PATENT DOCUMENT

Publication Number: US-10285303-B2
Application Number: US-201715730394-A
Country: US
Kind Code: B2

Title: Electronic device with integrated passive and active cooling

Abstract:
An exemplary electronic device with integrated passive and active cooling includes a main logic board, a heat sink, and a cooling fan. A first surface of the heat sink faces the main logic board and contacts a heat-generating component of the main logic board. A second surface of the heat sink faces away from the main logic board and has a recess formed thereon. The heat sink further includes a plurality of fins that surround the recess. The cooling fan is at least partially enclosed within the recess by a fan shroud. The cooling fan is operable to draw air into the recess via channels defined by a first subset of the plurality of fins, and expel air from the recess via channels defined by a second subset of the plurality of fins.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a main logic board; 
 a heat sink including:
 a first surface facing the main logic board, the first surface contacting a heat-generating component of the main logic board; 
 a second surface facing away from the main logic board, the second surface having a recess formed thereon; and 
 a plurality of fins each surrounding the recess; and 
 
 a cooling fan at least partially enclosed within the recess by a fan shroud, wherein the cooling fan is operable to draw air into the recess via channels defined by a first subset of the plurality of fins, and to expel air from the recess via channels defined by a second subset of the plurality of fins, wherein each fin in the first subset of the plurality of fins is positioned apart from a rim of the recess and apart from the fan shroud. 
 
     
     
       2. The device of  claim 1 , wherein the second subset of the plurality of fins defines a portion of an inner sidewall of the recess. 
     
     
       3. The device of  claim 1 , wherein the fan shroud directly contacts the second subset of the plurality of fins. 
     
     
       4. The device of  claim 1 , wherein the cooling fan includes an impeller, and wherein a sidewall of the recess is immediately adjacent to a perimeter of the impeller. 
     
     
       5. The device of  claim 4 , wherein a diameter of the fan shroud is greater than a diameter of the recess. 
     
     
       6. The device of  claim 4 , wherein the cooling fan does not include a fan housing disposed between the perimeter of the impeller and the sidewall of the recess. 
     
     
       7. The device of  claim 1 , wherein the heat sink extends from a first edge of the main logic board to a second edge of the main logic board opposite the first edge of the main logic board. 
     
     
       8. The device of  claim 1 , wherein the heat-generating component of the main logic board comprises a central processing unit or a graphics processing unit. 
     
     
       9. The device of  claim 1 , further comprising a second heat sink, wherein the main logic board is disposed between the heat sink and the second heat sink. 
     
     
       10. The device of  claim 9 , wherein the heat sink and the second heat sink have a combined mass that is greater than half of a mass of the electronic device. 
     
     
       11. The device of  claim 9 , further comprising a thermal interface layer disposed between the heat sink and the second heat sink, wherein the heat sink and the second heat sink each directly contact the thermal interface layer. 
     
     
       12. The device of  claim 9 , wherein the main logic board includes a second heat-generating component contacting a surface of the second heat sink. 
     
     
       13. The device of  claim 1 , further comprising one or more conductive frames that surround one or more heat-generating components of the main logic board. 
     
     
       14. The device of  claim 13 , wherein the one or more heat-generating components are disposed within a conductive enclosure defined by the heat sink, the second heat sink, and the one or more conductive frames, and wherein the conductive enclosure impedes electromagnetic interference generated by the one or more heat-generating components from escaping the conductive enclosure. 
     
     
       15. The device of  claim 1 , further comprising a device housing enclosing the main logic board and the heat sink, the device housing including a top casing and a base. 
     
     
       16. The device of  claim 15 , wherein the heat sink extends from a first side of the device housing to a second side of the device housing opposite the first side of the device housing. 
     
     
       17. The device of  claim 15 , wherein one or more protrusions extend from an inner surface of the base, and wherein the one or more protrusions are positioned directly adjacent to a surface of the fan shroud without contacting the surface of the fan shroud. 
     
     
       18. The device of  claim 15 , further comprising a seal positioned between the base of the device housing and the heat sink, the seal surrounding the second subset of the plurality of fins and configured to resist air flowing out of the recess via the channels defined by the second subset of the plurality of fins from being drawn back into the recess via an inlet opening of the fan shroud. 
     
