Low-Cost Millimeter-Wave Transceiver Module using
SMD packaged MMICs
M. van Heijningen1, G. Gauthier2
1
TNO Physics and Electronics Laboratory (TNO-FEL), Oude Waalsdorperweg 63, 2597 AK The Hague,
The Netherlands, email: M.vanHeijningen@fel.tno.nl
2
Thales Airborne Systems, 2 avenue Gay-Lussac, 78851 Elancourt Cedex, France,
email: gildas.gauthier@fr.thalesgroup.com
Abstract — This paper presents a novel approach to
realize low-cost millimeter-wave modules using only SMD
packaged MMICs integrated on a single organic substrate.
This approach is demonstrated on a 38 GHz transceiver
module for point-to-point LMDS communication systems.
The required SMD package technology and demonstrator
have been developed in the 5th framework European IST
project “Surface Mount Assembly for Communication Kband Systems” (SMACKS). Two types of SMD packages
have been developed based on LTCC technology for the
low-power devices and an organic package for the highpower amplifier. The use of only packaged devices enables
low-cost module manufacturing without the need for
specialized equipment and without yield loss from handling
bare die MMICs. The estimated cost reduction of such a
module, with respect to a module using bare die components
and mixed substrate technologies, is around 20%. A
disadvantage of this approach is that the density of
integration is low, since each active device is housed in its
own package.
I. INTRODUCTION
Increase in mobile communication and deployment of
new 3G systems requires extension of the mobile and
cellular backhaul infrastructure. The required microwave
transceiver modules are generally constructed using several different substrate materials and dedicated mounting
technologies for each type of MMIC, ranging from Surface Mount Device (SMD) packaged MMICs to wirebonded bare dies. The design and assembly of these
modules is a complex and costly task. Strong price pressure on these millimeter-wave transceiver modules however, calls for a new low-cost design approach. Recently,
more and more MMICs are available as SMD components [1]-[4], which enable low-cost manufacturing of
transceiver modules. This concept has been proven up to
frequencies around 30 GHz [5]. The 5th framework European IST project “Surface Mount Assembly for Communication K-band Systems” (SMACKS) is aimed at extending the Surface Mount Technology (SMT) to millimeter-wave frequencies. This will enable low-cost millimeter-wave transceiver modules, manufactured on a
single substrate material, using only packaged MMICs.
This concept is proven by realizing a 38 GHz demonstrator transceiver for point-to-point LMDS communication systems, using new SMD packages based on organic
and Low-Temperature Co-fired Ceramic (LTCC) tech-
nologies. The demonstrator module is currently under
characterization.
II. TECHNOLOGY CHARACTERIZATION
The performance of a millimeter-wave module
depends heavily on the electrical properties of the
materials used for packaging and motherboard. Often
these data are only available up to 10 GHz. Therefore it
is necessary to characterize the used materials for the
SMD packages and motherboard, organic Rogers4003
and DuPont951 LTCC, up to at least 38 GHz. This
characterization has been performed on a number of test
runs. Two important electrical parameters are the
dielectric constant and the loss of transmission lines.
These parameters have been calculated from “on-wafer”
measurements of 50 ȍ transmission lines on a 200 µm
thick Rogers4003 substrate and 200 µm thick DuPont951
LTCC substrate. The measured effective dielectric
constant İeff shows a gradual increase from 10 GHz to
40 GHz, which corresponds with the theoretical
behavior. The measured İeff is 2.76 and 2.86 for
Rogers4003 and 5.38 and 5.69 for DuPont951 at
respectively 10 and 40 GHz. The measured loss of a
50 ȍ transmission line at 40 GHz is 0.065 dB/mm for
Rogers4003 and 0.091 dB/mm for DuPont951. These
experiments have shown that both materials can be used
for applications at 40 GHz and the results have been used
during the design of the SMD packages and the
transceiver motherboard.
