Abstract:
A field-replaceable active pumped liquid heat sink module includes a liquid pump, a radiator, an optional receiver, and a gasketed cold heat exchanger box, all of which are connected together in a liquid pump loop through which a coolant such as water is circulated. The liquid pump, radiator, optional receiver and gasketed cold heat exchanger box are in a liquid pump loop and are self-contained in a field-replaceable active pumped liquid heat sink module. The heat sink module provides direct contact between the liquid coolant and the top portion of the targeted electronic component, which can be a CPU.

Description:
RELATED CASE INFORMATION 
   The present application is related to my two patent application Ser. No. 11/196,905, entitled “UNITARY FIELD-REPLACEABLE ACTIVE INTEGRATED LIQUID PUMP HEAT SINK MODULE FOR THERMAL MANAGEMENT OF ELECTRONIC COMPONENTS” and Ser. No. 11/196,963, entitled “MULTIPLE COMPONENT FIELD-REPLACEABLE ACTIVE INTEGRATED LIQUID PUMP HEAT SINK MODULE FOR THERMAL MANAGEMENT OF ELECTRONIC COMPONENTS” which are both hereby incorporated in their entirety by this reference. 
   FIELD OF THE INVENTION 
   The present invention is related to heat sinks for removing heat from electronic components such as integrated circuit processors. 
   BACKGROUND OF THE INVENTION 
   Removal of heat has become one of the most important challenging issues facing computer system designers today. As the rate of power dissipation from electronics components such as high performance server processors continues to increase, standard conduction and forced-air convection fan air cooling techniques no longer provide adequate cooling for such sophisticated electronic components. The reliability of the electronic system suffers if high temperatures at hot spot locations are permitted to persist. Conventional thermal control schemes such as air cooling with fans, thermoelectric cooling, heat pipes, and passive vapor chambers have either reached their practical application limit or are soon to become impractical for high power electronic components such as computer server processors. When standard cooling methods are no longer adequate, computer manufacturers have to reduce the frequency of their processors to match the capacity of existing cooling apparatus. Furthermore, reliability can be compromised due to inadequate cooling using an existing cooling apparatus, or product release delayed until a reliable cooling apparatus for removal of heat from high heat dissipating processors can be made available. 
   The computer industry is seriously considering utilizing active liquid cooling as an alternative to conventional passive air cooling for high performance and high power processors. A number of attempts to incorporate liquid for cooling of high powered processors in the form of submerged liquid, liquid spray cooling, refrigeration cooling, and the like have been attempted in the past, but none of the existing active liquid cooling solutions has been utilized outside of specific design conditions. Additionally, these cooling solutions, while effective, can include a relatively high number of moving parts that can lead to increased product and maintenance costs. 
   What is desired, therefore, is a field-replaceable heat sink module that employs active liquid cooling, but has the same appearance as a traditional air-cooling heat sink, is sturdy, reliable, compact, simple to use, relatively inexpensive, and can be effectively employed in a wide range of applications. 
   SUMMARY OF THE INVENTION 
   According to an embodiment of the present invention, a field and/or customer replaceable integrated active pumped liquid heat sink module providing direct contact between the heat generating components and the coolant with built-in reliability features is suitable for thermal management of very high heat dissipation electronic components such as server processors. The field-replaceable integrated active pumped direct-contact liquid heat sink module is self-contained and is specifically designed to have physical dimensions similar to those of a standard air-based cooling system, such as a finned heat sink or heat pipe. As a result, the field-replaceable integrated active direct-contact liquid pumped heat sink module of the present invention can be utilized in existing electronic systems without the need for board or cabinet/rack modification or the “plumbing” associated with prior art liquid-based cooling systems. The gasket design of the heat sink module is such that a leak-free and reliable contact between the cooling fluid and the source of heat generation (bare die or the lid on top of the die) can be made. 
   According to an embodiment of the present invention, the field-replaceable active direct liquid contact pumped heat sink module includes a pump, a radiator cooling heat exchanger (heat sink fin), an optional liquid receiver, and embedded plumbing for cooling the liquid flow, all of which are connected together in a liquid pump cooling loop through which a coolant such as water is circulated. The liquid pump, radiator cooling heat exchanger, optional receiver and plumbing in an active direct-liquid contact liquid pump module are self-contained in a field-replaceable pumped liquid heat sink module. 
   From the view point of the end user, the entire liquid pump apparatus is sealed and contained in the heat sink module with two or more gaskets at the base of the heat sink. The target electronic component structure (such as the lid of a server processor) is placed into the liquid path of the direct-contact pumped liquid cooling loop for maximum cooling efficiency. Except for the electric wires needed to power the liquid pump, there is no difference in external appearance between a conventional heat sink and the heat sink module of the present invention. The function of the gaskets is to contain the cooling liquid inside the heat sink module while not assembled and to provide support and sealing to prevent liquid leakage when the electronic component is engaged with the gasketed direct liquid contact pumped integrated heat sink module. The coolant is pumped over a top portion of an electronic component (such as bare die or the lid of a server processor) extending into a into a cold heat exchanger box of the heat sink module, absorbing heat and therefore cooling the target electronic component to a desired temperature level. The pump action further causes the cooling fluid to flow into a radiant cooling heat exchanger of the heat sink module, where the heat is removed by air blown by a system fan. In the radiant cooling heat exchanger, the coolant is circulated such that it is cooled before being conveyed to an optional liquid receiver. From the optional receiver, the cooling fluid is returned to the pump for continuous recirculation. The liquid coolant is heated up in direct contact with the target electronic components, and in this process absorbs heat from heat generating source (such as a bare die or lid of a server processor) to produce the desired cooling effect. 
