PATENT DOCUMENT

Publication Number: US-8742997-B2
Application Number: US-201113111926-A
Country: US
Kind Code: B2

Title: Testing system with electrically coupled and wirelessly coupled probes

Abstract:
Conductive electronic device structures such as a conductive housing member that forms part of an antenna may be tested during manufacturing. A test system may be provided that has a pair of pins or other contacts. Test equipment such as a network analyzer may provide radio-frequency test signals in a range of frequencies. The radio-frequency test signals may be applied to the conductive housing member or other conductive structures under test using the test probe contacts. An antenna may be used to gather corresponding wireless radio-frequency signal data. Forward transfer coefficient data may be computed from the transmitted and received radio-frequency signals. The forward transfer coefficient data or other test data may be compared to reference data to determine whether the conductive electronic device structures contain a fault.

Claims:
What is claimed is: 
     
       1. A method for testing conductive electronic device housing structures using test equipment that includes an associated test probe with test probe contacts and that includes an associated antenna, comprising:
 placing the test probe contacts into contact with the conductive electronic device housing structures; 
 while the test probe contacts are in contact with the conductive electronic device housing structures, conveying radio-frequency test signals through the test probe contacts to test the conductive electronic device housing structures; and 
 with the antenna, wirelessly receiving corresponding wireless test signals while the radio-frequency test signals are being conveyed through the test probe contacts. 
 
     
     
       2. The method defined in  claim 1  wherein the conductive electronic device housing structures comprise a peripheral conductive housing member having a gap and wherein conveying the radio-frequency test signals comprises transmitting radio-frequency test signals to the peripheral conductive housing member through the test probe contacts. 
     
     
       3. The method defined in  claim 1  wherein the conductive electronic device housing structures comprise at least part of an electronic device antenna structure and wherein conveying the radio-frequency test signals comprises transmitting radio-frequency test signals through the part of the electronic antenna structure using the test probe contacts. 
     
     
       4. The method defined in  claim 1  wherein conveying the radio-frequency test signals comprises:
 transmitting the radio-frequency test signals from the test equipment to the conductive electronic device housing structures through the test probe contacts; and 
 receiving the radio-frequency test signals at the test equipment from the conductive electronic device housing structures through the antenna. 
 
     
     
       5. The method defined in  claim 4  further comprising:
 with the test equipment, computing a forward transfer coefficient from the transmitted and received radio-frequency test signals. 
 
     
     
       6. The method defined in  claim 5  wherein computing the forward transfer coefficient comprises computing a forward transfer coefficient over a frequency range that includes at least some frequencies in the range of 3.5 to 5 GHz. 
     
     
       7. The method defined in  claim 2 , wherein the test probe contacts comprise first and second contacts, wherein placing the test probe contacts into contact with the conductive electronic device housing structures comprises connecting the first and second contacts to respective portions of the peripheral conductive housing member on opposing sides of the gap. 
     
     
       8. The method defined in  claim 5  further comprising:
 with the test equipment, comparing the forward transfer coefficient to reference forward transfer coefficient data to determine whether the conductive electronic device housing structures contain a fault. 
 
     
     
       9. The method defined in  claim 1  further comprising:
 with network analyzer equipment in the test equipment that is coupled to the antenna, receiving the wireless test signals corresponding to the conveyed radio-frequency test signals from the antenna. 
 
     
     
       10. The method defined in  claim 9 , wherein conveying the radio-frequency test signals comprises using the network analyzer to transmit the radio-frequency test signals. 
     
     
       11. The method defined in  claim 1 , further comprising:
 with the test equipment, using at least the received wireless test signals to determine whether the conductive electronic device housing structures contain a fault.

