Development of thermoplastic films via formulation design technology for millimeter-wave communication applications

Abstract

Advanced communication technology using millimeter waves (mmWaves) requires new polymeric materials with low dielectric properties to minimize signal transmission losses. The dielectric polarization of polymers, including electronic, vibrational, orientational, ionic, and interfacial contributions, as well as the water molecules absorbed within them, is strongly related to their dielectric properties in the mmWave region. This has led to the emergence of liquid crystal polymers (LCPs) and fluoropolymers as candidate materials for mmWave communication. However, their poor secondary processability and adhesion to copper wiring often limit their practical application. This focus review describes two types of thermoplastic films developed via formulation design technology for mmWave communication. A crystalline polyaryletherketone-based film, compounded with a plate-like, low-polarity filler and blended with miscible noncrystalline polymers to control the crystallization behavior, exhibits a low transmission loss capability comparable to that of LCPs. Additionally, this film offers solder reflow heat resistance, a low coefficient of thermal expansion (CTE), and excellent multilayer processing capabilities at low temperatures, making it suitable for use in multilayer substrates for mmWave communication applications. A polyolefin-based film demonstrates ultralow dielectric properties comparable to those of fluoropolymers and strong adhesion to copper foil. Furthermore, this film offers customizable functionalities, including laser processability, transparency, a low CTE, and flame retardancy, enabling its application in flat, flexible cables and transparent antennas. Owing to their unique characteristics, these films are promising candidates for mmWave communication materials. This focus review describes two types of thermoplastic films developed via formulation design technology for mmWave communication. The first type is a crystalline polyaryletherketone (PAEK)-based film, which is improved with plate-like fillers and miscible noncrystalline polymers. This film exhibits low dielectric properties, heat resistance, low thermal expansion, and excellent multilayer processing capabilities. The second type is a specialized polyolefin resin-based film, which achieves ultralow dielectric properties comparable to those of PTFE and combines excellent copper adhesion with customizable functionalities such as laser processability, transparency, and flame retardancy.