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Table 1: CTE of LTCC materials is close to the CTE of a semiconductor material.

Table 2: Thermal conductivity comparison among different types of substrates.
substrate and HTCC. Like thick film, LTCC materials can be
used with high-conductivity metals (e.g., Au and Ag), have
a low dielectric constant (Dk), can be used to print resistors,
and are processed at a relatively low temperature. Like
HTCC technology, LTCC materials allow high resolution
for printed conductors, use a single firing, provide good
dielectric thickness control, and multiple layers.
LTCC is inherently hermetic and therefore immune to
moisture absorption. The coefficient of thermal expansion
(CTE) of certain LTCC materials are much lower than
the CTE of printed circuit boards. This allows for a close
match to integrated circuit (IC) chips (Table 1). Compared
to general LTCC materials and other circuit board
materials, DuPont™ MCM GreenTape™ offers better
thermal conductivity (Table 2).
With induced low-dissipation factor (Df) degradation,
DuPont™ GreenTape™ dielectric properties are very stable
with respect to temperature (Figure 3) because of a low
CTE, and polarization modes that are not strongly influenced Figure 4: DuPont™ GreenTape™ provides: a) a low loss tangent (Df), and b) a
stable dielectric constant (Dk) over a range of mmWave frequencies.
by ambient temperatures. At the same time, the tape has
a very low loss tangent of transmissions over mmWave
frequencies (Figure 4). For the reasons outlined above, we
chose this tape as a test material for AiP applications.

AiP prototyping, testing, and validation
Our Microcircuit and Component Materials team collaborated
with the Industrial Technology Research Institute (ITRI) of
Taiwan to design and test mmWave AiP prototypes made with
DuPont™ GreenTape™. After firing, test results indicate that the
electric properties of LTCC substrates perfectly match the design,
with an attainable bandwidth of 2GHz and higher as shown in
Figure 5. After chips and passive components were packaged
onto the substrates (Figure 6), further testing in an anechoic room
was used to validate beam-forming properties.
Once installed in the system (Figure 7), the antenna module
underwent mmWave signal transmission field testing. Because
of its low-loss features, we could validate the quality of signal
transmission by using error vector magnitude (EVM) testing
(Figure 8). We observed the clean image and audio at the receiving
end when a high-resolution video file is transmitted from one
device to another (Figure 9). This fully demonstrates the feasibility
of using our tape system in AiPs for mmWave applications.
Future development
Using highly-integrated circuitry and exceptionally
stable and reliable low-loss LTCC materials in the antennae
Figure 3: DuPont™ GreenTape™ maintains: a) a low dissipation factor (Df), and b) arrays (or multiple antennae in one or more arrays) and RF
a low dielectric constant (Dk) in extreme cold and extreme heat.

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