Preliminary solder forming method and preliminary solder forming device

Abstract

Disclosed is a preliminary solder forming method with which a preliminary solder is formed on an aluminum electrode that is formed from aluminum. This preliminary solder forming method includes: a disposition step in which a solder is disposed on an aluminum electrode; and a joining step in which the solder is joined to the aluminum electrode by melting and solidifying the solder with use of laser light. In the joining step, the laser light is irradiated so that the energy amount of the laser light irradiated onto the aluminum electrode is larger than the energy amount of the laser light irradiated onto the solder.

Description

Preliminary solder forming method and preliminary solder forming device

[0001] One aspect of the present disclosure relates to a pre-solder forming method and a pre-solder forming apparatus.

[0002] For example, Patent Document 1 describes a method of joining solder placed on an LSI chip to the LSI chip by irradiating the solder with laser light.

[0003] Japanese Patent Application Publication No. 9-237963

[0004] When attempting to form preliminary solder on an aluminum electrode using the above-mentioned method, the aluminum electrode does not have good wettability with respect to the solder, and therefore the solder may not be bonded well.

[0005] Therefore, an object of one aspect of the present disclosure is to provide a preliminary solder forming method and a preliminary solder forming apparatus that can successfully form preliminary solder on an aluminum electrode.

[0006] A preliminary solder forming method according to one aspect of the present disclosure is [1] "a preliminary solder forming method for forming preliminary solder on an aluminum electrode formed from aluminum, comprising: a placement step of placing solder on the aluminum electrode; and a joining step of joining the solder to the aluminum electrode by melting and solidifying the solder using laser light, wherein in the joining step, the laser light is irradiated so that the amount of energy of the laser light irradiated to the aluminum electrode is greater than the amount of energy of the laser light irradiated to the solder."

[0007] In the joining step of this preliminary solder forming method, laser light is irradiated so that the energy amount of the laser light irradiated onto the aluminum electrode is greater than the energy amount of the laser light irradiated onto the solder. This allows the aluminum electrode to be heated before the solder, and the aluminum electrode can be in a heated state by the time the solder melts. As a result, the aluminum electrode can be made more easily wetted by the solder at the joining point with the solder, making it possible to successfully join the solder to the aluminum electrode. Therefore, this preliminary solder forming method allows for successful formation of preliminary solder on the aluminum electrode. Note that "the energy amount of the laser light irradiated onto the aluminum electrode is greater than the energy amount of the laser light irradiated onto the solder" also includes the case where the energy amount of the laser light irradiated onto the solder is zero (i.e., no laser light is irradiated onto the solder).

[0008] A preliminary solder forming method according to one aspect of the present disclosure may be [2] "the preliminary solder forming method according to [1], wherein in the joining step, the aluminum electrode is irradiated with the entire laser light." In this case, the aluminum electrode can be stably heated, and yield can be improved.

[0009] A preliminary solder forming method according to one aspect of the present disclosure may be [3] "the preliminary solder forming method according to [1], wherein in the joining step, a part of the laser light is irradiated onto the aluminum electrode and the remaining part of the laser light is irradiated onto the solder." In this case, the aluminum electrode and the solder can be heated in a balanced manner, and the process can be shortened.

[0010] A preliminary solder forming method according to one aspect of the present disclosure may be [4] "the preliminary solder forming method according to any one of [1] to [3], wherein in the joining step, the laser light is irradiated so that the center of the laser light is positioned outside the solder." In this case, the laser light can be easily irradiated so that the energy amount of the laser light irradiated onto the aluminum electrode is greater than the energy amount of the laser light irradiated onto the solder.

[0011] A preliminary solder forming method according to one aspect of the present disclosure may be [5] "the preliminary solder forming method according to any one of [1] to [4], wherein in the joining step, the laser light is irradiated so that the area of ​​the laser light irradiated onto the aluminum electrode is larger than the area of ​​the laser light irradiated onto the solder." In this case, the laser light can be easily irradiated so that the energy amount of the laser light irradiated onto the aluminum electrode is larger than the energy amount of the laser light irradiated onto the solder.

[0012] A preliminary solder forming method according to one aspect of the present disclosure may be [6] "the preliminary solder forming method according to any one of [1] to [5], wherein in the joining step, the laser light is applied in a state in which a pressing member arranged on the opposite side of the solder from the aluminum electrode is in contact with the solder." In this case, the solder can be joined to the aluminum electrode more satisfactorily.

[0013] A preliminary solder forming method according to one aspect of the present disclosure may be [7] "the preliminary solder forming method according to [6], wherein the pressing member is transparent to the laser light, and in the joining step, the laser light is irradiated via the pressing member onto the surface of the aluminum electrode on which the solder is disposed." In this case, the laser light can be irradiated onto the area overlapping with the pressing member.

