Ultrasonic bonding chip, ultrasonic bonding device using same, and ultrasonic bonding method

Abstract

Provided are an ultrasonic bonding chip capable of improving the quality of bonding between workpieces, and an ultrasonic bonding method and an ultrasonic bonding device using the ultrasonic bonding chip. In a direction perpendicular to the axial direction of a substantially cylindrical rod section 44, the ratio (D1 / d1) of an axial-direction length D1 of the rod section 44 to a maximum distance d1 (radius of the substantially circular cross-section) from the center of the cross-section having the maximum cross-sectional area to the peripheral edge of the cross-section is 30 or more. On the other hand, in a direction perpendicular to the axial direction of the substantially cylindrical rod section 44, the ratio (D1 / d1) of the axial-direction length D1 of the rod section 44 to the maximum distance d1 from the center of the cross-section having the maximum cross-sectional area to the peripheral edge of the cross-section is 120 or less.

Description

Ultrasonic bonding tip, ultrasonic bonding device using the tip, and ultrasonic bonding method

[0001] The present invention relates to an ultrasonic bonding tip that comes into contact with one of workpieces, such as metal, semiconductor, and / or plastic, in order to bond the workpieces together using ultrasonic vibrations, and to an ultrasonic bonding device and ultrasonic bonding method that use the ultrasonic bonding tip.

[0002] Ultrasonic welding has traditionally been used to join plastics used in food packaging, etc., or metals used in battery components, etc. A typical ultrasonic welding device ultrasonically vibrates the tip of a welding tip (tool) and repeatedly applies pressure to the workpieces to be joined.

[0003] In ultrasonic bonding, there is an appropriate time for applying ultrasonic vibrations to the workpiece, and as described in Non-Patent Document 1 below, if the application time is too long, the bonding strength of the bonded part will decrease and damage such as cracks may occur in the workpiece.

[0004] Conventionally, bonding methods have been implemented in which bonding is performed for a predetermined application time of ultrasonic vibration. For example, in Patent Document 1 listed below, the amplitude of the ultrasonic waves is increased at the start of bonding, and then the amplitude of the ultrasonic vibration horn is reduced when a preset decay start time is reached. After a certain time has passed, the application of the ultrasonic vibration is stopped to complete the bonding process.

[0005] Hideo Sakuyama, Takehiko Watanabe, Atsushi Yanagisawa, Shizuyo Konuma, "Ultrasonic Welding of Aluminum Alloy and Steel", "Summary of Lectures at the National Convention of the Japan Welding Society", 2005, Vol. 2005f, 2005 Autumn National Convention, Session ID 416, p. 167

[0006] Patent Publication No. 2006-263816

[0007] However, the above method has the following problems.

[0008] The duration of ultrasonic vibration application to one workpiece varies depending on the material, shape, how the workpiece is held, and / or variations in the shape of the workpiece. Therefore, it is difficult to individually or accurately determine the appropriate application time in advance. Furthermore, simply setting the application time in advance to account for variations in the shape of the workpieces can be difficult to stabilize the bond strength between the workpieces. Furthermore, simply setting the tip decay time in advance can result in applying more ultrasonic waves than necessary, which can degrade the quality of the bond between the workpieces.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide an ultrasonic bonding tip that can improve the quality of bonding between workpieces, as well as an ultrasonic bonding device and ultrasonic bonding method using the same.

[0010] The ultrasonic bonding tip according to a first aspect of the present invention has a base and a rod portion extending continuously in the axial direction from the base, and is formed so that the ratio (D1 / d1) of the axial length D1 of the rod portion to the maximum distance d1 from the center of a cross section having the largest cross-sectional area to the periphery of the cross section in a direction perpendicular to the axial direction of the rod portion is within the range of 30 to 120.

