Ultrasonic welding device and ultrasonic welding system

Abstract

The present invention discloses an ultrasonic welding apparatus and an ultrasonic welding system configured to prevent softening from occurring in an undesired portion of the surface of a workpiece to be welded or the workpiece from being bent. The ultrasonic welding apparatus according to one aspect of the present invention includes a horn that presses the first member to ultrasonically weld the first member and the second member, and the horn includes a knurled portion having a plurality of protrusions configured to protrude toward the first member to form an uneven shape on the first member, and the length m of each of the plurality of protrusions protruding toward the first member may be greater than or equal to the thickness of the first member.

Description

Technical Field

[0001] The present invention relates to an ultrasonic welding apparatus. More specifically, the present invention relates to an ultrasonic welding apparatus and an ultrasonic welding system configured to prevent softening from occurring in an undesired portion of the surface of a workpiece to be welded or the workpiece from being bent.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0101926 filed on August 16, 2022, and all of the content disclosed in the specification and drawings of the application is incorporated herein by reference.

Background Art

[0003] In recent years, the demand for portable electronic products such as notebook computers, video cameras, and mobile phones has increased rapidly. As the commercialization of robots, electric bikes (E-bikes), and electric vehicles (EVs) has become full-fledged, efforts have been actively made to research high-performance secondary batteries that can be repeatedly charged and discharged.

[0004] Currently commercialized secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among them, lithium secondary batteries have attracted attention for their advantages of being almost free from the memory effect compared to nickel-based secondary batteries, allowing for free charging and discharging, having a very low self-discharge rate, and a high energy density.

[0005] On the other hand, as types of secondary batteries, cylindrical, square, and pouch-type batteries are known. In the case of a cylindrical battery, a separator, which is an insulator, is interposed between the positive electrode and the negative electrode, and this is wound up to form a jelly roll-shaped electrode assembly, which is inserted into the housing together with an electrolyte to form a battery. And, strip-shaped electrode tabs can be connected to the plain portions of the positive electrode and the negative electrode respectively, and the electrode tabs are joined to the terminals by welding to electrically connect the electrode assembly and the electrode terminals exposed to the outside.

[0006] For such welding, methods such as laser welding and ultrasonic welding are utilized.

[0007] Among them, laser welding is a method in which a laser beam is irradiated onto the welding part, and the welding part is melted by the energy of the laser beam, and then the melted part is joined while solidifying.

[0008] On the other hand, ultrasonic welding is a method of joining by applying ultrasonic vibration while applying a load to the welding part to generate vibration frictional heat, and its application range is wide up to dissimilar materials including non-metals as well as metals. For such ultrasonic welding, a horn and an anvil are used. The horn includes a knurled part (also called a nailing part) including a plurality of protrusions protruding toward the workpiece to increase the frictional force.

[0009] However, conventionally, there has been a problem that softening occurs in an undesired part of the surface of the workpiece or the workpiece bends according to the shape of the knurled part. Summary of the Invention Problems to be Solved by the Invention

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic welding apparatus configured to solve the problem that softening occurs in an undesired part of the surface of the workpiece or the problem that the workpiece bends.

[0011] However, the technical problems to be solved by the present invention are not limited to the above-described problems, and other problems not mentioned should be clearly understood by those skilled in the art from the description of the invention described below. Means for Solving the Problems

[0012] The ultrasonic welding apparatus according to an embodiment of the present invention includes a horn that presses the first member to ultrasonically weld the first member and the second member. The horn includes a knurled portion having a plurality of protrusions configured to protrude toward the first member to form a concavo-convex shape on the first member. For each of the plurality of protrusions, the length m protruding toward the first member may be greater than or equal to the thickness of the first member.

[0013] The plurality of protrusions may be regularly provided at a constant interval n.

[0014] For each of the plurality of protrusions, the cross-sectional area may be configured to decrease as it advances toward the first member.

[0015] For each of the plurality of protrusions, it may be inclined to have a constant angle θ with respect to the first member.

[0016] For each of the plurality of protrusions, the length m protruding toward the first member may satisfy the following Mathematical Formula 1. [Mathematical Formula 1]

Number

[0017] For each of the plurality of protrusions, the end portion protruding toward the first member may be configured to be cut by a certain length L along a plane parallel to the first member to form a flat surface.

[0018] For each of the plurality of protrusions, the value obtained by subtracting the certain length L from the protruding length m may be greater than or equal to the thickness of the first member.

