Search

The rapid development of the 5G communication technology requires the improvement of the thermal stability and dielectric performance of high-frequency copper clad laminates (CCL). A cyclic olefin copolymer (COC) resin was added to the original 1,2-polybutadienes (PB)/styrene ethylene butylene styrene (SEBS) binary resin system to construct a PB/SEBS/COC ternary polyolefin system with optimized dielectric properties, mechanical properties, and water absorption. Glass fiber cloths (GFCs) and SiO2 were used to fill the resin matrix so to reduce the thermal expansion coefficient (CTE) and enhance the mechanical strength of the composites. It was found that the CTE of polyolefin/GFCs/SiO2 composite laminates decreased with the increase of SiO2 loading at first, which was attributed to the strong interfacial interaction restricting the segmental motion of polymer chains between filler and matrix. It was obvious that the addition of COC and SiO2 had an effect on the porosity, as shown in the SEM graph, which influenced the dielectric loss (Df) of the composites directly. When the weight of SiO2 accounted for 40% of the total mass of the composites, the laminates exhibited the best comprehensive performance. Their CTE and Df were reduced by 63.3% and 22.0%, respectively, and their bending strength increased by 2136.1% compared with that of the substrates without COC and SiO2. These substrates have a great application prospect in the field of hydrocarbon resin-based CCL. [ABSTRACT FROM AUTHOR]

High-frequency communication equipment urgently needs substrate materials with lower dielectric loss, better heat dissipation, and higher stability, to ensure real-time low-loss and high-speed signal transmission. The core-shell structure of Sr2CeO4@SiO2 was prepared by the sol-gel method, and the modified powders with different volume contents were introduced into the cyclic olefin copolymer (COC) to prepare hydrocarbon resin-based composites. Due to the protective effect of the SiO2 shell, the stability of the powders is significantly improved, and the moisture barrier and corrosion resistance of the composites are enhanced, which is conducive to the normal operation of electronic equipment in harsh and complex environments. When the filler content is 20 vol%, the composite has a dielectric loss of 0.0023 at 10 GHz, a dielectric constant of 3.5, a thermal conductivity of 0.9 W·m−1·K−1, a water absorption of 0.32% and a coefficient of thermal expansion of 37.7 ppm/°C. The COC/Sr2CeO4@SiO2 composites exhibit excellent dielectric properties and thermal conductivity, while maintaining good moisture resistance and dimensional stability, which shows potential application prospects in the field of high-frequency substrates. [ABSTRACT FROM AUTHOR]

In this research, we designed a feasible method to prepare composite films with high permittivity and significantly enhanced hydrophobic performance, which showed huge potential in the electrowetting field. TiO2 nanowire arrays were prepared by a one-step hydrothermal process, and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was spin-coated on the nanowire arrays to form composite, the surface of which was modified by electrospinning. Due to the great orientation of TiO2 nanowires, dipoles and space charges are in ordered arrangement along the electric field, and this strongly reinforced the Maxwell–Wagner–Sillars (MWS) polarization, thus the permittivity of the composite (TiO2 nanowire length/film thickness is 0.769) reaches 53 at 1 kHz, which is nearly 3 times higher than pure P(VDF-TrFE). Meanwhile the composite film possesses low dielectric loss (0.07) and low conductivity (2.69 × 10−9 S/cm), showing good insulation. The contact angle of the composite after electrospinning (about 137°) was greatly enhanced from pure P(VDF-TrFE) spin-coated film (about 89°), which can be attributed to the microrough structure built by P(VDF-TrFE) nanofibers. [ABSTRACT FROM AUTHOR]