[0014] A preliminary solder forming method according to one aspect of the present disclosure may be [8] "the preliminary solder forming method according to any one of [1] to [7], wherein in the joining step, the laser light is irradiated in a state in which the solder is surrounded by a surrounding member when viewed from the irradiation direction of the laser light." In this case, the surrounding member can suppress movement of the molten solder, allowing for better joining of the solder to the aluminum electrode.

[0015] A preliminary solder forming method according to one aspect of the present disclosure may be [9] "the preliminary solder forming method according to [8], wherein the enveloping member is formed of epoxy glass or silicone." In this case, the thermal conductivity of the enveloping member can be reduced, and heat loss from the solder through the enveloping member can be suppressed. Furthermore, the heat resistance of the enveloping member can be increased, and damage to the enveloping member due to the temperature during processing can be suppressed.

[0016] A preliminary solder forming method according to one aspect of the present disclosure may be

[10] "the preliminary solder forming method according to [8] or [9], wherein the surrounding member is transparent to the laser light." In this case, since it is not necessary to irradiate the laser light while avoiding the surrounding member, irradiation of the laser light can be simplified.

[0017] A preliminary solder forming method according to one aspect of the present disclosure may be

[11] "the preliminary solder forming method according to any one of [1] to

[10] , wherein in the joining step, a pressing member arranged on the opposite side of the solder from the aluminum electrode is in contact with the solder, and the solder is surrounded by a surrounding member as viewed from the direction of the laser light irradiation, and the pressing member and the surrounding member are integrally formed." In this case, the use of the pressing member and the surrounding member allows the solder to be joined to the aluminum electrode more effectively. Furthermore, because the pressing member and the surrounding member are integrally formed, the number of parts can be reduced, and the working time can be shortened.

[0018] A preliminary solder forming method according to one aspect of the present disclosure may be

[12] "the preliminary solder forming method according to any one of [1] to

[11] , wherein in the joining step, the laser light is irradiated onto the surface of the aluminum electrode on which the solder is disposed." In this case, the solder can be reliably joined to the aluminum electrode.

[0019] A preliminary solder forming method according to one aspect of the present disclosure may be

[13] "the preliminary solder forming method according to any one of [1] to

[11] , wherein in the joining step, the laser light is irradiated onto a surface of the aluminum electrode opposite to the surface on which the solder is disposed." In this case, the laser light irradiation does not need to avoid the solder, and therefore the laser light irradiation can be simplified.

[0020] A preliminary solder forming method according to one aspect of the present disclosure may be

[14] "the preliminary solder forming method according to any one of [1] to

[13] , in which, in the placing step, the solder containing flux is placed on the aluminum electrode." With this preliminary solder forming method, even solder containing flux can be well bonded to the aluminum electrode.

[0021] A pre-solder formation device according to one aspect of the present disclosure is

[15] "a pre-solder formation device for forming pre-solder on an aluminum electrode made of aluminum, comprising: an irradiation unit that irradiates laser light; and a control unit that controls the irradiation unit, wherein the control unit causes the irradiation unit to irradiate the laser light so that the energy amount of the laser light irradiated to the aluminum electrode is greater than the energy amount of the laser light irradiated to the solder placed on the aluminum electrode, thereby melting and solidifying the solder, thereby joining the solder to the aluminum electrode." This pre-solder formation device enables good joining of solder to the aluminum electrode for the reasons described above.

[0022] According to one aspect of the present disclosure, it is possible to provide a preliminary solder forming method and a preliminary solder forming apparatus that can satisfactorily join solder to an aluminum electrode.

[0023] FIG. 1 is a configuration diagram of a preliminary solder forming device. FIG. 2 is a cross-sectional view illustrating a preliminary solder forming method. FIG. 3 is a flowchart illustrating the operation of the preliminary solder forming device. (a) and (b) are diagrams illustrating the irradiation position of laser light. FIG. 1 is a cross-sectional view illustrating a preliminary solder forming method of a comparative example. FIG. 2 is a cross-sectional view illustrating a preliminary solder forming method of a first modified example. FIG. 3 is a cross-sectional view showing a state in which solder is placed on flux. FIG. 4 is a cross-sectional view illustrating a preliminary solder forming method of a second modified example. FIG. 4 is a cross-sectional view illustrating a preliminary solder forming method of a third modified example. FIG. 4 is a cross-sectional view illustrating a preliminary solder forming method of a fourth modified example. FIG. 5 is a configuration diagram of a preliminary solder forming device of a fifth modified example. FIG. 5 is a flowchart illustrating the operation of the preliminary solder forming device of the fifth modified example.

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and redundant description will be omitted.

