Low Dielectric Constant Research Articles

Physical analysis of high refractive index metamaterial-based radiation aggregation engineering of planar dipole antenna for gain enhancement of mm-wave applications

A metamaterial-incorporated high-gain and broadband dipole antenna is proposed for 5G mm-wave applications. The designed high refractive index metamaterial (HRIM) properties are presented in detail with supporting results. The proposed dipole antenna achieved broadband features, and the antenna gain increased significantly by incorporating HRIM in the electromagnetic (EM) wave propagation path. Besides, the EM wave aggregation engineering of utilizing the HRIM on the dipole antenna is analyzed using the electric field, magnetic field, and power flow distributions. Both conventional and HRIM-based dipole antenna (HRIMDA) were fabricated on thin (0.254 mm) Rogers RT5880 substrate material with a low dielectric constant of 2.2, where the noticeable gain enhancement by HRIM is observed. The measured results show the operational bandwidth (BW) from 23 to 38 GHz frequency, and the highest gain of 9.5 dBi is accomplished at 35 GHz frequency. Finally, a four-element MIMO configuration is numerically and experimentally analyzed where the isolation of the two conjugated MIMO elements is < − 20 dB. The MIMO parameters like envelop correlation coefficient (ECC) < 1 × 10–3 and diversity gain (DG) value of > 9.9 were also achieved. Hence, the proposed HRIM base dipole antenna is a potential candidate for 5G mm-wave applications.

Molecular design and application of low dielectric bismaleimide resin

AbstractWith the development of communications technology, the copper‐clad laminate (CCL) for integrated circuits (IC) pointed to the direction of high‐frequency and high‐speed development, that is, a lower dielectric constant and dielectric loss requirements. Bismaleimide (BMI) resins feature stable dielectric properties and excellent thermal stability over a wide temperature range, widely used in the manufacture of high‐frequency and high‐speed CCL substrates. However, the comprehensive performance of BMI resin itself, including dielectric properties, still cannot fully meet the needs of the ever‐changing communications industry, so the molecular design modification of BMI resin to enhance the dielectric properties is currently one of the key research directions for integrated circuit CCL. This paper reviews the development of BMI resins and their applications, focusing on the main methods of molecular design modification and formulation optimization, including allyl, diamine, internal chain‐extended, and chemical/physical blending modification. Finally, the low dielectric BMI resin and its application and development in high‐frequency and high‐speed CCL are summarized and prospected. Future research directions include the design and synthesis of multi‐component copolymers to further realize the balance between low dielectric and comprehensive performance, as well as exploring the possibility of novel composite modifications to provide more competitive high‐performance materials for the IC laminate field.Highlights The development of bismaleimide resin and their applications are reviewed. Bismaleimide monomers' synthesis and chemical reaction are summarized. The modified methods of bismaleimide resin in low dielectric are reviewed. Future research directions of low dielectric bismaleimide are prospected.

Introducing Y2O3 passivation layer for utilizing TiSiN electrode on ZrO2-based metal-insulator-metal capacitor applications

This study investigates the degradation and improvement of the dielectric properties of ZrO2-based metal-insulator-metal (MIM) capacitors using TiSiN electrodes. As dynamic random-access memory (DRAM) design rules scale down, the mechanical properties of TiSiN electrodes provide advantages over conventional TiN, but also introduce challenges due to Si diffusion into ZrO2 films, forming low-dielectric constant (k) Zr-silicate and defect-related dielectric degradation. We evaluate the dielectric properties of ZrO2 films on TiSiN electrodes and identify significant reductions in the dielectric constant and an increase in DC and AC non-linearity due to Zr-silicate formation. To mitigate these problems, a Y2O3 passivation layer is introduced between the TiSiN electrode and ZrO2 dielectric film. Physical and chemical analyses, including X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), confirm that Y2O3 passivation effectively suppresses Si diffusion, preventing formation of Zr silicate, and preserving the high-k tetragonal phase of ZrO2. Electrical measurements show that the Y2O3 layer significantly improves the dielectric constant and reduces non-linearity effects. Notably, even at a reduced ZrO2 thickness of 4 nm, a relatively high k value is maintained with Y2O3 passivation. This study concludes that the Y2O3 passivation layer is indispensable for maintaining high dielectric performance in ZrO2-based MIM capacitors with TiSiN electrodes, ensuring stability and efficiency in advanced DRAM applications.