   In accordance with the present invention, the liquid pump used is one of several new generation pumps that are relatively small, on the order of two inches in diameter and three to four inches long. 
   The field-replaceable gasketed direct liquid contact pumped integrated heat sink module of the present invention is modular, self-contained, and can remove a great deal of heat by providing direct liquid contact to the heat generating sources of electronic components. The heat sink module of the present invention is field and/or customer replaceable with minimal effort using standard tools. In addition, unlike prior art liquid-based cooling system, the gasketed field-replaceable direct liquid contact pumped integrated heat sink module of the invention is capable of being attached directly to the components (such as server processors) that need cooling. In addition, the gasketed field-replaceable direct liquid contact pumped integrated heat sink module of the invention is compact and simple in both operation and installation, with minimal parts to fail or break and minimal added complexity. Therefore, the gasketed field-replaceable direct liquid contact pumped integrated heat sink module of the invention is sturdy and reliable. 
   The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of an embodiment of the invention as illustrated in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows two cross-sectional views and a bottom view of a gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention; 
       FIG. 2  shows a cross-sectional of the gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention in an unassembled configuration, as well as the target CPU; and 
       FIG. 3  shows the same cross-sectional view as in  FIG. 2  of the gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention in an assembled configuration, wherein a top portion of the target CPU is in direct contact with the sealed liquid coolant. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , a first cross-sectional view  100  of a gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention includes a heat sink casing  114 , which is typically fabricated out of aluminum, copper, or alloys thereof, or other similar metals or alloys, and is about 0.25 inches thick. The overall dimensions of the heat sink casing are typically about 5.0 inches by 3.0 inches by 1.75 inches, but can of course be changed as desired for a particular application. A cold heat exchanger box  106  is embedded into the heat sink casing  114 . A spring-loaded inner gasket  108  is attached to a moveable heat sink pedestal that is flush with and forms part of the bottom surface of the heat sink casing  114 . The actual moveable heat sink pedestal is not shown in  FIG. 1  because it is obscured by the heat sink casing  114 , but is identified and described in further detail below. A cross sectional view of the inner gasket  108  and attaching springs  134  are shown in  FIG. 1 . A fixed outer gasket  136  is affixed to the bottom surface of the heat sink casing  114  as shown. A hot liquid output line  118  is coupled to a radiator heat exchanger  120 . The hot liquid output line  118  is fabricated out of copper or aluminum. The dimensions of the hot liquid output line  118  are about 1.5 inches long by about 0.125 inches, outside diameter, but these dimensions are tailored to the form factor of the overall heat sink casing. The wall thickness of the hot liquid output line  118  is between 1.0 and 2.0 mm. The dimensions of the hot liquid output line  118  are maintained for the other liquid lines throughout the radiator heat exchanger  120 . The fluid lines in the radiator heat exchanger  120  are separated by a number of radiator fins  122 , which are fabricated out of aluminum or copper. The radiator fins  122  can be any dimensions required for a required form factor, but are typically about 4.0 inches long and about 0.125 inches thick. A fluid such as water or a mixture of water and glycol or other such media flows through the lines in the radiator heat exchanger  120 , and is gradually cooled without any phase change. The fluid is fully cooled at the uppermost line in the radiator heat exchanger  120  and emerges as the cold liquid return line  124  once fully cooled. In a typical application, the temperature of the fluid in the hot liquid output line  118  could be as high as 110° C., and, with proper air flow from an accompanying fan (not shown in  FIG. 1 ) the temperature of the fluid in the cold liquid return line  124  can be as low as 25° C. The cold liquid return line  124  is coupled to the input port of a liquid pump  126 . In accordance with an embodiment of the present invention, the liquid pump  126  is one of several new generation pumps that are relatively small, on the order of 1.5 inches in diameter and 3.0 to 4.0 inches long, although other dimension pumps can of course be used to fit a particular form factor. A suitable pump  126  for the unitary heat sink embodiment shown in  FIG. 1  is a brushless miniature spherical pump. A miniature diaphragm pump or a positive displacement pump could also be used. The output port of liquid pump  126  is coupled to the cold liquid input line  116 , which in turn is coupled to the input port of the cold heat exchanger  106  to complete the closed liquid flow path. Electrical connections  132  are provided to activate the liquid pump  126 , which are the only outside connections required by the unitary heat sink module according to the present invention. The liquid pump  126  typically consumes about 10.0 watts of power, and is energized by a 12.0 volt connection and a ground connection. In the multi-component embodiment each liquid pump consumes about 10.0 watts of power. 
