JP6328284B2 - Electronics - Google Patents

Description

  The present invention relates to an electronic device and a method for manufacturing the same, and more particularly to an electronic device including a coaxial connector used when electrically connecting electronic devices that handle high-frequency electrical signals and a method for manufacturing the same.

  High-frequency equipment that handles high-frequency electrical signals, such as wireless communication equipment, broadcast equipment, network equipment, and electronic measuring instruments, has an electronic circuit that is mounted on a circuit board with electronic components typified by high-frequency semiconductor devices. It is configured.

  When such a circuit board is used for a long time without being protected, it is easily affected by environmental changes such as contamination and moisture. In this case, the proper operation of the electronic circuit may be impaired. For this reason, the circuit board is generally used in a state where it is housed in a casing for protection from the external environment.

  On the other hand, high frequency equipment casings have unique problems: blocking electromagnetic noise entering from the outside and preventing leakage of noise generated by internal electronic circuits to the outside, so-called electromagnetic shielding function Is also required. For this reason, the housing | casing of a high frequency apparatus is mainly comprised with the metal.

  In addition, high-frequency devices are rarely used alone, and are usually electrically connected to other high-frequency devices and configured to exhibit functions by being systematized. For transmission of electric signals between high-frequency devices, a dedicated covered electric wire for transmitting high-frequency electric signals called a coaxial cable is used.

  A coaxial cable is a coaxial cylindrical structure, consisting of a metal conductor located at the center (hereinafter referred to as the center conductor) and a metal conductor that concentrically surrounds it, and between the two conductors is usually a solid with a low dielectric loss. Filled with dielectric. The impedance (characteristic impedance) of the coaxial cable is determined by the inner / outer diameter ratio of both conductors and the dielectric constant of the dielectric interposed between the two conductors, and a general coaxial cable having 75Ω or 50Ω is used.

  Although it is a coaxial cable that plays a role of connecting high-frequency devices, a function that can be freely attached and detached is required in actual use. For this reason, coaxial connectors are attached to both ends of the coaxial cable and the casing of the high-frequency device. Coaxial connectors are dedicated connectors made to match the dimensions and impedance of the coaxial cable, and many types are made to meet the purpose of use.

  The connection between the coaxial connector and the circuit board inside the housing is performed by soldering, ribbon bonding (ribbon bonding) or the like so as not to cause circuit discontinuity as much as possible from the viewpoint of impedance matching.

  A ball bonding (ball bonding) method generally called wire bonding (wire bonding) is connected in such a manner that metal wires draw a loop due to its construction method. A connection configuration in which a metal wire draws a loop has discontinuity due to an inductance component generated according to the area of the loop when viewed from a high-frequency circuit. Therefore, when connecting high-frequency circuits by wire bonding, a design that allows for the height and distance of the loop is required.

  On the other hand, in the ribbon bond method using a flat metal ribbon as the connection conductor, the end of the ribbon is pressed from the upper surface with a dedicated tool at the location where the metal ribbon is positioned, and bonded by pressure thermocompression connection or ultrasonic vibration. Therefore, no harmful loops or discontinuities occur without going through operations such as wire bonding. For this reason, the reflection loss due to impedance mismatching can be kept low. Further, since the cross-sectional area is large, the skin effect can be suppressed to a low level, and the wiring length of the connection portion can be shortened, so that an increase in wiring inductance can be suppressed to a low level. In addition, although many high-frequency devices are devices that handle power, it is desirable for such a circuit to have a large cross-sectional area structure that has a low electrical resistance at the connection and can secure a larger current capacity. It is.

  As described above, since the ribbon bond method has many advantages, it is preferably used for a high-frequency device. Metal ribbons are connected by pressure thermocompression ribbon bonding using a bonding tool that applies a load and high temperature environment to the ribbon during bonding, ultrasonic bonding by applying ultrasonic waves to the tool, or ultrasonic combined thermocompression that combines the two. Done. When the metal ribbon is bonded to the metal conductor to be bonded, the metal ribbon is bonded at one location or at a plurality of adjacent sites. Multiple tool joints are repeated to obtain multiple joints.

  Conventionally, in order to improve impedance matching and reflection characteristics of the input / output section of high-frequency equipment and to improve reliability, various approaches have been made to connect the coaxial connector fixed to the casing to the circuit board. It is. (See JP 2009-99283 A, JP 61-77567 A, JP 2007-37010 A, etc.)

JP 2009-99283 A Japanese Utility Model Publication No. 61-77567 JP 2007-37010 A

  However, the method described in Japanese Patent Application Laid-Open No. 2009-99283 has a problem in terms of reliability because the central conductor of the coaxial connector and the strip line of the circuit board are directly joined by solder. That is, troubles may occur in which the solder joint between the central conductor of the coaxial connector and the circuit board breaks due to thermal stress caused by changes in environmental temperature, heat generation of the high-frequency equipment or the electronic circuit itself, and the like.

  Further, in the method described in Japanese Utility Model Laid-Open No. 61-77567, when the frequency handled by the high-frequency device is increased, impedance mismatch is likely to occur because of the physically discontinuous portion. Further, since the connection method between the coaxial cable and the circuit board becomes complicated, it is not suitable for automation.

  The method described in Japanese Patent Application Laid-Open No. 2007-37010 is a method of ribbon bonding or soldering while giving a slight slack to the metal ribbon. The slack of the metal ribbon is effective for stress relief, and a simple connection configuration. Is a preferable method from the viewpoint of impedance matching. However, the method of joining the metal ribbon with solder requires work on very fine parts, and it is necessary to grip the molten solder until it cools and solidifies, and after connection, it is necessary to remove the flux with large dielectric loss For example, there is a problem that the mounting method becomes high due to the complexity of the work method, and is not suitable for automation.

