Tip structure for ultrasonic joining, ultrasonic joining device, and ultrasonic joining program

Abstract

To provide a structure etc. in which a tip for ultrasonic joining is fixed to a base part of an ultrasonic complex vibration element etc. more securely.SOLUTION: A base part 14 and a horn tip 40 are coupled by a coupling mechanism such as a bolt B. The base part 14 formed of a stainless-steel material and the horn tip 40 formed of a high speed steel material having a lower melting point than that of the stainless steel material are coupled through a welding portion wld where a larger amount of the high speed steel material is welded than that of the stainless steel material.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic bonding tip for bonding multiple workpieces made of various materials such as metals using ultrasonic vibrations, and to an ultrasonic bonding technique using the ultrasonic bonding tip. [Background technology]

[0002] The present applicant has proposed a technology for joining multiple workpieces using ultrasonic complex vibration (see, for example, Patent Document 1). Ultrasonic complex vibration is achieved by combining ultrasonic vibrations in two directions perpendicular to the axial direction of an ultrasonic joining tip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7219495 Summary of the Invention [Problem to be solved by the invention]

[0004] When the ultrasonic bonding tip is connected to the ultrasonic composite vibration element by a mechanical fixing mechanism such as a screw fastening mechanism, the fixing strength may be insufficient, and therefore, the ultrasonic bonding tip may be partially or entirely displaced relative to the ultrasonic composite vibration element after repeated joining of workpieces.

[0005] Therefore, it is conceivable to improve the fixing strength between the ultrasonic bonding tip and the ultrasonic composite vibration element by not only mechanically connecting the tip to the ultrasonic composite vibration element but also welding the tip to the element.

[0006] However, depending on the type of welding, the fixing strength of the ultrasonic welding tip to the ultrasonic composite vibration element may still be insufficient, and repeated welding of workpieces may cause cracks to appear in the welded area.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a structure in which an ultrasonic bonding tip is more reliably fixed to a base of an ultrasonic composite vibration element or the like. [Means for solving the problem]

[0008] The ultrasonic bonding chip structure of the present invention comprises: An ultrasonic bonding tip structure including an ultrasonic bonding tip and a base for propagating ultrasonic vibrations to the ultrasonic bonding tip, the base and the ultrasonic bonding tip are connected by a connecting mechanism; The base, which is made of stainless steel, and the ultrasonic bonding tip, which is made of high-speed steel having a lower melting point than the stainless steel, are connected via a welding portion where the high-speed steel is welded more heavily than the stainless steel.

[0009] According to the ultrasonic bonding chip structure (hereinafter sometimes simply referred to as "chip structure") having this configuration, a base made of stainless steel and an ultrasonic bonding chip (hereinafter sometimes simply referred to as "chip") made of high-speed steel with a lower melting point than the stainless steel are connected via a welded portion. The welded portion is formed by welding the high-speed steel more heavily than the stainless steel, and the welded portion contains more components derived from the high-speed steel than from the stainless steel.

[0010] According to the findings of the present inventors, in this case, the strength of the welded portion is higher than when the components derived from the high-speed steel material are contained equally with the components derived from the stainless steel material, and when the components derived from the high-speed steel material are contained less than the components derived from the stainless steel material at the welded portion, thereby improving the fixing strength to the base of the tip and improving the mechanical strength of the tip structure as a whole.

[0011] The ultrasonic bonding device of the present invention comprises: an ultrasonic bonding tip; an ultrasonic complex vibration element configured to induce ultrasonic complex vibration by combining longitudinal vibration and torsional vibration and propagate the ultrasonic complex vibration to the ultrasonic bonding tip; a control device for controlling the complex vibration of the ultrasonic complex vibration element; An ultrasonic bonding apparatus comprising: The ultrasonic bonding chip structure according to the present invention is composed of a base portion that is a part of the ultrasonic complex vibration element, and the ultrasonic bonding chip.

[0012] The ultrasonic bonding program of the present invention includes: An ultrasonic bonding program that gives a computer constituting the control device a function of performing an ultrasonic bonding method for bonding one workpiece and another workpiece using the ultrasonic bonding device according to the present invention, The ultrasonic bonding method comprises: a step of determining whether or not the joining of the one workpiece and the other workpiece has been completed based on a signal corresponding to a value of a designated parameter that changes depending on the progress of joining of the one workpiece to the other workpiece while the ultrasonic joining tip is in contact with the one workpiece to be joined; and stopping the complex vibration of the ultrasonic complex vibration element when it is determined that the joining of the one workpiece and the other workpiece has been completed.

