Editing Computer cooling (section)

==Passive cooling==
{{see also|Passive cooling}}
[[File:NeXTcube motherboard.jpg|thumb|[[Mainboard]] of a [[NeXTcube]] computer (1990) with 32 bit microprocessor [[Motorola 68040]] operated at 25 [[MHz]]. At the lower edge of the image and left from the middle, the heat sink mounted directly on the CPU can be seen. There was no dedicated fan for the CPU. The only other IC with a heat sink is the [[RAMDAC]] (right from CPU).]]
[[Passive cooling|Passive]] heatsink cooling involves attaching a block of machined or extruded metal to the part that needs cooling. A thermal adhesive may be used. More commonly for a personal computer CPU, a clamp holds the heatsink directly over the chip, with a thermal grease or thermal pad spread between. This block has fins and ridges to increase its surface area. The heat conductivity of metal is much better than that of air, and it radiates heat better than the component that it is protecting (usually an integrated circuit or CPU).

Dust buildup between the metal fins of a heatsink gradually reduces efficiency, but can be countered with a gas duster by blowing away the dust along with any other unwanted excess material.

Passive heatsinks are commonly found on older CPUs, parts that do not get very hot (such as the chipset), low-power computers, and embedded devices. Many smartphones use only passive cooling.

Usually a heatsink is attached to the integrated heat spreader (IHS), essentially a large, flat plate attached to the CPU, with conduction paste layered between. This dissipates or spreads the heat locally. Unlike a heatsink, a spreader is meant to redistribute heat, not to remove it. In addition, the IHS protects the fragile CPU.

Passive cooling involves no fan noise, as [[convection]] forces move air over the heatsink.