Patent Description:
Computer users often focus on the speed of computer microprocessors (e.g., megahertz and gigahertz). Many forget that this speed often comes with a cost-higher power consumption. This power consumption also generates heat. That is because, by simple laws of physics, all the power has to go somewhere, and that somewhere is, in the end, conversion into heat. A pair of microprocessors mounted on a single motherboard can draw hundreds of watts or more of power. Multiply that figure by several thousand (or tens of thousands) to account for the many computers in a large data center, and one can readily appreciate the amount of heat that can be generated. The effects of power consumed by the critical load in the data center are often compounded when one incorporates all of the ancillary equipment required to support the critical load.

Many techniques may be used to cool electronic devices (e.g., processors, memories, networking devices, and other heat generating devices) that are located on a server or network rack tray. For instance, forced convection may be created by providing a cooling airflow over the devices. Fans located near the devices, fans located in computer server rooms, and/or fans located in ductwork in fluid communication with the air surrounding the electronic devices, may force the cooling airflow over the tray containing the devices. In some instances, one or more components or devices on a server tray may be located in a difficult-to-cool area of the tray; for example, an area where forced convection is not particularly effective or not available.

The consequence of inadequate and/or insufficient cooling may be the failure of one or more electronic devices on the tray due to a temperature of the device exceeding a maximum rated temperature. While certain redundancies may be built into a computer data center, a server rack, and even individual trays, the failure of devices due to overheating can come at a great cost in terms of speed, efficiency, and expense.

<CIT> discloses a datacenter having a plurality of liquid cooled computer systems. The computer systems each include a processor coupled with a cold plate that allows direct liquid cooling of the processor. The cold plate is further arranged to provide adapted flow of coolant to different portions of the processor whereby higher temperature regions receive a larger flow rate of coolant. The flow is variably adjusted to reflect different levels of activity. By maximizing the coolant temperature exiting the computer systems, the system may utilize the free cooling temperature of the ambient air and eliminate the need for a chiller. A datacenter is further provided that is coupled with a district heating system and heat is extracted from the computer systems is used to offset carbon emissions and reduce the total cost of ownership of the datacenter.

<CIT> discloses a cooling member for withdrawing heat from a heat containing device. The cooling member can have a housing with a fluid inlet, a fluid outlet and a plurality of irregular-shaped fins located at least partially therewithin. In addition, a plurality of irregular-shaped and hierarchical branched fluid pathways can be located between the plurality of fins and the housing and/or the plurality of fins can be in physical contact with the heat containing device.

<CIT> discloses a cold plate assembly consisting of a thermally conductive base component with an insert having a high thermal transfer characteristic adapted for contacting the surface of a heat source on one side. The surface of the base component opposite from the insert is surrounding by a housing defining an enclosed volume through with a flow of liquid coolant is directed. Inlet baffles adjacent to a fluid inlet in the housing direct the incoming flow of liquid coolant towards the surface of the base component in proximity to the insert, facilitating an efficient transfer of thermal energy from the heat source to the liquid coolant through the insert and base component. Optional extensions or fins extending into the liquid coolant contained in the enclosed volume from the surface of the base component further facilitate the transfer of thermal energy from the heat source.

This disclosure describes a cooling system, for example, for rack mounted electronic devices (e.g., servers, processors, memory, networking devices or otherwise) in a data center is disclosed. In various disclosed implementations, the cooling system includes a liquid cold plate assembly that is part of or integrated with a server tray package. In some implementations, the liquid cold plate assembly includes a base portion and a top portion that, in combination, form a cooling liquid flow path through which a cooling liquid is circulated and a thermal interface between one or more heat generating devices and the cooling liquid. The top portion of the liquid cold plate assembly includes multiple inlets and/or multiple outlets to customize a flow path through which a liquid coolant flows to cool the electronic devices in conductive thermal contact with the cold plate assembly.

