What Is The Mechanical Properties of Thermal Pads

What Is The Mechanical Properties of Thermal Pads

The thermal pads often needs to be assembled between the frames of the heat sink to play the role of heat conduction, buffering and shock absorption. However, in practical applications, in order to ensure that the thermal conductive gasket can be intact during assembly, can fill the gap correctly, and the gasket is not damaged and fallen off during use, we need to evaluate the mechanical properties of the thermal conductive gasket.

The mechanical performance indicators of thermal silicone pads mainly include tensile strength (tensile strength), tear strength, compression rate, rebound rate, etc. Let’s give a brief introduction.

The test methods for tensile strength and tear strength of thermally conductive gaskets refer to ASTM D412 and ASTM D624, respectively. Tensile strength refers to the tensile stress applied to a specimen to rupture it. Tear strength refers to the maximum force required to completely tear the sample when the two “trouser legs” of the elongated film sample with a slit are subjected to tension by a tensile testing machine, divided by the thickness of the sample, in kN/ m is expressed in units. These two properties of the thermally conductive gasket and the elongation at break obtained in the test at the same time reflect the ability of the product to be deformed by force and the difficulty of being damaged by force during assembly and use, and are the embodiment of the strength and toughness of the product.

The ratio of the compressed amount of the thermal silicone pads after installation to the actual thickness in the free state is called the compression ratio. The compression rate of thermally conductive gaskets is a mechanical property index for evaluating the compressive properties of thermally conductive gaskets, and the test method refers to the standard ASTM D575. The deformation characteristics of thermal pads during loading are an important condition for forming the initial sealing ability, which has a great relationship with the compression rate and rebound rate.

The harder the thermal pad, the smaller the compression rate under the same pressure. Under normal installation preload, it is easy to cause structural damage to the thermally conductive silicone gasket; the softer the thermally conductive gasket, the greater the compression rate of the thermally conductive gasket under the same pressure. The initial installation pre-tightening force required during use is large, and it is difficult to achieve the sealing effect. Generally, the compression performance is evaluated by testing the compression rate of the thermal silicone pads under the pressure of 0~100psi, and drawing a pressure-compression rate curve.

Rebound ability or rebound rate of thermally conductive silicone gasket: The rebound rate of thermally conductive gasket is the ability of the gasket to restore elasticity after the gasket is unloaded, and it is the ratio of the thickness of the gasket after the pressure is removed for a period of time to the initial thickness. The high rebound rate of the thermally conductive silicone gasket indicates that the thermally conductive gasket has a strong compensation ability and a good sealing effect.

On the premise of meeting the compression rate requirements, the higher the rebound rate, the better. On the premise of meeting the requirements of the rebound rate standard, the larger the test value of the compression rate, the better. In practical applications, thermally conductive silicone gaskets with good sealing performance, moderate compression rate and maximum rebound rate should be selected.

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