PATENT DOCUMENT

Publication Number: US-8773310-B2
Application Number: US-75066010-A
Country: US
Kind Code: B2

Title: Methods for forming cavity antennas

Abstract:
An antenna resonating element may be mounted in an antenna cavity. The antenna resonating element may have a printed circuit board substrate with a patterned metal layer. Components may be soldered to the antenna resonating element using solder with a given melting point before soldering the antenna resonating element the antenna cavity using solder with a lower melting point. Solder widow openings may be formed in the antenna resonating element and antenna cavity to allow for application of solder paste. Engagement features and alignment structures may be used to align the antenna resonating element relative to the antenna cavity. The antenna cavity may have a curved opening. The printed circuit board substrate may be bent to the shape of the curved opening before soldering components to the printed circuit board. An elastomeric fixture may be used to hold the antenna resonating element to the cavity during soldering.

Claims:
What is claimed is: 
     
       1. A method for forming a cavity antenna, comprising:
 soldering peripheral edges of an antenna resonating element to a conductive antenna cavity, wherein the conductive antenna cavity comprises a non-planar antenna cavity opening with curved edges and wherein soldering the peripheral edges of the antenna resonating element to the conductive antenna cavity comprises soldering the peripheral edges of the antenna resonating element to the curved edges of the conductive antenna cavity. 
 
     
     
       2. The method defined in  claim 1  wherein the antenna resonating element has an antenna resonating element substrate, the method further comprising soldering an electrical component onto the antenna resonating element substrate. 
     
     
       3. The method defined in  claim 2  wherein soldering the electrical component onto the antenna resonating element substrate comprises soldering the electrical component onto the antenna resonating element substrate at a first temperature and wherein soldering the peripheral edges of the antenna resonating element to the conductive antenna cavity comprises soldering the peripheral edges of the antenna resonating element to the conductive antenna cavity at a second temperature that is lower than the first temperature. 
     
     
       4. The method defined in  claim 1  further comprising holding the antenna resonating element to the antenna cavity with an elastomeric fixture while soldering the peripheral edges of the antenna resonating element to the conductive antenna cavity. 
     
     
       5. The method defined in  claim 4  wherein holding the antenna resonating element to the antenna cavity with the elastomeric fixture comprises holding the antenna resonating element in a non-planar flexed configuration against curved edges of the conductive antenna cavity. 
     
     
       6. A cavity antenna comprising:
 a conductive antenna cavity having conductive walls and a non-planar cavity opening with edges; and 
 an antenna resonating element having a printed circuit board substrate with a layer of patterned metal, wherein the printed circuit board substrate has edges that are soldered to the edges of the non-planar cavity opening. 
 
     
     
       7. The cavity antenna defined in  claim 6  wherein the printed circuit board substrate comprises a flexed non-planar epoxy substrate. 
     
     
       8. The cavity antenna defined in  claim 6  further comprising at least one mounting bracket attached to the conductive antenna cavity. 
     
     
       9. The cavity antenna defined in  claim 6  wherein the edges of the cavity opening and the peripheral edges of the printed circuit board substrate are configured to form a lap joint. 
     
     
       10. The cavity antenna defined in  claim 6  wherein the edges of the cavity opening and the peripheral edges of the printed circuit board substrate are configured to form a joint selected from the group consisting of: a T-joint, a butt joint, and a corner joint. 
     
     
       11. The cavity antenna defined in  claim 6  wherein the antenna resonating element and the antenna cavity have interlocking engagement features. 
     
     
       12. The cavity antenna defined in  claim 6  wherein the antenna resonating element and the antenna cavity have interlocking tooth and groove structures. 
     
     
       13. A method for soldering antenna resonating elements to conductive antenna cavities, comprising:
 holding an antenna resonating element in place in an opening in an antenna cavity using an elastomeric fixture; and 
 while holding the antenna resonating element in place with the elastomeric fixture, soldering the antenna resonating element to the antenna cavity. 
 
     
     
       14. The method defined in  claim 13  further comprising bending the antenna resonating element before soldering a component to the antenna resonating element. 
     
     
       15. The method defined in  claim 14  wherein soldering the antenna resonating element to the antenna cavity comprises melting solder at a first temperature and wherein soldering the component to the antenna resonating element comprises melting solder at a second temperature that is higher than the first temperature. 
     
     
       16. The method defined in  claim 13  further comprising dispensing solder paste onto the antenna resonating element through a hole in the antenna cavity. 
     
     
       17. A cavity antenna comprising:
 a conductive antenna cavity having conductive walls and a cavity opening with edges; 
 an antenna resonating element having a printed circuit board substrate with a layer of patterned metal, wherein the printed circuit board substrate has edges that are soldered to the edges of the cavity opening; and 
 alignment structures on the printed circuit board substrate that are received within the conductive antenna cavity and that align the antenna receiving element relative to the conductive antenna cavity. 
 
     
     
       18. The cavity antenna defined in  claim 17  further comprising solder windows in the conductive antenna cavity at the edges of the cavity opening. 
     