     
       19. The device of  claim 1 , wherein each fin in the first subset of the plurality of fins extends from a first plane of the heat sink and each fin in the second subset of the plurality of fins extends from a second plane of the heat sink, wherein the second plane corresponds to a base surface of the recess, and wherein the recess is at least partially defined by a continuous sidewall that extends from the second plane towards the first plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Ser. No. 62/532,788, filed on Jul. 14, 2017, entitled “Electronic Device with Integrated Passive and Active Cooling,” which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     FIELD 
     This application relates generally to electronic devices, and more specifically, to electronic devices with integrated passive and active cooling. 
     BACKGROUND 
     Electronic devices contain components, such as integrated circuits, that generate heat during operation. As electronic components become smaller and more powerful, they generate more heat in a smaller and more confined area. At the same time, electronic devices are being designed with increasingly small form factors, which can result in components being spaced more closely within the device. This can intensify the effect of heat generated by the components during operation. To maintain the longevity and proper functionality of the device, fans, heat sinks, and/or other heat management components are used to dissipate heat from the device. However, designing heat management components that can be integrated into smaller overall volumes while still providing effective and reliable heat dissipation can create challenges. 
     SUMMARY 
     Electronic devices with integrated passive and active cooling are described herein. In one example, an electronic device includes a main logic board, a heat sink, and a cooling fan. A first surface of the heat sink faces the main logic board and contacts a heat-generating component of the main logic board. A second surface of the heat sink faces away from the main logic board and has a recess formed thereon. The heat sink further includes a plurality of fins that surround the recess. The cooling fan is at least partially enclosed within the recess by a fan shroud. The cooling fan is operable to draw air into the recess via channels defined by a first subset of the plurality of fins, and expel air from the recess via channels defined by a second subset of the plurality of fins. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a top perspective view of an electronic device, according to various examples. 
         FIG. 1B  illustrates a bottom perspective view of an electronic device, according to various examples. 
         FIG. 2  illustrates an exploded bottom perspective view of an electronic device, according to various examples. 
         FIGS. 3A-3C  illustrate cross-sectional views of an electronic device, according to various examples. 
         FIG. 4  illustrates a bottom perspective view of an electronic device with the base omitted, according to various examples. 
         FIG. 5  illustrates a bottom perspective view of an electronic device with the base and seal omitted, according to various examples. 
         FIG. 6  illustrates a bottom perspective view of an electronic device with the base, seal, and fan shroud omitted, according to various examples. 
         FIGS. 7A-7B  illustrate top and bottom perspective views of a base of an electronic device, according to various examples. 
         FIGS. 8A-8B  illustrate top and bottom perspective views of a bottom heat sink of an electronic device, according to various examples. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the various embodiments. Thus, the various embodiments are not intended to be limited to the examples described herein and shown, but are to be accorded the scope consistent with the claims. 
     Electronic devices contain components that produce heat during normal operation. As such, fans, heat sinks, and other heat diversion components can be used to manage operating temperatures in some electronic devices. Passive thermal-management solutions (e.g., heat sinks) can be desirable for their simplicity, reliability, and low acoustic footprint. However, with increasingly fast and powerful circuitry that generates increased levels of heat, implementing only passive thermal-management solutions can limit the speed and power of electronic components used in the device. Active thermal-management solutions (e.g., cooling fans) can provide greater heat-dissipation rates. However, such solutions can increase the cost, complexity, and overall footprint of the device. In addition, active thermal-management solutions can generate undesirable aeroacoustic noise. In accordance with some embodiments described herein, electronic devices that integrate both passive and active thermal-management solutions are provided. As described in greater detail below, the passive portion of the thermal-management solution can be configured to provide sufficient heat dissipation during a majority (e.g., greater than 50%, 75%, or 90%) of the device&#39;s operating conditions. The active portion of the thermal-management solution can be configured to activate only during higher power operating conditions. In this way, the active portion of the thermal-management solution can be relied upon less frequently, which can reduce the acoustic footprint of the electronic device. In addition, as will become apparent in the description below, the passive and active thermal-management structures in the electronic devices are integrated in a manner that can reduce the cost, complexity, and overall footprint of the devices. 
     In one example of an electronic device with integrated passive and active cooling, a main logic board, a heat sink, and a cooling fan are included. A first surface of the heat sink faces the main logic board and contacts a heat-generating component of the main logic board. A second surface of the heat sink faces away from the main logic board and has a recess formed thereon. The heat sink further includes a plurality of fins that surround the recess. The cooling fan is at least partially enclosed within the recess by a fan shroud. The cooling fan is operable to draw air into the recess via channels defined by a first subset of the plurality of fins, and expel air from the recess via channels defined by a second subset of the plurality of fins. 
       FIGS. 1A-1B  illustrate exemplary electronic device  100 , according to various examples. Specifically,  FIG. 1A  illustrates a top perspective view of device  100 , and  FIG. 1B  illustrates a bottom perspective view of device  100 . In some examples, device  100  is a computer, a set-top box, a wireless access point, a portable electronic device, or any other suitable electronic device. In a specific example, device  100  is a digital media extender (e.g., an Apple TV®). Device  100  has a device housing that encloses the internal components of the device. In the present example, the device housing of device  100  includes top casing  102  and base  104 . Top casing  102  is a single part (e.g., not an assembly of two or more parts) having a top wall and sidewalls. To accommodate connectors for displays, device peripherals, network cables, power cables, and other accessories, a sidewall of top casing  102  includes one or more openings  106  (e.g., port openings). 
