Patent Publication Number: US-2022239024-A1

Title: Electrical connector and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This non-provisional application claims priority to and the benefit of, pursuant to 35 U.S.C. § 119(a), patent application Serial No. CN202110103504.6 filed in China on Jan. 26, 2021. The disclosure of the above application is incorporated herein in its entirety by reference. 
     Some references, which may include patents, patent applications and various publications, are cited and discussed in the description of this disclosure. The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to the disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference were individually incorporated by reference. 
     FIELD 
     The present invention relates to an electrical connector and a method of manufacturing the same, and particularly to an electrical connector electrically connecting a chip module and a circuit board and a method of manufacturing the same. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     To satisfy the high frequency signal transmission requirement of the existing chip module, the pads of the existing chip module are arranged in high density to transmit more signals, that is, the distance between the pads is reduced. With the increasing quantity of the terminals of the LGA electrical connector, the terminal arrangement becomes denser, and the distance between the terminals correspondingly becomes shorter. 
     The Chinese Patent No. 99119994.4 discloses an electrical connector, and the method of manufacturing the same includes the steps of: firstly, a metal strip is integrally punched to form a plurality of terminal blanks and connecting portions located on the same plane with the metal strip, and the terminal rough blanks are mechanically electrically connected together by the connecting portions. Each terminal rough blank includes a pair of wing portions, and the wing portions are provided to extend laterally from a main body portion of each terminal rough blank along opposite directions. Secondly, the insulating body covers an upper surface and a lower surface of the metal strip, and the metal strip is clamped therebetween. The insulating body is provided with a plurality of first openings aligned to the terminal rough blanks and second openings aligned to the connecting portions. Thirdly, an assisting tool is used to act on the terminals and the connecting portions through the first and second openings, such that the free ends of each terminal bend on the upper and lower end surfaces of the insulating body. Finally, the connecting portions are separated from the terminals. 
     However, to achieve a shorter distance between the terminals in the lateral direction, the lengths of the wing portions are limited by the metal strip, such that the length of each wing portion is shorter, which results in bad elasticity of the wing portions, and easily causing ill contact between the wing portions and the pads of the chip module. If the lengths of the wing portions are increased, the distance between the terminals in the lateral direction is increased, which cannot satisfy the design requirement to have a shorter distance between the terminals. 
     Therefore, a heretofore unaddressed need to design a novel electrical connector exists in the art to address the aforementioned deficiencies and inadequacies. 
     SUMMARY 
     In view of the deficiency of the background, the present invention is directed to an electrical connector and a method of manufacturing the same, which may achieve the short distance between the terminals and a long elastic arm of each terminal. 
     To achieve the foregoing objective, the present invention adopts the following technical solutions. 
     An electrical connector is configured to electrically connect a mating component to a circuit board. The electrical connector includes: an insulating body; a plurality of lower terminals and a conductive plate, wherein the insulating body, the lower terminals and the conductive plate are insert-molded; each of the lower terminals has a base portion and a conductive portion integrally connected to the base portion, the conductive portion is exposed downward to the insulating body to abut or be soldered to the circuit board; the lower terminals comprise a plurality of lower signal terminals and a plurality of lower ground terminals, the conductive plate is integrally connected to the lower ground terminals, and the conductive plate is separated from the lower signal terminals; and a plurality of upper terminals arranged in a plurality of columns in a left-right direction and arranged in a plurality of rows in a front-rear direction, wherein the upper terminals comprise a plurality of upper signal terminals and a plurality of upper ground terminals; each of the upper terminals and each of the lower terminals are formed separately, each of the upper terminals has a fixing portion and an elastic arm integrally connected to the fixing portion, the fixing portion is located above the base portion and is fixed to the base portion, the elastic arm has a contact portion configured to abut the mating component, the contact portion is located in front of the fixing portion and is higher than the fixing portion; wherein a metal sheet exists between two adjacent ones of the fixing portions of the upper terminals in the left-right direction, the upper signal terminals are separated from the metal sheet, the metal sheet is integrally connected with the upper ground terminals adjacent thereto in the left-right direction and is separated from the upper ground terminals adjacent thereto in the front-rear direction, the metal sheet is located above the conductive plate and is fixed to the conductive plate, and a portion of the elastic arm is located right above the upper terminal or the metal sheet adjacent thereto in the front-rear direction. 