  In addition, when joining metal ribbons by thermocompression bonding or ultrasonic bonding, or by thermocompression bonding with ultrasonic waves, bonding depends on the surface contamination of the central conductor of the coaxial connector, plating quality, and finishing accuracy. The strength may not be constant.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide an electronic device with high connection reliability between a central conductor of a coaxial connector and a circuit board.

  The electronic device of the present invention is an electronic device that handles high-frequency electrical signals. The electronic device of the present invention includes a coaxial connector having a center conductor, a circuit board having a strip line formed on the surface thereof, and a metal ribbon that electrically connects the center conductor and the strip line. The metal ribbon is connected to the center conductor via a metal stud bump formed on the center conductor. The height of the metal stud bump in a state where the center conductor and the metal ribbon are connected is 20 μm or more and 40 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the electronic device with high connection reliability of the center conductor of a coaxial connector and a circuit board can be obtained.

4 is a diagram illustrating a connection region between a coaxial connector and a circuit board in the electronic apparatus according to Embodiment 1. FIG. 4 is a flowchart of a method for manufacturing the electronic device according to the first embodiment. It is a figure for demonstrating the process (S20) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the process (S30) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. (A) It is the figure which looked at FIG. 4 from the upper surface. (B) It is the figure which looked at FIG. 4 from the side. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 1. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 2. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 2. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 2. FIG. It is a figure for demonstrating the process (S30) of the manufacturing method of the electronic device which concerns on Embodiment 3. FIG. It is a figure for demonstrating the process (S40) of the manufacturing method of the electronic device which concerns on Embodiment 3. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Embodiment 1)
First, the connection structure of the coaxial connector according to the first embodiment will be described with reference to FIG. The electronic device according to the present embodiment includes a coaxial connector 10, a circuit board 20, and a housing 30 to which the coaxial connector 10 and the circuit board 20 are fixed.

  The coaxial connector 10 includes a central conductor 11 that is electrically connected to a core wire of a coaxial cable (not shown), an insulator 12 that is interposed between the central conductor 11 and the casing 30, and is insulated. And a flange 14 connected to the outer peripheral surface. The shape of the center conductor 11 is, for example, a cylindrical shape having a diameter of 0.38 mm. The material constituting the central conductor 11 is, for example, beryllium copper, and a Ni (5 μm thickness) / Au (2.5 μm thickness) plating layer is formed on the surface thereof. The Au plating in the plating layer is, for example, hard Au plating with a purity of 98.5% to 99.5%. The material constituting the insulator 12 is an insulator having a small dielectric loss, such as PTFE (polytetrafluoroethylene) resin. The coaxial connector 10 is provided with two or four screw holes 16 in a metal flange 14.

  The circuit board 20 includes a low-loss printed board 21 used for a high-frequency device and a strip line 22 formed on the printed board 21. The material constituting the printed circuit board 21 is, for example, PTFE resin. The strip line 22 has, for example, a layer structure in which a plated layer of Ni (5 μm thick) / Au (0.1 μm thick) is formed on a Cu foil (18 μm thick) formed on the printed circuit board 21. Yes.

  The coaxial connector 10 and the circuit board 20 are connected and fixed to the housing 30. The material which comprises the housing | casing 30 is metals, such as aluminum, brass, copper, or an alloy which has them as a main component, for example. An opening for screwing and fixing the coaxial connector 10 with a mounting screw 15 is provided on a side surface of the housing 30, and a circuit board 20 having a strip line 22 is attached to the inside thereof.

  The central conductor 11 of the coaxial connector 10 and the strip line 22 formed on the surface of the circuit board 20 are electrically connected by the metal ribbon 1.

  The material constituting the metal ribbon 1 is Au. For example, a commercially available product made of an Au material having a purity of 99.7% or more may be used. The dimensions of the metal ribbon 1 are, for example, a width of about 0.2 mm to 1 mm and a thickness of about 25 μm with respect to the direction in which the metal ribbon extends (the direction extending from the central conductor 11 to the strip line 22).

  The one end 1a of the metal ribbon 1 and the strip line 22 are connected by thermocompression bonding, ultrasonic waves, ultrasonic thermocompression bonding, or the like. The other end 1b of the metal ribbon 1 and the central conductor 11 are connected via the metal stud bump 2 by thermocompression bonding, ultrasonic waves, ultrasonic combined thermocompression bonding, or the like. The metal ribbon 1 may be provided with a bent portion between one end 1a and the other end 1b. Further, the metal ribbon 1 may be provided between the one end 1a and the other end 1b so as to have a sag so as not to cause loss of the high-frequency circuit. In this way, stress is applied to the joint portion with the central conductor 11 of the coaxial connector 10 and the joint portion with the strip line 22 of the circuit board 20 via the metal stud bump 2 due to thermal deformation of the metal ribbon 1 or the like. As a result, it is possible to suppress the occurrence of bonding failure or the like.

  The metal stud bump 2 is formed by tearing a wire made of Au, and the shape of the metal stud bump 2 has a quasi-jewel shape in which the lower portion extends laterally from the upper portion. The dimensions of the metal stud bump 2 in a state where the center conductor 11 and the metal ribbon 1 are connected are, for example, a maximum diameter of 65 μm to 70 μm and a height of about 20 μm to 40 μm. The Au wire used as the material for the metal stud bump 2 is, for example, a commercially available Au wire for forming a stud bump having a wire diameter (diameter) of 15 μm to 38 μm (purity 99.9%, for example, Tanaka Denshi Kogyo GBE type ) May be used. A plurality of metal stud bumps 2 are formed at intervals in the direction in which the central conductor 11 extends. The interval may be about 0.2 mm.

