The present invention generally relates to microelectronic devices, and more particularly relates to a system for cooling microelectronic devices.
As technology advances, the demand for more lightweight and compact electronic devices continues to increase. To keep up with the demand, smaller microprocessors configured to output more power have been implemented in these devices. These microprocessors allow the devices to perform complex operations at high speeds. During operation, however, the internal temperature of a device may rise to unacceptable levels as the power from the microprocessor is converted into heat. In some instances, the increased temperature may cause the device to function more slowly. In other cases, the device may malfunction. Thus, cooling systems are typically incorporated into the devices.
One type of cooling system includes a thermal interface material, a heat spreader, a single heat pipe, and a heat sink. A heat-generating item, (e.g. a microprocessor) is coupled to the heat spreader, and a thermal interface material is disposed therebetween. The heat pipe extends between the heat spreader and the heat sink. Although this system transfers heat away from the heat-generating item, it has drawbacks. For example, because the system only includes a single heat pipe, an insufficient amount of heat may be removed from the device if the heat pipe fails to operate. Additionally, the system has a limited cooling capability and does not efficiently cool devices including microprocessors, such as those described above.
Another type of cooling system employs a plurality of parallel heat pipes that unidirectionally removes heat from a heat-generating item. The heat pipes are parallel relative to one another and are either (1) all parallel to or (2) all perpendicular to the heat-generating item. Typically, a portion of the item is disposed over at least one of the heat pipes. Thus, the heat pipes closest to the heat-generating item will dissipate more heat than those heat pipes furthest from the item. However, if those heat pipes closest to the item fail to operate, the ability of the cooling system to remove heat may be significantly reduced.
Accordingly, it is desirable to provide a system that efficiently cools a microelectronic device. In addition, it is desirable for the system to be relatively lightweight, compact, and inexpensive to implement. Moreover, it is desirable for the system to continue to cool the device even when a portion of the system is inoperable.
Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Fins 112 are configured to provide additional surface area from which heat from item 102 is dissipated. As briefly mentioned previously, fins 112 extend from bottom side 116 of base plate 110 and may be attached to or integrally formed as part of base plate 110. Fins 112 preferably extend from an outer periphery of base plate 110. Alternatively, fins 112 may reside inside the outer periphery of base plate 110, on either side of the base plate 110. Moreover, although a double row of fins 112 is shown in
A cross section of an exemplary heat pipe 300 is illustrated in
Returning now to
In one exemplary embodiment shown in
Although the first and second heat pipes 106 and 108 are shown as being substantially similar in length, it will be appreciated that in other embodiments, the heat pipes may have unequal lengths. For example, as shown in
Additionally, it will be appreciated that although
In still another exemplary embodiment, as shown in
Cooling system 100 may alternatively include additional features that cooperate with heat sink 104 to further reduce that amount of heat that may be present therein. For example, as shown in
Also shown in
During operation, with reference to
Additionally, the inventors have discovered that the above-described method and system dissipate heat more effectively than other known designs. In one experiment, a die with four heat sources dissipating up to about 170 Watts was placed over a prior art cooling system having heat pipes disposed along parallel lines, and a similar die was placed over a cooling system 100 having heat pipes disposed along non-parallel lines, for example, in a cross configuration. The temperature of the die over the parallel heat pipe configuration was measured to be 99.3° C., while the temperature of the die over the non-parallel heat pipe configuration was advantageously lower and measured as 99.1° C. In another example, flanges 150 were inserted between the die and the heat pipes in the parallel and non-parallel configurations. The temperature of the die over the parallel heat pipes was measured at 93.0° C., while the temperature of the die over the non-parallel heat pipes was about 92.1° C.
The results from the experiments described above indicate that heat from a die disposed over a crossed heat pipe configuration is being removed more efficiently than in a parallel heat pipe configuration. Exposure of a die to lower temperatures reduces wear caused by thermal exposure and increases the useful life of the die. Thus, the crossed heat pipe configuration provides a simple solution for improving the thermal performance of a cooling system, while maintaining associated manufacturing costs within reasonable bounds.
