Patent Publication Number: US-2022224053-A1

Title: Electrical Connector, Connector Assembly and Method For Manufacturing Electrical Connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Chinese Patent Application No. 202110045442.8 filed on Jan. 13, 2021 in the China National Intellectual Property Administration, the whole disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present disclosure relates to an electrical connector, and in particular, to an electrical connector suitable for high-speed signal transmission, a connector assembly, and a method for manufacturing the electrical connector. 
     BACKGROUND 
     In recent years, with the development of digital information technology, data transmission rates have increased rapidly. For example, in the field of communication technology, a high-speed connector is required to achieve high-speed signal transmission of at least 112 Gbps. As an electrical connector is required to connect with different interfaces in data transmission, a signal transmission speed and quality of the electrical connector will greatly affect the speed and stability of the data transmission. In one application, an electrical connector may be used to electrically connect two printed circuit boards (PCBs). 
     Generally, an electrical connector suitable for the high-speed signal transmission mainly includes a base made of an insulation material and a plurality of terminal rows mounted in the base. Grounding terminals and differential signal terminal pairs are alternately arranged in each terminal row. Further, in adjacent terminal rows, the grounding terminal is positioned to correspond to the differential signal terminal pair so that a separate grounding shield is formed for each of the differential signal terminal pairs. In such electrical connector, in order to take into account high-speed performance and high-density requirement of the electrical connector, some of the differential signal terminal pairs and the grounding terminals are arranged in a staggered manner. However, as high-frequency performance is very sensitive to manufacturing tolerances of the terminals, the terminals must be manufactured to a high degree of accuracy by conventional technology, which increases the manufacturing difficulty and cost. In addition, crosstalk may be generated between the differential signal terminal pair located in one terminal row and the differential signal terminal pair located in an adjacent terminal row. In order to reduce this crosstalk, an interval between the terminal rows is generally set to be relatively large, which will reduce a density of transmission channels. 
     Improved electrical connectors addressing the above shortcomings are desired. 
     SUMMARY 
     According to an embodiment of the present disclosure, an electrical connector includes an insulation base, a plurality of grounding terminals mounted in the insulation base and a plurality of differential signal terminal pairs mounted in the insulation base. The plurality of grounding terminals and the plurality of differential signal terminal pairs are arranged into a plurality of terminal rows. Each of the plurality of differential signal terminal pairs is located between two adjacent grounding terminals in one terminal row and between two other grounding terminals of two terminal rows adjacent to the one terminal row. The insulation base is provided with an electrical connection layer by which at least two of the plurality of grounding terminals are electrically connected to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying Figures, of which: 
         FIG. 1  shows a schematic perspective view of an electrical connector according to an exemplary embodiment of the present disclosure; 
         FIG. 2  shows a schematic enlarged view of a part ‘A’ shown in  FIG. 1 ; 
         FIG. 3  shows another schematic perspective view of the electrical connector shown in  FIG. 1 ; 
         FIG. 4  shows a schematic perspective view of an insulation base according to an exemplary embodiment of the present disclosure; 
         FIG. 5  shows a schematic enlarged view of a part ‘B’ shown in  FIG. 4 ; 
         FIG. 6  shows a schematic perspective view of a metallization layer according to an exemplary embodiment of the present disclosure, without showing the insulation base; 
         FIG. 7  shows another schematic perspective view of the electrical connector shown in  FIG. 1 , without showing a conductive layer and a metallization layer; 
         FIG. 8  shows a further another schematic perspective view of the electrical connector shown in  FIG. 1 , without showing the conductive layer and the metallization layer; 
         FIG. 9  shows a schematic enlarged view of a part ‘C’ shown in  FIG. 8 ; 
         FIG. 10  shows another schematic perspective view of the electrical connector shown in  FIG. 1  with an isolation pad shown; 
         FIG. 11  shows a top view of the electrical connector shown in  FIG. 7 ; 
         FIG. 12  shows a transverse cross-sectional view of the electrical connector shown in  FIG. 7 ; 
         FIG. 13  shows a top view of an arrangement of terminals of the electrical connector according to an exemplary embodiment of the present disclosure; 
         FIG. 14  shows a schematic perspective view of an arrangement of the terminals of the electrical connector according to an exemplary embodiment of the present disclosure; 
         FIG. 15  shows a schematic plan view of three types of terminals of the electrical connector according to an exemplary embodiment of the present disclosure; 
         FIG. 16  shows a schematic plan view of a first grounding terminal according to another exemplary embodiment of the present disclosure; and 
         FIG. 17  shows a transverse cross-sectional view of a connector assembly according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present disclosure will be described hereinafter in detail with reference to the attached drawings, wherein the like reference numerals refer to the like elements. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art. 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     According to an embodiment of the present disclosure, an electrical connector includes an insulation base, a plurality of grounding terminals mounted in the insulation base and a plurality of differential signal terminal pairs mounted in the insulation base. The plurality of grounding terminals and the plurality of differential signal terminal pairs are arranged into a plurality of terminal rows. Each of the plurality of differential signal terminal pairs is located between two adjacent grounding terminals in one terminal row and between two other grounding terminals of two terminal rows adjacent to the one terminal row. The insulation base is provided with an electrical connection layer by which at least two ones of the plurality of grounding terminals are electrically connected to each other. 
