PATENT DOCUMENT

Publication Number: US-9095076-B2
Application Number: US-201414271353-A
Country: US
Kind Code: B2

Title: Electronic device enclosures and heatsink structures with thermal management features

Abstract:
An electronic device may have a housing in which electronic components are mounted. The electronic components may be mounted to a substrate such as a printed circuit board. A heat sink structure may dissipate heat generated by the electronic components. The housing may have a housing wall that is separated from the heat sink structure by an air gap. The housing wall may have integral support structures. Each of the support structures may have an inwardly protruding portion that protrudes through a corresponding opening in the heat sink structure. The protruding portions may each have a longitudinal axis and a cylindrical cavity that lies along the longitudinal axis. Each of the support structures may have fins that extend radially outward from the longitudinal axis.

Claims:
What is claimed is: 
     
       1. An electronic device having an electrical component, the electronic device comprising:
 a housing having a housing wall, the housing wall having at least one support structure protruding from an internal surface of the housing wall, the housing wall continuous with the at least one support structure, the at least one support structure having a shoulder portion and a shaft portion that extends from a top surface of the shoulder portion; and 
 a heat sink structure positioned between the housing wall and the electrical component and arranged to absorb heat generated by the electrical component, the heat sink structure having at least one opening that accepts the shaft portion of the at least one support structure, wherein the shoulder portion separates the housing wall from the heat sink structure by a gap corresponding to a height of the shoulder portion, the gap decreasing an amount of heat transferred from the electrical component to the housing wall. 
 
     
     
       2. The electronic device of  claim 1 , wherein the shoulder portion is arranged to support the heat sink structure. 
     
     
       3. The electronic device of  claim 1 , wherein the shaft portion aligns the heat sink structure with respect to the housing wall. 
     
     
       4. The electronic device of  claim 1 , wherein the shoulder portion has a larger width than the shaft portion. 
     
     
       5. The electronic device of  claim 1 , wherein the heat sink structure includes an upper surface and a lower surface, the at least one opening is disposed through both the upper surface and the lower surface. 
     
     
       6. The electronic device of  claim 5 , wherein a tip of the shaft portion extends above the upper surface of the heat sink structure. 
     
     
       7. The electronic device of  claim 6 , wherein the tip of the shaft portion is bent such that the tip secures the heat sink structure to the housing. 
     
     
       8. The electronic device of  claim 1 , wherein the shaft portion has a hollow cavity. 
     
     
       9. The electronic device of  claim 1 , wherein the shoulder portion includes a plurality of fins radially extending from the shaft portion. 
     
     
       10. The electronic device of  claim 1 , wherein the housing wall includes a sidewall adjacent the housing wall, wherein the at least one support structure is positioned a second distance from the sidewall. 
     
     
       11. A method of forming a heat dissipating assembly within a housing for an electronic device, the method comprising:
 forming a housing having a housing wall, the housing wall having at least one support structure protruding from an internal surface of the housing wall, the housing wall continuous with the at least one support structure, the at least one support structure having a shoulder portion and a shaft portion that extends from a top surface of the shoulder portion; and 
 positioning a heat sink structure positioned between the housing wall and an electrical component and such that the heat sink structure absorbs heat generated by the electrical component, the heat sink structure having at least one opening that accepts the shaft portion of the at least one support structure, wherein the shoulder portion separates the housing wall from the heat sink structure by a gap corresponding to a height of the shoulder portion, the gap decreasing an amount of heat transferred from the electrical component to the housing wall. 
 
     
     
       12. The method of  claim 11 , wherein the heat sink structure includes an upper surface and a lower surface, the at least one opening is disposed through both the upper surface and the lower surface and wherein a tip of the shaft portion extends above the upper surface of the heat sink structure, the method further comprising:
 bending a tip of the shaft portion such that the tip secures the heat sink structure to the housing. 
 
     
     
       13. The method of  claim 11 , wherein the positioning the heat sink structure comprises:
 aligning the shaft portion of the at least one support structure with corresponding at least one opening. 
 
     
     
       14. The method of  claim 11 , wherein the positioning the heat sink structure comprises supporting the heat sink structure on shoulder portion of the at least one support structure. 
     
