Abstract:
An electronics case, a method of manufacturing the same and a power module incorporating the case. In one embodiment, the case includes: (1) an enclosure including a metal substrate that forms walls of the enclosure and a dielectric material located on inner surfaces of the walls that insulate the substrate from electronics components located within the enclosure and (2) an electrically conductive pin, affixed to a sidewall of the enclosure substrate and extending to without the enclosure, that allows the substrate to be electrically coupled to a structure supporting the case for EMI (electromagnetic interference) shielding or case-grounding purposes.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention is directed, in general, to electronics packaging and, more specifically, to a fixed, electrically conductive pin for an electronics case that also serves as a printed wiring substrate and a method of manufacturing the same. 
     BACKGROUND OF THE INVENTION 
     Electronic devices for power supplies and similar applications are conventionally provided in a protective, heat-dissipation package. These board mounted power conversion modules are widely used in telecommunications or computer-related electronic data processing environments. 
     Similar to other consumer electronic products (for example, notebook computers), these board mounted power conversion modules are being packaged with more functions and more output power in smaller size, lighter weight, lower profile, and higher efficiency modules. The power density (total output power divided by the volume of the power module) of today&#39;s board mounted power modules is increasing as new products are introduced. However any improvements in power, density and profile cannot be at the expense of the electrical characteristics of the components and the overall power supply. A significant improvement in types of board mountable electronic devices was made in the encapsulated board mountable power supply of the type described in Stevens U.S. Pat. No. 5,835,350, entitled “Encapsulated, Board-Mountable Power Supply and Method of Manufacture Therefor.” Such a device represents a significant manufacturing advance and convenience from both a time and monetary perspective. 
     While the invention described in Stevens provided a significant advance in the manufacture of electronic equipment, it shares a limitation with other new generation, small-sized, board mountable electronic circuits. That limitation is the fact that it lacks a convenient method of providing a case grounding connection between the substrate of the device housed in the case and the supporting substrate upon which the device is mounted. 
     Accordingly, what is needed in the art is a device or method to provide a case grounding connection between a substrate of a circuit contained in a board mountable case and the substrate that supports the cased circuit as a part or component of a larger circuit. Such a case grounding device or method must provide a reliable case ground while preserving the convenience of permitting an assembly process that only requires the cased circuit to be plugged into a supporting substrate. Preferably, the technique should be cost-effective and suitable for mass production. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, the present invention provides an electronics case, a method of manufacturing the same and a power module incorporating the case. In one embodiment, the case includes: (1) an enclosure including a metal substrate that forms walls of the enclosure and a dielectric material located on inner surfaces of the walls that insulate the substrate from electronics components located within the enclosure and (2) an electrically conductive pin, affixed to a sidewall of the substrate enclosure and extending to without the enclosure, that allows the substrate to be electrically coupled to a structure supporting the case. 
     The present invention therefore introduces the broad concept of providing a pin (most advantageously a case ground pin) that is directly affixed to a sidewall of an electronics enclosure/component substrate. In an embodiment to be illustrated and described, the pin is affixed by forming an aperture in the sidewall and riveting the pin to within the aperture. 
     In one embodiment of the present invention, the case further includes a plurality of electrically conductive traces located on the material and insulated from the substrate. In the embodiment to be illustrated and described, the pin passes through the material, and through an interior of the enclosure before extending to without the enclosure. Of course, the pin may protrude from the enclosure, never passing through its interior. 
     In one embodiment of the present invention, the components are components of a power converter. In the embodiment to be illustrated and described, the power converter components and case cooperate to form a power module, which may itself be board-mounted as a single unit. Thus, in one embodiment of the present invention, the structure is a printed circuit board having electrically conductive traces located thereon. 
     In one embodiment of the present invention, the case further includes an encapsulant at least partially occupying the enclosure. The encapsulant, while not necessary to the present invention, nonetheless provides support for electronic components within the enclosure and rigidity to the case as a whole. 
