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September 2014 • The PCB Magazine 45 AEROSOL JET TECHNOLOGy FOR PRODuCTION GRADE/SCALE PRINTED ELECTRONICS continues Output In the print head (deposition mechanism), the aerosol is surrounded on all sides of its flow path by a second gas stream. This "sheath" gas compresses the mist towards the center-line, and further directs it towards a focusing nozzle that collimates the aerosol into a precise contin- uous beam of material, as small as 10 microns wide. The continuous multitude of droplets exit the nozzle at velocities as high as 50 m/s and impact on the substrate, which is moved in the X-, Y-, and Z-axis using CAD/CAM control. Pat- terns are further defined using a shutter to pro- duce stops and starts. The aerosol jet approach has a number of advantages including: • Prints a wide variety of inks, with high solids loading and viscosities up to 1000 cP • Prints feature sizes ranging from 10 microns to centimeters. • Prints on low temperature substrates • Non-contact, conformal printing with high stand-off distances of 1–5 mm • Prints on textured, non-planar, and 3D surfaces • Able to mix multiple materials on the fly and print gradient structures • Scalable for high-volume production application using multiplexing Materials The aerosol jet process is capable of han- dling a wide range of material classes required for manufacturing electronic circuits and com- ponents. Some example materials are shown in Figure 2. Aerosol jet can print deposits on virtually any surface material—polymers, silicon, glass, metals and ceramics. The long focal length of the aerosol jet beam enables conformal printing on irregular and 3D surfaces. Applications Applications for PE are as far reaching as electronics themselves. Figure 3 illustrates some of the many aerosol jet applications that are un- der development by Optomec and its end users, which includes solutions for the semiconduc- tor, display, energy, and life sciences industries. Many of the near-term mass production appli- cations are being driven by the strong demand for smartphones and tablets. Printed Antennas for Mobile Devices A new high volume PE process is available that lowers manufacturing costs for antennas used in mobile devices. The process works with standard injection molded plastics—no special additives or coatings are required. Based on aerosol jet technology, the digital process prints conformal antennas using conductive nanopar- ticle silver inks. The printing process accurately controls the location, geometry and thickness of the deposit and produces a smooth mirror- like surface finish to ensure optimum antenna performance. No plating or environmentally harmful materials are used in the process. Mobile device antennas for LTE, NFC, GPS, WiFi, WLAN, and BT have been printed using the aerosol jet process and independently test- ed by a leading cell phone component supplier. Measured antenna performance is comparable to other production methods. The aerosol jet printing process is scalable: antennas can be figure 2: partial list of aerosol jet materials used for printed electronics applications.