solid-phase bonding method

Abstract

The objective is to provide a technology that can stabilize the bonding results when performing solid-state bonding. [Solution] A solid-state bonding method using a solid-state bonding apparatus comprising a pair of pressurizing shafts for pressing multiple conductive workpieces that overlap in the thickness direction from both sides in the thickness direction, and a pair of electrodes arranged around the pair of pressurizing shafts, wherein the multiple workpieces include a first workpiece having a through hole extending through in the thickness direction and a second workpiece covering the through hole, and the method comprises the steps of pressing the first workpiece and the second workpiece with the pair of pressurizing shafts to create a projection on the second workpiece that contacts the peripheral edge of the through hole in the first workpiece (steps S3, S4), and pressing the first workpiece and the second workpiece with the pair of pressurizing shafts while applying current from the pair of electrodes so that current flows through the region where the peripheral edge of the through hole and the projection are in contact in the first workpiece and the second workpiece, thereby bonding the first workpiece and the second workpiece (steps S5, S6).

Description

Technical Field

[0001] The present disclosure relates to a solid-phase bonding method.

Background Art

[0002] Japanese Patent No. 7242112 (Patent Document 1) discloses a solid-phase point bonding apparatus including a pressurizing mechanism including a pressing part and an energizing mechanism including a pair of welding electrodes. In the solid-phase point bonding apparatus disclosed in Patent Document 1, a solid-phase bonding method is performed in which a constant current is passed from the electrodes to the bonding region of the workpiece to be bonded to soften the bonding region and the workpiece is pressed by the pressing part to bond the workpiece.

[0003] In such a solid-phase bonding method, plastic flow occurs in the workpiece due to the pressing pressure by the pressurizing mechanism. The plastic flow occurring in the workpiece can change in its flow state depending on factors that greatly affect the flow state of the plastic flow, such as, for example, the material of the workpiece and the size of the gap between the workpieces.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional solid-phase bonding method, when performing solid-phase bonding, it has been impossible to suppress the change in the flow state when the workpiece undergoes plastic flow. Therefore, there has been a problem in the conventional solid-phase bonding method that the flow state of the plastic flow of the workpiece does not become constant, and a stable bonding result may not be obtained.

[0006] An object of the present disclosure is to provide a technique capable of stabilizing the bonding result in the case of performing solid-phase bonding.

Means for Solving the Problems

[0007] The solid-state joining method of this disclosure is a solid-state joining method using a solid-state joining apparatus comprising a pair of pressurizing shafts for pressing a plurality of conductive workpieces that overlap in the thickness direction from both sides in the thickness direction, and a pair of electrodes arranged around the pair of pressurizing shafts, wherein the plurality of workpieces include a first workpiece having a through hole extending through in the thickness direction and a second workpiece covering the through hole, and comprises the steps of pressing the first workpiece and the second workpiece with the pair of pressurizing shafts to create a projection on the second workpiece that contacts the peripheral edge of the through hole in the first workpiece, and pressing the first workpiece and the second workpiece with the pair of pressurizing shafts while flowing an electric current from the pair of electrodes so that an electric current flows through the region where the peripheral edge of the through hole and the projection are in contact in the first workpiece and the second workpiece, thereby joining the first workpiece and the second workpiece. [Effects of the Invention]

[0008] According to this disclosure, the first and second workpieces are joined by applying current from a pair of electrodes to the first and second workpieces through a region where the periphery of a through-hole in the first workpiece and a projection made on the second workpiece are in contact, while pressing the first and second workpieces with a pair of pressure shafts. In this way, since the periphery of the through-hole in the first workpiece and the projection in the second workpiece are in contact, the current flowing from the pair of electrodes is concentrated near the region where the periphery of the through-hole and the projection are in contact. This concentration of current near the region where the periphery of the through-hole and the projection are in contact makes it easier for plastic flow of the material to occur at the periphery of the through-hole in the first workpiece and at the projection in the second workpiece. When plastic flow occurs near the region where the periphery of the through-hole and the projection are in contact, the material undergoing plastic flow is more likely to flow into the space of the through-hole than in other regions. Therefore, when solid-state joining the first and second workpieces, the main direction of flow when plastic flow occurs may be towards the through-hole. This allows for a constant flow state when plastic flow occurs, thereby stabilizing the bonding results when performing solid-state bonding. [Brief explanation of the drawing]

[0009] [Figure 1] This figure schematically shows a solid-phase bonding system that performs the solid-phase bonding method according to the embodiment. [Figure 2] This is a schematic diagram of a solid-phase bonding apparatus. [Figure 3] This diagram shows the state changes of the first and second workpieces during solid-state bonding. [Figure 4] This figure shows a magnified view of a portion of the state of the first and second workpieces shown in Figure 3. [Figure 5] This flowchart shows the flow of a solid-state bonding method according to other embodiments. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] <Description of the configuration of the solid-phase bonding system 100> Figure 1 is a schematic diagram showing a solid-phase bonding system 100 that performs the solid-phase bonding method according to an embodiment. The solid-phase bonding system 100 comprises a robot 200, solid-phase bonding equipment 10, a control device 30, and a power supply device 35. Note that the robot 200 is depicted smaller than its actual size relative to the solid-phase bonding equipment 10.

[0012] The robot 200 includes a robot arm 210. The robot arm 210 is a multi-jointed arm, for example, a 6-axis multi-jointed arm. The robot arm 210 is controlled by the control device 30 to perform a set motion. However, the robot arm 210 may be controlled by another control device that controls the robot 200, rather than the control device 30.