[0019] The ultrasonic welding system according to the present invention includes an electrode assembly, a current collector coupled to one side of the electrode assembly, a terminal electrically coupled to the current collector, and an ultrasonic welding device for ultrasonically welding the current collector and the terminal. The ultrasonic welding device includes a plurality of protrusions configured to protrude toward the current collector, and the length of each of the plurality of protrusions protruding toward the current collector may be greater than or equal to the thickness of the current collector.

[0020] The electrode assembly includes a central hole, and the current collector may include a second coupling portion that couples to the terminal at a position corresponding to the central hole.

[0021] The current collector may include a first coupling portion that couples to the electrode assembly and a second coupling portion that is at least partially formed thinner than the thickness of the first coupling portion.

Advantages of the Invention

[0022] According to one aspect of the present invention, it is possible to prevent softening from occurring on the surface of the workpiece to be welded or the workpiece from being bent. Returning to FIG. 2 for a more detailed explanation. To perform ultrasonic welding, a plurality of protrusions must be pressed against the upper member of the workpiece to be welded with a certain load while in contact with it, and at the same time, ultrasonic waves must be applied. When the plurality of protrusions are smaller than the thickness of the upper member of the workpiece to be welded, the upper member also comes into contact between the plurality of protrusions during the pressing process with a certain load. Therefore, softening also occurs in the undesired portion of the surface of the workpiece to be welded, affecting the welding strength. However, when the plurality of protrusions are larger than or equal to the thickness of the upper member of the workpiece to be welded as in the present invention, such problems can be prevented.

[0023] According to another aspect of the present invention, the arrangement of the plurality of protrusions can be changed according to the frictional force required for ultrasonic welding. Under the assumption that the protruding length is greater than or equal to the thickness of the upper member among the objects to be welded, when a large frictional force is required, the arrangement of the plurality of protrusions increases a fixed angle, decreases a fixed interval, and increases the density of the plurality of protrusions in the knurled portion. When a small frictional force is required, the fixed angle can be decreased, the fixed interval can be increased, and the density of the plurality of protrusions in the knurled portion can be decreased.

[0024] According to still another aspect of the present invention, when welding a thin upper member, it is possible to prevent the upper member from being broken by a plurality of sharp protrusions. Under the assumption that the value obtained by subtracting a certain length from the protruding length is greater than or equal to the thickness of the upper member among the objects to be welded, by adjusting the certain length to be cut according to the frictional force required for ultrasonic welding, the area where the plurality of protrusions come into contact with the upper member can be adjusted.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

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Figure 13

Embodiments for Carrying Out the Invention

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The drawings attached to this specification illustrate the preferred embodiments of the present invention and are for the purpose of further understanding the technical idea of the present invention together with the detailed description of the invention to be described later. Therefore, the present invention is not construed as being limited only to the matters described in such drawings. The same reference numerals refer to the same components. Also, in the drawings, the thickness, ratio, and dimensions of the components may be exaggerated for an effective explanation of the technical content.

[0027] The terms and words used in this specification and the claims are not to be construed as being limited to the ordinary meaning or the dictionary meaning, and the inventor interprets them in the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain the invention in the best way.

[0028] In this specification, terms indicating directions such as up, down, left, right, front, and back are used, but it is self-evident to those skilled in the art of the present invention that these terms are merely for convenience of explanation and may vary depending on the position of the object in question, the position of the observer, etc.

[0029] Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Thus, there may be various equivalents and modified embodiments that can replace these at the time of this application.

[0030] FIG. 1 is a diagram showing an ultrasonic welding apparatus 3, and workpieces A and B according to an embodiment of the present invention. FIG. 2 is a diagram showing the ultrasonic welding process of the ultrasonic welding apparatus 3 according to an embodiment of the present invention.

[0031] Referring to FIGS. 1 and 2, the ultrasonic welding apparatus 3 according to the present invention includes a horn 5.

[0032] The horn 5 can form a concavo-convex shape on the first member A. The horn 5 presses against the first member A with a certain load while in contact therewith, and at the same time applies ultrasonic waves, thereby enabling ultrasonic welding of the first member A and the second member B. The horn 5 may include a knurled portion N having a plurality of protrusions T configured to protrude toward the first member A. The plurality of protrusions T can press against the first member A with a certain load while in contact therewith, and at the same time apply ultrasonic waves, thereby enabling ultrasonic welding of the first member A and the second member B. However, the present invention is not limited to ultrasonic welding of the first member A and the second member B. That is, the ultrasonic welding apparatus 3 according to the present invention can also ultrasonic-weld two or more members.

