Abstract:
Header pins having improved positional stability and increased terminal retention are disclosed. The header pins have retention features spaced longitudinally apart and rotated around an axis. In one embodiment, two pairs of swaged retention features are created, spaced longitudinally apart, and the planes defining the retention features are displaced approximately ninety degrees (90°) apart. The pairs of retention features are disposed relatively near a central section of the header pin and at a distance from one another that is relatively less than the overall length of the header pin. A notch disposed in the body of the header pin is longitudinally spaced from the two pairs of retention features. Methods of making a header pin and improved methods of assembling a header block are also disclosed.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to an electrical connector assembly, and more particularly, the invention relates to header pins used in board-to-board and wire-to-board headers. 
   BACKGROUND OF THE INVENTION 
   Electrical connectors operate to provide an electrical pathway or junction, and in so doing provide a mechanical connection between wires, circuit boards, components or other current carrying devices. Headers are examples of connectors that provide an electrical junction between two circuit bards (“board-to-board”) or between a cable assembly and a circuit board (“wire-to-board”), although, as is typically understood, a “board” may be an electrical component, circuit block or other device, and need not necessarily be a printed circuit board. In a typical header, a number of pins are inserted through a housing so that a portion of the pin remains extended from each side of the housing. The pins are made of an electrically conductive material and the housing is made of a dielectric material. The pins are usually retained within the housing by a press fit or similar mechanical connection, such as tabs or ears that engage the dielectric material of the housing primarily by friction. 
   Currently, the tabs that retain connector pins lack positional support in one plane. In other words, with conventional pin retention features, there is one direction in which there is little support resulting in possible true positional errors. Moreover, in currently available designs the retention forces required in particular applications are often difficult to maintain. 
   There exists, therefore, a need to provide improvements to the design of header pins, however, any improvements in the shortcomings noted above must be made in a manner in which the resulting design is capable of being manufactured in high volumes at high speeds to meet the demands of the electronics industry. For example, pressing and shaping pin stock into tabs using conventional presses has a limited number of directional and dimensional features that can be efficiently produced. 
   Certain prior art pins use a “star” feature and have four interference features arrayed around the body of a header pin. The pin necessarily has a thick cross-section to accommodate the four interference features. However, localizing the interference features also localizes the stresses in the assembly and thus increases the chances of localized cracking, particularly in the type of brass typically used for connector pins, which is relatively hard and non-malleable. Furthermore, the “star” feature design suffers in positional stability from not having its ears/tabs displaced from one another longitudinally. 
   Therefore, it would be desirable to provide connector pins that improve the retention and positional accuracy of the header, while reducing or eliminating stress concentrations. It would be further desirable to provide a design for such header pins that can be manufactured using conventional production equipment so that large quantities of such pins can be produced economically. 
   SUMMARY OF THE INVENTION 
   It has now been found that improved positional stability of header pins and increased terminal retention can be achieved while providing a design that is easy to manufacture by creating header pins that have retention features spaced longitudinally apart and rotated around the axis of the header pin. In accordance with an embodiment of the invention, a header pin is provided that has a first pair of pin retention features formed at a first location and defining a first plane, and a second pair of retention features formed at a second location spaced longitudinally along the body from the first location and defining a second plane displaced rotationally from the first plane. In one embodiment, the planes in which the sets of retention features are defined are displaced approximately ninety degrees (90°) from one another. 
   The body can have a circular cross-section and one of the ends can have a layer of solder. In some embodiments, the first and second locations are disposed relatively near a central section of the header pin are also preferably a distance from one another that is relatively less than the overall length of the header pin. Either one or both sets of retention features may be a swaged section forming laterally extending features, and these laterally extending features can be trapezoidal in cross-section and each one of them extends beyond the body of the header pin. In some embodiments, there is a notch disposed in the body of the header pin that is particularly useful if a plurality of the pins is placed in a bandolier. 
   The embodiments disclosed herein further include methods of making a header pin by providing a header pin having a body, swaging a first set of retention features at a first location along the body, and then swaging a second set of retention features at a second location along the body, such that the second location is displaced longitudinally from the first location. The swaging preferably forms a pair of laterally extending features to define a first plane and the step of swaging the second set of retention features comprises forming a pair of laterally extending features to define a second plane, and in certain embodiments, these are displaced approximately ninety degrees (90°) from one another. After each pin is manufactured, it can then be pressed into a bandolier, and preferably a notch has been formed in the pin for this purpose. 
