Abstract:
A method of using ultrasonic energy to secure a first and a second component is described, and an apparatus formed therefrom. A first layer is bonded to a second layer by converting ultrasonic energy into thermal energy. The energy conversions means is an energy director. A thermally sensitive layer receives the thermal energy and at least a portion of the thermally sensitive layer melts. The resultant melting bonds the first layer with the second layer. A different energy director may also be included and used to convert thermal energy in order to de-bond the first layer from the second layer in order to perform, for example, a rework.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C §119(e) to U.S. Provisional Application No. 61/914,324, filed on Dec. 10, 2013, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    This disclosure relates generally to display devices and more particularly to using ultrasonic welding techniques to secure components of a cover glass assembly used to protect an underlying display assembly. 
       BACKGROUND 
       [0003]    Many electronic devices include display assemblies that are used to present visual content. Generally, the display assembly includes a display unit having an electronic display having display elements (also referred to as picture elements, or pixels). The display elements can be easily damaged by errant contact or rough handling (such as occurs during a drop event) or can be rendered unreliable in the face of environmental contamination such as dust or moisture. Therefore, the display elements are overlaid by a series of protective layers used to provide protection against damage cause by either or both handling and the environment. The protective layers are generally coupled to a frame assembly by way of an adhesive, such as pressure sensitive adhesive, or PSA. However, in order to minimize the possibility of the PSA (or whatever adhesive is used) from marring the appearance of the electronic device (for example, too much adhesive or mis-located adhesive can overflow a designated area onto the transparent cover glass). These types of visible defects can detract from the cosmetic appearance of the part. 
       SUMMARY 
       [0004]    In one aspect, a method of using ultrasonic energy to secure a first and a second component is described. The method is carried out by forming a laminate structure comprising a plurality of layers at least one of which is an adhesive layer where at least one of the first and second components includes an array of ultrasonic energy directors configured to provide thermal energy in response to incident ultrasonic energy, positioning the laminate structure relative to the first and second components, and exposing the laminate structure to the incident ultrasonic energy causing at least some of the array of ultrasonic energy directors to emit thermal energy sufficient to melt associated portions of the laminate structure resulting in a corresponding bond between the first and second components. 
         [0005]    In another aspect, a method of securing a cover glass to a frame member is described. The method is carried out by providing ultrasonic energy to a laminate structure which includes the cover glass, the frame member, and a thermally sensitive layer disposed between the cover glass and the frame member, and providing ultrasonic energy to a first energy director positioned on at least the one of the cover glass or the frame member, the first energy director configured to convert at least some of the ultrasonic energy to thermal energy, the thermal energy emitted from the first energy director melts a portion of the thermally sensitive layer thereby bonding the cover glass to the frame member. 
         [0006]    In another aspect, a laminate structure is described. The laminate structure includes a first layer, a second layer, a first energy director configured to receive ultrasonic energy and convert at least some of the ultrasonic energy into thermal energy, and a thermally sensitive layer. A portion of the thermally sensitive layer melts in response to the thermal energy in order to bond the first layer to the second layer. 
         [0007]    Other apparatuses, methods, features and advantages of the disclosure will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the disclosure, and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The included drawings are for illustrative purposes and serve only to provide examples of possible structures and arrangements for the disclosed apparatuses, assemblies, methods, and systems. These drawings in no way limit any changes in form and detail that may be made to the disclosure by one skilled in the art without departing from the spirit and scope of the disclosure. 
           [0009]      FIG. 1  shows a top view of a portable computing device in accordance with the described embodiments; 
           [0010]      FIG. 2  shows an exploded view of a display assembly in accordance with the described embodiments; 
           [0011]      FIG. 3  shows an embodiment of an energy director; 
           [0012]      FIG. 4  shows another embodiment of an energy director; 
           [0013]      FIG. 5  shows a cross section of a display assembly in accordance with the described embodiments; 
           [0014]      FIG. 6  shows an ultrasonic welding process of a display assembly in accordance with the described embodiments; and 
           [0015]      FIG. 7  shows a flow chart detailing a process in accordance with a described embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Representative applications of methods according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent 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 described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
         [0017]    A method of using ultrasonic energy to bond a first and second component using a laminate structure disposed between the first and second components is described. In one embodiment, at least some of the ultrasonic energy is received at receptors positioned within or in proximity to the laminate structure. The receptors can have a size and shape that cooperates with the directed ultrasonic energy to emit thermal energy of sufficient magnitude to melt a corresponding portion of the laminate structure. The melting of the corresponding portion of the laminate structure can form a bond between the first and second components. In this way, components not generally suitable for attachment using conventional adhesives or ultrasonic bonding alone can nonetheless be attached to each other forming a robust and environmentally secure seal. 