     The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates an exploded isometric view of an electronics case, supporting substrate and electrically conductive pin; 
     FIG. 2 illustrates an isometric view of an electronics case and supporting substrate with an electrically conductive pin to fastened to the side of the electronics case by a rivet joint; 
     FIG. 3A illustrates a side elevational view of an electronics case mounted on a supporting substrate with electrical pins and an electrically conductive pin inserted through apertures on the supporting substrate; 
     FIG. 3B illustrates an end elevational view of an electronics case mounted on a supporting substrate with electrical pins and an electrically conductive pin inserted through apertures on the supporting substrate; 
     FIG. 4 illustrates a cut away isometric view of an electronics case showing an embodiment of the invention with the electrically conductive pin fastened to an interior sidewall; and 
     FIG. 5 is a flow diagram of a method of manufacturing an embodiment of an electronics case that is constructed in accordance with the principles of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring initially to FIG. 1, illustrated is an exploded isometric view of an electronics case  110 , a supporting substrate  120  and an electrically conductive pin  130 . The electronics case  110  is an enclosure that contains the various electronic components that make up an electronic circuit. The case  110  is formed from a metal substrate and usually only has a top wall  111  and sidewalls  113 . When initially formed, illustrated embodiment of the case  110  has no bottom surface. As hereinafter described, the illustrated embodiment of the invention calls for the surface of the bottom  112  of the case  110  to be formed by an encapsulant around the components in the case  110 . 
     The inner surface of the metal substrate making up the sides  113  and top  111  of the case  110  is lined with a dielectric material (not shown) that insulates the metal substrate from electronics components located within the case  110 . The metal substrate of the case  110  also serves as a printed wiring or circuit board for the electronic components contained therein. In one embodiment of the invention, the electronic components contained within the case  110  make up a power converter. In another embodiment of the invention, the dielectric lining of the case  110  substrate makes up a printed circuit board with electrically conductive traces located thereon. 
     Extending from the bottom  112  of the case  110  are electrical pins  122  to provide electrical connectivity between the electronic components enclosed within the case  110  and the electronic circuit associated with the supporting substrate  120  upon which the case  110  is mounted. On the surface of the supporting substrate  120  are corresponding apertures  121  to accept the electrical pins  122  and complete the electrical connection between the components within the case  110  and the circuit located on or within the supporting substrate  120 . 
     A mountable case  110  of the type illustrated, permits a manufacturer to use off-the-shelf preassembled circuits contained in cases  110 , such as that illustrated, to assemble and manufacture electronic systems. This provides an advantageous manufacturing method for using electronic circuits of wide application that have become largely standardized, such as certain power supply configurations. 
     In some mountable cases  110 , the circuit and components contained therein are held in place by an encapsulant, such as epoxy or some other dielectric polymers. The encapsulant occupies at least part of the case  110  enclosure and may actually be the surface that directly contacts the supporting substrate  120  when the case  110  is mounted. The encapsulant, while not necessary in some embodiments of the present invention, provides support for electronic components within the case  110  and rigidity to the case  110  as a whole. A power supply and method of manufacture of a mountable case  110  of this type is described in Stevens U.S. Pat. No. 5,835,350, entitled “Encapsulated, Board-Mountable Power Supply and Method of Manufacture Therefor,” a copy of which is incorporated herein by this reference thereto. 
     Returning to FIG. 1, attached to one side  113  of the metal substrate that makes up the case  110  is an electrically conductive pin  130 . In one embodiment on the invention, a rivet joint is used to affix the electrically conductive pin  130  to the surface  113  of the case  110 . Illustrated is an exploded drawing of an embodiment of a rivet joint. To receive the rivet  135 , the side  113  of the case  110  has an aperture  115  located thereon. A rivet  135  is inserted through the aperture  115  and a hole  131  in the electrically conductive pin  130 . The rivet joint is then formed to secure the electrically conductive pin  130  to the case  110 . Turning to FIG. 2, illustrated is an isometric view of the case  110  and supporting substrate  120  with the electrically conductive pin  130  fastened to the side  113  of the case by a rivet joint  230 . 
