Patent Publication Number: US-9854683-B2

Title: Lightweight electronic device for automotive applications and method

Description:
RELATED APPLICATIONS 
     The present application is a divisional of U.S. Ser. No. 14/100,794, filed 9 Sep. 2013, entitled “LIGHTWEIGHT AUDIO SYSTEM FOR AUTOMOTIVE APPLICATIONS AND METHOD”, which is a divisional of U.S. Ser. No. 13/344,807, filed 6 Jan. 2012, entitled “LIGHTWEIGHT AUDIO SYSTEM FOR AUTOMOTIVE APPLICATIONS AND METHOD”, which is a divisional of U.S. Ser. No. 12/370,319, filed 12 Feb. 2009, entitled “LIGHTWEIGHT AUDIO SYSTEM FOR AUTOMOTIVE APPLICATIONS AND METHOD”, which is a continuation-in-part of U.S. Ser. No. 11/893,357, filed Aug. 15, 2007, entitled “LIGHTWEIGHT AUDIO SYSTEM FOR AUTOMOTIVE APPLICATIONS AND METHOD”, which claims the benefit of U.S. Ser. No. 60/838,698 filed Aug. 18, 2006 and U.S. Ser. No. 60/931,467, filed May 23, 2007, which are assigned to a common assignee. The instant application also claims the benefit of U.S. Ser. No. 61/066,065, filed Feb. 15, 2008, entitled ‘LIGHTWEIGHT ELECTRONIC DEVICE FOR AUTOMOTIVE APPLICATIONS AND METHOD. The teaching and specifications of the forgoing related applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to apparatus for enclosing electrical subassemblies, and more specifically relates to apparatus for efficiently securing subassemblies to a chassis of an electrical assembly such as an automobile radio, compact disc playing mechanism, cassette tape playing mechanism, navigational aid, personal computer, personal and telematic communication devices or disk drive mechanism. 
     BACKGROUND OF THE INVENTION 
     Devices such as automobile radios or personal computers contain subassemblies such as cassette playing mechanisms or disk drives that are attached to the chassis using threaded fasteners. The chassis provides structural support for the subassemblies and also provides electromagnetic shielding to limit electromagnetic interference (EMI) experienced by, and/or created by the device. The fasteners ensure that each subassembly within the chassis is properly located and securely retained within the chassis. 
     The use of such fasteners can have numerous drawbacks, particularly in a high volume production setting. The process for applying or installing fasteners can vary, but there is usually some degree of automation required, ranging from manually loading a screw into a bit on a pneumatic driver to using self-feeding automated machines. Typically, the torque applied by the device used to drive the fasteners must be monitored regularly and adjusted in order to assure proper seating of the fasteners. When fasteners are used, sheet metal tolerances, as well as tolerances of the fasteners themselves, have to be maintained at tight levels to allow for the minimization of stress in the assembly when aligning multiple fasteners with corresponding holes in the chassis and in the subassembly. 
     When threaded fasteners are used to assemble an electrical device, the assembly cycle time can be very long especially in high volume production. An operator assembling the device must typically first obtain the threaded fastener, orient and position it in alignment with the driver bit, then manipulate or actuate the machine to drive the threaded fastener. Furthermore, using threaded fasteners presents a risk of any one of the following upstream failures occurring: stripping of fastener threads; insufficient torque resulting in an unseated fastener; excessive torque resulting in distension/deformation of the fastener or adjacent electrical components; installation of the wrong fastener type or size; foreign object damage due to fasteners and/or metal shavings dropping onto the assembly and/or subassembly; and stripping of the head of the threaded fastener. Also, a fastener installation tool such as a driver and bit can slip off the fastener and impact an electrical component resulting in a damaged assembly. 
     If self-tapping fasteners are used, the process of driving the self-tapping fasteners into sheet metal often causes shavings of sheet metal to disperse into the assembly. Such shavings have been known to cause electrical failures, such as shorts or corruption of magnetic components that can permanently damage the product. If self-tapping fasteners are not used, an extra production step is required to pre-form threads in the sheet metal of the chassis and/or the subassembly to be installed within the chassis. 
     Fasteners further require an additional inventory burden on the production line in that the production line must be continuously stocked with part numbers (fasteners) other than the integral components that add value to the assembly. Also special tools specifically required for assembly, using fasteners, such as drivers and bits, must be continuously monitored and maintained for proper performance, wear and torque specifications. Typically, the top and/or bottom surface of the chassis must be secured in place after the subassembly is attached to the chassis. 
     Special fixtures are often required on the production line to secure a subassembly in a proper location and orientation while it is mounted within the chassis with fasteners. Such fixtures can be very complex, and the use of such fixtures usually requires extra handling of both the subassembly and of the resulting assembly thereby adding to the production cycle time and potentially compromising quality of the final product. 
       FIG. 1  illustrates the construction of a typical prior art automotive radio/compact disc (CD) player  10 . Radio/CD player  10  comprises a radio subassembly whose principle circuit components are carried on a circuit board  12  and a CD player subassembly  14 . The circuit board  12  and the CD player  14  are encased within a common chassis  16  made up of sheet metal components. Chassis  16  includes a wraparound housing  18  defining a back and sidewalls, a top cover  20 , a bottom cover  22  and a front plate  24  which are interconnected by numerous threaded fasteners to collectively enclose the subassemblies. The top and bottom covers  20  and  22 , respectively, are provided with large arrays holes or openings for airflow and ventilation of heat generated within the radio/CD player  10 . A convector or heat sink  26  is carried on an outer surface of one of the chassis sidewalls and is interconnected through a port/window  28  to a power device assembly  30 . A trim plate assembly  32 , along with a support pad  34  and CD dust cover  36  are affixed to the front plate  24 , providing an operator control interface with the radio/CD player  10 . Circuit board  12  is electrically in-circuit with the CD player subassembly  14  through an intermediate flex wire cable  38  and with the power device assembly  30  through a jumper cable  40 . Information bearing labels  42  and  44  are provided for future reference by the operator and service technicians. The radio/CD player  10  is electrically interconnected with an antenna, power supply, speakers and other related systems of a host vehicle by rear-facing connectors  46  carried on the circuit board  12  which are registered with openings  48  in the rear wall of wraparound housing  18 . The radio/CD player  10  is mounted within a host vehicle by threaded fasteners passing through openings in mounting features  50  extending from front plate  24  and a rearwardly directed mounting bushing  52  which is threadably affixed to a stud  54  carried on the outer surface of the rear wall  56  of wraparound housing  18 . As best seen in  FIGS. 11 and 12 , the shank of the stud  54  extends outwardly through a hole  58  disposed concentrically with a localized recess  60  and the stud  54  is seated within the recess  60 .  FIG. 90  illustrates another known stud design including a threaded shank secured to the rear wall  53  of a radio set  51  by a set nut  55  and receiving a molded rubber, plastic or vinyl stud  57  thereover. Note the large number of threaded fasteners  59 . 
     The radio/CD player  10  of  FIG. 1  is of ordinary complexity and may require fifty or more threaded fasteners to complete the manufacturing process. Installation of that many fasteners may require that the in-process chassis be re-positioned/re-fixtured ten to fifteen times as it passes along an assembly line of eight to ten skilled workers/work stations. 
     Vehicle entertainment systems usually include an audio component such as a radio to enable receiving signals from antennas, contain various forms of playback mechanisms, and have the capacity to accept data from user devices like MP3 players. Typically, the radio has a decorative assembly that provides man-machine interface as well as displaying pertinent data relative to the selected media and audio settings. Also, the back-end or chassis is constructed of metal to provide various functions to ensure the performance of the radio in the vehicular environment. The structure to contain the mass from playbacks, the heat conductive properties, and the electrical shielding and grounding are just a few of the advantages to using the metal construction. Unfortunately, with the density of the metal, the disadvantage of added weight is a side effect of the typical construction. In a vehicle, added weight impacts fuel economy, as well as other hidden costs during assembly that can effect the cost of the product, like sharp edges of metal can be a potential hazard for assemblers in the manufacturing plant as well as added weight can limit the packaging of multiple parts in containers for inter and outer plant distribution. 
     Special fixturing is often required to hold a component in the proper location while it is mounted to the convector using one or more fasteners. Such fixturing can be very complex and use of such fixturing usually requires extra handling of both the component and of the resulting assembly, thereby adding to the production cycle time and potentially compromising quality of the final product. 
