Patent Document

[0001]    This application is a continuation of U.S. application Ser. No. 11/739,550, filed Apr. 24, 2007, which claims the benefit of U.S. Provisional Application No. 60/796,716, filed May 2, 2006 and U.S. Provisional Application No. 60/811,927, filed Jun. 8, 2006, the entirety of each of which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This application relates generally to the field of flexible electronic circuits, and more particularly to methods and apparatuses for shielded electronic circuits supported on a flexible member. 
       BACKGROUND 
       [0003]    The advent of mobile communication devices have permitted individuals to communicate with one another via wireless digital signal transmissions. Increasingly, individuals rely on mobile communication devices to also transfer data between one another via the World Wide Web (WWW), computers, computer networks and so forth. Individuals use mobile communication devices to transfer various types of data such as high quality digital audio, digital video, streaming digital video, photographic images, computer files and so forth. Accordingly, applications supporting this type of data transfer are congruous with the design of mobile communication devices, and such devices include, for example, mega-pixel cameras, video cameras, and digital audio recorders. Moreover, many commercially available cellular phones and personal digital assistant devices are capable of running typical computer-based application programs that create, utilize, and communicate large data files. As a result, there is a need in the art for mobile communication devices to transfer large amounts of data at high rates. 
         [0004]    Many electronic devices, including mobile communication devices, generate electromagnetic fields in the radio frequency spectrum. Specifically, the transmission of electrical signals along a conductive path generates electromagnetic fields. As transmission frequencies increase, the magnitude and effective spatial reach of corresponding electromagnetic fields also increase. When two physically unconnected conductive paths are in close proximity to one another, a high frequency transmission on one of the conductive paths may result in electromagnetic interference (EMI) with respect to the transmission on the other conductive path. EMI has many deleterious effects on the operation of mobile communication devices. For example, EMI may cause the distortion of transmitted data and even the complete loss of data. 
         [0005]    Due to higher data rates, mobile communication devices increasingly require conductors that are not susceptible to EMI. Specifically, flip phones, phones in which the screen is connected to the body of the phone via a rotating hinge, and slider phones, phones in which the screen is connected to the body of the phone via a laterally sliding mechanical connector, require flexible conductors to transmit data across the rotating hinge or mechanical connector. Thus, a need exists for flexible conductors capable of shielding against EMI generated during high-frequency transmissions. 
         [0006]    One approach, well known in the prior art, for shielding against EMI are coaxial cables. Coaxial cables comprise a pair of conductors disposed around a common axis. A first conductor is positioned along the central axis of the cable and carries the transmitted signal. A second conductor, connected to an electrical ground, is cylindrically disposed around the first conductor by an insulative or dielectric material. By shielding the first conductor with the second conductor, a coaxial cable is able to confine the electromagnetic field generated by the conductor to an area inside the cable. Accordingly, coaxial cables are widely used for television and broadband transmission. 
       SUMMARY 
       [0007]    The apparatuses and methods disclosed herein for a shielded flexible circuit advantageously enable high data transmission rates along closely spaced conductors on a flexible circuit. The apparatuses and methods are suitable for use in flip phones and slider phones. Additionally, they are capable of shielding conductive traces against EMI when data transmission rates exceed 1 GHz. As a result, in some embodiments, cell phones are able to transmit data at rates needed for streaming video and other high-rate applications without substantial signal loss or distortion. In further embodiments, shielded flexible circuits are capable of transmitting data at rates between 2 and 4 GHz. 
         [0008]    In one embodiment, an apparatus comprises a flexible support member; a first conductor and a second conductor in contact with said flexible support member; said first and second conductors electrically insulated from the other; a first conductive material co-axially disposed around said first conductor, said first conductive material electrically insulated from said first conductor; and a second conductive material co-axially disposed around said second conductor, said second conductive material electrically insulated from said second conductor. 
         [0009]    In another embodiment, a method of shielding a flexible circuit comprises forming a first conductor and a second conductor from a first conductive material adhered to a top side of a flexible support member, said first and second conductors electrically insulated from one another; forming a second conductive material co-axially disposed around said first conductor, said second conductive material electrically insulated from said first conductor; forming a third conductive material co-axially disposed around said second conductor, said third conductive material electrically insulated from said second conductor. 
         [0010]    For purposes of this summary, certain aspects, advantages, and novel features of the invention are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1A  is a top perspective view of one embodiment of a flexible circuit with one conductive layer. 
           [0012]      FIG. 1B  is a top perspective view of the flexible circuit of  FIG. 1A  with etched traces. 
           [0013]      FIG. 1C  is a top perspective view of the flexible circuit of  FIG. 1B  with a dielectric layer insulating the etched traces. 
           [0014]      FIG. 1D  is a top perspective view of the flexible circuit of  FIG. 1C  with channels exposing alternate grounded traces on a top side of the flexible circuit. 
