Abstract:
A socket includes: a circuit board; a plurality of connection terminals disposed on the circuit board; a plurality of contacts each fixed to a corresponding one of the connection terminals, wherein each of the contacts is formed of a conductive elastic member, each of the contacts comprising: a tail portion fixed to the corresponding connection terminal; an extending portion connected to the tail portion and extending in a direction substantially parallel with a surface of the circuit board; a rise portion connected to the extending portion and extending in a direction substantially perpendicular to the surface of the circuit board; and a tip portion connected to the rise portion.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a socket and a semiconductor device including the socket and a semiconductor package connected to the socket. 
         [0003]    2. Related Art 
         [0004]    Various techniques have been disclosed for sockets that are used for electrical connection between electronic components. 
         [0005]    For example, a structure is known in which connection pads of an LGA (land grid array) semiconductor package are brought into pressure contact with contacts of a high-springiness socket in connecting the semiconductor package to a mounting circuit board via the socket (see e.g., U.S. Pat. No. 7,264,486). 
         [0006]    However, in the structure for connecting an LGA semiconductor package to a mounting circuit board using a socket as disclosed in U.S. Pat. No. 7,264,486, for example, the thickness of the socket is generally larger than 4 mm. Furthermore, this structure is associated with a problem that it cannot be used for products that are strongly required to be reduced in thickness and weight because the structure needs a heavy reinforcement member such as a back plate. 
         [0007]    A structure for connecting a semiconductor package to a mounting circuit board using a socket will be described below with reference to a semiconductor device  101  shown in  FIG. 8 , which uses a socket as disclosed in U.S. Pat. No. 7,264,486. 
         [0008]    As shown in  FIG. 8 , the semiconductor device  101  has a structure that an LGA semiconductor package  103  in which a semiconductor chip  105  is mounted on its top surface and its bottom surface is formed with electrical conduction terminals (hereinafter referred to as pads)  131  is connected to a mother board  104  (mounting circuit board) via a socket  102 . 
         [0009]    In this connection structure, in the socket  102 , metal contacts  121  are inserted in through-holes  129  of a housing  120 , which are located at such positions as to face the respective pads of the LGA semiconductor package  103 . The housing  120  is made of an insulative resin. Tip portions  121   a  of the contacts  121  are in contact with the respective pads  131  of the semiconductor package  103 . On the other hand, rear end portions (base portions)  121   b  of the contacts  121  are fixed (joined) to the mounting circuit board  104  with solder balls  160 . 
         [0010]    To ensure the electrical connections, the LGA semiconductor package  103  is fixed to the socket  102  in a state that the former is pressed, by strong force, against (and into) the latter in the direction (indicated by arrows in  FIG. 8 ) that is perpendicular to a pad formation surface  130   a . The force is applied to the top surface of a heat spreader  109  which is provided on the semiconductor package  103 . 
         [0011]    For example, the semiconductor package  103  has outer dimensions of about 35 mm×35 mm or about 45 mm×45 mm and is provided with about 1,400 pads  131 . Therefore, the socket  102  which is connected to the semiconductor package  103  is also provided with about 1400 contacts  121 . Therefore, to bring each contact  121  into contact with the corresponding pad  131  with prescribed pressure, the semiconductor package  103  needs to be pressed against the socket  102  by strong force of about 20 to 30 kgf. 
         [0012]    In the semiconductor device  101 , the prescribed pressure that is necessary for the connection is obtained by pressing the semiconductor package  103  against the socket  102  by means of a pressing means (urging member)  106 . However, the strong force that is applied to the socket  102  in the direction perpendicular to the pad formation surface  130   a  acts on the mounting circuit board  104  as it is. Therefore, to prevent a warp or breakage of the mounting circuit board  104 , the bottom surface of the mounting circuit board  104  is provided with a back plate  108  which serves as a reinforcement member for receiving the force. The back plate  108  is fixed, via support members  151 , to a frame body  107  in which the pressing means (urging member)  106  is provided. For example, the back plate  108  is made of an iron-based material, and is a heavy component that weighs up to 150 g. 