   In another aspect of the invention improved methods of assembling a header are provided. In accordance with an embodiment of the invention, a plurality of pins are inserted into a header block, with the inserting step comprising inserting the header pin a sufficient depth so that a first retention feature and a second retention feature are displaced longitudinally and are frictionally engaged with the header block. Preferably, the engagement of the header pin and the header block comprises engaging the first retention feature along a first plane and the second retention feature along a second plane, wherein the first and the second planes are rotationally spaced around an axis. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of a header pin in accordance with an embodiment of the present invention; 
       FIG. 2  is a cross-sectional view of the header pin of  FIG. 1  taken along line  2 — 2  shown in  FIG. 1 ; 
       FIG. 3  is a plan view of a plurality of header pins similar to that shown in  FIG. 1 , illustrated with a bandolier; 
       FIG. 4  is an elevational view of the plurality of header pins and bandolier shown in  FIG. 3 ; 
       FIG. 5  is a plan view of a header pin in accordance with another embodiment of the present invention; 
       FIG. 5A  is a cross-sectional view of the header pin of  FIG. 5  taken along line  5 A— 5 A shown in  FIG. 5 ; 
       FIG. 6  is a plan view of a plurality of header pins similar to that shown in  FIG. 5 , illustrated with a bandolier; 
       FIG. 7  is an elevational view of the plurality of header pins and bandolier shown in  FIG. 6 ; and 
       FIGS. 8A-8B  illustrate an exemplary orientation of header pins held on a bandolier and rolled on to a reel during manufacture. 
   

   DETAILED DESCRIPTION 
   Referring now to the drawings in detail, wherein like reference numerals indicate like elements throughout the several views, there is illustrated in  FIG. 1   a  header pin in accordance with an embodiment of the present invention. The header pin  100  as shown comprises a body  101  and two ends  102 , 104 . In this embodiment, one of the two ends  102 ,  104  may be provided having a layer of solder, but is not required. The header pin  100  also includes one or more and preferably a pair of pin retention features  106  formed at a first location along the body  101 , and one or more and preferably a pair of retention features  108  formed at a second location spaced longitudinally along the body  101  from the first pair of retention features  106 . The first pair of retention features  106  are preferably disposed in a plane displaced rotationally from the plane of the second pair of retention features  108 . In certain embodiments, it may be desirable to form a notch  110  in the body  101 , such as shown in FIG.  1 . Generally, the first and second sets of retention features or “fins”  106 , 108  are located proximate the central area of the body  101 . In the embodiment illustrated in  FIG. 1 , since retention features  106 ,  108  are not located directly at the center of the body  101 , upon assembly into a header block (not shown), one end will extend a longer length than the other end. For example, assuming an overall length of the header pin  100  being 23.5 millimeters, the first set of retention features  106  may be displaced about 7.5-8.0 millimeters from the first end  102 , and the second set of retention features may be spaced about 10.0-10.5 millimeters from the first end  102 . It should be understood, therefore, that the first and second sets of retention features  106 , 108  are relatively close together in the present embodiment. In the example illustrated in  FIG. 1 , the first and second sets of retention features  106 , 108  are spaced about 2.5-3.0 millimeters apart. These spacings and arrangements are representative and the present embodiment is not limited to these dimensions or relative spacing. 
   Referring now to  FIG. 2 , there is shown a cross-sectional view of pin  100  taken along line  2 — 2  in FIG.  1 . As shown, the body  101  is substantially circular in cross-section and the first set of retention features  106  comprise a pair of laterally extending features  107 , 117  spaced approximately one-hundred eighty degrees apart, and with each being substantially trapezoidal in cross-section and extending laterally from the body  101 . It should be noted however, that the laterally extending features  107 ,  117  may take on a variety of cross sectional geometrical shapes, such as rectangular. Although not shown in  FIG. 2 , the second set of retention features  108  are also approximately one-hundred eighty degrees apart from one another in this embodiment and of the same configuration as features  107 ,  117 . A comparison of FIG.  1  and  FIG. 2  illustrates that in the present embodiment of the invention, the plane of the first set of retention features  106  and the plane of the second set of retention features  108  are displaced approximately ninety degrees (90°) apart from one another. It should be understood, however, that other configurations and/or rotational displacements of the various retention features can be utilized where desired and still provide the advantages of the header pins disclosed herein. 
