PATENT DOCUMENT

Publication Number: US-7672142-B2
Application Number: US-65011607-A
Country: US
Kind Code: B2

Title: Grounded flexible circuits

Abstract:
Electronic devices may be provided with one or more electrical components that may be coupled to one or more circuit boards by flexible circuits that can have reduced ground lengths. Each flexible circuit can include at least one ground conductor that may run along its length and that may have at least one portion exposed for coupling to a grounding element that may also be coupled to a ground plane.

Claims:
1. An electronic device, comprising:
 an electrical component; 
 a circuit board; 
 a flexible printed circuit coupled between the electrical component and the circuit board, wherein the flexible printed circuit has a first end coupled to the electrical component and a second end coupled to the circuit board; wherein the flexible printed circuit is formed from flexible polymer films, wherein the flexible printed circuit includes a ground conductor trace that has a length and includes a signal conductor trace, and wherein the ground conductor trace and the signal conductor trace are formed from metal traces surrounded by the flexible polymer films of the flexible printed circuit; 
 a conductive housing that encloses the electronic device and that forms a ground plane; and 
 at least one grounding element electrically coupled between the ground conductor trace and the conductive housing, wherein the grounding element is electrically coupled to the ground conductor trace at least one point along the length of the ground conductor trace between the first and second ends of the flexible printed circuit and wherein the flexible polymer films have at least one hole through which the grounding element passes to electrically couple the ground conductor trace that is surrounded by the flexible polymer films to the conductive housing. 
 
     
     
       2. The electronic device of  claim 1 , wherein the grounding element is a conductive adhesive. 
     
     
       3. The electronic device of  claim 1 , wherein the grounding element is a solder. 
     
     
       4. The electronic device of  claim 1 , wherein the grounding element is a clip. 
     
     
       5. The electronic device of  claim 1 , wherein the grounding element is a weld. 
     
     
       6. The electronic device of  claim 1 , wherein the electrical component is an antenna. 
     
     
       7. The electronic device of  claim 1 , wherein the electronic device is a mobile telephone. 
     
     
       8. The electronic device of  claim 1 , wherein the electronic device is a remote control. 
     
     
       9. The electronic device defined in  claim 1  wherein the at least one grounding element is electrically coupled to the ground conductor trace substantially along the entire length of the flexible printed circuit between the electrical component and the circuit board. 
     
     
       10. The electronic device defined in  claim 1  further comprising a conductive metal layer between the conductive housing and the flexible printed circuit, wherein the grounding element is electrically coupled between the ground conductor trace and the conductive metal layer and wherein the conductive metal layer is electrically coupled to the conductive housing. 
     
     
       11. The electronic device defined in  claim 1  further comprising a conductive metal layer of copper between the conductive housing and the flexible printed circuit, wherein the grounding element is electrically coupled between the ground conductor trace and the conductive metal layer of copper and wherein the conductive metal layer of copper is electrically coupled to the conductive housing. 
     
     
       12. The electronic device defined in  claim 1  wherein the at least one grounding element is electrically coupled to the ground conductor trace along the entire length of the flexible printed circuit between the electrical component and the circuit board. 
     
     
       13. A flexible printed circuit in an electronic device having a conductive housing that encloses the electronic device, comprising:
 a first end for coupling to an electrical component; 
 a second end for coupling to a circuit board; 
 at least one grounding element; 
 flexible polymer films extending between the first end and the second end; 
 a flexible circuit ground trace extending between the first end and the second end; and 
 a flexible circuit signal trace extending between the first end and the second end, wherein the flexible circuit ground trace and the flexible circuit signal trace are formed from metal traces surrounded by the flexible polymer films, wherein the flexible circuit ground trace is electrically coupled to the conductive housing through the grounding element at least one point along the flexible polymer films between the first end and the second end, and wherein the flexible polymer films have at least one hole through which the grounding element passes to electrically couple the flexible circuit ground trace that is surrounded by the flexible polymer films to the conductive housing. 
 
