Intelligent Warning Sign System Utilising Printed Functionalities and Hybrid Integration

Transcription

1 Intelligent Warning Sign System Utilising Printed Functionalities and Hybrid Integration Kimmo Keränen, Samuli Yrjänä, Arttu Huttunen, Marko Korkalainen and Markus Tuomikoski VTT Technical Research Centre of Finland Kaitoväylä 1, Oulu, FINLAND Abstract The direct medical care cost of all hospital treated injuries in the EU is estimated to be at least 78 billion Euros each year. Therefore, significant savings can be achieved in economical and human resources, when amount of injuries are decreased. graphical warning sign. Intelligent and active warning sign alerts person approaching potentially dangerous spot using both visual and audible warning. In areas without infrastructure, however, intelligent warning sign need to be autonomous. We have manufactured an intelligent and autonomous warning sign prototype utilising printed functionalities and hybrid integration. Our intelligent warning sign system utilises low energy radio network operating at 2.4 GHz ISM waveband in wireless communication. Radio system provides wireless link to other warning signs nearby and up and down gateway to server. In addition, system retains energy harvesting system based on flexible solar cell and bendable Li-Ion battery. Sensing is based on infrared sensor enabling person detection by emitted thermal radiation from 2 meter distance. Microcontroller decodes sensor signal and controls operations for warning signals based on six blinking LEDs and beeping buzzer. LED flexible substrate was PET foil on which conductive traces were printed using Asahi 411AW silver ink. Miniature high brightness 0402 size µsmd LEDs producing up to 50 mcd in ±65º angle were bonded on PET foil using isotropic conductive adhesive, type EPOTEK H20E. Final measures of the prototype were 75 mm x 220 mm with maximum thickness of 20 mm and weight of 58 grams. System assembly with rigid central part and flexible flanges enabled prototype attachment on flat, angulated or curved surfaces. Implemented warning sign system platform offers also possibility to implement other intelligent guiding and sensing information transmission applications in areas lacking connection to grid and wired Internet. Introduction Injuries are an important and largely preventable public health problem. In fact, with almost one quarter of a million fatalities each year, injury is after cardiovascular disease, cancer and respiratory disease the fourth common cause of death within the EU [1]. Accidents and injuries are the leading cause of death in children, adolescents and young adults. The direct medical care cost of all hospital treated injuries (inpatients and outpatients) in the EU is estimated to be at least 78 billion Euros each year. While the health burden of communicable diseases is reducing owing to better prevention and treatment, injury morbidity remained almost unchanged over the past decades, resulting into an increased share of injuries in the total burden of ill health. Typically most probable areas for accidents are construction sites and factories [2]. In construction sites there is typically lot of independent actors and unfinished infrastructure, which causes difficulty in effective communication between workers about potentially dangerous spots or actions. Also in harbours and excavations there might be items, such as pillars and machines or possibility to fall, which may cause damages or potential danger to persons approaching dangerous locations. graphical warning sign according to the observations made in research with drivers and dynamic signing [3]. Same way it seems logical that persons approaching potentially dangerous spot can be alerted more effectively with active warning sign compared to traditional passive graphical sign. In order to effectively draw person s attention to warning sign it is beneficial to use combination of different alerting signals. Combination of both visual and noise signals advance perceiving and reacting of persons to potential danger [2]. In areas missing infrastructure, however, warning sign need to be autonomous. Autonomous operation of a warning system is possible to attain by integrating energy harvesting and energy reservoir functionalities in the system [4]. Organic and large area electronics (OLAE) is an emerging technology with potential for disruption, based on organic and oxide semiconducting materials instead of conventional silicon semiconductors [5]. On the other hand new mega trend, Internet-of-Things (IoT), has rapidly grown a driving force to development of OLAE field. Not only people are connected to internet but all objects around will have unique digital identity. According to Cisco this is an opportunity for