     Base  104  forms the bottom wall of the device housing. Like top casing  102 , base  104  is a single part. Base  104  engages with the sidewalls of top casing  102  to form the device housing of device  100 . For example, base  104  includes features (e.g., openings  201  of  FIGS. 2 and 7A-7B ) along the edges of base  104  that are configured to engage with corresponding features (e.g., tabs  211  of  FIG. 2 ) along the sidewalls of top casing  102 . Base  104  further includes openings  108  that facilitate heat-dissipation. As described in greater detail below, device  100  includes internal electronic components, such as integrated circuits, that generate heat during operation. Thermal-management features are incorporated into the internal structures of electronic device  100  to passively and/or actively dissipate heat from the internal electronic components. Openings  108  allow air flow into and out of device  100 . In particular, ambient air is drawn into device  100  via openings  108 . The ambient air removes heat from the internal components of device  100  and is discharged from device  100  via openings  108 . A more detailed illustration of base  104  is shown in  FIGS. 7A-7B , described below. 
     Although in the present example the device housing of electronic device  100  has two parts (top casing  102  and base  104 ), it should be appreciated that, in other examples, the device housing of electronic device  100  can include alternative configurations. For example, the device housing can include any number of parts that are assembled together. In the present example, top casing  102  and base  104  are formed of plastic. In other examples, the device housing can be formed of any suitable material, such as glass, ceramic, metal, carbon fiber, fiberglass, or any combination thereof. 
     Reference lines  112 ,  114 , and  116  are depicted in  FIG. 1A . As will become evident in the description below, reference lines  112 ,  114 , and  116  define the orientations of the cross-sectional views of device  100  shown in  FIGS. 3A-3C . 
       FIG. 2  illustrates an exploded bottom perspective view of device  100 , according to various examples. The main internal components of device  100  are depicted in  FIG. 2 . For simplicity, some internal components (e.g., the power supply unit, such as power supply unit  302  of  FIGS. 3B-3C ) have been omitted from  FIG. 2 . As shown, device  100  includes bottom heat sink  202 , main logic board  208 , and top heat sink  212 , which are enclosed within the device housing formed by top casing  102  and base  104 . Main logic board  208  includes electronic components (e.g., electronic component  214 ) that generate heat during operation. The electronic components are disposed on opposite sides of main logic board  208 . In the present example, electronic component  214  of main logic board  208  is a system on chip (SOC) that integrates a microprocessor (central processing unit) and peripherals, such as a graphics processing unit (GPU). In other examples, electronic component  214  is a discrete microprocessor or GPU. During operation, electronic component  214  can be the component that generates the most heat per unit time on main logic board  208 . Top and bottom heat sinks  212 ,  202  serve to dissipate heat from main logic board  208  by conducting heat away from the electronic components of main logic board  208 . Heat from heat sinks  212 ,  202  can then dissipate passively into the ambient environment around device  100  (e.g., through the device housing and openings  108 ). In addition, cooling fan  206  is housed in bottom heat sink  202  to actively dissipate heat from bottom heat sink  202 . The manner in which the internal components of device  100  are integrated within the outer housing is shown in greater detail in  FIGS. 3A-3C . 
       FIGS. 3A-3C  illustrate cross-sectional views of device  100 , according to various examples. Specifically,  FIG. 3A  illustrates a cross-sectional view of device  100  along reference line  112  of  FIG. 1A ,  FIG. 3B  illustrates a cross-sectional view of device  100  along reference line  114  of  FIG. 1A , and  FIG. 3C  illustrates a cross-sectional view of device  100  along reference line  116  of  FIG. 1A . As shown, main logic board  208  is disposed between top and bottom heat sinks  212 ,  202 . One or more heat-generating components (e.g., electronic components) of main logic board  208  contact a first surface of bottom heat sink  202 . In some examples, the one or more heat-generating components contact the first surface of bottom heat sink  202  directly or indirectly (e.g., via a thermal interface layer, such as a thermal grease layer or a thermal gap pad). In this way, the one or more heat-generating components are thermally coupled to bottom heat sink  202 , which can enable efficient heat transfer from the one or more heat-generating components to bottom heat sink  202 . In the present example shown in  FIG. 3C , electronic component  214  indirectly contacts a portion of the first surface of bottom heat sink  202  via a thermal interface layer disposed between electronic component  214  and bottom heat sink  202 . In particular, electronic component  214  and the first surface of bottom heat sink  202  directly contact opposite sides of the thermal interface layer. The portion of the first surface of bottom heat sink  202  that is in contact with electronic component  214  is more clearly shown in  FIG. 8B . 
       FIGS. 8A-8B  illustrate top and bottom perspective views of bottom heat sink  202 , according to various examples. Specifically,  FIG. 8A  is a perspective view of a first side of bottom heat sink  202  that faces base  104  of device  100 .  FIG. 8B  is a perspective view of a second side (e.g., opposite of the first side) of bottom heat sink  202  that faces main logic board  208 . As shown in  FIG. 8B , the first surface on the second side of bottom heat sink  202  includes portion  802 . In some examples, portion  802  protrudes from the first surface of bottom heat sink  202 . Electronic component  214  contacts portion  802  of the first surface of bottom heat sink  202  (e.g., via a thermal interface layer), which can enable efficient heat transfer from electronic component  214  to bottom heat sink  202 . 
