In electronics cooling, usually heat is transferred from chip to ambient. Heat sink is common to be attached at chip as cooling system. Surface area of heat sink usually larger than chip, this condition makes spreading heat transfer.
What is spreading Thermal resistance?
Thermal resistance is the ratio of temperature difference to the corresponding power. The difference temperature here refers to the place or point. At a processor with heat sink, heat dissipation is started from ship to heat sink. So obviously chip temperature is higher than heat sink. The temperature difference in this case is the difference of chip temperature and the heat sink, so we called chip to heat sink thermal resistance. It also can be determined, thermal resistance of other point. The total thermal resistance is from the source to the ambient.
Spreading thermal resistance occurs when heat source is smaller than cooling system, such as heat sink. That geometry doesn’t distribute uniformly through the heat sink, but centralized on the middle where the chip is attached.
To analyzed and design cooling system in electronic, usually uses one dimension analysis. Therefore spreading thermal resistance is one of the interests of researcher and electronics cooling engineer.
Besides spreading thermal resistance, Thermal contact interface also influences heat transfer. When chip is attached to heat sink, there is contact between two surfaces. To optimize heat transfer, there are several ways to be applied in thermal interface material. Those are: grease, elastomeric pads, thermal tapes, phase change materials, gels, thermally conductive epoxy, solder, and soft metal.
Thanks a lot.
ReplyDeleteA Heat Sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium.