METHOD OF INTERCONNECTING ELECTROCONDUCTIVE WIRES BY MEANS OF HARD SOLDERING

Abstract: The invention relates to hard soldering by means of electrodes of an iron alloy in order to make connections which must be resistant to operating temperatures of approximately 100 DEG C or more and/or which soldering operation involves the burning away of insulating material from the wires. The invention can be used, for example, to attach a ringing-damping circuit to a deflection coil in a television receiver or monitor.

Description: Method of interconnecting electroconductive wires by means of hard soldering. The invention relates to a method of connecting an electroconductive wire to another wire by means of soldering. The invention can be used in every field of application where an electroconductive wire is connected to another wire. The invention can be used to advantage if the wire to which the conductive wire is connected is provided with an insulating material, if the operating temperature of a product in which the connection is used exceeds 110 °C, or if, in operation, the product vibrates strongly or is mechanically taxed. This may apply, for example, to line deflection coils in a display device, components in a motorcar or driving motors. In a display device comprising a cathode ray tube and line deflection coils, it may be necessary to attach a ringing-damping circuit to the line deflection coils. This circuit may comprise a resistor and a capacitor which are arranged in series. Said resistor may be a component. Alternatively, however, an outwardly projecting loop of the coil can be used as a resistor. A connecting wire of the ringing-damping circuit must be in electric contact with at least one wire of the line deflection coil. If it contacts more than one wire, the result is in general neither better nor worse. For the wire in line deflection coils use is sometimes made of Litzendraht wire. This is a multiple-stranded wire in a jacket. Providing a wire with a connection without touching adjacent wires often constitutes a problem. Touching of adjacent wires may cause damage and hence a short-circuit. It can be precluded if, during the winding process of the coil, a turn is made to project from said coil, thereby permitting a wire to be attached more easily in said location at a later stage. In a display device comprising a cathode ray tube and line deflection coils, the ringing-damping circuit was hitherto attached to the line-deflection coil by means of soft soldering. Soft soldering means that a solder material having a low melting point for instance 100°C, generally a tin-lead solder, is used. In this method, first the insulation must be removed from a part of the wire(s) of the line-deflection coil to which the connecting wire of the circuit is attached. This is laborious. In addition, there is a substantial risk that the remaining wires are damaged during the connecting process. Moreover, a problem arises if the connection is used in a type of line-deflection coil having an operating temperature of approximately 110 °C and higher. A connection formed by soft soldering is no longer stable at a temperature of approximately 110 °C and higher. Such a connection can break easily. In the automobile industry, this problem is precluded by using plug-and-socket connections to mount components. However, said connections are unsuitable for attaching a circuit to the line deflection coil. It is an object of the invention to provide a simple, rapid and, preferably, reliable manner of electrically interconnecting two electroconductive wires one of which is provided with an insulating material. In accordance with the invention, this object is achieved by hard soldering. Hard soldering is to be understood to mean soldering using a solder material having a high melting temperature, such as silver. Due to the high solder temperature, the insulation of the insulated wire may be burned away during the course of the soldering process. Consequently, removal of the insulation in a separate process prior to soldering can be dispensed with. As a result, the method becomes simpler and quicker. The connection thus formed is also more reliable because connections formed by hard soldering are stronger and more resistant to relatively high temperatures than connections formed by soft soldering. To render the process even more reliable, use can be made, during hard soldering, of electrodes which are made entirely of a metallic material having a higher resistance than copper or which have a tip made of said material. For hard soldering use is customarily made of electrodes which consist entirely of a copper alloy. This has the disadvantage that a current intensity of approximately 1200 amperes is necessary for soldering. At this current intensity, the turns of the coil are liable to be blown. If use is made of electrodes of a material having a higher resistance than copper, or if they are provided with a tip of said material, a lower current intensity suffices to reach a temperature at which the insulation burns away and the solder material melts. Preferably, this material is an iron alloy, such as chromium nickel steel or a molybdeen or wolfram alloy. Since these materials are poor electric conductors, the electrodes themselves often reach the soldering temperature at a current intensity of only 300 amperes. The heat of the electrode tips together with the heat produced by the current passing through the wire cause the insulating material to be burned away and the hard-soldered connection to be formed, without the risk of the wire melting away. If, for example, a ringing-damping circuit is attached to a line-deflection coil, it is advantageous to attach the wire of the circuit to be connected around a bundle of wires of the coil. The reason for this being that, in order to effectively connect the circuit, it is sufficient if only one wire makes a properly electroconducting connection. This makes the method even more reliable. The fastening operation in accordance with the invention is carried out as follows: A conductive wire which is provided with a conductive coating of the solder material is attached to an insulated wire or bundle of wires (for example by means of PUR L&K insulation or PEI insulation). The conductive wire is folded around the insulated wire or bundle of wires so as to form a "sandwich". An electrode is provided on either side of the "sandwich". A voltage is applied to the electrodes. - A current is running through the wire folded around the turn. The heat causes the insulating material to disappear and the conductive coating of solder material to melt. After removal of the electrodes, the conductive coating becomes hard again and forms the connection. The conductive coating preferably comprises silver, however, another material may alternatively be used. Additional advantages of the invention are: The time which is necessary to burn away the insulating material of the wires during connecting another wire to said wires can be reduced from between approximately three and five seconds (characteristic for a traditional soldering process) to less than three seconds or even less than one second. Soft solder is not used, so that spattering of this material during operation cannot take place. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings: Fig. 1 is a current diagram of the line-deflection coils of a display device comprising ringing-damping circuits. Fig. 2A is an embodiment of a line-deflection coil in which the location of the wire of the ringing-damping circuit is indicated. Fig. 2B is an embodiment of a line-deflection coil in which the location of the wire of the ringing-damping circuit is indicated. Fig. 3A is a sectional view of an embodiment of the assembly of wires, wire to be attached and electrodes, during soldering. Fig. 3B is a sectional view of an embodiment of the assembly of wires, wire to be attached and electrodes, during soldering. Fig. 1 shows the current diagram of line-deflection coils. In this case, a branch is attached to a coil turn in the middle (4) of the coils (1), which branch is connected to a ringing-damping circuit. In this case, these circuits comprises a resistor (2) and a capacitor (3): an RC circuit. Fig. 2A and Fig. 2B both show an embodiment of the line deflection coil (1) to which a ringing-damping circuit (5) is attached. In this case, the circuit is provided in the middle of the coil. This location is indicated by reference numeral (4). As regards die types of coils shown, the circuit is attached to an already detached bundle of wires. Consequently, the invention can advantageously be used with these types of coils as the production process of the coil can remain unchanged. In the production process, it is not necessary to feed a turn outwards in order to enable the circuit to be attached to said turn at a later stage without much risk of damage. Figs. 3A and 3B show how a wire (6) is folded around a bundle of other wires (7) and how, on either side thereof, an electrode is provided having a base (8) of a copper alloy and an iron tip (9). Two embodiments of the electrodes are shown. In one embodiment (Fig. 3 A) the tips (9) of the steel alloy cover the entire upper surface of the base (8). In the other embodiment (Fig. 3B), the tip (9) protrudes from the base (8) and does not cover the entire upper surface of said base. The bundle of wires (7) around which the fastening wire (6) is folded may, of course, alternatively be a single wire, a Litzendraht wire or a bundle of Litzendraht wires. In brief summary, the invention relates to hard soldering by means of electrodes of an iron alloy in order to make connections which must be resistant to operating temperatures of approximately 100 °C or more and/or which soldering operation involves the burning away of insulating material from the wires. This invention can be used, for example, to attach a ringing-damping circuit to a deflection coil in a television receiver or monitor.

