Selected "Tiny Cooling Fan" radiator select volume to meet the requirements of several radiator. Using the selected data sink (preferably data under the harshest ambient temperature Ta), the thermal resistance of the heat sink available natural convection time. In the installation "Tiny Cooling Fan" space and cost conditions allowed, should use the lowest heat sink thermal resistance. It should be remembered, the substrate temperature is slightly lower that the average time between failures (MTBF) will be significantly improved. If you choose "Tiny Cooling Fan" heat sink thermal resistance is greater than the calculated thermal resistance, should be used in a larger volume of the radiator, or use other cooling methods (such as forced convection cooling, etc.).