Abstract:
One aspect of this disclosure provides an electrical connector pin for a printed wiring board. This embodiment includes an unmachined, collar having an acircular configuration and including a side wall. This embodiment further includes a machined first cylindrical connector shaft integrally formed with the collar and extending from collar along the longitudinal axis, and a machined second cylindrical connector shaft integrally formed with the collar and extending from the collar and along the longitudinal axis in a direction opposite to that of the first cylindrical connector shaft.

Description:
TECHNICAL FIELD 
       [0001]    This application is directed, in general, to a connector pin for a printed wiring board and, more specifically, to a printed wiring board connector pin that has an acircular profile. 
       BACKGROUND 
       [0002]    Many current electronic product assemblies are manufactured from components or sub-assemblies provided to a manufacturer by a vendor/subcontractor. A common method of assembly of such products is to connect leads/terminals of the components or subsystem printed wiring assemblies (PWAs) onto the main system PWB by mass soldering. The two most common continuous mass soldering processes are wave soldering and reflow soldering. Wave soldering is commonly used when a high mix of through-hole components are involved in the product assemblies. Often, in such applications, the sub-assembly is connected to the main system PWB by one or more connector pins that are lathed from a cylindrical, material stock of conductive material, such as copper or aluminum. A segment of the connector pin is lathed from the cylindrical stock material to include a set-off or spacing segment. The spacer segment is lathed to have a diameter larger than the connecting via that goes through the PWB. 
         [0003]    The spacer segment is typically seated against the surface of the main system and covers the connecting via. Due to this configuration, it is often difficult to get a lead-free solder to flow into the space between the wall of the via and the connector pin. This can result in a poor or inoperative connection. This flow problem has arisen recently due to the shift in the industry from lead based solders, which have a greater affinity of wetting the PWB than lead-free solders. 
       SUMMARY 
       [0004]    One aspect of this disclosure provides an electrical connector pin for a printed wiring board. This embodiment includes an unmachined, collar having an acircular configuration and including a side wall and first and second opposing planar faces perpendicular to a longitudinal axis of the collar. This embodiment further includes a machined first cylindrical connector shaft integrally formed with the collar and extending from the collar along the longitudinal axis, and a machined second cylindrical connector shaft integrally formed with the collar and extending from the collar and along the longitudinal axis in a direction opposite to that of the first cylindrical connector shaft. 
         [0005]    Another aspect provides an electrical printed wiring board assembly. This embodiment comprises a first printed wiring board (PWB) having a via located therethrough and an electrical connector pin extending through the PWB. In one embodiment, the electrical connector pin comprises a collar having a sidewall that defines a perimeter of the collar. The sidewall has a bar stock profile that has a cross-section dimension perpendicular to a longitudinal axis of the bar stock that is less than a diameter of the via that forms a vent space between the via and a portion of the cross-section dimension. The connector pin further includes a machined first cylindrical connector shaft extending from the collar along the longitudinal axis. At least a portion of the connector shaft is received within the via and electrically connected to the PWB by a conductive material located within the via. The pin further includes a machined second cylindrical connector shaft extending from the collar along the longitudinal axis in a direction opposite to that of the first cylindrical connector shaft. 
         [0006]    Another embodiment provides a method of fabricating an electrical assembly. This embodiment comprises providing a bar stock of a conductive material, wherein the bar stock has an acircular profile. Portions of the bar stock are removed to leave a collar having a sidewall that defines a perimeter of the collar and an acircular profile. The removal step forms a machined first cylindrical connector shaft integrally formed with the collar and extending from the collar along the longitudinal axis and a machined second cylindrical connector shaft integrally formed with the collar and extending from the collar along the longitudinal axis in a direction opposite to the first cylindrical connector shaft. The method further includes placing the first cylindrical connector shaft into a via of a first printed wiring board (PWB), such that at least a portion of the first cylindrical connector shaft is located within the via and electrically coupling the first cylindrical connector shaft to the PWB. 
     
    
     
       BRIEF DESCRIPTION 
         [0007]    Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  illustrates a sub-assembly and an embodiment of a connector pin as provided herein; 
           [0009]      FIG. 2A  illustrates the sub-assembly and connector pin of  FIG. 1  connected to a main printed wiring board to form an electrical printed wiring board assembly; 
           [0010]      FIG. 2B  illustrates an overhead view of the assembly of  FIG. 2A . 
