JP2011076908A - Connection structure and its connection method of coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection structure of a coaxial cable corresponding to high-density mounting through restraint of electric short circuit between an outer conductor and a center conductor. <P>SOLUTION: Of the connection structure 10 of the coaxial cable 1 in which terminal parts of the coaxial cable 1 are peeled off in steps to expose from an outer insulator 5 an outer conductor 4, an inner insulator 3, a center conductor 2 in turn, and the center conductor 2 and the outer conductor 4 exposed are electrically connected to corresponding electrodes 12a, 13a formed on a printed circuit board 11 through connecting materials 14, 15, respectively, the first connecting material for electrically connecting the center conductor 2 and the electrode 12a and the second connecting material for electrically connecting the outer conductor 4 and the electrode 13a are with different melting points. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a coaxial cable connection structure for connecting a coaxial cable to a printed circuit board and a connection method therefor.

  In recent years, in the field of electronic information devices such as mobile phones and laptop computers, and medical devices such as ultrasonic diagnostic devices and endoscopes, along with the reduction in size and weight of devices, higher functionality, that is, higher accuracy and speed of information images. Is required.

  In connection with this, the coaxial cable used for the connection inside the apparatus or between the components (assemblies) constituting the apparatus has been reduced in diameter, while the number of coaxial cables to be used has increased.

  In order to achieve both compact and lightweight equipment with high functionality, it is necessary to increase the mounting density of the coaxial cable connection, shorten the length of the coaxial cable terminal, and connect the electrode part of the printed circuit board. In order to shorten the size in the width direction, a narrow pitch connection of coaxial cables is indispensable.

  A coaxial cable is generally used in which an inner insulator, an outer conductor, and an outer insulator are sequentially formed on the circumference of a central conductor made of a stranded wire formed by twisting a plurality of fine wires. The outer conductor is formed by, for example, spirally winding a plurality of fine wires around the inner insulator.

  In the connection between the central conductor of the coaxial cable and the electrode part of the printed circuit board, the central conductor is exposed by stepping off the ends of a plurality of coaxial cables arranged in parallel, and each central conductor is formed on the printed circuit board. In addition, electrical connection to the corresponding electrode portions is performed.

  As connection methods in this case, there are a method in which individual center conductors are individually connected manually by using a soldering iron, and a method in which connection is performed collectively with a thermocompression bonding apparatus or the like. In addition, a means for connecting the central conductor directly by soldering or indirectly through a connecting component is used (for example, see Patent Document 1).

  Similarly to the central conductor, the outer conductor of the coaxial cable is stepped off to expose the outer conductor and connected to the corresponding electrode portion formed on the printed board.

  As a connection method in this case, ground bars are installed on the upper and lower surfaces of the outer conductor or one of the outer conductors so as to cross the coaxial cables arranged in parallel on the exposed outer conductor portions, The solder material supplied to the ground bar is melted and electrically connected together. Thereafter, the ground bar and the corresponding electrode portion of the printed circuit board are connected by soldering or the like.

  At this time, heat for melting the solder is applied to the ground bar, and pressure is applied to facilitate soldering by bringing the relatively rigid ground bar into contact with the corresponding electrode portion of the printed circuit board. (See, for example, Patent Documents 2 and 3).

  In addition to this, means for filling the space between and around the outer conductor with solder without using the ground bar and soldering the outer conductor to the corresponding electrode portion of the printed circuit board is used (for example, patents). Reference 4).

JP 2002-95129 A Japanese Patent No. 3371797 JP 2008-181817 A JP 2003-348726 A

  As described above, in order to achieve both miniaturization and weight reduction and high functionality of the device, the size of the coaxial cable terminal portion has been reduced, and the outer conductor portion, the inner insulator portion, and the stepped portion at the terminal portion, and The length of each part of the center conductor is shortened.

  The internal insulator portion formed between the outer conductor portion and the center conductor portion is provided to maintain electrical insulation between the outer conductor and the center conductor. As the length of the inner insulator portion becomes shorter, there is a problem that an electrical short circuit between the outer conductor and the center conductor is more likely to occur.

  In general, the outer conductor and the central conductor are connected to the corresponding electrode portions formed on the printed circuit board in separate processes. For example, the outer conductor is first connected to the corresponding electrode portion first. Later, the central conductor is connected to the corresponding electrode part.

