Abstract:
A compliant pin for use with a shielding cage or electrical connector is disclosed that has improved insertion capabilities that increase the resistance of the compliant pin to buckling during mounting of the cage or connector to a circuit board. The pin has a base and tip portion that are interconnected together by a body portion. An opening is disposed in the pin body portion and the top edge of the opening is positioned at a level therein that is spaced apart from and beneath the top surface of the circuit board. In another embodiment, the pin opening is generally non-symmetrical with a configuration that approximates a triangle, i.e., the wider base portion of the pin opening is closer to the pin tip portion than the narrower, apex portion of the pin opening.

Description:
BACKGROUND OF THE PRESENT DISCLOSURE 
       [0001]    The Present Disclosure relates generally to board mounted connectors, and more particularly, to such connectors having improved compliant mounting pins that offer beneficial insertion and retention capabilities. 
         [0002]    Many electronic devices utilize internal circuit boards for circuitry and as a platform upon which to mount integrated circuits, switches, components and the like, including connectors. These connectors are often surrounded with a conductive shielding member that takes the form of a cage to provide grounding and shielding against electromagnetic interference radiation, known as “EMI.” These shields may be mounted to the surface of the circuit board, such as by soldering, or they may be provided with a plurality of members in the form of mounting pins that extend downwardly therefrom and which are received in openings formed in the circuit board. These openings are formed as plated through holes, or “vias,” directly in the circuit board and have a conductive metal plating applied to their inner surfaces, or sidewalls. The pins are formed as compliant members and are known in the art as press-fit pins or compliant pins. These pins are larger in overall size than the holes and this dimensional difference permits the pins to firmly engage the sidewalls of the holes and thereby form an electrical connection between the cage and the circuit boards. In addition to their use with shielding cages, compliant pins may also be used with electrical connectors for the same mounting purpose, and may be used directly as terminal tail portions in both connectors and other electronic components, such as switches, integrated circuits and the like. 
         [0003]    There are problems in the use of press-fit compliant pins and these problems include inadequate performance during insertion into and retention by a circuit board. The cross-section of some pins may be lacking in structural integrity such that those pins may bend or buckle when the pins are inserted into their associated through holes. If the pins buckle during insertion they will not be fully inserted into the holes and may deform more than expected. This lack of full insertion and/or excessive deformation negatively affects the electrical contact between the pins and the surrounding vias and requires the cage to be removed and replaced, but in doing so, the buckled configuration of the pins may give rise to the possibility of damage to the expensive circuit board. 
         [0004]    Similarly, if the pins buckle during insertion, they may provide adequate electrical contact with the circuit board but their retention capability may be diminished to the point where the electrical contact becomes sporadic and intermittent after the device in which the cage is used proceeds through assembly, packing, shipping and installation at an end user. This intermittent contact may not be discovered until the product is placed into service at the end user or shortly thereafter, thereby necessitating return of the device to the manufacturer. 
         [0005]    The Present Disclosure is therefore directed to a compliant pin having an improved structure that offers greater resistance to buckling. 
       SUMMARY OF THE PRESENT DISCLOSURE 
       [0006]    Accordingly, there is provided an improved compliant pin that has a cross-section configured to better resist buckling during insertion into a circuit board opening. 
         [0007]    In accordance with a first embodiment as described in the following Present Disclosure, a compliant pin particularly suitable for use in association with a conductive shielding cage is provided with an elongated body which has an internal opening, or “eye,” positioned within the pin body at a level beneath the circuit board-cage interface so that more material is present in this area which enhances the resistance to buckling of the compliant pin upon insertion and removal. 
