Ultrasonic joining device

Abstract

The present invention makes it possible to favorably surface-join two joining members with a simple configuration, while suppressing the occurrence of voids at the joining interface.　A joining sheet 10, on both surfaces of which a plurality of protrusions 11 are formed, is disposed between two metallic joining members 8 and 9. While an object W to be joined is pressed by applying a pressing force to a horn and a joining tool 34 by a pressing means, ultrasonic vibration is applied by an ultrasonic vibration means in the transverse vibration direction orthogonal to the pressing direction, thereby performing joining. At this time, truncated cone-shaped protrusions 11, which each have a circular end face with a diameter of 10-3000 μm and have a height of 10-1000 μm, are formed on the joining sheet 10 at a pitch of 1.5-4.0 times the diameter.

Description

Ultrasonic bonding equipment

[0001] The present invention relates to an ultrasonic bonding apparatus for ultrasonically bonding two bonding members together.

[0002] Conventionally, when applying ultrasonic vibration energy to two metal joining members to join them, the two joining members are placed one on top of the other on a support (anvil) of an ultrasonic joining device, and both joining members are sandwiched between the horn of the ultrasonic vibration device and the support, and ultrasonic vibrations are applied while applying pressure to both joining members with the horn to join them.

[0003] In order to suppress the generation of voids at the bonding interface between the two bonding members and enable bonding at a surface that is a collection of points, the applicant of the present application has proposed an invention in which a regular uneven pattern is formed on the entire surface of a predetermined bonding area of ​​at least one of the bonding members, and the convex parts of the uneven pattern are crushed by ultrasonic vibration and pressure to bond the two members (see Patent Document 1).

[0004] JP 2016-34656 A

[0005] However, in the case of the invention described in Patent Document 1, it is necessary to form a regular uneven pattern in advance on at least one of the joining members, so if there are many different types of joining members, it is necessary to process an uneven pattern for each joining member.While this makes it possible to suppress the occurrence of voids at the joining interface and achieve a joining that is close to surface joining, it also has the problem that the uneven processing of the joining members is complicated and costly, making it somewhat less versatile.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a simple structure that enables two joining members to be joined together satisfactorily by suppressing the occurrence of voids at the joining interface.

[0007] In order to solve the above-mentioned problems, the ultrasonic bonding device of the present invention is an ultrasonic bonding device for ultrasonically bonding two bonding members, comprising: a metal bonding sheet placed between the two bonding members; a support for supporting an object to be bonded, formed by inserting the bonding sheet between the two bonding members, in a placed state; ultrasonic vibration means having a vibrator and a horn for clamping the object to be bonded between the support and the horn and applying ultrasonic vibrations; and pressure means for applying a pressure to the horn in the direction of the support while the object to be bonded is clamped between the support and the horn, wherein the bonding sheet has a plurality of protrusions formed on each side, and the object to be bonded is bonded by applying ultrasonic vibrations by the ultrasonic vibration means in a direction perpendicular to the pressure direction of the pressure means while the object to be bonded is pressurized by the pressure means.

[0008] According to this configuration, a bonding sheet having a plurality of protrusions formed on both sides is placed between two bonding members, and the bonding members are bonded by applying ultrasonic vibrations in a direction perpendicular to the pressure direction using the ultrasonic vibration means while applying pressure to the horn using the pressure means. This reduces the contact area between the protrusions of the bonding sheet and the bonding members, thereby reducing the contact (static) friction force. When ultrasonic vibrations are applied, a large amount of slip occurs between the contact surfaces of the bonding sheet and the bonding members, increasing the active newly formed surface. This promotes solid-state bonding and allows the two bonding members to be bonded surface-to-surface while preventing the generation of voids at the bonding interface.

[0009] Furthermore, it is preferable that the protrusions formed on both sides of the bonding sheet have an approximately truncated cone or cylindrical shape, and that the circular diameter of the end face of the truncated cone or cylinder is 10 μm to 3000 μm and the height is 10 μm to 1000 μm.

[0010] According to this configuration, a truncated cone-shaped or cylindrical protrusion having a circular end surface diameter of 10 μm to 3000 μm and a height of 10 μm to 1000 μm is formed on the joining sheet, thereby reducing the contact (static) friction force between the joining sheet and the joining member, and enabling large slippage between the contact surfaces to achieve surface joining.

[0011] The plurality of protrusions may be formed on both sides of the bonding sheet in a twill or grid pattern, thereby obtaining a bonding sheet having a plurality of protrusions uniformly formed on both sides.