     When threaded fasteners are used, the assembly cycle time can be very long, especially in high volume production. The operator must specifically obtain the threaded fastener, bring it in contact with the driver bit, then drive the threaded fastened. If self-tapping fasteners are used, the process of driving the self-tapping fasteners into metal often causes metal shavings to disperse into the assembly. Such shavings have been known to cause electrical failures that can permanently damage the product. If self-tapping fasteners are not used, an extra production step is necessary to form threads in the metal of the convector. 
     Accordingly, there is a need for electrical assemblies that do not require fasteners or tooling for securing a component to a convector. 
     SUMMARY OF THE INVENTION 
     The present invention provides numerous product and process advantages which collectively result in substantial cost and labor savings. By way of example, the preferred design optimizes the assembly process. It minimizes the required handling of major components and subassemblies during the assembly cycle. Final assembly is optimized, wherein only seven major components and subassemblies are involved. This minimizes the number of work stations and fixtures, in-process transfers between work stations and total assembly cycle time. The inventive design permits selection of the optimal mechanical product configuration for a given receiver family. Furthermore, it permits idealized electrical and mechanical building block partitioning for common and unique elements. 
     The preferred embodiment of the invention contemplates screwless final assembly without the use of tools, fixtures and assembly machines. This greatly enhances in-process product flow in the factory, improves scheduling of final assembly, and allows labor intensive processes such as stick lead assembly to be largely moved off-line. This greatly reduces both direct and indirect labor requirements. Furthermore, inventory control is simplified inasmuch as position part proliferation is deferred to or near the end of process. 
     These and other features and advantages of this invention will become apparent upon reading the following specification, which, along with the drawings, describes preferred and alternative embodiments of the invention in detail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1 , is an exploded, perspective view of a prior art automotive radio/CD player combination in a common chassis constructed of sheet metal and a large number of threaded fasteners; 
         FIG. 2 , is a front-left perspective view of the preferred embodiment of the present invention embodied in an automotive radio/CD player; 
         FIG. 3 , is an exploded, perspective view of the radio/CD player of  FIG. 2 , illustrating the major subcomponents and subassemblies thereof; 
         FIG. 4 , is an exploded, perspective view of the radio/CD player of  FIG. 2 , illustrating final assembly step I in the production thereof wherein the playback mechanism and circuit board assembly are slid and snapped to the faceplate; 
         FIG. 5 , is an exploded, perspective view of the radio/CD player of  FIG. 2 , illustrating final assembly step II in the production thereof wherein the case is slid and snapped to the faceplate; 
         FIG. 6 , is a perspective view of the circuit board assembly with ground clips installed thereon; 
         FIG. 7 , is a fragmentary, cross-sectional view of a ground clip and an associated portion of the printed circuit board on an enlarged scale in assembly with an adjacent portion of the case to effect a grounding point with the integral wire mesh; 
         FIG. 8 , is a fragmentary, perspective view of a keypad grounding clip integrally formed on the front side of the faceplate; 
         FIG. 9 , is a cross-sectional view taken on lines  9 - 9  of  FIG. 8 ; 
         FIG. 10 , is a cross-sectional view taken on lines  10 - 10  of  FIG. 8 ; 
         FIG. 11 , is a cross-sectional view taken on lines  11 - 11  of  FIG. 8 ; 
         FIG. 12 , is a fragmentary, cross-sectional view of the initial positioning of a CD mechanism bracket with respect to a support shelf integrally formed within the case; 
         FIG. 13 , is a fragmentary, cross-sectional view of the CD mechanism in an intermediate position with respect to the support shelf during its installation; 
         FIG. 14 , is a fragmentary, cross-sectional view of the CD mechanism in its final installed position with respect to its associated support shelf; 
         FIG. 15 , is a fragmentary detail, on an enlarged scale, of the rear end portion retention tab of the CD mechanism bracket depicted in  FIGS. 12-14 ; 
         FIG. 16 , is a cross-sectional view of a first portion of the retention tab of the CD mechanism bracket taken on lines  16 - 16  of  FIG. 15  illustrating an integral dimply/crush rib formed therein; 
         FIG. 17 , is a cross-sectional view of another portion of the retention tab of the CD mechanism bracket taken on lines  17 - 17  of  FIG. 15 ; 
         FIG. 18 , is an end plan view of the retention tab of the CD mechanism bracket in its assembled position within the rear wall portion of the case of the radio/CD player as depicted in  FIG. 14 ; 
         FIG. 19 , is a cross-sectional view of an alternative, lighter weight outer case configuration in representative assembly with a bifurcated PC board wherein wire screen mesh provides both electromagnetic shielding as well as a significant portion of the overall structural strength of the case; 
         FIG. 20 , is a front perspective view of the interior surface details of the case/back-end illustrating the wire mesh screen which has been insert molded within the case adjacent the inner surface portions thereof; 
         FIG. 21 , is a front-above perspective view of a partially assembled radio/CD player, substantially similar to that previously depicted (prior to installation of the trim plate assembly), illustrating, inter alia, (1) three outwardly directed spring contacts carried by resilient members integrally formed with the faceplate and (2) the juxtaposition of the wire mesh within the faceplate adjacent the outer surface thereof; 
         FIG. 22 , is a front-left perspective view of the partially assembled radio/CD player of  FIG. 21 , illustrating the same features from a different perspective; 
         FIG. 23 , is a broken, bottom-rear perspective view of an audio system assembly embodying an alternative embodiment of the present invention illustrating internal PCB front and rear edge self-grounding with integral features of the audio system housing assembly; 
         FIG. 24 , is a broken, cross-sectional view, on an enlarged scale, of the rear edge of the PCB of  FIG. 23  self-engaging and self-grounding with exposed electrically conductive shield and guide tangs integrally formed with the audio system housing assembly; 
         FIG. 25 , is a broken, cross-sectional view, on an enlarged scale, of the front edge of the PCB of  FIG. 23  self-engaging and self grounding with exposed electrically conductive shield and guide tangs integrally formed with the audio system housing assembly; 
         FIG. 26 , is a broken, rear facing perspective view of the exposed electrically conductive shield and guide tangs of  FIG. 24 , with the PCB removed; 
         FIG. 27 , is a broken, forward facing perspective view of the exposed electrically conductive shield and guide tangs of  FIG. 25 , with the PCB removed; 
         FIG. 28 , is a cross-sectional view taken on lines  28 - 28  of  FIG. 13 , illustrating the juxtaposition of an associated pair of guideways formed by a housing case and guide members formed by a CD changer mounting bracket with the bracket partially installed within the case; 
         FIG. 29 , is a cross-sectional view taken on lines  29 - 29  of  FIG. 14 , illustrating the juxtaposition of the associated pair of guideways and guide members with the bracket fully installed within the case; 
         FIG. 30 , is a cross-sectional view of an alternative configuration of the guideways/guide members of  FIGS. 28 and 29 , with the respective contacting surfaces angularly converging; 
         FIG. 31 , is a cross-sectional view of a second alternative configuration of the guideways/guide members of  FIGS. 28 and 29 , with the respective contacting surfaces diverging and an electrical grounding connection established therebetween; 
         FIG. 32 , is a fragmentary, cross-sectional view of the initial positioning of a CD mechanism bracket with respect to an alternative support shelf integrally formed within the case, similar to  FIG. 12 , with the wall surfaces defining the guideways each tapered on their upper and lower surfaces to provide a drafted condition to enhance injection molding formation of the case; 
         FIG. 33 , is an exploded, left-rear perspective view of another feature of the present invention embodied in a lightweight electronic device configured for automotive applications featuring selectively embossed segments of exposed composite case electrical shielding material operative to enhance screwless assembly of subassembly brackets within (or exterior of) the case; 
         FIG. 34 , is a fragmentary, exploded, top cross-sectional view of the exemplary automotive audio system composite case of  FIG. 33 , juxtaposed for installation of a cooperating pair of (CD player) subassembly mounting brackets therein, prior to contact between the bracket and case; 
         FIG. 35 , is a fragmentary, exploded, cross-sectional view of a portion of the case and one of the mounting brackets of  FIG. 34  on an enlarged scale; 
         FIG. 36 , is a fragmentary, exploded, top cross-sectional view of the exemplary automotive audio system composite case of  FIG. 33 , juxtaposed for installation of a cooperating pair of (CD player) subassembly mounting brackets therein, at a point of initial contact between the bracket and case; 
         FIG. 37 , is a fragmentary, exploded, cross-sectional view of a portion of the case and one of the mounting brackets of  FIG. 36  on an enlarged scale; 
         FIG. 38 , is a fragmentary, exploded, top cross-sectional view of the exemplary automotive audio system composite case of  FIG. 33 , juxtaposed for installation of a cooperating pair of (CD player) subassembly mounting brackets therein, at a point of contact between the bracket and case affecting maximum lateral displacement of integral case mounting tabs, prior to their locking engagement with a mounting feature of the adjacent subassembly mounting bracket illustrating the momentary distention of the upset bead finned in the exposed conductive material (screen mesh); 
         FIG. 39 , is a fragmentary, exploded, cross-sectional view of a portion of the case and one of the mounting brackets of  FIG. 38  on an enlarged scale; 
         FIG. 40 , is a fragmentary, exploded, top cross-sectional view of the exemplary automotive audio system composite case of  FIG. 33 , juxtaposed for installation of a cooperating pair of (CD player) subassembly mounting brackets therein, wherein the bracket and case are fully assembled and the integral case mounting tabs have resiliently returned to their nominal rest positions affecting locking engagement with a mounting feature of the adjacent subassembly mounting bracket; 
         FIG. 41 , is a fragmentary, exploded, cross-sectional view of a portion of the case and one of the mounting brackets of  FIG. 40  on an enlarged scale; 
         FIG. 42 , is a fragmentary, cross-sectional view of the fully assembled automotive electronic device and subassembly mounting bracket of  FIG. 33  on an enlarged scale, taken on line  42 - 42  of  FIG. 41 ; 
         FIG. 43 , is a fragmentary plan view of a portion of a composite case wall illustrating a window opening in the polymer based material exposing conductive material (conductive screen mesh) with multiple concentric upset beads formed therein circumscribing a discrete segment of polymer based material (island); 
         FIG. 44 , is a fragmentary, cross-sectional view of the case window opening, taken on line  44 - 44  of  FIG. 43 ; 
         FIG. 45 , is a fragmentary plan view of a portion of a composite case wall illustrating a window opening in the polymer based material exposing conductive material (conductive screen mesh) with multiple concentric upset beads formed therein similar to  FIG. 43 , but lacking a discrete segment of polymer based material (island); 
         FIG. 46 , is a fragmentary, cross-sectional view of the case window opening, taken on line  46 - 46  of  FIG. 45 ; 
         FIG. 47 , is a perspective view of a solid model of a male die portion of a die set configured to affect formation of the composite electronic device case of  FIG. 33 , illustrating the detail of the region of the die portion which establishes the case side window and affects formation of the conductive material upset bead upon closure with a mating die portion (not illustrated); 
         FIG. 48 , is a exemplary dimensioned profile of the male die portion of  FIG. 47  through its region which forms the case window; and 
         FIG. 49 , is a Product Data Sheet of steel mesh employed by the applicant in certain embodiments of the composite case of the present invention. 