     
       15. An electronic device having a heat generating component, the electronic device comprising:
 a housing having a housing wall, the housing wall having a plurality of support structures protruding from an internal surface of the housing wall, each of the support structures having a shoulder and a shaft that extends from a top surface of the shoulder, each of the shoulders including a plurality of fins radially extending from a corresponding shaft; and 
 a heat sink structure positioned between the housing wall and the heat generating component and arranged to absorb heat generated by the heat generating component, the heat sink structure having a plurality of openings that accepts shafts of corresponding support structures such that the corresponding support structures cooperate to support the heat sink structure, wherein the shoulder separates the housing wall from the heat sink structure by a gap corresponding to a height of the shoulder, the gap decreasing an amount of heat transferred from the heat generating component to the housing wall. 
 
     
     
       16. The electronic device of  claim 15 , wherein the shafts of the plurality of support structures cooperate together to align the heat sink structure with respect to the housing wall. 
     
     
       17. The electronic device of  claim 15 , wherein each of the shafts includes a hollow cavity. 
     
     
       18. The electronic device of  claim 15 , wherein each of the plurality of support structures is continuous with the housing wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 13/221,796 filed Aug. 30, 2011 entitled “Electronic Device Enclosures and Heatsink Structures with Thermal Management Features”, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This relates to electronic devices, and more particularly, to thermal management features for electronic devices. 
     Electronic devices contain electronic components that are mounted within housings. For example, an electronic device may contain integrated circuits. During operation, electronic components such as integrated circuits produce heat. If care is not taken, the heat from components in an electronic device may produce localized hot spots. The hot spots can make some portions of the housing of the device undesirably warm relative to other portions. 
     It would therefore be desirable to be able to provide improved housing configurations for electronic devices. 
     SUMMARY 
     An electronic device may have a housing in which electronic components are mounted. The electronic components may be mounted to a substrate such as a printed circuit board. During operation, the electronic components may generate heat. 
     A heat sink structure may be mounted adjacent to the electronic components to dissipate the heat generated by the electronic components. The housing may have a housing wall that is separated from the heat sink structure by an air gap. 
     The housing wall may have support structures that separate heat sink structure from the housing wall to produce the air gap. Each of the support structures may have a protruding portion that passes through a corresponding opening in the heat sink structure. The protruding portions may each have a longitudinal axis and a cylindrical cavity that lies along the longitudinal axis. A tip portion of each protruding portion may be bent using a heat staking process to attach the heat sink structure to the housing wall. Each of the support structures may have shoulder portions formed from fins that extend radially outward from the longitudinal axis. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of a device of the type shown in  FIG. 1  showing how components may be mounted to a heat sink structure in a housing in accordance with an embodiment of the present invention. 
         FIG. 3  is a cross-sectional side view of a portion of a heat sink structure and housing in the vicinity of a support structure that is used to heat stake the heat sink structure to the housing in accordance with an embodiment of the present invention. 
         FIG. 4  is a top view of a heat stake support structure of the type shown in  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of an illustrative electronic device housing and heat sink with recessed areas and protruding areas to manage the flow of heat from internal components in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Thermal management features may be incorporated into an electronic device to control the flow of heat from internal device components. An illustrative electronic device of the type that may be provided with thermal management features is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a computer, a set-top box, a wireless access point, a portable electronic device, or any other suitable electronic equipment. Configurations for electronic device  10  in which device  10  is implemented as a wireless access point are sometimes described herein as an example. This is, however, merely illustrative. Electronic device  10  may include any suitable type of electronic equipment if desired. 