           [0011]      FIG. 3  illustrates different embodiments of collar pin having acircular profiles; 
           [0012]      FIG. 4  illustrates a perspective view of a bar stock having one acircular configuration; 
           [0013]      FIGS. 5A-5B  illustrate perspective views of the formation of a connector pin from a bar stock; and 
           [0014]      FIGS. 6-9  illustrate embodiments of different pin configurations having collars with acircular profiles. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  illustrates one embodiment of a printed wiring board (PWB) sub-assembly  100 . In this embodiment, the assembly  100  includes a PWB  105  and a connector pin  110 . The PWB  105  may be of conventional design and has at least one via  115  located in the PWB  105 . The electrical applications that can benefit from the embodiments of this disclosure may vary greatly, and though the discussions herein are directed to a sub-assembly PWB for a power supply, many other electrical applications are also within the scope of this disclosure. The connector pin  110  includes a collar  120  and first and second cylindrical connector shafts  125  and  130  that are coupled to the collar  120 . As seen in this embodiment, at least a portion of the first cylindrical connector shaft  125  is received within the via  115  and is coupled to the PWB  105  within the via  115  by a solder joint  135 . 
         [0016]    As discussed below, the collar  120  has an acircular cross-sectional profile such that a portion of the perimeter of the collar  120  is less than a diameter of a via in which the connector pin  110  is inserted. The acircular profile provides a vent through which air may escape, which allows solder to more readily flow between the connector pin and the via. Since the acircular profile can be achieved without the need of machining, the cost and time of manufacture is advantageously reduced. 
         [0017]    The acircular profile is original to the material stock or bar stock that is provided (e.g. either obtained from an internal supplier or from an outside supplier) and from which the connector pin  110  is made. As such, the collar  120  is not machined, or “unmachined,” during the formation of the connector pin  110 . That is, the original or bar stock material that makes up the collar  120  is not cut or substantially removed such that the original surface profile of the collar  120  is left substantially unchanged or unaltered. For example, drilling a hole in the collar  120  or merely marring the surface does not substantially change the original surface profile. Moreover, the collar is considered not to be machined in those instances where the collar is merely buffed, polished, otherwise smoothed, or is left substantially unchanged. 
         [0018]    This is in contrast to conventional connector pins that are typically formed from a circular stock, which results in a circular collar. In such instances, the manufacturers must perform additional machining steps by removing a portion of or beveling an edge of the collar such that a vent is formed between the via of the PWB and the collar. These additional manufacturing steps add cost and time to the manufacturing, which are undesirable. 
         [0019]      FIG. 2A  illustrates another embodiment wherein the PWB sub-assembly  100  is coupled to a main PWB assembly  200  by the connector pin  110  to form a PWB assembly  202 . In this embodiment, the PWB sub-assembly  100  may include a conventional power supply  210  that is electrically connected to the connector pin  110  by one or more conductive traces  215  located within the PWB  105 . The main PWB assembly  200  includes a conventional PWB  220 , which may be designed to include many other conventional electrical components, which are generally designated by the box  225 . As seen in  FIG. 2A , the second cylindrical connector shaft  130  is at least partially received in a via  230  located within the PWB  220  and is coupled to the PWB  220  within the via  230  by a joint  235 . In a preferred embodiment, the joint  235  is formed with a lead-free solder. However, in other embodiments other conventional solders, such as lead based solder, may be used. The second cylindrical connector shaft  130  is electrically connected to the electrical component  225  by one or more conductive traces  240 . 
         [0020]    As seen in this embodiment, the collar  120  includes a sidewall  245  and first and second faces  250 ,  255 , in which the second face  255  contacts the surface of the PWB  220 . For purposes discussed herein, the second face  255  is considered to contact the surface of the PWB  220  even though it does not contact the surface of the PWB  220  directly, for example, a thin layer of solder (not shown) may be located between these two structures. 
         [0021]      FIG. 2B  illustrates an overhead view of the PWB assembly  202 . In this embodiment, the collar  120  has an acircular profile such that portions of the perimeter of the sidewall  245  of the collar  120  do not cover the via  230 . As such, one or more vents or spaces  260  are formed between the portion of the sidewall  245  of the collar  120  and the via  230 , which allow for air to escape during the soldering process. In this particular embodiment, the acircular profile is the notches  265  formed in the sidewall  245  such that a portion of the perimeter of the collar  120  does not extend over the via  230 . Other embodiments of the acircular profile are discussed below regarding  FIG. 3 . 
         [0022]    The presence of the vents or spaces  260  are important because industry standards prefer to not use lead based solder for environmental concerns and have turned to the use of lead-free solders that have a high percentage of tin. Lead based solders had the capacity to wet the inside of the via more readily than lead-free solders. Thus, when lead based solders were used, the solder was still able to move up into the space between the via and the connector pin. However, since lead-free solders do no wet as easily, the vent is necessary to allow the air to escape and thereby allow the lead-free solder to move into the space between the via and connector pin more readily. 
         [0023]      FIG. 3  illustrates overhead views of cross-sections of various acircular configurations of the collar  120  of the connector pin  110 . These cross-section are taken though a plane perpendicular to a longitudinal axis of the collar  120 . For example, in embodiment  305 , the collar  120  may have a notched configuration that presents a clover leaf-type cross section. The via  230  in the assembly PWB  200  is shown in a dashed line. As seen in this embodiment, portions of the perimeter of the sidewall of the collar  120  do not over lap the via  230 . Thus, the vents  260 , as discussed above, are formed. 
