solid phase bonding device

Abstract

The objective is to provide a technology that can stabilize the bonding results when performing solid-state bonding. [Solution] In the first workpiece, the surface layer of a portion of the first surface that contacts one of a pair of pressurizing shafts is heated with a heating device so that it receives a force that causes plastic deformation of the surface layer. Then, the heating of the surface layer of the first surface is stopped by the heating device so that the surface layer of the first surface is cooled and the first workpiece protrudes to the second surface on the opposite side of the first surface. Then, a second control is performed in which, with respect to the first workpiece and the second workpiece that are in contact via the portion of the first workpiece that protrudes to the second surface, current is passed from a pair of electrodes, and the region of the first workpiece that is in contact with the second workpiece is pressed from both sides in the thickness direction of the first workpiece and the second workpiece with a pair of pressurizing shafts to join the first workpiece and the second workpiece.

Description

Technical Field

[0001] This disclosure relates to a solid-phase bonding device.

Background Art

[0002] Japanese Patent No. 7242112 (Patent Document 1) discloses a solid-phase bonding device including a pressurizing mechanism including a pressing portion and a current-carrying mechanism including a pair of welding electrodes. In the solid-phase bonding device disclosed in Patent Document 1, a constant current is passed through the bonding region of two workpieces to be joined from the electrodes to soften the bonding region, and the workpieces are joined by pressing the workpieces with the pressing portion.

[0003] In such a solid-phase bonding device, as a preparation step before the step of joining the workpieces, projections are formed on each of the two workpieces to be joined in such a manner that the tip portions of the projections face each other by the pressing pressure of the pressurizing mechanism. Such projections are provided to bring the two workpieces to be joined into point contact or line contact by bringing the projections formed on the two workpieces to be joined that overlap in the thickness direction into contact with each other. When joining the workpieces, if the two workpieces to be joined are not brought into point contact or line contact, there is a problem that a practically effective joining strength cannot be obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with conventional solid-state bonding equipment, the following problem may occur during the preparation process when attempting to form protrusions on two workpieces to be joined that overlap in the thickness direction by pressing pressure: If the two workpieces to be joined have different material hardnesses, the difference in material hardness may cause, for example, a protrusion formed on one workpiece with higher hardness to become embedded in the other workpiece with lower hardness, resulting in no protrusion being formed on the other workpiece. In such cases, the two workpieces to be joined become surface contact, reducing the bonding strength.

[0006] The purpose of this disclosure is to provide a technology that can suppress a decrease in bonding strength even when the hardness of the two workpieces to be joined is different. [Means for solving the problem]

[0007] The solid-state bonding apparatus of this disclosure comprises a pair of conductive pressure shafts that press a first workpiece and a second workpiece, which overlap in the thickness direction, from both sides in the thickness direction; a pair of electrodes arranged around the pair of pressure shafts; a heating device; and a control device that controls the pair of pressure shafts, the pair of electrodes, and the heating device. The control device performs a first control in which it heats the surface layer of a portion of the surface layer on the first surface side in which the pair of pressure shafts contact, with the heating device so that the surface layer is subjected to a force that causes plastic deformation, and then stops heating the surface layer with the heating device so that the surface layer cools and the first workpiece protrudes to the second surface side opposite the first surface side. The control device then performs a second control in which it presses the region in the first workpiece where the portion protruding to the second surface side contacts the second workpiece with the pair of pressure shafts from both sides in the thickness direction of the first workpiece and the second workpiece, while flowing an electric current from the pair of electrodes, to join the first workpiece and the second workpiece. [Effects of the Invention]

[0008] According to this disclosure, in the first workpiece, the surface layer of a portion of the surface on the first surface side where a pair of pressurizing shafts contact is heated by a heating device so that it receives a force that causes plastic deformation of the surface layer, and then a first control is performed to stop heating the surface layer by the heating device so that the surface layer cools and the first workpiece protrudes to the second surface side opposite the first surface side. This makes it possible to create a portion of the first workpiece that protrudes to the second surface side without operating the pair of pressurizing shafts. Then, with respect to the first workpiece and the second workpiece that are in contact via the portion of the first workpiece that protrudes to the second surface side, a second control is performed to press the region in the first workpiece where the portion protruding to the second surface side contacts the second workpiece with the pair of pressurizing shafts from both sides in the thickness direction of the first workpiece and the second workpiece, while passing an electric current from a pair of electrodes, thereby joining the first workpiece and the second workpiece. This makes it possible to solid-state join the first workpiece and the second workpiece that are in contact via the portion protruding to the second surface side of the first workpiece. This allows for solid-state bonding of the first and second workpieces even when they have different hardnesses, by maintaining point or line contact between them. Therefore, even when the two workpieces to be joined have different hardnesses, a decrease in bonding strength can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows a solid-phase bonding apparatus according to Embodiment 1. [Figure 2] This diagram illustrates the preparation process when a solid-phase bonding apparatus performs solid-phase bonding. [Figure 3] This diagram illustrates the relationship between temperature and pressure in the surface layer during the preparation process. [Figure 4] This diagram illustrates the bonding process in solid-phase bonding performed by a solid-phase bonding apparatus. [Figure 5] This is a flowchart showing the control of solid-phase bonding in the solid-phase bonding apparatus according to Embodiment 1. [Figure 6] This is a flowchart showing the control of solid-phase bonding in the solid-phase bonding apparatus according to Embodiment 1. [Figure 7]This figure schematically shows a solid-phase bonding apparatus according to Embodiment 2. [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 following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their descriptions will not be repeated in principle. While multiple embodiments will be described below, it has been intended from the outset that the configurations described in each embodiment may be combined as appropriate.

[0011] <Embodiment 1> [Configuration of the solid-phase bonding apparatus 1 according to Embodiment 1] Figure 1 is a schematic diagram of a solid-phase bonding apparatus 1 according to Embodiment 1. The solid-phase bonding apparatus 1 joins multiple workpieces that are stacked on top of each other in a solid state. This type of joining is called solid-phase bonding. Figure 1 shows the state of the solid-phase bonding apparatus 1 before solid-phase bonding is started.

[0012] In the example in Figure 1, the workpieces include a first workpiece W10 and a second workpiece W20. Figure 1 illustrates an example in which the first workpiece W10 and the second workpiece W20 are joined together. The first workpiece W10 and the second workpiece W20 are collectively referred to as "workpiece W". Workpiece W is held by a holding device, which is not shown in the figure.

[0013] The solid-phase bonding apparatus 1 is a device that bonds multiple workpieces W10 and W20 without melting them by applying current to multiple workpieces W10 and W20 that are stacked on top of each other to form a softened region as a bonding region at the interface of the multiple workpieces W10 and W20, and then pressing the workpieces W10 and W20 from both sides in the thickness direction with the pair of pressure shafts 11 and 12 to plastically deform the softened region. The solid-phase bonding apparatus 1 is also capable of heating the area of ​​the first workpiece W10 irradiated with laser light L from a heating device 13.

[0014] The first workpiece W10 and the second workpiece W20 are, for example, conductors, and more typically, are made of metals such as iron or aluminum. The first workpiece W10 and the second workpiece W20 are formed, for example, in the shape of flat plates. The first workpiece W10 and the second workpiece W20 are, for example, metals with different hardnesses. However, the first workpiece W10 and the second workpiece W20 may be made of the same type of metal. 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.

[0015] Referring to Figure 1, the solid-phase bonding apparatus 1 comprises a solid-phase bonding device 10 and a control device 30. The control device 30 controls each component of the solid-phase bonding device 10. The solid-phase bonding device 10 comprises a pair of pressurizing shafts 11 and 12, a pair of electrodes 21 and 22, a pressure sensor 40, a heating device 13, a housing 14, an actuator 151, and a deformation sensor 36. Note that the "pressurizing shafts" may also be referred to as "pressurizing members" or "pressing members."