  In addition, regarding the formation of the metal stud bump 2 and connecting the coaxial connector 10 and the metal ribbon 1 via the metal stud bump 2, the influence on the high frequency characteristics of the electronic device is negligible. This is because the height of the metal stud bump 2 in the state where the center conductor 11 and the metal ribbon 1 are connected is about 20 μm or more and 40 μm or less. is not.

  Next, with reference to FIG. 2, the manufacturing method of the electronic device according to the present embodiment will be described. The manufacturing method of the electronic device according to the present embodiment includes a step (S10) of preparing the coaxial connector 10 having the center conductor 11 and the circuit board 20 having the strip line 22 formed on the surface, the strip line 22 and the metal. The step of connecting one end 1a of the ribbon 1 (S20), the step of forming the metal stud bump 2 on the center conductor 11 of the coaxial connector 10 (S30), and the center conductor 11 and the metal via the metal stud bump 2 Connecting the other end 1b of the ribbon 1 (S40).

  First, in the step (S10), the coaxial connector 10 having the central conductor 11 and the circuit board 20 on which the strip line 22 is formed are prepared. The circuit board 20 is attached to the inside of the housing 30 with screws, an adhesive, or the like.

  Next, referring to FIG. 3, in step (S20), strip line 22 and one end 1a of metal ribbon 1 are connected. The metal ribbon 1 is connected to an end portion (connecting end with the coaxial connector) located on the coaxial connector 10 side in the strip line 22 by a thermocompression bonding method. The connection is performed by, for example, using a pulse heat type thermo-compression ribbon bonding apparatus to lower the bonding tool 50 under the condition that the temperature of the bonding tool 50 is 450 ° C., the load is 10 N, and the pressurizing time is 1 second. . The connection is made at a plurality of positions with intervals, for example, 3 to 5 connections are made at 0.2 mm intervals.

  Next, with reference to FIG. 4 and FIG. 5, the metal stud bump 2 is formed on the center conductor 11 of the coaxial connector 10 in a process (S30). In this step (S30), first, the coaxial connector 10 is fixed to the housing 30. Specifically, the flange 14 formed on the coaxial connector 10 is fixed by being screwed to the housing 30 by the mounting screw 15.

  Next, the Au wire having a ball-shaped tip is bonded onto the central conductor 11 of the coaxial connector 10 by using any one of the ball bonding methods of the thermocompression bonding method, the ultrasonic method, and the ultrasonic thermocompression bonding method. To do. Specifically, the tip of a bonding capillary having an Au ball formed by discharge is brought down and brought into contact with a predetermined place on the central conductor 11 where the metal stud bump 2 is formed, and ultrasonic vibration is applied to the metal ball. Apply first bond. Next, after closing the wire clamp, the bonding capillary is raised, and the Au wire extending from the Au ball is pulled upward in the vertical direction. When the tensile force applied to the Au wire exceeds the tensile strength of the Au wire, the Au wire is torn. As a result, a pseudo-jewel-like metal stud bump 2 (Au stud bump) can be formed on the central conductor 11 of the coaxial connector 10. By performing this three times in succession, with reference to FIGS. 5A and 5B, three metal stud bumps 2 are provided on the center conductor 11 with a space in the direction in which the center conductor 11 extends. Form. The metal stud bump 2 formed by this method has, for example, a maximum diameter of 65 μm to 70 μm and a height of about 90 μm.

  Here, the bonding strength between the central conductor 11 and the metal stud bump 2 in this step (S30) is determined by the size of the area of the bonded portion if there is no void or impurity at the bonded interface. This is because the bonding interface of the ball bond is connected by an intermetallic bond due to solid phase diffusion of metal atoms (Au atoms).

  The inventors of the present application have experimented with the step of forming the metal stud bump 2 on the central conductor 11 of the coaxial connector 10 by the wire bonding method in the step (S30), and the bonding strength between the central conductor 11 and the metal stud bump 2 is increased. It was confirmed to have the same effect as the tensile test to be evaluated. That is, when there is an abnormality such as surface contamination on the center conductor 11, the Au wire cannot be pulled up until the Au wire breaks in this step (S30), and the metal stud bump 2 is placed on the center conductor 11. It was confirmed that it could not be formed. In other words, in the present step (S30), when there is an abnormality on the surface of the central conductor 11 that may cause a reduction in the bonding strength with the metal stud bump 2 to be less than the strength at the time of tearing of the Au wire, This is detected as an abnormality that the metal stud bump 2 cannot be formed on the central conductor 11. As described above, since the bonding failure between the center conductor 11 of the coaxial connector 10 and the metal stud bump 2 can be known in this step (S30), the manufacturing failure of the electronic device can be reduced, and the high-frequency circuit in the electronic device can be reduced. The connection reliability can be improved. This is difficult in the conventional method in which the metal ribbon 1 is directly joined to the central conductor of the coaxial connector 10. Details of the experiment are shown in the examples described later.