     According to another embodiment of the present disclosure, a method for manufacturing the electrical connector includes the steps of forming an insulation base and forming a metallization layer on a surface of the insulation base. The method further includes the steps of laying a conductive layer on the metallization layer, and mounting a plurality of grounding terminals in the insulation base, respectively, such that at least two grounding terminals of the plurality of grounding terminals are electrically connected to each other by the conductive layer. 
       FIG. 1  shows a schematic perspective view of an electrical connector according to an exemplary embodiment of the present disclosure.  FIG. 2  shows a schematic enlarged view of a part ‘A’ shown in  FIG. 1 .  FIG. 3  shows another perspective view of the electrical connector shown in  FIG. 1 .  FIG. 4  shows a schematic perspective view of an insulation base according to an exemplary embodiment of the present disclosure.  FIG. 5  shows a schematic enlarged view of a part ‘B’ shown in  FIG. 4 .  FIG. 6  shows a schematic perspective view of a metallization layer according to an exemplary embodiment of the present disclosure, without showing the insulation base. 
     According to an exemplary embodiment of the present disclosure, as shown in  FIGS. 1-6 , an electrical connector suitable for being applied in a communication system and transmitting signals at a high speed of for example no less than 112 Gbps. The electrical connector includes an insulation base  1 , a plurality of grounding terminals  211 ,  221  mounted in the insulation base  1 , and a plurality of differential signal terminal pairs  222  mounted in the insulation base  1 . The plurality of grounding terminals  211 ,  221  and the plurality of differential signal terminal pairs  222  are arranged into a plurality of terminal rows, each of the plurality of differential signal terminal pairs  222  is located between two adjacent grounding terminals  221  in one terminal row and between two other grounding terminals  211  of two terminal rows adjacent to the one terminal row. The insulation base  1  is provided with an electrical connection layer  16  electrically insulated from the differential signal terminal pairs  222 . At least two ones of the plurality of grounding terminals are electrically connected to each other by the electrical connection layer  16 . With the electrical connection layer, a sensitivity of the high-frequency transmission performance of the electrical connector to manufacturing tolerance in dimension of a product such as the grounding terminals can be reduced, and a resonance generated during transmitting of high-frequency signals can be improved to make the signal transmission more stable. 
     In an exemplary embodiment of the present disclosure, the electrical connection layer  16  includes a metallization layer  161  laid on the insulation base  1 , and a conductive layer  162  covering the metallization layer. The metallization layer  161  is formed on the insulation base  1  by injection molding. The metallization layer  161  is a plastic layer containing conductive particles therein. The conductive particles include metal particles. For example, the metal particles include palladium particles. The conductive layer  162  includes a metal layer with a good conductivity, such as a nickel layer, a copper layer, or a gold layer. 
