Preparation And Performance Study Of Thermally Conductive Composite Gel Thermal Interface Materials

With the rapid development of miniaturization,integration and functionalization of electronic products,the power density and heat flow density have risen dramatically,greatly increasing the overheating problems of devices and putting the reliability and lifetime of electronic devices at risk.Therefore,how to achieve efficient heat dissipation during the operation of electronic devices has become the key to thermal management of electronic devices.Thermal interface materials(TIMs)are often placed between the chip and the heat sink to achieve efficient thermal management.In TIM,thermal conductivity and thermal contact resistance(TCR)are among the important factors.High thermal conductivity and low TCR can significantly enhance the interface heat transfer.In this thesis,relying on gel polymers,three composite gel TIMs based on thermally conductive fillers are designed and the comprehensive performance of TIMs is systematically investigated.This thesis is divided into three main sectionsPartⅠ:Using the high thermal conductivity of graphene,a graphene double cross-linked hydrogel TIM was constructed and the performance of the graphene double cross-linked hydrogel in terms of heat transfer,mechanics and heat dissipation was investigated.The results showed that the thermal conductivity of the composites was 0.71 W/(m·K)when the loading of graphene was 0.9 wt%.And the content of graphene was able to influence the mechanical properties of the composite hydrogels with a maximum stretch of 840%.The hydrogel with a double cross-linked structure is capable of self-healing,providing flexible support to address the reduction in TIMs performance due to thermal shock.The TCR performance of the graphene double cross-linked composite hydrogel was investigated.The contact area increased with increasing pressure,and the TCR was 0.069 K?cm~2/W at a pressure of 50 Psi(35°C),showing good thermal conductivity.And at a certain pressure,the temperature has less effect on the TCR of graphene double cross-linked hydrogel,and the TCR is stable at a lower level,which can produce a more stable thermal performance.PartⅡ:The use of phase change material as the main body of the TIM,using the solid-liquid transformation characteristics of the phase change material after warming up,improves the wettability of the TIMs interface after contact,while using high thermal conductivity graphene as a thermally conductive filler material.In response to the problem that phase change materials are prone to leakage,hydrogels are innovatively introduced into the phase change material to achieve 100%coverage of the phase change material.At a graphene loading of 7 wt%,the thermal conductivity of the composite was 1.23 W/(m?K),an increase of 324%compared to the base material.In the TCR test,the TCR decreased significantly(from 5-20 K?cm~2/W to 0.5 K?cm~2/W)when the temperature was 80°C and the pressure was from 10 Psi to 40 Psi.When the pressure was at 40 Psi and the temperature increased from 50°C to 80°C,the TCR decreased to 0.2 K?cm~2/W.Through actual heat dissipation tests,the graphene phase change hydrogel thermal interface material has some heat dissipation capability,providing a new idea for the construction of new TIMs.PartⅢ:Deep eutectic solvent have received a lot of attention for their good electrical conductivity,stability,environmental friendliness and ease of preparation.And the polymerizable deep eutectic solvent(PDES)initiated by solvents have good thermal stability and tensile properties.Based on this,the monomers are initiated into polymers by acrylic acid and liquid metal,while the addition of spherical boron nitride enhances the thermal conductivity of the composites.The thermal stability and TCR properties of the boron nitride based low eutectic melt gel TIM were investigated.The results showed that the thermal conductivity of 20 wt%BN-PDES reached 1.18 W/(m?K).The tests concluded that the boron nitride low eutectic fusion gel has a low contact thermal resistance and good stability in cycling tests.The actual thermal tests also reflect that the composite has some thermal management properties.