Abstract:
A socket for a camera module includes an insulative terminal assembly housing that supports a plurality of conductive terminals. The housing serves as the bottom of a socket and it is surrounded with a conductive metal shell that defines a cavity which receives a camera module. The shell has one or more elastic arms that extend into contact with the housing. The shell is movable on the housing, and the housing has one or more projections that serve as stops for the elastic arms to limit the vertical movement of the shell with respect to the housing. This vertical movement permits the shell to move relative to the housing and thereby compensate for warping and the like which may occur on circuit boards to which the socket is mounted.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to sockets for camera modules, and more particularly to a socket in which the outer shell is movable with respect to the inner terminal assembly. 
   Conventionally, module sockets have been used to mount camera modules, which are typically composed of an image capturing element, such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) and an optical lens. These two elements are integrated together and mounted to a substrate of a small-sized electronic device such as a cellular phone or a PDA (Personal Digital Assistance) (see, for example, Japanese Design Registration No. 1179175). 
     FIG. 2  is an exploded perspective view of such a conventional module socket that is used in small electronic devices, such as cellular telephones. In  FIG. 2 , the housing body  311  of the terminal assembly is made of resin and supports conductive terminals  313 . The assembly is mounted on a printed circuit board  314 , which serves as a substrate; and the camera module  320  is inserted into the housing body  311  for attachment. The circumferential wall of the housing body  311  is covered with the shell  312  made of metal so as to prevent electromagnetic interference (“EMI”). After the camera module  320  is placed in the housing body  311 , the metal cover  301  is attached from above. 
   However, in this type of module socket, the cover  301  is retained from coming off of the camera module  320 , and this increases the number of parts needed. Therefore, the number of steps for mounting the camera module  320  onto the printed circuit board  314  increases, along with costs for mounting. Moreover, because the housing body  311  has a side wall made of resin at each of four sides, the external dimensions increase because of the thickness of the side wall, so that the area occupied on the printed circuit board  314  increases. In particular, in small-sized electronic devices, the available surface area of the printed circuit board  314  is limited, and the large occupied area poses a serious sizing problem. 
   The shell  312  covers the circumferential wall of the housing body  311 , and is formed by assembling two metallic plate members. If the shell is out of tolerance, the dimensional accuracy of the parts deteriorates. Particularly, because the housing body  311  and the shell  312  are fixed to each other, the flatness of the bottom surface of the module socket deteriorates, and a difference is produced between the height of the lower surface of the solder tails of the terminals  313  and the height of the lower surfaces of lower projections of the shell  312  with respect to the upper surface of the printed circuit board  314 . 
   The module socket is used to establish electrical connection between the camera module  320  and wiring traces on the circuit board  314  as follows. The contact portions of the terminals  313  come into contact with electrodes on the bottom surface of the camera module  320 , while the lower surface of the solder tails of the terminals  313  are soldered to wiring traces exposed on the circuit board  314  or pads of the wiring traces. A thin metal film is formed on the surface of the camera module  320  through plating, and is electrically connected to the shell  312  via the cover  301  or the like, so as to cope with static electricity and noise. The lower surfaces of the lower projections of the shell  312  are soldered to ground traces of the circuit board  314  or pads connected thereto so that the shell  312  is grounded. When the module socket is mounted on the circuit board  314 , solder is applied to the traces or pads on the circuit board  314 , and is heated for reflow soldering. The thickness of the solder in the form of a paste applied to the traces or pads is approximately 0.1 mm. Therefore, if a difference greater than 0.1 mm is present between the height of the lower surface of the solder tails of the terminals  313  and the height of the lower surfaces of lower projections of the shell  312  with respect to the upper surface of the printed circuit board  314 , the lower surface of the solder tails of some terminals  313  or the lower surfaces of some lower projections of the shell  312  may fail to become soldered to the circuit board traces or pads. In such cases, electrodes of the camera module  320  may not be reliably connected to the circuit board  314 , with the result that the camera module  320  fails to operate properly. In addition, since the shell  312  is not properly grounded, blocking of noise becomes incomplete. 
   The present invention is therefore directed to an improved camera module socket that avoids the above-mentioned shortcomings. 
   SUMMARY OF THE INVENTION 
   It is therefore a general object of the present invention to provide a camera module socket which has a reduced number of parts, reduced external dimensions, and a reduced occupying area on a substrate, which provides freedom to the vertical positional relationship between terminals and a side wall member and has improved dimensional accuracy, and which enables easy, reliable mounting of a module at low cost. 
   It is another object of the present invention to provide a camera module socket that utilizes an outer grounding shell that contacts the camera module and which is loosely fixed to the base member of the terminal assembly, thereby permitting a slight amount of movement between the shell and the terminal assembly in order to compensate for out of tolerance circuit boards and the like. 
   It is still another object of the present invention to provide a socket for a camera module which includes an inner terminal assembly having an insulative base member and a plurality of conductive terminals, and a conductive socket that encloses the base member, the socket having pairs of retention arms that engage sides of the terminal assembly base member, the base member having stops that permit movement of the retention arms on the base member so that the socket can “float” in its engagement to the base member. 
