New composites with high thermal conductivity and low dielectric constant for microelectronic packaging

Three composites based on cyanate (CE) resin, aluminum nitride (AlN), surface‐treated aluminum nitride [AlN(KH560)], and silicon dioxide (SiO₂) for microelectronic packaging, coded as AlN/CE, AlN(KH560)‐SiO₂(KH560)/CE, and AlN‐SiO₂/CE composite, respectively, were developed for the first time. The thermal conductivity and dielectric constant of all composites were investigated in detail. Results show that properties of fillers in composites have great influence on the thermal conductivity and dielectric constant of composites. Surface treatment of fillers is beneficial to increase the thermal conductivity or reduce dielectric constant of the composites. Comparing with binary composite, when the filler content is high, ternary composites possess lower thermal conductivity and dielectric constant. The reasons leading to these outcomes are discussed intensively. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Properties and application of polyimide‐based composites by blending surface functionalized boron nitride nanoplates

Ball milling was used to decrease the particle size of boron nitride (BN) nanoplates and to form more silylated functionalization of their surface. Such functionalized BN nanoplates enhanced their homogeneous dispersion in polyimide (PI) matrix. Thermal conductivities, thermal stabilities, and dielectric properties were characterized to investigate the particular effects on the performance of PI‐based composites with functionalized BN nanoplates. When the concentration of functionalized BN nanoplates increased to 50 wt %, thermal conductivity of the composite increased up to 1.583 W m^?1 K^?1, and the temperature of final thermal decomposition was improved to 600°C. An increasing trend was found in the dielectric constant of the composites while the dielectric loss decreased with the increase in the fraction. An appropriate fraction of functionalized BN nanoplates in PI‐based composites were necessary to meet the requirement of withstanding drilling forces for the interconnecting through holes of flexible circuits. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41889.     

PP/AlN复合材料导热机理研究

以氮化铝(AlN)粉末、聚丙烯(PP)为原料,通过共混-模压法制备了PP/AlN导热复合材料,并对其导热性能进行检测。研究发现,该复合材料的导热系数与AlN添加量之间不是线性关系而是呈幂函数关系,与介电逾渗理论基本吻合。根据检测数据并参考介电逾渗理论,提出了导热逾渗模型,并利用该模型和其他导热预测模型对PP/AlN复合材料的导热系数进行了计算。结果表明:复合材料的导热系数随AlN质量分数的增加呈幂函数增加趋势;实际检测结果与导热逾渗模型的预测结果基本相符,使该理论得到了验证。     

Alkylated modified boron nitride nanosheets/polyimide composite films with advanced thermal conductivity and low dielectric constant

Owing to the rapid development of the latest micro-electronic devices, polymer composite materials that combine high thermal conductivity and low permittivity have aroused the interest of researchers. However, it is a huge challenge to balance the above parameters. In this work, hexagonal boron nitride (h-BN) powder was ultrasonically exfoliated to obtain alkylated boron nitride nanosheets (Alkyl-BNNS). Then, a series of polyimide (PI) composites were synthesized with different amounts of Alkyl-BNNS. Attributed to more robust interfacial non-covalent interactions between Alkyl-BNNS and polymer chains to inhibit interfacial polarization, Alkyl-BNNS can be scattered well in PI substrate. Thus, the obtained PI composite behaved a high thermal conductivity of 6.21 W/(mK) and a low dielectric constant (3.23) under the load of 20 wt%. Besides, Alkyl-BNNS/PI composites have efficient thermal management capability, low water absorption, favorable electrical resistance, and prominent tensile strength. Importantly, these composite films are expected to be excellent candidates in the field of microelectronics.     

Thermal,dielectric, and rheological properties of aluminum nitride/liquid crystalline copoly(ester amide) composite for the application of thermal interface materials

In this article, thermally conductive and relatively low dielectric constant polymer matrix composites of an aluminum nitride filler (AlN) and a novel liquid crystalline copoly(ester amide) (LCP) were prepared via a solution blending method in the presence of a phosphate containing dispersant. The viscosities, thermal conductivities, and dielectric properties of the prepared AlN/LCP composites were investigated as a function of AlN loading. Our experimental results demonstrated that the AIN/LCP composite with AlN concentration of 50 wt% had 2.5 times higher thermal conductivity than pure LCP (2.020 and 0.817 W/mK for composite with 50 wt% of AlN and pure LCP, respectively), but its dielectric constant remained at low level, i.e., < 9.0 at frequency of 900 Hz. In addition, viscosities of AlN/LCP pastes in the N‐methyl‐2‐pyrrolidinone solvent remained at acceptable levels with the high AlN loading of 50 wt%. The morphologies of the prepared composites were also investigated by scanning electron microscopy. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

