Patent Publication Number: US-6902408-B2

Title: Coaxial electrical connector

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to coaxial electrical connectors. 
   2. Description of the Related Art 
   Japanese Patent Application Kokai No. 8-321361 discloses a coaxial connector receptacle of this type. 
   As shown in FIGS.  16 (A) and (B), this connector comprises a rectangular dielectric block  51  having a recessed section, a tubular outer conductor  52  having a substantially S-shaped cross-section in a plane including an axial line and provided on the recessed section, and a central conductor  53  having a contact section  54  that extends upwardly into the recessed section. 
   The central conductor  53  has a connection section  55  together with the contact section  54 . The connection section  55  extends in a radial direction (FIG.  16 (B)) and is flush with the bottom face of the dielectric block  51  so that when the connector is placed on the circuit trace of a circuit board, it is brought into contact with the trace and soldered for connection. 
   The central and outer conductors  53  and  52  are made by pressing a metal sheet and are held together by the molded dielectric block  51 . 
   In the above connector, however, the joint between the dielectric block  51  and the central conductor  53 , especially, its connection section  55  presents the following problems. 
   The thermal stress on soldering or plug-in/out forces make a gap between the dielectric block  51  and the connection section  55  or even separate them. In addition, upon soldering, the molten solder or flux (hereinafter simply “molten solder”) can enter the gap. This molten solder can reach the contact section  54 , making poor contact with a mating connector. 
   Since the connector must be low in profile, the bottom wall of the dielectric block is made so thin that it is prone to displacement by external forces or thermal expansion, making more gaps. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the invention to provide a low-profile coaxial electrical connector that is able to prevent the molten solder from reaching the central conductor and permit the dielectric block to hold the central conductor sufficiently firmly to prevent displacement. 
   According to the invention there is provided a coaxial electrical connector comprising an outer conductor having a tubular section, a central conductor having a contact section that extends in the axial direction into the tubular section, and a dielectric block molded so as to hold together both the conductors. The central conductor has a radial section that extends outwardly in the axial direction from the bottom of the central conductor and has a connection portion extending from the radial section for contact with a circuit board. 
   The central conductor has a surface-processed portion so as to form at least one of a raised portion and an indented portion on a face that is in contact with the dielectric block so that it engages with the dielectric block at the surface-processed portion. 
   Since the central conductor is meshed with the dielectric block at the raised and/or indented portion, the gripping power of the central conductor by the dielectric block is improved. Consequently, the central conductor is hardly separated by external forces, and the soldering heat makes little gap between the dielectric block and the central conductor to prevent advancement of the molten solder into the gap. 
   It is preferred that the surface-processed portion is an indented portion formed on the bottom edge of the radial section and filled with part of the dielectric block. Consequently, the central conductor is embraced by the dielectric block with the improved retention power. Not only the width of the edge is so small that little influence is made on the area of the connection portion but also the length of the edge is so large that the strength is improved. The width of the edge that is filled with the dielectric block may be increased on the area that is not used as the connection portion. 
   The indented portion may be formed as a through-hole. The dielectric block fills the through-hole and holds the central conductor between the upper and lower portions, thereby improving the retention power. 
   The central conductor is made by bending and forming a metal sheet, and the surface-processed portion is made by a pressing process. Both the bending/forming and pressing processes may be done in the same step. 
   It is preferred that the central conductor engages with the dielectric block at the radial section. 
   The contact section is made hollow and filled with part of the dielectric block. In this case, the indented portion may be formed in the inside of the follow contact section. 
   The radial section has an extension portion extending outwardly in the radial direction beyond the outer conductor. It is preferred that a connection portion is provided on the bottom face of the extension portion and one of a ridge and a groove extends across the radial section on the top face in contact with the dielectric block. 
   Even if there is a small gap between the radial section and the dielectric block, the ridge or groove prevents the molten solder from passing through the gap to reach the contact section (labyrinth function). It is preferred that the ridge and groove extend in the circular direction so as to surround the base portion of the contact section of the central conductor. 