     
       19. The cavity antenna defined in  claim 17 , wherein the alignment structures comprise:
 plastic alignment structures on the printed circuit board substrate that are received within the conductive antenna cavity and that align the antenna receiving element relative to the conductive antenna cavity. 
 
     
     
       20. The cavity antenna defined in  claim 17 , wherein the alignment structures comprise metal alignment clips soldered to the printed circuit board substrate that are received within the conductive antenna cavity and that align the antenna receiving element relative to the conductive antenna cavity.

Description:
BACKGROUND 
     This relates generally to antennas, and more particularly, to cavity antennas and methods for forming cavity antennas. 
     Electronic devices often incorporate wireless communications circuitry. For example, computers may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz. Communications are also possible in cellular telephone telecommunications bands and other wireless bands. 
     To satisfy consumer demand for compact and aesthetically pleasing wireless devices, manufacturers are continually striving to produce antennas with appropriate shapes and small sizes. At the same time, manufacturers are attempting to ensure that antennas operate efficiently and do not interfere with nearby circuitry. These concerns are sometimes at odds with one another. If care is not taken, a small antenna or an antenna with a shape that allows the antenna to fit within a confined device housing may tend to exhibit poor efficiency or generate radio-frequency interference. 
     To satisfy design constraints while taking account of performance and interference concerns, wireless devices such as computers have been provided with cavity antennas. Cavity antennas include an antenna cavity and an antenna resonating element that is mounted in the cavity. The presence of the antenna cavity may help block radio-frequency interference and direct radio-frequency signals in desired directions. However, conventional cavity antennas can be difficult to fabricate and do not always offer desired levels of performance. 
     It would therefore be desirable to be able to provide improved cavity antennas and methods for forming cavity antennas. 
     SUMMARY 
     A cavity antenna may have an antenna resonating element mounted in an opening in an antenna cavity. The antenna resonating element may have an antenna resonating element substrate with a patterned metal layer that forms an antenna slot, an antenna patch, or other antenna resonating element trace patterns. The substrate may be formed from a printed circuit board material such as a thin flexible sheet of fiberglass-filled epoxy. The substrate may be flexed about a flex axis so as to mate with curved edges in the opening of the antenna cavity. 
     Peripheral edges of the antenna resonating element may be provided with a ring of gold or other material that accepts solder. Solder may be used to connect the peripheral edges of the antenna resonating element to the curved edges of the opening of the antenna cavity. 
     The edges of the antenna resonating element and the edges of the opening may be provided with mating engagement features such as tooth-and-groove features. Alignment clips or plastic alignment structures may be attached to the antenna resonating element and used to align the antenna resonating element to the antenna cavity. Solder paste windows may be formed at the edges of the opening to allow solder to be applied. 
     Components such as capacitors, cable connectors, and other electrical components may be soldered to the printed circuit board substrate of the antenna resonating element. To ensure that the printed circuit board substrate can flex properly during subsequent assembly operations, the printed circuit board substrate can be bent into a flexed non-planar shape before the components are soldered to the board. Solder with a lower melting temperature than that used to solder the components may be used to solder the antenna resonating element to the cavity. 
     An elastomeric support structure or other fixture may be used to hold the antenna resonating element to the cavity during soldering. The elastomeric support structure may be formed from a soft material that has a low thermal conductivity and low heat capacity such as silicone. 
     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 with antennas in accordance with an embodiment of the present invention. 
         FIG. 2  is a circuit diagram of an illustrative electronic device with antennas in accordance with an embodiment of the present invention. 
         FIG. 3  is a bottom perspective view of an illustrative antenna in accordance with an embodiment of the present invention. 
         FIG. 4  is an exploded top perspective view of an illustrative antenna in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of a flexible printed circuit substrate on which an antenna resonating element such as a slot antenna resonating element for an electrical device antenna may be formed in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of an illustrative cavity antenna in accordance with an embodiment of the present invention. 
         FIG. 7  is an exploded perspective view of a portion of an antenna resonating element and a corresponding portion of an antenna cavity showing how the antenna resonating element and cavity may be provided with mating engagement features in accordance with an embodiment of the present invention. 
         FIG. 8  is a perspective view of a portion of an antenna resonating element and a corresponding portion of an antenna cavity showing how the antenna resonating element and cavity may be provided with mating features and openings to permit the introduction of solder along the cavity seam during manufacturing in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of an antenna resonating element that has been attached an antenna cavity using a corner joint in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of an antenna resonating element that has been attached an antenna cavity using a T-joint in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional view of an antenna resonating element that has been attached an antenna cavity using a butt joint in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional view of an antenna resonating element that has been attached an antenna cavity using a lap joint in accordance with an embodiment of the present invention. 