[0025] As shown in Fig. 1, the preliminary solder forming apparatus 1 includes a frame 2, an irradiation head 3 (irradiation unit), a camera 4, and a control unit 5. The preliminary solder forming apparatus 1 is an apparatus for forming preliminary solder 30 (Fig. 2) on an aluminum electrode 10 formed from aluminum. The preliminary solder 30 is solder that is formed in advance on the aluminum electrode 10 before joining it to a joining object. When soldering the aluminum electrode 10 to the joining object, for example, the preliminary solder 30 may be melted and solidified to join the aluminum electrode 10 to the joining object, or additional solder may be added onto the preliminary solder 30 to join the aluminum electrode 10 to the joining object.

[0026] In the preliminary solder forming apparatus 1, a laser beam L is irradiated from an irradiation head 3 onto an aluminum electrode 10 arranged on a frame 2. The aluminum electrode 10 is formed, for example, in the shape of a rectangular plate. Solder 20 is arranged on the aluminum electrode 10, and the solder 20 is melted and solidified using the laser beam L, thereby bonding the solder 20 to the aluminum electrode 10 and forming preliminary solder 30 on the aluminum electrode 10. Details of this bonding process will be described later.

[0027] The frame 2 has a base portion 2a and a cover portion 2b disposed on the base portion 2a. The frame 2 is formed in a box shape as a whole, and the base portion 2a constitutes its bottom wall portion. An aluminum electrode 10 to be processed is disposed on the base portion 2a. Solder 20 is disposed on the aluminum electrode 10. This solder 20 is a solder material before being joined to the aluminum electrode 10. The solder 20 may be, for example, a solder paste in which spherical metal material is covered with a resin material.

[0028] The irradiation head 3 irradiates the aluminum electrode 10 with laser light L. The irradiation head 3 is attached to the cover portion 2b of the frame 2 so as to be movable along, for example, the XY plane. The XY plane is a plane perpendicular to the Z direction, which is the direction of irradiation of the laser light L by the irradiation head 3. It is only necessary that the irradiation head 3 and the pedestal portion 2a are movable relative to each other along the XY plane, and the pedestal portion 2a may be configured as a stage that is movable along the XY plane.

[0029] The camera 4 captures an image of the aluminum electrode 10 placed on the base 2a. The camera 4 is attached to, for example, the cover 2b of the frame 2. An example of an image P captured by the camera 4 is shown in FIG.

[0030] The control unit 5 is communicably connected to each element of the preliminary solder forming apparatus 1, including the irradiation head 3 and the camera 4, and controls each element of the preliminary solder forming apparatus 1. The control unit 5 is configured by a computer including, for example, a processor such as a CPU, and storage media such as a RAM and a ROM.

[0031] A preliminary solder forming method performed by the preliminary solder forming apparatus 1 will be described. First, an aluminum electrode 10 is placed on the pedestal 2a, and solder 20 is placed on the aluminum electrode 10 (placement step). The placement step can be performed by, for example, a predetermined work machine. In the placement step, the solder 20 may be placed on the aluminum electrode 10 placed on the pedestal 2a, or the aluminum electrode 10 with the solder 20 placed thereon may be placed on the pedestal 2a. The solder 20 is placed on the aluminum electrode 10 by, for example, a dispenser (dispenser 6 shown in FIG. 11 , which will be described later).

[0032] Next, the solder 20 is melted and solidified using a laser beam L, thereby joining the solder 20 to the aluminum electrode 10 (joining step, FIG. 2 ). More specifically, the solder 20 is melted by irradiation with the laser beam L, and then the irradiation of the laser beam L is stopped, thereby cooling and solidifying the solder 20. In the joining step, the laser beam L is irradiated from the irradiation head 3. More specifically, the control unit 5 controls the irradiation head 3 and causes the irradiation head 3 to irradiate the laser beam L.

[0033] In the joining process, the laser light L is irradiated so that the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20. In this example, the laser light L is not irradiated onto the solder 20, and therefore the energy amount of the laser light L irradiated onto the solder 20 is zero. In this example, as shown in Fig. 2 , at the start of the joining process (the state shown on the left side of Fig. 2 ), all of the laser light L is irradiated onto the aluminum electrode 10. In addition, the laser light L is irradiated onto the surface 10a of the aluminum electrode 10 on which the solder 20 is arranged.