     In certain embodiments, the portion of the elastic arm is located right above the upper terminal adjacent thereto in the front-rear direction, and the elastic arm passes forward beyond the metal sheet. 
     In certain embodiments, a front end of the elastic arm is located right above the fixing portion of another one of the upper terminals. 
     In certain embodiments, a through slot exists between the conductive plate and the base portion, each of a left side and a right side of the fixing portion of each of the upper signal terminals is provided with a cutting surface, and the cutting surface is exposed to the through slot. 
     In certain embodiments, each of a left side and a right side of the base portion of each of the lower signal terminals is provided with a breaking surface, and the breaking surface and the corresponding cutting surface are located on a same vertical plane. 
     In certain embodiments, the insulating body has a plurality of accommodating slots running vertically therethrough, the base portion has a first portion accommodated in a corresponding one of the accommodating slots, the first portion and a portion of the conductive plate surroundingly provided outside the first portion are exposed to the corresponding one of the accommodating slots, and the fixing portion is fixed to the first portion. 
     In certain embodiments, the first portion is provided horizontally, the fixing portion is fixed to the first portion by laser soldering, the base portion has a second portion extending horizontally forward from a front end of the first portion and then bending downward and extending, the second portion is fixed by the insulating body, the conductive portion is formed by extending downward from the second portion, a rear end of the first portion passes backward beyond a rear end of the corresponding fixing portion, and the front end of the first portion passes forward beyond a front end of the corresponding fixing portion. 
     A method of manufacturing an electrical connector is provided. The electrical connector is configured to electrically connect a first mating component and a second mating component. The method includes: step 1: providing a lower metal plate, and cutting the lower metal plate to form a plurality of lower terminals, wherein each of the lower terminals has a base portion and a conductive portion integrally connected to the base portion, the conductive portion is configured to be electrically connected to the circuit board, a remaining portion of the lower metal plate after forming the lower terminals is defined as a conductive plate, and the conductive plate has a plurality of connecting portions integrally connected to the base portions of the lower terminals; step 2: forming an insulating body on the lower terminals and the conductive plate by insert-molding, wherein a portion of the base portion is covered by the insulating body, and the conductive portion is exposed downward to the insulating body; step 3: providing a plurality of upper metal plates, wherein each of the upper metal plates comprises a plurality of upper terminals provided in a row in a left-right direction and a plurality of metal sheets integrally connected to the upper terminals, each of the upper terminals comprises a fixing portion and an elastic arm integrally connected to the fixing portion and bending upward, the elastic arm has a contact portion configured to abut the mating component, the contact portion is located in front of the fixing portion and is higher than the fixing portion, the upper terminals comprise a plurality of upper signal terminals; the upper metal plates are fixed to the lower metal plate and are provided at intervals in a front-rear direction, such that of two of the upper metal plates in the front-rear direction, a portion of the elastic arm of the upper metal plate located therebehind overlaps with the upper metal plate located in front thereof viewing along a vertical direction, the fixing portion is located above the base portion and is fixed to the base portion, and the metal sheets are located above the conductive plate and are fixed to the conductive plate; and step 4: cutting the upper signal terminals, such that the upper signal terminals are separated from the metal sheets. 
     In certain embodiments, in the step 3, the portion of the elastic arm is located right above the metal sheet adjacent thereto in the front-rear direction, and the elastic arm passes forward beyond the metal sheet adjacent thereto in the front-rear direction. 