   The present invention accomplished these and other objects by way of its structure. The module socket includes a base member formed of an insulating material, and a side wall member, or shell, formed from a single metal plate. The shell is attached to the base member so as to form a side wall which extends perpendicular to the base member, and surrounds the circumference of the base member, whereby a socket in the form of a bottomed container is formed. The shell is attached to the base member such that the shell is movable with respect to the bottom member in the height direction. 
   Terminals are mounted to the base member and the shell is attached to the base member to be movable in the vertical direction, the shell entirely surrounding at least a portion of a side surface of the module in the circumferential direction, the portion extending over a predetermined range in the height direction. The terminals and the shell are connected to an upper surface of a substrate. 
   Preferably, the shell includes an elastic engagement piece in the form of an inwardly projecting first arm, the first arm engaging recesses formed on the side surfaces of the module to thereby lock the module in place within the shell. Preferably, the first arm is a tongue-shaped member having one end connected to a body of the shell, wherein portions of the body of the shell sandwich a portion of the body to which the elastic engagement piece is connected function as torsion springs. 
   Preferably, the shell includes a second arm projecting inward, the second arm contacting a metal coating layer formed on the side surface of the module to thereby shield the module. Preferably, the terminals each include an elastic arm portion projecting upward from the bottom member and coming into contact with a wiring trace on the bottom surface of the module. 
   The shell also includes a third arm, and the base member includes an engagement projection which opposes the third arm. The third arm comes into engagement with the engagement projection such that the third arm is movable vertically for a predetermined distance. Preferably, the engagement projection includes upper and lower engagement projections and formed on a side surface of the base member, wherein the upper engagement projection comes into contact with the upper end of the third arm so as to restrict upward movement of the shell with respect to the base member, and the lower engagement projection comes into contact with the lower end of the third arm so as to restrict downward movement of the shell with respect to the base member. 
   The module socket according to the present invention has a reduced number of parts, reduced external dimensions, and a reduced occupying area on a substrate; provides freedom to the vertical positional relationship between terminals and its shell member and has improved dimensional accuracy; and enables easy, reliable mounting of a module at low cost. 
   These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the course of this detailed description, the reference will be frequently made to the attached drawings in which: 
       FIG. 1  is an exploded perspective view of a camera module socket constructed in accordance with the principles of the present invention; 
       FIG. 2  is an exploded perspective view of a conventional camera module socket; 
       FIG. 3  is a front view of the camera module socket of  FIG. 1 ; 
       FIG. 4  is a side view of the camera module socket of  FIG. 1 ; 
       FIG. 5  is a sectional view of the camera module socket taken along line B-B of  FIG. 4 ; 
       FIG. 6  is a sectional view of the camera module socket taken along line A-A of  FIG. 3 ; 
       FIG. 7  is an enlarged detail view of a portion of the camera module socket at area C in  FIG. 4 ; 
       FIG. 8  is an enlarged partial sectional view of the camera module socket taken along line D-D of  FIG. 7 ; 
       FIG. 9  is an enlarged partial sectional view of the camera module socket taken along line E-E of  FIG. 7 ; 
       FIG. 10  is a side view of the shell of the camera module socket of  FIG. 1 ; 
       FIG. 11  is a bottom view of the shell of  FIG. 10 ; 
       FIG. 12  is an enlarged partial view of a portion of the shell corresponding to area G in  FIG. 11  and illustrating the third engagement arm; 
       FIG. 13  is an enlarged partial view of a portion of the shell corresponding to an area in a cross section taken along line F-F of  FIG. 10  and of area G in  FIG. 11 ; 
       FIG. 14  is a perspective view of the camera module socket shown mounted to a substrate; 
       FIG. 15  is a front elevational view of the mounted camera module socket of  FIG. 14 ; 
       FIG. 16  is a first sectional view of the mounted camera module socket taken along line H-H of  FIG. 15 ; 
       FIG. 17  is a side elevational view of the mounted camera module socket of  FIG. 14 ; and, 
       FIG. 18  is a second sectional view of the camera module socket taken along line I-I of  FIG. 17 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a camera module socket  10  constructed in accordance with the principles of the present invention, and which is used to electrically connect a module to a substrate  51 . The module  53  is preferably a camera module, which is composed of an image capturing element (e.g., a CCD or a CMOS image sensor) and an optical lens which integrated together as a single component. However, the module  53  may be a module of any type, such as a sensor module including a sensor (e.g., an infrared sensor or a fingerprint reading sensor) or an acoustic element module (e.g., a microphone). The camera module socket  10  is used to mount the camera module  53  to a small-sized electronic device such as a cellular phone or a PDA. The camera module socket  10  may be used to mount the module  53  to other apparatuses, such as home appliances (e.g., a television, a washer, or a refrigerator), monitoring apparatuses for security, and automobiles. The camera module socket  10  is mounted to a substrate such as a printed circuit board, however, no limitation is imposed on the type of the substrate. 
