Patent Publication Number: US-10775844-B2

Title: Handheld computing device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/558,219 filed Jul. 25, 2012, which is a continuation of U.S. patent application Ser. No. 12/712,900 filed Feb. 25, 2010 issued Aug. 28, 2012 as U.S. Pat. No. 8,250,724, which is a continuation of U.S. patent application Ser. No. 12/205,824 filed Sep. 5, 2008, issued Apr. 13, 2010 as U.S. Pat. No. 7,697,281, contents of which are incorporated herein by reference in their entirety for all purposes. 
     This application is related to U.S. patent application Ser. No. 12/205,826 filed Sep. 5, 2008 and is incorporated herein by reference. This patent application is also related to (i) U.S. Provisional Patent Application No. 61/094,811, filed Sep. 5, 2008, entitled “ELECTROMAGNETIC INTERFERENCE SHIELDS WITH PIEZOS”, which is incorporated herein by reference and (ii) U.S. Provisional Patent Application No. 61/094,816, filed Sep. 5, 2008, entitled “COMPACT HOUSING FOR PORTABLE ELECTRONIC DEVICE WITH INTERNAL SPEAKER”, each of which are herein incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates generally to portable computing devices. More particularly, the present invention relates to enclosures of portable computing devices and methods of assembling portable computing devices. 
     Description of the Related Art 
     The outward appearance of a portable electronic device, including its design and its heft, is important to a user of the portable electronic device, as the outward appearance contributes to the overall impression that the user has of the portable electronic device. At the same time, the assembly of the portable electronic device is also important to the user, as a durable assembly will help extend the overall life of the portable electronic device and will increase its value to the user. 
     One design challenge associated with the portable electronic device is the design of the enclosures used to house the various internal components. This design challenge generally arises from a number conflicting design goals that includes the desirability of making the enclosure lighter and thinner, the desirability of making the enclosure stronger and making the enclosure more esthetically pleasing. The lighter enclosures, which typically use thinner plastic structures and fewer fasteners, tend to be more flexible and therefore they have a greater propensity to buckle and bow when used while the stronger and more rigid enclosures, which typically use thicker plastic structures and more fasteners, tend to be thicker and carry more weight. Unfortunately, increased weight may lead to user dissatisfaction, and bowing may damage the internal parts 
     Furthermore, in most portable electronic devices, the enclosures are mechanical assemblies having multiple parts that are screwed, bolted, riveted, or otherwise fastened together at discrete points. For example, the enclosures typically have included an upper casing and a lower casing that are placed on top of one another and fastened together using screws. These techniques typically complicate the housing design and create aesthetic difficulties because of undesirable cracks, seams, gaps or breaks at the mating surfaces and fasteners located along the surfaces of the housing. For example, a mating line surrounding the entire enclosure is produced when using an upper and lower casing. Not only that, but assembly is often a time consuming and cumbersome process. For example, the assembler has to spend a certain amount of time positioning the two parts and attaching each of the fasteners. Furthermore, assembly often requires the assembler to have special tools and some general technical skill. 
     Another challenge is in techniques for mounting structures within the portable computing devices. Conventionally, the structures have been laid over one of the casings (upper or lower) and attached to one of the casings with fasteners such as screws, bolts, rivets, etc. That is, the structures are positioned in a sandwich like manner in layers over the casing and thereafter fastened to the casing. This methodology suffers from the same drawbacks as mentioned above, i.e., assembly is a time consuming and cumbersome. 
     Therefore, it would be beneficial to provide a portable electronic device that is aesthetically pleasing and lightweight, yet durable. It would also be beneficial to provide methods for assembling the portable electronic device. 
     SUMMARY OF THE INVENTION 
     The invention relates, in one embodiment, to a handheld electronic device. The handheld electronic devices includes at least a single seamless housing having a front opening and a cover disposed within the front opening and attached to the seamless housing without a bezel. 
     The invention relates, in another embodiment, to seamless housing formed of a single sheet of metal. The seamless housing includes a top opening, an integral bottom and side walls that cooperate to form a cavity in cooperation with the top opening, the bottom wall having a curved bottom surface, the side walls being rounded such that they form a curved side surface and an undercut within the cavity, an inside edge of the side walls surrounding and defining the top opening, and an outside edge, a mounting bracket attached to the bottom wall suitable for securing an electronic assembly to the bottom wall of the housing and an opening in at least one sidewall having a depth of trim at least greater than that provided by the housing alone. 
     The invention relates to in another embodiment to a small form factor electronic device that includes at least a seamless housing having an integral bottom and side walls that cooperate to form a cavity in cooperation with a front opening having a flat top surface, the bottom wall having a curved bottom surface, the side walls being rounded such that they form a curved side surface and an undercut within the cavity, an edge of the side walls surrounding and defining the front opening and a plurality of electronic assemblies inserted into the seamless housing through the front opening and secured to the bottom surface of the housing, wherein a Z height tolerance of the plurality of electronic assemblies is minimized such that an upper surface of a topmost electronic assembly is substantially coplanar with the flat top surface of the housing. 
     A method of self centering a topmost glass unit in a small form factor electronic device is also disclosed. The small form factor electronic device is formed of a seamless housing having a front opening having a flat top surface and side walls where an edge of the side walls surrounds and defines the front opening and wherein the glass unit includes an environmental seal having a tapered portion, wherein at least some of the tapered portion of the environmental seal extends beyond an inner edge of the front opening. The method can be carried out by, inserting the glass unit into the front opening and self aligning the glass unit during the insertion by, interacting of the inner edge of the front opening that the portion of the environmental seal that extends beyond the inner edge of the opening, and concurrently with the interacting of the inner edge and the extended portion of the environmental seal, glass unit fasteners cooperating with a lead in device. 
     In another embodiment an integrated speaker assembly suitable for use in a small form factor portable hand held device is described. The integrated speaker assembly includes at least a piezoelectric speaker arranged to produce at least audible sounds, an acoustic seal having a plurality of acoustic seal gaps that work in cooperation with the piezoelectric speaker to direct the sound produced by the piezoelectric speaker to a desired location in the small form factor portable hand held device, and an acoustic barrier arranged to prevent audible sounds leaking to undesired locations in the small form factor electronic device. 
     The invention relates to in another embodiment to a minimum Z height mounting bracket system to secure an operational component in a handheld computing device having a seamless enclosure. The mounting bracket includes a plurality of sacrificial z adjustment bumps having a sacrificial portion arranged along the length of the mounting bracket wherein after the mounting bracket is attached to the seamless enclosure, a top portion of the seamless enclosure and the sacrificial portion of the sacrificial z adjustment bumps are machined off concurrently with a drilling a plurality of xy alignment holes, wherein the machining and the drilling are performed in a single machine set up thereby minimizing alignment tolerance in xy and z directions. 
