Heat sink assembly for electronic equipment

A heat sink assembly for a cage for a field replaceable computing module includes a heat sink, a thermal interface material (TIM), and an actuation assembly. The heat sink includes a mating surface. The TIM includes a first surface that is coupled to the mating surface and a second surface that is opposite the first surface. Thus, the second surface can engage a heat transfer surface of a field replaceable computing module installed adjacent the heat sink. The actuation assembly includes a shape memory alloy (SMA) element. When the SMA element is in a first position, the second surface of the TIM contacts the heat transfer surface of the computing module. When the SMA element moves to a second position, the second surface of the TIM is moved a distance away from the heat transfer surface of the computing module.

TECHNICAL FIELD

The present disclosure relates to high performance and/or high density computing solutions, such as line cards and computing blades, that can receive field replaceable computing modules, and in particular to a heat sink assembly for these computing solutions.

BACKGROUND

Over the past several years, the information technology field has seen a tremendous increase in the performance of electronic equipment coupled with a decrease in geometric floor space to house the equipment. For instance, due at least to recent advances in high throughput computing, field replaceable computing modules, such as optical transceivers, are dissipating more power (e.g., 25 Watts (W) or more) in smaller form factors (i.e., computing modules are being provided with increasingly higher power densities). However, permissible operating temperatures, which may be defined by temperature limits of internal components included in the field replaceable computing modules, have remained relatively stagnant. Moreover, as computing solutions become denser, less space is available for cooling solutions. Thus, cooling solutions for field replaceable computing modules that can provide improved cooling in smaller form factors are continuously desired.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

A heat sink assembly for a cage for a field replaceable computing module, an apparatus including the cage, and a system including the apparatus and the field replaceable computing module are presented herein. In one embodiment, a heat sink assembly for a cage for a field replaceable computing module includes a heat sink, a thermal interface material, and an actuation assembly. The heat sink facilitates heat dissipation and includes a mating surface. The thermal interface material includes a first surface that is coupled to the mating surface of the heat sink and a second surface that is opposite the first surface. Thus, the second surface can engage a heat transfer surface of a field replaceable computing module installed adjacent to the heat sink. The actuation assembly includes a shape memory alloy (SMA) element. When the SMA element is in a first position, the second surface of the thermal interface material contacts the heat transfer surface of the field replaceable computing module, and when the SMA element is moved to a second position, the second surface of the thermal interface material is moved a distance away from the heat transfer surface of the field replaceable computing module.

Example Embodiments

The heat sink assembly presented herein enables high performance and/or high density computing solutions, such as line cards and computing blades, to effectively dissipate heat from field replaceable computing modules without inhibiting insertion or removal of the field replaceable computing modules (also referred to herein as “modules,” “pluggable modules,” “swappable modules,” and the like), such as during online insertion and removal (“OIR”) operations. Specifically, the heat sink assembly presented provides a movable or “floating” heat sink and an actuation assembly that can move the floating heat sink towards and/or away from a module cage included in a computing solution.

Notably, the heat sink assembly presented herein may be primarily actuated via an electrical actuation. Thus, the actuator may occupy a minimal amount of space on a front panel of a computing solution, which may be beneficial, if not required, for computing solutions with dense front panel layouts. In fact, in some instances, the heat sink assembly presented herein may be actuated via a purely electrical actuation (i.e., only an electrical actuation). In these instances, the heat sink assembly need not include a physical/mechanical actuator. That is, in at least some instances, the heat sink assembly may eliminate any need for a physical/mechanical actuator. Regardless, the heat sink assembly presented herein can also lock a heat sink in a raised position or a lowered position, which may simplify insertion and removal of a module. This locking may also allow that the heat sink assembly presented herein to compress a heat sink and a thermal interface material (“TIM”) included thereon against a module.

Moreover, in at least some embodiments, the actuation assembly moves the entire heat sink away from the module cage (and/or a module installed therein), thereby reducing, if not eliminating, the risk of a module scraping against the heat sink assembly during insertion or removal operations. In fact, the actuation assembly may move the heat sink so that the mating surface of the heat sink (e.g., a bottom surface) remains parallel to a heat transfer surface of a module (e.g., a top surface). Consequently, during insertion or removal of the module, the entire mating surface of the heat sink (e.g., the bottom surface) will be equally spaced apart from the heat transfer surface of the module (e.g., the top surface) by a gap and the module will not rub or slide against the mating surface of the heat sink. This gap, in turn, allows a TIM, which would be damaged by sliding or rubbing, to be included on the mating surface. The TIM increases thermal conductivity between the heat sink and a module and, thus, improves cooling for the module. Additionally, parallel motion of the heat sink with respect to the module cage may provide a substantially consistent gap between the heatsink and the module, which may allow the gap required for module removal to be minimized.

Additionally or alternatively, the actuation assembly may move the heat sink along one degree of freedom (e.g., vertically). Moving the heat sink along one degree of freedom (e.g., vertically) may ensure that the heat sink does not need to be positioned adjacent open space, which is necessary when a heat sink moves in a lateral or depth direction (e.g., a front-to-back direction). Instead, the surface area of the heat sink size may be maximized to span a perimeter of a module and/or module cage and the cage need not be positioned with open space surrounding its peripheral boundaries. That is, moving the heat sink along one degree of freedom may maximize a thermal contact area. Furthermore, moving the heat sink along one degree of freedom may allow the heat sink to generate compression forces on a TIM (e.g., if the one degree of freedom is linear, vertical movement) that are often necessary to maximize TIM performance with the assembly that moves the heat sink. This may reduce the number of components in the assembly, reducing costs of manufacture and servicing. The TIM also tends to reduce, if not eliminate, the effects of minor dimensional differences between different pluggable modules.

In order to describe the heat sink assembly, computing apparatus, and computing system presented herein, terms such as “left,” “right,” “top,” “bottom,” “front,” “rear,” “side,” “height,” “length,” “width,” “upper,” “lower,” “interior,” “exterior,” “inner,” “outer,” “depth,” and the like as may be used. However, it is to be understood that these terms merely describe points of reference and do not limit the embodiments to any particular orientation or configuration. For example, the terms “height,” “width,” and “depth” may be used to describe certain embodiments presented herein, but it is to be understood that these terms are not intended to limit the present application to specific implementations. Instead, in at least some embodiments, the heat sink assembly presented herein may be oriented horizontally (as shown) or vertically (i.e., a housing of a computing solution may be rotated 90 degrees about an axis extending through a front and back of the housing), or in any other manner during use (e.g., when installed into a blade chassis/enclosure). Consequently, even if a certain dimension is described herein as a “width,” it may be understood that this dimension may provide a height or depth when a computing solution in which it is included is moved to different orientations.