           [0015]      FIG. 1E  is a top perspective view of the flexible circuit of  FIG. 1D  with a conductive shielding layer on the top side in communication with the alternate grounded traces. 
           [0016]      FIG. 1F  is a top perspective view of the flexible circuit of  FIG. 1E  with channels exposing the alternate grounded traces on a bottom side of the flexible circuit. 
           [0017]      FIG. 1G  is a top perspective view of the flexible circuit of  FIG. 1F  with a conductive shielding layer on the bottom side in communication with the alternate grounded traces. 
           [0018]      FIG. 1H  is a cross-sectional view of the single copper layer shielded flexible circuit of  FIG. 1G  with alternate grounded traces. 
           [0019]      FIG. 2  is a process diagram illustrating one embodiment of a method for manufacturing the single copper layer shielded flexible circuit of  FIG. 1H  with alternate grounded traces. 
           [0020]      FIG. 3  is a cross-sectional view of one embodiment of a single copper layer flexible circuit with all traces shielded. 
           [0021]      FIG. 4  is a process diagram illustrating one embodiment of the method for manufacturing a single copper layer flexible circuit of  FIG. 3  with all traces shielded. 
           [0022]      FIG. 5A  is a top perspective view of one embodiment of a flexible circuit with two conductive layers. 
           [0023]      FIG. 5B  is a top perspective view of the flexible circuit of  FIG. 5A  with etched traces. 
           [0024]      FIG. 5C  is a top perspective view of the flexible circuit of  FIG. 5B  with a dielectric layer on a top side of the flexible circuit. 
           [0025]      FIG. 5D  is a top perspective view of the flexible circuit of  FIG. 5C  with channels between the etched traces on the top side. 
           [0026]      FIG. 5E  is a top perspective view of the flexible circuit of  FIG. 5D  with a conductive shielding layer on the top side in communication with a copper layer on a bottom side. 
           [0027]      FIG. 5F  is a cross-sectional view of the two copper layer shielded flexible circuit of  FIG. 5E . 
           [0028]      FIG. 6  is a process diagram illustrating one embodiment of a method for manufacturing the two copper layer shielded flexible circuit of  FIG. 5F . 
           [0029]      FIG. 7A  is a top perspective view of one embodiment of a flexible circuit with two conductive layers. 
           [0030]      FIG. 7B  is a top perspective view of the flexible circuit of  FIG. 7A  with etched traces. 
           [0031]      FIG. 7C  is a top perspective view of the flexible circuit of  FIG. 7B  with a dielectric layer and a conductive shielding layer on a top side. 
           [0032]      FIG. 7D  is a top perspective view of the flexible circuit of  FIG. 7C  with channels between the etched traces 
           [0033]      FIG. 7E  is a top perspective view of the flexible circuit of  FIG. 7D  with plated channels. 
           [0034]      FIG. 7F  is a top perspective view of the flexible circuit of  FIG. 7E  with a dielectric layer on the top side. 
           [0035]      FIG. 7G  is a cross-sectional view of the three layer shielded flexible circuit of  FIG. 7F . 
           [0036]      FIG. 8  is a process diagram illustrating one embodiment of the method for manufacturing the three copper layer shielded flexible circuit of  FIG. 7G . 
           [0037]      FIG. 9A  illustrates one type of a mobile communication device with a hinge. 
           [0038]      FIG. 9B  illustrates a flexible circuit that provides electrical communication between the screen of the mobile communication device and the body of the mobile communication device. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Apparatuses and methods which represent various embodiments and an example application of an embodiment of the invention will now be described with reference to  FIGS. 1-9 . Variations to the apparatuses and methods which represent still other embodiments will also be described. 
         [0040]    For purposes of illustration, some embodiments will be described in the context of a mobile communication device and/or mobile phones. The invention(s) disclosed herein are not limited by the context in which the apparatuses and methods are used, and that the apparatuses and methods may be used in other environments. Additionally, the specific implementations described herein are set forth in order to illustrate, and not to limit, the invention(s) disclosed herein. The scope of the invention(s) is defined only by the appended claims. 
         [0041]    These and other features will now be described with reference to the drawings summarized above. The drawings and the associated descriptions are provided to illustrate embodiments of the invention(s) and not to limit the scope of the invention. Throughout the drawings, reference numbers may be re-used to indicate correspondence between referenced elements. 
       I. OVERVIEW 
       [0042]    The apparatuses and methods disclosed herein pertain to shielding active signal traces on a flexible support member. 
         [0043]    In one set of embodiments, a shielded flexible circuit is constructed using a base flexible material that comprises a flexible non-conductive substrate on a top side and a copper layer on a bottom side. In these embodiments, alternate traces are grounded to the copper layer and used to shield the traces between them. For ease of reference, embodiments of this type will hereinafter be referred to as a “Single-Copper Layer Shielding With Alternate Grounded Traces” embodiment. 