[0012] In this case, the projections formed on the bonding sheet may have different shapes and / or different arrangement patterns on both sides.

[0013] The two joining members may be made of the same metal or have the same metal film on their joining surfaces. Furthermore, the two joining members may be made of different metals or have different metal films on their joining surfaces. Here, the joining members may be made entirely of solid metal or have a metal film formed by plating. It is preferable to use metals such as copper (Cu), aluminum (Al), nickel (Ni), silver (Ag), gold (Au), brass, and other alloys, or materials having a metal film formed from these metals, as joining members.

[0014] Furthermore, the joining sheet may be made of a metal that is more easily displaced than the two joining members when ultrasonic vibrations are applied by the ultrasonic vibration means. In this case, since the joining sheet is made of a metal that is more easily displaced than the two joining members, when ultrasonic vibrations are applied while pressure is applied, the protrusions on the joining sheet are easily displaced by ultrasonic vibration energy, making it easier for the joining sheet to be solid-state bonded to the two joining members, thereby enabling the two joining members to be joined well. Specifically, in addition to aluminum, nickel (Ni), silver (Ag), gold (Au), copper (Cu), tin (Sn), etc. may also be used as a material that is easily displaced by ultrasonic vibration energy.

[0015] The plurality of protrusions on both sides of the bonding sheet may be made of the same or different metal as the bonding sheet. In this case, the plurality of protrusions may be formed on both sides of the bonding sheet by, for example, plating. However, the protrusions may also be formed by a method other than plating.

[0016] The protrusions of the joining sheet may have a truncated pyramidal or prismatic shape, and a plurality of the truncated pyramidal or prismatic protrusions may be arranged on the joining sheet in a twill or lattice pattern. In this way, even if the protrusions are truncated pyramidal, a large slippage can be generated between the contact surfaces of the joining sheet and the joining members, and the two joining members can be satisfactorily joined on the surface without generating voids at the joining interface.

[0017] According to the present invention, with a simple configuration, two joining members can be satisfactorily joined by surface-to-surface bonding while suppressing the generation of voids at the joining interface.

[0018] 4 is a side view of an embodiment of an ultrasonic bonding device according to the present invention; FIG. 5 is a front view of the device of FIG. 1; FIG. 6 is a diagram showing a state when parts to be bonded are bonded by the device of FIG. 1; FIG. 7 is a side view of a bonding sheet used for bonding by the device of FIG. 1; FIG. 8 is a perspective view of a part of the bonding sheet of FIG. 4, which is an explanatory diagram of the bonding operation by the device of FIG. 1; FIG. 9 is a diagram showing the bonding cross section of two bonding members bonded by the device of FIG. 1 at different bonding progress times; and FIG. 10 is an explanatory diagram of the operation of FIG.

[0019] An embodiment of an ultrasonic bonding apparatus according to the present invention will be described with reference to FIGS. 1 to 8. FIG.

[0020] 1 and 2 show an ultrasonic bonding apparatus 1, which includes a support body 2, a head unit 3, a control device 4, and a pressure means 5. The support body 2 has a horizontal support surface 21, and is configured to sandwich the objects to be bonded between the support body 2 and a bonding tool 34 attached to a horn 32 (described later) of the head unit 3, which ultrasonically vibrates in the Y-axis direction in FIGS. 1 and 2 that is parallel to the support surface 21. With the objects to be bonded sandwiched between the support body 2 and a bonding tool 34, the bonding tool 34 is attached to a horn 32 (described later) of the head unit 3, which ultrasonically vibrates in the Y-axis direction in FIGS. 1 and 2 . With the objects to be bonded sandwiched between the support body 2 and a bonding tool 34, the bonding tool 34 is controlled by a microcomputer-based control device 4 having a CPU and memory. While pressing the objects to be bonded in the vertical direction (Z-axis direction), the pressure means 5 applies ultrasonic vibration energy in the form of so-called lateral vibration in the left-right direction (Y-axis direction), thereby bonding the objects to be bonded.

[0021] Here, the objects to be joined are two flat metal (for example, copper (Cu)) joining members 8 and 9, which are used for electrodes of semiconductor devices such as power devices and other electronic components, as shown in Fig. 3. Note that one of the joining members 8 and 9 may be Cu and the other Al, or they may be made of the same metal other than Cu or Al, or they may be made of different metals.

