Patent Publication Number: US-2002002007-A1

Title: Board terminal and method of producing same

Description:
BACKGROUND OF INVENTION  
       [0001] 1. Field of Invention  
       [0002] This invention relates to a tab-like board terminal which is designed to be inserted into a through hole in a printed circuit board to be connected thereto, and the invention also relates to a method of producing this board terminal.  
       [0003] 2. Related art  
       [0004]FIGS. 5 and 6 show a conventional method of producing board terminals. The board terminals are produced using a wide sheet  1  (shown in FIG. 5( a )) having a predetermined small thickness, for example, of 0.64 mm. Electrically-conductive metal is plated on the surfaces of the sheet  1 , and then this sheet is blanked or stamped by a pressing die, thereby forming a pressed product  2  shown in FIG. 5( b ).  
       [0005] The pressed product  2  includes two pre-shaped portions  3  (to serve as board terminals) interconnected by a first carrier portion  4  and a second carrier portion  5 . The first carrier portion  4  serves as a portion through which the sheet is fed when the blanking operation is to be effected by the pressing die. The second carrier portion  5  serves to prevent the board terminals from being deformed when taking up the board terminals. These carrier portions are cut off and discarded simultaneously when cutting off the pre-shaped portions  3  from the pressed product  2 .  
       [0006] Each of the pre-shaped portions  3  includes a tapering insertion portion  6  connected to the first carrier portion  4 , a soldering portion  7  extending from the insertion portion  6 , and a connection portion  8  extending from the soldering portion  7 . The insertion portion  6  is adapted to be inserted into a through hole in a printed circuit board, and the soldering portion  7  is adapted to be soldered to the printed circuit board, and the connection portion  8  is adapted to be connected to a mating terminal. The blanking is effected in such a manner that the width h1 (see FIG. 6) of the soldering portion  7  is 0.60 mm, and the width h2 of the connection portion  8  is 1.00 mm.  
       [0007] In the above conventional method, however, a waste portion  9  as indicated by hatching in FIG. 6 is produced, and besides the first carrier portion  4  and the second carrier portion  5  must be discarded. Therefore, the loss of the material is large, and the yield rate of the products relative to the used material is low.  
       [0008] And besides, the plating is not formed on those portions press-cut by the pressing die, and therefore there is encountered another problem that the reliability of soldering is low. Furthermore, the pressed product  2  (shown in FIG. 5( b )) of a complicated shape is formed from the sheet  1  (shown in FIG. 5( a )), and therefore the pressing die is complicated, and is expensive.  
       SUMMARY OF INVENTION  
       [0009] It is therefore an object of this invention to provide a board terminal which can be formed with a reduced loss of a material, and can enhance a soldering reliability, and does not need a complicated pressing die in the production, and an another object is to provide a method of producing this board terminal.  
       [0010] The above object has been achieved by a board terminal of the present invention including a tapering insertion portion for insertion into a through hole in a board, a soldering portion to be soldered to the board, and a connection portion for connection to a mating terminal, the insertion portion, the soldering portion and the connection portion being continuously arranged in this order in a direction of a length of the board terminal, provided in that the insertion portion is formed by pressing a square wire having a width larger than a thickness thereof; and the soldering portion is formed by cutting or pressing widthwise opposite side portions of the square wire, and has a width smaller than the width of the square wire.  
       [0011] In the board terminal of this invention, the insertion portion is formed by pressing the square wire having the width larger than the thickness thereof, and the soldering portion is formed by cutting the widthwise opposite side portions of the square wire, and has the width smaller than the width of the square wire. Those portions, which are cut off from the square wire, and are discarded, are produced only when the soldering portion is formed by the above cutting operation. Therefore, generally the whole of the square wire can be formed into the board terminal, and the production can be performed with a minimum loss of the material.  
       [0012] The soldering portion, formed by cutting or pressing the square wire, has the width which is smaller than the width of the square wire, and is generally equal to the thickness of the square wire, so that this soldering portion has a generally square cross-section. Therefore, a thermal stress, developing when soldering the board terminal to the printed circuit board, is uniform, and a crack will not develop during the soldering operation. And besides, since the soldering portion has a reduced width, the diameter of the through hole can be reduced, and the board terminals can be mounted at a high density on the printed circuit board.  
       [0013] In the first aspect of the present invention, recesses are formed in the connection portion.  
       [0014] The connection portion is connected to the mating terminal, and therefore part of the connection portion is embedded in the connector. In this invention, the recesses are formed in the connection portion, and a resin of the connector intrudes into the recesses, so that the resin and the recesses engage each other. Therefore, the board terminal can be stably mounted on the connector.  
       [0015] In the first or second aspect of the present invention, electrically-conductive metal is plated on an outer surface of the board terminal.  
       [0016] In this invention, since the electrically-conductive metal is plated on the outer surface, the reliability of the soldering is enhanced.  
