PATENT DOCUMENT

Publication Number: US-9192057-B2
Application Number: US-201213726890-A
Country: US
Kind Code: B2

Title: Electromagnetic interference shielding structures

Abstract:
Electrical components are mounted on a printed circuit in an electronic device housing. Shielding can structures may include a sheet metal shield can layer with a conductive gasket. The printed circuit may have an opening. A screw passes through the opening in the printed circuit and openings in the conductive gasket and sheet metal shield can layer to secure the shielding can structures to the housing. When secured, a lip in the gasket lies between the printed circuit substrate and the housing. The gasket may be formed from conductive elastomeric material. A shield can lid and a flexible printed circuit may be embedded within conductive elastomeric material that provides a thermal conduction path to dissipate heat from electrical components under the lid. Shield can members that are located on opposing sides of a bend in a flexible printed circuit substrate may be coupled by a conductive elastomeric bridging structure.

Claims:
What is claimed is: 
     
       1. Apparatus, comprising:
 a substrate; 
 electrical components mounted on the substrate; and 
 shielding can structures that cover the electrical components, wherein the shielding can structures include metal structures and conductive elastomeric structures, wherein the conductive elastomeric structures have an opening, wherein the metal shielding can structures have an opening, and wherein the opening in the conductive elastomeric structures is aligned with the opening in the metal structures. 
 
     
     
       2. The apparatus defined in  claim 1  wherein the substrate has an opening that is aligned with the opening in the conductive elastomeric structures and the opening in the metal structures. 
     
     
       3. The apparatus defined in  claim 2  further comprising a screw having a shaft that passes through the opening in the substrate, the opening in the conductive elastomeric structures, and the opening in the metal structures. 
     
     
       4. The apparatus defined in  claim 3  further comprising electronic device housing structures with a threaded opening that receives the shaft. 
     
     
       5. The apparatus defined in  claim 4  wherein the conductive elastomeric structures have a lip that is compressed between the substrate and the electronic device housing structures. 
     
     
       6. The apparatus defined in  claim 5  wherein the substrate comprises a printed circuit with metal traces and wherein the lip is shorted to the metal traces. 
     
     
       7. The apparatus defined in  claim 6  wherein the electronic device housing structures comprise a screw boss in which the threaded opening is formed. 
     
     
       8. The apparatus defined in  claim 1  wherein the conductive elastomeric structures comprise a ring-shaped gasket formed from an elastomeric polymer with a conductive filler. 
     
     
       9. The apparatus defined in  claim 1  wherein the metal structures comprise:
 a first metal shielding can member; and 
 a second metal shielding can member. 
 
     
     
       10. The apparatus defined in  claim 1  wherein the metal structures comprise lower shielding can structures and upper shielding can structures, wherein the conductive elastomeric structures comprises plastic with conductive filler, and wherein the plastic is molded over the upper shielding can structure. 
     
     
       11. The apparatus defined in  claim 10  further comprising a flexible printed circuit having a ground trace that is shorted to the upper shielding can structure, wherein the plastic is molded over the flexible printed circuit. 
     
     
       12. The apparatus defined in  claim 11  wherein the plastic has a lower surface that is configured to contact upper surfaces of the electrical components. 
     
     
       13. The apparatus defined in  claim 12  further comprising an electronic component mounted to the flexible printed circuit. 
     
     
       14. The apparatus defined in  claim 13  wherein the electronic component mounted to the flexible printed circuit comprises a connector. 
     
     
       15. The apparatus defined in  claim 14  wherein the lower shielding can structures comprise a metal shielding can base and wherein the upper shielding can structures comprise a shielding can lid that is mounted to the metal shielding can base. 
     
     
       16. Apparatus, comprising:
 a substrate; 
 electrical components mounted on the substrate; and 
 shielding can structures that cover the electrical components, wherein the shielding can structures include metal structures and conductive elastomeric structures, and wherein the metal structures comprise:
 a first metal shielding can member; and 
 a second metal shielding can member, wherein the first metal shielding can member and the second metal shielding can member are separated by a gap and wherein the conductive elastomeric structures comprise bridging structures that are coupled between the first metal shielding can member and the second metal shielding can member across the gap. 
 
 
     
     
       17. The apparatus defined in  claim 16  further comprising a support structure having a non-planar surface with a bend, wherein the substrate is supported on the support structure so that the first and second metal shielding can members lie on opposing sides of the bend and wherein the conductive elastomeric structure overlaps the bend. 
     
     
       18. Apparatus, comprising:
 an electronic device housing having a protrusion; 
 a printed circuit board; 
 electrical components mounted on the printed circuit board; and 
 shielding can structures that shield the electrical components from electromagnetic interference and that have a metal gasket with an opening, wherein the metal gasket has a lip that lies between the protrusion and the printed circuit board. 
 
     
     
       19. The apparatus defined in  claim 18  wherein the printed circuit board includes metal traces and wherein the lip contacts the metal traces. 
     
     
       20. The apparatus defined in  claim 19  wherein the protrusion comprises a screw boss, the apparatus further comprising as screw that screws into the screw boss and attaches the printed circuit board and the shielding can structures to the electronic device housing. 
     
     
       21. The apparatus defined in  claim 18  wherein the shielding can structures comprise sheet metal and wherein the metal gasket is welded to the sheet metal. 
     