  Solder materials are used to connect these external conductors and center conductors to the corresponding electrode portions, and the same solder materials must be used to connect the external conductor and center conductor electrode portions. Is generally done. Here, the same solder material is a solder material having the same material composition and substantially the same melting temperature. Therefore, the connection temperature of the outer conductor to the electrode portion and the connection temperature of the central conductor to the electrode portion are substantially the same. Therefore, as described above, when the central conductor is connected to the electrode portion after the external conductor is first connected to the electrode portion, the central conductor connecting portion is heated to the same temperature as the external conductor connecting temperature.

  In the conventional coaxial cable connecting portion that does not require high-density mounting, the inner insulator portion between the outer conductor portion and the central conductor portion can also be made relatively long. Therefore, one conductor connection part (for example, external conductor connection part) previously connected to the electrode part of the printed circuit board is extremely heated by heating when the other conductor (for example, center conductor) to be connected later is connected. The temperature does not increase, and remelting of the connecting material of the conductor connecting portion connected previously does not occur. Even if remelting occurs, since the inner insulator portion is formed long, it was possible to prevent the molten solder material from flowing out and reaching the other conductor connection portion.

  However, when the length of the internal insulator portion is shortened due to the recent demand for high-density mounting, the temperature of one conductor connection portion connected to the electrode portion of the printed circuit board increases due to the heating during the connection of the other conductor. Therefore, there is a possibility that the connecting material of the conductor connecting portion connected earlier is remelted. The remelted connecting material has a short inner insulator part, so it flows out to the other conductor connection part relatively easily, causing an electrical short circuit between the two conductors. There is a problem that disturbs.

  Moreover, in the connection of a coaxial cable, the center conductor and the outer conductor of the continuous terminal part formed in one coaxial cable are connected. The conductor itself may be made of copper or copper alloy with good thermal conductivity, and the heat applied when connecting one conductor (for example, the outer conductor) is connected to the other conductor (for example, the center conductor). Because it is easily conducted through the conductor, the structure is easily affected by heat unlike the case of connecting separate individual components and coaxial cables individually.

  Furthermore, with the recent high-density mounting, printed circuit boards that electrically connect the outer conductor and the central conductor are also made multilayer. Since the occupancy ratio of the copper wiring used for the printed circuit board is increased by the multilayered printed circuit board, the thermal conductivity of the printed circuit board is also increased. For this reason, the temperature of the conductor connecting portion connected earlier is increased by heating at the time of subsequent conductor connection, and remelting of the connecting material is likely to occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a coaxial cable connection structure and a connection method thereof that can suppress the occurrence of an electrical short circuit between an outer conductor and a center conductor, and can be used for high-density mounting.

  The present invention has been devised to achieve the above object, and the invention of claim 1 is such that the end portion of the coaxial cable is stepped and the outer conductor, the inner insulator, and the center conductor are sequentially exposed from the outer insulator. In the connection structure of the coaxial cable that electrically connects the exposed central conductor and the external conductor to the corresponding electrode portions formed on the printed circuit board through the connecting material, the central conductor and the electrode portions 1 is a coaxial cable connection structure in which the melting point of the first connection material for electrically connecting the external conductor and the electrode portion is different from each other.

  A second aspect of the present invention is the coaxial cable connection structure according to the first aspect, wherein a plurality of solder particles dispersed in a thermosetting resin are used as the first and second connection members.

  In the invention of claim 3, the end portion of the coaxial cable is stepped off to sequentially expose the outer conductor, the inner insulator, and the center conductor from the outer insulator, and the exposed center conductor and outer conductor are placed on the printed circuit board. In the method of connecting coaxial cables, each of which is electrically connected to a corresponding electrode part formed through a connecting material, the first connection temperature of either one of the central conductor and the outer conductor that is connected first. Is a method of connecting a coaxial cable that makes the temperature higher than the second connection temperature of the other conductor to be connected later.

  In the invention of claim 4, the melting point of the first connecting member of one of the central conductor and the outer conductor connected earlier is higher than the melting point of the second connecting member of the other conductor connected later. The coaxial cable connection method according to claim 3, wherein the second connection temperature is lower than the melting point of the first connection member and is equal to or higher than the melting point of the second connection member.

