A heat sink’s aspect ratio is basically the comparison of its fin height to the distance between its fins. In typical heat sinks the aspect ratio is between 3:1 and 5:1. A high aspect ratio heat sink has taller fins with a smaller distance between them for a ratio that can be 8:1 to 16:1 or greater.
Thus, a high aspect ratio heat sink provides greater density of fins in a given footprint than a more common sink, and/or stands taller than its conventional counterpart. The great benefit from a high aspect ratio heat sink is the increased amount of heat dissipating surfaces it provides due to its additional fins. Further, these heat sinks do not occupy any more length or width. The result is a more efficient heat sink with higher performance per gram in the same footprint.
Many common heat sinks are unable to serve the needs of high volume applications, due to the fact that their cooling capacity – measured in part by the aspect ratio – is simply not great enough. By nearly doubling a heat sink’s aspect ratio the cooling performance is optimized and heat issues resolved without the need for more complex solutions.
Because high aspect ratio heat sinks are manufactured in similar fashion as conventional heat sinks, their cost is not significantly higher. They can be extruded or bonded. Fins can be straight or folded. For omnidirectional purposes a high density of pins can be used as heat spreaders in place of fins.
High aspect ratio heat sinks are often ideal thermal solutions for workstation CPUs, high performance power supplies and converters, and high-end amplifiers.
Of critical importance when using high aspect ratio heat sinks is providing sufficient airflow to carry away the radiating heat. Passive cooling, e.g. conduction and radiation may be inadequate. Convective heat transfer removes essentially all of the energy from a heat sink under forced air cooling. Particularly with dense fin fields, an improperly directed fan may create stagnation points and high pressure loss. Thermal modeling is recommended when determining the needed active cooling resources.