360° View - Apack Zerotherm BTF90 Heatsink Information on Frostytech's test methodology is available here.
	The Heatsink Fan: The 92x92x25mm fan spins at 750-2500RPM by way of PWM which is controlled by the motherboard. When attached to a standard 3-pin motherboard header it rotates at a fixed 2500RPM. The lack of any fan guard presents a challenge for systems with many loose wires dangling around inside the case, and the Apack ZeroTherm BTF90's height of 126mm precludes it from being used in compact or SFF-PC cases. The fan draws power from a PWM 4-pin motherboard fan header. The seven bladed impeller is internally illuminated by a pair for red LEDs.
	Heatsink Top: From the top, the Apack ZeroTherm BTF90 looks like a butterfly, and is internally split down the center so in effect there are two separate towers of copper cooling fins. While there are just four 6mm heatpipes used in this heatsink, they are bent around extensively so in effect there are eight heatpipes weaving through the copper fins. The fan can be quickly removed by pulling up on the triangular piece of red plastic, for easy cleaning or even replacement.
	Heatsink Side A: From the rear, the copper fins of the Apack ZeroTherm BTF90 are spaced about 1.8mm apart. Each copper fin is ~0.1mm thick. The heatpipes are soldered to a 4mm thick copper base plate, which is in turn covered by a die-cast aluminum bracket that holds the mounting clip in place and transfers clamping force to the remainder of the heatsink. The BTF90 stands 126mm tall, and is 109mm wide.
	Heatsink Base: The copper base measures 36mm x 48mm and is soldered to each section of heat pipe (it's end-to-end 6mm copper heatpipe on the other side). The base has a smooth machined finish and is pretty flat, although some slight doming is visible when held up to an engineers straight edge. The surface roughness is ~8 microinches, which is considered very good. Note the screw holes in the die-case aluminum portion where the mounting clip attaches to.