III. SMT PACKAGE TECHNOLOGY
Currently many MMIC packaging technologies can be
used, depending on the MMIC type, application and frequency range. Still, the high-power amplifier MMIC is
often mounted on a special metal carrier for good thermal
conductivity. Within the SMACKS project, two different
low-cost MMIC packages have been developed: an organic package for high-power applications and an LTCC
package for low- and medium-power MMICs. The organic package is constructed from one layer of 200 µm
thick Rogers4003. The high-power MMIC is mounted on
a piece of copper plating in a cavity that is directly connected to the backside metal. Thus, the package adds
34th European Microwave Conference - Amsterdam, 2004
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almost no extra thermal resistance and also provides a
very low inductive path from MMIC to ground, which is
needed to prevent instability. A cross section of the organic package is shown in Fig. 1. Fig. 2 shows a power
amplifier MMIC including barcaps mounted in this package. Measurements on the packaged power amplifier
have shown that the added insertion loss caused by the
package is around 1.5 dB at 40 GHz. The return loss after
packaging is better than 10 dB.
lid
MMIC
copper plating
Fig. 1.
200 um
RO4003
Cross section of the organic SMD power package.
Fig. 4. 36-40 GHz low noise amplifier MMIC mounted on
top of the LTCC package.
Fig. 2. Top view of a 38 GHz power amplifier MMIC
including barcaps mounted in an organic SMD power package.
Fig. 5.
The LTCC package is constructed from two layers of
200 µm thick DuPont951. The MMIC is mounted on a
ground pad that is connected with an array of vias to the
bottom side. The MMIC can be mounted on the top layer,
but also in a cavity created in the top layer. When the
MMIC is placed in a cavity, the thermal resistance and
parasitics ground inductance are lowered, which is often
needed for reliable and stable operation. Fig. 3 shows the
cross section of this package. Fig. 4 shows a 36-40 GHz
low noise amplifier MMIC mounted on the top layer of
the LTCC package. Fig. 5 shows an MMIC that is placed
in the cavity of the LTCC package, before the packages
are cut from the fired tape.
Both package types can easily be fabricated using
standard low-cost printed circuit board and LTCC
processing. The design can easily be adapted to fit any
MMIC size, include decoupling capacitors and provide
compensation circuits in the package RF lines, as can be
seen in Fig. 5 on the left. The current footprint is
designed for microstrip connection, but a coplanar design
is also possible.
lid
MMIC
200 um
LTCC
200 um
LTCC
Fig. 3. Cross section of the LTCC SMD package, with the
MMIC mounted in a cavity.
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MMIC placed in the cavity of the LTCC package.
IV. LOW-COST MODULE TECHNOLOGY
The transceiver module is constructed on a single layer
organic substrate of 200 µm thick Rogers4003. This
substrate is bonded to an aluminum backplate with a
100 µm thick electrically and thermally conductive glue
layer. All active MMIC devices, including a custom
designed 30 dBm P1dB 38 GHz high-power amplifier,
have been packaged in LTCC or organic SMD packages.
Beneath the ground-pad of each MMIC an array of vias
is made for electrical and thermal connection of the
package ground to the backplate. The necessary filtering
is performed using coupled-line filters that are integrated
on the same substrate. A cross section of the motherboard
is shown in Fig. 6.
34th European Microwave Conference - Amsterdam, 2004
low: each MMIC is mounted in a single package and the
SMD packages need to be separated by a small distance.
Also, the maximum gain for an active device inside a
package is limited to prevent oscillations and instability.
MMIC
200um
RO4003
100um glue layer
Metal
backplate
Fig. 6. Cross section of the motherboard showing an organic
power package connected with thermal vias to the metal
backplate.
