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Towards Large-Area Electronic Systems Using Non-Conventional Substrate and Conductor Materials
Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.ORCID iD: 0000-0002-1125-1150
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flexible circuits, also known as flexible printed circuit boards, were originally developed in the 1950s for interconnection between multiple electronic devices when flexibility and movement were required. Nowadays, flexible circuits can be used for implementing electronic systems much more complicated than just interconnections. A commonly seen material combination of flexible circuits is copper foils laminated on polyimide substrates, although these solutions are both expensive and environmentally hazardous. With developments in printed electronics, many non-conventional materials can be used in fabricating flexible circuits that have advantages such as increased flexibility, low cost, a small environmental impact, etc. In addition, fast and efficient manufacturing methods can produce flexible electronics in large volumes. This opens a window of opportunity to create electronic systems over geometrically large areas. This thesis proposes methods and guidelines for how to implement largearea electronic devices using non-conventional flexible materials and technologies. The thesis specifically focuses on electronic systems that integrate both digital and analogue signals. Further, it demonstrates and provides examples of how signals in the microwave frequencies, commonly requiring expensive materials, can be handled with non-conventional materials and technologies. Several conductor-substrate material combinations are used, which are fabricated using industrial processes. The conductor materials include conductive inks, copper foils, and aluminium foils, while the substrate materials comprise papers, a nonwoven fabric, and a polyimide. In particular, methods are investigated in order to achieve a low DC resistance in printed conductiveink-based tracks, which opens the possibilities for them to be used in highcurrent applications. Several surface mounting techniques are developed for incorporating surface mount devices within the fabricated flexible circuits, including the use of low-temperature solder paste, isotropic conductive adhesives, and anisotropic conductive adhesives. Some of the techniques have achieved sufficiently low contact resistance and adequate component bonding strengths, and thus can be used in implementing hybrid electronic systems. In addition, most of the techniques have the potential to be used in automated component assembly lines. As demonstrators, two antenna systems for commercial RFID readers operating at high frequency (13.56 MHz) and ultra-high frequency (867 MHz) iv Abstract bands are implemented, which comprise both digital and analogue signals. The two antenna systems are designed as part of SP4T switching networks using standard antenna elements as the loads of the network. It is shown in the results that both antenna systems have low RF attenuations, the potential to perform passive RFID tag positioning, and the possibility to be expanded to larger areas. Based on the characterisations to the two antenna systems, discussions are made about how large the antenna system areas can be as well as how many antenna elements can be achieved in a single antenna system. This thesis provides a material-to-system approach and demonstrates that non-conventional flexible materials and printed electronic technologies are suitable choices for large-area electronics.

Abstract [sv]

Flexibla kretsar, även kända som flexibla tryckta kretskort, utvecklades ursprungligen på 1950-talet för sammankoppling mellan flera elektroniska enheter när flexibilitet och rörelse var nödvändig. Numera kan flexibla kretsar användas för att implementera elektroniska system som är mycket mer komplicerade än bara sammankopplingar. En vanligt sett materialkombination av flexibla kretsar är kopparfolier laminerade på polyimid-substrat, även om dessa lösningar är både dyra och miljöfarliga. Med utvecklingen inom tryckt elektronik kan många icke-konventionella material användas för att tillverka flexibla kretsar som har fördelar såsom ökad flexibilitet, låg kostnad, en liten miljöpåverkan, etc. I tillägg kan snabba och effektiva tillverkningsmetoder producera flexibel elektronik i stora volymer. Detta öppnar ett fönster av möjligheter att skapa elektroniska system över geometriskt stora områden. Flera kombinationer av material för ledare och substrat används i denna avhandling, som tillverkas med industriella processer. Ledarmaterialen inkluderar ledande bläck, kopparfolier och aluminiumfolier, medan substraten innefattar papper, ett nonwoven-tyg och en polyimid. I synnerhet undersöks metoder för att uppnå låg DC-resistans i tryckta bläckbaserade ledare, vilket också möjliggör användning i högströmstillämpningar. Flera ytmonteringsmetoder utvecklas för att införliva ytmonterade komponenter i de tillverkade flexibla kretsarna, inklusive användning av lödpasta med låg temperatur, isotropa ledande lim och anisotropa ledande lim. Vissa av teknikerna har uppnått tillräckligt lågt kontaktmotstånd och adekvata komponentbindningsstyrkor och kan således användas vid implementering av hybridelektroniska system. Dessutom har de flesta tekniker potentialen att användas i automatiserade komponentmonteringslinjer. Som demonstrator implementeras två antennsystem för kommersiella RFID-läsare som arbetar med högfrekvensband (13.56 MHz) och ultrahögfrekvensband (867 MHz), som innefattar både digitala och analoga signaler. De två antennsystemen är konstruerade som en del av SP4T-nätverk med standardantennelement som nätverksbelastningar. Det visas i resultaten att båda antennsystemen har låga RF-dämpningar, potentialen att utföra passiv RFIDtaggpositionering och möjligheten att utökas till större områden. Baserat på resultaten diskuteras hur stora antennsystemområdena kan vara och hur många antennelement som kan uppnås i ett enda antennsystem. Sammanfattning vi Denna avhandling ger ett material-till-system-tillvägagångssätt och demonstrerar att icke-konventionella flexibla material och tryckt elektronisk teknik är lämpliga val för storskalig elektronik.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2020. , p. 51
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 321
Keywords [en]
Non-conventional materials, large-area electronics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-38955ISBN: 978-91-88947-47-5 (print)OAI: oai:DiVA.org:miun-38955DiVA, id: diva2:1426732
Public defence
2020-05-28, C312, Holmgatan 10, Sundsvall, 09:30 (English)
Opponent
Supervisors
Projects
IDPOSSmartArea
Note

