Bonding device and method for manufacturing bonded body

Abstract

To provide a joining device and a manufacturing method for a joining body that are able to prevent scattering of spatter.SOLUTION: A joining device has a laser device, a temperature sensor, and a control device. The laser device emits a laser beam to a laser emission area set on a surface of one of two metal members while movement of the overlapped two metal members in an overlapping direction is kept restricted. Thus, heat for generating solid phase diffusion is applied to a joining interface of the two metal members. The control device controls output of the laser device, based on a surface temperature of a laser emission area detected through the temperature sensor. After starting continuous emission of a laser beam to the laser emission region, the control device switches to intermittent emission of a laser beam before the surface temperature of the laser emission region reaches the melting point of the metal member that is an emission target of the laser beam.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a bonding apparatus and a method for manufacturing a bonded body. [Background technology]

[0002] Conventionally, there are devices that bond two metal members by irradiating them with laser light. For example, Patent Document 1 describes a bonding device that bonds two metal members by solid-phase diffusion bonding. Solid-phase diffusion bonding is a method in which two metal members to be bonded are brought into close contact with each other, pressurized to a degree that minimizes plastic deformation under a temperature condition below the melting point of these metal members, and bonded by utilizing the diffusion of atoms that occurs between the bonding surfaces.

[0003] The bonding device of Patent Document 1 has a restricting member and a heating device. The restricting device restricts the movement of the two overlapping metal members in the overlapping direction (movement in the direction opposite to the bonding interface). The heating device irradiates a laser beam onto the surface of one of the two metal members while the movement of the two metal members is restricted by the restricting device. This provides heat to generate solid-phase diffusion at the bonding interface between the two metal members.

[0004] Heat is applied to the bonding interface between two metal components to cause solid-state diffusion, which causes the metal components to thermally expand. Because the movement of the two metal components in the overlapping direction is restricted, the bonding interface is pressurized by the thermal expansion of the metal components. As a result, the bonding interface between the two metal components is brought into close contact, and solid-state diffusion occurs at the bonding interface between the two metal components, joining the two metal components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-35960 A Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when joining metal members with a lower absorption rate of laser light, it is possible to increase the laser output to provide heat to generate solid-phase diffusion at the joining interface between the two metal members. However, when a high-power laser light is irradiated onto the metal members, the parts of the metal members irradiated with the laser light melt instantly, and the molten metal starts to evaporate. The pressure of the metal vapor that accompanies this evaporation can cause the molten metal to scatter as spatter.

[0007] An object of the present invention is to provide a bonding apparatus and a method for manufacturing a bonded body capable of suppressing scattering of spatter. [Means for solving the problem]

[0008] A joining device capable of achieving the above object includes a laser device that applies heat for generating solid-phase diffusion at a joining interface between two overlapping metal members by irradiating a laser beam to a laser irradiation area set on one of the surfaces of the two overlapping metal members while restricting the movement of the two overlapping metal members in the overlapping direction, a sensor that detects the surface temperature of the laser irradiation area irradiated with the laser beam, and a control device that controls the output of the laser device based on the surface temperature of the laser irradiation area detected by the sensor. After starting continuous irradiation of the laser beam to the laser irradiation area, the control device switches to intermittent irradiation of the laser beam before the surface temperature of the laser irradiation area reaches the melting point of the metal member that is the target of irradiation with the laser beam.

[0009] According to this configuration, the surface temperature of the laser irradiation area, and therefore the temperature of the joining interface between the two metal members, repeatedly rises and falls. The surface temperature of the laser irradiation area repeatedly rises and falls, which prevents the surface temperature of the laser irradiation area from reaching the melting point of the metal member that is the target of the laser light irradiation. This prevents the molten metal from scattering as sputters.

[0010] In addition, as the temperature of the bonding interface repeatedly rises and falls, the pressure at the bonding interface also repeatedly rises and falls. That is, the bonding interface is pressurized intermittently, so that the pressure required for bonding the two metal members is compensated for. This promotes the bonding of the two metal members. Therefore, it is possible to further shorten the processing time required for bonding the two metal members while suppressing the generation of spatter.

[0011] In the above-mentioned joining device, the control device may start irradiating the laser irradiation area with continuous laser light, and then, when the surface temperature of the laser irradiation area reaches a value close to the melting point of the metal component that is the target of irradiating with the laser light, reduce the output of the laser device and switch to irradiating with intermittent laser light.

[0012] According to this configuration, the surface temperature of the laser irradiated region is preferably prevented from reaching the melting point of the metal member that is the target of the laser light irradiation. In the above joining apparatus, the laser device may irradiate laser light having a higher absorption rate in the metal member that is the target of irradiation with the laser light than an infrared laser.

[0013] According to this configuration, it is possible to heat the metal member more stably, and also to more easily control the temperature of the metal member. A method for manufacturing a bonded body that can achieve the above object is to bond two overlapping metal members by applying heat for generating solid-phase diffusion at the bonding interface between the two metal members through irradiation of a laser beam to a laser irradiation area set on the surface of one of the two metal members while restricting the movement of the two overlapping metal members in the overlapping direction. In this manufacturing method, after starting continuous irradiation of the laser beam to the laser irradiation area, the irradiation is switched to intermittent laser beam irradiation before the surface temperature of the laser irradiation area reaches the melting point of the metal member that is the target of the laser beam irradiation.