[0011] With the ultrasonic bonding tip having this configuration, (D1 / d1) is 30 or more. Therefore, the sensitivity of the ultrasonic bonding tip to changes in the amplitude of ultrasonic vibration in response to changes in the force acting on the ultrasonic bonding tip from one workpiece before and after completion of ultrasonic bonding of the first and second workpieces that the ultrasonic bonding tip is in contact with is improved. Meanwhile, (D1 / d1) is 120 or less. Therefore, the ultrasonic vibration of the ultrasonic bonding tip is efficiently transmitted to the first workpiece, thereby improving the efficiency of bonding the first and second workpieces.

[0012] Therefore, whether the joining of the one workpiece and the other workpiece is complete can be accurately determined based on the change in the value of a specified parameter, such as the amplitude of the ultrasonic vibration of the ultrasonic bonding tip, which changes depending on the progress of the joining of the one workpiece and the other workpiece. If the determination result indicates that the joining 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 joining of the one workpiece and the other workpiece.

[0013] In the ultrasonic bonding tip having the above configuration, it is preferable that the ratio (S1 / s1) of the maximum cross-sectional area S1 in a direction perpendicular to the axial direction of the base portion to the maximum cross-sectional area s1 in a direction perpendicular to the axial direction of the rod portion is formed to be within a range of 6.2 to 52.9.

[0014] With this ultrasonic bonding tip, (S1 / s1) is 6.2 or more. This allows the ultrasonic vibrations of the ultrasonic bonding tip to be efficiently transmitted to one workpiece, thereby improving the efficiency of bonding between the one workpiece and the other workpiece. Meanwhile, (S1 / s1) is 52.9 or less. This improves the sensitivity of the ultrasonic bonding tip to changes in the amplitude of the ultrasonic vibrations in response to changes in the force acting on the ultrasonic bonding tip from one workpiece before and after completion of ultrasonic bonding of the one workpiece and the other workpiece that the ultrasonic bonding tip is in contact with.

[0015] In the ultrasonic bonding tip having the above configuration, it is preferable that when the ultrasonic bonding tip is not in contact with one of the workpieces, the ratio f2 / f1 of the resonant frequency f2 of the ultrasonic bonding tip alone to the resonant frequency f1 of the entire vibration system including the ultrasonic bonding tip is within the range of 1.005 to 1.07.

[0016] With this ultrasonic bonding tip, it is possible to accurately determine whether the bonding of the first workpiece and the second workpiece is complete based on the change in the value of a specified parameter, such as the amplitude of ultrasonic vibration of the ultrasonic bonding tip, which changes depending on the progress of the bonding of the first workpiece and the second workpiece. If the determination result indicates that the bonding of the first workpiece and the second 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 first workpiece and the second workpiece.

[0017] In the ultrasonic bonding tip having the above configuration, it is preferable that the cross-sectional area of ​​the base in a direction perpendicular to the axial direction or the maximum distance to the periphery of the cross section is formed so as to become smaller toward the rod portion.

[0018] With this ultrasonic welding tip, the cross-sectional area of ​​the base of the tip in the direction perpendicular to the axial direction decreases toward the rod, which allows uniform transmission of ultrasonic energy to one workpiece, thereby improving the quality of welding between the one workpiece and the other workpiece.

[0019] In the ultrasonic bonding tip having the above configuration, it is preferable that the base portion and the rod portion are made of different materials, so that the sound velocity in the rod portion is greater than the sound velocity in the base portion.

[0020] The ultrasonic welding tip having this configuration suppresses the rate of increase in the amount of displacement of the rod portion in the direction perpendicular to the axial direction at the point where the rod portion connects to the base, thereby stabilizing the ultrasonic complex vibration in the rod portion and ultimately improving the quality of the welding of the first and second workpieces.

[0021] An ultrasonic bonding tip according to a second aspect of the present invention is an ultrasonic bonding tip formed to extend in an axial direction, wherein in a cross section perpendicular to the axial direction of the ultrasonic bonding tip, the ultrasonic bonding tip has a single designated portion that is locally narrowed in the middle in the axial direction, the ratio (D2 / d2) of the axial length D2 of the ultrasonic bonding tip to the axial length d2 of the single designated portion is within a range of 1.5 to 3.5, and the ratio (S2 / s2) of the maximum cross-sectional area S2 of the ultrasonic bonding tip to the minimum cross-sectional area s2 of the single designated portion in a cross section perpendicular to the axial direction is within a range of 2 to 7.