   In the description of the present embodiment, terms for expressing direction, such as up, down, left, right, front, and rear, are for explaining the structure and action of portions of the ; camera module sockets  10 . However, these terms represent respective directions for the case where the camera module socket  10  is used in an orientation shown in the drawings, and must be construed to represent corresponding different directions when the orientation of the camera module socket  10  is changed. 
   As shown in  FIG. 1 , the camera module socket  10  is adapted to receive the camera module  53  and includes a terminal assembly that includes an insulative housing or base member  11  and conductive terminals  21  that are supported by the base member  11 . A conductive shell  31  is attached to the housing member  11 . The socket  10  assumes the form of a bottomed container having an opened upper end. The shell  31  entirely surrounds at least a portion of a side surface  55  of the module  53  in the circumferential direction, the portion extending over a predetermined range in the height direction. That is, the shell  31  is not required to cover the side surface  55  of the module  53  over the entire range in the height direction, from the lower end to the upper end of the side surface  55 , but is only required to cover the side surface  55  over a portion of the range. Notably, the present embodiment will be described with reference to the case where the above-mentioned bottomed container assumes a generally parallelepiped shape; that is, the case where the shell  31  assumes the form of a rectangular tube, one end of which is closed by means of the housing member  11 , and the other end of which is opened. 
   The housing member  11  has a low profile and is formed of an insulating material such as synthetic resin, and preferably without any side walls. At opposite lateral ends of the body portion of the housing member  11 , there are end projections  13  and intermediate projections  14  formed to extend laterally outward. The number of the intermediate projections  14  is shown as two for each side, however, others may be used. Side surfaces  13   a  of the end projections  13  are flush with the corresponding longitudinal end surfaces of the body of the housing member  11  and face the inner surface of the shell  31  near the lower edge thereof. The end surfaces  13   b  of the end projections  13  and end surfaces  14   a  of the intermediate projections  14  extend along a direction perpendicular to the side surfaces  13   a  and face the inner surface of the shell  31  in the vicinity of the lower edge thereof. 
   Upper and lower engagement projections  12   a  and  12   b , which come into engagement with engagement arms  43  of the shell  31  (described later) are formed on the side surfaces  13   a  of the end projections  13 , or on the opposite end surfaces of the body of the housing member  11  with respect to the longitudinal direction thereof. The upper and lower engagement projections  12   a  and  12   b  project outward from the opposite longitudinal end surfaces of the body of the housing member  11 . The lower ends of the upper engagement projections  12   a  come into engagement with upper ends of the corresponding engagement arms  43  so as to restrict upward movement of the shell  31  with respect to the housing member  11 . The upper ends of the lower engagement projections  12   b  come into engagement with lower ends of the corresponding engagement arms  43  so as to restrict downward movement of the shell  31  with respect to the housing member  11 . Notably, an inclined surface or tapered surface is preferably formed on the upper end of each upper engagement projection  12   a  so as to enable the corresponding engagement arm  43  to easily pass over the upper engagement projection  12   a . When the upper and lower engagement projections  12   a  and  12   b  are collectively described, they are referred to as “engagement projections  12 .” 
   At the opposite lateral ends of the body portion of the housing member  11 , seven terminal-receiving grooves  15  are shown as being formed at a predetermined pitch such that the terminal-receiving grooves  15  extend laterally. A single terminal is shown disposed in each terminal-receiving groove  15 . The pitch and number of the terminal-receiving grooves  15  can be determined freely. The terminals  21  are not necessarily required to be disposed in all the terminal-receiving grooves  15 , and some of the terminals  21  may be omitted in accordance with the arrangement of signal wiring traces exposed at a bottom surface  56  of the module  53 . As shown in  FIG. 6 , recesses  15   a  are formed in the body of the housing member  11 . The recesses  15   a  communicate with the terminal-receiving grooves  15  and extend toward the center of the body of the housing member  11 . The body portions of the terminals  21  are accommodated within the recesses  15   a . Entrance portions of the terminal-receiving grooves  15  are located closer to the center of the body of the housing member  11  as compared with the end surfaces  13   b  of the end projections  13  and the end surfaces  14   a  of the intermediate projections  14 , whereby, as shown in  FIG. 6 , spaces are provided between the entrance portions of the terminal-receiving grooves  15  and the inner surface of the shell  31  so as to enable movement of connection arm portions (elastic arm members)  23  of the terminals  21 . 
   The terminals  21  are formed through punching and forming a metal plate such that each terminal has a generally U-shaped body having a lower base portion  21   a  and an upper base portion  21   b . The lower base portion  21   a  and the upper base portion  21   b  are connected together via a curved portion. The curved portion enables the U-shaped body to function as a spring. The lower base portion  21   a  is wider than the upper base portion  21   b , and has protrusions for biting into the side walls of the corresponding accommodation recess  15   a  of the housing member  11 . Further, a tail portion (solder tail)  22  extends from the distal end of the lower base portion  21   a . A connection arm portion  23  extends from the distal end of the upper base portion  21   b . The connection arm portion  23  serves as a contact piece to be electrically connected to a signal wiring trace exposed at the bottom surface  56  of the module  53 . The connection arm portion  23  extends from the distal end of the upper base portion  21   b  via a bent portion and extends obliquely upward. The free end (upper end) of the connection arm portion  23  is formed in an outwardly bulged shape so as to form a contact portion  23   a , which comes into contact with the surface of the signal wiring trace of the module  53 . 