[0033] Each of the plurality of protrusions T may have a protruding length m towards the first member A that is greater than or equal to the thickness d of the first member A. The protruding length m may be the vertical distance from one surface of the horn 5 along the negative direction of the Z-axis to the outermost end that protrudes.

[0034] However, when the height at which each of the plurality of protrusions T begins to be formed from one surface of the horn 5 in the Z-axis direction is the same and the protruding lengths m in the negative direction of the Z-axis are formed to be different from each other, the maximum value of the protruding lengths m of each of the plurality of protrusions T may also be greater than or equal to the thickness d of the first member A.

[0035] According to such a structure of the present invention, it is possible to prevent softening from occurring on the surface of the upper member A among the workpieces to be welded or the upper member A among the workpieces to be welded from being bent. Returning to FIG. 2, it will be described in more detail. In order to perform ultrasonic welding, a plurality of protrusions T must be pressed against the upper member A among the workpieces to be welded with a certain load while ultrasonic waves are applied at the same time. When the plurality of protrusions T are smaller than the thickness of the upper member A among the workpieces to be welded, the upper member will also come into contact between the plurality of protrusions T during the process of pressing with a certain load. Therefore, softening also occurs in the undesired portion of the surface of the upper member A of the workpiece to be welded, which affects the welding strength. However, when the plurality of protrusions T are greater than or equal to the thickness of the upper member A among the workpieces to be welded as in the present invention, such problems can be prevented.

[0036] FIG. 3 is a diagram showing the horn 5 included in the ultrasonic welding apparatus 3 according to an embodiment of the present invention. FIG. 4 is a diagram showing the ultrasonic welding apparatus 3 and the first member A according to an embodiment of the present invention.

[0037] Referring to FIGS. 3 and 4, the plurality of protrusions T can be regularly provided at regular intervals n. The plurality of protrusions T can be regularly provided at regular intervals n along the X-axis and Y-axis from other adjacent protrusions T. The plurality of protrusions T can be square in shape. For example, as shown in FIG. 3(a), the plurality of protrusions T may be provided so as to be in point contact with adjacent protrusions T, or as shown in FIG. 3(b), the plurality of protrusions T may be provided so as to be in line contact with adjacent protrusions T. In this case, the constant interval n can be the distance between the outermost ends protruding along the negative direction of the Z-axis of adjacent protrusions T.

[0038] Each of the plurality of protrusions T can be configured such that its cross-sectional area decreases as it advances toward the first member A (in the negative direction of the Z-axis). Each of the plurality of protrusions T can be a polyhedron. For example, as shown in FIG. 3, each of the plurality of protrusions T can be a square pyramid.

[0039] Each of the plurality of protrusions T can be inclined so as to have a constant angle θ with respect to the first member A. For example, when each of the plurality of protrusions T has a rectangular pyramid, the angle formed by the side edge of the rectangular pyramid with respect to the XY plane can be the constant angle θ. For example, as shown in FIG. 4, each of the plurality of protrusions T can have a rectangular pyramid, and the angle formed by its side edge with respect to the XY plane can be 45°.

[0040] The length by which each of the plurality of protrusions T protrudes toward the first member A can satisfy Equation 1. [Equation 1]

Number

[0041] According to such a structure of the present invention, the arrangement of the plurality of protrusions T can be changed according to the frictional force required for ultrasonic welding. Under the assumption that the protruding length m is greater than or equal to the thickness of the upper member A among the members to be welded, when a large frictional force is required, the arrangement of the plurality of protrusions T increases a certain angle θ and decreases a certain interval n to increase the density of the plurality of protrusions T in the knurled portion N. When a small frictional force is required, the certain angle θ can be decreased and the certain interval can be increased to decrease the density of the plurality of protrusions T in the knurled portion N.

[0042] FIG. 5 is a diagram showing a horn 5 included in the ultrasonic welding apparatus 3 according to another embodiment of the present invention. FIG. 6 is a diagram showing the ultrasonic welding apparatus 3 and the first member A according to another embodiment of the present invention.

[0043] Referring to FIGS. 5 and 6, each of the plurality of protrusions T may be configured such that an end portion protruding toward the first member A is cut by a certain length L along a plane parallel to the first member A to form a flat surface. The certain length L may be a vertical distance from the flat surface formed by cutting along the negative direction of the Z axis to the outermost protruding end before being cut.

