Printed and Flexible electronics have already started to appear in our daily lives, for example in car manufacturing with printed aerials, smart textiles with pressure sensors to recognize seat occupancy and self-dimming rearview mirrors, or in the medical field with medical test strips with diagnostic electrodes. Engineers at the University of California San Diego have developed a flexible wearable sensor that can accurately measure a person’s blood alcohol level from sweat and transmit the data wirelessly to a laptop, smartphone or other mobile device.
Researchers at the University of Tokyo have developed “optoelectronic skin”, with an ultra-thin, flexible LED display that can be worn on the back of your hand. China has developed a new electronic paper, heralded as “the world’s first graphene electronic paper,” by Chen Yu, general manager of Guangzhou OED Technologies. The material can be used to create hard or flexible graphene displays, used in electronic products such as e-readers and wearable smart devices.
Printed and flexible electronics have thus far failed to achieve widespread adoption due to significant unresolved technical challenges. Major gaps exist between expectations and performance of printed electronics in the areas of logic, memory, analog circuitry, power, and light generation. Flexible Hybrid Systems is a Combination of flexible printed materials and flexible silicon-based ICs to create a new class of flexible electronics.
The convergence of the use of PFE, with its advantages in available envelope and format, with the performance of conventional electronics has become known as the hybrid approach. A PFE hybrid is created when nonprinted technologies, such as single crystalline silicon ICs, are integrated with PFE. Flexible hybrid integration of printed electronics and conventional silicon ICs has become an accepted near-term solution for flexible system commercialization.
NextFlex describes FHE as the intersection of additive circuitry, passive devices, and sensor systems that may be manufactured using printing methods (sometimes referred to as printed electronics) and thin flexible silicon chips or multichip interposer structures. These devices take advantage of the power of silicon and the economies and unique capabilities of printed circuitry to form a new class of devices for IoT, medical, robotics, consumer and communication markets. FHE devices conform to any shape, but are also bendable, twistable, and stretchable.
Project Call 3.0 (PC 3.0) focuses on areas identified in the Flexible Hybrid Electronics (FHE) Roadmap developed by NextFlex Technical Working Groups.
Flexible Hybrid Systems (FHS)
FHS is a flexible electronics hybrid that is differentiated by the utilization of flexible silicon-on-polymer (SoP) ICs rather than conventional packaged ICs or bulk silicon bare die for the single crystalline silicon devices. SoP is a single crystalline IC technology that results from the conversion of conventional silicon wafers to SoP by replacing the majority of the silicon wafer with a polymer. SoP ICs retain the functionality of conventional devices, but are fully flexible and ultra thin.
FHS is a hybrid technology that utilizes SoP to provide the performance that PFE needs and the format that conventional packaged ICs or bare die cannot reliably provide. SoP has the capability to mitigate the reliability issue by having deformation characteristics much closer to PFE than bulk silicon
This approach addresses the full technology solution necessary for modern electronic products in the desired flexible format. FHS can include power sources and displays as part of the hybrid integration.
An FHS approach allows the ability to deliver a spatially distributed response to signals from spatially distributed sensing. With the ability to deploy sensors integrated with adequate processing and communication comes the opportunity for truly ubiquitous applications—smart surfaces, closed-loop diagnostics and therapeutics, and real-time monitoring of individuals or structures.
Optomec to Showcase 3D Printed Electronics at UK Conference
Dr. Renn’s Chief Technology Officer for Optomec, discussed at the Genome Campus Conference Centre in Cambridge, U.K how flexible hybrid circuits typically require interconnecting rigid bare silicon or packaged die to a flexible circuit board. Flexing these assemblies can cause extreme stress on the electrical connections, especially near the edge of the chip where it mates with the substrate. Much of the stress can be relieved by first printing an elastic fillet at the base of the chip to form a flexible ramp leading to the surface. Metal ink traces can then be printed along the ramp to connect between the board and chip I/O.
Optomec, a leading global supplier of production grade additive manufacturing systems for 3D Printed Metals and 3D Printed Electronics, has developed Aerosol Jet 3D technology. Aerosol Jet is a non-contact, high resolution printing technology that is compatible with a wide range of conductive, insulating, and resistive materials.
Dr. Renn will explain how Aerosol Jet is an ideal printing tool for precision deposition of polymeric and metal inks in this 3D application.. He will discuss the printing of robust, flexible and stretchable 3D interconnects with line and space below 50 micrometers and good stability under thermal cycling. Dr. Renn will also provide details on the printing of passive electronic components and sensors.
The FlexTech Alliance
Formed in 2015 through a cooperative agreement between the US Department of Defense (DoD) and FlexTech Alliance, NextFlex is a consortium of companies, academic institutions, non-profits and state, local and federal governments with a shared goal of advancing U.S. Manufacturing of FHE. By adding electronics to new and unique materials that are part of our everyday lives in conjunction with the power of silicon ICs to create conformable and stretchable smart products, FHE is ushering in an era of “electronics on everything” and advancing the efficiency of our world.
The U.S. Department of Defense (DoD) has awarded FlexTech Alliance a Cooperative Agreement to establish and manage a Manufacturing Innovation Institute (MII) for Flexible Hybrid Electronics (FHE MII). FlexTech Alliance comprises 96 companies, 11 laboratories and non-profits, 42 universities, and 14 state and regional organizations.