       FIG. 7  shows another schematic perspective view of the electrical connector  100  shown in  FIG. 1 , without showing the conductive layer and the metallization layer.  FIG. 8  shows another schematic perspective view of the electrical connector shown in  FIG. 1 , without showing the conductive layer and the metallization layer.  FIG. 9  shows a schematic enlarged view of a part ‘C’ shown in  FIG. 8 .  FIG. 10  shows another schematic perspective view of the electrical connector shown in  FIG. 1 , with an isolation pad being shown.  FIG. 11  shows a top view of the electrical connector shown in  FIG. 7 .  FIG. 12  shows a transverse cross-sectional view of the electrical connector shown in  FIG. 7 . 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 1-3 and 7-12 , the insulation base  1  includes a bottom wall  11  and a plurality of protruding bars  12 . The grounding terminals and the differential signal terminal pairs  222  extend from a first side to a second side of the bottom wall  11  in a first direction (e.g., a height direction). The plurality of protruding bars  12  protrude from the first side of the bottom wall  11  and extend in a second direction (e.g., a row direction or length direction) perpendicular to the first direction. The grounding terminals and/or the differential signal terminals protruding from the second side of the bottom wall are held against a side wall of the respective protruding bar  12 . 
       FIG. 13  shows a top view of an arrangement of terminals of the electrical connector according to an exemplary embodiment of the present disclosure.  FIG. 14  shows a schematic perspective view of an arrangement of the terminals of the electrical connector according to an exemplary embodiment of the present disclosure.  FIG. 15  shows a schematic plan view of three types of terminals of the electrical connector according to an exemplary embodiment of the present disclosure. 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 1-3 and 13-15 , the plurality of terminal rows  2  includes a plurality of grounding terminal rows  21  and a plurality of hybrid terminal rows  22 . Further, each of the grounding terminal rows is composed of a plurality of first grounding terminals  211 , with no differential signal terminal included in each grounding terminal row  21 . The plurality of hybrid terminal rows  22  are composed of a plurality of second grounding terminals  221  and a plurality of differential signal terminal pairs  222 . Further, each of the differential signal terminal pairs  222  is located between two second grounding terminals  221 . Each of the differential signal terminal pairs  222  is located between two adjacent grounding terminals  221  in one terminal row and between two other grounding terminals  221  of two terminal rows adjacent to the one terminal row. Each of the differential signal terminal pairs  222  includes two adjacent differential signal terminals. With this arrangement, any two hybrid terminal rows are not disposed directly adjacent to each other. 
     Each of the differential signal terminal pairs  222  is located between two adjacent first grounding terminals  221  in a third direction (e.g., a width direction or column direction) perpendicular to the first direction (e.g., the height direction) and the second direction (e.g., the row direction). In this way, each of differential signal terminal pairs is disposed adjacent to the grounding terminals in the row direction and in the column direction. Thus, each of differential signal terminal pairs is surrounded by the grounding terminals. In this way, a signal crosstalk between the differential signal terminal pairs can be suppressed, which allows the grounding terminals and the differential signal terminals to be arranged at a higher density while ensuring the high-speed signal transmission performance of the electrical connector. 
     In an alternative embodiment of the present disclosure, each of the terminal rows is a hybrid terminal row including the grounding terminals and the differential signal terminal pairs, and further, the grounding terminals are arranged at both sides of each of the differential signal terminal pairs in the row and column directions. 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 7-12 , the plurality of protruding bars  12  include a first outer protruding bar  121 , a second outer protruding bar  122 , and at least one middle protruding bar  123  located between the first outer protruding bar and the second outer protruding bar. One of two adjacent terminal rows is defined as the grounding terminal row  21 , and the other is defined as the hybrid terminal row  22 . One grounding terminal row  21  is provided on an inner side of the first outer protruding bar  121 , and one grounding terminal row  21  and one hybrid terminal row  22  are provided on outer and inner sides of the second outer protruding bar  122  respectively. One grounding terminal row  21  and one hybrid terminal row  22  are provided on either side of each of the middle protruding bars  123  respectively. In this way, except the first outer protruding bar  121 , each of the protruding bars is arranged such that the grounding terminal row  21  is disposed on one of two side walls of the protruding bar extending in the second direction and the hybrid terminal row  22  is disposed on the other side wall of the protruding bar. Thus, no protruding bar is arranged with the grounding terminal row on the each of two opposite side walls thereof or with the hybrid terminal row on each of two opposite side walls thereof. With this arrangement, the grounding terminal is located at the outermost side, and no signal terminal is located on the outermost side, thereby avoiding the crosstalk between the signal terminals and other external terminals. 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 8-12 , an insertion slot  13  is formed between two adjacent protruding bars  12 , and the grounding terminal row  21  and the hybrid terminal row  22  are arranged on two side walls of the insertion slot  13 , respectively. In this way, the grounding terminal row  21  is arranged on one of the two side walls of the insertion slot  13 , and the hybrid terminal row  22  is arranged on the other side wall of the insertion slot  13 . Thus, no insertion slot is arranged with the grounding terminal row on each of the two side walls thereof or with the hybrid terminal row on each of the two side walls thereof. 
