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Aluminum Heat Sink & Profile Manufacturing

address:No. 51 Luming Road Heavy River Management District - Qing Town Dongguan City

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Telephone:+86 13827205356


Calculation of heat dissipation and choice of heat sink

time:2021-01-26 17:44 author:Heat sink design click:

Heat sink of stamped aluminum alloy
Current electronic products mainly use SMD packaging devices, but many high-power devices and some power modules still use perforated packaging. This is mainly because it can be easily installed on the heat sink to facilitate heat dissipation. Calculate the heat dissipation of high-power devices and power modules. Its purpose is to select a suitable heat sink under certain heat dissipation conditions to ensure safe and reliable operation of the device or module.

Introduction to radiator
The small radiator (or heat sink) is made of aluminum alloy sheet by stamping process and surface treatment. The large radiator is made of aluminum alloy extrusion to form a profile, which is then made by mechanical processing and surface treatment. They have various shapes and sizes for different device installations and devices with different power consumption. The radiator is generally a standard part, but profiles can also be provided, which can be cut into a certain length by the user to make a non-standard radiator. The surface of the radiator is treated with electrophoretic paint or black oxygen polarization treatment, the purpose of which is to improve heat dissipation efficiency and insulation performance. It can increase by 10 15% under natural cooling and 3% under ventilation cooling. Electrophoresis painting can withstand voltage of 500 800V.

The radiator manufacturers give different thermal resistance values or related curves for different types of radiators, and give different thermal resistance values under different heat dissipation conditions.

 heat dissipation calculation
Any device has a certain loss during operation, and most of the loss becomes heat. Low-power devices have low loss and no heat sink is required. High-power devices have large losses. If heat dissipation measures are not taken, the temperature of the die can reach or exceed the allowable junction temperature, and the device will be damaged. Therefore, a heat dissipation device must be added. The most common method is to install the power device on the radiator, use the radiator to dissipate the heat to the surrounding space, and add a heat dissipation fan when necessary to enhance cooling and heat dissipation at a certain wind speed. Flow cold water cooling plates are also used on the power devices of some large-scale equipment, which have better heat dissipation effects. Heat dissipation calculation is to determine suitable heat dissipation measures and heat sinks through calculations under certain working conditions. The power device is installed on the heat sink. Its main heat flow direction is from the die to the bottom of the device, and the heat is dissipated to the surrounding space through the heat sink. If there is no fan to cool at a certain wind speed, this is called natural cooling or natural convection heat dissipation.

The heat transfer process has a certain thermal resistance. The thermal resistance transferred from the device wafer to the device surface is RJC, the thermal resistance between the device surface and the heat sink is RCS, and the thermal resistance of the heat sink to dissipate heat to the surrounding space is RSA, and the total thermal resistance RJA=Rjc+Rcs+ Rsa. If the maximum power loss of the device is PD, and the allowable junction temperature of the device is TJ and the ambient temperature is TA, the allowable total thermal resistance R JA can be obtained by the following formula.

  R JA≤(TJ-TA) / PD
   then calculate the maximum allowable thermal resistance R SA from the radiator to the ambient temperature as
  R SA≤({T_{J}-T_{A}}Over{P_{D}})-(R JC+R CS)
Out of consideration of leaving room for design, TJ is generally set to 125°C. The environment temperature should also consider the worse case, generally set TA=40℃ 60℃. The size of R JC is related to the die size and packaging structure, which can generally be found in the device data. The size of R CS is related to mounting technology and device packaging. If the device is installed with a heat sink after using thermal grease or thermal pad, the typical value of R CS is 0.1 0.2℃/W; If the bottom surface of the device is not insulated and an additional mica sheet is required for insulation, its R CS can reach 1°C/W. PD is the actual maximum power loss, which can be calculated according to the working conditions of different devices. In this way, R SA can be calculated, and a suitable radiator can be selected according to the calculated R SA value.