High-Thermal-Conductivity AlN Filler for Polymer/Ceramics Composites

To increase the thermal conductivity of polymer/ceramic composites, aluminum nitride (AlN) granules were added as a ceramic filler. Granules, sintered at 1850°C for 24 h, showed a very high conductivity of 266±26 W (m·°C)⁻¹, as measured by a thermal microscope equipped with thermoreflectant and periodic heating techniques. This conductivity exceeds 80% of the theoretical value of AlN. Ceramic fillers consisting of the obtained AlN granules and commercially available hexagonal boron nitride particles (h-BN) powder plus polyimide resins were mixed and then molded at 100 MPa and 420°C in a vacuum. The resultant composite showed a high conductivity of 9.3 W (m·°C)⁻¹. This study demonstrates that a high-thermal-conductivity filler effectively enhances the conductivity of polymer/ceramic composites.     

Synthesis and Dielectric Properties of Polyimide-Titania Hybrid Composites

A new class of polyimide-titania (TiO₂) composites with chemical bonds between the polyimide and titania system has been synthesized by the sol–gel reaction and characterized. The hybrid composite films were obtained by the reaction of lysine-organotitane monomer, which is formulated as [(EtO)₃Ti (lysinate)]_2, followed by polycondensation with dianhyride in N-methyl-2-pyrrolidone (NMP) solution, followed by heating at 100, 200, and 300 °C. The presence of chemical bonds between polyimide (PI) and titania has great effect on the properties of polyimide films, especially on their thermal and dielectric properties. The dielectric constants of the resultant nanocomposites are lower than the usual polyimide films due to the increased free volume and less polar Ti–O–Ti groups, and can be tuned by varying the molar ratio of tetraethoxysilane (TEOT) in the feed. The polyimide units offer additional advantages of imparting thermal and mechanical strength.     

Thermal and dielectric properties of the aluminum particle/epoxy resin composites

Microsized aluminum/epoxy resin composites were prepared, and the thermal and dielectric properties of the composites were investigated in terms of composition, aluminum particle sizes, frequency, and temperature. The results showed that the introduction of aluminum particles to the composites hardly influenced the thermal stability behavior, and decreased T_g of the epoxy resin; moreover, the size, concentration, and surface modification of aluminum particles had an effect on their thermal conductivity and dielectric properties. The dielectric permittivity increased smoothly with a rise of aluminum particle content, as well as with a decrease in frequency at high loading with aluminum particles. While the dissipation factor value increased slightly with an increase in frequency, it still remained at a low level. The dielectric permittivity and loss increased with temperature, owing to the segmental mobility of the polymer molecules. We found that the aluminum/epoxy composite containing 48 vol % aluminum‐particle content possessed a high thermal conductivity and a high dielectric permittivity, but a low loss factor, a low electric conductivity, and a higher breakdown voltage. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyimide hollow glass microspheres composite films with low dielectric constant and excellent thermal performance

Nowadays, polyimide (PI) with low dielectric constant is expected to be widely applied in microelectronics. For this reason, hollow glass microspheres (HGM) modified by silane coupling agent KH-550 (K-HGM), a series of HGM/PI and K-HGM/PI composite films with excellent thermal performance, hydrophobic and low dielectric constant were fabricated by in situ polymerization. The effect of HGM/K-HGM content on the properties of composite films was studied. The superior heat resistance of HGM can improve the thermal performance of composite films. Due to silane coupling agent KH-550, K-HGM exhibits a good interfacial compatibility with PI matrix and forms an interfacial adhesion region. With the HGM loading of 6%, comparing with pure PI films, the glass transition temperatures (T_g) of composite films were dramatically increased by 32.3°C. Especially, the low dielectric constant of 2.21 and dielectric loss of 0.0059 at 1 MHz were obtained for the PI/K-HGM composite film with addition of 8 wt%. Thus, PI/K-HGM composite films show more excellent performance. The current work provides a promising solution for fabrication of PI with low dielectric constant and superior thermal performance that may be applied in microelectronics industry.     