   The surface-processed portion is made by an embossing or stamping process. 
   The central conductor and the outer conductor is bottomed up from the bottom level of the connection portion of the central conductor in a circular area whose diameter is larger than the outside diameter of the connection section but smaller than the inside diameter of the outer conductor, forming a circular ridge on the bottom face of the dielectric block. The bottom face of the circular ridge is level with the bottom face of the connection portion. Consequently, the molten solder does not adhere to the central conductor in the circular area. Since the connection portion is so remote from the contact section that the molten solder is prevented effectively by that much. 
   The indented portion may be provided on the bottom face of the extension portion and filled with part of the dielectric block. 
   As described above, according to the invention, there is provided the surface-processed portion on the face of the central conductor that is in contact with the dielectric block so as to form at least one of the raised portion and the indented portion so that the retention and engaging forces of the central conductor by the dielectric block are improved but also the separation of the central conductor from the dielectric block is prevented, which eliminates adherence of the molten solder to the central conductor. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS.  1 (A), (B), and (C) are top, side, and bottom views of a coaxial electrical connector according to the first embodiment of the invention; 
     FIGS.  2 (A) and (B) are sectional views taken along lines IIA—IIA and IIB—IIB of FIG.  1 (A), respectively; 
     FIGS.  3 (A), (B), and (C) are top, side, and bottom views of a central conductor for the connector.; 
     FIGS.  4 (A), (B), and (C) are sectional views taken along lines IVA—IVA, IVB—IVB, and IVC—IVC of FIG.  3 (A), respectively; 
       FIG. 5  is a sectional view of the first variation of the first embodiment; 
       FIG. 6  is a sectional view of the second variation of the first embodiment; 
       FIG. 7  is a sectional view of the second embodiment; 
       FIG. 8  is a sectional view of the third embodiment; 
       FIG. 9  is a sectional view of a variation of the third embodiment; 
       FIG. 10  is a sectional view of the fourth embodiment; 
       FIG. 11  is a sectional view of a variation of the fourth embodiment; 
       FIG. 12  is a sectional view of the fifth embodiment; 
       FIG. 13  is a sectional view of the first variation of the fifth embodiment; 
       FIG. 14  is a sectional view of the second variation of the fifth embodiment; 
     FIGS.  15 (A) and (B) are sectional views and (C) a bottom view of the sixth embodiment; 
     FIGS.  16 (A) and (B) are sectional and bottom views of a conventional connector. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the invention will now be described with reference to  FIGS. 1-15 . 
   First Embodiment 
   In  FIGS. 1 and 2 , a coaxial connector  1  according to the first embodiment comprises a dielectric block  30  that integrally holds an outer conductor  10  and a central conductor  20  as a unit. 
   The outer conductor  10  is made by bending and forming a metal sheet so as to provide a tubular section  11  having an axial line in the plugging direction with a mating connector and three leg sections  12  extending outwardly from the bottom of the tubular section  11 . The tubular section  11  is provided with an engaging groove  13  for engagement with the outer conductor of a mating connector (not shown) for preventing separation. A pair of leg sections  12 A and  12 B, which are diametrically opposed to each other, are made relatively wide and the other leg section  12 C is narrower than these two leg sections. The leg sections  12 A and  12 B are flush with the bottom face of the connector  1  so that when the connector is placed on a circuit board, they are brought into contact with the circuit traces. The leg section  12 C, however, is positioned so as to make a gap between the circuit board and itself. 
   As shown in  FIGS. 3 and 4 , the central conductor  20  is made by bending and forming a metal sheet so as to provide a contact section  21  that extends in the axial direction and a radial section  22  that extends in a radial direction from the bottom of the contact section  21 . 
   The contact section  21  is made by deep-drawing pressing a metal sheet so as to provide a hollow form having a semi-spherical tip and flared bottom that leads to the radial section  22 . An extension portion  23  extends in a radial direction from part of the radial section  22  beyond the tubular section  11  of the outer conductor  10 . The lower face of the extension portion  23  is flush with the circuit traces, forming a connection portion  23 A. 
