Heat dissipation paste is also often called thermal conductive silicone grease. In fact, it should be called silicone paste. It consists of silicone oil and filler. Silicone oil is a kind of polysiloxane. From the structural point of view, many silanes are joined together to form a long chain with molecular weight of tens of thousands to hundreds of thousands, which has excellent heat resistance, electrical insulation, thermal conductivity, damping, and viscosity is insensitive to temperature. Its chemical properties are stable, non-volatile, non-toxic and tasteless.
Silicon paste fillers are very fine powders with zinc oxide/alumina/boron nitride/silicon carbide/aluminium powder, etc. (that is what we usually see in white). Silicone oil guarantees a certain fluidity, and the filler fills a small gap between the CPU and the heat sink to ensure thermal conductivity. Because silicone oil has low sensitivity to temperature, does not become thick at low temperature, does not become thinner at high temperature, and does not volatilize, it can be used for a long time.
Heat transfer between radiator and CPU is mainly through conduction, mainly through direct contact between radiator and CPU. The significance of thermal conductive silicone grease is to fill the gap between them to contact more completely. If the silicone grease is used excessively and a silicone layer is formed between the CPU and the radiator, the way of heat dissipation becomes CPU - silicone grease - radiator. The thermal conductivity of silicone grease is about 1~2 W/(mK), while the heat sink of aluminium alloy is above 200 W/(mK). In this case, silicone grease becomes an obstacle to heat transfer. Therefore, the amount of silicone grease must be appropriate, just coat a thin layer on the CPU core. At present, some high-grade thermal conductive silicone greases use silver or aluminium powder as fillers to make use of the high thermal conductivity of metals, but relatively speaking, metal particles are larger, filling effect is worse, its performance is not greatly improved, and the silicone grease has conductivity, which is easy to cause short circuit when used improperly.
It should be pointed out that the "non-volatile" of silicone oil is relative, and some of the worse silicone oil will dry due to slight loss after a long time of use.
Heat dissipation paste is a heat transfer medium based on polysiloxane, supplemented by high thermal conductivity filler. It is non-toxic, odorless and non-corrosive. Its chemical and physical properties are stable. It has excellent electrical insulation and excellent thermal conductivity. It can also withstand high and low temperatures. It can work for a long time in the temperature range of - 60 250 without air-drying hardening or melting. It is mainly used for filling and heating. The gap between the body and the radiator can improve the heat dissipation effect.