[0014] According to this manufacturing method, the surface temperature of the laser irradiation area, and therefore the temperature of the joining interface between the two metal members, repeatedly rises and falls. By repeatedly rising and falling the surface temperature of the laser irradiation area, the surface temperature of the laser irradiation area is prevented from reaching the melting point of the metal member that is the target of the laser light irradiation. This prevents the molten metal from scattering as sputters.

[0015] In addition, as the temperature of the bonding interface repeatedly rises and falls, the pressure at the bonding interface also repeatedly rises and falls. That is, the bonding interface is pressurized intermittently, so that the pressure required for bonding the two metal members is compensated for. This promotes the bonding of the two metal members. Therefore, it is possible to further shorten the processing time required for bonding the two metal members while suppressing the generation of spatter.

[0016] In the above-mentioned method for manufacturing a joint body, after starting continuous irradiation of the laser light to the laser irradiation region, when the surface temperature of the laser irradiation region reaches a value close to the melting point of the metal member that is the target of the laser light irradiation, the output of the laser light may be reduced and then the irradiation of the laser light may be switched to intermittent irradiation.

[0017] According to this manufacturing method, the surface temperature of the laser irradiated region is suitably prevented from reaching the melting point of the metal member that is the target of the laser light irradiation. In the above-described method for producing a bonded body, the laser beam may be laser beam having a higher absorption rate in the metal member that is the target of the laser beam than an infrared laser.

[0018] According to this manufacturing method, it is possible to heat the metal member more stably, and also to more easily control the temperature of the metal member. Effect of the Invention

[0019] According to the bonding apparatus and the method for manufacturing a bonded body of the present invention, scattering of spatter can be suppressed. [Brief description of the drawings]

[0020] [Figure 1] 1 is a front view of a joined body formed by joining two parts using an embodiment of the joining device; [Diagram 2] FIG. 1 is a diagram showing a schematic configuration of a joining device according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a cross-sectional view of a main part of the bonding device, illustrating a state in which a wiring member is heated according to the embodiment; [Figure 4] 4 is a two-dimensional model of a bonded interface showing atomic flow at the bonded interface between two metal members according to one embodiment. [Diagram 5] 4 is a graph showing an example of a first laser irradiation pattern in one embodiment. [Figure 6] 6 is a graph showing an example of a temperature change of a laser irradiation unit in one embodiment. [Figure 7] 4 is a graph showing an example of a first laser irradiation pattern in one embodiment. [Figure 8] 5 is a graph showing an example of a temperature change in a laser irradiated portion and a pressure change at a joining interface when a metal member is irradiated with a laser according to an embodiment in a first irradiation pattern. [Figure 9] 6 is a graph showing an example of a second laser irradiation pattern in one embodiment. [Figure 10] 6 is a graph showing an example of a temperature change in a laser irradiated portion and a pressure change at a joining interface when a metal member is irradiated with a laser according to an embodiment in a second irradiation pattern. [Figure 11] 2 is a two-dimensional model of a joint interface between two metal members according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An embodiment of a joining device will be described below. The joining device is a device that joins two components that are made of metal or contain a metal part by using a laser beam as an electromagnetic wave beam. First, an example of a joined body formed by joining two parts will be described.

[0022] 1, the bonded body 11 is formed by bonding an electrode member 14 provided on a substrate 12 to a wiring member 15. The electrode member 14 is a metal member made of copper (Cu) in the form of a flat plate or thin film. However, the electrode member 14 may be plated with nickel (Ni) or the like. The wiring member 15 is a metal member such as a bus bar or lead frame made of copper in the form of a flat plate.

[0023] The electrode member 14 and the wiring member 15 are bonded by solid-phase diffusion bonding. Solid-phase diffusion bonding refers to a method of bonding two base materials (here, the electrode member 14 and the wiring member 15) to be bonded by closely contacting them and applying pressure to an extent that causes minimal plastic deformation at a temperature condition below the melting points of these base materials, utilizing the diffusion of atoms that occurs between the bonding surfaces.

[0024] Next, the joining device will be described. As shown in FIG. 2, the bonding device 21 includes a support table 22, a regulating member 23, a driving device 24, a laser device 25 as a heating device, a temperature sensor 26, and a control device 27.

[0025] The support base 22 has a mounting surface 22a on which the substrate 12 and the wiring members 15 are placed. The substrate 12 is placed on the mounting surface 22a with the electrode members 14 facing upward (the side opposite to the mounting surface 22a). The wiring members 15 are placed on top of the electrode members 14.

[0026] The restricting member 23 is provided in a flat plate shape. The restricting member 23 is parallel to the mounting surface 22a of the support base 22. The restricting member 23 has a first portion 31 and a second portion 32.

[0027] The first portion 31 is made of a metal material such as carbon steel or stainless steel and has a flat plate shape. The first portion 31 is provided with a hole 23a penetrating in its thickness direction (the vertical direction in FIG. 2). In the first portion 31, the hole 23a has an inner peripheral edge at an opening on the side opposite the mounting surface 22a (the upper side in FIG. 2) of the hole 23a, which has a tapered surface that increases in diameter toward the side opposite the mounting surface 22a.