     
    
    
     Although the drawings represent varied embodiments and features of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to illustrate and explain the present invention. The exemplification set forth herein illustrates several aspects of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     The present invention can be applied in its broadest sense to electronic devices and systems where shielding from radio frequency interference (RFI), electromagnetic interference (EMI), bulk current injection (BCI) and/or electrostatic discharge (ESD) is required. In addition to vehicle based radios and audio entertainment systems, the invention can be advantageously applied in “infotainment” and telematic systems. Furthermore, the present invention employs virtually “fastenerless” design architecture to facilitate low-cost, high volume production techniques. 
     For convenience of understanding, the following description will be focused primarily upon an automotive radio/CD player system. 
     The present invention reflects an improved design to reduce the overall weight of an automotive radio/CD player without compromising the strength of the unit. The present invention employs a polymer based, electrically insulative material that can be molded to provide the necessary features for the chassis as well as the frontal interface to the decorative front-end assembly described for the man-machine interface. By molding a case with the necessary details to accept the playback mechanisms (if desired) as well as the circuit board(s) needed for the electrical control, the required functionality of the unit is maintained as compared to the typical metal box. The necessary shielding and grounding is accomplished by insert-molding electrically conductive sheet-like material such as a mesh screen wire that has been pre-formed to contour with the molding operation. The grounding of the circuit boards may be accomplished by using ground clips attached directly to the ground pads of the circuit board that would interface directly with exposed screen wire mesh of the molded part. While metal is also a good conductor for the thermal load inside the unit, openings must be incorporated to allow airflow for additional cooling. The same openings can compromise the shielding. With in-molded mesh screen wire, the mesh acts as a Faraday cage to shield the electronics, but the open weave allows airflow to promote the dissipation of the thermal load from inside the unit, to the exterior. Besides the reduction of mass offered by the molded polymer material for the unit chassis and front plate, the hidden benefits include ease of handling in the assembly process as well as less container and shipping weight. 
     To facilitate assembly, the molded polymer chassis and front plate can use integral or molded in guideways and snaps, thereby eliminating the typical screw fastener assembly method previously used for these components. To enhance the rigidity, the component parts that comprise the assembly are sandwiched at the common vehicle instrument panel attachment points such that when the mounting screws are driven, they firmly clamp the component pieces to the host vehicle. In the event a playback mechanism of substantial mass and volume is required, the sub-assembly structure for the mechanism would utilize formed attachment tabs that would be an intermediate layer in the aforementioned component part sandwich. Another benefit for the mounting at the back of the radio is often vehicles have a receptive hole or slot in the inner cavity of the instrument panel carrier that accepts a mounting bushing or “bullet” shaped extension that is screwed to a mounting stud that is typically swaged to the back of the metal enclosure of the radio. The mounting “bullet” can be molded directly in the polymer-based case eliminating the additional part and the assembly of that additional part. 
     To replace the metal structure of the vehicle radio, a galvanized (or appropriately coated) steel mesh wire screen will be cut, formed, and molded with a polymer resin to provide necessary details for assembly of components required for the functionality of the radio including, but not limited to, a circuit board assembly, a heat sink for audio power and switching components, a playback mechanism, and a man-machine interface or trim plate assembly, as well as vehicle mounting features. While the polymer or plastic provides the majority of the mechanical structure for the radio, the in-molded mesh screen wire provides the needed protection from various electrical anomalies including electromagnetic contamination, radio frequency interference, bulk current injection, and electrostatic discharge, to name a few. The screen mesh also allows openings necessary for air passage or venting of heat from the radio by molding the radio back end or case and front plate. The many details and features needed in a typical assembly can be incorporated directly into the parts, eliminating the need for fasteners and separate additional parts often required with parts fabricated in metal. 
     The specific materials selected for fabricating the radio case and front plate will vary depending upon the application, including the contained mass of the mechanisms employed as well as the severity of the contemplated environment (esp. temperature and vibration). Examples of materials that could be employed for typical automotive applications are: 
     Case: Glass-filled polyester, Glass-filled polypropylene, Polycarbonate, ABS. 
     Front Plate: Polycarbonate, ABS, PC/ABS and Noryl. 
     Major components which contact one another or are mechanically interconnected preferably are formed from material having substantially differing surface finish and hardness characteristics to minimize the possibility of resulting squeaks, rattles and the like. 
     Although presently viewed as cost prohibitive for automotive applications, it is contemplated that nano carbon tube filler can be employed within the plastic material forming the case and front plate to provide effective shielding and enhance the structural strength of the case assembly. 
     In addition to weight savings, which may amount to well over one pound (0.4536 Kg), the part handling is improved to reduce the amount of fasteners as well as separate component parts. Often a radio may be constructed from a wrap-around, a cover and the fasteners along with a mounting bushing or “bullet” screwed to a “swaged” threaded stud in the metal case. Also, the metal pieces require assembly personnel to wear gloves during handling to avoid any cuts or damage to their hands as well as protection from any metal fabrication fluid residue. Molded plastic does not require any special gloves, or the concerns of cuts to the skin. Aside to the benefit to the vehicle by reducing the radio weight by over one pound (0.4536 Kg), the savings for a manufacturer include reduced shipping cost through the weight reduction and potential container efficiency improvements. Product labeling can be improved through laser engraving the plastic with the desired number, customer logos, etc. Metal typically requires a stamping detail (not easily changed) and/or a printed label that is adhesively applied. This offers greater flexibility and eliminates additional parts (like labels) to use the plastic, as well as better durability than a label. 
     Referring to  FIGS. 2-5 , a consolidated radio/CD player apparatus  62  embodying many aspects of the present invention is illustrated. The radio/CD player  62  is an assemblage of six major components or subassemblies, a circuit board subassembly  64 , a CD player subassembly  66 , a box-like housing case  68 , a front closure member or front plate  70 , a convector or heat sink  72  and a trim plate subassembly  74 . 
     It is envisioned that each of the major components/subassemblies would be produced “off-line” and the final assembly process would comprise the efficient, high volume joining of the major components/subassemblies and end-of-line testing of the completed units. 
