SEMI-FlexTech’s FLEX 2019 looked at a wide range of topics on its middle day, Feb. 20, in Monterey, CA. Sessions covered a wide gamut of topics, from Applications and Reliability to Manufacturing, Sensors, Devices and more, and attendees received a wealth of information on the state of the flexible hybrid electronics (FHE) industry, including what’s available in the market and what is being developed in the labs.

Applications were the focus of FLEX Session 5, which started with John Pan, professor, California Polytechnic State University, who presented an overview with “Printed Electronics – A Benchmark Study.” Professor Pan noted that the mobility of organic semiconductors has been increased more than 1,000 times since 2000.
 
“We see what current performance levels are,” Pan observed. “We have investigated printed passives and graphics with embedded electronics; sensors, divided by chemical (gas, biomarkers), electrical, mechanical (strain gage), thermal and EMR (pulse ox); batteries; antennas; audio; photovoltaics and energy harvesting; and integration, high performance circuity and testing, such as organic semiconductors and wafer thinning, and 3D electronics. We introduced a new category, high-performance circuitry, which has relatively low resistance.”
 
Silent Sensors Ltd.’s Brian Zahnstecher followed with his talk on “Batteryless Monitoring System for Real-World Automotive & Flex Applications,” beginning with his definition of energy harvesting and then talking about how it can be used.
 
“Energy harvesting is power capture of free, ambient energy sources,” said Zahnstecher. “There so no such thing as waste heat, just underutilized energy recycling opportunities. The short term goal is to mitigate battery usage, and long term is complete utilization of free energy.”
 
Zahnstecher added that energy harvesting is not all or nothing. “It can be complementary and extend battery life,” he observed. “Opportunities in automotive include vehicle to vehicle autonomous vehicles; onboard sensor networks – tire pressure, oil/water temp, fuel level, passenger telemetry, entry security, anti-counterfeiting; embedded photovoltaic external paneling; and kinetic/vibrational/thermal energy harvesting.” He then offered a case study on tire pressure monitoring systems.
 
Tekscan, Inc. has successfully developed sensors for numerous markets, from health care to automotive, for more than 30 years. Tekscan CTO Robert Podoloff offered his insights in “Development of a High-Speed System for Measuring Dynamic Tire Footprints.”
 
“A pressure mapping system can be used to monitor tires,” Podoloff said. “A pressure mapping system consists of a sensor, electronics and software. The sensor is ultra-thin and customizable, using screen-printed conductive traces. The electronics role is to scan and isolate and report on specific pressure points. With our CrossDrive system, we concentrated on the tire footprint itself; for example, the sensor characterizes tire expansion from centrifugal force.”
 
Yun-Soung Kim, postdoctoral research fellow, Georgia Institute of Technology, concluded the Applications session with “Wireless Skin-Like Electronics (SKINTRONICS) for Persistent Human-Machine Interfaces,” a look at multifunctional real-time health monitors.
 
Another session of interest was Flexible Hybrid Electronics Technology, which featured two talks by Douglas Hackler, president and CEO, American Semiconductor. Hackler’s first talk was on “Automated High-Volume Flip-Chip Assembly for FHE.”
 
“One of the things we are focusing on is direct interconnects,” Hackler said. “One of the bridges we see is an interposer. HD has agreed to coordinate with us to bring it commercially. Let’s push these electronics into places they have never been before.”
 
In his second presentation, “Ultra-Thin and Flexible Bluetooth Low Energy ICs,” Hackler covered the recent introduction of the new FleX-BLE Bluetooth system on chip, which he noted is the industry’s first ultra-thin and flexible 2.4 GHz BLE system on chip. American Semiconductor partnered with Nordic on this system.
 
“Flexible hybrid electronics provide a product solution that combines the best of silicon-based components and flexible organic and printed electronics,” Hackler said. “Reliability is really tied to how robust you can make the thin ICs. Semiconductor on Polymer (SoP) results in ultrathin semiconductor materials that are less than the thickness possible with bare die. 
 
“We feel the flexible electronics market is ideal for SoP,” Hackler added. “Since the technology is so thin, it has come to the attention of the mainstream electronics world. There is a lot of convergence between the flexible electronics world and the traditional electronics world. You can see this in smartphones.”
 
Hackler also reported on two NextFlex projects American Semiconductor is working on. With Boeing, the program objective is to overcome cabling, access and sensor system size constraints, and enable point-of-interest condition monitoring of equipment, test platforms, logistics items and more. NASA is using FleX-BLE to integrate its flexible circuit board motherboard with printed sensors.

During the Devices I session, Brian Berland, chief science officer, ITN Energy Systems, Inc., discussed the latest advances in “Ultra-Thin, Self-Charging Solid-State Battery for Flexible Hybrid Electronic Devices.”
 
“We can create a solid state, thin film battery that is very thin and flexible, as thin as 50 microns,” Borland said. “Because it is a deposited material, you can make it any size that you want. The ultimate idea is to add whatever functionality we want, from gas sensing to navigational sensors, indicator lights, Bluetooth connectivity and more.
 
“A coin cell battery has a lot of energy,” Borland added. “When the battery package thickness comes down, so does energy density. We can achieve the same energy density if we add a photovoltaic (PV) layer to the stack. We developed the Flexible Integrated Power Pack with Lucintech, creating a self-charging solid-state lithium battery (SSLB), and worked with Molex on a charge control circuit so the PV can charge the battery, which can extend the life of the battery almost infinitely when the sun is out.”  
    
Reliability was the focus of FLEX Session 14, with Naotsugu Ando, chief designer, Yuasa System Co. Ltd., discussing “Analysis of Mechanical Stresses on Flexible Devices.”
 
‘We want to find how strain energy affects a sample, what structure is best for each market, and how to reproduce the motions that the market wants,” Ando said.
 
Mark D. Poliks, Empire Innovation professor engineering, professor systems science and industrial engineering, and director, Center for Advanced Microelectronics Manufacturing Binghamton State University, closed the Reliability segment with “Reliability of Printed Flexible Hybrid Electronics.”
  
“We prefer distributed bending for quantitative and qualitative studies,” Poliks noted. “Bending is not only more damaging but also accelerates damage in subsequent testing.”