Now turning toFIG.1A, this Figure schematically illustrates an example embodiment of a computing solution10that includes an example embodiment of the heat sink assembly30presented herein (for simplicity, at least some components of the heat sink assembly30are not shown inFIG.1A). The computing solution10may also be referred to as a computing system; however, it is to be understood that the term “system,” when used herein, does not imply that the solution/system10is a stand-alone system. Instead, a solution/system10may be a stand-alone system or a portion/subsystem of a larger system (e.g., solution10may be a blade of a server). That said, inFIG.1A, the computing solution10includes an apparatus12and a removable computing module20. The apparatus12includes a housing14that houses a PCB16and a module cage18(e.g., an optical cage). Additionally, the housing14houses a heat sink assembly30with a heat sink31and a thermal interface material (TIM)35. The TIM35is included on a bottom or mating surface of the heat sink31and, as is depicted, during insertion or removal of the computing module20into the module cage18, the heat sink assembly30moves the heat sink31and TIM35away from the module cage18to provide a gap “G” between the computing module20and the TIM35.

In the depicted embodiment, the heat sink assembly30moves the heat sink31and the TIM35upwards. More specifically, the heat sink assembly30moves the entire heat sink31and entire TIM35upwards, away from the module cage18. In at least some embodiments, the heat sink assembly30moves the heat sink31and TIM35while keeping the TIM35parallel to a top of the module cage18. Alternatively, the heat sink31and TIM35might be moved upwards in any manner, but are moved into a raised position that is parallel to a top of the module cage18. Still further, in some embodiments, the TIM35is not parallel to the top of the module cage18when in a raised position, but is spaced apart from the top of the module cage18across its surface area (e.g., so that the gap G spans the whole TIM35). Regardless of how the heat sink31and TIM35are moved to a raised position (and regardless of how the TIM35is oriented in its raised position), the gap G allows the computing module20to be inserted into or removed from module cage18without contacting and damaging TIM35. If, instead, only a portion of the TIM35was moved away from the module cage18(e.g., if the heat sink assembly30was tipped about a lateral axis, which would extend into the plane of the drawing sheet on whichFIG.1Ais included), the computing module20might contact and damage the TIM35(e.g., by scraping a portion of the TIM35off of the heat sink assembly30).

Alternatively, and now turning toFIG.1B, if the heat sink assembly30does not include a TIM35, a metal surface of a heat sink31included in the heat sink assembly30might not form an effective thermal connection with the computing module20. For example, since metal surfaces (e.g., a bottom of a heat sink and/or top of a module) can have surface irregularities, such as flatness irregularities, waviness irregularities, roughness irregularities, etc., air gaps may form between the metal surfaces of a heat sink31and a computing module20. InFIG.1B, the left image illustrates air gaps AG1that form between metal surfaces with surface flatness irregularities while the right image illustrates air gaps AG2that form between metal surfaces with surface roughness irregularities. Notably, many riding heat sinks, which are often biased into contact with a module via spring clips that press the heat sink against a module during insertion or removal, provide inefficient heat transfer away from computing modules20due to air gap issues. These issues cannot be remedied by a TIM35, because the TIM would be scraped off or otherwise damaged as a heat sink “rides” on a sliding module. Regardless of how air gaps form between the module20and the heat sink assembly30, air gaps are detrimental to heat transfer because the low thermal conductivity of air provides significant contact resistance. A TIM can reduce or eliminate these air gaps and significantly reduce contact resistance, especially if the TIM is compressed to a specific compression to maximize heat transfer (which may differ for different materials).

FIG.2Aillustrates a top perspective view of a computing apparatus12and a replaceable computing module20that may be installed within the apparatus12to form a computing solution10. As is shown, the computing apparatus12includes a front surface or panel100with an opening101that provides access to the module cage18defined therein. In the depicted embodiment, the module cage18extends in a depth direction (e.g., front-to-back) within the housing14of the apparatus12. That is, the module cage18extends from the front panel100towards a back end102of the housing14. Additionally, in the depicted embodiment, the module cage18is arranged to be substantially flat within the housing14, such that the module cage18is parallel to a cover104that defines a top of the housing14.

Meanwhile, and now referring toFIG.2Ain combination withFIG.2B, the module20includes a top surface22, a back surface24with a connector25, a bottom surface26, and a front surface28. As is discussed in further detail below, in the depicted embodiment, the top surface22of the computing module20is a heat transfer surface for the computing module20. However, in other embodiments, any surface of the computing module20could serve as a heat transfer surface. During insertion of the computing module20into the module cage18, the perimeter of back surface24is aligned with the module cage18and then the computing module20is pushed into the module cage18to connect the connector25on the back surface24with a connector124included in the module cage18(seeFIG.3B). During removal of the computing module20from the module cage18, the front surface28may be grasped, e.g., by handle29, and pulled out of the module cage18. However, handle29is merely representative of a feature that enables a user to easily grasp the front surface28and, in other embodiments, the module20could include any other features instead of or in addition to handle29. Alternatively, the computing module20can be ejected or removed from the module cage18in any manner now known or developed hereafter (including mechanical ejections). Before or after the computing module20is installed in the module cage18, the housing14may be installed into another computing solution (e.g., a rack) and secured thereto with installation member112(seeFIGS.2A and3A).

InFIG.2A(as well as many other Figures), the computing solution10is a line card; however, it is to be understood that a line card is simply one example of a computing solution in which the heat sink assembly presented herein may be included. For example, the computing solution10could also be a rack server, a storage drawer, a stand-alone computing solution, or any other computing solution that accepts modular computing components (e.g., “field replaceable computing modules”). Likewise, inFIGS.2A and2B(as well as many other Figures), the module20is an optical transceiver, but it is to be understood that an optical transceiver is simply one example of a module with which the heat sink assembly presented herein may be used. That said, it may be beneficial to utilize the heat sink presented herein with optical transceivers because technical advancements in optical transceivers have generated high power dissipation (e.g., 25 W or more) in a small form factor (e.g., C form-factor pluggable 2 (“CFP2”) form factor, which has dimensions of 41.5 millimeters (“mm”)×12.4 mm×107.5 mm (w×h×d)). These characteristics make it difficult to satisfy Network Equipment-Building System (NEBS) thermal standards for these modules.