         FIG. 13  is a perspective view of a portion of an antenna resonating element showing how a ring of conductive material may be formed around the periphery of the antenna resonating element to short the periphery of the antenna resonating element to the edges of an antenna cavity opening in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional view of a joint between an antenna resonating element and a cavity edge showing how layers of material such as solder may be used in connecting the antenna resonating element to the cavity edge in accordance with an embodiment of the present invention. 
         FIG. 15  is a perspective view of an illustrative antenna resonating element showing how the antenna resonating element may be provided with alignment structures such as metal spring clips in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional end view of an illustrative cavity antenna showing how alignment structures such as the metal clips of  FIG. 15  may be used to orient an antenna resonating element within an antenna cavity for the cavity antenna in accordance with an embodiment of the present invention. 
         FIG. 17  is a perspective view of an illustrative antenna resonating element showing how the antenna resonating element may be provided with alignment structures such as injection molded plastic alignment structures in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional end view of an illustrative cavity antenna showing how alignment structures such as the injection molded plastic alignment structures of  FIG. 17  may be used to orient an antenna resonating element within an antenna cavity for the cavity antenna in accordance with an embodiment of the present invention. 
         FIG. 19  is a perspective view of an illustrative elastomeric fixture that may be used in holding a flexible antenna resonating element to an antenna cavity during fabrication in accordance with an embodiment of the present invention. 
         FIG. 20  shows how a surface mount technology (SMT) pick and place tool may be used to mount components to the substrate of an antenna resonating element in accordance with an embodiment of the present invention. 
         FIG. 21  is a side view of an illustrative roller system that may be used to impart a predetermined curve to an antenna resonating element before performing solder reflow operations in accordance with an embodiment of the present invention. 
         FIG. 22  is a cross-sectional side view of a reflow oven showing how components may be mounted to a pre-flexed antenna resonating element substrate using a solder reflow process performed at a first temperature in accordance with an embodiment of the present invention. 
         FIG. 23  is a side view of an antenna resonating elements showing how solder may be placed in a ring around the periphery of the antenna resonating element in accordance with an embodiment of the present invention. 
         FIG. 24  is a cross-sectional side view of a cavity antenna showing how the antenna resonating element of  FIG. 23  may be mounted to an antenna cavity using a solder reflow process at a second temperature that is lower than the first temperature in accordance with an embodiment of the present invention. 
         FIG. 25  is a cross-sectional side view of a cavity antenna formed using techniques of the types shown in  FIGS. 20 ,  21 ,  22 ,  23 , and  24  in accordance with an embodiment of the present invention. 
         FIG. 26  is an exploded perspective view of a cavity antenna showing how an antenna resonating element for the cavity antenna may be mounted to an antenna cavity using an elastomeric fixture in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Antennas are used in wireless electronic devices to support wireless communications. The wireless electronic devices may be desktop computers, computer monitors, computer monitors containing embedded computers, wireless computer cards, wireless adapters, televisions, set-top boxes, gaming consoles, routers, or other electronic equipment. If desired, portable electronic devices such as laptop computers, tablet computers, or small portable computers of the type that are sometimes referred to as handheld computers may be provided with antennas. Antennas may be used in wireless electronic devices such as cellular telephones or media players. The wireless electronic devices in which the antennas are used may also be somewhat smaller devices. Examples of smaller wireless electronic devices include wrist-watch devices, pendant devices, handheld devices, headphone and earpiece devices, and other wearable and miniature devices. 
     An illustrative electronic device that includes antennas is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may have a housing such as housing  12 . Housing  12  may include plastic walls, metal housing structures, structures formed from carbon-fiber materials or other composites, glass, ceramics, or other suitable materials. Housing  12  may be formed using a single piece of material (e.g., using a unibody configuration) or may be formed from a frame, housing walls, and other individual parts that are assembled to form a completed housing structure. 
     Antennas such as antennas  14  may be mounted within housing  12  (as an example). In general, there may be one antenna, two antennas, or three or more antennas in housing  12 . In the example of  FIG. 1 , there are two antennas in device  10  formed flush with curved walls in housing  12 . This is merely illustrative. 
