Flame Retarding Cyanate Ester Resin with Low Curing Temperature, High Thermal Resistance, Outstanding Dielectric Property, and Low Water Absorption for High Frequency and High Speed Printed Circuit Broads

Characterization of Mechanical, Electrical and Thermal Properties of Bismaleimide Resins Based on Different Branched Structures

Bismaleimide (BMI) resin is an excellent performance resin, mainly due to its resistance to the effect of heat and its insulating properties. However, its lack of toughness as a cured product hampers its application in printed circuit boards (PCBs). Herein, a branched structure via Michael addition was introduced to a BMI system to reinforce its toughness. Compared with a pure BMI sample, the flexural strength of the modified BMI was enhanced, and its maximum value of 189 MPa increased by 216%. The flexural modulus of the cured sample reached 5.2 GPa. Using a scanning electron microscope, the fracture surfaces of BMI samples and a transition from brittle fracture to ductile fracture were observed. Furthermore, both the dielectric constant and the dielectric loss of the cured resin decreased. The breakdown field strength was raised to 37.8 kV/mm and the volume resistivity was improved to varying degrees. Consequently, the resulting modified BMI resin has the potential for wide application in high-frequency and low-dielectric resin substrates, and the modified BMI resin with a structure including three different diamines can meet the needs of various applications.

Effects of trace phenolic hydroxyl groups on the cure behaviours and properties of cyanate esters

To improve the curing properties of cyanate esters and retain their heat resistance, dielectric properties and adhesion properties, modified cyanate copolymers were prepared by blending bisphenol A cyanate (BADCy) ester with phenol, hydroquinone (HO), resorcinol and phloroglucinol (LO). Differential scanning calorimetry analysis (DSC) and Fourier transform infrared spectroscopy were used to investigate the cure behaviours of the prepared compounds. The prepared materials were compared with the BADCy ester containing trace of cobalt acetylacetonate (CoAt). The CoAt/BADCy blend modified by HO exhibited better curing properties. The exothermic peak temperature ( T p) of the CoAt/BADCy blend dropped to 169°C after introducing 1 wt% HO, likely due to the hydroxyl functional groups at the para position of the benzene ring resulting in higher symmetry and reactivity for the HO. In addition, compared with original CoAt/BADCy, the cyanate esters modified by phenolic hydroxyl groups demonstrated higher adhesive properties and a similar glass transition temperature (approximately 290°C) as well as stable dielectric properties. The experimental results indicate potential applications of the cyanate ester under high-temperature conditions.

Synthesis and characterization of divinylbenzene-based cyanate resin and its quartz fiber-reinforced composite

Cyanate ester (CE) resins are important polymeric materials with excellent dielectric properties, low moisture absorption, and good heat resistance, which have shown great superiority for use in electronic and aerospace industries. In this article, a novel CE resin was designed and synthesized from divinylbenzene. The proposed structures were characterized with Fourier transform infrared spectroscopy, gel permeation chromatography, and mass spectrometry. The chemical reaction activity, heat resistance, dielectric properties, and water adsorption of the synthesized CE derived from divinylbenzene (DVBCy) were examined and compared with the traditional bisphenol A and bisphenol M (4,4′-[1,3-phenylenebis(1-methyl-ethylidene)]bisphenol)-based CE. The DVBCy resin exhibits a glass transition temperature ( T g) of 162.7°C, a dielectric constant of 2.61, a dielectric loss tangent angle of 0.0035 at about 10 GHz, and a lower water absorption of 0.77%. Compared with the bisphenol M type CE, DVBCy resin provides slightly superior dielectric properties, higher mechanical properties, more favorable process technology for prepreg construction, and lower costing. The DVBCy blend resin modified with bisphenol A-based CE and core–shell particles possesses suitable rheological properties, and the corresponding quartz fiber-reinforced composite exhibits excellent mechanical as well as dielectric properties.

An effective strategy for the preparation of intrinsic low-k and ultralow-loss dielectric polysiloxanes at high frequency by introducing trifluoromethyl groups into the polymers

Two new CF₃-containing polysiloxanes with low dielectric constant (D_k) and dielectric loss (D_f ) at a high frequency of 5 GHz were reported. The sample with two −CF₃ groups exhibits better dielectric properties with D_k of 2.53 and ultralow D_f of 1.66 × 10⁻³.