         [0044]    In another set of embodiments, a shielded flexible circuit is constructed using a base material that comprises a flexible substrate on a top side and a copper layer on a bottom side. In these embodiments, substantially every trace may be used as an active signal trace. For ease of reference, embodiments of this type will hereinafter be referred to as a “Single Copper Layer With All Traces Shielded” embodiment. 
         [0045]    In yet another set of embodiments, a shielded flexible circuit is constructed using a base material that comprises a flexible substrate with a copper layer on a top side and a copper layer on a bottom side of the flexible substrate. For ease of reference, embodiments of this type will hereinafter be referred to as a “Two Copper Layer” embodiment. 
         [0046]    In a further set of embodiments, a shielded flexible circuit is constructed using a base material that comprises a flexible substrate with a copper layer on a top side and a copper layer on a bottom side of the flexible substrate. In these embodiments, copper may be used to shield the copper traces on all sides. For ease of reference, embodiments of this type will hereinafter be referred to as a “Three Copper Layer” embodiment. 
         [0047]    Additionally, terms such as “above,” “below,” “top,” and “bottom” are used throughout the specification. These terms should not be construed as limiting. Rather, these terms are used relative to the orientations of the applicable figures. 
         [0048]    Moreover, the “process diagrams” are each illustrative of one embodiment of the invention(s) only. The invention(s) disclosed herein should not be limited to the steps of the process diagrams in the order that they appear. It is recognized that the steps may be performed in any order that is recognized as suitable by one with ordinary skill in the art. 
       II. SINGLE COPPER LAYER SHIELDING WITH ALTERNATE GROUNDED TRACES EMBODIMENTS 
       [0049]      FIG. 1H  illustrates one embodiment of a single copper layer shielding with alternate grounded traces.  FIG. 2  illustrates a process diagram, including steps  501 - 508 , for manufacturing a shielded flexible circuit, and  FIGS. 1A-H  illustrate the structure of the shielded flexible circuit as each step of the method is practiced. As described herein, the figures associated with the structure of the circuit at each step of the method will be expressly referenced. In contrast, each step of the method of  FIG. 2  will be referred to using the reference numbers of  FIG. 2  only. 
         [0050]    In this embodiment, the method for manufacturing a shielded flexible circuit begins with the flexible support member  100  illustrated in  FIG. 1A . The flexible support member  100  is comprised of two layers, a flexible substrate  102  and a base conductive layer  101 . It is known to one with ordinary skill in the art that the flexible support member  100  is commercially manufactured and readily available for purchase. In other embodiments, the method may begin by applying the base conductive layer  101  to the flexible substrate  102  using plating, lamination, vapor deposition or other known techniques. 
         [0051]    In one preferred embodiment, the flexible substrate  102  is made of a polyimide material. In other embodiments, the flexible substrate  102  may be any of the commonly used “Flex” or printed circuit board (“PCB”) materials such as FR4, PET/PEN, Teflon/High speed materials, and so forth. 
         [0052]    In one preferred embodiment, the base conductive layer  101  is a copper layer. In other embodiments, the base conductive layer  101  may be any electrically conductive material such as gold or silver. Though it is contemplated that other materials may be used, the base conductive layer  101  will be referred to herein as a copper base conductive layer  101 . 
         [0053]    Traditional PCB manufacturing methods may be used to create tooling holes or vias in the flexible support member  100 . 
         [0054]      FIG. 1B  illustrates the copper traces  111 ,  112 ,  113 ,  114  formed after completion of step  501 . In one embodiment, the copper traces  111 ,  112 ,  113 ,  114  are printed and etched using photolithography techniques well known to those skilled in the art. One photolithography technique requires laminating a dry film etch resist to the base conductive layer  101  using a hot roll laminator or a vacuum lamination process. Many dry film etch resist layers are commercially available and are produced by companies such as Dupont®. In some embodiments, the thickness of the dry film etch resist layer is between 0.0007″ to 0.0020″. A circuit image is then transferred to the etch resist layer using Ultraviolet (“UV”) energy and an appropriate tool such as a photo tool, a Mylar® film, or a Mylar® glass. The areas of etch resist which were not exposed to UV energy are then chemically washed off of the panel. For example, a solution containing Potassium Carbonate may be used to wash off the undeveloped (that is, not exposed to UV energy) etch resist. Next, the copper which is exposed through the developed etch resist is chemically removed. For example, an aqueous wash of cupric chloride etchant may be used to remove the copper. Alternatively, other types of copper etchants may be used, such as alkaline-based etchants and ferric chloride-based etchants. 