   In a state in which the terminal  21  is disposed in the corresponding terminal-receiving groove  15  of the housing member  11 , the lower base portion  21   a  is sandwiched from the opposite lateral sides by the opposite side walls of the accommodation recess  15   a , whereby the lower base portion  21   a  is fixed. In this case, since the protrusions of the lower base portion  21   a  bite into the side walls of the recess  15   a , the lower base portion  21   a  is reliably fixed. As shown in  FIG. 6 , the lower surface of the tail portion  22  projects a short distance downward from the lower surface of the housing member  11 , and the connection arm portion  23  projects a great distance upward from the upper surface of the housing member  11 . The tail portion  22  is connected, by means of solder, for example, to a wiring trace formed on the substrate  51  or a land connected to the wiring trace. 
   In the present embodiment, the shell  31  is shown as formed from a single metal plate member, and assumes the form of a rectangular tubular body which is formed through a process of bending at right angles the plate member at four bending portions  35   a , and causing opposite ends of the plate member to engage and be joined together. That is, the shell  31  assumes a shape formed by four rectangular walls connected together such that adjacent walls intersect each other perpendicularly. The shell  31  is connected, at its lower edge, to a circumferential edge of the housing member  11 , and serves as a side wall of the socket  10 . The four walls of the shell  31  cooperate to define a side wall that surrounds the housing member  11  on all four sides thereof. The shell  31  has a rectangular cross section such that one pair of opposite sides are slightly longer along the substrate than the other pair of opposite sides. In this case, as shown in  FIG. 4 , a joint portion  37  formed as a result of joining the opposite ends of the plate member is located at a central portion of one side surface of the rectangular tubular body, and extends vertically from the upper end of an inclined portion  36  to the lower end of a connection arm support projection  32 . A convexly shaped portion  37   a  is formed at one end of the plate member, and a concavely shaped portion corresponding to the convexly shaped portion  37   a  is formed at the other end of the plate member. The convexly shaped portion  37   a  is engaged with the concavely shaped portion, and the two portions are then subjected to crimping, whereby the convexly shaped portion  37   a  and the concavely shaped portion are mutually tightened, and the joining of the opposite ends at the joint portion  37  is made solid. 
   A plurality of lower projections project downward from the lower edges of the shell  31  for contacting traces or pads on the circuit board. The lower projections include connection arm support projections  32 , wide projections  33 , and narrow projections  34 . The connection arm support projections  32  and the wide projections  33  are formed at the shorter lower edges corresponding to the shorter sides. The narrow projections  34  are formed at the longer lower edges corresponding to the longer sides. The narrow projections  34  are such that four narrow projections  34  are formed at a predetermined pitch at each of the longer lower edges. The connection arm support projections  32  are formed at the centers of the shorter lower edges, and the wide projections  33  are formed on the opposite sides of each connection arm support projection  32 . The above-described joint portion  37  is located at the center of the connection arm support projection  32 . An engagement opening portion  44  is formed between the connection arm support projection  32  and each of the wide projections  33 . The engagement arms  43  project from the opposite lateral edges of each connection arm support projection  32  toward the corresponding wide projections  33 , and extend horizontally within the corresponding engagement opening portions  44 . Each of the engagement arms  43  is a cantilever member formed integrally with the shell  31 . Proximal end portions of the engagement arms  43  are connected to the opposite lateral edges of the connection arm support projection  32 , and distal end portions of the engagement arms  43  are free ends. These arms  43  preferably press against the sides of the housing member  11 . 
   In a state in which the shell  31  is attached to the housing member  11 , as shown in  FIGS. 4 and 7 , the upper and lower engagement projections  12   a  and  12   b  are located within the corresponding engagement openings  44 . The upper engagement projection  12   a  is located above the corresponding engagement arm  43  in the vicinity of the distal end of the engagement arm  43 . The lower engagement projection  12   b  is located below the corresponding engagement arm  43  in the vicinity of the proximal end of the engagement arm  43 . As shown in  FIG. 8 , the tip end (left end in  FIG. 8 ) of the upper engagement projection  12   a  enters the corresponding engagement opening  44 , and the lower end of the upper engagement projection  12   a  comes into engagement with the upper end of the corresponding engagement arm  43  in the vicinity of the distal end thereof, to thereby restrict or limit upward movement of the shell  31  with respect to the housing member  11 . Further, as shown in  FIG. 9 , the tip end (left end in  FIG. 9 ) of the lower engagement projection  12   b  enters the corresponding engagement opening  44 , and the upper end of the lower engagement projection  12   b  comes into engagement with lower end of the corresponding engagement arm  43  in the vicinity of the proximal end thereof so as to restrict or limit downward movement of the shell  31  with respect to the housing member  11 . Notably, in  FIGS. 4 and 7 , a clearance is formed between the lower end of the upper engagement projection  12   a  and the upper end of the engagement arm  43  in the vicinity of the distal end thereof, and a clearance is formed between the upper end of the lower engagement projection  12   b  and the lower end of the engagement arm  43  in the vicinity of the proximal end thereof. The shell  31  can move vertically with respect to the housing member  11  by the total distance of these clearances. 