[0044] Each of the plurality of protrusions T may be a frustum of a pyramid formed by cutting an end portion of a pyramid by a certain length along a plane parallel to the XY plane. For example, each of the plurality of protrusions T may be a frustum of a rectangular pyramid.

[0045] The value obtained by subtracting the certain length L obtained by cutting the end portion protruding toward the first member A along a plane parallel to the first member A from the length m of each of the plurality of protrusions T protruding toward the first member A may be greater than or equal to the thickness of the first member A. Even in this case, the above formula 1 can be satisfied.

[0046] According to such a structure of the present invention, when welding the thin upper member A, it is possible to prevent the upper member A from being torn by the plurality of sharp protrusions T. Under the assumption that the value obtained by subtracting a certain length L from the protruding length m is greater than or equal to the thickness of the upper member A among the objects to be welded, by adjusting the certain length L to be cut according to the frictional force required for ultrasonic welding, the area where the plurality of protrusions T come into contact with the upper member can be adjusted.

[0047] The effects of the present invention described above are shown in FIGS. 7 to 9. FIGS. 7 to 9 are photographs of the upper member A among the objects to be welded welded by the ultrasonic welding apparatus 3 according to the present invention.

[0048] FIG. 7 is a photograph of the upper member A where ultrasonic welding was performed when the protruding length m is 0.4 mm, the certain length L is 0.07 mm, and the thickness of the upper member is 0.3 mm. FIG. 8 is a photograph of the upper member A where ultrasonic welding was performed when the protruding length m is 0.6 mm, the certain length L is 0.07 mm, and the thickness of the upper member is 0.3 mm. FIG. 9 is a photograph of the upper member A where ultrasonic welding was performed when the protruding length m is 0.6 mm, the certain length L is 0.07 mm, and the thickness of the upper member is 0.3 mm.

[0049] Referring to FIGS. 7 to 9, no softening occurs or the peripheral portion bends in other portions of the upper member except for the portions where the upper member comes into contact with the plurality of protrusions T.

[0050] FIG. 10 is a graph showing the tensile strength of the welded portion for each condition after performing ultrasonic welding under certain conditions.

[0051] The graph shown in FIG. 10 means that the X-axis represents the pressing time (unit: second), the Y-axis represents the pressing force (unit: MPa), and this is shown as contour lines according to the tensile strength of the welded portion after ultrasonic welding for each condition.

[0052] Referring to Fig. 10, under the condition that the protruding length m is set to be larger than the thickness of the upper member, although the tensile strength of the welded part is sufficiently ensured, there may be cases where this is not the case depending on the pressing force and the pressing time. The criterion for sufficiently ensuring the tensile strength of the welded part is set to a level of about 0.5 compared to the tensile strength of the base material. In the graph of Fig. 10, 15.5Kgf, which is about 0.5 of 31Kgf, the tensile strength of the upper member, is used as the criterion.

[0053] When the protruding length m is 0.6mm, the constant length L is 0.07mm, and the thickness of the upper member is 0.3mm, a high value of the tensile strength of the welded part was obtained without being affected by the pressing force and the pressing time, except when the pressing force is 0.15MPa and the pressing time is 0.07 seconds or less. It can be inferred that in other conditions, the tensile strength of the welded part is not sufficiently ensured in a wide range of the pressure and the pressing time.

[0054] A preferred embodiment in the ultrasonic welding apparatus 3 according to the present invention may be a case where the protruding length m is about 1.33 times or more and about 2 times or less the thickness of the upper member A.

[0055] A preferred embodiment in the ultrasonic welding apparatus 3 according to the present invention may be a case where the protruding length m is about 1.5 times or more and about 1.8 times or less the thickness of the upper member A.

[0056] A preferred embodiment in the ultrasonic welding apparatus 3 according to the present invention may be a case where the constant length L is about 0.117 or more and about 0.175 or less the protruding length m.

[0057] A preferred embodiment in the ultrasonic welding apparatus 3 according to the present invention may be a case where the constant length L is about 0.13 or more and about 0.15 or less the protruding length m.

[0058] FIG. 11 is a diagram showing an ultrasonic welding system 1 according to an embodiment of the present invention. FIG. 12 is a diagram showing a first current collector included in the ultrasonic welding system 1 according to an embodiment of the present invention. FIG. 13 is a cross-sectional view schematically showing a cross-section taken along line C-C' of FIG. 12.