[0013] According to the ultrasonic bonding program of the present invention and the ultrasonic bonding method implemented by a computer constituting a control device with the functions provided by the ultrasonic bonding program, it is possible to accurately determine whether the bonding is complete or not based on the change in the value of a specified parameter, such as the amplitude of ultrasonic vibration of the ultrasonic bonding tip of the present invention, which changes depending on the progress of the bonding of the one workpiece and the other workpiece. If the determination result indicates that the bonding of the one workpiece and the other workpiece is complete, the ultrasonic vibration of the ultrasonic bonding tip is stopped, and as a result, the period during which the ultrasonic bonding tip is ultrasonically vibrated can be appropriately controlled from the perspective of improving the quality of the bonding of the one workpiece and the other workpiece. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating the configuration of an ultrasonic bonding device according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a first embodiment of the present invention; [Figure 3] 1 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a first embodiment of the present invention; [Figure 4] 3 is a flowchart showing the function of the ultrasonic bonding device. [Figure 5] FIG. 4 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a second embodiment of the present invention. [Figure 6] FIG. 4 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a diagram illustrating the configuration of an ultrasonic bonding chip structure according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Configuration of ultrasonic bonding device) The ultrasonic bonding device according to one embodiment of the present invention shown in Fig. 1 includes an ultrasonic complex vibration device 10, a horn tip 40 (ultrasonic bonding tip), and an anvil 18. The anvil 18 may be omitted. For the purpose of explaining the configuration, a three-dimensional Cartesian coordinate system (x, y, z) as shown in Fig. 1 will be used as appropriate.

[0016] The ultrasonic complex vibration device 10 includes a first vibration element 110 having a substantially cylindrical shape, an intermediate vibration element 100 having a substantially cylindrical, cylindrical, or bottomed cylindrical shape, and a second vibration element 120 having a substantially cylindrical or bottomed cylindrical shape. The first vibration element 110, the intermediate vibration element 100, and the second vibration element 120 constitute "vibration elements."

[0017] The first vibration element 110 and the intermediate vibration element 100 are coaxially connected by a mechanical connecting mechanism (such as a bolt and / or a clamp mechanism) at the middle or intermediate portion of the ultrasonic complex vibration device 10. The intermediate vibration element 100 and the second vibration element 120 are coaxially connected by a mechanical connecting mechanism at the middle portion of the ultrasonic complex vibration device 10. The first vibration element 110, the intermediate vibration element 100, and the second vibration element 120 may be integrally configured rather than being mechanically connected.

[0018] The intermediate vibration element 100 may be a component of the first vibration element 110. That is, the first vibration element 110 may be composed of two vibration elements. In this case, the first vibration element 110 and the intermediate vibration element 100 may be integrally configured rather than being mechanically connected. The intermediate vibration element 100 may be a component of the second vibration element 120. That is, the second vibration element 120 may be composed of two vibration elements. In this case, the second vibration element 120 and the intermediate vibration element 100 may be integrally configured rather than being mechanically connected.

[0019] As shown in FIG. 1, the first vibration element 110 is provided with a piezoelectric body 112 whose axial direction (parallel to the first axis) is the piezoelectric polarization direction.

[0020] As shown in FIG. 1 , the intermediate vibration element 100 is formed with a substantially annular plate-shaped intermediate flange 102 that protrudes radially around its entire circumference at a central position in the axial direction. The intermediate vibration element 100 is configured to be clamped or supported around its entire circumference by a clamping mechanism (not shown) at least at the intermediate flange 102. If it is ensured that the intermediate vibration element 100 is supported by a mechanical support mechanism, the intermediate flange 102 may be omitted. As shown in FIG. 1 , the intermediate vibration element 100 has a substantially cylindrical shape with a substantially constant outer diameter in the axial direction behind the intermediate flange 102 (leftward in FIG. 1 ). As shown in FIG. 1 , the intermediate vibration element 100 has a substantially cylindrical shape (a shape in which a substantially truncated conical shape and a substantially cylindrical shape are coaxially connected) with a substantially constant outer diameter after continuously tapering partway toward the tip of the intermediate vibration element 100 ahead of the intermediate flange 102 (+x direction in FIG. 1 ).

[0021] 1, the second vibration element 120 is provided with a frequency adjustment element 122 in the shape of a generally regular octagonal plate with rounded corners, which extends radially around the entire circumference at a midpoint in the axial direction of the second vibration element 120. The frequency adjustment element 122 adjusts the resonance frequencies of the longitudinal vibration component and the torsional vibration component of the ultrasonic vibration. The outer shape of the frequency adjustment element 122 may be a generally circular, generally elliptical, or generally regular n-polygonal plate (e.g., n = 4, 6, 8, 12, 16, etc.) plate, columnar, or frustum shape, which shares a common central axis with the second vibration element 120, or any combination thereof.

