | Highest temperature in a semi-conductor |
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| Thermal Resistance \[°C / W] | Ability to dissipate internally generated heat. Increase in Tj per dissipated Watt of Power. This value in the datasheet is usually empirically determined. | Case Temperature Tc | Temperature of the case |
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| Maximum Junction Temperature Tjmax | device must be kept below this, else it stops working | Power dissipation Pd \[W] | Power consumed during operation |
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# Introduction
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Junction Temperature Tj is affected by:
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- ambient temperature Ta
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- Airflow / or other cooling methods
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- IC packaging material and technique (flip chip vs wire bond)
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- PCB material
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- Heat from other sources
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The junction temperature can be decreased by adding airflow or heat sinks but it will always be above the ambient temperature.
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# Cooling methods
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All cooling methods basically reduce thermal resistance.
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The most effective way to transport away the heat is to have a large via array below the IC to move the heat through the pcb copper to the opposite layer and distribute it into the entire board. From there it will then go into the sourroundings.
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# Modeling
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A good explanation can be found in [this video](https://www.youtube.com/watch?v=RV6b9horB-I&ab_channel=PowerElectronics) by Martin Ordonez.
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![[Pasted image 20240220154606.png]]
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Heat transfer happens as conduction, convection or radiation, whereas in PCB design its mostly conduction that is important (convection is important for heatsink calculations, but those can usually be found in their datasheets).
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A thermal resistance is used to model the process (just as an electrical resistance):
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![[Pasted image 20240220154835.png]]
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The thermal resistance depends on the material, the length and the area of the conduction path.
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Towards the end of the video you can find details on how to calculate the final junction temperature in different scenarios (no heatsink, heatsink, forced airflow).
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# Sources
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- [Infineon Guide](https://www.infineon.com/dgdl/Infineon-AN4017_Understanding_Temperature_Specifications_An_Introduction-ApplicationNotes-v11_00-EN.pdf?fileId=8ac78c8c7cdc391c017d071d497a2703). |