Regarding the testing standards and methods of thermally conductive materials (thermal pads, thermal grease, thermal adhesive tape), etc., many people have little knowledge. CoolThermo Technology Co., Ltd. wrote this article to popularize it.
1. Why use thermally conductive materials (thermally conductive silicone grease, thermally conductive silicone sheet, thermally conductive ceramic sheet)
The main reason is to improve the heat dissipation efficiency of heating products and reduce the impact of high temperature rise.
- Reduced lifespan: Long-term use of heating products without paying attention to heat dissipation will cause the temperature of the internal components of the product to continue to rise, thereby reducing the product lifespan. The lifespan of a temperature rise of 50 degrees Celsius is only half of that of a temperature rise of 25 degrees Celsius.
- Reliability decreases: for every 2 degrees Celsius increase, the reliability of product usage decreases by 10%
- The processing speed is reduced and the signal is delayed
- Increased idle power dissipation
2. The key characteristics of thermal conductive materials (silica gel sheet, thermal conductive silicone grease, thermal conductive ceramic sheet) need to be tested
- Tear strength
- Tensile strength
- Breakdown voltage
- Dielectric constant
- Volume resistivity
- Thermal conductivity and resistance
How to measure thickness:
Required measuring instruments: thickness gauge, caliper
Test reference standard: ASTM D37
Test focus: Because of the softness of the silicone sheet product itself, human factors play a key role in the measurement. We generally use the caliper to operate the inspection workers who are skilled in the inspection. The force cannot be too large during the inspection, otherwise It will cause compression, so the thermal designers are reminded: the selection of thermal conductive materials should be at least 20%-30% larger than the size of the gap of the structural parts during design.
How to measure hardness
Test instrument: hardness tester
Test Standard: ASTM D2240
Main content: The test standards used by different companies are different. Due to the softness of the thermal conductive material (Zhire silicone sheet), it is recommended to use C-type hardness. During the test, the thickness of the sample is generally required to be 6MM
Measurement method of tear strength
Test equipment: material testing machine
Test Standard: ASTM D412
The main points of the test: form the material into a standard sample according to the requirements, and the universal material testing machine is connected to the computer through the data cable. According to the stroke and force changes, the computer will calculate the cracking strength of the product and present the test results in the form of numerical values.
Measurement method of breakdown voltage
Test instrument: Withstand voltage tester
Test reference standard: ASTM D149
The tensile strength test is similar to tearing, and it is also tested by a universal material testing machine. The difference is that the shape of the sample has special requirements (as shown on the left). The computer will instruct the testing machine to pull the material off until the tensile strength is calculated.
Thermal conductivity refers to the heat transfer through 1 square meter area in 1 second for a material with a thickness of 1m and a temperature difference of 1°C on both sides of a material with a thickness of 1m under stable heat transfer conditions. degrees), w/(m k)
Thermal conductivity, like quality, is a property of the material itself and is not affected by external factors.
Thermal conductivity test method(1)
Test equipment: thermal conductivity tester
Testing in a vacuum state can effectively remove the influence of air on the test. The standard thickness and pressure of the test sample are issues that need to be paid attention to.