         [0013]    In semiconductor devices in which a semiconductor package is connected to a mounting circuit board via a socket as described above, recent increase in the number of pins of a semiconductor chip requires reduction in the socket-side terminal pitch. However, in the above-described semiconductor device  101 , it is difficult to reduce the socket-side terminal pitch while giving each contact  121  a sufficient operation area for good electrical contact because of restrictions relating to the design of the contacts  121  and insufficient strength of the housing  120 . 
         [0014]    In addition, to secure good electrical contact, strong force needs to be applied to the socket  102  in the direction perpendicular to the pad formation surface  130   a . This necessitates a component (e.g., back plate  108 ) that is heavy and makes the structure complex. Such a component is an obstruction to reduction in thickness and weight of an electrical product incorporating the semiconductor device  101 . 
         [0015]    Furthermore, to increase the processing speed of the semiconductor device  101 , the socket  102  is required to be reduced in thickness. However, it is difficult to satisfy this requirement because of the same reasons mentioned above, that is, restrictions relating to the design of the contacts  121  and insufficient strength of the housing  120 . 
       SUMMARY OF THE INVENTION 
       [0016]    Exemplary embodiments of the present invention address the above disadvantages and other disadvantages not described above. However, the present invention is not required to overcome the disadvantages described above, and thus, an exemplary embodiment of the present invention may not overcome any disadvantages described above. 
         [0017]    According to one or more illustrative aspects of the present invention, there is provided a socket. The socket includes: a circuit board; a plurality of connection terminals disposed on the circuit board; a plurality of contacts each fixed to a corresponding one of the connection terminals, wherein each of the contacts is formed of a conductive elastic member. Each of the contacts includes: a tail portion fixed to the corresponding connection terminal; an extending portion connected to the tail portion and extending in a direction substantially parallel with a surface of the circuit board; a rise portion connected to the extending portion and extending in a direction substantially perpendicular to the surface of the circuit board; and a tip portion connected to the rise portion. 
         [0018]    According to one or more illustrative aspects of the present invention, there is provided a semiconductor device including a socket and a semiconductor package. The socket includes: a circuit board; a plurality of connection terminals disposed on the circuit board; a plurality of contacts each fixed to a corresponding one of the connection terminals, wherein each of the contacts is formed of a conductive elastic member, each of the contacts including: a tail portion fixed to the corresponding connection terminal; a n extending portion connected to the tail portion and extending in a direction substantially parallel with a surface of the circuit board; a rise portion connected to the extending portion and extending in a direction substantially perpendicular to the surface of the circuit board; and a tip portion connected to the rise portion. The semiconductor package is electrically connected to the socket. The semiconductor package includes: a plurality of recesses each comprising a bottom surface and a side wall; and a plurality of pads each provided in at least a corresponding one of the recesses. Each of the tip portions of the contacts comes into contact with a corresponding one of the pads provided on the side walls of the recesses to give an elastic force to the corresponding pad provided on the side wall, so that the socket and the semiconductor package are electrically connected to each other. 
         [0019]    Other aspects and advantages of the present invention will be apparent from the following description, the drawings and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a schematic front sectional view of an example semiconductor device according to an embodiment of the present invention; 
           [0021]      FIG. 2  is a schematic top sectional view of the example semiconductor device according to the embodiment of the invention; 
           [0022]      FIG. 3  is a schematic enlarged sectional view of part A of the semiconductor device shown in  FIG. 1 ; 
           [0023]      FIG. 4  is a schematic bottom view of a contact  21  shown in  FIG. 3 ; 
           [0024]      FIG. 5  is a schematic perspective view of an example of the contact  21  according to the embodiment of the invention; 
           [0025]      FIG. 6  is a schematic perspective view of another example of the contact  21  according to the embodiment of the invention; 
           [0026]      FIG. 7  is a schematic sectional view of another example pad of a semiconductor package of the semiconductor device according to the embodiment of the invention; and 
           [0027]      FIG. 8  is a schematic front sectional view showing the configuration of a related-art semiconductor device. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0028]    Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings for the explanation of the embodiments, the members having the same functions are represented by the same reference numerals, and repeated description thereof will be omitted. 