     Referring to  FIG. 17 , according to an exemplary embodiment of the present disclosure, there is provided a connector assembly including two electrical connectors  100  and  100 ′, each of which is the electrical connector described according to any one of the above embodiments. In the connector assembly, the grounding terminals in the two electrical connectors are electrically connected to each other and the differential signal terminal pairs in the two electrical connectors are electrically connected to each other, so as to realize an electrical connection of the two electrical connectors with each other. Specifically, the first grounding terminals  211  of one electrical connector  100  are electrically connected to the first grounding terminals  211 ′ of the other electrical connector  100 ′, the second grounding terminals  221  of the one electrical connector  100  are electrically connected to the second grounding terminals  221 ′ of the other connector  100 ′, and the differential signal terminal pairs  222  of the one electrical connector  100  are electrically connected with the differential signal terminal pairs  222 ′ of the other electrical connector  100 ′ respectively. Further, circuit boards  3 ,  3 ′ are provided at first sides of bottom walls of the electrical connectors  100 ,  100 ′ to be electrically with the grounding terminals and the differential signal terminals for establishing the electrical connection between the two circuit boards. In this way, signal transmission between the two circuit boards can be realized through the electrical connectors of the present disclosure. 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 12 and 17 , the insertion slot  13  has a width approximately equal to or slightly greater than that of the protruding bar  12  or  12 ′, such that the protruding bar  12  of the one electrical connector  100  can be inserted into the insertion slot of the other electrical connector  100 ′ so as to assemble the one electrical connector and the other electrical connector together. In this way, when electrically connecting the two circuit boards  3 ,  3 ′, only one type of electrical connector is required, and the protruding bar and the insertion slot of the two electrical connectors  100  and  100 ′ are engaged with each other, which reduces the manufacturing cost of the electrical connector. 
     In an exemplary embodiment of the present disclosure, referring to  FIG. 12 , a width of a projection of each of the differential signal terminal pairs  222  in the third direction (e.g., the width direction) perpendicular to the first and second directions is less than that of the first grounding terminal  211  in the third direction. In other words, the width of the projection of each of the differential signal terminal pairs  222  in the third direction is defined within the projection of the first grounding terminal  211  in the third direction. 
     Referring to  FIGS. 12 and 14 , the first grounding terminal  211  includes a first body portion  2111  and a first elastic portion  2112  extending from the first body portion  2111 . Further, the first elastic portion  2112  has a free end formed as a first arc-shaped contact portion  2113 . The second grounding terminal  221  includes a second body portion  2211  and a second elastic portion  2212  extending from the second body portion  2211 . Further, the second elastic portion  2212  has a free end formed as a second arc-shaped contact portion  2213 . The differential signal terminal includes a third body portion  2221  and a third elastic portion  2222  extending from the third main body  2221 . Further, the third elastic portion  2222  has a free end formed as a third arc-shaped contact portion  2223 . In addition, each of the first body portion  2111  of the first grounding terminal  211 , the second body portion  2211  of the second grounding terminal  221  and the third body portion  2221  of the differential signal terminal is provided with a soldering portion  2115 . After respectively terminals are mounted in the insulation base, solder balls  4  may be pre-arranged on the soldering portions  2115  to be soldered together with electrical contacts of the circuit board. 
     As shown in  FIG. 17 , when the one electrical connector  100  is assembled with the other electrical connector  100 ′, the contact portions of the terminals of the one connector  100  are brought into contact with the respective elastic portions of the terminals of the other electrical connector. At the same time, the contact portions of the other electrical connector  100 ′ are brought into contact with the respective elastic portions of the one electrical connector  100 . For example, when the one electrical connector  100  is assembled with the other electrical connector  100 ′, the first contact portion  2113  of the first grounding terminal  211  of the one connector  100  is brought into in contact with the first elastic portion  2112 ′ of the first grounding terminal  211  of the other electrical connector  100 ′. At the same time, the first elastic portion  2112 ′ of the other electrical connector  100 ′ is brought into contact with the first elastic portion  2113  of the one electrical connector  100 . Therefore, the two first grounding terminals  211  engaged with each other of the two electrical connectors are brought into electrical contact with each other at the four first elastic contact portions, such that four electrical contacts are formed at the two sets of first contact portions engaged with each other of the two first grounding terminals. The mated differential signal terminals are engaged with each other at the third contact portions, at which two contact points are formed. In this way, the terminals of the two electrical connectors corresponding to each other can be electrically connected reliably. 
