Application of heatpipe and vapor chamber in 5G cell phone
From the 4G era to the 5G era, there has been a significant improvement in the performance of smartphone chips, data transmission rates, RF modules, and other features. Wireless charging, NFC, and other functions have gradually become standard equipment, and the heat dissipation pressure on mobile phones continues to grow. Due to the continuous increase in indicators such as integration, power density, and assembly density, electronic devices in the 5G era are experiencing a sharp increase in operating power consumption and heat generation while their performance continues to improve. According to statistics, material failure caused by thermal concentration in electronic devices accounts for 65-80% of the total failure efficiency. In order to avoid device failure caused by overheating, thermal conductive silicone grease, thermal conductive gel, graphite thermal conductive sheet, heat pipe ,vapor chamber and other technologies have emerged and continued to evolve. Heat dissipation management has become an important choice for electronic devices in the 5G era.
Generally speaking, there are two ways for electronic devices to dissipate heat: active cooling (to reduce the spontaneous heat of the phone) and passive cooling (to accelerate the heat dissipation outward). Among them, active cooling mainly utilizes power components unrelated to the heating element to forcibly dissipate heat, which is generally applied to high-power density and relatively large electronic devices, such as fans equipped in desktop computers and laptops, and liquid cooled cooling for data center servers; Passive heat dissipation mainly releases the heat generated by components into the environment through thermal conductive materials and devices. It is a heat dissipation method without the participation of power components and is widely used in mobile phones, tablets, smartwatches, outdoor base stations, etc.
At present, the thermal technologies used in electronic devices mainly include thermal conductive materials such as graphite heat dissipation, metal backplane, frame heat dissipation, thermal conductive gel heat dissipation, and thermal conductive devices such as heat pipes and VC. Among them, thermal conductive gel, thermal conductive silicone grease, graphite sheet and metal sheet are mainly used in small and medium-sized electronic products, while heat pipe and VC are mainly used in large and medium-sized electronic devices such as laptops, computers and servers.
Heat pipes and vapor chamber utilize the rapid heat transfer properties of heat conduction and cooling media, resulting in a thermal conductivity increase of more than 10 times compared to metal and graphite materials. As an emerging cooling technology solution, they have been widely used in the field of smartphones in recent years. Among them, the thermal conductivity of the heat pipe ranges from 10000 to 100000 W/mK, which is 20 times that of pure copper film and 10 times that of multi-layer graphite film; As an upgrade of heat pipe technology, the vapor chamber further improves the thermal conductivity.
A heat pipe is generally composed of a shell, a suction core, and an end cover, which draws the inside of the pipe into 1.3 × After a pressure of (10-10-2) Pa, fill an appropriate amount of working liquid to fill the capillary porous material of the suction core tightly against the inner wall of the tube with liquid and seal it. One end of the pipe is the evaporation section (heating section), and the other end is the condensation section (cooling section). An insulation section can be arranged between the two sections according to application needs. The suction core adopts capillary microporous material, which utilizes capillary suction (generated by liquid surface tension) to reflux the liquid. The liquid inside the tube absorbs heat and evaporates in the heat absorption section, condenses and reflux in the cooling section, and circulates heat away.
The working principle of vpaor chamber is similar to that of a heat pipe, which also includes four main steps: conduction, evaporation, convection, and condensation. The main difference between the two lies in the different ways of heat conduction. The heat conduction mode of a heat pipe is one-dimensional, which is a linear heat conduction mode, while the heat conduction mode of vpaor chamber is two-dimensional, which is a surface heat conduction mode. Compared to heat pipes, the contact area between the homogenizing plate, heat source, and heat dissipation medium is larger, which can make the surface temperature more uniform; Secondly, using vpaor chamber can directly contact the heat source and equipment to reduce thermal resistance, while the heat pipe needs to be embedded with a substrate between the heat source and the heat pipe; Finally, vpaor chamber is lighter and more adaptable to the trend of integrated and lightweight mobile phones. Related studies have shown that the performance of VC radiators is improved by 20% to 30% compared to heat pipes.
Although the thermal conductivity of heat pipes and vapor chamber is higher, the principle is to accelerate the transfer of heat from the heating components of the phone to the environment. The final thermal effect still depends on the thermal convection between the thermal material and the air. Therefore, the thermal characteristics of thermal materials have an undeniable impact on the thermal effect of mobile phones. At present, the overall solution of "heat sink (graphene film/graphite sheet)+heat pipe/vapor chamber" is gradually recognized by the market.
