Electronic Design

For More Efficient Cooling, Try Splayed Pin-Fin Heatsinks

The immense processing power generated by today’s cutting-edge ICs enables engineers to design extremely powerful applications. Unfortunately, the higher processing power comes with a dramatic increase in the magnitude of heat dissipation that makes heatsink selection a very complex task.

Splayed pin-fin heatsinks consist of a base and an array of embedded round pins splayed outwards (Fig. 1). Forged from aluminum or copper, they range in size from 0.27 by 0.27 in. to 2 by 2 in. and in heights from 0.3 to 1.1 in. Splayed pin fins are derivatives of traditional pin-fin heatsinks that contain an array of vertical round pins (Fig. 2).

Traditional pin fins generate substantial cooling power and are widely used in a variety of applications requiring considerable cooling power. Pin fins use round pins, which boost the cooling power generated by a heatsink by improving air turbulence inside the pin array and providing lower resistance to incoming airstreams.

Compared to traditional pin fins, splayed pin fins generate superior cooling power in limited-airspeed environments as well as lower pressure drop in any given airspeed environment. In limited-airspeed environments, splayed pin fins offer up to a 20% cooling premium over traditional pin fins and significantly larger cooling premiums over most other existing heatsink technologies.

The performance premiums offered by splayed pin fins come from the unique splay structure that produces larger distances between the pins while preserving large surface areas. The larger spacing enables airstreams to enter and exit the pin array more efficiently.

From a cooling perspective, the large surface area of the heatsink is exposed to a large air volume and therefore able to provide more effective cooling. From a pressure-drop perspective, the wider spacing enables more air to exit the pin array, reducing pressure drop.

LOW-AIRSPEED COOLING
The challenge of cooling devices in low-airspeed environments stems from the fact that slow-moving air cannot penetrate the fin arrays on most standard heatsinks. To ensure that surrounding airspeeds do penetrate through fin arrays, designers have traditionally opted to use sparsely configured heatsinks. Although they generally perform better than standard heatsinks, their cooling ability depends on their surface area.

Placing a splayed pin-fin heatsink in a low-airspeed environment generates a substantial cooling premium. Its structure features considerable spacing between the pins, which reduces the resistance to incoming air and allows air to flush through the pin array. At the same time, splayed pin fins still possess a large surface area.

COOLING HEAVILY POPULATED BOARDS
The heatsink selection process for boards hosting a large number of devices is tedious. Designers not only must consider the performance of a given heatsink but also must ensure that surrounding airstreams are efficiently allocated across the board.

Splayed pin fins provide a significant premium for densely populated applications. In addition to substantial cooling power for individual devices, they also exhibit low pressure-drop characteristics that allow more air to flush through their pin arrays, leaving stronger airflows for other devices that reside on the board.

In other words, devices residing downstream from the sources will receive stronger airflow. The larger the number of heatsinks that reside on the board, the more significant the impact of the splayed technology will be.

EXTREME COOLING NEEDS
Devices dissipating heavy thermal loads require additional cooling power, usually in the form of a heatsink much larger than the device it cools. Splayed copper pin fins are highly recommended as an alternative for such extreme applications.

Copper enables quick and efficient spreading of the heat along the heatsink’s base, eliminating local hot spots. The added value generated by a splayed copper heatsink can be as high as 35% over a traditional pin-fin heatsink of the same size.

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