Abstract:
An electronic system includes an array of electronic assemblies at a first location within a system. An array of liquid cooling assemblies is placed at a second location within the system. Hoses or other liquid transport pathways connect the cooling assemblies to the electronic assemblies, for cooling the electronic assemblies. As more electronic assemblies are added to the system, additional cooling assemblies may be provided to manage the increased thermal demands.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     Not Applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0003]     Not Applicable.  
       BACKGROUND  
       [0004]     1. Field of the Invention  
         [0005]     This invention relates generally to electronic assemblies, and, more particularly, to thermal management of electronic assemblies.  
         [0006]     2. Description of Related Art  
         [0007]     Many modern electronic systems are constructed from circuit board assemblies. As is known, a circuit board assembly includes electronic components that mount to an insulative substrate. Wires or traces are placed on different layers of the substrate to electrically interconnect the components. A circuit board assembly generally includes one or more connectors for attaching the assembly to other parts of an electronic system, and may include multiple tiers of circuit boards connected together.  
         [0008]     Circuit board assemblies are typically provided in standard sizes and shapes. Standardization allows the assemblies to plug into a standardized chassis, or “card cages.” A typical card cage has a front face with an opening for receiving circuit board assemblies and a backplane located toward the rear of the card cage. The backplane has connectors for making blind mate connections with the circuit board assemblies. Circuit board assemblies are generally inserted into the opening of the card cage at fixed locations, called “slots.” One or more connectors on each circuit board assembly mates with one or more respective connectors on the backplane. Conductive pathways within the backplane allow transmission of electrical signals between different circuit board assemblies.  
         [0009]     A card cage can generally accommodate different numbers and types of electronic assemblies. Numerous instances of any one type of assembly may be provided together in a card cage. In addition, different types of assemblies can be provided within a card cage.  
         [0010]     Within electronic systems, a card cage is often bolted to a frame, generally called a “rack.” The rack may hold multiple card cages, as well as other equipment. Racks for holding electronic equipment are generally provided in standard sizes, such as the common 19 inch (48.3 cm) rack.  
         [0011]     As is known, electronic assemblies require adequate cooling to function properly. As electronic components become smaller, packaging density tends to increase. Not only are more components packed into smaller spaces, but also more power is often consumed in smaller spaces. This increased “power density” creates new challenges for system designers.  
         [0012]     As is known, liquid is generally capable of conducting away heat from electronic components more effectively than air. Consequently, system designers are increasingly turning to liquid cooling techniques to address the thermal needs of assemblies having high power density.  
         [0013]     System designers often wish to continue to use the same standard sized assemblies and racks as have been used in the past. They also wish to have the same flexibility as before, in terms of being able to vary the number of assemblies of any one type and the different types of assemblies installed in a card cage.  
         [0014]     Therefore, it would be desirable for a liquid cooling system to be suitable for use with standard sized circuit board assemblies, card cages, and racks. It would also be desirable to be able to vary the amount of liquid cooling capacity according to the number and types of circuit board assemblies used.  
       SUMMARY  
       [0015]     According to an illustrative embodiment of the invention, a plurality of liquid-coolable electronic assemblies are placed in a system at a first location, and a plurality of liquid cooling assemblies are placed in the system at a second location, which is generally above or below the first location. Liquid transport pathways, such as hoses, are connected between the plurality of electronic assemblies and the plurality of cooling assemblies for circulating liquid coolant. The arrangement is modular, and different numbers of liquid cooling assemblies may be provided for cooling different numbers or types of electronic assemblies, as the target application requires.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The ensuing description will be better understood by reference to the accompanying drawings, in which— 
         [0017]      FIG. 1  is an isometric view of an illustrative embodiment of an electronic system employing modular cooling assemblies;  
         [0018]      FIG. 2  is an isometric, rear view of one of the cooling assemblies shown in  FIG. 1 ;  
         [0019]      FIG. 3  is a plan, side view of one of the cooling assemblies shown in  FIGS. 1 and 2 ; and  
         [0020]      FIG. 4  is a plan, side view of an embodiment of a cooling assembly that uses a liquid-to-liquid heat exchanger.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     As used throughout this document, the words such “comprising,” “including,” and “having” are intended to set forth certain items, steps, elements, or aspects of something in an open-ended fashion. Unless a specific statement is made to the contrary, these words do not indicate a closed list to which additional things cannot be added.  