To verify the maximum junction temperature of the
packaged 30 dBm HPA, mounted on this motherboard,
thermal simulations have been performed using
HarvardThermal TAS [6]. The cross section of the
simplified 3D thermal model is shown in Fig. 7. Only the
copper ground-pad part of the organic package has been
included in the model. The heat is generated by two
8x75um FETs, dissipating 1 W/mm gate width. The
maximum junction temperature at the worst case ambient
of 80°C is around 159°C, which is well below the
maximum junction temperature of 175°C. It can be seen
that a large temperature difference occurs across the
conductive glue layer, which has a thermal conductivity
of only 7 W/mK. Also the functioning of the thermal vias
in the Rogers substrate can be seen that conduct the heat
towards the baseplate. The maximum allowable power
dissipation in the organic package is not limited by the
package itself, but only by the construction of and
mounting on the motherboard.
2 8x75um FETs
GaAs
copper groundpad
Rogers
4003
copper
vias
IV. DEMONSTRATOR MODULE
The 38 GHz SMACKS demonstrator module is shown
in Fig. 8. The transmit and receive part are physically
separated on two boards. The RF is connected through
waveguide connectors at the side of the module. The
maximum gain for a packaged MMIC has been limited to
approximately 20 dB. This has an impact on the
definition of the MMIC line-up. The chosen line-up is
shown in Fig. 9. Each solid block represents one
packaged MMIC. Variable attenuators have been
included in both the transmit and receive chain for gain
control and temperature compensation.
Fig. 8. SMACKS demonstrator module using only SMD
packaged MMICs showing the RF waveguide connections at
both sides and the IF/LO connectors at the front.
The HPA MMIC has been specifically designed for
this project. This HPA and the driver are packaged in the
organic power packages. All other MMICs are
commercially available products that have been mounted
in the LTCC packages.
RX RF
37-40 GHz
TX RF
37-40 GHz
conductive glue
copper backplate
Fig. 7. Cross section of simplified thermal model and simulated temperature profile.
The major advantages of this module technology are:
standard pick-and-place assembly and reflow soldering,
no yield loss during mounting of the MMICs and easy
rework. A drawback can be that the integration density is
X2
LO
9-10 GHz
X2
TX IF
2.5 GHz
LO
RX IF
1.2 GHz 9-10 GHz
Fig. 9. Transmitter and receiver chain indicating each SMD
packaged MMIC (solid blocks).
34th European Microwave Conference - Amsterdam, 2004
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The target specifications for this demonstrator are
summarized in Table I.
Channel
TX
Parameter
RF frequency range
IF frequency
Output power range
Dynamic range
IM3 @ 17.5 dBm
RX
RF frequency range
IF frequency
NF min.
Gain
Dynamic range
Temperature range
Specification
37-39.5 GHz
2.34 GHz
-5 to +21 dBm
> 50 dB
< -38 dBc
37-39.5 GHz
1.08 GHz
< 6 dB
12 ± 2 dB
> 25 dB
-35°C to +80°C
Table I. Target specifications for the 38 GHz demonstrator.
Measured performance figures are not yet available
since the demonstrator is still under characterization. The
estimated cost reduction for this transceiver module, with
respect to modules using mixed substrates and bare die
MMICs, is around 20%.
VI. CONCLUSION
The realization of a low-cost 38 GHz transceiver
module for wireless point-to-point communication has
been presented. The module is fabricated on a single
layer organic substrate using only packaged MMICs. The
SMD packages and transceiver demonstrator have been
developed in the framework of the European SMACKS
project. Through substrate and package technology
characterization and demonstrator development this
project has shown the feasibility of extending the SMT
approach to millimeter-wave frequencies. The estimated
cost reduction of the complete module is around 20%,
due to lower manufacturing cost and reduction of yield
loss.
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ACKNOWLEDGEMENT
This work has been funded by the EC within the 5th
framework SMACKS project (IST-2000-30060). The
authors would like to thank the project partners Labtech
for the organic package and motherboard development,
Thales Microelectronics for developing the LTCC
packages, Alcatel WTD for the demonstrator
specification and testing and UMS for the MMIC supply
and processing and assistance in the package
development.
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34th European Microwave Conference - Amsterdam, 2004