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RF Electronics Chapter 11: Circuit Manufacture Page 377 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. RF Applications of Thick Film Circuits The Alumina substrate has a very low loss, and that is why it is used for thin film circuits. The application of the required tracks using thick film techniques is a lot cheaper than doing the same using thin film techniques. For accurate transmission line widths, fine screens need to be used and allowances need to be made for spreading of the inks. Figure 11.9 shows a circuit for a low noise amplifier and I-Q gain control circuit for a receiver beam steering application at 1.6 GHz. The circuit is 100 mm x 100 mm in size. Thick film techniques are also used to produce patch antennae for mobile radio systems. In many cases, the antenna needs to be shaped to conform to the contours of the mobile phone. Thick film techniques are also used to coat the ceramic blocks of the dielectric filters used as a diplexer shown on the left of the mobile phone in figure 11.3. Manufacturing using 3D printing Figure 11.10. Multilayer 3D printed circuit board. [31] Recently 3D printers capable of printing printed circuit boards have become available. [31 - 33]. The printer prints dielectric ink, or conductive ink in the location required in order to make the required printed circuit board. The dielectric ink from Nano Dimension [31] has a dielectric constant of 2.2 to 3.7 at 1 MHz. and a loss tangent of 0.02 to 0.04 at 1 MHz. Having such a wide range of dielectric constant makes it difficult to produce accurate transmission lines or accurate Stripline or Microstrip RF filters. The AgCite [31] conductive ink uses silver nanoparticles and has a conductivity up to 35 MS/m. Silver has a conductivity of 63 MS/m, Copper 59.6 MS/m, Gold 41 MS/m and Aluminium 35 MS/m. The inks thus have a similar conductivity to Aluminium. No ink is deposited where a hole is required and a pad is made by surrounding the hole with conductive ink. The inks use UV curing. A 200 x 200 mm printing area with a 3 mm thickness can be deposited. The smallest print trace width and pitch is 90 µm. Conventional thickness PCB's can be made and may contain many connector layers, so that very dense boards can be made. However, it is not possible to print on ceramic substrates, so the Nano Dimension's PCB printer has limited microwave application. Figure 11.10 shows a 4 layer 3D demonstration printed circuit board. RF Electronics: Design and Simulation 37 7 www.cadence.com/go/awr

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