         [0022]      FIG. 1  shows an illustrative embodiment  100  of an electronic system. The system  100  includes a frame  110 , which is preferably a rack, such as a standard 19-inch (48.3 cm) rack. The rack  110  preferably has vertical supports  110   a,    110   b,    110   c,  and  110   d,  a top shelf  110   e,  and a bottom shelf  110   f.    
         [0023]     A card cage  112  is inserted into the rack, where it is preferably attached using bolts. The card cage  112  preferably houses a backplane  116 , which has backplane connectors  118 . The card cage  112  is at least partially loaded with circuit board assemblies  120 , installed side-by-side.  
         [0024]     As shown at the bottom-left of  FIG. 1 , each circuit board assembly  120  preferably has a front panel  122 . An electrical connector  124  may be attached to the front panel  122  for exchanging electrical signals with other equipment in the system. Coolant ports  126   a  and  126   b  are also preferably attached to the front panel  122 .  
         [0025]     Each circuit board assembly  120  preferably includes a cold plate  129 . The cold plate  129  is preferably placed in close thermal contact with power dissipative components within the assembly  120 . The cold plate is coupled to the pair of coolant ports,  126   a  and  126   b.  Liquid coolant is made to flow into port  126   b,  through the cold plate  129 , and then back out of the assembly via port  126   a.  Heat from the components of the assembly  120  is thus drawn into the cold plate and then away from the assembly  120 .  
         [0026]     The circuit board assemblies plug into the backplane  116  via the connectors  118 . The backplane  116  has conductive wires or traces (not shown) running between different connectors  118 , for allowing the circuit board assemblies to communicate and exchange signals, both with one another and with other types of circuit board assemblies plugged into the backplane  116 , as needed. In the preferred embodiment, the circuit board assemblies are computer servers.  
         [0027]     The system  100  also includes a plurality of liquid cooling assemblies  130 . These assemblies are preferably attached to a support  114 , located directly above the card cage  112 . The support, such as a cage  114 , is preferably bolted to the rack  110 . Alternatively, the support can be a shelf or a simple frame.  
         [0028]     As shown toward the top-left of  FIG. 1 , each liquid cooling assembly  130  preferably has a front  130   a,  a top  130   c,  and a bottom  130   d.  A vent  134  is preferably provided toward the top front  130   a  of the unit. Coolant ports  136   a  and  136   b  are also preferably provided at the front  130   a  of the unit. Multiple pairs of coolant ports may be provided. In addition, an access door  138  is preferably provided on the front face to facilitate servicing. The access door  138  preferably attaches to the liquid cooling assembly  130  via thumb screws  138   a.    
         [0029]     Each liquid cooling assembly  130  is connected to at least one circuit board assembly  120  for exchanging liquid coolant with the assembly. A liquid transport pathway, such as a hose  146   a,  is connected between a coolant port  136   a  and a coolant port  126   b.  Similarly, a hose  146   b  is connected between a coolant port  136   b  and a coolant port  126   a.  Other types of liquid connection pathways can be used, such as rigid pathways or blind-mate pathways. Coolant flows out of the port  136   a  of the liquid cooling assembly  130  and into the port  126   b  of the circuit board assembly  120 . Spent coolant flows out of port  126   a  and back to the liquid cooling assembly  130 , where it enters via port  136   b.    
         [0030]     In the preferred embodiment, each liquid cooling assembly  130  has three source ports  136   a  and three return ports  136   b,  for simultaneously cooling up to three circuit board assemblies  120 . The hoses  146   a / 146   b  for cooling different circuit board assemblies are preferably all the same length. They preferably pass straight down, from the liquid cooling assembly  130  to the circuit board assemblies  120  they service. To reduce clutter in the figure, only one pair of hose connections is shown (it is shown schematically). It is understood, however, that each circuit board assembly  120  has a pair of hoses  146   a / 146   b  (or other liquid transport pathways) attached between its ports  126   a / 126   b  and a pair of coolant ports  136   a / 136   b  on a liquid cooling assembly  130 .  