   A second cross-sectional view  102  of the gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention is also shown in  FIG. 1 , which is orthogonal to cross-sectional view  100 . Cross-sectional view  102  allows further detail of the heat sink module to be shown. The cross-sectional view of the heat sink casing  114  shows embedded cold heat exchanger box  106  as well as the moveable inner gasket  108  and attached springs  134  for allowing the gasket to traverse upwards inside the heat exchanger box  106 . The fixed outer gasket  136  attached to the bottom of the heat sink casing  114  can also be seen in cross-sectional view  102 . In cross-sectional view  102 , the individual radiator heat exchanger liquid flow channels  128  are visible, as well as a side view of one course of the radiator heat exchanger fin plates  130 . 
   A bottom view  104  of the gasketed field-replaceable active integrated liquid pump heat sink module according to an embodiment of the present invention is also shown in  FIG. 1 . The bottom view  104  shows the “footprint” of the heat sink base plate  110 , as well as the footprint of the moveable pedestal  112  of the cold heat exchanger base box  106 . The pedestal  112  (not shown in  FIG. 1 ) retracts upwards into the heat sink module to allow the lid or upper portion of the integrated circuit processor or other target circuit (also not shown in  FIG. 1 ) to come directly into contact with the coolant liquid. The footprint of the inner moveable gasket  108  and outer fixed gasket  136  are also shown in the bottom view  104 . Two cross-sectional lines  100  and  102  are shown in the bottom view  104 , representing the relative cross-sectional cuts for first and second cross-sectional views  100  and  102 . 
   Referring now generally to  FIG. 2 , the gasketed heat sink module of the present invention is shown as a system  200  including a target circuit for cooling such as a CPU. Certain identification numerals are removed in  FIG. 2 , and other identification numerals associated with the CPU are included. In  FIG. 2 , the heat sink module system is shown in an unassembled state in which the CPU is positioned directly below the heat sink module in preparation for assembly and cooling according to the present invention. The actual CPU is shown as a “flip-chip”  212  with a solder bump attachment or the like to a substrate  204  having a number of interconnect pins  202 . The CPU chip  212  is centrally positioned to push back the pedestal  112  of the cold heat exchanger box  106 , which is shown in  FIG. 3 . The substrate also provides support for a CPU lid frame having an input  208  and an outlet  210 . Input  208  and output  210  are perforated in a manner to allow the coolant liquid to flow, yet maintaining the structural integrity of the lid frame. The lid frame is glued to substrate  204  at points  206 . 
   Referring now generally to  FIG. 3 , the gasketed heat sink module of the present invention is shown as a system  300  including a target circuit for cooling such as a CPU. Certain identification numerals are removed in  FIG. 3 , and other identification numerals associated with the CPU are included. In  FIG. 3 , the heat sink module system is shown in an assembled state in which CPU frame engages the moveable pedestal  112  such that the lid or upper portion of the CPU chip  212  is placed directly into the coolant liquid flow  302  according to the present invention. It is important to note in  FIG. 3  that while the CPU chip  212  is placed in direct contact with the coolant liquid flow, all of the coolant liquid is still hermetically contained within the heat sink module. The inner gasket  108  is retracted into the cold heat exchanger box  106 , and the springs  134  are compressed in the assembled state. Note that the outer stationary gasket  136  prevents any leakage of the coolant liquid at the bottom of the heat sink module, and the moveable pedestal  112  prevents any leakage at the top of the heat sink module. Thus, the coolant fluid is directed into a narrow channel, flowing directly over the CPU or other target circuit for removing heat with maximum efficiency. It is also important to note that the heat sink module shown in the assembled state of  FIG. 3  returns to the unassembled state of  FIG. 2  when the CPU assembly is removed. The moving pedestal  112  returns to the bottommost portion of the heat sink module, the inner gasket  108  and springs  134  return to their original position, and the coolant liquid ceases to flow as is shown in  FIG. 2 . 
   The heat sink module of the present invention may be used with a lidded or lidless CPU or other electronic component as discussed above. The choice of water as a coolant fluid is ideally only for the lidded case and not the lidless case. It will be apparent to those skilled in the art that many different coolant fluids can be used including, but not limited to water and water/glycol mix, as well as dielectric-type coolant fluids. Additionally, many different packaging types can be used in the lidded case. Finally, many different sealing and passivation techniques can be used in the lidless case to assure proper operation in conjunction with the coolant fluid chosen. 
   It will also be apparent to those skilled in the art that the CPU can be locked in to the heat sink module in a number of different ways. Possibilities include using a traditional attachment technique such as nuts and bolts, or engagement by pressing the CPU into the cold heat exchanger box, where the tip of the lid is engaged into a locking device built in to the heat sink cold heat exchanger box. Numerous other such locking or attachment mechanisms can be used. 
   While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention. It should be understood that this description has been made by way of example, and that the invention is defined by the scope of the following claims.