Emerging and developing cooling technology
Two-dimensional materials
Two-dimensional materials refer to materials in which electrons can only move freely on the nanometer scale in two dimensions, that is, electrons can only move in a plane. Common two-dimensional materials include graphene, hexagonal boron nitride, superlattices, quantum wells, etc. . Because of its very good thermal conductivity, two-dimensional materials can be used in the packaging of electronic chips to enhance heat dissipation. Graphene, as a typical representative, has an ultra-high thermal conductivity of 5300 W/(m·K) due to its strong sp2 bond, which can be used as a promising heat dissipation material. Many documents have reported that various graphene-based films, graphene paper, multilayer graphene/epoxy polymer materials, and graphene sheets can be used as heat dissipation layers in electronic devices. Hexagonal boron nitride, as a two-dimensional material that conducts heat but does not conduct electricity, has a thermal conductivity of 390 W/(m·K), and the coefficient of expansion is the smallest among currently known ceramic materials. Figure 6 is a schematic diagram of using two-dimensional materials to package an IGBT (Insulated Gate Bipolar Transistor).
Through numerical simulation, Liu Shutian et al. found that the two-dimensional porous material with the best heat dissipation performance is a type of regular hexagonal microstructure. Wu Xiangshui and others introduced in detail the thermal conductivity measurement technology of two-dimensional materials and the thermal conductivity of various two-dimensional materials. Bao Jie uses the two-dimensional layered material hexagonal boron nitride to solve the heat dissipation problem of high-power electronic devices, and proposes a plan to further enhance its heat dissipation effect. The heat dissipation application of graphene in two-dimensional materials is the most representative. The author believes that the graphene film can be covered on the chip during the heat dissipation of the electronic chip, and the hexagonal boron nitride can be filled in the packaging resin, which can be very large. The degree of reduction of thermal resistance. Two-dimensional material heat dissipation is currently in the development stage in the industry, and there is still a long way to go in this field. When mature, two-dimensional materials will definitely shine in the field of chip heat dissipation.
2.2 Ion wind heat dissipation When an electric field is applied between a sharp surface and a blunt surface, a large number of negative ions will be ionized near the sharp surface, and a large number of positive ions will be generated near the blunt surface. The positive and negative ions need to be neutralized, and the negative ions fly away to the positive ions. The movement of ions will cause great disturbance to the surrounding fluid. Due to inertia, other molecules in the air are driven to move together, generating ion wind. Figure 7 is a schematic diagram of ion wind generation. Ion wind heat dissipation technology was first invented by Professor Alexander Mamishev in 2006. Tessera, a global electronic product miniaturization technology supplier, launched an Electrohydro Dynamic (EHD) heat dissipation solution based on ion wind heat dissipation. The surface area is only 3cm2 and can be installed. In the laptop. The biggest advantage of this heat dissipation method is that there is no mechanical mechanism and no noise is generated. There are some problems with ion wind heat dissipation. For example, the energy consumption of the system may increase, and the electromagnetic radiation generated by ion wind will also affect human health. However, these problems have been solved. The problems of how to prevent dust and how to extend the service life are still being solved.
After sorting out and analyzing the above several heat dissipation methods, it is not difficult to see that with the continuous update and progress of electronic devices, the heat dissipation methods of electronic devices are increasingly pursuing portability and higher efficiency. While electronic devices and electronic chips are more precise and compact, they also bring heat dissipation problems. The impact of temperature on electronic equipment is mainly reflected in two aspects: one is the thermal failure of the chip, and the other is the stress damage. Comparing the above heat dissipation methods, if one method alone has too many deficiencies, multiple methods can be used to dissipate heat, such as: ion wind and forced air cooling for heat dissipation; phase change energy storage and heat pipes for heat dissipation; 2. Dimensional materials are packaged and combined with other heat dissipation methods. "5D electronic blood" is a very promising technology, and it will be a big change in electronic equipment to be developed. The use of two-dimensional materials for packaging of electronic equipment and the use of microchannels on the bottom plate will become more and more widely used, and other heat dissipation methods need to be selected for different situations. The author personally prefers phase change energy storage cooling and heat pipe cooling.
At present, the theoretical research on heat dissipation is relatively complete, but there are also many technical difficulties. The bottleneck problem of heat dissipation technology also indirectly hinders the further development of electronic equipment. There is a long way to go. Breaking through the current problems and finding better heat dissipation materials will always be a hot issue in the field of heat dissipation.
