| Substrate materials and thermal interface materials(TIMs)are two important components in the electronic packaging process.The main function of the substrate material is as a carrier for electronic devices,which is a circuit between electrons and devices.Welding provides a platform,and its electrical insulation,high thermal conductivity,thermal stability and other properties provide a reliable guarantee for the safe and stable operation of electronic devices.The main function of the thermal interface materials is to fill the gap between the electronic device and the substrate or the electronic devices to enhance the interface heat transfer.In recent years,with the rapid development of the electronics industry,electronic devices are inevitably moving toward miniaturization,thinning,high speed,and high integration.However,the highly concentrated assembly density of electronic devices and the high heat dissipation of electronic devices have become the bottleneck restricting the development of next-generation new electronic devices,which deserves the attention of researchers and engineers in the global electronic packaging field.At the same time,electronic packaging materials are usually point-to-point to solve the needs of a certain material,lack of universality,and also cause a lot of inconvenience in the production,processing,sales and after-sales service of electronic packaging materials.Therefore,it is imperative to develop new high-performance electronic packaging materials to meet the development needs of the future microelectronics industry.After analyzing and researching the development trend of new electronic packaging materials for the current research situation of electronic packaging materials at our country and abroad and meeting the needs of next-generation electronic devices.The intergrated circuit industry has become the main driing force for China’s economic development and the urgent need for national information security.We aim at preparing high-performance substrate materials and thermal interface materials with high thermal conductivity and oriented structure.And proposing the concept of modularization of electronic packaging materials.The heat transfer performance,electrical insulation properties,mechanical properties,bonding properties,dielectric properties and microstructure and properties of these materials were studied.The main research results are as follows:1.Single-oriented polymer-based thermal conductive materials:The work of this part mainly focuses on the horizontal orientation,structural design and thermal conductivity enhancement of two-dimensional thermally conductive reinforcing fillers(for example:hexagonal boron nitride,flake graphite and multilayer graphene)in the polymer matrix.The work of this part will be stated in the following four sections:1.1 High thermal conductive filler(graphite flake)reinforced polymer composites have obtained a growing attention in the microelectronic industry.In order to overcome the obstacles in surface modification,in this study,dopamine chemistry was used to achieve the facile modification of graphite flake via forming a polydopamine(PDA)shell on the surface in a solvent-free aqueous condition.The strong π-π interaction between the hexagonal structural graphite flake and aromatic dopamine molecules ensured the effective modification.The PDA coating on graphite flake enhanced the compatibility between the filler and the flexible cycloaliphatic epoxy resin(CER)matrix via hydrogen bond,and promoted the epoxy curing process by forming covalent bond.Under the assistance of gravity,the PDA@graphite flake stacked along the horizontal direction in the polymer matrix.The procedure of filler alignment and mechanism of thermal decomposition were investigated by XRD measurement and thermodynamic/kinetics analysis,respectively.The dynamic mechanical analysis(DMA)was also used to investigate the relationship between microstructure and performance.Due to the combination of surface modification and alignment of PDA@graphite flake,the prepared CER/PDA@graphite has higher in-plane thermal conductivity.In addition,excellent adhesion property and thermal stability demonstrated that the CER/PDA@graphite composites was a good candidate as thermal interface material(TIMs),which could be applied in the thermal management areas.The procedure was environment friendly,easy operation,and suitable for the practical application in large scale.1.2 Adding thermal conductive filler is an effective method to improve the thermal conductivity of polymer matrix.In this research,we demonstrated that the polymer composites with much improved thermal conductivity while maintaining low electrical conductivity,which could be achieved via using hybrid 2D stacked filler and controlling the alignment of the filler in polymer matrix.In order to do this,the graphene oxide(GO)was prepared and simultaneously reduced/functionalized by diethylenetriamine(DETA)to obtain NH2-fuctionalized graphene(NfG)which designed to be immobilized on the surface of large-sized insulating hexagonal boron nitride(h-BN)via π-π stacking interaction.In this situation,since the NfG sheets were fixed on the surface of h-BN,the NfG sheets were well separated from each other and participated in the resin curing process.Hence,not only significantly enhanced thermal conductivity(～3.409 W/m·K,in-plane direction)was obtained,but also a very low electrical conductivity was