       (Entire Configuration) 
       [0029]    The entire configuration of a semiconductor device according to an embodiment of the present invention will be hereinafter described with reference to  FIGS. 1 and 2 .  FIG. 1  is a schematic front sectional view of an example semiconductor device  1  according to the embodiment of the invention.  FIG. 2  is a sectional view taken along line X-X in  FIG. 1 . 
         [0030]    The semiconductor device  1  according to the embodiment has a structure that a semiconductor package  3  is connected to a mounting circuit board  4  via a socket  2 . The individual components will be described below in detail. 
       (Semiconductor Package) 
       [0031]    In the semiconductor package  3 , electronic components such as a semiconductor chip  5  are mounted on a printed circuit board  30 . In the semiconductor package  3 , one surface (the bottom surface in  FIG. 1 ) of the printed circuit board  30  is formed with plural external connection pads  31 . On the other hand, the semiconductor chip  5  is mounted on the other surface (the top surface in  FIG. 1 ) of the printed circuit board  30  by a flip-chip connection method, for example. Although not shown in  FIG. 1 , the printed circuit board  30  has an internal wiring structure for connecting the semiconductor chip  5  to the pads  31 . 
         [0032]    The mounting area of the semiconductor chip  5  is not limited to the top surface of the printed circuit board  30 , and its mounting method is not limited to the above-described one. 
         [0033]    The pads  31  of the semiconductor package  3  are in pressure contact with and hence are electrically connected to respective contacts  21  of the socket  2  (described later).  FIGS. 3 and 4  illustrate how the pads  31  are in contact with the respective contacts  21 .  FIG. 3  is a schematic enlarged sectional view of part A shown in  FIG. 1 , and  FIG. 4  is a schematic bottom view of the contact  21  shown in  FIG. 3 . 
         [0034]    As shown in  FIGS. 1 and 3 , each pad  31  has a groove-like recess  32  which is formed in a pad formation surface  30   a  (the bottom surface of the printed circuit board  30 ), and is composed of the recess  32  and a conductive coating  32 A which is formed on inner side surfaces  32   a - 32   d  and a bottom surface  32   e  of the recess  32 . According to the embodiment, each pad  31  comes into contact with the corresponding contact  21  when the inner side surface  32   a  of the recess  32  is brought into contact with a tip portion  21   a  of the contact  21  (described later in detail). An interconnection that leads from the conductive coating  32 A formed in the recess  32  to the semiconductor chip  5  is not shown in  FIG. 3 . 
         [0035]    As shown in  FIGS. 3 and 4 , the recess  32  is a groove that is generally shaped like a rectangular parallelepiped formed by the inner side surfaces  32   a - 32   d  and the bottom surface  32   e . That is, for example, the recess  32  is a groove that extends straightly in the pressing direction (indicated by arrow B in  FIG. 4 ) of a pressing member  6  (pressing means). In other words, the recess  32  is formed in a rectangular shape in a plan view, which is long in the pressing direction (indicated by arrow B in  FIG. 4 ) of the pressing member  6 . However, the shape of the recess  32  is not limited thereto. 
         [0036]    The conductive coating  32 A made of a conductive metal material is formed on the inner side surfaces  32   a - 32   d  and the bottom surface  32   e  of the recess  32 . It suffices that the conductive coating  32 A be at least formed on the inner side surface  32   a  of the recess  32 . 