[0034] As described above, in this example, the laser light L is not irradiated onto the solder 20, and all of the laser light L is irradiated onto the aluminum electrode 10. As a result, the aluminum electrode 10 is first heated. Next, the solder 20 is heated by the heat from the aluminum electrode 10 and melts. The melted solder 20 moves to the heated portion of the aluminum electrode 10 (the portion irradiated with the laser light L), as shown on the right side of FIG. 2 . The moved solder 20 solidifies in that portion and is bonded to the aluminum electrode 10. In this manner, preliminary solder 30 is formed on the aluminum electrode 10. In this bonding process, the solder 20 easily wets the heated portion of the aluminum electrode 10, so that the solder 20 can be reliably bonded to the aluminum electrode 10.

[0035] The operation of the preliminary solder forming apparatus 1 in the joining process will be described with reference to FIG. 3 . The control unit 5 controls each element of the preliminary solder forming apparatus 1 to perform the following operations. First, the camera 4 acquires an image of the aluminum electrode 10 (step S11). Next, the control unit 5 determines whether the entire area to be irradiated with the laser light L is located outside the solder 20 based on the image acquired by the camera 4 (e.g., by image processing) (step S12). If the control unit 5 determines that the entire area is located outside the solder 20 (YES in step S12), it controls the irradiation head 3 to start irradiating the laser light L (step S13). On the other hand, if the control unit 5 determines that at least a portion of the area is located inside the solder 20 (NO in step S12), it controls the irradiation head 3 to move (step S14). Then, the control unit 5 again executes the process of step S11. Through the above process, irradiation of the laser light L is started with the entire laser light L irradiating the aluminum electrode 10.

[0036] Here, the irradiation position of the laser light L will be described with reference to FIG. 4 . Cross-sectional views are shown at the top of FIGS. 4( a) and 4(b), and plan views are shown at the bottom. As shown in FIG. 4(a), in the above-described example, the entire laser light L is irradiated onto the aluminum electrode 10. In FIG. 4(a), the center C of the laser light L is located outside the solder 20 (the solder 20 before melting) (the solder 20 at the start of the joining process). The center C is the center of the irradiation area (irradiation spot) of the laser light L on the surface 10a of the aluminum electrode 10. Also, in FIG. 4(a), in a plan view (when viewed from the Z direction), the area of ​​the laser light L irradiated onto the aluminum electrode 10 is larger than the area of ​​the laser light L irradiated onto the solder 20. Note that in this example, the laser light L is not irradiated onto the solder 20, and therefore the area of ​​the laser light L irradiated onto the solder 20 is zero. "The center of the laser beam is located outside the solder" means that the center of the laser beam is located outside the area where the solder is placed. For example, when the solder 20 is circular as in the example of Figure 4, this means that the center C of the laser beam L is located outside the outer periphery of the solder 20, and when the solder 20 is annular, this means that the center C of the laser beam L is located outside the outer periphery or inside the inner periphery of the solder 20.

[0037] The laser light L may be irradiated as shown in Fig. 4(b). In Fig. 4(b), part of the laser light L is irradiated onto the aluminum electrode 10, and the remaining part of the laser light L is irradiated onto the solder 20. In Fig. 4(b) as well, the center C of the laser light L is located outside the solder 20. Also in Fig. 4(b), the area of ​​the laser light L irradiated onto the aluminum electrode 10 is larger than the area of ​​the laser light L irradiated onto the solder 20 in a plan view.

[0038] 4(b), the center C of the laser beam L may be located on the outer edge of the solder 20. In this case as well, the area of ​​the laser beam L irradiated onto the aluminum electrode 10 is larger than the area of ​​the laser beam L irradiated onto the solder 20 in a plan view.

[0039] In either case described above, the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20. For example, when the intensity distribution of the laser light L is uniform, these energy amounts are proportional to the irradiation area of ​​the laser light L. When the intensity distribution of the laser light L is not uniform, the energy amount is a value obtained by integrating the intensity distribution of the laser light L over the irradiation area of ​​the corresponding laser light L. The intensity distribution of the laser light L may be a Gaussian distribution or a top-hat distribution (uniform distribution). Note that it is sufficient that the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20, and unlike the examples of FIGS. 4( a) and 4(b), the center C of the laser light L may be located inside the solder 20.

[0040] The advantages of the pre-soldering method of the embodiment will be described with reference to the comparative example of FIG. 5 . In the pre-soldering method of the comparative example of FIG. 5 , the entire laser beam L is irradiated onto the solder 20. In this case, the energy amount of the laser beam L irradiated onto the aluminum electrode 10 is zero, which is less than the energy amount of the laser beam L irradiated onto the solder 20. Therefore, the solder 20 is heated first and melts before the aluminum electrode 10 is heated. As a result, the solder 20 does not easily wet the unheated aluminum electrode 10. As shown on the right side of FIG. 5 , the solder 20 becomes spherical and moves over the aluminum electrode 10, preventing the solder 20 from being properly bonded to the aluminum electrode 10. Furthermore, because the contact area between the solder 20 and the aluminum electrode 10 is small, it is difficult to heat the aluminum electrode 10 with the heat from the solder 20, which also prevents the solder 20 from being properly bonded. Note that the solder 20 becomes spherical as shown on the right side of FIG. 5 because the free energy of the solder 20 is large.

