PATENT DOCUMENT

Publication Number: US-7385821-B1
Application Number: US-2038401-A
Country: US
Kind Code: B1

Title: Cooling method for ICS

Abstract:
The present invention is a cooling device for removing heat from an integrated circuit. In one embodiment, the cooling device includes a conduit and a flexible channel having a first open end and a second closed end. The flexible channel&#39;s first open end has an internal width and is coupled with the conduit. The flexible channel is comprised of a resilient material having spring-like characteristics. In one embodiment, this material provides a spring-like restoring force when compressed. The cooling device also includes an interconnect mechanism between the conduit and the flexible channel to allow a gas or a fluid introduced within the conduit to move between the conduit and the flexible channel.

Claims:
1. A cooling device for removing heat from an integrated circuit, said cooling device comprising:
 a conduit; 
 a flexible channel to alternate between a compressed position and an extended position and having a first open end and a second closed end, said first open end coupled with said conduit, said open end having an internal width, said flexible channel comprised of a resilient material having spring-like characteristics, said material to provide a spring-like restoring force when compressed, the second closed end comprising a thermally conductive material attached to said flexible channel, said thermally conductive material having a substantially planar surface to interface directly with said integrated circuit when said flexible channel is extended and to detach from said integrated circuit in said compressed position, said flexible channel being conformable with an integrated circuit disposed at an angle relative to the first open end; 
 an interconnect mechanism between said conduit and said flexible channel to allow a fluid introduced within said conduit to move between said conduit and said flexible channel; and 
 a heat sink attached to an interior surface of said closed end in the compressed position and in the extended position to cause heat absorbed by said closed end to be conducted through said conduit and said flexible channel wherein said heat sink comprises a plurality of spaced apart planar fins wherein a portion of said spaced apart planar fins extends into said conduit in said extended position, the planar fins being perpendicular to a flow of the fluid through the conduit. 
 
   
   
     2. A cooling device as in  claim 1 , wherein said interconnect mechanism is an opening in a surface of said conduit. 
   
   
     3. A cooling device as in  claim 1 , wherein said opening has a width equal to said internal width of said open end. 
   
   
     4. A cooling device as in  claim 1 , wherein said open end is coupled with said conduit by a technique selected from the group consisting of soldering, sautering, welding, and adhering. 
   
   
     5. A cooling device as in  claim 4 , wherein said flexible channel, including said closed end, is sealed, and further comprising:
 a port for coupling to a pump coupled to said conduit configured to reduce a pressure in said conduit and said flexible channel to compress said flexible channel and to remove said conductive material from said integrated circuit. 
 
   
   
     6. A cooling device as in  claim 1 , wherein said thermally conductive material is copper. 
   
   
     7. A cooling device as in  claim 1 , wherein said resilient material comprises a material selected from the group of which phosphor bronze and beryllium copper are members. 
   
   
     8. A cooling device as in  claim 1 , wherein said resilient material is pleated. 
   
   
     9. A cooling device as in  claim 1 , wherein said flexible channel is in a compressed state. 
   
   
     10. A cooling device as in  claim 9 , further comprising:
 a vacuum pressure within said conduit and said flexible channel. 
 
   
   
     11. A cooling device as in  claim 9 , wherein a pressure within said flexible channel is less than 1.0 atmosphere. 
   
   
     12. A cooling device as in  claim 9 , wherein said fluid is within said flexible channel. 
   
   
     13. A cooling device as in  claim 1 , wherein said flexible channel is in an extended state. 
   
   
     14. A cooling device as in  claim 13 , wherein a pressure within said extended flexible channel approximately equals 1.0 atmosphere. 
   
   
     15. A cooling device as in  claim 13 , wherein a pressure within said extended flexible channel is not a vacuum pressure. 
   
   
     16. A cooling device as in  claim 15 , wherein said fluid is contained within said conduit and said flexible channel. 
   
   
     17. A cooling device as in  claim 16 , wherein said fluid is heated. 
   
   
     18. A cooling device as in  claim 16 , wherein said fluid is cooled. 
   
   
     19. A cooling device as in  claim 16 , wherein said closed end contacts said integrated circuit and wherein heat from said integrated circuit is dissipated by said fluid contained within said conduit and said flexible channel. 
   
   
     20. A cooling device as in  claim 16 , further comprising:
 a plurality of flow diverters attached within said conduit to create turbulence in said fluid. 
 
