Abstract:
A socket may be formed with socket pins that include two spring biased arms biased to extend away from one another. The arms may be provided with tapered upper surfaces that engage contact holes on a pin guide  18  of an integrated circuit package, camming the socket pin arms together. The pin guide may have a tapered via structure that expands as it extends into the package. Thus, as the spring arms spread apart inside the pin guide, they may rotate through an angle which causes contacting surfaces on the spring arms and the pin guide to be parallel, creating good surface contact.

Description:
BACKGROUND 
   This invention relates generally to connecting electrical integrated circuits to printed circuit boards and other devices. 
   Generally, a socket is used to electrically couple a package containing a semiconductor integrated circuit to a printed circuit board. The socket may be a number of types, including a pin grid array or land grid array architecture. In a pin grid array architecture, pins are mounted on the package land pads. This method may tend to be more expensive and may require maintaining the pins in an unbent configuration. Because a large number of pins are provided and their structural integrity is limited, it may be difficult to avoid damaging the pins. 
   The land grid array packing approach may involve significant pressure to maintain low contact resistance. This may require a relatively robust and mechanically stiff construction for the socket housing and for the board to which the socket connects. The land grid array may use bent pins that touch land pads located on the package. 
   Thus, there is a need for other types of packages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an enlarged, partial, cross-sectional view of one embodiment of the present invention; 
       FIG. 2  is an enlarged, cross-sectional view of one embodiment of the present invention; 
       FIG. 3  is an enlarged, cross-sectional view of another embodiment of the present invention; 
       FIG. 4  is an enlarged, cross-sectional view of another embodiment of the present invention; 
       FIG. 5  is an enlarged, cross-sectional view of another embodiment of the present invention; and 
       FIG. 6  is an enlarged, cross-sectional view of another embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , a socket pin  10  may protrude from a socket (not shown). The socket pin  10  may engage a package  34 . The package  34  may include a U-shaped pin guide  18 . While one pin guide  18  and one socket pin  10  is shown, conventionally there would be a very large number of socket pins  10  on the socket and a very large number of mating pin guides  18  on the package  34 . 
   A pair of opposed surfaces  24  define a slightly narrowed opening  25  to receive the socket pin  10 . The pair of opposed sidewalls  22  extend inwardly into the package  34  from the surfaces  24 . The sidewalls  22  diverge as they extend inwardly so that the inward surface  23  may be wider than the opening  25  defined by the surfaces  24 . 
   The socket pin  10  may be made up of two or more arms  15  which are separated by a slot  12 , which extends inwardly into the pin  10 . Conventionally, the pin  10  may be made of resilient material so that the arms  15  tend to resiliently spread apart and away from one another. 
   Each arm  15  includes a tapered leading edge surface  16 . The surface  16  allows the arm  15  to be wedged towards its opposed arm  15  by the interaction with the surface  24 . Each arm  15  also includes a contact surface  14  which contacts a sidewall  22  of the pin guide  18 . 
   Thus, when the socket pin  10  engages the opening  25 , the surface  24  cams the surface  16  to move the arms  15  together and allow the socket pin  10  to enter the pin guide  18 . As it enters the diverging via contact  28 , the arms  15  are allowed to spring outwardly, maintaining good contact between the sidewalls  22  and the surfaces  14  on the socket pin  10 . Moreover, a parallel contact surface is achieved because of the angulation of the spreading arms  15  and the pre-angulation of the via contact  28  sidewalls  22 . 
   In some embodiments, a slide plate (not shown) can be used to hold the arms  15  in an abutting position for insertion. The closing force supplied by the slide plate may then be removed once the pins  10  are inserted into the pin guides  18 , by an appropriate displacement of the slide plate. 
   In some embodiments, the socket pin  10  may have a higher contact pressure and, therefore, contact resistance may be lower. Also, the loop inductance for the pin may be lower in some embodiments, compared to land grid arrays and pin grid array designs. The improvement may be due to the shape of the pin  10  in some embodiments. The total pin length for land grid array pins may be larger than that of the pin  10  in some embodiments. Compared to the pin grid array design, the electrical current path through the pin  10  may be shorter in some embodiments and, therefore, the performance may be better. In some embodiments, the pin  10  has a smaller landing via pad and, therefore, the negative discontinuity effect is lower in higher frequency applications. 
