Method for joining linear members, linear members

Abstract

To increase the bonding strength in diffusion bonding. [Solution] The method for joining linear members comprises a polishing step of polishing the first end face of a first linear member and the second end face of a second linear member different from the first member to an arithmetic mean roughness of 0.1 μm or less; a bonding step of bringing the first end face and the second end face into close contact; and a pressurizing and energizing step of applying a voltage to the first member and the second member to generate heat in a region including at least the first end face and the second end face due to electrical resistance, thereby diffusing and bonding the first member and the second member, wherein the bonding step is performed such that 90% or more of the area of ​​the first end face is in contact with the second end face.

Description

[Technical Field]

[0001] The present invention relates to a joining method for linear members and the like. [Background Art]

[0002] Conventionally, diffusion bonding apparatuses have been proposed as disclosed in Patent Document 1. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 10-6038 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] However, the presence of minute unbonded portions at the bonding interface may cause a decrease in bonding strength.

[0005] Accordingly, one object of the present invention is to increase the bonding strength in diffusion bonding. Other objects of the present invention will become apparent from the description of the present specification. [Means for Solving the Problems]

[0006] One aspect of the present invention is a method for joining linear members, comprising: a polishing step of polishing a first end face of a first linear member and a second end face of a second linear member different from the first linear member such that an arithmetic average roughness thereof becomes 0.1 µm or less; an adhering step of bringing the first end face and the second end face into close contact with each other; and a pressurized energization step of applying a voltage to the first member and the second member to cause a region including at least the first end face and the second end face to generate heat by electric resistance, thereby diffusion-bonding the first member and the second member, wherein the adhering step is performed such that 90% or more of the area of the first end face is in contact with the second end face.

[0007] One aspect of the present invention is a linear member comprising a first member having a first end face polished to have an arithmetic mean roughness of 0.1 μm or less, and a second member having a second end face polished to have an arithmetic mean roughness of 0.1 μm or less, wherein a voltage is applied to the first member and the second member while 90% or more of the area of ​​the first end face is in contact with the second end face, and at least the area including the first end face and the second end face is heated by electrical resistance, and the first member and the second member are joined by diffusion bonding.

[0008] According to the above embodiment of the present invention, the bonding strength in diffusion bonding can be increased. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of the joining apparatus at the point when the holding process is completed. [Figure 2] This figure plots the results of the first experiment on a graph where the horizontal axis represents the current value A and the vertical axis represents the tensile strength N. [Figure 3] This is a box plot showing the results of the second experiment. [Figure 4] This is a side view of the bonding apparatus at the point when the adhesion process is completed. [Figure 5] This is a side view of the bonding device in the pressurized current application process. [Figure 6] This is a side view of the linear member after the removal process. [Modes for carrying out the invention]

[0010] The joining device 1 according to this embodiment will be described below with reference to the figures. Note that the embodiments are not limited to those described below. Furthermore, the contents described in one embodiment are, in principle, applicable to other embodiments as well. Also, each embodiment and each modification can be combined as appropriate.

[0011] To explain the directions, we define the x, y, and z directions. The x direction is the horizontal direction in which the first member 11 extends. The y direction is the horizontal direction perpendicular to the x direction. The z direction is the vertical direction perpendicular to both the x and y directions. In this embodiment, the x direction is described as the front-back direction, the y direction as the left-right direction, and the z direction as the up-down direction. In Figure 1 and other figures, the directions indicated by the arrows for the x and z axes are defined as the front and up directions, respectively. Note that Figures 1, 4 to 6 are side views illustrating the front-back and vertical directions, and therefore the y-axis is not shown.

[0012] Figures 1, 4 to 6 illustrate the region of the first member 11 that is held by the first holding device 21, and omit the illustration of the region extending forward in the x-direction. Figures 1, 4 to 6 illustrate the region of the second member 12 that is held by the second holding device 22, and omit the illustration of the region extending backward in the x-direction.