[0028] The second portion 32 is provided inside the hole 23a of the first portion 31. The second portion 32 covers the opening of the hole 23a on the mounting surface 22a side (the lower side in FIG. 2). The second portion 32 is provided in a flat plate shape and made of a material that transmits laser light, such as sapphire, diamond, calcium fluoride, silicon carbide (SiC), and silicon (Si). The thickness of the second portion 32 is set to be thinner than the thickness of the first portion 31. The bottom surface of the second portion 32 and the bottom surface of the first portion 31 are flush with each other (i.e., there is no step).

[0029] The restricting member 23 is provided so as to be movable along a direction perpendicular to the placement surface 22a. The restricting member 23 moves between an initial position P1 and a restricting position P2. The initial position P1 is a position higher than a height H of the upper surface of the wiring member 15 based on the placement surface 22a when the board 12 and the wiring member 15 are placed on the placement surface 22a. The restricting position P2 is a position at a height approximately equal to the height H based on the placement surface 22a when the board 12 and the wiring member 15 are placed on the placement surface 22a. Incidentally, in FIG. 2, the initial position P1 and the restricting position P2 indicate the positions of the lower surface (the side surface on the placement surface 22a side) of the restricting member 23.

[0030] The restricting member 23 and the mounting surface 22a of the support base 22 cooperate with each other to form a restricting device that restricts the movement of the two metal members (here, the electrode members 14 and the wiring members 15) in the overlapping direction without pressing these metal members against each other. The overlapping direction of the two metal members is also perpendicular to the mounting surface 22a.

[0031] The driving device 24 moves the regulating member 23 in a direction perpendicular to the placement surface 22a. The driving device 24 has a driving source such as a motor or a cylinder, and a transmission mechanism that transmits the power generated by the driving source to the regulating member 23. In FIG. 2, the power transmission from the driving device 24 to the regulating member 23 is indicated by a dashed line. The driving device 24 also has a fixing mechanism that fixes the regulating member 23 at the regulating position P2 when the regulating member 23 is moved from the initial position P1 to the regulating position P2. As the fixing mechanism, for example, a brake mechanism or a lock mechanism that regulates the movement of the driving source or the transmission mechanism is used.

[0032] The laser device 25 irradiates the surface of the wiring member 15 with laser light L through the hole 23a of the first portion 31 of the restricting member 23 and the second portion 32. The temperature sensor 26 detects, in a non-contact manner, the surface temperature of a laser irradiation area 15a which is an area on the surface of the wiring member 15 that is irradiated with the laser light L. The laser irradiation area 15a is an area exposed from the hole 23a via the second portion 32 of the restricting member 23.

[0033] The control device 27 controls the operation of the driving device 24 and the laser device 25. The control device 27 moves the restricting member 23 between the initial position P1 and the restricting position P2 through the driving device 24. The control device 27 also estimates the temperature of the joint interface Sb between the electrode member 14 and the wiring member 15 based on the surface temperature of the laser irradiation area 15a detected by the temperature sensor 26. The joint interface Sb refers to the boundary between two joint surfaces 14a, 15b which are the parts of the electrode member 14 and the wiring member 15 which are joined to each other. The joint surface 14a is the surface of the electrode member 14 (the interface on the wiring member 15 side). The joint surface 15b is the back surface of the wiring member 15 (the interface on the electrode member 14 side). The control device 27 adjusts the output of the laser device 25 based on the temperature of the joint interface Sb.

[0034] The control device 27 has a memory device 27a. The memory device 27a stores a target temperature T * The target temperature T *is the target value of the temperature of the bonding interface Sb required to properly bond the electrode member 14 and the wiring member 15. * is set to a temperature within a range of not less than the lowest temperature at which the metal members (14, 15) to be joined can be solid-phase diffusion bonded (for example, about 200°C in the case of copper) and not more than the melting point of the metal members (14, 15) to be joined.

[0035] Target temperature T * is set based on the relationship between the bonding rate between the electrode member 14 and the wiring member 15 and the temperature of the bonding interface Sb. The bonding rate is the ratio of the true bonding area, which is the area of ​​the actually bonded portion of the bonding interface Sb, to the total area of ​​the true bonding area and the apparent bonding area, which is the area of ​​the portion of the bonding interface Sb that is not actually bonded. The relationship between the bonding rate and the temperature of the bonding interface Sb can be obtained by experiment or simulation. For example, the bonding rate gradually increases with an increase in the temperature of the bonding interface Sb, and eventually the bonding rate becomes a constant value regardless of the temperature. When bonding the electrode member 14 and the wiring member 15, a target bonding rate is first determined, and a target temperature T * is determined.

[0036] The control device 27 controls the temperature of the bonding interface Sb to a target temperature T * The irradiation conditions of the laser light L are controlled so as to coincide with the above. The irradiation conditions of the laser light L include, for example, the irradiation power and the irradiation time. As the irradiation power and the irradiation time of the laser light L increase, the temperature of the bonding interface Sb increases.