     In an exemplary embodiment of the present disclosure, referring to  FIG. 15 , the first elastic portion  2113  includes two sub-elastic portions  2114  spaced apart, which can reduce an elastic force of the first elastic portion so as to facilitate the connection of the two electrical connectors. The first body portion  2111  of the first grounding terminal  211  has a maximum width W 1  greater than a total width W 2  of the two third body portions  2221  of the differential signal terminal pair. The second body portion  2211  of the second grounding terminal  221  has a width W 3  greater than a width W 4  of the third body portion. The width W 3  of the second body portion  2211  of the second grounding terminal  221  is smaller than the total width W 2  of the two third body portions  2221  of the differential signal terminal pair. The sub-elastic portion  2114  of the first grounding terminal  211  has a width W 5  greater than a width W 6  of the third elastic portion. 
       FIG. 16  shows a schematic plan view of the first grounding terminal according to another exemplary embodiment of the present disclosure. The first body portion  2111  of the first grounding terminal  211  includes two sub-body portions  2111 ′ spaced apart. 
     In an exemplary embodiment of the present disclosure, referring to  FIGS. 1, 7, 8 and 10 , the insulation base  1  is provided with a guide groove  14  and a guide post  15 . The guide post  15  of the one electrical connector  100  is insertable into the guide groove  14  of the other electrical connector  100 ′. When assembling the two electrical connectors together, the two electrical connectors can be connected only if the guide post and the guide groove of the two electrical connectors are aligned with each other. Otherwise, the two electrical connectors will not be connected with each other. Therefore, the guide post and the guide groove not only have a guiding function, but also can prevent the two electrical connectors from being mistakenly assembled together. In an exemplary embodiment of the present disclosure, the guide groove  14  and/or the guide post  15  has a height no less than that of the protruding bar  12 . 
     In an exemplary embodiment of the present disclosure, as shown in  FIGS. 1-3 and 10 , the bottom wall  11  of the insulation base  1  is formed with a plurality of first through holes  125  and a plurality of second through holes  126 , and the side wall of the protruding bar  12  is formed with a plurality of first recesses  124  and a plurality of second recesses  127  in communication with the first through holes  125  and the second through holes  126  respectively. The first grounding terminal  211  and the second grounding terminal  221  are each mounted in the first through hole  125  and the first recess  124 . Further, the differential signal terminal of the differential signal terminal pairs  222  is mounted in the second through holes  126  and the second recesses  127 . The body portion of each terminal of the first grounding terminal  211 , the second grounding terminal  221  and the differential signal terminal pair  222  is mounted in the first through hole  125  and the second through hole  126 , and the elastic portion and the contact portion of each terminal of the first grounding terminal  211 , the second grounding terminal  221  and the differential signal terminal pair  222  are at least partially received in the first recess  124  and the second recess  127 . When the two electrical connectors  100  and  100 ′ are assembled together, the elastic portion and the contact portion of each terminal may be at least partially biased into the first recess  124  and the second recess  127 , which facilitates the insertion and assembly operation of the two electrical connectors. The electrical connection layer  16  extends into the first through hole  125  to achieve a reliable electrical connection between the grounding terminal and the electrical connection layer and to facilitate the insertion and assembling operation of the two electrical connectors. At least two grounding terminals including the first grounding terminal  211  and the second grounding terminal  221 , or all of the grounding terminals, can be electrically connected by the electrical connection layer  16 , which can reduce the sensitivity of the high-frequency transmission performance of the electrical connector to manufacturing tolerance in dimension of a product, such as the grounding terminal, and can improve the resonance generated during transmitting of the high-frequency signals to make the signal transmission more stable. 