In an example implementation, a server tray package includes a motherboard assembly that includes a plurality of data center electronic devices; and a liquid cold plate assembly. The liquid cold plate assembly includes a base portion mounted to the motherboard assembly, the base portion and motherboard assembly defining a volume that at least partially encloses the plurality of data center electronic devices; and a top portion mounted to the base portion and including a heat transfer member that includes a first number of inlet ports and a second number of outlet ports that are in fluid communication with a cooling liquid flow path defined through the heat transfer member, the first number of inlet ports being different that the second number of outlet ports.

An aspect combinable with the example implementation further includes a first thermal interface material positioned between a top surface of the base portion and at least a portion of the plurality of data center electronic devices; and a second thermal interface material positioned between the top surface of the base portion and a bottom surface of the top portion.

In another aspect combinable with any of the previous aspects, the liquid cold plate assembly further includes a plurality of heat transfer surfaces enclosed within the cooling liquid flow path.

In another aspect combinable with any of the previous aspects, the first number of inlet ports are greater than the second number of outlet ports.

In another aspect combinable with any of the previous aspects, the first number of inlet ports include at least two inlet ports positioned on opposed edges of the top portion of the liquid cold plate assembly.

In another aspect combinable with any of the previous aspects, the at least two inlet ports include at least four inlet ports positioned as pairs of inlet ports on opposed edges of the top portion of the liquid cold plate assembly.

Another aspect combinable with any of the previous aspects further includes a plurality of cooling liquid flow circuits defined by heat transfer surfaces positioned in the cooling liquid flow path.

In another aspect combinable with any of the previous aspects, the plurality of cooling liquid flow circuits extend between the at least two inlet ports and the second number of outlet ports.

Another aspect combinable with any of the previous aspects further includes at least one flow diverter positioned across one or more of the plurality of cooling liquid flow circuits.

In another aspect combinable with any of the previous aspects, the heat transfer surfaces include pin fins.

In another aspect combinable with any of the previous aspects, the plurality of data center electronic devices include at least one hardware processing device and a plurality of memory devices.

In another aspect combinable with any of the previous aspects, each of the plurality of memory devices is mounted to the motherboard between the at least one hardware processing device and at least one of the at least two inlet ports.

In another example implementation, a method for cooling heat generating devices in a data center includes circulating a flow of a cooling liquid to a server tray package. The server tray package includes a motherboard assembly that includes a plurality of data center electronic devices, and a liquid cold plate assembly that includes a base portion mounted to the motherboard assembly, the base portion and motherboard assembly defining a volume that at least partially encloses the plurality of data center electronic devices, and a top portion mounted to the base portion. The method includes circulating a flow of a cooling liquid into a first number of inlet ports of the heat transfer member; circulating the flow of the cooling liquid from the first number of inlet ports through a cooling liquid flow path defined through the heat transfer member to transfer heat from the plurality of data center electronic devices into the cooling liquid; and circulating the heated flow of the cooling liquid from the cooling liquid flow path to a second number of outlet ports of the heat transfer member, the first number of inlet ports being different that the second number of outlet ports.

An aspect combinable with the example implementation further includes transferring the heat from the plurality of data center electronic devices through a first thermal interface material positioned between the plurality of data center electronic devices and to a top surface of the base portion.

Another aspect combinable with any of the previous aspects further includes transferring the heat from the top surface of the base portion through a second thermal interface material positioned between a bottom surface of the top portion of the liquid cold plate assembly and to the cooling liquid.

In another aspect combinable with any of the previous aspects, circulating the flow of the cooling liquid through the cooling liquid flow path defined through the heat transfer member includes circulating the cooling liquid through a plurality of flow channels defined by a plurality of heat transfer surfaces enclosed within the cooling liquid flow path.

Another aspect combinable with any of the previous aspects further includes circulating the flow of the cooling liquid into at least two inlet ports positioned on opposed edges of the top portion of the liquid cold plate assembly.