     As shown in  FIG. 1 , electronic device  10  may have a housing such as housing  12 . Housing  12  may be formed from materials such as plastic, glass, ceramic, metal, carbon fiber, fiberglass, and other fiber composites, other materials, or combinations of these materials. Housing  12  may have one or more parts. For example, housing  12  may have mating upper and lower parts formed from plastic or other housing materials. If desired, housing  12  may have more than two parts. In the configuration shown in  FIG. 1 , housing  12  has a rectangular box shape with planar upper and lower surfaces and four perpendicular (vertical) planar sidewalls. The corners of housing  12  may be rounded. Other shapes may be used for housing  12  if desired (e.g., shapes with curved sides, shapes with circular footprints, shapes with combinations of curved and straight edges and surfaces, etc.). The example of  FIG. 1  is merely illustrative. 
     To accommodate connectors for displays, device peripherals, power cables, and other accessories, housing  12  may have openings (e.g., port openings) such as openings  14 . 
     Device  10  may contain internal electronic components such as integrated circuits and other components that generate heat. Thermal management features may be incorporated into the structures of device  10  to control the flow of heat from the interior to the exterior of housing  12 . 
     A cross-sectional side view of an illustrative electronic device with thermal management features is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may have a housing  12  with planar upper housing wall  12 A, planar lower housing wall  12 B, and planar sidewalls such as left sidewall  12 C and right sidewall  12 D. Electrical components  24  may be mounted within housing  12 . Electrical components  24  may include integrated circuits, switches, sensors, input-output devices, wireless circuits, discrete components such as resistors, capacitors, and inductors, power supply components, displays, audio components, and other electronic equipment. During operation, electrical components  24  may generate heat. 
     Electrical components  24  may be mounted on one or more substrates such as substrate  26 . Substrates such as substrate  26  may be rigid printed circuit boards (e.g., printed circuit boards formed from fiberglass-filled epoxy such as FR 4  printed circuit boards), flexible printed circuits (“flex circuits”) formed from flexible sheets of polymer such as polyimide, printed circuit boards that contain both flexible and rigid portions (sometimes referred to as “rigid flex” boards), plastic, glass, ceramic, or other suitable substrate materials. 
     Components  24  may be electrically and mechanically connected to substrate structures  26  using solder, welds, conductive adhesive, fasteners, and other electrical and mechanical attachment mechanisms. In the example of  FIG. 2 , there are three components  24  mounted on a single substrate  26 . In general, device  10  may contain any suitable number of components (e.g., one or more, five or more, ten or more, etc.) and any suitable number of substrates  26  (e.g., one or more, two or more, three or more, five or more, ten or more, etc.). When multiple substrates are used for mounting components  24 , cables such as flex circuit cables and other interconnection structures may be used to route signals between different substrates  26 . Components  24  may be mounted on one or both sides of substrate structures  26 . In the example of  FIG. 2 , components  24  are mounted to the underside (inner side) of substrate  26 . Components  24  may be mounted on the top side (outer side) of substrate  26  if desired. 
     Heat dissipation from components  24  may be promoted using one or more heat sinks As shown in  FIG. 2 , for example, one or more heat sinks such as heat sink  18  may be placed in contact with components  24  to dissipate heat produced by components  24 . One heat sink  18  is shown in  FIG. 2 , but, in general, device  10  may contain any suitable number of heat sinks  18  (e.g., one or more, two or more, three or more, five or more, ten or more, etc.). The arrangement of  FIG. 2  in which a single heat sink is used to dissipate heat from multiple components  24  is merely illustrative. If desired, each component  24  may be provided with an individual heat sink or heat sinks may be provided that are each used in dissipating heat from a respective subset of component  24  in device  10 . 
     Heat sink structures  18  may be formed from one or more materials that exhibit satisfactory thermal conductivity. As an example, heat sink structures  18  may be formed from one or more metals such as aluminum (e.g., aluminum alloys), copper, etc. To enhance thermal transfer between components  24  and heat sink structures  18 , high thermal conductivity materials may be placed between components  24  and heat sink structures  18  (e.g., conformal thermal pads, heat sink compound, etc.). 