[0013] (Joining device 1) The joining device 1 of this embodiment is a device that joins two members to be joined (first member 11, second member 12) by diffusion bonding. As shown in Figure 1, the joining device 1 comprises a first holding device 21, a second holding device 22, a first base 23, a second base 24, a power supply 25, a first polishing device 26, a vibration transmission device 27, and a second polishing device 28.

[0014] (First member 11, second member 12) The first member 11 is a conductive linear member. The second member 12 is a different member from the first member 11 and is also a conductive linear member. The yz cross-sections of the first member 11 and the second member 12 are circular and have approximately the same size. One of the first member 11 and the second member 12 is made of, for example, nickel-titanium, and the other of the first member 11 and the second member 12 is made of, for example, stainless steel (SUS).

[0015] (First end surface 11a, second end surface 12a) An end face on the rear side in the x-direction of the first member 11 (first end face 11a), that is, an end face on the side of the first member 11 facing the second member 12, is polished such that the arithmetic mean roughness Ra becomes 0.1 µm or less before joining with the second member 12. An end face on the front side in the x-direction of the second member 12 (second end face 12a), that is, an end face on the side of the second member 12 facing the first member 11, is polished such that the arithmetic mean roughness Ra becomes 0.1 µm or less before joining with the first member 11.

[0016] (First Holding Device 21) The first holding device 21 holds the first member 11, and is used as one of a positive electrode and a negative electrode when energizing the first member 11 and the second member 12.

[0017] (Second Holding Device 22) The second holding device 22 holds the second member 12, and is used as the other of a positive electrode and a negative electrode when energizing the first member 11 and the second member 12.

[0018] (Positional Relationship Between First Holding Device 21 and Second Holding Device 22) The second holding device 22 is arranged on the rear side in the x-direction relative to the first holding device 21. For alignment in the adhesion step described later, the first holding device 21 may hold the first member 11 in a state of being movable in the y-direction and the z-direction. Similarly, the second holding device 22 may hold the second member 12 in a state of being movable in the y-direction and the z-direction.

[0019] (First Base Part 23, Second Base Part 24) The first base part 23 holds the first holding device 21. The second base part 24 holds the second holding device 22. The first base part 23 and the second base part 24 are movable in the x-direction. However, only one of the first base part 23 and the second base part 24 may be movable in the x-direction. The movement of the first base part 23 and the second base part 24 in the x-direction may be automatically performed by a machine or may be performed manually.

[0020] (Power Supply 25) The power supply 25 is a DC power supply device that supplies current to a circuit including the first holding part 21, the first member 11, the second member 12, and the second holding part 22.

[0021] (1st polishing device 26) The first polishing device 26 polishes the first end face 11a of the first member 11 and the second end face 12a of the second member 12. The first polishing device 26 may be driven based on power supplied from the power supply 25, or based on power supplied from another power source. The first polishing device 26 may also be driven by a power source other than electricity.

[0022] (Vibration transmission device 27) The vibration transmission device 27 transmits ultrasonic vibrations to at least one of the first member 11 and the second member 12. The vibration transmission device 27 may be driven based on power supplied from the power supply 25 or based on power supplied from another power source.

[0023] (Second polishing device 28) The second polishing device 28 removes protrusions formed by deformation of at least a portion of the first member 11 and the second member 12 during joining. The second polishing device 28 may be driven based on power supplied from the power supply 25 or from another power supply. The first polishing device 26 and the second polishing device 28 may be the same polishing device or different polishing devices.

[0024] (Joining procedure) Next, the procedure for joining the first member 11 and the second member 12 will be described. The user uses the first polishing device 26 to polish the first end face 11a of the first member 11 and the second end face 12a of the second member 12 to a level where the arithmetic mean roughness Ra is 0.1 μm or less (polishing process).

[0025] The user holds the first member 11 with the first holding device 21 and the second member 12 with the second holding device 22 (holding process).

[0026] In the holding process, the first member 11 is held with its first end face 11a protruding from the first holding device 21 by a first distance L1. The first distance L1 is 1.30 to 3.00 times the diameter of the first member 11 (first diameter D1). The following experimental results show that a ratio of 1.30 to 3.00 between the first diameter D1 and the first distance L1 (D1 / L1 ratio) is desirable (see Figures 2 and 3). Also in the holding process, the second member 12 is held with its second end face 12a protruding from the second holding device 22 by a second distance L2. The second distance L2 is 1.30 to 3.00 times the diameter of the second member 12 (second diameter D2).

