Views: 1023 Author: Site Editor Publish Time: 2021-11-22 Origin: Site
The thermal conductivity of thermal conductive silicon film is a physical quantity reflecting the thermal conductivity of materials. ASTM D5470 is a common test method to measure the thermal conductivity of materials in scientific experiments and engineering technology. Generally, it can be divided into steady-state method and dynamic method. Through the experiment, we can deepen the understanding of the law of heat conduction, experience the design idea of using the parameter conversion method, and master the method of measuring with the temperature sensor.
Thermal conductivity of thermal conductive silicon pad refers to the ability of material to conduct heat directly, also known as heat conductivity. Thermal conductivity is defined as the heat directly conducted by the material of unit section and length under unit temperature difference and unit time; The unit of thermal conductivity is w / M.K. It can be seen from the law of Fourier equation that:
Among them, A is the cross-sectional area of the heat-conducting material, Q is the heat conducted per unit time, d is the thickness of the heat conductor between the two heat sources, △T is the temperature difference, and R is the thermal resistance value.
The steps of the thermal conductivity test method of thermal pad are as follows:
1、 Sample preparation of thermal conductive silicon pad
(1) The sample of thermal conductive silicone film should be homogeneous thermal conductive silicone film material, and the two surfaces should be flat, smooth and parallel, without cracks and other defects.
(2) Flat specimens require unevenness within 0.5 mm/m.
(3) A wooden frame is required for soft thermally conductive silicone sheet material, and the thermally silicone pad sample should be homogeneous on the whole.
(4) The thermal conductive silicon film sample is round or square, its diameter or side length is equal to that of the heating plate, its thickness is not less than 5mm, and its maximum thickness should not exceed 1 / 8 of its diameter or side length.
(5) Each group has 2 thermal silicon pad samples.
The thermal conductive silicon pad sample was adjusted and treated for 24 hours according to the required state.
2、 Determination steps
(1) Measure at least four points around the sample of thermal conductive silicon film. The average value is taken as the thickness of the sample before the test.
(2) Put the heat-conducting silicon pad sample whose state has been adjusted between the cold and hot plates of the instrument, so that the heat-conducting silicon film sample is in close contact with the cold and hot plates.
(3) Keep the temperature of the hot and cold plate constant and the selected temperature difference. The temperature reading should be accurate to 0.1k.
The temperature of hot plate is lower than 333k;
Cold plate temperature room temperature or required temperature.
The temperature difference between the cold plate and the hot plate is not less than 10k, and the temperature gradient of the sample passing through the thermal conductive silicon film is between 400k / M and 2000K / m.
(4) When the temperature difference between the main heating plate and the guard heating plate is less than ± At 0.1k, the temperature is considered to be in equilibrium.
(5) Under the condition of constant main heating power, the temperature fluctuation of main heating plate does not exceed 10 ℃ ± At 0.1k/h, it is considered to be stable.
(6) The heat flux through the effective heat transfer surface and the temperature difference between the two sides of the conductive silicon film sample were measured three times every 30 minutes.
(7) Calculate the thermal conductivity of the silicone pad, and end the test when the difference between the measured value and the average value is less than 1%.
(8) After the test is completed, measure the thickness of the sample, and take the average of the thickness of the thermally conductive silicone pad sample before and after the test as the thickness of the thermal pad sample.