     
     
       14. The flexible circuit of  claim 13 , wherein the grounding element is a conductive adhesive. 
     
     
       15. The flexible circuit of  claim 13 , wherein the grounding element is a solder.

Description:
BACKGROUND OF THE DISCLOSURE 
     The present invention can relate to apparatus and methods for coupling electrical components to a circuit board. 
     In some cases, an electronic device can include a housing with one or more electrical components and a circuit board. The circuit board can be used to mechanically support and electronically connect the one or more electrical components (e.g., input/output (I/O) components) to one another. Flexible circuits are typically used to couple electrical components to the circuit board. 
     Electrical components may be mechanically and electrically coupled to the circuit board by flexible circuits before or after the circuit board is disposed in the housing. Therefore, it is generally desirable to provide extra lengths of flexible circuit between each electrical component and the circuit board to facilitate easy insertion of the circuit board and electrical components into their appropriate locations with respect to the housing. Each electrical component and circuit board may be coupled to a respective end of a flexible circuit in such a way that they are grounded at those coupling points. However, a long ground length (i.e., the length between grounded points) of a signal path along a flexible circuit between an electrical component and the circuit board of an electronic device may provide a significant stretch of interconnect that floats, creates resonance, and is susceptible to electromagnetic and radio interference. 
     SUMMARY OF THE DISCLOSURE 
     Apparatus and methods for making connections between electrical components and circuit boards with reduced ground lengths are provided. 
     According to a particular embodiment of the present invention, an electronic device is provided that includes an electrical component, a circuit board, a flexible circuit coupled between the electrical component and the circuit board, and at least one grounding element coupled between the flexible circuit and a ground plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention, its nature and various advantages will become more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a perspective view of an exemplary electronic device in accordance with the principles of the present invention; 
         FIG. 2  is a horizontal cross-sectional view of the electronic device of  FIG. 1 , taken from line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a horizontal cross-sectional view of a portion of the electronic device of  FIGS. 1 and 2 , taken from line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a horizontal cross-sectional view of a portion of the electronic device of  FIGS. 1-3 , taken from line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a horizontal cross-sectional view of a portion of the electronic device of  FIGS. 1-4 , taken from line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a horizontal cross-sectional view of a portion of the electronic device of  FIGS. 1-5 , taken from line  6 - 6  of  FIG. 2 ; 
         FIG. 7  is a horizontal cross-sectional view of a portion of the electronic device of  FIGS. 1-6 , taken from line  7 - 7  of  FIG. 2 ; and 
         FIG. 8  is a flowchart of steps that may be taken for reducing the ground length of a circuit in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Apparatus and methods for making connections with reduced ground lengths in electronic devices are provided and described with reference to  FIGS. 1-8 . 
       FIGS. 1 and 2  illustrate an exemplary electronic device that can incorporate the present invention. Electronic device  10  can be any electronic device that has at least one electrical component coupled to a circuit board, including portable, mobile, hand-held, or miniature consumer electronic devices. Illustrative electronic devices can include, but are not limited to, music players, video players, still image players, game players, other media players, music recorders, video recorders, cameras, other media recorders, radios, medical equipment, calculators, cellular phones, other wireless communication devices, personal digital assistants, remote controls, pagers, laptop computers, printers, or combinations thereof. Miniature electronic devices may have a form factor that is smaller than that of hand-held devices. Illustrative miniature electronic devices can include, but are not limited to, watches, rings, necklaces, belts, accessories for belts, headsets, accessories for shoes, virtual reality devices, other wearable electronics, accessories for sporting equipment, accessories for fitness equipment, key chains, or combinations thereof. Alternatively, electronic devices of the present invention may not be portable at all. 
     Electronic device  10  can have one or more electrical components, such as input/output (I/O) components  12 A- 12 D, at least partially disposed within a housing  14 . The I/O components can include any type of component that receives and/or transmits digital and/or analog data (e.g., audio data, video data, other types of data, or a combination thereof). For example, I/O component  12 A may be a display that provides graphic images to a user, I/O component  12 B may be a user input component that can permit a user to input data into the electronic device, I/O component  12 C may be a multiple-pin connector that can permit electronic device  10  to interact with a computer, and I/O component  12 D may be a media output connector that can output media data to an accessory. Accessories can include, but are not limited to, docks, printers, external storage devices, external displays, speakers, lanyards having headphones coupled thereto, and other audio and/or visual output devices. 