Copper clad laminates (CCLs) with low dissipation factor (Df) are urgently needed in the fields of high-frequency communications devices. A novel resin matrix of modified poly (2,6-dimethyl-1,4-phenylene ether) (MPPE) and styrene-ethylene/butylene-styrene (SEBS) was employed in the fabrication of high-frequency copper clad laminates (CCLs). The composites were reinforced by E-glass fabrics, which were modified with phenyltriethoxysilane (PhTES). The composite laminates obtained exhibited impressive dielectric loss of 0.0027 at 10 GHz when the weight ratio of MPPE to SEBS was 5:1. In order to modify the dielectric constant (Dk), coefficient of thermal expansion (CTE) and other performances of laminates, Li2TiO3 (LT) ceramic powders were introduced into the resin matrix. The composite laminates showed low dielectric loss of 0.0026 at 10 GHz and relatively high flexural strength of 125 MPa when the mass ratio of LT fillers to resin is 0.4. Moreover, the composite laminates all maintain low water uptake (<0.5%). The microstructure and thermal properties of composite laminates filled with LT ceramic powders were also tested. These results show that copper clad laminates prepared with modified polyphenylene ether (MPPE)/SEBS and LT ceramic fillers have strong competitiveness to fabricate printed circuit boards (PCBs) for high-frequency and high-speed applications. [ABSTRACT FROM AUTHOR]

In this work, we presented a simple strategy to fabricate medium dielectric constant and low‐loss composites for microwave substrate applications. MgO‐LiF co‐doped Li2TiO3 (LT) powders were fabricated by the solid‐state reaction route and modified by perfluorooctyltriethoxysilane (F8261). The LT/polytetrafluoroethylene (PTFE) composites were fabricated by cold pressing and hot treatment. The XPS and contact angle analysis indicated that the fluorinated group was introduced to LT particle successfully. The effects of modified LT powders content on the dielectric, thermal, and mechanical properties of composites were investigated. As the modified LT content increases, the dielectric constant, dielectric loss, and temperature coefficient of dielectric constant (τε) increase while the bending strength and coefficient of thermal expansion (CTE) decrease, which is attributed to the higher dielectric constant of LT ceramic, more pores, stable τε of LT ceramic, interface defects and low CTE of LT ceramic, respectively. The composites with 60 wt % LT exhibit the best microwave dielectric properties: εr = 6.8, tanδ = 0.001, τε = −29.6 ppm °C−1 at 8 GHz and acceptable coefficient of thermal expansion (28.3 ppm °C−1). Therefore, modified LT powders filled PTFE composites are potential materials for high‐frequency microwave substrate applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47980. [ABSTRACT FROM AUTHOR]

Polymer dielectric materials are extensively used in electronic devices. To enhance the dielectric constant, ceramic fillers with high dielectric constant have been widely introduced into polymer matrices. However, to obtain high permittivity, a large added amount (>50 vol%) is usually needed. With the aim of improving dielectric properties with low filler content, satellite–core-structured Fe2O3@BaTiO3 (Fe2O3@BT) nanoparticles were fabricated as fillers for a poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix. The interfacial polarization effect is increased by Fe2O3 nanoparticles, and thus, composite permittivity is enhanced. Besides, the satellite–core structure prevents Fe2O3 particles from directly contacting each other, so that the dielectric loss remains relatively low. Typically, with 20 vol% Fe2O3@BT nanoparticle fillers, the permittivity of the composite is 31.7 (1 kHz), nearly 1.8 and 3.0 times that of 20 vol% BT composites and pure polymers, respectively. Nanocomposites also achieve high breakdown strength (>150 KV/mm) and low loss tangent (~0.05). Moreover, the composites exhibited excellent flexibility and maintained good dielectric properties after bending. These results demonstrate that composite films possess broad application prospects in flexible electronics. [ABSTRACT FROM AUTHOR]