     
       22. Apparatus, comprising:
 a substrate; 
 electrical components mounted on the substrate, wherein the electrical components have upper surfaces; 
 plastic with a conductive filler, wherein the plastic contacts the upper surfaces; and 
 a shielding can lid embedded within the plastic. 
 
     
     
       23. The apparatus defined in  claim 22  further comprising:
 a flexible printed circuit embedded within the plastic, wherein the flexible printed circuit has metal traces that contact the shielding can lid. 
 
     
     
       24. The apparatus defined in  claim 23  further comprising:
 a shielding can base to which the shielding can lid is attached. 
 
     
     
       25. The apparatus defined in  claim 23  further comprising a connector mounted on the flexible printed circuit. 
     
     
       26. The apparatus defined in  claim 25  wherein the substrate comprises a rigid printed circuit board. 
     
     
       27. Apparatus, comprising:
 a substrate having a bend; 
 electrical components mounted on the substrate; and 
 shielding can structures having first and second shielding can members that are separated by a gap and that are located on opposing sides of the bend and having conductive elastomeric bridging structures that span the gap and overlap the bend. 
 
     
     
       28. The apparatus defined in  claim 27  wherein the substrate comprises a flexible printed circuit. 
     
     
       29. The apparatus defined in  claim 28  wherein the flexible printed circuit comprises metal traces and wherein the first and second shielding can members are mounted on the metal traces. 
     
     
       30. The apparatus defined in  claim 29  further comprising a support structure with a non-planar surface, wherein the substrate is mounted to the non-planar surface. 
     