     In certain embodiments, the lower terminals comprise a plurality of lower signal terminals; and after the step 3, the connecting portions connected to the lower signal terminals are cut, such that the lower signal terminals are separated from the conductive plate. 
     In certain embodiments, a breaking position of each of the lower signal terminals and a corresponding one of the connecting portions and a breaking position of each of the upper signal terminals and a corresponding one of the metal sheets in the step 4 are located on a same vertical plane. 
     In certain embodiments, when the lower terminals are cut in the step 1, a through slot is formed between the conductive plate and the base portion, and a breaking position of each of the upper signal terminals and a corresponding one of the metal sheets in the step 4 is exposed to the through slot. 
     Compared with the related art, the electrical connector and the method of manufacturing the same according to certain embodiments of the present invention has the following beneficial effects. 
     The upper terminals are formed on the upper metal plates (and not a single metal plate), so the length of the elastic arm located therebehind is not limited by the metal sheet or the upper terminal located in front thereof. In addition, the terminals are formed by upper terminals and lower terminals, thus achieving a short distance between the terminals and a long elastic arm of each terminal. Further, the insulating body is insert-molded with the lower metal plate, and then the upper metal plates are fixed to the lower metal plate, thereby implementing a simple and fast mounting process of the upper terminals and the lower terminals. 
     These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be effected without departing from the spirit and scope of the novel concepts of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate one or more embodiments of the disclosure and together with the written description, serve to explain the principles of the disclosure. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein: 
         FIG. 1  is a perspective sectional view of a step 1 of a method of manufacturing an electrical connector according to certain embodiments of the present invention. 
         FIG. 2  is a perspective sectional view of a step 2 of a method of manufacturing an electrical connector according to certain embodiments of the present invention. 
         FIG. 3  is a perspective sectional view of a step 3 of a method of manufacturing an electrical connector according to certain embodiments of the present invention. 
         FIG. 4  is a perspective view of a step 3 of a method of manufacturing an electrical connector according to certain embodiments of the present invention. 
         FIG. 5  is a top view of  FIG. 4 . 
         FIG. 6  is a bottom view of  FIG. 4 . 
         FIG. 7  is a partial enlarged view of a portion A in  FIG. 5 . 
         FIG. 8  is a sectional view of the electrical connector of  FIG. 5  sectioned along a line B-B and mated with a mating component and a circuit board. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like components throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. Moreover, titles or subtitles may be used in the specification for the convenience of a reader, which shall have no influence on the scope of the present invention. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower”, can therefore, encompasses both an orientation of “lower” and “upper,” depending of the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     As used herein, “around”, “about” or “approximately” shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around”, “about” or “approximately” can be inferred if not expressly stated. 
     As used herein, the terms “comprising”, “including”, “carrying”, “having”, “containing”, “involving”, and the like are to be understood to be open-ended, i.e., to mean including but not limited to. 
     The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings in  FIGS. 1-8 . In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to an electrical connector and a method of manufacturing the same. 
       FIG. 1  to  FIG. 8  shows an electrical connector  100  according to certain embodiments of the present invention, in which a forward direction in a front-rear direction is defined as a positive direction of the X-axis, a leftward direction in a left-right direction is defined as a positive direction of the Y-axis, and an upward direction in a vertical direction is defined as a positive direction of the Z-axis. 
     As shown in  FIG. 3 ,  FIG. 4  and  FIG. 8 , the electrical connector  100  is used to electrically connect a mating component  200  to a circuit board. The electrical connector  100  includes a lower metal plate  1 , an insulating body  2 , and a plurality of upper metal plates  3  located above the lower metal plate  1  and fixed to the lower metal plate  1 . The lower metal plate  1  and the insulating body  2  are insert-molded. In this embodiment, the mating component  200  is a chip module. In other embodiments, the mating component  200  may be other components. 
