Three-dimensional printing technology is one of our industry’s most exciting innovations. And the promising field of 3-D printed electronics is poised to revolutionize the way engineers design and manufacture electrical systems for years to come. In the following essay, Dr. Martin Hedges of Neotech AMT presents his thoughts on the future of 3-D printed electronics.
Three-dimensional (3-D) printing for prototyping has been around for nearly three decades since the introduction of the first SL systems. The last few years have seen this technology receiving considerable attention to the point of hype in the mainstream media. However, there is a new emerging 3-D printing market that is increasing in importance: 3-D printed electronics (3-D PE). Whilst traditional 3-D printing builds structural parts layer by layer, 3-D PE prints liquid inks that have electronic functionality on to existing 3-D components. 3-D PE is achieved by combining advanced printing technologies, such as Aerosol Jet, with specially designed five-axis systems and advanced software controls that allow complex print motion to be achieved. The integrated print systems allow the full range of electronic functionality to be applied: conductors, semiconductors, resistors, dielectrics, optical, and encapsulation materials.
These can be printed on to virtually any surface material of almost any shape. Once deposited the inks are post processed: sintered, dried, or cured to achieve their final properties. Multiple materials can be printed to build up functionality, or surface mount devices (SMD) can be added to make the final electro-mechanically integrated system (see Photo 1).
In this example, two capacitive sensor structures have been printed on the ends of an injection-molded PA6 tank. The sensors are connected by a printed circuit (conductive Ag) and SMD components are added to complete the device. When water is pumped into the tank, the sensors register the water level as it rises, lighting the LEDs to indicate the fill level. When the tank compartment is full, the circuit senses the water fill level and reverses the pump direction.
3-D PE has the potential to provide enormous technical and economic benefits in comparison to conventional electronics based on 2-D printed circuit boards. It allows the combination of electronic, optic, and mechanical functions on shaped circuit carriers. Therefore, it enables entirely new product functions and supports the miniaturization and weight-saving potential of electronic products. By eliminating mechanical components, process chains can be shortened and reliability is increased. As a digitally driven, additive manufacturing process materials are only applied where needed, improving the ecological balance of electronics production. With no fundamental limitation on substrate material, the user is able to select low-cost, easy-to-recycle and more environmentally friendly materials. The novel design and functional possibilities offered by 3-D PE and the potential for rationalization of production steps indicate a potential quantum leap in electronics production.
Advances in this field have been rapid since the first developments that focused on 3-D chip packaging. In this field, printing is conducted over small changes in z-height to connect SMDs. Photo 2 shows an example where wire bonds are replaced by printing interconnects, from the PCB, up the side of a chip, and over onto the top contact pads.
Such applications only require relatively simple print motion. The current “state of the art” is to use five axes of coordinated motion to print high complex shapes. This capability enables the production of truly 3-D PE systems, such as a 3-D antenna for mobile devices (see Photo 3).
This application is well advanced and moving towards high-volume mass production driven by the benefits of a flexible manufacturing, novel design capabilities, and cost reduction compared to the current methods based on wet chemical plating processes. 3-D PE is also being scaled to print on large components beyond the size range possible with current manufacturing methods. For example, in the automotive field, 3-D prints of heater patterns are being developed for molded PC windscreens of up to 2 m × 1 m in size.
Currently, 3-D PE applications are mainly limited to circuits, antennas, strain gauges, or sensors using conductive metal as the print media with additional electronic functionality being added as SMDs. However, the technology also has the potential to leverage new material and process developments from the printed and organic electronics world. In this field, many different material systems are currently being applied on planar surfaces to create multi-material and multi-layer devices. Functionality such as resistors, capacitors, sensors, and even transistors are being incorporated into fully printed 2-D electronic systems. As these print materials and processes mature, they can be adapted to 3-D applications. It is expected that the coming years will see a rapid increase in the range of fully printed 3-D electronic devices of novel functionality.
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