Phase Change Inhibited (PCI for short) heat transfer technology is to inject a special working medium into a specially designed closed channel cavity, and use the change of the local pressure of the heat transfer working medium to suppress its boiling during the heat transfer process. The occurrence of the phenomenon, a new heat dissipation technology that realizes the efficient heat conduction of the entire heat transfer device. At present, it has been widely used in communication, energy, power electronics and other industries.
PCI heat dissipation plate is a flat-plate two-dimensional heat transfer device made of aluminum inflation plate technology and PCI heat transfer technology. It has high thermal conductivity, high thermal conductivity and heat flux density, and high temperature uniformity.
· High heat transfer rate:
A typical experiment used to qualitatively demonstrate the high heat transfer rate of PCI heat transfer devices is to use an arc torch with a thermal power of up to kilowatts to burn 1.0cm² or less on the upper surface of a PCI heat transfer device with a wall thickness of 2mm. Once the heat source is removed, the backside of the device can be touched by a human hand, and the device at the far end of the heat source is already warmer than the near end. If the torch temperature is around 500°C, the back of the device can be touched with bare hands while burning. This experiment cannot be done by any other excellent heat transfer device at present. Due to the limitations of measurement methods, although this experiment is intuitive, there is a lack of quantitative data in this regard. Estimated heat transfer rates can be on the order of milliseconds. In fact, it is its high heat transfer rate that keeps the inner walls of the device heat transfer channels from drying out.
·High heat transfer density:
Heat transfer heat flux density refers to the heat power passing through the unit area of the heating surface. With the increasing power and size of various new electronic devices, the thermal power of the heating surface is getting higher and higher, that is, the heat flux density here will reach a high value. Restricted by the existing heat transfer technology capabilities, this has become a bottleneck for the successful development of high-tech. Its heat flux density can also be estimated in the same experiment above. Using thin film heaters or high-power torches to burn PCI heat transfer devices, it is estimated that the heat transfer density can reach 100-1000 W/cm2, which is the high heat transfer flux density range suggested by some literature. Therefore, it can provide solutions for various high-tech heat dissipation problems.
PCI heat generation technology is Jiaxi's proprietary new heat transfer technology. Since its establishment in 2012, Jiaxi has been focusing on the research and development of PCI heat transfer technology and PCI heat transfer devices and their applications. At present, it has more than 200 domestic and foreign inventions and The utility model patent has been widely used in LED lighting, high-definition display, high-power components and other power electronics industries.
The key technology of PCI heat transfer device affecting its heat transfer performance: specially designed interconnected closed pipeline structure cavity, specially equipped with heat transfer medium.
Jiaxi Technology cooperates closely with the thermal design team of ZTE, using Jiaxi's PCI heat transfer technology design and manufacturing experience and conditions, combined with the chip layout and heat dissipation requirements of ZTE's 5G base station, to jointly research and develop a new technology of PCI heat dissipation plate for 5G communication base station , successfully applied products and continued to optimize and improve, and at the same time promoted the re-innovation and re-development of PCI technology.
1. The PCI heat dissipation plate is used as the heat dissipation fin of the 5G base station AAU chassis heat sink to improve efficiency and reduce weight: The PCI heat dissipation plate is inlaid on the semi-solid die-casting aluminum chassis to improve the heat dissipation efficiency of the fins and significantly reduce the weight of the heat sink. This part mainly includes: the improvement and optimization of the new PCI pipeline structure, and the thinning of the thickness of the PCI cooling plate.
1.1 Research and develop a new pipeline structure for the PCI heat sink to improve the heat dissipation performance of the PCI heat sink on the 5G base station. On the basis of the general-purpose PCI heat dissipation plate with hexagonal honeycomb pipe structure, a vertical installation natural heat dissipation scenario suitable for 5G base stations is developed and the PCI heat dissipation plate is set on the chassis, and the heat is transmitted from the chassis to the PCI and the computer. To meet the special requirements such as the side where the shell is combined, the heat transfer pipeline structure of 3 kinds of PCI heat sinks is specially designed, which can not only meet the heat dissipation requirements of 5G base stations, but also reduce the work quality and reduce the weight and cost of the radiator.