[0022] With the ultrasonic bonding tip having this configuration, (D2 / d2) is 3.5 or less, and (S2 / s2) is 2 or more. Therefore, the sensitivity of the ultrasonic bonding tip to changes in the amplitude of ultrasonic vibration in response to changes in the force acting on the ultrasonic bonding tip from one workpiece before and after completion of ultrasonic bonding of the first and second workpieces that the ultrasonic bonding tip is in contact with is improved. Meanwhile, (D2 / d2) is 1.5 or more, and (S2 / s2) is 7 or less. Therefore, the ultrasonic vibration of the ultrasonic bonding tip is efficiently transmitted to the first workpiece, thereby improving the efficiency of bonding the first and second workpieces.

[0023] Therefore, whether the joining of the workpiece and the other workpiece is complete can be accurately determined based on the change in the value of a specified parameter, such as the amplitude of the ultrasonic vibration of the ultrasonic bonding tip, which changes depending on the progress of the joining of the workpiece and the other workpiece. If the determination result indicates that the joining of the 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 joining of the workpiece and the other workpiece.

[0024] An ultrasonic bonding device according to a first aspect of the present invention comprises: a vibration element that induces a composite vibration by combining longitudinal vibration and torsional vibration; an ultrasonic bonding tip according to the first aspect of the present invention; and a control device that controls the composite vibration of the vibration element, wherein the ultrasonic bonding tip is in contact with one workpiece and the control device comprises a designated sensor that outputs a signal according to the value of a designated parameter that changes according to the progress of joining of the one workpiece to the other workpiece based on the output signal of the designated sensor, and the control device determines whether or not the joining of the one workpiece to the other workpiece has been completed, and stops the composite vibration of the vibration element when it determines that the joining of the one workpiece to the other workpiece has been completed.

[0025] According to the ultrasonic bonding device of the present invention, whether the bonding is complete or not can be determined accurately based on the change in the value of a specified parameter, such as the amplitude of the ultrasonic vibration of the ultrasonic bonding tip, which changes depending on the progress of the bonding of the first workpiece and the second workpiece. If the determination result indicates that the bonding of the first workpiece and the second 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 viewpoint of improving the quality of the bonding of the first workpiece and the second workpiece.

[0026] An ultrasonic bonding device according to a second aspect of the present invention comprises: a vibration element that induces a composite vibration by combining longitudinal vibration and torsional vibration; an ultrasonic bonding tip according to the second aspect of the present invention that is fixed to or detachably attached to the vibration element; and a control device that controls the composite vibration of the vibration element, wherein the ultrasonic bonding tip is in contact with one workpiece and the control device comprises a designated sensor that outputs a signal according to the value of a designated parameter that changes depending on the progress of joining of the one workpiece to the other workpiece based on the output signal of the designated sensor, and the control device determines whether the joining of the one workpiece to the other workpiece has been completed based on the output signal of the designated sensor, and stops the composite vibration of the vibration element when it determines that the joining of the one workpiece to the other workpiece has been completed.

[0027] According to the ultrasonic bonding device of the present invention, whether the bonding is complete or not can be determined accurately based on the change in the value of a specified parameter, such as the amplitude of the ultrasonic vibration of the ultrasonic bonding tip, which changes depending on the progress of the bonding of the first and second workpieces. If the determination result indicates that the bonding of the first and second workpieces 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 viewpoint of improving the quality of the bonding of the first and second workpieces.