[0022] 3, a joining object W, which is formed by disposing a joining sheet 10 made of metal (for example, aluminum (Al)) between the joining members 8 and 9, is placed on the support 2 and is joined by applying ultrasonic vibrations while being held between the support 2 and the horn 32 of the head unit 3. The joining sheet 10 is not limited to being made of Al, but may be made of Cu, or may be made of a metal (for example, Ni, Ag, Au, etc.) that is more easily displaced than Al by ultrasonic vibration energy.

[0023] As shown in FIG. 4 , the bonding sheet 10 has a plurality of truncated cone-shaped protrusions 11 arranged in a twill pattern on both one side and the opposite side. Specifically, as shown in FIG. 5 , the plurality of protrusions 11 have a circular end face with a diameter of 10 μm to 3000 μm and a truncated cone shape with a height of 10 μm to 1000 μm. The protrusions 11 are preferably formed at a pitch of 1.5 to 4.0 times the diameter. The diameter of the protrusions 11 may be appropriately set within the range of 10 μm to 3000 μm depending on the ultrasonic frequency, as well as the height. The plurality of protrusions 11 are preferably formed from the same or a different metal as the bonding sheet 10. The plurality of protrusions 11 can be formed on both sides of the bonding sheet 10 by, for example, plating. The protrusions 11 may also be formed by a method other than plating.

[0024] 1 and 2, the head unit 3 includes a vibrator 31 that applies ultrasonic vibrations in a Y-axis direction (left-right direction) that is perpendicular to the Z-axis direction (up-down direction) in Figures 1 and 2, which is the pressure direction, a horn 32 connected to one end of the vibrator 31, and support means 33 that supports the vibrator 31 and the horn 32 so that they can move freely in the up-down direction (Z-axis direction) that is perpendicular to the left-right direction (Y-axis direction), which is the vibration direction, and the vibrator 31 ultrasonically vibrates the horn 32, thereby applying ultrasonic vibrations to the workpieces W to bond them, thereby bonding the workpieces W. Here, a welding tool 34 that applies pressure to the workpieces W to apply ultrasonic vibrations is attached to the underside of the horn 32 by bolts or the like, and the vibrator 31 and the horn 32 (including the welding tool 34) correspond to the ultrasonic vibration means in the present invention.

[0025] Specifically, the horn 32 resonates with ultrasonic vibrations generated by the vibrator 31 controlled by the control device 4 and ultrasonically vibrates in the left-right direction (the Y-axis direction / horizontal direction in FIGS. 1 and 2 ), which is the direction of its central axis. The horn 32 is formed, for example, with a length of one wavelength of the resonant frequency so that its approximate center in the Y-axis direction and its two opposite ends have maximum amplitude points. A welding tool 34 is attached to the maximum amplitude point at the center of the horn 32. Two positions ¼ wavelength away from each maximum amplitude point in the Y-axis direction correspond to a first minimum amplitude point and a second minimum amplitude point of the horn 32, respectively, and the horn 32 is supported by a support means 33 at these first and second minimum amplitude points. The horn 32 is formed in a columnar shape, for example, with an octagonal cross section. The vibrator 31 is connected to the right end of the horn 32 by a headless screw or the like so as to be coaxial with the central axis of the horn 32.

[0026] Here, the horn 32 and the welding tool 34 may be formed from various metal materials commonly used to form resonators, such as titanium, titanium alloys, iron, stainless steel, aluminum, aluminum alloys such as duralumin, high-carbon steel that can be heat-treated, or iron with a tungsten carbide tip, etc. The horn 32 is preferably configured so that its resonant frequency is about 15 kHz to about 60 kHz and its vibration amplitude (the amplitude of expansion and contraction in the Y-axis direction in FIGS. 1 and 2) is about 1 μm to about 300 μm.

[0027] Support means 33 includes a base 33a, a vertical support pillar 33b (in the Z-axis direction in FIGS. 1 and 2) whose upper end is connected to base 33a, a support portion 33c connected to the lower end of support pillar 33b, and a pair of clamp portions 33d connected to the lower surface of support portion 33c. Support means 33 supports horn 32 by using both clamp portions 33d to grip gripped portions of horn 32 at positions corresponding to the first and second minimum amplitude points.

[0028] Here, each of the clamping portions 33d is made up of two, upper and lower, separable gripping members 33d1 and 33d2, and the upper gripping member 33d1 is fixed to the underside of the support portion 33c, and the upper and lower gripping members 33d1 and 33d2 clamp and grip the gripped portion at positions corresponding to the first and second minimum amplitude points of the horn 32.