     The invention relates in another embodiment to a method of centering a racetrack between a formed edge and an inside edge of a seamless enclosure used for supporting a handheld computing device. The method is carried out by optically determining a plurality of reference points on the formed edge of the seamless enclosure and cutting the inside edge using the plurality of optical reference points. 
     The invention relates in another embodiment to a method of centering a racetrack between a formed edge and an inside edge of a seamless enclosure having a single open end, wherein the seamless enclosure supports a handheld computing device having display portion located in the single open end. The method is carried out by determining a center point of the display portion, determining an angle of tilt of the display portion, and cutting the inside edge based upon the center point and the angle of tilt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention 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: 
         FIGS. 1A-1B  are perspective diagrams of a handheld computing device in its assembled form. 
         FIG. 1C  is a cross sectional view of the housing highlighting the nature of the undercut geometry. 
         FIGS. 2A-2E  are an exploded perspective diagrams of an electronic device in its unassembled form. 
         FIG. 3  are view diagrams of the housing showing the racetrack. 
         FIGS. 4A-4B  graphically illustrate centering a racetrack in accordance with an embodiment of the invention. 
         FIGS. 5A-5C  show low Z height integrated speaker system suitable for use in a small form factor electronic device. 
         FIGS. 6A-6B  show audio jack opening in accordance with an embodiment of the invention. 
         FIGS. 7A-7C  show assembly of G unit in accordance with an embodiment of the invention. 
         FIGS. 8A-8B  show gas relief structures in accordance with an embodiment of the invention. 
         FIG. 9  shows a representative cross sectional view of the housing where the dock opening formed by folding over a portion of the housing in accordance with an embodiment of the invention. 
         FIGS. 10A-10B  shows a representative cross sectional view of the housing where the dock opening is to be created by way of a punching/forming/machining process. 
         FIGS. 11A-11C  graphically illustrate the process for forming a short span opening in the housing. 
         FIGS. 12A-12C  graphically illustrate the process for forming a long span opening in the housing. 
         FIG. 13  shows a corner stiffener in accordance with an embodiment of the invention 
         FIG. 14  shows representative sacrificial z alignment bumps pre and post machining. 
         FIG. 15  shows a flowchart detailing a process for installing mounting brackets into a housing in accordance with an embodiment of the invention. 
         FIG. 16  shows a flowchart detailing a process for assembling the device in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to a preferred embodiment of the invention. An example of the preferred embodiment is illustrated in the accompanying drawings. While the invention will be described in conjunction with a preferred embodiment, it will be understood that it is not intended to limit the invention to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     The described embodiments relate to an aesthetically pleasing portable electronic device. The portable electronic device is formed of a curved seamless housing and an aesthetically pleasing polished flat top glass layer. The uniformity of the appearance of the portable electronic device is enhanced since unlike conventional portable electronic devices, the polished top glass layer is mounted to the seamless housing without the use of a bezel. The seamless nature of the housing and the lack of a bezel provide several advantages besides the uniform and appealing appearance. Such advantages include the fact that fewer components are required for assembly, the portable electronic device is able to more readily withstand the impact of drop event, and better protection is provided to the polished glass top layer and any sensitive operational components therein. 
     The seamless housing is formed from a single sheet of metal (such as stainless steel). The housing has an undercut geometry in which the linear dimensions of an opening into which the operational components are inserted during assembly are smaller than the linear dimensions of the body of the housing itself. Moreover, the curvature of the housing is asymmetric in that an upper portion of the housing is formed to have a deep spline (i.e., higher curvature) whereas a lower portion of the housing is formed to have a more shallow spline. This asymmetry aids in a user&#39;s tactile sensation in part because it provides a better fit to the user&#39;s hand. Moreover, the metallic nature of the housing provides good electrical grounding for built-in RF antenna as well as to mitigate the effects of electromagnetic interference (EMI) and electrostatic discharge (ESD). 
     Unlike the assembly of conventional portable electronic devices where components are assembled in a top-down manner (i.e., the components are inserted into the housing before the bezel is snapped on), the undercut geometry of the housing requires that all components fit within the smaller dimensions of the window opening in the housing. Moreover, the assembly of the portable electronic device is carried out in a bottom-up manner using what is referred to as a blind assembly. In order to facilitate the bottom-up, blind assembly of the portable electronic device and to minimize any offsets between the polished top glass layer and an uppermost portion of the housing (referred to as the racetrack), various techniques, apparatus and systems are presented that minimize stack (i.e., z direction) tolerance. For example, portions of brackets used to mount subassemblies are welded to the housing and are subsequently machined at the same time and with the same set up as a topmost portion of the housing. In this way accurate Z datums for mounting various components are provided. It should be noted that machining is preferred since machined tolerances on the order of 0.05 mm can be achieved whereas conventional weldment position tolerances are typically on the order of 0.2 mm. 
     Other aspects of the invention relate to specific approaches to minimizing the Z height of the assembled components. In other words, in keeping with both the aesthetic look and feel, the Z height of the portable electronic device is maintained to a value consistent with providing a favorable user experience. This can be accomplished in a number of ways in addition to those already discussed with regards to, for example, the mounting brackets. A minimum Z height speaker assembly can be fabricated using a piezoelectric speaker in combination with a horizontal acoustic barrier. Gaps in the horizontal acoustic barrier have the effect of directing the sound produced by the piezoelectric speaker to any desired location in the housing. For example, the sound can be directed to specific openings in the housing otherwise unrelated to the broadcasting of sound. Such openings can include for example a dock opening and/or an audio jack opening. Enhancing the perceived sound by providing a back volume (i.e., using the back surface of the housing as a resonator) can be achieved using existing components and an appropriately placed back volume acoustic seal. In order to assure that the back volume seal integrity is maintained in spite of the variance in Z tolerance between the shield and housing changes from device to device, adapters are placed in close proximity to the back volume acoustic seal. 
     Other aspects of the invention that preserve the available Z height relate to the organization of circuits associated with the battery and display screen. In particular, as described below battery and display screen circuitry co-exist in the same Y location thereby reducing the overall Y component of the circuits. In the described embodiments, the battery circuitry can include a battery safety circuit and the display circuitry can include a display controller (in the particular embodiments, the display is a liquid crystal display, LCD, and the controller is a LCD controller). Conventional designs dictate that the battery safety circuit be placed in a central portion of the battery and that the LCD controller not be aligned to a far edge of the display (this would likely increase line width and parasitic capacitance reducing the available drive of the LCD controller). Furthermore, in order to conform to the spline of the housing and to reduce the overall Z of the product, the CD controller flex is bent around the battery. 
     Furthermore, providing gas relief structures on a plastic frame used to mount the protective glass layer enhances the adhesion of glass layer to plastic frame. Such structures can be formed by, for example, removing predetermined sections of plastic frame in appropriate locations by punching holes of a predetermined size and location. In this way, any trapped gases, such as air, can escape providing a more uniform distribution of adhesive resulting in a stronger and more reliable bond between the glass layer and the plastic frame. 