         [0031]      FIG. 2  shows a rear view of one of the liquid cooling assemblies  130  of  FIG. 1 . The liquid cooling assembly  130  has a rear face  130   b.  A power supply module  210  is preferably inserted into an opening toward the top of the rear face  130   b.  A fan module  220  is preferably inserted into an opening toward the bottom of the rear face  130   b.  To provide an additional view,  FIG. 2  also shows the power supply module  210  and the fan module  220  removed from the liquid cooling assembly  130 , above and below the module  130 , respectively.  
         [0032]     The power supply module  210  has a front face  210   a.  A handle  212  is preferably attached to the front face, to facilitate manual insertion and removal of the module  210  from the liquid cooling assembly  130 . A vent  214  is preferably formed in the front face  210   a,  for promoting air flow through the power supply module. Thumb screws  216  are preferably used to fasten the power supply module to the liquid cooling assembly  130 . The power supply module  210  may include a fan  218  (seen in  FIGS. 3 and 4 ) to provide localized cooling.  
         [0033]     Similarly, the fan module  220  has a front face  220   a,  on which a handle  222  and thumb screws  216  are mounted. The fan module includes fans  224   a - d.  The fan module  220  is preferably open at its top and bottom, to allow air to readily pass from top to bottom. Alternatively, vented covers can be provided at the top and bottom.  
         [0034]     The accessibility of the power supply module  210  and fan module  220  from the rear of the liquid cooling assembly  130  promotes ease of servicing. For example, these modules can be replaced or repaired without disturbing the hoses  146   a  and  146   b.    
         [0035]      FIG. 3  shows a side, plan view of the liquid cooling assembly  130 . The front of the assembly  130  appears to the left of the figure, and the rear of the assembly appears to the right. From this perspective, the power supply module  210  and the fan module  220  are clearly visible. In addition, the liquid cooling assembly  130  is seen to include an air inlet region  310  and an air outlet region (plenum)  312 . Also evident are the outlet port  136   a,  the inlet port  136   b,  a reservoir (e.g., a tank)  314 , a pump  316 , and a liquid-to-air heat exchanger (e.g., a radiator)  318 .  
         [0036]     In the preferred embodiment, the liquid cooling assembly  130  operates essentially as follows. The power supply module  210  provides DC power for running the fan module  220  and the pump  316 . The pump  316  generates an elevated liquid pressure at its output (shown to the left of the pump). The increased pressure causes liquid coolant to flow out of the port  136   a  and into one or more assemblies to be cooled. Coolant flows back into the liquid cooling assembly  130 , via port  136   b,  and into the radiator  318 . Coolant then flows into the tank  314  and is returned to the pump  316 , whereupon the process repeats itself indefinitely.  
         [0037]     The radiator  318  cools the liquid coolant. The fan assembly  220  establishes a downward flow of air. Air is drawn through the vent  134  and into the inlet region  310 . It is then pulled through the radiator  318 . Heated air then flows into the outlet plenum  312  and out of the vent  234 . Air is thus made to flow front-to-back, top-to-bottom, with respect to the liquid cooling assembly  130 .  
         [0038]      FIG. 3  shows only one pair of cooling ports  136   a / 136   b.  Additional ports are connected in parallel. In the preferred embodiment, the pump  316  has an outlet (to the left) that is branched into three parallel paths. Each of these paths is terminated in a port  136   a.  Similarly, the radiator  318  preferably has an inlet (to the left) that is branched into three parallel paths, each being terminated in a port  136   b.    
         [0039]     Electrical cables are preferably used to distribute electrical power within the liquid cooling assembly  130 . One cable connects the pump  316  to the power supply module  210 , and another cable connects the fan module  220  to the power supply module  210 .  
         [0040]     In the preferred embodiment, the pump  316  has a magnetically coupled motor. The motor can be serviced and/or replaced, such as via the access door  138 , without disturbing the liquid plumbing to the pump or the hoses  146   a / 146   b.    
         [0041]     The embodiments disclosed herein provide system designers with the benefits of modularity. Liquid cooling can be supplied where needed, and only to the extent needed. Systems with only modest liquid cooling needs can have those needs satisfied without a large investment. Systems with greater liquid cooling needs can receive as much liquid cooling capacity as needed.  