  The invention of claim 5 uses, as the coaxial cable, a multi-core coaxial cable in which a plurality of coaxial cables are arranged in parallel, and the exposed external conductors of the multi-core coaxial cable are maintained in the parallel state. After electrically connecting to the ground bar in advance using the first connecting material, each exposed central conductor of the multi-core coaxial cable is connected to the corresponding electrode portion of the printed circuit board using the first connecting material. The coaxial cable connection method according to claim 4, wherein the ground bars are electrically connected to the corresponding electrode portions of the printed circuit board using the second connection material.

  A sixth aspect of the present invention is the coaxial cable connection method according to the fourth or fifth aspect, wherein a plurality of solder particles dispersed in a thermosetting resin are used as the first and second connection members.

  According to the present invention, the occurrence of an electrical short circuit between the outer conductor and the center conductor can be suppressed, and high-density mounting can be accommodated.

It is sectional drawing which shows the coaxial cable used for the connection structure of the coaxial cable which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the multi-core coaxial cable comprised with the coaxial cable of FIG. It is a top view which shows the connection structure of the coaxial cable which concerns on the 1st Embodiment of this invention. FIG. 4 is a sectional view taken along line AA in FIG. 3. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is CC sectional view taken on the line of FIG. It is a schematic diagram explaining the relationship between melting | fusing point of a connection material and connection temperature in the case of connecting a center conductor and an external conductor with a connection material, respectively. It is sectional drawing which shows the connection structure of the coaxial cable which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the connection part of the center conductor in the connection structure of the coaxial cable of FIG. It is sectional drawing which shows the connection structure of the coaxial cable which concerns on the 3rd Embodiment of this invention.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, a coaxial cable used in the coaxial cable connection structure according to the first embodiment will be described with reference to FIG.

  As shown in FIG. 1, the coaxial cable 1 includes a center conductor 2, an inner insulator 3, an outer conductor 4, and an outer insulator 5 that are sequentially formed on the circumference of the center conductor 2.

  The center conductor 2 is composed of a stranded wire obtained by twisting a plurality of (7 in FIG. 1) metal thin wires 6, and the outer conductor 4 is composed of a plurality (16 in FIG. 1) of metal thin wires 7. It is configured by spirally winding around the inner insulator 3.

  In the first embodiment, as shown in FIG. 2, a plurality of coaxial cables 1 (16 in FIG. 2 is actually shown for simplification, but actually 16) are arranged in parallel, and these coaxial cables 1 are arranged in parallel. The connection structure of the coaxial cable for connecting the multi-core coaxial cable 8 bundled by attaching a laminate film on the upper and lower surfaces of the cable 1 and the printed circuit board will be described.

  As shown in FIG. 3, the coaxial cable connection structure 10 according to the first embodiment is formed by stripping the terminal portion of each coaxial cable 1 of the multicore coaxial cable 8 from the external insulator 5 to the external conductor 4, The internal insulator 3 and the central conductor 2 are sequentially exposed, and the exposed central conductor 2 and external conductor 4 are connected to corresponding electrode portions (a central conductor electrode portion 12 and an external conductor electrode portion 13) formed on the printed circuit board 11. ) To each other via a connecting material.

  For the exposed structure of the outer conductor 4, the inner insulator 3, and the center conductor 2 from the outer insulator 5, for example, the conductor and insulator are cut by laser irradiation or cutting, and the stripping process including strips is sequentially performed. Formed by.

  The center conductor electrode portion 12 and the outer conductor electrode portion 13 are formed on the printed circuit board 11 in accordance with the arrangement and size of the center conductor 2 and the outer conductor 4. The center conductor electrode portion 12 is formed by electrically separating a number (16 in FIG. 3) of electrodes 12a corresponding to the center conductor 2 of each coaxial cable 1, and the outer conductor electrode portion 13 is formed by each coaxial cable. One common electrode 13 a is formed in the cable 1.

  As shown in FIG. 3, the center conductor 2 and the outer conductor 4 are aligned on the center conductor electrode portion 12 and the outer conductor electrode portion 13, respectively, and then, as shown in FIGS. It is electrically connected to the electrode 13a. In general, the conductors 2 and 4 are connected to the electrodes 12a and 13a through connecting members 14 and 15. The connecting members 14 and 15 are melted by heating and connected ( For example, a solder material that can connect the center conductor 2 or the outer conductor 4) and an object to be connected (for example, the electrode 12a or the electrode 13a of the printed board 11) is used.