Investigation on the fabrication and mechanism of thermally conductive bismaleimide composites with low dielectric constant via a branched crosslink structure

In order to address the challenges associated with the low mechanical strength and inadequate thermal conductivity of bismaleimide resin(BMI), trifunctional maleimide (TMI) was synthesized by reacting toluene diisocyanate (TDI trimer) with maleic anhydride (MA) in this study and reacted with diallyl bisphenol A (DBA) and BMI to prepare BMI-TMI resin with a micro-branching structure. This well-designed micro-branching structure resulted in an 8.8 % decrease in the dielectric constant by increasing the free volume of BMI. Additionally, the micro-branching structure endowed BMI resin with improved mechanical properties, as evidenced by a 140 % increase in bending strength and a 149 % increase in impact strength of the cured product. Similarly, utilizing the free volume in micro-branched polymers to construct voids in molecular chain segments facilitates better dispersion of aluminium oxide (Al2O3) thermal conductive fillers, forming a continuous thermal conductive network and providing a high-speed channel for phonon transport, thereby significantly improving the thermal conductivity of the composite material.

Effect of Mn2+ substitution on the dielectric properties of NaMg(PO3)3 ceramics at microwave and terahertz frequencies

In this study, NaMg1-xMnx(PO3)3 (0.00 ≤ x ≤ 0.0625) ceramics with low dielectric constant were prepared via the solid-state reaction method. The effects of Mn2+ substitution on the microstructure and dielectric properties (at microwave and terahertz frequencies) of the NaMg(PO3)3 ceramics were studied by means of the Rietveld refinement, morphology, and ionic polarizability analysis. It is obtained that the NaMg0.0975Mn0.025(PO3)3 ceramic sintered at 880 °C for 4 h exhibited optimal dielectric properties at microwave frequencies, where εr = 4.585, Q × f = 48,313 GHz (@17.228 GHz), and τf = −40.83 ppm/°C. The Q × f and τf values were changed by 74.2 % and 27.8 %, as compared to the values of 27,728 GHz and −56.52 ppm/°C for the pure NaMg(PO3)3 ceramic, respectively. For terahertz frequencies (0.2–1.0 THz), the εr values were decreased to 3.79–3.98, and the tanδ values were between 0.0203 and 0.1152. All the experimental results indicate that this system exhibits great potentials both at microwave and terahertz frequencies.

A novel microwave dielectric ceramic CaB2O4 with low dielectric constant

A novel microwave dielectric ceramic CaB2O4 with low dielectric constant was synthesized by the solid-state reaction method. The impact of diverse Ca/B ratios on the phase composition, microstructure and dielectric properties of CaB2+xO4+3x/2 (x = 0–0.6) ceramics was investigated. The bond ionicity and the lattice energy of CaB2+xO4+3x/2 ceramics were calculated by the P-V-L theory. The appropriate excess of boron facilitated the densification of CaB2O4 ceramics, resulting in the stable crystal structure and enhanced dielectric properties. CaB2.3O4.45 ceramic sintered at 950 °C had excellent properties: εr = 6.03, Q×f = 37,962 GHz, and τf = −24.7 ppm/°C. The influence of TiO2 on the microwave dielectric properties of CaB2O4 was investigated, 87 wt% CaB2O4 - 13 wt% TiO2 ceramics sintered at 950 °C showed a zero τf value.

Enhanced buoyancy and propulsion in 3D printed swimming micro-robots based on a hydrophobic nano-fibrillated cellulose aerogel and porous lead-free piezoelectric ceramics

This paper provides the first demonstration of additively manufactured swimming micro-robots which combine a hydrophobic nanofibrillated cellulose aerogel, to provide long-term buoyancy, with a low acoustic impedance porous piezoelectric ceramic for improved propulsion. The hydrophobic nanocellulose aerogel is shown to exhibit a high and stable contact angle that was maintained for extended periods of time, which facilitates long-term and stable buoyancy of the micro-robot. To quantify the benefits of introducing porosity into the active piezoelectric element, a new analysis model was developed to inform material design and maximize the acoustic propulsion force. Detailed characterisation and modelling of the swimming robots demonstrated that a swimming robot based on a lead-free porous Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic exhibited a higher acoustic radiation propulsion force and a faster swimming speed compared to a robot fabricated using a dense ceramic element. These benefits were associated with the lower elastic modulus, density and acoustic impedance of the porous piezoelectric material. The lower dielectric constant, reduced device capacitance, and lower resonant frequency of the porous piezoelectric element also significantly reduced the driving current and power requirements of the robot. This work therefore provides new insights on the impact of hydrophobic and acoustically matched piezoelectric materials on the performance of swimming micro-robots, and successfully demonstrates the use of porosity to improve acoustic impedance matching of resonant piezoelectric devices, such as micro-robots and ultrasonic transducers.

