Heat Dissipation of 5G Optical Devices

In the era of 5G network, every kind of 5G carrying scheme is inseparable from 5G communication devices, and 5G has increasingly higher requirements on optical devices, such as small size, high integration, high speed, low power consumption and higher speed. The volume is getting smaller and smaller, which is the inevitable trend of the development of optical devices, but also brings higher requirements for the internal thermal management of optical devices. Therefore, heat dissipation is a serious problem to be taken seriously.

1. Why Consider Thermal Design?

Let us first generalize the three basic modes of heat transfer: heat conduction, heat convection, and heat radiation.

(1) Heat Conduction:

When there is no relative displacement between the parts of an object, the heat generated by the thermal motion of molecules, atoms, free electrons and other microscopic examples is called heat conduction. For example, the chip dissipates heat through the heat sink at the bottom, and the optical device dissipates heat through the silicon grease contacting the housing. The Vapor Chamber Heatsink, also known as the VC heatsink, plays an important role in the heat dissipation of optical devices. 

(2) Heat Convection:

Heat convection refers to the way of heat transfer caused by mixing of cold and hot fluids due to macroscopic movement of fluids. This heat transfer occurs only in liquids and gases. Because the molecules in the fluid are moving irregularly at the same time, convection must be accompanied by heat conduction.

(3) Thermal Radiation:

The way an object transmits energy through electromagnetic waves is called radiation. There are many types of radiation, among which the phenomenon of emitting radiant energy because of heat is called thermal radiation.

2. Thermal Analysis Of Optical Devices

(1) Overall Cooling Path Of The Device

After the pluggle transceiver module is inserted into the panel, a small part of the heat generated internally is dissipated by the natural convection of the surrounding air, and most of the heat is dissipated by conduction. The heat is always transferred from the high end of the temperature to the low end, and the heat of the module is transferred up to the package shell and down to the main board. The extrusion heatsink plays an important role in the cooling system of optical devices.

(2) Internal Cooling Path Of Optical Device

The main internal heating components include TOSA transmitter, ROSA receiver, PCB board components and IC control chip. Chip heat mainly through the top and bottom and side heat dissipation, and after a lead frame from two sides heat conduction to the outside world. in fact, due to the top, side is too small can be neglected, in order to improve the module as a whole the cooling efficiency, to improve as much as possible at the bottom of the heat capacity, reduce the path of the size of the thermal resistance and improve its thermal conductivity. There are a number of heatpipe solutions, one of which is to replace the proper heatsink.

(3) Important Factors Influencing The Heat Dissipation Of Optical Devices

Through the internal and external analysis of the optical device, the heat of the power device is derived in time, the thermal conductivity of the shell, the device layout, the contact thermal resistance, the contact area between the radiator and the device shell are the important factors affecting the heat dissipation of the optical device.