tens of trillion dollars business [6]. This will bring a lot of opportunities for OLAE technologies because large area cost efficient production technologies, flexible and 3D integrated components are needed to embed this intelligence everywhere. Huge sensor visions for IoT s needs are presented for the future [7]. In order to respond this need new technologies to produce electronics and integrate it must be developed. Existing sensor production capacities are simply insufficient and new ways to fulfill future needs. Roll-to-roll (R2R) manufacturing technologies are strong candidates to offer required high volume production capabilities not only for sensors but also for energy harvesting and energy storing required in /14/$ IEEE 2014 ELECTRONICS SYSTEM-INTEGRATION CONFERENCE

2 autonomous sensor systems. Flexible energy harvesting and storing components can be processed by printing methods enabling high volume production of these devices [8-10]. Our warning sign demonstrator utilises hybrid integration technology potentially combining best parts of OLAE technologies and conventional semiconductor electronics and high volume R2R manufacturing processes. Printing, device assembly and lamination processes can be performed in R2R production mode at VTT s pilot line enabling cost efficient manufacturing of system, when the structure is thin and flexible. In Figure 1 Maxi R2R pilot printing machine is shown. In Maxi line shielding of printed structures and assembled components by lamination can be processed. (ACA). Non- conductive adhesive (NCA) can be used for mechanical attachment of components. In Figure 3 a red LED chip is bonded on silver ink printed contact area on polymer substrate. Figure 3. Red LED chip bonded on silver ink printed contact area. Figure. 1. Maxi R2R pilot printing machine In Figure 2 Datacon 2200 EVO R2R pick-and-place assembly machine is shown. Warning sign design At the beginning of the design process target functionalities and requirements for intelligent warning system were listed as following: - system needs to be intelligent and active meaning that there need to be sensing of person and active warning of person using both visual and audible signals in addition to passive graphical warning information. - system needs to be autonomous meaning that connection to the grid is not needed and energy required for system operation is achieved by energy harvesting using solar cells and stored to energy reservoir, such as flexible battery. - system needs to have wireless connection to server proving up and down gateway to Internet. - system needs to be as thin and flexible as possible to provide easy mounting of sign and minimise usage and weight of materials. In the next phase preliminary design concepts to meet the targeted functionalities were created, see Figure 4. Figure 2. Datacon 2200 EVO R2R pick-and-place assembly machine Modern bonding machines, such as Datacon 2200 EVO pick-and-place bonding machine, allows fast and versatile device, component and flexible PWB bonding on FR4, LTCC, silicon and polymer substrates. Machine operates in stop-and-go mode so that assembly is performed on 200 mm (W) x 300 mm (L) work area on halted foil. When the assembly is finalised on the whole work area the roll is transferred 300 mm forward and halted again in sequential assembly process. EVO can pick-and-place bare dies, SMD components and flex components. Bonding of devices and components is performed using adhesives, such as isotropic conductive adhesive (ICA) and anisotropic conductive adhesive Figure 4. Preliminary design concepts to meet targeted functionalities of the active warning sign. From Figure 4 we can see that the sensing of person will be implemented using passive infrared (PIR) sensor. When the person is detected, combination of both visual and audible warning signals will be produced using

3 blinking LEDs and a beeping buzzer in order to ensure excellent observation of the warning sign alert. Energy harvesting will be provided by a flexible solar cell and harvested energy will be stored in a bendable battery. Wireless connection to server is provided by a low energy radio network operating at 2.4 GHz ISM waveband. System PWBs will be a thin and flexible polymer substrates with silver ink printed conductors and bonding pads. LEDs, solar cell and battery are assembled on these substrates. Next the components needed to implement functionalities were selected and alerting LED module substrate, battery and solar cell layouts were designed. Custom rigid PCB was designed to integrate radio link, PIR sensor and buzzer. This rigid PCB part was designed to be placed in the middle of the warning sign. In addition, a mechanical cover for this rigid PCB was designed and to be manufactured by rapid