Description:
BACKGROUND 
     This relates generally to testing, and more particularly, to testing electronic device structures for manufacturing faults. 
     Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry and short-range wireless communications circuitry such as wireless local area network circuitry. 
     In some devices, conductive housing structures may form part of an electronic device antenna. The performance of this type of antenna may depend on how accurately the conductive housing structures are manufactured. Excessive variations in the size and shape of conductive electronic device housing structures or other manufacturing variations may have a negative impact on the performance of antennas formed using the structures. Variations in conductive electronic device structures of other types may also impact device performance. 
     It would be desirable to be able to provide ways to test electronic device structures such as conductive electronic device structures that form parts of antennas and other structures. 
     SUMMARY 
     Electronic devices may include conductive structures such as conductive housing structures. Conductive electronic device housing structures may form part of an antenna or other structures. 
     To ensure that conductive electronic device structures have been fabricated properly, conductive electronic device structures may be tested during manufacturing. A test system may be provided that has a test probe with pins or other contacts and an antenna that serves as a wireless test probe. 
     Test equipment such as a network analyzer may provide radio-frequency test signals in a range of frequencies. The radio-frequency test signals may be applied to the conductive housing member or other conductive structures under test using the test probe contacts. The antenna may be used to gather corresponding wireless radio-frequency data. 
     Forward transfer coefficient data may be computed from the transmitted and received radio-frequency signals. The forward transfer coefficient data or other test data may be compared to reference data to determine whether the conductive electronic device structures contain a fault. 
     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 of the type that may include conductive housing structures that may be tested in accordance with an embodiment of the present invention. 
         FIG. 2  is a top view of an illustrative electronic device of the type shown in  FIG. 1  showing the locations of gaps in a peripheral conductive housing member and the locations of possible antennas within the electronic device in accordance with an embodiment of the present invention. 
         FIG. 3  is a side view of a test system showing how an electronic device structure such as a peripheral conductive housing member with a gap may be tested using an electrically connected probe and an antenna in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of an illustrative loop antenna that may be used in implementing the antenna of the test system of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagram of an illustrative test system having a test chamber in which electronic device structures under test may be tested using electrically coupled and wirelessly coupled probes in accordance with an embodiment of the present invention. 
         FIG. 6  is an exploded perspective view of illustrative electronic device structures under test in a test system in accordance with an embodiment of the present invention. 
         FIG. 7  is an exploded perspective view of an illustrative test fixture in accordance with an embodiment of the present invention. 
         FIG. 8  is a perspective view of an illustrative test system having the test fixture of  FIG. 7  and an antenna test fixture in accordance with an embodiment of the present invention. 
         FIG. 9  is a graph in which forward transfer coefficient magnitude data that has been gathered using a test system of the type shown in  FIG. 5  has been plotted as a function of applied signal frequency in accordance with an embodiment of the present invention. 
         FIG. 10  is a graph in which forward transfer coefficient phase data that has been gathered using a test system of the type shown in  FIG. 5  has been plotted as a function of applied signal frequency in accordance with an embodiment of the present invention. 
         FIG. 11  is a flow chart of illustrative steps involved in using a test system of the type shown in  FIG. 5  in testing electronic device structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with wireless communications circuitry such as antennas and associated transceiver circuits. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include one or more antennas. 
     The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. The conductive electronic device structures may include conductive housing structures. The housing structures may include a peripheral conductive member that runs around the periphery of an electronic device. The peripheral conductive member may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, or may form other housing structures. Gaps in the peripheral conductive member may be associated with the antennas. 
     The size of the gaps and the presence or absence of manufacturing artifacts such as metal burrs or other unintended conductive structures in the gaps that are produced during manufacturing can influence the electrical properties of the antennas that are formed using the peripheral conductive housing members. To ensure that the gaps are formed appropriately, it may be desirable to electrically test the peripheral conductive housing member during manufacturing. The electrical test measurements may reveal undesired manufacturing variations in the gaps. Other conductive electronic device structures may also be tested in this way if desired. 