         [0037]    For example, the conductive coating  32 A is formed by electrolytic plating of copper (Cu), a first plating layer (nickel plating layer; not shown) is formed on the surface of the conductive coating  32 A, and a second plating layer (gold plating layer; not shown) is formed on the first plating layer for reduction of contact resistivity and other purposes. 
         [0038]    As shown in  FIG. 3 , the conductive coating  32 A may be formed so as to extend to a portion, around the opening of the recess  32 , of the pad formation surface  30   a . In this case, the edges of those portions of the conductive coating  32 A which are formed on the inner side surfaces  32   a - 32   d  of the recess  32  are not exposed, whereby those portions of the conductive coating  32 A can be prevented from being peeled off. For the sake of simplification, that portion of the conductive coating  32 A which is formed around the opening of the recess  32  of the pad  31  is not shown in  FIG. 4 . 
         [0039]    As shown in  FIG. 4 , the inner side surface  32   a  of the recess  32  to contact the contact  21  is the surface that is perpendicular to the direction (indicated by arrow B in  FIG. 4 ) in which the semiconductor package  3  is pressed by the pressing member  6 . As a result, even if the tip portion  21   a  of the contact  21  is deviated in the direction that is perpendicular to the direction indicated by arrow B, it can come into contact with the inner side surface  32   a  reliably, whereby a contact failure can be avoided and the electrical characteristics can be improved. 
         [0040]      FIG. 7  shows another example of the pad  31 . In the pad  31  shown in  FIG. 3 , the inner side surface  32   a  is perpendicular to the pad formation surface  30   a . In contrast, in the pad  31  shown in  FIG. 7 , the inner side surface  32   a  of the recess  32  to contact the tip portion  21   a  of the contact  21  forms an angle α (&lt;90°) with the pad formation surface  30   a . This structure more reliably prevents the tip portion  21   a  of the contact  21  from coming out of the recess  32 . 
       (Socket) 
       [0041]    The socket  2  employs a circuit board (printed circuit board)  20  as a base member. One surface (the top surface in  FIG. 1 ), to be connected to the semiconductor package  3 , of the circuit board  20  is provided with the contacts  21  to be electrically connected to the respective pads  31  of the semiconductor package  31 . As shown in  FIG. 3 , connection terminals  22  are formed on the circuit board  20  and the contacts  21  are joined to the respective connection terminals  22  with solder  60 . Through vias  70  for connecting the connection terminals  22  to respective connection terminals  39  are formed in the circuit board  20 . Reference numeral  23  denotes solder resist patterns. 
         [0042]    The circuit board  20  may be a printed circuit board. The semiconductor device  1  can be made thinner than the related-art semiconductor device  101  which uses the resin housing  120 . For example, the circuit board  20  may be made of a glass epoxy substrate, and the connection terminals  22 ,  39  and the through vias  70  might be formed by a subtractive method or a semi-additive method. Since no through-holes need to be formed through the circuit board  20  unlike in the case of the resin housing  120 , the circuit board  20  is simple in structure and can be provided with the contacts  21  at a narrower pitch. Furthermore, interconnections can be formed inside the circuit board  20 , and the connection terminals  39  which are formed in the other surface (the bottom surface in  FIG. 1 ) to be connected to mounting circuit board  4  can be increased in the degree of freedom of arrangement. 
         [0043]    Each contact  21  is made of a conductive, high-springiness metal material. Individual contacts  21  are formed by preparing a reel or a sheet of such a metal material and performing punching and bending on it. As shown in  FIG. 5  (schematic perspective view) and  FIGS. 3 and 4  referred to above, each contact  21  is a long and narrow metal piece and is bent three-dimensionally. 
         [0044]    Taking conductivity, springiness, punching workability, bending workability, the price into consideration, phosphor bronze, beryllium copper, Corson alloy, and the like are typically suitable as the metal material of the contact  21 . Although no particular limitations are imposed on the thickness of the contact  21 , the thickness of the contact  21  is set so that the contact  21  can endure repetitive application of pressure in the elastically deformable range. For example, the thickness of the contact  21  is set at about 0.04 to 0.2 mm. 