     Antennas  14  may include an antenna resonating element and, if desired, a cavity structure. In a cavity-type antenna, a resonating element structure is placed adjacent to an opening in a conductive antenna cavity. The presence of the cavity can help prevent radio-frequency interference between the antenna and surrounding electrical components in device  10  and can help direct radio-frequency antenna signals in desired directions. A cavity structure may be used in connection with a patch antenna, a strip antenna, antenna resonating element traces with multiple arms, bends, and other features, or other suitable antenna resonating element structures. With one suitable configuration, which is sometimes described herein as an example, cavity-backed slot antennas are formed in which a slot antenna resonating element is backed by an antenna cavity. This is merely illustrative. In general, any suitable cavity antenna structures may be used in device  10  if desired. 
     As shown in  FIG. 2 , device  10  may include storage and processing circuitry  16 . Storage and processing circuitry  16  may include one or more different types of storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory), volatile memory (e.g., static or dynamic random-access-memory), etc. Storage and processing circuitry  16  may be used in controlling the operation of device  10 . Processing circuitry in circuitry  16  may be based on processors such as microprocessors, microcontrollers, digital signal processors, dedicated processing circuits, power management circuits, audio and video chips, and other suitable integrated circuits. 
     With one suitable arrangement, storage and processing circuitry  16  may be used to run software on device  10 , such as internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, antenna and wireless circuit control functions, etc. Storage and processing circuitry  16  may be used in implementing suitable communications protocols. Communications protocols that may be implemented using storage and processing circuitry  16  include internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, protocols for handling cellular telephone communications services, etc. 
     Input-output devices  18  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Examples of input-output devices  18  that may be used in device  10  include display screens such as touch screens (e.g., liquid crystal displays or organic light-emitting diode displays), buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers and other devices for creating sound, cameras, sensors, etc. A user can control the operation of device  10  by supplying commands through devices  18  or by supplying commands to device  10  through an accessory such as a keyboard or mouse that communicates with device  10  through a wireless or wired communications link. Devices  18  or accessories that are in communication with device  10  through a wired or wireless connection may be used to convey visual or sonic information to the user of device  10 . Device  10  may include connectors for forming data ports (e.g., for attaching external equipment such as computers, accessories, etc.). 
     Wireless communications devices  20  may include communications circuitry such as radio-frequency (RF) transceiver circuitry  22 . Circuitry  22  may include one or more integrated circuits such as baseband processors, radio-frequency transceivers, power amplifiers, matching circuits, filters, and switching circuitry. One or more transmission lines such as transmission lines  24  may be used to route radio-frequency antenna signals between antennas  14  and transceiver circuitry  22 . Transmission lines  24  may include microstrip transmission lines, coaxial cable transmission lines, etc. 
     As shown in  FIG. 1 , device  10  may have a housing with curved sidewalls. To accommodate curved sidewalls or to satisfy other design constraints, it may be desirable to form a cavity-backed antenna with a curved antenna resonating element and a corresponding curved cavity opening.  FIG. 3  shows an illustrative cavity antenna having a curved surface that may be used in a device such as device  10  of  FIG. 1 .  FIG. 3  is a bottom perspective view of cavity antenna  14 . As shown in  FIG. 3 , cavity antenna  14  may have a cavity structure such as cavity  26  and an antenna resonating element such as antenna resonating element  30 . Cavity structure  26  may be formed from metal or other conductive materials, plastic or other dielectric support structures that have been coated with metal or other conductive materials, or other suitable conductive structures. If desired, cavity structure  26  may be formed from first and second pieces. For example, cavity structure  26  may be formed from first and second metal structures that are joined and laser welded at seam  28 . 
     Antenna resonating element  30  may be formed on a substrate such as a printed circuit board that is mounted in an opening in cavity  26 . In  FIG. 3 , cavity  26  is oriented so that its opening faces downward. As shown, cavity  26  may include planar vertical sidewall structures such as sidewalls  26 A,  26 B, and  26 C and planar rear wall  26 D. If desired, cavity  26  may be formed in other shapes (e.g., shapes with horizontally and vertically curved walls, shapes with bends, etc.). The example of  FIG. 3  is merely illustrative. 
       FIG. 4  is an exploded perspective view of antenna  14  of  FIG. 3  in an orientation in which cavity  26  is facing upwards. In this orientation, cavity opening  32  is visible at the top of cavity  26 . Cavity opening  32  has four edges (in the  FIG. 4  example), including curved edges  34  and straight edges  36 . Because edges  34  are curved, opening  32  and other openings of this type are sometimes referred to as curved and non-planar antenna cavity openings. Antenna resonating element  30  may have a curved shape such as a non-planar curved layer that is formed by flexing element  30  about flex axis  33 . As a result, element  30  mates with the curved shape of non-planar opening  32 . This provides antenna  14  with a curved shape that may fit against curved housing walls  12  of device  10 , as shown in  FIG. 1 . 