     A typical test setup used to detect such types of manufacturing defects involves passive antenna testing. During passive antenna testing, the antenna is energized using an input signal, the reflection of which is measured to obtain a reflection coefficient (S11). Simply monitoring S11 may not sufficiently characterize the antenna because no radiated signal from the antenna is measured. There are some defects which cause a drop in antenna efficiency without a corresponding or measurable change to the antenna input impedance. In these cases, only a radiated test is capable of detecting such variations. Such a measurement requires a second port connected to the test antenna that samples signals radiated from the antenna structures under test. 
     An illustrative electronic device of the type that may be provided with conductive electronic device structures such as a peripheral conductive housing member that forms part of one or more antennas is shown in  FIG. 1 . Electronic device  10  may be a portable electronic device or other suitable electronic device. For example, electronic device  10  may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, a media player, etc. 
     Device  10  may include a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing  12  may be formed from dielectric or other low-conductivity material. In other situations, housing  12  or at least some of the structures that make up housing  12  may be formed from metal elements. 
     Device  10  may, if desired, have a display such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass layer may cover the surface of display  14 . Buttons such as button  19  may pass through openings in the cover glass. 
     Housing  12  may include structures such as housing member  16 . Member  16  may run around the rectangular periphery of device  10  and display  14 . Member  16  or part of member  16  may serve as a bezel for display  14  (e.g., a cosmetic trim that surrounds all four sides of display  14  and/or helps hold display  14  to device  10 ). Member  16  may also, if desired, form sidewall structures for device  10 . 
     Member  16  may be formed of a conductive material and may therefore sometimes be referred to as a peripheral conductive housing member or conductive housing structures. Member  16  may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming member  16 . 
     It is not necessary for member  16  to have a uniform cross-section. For example, the top portion of member  16  may, if desired, have an inwardly protruding lip that helps hold display  14  in place. If desired, the bottom portion of member  16  may also have an enlarged lip (e.g., in the plane of the rear surface of device  10 ). In the example of  FIG. 1 , member  16  has substantially straight vertical sidewalls. This is merely illustrative. The sidewalls of member  16  may be curved or may have any other suitable shape. In some configurations (e.g., when member  16  serves as a bezel for display  14 ), member  16  may run around the lip of housing  12  (i.e., member  16  may cover only the edge of housing  12  that surrounds display  14  and not the rear edge of the sidewalls of housing  12 ). 
     Display  14  may include conductive structures such as an array of capacitive electrodes, conductive lines for addressing pixel elements, driver circuits, etc. Housing  12  may include internal structures such as metal frame members, a planar housing member (sometimes referred to as a midplate) that spans the walls of housing  12  (i.e., a sheet metal structure that is welded or otherwise connected between the opposing right and left sides of member  16 ), printed circuit boards, and other internal conductive structures. These conductive structures may be located in center of housing  12  (as an example). 
     In regions  20  and  22 , openings may be formed between the conductive housing structures and conductive electrical components that make up device  10 . These openings may be filled with air, plastic, and other dielectrics. Conductive housing structures and other conductive structures in device  10  may serve as a ground plane for the antennas in device  10 . The openings in regions  20  and  22  may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, or may otherwise serve as part of antenna structures formed in regions  20  and  22 . 
     Portions of member  16  may be provided with gap structures  18 . Gaps  18  may be filled with dielectric such as polymer, ceramic, glass, etc. Gaps  18  may divide member  16  into one or more peripheral conductive member segments. There may be, for example, two segments of member  16  (e.g., in an arrangement with two gaps), three segments of member  16  (e.g., in an arrangement with three gaps), four segments of member  16  (e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive member  16  that are formed in this way may form parts of antennas in device  10 . 
     A top view of an interior portion of device  10  is shown in  FIG. 2 . If desired, device  10  may have upper and lower antennas (as an example). An upper antenna such as antenna  40 U may, for example, be formed at the upper end of device  10  in region  22 . A lower antenna such as antenna  40 L may, for example, be formed at the lower end of device  10  in region  20 . The antennas may be used separately to cover separate communications bands of interest or may be used together to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme. 