[0028] 1 is a diagram illustrating the configuration of an ultrasonic bonding device; 2 is a diagram illustrating the configuration of an ultrasonic bonding tip according to one embodiment of the present invention; 3 is a flowchart illustrating the function of an ultrasonic bonding device; 4 is a diagram illustrating changes in amplitude and power of an ultrasonic bonding tip (conventional); 5 is a diagram illustrating the configuration of an ultrasonic bonding tip according to another embodiment of the present invention; 6 is a diagram illustrating differences in amplitude change patterns due to differences in the configuration of the ultrasonic bonding tip;

[0029] 1 is a component of an ultrasonic bonding apparatus that bonds workpieces W1 and W2, such as metal plates, using ultrasonic complex vibrations. The ultrasonic bonding apparatus is used, for example, to bond electrodes of lithium-ion batteries and / or semiconductor devices, or to bond metals of the same or different types.

[0030] 1, the ultrasonic complex vibration device 1 includes a substantially cylindrical first vibration element 11, a substantially cylindrical, cylindrical, or bottomed cylindrical intermediate vibration element 10, and a substantially cylindrical or bottomed cylindrical second vibration element 12. The first vibration element 11, the intermediate vibration element 10, and the second vibration element 12 constitute "vibration elements." The ultrasonic bonding device includes the ultrasonic complex vibration device 1, a horn tip 40 (ultrasonic bonding tip), and an anvil 18.

[0031] The first vibration element 11 and the intermediate vibration element 10 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 1. The intermediate vibration element 10 and the second vibration element 12 are coaxially connected by a mechanical connecting mechanism at the middle portion of the ultrasonic complex vibration device 1. The first vibration element 11, the intermediate vibration element 10, and the second vibration element 12 may be integrally configured rather than being mechanically connected.

[0032] The intermediate vibration element 10 may be a component of the first vibration element 11. That is, the first vibration element 11 may be composed of two vibration elements. In this case, the first vibration element 11 and the intermediate vibration element 10 may be integrally configured rather than being mechanically connected. The intermediate vibration element 10 may be a component of the second vibration element 12. That is, the second vibration element 12 may be composed of two vibration elements. In this case, the second vibration element 12 and the intermediate vibration element 10 may be integrally configured rather than being mechanically connected.

[0033] As shown in FIG. 1, the first vibration element 11 is provided with a piezoelectric body 112 whose axial direction is the piezoelectric polarization direction.

[0034] As shown in FIG. 1 , the intermediate vibration element 10 is formed with a substantially annular plate-shaped intermediate flange 100 at a central position in the axial direction, protruding radially along its entire circumference. The intermediate vibration element 10 is configured to be clamped or supported at least at the intermediate flange 100 by a clamping mechanism (not shown) around the entire circumference. If it is ensured that the intermediate vibration element 10 is supported by a mechanical support mechanism, the intermediate flange 100 may be omitted. As shown in FIG. 1 , the intermediate vibration element 10 has a substantially cylindrical shape with a substantially constant outer diameter in the axial direction behind the intermediate flange 100 (leftward in FIG. 1 ). As shown in FIG. 1 , the intermediate vibration element 10 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 10 (rightward in FIG. 1 ).

[0035] 1, the second vibration element 12 is provided with a frequency adjustment element 120 having a generally regular octagonal shape with rounded corners that protrudes radially around the entire circumference at a midpoint in the axial direction of the second vibration element 12. The frequency adjustment element 120 adjusts the resonance frequencies of the longitudinal vibration component and the torsional vibration component of the ultrasonic vibration.

[0036] 1, the second vibration element 12 has a plurality of slits 124 formed on its outer surface behind the frequency adjustment element 120. A plurality of slits 124 may also be formed on the outer surface of the second vibration element 12 ahead of the frequency adjustment element 120. The slits 124 extend obliquely in the second vibration element 12 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 12.

[0037] 1, the second vibration element 12 is provided with a tip portion 126 that is approximately regular octagonal in shape with rounded corners and that protrudes radially around the entire circumference at the tip position in the axial direction. Holes 128 (or through holes) are formed in the tip portion 126 at a plurality of locations spaced apart in the circumferential direction. The N (N=2, 3, ...) holes 128 may be arranged to have N-fold rotational symmetry (e.g., N=4) around the central axis of the second vibration element 12. A female thread is provided on the inner surface of the hole 128.

