Abstract:
A self-leaded, surface mountable component package is provided for holding a wide variety of electrical components having widely variant conductor wire sizes in a manner achieving standardized conductor contact positioning. The general box-like configuration provides for component style variability and has a set of progressively stepped or tapered winding bosses to position and secure component conductors of multiple wire size, thereby ensuring proper registration with conductive traces of surface mount printed circuit boards and substrates.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to electrical circuit component holders adapted to surface mount technology. More particularly, the present invention relates to a self-leaded surface mount component holder handling component connection wires of a variety of sizes while providing precise wire registration and a secure clinching thereof.  
           [0003]    2. Introduction to the Invention  
           [0004]    Due to the popularity and efficiency of surface mounting of electrical components onto printed circuit boards and substrates, there has been an ever increasing demand for converting non-surface-mount components into surface mount components.  
           [0005]    Examples of surface mount component holders of the prior art are provided by U.S. Pat. No. 4,754,370 to DeTizio et al., for “Electrical Component with Added Connecting Conducting Paths”, U.S. Pat. No. 5,212,345 to Gutierrez for “Self-leaded Surface Mounted Coplanar Header”, U.S. Pat. No. 5,309,130 to Lint for “Self Leaded Surface Mount Coil Lead Form”, and U.S. Pat. No. 5,760,669 to Dangler et al. for “Low Profile Inductor/Transformer Component”.  
           [0006]    Although a large proliferation of surface mounting options are available in the prior art, few if any such options are presently known or available to offer pick and place compatibility, flexibility for multiple component conductor sizes, and accurate placement of the component conductors (in self-leaded designs) in a single package.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    A general object of the present invention is to provide a self-leaded, surface mountable component package for holding a wide variety of electrical components having variant conductor wire sizes in a manner achieving standardized conductor contact positioning thereby overcoming limitations and drawbacks of the prior art.  
           [0008]    Another object of the present invention is to provide a self-leaded, surface mountable component holder formed of a plastic material in a box-like configuration to hold and connect a wide variety of electrical components.  
           [0009]    Another object of the present invention is to provide a set of winding bosses for a surface mountable component holder, each boss including a groove that converges in two dimensions or planes in order to receive and clinch a component connection wire having a diameter within a range of wire diameters adapted to be placed in the groove and clinched by narrowing portions of facing walls.  
           [0010]    Another object of the present invention is to provide each winding boss of the holder with a set of progressively stepped or tapered steps to position and secure component conductors of multiple wire size in a manner ensuring proper registration with conductive traces of surface mount printed circuit boards and substrates as well as effectively clinching the wire, in a manner overcoming limitations and drawbacks of the prior art.  
           [0011]    In accordance with principles and aspects of the present invention, a self-leaded surface mount component holder includes a unitary housing formed of a plastic material for containing a particular electrical component. The unitary housing includes a substantially planar top wall portion and at least two sidewall portions depending downwardly from opposite edge regions of the top wall portion to define a component cavity for receiving an electrical component therein. A plurality of winding bosses extend outwardly from each sidewall portion. Each winding boss includes a bottom face lying in a bottom plane substantially parallel with a plane of the top wall portion, an outer wall segment including an outer winding post projecting upwardly from a bottom segment including the bottom face, and an inner wall segment. Interior faces of the outer wall segment and the inner wall segment lie in converging planes in a direction substantially normal to the bottom plane and define an interior groove sized to receive and clinch a component connection wire of the electrical component after being first wrapped across the bottom segment. The winding post is provided to receive at least a portion of one wrap of the component connection wire after it has first been wrapped across the bottom wall face and through the interior groove.  
