Integrated Passives... Are We There Yet?
Philip Garrou, CPMT Society president, MCNC Research & Development
Institute, Research Triangle Park, N.C. -- Semiconductor International, 10/1/2005
At a Glance The use of integrated passive devices is clearly one of the
few ways to slim down the size of portable devices or add more features or
benefits.
The drive for passive integration began almost a decade ago, in 1996, when
research institutes at IZM Berlin, IMEC and the University of Arkansas began
showing that resistors, capacitors, inductors and diodes could be fabricated
into a single integrated passive device (IPD) by using thin-film technology.
During the past nine years, this research has grown into a massive body of
work, and has now begun to become a mainstream technology for fabrication of
commercial devices for portable electronics.
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ord=1129166740?) It was clear a decade ago that these IPDs met at least
three of the four key criteria for commercialization (faster, smaller, lighter
and cheaper). The circuits were certainly smaller, lighter and of better
performance than their discrete counterparts, but would they ever be cheaper?
Unless these solutions became price-competitive, they would not become mainstream
technology.
While IPD component price may still be higher today, IPD prices have
continued to drop as order volumes have increased. In addition, it is clear that the
assembled cost of an IPD can compare very favorably with the discrete
solution it is intended to replace. The total assembled cost includes the price of
the discrete components and placement cost, as well as the cost of
procurement and storage. The assembly cost for discrete chip components is nearly
always significantly higher than the cost of the components themselves.
In addition to the clear assembly savings, the proliferation of chip-scale
and wafer-level packaging (WLP) technologies (where the package size is only
slightly larger than the die size) has been quickly assimilated by the IPD
manufacturing community, which is keenly aware of the significant savings in
board space that these low-profile chip scale packages can provide circuit
designers of portable devices. _Figure 1_
(http://www.reed-electronics.com/semiconductor/article/CA6260710?industryid=3026&nid=2012#fig1) shows an example
derived by Bourns, where the discrete components needed to construct a
six-channel ESD/RF filter are compared to its chip-scale IPD counterpart.
1. Discrete vs. an integrated passive device solution for six-channel
ESD/RF filters are compared. (Source: Bourns)
The application driver is mobile communication devices. While the
mid-to-late '90s were a major growth period for mobile phones and laptops, it has only
been in the past five years or so that the premium has been placed on added
functionality, as well as the development of other mobile consumer products,
such as PDAs, digital cameras and digital music devices (i.e., iPODs and
portable GPS devices), driving IPDs to volume manufacturing.
The ~400 components present in today's dual-band cell phones are expected
within three years to be reduced to <150 components. Knowing that 95% of the
total components are passives and that they represent ~70% of the total board
area, one must conclude that cell phone manufacturers' demand for IPDs will
continually increase through this decade. Space on a cell phone board, or other
portable device, is at a premium. The use of IPDs is clearly one of the few
ways to slim down the size of the device or add more features or benefits.
Bourns
Many of Bourns' ESD and EMI/RFI filtering IPDs in chip-scale packages
integrate up to 20-30 components, including resistors, capacitors and diodes. In
some instances, they also include oscillator functions and transistors. Volume
usage for these devices has increased significantly over the past few years
to the point where they are now considered standard product lines. Many of
these devices are available in chip-scale and wafer-level packages.California
Micro Devices (CMD)
CMD's ASIP (application-specific passive device) technology allows for the
integration of spiral inductors, resistors, capacitors and/or ESD protection
diodes onto IPDs to provide EMI filtering, ESD protection and power management
solutions for mobile products, many in their CSP/WLP IPD format. 2.
CMD Praetorian technology includes spiral inductors. (Source: CMD)
A big seller for CMD has been its IEEE 1284 filter for parallel ports. This
device includes 25 resistors, 17 capacitors and 17 ESD protection circuits in
a 28-pin QSOP.
To provide ESD protection and EMI filtering for a cell phone's LCD interface
typically requires as many as 70-80 discrete resistors, capacitors and
diodes. CMD reports that its CM1423 EMI filter and ESD protection array for Secure
Digital interfaces offers a space savings of 90% and a cost savings of 50%
vs. discrete implementation.For high-resolution imagers and color LCDs in
wireless handsets, current EMI filter arrays do not provide effective filtering
performance in the 800 MHz to 2.7 GHz frequency range. The attenuation
performance of low-pass L-C filters developed using CMD's Praetorian technology with
integrated spiral inductors provides -30 to -45 dB attenuation over the 800
MHz to 6 GHz frequency range, a high level of ESD protection and low
parasitic inductances within the device and between the device and the PWB (_Fig. 2_
(http://www.reed-electronics.com/semiconductor/article/CA6260710?industryid=30
26&nid=2012#fig2) ).
STMicroelectronics
STMicroelectronics has been commercializing its IPAD (integrated passive and
active device) technology for several years, and offers a wide array of
integrated passives for mobile phone, PDA, digital camera and notebook computer
wireless functions, such as ESD protection diodes, EMI low-pass filters, line
terminations, pull-up or pull-down resistors, signal switches and RF
components.The application space is expanding
A number of applications are now available as cost-competitive thin-film IPD
devices:
* Low-pass filter — Devices such as cell phones often have data and/or
audio ports for connection to external devices. By their nature, cell phones
generate RF noise, which can be coupled into the data/audio port. The use of
integrated passive low-pass filters attenuates the RF noise, which could
otherwise interfere with the circuitry of the cell phone.
