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TB 70 6pg for pdf Phase-change thermal interface materials
Thermally conductive gap fillers
Thermally conductive insulator pads
Thermally conductive adhesive tapes
Thermally conductive silicone compounds
Flexible heat spreaders Thermal management for BGAs
TECHNICAL
BULLETIN
70
LEADER IN THERMAL MANAGEMENT: DESIGN, INNOVATION AND MATERIALS
THERM-A-GAP
TM
Interface Materials
Highly Conformable,Thermally Conductive Gap Fillers
MATERIAL COMPOSITION
THERM-A-GAP materials consist of an
extremely soft silicone elastomer loaded
with ceramic particles. They are available
with aluminum foil, dielectric film, or fiber-
glass carriers.
For applications requiring
electrical isolation
The materials designated
T
are rein-
forced with a thin, thermally conductive
fiberglass reinforced insulator that resists
puncture and provides electrical isola-
tion. Six standard thicknesses are avail-
able. Pressure-sensitive adhesive on the
carrier side is standard.
In the materials designated
F
fea-
ture an integral fiberglass reinforcing
mesh that provides mechanical strength.
This mesh is filled with the ceramic com-
pound. Four standard thicknesses are
available. These materials are inherently
tacky, eliminating the need for mounting
adhesives.
For applications not requiring
electrical isolation
The materials designated
A
utilize a
0.002 in. (0.050 mm) or 0.005 in. (0.127 mm)
aluminum foil carrier. The foil acts as a
heat spreader to eliminate hotspots over
high heat generating components. The
foil side is mounted to the chassis
or other heat spreader with the compliant
silicone surface contacting the compo-
nent. Seven standard thicknesses are
available. Pressure-sensitive adhesive
applied to the aluminum foil carrier side
is standard.
The A materials are recom-
mended where maximum adhesive
strength is required when mounting a
component or heat sink.
Standard sheet sizes for all flat
THERM-A-GAP materials are 9 x 9 in.
(23 x 23 cm) and 18 x 18 in. (46 x 46
cm). Ribbed profile sheets are 8 x 8 in.
(20 x 20 cm). Alternate thicknesses and
sheet sizes can be produced on request.
Solvent extraction studies have shown
that compared with similar products,
THERM-A-GAP materials contain a lower
percentage of free migratory silicone.
This property is important in optical
applications or those with high compres-
sion load.
In addition, THERM-A-GAP materials
have been shown to be non-nutritive,
and do not promote fungal growth.
CHOICE OF PERFORMANCE
LEVEL, PROFILE, OR
COMPLETE CUSTOMIZATION
Three types of THERM-A-GAP materials
are described in the following pages:
174 Series Materials
Good thermal performance
Most economical
Flat sheets
Light purple
274 Series Materials
Moderate thermal performance
Flat or ribbed sheets and custom
molded shapes
Green
574 Series Materials
High thermal performance
Softest materials
Flat sheets
Gray
Chomerics THERM-A-GAP elastomers are
used to fill air gaps between components or PC
boards and heat sinks, metal enclosures and
chassis. The exceptional conformability
of these advanced materials enables them to
blanket highly uneven surfaces, transferring
heat away from individual components or entire
boards, and allowing chassis parts to be used
as heat spreaders where space is restricted.
Pioneered by Chomerics, THERM-A-GAP
materials are used throughout the world in
hundreds of applications where limited air flow,
irregular surfaces and/or dense packaging
conditions create the need for an efficient
heat transfer mechanism. More practical and
efficient than potting compounds, THERM-A-
GAP materials allow the designer to be less
concerned with component proximity to heat
sinks or heat spreaders. 70
56
42
28
14
0
0
8
16
24
32
40
Deflection (%)
THERM-A-GAP T174 and A174 (.070 in.) Material
Compressive Force (psi)
Tel: 781-935-4850
Fax: 781-933-4318
Seals
THERM-A-GAP
TM
Highly Conformable, Thermally Conductive Gap Fillers
continued
350
300
250
200
150
100
50
0
30
20
10
0
Deflection (%)
THERM-A-GAP F174 (.070 in.) Material
Compressive Force (psi)
TYPICAL PROPERTIES
T174
A174
F174
Composition
Aluminum Oxide Filled Silicone on
Aluminum Oxide Filled Silicone on
Aluminum Oxide Filled Silicone
Fiberglass Reinforced Carrier
Aluminum Foil Carrier
with Interior Fiberglass Mesh
Color
Light Purple
Light Purple
Light Purple
Thickness, inch (mm)
.040
.070
.100
.130
.160
.200 .020
.040
.070
.100
.130
.160
.200
.020
.040
.070 .100
(1.0)
(1.8)
(2.5)
(3.3)
(4.1)
(5.1) (.51)
(1.0)
(1.8)
(2.5)
(3.3)
(4.1)
(5.1)
(.51)
(1.0)
(1.8)
(2.5)
Thickness Tolerance,
.004
.007
.010
.010
.010
.010 .002
.004
.007
.010
.010
.010
.010
.002
.004
.007
.010
Batch, � inch (mm)
(.10)
(.18)
(.25)
(.25)
(.25)
(.25) (.05)
(.10)
(.18)
(.25)
(.25)
(.25)
(.25)
(.05)
(.10)
(.18)
(.25)
Thermal Impedance
�C-in
2
/W @ 10 psi
1.3
1.8
2.2
2.3
2.6
3.0
0.9
1.1
1.5
2.1
2.3
2.5
2.8
1.0
1.2
2.0
2.4
(�C-cm
2
/W @ 0.07 MPa)
(8.4)
(11.6) (14.2) (14.8) (16.8) (19.3) (5.8)
(7.1)
(9.7)
(13.6)
(14.8)
(16.1) (18.1)
(64)
(7.8)
(12.9)
(15.5)
(Modified ASTM D5470)
Thermal Conductivity,
W/m-K @ 10 psi initial pressure
1.0
1.0
1.0
(Modified ASTM D5470)
Operating Temperature Range,�C
55 to +200
55 to +200
55 to +150
Dielectric Strength,
Vac/mil (ASTM D149)
>300
Not Applicable
>300
Hardness, Shore A (ASTM D2240)
<15
<15
<30
Specific Gravity (ASTM D792)
2.3
2.3
2.3
Flammability Rating
V-1
V-0
HB
(UL 94 File No. E140244)
(min. thickness, 3.5 mm)
(min. thickness, 3.0 mm)
Adhesive Peel Strength,
12 (345)
16 (454)
Not Applicable
oz/in (gm/in) (PSTC-1)
Adhesive Shelf Life
6 months
12 months
Not Applicable
Most Economical
Moderate Performance
The 174 Series materials are ideal for high-
volume, cost-sensitive applications that
do not require the interface material to
possess a special profile. These products
have been designed into numerous appli-
cations, including laptop computers and
automotive electronics packages.