         [0055]      FIG. 1C  illustrates the insulative or dielectric layer  121  applied to the top side of the flexible circuit  100  with the traces  111 ,  112 ,  113 ,  114 . This layer is formed by step  502  to insulate the etched traces  111 ,  112 ,  113 ,  114  from the grounded shielding that is created later in the method so as to prevent an electrical short and to protect the traces  111 ,  112 ,  113 ,  114  from contamination. Any number of dielectric or non-conductive insulative materials may be used. For example, in one embodiment the dielectric layer  121  is comprised of a polyimide film with a thermal set adhesive on one side of the film. In this example, the polyimide film may range in thickness from 0.0005″ to 0.0010″, and the thermal set adhesive may range in thickness from 0.0005″ to 0.0015″. The film  121  is placed on top of the etched traces  111 ,  112 ,  113 ,  114  with the adhesive layer contacting the etched traces  111 ,  112 ,  113 ,  114 . Then, using an autoclave or a vacuum press, the film is laminated to the flexible circuit  100 . For example, lamination parameters such as 210 psi at 385 degrees Fahrenheit for 60 minutes may be used. It is recognized that other known techniques may be used to adhere the dielectric layer  121  to the flexible circuit  100 . 
         [0056]      FIG. 1D  illustrates the channels  131 ,  133  in the dielectric layer  121  created by step  503 . The channels  131 ,  133  are created in locations corresponding to alternate traces  111 ,  113  and form discontinuities that will later form the shielding for the trace(s)  112  between them. The channels  131 ,  133  expose the alternate grounded traces  111 ,  113  along the length of each trace by removing the dielectric layer  121  above them. In one embodiment, the channels are created using laser ablation techniques. In other embodiments, other processing techniques, such as plasma etching and chemical milling, may be used. 
         [0057]    It is recognized that in other embodiments, that channels may be created in locations corresponding to more or less than every other trace. In these embodiments, the traces between the created channels are shielded. 
         [0058]    Next, in some embodiments, the exposed alternate grounded traces  111 ,  113  are metalized to protect the traces  111 ,  113  from oxidation. For example, a Nickel and Gold compound may be used to metalize the traces  111 ,  113 . 
         [0059]      FIGS. 1E and 1F  illustrate a conductive shielding layer  141  and a dielectric layer  171  formed on the top side of the flexible circuit  100  by steps  504  and  505 . The conductive layer  141  is applied to the flexible circuit  100  such that it is in electrical communication with the alternate grounded traces  111 ,  113 . The conductive layer  141  may be comprised of any conductive material capable of adhering to the alternate grounded traces  111 ,  113  and the dielectric layer  121 . Suitable conductive layer  141  materials include, but are not limited to, a silver based film and silver ink. The conductive layer  141  may be applied to the flexible circuit  100  using techniques similar to those used for adhering the dielectric layer  121  to the flexible circuit  100  (for example, lamination). Next, a dielectric layer  171  is applied to the flexible circuit  100  such that it is on top of the conductive layer  141 . Techniques such as lamination may be used to adhere the dielectric layer  171  to the conductive layer  141 . A suitable dielectric layer  171  material includes, but is not limited to, the material used for dielectric layer  121 . 
         [0060]    It is contemplated that the conductive layer  141  and the dielectric layer  171  may be adhered to the flexible circuit  100  separately, as described above, or concurrently (that is, steps  504  and  505  may be performed as one step). In one embodiment, concurrent application of the conductive layer  141  and the dielectric layer  171  may be performed using a pre-made material comprising a conductive layer and a dielectric layer. Examples of such materials can be found in Tatsuta&#39;s® PC series of materials. These materials comprise a conductive layer of silver foil, sandwiched between a conductive adhesive layer and a dielectric layer. The material is placed on the flexible circuit  100  such that the conductive adhesive is in contact with the dielectric layer  121 . Then, the material may be laminated or otherwise adhered to the flexible circuit  100 . 
         [0061]      FIG. 1F  illustrates channels  151 ,  152  formed by step  506  in the flexible substrate  102 , on the bottom side of the flexible circuit  100 , below the alternate grounded traces  111 ,  113 . The channels  151 ,  152  may be created using techniques similar to those employed in step  503  (for example, laser ablation). In one embodiment, the channels are created in the flexible substrate  102  such that the alternate grounded traces  111 ,  113  are exposed along the length of the trace. Next, in some embodiments, the exposed copper traces  111 ,  113  are metalized using a Nickel/Gold compound in order to prevent oxidation. 
         [0062]      FIG. 1G  illustrates the conductive shielding layer  161  applied by step  507  to the side of the flexible circuit  100  below the flexible substrate  102 . This conductive shielding layer  161  is applied such that it is in electrical communication with the alternate grounded traces  111 ,  113 . As stated above with respect to step  508 , the conductive shielding layer  161  may be laminated to the flexible circuit  100  and further, may be comprised of any conductive material such as copper or silver. 
