The heat generated due to power dissipation can be taken away by the use of heat sinks. A heat sink has lower thermal resistance than the package and hence draws heat from it. For the heat to be effectively removed, the rate of heat transfer from the area of heat generation to the ambient should be greater than the rate of heat generation. This rate of heat transfer depends on the thermal resistance.
The thermal resistance, is given by the following relation:
(Eq 26.2)
where,
l = length,
A = Area and
= thermal conductivity of the heat sink
From the above relation it can be seen that large implies smaller .
is also given by the relation,
(Eq 26.3)
Using this relation, we can see that for a given power dissipation,
(Eq 26.4)
where,
= junction temperature, and
= ambient temperature.
Heat sink materials are generally coated black to radiate more energy
is given by the following relation:
= thermal conductivity of the heat sink 
= junction temperature, and 
= ambient temperature. 
