Method for fixing by brazing a portion of a conductive wire from a cable to a conductive pin on an electronic board and corresponding system

Abstract

The invention relates to a method for brazing a conductive pin (11) of an electronic board (1) to a portion (211) of a conductive wire (21) of a cable (2). The method comprises winding a stripped portion (211) of the conductive wire (21) and an unstripped portion (221) around and in contact with the pin (11); cleaning and immersing the assembly in a solder bath (4) so ​​that the free end (119) of the pin (11) is embedded in the solder (3); cleaning the assembly that has been immersed in the solder bath; and repeating the immersion step. The invention also relates to a corresponding system. Figure for the abstract: Fig. 2C

Description

Title of the invention: Method for fixing by soldering a part of a conductive wire of a cable on a conductive pin of an electronic card and corresponding system FIELD OF THE INVENTION

[0001] The present invention relates generally to the fixing of a conductive wire of a cable on a pin of an electronic card (printed circuit card). PREVIOUS ART

[0002] When a conductive wire of a cable is soldered to a pin of an electronic card, it is found that the fixing of the conductive wire to the pin may be of poor quality and / or that the card has been damaged during the soldering operation.

[0003] It is thus desirable to be able to provide a method for fixing at least one conductive wire of a cable to an electronic card pin which makes it possible to reliably obtain a quality fixing, and with a reduced risk of damage to the card. Summary of the invention

[0004] To this end, the invention relates to a method of fixing by soldering a part of a conductive wire of a cable, on a conductive pin of an electronic card, said cable comprising said conductive wire and an insulating sheath surrounding said conductive wire, characterized in that the method comprises the following steps: - stripping a part of the cable to reveal a part of the conductive wire of a given length to allow the stripped part of the conductive wire to be wound around the pin in order to ensure electrical conduction between the wire and the pin; -winding the stripped part of the conductive wire and an unstripped part of the cable around and in contact with the pin; - stripping the entire stripped portion of the conductive wire wound around the pin and at least the portion of the pin around which the stripped portion of the conductive wire is wound, - dipping said assembly into a brazing bath, over at least a given length of said assembly and so that the free end of the pin is embedded in a brazing material; - stripping of said assembly which has been dipped in the brazing bath; - repeating the step of soaking said assembly.

[0005] The method makes it possible to improve the quality of fixing a conductive wire to an electronic card pin, as well as its repeatability. Thanks to the method according to the invention, the risk of damage to the card is reduced because this method is less aggressive for the card and its components than usual soldering methods known from the state of the art. Indeed, with the method according to the invention, the components on the card are subjected to a limited temperature, which reduces the risks of damage to the components.

[0006] Furthermore, the method makes it possible to limit the time required for the operation to fix one or more cable conductor wires to the spindle. The method also makes it possible to improve operator safety.

[0007] The method may also comprise one or more of the following features taken in any technically admissible combination.

[0008] According to one embodiment, the repetition of the soaking step is followed by a drying step.

[0009] According to one embodiment, after repeating the soaking step, the method comprises a stripper cleaning step, for example for 2 minutes, by applying a stripper cleaner, also called a flux cleaner, in order to dissolve stripper residues used during the stripping operations.

[0010] According to one embodiment, the step of cleaning the stripper is followed by a step of rinsing said assembly using isopropyl alcohol.

[0011] According to one embodiment, the brazing bath with which the dipping steps are carried out comprises a molten filler metal composed mainly of lead, and preferably also comprises antimony and tin.

[0012] According to one embodiment, the brazing bath in which the dipping steps are carried out mainly comprises gold.

[0013] According to one embodiment, each soaking step is carried out: - at a temperature in the range [345-355] degrees Celsius (preferably 350°C), and - for a duration between 3.5s and 5s, preferably for 4s.

[0014] According to one embodiment, the conductive wire has a diameter of 0.3 to 0.35 millimeters, preferably 0.32 millimeters (gauge 28), and the pin has: - a height in the range [2.9 - 3.1] millimeters, for example 3 millimeters, and - a diameter in the range [0.47-0.49] millimeters.

[0015] According to one embodiment, the end of the solder which covers the free end of the pin has a generally curved shape.

[0016] According to one embodiment, the free end of the stripped portion of the conductive wire is in contact with a portion of the pin which is spaced from the free end of the pin.