         [0063]      FIG. 1H  illustrates a dielectric layer  172  applied by step  508  to the conductive shielding layer  161 . This dielectric layer  172  shields the exposed conductive shielding layer from electrical interference and contamination. The dielectric layer  172  may be adhered to the flexible circuit  100  using techniques such as lamination and may be comprised of materials similar to those used in step  502  (for example, a polyimide film). 
         [0064]    As stated with respect to steps  504  and  505 , it is similarly contemplated that the conductive shielding layer  161  and the dielectric layer  172  may be applied to the flexible circuit  100  in one step using materials such as those included in the Tatsuta® PC series. 
         [0065]    As shown in  FIG. 1H , the center copper trace  112  is shielded on all sides. It is first shielded by non-conductive dielectric materials and then the non-conductive materials are surrounded by conductive materials. In particular, the trace  112  is electrically insulated from the ground plane  111 ,  113 ,  141  on the top and sides by dielectric layer  121  and electrically insulated from the ground plane  161  on the bottom by the flexible substrate  102 . In this illustration, the conductive shielding comprises the conductive layer  141  on the top side of the trace  112 , the conductive layer  161  on the bottom side of the trace  112 , and the alternate grounded traces  111  and  113  on the sides of the trace  112 . 
         [0066]    Additionally, it is recognized that dielectric layers  171  and  172  are not required to shield the circuit from EMI. In some embodiments, neither or only one of the layers  171 ,  172  may be employed. 
       III. “SINGLE COPPER LAYER WITH ALL TRACES SHIELDED” EMBODIMENTS 
       [0067]      FIG. 3  illustrates one embodiment of a single copper layer with all traces shielded.  FIG. 4  illustrates a process diagram, including steps  601 - 608 , for one method of manufacturing the shielded flexible circuit  900  shown in  FIG. 3 . As described herein, the steps of the method of  FIG. 4  will be referred to using the reference numbers provided in  FIG. 4 . 
         [0068]    The apparatus and method for manufacturing the apparatus of  FIGS. 3 and 4  share characteristics with the embodiment depicted in  FIGS. 1A-H  and  FIG. 2 . That is, many of the possible materials and techniques suggested and/or employed with respect the single copper layer shielding with alternate grounded traces embodiments may be used in connection with the single copper layer with all traces shielded embodiments. However, differences between the two sets of embodiments are noted below. 
         [0069]    Moreover, the title given to the set of embodiments described in this section should not be construed as limiting. It is recognized that every trace  111 ,  112  need not be shielded. Rather, with these embodiments, it may be possible to shield every trace  111 ,  112 . 
         [0070]    In one embodiment, the method for manufacturing a shielded flexible circuit  900  begins with a flexible support member such as the member  100  depicted in  FIG. 1A . Referring to  FIGS. 3 and 4 , active signal traces  111 ,  112  are formed from the base conductive layer  101  using print and etch techniques  601 . A dielectric layer  121  is then applied to the top of the traces  111 ,  112  so as to electrically insulate the traces  111 ,  112  from the conductive portion of the shielding  141  that is applied in step  604 . 
         [0071]    Next, in step  603 , channels  182 ,  183 ,  184  are created between the active signal traces  111 ,  112 . The channels  182 ,  183 ,  184 , may be created using laser ablation techniques to remove portions of the dielectric layer  121  located between the traces  111 ,  112 . In the embodiment depicted in  FIG. 3 , the traces  111 ,  112  are not exposed to the channels. 
         [0072]    Subsequently, a conductive shielded layer  141  is placed on top of the dielectric layer  121  and in the channels  182 ,  183 ,  184  in step  604 . The conductive shielding layer  141  is adhered  604  to the top side of the flexible circuit  900  such that it is in contact with the flexible substrate  102 . Next, an insulative layer  171  is adhered  605  to the top of the conductive shielding layer. It is recognized that in addition to performing steps  604  and  605  sequentially steps  604  and  605  may be performed as one step using a Tatsuta® PC series material. 
         [0073]    A second set of channels  185 ,  186 ,  187  are created  606  on the bottom side of the flexible circuit  900 . The channels  185 ,  186 ,  187  are located between the traces  111 ,  112  and positioned such that they expose the conductive shielding layer  141  located between the first set of channels  182 ,  183 ,  184 . The second set of channels  185 ,  186 ,  187  may be created by employing laser ablation techniques to remove portions of the flexible substrate  102  in these locations. 
         [0074]    A conductive shielded layer  161  is then adhered in step  607  to the bottom side of the flexible circuit  900  using, for example, lamination techniques. This conductive shielding layer  161  is applied in the channels  185 ,  186 ,  187  and is in electrical communication with conductive shielding layer  141 . Next, a dielectric layer  199  may be adhered in step  608  to the conductive shielding layer  161  also using lamination techniques. As stated with respect to steps  604  and  605 , it is recognized that steps  607  and  608  may be performed sequentially or as one step. 