[0029] The gripped portion of the horn 32 may be supported by the support means 33 via an elastic member such as an O-ring or a diaphragm.

[0030] The pressure applying means 5 moves the support means 33 that supports the horn 32 in the vertical direction (Z-axis direction), thereby moving the horn 32 in the vertical direction so as to move the horn 32 closer to or further away from the support 2. The pressure applying means 5 includes a drive motor 51, a vertical (Z-axis) ball screw 52 that is rotated by the drive motor 51, a base 53 that is U-shaped in a side view and that rotatably supports the upper and lower ends of the ball screw 52, ​​and a rectangular parallelepiped movable support 54 that has a base 33a of the support means 33 connected to its front side and has a vertical female screw formed in its center and into which the ball screw 52 is threaded.

[0031] The base 53 includes a flat plate portion 53a that is long in the vertical direction (Z-axis direction), horizontal extension portions 53b that are integral with the upper and lower ends of the flat plate portion 53a and rotatably support the upper and lower ends of the ball screw 52, ​​and a vertical (Z-axis) guide rail 53c that is attached to the front side of the flat plate portion 53a between the upper and lower extension portions 53b and along the flat plate portion 53a. Here, the drive motor 51 is placed on the upper surface of the upper extension portion 53b, and the guide rail 53c is inserted into a vertical (Z-axis) guide groove formed on the rear side of the movable support 54. The drive motor 51 is controlled by the control device 4 to rotate, and the ball screw 52 is rotated, whereby the movable support 54 moves in the vertical direction (Z-axis direction) along the guide rail 53c and applies pressure to the workpiece W downward (Z-axis direction).

[0032] At this time, the movable support 54 moves upward or downward depending on the rotation direction of the ball screw 52, ​​causing the base 33a of the support means 33 connected to the movable support 54 to move up and down, and the horn 32 moves closer to the support 2 or away from the support 2. Then, the downward movement of the base 33a caused by the downward movement of the movable support 54 applies pressure to the workpiece W sandwiched between the welding tool 34 of the horn 32 and the support 2.

[0033] Incidentally, a pressure sensor (not shown) constituted by a load cell or the like is provided on the support body 2 or the head unit 3, and the pressure sensor detects the pressure applied by the pressure means 5 to the workpiece W sandwiched between the welding tool 34 and the support body 2. Also, a linear encoder 6 (see FIG. 1) is provided on the movable support body 54, which detects the height of the head unit 3 in the vertical direction (Z-axis direction). Here, the control device 4 controls the drive motor 51 based on the detection signal of the linear encoder 6, thereby adjusting the height of the head unit 3 and thereby adjusting the height of the horn 32 relative to the support body 2.

[0034] <Joining Operation> The joining operation of the two joining members 8 and 9 shown in FIGS. 3 and 4 will be described.

[0035] As shown in FIG. 3 , a workpiece W, which is formed by placing an Al joining sheet 10 having a plurality of protrusions 11 formed in a twill pattern on both sides between two joining members 8 and 9 made of, for example, Cu, is placed on a support 2, and the workpiece W is held between the support 2 and the horn 32 of the head unit 3. With the workpiece W sandwiched between the support 2 and the horn 32 of the head unit 3, a predetermined pressure is applied to the horn 32 and the joining tool 34 by the pressure means 5 to pressurize the workpiece W, while ultrasonic vibrations are applied to the horn 32 in a lateral vibration direction (Y-axis direction in FIGS. 1 and 2 ) perpendicular to the pressure direction (Z-axis direction in FIGS. 1 and 2 ), thereby ultrasonically joining the workpieces W.

[0036] At this time, the joining tool 34 attached to the horn 32 is formed so that the Y-direction width of the contact surface with the joining object W is larger than the Y-direction width of the upper joining member 8, which allows the joining tool 34 to grip the upper joining member 8, and when ultrasonic vibrations are applied, the two joining members 8, 9 can be vibrated relative to each other, thereby joining the two joining members 8, 9 together by surface joining.

[0037] The two joining members 8, 9 and the joining sheet 10 joined in this way become one unit, but the joining condition in the cross section changes as the joining progresses over time, as shown in Fig. 7. Note that "joining progress" in Fig. 7 indicates the progress over time from the start of joining in the direction of the arrow, and in Fig. 7, voids (spaces / gaps) occurring at the joining interfaces between the joining members 8, 9 and the joining sheet 10 are represented by black horizontal lines.