   Part of the edge of the radial section  22  is embossed so as to provide an indented portion  22 A that is stepped up from the lower face of the extension portion  23 . Consequently, there is provided a raised portion  24  on the position corresponding to the indented portion  22 A. Both the indented portion  22 A and the raised portion  24  surround the contact section  21  and a half of the extension portion  23 . 
   The dielectric block  30  is made of a synthetic resin and molded together with the outer and central conductors  10  and  20  as a unit. It holds the central conductor  20  inside the tubular section  11  of the outer conductor  10  and the leg sections  12 A,  12 B, and  12 C outside the tubular section  11 , providing a receiving space  14  between the central and outer conductors  20  and  10  for receiving a mating connector. It has a rectangular shape outside the tubular section  11  (FIGS.  1 (A) and (C)). 
   The dielectric block  30  enters the indented portion  22 A of the central conductor  20  to support the radial section  22 . Also, it enters the indented portion  22 B defined by the raised portion  24  to increase the engaging power with the central conductor  20 . 
   Thus, the central conductor  20  is held firmly by the dielectric block  30  by permitting the mold material to enter the indented portion  22 A of the radial section  22 . Consequently, it is held without failure by the dielectric block  30  when it receives the thermal stress on soldering or plugging-in/out forces in sue. In addition, even if there is a small gap between the radial section  22  and the dielectric block  30  upon soldering to a circuit board, the molten solder is prevented from reaching the contact section  21  by the indented portion  22 A, the raised portion  24 , and the indented portion  22 B. 
   According to a modification to the embodiment, it is possible to extend the indented portion  22 A and the raised portion  24 . As shown in FIGS.  3 (A) and (B), they are extended to the Left end of the extension portion  23  so as to surround the extension portion  23  as indicated by broken line. As shown in FIGS.  2 (A) and (B), the dielectric block,  30  extends along the extension portion  23  so that when the raised portion  24  is extended, the engagement between the raised portion  24  and the dielectric block  30  is extended, improving the retention power. Furthermore, the raised portion  24  and the indented portion  22 A at the left end of the extension portion  23 , which is not in contact with the dielectric block  30 , effectively prevent advancement of the molten solder. 
   As shown in  FIG. 5 , according to a variation to the embodiment, the indented portion  22 A takes a tapered or tapered/stepped combination form. The thickness of the portion of the dielectric block  30  under the indented portion  22 A gradually increases to provide more strength. 
   As shown in  FIG. 6 , according to another variation to the embodiment, the fact that the indented portion  22 A is provided on the edge of the radial section  22  is the same as the embodiment, but a through-hole  31  is provided in the dielectric block  30  on the extension portion  23 . Consequently, even if there is no embossed edge, the through-hole  31  prevents the molten solder from running along the extension portion  23  to the contact section  21 . 
   Second Embodiment 
   The second embodiment will be described with reference to  FIG. 7. A  ridge portion  23 B extends in a widthwise direction of the extension portion  23  It is made by embossing a groove portion  23 C under the ridge portion  23 B. It is preferred that it extends across the entire or almost entire width of the extension portion  23 . It not only increases the engaging power between the extension portion  23  and the dielectric block  30  but also prevents the molten solder from advancing beyond the ridge portion  23 B even if there is a small gap between the extension portion  23  and the dielectric block  390 . In order to provide this labyrinth effect, a recessed portion may be added to the ridge portion or to replace it. It may be replaced by a plurality of corrugations without the groove portion  23 C. It not only has the labyrinth function but also increases the engaging power with the dielectric block  30 . It is not necessary to be a narrow ridge but may be a wide ridge. 
   Third Embodiment 
   The third embodiment will be described with reference to  FIGS. 8 and 9 . Similarly to the first embodiment, there are provided on the edge of the radial Section  22  the indented portion  22 A and the indented portion  22 B that is defined by the raised portion  24  and filled with the dielectric block  30 . 