[0022] 1, the second vibration element 120 has a plurality of slits 124 formed on its outer surface behind the frequency adjustment element 122. A plurality of slits 124 may be formed on the outer surface of the second vibration element 120 ahead of the frequency adjustment element 122. The slits 124 extend obliquely in the second vibration element 120 when viewed from the side, or extend in the axial direction while being displaced in the circumferential direction in phase with each other. N (N=2, 3, ...) slits 124 may be arranged to have N-fold rotational symmetry (e.g., N=8, 12, or 16) around the central axis of the second vibration element 120.

[0023] As shown in FIG. 1, the second vibration element 12 has a base 14 at its axial tip. The base 14 has a generally rectangular cross section from the proximal end (left end in FIG. 2) to the distal end (right end in FIG. 2), with the long sides of the rectangle remaining generally constant while the short sides of the rectangle decrease relatively steeply and then continue to a constant length (see FIGS. 2 and 3). The base 14 may be integral with the second vibration element 12, or may be detachably fixed or connected to the second vibration element 12. The base 14 has multiple female threads 142 extending upward from its lower surface 14C. The base 14 is made of stainless steel. Examples of stainless steel include nickel-molybdenum-chromium steel. The melting point of the stainless steel is, for example, within a temperature range of 1400°C to 1500°C.

[0024] The base 14 may be provided with a female thread extending downward from its upper surface (or extending laterally from its side surface). The male thread of a balancer for adjusting the phase difference between the longitudinal vibration and the torsional vibration in the horn tip 40 may be screwed into the female thread, thereby removably fixing the balancer to the base 14 of the second vibration element 12.

[0025] The anvil 18 is disposed so as to face the tip of the horn tip 40 in the vertical direction. A first workpiece W1 and a second workpiece W2 as multiple workpieces are placed on the upper surface of the anvil 18. The anvil 18 may be configured to passively or actively displace up and down in response to the pressure of the horn tip 40 received through the first workpiece W1 and the second workpiece W2.

[0026] As shown in FIG. 1, the ultrasonic bonding apparatus according to one embodiment of the present invention further includes an operating device 20, a control device 22, a high-frequency power supply device 221, a translational drive device 222, and a status sensor 224.

[0027] The operation device 20 is configured, for example, by a display, and displays or outputs on the display the displacement amount of the pressure block and / or the time series of the pressure according to the output signal of the status sensor 224. The display may be configured by a touch panel display, and may be configured to accept a setting operation for allowing the user to directly or indirectly specify parameters, such as one of a plurality of bonding modes that determine a time series pattern of the target pressure.

[0028] The control device 22 is configured to include a microcomputer, an arithmetic processing unit (CPU, microprocessor, processor core, etc.), and a storage device (memory such as ROM and RAM). The control device 22 is configured to read software such as an ultrasonic bonding program stored in the storage device, and to control the displacement operation of the pressure block by the translation drive device 222 in accordance with the program based on, for example, a time series of the displacement amount of the pressure block represented by the output signal of a stroke sensor constituting the status sensor 224. The control device 22 is configured to control the power supplied to the piezoelectric body 112 based on the amplitude (corresponding to a specified parameter) of the horn tip 40 represented by the output signal of an amplitude sensor constituting the status sensor 224, and thereby to control the ultrasonic vibration power of the vibration elements (first vibration element 110, intermediate vibration element 100, and second vibration element 120) and the ultrasonic vibration power of the horn tip 40.

[0029] The high-frequency power supply device 221 is configured to excite the first vibration element 110 in the axial direction by applying a high-frequency AC voltage to the piezoelectric element 112 of the first vibration element 110 in accordance with power supplied from a commercial power source (not shown).

[0030] The translational drive device 222 is equipped with a pressure block and is configured to apply pressure from the horn tip 40 to the first workpiece W1 and the second workpiece W2 by displacing a support mechanism such as a clamping mechanism that supports the intermediate vibration element 100 using the pressure block.

[0031] The status sensor 224 includes a stroke sensor that outputs a signal corresponding to the displacement of the pressure block that constitutes the translational drive device 222, as well as an amplitude sensor that outputs a signal corresponding to the amplitude (corresponding to a specified parameter) of the horn tip 40. The amplitude sensor may be a sensor module configured with an imaging device and a device that calculates the amplitude by analyzing an image captured by the imaging device. The status sensor 224 may be provided with a pressure sensor that outputs a signal corresponding to the pressure acting on the intermediate vibration element 100 from the pressure block of the translational drive device 222 (i.e., the pressure that the horn tip 40 applies to the first workpiece W1 and the second workpiece W2), and the control device 22 may control the time series of the pressure to be constant or in a specified manner based on the output signal of the pressure sensor.

[0032] (Ultrasonic bonding chip structure (first embodiment)) The ultrasonic bonding tip structure according to the first embodiment of the present invention, shown in Figures 2 and 3, is made up of a base 14 and a horn tip 40, which are fixed to each other. The horn tip 40 is made of high-speed steel, which has a lower melting point than the stainless steel that makes up the base 14. Examples of high-speed steel include tungsten-based steel and molybdenum-based steel. The melting point of high-speed steel is lower than that of stainless steel, and is within the temperature range of 1300°C to 1500°C, for example.