Another aspect combinable with any of the previous aspects further includes circulating the flow of the cooling liquid into at least four inlet ports positioned as pairs of inlet ports on opposed edges of the top portion of the liquid cold plate assembly.

Another aspect combinable with any of the previous aspects further includes circulating the flow of the cooling liquid through a plurality of cooling liquid flow circuits defined by heat transfer surfaces positioned in the cooling liquid flow path that extend between the at least two inlet ports and the second number of outlet ports.

Another aspect combinable with any of the previous aspects further includes diverting at least a portion of the cooling liquid that flows within one or more of the plurality of cooling liquid flow circuits.

Another aspect combinable with any of the previous aspects further includes circulating the flow of the cooling liquid from the first number of inlet ports over a portion of the cooling liquid flow path positioned above at least one of the plurality of memory devices; circulating the flow of the cooling liquid from the portion of the cooling liquid flow path positioned above at least one of the plurality of memory devices to another portion of the cooling liquid flow path positioned above the at least one hardware processing device; and circulating the flow of the cooling liquid from the another portion of the cooling liquid flow path positioned above the at least one hardware processing device to the second number of outlet ports.

Various implementations of a data center cooling system according to the present disclosure may include one, some, or all of the following features. For example, a server tray package according to the present disclosure may provide for direct liquid cooling to high heat generating electronic devices in a data center with uniform flow and uniform temperature of a cooling liquid that flows through a liquid cold plate assembly. As another example, a server tray package according to the present disclosure may provide for multiple functionality including cooling, mechanical rigidity, and liquid coolant sealing. As another example, a server tray package according to the present disclosure may provide for custom cooling liquid flow paths and flow geometries to cool both high and low heat generating electronic devices mounted on a single substrate. As a further example, a server tray package according to the present disclosure may allow for hot spot spreading in combination with high performance liquid cooling via cold plates. As another example, a server tray package according to the present disclosure may allow for higher power computing components (e.g., processors) to be cooled by direct conductive contact with a liquid cooled cold plate for better performance.

In some example implementations, a cooling system, for example, for rack mounted electronic devices (e.g., servers, processors, memory, networking devices or otherwise) in a data center is disclosed. In various disclosed implementations, the cooling system includes a liquid cold plate assembly that is part of or integrated with a server tray package. In some implementations, the liquid cold plate assembly includes a base portion and a top portion that, in combination, form a cooling liquid flow path through which a cooling liquid is circulated and a thermal interface between one or more heat generating devices and the cooling liquid. The top portion of the liquid cold plate assembly includes multiple inlets and/or multiple outlets to customize a flow path through which a liquid coolant flows to cool the electronic devices in conductive thermal contact with the cold plate assembly.

<FIG> illustrates an example system <NUM> that includes a server rack <NUM>, e.g., a <NUM> inch or <NUM> inch server rack, and multiple server rack sub-assemblies <NUM> mounted within the rack <NUM>. Although a single server rack <NUM> is illustrated, server rack <NUM> may be one of a number of server racks within the system <NUM>, which may include a server farm or a co-location facility that contains various rack mounted computer systems. Also, although multiple server rack sub-assemblies <NUM> are illustrated as mounted within the rack <NUM>, there might be only a single server rack sub-assembly. Generally, the server rack <NUM> defines multiple slots <NUM> that are arranged in an orderly and repeating fashion within the server rack <NUM>, and each slot <NUM> is a space in the rack into which a corresponding server rack sub-assembly <NUM> can be placed and removed. For example, the server rack sub-assembly can be supported on rails <NUM> that project from opposite sides of the rack <NUM>, and which can define the position of the slots <NUM>.

The slots <NUM>, and the server rack sub-assemblies <NUM>, can be oriented with the illustrated horizontal arrangement (with respect to gravity). Alternatively, the slots <NUM>, and the server rack sub-assemblies <NUM>, can be oriented vertically (with respect to gravity). Where the slots are oriented horizontally, they may be stacked vertically in the rack <NUM>, and where the slots are oriented vertically, they may be stacked horizontally in the rack <NUM>.