     
       31. The apparatus defined in  claim 30  wherein the support structure comprises a speaker box. 
     
     
       32. The apparatus defined in  claim 27 , wherein the conductive elastomeric bridging structures are coupled between the first shielding can member and the second shielding can member.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with electromagnetic interference shielding structures. 
     Electronic devices include electrical components. Components such as integrated circuits have the potential to emit electromagnetic interference and have the potential to be disrupted by the presence of electromagnetic interference from nearby components. To reduce electromagnetic interference, components are often covered with electromagnetic shielding cans formed from one or more metal parts. The shielding cans enclose components on a printed circuit board so that the cans do not emit harmful electromagnetic interference signals and are isolated from interference from nearby components. 
     Challenges can arise when mounting shielding cans in electronic devices. In some designs, insufficient room is available to mount a conventional shielding can. In other designs, signal paths may not be well secured or grounded to shielding cans or the components within a shielding can may be thermally isolated from surrounding structures. Conventional shielding can arrangements may also be unable to accommodate substrates mounted on non-planar surfaces. 
     It would therefore be desirable to be able to provide improved shielding arrangements for electronic components in electronic devices. 
     SUMMARY 
     An electronic device may have a housing such as a metal housing with a protrusion. The protrusion may be a screw boss with a threaded opening. 
     Electrical components may be mounted on a substrate in the housing. The substrate may be a printed circuit substrate such as a flexible printed circuit or rigid printed circuit board. 
     Shielding can structures may shield the electrical components from electromagnetic signal interference. The shielding can structures may be formed from metal parts such as a base and a lid attached to the base, metal members stamped from sheet metal, and other conductive shielding structures. 
     The shielding can structures may include metal shielding can structures such as a sheet metal layer with a conductive gasket. The metal shielding can structures may have an opening. The conductive gasket may have an opening that is aligned with the opening in the metal shielding can structures. The printed circuit substrate may have an opening that is aligned with the openings in the metal shielding can structures. A screw that passes through the opening in the printed circuit and the openings in the conductive gasket and metal shielding can structures may secure the shielding can structures to the housing so that a lip in the gasket lies between the printed circuit substrate and the housing. The gasket may be formed from conductive elastomeric material such as plastic with conductive filler that is molded over the metal shielding can structures around the opening in the metal shielding can structures or may be formed from a material such as metal. 
     Shielding can structures may include metal shielding can structures such as a metal lid and a metal base. The metal lid and a flexible printed circuit may be embedded within conductive elastomeric material that covers at least some of the flexile printed circuit and metal lid. The conductive elastomeric material may contact electrical components on the substrate under the lid, thereby forming a thermal path to dissipate heat from the electrical components. Traces on the flexible printed circuit may be shorted to the metal lid. 
     Shield can members that are located on opposing sides of a bend in a flexible printed circuit substrate may be coupled by a conductive elastomeric bridging structure. The conductive elastomeric bridging structure may be plastic with a conductive filler that is molded to the shield can members. 
     Further features, their 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 of the type that may be provided with electrical component shielding structures in accordance with an embodiment. 
         FIG. 2  is an exploded perspective view of a shielding can of the type that may be used to electromagnetically shield electronic components mounted on a printed circuit in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a portion of a printed circuit on which electronic components and an associated electromagnetic interference shielding can have been mounted in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of a printed circuit to which a shielding can has been soldered to electromagnetically shield electrical components on the printed circuit in accordance with an embodiment. 
         FIG. 5  is an exploded perspective view of an electromagnetic shielding can with a molded plastic structure that surrounds an opening in the shielding can and a printed circuit to which the electromagnetic shielding can is being mounted in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of a portion of an electronic device having a shielding can and printed circuit of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of a portion of a shielding can having an opening and an attached conductive structure that surrounds the opening in accordance with an embodiment. 
         FIG. 8  is a diagram of equipment and operations involved in forming shielding can structures of the type shown in  FIG. 5  in accordance with an embodiment. 
         FIG. 9  is a diagram of equipment and operations involved in forming shielding can structures of the type shown in  FIG. 7  in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps of forming an electronic device having a printed circuit with components that have been shielded using an electromagnetic interference shielding can in accordance with an embodiment. 
         FIG. 11  is an exploded perspective view of an illustrative two-part shielding can structure to which a signal path such as a flexible printed circuit has been secured using molded plastic in accordance with an embodiment. 
         FIG. 12  is a diagram of equipment and operations involved in forming a shielding can structure that shields electronic components on a printed circuit and that has molded plastic to provide a thermal pathway that allows heat to be conducted away from the electronic components in accordance with an embodiment. 
         FIG. 13  is a flow chart of illustrative steps involved in forming electronic device structures in which electrical components are mounted to a printed circuit and covered using electromagnetic shielding structures having a two-part configuration of the type shown in  FIG. 11  in accordance with an embodiment. 
         FIG. 14  is a perspective view of electromagnetic interference shielding can structures having two shielding can portions that have been joined using a material such as a molded conductive elastomeric plastic material in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of a printed circuit to which electrical components have been mounted that are covered by a multi-part electromagnetic interference shielding can with portions joined using a plastic molded structure in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of shielding can structures of the type shown in  FIG. 15  that have been mounted on a non-planar surface such as a curved surface of a speaker box or other supporting structure in accordance with an embodiment. 