achieved.The low electrical conductivity was believed to be ascribed to both embedded insulating network of h-BN to inhibit the mobility of charge carrier and well-separated NfG sheets via π-π stacking interaction.In addition,the nanocomposites also exhibited good thermal stability and adhesive properties.We believed that this special structure will provide a new thought for fabricating thermal interface materials(TIMs)with much high thermal conductivity as well as low electrical conductivity.1.3 High thermal conductive filler(hexagonal boron nitride and carbon nanotube)reinforced polymer composites have obtained a growing attention in the microelectronic industry for their good thermal conductivity but electrical insulating.In this work,a synergistic hybrid structure of two fillers with different dimensions had been designed and prepared by taking hexagonal born nitride(h-BN)platelets and ammine carbon nanotubes(CNT-NH2)into the flexible polymer matrix.Using cycloaliphatic epoxy resin(CER)as the polymer matrix,a serious of(a)h-BN/CER based,(b)hybrid filler h-BN@CNT-NH2/CER based,and(c)mixed filler CNT-NH2 and h-BN/CER based composites were prepared.In this structure,h-BN(and h-BN@CNT-NH2)platelets stacked along the horizontal direction under the assistance of gravity force and interactivity between the fillers.The orientation of the h-BN platelets was investigated by scanning electron microscope(SEM)of the cracked cross-section of the composite film and XRD measurement via calculating the orientation function(f).The CNT-NH2 was embedded within the network to improve the filler-filler contact or network-density.Due to the anisotropic properties of h-BN platelets and dispersion states of CNT-NH2,the composites with different structures presented different and special properties,including thermal/electrical conductivity properties,mechanical properties,and thermal decomposition properties.The analysis of structure and mechanism of thermal decomposition were then proposed to explain those interesting properties.The incorporation and dispersion states of CNT-NH2 in the composites played an important effect on the enhancement of the thermal conductivity properties both included in-plane(～1.76 W/m·K)and through-plane(～1.09 W/m·K)thermal conductivity.Additionally,the good electrical insulating properties and mechanical properties of the composites provided a potential application in the thermal management areas.The solvent-free procedure was environment friendly,easy operation,and suitable for the practical application in large scale.1.4 In this work,we presented novel cycloaliphatic epoxy resin composites filled with multi-layer graphene(mG)/hexagonal boron nitride(h-BN)with high thermal conductivity and good electrical insulating.Firstly,the h-BN platelets were modified by mussel-inspired method with dopamine chemistry to obtain the modified filler h-BN@PDA.And the attachment of polydopamine molecule improved the interfacial adhesion between polymer matrix and filler.Secondly,the mG with fixed content was mixed with h-BN@PDA and then the hybrid filler mG/h-BN@PDA was added to the cycloaliphatic epoxy resin to obtain the polymer composites.Because of the high aspect of the filler,low viscosity of the polymer matrix,and assistance of the gravity force,the hybrid filler would stack alignment.It was found that the hybridization of the filler and alignment of the hybrid filler resulted in the enhancement of properties of the composites such as the thermal decomposition,mechanical(tensile strength=5.50 MPa),thermal(through-plane～1.27 W/m·K,in-plane～1.31 W/m·K)and electrical insulating(electrical conductivity<1.5×10-10 S/cm)properties.The obtained composites could be applied in thermal management area.2.Dual-oriented polymer-based thermal conductive materials:The single-oriented polymer-based thermal conductive materials utilizes a two-dimensional heat conduction to enhance the high contact area between the fillers,effectively,reducing the contact thermal resistance between the fillers,thereby obtaining efficient heat conduction in a certain direction.However,in some cases,we need heat to conduct simultaneously along the horizontal and vertical directions.Conventional one-dimensional fillers can usually achieve the isotropic conduction of heat,but the high contact thermal resistance caused by the low contact area between the one-dimensional fillers often results in a low thermal conductivity of the material or a high filler loading.Therefore,we try to construct the dual-oriented heat transfer channels along horizontal and vertical direction base on the work of single-directed heat transfer to meet the demand for isotropic heat transfer performance in special occasions.2.1 The orientation of ultrahigh aspect ratio thermally conductive fillers can construct heat transfer path and enhance the thermal conductivity of composites effectively at low filler loading.Nevertheless,single orientation(vertical or horizontal)limits the application of these materials when needs isotropic heat transferring.Here we report a novel and simple strategy to prepare thermally conductive flexible cycloaliphatic epoxy resin(CER)nanocomposites with an oriented three-dimensional staggered interconnected network of vertical aligned hexagonal boron nitride(h-BN)platelets and randomly dispersed aminated carbon nanotubes(CNT-NH2).In this structure,h-BN platelets coated with magnetic particles can response