     Antenna  40 L may be formed from the portions of midplate  58  and peripheral conductive housing member  16  that surround dielectric-filled opening  56 . Antenna  40 L may be fed by transmission line  50 , which is coupled to positive feed terminal  54  and ground feed terminal  52 . Other feed arrangements may be used if desired. The arrangement of  FIG. 2  is merely illustrative. 
     Antenna  40 U may be formed from the portions of midplate  58  and peripheral conductive housing member  16  that surround dielectric-filled opening  60 . Member  16  may have a low-band segment LBA that terminates at one of gaps  18  and a high-band segment HBA that terminates at another one of gaps  18 . Antenna  40 U may be fed using transmission line  62 . Transmission line  62  may be coupled to positive antenna feed terminal  66  and ground antenna feed terminal  64  (as an example). Conductive member  68  may span opening  60  to form an inverted-F antenna short-circuit path. Segments LBA and HBA may form low-band and high-band cellular telephone inverted-F antennas (as an example). 
     Gaps  18  separate respective portions of peripheral conductive housing member  16 . Due to manufacturing variations, the structures associated with gaps  18  may not always be perfect. For example, during machining operations, small conductive filaments (metal burrs) may be produced within gap  18 . These burrs may adversely affect antenna operation (e.g., by giving rise to inductances or other parasitic electrical characteristics that detune the antenna and/or reduce antenna efficiency at desired frequencies of operation). 
     The metal burrs in gaps  18  may be too small to reliably detect using visual inspection. As a result, the metal burrs may not be noticed before gaps  18  are filled with plastic. After gaps  18  have been filled with a dielectric such as plastic, it may be impossible to visually detect the presence of the burrs. 
     Conventionally, wireless over-the-air communications testing on completed devices such as device  10  may reveal the presence of wireless performance problems, but may not reveal whether or not these problems are due to burrs or other manufacturing defects and may not detect these problems at a sufficiently early stage in the manufacturing process. 
     A test system of the type that may be used in testing electronic device structures such as peripheral conductive housing member  16  at a potentially earlier stage in the assembly process is shown in  FIG. 3 . As shown in  FIG. 3 , test system  94  may include test equipment  96  for testing device structures under test  98 . Device structures under test  98  may include conductive electronic device housing structures such as peripheral conductive housing member  16  and other conductive electronic device structures. As described in connection with  FIGS. 1 and 2 , the conductive electronic device structures may form part of one or more antennas in device  10 . 
     Test equipment  96  may include wired test probe  76  and wireless probe  86 . Probe  76  may have a body such as probe structure  80  and associated electrical contacts  78 . Probe structure  80  may have a radio-frequency connector or other interface with which probe structure  80  can be coupled to radio-frequency transmission line path  82 . Path  82  may be implemented using a coaxial cable or other transmission line structure and may be coupled to test equipment  84 . Contacts  78  may be spring-loaded pins, metal pads on a flexible printed circuit (“flex circuit”) substrate or other dielectric substrate, springs, or other conductive contact structures. For example, test probe  76  may be a pogo-pin test probe that includes first and second electrical contacts  78  operable to make contact with feed terminal points  64  and  66 , respectively, or other regions of the antenna structures under test (e.g., other points along conductive member  16 , midplate  58 , conductive path  68 , etc.). 
     Wireless probe  86  may be formed from one or more antennas, so probe  86  may sometimes be referred to herein as a test system antenna. Antenna  86  may be coupled to test equipment  84  by radio-frequency path  24 . Path  24  may be formed from a coaxial cable or other transmission line structure. Antenna test probe  86  may be implemented using any suitable antenna type (e.g., loop antennas, patch antennas, dipole antennas, monopole antennas, inverted-F antennas, planar inverted-F antennas, coil antennas, open-ended waveguides, horn antennas, etc.). 
     Test equipment  84  may include a network analyzer (e.g., a vector network analyzer) and one or more computers or other computing equipment. The network analyzer or other test equipment may be used to generate test signals over a desired range of frequencies. For example, the network analyzer may be used to generate test signals in a frequency range of 0 to 5 GHz (as an example). Other frequency ranges may be used in testing device structures under test  98  if desired (e.g., a frequency range of 4 to 5 GHz, a frequency range of 3 to 5 GHz, a frequency range with a size of more or less than 5 GHz starting at a frequency below or above 5 GHz), etc. 