     As shown in  FIG. 1 ,  FIG. 6  and  FIG. 7 , the lower metal plate  1  includes a plurality of lower terminals  11  and a conductive plate  12 , and a remaining portion of the lower metal plate  1  after forming the lower terminals  11  is defined as the conductive plate  12 . The conductive plate  12  surrounds outside each of the upper terminals  31 . The lower terminals  11  are arranged in a plurality of columns in the left-right direction and in a plurality of rows in the front-rear direction. Each lower terminal  11  has a base portion  111  and a conductive portion  112  integrally connected to the base portion  111 . A through slot  13  is formed between the base portion  111  and the conductive plate  12 . The base portion  111  includes a first portion  1111  provided horizontally and a second portion  1112  extending horizontally forward from a front end of the first portion  1111  and then bending downward and extending. The conductive portion  112  is formed by extending downward from the second portion  1112 , and the conductive portion  112  and the first portion  1111  are perpendicular from each other. The lower terminals  11  include a plurality of lower signal terminals  11 S and a plurality of lower ground terminals  11 G. The conductive plate  12  is provided with a plurality of connecting portions  121 . Each connecting portion  121  is located at a front side of a corresponding through slot  13 , and the conductive portion  112  is located in front of a corresponding connecting portion  121 . The connecting portions  121  are integrally connected to the base portions  111  of the lower ground terminals  11 G, but the connecting portions  121  are provided to be separated from the lower signal terminals  11 S, thereby forming two breaking surfaces  111 S at a left side and a right side of the base portion  111  of each lower signal terminal  11 S. Each breaking surface  111 S is formed by extending along the front-rear direction. 
     As shown in  FIG. 2 ,  FIG. 6  and  FIG. 7 , the insulating body  2  includes a plurality of accommodating slots  21  running vertically therethrough, and the first portion  1111  is accommodated in a corresponding accommodating slot  21 . The first portion  1111  and a portion of the conductive plate  12  surroundingly provided outside the first portion  1111  are exposed downward to the corresponding accommodating slot  21 . The second portion  1112  is fixed by the insulating body  2 . The conductive portion  112  located therebehind is provided to correspond to an accommodating slot  21  located in front thereof in the left-right direction. The conductive portion  112  is exposed downward to the insulating body  2  to be soldered to the circuit board  300 . (In other embodiments, the conductive portion may abut the circuit board  300 .) The insulating body  2  further includes a plurality of position limiting portions  22  and a plurality of positioning portions  24 . The position limiting portions  22  and the positioning portions  24  are provided to align along the front-rear direction. Along the left-right direction, a left side and a right side of each positioning portion  24  are integrally connected to corresponding position limiting portions  22  respectively, and the position limiting portions  22  and the positioning portions  24  are alternately provided in the left-right direction. A stopping portion  23  is integrally connected to each position limiting portion  22 . The positioning portions  24  and the position limiting portions  22  all press downward on the conductive plate  12 . The connecting portions  121  are exposed upward to the insulating body  2 , allowing the lower signal terminals  11 S to break from the conductive plate  12 . 
