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Advancing 5G communications using LTCCs

By Andy Kao [DuPont]

I n 5G communication, millimeter

wave (mmWave) radio frequencies
a re u sed to a ch ieve u lt r a-
high speed, large capacity, and ultra-
low latency data transfers. However,
mmWave transmissions can’t penetrate
buildings. To optimize 5G, more and
smaller cell antennas are required. Use
of low-temperature co-fired ceramic
(LTCC) conductive pastes and tapes in
radio frequency components (such as
those used in band bass filters (BPF),
substrates and antenna-in-package
(AiP) for radio frequency front-end
modules [RF FEM]) can help expand
access to 5G mmWave bandwidth
devices. Components made with
LTCC materials have high reliability,
excellent electrical performance, good
thermal conductivity, and outstanding
environmental resistance. In addition, the Figure 1: Low-temperature co-fired ceramic (LTCC) process flow.
physical properties of LTCC materials
enable a higher degree of design freedom materials allow for the design of more used in conventional high-temperature
compared to printed circuit boards highly integrated circuitry. Plus, these co-fired ceramic (HTCC) processing.
because they allow for stacking up to materials are key to achieving high- Circuits made with LTCC materials can
80 layers while still providing dielectric performance efficiency at low levels of also withstand post-firing of thick film,
constant stability and low insertion power consumption. plating, soldering, or brazing to make a
loss. They have also been proven to A f t e r l a ye r s a r e s t a c k e d a n d fully functional package (Figure 2).
enable smooth functioning across laminated, they are co-fired at 850°C. LTCC materials combine the positive
a wide frequency range – including high- This is much lower than the >1500°C attributes of a thick film on a ceramic
frequency applications – in challenging
environments.

LTCC uses and properties
LTCC material systems combine the
benefits of multi-layer ceramic and
thick-film technologies used in high-
frequency, microwave, and mmWave
electronic applications. Most often,
these systems are used for high-
reliability circuit boards. Recent
developments have led to the use of
LTCC materials in AiP for RF FEMs.
In the unfired green state, each layer
of dielectric can be via punched, filled,
and screen-printed with conductor
and resistor traces (Figure 1). Up to
80 layers can be stacked together.
Compared to t radit ional pr i nted
circuit boards that are limited to a few Figure 2: LTCC material systems allow package design flexibility with up to 80 layers for integrating passive
layers (usually 20 or fewer), LTCC components, e.g., capacitors and resistors, as well as the ability to create cavities, and physical properties that
withstand post-firing.

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