     The test signals that are generated by test equipment  84  may be applied to device structures under test  98  using test probe  76 . In particular, radio-frequency test signals from test equipment  84  may be conveyed to probe  76  via path  82 . Path  82  may include a positive conductor that is coupled to a first of contacts  78  and a ground conductor that is coupled to a second of contacts  78 . In the illustrative arrangement of  FIG. 3 , the left-hand probe contact is contacting to the left-hand segment of peripheral conductive housing member  16  and the right-hand probe contact is contacting the right-hand segment of peripheral conductive housing member  16 . In other configurations, contacts  78  may be coupled to other portions of a conductive electronic device structure. The configuration of  FIG. 3  is merely illustrative. 
     As shown in  FIG. 3 , gap  18  may be filled with a dielectric such as dielectric  90 . Dielectric  90  may be a polymer, glass, ceramic, or other suitable dielectric materials. Structures such as conductive filament  70  (e.g., a metal burr) may sometimes be formed within gap  18  as an side effect of a machining process or other manufacturing process (molding, stamping, welding, etc.) that is used in forming and shaping peripheral conductive housing member  16  and gap  18 . The presence of manufacturing faults such as burr  70  may be detected by using a wireless probe such as antenna  86  to wirelessly monitor electromagnetic radio-frequency signals  88  that are emitted by device structures under test  98  while test equipment  84  is driving test signals from probe  76  into device structures under test  98 . Antenna  86  can convey these measured electromagnetic signals to test equipment  84  (e.g., the network analyzer in equipment  84 ) via path  94  (e.g., a coaxial cable or other transmission line). 
     Antenna probe  86  may be formed from any suitable type of antenna (e.g., a loop antenna, an inverted-F antenna, a strip antenna, a planar inverted-F antenna, a slot antenna, a monopole, a dipole, a patch antenna, a hybrid antenna that includes antenna structures of more than one type, or other suitable antennas).  FIG. 4  is a top view of an illustrative loop antenna that may be used to form antenna probe  86 . As shown in  FIG. 4 , antenna  86  may include a substrate such as substrate  356 . Substrate  356  may be formed from a dielectric such as plastic, may be formed from a rigid printed circuit board substrate such as fiberglass-filled epoxy, may be formed from a flexible printed circuit (“flex circuit”) substrate such as a sheet of polyimide, or may be formed from other dielectric substrate materials. Conductive traces such as conductive metal traces may be used to form antenna structures on substrate  356 . 
     In the example of  FIG. 4 , conductive traces  370  on substrate  356  have been used to form a loop antenna. Coaxial cable  24  (or other transmission line) may have a positive conductor coupled to positive antenna feed terminal  376  and a ground conductor coupled to ground antenna feed terminal  378 . Positive antenna feed terminal  376  is coupled to upper conductive trace  370 . Via  374  couples upper trace  370  to lower trace  372  (e.g., a trace on an opposing surface of a printed circuit board substrate or in a different layer of substrate  356 ). After looping around the periphery of substrate  356  lower trace  372  may be connected to ground feed terminal  378  by a via structure. The illustrative loop antenna of  FIG. 4  uses two loops (upper and lower), but additional loops (e.g., three or more loops) or fewer loops (e.g., a single loop) may be used in wireless probe  86  if desired. 
     As shown in  FIG. 5 , test equipment  96  and device structures under test  98  may be mounted in an optional test chamber. Test chamber  200  may have radio-opaque walls (e.g., metal walls) to reduce electromagnetic interference. 
     Device structures under test  98  may, if desired, be mounted in a test fixture such as test fixture  206 . Test fixture  206  may be formed from a dielectric such as plastic and may include a lower test fixture portion such as base  210  and an upper test fixture portion such as cover  208 . Contact probe  76  and its contacts  78  may be mounted in an opening in upper fixture  208  (as an example). When device structures under test are mounted in fixture  206 , conductive portions of the device structures such as segments of peripheral conductive member  16  on opposing sides of gap  18  may be contacted by respective contacts  78 . Connectors such as mating connectors  204  and  202  may be used in coupling cable  82  to probe  76 . Antenna  86  may be mounted on or near to lower fixture portion  210 . Cables  82  and  24  may be respectively used to couple probes  76  and  86  to network analyzer  212 . Test equipment  84  may include one or more computers or other computing equipment  214  coupled to network analyzer  212  for gathering and processing data from network analyzer  212 . Computing equipment  214  may, if desired, include input-output devices such as keyboards, mice, and displays, for gathering input from an operator of the test system and for displaying alerts and other information to the operator. Network analyzer  212  may also include input-output components such as a display, keypad, keys, etc. 
     Using test system  94 , test equipment  84  (e.g., network analyzer  212 ) may produce radio-frequency test signals that are applied to device structures under test  98  using cable  82 , connectors  202  and  204 , and probe  76 . Even without being connected to other components to form a completed antenna assembly for device  10 , device structures under test  98  may emit wireless radio-frequency signals when driven using the test signals from probe  76 . Antenna  86  may be placed in the vicinity of device structures under test  98  (e.g., within 1 to 10 cm of device structures under test  98  or more than 10 cm or less than 10 cm away from device structures under test  98 ) or may be placed at a far-field location (e.g., meters away from device structures under test  98  or closer or farther). During operation, as test electromagnetic signals are transmitted by network analyzer  212  and applied to device structures under test  98  through probe  76 , corresponding transmitted wireless electromagnetic test signals may be received through antenna  86 . Network analyzer  212  may also receive reflected signals from cable (i.e., signals that were reflected from device structures under test  98  in response to the signals transmitted through probe  76 ). 