         [0018]    In a particular embodiment, a method is described for securing a cover glass assembly to a frame (generally formed of plastic) forming part of a display module configured for presenting visual content. In some embodiments, the display module can be associated with a portable computing device that can take many forms such as a tablet computer, smart phone and so on. Moreover, the portable computing device can include at a least single piece housing. The single piece housing can be used to enclose and support a plurality of operational components (such as the display module) used to provide a desired set of functions. In particular embodiments, the display module can include the cover glass that can be bonded to a display frame using ultrasonic energy directed at receptors disposed within or in proximity to the laminate structure. The receptors can absorb at least some of the directed ultrasonic energy that is then converted to thermal energy. The thermal energy can cause at least a portion of the laminate structure to melt resulting in a bond formation between the frame and cover glass. In one embodiment, the laminate structure can include an optically clear adhesive layer and an optically clear plastic layer. The optically clear adhesive layer can be disposed between the cover glass and the optically clear plastic layer. In this way, the optically clear adhesive layer can provide mechanical support for the cover glass and enhance the bond formation between the cover glass and the frame. 
         [0019]    Selected portions of the display frame can include an array of receptors hereinafter referred to as ultrasonic energy directors arranged to convert ultrasonic energy to thermal energy used to melt corresponding portions of the laminate structure. In some embodiments, a first set of ultrasonic energy directors can be positioned on the frame in a first pattern and be configured to convert ultrasonic energy at a first frequency range to a corresponding amount of thermal energy. In one embodiment, the first frequency range can include ultrasonic energy having an approximate frequency of 30 kHz. In other embodiments, a second set of ultrasonic energy directors can be positioned on the frame in a second pattern and/or be configured to convert ultrasonic energy to thermal energy at a second frequency range. In this way, during an assembly process, the first set of energy directors can be used to the melt selected portions of the laminate structure to form the bond between the cover glass and the frame. However, during a rework process, the bond between the cover glass and frame can be weakened such that the cover glass and frame can be separated from each other without causing undue damage. Accordingly, during the rework process, ultrasonic energy at the second frequency range can be directed at the second set of energy directors that can generate sufficient thermal energy to weaken the bond between the cover glass and the frame. 
         [0020]      FIG. 1  illustrates a specific embodiment of portable computing device  100 . More specifically,  FIG. 1  shows a full top view of fully assembled portable computing device  100 . Portable computing device  100  can process data and more particularly media data such as audio, video, images, etc. By way of example, portable computing device  100  can generally correspond to a device that can perform as a music player, game player, video player, personal digital assistant (PDA), tablet computer, or a combination thereof. With regards to being handheld, portable computing device  100  can be held in one hand by a user while being operated by the user&#39;s other hand (i.e., no reference surface such as a desktop is needed). For example, the user can hold portable computing device  100  in one hand and operate portable computing device  100  with the other hand by, for example, operating a volume switch, a hold switch, or by providing inputs to a touch sensitive surface such as a display or pad. 
         [0021]    Portable computing device  100  can include single piece seamless housing  102  that can be formed of any number of materials such as plastic or metal that can be forged, molded, or otherwise processed into a desired shape. In those cases where portable computing device  100  has a metal housing and incorporates RF (radio frequency) based functionality, it may be advantageous to provide at least a portion of housing  102  in the form of radio (or RF) transparent materials such as ceramic, or plastic. In any case, housing  102  can be configured to at least partially enclose any suitable number of internal components associated with the portable computing device  100 . For example, housing  102  can enclose and support internally various structural and electrical components (including integrated circuit chips and other circuitry) to provide computing operations for portable computing device. The integrated circuits can take the form of chips, chip sets, modules any of which can be surface mounted to a printed circuit board, or PCB, or other support structure. For example, a main logic board (MLB) can have integrated circuits mounted thereon that can include at least a microprocessor, semi-conductor (such as FLASH) memory, various support circuits and so on. 
         [0022]    Housing  102  can include opening  104  for placing internal components and may be sized to accommodate a display assembly  200  (see  FIG. 2 ) or system suitable for providing a user with at least visual content as for example via a display. In some cases, the display assembly can include touch sensitive capabilities providing the user with the ability to provide tactile inputs to portable computing device  100  using touch inputs. The display assembly can be formed of a number of layers including a topmost layer being a transparent protective layer  106  formed of polycarbonate or other appropriate plastic or highly polished glass. Using highly polished glass, transparent protective layer  106  can take the form of cover glass  106  substantially filling opening  104 . 