[0017] According to one embodiment, each step of dipping in the brazing bath of the said set, is carried out: - over at least half the length of the pin starting from its free end; and / or - over a distance which, starting from the free end of the pin, covers at least 1.5 turns of the stripped part of the conductive wire around the pin.

[0018] According to one embodiment, the winding of the stripped portion of the conductive wire around the pin is obtained by making two turns of the stripped portion of the conductive wire around and along the pin over a given length of the pin.

[0019] According to one embodiment, said cable being a first cable, a stripped portion of a conductive wire of a second cable is also wound and fixed by soldering on the pin; - the stripping step also comprising stripping the second additional cable to reveal the conductive wire of the second cable over a given length allowing the stripped portion of the conductive wire of the second cable to be wound around the pin in order to ensure electrical conduction between the wire and the pin; - the winding step also comprising winding the stripped portion of conductive wire of each cable around the pin and an unstripped portion of each cable; said assembly to which the stripping and dipping steps are applied comprising the stripped portion of conductive wire of each cable wound around the pin and the corresponding portion of the pin.

[0020] The invention also relates to a system comprising an electronic card having at least one conductive pin and at least one cable having a conductive wire and an insulating sheath, in which a stripped portion of the conductive wire of the cable and an unstripped portion of the cable located in the extension of the stripped portion are arranged around and in contact with the pin, the system comprising a solder which fixes at least a portion of the stripped portion of the conductive wire of the cable to the pin.

[0021] According to one embodiment, said system comprising a second cable, a stripped portion of the conductive wire of each cable and an unstripped portion of each cable located in the extension of the stripped portion, are arranged around and in contact with the pin; the system comprising a solder which fixes at least a portion of the stripped portion of the conductive wire of each cable to the pin. Brief description of the drawings

[0022] Other characteristics and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the appended drawings, in which:

[0023] - [Fig.l] [Fig.l] is a schematic view of an electronic card comprising pins (electrically conductive parts) to which electrical cables are soldered;

[0024] - [Fig.2A] [Fig.2A] is a schematic view of part of an electronic card and in particular a pin which projects from the card plate, and around which is wound a cable having a stripped part which is wound on the upper part of the pin and an unstripped part, which is wound on the lower part of the pin;

[0025] - [Fig.2B] [Fig.2B] is a schematic view of the board pin assembly and the cable of [Fig.2A] in the returned state to be dipped over a portion of the height of the pin in a soldering bath;

[0026] - [Fig.2C] [Fig.2C] is a schematic view of the board pin assembly and the cable of [Fig.2B], with a solder which results from the dipping shown diagrammatically in [Fig.2B];

[0027] - [Fig.3] [Fig.3] is a schematic view of another embodiment of the invention according to which two electric cables are wound and soldered at their stripped part on the pin.

[0028] - [Fig.4] [Fig.4] is a schematic view of several steps of a method of fixing by soldering a part of a conductive wire of a cable, on a pin of an electronic card, according to an embodiment of the invention. DETAILED DESCRIPTION

[0029] Embodiments of the invention are described below with reference to the accompanying drawings. In the drawings, the size and relative sizes of the elements may be exaggerated for clarity. Like numerals refer to like elements throughout the drawings. However, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0030] A reference throughout the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the occurrence of the phrase "in an embodiment" at various locations throughout the specification does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0031] With reference to the figures, a system is proposed comprising an electronic card 1 having at least one conductive pin 11 and at least one cable 2 having a conductive wire 21 and an insulating sheath 22, as for example illustrated in [Fig.2C]. A stripped portion 211 of the conductive wire 21 of the cable 2 and a non-stripped portion 221 of the cable 2 located in the extension of the stripped portion 211, are arranged around and in contact with the pin 11. A solder 3 fixes at least a portion of the stripped portion 211 of the conductive wire 21 of the cable 2 to the pin 11.

[0032] Such a system can be obtained by a method presented below. A method and a corresponding system are presented below for which a single cable is soldered to a pin (Figures 2A-2C in particular), but, as illustrated in [Fig. 3], another embodiment (which is presented later in the description) according to which several cables are soldered to the pin, is also conceivable.

[0033] A method is thus proposed for fixing by soldering a conductive pin 11 of a track of an electronic card 1 with a part 211 of a conductive wire 21 of a cable 2. The method is also generally called “solder welding”. Soldering comprises the addition of molten metallic material between the pin and the conductive wire.

