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Air-Cooled Multi-Module Heatsink with Manufacturing Technique Unified Heatsink-Piston with Oil Interface

IP.com Disclosure Number: IPCOM000115617D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 176K

Publishing Venue

IBM

Related People

Brodsky, WL: AUTHOR [+3]

Abstract

A method of air cooling a printed circuit card having a number of modules with moderate to large power dissipation, while maintaining a relatively low pressure drop through the heatsink is discussed. Included is a means to build and manufacture the thermal solution at a reasonable price/performance.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 48% of the total text.

Air-Cooled Multi-Module Heatsink with Manufacturing Technique Unified
Heatsink-Piston with Oil Interface

      A method of air cooling a printed circuit card having a number
of modules with moderate to large power dissipation, while
maintaining a relatively low pressure drop through the heatsink is
discussed.  Included is a means to build and manufacture the thermal
solution at a reasonable price/performance.

      Fig. 1 is a cross-section of the module/heatsink including the
heat transfer path.  Item H is a stiffener on the back side of the
printed circuit card.  This could be replaced by a second heatsink
assembly.  On the printed circuit card (J) are the modules (K) that
need to be cooled.  The modules used in this package are
conventionally capped modules, preferably the modules would have
copper caps to improve the thermal path.  An oil film joint is used
between the module cap and head of the thermal piston (thermal
resistance approximately 0.03 C/W per 32mm square).  Thermal energy
is then transferred down the shaft of the piston (I) and distributed
into the base of the individual fins (B&C) using a second oil film
connection (M) between the shaft and the heatsink.  Alternately, the
cavity of the heatsink can be filled with oil, if cleaning, leakage,
weight, etc.  are not a concern.  The heatsink assembly, printed
circuit card and supporting stiffener (H) are all integrated together
as a functional unit.

      Fig. 2 is a top view of the heat sink showing multi-module
sites each module having its own piston.  As can be seen, the module
sites can be in various patterns creating a hybrid pin/cross-flow
heatsink.

      The spring loaded thermal piston is set into the heatsink body
and follows or tracks the motion/movement, (expansion/contraction
characteristics) of the module, its associated solder joints (SCC or
SBC), and the PC card.  As the circuit controlling this PC card and
modules turn on and off, the elements of the system change
temperature, dimensions, and relative location.  The spring loaded
piston can move during these changes and induce shear in the oil
joint which is self-healing.  The force exerted on the module by the
piston can be tailored by changing the spring used in the assembly or
the amount it is compressed at assembly, therefore the load per
solder joint can be managed to protect that connection.  The spring
force insures that the oil joint is in compression, insuring an
effective thermal path.

      The piston can be solid or an enhanced version can be a heat
pipe, with boiling and condensing fluid.

      The oil used in the oil film connections can be any number of
oils; at this time we are working with mineral oil.  As previously
mentioned the oil fills all the joints, a reservoir of oil can be
deposited on the top of the piston at the time of system assembly or
the whole cavity can be filled.  However, forces generated by changes
in pressure need to be controlled...