       FIG. 2  depicts a perspective view of the fully assembled radio/CD player apparatus  62 .  FIG. 3  is an exploded view illustrating the juxtaposition of the respective major components during the assembly process.  FIGS. 4 and 5  depict specific assembly steps of the major components as will be described hereinbelow. 
     The case  68  and front plate  70  are each preferably injection molded of polymer based material and collectively comprise a substantially closed housing assembly  76 . The case  68  has a box-like structure, including upper and lower wall portions  78  and  80 , respectively, left and right side wall portions  82  and  84 , respectively, and a rear wall portion  86 . The case  68  also has mounting features extending externally of the case walls, including left and right front mounting flanges  88  and  90 , respectively, extending from the forward edges of the left and right side walls  82  and  84 , respectively, and a mounting stud  92  extending rearwardly from the rear wall  86 . All of the case wall portions and mounting features of the case  68  are integrally formed in a single injection molding process. The case defines a front opening  94  which, upon assembly, is closed by front plate  70 . An assembly axis  96  extends symmetrically from front to rear of the case  68 , exiting opening  94  along the nominal centerline of the case  96 . 
     The circuit board subassembly  64  consists of a common or main printed circuit board (PCB)  98  and a unique, application specific PCB  100  which are electrically and mechanically interconnected by several pin connectors  102 . It is envisioned that edge connectors, ribbon connectors or the like could be substituted for the pin connectors  102 . The common PCB  98  contains all surface mount components. The circuit board subassembly  64  comprises an audio component. 
     The CD player subassembly  66  consists of a conventional multi-disc player unit  104  and substantially mirror-image left and right side mounting brackets  106  and  108 , respectively, affixed thereto by integral fastener devices such as “squirts”. Note that there are slight differences between the left and right mounting brackets  106  and  108 , but they are deemed to be inconsequential for purposes of the present invention. The left and right mounting brackets  106  and  108  have outwardly directed mounting flanges  110  and  112 , respectively, which, upon assembly, register with case mounting flanges  88  and  90 , respectively. The CD player subassembly  66  comprises an audio component. 
     The heat sink  72  comprises a substantially flat, stamped aluminum plate adapted for mounting to the outer surface of the left case sidewall  82  and includes a recessed portion  114  which, upon installation, extends inwardly through a port  116  in left case sidewall  82  for thermal interconnection to heat generating and power circuit components  118 ,  120  and  122  carried on the main PCB  98 . 
     The trim plate subassembly  74  is configured to organize audio system input/output and display devices, informational indicia and decorative display devices for an associated host vehicle operator. 
     Referring particularly to  FIGS. 4 and 5 , a method of assembly of the lightweight audio system  62  of the present invention is illustrated. Audio system  62  can be assembled manually by an ordered process wherein a single (preferably, but not limited to) operator, who sequentially assembles the six major components or subassemblies on a designated work surface  124 . No specialized tools or separate/dedicated fixtures are required. No threaded fasteners/screws are required. Each or the major components and subassemblies form integral features which cooperate to interact with features of the other components and subassemblies to register, align and guide the components and subassemblies during adjoining thereof as well as to removably affix the components and subassemblies to one another when in their final design position. This process is referred to herein as the Slide-lock Snap-Lock™ Screwless Assembly Technology and Method or “SLAT”. In effect, the components “self-fixture one another in combination the manipulation of the Assembly of the radio/CD player  62  is affected by the assembly technician or operator taking the following steps: 
     As illustrated in  FIG. 4 , place the front plate  70  on the work surface  124  in an inverted position with the outer surface of the front plate disposed upon the work surface  124 . The centerline of the front plate  70  defines an assembly axis, as designated by arrow  96  extending normally to the work surface  124 . 
     The front plate has two laterally spaced, rearwardly directed extensions  126  and  128  integrally formed therewith. Extensions  126  and  128  form guideways or opposed slots  130  and  132 , respectively, which open towards one another and are directed parallel to the assembly axis  96 . Lateral edge guide surfaces  134  and  136  of the application specific PCB  100  register within slots  130  and  132  and are guided thereby during the insertion process until the leading edge surface  138  of the PCB  100  contacts the inside (upward facing in  FIGS. 4 and 5 ) surface of front plate  70 . At this point, common PCB  98  is cantilever suspended from PCB  100  via pin connectors  102  and other supports (not illustrated). Referring  FIG. 5 , the circuit board subassembly  64  is retained in position by the interfit of the edge surfaces  134  and  136  within slots  130  and  132 . 
     The CD player subassembly  66  is next installed by manipulating it along the assembly axis  96  until through holes  140  and  142 , formed in bracket mounting flanges  110  and  112 , register with locating pins or nibs  144  and  146  integrally formed in laterally extending mounting flanges  148  and  150 , respectively, integrally formed in front plate  70 . Thereafter, the CD player subassembly is displaced downwardly along the assembly axis  96  until the lower surfaces of bracket mounting flanges  110  and  112  abut the upper surfaces of front plate mounting flanges  148  and  150 . The CD player subassembly  66  is retained in the position illustrated in  FIG. 5  by an interference fit between the front plate nibs  144  and  146 , and the mounting bracket flange through holes  140  and  142 . 
     Mounting bracket flanges  110  and  112  have secondary, larger diameter through holes  152  and  154  formed therein which register with similarly dimensioned through holes  156  and  158 , respectively, formed in front plate mounting flanges  148  and  150  for receiving attachment means such as bolts, for affixing the completely assembled radio/CD player  62  to a host vehicle. 
     The steps of installing the circuit board subassembly  64  and the CD player subassembly can be reversed from that describer hereinabove. 
     The housing case  68  is next installed by manipulating it along the assembly axis  96  whereby the case wall portions  78 ,  80 ,  82 ,  84  and  86  fully envelop the circuit board subassembly  64  and CD player subassembly  66  in combination with the front plate  70 . 
     As best viewed in  FIGS. 3, 5 and 20 , the centerline of the case  68  is first manually aligned with the assembly axis  96  and rotationally positioned with the subassembly consisting of the circuit board subassembly  64 , CD player subassembly  66  and the front plate  70 , whereby a first cooperating pair of guideways  160  and  162  integrally formed in case sidewall portions  82  and  84  register with the CD player mounting brackets  106  and  108  and, simultaneously, a second cooperating pair of guideways  164  and  166  integrally formed in case sidewall portions  82  and  84  register with lateral edge guide surfaces  168  and  170  of common PCB  98 . The case  68  is then manually displaced along the assembly axis  96  until the leading edge thereof defining front opening  94  contacts the rear surface of the front plate  70 . Thereafter, cooperating ramped snap-engagement features  172  and  174  integrally formed with upper and lower wall portions  78  and  80  of the case  68  and the front plate  70 , respectively, momentarily self-displace one another and snap back to self-engage to establish a positive interlock therebetween. 
     The case mounting flanges  88  and  90  form through holes  176  and  178  which register and self-engage with nibs  144  and  146 , respectively, to provide a redundant engagement feature. Furthermore, the case mounting flanges  88  and  90  form a second set of through holes  180  and  182 , respectively, which register with through holes  152  and  154  of mounting brackets  106  and  108 , and through holes  152  and  154  of front plate mounting flanges  148  and  150 , respectively. 
     As best viewed in  FIG. 2 , the heat sink  72  is next installed. The heat sink  72  includes several locating tabs  182  integrally formed along one edge thereof and a locator recess  184  formed in an opposed edge. The heat sink  72  is manually affixed to the outer surface of the case left side wall portion  82  which defines integral tab receiving extensions  186  along the upper edge thereof. Once the heat sink locating tabs  182  are inserted within their respective case wall portion extensions  186 , the heat sink  72  is rotated into its design position wherein a resilient ramped catch member  188  integrally formed along the bottom edge of the left side wall portion  82  snap engages the recess  184  to fixedly interlock the heat sink  72  to the case  68 . 
     When the heat sink  72  is in its installed position, the recessed portion  114  extends inwardly into the case  68  through the port  116 . The inner surface of the recessed portion  114  establishing an abutting relationship against the power circuit components  118 ,  120  and  122  to provide a cooling thermal convector to the exterior of the case  68 . Means are provided to ensure that components  118 ,  120  and  122  remain in intimate contact with the heat sink  72  such as screws  190 , or, preferably to continuously resiliently urge the components into engagement with the recessed portion  114  of the heat sink  72 . 
     It is contemplated that the heat sink  72  could be alternatively mounted to the case rear wall portion  86 , whereby it would be installed along the assembly axis  96 . 