   When the shell  31  is attached to the housing member  11 , the lower edges of the shell  31  surround the entire circumference of the housing member  1 . As shown in  FIGS. 3 to 6 , as in the case of the lower surfaces of the tail portions  22  of the terminals  21 , the lower end surfaces of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  project a short distance downward from the lower surface of the housing member  11 . In the present embodiment, in the state in which the shell  31  is attached to the housing member  11 , the shell  31  can be moved with respect to the housing member  11  in the vertical direction; i.e., the height direction. The movable range, i.e., a predetermined distance over which the shell  31  is movable, is restricted by means of engagement between the engagement arms  43  and the upper and lower engagement projections  12   a  and  12   b . Thus, the vertical positions of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34 , as well as the vertical positions of the lower surfaces of the tail portions  22  of the terminals  21 , are automatically adjusted individually. Therefore, the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34 , as well as the tail portions  22  of the terminals  21 , can be reliably connected, by means of soldering or a like process, to wiring traces formed on the substrate  51  or connection pads connected to the wiring traces. Notably, at least some of the wiring traces or connection pads are connected to a ground wiring trace of the substrate  51 . Thus, the shell  31  is grounded, and functions as an electromagnetic shield. The numbers and pitches of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  can be freely changed so long as these projections do not interfere with signal wiring traces formed on the substrate  51 . 
   The body of the shell  31  preferably includes a thick wall portion  31   a  having a relatively large thickness and a thin wall portion  31   b  having a relatively small thickness. In this case, in view of strength of the shell  31 , the thin wall portion  31   b  preferably extends over only a limited range; i.e., over a predetermined distance from the upper end of the shell  31 . Reference numeral  31   c  denotes a border between the thick wall portion  31   a  and the thin wall portion  31   b . An upper end portion of the shell  31  is bent at a bending portion  36   a  so as to form the inclined portion or lip  36 , which inclines outward. Notably, the inclined portion  36  is a portion of the thin wall portion  31   b . The inclined portion  36  increases the cross sectional area of the shell  31  at the upper end such that the cross sectional area gradually increases upward. Therefore, at the time of mounting the module  53 , a task for inserting the module  53  into the shell  31  from above can be easily performed. Moreover, cutaway portions  35  are formed at positions corresponding to the bending portions  35   a , so that the thin wall portion  31   b  is divided into four sections which correspond to the four walls and which are independent of one another. 
   As shown in  FIGS. 1 and 6 , a vertically extending engagement slot  47  is formed in the wall of the shell  31  in which the connection arm support projection  32  is formed and which does not include the joint portion  37 . A polarity key  58  (a projection indicating the orientation or polarity of the module  53 ) is formed on one side surface of the module  53  such that the polarity key  58  projects outward. At the time of mounting the module  53 , the module  53  is inserted into the shell  31  from above in an orientation such that the polarity key  58  is fitted into the engagement slot  47 . Thus, the module  53  is attached to the socket  10  in a predetermined orientation, and the signal wiring traces exposed at the bottom surface  56  of the module  53  are connected to the connection arm portions  23  of the corresponding terminals  21 . 
   The upper end of the engagement slot  47  is surrounded by a bridge portion  48 , which is formed integrally with the inclined portion  36  such that the bridge portion  48  projects from the upper edge of the inclined portion  36 . Since the bridge portion  48  connects portions of the inclined portion  36  located on the opposite sides of the engagement slot  47 , the strength of the wall of the shell  31  in which the engagement slot  47  is formed is increased, and deformation of the wall can be prevented. As shown in  FIG. 5 , the bridge portion  48  extends from the inclined portion  36 , while being bent at an angle of about 180 degrees, so that its distal end extends vertically. Therefore, as shown in  FIGS. 1 and 6 , in the vicinity of the upper end, the engagement slot  47  is opened upward. Therefore, at the time of mounting the module  53 , a task for inserting the polarity key  58  of the module  53  into the engagement slot  47  from above can be easily performed. 
   Moreover, two grounding spring portions (elastic contact pieces)  41  are formed on each of the walls of the shell  31  on which the connection arm support projections  32  are formed. The grounding spring portions  41  come into contact with the side surface  55  of the module  53  mounted to the socket  10 , and are electrically connected to a metal coating layer formed on the side surface  55 . The metal coating layer of the module  53  functions as an electromagnetic shield. Upon contact with the grounding spring portions  41 , the metal coating layer is electrically connected to the ground wiring trace of the substrate  51  via the shell  31 . Notably, the number and positions of the grounding spring portions  41  can be determined freely. Since the grounding spring portions  41  are formed by removing a portion of the shell  31  by means of punching or other suitable machining method, an opening  42  is formed around each of the grounding spring portions  41 . 
