30 The PCB Magazine • June 2015
in a matrix with stretchable copper conductors
similar to Figure 5 where the PCBs act as func-
tional islands where the surface mount com-
ponents are adhered and then the entire PCB
island matrix is encapsulated with a protective
elastomeric material. This design affords the en-
tire system to be stretchable. The final wearable
device may be used for close-to-body or on-the-
body applications.
As explained by Wagner and Bauer
[9]
, design
configurations for stretchable circuits includes
waves, meanders, conductive particles embed-
ded in an elastomeric matrices, meshes and
other. The design challenges include protecting
the stretchable circuit from exceeding its elon-
gation to break. The solution is to design the
wearable device as a stretchable system.
Summary
As breakthroughs continue in wearable
technology, any one of these interconnect tech-
nologies could leapfrog past the others in terms
of usability and applicability. Printed circuits
and printed electronics have advanced wearable
technology market. These interconnect tech-
nologies have enabled the growth
of stretchable electronics solutions.
The future of flexible and stretch-
able circuit technologies will require
advancement in materials, standard-
ized commercial design software and
equipment for advanced assembly
and a broad systems understanding
by the product designers to account
for continuous dynamic stresses and
strains brought on by flexing, bend-
ing, twisting, stretching and drop-
ping in an uncontrolled use environ-
ment.
PCB
References
1. "Gartner Says the Internet of
Things Installed Base Will Grow to
26 Billion Units By 2020," Gartner,
12 December 2013.
2. Main Report: An In-depth Look
at Expert Responses |Pew Research
Center's Internet & American Life
Project, May 14, 2014.
3. Global Wearable Technology Market Re-
search Report 2018
4. Wearable Electronics and Technology
Market by Applications
5. IDC 2014.
6. Printed Circuits Handbook v.6, C. Coombs
and H. Holden, McGraw Hill Professional, 2007.
7. High Density Interconnects: Enabling the
Intelligence of Things, W. Beckenbaugh and
J. K. Vrtis, The PCB Magazine, April 2015, pp.
20–30.
8. Design Considerations: Flexible Circuit
vs. Traditional PCB, J. Talbot, The PCB Maga-
zine, April 2015, pp 68–72.
9. "Materials for Stretchable Electronics,"
Sigurd Wagner and Siegfried Bauer, MRS Bulle-
tin v.37 (3), March 2012 pp 207–213.
Figure 6: Example of a stretchable printed electronic
circuit, with ag printed ink patterned on elastomeric
substrate. (courtesy of Flextronics advanced Engineering
Group)
Joan K. Vrtis is the chief
technology officer at Multek
Technologies ltd. in San Jose,
california.
ENABLING SMART WEARABLE TECHNOLOGY continues
FeAtuRe