     As shown in  FIG. 4 ,  FIG. 7  and  FIG. 8 , the upper metal plates  3  are provided at intervals in the front-rear direction. Each upper metal plate  3  includes a plurality of upper terminals  31  provided in a row along the left-right direction and a plurality of metal sheets  32 , and each upper terminal  31  is located between two metal sheets  32 . Each upper terminal  31  includes a fixing portion  311  and an elastic arm  312  integrally connected to the fixing portion  311 . In this embodiment, two rows of the upper terminals  31  adjacent in the front-rear direction are provided to be staggered, and a portion of the elastic arm  312  is located right above the metal sheet  32  adjacent thereto in the front-rear direction. (In other embodiments, the two rows of the upper terminals  31  adjacent in the front-rear direction may be provided to align, and portion of the elastic arm  312  is located right above the upper terminal  31  adjacent thereto in the front-rear direction.) The elastic arm  312  passes forward the metal sheet  32  in front of the fixing portion  311  connected to the elastic arm  312 , and a front end of the elastic arm  312  is located right above the fixing portion  311  of another upper terminal  31 . The elastic arm  312  has a contact portion  3121 . The contact portion  3121  is exposed upward to the insulating body  2  to abut the mating component  200 . The contact portion  3121  is located in front of the fixing portion  311  and is higher than the fixing portion  311 . The fixing portion  311  is located above the first portion  1111  and is fixed to the first portion  1111  by laser soldering. (In other embodiments, the fixing portion  311  may be fixed to the first portion  1111  by other methods.) A rear end of the first portion  1111  passes backward beyond a rear end of the corresponding fixing portion  311 , and the front end of the first portion  1111  passes forward beyond a front end of the corresponding fixing portion  311 . The metal sheet  32  is located above the conductive plate  12  and is soldered to the conductive plate  12  by laser. (In other embodiments, the metal sheet  32  may be fixed to the conductive plate  12  by other methods.) The elastic arm  312  is located below the stopping portion  23 . The stopping portion  23  is used to suppress the elastic arm  312  from excessively moving downward. The position limiting portions  22  are respectively located at the left side and the right side of the elastic arm  312  to suppress the elastic arm  312  to excessively deviate in the left-right direction. The positioning portions  24  press on the conductive plate  12 . 
     As shown in  FIG. 1 ,  FIG. 5  and  FIG. 7 , the upper terminals  31  include a plurality of upper signal terminals  31 S and a plurality of upper ground terminals  31 G. The upper ground terminals  31 G are integrally connected with the metal sheets  32 . The upper signal terminals  31 S are provided to be separated from the metal sheets  32 , thereby forming two cutting surfaces  311 S at a left side and a right side of the fixing portion  311  of each upper signal terminal  31 S. The two cutting surfaces  311 S are exposed to the through slot  13  and are located behind the corresponding breaking surfaces  111 S. Further referring to  FIG. 6 , each breaking surface  111 S and a corresponding cutting surface  311 S are located on a same vertical plane. 
     The method of manufacturing the electrical connector  100  according to certain embodiments of the present invention includes the following steps: 
     As shown in  FIG. 1 , step 1: providing the lower metal plate  1 , and cutting the lower metal plate  1  to form a plurality of lower terminals  11 . The lower terminals  11  include a plurality of lower signal terminals  11 S and a plurality of lower ground terminals  11 G. Each lower terminal  11  has a base portion  111  and a conductive portion  112  integrally connected to the base portion  111 , and the conductive portion  112  is used to be electrically connected to the circuit board  300 . A remaining portion of the lower metal plate  1  after forming the lower terminals  11  is defined as the conductive plate  12 . A through slot  13  is formed between the conductive plate  12  and the base portion  111 . The conductive plate  12  has a plurality of connecting portions  121  integrally connected to the base portions  111  of the lower terminals  11 . 
     As shown in  FIG. 2 , step 2: fixing the lower metal plate  1  in a mold cavity of the mold, and after the mold is clamped, injecting plastic to form the insulating body  2  on the lower terminals  11  and the conductive plate  12 . A portion of the base portion  111  is covered by the insulating body  2 . The connecting portions  121  are exposed upward to the insulating body  2 . The portions of the first portion  111  and the conductive plate  12  surrounding outside the first portion  1111  and the conductive portion  112  are exposed downward to the insulating body  2 . 