         [0008]    In accordance with a second embodiment as described in the Present Disclosure, a non-symmetrical opening is formed in the pin body. The opening is symmetrical around a vertical axis, but not around an associated horizontal axis. As such, the opening has a given width at its upper extent that increases along the depth of the pin body so that the width of the bottom of the pin opening is wider, or larger, than that at the top of the pin opening and this larger opening is located below the circuit board-cage interface. More material is thus present in the upper portions of the pin body, and as such, the pin body has a greater moment of inertia and therefore a greater resistance to bending and buckling 
         [0009]    These and other objects, features and advantages of the Present Disclosure will be clearly understood through a consideration of the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]    The organization and manner of the structure and operation of the Present Disclosure, together with further objects and advantages thereof, may best be understood by reference to the following Detailed Description, taken in connection with the accompanying Figures, wherein like reference numerals identify like elements, and in which: 
           [0011]      FIG. 1  is a perspective view of a shielding cage with compliant pins in accordance with the principles of the Present Disclosure and shown mounted to a circuit board; 
           [0012]      FIG. 2  is a perspective view of the shielding cage of  FIG. 1  removed from the circuit board; 
           [0013]      FIG. 3  is a side elevational view of the shielding cage of  FIG. 1 , but removed from the circuit board for clarity to illustrate the complaint mounting pins of the shielding cage; 
           [0014]      FIG. 4A  is an enlarged view of a portion of the shielding cage of  FIG. 1 , which better illustrates a first embodiment of a compliant mounting pin constructed in accordance with the principles of the Present Disclosure; 
           [0015]      FIG. 4B  is an enlarged detail view of  FIG. 4A , illustrating a single compliant pin and it relation to a circuit board into which it is inserted; 
           [0016]      FIG. 4C  is a diagrammatic view of a section through the pin base portion of the compliant pin of  FIG. 4A , taken along Line C-C thereof, to illustrate geometry used to calculate the moment of inertia through a solid area of the pin base portion; 
           [0017]      FIG. 4D  is a diagrammatic view of a section through the pin base portion of the compliant pin of  FIG. 4A , taken along Line D-D thereof, to illustrate the geometry used to calculate the moment of inertia through an area of the pin base portion which contains a pin opening; 
           [0018]      FIG. 5A  is a side elevational view of a shielding cage, removed from a circuit board but which utilizes a second embodiment of a compliant pin constructed in accordance with the principles of the Present Disclosure; 
           [0019]      FIG. 5B  is an enlarged detail view of  FIG. 5A , illustrating a single compliant pin thereof; 
           [0020]      FIG. 6  is a side elevational view of a connector that houses a plurality of terminals with tail portions that incorporate compliant pins of the Present Disclosure; and 
           [0021]      FIG. 7  is an enlarged view of a connector terminal incorporating a compliant pin tail portion constructed in accordance with the principles of the Present Disclosure. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    While the Present Disclosure may be susceptible to embodiment in different forms, there is shown in the Figures, and will be described herein in detail, specific embodiments, with the understanding that the Present Disclosure is to be considered an exemplification of the principles of the Present Disclosure, and is not intended to limit the Present Disclosure to that as illustrated. 
         [0023]    As such, references to a feature or aspect are intended to describe a feature or aspect of an example of the Present Disclosure, not to imply that every embodiment thereof must have the described feature or aspect. Furthermore, it should be noted that the description illustrates a number of features. While certain features have been combined together to illustrate potential system designs, those features may also be used in other combinations not expressly disclosed. Thus, the depicted combinations are not intended to be limiting, unless otherwise noted. 
         [0024]    In the embodiments illustrated in the Figures, representations of directions such as up, down, left, right, front and rear, used for explaining the structure and movement of the various elements of the Present Disclosure, are not absolute, but relative. These representations are appropriate when the elements are in the position shown in the Figures. If the description of the position of the elements changes, however, these representations are to be changed accordingly. 
         [0025]      FIGS. 1-5B  illustrate shielding cages  20  that incorporate compliant mounting pins constructed in accordance with the principles of the Present Disclosure. As can be seen in the Figures, the cage  20  is mounted to a circuit board  21  and has a hollow opening  23  that permits it enclose a connector  22 , typically a receptacle connector, that has a slot disposed therein for receiving a mating blade of a plug connector (not shown) that is inserted into the interior of the cage  20 . The cage is formed from a conductive material, typically metal, and may be mounted to the circuit board by way of a plurality of mounting members  24 , shown formed integral with the sidewalls  25  of the cage  20 . These mounting members  24  take the form of vertically extending pins and they are known in the art as “compliant” pins  26 , which are inserted into a corresponding through hole, or via  27 , formed in the circuit board. The compliant pins  26  have openings formed therein and the width of these pins in their associated body portions  36  is slightly bigger than the width of the vias  27 . This is so that the pins  26  deform upon insertion into the circuit board vias  27  so as to make reliable contact with the inner surfaces  28  vias  27 . The inner surfaces  28  of the vias  27  are plated with a conductive material to establish an electrical connection between the compliant pins  26  and the vias  27  and consequently to various circuits on the circuit board  21  that make contact with the interior plating of the vias  27 . 
         [0026]    The compliant pins  26  are arranged in a pattern around the outer edges  29  of the bottom of the shielding cage  20 . Some of these pins  26  may be formed with the sidewalls  25  of the cage  20  while others may be formed as part of the endwall  30  of the shielding cage  20 . The pattern of the compliant pins preferably is staggered as between the two rows of pins  26  depending down from the two opposing sidewalls  25  of the cage  20 , as shown in  FIG. 3 . As shown best in  FIGS. 3-4A , the pins  26  are preferably formed as part of the side and end walls  25 ,  30  of the cage  20  and have three distinct portions. 
         [0027]    These distinct pin portions include a pin tip portion  32 , which extends from the bottom end  33  of the compliant pin  26  to approximately the bottom edge  34  of a pin opening  35 . A pin body portion  36  is disposed adjacent the pin tip portion  32 , and it extends lengthwise along the pin  26  between the pin tip portion  32  and the pin base portion  37 . As such, the pin body portion  36  extends along the outer edges  38  of the pin opening  35  and may be considered as at least partially enclosing the pin opening  35 . The pin body portion  36  has a width greater than the widths of either the pin tip portion  32  or the pin base portion  37 . This width varies along the length of the compliant pin  26 . 
