LU Zhipeng ¹, GUO Baolin ¹, LI Haiyan ², YAO Qing ¹

(1. School of Mechanical Engineering, Nantong University, Nantong 226019, Jiangsu, China; 2. Engineering Training Center of

Nantong University, Nantong University, Nantong 226019, Jiangsu, China)

Extended abstract:[Significance] Microwave dielectric ceramics are vital for radar systems, wireless communication and so on, due to their optimizable dielectric constant, high temperature stability and ultra-low loss tangent. These properties make precise electromagnetic wave transmission available by virtue of microstrip antenna ceramic substrates. Their performance heavily depends on fabrication methods, which govern microstructural uniformity, dimensional precision and efficiency of the final products. However, there exist persistent challenges in balancing defect minimization, scalability and cost-effectiveness.[Progress] Gel casting can be divided into water-based and non-water-based systems. Water-based gel casting requires polymer additives, such as acrylamide, gelatin, sodium alginate and isobam, to tailor rheology and curing behaviors of slurries. Non-water-based systems involve alcohol or organic solvents. Tape casting is classified into two primary modalities, one is the aqueous-based technique with water as the dispersion medium, while the other is non-aqueous-based approach utilizing organic solutions. The aqueous-based tape casting can be further categorized into singular-layer formation and multi-layer co-casting. The aqueous methodology offers substantial benefits, including superior economic viability and reduced ecological pollution, in addition to sintering enhancement properties. Press forming has two principal methodologies. One is dry pressing and the other is isostatic pressing. The isostatic pressing technique can be further categorized into two distinct variants, one is cold isostatic pressing and the other is hot isostatic pressing. The paramount advantage of employing such advanced technology lies in its exceptional capability to precisely regulate the dimensional accuracy of the ceramic substrate, while simultaneously ensuring superior density of the ceramic components. Non-aqueous systems are classified into ester-based and non-ester-based solvent formulations, which typically improve slurry dispersion and sintering performance, respectively. Extrusion forming adopts two ways, including screw extrusion and hydraulic extrusion. Clearly, this method excels in continuous production of elongated or tubular ceramic components. Actually, it is also applicable to the production and manufacturing of substrates. Additive manufacturing is an emerging approach. It integrates SLA (stereolithography apparatus), SLM (selective laser melting) and FDM (fused deposition modeling). These technologies are facilitative for rapid prototyping and customized fabrication of geometrically complex structures.[Conclusions and prospects] This paper was aimed to systematically analyze five key forming methods, including gel casting, cast film molding, compression molding, extrusion molding and additive manufacturing. Focuses are mainly on their fundamental technical mechanisms, comparative advantages and applicable scenarios, thus offering references for the fabrication and optimization of microstrip antenna substrates. In future, software for simulation experiments is needed, which is helpful to optimize the parameters to reduce times of experiments. It is possible to combine different methods to minimize their respective limitations. Meanwhile, eco-friendly forming is an important consideration.

Key words: microstrip patch antenna substrate; microwave dielectric ceramic; forming method