     Antenna resonating element  30  may be formed from stamped metal foil, wires, traces of copper or other conductive materials that are formed on a dielectric substrate, combinations of these conductive structures, or other suitable conductive structures. The resonating elements may be based on patch antenna designs, inverted-F antenna designs, monopoles, dipoles, slots, antenna coils, planar inverted-F antennas, or other types of antenna. With one suitable arrangement, which is sometimes described herein as an example, antenna resonating element  30  is formed from a layer of metal or other conductive material (sometimes referred to as a ground plane element or ground plane) in which one or more slot antenna structures have been formed. The slot structures may, for example, be defined by rectangular or angled-rectangular openings in the conductive layer. The conductive layer may be formed from one or more copper layers (e.g., patterned copper traces) or other metals (as examples). 
     The conductive portions of antenna resonating element  30  may be formed on a dielectric substrate such as an injection-molded or compression-molded plastic part, on a rigid printed circuit board, or on a substrate formed from rigid and flexible portions (“rigid flex”). Antenna resonating element  30  may also be formed on a flexible printed circuit board that is based on a thin flexible layer of polymer such as a thin flexible sheet of polyimide. If desired, a support structure (e.g., a rigid support or a flexible layer of plastic) may be used to support the thin flexible polyimide sheet. 
     Antenna resonating element  30  may also be formed from rigid printed circuit board materials that have been formed in sufficiently thin layers to render them flexible. For example, antenna resonating element  30  may be formed from a layer of FR-4 (a flame retardant fiberglass-filled epoxy printed circuit board substrate material) that is about 0.09 to 0.2 mm thick, is about 0.05 to 0.3 mm thick, is less than 0.25 mm thick, is less than 0.2 mm thick, is about 0.14 mm thick, or is another suitable thickness that allows antenna resonating element  30  to be flexed to accommodate the shape of non-planar opening  32 . 
     With this type of configuration, element  30  can be both sufficiently flexible to conform to curved opening  32  and sufficiently rigid to hold a desired shape without resting on an additional dielectric support structure (e.g., without using a plastic support in cavity  26 ). Because dielectric support structures can (if desired) be omitted from cavity  26 , cavity  26  can be filled exclusively with air. As a result, there will be no dielectric support under antenna resonating element  30  in the interior of cavity  26 . This may help reduce performance variations that might otherwise arise when placing element  30  adjacent to a dielectric support (e.g., performance variations that might arise from uncertainty in the small separation between the antenna element and the underlying dielectric support). 
       FIG. 5  is a perspective view of an illustrative antenna resonating element. As shown in  FIG. 5 , antenna resonating element  30  may be formed from a substrate such as a rigid or flexible printed circuit board substrate (substrate  38 ). Substrate  38  may contain layers of dielectric and patterned metal (shown schematically as layers  40  in  FIG. 5 ). Components such as component  50  may be formed on the underside of substrate  38  (in the orientation of  FIG. 5 ) and components such as component  44  may be formed on the top side substrate  38  (in the orientation of  FIG. 5 ). Configurations in which components are mounted on only a single side of substrate  38  may also be used. 
     Components  44  and  50  may include electrical components such as surface mount technology (SMT) capacitors, resistors, inductors, switches, filters, radio-frequency connectors (e.g., miniature coaxial cable connectors), cables, clips, or other suitable components. Conductive traces in element  30  (e.g., patterned or blanket metal films on the surfaces of substrate  38  or in layers  40  of substrate  38 ) may be used to interconnect electrical components and to form antenna resonating element structures. Surface traces may be formed on upper surface  42  of antenna resonating element  30  (i.e., the interior surface of antenna resonating element  30  in the orientation of  FIG. 4 ) or may be formed on the lower surface of antenna resonating element  30  (i.e., the exterior surface of antenna resonating element  30  in the orientation of  FIG. 4 ). 
     One or more slots for antenna resonating element  30  such as antenna slot  48  may be formed within the layer of metal or other conductive material on surface  42  (or in layers  40 ). In the example of  FIG. 5 , slot  48  is formed in within metal layer  42  (e.g., a copper layer). Component  44  may be, for example, an SMT capacitor that bridges slot  48 . 
     During assembly, a ring of conductive material such as a ring of solder formed on a ring of gold or other ring of material at the periphery of surface  42  that accepts solder (i.e., ring  46 ) may be used to electrically short and thereby seal the edges of antenna resonating element  30  to edges  34  and  36  of antenna cavity  26  ( FIG. 4 ). Solder ring  46 , which is sometimes referred to as a sealing ring or conductive sealing ring, may surround the periphery of layer  38  and may have a rectangular shape, a shape with curved edges, a shape with angled edges, a shape with combinations of straight and curved edges, etc. 
     A cross-sectional end view of cavity antenna  14  of  FIG. 3  is shown in  FIG. 6 . As shown in  FIG. 6 , a transmission line such as coaxial cable  24  may be used to feed antenna  14 . Transmitted radio-frequency antenna signals may be routed from transceiver circuitry  22  to antenna  14  using cable  24 . During signal reception, received radio-frequency antenna signals may be routed from antenna  14  to transceiver circuitry  22  using cable  24 . Cable  24  (or other transmission line structures in device  10 ) may be coupled to antenna  14  using antenna feed terminals such as positive antenna feed terminal  58  and ground antenna feed terminal  56 . Ground feed  56  may be electrically connected to a conductive outer braid in cable  24  (e.g., a ground path in cable  24 ) using solder or a connector. Positive feed  58  may be connected to positive center wire  54  (e.g., a positive signal path in cable  24 ) using solder or a connector. Antenna feed terminals  56  and  58  may bridge one or more slots such as slot  48  of  FIG. 5 . 