[0041] The reason why the aluminum electrode 10 has poor wettability with the solder 20 is the influence of a passivation film formed on the surface of the aluminum electrode 10. When aluminum is placed in the air, aluminum oxide (Al ２ O３ The presence of this passive film makes it difficult for solder to wet the aluminum electrode.

[0042] To solve this problem, solder may contain flux to promote soldering. The flux is added to the solder to remove the passivation film that forms on the surface of the aluminum electrode. However, even in this case, it takes time to remove the passivation film with the flux, and there is a risk that the solder will melt before the passivation film is removed, forming balls and moving on the aluminum electrode.

[0043] In this regard, as described above, in the preliminary solder forming method of the embodiment, the aluminum electrode 10 is irradiated with laser light L, and the aluminum electrode 10 is heated ( FIG. 2 ). The heat from the aluminum electrode 10 then heats and melts the solder 20. The melted solder 20 moves to the heated portion of the aluminum electrode 10 and solidifies. Because the solder 20 easily wets the heated portion of the aluminum electrode 10, the solder 20 can be reliably joined to the aluminum electrode 10. Furthermore, because the solder 20 moves (gathers) to the heated portion of the aluminum electrode 10, the solder 20 can be easily positioned. [Operation and Effects]

[0044] In the pre-solder forming method of the embodiment, the laser light L is irradiated so that the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20. This allows the aluminum electrode 10 to be heated before the solder 20, and the aluminum electrode 10 can be in a heated state when the solder 20 melts. As a result, the aluminum electrode 10 can be made more easily wetted by the solder 20 at the joint with the solder 20, and the solder 20 can be satisfactorily joined to the aluminum electrode 10. Therefore, according to the pre-solder forming method of the embodiment, the pre-solder 30 can be satisfactorily formed on the aluminum electrode 10. Note that "the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20" also includes a case where the energy amount of the laser light L irradiated onto the solder 20 is zero (i.e., the laser light L is not irradiated onto the solder 20).

[0045] In the bonding process, the aluminum electrode 10 is irradiated with the entire laser beam L. This allows the aluminum electrode 10 to be stably heated, improving yield. That is, compared to the case where the aluminum electrode 10 is irradiated with only a portion of the laser beam L, for example, it is easier to adjust the irradiation position of the laser beam L, and the aluminum electrode 10 can be stably heated.

[0046] In the joining step, a part of the laser light L may be irradiated onto the aluminum electrode 10, and the remaining part of the laser light L may be irradiated onto the solder 20. In this case, the aluminum electrode 10 and the solder 20 can be heated in a well-balanced manner, and the process can be shortened.

[0047] In the joining step, the laser light L is irradiated so that the center of the laser light L is located outside the solder 20. This makes it possible to easily irradiate the laser light L so that the amount of energy of the laser light L irradiated onto the aluminum electrode 10 is greater than the amount of energy of the laser light L irradiated onto the solder 20. The preliminary solder forming method of the embodiment is particularly effective when the intensity distribution of the laser light L is a Gaussian distribution in which the light intensity is high in the center, or a top-hat distribution in which the light intensity is uniform.

[0048] In the joining step, the laser light L is irradiated so that the area of ​​the laser light L irradiated onto the aluminum electrode 10 is larger than the area of ​​the laser light L irradiated onto the solder 20. This makes it possible to easily irradiate the laser light L so that the amount of energy of the laser light L irradiated onto the aluminum electrode 10 is larger than the amount of energy of the laser light L irradiated onto the solder 20.

[0049] In the joining step, the surface 10a of the aluminum electrode 10 on which the solder 20 is disposed is irradiated with laser light L. This allows the solder 20 to be reliably joined to the aluminum electrode 10.

[0050] The preliminary solder forming apparatus 1 is an apparatus for forming preliminary solder 30 on an aluminum electrode 10 made of aluminum. The preliminary solder forming apparatus 1 includes an irradiation head 3 (irradiation unit) that irradiates laser light L, and a control unit 5 that controls the irradiation head 3. The control unit 5 causes the irradiation head 3 to irradiate the laser light L so that the energy amount of the laser light L irradiated onto the aluminum electrode 10 is greater than the energy amount of the laser light L irradiated onto the solder 20 arranged on the aluminum electrode 10, thereby melting and solidifying the solder 20 and joining the solder 20 to the aluminum electrode 10. For the reasons described above, the preliminary solder forming apparatus 1 makes it possible to satisfactorily join the solder to the aluminum electrode 10. [Modification]