P(VDF-TrFE) (vinylidene fluoride-co-trifluoroethylene)/PMMA (PVT/PMMA) blended films synthesized through a facile solution-blending method show outstanding performance for practical electrowetting and energy storage applications. The van der Waals forces and dipolar interactions in neighboring P(VDF-TrFE) and PMMA chains, together with the suppressed free volume (or defect) are critical to the significantly-enhanced electrical properties. Typical, Teflon-covered P(VDF-TrFE)/PMMA blended film exhibits a high dielectric constant of 13 with low dielectric loss (~0.05) at 100 Hz and a large initial contact angle of 122°. Its electrowetting response with a contact angle modulation of 50° in air and low contact angle hysteresis demonstrate that it is promising for low-voltage electrowetting applications. Furthermore, with an energy density of 11.8 J/cm3, approximately double that of pure P(VDF-TrFE), PVT/PMMA blended films containing 20 wt % PMMA turn out to be superior materials for energy storage applications, due to their significantly-enhanced polarization and reduced remnant polarization. [ABSTRACT FROM AUTHOR]

Hydrocarbon resin-based substrate materials with low dielectric constant, low dielectric loss and high thermal conductivity are eagerly demanded by electronic equipment operating at high-frequency and high-speed signal transmission situation. Nevertheless, existing substrate materials were fabricated by directly adding inorganic ceramic fillers, whose thermal conductive properties and comprehensive properties were not enough to meet practical applications. Herein a facile and effective method to obtain the cyclic olefin copolymer (COC)-based substrate materials with high thermal conductivity was reported by coating flower-like Al 2 O 3 (f-Al 2 O 3) on the surface of BNNs to construct the continuous thermal conductive pathways in polymer matrix. BNNs@f-Al 2 O 3 filled COC composites show higher thermal conductivity, higher flexure strength and lower coefficient of thermal expansion (CTE) than BNNs and BNNs + commercial Al 2 O 3 filled COC composites with the same content of BNNs and Al 2 O 3. At the BNNs loading of 15 wt%, the BNNs@f-Al 2 O 3 filled COC composites exhibit a low dielectric constant of 2.65, a low dielectric loss of 1.4 × 10−3 at 10 GHz, a high thermal conductivity of 3.2 W/(mK) and a low CTE of 22 ppm/°C near to copper foil. The COC/BNNs@f-Al 2 O 3 composites with fine comprehensive properties show huge application potentiality in high-frequency and high-speed substrates. [Display omitted] [ABSTRACT FROM AUTHOR]

The modified 0.7Ba (Co 1/3 Nb 2/3)O 3 -0.3Ba(Zn 1/3 Nb 2/3)O 3 (BCZN) powders filled PTFE composites were synthesized by hot-pressing. The influences of BCZN content on the microstructure, dielectric, thermal, mechanical properties and moisture absorption were investigated systematically. The modified BCZN powders filled PTFE composites exhibited better microstructure and dielectric properties compared with untreated powders. Various mathematic models were utilized to predict the dielectric constant of different composites and the effective medium theory (EMT) showed perfect consistency with the experimental results. The modified BCZN/PTFE composites possess the best comprehensive properties at the powders content of 50 vol% with high dielectric constant (ε r) of 7.7, low loss (tanδ) of 0.0014, acceptable temperature coefficient of dielectric constant (τ ε) of −125.6 ppm/°C and temperature coefficient of resonant frequency (τ f) of 29.4 ppm/°C at 7 GHz, low moisture absorption of 0.07% and low coefficient of thermal expansion (CTE) of 33 ppm/°C. All the results show modified BCZN/PTFE composites are the potential materials for microwave substrate applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The homogenous core-shell AgNWs@SiO 2 has been successfully fabricated. • The dielectric constant improved effectively by enhanced interfacial polarization. • The extremely low dielectric loss and conductivity achieved by introducing SiO 2 insulating interfacial layer. • The static contact angle of composites was notably improved through creating a hydrophobicity surface. • The films behaved high electromechanical sensitivity due to the enhanced ε and reduced Y. Abstract This paper reports a feasible method to prepare polymeric nanocomposites with enhanced dielectric, electromechanical and hydrophobic performance by introducing the core-shell AgNWs@SiO 2 filler into polydimethylsiloxane (PDMS). The homogenous core-shell AgNWs@SiO 2 was firstly synthesized through a two-step sol-gel process. The thicknesses of AgNWs and SiO 2 coating layer are approximately 70 nm and 20 nm, respectively. The dielectric constant is improved effectively due to enhanced interfacial polarization, while extremely low dielectric loss and conductivity are achieved by introducing the insulating SiO 2 interlayer to moderate the internal surface area of core-shell nanowires and restrict the electron transfer between Ag nanowires. Typically, the PDMS nanocomposites with 20 wt% AgNWs@SiO 2 have a dielectric constant of 6.7, nearly 2.7 times larger than that of pure PDMS, and remains a quite low loss of 0.02 at 1 kHz. Meanwhile, nanocomposites also show improved electromechanical and hydrophoic properties. Nanocomposites with 10 wt% AgNWs@SiO 2 exhibit the highest electromechanical sensitivity (β= 9.04), about 12.6 times higher than that of pure PDMS at 1 kHz. The static contact angle of nanocomposties with 20 wt% AgNWs@SiO 2 reaches 129°. All the improved performances show great potential application for dielectric elastomer material and electrowetting devices. [ABSTRACT FROM AUTHOR]