[0013] The solid-phase bonding device 10 includes a drive unit 13, a C-gun 14, and a pair of electrodes 21 and 22. The solid-phase bonding device 10 also includes a pair of pressure shafts 11 and 12 as shown in Figure 2. The solid-phase bonding device 10 is mounted on the tip of a robot arm 210.

[0014] The drive unit 13 is controlled by the control unit 30. Voltage and current are supplied to the pair of electrodes 21 and 22 from the power supply unit 35. The C gun 14 is movable to a position that clamps the first workpiece W10 and the second workpiece W20, which are fixed to the jig 15, in the thickness direction. The control unit 30 operates the robot arm 210 by controlling a servo motor (not shown) so that the pair of electrodes 21 and 22 and the pair of pressurizing shafts 11 and 12 move to the positions of the first workpiece W10 and the second workpiece W20.

[0015] <Explanation of the configuration of the solid-phase bonding apparatus 1> Figure 2 is a schematic diagram showing a solid-phase bonding apparatus 1 that performs the solid-phase bonding method according to the embodiment. The solid-phase bonding apparatus 1 is a device that forms a soft region as a bonding region at the interface of multiple workpieces W10 and W20 that are stacked on top of each other by applying an electric current to the multiple workpieces W10 and W20, and then plastically deforms the soft region to bond the multiple workpieces W10 and W20 together in a solid state without melting them.

[0016] Multiple workpieces W10, W20 include a first workpiece W10 and a second workpiece W20. Each workpiece W10, W20 is made of a metal such as iron or aluminum. For example, each workpiece W10, W20 is formed in the shape of a flat plate. Multiple workpieces W10, W20 are stacked in the thickness direction. In this embodiment, the first workpiece W10 and the second workpiece W20 are made of the same material. Note that each workpiece W10, W20 may be made of a material other than metal, as long as it is conductive and suitable for solid-state bonding.

[0017] As shown in FIG. 2, the solid-phase bonding apparatus 1 includes a solid-phase bonding device 10, a control device 30, a power supply device 35, a driving device 13, and an input device 5. The solid-phase bonding device 10 includes a pair of pressure shafts 11, 12, a pair of electrodes 21, 22, and a pressure sensor 40.

[0018] In addition to the solid-phase bonding device 10, the control device 30, the power supply device 35, the driving device 13, and the input device 5, the solid-phase bonding apparatus 1 may include the jig 15 shown in FIG. 1. Further, the solid-phase bonding apparatus 1 may further include a robot 200.

[0019] The pair of pressure shafts 11, 12 includes a first pressure shaft 11 and a second pressure shaft 12. The pair of pressure shafts 11, 12 can apply pressure from both sides in the thickness direction in which the plate-like first workpiece W10 and the second workpiece W20 are stacked. The first pressure shaft 11 is driven by the driving device 13. The second pressure shaft 12 is fixed. Specifically, the first pressure shaft 11 is movably arranged at one end of the C-gun 14 shown in FIG. 1 and is driven by the driving device 13. The second pressure shaft 12 is fixed to the other end of the C-gun 14 shown in FIG. 1. With such a configuration, the first pressure shaft 11 is movable relative to the second pressure shaft 12.

[0020] The first pressure shaft 11 can press the first workpiece W10 so that the first workpiece W10 is plastically deformed. The first pressure shaft 11 is made of, for example, tungsten carbide. In the present embodiment, the first pressure shaft 11 is formed in an elongated columnar shape. The first pressure shaft 11 has a pressing surface 11a for pressing the first workpiece W10. The pressing surface 11a is an end surface of the first pressure shaft 11. The pressing surface 11a is formed in a circular shape.

[0021] The second pressure shaft 12 has the same configuration as that of the first pressure shaft 11. The second pressure shaft 12 is arranged such that the central axis of the second pressure shaft 12 is located on the extension line of the central axis of the first pressure shaft 11, and the pressing surface 12a of the second pressure shaft 12 faces the pressing surface 11a of the first pressure shaft 11. Note that the first pressure shaft 11 and the second pressure shaft 12 may have a shape other than a columnar shape.

[0022] In the first workpiece W10, a through hole 50 penetrating in the thickness direction of the first workpiece W10 is provided in a region where the pressing surface 11a of the pressing shaft 11 contacts. The through hole 50 is a circular hole, and its diameter is smaller than the diameter of the pressing surface 11a of the pressing shaft 11.

[0023] The pressing shaft 11 contacts the first workpiece W10 such that the center position of the pressing surface 11a coincides with the center position of the through hole 50. Thereby, the pressing shaft 11 contacts the first workpiece W10 in a state where the pressing surface 11a covers one end side of the through hole 50 of the first workpiece W10.

[0024] The second workpiece W20 is not provided with a hole such as the through hole 50. When the first workpiece W10 and the second workpiece W20 are overlapped, the second workpiece W20 faces the first workpiece W10 so as to cover the through hole 50 of the first workpiece W10. Thereby, when the first workpiece W10 and the second workpiece W20 are overlapped, the other end side of the through hole 50 is covered by the second workpiece W20.

[0025] In FIG. 2, as will be described later, due to the pressing force of the first workpiece W10 by the pressing shaft 11 and the pressing force of the second workpiece W20 by the pressing shaft 12, a protrusion 60 is formed on the second workpiece W20, and a state where a part of the protrusion 60 enters the inside of the through hole 50 is shown. In the state shown in FIG. 2, the peripheral portion 51 of the through hole 50 in the first workpiece W10 and the protrusion 60 of the second workpiece W20 are in contact.

[0026] The pressure sensor 40 is provided, for example, on the first pressing shaft 11. In the present embodiment, a load cell is used as the pressure sensor 40. Note that the installation location of the pressure sensor 40 is not limited to the first pressing shaft 11, and it may be provided in the drive device 13 or the like.