[0016] The first workpiece W10 and the second workpiece W20 are both plate-shaped and stacked in the thickness direction. The pair of pressurizing shafts 11 and 12 include the first pressurizing shaft 11 and the second pressurizing shaft 12. The first pressurizing shaft 11 is driven by an actuator 151 and moves in the axial direction of the first pressurizing shaft 11. The second pressurizing shaft 12 is fixed. With this configuration, the first pressurizing shaft 11 is movable relative to the second pressurizing shaft 12. Since the second pressurizing shaft 12 is fixed, when the first pressurizing shaft 11 moves in the direction of pressing the first workpiece W10, the first workpiece W10 and the second workpiece W20 are sandwiched between the first pressurizing shaft 11 and the second pressurizing shaft 12 and pressed from both sides in the thickness direction by the first pressurizing shaft 11 and the second pressurizing shaft 12.

[0017] In Embodiment 1, the thickness direction of the first workpiece W10 and the second workpiece W20 is the Z-axis direction. The plane perpendicular to the Z-axis direction is the XY plane. In the example in Figure 1, the X-axis of the XY plane is shown. The first workpiece W10 and the second workpiece W20 are stretched in the XY plane.

[0018] Further, in the Z-axis direction, the direction of gravity is defined as the Z1-axis direction, and the direction opposite to the Z1-axis direction is defined as the Z2-axis direction. The Z1-axis direction corresponds to the "first direction" of the present disclosure. Also, the Z2-axis direction corresponds to the "second direction" of the present disclosure. Further, in the example of FIG. 1, the X1-axis direction and the X2-axis direction are shown.

[0019] First, the first pressing shaft 11 and the second pressing shaft 12 will be described. The first pressing shaft 11 and the second pressing shaft 12 have a shape extending in the Z-axis direction. In Embodiment 1, the first pressing shaft 11 and the second pressing shaft 12 are cylindrical.

[0020] A through hole 50 is formed inside the first pressing shaft 11. That is, the first pressing shaft 11 has a hollow shape. In the through hole 50, the laser beam L output from the heating device 13 passes through. The cross-sectional shape of the through hole 50 in the XY plane is circular. Also, at least a part of the technical idea of the first pressing shaft 11 described below can be applied to the second pressing shaft 12. For example, the second pressing shaft 12 has the same configuration as that of the first pressing shaft 11 except that the through hole 50 is not formed.

[0021] The control device 30 moves the first pressing shaft 11 in the Z-axis direction (Z1-axis direction and Z2-axis direction) by driving the actuator 151.

[0022] Also, the control device 30 can specify the amount of movement (position of the first pressing shaft 11) of the first pressing shaft 11 based on the driving amount of the actuator 151.

[0023] The first pressing shaft 11 presses the first workpiece W10 in the Z1 axis direction (first direction). As a result, the first workpiece W10 undergoes plastic deformation. Since the second pressing shaft 12 is fixed, in response to the first pressing shaft 11 pressing the first workpiece W10, the second pressing shaft 12 presses the second workpiece W20 in the Z2 axis direction (second direction). As a result, the second workpiece W20 undergoes plastic deformation. In this way, the control device 30 applies pressure to the first workpiece W10 and the second workpiece W20 from both sides in the Z axis direction using the first pressing shaft 11 and the second pressing shaft 12.

[0024] The pressure sensor 40 detects the load applied to the first workpiece W10 by the first pressurizing shaft 11. The detected load is output to the control device 30. The control device 30 controls the first pressurizing shaft 11 based on the load.

[0025] The pressure sensor 40 is placed, for example, inside the actuator 151. A load cell is used as the pressure sensor 40. The pressure sensor 40 may be installed in a location other than inside the actuator 151 (for example, the first pressurizing shaft 11).

[0026] The pair of electrodes 21, 22 includes a first electrode 21 and a second electrode 22. The first electrode 21 is capable of contacting the portion of the first workpiece W10 surrounding the portion 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.

[0027] The control device 30 can control the movement of the first electrode 21 along the axial direction of the first pressurizing shaft 11 using a first electrode drive device (not shown). The control device 30 can also control the movement of the second electrode 22 along the axial direction of the second pressurizing shaft 12 using a second electrode drive device (not shown).

[0028] 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.

[0029] As shown in Figure 4(A) described later, the pair of electrodes 21 and 22 can energize the first workpiece W10 and the second workpiece W20 when the contact surface 21a of the first electrode 21 is in contact with the first workpiece W10 and the contact surface 22a of the second electrode 22 is in contact with the second workpiece W20. For example, when the pair of electrodes 21 and 22 are in contact with the first workpiece W10 and the second workpiece W20, applying a voltage to the pair of electrodes 21 and 22 supplies power to the first electrode 21, the first workpiece W10, the second workpiece W20, and the second electrode 22. As a result, current flows between the first electrode 21 and the second electrode 22 through the first workpiece W10 and the second workpiece W20.

[0030] The first pressurizing shaft 11 is provided with a through-hole 50 that penetrates axially. A heating device 13 is provided inside the housing 14. The heating device 13 can heat the surface of the first workpiece W10 by irradiating it with laser light L through the through-hole 50, as shown in Figure 2(A), which will be described later. The control device 30 transmits an irradiation signal to the heating device 13. The irradiation signal is a signal to cause the heating device 13 to irradiate with laser light L. When the heating device 13 receives the irradiation signal from the control device 30, it irradiates with laser light L in the Z1 axis direction.

[0031] A deformation amount sensor 36 is provided to the side of the position where the first workpiece W10 and the second workpiece W20 are placed. This sensor is capable of detecting the amount of deformation of the first workpiece W10 when its surface is heated by irradiation with laser light L. The deformation amount sensor 36 is composed of an image sensor or the like capable of capturing images of the first workpiece W10 and the second workpiece W20. The image data captured by the deformation amount sensor 36 is sent to the control device 30. The control device 30 can detect the amount of deformation of the first workpiece W10 by analyzing the image data sent from the deformation amount sensor 36.

[0032] The control device 30 is connected to an input device 61 and a display device 62. The display device 62 displays various screens under the control of the control device 30. Various information is input by the user to the input device 61. The input information is output to the control device 30.

[0033] 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.

[0034] The arithmetic unit 31 is an arithmetic entity (computer) that performs predetermined processing. The arithmetic unit 31 is composed of processors such as a CPU (Central Processing Unit), MPU (Micro-Processing Unit), TPU (Tensor Processing Unit), or GPU (Graphics Processing Unit). A processor, which is an example of the arithmetic unit 31, has the function of performing predetermined processing by executing a predetermined program. However, the arithmetic unit 31 may implement some or all of this function using dedicated hardware circuits such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array). The arithmetic unit 31 may also be referred to as "at least one processor" or "arithmetic circuit".

[0035] 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. Memory 32 includes ROM (Read Only Memory), RAM (Random Access Memory), and flash memory.

[0036] The storage device 33 stores various programs or data executed by the arithmetic unit 31. For example, the storage device 33 stores a control program 330 that controls the operation of the first pressurizing shaft 11, the second pressurizing shaft 12, the first electrode 21, the second electrode 22, and the heating device 13, which are 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. An example of a storage device 33 is an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0037] The input / output interface 34 communicates with external devices (pressure sensor 40, deformation sensor 36, input device 61, display device 62, etc.).

[0038] The control device 30 controls the stroke of the first pressurizing shaft 11 by controlling the actuator 151. The control device 30 controls the current supplied to the pair of electrodes 21 and 22 by controlling the power supply device 35.

