JP7355486B2 - Ultrasonic bonding tool and method for manufacturing ultrasonic bonding tool - Google Patents

Description

The present invention relates to an ultrasonic bonding tool and a method for manufacturing an ultrasonic bonding tool.

For example, an electrode tab derived from a unit cell that constitutes a secondary battery is joined to a current collector housed inside the unit cell. The electrode tab and the current collector are generally joined by ultrasonic bonding using an ultrasonic bonding tool such as a horn and an anvil.

Generally, an ultrasonic welding tool is provided with a protrusion for preventing slippage between the ultrasonic welding tool and the materials to be welded. This protrusion wears and scrapes with the number of times we join, so the usage limit of the ultrasonic welding tool is determined by the predetermined number of times or the amount of wear on the protrusion, and if the ultrasonic welding tool exceeds the limit, Grind the vicinity and use it again.

In such an ultrasonic bonding tool, when the protrusion of the ultrasonic bonding tool comes into contact with the material to be welded, there is a possibility that the protrusion may adhere to the material to be welded.

In connection with this, for example, Patent Document 1 listed below discloses an ultrasonic bonding tool in which a carbide layer is coated on the surface of at least a portion of a tool base material that is in contact with a material to be bonded. According to such an ultrasonic bonding tool, it is possible to prevent the materials to be bonded from adhering to the ultrasonic bonding tool.

Japanese Patent Application Publication No. 2003-266180

However, in a structure in which the surface of the tool base material is coated like the ultrasonic welding tool described in Patent Document 1, the ultrasonic welding tool expands and contracts due to frictional heat during welding, and the frictional heat itself This causes the coating to peel off and shorten tool life. This may increase the frequency of tool replacement and reduce productivity.

The present invention has been made to solve the above problems, and provides an ultrasonic bonding tool and a method for manufacturing an ultrasonic bonding tool that can suitably prevent the hard layer formed on the surface from peeling off. The purpose is to provide.

An ultrasonic bonding tool according to the present invention that achieves the above object is an ultrasonic bonding tool used for ultrasonic bonding of materials to be bonded. The ultrasonic bonding tool includes a tool base material having a protrusion formed on its surface, a base layer provided on the surface of the protrusion and absorbing thermal expansion of the tool base material, and a base layer provided on the surface of the base layer. , a hard layer having higher hardness than the base layer. Further, the protrusion has a hemispherical part whose tip on the base layer side is formed into a hemispherical shape, and a linear part that is continuously provided at both ends of the hemispherical part, and has a straight line part that is continuous with the base layer and the hemispherical part. The hard layer is formed to have a constant thickness.

Moreover, the method for manufacturing an ultrasonic bonding tool according to the present invention that achieves the above object is a method for manufacturing an ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded. Further, a base layer that absorbs thermal expansion of the tool base material is formed on the surface of the protrusion formed on the surface of the tool base material, and a hard layer having higher hardness than the base layer is formed on the surface of the base layer. Form. Further, the base layer and the protrusion include a hemispherical portion having a hemispherical tip on the base layer side, and a linear portion continuously formed in a straight line at both ends of the hemispherical portion. A coating agent for forming a hard layer is irradiated from a direction perpendicular to the straight line portion and from a direction in which the protrusion portions protrude, so that the base layer and the hard layer each have a constant thickness.

According to the above-mentioned ultrasonic bonding tool, the underlayer can reduce vibrations and shocks to the hard layer during bonding, so peeling of the hard layer can be prevented. Therefore, it is possible to provide an ultrasonic bonding tool that can suitably prevent the hard layer formed on the surface from peeling off.

Further, according to the ultrasonic bonding tool manufactured by the above-described method for manufacturing an ultrasonic bonding tool, the base layer can reduce vibration and impact on the hard layer during bonding, thereby preventing peeling of the hard layer. be able to. Therefore, it is possible to provide a method for manufacturing an ultrasonic bonding tool that can suitably prevent the hard layer formed on the surface from peeling off.

