WO2013133409A1 - Method for manufacturing coaxial cable having attached substrate - Google Patents

Abstract

One of the purposes of the present invention is to provide a method for manufacturing coaxial cable having an attached substrate, by which it is possible for a fine electrical wires to be readily and reliably connected by soldering to electrode pads arranged at high density on an insulating substrate. The present invention is a method for manufacturing a coaxial cable having an attached substrate, by connecting a plurality of fine electrical wires (10) through soldering to a plurality of electrode pads (22) arranged at high density on a wiring substrate (20), and is provided with a step of applying and reflowing a predetermined amount of solder powder on the plurality of electrode pads (22) of the wiring substrate, to form a solder precoat (24). The center conductors (11) of the plurality of fine electrical wires are then arranged over the plurality of electrode pads (22) on which the solder precoat (24) has been formed, and the center conductors (11) of the fine electrical wires are connected by soldering to the electrode pads (22). Optionally, a step of forming a solder precoat (15) at the connection ends of the center conductors (11) of the plurality of fine electrical wires is provided.

Description

Manufacturing method of multi-core cable with substrate

The present invention relates to a method for manufacturing a multi-core cable with a substrate in which ends of ultra-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, the conductor used for the wiring in the device is reduced in diameter and conductors in order to realize downsizing and high functionality. The number is increasing. The number of conductors to be used is, for example, several hundreds. Usually, the conductors at the ends of the multi-core flat cable are connected to the electrode pads on the insulating substrate by soldering, and the multi-core cable with the substrate is manufactured.

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

Japanese Unexamined Patent Publication No. 2010-118318 Japanese Unexamined Patent Publication No. 2010-146939

For example, an endoscope using ultrasonic technology has a large number of signal lines (eg, 370) accommodated therein, but the thickness of the signal lines is extremely thin due to the property of being inserted into the human body. The size of the circuit board to be electrically connected is also limited. Therefore, for example, when connecting a signal line to a circuit board mounted on an endoscope, high-density mounting is required. When performing such high-density mounting, manual solder connection requires considerable skill and is not practical. In order to collectively connect extremely fine signal lines, solder connection by pulse heat is effective as disclosed in Patent Document 2. Further, when there is a difference in the thickness of the conductor to be connected, solder connection by laser light irradiation is effective as disclosed in Patent Document 1.

However, when the number of signal lines is large, the distance between adjacent conductors connected to each electrode of the insulating substrate (pitch between conductors) becomes small. 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 may be 0.07 mm or less. In such a case, depending on the amount of solder (solder precoat) applied in advance on the electrode pad, a solder bridge that electrically short-circuits between the electrodes tends to occur. Must be formed.

An object of the present invention is to provide a method for manufacturing a multi-core cable with a substrate, which can reliably and easily connect a fine wire to electrode pads on an insulating substrate arranged at a high density by solder.

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, and a solder precoat is applied by applying a predetermined amount of solder powder to a plurality of electrode pads on a wiring substrate and performing reflow. Forming. Then, the center conductors of the plurality of ultrafine wires are arranged on the plurality of electrode pads on which the solder precoat is formed, and the center conductors of the ultrafine wires are connected to the electrode pads by soldering. 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.

In connection with the above soldering, the central conductors can be collectively connected using pulse heat or can be connected using laser light irradiation.
In addition, when connecting with solder using the above laser beam irradiation, at least a part of the region on the wiring board other than the region where the central conductor of the ultrafine wire is connected to the electrode pad by soldering is covered with a metal mask. Then, laser light may be irradiated. By using a metal mask, it is possible to reduce damage caused by laser irradiation on the wiring board. Note that the width of the region irradiated with the laser light is preferably 50 to 90% of the width of the electrode pad.

According to the present invention, it is possible to reliably and easily connect an extremely fine electric wire to the electrode pads arranged at high density with solder.

It is a figure which shows an example of the multicore cable with a board | substrate manufactured by the manufacturing method of embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a manufacturing method according to an embodiment of the present invention, and FIGS. It is a figure for demonstrating the other example of solder connection, (A) in a figure is a figure for demonstrating the example which irradiates a laser beam and solder-connects, (B) in a figure is a laser beam. It is a figure for demonstrating the modification of the example which irradiates and connects with solder.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. 1 to 3, reference numeral 10 is a coaxial wire, reference numeral 11 is a central conductor, reference numeral 12 is an insulator, reference numeral 13 is an outer conductor, reference numeral 14 is an outer jacket, reference numeral 15 is a solder precoat on the electric wire side, and reference numeral 16 is a common coating. , 17 is a ground bar, 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, symbol 30 is a laser irradiation device, symbol 31 is a laser beam, symbol 32 is a metal mask, and symbol 33 is a mask opening.

This embodiment is a method for 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 solder connection portions 25 as shown in FIG. The wires connected to the wiring board 20 with solder may be insulated wires or coaxial wires, or a composite cable in which these wires are mixed. Hereinafter, in order to simplify the description, an example in which the coaxial wire 10 is used 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, an insulator 12, and an outer conductor 13 that are signal lines, which are arranged coaxially and whose outer periphery is covered with a jacket 14.
For the central conductor 11, for example, a single core wire made of a copper wire, silver or tin-plated copper alloy wire, a stranded wire made of copper wire, or a stranded wire made of silver or tin-plated copper alloy wire is used. The thickness of the central conductor 11 is preferably about AWG40 (conductor diameter 0.079 mm) to AWG49 (conductor diameter 0.028 mm). The central conductor 11 may have a configuration in which different thicknesses are mixed in the above range, for example.

