Patent Publication Number: US-2007099507-A1

Title: Electric connector

Description:
TECHNICAL FIELD  
      The present invention relates to an electric connector used for connection between a printed circuit board and a device or between printed circuit boards to each other in a computer, a server, or wiring between a backboard and a package, each connector being mainly for differential transmission for transmitting a high-frequency electric signal.  
     BACKGROUND ART  
      Conventionally, as an electric connector  11  for a high-speed transmission channel, as shown in  FIG. 9 , a connector has been known, which comprises a housing for female contacts  14  in which female-type contacts  12   a ,  12   b  are molded by insert molding, a joint housing  15  for holding connection parts of the contacts  12   a ,  12   b  in reception holes by press fitting, and a backboard connector  17  having male-type contacts  16  to be jointed with the female-type contacts.  
      As a noise-control measure of the electric connector  11 , a connector employing a differential transmission method is known, in which a signal is formed from a pair of terminals  12 , and a high-speed signal is transmitted by the terminal pair. The terminal pair  12  is designed in a way that even if crosstalk or leakage of signal energy to adjacent terminals occurs, it is removed as a common mode noise. As shown in  FIG. 10 , ground terminals  13  are provided among respective terminal pairs  12  to prevent crosstalk to adjacent terminal pairs; thereby leakage of energy from one signal to another signal is prevented.  
      It is known that a distance “a” between the terminals of the pair is decreased compared with a distance “b” between the adjacent terminal pairs in order to reduce a crosstalk level of electric signals between respective terminal pairs  12 . For example, it is known from JP-A-11-185886 and JP-A-2003-515896.  
      However, the electric connector  11  is intended to solve the problem by providing the ground terminals to reduce the crosstalk. This causes a problem of increase in number of components and complexity of the overall structure, resulting in increase in assembly cost. Furthermore, it causes a problem that the interval between the terminal pair  12  and the ground terminal  13  arranged between the terminal pairs is decreased due to progress of high-density package, thereby signal energy that is lost due to the ground terminal is increased, and consequently insertion loss is increased.  
      Moreover, there is a problem that since the interval (b) between the terminal pairs  12  is also decreased, terminal retaining force to be held as a press-in terminal is hardly secured, consequently terminals tend to bend, or bucking of the terminals occurs during press-fitting of the terminal.  
      Furthermore, there are various problems including a problem that since the contacts  12   a ,  12   b  of the terminal pair  12  are arranged in a vertical direction, length of lines to a circuit on a printed circuit board is different from each other, thereby propagation delay occurs in an electric signal, causing noise due to the relevant electric signal.  
      Thus, as shown in  FIG. 11  to  FIG. 12 , it is proposed that the terminal pair  12  for transmitting an electric signal are lined up in a horizontal direction so that each of the lines to the circuit on the printed circuit board has the same length, thereby the problem of the propagation delay is dissolved and noise is prevented, in addition, the distance “b” between the terminal pairs  12  is set long by a zigzag layout to reduce the crosstalk.  
      However, in this case, as shown in  FIG. 12 , the female-type contacts  12   a ,  12   b  configuring the terminal pair  12  are integrally molded in one of divided housings for female-type contacts (hereinafter, referred to as module housing)  14   a ,  14   b , . . . by insert molding, and the interval between the contacts is much reduced due to the progress of high-density package, therefore the terminal pair  12  of the relevant female-type contacts are hard to be fixed in a mold with the reduced interval.  
      Moreover, there is a problem that since thickness of the female-type contacts  12   a ,  12   b  is decreased in order to reduce the interval (a), the contacts are affected by injection pressure of melted resin during molding and thus transformed, therefore the interval (a) between the relevant female-type contacts does not become constant, consequently transmission characteristics are deteriorated.  
      Furthermore, there is a problem that when the interval between the female-type contacts  12   a ,  12   b  of a terminal pair  12  is further decreased, the relevant female-type contacts are sometimes touched to each other due to the injection pressure.  
      As another integral molding method of the module housing, the contacts can be molded in a method similar to double molding by inserting a thin insulating material between the terminals of the pair, however, in this case, the female-type contacts is hardly aligned with the thin insulating material, and workability is deteriorated because of the small thickness of the insulating material.  
      Thus, the electric connector according to the invention, which is proposed to dissolve such problems, aims to decrease the interval between the terminals of the pair and keep accuracy of parallelism of the terminals, and easily set the female-type contacts in a mold.  