1 is a schematic diagram showing a joining device according to an embodiment of the present invention. 2 is an enlarged view of section A in FIG. 1. FIG. FIG. 3 is a diagram for explaining the configuration near the protrusion of the anvil. FIG. 4(A) is a diagram for explaining the method of manufacturing an anvil, and FIG. 4(A) shows how a base layer is formed, and FIG. 4(B) shows how a hard layer is formed. It is a graph showing the relationship between the number of shots and the amount of tool wear. FIG. 4 is a diagram corresponding to FIG. 3 of an anvil according to a modified example. 1 is a schematic cross-sectional view of a secondary battery, which is an example of a target for which an anvil according to the present embodiment is used.

Embodiments of the present invention will be described below with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description will be omitted. The sizes and proportions of parts in the drawings are exaggerated for convenience of explanation and may differ from the actual sizes and proportions.

First, the configuration of a secondary battery 200 to which the anvil 30 (corresponding to an ultrasonic bonding tool) according to the present embodiment is applied will be described.

FIG. 7 is a cross-sectional view of a secondary battery 200 to which the anvil 30 according to the present embodiment is applied. Briefly, as shown in FIG. 7, the secondary battery 200 is configured by housing a power generating element 260 in an exterior body 250, which is a stack of unit cells 240 with a separator 230 interposed between a positive electrode 210 and a negative electrode 220. ing. The positive electrode 210 is configured by providing a positive electrode active material layer 212 on a positive electrode current collector 211, and the negative electrode 220 is configured by providing a negative electrode active material layer 222 on a negative electrode current collector 221. The secondary battery 200 shown in FIG. 7 is configured as a so-called stacked type secondary battery.

The positive electrode current collector 211 is joined to the positive electrode tab 213 near the outer periphery of the exterior body 250, as shown in FIG. Similarly to the positive electrode, the negative electrode current collector 221 is joined to the negative electrode tab 223 near the outer periphery of the exterior body 250. In this embodiment, the horn 20 and the anvil 30 are used when joining a negative electrode tab 223 (corresponding to a material to be joined) to a plurality of negative electrode current collectors 221 (corresponding to a material to be joined).

Next, the configuration of the welding apparatus 1 including the anvil 30 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic diagram showing a bonding apparatus 1 according to this embodiment. FIG. 2 is an enlarged view of section A in FIG. FIG. 3 is a diagram for explaining the configuration of the anvil 30 in the vicinity of the protrusion 31. As shown in FIG.

As shown in FIG. 1, the bonding device 1 includes a vibration generating section 10, a horn 20, an anvil 30, a motor 40, a spring 50, and a control section (not shown).

The vibration generator 10 includes an ultrasonic vibrator and a booster. The ultrasonic vibrator is composed of a transducer or the like, and generates vibrations corresponding to the frequency of ultrasonic waves using electric power supplied from the outside. One end of the ultrasonic transducer is connected to the booster, and the other end is connected to a power cable or the like. The booster is made of metal and is connected to the horn 20 and the ultrasonic vibrator. The booster amplifies the vibrations generated by the ultrasonic transducer.

The horn 20 generates frictional heat by applying ultrasonic waves to the negative electrode current collector 221 side of the joint where the negative electrode current collector 221 and the negative electrode tab 223 are joined to vibrate it. The horn 20 is configured to be able to approach and separate from the negative electrode current collector 221 along the vertical direction in FIG. 1 by the motor 40.

As shown in FIG. 2, numerous protrusions 21 are provided on the tip surface of the horn 20. As shown in FIG. The protrusion 21 comes into contact with the negative electrode current collector 221 . The protrusion 21 wears out through repeated use, and the tip of the protrusion 21 decreases, making it necessary to replace the tool or process the tool.

In this embodiment, since the horn 20 comes into contact with the relatively soft copper that constitutes the negative electrode current collector 221, the horn 20 is not provided with a base layer or a hard layer like an anvil 30 described later.

