Meeting High-Power and
High Frequency Challenges
with Adhesives and Potting
Compounds
Venkat Nandivada and Rohit Ramnath
MasterBond Inc., Hackensack, N.J.
The market is demanding all sorts of optical and electronic systems for military, aerospace, communica- tions and consumer systems. These
systems rely on high-power semiconductors,
diodes, converters, amplifiers, radio devices, antennas, high frequency ID tags and
optoelectronics devices. Electronics fabrication and assembly typically requires the
use of adhesives, die-attach compounds,
glob-top encapsulants, underfills and potting compounds. Since many materials exist, engineers should be familiar with how
the material affects design performance. In
the following discussion, we examine the
unique requirements high-power and high
frequency communications electronics place
on adhesives and encapsulants, as well as
the material characteristics needed to satisfy
performance objectives.
MANAGING THERMAL PERFORMANCE
To dissipate the heat that can degrade
device performance and transfer heat across
components, many designs use heat sinks
combined with other cooling methods
and technologies. These techniques of-
ten require thermal adhesives and potting
compounds that exhibit excellent thermal
conductivity and provide good structural
integrity. Thermally conductive adhesives or
potting compounds aid in transferring heat
from the electronics to the heat sink or other
cooling system that dissipates it. This reduc-
es the thermal load on these components,
especially useful when there are many heat-
sensitive components.
Thermally conductive adhesives can either be electrically conductive, act as insulators or provide electromagnetic shielding,
driven by the specific application requirements. The die attach of a high-power semiconductor application may need either an
electrically conductive or an electrically insulative die attach. Typically, an extremely fast
cure at temperatures from 125°C to 200°C
is also desirable. On the other hand, a high
frequency application such as an antenna
system may need an adhesive that shields
against electromagnetic interference (EMI).
Often, a conductive coating is applied to
housings to provide the desired shielding,
even at extremely high frequencies, e.g.,
to 18 GHz. In these cases there is similarity
in the thermal properties, because most of
these applications have high heat dissipation. In applications where electrical insulation is necessary, high volume resistivity and
high dielectric strength are often prerequisites.1