     Alignment brackets (spring clips) such as brackets  52  or other suitable alignment structures (e.g., plastic alignment structures) may be mounted to substrate  38  in antenna resonating element  30  (e.g., using solder, fasteners such as screws, clips, springs, welds, adhesive, etc.). Alignment structures such as brackets  52  may be received within antenna cavity  26  to help to align resonating element  38  with respect to antenna cavity  26  during assembly. If desired, mounting structures such as mounting brackets  60  may be connected to cavity structure  26  (e.g., using welds or other suitable attachment mechanisms). Brackets  60  may be provided with openings such as holes  62 . Screws, heat stakes, alignment posts, or other structures may pass through holes  62  when antenna  14  is mounted within housing  12  of device  10 . 
     It may be desirable to provide antenna resonating element  30  and antenna cavity  26  with mating features. Such features may help align antenna resonating element  30  to cavity  26  during assembly. 
       FIG. 7  shows how antenna resonating element  30  may be provided with engagement features such as recess (groove)  66  and how cavity walls  26  may be provided with mating engagement features such as protrusion (tab)  64 . In the  FIG. 7  example, protrusion  64  and recess  66  have rectangular outlines. This is merely illustrative. Interlocking structures on resonating element  30  and the walls of cavity  26  may, in general, have any suitable shape (e.g., triangular shapes, shapes with curved edges, shapes with combinations of curved and straight edges, etc.). 
       FIG. 8  shows how additional openings such as hole  68  may be formed along the seam between the peripheral edges of antenna resonating element  30  and the corresponding edges of the opening in cavity  26 . Openings such as hole  68  may have rectangular shapes, shapes with curved sides, shapes with combinations of curved and straight sides, etc. During fabrication, solder paste may be inserted along the mating edges of antenna resonating element  30  and the walls of cavity  26 . Ring-shaped structures of gold or other metals that accept solder may be formed along these peripheral edges (e.g., rings on the edges of antenna resonating element  30  and/or on the edges of cavity  26 ). When heat is applied to reflow the solder, the solder will wick along the gold ring and, upon cooling, will form a solder seal along the mating edges of antenna resonating element  30  and the cavity  26 . A solder mask layer may be formed over exposed metal traces on surface  42  of antenna resonating element  30  to ensure that the solder is confined to the seal region. There may, in general, be any suitable number of engagement structures such as engagements structures  64  and  66  and any suitable number of solder windows such as openings  68  (e.g., 1-20, 10-50, or more than 30). 
     The edges of antenna resonating element  30  may be connected to the edges of the opening in antenna cavity  26  using a corner joint (e.g., a corner joint of the type shown in  FIG. 9 ), a T-joint (e.g., a T-joint of the type shown in  FIG. 10 ), a butt joint (e.g., a butt joint of the type shown in  FIG. 11 ), a lap joint (e.g., a lap joint of the type shown in  FIG. 12 ), or other suitable joints. As shown in  FIGS. 9 ,  10 ,  11 , and  12 , solder  70  or other suitable conductive materials may be used in connecting the resonating element edges and the cavity opening edges along these joints. There may, if desired, be an overlap between the solder and its underlying metal ring on element  30  and the mating surface of the edge of cavity  26 . For example, the solder ring may have a width of about 0.7 mm and the edge of the cavity wall may have a width of about 0.2 mm (as an example). 
       FIG. 13  shows a peripheral ring of material such as gold  72  or other solder-attracting materials may be used to promote adhesion of solder  70  to member  74  (e.g., to promote adhesion of solder  70  to the edges of antenna resonating element  30  and/or to the edges of the cavity opening in cavity  26 ). Gold structures  72  may be deposited and patterned on the surface of member  74  using chemical vapor deposition, physical layer deposition, electrochemical deposition, using shadow masking, photolithography, screen printing, pad printing, painting, spraying, ink-jet printing, or other suitable techniques. Member  74  may be formed from a conductive material (e.g., when forming metal can walls for cavity  26 ) or from a conductive layer that is formed on a dielectric substrate (e.g., a layer of copper on a dielectric substrate for antenna resonating element  30 ). 
       FIG. 14  shows a cross-sectional view of a portion of cavity antenna  14  showing how antenna resonating element  30  may include one or more conductive layers such as a layer of metal (e.g., metal layer  42 ) on a substrate such as substrate  38 . Metal layer  42  may be a patterned layer of copper (as an example). The pattern of layer  42  may have an opening that defines a slot for a slot antenna resonating element or may have other suitable antenna resonating element shapes (e.g., inverted-F antenna shapes, patch antenna shapes, strip antenna shapes for monopole antennas, dipole antennas, and loop antennas, etc.). Electrical components such as capacitors, inductors, and resistors may be connected to the pattern of antenna traces that are formed layer  42  on substrate  38  (e.g., to tune antenna  14 ). 
     Substrate  38  may be formed from a dielectric such as plastic or a printed circuit board substrate material. For example, substrate  38  may be formed from a flexible printed circuit board substrate such as a substrate formed from a flexible sheet of polymer (e.g., polyimide) or a flexible sheet of fiberglass-filled epoxy (e.g., FR-4). 