Server rack <NUM>, as part of a larger data center for instance, may provide data processing and storage capacity. In operation, a data center may be connected to a network, and may receive and respond to various requests from the network to retrieve, process, and/or store data. In operation, for example, the server rack <NUM> typically facilitates the communication of information over a network with user interfaces generated by web browser applications of users who request services provided by applications running on computers in the datacenter. For example, the server rack <NUM> may provide or help provide a user who is using a web browser to access web sites on the Internet or the World Wide Web.

The server rack sub-assembly <NUM> may be one of a variety of structures that can be mounted in a server rack. For example, in some implementations, the server rack sub-assembly <NUM> may be a "tray" or tray assembly that can be slidably inserted into the server rack <NUM>. The term "tray" is not limited to any particular arrangement, but instead applies to the motherboard or other relatively flat structures appurtenant to a motherboard for supporting the motherboard in position in a rack structure. In some implementations, the server rack sub-assembly <NUM> may be a server tray package, server chassis, or server container (e.g., server box). In some implementations, the server rack sub-assembly <NUM> may be a hard drive cage.

<FIG> illustrates a schematic cross-sectional side view of an example implementation of a server tray package <NUM> that includes a liquid cold plate assembly <NUM>. In some implementations, the server tray package <NUM> may be used as one or more of the server rack sub-assemblies <NUM> shown in <FIG>. Referring to <FIG>, the server tray package <NUM> includes a printed circuit board <NUM> (e.g., motherboard <NUM>) that supports one or more heatgenerating data center electronic devices; in this example, two or more memory modules <NUM> and one or more processing devices <NUM> (e.g., one or more application-specific integrated circuits (ASIC)). In some aspects, the motherboard <NUM> may be mounted on a frame (not shown), which can include or simply be a flat structure that can be grasped by technicians for moving the motherboard <NUM> into place and holding it in position within the rack <NUM>. For example, the server tray package <NUM> may be mounted horizontally in the server rack <NUM> such as by sliding the frame into the slot <NUM> and over a pair of rails in the rack <NUM> on opposed sides of the server tray package <NUM> - much like sliding a lunch tray into a cafeteria rack. The frame can extend below the motherboard <NUM> or can have other forms (e.g., by implementing it as a peripheral frame around the motherboard <NUM>) or may be eliminated so that the motherboard itself is located in, e.g., slidably engages, the rack <NUM>. The frame can be a flat plate or include one or more side walls that project upwardly from the edges of the flat plate, and the flat plate could be the floor of a closed-top or open-top box or cage.

In some examples, one motherboard <NUM> is mounted on a frame; alternatively, multiple motherboards <NUM> may be mounted on a frame, depending on the needs of the particular application. In some implementations, one or more fans (not shown) can be placed on the motherboard <NUM> or a frame so that air enters at the front edge of the server tray package <NUM>, closer to the front of the rack <NUM> when the server tray package <NUM> is installed in the rack <NUM>, flows over the motherboard <NUM>, over some of the data center electronic components on the motherboard <NUM>, and is exhausted from the server tray package <NUM> at the back edge, closer to the back of the rack <NUM> when the server tray package <NUM> is installed in the rack <NUM>. The one or more fans can be secured to the motherboard <NUM> or a frame by brackets.

As illustrated, a substrate <NUM> and an interposer <NUM> (e.g., a silicon interposer) are positioned between the data center electronic devices <NUM> and <NUM> and the motherboard <NUM>. The substrate <NUM>, for example, provides an interface between one or more of the data center electronic devices (e.g., the processing device <NUM>) and the motherboard <NUM>, such as through pins that provide electrical and communication interfaces. The substrate <NUM> also, in this example, may provide a mounting location for one or more components of the liquid cold plate assembly <NUM>. The interposer <NUM>, for example, provides a high bandwidth connection between the data center electronic devices, such as between the memory modules <NUM> and the processing device <NUM>.