     These and other embodiments of the invention are discussed below with reference to  FIGS. 1-16 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
     Throughout the following discussion, the term “CNC” is used. The abbreviation CNC stands for computer numerical control and refers specifically to a computer controller that reads computer instructions and drives a machine tool (a powered mechanical device typically used to fabricate components by the selective removal of material). It should be noted however, that any appropriate machining operation can be used to implement the described embodiments and is not strictly limited to those practices associated with CNC. 
       FIGS. 1A-1B  are perspective diagrams showing various views of fully assembled portable electronic device  10  in accordance with an embodiment of the invention. The portable electronic device  10  may be sized for one-handed operation and placement into small areas such as a pocket, i.e., the portable electronic device  10  can be a handheld pocket sized electronic device. By way of example, the electronic portable electronic device  10  may correspond to a computer, media device, telecommunication device and/or the like. The portable electronic device  10  is capable of processing data and more particularly media such as audio, video, images, etc. The portable electronic device  10  may generally correspond to a music player, game player, video player, personal digital assistant (PDA), and/or the like. With regards to being handheld, the portable electronic device  10  can be operated solely by the user&#39;s hand(s), i.e., no reference surface such as a desktop is needed. In some cases, the handheld device is sized for placement into a pocket of the user. By being pocket sized, the user does not have to directly carry the device and therefore the device can be taken almost anywhere the user travels (e.g., the user is not limited by carrying a large, bulky and heavy device). 
     The portable electronic device  10  may be widely varied. In some embodiments, portable electronic device  10  may perform a single function (e.g., a device dedicated to playing and storing media) and, in other cases, the electronic device may perform multiple functions (e.g., a device that plays/stores media, receives/transmits telephone calls/text messages/internet, and/or performs web browsing). In some embodiments, the portable electronic device  10  is capable of communicating wirelessly (with or without the aid of a wireless enabling accessory system) and/or via wired pathways (e.g., using traditional electrical wires). In some embodiments, the portable electronic device  10  may be extremely portable (e.g., small form factor, thin, low profile, lightweight). In some cases, the portable electronic device  10  may be sized for being handheld. The portable electronic device  10  may even be sized for one-handed operation and placement into small areas such as a pocket, i.e., the portable electronic device  10  can be a handheld pocket sized electronic device. 
     By way of example, the portable electronic device  10  may correspond to consumer electronic products such as computers, media players, personal digital assistants (PDA), telecommunication devices (phone), personal e-mail or messaging devices and/or the like. In one example, the electronic device may correspond to any of those electronic devices an iPod™, an iPod Nano™, an iPod Shuffle™, an iPod™ Touch or an iPhone™ available by Apple Inc. of Cupertino, Calif. 
     The portable electronic device  10  includes a housing  100  configured to at least partially enclose any suitable number of components associated with the electronic portable electronic device  10 . For example, the housing may enclose and support internally various electrical components (including integrated circuit chips and other circuitry) to provide computing operations for the device. The integrated circuit chips and other circuitry may include a microprocessor, memory, a battery, a circuit board, I/O, various input/output (I/O) support circuitry and the like. Although not shown in this figure, the housing  100  may define a cavity within which the components may be positioned and housing  100  also may physically support any suitable number of mechanisms, within housing  100  or within openings through the surface of housing  100 . 
     In addition to the above, the housing may also define at least in part the outward appearance of portable electronic device  10 . That is, the shape and form of the housing  100  may help define the overall shape and form of the portable electronic device  10  or the contour of the housing  100  may embody the outward physical appearance of the portable electronic device  10 . Any suitable shape may be used. In some embodiments, the size and shape of the housing  100  may be dimensioned to fit comfortably within a user&#39;s hand. In some embodiments, the shape includes a slightly curved back surface and highly curved side surfaces. The shape will be described in greater detail below. 
     In one embodiment, the housing  100  is integrally formed in such as way as to constitute is a single complete unit. By being integrally formed, the housing  100  has a seamless appearance unlike conventional housings that include two parts that are fastened together thereby forming a reveal, a seam there between. That is, unlike conventional housings, the housing  100  does not include any breaks thereby making it stronger and more aesthetically pleasing. 
     The housing  100  can be formed of any number of materials including for example plastics, metals, ceramics and the like. In one embodiment, housing  100  can be formed of stainless steel in order to provide an aesthetic and appealing look and feel as well as provide structural integrity and support for all sub-assemblies installed therein. When metal, the housing  100  can be formed using conventional collapsible core metal forming techniques well known to those skilled in the art. 
     The portable electronic device  10  also includes a cover  106  that includes a planar outer surface. The outer surface may for example be flush with an edge of the housing wall that surrounds the edge of the cover. The cover  106  cooperates with the housing  100  to enclose the portable electronic device  10 . Although the cover can be situated in a variety of ways relative to the housing, in the illustrated embodiment, the cover  106  is disposed within and proximate the mouth of the cavity of the housing  100 . That is, the cover  106  fits into an opening  108 . In an alternate embodiment, cover  106  may be opaque and may include touch sensing mechanism that forms a touch pad. Racetrack  122  is defined as the uppermost portion of the housing  100  that surrounds the polished top glass layer  106 . In order to maintain the desired aesthetic look and feel of the portable electronic device  10 , it is desirable that any offsets between the housing  100  and the polished top glass layer  106  be minimized and the racetrack  122  be centered. 
     The cover  106  may be configured to define/carry the user interface of the electronic device  10 . The cover  106  may for example provide a viewing region for a display screen  104  used to display a graphical user interface (GUI) as well as other information to the user (e.g., text, objects, graphics). The display screen  104  may be part of a display unit (not shown) that is assembled and contained within the housing  100 . The display unit may for example be attached internally to a metal frame (e.g.,  302 ). The cover may also provide a user clickable input button  114  (home button) that can be used to provide a user input event to the portable electronic device  10 . Such user input events can be used for any number of purposes, such as resetting the portable electronic device  10 , selecting between display screens presented on display screen  104 , and so on. In one embodiment, the cover  106  is a protective top layer of transparent or semitransparent material (clear) such that the display screen  104  is visible therethrough. That is, the cover  106  serves as a window for the display screen  104  (i.e., the transparent cover overlays the display screen). In one particular embodiment, the cover is formed from glass (e.g., cover glass), and more particularly highly polished glass. It should be appreciated, however, that other transparent materials such as clear plastic may be used. 