     As described in connection with  FIG. 4 , use of a flexible structure for the substrate of antenna resonating element  30  allows element  30  to be flexed about a flex axis such as flex axis  33 . This permits antenna resonating element  30  to bend and form the shape of a non-planar curved layer that that mates with the curved non-planar opening of the antenna cavity. By using a flexible substrate that is sufficiently rigid to support the traces of the antenna resonating element (e.g., patterned metal layer  42 ), the need for underlying dielectric support structures can be reduced or eliminated. 
     As shown in  FIG. 14 , gold ring structure  72  (or other suitable pattern of metal that is placed around the peripheral edges of antenna resonating element  30 ) may be coated with solder  70  and thereby attached to cavity  26 . 
       FIG. 15  is a perspective view of an illustrative antenna resonating element. As shown in  FIG. 15 , antenna resonating element  30  may be formed from a patterned layer of metal such as layer  42  on substrate  38  (e.g., a layer of flexible FR-4). To facilitate mounting of antenna resonating element  30  in cavity  26  during fabrication of antenna  14 , antenna  14  may be provided with alignment structures. The alignment structures may, for example, be implemented using metal parts such as metal spring clips, molded plastic parts, parts attached to cavity  26 , parts attached to antenna resonating element  30 , interlocking structures on both antenna resonating element  30  and cavity  26  (see, e.g., the interlocking structures  64  and  66  of FIG.  8 ), etc. With the illustrative arrangement shown in  FIG. 15 , metal clips  52  have been attached to the substrate of antenna resonating element  38  (e.g., using solder, fasteners, adhesive, or other suitable attachment mechanisms). 
       FIG. 16  shows a cross-sectional end view of antenna resonating element  14  in which an antenna resonating element with spring clips  52  has been mounted. Spring clips  52  or such other alignment structures may be provided with base portions  76  that are attached to antenna resonating element substrate  38  using solder  70  and curved portions such as curved portions  78 . During assembly, curved portions  78  may help guide structures  52  into the interior portions of antenna cavity  26  and thereby align antenna resonating element  30  to cavity  26 . 
     In the illustrative arrangement of  FIG. 17 , alignment structures  52  have been implemented using a polymer ring that runs along the peripheral edge of antenna resonating element  38 . Alignment structure  52  of  FIG. 17  may be formed by insert molding (as an example). When inserted into cavity  26  as shown in  FIG. 18 , the outermost edges of alignment structure  52  may be used to guide antenna resonating element  30  into cavity  26 , as described in connection with spring clips  52  of  FIG. 16 . 
     Particularly when antenna resonating element  30  is formed from a flexible substrate material (e.g., when substrate  38  is a thin layer of flexible FR-4), it may be desirable to use a fixture to hold antenna resonating element substrate  38  and element  30  in place on cavity  26  during solder reflow operations. Any suitable fixture may be used to hold antenna resonating element  30  in place with respect to cavity  26 . For example, a metal fixture or a fixture formed of glass, ceramic, or rigid plastic may be used. 
     With one suitable arrangement, which is sometimes described herein as an example, an elastomeric fixture may be used to hold antenna resonating element  30  in place during at least some of the solder reflow operations used in constructing antenna  14 . An elastomeric fixture may exhibit a relatively low heat capacity and low thermal conductivity. This use of this type of fixture may help to prevent situations from arising in which too much heat is applied to the antenna resonating element during reflow operations, which could cause the layers of printed circuit board substrate  38  and antenna resonating element  30  to delaminate. An example of an elastomer that has a suitably low heat capacity and thermal conductivity is silicone. Other types of rubbery substances may be used if desired. The use of silicone and other materials that exhibit elasticity may help the fixture comply with small irregularities in the sizes of the components, thereby minimizing the possibility that gaps might be formed along the seam between antenna resonating element  30  and cavity  26 . 
     An illustrative elastomeric fixture that may be used to hold elongated antenna resonating elements of the types shown in  FIGS. 15 and 17  in place within antenna cavity  26  is shown in  FIG. 19 . As shown in  FIG. 19 , antenna assembly fixture  86  may have a main body portion such as main body portion  80  with optional guiding members  82 . Guiding members  82  may be formed at discrete locations around the periphery of member  80  or may be formed in a ring shape. The guiding structures may mate with the outer surfaces of cavity  26  and may hold antenna resonating element  30  within central region  84  during assembly operations. 
       FIGS. 20 ,  21 ,  22 ,  23 ,  24 , and  25  show illustrative equipment and operations involved in assembling antenna  14 . As shown in  FIG. 20 , pick and place tool  92  may be used to mount components such as component  90  (e.g., a capacitor or other antenna tuning element) to printed circuit board substrate  38 . Solder paste  88  may be patterned on the surface of substrate  38  prior to placing component  90  in substrate  38 . Pick and place tool  92  may have a computerized control stage such as stage  94  that moves head  96  and component  90 . Solder paste  88  is sticky and therefore retains components such as component  90  that have been placed on substrate  38 . 