   Referring to  FIG. 2 , a bi-directional solution is illustrated. In this case, a printed circuit board  42  includes vias  44  that receive the socket pins  10 . The vias  44  may correspond to pin guides  18  in one embodiment. The socket pins  10  may protrude from two opposed surfaces of a socket  40  in this embodiment. Thus, the socket pins  10 , on the upper surface of the socket  40 , engage vias  36  in the package  34 . The vias  36  may correspond to pin guides  18  in one embodiment. 
   The package  34  may carry a die  30  in one of a variety of configurations. In the embodiment illustrated in  FIG. 2 , which is not intended to limit the scope of the invention, the die  30  may be attached in a surface mount configuration using solder balls  32 . 
   Thus, in the embodiment shown in  FIG. 2 , the pins  10  may have pairs of arms  15  on two opposed sides to engage the package  34  above and the board  42  below. The package  34  and board  42  may each include pin guides  18  to receive the arm  15  pairs (not shown in  FIG. 2 ). 
   Moving to  FIG. 3 , in this case a mixed solution is illustrated using the via grid array connection shown in  FIG. 1  for the electrical connection between the package  34  and the socket  40  and using a land grid array type connection as well. Thus, the pins  54  may correspond to the pins  10  and include arms  15  (not shown in  FIG. 3 ) only on the upper side to engage vias  52  in the package  34 . The vias  52  may correspond to the pin guides  18  in one embodiment. The opposed surfaces of the pins  54  may be connected by solder balls  50  to the printed circuit board  42 . Additional pins  48  may be of the land grid array package type, contacting lands  46  on the package  34  in one embodiment. 
   Referring next to  FIG. 4 , pins  54  may correspond to socket pins  10  with arms  15  only on one end to engage vias  36  in the package  34 . The vias  36  may correspond to pin guides  18  in one embodiment. On the opposite end of the pins  54 , a solder ball connection  50  may be made to the printed circuit board  42 . In this embodiment, the land grid array pins  48  may not be used. 
   In another embodiment of the present invention, shown in  FIG. 5 , an array capacitor  60  may be mounted on the package  34 . In this case, the single ended pins  54  may plug into vias  62  in the array capacitor  60 . The vias  62  may correspond in all respects to the pin guide  18  in one embodiment of the present invention. The upper ends of the pins  54  may correspond, in one embodiment, to that shown in  FIG. 1  in one embodiment of the present invention. In this embodiment, the connections between the rest of the package  34  and the socket  64  may be implemented using land grid array pins  66  and lands  68  on the package  34 . The package shown in  FIG. 5  may be particularly applicable to high power devices. 
   In another embodiment, the connections to the package  34  may use a pin grid array approach. In other embodiments, all of the connections may utilize the connection type shown in  FIG. 1 . 
     FIG. 6  shows an embodiment corresponding to  FIG. 2 , except that the pins  10  extend completely through the socket  40  and the printed circuit board  42 , forming a so-called through-hole board interface solution. The through-hole  78  is formed completed through the printed circuit board  42 . The via  52  in the package  34  may correspond to the pin guide  18  in one embodiment. The pins  54  may have an upper end which corresponds to the socket pin  10  shown in  FIG. 1 . The pins  54  may be fixed to the printed circuit board  42  using standard solder reflow processes in one embodiment of the present invention. 
   In some embodiments, the engagement between the socket end  10  and the pin guide  18  may be self-aligned and the pin is self-guided. The contacting pressure for holding the pins of the socket structure in a package or board is relatively high and the contacted surfaces may be parallel in some embodiments. The via structures may, therefore, be arranged to distribute contact pressure in one embodiment. A relatively small via pad may be utilized in some embodiments to reduce high frequency discontinuity effects. A larger contacting surface may be provided in some embodiments, increasing contacting pressure compared to pin grid array and land grid array packages. Therefore, in some embodiments, significant socket electrical performance improvement may be achieved. 
   While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.