  Next, referring to FIG. 6 and FIG. 7, in step (S <b> 40), the center conductor 11 and the other end 1 b of the metal ribbon 1 are connected via the metal stud bump 2. Specifically, first, the metal ribbon 1 is placed on the metal stud bump 2 formed on the central conductor 11 of the coaxial connector 10 so as to face each other. After aligning the bonding tool 50 with respect to the metal ribbon 1 and the metal stud bump 2, the bonding tool 50 is pressed against the upper surface of the metal ribbon 1, and the metal ribbon 1 and the metal stud bump 2 are bonded by thermocompression bonding, ultrasonic bonding, Alternatively, bonding is performed using ultrasonic thermocompression bonding. For example, in the case of joining by thermocompression bonding, first, the bonding tool 50 is pressed against the metal stud bump 2 having a pseudo-jewel-like appearance so that the protrusion at the top of the pseudo-jewel is crushed, and then heating by load and pulse heat is performed. Thus, metal atoms (Au atoms) contained in the metal ribbon 1 and the metal stud bump 2 are bonded to each other by solid phase diffusion. For example, the bonding is performed under the conditions that the bonding tool temperature is about 405 ° C. or more and about 495 ° C. or less, the load is about 0.5 N or more and about 1 N or less, and the pressing time is about 1 second. In the joining, it is preferable not to apply a high load (for example, 10 N) so that the center conductor 11 is deformed or the metal stud bump 2 is partially pressed excessively and the joint is not distorted. Joining is performed one by one on a plurality of metal stud bumps 2 and is performed three times, so that the center conductor 11 and the metal are connected to each other via three metal stud bumps 2 formed on the center conductor 11 at intervals. The other end 1b of the ribbon 1 is connected. In this manner, the electronic device according to this embodiment can be obtained.

  At this time, referring to FIGS. 7 and 8, generally, the tip shape of the bonding tool 50 has a rectangular shape having a longitudinal direction in one direction, and the shape of the joint portion 3 is formed in a rectangular shape. In the step (S40), it is preferable that the longitudinal direction of the joint portion 3 is formed in a direction perpendicular to the direction in which the central conductor 11 extends. Thereby, a joining area can be expanded in the circumferential direction of the cylindrical center conductor 11.

  As described above, according to the electronic device and the manufacturing method thereof according to the present embodiment, the metal stud bump 2 is pulled upward in the vertical direction with respect to the Au wire joined on the central conductor 11 in the step (S30). As a result, it is torn and formed. At this time, when the metal stud bump 2 is formed on the central conductor 11 of the coaxial connector 10, if the joint strength between the central conductor 11 and the metal stud bump 2 is less than the tear strength of the Au wire, the metal stud bump 2 is peeled off from the central conductor 11. Therefore, for example, the presence of some abnormality or impurities on the plating surface of the central conductor 11 of the coaxial connector 10 causes the metal stud bump 2 and the central conductor 11 to be bonded with a bonding strength equal to or lower than the tear strength of the Au wire. If this is the case, this can be detected at the time when the metal stud bump 2 is formed on the central conductor 11 (step (S30)). As a result, the connection reliability between the coaxial connector 10 and the metal ribbon 1 via the metal stud bump 2 can be enhanced. Moreover, since the said defect can be detected in a process (S30) before a process (S40), without producing the connection defect of the coaxial connector 10 resulting from abnormality of the coaxial connector 10, and the metal ribbon 1, A defective product of the coaxial connector 10 can be screened.

  In the present embodiment, three metal stud bumps 2 are provided on the center conductor 11, but the present invention is not limited to this. For example, only one may be provided on the center conductor 11, or a plurality of three or more may be formed.

  In the first embodiment, the metal wire that is the material of the metal stud bump 2 is an Au wire having a diameter of 25 μm developed exclusively for the stud bump, but is not limited thereto. For example, it may be a single metal wire such as aluminum (Al) or copper (Cu), or may be an alloy wire containing a trace element added to improve these characteristics.

  In the present embodiment, in the step (S20), the connection between the strip line 22 and the one end 1a of the metal ribbon 1 is performed in a state where the circuit board 20 is attached to the inside of the housing 30 with screws, an adhesive, or the like. However, it is not limited to this. For example, the circuit board 20 may be attached to the housing 30 after connecting the strip line 22 and the one end 1a of the metal ribbon 1 in the step (S20).

  Moreover, although the metal stud bump 2 was formed with respect to the coaxial connector 10 fixed to the housing | casing 30 in process (S30), it is not restricted to this. In the step (S30), after forming the metal stud bump 2 on the coaxial connector 10 as shown in FIG. 9, the coaxial connector 10 on which the metal stud bump 2 is formed may be fixed to the housing 30. If it does in this way, the connection process of the coaxial connector 10 and the circuit board 20 by the metal ribbon 1 can be implemented efficiently in a short time. In addition, for example, even if some defect (for example, a bonding failure or a deformation due to bonding) occurs in the step (S30), the coaxial connector 10 may be replaced, and the load of rework work such as component replacement is reduced. Can be reduced.