     As a final step of assembling the major components and subassemblies, the subassembly of the components is manually inverted, with the case rear wall portion  86  disposed on the designated work surface  124 . Due to the localized outward projection of the stud  92 , a stability enhancing spacer (not illustrated) or, alternatively, a recess  192  in the work surface  124  ensures a stable platform to complete assembly. 
     The trim plate subassembly  74  is then manipulated to become in register with the case  68  and manually displaced along the assembly axis  96  until the lower surface of the trim plate assembly  74  contacts the upper surface of the front plate  70 . Thereafter, cooperating ramped snap-action engagement features  192  and  194  integrally formed with upper and lower edge skirt surfaces of the case trim plate assembly  74  and the front plate  70 , respectively, momentarily self-displace one another and snap back to self-engage to establish a positive interlock therebetween. 
     The completed assembly of the major components and subassemblies is depicted in  FIG. 2 . Following the assembly process, the completed radio/CD player  62  is placed in a queue for testing and quality checks. 
     The rear mounting bushing for current radios is typically attached by welding a threaded stud to the back wall of the wrap around and then the bushing is screwed on. With the plastic box receiver, the mounting bushing can be molded as an integral part of the receiver box, eliminating two part numbers and the labor to install them. 
       FIGS. 20-22  illustrate an alternative construction of the case  68  and front plate  70  of the housing assembly  76  wherein both elements of the case assembly  76  are formed of a composite of relatively rigid polymer material and electrically conductive material operable to shield the audio components (such as the circuit board subassembly  64  and the CD player subassembly  66 ) from electrical anomalies including radio frequency interference (RFI), electromagnetic interference (EMI), bulk current injection (BCI) and electrostatic discharge (ESD). The electrically conductive material comprises substantially continuous planer sheet portions applied to surfaces of or within polymer housing assembly wall portions as discrete elements, electrically conductive paint, foil or electrostatic or vacuum deposition applied material. Alternatively, the electrically conductive material comprises a wire mesh screen  212  which has been cut and folded to net shape and inserted within a mold cavity whereby it is effectively insert molded within the polymer based material. Preferably, the wire screen  212  is centered within the wall portions of the case and front plate whereby electrically insulating polymer material effectively covers the wire screen  212 , both inside and out, to prevent inadvertent grounding of the housing assembly to interior or exterior structures. 
     Through empirical testing and development, the inventors have found that it is preferable to locate the wire screen  212  near the inside surface of the case  68  and the outside surface of the front plate  70 . Openings  214  are provided in the case  68  by locally eliminating the polymer material but leaving the wire screen intact, whereby judiciously positioned openings  214  provide natural convection cooling to the ambient without having a break or gap in the electrical anomaly protection provided by the wire screen  212 . 
     The common circuit board and the unique circuit board are grounded to the molded in wire mesh by using a grounding clip that contacts the ground plane on the circuit board to the metal mesh by pressing the circuit board with the clip installed into a hole or recess in the plastic box that exposes the mesh. A point/ridge/protuberance is used on the clip to press into the mesh and increase the pressure for intimate contact. An alternative of this clip is one that gets surface mounted and soldered to the board and does not require manual assembly. 
     Referring to  FIGS. 6 and 7 , one form of grounding the ground plane  216  of the circuit board subassembly  64  to the wire screen  212  is illustrated. The leading edge surface  138  of the unique PCB  100  carries two beryllium copper grounding clips  218 , which are electrically and mechanically connected to the PCB ground plane  216 . Similarly, a trailing edge surface  222  of the common PCB  98  carries two grounding clips  218 . Each grounding clip  218  includes a resilient contact arm  220  extending outwardly along the assembly axis  96 . Upon assembly, the grounding clips  218  carried on the leading edge surface  138  of PCB  100  register with exposed wire screen  212  within windows  224  in front plate  70  (refer  FIGS. 21 and 22 ), and the grounding clips  218  carried on the trailing edge surface  222  of PCB  98  register with exposed wire screen  212  within windows  226  in the rear wall portion  86  of the case  68 . The contact are  220  of each grounding clip  218  is configured to continuously bear against the adjacent exposed wire screen  212  to maintain electrical contact therewith. 
     Referring to  FIGS. 23-27 , alternative forms of grounding the ground plane  216  of the circuit board subassembly  64  to the wire screen are illustrated.  FIG. 23  illustrates a radio/CD player  622  similar in all material respects to the radio/CD player  62  described hereinabove in connection with  FIGS. 2-11  inter alia, with the exceptions described immediately hereinbelow. In essence, in this embodiment, the four ground clips  218  contained on the circuit board subassembly  64  are deleted and replaced by connectors integrally formed with the housing assembly  76 . 
     Referring to  FIGS. 23, 25 and 27 , a circuit board subassembly  624  includes a common PCB  626  interconnected with a unique PCB  628  by pin connectors  630 . A leading edge  631  of the unique PCB  628 , when installed within a front plate  632 , engages two Z-clips  634  integrally formed within the front plate  632 , whereby wire screen  636  exposed in the Z-clip  634  engages a contact pad/plane  638  carried on the unique PCB  628  adjacent its leading edge  631 . A trailing edge  652  of the common PCB  626 , when installed in a housing case  654 , engages two grounding clips  658  integrally formed within the case  654 , whereby wire screen  636  exposed in the grounding clip  656  engages a contact pad/plane  658  carried on the common PCB  626  adjacent its trailing edge  652 . 
     As best viewed in  FIGS. 25 and 27 , the Z-clip  634  includes a frame  640  integrally formed adjacent one side of an associated opening  642  and extending inwardly (within an associated housing case  643 ) therefrom as a resilient cantilever. The frame  640  includes two parallel “L’ or “J” shaped leg portions  644  interconnected by a cross support portion  646 . A flap of wire screen  636  is die-cut prior to being injection molded within the front plate  632 . During the injection molding process, the edges of the wire screen flap are insert molded within the leg portions  644 , the cross-support portion  646  and the adjacent front panel of the front plate  632 , thereby exposing the wire screen flap  636  for electrical connection with the unique PCB contact pad  638 . An inwardly directed boss  648  is integrally formed on the front plate  632  adjacent an edge of the opening  642  opposite from the leg portions  644 , and extends substantially parallel to an assembly axis  649 . The boss  648  forms a guide/abutment surface  650  which is spaced from the exposed wire screen flap  636  by a dimension slightly less than the thickness of the unique PCB  628  to ensure a tight compressive fit when the leading edge  631  of the unique PCB  628  is inserted therebetween. The natural resiliency of the polymer material forming the Z-clip frame  640  ensures continued continuity of the electrical connection between the exposed wire screen  636  of the Z-clip and the unique PCB contact pad  638 . 
     As best viewed in  FIGS. 24 and 26 , the grounding clip  656  includes a cooperating pair of laterally spaced support members  660  and  662  integrally formed in a rear wall portion  664  of the case  654  adjacent the bottom edge of an associated opening  663  and extending inwardly therefrom. A flap of wire screen  666  is die-cut prior to being injection molded within the case  654 . During the injection molding process, the lateral edges of the wire screen flap  666  are insert molded within the support members  660  and  662  and the adjacent portion of the case rear wall portion  664 , thereby exposing the wire screen flap  666  for electrical connection to the common PCB  626  contact pad  658 . A wire screen positioning finger  668  is integrally formed in the rear wall portion  664  of the case  654  laterally intermediate the support members  660  and  662 , and extends inwardly from the rear wall portion  664  substantially parallel to an insertion axis  670  as a resilient cantilever. The positioning finger  668  is vertically positioned with respect to the support members  660  and  662  to continuously contact the lower surface of the wire screen flap  666  to ensure that the lateral center portion of the wire screen flap  666  is bowed slightly upwardly and resiliently maintained at least slightly above the upper surface portions  672  and  674  of the support members  660  and  662 , respectively. An inwardly directed boss  676  is integrally formed on the rear wall portion  664  of the case  654  adjacent the top edge of the opening  663  opposite from and laterally centered with the support members  660  and  662 . The boss  676  forms a guide/abutment surface  678  which is spaced from the exposed wire screen flap  666  by a dimension slightly less than the thickness of the common PCB  636  to ensure a tight compressive fit then the trailing edge  652  of the common PCB  636  is inserted therebetween. The natural resiliency of the polymer material forming the ground clip  656  structural elements ensures continued continuity of the electrical connection between the exposed wire screen  666  of the ground clip  656  and the common PCB contact pad  658 . 