[0034] Said cable 2 comprises said conductive wire 21 and an insulating sheath 22 surrounding said conductive wire 21. The conductive wire is usually made of copper, possibly gold.

[0035] According to one embodiment, the conductive wire 21 has a diameter of 0.37 millimeters, and the pin 11 has a height in the range [2.9 - 3.1] millimeters, for example 3 millimeters, and a diameter in the range [0.47-0.49] millimeters.

[0036] For example, it is possible to use a single-conductor AXON brand wire of the “Gauge 28” type (i.e. 0.32 or 0.321 millimeters in diameter).

[0037] A portion of the cable 2 is stripped (step 101 illustrated in [Fig.4]) to reveal a portion of the conductive wire 21 over a given length adapted (i.e. sufficient) to allow winding of the stripped portion 211 of the conductive wire 21 around the pin 11 and electrical conduction between the wire and the pin. The stripping is carried out cleanly, without tearing. The stripping allows contact of the wire with the pin, and the stripped length allows winding of the stripped portion around the pin.

[0038] The stripped portion 211 of the conductive wire 21 and an unstripped portion 221 of the cable 2 are then wound (step 102) around and in contact with the pin 11.

[0039] The stripped part 211 is located on the side of the free end of the pin and the non-stripped part 221 on the side of the card.

[0040] Preferably, the winding of the stripped part 211 of the conductive wire around the pin 11 is obtained by making two turns of the stripped part 211 of the wire conductor around and along pin 11 for a given length of the pin.

[0041] According to a preferred embodiment, the free end 219 of the stripped portion 211 of the conductive wire 21 is in contact with a portion of the pin 11 which is spaced from the free end 119 of the pin 11 as opposed to the end of the pin located on the side of the card. In other words, when the card is oriented so that the pin is directed upwards, the free end 219 of the stripped portion 211 of the conductive wire 21 is in contact with a portion of the pin 11 which is below the free end 119 of the pin 11.

[0042] Once the wire is wound on the pin, the stripping (step 103) of the entire stripped portion 211 of the conductive wire 21 wound around the pin 11 and of at least the portion of the pin around which the stripped portion 211 of the conductive wire 21 is wound is carried out. The stripping is preferably carried out using a gel usually called flux.

[0043] Said assembly is then dipped (step 104) in a brazing bath 4, over at least a given length of said assembly, and so that the free end 119 of the pin 11 is embedded in the brazing 3.

[0044] The soldering bath can also be called a solder bath. The board is turned over above the bath and lowered to immerse the pin with the stripped part of the wire, for example, up to half the height of the pin.

[0045] The quenched assembly is removed from the brazing bath. The method advantageously comprises waiting for a given period of time to allow it to cool, preferably a few seconds, for example around ten seconds.

[0046] In step 105, a new pickling step is carried out to pickle said assembly which has been dipped in the brazing bath.

[0047] The dipping of said assembly is repeated in step 106. Then the re-dipped assembly is removed from the brazing bath. Preferably, the repetition of the dipping step is followed by a drying step 107.

[0048] According to one embodiment, each soaking step 104, 106 is carried out at a temperature in the range [345-355] degrees Celsius, preferably 350°C, and for a duration of between 3.5s and 5s, preferably for 4 seconds.

[0049] Each dipping step 104, 106 in the brazing bath of said assembly can be carried out: - over at least half the length of the pin 11 starting from its free end 119; and / or - over a distance which, starting from the free end 119 of the pin 11, covers at least 1.5 turns of the stripped part 211 of conductive wire around the pin 11.

[0050] After repeating the soaking step, the method comprises a step 108 of cleaning the stripper, for example for 2 minutes, by applying a flux cleaner, also called flux cleaner, to dissolve residues of flux used during stripping operations and to make the solder shiny. For example, it is possible to use the flux cleaner of the CRC Kf brand, whose manufacturer reference is 1019.

[0051] According to a preferred embodiment, the cleaning step 108 of the stripper is followed by a rinsing step 109 of said assembly using isopropyl alcohol.

[0052] Such a process makes it possible to avoid a dry or granular appearance of the solder, or a hole in the solder, by good application of the flux, an appropriate temperature of the solder bath and a controlled soaking time.

[0053] The end 32 of the solder 3 which covers the free end 119 of the pin 11 has a generally curved shape. In particular, said shape is convex for an external view.