       [0017] According to the present invention, there is provided a method of producing a board terminal including a tapering insertion portion for insertion into a through hole in a board, a soldering portion to be soldered to the board, and a connection portion for connection to a mating terminal, the insertion portion, the soldering portion and the connection portion being continuously arranged in this order in a direction of a length of the board terminal; provided by the steps of forming the insertion portion by pressing a square wire having a width larger than a thickness thereof; and forming the soldering portion by cutting or pressing widthwise opposite side portions of that portion of the square wire extending from the insertion portion, the soldering portion having a width smaller than the width of the square wire.  
       [0018] In this invention, there is used the square wire having the width larger than its thickness, and the insertion portion is formed by pressing the square wire, and the soldering portion is formed by cutting or pressing the widthwise opposite side portions of the square wire. Therefore, there is no need to use a complicated pressing die, and the board terminal can be easily produced.  
       [0019] Those portions, which are cut off from the square wire, and are discarded, are only those portions cut for forming the soldering portion, and therefore generally the whole of the square wire can be formed into the board terminal, and therefore the production can be performed with a minimum loss of the material.  
       [0020] In the present invention, recesses are formed in a connection portion-forming portion of the square wire simultaneously when forming the insertion portion by pressing.  
       [0021] In this invention, the recesses in the connection portion are formed simultaneously when forming the insertion portion by pressing, and therefore the number of the process steps is not increased, and the board terminal can be easily produced.  
       [0022] In the present invention, electrically-conductive metal is plated on the board terminal after the pressing or the cutting of the widthwise opposite side portions.  
       [0023] Only the board terminal is formed using the square wire as the material, and therefore the construction is simple. Therefore, the plating can be applied to the board terminal over the entire surface thereof, and this plating enhances the reliability of the soldering. 
     
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
     [0024]FIG. 1 is a perspective view of a square wire used for producing one preferred embodiment of a board terminal of the present invention;  
     [0025]FIG. 2 is a perspective view of a pre-shaped product, having two board terminals serially connected together, which pre-shaped product is formed by processing the square wire;  
     [0026]FIG. 3 is a perspective view of the pre-shaped product, showing cut-off portions in the embodiment;  
     [0027]FIG. 4( a ) is a plan view showing the relation between a soldering portion of the embodiment and a through hole, and  
     [0028]FIG. 4( b ) is a plan view showing the relation between the square portion, not subjected to cutting, and a through hole; and  
     [0029]FIG. 5 shows a conventional production method, and FIG. 5( a ) is a perspective view showing a sheet, and  
     [0030]FIG. 5( b ) is a perspective view showing a pressed product formed by the conventional method; and  
     [0031]FIG. 6 is a plan view showing problems with the conventional method. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0032]FIGS. 1 and 2 show sequentially the steps of producing one preferred embodiment of board terminals of the present invention. In this embodiment, a square wire  1   1  of a rectangular cross-section is formed, and the board terminals  12  are produced, using this square wire  11  as a material.  
     [0033] As shown in FIG. 2, the board terminal  12  includes a tapering insertion portion  13 , a soldering portion  14  extending from the insertion portion  13 , and a connection portion  15  extending from the soldering portion  14 . The insertion portion  13  is adapted to be inserted into a through hole  20  (see FIG. 4) in a printed circuit board  19 , and the soldering portion  14 , passing through the through hole  20 , is adapted to be connected by soldering to a pattern (not shown) on the printed circuit board  19 .  
     [0034] The connection portion  15  is mounted on a connector (not shown) by embedding part of this connection portion  15  in the connector, and in this mounted condition, the connection portion  15  is contacted with and connected to a mating terminal (not shown). In FIG. 2, the connection portion  15  has an embedding portion  15   a  to be embedded in the connector, and a contact section  15   b  to be contacted with the mating terminal. A connection guide end  17  of a tapering shape to be inserted into a mating connector (not shown) is formed at the distal end of the connection section  15   b .  
     [0035] In this board terminal  12 , the largest stress acts on the connection portion  15  for contact with the mating terminal. Therefore, the connection portion  15  need to be larger in width than the insertion portion  13  and the soldering portion  14 , and the width H3 (see FIG. 3) of the connection portion is 1.00 mm.  
     [0036] In the board terminal  12  of this embodiment, recesses  16  are formed in the embedding portion  15   a  of the connection portion  15 . The recesses  16  are formed by recessing the relevant portions of the connection portion  15  in the direction of the thickness of the sheet (square wire), and a resin of the connector can intrude into the recesses  16 . As a result of the intrusion of the resin, the recesses  16  and the resin engage each other, so that the board terminal  12  can be firmly mounted on the connector.  
     [0037] Next, the production of the board terminal  12  will be described. As shown in FIG. 1, the square wire  11 , serving as the material for the board terminal  12 , is elongate. The width H1 of this square wire  11  is larger than its thickness T1.  