Now turning toFIGS.3A,3B, and3C, these Figures illustrate portions of the apparatus12in further detail. InFIG.3A, the apparatus12is shown with its top cover104removed. With the top cover104removed, the heat sink assembly30can be seen disposed above the module cage18. Meanwhile,FIG.3Billustrates the module cage18removed from the housing14andFIG.3Cillustrates a heat sink31of heat sink assembly30removed from the apparatus12. As can be seen inFIG.3B, the module cage18extends from an open front end120to a back end122. The back end122includes a connector124that may connect a computing module20to an apparatus12in which the module cage18is included (e.g., via PCB16). That is, the connector124may be configured to provide a Small Computer System Interface (SCSI) connection, Serial Attached SCSI (SAS) connection, an advanced technology attachment (ATA) connection, a Serial ATA (SATA) connection, and/or or any other type of connection for field replaceable computing modules.

Additionally, the module cage18extends from a first side126to a second side128and includes an open top130. Collectively, the open front end120, the back end122, the first side126, the second side128, and the open top130define an internal chamber132. That is, the open front end120, the back end122, the first side126, the second side128, and the open top130define a perimeter or periphery of chamber132(with sides126and128defining a lateral periphery while front end120and back end122defining a longitudinal periphery). The chamber132is sized to house/receive computing module20and the open top130allows the heat sink assembly30to access and engage the top surface22(i.e., the heat transfer surface) of a computing module20installed within a chamber132.

In different embodiments, the open top130may provide access to the chamber132in any desirable manner, such as via one or more windows, cut-outs, segments, etc. However, in the depicted embodiment, the open top130spans the entire surface area of the chamber132, extending a length L1from the open front end120to the back end122(e.g., in a front-to-back or depth dimension) and a width W1from the first side126to the second side128(e.g., in a lateral or width dimension). Thus, the depicted embodiment may maximize the area within which heat may transfer from the computing module20to the heat sink assembly30.

InFIG.3C, the heat sink31is shown from a bottom perspective view, which illustrates the TIM35that is included on a mating surface133of the heat sink31. The TIM35includes a first surface135and a second surface136. The second surface136is fixedly coupled to the mating surface133of the heat sink31(e.g., via adhesive, ultrasonic welding, etc.) and the first surface135is disposed opposite the second surface136. Thus, the first surface135faces the open top130of the module cage18when the heat sink31is installed above the module cage18. In at least some embodiments, the first surface135may include or be coated with a protective film that prevents the first surface135from sticking to a module20. In the depicted embodiment, the first surface135and second surface136converge towards both a front144and a back146(seeFIG.5) of the heat sink31so that the second surface135includes convergent sections137and a flat section138. However, in other embodiments, the first surface135and the second surface136need not converge and, for example, may be parallel to each other across the dimensions of the TIM35.

Regardless of the shape of the TIM35, the mating surface133of the heat sink31may have dimensions L2(e.g., a front-to-back dimension) and W2(e.g., a width) that are at least as large as the corresponding top dimensions (L1and W1, respectively) of the chamber132(defined by the open top130) and a heat receiving portion of the TIM35(e.g., the flat section138) may span or cover a majority of the mating surface133. More specifically, the TIM35may span (e.g., cover) at least a depth or front-to-back dimension L1of the open top130(which defines a depth of a top of the chamber132). Additionally or alternatively, the TIM35may span a lateral dimension L2of the open top130(which defines a lateral dimension of a top of the chamber132). For example, the flat section138of the TIM35may have a lateral dimension W3(e.g., width W3) that is equal to or greater than W1and/or the flat section138of the TIM35may have a front-to-back dimension L3(e.g., depth L3) that is equal to or greater than L1. Consequently, the flat section138of the TIM35may cover as much of the computing module20as possible and maximize heat transfer between a computing module20and the heat sink31.

Notably, with the heat sink assembly presented herein, the TIM35can span the entire surface area (e.g., L1by W1) of the chamber132because, in at least some embodiments, the heat sink assembly30only moves the heat sink31vertically with respect to the module cage18(and a computing module20installed therein). If, instead, the heat sink31moved laterally or in a front-to-back direction, open space would need to be available to allow movement of heat sink31. In some instances, this issue might be addressed by moving the heat sink31outside the peripheral boundaries of the module cage18(e.g., laterally beyond side126or128). However, such movement would increase the dimensional footprint of the heat sink assembly30, which is often undesirable, if not impossible, in high-density computing solutions.

Still referring toFIG.3C, the mating surface133of the heat sink31forms a bottom of the heat sink31and fins140extend upwards therefrom. Specifically, the fins140and/or the mating surface133may include/define a base142and the fins140may extend from the base142to a top143of the heat sink31. In the depicted embodiment, the fins140cover a majority of the base142between a front144and a back146of the heat sink31to maximize cooling and each of the fins140extends in a side-to-side direction across the heat sink31. However, in other embodiments, the fins140may be arranged in any orientation or configuration. For example, the fin geometry, profile, and dimensions can be customized for different types of applications and airflow directions (e.g., front-to-back and/or side-to-side airflow). Still further, in yet other embodiments, heat sink31might be finless and may, for example, dissipate heat via heat pipes, fluid thermal management, or other mechanisms/arrangements that dissipate heat.

Now turning toFIGS.4and5, the fins140may also define a number of openings, cavities, channels, mounting features, etc. to accommodate and secure portions of the heat sink assembly30, such as an actuation assembly150of the heat sink assembly30. In the depicted embodiment, the fins140define a passageway152that extends in a front-to-back direction through the heat sink31and also define three mounting points154spaced along top edges of the passageway152(i.e., at a top of sides of the passageway152). The passageway152is an open-top passageway that is centered with respect to the fins140, but in other embodiments, the passageway152could be a through hole, a partially covered passageway, or any other opening/passageway/cavity. Additionally or alternatively, in other embodiments, the passageway152need not be centered with respect to the fins140and/or could be one of a plurality of passageways. Moreover, although not shown, in some embodiments the fins140may define additional channels configured to accommodate other features or elements, such as longitudinal channels for guide pins that extend fully or partially through the fins140. Still further, in some embodiments the fins140need not define any openings, cavities, channels, etc. For example, the actuation assembly150might extend along one or more sides of heat sink31(such an actuation assembly150might have a height that is low enough not to impair airflow through the heat sink31).