[0037] Next, a method for producing the bonded body 11 will be described. However, the substrate 12 on which the electrode members 14 are provided is prepared in advance. In addition, in the bonding device 21, the regulating member 23 is held at the initial position P1. The substrate 12 is placed on the placement surface 22a with the electrode members 14 facing upward. The wiring members 15 are placed on the electrode members 14. In this state, the operation of the bonding device 21 is started.

[0038] As shown in FIG. 3, the control device 27 moves the regulating member 23 from the initial position P1 to the regulating position P2 through the driving device 24. As a result, the lower surface (the side surface on the mounting surface 22a side) of the regulating member 23 is maintained in contact with the upper surface (the side surface opposite to the electrode member 14) of the wiring member 15. At this time, the wiring member 15 is not actively pressed against the electrode member 14 against the movement in the overlapping direction. The substrate 12 on which the electrode member 14 is provided and the wiring member 15 are sandwiched between the mounting surface 22a and the regulating member 23, so that the movement of the electrode member 14 and the wiring member 15 in the directions D1 and D2 (directions perpendicular to the mounting surface 22a) in which they move away from each other is restricted. The directions D1 and D2 are directions perpendicular to the mounting surface 22a and are also the overlapping directions (anti-joining interface directions) of the electrode member 14 and the wiring member 15.

[0039] Next, the control device 27 irradiates the laser beam L onto the laser irradiation region 15a of the wiring member 15 via the laser device 25. The laser beam L is absorbed by the wiring member 15, thereby heating the wiring member 15. As shown by the hatched area in FIG. 3, the heat generated by the irradiation of the laser beam L is transferred from the front surface to the back surface of the wiring member 15. The control device 27 controls the laser device 25 to control the temperature of the boundary between the bonding surface 15b, which is the back surface of the wiring member 15, and the bonding surface 14a, which is the front surface of the electrode member 14, i.e., the bonding interface Sb, to finally reach the target temperature T * 3, the denser the mesh (dots) is, the higher the temperature of the region is, and the coarser the mesh is, the lower the temperature of the region is.

[0040] The wiring member 15 thermally expands with a rise in temperature due to heating. Here, the wiring member 15 expands toward the electrode member 14 side (the lower side in FIG. 3), which is the most easily deformed side, because the restricting member 23 restricts the deformation of the wiring member 15 toward the opposite side to the mounting surface 22a (the upper side in FIG. 3). Therefore, a downward pressure P generated by the thermal expansion of the wiring member 15 in the thickness direction acts on the bonding surface 14a, which is the surface of the electrode member 14. With this pressure, the peaks of the minute irregularities of the bonding surface 15b of the wiring member 15 and the bonding surface 14a of the electrode member 14 come into contact with each other and collapse, so that the bonding surface 15b and the bonding surface 14a become tightly attached to each other.

[0041] As shown in the two-dimensional model of the bonding interface in FIG. 4, immediately after the start of bonding, a void (air gap) Vs is generated at the bonding interface Sb, which is the boundary between the bonding surface 15b and the bonding surface 14a. As the adhesion between the bonding surface 15b and the bonding surface 14a progresses, atomic diffusion (surface diffusion As, interface diffusion Ab, volume diffusion Av) eventually occurs at the bonding interface Sb between the electrode member 14 and the wiring member 15. The surface diffusion As refers to diffusion that uses the surface of the void Vs as a route. The interface diffusion Ab refers to diffusion that uses the bonding interface Sb as a route. The volume diffusion Av refers to diffusion that uses the inside of the crystal (crystal lattice) as a route. Through this atomic diffusion (solid-phase diffusion) and creep deformation in the vicinity of the bonding interface Sb, the void Vs at the bonding interface Sb shrinks or disappears, and the bonding between the bonding surface 14a of the electrode member 14 and the bonding surface 15b of the wiring member 15 progresses. In other words, as the voids Vs shrink and disappear, the apparent bonded area, which is the area of ​​the parts of the bonded interface Sb that are not actually bonded, decreases, while the true bonded area, which is the area of ​​the parts of the bonded interface Sb that are actually bonded, increases.

[0042] The control device 27 controls the temperature of the bonding interface Sb to a target temperature T *When the bonding ratio reaches 1, this state is continued for a predetermined heating time. As a result, the shrinkage and disappearance of the voids Vs progresses due to creep deformation and atomic diffusion in the vicinity of the bonding interface Sb. That is, as the shrinkage and disappearance of the voids Vs progresses, the bonding ratio increases and eventually reaches the target bonding ratio (bonding strength). When the target bonding ratio is, for example, "1 (maximum value)", the bonding surface 14a of the electrode member 14 and the bonding surface 15b of the wiring member 15 are completely bonded over the entire target bonding range of the bonding surfaces 14a and 15b. In the portion of the bonding surfaces 14a and 15b corresponding to the bonding range where they are bonded to each other, the bonding interface Sb that existed immediately after the start of bonding has disappeared.

[0043] Here, for example, an infrared laser light is used as the laser light L. The wavelength of the infrared laser light is, for example, 1070 nm. However, copper, which is the material from which the wiring member 15 is made, has a lower absorption rate of the infrared laser light than iron or gold. For this reason, it is considered to increase the laser output in order to provide heat for generating solid-phase diffusion at the bonding interface Sb between the electrode member 14 and the wiring member 15. The laser output refers to the energy density of the laser light L.