     One or more air gaps may be formed between the outermost surfaces of heat sink structures  18  and the inner surfaces of housing  12 . The air gaps may serve to retard heat flow from the interior of device  10  to the exterior of device  10 . This retardation of heat flow may help ensure that heat is distributed laterally so that hot spots are reduced. Air gaps may be provided locally or may be provided globally (e.g., over most or all of the available surface of heat sink structures  18 ). In the example of  FIG. 2 , air gap  20  is formed globally between the lower (outermost) surface of heat sink structures  18  and the upper (innermost) surface of lower planar housing wall  12 B. Other types of air gaps and air gaps of locally varying thickness may also be used. If desired, some or all of an air gap may also be filled with a material such as foam or low density plastic that has a low thermal conductivity instead of air. The example of  FIG. 2  is merely illustrative. 
     With a configuration of the type shown in  FIG. 2 , heat that is locally produced in the vicinity of each component  24  travels into heat sink  18 . Because of the presence of air gap  20 , the heat in heat sink  18  tends to become evenly distributed laterally (in dimensions X and Y). Gap  20  may be sufficiently thin (e.g., 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, 1 mm or less, etc.) to ensure that there is sufficient heat transfer outwards (in dimension Z) through housing wall  12 B. This prevents the temperatures of components  24  from becoming too high during operation. The increase in the lateral spreading of heat within heat sink  18  that is produced by air gap  20  may ensure that there are few or no perceptible hot spots on housing  12  when the exterior of housing  12  is touched by a user. Air gaps  20  may be interposed between heat sink structures  18  and any suitable surfaces of housing  12  (e.g., between heat sink structures  18  and the upper surface of housing  12 , between heat sink structures  18  and the lower surface of housing  12 , between heat sink structures  18  and sidewall surfaces of housing  12 , and/or between heat sink structures  18  and other suitable housing surfaces). The example of  FIG. 2  in which there is one gap  20  adjacent to housing wall  12 B is merely illustrative. 
     Air gaps such as air gap  20  may be created by supporting heat sink structures  18  with support structures such as support structures  16 . Support structures  16  may be formed from part of heat sink structures  18 , from housing structures such as part of housing  12 , from internal frame structures, from combinations of these structures, or from other suitable structures. There may be any suitable number of support structures in device  10  (e.g., four so that each of four corners of a rectangular heat sink may be supported, six, eight, three or more, etc.). Support structures  16  may form spacers that serve to create a desired amount of separation for air gap  20 . Support structures  16  may be formed from discrete structures that are attached to housing  12  or may be formed from part of housing  12 . 
     With one suitable arrangement, which is sometimes described herein as an example, support structures  16  may be formed from integral protruding portions of housing wall  12 .  FIG. 3  is a cross-sectional side view of an illustrative support structure  16 . As shown in  FIG. 3 , heat sink structures  18  may have openings through which portions  30  of support structures  16  protrude. For example, if there are four support structures  16  in device  10 , heat sink structures  18  may have four corresponding openings for receiving respective portions  30  of the four support structures  16 . 
     Support structures  16  may have shoulder structures  28  that support heat sink structures  18  and establish the size of air gap  20 . Portions  30  may have the shape of a hollow cylinder. Cylindrical cavity  32  may run parallel to at least some of the length of support structures  16  along longitudinal axis  33  of portions  30 . Portions  30  of support structures  16  may form a heat stake attachment structure that is deformed upon application of heat. In particular, the tips of portions  30  may be heated and bent downwards to positions  30 ′ during application of heat to the tips of portions  30  in a heat staking process. In this position, heat stake portions  30  may be received within circular recess  34  of heat sink structures  18  to attach (heat stake) heat sink structures  18  to housing  12 B. The presence of an internal cavity within the protruding cylindrical portion  30  of support structures  16  may help to reduce thermal transfer between heat sink  18  and housing  12 B. In the absence of cavity  32 , heat might be transferred from heat sink  18  to location  35  of housing  12 B so effectively that location  35  of housing  12 B might exhibit an unsightly heat-induced depression (sink mark). 
     Localized thermal transfer between heat sink structures  18  and housing  12 B can also be minimized by minimizing the footprint of shoulder portions  28  of support structures  16 . With one suitable arrangement, the surface area on housing  12 B that is consumed by shoulder portions  28  may be minimized by forming portions  28  in the shape of a set of fins that protrude radially outward from cavity  32  and longitudinal axis  33  of cavity  32 .  FIG. 4  is a top view of support structures  16  that have been formed using this type of approach. As shown in  FIG. 4 , portions  28  of support structures  16  may include four radially extending fins  28 A,  28 B,  28 C, and  28 D. Areas  35  between the fins are free of support structures  16 . Because air is present in areas  35 , thermal transfer through areas  35  and therefore through support structures  16  is minimized, reducing the likelihood of forming a sink mark under support structures  16 . The  FIG. 4  example includes four fins, but support structures  16  may have one or more fins, two or more fins, three or more fins, four or more fins, etc. 