   In  FIG. 8 , a wide indented portion  23 D is provided in the extension portion  23  and filled with the dielectric block  31 . The formation of the indented portion  23 D provides a raised portion  23 E. These wide indented and raised portions  23 D and  23 E increase the engaging power by the dielectric block  30 . The raised portion  23 E also improves the function of preventing advance of the molten solder. 
   In  FIG. 9 , a through-hole  23 F is provided in the extension portion  23  on the indented portion  23 D so that the dielectric block  30  is connected through the through-hole  23 F, This permits the dielectric block  30  holds the extension portion  23  between the upper and lower portions, improving the gripping power. Also, this makes the dielectric block  30  in the indented portion  23 D stronger than that of FIG.  8 . 
   Fourth Embodiment 
   The fourth embodiment will be described with reference to  FIGS. 10 and 11 . It is characterized in that work is done on the contact portion  21  of the central conductor  20 . 
   The contact section  21  is provided with a circular groove  21 A ( FIG. 10 ) or a circular ridge ( FIG. 11 ) on its base portion to improve the engaging force or gripping power of the central conductor  20  by the dielectric block  30 . 
   Also, both the circular groove  21 A and the circular ridge  21 B are able to prevent rising of the molten solder. A plurality of the circular grooves  21 A and/or ridges  21 B may be provided. 
   Fifth Embodiment 
   The fifth embodiment is described with reference to  FIGS. 12 through 14 . The gripping force of the central conductor  20  by the dielectric block  30  is improved outside the contact section  21  in the fourth embodiment, but it is improved inside the contact section  21  and/or below the radial section  22 . 
   In  FIG. 12 , the hollow inside  21 C of the contact section  21  is filled with the dielectric block  30 , and the indented portion  22 A is provided on almost all of the radial section  22  except for the connection portion  23 A and filled with the dielectric block  30 . The dielectric materials under the indented portion  22 A and in the hollow inside  21 C are connected to improve the strength of the dielectric block  30 , thereby increasing the gripping power of the central conductor  20 . 
   In  FIG. 13 , a through-hole  21 D is provided in the base portion of the contact section  21  to connect the dielectric materials insides and outside the contact section  21  for improving the engaging force between the dielectric block  30  and the central conductor  20 . Also, the through-hole  21 D prevents passage of the molten solder. A plurality of the through-holes  21 D may be provided. 
   In  FIG. 14 , a circular groove  21 E is provided on the inside of the contact section  21  to improve the engaging force of the dielectric block  30 . The loss of strength of the contact section  21  is smaller in  FIG. 14  than in  FIG. 13. A  plurality of the circular grooves  21 E may be provided. 
   Sixth Embodiment 
   The sixth embodiment in FIGS.  15 (A)-(C) controls movement of the molten solder under the dielectric block  30  more effectively than that of the first embodiment in  FIGS. 1 and 2 . 
   FIGS.  15 (A) and (B) are sectional views corresponding to FIGS.  2 (A) and (B), and FIG.  15 (C) is a bottom view of the connector. 
   The lower faces of the radial section  22  and the dielectric block  30  are set at a slightly higher position than the lower faces of the connection portion  23 A of the central conductor  20  and the connection sections  12 A and  12 B of the outer conductor  10 . 
   A substantially closed circular ridge  30 A is. provided on the bottom face of the dielectric block  30  around the central conductor  20 , and its bottom face is substantially flush with the connection portions  12 A and  12 B of the outer conductor  10  and the connection portion  23 A of the central conductor  20 . The circular ridge  30 A is not completely closed but satisfactory. As shown in FIG.  15 (C), there is no circular ridge  30 A in the area corresponding to the extension portion  23 , forming an open circle. As indicated by broken line, the ridge may be provided on the extension portion  23  to provide a completely closed circular ridge. 
   According to the embodiment, the circular ridge prevents advance of the molten solder to the radial section more effectively than the first embodiment of  FIGS. 1 and 2 . 
   The invention is not limited to the illustrated embodiments and variations but a variety of modifications may be made. For example, the central conductor may be made by cutting and grinding instead of bending and forming or a combination of these.