[0027] The pair of electrodes 21, 22 includes a first electrode 21 and a second electrode 22. The pair of electrodes 21, 22 can energize the first workpiece W10 and the second workpiece W20 while in contact with them. Power is supplied to the first electrode 21, the first workpiece W10, the second workpiece W20, and the second electrode 22 by applying a voltage to the pair of electrodes 21, 22 while they are in contact with the first workpiece W10 and the second workpiece W20.

[0028] The first electrode 21 is capable of contacting the portion of the first workpiece W10 that is pressurized by the first pressurizing shaft 11. In this embodiment, the first electrode 21 is formed in a cylindrical shape that surrounds the first pressurizing shaft 11. A gap is provided between the inner circumferential surface of the first electrode 21 and the outer circumferential surface of the first pressurizing shaft 11. The first electrode 21 is made of, for example, copper. The first electrode 21 has a contact surface 21a that contacts the first workpiece W10. The contact surface 21a is formed in an annular shape. However, the shape of the contact surface 21a is not limited to an annular shape.

[0029] The second electrode 22 has the same configuration as the first electrode 21. The second electrode 22 is capable of contacting the area surrounding the part of the second workpiece W20 that is pressurized by the second pressurizing shaft 12. The second electrode 22 is positioned such that its central axis lies on the extension of the central axis of the first electrode 21, and its contact surface 22a faces the contact surface 21a of the first electrode 21.

[0030] The control device 30 comprises an arithmetic unit 31, a memory 32, a storage device 33, and an input / output interface 34. These components are connected via a bus.

[0031] The arithmetic unit 31 is a computing entity (computer) that performs predetermined processing. The arithmetic unit 31 is composed of a processor such as a CPU (Central Processing Unit), MPU (Micro-Processing Unit), TPU (Tensor Processing Unit), or GPU (Graphics Processing Unit). While a processor, as an example of the arithmetic unit 31, has the function of performing predetermined processing by executing a predetermined program, some or all of these functions may be implemented using dedicated hardware circuits such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array). The term "processor" is not limited to processors in the narrow sense that execute processing using a stored-program method, such as a CPU, MPU, TPU, or GPU, but may also include hardwired circuits such as ASICs or FPGAs. Furthermore, the arithmetic unit 31 is not limited to von Neumann type computers such as CPUs or GPUs, but may also consist of non-von Neumann type computers such as quantum computers or optical computers. The arithmetic unit 31 described above can also be read as a processing circuitry that performs predetermined processing. The arithmetic unit 31 may consist of one chip or multiple chips. Furthermore, the processor and associated processing circuits may consist of multiple computers interconnected by wired or wireless connections via a local area network or wireless network. The processor and associated processing circuits may also consist of a cloud computer that remotely performs calculations based on input data and outputs the calculation results to other devices located at a distance.

[0032] The memory 32 includes a storage area (for example, a working area) for storing program code or work memory when the arithmetic unit 31 executes various programs. Examples of memory 32 include volatile memory such as DRAM and SRAM, or non-volatile memory such as ROM and flash memory.

[0033] The storage device 33 stores various programs or data executed by the arithmetic unit 31. For example, the storage device 33 stores control programs 330 that control various devices executed by the arithmetic unit 31. The storage device 33 may be one or more non-transitory computer-readable media or one or more computer-readable storage media. Examples of storage devices 33 include HDDs (Hard Disk Drives) and SSDs (Solid State Drives).

[0034] The input / output interface 34 receives data detected by sensors, such as the pressure sensor 40. The control device 30 is connected to an input device 5. The input device 5 consists of one or more devices capable of inputting data, such as a keyboard, mouse, and touch panel. The data input from the input device can be input to the arithmetic unit 31 and memory 32 via the input / output interface 34.

[0035] The control device 30 controls the stroke of the first pressurizing shaft 11 by controlling the drive device 13. The control device 30 controls the current supplied to the pair of electrodes 21 and 22 by controlling the power supply device 35. Specifically, the control device 30 controls the load acting on the first workpiece W10 and the second workpiece W20 from each of the pair of pressurizing shafts 11 and 12 by controlling the drive device 13 to move the first pressurizing shaft 11 toward the first workpiece W10, the load acting on the first workpiece W10 and the second workpiece W20 from each of the pair of electrodes 21 and 22, and the amount of indentation of the pair of pressurizing shafts 11 and 12 and the pair of electrodes 21 and 22. Furthermore, the control device 30 controls the current X supplied to the pair of electrodes 21 and 22 by controlling the power supply device 35.

[0036] The control device 30 controls the drive device 13 so that a load F is applied to the first workpiece W10 and the second workpiece W20 from a pair of pressurizing shafts 11 and 12. As a result, a projection 60, as shown in Figure 2, is formed on the second workpiece W20.

[0037] The control device 30 then controls the power supply device 35 so that, in addition to applying pressure (pressure) to the first workpiece W10 and the second workpiece W20 by the pressure shafts 11 and 12, a pair of electrodes 21 and 22 energize the first workpiece W10 and the second workpiece W20. As a result, a current X flows through the first workpiece W10 and the second workpiece W20, as shown by the dashed line in Figure 2. Specifically, the control device 30 controls the power supply device 35 so that a current X flows through the first workpiece W10 and the second workpiece W20, with the contact surface 21a of the first electrode 21 in contact with the area surrounding the part of the first workpiece W10 that is pressed by the first pressure shaft 11, and the contact surface 22a of the second electrode 22 in contact with the area surrounding the part of the second workpiece W20 that is pressed by the second pressure shaft 12.