     [0038] In order that the board terminal  12  can be produced from the square wire  11  with a minimum loss of the material, it is necessary that the outside dimension of the square wire  11  should be equal to the largest one of the outside dimensions of the board terminal  12 . Therefore, the square wire  11  is so formed that its outside dimension coincides with the dimension of the connection portion  15  of the board terminal  12 . Therefore, in this embodiment, the square wire  11  is so formed that the thickness T1 is 0.64 mm, and that the width H1 is 1.00 mm which is larger than the thickness T1, and is equal to the width of the connection portion  15 .  
     [0039] In this embodiment, two board terminals  12  are produced from one square wire  11 , and the square wire  11  has a length equal to the sum of the lengths of two boar terminals  12 .  
     [0040] The square wire  11  is pressed, thereby simultaneously forming the tapering insertion portions  3 , the recesses  16  at the central portion of each connection portion  15 , and the tapering connection insertion end  17  at the end of each connection portion  15 . These portions are formed or shaped by one pressing operation, and by doing so, the number of pressing operations can be reduced, and the number of the process steps can be reduced.  
     [0041] After this pressing operation, the widthwise opposite side portions of each soldering portion-forming portion are subjected to cutting or pressing, thereby forming the soldering portions  14 . The width H2 (H2=0.6 mm) of each soldering portion  14 , thus formed by cutting the widthwise opposite side portions, is smaller than the width H1 (H1=1.00 mm) of the square wire  11 , and is close in value to the thickness T1 (T1=0.64 mm) of the square wire  11  (the board terminal  12 ).  
     [0042] As a result of the above pressing and cutting operations, a pre-shaped product  18 , having the two board terminals  12  serially connected together, is formed as shown in FIG. 2. Electrically-conductive metal is plated on the thus formed pre-shaped product  18 . With this plating, a film of electrically-conductive metal can be firmly formed on the pre-shaped product  18  uniformly over the entire surface thereof. The reason for this is that the pre-shaped product  18 , shown in FIG. 2, is simple in construction, and does not have any complicated hole and bent portion.  
     [0043] After this plating is effected, the pre-shaped product  18  is cut at its central portion, thereby separating the two board terminals  12  from each other. The thus separated board terminals  12  can be mounted on the printed circuit board  19 .  
     [0044] For mounting the board terminal on the printed circuit board  19 , the insertion portion  13  is inserted into the through hole  20  in the printed circuit board  19 , and the soldering portion  14  is soldered to a pattern on the printed circuit board  19 . The width H2 of the soldering portion  14  has been made generally equal to the thickness T1 by the above cutting operation, and therefore the soldering portion  14  has a generally square cross-section. Therefore, a thermal stress, developing during the soldering operation, is uniform, and the soldering can be effected satisfactorily without forming any crack.  
     [0045] In this production, those portions, which are cut off from the square wire  11 , and are discarded, are produced only when the soldering portions  14  are formed by the above cutting operation. Namely, the cut-off portions  21  are only those (indicated in broken lines in FIG. 3) disposed on the opposite sides of the soldering portions  14 , and the amount of the cut-off portions  21  is small, and generally the whole of the square wire  11  can be formed into the board terminals  12 . Therefore, a loss of the material is small, and the yield rate can be enhanced.  
     [0046]FIG. 4( a ) shows the relation between the soldering portion  14 , passing through the through hole  20  in the printed circuit board  19 , and the through hole  20  when the insertion portion  13  of this embodiment is inserted into the through hole  20 . As described above, the width of the soldering portion  14  is reduced by the cutting operation, and therefore the diameter of the through hole  20  can be reduced. Therefore, the board terminals  12  can be mounted at a high density on the printed circuit board  19 . FIG. 4( b ) shows the case where the cutting operation or the pressing operation is not effected, and in this case, the through hole  20  must have a diameter corresponding to the width Hi of the square wire  11 , and the board terminals can not be mounted at a high density.  
     [0047] As described above, generally the whole of the square wire can be formed into the board terminals, and the board terminals can be produced with a minimum loss of the material. And besides, any crack will not develop when soldering the board terminal to the printed circuit board, and also the diameter of the through holes can be reduced, so that the board terminals can be mounted at a high density on the printed circuit board.  
     [0048] In the present invention, the resin of the connector intrudes into the recesses in the connection portion, so that the resin and the recesses engage each other. Therefore, the board terminal can be stably mounted on the connector.  
     [0049] In the present invention, since the electrically-conductive metal is plated on the board terminal, the reliability of the soldering is enhanced.  
     [0050] In the present invention, generally the whole of the square wire can be formed into the board terminal, and therefore the production can be performed with a minimum loss of the material.  
     [0051] In the present invention, the recesses in the connection portion are formed simultaneously when forming the insertion portion by pressing, and therefore the number of the process steps is not increased, and the board terminal can be easily produced.  
     [0052] In the present invention, the plating can be applied to the board terminal over the entire surface thereof, and this plating enhances the reliability of the soldering.