Generally, and still referring toFIGS.4and5, the heat sink31is positioned atop the cage18, but is not directly connected to the module cage18. Instead, the heat sink31is “floating” with respect to the module cage18and the actuation assembly150movably couples the heat sink31to the module cage18. That is, the actuation assembly150included in the heat sink assembly30presented herein is configured to lift and lower the heat sink31. In the embodiment ofFIGS.2A-5, the actuation assembly150includes a biasing member160, a shape memory alloy (SMA) element172, and closure brackets180. Additionally, in the depicted embodiment, the heat sink assembly30includes a support frame190that helps couple the actuation assembly150to the module cage18.

In the depicted embodiment, the biasing member160is connected the module cage18via connectors166and includes spring members164that are positioned above the base142of the heat sink31. Specifically, the spring members164engage corners145of a top surface of the base142of the fins140, which are left open by shortened fins140disposed at a front144and back146of the heat sink31. The spring members164are connected together by support members162and, since the biasing member160is anchored to (i.e., fixedly coupled to) the module cage via connectors166, the spring members164resist upwards movement of the heat sink31. Thus, the spring members164exert a restorative force on the heat sink31in response to upwards movement of the heat sink31. That is, due to the aforementioned features and connections, the biasing member160will consistently urge the heat sink31towards the module cage18. However, biasing member160is only one example of an element, structure, and/or feature that may return the SMA element172to a rest or engaged position on or adjacent to the module cage18and, in other embodiments, SMA element172may be returned to its rest or engaged position in any desirable manner. In fact, other example techniques or elements are discussed in further detail below.

Meanwhile, the SMA element172includes a proximal end174, a distal end176, and an elongate section178extending between the proximal end174and the distal end176. The elongate section178is positioned in the passageway152of the heat sink31and secured therein by closure brackets180. To be clear, in this embodiment, the closure brackets180are not coupled to the SMA element172; instead, the closure brackets180close the passageway152to capture the elongate section178therein. By contrast, the proximal end174and the distal end176of the SMA element172are fixed or anchored with respect to the module cage18. Thus, elongate section178can flex or deform with respect to the proximal end174and the distal end176and act on (e.g., push) the closure brackets180and/or the heat sink31to move the heat sink31(which moves with the closure brackets180) with respect to the module cage18. In at least some embodiments, the elongate section178may be coated or covered with insulation, such as with a hot shrink tube, over molding, or any other technique, so that electric current does not leak between the SMA element172and the heat sink31(and/or closure brackets180).

In the depicted embodiment, the closure brackets180are secured to the mounting points154of the heat sink31with fasteners, but in other embodiments, the closure brackets180can be secured to the fins140in any manner (e.g., welding, soldering, etc.). Additionally, in the depicted embodiment, the proximal end174and the distal end176of the SMA element172are secured to the module cage18via support frame190, but in other embodiments the proximal end174and the distal end176of the SMA element172could be secured directly to the module cage18(e.g., the module cage18could include upwardly extending brackets that provide connection points).

That said, in the depicted embodiment, the support frame190includes a first frame portion192and a second frame portion194that are coupled together around the module cage18. Additionally, the first frame portion192and the second frame portion194can be coupled to the PCB16and/or the module cage18. Regardless, the first frame portion192includes or defines a first mounting portion196above the module cage18and the second frame portion194defines a second mounting portion198above the module cage18. Mounting portions196and198are or include insulated or non-conductive portions that can insulate SMA element172from the module cage18and/or the remainder of heat sink assembly30. Alternatively, the entire support frame190can be insulated or non-conductive. Either way, due to this insulation, current delivered to the SMA element172will not run into the heat sink31, the module cage18, and/or a module20installed in the module cage18.

Now referring toFIGS.4and6, generally, SMA actuates (e.g., deforms and/or contracts) in response to heating. Consequently, the SMA element172is included in or connected to circuitry200that can provide current to the SMA element172and cause resistive heating of the SMA element172. For example, inFIG.4, the proximal end174and the distal end176of SMA element172are coupled to positive and negative poles of a power source202via wires204A and204B (represented as wires204inFIG.6) to form a circuitry200including the SMA element172. The power source202can be a dedicated battery or any power source included in or connected to a computing solution in which the heat sink assembly30is installed.FIG.6illustrates this circuitry schematically in combination with additional electrical elements.

Specifically, inFIG.6, the circuitry200includes a switch206that can be closed to deliver current to the SMA element172. The switch206may be a mechanical switch actuated by a mechanical/physical actuator (e.g., a push button actuator) and/or an electrical/digital switch that is actuatable by a processor. Either way, closing the switch206may deliver current to the SMA element172that effectuates resistive heating of the SMA element172to cause an actuation of the SMA element172(e.g., a contraction or deformation). Additionally, in some embodiment, the circuitry200may include an indicator210, such as a light, arranged in parallel with the SMA element172. With such an arrangement, closing the switch206actuates the SMA element172and the indicator210, for example, to provide an illuminated indication. However, this is just one example arrangement for an indicator and indicators could be arranged and operated in any manner now known or developed hereafter. For example, circuitry200could have any other configuration that allows indicator210to be activated in one or more colors. Additionally or alternatively, circuitry200, or portions thereof, could be duplicated, to provide two or more indications (e.g., raised and lowered). Circuitry200may also include a constant-current feature that helps enable protracted actuation of SMA element172without exceeding thermal limits for the SMA material.

Now turning toFIG.7, this Figure illustrates an actuation of SMA element172. The initial or rest state or position P1of the SMA element172is shown in dashed lines and the actuated state or position P2is shown in solid lines. In this embodiment, SMA element172is a one-way SMA formed from any material that deforms when heated, including but not limited to copper-aluminum-nickel (Cu—Al—Ni), nickel-titanium (Ni—Ti), iron-manganese-silicon (Fe—Mn—Si), copper-zinc-aluminum (Cu—Zn—Al), and other alloys of zinc, copper, gold, and iron. Generally, the deformation behavior of a specific alloy can be modeled using hysteresis curves, which map material states of SMA as a function of temperature. Thus, specific alloy materials may be selected for SMA element172based on environmental characteristics of a computing solution in which the SMA element172is to be included and/or the current that will be delivered to the SMA element172. For example, the SMA element172may be designed to actuate at a temperature that is significantly higher than a temperature of heat sink31during cooling operations to prevent heating of the heat sink31from causing an actuation of the SMA element172.

