One of the most fundamental features of thermal planning is based around finding the best method of heatsink cooling. While the makers of heatsinks set out to design the perfect balance of surface area and internal conductivity, and while they struggle to make sure that the system of mounting the heatsink to the heat source is perfectly level so that the highest level of heat is transferred through, there is still the external cooling that must not be ignored. That's because a heatsink can only work if the air surrounding it is cooler, so that the heatsink's thermal trajectory from the heat source to its final destination - the outside, ambient air - is complete.
One type of heatsink actually relies on ventilation that does not come from a fan. It is called a passive heatsink, and its design optimizes cooling through a high level of surface area created by multiple thin fins. Yet while certain components are able to function with the passive model, the thermal requirements of many manufacturers today call for the use of external heatsink cooling systems, most commonly in the form of fans.
Fans provide the necessary air flow to make sure that heat is dispersed sufficiently and that the heatsink functions best. Commonly referred to as forced convection, the use of fans is necessarily coupled with a change in the design so that the heatsink has less surface area, but better channels of ventilation. For effective heatsink cooling, a fan that is powerful enough to draw out all of the heat on time must be implemented. However, one of the trade-offs that heatsink designers must make is based on noise level involved. Cooling heatsinks can be a very loud process if powerful or multiple fans are used. Therefore, it is necessary to have a cooling system that is effective yet consumer friendly.