         [0045]    To prevent corrosion and increase the springiness of the contact  21 , a first plating layer (nickel plating layer) on the surfaces of the contact  21  at a thickness of about 3 μm by immersing it in a nickel (Ni) plating bath. Furthermore, for reduction of contact resistivity and other purposes, a second plating layer (gold plating layer) is formed on the first plating layer at a thickness of about 0.2 μm by immersing it in a gold (Au) plating bath. From the viewpoint of cost reduction, the second plating layer may be formed on the surfaces of only the tip portion  21   a.    
         [0046]    Individual contacts  21  may be formed by preparing a wire, rather than a reel, of a metal material and performing cutting and bending on it. 
         [0047]    A tail portion  21   b  of each contact  21  is fixed to the circuit board  20 , and plural bent portions  21   c  exist between the tail portion  21   b  and the tip portion  21   a . The plural bent portions  21   c  are bent so as to extend three-dimensionally (i.e., not two-dimensionally (not in a plane)), whereby each contact is a three-dimensional body (see  FIG. 5 ). 
         [0048]    Each contact  21  has an intermediate portion  21   d  that is provided between the tail portion  21   d  and the tip portion  21   a  and extends in a direction that is approximately parallel with the pad formation surface  30   a . The expression “direction that is approximately parallel with the pad formation surface  30   a ” includes a direction that is parallel with the pad formation surface  30   a  and a direction that is inclined from the pad formation surface  30   a  by a very small angle θ, and thus covers a certain range of directions. 
         [0049]    In the embodiment, as shown in  FIGS. 4 and 5 , the intermediate portion  21   d  is generally U-shaped. 
         [0050]    More specifically, the one end portion (tail portion  21   b ) of each contact  21  is fixed to a connection terminal  22  of the circuit board  20  with solder  60 . The intermediate portion  21   d  exists between the one end portion and the other end portion (tip portion  21   a ) so as to extend in a direction that is approximately parallel with the pad formation surface  30   a  (in the embodiment, it can be regarded as a direction that is approximately parallel with the connection terminal  22  formation surface of the circuit board  20 ). Each contact  21  also has a rise portion  21   e  whose bottom portion is connected to the tip-side end of the intermediate portion  21   d  and whose major part extends in a direction that is approximately perpendicular to the pad formation surface  30   a  (in the embodiment, it can be regarded as a direction that is approximately perpendicular to the connection terminal  22  formation surface of the circuit board  20 ). As described above, each of the intermediate portion  21   d  and the rise portion  21   e  has a bent portion  21   c . For example, as shown in  FIG. 5 , the intermediate portion  21   d  first goes away from the one end portion (tail portion  21   b ) which is fixed to the circuit board  20 , is then bent into a generally U-shape portion (bent portion  21   c ), and then extends (returns) so that the tip-side end comes close the one end portion (tail portion  21   b ). With this structure, the tail portion  21   b , the tip-side end of the intermediate portion  21   d , the bottom portion of the rise portion  21   e , and a top portion (tip portion  21   a ) of the rise portion  21   e  are located, in a plan view, on a straight line that is parallel with the pressing direction (indicated by arrow B in  FIG. 4 ) of the pressing member  6 . The recess  32  also extends along the same straight line in the plan view. As shown in  FIGS. 3-5 , the tip portion  21   a  of each contact  21  extends parallel with the connection terminal  22  formation surface of the circuit board  20  (in the embodiment, parallel with the pad formation surface  30   a  of the printed circuit board  30 ). 
         [0051]    Having the above structure, each contact  21  is sufficiently elastic with respect to force that is applied by the pressing member  6  in the pressing direction (indicated by arrow B in  FIG. 4 ) and hence (the end face of) its tip portion  21   a  can reliably be brought into contact with the inner side surface  32   a  of the recess  32  of the corresponding pad  31 . 