   
   
     21. A cooling device as in  claim 1 , wherein said flexible channel is compressed by creating a vacuum pressure within said flexible channel. 
   
   
     22. A cooling device as in  claim 1 , wherein said flexible channel is compressed by creating a pressure of less than 1.0 atmosphere within said flexible channel. 
   
   
     23. A cooling device as in  claim 1 , wherein said flexible channel is extended by equalizing a vacuum pressure within said flexible channel to approximately equal 1.0 atmosphere. 
   
   
     24. A cooling device as in  claim 1 , wherein said flexible channel is extended by creating a pressure approximately equal to 1.0 atmosphere within said flexible channel. 
   
   
     25. A cooling device as in  claim 1  wherein said conduit is a heat pipe. 
   
   
     26. A cooling device as in  claim 25 , further comprising:
 wicking material contained within said heat pipe; and 
 a reservoir coupled with said heat pipe, said reservoir to contain said fluid. 
 
   
   
     27. A cooling device as in  claim 26 , wherein said fluid is contained within said heat pipe. 
   
   
     28. A cooling device as in  claim 26 , wherein a gas is contained within said heat pipe.

Description:
FIELD OF THE INVENTION 
   The present invention relates to cooling or dissipating heat generated by operation of integrated circuits and other electronic devices, and more particularly to methods and apparatus for cooling integrated circuits. More particularly, the present invention relates to techniques and assemblies for integrated circuits that use flexible attachments on pressurized air or liquid cooling heating ducts to make firm contact with the integrated circuit to be cooled. 
   BACKGROUND OF THE INVENTION 
   There are numerous assemblies and methods for making and using integrated circuit heat cooling devices in the prior art. For example, the classic technique for removing excess heat from an integrated circuit or other electronic device involves attaching a heat sink to the integrated circuit or other electronic device. This heat sink typically includes a plurality of extruded, planar fins whose large surface area efficiently dissipates heat into the surrounding air or into a coolant circulating inside the fins. 
   Typically, heat transfer between the hot surface of a heat generating device and the surrounding air is the least efficient means of dissipating excess heat. Use of a heat sink significantly improves this heat transfer by increasing the surface area in contact with the cooling ambient (e.g. air or liquid). As a result, the device&#39;s operating temperature is lowered, and its performance reliability and life expectancy are increased. 
   A thermally conductive path is formed by attaching the heat sink to a surface of the electronic device to be cooled. Typically, this path includes a thermal interface material sandwiched between a contact surface of the heat sink and a contact surface of the electronic device. Depending on the embodiment, the thermal interface material may be malleable, electrically conductive, or electrically isolating. Exemplary electrically conductive thermal interfaces include: thermal greases filled with metallic particles, thermal adhesives, and thin films. Exemplary electrically isolating thermal interfaces include: gap fillers, double sided tapes, and pads. Thermal greases include Sil-Free™, a metal-oxide filled, silicone-free, synthetic grease manufactured by Aavid Thermalloy of Concord, N.H. Sil-Free™ is specially designed for bonding heat sinks to semi-conductor cases, and will not dry out, harden, melt, or run even after long term continuous exposure to temperatures up to 200 degrees Celsius. 
   Other types of thermal interfaces include silicone-based thermal greases and phase-changing materials. One type of phase-changing material is a solid, silicone-free, paraffin-based thermal compound manufactured by Aavid Thermalloy of Concord, N.H. that changes phase at approximately 60 degrees Celsius, with a concurrent volumetric expansion that fills gaps between the mating surfaces. 
   Thermally conductive adhesives offer excellent heat transfer and high voltage isolation. Typically manufactured as epoxies that offer low shrinkage and coefficients of thermal expansion comparable to copper or aluminum, thermally conductive adhesives bond readily to metals, glass, ceramics, and most plastics. 
   Thin films are cost-effective alternatives to thermally conductive grease compounds. Thin films may be applied with commercial hot-stamping equipment to the surfaces of heat producing devices; and such films yield excellent thermal performance while obviating the need for adhesives. 
   Gap-fillers are “super-soft”, low durometer materials designed to fill gaps between hot components and their heat sinks. The flexible elastic nature of gap fillers allows them to blanket uneven surfaces, and to conduct heat away from individual components, or an entire printed circuit board, into metal covers, frames, or spreader plates. 