Cyanate ester resin based composites with high toughness and thermal conductivity

A new cyanate ester resin-based composite with higher toughness and thermal conductivity was developed. First, a poly(n-butyl acrylate)/poly(methyl methacrylate-co-acrylamide) (PBMAM) core-shell structured latex was prepared by seeded emulsion polymerization. Second, hexagonal boron nitride (h-BN) particles were modified by a surface coupling agent, 3-(2-amino ethyl amino)propyl trioxysilane, to improve the dispersion in cyanate ester resin (BADCy). Third, PBMAM and the modified boron nitride were mixed with BADCy resin to increase mechanical properties and thermal conductivity. The monomer conversion in the emulsion polymerization process of the PBMAM was monitored by determining the solid content. Its particle size was characterized by dynamic laser scattering, and the morphology of the particles was characterized using scanning and transmission electron microscopes. The modified boron nitride (ABN) was verified by FTIR and TGA measurements. The mechanical properties and thermal conductivity of the BADCy/PBMAM/ABN composites were determined at various BN contents. Results showed that the unnotched impact strength of the composite increased by 151% and the thermal conductivity increased by 85% at a PBMAM content of 5 wt% and ABN content of 6 wt%. With the enhanced properties and ease of fabrication, the developed composites have good potential for application in high-end industries such as microelectronic packaging.

Effects of hyperthermal atomic oxygen on a cyanate ester and its carbon fiber-reinforced composite

The durability of cyanate ester (CE) to hyperthermal atomic oxygen (AO) attack in low Earth orbit may be enhanced by the addition of carbon fiber to form a carbon fiber-reinforced cyanate ester composite (CFCE). To investigate the durability of CFCE relative to CE, samples were exposed to a pulsed hyperthermal AO beam in two distinct types of experiments. In one type of experiment, samples were exposed to the beam, with pre- and post-characterization of mass (microbalance), surface topography (scanning electron microscopy (SEM)), and surface chemistry (X-ray photoelectron spectroscopy (XPS)). In the second type of experiment, the beam was directed at a sample surface, and volatile products that scattered from the surface were detected in situ with the use of a rotatable mass spectrometer detector. CFCE exhibited less mass loss than pure CE with a given AO fluence, confirming that the incorporation of carbon fiber adds AO resistance to CE. Erosion yields of CE and CFCE were 2.63 ± 0.16 × 10−24 and 1.46 ± 0.08 × 10−24 cm3 O-atom−1, respectively. The reduced reactivity of CFCE in comparison to CE was manifested in less oxidation of the CFCE surface in XPS measurements and reduced CO, CO2, and OH reaction products in beam-surface scattering experiments. The surface topographical images collected by SEM implied different surface deterioration processes for CE and CFCE. A change of surface topography with increasing AO fluence for CE indicated a threshold AO fluence, above which the erosion mechanism changed qualitatively. CFCE showed almost intact carbon fibers after relatively low AO fluences, and while the fibers eventually eroded, they did not erode as rapidly as the CE component of the composite.

Thermally stabilized bismaleimide–triazine resin composites for 10-GHz level high-frequency application

A hybrid cured resin with excellent dielectric and thermal properties was prepared with bismaleimide–triazine (BT) resin modified with 2,2′-diallylbisphenol A (DBA). The thermal and dielectric properties of the resin were investigated, and the effect of DBA concentration on the curing reaction was determined. Results indicated that DBA significantly influenced the curing reaction and the properties of the cured product. The modified BT resins exhibited outstanding thermal stability (initial decomposition temperature was over 400°C), although the stability was slightly lower than that of pure BT resins. The dielectric constant and dielectric loss of the cured resin decreased when DBA was introduced into the BT resins. Moreover, the fabricated resins showed dielectric constant of 2.91–3.07 and dielectric loss lower than 0.0057 under the testing high-frequency range of 1 GHz to 15 GHz. Overall, the BT resins modified by DBA display great potential to be applied in high frequency field.

High-performance bismaleimide resins with low cure temperature for resin transfer molding process

High-performance bismaleimide resin systems (here coined LBMI resin series) based on 4,4-bismaleimidodiphenylmethane, 2,4-bismaleimidotoluene, bisphenol A bisallyl ether, 4,4′-bis[2-(1-propenyl)phenoxy]benzophenone, 2-allylphenol, and cumene hydroperoxide for resin transfer molding (RTM) process with low cure and post-cure temperatures (≦180°C) have been developed. Considering the optimum formulation conditions, the injection temperature is in the range of 70–160°C, and the pot life at 100°C is determined to be approximately 100 min. After curing at 180°C for 6 h, the resins exhibit high thermal resistances, excellent mechanical properties, and exceptionally low dielectric loss. Among others, these findings render the materials suitable for the use as high-performance resins for the production of advanced composites via RTM technique and with low cure temperatures.