[0038] Horn tip 40 has a substantially truncated cone-shaped base portion and a tip portion that abuts against workpiece W1, the uppermost of workpieces W1 and W2. A male thread provided at the base end of horn tip 40 screws into a female thread provided in hole 128 in tip portion 126 of second vibration element 12, thereby removably fixing horn tip 40 to second vibration element 12. Horn tips 40 of various shapes are available, so that horn tips 40 can be appropriately replaced depending on the type of metal to be joined, etc.

[0039] The balancer for adjusting the phase difference between the longitudinal vibration and the torsional vibration at the tip 126 of the second vibration element 12, and thus at the horn tip 40, may be removably fixed to the tip 126 of the second vibration element 12 by screwing the male thread of the balancer into the female thread of the hole 128.

[0040] The anvil 18 is disposed so as to face the tip of the horn tip 40 in the vertical direction. For example, substantially flat workpieces W1 and W2 are placed one on top of the other 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 that it receives through the workpieces W1 and W2.

[0041] As shown in FIG. 1, the ultrasonic bonding apparatus further includes a control device 20, a high frequency power supply device 21, a pressure device 22, a status sensor 24, and an interface device 26.

[0042] The high-frequency power supply device 21 is configured to apply a high-frequency AC voltage to the piezoelectric body 112 of the first vibration element 11 in response to power supplied from a commercial power source (not shown), thereby exciting the first vibration element 11 in the axial direction. The pressure device 22 includes a pressure block and is configured to apply pressure to the workpieces W1 and W2 from the horn tip 40 by displacing a support mechanism, such as a clamp mechanism, that supports the intermediate vibration element 10 using the pressure block. The status sensor 24 includes a stroke sensor that outputs a signal corresponding to the displacement of the pressure block constituting the pressure device 22, as well as an amplitude sensor that outputs a signal corresponding to the amplitude of the horn tip 40 (corresponding to a specified parameter). The amplitude sensor may be a sensor module composed of an imaging device and a device that calculates the amplitude by analyzing an image captured by the imaging device.

[0043] The interface device 26 is, for example, configured as 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 24. The display may be configured as a touch panel display, and may be configured to accept setting operations for allowing the user to directly or indirectly specify parameters, such as one of a plurality of bonding modes that defines a time series pattern of the target pressure.

[0044] The control device 20 is configured with a microcomputer, an arithmetic processing device (CPU, microprocessor, processor core, etc.), and a storage device (memory such as ROM and RAM). The control device 20 is configured to control the displacement operation of the pressure block by the pressure device 22, for example, based on a time series of the displacement amount of the pressure block represented by the output signal of a stroke sensor constituting the status sensor 24. The control device 20 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 24, and thereby to control the ultrasonic vibration power of the vibration elements (first vibration element 11, intermediate vibration element 10, and second vibration element 12) and the ultrasonic vibration power of the horn tip 40. As the status sensor 24, a pressure sensor is provided that outputs a signal corresponding to the pressure acting on the intermediate vibration element 10 from the pressure block of the pressure device 22 (the pressure applied by the horn tip 40 to the workpieces W1 and W2), and the control device 20 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.

[0045] As shown in FIG. 2 , the horn tip 40 includes a mounting portion 41, a base portion 42, and a rod portion 44. The mounting portion 41 is formed in a generally cylindrical shape, and its outer surface is formed with a male thread that screws into a female thread formed in the hole 128 of the tip portion 126 of the second vibration element 12. The base portion 42 is coaxially connected to the mounting portion 41 and has a generally cylindrical first portion with a larger diameter than the mounting portion 41, and a generally truncated cone-shaped second portion with a lower base surface having generally the same diameter as the first portion. The rod portion 44 is coaxially connected to the second portion of the base 42 and is formed in a generally cylindrical shape with a smaller diameter than the upper base surface of the second portion.

