Suggestions on the selection of thermal conductive materials for thermally conductive silicone sheets
When it comes to cooling systems, many people think of fans and heat sinks. In fact, they ignored an inconspicuous but important medium--the heat transfer medium. Computer CPU is a typical power device that needs good heat dissipation, so let's talk about thermal conductive materials. I hope you can discuss and express your experience and opinions on the heat dissipation of various power devices.
Why do you need a thermal medium? The thermal conductive silicone sheet manufacturer Pinyang will tell you that some people may think that the surface of the CPU or the bottom of the heat sink is very smooth, and no thermal medium is needed between them. This view is wrong! Since machining cannot make an idealized flat surface, there are many ravines or voids between the CPU and the heatsink, which are all air. We know that the thermal resistance of air is very high, so other substances must be used to reduce the thermal resistance, otherwise the performance of the heat sink will be greatly reduced, and it will not even work. So the heat transfer medium came into being, its function is to fill the gap between the processor and the heat sink, and increase the contact area between the heat source and the heat sink. Therefore, heat conduction is only a function of the heat transfer medium, and increasing the effective contact area between the CPU and the heat sink is its most important function.
What are the heat transfer media
1. Thermal grease
Thermal grease is the most widely used thermal conductive medium at present. It is an ester formed by adding silicone oil as raw material and adding fillers such as thickeners after heating, decompression, grinding and other processes. There is a certain consistency, no obvious graininess. The working temperature of thermal grease is generally -50 ℃ ~ 180 ℃, it has good thermal conductivity, high temperature resistance, aging resistance and waterproof properties. During the heat dissipation process of the device, after heating to a certain state, the thermal grease will appear in a semi-fluid state, fully filling the gap between the CPU and the heat sink, making the two more closely bonded, thereby enhancing heat conduction. Under normal circumstances, thermal grease is insoluble in water, not easy to be oxidized, and has certain lubricity and electrical insulation. (At present, the better brands in the market are: Dow Corning, Shin-Etsu, and the better domestic thermal greases are Tianzhongshan (it is said to be a brand in Hong Kong), Lifeng Electronics, Huaneng Zhiyan, among the domestic brands, I have tried Tianzhongshan The 940 and the Cool Energy Supreme have a thermal conductivity of 7.0. In terms of the effect, the temperature effect of the Cool Energy Supreme will be slightly better than that of the 940 by 0.5℃ in the early stage, but after 2 days, the temperature of the Cool Energy Supreme in Zhongshan has decreased by 1℃. I don’t know if it is The question of my method. After asking the manufacturers in the industry, they came to the conclusion that the Cool Energy Supreme is based on the radiator, the thermal grease is made of Dow Corning 5126 and Shin-Etsu 7762, and the other part is made of Tian The products of Zhongshan and Huaneng Zhiyan are used as raw materials for packaging, so they are not included in domestic brands.)
2. Thermally conductive silicone sheet (thermally conductive adhesive)
The thermally conductive silicone sheet used by the thermally conductive silicone sheet manufacturer uses a molecular chain base glue (107 glue) containing C-Si results, and thermally conductive powder is added to the base glue. Then, the molecular chains are cross-linked by a cross-linking agent, and finally a thermally conductive adhesive that can bond materials and conduct heat is formed. Its thermal conductivity is slightly lower than that of thermal grease, but it has one more bonding function than thermal conductivity. It can be widely used in some electronic heating elements that need to be bonded. However, because its thermal conductivity cannot reach as high as thermal grease, and its thermal resistance is higher than that of silicone grease, it cannot be used in fields with high thermal conductivity requirements.
NANJING JOYO COMPANY LIMITED
198, Kejian Road, Nanjing City
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