Electrical properties of flexible graphene reinforced polyimide composites

The electrical properties of polyimide and the composite at different volumes fractions were studied in the frequency range 200–20 kHz and in the temperature range 30–200 °C. Increasing the volume fraction of graphene up to 10%, resulted in an extremely large increase in the dielectric constant, which indicates the composites remarkable ability to store electric potential energy under the effect of alternating electric field. An increase in dielectric constant was also observed with increasing temperature and decreasing frequency. The outstanding dielectric properties of polyimide graphene nanocomposites are attributed to the large volume fraction of interfaces in the bulk of the material. The measured increase in dielectric constant with increasing temperature was attributed to the segmental mobility of the polymer chains. The AC conductivity for polyimide and the composites was calculated from the loss factor and a remarkably high conductivity was obtained for the composites due to the formation of conducting paths in the matrix by the graphene sheets. Also this study showed that the thermal conductivity of the composites increased sharply with increasing graphene concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45372.     

AlN改善Al2O3陶瓷导热性能的研究

本文选用导热系数较高的AlN来改善Al2O3陶瓷的导热性能;并借助SEM和XRD对材料的微观结构和物相进行了分析.结果表明：AlN/Al2O3基复合材料的导热性能随AlN含量的增加呈现先增大后减小的有规律变化,并在AlN的外加量达到7%时具有最佳值;另外,探讨了AlN的加入导致主晶相Al2O3的晶胞参数、晶粒大小、烧结气孔率的变化及它们对材料导热性的影响规律.     

Thermal and insulating properties of epoxy/aluminum nitride composites used for thermal interface material

We synthesized an epoxy matrix composite adhesive containing aluminum nitride (AlN) powder, which was used for thermal interface materials (TIM) in high power devices. The experimental results revealed that adding AlN fillers into epoxy resin was an effective way to boost thermal conductivity and maintain electrical insulation. We also discovered a proper coupling agent that reduced the viscosity of the epoxy‐AlN composite by AlN surface treatment and increased the solid loading to 60 vol %. For the TIM sample made with the composite adhesive, we obtained a thermal conductivity of 2.70 W/(m K), which was approximately 13 times larger than that of pure epoxy. The dielectric strength of the TIM was 10 to 11 kV/mm, which was large enough for applications in high power devices. Additionally, the thermal and insulating properties of the TIM did not degrade after thermal shock testing, indicating its reliability for use in power devices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

氮化铝陶瓷的研究与应用

氮化铝（ＡｌＮ）因具有高热导率,低介电常数、与硅相匹配的热膨胀率系数及其他优良的物理选场生在新领域越来越引起人们的关注,本文主要介绍分析了ＡｌＮ粉体合成、烧结技术、应用基础理论研究的最新动态和进展,以及ＡｌＮ陶瓷的应用领域与前景。     

Dielectric property of polyimide/barium titanate composites and its influence factors (Ⅱ)

Using poly(amic acid) (PAA) as a precursor followed by thermal imidization, the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process. The influence of processing factors, such as particle size, distribution mode and polymerization method on dielectric properties was studied. Results revealed that the dielectric constant (ɛ) of the composite film increased by using bigger fillers or employing in situ polymerization and bimodal distribution. When the composite film containing 50 Vol-% of BaTiO₃ with size in 100 nm was prepared via in situ process, its dielectric constant reached 45 at 10 kHz. __________ Translated from Journal of Functional Materials, 2008, 39(2): 264–267 [译自: 功能材料]     

氮化铝陶瓷的研制及应用

氮化铝 (AlN)因具有高热导率、低介电常数、与硅相匹配的热膨胀系数及其他优良的物理特性 ,在新材料领域越来越引起人们的关注。此文主要介绍并分析了AlN粉体合成、烧结、性能结构、AlN陶瓷的应用与前景     

Influence of curing temperature on properties of the polyacrylonitrile/polyimide composite films

A series of polyacrylonitrile/polyimide (PAN/PI) composite films with different PAN contents are prepared under given curing temperatures (250, 300, 350, and 400°C). The microstructure of the composite films is observed by SEM, and the thermal, dielectric and mechanical properties of the composite films are determined. The results show that the self‐assembly behavior of polyamic acid gives rise to connected network structure in the composite films and the variations in the microstructure of the composite films cured at different temperatures show important effects on the properties of PAN/PI composite films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40283.     

