Abstract:
An electrostatic discharge (ESD) blocking component is set forth for a computing device. The computing device can include a housing formed of non-conducting material and an overlaying display assembly supported by the housing. The display assembly can further include a plurality of display elements such as thin film transistors (TFTs) interconnected by corresponding metallic traces. The ESD block is used to block static charges associated with an ESD event so that essentially no ESD event related static charge is accumulated on the metallic traces thereby preventing ESD related damage to the plurality of TFTs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 61/875,613, entitled “ESD PROTECTION IN CONSUMER ELECTRONIC PRODUCTS” filed Sep. 9, 2013, the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     The described embodiments relate generally to consumer electronic products and more particularly to preventing damage to circuits within the consumer electronic product caused by electrostatic discharge events. 
     BACKGROUND 
     In recent years, small form factor computing devices such as media players and cellular phones have become smaller and lighter, while incorporating more powerful operating components into densely packed configurations. This reduction in size and increase in density can be attributed in part to a manufacturer&#39;s ability to fabricate various operational components such as processors and memory devices in more compact configurations. However, this trend to smaller size and increase in component density poses a number of continuing design and challenges related to durability. 
     For example, small form factor computing devices, such as mobile phones, can be randomly subject to electrical shock from static electricity. Because of their compact size, even a small shock can do extensive damage considering the size and volatility of many of the electrical components inside the computing device. Moreover, including certain grounding mechanisms may not be available when strictly designing a computing device to be compact and less costly. It has therefore been a challenge for designers to protect consumer devices against electrical discharges while also adhering to various design limitations. 
     SUMMARY 
     The described embodiments relate generally to consumer electronic products and more particularly to preventing damage to circuits within consumer electronic products caused by electrostatic discharge events. In one embodiment, an apparatus is set forth having a cover glass assembly and a non-conductive housing adjoined to a perimeter of the cover glass assembly. The apparatus also includes an electrostatic discharge (ESD) component abutting the cover glass assembly along a perimeter of the non-conductive housing. In this way, the ESD component is configured to prevent static charge from entering the non-conductive housing. 
     In another embodiment, a computing device is set forth having a cover glass assembly and a non-conductive housing configured to support a perimeter of the cover glass assembly. Additionally, the computing device can include a housing gap between formed by the configuration of the cover glass assembly and the non-conductive housing. The computing device can also include an electrostatic discharge (ESD) component configured to both overlap an end of the housing gap and abut the cover glass assembly along a perimeter of the non-conductive housing. A ground plate can be located within the non-conductive housing of the computing device. The ground plate is electrically coupled to the ESD component to provide a conductive pathway for static electricity to travel from the housing gap, along the perimeter of the non-conductive housing, to the ground plate, for protecting the computing device from damage caused by ESD. 
     In yet another embodiment, a method is set forth for protecting a mobile computing device from electrostatic discharge (ESD) using an ESD component material. The method can include the steps of receiving the ESD component material, and configuring the ESD component material along a perimeter of a cover glass assembly, or housing, of the mobile computing device. 
     Other aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  shows a cross-sectional view of a display assembly and housing; 
         FIG. 2  shows a cross-sectional view of the display assembly and housing of  FIG. 1 , and a non-conducting ESD block; 
         FIG. 3  shows a cross-sectional view of the display assembly and housing of  FIG. 1 , and an electrically conductive ESD block; 
         FIG. 4  shows an interior surface of a protective cover layer having a non-conductive cosmetic ink layer; 
         FIG. 5  shows an interior surface of a protective cover layer having a conductive cosmetic ink layer; 
         FIG. 6  shows the conductive ink layer of  FIG. 5  coupled to a chassis ground in accordance with the described embodiments; 
         FIGS. 7A-7C  show additional components used to couple the conductive ink layer to chassis ground; and 
         FIG. 8  is a flowchart detailing a process in accordance with the described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following paper, specific details are set forth to provide a thorough understanding of the concepts underlying the described embodiments. It will be apparent, however, to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the underlying concepts. 
     This paper discusses techniques and apparatus for protecting a computing device, such as a mobile phone, from damage caused by an electrostatic discharge (ESD) event. Some computing devices can include a housing formed of a conductive material suitable for providing a ground. The housing can be comprised of materials such as metal, conductive plastic, or conductive composite material. One of the advantages to using metal (e.g., aluminum) for the housing is to provide a convenient common electrical grounding for internal components of the computing device, and mitigate the detrimental effects of electrostatic discharge (ESD). 
