Intel 848P, Thermal Design Manual

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Reference Thermal Solution
R
22 Intel
®
848P Chipset Thermal Design Guide
The local ambient air temperature (T
A
) at the MCH heatsink is assumed to be 50
°
C. The thermal
designer must carefully select the location to measure airflow to get a representative sampling. These
environmental assumptions are based on a 35
°
C system external temperature measured at 1524 m
[5000 ft].
4.2 Mechanical Design Envelope
The motherboard component keep-out restrictions for the WSHS are included in Appendix B. The
WSHS extends 38.2 mm [1.5 in] nominally above the board when mounted. System integrators
should ensure no board or chassis components would intrude into the volume occupied by the
WSHS.
4.3 Thermal Solution Assembly
The reference thermal solution consists of a passively cooled Wave Solder Heatsink. The heatsink
consists of an extruded aluminum heatsink with four mounting pins pressed into each corner of the
heatsink base. A thermal interface material (Chomerics T-710) is pre-applied to the heatsink bottom
over an area in contact with the package die. A 45-degree dado cut is performed on the heatsink base
to create rails to reduce the possibility of tilt when assembling the WSHS
. Since the rails are
oriented at 45 degrees relative to the heatsink edges, the WSHS is only compatible with a
MCH rotated 45 degrees relative to the motherboard.
Section 4.3.1 describes an alternate WSHS
design that is compatible with a MCH that is not rotated relative to the motherboard. Note that the
rails do not touch the package substrate in the nominal position. The WSHS is shown in the installed
configuration in Figure 9 (the MCH cannot be seen in this view, as it is hidden by the WSHS base).
Drawings of the WSHS extrusion and with the entire WSHS assembly are shown in Appendix B.
Figure 9. Wave Solder Heatsink Installed on Board