Figure 14. Thermalloy #2328B Heat Sink-to-Ambient Thermal Resistance Versus Airflow Velocity
Assuming an air velocity of 0.5 m/s, we have an effective R of 5 °C/W, thus
sa
T = 30 °C + 5 °C + (0.03 °C/W + 1.0 °C/W + 5 °C/W) * 7.5 W,
j
resulting in a junction temperature of approximately 81 °C which is just below the maximum
operating temperature of the part. To ensure maximum reliability, it is desirable to operate the 604e
well within its operating temperature range. Thus, to keep a 7.5 W 604e within its proper operating
range, an air velocity greater than 0.5 m/s should be used with the Thermalloy #2333B pin-fin heat
sink.
Other heat sinks offered by Thermalloy, Aavid, Wakefield, and IERC offer different heat sink-to-
ambient thermal resistances, and may or may not need air flow. It is necessary to perform an
analysis as done above to select the desired heat sink.
Though the junction-to-ambient and the heat sink-to-ambient thermal resistances are commonly
used to compare the thermal performance of various microelectronic packaging technologies, one
should exercise caution when only using this metric in determining thermal management because
no single parameter can adequately describe three-dimensional heat flow. The final chip-junction
operating temperature is not only a function of the component-level thermal resistance, but the
system-level design and its operating conditions. In addition to the component's power
consumption, a number of factors affect the final operating die-junction temperature. These
factors might include airflow, board population (local heat flux of adjacent components), heat sink
efficiency, heat sink attach, next-level interconnect technology, system air temperature rise, etc.
Due to the complexity and the many variations of system-level boundary conditions for today's
microelectronic equipment, the combined effects of the heat transfer mechanisms (radiation,
convection and conduction) may vary widely. For these reasons, we recommend using conjugate
heat transfer models for the board as well as system-level designs. To expedite system-level
thermal analysis, several “compact” thermal-package models are available within FLOTHERM®.
These are available upon request.
9/17/99 Revision 1.4
PID9q-604e Hardware Datasheet
27
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
IBM [ IBM ]
