JP2013214734A - Method of manufacturing multiconductor cable equipped with substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a multiconductor cable equipped with a substrate in which very thin electric wires are effectively soldered to electrode pads on an insulation substrate which are arranged densely, requiring no skill.SOLUTION: A method of manufacturing a multiconductor cable equipped with a substrate, in which a plurality of very thin electric wires 10 are soldered to a plurality of electrode pads 22 arrayed densely on a wiring board 20, includes a step in which solder powder of a predetermined volume is supplied to the plurality of electrode pads 22 on the wiring board for reflowing, to form a solder pre-coat 24. Then, central conductors 11 of the plurality of very thin electric wires are arranged on the plurality of electrode pads 22 in which the solder pre-coat 24 is formed, so that the central conductors 11 of the very thin electric wires are soldered to the electrode pads 22. Further, there may be provided a step for forming a solder pre-coat 15 at a connection end of the central conductor 11 of the plurality of very thin electric wires.

Description

  The present invention relates to a method for manufacturing a multicore cable with a substrate in which ends of extremely fine insulated wires and coaxial wires are electrically connected to electrode pads of an insulated substrate.

  In small electronic information devices and medical electronic devices such as ultrasonic diagnostic equipment and endoscopes, in order to realize high functionality as well as downsizing of devices, the diameter of the conductor used for wiring in the device and the number of conductors are reduced. It has increased. The number of conductors used is several hundred, and these wires are usually multi-core cables with a substrate, with the conductor at the end of the multi-core flat cable connected to the electrode pads on the insulating substrate by soldering. .

In Patent Document 1, a connection member such as solder is formed in advance on a connection portion of an electrode portion of a printed circuit board, and then a central conductor (signal line) of a coaxial cable is overlapped and heated by laser light irradiation to connect the above connection member. It is disclosed that an electrical connection is made.
Patent Document 2 discloses that a predetermined amount of paste solder is applied in advance to the end portion of the central conductor (signal line) of the coaxial line, and solder connection is made to the connector terminal by pulse heat.

JP 2010-118318 A JP 2010-146939 A

  For example, an endoscope using ultrasonic technology has a large number of signal lines (for example, 370 cores) to be accommodated and is inserted into the human body, so that the thickness of the signal lines is extremely thin and is electrically connected. Since the size of the circuit board is also limited, high-density mounting is required. Manual soldering requires considerable skill and is not practical. Therefore, in order to connect extremely fine signal lines at once, solder connection by pulse heat that allows current to flow while being pressed against an electrode pad of a circuit board as disclosed in Patent Document 2 is effective, and the thickness of the conductor to be connected differs. In such a case, solder connection by laser light irradiation is effective as disclosed in Patent Document 1.

  However, the number of signal lines is large, and the pitch between adjacent conductors connected to the electrodes of the insulating substrate is reduced. For example, when the pitch between conductors is about 0.16 mm (corresponding to the coaxial wire of AWG49), the insulation gap between adjacent electrode pads is 0.07 mm or less. For this reason, the amount of solder (solder precoat) applied in advance on the electrode pad tends to cause a solder bridge that electrically shorts the electrodes, so it is necessary to accurately form the solder precoat applied on the electrodes. is there.

  Although the present invention has been made in view of the above-described actual situation, a multi-core cable with a substrate in which extra fine wires are effectively solder-connected to electrode pads on an insulating substrate arranged at high density without requiring skills. It aims at providing the manufacturing method of.

  A method of manufacturing a multicore cable with a substrate according to the present invention is a method of manufacturing a multicore cable with a substrate in which a plurality of ultrafine wires are solder-connected to a plurality of electrode pads arranged at high density on the wiring substrate. A step of forming a solder precoat by applying a predetermined amount of solder powder on the plurality of upper electrode pads and performing reflow is provided. Then, the center conductors of the plurality of extra fine wires are arranged on the electrode pads on which the solder precoat is formed, and the center conductors of the extra fine wires are soldered to the electrode pads. Moreover, you may make it provide the process of forming a solder precoat in the connection end of the center conductor of a several extra fine wire.

The solder connection can be performed by connecting the central conductors in a batch using pulse heat or by using laser light irradiation.
Further, when solder connection is performed using the laser beam irradiation described above, a metal mask is used to cover a region other than the solder connection region and laser beam irradiation is performed to reduce damage to the wiring substrate due to laser irradiation. In addition, it is preferable that the region irradiated with the laser light is 50 to 90% of the width of the electrode pad.

  According to the present invention, it is possible to reliably and easily solder and connect an extremely thin electric wire to electrode pads (arrangement pitch of 0.2 mm or less and an insulation gap between electrode pads of 0.1 mm or less) arranged at high density. it can.

It is a figure which shows an example of the multicore cable with a board | substrate solder-connected by this invention. It is a figure explaining an example of the manufacturing method of the multicore cable with a board | substrate connected by solder by this invention. It is a figure explaining the example of the solder connection by laser beam irradiation.

