5G telecom device thermal design principle

         Compared with 4G , 5G increases by at least 9 ~ 10 times. In the era of 5G network, no matter what 5G solution is inseparable from 5G communication devices, and 5G has higher and higher requirements for optical devices, such as small volume, high integration, high rate and low power consumption. The main commonly used device rates for 5G forward, middle and back transmission are 25G, 50G, 100G, 200G and 400G optical devices, Among them, 25G and 100G optical devices are the most widely used 5G communication devices.

           With the higher speed and smaller volume, this is the inevitable trend of the development of optical devices. At the same time, it also brings higher requirements for the internal thermal management of optical devices. How to quickly and effectively heat dissipation is a problem that must be taken seriously.

Why does thermal design is needed:

    As we all know, when our photoelectric chip works, it will not convert 100% of the injected current into output optoelectronics, and part of it will be used as energy loss in the form of heat. If a large amount of heat continues to accumulate and cannot be eliminated in time, it will have many adverse effects on the performance of components. Generally speaking, with the increase of temperature, the resistance value decreases and the service life of devices will be reduced, Poor performance, aging materials and damaged components; In addition, high temperature will also produce stress and deformation on the material, reduce the reliability and malfunction of the device.

   There are three basic ways of heat transfer: heat conduction, heat convection and heat radiation.

Heat conduction:

     The chip dissipates heat through the heat sink at the bottom, and the optical device contacts the shell for heat dissipation through heat dissipation silicone grease, all of which belong to heat conduction.

Heat convection:

  Natural convection mainly uses the buoyancy force caused by the difference of high and low temperature fluid density to exchange heat. It is a passive heat dissipation method, which is suitable for the environment with low calorific value. In mobile phones, optical modules and other terminal products, natural convection heat transfer is mainly used.

     Forced convection heat transfer is an efficient heat dissipation method caused by accelerating fluid heat exchange through external power sources such as pumps and fans, which requires additional economic investment. It is suitable for the situation of large calorific value and poor heat dissipation environment; Fan cooling is usually used for optical modules working in cabinets or switches, which is a typical forced convection heat transfer.

Heat radiation:

     The process of transmitting energy through electromagnetic waves. Thermal radiation is the process of emitting electromagnetic waves when the temperature of an object is higher than absolute zero. The transfer of heat between two objects through thermal radiation is called radiation heat transfer. This heat dissipation method is less used in thermal design because of its poor efficiency.