A cooling system for cooling a microelectronic device has now been provided. In one exemplary embodiment, the system includes a heat sink and a first and a second heat pipes. The heat sink has a top side and a bottom side, where the top side is coupled to the microelectronic device. The first and a second heat pipes are embedded in the heat sink. The first heat pipe is disposed along a first line, and the second heat pipe is disposed along a second line that is not parallel to the first line. Each of the first and second heat pipes includes a portion located beneath the microelectronic device. In another exemplary embodiment, the first heat pipe divides the heat sink into a first section and a second section and the second heat pipe is embedded in the first section. In another exemplary embodiment, the heat sink further comprises a plurality of fins disposed proximate a periphery of the heat sink. Alternatively, at least a portion of each heat pipe is thermally coupled to at least one fin of the plurality of fins. The system may further comprise a third heat pipe disposed along said second line and in the second section, and the third heat pipe may include a portion located beneath the microelectronic device. The second and third heat pipes may contact the first heat pipe.
In still another exemplary embodiment, the first line and said second line are disposed in substantially the same plane. Alternatively, the system may further comprise a flange disposed between said heat sink and the microelectronic device. The flange amy comprise copper. In an alternate embodiment, at least a portion of the heat sink comprises a material selected from the group consisting of copper and aluminum. In yet another exemplary embodiment, the system may further comprise a fan coupled to the bottom side of the heat sink. In still yet another exemplary embodiment, the first and second heat pipes each comprise a tubular housing having an inner peripheral surface defining a cavity, a wick structure disposed on the inner peripheral surface of the tubular housing, and a fluid disposed in the cavity of the tubular housing in an amount sufficient to at least partially saturate the wick structure.
In another exemplary embodiment, a system for cooling a microelectronic device is provided that includes a heat sink, and first and second heat pipes. The heat sink has a base and a plurality of fins. The base includes a top side and a bottom side, where the top side is coupled to the microelectronic device, and the plurality of fins extend from the bottom side and are disposed proximate an outer periphery of the base. The first heat pipe is embedded in the base and disposed along a first line and has a first portion disposed beneath the microelectronic device and a second portion thermally coupled to at least one fin of the plurality of fins. The second heat pipe is embedded in the base along a second line that is not parallel to the first line, and the second heat pipe has a first portion disposed beneath the microelectronic device and a second portion thermally coupled to at least one fin of the plurality of fins.
In an alternative embodiment, a third heat pipe is disposed along said second line, the first heat pipe divides the heat sink into a first section and a second section, the second heat pipe is disposed in the first section, and the third heat pipe is disposed in the second section. In another alternative embodiment, the first and second heat pipes contact each other. The first and second lines may be disposed in substantially the same plane. Alternatively, the first and second lines are substantially perpendicular with respect to each other. In still another exemplary embodiment, a flange is coupled between the microelectronic device and the heat sink.
In still yet another exemplary embodiment, a method of cooling a microelectronic device is provided where the microelectronic device includes a heat sink and a first and a second heat pipe, the heat sink coupled to the microelectronic device, and the first and the second heat pipes embedded in the heat sink and having at least a portion disposed below the microelectronic device, the first heat pipe disposed along a first line, the second heat pipe disposed along a second line that is not parallel to the first line, each heat pipe including liquid disposed therein and a portion thermally coupled to at least one fin. In one embodiment, the method comprises the steps of transferring heat from the device to at least a portion of the first and second heat pipes disposed proximate the device, vaporizing the heat pipe liquid into a gas, in response to the heat from the device, and transporting the gas radially outward from the portions of the first and second heat pipes proximate the device to the outer periphery of the heat sink.
Alternatively, the heat sink further comprises a plurality of fins extending from the outer periphery thereof and the step of transporting the gas comprises transferring heat from the gas to at least one of the plurality of fins.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.