[0038] The first workpiece W10 and the second workpiece W20 are electrically connected because the peripheral edge of the through hole 50 in the first workpiece W10 is in contact with the projection 60 of the second workpiece W20. Therefore, current X flows between the first electrode 21 and the second electrode 22 through the contact portion between the peripheral edge of the through hole 50 and the projection 60 to the first workpiece W10 and the second workpiece W20.

[0039] In this embodiment, as shown in Figure 2, in the first workpiece W10 and the second workpiece W20, a current is passed through the contact area between the peripheral edge of the through hole 50 and the projection 60 using a pair of electrodes 21 and 22, while the first workpiece W10 and the second workpiece W20 are pressed together using a pair of pressurizing shafts 11 and 12. Specifically, the first pressurizing shaft 11 presses the peripheral edge of the through hole 50 in the first workpiece W10, and the second pressurizing shaft 12 presses the first region covering the through hole 50 and the second region which is the peripheral region of the first region in the second workpiece W20. As a result, plastic flow occurs in the first workpiece W10 and the second workpiece W20, flowing toward the space of the through hole 50, and the first workpiece W10 and the second workpiece W20 are joined together in the region pressed by the pair of pressurizing shafts 11 and 12.

[0040] <Explanation of the state changes of the first workpiece W10 and the second workpiece W20 during solid-state bonding> In the following, the state changes of the first workpiece W10 and the second workpiece W20 during solid-phase bonding will be explained using Figures 3 and 4.

[0041] Figure 3 shows the state changes of the first workpiece W10 and the second workpiece W20 during solid-phase bonding. Figures 3(A) to 3(D) show the process by which the state of the first workpiece W10 and the second workpiece W20 changes during solid-phase bonding.

[0042] Figure 4 is a magnified view of a portion of the state of the first workpiece W10 and the second workpiece W20 shown in Figure 3. Figure 4(A) shows a magnified view of the first workpiece W10 and the second workpiece W20 in the state shown in Figure 3(A). Figure 4(B) shows a magnified view of the first workpiece W10 and the second workpiece W20 in the state shown in Figure 3(C). Figure 4(C) shows a magnified view of the first workpiece W10 and the second workpiece W20 in the states shown in Figures 3(C) and 3(D).

[0043] Before solid-state bonding begins, as shown in Figure 3(A), the plate-shaped first workpiece W10 and the plate-shaped second workpiece W20 are arranged so that they overlap in the thickness direction. Specifically, as shown in Figure 4(A), the first workpiece W10 is positioned so that the first press shaft 11 can press the peripheral edge 51 of the through hole 50 from above. As shown in Figure 4(A), the second workpiece W20 is positioned so that the central axis of the second press shaft 12 lies on the extension of the central axis of the first press shaft 11, and so that it can press the first region 91 covering the through hole 50 and the second region 92 at the periphery of the first region 91.

[0044] In the stage before solid-state bonding begins, as shown in Figure 3(A), the plate-shaped first workpiece W10 and the plate-shaped second workpiece W20 are arranged so that they overlap in the thickness direction.

[0045] Specifically, as shown in Figure 4(A), the first workpiece W10 is positioned so that the first pressurizing shaft 11 can press the peripheral edge 51 of the through hole 50 from above. As shown in Figure 4(A), the second workpiece W20 is positioned so that the central axis of the second pressurizing shaft 12 lies on the extension of the central axis of the first pressurizing shaft 11, and so that it can press the first region 91 covering the through hole 50 and the second region 92 at the periphery of the first region 91.

[0046] As shown in Figure 4(A), the first pressurizing shaft 11 has a pressing surface 11a that abuts against the peripheral edge 51 of the through hole 50 in the first workpiece W10. As shown in Figure 4(A), the second pressurizing shaft 12 has a pressing surface 12a that abuts against the first region 91 and the second region 92 in the second workpiece W20.

[0047] Next, from the state shown in Figure 3(A), as the first press shaft 11 presses the first workpiece W10 and the second press shaft 12 presses the second workpiece W20, as shown in Figure 3(B), a projection 60 is created in the second workpiece W20 that protrudes into the through hole 50 of the first workpiece W10 due to the pressing force of the second press shaft 12.

[0048] Specifically, when the second workpiece W20 is pressed by the second pressurizing shaft 12, the second region 92 shown in Figure 4(A) is in contact with the first workpiece W10 and therefore receives a resistive force from the first workpiece W10, but the first region 91 shown in Figure 4(B) is not in contact with the first workpiece W10 and therefore does not receive a resistive force from the first workpiece W10. As a result, as shown in Figure 4(B), the pressing force of the second pressurizing shaft 12 causes the portion of the second workpiece W20 corresponding to the first region 91 to protrude into the internal space of the through hole 50, forming a projection 60 that contacts the peripheral edge 51 of the through hole 50 of the first workpiece W10.

[0049] As shown in Figure 4(B), the projection 60 of the second workpiece W20 is created in a shape in which the outer wall of the projection 60 comes into contact with the inner wall of the peripheral edge 51 of the through hole 50 of the first workpiece W10.

[0050] Next, as shown in Figure 3(C), the first workpiece W10 and the second workpiece W20 are pressed with a pair of pressurizing shafts 11 and 12 while a current X is applied from a pair of electrodes 21 and 22 so that the current X flows through the region where the peripheral edge 51 of the through hole 50 and the projection 60 are in contact. Specifically, in the first workpiece W10 and the second workpiece W20, as shown in Figure 4(B), the current X flows through the region where the peripheral edge 51 of the through hole 50 and the projection 60 are in contact. In Figures 3 and 4, the current X is shown by a dashed line.

