Benzocyclobutene Research Articles

Thermosetting boron-nitride-filled polybutadiene composites with enhanced thermal conductivity and good dielectric properties

Low dielectric materials with high heat dissipation, low dielectric constant (Dk), and dielectric loss (Df) are urgently needed to address the issues of signal cross-talk and heat accumulation arising from the rapid development of modern communication technology and the integration of microelectronics. Polyolefins, as hydrocarbon polymers, have shown significant potential due to their excellent low dielectric properties. However, their low polarity and flexible structures limit their thermal conductivity and thermomechanical properties. In this study, we developed a method to prepare thermosetting polybutadiene composites with enhanced thermal conductivity and good dielectric performance by modifying hexagonal boron nitride (h-BN) and hydroxyl-terminated polybutadiene (HTPB) with thermally cross-linkable benzocyclobutene (BCB) groups. The properties of the resulting composites were tailored by varying the filler content. With 30 wt% of the BCB-modified filler, the composite (HB-30) displayed excellent dielectric properties (Dk = 2.70; Df = 1.67 × 10−3 @10 GHz). Meanwhile, it exhibited a thermal conductivity of 0.615 W/mK at 35 °C, which was 7.1 times that of pristine HTPB. It also showed significantly enhanced mechanical properties and thermal stability with a storage modulus of 2.7 GPa and a glass transition temperature (Tg) of 208.5 °C. This method proved effective for preparing polymer composites with enhanced thermal conductivity, heat resistance, mechanical properties and good dielectric properties, making them suitable for high-frequency communication applications.

A "Bottom-Up" Strategy for High-Performance Benzocyclobutene (BCB)-Subnanometer Inorganic Nanocomposites.

Developing benzocyclobutene (BCB) nanocomposites with ultra-small inorganic sizes represents a formidable challenge, although it offers great potential to produce materials with customizable structural and rich functional properties. In this study, we present a "bottom-up" design strategy for creating cross-linked benzocyclobutene (BCB) nanocomposites with highly dispersed nanodomains, such as organoalkoxysilane. This approach leverages ring-opening metathesis polymerization (ROMP) and thermally induced cycloaddition reactions to embed oligomeric silsesquioxanes, achieving a unique molecular structure with promising low-dielectric applications. The synthesis involves organoalkoxysilane and BCB as pendant groups of polynorbornenes that are covalently integrated. Additionally, the methoxyl groups of linear polymers could be further hydrolyzed under acidic conditions, and BCB groups could undergo thermal-induced ring-opening at high temperatures and Diels-Alder addition between themselves and vinyl groups, respectively. Fourier transform infrared (FTIR) spectroscopy analyses suggested the presence of ladder or network structures and high-resolution transmission electron microscopy (HRTEM) images presented the well-dispersed inorganic clusters, facilitating excellent dielectric properties with a dielectric constant (Dk) of 2.25 and a dissipation factor (Df) of 2.27 × 10-4. Compared with previously reported low-Dk materials, the cured nanocomposites also exhibited a significantly balanced enhancement of their comprehensive properties. This molecular bottom-up strategy provided a simple and universal method for constructing BCB-inorganic nanocomposites featuring a subnanometer inorganic structure, paving the way for future investigation into new classes of polymer-inorganic nanocomposites with a low Dk.

A facile strategy for preparing low dielectric polybutadienes with ultra-low dielectric loss and enhanced thermal stability