  Further, when the step (S30) is performed with the coaxial connector 10 attached to the housing 30, in order to perform this in an inert gas atmosphere, the housing 30 and the housing 30 must be housed in the inert gas atmosphere. There is. In this case, a chamber or the like having a large volume is required, and it is difficult to form the metal stud bump 2 in an inert gas atmosphere. However, by performing the process (S30) on the coaxial connector 10 that is not fixed to the housing 30, the process (S30) can be easily performed in an inert gas atmosphere. By forming the metal stud bump 2 on the center conductor 11 of the coaxial connector 10 in an inert gas atmosphere, the oxidation of the center conductor 11 that causes a poor connection between the center conductor 11 and the metal stud bump 2 is suppressed. be able to. Furthermore, since the oxidation of the center conductor 11 can be suppressed even in a high temperature environment of about 200 ° C. or more and 300 ° C. or less, the metal stud bump 2 can be formed while holding the center conductor 11 in the above temperature region. Therefore, it is possible to form the metal stud bump 2 with higher bonding strength with the central conductor 11.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIGS. The electronic device and the electronic device manufacturing method according to the present embodiment basically have the same configuration as the electronic device and the electronic device manufacturing method according to the first embodiment, but the other end 1b of the metal ribbon 1. However, it is different in that it has high flatness in a state where it is joined to the central conductor 11 via the metal stud bump 2. 10 to 12, the central conductor 11 and the insulator 12 are shown as side views, but the metal ribbon 1, the flattening tool 60 that holds the metal ribbon 1, and the metal stud bump 2 are shown as sectional views. ing.

  Specifically, referring to FIG. 10, in the step (S <b> 40), first, the other end 1 b of the metal ribbon 1 is gripped by the flattening tool 60. Thereby, it can be set as the state which planarized the other end 1b of the metal ribbon 1 (or the state which maintained flatness). The flattening tool 60 is made of a ceramic material or a metal material whose bottom surface is flattened with high accuracy. One or a plurality of vacuum suction holes 61 are provided on the bottom surface of the flattening tool 60, and the other end 1b of the metal ribbon 1 is gripped by vacuum suction. At this time, in order to prevent the deformation of the center conductor 11, a spacer 62 made of a ceramic material or a metal material may be disposed so as to be in contact with the bottom surface of the center conductor 11 as necessary.

  Next, referring to FIG. 11, the other end 1b of the metal ribbon 1 adsorbed and fixed to the vacuum adsorbing hole 61 is brought into contact with the metal stud bump 2, and then vertically from above the metal stud bump 2 (in FIG. 11). Apply a compressive load (in the direction of the arrow) to crush the metal stud bump 2. Thereby, the other end 1b of the metal ribbon 1 can be collectively press-fitted into the plurality of metal stud bumps 2 formed on the central conductor 11. At this time, by adjusting the load by the flattening tool 60 and / or the temperature of the flattening tool 60, the metal atoms (Au atoms) are locally generated in the contact region between the metal ribbon 1 and the metal stud bump 2. A solid phase diffusion phenomenon can be caused. As a result, the metal ribbon 1 and the center conductor 11 can be temporarily fixed.

  Next, referring to FIG. 12, with the metal ribbon 1 and the center conductor 11 temporarily fixed, a bonding tool is pressed against the upper surface of the metal ribbon 1 in the same manner as in the first embodiment, and the metal ribbon 1 and the metal The stud bump 2 is bonded using thermocompression bonding, ultrasonic bonding, ultrasonic combined thermocompression bonding, or the like. At this time, since the metal ribbon 1 and the center conductor 11 are temporarily fixed, it is possible to prevent positional displacement at the time of joining, and suppress the warping of the metal ribbon 1 at the time of joining as shown in FIG. Therefore, workability can be improved.

  In addition, according to the method for manufacturing an electronic device according to the present embodiment, even when the shape or size varies between the plurality of metal stud bumps 2 formed in the step (S20), The height of the metal stud bump 2 (distance between the center conductor 11 and the metal ribbon 1) through the connection with the metal ribbon 1 can be made uniform when temporarily fixing as described above. For example, in the step (S20), when the height of the metal stud bump 2 formed using the Au wire for forming the metal stud bump varies from 80 μm to 100 μm (not flattened), the metal stud bump By press-fitting with a load of about 0.5 N per 2, the metal stud bump 2 flattened to a height of about 20 μm or more and 25 μm or less can be formed. At this time, the maximum diameter of the metal stud bump 2 is about 85 μm to 95 μm after press-fitting if it is about 65 μm to 70 μm before press-fitting.

  Further, when the center conductor 11 of the coaxial connector 10 is deformed and the height varies among the plurality of metal stud bumps 2 formed in the step (S20), the temporary fixing is performed. In addition, since the metal stud bumps 2 are absorbed by different deformation amounts, the metal ribbon 1 can be flattened with high accuracy.

  Thereby, even when a plurality of metal stud bumps 2 whose heights are not flattened are formed on the central conductor 11 of the coaxial connector 10, the metal ribbon 1 flattened with high accuracy is formed. Therefore, the loss of the high frequency signal in the connection part of the center conductor 11 and the metal ribbon 1 can be reduced, and the influence on the high frequency characteristics of the electronic device can be suppressed.

  Note that a heating mechanism may be provided in the flattening tool 60, and the metal ribbon 1 may be pressed into the metal stud bump 2 while being heated. In this way, the metal ribbon 1 is softened in proportion to the heating temperature, and the effect of the solid phase diffusion phenomenon of Au atoms can be increased. Therefore, when the metal ribbon 1 and the central conductor 11 are temporarily fixed. The bonding strength between the metal ribbon 1 and the metal stud bump 2 can be further improved. In this case, the heating temperature of the flattening tool 60 is increased to about 300 ° C., and the metal ribbon 1 is press-fitted into the metal stud bump 2 while being heated by the flattening tool 60. The metal ribbon 1 may be thermocompression bonded to the other end 1b.