     As briefly described above, device  100  includes cooling fan  206  that is housed in bottom heat sink  202  to actively dissipate heat from bottom heat sink  202 . The manner in which cooling fan  206  is structurally integrated in device  100  is now described with reference to  FIGS. 3A, 5, 6, and 8A . As shown in  FIG. 8A , the second surface on the first side of bottom heat sink  202  has recess  314  formed thereon. Cooling fan  206  is disposed within recess  314 . For example, referring to  FIG. 6 , a bottom perspective view of device  100  is illustrated with base  104 , seal  304 , and fan shroud  204  omitted. As shown in  FIG. 6  (and also in  FIGS. 3A-3C ), cooling fan  206  is disposed within recess  314  of bottom heat sink  202 . Cooling fan  206  includes impeller  308  attached to fan motor  312  via fan shaft  313  ( FIGS. 3A-3C ). Fan motor  312  is operable to rotate impeller  308 . Fan motor  312  is attached to fan base  310 , which is mounted to the bottom surface of recess  314  by fasteners  604 . It should be recognized that, in other examples, fan base  310  is omitted such that cooling fan  206  is attached to bottom heat sink  202  via fan shaft  313  or fan motor  312 . 
     In the present example, with reference to  FIG. 8A , fan base  310  is mounted to bottom surface  806 . As shown, bottom surface  806  is a substantially continuous surface having a limited number of openings that extend from bottom surface  806  to the first surface on the second side ( FIG. 8B ) of bottom heat sink  202 . A limited number of openings can be desirable to reduce turbulent air flow during operation of cooling fan  206 , which can reduce the generation of aeroacoustic noise. In the present example, bottom surface  806  only includes openings  804  and  808 . Opening  804  allows the flexible printed circuit board (e.g., flexible printed circuit board  326  of  FIG. 3C ) of cooling fan  206  to connect with main logic board  208 . Openings  808  enable fasteners  604  to mount fan base  310  onto bottom surface  806 . In some examples, the openings (e.g., openings  804  and  808 ) that extend from bottom surface  806  to the first surface of bottom heat sink  202  occupy less than 5%, 10%, or 15% of the total area of bottom surface  806  of recess  314 . Additionally, in some examples, no cooling fins are disposed on bottom surface  806  of recess  314 . 
     It should be appreciated that, in device  100 , bottom heat sink  202  serves as the structural housing for cooling fan  206 . Notably, as shown in  FIGS. 3A-3C and 6 , cooling fan  206  does not include a separate fan housing that surrounds impeller  308  in the region between the perimeter of impeller  308  and sidewalls  316  of recess  314 . In other words, the tips of fan blades  306  of impeller  308  are immediately adjacent to sidewalls  316  of recess  314 . But integrating bottom heat sink  202  with cooling fan  206  such that bottom heat sink  202  serves as the structural housing for cooling fan  206 , the complexity of the thermal-management solution is reduced. This can reduce the cost and footprint of the device, and also improve the reliability of the device. 
     As shown in  FIGS. 6 and 8A , bottom heat sink  202  includes cooling fins that surround recess  314 . The cooling fins serve to provide additional surface area for bottom heat sink  202  to more efficiently dissipate heat passively and/or actively. The cooling fins can be oriented in a manner that reduces aeroacoustic noise. In the present example, cooling fins are oriented radially from recess  314 . In some examples, the angle at which each cooling fin is oriented with respect to the rim of recess  314  can be approximately the same. In the present example, the cooling fins are evenly spaced apart around recess  314 . In other examples, the spacing between the cooling fins can vary. 
     The cooling fins include inlet fins  318  and outlet fins  320 . As shown, inlet fins  318  surround more than half (e.g., greater than 50% or 60%) the perimeter of recess  314 . Inlet fins  318  are positioned apart from the rim of recess  314 . Specifically, the edge of each inlet fin  318  facing recess  314  is set back from the rim of recess  314  by a distance (e.g., the same distance for each inlet fin). Outlet fins  320  surround less than half (e.g., less than 50% or 40%) the perimeter of recess  314 . Outlet fins  320  define a portion of sidewalls  316  of recess  314 . Specifically, the edge of each outlet fin  320  facing recess  314  defines part of sidewalls  316  of recess  314 . Outlet fins  320  thus define openings along a portion of sidewalls  316  of recess  314  that allow air to flow out from recess  314 . In contrast, as shown in  FIGS. 6 and 8A , the portion of sidewalls  316  proximate to inlet fins  318  is a continuous portion of sidewall. Specifically, the portion of sidewalls  316  proximate to inlet fins  318  does not have openings for air to flow out from recess  314 . 
     Each inlet fin  318  has a height that extends from its base at a surface around the rim of recess  314  to its edge that faces base  104 . Each outlet fin  320  has a height that extends from its base at bottom surface  806  of recess  314  to its edge, which faces base  104 . The height of outlet fins  320  is greater than the height of inlet fins  318 . In some examples, portions of the edges of each cooling fin (inlet and outlet fins  318 ,  320 ) facing base  104  are aligned with the same plane. 
     Turning now to  FIG. 5 , a bottom perspective view of device  100  is illustrated with base  104  and seal  304  omitted. As shown, cooling fan  206  is at least partially enclosed within recess  314  by fan shroud  204 . Bottom heat sink  202  and fan shroud  204  thus form the structural housing of cooling fan  206 . In the present example, fan shroud  204  is a single part formed of metal only (e.g., aluminum). As discussed in greater detail below, the rigidity associated with fan shroud  204  being a single metal part can be desirable for resisting against deflection of fan shroud  204  toward impeller  308  from user handling of device  100 . In other examples, fan shroud  204  includes multiple parts and/or be formed of one or more other materials (e.g., plastic, fiberglass, etc.). 
     Fan shroud  204  includes an inlet opening that is positioned over the hub of impeller  308 . In particular, the center of the inlet opening of fan shroud  204  is substantially aligned with the center of the hub of impeller  308 . During operation of cooling fan  206 , the inlet opening of fan shroud  204  allows air to be drawn into recess  314 . The outer diameter of fan shroud  204  is greater than the diameter of recess  314 , where fan shroud  204  extends over the rim of recess  314 . In the present example, fan shroud  204  is directly attached to bottom heat sink  202  (e.g., at outlet fins  320  and at the surface between inlet fins  218  and the rim of recess  314 ) by fasteners or adhesives. A surface of fan shroud  204  facing cooling fan  206  contacts (e.g., directly or indirectly) a surface of bottom heat sink  202  between inlet fins  218  and the rim of recess  314 . Inlet fins  218  are positioned apart from fan shroud  204  and do not directly contact fan shroud  204 . The surface of fan shroud  204  facing cooling fan  206  also contacts (e.g., directly or indirectly) the edges of outlet fins  320  facing base  104 . Fan shroud  204  thus extends over a portion of outlet fins  320  such that fan shroud  204  and outlet fins  320  define channels  502  that are fluidically coupled to recess  314 . During operation of cooling fan  206 , channels  502  between outlet fins  320  allow air to be expelled from recess  314 . 