  In the coaxial cable connection structure 10 according to the first embodiment, the first connection temperature of one of the central conductor 2 and the outer conductor 4 to be connected first (for example, the central conductor) is set as follows. This is higher than the second connection temperature of the other conductor (for example, outer conductor) to be connected later.

  For this reason, in the coaxial cable connection structure 10, the melting point of the first connecting member of one of the central conductor 2 and the outer conductor 4 that is connected first (for example, the central conductor) is connected to the other one that is connected later. The melting point of the second connecting member of the first conductor (for example, the outer conductor) is set higher than the melting point of the first connecting member and the melting point of the second connecting member.

  A specific method for connecting the conductors 2 and 4 and the electrode portions 12 and 13 will be described.

  In the first embodiment, the connection between the center conductor 2 and the outer conductor 4 and the corresponding electrode portions 12 and 13 is performed by the following connection method. In the first embodiment, a method of connecting the center conductor 2 and the outer conductor 4 in this order will be described as an example.

  First, a method for connecting the central conductor 2 will be described.

  A paste-like high melting point solder material is applied as a connection material 14 (first connection material) to the central conductor electrode portion 12 of the printed circuit board 11 by a dispensing method or a printing method. As described above, the center conductor electrode portion 12 is formed in a state where the plurality of electrodes 12a are electrically separated corresponding to the number of the center conductors 2 to be connected, and is an aggregate of these. Yes. The high-melting-point solder material is usually applied to each electrode 12a of the central conductor electrode portion 12. However, the high-melting-point solder material melts and separates into the individual electrodes 12a when heated and melted at the time of connection. If this materialization is possible depending on the material that does not form or the connection conditions, a high-melting-point solder material can be applied so as to continuously traverse the plurality of electrodes 12a.

  Next, the end portions of the coaxial cables 1 where the center conductor 2 and the outer conductor 4 are exposed are placed on the printed circuit board 11 so that the center conductor 2 and the outer conductor 4 and the corresponding electrodes 12a and 13a are aligned. To do. A heater tool of a thermocompression bonding device is pressed from the upper part of each central conductor 2 placed on the central conductor electrode portion 12 and is pressurized together with heating, and each central conductor 2 is connected to the central conductor electrode portion 12 via a high melting point solder material. The electrodes 12a are electrically connected.

  Next, a method for connecting the outer conductor 4 will be described.

  First, a paste-like low melting point solder material is applied as a connecting material 15 (second connecting material) to the upper portion of the outer conductor 4 installed on the outer conductor electrode portion 13 by a dispensing method. Note that the same low melting point solder material as that of the second connection material may be precoated on the surface of the external conductor electrode portion 13 of the printed circuit board 11 before the connection of the external conductor 4.

  Next, the heater tool of the thermocompression bonding device is pressed from the upper part of each outer conductor 4 placed on the outer conductor electrode portion 13 and is heated and pressurized, and each outer conductor 4 is connected to the outer conductor via a low melting point solder material. It is electrically connected to the electrode 13a of the electrode part 13 for use. Since all the outer conductors 4 are all connected to the electrode 13a having the same potential (ground potential), as shown in FIG. 3, the second connecting member is formed by connecting a plurality of outer conductors 4 in the parallel direction. Connect by.

  The connection temperature (second connection temperature) when the external conductor 4 is connected to the electrode 13a via the low melting point solder material serving as the second connection material is lower than the melting point of the high melting point solder material used for the connection of the center conductor 2. The temperature is set in the range above the melting point of the low melting point solder material.

  Here, Sn-3Ag-0.5Cu (mass%) having a melting point of 218 ° C., Sn-3.5Ag (mass%) having a melting point of 221 ° C., or the like is used as the high melting point solder material serving as the first connecting material. As the low melting point solder material used as the second connecting material, Sn-58Bi (mass%) having a melting point of 139 ° C., Sn-40Bi-0.1Cu (mass%) having a melting point of 137 ° C., or the like is used.

  For example, when Sn-3Ag-0.5Cu, which is a high melting point solder material, is used for the first connecting material of the central conductor 2 to be connected first, the connection temperature when the central conductor 2 is connected is in the range of about 240 ° C. to 300 ° C. Set. A low melting point solder material Sn-58Bi is used for the second connection material of the outer conductor 4 to be connected thereafter, and the connection temperature in this case is set to about 200 ° C. which is lower than the melting point of the high melting point solder material of the first connection material. To do.