     However, in situations where the housing is formed of non-conductive material (e.g., plastic, ceramic, etc.), the option for utilizing the housing as a ground may not be available. Accordingly, when an ESD event occurs, static charge does not discharge at the housing, but rather moves to an interior of the computing device and potentially damages sensitive internal electrical components. In some cases, static charges can move through small gaps formed between a non-conducting housing and a cover layer (e.g., a cover glass), used to provide protection for a display of a mobile device. The gaps can be created for many reasons such as manufacturing and assembly tolerances for various components, but as a result, provide a conductive path for static charges to travel into the interior of the computing device. When the interior of the computing device includes display components such as transistors coupled by way of metallic traces, these metallic traces can collect static electrons from an ESD event causing over-voltages at one or more of the transistors, potentially causing a display of the computing device to completely fail. 
     Various approaches can be used to protect internal components from an ESD event. In one embodiment, an ESD blocking mechanism is used to block the transmission of static charge associated with the ESD event. When an ESD event occurs, sensitive components associated with a display (e.g., thin-film-transistors (TFT)) can be damaged due to over-voltages. The ESD blocking mechanism is configured to prevent a voltage spike at a termination point where a conductive element, such as a metallic trace, can be located within the housing. For example, an ESD path can start at non-conductive portions of a housing and terminate at metallic traces associated with display elements (e.g., TFT&#39;s). The voltages terminating at the metallic traces can result in voltage levels that exceed thresholds for various transistors rendering those transistors inoperative. In one embodiment, the ESD block can take the form of a dielectric material such as silicone disposed between the TFT layer in the display and an external surface of the computing device. The ESD block can be formed by placing the silicone around a perimeter of a cover layer used to protect a display assembly. The ESD blocking mechanism can be set, stamped, glued, or potted using any number of placement techniques (e.g., jetting) at a position that seals any gaps between the cover layer, non-conductive support, and/or housing members. 
     In one embodiment, the dielectric material can be doped with conductive material (e.g., silver, copper, gold, aluminum, calcium, magnesium, sodium, potassium, iron, chromium, titanium, manganese, or any other suitable conductive material or combination thereof). The doped dielectric material can then be electrically coupled to a ground plane by way of other metallic components within the housing. In one embodiment, a conductive ink layer (e.g., ink doped with conductive material) can be used to provide a conductive path. Such conductive inks can be used to enhance the aesthetic appeal of a front facing portion of the consumer electronic product, as well as electrically couple metallic structures within the housing. In this way, the conductive ink acts as a charge sink. In one embodiment, the conductive ink can be applied using a screen process. Additionally, the conductive ink can be coupled to ground traces for further grounding the consumer device and isolating the TFT layer. 
     These and other embodiments are discussed below with reference to  FIGS. 1-10 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  shows a cross section of portion  100  of a computing device that includes display assembly  102  overlaid by cover layer  104 . Display assembly  102  can take the form of a liquid crystal display (LCD) that uses thin-film-transistors (TFT) as display elements. The display assembly  102  can include a touch screen display for a user to control the computing device by touching a portion of the touch screen. In this way, cover layer  104  can be a glass layer for receiving touch commands from a user. The display assembly  102  can include a polarizer layer  106 , a color filter  108 , and a TFT layer  110 . The TFT layer  110  can include both metallic traces (not expressly shown) that couple image elements (TFT&#39;s) to form an array for outputting images and videos. Gap  112  can result from manufacturing and assembly tolerances in between cover layer  104 , support structure  114 , housing  116 , and adhesive  132 . When support structure  114  and housing  116  are formed of non-conducting material (e.g., plastic), charge carriers can be created allowing static electricity to flow between cover layer  104 , support structure  114 , and adhesive  132 .  FIG. 1  illustrates ESD event  118  traveling via gap  112  to sensitive electrical components (e.g., the TFT layer  110 ) potentially causing damage due to charge accumulation at metallic traces creating voltage spikes, and thus destroying TFT layer  110 . Embodiments are set forth herein for preventing such damage. 
