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SCB and SMI: two stretchable circuit technologies, based on standard printed circuit board processes

Jan Vanfleteren UGent, Thomas Loeher, Mario Gonzalez, Frederick Bossuyt UGent, Thomas Vervust UGent, Ingrid De Wolf and Michal Jablonski UGent (2012) CIRCUIT WORLD. 38(4). p.232-242
abstract
Purpose – In the past 15 years stretchable electronic circuits have emerged as a new technology in the domain of assembly, interconnections and sensor circuits and assembly technologies. In the meantime a wide variety of processes with the use of many different materials have been explored in this new field. The purpose of the current contribution is for the authors to present an approach for stretchable circuits which is inspired by conventional rigid and flexible printed circuit board (PCB) technology. Two variants of this technology are presented: stretchable circuit board (SCB) and stretchable mould interconnect (SMI). Design/methodology/approach – Similarly as in PCB 17 or 35mm thick sheets of electrodeposited or rolled-annealed Cu are structured to form the conductive tracks, and off-the-shelf, standard packaged, rigid components are assembled on the Cu contact pads using lead-free solder materials and reflow processes. Stretchability is obtained by shaping the Cu tracks not as straight lines, like in normal PCB design, but as horseshoe shaped meanders. Instead of rigid or flexible board materials, elastic materials, predominantly PDMS (polydimethylsiloxane), are used to embed the conductors and the components, thus serving as circuit carrier. The authors include some mechanical modeling and design considerations, aimed at the optimization of the build-up and combination of elastic, flexible and rigid materials towards minimal stress and maximum mechanical reliability in the structures. Furthermore, details on the two production processes are given, reliability findings are summarised, and a number of functional demonstrators, realized with the technologies, are described. Findings – Key conclusions of the work are that: supporting the metal meanders with a flexible carrier prior to embedding in an elastic substrate substantially increases the reliability under mechanical stress (cyclic uniaxial stretching) of the stretchable interconnect and the transition areas between rigid components and stretchable interconnects are the zones which are most sensitive to failure under mechanical stress. Careful design and technology implementation is necessary, providing a gradual transition from rigid to flexible to stretchable parts of the circuit. Originality/value – Technologies for stretchable circuits, with the same level of similarity to standard PCB manufacturing and assembly, and thus with the same high potential for transfer to an industrial environment and for mass production, have not been shown before.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
Stretchable circuits, Elastic circuits, DESIGN, ELECTRONICS, INTERCONNECTS, Circuits, PCB, Printed-circuit boards, Stretchable electronics
journal title
CIRCUIT WORLD
volume
38
issue
4
pages
232 - 242
Web of Science type
Article
Web of Science id
000314204300006
JCR category
ENGINEERING, ELECTRICAL & ELECTRONIC
JCR impact factor
0.683 (2012)
JCR rank
169/242 (2012)
JCR quartile
3 (2012)
ISSN
0305-6120
DOI
10.1108/03056121211280440
project
EC-FP6-STELLA
project
EC-FP7-PASTA
project
EC-FP7-PLACE-it
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
3067253
handle
http://hdl.handle.net/1854/LU-3067253
date created
2012-12-07 09:51:48
date last changed
2013-07-04 14:32:16
@article{3067253,
  abstract     = {Purpose -- In the past 15 years stretchable electronic circuits have emerged as a new technology in the domain of assembly, interconnections and sensor circuits and assembly technologies. In the meantime a wide variety of processes with the use of many different materials have been explored in this new field. The purpose of the current contribution is for the authors to present an approach for stretchable circuits which is inspired by conventional rigid and flexible printed circuit board (PCB) technology. Two variants of this technology are presented: stretchable circuit board (SCB) and stretchable mould interconnect (SMI). Design/methodology/approach -- Similarly as in PCB 17 or 35mm thick sheets of electrodeposited or rolled-annealed Cu are structured to form the conductive tracks, and off-the-shelf, standard packaged, rigid components are assembled on the Cu contact pads using lead-free solder materials and reflow processes. Stretchability is obtained by shaping the Cu tracks not as straight lines, like in normal PCB design, but as horseshoe shaped meanders. Instead of rigid or flexible board materials, elastic materials, predominantly PDMS (polydimethylsiloxane), are used to embed the conductors and the components, thus serving as circuit carrier. The authors include some mechanical modeling and design considerations, aimed at the optimization of the build-up and combination of elastic, flexible and rigid materials towards minimal stress and maximum mechanical reliability in the structures. Furthermore, details on the two production processes are given, reliability findings are summarised, and a number of functional demonstrators, realized with the technologies, are described. Findings -- Key conclusions of the work are that: supporting the metal meanders with a flexible carrier prior to embedding in an elastic substrate substantially increases the reliability under mechanical stress (cyclic uniaxial stretching) of the stretchable interconnect and the transition areas between rigid components and stretchable interconnects are the zones which are most sensitive to failure under mechanical stress. Careful design and technology implementation is necessary, providing a gradual transition from rigid to flexible to stretchable parts of the circuit.
Originality/value -- Technologies for stretchable circuits, with the same level of similarity to standard PCB manufacturing and assembly, and thus with the same high potential for transfer to an industrial environment and for mass production, have not been shown before.},
  author       = {Vanfleteren, Jan and Loeher, Thomas and Gonzalez, Mario and Bossuyt, Frederick and Vervust, Thomas and De Wolf, Ingrid and Jablonski, Michal},
  issn         = {0305-6120},
  journal      = {CIRCUIT WORLD},
  keyword      = {Stretchable circuits,Elastic circuits,DESIGN,ELECTRONICS,INTERCONNECTS,Circuits,PCB,Printed-circuit boards,Stretchable electronics},
  language     = {eng},
  number       = {4},
  pages        = {232--242},
  title        = {SCB and SMI: two stretchable circuit technologies, based on standard printed circuit board processes},
  url          = {http://dx.doi.org/10.1108/03056121211280440},
  volume       = {38},
  year         = {2012},
}

Chicago
Vanfleteren, Jan, Thomas Loeher, Mario Gonzalez, Frederick Bossuyt, Thomas Vervust, Ingrid De Wolf, and Michal Jablonski. 2012. “SCB and SMI: Two Stretchable Circuit Technologies, Based on Standard Printed Circuit Board Processes.” Circuit World 38 (4): 232–242.
APA
Vanfleteren, Jan, Loeher, T., Gonzalez, M., Bossuyt, F., Vervust, T., De Wolf, I., & Jablonski, M. (2012). SCB and SMI: two stretchable circuit technologies, based on standard printed circuit board processes. CIRCUIT WORLD, 38(4), 232–242.
Vancouver
1.
Vanfleteren J, Loeher T, Gonzalez M, Bossuyt F, Vervust T, De Wolf I, et al. SCB and SMI: two stretchable circuit technologies, based on standard printed circuit board processes. CIRCUIT WORLD. 2012;38(4):232–42.
MLA
Vanfleteren, Jan, Thomas Loeher, Mario Gonzalez, et al. “SCB and SMI: Two Stretchable Circuit Technologies, Based on Standard Printed Circuit Board Processes.” CIRCUIT WORLD 38.4 (2012): 232–242. Print.