Electronics

Although the possibilities it opens up are truly enormous in a huge industry such as electronics, direct electronics 3D printing of devices remains largely confined to two commercially viable technologies: Nano Dimension‘s multi-material jetting using conductive inks and Optomec‘s Aerosol Jet (and, more marginally, Neotech AMT). Both these companies are growing and their technologies are rapidly evolving, however, the adoption of directl electronics 3D printing is still far from mass adoption and the road ahead is not easy.

US-based Optomec is a relatively consolidated company. It was among the first in the world to develop commercial metal DED systems with its proprietary LENS technology and, while information on the commercial and technological evolution of its electronics 3D printing business is scarce, it seems to be able to leverage on a relatively broad customer basis as its technology is a relatively linear evolution of 2D printed electronics applied on either multiple layers or 3D surfaces. Nano Dimension’s technology is more potentially disruptive: it uses a derivation of nearby Stratasys’ polyjet technology to deposit layers of photopolymerizable polymers along with conductive nanosilver or nanocopper inks. While it has come a long way, recently introducing systems tailored for actual 3D printed PCB production, the company is still very much in a startup phase. Since it went public to raise capitals, it is also in a more challenging position as it needs to continuously ensure rapid business growth to maintain a high stock value: although business is effectively growing (the latest q2 financial report recorded a q on q growth of revenues) there are no guarantees that it is growing fast enough.

There is little doubt that 3D printing of electronics will eventually take hold, even for some mass production activities. Moore’s Law’s slow down due to quantum physics size limitations of transistors means that in order to improve performance it will be necessary to introduce more effective systems through advanced geometries and that is exactly where additive manufacturing does best.

History of printed electronics

Optomec also helps shed some light on the history of printed electronics: the idea of using printing technology to manufacture electronics dates back to the early 20th century, but its use for volume manufacturing didn’t become prevalent until the 1950s. Back then, photo plotters were used to produce master artwork circuit patterns on a clear mylar or glass substrate. The master artwork circuit pattern was then transferred onto a copper clad laminate coated with positive photoresist material. When exposed to light, the photoresist not masked by the circuit pattern became soluble and could be washed away leaving just the desired circuit pattern covered in resist material. An etching process was then used to remove the exposed copper leaving the desired circuit pattern. After removing the remaining photoresist from the circuit pattern, holes were drilled into the board and plated for mounting electrical components such as resisters, capacitors, integrated circuits. A wave soldering process was used to electrically connect the components to the circuits completing the printed circuit board (PCB) manufacturing process.

More recently, other graphic printing technologies, such as inkjet and screen printing, have been used to fabricate printed circuit boards. All of these processes serve the electronics industry well, but have limitations. For example, with photo plotting, a new master artwork is required to implement design changes and the process is not environmentally friendly. And, since all of these processes were developed to print on paper – they can only be used to manufacture circuits on a flat surface.

Consequently, in the late 1990s the Defense Advanced Research Program Agency (DARPA) initiated a project to develop a new tool specifically designed for the printing of electronics. The goal of the project, named Mesoscale Integrated Conformal Electronics (MICE), was to: “Develop a single tool capable of rapid production of electronics directly from CAD models. This tool must support processing of a wide variety of materials to produce robust, customized electronic components in a conformal manner on virtually any substrate, including low-temperature (<200˚C).”

The new tool developed under this DARPA program was Aerosol Jet and this is how Aerosol Jet has become an additive manufacturing technology for 3D printed electronics.

Electronics 3D printing: Optomec’s Aerosol Jet

The technology behind Aerosol Jet enables printing of interconnects on both 2D and 3D substrates. For 2D applications, multi-level interconnects can be created by printing a dielectric material at circuit cross over points – in essence emulating a multi-layer circuit board but on a single layer. This can be accomplished because the Aerosol Jet process supports multiple ink input devices allowing materials to be switched or even blended during printing. Aerosol Jet can print conformal interconnects on 3D surfaces eliminating the need for wire bonding – for example, printing electrical connections on 3D stacked die or for LED chip fabrication.

Electronic components such as resistors, capacitors, antennas, sensors, and thin film transistors have all been printed with Aerosol Jet technology. The performance parameters of printed components, for example the ohm value of a resistor, can be controlled through printing parameters. Components can also be printed onto 3-dimensional surfaces eliminating the need for a separate substrate thereby reducing the size, thickness and weight of the end product. For example, Aerosol Jet is used to print antennas and sensors that conform to the shape of the underlying substrate such as a cell phone case.

The Aerosol Jet process supports printing on a wide variety of substrates including plastics, ceramics and metallic structures. Commercially available materials, such as nano-particle inks, have been optimized for the Aerosol Jet process to allow printing (and subsequent ink sintering) onto plastic substrates with low heat deflection temperatures.

The process uses aerodynamic focusing to precisely and accurately deposit electronic inks onto substrates. The ink is placed into an atomizer, which creates a dense mist of material laden droplets between 1 to 5 microns diameter. The aerosol mist is then delivered to the deposition head where it is focused by a sheath gas (3), which surrounds the aerosol as an annular ring.

When the sheath gas and aerosol pass though the profiled nozzle, they accelerate and the aerosol becomes ‘focused’ into a tight stream of droplets flowing inside the sheath gas (4). The sheath gas also serves to insulate the nozzle from material contact preventing clogging. The gases used in the system are typically clean, dry Nitrogen or compressed air. The resulting high-velocity particle stream remains focused during its travel from the nozzle to the substrate over a distance of 2 to 5 mm maintaining feature resolution on non-uniform and 3D substrates (5). The system is driven by standard CAD data which is converted to make a vector-based tool path. This tool path allows patterning of the ink by driving a 2D or 3D motion control system. Printed features range from 10 microns to millimeters.