         [0024]    In embodiment  310 , the collar  120  may have a square-shaped cross-section or configuration. The via  230  in the assembly PWB  200  is shown in a dashed line. As seen in this embodiment, portions of the perimeter of the sidewall of the collar  120  do not over lap the via  230 . Thus, the vents  260 , as discussed above are formed. 
         [0025]    In embodiment  315 , the collar  120  may have a triangular-shaped cross-section or configuration. It should be noted that the acircular configurations disclosed herein may also include those embodiments where the sidewalls of the collar  120  may be curved. For example, embodiment  315  may also include a Reuleaux triangle shaped cross-section. The via  230  in the assembly PWB  200  is shown in a dashed line. As seen in this embodiment, portions of the perimeter of the sidewall of the collar  120  do not over lap the via  230 . Thus, the vents  260 , as discussed above are formed. 
         [0026]    In embodiment  320 , the collar  120  may have a cross-shaped cross-section or configuration. The via  230  in the assembly PWB  200  is shown in a dashed line. As seen in this embodiment, portions of the perimeter of the sidewall of the collar  120  do not over lap the via  230 . Thus, the vents  260 , as discussed above are formed. The foregoing examples illustrate different polygon shapes that may be used to construct the connector pin  110 . 
         [0027]    In another embodiment  325 , the collar  120  may have an elliptical or oval-shape cross-section or configuration. The via  230  in the assembly PWB  200  is shown in a dashed line. As seen in this embodiment, portion of the perimeter of the sidewall of the collar do not overlap the via  230 . Thus, the vents  260 , as discussed above are formed. 
         [0028]    As mentioned above, it is important to note that, unlike conventional pins, no additional machining is required to form the collars of these various embodiments, since the virgin or original profile of the bar stock material can be used to form the vent. Further, it should be understood that the foregoing are given as examples only and that many other acircular shapes are within the scope of this disclosure. 
         [0029]      FIG. 4  is a perspective view of a bar or rod (referred to herein as bar stock  405 ) material that has an acircular cross-section or surface profile, as discussed above regarding embodiment  305  of  FIG. 3 , and also has a longitudinal axis  410 . The bar stock  405  may be obtained from a supplier of such materials, either internally or externally to the manufacturer. As mentioned above, this surface profile presents a cross-sectional profile such that vents can be formed with a PWB. The material is comprised of a conductive material, such as metal, examples of which may include cooper, aluminum, or other materials from which electrical connector pins can be made. 
         [0030]      FIGS. 5A-5B  shows two perspective views of the embodiment  305  bar stock  405 .  FIG. 5A  shows the bar stock  405  after a portion of the bar stock  405  has been machined or removed to form a first cylindrical shaft  505  of the connector pin. The machine or lathe used to remove the portion of the bar stock  405  is set to achieve the overall desired pin length and collar dimensions. The various dimensions of the pin are laid out and machining continues on the bar stock  405  to arrive at the connector pin configuration  510  shown in  FIG. 5B . In this embodiment, the connector pin  510  includes a machined first cylindrical connector shaft  515  and a machined second cylindrical connector shaft  520 , which are coupled to a collar  525 . In one advantageous embodiment, the first and second cylindrical connector shafts  515 ,  520  are integrally formed with the collar  525 . In other embodiments, the first and second connector shafts  515 ,  520  may be coupled to the collar  525 , for example by cooperating threads or may be solder or welded together. The collar  525  is not machined, and thus, retains its original acircular surface profile. In an advantageous embodiment, the entire sidewall  527  of the collar  525  has the original acircular profile. The collar  525  has opposing first and second surfaces  530 ,  535  from which the first and second cylindrical connector shafts  515 ,  520  respectively extend along the longitudinal axis  410  in opposing directions. The connector pin  510  may be employed in the way described above to achieve the stated advantages. As seen, the cylindrical shafts  515 ,  520  may either be tapered or non-tapered. 
         [0031]      FIGS. 6-9 , which relate to embodiments illustrated in  FIG. 3 , show perspective views of various connector pin configurations that have collars with different types of acircular cross-sections. As discussed above regarding  FIG. 3 , all of these embodiments provide a connector pin that have a collar with an a circular cross-sectional profile, wherein at least a portion of a perimeter of the profile is less than a diameter of a via located in a PWB. As such, vents are inherently formed. 
         [0032]    It has been found that significant manufacturing costs and time can be saved in manufacturing the connector pins covered by this disclosure. For example, it has been unexpectedly found that the effort to produce the pin is reduced by about 20% when using the principles discussed herein. The savings achieved by this 20% reduction are substantial and particularly advantageous when large numbers of pins must be produced. Moreover, choosing an acircular profile is counter-intuitive to standard manufacturing procedures because it is typically desirable to begin with a circular bar stock since the connector pin is to have circular connector shafts. Thus, those who are skilled in the art would not seek to use a bar stock with an acircular configuration absent the teachings of this disclosure. 
         [0033]    Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.