Heat pipe and Vapor Chamber: VC takes advantage of the rapid heat transfer properties of heat conduction and refrigeration media. The thermal conductivity coefficient is more than 10 times higher than that of metal and graphite materials. As an emerging heat dissipation technology solution, it has begun to be widely used in recent years. The thermal conductivity of the heat pipe ranges from 10,000 to 100,000 W / m〃K, which is 20 times that of pure copper film and 10 times that of multilayer graphite film. As an upgrade of heat pipe technology, the soaking plate further improves the thermal conductivity.
The heat conduction path of the heat pipe / VC heat dissipation system is: the heat generated by the CPU is transferred to the heat pipe through the TIM (thermal interface material), the heat pipe quickly conducts the heat to the copper foil and spreads it evenly, and the heat of the copper foil is further transferred to the graphite heat dissipation film and then evenly spread At the same time, the graphite heat dissipation film conducts heat to the metal bracket in the plane direction of the mobile phone and finally opens.
The heat pipe is generally composed of a tube shell, a liquid wick and an end cap. The tube is pumped to a negative pressure and filled with an appropriate amount of working liquid, so that the capillary porous material close to the inner wall of the tube is filled with liquid and then sealed. One end of the tube It is the evaporation section (heating section), and the other end is the condensation section (cooling section). According to the application requirements, the heat insulation section can be arranged in the middle of the two sections. The wick adopts capillary microporous material, and uses capillary suction (which is generated by the surface tension of the liquid) to return the liquid. The liquid in the tube absorbs heat and evaporates in the endothermic section, condenses and returns in the cooling section, and circulates away heat.
The soaking plate is also called a flat heat pipe, and its working principle is similar to that of a heat pipe, including the four main steps of conduction, evaporation, convection, and solidification. The difference between the two is the way the heat is conducted. The heat conduction method of the heat pipe is one-dimensional, which is the linear heat conduction method, and the heat conduction method of the soaking plate is two-dimensional, which is the surface heat conduction method, so the heat dissipation efficiency is higher. Research shows that the performance of VC radiators is 20% to 30% higher than that of heat pipes.
From the perspective of application range and penetration rate, due to the early maturity of the heat pipe and the relatively low cost, it has been widely used in microelectronics and optoelectronics such as computers / notebooks, projectors, LEDs, high-power ICs, etc., and has also been extended to mobile phones . The current production cost of VC is high, and the mass production capacity is weak. The application field is limited to high-end notebooks, 5G smartphones and e-sports phones. Huawei began to heat up VC from Mate 20 X, and Samsung ’s new flagship machine Note 10 was first adopted. VC. At present, the average unit price of VC is 2 to 3 US dollars, which is 5 to 10 times that of heat pipes, and the unit price of light and thin models is higher. Under the background of light weight, ultra-thin and continuous performance upgrade of consumer electronics, heat pipes and VC are expected to give full play to the advantages of thermal conductivity and the penetration rate will continue to increase.
It is optimistic that by 2020, the penetration rate of heat pipe / VC in mobile phone terminals is expected to increase to 15%. According to the calculation of 1.5 billion mobile phone shipments, assuming that the average unit price of heat pipe / VC is 1.5 US dollars, the market space in 2020 will be 3.38 One hundred million U.S. dollars.
5.2. Thickness, length and appearance requirements are high, and the production process is difficult
Although the thermal conductivity of heat pipes and VC is much higher than that of metals, graphite and TIM materials, in the context of ultra-thin and lightweight development of electronic products, it is very challenging to control the thickness of heat pipes and VC within a reasonable range. The diameter of the heat pipe on the PC is generally 1 ~ 2 mm, the heat pipe on the portable computer and the flat board is generally 0.8 ~ 1.2 mm, and the heat pipe of the smartphone needs to be controlled within 0.6 mm. The thickness of the heat pipe in the Samsung S8 has dropped to 0.4mm. The soaking plate is the welding of two copper plates on all four sides. Due to the larger area, the heat dissipation effect is better. However, with the thinning and thinning requirements of the product, the capillary structure of the soaking plate transitions from copper powder sintering to etching, and the thickness drops to 0.4 Below mm is more demanding on welding accuracy, so it is more difficult to produce and expensive.
In addition to the thickness needs to meet the needs of smart phones, the actual thermal conductivity of the heat pipe is affected by two factors: length and appearance. The longer the length, the higher the thermal conductivity. In terms of appearance, the shape changes such as flattening and bending will affect the capillary limit of the heat pipe and the steam chamber limit. The lower of the two limit values determines the maximum heat transfer Qmax of the heat pipe. The capillary limit refers to the ability of the capillary structure to transport water from the condenser back to the evaporator; the steam chamber limit refers to the space where steam moves from the evaporator to the condenser. Therefore, by changing the appearance of the heat pipe and adjusting the capillary structure (porosity and thickness), it can meet the thermal conductivity requirements of different application scenarios. For example, when a heat pipe of a given diameter is required to operate under a higher power load or gravity, the capillary pressure needs to be increased; when a larger amount of heat transfer is required, the pore radius should be enlarged; when it is necessary to resist gravity, the pore radius must be Properly reduce or increase the pore thickness.
From the perspective of production process, the core technology of heat pipe is nano-sintered liquid-absorbing core technology. The specific process is: (1) coating a layer of nano-molecular liquid binder on the inner wall of the heat pipe; (2) coating a layer of metal powder on the binder; (3) feeding it into a high-temperature sintering furnace for sintering ; (4) After cooling, the heat pipe sintering core is completed. Due to the high production process requirements of heat pipes and VC, the main supply chain is currently overseas, and domestic manufacturers are actively seeking breakthroughs.
China Taiwanese manufacturers occupy the main share, and mainland Chinese manufacturers have achieved technological breakthroughs
The supply chain of heat pipes and VC soaking plates is mainly in Taiwan, and related manufacturers account for about 70% of the market share, including Chaozhong, Shuanghong, Taishuo, Qihong and Jiance, etc. Downstream customers cover the world's mainstream servers, computers, pens Electricity and mobile phone manufacturers. In the first half of 2019, in the context of the overall weak consumer electronics market, major Taiwanese cooling companies have achieved substantial revenue growth and revenue growth has picked up. We judge that the main reason is the rapid increase in demand for 5G base stations and related terminals.
At present, domestic manufacturers have made certain technological breakthroughs in heat pipes and VC, CZTY technology and SZFR technology have a layout. CZTY Company invested in the establishment of CZTY Thermal Conductivity Technology Co., Ltd. in 2018, which is mainly engaged in the development and production of ultra-thin heat pipes / VC and related materials, thereby providing complete terminal heat dissipation solutions including high thermal conductivity graphite, ultra-thin heat pipes and VC . SZFR acquired a 55% stake in KSPD in 2018. KSPD specializes in heat dissipation modules. It has heat pipe / VC, stamping parts and fan technologies and products. It has rich technologies in the fields of servers, medical devices, military products, new energy and consumer electronics. , Product and sales experience.