Abstract:
An electronic assembly is provided, having a plurality of spring elements interconnecting corresponding terminals of first and second arrays of terminals on first and second electronic devices. The arrays have rows and columns extending in x- and y-directions, respectively. Each spring element has a cantilever portion extending diagonally in the x- and y-directions between corresponding terminals of the first and second arrays.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1). Field of the Invention  
           [0002]    This invention relates to an electronic assembly of the kind that may have a socket with spring contacts for making contact with terminals on a semiconductor package substrate.  
           [0003]    2). Discussion of Related Art  
           [0004]    Integrated circuits are usually manufactured in and on wafers that are subsequently singulated into individual dies. A die may then be mounted to a package substrate for purposes of providing rigidity to the entire package and for purposes of routing of signals to a side of the package of the substrate opposing the die.  
           [0005]    A socket may be mounted to a circuit board, which may be shaped and dimensioned to receive the semiconductor package. The package substrate and the socket typically have matching substrate and socket contact terminals through which signals can be provided between the package substrate and the socket.  
           [0006]    The socket may have a plurality of socket springs. The substrate contact terminals may come into contact with free ends of the socket springs and then bend cantilever portions of the springs by movement of the substrate contact terminals toward a body of the socket. Forces created by the springs ensure good contact between the free ends of the springs and the socket contact terminals.  
           [0007]    Such cantilever portions are usually aligned with rows or columns of an array of contact terminals to which they are attached. By aligning the cantilever portions in such a manner, the number of contact terminals in a particular row or column is limited by the lengths of the cantilever portions. The cantilever portions of the springs thus limit the number of electric signals that can be routed over a given surface area.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention is described by way of example with reference to the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is a top plan view of portions of an electronic assembly including socket solder balls, socket springs, and substrate contact terminals;  
         [0010]    [0010]FIG. 2 is a side view in a direction  2  in FIG. 1 further illustrating additional components of the electronic assembly;  
         [0011]    [0011]FIG. 3 is a top plan view on  3 - 3  in FIG. 2 illustrating a layout of the socket solder balls on a socket body of the electronic assembly;  
         [0012]    [0012]FIG. 4 is a top plan view of an outline of the entire electronic assembly; and  
         [0013]    [0013]FIG. 5 is a side view of the electronic assembly illustrated in FIG. 4.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    [0014]FIGS. 1 and 2 of the accompanying drawings illustrate components of an electronic assembly  10 , according to an embodiment of the invention, including a printed circuit board  11 , a socket body  12 , printed circuit board contact terminals  14 , socket solder balls  16 , socket springs  18 , a package substrate  20 , and substrate contact terminals  22 .  
         [0015]    Referring specifically to FIG. 2, the socket springs  18  are all held within the socket body  12 . A base portion  24  of each socket spring  18  has a respective socket solder ball  16  secured thereto. Each socket solder ball  16  is attached to a respective one of the printed circuit board contact terminals  14 .  
         [0016]    Each socket spring  18  has a respective spacer portion  26  extending in a z-direction from the base portion  24  thereof, and a respective cantilever portion  28  extending diagonally at an angle relative to the z-direction from an upper end of the respective spacer portion  26  thereof. The spacer portions  26  are held within openings in the socket body  12 , and the cantilever portions  28  are above the socket body  12 . A free end  30  of a respective cantilever portion  28  can be moved in a z-direction against a bending spring force of the cantilever portion  28 .  
         [0017]    The substrate contact terminals  22  are located on a lower surface of the package substrate  20 . Each substrate contact terminal  22  is brought into contact with a respective free end  30  of a respective socket spring  18 . The package substrate  20  is subsequently moved closer to the socket body  12 . Movement of the package substrate  20  toward the socket body  12  bends the cantilever portions  28 , which creates a spring force between a respective free end  30  and a respective substrate contact terminal  22 . The spring force ensures good contact between the respective free end  30  and the respective substrate contact terminal  22 .  
         [0018]    As illustrated in FIG. 1, center points of the socket solder balls  16 , cantilever portions  28 , and center points of the substrate contact terminals  22  are dimensioned, spaced, and oriented in a manner that allows for a denser routing of signals over a given surface while still allowing sufficient flexibility of the cantilever portions  28 .  