[0039] Specifically, the control device 30 controls the actuator 151 to move the first pressurizing shaft 11 toward the first workpiece W10, thereby controlling the load acting on the first workpiece W10 and the second workpiece W20 from each of the pair of pressurizing shafts 11 and 12, and the amount of indentation of the pair of pressurizing shafts 11 and 12. The control device 30 also controls the power supply unit 35 to control the current supplied to the pair of electrodes 21 and 22. Furthermore, the control device 30 controls 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 by controlling the first electrode drive unit and the second electrode drive unit.

[0040] The control device 30 controls the laser light L emitted from the heating device 13 by controlling the heating device 13.

[0041] As shown in Figure 2, which will be described later, the control device 30 irradiates a portion of the surface layer 71 of the first workpiece W10 with laser light L from the heating device 13 to heat the surface layer 71, and then cools the surface layer 71 to form a protrusion 70 on the first workpiece W10.

[0042] As shown in Figure 4, which will be described later, the control device 30 applies a current X from a pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20 to soften the bonding area, while simultaneously applying pressure to the first workpiece W10 and the second workpiece W20 from both sides in the thickness direction with a pair of pressure shafts 11 and 12. In the solid-phase bonding apparatus 1, the control device 30 performs this control to bond the first workpiece W10 and the second workpiece W20 in a solid state, as shown in Figure 4(B), which will be described later.

[0043] [Preparation steps in solid-state bonding] Figure 2 is a diagram illustrating the preparation process when the solid-phase bonding apparatus 1 performs solid-phase bonding. Figures 2(A) to 2(C) show the progress of the preparation process for forming a protrusion on the first workpiece W10. This preparation process is performed by the control device 30 controlling the heating device 13.

[0044] Figure 2 basically shows cross-sections of the first workpiece W10, the second workpiece W20, and the first pressurizing shaft 11. In Figure 2, the hatching of the cross-section of the surface layer 71 of the first workpiece W10 is omitted to clearly distinguish it from the other areas.

[0045] The preparation process begins with the pair of pressurizing shafts 11, 12 and the pair of electrodes 21, 22 not in contact with the first workpiece W10 and the second workpiece W20, as shown in Figure 1. With the first pressurizing shaft 11 not in contact with the first workpiece W10, the laser beam L output from the heating device 13 shown in Figure 1 is irradiated onto the first surface of the first workpiece W10 through the through-hole 50 of the first pressurizing shaft 11, as shown in Figure 2(A).

[0046] The laser beam L is directed at the center of the first workpiece W10, where a protrusion 70 is formed as shown in Figure 2(C). In the first workpiece W10, a portion of the surface layer 71 is heated by the irradiated laser beam L, as shown in Figure 2(A). Hereafter, the portion of the entire surface layer of the first workpiece W10 that is heated by the irradiated laser beam L will be referred to as the surface layer 71.

[0047] In the first workpiece W10, when heated by laser light L, an expansion force F1 is generated in the direction of expansion of the surface layer 71 as the temperature of the heated surface layer 71 rises, as shown in Figure 2(B). On the other hand, when such an expansion force F1 is generated, a compressive force F2 is generated in the surface layer 71 as a stress against the expansion force F1, as shown in Figure 2(B), due to constraints from the surroundings of the surface layer 71, causing the surface layer 71 to compress.

[0048] In the state shown in Figure 2(B), elastic strain due to elastic deformation corresponding to the expansion force F1 and elastic strain corresponding to the compressive force F2 applied to the surface layer 71 from the surroundings may occur, but these elastic strains are in equilibrium. This is because, in this state, the expansion force F1 generated in the surface layer 71 and the compressive force F2 that the surface layer 71 receives from the surroundings are in equilibrium. Due to this equilibrium between the expansion force F1 and the compressive force F2, no apparent deformation occurs in the first workpiece W10, as shown in Figure 2(B).

[0049] Then, as the temperature of the surface layer 71 heated by the laser light L rises further, the expansion force F1 and compression force F2 reach the yield point of the material of the first workpiece W10, and the surface layer 71 undergoes plastic deformation. The control device 30 cools the surface layer 71 by stopping the heating by the laser light L after the surface layer 71 has undergone plastic deformation. As a result, the temperature of the surface layer 71 decreases. This cooling of the surface layer 71 is carried out by natural cooling.

[0050] As the surface layer 71 is cooled and its temperature decreases, the expansion force F1 and compression force F2, which were balanced as shown in Figure 2(B), change as shown in Figure 2(C). The expansion force F1 disappears, but the compression force F2 remains. This is because the expansion force F1 increased in accordance with the temperature of the surface layer 71, while the compression force F2 did not increase in accordance with the temperature of the surface layer 71.

[0051] As shown in Figure 2(C), when the expansion force F1 is eliminated and the compressive force F2 remains, the surface layer 71 is plastically deformed and is not compressed by the remaining compressive force F2. Therefore, the remaining compressive force F2 acts around the surface layer 71 of the first workpiece W10. Thus, when the expansion force F1 is eliminated and the compressive force F2 remains, as shown in Figure 2(C), the portion of the surface layer 71 of the first workpiece W10 that is surrounded by the compressive force F2 acts on it, causing it to bend in the direction indicated by the dashed arrow.

[0052] Specifically, as shown in Figure 2(C), the first workpiece W10 is in contact with the second workpiece W20 at the center of the opposite side of the surface layer 71, either at a point or line contact, and the surrounding portion of the surface layer 71 warps upward, as indicated by the dashed arrow. As a result, the surface layer 71 on the first side of the first workpiece W10 is cooled, and a portion of the first workpiece W10 protrudes to the opposite second side. Therefore, the first workpiece W10 and the second workpiece W20 are in contact at the protruding portion 70 of the first workpiece W10 and at the portion of the second workpiece W20 that faces the protruding portion 70 of the first workpiece W10.

[0053] [Relationship between temperature and pressure in the surface layer 71 during the preparation process] Figure 3 illustrates the relationship between temperature and pressure in the surface layer 71 during the preparation process. Figure 3(A) shows a graph illustrating the temperature change in the surface layer 71 during the preparation process. Figure 3(B) shows a graph illustrating the changes in the expansion and compression forces acting on the surface layer 71 during the preparation process.

[0054] In Figure 3(A), the vertical axis shows the temperature of the surface layer 71, and the horizontal axis shows the elapsed time. In Figure 3(B), the vertical axis shows the expansion and compression forces acting on the surface layer 71, and the horizontal axis shows the elapsed time. In the vertical axis of Figure 3(B), the positive direction indicates the expansion force generated on the surface layer 71, and the negative direction indicates the compression force that the surface layer 71 receives from its surroundings.

[0055] Figure 3(B) shows that the expansion force increases as the pressure increases in the positive direction. Figure 3(B) also shows that the compression force increases as the pressure increases in the negative direction.

[0056] In the preparation process, as shown in Figure 3(A), the temperature 41 of the surface layer 71 of the first workpiece W10 is heated from the first temperature to the second temperature in response to irradiation with laser light L, and then cooled from the second temperature to the first temperature when the laser light L is stopped. The first temperature is the temperature when the surface layer 71 is not heated. The second temperature is the temperature at which the surface layer 71 mainly undergoes plastic deformation, as explained using Figures 2(B) and 2(C).

[0057] In the preparation process, when the surface layer 71 is heated, an expansion force such as the expansion force F1 shown in Figure 2(B) is generated in the surface layer 71. In the surface layer 71, as the temperature 41 rises as shown in Figure 3(A), the expansion force 42 increases as shown in Figure 3(B). Then, in the surface layer 71, as the temperature 41 falls as shown in Figure 3(A), the expansion force 42 decreases as shown in Figure 3(B). Cooling from the second temperature to the first temperature by stopping the laser beam L is necessary because at the first temperature, the expansion force such as the expansion force F1 shown in Figure 2(B) decreases, thereby suppressing the expansion of the surface layer 71.

