Selection Of Thermal Conductive Materials

When it comes to heat dissipation systems, many people think of fans and fins. In fact, they have neglected a medium which is insignificant but plays an important role - heat conduction medium. Computer CPU is a typical power equipment that needs excellent heat dissipation, so let's talk about heat conduction data. I hope we can discuss and express our views on heat dissipation of various power equipment. Why do some people think that the surface of CPU or the bottom of radiator is very smooth, and there is no need for heat conduction media between them? This idea is wrong! Because it is impossible to make an ideal flat surface by mechanical processing, there are many ravines or vacancies between CPU and radiator, all of which are air. We know that the thermal resistance of air is very high, so we must use other materials to reduce the thermal resistance, otherwise the function of the radiator will be discounted, or even unable to play a role. Therefore, thermal conductive media came into being. Its function is to fill the large and small space between the processor and the radiator, and increase the touching area between the heat source and the radiator. Thereby, heat conduction is only one function of heat conduction medium, and the most important function is the effective touch area of CPU and radiator.

1. Thermal conductive silicone grease is one of the most widely used thermal conductive media. It uses silicone oil as raw material, and adds fillers such as thickeners, after heating, decompression and grinding.An ester-like substance formed by grinding and other processes. The substance has a certain viscosity and no significant granular sensation. The working temperature of the thermal conductive silicone grease is generally from - 50 C to 180 C. It has good thermal conductivity, high temperature resistance, aging resistance and waterproof properties. In the process of heat dissipation, after heating to a certain condition, the thermal conductive silicone grease presents a semi-fluid state, filling the space between CPU and radiator, making the joint between them more closely, and then strengthening the heat conduction. Usually, thermal conductive silicone grease is insoluble in water, not easy to be oxidized, and has certain smoothness and electrical insulation. (Now the better brands in the market are: Dow Corning, Xinyue, the better thermal conductive silicone grease made in China is Tianshan (said to be a brand in Hong Kong), Lifeng Electronics, Huaneng Zhiyan, and one of the domestic brands, which I have tried Tianshan 940 and Kuneng Supreme, a claim of 7.0 thermal conductivity coefficient. In terms of the effect, the former Kuneng Supreme Temperature will be slightly better than 940, but after two days, the effect will be 0.5 C. Tian Zhongshan's Bikuneng Supreme Decrease by 1 Celsius I do not know if it is my solution. After parting from the manufacturer and colleagues of this profession, we came to the conclusion that Coolness lives in the radiator. The thermal conductive silicone grease is packed by Dow Corning 5126 and Xinyue 7762. The other part is packed by Tianshan and Huaneng Zhiyan products as raw materials, so it is not put into the domestic brand.

2. Thermal conductive silica gel (thermal conductive adhesive) is a kind of molecular chain based gel (107 gel) containing C-Si results, which adds thermal conductive powder to the base gel. The molecular chains are then crosslinked by crosslinking agents to form a thermal conductive adhesive that can bind raw materials and conduct heat. Its thermal conductivity is slightly lower than that of silicone grease, but it has one more bonding function than that of thermal conductivity. It can be widely used in some electronic thermal components which need bonding. However, due to its thermal conductivity can not reach the high thermal conductivity silicone grease, thermal resistance is also higher than silicone grease, so it can not be used with high thermal conductivity requirements.The brand of thermal conductive silica gel on the market is the same as that of silicone grease, many are also very miscellaneous, but what I want to say is that. Because of its special functions and packaging requirements, thermal conductivity of silica gel can not be improved. Generally, the thermal conductivity of silica gel is between 0.8 and 1.5 at the domestic level, which is higher than that of silica gel. However, it is often achieved at the expense of some other functions, such as bonding force and shear strength. More importantly, its appearance humidity (as for the importance of appearance humidity is not clear to Baidu, maybe see my next article reported high.) Now, there are a few brands in this area, because they are not used very much. The recommended brands are: Dow Corning, Xinyue, TENSAN, and sisun).

3. Graphite gaskets are relatively rare heat conducting media and are generally used on objects with less calorific value. It uses graphite composite material, after certain chemical treatment, has excellent thermal conductivity, and is suitable for heat dissipation system of electronic chips, CPUs and other products. In the early Intel boxed P4 processors, the material attached to the bottom of the radiator was a graphite heat conducting gasket called M751 (Fig. 2). The advantage of this heat conducting medium was that it was not sticky and would not "pull" the CPU from the base when the radiator was dismantled. In addition to the common heat conducting media mentioned above, aluminum foil heat conducting gaskets, phase change heat conducting gaskets (plus maintenance film) are also attributed to heat conducting media, but these products are rare in the market.The recommended brands are American eGRAF Japan Panasonic

4. Flexible silica gel thermal conductive pad has excellent thermal conductivity and high-grade voltage insulation. Its thermal conductivity is 1.75W/mK and breakdown value is over 4000 volts. It is a substitute product for thermal conductive silica grease. Its data itself has certain flexibility. It fits well between power equipment and heat sink or machine shell, and then reaches the best thermal conductivity and dispersion. Thermal purpose, in line with the requirements of the electronic profession for thermal conductivity data, is the best product to replace the binary heat dissipation system of thermal conductive silicone grease heat conductive paste and mica sheet.