   Meanwhile, two locking spring portions (elastic engagement pieces)  45  are formed on each of the walls of the shell  31  on which the connection arm support projections  32  are not formed. The locking spring portions  45  come into engagement with engagement recesses  57  to be described later, which are formed on the side surface  55  of the module  53  mounted to the socket  10 , so as to lock the module  53 . As in the case of the grounding spring portions  41 , since the locking spring portions  45  are formed by removing a portion of the shell  31 , by means of punching or other suitable machining method, an opening  46  is formed around each of the locking spring portions  45 . Notably, in the case where the metal coating layer of the module  53  is formed within the engagement recesses  57 , the locking spring portions  45  servo as grounding spring portions in the same manner as the grounding spring portions  41 . In order to disengage the grounding and locking spring portions  41 ,  45 , a user can press the inclined portion or lip  36  to cam the portions  41 ,  45  away from the module. 
     FIG. 10  is a side view of the shell and as shown therein, the grounding spring portions  41  and the locking spring portions  45  projects inward from the inner wall surfaces of the side walls of the shell  31 . As shown in  FIGS. 1 and 4  to  6 , the grounding spring portions  41  and the locking spring portions  45  are elongated tongue-shaped members whose upper ends are connected to the thin wall portion  31  b of the body of the shell  31  and which extend obliquely downward. The lower ends of the grounding spring portions  41  and the locking spring portions  45  are free ends. As shown in  FIGS. 5 and 6 , distal end portions of the grounding spring portions  41  and the locking spring portions  45  are curved outward, and the curved portions project inward to the greatest extent. Therefore, when the module  53  is mounted, the curved surfaces of the curved portions of the grounding spring portions  41  and the locking spring portions  45  come into contact with the side surface  55  of the module  53 . Therefore, even when the side surface  55  of the module  53  moves in contact with the curved portions, the side surface  55  receives no resistance, and can move smoothly. 
   As shown in  FIG. 6 , the lower end of each locking spring portion  45  is curved greatly and generally extends horizontally, so that the bent angle at the curved portion is an acute angle. Thus, the curved portion of each locking spring portion  45  fits the inner surface of the engagement recess  57  formed on the side surface  55  of the module  53 , whereby the curved portion of each locking spring portion  45  reliably engages with the engagement recess  57 , and hardly comes off. Further, as shown in  FIGS. 5 ,  6 , and  11 , the amount of inward projection of the curved portion of each locking spring portion  45  is greater than the amount of inward projection of the curved portion of each grounding spring portion  41 , because the curved portion of each grounding spring portion  41  comes into contact with the side surface  55  of the module  53  attached to the socket  10 , whereas the curved portion of each locking spring portion  45  comes into engagement with the engagement recess  57  formed on the side surface  55  of the module  53 . 
   Incidentally, when the module  53  is mounted, the curved portion (free end) of each locking spring portion  45  is pushed outward by the side surface  55  of the module  53  to a position near the inner wall surface of the shell  31 , and enters the engagement recess  57  of the module  53  after completion of the mounting of the module  53 . Therefore, the curved portion moves within a wide moving range, and over the entire moving range, the curved portion is required to be urged toward the side surface  55  of the module  53  or the side surface of the engagement recess  57 . That is, over the entire moving range of the curved portion, the locking spring portion  45  is required to function as a spring. 
   Therefore, the locking spring portions  45  and the openings  46  have respective shapes as shown in  FIGS. 3 and 5 . Each of the openings  46  has a wide portion  46   a  at a location where the locking spring portion  45  is connected to the thin wall portion  31   b  of the shell  31 . The width portion  46   a  extends in the lateral direction. In order to widen the moving range of the curved portion of each locking spring portion  45  in which the locking spring portion  45  provides a spring function, the distance between a point at which the locking spring portion  45  is connected to the thin wall portion  31   b  and the free end of the locking spring portion  45 ; i.e., the length of the locking spring portion  45  is desired to be increased. However, sufficiently increasing the length of the locking spring portion  45  is difficult because of restrictive factors such as the vertical dimension of the shell  31 , and the position of the engagement recesses  57  of the module  53 . 
   The distance between the opposite ends of the wide portion  46   a  is increased to a possible extent, and the distance between the upper edge of the wide portion  46   a  and the upper edge of the inclined portion  36  is decreased to a possible extent. Thus, the area sandwiched between the upper edge of the wide portion  46   a  and the upper edge of the inclined portion  36  assumes an elongated rectangular shape, and functions as a torsion spring. That is, since the area is located in the thin wall portion  31   b  having a small wall thickness, even when the force received from the corresponding locking spring portion  45  is relatively weak, the area undergoes torsional deformation, and thus, functions as a torsion spring. This configuration widens the moving range of the curved portion of each locking spring portion  45  in which the locking spring portion  45  provides a spring function. The distance between the upper edge of the wide portion  46   a  and the upper edge of the inclined portion  36  can be freely determined such that the above-described area can function as a torsion spring. 
