A key driver of the high-frequency, high-speed era: Exploring new frontiers in Low Dk thermoplastic and elastomer materials.

 

Material Applications in the High-Frequency, High-Speed Era

 

With the explosive growth of AI servers, 5G/6G high-frequency communications, and automotive millimeter-wave radar systems, electronic devices are facing increasingly stringent demands for low-latency and ultra-low-loss signal transmission. Under this technological trend, low-dielectric materials with a dielectric constant (Dk) below 3 have become indispensable core materials for semiconductor packaging, advanced substrates, and high-end printed circuit boards (PCBs).

 

Most commercially available low-Dk materials are based on thermosetting resins, such as modified polyphenylene oxide (PPO/PPE), which are primarily used in rigid laminates. However, as the industry moves toward thinner, more flexible, and even lower-loss electronic systems, thermoplastic and elastomeric materials are emerging as a new generation of solutions due to their unique physical properties.  

 

Thermoplastic and elastomeric low-Dk materials offer excellent flexibility, processability, and extremely low molecular polarity, making them widely used in advanced electronic products. Typical applications include 5G flexible printed circuit (FPC) antennas in smartphones, RF components in microwave communication base stations, flexible circuits in wearable devices, and high-frequency cables and connectors used in new-energy vehicles. These applications require materials capable of maintaining signal integrity even under repeated bending cycles and high-temperature processing conditions.

 

 

Development and Applications of Hydrocarbon Resins

 

Among various low-dielectric materials, hydrocarbon resins have emerged as a core platform in thermoplastic and elastomer technologies due to their molecular backbones being composed almost entirely of carbon and hydrogen atoms, resulting in extremely low polarity. Based on their molecular structures, commercially available hydrocarbon resins can generally be classified into three major categories.

 

The first category is polybutadiene (PB), which exhibits excellent hydrophobicity and elasticity and is widely used as a performance modifier in high-frequency printed circuit boards. The second category is styrene-butadiene copolymers (SBC), which combine the toughness of rubber with the processing advantages of thermoplastics, making them suitable for high-frequency cable encapsulation and insulation applications. The third category is cyclic olefin copolymers/polymers (COC/COP), which possess rigid cyclic structures and high optical transparency. Their saturated alicyclic backbone provides extremely low moisture absorption and highly stable dielectric properties. Nevertheless, the development of hydrocarbon resins with even higher thermal resistance, greater rigidity, and lower coefficients of thermal expansion (CTE) remains a major focus for resin manufacturers aiming to meet the requirements of advanced applications beyond the 6G era.

 

When compared with other commercially available materials exhibiting dielectric constants below 3, the strengths and limitations of each system become evident. Polytetrafluoroethylene (PTFE) offers unmatched dielectric performance (Dk ≈ 2.0), while perfluoroalkoxy alkane (PFA) provides slightly higher dielectric constants (Dk ≈ 2.1). However, both fluoropolymers suffer from high melting temperatures, challenging processing requirements, and poor adhesion to copper foils. Liquid crystal polymers (LCPs) are regarded as benchmark materials for high-frequency flexible circuits due to their ultra-low moisture absorption and excellent thermal expansion characteristics, although they exhibit dielectric anisotropy and are relatively expensive. Modified polyimides (MPI) inherit the outstanding thermal stability and mechanical strength of conventional polyimides, making them attractive for advanced packaging applications. However, their relatively higher moisture uptake may lead to dielectric property drift under humid conditions. Meanwhile, elastomeric hydrocarbon resins such as PB and SBC offer low cost and extremely low polarity, but their polymer backbones contain residual unsaturated double bonds, resulting in limited thermo-oxidative stability, susceptibility to aging under prolonged high-temperature exposure, and relatively high CTE values.

 

Among a wide variety of materials, poly(4-methyl-1-pentene) (PMP) has gradually attracted attention as a uniquely structured high-performance thermoplastic polyolefin. Unlike cyclic hydrocarbon resins such as COC/COP, PMP contains bulky alkyl side chains that significantly reduce crystal packing density and create substantial free volume within the polymer matrix. This structural feature enables PMP to achieve an exceptionally low dielectric constant (Dk ≈ 2.1). Among low-Dk materials, its dielectric performance is surpassed only by fluorinated polymers such as PTFE, placing it at the forefront of non-fluorinated and hydrocarbon-based polymers.

 

Compared with PTFE, PMP offers significantly superior melt-processability while overcoming the poor high-temperature durability commonly associated with conventional hydrocarbon elastomers. In addition, PMP provides excellent chemical resistance, high optical transparency, and extremely low moisture absorption.

 

From the perspective of hydrocarbon-based dielectric materials, PMP effectively bridges the technological gap between ultra-low dielectric performance and conventional thermoplastic processability. As next-generation high-frequency communications and advanced electronic systems continue to demand an increasingly stringent balance of cost efficiency, manufacturing flexibility, and electrical performance, PMP is poised to become one of the most promising materials in the low-Dk landscape, offering both exceptional technical performance and strong commercial potential.

 

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