   Double-sided tapes may be used to adhere the heat sink to the hot component. They are easily applied, require no curing time, can be electrically conductive or isolating, and require no mechanical support to provide thermal or by physical contact between the heat conductive device and the heat sink. 
   Thermal interface pads are typically thicker than double sided tapes, but can be provided without adhesive if removal of the pad is necessary. Although pads can be either electrically conductive or insulating, performance of the interface depends on maintenance of correct, constant mounting pressure applied to the pads. 
   Based on the above discussion, it will be appreciated that a plurality of heat exchangers may be attached to one or more surfaces of an electronic device using mounting clips, adhesives, or extruded pins. It will also be appreciated that the cooling fins, and heat exchangers themselves, may take a variety of configurations. For example, the surfaces of the cooling fins may be flat or dimpled, and the fins themselves may be bonded or folded. Bonded fins tend to dissipate more heat than conventional aluminum heat sinks with the same footprint, and manufacturing techniques permit increased fin ratios of 30:1 and higher. Increasing the number of fins increases the surface area exposed to cooling air, and greater exposed surface area means more heat transferred away from the heat conducting device. Folded fin designs offer maximum cooling surface in minimum volume, and may be manufactured of such materials as aluminum or copper. Liquid-cooled cold plates can provide cooling where aircooling techniques are impractical or inadequate. Liquid-cooled cold plates dissipate more heat with less flow volume of cooling ambient (as compared to air), maintain better temperature consistency, and create less acoustic noise than air-cooled heat exchangers. 
   As shown in  FIG. 1 , a conventional heat sink  100  includes a base material  101  having a contact surface  102  and a finned surface  103 . The finned surface  103  is formed of a plurality of planar sections (or fins)  104  that are vertically disposed such that their planar surfaces parallel each other. Typically, adjacent fins are separated by an air channel  105 . The air channel  105  develops airflow through the heat sink fins  104 . The airflow cools an electronic device attached to the contact surface  102  of the heat sink  100  by dissipating the heat conducted through heat sink  100  and accumulated in fins  104 . The base material  101  and fins  104  may be manufactured of any suitable heat-conductive material, such as aluminum. 
     FIG. 2  shows one example of a prior art liquid-cooled heat exchanger  200 . As shown in  FIG. 2 , the base material  201  and fins  204  may be hollow, or may contain a hollow tube (or tubes) (not shown). A liquid coolant (or fluid)  206 , such as water, may be introduced into the hollow base material  201  and/or fins  204 , and heated or cooled in order to affect or control the temperature of the electronic device  207  attached to the heat exchanger  200 . Alternatively, the liquid coolant  206  may be introduced into the hollow tube (not shown) under pressure, and heated or cooled in order to affect or control the temperature of the electronic device  207  attached to the heat exchanger  200 . 
   In certain applications, however, such as portable computers, factors such as size, weight, and cost are important. However, adding conventional heat sinks to the computer&#39;s internal electrical components can increase its size, weight, and cost, thereby making the computer less profitable and less competitive in the marketplace. A significant drawback associated with conventional heat exchangers is the high cost of ensuring the near-perfect co-planarity of the heat exchanger and electrical component mating surfaces. Co-planarity of mating surfaces is important because the more co-planar the two surfaces are, the more efficient the heat transfer. However, it is difficult to manufacture co-planar mating surfaces smooth enough to produce an effective thermal contact. 
   Because of manufacturing limitations, several techniques and assemblies have been developed that can be used to form an efficient thermal contact between substantially co-planar mating surfaces. For example, a device manufactured by IBM of White Plains, N.Y., uses pistons which drive the heat exchanger (or cylindrical portions of the heat exchanger) down onto a printed circuit board or other electronic device. Although the pressure exerted by the expanding pistons ensures an efficient thermal contact with the heat producing device, such assemblies are expensive to manufacture, expensive to maintain, heavy, and rarely solve any co-planarity issues that might exist when making physical contact with multiple integrated circuits mounted on the heat producing device (e.g. printed circuit board). 
   Thus, it is desirable to provide an improved, non-conventional cooling device assembly and techniques which may take advantage of a hollow, resilient material having spring-like characteristics that provides a spring-like force when compressed against and in contact with a surface of an integrated circuit or other heat producing device. 
   SUMMARY OF THE INVENTION 