  As described above, for example, the connecting portion of the central conductor 2 to be connected first is a first connecting portion, and the connecting portion of the external conductor 4 to be connected thereafter is a second connecting portion. The relationship between each melting point and connection temperature is schematically shown in FIG.

  When connecting the conductors 2 and 4 to the electrode portions 12 and 13 of the printed circuit board 11 in the order of the center conductor 2 and the outer conductor 4, the connection portion of the outer conductor 4 and the electrode 13a is heated by using the method described above. Even so, since the temperature of the connecting portion between the central conductor 2 and the electrode 12a connected before this becomes lower than the melting point of the high melting point solder material used as the first connecting material, remelting of the first connecting material can be suppressed. The sound connection part without the electrical short circuit between the center conductor 2 and the outer conductor 4 can be provided.

  In the first embodiment, the central conductor 2 is first connected to the electrode 12a of the central conductor electrode portion 12 with the first connecting material, and then the external conductor 4 is connected to the external conductor electrode portion with the second connecting material. A method of connecting to 13 electrodes 13a was shown. However, these conductors 2 and 4 may be connected in the order of the outer conductor 4 and the center conductor 2, and in this case, the first conductor made of a high melting point solder material is used for the connection of the outer conductor 4, A second connecting material made of a low melting point solder material is used for connecting the central conductor 2 to be connected later.

  In the first embodiment, the method of using a thermocompression bonding apparatus for connecting the center conductor 2 and the outer conductor 4 has been described. However, in addition to the thermocompression bonding method, an infrared ray, hot air, laser, or the like is connected. There is no problem even if it is applied to the part and heated and connected via the connecting members 14 and 15.

  Next, a coaxial cable connection structure according to a second embodiment of the present invention will be described.

  As shown in FIGS. 8 and 9, the basic configuration of the coaxial cable connection structure 20 according to the second embodiment is the same as that of the coaxial cable connection structure 10 according to the first embodiment. Is that anisotropic conductive adhesives 22 and 23 in which solder particles are dispersed in a thermosetting resin 21 are used for connection to the electrode portions 12 and 13 corresponding to the center conductor 2 and the outer conductor 4, respectively. .

  Also in the second embodiment, as in the first embodiment described above, a method of connecting the central conductor 2 and the outer conductor 4 to the electrode portions 12 and 13 in this order will be described as an example.

  For connection between the center conductor 2 and the electrode 12a of the corresponding center conductor electrode portion 12, an anisotropic conductive adhesive 22 in which high melting point solder material particles 24 are dispersed in the thermosetting resin 21 is used as the first connection material. Use.

  For connection between the external conductor 4 and the electrode 13a of the external conductor electrode portion 13, an anisotropic conductive adhesive material 23 in which low melting point solder material particles 25 are dispersed in the thermosetting resin 21 is used as the second connection material.

  The electrical connection between the center conductor 2 and the outer conductor 4 and the corresponding electrode portions 12 and 13 is such that the solder particles 24 and 25 existing between the conductors 2 and 4 and the electrodes 12a and 13a are the conductors 2 and 4 and the electrodes. It is made by contacting or joining both 12a and 13a. Here, the connection of the central conductor 2 is performed by heating to a temperature higher than the melting point of the high melting point solder material particles 24, and the connection of the outer conductor 4 is lower than the melting point of the high melting point solder material particles 24 and the low melting point solder material particles It is set at a temperature in the range of 25 or higher.

  By adopting such a configuration, when connecting the conductors 2 and 4 to the electrodes 12a and 13a of the printed circuit board 11 in the order of the center conductor 2 and the outer conductor 4, the connecting portion of the outer conductor 4 is heated. However, since the temperature of the connecting portion of the central conductor 2 connected before this becomes lower than the melting point of the high melting point solder material particles 24 that electrically connect the center conductor 2 and the electrode 12a, the high melting point solder material particles 24 are regenerated. Does not melt. Moreover, according to the coaxial cable connection structure 20 according to the second embodiment, not only the electrical connection portion between the conductors 2 and 4 and the electrodes 12a and 13a by the solder particles, but also the center conductor 2 and the external conductor 4 are connected. Since the circumference | surroundings can each be covered with the thermosetting resin 21, the effect which ensures the mechanical strength of a conductor connection part is also acquired.

  Next, a coaxial cable connection structure according to a third embodiment of the present invention will be described.