     In one embodiment, user I/O component  12 B may be an antenna. In another embodiment, I/O component  12 B may be a scroll wheel similar to that used by the iPod™ device sold by Apple Computer, Inc. of Cupertino, Calif., that may include one or more buttons for selecting software entries and a capacitive touchpad. In yet even other alternative embodiments, user I/O component  12 B may include, for example, one or more buttons, a touchpad, a touch-screen display, electronics for accepting voice commands, infrared ports, or combinations thereof. 
     In one embodiment of the present invention, component  12 C may be a multiple-pin connector having 30 pins that transmit data to and from the electronic device. Media output connector  12 D can include, for example, an audio connector that transmits audio data to speakers or headphones. Alternatively, media output connector  12 D can output, for example, video data, still image data, games data, or other media data known in the art or otherwise. Media output connector  12 D also can output combinations of media data. 
     Housing  14  of electronic device  10  can be designed to protect the electrical components (e.g., I/O components  12 A- 12 D) and at least one circuit board  16  coupled thereto. With further reference to  FIG. 2 , the signals of each I/O component  12 A- 12 D may be coupled to circuit board  16 , and the signals of circuit board  16  may be coupled to each I/O component  12 A- 12 D, via a respective flexible circuit  18  (i.e., flexible circuits  18 A- 18 D). Each of flexible circuits  18 A- 18 D can include any flexible printed circuit (FPC), including one-sided, double-sided, multi-layer, dual access, rigid-flex FPCs, or combinations thereof. Circuit board  16  may be any type of circuit board, including, but not limited to, printed circuit boards (PCBs), logic boards, printed wiring boards, etched wiring boards, and other known boards, that may be used to mechanically support and electronically connect electrical components (e.g., I/O components  12 A- 12 D via flexible circuits  18 A- 18 D). Circuit board  16  may be constructed using one or more layers of a non-conductive substrate and signal conducting pathways. The signal conducting pathways can exist in one or more layers or in each layer of the non-conductive substrate. The signal conducting layers, sometimes referred to as traces, members, or leads, may be a metal conductive material (e.g., copper or gold) or an optical conductive material (e.g., fiber optics). 
     Electronic device  10  may include flexible circuit links at the coupling of each flexible circuit  18  with its respective electrical component  12  (e.g., component links  17 A- 17 D) and at the coupling of each flexible circuit  18  with circuit board  16  (e.g., board links  19 A-D). Component links  17  can couple the first ends of the conductive lines of each flexible circuit  18  to the signal receivers, transmitters, or transceivers of its respective electrical component (e.g., the pins of multiple-pin connector  12 C), while board links  19  can couple the second ends of the conductive lines of each flexible circuit  18  to the signal-conducting pathways of its respective circuit board (e.g., circuit board  16 ). Each of links  17  and  19  may be provided by any technique, including, but not limited to, a through-hole construction, a surface-mount construction, a soldering construction, or any combination thereof. Each one of links  17  and  19  can also ground any ground signals of the circuit board  16  and/or electrical component  12  to be transmitted across the respective flexible circuit  18 . Therefore, when electrical components  12  are physically and electrically coupled to board  16  via flexible circuits  18  and their respective links  17  and  19 , board  16  may communicate with each of the electrical components  12  of device  10  concurrently in order for the device to function properly. 
     In addition to the signal path between each electrical component  12  and board  16  being grounded at each end of its respective flexible circuit  18  (e.g., at links  17  and  19 ), each signal path can be grounded at one or more points along the length of its flexible circuit  18  to reduce the ground length of that signal path. As shown in  FIG. 2 , a flexible circuit (e.g., flexible circuit  18 C) can include at least one or more power conductors  20 C, one or more signal conductors  22 C, and one or more ground conductors  24 C. Each of these conductors, sometimes referred to as traces, members, or leads, may be made of any suitable metal conductive material, including, but not limited to, copper, aluminum, steel, gold, or combinations thereof. Signal traces are usually narrower than power or ground traces because their current carrying requirements are usually much less. 
     Moreover, as shown in  FIGS. 3-5 , for example, each conductor in a flexible circuit can be provided with a protective covering to insulate, isolate, and/or environmentally seal the conductors and to protect the conductors from shorting. This protective covering for each conductor may be made of any suitable flexible polymer, including, but not limited to, silicone rubber, polyurethane, acrylic, epoxy, polymide film (e.g., Kapton®), PC/ABS polymer, or combinations thereof. The outer cover may be used to both protect the flexible circuit from wearing and shorting as well as to maintain the form of the flexible circuit for circuit consistency. Also, Mylar® sheets or shims, for example, may be used as an insulator between the flexible circuits and the outer cover, while Teflon® or any other suitable material, for example, may be used as an insulator. Solvay IXEF® or any other suitable material, for example, may be used as the material of an inner frame that may help properly space the traces and/or flexible circuits at optimum distances from one another for optimum circuit performance and to help isolate grounds. 