     As shown in  FIG. 3 , step 3: providing a plurality of upper metal plates  3 . Each upper metal plate includes a plurality of upper terminals  31  provided in a row in the left-right direction and a plurality of metal sheets  32  integrally connected to the upper terminals  31 . Each upper terminal  32  includes a fixing portion  311  and an elastic arm  312  integrally connected to the fixing portion  311  and bending upward. A strip  33  is integrally connected the rear ends of the fixing portions  311  of the upper terminals  32  in a row, and the row of the upper terminals  32  are disposed on the corresponding lower terminals  11  by the strip  33 . Then, the upper metal plates  3  are fixed to the lower metal plate  1  by laser soldering and are provided at intervals in the front-rear direction, such that the metal sheets  32  are located above the conductive plate  12  and are fixed to the conductive plate  12 . Of two upper metal plates  3  in the front-rear direction, a portion of the elastic arm  312  of the upper metal plate  3  located therebehind overlaps with the upper metal plate  3  located in front thereof viewing along a vertical direction. Then, the strip  33  is broken from the fixing portions  311  to remove the strip  33 . 
     As shown in  FIG. 4  and  FIG. 7 , step 4: cutting the connecting portions  121  connected to the lower signal terminals  11 S, such that the lower signal terminals  11 S are separated from the conductive plate  12 . The upper terminals  31  include a plurality of upper signal terminals  31 S and a plurality of upper ground terminals  31 G. Cutting the upper signal terminals  31 S, such that the upper signal terminals  31 S and separated from the metal sheets  32 . At this time, a breaking position of each upper signal terminal  31 S and a corresponding metal sheet  32  and a breaking position of each lower signal terminal  11 S and the corresponding connecting portion  121  are located on a same vertical plane. The breaking position of each upper signal terminal  31 S and the corresponding metal sheet  32  is exposed to the through slot  13 . In other embodiments, it is possible to cut the connecting portions  121  connected to the lower signal terminals  11 S after the step 2 and prior to the step 3, such that the lower signal terminals  11 S are separated from the conductive plate  12 ; and in the step 4, it is possible that the breaking position of each upper signal terminal  31 S and a corresponding metal sheet  32  and the breaking position of each lower signal terminal  11 S and the corresponding connecting portion  121  are not located on the same vertical plane. 
     In sum, the electrical connector and the method of manufacturing the same according to certain embodiments of the present invention have the following beneficial effects: 
     (1) The upper terminals  31  are formed on the upper metal plates  3  (and not a single metal plate  3 ), so the length of the elastic arm  312  located therebehind is not limited by the metal sheet  32  or the upper terminal  31  located in front thereof. In addition, the terminals are formed by separate upper terminals  31  and lower terminals  11 , thus achieving a short distance between the terminals and a long elastic arm  312  of each terminal. Further, the insulating body  2  is insert-molded with one lower metal plate  1 , and then the upper metal plates  3  are fixed to the lower metal plate  1 , thereby implementing a simple and fast mounting process of the upper terminals  31  and the lower terminals  11 . 
     (2) Each of the left side and the right side of the fixing portion  311  of each upper signal terminal  31 S is provided with the cutting surface  311 S, and the cutting surface  311 S is exposed to the through slot  13 , thus ensuring the lower metal plate  1  not to block cutting the upper signal terminals  31 S. 
     (3) Each breaking surface  111 S and the corresponding cutting surface  311 S are located on a same vertical plane, which is convenient for performing laser cutting and has a simple process. 
     (4) The first portion  1111  and a portion of the conductive plate  12  surroundingly provided outside the first portion  1111  are exposed to the corresponding accommodating slot  21 , and the fixing portion  311  is fixed to the first portion  1111 , thus preventing the plastic in the process of insert-molding the lower signal terminals  11 S and the conductive plate  12  with the insulating body  2  to flow into the upper surface of the first portion  1111  and affect the soldering of the fixing portion  311  to the first portion  1111 . 
     (5) The rear end of the first portion  1111  passes backward beyond the rear end of the corresponding fixing portion  311 , and the front end of the first portion  1111  passes forward beyond the front end of the corresponding fixing portion  311 , thus providing sufficient area and flatness for the soldering of the fixing portion  311  to the first portion, allowing the soldering to be easily performed, and preventing from the insufficient soldering effect. 
     The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. 
     The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.