prototyping. In Figure 5 selected components and designed connections for system manufacturing are shown. producing up to 50 mcd in ±65º angle were selected to produce visual alert. Finally, detailed layout designs and connections for both rigid and flexible PWBs were performed. In addition, a graphical layout design for warning sign was performed. In Figure 6 designed mechanical cover, flexible PWBs and graphical layout is shown. Figure 6. Designed mechanical cover, flexible PWBs and graphical layout for warning sign. Figure 5. Selected components and designed connections for warning sign prototype. Commercial PIR sensor type EKMB manufactured by Panasonic was selected as a sensing element. Buzzer was also commercial component, type MAGN 2.3KHZ 12MM PC MT manufactured by Mallory Sonalert Products Inc. Buzzer height was 10 mm and PIR sensor height from the PCB surface was 14.4 mm. The height of the PIR sensor determined the total thickness of the rigid middle part to be 20 mm. Commercial thin and flexible amorphous silicon solar cell measures 36.5 mm (W) x 64 (L) mm x 0.22 mm (T) model SP-37 was selected as energy harvesting component. SP-37 was specified to provide 3V, when illuminated with AM1.5 sun light. Commercial rechargeable bendable battery, which measures were 36 mm (W) x 43 mm (L) x 0.6 mm (T) and capacity of 50 ma manufactured by PowerStream was selected as energy reservoir. Transparent PET foil, type Melinex 504ST, was selected as substrate material on which conducting traces and bonding pads will be printed using Asahi 411AW silver ink Miniature high brightness 0402 size red µsmd LEDs Manufacturing and operational testing of warning sign The mechanical cover of rigid PCB consisted of two parts, which were manufactured by rapid prototyping. In Figure 7 the machine used in manufacturing of parts, EDEN 260V, is shown. Figure 7. EDEN 260V rapid prototyping machine used in manufacturing of mechanical cover parts of sign. Two mechanical cover parts for rigid PCB were manufactured using Durus material, which is

4 polypropylene like white plastic material. Front cover was equipped with small towers providing alignment and fixing to the holes of rigid PCB. Rigid PCB was placed into the front cover and back cover was fixed to the front cover using small screws. At the same time, the rigid PCB was fixed between the front and back cover. In Figure 8 high brightness AlInGaP µsmd red LED type VLMS1500-GS08 is shown. The dimensions of the LED are 1 mm (Length) x 0.5 mm (Width) x 0.35 mm (Height). LED typical wavelength was specified to be 631 nm and brightness 54 mcd using 20 ma operating current and voltage of 2 V. Figure 8. High brightness red µsmd LED for visual alert. The LEDs were bonded on PET foil, type Melinex 504ST equipped with Asahi 411AW silver ink printed conduits and bonding pads. Six LEDs were bonded in triangular form on the PET substrate. Isotropic conductive adhesive was used in LED bonding and the adhesive was cured using heat. LED foil was attached on top of curved mechanical cover using pressure sensitive adhesive (PSA) and connected to the rigid PCB using flex connector. Solar cell and battery were bonded of PET substrate using isotropic conductive adhesive and contacted to the rigid PCB using flex connectors. Finally, a graphical polymer foil equipped with holes for sensor and buzzer and transparent windows for LEDs and solar cell was attached on top of mechanics, solar cell and battery using PSA. In addition, graphical polymer foil fixed solar cell foil, battery foil and mechanics together. Final measures of the manufactured prototype were 75 mm x 220 mm with maximum thickness of 20 mm and weight of 58 grams. System assembly with rigid central part and flexible flanges enabled prototype attachment on flat, angulated or curved surfaces. In Figure 9 the manufactured intelligent warning sign prototype is shown. Figure 9. Intelligent warning sign prototype. Warning sign system operation was successfully tested. Individual sign observed approaching person from two meters distance and alerted other signs nearby within one second through gateway. Distance between sensing sign and signal receiving sign from gateway station was typically some tens of meters in open air. Discussion In order to respond the need set by IoT concept to produce huge amount of intelligent sensors in the future, high volume production methods are pursued. We believe that R2R high volume manufacturing technologies are offering cost efficient solution to produce trillions of sensors and sensors systems in the future. At the moment, however, performance and reliability of all printed sensors and especially sensor systems is not typically at acceptable level for applications. We see that required performance and reliability