     In another example of self-grounding a PCB  680  includes an extension  682  projecting forwardly therefrom in line with an assembly axis  684  of a housing case  686  for an audio system  687 . Contact pads  688  and  690  are carried on upper and lower surfaces  692  and  694  of the PCB extension  682 . A rear wall portion  696  of the case  686  forms a window  698  exposing a portion of wire screen  700  which is aligned with the PCB extension  682 . When the wire screen  700  is insert molded within the polymeric material forming the case  686 , the portion thereof coinciding with the window  698  is left intact. During the assembly process of the audio system  687 , wherein the PCB is installed by insertion along guideways (not illustrated) within the case  686 , the PCB is inserted with sufficient force to locally rupture and penetrate the exposed wire screen  700  within the window  688 . Following the rupture of the wire screen  700 , the residual separation edges thereof are drawn into the window  698  by friction caused by motion of the upper and lower PCB surfaces  692  and  694 , respectively. When the PCB  680  assumes its installed position, as illustrated in  FIG. 139 , the rended portions of the wire screen  700  are compressively fit between the contact pads  688  and  690  and the adjacent edges of the window  698 , ensuring continued continuity of the electrical connection between the exposed wire screen  700  and the PCB contact pads  688  and  690 . It is contemplated that a single (one side of the PCB) contact pad can also be employed. However, the redundancy afforded by the dual contact pads  688  and  690  is preferable. 
     In a modification of the self-grounding system described hereinabove can enhance assembly of an audio system  702  for simplified and improved unit-to-unit repeatability. A housing case  704  includes a wall portion  706  forming a window  708  exposing a wire screen  710  to establish a point of electrical connection to an audio component within the case  704 . After the wire screen  710  is insert molded within the polymer material forming the case  704 , but before the assembly if the audio system  702 , a tool, such as a cooperating punch  712  and die  714  is pressed simultaneously against the inner and outer surfaces of the exposed screen  710  within the window  708  to form perforations or weakenings, indicated by dotted lines  716 . This process step is indicated by arrows  718 . The perforations  716  make the exposed wire screen  710  more predictably frangible for improved unit-to-unit quality. Thereafter, during final assembly of the audio system  702 , the wire screen  710  separates along the perforations  716  when contacted by the leading edge of a PCB extension  682 . 
     An alternative self grounding approach involves modifying a leading surface  720  of an extension  722  of a PCB  724  to form a sharpened, laterally extending leading edge  726 . The leading edge  726  can be formed by the PCB material itself or, preferably, by hardened material, such as a metal appliqué or band formed in a “U” or a “V” configuration engaging the PCB  724  by upper and lower members  728  and  730  affixed to the upper and lower surfaces  732  and  734  of the PCB extension  722  such as by soldering. The upper and lower members  730  and  732  can serve as electrical ground pads. Upon installation of the PCB  724 , the sharp leading edge  726  first contacts and cleaves the exposed wire screen  710  into the form illustrated in  FIG. 139 . 
     In addition to the forgoing, punch dies  712 / 714  such as those depicted in  FIG. 156  can be employed in modified form to actually sever and/or remove a portion (or all) of the wire screen  710  after the molding of the housing case  704 , but before the final assembly of the audio system  702 . Furthermore, one or more service access windows can be provided elsewhere in the walls of the housing case  704 . The service windows are closed at the time of manufacture by exposed screen including perforations. The exposed screen could be severed by a tool or process later in the service life of the audio system  702  to service or modify the system. 
     The method of grounding the plastic front plate (with molded in metal mesh) to the keyboard is by using plastic spring clip that contains an open window to expose the mesh where the spring clip comes into contact with a tinned pad on the keyboard. This provides an ESD path to ground when inserting a static charged CD into the CD changer. 
     Referring to  FIGS. 8-11 and 21-22 , several spring clip structures  228  are integrally formed in the front plate  70  which, in assembly, continuously resiliently bear locally exposed segments of the wire screen  212  against a tinned grounding pad  230  (only one is illustrated) on a keypad PCB  232  to establish a ground path therebetween. 
     Each spring clip structure  228  has a frame  234  including two parallel arc shaped portions  236  and  238  and a cross-support portion  240  integrally formed with front plate  70  and extending therefrom as a resilient cantilever. An opening  242  in the front plate registers with each spring clip  228  to permit flexure thereof. 
     Prior to molding of the wire screen  212  within the front plate  70  the screen preform is die-cut to form an integral flap which is captured within the mold and the edges thereof encased within arc-shaped portions  236  and  238  and cross-support portion  240 . The central portion of the exposed wire screen is expanded or stretched to form an outward bow shape (refer  FIGS. 9 and 10 ) to ensure that the resulting exposed screen protuberance firmly contacts the PCB grounding pad  230 . 
     A prior approach is illustrated wherein separate spring grounding clips  244  are each mechanically affixed to the front plate  246  of a radio/CD player assembly  248  by a rivet  250  or other suitable fastener. The rivets are required to establish an electrical ground path as well as to mechanically secure the spring clips  244  to the front plate  246 , adding labor, cost and complexity to the manufacturing process. 
     Using a plastic front plate enables assembly fixturing for the CD mechanism and circuit boards for slide lock and snap lock assembly instead of the screws used in a traditional receiver. 
     Referring to  FIGS. 4 and 5 , guideways in the form of slotted extensions  126  and  128 , as well as locator/retention features  144  and  146  integrally formed on the reverse (inside) surface of the front plate  70  provides a number of significant advantages in the manufacture and final assembly of the radio/CD player  62  by reducing product part count, assembly time, and substantially eliminates dedicated hard fixturing and tools to affect assembly. 
     Using a plastic box for the receiver enables low cost location and support for the CD mechanism and enables for slide lock assembly instead of the screws used in a traditional receiver. The brackets on the CD mechanism have a 1° taper that matches a 1° taper on the support shelf in the plastic box. This makes it easy for an operator to start the slide, but all of the clearances go to zero as the box snaps into place providing a strong rattle free assembly without the use of the traditional screws. 
     Referring to  FIGS. 12-18, 28, 29 and 32 , the details of the mounting of the CD player subassembly  66  within the housing case  68  (refer  FIG. 3 ) are illustrated in a simplified form.  FIGS. 12-14  represent a longitudinal cross-section of a case guideway  370 , including a rear wall portion  372  taken just laterally inside of the right side wall portion (not illustrated) of a housing case  374  to illustrate the spatial cooperation between the case guideway  370  and a right side CD player mounting bracket  376  during the insertion thereof in the assembly of a radio/CD player  378 . A mirror-image case guideway is integrally formed on the opposite, left wall portion of the case  374 . 
     The guideway  370  is integrally formed with the right sidewall portion (not illustrated) and the rear wall portion  372  of the housing case  374 , projecting laterally therefrom. The guideway  370  is generally “C” shaped, having laterally disposed upper and lower leg portions  380  and  382  extending longitudinally the entire depth of the case  374 . The leg portions  380  and  382  form continuously converging or tapered surfaces  384  and  386 , respectively, which are offset by an angle α (nominally 1°) vertically centered above and below a longitudinal assembly axis  388 . The mounting bracket  376  is preferably stamped from sheet aluminum or similar material and is also generally “C” shaped, having a vertical portion  390  and laterally disposed upper and lower leg portions  392  and  394  extending longitudinally substantially the entire depth of the case  374 . The leg portions  392  and  294  form continuously converging or tapered surfaces, respectively, which are offset by an angle φ (nominally 1°). The mounting bracket  376  has a leading edge surface  400  which, upon assembly, approaches the inside surface  402  of the case rear wall portion  372 . The vertical portion  390  of the mounting bracket  376  has a rearwardly directed integral tab  404  extending from edge surface  400 . The tab  404  has a localized upset bead or rib  406 . 
     The CD player subassembly is installed by manually aligning the leading edge surface  400  of the mounting brackets  376  with the opening  408  of the guideway  370  (refer to  FIG. 12 ) and rearwardly displacing it along the assembly axis  388 .  FIGS. 13 and 28  illustrate a mid-point in the insertion process wherein the guideway surfaces  384  and  386  remain substantially parallel to the cooperating mounting bracket surfaces  396  and  398 . The guideway serves to register, align and guide the insertion of the mounting brackets  376 . As the CD player subassembly  66  approaches the installed position depicted in  FIGS. 14 and 29 , the guideway surfaces  384  and  386  contact the mounting bracket surfaces to effectively provide a zero-tolerance interfit therebetween. This ensures precise positioning and effectively eliminates squeaks and rattles in application. As best viewed in  FIGS. 14-18 , in the installed position, the tabs  404  slip-fit penetrate into an opening or recess  410  in rear wall portion  372 . The upset rib  408  forms an interference-fit within the window  410  to lockingly engage the CSD player subassembly  66  within the case  374 . 