[0044] However, metals such as copper have the property of absorbing the laser light L better in a molten state than in a solid state. Therefore, when a high-power laser light is irradiated onto the surface of the wiring member 15, the portion of the surface of the wiring member 15 irradiated with the laser light L melts instantly, and the molten metal starts to evaporate. The pressure of the metal vapor caused by this evaporation may cause the molten metal to scatter as spatter. It is considered that the scattered spatter may adhere to the surface of the substrate 12, and there is a concern that the adhesion of the spatter to electronic components or electric circuits provided on the surface of the substrate 12 may cause malfunction of the electronic components or electric circuits, for example.

[0045] For this reason, it is required to suppress scattering of sputters while bonding the electrode member 14 and the wiring member 15. Therefore, in this embodiment, the bonding device 21 has the following configuration.

[0046] The laser device 25 irradiates blue laser light as the laser light L. The wavelength of the blue laser light is, for example, 450 nm. Copper has a higher absorptivity for blue laser light than for infrared laser light. This allows the wiring member 15 to be heated more stably. In addition, the temperature of the wiring member 15 can be more easily controlled. This also allows the electrode member 14 and the wiring member 15 to be joined together without melting the wiring member 15, i.e., without changing the absorptivity of the laser light L of the wiring member 15.

[0047] The control device 27 controls the output of the laser device 25 based on the surface temperature of the laser irradiation region 15a detected by the temperature sensor 26. More specifically, the control device 27 controls the output of the laser device 25 so that the surface temperature of the laser irradiation region 15a does not exceed the melting point of the wiring member 15. The control device 27 controls the output of the laser device 25 based on a preset irradiation pattern. The irradiation pattern of the laser light L includes a plurality of irradiation patterns.

[0048] Next, as an example of the irradiation pattern of the laser light L, a first irradiation pattern will be described. As shown by the solid line in the graph of FIG. 5, in a first period T1 based on the start of irradiation of the laser light L (time t0), the laser output is basically maintained at the first laser output P11 for initial heating. However, when the surface temperature of the laser irradiation area 15a reaches a value close to the set temperature, the laser output starts to change from the first laser output P11 to the second laser output P12 for temperature maintenance (time t1). The second laser output P12 is set to a value smaller than the first laser output P11. The set temperature is set to a temperature lower than the melting point of the wiring member 15 from the viewpoint of heating the wiring member 15 to a degree that does not melt the surface of the wiring member 15. In the first period T1, a transition period T2 during which the laser output changes from the first laser output P11 to the second laser output P12 is fixed in time. In the transition period T2, the laser output gradually decreases from the first laser output P11 to the second laser output P12.

[0049] In a second period T3 based on the time when the first period T1 has elapsed (time t2), the laser output is maintained at the second laser output P12 for maintaining the temperature. The second period T3 is a period from the time when the first period T1 has elapsed until the joining of the electrode member 14 and the wiring member 15 is completed. When the joining of the electrode member 14 and the wiring member 15 is completed, the irradiation of the laser light L is stopped (time t3).

[0050] When the laser light L is irradiated in this first irradiation pattern, the surface temperature of the laser irradiated region 15a changes, for example, as follows. As shown by the solid line in the graph of Fig. 6, when irradiation of the surface of the wiring member 15 with the laser light L begins (time t0), the surface temperature of the laser irradiation region 15a gradually increases. At this time, as shown in the graph of Fig. 5, the laser output is maintained at the first laser output P11. After this, the surface temperature of the laser irradiation region 15a gradually increases to the set temperature T th After reaching the set temperature T (time t4), the surface temperature of the laser irradiation area 15a th This is because, as shown in the graph of FIG. 5, the surface temperature of the laser irradiation area 15a is maintained at the set temperature T th After the set temperature T reaches a value close to the set temperature T, the laser output is gradually changed from the first laser output P11 to the second laser output P2, and after the laser output reaches the second laser output P12, the laser output is maintained at the second laser output P12. th is the melting point T of the wiring member 15 m When the joining of the electrode member 14 and the wiring member 15 is completed and the irradiation of the laser light L is stopped (time t3), the surface temperature of the laser irradiation area 15a gradually decreases. th By maintaining the temperature at 0° C., bonding due to creep deformation in the vicinity of the bonded interface Sb in the bonding mechanism shown in Fig. 4 is promoted. This creep deformation progresses the bonding with the passage of time.

[0051] Incidentally, as a comparative example of the irradiation pattern, when the laser output is maintained at the first laser output P11 from the start of irradiation of the laser light L until the joining is completed and the irradiation of the laser light L is stopped (time t0 to time T3) as shown by the dashed line in the graph of Fig. 5, the surface temperature of the laser irradiation area 15a changes as follows. That is, as shown by the dashed line in the graph of Fig. 6, when the irradiation of the laser light L to the surface of the wiring member 15 is started (time t0), the surface temperature of the laser irradiation area 15a gradually increases. When the surface temperature of the laser irradiation area 15a reaches the set temperature T th After reaching the melting point T m After that, the surface temperature of the laser irradiated region 15a continues to rise until the joining is completed and the irradiation of the laser light L is stopped. The portion of the surface of the wiring member 15 irradiated with the laser light L may instantaneously melt and evaporate, causing spatter to fly off.