         FIG. 17  is a cross-sectional side view of a shielding can structure of the type shown in  FIG. 15  that has been mounted so that the shielding can structure overlaps a right-angle bend in the surface of a supporting structure in an electronic device in accordance with an embodiment. 
         FIG. 18  is an exploded perspective view of an illustrative multi-part shielding can structure that has a conductive bridging structure formed from a material such as a conductive elastomeric material in accordance with an embodiment. 
         FIG. 19  is a perspective view of multi-part shielding can structures of the type shown in  FIG. 18  in accordance with an embodiment. 
         FIG. 20  is a flow chart of illustrative steps involved in forming electromagnetic shielding structures from multiple parts joined by a conductive bridging structure in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device that may be provided with electromagnetic interference shielding structures for shielding electrical components mounted on dielectric substrates such as printed circuits is shown in  FIG. 1 . Electronic devices such as device  10  of  FIG. 1  may be cellular telephones, media players, other handheld portable devices, somewhat smaller portable devices such as wrist-watch devices, pendant devices, or other wearable or miniature devices, gaming equipment, tablet computers, notebook computers, desktop computers, televisions, computer monitors, computers integrated into computer displays, or other electronic equipment. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14 . Display  14  has been mounted in a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies. 
     Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  16 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  18 . 
     Housing  12  may have one or more openings to accommodate structures such as buttons, status indicators, and connector ports. Housing  12  may, for example, connector ports such as connector port  20  in housing  12 . Connectors for connector ports such as connector port  20  may include audio jack connectors, power connectors, digital data port connectors (e.g., for forming a digital data port that receives digital data on digital signal lines and that receives power on power lines), a port that handles a mixture of analog signals, digital signals, and power signals, or other suitable connectors. 
     The components in device  10  may include radio-frequency transceiver circuitry for transmitting and receiving wireless signals using antenna structures in device  10 , clock circuits, display driver circuits, processors, memory, and other electrical components. Electrical components such as these have the potential to emit electromagnetic interference and have the potential to be disrupted when exposed to electromagnetic interference emitted by nearby components. To reduce the potentially harmful effects of interference, components in device  10  may be shielded using one or more electromagnetic interference shielding cans (sometimes referred to as shields, shielding structures, radio-frequency shields, etc.). 
       FIG. 2  is an exploded perspective view of an illustrative substrate to which components have been mounted and an associated electromagnetic shielding can. As shown in  FIG. 2 , electrical components  22  are mounted on substrate  24 . Electrical components  22  may include processing circuitry, memory, application-specific integrated circuits, communications circuitry, radio-frequency transceiver circuitry, display control circuitry, clock circuits, and other electrical devices. Substrate  24  may be formed from a dielectric. For example, substrate  24  may be a printed circuit such as a flexible printed circuit that is formed from a flexible layer of polyimide or other flexible polymer layer or may be a rigid printed circuit board formed from a material such as fiberglass-filled epoxy. Metal traces (e.g., copper traces, aluminum traces, or traces formed from other metals) may be formed in the interior of printed circuit substrate  24  and/or on the surface of printed circuit substrate  24 . These metal traces may include solder pads (contacts) to which components  22  may be attached using solder joints. 
     Shielding can structures such as metal shielding can structures  26  (sometimes referred to as a shield can, shielding can, metal shielding member, metal shield, etc.) may include a planar upper portion such as upper portion  30  and sidewalls such as sidewalls  28 . In some situations, shielding can structures  26  may be formed from multiple portions (e.g., multiple metal members). For example, shielding can structures  26  may have a frame or other base that is covered by a separate lid. The lid may include planar upper portion  30  and, if desired, may include vertically extending portions such as vertical sidewall portions  28 . Walls  28  may have straight edges such as lower edge  32  or may have notches, as shown by dashed line  34 . Other types of multipart structures (e.g., other sets of two or more metal members) may be used in forming metal shielding can structures  26  if desired. 
     A cross-sectional side view of shielding can  26  of  FIG. 2  taken along line  38  and viewed in direction  36  is shown in  FIG. 3 . Electrical components  22  are mounted to printed circuit  24  using solder joints  46 . Components  22  have contacts such as solder pads  44  formed from patterned metal traces. Printed circuit  24  has corresponding contacts such as solder pads  40  formed from patterned metal traces. Solder joints  46  may be formed between contacts such as solder pads  44  on components  22  and contacts such as solder pads  40  on printed circuit  24 . 
     Printed circuit  24  includes metal traces  42 . The metal traces of printed circuit  24  may include traces formed on the upper and/or lower surfaces of printed circuit  24  and/or internal traces. The traces on printed circuit  24  such as traces  42  are used in interconnecting components  22  and are therefore sometimes referred to as interconnects or interconnecting signal paths. Portions of the traces may form contact pads  40  to which frame  26  can be mounted (e.g., by using a screw or other fastener to apply a biasing force to shielding can  26  that presses shielding can  26  against pads  40 ). Traces  42  may include ground traces. If desired, the ground traces may be coupled to shielding can  26  using pads  40  that are in contact with shielding can  26 . As shown in the illustrative configuration of  FIG. 4 , shielding can  26  may, if desired, be coupled to metal traces  42  using solder  46  that is interposed between portions of shielding can  26  and corresponding solder pads  40  on printed circuit  24 . 
       FIG. 5  is an exploded perspective view of an illustrative shielding can having an opening to accommodate a fastener such as a screw. Components  22  are mounted on the underside of printed circuit  24 . Printed circuit  24  has opening  56  (sometimes referred to as a screw hole) through which threaded shaft  52  of screw  54  passes. Shaft  52  is received in threaded opening  50  of housing protrusion  48  in housing  12 . Housing protrusion  48  (sometimes referred to as a screw boss, a metal member, metal structures, or housing structures) may be formed from an integral portion of housing  12  (e.g., an integral metal portion) or may be a separate structure that is attached to housing  12  using attachment structures such as welds, solder, adhesive, engagement features, fasteners such as screws, or other attachment mechanisms. 