With the rapid development of high speed and high frequency communication, organic low dielectric (low-k) materials with both ultra-low dielectric constant (Dk) and ultra-low dielectric loss (Df) are urgently required to ensure signal transmission speed and reliability. 1,2-polybutadiene (1,2-PB) is renowned for its excellent dielectric properties, making it used in high-frequency printed circuit boards (PCBs). However, its poor thermal stability and mechanical properties hinder its application which requires persistent stability. To address this issue, a series of thermal-crosslinkable benzocyclobutene (BCB)-modified PBs were synthesized through a hydrosilylation reaction. These cured PBs exhibited significantly enhanced thermal stability with the glass transition temperature (Tg) exceeding 400 °C. In particular, they displayed ultra-low Dk (2.32–2.41) and ultra-low Df (<0.001). It was found that the properties of cured PBs were related to BCB loadings. Among the cured polymers, PB-g-B30 demonstrated the optimal dielectric properties with a Dk of 2.34 and a Df of 3.6 × 10−4. Subsequently, a PB-g-B30/glass fiber laminate was fabricated, exhibiting superior dielectric and comprehensive properties when compared to commercial low-k laminates. This study provides a facile method to develop PBs with ultra-low Dk and Df and enhanced thermal stability. The outstanding comprehensive properties indicate their potential as low-k materials in high-frequency communication applications.

Design of Silicon Core Coaxial TSVs to Reduce Crosstalk Effects for 3D IC Applications

This paper presents the effectiveness of the copper (Cu)-based coaxial through silicon vias (CTSVs) to reduce crosstalk noise and propagation delay. In the proposed CTSVs, the polymer liners are used as insulating material which cancels the crosstalk functional failures. The impacts of the proposed CTSVs on the electrical performance are noticed for different parameters and properties of the material. Simulations of the proposed CTSVs are executed using the standard HSPICE and SYMICAD tools. The results indicated that the effects of crosstalk are reduced using the polymer liners instead of silicon dioxide (SiO2) liners in the proposed CTSVs. The electrical performances of the proposed CTSVs are investigated for various thicknesses of Cu and BCB. Furthermore, a comparative study has been carried out for the SiO2 and benzocyclobutene (BCB) liners. It is observed that BCB liner-based CTSVs crosstalk noise and delay values are reduced by up to 25.06% and 27.8% compared to the SiO2 liner-based TSVs.

Boosting Hole Mobility: Indenofluorene-Arylamine Copolymers and Their Impact on Solution-Processed OLED Performance.

We introduce three newly designed thermally cross-linkable hole transport copolymers (PIF-TPD, PIF-F2PCz, and PIF-TPAPCz) for improving the performance of solution-processed organic light-emitting diodes (s-OLEDs). These copolymers, designed through a strategic molecular approach with benzocyclobutene (BCB) and styrene-based cross-linking monomers, show high solvent resistance at a low cross-linking temperature (150 °C). Furthermore, these conjugated copolymers based on planar indenofluorene with three different hole transport (HT) units, exhibit outstanding charge carrier mobility (1.61 × 10-2 cm2 V-1s-1), demonstrated by comparing hole reorganization energy and electronic coupling strength of HT units. Despite these copolymers showing the overall vertical orientation in the horizontal dipole moment measurement results, we demonstrated that the HT units can exhibit the preferred orientation, contributing to high hole transport properties. As a result, they perform exceptionally well as hole transport layers in green phosphorescent s-OLEDs, achieving a maximum external quantum efficiency of 15.3% and a maximum current efficiency of 53.9 cd A-1 with a small efficiency roll-off despite their relatively low triplet energy levels. These results are comparable to vacuum-deposited OLEDs, highlighting the potential of these copolymers in advancing OLED technology for display panels and lighting applications.

Flash vacuum pyrolysis of steroid propargyl ethers

Owing to its unique rearrangement and cyclization processes via flash vacuum pyrolysis (FVP), the acetylenic moiety has attracted considerable attention by organic chemists as a key building block in the construction of innovative organic architects. Herein, a series of seven steroid propargyl ether precursors have been successfully synthesized and pyrolyzed. Analysis and characterization of the FVP products revealed that the propargyl ethers of phenolic steroids undergo Claisen-rearrangement to give 2-indanone and benzo cyclobutene derivatives, while propargyl ethers of non-aromatic steroids resulted in the corresponding α, β-unsaturated ketones.