     In one embodiment, the viewing region may be touch sensitive for receiving one or more touch inputs that help control various aspects of what is being displayed on the display screen. In some cases, the one or more inputs can be simultaneously received (e.g., multi-touch). In these embodiments, a touch sensing layer (not shown) can be located below the cover glass  106 . The touch sensing layer may for example be disposed between the cover glass  106  and the display screen  104 . In some cases, the touch sensing layer is applied to the display screen  104  while in other cases the touch sensing layer is applied to the cover glass  106 . The touch sensing layer may for example be attached to the inner surface of the cover glass  106  (printed, deposited, laminated or otherwise bonded thereto). The touch sensing layer generally includes a plurality of sensors that are configured to activate as the finger touches the upper surface of the cover glass  106 . In the simplest case, an electrical signal is produced each time the finger passes a sensor. The number of signals in a given time frame may indicate location, direction, speed and acceleration of the finger on the touch sensitive portion, i.e., the more signals, the more the user moved his or her finger. In most cases, the signals are monitored by an electronic interface that converts the number, combination and frequency of the signals into location, direction, speed and acceleration information. This information may then be used by the portable electronic device  10  to perform the desired control function relative to the display screen  104 . 
     The portable electronic device  10  can also include one or more switches including power switches, volume control switches, user input devices and the like. A power switch  110  can be configured to turn the portable electronic device  10  on and off, whereas a volume switch  112  is configured to modify the volume level produced by the electronic portable electronic device  10 . The portable electronic device  10  may also include one or more connectors for transferring data and/or power to and from the portable electronic device  10 . The portable electronic device  10  may include an audio jack  116  and a data/power connector  118 . The audio jack  116  allows audio information to be outputted from the portable electronic device  10  by way of a wired connector. The connector  118  allows data to be transmitted and received to and from a host device such as a general purpose computer (e.g., desktop computer, portable computer). The connector  118  may be used to upload or down load audio, video and other image data as well as operating systems, applications and the like to and from the portable electronic device  10 . For example, the connector  118  may be used to download songs and play lists, audio books, photos, and the like into the storage mechanism (memory) of the portable electronic device  10 . The connector  118  also allows power to be delivered to the portable electronic device  10 . 
     The connector  118  can receive an external corresponding connector (not shown) that is capable of plugging into a host device (and/or power supply) in order to allow communications (e.g., data/power transfer) between the portable electronic device  10  and the host device. The connector may be widely varied. In one embodiment, the connector is a peripheral bus connector, such as a USB or FIREWIRE connector. These type of connectors include both power and data functionality, thereby allowing both power delivery and data communications to occur between the portable electronic device  10  and the host device when the portable electronic device  10  is connected to the host device. In some cases, the host device can provide power to the media portable electronic device  10  that can be used to operate the portable electronic device  10  and/or charge a battery included therein concurrently with the operating. In one particular embodiment, the connector is a  30  pin connector as used in many products manufactured by Apple Inc of Cupertino, Calif. Audio jack  116  can receive an audio post (not shown) that can provide audio signals to external audio rendering devices, such as headphones, speakers, etc. 
     Although the device may connect through various wired connections, it should be appreciated that this is not a limitation. In one embodiment, the electronic portable electronic device  10  also includes a mechanism for wireless communications. For example, as shown, the portable electronic device  10  may include an antenna (i.e., antenna  222 ). The antenna may be disposed internal to the housing  100 . The wireless communications can be based on many different wireless protocols including for example Bluetooth, RF, 802.11, and the like. In order to minimize any adverse impact on wireless communications in embodiments where the housing is metallic and therefore conductive, portable electronic device  10 , a portion of the housing  100  may replaced with a radio transparent cap  120  formed of a non-conductive material, such as plastic. 
       FIG. 1C  shows a cross sectional view of the housing  100  highlighting the nature of the undercut geometry. Although in general the inner cross sectional shape of the housing  100  may be the same or different from the external cross sectional shape of the housing  100 , the interior shape of housing  100  substantially conforms to the outer shape of housing  100 . The housing  100  can be formed having an undercut geometry with curvature that more easily receives the hand of a user (e.g., form fits). In particular, an interior wall of housing  100  substantially conforms to the shape of an exterior wall of housing  100 . More specifically, side wall  121  (both interior and exterior) is rounded and curved inwardly to form a concave undercut region  123  formed at an upper portion of the side wall  121  in proximity to cut edge  128 . By undercut it is meant that the side wall  121  curves back inwardly towards the interior of the housing  100 . In this way, the window opening  108  has at least smaller X dimension and Y dimension than does the body of the housing  100 . In one example, the housing  100  can have dimensions of approximately (x,y) housing =(61.8 mm, 111 mm) whereas the opening  108  can have dimensions of approximately (x,y) opening =(58.3 mm, 107.5 mm). 
       FIGS. 2A-2E  show various exploded perspective diagrams of the electronic portable electronic device  10  in its unassembled form. The portable electronic device  10  includes housing  100  shown in  FIG. 2A  into which are attached a number of operational and/or structural components. Housing  100  can take the form of a seamless enclosure. The seamless nature of the housing  100  provides an aesthetic look and feel to the portable electronic device  10  as well as provides added resistance to deformation and possible damage to internal components caused by the impact of a drop event. In the embodiments described herein, housing  100  is formed of stainless steel and having thickness of approximately 0.5 mm. It should be noted, however, that this configuration is representative in nature only and does not provide limitations constraining the ultimate scope of the invention. 
     The housing  100  extends along a vertical (Y) axis and a horizontal (X) axis having a height Z. The housing  100  can be of various sizes. For example, the housing  100  can have a height (Z) of approximately 8.5 mm, an X dimension of approximately 61.8 mm and a Y dimension of approximately 111 mm. The housing  100  includes a cavity  124  which is sized and dimensioned for the receipt of the internal components of the portable electronic device  10 . The internal components are assembled through window opening  108 . The undercut geometry of the housing  100  provides that the linear dimensions of the window opening  108  into which the operational components are inserted during assembly are smaller than the linear dimensions of the body of the housing  100 . For example, the window opening  108  can have an X dimension of approximately 58.3 mm and a Y dimension of approximately 107.5 mm. 
     One aspect of the desired look and feel is the symmetry in design and conformal appearance of portable electronic device  10 . One aspect of the symmetry of the portable electronic device  10  concerns the racetrack  122 . The racetrack  122  is the strip of metal around the cover  106  on the front face of the device. The width of the racetrack  122  is defined by an outer racetrack profile and inner racetrack profile. Since the housing  100  is made from a sheet metal material, the outer racetrack profile is achieved by sheet metal forming while the inner racetrack profile is achieved by machining where the forming tolerance is much greater than machining tolerance. In the described embodiment, the outer racetrack profile is consistent with a formed edge  126  whereas the inner racetrack profile is consistent with and cut edge  128  of housing  100  as illustrated in  FIG. 3  showing a representative cross section and top view of portable electronic device  10  highlighting the relationship of racetrack  122  and both the formed edge  126  and the cut edge  128 . 