Thermally Robust Aramid Triboelectric Materials Enabled by Heat‐Induced Cross‐Linking

AbstractThe rapid development of the Internet of Things has led to numerous functional electronic devices, making it a significant challenge to provide power for these distributed devices. Triboelectric self‐power technology is ideal for smart devices due to its material diversity and high energy efficiency. However, traditional triboelectric materials have weak electrostatic induction due to their low dielectric constant. Additionally, the thermionic emission effect reduces their electric output in high temperatures, limiting their applications. This study designes a thermally robust aramid triboelectric material with a high dielectric constant through heat‐induced cross‐linking heterogeneous interface engineering. This novel material not only achieves high triboelectric output but also maintains high performance across a wide temperature range. The heat‐induced cross‐linking process enhances the interaction between aramid nanofibers and Al2O3 nanosheets, significantly improving the electrical performance, and flame retardance of the material, and the relative dielectric constant increases 16‐fold. The triboelectric nanogenerator constructed with this material achieves a power density of 3.97 W m−2, and maintains high triboelectric output at 260 °C. Finally, a self‐powered detection system collects high‐temperature gas energy and drives sensors is designed. This research presents a novel strategy for high‐performance triboelectric materials, showing significant potential for self‐powered devices.

Surface‐Reengineering of BNNs@Hydrocarbon Polymer Composites for Ultra‐Low Dielectric Constant for High‐Frequency Applications

AbstractThis research investigates the synthesis and evaluation of cyclic olefin copolymer (COC) composites with surface‐engineered boron nitride nanosheets (BNNs) at various concentrations. The study focuses on the impact of Cetyltrimethylammonium bromide (CTAB) on BNNs′ surface functionalization to improve their dispersion within the COC matrix, including its dielectric behavior, dielectric breakdown strength, thermal management capabilities, hygroscopic properties, and mechanical robustness. The methodological approach adopted for the fabrication of COC/BNNs hybrid composites commenced with the synthesis of BNNs, surface functionalization of BNNs, in‐situ mixing and hot‐press. This step aimed to enhance compatibility and adhesion between BNNs and the COC matrix, facilitating more homogeneous nanofiller dispersion. The investigative scope of this study encompassed a rigorous evaluation of the resultant composites, with a particular emphasis on their dielectric properties. The dielectric constant (ϵ′) and loss tangent (δ) were measured at a frequency of 10 GHz, revealing an ultra‐low dielectric constant of 1.28, an exceptionally minimal loss tangent of 0.000146, a remarkable 327% (In‐plane) &amp; 129% (axial) increase of thermal conductivity, significant improvement of dielectric breakdown strength up to 88.4 mV/mm, and low water absorptions observed. These results indicate the potential of COC/BNNs composites for high‐frequency electronic packaging applications requiring low dielectric constants.

Stretchable Heat Transfer Eco-Materials: Mesogen Grafted NR-Based Nanocomposites with High Thermal Conductivity and Low Dielectric Constant.

Biomass-based functional polymers have received significant attention across various fields, in view of eco-friendly human society and sustainable growth. In this context, there are efforts to functionalize the biomass polymers for next-generation polymer materials. Here, stretchable heat transfer materials are focused on which are essential for stretchable electronics and future robotics. To achieve this goal, natural rubber (NR) is chemically modified with a thiol-terminated phenylnaphthalene (TTP), and then utilized as a thermally conductive NR (TCNR) matrix. Hexagonal boron nitride (h-BN), renowned for its high thermal conductivity and low electrical conductivity, is incorporated as a filler to develop stretchable heat transfer eco-materials. The optimized TCNR/h-BN composite elongates to 140% due to great elasticity of NR, and exhibits excellent dielectric properties (a low dielectric constant of 2.26 and a low dielectric loss of 0.006). Furthermore, synergetic phonon transfer of phenylnaphthalene crystallites and h-BN particles in the composite results in a high thermal conductivity of 0.87Wm-1K-1. The outstanding thermal, mechanical, and dielectric properties of the newly developed TCNR/h-BN composite enable the successful demonstration as stretchable and shape-adaptable thermal management materials.