         [0075]    Additionally, in some embodiments, it is recognized that one or both dielectric layers  171  and  199  will not be employed to insulate conductive layers  141  and  161 . The absence of the dielectric layers  171 ,  199  may not be required to shield the traces  111 ,  112  from EMI. 
         [0076]    Moreover, it is recognized that in some embodiments, step  606  of the method, laser ablating channels  185 ,  186 ,  187  on the bottom side of the flexible circuit  900  may be omitted. Omitting step  606  requires that in step  603 , laser ablation of channels  182 ,  183 ,  184  on the top side of the flexible support member, both the portions of the dielectric layer  121  and the polyimide layer  102  located between the traces  111 ,  112  be removed. 
         [0077]    As shown in  FIG. 3 , the traces  111 ,  112  are each shielded in 360 degrees, first by a dielectric shielding and next by a conductive shielding. Each trace  111 ,  112  is insulated in all directions from the conductive shielding material and the other traces  111 ,  112 . Dielectric layer  121  electrically insulates the top and sides of the traces  111 ,  112  from the ground plane  182 , and the flexible substrate  102  electrically insulates the bottom of the traces  111 ,  112  from the ground plane  161 . Accordingly, each trace  111 ,  112  is surrounded by grounded, conductive shielding materials. Conductive layer  141  provides conductive shielding on the top and sides of the traces  111 ,  112  and the bottom conductive layer  161  provides conductive shielding on the bottom of the traces  111 ,  112 ,  113 . 
       IV. “TWO COPPER LAYER” EMBODIMENTS 
       [0078]      FIG. 5F  illustrates one embodiment of a two copper layer shielded flexible circuit.  FIG. 6  illustrates a process diagram, including steps  701 - 706 , for manufacturing the shielded flexible circuit of  FIG. 5F , and  FIGS. 5A-F  illustrate the structure of the shielded flexible circuit as each step of the method is practiced. As described herein, the figures associated with the structure of the circuit at each step of the method will be expressly referenced. In contrast, each step of the process diagram of  FIG. 6  will be referred to using the reference numbers of  FIG. 6 . 
         [0079]    In embodiment depicted, the method for manufacturing a shielded flexible circuit begins with the flexible support member  200  illustrated in  FIG. 5A . The flexible support member  200  is comprised of three layers, a flexible substrate  202  sandwiched between a top conductive layer  203  and a bottom conductive layer  201 . It is known to one with ordinary skill in the art that flexible support member  200  is commercially manufactured and readily available for purchase. In other embodiments, the method may begin by applying the top and bottom base conductive layers  201 ,  203  to the flexible substrate  202  using plating, lamination, vapor deposition or other known techniques. Though the embodiments described herein are not limited to a top and bottom conductive layer  201 ,  203  comprised of copper, the embodiment depicted utilizes copper top and bottom conductive layers  201 ,  203 . 
         [0080]    Additionally, many alternate materials and techniques suggested with respect the single copper layer shielding with alternate grounded traces embodiments may be used in connection with the two copper layer embodiments. However, differences between the two sets of embodiments are noted below. 
         [0081]      FIG. 5B  illustrates the traces  211 ,  212 ,  213 ,  214  after they have been printed and etched in step  701  from the top copper layer  203 . As shown, traces  211 ,  212 ,  213 ,  214  are not in electrical communication with one another because the design requirements of the illustrated embodiment requires that the traces  211 ,  212 ,  213 ,  214  be electrically isolated from one another. 
         [0082]      FIG. 5C  illustrates an insulative or dielectric layer  221  applied in step  702  to the top side of the flexible circuit  200 . Using, for example, lamination techniques, the dielectric layer  221  is adhered to the flexible substrate  202  and the traces  211 ,  212 ,  213 ,  214 . 
         [0083]      FIG. 5D  illustrates channels  231 ,  232 ,  233 ,  234  formed in step  703  between the active signal traces  211 ,  212 ,  213 ,  214 . The channels  231 ,  232 ,  233 ,  234  are created by employing laser ablation or other known techniques to remove portions of the dielectric layer  221  and the flexible substrate  202  located between the traces  211 ,  212 ,  213 ,  214 . As shown, the channels  231 ,  232 ,  233 ,  234  expose the top portion of the bottom copper layer  201  but do not expose the traces  211 ,  212 ,  213 ,  214  (that is, the traces  211 ,  212 ,  213 ,  214  remain insulated). 
         [0084]      FIG. 5E  illustrates a conductive shielded layer  241  applied in step  704  to the top side of the flexible circuit  200 . The conductive shielding layer  241  is applied to the flexible circuit  240  such that it is in the channels  231 ,  232 ,  233 ,  234  and is in electrical communication with the bottom conductive layer  201 . In one embodiment, the conductive shielding layer  241  is a silver filled ink. Dupont&#39;s® CB208 product is a silver ink that is commercially available and known to those skilled in the art. Typically, the silver ink is screen printed onto the surface of the dielectric layer  221  that was previously laser processed to expose the bottom conductive layer  201 . In other embodiments, other conductive materials with the requisite flow characteristics may be used. 