     Shielding can  26  has an opening for receiving shaft  52  of screw  54 . Conductive gasket  58  has opening  60 . Opening  60  is aligned with the opening in shielding can  26 . Opening  60  is also aligned with opening  56  in printed circuit  24  and opening  50  in housing protrusion  48 , so that shaft  52  of screw  54  passes through opening  56  and opening  60  when screwing into opening  50  in screw boss  48 . There is one screw  54  and one corresponding threaded housing structure such as screw boss  48  in device  10  of  FIG. 5 . This is, however, merely illustrative. There may be any suitable number of threaded openings  50  on housing  12  and a corresponding number of openings in shielding can  26  and printed circuit  24 , if desired. 
     When screw  54  is screwed into opening  50 , the head of screw  54  will bear down on printed circuit  24 . This will press printed circuit  24  downwards towards housing  12 . The edges of shielding can  26  will press against ground traces (contact pads  40 ) on printed circuit  24 , as described in connection with  FIG. 3 . Conductive gasket  58  will help to fill any gaps between the conductive material of shielding can  26  and housing  12  (e.g., boss  48 ) that might otherwise arise, thereby helping to ensure that shielding can structure  26  serves as an effective electromagnetic interference shield. 
     Conductive gasket  58  may be formed from metal, plastic such as polycarbonate, an elastomeric polymer, an elastomeric polymer that has been filled with metal particles (e.g., copper particles or nickel particles), an elastomeric polymer that has been provided with other conductive filler material (e.g., nickel graphite powder) to ensure that gasket  58  exhibits a desired amount of conductivity, or other materials. Gasket  58  may, if desired, be formed from an elastomeric material such as silicone (e.g., silicone having a filler formed from conductive particles such as metal particles or other conductive particles to ensure that gasket  58  is conductive). The use of elastomeric materials for forming conductive structure  58  may help provide compliance when installing shielding can  26  within housing  12  of device  10 . The use of a protruding shape for conductive elastomeric structure  58  may allow shielding can  26  to be mounted deep within the interior of housing  12 , thereby consuming less height within housing  12 . 
       FIG. 6  is a cross-sectional side view of housing boss  48  and the other structures of  FIG. 5  taken along line  62  and viewed in direction  64  (following assembly of the structures of  FIG. 5 ). As shown in  FIG. 6 , housing boss  48  protrudes upwards in direction Z from the rest of housing  12 . If desired, housing boss  48  may be formed from an internal housing member such as a standoff that is welded or otherwise attached to housing  12 . Gasket  58  may include vertical sidewall portions such as sidewall portion  76  that extend parallel to housing boss  48  in direction Z to accommodate the mounting geometry for printed circuit board  24  that is shown in  FIG. 6 . With this arrangement, components  22  are attached using solder  46  that couples component contacts (solder pads  44 ) to respective contact pads  40  on printed circuit  24 . Electrical components  22  are mounted upside down in the orientation of  FIG. 6 . Shielding can  26  is also mounted upside down. To ground shielding can  26 , portions  26 ′ of shielding can  26  are pressed against grounding contact pads  40  on printed circuit  24 . If desired, solder may be used in coupling shielding can  26  to pads  40 , as described in connection with  FIG. 4 . 
     Gasket  58  of  FIG. 6  is formed from plastic that has been molded over inner edge  68  of the opening in the metal shielding can member forming shielding can structures  26  (e.g., by forming overmolded portions  66 ). Shielding can structures  26  have a bent sheet metal portion characterized by bend  74  surrounding housing boss  48 . Bend  74  raises sheet metal portion  68  in direction Z, so that lower surface  70  of the lower portion of overmolded plastic  66  lies flush with lower surface  72  of shielding can  26 . This allows shielding can structures  26  to be efficiently mounted within a potentially compact volume in the interior of electronic device housing  12 . 
     Overmolded plastic portions  66  of gasket  58  form a lower horizontally extending ring-shaped lip that surrounds housing boss  48  and couples gasket  58  to the sheet metal layer in metal shielding can structures  26 . Gasket  58  also has portions  78  that form an upper horizontally extending ring-shaped lip. Upper lip  78  is compressed between contact pad  40 ′ on printed circuit  24  and the upper planar surface of housing boss  48  when screw  54  is screwed into housing boss  48  so that the threads of threaded shaft  52  mate with the threads of opening  50  in housing boss  48 . Housing boss  48  is formed from metal in the  FIG. 6  configuration, so the mounting configuration of  FIG. 6  electrically couples (shorts) and thereby grounds housing  12 , lip  78  of gasket  58 , and contacts  40 ′ on printed circuit  24 . Ground traces  42  in printed circuit  24  may be used in grounding together the contact pads  40  that are coupled to shielding can  26  (including pads  40 ′, if desired). 
     With the illustrative configuration of  FIG. 6 , no solder is needed to connect gasket lip portion  78  of gasket  76  to ground contact structures  40 ′ on printed circuit  24 , which saves height in dimension Z. Gasket  58  can be formed from an elastomeric material that provides compliance in aligning and mounting shielding can  26  relative to printed circuit  24  and housing  12 . Shielding can structures  26  (e.g., the sheet metal structures other than gasket  58 ) may be formed from a relatively thin sheet metal part such as a stamped stainless steel sheet having a thickness of about 0.1 to 0.15 mm. It may be difficult or impossible to reliably bend an integral portion of this type of sheet metal to form the shape of gasket  48  that is shown in  FIG. 6 . The configuration of  FIG. 6  therefore helps eliminate the need for thicker sheet metal in shielding can  26 , saving additional height in dimension Z. Gasket  58  closes the potentially large electromagnetic interference opening that might otherwise be present between shielding can  26  and housing boss  48 , thereby reducing electromagnetic signal leakage. 
       FIG. 7  is a cross-sectional view of a gasket configuration for shielding can structures  26  in which gasket  58  has been formed from a conductive member that is attached to shielding can structures  26  using attachment structures  80 . Attachment structures  80  may be laser welds or welds formed using other welding equipment, may be conductive adhesive or other adhesive, may be fasteners such as screws, may be mechanical engagement features, or other attachment structures. With one suitable configuration, gasket  58  of  FIG. 7  may be formed from the same type of metal as the sheet metal forming shielding can structures  26  (e.g., stainless steel). 
       FIG. 8  is a diagram of equipment and operations involved in forming shielding can structures  26  of  FIG. 6 . As shown in  FIG. 8 , fabrication equipment such as stamping tool  84  may process sheet metal  82  to form stamped shielding can structures  86  having lip portions  68  surrounding a screw hole and having peripheral vertical portions that form shielding can sidewalls. Molding tool  88  may then overmold conductive plastic onto sheet metal shielding can structures  86  over edge portion  68  of shielding can structures  86  to form gasket  58 . Overmolded portions  66  help attach gasket  58  to sheet metal structures  86  of shielding can structures  26 . 