  In the present embodiment, the step (S40) is performed after connecting the one end 1a of the metal ribbon 1 and the stripline 22 in the step (S20), but the present invention is not limited to this. For example, after temporarily fixing the other end 1b of the metal ribbon 1 and the center conductor 11, the one end 1a of the metal ribbon 1 and the strip line 22 may be connected. Further, after temporarily fixing and connecting the other end 1b of the metal ribbon 1 and the center conductor 11, the one end 1a of the metal ribbon 1 and the strip line 22 may be connected. That is, the step (S20) may be performed after the step (S40). Even if it does in this way, since the metal ribbon 1 can be planarized with high precision while improving the workability in the step (S40), the loss of the high frequency signal at the connecting portion between the center conductor 11 and the metal ribbon 1 is reduced. Can be reduced.

(Embodiment 3)
Next, Embodiment 3 of the present invention will be described with reference to FIG. 13 and FIG. The electronic device and the method for manufacturing the electronic device according to the present embodiment basically have the same configuration as the method for manufacturing the electronic device and the electronic device according to the first embodiment. However, in the step (S40), a metal ribbon is provided. Before connecting 1 and the central conductor 11, the difference is that the joint between the metal stud bump 2 and the central conductor 11 is evaluated by a destructive test.

  Specifically, referring to FIG. 13, first, in step (S30), at least one metal stud bump 4 that is not connected to one end 1b of metal ribbon 1 in step (S40) is formed on central conductor 11 of coaxial connector 10. Form one. That is, in the present embodiment, the plurality of metal stud bumps 2 and 4 are formed in the step (S30), but the plurality of metal stud bumps 2 and 4 are formed on the central conductor 11 under the same conditions.

  Next, in the step (S40), a destructive test is performed on the metal stud bump 4 that is not connected to the one end 1b of the metal ribbon 1. The destructive test is intended to evaluate the bonding strength between the metal stud bump 4 and the central conductor 11, and is, for example, a tensile test or a shear test.

  In the tensile test, for example, a dedicated holding jig capable of holding the metal stud bump 4 is prepared, and the metal stud bump 4 is pulled at a constant speed by the holding jig so that the metal stud bump 4 is broken or centered. The tensile strength when peeled from the conductor 11 is measured. The direction in which the metal stud bump 4 is pulled up may be the same as the direction in which the Au wire is pulled when the metal stud bump 4 is formed in the step (S30).

  In the shear test, referring to FIG. 14, for example, the shear test tool 70 is pressed against the metal stud bump 4 from the side surface to apply a load, and the breaking strength (shear strength) of the metal stud bump 4 is measured.

  By performing these destructive tests, the bonding strength between the metal stud bump 4 and the central conductor 11 is evaluated, and only those having a reference value or more are transferred to the next process, so that a defective bonding product flows to the next process. This can be suppressed.

  The destructive test in the present embodiment is preferably a simple shear test when the metal stud bumps 2 and 4 are formed on the central conductor 11 before the coaxial connector 10 is attached to the housing 30 in the step (S30). It is. Further, when the metal stud bumps 2 and 4 are formed on the central conductor 11 in a state where the coaxial connector 10 is attached to the housing 30 in the step (S30), the metal stud bumps 2 and 4 are pulled due to space limitations by the housing 30. A test is preferred.

  Examples of the present invention will be described below.

  In this example, the effectiveness of serving as a tensile test was confirmed when forming a metal stud bump on the central conductor of the coaxial connector by the wire bond method. Specifically, the metal stud in the step (S30) of the manufacturing method of the electronic device according to the present embodiment is caused by a bonding failure between the center conductor and the metal stud bump, which is considered to be caused by surface contamination of the center conductor of the coaxial connector. It was confirmed whether it was detectable at the time of bump formation.

(sample)
First, ten coaxial connectors with PTFE (polytetrafluoroethylene) resin as the insulator and Ni (5 μm) / Au (2.5 μm) plating layer formed on the beryllium copper as the central conductor are prepared. did. The Au plating is a hard Au plating with a purity of 98.5% to 99.5%. An Au wire having a wire diameter of 25 μm was prepared as a material for the metal stud bump. The average value of the tensile strength of the Au wire (stud bump forming Au wire) having a wire diameter of 25 μm is about 0.15 N.

  Next, surface fouling was intentionally formed on the central conductors of the 10 coaxial connectors prepared. Specifically, by handling the center conductor of the coaxial connector with a bare hand, the fat component of the bare hand was transferred to the center conductor portion of the coaxial connector and adhered as a fouling substance.

  Next, the coaxial connectors to which surface contamination was intentionally attached were divided into two groups of five, and the following different processes were performed.

  One group was subjected to a process of forming metal stud bumps as it was without applying any treatment after surface fouling was applied.

  In the other group, after surface fouling was adhered, the central conductor portion was cleaned with IPA (2-propanol) with a clean cotton swab, and after drying, Ar ion plasma cleaning was performed. Then, the process of forming a metal stud bump was implemented.

(Evaluation method 1)
First, it was confirmed whether metal stud bumps could be formed on the center conductor for the above two groups.

(Result 1)
After attaching the surface fouling, the metal stud bump is formed in the tearing process when forming the metal stud bump in one group in which the metal stud bump is formed as it is without any treatment. In either case, the Au wire was peeled off from the central conductor of the coaxial connector. In other words, in this embodiment, in the process of forming the metal stud bump, this corresponds to performing the tensile test of the metal stud bump with a force of 0.15 N of the tensile strength of the Au wire. It was confirmed that screening for poor bonding due to surface contamination could be performed.