[0058] In the preparation process, when an expansion force F1, as shown in Figure 2(B), is generated in the surface layer 71, the surface layer 71 receives a compressive force from its surroundings, as a stress in response to the expansion force, such as the compressive force F2, also shown in Figure 2(B). Specifically, in the surface layer 71, as the expansion force 42 increases as shown in Figure 3(B), it receives a compressive force that is the sum of the first compressive force 43 and the second compressive force 44, as shown in Figure 3(B).

[0059] Of the compressive forces shown in Figure 3(B), the first compressive force 43 is the component that causes elastic deformation of the surface layer 71, and the second compressive force 44 is the component that causes plastic deformation of the surface layer 71. When the expansion force 42 increases as shown in Figure 3(B), the first compressive force 43 acts on the surface layer 71 at the beginning of the increase, and as the increase progresses, the second compressive force 44 acts in addition to the first compressive force 43.

[0060] As shown in Figure 3(B), the first compressive force 43 enters a first state in which the compressive force increases in response to an increase in the expansion force 42, and then enters a second state in which the compressive force remains constant even as the expansion force 42 increases. Furthermore, as shown in Figure 3(B), after entering the second state, the first compressive force 43 enters a third state in which the compressive force decreases in response to an increase in the expansion force 42. Since the first compressive force 43 is a component of the force that elastically deforms the surface layer 71, it changes from the first state to the third state in this way as the compressive force received by the surface layer 71 increases relative to the expansion force 42.

[0061] As shown in Figure 3(B), the second compressive force 44 enters a first state in which the compressive force increases in accordance with the increase in the expansion force 42, and then enters a second state in which the compressive force remains constant even when the expansion force 42 decreases. Since the second compressive force 44 is a component of the force that causes plastic deformation of the surface layer 71, it enters a first state in which the compressive force increases in accordance with the increase in the expansion force 42. Then, when the compressive force that the surface layer 71 receives from its surroundings exceeds the yield point relative to the expansion force 42, the surface layer 71 undergoes plastic deformation. When the temperature of the surface layer 71 is at the second temperature, the surface layer 71 is in a state of plastic deformation, so even if the temperature of the surface layer 71 decreases after it has reached the second temperature, the second compressive force 44 remains in a second state as a residual stress with a constant compressive force, even if the expansion force 42 decreases in accordance with the decrease in the temperature of the surface layer 71.

[0062] [Bonding process in solid-state bonding] Figure 4 is a diagram illustrating the bonding process in solid-phase bonding performed by the solid-phase bonding apparatus 1. Figures 4(A) and 4(B) show the progress of the bonding process in which the first workpiece W10 and the second workpiece W20 are joined. This bonding process is performed by the control device 30, which controls a pair of pressure shafts 11, 12 and a pair of electrodes 21, 22.

[0063] In solid-state bonding, the bonding process is carried out after the preparation steps shown in Figure 3 are performed, with the protruding portion 70 of the first workpiece W10 and the portion of the second workpiece W20 facing the protruding portion 70 of the first workpiece W10 in contact, such as line contact or point contact.

[0064] As shown in Figure 4(A), the first workpiece W10 is positioned so that the first press shaft 11 can press the center of the protrusion 70 from above. As shown in Figure 4(A), the second workpiece W20 is positioned such 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 the portion of the second workpiece W20 that is in contact with the protrusion 70 of the first workpiece W10 can be pressed by the second press shaft 12.

[0065] As shown in Figure 4(A), the first pressurizing shaft 11 is brought into contact with the first workpiece W10 at a position that allows it to press the center of the protrusion 70 from above. The second pressurizing shaft 12 is brought into contact with the second workpiece W20 at a position that allows it to press the portion of the first workpiece W10 that has been in contact with the protrusion 70 from below.

[0066] As shown in Figure 4(A), the first electrode 21 is brought into contact with the first workpiece W10 at a position around the center of the protrusion 70. The second electrode 22 is brought into contact with the second workpiece W20 at a position around the position that presses the portion of the first workpiece W10 that has been in contact with the protrusion 70.

[0067] The control device 30 then controls the flow of current X from a pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20, as shown in Figure 4(A). Between the first workpiece W10 and the second workpiece W20, the center of the protrusion 70 of the first workpiece W10 is in contact with the second workpiece W20, so current X flows through such contact.

[0068] With a current X flowing from the pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20 in this manner, the control device 30 further controls the actuator 151 so that the pair of pressure shafts 11 and 12 press against the first workpiece W10 and the second workpiece W20 from both sides in the thickness direction, as shown in Figure 4(A), thereby applying a load F to the first workpiece W10 and the second workpiece W20 from the pair of pressure shafts 11 and 12.

[0069] In this way, when a current X flows from a pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20, the bonding interface between the first workpiece W10 and the second workpiece W20 softens. Then, when the first workpiece W10 and the second workpiece W20 are pressed by a pair of pressure shafts 11 and 12, the softened regions of the first workpiece W10 and the second workpiece W20 are joined without changing the material while remaining in a low-temperature solid state, resulting in solid-state bonding between the first workpiece W10 and the second workpiece W20 as shown in Figure 4(B).

[0070] <Explanation regarding the control of solid-phase bonding> Next, the control of solid-phase bonding in the solid-phase bonding apparatus 1 according to Embodiment 1 will be described. Figures 5 and 6 are flowcharts showing the control of solid-phase bonding in the solid-phase bonding apparatus 1 according to Embodiment 1. The processes in the flowcharts of Figures 5 and 6 are repeatedly called and executed as subroutines from the main routine in the control of the control device 30.

[0071] In step S1, the control device 30 determines the joining position between the first workpiece W10 and the second workpiece W20. For example, in step S1, the central part of the first workpiece W10 and the central part of the second workpiece W20 are determined as the joining position between the first workpiece W10 and the second workpiece W20.

[0072] In step S2, the control device 30 controls the heating device 13 to start irradiating the first workpiece W10 with laser light L toward the bonding position determined in step S1.

[0073] In step S3, the control device 30 determines whether the temperature of the surface layer 71 of the first workpiece W10 has reached the second temperature shown in Figure 3(A). The second temperature is the temperature at which the surface layer 71 of the first workpiece W10 undergoes mainly plastic deformation, as described above.

[0074] In step S3, the control device 30 pre-sets the output value and irradiation time of the laser beam L according to the type and thickness of the material of the first workpiece W10, and determines that the surface layer 71 of the first workpiece W10 has reached the second temperature when the laser beam L is irradiated at a predetermined output value for a predetermined irradiation time. In step S3, in order to make this determination, the control device 30 measures the elapsed time from the start of laser beam L irradiation in step S2 and monitors the output value of the laser beam L.

[0075] In addition, the solid-phase bonding apparatus 1 may be configured to include a temperature sensor for detecting the temperature of the surface layer 71 of the first workpiece W10, and to input the detection data from the temperature sensor to the control device 30. In step S3, the control device 30 may determine whether the temperature of the surface layer 71 of the first workpiece W10 has reached the second temperature based on the detection data input from the temperature sensor.

[0076] In step S3, the control device 30 determines that the temperature of the surface layer 71 of the first workpiece W10 has reached the second temperature, and in step S4, controls the heating device 13 to terminate the irradiation of the laser light L to the surface layer 71 of the first workpiece W10. As a result, the surface layer 71 of the first workpiece W10 is cooled.