[0046] The mounting portion 41 may be omitted, and a screw hole may be formed extending axially from the end face of the first part of the base 42, and the horn tip 40 may be attached to the second vibration element 12 by threading a bolt or male screw threaded or fixed to the tip portion 126 of the second vibration element 12 into the female thread of the screw hole.

[0047] The rod portion 44 is formed so that the ratio (D1 / d1) of the axial length D1 of the rod portion 44 to the maximum distance d1 (the radius of the circular cross section) from the center of the substantially circular cross section having the largest cross-sectional area to the periphery of the substantially circular cross section in a direction perpendicular to the axial direction (or longitudinal direction) of the rod portion 44 is within a range of 40 to 100. For example, if the axial length D1 of the substantially cylindrical rod portion 44 is 60 mm, the radius of the rod portion 44 is designed to be within a range of (60 / 100) to (60 / 40) mm, i.e., 0.6 to 1.5 mm.

[0048] The horn tip 40 is formed so that the ratio (S1 / s1) of the maximum cross-sectional area S1 in a direction perpendicular to the axial direction of the base 42 to the maximum cross-sectional area s1 in a direction perpendicular to the axial direction of the rod portion 44 is within a range of 6.2 to 52.9. In this embodiment, since the rod portion 44 is approximately cylindrical, the maximum cross-sectional area S1 is expressed as πr2 using its radius r, and since the base 42 is a combination of a substantially cylindrical first portion and a substantially truncated cone-shaped second portion, the maximum cross-sectional area s1 is expressed as πR2 using the radius R of the first portion, so the ratio (S1 / s1) = (r2 / R2) is within a range of 6.2 to 52.9 ((r / R) is in a range of 2.89 to 7.27).

[0049] The base 42 may have a shape other than the combination of a substantially cylindrical first portion and a substantially truncated cone second portion. For example, the base 42 may be substantially cylindrical, substantially prismatic, substantially truncated cone, or substantially truncated pyramid. The cross-sectional shape of the rod portion 44 may be various shapes, such as a substantially circular shape, a substantially elliptical shape, a substantially rectangular shape (square shape, parallelogram shape, etc.), a substantially polygonal shape (e.g., a regular M-gon (e.g., M = 8 to 16), or a substantially star-shaped M-gon (e.g., M = 4 to 16)). The cross-sectional shape of the rod portion 44 in the axial direction may be formed so that it changes in various sequences along the axial direction, such as a substantially circular shape, a substantially elliptical shape, a substantially rectangular shape (square shape, parallelogram shape, etc.), or a substantially polygonal shape (e.g., a regular M-gon, a substantially star-shaped M-gon).

[0050] The horn tip 40 may be configured such that the ratio (f2 / f1) of the resonant frequency f2 of the horn tip 40 alone to the resonant frequency f1 of the entire vibration system including the horn tip 40 when the horn tip 40 is resonating at the resonant frequency when not in contact with the workpiece W1 is within the range of 1.005 to 1.07. This configuration allows for accurate determination of whether the joining of the first workpiece W1 and the second workpiece W2 is complete based on the change in the value of a designated parameter, such as the amplitude of the ultrasonic vibration of the horn tip 40, which changes depending on the progress of the joining. When the determination result indicates that the joining of the first workpiece W1 and the second workpiece W2 is complete, the ultrasonic vibration of the horn tip 40 is stopped, and as a result, the period during which the horn tip 40 is ultrasonically vibrated can be appropriately controlled from the perspective of improving the quality of the joining of the first workpiece W1 and the second workpiece W2.

