A thermal pad is part of a
thermal system. How does a thermal pad dissipate the heat generated by the CPU?
First, it is important to understand that there are three types of heat
conduction: conduction, convection and radiation.
Conduction refers to the
exchange of kinetic energy between molecules, the collision of lower energy
particles and higher energy particles to obtain energy (through direct physical
contact), a single piece of heat conduction is not able to achieve heat
conduction. In a word, conduction is the most important way that the heat
conductor gets heat from the CPU.
Convection is the transfer
of heat through the movement of hot matter. It means that heat comes from a
source of heat surrounded by a gas or liquid, which is transferred by the
movement of molecules. We can achieve forced convection by adding a fan to the
heat conducting sheet. Convection is the main mode of fan/heat exchanger
combination refrigeration. Most of the heat generated by the CPU is carried
away by the convection formed by the fan, and only a very small amount of the
heat is emitted through radiation.
In order to achieve this
effect, a heat conductor must be designed to enhance the effect.
Two methods are usually used
to achieve this: the surface area of the heat conductor is increased as much as
possible to facilitate the flow of air. The use of metal fins not only
increases the heat conduction area, but a good metal fin design also makes
convection more efficient. Make the contact surface between the thermal pad and
the CPU as smooth as possible, otherwise, the thermal insulation layer will be
formed between the CPU and the thermal pad. Of course, even if the contact
surface is very smooth, there will inevitably be the existence of gaps,
therefore, in the contact place can use thermal paste, thermal silicon grease
or special thermal patch as an aid to improve the contact area.
Radiation, as the name
suggests that heat is emitted directly from a heat source in the form of an
electromagnetic field (transmitted by photons). Radiation can take place in a
vacuum.
The heat transfer efficiency of radiation depends on the material of the heat source and the color of the surface.