[0051] As in a first modified example shown in FIG. 6 , in the joining process, laser light L may be applied while a pressing member 40, which is disposed on the opposite side of the solder 20 from the aluminum electrode 10, is in contact with the solder 20. The pressing member 40 is formed of a material that is transparent to the laser light L. In this example, the pressing member 40 is formed in a plate shape from glass. In this example, the laser light L is applied to the surface 10 a of the aluminum electrode 10 through the pressing member 40 (passing through the pressing member 40). In the first modified example as well, all of the laser light L is applied to the aluminum electrode 10. When the laser light L is applied while the pressing member 40 is pressed against the solder 20, the solder 20 melts, and the movement of the solder 20 can be restricted by the pressing member 40.

[0052] The preliminary solder forming method of the first modified example can be suitably used when flux is contained in the solder 20. As shown in Fig. 7 , when the solder 20 contains flux 21, the solder 20 ends up on the flux 21, which may prevent the solder 20 from being properly joined to the aluminum electrode 10.

[0053] 6, in contrast, when a pressing member 40 is used, the heated solder 20 expands, and the pressing member 40 restricts the solder 20 from moving upward in the figure, so a force is applied to the solder 20 in a downward direction in the figure (toward the side of the aluminum electrode 10). This force allows the solder 20 to push aside the flux 21 and come into contact with the aluminum electrode 10, as shown in FIG. 6, and the solder 20 can be satisfactorily joined to the aluminum electrode 10.

[0054] According to the first modified example, similar to the above embodiment, the preliminary solder 30 can be satisfactorily formed on the aluminum electrode 10. Furthermore, since the laser light L is applied while the pressing member 40, which is disposed on the opposite side of the aluminum electrode 10 from the solder 20, is in contact with the solder 20, the solder 20 can be more satisfactorily joined to the aluminum electrode 10. Furthermore, since the pressing member 40 is transparent to the laser light L, during the joining process, the laser light L is applied to the surface 10a of the aluminum electrode 10 on which the solder 20 is disposed via the pressing member 40, so the laser light L can be applied to the area overlapping the pressing member 40. Furthermore, even solder 20 containing flux 21 can be satisfactorily joined to the aluminum electrode 10. Note that, in the joining process of the first modified example, similar to the above embodiment, a portion of the laser light L may be applied to the aluminum electrode 10, and the remaining portion of the laser light L may be applied to the solder 20.

[0055] As shown in a second modified example in FIG. 8 , in the joining process, the laser light L may be irradiated while the solder 20 is surrounded by a surrounding member 50 in a plan view (when viewed from the direction of irradiation of the laser light L). The surrounding member 50 is formed of a material that has a melting point higher than that of the solder 20 and has low bonding strength with the solder 20. The surrounding member 50 is also formed of a material that is transparent to the laser light L. In this example, the surrounding member 50 is formed of epoxy glass or silicone. The surrounding member 50 has a pressing portion 51 disposed on the opposite side of the solder 20 from the aluminum electrode 10, and a side wall portion 52 that surrounds the solder 20 in a plan view. The pressing portion 51 and the side wall portion 52 are, for example, integrally formed with each other.

[0056] As shown in FIG. 8 , in this example, the laser light L is irradiated onto the outside of the surrounding member 50. In the second modification, the entire laser light L is irradiated onto the aluminum electrode 10. By irradiating the solder 20 with the laser light L while the surrounding member 50 surrounds it, the movement of the molten solder 20 can be suppressed, ensuring reliable bonding of the solder 20 to the aluminum electrode 10 inside the surrounding member 50. Also, in the second modification, as in the first modification, the pressing portion 51 is pressed against the solder 20, and the laser light L is irradiated to melt the solder 20, thereby limiting the movement of the solder 20 in the Z direction. That is, the pressing portion 51 can also be considered a pressing member that functions similarly to the pressing member 40 of the first modification. In this case, the side wall portion 52 can also be considered a surrounding member. In the bonding process of the second modification, the laser light L is irradiated while the pressing portion 51 is in contact with the solder 20 and the solder 20 is surrounded by the side wall portion 52. This allows the solder 20 to be joined to the aluminum electrode 10 well. Furthermore, because the pressing portion 51 and the side wall portion 52 are integrally formed, the number of components can be reduced, and the work time can be shortened. In the second modified example, the surrounding member 50 may have only the side wall portion 52 without the pressing portion 51. In the joining process of the second modified example, as in the above embodiment, a portion of the laser light L may be irradiated onto the aluminum electrode 10, and the remaining portion of the laser light L may be irradiated onto the solder 20. In the example of FIG. 8 , the laser light L is irradiated onto the aluminum electrode 10 from the outside of the side wall portion 52, but the laser light L may also be irradiated onto the aluminum electrode 10 from the inside of the side wall portion 52. In this case, the laser light L passes through the pressing portion 51 and is irradiated onto the aluminum electrode 10.