           [0012]    The present invention also provides a self-leaded surface mount component holder including a unitary housing formed of a plastic material for containing a particular electrical component such as a toroidal coil. The housing includes a substantially planar top wall portion and two sidewall portions depending downwardly from opposite edge regions of the top wall portion thereby defining a component cavity for receiving the toroidal coil therein. A plurality of winding bosses extend outwardly from each sidewall portion and include bottom faces lying in a bottom plane substantially parallel with a plane of the top wall portion. Each winding boss also includes an outer wall segment including an outer winding post portion projecting upwardly from the bottom face and an inner wall segment. The outer wall segment and the inner wall segments have interior faces, which converge along planes substantially normal to the bottom plane and thereby define an interior groove. Most preferably, the groove is defmed by a plurality of steps formed on the interior face of the inner wall segment which are generally parallel with the bottom plane and adjacent interior walls which converge relatively to an interior wall of the winding post portion, each step being of a size to receive a component connection wire of progressively smaller predetermined diameter. The holder also preferably defines a wire guide ramp extending outwardly adjacent one side of each winding boss for guiding a component connection wire into a predetermined winding position relative to the bottom face of the particular winding boss.  
           [0013]    As one aspect of the present invention the sidewall portions extend outwardly of the top wall portion and the holder further includes a plurality of end wall portions joining outer edge regions of the sidewall portions, thereby defining two top wall access/vent openings on either side of the top wall portion.  
           [0014]    The present invention also provides a surface mount electrical assembly including a self-leaded surface mount component holder and an electrical component such as a toroidal coil. The holder includes a unitary housing formed of a plastic material and having a substantially planar top wall portion, two sidewall portions depending downwardly from opposite edge regions of the top wall portion and extending outwardly of the top wall portion, two end wall portions joining outer edge regions of the sidewall portions thereby defining two top wall access/vent openings on either side of the top wall portion and a component cavity for receiving the electrical component therein. The holder includes a plurality of winding bosses extending outwardly on opposite outer sides of the unitary housing and including bottom faces lying in a bottom plane substantially parallel with a plane of the top wall portion. Each winding boss includes an outer wall segment including an outer winding post portion projecting upwardly from the bottom face and an inner wall segment, the outer wall segment and the inner wall segments converging in a direction substantially normal to the bottom plane thereby defining an interior groove, the groove most preferably being stepped to receive and clinch a component connection wire of one of a plurality of predetermined diameters. The component within the component cavity of the holder has plural component connection wires of one of the predetermined diameters. Each component connection wire is first wrapped across the bottom face of the winding boss, is then wound through the groove and clinched by the convergent interior faces of the outer wall segment and the inner wall segment and is then wound at least partially around the winding post portion. In this aspect of the invention, the holder preferably includes a wire guide ramp extending outwardly adjacent one side of each winding boss for guiding each component connection wire into a predetermined winding position relative to the bottom face of the winding boss.  
           [0015]    These and other objects, advantages, aspects and features of the present invention will be more filly understood and appreciated upon consideration of the detailed description of preferred embodiments presented in conjunction with the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention is illustrated by the drawings in which FIG. 1 is an enlarged, isometric projection of a self-leaded surface mount component holder in accordance with principles of the present invention.  
         [0017]    [0017]FIG. 2 is a view in front elevation of the FIG. 1 component holder.  
         [0018]    [0018]FIG. 3, showing detail B from FIG. 1, is an enlarged detail plan view of a portion of a winding boss  22  of the FIG. 1 component holder. FIG. 3 shows the winding boss securing features for different size component connection wires.  
         [0019]    [0019]FIGS. 4A, 4B,  4 C and  4 D are enlarged detail end views in elevation of a winding boss  22  of the FIG. 1 component holder identified by circular view line A in FIG. 2. They show the winding boss positioning component connection wires of progressively larger size (cross-section diameter).  