     The transmitted and reflected signals gathered using path  82  may be used to compute a reflection coefficient (sometimes referred to as an S11 parameter or S11 scattering parameter). The transmitted signal on path  82  and corresponding received signal on path  24  may be used to compute a forward transfer coefficient (sometimes referred to as an S21 parameter or S21 scattering parameter). The S11 and S21 data may include magnitude and phase components. During initial calibration operations, nominal (expected) values of S11 and/or S21 may be measured and stored in computing equipment  214 , network analyzer  212 , or other equipment in test equipment  84  to use as reference data. During testing, S11 data and/or S21 data gathered using test equipment  96  may be compared to the reference data. If the gathered data substantially matches the reference data, test equipment  96  may inform an operator that device structures under test  98  are satisfactory or may take other suitable action. If the gathered data deviates from the reference data by more than a predetermined amount, test equipment  96  may inform the operator that device structures under test  98  include a fault and should be reworked or scrapped or may take other suitable action. 
     In some situations, peripheral conductive housing member  16  may be formed from a metal (e.g., stainless steel) that has a non-negligible contact resistance when probed by spring-loaded pins or other contact-based probes. The surface of member  16  may also be susceptible to scratching when probed using pins. It may therefore be desirable to use a capacitively coupled probe arrangement of the type shown in  FIG. 6 .  FIG. 6  is a perspective view of an illustrative test system in which device structures under test  98  are being tested in test fixture  206 . Device structures under test  98  may include structures used in forming an electronic device such as electronic device  10  of  FIGS. 1 and 2 . For example, device structures under test  98  may include conductive housing structures such as peripheral conductive housing member  16 . Member  16  may have one or more dielectric-filled gaps  18 . Testing of device structures under test  84  may reveal whether member  16  contains a fault. 
     Fixture  206  may have a fixture base such as base  400 . Base  400  may be formed from a dielectric such as plastic (as an example). Base  400  may have a cavity such as cavity  416  that receives device structures under test  98  during testing. 
     When device structures under test  98  are placed within cavity  142 , levers  410  may be moved downwards in direction  412  around pivot  408 . This causes movable retention members  404  to move inwardly in direction  406  to serve as biasing structures that press against surface  403  of device structures under test  98 . When surface  403  is pressed in direction  406 , surface  98  is held firmly against probes  414  in cavity  416  of base  400 , ensuring satisfactory capacitive coupling between capacitive coupling probes  414  and member  16  during testing. Probes  414  may, if desired, have screen-printed alignment marks between their respective electrodes to help align structures  98  and probes  414 . If desired, a layer of compliant foam material may be interposed between probes  414  and base  400  to help secure device structures under test  98  firmly within cavity  416  during testing (e.g., to minimize possible gaps between structures  98  and probes  414  during testing). 
     Base  400  may have openings such as openings  418 . Openings  418  may be configured to receive mating spring-loaded probes  76 . For example, openings  418  may have an interior shape that matches the exterior shape of probes  76 . The shapes of openings  418  and probes  76  may be asymmetric (“keyed”) to ensure that probes  76  are inserted within openings  418  using a desired polarity. When moved in direction  424  by biasing structures  422 , probes  76  may be received within openings  418  of fixture base  400 , so that pins  78  mate with respective contact pads on probe  414  (i.e., pins  78  may make contact with capacitive coupling pads in probe  414 ). 
     For example, when probe  76  is mated with fixture  400 , first and second probe pins may be electrically connected to respective first and second probe pads (sometimes referred to as first and second electrodes) in capacitive coupling probe  414 . Probe terminals  78  may be placed in contact with the first and second probe pads using a robot or other computer-controlled positioner or manually. If desired, terminals  78  may be wires or other conductive paths associated with a cable and may be soldered directly to the probe pads without using a probe. The probe pads in probe  414  may be formed from metal traces in a flex circuit. 