[0038] 7, the black horizontal lines representing voids were thick at the beginning of bonding, but as bonding progressed, the black horizontal lines representing voids gradually became thinner, and by the end of bonding, the black horizontal lines disappeared, indicating that the two bonding members 8, 9 and the bonding sheet 10 were integrated and surface-to-surface bonding was achieved without the occurrence of voids at the bonding interface. The reason for this is thought to be that by forming multiple protrusions 11 on the bonding sheet 10, the contact area of ​​each protrusion 11 with the two bonding members 8, 9 can be reduced, thereby reducing the contact (static) friction force. As a result, large slippage occurs between the contact surfaces of the bonding sheet 10 and the two bonding members 8, 9, increasing the newly formed surface, promoting solid-state bonding and enabling surface bonding.

[0039] The contact surface of the welding tool 34 with the workpieces W is flat, and moreover, as described above, the width of the welding tool 34 in the Y direction is greater than the width of the upper welding member 8 in the Y direction. Therefore, at the contact point of the welding tool 34 with the welding member 8 after welding (the area surrounded by the dashed dotted line in FIG. 8 ), the welding tool 34 can grip the upper welding member 8 and vibrate the two welding members 8, 9 relatively. Moreover, no pressure marks, which are depressions in the welding tool 34 when the welding tool 34 pressurizes the workpieces W, are left on the upper welding member 8, and the welding members 8, 9 can be joined with an attractive finish. Therefore, the welding tool 34 may have a simple shape with a flat contact surface, and when the welding tool 34 is replaced, a replacement welding tool can be easily and inexpensively prepared.

[0040] Therefore, according to the above-described embodiment, the joining sheet 10 having a plurality of protrusions 11 formed on both sides is placed between the two metal joining members 8, 9, and the joining members W are joined by applying a pressure to the horn 32 using the pressure means 5 to pressurize the joining objects W while applying ultrasonic vibrations in a direction perpendicular to the pressure direction using the ultrasonic vibration means. Therefore, the plurality of protrusions 11 can reduce the contact area between the joining sheet 10 and the two joining members 8, 9, thereby reducing the contact (static) friction force. When the ultrasonic vibrations are applied, large slippage occurs between the contact surfaces of the joining sheet 10 and the two joining members 8, 9, increasing the active newly formed surface, thereby promoting solid-state joining. As a result, the two joining members 8, 9 can be well surface-joined while preventing the generation of voids at the joining interface.

[0041] Furthermore, a plurality of truncated cone-shaped protrusions 11, each having a circular end face diameter of 10 μm to 3000 μm and a height of 10 μm to 1000 μm, are formed in a twill pattern on both sides of the joining sheet 10. This reduces the contact (static) friction force between the protrusions 11 of the joining sheet 10 and the two joining members 8, 9, and generates a large amount of slippage between the contact surfaces of the joining sheet 10 and the two joining members 8, 9, thereby enabling good surface joining of the two joining members 8, 9.

[0042] Furthermore, the contact surface of the welding tool 34 that applies pressure to the workpieces W can be flat without being processed to have irregularities, so that after welding, no pressure marks, which are depressions caused by the pressure of the welding tool 34, remain at the contact points of the welding tool 34 on the workpieces W, and both welding members 8, 9 can be joined with an attractive finish. Furthermore, the welding tool 34 can be of a simple shape with a flat contact surface, and when the welding tool 34 is replaced, a replacement welding tool can be easily and inexpensively prepared.

[0043] The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.

[0044] For example, in the above embodiment, the bonding members 8 and 9 are both made of Cu and the bonding sheet 10 is made of Al, but the bonding members 8 and 9 may be made of different metals.

[0045] Furthermore, the joining members 8 and 9 may have the same Cu film or the same Al film on a resin substrate, or one of the joining members may be a metal body such as Cu or Al, and the other may be a resin substrate on which a metal film such as a Cu film or an Al film is formed by plating or the like.

[0046] Furthermore, the bonding sheet 10 is not limited to being made of aluminum, but may be made of copper, or may be made of a metal that is more easily displaced by ultrasonic vibration than the bonding members 8 and 9. In this case, it is preferable to form the protrusions 11 from the same or the same metal as the bonding sheet 10. Specifically, in addition to aluminum, it is preferable to use a metal that is more easily displaced, such as nickel (Ni), silver (Ag), gold (Au), copper (Cu), or tin (Sn), for the bonding sheet 10. In this way, when the bonding sheet 10 is made of a metal that is more easily displaced, the protrusions 11 of the bonding sheet 10 are easily displaced by ultrasonic vibration energy when ultrasonic vibration is applied while pressure is applied, making it easier for the bonding sheet 10 to be solid-state bonded to the two bonding members, thereby allowing the bonding members 8 and 9 to be well bonded together.