In this study, TiO 2 nanowires with various aspect ratios were prepared via a precursor-controlled hydrothermal process. Ternary composite films comprised of P(VDF-HFP) polymer, Ag particles and the as-synthesized TiO 2 nanowires were then fabricated. The results reveal that TiO 2 NWs with high aspect ratios (i.e., pa-TiO 2 ) exhibit superiority in enhancing the dielectric constants of composites in comparison with their low-aspect-ratio counterparts (i.e., pr-TiO 2 ). For instance, the dielectric constant of the Ag/pa-TiO 2 /P(VDF-HFP) composite with 30 vol% TiO 2 NWs reaches 33.4 at 100 Hz, which is 42.1% larger than that of Ag/pr-TiO 2 /P(VDF-HFP) sample and 227% higher than pristine P(VDF-HFP). In addition, TiO 2 nanowires also serve as physical obstacles to avoid aggregation of Ag particles. As a consequence, the ternary composites filled with high-aspect-ratio TiO 2 NWs exhibit suppressed dielectric losses (e.g., 0.023 at 100 Hz) and low conductivities, making them promising candidates for applications in integrated capacitors and energy storage devices. [ABSTRACT FROM AUTHOR]

Flexible circuit board materials with low dielectric constant (ε r), low dielectric loss (tanδ) and high thermal conductivity (TC) were highly desired for high-frequency and high-speed electronic equipment. Herein, hexagonal boron nitride (h-BN) sheets were filled into highly elastic styrene ethylene butylene styrene (SEBS) matrix and oriented along in-plane direction regularly by hot-pressing method. SEBS/h-BN films exhibited high TC and outstanding flexibility except relatively high tanδ and water absorption. The sandwich structure was designed utilizing pure cyclic olefin copolymer (COC) films as outer surface layers and SEBS/h-BN film as interlayer. The introduction of COC films reduced the tanδ and water absorption of SEBS/h-BN film without reducing original TC obviously. Hybrid SEBS/COC/BN films owning the same components with sandwich-structure films were also fabricated to verify the advantages of designed structure. Sandwich-structure films always kept good flexibility and exhibited low ε r (2.7–3.6), low tanδ (<1 × 10−3, 10 GHz), high TC (3.8–17.6 W m−1 K−1) and low water absorption (<0.1%). These films were also fabricated into flexible copper clad laminates and patch antenna operated in sub-6G band. The antenna exhibited a return loss of −32.8 dB and a gain of 7.04 dBi. The flexible substrates show great potential and satisfy large-scale production demand in high TC flexible circuit board materials field. [Display omitted] [ABSTRACT FROM AUTHOR]