[0027] Figure 2 shows the results of the first experiment in which the tensile strength N was measured when a first member 11 with a first diameter D1 (D1 = 0.12 mm) was joined to a second member 12 with a second diameter D2 (D2 = 0.12 mm) by varying the first distance L1 and the current value A.

[0028] Figure 3 shows the results of a second experiment in which the tensile strength N was measured when a first member 11 with a first diameter D1 (D1 = 0.20 mm) was joined to a second member 12 with a second diameter D2 (D2 = 0.20 mm) by varying the first distance L1.

[0029] The long dashed line in Figure 2 is a curve representing the relationship between current A and tensile strength N as a polynomial when the L1 / D1 ratio is 0.83. The angular dotted line in Figure 2 is a curve representing the relationship between current A and tensile strength N as a polynomial when the L1 / D1 ratio is 1.25. The circular dotted line in Figure 2 is a curve representing the relationship between current A and tensile strength N as a polynomial when the L1 / D1 ratio is 1.67. The dashed line in Figure 2 is a curve representing the relationship between current A and tensile strength N as a polynomial when the L1 / D1 ratio is 2.50.

[0030] Figure 2 shows that when the L1 / D1 ratio is 0.42 or less, the first member 11 and the second member 12 cannot be joined. Furthermore, Figure 4 shows that when the L1 / D1 ratio is 2.50 or more, the range of current values ​​A that can be joined is narrower than when the L1 / D1 ratio is 0.83, 1.25, and 1.67. Furthermore, Figure 4 shows that when the L1 / D1 ratio is 0.83, 1.25, and 1.67, the range of current values ​​A that can be joined is wider than when the L1 / D1 ratio is 2.50 or more. Figure 3 shows that when the L1 / D1 ratio is 1.25 and 1.00, the variation in tensile strength N is larger than when the L1 / D1 ratio is 1.40, 1.50, and 2.00. Furthermore, Figure 5 shows that when the L1 / D1 ratio is 1.40, 1.50, and 2.00, the variation in tensile strength N is smaller compared to when the L1 / D1 ratio is 1.25 and 1.00.

[0031] In other words, if the first distance L1 is too short, joining cannot be performed, and if the first distance L1 is too long, it will bend and joining cannot be performed. Also, if the current value A is too low, the amount of heat required for joining cannot be secured and joining cannot be performed, and if the current value A is too high, it will become brittle and joining cannot be performed. From the experimental results, it can be seen that joining can be performed when the ratio of the first distance L1 to the first diameter D1 is 1.30 to 2.00 and an appropriate current value A is applied.

[0032] As shown in Figure 4, the user moves the first base portion 23 and the second base portion 24 in the x-direction to bring the first other surface 11a of the first member 11 and the second end surface 12a of the second member 12 into close contact (contacting process). The contacting process is performed by adjusting the position of at least one of the first member 11 and the second member 12 so that more than 90% of the area of ​​the first end surface 11a is in contact with the second end surface 12a. The position of at least one of the first member 11 and the second member 12 is adjusted by moving at least one of the first holding device 21 and the second holding device 22.

[0033] The user drives the vibration transmission device 27 while it is in contact with at least one of the first member 11, the second member 12, the first holding device 21, and the second holding device 22, thereby applying ultrasonic vibrations to the first member 11 and the second member 12 (vibration process). The friction caused by the ultrasonic vibrations destroys the oxide film on the first end face 11a of the first member 11 and the second end face 12a of the second member 12. The vibration process is performed immediately before the pressurization and energization process, which will be described later.

[0034] The user stops the drive of the vibration transmission device 27. Immediately after stopping the drive of the vibration transmission device 27, the user moves the first base portion 23 to the rear in the x direction and the second base portion 24 to the front in the x direction, applying pressure in the x direction to the first member 11 and the second member 12. However, instead of moving both the first base portion 23 and the second base portion 24, either the first base portion 23 or the second base portion 24 may be moved. The user also applies voltage from the power supply 25 to the first holding portion 21 and the second holding portion 22 (pressurization and energization process).

