Connection structure of wire and terminal, connecting method therefor and a terminal

Abstract: A soldering material (28) is joined to a surface (13a) of a terminal (13). The terminal (13) is incorporated in a groove (18) of a connector housing (11) so that a covered wire (19) is made into contact with the terminal (13). A cover (12) is mounted so as to insert protrusions (22) into the grooves (18). By carrying out ultrasonic vibration while applying a pressure by a ultrasonic horn, a covering portion of the covered wire is melted and removed. The soldering material (28) is melted by heat generated when the covering portion is melted so that the soldering material (28) is made into contact with the cores thereby the cores and terminal (13) being connected with each other through the soldering material (28). As a result, the soldering material (28) makes a firm contact with the cores.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a connection method for connecting a covered wire and a terminal, and a terminal for use therein. Description of the Related Art Figs. 1 to 5 show a conventional connection structure by ultrasonic vibration described in Japanese Patent Application Laid Open No.Hei7-320842. In connection structures shown in Figs. 1 to 5, a pair of resin chips 2 in which soldering material 1 such as solder is filled or installed are used, and covered wires 5 the cores 3 of which are covered with each covering portion 4 intersect each other and are joined with each other. That is, as shown in Fig. 1, the intersecting portion of the covered wires 5 is pinched with a pair of the resin chips 2 from up and down. A ultrasonic horn (not shown) is fit to the resin chip 2 so as to apply a pressure to the intersecting portion. With this condition, ultrasonic waves are applied from the ultrasonic horn, so that as shown in Fig. 2, the resin chips 2 are melted and fused together. The covering portion 4 of the covered wire 5 is melted and removed so as to expose the cores 3. At the same time, the soldering material 1 is melted by heat generated when the chips 2 are melted, so that the exposed cores 3 are soldered with each other. In connection structures shown in Figs. 3, 4, resin chips 6 in which the soldering material 1 is buried such that its top is exposed are used. The resin chips 6 are contacted with the intersecting portion of the covered wires 5 such that the soldering material 1 is in contact therewith. By melting the resin chips 6 and then melting and removing the covering portion 4, the intersecting cores 3 are soldered with each other by the soldering material 1. In a connection structure shown in Fig. 5, a terminal metal 1 is connected to a covered wire 5. According to this structure, one resin chip 8 having the soldering material 1 is placed on an anvil 9 and then the terminal metal 7 and covered wire 5 are placed on the anvil 9 such that they are made in contact with each other. Then, the other resin chip 8 is contacted with the covered wire 5. By carrying out ultrasonic vibration by the ultrasonic horn 10, the covering portion 4 is melted and removed. At the same time, the resin chip 8 is melted and the soldering material 1 is melted so as to connect the cores 3 to the terminal metal 7. However, because the resin of the covering portion 4 and resin chip 2 exist between the intersecting cores 3 in the connection structure shown in Figs. 1, 2, even if the soldering material 1 is melted at the same time as the melting of the resin, the melted soldering material is obstructed by the resin, so that it cannot make an excellent contact with the cores thereby the connecting reliability being reduced. In the connection structures shown in Figs. 3 to 5, the melted soldering material 1 is expelled outside of the connecting portion together with a melted portion of the covering portion 4 of the covered wire 5, so that the reliability of the connection is also reduced. EP 0 465 173 A discloses a method comprising the steps of: incorporating a terminal into a groove formed on a first resin member; putting on the terminal a covered wire including cores covered with a covering portion made of resin; inserting a protrusion formed on a second resin member into the groove in such a manner that the protrusion and the groove pinch the terminal and the covered wire therebetween; and applying ultrasonic vibrations while applying a pressure to the covered wire and the terminal so as to melt and remove the covering portion. The method is used for manufacturing electronic circuit connectors. For this purpose, a first or bottom weldable section and a second or top weldable section are provided. The bottom section has a groove, and the top section has a protrusion formed to fit the groove. An elongated contact has the shape of a thin metallic plate or a thin round metal pin. A lead wire may be a vinyl-insulated thin twisted wire. When ultrasonic welding is performed (and simultaneous clamping under pressure), the vinyl insulation of the wire dissolves, and the lead wire is welded to the contact. Simultaneously, the top and bottom sections are welded together. In summary, this document discloses ultrasonic welding of the wire to the contact, and also of the top and bottom sections. Solder is not mentioned in this document. DE 27 57 038 A discloses ultrasonic soldering using a coat of a soldering metal, in particular tin. Claim 1 of this document discloses ultrasonic soldering of spring contacts to ends of a flat cable using a coating of a soldering metal provided on at least one of the contacts and the ends. Whereas figure 2 of this document shows an end of a conductor which is connected to a contact bed by direct ultrasonic welding, and additionally shows remainders of a cable insulation which was not removed before ultrasonic energy was applied, figure 3 of this document shows ultrasonic soldering of an end to a contact