         [0028]    Lastly, the pins  26  may also include a pin base portion  37  that extends down from the cage walls and joins the pin body portion  36  to the shielding cage walls (or in the case of a connector terminal, the terminal body portion). The pin base portion  37  extends to approximately the top edge  39  of the pin opening  35 . The compliant pin base portion  37  may be partially separated from the cage walls  25 ,  30 , illustrated by a pair of first slots  42 , shown as reentrant notches  43  that extend upwardly with respect to the compliant pins  26 . In the embodiment shown, these first slots  42  separate the pin base portions  37  from portions  45  of the sidewalls  25 , shown as stubs or the like, and which may serve as “standoffs”  46  that make direct contact with the top surface  22  of the circuit board  21 . These standoffs  46  serve as a point of direct contact “CI” with the circuit board  21  proximate to the compliant pin  26 , and accordingly, each has a hard, substantially flat, or linear edge  47 . This is in contrast to the approximate rounded edge  48  running the length of the sidewalls  25 , obtained from the ordinary forming of the cage  20 . A pair of second slots  49 , also extending upwardly into the cage walls are shown as flanking the standoffs  46  and permit them to be formed so that they occupy a preferred perpendicular orientation to the circuit board top surface  22 . 
         [0029]    In an important aspect of the Present Disclosure, the pin opening  35  is disposed at a certain location within the pin body portion  36 ; specifically, at a level beneath the connector-cage interface (best shown by “CI” in  FIG. 4A ), in contrast to conventional compliant pin openings, where the pin opening  35  intersects with interface CI and extends upward above the top surface  22  of the circuit board  21 . In the embodiment illustrated in  FIGS. 4A-B , the pin opening  35  may have a conventional configuration such as the elongated oval or ellipse illustrated. By relocating the pin opening  35  to a location where it does not intersect the interface CI and where the pin opening  35  is disposed entirely beneath the top surface  22  of the circuit board  21 , material is retained in the pin base portion  37  that ordinarily would be removed if the pin opening  35  were to intersect and extend past the interface line CI. This material makes the pin base portion  37  stronger and less susceptible to bending, and/or buckling upon insertion. 
         [0030]    The extra material in the pin base portion  37  increases the moment of inertia of the section taken through the pin base portion  37  and the section is a complete rectangle, having a width W and a thickness T as shown in  FIG. 4C . Hence, the moment of inertia for such a section is 3 WT/12. The moment of inertia of this section is greater than the corresponding moment of inertia of the pin base portion of a conventional compliant pin where the pin opening extends into the pin base portion and which intersects the interface CI and extends above the level of the top surface  22  of the circuit board  21 . Such a portion has a thickness T and two widths W 1  and W 2  as illustrated in  FIG. 4D . The moment of inertia about a bending axis for this section is equal to the sum of the two solid sections, or 3 W 1 T/12+3 W 2 T/12. In determining the bending stress of a member, the moment of inertia is used as a denominator in the bending stress formula; namely, F=M c /I, and hence the larger the denominator (moment of inertia) becomes, the lower the bending stress. Thus, the increased resistance results from the material that replaces the pin opening along the interface CI and any other horizontal section in the pin base portion above the level on the top surface of the circuit board. This permits the overall width of the pin body portion to be increased with a larger degree of deformation during insertion, thereby improving insertion performance with less pin buckling. 
         [0031]    Another embodiment of a compliant pin  26 ′ constructed in accordance with the Present Disclosure is illustrated in  FIGS. 5A-B , and in this embodiment, not only the pin opening  50  is located below the level of the top surface  22  of the circuit board  21 , but also the pin opening  50  has a particular configuration. As illustrated, the pin opening configuration is of a teardrop shape and generally approximates that of an imaginary triangle in that the pin opening  50  has a narrow portion  51  at its top edge  52  thereof and a wide portion  53  near its bottom edge  54  thereof. The triangular shape of the opening  50  generally approximates that of an imaginary isosceles triangle illustrated in  FIG. 5B  by the dashed line  57 , because the sides  55 ,  56  thereof are equal to each other in length and they extend outwardly equally around a vertical axis Y-Y ( 58 ). 
         [0032]    The narrow top portion  51  of this pin opening  50  coincides with a top apex  60  of the imaginary triangle, while the widest bottom portions  53  coincide with the bottom apexes  61  of the imaginary triangle. 
         [0033]    As such, the pin opening  50  of this embodiment is symmetrical around a vertical axis Y-Y, but asymmetrical around a horizontal axis X-X. Shapes other than that shown may be used provided that the bottom portion of the opening is wider than the top portion. 
         [0034]      FIG. 6  illustrates a connector  70  with a housing  71  that supports a plurality of conductive terminals  72  therein. The terminals  72  have tail portions  73  that incorporate compliant pins  74  constructed in accordance with the Present Disclosure. As shown in  FIG. 7 , the terminals  72  typically include an elongated body portion  75  that have tail portions  73  at one end thereof and contact portions  76  at the other end thereof. The tail portions  73  include complaint pin portions  78  with pin openings  79 , teardrop or other shape that are located beneath the terminal-circuit board interface CI. 
         [0035]    While a preferred embodiment of the Present Disclosure is shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the foregoing Description and the appended Claims.