Patent Publication Number: US-2015064941-A1

Title: Ic socket and connection terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-179689, filed on Aug. 30, 2013, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein relate to an IC socket and a connection terminal. 
     BACKGROUND 
     Semiconductor devices (large scale integrations: LSIs) used in computers and so forth are often mounted on wiring boards via IC sockets. 
     However, the development of information devices such as computers in recent years has been remarkable, and the transmission speed of signals transmitted between wiring boards and LSIs has increased considerably. In the future, when a further increase in the speed of signals is achieved, signal waveform disturbance due to stubs will become a problem. 
     Japanese Unexamined Utility Model Registration Application Publication No. 03-130172 and Japanese Laid-open Patent Publication No. 2008-41930 are examples of related art. 
     SUMMARY 
     According to an aspect of the embodiments, an IC socket includes: a socket main body having a flat plate section in which a plurality of through holes are provided; and a first connection terminal and a second connection terminal that are provided with the through holes of the socket main body, and protrude from an upper side and a lower side of the flat plate section, wherein a capacitor is provided within the first connection terminal. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic drawing depicting an example of a method for mounting a semiconductor device (LSI) on a wiring board; 
         FIG. 2  is a schematic drawing in which the portion indicated by reference numeral II in  FIG. 1  is enlarged and depicted; 
         FIG. 3A  is a schematic drawing of an IC socket according to an embodiment, and  FIG. 3B  is likewise a top view of that IC socket; 
         FIG. 4  is a schematic drawing depicting a method for mounting a semiconductor device on a wiring board in which an IC socket according to an embodiment is used; 
         FIG. 5A  is a longitudinal sectional view of a conductive column, and  FIG. 5B  is a longitudinal sectional view of a capacitor built-in column; 
         FIG. 6  is an assembly view of a capacitor built-in column; and 
         FIGS. 7A and 7B  are schematic drawings depicting the relationship between the length of a chip capacitor in a capacitor built-in column and the thickness of a wiring board. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, preliminary matters for facilitating understanding of the embodiment are described prior to describing an embodiment. 
       FIG. 1  is a schematic drawing depicting an example of a method for mounting a semiconductor device (LSI) on a wiring board, and  FIG. 2  is a schematic drawing in which the portion indicated by reference numeral II in  FIG. 1  is enlarged and depicted. 
     An IC socket  12  is mounted on a wiring board  11 , and a semiconductor device  13  is arranged on the IC socket  12 . A large number of contact pins  18  are arranged in the IC socket  12 , and electrodes  20  of the semiconductor device  13  and electrodes  21  of the wiring board  11  are electrically connected via those contact pins  18 . 
     The semiconductor device  13  generates heat when operating. Therefore, cooling fins  15  that radiate heat generated by the semiconductor device  13  into air are arranged on the semiconductor device  13 . 
     A reinforcing plate (bolster plate)  16  is arranged below the wiring board  11 , and the cooling fins  15  and the reinforcing plate  16  are linked by pressure screws  17 . When the pressure screws  17  are turned in the tightening direction, the distance between the cooling fins  15  and the reinforcing plate  16  reduces, and the adhesion between the cooling fins  15  and the semiconductor device  13  is ensured, and also the adhesion between the semiconductor device  13  and the contact pins  18  is ensured. 
     Furthermore, in the example depicted in  FIG. 1 , coupling capacitors  14  are mounted around the periphery of the reinforcing plate  16  on the rear surface side of the wiring board  11 . These coupling capacitors  14  are connected to the electrodes  21  and the contact pins  18  via internal wiring  25  of the wiring board  11 , and vias  26  that pass through the wiring board  11  in the vertical direction. 
     Incidentally, the portions of the vias  26  provided in the wiring board  11  that branch from the signal transmission path (indicated by the arrow mark in  FIG. 2 ) are referred to as stubs. The portions indicated by reference numeral  27  in  FIG. 2  are stubs. 
     The stubs are not a problem when the signal transmission speed is low. However, when the signal transmission speed increases to 15 Gbps to 20 Gbps for example, signals reflected by the stubs interfere with signals passing along the signal transmission path and waveform disturbance occurs, which causes electronic devices to malfunction. 
     It is possible to avoid the signal waveform disturbance caused by the stubs by removing the portions constituting the stubs by drilling for example. However, in that case complex steps such as drilling are desired, which leads to a rise in manufacturing costs. 
     In the following embodiment, a description is given with regard to an IC socket in which capacitors are built in, and with which it is possible to avoid signal waveform disturbance caused by stubs. 
     Embodiment 
       FIG. 3A  is a schematic drawing of an IC socket according to an embodiment, and  FIG. 3B  is likewise a top view of that IC socket. Furthermore,  FIG. 4  is a schematic drawing depicting a method for mounting a semiconductor device on a wiring board in which an IC socket according to the embodiment is used. In the present embodiment, a description is given with regard to an example in which an IC socket that connects a semiconductor device (LSI) of a land grid array (LGA) package and a wiring board is applied. 