     Referring now to  FIGS. 3A, 4, and 7A , device  100  further includes seal  304 . Seal  304  is formed of plastic or elastomer, and serves to resist heated air that is being expelled from recess  314  (e.g., via channels between outlet fins  320 ) by cooling fan  206  from being drawn back into recess  314  (e.g., via the inlet opening of fan shroud  204 ). In particular, seal  304  directs the heated air through a specific subset of openings  108  of base  104 . As shown in  FIG. 7A , seal  304  is attached (e.g., with an adhesive or fasteners) to the inner surface of base  104 . In some examples, seal  304  includes features that engage with corresponding features of base  104 . Seal  304  comprises a loop that surrounds a subset of openings  108 . Specifically, in the present example, seal  304  surrounds three of openings  108  that are facing a side of device  100  with one or more openings  106  for connectors. By surrounding the three openings of base  104 , seal  304  directs the heated air flowing from recess  314  in a common direction away from device  100 , thereby reducing the probability of the heated air being drawn back into device  100  via the remaining openings of base  104 . 
     When base  104  is engaged with top casing  102 , seal  304  is positioned around outlet fins  320  of bottom heat sink  202 , as shown in  FIG. 4 .  FIG. 4  illustrates a bottom perspective view of device  100  with base  104  omitted. Seal  304  surrounds outlet fins  320  and forms a barrier around outlet fins  320 . With reference now to  FIG. 3A , seal  304  is disposed between bottom heat sink  202  and base  104 . Specifically, one side of seal  308  directly contacts a surface of bottom heat sink  202  around outlet fins  320  and a surface of fan shroud  204  adjacent to outlet fins  320 . An opposite side of seal  308  directly contacts the inner surface of base  104 . Seal  304  defines a passage that fluidically couples the channels between outlet fins  320  to a subset of openings  108 . The passage defined by seal  304  directs heated air that is being expelled from recess  314  by cooling fan  206  out through the subset of openings  108 . As shown in  FIG. 3A , seal  308  forms a barrier between outlet fins  320  and the inlet opening of fan shroud  204 , and thus resists heated air that is being expelled from recess  314  by cooling fan  206  from flowing back into recess  314  via the inlet opening of shroud  204 . 
       FIG. 3A  illustrates how, during operation of cooling fan  206 , air circulates through device  100  between base  104  and bottom heat sink  202  to dissipate heat from bottom heat sink  202 . Specifically, as represented by the arrows in  FIG. 3A , ambient air is drawn into device  100  through a first subset of openings  108  (e.g., five of openings  108 ). The ambient air flows through channels (e.g., channels  504  of  FIG. 5 ) defined by inlet fins  318  and over a surface of fan shroud  204  facing base  104  before entering recess  314  through the inlet opening of fan shroud  204 . As the air flows through the channels defined by inlet fins  318 , heat is transferred from bottom heat sink  202  to the air via inlet fins  318 . Additional heat from bottom heat sink  202  is transferred to the air within recess  314 . Cooling fan  206  expels heated air from within recess  314  out through openings defined by outlet fins  320  along a portion of sidewalls  316  of recess  314 . The expelled heated air flows through channels (e.g., channels  502  of  FIG. 5 ) defined by outlet fins  320  and fan shroud  204  and through the passage defined by seal  308  before exiting device  100  through a second subset of openings  108 . As the air flows through the channels defined by outlet fins  320 , heat is further transferred from bottom heat sink  202  to the air via outlet fins  320 . It should thus be appreciated that, unlike some conventional thermal-management structures, heat is dissipated from bottom heat sink  202  both as air is being drawn into device  100  by cooling fan  206  (e.g., dissipated via inlet fins  318 ) and as air is being expelled out of device  100  by cooling fan  206  (e.g., dissipated via outlet fins  320 ). 
     Although cooling fan  206  can enable the active dissipation of heat from device  100 , device  100  can be configured to operate with only passive heat-dissipation (e.g., impeller  308  of cooling fan  206  not rotating) during a majority (e.g., greater than 50%, 75%, or 90%) of device operating conditions. In particular, top heat sink  212  and bottom heat sink  202  are each formed of materials with high conductivity (e.g., metals such as aluminum) that can enable heat from the electronic components of main logic board  208  to be efficiently transferred to top heat sink  212  and bottom heat sink  202 . In addition, top heat sink  212  and bottom heat sink  202  can have large masses to achieve higher heat capacities, which can enable larger amounts of heat to be absorbed before an upper allowable temperature limit is reached. For example, the combined mass of top heat sink  212  and bottom heat sink  202  is greater than 50%, 60%, 70%, or 80% of the total mass of device  100 . As a result of the large mass of top heat sink  212  and bottom heat sink  202 , top heat sink  212  and bottom heat sink  202  can occupy a large volume within the device housing of device  100 . For example, as shown in  FIGS. 2 and 3A-3C , top heat sink  212  and bottom heat sink  202  occupy greater than 20%, 30%, or 40% of the internal volume within the device housing. In addition, the cross-sectional area of top heat sink  212  and bottom heat sink  202  each occupy greater than 60%, 70%, 80%, or 90% of the inner cross-sectional area of the device housing of device  100 . Specifically, as shown in  FIGS. 3A and 3C , top heat sink  212  and bottom heat sink  202  each extend substantially from one inner sidewall of the device housing to an opposite inner sidewall of the device housing. In some examples, top heat sink  212  and bottom heat sink  202  are each a single part. For example, inlet fins  318 , outlet fins  320 , and recess  314  of bottom heat sink  202  are all formed of a single part (rather than from multiple parts assembled together). In some examples, top heat sink  212  and bottom heat sink  202  are each formed of only metal (e.g., aluminum). In a specific example, top heat sink  212  and bottom heat sink  202  are each formed of cast metal. 
