Automotive Engineering - March 2025 - 26

Advanced silicones
for ADAS
in light
vehicles
Silicone gap fillers are available in a range of thermal
conductivities. For example, the higher power demands
of ECUs may require products with high thermal
conductivity. Materials with lower (2.0 W/m-K)
and higher (9.5 W/m-K) thermal conductivities are
available to provide the right level of performance.
Because silicone gap fillers are stress-relieving, they
resist vibrations and are not prone to cracking when
PCB materials expand and contract at different rates.
These advanced silicones support automated dispensing
and room-temperature curing.
Thermally conductive silicone greases are one-part
Silicone materials, including thermally conductive silicones, encapsulants and
gels, and Si foams, could be used throughout an ADAS camera sensor assembly.
products that do not require curing and are easy to
dispense or print with automated equipment. Because
they do not cure, greases are easy to rework and can
be wiped clean. They come in a range of thermal conductivities
and can be used to dissipate heat from a
wide variety of ADAS electronics components. Among
their other benefits, thermal greases can support thin
bond lines for improved device performance.
Like gap fillers, thermally conductive silicone adhesives
are available in either one-part or two-part formulations.
Both are designed to cure at room temperature
but can use ovens for accelerated curing.
These adhesives are easy to dispense and have thermal
conductivities that can range from ~1 to 8 W/m-K.
These silicone adhesives provide mechanical adhesion
that can be used to fix the heat sink to the heat
source, which is a benefit in applications where there
may be limited space for mechanical fasteners.
Thermally conductive encapsulants are typically
An ADAS radar sensor could be made with Si EMI sealants, thermally conductive
silicones and Si Fast assembly adhesives, Dow claims.
with UV instead of in ovens. When electrically conductive fillers are
added, silicones can shield ADAS electronics from EMI. When thermally
conductive fillers are added, these compounds can move heat
away from sensitive electronics.
Thermal management
Thermally conductive silicones for ADAS include gap fillers, greases,
adhesives and encapsulants. These materials work by filling voids
between a heat sink and source that would otherwise be filled with
air, which has a thermal conductivity of just W/m-K. Gap fillers can
be used in applications with large gaps or where different component
sizes need to be managed. Greases also create a path for heat
to travel but are used in thinner gaps and are non-curing. Adhesives
provide a mechanical bond between electronic components within a
heat-generating assembly. Encapsulants dissipate heat while covering
or encapsulating whole electronic components.
26 March 2025
two-part products that cure as a soft elastomer at
room temperature or with added heat for accelerated
curing. They are readily flowable to fill into narrow
cavities and have viscosities ranging from 3,000 to
25,000 mPa after mixing. Not all silicone encapsulants
are thermally conductive, but they can be formulated
to have thermal conductivities up to 4 W/m-K. Silicone
encapsulants can be used for environmental protection
and product assembly. They can also provide
thermal management in certain applications.
Protection and assembly
Non-conductive silicone encapsulants and gels are
used to protect a wide variety of electronics across
automotive applications. These advanced materials
are waterproof, flame-retardant, stress-relieving, electrically
insulating and vibration-damping. Silicone gels
are soft and typically have low or no filler content.
This enables them to have significantly lower viscosities,
but they are not as tough as encapsulants. Both
gels and encapsulants can cure at a wide range of
temperatures and some can support UV curing for
accelerated assembly.
AUTOMOTIVE ENGINEERING
BOTH IMAGES: DOW
Automotive Engineering - March 2025

Table of Contents for the Digital Edition of Automotive Engineering - March 2025
