Conformal coating improves the reliability and life of solar inverters
Conformal coating improves
the reliability and life of
solar inverters
by Akira Morita and Brad Perkins, Asymtek, Carlsbad, CA, USA
introduction
conjunction with masking to shield com-
While the solar and photovoltaic
The solar inverter is an essential part of
ponents that could not be coated. These
industries have a long history,
every photovoltaic system. Its purpose is to
processes were done manually or using au-
the industry size is rapidly
change the direct current (DC) of electric-
tomated equipment. Coating was used for
expanding. Looking at existing
ity from a photovoltaic array to alternating
large areas where precision and accuracy
current (AC) to power home appliances
technologies used in other
weren’t required because of the masking
or a utility grid. Reliability is one of the
electronics industry applications
processes and board layouts; typical masked
most important aspects of the solar array.
components would be displays, connec-
can offer solutions to some of the
However, solar energy is still expensive. To
tors, and test points. However, electronics
manufacturing needs the solar
make it more competitive with other forms
have shrunk in size and, especially in the
and photovoltaics industries now of energy, and thus more affordable and
automotive and telecommunications in-
face. accessible for general use, it is necessary to
dustries where parts were small, there were
Conformal coating has
drive the cost down. In an effort to reduce
more components, and the space between
been used for many years in
cost, however, care must be taken not to
components was tight. Placement of the
the electronics and automotive
sacrifice the reliability of the photovoltaic
fluid had to be more exact. Speed became
industries to protect the
systems.
a factor as boards needed to keep up with
electronics from environmental
Inverters in solar installations are
the volumes in these industries. Automated
exposed to the sun, so there are moisture,
factors such as moisture, dirt
in-line coating solutions became a require-
humidity, temperature and contamination
and chemicals. New methods
ment. Accommodating smaller areas of
concerns. Inverter reliability is important,
coating became a challenge, along with de-
of selective coating and process
so maximum power can be pulled from
veloping new, selective coating applicators.
control make this technology
the solar cells and converted to electricity.
To meet these demands, manufacturers
easily adaptable to protect the The life expectancy of the solar cell is 25-30
of conformal coating equipment developed
electronics in solar inverters from years, so it makes sense for the inverter
new technologies and processes. One major
harsh environmental factors.
that operates a solar cell to be reliable for
technology development was jetting, which
This leads to improved reliability
that duration. Poor reliability can damage a
enables automated selective, precision coat-
and longer inverter life for the
manufacturer’s reputation.
ing at high speeds. Selectivity is important
photovoltaic (PV) system in the
Using conformal coating, an existing,
due to the process improvements in not
solar industry.
proven technology, is an efficient, cost-
having to mask sensitive components. It
effective method to achieve that reliability.
means the coating will be dispensed exactly
where intended. In older coating methods,
The conformal coating process
the coating was sprayed through an atom-
Keywords: Conformal Coating,
Conformal coating can be used to coat the
ized gun with a large spray area, so it was
printed circuit board, wiring and solder-
Solar Inverter, Jetting
difficult to control where the fluid landed.
ing between power switches and discrete
Masking was needed to cover the parts that
components of the inverter as well as those
didn’t need coating. The masking process
components themselves. The coating is
is labor intensive, time consuming and ex-
applied during the manufacture of the
pensive, and because it is removed after the
inverter by an automated conformal coat-
coating operation, it does not add value
ing system designed for precision coating
to the final product. It involves making a
of small electronic parts. Although several
mask to keep certain parts covered while
types of coating materials can be used,
exposing the parts that need coating. Preci-
silicones, urethanes or acrylics are the ones
sion jet dispensing eliminates the need for
generally used for a PV inverter.
masking.
Historically, non-selective spray coat-
Jetting is a form of dispensing that has
ing and dipping were the first conformal
been around since 1983. It is a non-contact
coating processes, but had to be used in
method of depositing fluids. Jetting is
16 – Global Solar Technology – March/April 2009 www.globalsolartechnology.com
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