   Referring now to  FIGS. 3-4 , a plurality of header pins  100  similar to that illustrated in  FIGS. 1-2  are shown attached to a bandolier  50  The header pins  100  can be pressed or snapped into the bandolier  50 , and in this manner, efficiently inserted into header blocks or similar structures using automated equipment. The notch  110  illustrated in  FIG. 1  may be provided to retain the header pins  101  in the bandolier  50 , as shown in  FIGS. 3-4 . 
   Another exemplary embodiment of a header pin is illustrated in  FIGS. 5-7 . In the embodiment illustrated in  FIG. 5 , the header pin  200  is somewhat longer and of a smaller cross section than the header pin  100  illustrated in FIG.  1 . As with the header pin  100 , header pin  200  includes retention features  206 ,  208  provided in two locations spaced longitudinally apart and also spaced rotationally in different planes, as shown in the cross-sectional view of FIG.  5 A. 
   In the present embodiment, the retention features  206 ,  208  are spaced from one another about 1.2 mm in a longitudinal direction and rotated to be at substantially right angles (i.e., 90 degrees apart). The cross-section of each of the fins  206 , 208  is relatively small in this embodiment (i.e., 0.23 mm+/−0.05 mm) and when combined with other dimensional features of the header pin  200 , provides suitable insertion and extraction values without unduly distorting or deforming the plastic material of the header block. In the present embodiment, for example, with four points of about 0.23 mm of cross-sectional interference, only about 0.17 mm per side or a total of about 0.342+/−0.05 mm of interference on the diameter is required. As illustrated in  FIGS. 6 and 7 , the embodiment shown in  FIG. 5  may also be manufactured into a bandolier  50  and include a notch  210  to assist in retaining the header pin  200  in the bandolier  50 , similar to the embodiment of FIG.  1 . 
   Those of skill in the art will appreciate that the embodiments disclosed herein provide a header pin having improved positional support on each of the four sides, i.e., in orthogonal directions. In addition, a plurality of retention features provides improved retention force, yet permits the pin to be easily inserted and removed, without causing excessive stress, either in the metal of the pin or the plastic of the connector. Finally, the longitudinal offset of the retention features in the illustrated embodiments allows the tooling to better form the necessary shape(s) without cracking material or deforming adjacent features. 
   Another aspect of the embodiments disclosed herein is to provide methods of manufacturing header pins. One exemplary method comprises the steps of forming a first set of retention features at a first location along the body of the header pin and then forming a second set of retention features at a second location along the body, the second location being displaced longitudinally from the first location. The steps of forming of the retention features may be accomplished in a variety of different ways. One example is swaging, although as should be understood, other suitable operations can be used, such as stamping, coining, forging and the like. Further, where desired, casting may also be utilized to create the features disclosed above or thermoforming using molds or dies. Regardless of the technique used, the step of swaging or forming the retention features involves forming two sets of retention features in two different planes, and as discussed above, in certain embodiments, it will be preferred that the first plane and the second plane are displaced from one another, such as approximately ninety degrees (90°). 
   An additional aspect of the manufacturing process is illustrated in  FIGS. 8A-8B . As discussed above, after the header pins are formed, they can be pressed into a bandolier  50 . It may be desirable in some instances for the header pins to include a notch formed in the body, so as to provide a more secure engagement with the bandolier  50 . For this purpose, the step of pressing the header pin  100 , 200  into the bandolier  50  will include the step of the bandolier  50  engaging the notch  110 , 210 . The bandolier may then be wrapped on a reel  52 , such as illustrated in  FIGS. 8A-8B . 
   Finally, the embodiments disclosed herein also include methods of assembling a header by inserting a plurality of pins into a header block. For example, with respect to the header pins in the illustrated embodiments, the step of inserting the header pins into the header block will include pushing the header pin to a sufficient depth so that the first retention feature and the second retention are frictionally engaged with the header block. As discussed above, the frictional engagement of the header block with the header pin results with a first retention feature along a first plane and a second retention feature along a second plane all being engaged with the header block, and with the first and the second planes being rotationally spaced around an axis. 
   As noted above, the retention features improve the positional stability of the pin, increase the terminal retention and result with the pins being easier to manufacture. The placement of retention features spaced longitudinally apart and rotated around the axis of the header pin provides these improvements yet results in a design that is readily manufactured. 
   Although this invention has been described with reference to particular embodiments, it will be appreciated that many variations adaptations, modifications, and alterations may be resorted to without departing from the spirit and scope of this invention as set forth in the appended claims.