     In order to maintain the desired appearance of portable electronic device  10  it may be desirable to properly center racetrack  122 . This centering can however be accomplished in a number of ways depending upon what is considered to be an important factor in the overall aesthetics of the design of portable electronic device  10 . In any case, a series of optical measurements are made using for example a CCD camera to measure the outside racetrack profile after a rough cut of same. Once the CCD measurements have been taken, any of a number of approaches can be used to center the racetrack  122 . However, depending upon which approach is taken can result in somewhat different results. For example, as shown in  FIG. 4A , centering the racetrack  122  using the outside racetrack profile (i.e., formed edge  126 ) will produce a consistent racetrack width, however, the gap from the housing to glass will be less consistent. On the other hand, the racetrack  122  can also be centered by forming the inner racetrack profile shape by cutting the cut edge  128  per the 3D CAD, but use the CCD measurements to find the center (x 0 , y 0 ) and any rotation angle φ for cutting the inner profile as shown in  FIG. 4B . This particular centering approach will give a less consistent racetrack width but a more consistent gap from the housing to glass. 
       FIGS. 2B-2E  illustrate the operational components of the portable electronic device  10 . In the described embodiment, the components of the portable electronic device  10  are organized in layers. The relationship and organization of the components within each layer and relationship between layers can be used to facilitate both the assembly and optimization of Z height tolerances of the portable electronic device  10 . By minimizing Z height tolerances, the electronic portable electronic device  10  is manufactured to be extremely compact, sturdy, aesthetically pleasing and ergonomic at relatively low cost. For example, the fact that the electronic portable electronic device  10  is assembled without the need of a bezel reduces manufacturing and assembly costs. The layers can include a first (main electronic) layer  200 , a second (metal frame or M-frame) layer  300  and a third (glass or G unit) layer  400  each of which is described in more detail below. 
       FIG. 2B  shows a detailed view of the first layer  200  (referred to hereinafter as PCB layer  200 ) in accordance with an embodiment of the invention. 
     The PCB layer  200  includes a first assembly  204  and a second assembly  206 , which are physically and operatively connected via a flex circuit  202 . The first assembly  204  includes a printed circuit board (PCB)  205  onto which the flex circuit  202  is attached. The printed circuit board  205  is configured to carry multiple components including for example processor, memory and the like. The printed circuit board  205  is also configured to carry an RF shield  207  that is disposed over the various components. RF shield  207  is formed from metal and configured to cover and surround the components. The first assembly also includes a speaker system  209  that is not a separate discrete system but rather a system that integrates with other components in order to properly output sound. At its core, the speaker system includes a piezo speaker  210 , acoustic seal  212  and acoustic barrier. The piezo speaker  210  is attached to the RF shield  207 , the acoustic seal  212  closes off gaps in order to form an acoustic volume between RF shield and housing. This embodiment will be described greater detail in  FIGS. 5A-5C . The printed circuit board  205  is also configured to carry the connector  118  and the audio jack assembly  116 . In the described embodiment, the audio jack  116  fits into audio jack opening  117  and acts as an interface to an external circuit (such as head or earphones) by way of a wire or other type connector. For proper fit of the audio jack  116  into the audio jack opening  117 , the audio jack opening  117  must have a shape that conforms to both the spline of the housing  100  as well as the shape of the audio jack  116  described in more detail in  FIGS. 6A-6B . 
     The PCB layer  200  can be fitted into cavity  124  of housing  100  and secured to an interior wall of the housing  100  using fasteners such as screws  208   a  and  208   b  that connect directly to housing  100  (it should be noted that screw  208   b  also facilitates RF antenna grounding discussed in more detail below). It should be noted that prior to assembly, the power button  110  is attached to the housing using a power button plate  228  and the volume button  112  is attached to the housing  110  using a volume button plate  230  each of which are electrically connected to each other by way of flex  232 . 
     One of the problems with having an active RF antenna assembly  218  in a close proximity to a number of active circuits is the generation of electromagnetic interference (EMI) that can detune or otherwise adversely affect the performance of the RF antenna  222 . For example, the relatively long conductors present in the flex  202  can act as a source of EMI that can detrimentally affect the performance of RF antenna  222 . In order to substantially reduce or even eliminate this source of EMI it would be desirable to RF ground the PCB  200 . Therefore, in order to provide a good RF ground, portions  226  of the insulating layer of flex  202  facing the inside surface of housing  100  are removed in order to expose the conductive layer therein. The portions  226  of the flex  202  that are removed typically are those regions that are relatively large and contiguous thereby having the greatest potential to provide good RF grounding when placed in contact with the metal of housing  100 . In the described embodiment, after the portions  226  of the flex  202  have been removed, the exposed conductive material is pressed down onto the housing  100 . The presence of pressure sensitive conductive adhesive (PSCA) placed between flex  202  and housing  100  provides the requisite mechanical and electrically conductive bond. In addition to providing good RF grounding, the conformance of the flex  202  to the inside surface of housing  100  reduces the overall Z profile of the PCB  200 . 
       FIGS. 2C and 2D  show a un-assembled top view and an assembled bottom view of third layer  300  referred to hereinafter as metal (M) frame assembly  300 , respectively, in accordance with an embodiment of the invention. Turning first to  FIG. 2C , M-frame assembly  300  can include M-frame  302 , battery  304  attached to the M-frame  302  by way of pressure sensitive adhesive (PSA) and display circuit  306  that includes display  104 . In the described embodiment, Z height requirements for the M-frame  300  can be reduced by using what is referred to as half shears  310 . Half shears  310  can be formed by removing portions of the M-frame  302  in those locations around screw holes in M-frame  300  used to accommodate screws  312   a  and  312   b  that attach M-frame  302  to housing  100 . In the described embodiment, a sufficient amount of material is removed from M-frame  302  such that a top portion of each of the screws  312   a  and  312   b  are essentially flush with a top surface  314  of the M-frame  302 . As described in more detail below, each half shear  310  is aligned with a Z height datum bump described in more detail below thereby further minimizing Z height requirements for portable electronic device  10 . Moreover, display unit alignment holes  316  are provided to accept alignment pins (not shown) on display unit  306  that provide x,y alignment to the housing  100  by way of alignment holes  316  in mounting brackets  136   a  and  136   b.    
     In addition to minimizing Z height requirements, the overall Y component of battery circuits and display circuits can be reduced as shown in  FIG. 2D  that graphically illustrates the organization of circuits associated with the battery  304  and display circuit  306 . In particular, battery circuitry  318  and display circuitry  320  co-exist in the same Y location thereby reducing the overall Y component of the circuits. In the described embodiments, the battery circuitry  318  can take the form of a battery safety circuit  318  and the display circuitry can include a LCD controller  320 . Conventional designs dictate that the battery safety circuit  318  be placed in a central portion of the battery  304  and that the LCD controller  320  should not be aligned to a far edge of the display circuit  306  (as this would likely increase line width and parasitic capacitance reducing the available drive of the LCD controller). However, by modifying the design of both battery safety circuit  318  and LCD controller  320 , the two circuits can be placed at the same Y location. In this way, the overall Y component of the two circuits taken together can be reduced. Furthermore, in order to conform to the spline of the housing  100  and to reduce the overall Z of the portable electronic device  10 , the LCD controller flex  322  is wrapped around and placed under the battery  304  in order for display connector  324  and battery connector  326  to mate as shown in  FIG. 2D . 
