Thermally conductive silicone pad is a heat-conducting medium used to reduce the contact thermal resistance between the heat source surface and the contact surface of the heat dissipation device. In the industry, it can also be called thermally conductive silicone sheet, thermally conductive silicone pad, soft heat dissipation pad, etc. There are certain differences in the production process of thermally conductive silicone pads of different manufacturers: thermally conductive materials with general solid organic silicone as raw materials, the production process of thermally conductive silicone pads mainly includes: raw material preparation → plasticizing, mixing → molding vulcanization → trimming and cutting → inspection and other five steps.

1. Raw material preparation

Ordinary organic silicone has poor thermal conductivity, and the thermal conductivity is usually only about 0.2W/m·K. However, mixing thermally conductive fillers in ordinary silicone can improve its thermal conductivity. Commonly used thermally conductive fillers are metal oxides (such as Al2O3, MgO, BeO, etc.) and metal nitrides (such as SiN, AlN, BN, etc.). The thermal conductivity of the filler is not only related to the material itself, but also closely related to the particle size distribution, morphology, interface contact, and degree of internal molecular bonding of the thermally conductive filler. Generally speaking, fibrous or foil-shaped thermal conductive fillers have better thermal conductivity.

2. Plastication and mixing

Plastication and mixing are a process of silicone processing, which refers to the use of mechanical or chemical methods to reduce the molecular weight and viscosity of raw rubber to improve its plasticity and obtain appropriate fluidity to meet the needs of further processing by mixing and molding. The raw materials for making thermal conductive silicone pads are generally destroyed by mechanical high-speed stirring. After color matching and mixing, the milky white silicone is transformed into sheets of various colors.

3. Molding vulcanization

If you want to make a soft, elastic and tensile thermal conductive silicone gasket, you need to use organic silicone that has undergone secondary vulcanization. Vulcanization can actually be called curing. After the liquid thermal conductive silicone is heated and molded in the first stage, its cross-linking density is not enough. It needs to be further vulcanized to increase the tensile strength, resilience, hardness, swelling degree, density, and thermal stability of the thermal conductive silicone sheet. It is much better than the primary vulcanization. If secondary vulcanization is not performed, the performance of the produced thermal conductive silicone sheet may be affected to a certain extent, and a product with better performance cannot be obtained. The parameters of the product after primary vulcanization are different from those after secondary vulcanization, which is also related to the actual operation process and steps.

4. Rest and cutting

The thermal conductive silicone sheet after high temperature treatment needs to be placed for a period of time to allow it to cool naturally before cutting into different sizes, and other rapid cooling methods cannot be used. Otherwise, it will directly affect the product performance of the thermal conductive silicone pad.

5. Finished product testing

The main items that need to be tested for the finished product include: thermal conductivity, temperature range, volume resistivity, voltage resistance, flame retardancy, tensile strength, hardness, thickness, etc.

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