     Referring to  FIG. 30 , an alternative mounting configuration of an installed CD player subassembly  412  within a housing case  414  is illustrated. A sidewall  416  of the case  414  integrally defines a guideway  417  which extends laterally outwardly to form facing acutely offset cooperating upper and lower guide surfaces  418  and  420 , respectively. Likewise, the CD player subassembly  412  carries left and right mounting brackets  422  (only one is illustrated) having acutely inwardly angled upper and lower legs  424  and  426 , respectively, defining upper and lower surfaces  428  and  430 , respectively. 
     Referring to  FIG. 31 , an additional alternative mounting configuration of an installed CD player subassembly  432  within a housing case  434  is illustrated. A sidewall  436  of the case  434  integrally defines a guideway  438  which extends laterally inwardly to form opposed acutely offset cooperating upper and lower guide surfaces  440  and  442 , respectively. Likewise, the CD player subassembly  432  carries left and right mounting brackets  444  (only one is illustrated) having acutely outwardly angled upper and lower legs  446  and  448 , respectively, defining upper and lower surfaces  450  and  452 , respectively. 
     A localized area of wire screen  454  can be formed in the guideway  438  to affect a ground path between the CD player subassembly  432  and the case  434 . 
     Referring to  FIG. 31 , an alternative guideway  456  for the CD player mounting bracket  376  (refer  FIGS. 12-14 ) has upper and lower leg portions  458  and  460 , each having a tapered, increasing thickness in the vertical dimension along their longitudinal extent (along the assembly axis  462 . Upper and lower guide surfaces  464  and  466 , respectively, are offset by angle α. Outer guideway edge surfaces  468  and  470  have a slight reverse taper at an offset angle ε (approximately 1°-3°) to provide release draft for the injection molding process. 
     Molding in metal mesh into the plastic receiver case and front plate increases the strength of the material (much like putting re-bar into concrete) while still weighing less than a steel case. The gauge of the wire forming the mesh can be increased and the amount of plastic material can be substantially reduced, resulting in a very thin wall, robust structure. 
     As an alternative to the structure illustrated in  FIG. 19 , the plastic can be eliminated from the center portions of some or all of the individual side, front, back, top and/or bottom panel portions of the case and front plate. This configuration would have the appearance of a screen box, with a molded plastic peripheral frame circumscribing each panel portion. 
     Referring to  FIG. 19 , a lightweight automotive audio system  471  can include a housing case  472  constructed of a composite of polymer based material with a wire screen  474  insert molded therein to isolate audio components therein from various electrical anomalies. To further reduce overall weight, the gauge of the wire screen can be increased whereby the screen contributes a significant component of the resulting overall structural strength of the case, while the nominal section or thickness of the polymer material can be substantially reduced. By way of example, the case  472  top and bottom wall portions  476  and  478 , respectively, and left and right side wall portions  480  and  482 , respectively, injection molded into a single unified structure, with the enlarged gauge wire screen  474  insert molded adjacent the inner surfaces thereof. Edges and corners of the case  472  formed at the intersection of two or three adjacent wall portions can be locally thickened to increase structural rigidity of the case  472  as well as to provide internal and external mounting and interface ports. The intersecting edges of the top wall portion  476  and the left and right side wall portions  480  and  482 , respectively, form thickened left and right upper edge frames  484  and  486 , respectively. Likewise, the intersecting edges of the bottom wall portion  478  and the left and right side wall portions  480  and  482 , respectively, form thickened left and right lower edge frames. Lower edge frames  488  and  490  are locally vertically extended openings  492  and  494  for exposing the wire screen  474  to establish electrical contact with contact clips  496  and  498  carried by PCBs  500  and  502 , respectively, interconnected by pin connectors  504  within the case  472 . 
     The example embodiment of  FIG. 19  can be further modified to form an extremely lightweight case  506  constructed of polymer based material and wire screen  508 . Case  506  is configured so that some or all of the wall portions comprise a polymer frame  510  about the perimeter thereof and the wire screen  508  closing the center portion of such wall portions. Portions of the wire screen  508  adjacent edges of the case  506  are affixed to the frame  510  such as by insert molding. Attachment features such as mounting flanges  512 , tab receiving extensions  514 , ramped snap-engagement features  516  can be molded as an integral portion of the frame  510 . Ports, such as wiring harness interconnections  518  and  520 , and coaxial cable antenna interconnections  522  can be easily molded within an extended frame portion  524 . Windows  526  and  528  can also be formed in extended frame portion  524  for electrically interconnecting the wire screen  508  with internal components. 
     Using plastic for a receiver case enables low cost assembly of the components. The circuit boards and the CD mechanism can slide into place and then be locked or they can be snapped into place without screws. This reduces the number of parts required in the assembly and reduces the amount of direct and indirect labor to put a receiver together. The plastic case can be easily molded into a net shape forming the slides and snaps needed for assembly. 
     Referring to  FIGS. 2-5 , the apparatus and assembly method described substantially reduces the labor and component cost of the radio/CD player  62 , as well as the required capital costs. Furthermore, it substantially enhances product quality by substantially eliminating the possibility of extraneous or missing (small) parts and/or improper assembly. 
     Using the molded in metal mesh in the receiver plastic box that is grounded to the circuit boards creates a Faraday cage that provides shielding protection for RFI (Radio Frequency Interference), EMI (Electro Magnetic Interference), BCI (Bulk Current Injection), and ESD (Electrostatic Discharge). 
     Referring to  FIGS. 33-49 , the electrically conductive material insert molded within the polymer based material to form the case of an electrical device is embossed through the formation of one or more elongated upset beads within exposed regions (windows) of the case. This establishes a localized resiliently displaceable portion of the case to facilitate its fastenerless assembly and/or interaction with the host vehicle. The exposed conductive material is, in assembly, in intimate contact with subassemblies, such as a CD player mounting bracket within the case and establishes a robust electrical ground path therebetween. The upset bead ensures localized flexibility of portions of the case, preventing rupture of the conductive material and possible leakage of electrical anomalies. 
     Preferably, an extension of polymer based material forms a cantilever tab or island within the window which is resiliently displaceable during the assembly process. The tab forms a self engaging feature which engages a mating projection extending from the mounting bracket of the subassembly to retain the subassembly in its design intent location. 
     The embodiments of the invention described in connection with  FIGS. 33-49  correspond in most respects with the embodiments previously described in connection with  FIGS. 12-18, 28, 29 and 32 , with the exception of specifics set forth hereinbelow. 
     Referring to  FIG. 33 , an exploded, left-rear perspective view of a lightweight electronic device  1850  configured for automotive applications is illustrated, including an electronic circuit component such as a CD changer  1852  and a housing assembly  1854  featuring selectively embossed segments of exposed composite case electrical shielding material operative to enhance screwless assembly of subassembly brackets  1856  within (or exteriorly of) the case. Definitionally, subassembly brackets  1856  constitute adjacent structural elements. As described hereinabove, the housing case  1854  is constructed as a composite of relatively rigid polymer based material and electrically conductive material such as wire screen insert molded therein. Case walls including the electrically conductive material substantially enclose and shield the electronic circuit component from electrical anomalies. 
     Opposed sidewalls  1858  form symmetrical guideways  1860  for receiving and guiding the brackets  1856  (and CD changer  1853 ) along assembly axes  1861 . Each bracket  1856  forms laterally diverging upper and lower legs  1862  and  1866 , respectively, which are separated by a vertical wall portion  1866 . The brackets  1856  are formed of electrically conductive material which is in-circuit with the CD changer  1852 . Each bracket  1856  has an engagement feature or “bump”  1868  integrally formed therewith which extends laterally outwardly from the wall portion  1866  at a point vertically intermediate the upper and lower legs,  1862  and  1864 , respectively. 
     Each guideway  1860  forms laterally diverging upper and lower wall portions  1870  and  1872 , respectively, interconnecting a vertical wall portion  1874  to its respective sidewall  1858 . A window  1876  is formed in vertical wall portion  1874  of guideway  1860 , the window  1876  extending entirely or substantially through the polymer material forming the sidewall  1858  and exposing a portion of wire screen  1878 . A peninsular extension or tab  1880  is integrally formed with vertical wall portion  1874  and extends as a cantilever into the window  1876 . A recess or opening  1882  is formed adjacent the free end of the tab  1880 . As best viewed in  FIG. 33 , as thus constructed, the portion of the window  1876  not closed by the tab  1880 , i.e. that portion closed only by the wire screen  1878 , forms a general “C” configuration, with a base portion of the “C” disposed adjacent the free end of the cantilever tab  1880  and upper and lower parallel leg portions of the “C” extending continuously from the free end of the tab  1880  to its point of attachment with the adjacent vertical wall portion  1874  of the guideway  1860 . 