     Portable electronic device  10  includes glass, or G, unit  400  shown in  FIG. 2E . G unit  400  includes cover glass  106 . G unit  400  also includes cover glass PSA  404  used to adhere cover glass  106  to recess  407  of plastic frame  406 . Environmental seal  408  can be used to prevent dust or other unwanted environmental contaminants from entering the portable electronic device  10  after assembly. During assembly, G unit  400  can be placed within window  108  of housing  100  on top of the M-frame assembly  300  as shown in  FIGS. 7A-7C . The G unit  400  self aligns during the insertion process and secured to M frame  302  using M-frame lead in  324 . G unit  400  includes a double shot arrangement formed of plastic frame  406  and an environmental, or cosmetic, seal  408  made of, for example, thermoplastic urethane (TPU), rubber, and the like that can act to protect portable electronic device  10  from dust and or moisture. As described below, the shape of environmental seal  408  in relation to housing  100  aids in self aligning G unit  400  to window  108  opening during assembly. During the assembly process as shown in  FIG. 7A , the G unit  400  is inserted into window opening  108  by bringing plastic frame  406  into contact with M-frame lead in  324 . In the described embodiment, both the environmental seal  408  and the M-frame lead in  324  have corresponding tapered shapes that provide for the G unit  400  to self align. For example, in  FIG. 7B , as the G unit  400  is being inserted into the window opening  108 , the plastic frame  406  encounters the tapered shape of the M-frame lead in  324 . The M-frame lead in  324  has the effect of both aligning and securing the G unit  400  until such time as shown in  FIG. 7C  that the tapered edge of the environment seal  408  encounters the inside, or cut edge,  128  of the housing  100 . A portion  410  of the environmental seal  408  extends beyond the cut edge  128 . In the described embodiment, the portion  410  has a tapered edge that causes the G unit  400  to self center to the window opening  108  as shown in  FIG. 7C  until the G unit  400  is captured by M-frame lead in  324 . 
     During assembly, when pressure is applied to G unit  400 , trapped gases coalesce into gas bubbles having the result of minimizing the bond area between the pressure sensitive adhesive (PSA) and the glass  106 . The gas become trapped due in part to the fact that due to assembly tolerances, the PSA would touch the seal closing off a gas escape route (see  FIG. 8A ). Therefore, it would be advantageous to provide gas relief structures or assembly techniques on plastic frame  406  thereby enhancing the adhesion of glass layer  106  to plastic frame  406 . Gas relief techniques can include removing predetermined sections of plastic frame  404  in appropriate locations by for example punching holes of a predetermined size and location or by removing small amounts of PSA from corners of the portable electronic device  10  allows trapped gas to escape more easily as shown in  FIG. 8B . In this way, a more uniform distribution of adhesive resulting in a stronger and more reliable bond between glass layer  106  and plastic frame  404  can be achieved. 
       FIG. 5A  shows an integrated, or minimum Z height speaker assembly  500  which is a particular embodiment of the integrated speaker assembly shown in  FIG. 2B . The minimum Z height speaker assembly  500  includes at least a piezoelectric speaker  210  in combination with acoustic seal  212  and a horizontal (Y) acoustic barrier  502 . Gaps  504  in the acoustic seal have the effect of directing the sound produced by the piezoelectric speaker  210  to any desired location in the housing  100 . For example, the sound can be directed to specific openings in the housing  100  otherwise unrelated to the broadcasting of sound. Such openings can include for example dock opening  119  and/or an audio jack opening  117 . The horizontal acoustic barrier  502  ensures that substantially no sound leaks to undesired portions of the housing  100  such as gaps associated with the volume button  112 , power button  110 , or the antenna cap  120 . Furthermore, as shown in  FIG. 5B , a back volume seal  506  can form an acoustic cavity  508 , also referred to as a back volume, in cooperation with the housing  100 . In this way, by using existing components, Z height requirements for creating the back volume  508  are reduced and a backside portion of the housing  100  can act as a resonator arranged to enhance the audio experience of a user. Since the back volume  508  is created using existing components (i.e., housing  100  and acoustic barrier  502 ), there is no adverse impact on the overall Z height of the portable electronic device  10 . 
       FIG. 5C  shows selected crush zones  510  that are provide for adjustments for variations in Z tolerances and assure the integrity of the back volume  508 . During assembly of portable electronic device  10 , pressure can be exerted onto PCB  200  that has the effect of compressing, or crushing, crush zones  510 . In this way, any variations in Z height of the various components of PCB  200  can be accommodated without comprising the integrity of the back volume  508 . It should be noted that crush zones  510  can take on any of a number of shapes and sizes and be formed of any resilient material able to form a seal between the housing  100  and the back volume seal  506 . 
     As shown in  FIG. 6A , one of the problems with the asymmetric geometry of the housing  100  is that as the bottom cut surface (point “A”) of audio jack opening  117  moves up in the positive Z direction, the edge of the cut moves in a negative Y direction due to the high curvature of the housing  100 . In other words, a small change in the positive Z direction results in a large change in the negative Y direction. Since the audio jack  116  is fixed in the Z direction, the size of the audio jack opening  117  must not come so close to the upper portion of the housing  100  so as to present a risk to the cover glass  106  as would be the case if the audio jack opening  117  were formed too far into the shallower portion of the housing  100 . In any case, having a fully circular portion in the shallower geometry of the housing  100  can result in very sharp edges (as shown in  FIG. 6A ) that must be machined down. Conventional machining processes, however, would cause the housing  100  in that region to become unacceptably thin presenting a risk of damage in an impact event. Therefore, in order to accommodate the circular shape of audio jack  116 , the spline of housing  100 , as well as to decrease the audio jack trim (the material around the audio jock structure itself) as little as possible, an non-symmetric audio jack opening  117  is formed as shown in  FIG. 6B  having circular portion  602  and a non circular portion  604  providing the non-symmetric shape for audio jack opening  117 . In this way, the audio jack opening  117  provides that the audio jack  116  and the audio jack opening maintains a centered and circular appearance especially when viewed from above. It should be noted that it has been discovered that subsequent to the forming of the audio jack opening  117  in this manner, a deburring process for touch up can be performed using materials considered unconventional in the art of deburring. Such materials can include, for example, a bamboo wooden stick, wooden chopsticks, and the like. 