     When placed against peripheral conductive housing member  16 , the first probe pad and member  16  form a first parallel plate capacitor, whereas the second probe pad and peripheral conductive housing member  16  form a second parallel plate capacitor. Because pins are not used to directly probe member  16 , member  16  will generally not be scratched during testing, which may be helpful when member  16  has a cosmetic surface that should not be damaged during testing. 
     Dielectric material in probe  414  may cover a portion of the first and second electrodes. When probe  414  is placed against conductive member  16  during testing, the dielectric material may serve to electrically isolate (insulate) the first and second electrodes from conductive member  16 . Because electrical coupling is achieved without requiring direct metal-to-metal contact between the probe electrodes and member  16 , satisfactory electrical coupling can be achieved at radio-frequencies even in the presence of an oxide or other coating that may give rise to a non-negligible contact resistance when probing the conductive structure with pins. 
     Biasing structures  422  may include a solenoid-based actuator, a pneumatic actuator, spring members to apply biasing force in direction  424 , or other suitable biasing structures. These structures may be passive (e.g., fixed springs) or may be manually or automatically controlled. For example, biasing structures  422  may be coupled to test equipment  84  by control paths  426 . Test equipment  84  may contain one or more computers or other computing equipment that issues commands to biasing structures  422  using paths  426 . Fixture  400  may slide on rails such as rails  420 . The position of fixture  400  may be adjusted manually or using a positioner such as computer-controlled positioner  402  that can be adjusted using computers in test equipment  84 . Using positioner  402  and/or positioners  422 , test structure  16  and probes  76  may be moved relative to each other to obtain optimal probe compression and placement. 
     The arrangement of  FIG. 6  includes a pair of probes  76 . These probes may be used individually or may be operated simultaneously. Additional capacitive coupling probes and other types of probes may be used in test fixture  206  if desired. 
     An exploded perspective view of test fixture  206  is shown in  FIG. 7 . As shown in  FIG. 7 , base  400  may have a cavity such as a substantially rectangular cavity  416  for receiving device structures under test  98  (see, e.g.,  FIG. 6 ). Retention members  404  may have holes or other features that allow retention members  404  to slide along rails  452  in base  400 . Springs  450  bias retention members  404  in direction  460 . When assembled, pivot members  456  are placed in holes  454  of rails  452  (passing through holes  411  in levers  410 ). Springs  450  push retention member  404  in direction  460  and create space within cavity  416  for structures  98 . When levers  410  are moved downward in direction  410 , levers  410  push retention member  404  in direction  462  and hold device structures under test  98  firmly against capacitive coupling probes  414  within cavity  416 . 
       FIG. 8  is a perspective view of test fixture  206  having a lower test fixture portion (e.g., the test fixture of the type described in connection with  FIGS. 5 and 6  that is used for receiving device structures under test  98  in cavity  416 ) and an upper test fixture portion  500 . As shown in  FIG. 8 , the lower test fixture portion may be attached to a mounting plate  520 . Upper test fixture portion  500  may include antenna  86  coupled to upper plate  502  through support members  504 . Cable clamping structures such as cable clamping structures  506  may be attached to upper plate  502 . Clamping structures may each include a lever  508  that, when moved in direction  508 , may be used to secure a radio-frequency cable inserted into hole  512 . A radio-frequency cable inserted into hole  512  of clamping structure  506  may mate with a corresponding cable connector in upper plate  510 . These cable connectors in upper plate  510  may be coupled to the positive and ground feeds of antenna  86  using conductive paths routed through support members  504 . Radio-frequency cables inserted in this way may be used to convey radio-frequency test signals between test equipment  84  and antenna  86  during test operations. 
     The illustrative test setup of  FIG. 8  may be used to test device structures under test  98  for manufacture variations without directly probing the surface of conductive members  16 . For example, radio-frequency test signals may be coupled to device structures under test  98  using cable  82 , probes  76 , and capacitive coupling probes  414  (see, e.g.,  FIGS. 5 and 6 ). Device structures under test  98  may emit wireless radio-frequency signals when driven using the test signals from probe  76 . Antenna  86  may be placed above device structures under test  98  (e.g., within 1 to 10 cm of device structures under test  98  or more than 10 cm or less than 10 cm away from device structures under test  98 , as an example. During testing, as test electromagnetic signals are transmitted by network analyzer  212  and applied to device structures under test  98  through probes  76 , corresponding transmitted wireless electromagnetic test signals may be received through antenna  86 . 