     Referring to  FIGS. 34 and 35 , a broken, overhead sectional view of the case  1854  and leading ends of the two brackets  1856  are illustrated with the elements juxtaposed similarly to that of  FIG. 171  wherein the CD charger  1852  and its attendant brackets  1856  are aligned along the assembly axes  1861  prior to contact between the brackets  1856  and case  1854 . 
     Referring to  FIGS. 36 and 37 , as the two brackets  1856  (and CD changer  1852 ) are inserted within the case  1854  along the assembly axes  1861 , the bracket bumps  1868  initially slidingly contact their respective inner surfaces of vertical wall portions  1874  of guideways  1860 . Advancement of the brackets  1856  along the assembly axes  1861  will cause the free ends of the brackets  1856  to resiliently deflect laterally inwardly as depicted by arrow  1885 . 
     Referring to  FIGS. 38 and 39 , as the two brackets further advance along the assembly axes  1861 , the bracket bumps  1868  slide along the inner surface of each tab  1880 , deflecting them outwardly. Simultaneously, the leading ends  1884  of the brackets  1856  register with and extend rearwardly outwardly through associated openings  1886  in the rear wall  1888  of the case  1854  to laterally secure the leading end  1884  of the brackets. When the leading ends  1884  of the brackets  1856  are engaged within their respective openings  1886 , the overall structure of the brackets  1856  is effectively stiffened and substantially preventing further inward lateral displacement as depicted by arrow  1885 . Thus, the interference fit of the bumps  1868  with the vertical wall portion  1874  results in a maximum outward lateral displacement of the free ends of the tabs  1880 . The leading ends  1884  of the brackets  1856  each have a localized upset bead or rib that is dimensioned for interference fit with openings  1886  to provide redundant interlocking engagement of the bracket  1856  with the back wall  1883  of the case  1854  similar to the embodiment of the invention described hereinabove in connection with  FIGS. 12-18 . 
     Referring to  FIGS. 40-41 , as the brackets  1856  (and CD changer  1852 ) are longitudinally inserted into their design intent positions, the bumps  1868  register with their respective openings  1882  within their tabs  1880 , resulting in the tabs  1880  resiliently relaxing and returning to their original orientation with respect to the vertical wall portions  1874  as depicted in  FIGS. 34-37 . Thus disposed, the rearwardly facing edge  1890  of each tab opening  1882  engages the forwardly facing edge  1892  of the respective bump  1868  to releasably interlock the brackets  1856  within the case  1854  without the use of separate components such as threaded fasteners. 
     As best seen in  FIG. 42 , the electrically conductive wire screen  1878  is exposed at selected locations of the inner surface of the case sidewalls  1858 . In particular, the inner surfaces of the wall portions  1870 ,  1872  and  1874  of the guideways  1860  expose the wire screen  1878  to ensure intimate contact with the brackets  1856  and thereby establish a reliable electrically conductive path therebetween. Preferably, a section of wire mesh  1878  corresponding with the tab openings  1882 , is removed to ensure full penetration of the bracket bump  1868  within each opening  1882 . 
     For the most part, the wire screen  1878  is formed in planer segments corresponding with the case walls. Portions of the wire screen  1878  exposed within openings formed by the windows  1876  are embossed, meaning that they have at least one laterally inwardly and/or outwardly extending upset bead  1894  formed therein which is elongated to enable localized flexure of the wire screen  1878  during cantilever flexure of the tab  1880  during insertion of the brackets  1856 . Preferably, the line of elongation of the upset bead  1894  extends parallel to and spaced from the edges of the rigid polymer material delimiting the window opening and is disposed intermediate the window edges and the cantilever portion of the tab  1880 . As best seen in  FIG. 39 , the upset bead  1894  is momentarily distended during the final stages of insertion of the brackets  1856  and, as best seen in  FIG. 41 , returns to its original configuration upon completion of the assembly process. Referring to  FIGS. 33, 41 and 42 , the upset bead  1894 , in this embodiment of the invention, mimics the open wire screen  1878  configuration, extending continuously vertically along the base of the “C” wire screen configuration and longitudinally forwardly along the entire length of the legs of the “C” wire screen configuration. 
     Although subject to variations depending upon specific design requirements, the degree of upset of the bead  1894  is preferably approximately equal to the nominal thickness of the adjacent rigid polymer based material. 
     Referring to  FIGS. 43 and 44 , an alternative design of the present invention is illustrated. A window  1896  formed in a wall  1898  of a case  1900  exposing a segment of wire screen  1902 . A discrete or “floating” island  1904  is insert molded with a central portion of the wire screen  1902  but is spaced from the wall  1898 . The wire screen  1902  is embossed with three concentric continuous upset beads, an inner bead  1906 , an outer bead  1908  and an intermediate bead  1910 . The upset beads  1906 ,  1908  and  1910  are spaced to function as a diaphragm for maximum momentary distension during the assembly process. The island  1904  has a recess  1912  formed in the inner surface thereof for engaging an electronic circuit component (not illustrated). Each of the upset beads  1906 ,  1908  and  1910  extend circumferentially continuously about the island  1094  to effect substantially symmetrical distension characteristics in both the “X” and “Y” axes designated by arrows  1914  and  1916 . 
     Referring to  FIGS. 45 and 46 , a second alternative design of the present invention is illustrated. A window  1918  formed in a wall  1920  of a case  1922  exposing a segment of wire screen  1924 . A discrete or “floating” island (not illustrated) such as that described in connection with the embodiment of  FIGS. 43 and 44  can also be insert molded with a central portion of the wire screen  1924  which is spaced from the wall  1920 . The wire screen  1924  is embossed with two concentric continuous upset beads, an inner bead  1926  and an outer bead  1928 . The upset beads  1926  and  1928  are spaced to function as a diaphragm for maximum momentary distension during the assembly process. Each of the upset beads  1926  and  1928  extend circumferentially continuously, but are circumferentially irregular to affect asymmetrical distension characteristics in the “X” and “Y” axes designated by arrows  1930  and  1932 , as well as to provide a decorative motif or distinguishing design. 
     Referring to  FIGS. 47 and 48 , a detailed exemplary solid model of a male die portion  1934  of a die set configured to affect formation of the composite electronic device case  1854  of  FIG. 33 , illustrating the detail of the region of the die portion  1934  which establishes the case side window  1876  and affects formation of the conductive material upset bead  1894  upon closure with a mating die portion (not illustrated).  FIG. 48  depicts an exemplary dimensioned profile of the male die portion  1934  of  FIG. 47  through its region which forms the case window  1876 . Male die portion  1934  has an external surface  1936  taken along section line  48 - 48  of  FIG. 47  defining details  1938  and  1940  for forming the inner surface of a case sidewall  1858 , details  1942  and  1944  for forming opposed legs of the case window  1876 , details  1946  and  1948  for forming opposed portions of the screen upset bead  1894 , details  1950  and  1952  for forming the integral tab  1880  within the window  1876 , and a detail  1954  for forming the tab recess/opening  1882 . 
       FIG. 49  depicts a Product Data Sheet of steel mesh employed by the applicant in certain embodiments of the composite case of the present invention. 
     It is to be understood that the invention has been described with reference to specific embodiments and variations to provide the features and advantages previously described and that the embodiments are susceptible of modification as will be apparent to those skilled in the art. 
     Furthermore, it is contemplated that many alternative, common inexpensive materials can be employed to construct the basis constituent components. Accordingly, the forgoing is not to be construed in a limiting sense. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used is intended to be in the nature of words of description rather than of limitation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, a number of the various radio/CD player case constructions illustrated herein are illustrated as being formed of solid molded polymer material for the sake of simplicity and clarity of understanding. It is to be understood, however, that the wire mesh depicted, for example in  FIG. 20 , can be employed in the other configurations and embodiments with equal success. Furthermore, several of the housing assembly structures are described herein as being formed of metal. However, a wide range of material substitutes, including plastics, ceramics, non-ferrous metals and composites can be substituted without departing from the spirit and scope of the present invention. The terms “snap-engaging” and “self-engaging” are intended to interpreted very broadly inasmuch as innumerable structural, process (e.g. weldments) and chemical (e.g. adhesives) equivalents are available. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for illustrative purposes and convenience and are not in any way limiting, the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents, may be practiced otherwise than is specifically described.