     In order to accommodate various interfaces (dock, audio jack, volume, power, for example), openings of various sizes must be created in the housing  100 . There are a number of approaches that can be used to create these openings and make the opening trim appear to be thicker than the thickness (0.5 mm) of the sheet metal used to create the housing  100 . One approach relies upon drawing or folding the sheet metal that forms the housing  100  as shown in  FIG. 9 . In any case, creating these openings in the housing  100  can result in long and thin webs of metal that can deform from the impact of a drop event, for example. In order to reinforce these areas, any of a number of different techniques can be used to add an additional layer of material (referred to as child material) to the parent material, which in this case is stainless steel having an approximate thickness of 0.5 mm. In some embodiments, the child material can be bonded to the parent material by welding, soldering, brazing or gluing. Once the child material is bonded to the parent material, a one stage cut is performed (machine or laser cut or punch, for example) in order to create the actual hole geometry. 
       FIGS. 10A-10B  shows a representative cross sectional view of the housing  100  in the area of the dock opening  119 . However, due to the thickness (approximately 0.5 mm), the material (stainless steel) from which the described housing is formed, and the geometry (i.e., deep spline) of the housing  100  obtaining the desired deep cut is difficult to achieve in a large scale manufacturing environment. In particular, looking at  FIG. 10A , due to the geometry of the housing  100  using a conventional punching operation to create the dock opening  119  would result in unacceptable asymmetric cut between the steep spline of the top portion and shallower spline of the lower portion of housing  100 . Therefore as illustrated in  FIG. 10A , a metal support bracket  1002  having a thickness approximately that of the housing  100  (which in this embodiment is approximately 0.5 mm) can be attached to the inside wall of housing  100  using solder or braze material or glued. By using solder or braze material or glue, the support bracket  1002  can be securely attached to the housing  100  as well as provides a good cosmetic result since the solder or braze material obscures the gap between the housing  100  and support bracket  1002 .  FIG. 10B  shows a result of the punching operation to form the dock opening  119 . By using the support bracket  1002 , a double wall is formed in the area of the housing  100  in which the dock opening  119  (or any opening in housing  100  for that matter). In the described embodiment, since any gaps between support bracket  1002  and housing  100  are filled with solder or braze, both the desired cosmetic appearance and the desired structural integrity and strength can be maintained. It should be noted that in order to provide optimal strength for holes having large spans (volume button opening), the respective support brackets are positioned such that the presumptive hole is positioned approximately midway of the support bracket. 
       FIGS. 11A-11C  graphically illustrate the process for forming the dock opening.  FIG. 11A  illustrates the placement of support bracket  1002  on housing  100  in relation to proposed dock opening  117 . The support bracket  1002  can be welded to housing  100 .  FIG. 11B  shows in profile view juxtaposition of support bracket  1002  and proposed dock opening. In this case, the support bracket  1002  covers the entire area of the proposed dock opening in order to provide maximum support post CNC. Accordingly,  FIG. 11C  shows in profile the post punching operation and CNC of dock opening  119 , the support bracket  1002  having an upper portion  1102  and a lower portion  1104 . It should be noted that in order to cosmetically hide the gap between the support bracket and housing  100 , solder or braze material can be used to fill any gaps post CNC. 
     In the case of openings having long spans, such as the volume control button,  FIGS. 12A-12C  graphically illustrate the process for forming a long span opening such as the volume button opening.  FIG. 12A  illustrates the placement of support bracket  1202  on housing  100  in relation to proposed volume button opening. It should be noted that in this case, the support bracket  1202  only extends approximately midway in the y direction since the primary area requiring support is that thin strip  1204  above the proposed volume control button. The thin strip  1204  is susceptible to deformation during an impact event.  FIG. 12B  shows a profile view of the juxtaposition of the support bracket  1202 , the housing  100 , and the proposed location of the volume control button.  FIG. 12C  shows the post laser cut of the volume control button illustrating the upper support bracket providing the requisite support for any long span openings in housing  100  such as volume button. 
     It should be noted, however, that the above procedures are predicated on materials, such as stainless steel, and geometries (i.e., those have steep splines) that are not conducive to providing symmetric cuts or the proper depth of cut in a punching type operation. However, it is contemplated that using material other than stainless steel, such as aluminum, can provide the requisite symmetry. In these cases, a one piece punch and CNC can be used. It should further be noted that the thickness of the support brackets can be varied but it is found that having a thickness approximate to that of the housing  100  works well. 
     In order to prevent interference with RF antenna  222 , housing material is removed from housing  100  to form antenna hole  127 . The antenna hole  127  by removing conductive housing material using a laser and replaced with non-conducting material such as plastic to form antenna cap  120 . In this way, the interference caused by the presence of a conducting material such as metal in the immediate vicinity of RF antenna  222  is eliminated. However this cutting away may cause the corner portion  128  of the housing  100  to become weakened to the point where it becomes susceptible to deformation or damage due to an impact event. Therefore, a corner stiffener  131  can be used to provide structural support for the corner portion  128  of the housing  100  by reinforcing the sidewall of housing  100  of the corner portion  128  as shown in  FIG. 13 . Corner stiffener  131  is welded to or otherwise attached to housing  100 . However, in contrast to other support brackets such as those for volume button and dock, the corner stiffener  131  serves two purposes, one to provide additional structural integrity to the corner  128  of housing  100  where material is to be removed and another as a ground for RF antenna  222 . In the described embodiment, antenna ground  132  is connected to RF antenna  222  by way of antenna screw  208   b . In order to provide good electrical connection between RF antenna  222  and corner stiffener  131 , antenna ground  132  must remain substantially intact both in order to mechanically receive antenna screw  208   b  and provide good electrical contact to corner stiffener  131  (and housing  100 ). 
     Due to the size and location of antenna hole  127 , a laser is used to remove the necessary amount of material from the housing  100  to form the antenna hole  127 . However, the antenna ground  132  extends into the region in close proximity to the material to be lasered off. Since antenna ground  132  must remain relatively intact, antenna ground  132  is protected against any dross generated by the laser removing material to form the antenna hole  127  by a shield formed of for example, foam, or any other protective material that can be easily removed subsequent to the forming of antenna hole  127 . 
     Returning to  FIG. 2A  showing a detailed view of housing  100 . As shown, the housing  100  includes a number of attachment fixtures used for attaching subassemblies to housing  100 . Such attachment features can include, for example, PCB subassembly securing fixtures  134   a  and  134   b , and  134   c  that can be used to attach PCB assembly  200  to housing  100  using fasteners such as screws  312   a ,  312   b  and screw  208   a , respectively. It should be noted that screws  208   a  attach M-frame assembly  300  and PCB  200  to housing  100  using fixtures  134   a  and  134   b  unlike screws  312   a  and  312   b  that attach M-frame assembly  300  directly to mounting brackets  136   a  and  136   b . As discussed above, RF ground  132  is used to both secure PCB  200  to housing  100  as well as provide a ground plane for RF antenna  222 . 
