Vapor Chamber’s Structure and Specification
The vapor chamber is a planar plat-like object on the appearance, with a cover close to each other on the top and bottom, and a copper column supporting it. The upper and lower copper plates of the vapor chamber are made of oxygen-free copper, usually with pure water as the working fluid, and the capillary structure is made of copper powder sintered or copper mesh. As long as the vapor chamber maintains its flat characteristics, the shape of the outer profile depends on the application of the heat dissipation module environment, and there is no restriction on the Angle of the use. In practical application, the temperature difference between two points on the plate can be less than 10℃, and the conduction effect to the heat source is more uniform than that of the heat conduit, hence the name of the vacuum chamber. The common vapor chamber has a thermal resistance of 0.25℃/W and is applied to 0℃ ~ 100℃.
How a Vapor Chamber Works.
The working principle of vapor chamber is the same as that of heat conduit, including conduction, evaporation, convection and solidification.
The vapor chamber is a two-phase fluid device in which pure water is injected into a microstructure-filled container. Heat from the external high temperature zone through heat conduction into the plate, close to the heat source around the water will quickly absorb heat gasification into steam, taking away a large amount of heat energy. Using the latent heat of water vapor, when the steam inside the plate diffuses from the high pressure area to the low pressure area (that is, the low temperature area), when the steam comes into contact with the lower temperature of the inner wall, the water vapor will quickly condense into liquid and release heat energy. The condensed water flows back to the heat source through the capillary action of the microstructure to complete a heat transfer cycle and form a two-phase circulation system in which water and water vapor coexist. The vaporization of water in the vacuum chamber continues, and the pressure in the chamber is balanced with the change of temperature. When water operates at low temperature, its thermal conductivity value is low, but because the viscosity of water changes with the temperature, the vapor chamber can also operate at 5℃ or 10℃.Because the liquid reflux is acting by capillary force, so the vapor chamber is less affected by gravity, and the application system design space can be used at any Angle. The vacuum chamber does not require power supply or any moving components and is a completely sealed passive device.
Composite Microstructure of Vapor Chamber
Unlike a heat pipe, the vapor chamber cooler is first vacuumed and then injected with pure water to fill all the microstructure. Filling medium does not use methanol, alcohol, acetone, etc., but use degassed pure water, there will be no environmental problems, and can improve the efficiency and durability of soaking plate. There are two types of microstructure in vacuum chamber: powder sintering and multilayer copper mesh, both of which have the same effect. However, it is difficult to control the powder quality and sintering quality of the powder sintered microstructure, while the multilayer copper mesh microstructure with diffusion bonding of copper sheet and copper mesh above and below the pit plate has better consistency of pore size and controllability than that of the powder sintered microstructure, and the quality is more stable. The higher consistency can make the liquid flow more smoothly, which can significantly reduce the thickness of the microstructure, reduce the thickness of the vacuum chamber, the industry has in 150W heat transfer of 3.00mm plate thickness. Because the quality of copper powder sintered soaking plate is not easy to control, the overall cooling module usually needs to be supplemented by the design of heat conduit. The multilayer copper mesh bonded by diffusion has the same bonding strength as the base metal, because of the high air tightness, it does not need any solder, and there will be no microstructure blocking in the bonding process. The quality of the vacuum chamber made is better and the durability is longer. If the hole leaks after the diffusion bonding process, it can also be repaired by heavy industry. The multilayer copper mesh is divided by diffusion, and the copper mesh with smaller aperture is joined near the heat source. The layered design can make the pure water in the evaporation area replenish quickly, and the circulation of the whole soaking plate is more smooth. More advanced micro-structure modular to do regional design, can be used in multi-heat source heat dissipation design.Therefore, the heat flux per unit area of the vacuum chamber designed with diffusion joint and regional hierarchies is greatly increased, and the heat transfer effect is better than that of the sintered microstructure vacuum chamber.</br></br>
The combination of vapor chamber with solid die casting and heat conduit is basically the same in principle and theoretical framework, but different in dimension, manufacturing method, vacuumization and water injection procedure. The vapor chamber has the advantages of low thermal resistance, uniform heat flux, rapid heat diffusion and light weight.