Development of High-speed Long Transmission FPC - Enables 3m Long; 10 Times Longer than Conventional FPC - [432KB]

Development of High-speed
Long Transmission FPC
- Enables 3m Long; 10 Times Longer than Conventional FPC Shigeru Kurihara
Digital equipment including image processing
equipment is increasingly going high-speed. High-speed
is achieved from the transmission properties of the
surrounding peripherals, interfaces and other circuits that
configure the system.
OKI Electric Cable’s high-speed transmission FPCs
(flexible printed circuits) have proven applications in various
fields and have contributed to speeding up, thinning and
lightening the weight of equipment. However, previous
products have been less than 0.3m long making them too
short for large equipment and interface applications.
“High-speed long transmission FPC” is the industry’s
first FPC to extend high-speed transmission to a length of
3m. This FPC can contribute to higher speed, thinner profile,
lighter weight and higher functionality of large equipment
and interfaces. The high-speed long transmission FPC
and efforts to improve the quality of next-generation highspeed transmission are described below.
Product Features
The features of the high-speed long transmission FPC
are given below, and some examples of those features
are shown in Photo 1 through Photo 3.
Three-layer
product
Single-sided
product
Photo 1. High-speed Long Transmission FPC
Double-sided
product
Photo 2. FPC for HDMI 1.3 (Cat.2)
R06pho01
 Impedance matching
It is possible to match impedance whether the line
is a differential transmission line or a single-ended line.
For example, 98Ω, 85Ω differential and 55Ω, 67Ω singleended designs are possible to take into account the
balance of the system.
 Structural design according to application
Wiring patterns, shields and various structural designs
can be amended to the basic structure shown in Figure 1
according to the needs of applications.
 EMC countermeasures
EMC countermeasures can be proposed with various
shielding patterns and materials.
Light-weight, thin-profile, and high-density wiring
FPC has overwhelming advantage over other materials
Oki Technical Review
April 2010/Issue 216 Vol.77 No.1
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Photo 3. Fine Long FPC
for light-weight, thin-profile, and high-density wiring.
As far as thickness of the products is concerned, 50μm
for single-sided and 150μm for double-sided structure is
possible.
For wiring, 180μm pitch (minimum) high-density wiring
Special Edition on Component Technologies Supporting Innovative Design 
Table 1. Market Forecast for Image Processing Equipment
+
GND
-
GND
+/-: Differential signal
GND: Ground
Single-sided structure
(Coplanar)
+
GND
-
GND
Double-sided structure
(Micro-strip)
+
GND
GND
Three-layer structure
(Strip)
Figure 1. Examples of High-speed
Long Transmission FPC Structures
can be achieved.
132.50%
Industrial cameras
(2 products)
25.3 billion yen
30.4 billion yen
120.20%
Inspection applications
(21 products)
180 billion yen
234.1 billion yen
130.10%
118.5 billion yen
165.1 billion yen
139.4%
21.2 billion yen
39.9 billion yen
188.2%
158.6 billion yen
178.6 billion yen
112.6%
565 billion yen
729.6 billion yen
129.1%
Medical
(5 products)
-
% change
81.5 billion yen
Automotive/ITS
(5 products)
GND
2010 estimates
61.5 billion yen
Security
(10 products)
GND
GND
2006
Processing equipment
(5 products)
Total
Source: Fuji-Keizai Group https://www.fuji-keizai.co.jp/market/07083.htm
billion yen in 2010 (up 29.1% from 2006). The research
also speculates an increasing demand for a wide range
of applications in various industries with automotive
and security fields showing the most considerable
growth. Furthermore, the demand for image processing
equipment is likely to spread to electronics, food and other
industries.
 High flexibility (high durability)
It is not possible for other materials to achieve the level
of flexing durability available with the FPC. Phenomenal
flex life can be achieved at micro-R movements that are
R06fig01 Trends in image processing equipment
unthinkable with other materials. For example with a
Image processing refers to the process of utilizing
1.5mm bend radius, flex life of more than a million times
camera
images to perform pattern matching for
is possible.
inspecting and verifying an object or to perform position
Usability in small spaces
measurements.
