Abstract
PTFE/GF(glass fiber) composites are widely applied in high-frequency printed circuit board (PCB) substrate materials due to the excellent dielectric properties of PTFE and the low thermal expansion coefficient of GF. However, the poor interface compatibility between PTFE and GF affects the performance of the composite substrates. In this study, tetraethyl orthosilicate (TEOS) was used as the silicon source, and polydimethylsiloxane (PDMS) was the organic precursor to modify the surface of GF through the sol–gel method to promote the interface compatibility of GF and PTFE. The modified GF noted T-GF was filled in PTFE to prepare PTFE/T-GF composites. SEM, FTIR, XPS, and contact angle confirmed that organic–inorganic hybrids were successfully loaded on GF's surface. Moreover, compared with PTFE/GF and the conventional coupling agent modified GF filled PTFE composites, the PTFE/T-GF exhibited improved dielectric constant (2.305), decreased dielectric loss (9.08E−4), higher bending strength (21.45 MPa) and bending modulus (522 MPa), better thermal conductivity (0.268 W/m*K) and lower CTE (70 ppm/°C), making it has promising application as the substrate materials for high frequency PCB.
Highlights
The rapid development of 5G communication technology requires the printed circuit board (PCB) substrate as the carrier to transmit high-speed signal should possess stable dielectric constant and low loss in the high-frequency range [1]
The absorption peak at 1000–1100 cm− 1 enhances, which is attributed to the hydrolysis condensation of Tetraethyl orthosilicate (TEOS) and glass fiber (GF), supporting the reaction mechanism presented in Scheme 1
The sol-gel method was used successfully to construct an organic-inorganic hybrids coating on the surface of GF, and the modified GF noted T-GF was filled into PTFE to obtain PTFE/T-GF composites, which showed better performance than PTFE composites filled with GF modified by coupling agents, with a dielectric constant of 2.305, a dielectric loss of 9.08E− 4, a bending strength of 21.45 MPa, and a bending modulus of 522 MPa, the moisture absorption of 0.0167%, the thermal conductivity of 0.268 W/m*K, and the coefficient of thermal expansion (CTE) of 70 ppm/°C
Summary
The rapid development of 5G communication technology requires the printed circuit board (PCB) substrate as the carrier to transmit high-speed signal should possess stable dielectric constant and low loss in the high-frequency range [1]. Inorganic layer from the hydrolysis and condensation of TEOS were designed to connect with the polydimethylsiloxane (PDMS) molecular chains through condensation reaction, which formed an organic-inorganic hybrid film with flake structure on the surface of GF. In this way, is the surface roughness of GF increased, and the improvement of SP on the GF surface is realized (PDMS has similar SP (14.9) to PTFE), which is expected to enhance the compatibility between the GF and the PTFE matrix and improve the interface and dielectric properties of the composites. The effects of different surface modifications of GF on the interface and dielectric properties between the fiber and the matrix were systematically studied
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