       FIG. 9  is a diagram of equipment and operations involved in forming shielding can structures  26  of  FIG. 7 . As shown in  FIG. 9 , fabrication equipment such as stamping tool  84  may process sheet metal  82  to form stamped shielding can structures  86  having edge portions  68  surrounding a screw hole and having peripheral vertical portions that form shielding can sidewalls. Edge portions  68  may lie flush with the planar surface of shielding can structures  26 . Fabrication equipment  90  such as plastic molding equipment, machining equipment, metal stamping equipment, or other tools process sheet metal, conductive plastic, or other material to form conductive gasket  58 . 
     Equipment  92  (e.g., laser welding equipment, adhesive application equipment, equipment that uses fasteners, or other equipment) may be used to attach gasket  58  to a metal shielding can member or other shielding can structures with attachment structures  80  (e.g., welds, adhesive, fasteners, engagement features, etc.). 
     A flow chart of illustrative steps involved in forming shielding can structures  26  with conductive gasket  58  is shown in  FIG. 10 . As shown in  FIG. 10 , shielding can structures with a screw hole opening (or multiple openings) are formed at step  94  (e.g., using stamping equipment to stamp a sheet metal layer into a desired shape, etc.). 
     At step  96 , equipment such as plastic molding tool  88  of  FIG. 8  or equipment  92  of  FIG. 9  may be used in attaching gasket  58  to the stamped metal structures of shielding can structures  26 . Gasket  58  may be an elastomeric conductive plastic gasket that is molded onto the sheet metal of shielding can structures  26 , may be a metal structure that is laser welded to the sheet metal of shielding can structures  26 , or may be other conductive structures that are attached to the sheet metal portions of shielding can structures  26  (e.g., using adhesive, fasteners, welds, solder, engagement features, etc.). 
     During the operations of step  98 , machining equipment or other fabrication equipment may be used for form housing  12  with threaded opening  50  (e.g., threaded screw boss  48 ). 
     At step  100 , printed circuit  24  with component  22  may be shielded by shielding can  26  by installing shielding can structures  26  and printed circuit  24  within housing  12  using a configuration of the type shown in  FIG. 6  in which screw  54  mounts printed circuit  24  and shielding can structures  26  to housing boss  48 . When mounting shielding can structures  26  in this way, screw  54  may press printed circuit  24  towards housing boss  48  while compressing lip  78  of gasket  58  between housing boss  48  and contacts  40 ′ on printed circuit  24 . This helps short contacts  40 ′ and associated ground traces  42  in printed circuit  42 , to gasket  58  and other portions of shielding can structures  26  and to housing  12 , thereby grounding shielding can structures  26  so that shielding can structures  26  may effectively provide electromagnetic interference shielding. Computer-controlled equipment such as robotic assembly tools may be used in performing the component assembly operations of step  100  and/or manual assembly techniques may be used. 
       FIG. 11  is an exploded perspective view of shielding can structures that include a two-part shielding can. As shown in  FIG. 11 , shielding can  26  includes upper portion  26 A and lower portion  26 B. Upper portion  26 A, which may sometimes be referred to as a lid or top, may have a planar upper surface and vertical peripheral sidewalls. The sidewalls may have notches as shown in  FIG. 11 . Lower portion  26 B, which may sometimes be referred to as a fence or base, may have vertical sidewalls with notches (as an example). Components  22  such as integrated circuits and other electrical devices are mounted on printed circuit  24 . Components  22  are provided with electromagnetic signal interference shielding by installing upper shielding can structure  24 A on lower shielding can structure  26 B to form shielding can  26 . 
     Device  10  includes signal paths for coupling electrical components together. As an example, a signal path may be formed from a flexible printed circuit such as flexible printed circuit cable  102  of  FIG. 11 . Flexible printed circuit cable  102  may be used to carry signals for a component such as electronic component  104 . Component  104  may be a connector that is mounted in connector port  20  of  FIG. 1 . With this type of arrangement, signal lines in printed circuit cable  102  couple control circuitry within device  10  to connector  104 . The signal lines may include data lines, power lines, analog signal lines, and ground lines (e.g., power and/or data ground lines). 
     To ensure satisfactory grounding of component  104 , it may be desirable to short the ground conductors in cable  102  to shielding can portion  26 A. As shown in  FIG. 11 , this may be accomplished by running cable  102  across the top surface of shielding can portion  26 A. Exposed ground traces on the lower surface of cable  102  are shorted to the top of shielding can portion  26 A so that connector  104  is grounded to shielding can  26 . Unlike conventional schemes that short flexible printed circuit ground traces to shielding cans using conductive adhesive that may warp and peel over time, the configuration of  FIG. 11  uses overmolded plastic  106  to attach flexible printed circuit  102  to shielding can  26 . With this approach, cable  102  and shielding can portion (lid)  26 A are embedded within overmolded plastic  106  so that the overmolded plastic covers at least some of cable  102  and at least some of shielding can lid  26 A. 
     Overmolded plastic  106  may, for example, hold conductive ground traces on flexible printed circuit  102  against the exposed upper surface of metal shielding can structures such as metal shielding can portion  26 A (i.e., shielding can lid  26 A may be embedded within conductive plastic  106  so that some of the conductive plastic lies above the upper surface of lid  26 A and so that some of the conductive plastic lies below the opposing lower surface of lid  26 A). Plastic  106  may be formed from an elastomeric material such as silicone or other types of plastic (polycarbonate, etc.). Conductive additives (e.g., metal particles of copper or nickel, nickel graphite powder, etc.) may be incorporated into plastic  106  to enhance the electrical and/or thermal conductivity of plastic  106 , thereby enhancing the ability of plastic  106  to assist in providing electromagnetic signal shielding, signal grounding, and heat dissipation. 
     Plastic  106  attaches flexible printed circuit  102  (e.g., a flexible printed circuit cable with exposed ground traces) to upper shielding can portion  26 A. After plastic  106  has been molded around flexible printed circuit  102  and upper metal shielding can structures  26 A, upper shielding metal can structures  26 A may be attached to lower metal shielding can structures such as lower shielding can portion  26 B to form shielding can  26  over components  22  on printed circuit  24 . 
