Heat exchange – Intermediate fluent heat exchange material receiving and... – Liquid fluent heat exchange material
Reexamination Certificate
2000-05-16
2003-04-22
Bennett, Henry (Department: 3743)
Heat exchange
Intermediate fluent heat exchange material receiving and...
Liquid fluent heat exchange material
C165S104260, C361S700000, C257S716000
Reexamination Certificate
active
06550531
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and methods for removal of heat from electronic devices. In particular, the present invention relates to a vapor chamber in conjunction with a heat sink for the removal of heat from a microelectronic die.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging density of integrated circuits are ongoing goals of the computer industry. As these goals are achieved, microelectronic dice become smaller. Accordingly, the density of power consumption of the integrated circuit components in the microelectronic die has increased, which, in turn, increases the average junction temperature of the microelectronic die. If the temperature of the microelectronic die becomes too high, the integrated circuits of the microelectronic die may be damaged or destroyed.
Various apparatus and techniques have been used and are presently being used for removing heat from microelectronic dice. One such heat dissipation technique involves the attachment of a high surface area heat sink to a microelectronic die.
FIG. 5
illustrates an assembly
200
comprising a microelectronic die
202
(illustrated as a flip chip) physically and electrically attached to a substrate carrier
204
by a plurality of solder balls
206
. A heat sink
208
is attached to a back surface
212
of the microelectronic die
202
by a thermally conductive adhesive
214
. The heat sink
208
is usually constructed from a thermally conductive material, such as copper, copper alloys, aluminum, aluminum alloys, and the like. The heat generated by the microelectronic die
202
is drawn into the heat sink
208
(following the path of least thermal resistance) by conductive heat transfer.
High surface area heat sinks
208
are generally used because the rate at which heat is dissipated from a heat sink is substantially proportional to the surface area of the heat sink. The high surface area heat sink
208
usually includes a plurality of projections
216
extending substantially perpendicularly from the microelectronic die
202
. It is, of course, understood that the projections
216
may include, but are not limited to, elongate planar fin-like structures and columnar/pillar structures. The high surface area of the projections
216
allows heat to be convectively dissipated from the projections
216
into the air surrounding the high surface area heat sink
208
. A fan
218
may be incorporated into the assembly
200
to enhance the convective heat dissipation. However, although high surface area heat sinks are utilized in a variety of microelectronic applications, they have not been completely successful in removing heat from microelectronic dice which generate substantial amounts of heat. One issue which may contribute to this lack of success is the fact that the geometry of standard high surface area heat sinks results in an air stagnation zone over the center of the heat sink (generally where the most heat is being generated within the microelectronic die). This air stagnation may occur even with the use of the fan
218
.
Another known method of removing heat from a microelectronic die is the use of a “heat pipe” or “vapor chamber”
240
, as shown in
FIG. 6. A
vapor chamber
240
is a simple device that can quickly transfer heat from one point to another without the need for external energy input. The vapor chamber
240
is generally formed by creating a low-pressure atmosphere within a sealed chamber
242
which contains a “working fluid”
244
, such as water or alcohol. The sealed chamber
242
is oriented with a first end
246
proximate a heat source
248
. The working fluid
244
, which is in a liquid phase proximate the heat source
248
, increases in temperature and evaporates to form a gaseous phase of the working fluid
244
, which moves (shown by arrows
252
) toward a second end
254
of the sealed chamber
242
. As the gaseous phase moves toward the sealed chamber second end
254
, it condenses to again form the liquid phase of the working fluid
244
, thereby releasing the heat absorbed during the evaporation of the liquid phase of the working fluid
244
. The liquid phase returns to the sealed chamber first end
246
proximate the heat source
248
, wherein the process is repeated. Thus, the vapor chamber
240
is able to rapidly transfer heat away from the heat source
248
. Various configurations of heat pipes and high surface area finned heat sink have been used to cool microelectronic dice, but they have not been entirely successful in efficiently removing heat from microelectronic dice which generate substantial amounts of heat. One issue which may contribute to this lack of success is the fact that “hotspots” occur in specific locations within the microelectronic dice. The current configurations do not compensate with a higher heat removal for these hotspots. Thus, the circuitry at or proximate these hotspots can be thermally damaged.
Therefore, it would be advantageous to develop apparatus and techniques to effectively remove heat from microelectronic dice while compensating for thermal variations, such as hot spots, within the microelectronic dice.
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patent: 5323292 (1994-06-01), Brzezinski
patent: 5390077 (1995-02-01), Paterson
patent: 5508884 (1996-04-01), Brunet et al.
patent: 5529115 (1996-06-01), Paterson
patent: 5694295 (1997-12-01), Mochizuki et al.
patent: 5844313 (1998-12-01), Hoffmann
patent: 5986884 (1999-11-01), Jairazbhoy et al.
patent: 6082443 (2000-07-01), Yamamoto et al.
patent: 6085831 (2000-07-01), DiGiacomo et al.
Dishongh Terrance J.
Dujari Prateek J.
Lian Bin
Searls Damion T.
Bennett Henry
McKinnon Terrell
Winkle Robert G.
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