bed. The description relating to figure 3 mentions a soldering metal between the end of a conductor and the contact bed. WO 86/02497 discloses according to the abstract thereof, terminals having insulations piercing, conductor engaging portions which have a layer of solder integral therewith. The method disclosed in this document is called IDC or insulation displacement correction (automatic stripping). Soldering is performed whereas ultrasonic energy is not mentioned in this document. SUMMARY OF THE INVENTION The present invention has been achieved with such points in mind. It therefore is an object of the present invention to provide a connecting method for a covered wire and a terminal allowing the soldering material to make a secure contact with the cores so as to improve reliability of connection, and a terminal for use therein. To achieve the object, according to a first aspect of the present invention, there is provided a connection method for a covered wire and a terminal according to claim 1. By pinching the terminal and covered wires with the resin members, the soldering material of the terminal comes into contact with the covered wire. If the covering portion is melted and removed by ultrasonic vibration with this condition, the soldering material comes into contact with the cores inside the covering portion and the soldering material is softened or melted. As a result, the cores bite into the soldering material so that the cores and terminal are conductively connected to each other through the soldering material. Therefore, because the soldering material makes a firm contact with the cores, a reliability of connection is improved. According to a second aspect of the invention, there is provided a connection method for a covered wire and a terminal according to claim 2. A preferred embodiment of the method according to claim 2 is indicated in dependent claim 3. A terminal for use in a method according to the present invention comprises: a conductive soldering material at the surface of the terminal, and at least one upright wall extending parallel to a covered wire which is put on the terminal, and having at least one aperture where the melted covering portion of the wire is relieved. Due to such a construction, the terminal is stabilized by the upright wall in the groove, thereby assembling working is facilitated. Furthermore, according to the aperture, the melted covering portion of the wire is easily relieved, thereby facilitating to remove the melted covering portion from the covered wire. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in conjunction with the accompanying drawings, in which: Fig. 1 is a sectional view of a conventional structure; Fig. 2 is a sectional view showing a connection with the structure of Fig. 1; Fig. 3 is a partly broken perspective view of a resin chip for use in another conventional connection structure; Fig. 4 is a partly broken perspective view of still another connection structure; Fig. 5 is an exploded perspective view of still another connection structure; Fig. 6 is an exploded perspective view of an embodiment of the present invention; Fig. 7 is a sectional view showing a state in which the terminal and covered wire are made into contact with each other; Fig. 8 is a sectional view showing a state in which the covering portion is melted and removed by ultrasonic vibration; Fig. 9 is a sectional view showing a state in which the cores and terminal are connected to each other through soldering material; Fig. 10 is an exploded perspective view of the connection structure according to a second embodiment of the present invention; Fig. 11 is a perspective view of the ultrasonic horn according to a second embodiment of the present invention; Fig. 12 is a perspective sectional view of the ultrasonic horn, the terminal and the covered wire according to a second embodiment of the present invention, and showing the stage where the covering portion of the covered wire is melted; Fig. 13 is a sectional view of the ultrasonic horn, the terminal and the covered wire, and showing the specific arrangement thereof; Fig. 14 is a sectional view of the connection structure where the melted covering portion of the covered wire is relieved into an aperture formed in the terminal; Fig. 15 is a perspective view which shows a first stage of the connection method of the second embodiment of the present invention; Fig. 16 is a perspective view which shows a second stage of the connection method of the second embodiment of the present invention; Fig. 17 is a perspective view which shows an ultrasonic vibration performing stage of the connection method of the second embodiment of the present invention; and Fig. 18 is a perspective view of a connector where the connector housing is covered with the cover by the connection method of the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS There will be detailed below the preferred embodiments of the present invention with reference to the accompanying drawings. Like members are designated by like reference characters. Fig. 6 is a disassembly perspective view of an embodiment of the present invention. Figs. 7 to 9 are sectional views showing steps of connection. As shown in FIG. 6, this embodiment includes a first resin member 11, second resin member 12 and terminals 13 made of conductive metal. In this embodiment, the present invention is applied to a connector. The first resin member 11 acts as a connector housing and the second resin member 12 acts as a cover. The first resin member 11 contains a hood portion 14 which is to be connected to a mating connector (not shown) through engagement and a wire introducing portion 15 which is provided on one side of the hood portion 14 integrally therewith. In the wire introducing portion 15, a bottom wall portion 16 extends from the hood portion 14 and a plurality of partition wall