Moreover, regardless of the specific composition of the SMA element172, the SMA element172can be trained with thermomechanical treatments now known or developed hereafter so that the SMA element172deforms to specific shape when heated to a specific temperature (e.g., with resistive heating). For example, the SMA element172may be trained to move vertically between positions P1and P2. Additionally or alternatively, the SMA element172may be trained to move along one degree of freedom (e.g., vertical, linear movement) and, thus, may restrict the heat sink assembly30to movement along one degree of freedom. Still further, the SMA element172can be trained to move in any direction and the heat sink assembly30might include additional features (e.g., guide pins) to control or restrict movement of the heat sink31(e.g., to one degree of freedom).

Still referring toFIG.7, but now in combination withFIGS.3A-6, regardless of how the SMA element172is trained or tuned, actuating the SMA element172presented herein may move the heat sink31vertically with respect to a module cage18(and, if installed, a computing module20). For example, in the embodiment ofFIGS.2A-7, actuating the SMA element172may contract the SMA element172and cause the elongated section178to move upwards along vertical axis A1. Upwards movement of the elongated section178along vertical axis A1pushes the closure brackets180upwards (seeFIGS.4and5) which may move the heat sink31upwards (along vertical axis A1) with respect to the module cage18(since the closure brackets180are fixedly secured to the heat sink31). More specifically, upwards movement of the elongated section178along vertical axis A1may move the heat sink31upwards a distance D1upwards along axis A1, creating a gap G (seeFIG.1A) of, for example, 2-3 millimeters between the computing module20and the TIM35. Notably, the proximal end174and the distal end176of the SMA element172remain fixed or anchored during deformation of the SMA element172and, thus, the elongate section178can drive vertical movement of the heat sink31, which is essentially floating on the SMA element172(or at least on the elongate section178of the SMA element172).

In the specific embodiment depicted inFIGS.3A-7, the SMA element172is a one-way SMA and, thus, provides movement in one direction (when it's crystalline structure changes), but must be restored to its original or rest position (position P1) before it can provide another actuation. Thus, the biasing member160works in combination with the circuitry200to control movement of the heat sink31. In particular, the circuitry200delivers a current to the SMA element172to cause a change to the crystalline structure of SMA element172that contracts the SMA element172to lift the heat sink31to its actuated position P2(e.g., to provide a gap G as shown inFIG.1A). Then, since the biasing member160is constantly exerting a restorative force on the heat sink31, the biasing member160will return the SMA element172to its rest position P1when current is no longer to the SMA element172. This lowers the heat sink31into engagement with the module cage18and/or a module20installed within the module cage18. Thus, to maintain the heat sink31in a raised position, current must be continually delivered to the SMA element172. In fact, in at least some embodiment, the voltage is continuously adjusted (in any manner now known or developed hereafter) to maintain a constant current across the SMA element172when the heat sink31should be in a raised position (e.g., based on a user actuation and/or processor generated instructions).

Further, in at least some embodiments, the SMA element172may be trained, tuned, or controlled (e.g., controlled with current delivery) to provide non-constant vertical motion of the heat sink31. This may be advantageous, for example, to provide an initially rapid downward motion of the heat sink, followed by a more gradual “seating” of TIM35onto the module20. Alternatively, the tuning/training/controlling could provide a slow initial raising of the TIM35away from the module20to prevent the TIM35from being damaged when the TIM35is disconnected from the module20. Additionally or alternatively, the configuration shown inFIGS.3A-7could be reversed and actuation of the SMA element172could compress the TIM35against a module20. In such embodiments, the SMA element172can be trained to provide a specific compression of the TIM35to maximize heat transfer (e.g., tuned for a specific TIM material), either in combination with or independent of additional components (e.g., spring clips) that create compression. Example embodiments including such an arrangement are discussed in further detail below.

Overall, when the SMA element172is in its actuated position P2(such that gap G is provided between the TIM35and the module cage18), a computing module20can be installed or removed from the module cage18. In at least some embodiments, the gap G may be consistent across the surface area of the TIM35(e.g., an area defined by W3and L3), such that the TIM35(or at least a portion thereof) is parallel to the module cage18and/or the computing module20(i.e., the heat sink assembly30may provide uniform lifting). In any case, after a computing module20is installed in module cage18(which may be detected, for example, in the manner discussed below in connection withFIG.9), the SMA element172may be moved to its rest position P1(e.g., by opening switch206or otherwise stopping the flow of current to SMA element172), which may move the TIM35into engagement with a heat transfer surface of the computing module20(e.g., top surface22). In fact, in some embodiments, moving the SMA element172to its rest position P1may compress the TIM35against the heat transfer surface of the computing module20(e.g., top surface22), further encouraging heat transfer.

Now turning toFIG.8-15B, these Figures depict additional embodiments of the heat sink assembly presented herein, or at least of portions thereof. In these Figures, components that are similar to components shown inFIGS.2A-7are labeled with like reference numerals and, any description of like reference numerals included above should be understood to apply to like components included inFIGS.8-15B. Thus, for brevity, the foregoing description focuses on differences between the embodiments. Additionally, if components ofFIGS.2A-7are not shown in embodiments depicted inFIGS.8-15B, these embodiments may nevertheless be described with reference to components ofFIGS.2A-7to provide clarity and/or context.

That said,FIGS.8and9depict a heat sink assembly30that can be actuated in response to a physical/mechanical actuator.FIG.8illustrates an example actuator220that may be included on a front panel100of computing apparatus12in combination with example indicators210A and210B. Notably, sinceFIG.8depicts two indicators210A and210B, the circuitry of this embodiment may be modified as compared to the circuitry200shown inFIG.6.FIG.9illustrates a method250of operating indicators210A and210B. As is described in detail below, indicators210A and210B may be operated based on actuations of actuator220and/or electrical actuations (e.g., based on commands generated by a processor). That is, with this arrangement, processing logic may control operations of indicator210A, indicator210B, and/or SMA element172, either in combination with actuations of actuator220or independent of actuations of actuator220. In fact, in some embodiments, the computing solution need not include an actuator and a processor248could execute instructions stored in memory249to control indicator210A, indicator210B, and/or SMA element172(or any other arrangement of indicators and SMA elements) with purely electrical operations.