Vid tidpunkten för disputationen var följande delarbete opublicerat: delarbete V (manuskript).

At the time of the doctoral defence the following paper was unpublished: paper V (manuscript).

Available from: 2020-04-30 Created: 2020-04-27 Last updated: 2020-04-30Bibliographically approved
List of papers
1. Soldering surface mount components on screen printed Ag patterns on paper and Polyimide substrates for hybrid printed electronics
Open this publication in new window or tab >>Soldering surface mount components on screen printed Ag patterns on paper and Polyimide substrates for hybrid printed electronics
2018 (English)In: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 3, no 1, article id 015003Article in journal (Refereed) Published
Abstract [en]

The development of printed electronics on flexible substrates is increasing rapidly, where the main benefit is large area and low cost. However, the functionality and performance of printed circuits cannot compete with standard silicon based microprocessors or integrated circuits, though the functionality and performance of printed circuits are increasing. Therefore, in this work we investigate the possibilities of using Sn42/Bi57.6/Ag0.4 low-temperature solder paste together with a reflow solder oven and hot air solder iron to mount regular SMD components on screen-printed silver tracks. It was found that it is possible to solder standard Si SMD pack-ages onto screen-printed Ag ink tracks on paper substrate, however, the component bonding strength to Polyimide were not satisfactory. The resistance of the solder joints was found to be no more than 240 mΩ. The bond strength was found to be higher using the manual hot air sol-der iron than the reflow solder oven. Bending tests show that the bonding strength is higher for the hot air soldered components. Reference samples on FR-4 based copper PCB show a bond strength ~10 times higher but we conclude that it is possible to solder regular Si SMD components onto Ag-printed conductors on paper substrate with good results. The process could be used to fabricate hybrid printed electronics on a standard solder process line.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-32305 (URN)10.1088/2058-8585/aa9dc7 (DOI)000423451500001 ()2-s2.0-85045650822 (Scopus ID)
Projects
IDPOS
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2020-04-27Bibliographically approved
2. Soldering Surface Mount Components onto Inkjet Printed Conductors on Paper Substrate using Industrial Processes
Open this publication in new window or tab >>Soldering Surface Mount Components onto Inkjet Printed Conductors on Paper Substrate using Industrial Processes
Show others...
2016 (English)In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 6, no 3, p. 478-485, article id 7422029Article in journal (Refereed) Published
Abstract [en]

This paper describes mounting of standard surface mount component packages on a paper substrate using an industrial solder process with a low-temperature solder. The use of paper as a substrate for printed flexible electronics is becoming more and more widespread as an alternative to the more commonly used plastic substrates, such as polyethylene and polyimide. Paper has the benefits of being environmentally friendly, recyclable, and renewable, as well as inexpensive. It is shown that it is possible to mount standard surface mount device components on paper substrates using low-temperature solder in an industrial soldering process. The contact resistances obtained are mostly low, although the yield of functioning contacts is low. The reason is cracking of the substrate coating layer that goes through the printed silver tracks. It was observed that the cracks appear mostly close to the contact pads, the most likely cause is thermal mismatch between the coating layer and solder and also thermal expansion of the photo paper resin coating. The smallest component package size, 0201, resulted in the highest yield of >80% with decreasing yield for larger package sizes.