Effects of Diethoxymethylsilane/Helium Flow Rate Ratio on Low-k Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

As the semiconductor industry has continuously reduced the integrated circuit (IC) chip size, a resistance-capacitance (RC) delay emerged, causing deterioration of the chip performance. To reduce the RC delay, low dielectric constant (low-k) films with suitable mechanical strengths have been adopted as intermetal dielectrics (IMDs). In this study, low-k plasma-polymerized diethoxymethylsilane (ppDEMS) films were fabricated by plasma-enhanced chemical vapor deposition of the DEMS precursor with a flow rate ratio of the DEMS precursor to helium (He) carrier gas (DEMS/He FRR) as a key parameter. As the DEMS/He FRR increased, the refractive index was reduced from 1.401 to 1.386, and the k value decreased from 2.77 to 2.10. From high-resolution scans of C1s, O1s, and Si2p peaks of X-ray photoelectron spectroscopy, the carbon contents increased, and the oxygen contents decreased, along with a decrease in the film density. With the increased DEMS/He FRR, hardness decreased from 2.5 to 1.8 GPa, and elastic modulus decreased from 17.08 to 11.50 GPa. Leakage current densities for all the ppDEMS films were less than 10−7 A cm−2 at 1 MV cm−1. The ppDEMS films could be suggested as the IMDs according to their electrical and mechanical performance.

A microwave-assisted, solvent-free approach for effective grafting of high-permittivity fillers to construct homogeneous polymer-based dielectric film with high energy density

Polymer-based dielectric film capacitors are essential energy storage components in high-power energy storage devices benefiting from their high breakdown strength (Eb) and ultra-fast charge storage/release capability. However, the state-of-the-art commercial capacitor, biaxially oriented polypropylene (BOPP), exhibits limited energy storage density primarily due to low dielectric constant, which hinders the advancement of the film capacitor industry. Introducing high-permittivity (high-k) nanofillers into PP matrix to improve polarization is a promising method but poor filler dispersion leads to a remarkable decrease of Eb, while various strategies to enhance dispersion of fillers typically require sophisticated process involving toxic procedure and consuming significant time and cost. Herein, we show that a novel and scalable surface grafting method for high-k fillers can be achieved by a facile and short-period microwave irradiation with the assistance of silane coupling agent (KH560). As a demonstration, the KH560 is effectively grafted onto the surface of barium titanate (BT), achieving a high grafting ratio of 4.91 % at a yield of 85.1 % within a short time (40s). Furthermore, the surface modified BT nanofillers are introduced into PP matrix and then biaxially stretched. The as-prepared film exhibits excellent dispersion and superior compatibility, resulting in a remarkable enhancement of tensile strength (from 82 MPa to 115.4 MPa), breakdown strength (from 200 MV/m to 254 MV/m), and energy density (from 1.49 J/cm3 to 2.21 J/cm3). This work proposes a new strategy for constructing homogeneous polymer-based dielectric film by microwave activating high-k fillers and is crucial for the design of next-generation energy storage devices.

Surface micro-welding strategy of h-BN assembled microspheres for composites with desirable thermal conductivity and a low dielectric constant

As electronic devices strive for higher integration and faster signal transmission, the demand rises for polymer composites with high thermal conductivity (TC) and low dielectric constant (εr). However, high TC composites often come with a high filler content, leading to a reduction in processibility and dielectric properties. Herein, by surface micro-welding strategy, we fabricated cohesive h-BN microspheres (SBO) with a quasi-hollow structure. The pre-constructed micro-nano network of h-BN inside the microsphere serves as a continuous pathway for heat transfer, while the internal space of the microsphere is divided into numerous gas chambers, establishing a foundation for low εr. Benefiting from this structure, the TC of the prepared composite is 2.12 W/m·K, and its εr is remarkably low at 3.24 (103 Hz), effectively balancing the TC and dielectric properties at a high filler loading. Furthermore, this designed structure significantly reduces the viscosity of the composite (measured 309 Pa s with a filler content of 50 wt% at 1s−1) due to the smooth surface of the microsphere. This strategy offers a facile approach for fabricating composites characterized by desirable TC, low εr and excellent processibility, showcasing promising prospects for advancement in the realm of microelectronics.