Nanophotonic integrated active-passive InP membrane devices and circuits fabricated using ArF scanner lithography

We present a novel fabrication approach to an integrated nanophotonic platform, based on a III-V membrane bonded to a Si substrate with benzocyclobutene (BCB). The process incorporates a hybrid lithography strategy combining deep-UV and electron-beam lithography on the same wafer. We report for the first time the usage of deep-UV scanner lithography for the fabrication of the active-passive tapers and sub-micron waveguides on the same wafer, which enables better critical dimension control, uniformity, and reproducibility. The platform uses an active-passive butt-joint interface and includes components such as distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, electro-optical (EO) and electro-absorption (EA) modulators, and sub-micron ultra-confined passive waveguides, all monolithically integrated into a single membrane layer. The active devices have a heat sink achieved by ultra-thin BCB bonding. Lasers demonstrate up to 26 mW of optical power in the waveguide and a direct modulation bandwidth of up to 21 GHz. The modulators show static extinction up to 28.8 dB.

All-hydrocarbon benzocyclobutene resin with low Dk and high-resolution photo-imageable dielectric performance

Low dielectric photoinduced patterned materials have attracted extensive attention owing to their potential applications in integrated circuits and semiconductor devices. In this work, we synthesized a low dielectric polymer that can be used for photolithography. The monomer, 1-(4-vinylphenyl)-2-(4-benzocyclobutenyl)ethene (DVB-S-BCB), was synthesized from divinylbenzene (DVB) and 4-bromobenzocyclobutene (4-BrBCB) using the Heck reaction. Subsequently, P-DVB based on DVB-S-BCB was prepared by anionic polymerization. As the structure comprised thermally curable benzocyclobutene (BCB) groups and photocurable vinyl groups (UV/Thermal dual curing structure), P-DVB has been used for high-performance negative photosensitive resin with 2,6-bis(4-azidobenzylidene) cyclohexanone (BAC) as a photoinitiator. Photolithography was carried out using a 365-nm UV light source to obtain various patterns, and the research results indicate that photosensitive resins exhibit stable patterning processes at different curing stages. Besides, the cured P-DVB exhibited high thermal stability (T5% above 420 °C in N2), low dielectric constant (2.55 at 10 MHz), low dielectric loss (1.56 × 10−3 at 10 MHz), and excellent mechanical performance. These properties make P-DVB a potential photoresist that can be widely used as interconnected dielectrics.

Transmission/reflection mode switchable ultra-broadband terahertz vanadium dioxide (VO2) metasurface filter for electromagnetic shielding application

In this paper, we present an ultra-broadband terahertz (THz) vanadium dioxides (VO2) metasurface (MS) filter with switchable transmission/reflection modes for electromagnetic (EM) shielding application. The MS filter is composed of a three-layer periodic composite structure, consisting of two VO2/metallic hybrid layers and a metal mesh layer, which are separated by two benzocyclobutene (BCB) dielectric layers. The transmission property of the proposed MS filter is illustrated by the numerical simulation based on the finite element method (FEM) and equivalent circuit model (ECM). When VO2 is in insulating state, the designed composite structure acts as a filter with ultra-broadband bandpass response (BPR), exhibiting that the transmission coefficient exceeds 90 % from 1.07 THz to 3.78 THz, with a relative bandwidth of 112 %. However, owing to thermal excitation, the VO2 converts from an insulating to a metallic state, the composite structure can be functioned as a filter with ultra-broadband bandstop response (BSR) with a transmission coefficient less than 6 % spanning the range of 0.1 to 4.5 THz. In addition, the physical mechanism of the designed MS filter is investigated utilizing impedance matching theory and electric field distribution analysis. Furthermore, the MS filter has good polarization insensitivity and angular stability. Finally, we quantify the shielding effectiveness (SE) in two states and evaluate the impact structural parameters of the unit-cell, resulting in a SE of more than 25 dB in reflection mode across the entire operating frequency range. Our proposed MS filter with its exquisite performance has the potential to be widely applied in EM shielding.