[0059] Referring to FIGS. 11 to 13, the ultrasonic welding system 1 according to the present invention may include an electrode assembly 10, a current collector 30, a terminal 40, and an ultrasonic welding device 3.

[0060] The electrode assembly 10 may include a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first electrode and the second electrode. The first electrode may be a negative electrode or a positive electrode, and the second electrode may correspond to an electrode having a polarity opposite to that of the first electrode. The electrode assembly 10 may be manufactured by winding a laminate formed by laminating at least once the first electrode, the separator, the second electrode, and the separator in this order. That is, the electrode assembly 10 applied to the present invention may be a jelly roll type electrode assembly 10.

[0061] Such a jelly roll type electrode assembly 10 may be provided with a central hole C formed substantially at its central portion and extending along the height direction (direction parallel to the Z axis).

[0062] The first electrode may include a first electrode plate and a first electrode active material layer formed by applying a first electrode active material on at least one surface of the first electrode plate. The second electrode may include a second electrode plate and a second active material layer formed by applying a second electrode active material on at least one surface of the second electrode plate. The first electrode may include a first plain portion 11 on which no positive electrode active material or negative electrode active material is applied to the electrode plate. The second electrode may include a second plain portion on which no positive electrode active material or negative electrode active material is applied to the electrode plate. At least a part of the first plain portion 11 may function as a first electrode tab, and at least a part of the second plain portion may function as a second electrode tab.

[0063] On one hand, at least a part of the first non-printing part 11 may include a plurality of segmented pieces divided along the winding direction of the electrode assembly 10. In this case, the plurality of segmented pieces may be bent along the radial direction of the electrode assembly 10. The plurality of bent segmented pieces may overlap multiple times. In this case, the current collector 30 described later may be coupled to a region where the plurality of segmented pieces overlap multiple times.

[0064] The current collector 30 may be coupled on one side of the electrode assembly 10. The current collector 30 may include a first coupling portion 31 that couples with the electrode assembly 10 and a second coupling portion 32 that couples with a terminal 40 described later.

[0065] The first coupling portion 31 may be disposed on one surface of the electrode assembly 10. The first coupling portion 31 may be coupled to the first non-printing part 11. The first coupling portion 31 may be coupled to the first non-printing part 11 by laser welding. The first coupling portion 31 may include a laser welding portion L that is laser welded to the first non-printing part 11. A plurality of the first coupling portions 31 may be provided.

[0066] The second coupling portion 32 may be coupled to the terminal 40. The second coupling portion 32 may be coupled to the terminal 40 by ultrasonic welding. The second coupling portion 32 may include an ultrasonic welding portion U that couples with the terminal 40. For example, the entire second coupling portion 32 may be the ultrasonic welding portion U, or the substantially central portion of the second coupling portion 32 may be the ultrasonic welding portion U.

[0067] At least a part of the second coupling portion 32 may be formed thinner than the thickness of the first coupling portion 31. In this way, the thickness reduction region having a relatively small thickness may include the ultrasonic welding portion U. The thickness of the thickness reduction region may be 50% or more and less than 90% of the thickness of the first coupling portion 31.

[0068] The terminal 40 includes a terminal exposed portion 41 and a terminal insertion portion 42. The terminal exposed portion 41 is exposed outside the battery housing. The terminal exposed portion 41 may be located at the substantially central portion of the closing portion of the housing 20.

[0069] The terminal insertion part 42 can be coupled to the second coupling part 32 of the current collector 30. The terminal insertion part 42 can be ultrasonically welded and coupled to the current collector 30 at a position corresponding to the central hole C of the electrode assembly 10.

[0070] It is advantageous to weld the current collector 30 and the terminal 40 by ultrasonic welding, which has the advantages that the equipment is less expensive compared to laser welding, there is less thermal deformation compared to laser welding, and the electrical resistance is low after welding. Also, in the welding process, for laser welding, in order to secure the laser focus, the aperture diameter of the central hole C must be secured to be a certain aperture diameter or more, but for ultrasonic welding, the horn 5 corresponding to the aperture diameter of the central hole C can be inserted to perform the welding process.