     DISCLOSURE OF INVENTION  
      The electric connector according to the invention has a plurality of signal terminals, a housing for female-type contacts in which the signal terminals are buried and integrally molded in a synthetic-resin housing with one ends of them being exposed, and a joint housing formed in a way that reception holes for receiving every one terminal pair, in which terminals are set close to each other in a horizontal direction in order to transmit an electric signal through the signal terminals, are lined up in the horizontal direction and set in several stages in a vertical direction, in which a relation of an interval (a) between the two signal terminals of the terminal pair to an interval (b) between the terminal pairs is a&lt;b; wherein the two signal terminals of the terminal pair are separately buried and integrally molded in a module housing which is formed by dividing the housing for female-type contacts along the vertical direction in alignment with the midpoint of the interval (a) in the terminal pair.  
      The electric connector includes a feature that the reception holes are arranged in a zigzag layout in vertical, two stages.  
      According to the electric connector of the invention, adjacent two module housings are combined, thereby a terminal pair for transmitting an electrical signal is configured. Accordingly, the interval between the signal terminals of the terminal pair can be set to be extremely small. Moreover, the interval between the terminal pairs can be held parallel. In that case, any spacer is not necessary.  
      As further advantage, when a contact at one side of the terminal pair is set into a mold, since the contact can be molded in a manner that halfway points of the relevant contact are supported and fixed from both sides, setting operation into the mold is facilitated, and transformation and bending of the contact can be prevented. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a perspective view showing an electric connector according to the invention;  
       FIG. 2  is a perspective view showing a module housing in the electric connector according to the invention;  
       FIG. 3  is a similar perspective view showing a module housing in which female-type contacts are set in a zigzag layout symmetrically with respect to the module housing shown in  FIG. 2 ;  
       FIG. 4  is a cross section view along a line A-A in  Fig.3 ;  
       FIG. 5  is an explanatory view showing formation of terminal pairs of the female-type contacts in a condition that adjacent module housings are aligned with each other;  
       FIG. 6  is a cross section view along a line B-B in  FIG. 5 ;  
       FIG. 7  is a schematic, explanatory view showing an arranged condition of terminal pairs of the female-type contacts and an effect of an electric field;  
       FIG. 8A  is an explanatory view in the case that through-holes in a circuit of a printed circuit board in correspondence with a layout of the female-type contacts are arrayed in a zigzag layout;  
       FIG. 8B  is an explanatory view in the case that the through-holes in the circuit of the printed circuit board in correspondence with the layout of the female-type contacts are arrayed in a lattice layout;  
       FIG. 9  is a cross section view of an electric connector according to a conventional example;  
       FIG. 10  is an explanatory view showing an arranged condition of terminal pairs of an electric connector  11  and an effect of an electric field in the conventional example;  
       FIG. 11  is an exploded perspective view showing the electric connector according to the conventional example; and  
       FIG. 12  is a cross section view showing a housing for female-type contacts. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      First, best mode for carrying out the invention is described with reference to  FIG. 1  to  FIG. 8B . As shown in  FIG. 1 , an electric connector  1  according to the invention comprises a female-type package connector  2  that is set on a printed circuit board and has one ends of contacts to be connected to a circuit and the other ends of contacts formed as female-type connection parts, and a backboard connector  3  that is provided in a chassis of a device with having male-type contacts for connection with the package connector  2 .  
      The package connector  2  comprises a joint housing  2   b  in which reception holes  2   c  for receiving the male-type connection parts are arranged, a housing  2   a  for female-type contacts, and female-type contacts  4  that are molded in the housing  2   a  for female-type contacts by insertion molding.  
      A joint part  4   a  that is a female-type joint part of the female-type contact  4  is received in the reception hole  2   c  as a terminal pair for transmitting an electrical signal. Then, the relevant reception holes  2   c  are arranged in a zigzag layout where the holes are shifted half the pitch among the reception holes  2   c  in a horizontal direction for each of vertical, six stages without changing an interval in a vertical direction.  
      The female-type contacts  4  are provided, for example, in six stages in the vertical direction, and female-type contacts  4 ,  4  having an interval (a), which are set parallel and close to each other (for example, about 0.4 mm to 0.5 mm) in a horizontal direction, are arranged in the reception hole  2   c  as the terminal pair for an electric signal. Thickness of the female-type contact  4  is, for example, about 0.4 mm.  
      It is preferable for reducing the crosstalk that the proximate condition of the female-type contacts  4 ,  4  as the terminal pair is kept parallel from the joint part  4   a  to be jointed with a male-type contact  5  that is the opposite pair contact to a portion directly before a terminal part  4   b  to be pressed-in in the printed circuit board.  