[0047] In the above embodiment, the protrusions 11 of the same shape are formed in the same twill pattern on both sides of the bonding sheet 10. However, a plurality of protrusions 11 may be formed in a lattice (matrix) pattern other than the twill pattern. Furthermore, protrusions of different shapes may be formed on both sides of the bonding sheet 10, or protrusions of different shapes may be formed in different patterns.

[0048] Furthermore, the protrusions formed on the joining sheet 10 are not limited to the above-mentioned truncated cone shape, but may also be cylindrical, or even truncated pyramid or prism-shaped. In this case, too, it is possible to create a large slip between the contact surfaces of the joining sheet and the joining members, and the two joining members can be joined well without creating voids at the joining interface.

[0049] Alternatively, the bonding sheet 10 may be formed by forming the above-described plurality of protrusions 11 on the surface of a clad material (a laminate of different metal sheets). In this case, since the materials of the front and back of the bonding sheet 10 are different, by using a clad material for the bonding sheet 10, in which metal sheets made of materials that are easily displaced to match the materials of the bonding members 8 and 9 to be bonded, the dissimilar bonding members 8 and 9 can be solid-state bonded more easily and satisfactorily by ultrasonic vibration.

[0050] Furthermore, in the above embodiment, the Y-direction width of the joining tool 34 is described as being larger than the Y-direction width of the upper joining member 8, but the Y-direction width of the joining tool 34 may also be smaller than the Y-direction width of the upper joining member 8.

[0051] The present invention can be applied to an ultrasonic bonding apparatus that ultrasonically bonds two bonding members together.

[0052] DESCRIPTION OF SYMBOLS 1 ultrasonic bonding device 2 support 5 pressure means 8, 9 bonding member 10 bonding sheet 11 protrusion 31 vibrator (ultrasonic vibration means) 32 horn (ultrasonic vibration means) 34 bonding tool (ultrasonic vibration means) W bonding object

Claims

1. An ultrasonic bonding device for ultrasonically bonding two bonding members, comprising: a metal bonding sheet placed between the two bonding members; a support that supports an object to be bonded, formed by inserting the bonding sheet between the two bonding members, in a placed state; ultrasonic vibration means having a vibrator and a horn that holds the object to be bonded between the support and the horn and applies ultrasonic vibrations; and pressure means that applies a pressure to the horn in the direction of the support while the object to be bonded is held between the support and the horn, wherein the bonding sheet has a plurality of protrusions formed on each side, and the object to be bonded is bonded by the pressure means applying ultrasonic vibrations in a direction perpendicular to the pressure direction of the pressure means.

2. The ultrasonic bonding device according to claim 1, characterized in that the protrusions formed on both sides of the bonding sheet have an approximately truncated cone or cylindrical shape, and the circular diameter of the end face of the truncated cone or cylinder is 10 μm to 3000 μm and the height is 10 μm to 1000 μm.

3. An ultrasonic bonding device according to claim 1 or 2, characterized in that the plurality of protrusions are formed on both sides of the bonding sheet in a twill or grid pattern.

4. The ultrasonic bonding device according to claim 1, wherein the projections formed on the bonding sheet have different shapes and / or different arrangement patterns on both sides.

5. The ultrasonic bonding device according to claim 1, wherein both of the bonding members are made of the same kind of metal or have the same kind of metal film on the bonding surfaces.

6. The ultrasonic bonding device according to claim 1, wherein the two bonding members are made of different metals or have different metal films on the bonding surfaces.

7. The ultrasonic bonding device according to claim 1, wherein the bonding sheet is made of a metal that is more easily displaced than the two bonding members when ultrasonic vibrations are applied by the ultrasonic vibration means.

8. The ultrasonic bonding device according to claim 7, wherein the plurality of protrusions on both sides of the bonding sheet are made of the same or a different metal as the bonding sheet.

9. An ultrasonic bonding device as described in claim 1 or claim 2, characterized in that the shape of the protrusions on the bonding sheet is approximately truncated pyramid or prism-shaped, and the truncated pyramid or prism-shaped protrusions are formed in multiple rows in a twill or lattice pattern on the bonding sheet.

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