         [0052]      FIG. 6  shows another example of each contact  21 . As shown in  FIG. 6 , an intermediate portion  21   d  extends straightly away from the one end portion (tail portion  21   b ), fixed to the circuit board  20 , of each contact  21 . 
         [0053]    The tip portion  21   a  of each contact  21  is tapered. In particular, in the embodiment, the end face of the tip portion  21   a  of each contact  21  is a curved surface or a spherical surface (see  FIG. 4 ). 
         [0054]    The contacts  21  are arranged and fixed to the circuit board  20 . Naturally, the positions and the intervals of the contacts  21  are set so as to be suitable for the associated pads  31 . Each contact  21  is oriented so that the end face of the tip portion  21   a  is directed to the upstream side of the pressing direction (indicated by arrow B in  FIGS. 1 ,  2 , and  4 ) of the pressing member  6 . 
         [0055]    For example, the contacts  21  are fixed (joined) to the circuit board  20  with solder  60 . A conductive adhesive or the like may be used instead of solder. 
         [0056]    Having the above structure, each contact  21  exhibits high springiness with respect to force that is applied by the pressing member  6  in the pressing direction (indicated by arrow B in  FIGS. 1 ,  2 , and  4 ). That is, when pressing force is applied by the pressing member  6 , the end face of the tip portion  21   a  of each contact  21  is brought into contact with the pad  31  (the inner side surface  32   a  of the recess  32 ) and its intermediate portion  21   d  is elastically deformed in the pressing direction. 
         [0057]    Unlike in the above-described semiconductor device  101  and the like in which the contacts exhibit high springiness in the direction that is perpendicular to the pad formation surface, in the semiconductor device  1  according to the embodiment no springiness generating regions are necessary in the contacts  21  in the direction that is perpendicular to the pad formation surface  30   a  and hence the height of the contacts  21  can be reduced. For example, whereas in the semiconductor device  101   a  distance of about 3 mm needs to be secured between the top surface of the mounting circuit board  104  and the tip portions  121   a  of the contacts  121 , in the semiconductor device  1  according to the embodiment the distance between the top surface of the mounting circuit board  4  and the tip portions  21   a  of the contacts  21  can be as short as about 1.2 mm. Therefore, the socket  2  and hence the entire device can be reduced in thickness to a large extent. 
       (Mounting Circuit Board) 
       [0058]    As shown in  FIG. 1 , one surface (the top surface in  FIG. 1 ) of the mounting circuit board  4  is formed with connection electrodes  41  to which the connection terminals  39  of the socket  2  are to be connected. For example, the socket  2  is fixed to the mounting circuit board  4  by joining the connection terminals  39  to the connection electrodes  41  with solder balls  61 . 
         [0059]    A frame body  7  whose outer circumferential portion is shaped like a rectangular picture frame is fixed to the mounting circuit board  4  by pins  43  (connection members) which are erected from the connection electrode  41  formation surface. 
         [0060]    The frame body  7  is provided with the pressing member  6  for pressing the semiconductor package  3  in the direction that is parallel with the pad formation surface  30   a . The pressing member  6  is an urging member, for example, and, in the embodiment, is a leaf spring made of a high-springiness metal material. 
         [0061]    Furthermore, a positioning means  8  for positioning the semiconductor package  3  in the direction perpendicular to the pad formation surface  30   a  with respect to the socket  2  which is joined to the mounting circuit board  4  is provided on top of the frame body  7 . 
         [0062]    The positioning means  8  is made of a metal material, for example, and is shaped like a plate or a rod that can be attached to and detached from the outer circumferential portion of the frame body  7 . It suffices that the positioning means  8  be able to prevent the semiconductor package  3  from deviating by more than a prescribed distance in the direction perpendicular to the pad formation surface  30   a ; the positioning means  8  may have either high springiness or no springiness. 