     Turning now to FIGS. 3A and 3B, illustrated are elevational views of the case  110  mounted on a supporting substrate  120 . FIG. 3A is a side  113  elevational view of the case  110  mounted on the supporting substrate  120  with electrical pins  122  and the electrically conductive pin  130  inserted in apertures  121  (see FIG. 1) on the supporting substrate  120 . FIG. 3B is an elevational end view of the case  110  mounted on the supporting substrate  120 . It is readily apparent that, when the case  110  is mounted on the supporting substrate  120 , the electrically conductive pin  130  provides a case ground connection between the metal substrate of the case  110  and the supporting substrate  120 . 
     Turning to FIG. 4, illustrated is a cut away isometric view of the case  110  showing an embodiment of the invention with the electrically conductive pin  130  fastened to an interior sidewall  113 . In one embodiment of the invention, a rivet joint  230  is used to fasten the electrically conductive pin  130  to the interior sidewall  113 . Those skilled in the art understand, however, that other methods, now known or later discovered, to secure the electrically conductive pin  130  to the interior sidewall  113  are well within the scope of the current invention. One such other method to secure the electrically conductive pin  130  to the interior sidewall  113  has the pin  130  located against the sidewall  113  and the case filled with an encapsulant that holds the pin  130  in place. In one embodiment of the invention, the case  110  is mounted on a supporting substrate  120  with the pin  130  fastened to an interior sidewall  113  and passing through the interior of the case  110  and the dielectric material that lines the interior walls  113  before it extends out of the case  110 . 
     Turning now to FIG. 5, illustrated is a flow diagram of an embodiment of a method of manufacturing an electronics case  110  according to the principles of the present invention. The method begins at a start step  510 . The next step is to fold a metal substrate to form the walls and top of an enclosure having a reservoir therein during a construct case step  520 . The peripheral walls may be sealed through several methods such as, without limitation, applying an adhesive, applying an interference-fit plastic insert, welding the corners of the walls, or soldering the interior corners to provide a solderable pattern on an interior layer of the case. Regardless of the selected method, if an encapsulant is to placed in the case, the corners should be meticulously sealed to prevent escape of the encapsulant while placing the encapsulant within the case or during curing of the encapsulant. 
     A dielectric material is then deposited on the inner surfaces of the case walls during a deposit dielectric material step  530 . The dielectric material provides insulation for electronic components to be located within the case. Of course, it is well within the scope of the current invention if the dielectric material is deposited on the substrate before the construct case step  520 . In one embodiment of manufacturing the electronics case, a plurality of electrically conductive traces are located on the dielectric material, which electrically conductive traces are insulated from the metal substrate. The electrically conductive traces are placed on the dielectric material at such time, or times, as those skilled in the art determine. 
     The electrically conductive pin  130  illustrated as being affixed to the side of the case in an affix pin step  540 . The conductive pin  130  can be either placed within or without the case and still be within the scope of the invention. During the affix pin step  540 , the pin is located so that the metal substrate of the case is electrically coupled to a supporting substrate structure on which the case is mounted. In one embodiment, the affix pin step  540  includes riveting the electrically conductive pin  130  to a sidewall (such as the sidewall  113  of FIG. 1) of the case. During the affix pin step  540 , the pin can be located so that it passes through the interior of the case enclosure before extending without the enclosure. 
     Other manufacturing embodiments steps within the scope of the present invention include a step to install the electronic components of a power converter (not shown) and at least partially filling the enclosure with an encapsulant (not shown), which steps occur at such time as those skilled in the art determine to be best. If an encapsulant is used to partially fill the enclosure, environmental protection (e.g., protection from dirt and moisture) for the electronic components located within the case is provided. The manufacturing method concludes at an end step  550 . 
     The completed case, which may be a power module, can then be coupled to a printed wiring or circuit supporting substrate using any number of techniques including, without limitation, through hole attachment, surface mounting, connector attachment or mechanical piece part attachment (e.g., compression mounting). 
     The electronics case  110  is constructed according to the principles of the present invention as described with respect to the preceding FIGURES. The aforementioned electronics case  110  and method of manufacturing are submitted for illustrative purposes only. Other case embodiments and alternative methods of manufacturing in accordance with the general principles as submitted herein are well within the broad scope of the present invention. 
     The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the invention. Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.