Gels are a special class of encapsulants that cure to an extremely soft
material. Cured gels retain much of the stress relief and self-healing
qualities of a liquid while providing the dimensional stability of an
elastomer.
Typically, gels are used to isolate circuits from the harmful effects of
moisture and other contaminants and provide electrical insulation for high
voltages. However, their primary advantage is to provide the ultimate in stress
relief in a cured material in order to protect a circuit and interconnections
from thermal and mechanical stresses. Gels are usually applied in thick layers
to totally encapsulate higher architectures and, in particular, high standing
wirebonds, often in depths exceeding 80 mils (2 mm).
Another key characteristic of most gels is a naturally tacky surface after
cure. This natural adhesion allows gels to gain physical adhesion to most
common surfaces without the need for primers. This tacky nature also results in
the unique ability to re-heal if the cured gel has been torn or cut. The
ability to re-heal also permits the use of test probes directly through the gel
for circuit testing.
Dow Corning® brand dielectric gels are supplied as solventless and typically
as low viscosity liquids. Most are designed as two part products with 1:1 mix
ratios (parts A and B). Others are formulated as one part products, eliminating
the need for mixing. The two part products generally allow for either room
temperature or heat accelerated cure. One part products require heat cure. A
few specialized one part gels allow for very rapid UV
cure.
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If you need a
material:
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Consider products:
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To be used in stress-sensitive applications
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With higher penetration or lower gel hardness values
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For use around heat-sensitive components that cannot withstand high cure
temperatures
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That cure at room temperature or with moderate heat or that cure with UV
light
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For rapid processing
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With fast cure times; for heat-curable products, these are usually two-part
rather than one-part materials
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For use without the need of mixing
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That are one part
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That is still a soft gel but with greater strength and dimensional
stability
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Designated as “tough gels”
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That promotes chemical adhesion in addition to the natural, tacky adhesion
of gels
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Designated as “tough gels” or “firm gels”
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With a high level of optical clarity
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Designated as “clear”
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That will fill small spaces
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With the lowest viscosity values; or, with higher viscosity products, use vacuum during
processing
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To minimize leakage from gaps in modules before curing
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With higher viscosity values, faster cure times or a thixo gel; also
consider a precured
gel
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To minimize the chance for trapping bubbles
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With the lowest viscosity values and fill the part on an
incline; or, with higher viscosity products, use vacuum during
processing
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That maintains its cured properties at extremely low temperatures
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Suited for use below –40C
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With very low levels of outgassing or extractable materials
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Designated as having “controlled volatility (CV)” or as “low
extractables”
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That will be exposed to fuels or solvents
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With solvent resistance properties (fluorosilicone-based products)
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For uses such as connector sealing, gasketing, wrapping or for anywhere
there is not a module for containment before curing
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That are precured
gels – pads and parts
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Product Finder
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or the Processing
Tutorial
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