[0054] According to one embodiment, the brazing bath with which the dipping steps 104, 106 are carried out comprises a molten filler metal composed mainly of lead, and preferably also comprises antimony and tin. Preferably, the filler metal of the brazing bath comprises 85% lead + 10% antimony + 5% tin.

[0055] According to another embodiment, the brazing bath in which the dipping steps 104, 106 are carried out mainly comprises gold.

[0056] According to one embodiment, the pin is made of kovar (Fe-Ni-Co) and a thin layer of gold ("gold flash") is applied on top, preferably a layer of approximately 0.1 micron, in order to avoid oxidation of the copper before brazing in the bath. The thin layer can also be made of silver or other materials. The gold allows good adhesion of the brazing.

[0057] Particular embodiment comprising the winding of two cables on a pin

[0058] As illustrated in [Fig.3], a particular embodiment is also proposed comprising the winding of two cables on a spindle.

[0059] By repeating the method described above for which said cable 2 is a first cable 2, it is provided according to this particular embodiment that a stripped part 211' of a conductive wire 21' of a second cable 2' is also wound and fixed by soldering on the pin 11.

[0060] The stripping comprises stripping the second additional cable 2' to reveal the conductive wire 21' of the second cable 2' over a given length allowing the stripped portion 211' of the conductive wire of the second cable 2' to be wound around the pin 11 in order to ensure electrical conduction between the wire and the pin.

[0061] The winding comprises winding the stripped portion 211,211' of conductive wire 21,21' of each cable 2,2' around pin 11 and an unstripped portion 221,221' of each cable 2,2'.

[0062] The assembly to which the stripping and soaking steps presented above are applied comprises the stripped part 211,211' of conductive wire 21,21' of each cable 2,2' wound around the pin 11.

[0063] Thus, the stripping step includes stripping the assembly formed from the stripped portion 211, 211' of conductive wire 21, 21' of each cable 2, 2' wound around the pin 11. The dipping step 104 includes dipping in a soldering bath the entire stripped portion 211, 211' of conductive wire 21, 21' of each cable 2, 2' wound around the pin 11, over a given length of said assembly. The stripping step 105 includes stripping said assembly which has been dipped in the soldering bath. The step of dipping said assembly is repeated as explained above.

[0064] As explained previously, such a method thus makes it possible to obtain a card system for which, as illustrated in [Fig.3], several cable conductor wires are soldered to the pin by soldering.

[0065] In particular, the system comprises a second cable 2', a stripped portion 211, 211' of the conductive wire 21, 21' of each cable 2, 2' and a non-stripped portion 221, 221' of each cable 2, 2' located in the extension of the stripped portion 211, 211', are arranged around and in contact with the pin 11.

[0066] The system comprises a solder 3 which fixes at least a portion of the stripped part 211,211' of the conductive wire 21,21' of each cable 2,2' to the pin 11.

[0067] The electronic board used may include a printed circuit board equipped with a microchip module (or MCM for Micro-Chip Module in English). A microchip module is an electronic assembly composed of several integrated circuits assembled into a single device. An MCM module functions as a single component and is capable of managing an entire function. The various components of a microchip module are mounted on a substrate, and the bare chips on the substrate may be connected to the surface by wiring, adhesive tape bonding, or "flip-chip" bonding. The module may be encapsulated by a plastic molding and is mounted on the printed circuit board. Microchip modules offer good performance and allow for a smaller system size.

[0068] The invention is not limited to the embodiments illustrated in the drawings.

[0069] Furthermore, the term "comprising" does not exclude other elements or steps. Furthermore, features or steps that have been described with reference to one of the embodiments set forth above may also be used in combination with other features or steps of other embodiments set forth above.

Claims

Claims

1. Method for fixing by soldering a part (211) of a conductive wire (21) of a cable (2), on a conductive pin (11) of an electronic card (1), said cable (2) comprising said conductive wire (21) and an insulating sheath (22) surrounding said conductive wire (21), characterized in that the method comprises the following steps: - stripping (101) of a part of the cable (2) to reveal a part of the conductive wire (21) of a given length to allow winding of the stripped part (211) of the conductive wire (21) around the pin (11) in order to ensure electrical conduction between the wire and the pin; -winding (102) the stripped part (211) of the conductive wire (21) and a non-stripped part (221) of the cable (2) around and in contact with the pin (11);-stripping (103) the entire stripped portion (211) of the conductive wire (21) wound around the pin (11) and at least the portion of the pin around which the stripped portion (211) of the conductive wire (21) is wound, -dipping (104) in a brazing bath (4) of said assembly, over at least a given length of said assembly and so that the free end (119) of the pin (11) is embedded in a brazing (3); -stripping (105) of said assembly which has been dipped in the brazing bath; -repeating the step of dipping (106) of said assembly.;