     As shown in  FIGS. 3A-3C , top heat sink  212  and bottom heat sink  202  are disposed on opposite sides of main logic board  208  and can dissipate heat from heat-generating components on both sides of main logic board  208 . In some examples, one or more heat-generating components (e.g., electronic components, such as integrated circuits) on a side of main logic board  208  facing top heat sink  212  contact (e.g., directly or indirectly) a surface of top heat sink  212 . For example, the one or more heat-generating components of main logic board  208  indirectly contact the surface of top heat sink  212  via a thermal interface layer (e.g., thermal grease or thermal gap pad). Specifically, in some examples the one or more heat-generating components and the surface of top heat sink  212  directly contact opposite sides of the thermal interface layer. In this way, the one or more heat-generating components are thermally coupled to top heat sink  212 , which can enable efficient heat transfer from the one or more heat-generating components to top heat sink  212 . 
     Top heat sink  212  and bottom heat sink  202  are each configured to provide heat-dissipation for a majority (e.g., greater than 50%, 75%, or 90%) of the heat-generating components of main logic board  208 . For example, as shown in  FIGS. 2 and 3A-3C , each of top heat sink  212  and bottom heat sink  202  extends at least from one edge of main logic board  208  to an opposite edge of main logic board  208 . In some examples, each of top heat sink  212  and bottom heat sink  202  extends across a majority (e.g., greater than 50%, 75%, or 90%) of a respective facing surface of main logic board  208 . Thus, a majority (e.g., greater than 50%, 75%, or 90%) of the heat-generating components of main logic board  208  are disposed between top heat sink  212  and bottom heat sink  202 , and can efficiently dissipate heat to top heat sink  212  and bottom heat sink  202 . This is in contrast to some conventional thermal-management systems of electronic devices that implement a combination of a heat pipe (e.g., that utilizes heat transport fluids), cooling fins, and a cooling fan to dissipate heat from heat-generating components. In these systems, the heat pipe is thermally coupled to only one or two heat-generating components of the electronic device, and thus heat-dissipation is only provided to a very small percentage of heat-generating components of the electronic device. In the present example, device  100  does not include a heat pipe and relies mostly on top heat sink  212  and bottom heat sink  202  for heat-dissipation. This can be advantageous for reducing the cost, reliability, and footprint of the device. 
     In some examples, top heat sink  212  and bottom heat sink  202  are thermally coupled to each other. For example, portions of top heat sink  212  and bottom heat sink  202  around main logic board  208  and proximate to the device housing are in direct or indirect contact with each other. In a specific example, as shown in  FIG. 3B , these portions of top heat sink  212  and bottom heat sink  202  directly contact opposite sides of thermal interface layer  328  (e.g., thermal grease layer or thermal gap pad). This can enable efficient heat transfer between top heat sink  212  and bottom heat sink  202 , where top heat sink  212  can dissipate heat from bottom heat sink  202  and vice versa. For example, during operation of cooling fan  206 , heat can be transferred from top heat sink  212  to bottom heat sink  202  and actively dissipated from bottom heat sink  202  by air flow generated by cooling fan  206 . As a result, top heat sink  212  and bottom heat sink  202  can function in effect as one continuous heat sink having high conductivity and large heat capacity to efficiently dissipate heat from the components of main logic board  208 . 
     Top heat sink  212  and bottom heat sink  202  can thus enable passive heat-dissipation to be the primary thermal-management mechanism for device  100  where cooling fan  206  is inactive for a majority (e.g., greater than 50%, 75%, or 90%) of the operating conditions of device  100 . Cooling fan  206  can thus only be activated during less frequent higher power operating conditions where processing loads are particularly high or heavy. This can be desirable for reducing the acoustic footprint of device  100 . Moreover, by requiring the activation of cooling fan  206  only for a smaller fraction (e.g., less than 50%, 25%, or 10%) of operating conditions of device  100 , the overall reliability and power consumption of device  100  can be improved. 
     It should be appreciated, that in addition to providing heat-dissipation functions, top heat sink  212  and bottom heat sink  202  also provide structural support for device  100 . As depicted in  FIGS. 2 and 3A-3C , top heat sink  212  and bottom heat sink  202  extend substantially across opposite sidewalls of the device housing and occupy a significant internal volume (e.g., greater than 20%, 30%, or 40%) within the device housing. Top heat sink  212  and bottom heat sink  202  thus provide structural rigidity to the device housing. For example, top heat sink  212  and bottom heat sink  202  can resist the translation and deformation of the device housing during user handling of device  100 . Top heat sink  212  and bottom heat sink  202  also house other internal components of device  100  (e.g., power supply  302 , main logic board  208 , and cooling fan  206 ). Thus, top heat sink  212  and bottom heat sink  202  provides structural support and mechanical protection for these internal components during user handling of device  100 . 
     Moreover, top heat sink  212  and bottom heat sink  202  provide electromagnetic interference (EMI) shielding for the electronic components of main logic board  208 . In particular, with reference to  FIGS. 3A-3C , top heat sink  212  and bottom heat sink  202  define opposite walls of a conductive enclosure that surrounds the electronic components of main logic board  208 . In some examples, the conductive enclosure is a metal enclosure. One or more conductive frames  210  are attached to main logic board  208  and form the sidewalls of the conductive enclosure. The one or more conductive frames  210  comprise metal, in some examples. In a specific example, the one or more conductive frames  210  are formed only of metal. As shown more clearly in  FIG. 2 , conductive frames  210  surround the electronic components on opposite surfaces of main logic board  208 . Referring back to  FIGS. 3A-3C , conductive frames  210  physically contact corresponding conductive rails  216 ,  322  that are attached to the respective surfaces of top heat sink  212  and bottom heat sink  322 . In particular, conductive rails  216  and  322  are disposed within grooves formed on the respective surfaces of top heat sink  212  and bottom heat sink  202 , and serve as metal gaskets that form a seal between conductive frames  210  and top and bottom heat sinks  212 ,  202 . In some examples, conductive rails  216  comprise metal. In a specific example, conductive rails  216  are formed only of metal. Conductive rails  216 ,  322  on top heat sink  212  and bottom heat sink  322  are more clearly depicted in  FIGS. 2 and 8B , respectively. 