InFIG.9, method250illustrates operations that processor248, which may comprise any processor included in the computing solution ofFIG.8may execute to control indicator210A, indicator210B, and/or SMA element172(or any other arrangement of indicators and SMA elements). Generally, the processor248may comprise one or more processing cores and the memory249may comprise at least one non-transitory computer readable medium or memory for holding instructions programmed according to the embodiments presented, for containing data structures, tables, records, etc. Instructions stores in memory249may include software code scripts, etc. for controlling indicators and/or the SMA element172. In any case, initially, at252, the processor248determines if an unlock command has been received. In some instances, the unlock command can be the actuation of actuator220. Alternatively, an unlock command could be a command input or generated via a graphical user interface or other computing interface connected to processor248. In response to such a command, electrical circuitry of the SMA element172is enabled. That is, current is delivered to SMA element172(e.g., by power source202). This actuates (e.g., deforms/contracts) the SMA element172and lifts the heat sink31in the manner described above.

Then, at256, the processor monitors the current and maintains a constant current across the SMA element172by adjusting the voltage, as was discussed above. During operations254and/or256, the processor248can activate indicator210B, for example, to provide a green light indication that the module cage18is “OPEN,” as is shown at258. Additionally or alternatively, as mentioned above, an actuation of actuator220might close a switch that activates indicator210B or allows processor248to activate indicator210B.

Once the module cage is “OPEN,” the processor248may, at260, monitor for presence of a module20in the module cage18. That is, once the heat sink31is in a raised position, the processor248may monitor for presence of a module20in the module cage18at260. For example, the module cage18may include an interrupt at or adjacent its back end122that provides a signal when a module20is fully installed in the module cage18. Additionally or alternatively, the processor248can monitor connector124to sense when the connector25of the module20has been fully inserted into the module cage18and connected with connector124. Still further, in some embodiments, a user might be able to actuate the actuator220a second time to indicate that a module20has been fully installed in the module cage18. Regardless, the processor248may ensure that the SMA element172stays activated (maintaining the heat sink31in a raised position) until the module20is detected as being installed in the module cage18. That is, the processor248may cause the power source202to continue delivering power to SMA element172(with continued instructions or by withholding a command to cut off power) until a module20is determined to be fully installed in module cage18.

When processor248determines that a module20is fully installed in the module cage18, the processor248may, at262, disable electrical circuitry of the SMA element172. That is, the processor248may disconnect power from the SMA element172to discontinue the delivery of current to SMA element172(e.g., by providing instructions to power source202). This may deactivate the SMA element172and allow biasing member160to move the heat sink31into contact with the module20and/or the module cage18. Additionally, indicator210A can be activated (while indicator210B is deactivated), for example, to provide a red light indication that the module cage18is “LOCKED,” as is shown at264. The heat sink assembly30may then remain in a locked position until a new unlock command is received at252.

Next,FIGS.10A and10Billustrate another example embodiment of a heat sink assembly30′ presented herein. Heat sink assembly30′ is substantially similar to the heat sink assembly30shown in at leastFIG.3A. Thus, to reiterate, like reference numerals are used to denote similar parts and, for brevity, the foregoing description focuses on differences between the embodiments. Most notably, in this embodiment, the heat sink assembly30′ does not include a support frame. Instead, the proximal end174of the SMA element is connected to the front panel100of the apparatus12and the distal end176is connected to a bracket276extending from the module cage18. Moreover, the SMA element172is not secured within the heat sink31by covers, such as closure brackets180and, instead, is directly connected to heat sink31via one or more insulated couplings279. Still further, heat sink assembly30′ does not include a biasing member160in the form of a spring clip, but instead, includes compression springs160′ that exert a constant restorative or biasing force BF (seeFIG.10B) on the heat sink31and SMA element172(like biasing member160).

Despite the differences between heat sink assembly30and heat sink assembly30′, heat sink assembly30′ still operates in a substantially similar manner to heat sink assembly30. That is, SMA element172is still a one-way SMA that contracts to an actuated position P2and lifts the heat sink along axis A1a distance D1to a raised position P4(seeFIG.10B) in response to resistive heating. This creates a gap G that allows a module20to be inserted or removed from cage20without damaging TIM35. Then, when power to the SMA element172is turned off, the biasing force BF of compression springs160′ returns the SMA element172to its rest position P1while lowering the heat sink31into a lowered position P3where it can compress TIM35against a module20(seeFIG.10A). Additionally, like previously described embodiments, heat sink assembly30′ includes an actuator220and indicator210that can actuate the heat sink assembly30′ and provide indications of how the heat sink31is positioned, respectively.

Still referring toFIGS.10A and10B, but now with reference toFIGS.11A and11Bas well, in this embodiment, the heat sink assembly30′ also includes a locking feature that can prevent insertion or removal of the module20when the heat sink assembly30′ is in its lowered position P3. Specifically, in this embodiment, the heat sink assembly30′ includes a protrusion282positioned forwardly of the TIM35on the mating surface133of the heat sink31(e.g., closer to the open front end120of the module cage18), as is shown clearly inFIG.11A. With this embodiment, and as is shown inFIG.11B, the computing module20includes a corresponding receptacle284configured to mate with the protrusion282when the computing module20is fully installed into a module cage18. Thus, when the heat sink assembly30′ moves the TIM35into engagement with the top surface22of the computing module20, the protrusion282will engage the receptacle284and resist movement in the front-to-back direction. Then, if the computing module20is pulled outwardly prior to the heat sink assembly30moving the TIM35out of engagement with the top surface22of the computing module20, the protrusion282and the receptacle284may resist this movement and prevent damage to the TIM35that can occur when the module20slides along the TIM35. This arrangement will also ensure that module20is not forcefully inserted or extracted which could cause an unintentional damage for the TIM35(insertion prevention is illustrated inFIG.10A).