         [0019]    Center points of the socket solder balls  16  are in an array having rows extending in an x-direction and columns extending in a y-direction. The columns in which the socket solder balls  16  are located are spaced from one another by a distance of 1.09 mm. The rows in which the socket solder balls  16  are located are spaced from one another by a larger distance of 1.17 mm. The larger pitch in the y-direction is due to design constraints for routing traces on a printed circuit board  11  to which the socket body  12  is mounted.  
         [0020]    Center points of the substrate contact terminals  22  are also in an array of rows extending in an x-direction and columns extending in a y-direction. The columns in which the substrate contact terminals  22  are located are spaced from one another by a distance of 1.09 mm. The rows in which the substrate contact terminals  22  are located are spaced from one another by a distance of 1.17 mm. The spacing of the rows and columns of center points of the substrate contact terminals  22  is thus exactly the same as the spacing between the rows and columns of center points of the socket solder balls  16 . The array formed by center points of the substrate contact terminals  22  is, however, offset relative to the array formed by center points of the socket solder balls  16  by a distance of 0.57 mm in the x-direction and 0.97 mm in the y-direction.  
         [0021]    The cantilever portions  28  are oriented at an angle of 30.44°, measured clockwise relative to the y-direction. The ideal angle can be represented by the formula:  
             A   =       TAN     -   1            (     pitch                 in                 x        -          direction   /     (     pitch                 in                 y        -        direction   ×   2     )         )                   =       TAN     -   1            (     1.09   /     (     0.97   ×   2     )       )                   =     29.33   ∘                                 
 
         [0022]    The difference between the actual angle of 30.44° and the ideal angle of 29.33° is due to manufacturing constraints. The actual angle is preferably not more than 5° more or less from the ideal angle.  
         [0023]    A line  32  can be drawn from a center point of the socket solder ball  16 A to a center point of the substrate contact terminal  22 A. A line  34  can be drawn from a center point of a socket solder ball  16 B, in the same column but in an adjacent row to the socket solder ball  16 A, to a center point of a socket solder ball  16 C in the same row but in a column adjacent the socket solder ball  16 B. An extension of the line  32  crosses through the line  34  and would cross through its center point if the angle were 29.33°.  
         [0024]    By orienting all the cantilever portions  28  at the stated angle relative to the y-direction, the cantilever portions  28  can be made relatively long while still positioning a relatively large number of the solder balls  16  over a given area. In the given example, the center point of the socket solder ball  16 A is spaced from a center point of the substrate contact terminal  22 A by a distance of 1.125 mm, although the rows are spaced from one another by only 1.17 mm, and the columns are spaced from one another by only 1.09 mm.  
         [0025]    As illustrated in FIG. 3, the socket body  12  has a generally square outline. As further illustrated in FIG. 3, the socket solder balls  16  form an array near four edges of the socket body  12 , while a central region of the socket body  12  is free of socket solder balls  16 . The 1.09 mm spacing between columns and 1.17 mm spacing between rows is maintained over the entire array of socket solder balls  16 .  
         [0026]    [0026]FIGS. 4 and 5 illustrate the electronic assembly in more detail. A microelectronic die, typically a semiconductor microelectronic die  38 , is mounted on the package substrate  20 . The package substrate  20  is then positioned on the free ends of the socket springs  18  and moved toward the socket body  12  to bend the cantilever portions  28  of the socket springs  18 . A clamp  40  secured to the socket body  12  is positioned over the package substrate  20  to retain the package substrate  20  and the socket body  12  in position in a z-direction relative to one another, so as to maintain the bend shape of the socket springs  18 .  
         [0027]    An integrated circuit in the microelectronic die  38  is connected to contacts on the package substrate  20 , and through vias in the package substrate  20  to the substrate contact terminals  22 . Electric interconnections provided by the printed circuit board contact terminals  14 , socket solder balls  16 , socket springs  18 , substrate contact terminals  22 , and vias in the package substrate  20  allow for signals to be transmitted between traces on the board  11  and the integrated circuit in the microelectronic die  28 .  
         [0028]    In the exemplary embodiment, a first electronic device in the form of the socket body  12  is electrically connected to a second electronic device in the form of the package substrate  20 . Another embodiment may make use of the principles of the invention to connect other electronic devices to one another.  
         [0029]    While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative and not restrictive of the current invention, and that this invention is not restricted to the specific constructions and arrangements shown and described since modifications may occur to those ordinarily skilled in the art.