[0033] The horn tip 40 has a first tip portion 41 in the shape of a substantially rectangular plate, and a second tip portion 42 in the shape of a substantially rectangular plate or a substantially oval plate that is continuous with the first tip portion 41 at the distal end of its lower end. The first tip portion 41 has a countersunk hole 402 that extends from its lower surface to its upper surface 40C. The second tip portion 42 abuts against one of the first workpieces W1 and the second workpieces W2, that is the uppermost workpiece W1. The abutting portion of the second tip portion 42 against the one workpiece W1 may be a flat surface or a convex curved surface, and may have one or more convex portions and / or one or more concave portions formed thereon.

[0034] The first tip portion 41 may be configured as a substantially circular cylinder, a substantially elliptical cylinder, a substantially n-sided prism (regular n-sided prism), a substantially truncated cone, or a substantially n-sided truncated pyramid (regular n-sided truncated pyramid). The second tip portion 42 may be configured as a connected body in which a substantially circular cylinder, a substantially elliptical cylinder, a substantially n-sided prism (regular n-sided prism), a substantially truncated cone, or a substantially n-sided truncated pyramid (regular n-sided truncated pyramid), or any combination thereof, are connected so as to be stacked coaxially.

[0035] 2, female thread portion 142 of base 14 and countersunk hole 402 of horn tip 40 are aligned, and then male thread portion B2 of bolt B inserted into countersunk hole 402 is screwed into female thread portion 142. Head B1 of bolt B presses the stepped portion of countersunk hole 402 toward base 14, thereby fixing horn tip 40 to base 14 with substantially flat upper surface 40C of horn tip 40 and substantially flat lower surface 14C of base 14 in pressure contact.

[0036] As shown in FIGS. 2 and 3, the weld region wld is formed by welding the distal end of the horn tip 40 and the distal end of the base 14. In FIGS. 2 and 3, the weld region wld is approximately represented by a laser spot weld mark that is substantially conical (or substantially cylindrical or substantially truncated conical) with a height D (e.g., 2.0 to 4.0 mm) and a substantially circular bottom surface with a diameter 2R (e.g., 1.5 to 3.5 mm). The central axis of the truncated cone extends substantially parallel to the boundary surface between the horn tip 40 and the base 14 (the upper surface 40C of the horn tip 40 and the lower surface 14C of the base 14). The central axis of the truncated cone is offset from the boundary surface toward the horn tip 40 by Δ (e.g., Δ = 0.16R to 0.48R (e.g., Δ = 0.20 to 0.60 mm when R = 1.25 mm)). As a result, in the welded portion wld, the components derived from the high-speed steel material constituting the horn tip 40 are greater than the components derived from the stainless steel material constituting the base portion 14 .

[0037] The welded portion wld may be formed by various welding methods such as laser welding, electron beam welding, and arc welding.

[0038] The bias ratio of the high-speed steel material in the welded portion wld is in the range of 0.60 to 0.80. For example, the bias ratio may be defined as the volume ratio (ΔV / V) of the portion (volume ΔV) present at the horn tip 40 in a truncated cone (volume V) that approximately represents the welded portion wld, based on the boundary surface between the base 14 and the horn tip 40 before the welded portion wld is formed. When the welded portion wld is approximately represented by a cylinder, the bias ratio is expressed as [{(π / 2)+arcsin(Δ / R)}(R) 2 +(R 2 -Δ 2 ) 1 / 2 Δ] / πR 2 =0.5+arcsin(Δ / R) / π+(R 2 -Δ 2 ) 1 / 2 Δ / πR 2 The content ratio of components derived from the high-speed steel material that constitutes the horn tip 40 in the welded portion may be defined as the bias ratio.

[0039] The direction of irradiation of the laser beam is adjusted to be parallel to the boundary surface between the horn tip 40 and the base 14, and the irradiation center position of the laser beam is adjusted to a position shifted by Δ toward the horn tip 40 from the boundary surface between the horn tip 40 and the base 14, and then laser spot welding is performed to form the welded area wld.

[0040] (Ultrasonic bonding method) The procedure of an ultrasonic bonding method according to one embodiment of the present invention using the ultrasonic bonding device 1 will be described with reference to the flowchart of Fig. 2. As shown in Fig. 3, a first workpiece W1 and a second workpiece W2 are placed on the anvil 18 in a stacked state from top to bottom.

[0041] The ultrasonic complex vibration device 10 and the horn tip 40 are moved in the radial direction by the translational drive device 222 so as to approach the first workpiece W1 and the second workpiece W2 (FIG. 4 / STEP 112).