For example, as shown in <FIG>, in some examples, there is a single processing device <NUM> mounted on the interposer <NUM> and at or near a center of the interposer <NUM> (e.g., such that centers of the processing device <NUM> and the interposer <NUM> are aligned). Memory modules <NUM>, in this example, are positioned (in pairs) on only two opposed sides of the processing device <NUM>. Thus, more heat may be generated (e.g., by the processing device <NUM>) at or near a center portion of the interposer <NUM> relative to a perimeter area of the interposer <NUM> (e.g., in which the memory modules <NUM> are mounted).

As another example, as shown in <FIG>, in some examples, there is a single processing device <NUM> mounted on the interposer <NUM> and at or near a center of the interposer <NUM> (e.g., such that centers of the processing device <NUM> and the interposer <NUM> are aligned). Memory modules <NUM>, in this example, are positioned (in pairs) on all four opposed sides of the processing device <NUM>. Thus, more heat may be generated (e.g., by the processing device <NUM>) at or near a center portion of the interposer <NUM> relative to a perimeter area of the interposer <NUM> (e.g., in which the memory modules <NUM> are mounted).

As shown in <FIG>, the liquid cold plate assembly <NUM> includes a top portion <NUM>, also referred to as a top hat <NUM>, and a base portion <NUM>. The base portion <NUM> includes a lid <NUM> that defines a top surface of the base portion <NUM> and sides <NUM> that couple the lid <NUM> to the substrate <NUM>. In combination, the lid <NUM> and the sides <NUM> define or enclose a volume <NUM> in which the interposer <NUM> and the data center electronic devices <NUM> and <NUM> (mounted thereon) are positioned in the server tray package <NUM>. As shown in this example, a thermal interface material <NUM> (e.g., a phase change material or otherwise thermally conductive material) is contactingly positioned between a bottom side of the lid <NUM> and the data center electronic devices <NUM> and <NUM> to provide a conductive heat transfer interface between these components.

In this example implementation, the top hat <NUM> is mounted to a top surface of the lid <NUM> through another thermal interface material <NUM> (e.g., a phase change material or otherwise thermally conductive material) that provides a conductive heat transfer interface between a bottom <NUM> of the top hat <NUM> and the lid <NUM> of the base portion <NUM>. The top hat <NUM>, as shown, includes a cap <NUM> that is connected to the bottom <NUM> through sides <NUM>. In combination, the cap <NUM>, sides <NUM>, and bottom <NUM> define a volume <NUM> through which a flow of a cooling liquid may be circulated.

As shown in this example, the cap <NUM> includes at least two cooling liquid inlets <NUM> through which a supply <NUM> of cooling liquid may enter. The cap <NUM> also includes (in this example) a single cooling liquid outlet <NUM> through which a return <NUM> of cooling liquid may exit. Thus, in this implementation, there is a two-to-one ratio of inlets <NUM> to outlets <NUM>. In some aspects, such a ratio may be implemented but with different quantities of inlets <NUM> and outlets <NUM>. For example, there may be four inlets <NUM> and two outlets <NUM>. Other quantities and ratios of inlets <NUM> to outlets <NUM> are also possible (e.g., four inlets <NUM> to one outlet <NUM>).

In <FIG>, as further shown in this example, the inlets <NUM> are each placed at or near a perimeter edge of the top hat <NUM>, while the single outlet <NUM> is positioned at or near a center of the top hat <NUM>. Other positions of the inlets <NUM> and the outlet <NUM> are also contemplated by the present disclosure, such as, for example, both inlets <NUM> positioned near the center of the top hat <NUM> and one or more outlets <NUM> positioned at or near the perimeter edge of the top hat <NUM>.