[0052] In this regard, according to the first irradiation pattern of the laser light L, the laser output is maintained at a level at which the wiring member 15 does not melt during the period from the initial stage of irradiation of the laser light L until the joining of the electrode member 14 and the wiring member 15 is completed. m Basically, the wiring member 15 does not melt, and therefore no spatter, which is molten metal, is generated.

[0053] Therefore, it is possible to bond the electrode member 14 and the wiring member 15 without generating spatter. Therefore, it is possible to eliminate the spatter inspection process and the spatter removal process. The spatter inspection process refers to a process of inspecting whether or not spatter has adhered to the substrate 12 or its electronic components, or whether or not there is a spatter mark, which is a mark caused by the adhesion of spatter. The spatter removal process refers to a process of removing spatter that has adhered to the substrate 12 or its electronic components.

[0054] In addition, since there is no scattering of spatter, spatter does not adhere to the second portion 32 of the regulating member 23. This makes it possible to suppress damage to the second portion 32 of the regulating member 23 caused by spatter. This makes it possible to reduce the running costs for maintaining the bonding device 21, such as the replacement work of the second portion 32 of the regulating member 23.

[0055] However, with the joining device 21 configured in this way, the following concerns arise. That is, copper, which is the material forming the wiring member 15, is one of the metal materials, along with gold, silver, and aluminum, whose heat absorption rate is very small compared to iron, etc. Also, the thickness of the wiring member 15 is set according to the product specifications, etc., and the thicker the wiring member 15 is, the longer it takes for heat to be conducted from the front surface of the wiring member 15 to the back surface where the laser light L is irradiated, so that it takes longer for the bonding interface Sb between the wiring member 15 and the electrode member 14 to be heated to an appropriate temperature.

[0056] Therefore, in order to appropriately heat the bonding interface Sb between the wiring member 15 as a thick plate member and the electrode member 14, and to bond the wiring member 15 and the electrode member 14 more stably, it is considered to secure a longer processing time. For example, the second period T3 during which the laser output is maintained at the second laser output P12 for maintaining the temperature is secured for a longer time. However, the longer the processing time, the longer the cycle time, which is the time for one bonding cycle, becomes. This also leads to an increase in product costs.

[0057] As shown in the graph of FIG. 7, the pressure P and temperature at the bonding interface Sb when the laser light L is irradiated onto the surface of the wiring member 15 in the same irradiation pattern as the first irradiation pattern described above were obtained by simulation, and the following results were obtained.

[0058] As shown by the dashed line in the graph of FIG. 8, the temperature T of the bonding interface Sb gradually rises with the irradiation of the laser light L. However, the slope, which is the amount of change in temperature per unit time, changes with the change in the laser output. For example, the slope when the laser light L is irradiated with the first laser output P11 is larger than the slope when the laser light L is irradiated with the second laser output P12. Therefore, the temperature T of the bonding interface Sb changes so that the slope gradually decreases with the change in the output of the laser light L from the first laser output P11 to the second laser output P12. Thereafter, the temperature T of the bonding interface Sb rises gently toward the saturation temperature.

[0059] In contrast, the pressure P at the bonding interface Sb decreases rapidly immediately after the start of irradiation with the laser light L, as shown by the solid line in the graph of Fig. 8. After that, the pressure P remains at a substantially constant level, although it fluctuates slightly. One of the reasons for this is thought to be that the temperature T at the bonding interface Sb changes little, so that thermal expansion is unlikely to occur in the wiring member 15.

[0060] In this way, when the electrode member 14 and the wiring member 15 are bonded together, if the laser output is controlled so that the surface temperature of the laser irradiation region 15a does not exceed the melting point of the wiring member 15, sputtering is suppressed, but there is a risk that an appropriate pressure P may not be applied to the bonding interface Sb. Solid-phase diffusion bonding progresses according to the temperature T and pressure P of the bonding interface Sb. For this reason, if an appropriate pressure P is not applied to the bonding interface Sb, there is a risk that an appropriate bonding state between the electrode member 14 and the wiring member 15 may not be obtained.

[0061] Therefore, in this embodiment, as the irradiation pattern of the laser light L, a second irradiation pattern is provided. As shown in the graph of FIG. 9, in a first period T1 based on the start of irradiation of the laser light L (time t0), the laser output is basically maintained at the first laser output P11 for initial heating. However, when the surface temperature of the laser irradiation area 15a reaches a value close to the set temperature, the laser output starts to change from the first laser output P11 to the second laser output P12 for maintaining the temperature (time t1). The set temperature is set to a temperature lower than the melting point of the wiring member 15. In the first period T1, a transition period T2 until the laser output reaches the second laser output P12 from the first laser output P11 is fixed in time. In the transition period T2, the laser output decreases stepwise from the first laser output P11 to the second laser output P12. In a second period T3 based on the time when the first period T1 has elapsed (time t2), the laser output is repeatedly turned on and off. That is, in the second period T3, the laser light L is repeatedly irradiated in a pulsed manner. The second period T3 is a period from the end of the first period T1 to the completion of bonding between the electrode member 14 and the wiring member 15. When the bonding between the electrode member 14 and the wiring member 15 is completed, the irradiation of the laser light L is stopped (time t3).