Claims: CLAIMS: 1. A method of connecting a first electroconductive wire to an insulated, second electroconductive wire by means of soldering, characterized in that the first wire is folded around the second wire, electrodes are provided on this assembly and a current is passed through said assembly, as a result of which the insulating material is burned away and the solder connection is formed. 2. A method as claimed in Claim 1, characterized in that the first wire is a fixing wire of an electronic component and the second wire is a wire of a coil. 3. A method as claimed in Claim 1 or 2, characterized in that the electrodes are made of a metallic material having a resistance which exceeds that of copper. 4. A method as claimed in Claim 1 or 2, characterized in that the electrodes have tips of a metallic material having an electric resistance which is higher than that of copper. 5. A method as claimed in Claim 4, characterized in that the metallic material is a steel alloy. 6. A method as claimed in Claim 2, 3, 4 or 5, characterized in that a wire or a bundle of wires is pulled loose from the coil, and in that the fixing wire of the electric component is attached thereto. 7. A method as claimed in Claim 1, 2, 3, 4, 5 or 6, characterized in that the first wire is provided with a coating of a solder material having a higher melting temperature than a tin-lead solder. 8. A method as claimed in Claim 7, characterized in that the solder material comprises silver. 9. A method as claimed in Claim 2, 3, 4, 5, 6, 7 or 8, characterized in that the coil is a line-deflection coil and the component forms part of a ringing-damping circuit. 10. A coil with a component which is attached to this coil, a connecting wire of the component being folded around a wire of the coil, and the connection containing a solder material having a higher melting temperature than a tin-lead solder.

Inventors: DANKERS JOHANNES ADRIANUS HEND, DEKKERS BERNARDUS HENDRIKUS JO, PEETERS HENRICUS HUBERTUS, VAN DEN BERG HENDRIK DIRK, DANKERS, JOHANNES, ADRIANUS, HENDRIK, DEKKERS, BERNARDUS, HENDRIKUS, JOHANNES, PEETERS, HENRICUS, HUBERTUS, VAN DEN BERG, HENDRIK, DIRK
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1997
Main classification: H01R4
IPC codes: H01R4, H01R43