Next,FIGS.12,13,14A, and14Billustrate yet further example embodiments of the heat sink assembly presented herein that can operate without a biasing member exerting a constant restorative force on the heat sink31. First,FIG.12provides a heat sink assembly30(2) with a bi-stable toggle element300disposed between two one-way SMA elements: SMA element172A and SMA element172B. When current is delivered to one of SMA element172A and SMA element172B, that SMA element may deform (e.g., contract) and move the bi-stable toggle element300to a first position. Then, when current is delivered to the other of SMA element172A and SMA element172B, that SMA element may deform (e.g., contract) and move the bi-stable toggle element300to a second position. Alternatively, SMA element172A and SMA element172B may have different compositions and/or characteristics (e.g., different “training” or “tuning”) that cause the different SMA elements to respond (e.g., deform or actuate) to different magnitudes of currents (and, thus, might be actuated by precisely controlling the current delivered to both SMA elements). Regardless, with this arrangement, actuation of one of SMA element172A and SMA element172B drives the bi-stable toggle element300to a specific position and then the bi-stable toggle element300holds or locks the heat sink31in that position. Consequently, current need not be constantly delivered to SMA element172A or SMA element172B to hold (e.g., lock) the heat sink assembly30(2) in a specific position (e.g., a raised or lowered position).

More specifically, in the depicted embodiment, delivering current to SMA element172B may contract SMA element172B, pivoting a bottom end of pivot points302inwards and moving (e.g., snapping) the bi-stable toggle element300to position P5(shown in solid lines). Pivoting pivot points302will also stretch or elongate SMA element172A (i.e., return SMA element172A to its rest position) so that SMA element172A is ready to actuate (e.g., contract) in response to receiving current. In the depicted embodiment, bi-stable toggle element300is coupled to heat sink31at pivot point302. Thus, moving the bi-stable toggle element300to position P5moves the heat sink upwards a distance D1. However, in other embodiments, the bi-stable toggle element300may be directly coupled to and/or enclosed within the heat sink31in any manner. Regardless, once the bi-stable toggle element300is in position P5, current need not be delivered to SMA element172B, as the bi-stable toggle element300will maintain (e.g., lock) the heat sink31in a raised position.

Then, to lower the heat sink31, current is delivered to SMA element172A to actuate (e.g., contract) SMA element172A and pivot top ends of pivot points302inwards. This moves (e.g., snaps) the bi-stable toggle element300to position P6(shown in dashed lines) and moves the heat sink downwards a distance D1. Again, once the bi-stable toggle element300is in position P6, current need not be delivered to SMA element172A, as the bi-stable toggle element300will maintain (e.g., lock) the heat sink31in a lowered position.

FIG.13illustrates another example embodiment of a heat sink assembly that can operate without a biasing member exerting a constant restorative force on the heat sink31. Heat sink assembly30(3) includes two SMA elements, like heat sink assembly30(2) ofFIG.12, but provides a first SMA element172C trained to deform to a shape that raises the heat sink31and a second SMA element172D trained to deform to a shape that lowers the heat sink31. For example, SMA element172C may be trained and/or arranged so that actuation of SMA element172C arcs or bends SMA element172C upwards. SMA element172C is connected to heat sink31at connection points179C and, thus, upward bending or arcing of SMA element172C moves heat sink31upwards. Meanwhile, SMA element172D may be trained and/or arranged so that actuation of SMA element172D arcs or bends SMA element172D downwards. SMA element172D is connected to heat sink31at connection points179D and, thus, downward bending or arcing of SMA element172D moves heat sink31downwards. However, SMA elements172C and172D are only shown directly attached to heat sink31as an example and SMA elements172C and172D could be coupled to heat sink31in any manner provided that actuation (e.g., contraction) of SMA element172C or172D moves the heat sink31up or down.

Now turning toFIGS.14A and14B, these Figures depict yet another example embodiment of a heat sink assembly that can operate without a biasing member exerting a constant restorative force on the heat sink31. Heat sink assembly30(4) is substantially similar to the heat sink assembly30′ shown inFIGS.10A and10B; however, now the heat sink assembly30(4) does not include compression springs160′ or any kind of biasing member160. Instead, SMA element172E is a two-way SMA element. Thus, in response to a first current being delivered to a first portion of the SMA element172E, the SMA element172E may lift heat sink31a distance D1along a vertical axis A1to a raised position P4(seeFIG.14B). Then, in response to a current being delivered to a second portion of the SMA element172E, the SMA element172E may lower heat sink31a distance D2(which may be equal to distance D1) along a vertical axis A1to a lowered position P3(seeFIG.14A). Alternatively, different magnitudes of current might cause SMA172E to raise and lower. Regardless, the arrangement shown inFIGS.14A and14Bis similar to the arrangement of heat sink assembly30(3) ofFIG.13, but now the functionality of SMA elements172C and172D fromFIG.13is achieved by a single SMA element172E.

Notably, with this embodiment, the currents that actuate SMA element172E may move the SMA element172E between a first actuated position P7(corresponding to lowered positon P3of heat sink31) and a second actuated position P8(corresponding to raised positon P4of heat sink31). However, since a restorative force (e.g., a biasing force) is not constantly acting on the heat sink31of heat sink assembly30(4), SMA element172E need not receive a constant current to stay in positions P7and P8. Instead, current can be delivered to SMA element172E to move the SMA element172E between positions P7and P8and can be turned off after an actuation (like the embodiments shown and described in connection withFIGS.12and13).

Now turning toFIGS.15A and15B, but with continued reference toFIGS.14A and14B, generally, two-way SMA toggles between two different shapes or “conformations.” To achieve this, SMA element172E includes two opposing SMA layers or SMA wires172E(1) and172E(2) that are joined and separated by a flexible and heat resistant material172E(3). The SMA wires172E(1) and172E(2) and the heat resistant material172E(3) extend longitudinally along a length of SMA element172E and may be contained within an outer casing (giving SMA element172E the appearance of a single wire). The first SMA layer/wire172E(1) and the second SMA layer/wire172E(2) are each trained or programmed to attain a specific shape when heated. That is, SMA layers/wires172E(1) and172E(2) may each be or function like one-way SMAs and, thus, any description of one-way SMAs included herein (e.g., relating to composition or training) should be understood to apply to SMA layers/wires172E(1) and172E(2). Consequently, to actuate SMA element172E, current may be applied independently and sequentially to SMA layer/wire172E(1) and172E(2) to toggle the configuration of SMA element172E between two configurations or states. Additionally or alternatively, first SMA layer/wire172E(1) and the second SMA layer/wire172E(2) may have different compositions that respond to different currents.FIG.15Aillustrates (in an exaggerated fashion) contraction of first SMA layer/wire172E(1) driving SMA element172E to its first actuated position P7andFIG.15Billustrates (in an exaggerated fashion) contraction of second SMA layer/wire172E(2) driving SMA element172E to its second actuated position P8.

