TS68040MR25A Atmel Corporation, TS68040MR25A Datasheet - Page 15

• Manufacturer Part Number: TS68040MR25A
• Manufacturer: Atmel Corporation

TS68040
All pin fin heat sinks tested were made from extrusion Al products. The planar face of
the heat sink mating to the package should have a good degree of planarity; if it has any
curvature, the curvature should be convex at the central region of the heat sink surface
to provide intimate physical contact to the PGA surface. All heat sinks tested met this
criteria. Nonplanar, concave curvature the central regions of the heat sink will result in
poor thermal contact to the package. A specification needs to be determined for the pla-
narity of the surface as part of any heat sink design.
Although there are several ways to attach a heat sink to the package, it was easiest to
use a demountable heat sink attach called “E-Z attach for PGA packages” developed by
Thermalloy (see Figure 6). The heat sink is clamped to the package with the help of a
steel spring to a plastic frame (or plastic shoes Besides the height of the heat sink and
plastic frame, no additional height added to the package. The interface between the
ceramic package and the heat sink was evaluated for both dry and wet (i.e., thermal
grease) interfaces in still air. The thermal grease reduced the
quite significantly
CA
(about 2.5 °C/W) in still air. Therefore, it was used in all other testing done with the heat
sink. According to other testing, attachment with thermal grease provided about the
same thermal performance as if a thermal epoxy were used.
Figure 6. Heat Sink with Attachment
A sample size of one TS68040 package was tested in still air with the heat sink and
attachment method previously described. This test was performed with 3W of power
being dissipated from within the package. Since the variance in
within the possible
JA
power range is negligible, it can be assumed for calculation purposes that
is con-
JA
stant at all power levels. Table 9 shows the result assuming a maximum power
dissipation of the part at 3 and 5W (refer to Table 6 to calculate other power dissipation
values).
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2116A–HIREL–09/02