Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi 2 Mo 2 O 9 (BMO, sintering temperature = 620-650°C, ε r = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (ε r) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a postprinting sintering step to create BMO/Ag 3D structures was thus demonstrated.

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Additive manufacturing (AM) has become more important and common in recent years. Advantages of AM include the ability to rapidly design and fabricate samples much faster than traditional manufacturing processes and to create complex internal geometries. Materials are crucial components of microwave systems and proper and accurate measurement of their dielectric properties is important to aid a high level of accuracy in design. There are numerous measurement techniques and finding the most appropriate method is important and requires consideration of all different factors and limitations. One limitation of sample preparation is that the sample size needs to fit in the measurement method. By utilizing the advantage of additive manufacturing, the material can be characterized using different measurement methods. In this paper, the additive manufacturing process and dielectric measurement methods have been critically reviewed. The test specimens for measuring dielectric properties were fabricated using fused filament fabrication (FFF)-based additive manufacturing and were measured using four different commercial dielectric properties measurement instruments including split post dielectric resonator (SPDR), rectangular waveguide, TE01δ cavity resonator, and open resonator. The measured results from the four techniques have been compared and have shown reasonable agreement with measurements within a 10 percent range.

his is a review article of the latest advances in 3D printing for enabling new materials and new geometries for radiofrequency (RF) devices, antennas, and metamaterials. The article discusses the achievable material properties and various optimized applications that are achievable by creating new shapes in either dielectric or metal. This article demonstrates what is currently possible with additive manufacturing and the current limitations. Various additively manufactured RF devices are reviewed.

The concept of the artificially engineered capacitor (AEC) is presented as a 3-D printable 3-D capacitive component for use in discrete RF/microwave electronic circuitry. The intention of the AEC concept is a highly customizable 3-D printable component whose capacitance value is stable over a wider frequency band when compared to commercial alternatives. AECs can be viewed as impedance structures with predominantly capacitive characteristics. Both series and shunt AEC configurations are considered with simulation and measurement data along with equivalent circuit models. The tolerance of the equivalent capacitance over frequency is focused upon in this article. Within the 40% tolerance band from the nominal value an improvement of 26% and 197% frequency band was achieved for the series and shunt variants, respectively, when compared to a commercial alternative. Further simulations show that with finer 3-D printing resolutions, this frequency-stable bandwidth can be further increased. Finally, an example design application of a half-wavelength microstrip resonator is presented in which the AECs' Q factor is measured, and its equivalent circuits are implemented and validated via simulations and measurements.