5G base station thermal challenges
By 2025, the communications industry will consume 20% of the world's electricity, and in mobile networks, base stations are big power consumers, with about 80% of their power coming from widespread base stations. Increasingly dense base stations mean higher energy consumption, a major cost challenge for 5G networks.
In terms of energy structure, power consumption means higher cost and greater indirect pressure on environmental pollution. From the perspective of thermal design, the heat generated by the base station increases, and the difficulty of temperature control increases sharply. According to the measured data, the power consumption of 5G base station is 2.5~4 times that of 4G base station.
Engineers who have worked in the communication industry all know that the communication base station is usually installed in the iron frame on the roof, high in the field. Volume and weight are very important for the convenience of equipment installation.Coincidentally, power consumption, volume and weight are the core design boundary conditions in thermal design.
From the previous design habits, base station is a typical enclosed natural heat dissipation equipment (outdoor application, need strict waterproof and dust-proof), heat from the components issued, there are only two places:
1. Absorbed by internal devices -- heat is converted into internal energy, resulting in device temperature rise;
2. Heat transfer from high temperature to low temperature due to temperature difference -- when temperature is stable, heat transfer rate = heat generation rate.
Enclosed natural heat dissipation products, when the temperature is stable, all the heat will be transferred to the shell, and then from the shell to the air.The heat transfer path is as follows:
Chip (heating source)→Interface materials→↓
thermal structure→internal air→shell→external environment
To reduce the volume and weight of products, the requirements for the thermal design of such products evolve into improving heat transfer efficiency and reducing heat transfer resistance as far as possible in the same space.The thermal resistance of heat transfer here is divided into internal thermal resistance and external thermal resistance. The reduction of internal thermal resistance requires a reasonable chip layout, so that the heat source itself is closer to the heat dissipation shell.This is a collaborative effort between hardware engineers and thermal design engineers.From the perspective of materials, heat-conducting interface materials need to be applied between the chip and the shell. 5G base station may promote the great improvement of thermal interface materials, which is shown in the following aspects:
1. Lower thermal resistance as far as possible -- higher thermal conductivity and better interface moisture;
2. Reliability -- base station is applied in outdoor complex environment, all over the world, temperature range reaches -40c ~55C, maintenance is difficult after failure -- excellent thermal stability, anti-vertical flow, anti-cracking.
3. Usability -- 5G base station requires a large amount of energy, and multi-chip Shared chassis radiates heat, which has requirements for material assembly automation and stress generated in the assembly process.
From the shell, the power consumption is increased, and a more reasonable fin form needs to be designed to match the high power consumption of the base station.At the material level, materials with lower density, better thermal conductivity and strong corrosion resistance are required.The application of blowout plate in base station is based on its characteristics of high thermal conductivity and low density.Due to its low density and high thermal conductivity, two-phase flow products will be widely used in base stations.The rise of semi-solid die casting technology also promotes the improvement of thermal conductivity of die casting shell materials.
The efficiency of natural heat dissipation is limited. With the approaching of power consumption wall, the air cooling and liquid cooling of base station are also under research.Good temperature control will not only affect the reliability of the product, but also reduce the power consumption of the equipment.The static power consumption caused by leakage current will increase rapidly with the rise of temperature. However, as the chip manufacturing process progresses, the size of transistors becomes smaller and smaller, and the leakage current will become larger and larger.This means that the influence of temperature on chip power consumption will also become more significant.If the temperature is not properly controlled, the power consumption of the product will increase, which will further heat up the product, causing the thermal cycle of the product to deteriorate.