How to apply thermal grease (thermal grease)? |
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| Reading Volume： 【 2076 】 | Time： 【 2017-12-13 】 | |
| Thermal grease is also often called thermally conductive silicone grease. In fact, it should be called silicone paste. Its composition is 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 a molecular weight of several thousand to several hundred thousand. It has excellent heat resistance, electrical insulation, thermal conductivity, damping, and viscosity is not sensitive to temperature. Its chemical properties are stable, non-volatile, non-toxic and tasteless. Silicone paste filler is a finely ground powder, the composition is zinc oxide/aluminum oxide/boron nitride/silicon carbide/aluminum powder, etc. (it is the white thing we usually see). Silicone oil ensures a certain degree of fluidity, and the filler fills the tiny gap between the CPU and the thermal paste to ensure thermal conductivity. However, due to the low temperature sensitivity of silicone oil, it will not thicken at low temperature, will not become thinner at high temperature, and it is not volatile, so it can be used for a long time. The heat transfer between the heat sink and the CPU is mainly through the conduction path, mainly through direct contact between the heat sink and the CPU. The significance of thermal grease is to fill the gap between the two to make contact more completely. If the silicone grease is used excessively, a silicone grease layer is formed between the CPU and the heat sink, and the heat dissipation path becomes CPU---silicone grease---heat sink. The thermal conductivity of silicone grease is about 1~2W/(mK), while the heat sink of aluminum alloy is above 200W/(mK). In this case, silicone grease becomes a factor hindering heat transfer. Therefore, the appropriate amount of silicone grease must be applied. Just apply a thin layer on the CPU core. Nowadays, some high-grade thermal conductive silicone greases use silver powder or aluminum powder as fillers, which take advantage of the high thermal conductivity of metals, but relatively speaking, the metal particles are relatively large, the filling effect is poor, and the performance improvement is not large, and the silicone grease With conductivity, improper use can easily cause short circuits. Regular painting method: The correct use of CPU thermal grease 1. First, clean the surface of the CPU core and radiator with a high-purity solvent such as high-purity isoamyl alcohol or acetone and a lint-free cloth (such as a cloth for cleaning the lens) (a fingerprint may be as thick as 0.005 inches). I personally feel that this step can be omitted, as long as the surface is clean and oil-free. 2. Determine the area on the heat sink that is in contact with the CPU, and squeeze enough thermal grease in the center of the area. 3. Use a clean tool such as a razor blade, the edge of a credit card or a clean knife to pick up a little thermal paste and transfer it to the corner of the CPU core (such as the lower left corner). Note that only a small piece is enough, about the size of a half grain of rice. 4. Put your fingers into the plastic bag, and then rub the thermal paste on the bottom of the radiator with your fingers until the thermal paste evenly covers the entire area in contact with the CPU. Clockwise and counterclockwise movement can be used to ensure that the thermal paste can fill the gaps and uneven places at the bottom of the radiator. Note: Do not apply directly with your fingers! 5. Wipe off the thermal grease on the bottom of the radiator with a lint-free cloth. At this time, you can see that the color of the thermal grease on the bottom of the radiator is different from other areas, indicating that the thermal grease has evenly filled the gap in the base. 6. Using a razor blade or other clean tool, start from the corner of the CPU core and spread the thermal grease evenly over the entire core. The flatter the surface to be touched, the thinner the need for thermal paste. For the bottom surface of a common radiator, the thickness of the thermal paste is about the thickness of a sheet of plain paper (0.003-0.005 inches). If the bottom surface of the radiator is bright and flat, the thermal paste can be as thin as translucent. 7. Confirm that there is no foreign matter on the surface of the heat sink base and the CPU core. Put the heat sink on the CPU. At this time, only lightly press the heat sink, and cannot rotate or translate the heat sink. Otherwise, the thickness of the thermal paste between the heat sink and the CPU may be uneven. |
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