[0042] Furthermore, it is determined whether the pressure P that horn tip 40 receives from first workpiece W1 (and second workpiece W2) is equal to or greater than first specified pressure P1 (FIG. 4 / STEP 114). The pressure P that horn tip 40 receives from first workpiece W1 is measured based on the output signal of a pressure sensor that constitutes state sensor 224. When the tip of horn tip 40 is separated from workpiece W1, P=0. For example, as shown in FIG. 3, when the tip of horn tip 40 comes into contact with first workpiece W1 that is inserted into through-hole W20 of second workpiece W2, a reaction force is received, so that P>0.

[0043] If the determination result is negative (FIG. 4 / STEP 114...NO), the translational drive device 222 moves the ultrasonic complex vibration device 10 and the horn tip 40 in the radial direction so as to approach the first workpiece W1 inserted into the through-hole W20 of the second workpiece W2 (FIG. 2 / connector X1 →STEP 112). As a result, the position of the horn tip 40, and therefore the static pressure applied from the horn tip 40 to the first workpiece W1 and the second workpiece W2, is adjusted to be within a specified static pressure range (e.g., 200 N to 800 N).

[0044] If the determination result is affirmative (FIG. 4 / STEP 114...YES), ultrasonic vibrations are generated in the vibration elements (FIG. 4 / STEP 116). Specifically, in response to power being supplied to the high-frequency power supply device 221 from a commercial power source (not shown) via a slip ring or the like, the high-frequency power supply device 221 applies a high-frequency AC voltage to the piezoelectric body 112 of the first vibration element 110. This causes the first vibration element 110 to vibrate in its axial direction at, for example, approximately 20 KHz, generating ultrasonic vibrations. The ultrasonic vibrations are transmitted from the first vibration element 110 to the intermediate vibration element 100 in its axial direction, and the amplitude of the ultrasonic vibrations is amplified. Furthermore, the ultrasonic vibrations with amplified amplitude are transmitted from the intermediate vibration element 100 to the second vibration element 120 in its axial direction.

[0045] In this way, a portion of the longitudinal vibration component (axial component of the second vibration element 120) of the ultrasonic vibration transmitted to the second vibration element 120 is converted into a torsional vibration component by the multiple slits 124 formed on the outer surface of the second vibration element 120. Then, a composite vibration generated by combining the longitudinal vibration component and the torsional vibration component is transmitted to the horn tip 40 fixed to the tip of the second vibration element 120.

[0046] In response, the horn tip 40 displaces or vibrates in a circular or elliptical orbit on a plane perpendicular to the contact direction of the first workpiece W1. As a result, the amplitude and ultrasonic vibration power of the horn tip 40 gradually increase from the vibration start time t=t0. During this process, impurities are removed from the contact surface between the first workpiece W1 and the second workpiece W2, further promoting plastic deformation of the contact surface between the first workpiece W1 and the second workpiece W2. After the rate of increase in the amplitude and ultrasonic vibration power of the horn tip 40 significantly decreases at time t=t1, the amplitude and ultrasonic vibration power of the horn tip 40 gradually increase. This is due to the removal of oxide coatings and other metals constituting the joining surfaces of the first workpiece W1 and the second workpiece W2, revealing clean, activated metal atoms at the joining surfaces. The temperature rise due to frictional heat activates the atomic movement, generating mutual attraction between the atoms.

[0047] At this time, the composite vibration is applied to the first workpiece W1 and the second workpiece W2 while adjusting the amount of pressing of the first workpiece W1 and the second workpiece W2 by the horn tip 40 and / or the static pressure applied to the first workpiece W1 and the second workpiece W2. As a result, as shown in Fig. 4, the outer surface and the peripheral edge of the lower surface of the first workpiece W1 can be solid-state welded to the stepped portion W22 of the second workpiece W2 over the entire circumference.

[0048] It is determined whether the time derivative δA (= current amplitude A(k) - previous amplitude A(k-1)) of the amplitude A of the horn tip 40 is negative and whether the amplitude A is equal to or less than the reference amplitude A0 (FIG. 4 / STEP 118). An amplitude sensor constituting the state sensor 224 optically measures the amplitude A at a specified location (e.g., a location where the amplitude is relatively large) of the horn tip 40. Instead of this determination process, it may be determined whether the amplitude A has decreased by the reference amplitude A0 (or a reference ratio based on the maximum value) using the maximum value at the time when the amplitude A started to decrease as a reference. For example, the reference amplitude A0, such as one of multiple joining modes for which the reference amplitude A0 is determined, may be directly or indirectly specified via a touch panel display constituting the operation device 20.

