An uncooled microprocessor will heat up and rapidly overheat, and undergo thermal stress as a result of heating up and cooling down when they are switched on and off. Often they are designed to power down if overheated, but this can make them unreliable in use. In practice heat must be removed from a chip by some cooling method. The cpu's in computers used to be cooled with the use of cooling fins – metal plates with large surface areas. More modern computers are usually air cooled by positioning fans over the cpu and more powerful computers may be liquid cooled.
An integrated circuit may be immersed in a fluorocarbon fluid. This fluid is an electrical insulator and chemically unreactive. They are not very efficient transporters of heat though because of small values of thermal conductivity and latent heat of vaporization. To improve the rate of heat transfer, convection channels may be cut into the base of the chip.
The chips used in mobile phone present very special problems. They must be powerful enough to operate modern smartphones but use very little power so they do not overheat. This could result in the phone being uncomfortable to use, having a very short battery life, repeatedly switching itself off, or even catching fire. In these phone, special low power chips have been developed than can perform operations in a reduced number of cpu cycles.
In the future calculations may be performed by DNA, light and quantum processes. These may present less problems of heat dissipation because the are inherently more efficient, but it may be dificult to have calculations performed at the press of a button. There may always be a need for microprocessors and the problem of dissipating heat reliably may always exist.