[0062] Incidentally, the pulse parameters are determined from the viewpoint of shortening the processing time without generating sputtering, for example, through experiments using an actual machine. Pulse parameters include, for example, on-time Ta, off-time Tb, output value P13, and the number of pulses. On-time Ta refers to the time when the laser output is on, that is, the time when the laser light L is irradiated. Off-time Tb refers to the time when the laser output is off, that is, the time when the irradiation of the laser light L is stopped. Output value P13 is the value of the laser output as the amplitude of the pulse. Although there is a balance with other parameters, for example, if the output value P13 is too large, there is a risk that the wiring member 15 will melt. For this reason, the output value P13 is set to a value between, for example, the first laser output P11 and the second laser output P12. Also, the more the number of pulses increases, the longer the processing time becomes.

[0063] When the laser light L is irradiated in the second irradiation pattern, the pressure P and temperature T of the bonding interface Sb change, for example, as follows. As shown by the dashed line in the graph of FIG. 10, in the first period T1 in which continuous laser irradiation is performed, the temperature T of the bonding interface Sb gradually rises with the irradiation of the laser light L. However, the temperature T of the bonding interface Sb changes so that the slope gradually becomes smaller with the irradiation of the laser light L. After that, the temperature T of the bonding interface Sb gently rises toward the saturation temperature. Here, in the second period T3 in which pulsed laser irradiation is performed, the temperature T of the bonding interface Sb temporarily rises at the timing when the laser light L is irradiated. Also, the temperature T of the bonding interface Sb temporarily drops at the timing when the irradiation of the laser light L is stopped. With this change in the temperature T of the bonding interface Sb, the pressure P of the bonding interface Sb also changes. That is, the pressure P of the bonding interface Sb also rises at the timing when the temperature T of the bonding interface Sb rises. Also, the pressure P of the bonding interface Sb also drops at the timing when the temperature T of the bonding interface Sb drops. That is, the pressure P at the bonding interface Sb repeatedly rises and falls due to thermal expansion of the wiring member 15 caused by temperature changes at the bonding interface Sb accompanying the pulsed laser irradiation. In this manner, the pressure P required for bonding the electrode member 14 and the wiring member 15 is supplemented by applying pressure to the bonding interface Sb in a pulsed manner. This provides the following effects.

[0064] 11, every time the bonding interface Sb is pressurized in a pulsed manner, stress is concentrated at the edge Ve of the void Vs at the bonding interface Sb, thereby facilitating bonding between the electrode member 14 and the wiring member 15.

[0065] Therefore, according to this embodiment, the following effects can be obtained. (1) After the surface temperature of the laser irradiated region 15a of the wiring member 15 is initially heated to a temperature not exceeding the melting point of the wiring member 15 through irradiation with the laser light L as the initial heating, the laser output is adjusted so as not to exceed the melting point of the wiring member 15. This prevents the wiring member 15 from melting, and thus prevents the evaporation from progressing rapidly. This prevents the molten metal from scattering as sputters.

[0066] (2) The bonding device 21 has a first irradiation pattern of the laser light L. That is, when bonding the electrode member 14 and the wiring member 15, the wiring member 15 is first irradiated with the laser light L at the first laser output P11 as initial heating. Thereafter, at the timing when the surface temperature of the laser irradiation region 15a reaches a temperature close to the melting point of the wiring member 15, the laser output is switched from the first laser output P11 to the second laser output P12. The second laser output P12 is a fixed value smaller than the first laser output P11, and is set based on the viewpoint of maintaining the surface temperature of the laser irradiation region 15a at a predetermined temperature lower than the melting point of the wiring member 15. By irradiating the laser light L with such an irradiation pattern, it is possible to suppress melting of the wiring member 15 and thus scattering of spatter.

[0067] (3) The bonding device 21 has a second irradiation pattern of the laser light L. That is, when bonding the electrode member 14 and the wiring member 15, first, the laser light L is continuously irradiated to the wiring member 15 with the first laser output P11 as initial heating. Thereafter, at the timing when the surface temperature of the laser irradiation region 15a reaches a temperature close to the melting point of the wiring member 15, the laser output is repeatedly turned on and off to perform intermittent pulsed laser irradiation on the wiring member 15. Accordingly, the surface temperature of the laser irradiation region 15a, and further the temperature T of the bonding interface Sb between the electrode member 14 and the wiring member 15, repeatedly rises and falls. This prevents the surface temperature of the laser irradiation region 15a from exceeding the melting point of the wiring member 15. In addition, as the temperature T of the bonding interface Sb repeatedly rises and falls, the pressure P of the bonding interface Sb also repeatedly rises and falls. That is, the bonding interface Sb is pressurized in a pulsed manner, so that the pressure P required for bonding the electrode member 14 and the wiring member 15 is supplemented. This promotes bonding between the electrode member 14 and the wiring member 15. Therefore, it is possible to further shorten the processing time required to bond the electrode member 14 and the wiring member 15 while suppressing the occurrence of sputtering. The second irradiation pattern of the laser light L is particularly suitable for bonding a thicker wiring member 15.