       FIG. 12  is a diagram of equipment and operations involved in forming shielding can structures of the type shown in  FIG. 11 . As shown in  FIG. 12 , flexible printed circuit  102  is formed from a layer of polymer having metal traces  108  including exposed ground traces  110  on the lower surface of flexible printed circuit  102 . Flexible printed circuit  102  may be placed in contact with upper shielding can portion  26 A so that metal traces  110  contact the upper surface of shielding can structures  26 A. Molding equipment  116  may then mold plastic  106  around flexible printed circuit  102  and upper shielding can structures  26 A, thereby securing flexible printed circuit  102  to upper shielding can metal structures  26 A. 
     Component mounting equipment  112  mounts structures on printed circuit  24  such as components  22  and lower shielding can metal structures  26 B. Component mounting equipment  112  may include equipment for soldering components  22  and lower shielding can portion  26 B to contacts on the surface of printed circuit  24 . For example, component mounting equipment  112  may include pick-and-place equipment and reflow oven equipment for forming solder joints  46 . 
     Assembly equipment  118  may include computer-controlled positioners and other tools for assembling device components. Using assembly equipment  118 , upper shielding can portion  26 A, flexible printed circuit  102 , and overmolded plastic  106  may be attached to lower shielding can portion  26 B to form shielding can structures  26 . Components such as connector  104  may be attached to flexible printed circuit  102  before or after assembly of shielding can structures  26  using equipment  118 . 
     As shown in the lower portion of  FIG. 12 , plastic  106  has lower inner surface  120 . Lower inner surface  120  is preferably configured to rest against upper surfaces  112  of components  22 . When plastic  106  contacts components  22  in this way, heat that is generated by components  22  during operation is transferred away from components  22  through plastic  106 . Plastic  106  therefore forms part of a thermal conduction path that dissipates excess heat from components  22 . Heat flows from components  22  through plastic  106  and through shielding can structures  26  and the other structures of  FIG. 12  to be dissipated into the environment surrounding shielding can structures  26 . If desired, supplemental heat sinking structures (e.g., metal fins that are formed as part of shielding can structures  26  or separate structures) may help dissipate heat. 
       FIG. 13  is a flow chart of illustrative steps involved in forming electronic devices with shielding can structures such as the shielding can structures of  FIG. 12 . 
     At step  124 , molding equipment  116  molds plastic  106  over upper shielding can structures  26 A (e.g., a shield can lid) and signal path structures such as wires, cables, etc. In the illustrative configuration of  FIG. 12 , molding equipment  116  has molded plastic  106  over flexible printed circuit  102 , so that flexible printed circuit traces such as exposed ground traces  110  contact the exposed conductive metal surface of upper metal shielding can structures  26 A. 
     At step  126 , component mounting equipment  112  mounts components  22  and lower shielding can metal structures  26 B to printed circuit  24 . Printed circuit  24  may be a flexible printed circuit formed from a layer of polyimide or other sheet of flexible polymer or may be a rigid printed circuit board formed from a layer of fiberglass-filled epoxy or other rigid printed circuit board material. If desired, components  22  and lower shielding can structures  26 B may be mounted on other substrates such as molded plastic parts, glass substrates, and ceramic substrates. 
     At step  128 , assembly equipment  118  forms shielding can structures  26  by attaching upper shielding can structures  26 A (e.g., a shield lid) to lower shielding can structures  26 B (e.g., a shield fence or other shielding can structures to which a shielding can lid may be attached). Plastic  106  is preferably configured so that lower surface  120  of plastic  106  contacts upper surfaces  122  of components  22  to provide a thermal path that dissipates heat from components  22  during operation of device  10 . Plastic  106  is molded over the signal path structure formed from flexible printed circuit  102  to retain flexible printed circuit  102  in place on shielding can  26 . The placement of flexible printed circuit  102  on upper shielding can structures  26 A shorts the traces in conductive paths  108  of flexible printed circuit  102  to shielding can structures  26 . 
     At step  130 , assembly equipment (e.g., assembly equipment  118  or other computer-controlled equipment) and/or manual assembly techniques may be used in mounting shielding can structures  26  and the structures attached to shielding can structures  26  such as flexible printed circuit  102  and printed circuit  24  to other device components (e.g., housing  12 , display  14 , etc.), thereby forming device  10 . 
     If desired, shielding can structures can be formed using metal parts such as stamped sheet metal members that are joined using conductive bridging structures. This type of arrangement is shown in  FIG. 14 . As shown in  FIG. 14 , shielding can  26  includes multiple shielding can metal structures such as metal shielding can structures  26 - 1  and metal shielding can structures  26 - 2  that are bridged by bridging structures such as bridging structures  132 . In the example of  FIG. 14 , there are two metal shielding can structures ( 26 - 1  and  26 - 2 ) and a single bridging member (bridging member  132 ). This is merely illustrative. Shielding can structures  26  may include two or more metal shielding can structures, three or more metal shielding can structures, or four or more metal shielding can structures. There may be one or more bridging members coupled between the metal shielding can structures. The arrangement of  FIG. 14  in which there are two metal shielding can structures and a single bridging member is merely illustrative. 
     Metal shielding can structures  26 - 1  and  26 - 2  may each be formed from a unitary metal member (e.g., a stamped sheet metal member) or may each be formed from multiple parts (e.g., a lower shielding can structure such as a frame structure or other base and an upper shielding can structure such as a lid). Metal shielding can structures  26 - 1  and  26 - 2  may be metal shielding can members formed from stamped metal that are separated by gaps such as gap  144  of  FIG. 14 . Bridging structures  132  may be coupled between the metal shielding can members across the gap (i.e., bridging structures  132  may span (bridge) the gap between the metal shielding can members). Bridging structures  132  are preferably formed from conductive material such as elastomeric polymer material with conductive filler, flexible structures that include a layer of metal, metal structures (e.g., flexible metal structures), or other conductive structures. Substrate  24  may be bent along bend axis  134 . Metal shielding can structures  26 - 1  and  26 - 2  may be located on opposing sides of the bend in substrate  24 . Bridging structures  132  may overlap the bend. 