         [0085]      FIG. 5F  illustrates insulative or dielectric layers  251 ,  252  applied in steps  705  and  706  to the top and bottom sides of the flexible circuit  200 . In some embodiments, a dielectric film  251 ,  252  is laminated to the flexible circuit  200 . The dielectric layers  251 ,  252  may serve to protect the flexible circuit  250  from external shorting. 
         [0086]    In other embodiments, step  704  is carried out by laminating or otherwise adhering a conductive film to the dielectric layer and the channels  231 ,  232 ,  233 ,  234 . In these embodiments, an insulative layer  252  may be then adhered to the top of the conductive shielding layer  251  in order to prevent external shorting. Alternatively, the conductive shielding layer  241  and the dielectric layer  252  are applied concurrently to the flexible circuit  250  by adhering materials such as those in the Tatsuta® PC series. 
         [0087]    As shown in  FIG. 5F , the traces  211 ,  212 ,  213  are shielded in 360 degrees. Each trace  211 ,  212 ,  213  is insulated in all directions from the conductive shielding material and the other traces  211 ,  212 ,  213 . Dielectric layer  221  electrically insulates the top and sides of the traces  211  from the grounded plane  241 ,  212 ,  213 , and the flexible substrate  202  electrically insulates the bottom of the traces  211 ,  212 ,  213  from the grounded plane  201 . Accordingly, each trace  211 ,  212 ,  213  is surrounded by grounded shielding materials. Conductive layer  241  provides conductive shielding on the top and sides of the traces  211 ,  212 ,  213 , and the bottom conductive layer  201  provides conductive shielding on the bottom of the traces  211 ,  212 ,  213 . 
       V. “THREE COPPER LAYER” EMBODIMENTS 
       [0088]      FIG. 7G  illustrates one embodiment of a three copper layer shielded flexible circuit.  FIG. 8  illustrates a process diagram, including steps  801 - 808 , for one embodiment of a method for manufacturing a shielded flexible circuit, and  FIGS. 7A-G  illustrate the structure of the shielded flexible circuit as each step of the method is practiced. As described herein, the figures associated with the structure of the circuit at each step of the method will be expressly referenced. In contrast, each step of the process diagram of  FIG. 8  will be referred to using the reference numbers of  FIG. 8  only. 
         [0089]    In this embodiment, the method for manufacturing a shielded flexible circuit begins with the flexible support member  300  illustrated in  FIG. 7A . The flexible support member  300  is comprised of three layers, a flexible substrate  302  sandwiched between a top conductive layer  303  and a bottom conductive layer  301 . It is known to one with ordinary skill in the art that flexible support member  300  is commercially manufactured and readily available for purchase. In other embodiments, the method may begin by applying the top and bottom base conductive layer to the flexible substrate using plating, lamination, vapor deposition or other known techniques. In yet other embodiments, the top and bottom conductive layers may comprise any conductive material such as copper, silver, or gold. 
         [0090]      FIG. 7B  depicts the traces  311 ,  312 ,  313 ,  314  used to carry electrical signals after they have been printed and etched in step  801 . The traces  311 ,  312 ,  313 ,  314  are etched from the top conductive layer  303 . 
         [0091]      FIG. 7C  depicts the flexible circuit  300  after steps  802  and  803  are complete. Step  802  requires applying a dielectric material  321  to the top side of the flexible circuit  300 . The dielectric layer  322  may be comprised of any of the electrically insulative materials disclosed above and may be adhered to the flexible circuit using any of the techniques described above (for example, lamination). Step  803  requires applying a conductive shielding layer  322  on top of the dielectric layer  321 . In one embodiment, the conductive shielding layer  322  is a copper foil. The copper foil is adhered to the flexible circuit  300  using lamination techniques or other techniques known in the art. 
         [0092]    In other embodiments, steps  802  and  803  can be carried out simultaneously by using a material comprised of a conductive layer and a dielectric layer. The material is adhered to the flexible circuit  300  with the dielectric layer in physical contact with the traces  311 ,  312 ,  313 ,  314 . In other embodiments, steps  802  and  803  can be carried out simultaneously by using a conductive material which adheres to the flexible circuit  300  via a dielectric adhesive. In these embodiments, where the conductive material is a copper foil, dielectric foil bonding adhesives such as ADH/PI/ADH may be used. 
         [0093]      FIG. 7D  illustrates channels  331 ,  332 ,  333 ,  334  formed between the traces  311 ,  312 ,  313 ,  314  by step  804 . The channels  331 ,  332 ,  333 ,  334  are created by removing portions of the flexible substrate  302 , the dielectric layer  321 , and the conductive layer  322  located between the traces  311 ,  312 ,  313 ,  314 . The channels  331 ,  332 ,  333 ,  334  are sufficiently deep so as to expose the bottom conductive layer  301 . As stated above, techniques such as laser ablation may be employed to create the channels  331 ,  332 ,  333 ,  334 . 
