ABSTRACT
Conduction is the transfer of heat from an area of high energy (temperature) to an area of lower relative energy. Conduction occurs by the energy of motion between adjacent molecules and, to varying degrees, by the movement of free electrons and the vibration of the atomic lattice structure. In the conductive mode of heat transfer we have no appreciable displacement of the molecules. In many applications, we use conduction to draw heat away from a device so that convection can cool the conductive surface, such as in an air-cooled heat sink. For a one-dimensional system,
qL *T = kAc
Therefore, increasing the surface area, A, of a given heat sink reduces Osa. Consequently, increasing the heat transfer coefficient, hc, also reduces the thermal resistance. When we mount a semiconductor on a heat sink, the relationship between junction temperature rise above ambient temperature and power dissipation is given by:
The focus of the remaining chapters is to explore and expand on these basic resistances to heat transfer, and then predict and minimize them (cost-effectively) wherever possible.