As the material constituting the horn 20, it is preferable to use steel from the viewpoints of strength, workability, cost, etc.

The anvil 30 places the negative electrode tab 223 side of the joint where the negative electrode current collector 221 and the negative electrode tab 223 are joined. The anvil 30 receives ultrasonic vibrations from the horn 20 and holds the material to be joined together with the horn 20.

As shown in FIGS. 2 and 3, the anvil 30 includes a tool base material 32 having a protrusion 31 formed on its surface, a base layer 33 provided on the surface of the protrusion 31, and a hard material provided on the surface of the base layer 33. layer 34.

Since the anvil 30 comes into contact with the relatively hard Ni plating formed on the negative electrode tab 223, a base layer 33 and a hard layer 34 are provided.

As shown in FIG. 3, the protrusion 31 has a hemispherical portion 31a formed in a hemispherical shape, and linear portions 31b continuously provided at both ends of the hemispherical portion 31a. In other words, the protrusion 31 is configured to be smoothly curved.

As the material constituting the tool base material 32, it is preferable to use steel from the viewpoints of strength, workability, cost, etc.

The base layer 33 absorbs thermal expansion of the tool base material 32 caused by frictional heat during ultrasonic welding. That is, the base layer 33 functions as a buffer material. As shown in FIG. 3, the base layer 33 is continuously formed on the surface of the tool base material 32 so that the film thickness is approximately constant.

From the viewpoint of being soft and durable, it is preferable to use Cr as the material constituting the base layer 33, but the material is not limited thereto.

The hard layer 34 has higher hardness than the base layer 33. As shown in FIG. 3, the hard layer 34 is continuously formed on the surface of the base layer 33 so that the thickness thereof is substantially constant.

The material constituting the hard layer 34 preferably has a lower affinity for the welded material than the steel material constituting the tool base material 32. As such a material, for example, TiAlCr can be used. By using such a material, the progress of adhesive wear of the hard layer 34 against the material to be joined during ultrasonic welding can be delayed, and the tool life can be extended.

The combined thickness of the base layer 33 and the hard layer 34 is not particularly limited, but is, for example, 10 to 14 μm.

For example, in the case of an anvil in which the base layer 33 is not provided, there is a risk that the hard layer 34 may peel off from the tool base material 32 starting from the point where the hard layer 34 contacts the material to be welded. On the other hand, according to the anvil 30 according to the present embodiment, the base layer 33 which is softer than the hard layer 34 is provided between the tool base material 32 and the hard layer 34, so the base layer 33 acts as a cushioning material. Therefore, peeling of the hard layer 34 from the tool base material 32 can be suitably suppressed.

Furthermore, for example, in the case of an anvil in which the base layer 33 is not provided, it is necessary to increase the thickness of the hard layer 34 in order to increase the wear resistance of the protrusion 31, and this may cause the coating to bulge on the protrusion 31. I end up. When a bulge in the coating occurs in this manner, the coating may be peeled off from the bulge due to vibrations and impacts during ultrasonic bonding, and the effectiveness of the coating may be reduced. On the other hand, according to the anvil 30 according to the present embodiment, since the base layer 33 which is softer than the hard layer 34 is provided between the tool base material 32 and the hard layer 34, the thickness of the hard layer 34 is increased. There is no need to do so, and the above-mentioned problem does not occur.

Next, with reference to FIG. 4, a method for manufacturing the anvil 30 according to this embodiment will be described. 4A and 4B are diagrams for explaining the method of manufacturing the anvil 30, in which FIG. 4A shows how the base layer 33 is formed, and FIG. 4B shows how the hard layer 34 is formed. This shows how it works. In the anvil 30, a base layer 33 and a hard layer 34 are formed on the surface of a tool base material 32 by, for example, physical vapor deposition.

First, after cleaning the surface of the tool base material 32, it is set in a physical vapor deposition furnace. After heating the inside of the furnace, vacuuming is performed. Here, the inside of the furnace is heated to 450° C. over a period of, for example, 4 hours.