As mentioned in item , FPC is a thin film and capable
Based on the previously mentioned research report,
of being bent or folded. For instance, it can be bent at
the trends and issues in the image processing equipment
0.1R. When FPC is bent or folded, a force will work
field are presented and the range to which the high-speed
to bend it back to the original state. This force can be
long transmission FPC can contribute is indicated.
minimized for higher flexibility. FPC is well suited for use
Adoption of systems that combine processing
in small spaces and helps contribute to smaller, thinner,
equipment, industry (FA) cameras and test applications
and lighter equipment.
is becoming commonplace in this field. Furthermore,
there is a continuing trend to include image processing
in the design of a production line. Due to digitization
Targeted market
(high-speed) and evolution of software technologies,
The market currently seeing downsizing and higher
applications are expected to expand leading to various
functionality alongside higher speeds is the imaging
new imaging equipment being offered and birth of new
equipment market, and this is where the use of high-speed
businesses. Systems in test applications often employ
long transmission FPC is believed to be most beneficial.
small robots equipped with cameras. The processing
Results of the market research conducted by Fujispeeds of the imaging equipment need to match the
Keizai Group in the field of image processing equipment1)
operating speeds of the robots.
are shown in Table 1. The research summarizes six
Monitoring is the main application in the security field,
markets that surround the industrial (FA) image processing
and surveillance cameras lead the market. Recently, there
equipment including security and automotive. According
has been progress in systems utilizing biometrics and other
to the research, the market is expected to grow to 729.6
image processing. From single-function security systems
Oki Technical Review
April 2010/Issue 216 Vol.77 No.1
to systems integrated with attendance management,
these systems back up the adoption of image processing
technologies. Digitization of image transmission and
miniaturization is also advancing in the security field.
In the automotive/ITS field, backup cameras will remain
the primary application, and demand is assumed to rise
once car navigation becomes standard equipment. Also
expected to increase is car-mounted cameras for image
recognition. Application is not limited to driving support
and can be expanded to authenticate drivers or detect
drivers falling asleep behind the wheel. High reliability and
ruggedness will be required from automotive equipment.
In the mist of sluggish X-ray market, the medical field
is considering the adoption of versatile FPD-equipped
models for use in other areas besides gastroenterological
such as urology and orthopedic surgeries. Interest in
MRIs, high magnetic field machines mainstream in Europe
and the U.S., is growing in Japan and likely to be adopted
by large hospitals. Insurance use and expansion in the
range of screening will spur the growth of advanced PET/
CT. Digitalization of fundus cameras is also progressing,
and solid transitions are expected in the areas of physical
examination and specific insurance guidance.
A common issue shared by all the fields is finding an
innovative way to deliver large volumes of information
“more beautifully and more quickly”. Additionally, wiring
components must evolve into high-density products to
cope with equipments that are getting faster, smaller,
thinner, lighter and packed with more functionalities. This
technical trend will accelerate even further in the future.
High-speed long transmission FPC is a new wiring
component that can contribute to solving issues faced by
image processing equipment.
Differential TDR
Transmission properties of highspeed long transmission FPC
The transmission properties of high-speed long
transmission FPC are outlined below.
 Characteristic impedance
Impedance matching is the basics of high-speed
transmission. FPC is a circuit board, and since circuitry
is formed using photolithographic photolithic methods,
high-resolution high-precision impedance matching is
possible. Value of Zo±5% can be secured. The circuit is
coated with thermoset resin enabling the FPC to retain a
constant structure when it is bend or folded, and there is
little change in impedance. Board material is a highly heatresistant (300ºC≤) polyimide film, so impedance variation
is small even in a high heat environment.
Figure 2 is impedance (100Ω differential) measurement
data for a HDMI 1.3 Cat.2 standard (3.4Gbit/s) FPC. It can
be confirmed that all differential lines are controlled within
100 ± 5%.
 Insertion loss (IL)
Figure 3 shows the insertion loss (IL) data for a single
and double-sided structure using polyimide material and
double-sided structure using higher-grade liquid crystal
polymer material.
No problems were observed with any of the structures
up to the 3GHz band. The differences between the
structures are explained below.