     Illustrative test data gathered using test system  94  is shown in  FIGS. 9 and 10 . In  FIG. 9 , the magnitude of forward transfer coefficient S21 has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. In  FIG. 10 , the phase of forward transfer coefficient S21 has been plotted as a function of test signal frequency for a frequency range of 0 to 5 GHz. There are two sets of curves in the graphs of  FIGS. 9 and 10 . Curves  300  correspond to reference data for device structures under test without conductive filaments and curves  302  correspond to data for device structures under test that include one or more conductive filaments. As indicated by illustrative frequency ranges 304 and 306 (e.g., about 3.5 to 5 GHz) in  FIGS. 9 and 10 , respectively, there are portions of these graphs in which the non-filament and filament versions of the test data exhibit significant variations. Other frequency ranges may be investigated if desired (e.g. a range of frequencies covering 1 to 5 GHz, a range of frequencies including frequencies between 2 and 4 GHz, etc.). Discrepancies between the expected (reference) and measured values of the S21 test data (or S11 test data or other test data measured using proves  76  and/or  86  in system  94 ) may be used to identify conductive electronic device structures that contains faults. 
     Illustrative steps involved in testing device structures under test  98  using a test system of the type shown in  FIG. 5  are shown in  FIG. 11 . 
     At step  150 , a test system operator may place one or more versions of electronic device structures under test  98  that have known satisfactory characteristics in test fixture  206  and may gather corresponding test results. For example, reflection coefficient measurements (magnitude and/or phase) and/or forward transfer coefficient measurements (magnitude and/or phase) may be obtained over a range of frequencies, as described in connection with  FIGS. 9 and 10 . The structures that are measured in this way may include substantially perfect (fault-free) structures and/or structures that exhibit acceptable manufacturing variations. For example, the structures that are measured may be members  16  that include gaps  18  that may or may not contain manufacturing faults such as burrs  70  ( FIG. 3 ). The test measurement data that is gathered during the operations of step  150  may be stored in test equipment  84  (e.g., vector network analyzer  212  and/or computing equipment  214 ) to serve as baseline data (sometimes referred to as reference data or calibration data) to which subsequent test data may be compared when testing device structures of unknown quality during manufacturing. 
     After gathering baseline data on device structures with known characteristics (e.g., device structures that are known to be filament free) during the operations of step  150 , device structures may be tested in a production environment. In particular, during the operations of step  152 , a test system operator may repeatedly place device structures under test  98  into test fixture  206  so that contacts  78  come into contact with portions of member  16  or other conductive portions of device structures under test  98  and, during the operations of step  154 , may gather test data on those structures. The test structures that are placed in test fixture  206  may include conductive structures such as bands  16  with gaps  18  that form part of one or more electronic device antennas or may be other conductive device structures. When gathering test data during the operations of step  154 , test equipment  84  may transmit radio-frequency signals via probe  76 . While transmitting radio-frequency signals via probe  76 , test equipment  84  may receive reflected radio-frequency signals via cable  82  (for measuring reflection coefficient data) and may wirelessly receive radio-frequency signals using test antenna  86  (for measuring forward transfer coefficient data). The transmitted and received signals may be processed (e.g., to compute magnitude and phase S11 and S21 data to determine whether filaments or other manufacturing defects are present in structures  98 ). 
     At step  156 , the test data that has been gathered from the device structures under test may be compared to the reference data that was collected during the calibration operations of step  150 . In particular, the test data may be evaluated to determine whether or not the test data deviates by more than an acceptable amount from the baseline data gathered during the operations of step  150 . In response to a determination that the test data is within acceptable limits, test equipment  84  may issue a corresponding alert to the test system operator (e.g., by displaying a “pass” message or other suitable information on a display in test equipment  84  or by issuing an audio alert) or may take other suitable actions (step  158 ). In response to a determination that the test data has varied from the reference data by more than acceptable limits, test equipment  84  may issue an alert that informs the system operator that the device structures under test have failed testing (e.g., a “fail message”) or may take other suitable action (step  160 ). Structures that have passed testing may, for example, be assembled into finished products and sold to customers. Structures that have failed testing may be reworked or scrapped. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20110519
Publication Date: 20140603
Grant Date: 20140603
Priority Date: 20110519
Inventors: NICKEL JOSHUA G.
MCPEAK JAMES L.
SHEN JR-YI
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B17/104", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R31/2822", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B17/104", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R27/28", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R31/2822", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R27/28", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47174551