Silicone potting compound
Potting materials are varied, but the most widely used ones are mainly synthetic polymers. Among them, epoxy resin, polyurethane elastomer and silicone polymer are the most widely used polymers. Silicone polymer materials are widely used in electronic appliances due to their unique silicone-bonded backbone structure, unique weather resistance, aging resistance, excellent high and low temperature resistance, good hydrophobic mechanical properties, electrical insulation, etc. Potting protection of components; display potting of semiconductor light-emitting diodes (LEDs) is mostly made of silicone potting.
product description
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2.1 Composition and classification of silicone potting compound
The silicone potting compound is composed of a silicone resin, a crosslinking agent, a catalyst, a heat conductive material and the like. Silicone rubber potting compound can be divided into room temperature vulcanized silicone rubber according to molecular structure and crosslinking method; two-component plus forming silicone rubber potting compound (ARC silicone rubber); two-component condensation type silicone rubber potting compound (RTV silicone rubber) )
ARC silicone rubber adhesive cures without small molecules, and the crosslinked structure is easy to control. The shrinkage rate is below 0.2%. The electrical properties and elasticity are better than RTV silicone rubber, and the process performance is superior. It can be cured at room temperature or at the same time. Cured in a short time after heating. Therefore, ARC silicone rubber potting compound is recognized as a new material for the electronics industry with great development at home and abroad.
2.2 two-component plus forming silicone rubber potting
Common two-component two-component plus shaped silicone rubber potting compound: composed of terminal vinyl silicone oil as base rubber, hydrogen-containing silicone oil as crosslinking agent, and aluminum oxide (A l2O3 ) as heat conductive filler. Methacryloxypropyltrimethoxysilane (KH570) may be added as a coupling agent, and a platinum catalyst (PL-2600) may be used as a catalyst.
2.2.1 curing characteristics
In this reaction, a hydrogen functional group-containing polysiloxane is used as a crosslinking agent (vulcanizing agent), chloroplatinic acid or a soluble platinum compound thereof as a catalyst. The vulcanization reaction is carried out at room temperature without releasing by-products, so the addition-molded silicone gel does not shrink during the vulcanization process. This type of vulcanizate is non-toxic, has excellent hydrolysis stability, good low compression set, low combustion, deep vulcanization, and vulcanization speed can be controlled by temperature.
2.2.2 Effect of particle size of thermal conductive material on the performance of potting compound
The larger the particle size of Al2O3, the higher the thermal conductivity of the potting compound, but the tensile strength and elongation at break are reduced. The suitable particle diameter of A l2O3 is 5μm or 18μm. With the increase of the amount of A l2O3, the irrigation The thermal conductivity and tensile strength of the sealant increase, the elongation at break increases first and then decreases, and the viscosity increases. The suitable addition amount of Al2O3 is 150-200 parts; the filling of different particle size Al2O3 into the potting glue can be improved. The thermal conductivity of the potting compound, when the mass ratio of 18μm Al2O3 and 5μm Al2O3 is 3:2, the thermal conductivity of the potting compound is higher, and has no effect on the viscosity and mechanical properties of the potting compound.