Research On Thermal Management System For Electronic Chips In Digital Network Devices

With the development of technology,electronic equipment nowadays plays an indispensable support and key central role in the military defense sector and in people’s daily lives.Electronic devices generate a lot of heat during operation due to high loads on the internal chips,which can lead to a high temperature inside the device.If the temperature rises inside the equipment is not effectively controlled,it will lead to a decrease in the working performance of the equipment,affect the working life and reliability of the equipment,and even burn up the equipment due to high temperature under overload.Thermal management is crucial to the development and operation of electronic equipment and is one of the hot spots in international research in the field of thermal science at this stage.The thermal conductivity and heat dissipation capabilities of the thermal conductivity/heat dissipation components inside electronic devices are key factors affecting the thermal management capabilities of electronic devices,and most of these thermal/heat sink components are made of polymers.Polymer composites are widely used in electronic devices due to their many advantages（corrosion resistance,light weight,flexibility,economy and ease of processing）.However,the thermal conductivity of the polymer matrix itself is very low and cannot meet the high thermal conductivity/heat dissipation requirements of composites in the field of electronic equipment.Therefore,there is a need to improve the thermal conductivity of polymer composites and the addition of high thermal conductivity fillers to polymer composites is an efficient and controllable solution.However,there are limitations to this approach,as the mechanical and processing properties of polymer composites can be poor when the thermal conductivity filler content is too high.The balance of high thermal conductivity and mechanical properties was not only the important point of this study,but also a puzzle for all scholars in this field.The thesis systematically investigates the effects of electronic device shell,thermal interface materials（TIMs）and printed circuit boards on the thermal management system of electronic devices.Different processing methods were used to prepare functionally specific thermally conductive polymeric materials,while the performance of the composite products was further validated in thermal management application scenarios.Specific studies include:（1）The thermal management system of electronic devices is systematically studied.The influence of the properties of the electronic equipment shell,thermal interface materials and printed circuit boards on the thermal management system of electronic devices is experimentally verified,and the optimum performance parameters of the components in the thermal management system are defined.The optimum performance parameters of the components in the thermal management system are defined and corresponding solutions are proposed to make the thermal management system of electronic devices meet the heat dissipation requirements.（2）In order to ensure the thermal and mechanical properties of the thermally conductive composite,a PC/ABS heat dissipation composite with a dual continuous phase structure was prepared for the manufacture of electronic equipment housings,with the ABS phase responsible for improving the thermal performance and the PC phase responsible for maintaining the mechanical properties.The results show that the highest thermal conductivity of the composites can reach 0.476 W/（m·K）,which is 138%higher than that of pure PC.The mechanical properties（tensile strength:38.85 MPa,flexural strength:48.10 MPa,elongation at break:6.40%）of the PC/ABS composites are also improved compared to that of the filled PC（fPC）.At the same time,the prepared PC/ABS composites have good electrical insulation and dielectric properties（dielectric constant:3.07,loss factor:0.0075）.（3）Thermal interface materials are a key component in the thermal conductivity of electronic equipment chips to the outside,so it is important to prepare thermal interface materials that are recyclable and have good thermal conductivity to keep the equipment working.A combination of vacuum-assisted filtration（VAF）technology and ultrasonic assisted forced infiltration（UAFI）method was used to construct a continuous thermally conductive network of carbon nanotubes（CNTs）-cellulose nanocrystals（CNCs）,followed by the introduction of poly（adipic acid）/butylene terephthalate poly（PBAT）with good mechanical properties into the CNTs-CNCs network as a matrix material.CNTs-CNCs/PBAT composites with high thermal conductivity and excellent mechanical properties were obtained.The properties of the composites are also optimized by changing the mass ratio of CNTs to CNCs.The results show that the best comprehensive performance is achieved when the CNTs:CNCs ratio is 10:1.The CNTs-CNCs（10:1）/PBAT composite have a thermal conductivity of 4.082W/（m·K）,a tensile strength of 6.69 MPa and an elongation at break of3.31%.The CNTs-CNCs（10:1）/PBAT composites also exhibite good electrical conductivity（41.67 S/m）,thermal stability(T_HRI:182.55℃)and electromagnetic shielding ability（23.82 dB）.It is also proposed that the effective separation and recovery of PBAT matrix and thermally conductive network skeleton is achieved by alcoholysis,and that recyclable PBAT composites have great potential for the application of electronic thermal management systems.（4）For the thermal conductivity requirements of printed circuit boards in the thermal management system of electronic devices.A glass fiber（GF）/boron nitride（BN）network with a highly thermally conductive heterogeneous structure is formed using polyvinyl alcohol（PVA）as a binder.GF andBN are further modified with3-aminopropyltriethoxysilane（APTES）to improve the thermal conductivity of the composites.The results show that the thermal diffusion coefficient and thermal conductivity of the obtained PVA-mBN@mGF（PBG）are 2.843 mm²/s and 1.394 W/（m·K）respectively,when the BN content is 30%.The epoxy（EP）resin is then introduced and the PBG/mBN/EP laminate is prepared by hot pressing for application as a thermally conductive composite.The highest thermal conductivity of the PBG/mBN/EP laminate is 0.67 W/（m·K）,which is three times higher than that of pure EP.In addition,the PBG/mBN/EP laminate has good mechanical（tensile strength:37.48 MPa,flexural strength:39.79 MPa,elongation at break:2.10%）,electrical insulation and dielectric properties（dielectric constant:5.11,loss factor:0.032）.