Investigating the electrochemical properties of poly(vinylidene fluoride)/polyaniline blends doped with lithium-based salt

Conductive polymers have attracted much attention in various applications, owing to their excellent chemical, thermal, and oxidative stability. However, they have low dielectric constant, which limits their performance in electrochemical devices. To overcome this drawback, blending with other polymers helps improving their electrochemical properties. Herein, we investigate structural and electrochemical properties of poly (vinylidene fluoride) (PVDF)/polyaniline (PANI) blends doped with lithium-based salt. Results showed that the blends exhibit phase separation of PANI and PVDF, which is confirmed by the thermodynamic interaction parameter. We found that the interaction between the two polymers enhanced the ionic conductivity from 4.9 × 10−5 S cm−1 for neat PVDF to 5.3 × 10−4 S cm−1 for composition of 50:50 (PANI50), whereas the ionic conductivity was inversely proportional to the temperature. Moreover, by adding lithium salt to the blend, the thermal stability increased from 376.6 to 478.5 °C for PANI50. The ionic conductivity of the blends depends on the PVDF content, which affects the interaction between the two polymers.

Epoxy Composite Films Filled with Sintered Multifaceted Boron Nitride for Thermal and Dielectric Applications

The miniaturization of electronic devices has led to an increase in power density and functional integration, resulting in rapid heat accumulation that adversely affects operational stability and service life. Dielectric composite films with excellent thermal conductivity and insulating properties are highly desired for addressing thermal management issues in electronic packaging applications. Hexagonal boron nitride (h-BN) is a promising filler for such composites due to its outstanding thermal conductivity, insulating properties, and chemical stability. However, the inherent platelike structure of h-BN causes significant anisotropy and poor miscibility with polymers, limiting the uniform conduction of heat. This study proposes a high-temperature sintering method that transforms flaky h-BN plates into irregular multifaceted particles. This transformation reduces thermal anisotropy and creates uniform heat conduction pathways. The resulting sintered BN/Epoxy (s-BN/EP) composite films exhibit exceptional thermal conductivity, with in-plane thermal conductivity increased by 36% to 6.0 W m-1 K-1 and through-plane thermal conductivity increased by 39% to 1.2 W m-1 K-1 compared to pristine h-BN/epoxy composites. Moreover, s-BN/EP films could maintain low dielectric constant (Dk, 3.22) and dielectric loss (Df, 0.015) at 5 GHz. This innovative approach provides a significant advancement in the development of high-performance insulating polymer composites, offering a promising solution for thermal management in high-power-density electronic packaging.

Epoxy composite films of superior dielectric properties promoted by active ester hardeners for applications in electronic packaging

Epoxy composites with ultralow dielectric dissipation factors (Df) are highly desired in advanced electronic packaging architectures to cater for high-frequency signal transmission. However, Df of epoxy systems traditionally cured by amine, anhydride or phenolic resin is too high due to the generated high-polarization groups like hydroxyl moieties. Using active esters as curing agents is an effective strategy to reduce polarization of cured epoxy by replacing hydroxyl moieties with ester groups. Herein, diallyl-based active ester hardeners (DAAE) are synthesized via one-step esterification reaction with a high yield of > 90 %. When DAAE is used to cure epoxy films containing SiO2 fillers, the cured epoxy composite films (DAAE-ECFs) demonstrate low dielectric constant (Dk, ∼3.0) and low Df (∼0.005) above 5 GHz at 25 ℃. Importantly, whether immersed in room-temperature water for 24 h or in boiling water for 1 h, DAAE-ECFs absorb < 0.6 wt% water with stable Dk and slightly increased Df (<0.0085). Moreover, DAAE-ECFs show excellent thermal stability (Td5% >365 ℃), dimensional stability (CTE of ∼ 30 ppm ℃-1 below 80 ℃), high storage modulus (∼10 GPa at 30 ℃). The appealing dielectric, thermal and mechanical properties imply that DAAE-ECFs could serve as promising candidates for electronic packaging materials in high-frequency signal transmission.

Bio-derived Schiff base vitrimer with outstanding flame retardancy, toughness, antibacterial, dielectric and recycling properties

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP1.0) was prepared. The CIP1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2%. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP1.0 with outstanding fire retardancy. The CIP1.0 shows excellent toughness with high elongation at break of 45.0% due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP1.0 result in a low dielectric constant. The CIP1.0 exhibits superior antimicrobial properties. The CIP1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins.

