Abstract:
A method for connecting a connector to a printed-circuit board that maintains the optimal terminal alignment accuracy and improves the terminal soldering reliability. The method includes forming a fastener for fastening the terminals from a metal having a fusion point that is substantially the same as solder, fastening the terminals at predetermined positions with the fastener in a state in which the terminals are accurately aligned to one another, inserting the terminals into the through holes, and releasing the terminals by fusing the fastener.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a connector and to a method for connecting a connector to a printed-circuit board. 
     A connector of a printed-circuit board has terminals, which are connected to a printed-circuit board. The terminals are soldered in through holes of the printed-circuit board. This connects the connector to the printed-circuit board. 
     It is difficult to accurately align the terminals with one another. Thus, to facilitate the insertion of the terminals, the diameter of the through holes must be significantly larger than the size of the terminals. 
     However, the reliability of the soldering decreases when the diameter of the through holes is significantly larger than the size of the terminals. This may cause, for example, cracking of the solder. Further, the large diameter of the through holes makes it difficult to decrease the pitch between terminals. As a result, the connector cannot be made more compact. 
     Therefore, a resin plate is attached to the terminals, to hold the terminal ends. By using the resin plate, the terminals are prevented from being deformed. However, the terminal alignment accuracy is insufficient due to the attaching tolerance, dimensional tolerance, and positional tolerance of the resin plate. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a connector and a method for connecting a connector to a printed-circuit board that maintains the optimal terminal alignment accuracy and improves the terminal soldering reliability. 
     To achieve the above object, the present invention provides a method for connecting a connector to a printed-circuit board having a plurality of through holes. The connector includes a case and a plurality of terminals attached to the case. The method includes forming a fastener from a metal having a fusion point that is substantially the same as solder to fasten the terminals, fastening the terminals at predetermined positions with the fastener in a state in which the terminals are accurately aligned to one another, inserting the terminals into the through holes, and releasing the terminals by fusing the fastener. 
     A further perspective of the present invention is a connector connected to a printed-circuit board having a plurality of through holes. The connector includes a case, a plurality of terminals attached to the case and soldered in the through holes to connect the connector to the printed-circuit board, and a fastener attached to the terminals to fasten the terminals at predetermined positions in a state in which the terminals are accurately aligned to one another. The fastener is formed from a metal having a fusion point that is substantially the same as solder. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
     FIG. 1A is a schematic front view showing a connector according to a preferred embodiment of the present invention is a state prior to the attachment of a fastener; 
     FIG. 1B is a schematic cross-sectional view taken along line  1 B— 1 B in FIG. 1A; 
     FIG. 2 is a schematic front view showing the connector of FIG. 1A in a state in which terminals are fastened by the fastener; 
     FIG. 3 is a partially cross-sectional view showing the connector of FIG. 1A in a state arranged on a printed-circuit board; and 
     FIG. 4 is a partially cross-sectional view showing the terminals of the connector of FIG. 1A in a soldered state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, like numerals are used for like elements throughout. 
     A connector  11  according to a preferred embodiment of the present invention will now be discussed with reference to FIGS. 1 to  4 . 
     FIG. 1A is a schematic front view showing the connector  11  in a state prior to the attachment of a fastener  15 . FIG. 1B is a schematic cross-sectional view taken along line  1 B— 1 B in FIG.  1 A. As shown in FIGS. 1A and 1B, the connector  11  has a resin case  12 . A plurality of (twenty) terminals  13  are press-fitted in the case  12 . In the preferred embodiment, two rows (upper and lower rows) of L-shaped terminals  13  are attached to the case  12 . 
     Referring to FIG. 2, in a state in which the terminals  13  are accurately aligned with one another, a fastener  15 , which is formed from solder, fastens the terminals  13  at predetermined positions. The fastener  15  is located at a position that is slightly above an attaching surface  12   a,  along which the case  12  is attached to a printed-circuit board. The fastener  15  is formed by injecting solder into a predetermined mold. The predetermined mold is formed so that the terminals  13  are accurately aligned with each other when arranged in the mold. 
     In the preferred embodiment, the fastener  15  is plate-like and includes a plurality of connecting portions  15   a,  which extend between adjacent terminals  13 , and holding portions  15   b,  which encircle and hold the terminals  13 . The holding portions  15   b  are thicker than the connecting portions  15   a.    
     A method for connecting the connector  11  to a printed-circuit board  21  will now be discussed. 