The end portions of the plurality of coaxial cables 10 are processed 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. 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 at a narrow pitch 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 is set to 0.2 mm or less, for example. In this case, the insulating gap S of the electrode pad 22 is set to about 0.1 mm or less, or about 0.07 mm or less, depending on the width of the electrode pad. It is not easy to accurately and reliably connect the coaxial cable 10 to each of the electrode pads 22 arranged at such a narrow pitch.

FIG. 2 is a diagram for explaining each process related to solder connection in the manufacturing method of the present embodiment. First, as shown in FIG. 2A, 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. Thus, the insulator 12 is exposed. Then, the exposed tip 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 to the exposed end of the central conductor 11 is formed. Is preferred. Although it is not essential to apply the solder precoat 15 to the central conductor 11, when a stranded wire is used for the central conductor, it is possible to prevent the stranded wire from being broken by providing the solder precoat 15. . For the formation of the solder precoat on the center conductor 11, the application amount can be made appropriate by using a method using 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 board 20, as shown in FIG. 2C, that is, an electrode pad 22, a wiring conductor (not shown), and a solder resist layer 23 are formed on an insulating substrate 21 by printed circuit technology. Things are 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 in a narrow insulating gap on the order of several tens of μm (for example, 70 μm or less). In the present embodiment, for example, 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-> peeling PPS sheet-> flux application-> cleaning 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, the connection failure with the conductor to be connected, and the solder bridge that short-circuits the insulation gap between the adjacent electrode pads. Generation can be reduced.
In addition, if the position of the conductor of the ultrafine wire is shifted on the electrode pad before the connection with solder, 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 to avoid 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 formed on the solder precoat 24 of the wiring board 20 as shown in FIG. The applied central conductor 11 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 connected together by soldering using a pulse heat device 29. can do.

In this case, the electrode part of the pulse heat device 29 is pressed against the central conductor 11 to be heated and connected with solder. 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 ultrafine wires to be connected is 64, for example, the pressing force that presses the electrode portion of the pulse heat device 29 is 4.5 N or less.
As described above, according to the manufacturing method of the present embodiment described above, a predetermined amount of solder powder can be uniformly and accurately applied on the electrode pad 22, and the solder precoat 24 formed on the surface of the electrode pad 22 can be applied. The amount of solder can be made appropriate. Therefore, the central conductor 11 of the coaxial cable 10 can be reliably and easily connected to the electrode pads 22 on the insulating substrate 21 arranged at high density by solder.

Further, as shown in FIG. 3A, a plurality of central conductors 11 can be connected by soldering using a laser irradiation device 30 instead of the pulse heat device 29 described above. In this case, the solder precoats 15 and 24 are heated and melted by irradiating the laser beam 31, and the central conductor 11 of the coaxial cable 10 is connected to the electrode pad 22 by soldering at the solder connection portion 25 formed thereby.

(B) of FIG. 3 is a figure for demonstrating the modification of the example which irradiates a laser beam and connects with solder. In this modification, a mask opening 33 having a predetermined size is provided in the metal mask 32, and the laser beam 31 is irradiated only on a predetermined region. By using the metal mask 32, the heating region can be limited, and damage to electrically insulated regions other than the electrode pads can be reduced. The size of the mask opening 33 is set such that the solder precoat 24 is exposed from the mask opening 33.
The irradiation width of the laser beam 31 is preferably about 50 to 90% of the lateral width (arrangement direction) of the electrode pads 22. If the width of the laser beam irradiation is less than 50%, the solder melting range is small, and the connection with the central conductor may be insufficient. Further, if the width of the laser light irradiation exceeds 90%, there is a possibility that the insulating surface of the substrate is irradiated with a slight deviation and damaged.

While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2012-051431 filed on March 8, 2012, and Japanese Patent Application No. 2013-044397 filed on March 6, 2013, the contents of which are here Incorporated as a reference.

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)

1. A method of manufacturing a multi-core cable with a board,
   A step of forming a solder precoat by applying a predetermined amount of solder powder on a plurality of electrode pads on a wiring board and reflowing,
   Manufacture of a multi-core cable with a substrate in which center conductors of a plurality of extra fine wires are arranged on the plurality of electrode pads on which the solder precoat is formed, and the center conductors of the extra fine wires are connected to the electrode pads by soldering Method.
2. The method for manufacturing a multi-core cable with a substrate according to claim 1, further comprising a step of forming a solder precoat at a connection end of a central conductor of the plurality of extra fine wires.
3. 3. The method of manufacturing a multicore cable with a substrate according to claim 1 or 2, wherein the central conductors of the plurality of extra fine wires are collectively connected to the electrode pads by soldering using pulse heat.
4. 3. The method of manufacturing a multi-core cable with a substrate according to claim 1 or 2, wherein the central conductor of the ultrafine wire is connected to the electrode pad by soldering with laser light.
5. 5. The laser beam according to claim 4, wherein at least a part of a region on the wiring board other than a region where the central conductor of the ultrafine wire is connected to the electrode pad by solder is covered with a metal mask, and the laser light is irradiated. Manufacturing method of multi-core cable with substrate.
6. 6. The method of manufacturing a multi-core cable with a substrate according to claim 5, wherein a width of the region irradiated with the laser light is 50 to 90% of a width of the electrode pad.
   
   
   

Images