TS68040 ATMEL Corporation, TS68040 Datasheet - Page 13

• Manufacturer Part Number: TS68040
• Description: 32-bit Mpu, 25-33 MHZ
• Manufacturer: ATMEL Corporation

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 planarity 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 (e.i., thermal grease) interfaces in still air. The thermal grease reduced the
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.
A sample size of one TS 68040 package was tested in still air with the heat sink and attachment method previously described.
This test was performed with 3 W of power being dissipated from within the package. Since the variance in
possible power range is negligible, it can be assumed for calculation purposes that
Table 9 shows the result assuming a maximum power dissipation of the part at 3 and 5 W (refer to Table 6 to calculate
other power dissipation values).
Table 9 - Thermal parameters with heat sink and no air-flow
Thermal characteristics with a heat sink and forced air
A sample size of three TS 68040 packages was tested in forced-air cooling in a wind tunnel with a heat sink. This test was
performed with 3 W of power being dissipated from within the package. As mentioned previously, the variance in
the possible power range is negligible ; it can be assumed for calculation purposes that
Table 10 shows the results, assuming a maximum power dissipation at 3 and 5 W with air flow and heat sink thermal
management (refer to Table 6 to calculate other power dissipation values).
Thermal Mgmt.
Technique
Heat sink
2338B
2338B
3 W
5 W
P D
Defined parameters
125°C
125°C
T J
Figure 6 : Heat sink with attachment.
1°C/W
1°C/W
JC
Measured
14°C/W
14°C/W
JA
13°C/W
13°C/W
CA
JA is constant at all power levels.
JA is valid at all power levels.
CA quite significantly (about
Calculated
122°C
120°C
T C
JA within the
83°C
55°C
T A
JA within
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