to the external magnetic field,however,the CNT-NH2 can’t.The obtained composites exhibit both through-plane(0.98 W/m·K)and in-plane(0.99 W/m-K)thermal conductivity enhancement at low h-BN loading of 30wt%,and also present excellent electrical insulating properties(<1.2×10-12 S/cm).In addition,the equal in-plane and through-plane thermal conductivity is shown when the loading of h-BN is above 25wt%,displaying the disappeared difference between in-plane and through-plane thermal conductivity.The infrared imaging tests show the outstanding heat dissipation capability of the composites by capturing the surface temperature variations of a heater with the composites as the heat dissipating material.2.2 0riented three-dimensional staggered interconnected network nanocomposites CER/LG/Fe@hBN were prepared under the external magnetic field filled with magnetically responsive hybrid filler Fe@hBN and non-magnetically responsive filler few-layer graphene sheets(LG).We change the orientation of the filler Fe@hBN by roating the external magnetic field.At the same time,the rotation of the external magnetic field would not affect the orientation of few-layer graphene sheets(LG).And then,we investigated the thermal conductivity,themal decomposition and electrical conductivity properties of the composite materials.The best in-plane thermal conductivity and through-plane thermal conductivity would arrive at 0.97 W/m·K and 0.85 W/m·K.The infrared imaging tests show the outstanding heat dissipation capability of the composites by capturing the surface temperature variations of a heater with the composites as the heat dissipating material.3.Polymer based thermal conductive interface adhesive material:The modular design of polymer-based thermal conductive material includes:(a)design and fabrication of oriented thermal conductive materials and(b)assembly between thermal conductive materials.Here,we try to achieve the assembly between the various materials by interface adhesion.However,not tight enough contaction between the thermal conductive materials produce the gaps,resulting in a decrease in heat transfer efficiency.Therefore,we need thermal conductive.interface adhesive material to ensure the existence of high-efficiency heat conduction channels while achieving a close interface between the materials.In addition,in order to achieve the reliability of the overall mechanical strength after the module’ assembling,the adhesive strength of the thermal condctive interface adhesive material can’t be ignored,the related work is as follows:3.1 Thermally conductive poly(2-ethylhexyl acrylate)(P2EHA)/functionalized graphene/h-boron nitride composites materials were fabricated by colloid blending and self-assembly approach.Here,self-assembly technology has been used to achieve the facile surface modification of hexagonal boron nitride(h-BN)microplatelets by forming a functionalized graphene(f-G)sheets on its surface via π-π interaction.The polar functionality on the graphene surface allowed the permeation of the polymer matrix through the secondary interaction between them,increasing the content of this hybridized filler in composite.The effective and successful fabrication of f-G@h-BN microplates have been confirmed by SEM,Raman spectroscopy,XRD,and TGA investigations.The self-alignment 2D stacked fillers result in higher in-plane thermal conductivities and excellent electrical insulation of the composites.In addition to the good adhesive properties,the procedure is environment-friendly,easy operation,and potential for the practical application in large scale.3.2Flexible fiber-reinforced laminated composite adhesive combining with functionalized-graphene(f-G)layer and hexagonal boron nitride(h-BN)layer was prepared by colloid-blending and self-assembly technology with the assistance of the secondary force and hydrophilic difference.In this system,poly(2-ethylhexyl acrylate)(P2EHA)as the polymer matrix linked the layer of functionalized-graphene and another layer of hexagonal boron nitride like the cross-linker or adhesive via self-assembly technology.Lewis acid-base(δ+-δ-)interaction and π-π stacking improved the compatibility between the filler and the polymer matrix.The effective and successful fabrication of flexible f-G/h-BN laminated composite adhesive has been confirmed by SEM,Raman spectroscopy,and XRD investigations.The oriented stacking and laminated structure resulted in much higher in-plane thermal conductivities(-4.20 W/m·K)and insulation in the direction through the plane and good adhesive properties.The procedure was environmental friendly,easy operation,and potential for the practical application in industry.4.Assembly and heat transfer simulation of modular electronic packaging materials components:In this part,we will pay more attention on the assembly and heat transfer simulation of the polyerm-based thermal conductive materials via Finite element analysis.Firstly,we investigated the thermal conductive materials with three different orientation structure:(i)in-plane orientation,(ii)out-plane orientation,and(iii)dual orientation.And we also study the influence of the orientation and interval space of the 2D thermal conductive filler.And then,we try to assemble and investigate the three different modular electronic materials.However,we don’t pay more attention on the real problem we may encounter in actual processing.We need to do more work in the future. |
PDF Full Text Request