[0077] In step S5, the control device 30 determines whether the temperature of the surface layer 71 of the first workpiece W10 has reached the first temperature shown in Figure 3(A). The first temperature is the temperature when the surface layer 71 is not heated, as described above.

[0078] In step S5, the cooling time required for the temperature of the surface layer 71 of the first workpiece W10 to change from the second temperature to the first temperature is predetermined according to the type and thickness of the material of the first workpiece W10. When the predetermined cooling time has elapsed since the end of irradiation with laser light L in step S4, it is determined that the surface layer 71 of the first workpiece W10 has reached the first temperature. In step S5, in order to make this determination, the elapsed time since the end of irradiation with laser light L in step S4 is measured.

[0079] In addition, the solid-phase bonding apparatus 1 may be configured to include a temperature sensor for detecting the temperature of the surface layer 71 of the first workpiece W10, and to input the detection data from the temperature sensor to the control device 30. In step S5, it may be determined whether or not the temperature of the surface layer 71 of the first workpiece W10 has reached the first temperature based on the detection data input from the temperature sensor.

[0080] In step S6, the control device 30 determines whether the deformation amount of the first workpiece W10 is greater than or equal to a set value. The deformation amount of the first workpiece W10 is, for example, the amount of deformation as the amount by which the part surrounding the surface layer 71 is warped, as shown in Figure 2(C). The set value is set to the deformation amount of the first workpiece W10 such that the joint strength between the first workpiece W10 and the second workpiece W20 is good, with respect to the protruding part 70, which is a protruding part of the first workpiece W10.

[0081] Specifically, in step S6, the deformation amount sensor 36 captures images of the first workpiece W10 and the second workpiece W20, and by analyzing the image data sent to the control device 30 through the capture, the deformation amount of the first workpiece W10 is detected, and it is determined whether or not the detected deformation amount is greater than or equal to a set value.

[0082] If the control device 30 determines in step S6 that the deformation amount of the first workpiece W10 is not greater than or equal to the set value, it returns to step S2 and repeatedly executes the processes in steps S2 to S5. On the other hand, if the control device 30 determines in step S6 that the deformation amount of the first workpiece W10 is greater than or equal to the set value, it executes the joining process in step S7.

[0083] The processes described above in steps S2 to S6 may be referred to as the first control, in which the control device 30 performs the preparation process.

[0084] The details of the joining process in step S7 are shown in Figure 6. When performing the joining process, the control device 30 controls the first electrode drive device that drives the first electrode 21 and the second electrode drive device that drives the second electrode 22 in step S11 so that the pair of electrodes 21 and 22 come into contact with the first workpiece W10 and the second workpiece W20.

[0085] In step S12, the control device 30 controls the first electrode drive device that drives the first electrode 21 and the second electrode drive device that drives the second electrode 22 so that the pair of electrodes 21 and 22 press against the first workpiece W10 and the second workpiece W20 in the manner shown in Figure 4(A).

[0086] In step S13, the control device 30 controls the power supply device 35 so that current X is supplied from the pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20 in the manner shown in Figure 4(A).

[0087] In step S14, the control device 30 determines whether the energizing time started in step S13 has elapsed to a set time. Specifically, in step S14, the control device 30 measures the duration of the energizing that started in step S13 and determines whether the energizing time has elapsed to a set time. The set time in step S14 is set, for example, to the time it is considered that the joint surface between the first workpiece W10 and the second workpiece W20 will soften to some extent due to the energizing.

[0088] In step S14, the control device 30 waits until the energized time has elapsed to the set time, and then proceeds to step S15. If the control device 30 determines in step S14 that the energized time has elapsed to the set time, in step S15, it controls the actuator 151 so that the pair of pressurizing shafts 11 and 12 press against the first workpiece W10 and the second workpiece W20 until the first workpiece W10 and the second workpiece W20 are joined together in the manner shown in Figure 4(B).

[0089] In step S15, when the first workpiece W10 and the second workpiece W20 are joined, the control device 30 controls the power supply device 35 in step S16 so that the current X flowing from the pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20 is terminated. Then, in step S17, the control device 30 controls the actuator 151 so that the pressing of the first workpiece W10 and the second workpiece W20 by the pair of pressure shafts 11 and 12 is terminated.

[0090] The processes described above in steps S11 to S17 may be referred to as the second control, in which the control device 30 executes the joining process.

[0091] <Embodiment 2> In Embodiment 2, a solid-phase bonding apparatus 1A is described that forms a protrusion on a second workpiece W20 similar to the protrusion 70 on the first workpiece W10, using the same structure and control as described in Embodiment 1 for forming a protrusion 70 on the first workpiece W10.

[0092] [Configuration of Solid-State Bonding Apparatus 1A according to Embodiment 2] Figure 7 is a schematic diagram showing a solid-phase bonding apparatus 1A according to Embodiment 2. The difference between the solid-phase bonding apparatus 1A of Embodiment 2 and the solid-phase bonding apparatus 1 of Embodiment 1 is that, in addition to forming a protrusion 70 on the first workpiece W10 as in Embodiment 1, a preparatory step is performed to form a protrusion similar to the protrusion 70 on the second workpiece W20 before the bonding step is performed.

[0093] The difference in configuration between the solid-phase bonding apparatus 1A in Figure 7 and the solid-phase bonding apparatus 1 in Figure 1 is that in the solid-phase bonding apparatus 10A, a second pressure shaft 120 and a heating device 13A are provided instead of the second pressure shaft 12. The second pressure shaft 120 is provided with a through hole 50A similar to the through hole 50 provided in the first pressure shaft 11. In this configuration in which the heating device 13A is provided, the heating device 13 may be referred to as the first heating device 13, and the heating device 13A may be referred to as the second heating device 13A.

[0094] The heating device 13A is a device that outputs a heating laser beam LA, similar to the heating device 13. The heating device 13A can heat the surface layer of the first surface of the second workpiece W20 by irradiating the laser beam LA through the through hole 50A onto the first surface of the second workpiece W20 (the side opposite to the surface that contacts the first workpiece W10). In this case, the control device 30 controls the heating device 13A in the same way as the heating device 13. When the heating device 13A receives an irradiation signal from the control device 30, it irradiates the laser beam LA in the Z2 axis direction. Hereinafter, the first surface of the second workpiece W20 will be referred to as the third surface to distinguish it from the first surface of the first workpiece W10.

[0095] In Embodiment 2, the deformation amount sensor 36 detects the amount of deformation of the first workpiece W10 when its surface is heated by irradiation with laser light L, and also detects the amount of deformation of the second workpiece W20 when its surface is heated by irradiation with laser light LA.

[0096] In Embodiment 2, the control device 30, after determining the joining position in step S1 in Figure 5, executes control in steps S2 to S6 to heat the surface of the first workpiece W10 with laser light L, and then cool it, and also executes control to heat the surface of the second workpiece W20 with laser light LA, and then cool it, with the second workpiece W20 as the target of heating. Then, the joining process in step S7 in Figure 5 is executed. This control, which uses the second workpiece W20 as the target of heating, is achieved by replacing the workpiece to be heated in steps S2 to S6 from the first workpiece W10 to the second workpiece W20 in the solid-phase joining control shown in Figures 5 and 6, and then executing control to heat the surface of the second workpiece W20 in the same way as the surface of the first workpiece W10, and then cool it. As a result, in the solid-phase bonding apparatus 1A, the second workpiece W20 is also formed in a shape such that a protrusion similar to the protrusion 70 formed on the first workpiece W10 protrudes from the second surface side (opposite the third surface side) of the second workpiece W20. Hereafter, the second surface side of the second workpiece W20 will be referred to as the fourth surface side to distinguish it from the second surface side of the first workpiece W10.