[0051] As shown in Figure 3(C), when a current X is applied to the first workpiece W10 and the second workpiece W20 from a pair of electrodes 21 and 22, and the first workpiece W10 and the second workpiece W20 are pressed with a pair of pressurizing shafts 11 and 12, the first workpiece W10 and the second workpiece W20 undergo plastic deformation. When such plastic deformation occurs in the first workpiece W10 and the second workpiece W20, plastic flow occurs. This plastic flow is a phenomenon in which the material constituting the first workpiece W10 undergoes plastic deformation, and the material constituting the second workpiece W20 undergoes plastic deformation, causing these materials to flow as a fluid.

[0052] By passing an electric current through the region where the peripheral edge 51 of the through-hole 50 in the first workpiece W10 and the projection 60 made on the second workpiece W20 come into contact, the current flowing from the pair of electrodes 21 and 22 concentrates in the vicinity of the region where the peripheral edge 51 of the through-hole 50 and the projection 60 come into contact. This concentration of current in the vicinity of the region where the peripheral edge 51 of the through-hole 50 and the projection 60 come into contact makes it easier for plastic flow of the material to occur in the peripheral edge 51 of the through-hole 50 in the first workpiece W10 and in the projection 60 of the second workpiece W20.

[0053] As shown in Figure 3(C), when a through hole 50 is provided in the first workpiece W10, in both the first workpiece W10 and the second workpiece W20, the direction in which the fluid of the plastically deformed material flows is toward the through hole 50, which offers the least resistance to fluid flow compared to other directions. This is because the space of the through hole 50 does not obstruct the flow of the plastically flowing fluid. Therefore, in both the first workpiece W10 and the second workpiece W20, the direction in which the plastically flowing fluid flows most easily is toward the through hole 50. Consequently, when plastic flow occurs near the region where the peripheral edge 51 of the through hole 50 and the projection 60 are in contact, the space of the through hole 50 is more easily filled with the plastically flowing material than other regions.

[0054] For the reasons explained above, when plastic flow occurs in the first workpiece W10 and the second workpiece W20, the plastically flowing fluid flows from the first workpiece W10 and the second workpiece W20 towards the through hole 50, as shown in Figures 3(D) and 4(C). As a result, when solid-state joining the first workpiece W10 and the second workpiece W20, the flow state when plastic flow occurs can be kept constant, thereby stabilizing the joining result when solid-state joining is performed.

[0055] As shown in Figure 3(D), when a plastically flowing fluid flows from the first workpiece W10 and the second workpiece W20 into the through hole 50, a joint surface 90 is formed between the first workpiece W10 and the second workpiece W20, as shown in Figure 4(C). Specifically, as shown in Figure 4(C), the joint surface 90 is formed at the contact point between the peripheral edge 51 of the through hole 50 in the first workpiece W10 and the projection 60 in the second workpiece W20.

[0056] Figure 4(C) shows the state in which the first workpiece W10 and the second workpiece W20 are pressed by a pair of pressurizing shafts 11 and 12, but the pair of pressurizing shafts 11 and 12 are omitted from the illustration to simplify the explanation of the flow of the plastically flowing fluid. Figure 4(C) shows the state in which current X is flowing through the first workpiece W10 and the second workpiece W20, but the current X is omitted from the illustration to simplify the explanation of the flow of the plastically flowing fluid.

[0057] As shown in Figure 4(C), in the first workpiece W10 and the second workpiece W20, where a joint surface 90 is formed, the direction in which the plastically flowing fluid flows most easily is toward the through hole 50, as described above. Therefore, as shown in Figure 4(C), in the first workpiece W10 and the second workpiece W20, the plastically flowing fluid flows from the peripheral portion 51 and projection 60 of the through hole 50, centered on the first joint portion 70 of the first workpiece W10 and the second joint portion 80 of the second workpiece W20 that protrude into the through hole 50, toward the through hole 50 as indicated by the white arrows. As a result, the through hole 50 is filled by the plastically flowing fluid as shown in Figure 3(D). Finally, the first workpiece W10 and the second workpiece W20 are joined in the state shown in Figure 3(E).

[0058] Furthermore, as shown in Figures 3(B) and 4(B), if the projection 60 is provided such that the inner wall of the peripheral edge 51 of the through hole 50 in the first workpiece W10 contacts the outer wall of the projection 60 in the second workpiece W20, then, as shown in Figure 4(C), the contact area between the peripheral edge 51 of the through hole 50 in the first workpiece W10 and the outer wall of the projection 60 in the second workpiece W20 becomes a joint surface 90. By forming a joint surface 90 in such a portion, the contact positions of the first workpiece W10 and the second workpiece W20 can be prevented from shifting during solid-state bonding, and the joint positions of the first workpiece W10 and the second workpiece W20 can be prevented from shifting.

[0059] With this type of solid-state bonding method, even if there are factors that easily affect the flow state of plastic flow, such as the material of the workpiece and the size of the gap between the workpieces, the bonding results in solid-state bonding can be stabilized.

[0060] <Explanation of the flow of the solid-state bonding method according to the embodiment> Next, the flow of the solid-state bonding method according to the embodiment will be described. Figure 5 is a flowchart showing the flow of the solid-state bonding method according to the embodiment.

[0061] In the solid-state bonding method according to this embodiment, in step S1, as shown in Figure 1, in the solid-state bonding system 100, a first workpiece W10 having a through hole 50 and a second workpiece W20 covering the through hole 50 are stacked in the thickness direction and fixed with a jig 15.

[0062] In step S2, the control device 30 controls the robot arm 210 to operate so that the first pressurizing shaft 11 can press the peripheral edge 51 of the through hole 50, and the second pressurizing shaft 12 can press the first region 91 covering the through hole 50 and the second region 92 on the periphery of the first region 91, thereby arranging the pair of pressurizing shafts 11, 12 and the pair of electrodes 21, 22 as shown in Figures 3(A) and 4(A).