     An IC socket  30  according to the present embodiment includes, as depicted in  FIG. 3A  and  FIG. 3B , a socket main body  31 , capacitor built-in columns  32 , and conductive columns  33 . The capacitor built-in columns  32  are examples of a first connection terminal, and the conductive columns  33  are examples of a second connection terminal. 
     The socket main body  31  is formed from an insulating resin or the like, and includes a flat plate section  34  that has a size corresponding to a semiconductor device  46 , and an edge section  35  that is provided around the periphery of the flat plate section  34  and protrudes upwards and downwards. 
     A plurality of through holes are provided in the flat plate section  34  at locations in alignment with electrodes  40  of the semiconductor device  46 , and the capacitor built-in columns  32  and the conductive columns  33  are fitted into those through holes. Both end sections of both the capacitor built-in columns  32  and the conductive columns  33  protrude from the upper side and the lower side of the flat plate section  34 . 
     The semiconductor device  46  is arranged on the IC socket  30  as depicted in  FIG. 4 , and the electrodes  40  of the semiconductor device  46  and electrodes  41  of a wiring board  45  are electrically connected via the capacitor built-in columns  32  or the conductive columns  33 . 
     Furthermore, cooling fins  47  are arranged on the semiconductor device  46  with heat radiating grease  43  (and/or a thermal conduction sheet) therebetween. These cooling fins  47  are formed from copper or a metal having satisfactory thermal conductivity such as aluminum. A reinforcing plate  48  is arranged below the wiring board  45 , and the cooling fins  47  and the reinforcing plate  48  are linked by pressure screws  49 . 
     The lower surface of the edge section  35  of the IC socket  30  comes into contact with the wiring board  45 , and a gap is formed between the wiring board  45  and the flat plate section  34  of the IC socket  30  in which protruding sections (head sections  32   a  and  33   a  described hereafter) of the capacitor built-in columns  32  and the conductive columns  33  are arranged. 
       FIG. 5A  is a longitudinal sectional view of a conductive column  33 , and  FIG. 5B  is a longitudinal sectional view of a capacitor built-in column  32 . 
     As depicted in  FIG. 5A , the conductive column  33  includes a pair of truncated conical head sections  33   a  arranged in a vertically symmetrical manner, and a cylindrical body section  33   b  connecting those head sections  33   a . Furthermore, the head sections  33   a  and the body section  33   b  are integrally formed from a conductive rubber. The length La of the conductive column  33  is approximately 2 mm for example, and the length Lb of the body section  33   b  is approximately 0.4 mm for example. 
     The diameter of the body section  33   b  is set to be approximately the same as the diameter of the through holes provided in the flat plate section  34  of the socket main body  31 . Furthermore, the diameter of the base end side (body section  33   b  side) of the head sections  33   a  is set to be slightly larger than the diameter of the through holes provided in the flat plate section  34 , and the diameter of the tip end side of the head sections  33   a  is set to be slightly smaller than the diameter of the through holes provided in the flat plate section  34 . 
     As depicted in  FIG. 5B , the capacitor built-in column  32  also includes a pair of head sections  32   a  arranged in a vertically symmetrical manner, and a body section  32   b  connecting those head sections  32   a.  The external shape and size of the capacitor built-in column  32  is the same as the conductive column  33 ; however, a chip capacitor  36  is arranged in the capacitor built-in column  32 . 
     The head sections  32   a  of the capacitor built-in column  32  are formed from a conductive rubber. One head section  32   a  is connected to one electrode  37  of the chip capacitor  36 , and the other head section  32   a  is connected to the other electrode  37  of the chip capacitor  36 . 
     Furthermore, the body section  32   b  is formed from an insulating rubber. The pair of head sections  32   a  are electrically separated by this body section  32   b.    
     Moreover, the conductive rubber is an example of a resin having elasticity and conductivity. Furthermore, one head section from among the pair of head sections  32   a  is a first head section, and the other head section is a second head section. 
       FIG. 6  is an assembly view of a capacitor built-in column  32 . As depicted in  FIG. 6 , it is possible for a capacitor built-in column  32  to be produced by individually manufacturing the head sections  32   a  and the body section  32   b , and attaching those head sections  32   a  and the body section  32   b  to the chip capacitor  36 . 
     A capacitor built-in column  32  may be produced by insert-molding the body section  32   b  after the head sections  32   a  have been attached to the chip capacitor  36 . 
     Moreover, with regard to the conductive rubber that forms the head sections  32   a  of the capacitor built-in columns  32  and the conductive columns  33 , it is possible to use a rubber obtained by, for example, mixing a carbon or silver (Ag) filler with a natural rubber or a synthetic rubber and imparting conductivity thereto. 