Efficient heat sink by ultrathin BCB bonding for InP membrane lasers

Wafer bonding is a key process in heterogeneous photonic integration and benzocyclobutene (BCB) is widely used for adhesive wafer-to-wafer bonding when it comes to handling complex topography on both wafers. However, until now a major drawback of bonding with BCB was the high thermal impedance of lasers due to the low thermal conductivity of BCB. We demonstrate, that by optimizing the membrane device topography and introducing the BCB reflow step into the process flow it is possible to achieve full planarization of 1 μm topography at the wafer scale while ensuring only 135 nm of BCB between the laser p-contact and the substrate. We show experimentally, that the thermal impedance of 500 μm long distributed feedback (DFB) laser was reduced from 585 to 271 K W−1 when bonded to Si substrate, and to 174 K W−1 when bonded to SiC substrate using the new method.

A polymer trench filling based silicon isolation technique and its application to two-axis scanning comb-drive micromirrors

Electrostatic micromirrors can be widely used in LiDAR, displays, AR/VR and medical imaging. Electrically insulated silicon enabled by trenches filled with thermal oxide and polysilicon is commonly used for 2-axis electrostatic comb-drive scanning mirrors made on SOI (silicon-on-insulator) wafers. These trenches provide both electrical isolation and mechanical stability. However, this method has drawbacks such as high deposition temperature, voids, and high residual stress. In this work, a polymer filling method is proposed to form electrical insulation trenches in the silicon device layer of SOI wafers. Only low-temperature processes are used in this method and the silicon trenches can be fully filled up reliably. Furthermore, the filling polymer not only relieves residual stresses but also significantly increases the shock resistance of the micromirrors made with this method. In particular, Benzocyclobutene (BCB) is employed and a process has been developed to effectively fill deep silicon trenches. Using this method, two-axis electrostatic micromirrors have been successfully fabricated and tested. Experimental results show that the BCB-filled trenches demonstrate excellent electrical insulation performance and mechanical stability and the fabricated 2-axis mirrors can achieve a large field of view of 60°×40° and stand high impact over 2500 g.

Low‐temperature‐curable and photo‐patternable benzocyclobutene‐derived aggregation‐induced emission‐active polymer dielectrics

AbstractThe high curing temperatures required for traditional benzocyclobutene (BCB) materials have posed limitations on their applicability in high‐temperature‐sensitive fields. To address this challenge, our work focuses on the synthesis of a novel tetraphenylethylene (TPE)‐functionalized BCB monomer, TPE–BCB, achieved through the introduction of an ether bond onto the BCB's four‐membered ring via Williamson reaction. TPE–BCB demonstrates remarkable low‐temperature curing properties, characterized by a ring‐opening peak temperature of 190°C, representing a reduction of 60°C compared to conventional BCBs. Fully cured TPE–BCB resins exhibit exceptional dielectric and mechanical properties, coupled with minimal water absorption. Additionally, the incorporation of TPE with aggregation‐induced emission characteristics enhances the resins’ luminescence and photolithographic capabilities. Notably, our TPE–BCB resins achieve impressive photolithography performance with a resolution ratio of up to 10 μm. In contrast to conventional BCB‐functionalized resins, TPE–BCB offers the dual advantage of low‐temperature curing and luminescence. This development marks a significant step in the advancement of low‐temperature curing BCB materials and serves as a pioneering example in the realm of multilayer wafer bonding materials.

Mechanochemical generation of aryne.

Mechanical force is unique in promoting unusual reaction pathways and especially for the generation of reactive intermediates sometimes inaccessible to other forms of activation. The mechanochemical generation of reactive species could find application in synthetic and materials chemistry alike. However, the nature of these reactive intermediates has been mostly limited to radicals or carbenes. Here, we present a new mechanophore that generates a reactive aryne intermediate upon dissociation of a benzocyclobutene (BCB) core via a force-promoted retro [2 + 2] cycloaddition.

