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Metallic Cushion for Internal Cooling Enhancement

IP.com Disclosure Number: IPCOM000119969D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Eid, JC: AUTHOR [+2]

Abstract

Cooling of high-powered multi-chip modules dictates thermal/mechanical packaging requirements wherein high heat fluxes must be removed from an array of sources whose position is somewhat uncertain and mechanical loading requirements must be kept within limits. In the past, these requirements have been met by placing an insert into a mating socket. Specific examples include the IBM TCM (Thermal Conduction Module) and the NEC LCM (Liquid Cooled Module). The insert is in contact with the chip, and the gap between the insert and hat is filled with a conductive fluid, such as helium or oil. In order to meet the mechanical requirements, such schemes require that heat flow across two gaps, one at the chip-to-insert interface and a second at the insert-to-hat interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Metallic Cushion for Internal Cooling Enhancement

      Cooling of high-powered multi-chip modules dictates
thermal/mechanical packaging requirements wherein high heat fluxes
must be removed from an array of sources whose position is somewhat
uncertain and mechanical loading requirements must be kept within
limits.  In the past, these requirements have been met by placing an
insert into a mating socket. Specific examples include the IBM TCM
(Thermal Conduction Module) and the NEC LCM (Liquid Cooled Module).
The insert is in contact with the chip, and the gap between the
insert and hat is filled with a conductive fluid, such as helium or
oil.  In order to meet the mechanical requirements, such schemes
require that heat flow across two gaps, one at the chip-to-insert
interface and a second at the insert-to-hat interface.

      Substantially greater heat transfer can be obtained if the
number of gaps is reduced.  This article describes a technique to
eliminate the insert-to-hat gap while still maintaining the necessary
mechanical compliance.  The result is a very high performance
conduction scheme which carries into the 100+ watts/chip range.

      The specific idea is shown in Fig. 1-a.  A metallic cushion
makes the connection between the chip and hat.  The cushion is made
of a low melting point ostalloy material which is preformed into
circular (or square) cavities in the hat.  The hat is inverted into
the chip array. Heating above the liquidus temperature of the
ostalloy reflows the metal and achieves the required chip to ostalloy
interface.  A pad around the individual chips serves to sponge up any
excess material during the reflow process.  A suitable convective
surface is mounted directly to the hat, thereby making an integral
cold plate.  Here, fins can be machined directly into or stamped and
subsequently brazed to the hat.  A clamping mechanism is shown where
the hat indexes off the top surface of the substrate.  This
eliminates the need for the ostalloy cushion to accommodate the
tolerances associated with the substrate thickness and thereby
improves performance by reducing the required cushion thickness.
Thermal expansion is accommodated by the softness of the ostalloy
itself.  The global chip position is accommodated by the initial
re...