     In an exemplary embodiment of the present disclosure, as shown in  FIGS. 3-5 , the electrical connection layer  16  extends over regions of the bottom wall  11  expect a region where the differential signal terminal pairs  22  are located. Further, the electrical connection layer  16  extends into the first through hole  125 . As there is no plastic layer and conductive layer in the region where the differential signal terminals are located, different differential signal terminals are electrically insulated from each other, and the differential signal terminal is also electrically insulated from the grounding terminal. In this way, each terminal can be electromagnetically shielded at a bottom portion of the electrical connector to further suppress the signal crosstalk. 
     According to an exemplary embodiment of another aspect of the present disclosure, there is provided a method for manufacturing the electrical connector  100 , including: forming an insulation base  1  from a liquid crystal polymer (LCP) through for example an injection molding process (primary-shot injection); forming a metallization layer  161  on a surface of the insulation base  1 ; laying a conductive layer  162  on the metallization layer; mounting a plurality of grounding terminals, including a first grounding terminal  211  and a second grounding terminal  221 , in the insulation base  1  respectively, such that at least two grounding terminals of the plurality of grounding terminals are electrically connected to each other through the conductive layer  162 . The metallization layer and the conductive layer constitute an electrical connection layer  16 . As the insulation base  1  is made of a plastic material, the surface of the insulation base  1  is difficult to be directly plated with a metal material. By forming the metallization layer on the insulation base  1 , the conductive layer can be plated on the insulation base with the metallization layer to achieve an electrical connection of the plurality of grounding terminals. 
     In an exemplary embodiment of the present disclosure, forming an insulation base  1  through an injection molding process includes forming, in a bottom wall  11  of the insulation base  1 , a second through hole  126  for mounting a differential signal terminal therein. The forming of the insulation base  1  further includes forming, in a protruding bar  12 , a first recess  124  for receiving the grounding terminals (the first grounding terminal and the second grounding terminal) therein and a second recess  127  communicating with the second through hole  126  and configured for receiving the differential signal terminal therein. 
     In an exemplary embodiment of the present disclosure, forming a metallization layer  161  on a surface of the insulation base  1  includes injecting plastic containing conductive particles onto a portion of the surface of the insulation base through the injection molding process (secondary-shot injection). The metallization layer is a plastic layer containing the conductive particles therein. For example, the conductive particles include palladium particles. In an example, the conductive layer includes a metal layer having a good conductivity, such as a nickel layer or a gold layer. 
     In an exemplary embodiment of the present disclosure, as shown in  FIGS. 14-16 , during injecting a plastic containing conductive particles onto a portion of the surface of the insulation base, the first through hole  125  is formed to be in communication with the first recess  124  and suitable for receiving the grounding terminal, so that the metallization layer is formed in the first through hole to form the conductive layer. Specifically, during forming the insulation base  1  through primary-shot injection process, the first through hole  125  is not formed, and only the second through hole  126  suitable for receiving the differential signal terminal therein is formed in the bottom wall  11 , then the first through hole  125  suitable for mounting the grounding terminal therein is formed during forming the plastic layer  161  through the secondary-shot injection molding process. The first through hole  125  penetrates through the bottom wall  11  of the insulation base  11  to be in communication with the first recess  124 . 
     In an exemplary embodiment of the present disclosure, the conductive layer is plated on the metallization layer using a molded interconnect devices (MID) molding process, or the conductive layer is deposited on the metallization layer using a physical vapor deposition (PVD). 
     In an exemplary embodiment of the present disclosure, an isolation pad  3  is provided on the bottom wall to cover the conductive layer. After the grounding terminal and the differential signal terminal are mounted in the insulation base  1 , the isolation pad  3  is mounted onto a first side (upper side of  FIG. 3 ) of the bottom wall  11  of the electrical connector  100 , and the soldering portion  2115  of each terminal passes through the isolation pad  3 . Then, solder balls  4  made of a solder material are formed on the soldering portions  2115  so as to be electrically connected with the electrical contact of the circuit board. 
     In addition, those areas in which it is believed that those of ordinary skill in the art are familiar, have not been described herein in order not to unnecessarily obscure the invention described. Accordingly, it has to be understood that the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims. 
     It should be appreciated for those skilled in this art that the above embodiments are intended to be illustrated, and not restrictive. For example, many modifications may be made to the above embodiments by those skilled in this art, and various features described in different embodiments may be freely combined with each other without conflicting in configuration or principle. 
     Although several exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 
     As used herein, an element recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of the elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.