     The conductive enclosure formed by top heat sink  212 , bottom heat sink  202 , and conductive frames  210  absorbs EMI generated by the electronic components of main logic board  208 . In some examples, the conductive enclosure functions as a faraday cage around the electronic components of main logic board  208 . The conductive enclosure thus impedes EMI generated by the electronic components from escaping the conductive enclosure. This can shield EMI-sensitive components (e.g., cooling fan  206 , antenna, or wireless communication components) within device  100  from the generated EMI. In addition, the conductive enclosure can resist penetration of external EMI, thereby shielding the electronic components of main logic board  208  from the external EMI. Because top heat sink  212  and bottom heat sink  202  provide EMI shielding around the electronic components of main logic board  208 , a separate EMI shielding layer (e.g., aluminized Mylar layer) separate from top heat sink  212  and bottom heat sink  202  can be unnecessary. Specifically, as shown in  FIGS. 3A-3C , the electronic components on the side of main logic board  208  facing top heat sink  212  are immediately adjacent to the surface of top heat sink  212 . Similarly, the electronic components on the opposite side of main logic board  208  facing bottom heat sink  202  are immediately adjacent to the surface of bottom heat sink  202 . Thus, in the present example, device  100  does not include separate EMI shielding layers disposed between the electronic components and top heat sink  212  and/or between the electronic components and bottom heat sink  202 . This can be desirable for reducing the cost, complexity, and overall footprint of device  100 . 
     As should be appreciated from the above description, top heat sink  212  and bottom heat sink  202  are configured to serve multiple functions in device  100 . In addition to providing passive and active heat-dissipation, top heat sink  212  and bottom heat sink  202  provide structural support for device  100  and its internal components. For example, bottom heat sink  202  serves as the structural housing for cooling fan  206 . Furthermore, top heat sink  212  and bottom heat sink  202  provide EMI shielding for the electronic components of main logic board  208 . The multiple integrated functions of top heat sink  212  and bottom heat sink  202  can enable efficient thermal-management to be provided with less aeroacoustic noise while reducing the cost, complexity, and overall footprint of device  100 . 
     Turning now to  FIGS. 7A-7B , top and bottom perspective views of base  104  are depicted, according to various examples. In particular,  FIG. 7A  illustrates a perspective view of the inner side of base  104  that faces bottom heat sink  202 , and  FIG. 7B  illustrates a perspective view of the outer side of base  104  that faces away from bottom heat sink  202 . Base  104  includes inner portion  702  and outer portion  704  that surrounds inner portion  702 . As shown in  FIG. 7B , inner portion  702  protrudes with respect to outer portion  704  in an outward direction away from bottom heat sink  202 . Openings  108  are disposed between the inner portion  702  and outer portion  702  of base  104 . In this example, openings  108  are symmetrically arranged around inner portion  702 . In addition, the size and shape of each opening  108  are substantially uniform with respect to one another. In other examples, the size, shape, and arrangement of openings  108  can vary. As shown in  FIG. 1B , openings  108  are positioned around cooling fins  110  (e.g., inlet fins  318  and outlet fins  320 ) of bottom heat sink  202 . In some examples, the outer tips of cooling fins  110  are immediately adjacent to openings  108 . For example, a portion of cooling fins  110  extends past outer portion  704  and be positioned between inner portion  702  and outer portion  704 . 
     With reference now to  FIGS. 3A and 7A , base  104  further includes one or more protrusions  324  that extend from the inner surface of base  104 . Specifically, protrusions  324  extend from the inner surface of the inner portion (e.g. inner portion  702 ) of base  104 . Protrusions  324  serve to resist the inner surface of base  104  from coming into contact with the hub of impeller  308  when the inner portion of base  104  is deflected toward bottom heat sink  202  during user handling. As is more clearly shown in  FIG. 3B , protrusions  324  are aligned with fan shroud  204  such that the tips of protrusions  324  are directly adjacent to the surface of fan shroud  204  without physically contacting the surface of the fan shroud. In the present example, base  104  includes four protrusions  324  that are positioned evenly around the inlet opening of fan shroud  204 . It should be recognized that, in other examples, base  104  can include any number of protrusions  324 . During user handling of device  100 , if a load is applied to the outer surface of base  104  to cause the inner portion of base  104  to translate toward bottom heat sink  202 , protrusions  324  can physically contact the surface of fan shroud  204  and transfer the load to bottom heat sink  202  (e.g., via outer fins  320  and the surface surrounding the rim of recess  314 ). In this way, the likelihood that the inner surface of base  104  comes into contact with the hub of impeller  308  to cause fan rubbing can be reduced. This in turn reduces the likelihood of damage to cooling fan  206  during user handling. In addition, as discussed briefly above, it can be desirable for fan shroud  204  to have a strong and rigid construction (e.g., single part formed of metal, such as aluminum). A strong and rigid fan shroud  204  can thus transfer the load from protrusions  324  to bottom heat sink  202  without being deflected toward and physically contacting impeller  308 . 
     The terminology used in the description of the various described examples herein is for the purpose of describing particular examples only and is not intended to be limiting. As used in the description of the various described examples and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Although the following description uses terms “first,” “second,” etc. to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, a first surface could be termed a second surface, and, similarly, a second surface could be termed a first surface, without departing from the scope of the various described examples. The first surface and the second surface are both surfaces, but are separate and different surfaces. 
     The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated. 
     Although the disclosure and examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims.