portions 17 are protruded in parallel to each other from a top face of the bottom wall portion 16 so that portions surrounded by the partition wall portions act as a groove 18. The groove 18 provides a rectangular section the top of which is open. The terminal 13 is incorporated in each groove 18 so as to achieve connection with a covered wire 19. A portion outside of the partition wall portion 17, of the bottom wall portion 16 acts as a welding portion 20 on which the cover 12 is to be welded. The cover 12 comprises a closed plate portion 21 for covering the wire introducing portion 15, a plurality of protrusions 22 formed on a face of this closed plate portion 21 opposing the wire introducing portion 15 and side wall portions 23 provided outside of the protrusions 22. The protrusions 22 have the same rectangular sections as the grooves 18 and are formed on positions opposing the grooves 18. The protrusions 22 are formed with a slightly smaller dimension than the grooves 18 and inserted into the corresponding grooves 18 when the cover 12 is placed over the wire introducing portion 15. By this insertion, the protrusions 22 make a contact with the covered wire 19 introduced in the grooves 18 so as to press the covered wire 19 against the terminal 13. According to the present embodiment, each protrusion 22 has a cutout portion 24 at its middle portion so that it is discontinuous. Thus, the protrusions 22 do not contact the entire length of the covered wire 19 in the groove 18 so that the cutout portion 24 is not in contact with the covered wire 19. By forming the cutout portion 24 which is never in contact with the covered wire 19, it is possible to let the covering portion melted by ultrasonic vibration or ultrasonic wave oscillation go into the cutout portion 24. The side wall portions 23 of the cover 12 oppose the welding portions 20 of the wire introducing portion 15, so that when the cover 12 is placed on the wire introducing portion 15, the side wall portions 23 make contact with the welding portions 20. A tip of this side wall portion 23 is a sharp edged welding portion 25 and welded to the welding portion 20 of the wire introducing portion 15 by ultrasonic vibration. The connector housing 11 and cover 12 are made of acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, PC (polycarbonate) resin, PVC (polyvinyl chloride) resin, polyethylene resin, olefin base resin such as polypropylene, PEI (polyetherimide) base resin , PBT (polyethylene terephtalate) base resin, ABS/vinyl chloride alloy, acrylic/vinyl chloride alloy, polyester elastomer or block copolymer of PBT and poly ether. The covered wire 19 is formed by covering a plurality of cores 26 with a covering portion 27 made of insulating resin such as vinyl chloride or the like as shown in FIG. 7. The terminal 13 is formed in the form of a flat plate and inserted in the groove 18 in the connector housing 11. The terminal 13 is inserted through the hood portion 14 of the connector housing 11 so that an insertion end thereof makes contact with a terminal of a mating connector engaged in the hood portion 14 thereby attaining an electrical connection. This terminal 13 is conductively connected to the cores 26 of the covered wire 19. On a contacting portion of the terminal 13 with the covered wire 19 or surface 13a is placed conductive soldering material 28. The soldering material 28 is made of soft solder or low melting solder, and melted over the surface 13a of the terminal 13 before connected to the cores 26. This connection can be carried out easily by dropping the melted soldering material 28 on the surface 13a of the terminal 13 or coating the surface 13a therewith and then cooling. Although joining by the soldering material 28 is permitted to be carried out over the entire area of the surface 13a of the terminal 13, by carrying out the joining at only portions opposing the protrusions 22 of the cover 12 as shown in Fig. 6, the amount of the soldering material 28 can be saved so that it is economical and the joining work is simplified. Next, the assembly work of the present embodiment will be described. As shown in Fig. 6, the terminal 13 on which the soldering material 28 is preliminarily placed is introduced in each of the grooves 18 of the connector housing 11 so that the end portion of the terminal 13 is inserted through the hood portion 14. Then, the covered wire 19 is placed on each of the terminals 13 and the cover 12 is mounted over the wire introducing portion 15. At this time, as shown in Fig. 7, each of the protrusions 22 is aligned with the groove 18 and inserted into the groove 18, so that the covered wire 19 and terminal 13 are pinched with the connector housing 11 and cover 12. With this condition, a ultrasonic horn (not shown) is fit to the cover 12 and ultrasonic vibration or ultrasonic wave oscillation is carried out while applying a pressure. This applied ultrasonic waves vibrate in a longitudinal direction which is the same direction as a pressure applying direction of the ultrasonic horn. This ultrasonic waves are transmitted to the covered wire through the protrusion 22. As a result, the covering portion 27 of the covered wire 19 is heated and the covering portion 27 is melted and removed as shown in Fig. 8. By melting and removing the covering portion 27, the cores 26 make contact with the soldering material 28 on the terminal 13. Further, because a pressure is applied by the ultrasonic horn, the protrusion 22 is lowered and the protrusion 22 itself begins to melt. The soldering material 28 absorbs heat produced when the covering portion 27 is melted and heat produced when the protrusions 22 are melted. By this absorption, the soldering material 28 is softened or melted. Because of this softening or melting of the soldering material 28, the cores 26 bite into the soldering material 28 so that as shown in Fig. 9, the cores 26 