         [0020]    [0020]FIG. 5 is an enlarged, isometric projection of an electrical component (toroidal coil transformer) included within the FIG. 1 component holder and having coil connection wires wrapped around four winding bosses of the type shown in FIGS. 2, 3 and  4 A- 4 D. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    A component holder  10  in accordance with principles of the present invention is integrally formed as a general box-like geometry having a top wall portion  12 , curved sidewalls  14  and  16 , end walls  18  and  20 , and an open bottom plane to enable a component  24  to be positioned in the holder  10 . The holder  10 , often referred to as a “header” in the electrical component industry, is typically formed by molding of a suitable dielectric plastic material selected to satisfy the particular component application in terms of electrical and mechanical properties. As formed, the holder  10  defines an interior component cavity (denoted by reference numeral  25 ) that is dimensioned and configured to receive a particular electrical component, such as a toroidal coil or transformer  24  (shown in FIG. 5) through the bottom. Once the component is in place in the holder  10 , a suitable potting material, compound, or other suitable means or medium, may be used to secure the component in the interior space  25 . As shown in FIG. 1 the end walls  18  and  20  are located outwardly of adjacent edges of the top wall portion  12 , so that openings  27  are provided to facilitate adequate cooling of the electrical component  24  in the holder  10  and to enable conductor wire ends  26  of the electrical component  24  to be passed therethrough and wrapped around appropriately positioned exterior winding bosses  22 . Also, curved walls  14  and  16  extend downwardly slightly beyond end walls  18  and  20  thereby defining two elongated rails  19  and  21  extending the length of walls  18  and  20  and lying in a bottom opening plane. In the example shown in FIG. 1 the side walls  14  and  16  are curved to accommodate a toroidal component, such as a coil or transformer wound upon a toroid core. Other shapes and geometries for the side walls of the holder  10  may be adapted and used, depending upon a particular application.  
         [0022]    The winding bosses  22  are formed to receive and secure terminal end wires  26  of the electrical component  24  irrespective of particular wire size or diameter. The winding bosses  22  are formed and positioned to align with printed circuit connection pad locations formed on circuit boards or substrates in accordance with predetermined dimensions and locations. Two or more winding bosses may be provided by the holder  10 . In the preferred arrangement shown in FIG. 1, four winding bosses  22  are formed at corners of the curved sidewalls  14  and  16 . In the preferred arrangement of FIG. 5, six winding bosses are shown, with two additional winding bosses  22  being formed at end walls  18  and  20 . A holder may be provided with more than six winding bosses, depending upon the surface mounting-connection requirements of a particular electrical component.  
         [0023]    Each winding boss  22  defines a progressively narrowing interior groove  23 . In its most general form, the groove  23  has walls that converge in two dimensions, i.e., both horizontally and vertically, see FIGS. 2 and 3. In a presently preferred form, the groove  23  is formed by an interior stepped-wall portion  30  and an inside face  32  of a winding post portion  34 . A bottom face  36  of the boss  22  is aligned with the bottom plane of the holder  10 . A gap  38  may be formed in the structure of the bottom face  36  to permit vapor phase solder deposition gases to pass therethrough in order to facilitate soldering the terminal end conductor to a pad of a printed circuit board or substrate.  
         [0024]    A series of steps are formed in the stepped-wall portion  30 . Four steps  40 ,  42 ,  44 , and  46  are shown in the FIG. 3 detail view. More steps or fewer steps may be provided. Alternatively, the steps may be replaced with a continuous-wall Vee groove extending to an apex. Most preferably, lateral segments of the interior wall portion adjacently normal to each step  40 ,  42 ,  44 , and  46  have graduated decreases in width, so that the groove  23  is wider at an opening on one side than an opening on another side. This graduated decrease in width of groove  23  provides an auto-clinching function which is sized and adapted to clinch and thereby secure a terminal end conductor wire  26  of appropriate size when it is wrapped first around the bottom face  36  and then dressed up the opposite side of the boss, then through the interior opening  23 , and finally wrapped around the winding post portion  34 , as shown in FIGS.  4 A- 4 D and FIG. 5. (FIG. 5 shows a relatively large diameter wire  26  being partially wrapped around winding post portion  34 .)  
         [0025]    An end conductor wire  26  is wound around the post portion  34  of each winding boss  22  in the direction of decreasing width of groove  23 , so that the winding boss  22  clinches the wire end and positively secures it in place. The dielectric plastic material from which the holder is formed is selected to be sufficiently rigid to provide effective clinching of the wire in the groove  23 . An example of a preferred plastic material for holder  10  is any epoxy, phenolic, glass filled nylon, or other plastic material having appropriate mechanical properties to clinch the wire end  26  as well as withstand temperatures encountered in surface mounting soldering procedures. We currently prefer to use RytonTm R 4  glass-fiber reinforced polyphenylene sulfide, supplied by Chevron Phillips Chemical Company LP.  