[0035] As shown in Figure 5, due to plastic deformation caused by pressure, the x-direction dimensions of the region of the first member 11 that protrudes rearward in the x-direction from the first retaining device 21 and the region of the second member 12 that protrudes frontward in the x-direction from the second retaining device 22 are shortened as they are crushed. In addition, a radially extending bulge is formed between the first retaining device 21 and the second retaining device 22, based on the first member 11 and the second member 12.

[0036] When a voltage is applied, current flows through the DC circuit including the first holding part 21, the first member 11, the second member 12, and the second holding part 22, and the first member 11 and the second member 12 generate heat due to electrical resistance. Due to the pressure and heat, the first end face 11a and the second end face 12a are joined by diffusion bonding.

[0037] The user uses the second polishing device 28 to remove the protrusions on the rear side of the first member 11 in the x-direction and the protrusions on the front side of the second member 12 in the x-direction (removal step). As shown in Figure 6, the removal of the protrusions forms a linear member 2 in which the first member 11 and the second member are joined together.

[0038] In other words, the linear member 2 comprises a first member 11 having a first end face 11a that has been polished to have an arithmetic mean roughness of 0.1 μm or less, and a second member 12 having a second end face 12a that has been polished to have an arithmetic mean roughness of 0.1 μm or less, wherein a voltage is applied to the first member 11 and the second member 12 with more than 90% of the area of ​​the first end face 11a in contact with the second end face 12a, and the area including at least the first end face 11a and the second end face 12a is heated by electrical resistance, and the first member 11 and the second member 12 are joined by diffusion bonding.

[0039] The removal process is performed after the first member 11 is removed from the first retaining device 21 and the second member 12 is removed from the second retaining member 22. However, the removal process may be performed before the removal. The linear member 2 is, for example, a medical device and is used in intravascular treatment devices (such as guidewires).

[0040] (The effect of performing diffusion bonding between end faces that have been polished to an arithmetic mean roughness of 0.1 μm or less) Compared to a configuration in which the first end face 11a and the second end face 12a are brought into close contact without polishing, this method reduces the minute unjoined portion at the joint interface and increases the contact area between the first end face 11a and the second end face 12a. As a result, there are more diffusion paths, making it possible to easily join linear members 2 with high joint strength and high impact strength.

[0041] (The effect of forming raised areas) Compared to forms that are not compressed by pressure, current flows more easily, the temperature rises faster, and diffusion bonding is promoted.

[0042] (The effect of removing raised areas by polishing) The linear member 2 can be easily finished.

[0043] (The effects of applying ultrasonic vibrations) The first end face 11a and the second end face 12a generate heat due to friction, and the oxide film on the first end face 11a and the second end face 12a is destroyed. Therefore, the bonding strength can be improved compared to a configuration in which diffusion bonding is performed without destroying the oxide film.

[0044] (Effects of use in medical devices) The linear member 2 of this embodiment can be used in medical devices that join two conductive members, such as guide wires.

[0045] (Examples of applications of the yz cross-sectional shapes of the first member 11 and the second member) In this embodiment, the yz cross-sections of the first member 11 and the second member 12 are described as being circular, but other shapes such as elliptical shapes may also be used.

[0046] (Examples of applications of the removal process) In the removal process, the removal of raised material was described in an example where it was performed by polishing using the second polishing device 28. However, the removal of raised material in the removal process may also be performed by other processes such as cutting.

[0047] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0048] According to this specification, a method for joining linear members in the following embodiments is provided. (Aspect 1) Embodiment 1 comprises a polishing step of polishing the first end face of a first linear member and the second end face of a second linear member different from the first member to an arithmetic mean roughness of 0.1 μm or less; a bonding step of bringing the first end face and the second end face into close contact; and a pressurizing and energizing step of applying a voltage to the first member and the second member to generate heat in a region including at least the first end face and the second end face due to electrical resistance, thereby diffusing and bonding the first member and the second member, wherein the bonding step is performed such that 90% or more of the area of ​​the first end face is in contact with the second end face.