Low dielectric polymers at high frequency with bulky adamantane groups as the linker

Two monomers with adamantane and thermo-crosslinkable benzocyclobutene (BCB) groups have been successfully synthesized. These two monomers can be cured to form polymers with low dielectric properties at a high frequency of 10 GHz.

Dielectric Properties of Benzocyclobutene-Based Resin: A Molecular Dynamics Study.

Benzocyclobutene (BCB)-based resins have garnered considerable attention because of their remarkable dielectric properties and thermal stability. However, in molecular dynamics (MD) simulations, progress in BCB-based resin research has yet to keep pace with experimental advancements, resulting in a shortage of theoretical underpinnings at the molecular level. This study focuses on a novel homopolymer, poly(2-(4-benzocyclobutenyl)-divinylbenzene(DVB-S-BCB)), and devises an interactive methodology suitable for BCB-based resins. We implemented a Python script for the joint relaxation method to construct a three-dimensional model of the cured polymer using MadeA and LAMMPS. We conducted MD simulations to investigate how the cross-linking degree and resin molecular weight influence the dielectric properties of the cured polymer. Furthermore, we analyzed the thermodynamic properties through simulation. The results illustrate that augmenting the cross-linking degree and resin molecular weight results in a higher cross-linking density and reduced free volume, thereby increasing the dielectric constant of the resin. The cross-link density does not increase indefinitely with molecular weight, and after a certain threshold is reached, it cannot have a significant effect on the dielectric constant. The degree of cross-linking exerts a more pronounced impact on the dielectric constant than the molecular weight of the resin. In addition, the simulation results denote the excellent thermodynamic properties of the cured polymer. This study also examines the dielectric and thermodynamic properties of the resin samples that were experimentally prepared. The obtained data successfully confirm the reliability of the simulation results. This study offers novel insights for future simulation research on benzocyclobutene-based resins. Additionally, it provides theoretical support for exploring experimental work on low-dielectric materials in the electronic field.

Broadband metasurface based on metallic stereo split-ring structure for full-space terahertz beam deflection and focusing effect

In this paper, we proposed an all-metal metasurface that enables circular polarization (CP) conversion and wavefront manipulation of the both transmitted and reflected terahertz (THz) waves over a wide frequency range. The proposed metasurface consists of a periodic array of the metallic stereo split-ring (MSSR) structure adhered on an ultrathin dielectric substrate made of benzocyclobutene (BCB). Numerical simulations show that the incident CP waves through the proposed MSSR can be converted into their orthogonal components in the full-space in a broadband range, with transmission conversion coefficients exceeding 40 % and reflection conversion coefficients exceeding 50 % between 0.8 and 1.1 THz (relative bandwidth of 31.6 %). Based on the geometric phase principle, 2π-phase full coverage can be realized by changing the rotation angle of the MSSR structure in the operating frequency range. Specifically, to demonstrate the multifunctional wavefront manipulation, we numerically simulated the anomalous deflection of THz beams and the full-space planar focusing functionality, respectively. Our research provides a valuable reference for the study of multifunctional components that possess full-space amplitude and phase modulation capabilities. This work holds particular significance in the field of device research in the THz region.

Low‐Energy Driven Ring‐Opening Behavior of Benzocyclobutene Derivatives

Comprehensive SummaryIt's urgent to develop benzocyclobutene (BCB)‐based polymers with low curing temperature for temperature‐sensitive applications such as liquid crystal displays (LCDs) and flexible electronics. Herein, the effect of substituents on the ring‐opening behavior of BCB derivatives was investigated. The ring‐opening activation energy barriers (ΔGA) of BCB derivatives with one or two substituents on the four‐membered alkyl ring were systematically calculated using the B3LYP function. Both mono‐ and di‐substituted BCBs adopted the conrotatory ring‐opening process, obeying the Woodward‐Hoffmann's Rules upon heating. The mono‐/di‐substituted BCBs exhibited 8.2%—69% lower ΔGA compared with BCB, attributed to the electronic effects of the substituents. Disubstituted BCBs with both electron‐donating and electron‐withdrawing groups, e.g., 1‐NH2‐8‐NO2‐BCB, demonstrated the lowest ΔGA. In addition, BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules, and their ring‐opening temperature can be decreased by 20 °C compared to the unsubstituted one, also consistent with our calculation results. This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next‐generation BCB functional packaging materials with low ring‐opening temperature.