   The present invention is a cooling device for removing heat from an integrated circuit. In one embodiment, the cooling device includes a conduit and a flexible channel having a first open end and a second closed end. The flexible channel&#39;s first open end has an internal width and is coupled with the conduit. The flexible channel is comprised of a resilient material having spring-like characteristics. In one embodiment, this material provides a spring-like restoring force when compressed. The cooling device also includes an interconnect mechanism between the conduit and the flexible channel to allow a gas or a fluid introduced within the conduit to move between the conduit and the flexible channel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a conventional heat exchanger. 
       FIG. 2  is a sectional view of a second conventional heat exchanger. 
       FIG. 3  is a cross-sectional view of a cooling device having flexible channels attached thereto, according to one embodiment of the invention. 
       FIG. 4  is another cross-sectional view of a cooling device having flexible channels attached thereto, according to one embodiment of the invention. 
       FIG. 5A  is a cross-sectional view of a cooling device showing the flexible channels in a first compressed state, according to one embodiment of the invention. 
       FIG. 5B  is a cross-sectional view of a cooling device showing the flexible channels in a second extended state, according to one embodiment of the invention. 
       FIG. 6A  is a perspective view of a flexible channel, according to one embodiment of the invention. 
       FIG. 6B  is a perspective view of a flexible channel, according to another embodiment of the invention. 
       FIG. 7  is a cross-sectional view of a cooling device that includes a flow diverter within the conduit and a heat exchanger within each of the flexible channels, according to another embodiment of the invention. 
       FIG. 8A  is a cross-sectional view of a cooling device having flexible channels attached thereto, according to one embodiment of the invention. 
       FIG. 8B  is a cross-sectional view of a cooling device having flexible channels attached thereto, according to another embodiment of the invention. 
       FIG. 9  is a cross-sectional view of another cooling device having a wick therein and having flexible channels attached thereto, according to another embodiment of the invention. 
       FIG. 10  is cross-sectional view of a plurality of cooling devices, each having a plurality of flexible channels attached thereto, according to another embodiment of the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   An apparatus and techniques for cooling electronic and electrical devices are disclosed. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details need not be used to practice the present invention. In other circumstances, well-known structures, materials, or processes have not been shown or described in detail in order to not unnecessarily obscure the present invention. 
     FIG. 3  is a cross-sectional view of a cooling device having flexible channels attached thereto, according to one embodiment of the invention. The cooling device  300  shown in  FIG. 3  may be formed by any number of methods. For example, the open ends of flexible channels  303 A and  303 B may be mechanically secured to conduit  301  by a soldering, welding, sautering, or adhering operation. The flexible channels  303 A and  303 B may be made of a flexible material having spring-like characteristics that produces a spring-like restoring force when compressed. As shown in  FIG. 3 , the flexible material may be pleated with accordion-like folds. The flexible channels  303 A and  303 B are shown with corrugated cross-sections which illustrate their resilient or spring-like compressive nature. It will be appreciated that the cross-section of the flexible channel may have a variety of profiles as long as it proves compressible and capable of producing a spring-like restoring force when compressed. Examples of resilient materials that may be used to form the middle portions of flexible channels  303 A and  303 B include, but are not limited to, phosphor bronze and berillium copper. 
   Internally, flexible channels  303 A and  303 B are hollow. Interconnect mechanisms (e.g. an opening)  313 A and  313 B may be provided in the surface of conduit  301  to allow a fluid, such as a liquid or a gas, to move freely between the interior of conduit  301  and the interior of flexible channels  303 A and  303 B. The width of the interconnect mechanisms  313  may be the same as or less than the internal width of the flexible channels&#39; open ends. 