     To ensure that components such as components  90  do not disrupt the smooth curved shape into which antenna resonating element  30  is formed when mounted to antenna cavity opening  32  ( FIG. 4 ), it may be desirable to bend substrate  38  before performing solder reflow operations. Antenna resonating element substrate  38  may, for example, be bent using a fixture, manual bending, etc. As shown in  FIG. 21 , antenna resonating element substrate  38  may be bent by passing substrate  38  through a set of rollers such as rollers  98 . When flexed as shown on the right hand side of  FIG. 21 , the points of contact between the leads of component  90  and the surface of substrate  38  will be slightly closer together on surface  38  than when substrate  38  is in the unflexed position. 
     Following the flexing operations shown in  FIG. 21 , substrate  38  may be placed in a solder reflow oven (e.g., oven  102  of  FIG. 22 ) or may otherwise be heated to solder melting temperature T 1  (e.g., using a heated fixture, a source of heated air, infrared heat lamps, etc.). Temperature T 1  is sufficiently large to convert solder paste  88  into solder and thereby attach components such as component  90  to substrate  38 . A curved fixture such as fixture  100  may be used to maintain substrate  38  in its curved shape during these solder reflow operations. Because substrate  38  is curved during the process of attaching components to substrate  38 , the attached components will not cause substrate  38  to buckle or exhibit undesired flat portions which might otherwise be formed if the substrate were bent only after components were soldered in place. 
     After soldering components  90  to substrate  38  at temperature T 1 , substrate  38  may be soldered to antenna cavity  26 . To ensure that the components that have already been attached to substrate  38  do not become detached when soldering antenna resonating element substrate  38  to cavity  26 , the solder paste that is used in soldering antenna resonating element  30  to cavity  26  (i.e., solder  70 ) may have a lower melting temperature than the solder of paste  88 . 
     The solder that is used to seal antenna resonating element  30  to antenna cavity  26  may be applied to antenna resonating element  30  and cavity  26  using equipment of the type shown in  FIG. 23 . As shown in  FIG. 23 , solder paste may be stored in a reservoir such as reservoir  104 . Air pump  110  may pressurize reservoir  104  via hose  112 . The pressurized solder paste is applied to substrate  38  (as solder paste  70 ) using needle  106 . Computer-controlled positioning stage  108  may be used to accurately control the position of needle  106  relative to the workpiece. In the arrangement shown in  FIG. 23 , solder paste  70  is being applied to the edges of substrate  38  before substrate  38  is attached to cavity  26 . This is merely illustrative. If desired, solder paste  70  may be applied after substrate  38  is attached to cavity opening  32  (e.g., by using the solder dispensing equipment of  FIG. 23  to apply solder paste through solder windows such as window  68  of  FIG. 8 ). Solder paste may also be applied to the edges of antenna cavity opening  32  and combinations of these approaches may be used. 
     As shown in  FIG. 24 , antenna resonating element  30  may be mounted to cavity  26  while heat is applied to raise the temperature to solder temperature T 2 . Heat may be applied using oven  113 , or other suitable heating apparatus. Solder paste  70  melts at a lower temperature than solder paste  88 , so temperature T 2  may be lower than temperature T 1 . As a result, solder  88  remains solid while solder  70  is being melted to seal antenna resonating element  30  to antenna cavity  26 . To ensure that antenna resonating element  30  is well sealed and to ensure that there are no gaps between antenna resonating element substrate  38  and the edges of antenna cavity opening  32 , elastomeric fixture  86  may be used to hold antenna resonating element substrate  38  in place against antenna cavity  26  as shown in  FIG. 24 . Rubber bands  114  or other biasing structures may be used to hold antenna resonating element substrate  38  in place while forming the seal of solder  70  around the periphery of antenna resonating element substrate  38 . After soldering at temperature T 2  is complete, antenna  14  appears as shown in  FIG. 25  (i.e., with fixture  86  removed). If desired, fixture  86  of  FIG. 24  may be used during the solder melting operations shown in  FIG. 22 . 
     Antenna  14  may be formed from cavities of other shapes. A cavity with angled sidewalls is shown in  FIG. 26 . As shown in  FIG. 26 , an angled version of elastomeric fixture  86  with an angled recessed portion  84  formed by a peripheral raised ring may be used to hold angled antenna resonating element  30  in place within angled can  26 . Mounting brackets  60  may be provided with holes  62  to attach antenna  14  to housing  12  of device  10 . Opening  32  may be curved (i.e., the edges of antenna cavity  26  may be curved to mate with antenna resonating element  30  when antenna resonating element  30  is flexed into a curved non-planar shape). Antenna resonating element  30  may also be formed using planar substrates (e.g., using rigid printed circuit boards). Elastomeric fixtures such as fixture  86  may be used in mounting both rigid and flexible antenna resonating elements to antenna cavities. 
     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. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20100330
Publication Date: 20140708
Grant Date: 20140708
Priority Date: 20100330
Inventors: SHIU SAM
SCHLUB ROBERT W.
CABALLERO RUBEN
Assignee: APPLE INC
CPC Classifications: [{"code": "B23K1/0016", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K1/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "B23K1/0016", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K1/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K33/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q13/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "B23K33/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01Q9/04", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 44709011