[0097] Steps S2 to S6, in which the workpiece to be heated is replaced with the second workpiece W20, are sometimes referred to as the third control.

[0098] In Embodiment 2, after forming the protrusion 70 on the first workpiece W10, a protrusion similar to the protrusion 70 may be formed on the second workpiece W20, or a protrusion similar to the protrusion 70 may be formed on the second workpiece W20, and then the protrusion 70 may be formed on the second workpiece W20. Also in Embodiment 2, a protrusion similar to the protrusion 70 may be formed on the second workpiece W20 in parallel with the formation of the protrusion 70 on the first workpiece W10.

[0099] In Embodiment 2, after forming a protrusion 70 on the first workpiece W10 and a protrusion similar to the protrusion 70 on the second workpiece W20, the first workpiece W10 and the second workpiece W20 are stacked so that their protrusions come into contact with each other, and the joining process in step S7 of Figure 5 is performed, thereby performing the same joining process as in steps S11 to S17 of Figure 6. For example, in step S13 of Figure 6, a current X is passed from a pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20, and in step S15 of Figure 6, control is performed to press the first workpiece W10 and the second workpiece W20 with a pair of pressure shafts 11 and 12, thereby joining the first workpiece W10 and the second workpiece W20.

[0100] Steps S11 to S17, which are performed to join the first workpiece W10 and the second workpiece W20 after forming a protrusion 70 on the first workpiece W10 and a protrusion similar to the protrusion 70 on the second workpiece W20, while the protrusions are in contact with each other, are sometimes referred to as the fourth control.

[0101] In Embodiment 2, a protrusion 70 is formed on the first workpiece W10, and a protrusion similar to the protrusion 70 is formed on the second workpiece W20. Then, with the first workpiece W10 and the second workpiece W20 stacked on top of each other so that these protrusions come into contact, a joining process similar to the joining process in Figure 6 is performed. As a result, Embodiment 2 can obtain the same technical effects as those obtained in Embodiment 1.

[0102] <Explanation of variations> (1) In the embodiment described above, an example was described in which a protrusion 70 is formed on the first workpiece W10 by irradiating the first workpiece W10 with laser light L in the solid-phase bonding apparatus 1. However, the invention is not limited to this, and in the solid-phase bonding apparatus 1, a protrusion similar to the protrusion 70 may be formed on the second workpiece W20 by irradiating the second workpiece W20 with laser light L in the second workpiece W20.

[0103] (2) In the embodiments 1 and 2 described above, examples were shown in which the surface layer 71 of the workpieces to be heated, such as the first workpiece W10 and the second workpiece W20, is heated by irradiating them with laser light L from the heating device 13. However, the invention is not limited to this, and the surface layer of the workpieces to be heated may be heated using other heating devices such as infrared heating devices.

[0104] (3) In the embodiments 1 and 2 described above, a configuration may be adopted in which a temperature sensor, such as an infrared sensor, is provided to detect the temperature of the surface layer, such as the surface layer 71. In that case, the control device 30 may determine in step S3 that the temperature of the surface layer 71 has reached the second temperature, and in step S5 that the temperature of the surface layer 71 has reached the first temperature, based on the detection data from such a temperature sensor.

[0105] (4) In the embodiments 1 and 2 described above, the first workpiece W10 and the second workpiece W20 were made of different types of materials, but the first workpiece W10 and the second workpiece W20 may be made of the same type of material.

[0106] (5) The first workpiece W10 and the second workpiece W20 shown in Embodiments 1 and 2 above may have the same thickness or may have different thicknesses.

[0107] (6) The solid-phase bonding apparatus 1 shown in Embodiment 1 and the solid-phase bonding apparatus 1A shown in Embodiment 2 above show the second pressing shaft 12 to be fixed, but the invention is not limited to this, and the second pressing shaft 12 may be able to press the second workpiece W20 by moving in the axial direction by an actuator, similar to the first pressing shaft 11.

[0108] (7) In the embodiment described above, the first workpiece W10 was irradiated with laser light L to heat the surface layer 71 from the first temperature before heating to the second temperature at which plastic deformation occurs, and then cooled to the first temperature before performing the joining process. However, the invention is not limited to this, and the temperature of the surface layer 71 when the joining process is started may be higher than the first temperature, as long as it is the temperature at which the protrusions 70 are formed by cooling. Therefore, the temperature of the surface layer 71 when the joining process is started may be lower than the second temperature and correspond to a third temperature at which the expansion force acting on the surface layer 71 is suppressed.

[0109] <Description of the effects of the embodiment> The embodiments described above can be obtained to achieve the following effects.

[0110] (1) As shown in Figures 1, 2, and 5, the solid-phase bonding apparatus 1 of Embodiment 1 heats the surface layer 71 of the first workpiece W10 with a heating device 13 so that the surface layer 71 in a part of the first surface side where the pair of pressurizing shafts 11 and 12 contact is subjected to a force that causes plastic deformation of the surface layer 71, and then performs a first control (steps S1 to S6) in which the heating device 13 stops heating the surface layer 71 so that the surface layer 71 is cooled and the first workpiece W10 protrudes to the second surface side opposite the first surface side. This makes it possible to provide a portion of the first workpiece W10 that protrudes to the second surface side without operating the pair of pressurizing shafts 11 and 12. Then, as shown in Figures 1, 4, and 6, a second control (steps S11 to S17) is performed to join the first workpiece W10 and the second workpiece W20, which are in contact via a protrusion 70 protruding from the second surface side of the first workpiece W10. This second control involves applying a current X from a pair of electrodes 21 and 22 to the area on the first workpiece W10 where the protrusion 70 protruding from the second surface side of the first workpiece W10 is in contact with the second workpiece W20, and applying pressure from a pair of pressure shafts 11 and 12 from both sides in the thickness direction of the first workpiece W10 and the second workpiece W20, thereby solid-phase joining the first workpiece W10 and the second workpiece W20, which are in contact via the protrusion 70 protruding from the second surface side of the first workpiece W10. This allows for solid-state bonding of the first workpiece W10 and the second workpiece W20 even when the two workpieces to be joined have different hardnesses, by maintaining point contact or line contact between them. Therefore, even when the two workpieces to be joined have different hardnesses, a decrease in bonding strength can be suppressed.

[0111] (2) As shown in Figures 1, 2, and 5, the solid-state bonding apparatus of Embodiment 1 is configured such that the control device 30 controls the heating device 13 in the first control (steps S1 to S6) to heat the surface layer 71 on the first side from a first temperature to a second temperature, and the second temperature is the temperature at which the surface layer 71 on the first side undergoes plastic deformation when the expansion force F1 generated in response to heating from the heating device 13 and the compressive force F2 that the surface layer 71 on the first side receives from the surroundings against the expansion force F1 are in equilibrium. Therefore, when heating of the surface layer 71 on the first side by the heating device 13 is stopped in the first control (steps S1 to S6), the expansion force F1 on the surface layer 71 on the first side decreases, and the compressive force F2 becomes greater than the expansion force F1, so the balance between the expansion force F1 and the compressive force F2 is lost. Then, when the surface layer 71 is heated to the second temperature, it undergoes plastic deformation, and the compressive force F2 acts mainly around the surface layer 71 of the first workpiece W10, causing the area around the surface layer 71 of the first workpiece W10 to warp away from the second workpiece W20. As a result, in the first control, the first workpiece W10 can be made to protrude to the second surface side opposite the first surface side.