   Each flexible channel  303  has a closed end  305 . This closed end is formed by attaching a thermally conductive material to the resilient material forming the middle portion of flexible channels  303 A and  303 B. Preferably, the thermally conductive material is attached in such a way that closed ends  305  are completely sealed. Various attachment methods may be used, including welding, adhering, soldering, and sautering. Similarly, various thermally conductive materials, well known in the art, may be used. Preferably, however, the thermally conductive material is copper, a copper alloy, or similar metal. The thermally conductive material is manufactured to have a substantially planar exterior surface. Preferably, the exterior surface is as smooth and planar as possible to ensure co-planarity (e.g. as continuous a fit as possible) with the electronic or electrical device to be cooled. Thus, the exterior surface of the thermally conductive material may be polished to a mirror-like finish. In another embodiment, a heat conductive paste may be disposed between the substantially planar exterior surface and the electronic or electrical device to be cooled. This heat conductive paste improves heat transfer by virtually eliminating air pockets trapped between discontinuities in the mating surfaces. 
   In  FIG. 3 , the flexible channels  303 A and  303 B are shown in an extended state and in contact with two integrated circuits (IC&#39;s)  310  and  311 , which are shown mounted to a printed circuit board (PCB)  320 . IC&#39;s  310  and  311 , are shown packaged with leads soldered to the PCB  320 . However, it will be appreciated that IC&#39;s  310  and  311  may be modified to accommodate socketed, pin grid array, ball grid array, and other IC technologies, including various packaging technologies. It will also be appreciated that although two flexible channels  303 A and  303 B and two IC&#39;s  310  and  311  are shown, the invention is not so limited. Rather, the invention includes a single flexible channel  303 . It also includes more than two flexible channels  303 A and  303 B in combination with a corresponding number of IC&#39;s. 
     FIG. 4  is another cross-sectional view of a cooling device  300  having flexible channels attached thereto, according to one embodiment of the invention. In  FIG. 4 , a conduit  301  is attached to an open end of a single flexible channel  303 . A portion of the closed end of flexible channel  303  (e.g. the exterior surface of thermally conductive material  410 ) is shown contacting a single IC  415 , which is mounted on a PCB  320 . In order not to unnecessarily complicate the invention, only a single flexible channel  303  and single IC  415  are shown, but it will be appreciated that the invention may be modified to include a plurality of flexible channels  303 A and  303 B together with a corresponding plurality of IC&#39;s  415 . As shown, flexible channel  303  is able to conform to electronic and electrical devices that are not co-planar with the cooling device or that are not co-planar with the printed circuit board. 
   Illustratively, the co-planarity difference between the closed end of flexible channel  303  and IC  415  is depicted as angle  420 . As the closed end of flexible channel  303  contacts a non-coplanar IC or other electronic or electrical device, the resilient, spring-like characteristics of the flexible material forming the middle portion of flexible channel  303  allow the flexible channel  303  to conform to the non-coplanar surface of the IC  415 . In this manner, a near uniform compressive force and contact with the surface of the IC  415  are provided. It will be appreciated that the flexible channel  303  varies its dimensional or cross-sectional shape when accommodating a non-coplanar electrical or electronic device. This variation is shown in  FIG. 4  as one side  404  of the closed end of flexible channel  303  having been compressed less than the other side  405 . 
     FIG. 5A  is a cross-sectional view of a cooling device showing the flexible channels in a first resting position, according to one embodiment of the invention. Both  FIGS. 5A and 5B  show a cooling device  500  positioned over two IC&#39;s  510  and  511 . In a preferred embodiment, conduit  301  and flexible channels  503 A and  503 B are not sealed, and the respective interior and exterior pressures are approximately equal. When there is no contact with IC&#39;s  510  and  511  or other electronic or electrical devices, the flexible channels will have a natural resting position, such as the extended position illustratively shown in  FIG. 5A , due to the spring-like nature of the flexible material forming the middle portions of flexible channels  503 A and  503 B. 
   Referring now to  FIG. 5B , which is a cross-sectional view of a cooling device  500  showing the flexible channels  503 A and  503 B in a second operating position, IC&#39;s  510  and  511  may be brought into contact with the closed ends of flexible channels  503 A and  503 B by moving the cooling device  500  toward a PCB  520  that has been fixed to a frame, housing or enclosure. In such an embodiment, the flexible channels compress to conform to the top surface of the IC&#39;s  510  and  511 , as shown. As the distance between conduit  301  and IC&#39;s  510  and  511  decreases, the flexible channels  302 A and  302 B compresses in comparison to their resting state and their resilient nature produces a spring-like restoring force that pushes the closed ends of flexible channels  503 A and  503 B towards the top surfaces of IC&#39;s  510  and  511 . In this manner, a uniform area of contact is provided. Once the flexible channels  503 A and  503 B contact IC&#39;s  510  and  511 , the amount of pressure exerted on each IC by flexible channels  503 A and  503 B may be controlled by variation of the physical proximity of PCB  520  to conduit  301 . 