[0057] As with the above embodiment, the second modification also allows for good formation of the preliminary solder 30 on the aluminum electrode 10. Furthermore, because the laser light L is irradiated onto the solder 20 while it is surrounded by the surrounding member 50 in a plan view, the surrounding member 50 can suppress movement of the molten solder 20, thereby enabling better bonding of the solder to the aluminum electrode 10. Furthermore, because the surrounding member 50 is made of epoxy glass or silicone, the thermal conductivity of the surrounding member 50 can be reduced, preventing heat from escaping from the solder 20 through the surrounding member 50. Furthermore, the heat resistance of the surrounding member 50 can be improved, preventing damage (e.g., scorching) of the surrounding member 50 due to the processing temperature. Furthermore, because the surrounding member 50 is transparent to the laser light L, it is not necessary to avoid the surrounding member 50 when irradiating the laser light L, simplifying the application of the laser light L.

[0058] As shown in a third modified example in FIG. 9 , in the joining process, laser light L may be irradiated onto a surface 10b of the aluminum electrode 10 opposite the surface 10a, while the surface 10a is in contact with a solder paste layer 60, which is the base material of the solder 20. In the third modified example, the surface 10b is heated by the irradiation of the laser light L, and the heat is transferred to the surface 10a, melting a portion of the solder paste layer 60 (solder 20). The molten solder paste layer 60 solidifies and bonds to the surface 10a of the aluminum electrode 10. In the third modified example, the unmelted portion of the solder paste layer 60 surrounds the molten portion of the solder paste layer 60 (solder 20), thereby suppressing the movement of the molten solder 20 and reliably joining the solder 20 to the aluminum electrode 10. In other words, the unmelted portion of the solder paste layer 60 can be considered a surrounding member that performs the same function as the surrounding member 50 of the second modified example.

[0059] As with the above embodiment, the third modified example also makes it possible to satisfactorily form preliminary solder 30 on aluminum electrode 10. Furthermore, because laser light L is irradiated onto surface 10b of aluminum electrode 10 opposite surface 10a on which solder 20 is disposed, there is no need to irradiate laser light L while avoiding solder 20, which simplifies the irradiation of laser light L.

[0060] 10 , in the joining step, laser light L may be irradiated onto surface 10b of aluminum electrode 10 opposite surface 10a. In the fourth modification, surface 10b is heated by irradiation with laser light L, and the heat is transferred to surface 10a, melting solder 20. The molten solder 20 solidifies and joins to surface 10a of aluminum electrode 10.

[0061] As with the above embodiment, the fourth modification also makes it possible to satisfactorily form preliminary solder 30 on aluminum electrode 10. Furthermore, because laser light L is irradiated onto surface 10b of aluminum electrode 10 opposite surface 10a on which solder 20 is disposed, there is no need to irradiate laser light L while avoiding solder 20, which simplifies the irradiation of laser light L.

[0062] As in a fifth modified example shown in FIG. 11 , the pre-solder forming apparatus 1 does not need to include a camera 4. In this case, the control unit 5 controls the irradiation position of the laser light L by the irradiation head 3 using numerical control instead of image recognition. In this case, as shown in FIG. 12 , first, the dispenser 6 deposits (applies) a predetermined amount of solder 20 at a predetermined position on the aluminum electrode 10 (step S21). Next, the control unit 5 acquires position information of the solder 20 from the dispenser 6 (step S22). Next, the control unit 5 moves the irradiation head 3 to a position corresponding to the solder 20 (step S23). Next, the control unit 5 causes the irradiation head 3 to start irradiating the laser light L (step S24). Through the above process, irradiation of the laser light L is started, for example, with the entire laser light L irradiated onto the aluminum electrode 10. As with the above embodiment, the fifth modified example also enables the solder 20 to be successfully joined to the aluminum electrode 10. In the joining step of the fifth modified example, as in the above embodiment, a part of the laser light L may be irradiated onto the aluminum electrode 10 and the remaining part of the laser light L may be irradiated onto the solder 20 .

[0063] The present disclosure is not limited to the above-described embodiments and modifications. For example, the materials and shapes of each component are not limited to those described above, and various materials and shapes can be adopted. The shape of the irradiation area of ​​the laser light L is not limited to the circular shape shown in FIG. 5 and may be any shape. The shape of the irradiation area of ​​the laser light L may be a donut shape (annular ring). The shape of the aluminum electrode 10 is not limited to a plate shape and may be any shape.

