As 3D printing (3DP), additive manufacturing technology advances, one area manufacturers are working on is including electronics into the 3DP process. Several industries, including aerospace and the military, are particularly interested in this development as it promises to reduce the weight and size of components.
At the recent AMUG conference, we had a chance to see the possibilities of this technology up close. Optomec (Albuquerque, NM) offers a 3D printing process, Aerosol Jet printing, which uses 3DP, additive manufacturing technology to incorporate electronics into a 3D printed part. Nanomaterials are used to produce fine feature circuitry and embedded components without the use of masks or patterns, as well as reduce the overall size of electronic systems. The resulting functional electronics can “have line widths and pattern features ranging from 10’s of microns to centimeters.”
According to Optomec, common electronic materials including conductor, dielectric, resistor, and semiconductor inks can be processed by its Aerosol Jet system to print conformal sensors, antennae, shielding and other active and passive components. The ability to print these electronic components on or in a physical device eliminates the need for separate printed circuit boards, cabling and wiring, simplifying assembly.
One example of the use of this technology was a 3D printing UAV wing. The Aerosol Jet system was used to print a conformal sensor, antenna, and power and signal circuitry directly onto the wing of a UAV model. The wing itself was 3D printed with Stratasys FDM 3D printer. The electrical and sensor designs were provided by Aurora Flight Sciences, a supplier of UAVs.
Optomec developed the Aerosol Jet process for a DARPA project. Initially, the print material is atomized to produce droplets of one to two microns in diameter. According to Optomec, materials with viscosities ranging for 1 cP to 1,000 cP have been successfully atomized and deposited.
The atomized femtoliter size droplets are then entrained in a gas stream and delivered to the material deposition print head. Here a second gas is introduced around the aerosol stream to focus the droplets into a tightly collimated beam and also to eliminate clogging of the nozzle. The combined gas streams exit the print head through a converging nozzle that compresses the aerosol stream to a diameter as small as 10 microns. The jet stream of droplets exits the print head at high velocity onto the substrate, which enables a relatively large separation (about 2 to 5 mm) between the print head and the substrate. The aerosol stream stays tightly focused over this distance, resulting in the ability to print conformal patterns on three-dimensional substrates. Despite the high velocity, the printing process is gentle; substrate damage does not occur and there is generally no splatter or over-spray from the droplets.
The print head is scalable supporting 2, 3, 5, or more nozzles at a time. It is pitch dependent, enabling throughputs as high as 25,000 or more interconnects per hour. The print head comes with a mechanical shutter for rapid on/off of the print stream and can extend print runtimes of twelve hours or more before ink refill is required.
Aerosol Jet systems can also print fine line conformal circuitry on non planar surfaces, a capability seen as a key enabler for fully printed electronics on 3D surfaces. The relatively large stand-off, up to 5 mm from the nozzle tip to the substrate, and high velocity particle stream enable the Aerosol Jet material deposition head to print on surfaces with inclines of up to 60 degrees without tilting the head.