   Meanwhile, the curved portion (free end) of each grounding spring portion  41  is not required to move over a large distance when the module  53  is mounted. Therefore, the moving range of the curved portion of each grounding spring portion  41  in which the grounding spring portion  41  provides a spring function may be shorter than that of each locking spring portion  45 . Therefore, an area which functions as a torsion spring is not required. Therefore, as shown in  FIGS. 4 and 6 , a location where the grounding spring portion  41  is connected to the thin wall portion  31   b  of the shell  31  is away from the upper edge of the inclined portion  36  by a relatively large distance. Notably, as in the case of the locking spring portions  45 , for which the wide portions  46   a  are provided, wide portions may be formed in the openings  42  for the grounding spring portions  41 . 
   Moreover, as shown in  FIGS. 12 and 13 , each engagement arm  43  is a plate-shaped portion, whose proximal end portion has a thickness similar to that of the connection arm support projection  32 , and whose distal end portion is thinner than the proximal end portion. This configuration enables the engagement arm  43  to function as a plate spring, especially, in the vicinity of the distal end portion. Therefore, when the shell  31  is mounted to the housing member  11 , the distal end portion of each engagement arm  43  is caused to elastically curve toward the outside (upper side in  FIGS. 12 and 13 ) of the shell  31 , and easily pass over the corresponding upper engagement projection  12   a . Notably, an inclined surface or taper surface  43   a  is formed on the lower end of the distal end portion (and the vicinity thereof) of each engagement arm  43  at the inner edge thereof (the lower edge in  FIGS. 12 and 13 ). When the shell  31  is mounted to the housing member  11 , the taper surface  43   a  comes into engagement with the taper surface formed on the upper end of the corresponding tipper engagement projection  12   a . Therefore, the sliding movement between the lower end of each engagement arm  43  and the upper end of the corresponding upper engagement projection  12   a  becomes smooth, and the distal end portion of each engagement arm  43  can easily pass over the upper engagement projection  12   a.    
   Accordingly, during a task for assembling the shell  31  and the housing member  11  together, strong external force does not act on the shell  31  and the housing member  11 . Therefore, the shell  31  and the housing member  11  are neither deformed nor damaged. In addition, a task for assembling the shell  31  and the housing member  11  together can be performed easily and accurately. 
   As shown in  FIG. 14 , the socket  10  is previously mounted on the substrate  51 . The substrate  51  has wiring traces for signals, and the wiring traces are exposed at the upper surface and form connection portions at least at a location where the socket  10  is mounted, or are connected to connection portions such as connection pads exposed at the upper surface. The terminals  21  of the socket  10  can be connected to the connection portions by use of connection means such as soldering. Specifically, the lower surfaces of the tail portions  22  of the terminal  21  are connected to the connection portions by use of connection means such as soldering. Further, the substrate  51  has wiring traces for grounding, and the wiring traces are exposed at the upper surface and form grounding connection portions  51   a  at least at a location where the socket  10  is mounted, or are connected to grounding connection portions  51   a  such as connection pads exposed at the upper surface. The connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  of the socket  10  can be connected to the grounding connection portions  51   a  by use of connection means such as soldering. Specifically, the lower end surfaces of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  are connected to the grounding connection portions  51   a  by use of connection means such as soldering. 
   For example, in the case where the socket  10  is mounted to the substrate  51  by using soldering as a connection means, solder in the form of paste is applied to the upper surfaces of the connection portions and the grounding connection portions  51   a  exposed at the upper surface of the substrate  51 , and is subjected to reflow, whereby soldering is performed. In this case, the socket  10  is placed on the substrate  51  in such a manner that the tail portions  22  of the corresponding terminals  21 , the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  are located on the connection portions and the grounding connection portions  51  a, to which soldering has been applied. In a state in which the socket  10  is placed on the substrate  51 , the solder is heated by use of heating means such as a heating furnace and is caused to reflow, whereby soldering is performed. In the socket  10  according to the present embodiment, as described above, the shell  31  can move vertically with respect to the housing member  11  by a predetermined distance. Thus, when the socket  10  is placed on the substrate  51 , the vertical positions of the lower surfaces of the tail portions  22  of the terminals  21 , as well as the vertical positions of the lower end surfaces of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34 , are automatically adjusted individually. Therefore, even when the solder applied to the connection portions and the grounding connection portions  51   a  exposed at the upper surface of the substrate  51  is thin (e.g., approximately 0.1 mm), the lower surfaces of the tail portions  22  of all the terminals  21 , as well as the lower end surfaces of the vertical positions of the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34 , reliably come into contact with the solder applied to the corresponding connection portions and the grounding connection portions  51   a , whereby the lower surface and lower end surfaces are reliably soldered to the corresponding connection portions and the grounding connection portions  51   a.    