     Shielding can structures  26  may form an electromagnetic interference shield that shields electrical components  22  that are mounted within the interior of shielding can structures  26  on substrate  24 . Substrate  24  may be a flexible printed circuit, a rigid printed circuit board, a molded plastic carrier, a glass member, a ceramic structure, or other dielectric substrate. Particularly in configurations in which substrate  24  is formed from a flexible structure such as a flexible printed circuit, it may be desirable to form bridging structures  132  from flexible materials. The use of flexible material in forming bridging structures  132  allows shielding can structures  26  to be bent (e.g., to accommodate mounting on a non-planar substrate that is supported by a non-planar support structure, to help configure shielding can  26  for mounting within the potentially tight confines of an interior space within housing  12 , etc.). 
     In the example of  FIG. 14 , the presence of flexible conductive bridging structures  132  allow shielding can  26  to flex along bend axis  134  when edge  138  of substrate  24  is moved in directions  136  and/or when opposing edge  140  of substrate  24  is moved in directions  142 . 
       FIG. 15  is a cross-sectional side view of the shielding can structures of  FIG. 14  taken along line  148  and viewed in direction  146 . Components  22  and metal shielding can structures  26 - 1  and  26 - 2  (or parts of structures  26 - 1  and  26 - 2  in configurations in which structures  26 - 1  and  26 - 2  are formed from lower and upper portions) are mounted to substrate  24  using solder  46 . As shown in  FIG. 15 , bridging structures  132  may include portions  150  that extend over opposing edges  152  and  154  of respective metal shielding can structures  26 - 1  and  26 - 2 . Bridging structures  132  may be molded into place using molding equipment or may be attached to metal shielding can structures  26 - 1  and  26 - 2  by inserting edges  152  and  154  into slots or other openings formed between portions  150  of bridging structures  132 . If desired, adhesive, fasteners, or other structures may be used in attaching bridging structures  132  to metal shielding can structures. 
     As shown in  FIG. 16 , substrate  24  may be mounted on a curved support structure such as support structure  156 . Support structures  156  may be formed from materials such as plastic or metal. As an example, support structures  156  may form all or part of a component such as a plastic speaker box. Substrate  24  may be bent along curved outer surface  158 . Bridging structures  132  may be formed from a flexible material such as a conductive elastomeric material (e.g., silicone or other elastomeric polymer material with conductive filler). This allows bridging structures  132  (which may sometimes also be referred to as conductive elastomeric structures or flexible conductive structures) to bend about bend axis  134 . As shown in the illustrative configuration of  FIG. 17 , surface  158  may contain a right-angle bend. Substrate  24  and bridging structures  132  may be bent at a right angle about bend axis  134  so that substrate  24  and shielding can structures  26  accommodate the right angle bend formed on surface  158  of non-planar support structures  156 . 
       FIG. 18  is an exploded perspective view of shielding can structures formed from metal shielding can structures  26 - 1  and  26 - 2  that are bridged using conductive elastomeric bridging structures  132 . As shown in  FIG. 18 , printed circuit substrate  24  includes metal traces  30  (e.g., traces for forming grounding contact pads for shielding can structures  26  such as metal shielding can structure  26 - 1  and metal shielding can structure  26 - 2 ). Printed circuit substrate  24  may be formed from a flexible printed circuit substrate material to allow substrate  24  and shielding can structures  26  to be bent, described in connection with  FIGS. 16 and 17 . 
     A perspective view of shielding can structures  26  of  FIG. 18  following attachment of metal shielding can structures  26 - 1  and  26 - 2  to substrate  24  is shown in  FIG. 19 . As shown in  FIG. 19  shielding can structures  26  may have openings such as openings  160  (e.g., openings between sidewall portions of structures  26 , openings under bridging structures  132  and between bridging structures  132  and metal shielding can structures  26 - 1  and  26 - 2 , etc.). For effective electromagnetic shielding, it may be desirable to restrict the maximum lateral dimensions of these openings. For example, the maximum size of the gaps in shielding structures  26  may be less than one tenth of a wavelength at electromagnetic interference frequencies of interest (as an example). 
     Illustrative steps involved in forming shielding can structures of the type described in connection with  FIGS. 14-19  are shown in  FIG. 20 . As step  200 , component mounting equipment (e.g., pick-and-place equipment, solder reflow oven equipment, etc.) can be used to mount electrical components on a substrate such as flexible printed circuit substrate  24 . Metal shielding can structures  26 - 1  and  26 - 2  may also be mounted to substrate  24  during the operations of step  200  or metal shielding can structures  26 - 1  and  26 - 2  may be mounted to substrate  24  at step  202 , following the mounting of components  22  to substrate  24  at step  200 . 
     Bridging structures  132  may be coupled between metal shielding can structures  26 - 1  and  26 - 2  before or after metal shielding can structures  26 - 1  and  26 - 2  are mounted on substrate  24 . If desired, bridging structures  132  may be formed from conductive elastomeric material such as silicone or other elastomeric plastic with conductive filler. In this type of scenario, bridging structures  132  may, during the operations of step  204 , be molded onto metal shielding can structures  26 - 1  and  26 - 2  using plastic molding equipment or may be attached to metal shielding can structures  26 - 1  and  26 - 2  by inserting the edges of the metal shielding can structures into slits in the ends of the bridging structures (as examples). If desired, bridging structures  132  may also be coupled to metal shielding can structures using adhesive (e.g., conductive adhesive), screws or other fasteners, springs or other engagement structures, or other attachment structures. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20121226
Publication Date: 20151117
Grant Date: 20151117
Priority Date: 20121226
Inventors: MALEK SHAYAN
STEPHENS GREGORY N.
WITTENBERG MICHAEL B.
KOLE JARED M.
JONES WARREN Z.
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K3/30", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2224/16227", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10409", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15192", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/16251", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K9/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/10409", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4913", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09063", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4913", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/09063", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10371", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10371", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10409", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K9/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K2201/09063", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4913", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K2201/10371", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K3/30", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K9/0028", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50974401