[0049] If the determination result is negative (FIG. 4 / STEP 118...NO), ultrasonic vibrations are continuously generated in the vibration element (FIG. 2 / connector X2 →STEP 116). On the other hand, if the determination result is positive (FIG. 4 / STEP 118...YES), the translational drive device 222 moves the ultrasonic complex vibration device 10 and the horn tip 40 away from the first workpiece W1 and the second workpiece W2 (FIG. 4 / STEP 122).

[0050] Furthermore, it is determined whether the pressure P that the horn tip 40 receives from the first workpiece W1 (and the second workpiece W2) has become equal to or less than a second designated pressure P2 (FIG. 4 / STEP 124). The second designated pressure P2 is set to a value smaller than the first designated pressure P1, for example, 0 or a very small value.

[0051] If the determination result is negative (FIG. 4 / STEP 124...NO), the translational drive device 222 moves the ultrasonic complex vibration device 10 and the horn tip 40 away from the first workpiece W1 and the second workpiece W2 (FIG. 2 / connector X4 →STEP 122). This adjusts the radial position of the horn tip 40, and therefore the static pressure applied by the horn tip 40 to the first workpiece W1 and the second workpiece W2, so as to decrease.

[0052] If the determination result is positive (FIG. 4 / STEP 124...YES), the generation of ultrasonic vibrations in the vibration element is stopped (FIG. 4 / STEP 126). For example, after the time t=t2 when the amplitude of the horn tip 40 changes from increasing to decreasing and falls below the reference amplitude A0, the ultrasonic power of the horn tip 40 is controlled to become 0 with a slight response delay. This stops the series of processes.

[0053] (Action and effect) In the ultrasonic bonding tip structure used in the ultrasonic bonding device configured as described above, which is composed of a horn tip 40 (ultrasonic bonding tip) and a base 14, the base 14, which is made of stainless steel, and the horn tip 40, which is made of high-speed steel having a lower melting point than the stainless steel, are connected via a welded portion wld (see FIGS. 2 and 3). The welded portion wld is configured by welding the high-speed steel more heavily than the stainless steel, and the welded portion wld contains more components derived from the high-speed steel than from the stainless steel.

[0054] According to the findings of the present inventors, in this case, the strength of the welded portion wld is higher than when the components derived from the high-speed steel material are evenly mixed with the components derived from the stainless steel material, or when the components derived from the high-speed steel material are less than the components derived from the stainless steel material in the welded portion wld, thereby improving the fixing strength of the horn tip 40 to the base 14 and improving the mechanical strength of the entire tip structure.

[0055] (test) (Test Example 1) According to the first embodiment of the present invention, a welded portion wld having 2R=2.5 mm, D=3.0 mm, and Δ=0 mm was formed to fabricate an ultrasonic bonding tip structure of Test Example 1 (see FIGS. 2 and 3). Nickel-chromium-molybdenum steel was used as the stainless steel material constituting the base 14, and molybdenum-based steel was used as the high-speed steel material constituting the horn tip 40.

[0056] (Test Example 2) By forming a welded portion wld with 2R=2.5 mm, D=3.0 mm, and Δ=0.10 mm, the other manufacturing conditions were the same as in Test Example 1, and an ultrasonic bonding chip structure of Test Example 2 was manufactured.

[0057] (Test Example 3) By forming a welded portion wld with 2R=2.5 mm, D=3.0 mm, and Δ=0.20 mm, the other manufacturing conditions were the same as in Test Example 1, and an ultrasonic bonding chip structure of Test Example 3 was manufactured.

[0058] (Test Example 4) By forming a welded portion wld with 2R=2.5 mm, D=3.0 mm, and Δ=0.40 mm, the other manufacturing conditions were the same as in Test Example 1, and an ultrasonic bonding chip structure of Test Example 4 was manufactured.

[0059] (Test Example 5) By forming a welded portion wld with 2R=2.5 mm, D=3.0 mm, and Δ=0.60 mm, the other manufacturing conditions were the same as in Test Example 1, and an ultrasonic bonding chip structure of Test Example 5 was manufactured.

[0060] (Test Example 6) By forming a welded portion wld with 2R=2.5 mm, D=3.0 mm, and Δ=0.70 mm, the other manufacturing conditions were the same as in Test Example 1, and an ultrasonic bonding chip structure of Test Example 6 was manufactured.

[0061] Using the ultrasonic bonding tip structures of each test example, workpieces were repeatedly bonded using an ultrasonic bonding device. As a result, the presence or absence of cracks in the welded portion wld was confirmed. The test results are summarized in Table 1.

[0062] [Table 1]

[0063] (Ultrasonic bonding chip structure (second embodiment)) In the ultrasonic bonding tip structure according to the third embodiment of the present invention shown in Figures 5 and 6, the welded portion wld is approximately represented by a laser weld mark or weld bead having a substantially rectangular parallelepiped shape (or a substantially trapezoidal column shape). Specifically, the rectangular parallelepiped is divided into approximately equal parts by the boundary between the horn tip 40 and the base 14. The direction of the laser beam is adjusted to be parallel to the boundary between the horn tip 40 and the base 14, and the center of the laser beam is adjusted to be displaced from the horn tip 40 to the base 14. Then, laser welding is performed to form the welded portion wld. As a result, the welded portion wld contains more components derived from the high-speed steel material that constitutes the horn tip 40 than from the stainless steel material that constitutes the base 14.