[0112] (3) As shown in Figures 1, 2, and 5, the solid-state bonding apparatus of Embodiment 1 is configured such that after heating of the surface layer 71 on the first side by the heating device 13 stops, the control device 30 executes the second control (steps S11 to S17) when the surface layer 71 on the first side has cooled to a third temperature (first temperature) which is lower than the second temperature and suppresses the expansion force F1. Therefore, when heating of the surface layer 71 on the first side by the heating device 13 stops, the expansion force F1 in the surface layer 71 on the first side decreases significantly, and the compressive force F2 becomes even greater than the expansion force F1. As a result, the amount of deformation that causes the periphery of the surface layer 71 to warp away from the second workpiece W20 becomes even greater.

[0113] (4) As shown in Figures 1 and 2, the solid-phase bonding apparatus of Embodiment 1 heats the surface layer 71 on the first surface side by irradiating the first workpiece W10 with laser light L using the heating device 13. Therefore, the surface layer 71 can be easily heated by adjusting the output of the laser light L, etc.

[0114] (5) In the solid-state bonding apparatus 1 of Embodiment 1, as shown in Figures 1 and 2, the heating device 13 irradiates the surface layer 71 on the first surface side with laser light L through a through hole 50 provided in one of the pair of pressurizing shafts 11 and 12. This allows the laser light L to be irradiated onto the surface layer 71 on the first surface side in such a way that it does not interfere with the structure included in the solid-state bonding apparatus 1.

[0115] (6) The solid-phase bonding apparatus 1A of Embodiment 2 can provide a portion that protrudes to the fourth surface of the second workpiece W20 by heating the surface layer on the third surface side of the second workpiece W20 with the heating device 13A and then cooling it. As a result, when solid-phase bonding the first workpiece W10 and the second workpiece W20, in addition to providing a portion that protrudes to the second surface side of the first workpiece W10, a portion that protrudes to the fourth surface side of the second workpiece W20 can be provided. Then, while applying current from a pair of electrodes 21 and 22 to the first workpiece W10 and the second workpiece W20, which are in contact via protruding portions of the first workpiece W10 and the second workpiece W20, the area where the first workpiece W10 and the second workpiece W20 are in contact is pressed from both sides in the thickness direction of the first workpiece W10 and the second workpiece W20 with a pair of pressure shafts 11 and 12. This allows for solid-state bonding of the first workpiece W10 and the second workpiece W20, which are in contact via protruding portions of the second surface side of the first workpiece W10 and the second workpiece W20. As a result, even if the hardness of the two workpieces to be bonded is different, the first workpiece W10 and the second workpiece W20 can be solid-state bonded while they are in point contact or line contact. Therefore, even if the hardness of the two workpieces to be bonded is different, a decrease in bonding strength can be suppressed.

[0116] <Summary> (1) The solid-phase bonding apparatus of the present disclosure (solid-phase bonding apparatus 1, 1A) comprises a pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12) that press a conductive first workpiece (first workpiece W10) and a second workpiece (second workpiece W20) that overlap in the thickness direction from both sides in the thickness direction, 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), a heating device (heating device 13), and the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12), The device comprises a pair of electrodes (first electrode 21, second electrode 22) and a control device (control device 30) that controls the heating device (heating device 13). The control device (control device 30) heats the surface portion (surface portion 71) on the first surface side of the first workpiece (first workpiece W10) with the heating device (heating device 13) so that the surface portion (surface portion 71) in a portion of the first surface side that is in contact with one of the pair of pressurizing shafts receives a force that causes plastic deformation of the surface portion (surface portion 71) on the first surface side, and then the heating device (heating device 13) A first control (steps S1 to S6) is performed to stop heating the surface portion (surface portion 71) on the first surface side by the heating device (heating device 13) so that the first workpiece (first workpiece W10) is cooled and protrudes to the second surface side opposite to the first surface side, and a current (current) is supplied from the pair of electrodes to the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) that are in contact with each other via the portion (protrusion 70) of the first workpiece (first workpiece W10) that protrudes to the second surface side, and While flowing X), a second control (steps S11 to S17) is performed in which the region where the portion of the first workpiece (first workpiece W10) that protrudes toward the second surface side contacts the second workpiece (second workpiece W20) is pressed from both sides in the thickness direction of 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) to join the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20).

[0117] With this configuration, in the first workpiece, the surface layer of a portion of the surface on the first surface side where the pair of pressurizing shafts contact is heated by a heating device so that it receives a force that causes plastic deformation. Then, a first control is performed to stop heating the surface layer by the heating device so that the surface layer cools and the first workpiece protrudes to the second surface side opposite the first surface side. This makes it possible to create a portion of the first workpiece that protrudes to the second surface side without operating the pair of pressurizing shafts. Then, with respect to the first and second workpieces that are in contact via the portion of the first workpiece that protrudes to the second surface side, a second control is performed to press the region in the first workpiece where the portion protruding to the second surface side contacts the second workpiece with the pair of pressurizing shafts from both sides in the thickness direction of the first and second workpieces while flowing current from a pair of electrodes, thereby joining the first and second workpieces. This makes it possible to solid-state join the first and second workpieces that are in contact via the portion protruding to the second surface side of the first workpiece. This allows for solid-state bonding of the first and second workpieces even when they have different hardnesses, by maintaining point or line contact between them. Therefore, even when the two workpieces to be joined have different hardnesses, a decrease in bonding strength can be suppressed.

[0118] (2) In the solid-phase bonding apparatus (solid-phase bonding apparatus 1, 1A) described in (1), the control device (control device 30) controls the heating device (heating device 13) in the first control (steps S1 to S6) to heat the surface layer (surface layer 71) on the first surface side from a first temperature (first temperature) to a second temperature (second temperature), and the first temperature (first temperature) is when the surface layer (surface layer 71) on the first surface side is heated by the heating device (heating device 13) The second temperature is the temperature at which the surface layer (surface layer 71) on the first surface undergoes plastic deformation when the expansion force (expansion force F1) generated in response to heating from the heating device (heating device 13) and the compressive force (compressive force F2) that the surface layer (surface layer 71) on the first surface receives from its surroundings against the expansion force (expansion force F1) are in equilibrium.

[0119] With this configuration, the control device controls the heating device in the first control to heat the surface layer on the first side from a first temperature to a second temperature, and the second temperature is the temperature at which the surface layer on the first side undergoes plastic deformation when the expansion force generated in response to heating from the heating device and the compressive force that the surface layer on the first side receives from its surroundings against the expansion force are balanced. Therefore, in the first control, when heating of the surface layer on the first side by the heating device is stopped, the expansion force on the surface layer on the first side decreases, and the compressive force becomes greater than the expansion force, so the balance between the expansion force and the compressive force is lost. Then, when the surface layer is heated to the second temperature, it undergoes plastic deformation, and the compressive force acts mainly around the surface layer of the first workpiece, causing the area around the surface layer of the first workpiece to warp away from the second workpiece. As a result, in the first control, the first workpiece can be made to protrude to the second side, which is opposite to the first side.

[0120] (3) In the solid-phase bonding apparatus (solid-phase bonding apparatus 1, 1A) described in (2), the control device (control device 30) executes the second control (steps S11 to S17) when the heating of the surface portion (surface portion 71) on the first surface side by the heating device (heating device 13) has stopped, and the surface portion (surface portion 71) on the first surface side has cooled to a third temperature (first temperature, etc.) which is lower than the second temperature and suppresses the expansion force (expansion force F1).

[0121] With this configuration, the control device performs the second control after the heating of the first surface layer by the heating device has stopped, and the first surface layer has cooled to a third temperature lower than the second temperature, where the expansion force is suppressed. Therefore, when the heating of the first surface layer by the heating device stops, the expansion force in the first surface layer decreases significantly, and the compressive force becomes even greater than the expansion force. As a result, the amount of deformation that causes the periphery of the surface layer to warp away from the second workpiece becomes even greater. Consequently, in the first control, the amount of protrusion of the first workpiece to the second surface on the opposite side of the first surface can be increased even further.