Thermal,mechanical, and dielectric properties of aluminum silicate fiber reinforced aluminum phosphate–poly(ether sulfone) layered composites

In this study, a novel aluminum phosphate (AlPO₄) heat‐resistant layer reinforced with aluminum silicate fiber (ASF) was successfully compounded on a poly(ether sulfone) (PES) matrix via the preparation process of high‐temperature heat treatment and vacuum hot‐pressing sintering technique. The influence of the ASF content on the morphology, thermal, mechanical, and dielectric properties of the as‐fabricated aluminum silicate fiber reinforced aluminum phosphate–poly(ether sulfone) (ASF/AlPO₄–PES) layered composite was investigated. The results reveal that the incorporation of aluminum silicate fiber/aluminum phosphate (ASF/AlPO₄) heat‐resistant layer can significantly improve the thermal stability and mechanical performances of the PES matrix composites. Compared with the pristine PES, the ASF/AlPO₄–PES layered composite containing 8.0 wt % ASF exhibited better high‐temperature resistance properties (300 °C) and a lower thermal conductivity (0.16 W m^?1 K^?1). Furthermore, the dielectric constant and dielectric loss tangent of this PES matrix composite decreased to 2.16 and 0.007, respectively. Meanwhile, the frequency stability of the dielectric properties for the ASF/AlPO₄–PES layered composites was remarkably enhanced with increasing ASF addition at frequencies ranging from 10² Hz to 5 MHz. This was attributed to the existence of microscopic pores within the ASF/AlPO₄ layer and the strong interfacial bonding between the ASF/AlPO₄ layer and the PES matrix. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45542.     

Novel organic–inorganic composites with high thermal conductivity for electronic packaging applications: A key issue review

Significant progress has been made recently in developing the organic–inorganic composites with high thermal conductivity, low dielectric constant, and dielectric loss, for applications in the electronic packaging and substrates. Many studies have shown that some polymers filled with high thermal conductivity and low dielectric loss ceramics are suitable for electronic packaging for device encapsulation. Until now, extensive attentions have been paid to the preparation of polymeric composites with high thermal conductivity and low dielectric loss for the application in electronic packaging. In contrast, the thermal conductivities of these dielectric materials are still not high enough and that might restrict their serviceable range. Herein, we briefly reviewed recent progress in this field and introduced a kind of novel composites with surface insulation modified metal aluminum cores to form multilayer coating structures as fillers in polyimide matrix for electronic applications. This structure can significantly improve the thermal conductivity and dielectric properties of composites and give some insights into the effects of modified fillers of composite materials. Such multilayer core–shell structures should have great potentials for the improvement of nanoparticle‐based fillers and applications of electronic packaging. POLYM. COMPOS., 38:803–813, 2017. © 2015 Society of Plastics Engineers     

Porous pyridine based polyimide–silica nanocomposites with low dielectric constant

Highly porous polymer–silica hybrid materials were prepared based on the organo-soluble polyimides of four various dianhydride and 2,5-diaminopyridine. 3-Aminopropyltriethoxysilane (APS) was used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. The produced polyimide–silica composites were investigated by X-ray diffraction analysis, scanning electron microscope and thermal analysis tecniques. The effect of silica modified with functional group of 3-aminopropyltriethoxy silane on the porous structure and dielectric properties as well as the thermal stability of films were investigated. Capacitances were determined with a HP4294A at a frequency between 1 kHz and 1 MHz. The dielectric constant was significantly reduced with increasing silica modified with APS. The result indicates that the composite materials are potentially useful in low dielectric materials.     

A novel electrochemical biosensor based on polyimide-boron nitride composite membranes

Polyimide (PI) and polyimide-boron nitride (PI-BN) composites as dopamine-selective membrane were synthesized. The structures of the monomer, pure PI, and PI-BN composites were characterized by FT-IR, SEM, and thermal analysis techniques. Experiment results showed that introduction of BN particles increased porosity, selectivity and improved heat-resistance of polyimide matrix. Selectivity of PI-BN composite membranes toward dopamine and interferences was examined by DPV technique. Electrochemical measurement results illustrated that polyimide membrane containing 5%BN possessed wide linear ranges, excellent sensitivity, selectivity, reversibility, and low detection limits (4?×?10^?8?M). The polyimide membrane was very high R value (0.9904).