[0064] (Ultrasonic bonding chip structure (third embodiment)) In the ultrasonic bonding chip structure according to the third embodiment of the present invention shown in Figure 7, the lower surface 14C of the base 14 and the upper surface 40C of the horn tip 40 are each generally inclined with respect to a plane s (see the dashed line) extending in the ultrasonic vibration direction of the horn tip (the ±x and ±y directions in Figure 7). The boundary surface is inclined so that it approaches the +z direction as it moves in the -x direction with respect to plane s. In other words, plane s includes the outer edge of the boundary surface between the base 14 and the horn tip 40, and virtually extends into the space inside the ultrasonic bonding chip structure in which the horn tip 40 exists. The inclined surface may be flat or curved.

[0065] The welded portion wld is formed by welding the high-speed steel material and the stainless steel material evenly at the outer edge of the boundary surface, while on the inside of the outer edge, the high-speed steel material is welded more heavily than the stainless steel material. That is, the welding spot of the base 14 and the horn tip 40 is located at the boundary between the base 14 and the horn tip 40 on the surface of the ultrasonic bonding tip structure. Therefore, the welded portion wld can be formed by welding the high-speed steel material more heavily than the stainless steel material overall, while maintaining ease of alignment of the welding spot.

[0066] Other configurations are almost the same as those in the first embodiment (see FIGS. 2 and 3), so the same reference numerals are used for the similar configurations and the description thereof will be omitted.

[0067] The lower surface 14C of the base 14 and the upper surface 40C of the horn tip 40 may each be partially inclined with respect to the plane s. The boundary surface between the base 14 and the horn tip 40 may have portions with different inclinations with respect to the plane s. For example, the boundary surface may have two of the following inclined surfaces: a surface inclined toward the +z direction as it approaches the +x direction, a surface inclined toward the +z direction as it approaches the -x direction, a surface inclined toward the +z direction as it approaches the +y direction, and a surface inclined toward the +z direction as it approaches the -y direction. The boundary surface may also have two inclined surfaces: a surface inclined toward the +z direction as it approaches the +x direction and a surface inclined toward the +z direction as it approaches the -x direction. The boundary surface may also have two inclined surfaces: a surface inclined toward the +z direction as it approaches the +y direction and a surface inclined toward the +z direction as it approaches the -y direction. At least a portion of the lower surface 14C of the base 14 may be formed to protrude downward in a frustum or pyramidal shape, and at least a portion of the upper surface 40C of the horn tip 40 may be formed to be recessed downward to fit the frustum or pyramidal shape.

[0068] (Ultrasonic bonding chip structure (fourth embodiment)) In the ultrasonic bonding chip structure according to the fourth embodiment of the present invention shown in Figure 8, the lower surface 14C of the base 14 and the upper surface 40C of the horn tip 40 are each generally inclined with respect to a plane s (see the dashed line) extending in the ultrasonic vibration direction of the horn tip (the ±x and ±y directions in Figure 8). The boundary surface is inclined so that it approaches the -z direction as it moves in the -x direction with respect to plane s. In other words, plane s includes the outer edge of the boundary surface between the base 14 and the horn tip 40, and virtually extends into the space inside the ultrasonic bonding chip structure where the base 14 exists. The inclined surface may be flat or curved.

[0069] The welded portion wld is formed by welding the high-speed steel material more heavily than the stainless steel material from the outer edge of the boundary surface to the inside.

[0070] Other configurations are almost the same as those in the first embodiment (see FIGS. 2 and 3), so the same reference numerals are used for the similar configurations and the description thereof will be omitted.

[0071] The lower surface 14C of the base 14 and the upper surface 40C of the horn tip 40 may each be partially inclined with respect to the plane s. The boundary surface between the base 14 and the horn tip 40 may have portions with different inclinations with respect to the plane s. For example, the boundary surface may have two of the following inclined surfaces: a surface inclined toward the +z direction as it approaches the +x direction, a surface inclined toward the +z direction as it approaches the -x direction, a surface inclined toward the +z direction as it approaches the +y direction, and a surface inclined toward the +z direction as it approaches the -y direction. The boundary surface may also have two inclined surfaces: a surface inclined toward the +z direction as it approaches the +x direction and a surface inclined toward the +z direction as it approaches the -x direction. The boundary surface may also have two inclined surfaces: a surface inclined toward the +z direction as it approaches the +y direction and a surface inclined toward the +z direction as it approaches the -y direction. At least a portion of the lower surface 14C of the base 14 may be formed to protrude downward in a frustum or pyramidal shape, and at least a portion of the upper surface 40C of the horn tip 40 may be formed to be recessed downward to fit the frustum or pyramidal shape.