       FIG. 2  illustrates embodiments where ESD block  124  (also referred to as ESD component, or ESD blocking component) and conductive ink  134  are used to prevent damage from ESD events  118  and  120 . As illustrated in  FIG. 2 , static charge associated with ESD events  118  and  120  can propagate between support structure  114 , housing  116 , and cover layer  104 . Depending on the magnitude of ESD events  118  and  120 , the static charge can collect at grounded metal object  122  or the display assembly  102 . In order to further to prevent collection of charge from destroying the display assembly  102 , and particularly the TFT layer  110 , an ESD block  124  can be installed. In this way, both TFT layer  110  and circuitry  126  associated with display assembly  102  can be protected from ESD events  118  and  120 . The ESD block  124  can be made from a non-conductive material having a high dielectric breakdown strength in order to deflect static charge. In one embodiment, ESD block  124  is formed from silicone. In some embodiments, the ESD block  124  incorporates conductive ink  134  for preventing damage during ESD events  118  and  120 . In this way, the conductive ink  134  can provides a path to carry static charges away from display assembly  102  and ESD block  124 . The conductive ink  134  can be an ink, adhesive, or any suitable material that will be reasonably permanent when incorporated into a computing device. Moreover, in some embodiments ESD block  124  can be electrically coupled to grounded metal object  122 , providing additional means for dissipating static charges. The ESD block  124  can be configured to abut the display assembly  102  (i.e., cover glass assembly), cover layer  104 , support structure  114 , and/or housing  116 . In some embodiments the ESD block  124  is glued to the display assembly  102 , cover layer  104 , support structure  114 , and/or housing  116 . 
       FIG. 3  shows another embodiment whereby ESD block  124  can be doped with electrically conductive particles (as listed herein) such as silver particles. In this way, ESD block  124  can be electrically coupled to a ground plane, ground plate, or other similar structure well suited for accumulating charge associated with ESD events  118  and  120 . In some embodiments, the ESD block  124  can be connected to or abut conductive ink  134  to provide a conducting path to ground (i.e., a path of least resistance) for static charges to dissipate during ESD events  118  and  120 . 
       FIG. 4  shows a conventional cover glass assembly  400  having a conventional cosmetic ink  402 . Cosmetic ink  402  can be used to enhance the appearance of cover glass assembly  400  by obscuring artifacts (e.g., joints) that would otherwise be visible to an end user. However, as shown in  FIG. 5 , an embodiment set forth herein includes a cover glass assembly  500  with the cosmetic ink  402  (which is non-conducting) replaced by conductive ink  502  providing a conducting path that can be configured anywhere around cover layer  104 . In some embodiments, conductive ink  502  can be configured to provide the cosmetic features associated with cosmetic ink  402 , therefore only a single layer of conductive ink  502  instead of two separate layers (cosmetic ink  402  and conductive ink  502 ) needs to be applied to the cover glass assembly  500 . In some embodiments, as shown in  FIG. 6 , conductive ink  502  can be configured around and coupled to metal feature  602  such that the resulting conducting path can be grounded accordingly. 
       FIGS. 7A-7C  illustrate the grounding of conductive ink  502 . In  FIG. 7A , the conductive ink  502  is electrically coupled to metal feature  602 . Next, in  FIG. 7B  the metal feature  602  receives a mid-plate  604  that provides a conductive pathway to chassis ground  606 .  FIG. 7C  illustrates a cross-sectional view of  FIG. 7B  wherein the conductive ink  502  is electrically coupled to a mid-plate  604  and the chassis ground  606 . Pathway  608  is illustrated in  FIG. 7C  to demonstrate a possible pathway to chassis ground  606  (or a ground plate  606 ) from conductive ink  502 . In some embodiments, conductive ink  502  can be coupled to ground features of display assembly  102  (not shown in  FIGS. 7A-7C ). 
       FIG. 8  shows a flowchart detailing a method  1000  in accordance with the described embodiments. Method  1000  can include step  1002  for creating a conductive pathway using conductive ink around the perimeter of a display assembly. The conductive pathway can be created by configuring the conductive cosmetic ink on the display assembly during a screen printing process. At step  1004 , the conductive ink can be electrically coupled to a grounded metal object on the computing device (e.g., a chassis ground). In one embodiment, grounding elements in the display assembly can be coupled to the conductive path during placement of the display assembly. The method  1000  can optionally, or exclusively, include a step  1006  of placing an ESD block on a cover layer within a housing of a computing device. The ESD block can be formed of a material having a viscosity high enough to maintain a suitable shape of ESD block within the computing device. In one embodiment, a cross section of the ESD block can be triangular, or include a suitable angle such as a right angle, in order to accommodate subsequent placement of a display assembly. The display assembly can include, for example, a polarizer layer, a color filter layer, and a TFT layer. In some embodiments, the ESD block can be rendered conductive by incorporating electrically conductive atoms (as discussed herein). In this way, the ESD block can prevent the propagation of charge carriers associated with an ESD event from collecting on certain elements within the display assembly, and potentially damaging sensitive components (such as TFT&#39;s). 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Software, hardware or a combination of hardware and software can implement various aspects of the described embodiments. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data, which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.