         [0042]     The modular liquid cooling arrangement disclosed herein can easily be incorporated into existing systems. Circuit board assemblies can employ liquid cooling, while still fitting into standardized card cages and racks.  
         [0043]     Having described certain embodiments, numerous alternative embodiments or variations can be made. For example, although the system  100  has been shown and described with the liquid cooling assemblies  130  placed above the card cage  112 , this is not required. The liquid cooling assemblies  130  can alternatively be placed below the card cage  112  or beside the card cage  112 . The liquid cooling assemblies  130  need not be mounted in the same rack as the card cage. They need not be mounted in a rack at all.  
         [0044]     As shown and described, the power supply module  210  is removable through an opening in the rear  130   b  of the liquid cooling assembly  130 . This is not required, however. Alternatively, the assembly  130  can be designed so that the power supply module  210  is removable through an opening in the front  130   a.  To preserve ease of servicing, the power supply module should be preferably located above the coolant ports  136   a  and  136   b.    
         [0045]     Similarly, the fan assembly  220  can be made removable from the front  130   a.  Once again, however, to preserve the ease of servicing, the fan assembly should placed above the ports  136   a  and  136   b.    
         [0046]     If the liquid cooling assemblies  130  are placed below the card cage and the power supply module  210  is removable from the front, the liquid cooling assembly  130  should preferably be turned upside down, or the internal arrangement of its components modified, to preserve the ability to remove the power supply module  210  without disturbing the liquid connections.  
         [0047]     As shown and described, each liquid cooling assembly  130  cools three circuit board assemblies  120 . This is not required, however. Each liquid cooling assembly  130  can be arranged to cool an arbitrary number of circuit board assemblies. Liquid cooling assemblies  130  can thus have any number of coolant ports  136   a  and  136   b.  In addition, multiple liquid cooling assemblies  130  (or coolant ports thereof) can be connected in parallel for cooling a single, high power assembly.  
         [0048]     Although the circuit board assemblies in the preferred embodiment are computer servers, the invention applies equally well to any type of assembly that employs liquid cooling. This includes, but is not limited to, line cards and switch cards used in telecom and datacom applications.  
         [0049]     As shown and described the liquid cooling assemblies  130  are provided for cooling circuit board assemblies. Alternatively, or in addition, the assemblies  130  can be used to cool other types of equipment, such as equipment that mounts directly to a rack.  
         [0050]     Although the system  100  is vertically arranged, it is understood that the system can also be horizontally arranged. For example, both the card cage  112  and the liquid cooling assemblies  130  can be rotated 90 degrees or 270 degrees.  
         [0051]     Each liquid cooling assembly  130  has been shown and described as cooling spent liquid coolant using a radiator  318  and fan module  220 . However, the liquid cooling assemblies  130  may alternatively employ refrigeration. For example, the spent coolant can be passed through a refrigeration unit before being sent back to the assembly/assemblies to be cooled.  
         [0052]     As shown and described, hoses are used to transport liquid coolant between the liquid cooling assemblies  130  and the electronics assemblies  120 . Alternatively, blind mate liquid transport pathways can be used. According to this variation, the coolant ports  136   a  and  136   b  are preferably positioned at the rear  130   b  of the liquid cooling assembly  130  and coolant ports  126   a  and  126   b  are preferably positioned on the backplane  116 .  
         [0053]      FIG. 4  shows another variation of the liquid cooling assembly. A liquid cooling assembly  430  employs a liquid-to-liquid heat exchanger  418 . No fan module is required. Separate coolant, such as facility water, is piped into the heat exchanger  418 . Facility water is circulated through the heat exchanger  418 . Spent coolant from the assemblies  120  is also pumped through the heat exchanger  418 . Heat is exchanged between the spent coolant and the facility water, to reduce the temperature of the spent coolant.  
         [0054]     As used herein, the designations “top,” “bottom,” “front,” and “back” indicate positions of items or parts thereof. These designations are relative and are not required to correspond to any absolute positions. Thus, for example, nothing prevents the “top” of an item from facing the floor.  
         [0055]     Those skilled in the art will therefore understand that various changes in form and detail may be made to the embodiments disclosed herein without departing from the scope of the invention.