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Description / Abstract:
For the purpose of this document potting can be thought of as
the ‘‘liquid material'' and encapsulation can be interpreted as the
application process and cure. Please keep in mind however that the
terms potting and encapsulation are commonly interchanged with each
other in a variety of electronic protection processes.
Encapsulation, for the purpose of this document, is defined as a
potting material, e.g., epoxy, silicone, urethane that is applied
in a liquid state and subsequently processed (i.e., cured) to form
a rigid or rubber-like state.
Processing characteristics and curing mechanisms are dependent
on the encapsulation chemistries used. The desired performance
characteristics of an encapsulation depend on the application and
must be considered when selecting encapsulation materials and
encapsulation processes. Users are urged to consult the suppliers
for detailed technical data.
This guide enables a user to select an encapsulant based on
industry experience and pertinent considerations. It is the
responsibility of the user to determine the suitability, via
appropriate testing, of the selected encapsulation and application
method for a particular end use application.
Encapsulation may have several functions depending on the type
of application. The most common are to:
• Inhibit current leakage and short circuit due to humidity and
contamination from service environment.
• Inhibit corrosion.
• Improve fatigue life of solder joints to leadless
packages.
• Inhibit arcing and corona, in particular for high voltage
applications.
• Provide mechanical support and to prevent damages due to
mechanical shock and vibration.
• Provide a mitigation method for the growth of
tin-whiskers.
Purpose The terms ‘‘potting'' and
‘‘encapsulation'' (P/E) can be confusing terms and be interpreted
to mean many things in various industry assembly processes.
The purpose of this handbook is to assist the individuals who
must either make choices regarding encapsulation or who must work
in encapsulation operations and to provide guidelines for the
design, selection, and application of Potting and Encapsulation as
it pertains to electronic components and printed board assembly
only.