Mobile phones generate a lot of heat during operation, and CPU, battery, camera and LED are all important heat sources. At the same time, with the continuous upgrade of mobile phone performance, including the improvement of camera pixels, the increase of battery capacity, the design of curved screens, and the application of non-metal chassis such as glass ceramics, all have higher requirements for heat dissipation. Excessive heat will adversely affect cell phone performance, cell phone life and user experience. According to the provisions of international safety standards, the upper limit of the surface temperature of the handheld terminal is 48 ° C. Exceeding this will cause safety problems such as CPU frequency reduction and battery damage. Therefore, a good heat dissipation solution has become one of the keys that accompanies the iterative upgrade of mobile phones, and is also an important promotion point for mobile phone brands when launching a new generation of mobile phones.
In general, chip processing power, RF power consumption, chassis material and thin and light design are the main factors that affect the cooling requirements of mobile phones. On the one hand, with the development of smart phones, the main frequency of mobile phone chips is getting higher and higher, and the power is getting bigger and bigger. 5G chip processing capacity is 5 times that of existing chips; the total power of 5G mobile phones is about 9.6W, which is 2 times that of 4G; 5G mobile phones operate on multi-band and high-frequency networks, and Massive MIMO (mass multiple input multiple output) antenna technology is commercialized The energy consumption is 2.5 times that of 4G chips; plus high-speed processing of large amounts of data, and the high-definition of mobile video content and game content.
Thermal conductivity and thickness are the core indicators for evaluating heat dissipation materials. The traditional mobile phone heat dissipation materials are mainly TIM materials such as graphite sheets and thermally conductive gels. However, graphite sheets have relatively low thermal conductivity and relatively thick TIM materials. Driven by mobile phone brands, heat pipes and VCs have penetrated into smart phone terminals from the fields of computers and servers, and have continued to make breakthroughs in graphene materials. They have also begun to cut into consumer electronics cooling applications. Relatively speaking, VC and graphene have a high thermal conductivity coefficient and a thin thickness, making them a better choice for heat dissipation materials.
Huawei uses a 9-layer three-dimensional heat dissipation method in the Honor Note 10 4G mobile phone. The graphite sheet + metal + TIM + heat pipe, starting from the screen side of the phone, are the middle frame graphite sheet, PC grade liquid cooling tube, high thermal conductivity aluminum alloy middle frame, Thermally conductive copper sheet, processor shield, two layers of thermally conductive gel, and back cover graphite sheet. The specific solution is: a part of the heat of the CPU is transferred to the evaporation section of the heat pipe through the heat dissipation silicone grease, copper alloy shield, copper sheet, and solder. The heat pipe is responsible for quickly transmitting these energy to the cold area of the whole machine, and through the aluminum alloy temperature plate, large Area graphite flakes to quickly dissipate the heat transferred to the cold zone. The other part of the heat of CP U is radiated to the graphite sheet of the rear shell after being soaked by the PCB board, so as to soak the rear shell.
Huawei took the lead in using the graphene + VC cooling technology in the Mate 20 X released in 2019, and Samsung's new flagship Note 10 also adopted the VC cooling solution for the first time.
With the increase in the penetration rate of graphene, heat pipes and VC in smart phones, the stand-alone ASP in the 5G era is expected to reach a high level of US $ 5 ~ 10, realizing a value increase of 3-4 times. First, the number of high-end model stand-alone graphite sheets / graphene is 3 ~ 6 pieces, of which the price of graphite sheet is 0.2-0.3 US dollars, and the price of graphene is higher; second, the number of stand-alone heat pipes is 1 and the price is 0.3 ~ 0.6 USD, soaking plate VC price is 2 ~ 3 USD; TIM depends on different phase change materials, value range is 0.5 ~ 2.5 USD.
In addition to the doubling of ASP per unit price, smartphone shipments are expected to leverage on 5G to achieve substantial growth. According to a report released by IDC, global smartphone shipments are expected to continue to decline in 2019, down 0.8% year-on-year to 1.39 billion units.
However, with the commercialization of foldable screens and 5G mobile phones, the smartphone industry is expected to resume growth in the second half of 2019. It is estimated that this trend will continue until 2023, when global smartphone shipments will reach 1.542 billion units, of which 5G mobile phones The penetration rate reaches 25%.