The volume <NUM> defines or includes a cooling liquid flow path between the inlets <NUM> and the outlets <NUM>. As shown in this example, one or more heat transfer surfaces <NUM> (e.g., fins, undulations, ridges, or other extended surfaces that increase a heat transfer area) are positioned in the volume <NUM>. The heat transfer surfaces <NUM> define channels <NUM>, for example, through which the cooling liquid may be circulated to increase an amount of heat transferred from the data center electronic devices <NUM> and <NUM> to the cooling liquid (e.g., relative to an amount transferred in an implementation of the server tray package <NUM> that does not include the heat transfer surfaces <NUM>).

Turning briefly to <FIG>, this top view of the example implementation of the server tray package <NUM> shown in <FIG> and <FIG> further shows the two cooling liquid inlets <NUM> and the single cooling liquid outlet <NUM>. In this example, each inlet <NUM> is shaped as a rectangular opening with a length generally commiserate with a dimension of the interposer <NUM> and a width much less than the length. Here, each of the two inlets <NUM> is positioned on a particular edge of the perimeter of the top hat <NUM> (and vertically above a corresponding edge of the interposer <NUM>). The single outlet <NUM>, positioned from one edge of the top hat <NUM> to an opposed edge of the top hat <NUM> also has a similar opening shape as the inlets <NUM>. Here, heat transfer area <NUM> represents the portion of the bottom <NUM> which is in conductive thermal contact with the heat generating devices (processor <NUM>, memory modules <NUM>, and others) through the top208 of the base portion <NUM>.

In an example operation of the server tray package <NUM> to cool the data center electronic devices <NUM> and <NUM>, the server tray package <NUM> may be deployed, for example, in a data center server rack <NUM> in a data center. During operation of the server tray package <NUM>, the processing device <NUM> and memory modules <NUM> generate heat that may need to be dissipated or removed from the server tray package <NUM> (e.g., for proper operation of the server tray package <NUM>). Heat generated by the processing device <NUM> and memory modules <NUM> is transferred through the thermal interface material <NUM> and to the lid <NUM> of the base portion <NUM> of the liquid cold plate assembly <NUM>. The transferred heat is further transferred from the lid <NUM>, through the thermal interface material <NUM>, and to the bottom <NUM> of the top hat <NUM>. In some examples, one or more components of the liquid cold plate assembly <NUM> may be formed or made from a thermally conductive material, such as copper, aluminum, a combination of copper and aluminum, or other thermally conductive materials.

The heat transferred to the bottom <NUM> of the top hat <NUM> is then transferred to the supply <NUM> of the cooling liquid that is circulated through the inlets <NUM> and into the volume <NUM> of the top hat <NUM>. In some examples, the cooling liquid may be a chilled water or glycol, such as from one or more chillers fluidly coupled to the server tray package <NUM>. In alternative examples, the cooling liquid may be a condenser water or other evaporatively-cooled liquid (e.g., without mechanical refrigeration). In other examples, the cooling liquid may be a dielectric single or two-phase fluid. In any event, the cooling liquid supply <NUM> may be at an appropriate temperature and flow rate to remove a desired amount of heat from the data center electronic devices <NUM> and <NUM>.

In some examples, heat is transferred directly from the bottom <NUM> to the cooling liquid supply <NUM>. Heat may also be transferred from the bottom <NUM>, through one or more heat transfer surfaces <NUM>, and then to the cooling liquid supply <NUM> that flows through channels <NUM>. As shown in <FIG>, the supply <NUM> of the cooling liquid first flows through a portion of the volume <NUM> that is vertically above the memory modules <NUM> (on two sides). Some of the supply <NUM> of the cooling liquid, after receiving heat generated by the memory modules <NUM>, flows through another portion of the volume <NUM> that is vertically above the processing device <NUM> and then to the outlet <NUM> (now heated by the memory module(s) <NUM> and processing device <NUM>). Given that the memory modules <NUM> usually run at lower temperature than processing devices <NUM>, the liquid cold plate assembly <NUM> described herein results in a more efficient usage of the cooling liquid as the cooling liquid can first receive some heat from the memory modules and subsequently receive further heat from the processing device. Some of the supply <NUM> of the cooling liquid, after receiving heat generated by the memory modules <NUM>, flows to the outlet <NUM> and through the outlet <NUM> as return <NUM> of the cooling liquid (now heated by the memory modules <NUM>).