     FIGS. 6A and 6B  are perspective views of a flexible channel, according to various embodiments of the invention.  FIG. 6A  illustrates one embodiment of a flexible channel  600 A having a squarish cross-section. Flexible channel  600 A includes a closed end  601 , a flexible, pleated middle portion  603 , and an open end  602 , which attaches to a conduit (not shown). Closed end  601  is formed of a thermally conductive material, and the exterior (top) surface of closed end  601  may be substantially planar, as described above. In one embodiment, closed end  601  is attached to flexible, pleated middle portion  603  in such a way that the connection between closed end  601  and flexible, pleated middle portion  603  is sealed (e.g. airtight). In such an embodiment, the connection between open end  602  and a conduit (not shown) may also be sealed. Sealing the connections permits flexible channel  600  to be compressed by creating a vacuum within its interior. The vacuum compressed flexible channel may be extended by equalizing the internal vacuum pressure to approximately equal 1.0 atmosphere. 
   Alternatively, the connections between closed end  601  and flexible, pleated middle portion  603  and between open end  602  and a conduit (not shown) may be unsealed. In such an embodiment, the flexible, pleated middle portion  603  may occupy a first extended position when not in contact with a device to be cooled. Similarly, when brought into contact with such a device, flexible, pleated middle portion may occupy a second compressed position. 
     FIG. 6B  illustrates another embodiment of a flexible channel  600 B having a circular cross-section. In  FIG. 6B , flexible channel  600 B includes a closed end  604 , a pleated middle portion  605 , and an open end  606 , which attaches to a conduit (not shown). As discussed above, the connections between closed end  604  and flexible, pleated middle portion  605 , and between open end  606  and a conduit (not shown), may be sealed, or unsealed, depending upon the embodiment. It will be appreciated that the cross-sectional shape of flexible channel  600  may take a variety of shapes, and is not limited to the illustrative examples depicted in  FIGS. 6A and 6B . It will also be appreciated that the dimensions of flexible channel are scalable. However, in a preferred embodiment, closed end  604  has a surface area measuring approximately 2 cm; flexible, pleated middle portion has an inner diameter of approximately 1 cm to approximately 2 cm; and open end  606  has an inner diameter of approximately 2 cm. Similarly, a length of flexible channel  600 B, as measured from an edge of closed end  604  to an edge of open end  606 , may measure approximately 0.8 cm when extended. When compressed, the length of flexible channel  600 B may measure approximately 0.4 cm. 
     FIG. 7  is a cross-sectional view of a cooling device  700  that includes a flow diverter  770  within the conduit  301  and a heat exchanger  730  and  731  within each of the flexible channels  715 A and  715 B, according to another embodiment of the invention. In  FIG. 7 , a cooling device  700  is positioned over two IC&#39;s  710  and  711  mounted on a PCB  720 . Flexible channels  715 A and  715 B have been extended from a first compressed position to contact the top surfaces of IC&#39;s  710  and  711 . Attached to the inner surface of closed ends  718 A and  718 B, are two heat exchangers  730  and  731 . The heat exchangers  730  and  731  each have base portions  750 A and  750 B, which mate with the inner surfaces of closed ends  718 A and  718 B. The heat exchangers  730  and  731  also each have a plurality of fins  740 A and  740 B, respectively. 
   A wide variety of thermally conductive materials well known to those skilled in the art may be used to form base portions  750 A and  750 B and the plurality of fins  740 A and  740 B. Exemplary materials include, but are not limited to: aluminum, copper, aluminum alloys, copper alloys, and similar thermally conductive materials. 
   As shown in  FIG. 7 , the height of fins  740 A may be less than the interior length of compressed flexible channel  715 A. In such an embodiment, the tips of fins  740 B do not break the plane of the conduit&#39;s  301  lower wall when flexible channel  715 A is compressed. Alternatively, as shown in  FIG. 7 , the height of fins  750  may be more than the interior length of compressed flexible channel  715 B. In such an embodiment, the tips of fins  740 B break the plane of the conduit&#39;s  301  lower wall when flexible channel  715 B is compressed. 
   Where flexible channels  715 A and  715 B, and the connections between them and conduit  301 , are sealed, a gas or fluid (e.g. liquid such as water or an inert coolant) may be contained within the interior portion of conduit  301  and within the interior portions of flexible channels  715 A and  715 B. This gas or fluid may be pressurized or not, and may be either heated or cooled using external heating and cooling mechanisms (not shown) coupled with conduit  301 . Alternatively, hot or cold air may be contained within the interior portion of conduit  301  and within the interior portions of flexible portions  715 A and  715 B. 