[0063] In step S3, the control device 30 controls the drive device 13 to start the operation of the pair of pressurizing shafts 11 and 12, so that pressing by the pair of pressurizing shafts 11 and 12 is started on the first workpiece W10 and the second workpiece W20, as shown in Figure 3(B).

[0064] In step S4, the pressing by the pair of pressure shafts 11 and 12 that started in step S3 creates a projection 60 on the second workpiece W20 that contacts the peripheral edge 51 of the through hole 50 of the first workpiece W10, as shown in Figure 3(B).

[0065] In step S5, the control device 30 controls the power supply device 35 to start supplying power to the pair of electrodes 21 and 22, in addition to controlling the operation of the pair of pressurizing shafts 11 and 12, so that, as shown in Figures 3(B) and 4(B), the first workpiece W10 and the second workpiece W20 are subjected to pressure by the pair of pressurizing shafts 11 and 12, and current is supplied by the pair of electrodes 21 and 22.

[0066] In step S6, the pressing and energizing of the first workpiece W10 and the second workpiece W20 in step S5 generates a plastic flow in the first workpiece W10 and the second workpiece W20 that flows toward the through hole 50, as shown in Figures 3(D) and 4(C), and joins the first workpiece W10 and the second workpiece W20, as shown in Figure 3(E).

[0067] <Explanation of variations> (1) The solid-state bonding method according to the embodiment described above may include the step of providing a through hole 50 in the first workpiece W10. Below, a first modified example of the solid-state bonding method that includes the step of providing a through hole 50 in the first workpiece W10 will be described. In the first modified example, in addition to the solid-state bonding method according to the embodiment described above, a through hole 50 is provided in the first workpiece W10 by step S0, which is shown by the dashed line in Figure 5. Specifically, in order to realize step S0, it is necessary to provide a cutting machine capable of forming a through hole 50 in the first workpiece W10 in the solid-state bonding apparatus 1 or solid-state bonding system 100.

[0068] In the solid-state bonding method according to the first modified example, a control configuration is required in which the control device 30 controls the operation of the cutting machine. In such a configuration, for example, the first workpiece W10, which does not have a through hole 50 formed therein, is fixed to the jig 15, and in step S0, the control device 30 executes a control to operate the cutting machine, and the first workpiece W10 is cut by the cutting machine to form a through hole 50, thereby providing the first workpiece W10 with a through hole 50.

[0069] In the solid-state bonding method according to the first modified example, after providing a through hole 50 in the first workpiece W10 in step S0, steps S1 to S6 in Figure 5 are performed to obtain the same effects as those obtained in the solid-state bonding method according to the above embodiment.

[0070] (2) Next, a solid-state bonding method according to a second modification will be described. In the solid-state bonding method according to the second modification, when creating the projection 60 described in step S4 of Figure 5 on the second workpiece W20, in addition to pressing the first workpiece W10 and the second workpiece W20 with a pair of pressure shafts 11 and 12, a current X may be passed through the first workpiece W10 and the second workpiece W20 using a pair of electrodes 21 and 22.

[0071] (3) Next, a solid-state bonding method according to a third modified example will be described. In the solid-state bonding method according to the third modified example, both the first pressure shaft 11 and the second pressure shaft 12 may be driven by the drive device 13.

[0072] (4) Next, a solid-state bonding method according to the fourth modified example will be described. In the solid-state bonding method according to the fourth modified example, the first workpiece W10 and the second workpiece W20 may be made of different materials.

[0073] (5) Next, a solid-state joining method according to a fifth modification will be described. In the solid-state joining method according to the fifth modification, when solid-state joining is performed by stacking three or more workpieces, through holes 50 may be created in one or more workpieces, and the other workpieces may be stacked so that they cover the through holes 50, and solid-state joining may be performed as in the above-described embodiment. For example, when solid-state joining is performed by stacking three or more workpieces, a through hole such as the through hole 50 is created in the first workpiece, and the first workpiece, second workpiece, and third workpiece are stacked so that the first workpiece is sandwiched between the second and third workpieces on both sides, the first and second sides. Then, the second and third workpieces are pressed from both sides of the first workpiece by a pair of pressure shafts 11 and 12 to form protrusions such as the projection 60 on both the second and third workpieces so as to contact the through hole of the first workpiece. Subsequently, while applying current X to the first, second, and third workpieces using a pair of electrodes 21 and 22, the first, second, and third workpieces are pressed by a pair of pressurizing shafts 11 and 12, generating plastic flow from the first, second, and third workpieces toward the through-hole, thereby solid-state bonding the first, second, and third workpieces.

[0074] (6) Next, a solid-state bonding method according to the sixth modified example will be described. In the solid-state bonding method according to the sixth modified example, the through-hole 50 may be composed of polygonal holes such as triangles and squares.

[0075] <Description of the effects of the embodiment> The embodiments described above can be obtained to achieve the following effects.