     For example, as shown in  FIGS. 3-5 , respectively, each one of power conductor  20 C, signal conductor  22 C, and ground conductor  24 C of flexible circuit  18 C may be insulated by a protective cover  21 C along its length between board link  19 C and component link  17 C. As shown in  FIG. 5 , for example, the ground length of flexible circuit  18 C containing ground conductor  24  between board link  19 C and component link  17 C (i.e., original ground length G.L.) may be reduced by removing one or more portions of protective cover  21 C and coupling the one or more resultantly exposed portions of ground conductor  24 C to a ground plane  27 C with one or more grounding elements  25 C. 
     Each one of grounding elements  25 C may be provided by anyone of various technique, including, but not limited to, conductive adhesives (e.g., electrical tape), soldering, sponge gaskets, screw points, alligator clips, metal spring clips or fingers secured with metal screws or any other securable pressure/force device (e.g., rivets, nails, pins) or bonding agent or glue or laser welding or spot welding, crimp metal conductors that snap or solder into metal brackets that are laser welded to a main frame structure for ground, or any combination thereof. Furthermore, each grounding element  25 C can extend to one or more ground planes  27 C, each of which may be any electrically conductive surface that appears to most signals as an infinite ground potential, including, but not limited to, a specifically provided surface within the housing of the device (e.g., housing  14 ), or the housing itself, for example. 
     As shown in  FIG. 5 , four grounding elements  25 C can be respectively coupled to four equally spaced exposed portions of ground conductor  24 C and to ground plane  27 C (e.g., a conductive layer of copper provided at least between housing  14  and the shown portion of flexible circuit  18 C), thereby reducing the longest ground length along flexible circuit  18 C between grounded links  17 C and  19 C to a reduced length of G.L.′ (i.e., a ground length that is substantially one-fifth the length of original ground length G.L.). This reduction of the original ground length G.L. to that of five equally proportioned reduced ground lengths G.L.′, by coupling a grounding element  25  between each of four exposed portions of ground conductor  24  and a ground plane  27 , for example, can reduce the length of stretches of the signal path along flexible circuit  18 C that float, create resonance, and are susceptible to electromagnetic and radio interferences. Therefore, this reduction of the original ground length G.L. may provide a more reliable and effective interconnect between an electrical component (e.g., component  12 C) and a circuit board (e.g., board  16 ) on an electronic device  10 . 
     Moreover, besides bolstering the performance of a flexible circuit, providing one or more grounding elements along the length of a ground conductor can reduce the space occupied by the flexible circuit within the housing of its electronic device. For example, as shown in  FIG. 3 , for example, flexible circuit  18 C at power conductor  20 C can extend to a height H above housing  14  (or, in this embodiment, above ground plane  27 C) of device  10 , because flexible circuit  18 C may have an original length that can be greater than that between board link  19 C and component link  17 C when device  10  is assembled. This may be due to certain methods of assembling electronic devices that may require its flexible circuits to have some slack between its respective electronic component and circuit board, for example. However, as shown in  FIG. 5 , for example, the height at which flexible circuit  18 C at ground conductor  24 C may extend above housing  14  (or, in this embodiment, above ground plane  27 C) of device  10  may be limited to a height H″ that is significantly less than height H of  FIG. 3 , due to the one or more grounding elements  25 C coupling ground conductor  24 C to ground plane  27 C. Therefore, in addition to reducing the ground length of a flexible circuit, coupling one or more grounding elements between exposed portions of a ground conductor and a ground plane can reduce the space consumed by and/or the warping of the flexible circuit. 
     The flexible circuit at conductors other than its one or more ground conductors may be coupled to portions of the housing along the length of the flexible circuit to similarly reduce the height to which that flexible circuit extends above the housing. For example, as shown in  FIG. 4 , the height at which flexible circuit  18 C at signal conductor  22 C may extend above housing  14  (or, in this embodiment, above ground plane  27 C) of device  10  may be limited to a height H″ that is significantly less than height H of  FIG. 3 , and can be equal to height H′ of  FIG. 5 , due to the one or more coupling elements  29 C coupling protective cover  21 C about signal conductor  22 C to ground plane  27 C. By placing coupling elements  29 C of a particular height with a particular spacing along the length of protective cover  21 C about signal conductor  22 C (as shown in  FIG. 4 ) and along the length of protective cover  21 C about power conductor  20 C, the heights at which flexible circuit  18 C at signal conductor  22 C and power conductor  20 C extend above housing  14  may be similar to that of circuit  18 C at ground conductor  24 C, thereby creating a relatively smooth profile for flexible circuit  18 C at all its conductors. 
