Automotive Engineering - June 2021 - 28

HOW EVs AND THEIR ELECTRONICS
ELECTRIFICATION | ADHESIVES FEATURE
STICK
TOGETHER
Specialized epoxies may have
a silver filler, providing uniform
electrical conductivity.
EMI shielding, process flexibility
With the proliferation of electronics, high-voltage
current, cell-phone signals and Wi-Fi, the importance
of electromagnetic interference (EMI) shielding is
critical. A device or compartment can be shielded
from EMI by surrounding it with an electrically conductive
shell that creates a discontinuity in the electromagnetic
field. Conductive metal films or weaves
of metallic threads work but can be heavy and difficult
to process with off-cuts and scrap resulting.
Alternatively, adhesive coatings and encapsulants
loaded with electrically conductive fillers can instead
be used to coat surfaces and provide excellent EMI
shielding capability, at frequencies ranging from a
few hundred MHz up to 10-20 GHz.
Epoxy and silicone adhesives can be formulated to
cure at room temperature or at elevated temperatures.
The development of dual-cure systems that can be
cured with a combination of UV light and thermal
post-cure enable improvements to throughput and
manufacturing speed. With the case of dual-curing
systems, UV light can be used to initiate cure and increase
the efficiency of the manufacturing process by
providing a strong, near-instantaneous bond.
For one-part and two-part curing systems, the adhesive
industry has extensively innovated its packaging
and delivery systems. A well-designed system
seeks to minimize adhesive waste providing additional
efficiencies. Further, the viscosity of adhesive
systems can be optimized depending on the desired
bond thickness and dispensing rates allowing for use
28 June 2021
in automated, robotic manufacturing processes.
Sustainable ingredients to lower the carbon footprint of structural
adhesives are being utilized in formulations. This has led to the
development and use of 100% solid formulations that have low concentrations
of volatile organic components (VOC). The European
Commission's Restriction of Hazardous Substances (RoHS) directive
has been essential for minimizing the environmental impact of electronic
assemblies. In addition to restricting heavy metals such as
lead and cadmium, RoHS seeks to prevent the use of toxic brominated
flame retardants and biological toxins, including phthalates.
As such, it is essential to use only adhesives that comply with RoHS
restrictions when manufacturing electronic assemblies.
Future adhesives and coatings
Nano-fillers have and will continue to provide great innovations in
the field of adhesives development. There exists in this composite
an interfacial area between the polymer matrix and the filler particles.
Many mechanical, thermal, and electrical properties can be
modulated with the inclusion of functional fillers, and it is often this
interface that is critical in controlling the properties.
Micro alumina particles or even nanoparticles of alumina or silica
can be formulated to exhibit excellent thermal properties while being
non-electrically conductive for electronic applications.
Speed and cost of manufacturing complex parts and prototypes
can be improved with 3-D printing and other additive manufacturing
processes. Dual-cure, UV + Heat resin systems allow 3-D printing with
UV-induced cure while allowing for thermal post-cure to provide superior
structural and thermal stability when compared to thermoplastic
printing resins.
Venkat Nandivada, a chemical engineer, is manager of technical support,
and Rohit Ramnath is a senior product engineer, for Master Bond Inc.
AUTOMOTIVE ENGINEERING
MASTER BOND
Automotive Engineering - June 2021

Table of Contents for the Digital Edition of Automotive Engineering - June 2021