Now turning toFIGS.16and17, these Figures illustrate example solutions that can utilize the heat sink assembly30presented herein. First, inFIG.16, system400is a server or switch assembled in an apparatus12that is a pizza-box style chassis. The apparatus12includes a cage to receive a module20in the form of a modular port adapter (MPA). This provides flexibility for customer-based specializations and the heat sink assembly30presented herein can provide cooling for any MPA. Second,FIG.17illustrates a solution500with an apparatus12in the form of an MPA that can support computing modules20in the form of CFP2 optical transceivers. In this instance, the heat sink assembly30can be installed in the MPA to provide cooling for the CFP2 optical transceivers. Then, if the MPA was installed in, for example, a line card, the line card might also include a heat sink assembly30formed accordance with the embodiments presented herein to cool the MPA within the line card.

Among other advantages, the heat sink assembly presented herein may improve cooling of computing modules while minimizing a footprint of cooling components (at least because a heat sink may cover an entire computing module without moving beyond a lateral periphery of a computing module). In fact, in at least some embodiments, the heat sink assembly presented herein may completely eliminate the need for an actuator and leave the front panel unobstructed with any actuators. These embodiments may utilize a purely electrical actuation of the heat sink assembly. Alternatively, the heat sink assembly may provide a small button that requires only a push actuation and, thus a computing solution need not be installed or manufactured in a manner that provides space to accommodate linear or rotational movement of a user's hand at the front panel.

InFIG.18, diagram600illustrates the temperature improvements provided by the heat sink assembly30as compared to a heat sink31that is not modified to support the actuation assembly170of heat sink assembly30(e.g., a heat sink31of the same size, but without the features (including the TIM35) of heat sink assembly30described herein). Notably, the heat sink assembly30presented herein achieves lower temperatures under the same airflow conditions. For example, the heat sink assembly30may cool a module case to 70 degree Celsius with approximately 9 cubic feet per minute (CFM) of airflow while the unmodified heat sink requires approximately 12 CFM to achieve the same temperature. Thus, the heat sink assembly30may provide approximately 25% improvement.

Moreover, the thermal data from diagram600indicates that the heat sink assembly30does not induce thermal spreading that mitigates improvements in contact resistance provided by the TIM35engaging the computing module20. That is, forming passageway152and/or corners145in/on heat sink31will not generate thermal spreading that counteracts the thermal effectiveness of the heat sink31. Thus, the heat sink assembly presented herein may support higher operational temperatures while still meeting regulatory standards. Additionally or alternatively, the heat sink assembly presented herein may reduce operating temperatures which may lower power consumption (e.g., due to reduced fan speeds) and/or reduce acoustic noise (e.g., from fans). The heat sink assembly presented herein may also achieve these advantages with an inexpensive solution that, for example, does not require expensive and maintenance intensive spring clips.

In summary, an apparatus is provided comprising: a cage defining a chamber; a heat sink to facilitate heat dissipation, the heat sink including a mating surface; a thermal interface material including a first surface and a second surface, the first surface being coupled to the mating surface of the heat sink and the second surface being opposite the first surface so that the second surface can be positioned against a perimeter of the chamber; and an actuation assembly including a shape memory alloy (SMA) element, wherein when the SMA element is in a first position, the second surface of the thermal interface material is disposed within or adjacent the perimeter of the chamber, and when the SMA element is moved to a second position, the second surface of the thermal interface material is moved a distance away from the perimeter of the chamber.

In another form, a heat sink assembly for a cage for a field replaceable computing module is provided, comprising: a heat sink to facilitate heat dissipation, the heat sink including a mating surface; a thermal interface material including a first surface and a second surface, the first surface being coupled to the mating surface of the heat sink and the second surface being opposite the first surface so that the second surface can engage a heat transfer surface of the field replaceable computing module installed adjacent the heat sink; and an actuation assembly including a shape memory alloy (SMA) element, wherein when the SMA element is in a first position, the second surface of the thermal interface material contacts the heat transfer surface of the field replaceable computing module, and when the SMA element moves to a second position, the second surface of the thermal interface material is moved a distance away from the heat transfer surface of the field replaceable computing module.

In yet another form, a system is provided, comprising: a cage defining a chamber sized to receive the field replaceable computing module with a heat transfer surface; a heat sink to facilitate heat dissipation, the heat sink including a mating surface; a thermal interface material including a first surface and a second surface, the first surface being coupled to the mating surface of the heat sink and the second surface being opposite the first surface so that the second surface can selectively engage the heat transfer surface of the field replaceable computing module when the field replaceable computing module is installed in the chamber of the cage; and an actuation assembly including a shape memory alloy (SMA) element, wherein when the field replaceable computing module is installed in the chamber of the cage and the SMA element is in a first position, the second surface of the thermal interface material contacts the heat transfer surface of the field replaceable computing module, and when the SMA element moves to a second position, the second surface of the thermal interface material is moved a distance away from the heat transfer surface of the field replaceable computing module.

The above description is intended by way of example only. Although the techniques are illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made within the scope and range of equivalents of the claims. In addition, various features from one of the embodiments may be incorporated into another of the embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure as set forth in the following claims.

It is also to be understood that the heat sink assembly, apparatus, and system presented herein described herein, or portions thereof, may be fabricated from any suitable material or combination of materials, such as plastic, metal, foamed plastic, wood, cardboard, pressed paper, supple natural or synthetic materials including, but not limited to, cotton, elastomers, polyester, plastic, rubber, derivatives thereof, and combinations thereof. Suitable plastics may include high-density polyethylene (HDPE), low-density polyethylene (LDPE), polystyrene, acrylonitrile butadiene styrene (ABS), polycarbonate, polyethylene terephthalate (PET), polypropylene, ethylene-vinyl acetate (EVA), or the like.

Finally, when used herein, the term “approximately” and terms of its family (such as “approximate,” etc.) should be understood as indicating values very near to those that accompany the aforementioned term. That is to say, a deviation within reasonable limits from an exact value should be accepted, because a skilled person in the art will understand that such a deviation from the values indicated is inevitable due to measurement inaccuracies, etc. The same applies to the terms “about” and “around” and “substantially.”