Preparation and Properties of Fluorinated Poly(aryl ether)s with Ultralow Water Absorption and Dielectric Constant by Cross-Linked Network Strategy.

Poly(aryl ether) materials are used in a wide range of applications in the communications and microelectronics fields for their outstanding mechanical and dielectric properties. In order to further improve the comprehensive performance, this work reports a series of cross-linkable poly(aryl ether)s (UCL-PAEn) containing trifluoroisopropyl and perfluorobiphenyl structures using 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,2'-diallyl bisphenol A, and perfluorobiphenyl as starting materials. Their chemical structures and the effect of changes in the allyl content on the properties are thoroughly investigated. Owing to the introduction of fluorine atoms and cross-linked networks, the cross-linked poly(aryl ether) films present low dielectric constants (Dk = 1.93-2.24 at 1 MHz), low water absorption (0.14% -0.25%), and hydrophobic film surfaces (94.3-99.4°). Additionally, because of the presence of cross-linked networks, the CL-PAEn films exhibit superior thermal stability, with the 5% weight loss temperatures all above 445 °C and the maximum thermal decomposition rate temperatures all above 550 °C. The cross-linked films also demonstrate excellent mechanical properties, with tensile strength in the range of 57.1 -146.7 MPa and tensile modulus in the range of 1.8 GPa-4.5 GPa.

Remote vapor-phase dual alkali halide salts assisted quasi-van der Waals epitaxy of m-phase ZrO2 thin films with high dielectric constant and stable flexible properties

High-κ dielectric constant and wideband gap of ZrO2 material render it as an excellent candidate for transistor gate dielectric layers. However, current reported synthesis techniques suffer the problems of high precursor volatilization rate, ultrasmall grains with low dielectric constant, and high leakage current, which largely impede its application in electronic devices. Here, the quasi-van der Waals epitaxy growth of compact m-phase ZrO2 thin films has been developed, in which the stable supply of Zr source is realized by the tuned sublimation of ZrC powder with remote vapor-phase dual halide salts assistant. The formation of m-phase ZrO2 is due to the lower Gibbs free energy, in which the crystal nucleates at the etched hole edges of mica substrate, thus forming hexagonal shape polycrystal grains and merging as the continuous thin films. The microstructures and Raman spectrum characterization reveal the two dominated growth orientations and good crystal qualities, which indicate the uniform dielectric constant. The excellent growth reproducibility could be easily adapted to thin metal substrates, such as tungsten, molybdenum, and stainless steel, where the adhesion strength is strong because of the higher density of interfacial chemical bonding. Meanwhile, the metal–insulator–metal flexible capacitors show the high dielectric constant of 23–26 and low leakage current density of 10−4 A/cm2 at large voltage and only exhibit the decreased capacitance density of 7% after several hundred bending cycles. Our work paves a way to achieve the high-quality dielectric thin films on various substrates by the unique chemical vapor deposition design strategy.

Fluorinated polyetherimide as the modifier for synergistically enhancing the mechanical, thermal and dielectric properties of bismaleimide resin and its composites

The aviation industry has a substantial demand for bismaleimide (BMI) resins that possess high toughness, excellent thermal stability, and low dielectric constant, which are critical for wave-transparent materials. This study presents the synthesis of a novel fluorinated polyetherimide (F-PEI) and its integration with BMI resin using an in situ pre-polymerization method. Upon blending 4 wt% F-PEI with bismaleimide resin, the resulting blending resin (BDP-4) demonstrated a significant enhancement in both impact strength (59.6 % increase) and flexural strength (13.9 % increase) compared to the unmodified BMI. Additionally, the glass transition temperature of BDP-4 was enhanced to 299.3 °C, representing a 5 °C increase, and the corresponding dielectric constant (k) and dielectric loss (tan δ) at 15.2 GHz were decreased from 3.02 to 2.96 and from 0.010 to 0.009, respectively. These improvements are attributed to the phase separation induced by the F-PEI content, which engendered a synergistic toughening mechanism beneficial for both thermal and dielectric attributes. Notably, the flexural strength (630.1 MPa), flexural modulus (26.5 GPa), and interlaminar shear strength (67.1 MPa) of quartz fiber reinforced F-PEI/BMI composites (QF/BDP-4) exceeded those of pure BMI composites. The findings indicate that F-PEI modification is an effective strategy for advancing BMI resin performance, with potential applications in high-performance industries such as aerospace and electronics.