         [0023]      FIG. 2  shows a cross section of display assembly  200  in accordance with the described embodiments. Display assembly  200  can be sized in accordance with opening  104  and used to present visual content by portable computing device  100 . More specifically, display assembly  200  can include cover glass  202  used to provide protection to underlying display elements used to provide visual content. Cover glass  202  can be formed of optically clear material such as glass or plastic. Display assembly  200  can also include a number of layers used to support cover glass  202  as well as provide a bonding medium for attachment of cover glass  202  to frame  204 . For example, in order to prevent the liquid adhesive from over running cover glass attach area  206  (area used to bond to cover glass  202 ), conventional assembly techniques rely upon a pre-curing operation that partially cures the liquid adhesive. Although the partially cured liquid adhesive has a reduced tendency to over run attach area  206  (and thus mar the appearance of portable computing device  100 ), the likelihood of forming an impaired bond is increased. The impaired bond can result in an increased possibility of problems associated with contamination by dust particles, moisture, etc. or by increasing the likelihood of delamination of display assembly  200  due to external events, such as those associated with a drop event. 
         [0024]    Accordingly, laminate structure  208  can be used to provide precision bonding between cover glass  202  and frame  204 . The precision bonding can be accomplished without adhesive over run associated with conventional techniques. In one embodiment, laminate structure  208  can include optically clear adhesive layer  210  attached to an underside portion of cover glass  202 . In this way, adhesive layer  210  can provide mechanical support for cover glass  202  as well as enhance the bond formed between laminate structure  208  and frame  204 . In some embodiments, laminate structure  208  can also include optically clear plastic layer  212 . In some cases, optically clear adhesive layer  210  can be disposed between optically clear plastic layer  212  and cover glass  202 . Ultrasonic energy directors  214  can be arranged in specific patterns and positioned at specific locations on frame  204  within frame attach area  216 . During an assembly operation, ultrasonic energy corresponding to a pre-determined frequency range can be directed at the ultrasonic energy directors  214 . At least some of the directed ultrasonic energy can be absorbed by ultrasonic energy directors  214  in a manner that causes ultrasonic energy directors  214  to melt and/or emit thermal energy. The thermal energy in turn causes a corresponding portion of laminate structure  208  to melt resulting in a bond formation between cover glass  202  and frame  204  mediated by the melted portions of laminate structure  208 . 
         [0025]    In some embodiments, ultrasonic energy directors  214  can have a size and shape in accordance with a specific range of ultrasonic energy. For example, as shown in  FIGS. 3  and  4 , ultrasonic energy directors  214  have a pyramidal shape having an apex region and a base region. 
         [0026]    The apex region  224  of energy directors  214  concentrates incident ultrasonic energy from an ultrasonic energy source  250  (shown in  FIGS. 5 and 6 ), thereby causing each energy director to melt from the apex region down to the corresponding base region forming a flattened structure that emits sufficient thermal energy to melt a corresponding portion laminate structure  208  including both optically clear plastic layer  212  and optically clear adhesive layer  210 . In this way, the location, size, and shape of energy directors  214  can be used to selectively bond portions of frame  204  and cover glass  202  in a precise manner.  FIG. 6  illustrates energy directors  214  being flattened, or melted, after sufficient ultrasonic energy is applied. 
         [0027]    Accordingly, judicious placement of ultrasonic energy directors  214  can be enhance bond strength at specific locations prone to excess stress during abnormal use events (such as being dropped). For example, ultrasonic energy directors  214  can be positioned at a specific angle (such as 45 degrees) with respect to an external featured (such as a corner) to promote bond formation. In this way, those portions of display assembly  200  (such as those associated with a corner region) susceptible to damage caused by abnormal use events can be bolstered to reduce the possibility of, for example, delamination. 
         [0028]      FIG. 7  shows a flowchart detailing process  400  in accordance with the described embodiments. More specifically, at  402 , an intermediate laminate structure is formed. The intermediate laminate structure can be formed in many ways. For example, referring to  FIG. 2 , the intermediate laminate structure can be formed by attaching adhesive layer  210  to cover glass  202  that, in turn, can be attached to plastic layer  212  (via adhesive layer  210 ). In another embodiment, the laminate structure can be formed by die cutting adhesive layer  210  and plastic layer  212 . The laminate structure can then be attached to cover glass  202  for ultrasonic bonding to frame  204 . At  404 , the intermediate structure positioned for bonding. At  406 , the laminate structure is exposed to ultrasonic energy at a frequency range suitable for causing energy directors to emit thermal energy sufficient to melt selected portions of the laminate structure resulting in a bond formation between the cover glass and frame mediated by the melted portions of the laminate structure. In some embodiments, a rework operation can include exposed an assembly part to ultrasonic energy at a different frequency having the effect of weakening the adhesive bond allowing for easy removal of the display assembly from the frame. 
         [0029]    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 described embodiments. 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 described embodiments 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.