  Embodiments of the present invention will be described with reference to the drawings. In the figure, 10 is a coaxial wire, 11 is a central conductor, 12 is an insulator, 13 is an external conductor, 14 is a jacket, 15 is a solder precoat on the wire side, 16 is a common coating, 17 is a ground bar, and 20 is a wiring board. , 21 is an insulating substrate, 22 is an electrode pad, 23 is a solder resist layer, 24 is a solder precoat on the electrode side, 25 is a solder connection part, 29 is a pulse heat device, 30 is a laser irradiation device, 31 is a laser beam, and 32 is a laser beam. A metal mask 33 indicates a mask opening.

  As shown in FIG. 1, the present invention is a method of manufacturing a multi-core cable with a substrate in which a plurality of insulated wires or coaxial wires 10 are electrically connected to a wiring substrate 20 by a solder connection portion 25. The electric wire to be solder-connected to the wiring board 20 may be an insulated electric wire, a coaxial electric wire, or a composite cable in which these are mixed, but in order to simplify the description, an example using the coaxial electric wire 10 will be described. In addition, although the insulated wire has a conductor covered with an insulator, a portion called a central conductor in the following description corresponds to a conductor in the insulated wire.

The coaxial electric wire 10 includes a central conductor 11 serving as a signal line, an insulator 12 and an outer conductor 13 arranged coaxially, and the outer periphery thereof is covered with a jacket 14.
The central conductor 11 is a single core wire or stranded wire made of copper, silver, or tin-plated copper alloy wire, and has a thickness of about AWG 40 (conductor diameter 0.079 mm) to AWG 49 (conductor diameter 0.028 mm). Is used. The central conductor 11 may have a form in which different thicknesses are mixed in the above range, for example.

  The plurality of coaxial cables 10 are subjected to end processing so that the center conductor 11, the insulator 12, and the outer conductor 13 are exposed stepwise within a predetermined range at the end portions thereof. The plurality of coaxial electric wires 10 may be collectively formed into a flat cable shape with the common coating 16. Further, the outer conductor 13 may be commonly grounded by the ground bar 17 or the like, and the arrangement of the coaxial wires may be held.

  The wiring board 20 is formed by forming a large number of electrode pads 22 with a small pitch at a high density on an insulating board 21 made of a flexible or hard insulator. For example, when the insulating substrate 21 is 4 mm square and a 20-25 core coaxial cable is connected to the insulating substrate 21, the center interval (pitch) P of the electrode pads 22 needs to be 0.2 mm or less. In this case, the insulating gap S of the electrode pad 22 needs to be about 0.07 mm or less, although it depends on the width of the electrode pad. It is not easy to solder the coaxial wire 10 accurately and reliably to each of the electrode pads 22 arranged at such a narrow pitch.

  FIG. 2 is a diagram illustrating an example of solder connection according to the present invention. First, the outer sheath 14 at the end of the coaxial cable 10 is removed to expose the outer conductor 13 for a predetermined length, and then the exposed outer conductor 13 is removed for a predetermined length to expose the insulator 12. Then, the exposed end of the insulator 12 is removed by a predetermined length to expose the connection end of the center conductor 11.

  Next, as shown in FIG. 2B, a solder layer (hereinafter referred to as a solder precoat 15) in which solder is applied in advance by applying flux is formed on the exposed end of the central conductor 11. preferable. The center conductor 11 does not need to be provided with the solder precoat 15, but when a twisted wire is used for the center conductor, it is possible to prevent the twisted wire from being broken by providing the solder precoat 15. . In addition, for formation of the solder precoat with respect to the center conductor 11, for example, the application amount can be made appropriate by using a method using a solder powder described later.

In parallel with the end processing of the coaxial cable 10 described above, a solder powder is previously attached to the electrode pads 22 of the wiring board 20 and reflow processing (pre-coating) is performed. As the wiring substrate 20, as shown in FIG. 2C, a substrate in which an electrode pad 22, a wiring conductor (not shown), and a solder resist layer 23 are formed on an insulating substrate 21 by a printed circuit technique is used.
On the surface of the electrode pad 22 of the wiring board 20, as shown in FIG. 2D, a predetermined amount of solder powder is applied in advance and reflowed solder layer (hereinafter referred to as solder precoat 24) is formed.