         [0026]    A chamfered edge  48  may be formed on the winding post portion  34  at the first outer corner encountered by the wire upon leaving the groove. A guide ramp or surface  50  may be formed in the wall of holder  10  adjacent the bottom face  36  of winding boss  22  to serve as a conductor guide to position the wire  26  in an appropriate outward alignment relative to the holder  10  and a corresponding winding boss  22 . In this way, the portion of wire  26  that passes across the bottom face  36  will be aligned with a conductive trace of a printed circuit board to which the resultant assembly will be attached. The portion of wire  26  passing across bottom face  36  will first be suitably prepared or tinned in order to be soldered to the conductive trace as is conventionally practiced in the surface mounting art.  
         [0027]    As seen in FIG. 5 a wire end  26  from toroidal coil  24  exits the opening between the top wall portion  12  and the endwall  20  and is dressed downwardly along a portion of side wall  16  adjacent to a winding boss  22 . The wire end  26  is directed away from the sidewall  16  by the wire guide surface  50 . A sharp turn is then made in the wire to direct it across the bottom face  36  of the winding boss  22  and then up the back side and into the groove  23 . In the example shown in FIG. 5 the wire end  26  has a cross-sectional diameter which requires use of the widest, uppermost portion of the groove  23 , defined by first step  40 . The wire end  26  is drawn through the narrowing groove  23  and wrapped one-quarter turn around the winding post  34 .  
         [0028]    [0028]FIGS. 4A, 4B,  4 C and  4 D illustrate how the holder  10  accommodates wire ends of widely variant diameter. In FIG. 4A a conductor wire end  26 A has a small diameter and fits into a deepest recess of the groove  23  defined by lowermost step  46  and having a narrowest width w1. An adjacent sidewall  52  to step  46  has a height dimension dl set to correspond to, e.g., four diameters of wire end  26 A, and four turns are made around the wrapping post  34  in this example (all but the uppermost one of the turns being cut away in FIGS. 4A, 4B, and  4 C to add clarity in explaining these examples). In FIG. 4B a wire  26 B of larger diameter fits into groove  23  and rests on the second step  44 . In this example, the width of the groove at step  44  is w2 and the height of the wall segment adjacently above step  44  is d2. Three turns are made of wire end  26 B around wrapping post  34 . In FIG. 4C a wire end  26 C of larger diameter is placed in groove  23  and seats against step  42 . The width of the groove  23  at step  42  is w3 and the height of the wall segment adjacently above step  42  is d3. In this example two turns are made around wrapping post  34 . Finally, in FIG. 4D, the conductor  26  has a sufficiently large diameter that the widest step  40  must be used, and a single turn is made around the wrapping post  34 . The width of the groove  23  at step  40  is w4 and the height of the wall segment adjacently above step  40  is d4.  
         [0029]    The stepped width of the groove  23  ensures accurate positioning for the various conductor sizes that may be used for a particular component assembly. The depth of each channel through the groove  23  is determined by the physical requirements of the assembly and how many conductors will be needed to withstand vibration and shock encountered in the intended application or use environment. As shown in FIGS.  4 A- 4 D smaller conductor sizes will typically use two or more wraps around wrapping post  34 , while larger conductors may use only a single wrap to achieve the desired mechanical and mounting strength. Alternatively, a wire pair commonly encountered with an inductor center tap may be wrapped around the winding boss  22  and secured thereto, with the groove  23  being adapted to accommodate at least two wire diameters for that particular application.  
         [0030]    The conductor wire end is typically wrapped around the holder  10  in one of two ways. Each conductor end is either wrapped around a single winding boss as shown in FIG. 5, or each conductor end is wrapped around two adjacent winding bosses in order to accommodate two terminal components such as a toroidal single coil inductor.  
         [0031]    Having thus described preferred embodiments of the invention, it will now be appreciated that the objects of the invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. Therefore, the disclosures and descriptions herein are purely illustrative and are not intended to be in any sense limiting.