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44 The PCB Magazine • September 2014 ing lines and existing commercial products. For example: • Solar cell: replace screen-printing to reduce the size of collector lines • Display: replace photolithography to lower cost of jumper circuits • Smartcard: replace wirebond to produce robust conformal interconnects While implementations such as these are gaining traction with industry, the pace of more widespread adoption has been slowed by many factors, including risk aversion to replac- ing entrenched solutions, limited availability of low-cost electronic inks, and the lack of reliable high-volume systems for printing electronics. Moving Toward Production-Grade Solutions However, there are many PE projects that are far down the path in terms of development and deployment, and it is fair to expect that 2015 will begin to see the rollout of PE solutions as a key element of mass production of high- volume consumer end-products, most notably in the smartphone and tablet space. And, while PE has a long way to go to realize the vision of implementing an entire complex end-product, the technology has shown the potential to contribute to the manufacture of many of its constituent elements in the foresee- able future. For example, Optomec, the inventors of the patented Aerosol Jet printing technology, has active projects printing the following portions of a smartphone: • 3D antennas onto the back cover case • Edge circuits for the display • Jumper circuits for the touch screen • 3D interconnects for the chips • <50 micron underfill dispense for increased board density Printing Technologies—Aerosol Jet The Optomec Aerosol Jet technology is a material deposition solution used to directly print functional electronic circuitry and com- ponents onto a wide variety of planar and non- planar substrates, without the need for masks, screens or subtractive post-processing. The pro- cess utilizes an innovative aerodynamic focus- ing technique to collimate a dense mist of ma- terial-laden micro droplets into a tightly con- trolled beam that can produce features as small as 10 microns or as large as 1+ centimeter in a single pass. Coupled with a motion control sys- tem that moves either the head or the substrate, high resolution patterns can be created to pro- duce electronic and physical structures, as well as wide area conformal coatings. Aerosol jet technology is a combination of two separate mechanisms, atomization and deposition, with independent control and op- eration. These fundamental building blocks are highly flexible in terms of their ability to sup- port both low and high viscosity inks, produce both thin and thick layers, and print both small and large features. Input The first step in the process is based on at- omization of a liquefied material into a dense mist of micro-droplets ranging from ca. 1–5 mi- cron. Varied mist generation techniques, such as ultrasonic and pneumatic methods, enable the system to support a very broad range of ma- terial types and material formulations; e.g., na- no-particle inks, conductive polymers, insula- tors, adhesives, and even biological matter. The mist, or "aerosol", is then propelled by a carrier gas to the aerosol jet print head. AEROSOL JET TECHNOLOGy FOR PRODuCTION GRADE/SCALE PRINTED ELECTRONICS continues figure 1: aerosol jet input (l) and output (r) illustration.