   In  FIG. 7 , the flow of air, gas, or fluid is depicted by arrows  721  and  722 . In some embodiments, one or more flow diverters  770  may be attached at various points within conduit  301  to create turbulence in the flow of air, gas, or fluid within the interior portion of conduit  301 . Flow diverters  770  may also be attached within the interior portions of flexible channels  715 A and  715 B. Because heat is dissipated through heat exchangers  730  and  731  into the air, gas, or fluid flowing over and around fins  740 A and  740 B, creating turbulence provides a more efficient heat transfer by continually mixing cooler air, gas, or fluid with warmer air, gas, or fluid. 
   Though shown in  FIG. 7  as having a triangular cross-sectional shape, it will be appreciated that the cross-sectional shape of flow diverter  770  may take a variety of forms. It will also be appreciated that flow diverter  770  may be formed of a wide variety of materials, including thermally conductive materials such as aluminum and copper, and from non-thermally conductive materials such as plastic, fiberglass, or polymers. 
     FIG. 8A  is a cross-sectional view of a cooling device  800  having sealed flexible channels  803 A and  803 B attached thereto, according to one embodiment of the invention. In  FIG. 8A , there is shown a sealed conduit  301  containing a gas under less than 1.0 atmosphere pressure (e.g. a vacuum). Sealed conduit  301  is positioned over two IC&#39;s  810  and  811  mounted on a PCB  820 . In one embodiment, a complete vacuum may exist within conduit  301  and within flexible channels  803 A and  803 B, meaning that the interiors of conduit  301  and flexible channels  803 A and  803 B contain no gas, air, or fluid at all. In  FIG. 8A , flexible channels  803 A and  803 B are shown compressed due to the compressive force of external atmospheric pressure, which is greater than the internal pressure. 
   When compressed, flexible channels  803 A and  803 B do not contact the top surfaces of IC&#39;s  810  and  811 . However, IC&#39;s  810  and  811  are positioned a distance  830  from the lower side of conduit  301  so that they can contact flexible channels  803 A and  803 B when the flexible channels are extended. It will be appreciated that distance  830 , as measured vertically from a bottom side of conduit  301  to a top surface of IC  810  or  811 , is less than the maximum distance  840  that flexible channels  803 A and  803 B can be extended. This ensures that flexible channels  803 A and  803 B will exert sufficient compressive force to ensure the co-planarity needed for an efficient heat transfer. 
     FIG. 8B  is a cross-sectional view of a cooling device  800  having flexible channels attached thereto, according to another embodiment of the invention. In  FIG. 8B , an unsealed conduit  301  is shown positioned above IC&#39;s  810  and  811  mounted on a PCB  820 , such that flexible channels  803 A and  803 B contact the top surfaces of IC&#39;s  801  and  811 , respectively. In  FIG. 8B , flexible channels  803 A and  803 B are shown extended as a result of equalized internal and external atmospheric pressure (e.g. the internal pressure approximately equals 1.0 atmosphere). In the absence of vacuum pressure, the flexible, pleated material forming the middle portions of flexible channels  803 A and  803 B provides a spring-like restoring force that extends flexible channels  803 A and  803 B from the compressed position shown in  FIG. 8A  to the extended position shown in  FIG. 8B . When extended, the flexible channels  803 A and  803 B mate with the top surfaces of IC&#39;s  810  and  811 , provided of course, that IC&#39;s  810  and  811  are positioned a distance  830  from the bottom side of conduit  301  that is less than the maximum distance  840  that flexible channels  302 A and  302 B can extend. 
   Referring again to  FIG. 8A  another embodiment is described. In this embodiment, sealed conduit  301  contains a air, gas, or a fluid, and flexible channels  803 A and  803 B are formed of a resilient spring-like material that tends to naturally compress, such that flexible channels  803 A and  803 B occupy the positions shown in  FIG. 8A  when the internal air, gas, or fluid pressure approximately equals the exterior air pressure of about 1.0 atmosphere. 
   Referring again to  FIG. 8B , conduit  301  remains sealed and the internal air, gas, or fluid pressure is increased to greater than about 1.0 atmosphere to extend the flexible channels  803 A and  803 B into contact with IC&#39;s  810  and  811 , which are mounted on a PCB  820  positioned near conduit  301 . In this manner, the internal pressure is maintained for as long as needed to cool the IC&#39;s  810  and  811 . When the internal pressure is lowered to about 1.0 atmosphere or less, flexible channels  803 A and  803 B retract to the compressed state shown in  FIG. 8A . 