Keywords
Electronic components, printing, soldering, surface-mount technology
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-26841 (URN)10.1109/TCPMT.2016.2522474 (DOI)000372787300017 ()2-s2.0-84960154273 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Projects
IDPOS
Funder
Knowledge Foundation, 20130324
Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2020-04-27Bibliographically approved
3. Enabling paper-based flexible circuits with aluminium and copper conductors
Open this publication in new window or tab >>Enabling paper-based flexible circuits with aluminium and copper conductors
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2019 (English)In: IOP Flexible and Printed Electronics, ISSN 2058-8585, Vol. 4, article id 045007Article in journal (Refereed) Published
Abstract [en]

Implementing electronics systems on paper is an important area of flexible circuit technologies. One of the approaches is to print conductive inks onto paper substrates, on which silicon-based surface mount device components are mounted. However, one of the problems is that the printed conductors have unneglectable resistivity. In this paper, we present paper-based flexible circuits, using copper and aluminium conductors that are laminated onto paper substrates using a high-speed roll-to-roll method. Edge roughness inspections and repeated two-point bending tests are carried out to evaluate the manufactured flexible circuits. Three surface mount techniques are used to assemble standard surface mount device components onto the flexible circuits, including an isotropic conductive adhesive, an anisotropic conductive adhesive, and a low-temperature solder paste. Several characterizations are performed to the surface mount techniques, including contact resistance measurements, component bonding strength tests, assembled circuit bending tests, and scanning electron microscopy. The results of the characterizations suggest that flexible circuits made from Cu with paper substrate achieve satisfactory results for mechanical reliability, all surface mount techniques, and have the potential to be used on automatic component assembly lines. In order to test whether such flexible circuits and surface mount techniques can be used in implementing electronics systems, passive NFC tags with relative humidity sensing functionality are made, which are interrogated by an NFC equipped mobile phone.

Place, publisher, year, edition, pages
Temple Way, Bristol BS1 6HG, United Kingdom: , 2019
Keywords
paper substrate, copper and aluminium conductors, hybrid electronics, surface mounting tecniques, isotropical conductive adhesive, anisotropic conductive adhesive, low-temperature solder paste
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-38098 (URN)10.1088/2058-8585/ab5cef (DOI)000504314100002 ()2-s2.0-85081626216 (Scopus ID)
Projects
SmartArea
Available from: 2019-12-16 Created: 2019-12-16 Last updated: 2020-04-27Bibliographically approved
4. Flexible Circuits Based on Aluminum Conductor and Nonwoven Substrate
Open this publication in new window or tab >>Flexible Circuits Based on Aluminum Conductor and Nonwoven Substrate
Show others...
2019 (English)In: 2019 IEEE International Flexible Electronics Technology Conference (IFETC), IEEE, 2019, p. 1-4Conference paper, Published paper (Refereed)
Abstract [en]

Electronic textiles, integrating functional electronics circuits into fabric materials, are emerging as an important branch of flexible circuits. In this paper, we introduce a novel material combination for electronic textiles that can be used in implementing hybrid electronics. This type of circuits is fabricated by laminating patterned aluminum foils onto a nonwoven substrate in a high-speed roll-to-roll method. An isotropic conductive adhesive and an anisotropic conductive adhesive are used to assemble standard surface mount device components onto the fabricated circuits. The surface mount techniques are characterized by means of contact resistance measurements, component bonding strength tests, circuit bending tests, and scanning electron microscopy. An NFC tag with relative humidity sensing functionality is fabricated to evaluate the fabricated circuits to an electronic system level.

Place, publisher, year, edition, pages
IEEE, 2019
Keywords
Substrates, Bonding, Contact resistance, Surface resistance, Electrical resistance measurement, Sensors, Standards
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-38954 (URN)10.1109/IFETC46817.2019.9073775 (DOI)2-s2.0-85084665118 (Scopus ID)978-1-7281-1778-2 (ISBN)
Conference
2019 IEEE International Flexible Electronics Technology Conference (IFETC)
Available from: 2020-04-27 Created: 2020-04-27 Last updated: 2020-05-26Bibliographically approved
5.
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6. Flexible Circuits and Materials for Large-Area UHF RFID Reader Antenna Systems
Open this publication in new window or tab >>Flexible Circuits and Materials for Large-Area UHF RFID Reader Antenna Systems
2018 (English)In: IOP Flexible and Printed Electronics, ISSN 2058-8585, Vol. 3, no 1, article id 015005Article in journal (Refereed) Published
Abstract [en]

