Brochure

10
THERMALLY CONDUCTIVE ADHESIVES
Dow Corning offers a variety of noncorrosive, thermally
conductive silicone adhesives that are ideally suited for use
in bonding hybrid circuit substrates, power semiconductor
components and devices to heat sinks as well as for use in
other bonding applications where flexibility and thermal
conductivity are major concerns. The flowable versions are
also ideal for use as thermally conductive potting materials
for transformers, power supplies, coils and other electronic
devices that require improved thermal dissipation.
The thermally conductive adhesives cure either with
moisture or heat to produce durable, relatively low-stress
elastomers. The one-part RTV-cure materials have a
noncorrosive by-product and are available in a variety of
viscosities. RTV-cure thermally conductive adhesives with
controlled volatility and UL listings are available.
The heat-cure, thermally conductive adhesives produce no
by-products in the cure process, allowing their use in deep
section and complete confinement. These adhesives will
develop good, primerless adhesion to a variety of common
substrates including metals, ceramics, epoxy laminate
boards, reactive materials and filled plastics. Controlled
volatility adhesives and UL-rated adhesives are available.
THERMALLY CONDUCTIVE ENCAPSULANTS
Dow Corning thermally conductive silicone encapsulants
are supplied as two-part liquid component kits. When the
liquid components are thoroughly mixed, the mixture cures
to a flexible elastomer, suitable for the protection of electri-
cal/electronic applications where heat dissipation is critical.
These elastomers cure without exotherm at a constant rate
regardless of sectional thickness or degree of confinement.
Dow Corning thermally conductive elastomers require no
post-cure and can be placed in service immediately at oper-
ating temperatures of -45 to 200°C (-49 to 392°F) following
the completion of the cure schedule.
THERMALLY CONDUCTIVE COMPOUNDS
Dow Corning thermally conductive compounds are grease-
like silicone materials, heavily filled with heat-conductive
metal oxides. This combination promotes high thermal
conductivity, low bleed and high-temperature stability. The
compounds resist changes in consistency at temperatures up
to 177°C (350°F), maintaining a positive heat sink seal to
improve heat transfer from the electrical/electronic device to
the heat sink or chassis, thereby increasing the overall effi-
ciency of the device. Refer to Table I for specific test results.
THERMALLY CONDUCTIVE GELS
Dow Corning silicone gels are soft and cure to form a cush-
ioning, low-modulus, resilient, gelled material. Cured gels
retain much of the stress relief capability while developing
the dimensional stability of an elastomer.
Dow Corning offers a line of thermally conductive gels
that couple the stress-relieving capability of a silicone
gel with the ability to dissipate heat from devices. These
thermally conductive gels can be used as potting materials
for transformers, power supplies, coils, relays and other
electronic devices that require a low-modulus material for
thermal dissipation. They can also be used as ingredients in
formulations for thermally conductive gel sheets.
These silicone gels cure without exotherm at a constant rate
regardless of sectional thickness or degree of confinement.
Dow Corning features thermally conductive gels that have
controlled volatility, including one UL 94 V-0 approved
product.
Specific versions of thermally conductive gels contain glass
beads designed to guarantee a minimum bond line, ensuring
a reliable electrical insulation. Those materials find their use
as liquid gap fillers and can favorably replace thermal pads.
Table I. Thermally Conductive Compound Properties
Dow Corning Product Test Test Method Result
SC102 Thermally Oil Separation JIS K 2220 0.02%
Conductive Compound Consistency JIS K2220 10/mm 308
Volatile Content 24 hr/120°C 0.40%
340 Heat Sink Bleed after 24 hr/200°C Fed Std 791 Method 321.2 0.05%
Compound Consistency ASTM D 217 300
Evaporation after 24 hr/200°C Fed Std 791 Method 321.2 0.50%
SE4490CV Thermally Oil Separation JIS K 2220 0.00%
Conductive Compound Consistency JIS K2220 10/mm 250
Volatile Content 24 hr/120°C 0.40%
TC-5021 Thermally Volatile Content 24 hr/150°C <1%
Conductive Compound Bleed 24 hr/150°C 0.15%
TC-5022 Thermally Volatile Content 24 hr/150°C <0.05%
Conductive Compound Thermal Resistance 0.02-mm Bond Line, 40 psi 0.06°C
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