The Study On The Hollow Glass Microsphere And Ceramic Particles Filled Polymer-matrix Composites With The High Thermal Conductivity And The Low Dielectric Properties

With the higher integration density and faster performance of the electronics, the newgeneration packaging and substrate materials with high thermal conductivity, low dielectricconstant and dielectric loss are required to guarantee the heat dissipation and singalpropagation of the integrated circuits. In this paper, the low-density polyethylene (LDPE) andthe immisible LDPE/epoxy blends reinforced with hybrid fillers containing hollow glassmicrosphere (HGM)(S60HS, S38HS, K20) and ceramic particles (aluminum nitride (AlN),boron nitride (BN)) were prepared via hot pressing and mold casting method, respectively. Thethermal and dielectric properties and microstructrue of the composites were measured byvirtue of the apparatus for measurement of the thermal conductivity, impedance analyzer,fourier transform infrared spectrometer (FT-IR) and scanning electron microscope (SEM).Moreover, the effects of surface modification, type, content, volume ratio, particle size of thefillers and volume ratio, particle size of the matrix on the thermal and dielectric properties ofthe composites were investigated.The experimental results of HGM/LDPE composites show that the thermal and dielectricproperties of the composites are influenced by the dosage of silane coupling agent (KH570),and it processes the highest thermal conductivity and lowest dielectric constant and dielectricloss when the dosage of KH570is3%of the HGM mass. The thermal conductivity anddielectric constant of the composites decrease and the dielectric loss increases with increasingthe filler content. The composite filled with S38HS processes the lowest thermal conductivity,dielectric constant and dielectric loss. The dielectric constant of2.08and the dielectric loss of3.16×10-3are obtained for50vol%S38HS filled composites. It is found that Lichteneckermodel and Agari model are adaptable for prediciting the thermal conductivity of thecomposites and the predicitive values of the dielectric constant via several typtical models arelower than the experimental data.On the basis of the study on the HGM filled LDPE composite, the results of(HGM+ceramics)/LDPE composites show that the overall performance of the compositesfilled with hybride fillers in the volume ratio of1:1is superior. The addition of hybride fillersat a certain volume ratio enhances the thermal conductivity, dielectric constant and dielectricloss of the composites, and the HGM/BN filled composites exhibit the higher thermalconductivity, dielectric loss and lower dielectric constant than that of HGM/AlN filledcomposites. The thermal conductivity of the composites filled with different HGM are almostthe same, and the dielectric constant and dielectric loss are ranked as follows: S60HS> S38HS > Κ20. The composites incorporated the smaller AlN or bigger BN particles achieve the higherthermal conductivity and dielectric constant, and the particle size of LDPE has little effects onthe properties of the composites. It is observed that the agglomerations of hybrid fillersdisperse around the LDPE matrix and the ceramic particles surround the HGM, touch eachother and form the thermal conductive networks in the composites. The high thermalconductivity of0.82W/(m K), low dielectric constant of2.4and low dielectric loss of2.65×10-3are obtained simultaneously for (K20+BN)/LDPE composites. Comparing sometypical model with experimental data of the composites, it is found that Agari model areadaptable for prediciting the thermal conductivity of the composites, and the predition of thedielectric constant shows the fitted values at low filler content and higher values at high fillercontent respectively.The experimental results of (HGM+ceramics)/(LDPE+epoxy) composites show that theblend ratio of LDPE and epoxy affects the thermal and dielectric properties of the compositesgreatly. As the volume fraction of LDPE in blended matrix increasing, the thermalconductivity of the composites firstly increases and reaches the maximum at the content of30vol%and then decreases, while the dielectric properties decrease continuously, which isattributed to the changes of ceramics concerntration in the epoxy and the continuous phase ofepoxy matrix. The composite filled with BN exhibit better performance than that of filled withAlN, and the S60HS filled composites have the higher thermal conductivity and dielectricconstant than that filled with S38HS. From SEM it is observed that ceramic particles mainlydistribute in the epoxy matrix, bypassing the HGM, and construct the thermal conductivenetworks. The high thermal conductivity of0.7W/(m K), low dielectric constant of3.12andlow dielectric loss of1.1×10-2are also obtained for (S38HS+BN)/(LDPE+epoxy) composites.It is found that values of the thermal conductivity deduced from Agari model fit well with theexperimental data and the choosed typical models are not adaptable for predict the dielectricconstant of the composites.