     Furthermore, it is preferable to coat the electrodes  37  of the chip capacitor  36  with a metal such as silver (Ag) or gold (Au) in order to avoid oxidation due to contact with the head sections  32   a  and so forth formed from a conductive rubber. 
     In addition, in order for it to be easy to visually distinguish between the capacitor built-in columns  32  and the conductive columns  33 , the color of the head sections  32   a  of the capacitor built-in columns  32  may be a color that is different from the head sections  33   a  of the conductive columns  33 . 
     Hereafter, with reference to  FIG. 4 , a description is given with respect to a method for mounting the semiconductor device  46  on the wiring board  45  by using the IC socket  30  according to the aforementioned embodiment. 
     First, the capacitor built-in columns  32  and the conductive columns  33  are attached in the through holes provided in the flat plate section  34  of the IC socket  30 . At such time, the capacitor built-in columns  32  are attached in places where high-frequency signals pass, and the conductive columns  33  are attached in places where low-frequency signals pass and places that are power source lines. 
     Since both the capacitor built-in columns  32  and the conductive columns  33  are formed from elastic bodies (rubber), when the head sections  32   a  and  33   a  are pushed into the through holes of the IC socket  30 , the head sections  32   a  and  33   a  elastically deform and pass through the through holes. The head sections  32   a  and  33   a  then protrude from the upper side and the lower side of the IC socket  30 . 
     Next, the IC socket  30  is attached at a predetermined location on the wiring board  45 . Thereafter, the semiconductor device  46  is arranged on the IC socket  30 . 
     Next, after the heat radiating grease  43  has been applied onto the semiconductor device  46 , the cooling fins  47  are arranged on the semiconductor device  46  with the heat radiating grease  43  therebetween. The reinforcing plate  48  is then arranged at the lower side of the wiring board  45 , and the cooling fins  47  and the reinforcing plate  48  are linked by the pressure screws  49 . 
     Thereafter, the pressure screws  49  are turned in the tightening direction, and the adhesion between the cooling fins  47  and the semiconductor device  46  is ensured, and also the adhesion between the semiconductor device  46  and the capacitor built-in columns  32  and conductive columns  33  is ensured. 
     In this way, the mounting of the semiconductor device  46  on the wiring board  45  is completed. 
     As described above, in the IC socket  30  according to the present embodiment, the capacitor built-in columns  32  are attached in places where high-frequency signals pass, and the conductive columns  33  are attached in other places. It is possible for the chip capacitors  36  provided within the capacitor built-in columns  32  to be used as coupling capacitors or decoupling capacitors for example. 
     If the chip capacitors  36  provided within the capacitor built-in columns  32  are used as coupling capacitors or decoupling capacitors, coupling capacitors or decoupling capacitors no longer have to be mounted on the wiring board  45 . Thus, it is possible to simplify the signal transmission paths of the wiring board  45 , and to remove the wiring constituting the stubs. As a result, an effect is demonstrated in that signal waveform disturbance caused by stubs is avoided, and malfunctions of electronic devices are avoided. 
     Furthermore, since it is possible for the number of capacitors mounted on the wiring board  45  to be reduced by using the IC socket  30  according to the present embodiment, there is also an advantage in that the design of the wiring pattern for the wiring board  45  becomes simpler. 
     Moreover, since the shape and size of the capacitor built-in columns  32  and the conductive columns  33  are the same in the IC socket  30  according to the present embodiment, it is possible to alter the number and arrangement of the capacitor built-in columns  32  and the conductive columns  33  in accordance with the semiconductor device  46  used. 
     Incidentally, in the example depicted in  FIG. 7A , the length L of the chip capacitor  36  within the capacitor built-in column  32  is greater than the thickness D of the wiring board  45 , and the upper end and the lower end of the chip capacitor  36  are positioned above or below the upper surface and the lower surface of the wiring board  45 . When the upper end and the lower end of the chip capacitor  36  protrude from the upper surface and the lower surface of the wiring board  45  in this manner, the apparent elasticity of the head sections  32   a  of the capacitor built-in column  32  is lower than the apparent elasticity of the head sections  33   a  of the conductive column  33 . 
     As a result, the contact pressure between the semiconductor device  46  and the conductive columns  33  is less than the contact pressure between the semiconductor device  46  and the capacitor built-in columns  32 , and it is thought that poor contact occurs between the semiconductor device  46  and the conductive columns  33 . 
     In order to avoid this kind of defect, as depicted in  FIG. 7B , it is preferable for the length L of the chip capacitor  36  to be equal to or less than the thickness D of the wiring board  45  (L≦D), such that the chip capacitor  36  does not protrude from the surface of the wiring board  45 . Thus, the elasticity of the head sections  32   a  of the capacitor built-in columns  32  is the same as the elasticity of the head sections  33   a  of the conductive columns  33 . 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.