(Evaluation method 2)
The group that performed the cleaning process was able to form a metal stud bump on the center conductor, but for this, a tensile test was performed to measure the breaking strength of the metal stud bump. A tensile tester (manufactured by Dage Precision Industries, DAGE4000) and a dedicated tweezer (tweezer-shaped gripping jig) prepared so as to be sandwiched from both ends of the side surface of the metal stud bump 2 were used for the test. The tensile strength was measured when the metal stud bump 2 was broken or peeled off from the central conductor 11 when the metal stud bump was pulled upward at a constant speed of 50 μm / second with the tweezers.

(Result 2)
The tensile strength of the metal stud bump formed on the central conductor subjected to the cleaning process was 0.4N or more and 0.52N or less. That is, the average value of the tensile strength when the metal stud bump was normally formed on the central conductor was about 0.48 N, and when converted into stress, the average value was 304 MPa. In this example, the average value of the diameter (joint diameter) of the joint (joint between the center conductor 11 and the metal stud bump 2) formed by ball bonding using an Au wire having a diameter of 25 μm is approximately 45 μm. Met. On the other hand, the average value of the tensile strength of the metal stud bump forming Au wire having a diameter of 25 μm was 0.15 N, and the average value of the breaking stress was 300 MPa. From the viewpoint of stress, the bonding strength of the normal bonding portion between the center conductor 11 and the metal stud bump 2 produced by ball bonding was almost the same value as the tensile breaking strength of the Au wire for forming the metal stud bump. . In other words, the joint strength of the joint between the central conductor 11 and the metal stud bump 2 is about 0.48N, and the strength when the Au wire is torn is about 0.15N. Met. That is, in the step (S30), forming the metal stud bump by tearing the Au wire means that the metal stud has a force of about 1/3 of the bonding strength when the center conductor and the metal stud bump are normally bonded. It can be said that this is equivalent to performing a bonding strength evaluation test between the bump (Au wire) and the central conductor. Therefore, it can be confirmed that when the surface contamination is present on the central conductor as in this embodiment, it is detected as an abnormality that the metal stud bump cannot be formed on the central conductor in the step (S30). It was. In addition, although the evaluation result about the abnormality of the surface fouling by fats and oils, organic polymers, etc. was shown in this example, other than the abnormality of the center conductor (for example, the ground when the pin hole is formed in the Au plating layer) Similarly, when there is surface diffusion of the Ni plating layer and accompanying plating corrosion, etc., it can be detected as an abnormality. Further, a decrease in the bonding strength between the metal stud bump and the center conductor due to variations in the finishing accuracy of the coaxial connector can be detected as an abnormality.

  Here, although there is a part which overlaps with embodiment mentioned above, the characteristic structure of this invention is enumerated.

  The electronic device according to the present invention includes a coaxial connector 10 having a center conductor 11, a circuit board 20 having a strip line 22 formed on the surface thereof, and a metal ribbon for electrically connecting the center conductor 11 and the strip line 22. 1. The metal ribbon 1 is connected to the center conductor 11 through a metal stud bump 2 formed on the center conductor 11.

  In this way, the metal stud bump 2 is formed by being pulled up by pulling upward in the vertical direction with respect to the Au wire joined on the central conductor 11. At this time, when the metal stud bump 2 is formed on the central conductor 11 of the coaxial connector 10, if the joint strength between the central conductor 11 and the metal stud bump 2 is less than the tear strength of the Au wire, the metal stud bump 2 is peeled off from the central conductor 11. Therefore, for example, the presence of some abnormality or impurities on the plating surface of the central conductor 11 of the coaxial connector 10 causes the metal stud bump 2 and the central conductor 11 to be bonded with a bonding strength equal to or lower than the tear strength of the Au wire. If this is the case, this can be detected when the metal stud bump 2 is formed on the central conductor 11. As a result, the connection reliability between the coaxial connector 10 and the metal ribbon 1 via the metal stud bump 2 can be enhanced. Further, defective products of the coaxial connector 10 can be screened without causing a connection failure between the coaxial connector 10 and the metal ribbon 1 due to the abnormality of the coaxial connector 10.

  A plurality of the metal stud bumps 2 may be formed on the center conductor 11 with an interval in the direction in which the center conductor 11 extends.

  Thereby, the joining area of the coaxial connector 10 and the metal ribbon 1 can be increased, and the joining strength between these can be raised.

  The method of manufacturing an electronic device according to the present invention includes a step (S10) of preparing the coaxial connector 10 having the center conductor 11 and the circuit board 20 having the strip line 22 formed on the surface, the strip line 22 and the metal ribbon. 1 is connected to one end 1a (S20), the metal stud bump 2 is formed on the central conductor 11 of the coaxial connector 10 (S30), and the central conductor 11 and the metal are connected via the metal stud bump 2. Connecting the other end 1b of the ribbon 1 (S40).

  In this way, the metal stud bump 2 is formed torn by pulling upward in the vertical direction with respect to the Au wire bonded onto the central conductor 11 in the step (S30). At this time, when the metal stud bump 2 is formed on the central conductor 11 of the coaxial connector 10, if the joint strength between the central conductor 11 and the metal stud bump 2 is less than the tear strength of the Au wire, the metal stud bump 2 is peeled off from the central conductor 11. Therefore, for example, the presence of some abnormality or impurities on the plating surface of the central conductor 11 of the coaxial connector 10 causes the metal stud bump 2 and the central conductor 11 to be bonded with a bonding strength equal to or lower than the tear strength of the Au wire. If this is the case, this can be detected at the time when the metal stud bump 2 is formed on the central conductor 11 (step (S30)). As a result, the connection reliability between the coaxial connector 10 and the metal ribbon 1 via the metal stud bump 2 can be enhanced. Moreover, since the said defect can be detected in a process (S30) before a process (S40), without producing the connection defect of the coaxial connector 10 resulting from abnormality of the coaxial connector 10, and the metal ribbon 1, A defective product of the coaxial connector 10 can be screened.