      Thus, in the electric connector  1 , as shown in  FIG. 2 , the housing  2   a  for female-type contacts comprises several module housings  2   d  formed by dividing the housing  2   a  along the vertical direction in alignment with the midpoint of the interval (a) of the terminal pair, and one of the female-type contacts  4  of the terminal pair is buried and integrally molded in the module housing  2   d  by the insert molding.  
      When the one of the contacts  4  of the terminal pair is set in a mold, as shown in  FIG. 1 , halfway points A, B of the relevant contact  4  are supported and fixed from both sides for molding. Accordingly, setting operation into the mold is facilitated.  
      In this way, the female-type contacts  4  at one side of respective terminal pairs are arranged in six stages in the vertical direction in the zigzag layout. A minimum distance between the female-type contacts  4  and an alignment surface  2   f  that is a sidewall of the module housing  2   d  is equal to half the interval (a).  
      A module housing  2   e  shown in  FIG. 3  to  FIG. 4  is formed in a way that the female-type contacts  4  are disposed symmetrically with respect to the module housing  2   d  as shown in  FIG. 2  so that they are formed as the other female-type contacts  4  of the terminal pairs.  
      Once the module housings  2   d ,  2   e  are contacted at the alignment surface  2   f  to be adjacent to each other, as shown in  FIG. 5  to  FIG. 6 , the female-type contacts  4 ,  4  of the terminal pairs appear in six stages in the vertical direction (with the same vertical interval (a) in the conventional example) and in the zigzag layout.  
      Furthermore, as shown in  FIG. 7 , the contacts  4  are set in the zigzag layout such that a ratio of the interval (a) (about 0.4 mm to 0.5 mm) between the two signal terminals of the female-type contact  4 ,  4  of the terminal pair to the interval (b) between the relevant terminal pairs is a/b≦⅓, so that the crosstalk is reduced in a high-speed transmission channel. The interval (b) between the relevant terminal pairs is easily set large by the zigzag layout of the terminals  4 ,  4  of the pairs.  
      In this way, each one of terminals of every one pair for transmitting an electric signal is integrated to several module housings  2   d ,  2   e  configuring the housing  2   a  for female-type contacts by insert molding. Since the integrally molded module housings  2   d ,  2   e  are aligned at the alignment surface  2   f , the interval (a) between the female-type contacts  4 ,  4  of the terminal pair is not unevenly decreased or increased, consequently transmission characteristics are excellently maintained.  
      As shown in  FIG. 8A , again in through-holes  6  in the printed circuit board into which the terminal parts  4   b  at the side facing the printed circuit board of the female-type contact  4  is pressed in, a method of leading out wiring patterns  7  is practiced in a way that the wiring patterns  7  are led out in a zigzag layout from the through-holes  6  in an approximately lattice layout, thereby wiring patterns are overlapped triply, consequently the wiring patterns can be formed using a three-layer board. For comparison, the wiring patterns are led out in a manner as shown in  FIG. 8B ; a five-layer board is needed, leading to increase in cost.  
      Next, the backboard connector  3  is described. The backboard connector  3  comprises a housing  3   a  for male-type contacts, and male-type contacts  5  which are pressed-in into contact insertion holes  3   b  arranged in the housing  3   a  and supported thereby. The contact insertion holes  3   b  are arrayed in correspondence with the array of the reception holes  2   c  of the package connector  2 .  
      As above, in the electric connector  1  according to the invention, since one of the terminals of every one pair for transmitting an electric signal are integrally molded by insert molding in the housing  2   a  for female-type contacts, the interval (a) between the terminals of the pair is secured and securely held parallel. Accordingly, the reception holes  2   c  are arrayed in the zigzag layout to increase the interval (b) between the terminal pairs, in addition, the interval (a) between the terminals of the pair can be decreased, and therefore high-speed transmission characteristics can be improved.  
     INDUSTRIAL APPLICABILITY  
      As above, the electric connector according to the invention improves crosstalk at a transmission channel for a high-frequency electric signal, wherein a terminal pair for transmitting an electric signal is configured by combining adjacent module housings, consequently an interval between signal terminals of the terminal pair can be set extremely small.  
      Moreover, an interval between terminal pairs can be easily held parallel. In that case, separate articles such as a spacer are not needed, therefore the number of components is not increased.  
      Furthermore, when a contact at one side of the terminal pair is set in a mold, since halfway points of the relevant contact can be supported and fixed from both sides for molding, setting operation into the mold is facilitated, and transformation and bend of the contact can be prevented; which is useful.  
      Moreover, the reception holes are arrayed in the zigzag layout, thereby the interval (b) between the terminal pairs received therein is increased, and consequently crosstalk can be much reduced.