       FIG. 5  is a cross-sectional side view showing how the thickness of air gap  20  may be adjusted locally to help evenly distribute heat on the exterior surface of housing  12 . As shown in  FIG. 5 , the thickness of gap  20  may have different magnitudes in different locations. In some areas, the thickness of gap  20  may have a nominal thickness of T. In regions of device  10  where it is desired to decrease thermal resistance, the thickness of gap  20  may be locally decreased to a value below nominal thickness T. When it is desired to increase thermal resistance, the thickness of gap  20  may be increased to be larger than nominal thickness T. As an example, if it is desired to retard the flow of heat under a component that has an area of 1 cm 2 , a 1 cm 2  area of device  10  that overlaps the component may be provided with an increased air gap thickness. If particular regions of device  10  are generating small amounts of heat, the thickness of air gap  20  may be reduced in those regions. 
     In the example shown in  FIG. 5 , air gap thickness adjustments have been made using combinations of recessed areas and protruding areas in heat sink structures  18  and in housing wall  12 B. 
     In area T−D 1 , the thickness of air gap  20  has been decreased to a value of T−D 1  by creating protrusion  36  in this area on the lower (outermost) surface of heat sink structures  16 . Protrusion  36  has a thickness of D 1 , which reduces the thickness of air gap  20  by D 1  over the area covered by protrusion  36 . 
     In area T+D 2 , the thickness of air gap  20  has been increased to a value of T+D 2  by creating recess  38  in this area on the upper (innermost) surface of housing wall  12 B. Recess  38  has a depth of D 2 , which increases the thickness of air gap  20  by D 2  throughout the area covered by recess  38 . 
     In area T−D 3 −D 4 , an air gap thickness adjustment has been made using protrusions on both heat sink structures  18  and housing wall  12 B. In particular, the thickness of air gap  20  has been decreased to a value of T−D 3 −D 4  by creating protrusion  40  in this area on the lower (outermost) surface of heat sink structures  16  and by creating protrusion  42  on the upper (innermost) surface of housing wall  12 B. Protrusion  40  has a thickness of D 4  and protrusion  42  has a thickness D 3 , so there is an overall reduction in the thickness of air gap  20  from T to T−D 3 −D 4  over the area covered by protrusions  40  and  42 . Protrusions  40  and  42  may, for example, have the same surface area and may have identical footprints (as an example). 
     In area T+D 5 , the thickness of air gap  20  has been increased to a value of T+D 5  by creating recess  44  in this area on the lower (outermost) surface of heat sink structure  18 . Recess  38  has a depth of D 2 , which reduces the thickness of air gap  20  by D 2  throughout the area covered by recess  44 . 
     In area T−D 6 , the thickness of air gap  20  has been decreased to T−D 6  by creating a protrusion on housing wall  12 B having a thickness of D 6 . 
     These are merely illustrative configurations for forming thermal management features in device  10 . In general, any suitable combinations of protrusions and recesses on housing walls  12  and/or heat sink structures  18  may be used to narrow and/or expand air gap  20  and thereby control the flow of heat through air gap  20  and the evenness with which heat spreads throughout dimensions X and Y before escaping outwards through housing  12  (housing wall  12 B) in dimension Z. If desired, additional layers of material, protrusions on other surfaces of heat sink structures  18 , housing walls  12 , and/or other structures in device  10  may be used in controlling the flow of heat in device  10 . Arrangements of the type shown in  FIG. 5  are merely illustrative. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20140506
Publication Date: 20150728
Grant Date: 20150728
Priority Date: 20110830
Inventors: DIEP Vinh
GOH CHIEW-SIANG
HEIRICH DOUG
KWAN ALEXANDER MICHAEL
VILLARREAL CESAR LOZANO
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K13/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K7/20436", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49002", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49002", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K13/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K7/20436", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K7/20436", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49002", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K7/20436", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K5/0209", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K7/20436", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K13/00", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 47743453