   Various means may be used to compress flexible channels  803 A and  803 B. Illustratively, an air pump may be used to create a vacuum pressure within the interior of conduit  301  and/or within the interior of flexible channels  803 A and  803 B. As used herein, the term “vacuum pressure” generally means any interior pressure less than about 1.0 atmosphere that allows flexible channels  803 A and  803 B to compress due to the external air pressure. Preferably, however, the term “vacuum pressure” means about 0.0 atmosphere. The phrase “not a vacuum pressure”, as used herein, means a pressure of about 0.01 atmosphere or greater. 
     FIG. 9  is a cross-sectional view of another cooling device  900  having a wick  902  therein and having flexible channels  903 A and  903 B attached thereto, according to another embodiment of the invention. In  FIG. 9 , conduit  301  is positioned above IC&#39;s  910  and  911 , which are mounted on a PCB  920 . In this embodiment, conduit  301  is a heat pipe, e.g. a tubular structure containing a wick  902  and coupled with a reservoir  930 . Reservoir  930  may be mounted on or within conduit  301 , or may be external to conduit  301  as shown in  FIG. 9 . If external, a pump  932  and a connector (e.g. tube or hose)  933  may be provided to couple reservoir  930  with conduit  301 . Reservoir  930  may contain a liquid coolant  931  such as water or similar coolants. The coolant  931  is conveyed by capillary action through wick  902  until it is vaporized by the heat transferred through flexible channels  903 A and  903 B from IC&#39;s  810  and  811  (or other electronic or electrical devices). As the vapor reaches cooler portions of heat pipe  301  (e.g. a heat sink attached to heat pipe  301 ), it cools, condenses, and the condensation is again conveyed by capillary action through wick  902  to flexible channels  903 A and  903 B. 
   In this embodiment, the internal pressure approximates the external pressure of about 1.0 atmosphere, and flexible channels occupy a first extended position, as discussed with reference to  FIG. 5A , above. IC&#39;s  910  and  911  are mounted on a PCB  920 . Where cooling device  900  is fixed, PCB is moved such that the top surfaces of IC&#39;s  910  and  911  contact and compress flexible channels  903 A and  903 B, again, as discussed above with reference to  FIG. 5B . Alternatively, PCB  920  may be fixedly positioned, and cooling device  900  moved to contact and compress flexible channels  903 A and  903 B. 
     FIG. 10  is cross-sectional view of a plurality of cooling devices  1000 A and  1000 B, each having a plurality of flexible channels  1006 A,  1006 B,  1008 A,  1008 B, attached thereto, according to another embodiment of the invention. In  FIG. 10 , a PCB  1020  is positioned between two cooling devices  1000 A and  1000 B, and has mounted on its top surface IC&#39;s  1011 A and  1011 B. IC&#39;s  1012 A and  1012 B are mounted on the PCB&#39;s bottom surface. Cooling device  1000 A includes a conduit  301 A to which are attached flexible channels  1006 A and  1006 B. Flexible channels  1006 A and  1006 B are shown compressively mated with the top surfaces of IC&#39;s  1011 A and  1011 B, respectively. Cooling device  1000 B includes a conduit  301 B to which are attached flexible channels  1008 A and  1008 B. Flexible channels  1008 A and  1008 B are shown compressively mated with the bottom surfaces of IC&#39;s  1012 A and  1012 B, respectively. 
   Although  FIG. 10  only shows two sets of flexible channels and corresponding IC&#39;s, it will be appreciated that the invention is not so limited, but that it may include one or more sets of flexible channels and corresponding IC&#39;s, depending on the embodiment. In the embodiment shown in  FIG. 10 , cooling device  1000 A and cooling device  1000 B are fixedly positioned, while PCB  1020  is movably positioned between them. However, PCB  1020  may be locked into a fixed position just prior to and just after the IC&#39;s mounted thereon contact the flexible channels. Before inserting or removing PCB  1020 , flexible channels  1006 A,  1006 B,  1008 A, and  1008 B should be returned to their compressed states. 
   Thus, a cooling apparatus and techniques are disclosed. Although the present invention is described herein with reference to a specific preferred embodiment, many modifications and variations therein will readily occur to those with ordinary skill in the art. Accordingly, all such variations and modifications are included within the intended scope of the present invention as defined by the following claims.

Metadata:
Filing Date: 20011206
Publication Date: 20080610
Grant Date: 20080610
Priority Date: 20011206
Inventors: FEIERBACH GARY F.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L2924/0002", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/4332", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2924/0002", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/09701", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/09701", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/4332", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 39484414