of sensor systems for many applications can be achieved now utilising hybrid integration technologies. Performance and reliability of systems is based on utilisation of conventional semiconductor devices providing processing, driving and communicating functionalities required in applications. In our hybrid integration manufacturing concept sensor system backplane is R2R printed on thin and flexible polymer substrates, conventional semiconductor devices and components are R2R bonded on substrate and devices and bonds are shielded by lamination or overmoulding when needed. In addition, we are developing roll-to-sheet (R2S) and (R2R) manufacturing technologies to add optical and mechanical structures on assembled systems. Adding of optical and mechanical structures is typically implemented utilizing advanced injection overmoulding or 3D printing technologies. Autonomy of future IoT sensor systems can be achieved by R2R printed organic solar cells (OSCs) and rechargeable batteries, which can be printed directly on the sensor system backplane. Development of printed sensors and sensor signal processing electronics will enable manufacturing of very cost efficient sensor systems in the future. Despite the on-going very positive development related to all printed sensor systems, integration of high performance intelligence and connectivity functionalities into the IoT sensor systems, however, will still require utilisation of conventional

5 semiconductor devices and hybrid integration manufacturing processes during coming years. Conclusions graphical warning sign. We have manufactured an intelligent and autonomous warning sign prototype utilising printed functionalities and hybrid integration potentially combining best parts of OLAE technologies and conventional semiconductor electronics and high volume R2R manufacturing processes. Our intelligent warning sign system provides wireless link to other warning signs nearby and wireless gateway to Internet utilising low energy radio network operating at 2.4 GHz ISM waveband. In addition, system retains energy harvesting system based on flexible solar cell and bendable Li-Ion battery. Sensing was based on infrared sensor sensing thermal radiation created by a person. Microcontroller decoded sensor signal and controlled operations for warning signals. Both audible and visual alerting signals based on six blinking LEDs and beeping buzzer were utilised for increased perceptivity of warning. Final measures of the prototype were 75 mm x 220 mm with maximum thickness of 20 mm and weight of 58 grams. System assembly with rigid central part and flexible flanges enabled prototype attachment on flat, angulated or curved surfaces. Warning sign system operation was successfully tested. Individual sign noticed approaching person from two meters distance and alerted other signs nearby within one second through gateway. The demonstrated warning sign system platform offers also possibility to implement other intelligent guiding and sensing information transmission applications in areas lacking connection to grid and wired Internet. Acknowledgments This study was performed under VTT s PRO-IoT program and financial support. Co-workers at VTT providing assistance and advice are acknowledged. References 1. EuroSafe, Injuries in the European Union, Report on injury statistics , Amsterdam, Chan, A. and Ng, A., Perceptions of implied hazard for visual and auditory alerting signals Safety Science, Vol. 47, No. 3 (2009), pp Sisiopiku, V. and Elliot, J., Active Warning Systems: Synthesis, Journal of Transportation Engineering, Vol. 131, No. 3 (2005), pp Keränen, K. et al., Demonstrators for autonomous automotive and signage applications by bonding flexible solar cells, batteries and LED elements on large area polycarbonate backplanes, Proc 4 th Electronic System-Integration Technology Conference (ESTC), Amsterdam, Netherlands, Sept. 2012, pp Photonics21 A European strategy for Organic and Large Area Electronics (OLAE), vision paper Bradley, J. et al. Embracing the Internet of Everything To Capture Your Share of $14.4 Trillion More Relevant, Valuable Connections Will Improve Innovation, Productivity, Efficiency & Customer Experience, White Paper, Cisco Systems Inc., Sensors Summit, Trillion sensor roadmap, Stanford University, October 23-25, Krebs, F., Fabrication and processing of polymer solar cells: A review of printing and coating technologies, Solar Energy Materials & Solar Cells, Vol. 93, No. 1-2 (2009), pp Kopola, P. et al., Gravure printed flexible organic photovoltaic modules, Solar Energy Materials & Solar Cells, Vol. 95, No. 5 (2011), pp Gaikwad, A. et al., A flexible high potential printed battery for powering printed electronics, Applied Physics Letters, Vol. 102, No. 23 (2013), pp