[0072] (Another embodiment of the present invention) In the above embodiment, the amplitude A of the horn tip 40 was measured as a specified parameter that changes depending on the progress of joining one workpiece W1 and the other workpiece W2, but in other embodiments, the axial displacement amount, displacement speed and / or displacement acceleration of the vibration element (e.g., the second vibration element 12) may be measured as a specified parameter. [Explanation of symbols]

[0073] 10. Ultrasonic complex vibration device 100...Intermediate vibration element 102...Intermediate flange 110...First vibration element 112. Piezoelectric material 120...Second vibration element 122...Frequency adjustment element 124. Slit 14‥Base 142... Female thread 14C‥Bottom surface (boundary surface) 18. Anvil 20‥Operation device 22. Control device 221‥High frequency power supply equipment 222...Translation drive device 224...Status sensor 40. Horn tip (tip for ultrasonic bonding) 41. First tip part 42. Second chip part 402...Counterbore 40C‥Top surface (boundary surface) B...Bolt B1...Head B2...Male thread s‥Plane W1: First work W2: Second work wld...welded area Int...intermediate part.

Claims

1. An ultrasonic bonding tip structure including an ultrasonic bonding tip and a base for propagating ultrasonic vibrations to the ultrasonic bonding tip, the base and the ultrasonic bonding tip are connected by a connecting mechanism; The base portion made of stainless steel and the ultrasonic bonding tip made of high-speed steel having a lower melting point than the stainless steel are connected via a welding portion where the high-speed steel is welded more heavily than the stainless steel. Tip structure for ultrasonic bonding.

2. 2. The ultrasonic bonding chip structure according to claim 1, The welding portion is unevenly distributed on the ultrasonic bonding tip across the boundary surface between the base portion and the ultrasonic bonding tip. Tip structure for ultrasonic bonding.

3. 2. The ultrasonic bonding chip structure according to claim 1, The weight distribution ratio of the high-speed steel material at the welded portion is in the range of 0.60 to 0.

80. Tip structure for ultrasonic bonding.

4. 2. The ultrasonic bonding chip structure according to claim 1, At least a part of the boundary surface between the base and the ultrasonic bonding tip is inclined with respect to a plane extending in the ultrasonic vibration direction of the ultrasonic bonding tip. Tip structure for ultrasonic bonding.

5. 3. The ultrasonic bonding chip structure according to claim 2, A portion of the boundary surface between the base and the ultrasonic bonding tip, where the welding portion is formed, is inclined with respect to a plane extending in the ultrasonic vibration direction of the ultrasonic bonding tip. Tip structure for ultrasonic bonding.

6. 5. The ultrasonic bonding chip structure according to claim 4, a portion of the boundary surface between the base and the ultrasonic bonding tip where the welding portion is formed is inclined with respect to a plane including an outer edge of the boundary surface so that the plane extends in a space where the ultrasonic bonding tip is present; The welded portion is configured by uniformly welding the high-speed steel material and the stainless steel material at the outer edge of the boundary surface, while the high-speed steel material is biasedly welded more heavily than the stainless steel material inside the outer edge. Tip structure for ultrasonic bonding.

7. 5. The ultrasonic bonding chip structure according to claim 4, The base and the ultrasonic bonding tip have boundary surfaces at which portions having different inclinations with respect to the plane exist together. Tip structure for ultrasonic bonding.

8. an ultrasonic bonding tip; an ultrasonic complex vibration element configured to induce ultrasonic complex vibration by combining longitudinal vibration and torsional vibration and propagate the ultrasonic complex vibration to the ultrasonic bonding tip; a control device for controlling the complex vibration of the ultrasonic complex vibration element; An ultrasonic bonding apparatus comprising: The ultrasonic bonding chip structure according to any one of claims 1 to 7 is configured by a base portion that is a part of the ultrasonic composite vibration element and the ultrasonic bonding chip. Ultrasonic bonding equipment.

9. An ultrasonic bonding program that gives a computer constituting the control device a function of performing an ultrasonic bonding method for bonding one workpiece and another workpiece using the ultrasonic bonding device according to claim 8, The ultrasonic bonding method comprises: a step of determining whether or not the joining of the one workpiece and the other workpiece has been completed based on a signal corresponding to a value of a designated parameter that changes depending on the progress of joining of the one workpiece to the other workpiece while the ultrasonic joining tip is in contact with the one workpiece to be joined; and stopping the complex vibration of the ultrasonic complex vibration element when it is determined that the joining of the one workpiece and the other workpiece is completed. Ultrasonic welding program.

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