Apack ZeroTherm BTF80 & BTF90 CPU Heatsink/Fans

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The butterfly shape lends itself surprisingly well to its role as a heatsink. Two stacks of fins form the wings and the base of the fan forms the body. Decorative as they are, the shape of the wings is also quite functional: Each wing has a total of four evenly spaced heatpipes that run the full vertical length of the heatsink. The heatpipes are grouped in pairs, each pair connected at the top of the heatsink so that, even though there are eight vertical pipes in total, only four long pipes need be manufactured. Doubling up heatpipes in this way is not uncommon.

Front and back.

The pairs of heatpipes form a V that is roughly followed by the shape of the wings themselves. In addition to giving the heatsink its distinctive shape, the contours of the wings cut away fin material that is a long way from the heatpipes, reducing impedance where heat transfer is likely to be low.

The decorative ridges, the holes on the tips of the wings, and the trailing "tail" on each wing may also have useful purposes that go beyond aesthetic appeal. The ridges are likely intended to direct airflow, and they are arranged to channel the air as close to the heatpipes as possible. The holes in the wingtips are located where air pressure is likely to be weakest, and should reduce impedance to some extent. The "tail" fins serve a double purpose: They prevent stray cables from fouling the fan, and take advantage of the lateral airflow the comes off the tips of the fan blades.

The fins themselves are thin and loosely spaced — both good signs for when the fan is turned down. Our only concern is that, with all of the contouring, there is less surface area compared to many tower heatsinks. The larger the surface area, the better the ability of the fins to transfer the heat from the CPU into the air.

The fins are fixed at the base.

Like the fins, the red plastic body also looks as though it is functional. The "tail" of the body forms a wedge shape that splits the airflow, forcing it out sideways instead of allowing it to blow straight through. This forces the air towards the heatpipes where it is most useful. The wedge shape continues through the length of the body, with the two antennae pushing the air outwards as it leaves the fins.

Does this butterfly have propeller-assisted flight?

Although it is necessary for the design of the heatsink, the rear-mounted fan looks a bit odd attached to the back of a butterfly. With the fan direction reversed, it looks as though it could be the butterfly equivalent of a wheelchair; perhaps it is unable to fly without the fan. It even has a taillight: The fan glows red whenever it is spinning thanks to a red LED embedded in the hub.


Getting back to the technical details, the copper base on both of our samples was slightly tarnished, but otherwise flat and smooth.

Slight discolorations on the base are unlikely to affect performance.

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