Next, the surface of the tool base material 32 is cleaned by colliding ion particles with the surface of the tool base material 32 using a cleaning device.

Next, as shown in FIG. 4(A), a base layer 33 is formed on the surface of the tool base material 32 using a base layer generation device 80. Specifically, as shown in FIG. 4A, the coating agent forming the base layer 33 is irradiated from the direction V1 perpendicular to the straight portion 31b, and the protrusion direction V2 of the protrusion 31 (up and down in FIG. 4) is applied. direction) toward the tool base material 32. In this way, by irradiating the coating agent for forming the base layer 33 from the direction V1 perpendicular to the straight portion 31b and the protrusion direction V2 of the protrusion 31, the film thickness of the base layer 33 becomes approximately constant (Fig. 3 reference).

Next, as shown in FIG. 4(B), a hard layer 34 is formed on the surface of the base layer 33 using a hard layer generation device 90. Specifically, as shown in FIG. 4B, the coating agent forming the hard layer 34 is irradiated from the direction V1 perpendicular to the straight portion 31b, and the protrusion direction V2 of the protrusion 31 (up and down in FIG. 4) is applied. direction) toward the tool base material 32. In this way, by irradiating the coating agent for forming the hard layer 34 from the direction V1 perpendicular to the straight portion 31b and from the protruding direction V2 of the projection 31, the thickness of the hard layer 34 becomes approximately constant (see FIG. 3). ). Here, in order to improve the reliability of the hard layer 34, the film formation rate of the hard layer 34 is preferably slower than the film formation rate of the base layer 33.

The total coating time for forming the base layer 33 and the hard layer 34 is, for example, 6 hours, although it is not particularly limited.

Next, after cooling the inside of the furnace, the anvil 30 is taken out. Here, the cooling time in the furnace is, for example, 4 hours, although it is not particularly limited. Next, the film thickness, film hardness, and surface condition of the base layer 33 and hard layer 34 are inspected using a test piece for quality check.

Through the above steps, the base layer 33 and the hard layer 34 are formed on the surface of the tool base material 32, and the anvil 30 is manufactured.

Next, with reference to FIG. 5, the effects of the anvil 30 according to this embodiment will be described.

In FIG. 5, the horizontal axis shows the number of shots (the number of times of joining), and the vertical axis shows the amount of wear on the anvil. Further, the solid line indicates the amount of tool wear on the anvil 30 according to the present embodiment, and the dotted line indicates the amount of tool wear on the anvil without coating.

As shown in FIG. 5, for example, when the tool is replaced when the amount of tool wear is approximately 95 μm, it was found that the tool life of the anvil 30 according to this embodiment is three times that of an uncoated anvil. .

As explained above, the anvil 30 according to the present embodiment is an ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded. The anvil 30 includes a tool base material 32 having a protrusion 31 formed on its surface, a base layer 33 provided on the surface of the protrusion 31 to absorb thermal expansion of the tool base material 32, and a base layer 33 provided on the surface of the base layer 33. , and a hard layer 34 having higher hardness than the base layer 33. According to the anvil 30 configured in this manner, the base layer 33 can reduce vibration and impact on the hard layer 34 during bonding, thereby preventing the hard layer 34 from peeling off.

Furthermore, the material that makes up the hard layer 34 has a lower affinity for the materials to be joined than the material that makes up the tool base material 32 . According to the anvil 30 configured in this way, the possibility that the hard layer 34 will peel off during bonding is further reduced compared to an anvil in which the hard layer 34 is not provided.

Further, the protrusion 31 has a hemispherical part 31a whose tip on the side of the base layer 33 is formed into a hemispherical shape, and a linear straight part 31b that is continuously provided at both ends of the hemispherical part 31a. 33 and the hard layer 34 are formed to have constant film thicknesses. According to the anvil 30 configured in this way, the film thicknesses of the base layer 33 and the hard layer 34 are constant, so that the reliability of coating is improved.