Performance properties are similar to
those of the 274 Series materials, but
availability is limited to flat sheets.
Standard thicknesses for each of these
materials are shown in the table below.
Pressure-sensitive adhesive is standard on
A174 and T174, while the F174 material is
inherently self-adhering.
While custom molding is not available
for the 174 Series, these materials can be
provided die-cut to customer specification.
Standard sheet sizes are 9 x 9 in. (23 x 23
cm) and 18 x18 in. (45 x 45 cm).
(These
materials are also offered in 100 foot [30 m}
rolls.)
THERM-A-GAP
TM
T174, A174 AND F174 MATERIALS
Typical Compression/Deflection Characteristics
Figure 1a
Figure 1b
ELEC
.
MECHANICAL
CONSTRUCTION
THERMAL Moderate Performance,
Ribbed Profile Option,
Custom Molded Shapes
The original THERM-A-GAP materials,
the widely used 274 Series offers good
thermal performance, a choice of standard
flat or ribbed profiles, and the ability to be
molded into virtually any shape or special
profile. Used as PCB blankets or in
elaborate molded configurations, they
have been designed into applications as
divergent as cellular phone infrastructure
equipment, avionics packages, automotive
electronics, and advanced HPLC instru-
mentation systems. Special profiles have
enabled these materials to meet extremely
challenging performance requirements,
such as efficient cooling of multi-processor
workstations.
Standard thicknesses for each material
are shown in the table below. Pressure-
sensitive adhesive is standard on both
A274 and T274. Standard sheet sizes for
flat materials are 9 x 9 in. (23 x 23 cm)
and 18 x 18 in. (46 x 46 cm). For ribbed
materials, the standard sheet size is 8 x 8
in. (20 x 20 cm). Both materials can be
provided in non-standard sheet sizes or
die-cut to customer specification.
THERM-A-GAP
TM
T274 AND A274 MATERIALS
TYPICAL PROPERTIES
T274
A274
Composition
Aluminum Oxide Filled Silicone on
Aluminum Oxide Filled Silicone on
Fiberglass Reinforced Carrier
Aluminum Foil Carrier
Color
Blue/Green
Green/Aluminum
Thickness, inch (mm)
.040
.070
.100
.130
.160
.200
.020
.040
.070
.100
.130
.160
.200
(1.0)
(1.8)
(2.5)
(3.3)
(4.1)
(5.1)
(.51)
(1.0)
(1.8)
(2.5)
(3.3)
(4.1)
(5.1)
Thickness Tolerance, Batch,
.004
.007
.010
.010
.010
.010
.002
.004
.007
.010
.010
.010
.010
� inch (mm)
(.10)
(.18)
(.25)
(.25)
(.25)
(.25)
(.05)
(.10)
(.18)
(.25)
(.25)
(.25)
(.25)
FLAT
FLAT
1.7
2.1
2.4
2.6
3.2
4.5
0.9
1.6
2.1
2.3
2.5
3.0
4.1
(11.0)
(13.5)
(15.5)
(16.8)
(20.6)
(29.0)
(5.8)
(10.3)
(13.5)
(14.8)
(16.1)
(19.4)
(26.4)
RIBBED
RIBBED
2.0
2.4
3.2
4.0
4.3
4.6
NA
1.9
2.3
3.1
3.8
4.2
4.4
(12.9)
(15.5)
(20.6)
(25.8)
(27.7)
(29.7)
(12.3)
(14.8)
(20.0)
(24.5)
(27.1)
(28.4)
Thermal Conductivity,
W/m-K @ 10 psi initial pressure
0.9
0.9
(Modified ASTM D5470)
Operating Temperature Range,�C
50 to +200
50 to +200
Dielectric Strength,
Vac/mil (ASTM D149)
>300
Not Applicable
Hardness, Shore A (ASTM D2240)
<15
<15
Specific Gravity (ASTM D792)
2.2
2.0
Flammability Rating
V-0
V-0
(UL 94 File No. E140244)
Adhesive Peel Strength,
12 (345)
16 (454)
oz/in (gm/in) (PSTC-1)
Adhesive Shelf Life
6 months
12 months
Thermal Impedance
�C-in
2
/W @ 10 psi
(�C-cm
2
/W @ 0.07 MPa)
(Modified ASTM D5470)
Typical Compression/Deflection Characteristics
Figure 2a
CONSTRUCTION
THERMAL
ELEC
.
MECHANICAL
Tel: 781-935-4850
Fax: 781-933-4318
Seals
30
25
20
15
10
5
0
4
8
12
16
20
Compressive Force (psi)
THERM-A-GAP T274 or A274 Material
Deflection (%)