How Are Thermal Pad Tested?

How Are Thermal Pad Tested?

Whether it is the staff of the thermal pads manufacturer or the customer, everyone knows the thermal pads, and the specifications of the thermal pads can also be known a little, but how are the specifications and parameters of the thermal pads tested? I believe that few people can fully answer it, so CoolThermo feels that it is necessary to introduce the knowledge points of the physical property test standard of this thermal silicone gasket to everyone here, friends, come and watch!

Why use thermal silicone gaskets? The main reason is to improve the heat dissipation efficiency of heating products and reduce the impact of high temperature rise.

  1. 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;
  2. Reduced reliability: for every 2 degrees Celsius increase, the reliability of product usage decreases by 10%;
  3. The processing speed is reduced and the signal is delayed;
  4. Increased idle power dissipation.

Therefore, when the user chooses whether the thermal silicone gasket is qualified, the following very important specifications should not be ignored by the customer: thermal conductivity, thermal resistance, thickness, hardness, tensile strength, tear strength, impact Breakthrough voltage, dielectric constant, volume resistivity and other physical properties; below, CoolThermo Technology will explain in detail what instrument, what standard, what method and how to test these specifications.

Test method for thermal conductivity of thermal pad

Thermal conductivity: It refers to the heat transferred through 1 square meter area in 1 second with a 1mm thick thermal pad, the temperature difference between the two sides is 1°C, in 1 second, expressed by λ, the unit is W/ mk, thermal conductivity, like mass, is the property of the material itself and is not affected by external factors.
Apparent thermal conductivity: This value is different from thermal conductivity because apparent thermal conductivity also includes the contact thermal resistance at the time of measurement.

Test method for thermal conductivity of thermal pads (1)

Test equipment: thermal conductivity tester
Test reference standard: ASTM D5470
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.

Test method for thermal conductivity of thermal pads (2)

Test instrument: HOT DISK thermal conductivity tester
Test reference standard: TPS

Thermal resistance test method of thermal pad

Test instrument: material thermal resistance tester
Test reference standard: ASTM D5470
This standard simulates the test of structural components applying pressure on thermally conductive materials. The change of temperature conduction is monitored by the probes (six probes) attached to the bottom of the thermal conductive material, and then the thermal resistance is obtained by calculating with the computer.

How to measure the thickness of thermal pad

Measuring instruments: thickness gauge, caliper
Test reference standard: ASTM D374
Due to the softness of the product itself, the human operation factor plays a key role in the thickness test process, and the inspection workers who are skilled in caliper operation should perform the inspection as much as possible, whichever is in contact with the product. Excessive force will cause the product to compress, so here is a reminder for thermal design work. Personnel: When designing, the selection of thermally conductive materials should be at least 20% to 30% larger than the size of the gap of the structural parts.

How to measure the hardness of thermal pad

Testing instrument: Shore hardness tester
Test reference standard: ASTM D2240
There are currently three types of Shore hardness testers: shore00, shoreA, and shoreC. Different companies have different standards. Due to the softness of the thermal pad, it is recommended to use C-type hardness. Note that the thickness of the specimen is required to be at least 6mm.

Measuring method of tensile strength of thermal pad

Test equipment: universal material testing machine
Test reference standard: ASTM D412
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. The computer will instruct the testing machine to pull the material until it breaks, so as to calculate the tensile strength.

Method for measuring tear strength of thermal pad

Test equipment: universal material testing machine
Test reference standard: ASTM D412
The thermal pads must be formed into a standard sample as required (usually die-cutting is used). The universal material testing machine is connected to the computer through a data cable. According to the change of stroke and force, the computer will calculate the tear strength of the product and present it in the form of a numerical value .

Measurement method of breakdown voltage of thermal pad

Test instrument: Withstand voltage tester
Test reference standard: ASTM D149

Test method for dielectric constant of thermal pad

Dielectric constant: also known as permittivity, the medium will generate induced charges and weaken the electric field in the external electric field. The ratio of the permittivity in a medium to the permittivity in vacuum in the same original electric field is the relative permittivity, also known as the relative permittivity. Relative permittivity, if a material with a high dielectric constant is placed in an electric field, the strength of the field will drop significantly in the dielectric.
The dielectric constant is an important data to characterize the electrical properties of dielectrics or insulating materials. It is often expressed by ε. The dielectric constant of vacuum is 1.0, the dielectric constant of thermally conductive products is 2~10, and the dielectric constant of superconductors is infinite.
Test instrument: WY2851Q meter
Test reference standard: ASTM D150
Introduction to the test method: It is composed of two micro-measuring capacitors. The plate capacitor is used to hold the sample. The cylindrical capacitor is equipped with a Q meter as an indicator. The change of the Q value of the sample is converted from the change of the scale reading value of the cylindrical capacitor, and the dielectric constant is converted from the change of the scale value of the plate capacitor.

Test method for volume resistivity of thermal pad

Test instrument: high resistance meter
Test reference standard: ASTM D257
Keep a standard volume of thermal pads under the specified voltage for the required time, measure the generated current, and inversely calculate the resistance of the material itself through the generated current. The higher the volume resistivity, the more effective the material is as an electrically insulating component.

The above is the sharing of CoolThermo’s introduction to the testing standards and methods of thermal pads. I believe that after reading the small partners, the thermal conductivity, thermal resistance, thickness, hardness, tensile strength, tear strength, breakdown voltage, dielectric Have a clear understanding of the test methods and standards for physical properties such as constants and volume resistivity!

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