Views: 13 Author: Site Editor Publish Time: 2021-02-10 Origin: Site
With the electronic products becoming more and thinner, due to the narrow internal space of the body, its cooling capacity is also limited. The main heat sources of smart phones include the following five aspects: main chip work, LCD drive, battery release and charging, CCM drive chip, PCB structure design, uneven heat conduction and heat dissipation. In order to solve these heat dissipation problems, there are four main heat dissipation technologies in the market at present. Through comparison, we find that the heat pipe and vapor chamber have obvious advantages.
Comparison of advantages and disadvantages of heat dissipation scheme
Cooling scheme | Advantage | Disadvantages | Representative type |
Graphite sheet | Relatively cheap, easy to produce, low density, small volume | Low yield and complex process | Iphone 11 |
Graphene sheet | Strong flexibility, ultra-thin, customizable thickness, high theoretical thermal conductivity, high stability | Large scale application is difficult and costly | Huawei mate30 |
vapor chamber | Strong thermal conductivity, high heat dissipation power, good temperature sharing performance and strong structural adaptability | Increase product weight, volume and cost | Vivo NEX S 5G |
Heat pipe | Small size, large heat dissipation power and low cost | The diameter of heat pipe for mobile phone is smaller than that of common heat pipe | Glory note10 |
1. The thermal conductivity of heat pipe and vapor chamber is higher than that of other schemes, and the advantage of thermal conductivity is outstanding
The thermal conductivity of heat pipe is more than 10 times higher than that of metal and graphite, and the efficiency of vapor chamber is higher than that of heat pipe. In terms of thermal conductivity, the advantages of heat pipe and vapor chamber are obvious. After absorbing the chip heat, the liquid at the bottom of the vacuum chamber evaporates and diffuses to the vacuum chamber, which conducts the heat to the fins, and then condenses to the liquid back to the bottom. This kind of evaporation and condensation process circulates rapidly in the vacuum chamber, and achieves high heat dissipation efficiency.
5000-10000 W / mK. This is 250 times that of solid copper and 500 times that of solid aluminum. But the thermal conductivity of the heat pipe changes with the temperature. When the length of 75mm heat pipe can reach the thermal conductivity of 10000 w / MK, while the thermal conductivity of 200mm long heat pipe just exceeds 44000 w / MK. For example, the length of glory note 10 heat pipe is about 113mm, the heat dissipation area through it is 177mm * 85mm, and the metal heat dissipation area through it is 15000 mm2. The overall temperature equalization effect is good.
The performance of vapor chamber is 15-30% better than that of heat pipe. On the one hand, vapor chamber is usually in direct contact with the heat source, so as to reduce the total thermal resistance and improve the performance. The heat pipe needs to install a mounting plate between the heat source and the heat pipe. On the other hand, vapor chamber achieves better isothermal at the chip interface to reduce hot spots and has higher performance than heat pipe products.
2. Heat pipe / vapor chamber has good temperature equalization effect and long service life
Even temperature plate has a large area, which can better reduce the hot spots and achieve the isothermal under the chip. At the same time, even temperature plate is also lighter and thin, which is more in line with the current development trend of cell phone's more light and space utilization maximization at the same time of rapid absorption and heat emission. In addition, vapor chamber has the advantages of high heat transfer speed, low starting temperature, good temperature sharing performance and long service life.
The fullness of the steam in the inner cavity of the heat pipe can make the heat pipe isothermal. The principle is that when the main steam is full, the temperature will be saturated, so the heat pipe will have isothermal characteristics. In addition, the heat pipe in the mobile phone will not undergo mechanical or chemical degradation, and its service life is about 20 years, which has exceeded the average life of the liquid cooling system.
3. Vapor chamber and heat pipe cooling technology will be developed in a lighter and more efficient direction in the future
With the trend of thinness of various kinds of consumer electronics, such as smart phones, electronic components are becoming thinner and thinner. Developing thinner heat pipes and vapor chambers, as well as being able to be used in highly thin products, has become one of the evolution directions of vapor chambers and heat pipes in the future. At present, many heat sink manufacturers in Japan and Taiwan have made preparations for mass production of 0.6mm ultra-thin heat pipe, and plan to continue to reduce 25% on this basis, reaching the 0.45mm level. The main material of the heat pipe is copper, which must have a certain thickness to maintain the shape, but the internal space of mobile phones and flat plates is limited, so the heat pipe has to be as thin as possible, which is a problem that needs to be balanced and grasped and also the future development direction. At present, companies in Japan, Taiwan and China have been developing ultra-thin heat pipes for smart phones. The diameter of heat pipe used in PC is generally 1-2mm, that of ultra-thin PC and tablet is 1-1.2mm and 0.8mm respectively, and that of smart phone is further reduced to within 0.6mm. In the future, the diameter of mobile phone heat pipe will continue to shrink to 0.4-0.5mm.
Developing high-efficiency heat pipe / vapor chamber to be widely used in high wattage demand products is the future direction of heat pipe / vapor chamber evolution. With the development of the Internet of things, 5G and artificial intelligence, more and more requirements are expected to be generated for the operation of products, which will also promote the heat dissipation of consumer electronics and other electronic products to higher specifications.