         [0063]    In the embodiment, the positioning means  8  positions the semiconductor package  3  (and a heat spreader  9 ) with the heat spreader  9  connected to the top surface of the semiconductor package  3 . 
         [0064]    The frame body  7  has a movement restricting means  7   a  for restricting a movement of the socket  2  in the direction that is parallel with the pad formation surface  30   a . As shown in  FIG. 1 , the frame body  7  is composed of a side wall portion  7 A and a bottom portion  7 B. The bottom portion  7 B is formed with an opening portion having a shape (e.g., rectangular shape) that is similar to the external shape of the socket  2 , and the opening portion serves as the movement restricting means  7   a . That is, the socket  2  is fitted into and held by the opening portion (movement restricting means  7   a ), whereby a movement of the socket  2  in the direction that is parallel with the pad formation surface  30   a  is restricted. Therefore, when the semiconductor package  3  is pressed by the pressing means  6 , the socket  2  is prevented from being deviated by the pressing force. 
       (Connection Structure) 
       [0065]    The structure that joins the above-described constituent members will be described below. 
         [0066]    For example, in the connection structure according to the embodiment, to connect the semiconductor package  3  to the mounting circuit board  4  via the socket  2 , the socket  2  is joined to the mounting circuit board  4  in advance and the semiconductor package  3  is brought into pressure contact with, so to speak, a mounting circuit board with a socket. 
         [0067]    As described above, the semiconductor package  3  is positioned by the positioning means  8  in the direction perpendicular to the connection terminal  22  formation surface of the circuit board  20  so that the tip portions  21   a  of the contacts  21  of the socket  2  go into the recesses  32  of the pads  31  of the semiconductor package  3 . 
         [0068]    In this state, the semiconductor package  3  is pressed by the pressing member (urging member)  6  in the direction that is parallel with the pad formation surface  30   a , whereby the pads  31  (the inner side surfaces  32   a  of the recesses  32 ) of the semiconductor package  3  come into pressure contact with the tip portions  21   a  of the contacts  21  of the socket  2 , respectively, in an elastic manner. 
         [0069]    As a result, the semiconductor package  3  is electrically connected to the socket  2 . That is, prescribed electric circuits are formed between the semiconductor chip  5  and the mounting circuit board  4 . 
         [0070]    As can be seen from the above description, unlike in the related-art semiconductor device  1  described above, in the semiconductor device  1  according to the embodiment no structure for pressing the semiconductor package  3  in the direction that is perpendicular to the pad formation surface  30   a . Therefore, a reinforcement member such as a back plate can be omitted and the weight can be reduced accordingly. Furthermore, the printed circuit board  20  can be used as a base member of the socket  2  instead of a housing, whereby electrical contact between the semiconductor package  3  and the socket  2  can be made with a narrow pitch. 
         [0071]    As another mode of use, the mounting circuit board with a socket which is formed by joining the socket  2  to the mounting circuit board  4  can be used for checking whether a semiconductor chip  5  or a semiconductor package  3  is defective or not. That is, the socket  2  is joined in advance to a test mounting circuit board ( 4 ) that is connected to a testing instrument and then a semiconductor chip  5  or a semiconductor package  3  is set with respect to the socket  2 . Whether the semiconductor chip  5  or the semiconductor package  3  is defective or not can thus be determined. 
         [0072]    As a further mode of use, the socket  2  can be used as an interposer by forming the contacts  21  on both surfaces of the socket  2  and each pair of contacts  21  that are symmetrical with each other are electrically connected to each other. 
         [0073]    As described above, with the above-described socket, semiconductor package, and connection structure, a semiconductor device can be provided which can be reduced in thickness, weight, and terminal pitch, is simple in structure and easy to manufacture, can be improved in electrical characteristics, and can be implemented at a lower cost. 
         [0074]    While the present invention has been shown and described with reference to certain exemplary embodiments thereof, other implementations are within the scope of the claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.