and soldering material 28 contact with each other through a large contacting area. Due to this contacting between the soldering material 28 and cores 26, the cores 26 are conductively connected to the terminal 13. In this connection structure, the melted resin does not turn to an obstacle to the contact between the soldering material 28 and cores 26 and further the soldering material 28 is never expelled outside. As a result, the soldering material 28 and cores 26 make a firm contact with each other so that a highly reliable connection is achieved. Further because the cores 26 bite into the soldering material 28 so as to attain the firm contact and the melted soldering material 28 adhere to the surrounding of the cores 26, the contacting area between the soldering material 28 and cores 26 is enlarged, so that the contact resistance can be reduced, thereby achieving a stable connection between the cores 26 and terminal 13. The covering portion 27 melted by ultrasonic vibration is filled between the groove 18 and protrusion 22 as indicated by reference numeral 29 of Figs. 7, 8. This melted portion 29 presses the terminal 13 and cores 26 such that they are fixed. Thus, there is no possibility that the terminal 13 is separated from the cores 26 thereby keeping a reliable connection. Connection of the connector housing 11 and cover 12 is carried out by making the respective welding portions 20, 25 into contact with each other and then melting them while applying a pressure by ultrasonic vibration. In this case, because the melted portion 29 of the covering portion 27 is filled between the internal wall of the groove 18 and the external wall of the protrusion 22 so that this filled melted portion 29 acts to join the connector housing 11 with the cover 12, its joining force is intensified. Therefore, the protrusion 22 can firmly hold the cores 26 against the terminal 13, so that a highly reliable connection is attained. Referring now to Figs. 10 to 18, a second embodiment will be explained hereinafter. The embodiment includes a connection structure or a connection method for a wire and a terminal where an ultrasonic horn directly contacts to the wire to apply or to perform the ultrasonic vibration. Fig. 10 shows an exploded perspective view of the connection structure of the embodiment. Fig. 11 shows a perspective view of the ultrasonic horn 110 to be contact to the covered wires 19. The ultrasonic horn 110 has a plurality of protrusions 110a. To connect the covered wires 19 with a terminal 113, first of all, the terminal 113 is introduced or incorporated in the groove 18 of the connector housing 111 as shown in Fig. 15. The terminal 113 has two upright walls 113a which are formed with apertures 113b where the soldering materials 28 are located so that the melted covering portion 29 of the covered wires 19 is relieved as shown in Figs. 10, 12 and 15. Next, the covered wires 19 are put on the terminals 113 as shown in Fig. 16. After that, the ultrasonic horn 110 is put and pressed on the covered wires 19 in a manner such that the plurality of protrusions 110a contact to the covered wires 19 as shown in Fig. 17, then applying and performing the ultrasonic vibration. By applying the ultrasonic vibration by ultrasonic horn 110, the covering portion 27 of the covered wires 19 is melted and removed from the covered wires 19, so that the melted covering portion 29 of the covered wires 19 is relieved to the apertures 113b, as shown in Figs. 13, and 14. In this stage, the soldering materials 28 are melted and the stripped cores 26 are pressed against the melted soldering materials 28 so that the surfaces of the soldering materials 28 are formed with concave portions which are depending and according to contours of the stripped cores 26 as shown in Figs. 12 and 14. Therefore, the contact area between the stripped cores 26 and the soldering materials 28 can be increased, thereby reducing the contact resistance therebetween for the electrical current. As the next stage, after removing the ultrasonic horn 110 from the partially melted covered wires 19, a cover 112 is fitted to the connector housing 111 as shown in Fig. 18, in such a manner that protrusions 112a protruding from the bottom surface of the cover 112 are inserted into the holes shown in Fig. 12 formed in the covering portion 27 by the ultrasonic horn 110. In the embodiment, the number of the grooves 18 of the connector housing 111 is five(5), and the number of the soldering materials 28 of the terminal 113 is two(2). The number of the protrusions 110a is ten(10 = 5 X 2). Furthermore, the cover 112 is formed with the ten(10) protrusions 112a protruding from the bottom surface thereof in such a manner that the location, arrangement and numbers are corresponding to the location, arrangement and numbers of the protrusions 110a of the ultrasonic horn 110. Therefore, the covered wires 19 are kept to be firmed in the connector housing 111 even when the covered wires 19 are pulled by an outer force which is not intended. Furthermore, depending on the two soldering materials 28 for one terminal 113, the covered wire 19 is stabilized and the cores 26 can avoid from being broken by the Bauschinger effect. Designing the outer size of the terminal 113 to fit into the inner size of the groove 18, the terminal 113 is stabilized in the groove 18. Therefore, productivity of the connection structure can be improved and facilitated. According to the state where the cover 112 is fitted to the connector housing 111, the ten(10) protrusions protruding from the bottom surface of the cover 112 are kept to push and to press the stripped cores 26 against the terminal 113 to electrically contact each other. While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes, and it is to be understood that changes and variations may be made without departing from the scope of the following claims.