[0071] The ultrasonic welding device 3 can ultrasonically weld the current collector 30 and the terminal 40. The ultrasonic welding device 3 may include a horn 5 that presses against the current collector 30. The ultrasonic welding device 3 may include an anvil 7 that supports the terminal 40. The ultrasonic welding device 3 may be provided with a plurality of protrusions T each protruding toward the current collector 30 and having a length equal to or greater than the thickness of the current collector 30. The thickness of the current collector 30 may mean the thickness at the portion of the current collector 30 where ultrasonic welding is performed. That is, it may mean the thickness of the ultrasonic welding part U of the second coupling part 32 of the current collector 30. The horn 5 of the ultrasonic welding device 3 can be inserted into the central hole C of the electrode assembly 10 to weld the current collector 30 and the terminal 40.

[0072] In ultrasonic welding, vibration frictional heat is generated between the upper member and the lower member by ultrasonic vibration generated by the ultrasonic welding device 3, and welding is performed. Therefore, if the second coupling part 32 is too thick, the ultrasonic vibration by the ultrasonic welding device 3 cannot be smoothly transmitted, and as a result, there is a risk that the welding strength cannot be ensured. Therefore, in order to ensure the welding strength during ultrasonic welding, the second coupling part 32 must be below a predetermined thickness.

[0073] Therefore, according to such a configuration of the present invention, if the second joint portion 32 that is unavoidably formed thinly for the efficiency of ultrasonic welding and the terminal 40 are ultrasonically welded, there may occur problems such as softening occurring in the undesired portion of the surface of the second joint portion 32, the peripheral portion lifting up, or tearing. However, according to the ultrasonic welding apparatus 3 according to the present invention described above, such problems can be prevented.

[0074] As described above, the present invention has been described mainly with reference to the preferred embodiments with reference to the accompanying drawings. However, it is obvious to those skilled in the art that many diverse and obvious modifications can be made without departing from the scope of the present invention from such a description. Therefore, the scope of the present invention should be interpreted by the claims described so as to include such many modified embodiments.

Explanation of Reference Numerals

[0075] 1 Ultrasonic welding system 3 Ultrasonic welding apparatus 5 Horn N Knurled portion T Plurality of protrusions 7 Anvil A First member B Second member 10 Electrode assembly 11 First plain portion C Central hole 30 Current collector 31 First joint portion L Laser welding portion 32 Second joint portion U Ultrasonic welding portion 40 Terminal 41 Terminal exposed portion 42 Terminal insertion portion

Claims

1. In an ultrasonic device including a horn for pressing the first member to ultrasonically weld the first member and the second member, the horn includes a knurled portion having a plurality of protrusions configured to protrude toward the first member to form an uneven shape on the first member, each of the plurality of protrusions having a length (m) protruding toward the first member that is greater than or equal to the thickness of the first member, an ultrasonic welding device.

2. The ultrasonic welding device according to claim 1, wherein the plurality of protrusions are regularly provided at regular intervals (n).

3. The ultrasonic welding device according to claim 2, wherein each of the plurality of protrusions is configured such that the cross-sectional area decreases as it advances toward the first member.

4. The ultrasonic welding device according to claim 3, wherein each of the plurality of protrusions is inclined to have a certain angle (θ) with respect to the first member.

5. The ultrasonic welding device according to claim 4, wherein each of the plurality of protrusions satisfies the following formula 1 in terms of the length (m) protruding toward the first member. [Formula 1] 【Number 1】

6. The ultrasonic welding device according to claim 4 or 5, wherein each of the plurality of protrusions is configured such that the end portion protruding toward the first member is cut by a certain length (L) along a plane parallel to the first member to form a flat surface.

7. The ultrasonic welding device according to claim 6, wherein the value obtained by subtracting the certain length (L) from the protruding length (m) is greater than or equal to the thickness of the first member.

8. An electrode assembly, A current collector coupled to one side of the electrode assembly, A terminal electrically coupled to the current collector, An ultrasonic welding device for ultrasonically welding the current collector and the terminal, In an ultrasonic welding system including: the ultrasonic welding device includes a plurality of protrusions configured to protrude toward the current collector, each of the plurality of protrusions having a length protruding toward the current collector that is greater than or equal to the thickness of the current collector, an ultrasonic welding system.

9. The electrode assembly includes a central hole, The ultrasonic welding system according to claim 8, wherein the current collector includes a second coupling portion that couples to the terminal at a position corresponding to the central hole.

10. The current collector includes a first coupling portion that couples with the electrode assembly, and a second coupling portion at least a part of which is formed thinner than the thickness of the first coupling portion, in the ultrasonic welding system according to claim 9.

Images