[0064] In the above embodiment, the laser light L is irradiated so that the amount of energy of the laser light L irradiated onto the aluminum electrode 10 is greater than the amount of energy of the laser light L irradiated onto the solder 20. However, the laser light L may be irradiated so that the amount of energy of the laser light L absorbed by the aluminum electrode 10 is greater than the amount of energy of the laser light L absorbed by the solder 20. That is, the laser light L may be irradiated while further considering the absorptance of the laser light L of the aluminum electrode 10 and the solder 20. The absorptance of the solder 20 is higher than the absorptance of the aluminum electrode 10. The amount of energy of the laser light L absorbed by the aluminum electrode 10 is the amount obtained by multiplying the amount of energy of the laser light L irradiated onto the aluminum electrode 10 by the absorptance of the laser light L of the aluminum electrode 10, and the amount of energy of the laser light L absorbed by the solder 20 is the amount obtained by multiplying the amount of energy of the laser light L irradiated onto the solder 20 by the absorptance of the laser light L of the solder 20. In this case as well, the solder 20 can be satisfactorily joined to the aluminum electrode 10.

[0065] 1...preliminary solder forming device, 3...irradiation head (irradiation unit), 5...control unit, 10...aluminum electrode, 10a, 10b...surface, 20...solder, 21...flux, 30...preliminary solder, 40...pressing member, 50...surrounding member, 51...pressing unit (pressing member), 52...side wall portion (surrounding member), C...center, L...laser light.

Claims

1. A method for forming preliminary solder on an aluminum electrode formed from aluminum, comprising: a placement step of placing solder on the aluminum electrode; and a joining step of joining the solder to the aluminum electrode by melting and solidifying the solder using a laser beam, wherein in the joining step, the laser beam is irradiated so that the energy amount of the laser beam irradiated to the aluminum electrode is greater than the energy amount of the laser beam irradiated to the solder.

2. The preliminary solder forming method according to claim 1, wherein in the joining step, the entirety of the laser light is irradiated onto the aluminum electrode.

3. The preliminary solder forming method according to claim 1, wherein in the joining step, a portion of the laser beam is irradiated onto the aluminum electrode, and the remaining portion of the laser beam is irradiated onto the solder.

4. A preliminary solder forming method according to claim 1 or 3, wherein in the joining step, the laser light is irradiated so that the center of the laser light is positioned outside the solder.

5. A method for forming preliminary solder as described in claim 1 or 3, wherein in the joining step, the laser light is irradiated so that the area of ​​the laser light irradiated to the aluminum electrode is larger than the area of ​​the laser light irradiated to the solder.

6. A method for forming preliminary solder as described in claim 1 or 2, wherein in the joining step, the laser light is irradiated while a pressing member arranged on the opposite side of the solder from the aluminum electrode is in contact with the solder.

7. A preliminary solder forming method as described in claim 6, wherein the pressing member is transparent to the laser light, and in the joining step, the laser light is irradiated via the pressing member onto the surface of the aluminum electrode on which the solder is disposed.

8. A preliminary solder forming method according to claim 1 or 2, wherein in the joining step, the laser light is irradiated in a state in which the solder is surrounded by a surrounding member when viewed from the irradiation direction of the laser light.

9. The method for forming pre-solder according to claim 8, wherein the surrounding member is made of epoxy glass or silicone.

10. The method for forming pre-solder according to claim 8, wherein the surrounding member is transparent to the laser light.

11. A preliminary solder forming method as described in claim 1 or 2, wherein in the joining step, a pressing member arranged on the opposite side of the solder from the aluminum electrode is in contact with the solder, and the laser light is irradiated in a state in which the solder is surrounded by a surrounding member when viewed from the irradiation direction of the laser light, and the pressing member and the surrounding member are formed integrally.

12. A preliminary solder forming method as described in claim 1 or 2, wherein in the joining step, the surface of the aluminum electrode on which the solder is disposed is irradiated with the laser light.

13. A method for forming preliminary solder as described in claim 1 or 2, wherein in the joining step, the laser light is irradiated onto a surface of the aluminum electrode opposite to the surface on which the solder is disposed.

14. A method for forming preliminary solder according to claim 1 or 2, wherein in the placing step, the solder containing flux is placed on the aluminum electrode.

15. A pre-solder forming apparatus for forming pre-solder on an aluminum electrode formed from aluminum, comprising: an irradiation section that irradiates laser light; and a control section that controls the irradiation section, wherein the control section causes the irradiation section to irradiate the laser light so that the amount of energy of the laser light irradiated to the aluminum electrode is greater than the amount of energy of the laser light irradiated to the solder placed on the aluminum electrode, thereby melting and solidifying the solder, thereby joining the solder to the aluminum electrode.

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