Performance analysis of Cu-MWCNT bundled HCTSVs using ternary logic

This paper presents an investigation of crosstalk issues for coupled heterogeneous coaxial through silicon vias (HCTSVs) in ternary logic. Crosstalk issues are investigated for coupled HCTSVs using Cu-MWCNT as a conductive filler and polymer liners such as polyimide, polypropylene carbonate (PPC), and benzocyclobutene (BCB) as insulating materials. The electrical equivalent circuit model is utilized to investigate the crosstalk induced by the ternary inverter in coupled HCTSVs. The effects of crosstalk such as functional and dynamic crosstalk for proposed HCTSVs are compared with Multi-walled CNT (MWCNT) TSVs using Hewlett simulation program with integrated circuit emphasis (HSPICE) simulations. Other performance parameters are also investigated, including power dissipation, power delay product (PDP), and energy delay product (EDP). The proposed model's crosstalk effects are also investigated for various TSV heights. The BCB-based coupled Cu-MWCNT HCTSVs provide a significant improvement in crosstalk at reduced TSV height. The proposed HCTSVs also improved overall performance by 32.12% when compared to the MWCNT based TSVs. As a result, Cu-MWCNT based HCTSVs with BCB liner are better than conventional TSVs for ternary logic integrated circuits (ICs).

Low dielectric post-cured benzocyclobutene-functionalized fluorine-containing polyimide material

Low dielectric constant (Dk) polyimide polymer materials are one of most attractive materials for their importance in microelectronic industries, such as high speed communication field. Herein, a novel benzocyclobutene (BCB) and trifluoromethyl functionalized diamine monomer (BFDA) was synthesized and used to prepare a series of co-polyimides with different BCB content (PI-BFs). Both trifluoromethyl and BCB structure can facilitate to low down Dk and dissipation factor (Df). For the cured PI-BFs, dielectric property test showed that the dielectric constant decreased significantly with the increase of BCB content, and the dielectric constant of PI-BF40% could reach 2.72 at 1 MHz. Besides, BCB can also contribute to improve glass transition temperature and initial storage modulus of PI-BFs. The Tg of PI-BF40% was 360 °C, and the initial storage modulus reached 2.83 GPa. Meanwhile, TMA test indicates that the post-curing by BCB group contributes to enhance the thermo-size stability. Moreover, PI-BFs show excellent thermal stability (Td5 > 499 °C), good transparency and low water uptake.

Fluorinated intrinsic low-k materials at high frequency with good dielectric performance and excellent hydrophobicity

Through the Grubbs reaction, two fluorinated precursors (M1 and M2) with the thermo-crosslinkable benzocyclobutene (BCB) groups and an unconjugated double bond have been successfully synthesized. The thermally cured products of the precursors exhibit low Dk and Df at a frequency of 10 GHz, as well as excellent hydrophobicity even being immersed in boiling water for 72 h. Among the cured resins, cured M1 exhibits the best comprehensive performance, including a Dk of 2.41, a Df of 1.02 × 10−3, and water uptake (Wa) of 0.013%. For comparison, a control precursor M3 without the unconjugated double bond in the molecular backbones has been also prepared, displaying that the unconjugated double bond has a positive effect on the dielectric and mechanical properties of the resins. Further investigation indicates that cured M1 displays low density than cured M3. This contribution has given an insight to design the intrinsic low-k materials, as well as provided a facile way for the preparation of the materials.