[0049] According to the above-described embodiment, compared to the embodiment in which the first end face and the second end face are brought into close contact without polishing, the minute unjoined portion at the joining interface is reduced, and the contact area between the first end face and the second end face is increased. As a result, the number of diffusion paths increases, making it possible to easily join linear members with high joining strength and high impact strength.

[0050] (Aspect 2) In embodiment 2, during the pressurized and energized process, at least a portion of the first member and the second member deforms to form a raised object.

[0051] According to the above-described embodiment, compared to a form that is not crushed by pressure, electric current flows more easily, the temperature rises more rapidly, and diffusion bonding is promoted.

[0052] (Aspect 3) Embodiment 3 further includes a removal step of removing the raised material by polishing.

[0053] According to the above-described embodiment, linear members can be easily finished.

[0054] (Aspect 4) Embodiment 4 further comprises a vibration step in which ultrasonic vibrations are applied to the first member and the second member immediately before the pressurizing and energizing step.

[0055] According to the above-described embodiment, the first and second end faces generate heat due to friction, and the oxide films on the first and second end faces are destroyed. Therefore, the bonding strength can be improved compared to an embodiment in which diffusion bonding is performed without destroying the oxide film.

[0056] (Appendix 5) In embodiment 5, the linear member formed by joining the first member and the second member is used in a medical device.

[0057] According to the above-described embodiment, the linear member of this embodiment can be used in medical devices that join two conductive members, such as guide wires.

[0058] According to this specification, linear members in the following embodiments are provided. (Aspect 6) Embodiment 6 comprises a first member having a first end face polished to have an arithmetic mean roughness of 0.1 μm or less, and a second member having a second end face polished to have an arithmetic mean roughness of 0.1 μm or less, wherein a voltage is applied to the first member and the second member while 90% or more of the area of ​​the first end face is in contact with the second end face, and at least the area including the first end face and the second end face is heated by electrical resistance, and the first member and the second member are joined by diffusion bonding.

[0059] According to the above-described embodiment, compared to the embodiment in which the first end face and the second end face are brought into close contact without polishing, the minute unjoined portion at the joining interface is reduced, and the contact area between the first end face and the second end face is increased. As a result, the number of diffusion paths increases, making it possible to easily join linear members with high joining strength and high impact strength. [Explanation of symbols]

[0060] 2 Linear members 11. First Member 11a First end surface 12 Second Member 12a Second end surface

Claims

1. A polishing step is performed on the first end face of the first linear member and the second end face of the second linear member, which is different from the first linear member, to achieve an arithmetic mean roughness of 0.1 μm or less. A bonding step of bringing the first end face and the second end face into close contact, The process includes a pressurized current application step, in which a voltage is applied to the first member and the second member to generate heat in a region including at least the first end face and the second end face due to electrical resistance, thereby diffusing the first member and the second member together. A method for joining linear members, wherein the contact process is performed such that 90% or more of the area of ​​the first end face is in contact with the second end face.

2. The joining method according to claim 1, wherein in the pressurized and energized step, at least a portion of the first member and the second member deforms to form a raised object.

3. The joining method according to claim 2, further comprising a removal step of removing the raised material by polishing.

4. The joining method according to claim 1, further comprising a vibration step of applying ultrasonic vibrations to the first member and the second member immediately before the pressurizing and energizing step.

5. The joining method according to any one of claims 1 to 4, wherein the linear member formed by joining the first member and the second member is used in medical devices.

6. A first member having a first end face that has been polished to have an arithmetic mean roughness of 0.1 μm or less, A second member having a second end face that has been polished to have an arithmetic mean roughness of 0.1 μm or less, A linear member in which, with more than 90% of the area of ​​the first end face in contact with the second end face, a voltage is applied to the first member and the second member, and at least the area including the first end face and the second end face is heated by electrical resistance, and the first member and the second member are joined by diffusion bonding.

Images