The pipeline structure 1 is a universal hexagonal honeycomb-shaped interconnected closed pipeline structure PCI cooling plate, which has a stable structure and is widely used.
The pipeline structure 2 is a PCI cooling plate with a rapid-fall pipeline structure suitable for vertical application and the heat source is arranged on one side.
Pipeline structure 3 is an improved downhill pipeline suitable for vertical application, with heat source set on one side for partial separation of gas and liquid phase.
Pipeline structure 4 is a hybrid pipeline structure suitable for vertical application, with the heat source set on one side for gas-liquid phase separation.
After theoretical analysis and actual test verification, the improved pipeline performance is significantly improved, and the cost is also significantly reduced.
1.2 Develop a new process technology to reduce the thickness of the PCI heat sink, reduce the weight and reduce the cost.
The initial 1.5mm thickness of the PCI cooling plate, in order to meet the requirements of 5G base station for lightweight, and at the same time to meet the process temperature resistance requirements of invariance at 130℃@30min, through the joint efforts of both parties, the 1.2mm thickness single-sided flat panel has been successfully developed one after another. PCI heat dissipation plate, 0.8mm thick single-sided flat PCI heat dissipation plate, these two thicknesses of PCI heat dissipation plate have been applied in large-scale batches on ZTE 5G base stations, and have achieved good results. The weight of the radiator is reduced, it is more convenient to install and fix the 5G AAU equipment on the iron tower, and the cost is reduced and the cost is saved. At present, the 0.6mm thick PCI heat sink has been successfully developed, and the relevant reliability test verification has been completed.
2. The PCI board is used as the substrate of the 5G base station radiator. According to the different positions of the heating chips, the partition design method is adopted to solve the heat dissipation problem of the heat concentration of the chips. Improve the heat dissipation capacity of the 5G radiator.
For 5G base station AAU, the heat of multiple heating chips is concentrated and distributed at different heights. At present, the general solution is to embed several sintered copper heat pipes or copper VCs directly under the heating chips of the radiator casing. The heat of the chip is quickly transferred to other positions of the substrate through the heat pipe or VC. It is determined that it is necessary to slot the surface of the heat dissipation casing to install the chip, bury the heat pipe or VC, and mill the surface to be combined with the chip. The disadvantage is the amount of processing. It is relatively large, and the cost is high, and the effect of solving the high-power heating chip is limited by the heat transfer capacity and distance between the heat pipe and the VC. Jiaxi and ZTE's R&D team designed a PCI radiator substrate with partition and diversion structure according to the power and location of the 5G base station AAU high-power heating chip. The combination of aluminum radiator and PCI partition radiator substrate is made of vacuum. The PCI substrate 5G base station AAU radiator made by the brazing process has the advantage that the heat of the high-power heating chip quickly diffuses to the entire radiator substrate, and the fins and the PCI substrate are integrally formed aluminum extruded fins or welded aluminum fins It eliminates the combined thermal resistance between the fin and the substrate, and greatly improves the heat dissipation efficiency and cost.
3. Research and develop a new type of working fluid for PCI heat dissipation plate, on the basis of improving heat dissipation performance, reduce production cost, improve reliability and environmental safety and friendliness. Before and after the cooperation and cooperation with scientific research institutes such as the Chinese Academy of Sciences, colleges and universities, large enterprises, etc., to develop environmentally friendly, safe and reliable, and good performance for PCI cooling technology. , Improve the performance of the PCI heat sink and reduce the production cost. Under the promotion of ZTE, various series of working fluids have been successfully introduced and developed based on the original working fluids, realizing independent and controllable technology and reducing supply risks.
With the continuous breakthrough of process forming technology and the continuous improvement of PCI technology, it perfectly supports the design requirements of lightweight and miniaturization of 5G base stations. In the future, it will develop from 2D to 3D to further improve product performance.