   Notably, before mounting of the module  53 , as shown in  FIG. 14 , the free ends of the connection arm portions  23  of the terminals  21  greatly project upward from the upper surface of the housing member  11 . Further, the curved portions of the grinding spring portions  41  and the locking spring portions  45  greatly project inward from the inner wall surface of the shell  31 . The module  53  is inserted into the shell  31  from the above, and thus is mounted to the socket  10 , as shown in  FIGS. 15 to 18 . The module  53  has the upper surface  54 , the side surface  55 , and the bottom surface  56 , and a metal coating layer is formed on the upper surface  54  and the side surface  55  by means of, for example, plating. Further, predetermined signal wiring traces are exposed at the bottom surface  56  and are connected to the connection arm portions  23  of the corresponding terminals  21 . 
   Since the inclined portion  36  is formed at the upper end of the shell  31  to thereby increase the cross sectional area of the shell  31  upward at the upper end thereof, the module  53  can be easily inserted into the shell  31 . Further, an unillustrated polarity key  58  is formed on the side surface  55  of the module  53  such that its projects outward. Therefore, the module  53  is inserted into the shell  31  from above in such a manner that the polarity key  58  is fitted into the engagement slot  47  of the shell  31 . Notably, since the upper end portion of the engagement slot  47  is opened upward, the polarity key  58  of the module  53  can be easily inserted into the engagement slot  47  from the above. In this manner, the module  53  is attached to the socket  10  in a predetermined orientation, and the predetermined signal wiring traces exposed at the bottom surface  56  of the module  53  are connected to the connection arm portions  23  of the corresponding terminals  21 . 
   When the module  53  is inserted into the shell  31 , the side surface  55  of the module  53  moves while being contact with the curved portions of the grounding spring portions  41  and the locking spring portions  45 . In this case, the curved portions are pushed outward by the side surface  55  of the module  53  to positions near the inner wall surface of the shell  31 . When the state shown in  FIGS. 15 to 18  is established after completion of the mounting of the module  53 , the covered portions (free ends) of the locking spring portions  45  enter the engagement recesses  57  of the module  53  and come into engagement with the engagement recesses  57 . Notably, the curved portions of the grounding spring portions  41  are pressed by the side surface  55  of the module  53 . In this case, by virtue of the spring function of each grounding spring portion  41 , electrical connection is secured between the curved portions and the metal coating layer formed on the side surface  55 . 
   In a state in which the module  53  has been mounted, since the terminals  21  are pressed by the bottom surface  56  of the module  53 , the terminals  21  elastically deform into a shape as shown in  FIG. 16 . Therefore, by virtue of the spring function of each terminal  21 , electrical connection is secured between the contact portions  23   a  of the connection arm portions  23  and the signal wiring traces on the bottom surface  56  of the module  53 . Moreover, although the module  53  receives an upward pushing force because of the spring function of each terminal  21 , upward movement of the module  53  is restricted because the curved portions of the locking spring portions  45  are in engagement with the engagement recesses  57 . In this manner, the module  53  is elastically held while being sandwiched from the upper and lower sides thereof by the terminals  21  and the locking spring portions  45 . Therefore, the module  53  does not play in the vertical direction. 
   Moreover, since the module  53  is elastically held while being sandwiched from the four sides thereof by the spring functions of the locking spring portions  45  and the grounding spring portions  41 . Therefore, the module  53  does not play in the lateral or horizontal direction. 
   As described above, the socket  10  according to the present embodiment includes the housing member  11 , which is formed of an insulating material and has no side wall, and the shell  31 , which is formed from a single metal plate and is attached to the housing member  11  so as to surround at least a portion of the side wall  55  of the module  53  over the entire circumference, to thereby elastically hold the accommodated module  53 . 
   Since a cover for preventing the module  53  from coming off becomes unnecessary, the number of parts can be reduced, and the number of steps of mounting the module  53  decreases, whereby mounting costs can be reduced. Further, a side wall formed of an insulating material is not provided, and the module  53  is surrounded by the shell  31  formed from a metal plate. Therefore, the external dimensions of the socket  10  can be reduced, and the occupying area on the substrate  51  can be reduced. Moreover, since the shell  31  is formed from a single metal plate, and is not composed of a plurality of members, it is possible to prevent deterioration in the dimensional accuracy of the shell  31 , which deterioration would otherwise occur due to an unavoidable dimensional error produced at the time of assembly. 
   Further, the shell  31  is attached to the housing member  11  to be movable in the height direction with respect to the housing member  11 . This provides freedom to the vertical positional relationship between the tail portions  22  of the terminals  21  and the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34 . Thus, the tail portions  22  of the terminals  21 , the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  can be reliably connected to the connection portions and the grounding connection portions  51   a  of the substrate  51 . Therefore, the signal wiring traces on the bottom surface  56  of the module  53  are reliably connected to the corresponding connection portions of the substrate  51 , so that the module  53  operates properly. Moreover, since the connection arm support projections  32 , the wide projections  33 , and the narrow projections  34  are reliably connected to the corresponding grounding connection portions  51   a  of the substrate  51 , the shell  31  is reliably grounded and properly functions against static electricity and noise, whereby influences of static electricity and noise can be eliminated completely.