         [0094]      FIG. 7E  illustrates the copper plating  341 ,  342 ,  343 ,  344  applied to the channels  331 ,  332 ,  333 ,  334  in step  805 . The copper plating provides an electrical connection between the conductive shielding layer  322  and the bottom conductive layer  301 . To copper plate the channels  341 ,  342 ,  343 ,  344 , conventional processes such as the SHADOW® process may be used. SHADOW® is a graphite based direct metallization process that facilitates the copper plating process. 
         [0095]    In some embodiments, techniques and materials other than those used in copper plating are used to electrically connect the conductive shielding layer  322  and the bottom conductive layer  301 . Such techniques and materials may include applying silver ink using screening techniques. 
         [0096]    After an electrical connection between the conductive shielding layer  322  and the bottom conductive layer  301  has been formed, unwanted copper is removed from the flexible circuit  300  using commonly known techniques such as photolithography in step  806 . For example, copper that was inadvertently plated on the top of conductive shielding layer  322  is removed in step  806 . 
         [0097]      FIG. 7F  illustrates a dielectric layer  351  applied to the top of the conductive shielding layer  322  and the plated channels  341 ,  342 ,  343 ,  344  in step  807 .  FIG. 7G  illustrates a dielectric layer  352  applied to the bottom of the bottom conductive layer  301  in step  808 . The dielectric layers  351 ,  352  may protect the flexible circuit  350  from external shorting. However, as noted above, some embodiments employ only one or no dielectric layers  351 ,  352 . 
         [0098]    As shown in  FIG. 7G , the traces  311 ,  312 ,  313  are shielded in 360 degrees. Each trace  311 ,  312 ,  313  is insulated in all directions from the conductive shielding material and the other traces  311 ,  312 ,  313 . Dielectric layer  321  electrically insulates the top and sides of the traces  311 ,  312 ,  313  from the grounded plane  322 ,  341 ,  342 ,  343 ,  344 , and the flexible substrate  302  electrically insulates the bottom of the traces  311 ,  312 ,  313  from the grounded plane set. Accordingly, each trace  311 ,  312 ,  313  is surrounded by grounded shielding materials. Conductive layer  322  is the top grounded shielding material, and the bottom conductive layer  301  is the bottom shielding material. The plated channels  341 ,  342 ,  343 ,  344  shield the sides of the traces  311 ,  312 ,  313  and electrically connect conductive layer  322  and the bottom conductive layer  301 . 
       VI. APPLICATION EXAMPLE 
       [0099]    The apparatuses and methods for manufacturing the shielded flexible circuit disclosed herein may be employed, in one instance, in a flip phone.  FIG. 9A  depicts one type of flip phone  400 . A typical flip phone  400  comprises a body  420 , a screen  430 , and an antenna  410 . The body  420  is mechanically connected to the screen  430  via a hinge  450 . The body  420  comprises circuitry which processes data transmitted and received by the antenna  410 . Accordingly, images corresponding to the transmitted and received data are displayed on the screen  430 . 
         [0100]      FIG. 9B  depicts the flip phone  400  after the body  420  has been physically separated from the screen  430 . As shown, a shielded flexible circuit  440  according to the apparatuses and methods for manufacturing disclosed herein provides an electrical connection between the body  420  and the screen  430 . The shielded flexible circuit  440  must be mechanically flexible along the hinge&#39;s  450  axis of rotation. Such flexibility is required in order for the flip phone  400  to open and close. Moreover, due to high data rate transfers required for applications such as streaming video, the traces on the shielded flexible circuit  440  must be capable of shielding each trace from EMI created by external sources and the other traces on the flexible circuit  440 . Therefore, the shielded flexibly circuit  440  advantageously provides an electrical connection between the body  420  and the screen  430  in flip phone  400  applications. 
         [0101]    By way of example only, one embodiment of the shielded flexible circuit  440  can accommodate data transmission rates between 2 to 4 GHz without substantial signal loss or distortion due to EMI. Furthermore, in this embodiment, the distance between the centers of proximate traces may be as small as 20 thousandths of an inch. 
       VII. CONCLUSION 
       [0102]    The above presents a description of the best mode contemplated for the apparatuses and methods of manufacturing said shielded flexible circuit in such full, clear, and exact terms as to enable any person skilled in the art to which it pertains to produce these components and practice these methods. These apparatuses and methods are, however, susceptible to modifications that are fully equivalent to the embodiment discussed above. Consequently, these apparatuses and methods are not limited to the particular embodiments disclosed. On the contrary, these apparatuses and methods cover all modifications coming within the spirit and scope of the present invention.

Technology Category: 4