     Mounting brackets  136   a  and  136   b  are used to secure M-frame subassembly  300  to housing  100 . However, conventional approaches to attaching mounting brackets to housing  100  utilize high temperature attaching processes, such as laser welding, that can and usually do result in cosmetic damage to the exterior surface of the housing  100 . This cosmetic damage can require expensive and time consuming remediation, such as polishing, that can increase the cost of and time required to assembly the portable electronic device  10 . Therefore, in order to avoid the creation of the cosmetic damage, only low temperature attachment processes are used to attach mounting brackets  136   a  and  136   b  to housing  100 . In order to eliminate cosmetic damage caused by high temperature attachment processes (such as laser welding), mounting brackets  136   a  and  136   b  are placed in appropriate locations on inside surface of housing  100  using a low temperature weld process. Once positioned, mounting brackets  136   a  and  136   b  are securely attached to inside surface of housing  100  using a low temperature solder process. By using low temperature weld and solder processes, any damage, cosmetic or otherwise, to external surface of housing  100  that would have been caused by the attachment of mounting brackets  136   a  and  136   b  to housing  100  using conventional methods such as high temperature processes is eliminated. Therefore, in contrast to the conventional approach of using high temperature attachment processes, using low temperature attachment processes eliminates the necessity to perform a post attach polishing or other remediation on the exterior surface of the housing  100 . In this way, the aesthetic look and feel of portable electronic device  10  is preserved. In this way, the mounting brackets  136   a  and  136   b  provide reference surfaces for receiving and supporting some portion of the internal components. Furthermore, the mounting brackets  136   a  and  136   b  provide Z datum bumps  138  that minimize Z height, or stack, tolerance of the assembled internal components discussed in more detail below. 
     During the assembly of portable electronic device  10 , the PCB  200 , M-frame assembly  300  and G unit  400  are placed one atop the other during what is referred to as a blind assembly operation in which each layer must align with each every other layer with minimum Z height tolerance. As well known in the art, whenever a manufacturing operation requires a number of different setups, each separate setup has an associated tolerance each of which is added to all the other tolerances. By minimizing the number of setups in a manufacturing operation, the total Z height tolerance for the operation can be kept to a minimum. Therefore, in order to minimize Z height tolerances in the assembly of portable electronic device  10 , a number of novel approaches have been devised. For example, in order to minimize the Z height tolerance in attaching the M-frame assembly  300  to the housing  100 , the mounting brackets  136   a  and  136   b  include the aforementioned Z datum bumps  138  (where two Z datum bumps are located on either side of M-frame screw holes  144  and  146 ). It should be noted that the Z datum bumps  138 , the machined top surface  140  of the housing  100 , and display unit alignment holes  142  are machined at the same time using a single set up (as illustrated in  FIG. 14 ). In this way, a Z height tolerance in relation to the top surface  140  of the housing  100  of approximately 0.05 mm can be achieved (compared to a Z height tolerance of approximately 0.2 mm using a standard soldering approach with multiple set ups). 
       FIG. 15  shows a flowchart detailing a process  1500  for installing mounting brackets into a housing in accordance with an embodiment of the invention. The process  1500  begins at  1502  by providing mounting brackets having sacrificial z adjustment bumps located thereon. In the described embodiment, the z adjustment bumps are arranged to have a portion of which can be machined away during a subsequent machining process during which a top portion of the housing is also machined off. At  1504 , the mounting brackets are positioned within the housing using a low energy attachment process such as a low energy weld. Next at  1506 , the positioned brackets are soldered in place. The following operations are performed during a single set up, where at  1508  the top portion of the housing is machined off, the sacrificial portion of the z adjustment bumps is removed at  1510 , and display unit x,y alignment holes are drilled in the bracket at  1512 . 
       FIG. 16  shows a flowchart detailing a process  1600  for assembling the portable electronic device  10  in accordance with an embodiment of the invention. Firstly, at  1602 , a pre-assembled housing is received. In the described embodiment, the housing has had all appropriate openings formed, support brackets and attachment fixtures affixed thereto. At  1604 , the PCB assembly is placed within the housing cavity. Since the window opening is smaller than the housing body, the insertion of the PCB assembly is done by inserting either the first or the second portion first followed by the remaining portion. For example, when inserting the PCB assembly, if the first portion of the PCB assembly is inserted first, then the dock and the audio jack are inserted into their appropriate openings in the housing. Once the dock and the audio jack are properly seated, then the second portion of the PCB assembly is inserted, which in this case includes the RF antenna assembly. Once the PCB assembly is in place, then a portion of the conductive layer of the flex portion of the PCB assembly is exposed at  1606 . It should be noted that this step can be performed anytime prior to the insertion of the PCB into the housing. By exposing a portion of the conductive layer of the flex portion, an RF ground plane can be established by the housing. Once the conductive layer of the flex portion has been exposed, the PCB assembly is secured to the housing at  1608 . In the described embodiment, the PCB assembly can be secured using screws to attach the first portion of the PCB assembly including the dock and the audio jack to the housing directly using PCB attachment fixtures. Once the PCB has been secured to the housing, the exposed conductive layer of the flex is conformally pressed to the inside surface of the housing at  1610 . In the described embodiment, pressure sensitive conductive adhesive can be used to adhere the exposed portions to the housing. In addition to providing a good electrical contact thereby providing a good RF ground—by pressing the flex onto the inside surface of the housing, the flex is mechanically secured to the housing and also the amount of space taken up by the flex is concomitantly reduced. 
     Once the PCB is in place and secured, a pre-assembled M-frame and battery are received at  1612 . By pre-assembled it is meant that the battery has already been attached to the M-frame by way of the pressure sensitive adhesive (PSA). At  1614 , the display unit is placed upon the side of the M-frame opposite to that of the battery. It should be noted that the display unit is not attached to the M-frame at this point since the display unit must be tilted up in order to gain access to the display flex. The display flex is then placed under the battery and electrically connected to the battery electrical connector at  1616 . Once the battery and the display unit have been electrically connected to each other, the M-frame assembly, including the battery and the display unit are secured to the housing using a number of available screws at  1618 . Again since the display unit is not attached directly to the M-frame, the display unit is lifted in order to gain access to the screw holes in the M-frame. 
     It should be noted that in the described embodiment, a number of the available screws used to attach the M-frame assembly to the housing utilize mounting brackets attached directly to the housing. These mounting brackets include a number of Z height datum bumps that provide a Z reference for M-frame assembly. In addition, some of the remaining available screws are used to attach the M-frame assembly as well as the PCB to the housing. Once the M-frame has been secured to the housing, the display unit is aligned using a number of alignment pins placed diagonally from each other on either side of the display unit at  1620 . The alignment pins can be used to mate with alignment holes in the mounting brackets. At  1622 , the touch panel is electrically connected to the battery and at  1624 , the glass unit is inserted into the window opening and secured to the M-frame at  1626 . 
     While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. For example, although an die cast process is preferred method of manufacturing the seamless enclosure, it should be noted that this is not a limitation and that other manufacturing methods may be used. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.