The heated cooling liquid supply <NUM> is circulated to the outlet <NUM> and exits the top hat <NUM> as the cooling liquid return <NUM> (e.g., that is at a higher temperature than the cooling liquid supply <NUM>). The cooling liquid return <NUM> is circulated back, e.g., to a source of the cooling liquid, to expel the heat (e.g., in a chiller, cooling tower, or other heat exchanger) from the return <NUM>.

<FIG> illustrates a schematic cross-sectional top view of another example of a portion of the example implementation of a server tray package <NUM> that includes a liquid cold plate assembly <NUM>. In this example, one or more flow diverters <NUM> are mounted within the volume <NUM> on a top surface of the bottom <NUM> of the top hat <NUM>. As shown in this example, four flow diverters <NUM> are mounted within the volume <NUM> to impede the supply <NUM> of the cooling liquid as it flows from the inlets <NUM> toward the outlet <NUM>. In this example, the flow diverters <NUM> are positioned to impede a flow of the supply <NUM> of the cooling liquid that flows only over one or more memory modules <NUM> between a particular one of the inlets <NUM> to the outlet <NUM>. In some aspects, the flow diverters <NUM> may promote temperature uniformity of the supply <NUM> of the cooling liquid at the outlet <NUM>.

In some example implementations, the flow diverter <NUM> is shaped as a solid wall that, for example, extends all or partially from the bottom <NUM> of the top hat <NUM> toward the cap <NUM>. <FIG> illustrates an example flow diverter <NUM> in which one or more perforations <NUM> are formed in the flow diverter <NUM>. In some aspects, the perforations <NUM> may be designed to promote flow and temperature uniformity of the supply <NUM> of the cooling liquid at the outlet <NUM>.

<FIG> illustrates a schematic cross-sectional top view of another example of a portion of the example implementation of the server tray package <NUM> that includes the liquid cold plate assembly <NUM>. In this example implementations, flow circuits <NUM> are formed in a surface of the bottom <NUM> of the top hat <NUM>. In this example, the flow circuits <NUM> are formed by ridges <NUM> formed in the surface of the bottom <NUM>. Alternatively, the circuits <NUM> may be formed as troughs embedded in the surface of the bottom <NUM>. The flow circuits <NUM>, are oriented in this example in a parallel or substantially parallel direction of flow of the supply <NUM> of the cooling liquid from the inlets <NUM> to the outlet <NUM>. In this example, the flow circuits <NUM> are formed from one edge of the bottom <NUM> that is orthogonal to the direction of flow to an opposed edge of the bottom <NUM> (in this drawing, from top edge of the heat transfer area <NUM> to bottom edge of the heat transfer area <NUM>). In operation, the flow circuits <NUM> may channel the flow of the supply <NUM> of the cooling liquid as it circulates from the inlets <NUM> toward the outlet, thereby, e.g., promoting heat transfer of heat from the bottom <NUM> into the supply <NUM> of the cooling liquid.

<FIG> illustrates a schematic cross-sectional top view of another example of a portion of the example implementation of the server tray package <NUM> that includes the liquid cold plate assembly <NUM>. In this example implementation, flow circuits <NUM> and <NUM> are formed in a surface of the bottom <NUM> of the top hat <NUM>. In this example, the flow circuits <NUM> are formed by ridges <NUM> formed in the surface of the bottom <NUM>, and the flow circuits <NUM> are formed by ridges <NUM> formed in the surface of the bottom <NUM>. Alternatively, the circuits <NUM> and <NUM> may be formed as troughs embedded in the surface of the bottom <NUM>. As shown in this example, flow circuits <NUM> are more closely spaced (e.g., a higher pitch) relative to the flow circuits <NUM>. Also, as shown, the flow circuits <NUM> are formed in the heat transfer area <NUM> above portions of the bottom <NUM> that are vertically above only memory modules <NUM> on the interposer <NUM>. The flow circuits <NUM> are formed in the heat transfer area <NUM> above portions of the bottom <NUM> that are vertically above memory modules <NUM> and the processing device <NUM> on the interposer <NUM>.