     Grounding elements may be coupled to various sides of a flexible circuit along its length and to various grounding planes, rather than coupling multiple grounding elements between the same ground plane and multiple exposed portions of a ground conductor along the same side thereof (see, e.g.,  FIG. 5 ). One or more grounding elements can be coupled between a first ground plane and exposed portions of a flexible circuit on a first one of its sides and one or more additional grounding elements may be coupled between a second ground plane and exposed portions of the flexible circuit on a second one of its sides. As shown in  FIG. 6 , for example, flexible circuit  18 A may be provided with two grounding elements  25 A′ that can extend to first ground plane  27 A′ from portions of ground conductor  24 A exposed by removing respective portions of upper protective covering  21 A′. Furthermore, flexible circuit  18 A may be provided with two grounding elements  25 A″ that can extend to second ground plane  27 A″ from portions of ground conductor  24 A exposed by removing respective portions of lower protective covering  21 A″. First ground plane  27 A′ can be the portion of housing  14  above flexible circuit  18 A, while second ground plane  27 A″ can be the portion of housing  14  below flexible circuit  18 A. 
     Moreover, rather than coupling multiple grounding elements between ground planes and multiple exposed portions of a ground conductor (see, e.g.,  FIGS. 5 and 6 ), the entire length of a ground conductor of a flexible circuit can be exposed and coupled to a ground plane by a single grounding element. As shown in  FIG. 7 , flexible circuit  18 B may be provided with only one grounding element  25 B that can extend to a grounding plane  27 B from the portion of ground conductor  24 B exposed by removing the entire portion of protective covering  21 B running along the bottom of the ground conductor. Ground plane  27 B can be a conductive layer of metal provided exclusively between housing  14  and the exposed length of ground conductor  24 B. Therefore, there may be no ground length between component link  17 B and board link  19 B of flexible circuit  18 B. 
       FIG. 8  is an illustrative flowchart showing steps that may be taken for reducing the ground length of a circuit (e.g., circuits  18 A-D of  FIGS. 2-7 ) that may include a first end, a second end, and a signal path having a ground conductor (e.g., conductors  24 A-C) that extends between the first end and the second end and that is surrounded by a covering (e.g., covering  21 A-C). At step  810 , one or more portions of the covering about one or more portions of the ground conductor between the first end and the second end may be removed. At optional step  820 , the first end of the circuit may be coupled to an electrical component (e.g. components  12 A-D). At optional step  830 , the second end of the circuit may be coupled to a circuit board (e.g., board  16 ). At step  840 , at least one of the one or more portions of the ground conductor, between the first end and the second end of the circuit where the covering has been removed, may be coupled to a ground plane by at least one grounding element (e.g., grounding elements  25 A-C). 
     It is to be understood that the steps shown in  FIG. 8  are merely illustrative and that the steps may be modified, additional steps may be added, and one or more of the steps may be omitted. 
     While there have been described electronic devices with electrical components coupled to circuit boards by flexible circuits having reduced ground lengths, it is to be understood that many changes may be made therein without departing from the spirit and scope of the present invention. It will also be understood that various directional and orientational terms such as “upper” and “lower,” “length” and “height,” and the like are used herein only for convenience, and that no fixed or absolute directional or orientational limitations are intended by the use of these words. For example, the devices of this invention can have any desired orientation. If reoriented, different directional or orientational terms may need to be used in their description, but that will not alter their fundamental nature as within the scope and spirit of this invention. Moreover, an electronic device constructed in accordance with the principles of the present invention may be of any suitable three-dimensional shape, including, but not limited to, a sphere, cone, octahedron, or combination thereof, rather than a hexahedron, as illustrated by device  10  of  FIGS. 1-8 . Those skilled in the art will appreciate that the invention can be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation, and the invention is limited only by the claims which follow.

Metadata:
Filing Date: 20070105
Publication Date: 20100302
Grant Date: 20100302
Priority Date: 20070105
Inventors: WANG ERIK L.
HOBSON PHILIP MICHAEL
JENKS KENNETH A.
HILL ROBERT J.
SCHLUB ROBERT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/189", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/189", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K1/0215", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/118", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K9/0039", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K9/0039", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K1/118", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K1/0215", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 39593303