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Thermal Interfaces
15
20092B/0—Sep1996
AMD-K5 Processor Thermal Considerations
Thermal Adhesive Tape
Thermal tapes consist of the following: thermally conductive
carrier, adhesive material coated on both sides, and a clear
release liner used to protect the adhesive surface during ship-
ping and handling. These tapes provide a thermal interface
between the processor case and the heat sink. The adhesive
material provides the mechanical attachment between the
heat sink and processor case. This interface is prone to
mechanical failures if one or more of the following conditions
exist:
I
Foreign material on the heat sink, processor case, or ther-
mal interface tape
Incorrect thickness of thermal interface tape. If the tape is
too thin, air pockets may form. If the tape is too thick, the
thermal resistance increases.
Insufficient pressure applied during installation of tape.
Failure to prepare the surface of the processor case with
ceramic sealer.
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For these reasons, thermal tapes are not recommended. But, if
the personal computer design requires the use of thermal tape,
the materials and procedures described below should be used.
Table 3. Thermal Conductive Adhesive Tapes
Typical Properties
Chomerics
T405
Chomerics
T412
Expanded
Aluminum
Gray
Test Method
Carrier
Aluminum
n/a
Color
Thermal Resistance,
(
o
C · inch
2
)
/ Watt
Thermal Conductivity,
Watt / (Meters ·
o
C)
Thickness (in inches)
Shear Adhesion,
psi @ 25
o
C
Shear Adhesion,
psi @ 150
o
C
White
n/a
0.5
1.40
MIL-l-49456A
0.5
0.25
MIL-I-49456A
0.006
0.009
n/a
125
135
Chomerics
T.P. 54
55
25
Chomerics
T.P. 54