The flow circuits <NUM> and <NUM> are oriented in this example in a parallel or substantially parallel direction of flow of the supply <NUM> of the cooling liquid from the inlets <NUM> to the outlet <NUM>. In this example, the flow circuits <NUM> and <NUM> are formed from one edge of the bottom <NUM> that is orthogonal to the direction of flow to an opposed edge of the bottom <NUM> (in this drawing, from top edge of the heat transfer area <NUM> to bottom edge of the heat transfer area <NUM>). In operation, the flow circuits <NUM> and <NUM> may channel the flow of the supply <NUM> of the cooling liquid as it circulates from the inlets <NUM> toward the outlet, thereby, e.g., promoting heat transfer of heat from the bottom <NUM> into the supply <NUM> of the cooling liquid.

Turning to <FIG>, this figure illustrates a schematic cross-sectional top view of another example of a portion of the example implementation of the server tray package <NUM> that includes the liquid cold plate assembly <NUM>. As shown in this example, there are four inlets <NUM>, each of which is positioned at a perimeter edge of the top hat <NUM>. There is a single outlet <NUM> (shown as a circular cross-sectional outlet in this example) positioned in the center of the heat transfer area <NUM> of the top hat <NUM>. Thus, during operation of the liquid cold plate assembly <NUM> in <FIG>, the supply <NUM> flows in the volume <NUM> in a direction from the inlets <NUM> and toward a center of the top hat <NUM> where the outlet <NUM> is located. In this example, all or much of the supply <NUM> of the cooling liquid flows first within a portion of the volume <NUM> vertically above one or more memory modules <NUM> and then within another portion of the volume <NUM> vertically above the processing device <NUM> to receive heat from the devices, through the bottom <NUM> and into the cooling liquid.

Turning to <FIG>, the implementation of the liquid cold plate assembly <NUM> is shown (e.g., with four inlets <NUM> and a single, center outlet <NUM>) with multiple pin fins <NUM> mounted onto the bottom <NUM> of the top hat <NUM> within the volume <NUM>. As shown, the pin fins <NUM> define multiple tortuous flow paths for the supply <NUM> of the cooling liquid to flow through from the inlets <NUM> to the outlet <NUM>. In this example, the pin fins <NUM> may cover all or most of the heat transfer area <NUM> and, for instance, extend from the bottom <NUM> to the cap <NUM>. In alternative implementations, there may be some portions of the heat transfer area <NUM> that do not include pin fins <NUM>. In alternative implementations, the pin fins <NUM> my only extend partially from the bottom <NUM> into the volume <NUM> and toward the cap <NUM>.

Claim 1:
A server tray package, comprising:
a motherboard (<NUM>) assembly that comprises a plurality of data center electronic devices (<NUM>, <NUM>); and
a liquid cold plate assembly (<NUM>) that comprises:
a base portion (<NUM>) mounted to the motherboard (<NUM>) assembly, the base portion (<NUM>) and motherboard (<NUM>) assembly defining a volume (<NUM>) that at least partially encloses the plurality of data center electronic devices (<NUM>, <NUM>); and
a top portion (<NUM>) mounted to the base portion (<NUM>) and comprising a heat transfer member that comprises a first number of inlet (<NUM>) ports and a second number of outlet (<NUM>) ports that are in fluid communication with a cooling liquid flow path defined through the heat transfer member, the first number of inlet (<NUM>) ports being different than the second number of outlet (<NUM>) ports, wherein respective ports larger in number are each placed at or near a perimeter edge of the top portion (<NUM>) and respective ports smaller in number are positioned at or near a center of the top portion (<NUM>).