[0122] (4) In any of the solid-phase bonding apparatuses (1, 1A) described in (1) to (3), the heating apparatus (heating apparatus 13) heats the surface layer (surface layer 71) on the first surface side by irradiating the first workpiece (first workpiece W10) with laser light (laser light L).

[0123] With this configuration, the heating device heats the surface layer on the first side of the workpiece by irradiating it with laser light, so the surface layer can be easily heated by adjusting the output of the laser light, etc.

[0124] (5) In the solid-phase bonding apparatus (solid-phase bonding apparatus 1, 1A) of (4), in the solid-phase bonding apparatus (solid-phase bonding apparatus 1) of (4), one of the pair of pressurizing shafts (first pressurizing shaft 11) is provided with a through hole (through hole 50) that penetrates in the axial direction, and the heating device (heating device 13) irradiates the laser light (laser light L) through the through hole (through hole 50) onto the surface layer (surface layer 71) on the first surface side.

[0125] With this configuration, the heating device irradiates the surface layer on the first side with laser light through a through-hole provided in one of the pair of pressurizing shafts, so that the laser light is irradiated onto the surface layer on the first side without interference between the structure included in the solid-state bonding device and the laser light.

[0126] (6) In the solid-phase bonding apparatus (solid-phase bonding apparatus 1, 1A) of (1) above, the heating apparatus (heating apparatus 13) includes a first heating apparatus (heating apparatus 13) and a second heating apparatus (heating apparatus 13A), and the control device (control device 30) is configured such that the third heating apparatus (control device 30) receives a force that causes plastic deformation of a portion of the surface layer (a surface layer similar to the surface layer 71) in a part of the third surface side where the other of the pair of pressurizing shafts (first pressurizing shaft 11, second pressurizing shaft 12) contacts the second workpiece (second workpiece W20). After heating the surface layer portion on the face side (a surface layer portion similar to the surface layer portion 71) with the second heating device (heating device 13A), the heating of the surface layer portion on the third face side (a surface layer portion similar to the surface layer portion 71) by the second heating device (heating device 13A) is stopped so that the surface layer portion on the third face side (a surface layer portion similar to the surface layer portion 71) is cooled and the second workpiece (second workpiece W20) protrudes to the fourth face side opposite the third face side. This is done in a third control (steps S1 to S6 which are replaced in Embodiment 2). ) and, instead of the second control (steps S11 to S17), the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20), which are in contact via the portion (protrusion 70) protruding from the second surface side of the first workpiece (first workpiece W10) and the portion (protrusion similar to the protrusion 70) protruding from the fourth surface side of the second workpiece (second workpiece W20), are subjected to the current (current X) flowing from the pair of electrodes (first electrode 21, second electrode 22). A fourth control (steps S11 to S17, which are replaced in Embodiment 2) is performed to join the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) by pressing the area where the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20) are in contact with the pair of pressure shafts (first pressure shaft 11, second pressure shaft 12) from both sides in the thickness direction of the first workpiece (first workpiece W10) and the second workpiece (second workpiece W20).

[0127] With this configuration, by heating the surface layer on the third side of the second workpiece with the heating device 13A and then cooling it, a portion protruding to the fourth side of the second workpiece can be provided. This allows for solid-state bonding of the first workpiece W10 and the second workpiece W20, not only to provide a portion protruding to the second side of the first workpiece, but also to provide a portion protruding to the fourth side of the second workpiece. Then, while applying current from a pair of electrodes to the first and second workpieces that are in contact via the protruding portion of the first workpiece and the protruding portion of the second workpiece, the area in contact between the first and second workpieces is pressed from both sides in the thickness direction of the first and second workpieces with a pair of pressure shafts, thereby enabling solid-state bonding of the first and second workpieces that are in contact via the protruding portion of the second side of the first workpiece and the protruding portion of the second workpiece. This allows for solid-state bonding of the first and second workpieces even when they have different hardnesses, by maintaining point or line contact between them. Therefore, even when the two workpieces to be joined have different hardnesses, a decrease in bonding strength can be suppressed.

[0128] 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]

[0129] 1,1A Solid-phase bonding apparatus, W10 First workpiece, W20 Second workpiece, 11 First pressurizing shaft, 12 Second pressurizing shaft, 21 First electrode, 22 Second electrode, 13 Heating device, 30 Control device, 71 Surface layer, 70 Protruding part, X Current, F1 Expansion force, F2 Compression force, L Laser light, 50 Through hole.

Claims

1. A pair of pressurizing shafts that press a first workpiece and a second workpiece, which are conductive and overlap in the thickness direction, from both sides in the thickness direction, A pair of electrodes are arranged around the pair of pressure shafts, Heating device, The heating device comprises the pair of pressurizing shafts, the pair of electrodes, and a control device for controlling the heating device. The control device is In the first workpiece, the heating device is used to heat the surface layer of a portion of the first surface where one of the pair of pressurizing shafts contacts, so that the surface layer of that portion receives a force that causes plastic deformation. Then, the heating device is used to stop heating the surface layer of the first surface so that the surface layer of the first surface cools down and the first workpiece protrudes to the second surface on the opposite side of the first surface. A solid-phase bonding apparatus that performs a second control to join the first workpiece and the second workpiece, by applying current from the pair of electrodes to the area in the first workpiece where the portion protruding to the second surface side of the first workpiece is in contact with the second workpiece, using the pair of pressure shafts on both sides in the thickness direction of the first workpiece and the second workpiece.

2. In the first control, the control device controls the heating device to heat the surface layer on the first side from a first temperature to a second temperature. The first temperature is the temperature at which the surface layer on the first side is not heated by the heating device. The solid-phase bonding apparatus according to claim 1, wherein the second temperature is the temperature at which the surface layer on the first surface undergoes plastic deformation when the expansion force of the surface layer on the first surface, generated in response to heating from the heating device, and the compressive force that the surface layer on the first surface receives from the surroundings against the expansion force are in equilibrium.

3. The solid-phase bonding apparatus according to claim 2, wherein the control device executes the second control after the heating of the surface layer on the first surface by the heating device has stopped, and the surface layer on the first surface has cooled to a third temperature which is lower than the second temperature and suppresses the expansion force.

4. The solid-phase bonding apparatus according to claim 1 or claim 2, wherein the heating device heats the surface layer on the first surface side by irradiating the first workpiece with laser light.

5. One of the pair of pressurizing shafts is provided with a through hole that penetrates in the axial direction. The solid-phase bonding apparatus according to claim 4, wherein the heating device irradiates the surface layer on the first surface side with the laser light through the through hole.

6. The heating device includes a first heating device and a second heating device. The control device is In the second workpiece, the surface layer on the third surface side, where the other of the pair of pressurizing shafts makes contact, is heated by the second heating device so that it receives a force that causes plastic deformation of the surface layer on that side. Then, a third control is performed to stop heating the surface layer on the third surface side by the second heating device so that the surface layer on the third surface side cools down and the second workpiece protrudes to the fourth surface side opposite the third surface side. The solid-phase bonding apparatus according to claim 1, wherein, instead of the second control, a fourth control is performed in which, with respect to the first workpiece and the second workpiece that are in contact via a portion of the first workpiece protruding to the second surface side and a portion of the second workpiece protruding to the fourth surface side, a current is passed from the pair of electrodes, and the region in which the first workpiece and the second workpiece are in contact is pressed from both sides in the thickness direction of the first workpiece and the second workpiece with the pair of pressure shafts to join the first workpiece and the second workpiece.

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