  As shown in FIG. 10, the basic configuration of the coaxial cable connection structure 30 according to the third embodiment is the same as that of the coaxial cable connection structure 10 according to the first embodiment. Each external conductor 4 is electrically connected to the ground bar 31 while maintaining its parallel state, and then the ground bar 31 is electrically connected to the electrode 13 a of the external conductor electrode portion 13.

  The outer conductor 4 and the ground bar 31 are the same solder material as the refractory solder material used to connect the center conductor 2 to the electrode 12a before connecting the terminal portion of the coaxial cable 1 to the electrodes 12a and 13a of the printed circuit board 11. Connect at 32. For connecting the outer conductor 4 to the electrode 13a after the connection of the center conductor 2, a low melting point solder material is used.

  With such a configuration, even if the connecting portion of the center conductor 2 is heated to connect the center conductor 2, the external conductor 4 is not yet connected to the electrode 13a, and the heat conduction path is the conductor 2, Therefore, the connecting portion between the outer conductor 4 and the ground bar 31 does not rise to a temperature at which the second connecting material is remelted.

  Further, since the low melting point solder material is used for the connection of the external conductor 4, the connection temperature when the external conductor 4 is connected to the electrode 13a of the printed circuit board 11 is set to the high melting point solder material (first connection material and solder material 32). The melting point of the solder can be set lower than the melting point, and these solder materials do not remelt.

  Further, by connecting the outer conductor 4 to the ground bar 31 before connecting the coaxial cable terminal portion, it is possible to fix the arrangement state of the coaxial cable terminal portions in the parallel direction. The effect that alignment with the electrode 12a becomes easy is also acquired.

  As described above, according to the coaxial cable connection structures 10, 20, 30 and the connection method thereof according to the embodiment, either one of the central conductor 2 and the outer conductor 4 of the coaxial cable 1 is connected. When connecting to the electrodes 12a and 13a of the printed circuit board 11 in order, the connecting material used for connecting the conductor connecting portion connected earlier reflows and flows out due to the heating at the time of connecting the conductor to be connected later. It is possible to provide a sound connection portion that prevents the occurrence of a mechanical short circuit.

DESCRIPTION OF SYMBOLS 1 Coaxial cable 2 Center conductor 3 Inner insulator 4 Outer conductor 5 Outer insulator 11 Printed circuit board 12 Center conductor electrode part 13 External conductor electrode parts 14 and 15 Connecting material

Claims (6)

The end portion of the coaxial cable is stepped off to expose the outer conductor, the inner insulator, and the center conductor in order from the outer insulator, and the exposed center conductor and the outer conductor are formed on the printed circuit board. In the connection structure of coaxial cables that are electrically connected to each other via a connecting material,
The first connecting material for electrically connecting the central conductor and the electrode portion and the second connecting material for electrically connecting the outer conductor and the electrode portion have different melting points. Coaxial cable connection structure.   The coaxial cable connection structure according to claim 1, wherein a plurality of solder particles dispersed in a thermosetting resin are used as the first and second connection members. The end portion of the coaxial cable is stepped off to expose the outer conductor, the inner insulator, and the center conductor in order from the outer insulator, and the exposed center conductor and the outer conductor are formed on the printed circuit board. In the method of connecting coaxial cables that are electrically connected to each other via a connecting material,
A method for connecting coaxial cables, wherein the first connection temperature of one of the central conductor and the outer conductor connected earlier is set higher than the second connection temperature of the other conductor connected later. .   Of the central conductor and the outer conductor, the melting point of the first connecting member of one of the conductors connected first is higher than the melting point of the second connecting member of the other conductor connected later, and the second conductor The method for connecting coaxial cables according to claim 3, wherein the connection temperature is lower than the melting point of the first connection member and is equal to or higher than the melting point of the second connection member.   As the coaxial cable, a multi-core coaxial cable in which a plurality of coaxial cables are arranged in parallel is used, and the exposed external conductors of the multi-core coaxial cable are used in the first connection material while maintaining the parallel state. After the electrical connection to the ground bar in advance, each exposed central conductor of the multi-core coaxial cable is connected to the corresponding electrode portion of the printed circuit board using the first connection material, and the ground bar is connected The coaxial cable connection method according to claim 4, wherein the second connection member is used to electrically connect to the corresponding electrode portion of the printed circuit board.   The method for connecting coaxial cables according to claim 4 or 5, wherein a plurality of solder particles dispersed in a thermosetting resin are used as the first and second connecting members.

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