RF electronics commonly incorporate PCB-materials with low loss tangents, which limits its use for large-area applications due to its high cost. This work verifies one alternative solution how non-conventional flexible circuit materials can be used to manufacture large functional surfaces for RF-based applications. Laminated Al foils are used for conducting layers and a flexible foam material is used for substrate. An RFID reader system has been developed to demonstrate the functionality, comprising of eight microstrip antenna elements arranged in a SP4T switching structure covering an area of 1.2 m × 0.6 m. Each antenna element is individually addressable with aid of distributed digital and analogue multiplexer circuitry and it is shown how these components can be soldered directly onto the Al conductors. The constructed system shows good RF performance, both with regards to the materials and to the interconnections with the distributed multiplexer circuitry. It can perform far-field RFID tag reading above its surface without dead zones and the system characterization implies that the concept can be further expanded to cover geometrical areas up to 1000 square meters.

Keywords
UHF RFID, large-area reader antenna system, flexible circuits and materials
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-32307 (URN)10.1088/2058-8585/aaa1f3 (DOI)000424097500002 ()2-s2.0-85045646881 (Scopus ID)
Note

Accepted Manuscript online 15 December 2017

Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2020-04-27Bibliographically approved
7. UHF RFID Shelf Reader Antennas for Object Classification and Distance Estimation of Non-Tagged RFID Objects
Open this publication in new window or tab >>UHF RFID Shelf Reader Antennas for Object Classification and Distance Estimation of Non-Tagged RFID Objects
2017 (English)In: 2017 Ieee International Conference On Microwaves, Antennas, Communications And Electronic Systems (Comcas), IEEE, 2017, p. 289-292Conference paper, Published paper (Refereed)
Abstract [en]

RFID readers serve the obvious role of extracting information from RFID tagged objects. Objects without RFID tags or objects with tags that for some reason are unreadable will not be noted at all when positioned within an RFID reader antenna's interrogation zone. In this paper, we investigate how UHF RFID reader systems for smart shelf applications could also be used for classification and distance estimation of non RFID tagged objects, if the reader modules provide access to antenna S-parameters. The investigation is performed with an inset fed microstrip antenna where objects of different materials are positioned at different heights above the antenna. It is shown how objects are detected and classified in terms of their materialistic properties through S-parameter analysis and how the distance from the antenna to the object could be estimated.

Place, publisher, year, edition, pages
IEEE, 2017
Series
IEEE International Conference on Microwaves Communications Antennas and Electronic Systems, ISSN 2150-895X
Keywords
Antennas, RFID, Dielectrics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-33394 (URN)000426968600065 ()2-s2.0-85045838621 (Scopus ID)978-1-5386-3169-0 (ISBN)
Conference
IEEE International Conference on Microwaves, Antennas, Communications and Electronic Systems (COMCAS), Tel Aviv, ISRAEL, NOV 13-15, 2017
Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2020-04-27Bibliographically approved
8. A Paper-Based Screen Printed HF RFID Reader Antenna System
Open this publication in new window or tab >>A Paper-Based Screen Printed HF RFID Reader Antenna System
2018 (English)In: IEEE Journal of Radio Frequency Identification, ISSN 2469-729X, Vol. 2, no 3, p. 118-126Article in journal (Refereed) Published
Abstract [en]

Screen printing is a stencil process where conductive inks are patterned onto substrates through a fine mesh of threads. Nowadays, screen printing can be used to print RFID antenna structures onto flexible and ultra-low-cost substrates such as pa-per. In this manuscript, we present an HF RFID reader antenna system, operating at 13.56 MHz, using screen printed Ag particle ink as conductor and using HP photo paper as substrate. The proposed antenna system comprises four loop antenna elements, matched to 50 Ω, and one I2C addressed SP4T multiplexer circuitry, controlled through an exterior embedded system. The geometries, designs and characterizations of the antenna system are described in the manuscript in details. Measurement results show that the antenna system has low power reflections and a suitable Q factor. It has a maximum 11.1 cm RFID tag read range at an antenna system input power of 33 dBm. 2D RFID tag positioning can be enabled by utilizing the RFID tag interrogation zones formed by the four loop antenna elements. In addition, a parametric study is carried out to investigate the effect of loop antenna element DC resistance on the antenna element performance. It can be concluded that the proposed method can be used to create low-cost and large-area HF RFID reader antenna systems.

Place, publisher, year, edition, pages
445 Hoes Lane Piscataway, NJ 08854, USA: IEEE, 2018
Keywords
HF reader antenna system, 13.56 MHz, screen printed, paper substrate
National Category
Paper, Pulp and Fiber Technology Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-34384 (URN)10.1109/JRFID.2018.2869494 (DOI)
Projects
IDPOS
Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2020-04-27Bibliographically approved

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