Metadata:
Filing Date: 20171011
Publication Date: 20190507
Grant Date: 20190507
Priority Date: 20170714
Inventors: WILLIAMS, REUBEN J.
DIEP, VINH H.
MATHESON, JONATHAN
Assignee: APPLE INC
CPC Classifications: [{"code": "F05D2250/51", "inventive": false, "first": false, "tree": "[]"}, {"code": "F04D29/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "F04D29/282", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/203", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "F04D25/0613", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/206", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K7/20154", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20145", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/467", "inventive": false, "first": false, "tree": "[]"}, {"code": "F28D2021/0029", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2023/4062", "inventive": false, "first": false, "tree": "[]"}, {"code": "F28D7/0075", "inventive": true, "first": false, "tree": "[]"}, {"code": "F28D2021/0029", "inventive": false, "first": false, "tree": "[]"}, {"code": "F28D7/0075", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/203", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20145", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2023/4062", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20154", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20163", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K7/20163", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/467", "inventive": false, "first": false, "tree": "[]"}, {"code": "F04D29/282", "inventive": true, "first": false, "tree": "[]"}, {"code": "F04D25/0613", "inventive": true, "first": false, "tree": "[]"}, {"code": "F04D29/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/206", "inventive": true, "first": false, "tree": "[]"}, {"code": "F05D2250/51", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/20", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 64999352