Fixed conductive pin for printed wiring substrate electronics case and method of manufacture therefor

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.

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'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.

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.