[0068] (4) After starting continuous irradiation of the laser irradiation region 15a with the laser light L, when the surface temperature of the laser irradiation region 15a reaches a value close to the melting point of the wiring member 15, the control device 27 reduces the output of the laser device 25 from the first laser output P11 to the second laser output P12 and switches to intermittent irradiation of the laser light L. This effectively prevents the surface temperature of the laser irradiation region 15a from reaching the melting point of the wiring member 15.

[0069] (5) Laser device 25 irradiates blue laser light as laser light L. Copper, which is the material from which wiring member 15 is formed, has a higher absorptance of blue laser light than infrared laser light. This allows wiring member 15 to be heated more stably. In addition, the temperature of wiring member 15 can be more easily controlled. This also allows electrode member 14 and wiring member 15 to be joined together without melting wiring member 15, i.e., without changing the absorptance of laser light L in wiring member 15.

[0070] (6) Since scattering of sputtering is suppressed, it is possible to eliminate the step of inspecting the substrate 12 or electronic components for sputtering and the step of removing the sputtering. In addition, sputtering does not adhere to the second portion 32 of the regulating member 23. This makes it possible to suppress damage to the second portion 32 of the regulating member 23 caused by sputtering. This makes it possible to reduce the running costs for maintaining the bonding device 21, such as the replacement work of the second portion 32 of the regulating member 23.

[0071] <Other embodiments> This embodiment may be modified as follows. 1, a pressure sensor 28 may be provided in the bonding device 21. The pressure sensor 28 is provided, for example, in the support base 22. The pressure sensor 28 detects the pressure caused by the thermal expansion of the wiring member 15. In this case, the control device 27 may adjust the laser output of the laser device 25 based on the temperature detected through the temperature sensor 26 and the pressure detected through the pressure sensor 28 so that the wiring member 15 does not melt. The control device 27 may also store in advance the relationship between the pressure caused by the thermal expansion of the wiring member 15 and the bonding rate, and determine that the bonding interface Sb has reached a temperature corresponding to the target bonding rate when the pressure detected by the pressure sensor 28 reaches a value corresponding to the target bonding rate.

[0072] The laser device 25 may irradiate green laser light as the laser light L. The wavelength of the green laser light is, for example, 532 nm. Any laser light may be used as long as the laser absorption rate of the metal material to be joined is higher than that of an infrared laser.

[0073] During the off time Tb when the laser output is turned off, the laser output value needs to be equal to or greater than 0 and less than the output value P13 shown in FIG. The number of pulses must be 1 or more.

[0074] The bonding device 21 is capable of bonding metal members having various shapes together, such as bonding the electrode member 14 as a pad on the substrate 12 to a metal wire, or bonding the wiring member 15 to a metal film formed on the surface of the substrate 12 by plating or the like. The bonding device 21 can also bond a surface electrode of a semiconductor element as a metal member provided on the substrate 12 to a heat dissipation member (heat sink) as another metal member. By performing a bonding method utilizing solid-phase diffusion, it is possible to bond the semiconductor element and the heat dissipation member while suppressing the thermal effect on the semiconductor element or the substrate 12.

[0075] The metal material to be joined can be not only copper, but also various other metal materials such as gold (Au), silver (Ag), aluminum (Al), aluminum silicon alloy (Al-Si type), etc. The joining device 21 can join the same kind of metals and different kinds of metals. [Explanation of symbols]

[0076] 14...Electrode member (metal member) 15...Wiring components (metal components) 15a...Laser irradiation area 21…Joining device 25...Laser device 26...Temperature sensor 27...Control device L: Laser light Sb...joint interface

Claims

1. a laser device that applies heat to generate solid-phase diffusion at a joining interface between two overlapping metal members by irradiating a laser irradiation region set on one of the surfaces of the two overlapping metal members with a laser beam while restricting the movement of the two overlapping metal members in the overlapping direction; a sensor for detecting a surface temperature of the laser irradiation area where the laser light is irradiated; a control device for controlling an output of the laser device based on a surface temperature of the laser irradiation area detected by the sensor; The control device is a joining device that starts continuous irradiation of the laser light to the laser irradiation area, and then reduces the output of the laser device and switches to intermittent irradiation of the laser light when the surface temperature of the laser irradiation area reaches a value close to the melting point of the metal component that is the target of the laser light irradiation.

2. The joining device according to claim 1 , wherein the laser device irradiates the laser light having a higher absorption rate in a metal member that is an object of irradiation with the laser light than an infrared laser.

3. A method for manufacturing a joined body, in which two overlapped metal members are joined by applying heat for generating solid-phase diffusion at a joining interface between the two metal members through irradiation of a laser beam to a laser irradiation region set on one of the surfaces of the two metal members while the movement of the two overlapped metal members in an overlapping direction is restricted, the method comprising the steps of: A method for manufacturing a joint body, in which, after starting continuous irradiation of the laser light on the laser irradiation area, when the surface temperature of the laser irradiation area reaches a value close to the melting point of the metal member that is the target of the laser light irradiation, the output of the laser light is reduced and the irradiation of the laser light is switched to intermittent irradiation.

4. The method for producing a joint body according to claim 3 , wherein the laser beam is a laser beam having a higher absorption rate in the metal member that is an object of the laser beam irradiation than an infrared laser beam.

Images