Furthermore, as explained above, the method for manufacturing the anvil 30 according to the present embodiment is a method for manufacturing an ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded. In the method for manufacturing the anvil 30, a base layer 33 that absorbs thermal expansion of the tool base material 32 is formed on the surface of the protrusion 31 formed on the surface of the tool base material 32, and a base layer 33 is formed on the surface of the base layer 33. A hard layer 34 having a higher hardness than the above is formed. According to the anvil 30 manufactured by this manufacturing method, the base layer 33 can reduce vibration and impact on the hard layer 34 during bonding, thereby preventing the hard layer 34 from peeling off.

Further, the coating agent for forming the base layer 33 and the hard layer 34 is irradiated onto the protrusion 31 including the hemispherical part 31a and the straight part 31b from the direction V1 perpendicular to the straight part 31b and the protrusion direction V2 of the protrusion 31. do. Then, the base layer 33 and the hard layer 34 are formed to have constant film thicknesses. According to this manufacturing method, the film thicknesses of the base layer 33 and the hard layer 34 are constant, so that the reliability of the coating is improved.

The present invention is not limited to the embodiments described above, and can be variously modified within the scope of the claims.

For example, in the embodiment described above, the anvil 30 was provided with the base layer 33 and the hard layer 34. However, the horn may also be provided with a base layer and a hard layer.

Further, in the above-described embodiment, the negative electrode current collector 221 and the negative electrode tab 223 are exemplified as the materials to be joined, but the materials to be joined may be a positive electrode current collector and a positive electrode tab.

Furthermore, in the embodiment described above, the protrusion 31 has a hemispherical portion and a straight portion. However, the protrusion 131 may have a triangular shape, as shown in FIG.

1 joining device,
10 vibration generating section,
20 horn,
30 Anvil (ultrasonic bonding tool),
31 protrusion,
31a hemisphere,
31b straight section,
32 tool base material,
33 Base layer,
34 hard layer,
221 Negative electrode current collector (material to be joined),
223 Negative electrode tab (material to be joined),
V1 Direction perpendicular to the straight line,
V2 Projection direction of the protrusion.

Claims (4)

An ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded,
A tool base material with protrusions formed on its surface;
a base layer provided on the surface of the protrusion and absorbing thermal expansion of the tool base;
a hard layer provided on the surface of the base layer and having higher hardness than the base layer,
The protruding portion has a hemispherical portion whose tip on the base layer side is formed into a hemispherical shape, and linear portions that are continuously provided at both ends of the hemispherical portion, and
In the ultrasonic bonding tool, the base layer and the hard layer are formed to have constant film thicknesses. An ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded,
A tool base material with protrusions formed on its surface;
a base layer provided on the surface of the protrusion and absorbing thermal expansion of the tool base;
a hard layer provided on the surface of the base layer and having higher hardness than the base layer,
The base layer and the hard layer are formed to have constant film thicknesses,
In the ultrasonic welding tool, the protrusion has a smoothly curved shape or a triangular cross section. The ultrasonic bonding tool according to claim 1 or 2, wherein the material constituting the hard layer has a lower affinity for the material to be welded than the material constituting the tool base material. A method for manufacturing an ultrasonic bonding tool used for ultrasonic bonding between materials to be bonded, the method comprising:
forming a base layer on the surface of the protrusion formed on the surface of the tool base material to absorb thermal expansion of the tool base material;
forming a hard layer with higher hardness than the base layer on the surface of the base layer;
The protrusion includes a hemispherical portion whose tip on the base layer side is formed into a hemispherical shape, and a linear portion continuously formed in a straight line at both ends of the hemispherical portion,
A coating agent forming the base layer and the hard layer is irradiated from a direction perpendicular to the straight line portion and from a direction in which the protrusion portions protrude, so that the thicknesses of the base layer and the hard layer are each constant. A method for manufacturing an ultrasonic bonding tool.