[0076] (1) As shown in Figures 2 to 5, the solid-state joining method of the embodiment includes steps S3 and S4, in which a pair of pressurizing shafts 11 and 12 are used to press the first workpiece W10 and the second workpiece W20, which cover the through hole 50, and a projection 60 is created on the second workpiece W20 that contacts the peripheral edge 51 of the through hole 50 in the first workpiece W10. Then, as shown in Figures 2 to 5, the solid-state joining method of the embodiment includes steps S5 and S6, in which a pair of pressurizing shafts 11 and 12 are used to press the first workpiece W10 and the second workpiece W20, while a current X is applied from a pair of electrodes 21 and 22 so that a current X flows through the region where the peripheral edge 51 of the through hole 50 and the projection 60 are in contact, thereby joining the first workpiece W10 and the second workpiece W20. As a result, the pair of electrodes 21 and 22 apply current to the first workpiece W10 and the second workpiece W20 through the region where the peripheral edge 51 of the through hole 50 in the first workpiece W10 and the projection 60 made on the second workpiece W20 are in contact, and the pair of pressure shafts 11 and 12 press the first workpiece W10 and the second workpiece W20, thereby joining the first workpiece W10 and the second workpiece W20. In this way, since the peripheral edge 51 of the through hole 50 in the first workpiece W10 and the projection 60 in the second workpiece W20 are in contact, the current flowing from the pair of electrodes 21 and 22 is concentrated in the vicinity of the region where the peripheral edge 51 of the through hole 50 and the projection 60 are in contact. When current concentrates near the area where the peripheral edge 51 of the through hole 50 and the projection 60 come into contact, plastic flow of the material is more likely to occur in the peripheral edge 51 of the through hole 50 of the first workpiece W10 and in the projection 60 of the second workpiece W20. When plastic flow occurs near the area where the peripheral edge 51 of the through hole 50 and the projection 60 come into contact, the space of the through hole 50 is more easily filled with the material undergoing plastic flow than other areas. Therefore, when solid-state bonding the first workpiece W10 and the second workpiece W20, the main direction of flow when plastic flow occurs may be towards the through hole 50. This makes it possible to stabilize the flow state when plastic flow occurs, thereby stabilizing the bonding results when solid-state bonding is performed.

[0077] (2) In the solid-state joining method of the embodiment, as shown in Figures 3 to 5, in steps S5 and S6 in which the first workpiece W10 and the second workpiece W20 are joined, a plastic flow is generated such that the material of the first workpiece W10 and the material of the second workpiece W20 flow toward the through hole 50. As a result, a plastic flow is generated such that the material of the first workpiece W10 and the material of the second workpiece W20 flow toward the through hole 50, so that the flow state when plastic flow occurs can be kept constant.

[0078] (3) In the solid-state bonding method of the embodiment, as shown in Figures 3 to 5, in steps S3 and S4 in which a projection 60 is created on the second workpiece W20, the projection 60 is made in such a shape that the outer wall of the projection 60 comes into contact with the inner wall of the peripheral edge 51 of the through hole 50 in the first workpiece W10. As a result, current can be passed from the pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20 through the contact portion between the inner wall of the peripheral edge 51 of the through hole 50 and the outer wall of the projection 60.

[0079] (4) In the solid-state joining method of the embodiment, as shown in Figures 3 to 5, in steps S3 and S4 in which a projection 60 is made on the second workpiece W20, and in steps S5 and S6 in which the first workpiece W10 and the second workpiece W20 are joined, the first press shaft 11 presses the peripheral edge 51 of the through hole 50, and the second press shaft 12 presses the first region 91 covering the through hole 50 and the second region 92 on the periphery of the first region 91. As a result, a projection 60 can be easily made on the second workpiece W20, and a plastic flow that flows in the direction toward the through hole 50 can be easily generated.

[0080] (5) In the solid-state bonding method of the embodiment, as shown in Figures 3 and 4, the through hole 50 has a volume such that when the material of the first workpiece W10 and the material of the second workpiece W20 undergo plastic flow toward the through hole 50, the through hole 50 can be filled with the plastically flowed material, so the through hole 50 can appropriately receive the plastically flowed material.

[0081] <Summary> (1) The solid-phase bonding method of the present disclosure is a solid-phase bonding method using a solid-phase bonding apparatus (solid-phase bonding apparatus 1) comprising a pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12) that press a plurality of conductive workpieces (first workpiece W10, second workpiece W20) overlapping in the thickness direction from both sides in the thickness direction, and a pair of electrodes (first electrode 21, second electrode 22) respectively arranged around the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12), wherein the plurality of workpieces (first workpiece W10, second workpiece W20) include a first workpiece (first workpiece W10) having a through hole (through hole 50) that penetrates in the thickness direction, and a second workpiece (second workpiece W20) that covers the through hole (through hole 50), and the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) are pressed by the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12), and Steps (S3, S4) are made on the second workpiece (second workpiece W20) to create a projection (projection 60) that contacts the peripheral edge (peripheral edge 51) of the through hole (through hole 50) in the first workpiece (first workpiece W10), and through the region in the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) where the peripheral edge (peripheral edge 51) of the through hole (through hole 50) and the projection (projection 60) are in contact. The method includes steps (S5, S6) of joining the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) by applying current (current X) from the pair of electrodes (first electrode 21, second electrode 22) so that current (current X) flows, while pressing the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) with the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12).

[0082] With this configuration, the first and second workpieces are joined by applying pressure with a pair of pressure shafts while a current is passed from a pair of electrodes through the region where the periphery of the through-hole in the first workpiece and the projection created in the second workpiece are in contact. In this way, since the periphery of the through-hole in the first workpiece and the projection in the second workpiece are in contact, the current flowing from the pair of electrodes is concentrated near the region where the periphery of the through-hole and the projection are in contact. This concentration of current near the region where the periphery of the through-hole and the projection are in contact makes it easier for plastic flow of the material to occur at the periphery of the through-hole in the first workpiece and at the projection in the second workpiece. When plastic flow occurs near the region where the periphery of the through-hole and the projection are in contact, the material undergoing plastic flow is more likely to flow into the space of the through-hole than in other regions. Therefore, when solid-state joining the first and second workpieces, the main direction of flow when plastic flow occurs may be towards the through-hole. This allows for a constant flow state when plastic flow occurs, thereby stabilizing the bonding results when performing solid-state bonding.

