Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
2002-03-27
2004-07-27
Zarneke, David A. (Department: 2827)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
Reexamination Certificate
active
06767765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and methods for disposing a thermal interface material between a heat source and a heat dissipation device. In particular, the present invention relates to a microelectronic package comprising a heat dissipation device having an inlet over a back surface of a microelectronic device and an outlet away from the microelectronic device back surface, wherein the thermal interface material is disposed between the heat dissipation device and the microelectronic device through the inlet.
2. State of the Art
Higher performance, lower cost, increased miniaturization of integrated circuit components, and greater packaging densities of integrated circuits are ongoing goals of the microelectronic industry. As these goals are achieved, microelectronic dice become smaller. Accordingly, the density of power consumption of the integrated circuit components in the microelectronic device has increased, which, in turn, increases the average junction temperature of the microelectronic device. If the temperature of the microelectronic device becomes too high, the integrated circuits of the microelectronic device may be damaged or destroyed.
Various apparatus and techniques have been used and are presently being used for removing heat from microelectronic devices. One such heat dissipation technique involves the attachment of a heat dissipation device to a microelectronic device.
FIG. 9
illustrates an assembly
200
comprising a microelectronic device
202
(illustrated as a flip chip) physically and electrically attached by an active surface
204
thereof to a first surface
206
of a carrier substrate
208
by a first plurality of interconnects
212
, such as solder balls. An underfill material
214
may be disposed between the microelectronic device active surface
204
and the carrier substrate
208
. A second plurality of interconnects
216
may be attached to a second surface
218
of said carrier substrate
208
for connection to external components (not shown).
An interior surface
224
of a heat dissipation device
226
may be attached to a back surface
228
of the microelectronic device
202
by a thermal interface material
232
, such as thermally conductive adhesive or solder. The heat dissipation device
226
may further comprise a lip portion
234
extending toward and attached to the carrier substrate
208
with an adhesive material
236
, such as epoxies, urethane, polyurethane, silicone elastomers, and the like. The heat dissipation device
226
may be constructed from a thermally conductive material, such as copper, copper alloys, aluminum, aluminum alloys, and the like.
However, the disposition of the thermal interface material
232
between the microelectronic device
202
and the heat dissipation device
226
is a difficult process.
FIG. 10
illustrates a known process for disposing the thermal interface material. The thermal interface material is placed as pre-formed sheet
242
between the microelectronic device back surface
228
and the heat dissipation device interior surface
224
. The assembly is then pressurized (first force
244
on the heat dissipation device
226
and/or second force
246
on the microelectronic device
202
) while being heated, such as in an oven, which melts the thermal interface material pre-formed sheet
242
and adheres it to the heat dissipation device
226
and the microelectronic device
202
. Unfortunately, this process can easily trap air pockets or voids
248
between the thermal interface material pre-formed sheet
242
and the heat dissipation device interior surface
224
, and/or the thermal interface material pre-formed sheet
242
and the microelectronic device back surface
228
. The voids
248
greatly reduce the heat transfer from the microelectronic device
202
, as will be understood to those skilled in the art.
FIGS. 11 and 12
show methods of forming a void-free thermal interface.
FIG. 11
illustrates one method which comprises placing a liquid thermal interface material
252
on an edge
254
of a gap
256
between the heat dissipation device interior surface
224
and the microelectronic device back surface
228
. The liquid thermal interface material
252
is drawn into the gap
256
in direction
258
by capillary action. One way to achieve this is dip the edge
254
into a solder bath. However, as it is understood by those skilled in the art, it is difficult to apply this method to the assembly, as shown in
FIG. 9
, due to the larger sizes of the heat dissipation device
226
and carrier substrate
208
, relative to the microelectronic device
202
.
FIG. 12
illustrates another method which comprises placing a small, thick thermal interface material globule
262
between the heat dissipation device interior surface
224
and the microelectronic device back surface
228
at or near a center of the microelectronic device back surface
228
. The thermal interface material globule
262
is then heated, such as in an over, so that it becomes flowable and a first force
264
is placed on the heat dissipation device
226
and/or second force
266
is placed on the microelectronic device
202
, such that the thermal interface material
262
is dispersed across the microelectronic device back surface
228
. This method can be used in situations were the microelectronic device
202
is small (i.e., small bonding applications). However, for microelectronic devices
202
larger than about 300 mils in length, this method becomes ineffective, as the thermal interface material may not extend to the edges of the microelectronic device
202
without considerable pressure and/or temperature.
Therefore, it would be advantageous to develop an improved method and related apparatus for dispersing a thermal interface material between a microelectronic device and a heat dissipation device.
REFERENCES:
patent: 5608262 (1997-03-01), Degani et al.
patent: 5796582 (1998-08-01), Katchmar
patent: 6015722 (2000-01-01), Banks et al.
patent: 6016006 (2000-01-01), Kolman et al.
patent: 6117382 (2000-09-01), Thummel
patent: 6552906 (2003-04-01), Kanada
Winkle Robert G.
Zarneke David A.
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