* ESD protection — Many handheld devices have external ports, which
are potential paths for ESD to enter the handheld device and damage the
internal circuitry. Integrated passive and active devices are a very suitable
solution for this type of problem where board area is an issue. Bourns uses a
proprietary back-to-back Zener diode arrangement to provide ESD protection.
* Low-pass filter with ESD protection — This is a combination of
low-pass filter and ESD protection fabricated into a single component.
* Line termination — System bus speeds are increasing all the time,
making line termination a more important consideration. Transmission line
effects, such as reflections, must be controlled in order to prevent data errors.
Terminating bus lines with high-speed Schottky diodes is an effective method
to eliminate this issue.
* Voltage-controlled oscillator — Bourns has designed an 800 MHz VCO
for use in the receiver section of a cell phone. This VCO solution is
fabricated in a 1.5 × 1.0 mm format.
* Diplexer — Dual-band cell phones have a requirement to switch
between two transmit frequencies. Use of a diplexer assists the frequency
selection, while at the same time providing impedance matching and band-pass
filtering.
* EMI filter for LCDs — In mobile phones equipped with color LCDs, the
connections between the graphic controller and the LCD are exposed to the
electromagnetic interferences coming from the antenna. It is necessary to
filter these frequencies to avoid disturbing the video signals. In addition,
mobile phones and PDAs must be protected from potential ESD damage to the ASIC LCD
controller.
* EMI filter and ESD protection for speakers and microphones — EMI/RFI
IPDs have become essential for mobile phone audio circuits where antenna
radiation can cause audible interferences. In addition, most audio amplifiers
integrated in the base band or mounted as standalone devices are sensitive to
ESD when the circuit is exposed to the external headsets, speaker ports or
hands-free devices. IPDs in use in digital cameras are shown in _Figure 3_
(http://www.reed-electronics.com/semiconductor/article/CA6260710?industryid=3026&ni
d=2012#fig3) .
3. IPDs are available for digital camera functions. (Source:
STMicroelectronics)
Packaging foundries coming on board
A sure sign that a technology has "made it" is when it is offered by key
foundries. STATS ChipPAC licensed the SyChip integrated passives technology a
few years ago and currently offers it as its chip-scale module packaging (CSMP)
technology. Its foundry service includes fully characterized resistor,
capacitor, inductor, filter and BALUN libraries complete with electrical models.
It features resistors to 100,000 Ω, capacitors to 1000 pF, inductors to 80 nH
and compact BALUNs for RF applications. Packaging is available in LFBGA, FLGA
and QFN formats. Intarsia technology coming back?
Intarsia, a joint venture between Dow Chemical and Flextronics, started
addressing the integrated passives issue in 1997, developing its
thin-film-on-glass and thin-film-on-silicon technologies for a variety of wireless and RF
applications. Unfortunately, funds ran out, and Intarsia closed its doors in the
spring of 2001 amid the general downturn in the wireless industry. The
Intarsia film technology package and its Passport design library are in the
process of being acquired by Research Triangle Institute (formerly the
Microelectronic Center of North Carolina [MCNC]), which intends to revive the technology
and offer integrated passive development and prototyping activities to go
along with its current bumping and 3-D through-via technologies. Next: IPDs
for implantable medical devices?
There is every indication that progress in electronic miniaturization will
continue to fuel growth in the development of effective medical implants.
Because so much of the body's operation is electrical in nature, nervous
response, sensory input, and muscle control are all likely areas for treatment,
enhancement or replacement using miniaturized electronics.
Medical devices incorporating miniaturized electronics are causing a
rethinking of chronic illness and disability treatment. Hearing aids are one of the
first devices to take advantage of electronic miniaturization. Current areas
of implementation include neuromuscular stimulation, artificial vision and
disc replacement.
For instance, Theken Disc and Valtronic have developed an artificial disc to
replace spinal fusion. The embedded circuitry for this device has several
ICs for performing data acquisition, processing, storage, data transmission,
and power management functions and >80 surface-mount components, mainly
passives. One can easily predict that passive integration will be a major driver for
further reducing the size of such implantable medical devices.
This article was provided by the IEEE Components, Packaging and
Manufacturing Technology (CPMT) Society. _www.cpmt.org_ (http://www.cpmt.org/)
____________________________________
Author Information Philip Garrou is program consultant for the
_Microelectronics Center of North Carolina's Research & Development Institute
(MCNC-RDI)_ (http://www.mcnc.org/) , working on its DARPA 3-D programs. He is
president of the IEEE Components, Packaging and Manufacturing Technology (CPMT)
Society, as well as a Fellow of IEEE and IMAPS. He worked 29 years for Dow
Chemical, where he most recently was director of technology and director of
new business development in Dow's Advanced Electronic Materials business. He
has a B.S. in chemistry from North Carolina State University and a Ph.D. in
chemistry from Indiana University.
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