Electronics 3D printing: Neotech AMT

Neotech’s 3D Printed Electronics technology is based on the expert combination of three key modules: a Motion 3D Tool-path Generation Software; a 5 axis CNC Motion Platform and a 3D Capable Print Head, providing a single source for a complete optimized Hard- and Software package.

The Motion 3D Tool-path Generation Software is novel CAD/CAM system that is specifically configured for 3D Printed Electronics. It takes a component’s geometrical data and generates the tool-path (machine code) for controlling the CNC motion platform. Up to 5 simultaneous co-ordinated axes of motion can be controlled allowing the implementation of the most effective print strategies for even the most complex 3D designs.
Watch a 3D tool-path simulation.

Neotech’s 5 Axis CNC Motion Platforms are industrial-grade, high-speed and high-accuracy machine tools. With up to 4 print heads and 5 axes of simultaneous motion, the systems allow scalability from R&D and rapid prototyping through to high volume mass manufacture. They utilize the tool path data to move the print heads in 3D space to print the desired patterns.

A variety of 3D print heads can be offered with the choice dependent on the final application. These include piezo-driven dispense systems, needle valve, and Aerosol Jet (multi-station production systems only) print technologies. The print heads are mounted in the CNC motion platform and driven relative to the substrate in 3D space, producing in the desired pattern. After deposition, the ink is post-processed to obtain the final electronic properties. A very wide range of inks can be utilized enabling a full range of printed electronics functionality: conductors, semiconductors, dielectrics, resistors and more.

Electronics 3D printing: Nano Dimension

By combining high-resolution conductive and dielectric traces and spaces in a single print job, Nano Dimension’s technology and its DragonFly range of systems make it possible to print a full range of multi-layer PCB features, from intricate geometries to interconnections such as buried vias and plated through holes, seamlessly into multi-layer PCBs for agile product development. The result is a high-quality, densely packed PCB, printed in less than 24 hours, ready for component placement and soldering.

The DragonFly system makes it possible to 3D print antennas, arrays and Radio Frequency Identification (RFID) tags using conductive nano-particle silver and dielectric inks. This innovation enables antennas to play a role in more products and locations. Additive manufacturing of sensor components also opens up new possibilities for emerging applications and eliminates many design limitations, especially those related to rigid planar electrical designs. Finally, with the DragonFly system, creating dense and functional multi-layer PCBs becomes a one-day in-house job involving an unrivaled degree of automation.

The next frontier is additive manufacturing of semiconductor devices. As Nano Dimension’s Co-Founder Simon Fired wrote on the Nano Dimension’s blog, as the range of materials available for use in additive manufacturing systems, as well as the diversity of systems themselves, continue to expand, unique semiconductor devices that include exotic materials and unique architecture will become incorporated into 3D printed electronics. Additive manufacturing for semiconductor devices provides many of the benefits found in other products, and these devices can be incorporated into 3D printed PCBs and other electronics.

Semiconductor devices encompass more than just computer chips. LEDs, nonlinear passive components like diodes, transistors, sensors, and other electronic devices are made from a variety of semiconductors. Anyone familiar with Moore’s Law knows that continued miniaturization has been the primary focus in the semiconductor industry for the last 50+ years, but major manufacturers are struggling to break past the physical limitations in semiconductor devices. To overcome some basic phenomena in quantum physics, current research in this area has focused on designing new device architecture to continue miniaturization and increase component density.

A prime example from the semiconductor industry is the use of Fin-FETs, which is now the standard architecture in computer processors. This unique gate architecture provides lower power consumption, high ON-OFF current ratio, and better control over tunneling current in these devices. In solid-state semiconductor devices, the architecture in experimental tunnel FETs takes advantage of quantum tunneling in III-V materials, Ge, non-stoichiometric InGaAs, and Si to provide extremely high ON-OFF current ratios. Other avenues of research have focused on the use of organic and inorganic polymers to continue miniaturization and fabricate semiconductor devices with unique functionality. Polymers can be doped with a wide variety of low-temperature processes, making them ideal for use in unique devices, such as fully flexible electronics. The use of functionalized polymers and doping in polymers also allows materials and systems designers to tune the material properties of these devices to meet specific design goals.

This is where additive manufacturing can play a major role in the near future, both in research on new devices and in mass manufacturing of semiconductor devices. Polymers are naturally adaptable for use in additive manufacturing systems because they can be used in low-temperature, low-pressure fabrication processes, like inkjet printing, aerosol printing, screen printing, and similar processes. With the right additive manufacturing system and process, polymer materials can be co-deposited alongside nanoparticle materials to form insulating and conductive elements simultaneously in a single fabrication run.

When combined with different processes for 3D printing PCBs, inkjet printing and similar additive processes allow these unique semiconductor devices to be printed alongside novel 3D printed electronic components, such as unique antennas and RF devices, sensors and embedded passive components. When incorporated within a traditional electronics assembly process, 3D printed PCBs with printed semiconductor devices can interface with standard surface-mount or through-hole components.

Working with an additive manufacturing system that is designed for 3D printing PCBs is an excellent way to complement an existing manufacturing process for low-volume, high-complexity PCBs. Additive manufacturing for semiconductor devices with novel architecture and materials is likely to become mainstream sooner than we think: the latest DragonFly LDM allows semiconductor devices to be integrated into planar and non-planar 3D printed electronics.