     As shown in FIG. 3, the printed-circuit board  21  has a plurality of through holes  22  corresponding to the terminals  13 . In the preferred embodiment, a conductive pattern is printed on both sides of the printed-circuit board  21 . In FIGS. 3 and 4, the through holes  22  are shown having a diameter that is greater than actual. 
     The terminals  13  are inserted in the through holes  22  of the printed-circuit board  21 . The connector  11  is arranged on a mounting surface  21   a  of the printed-circuit board  21  with the attaching surface  12   a  contacting the mounting surface  21   a.  In this state, the fastener  15  is located just above the mounting surface  21   a.    
     In a state in which the case  12  is mounted, the printed-circuit board  21  is placed in a furnace, such as an infrared furnace, and heated to melt the fastener  15 . The fusion of the fastener  15  releases the terminals  13 . This disconnects the terminals  13  from one another. The fused fastener  15 , or the fused solder, enters the through holes  22 . With reference to FIG. 4, the fused solder in the through holes  22  then solders the terminals  13  to the printed-circuit board  21 . 
     The preferred embodiment has the advantages described below. 
     (1) The terminals  13  of the connector  11  are fixed by the fastener  15 , which is made of metal (solder), in an accurately aligned state. This facilitates the insertion of the terminals  13  into the through holes  22  of the printed-circuit board  21 . 
     (2) The fastener  15  keeps the terminals  13  in an accurately aligned state. Thus, the terminals  13  are easily inserted into the through holes  22  even when the diameter of the through holes  22  is reduced. Reduction in the diameter of the through holes  22  prevents the solder from cracking. This improves the soldering reliability of the terminals  13 . 
     (3) By reducing the diameter of the through holes  22 , the pitch of the through holes  22  and the pitch of the terminals  13  are decreased. This enables the connector  11  to be made more compact. 
     (4) The fastener  15  is melted and fused. Thus, the fastener  15  is removed in a relatively simple manner. 
     (5) The fused fastener (solder)  15  solders the terminals  13  to the printed-circuit board  21 . Thus, additional solder is not required. 
     (6) The fastener  15  is arranged on the terminals  13  at a position that is slightly higher than the attaching surface  12   a.  Thus, when the connector  11  is arranged on the mounting surface  21   a,  the fastener  15  is located just above the mounting surface  21   a.  As a result, the fused fastener (solder)  15  enters the through holes  22  and optimally solders the terminals  13  to the printed-circuit board  21 . 
     (7) The holding portions  15   b  are thicker than the connecting portions  15   a  in the fastener  15 . Thus, when the fastener  15  fuses, the connecting portions  15   a  fuse more easily than the holding portions  15   b.  Consequently, the terminals  13  are released and disconnected from each other while the holding portions  15   b  are provided with the necessary amount of solder. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     Additional terminals  13  may be soldered to a rear surface  21   b  of the printed-circuit board  21  that is opposite to the mounting surface  21   a.  In this case, the fused fastener (solder)  15  may be used only to solder the terminals  13  that are connected to the mounting surface  21   a,  and conventional soldering may be performed to solder the terminals  13  that are connected to the rear surface  21   b.  This would decrease the solder amount of the fastener  15 . 
     The fastener  15  may be formed separately from the terminals  13 , and holes may be formed in the fastener  15  for insertion of the terminals  13 . In this case, the terminals  13  are inserted through the holes in an accurately aligned state. 
     Solder having a decreased lead content or solder that is free of lead may be used to form the fastener  15 . 
     The fastener  15  may be formed from a metal having a fusion point that is substantially equal to that of solder. In this case, the fused fastener  15 , or fused metal, may be eliminated without being used to solder the terminals  13 . Solder is prepared to solder the terminals  13 . 
     The printed-circuit board  21  may be a single-sided board on which the conductive pattern is printed on only the mounting surface  21   a.    
     The terminals  13  may be insert molded to the connector  11 . 
     The furnace used to heat the fastener  15  may be a hot blast furnace. Further, the fastener  15  does not necessarily have to be fused by the heat of a furnace. 
     The fastener  15  may be formed at a position separated from the attaching surface  12   a  toward the distal portions ( 13 A) of the terminals  13 . 
     The terminals  13  may be arranged in any number of rows on the connector  11 . 
     The terminals  13  may be arranged along the same line on the mounting surface  21   a  of the connector  11 . 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.