  The step of forming (S30) may be performed before attaching the coaxial connector 10 to the housing 30 on which the circuit board 20 and the coaxial connector 10 are mounted.

  Thereby, the metal stud bump 2 can be formed on the center conductor 11 of the coaxial connector 10 in an inert gas atmosphere. As a result, it is possible to suppress the oxidation of the center conductor 11 that causes a bonding failure between the center conductor 11 and the metal stud bump 2. Further, since the oxidation of the center conductor 11 can be suppressed even in a high temperature environment of about 200 ° C. or more and 300 ° C. or less, the metal stud bump 2 can be formed while holding the center conductor 11 in the above temperature region. Therefore, it is possible to form the metal stud bump 2 with higher bonding strength with the central conductor 11. In addition, when forming the metal stud bump 2 in a state where the coaxial connector 10 is attached to the housing 30, it is necessary to store the metal stud bump 2 including the housing 30 in an inert gas atmosphere. Therefore, it is difficult to form the metal stud bump 2 in an inert gas atmosphere.

  In the step of forming (S30), a plurality of metal stud bumps 2 may be formed on the center conductor 11 with an interval in the direction in which the center conductor 11 extends.

  Thereby, the joining area of the coaxial connector 10 and the metal ribbon 1 can be increased, and the joining strength between these can be raised.

  In the connecting step (S40), the plurality of metal stud bumps 2 and the other end 1b of the metal ribbon 1 are temporarily joined with metal atoms while the entire other end 1b of the metal ribbon 1 is kept flat. Thereafter, the flat other end 1 b and the central conductor 11 may be connected via the plurality of metal stud bumps 2.

  Thereby, since the center conductor 11 and the other end 1b of the metal ribbon 1 are connected, for example, after temporary joining of the solid-phase diffusion phenomenon of metal atoms (Au atoms), the positional deviation at the time of connection is suppressed. Can do. Further, when the center conductor 11 and the other end 1b of the metal ribbon 1 are connected, the warp of the metal ribbon 1 can be suppressed. Therefore, in the connection work performed through the individual metal stud bumps 2, the second and subsequent connection work can be easily performed. Further, for example, when the heights of the plurality of metal stud bumps 2 formed on the center conductor 11 of the coaxial connector 10 are uneven, or the center conductor 11 of the coaxial connector 10 is deformed or there is a variation in dimensions. Even in such a case, the coaxial connector 10 and the metal ribbon 1 can be easily connected. Moreover, since the other end 1b of the metal ribbon 1 can be flattened, the loss of a high frequency signal can be reduced and the deterioration of the performance of equipment operating at a high frequency can be suppressed.

  After the step of forming (S30) and before the step of connecting the center conductor 11 and the other end 1b of the metal ribbon 1 (S40), the plurality of metal stud bumps 2 formed on the center conductor 11 , 4 may include a step (31) of evaluating the bonding strength between the central conductor 11 and the stud bump 4 with respect to at least one of the metal stud bumps 4. In the step of evaluating (S31), after confirming that the bonding strength between the center conductor 11 and the metal stud bump 4 is equal to or higher than a reference value, the step of forming (S40) may be performed.

  Thereby, for example, when it is necessary to ensure that the bonding strength between the center conductor 11 and the metal stud bump 4 is higher than a reference value higher than the tear strength of the Au wire, a destructive test is performed after the bump formation. It is possible to suppress the outflow of a defective sample that can be confirmed and the bonding strength is less than the reference value to the next step.

  The step of evaluating (S31) is a tensile test performed by grasping the metal stud bump 4 and pulling it away from the center conductor 11, or a direction along the surface of the center conductor 11 of the metal stud bump 4. You may evaluate the joint strength of the said center conductor 11 and the said metal stud bump 4 by the shear test which adds a load from a horizontal direction.

  Thereby, the joint strength between the central conductor 11 and the metal stud bump 4 can be easily evaluated.

  Although the embodiments and examples of the present invention have been described above, various modifications can be made to the above-described embodiments and examples. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Metal ribbon, 1a One end, 1b The other end, 2, 4 Metal stud bump, 3 Joint part, 10 Coaxial connector, 11 Center conductor, 12 Insulator, 14 Flange, 15 Mounting screw, 16 Screw hole, 20 Circuit board, 21 printed circuit board, 22 strip line, 30 housing, 50 bonding tool, 60 flattening tool, 61 vacuum suction hole, 62 spacer, 70 shear test tool.

Claims (4)

An electronic device that handles high-frequency electrical signals,
A coaxial connector having a central conductor;
A circuit board having a stripline formed on the surface;
A metal ribbon that electrically connects the central conductor and the stripline;
The metal ribbon is connected to the center conductor via a metal stud bump formed on the center conductor,
The height of the metal stud bumps in a state that connects the metal ribbon and the center conductor state, and are more 40μm or less 20 [mu] m,
The electronic device in which the planar shape of the joint between the metal ribbon and the metal stud bump is rectangular . Longitudinal direction are formed so as to face the direction perpendicular to the direction of extension of said center conductor, an electronic device according to claim 1 of the joint. It said strip line, the material constituting the metal ribbon, and the metal stud bump comprises gold, electronic apparatus according to claim 1 or 2. The metal stud bump, on the central conductor, at an interval in a direction in which the central conductor extends is formed with a plurality of electronic apparatus according to any one of claims 1-3.

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