2. The method of claim 1, wherein the repetition of the soaking step (106) is followed by a drying step (107).

3. A method according to claim 1 or 2, wherein after repeating the soaking step, the method comprises a stripper cleaning step (108), for example for 2 minutes, by applying a stripper cleaner, also called a flux cleaner, in order to dissolve stripper residues used during the stripping operations.

4. Method according to claim 3, in which the step of cleaning (108) the stripper is followed by a step of rinsing (109) said assembly using isopropyl alcohol.

5. A method according to any preceding claim, wherein the brazing bath with which the steps of dipping (104, 106) comprises a molten filler metal composed predominantly of lead, and preferably also comprises antimony and tin.

6. Method according to any one of the preceding claims, in which the soldering bath in which the dipping steps (104, 106) are carried out comprises predominantly gold.

7. A method according to any preceding claim, wherein each soaking step (104, 106) is carried out: - at a temperature in the range [345-355] degrees Celsius (preferably 350°C), and - for a duration of between 3.5s and 5s, preferably for 4s.

8. A method according to any preceding claim, wherein the conductive wire (21) has a diameter of 0.3 to 0.35 millimeters, preferably 0.32 millimeters, and the pin (11) has: - a height in the range [2.9 - 3.1] millimeters, for example 3 millimeters, and - a diameter in the range [0.47-0.49] millimeters.

9. A method according to any preceding claim, wherein the end (32) of the solder (3) which covers the free end (119) of the pin (11) has a generally curved shape.

10. A method according to any preceding claim, wherein the free end (219) of the stripped portion (211) of the conductive wire (21) is in contact with a portion of the pin (11) which is spaced from the free end (119) of the pin (11).

11. Method according to any one of the preceding claims, in which each dipping step (104, 106) in the soldering bath of said assembly is carried out: - over at least half the length of the pin (11) starting from its free end (119); and / or - over a distance which, starting from the free end (119) of the pin (11), covers at least 1.5 turns of the stripped portion (211) of conductive wire around the pin (11).

12. A method according to any preceding claim, wherein the winding (102) of the stripped portion (211) of the conductive wire around the pin (11) is obtained by making two turns of the stripped portion (211) of the conductive wire around and along the pin (11) over a given length of the pin.

13. A method according to any preceding claim, in wherein said cable (2) being a first cable (2), a stripped portion (211') of a conductive wire (21') of a second cable (2') is also wound and fixed by soldering on the pin (11); - the stripping step (101) also comprising stripping the additional second cable (2') to reveal the conductive wire (21') of the second cable (2') over a given length allowing winding of the stripped part (211') of the conductive wire of the second cable (2') around the pin (11) in order to ensure electrical conduction between the wire and the pin; - the winding step (102) also comprising winding the stripped portion (211, 211') of conductive wire (21, 21') of each cable (2, 2') around the pin (11) and an unstripped portion (221, 221') of each cable (2, 2'); said assembly to which the stripping and dipping steps are applied comprising the stripped part (211, 211') of conductive wire (21, 21') of each cable (2, 2') wound around the pin (11) and the corresponding part of the pin (11).

14. System comprising an electronic card (1) having at least one conductive pin (11) and at least one cable (2) having a conductive wire (21) and an insulating sheath (22), in which a stripped portion (211) of the conductive wire (21) of the cable (2) and a non-stripped portion (221) of the cable (2) located in the extension of the stripped portion (211), are arranged around and in contact with the pin (11); the system comprising a solder (3) which fixes at least a portion of the stripped portion (211) of the conductive wire (21) of the cable (2) to the pin (H).

15. System according to claim 14, wherein, said system comprising a second cable (2'), a stripped portion (211, 211') of the conductive wire (21, 21') of each cable (2, 2') and a non-stripped portion (221, 221') of each cable (2, 2') located in the extension of the stripped portion (211, 211'), are arranged around and in contact with the pin (11); the system comprising a solder (3) which fixes at least a portion of the stripped portion (211, 211') of the conductive wire (21, 21') of each cable (2, 2') to the pin (11).

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