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The Rog Blog is contributed by John Coonrod and various other experts from Rogers Corporation, providing technical advice and information about RF/microwave materials.

3D-Print Antennas with Printable Dielectric Resin

March 24, 2022

Creating electronic components and circuits with three-dimensional (3D) printers holds great promise for high-frequency-analog and high-speed-digital (HSD) devices. With the right printable electronic materials, 3D printing can form fine feature sizes needed for new levels of dielectric component performance. Fortunately, Radix™ Printable Dielectric materials from Rogers Corp. are now available for 3D printers using digital light processing (DLP) and stereolithography (SLA) additive manufacturing methods. With this material technology and the right 3D printing systems, engineers can create circuits and components with the electrical, mechanical, and thermal properties designers have come to expect from sheets of Rogers’ more traditional circuit materials—except in this case Radix can be 3D-printed into a user’s desired shape rather than trimmed to size!

Radix Printable Dielectric is a bluish-black resin system fine-tuned with embedded ceramic microparticles to achieve a low dielectric constant (Dk) and low dielectric loss as printed. It exhibits a Dk or permittivity of 2.8 when measured at 10 and at 24 GHz. It achieves new levels of low loss for a 3D printable dielectric, with a dissipation factor (Df) of 0.0043 in the z-axis at 10 GHz and still only 0.0046 in the z-axis at 24 GHz. These electrical characteristics are uncommon for DLP 3D printable materials – standard resin systems can be up to an order of magnitude more lossy than Radix material. In addition, components and circuits 3D printed with Radix dielectrics can deliver consistent performance even when operating in environments with high humidity since the Radix printable dielectric material has a low moisture absorption of 0.08 wt.%.

Circuits and components printed with Radix 3D printable dielectric are stable with temperature, as evidenced by the material’s coefficient of thermal expansion (CTE) minimizing physical changes with temperatures from -50 to +250 °C. From -50 to +50 °C, the CTE of the z-axis or thickness of the material is 75 ppm/°C and 76 ppm/°C in the x-y plane of a 3D printed object. From +50 to +250 °C, the CTE of the z-axis is 120 ppm/°C and 123 ppm/°C in the x-y plane. The isotropy of the material’s thermal expansion exemplifies one of the benefits of DLP printing: no matter the orientation you can typically expect similar material properties unlike other nozzle-based printing systems.

Radix dielectrics can also manage the heat, with a z-axis thermal conductivity (k) of 0.3 W/mK and has a decomposition temperature (Td) of +313 °C, ensuring stable 3D printed dielectric structures even at temperatures required for soldering. For more details on the roles of material innovations for advances in the 3D printing of high frequency components, please see “New Material Innovations Guide for 3D Printing High Performance RF Components,” https://www.microwavejournal.com/articles/29250-ebook-library

Radix 3D Printable Dielectrics compare similarly in electrical, thermal, and mechanical characteristics to some of Rogers’ traditional “sheet-form” circuit materials, except that it is a photopolymer resin designed for curing by exposure to ultraviolet light. Rogers has tuned the material to be compatible with DLP printing processes, enabling high resolution and high throughput 3D printing. Like Rogers’ circuit materials, there are metallization options for Radix Printable Dielectrics. Radix materials can be used in conjunction with additive metallization techniques for conformal 3D circuit geometries.

Radix dielectrics are compatible with aerosol and ink jetting techniques that can deposit nanoparticle or reactive silver inks that are sintered for increased conductivity. They are also compatible with laser-activated plating processes that can deposit bulk copper for additional flexibility. This capability, with the ability to produce complex dielectric structures like lens antennas, has the opportunity to provide unprecedented design freedom for RF systems well into the mmWave frequency range.

This high-performance 3D-printable dielectric material technology is an important option to consider versus traditional materials used in PCBs and dielectric components such as antennas. Increasing use of wireless technologies is fueling growing demand for frequency bandwidth and mmWave frequency bands contain generous bandwidth if signals at those frequencies can be processed cost-effectively. Interest in mmWave frequency bands is growing for commercial and military 5G cellular wireless communications, automotive safety systems, and satellite communications systems. Radix printable dielectric materials may be part of a solution for meeting growing demand for mmWave signals, providing it can be formed into components that take advantage of the design freedom of DLP 3D printing to offer new levels of antenna performance. The examples of gradient index RF lenses and conformal antenna structures are just some of the potential applications that are uniquely enabled by 3D printing processes and new dielectric materials from Rogers Corporation.

To learn more, please refer to the previous Coonrod’s Corner, “An Overview of 3D Printable RF Structures” (https://youtu.be/7Qtq_dDrf_s). Do you have a design or fabrication question? Rogers Corporation’s experts are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.

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