“Flexible Hybrid Electronics (FHE) is an emerging technology that has the potential to reshape the electronics industry. Electronic devices can now be printed and attached to flexible, conformal materials like fabric or curved surfaces.” FHE has the potential to re-shape entire industries, from the electronic wearable devices market, to medical health monitoring systems, to the ubiquitous sensing of the world around us – also known as the Internet of Things.
FHE has wide range of applications from US military exploring FHEs for wearable electronics and beyond defense, including automotive, communications, consumer electronics, medical devices, health care, transportation and logistics, and agriculture.
Flexible hybrid electronics, an emerging manufacturing capability, enables the integration of thin silicon electronic devices, sensing elements, communications, and power on non-traditional flexible substrates.
To be successful, the Institute will need to engage aspects of the integrated circuit (IC) industry, the graphics printing industry, and the electronic assembly/packaging industry. To complement the San Jose hub, key technology nodes will be linked and include IC thinning, system design and fabrication, integration and assembly, and FHE applications.
FHE Roadmap 3.0
The Institute will leverage the electronics industry and the high-performance printing industry, both well-established US industrial and academic areas of strength. A comprehensive roadmap was developed in collaboration with industrial partners, academics, and subject matter experts (SMEs) in a variety of fields.
The roadmap topics included different facets of application-specific devices/components for technology demonstration as well as various aspects covering design, materials, process, equipment, and test development that would enable realizing advanced manufacturing capabilities to meet the overall vision of the Institute and the FHE eco-system. The following topics were the focus of the Technical Working Groups that developed the roadmap:
Manufacturing Thrust Area (MTA)
- Device Integration and Packaging
- Printed Flexible Components and Microfluidics
- Modeling and Design
- Standards, Test and Reliability
Technology Platform Demonstrators (TPD)
- Human Health Monitoring Systems
- Asset Monitoring Systems
- Integrated Array Antennas
- Soft & Wearable Robotics
Project Call 3.0 Details
PC Topic MTA 3.1: Printed Circuit Elements for RF and High-Speed Applications ($750K maximum government funds): Prototype and demonstrate direct-write printing of RF and high-speed circuit features and characterize electrical performance over frequency range, 1 MHz – 50 GHz. Applications for rapid prototyping and custom designs of RF circuits, antennas, hybrids, amplifiers, meta-materials, etc. Demonstrate the following attributes in prototypes for electrical characterization:
- Low resistance conductors and low dielectric material printing
- Printed RF transmission lines, differential pairs, waveguides and power dividers
- Low-loss chip interconnections including all printed connections
- Printed power/ground planes for impedance control
- Antenna elements; broadband, narrowband, beamforming, phased array, meta-material, FSS
- Cooling and heat management for high power
- Characterize conductor electrical stability over temperature
- Characterize conductor surface roughness and skin effect (as appropriate)
PC Topic MTA 3.2: Printed Passives for FHE including Materials, Tools, and Process Documentation ($500K maximum government funds): Projects in this topic area will produce optimized printing process recipes (including materials, equipment, and process) for passive components such as resistors, capacitors, and inductors. The resultant effort should improve the consistency and accuracy in tolerance for these printed passive elements from current state of the art. The target tolerance for printed passive components is ±10%. Printed passive proposals should include preliminary cost models as a comparison between printed passives and pick-and-place fully yielded components. The proposed program should include consideration and a proposed design for in situ test and repair of passives, but not necessarily demonstrating the capability in this phase.
PC Topic MTA 3.3: Z-Axis Interconnect and Via Formation ($200K maximum government funds): Projects in this topic area will identify best practice methods and process for producing Z-axis interconnects in FHE devices on multi-layer organic and film substrates. Various via formation methods may be utilized using conductor deposition techniques compatible with FHE. If laser processing is used, then the wavelength, pulse profile, and other process parameters should be documented so that the process may be reliably reproduced. In addition to the via formation, conductive interconnection in the z-axis should be tested and characterized, and basic reliability tests on these should be carried out.
PC Topic MTA 3.4: Additive and Semi-Additive Manufacturing Methods for High Density Interconnects ($500K maximum government funds): The objective of this project topic is to identify the most suitable additive or semi-additive manufacturing technologies for producing high density flexible circuits, defined as line width and spacing less than or equal to 50 μm. Additive manufacturing methods have shown promise in reducing manufacturing cost compared to subtractive, lithography based, approaches. Therefore, technologies proposed should show some potential cost reduction compared to current printed circuit board manufacturing methods as one factor. Proposed technologies should be able to achieve sheet resistances of 10 milliohms per square per mil or less; which is comparable to a 2-micron thick copper foil. Preference will be given to technologies enabling layer counts of two or more; especially those with functioning through vias
Flexible Electronics market
Market size from 2016 to 2026 IDTechEx find that the total market for printed, flexible and organic electronics will grow from $26.54 billion in 2016 to $69.03 billion in 2026. The majority of that is OLEDs (organic but not printed) and conductive ink used for a wide range of applications. On the other hand, stretchable electronics, logic and memory, thin film sensors are much smaller segments but with huge growth potential as they emerge from R&D.
Thin, flexible and printed batteries have the potential to be widely used in wearable and medical devices and will reach a market of over $400 million in a decade, according to IDTechEx report Flexible, Printed and Thin Film Batteries 2015-2025: Technologies, Forecasts, Players.
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