A powerful thermal solution for 5G communication cooling

   Heat dissipation is an important link in ensuring the long-term safe and reliable operation of electronic devices and products. As the most densely used field for heat dissipation devices such as chips, the development of communication and information technology has promoted heat dissipation or thermal design to become a systematic industry. Research and development in the fields of power, security, consumer electronics, automotive, LED, etc. are also increasingly emphasizing the thermal performance of products in order to have more advantages in market competitiveness. Currently, 5G communication and information products are developing towards the goals of larger capacity, higher performance, energy efficiency, and low noise. The level of device integration is increasing, with more powerful single-chip functions and significantly increased power consumption. However, the layout is becoming more compact, and the heat flux density has doubled, posing severe challenges to thermal technology.

    Traditional thermal systems mainly rely on single-phase materials to conduct heat from the device to the surface of the heat sink, and then dissipate the heat to the environment through natural convection (natural cooling system) or forced convection (forced air cooling system) by air. The efficiency of heat conduction depends on and is also limited by the inherent thermal conductivity of the material.
    The phase change heat transfer technology represented by heat pipes and VC (Vapor Chamber) utilizes the medium to evaporate in the heated area and condense in the cooled area, while absorbing or releasing the corresponding latent heat of phase change, alternately circulating to achieve rapid diffusion or migration of heat. The absorption and release of latent heat is a rapid and efficient process, and when using two-phase heat transfer, working fluids with higher latent heat are usually selected, resulting in very high heat transfer efficiency. The equivalent thermal conductivity can reach over 2000 W/m · K

    Vapor Chamber is currently the most widely used phase change heat transfer product in the communication and electronics industries, with mature processes other than heat pipes. A typical VC is a flat closed form, consisting of a shell, capillary structure, support structure, and working fluid. Through the evaporation, condensation, and capillary transport of the working fluid, efficient heat conduction is achieved, spreading heat from the concentrated area to the entire structural plane.

       Thanks to the advantages of large-area capillary characteristics and two-dimensional or even three-dimensional thermal diffusion, VC has a higher heat flux carrying capacity, especially for cooling electronic devices with heat flux densities exceeding 50W/cm2. The temperature equalization effect is significantly better than pure metal or embedded heat pipe heat dissipation substrates, which can greatly improve the efficiency of heat sinks. Under the development trend of chip heat flux density exceeding 100W/cm2, VC is undoubtedly a key technology supporting the performance upgrade of communication equipment.

     Higher performance VC often corresponds to the local capillary structure densification in the evaporation zone corresponding to the heat source location. In addition to enhancing capillary force and liquid reflux, the surface of these capillary structures also expands the evaporation area and increases the evaporation rate. From this perspective, the design also includes a layer of capillary material covering the outer part of the encrypted pure metal structure. Because pure metals, especially pure copper, have a higher thermal conductivity than capillary structures, the internal pure metal conducts heat to the surface capillary structure more efficiently, and the strength of pure metals is also better. There are various design forms of this type, and the VC heat flux carrying capacity can reach 30-100W/cm2.

    With the development trend of high power consumption and high heat flux density chips, there is a higher demand for the temperature equalization performance of VC. The optimization design of VC must improve the capillary performance while enhancing the efficiency of heat conduction and gas-liquid transport from multiple aspects of materials and structures, thereby significantly reducing the thermal resistance of VC. Only then can the temperature difference from the heat source to the cold surface of VC still be comparable to the current level under low heat flux density application conditions, even when the working heat flux density is doubled or even multiplied.