The thermally conductive silicone sheet is a thermally conductive medium material synthesized by a special process with silica gel as the base material and various auxiliary materials such as metal oxides added. In the industry, it is also known as thermally conductive silicone pad, thermally conductive silicone sheet, soft thermally conductive pad, thermally conductive silicone gasket and so on. It is specially produced for the design scheme of using the gap to transfer heat. It can fill the gap and complete the heat transfer between the heat-generating part and the heat-dissipating part. At the same time, it also plays the role of insulation, shock absorption and sealing, which can meet the requirements of miniaturization and ultra-thin equipment. The design requirements are that it is extremely manufacturable and usable, and has a wide range of thicknesses. It is an excellent thermal conductive filling material.
The production process of thermally conductive silicone sheet, the main production process steps are: raw material preparation → plasticizing, mixing → molding and vulcanization → trimming and cutting → inspection, etc. The following is a brief introduction to the production process of thermally conductive silicone sheets:
1. Raw material preparation
The thermal conductivity of ordinary silicone is usually only about 0.2W/m·K. However, mixing thermal conductive fillers in ordinary silica gel can improve its thermal conductivity. Commonly used thermally conductive fillers are metal oxides (such as Al2O3, MgO, BeO, etc.), metal nitrides (such as SiN, AlN, BN, etc.). The thermal conductivity of fillers is not only related to the material itself, but also closely related to the particle size distribution, morphology, interfacial contact, and intramolecular bonding degree of thermally conductive fillers. In general, fibrous or foil-like thermally conductive fillers have better thermal conductivity.
2. Plasticizing and mixing
Plasticizing and mixing is a process of silica gel 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 of mixing and molding. The raw materials of thermally conductive silicone sheets are generally destroyed by mechanical high-speed stirring. After color matching and mixing, the flakes of various colors are transformed from milky white silica gel.
3. Forming and vulcanization
If you want to make a soft, elastic and tensile-resistant thermally conductive silicone sheet, you need to use silicone that has undergone secondary vulcanization. Vulcanization can actually also be called curing. After the liquid thermal conductive silica gel is heated and formed in the first stage, its cross-linking density is not enough, and further vulcanization reaction can increase the tensile strength, resilience, hardness, swelling degree, density and thermal stability of the thermal conductive silica gel sheet. Vulcanization has greatly improved. If the secondary vulcanization is not carried out, the performance of the thermally conductive silicone sheet produced 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 of secondary vulcanization, which are also related to the actual operation process and steps.
4. Trimming and cutting
The thermally conductive silicone sheet after high temperature treatment needs to be placed for a period of time to allow it to cool naturally before cutting to different sizes, and other rapid cooling methods cannot be used. Otherwise, it will directly affect the product performance of the thermally conductive silicone pad.
5. Finished product inspection
The main items that need to be tested for finished products include: thermal conductivity, temperature resistance range, volume resistivity, voltage resistance, flame retardancy, tensile strength, hardness, thickness, etc.
