BOARD TERMINAL AND METHOD OF PRODUCING SAME

Board terminals 12 , each including a tapering insertion portion 13 for insertion into a through hole in a board, a soldering portion 14 to be soldered to the board, and a connection portion 15 for connection to a mating terminal, are produced from a square wire 11 , 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. The square wire 11 has a width larger than a thickness thereof. The insertion portion 13 is formed by pressing the square wire, and the soldering portion 14 is formed by cutting or pressing widthwise opposite side portions of that portion of the square wire extending from the insertion portion 13 , the soldering portion having a width smaller than the width of the square wire. Those portions, removed from the square wire by cutting or pressing, are very small, and generally the whole of the square wire can be formed into the board terminal, and therefore a loss of the material is reduced.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 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. 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 . 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 . 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. 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. 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. 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 . 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 . 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. 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&equals;0.6 mm) of each soldering portion 14 , thus formed by cutting the widthwise opposite side portions, is smaller than the width H1 (H1&equals;1.00 mm) of the square wire 11 , and is close in value to the thickness T1 (T1&equals;0.64 mm) of the square wire 11 (the board terminal 12 ). 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. 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 . 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. 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. 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. 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. 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. In the present invention, since the electrically-conductive metal is plated on the board terminal, the reliability of the soldering is enhanced. 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. 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. 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.