What is Heatsink
This page covers Heatsink basics and mention parameters to select the correct Heatsink.
Heat transfer: It occurs when two surfaces have different temperatures.
This will cause heat energy to transfer from hot surface to cold surface.
Example:
➨voltage is the
driving force that causes current to flow.
➨Similarly, temperature is the force that causes heat to flow.
Amount of heat flow depends on difference in temperature between the two surfaces.
There are three modes of heat transfer viz. Conduction, Convection and Radiation.
These have been illustrated below.
Conduction:It is transfer of heat energy through or across medium.
Convection:It is transfer of heat energy from hot surface to moving fluid (e.g. water, air etc.)
which is at lower temperature comparatively.
Radiation:It is transfer of heat energy which is
in the form of electro-magnetic waves between the two surfaces possessing
different temperatures.
Heatsink is the hardware structure designed using metal to dissipate heat at a fast rate to prevent excessive temperature rise in the circuit.
This is planned at the PCB design stage itself. This is required because all the semiconductor devices will introduce some amount of resistance in the circuit similar to discrete resistor and coil. Due to this fact, while controlling current these devices dissipate power in the form of heat energy.
Parameters to select Correct Heatsink
Following parameters are considered while designing or
selecting heatsink for the need.
• Q-Amount of heat (W)
• Tjmax maximum allowable junction temperature (degree C)
• Ta - ambient fluid temperature (degreeC)
• RΘjc - thermal resistance of the device
• RΘcs - thermal resistance of the interface material
• Thermal resistivity (ρ), contact area(A) and thickness(t)
• Natural or forced convection cooling
• Air flow (i.e. LFM) in the case of forced convection
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