First, comparing the two polyimide-based structures,
the single-sided structure exhibited lower loss. This can
be attributed to the large cross-sectional area and small
conductor loss of the single-sided structure’s wirings. The
cross-sectional area of the single-sided structure is 1.4
× 10-2mm2 as opposed to 4.8 × 10-3mm2 for the double-
(Params) : t(s)
120.0
par(tdr_diff)
0
par(tdr_diff)
115.0
-5
par(tdr_diff)
110.0
-10
-15
par(tdr_diff)
[dB]
(Params)
105.0
100.0
95.0
Liquid crystal polymer double-sided
structure
Polyimide double-sided structure
-35
-40
90.0
-45
85.0
-50
80.0
0.0
2n
4n
6n
t(s)
8n
10n
12n
14n
Figure 2. Impedance of High-speed Long
Transmission FPC (100Ω Differential)
Polyimide single-sided structure
-20
-25
-30
0.1
1
[GHz]
2
3
4
Figure 3. Insertion Loss (IL) of Highspeed Long Transmission FPC
Oki Technical Review
April 2010/Issue 216 Vol.77 No.1
R06fig02
5
10
Special Edition on Component Technologies Supporting Innovative Design 
CLK
DATA0
(H):time(s)
0.4
hex_MASK
0.3
eye((ch1-ch3))
(H)
(H)
DataY=0.15
0.0
DataX=222p
DataY=0.15
-0.1
-0.1
-0.2
-0.2
-0.3
-0.3
-0.4
0.0
-0.4
0.0
222p
444p
time(s)
666p
DATA1
888p
eye((ch1-ch3))
0.4
hex_MASK
0.3
0.3
444p
time(s)
666p
DATA2
(H):time(s)
0.4
222p
0.2
888p
(H):time(s)
eye((ch1-ch3))
hex_MASK
0.2
0.1
0.1
0.0
(H)
DataY=0.15
0.0
-0.2
-0.2
-0.3
-0.3
USB
6
IEEE1394
5
4
PCI Express
(1 lane)
3
Serial ATA
2
SSD
(sequential read
speed)
1
0
DataX=222p
-0.1
7
DataY=0.15
DataX=222p
-0.1
Data transmission (transfer) rate (Gbit/s)
0.1
DataX=222p
0.0
HDMI
(signal line pair)
8
0.2
0.1
(H)
9
hex_MASK
0.3
0.2
-0.4
0.0
(H):time(s)
0.4
eye((ch1-ch3))
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 (year)
Source: Nikkei Electronics No.998, p.41, 2009
-0.4
222p
444p
666p
888p
0.0
222p
time(s)
444p
time(s)
666p
888p
Figure 5. Next Generation Interface Trends
Figure 4. Eye Pattern of High-speed Long Transmission FPC
sided structure. Since the thin double-sided FPC takes
the cross-sectional structure shown in Figure 1, it is
greatly affected by the GND on the backside. Impedance
matching cannot be performed unless the width of the
wiring is narrowed. However, the single-sided structure
does not have a backside GND, and impedance matching
R06fig04
is done with the adjacent GND on the same layer enabling
a wider wiring design.
Next, when the two double-sided structures, one
polyimide and the other liquid crystal polymer, are
compared, the liquid crystal polymer provides lower
loss. This is because liquid crystal polymer is a low-loss
dielectric material, but the material is expensive.
High-speed long transmission FPC material can be
selected from a wide variety of products to balance use,
properties and cost.
Eye pattern
Figure 4 shows the eye pattern data of a polyimide
double-sided structure. Markings shown in the diagram
indicate HDMI standards, and it is considered no good
if the measurements make contact with the markings.
Measurements taken for the high-speed long transmission
FPC show an opening that sufficiently clears the standard
opening and proves the performance of the product is
good.
High-speed trends
Demand for faster image processing equipment is
accelerating. Currently, the interface standards for image
processing equipment are in a transitional period to the
next generation standards. The trends of the standards
are shown in Figure 5. The figure shows transition to
the higher speeds and acceleration of the transitioning in
recent years.
Future development
The high-speed long transmission FPC is capable of
2Gbit/s transmission up to 3m. This long transmission
R06fig05
(10 times than before) was achieved due to OKI Electric
Cable’s expertise in FPC design and manufacturing.
However, high-speed demands and technologies
are only headed in the direction of evolution. This is
evident from the trend toward higher speeds. Further
improvements in transmission quality is required for highspeed long transmission FPC longer than 0.6m to comply
with next generation standards.
OKI Electric Cable is advancing technical innovation
and product development in response to market needs,
and we aim to contribute to the development of future
markets.
In closing, an example way of improving performance
to meet the next generation standards is given. Component
implementation is possible with FPC. If a repeater is
implanted into the FPC, the length can be extended to
more than 2m while still satisfying the next generation
standards. This approach is not possible with any other
wiring material, and it shows one of the advantages of the
FPC. 
References
References
1) Fuji-Keizai
Group Market Information, https://www.fuji-keizai.
co.jp/market/07083.html
Authors
Authors
Shigeru Kurihara, Product Technologies Department, OKI
Electric Cable Flexible Circuit Co., Ltd.
Oki Technical Review
April 2010/Issue 216 Vol.77 No.1
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