[0083] (2) In the solid-state joining method of (1) above, in the step (steps S5, S6) of joining the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20), a plastic flow is generated such that the material of the first workpiece (first workpiece W10) and the material of the second workpiece (second workpiece W20) flow toward the through hole (through hole 50).

[0084] With this configuration, in the step of joining the first workpiece and the second workpiece, plastic flow is generated such that the material of the first workpiece and the material of the second workpiece flow toward the through hole, thus making it possible to keep the flow state constant when plastic flow occurs.

[0085] (3) In the solid-state bonding method of (1) or (2), in the step (steps S3, S4) of creating the projection on the second workpiece (second workpiece W20), the projection (projection 60) is made to have a shape such that the outer wall of the projection comes into contact with the inner wall of the peripheral edge of the through hole (through hole 50) in the first workpiece (first workpiece W10).

[0086] With this configuration, in the step of creating a protrusion on the second workpiece, the protrusion is made in such a shape that the inner wall of the peripheral edge of the through hole in the first workpiece and the outer wall of the protrusion come into contact. As a result, current can be passed from the pair of electrodes to the first workpiece and the second workpiece through the contact portion between the inner wall of the peripheral edge of the through hole and the outer wall of the protrusion.

[0087] (4) In any of the solid-state bonding methods of (1) to (3), the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12) includes a first pressurizing shaft (first pressurizing shaft 11) that presses the first workpiece (first workpiece W10) and a second pressurizing shaft (second pressurizing shaft 12) that presses the second workpiece (second workpiece W20), wherein the first pressurizing shaft (first pressurizing shaft 11) is positioned to press the peripheral edge (peripheral edge 51) of the through hole (through hole 50) in the first workpiece (first workpiece W10), and the central axis of the second pressurizing shaft (second pressurizing shaft 12) is located on the extension of the central axis of the first pressurizing shaft (first pressurizing shaft 11), In the steps of creating the projection (projection 60) on the second workpiece (second workpiece W20) (steps S3, S4) and joining the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) (steps S5, S6), the first pressing shaft (first pressing shaft 11) presses the peripheral edge (peripheral edge 51) of the through hole (through hole 50), and the second pressing shaft (second pressing shaft 12) presses the first region (first region 91) and the second region (second region 92).

[0088] With this configuration, in the steps of creating a protrusion on the second workpiece and joining the first and second workpieces, the first pressing shaft presses the periphery of the through hole, and the second pressing shaft presses the first region covering the through hole and the second region on the periphery of the first region. As a result, a protrusion can be easily created on the second workpiece, and a plastic flow that flows toward the through hole can be easily generated.

[0089] (5) In any of the solid-state bonding methods of (1) to (4), the through hole (through hole 50) has a volume such that it can be filled by the plastically flowed material when the material of the first workpiece (first workpiece W10) and the material of the second workpiece (second workpiece W20) undergo plastic flow toward the through hole (through hole 50).

[0090] With this configuration, the through-hole has a volume that allows it to be filled by the plastically flowed material when the material from the first workpiece and the material from the second workpiece undergo plastic flow toward the through-hole. This allows the through-hole to properly receive the plastically flowed material.

[0091] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0092] W10 First workpiece, W20 Second workpiece, 11 First pressurizing shaft, 12 Second pressurizing shaft, 21 First electrode, 22 Second electrode, 1 Solid-phase bonding device, 50 Through hole, 51 Peripheral edge, 60 Protrusion, X Current, 91 First region, 92 Second region.

Claims

1. A pair of pressurizing shafts that are conductive and press multiple workpieces overlapping in the thickness direction from both sides in the thickness direction, A solid-state bonding method using a solid-state bonding apparatus comprising a pair of electrodes arranged around the pair of pressure shafts, The plurality of workpieces include a first workpiece having a through hole extending through it in the thickness direction, and a second workpiece covering the through hole. The steps include pressing the first workpiece and the second workpiece with the pair of pressure shafts to create a projection on the second workpiece that contacts the peripheral edge of the through hole in the first workpiece, A solid-state joining method comprising the steps of pressing the first workpiece and the second workpiece with a pair of pressure shafts while applying current from the pair of electrodes such that current flows through the region where the peripheral edge of the through hole and the projection are in contact, thereby joining the first workpiece and the second workpiece.

2. The solid-state joining method according to claim 1, wherein in the step of joining the first workpiece and the second workpiece, a plastic flow is generated such that the material of the first workpiece and the material of the second workpiece flow toward the through hole.

3. The solid-state bonding method according to claim 1 or claim 2, wherein in the step of creating the projection on the second workpiece, the projection is made to have a shape such that the outer wall of the projection comes into contact with the inner wall of the peripheral edge of the through hole in the first workpiece.

4. The pair of pressurizing shafts includes a first pressurizing shaft for pressing the first workpiece and a second pressurizing shaft for pressing the second workpiece. The first pressure shaft is positioned so as to be able to press the peripheral edge of the through hole in the first workpiece. The second pressurizing shaft is positioned such that its central axis lies on the extension of the central axis of the first pressurizing shaft, and is capable of pressing a first region covering the through hole and a second region at the periphery of the first region. The solid-state joining method according to claim 1 or claim 2, wherein in the steps of creating the projection on the second workpiece and joining the first workpiece and the second workpiece, the first pressurizing shaft presses the peripheral edge of the through hole and the second pressurizing shaft presses the first region and the second region.

5. The solid-state bonding method according to claim 2, wherein the through hole has a volume such that it can be filled by the plastically flowed material when the material of the first workpiece and the material of the second workpiece undergo plastic flow toward the through hole.

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