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RF Electronics Chapter 11: Circuit Manufacture Page 378 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. The Voltera PCB printer [32] is much lower in cost and can process a conventional 4 x 5.3 or 101 x 134mm FR4 substrate. It deposits silver nanoparticle inks to print tracks. No dielectric inks are available, so only 2 layer boards can be built. The inks use heat curing. The minimum track width is 0.2 mm. The datasheet gives no accuracy of the track widths and this may limit the accuracy of Stripline impedances. The cost of the inks is high, but since very little conductive ink is required for a typical board, this technology may soon be economical for RF circuit prototyping. Sonoplot [34] have plotters that use ultrasonics to deposit fluid in a noncontact manner. The printed tracks can be 20 µm wide. A board size of 310 x 310 mm can be accommodated. After printing nanometalic silver ink tracks, they are annealed at 100 °C to transform the lines into solid tracks. The plotters have a position accuracy down to 5 µm. The Optomec company [33], uses aerosol jet technology to spray conductive, resistive or dielectric inks onto a surface. Having an aerosol jet, removes the tight milling/printing head to PCB distance constraints and thus allows the inks to be deposited on curved surfaces. In one mass-production example, microwave 3D antennas are printed onto odd shaped surfaces for use inside smart phones. A minimum line thickness of 10 µm and a line spacing of 20 µm is possible, though a larger spacing is preferred. That is a 9 times thinner line width, than is possible for etched PCB's [12-14]. It is also possible to print semiconductors, so that advanced microwave electronic circuits can be fully printed on virtually any substrate. This may also lead to new sensors, which include the sensor, electronics, transmitter and antenna, as well as a battery and photovoltaic devices, all made using 3D printed technology. Electronic circuits, their antenna, as well as the leads connecting them can all be printed onto a contoured substrate. Figure 11.11. 3D lenses being printed. [36] Rogers and Fortify [35, 36] have teamed up to produce RF photo polymer resin for 3D printing of dielectric lenses for antennae. Figure 11.11 shows the lens being printed and in figure 11.12 shows the cleaned up lens being tested. Some of these printers are suitable for University prototyping and others are capable of producing 30 000 circuits per week and are used for consumer devices. Typical examples of applications and their resulting circuits are shown in "Top10 Industrial Applications for Additive Manufacturing" [37]. Due to the ability of being able to make the circuits in any shape, the 3D circuit board printing is also used for military and aeronautical applications. This technique will become more common in future. RF Electronics: Design and Simulation 378 www.cadence.com/go/awr

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