Claims: A method of connecting a covered wire (19) and a terminal (13) in an electrical connector comprising a connector housing in the form of a first resin member (11) and a cover in the form of a second resin member (12); the method comprising the steps of: providing a conductive soldering material (28) at the surface (13a) of the terminal (13) prior to incorporating the terminal (13) into a groove (18) of the first resin member (11); incorporating the terminal (13) into the groove (18) formed on the first resin member; putting on the terminal (13) a covered wire (19) including cores (26) covered with a covering portion (27) made of resin; inserting a protrusion (22) formed on the second resin member (12) into the groove (18) in such a manner that the protrusion (22) and the groove (18) pinch the terminal (13) and the covered wire (19) therebetween; and applying ultrasonic vibrations while applying a pressure to the second resin member (12) and thereby to the covered wire (19) and the terminal (13) so as to melt and remove the covering portion (27); softening the soldering material (28) by heat generated when the covering portion (27) is melted by the ultrasonic vibrations and relieved through at least one aperture in the terminal; and bringing the cores (26) into contact with the softened soldering material (28) for soldering the cores (26) to the terminal (13). A method of connecting a covered (19) wire and a terminal (113) in an electrical connector comprising a connector housing in the form of a first resin member (111) and a cover in the form of a second resin member (112); the method comprising the steps of: providing a conductive soldering material (28) at the surface of the terminal (113) prior to incorporating the terminal (113) into a groove (18) formed on the first resin member (111); incorporating the terminal (113) into the groove (18) formed on the first resin member (111); putting on the terminal (113) a covered wire (19) including cores (26) covered with a covering portion (27) made of resin; inserting a protrusion of an ultrasonic horn (110) into the groove (18) in such a manner that the ultrasonic horn (110) and the groove (18) pinch the terminal (113) and the covered wire (19); and applying ultrasonic vibrations while applying a pressure to the covered wire (19) and the terminal (113) so as to melt and remove the covering portion (27); softening the soldering material (28) by heat generated when the covering portion (27) is melted and removed by the ultrasonic vibrations and relieved through at least one aperture in the terminal; and bringing the cores (26) into contact with the softened soldering material (28) for soldering the cores (26) to the terminal (113); removing the ultrasonic horn (110); and inserting at least one protrusion (112a) formed on a second resin member (112) into the groove (18) in such a manner that the protrusion (112a) and the groove (18) pinch the terminal (113) and the wire (19). A method according to claim 2, characterized in that the ultrasonic horn (110) has a plurality of protrusions (110a); and the second resin member (112) has a plurality of protrusions (112a) corresponding in location, arrangement and number to the location, arrangement and number of the protrusions (110a) of the ultrasonic horn (110). A terminal for use in a method according to one of claims 1 to 3, the terminal (113) comprising: conductive soldering material (28) at the surface of the terminal (113); and at least one upright wall (113a) extending parallel to a covered wire (19) which is put on the terminal (113), said upright wall having at least one aperture (113b) for relieving the melted covering portion (29) of the covered wire (19).

Inventors: SHINCHI AKIRA, SHINCHI, AKIRA, Shinchi, Akira, Yazaki Parts Co., Ltd.
Applicants: YAZAKI CORP, YAZAKI CORPORATION
Application year: 1998
Main classification: H01R4
IPC codes: H01R43, H01R13, H01R4