DirectFET®; MOSFET: Fin Performance Analysis
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Fin Types |
Heat Pipe |
Pin Fin |
Stamped |
Extrusion
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Fin Specifications
- Predicting fin performance appears simple with the aid of vendor data
- Beware –the data is produced with the assumptions of:
- Fully confined airflow
- Uniform power density
- Power supply fin and fan systems are typically much more difficult to estimate performance compared to “packaged” CPU systems
- Power supply systems are not “packaged”
Aavid Thermaloy
Part Number |
Thermal
Resistance
at 3in
length |
Width |
Height |
Surface
Area |
Weight |
Part
Class |
| 65060 |
6.48°C/W |
1.75in |
0.25in |
10.8in2/in |
0.30lb/ft |
C |
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Confined and Unconfined Airflow
- This factor can significantly change the performance of the heat sink
- Fully confined airflow –all air is forced through the fin passages
- Requires ducting around the fin
- Unconfined airflow –air is allowed to “bypass” the fin
- Most common –the actual airflow that passes through the fin is a complex relationship
- Fins used in this mode should be de-rated from the vendors data
- Methods for estimation
- Place an anemometer (air flow meter) at the exit of the fins
- Use that reading to extrapolate performance off the vendor curve
- Send us the geometry and we can simulate
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Uniform Power Density
- This factor can significantly change the performance of the sink.
- Uniform power density assumes the dissipating components are uniformaly distributing their
power to the sink.
- Typically not the case –fins should be de-rated from the vendors data.
- Estimating Performance
- Very difficult –typically based on experience.
- If the fin has a thick base and is close to the size of the components there should
be minimal de-rating.
- If the fin has a thin base and is much larger than the size of the components 10-
50% de-rating is typical.
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Fans
- Proper design and selection of a fan is critical to high performance systems
- A given fan can deliver only one flow and one pressure in a given system
- This flow and pressure dictate the performance of the entire thermal system
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Fans and Heat Sinks
- Heat sinks and fans should be selected and designed together, early in the design, to optimize performance.
- Often the fan or heat sink is brought in late to the design and system performance is marginal.
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"Play Audio
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IR’s proprietary DirectFET®; technology is covered by US Patent 6,624,522 and
other US and foreign pending patent applications.
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