Various methods are conceivable for forming the solder precoat 24 on the electrode pads 22 arranged with a narrow insulating gap on the order of several tens of μm (for example, 70 μm or less). A method of applying a predetermined amount of solder powder on the electrode pad and reflowing it to form a solder precoat is used.
(1) Super Just (SJ) method “Applying adhesive to electrode pad surface → Attaching solder powder to surface → Applying flux to entire surface of substrate → Cleaning after reflow”
(2) Precoat by Powder Sheet (PPS) method “Applying adhesive flux on wiring board → PPS sheet with solder powder adhered and held on electrode pad, press heating → PPS sheet peeling → Flux application → Washing after reflow”

According to the above method, a predetermined amount of solder powder can be uniformly and accurately applied on the electrode pad. As a result, the solder amount of the solder precoat formed on the surface of the electrode pad can be made appropriate, resulting in poor connection with the connection conductor and generation of a solder bridge that short-circuits the insulation gap between adjacent electrode pads. Can be reduced.
Further, if the conductor of the ultrafine wire is displaced on the electrode pad before the solder connection, a solder bridge is likely to occur in the case of a narrow pitch connection. In order to accurately arrange the conductor on the electrode pad so as not to cause such a situation, it is effective to make the solder on the electrode pad flat, and the solder thickness is suitably 5 to 40 μm.

After the solder precoat is formed on the wiring board 20 or both the coaxial cable 10 and the wiring board 20, the solder precoat 15 is applied on the solder precoat 24 of the wiring board 20, as shown in FIG. The center conductor 11 thus formed is positioned and placed.
Next, when the outer diameters of the plurality of central conductors 11 to be connected are the same, as shown in FIG. 2F, the plurality of central conductors 11 are collectively soldered using the pulse heat device 29. Can do.

  In this case, the electrode portion of the pulse heat device 29 is pressed against the central conductor 11 and heated to be soldered. For example, as a first step, after the temperature of the connecting portion is raised to 230 ° C. in 1 second, this temperature is held for 1 second. Next, as a second step, the temperature is raised to 300 ° C. in 1 second, and this temperature is maintained for 1.5 seconds. When the number of extra fine wires to be connected is 64 or less, for example, the pressing force that presses the electrode portion of the pulse heat device 29 is 4.5 N or less.

  As shown in FIG. 3A, a plurality of center conductors 11 can be soldered using a laser irradiation apparatus 30 instead of the pulse heat apparatus. In this case, the solder precoats 15 and 24 are heated and melted by irradiation with the laser beam 31, and the central conductor 11 of the coaxial cable 10 is solder-connected to the electrode pad 22 by the solder connection portion 25.

FIG. 3B is a method illustrating another example of laser light irradiation. This method is an example in which a mask opening 33 having a predetermined size is provided in the metal mask 32 and only a predetermined region is irradiated with the laser light 31. By using the metal mask 32, a heating region can be specified, and damage to an electrically insulated region other than the electrode pad can be reduced.
The irradiation range of the laser beam 31 is preferably about 50 to 90% of the lateral width (arrangement direction) of the electrode pads 22. If the laser light irradiation range is less than 50%, the solder melting range is small, and the connection with the central conductor may be insufficient. Further, when the laser light irradiation range exceeds 90%, there is a possibility that the insulating surface of the substrate is irradiated with a slight deviation and damaged.

DESCRIPTION OF SYMBOLS 10 ... Coaxial electric wire, 11 ... Center conductor, 12 ... Insulator, 13 ... Outer conductor, 14 ... Outer coat, 15 ... Solder precoat, 16 ... Common coating | cover, 17 ... Ground bar, 20 ... Wiring board, 21 ... Insulation board, DESCRIPTION OF SYMBOLS 22 ... Electrode pad, 23 ... Solder resist layer, 24 ... Solder precoat, 25 ... Solder connection part, 29 ... Pulse heat apparatus, 30 ... Laser irradiation apparatus, 31 ... Laser beam, 32 ... Metal mask, 33 ... Mask opening.

Claims (6)

A method of manufacturing a multi-core cable with a substrate in which a plurality of extra fine wires are soldered to a plurality of electrode pads arranged at high density on a wiring substrate,
Including a step of forming a solder precoat by applying a predetermined amount of solder powder on a plurality of electrode pads on the wiring board and reflowing,
Manufacture of a multi-core cable with a substrate in which center conductors of the plurality of extra fine wires are disposed on the plurality of electrode pads on which the solder precoat is formed, and the center conductors of the extra fine wires are soldered to the electrode pads. Method.   The manufacturing method of the multicore cable with a board | substrate of Claim 1 provided with the process of forming a solder precoat in the connection end of the center conductor of the said several ultrafine electric wire.   The manufacturing method of the multicore cable with a board | substrate of Claim 1 or 2 which solder-connects the center conductor of the said several extra-fine electric wire collectively using pulse heat.   The manufacturing method of the multicore cable with a board | substrate of Claim 1 or 2 which carries out solder connection using laser beam irradiation.   The manufacturing method of the multi-core cable with a board | substrate of Claim 4 which covers the area | regions other than the said soldering connection area | region using a metal mask, and irradiates the said laser beam.   The manufacturing method of the multi-core cable with a board | substrate of Claim 5 which makes the area | region to which the said laser beam irradiation is 50 to 90% of the width | variety of the said electrode pad.

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