[0051] When the horn tip 40 is not in contact with the workpiece W1, the free end of the rod portion 44 forms an antinode of the standing wave of the ultrasonic complex vibration. Therefore, the phase difference between the free end of the rod portion 44 and the node of the standing wave closest to the free end is (π / 2). In FIG. 2 , the solid line shows the standing wave of the ultrasonic complex vibration (the amplitude represents the amplitude in the direction perpendicular to the axial direction or the displacement of the horn tip 40) when the horn tip 40 is in contact with the workpiece W1 and resonating at the resonant frequency. In FIG. 2 , the dashed line shows the change in the bending angle of the horn tip 40. The contact state (contact pressure, etc.) between the horn tip 40 and the workpiece W1 may be adjusted so that the phase difference between the standing wave between the base end of the rod portion 44 and the node of the standing wave closest to the free end falls within the range of 0.10π to 0.21π.

[0052] A reference amplitude A0 is set (FIG. 3 / STEP 01). For example, the reference amplitude A0 may be directly or indirectly designated, such as one of a plurality of bonding modes for which the reference amplitude A0 is determined, via a touch panel display constituting the interface device 26.

[0053] The pressure device 22 moves the first vibration element 11, the intermediate vibration element 10, the second vibration element 12, and the horn tip 40 downward (FIG. 3 / STEP 02). The pressure P that the tip of the horn tip 40 (the free end of the rod portion 44) receives from the workpieces W1 and W2 is measured based on the output signal of the pressure sensor that constitutes the state sensor 24 (FIG. 3 / STEP 04). When the tip of the horn tip 40 is separated from the workpiece W1, P=0, and when it abuts against the workpiece W1, P>0.

[0054] It is determined whether the pressure P received by the horn tip 40 is equal to or greater than the designated pressure P0 (FIG. 3 / STEP 06). If the determination result is negative (FIG. 3 / STEP 06...NO), the pressure device 22 moves the first vibration element 11, the intermediate vibration element 10, the second vibration element 12, and the horn tip 40 downward (FIG. 3 / STEP 02). This adjusts the vertical position of the horn tip 40, and therefore the static pressure applied from the tip of the horn tip 40 to the workpieces W1 and W2, to fall within the designated static pressure range (e.g., 200 N to 800 N).

[0055] If the determination result is affirmative (FIG. 3 / STEP 06...YES), ultrasonic vibrations are generated in the vibration element (FIG. 3 / STEP 08). Specifically, in response to power being supplied to the high-frequency power supply device 21 from a commercial power source (not shown), the high-frequency power supply device 21 applies a high-frequency AC voltage to the piezoelectric body 112 of the first vibration element 11. This causes the first vibration element 11 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 11 to the intermediate vibration element 10 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 10 to the second vibration element 12 in its axial direction.

[0056] In this way, a portion of the longitudinal vibration component (axial component of the second vibration element 12) of the ultrasonic vibration transmitted to the second vibration element 12 is converted into a torsional vibration component by the multiple slits 124 formed on the outer surface of the second vibration element 12. 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 126 of the second vibration element 12.

[0057] In response, the tip of the horn tip 40 displaces or vibrates horizontally, tracing a circular or elliptical orbit. As a result, as shown schematically in FIG. 4 , the amplitude and ultrasonic vibration power of the horn tip 40 gradually increase from the vibration start time t = t0. During this process, impurities on the contact surfaces of the workpieces W1 and W2 are removed, further promoting plastic deformation of the contact surfaces of the workpieces W1 and W2. Then, as shown in FIG. 4 , the rate of increase in the amplitude and ultrasonic vibration power of the horn tip 40 significantly decreases at time t = t1, after which the amplitude and ultrasonic vibration power of the horn tip 40 gradually increase. This is because the metal oxide coatings constituting the joining surfaces of the workpieces W1 and W2 are removed, revealing clean, activated metal atoms on the joining surfaces. The temperature rise due to frictional heat activates the atomic movement, generating a mutual attractive force between the atoms.

[0058] At this time, the amount of pressing of the workpieces W1 and W2 by the horn tip 40 and / or the static pressure applied to the workpieces W1 and W2 are adjusted, and a composite vibration is applied to one of the workpieces W1 and W2, thereby solid-state joining the workpieces W1 and W2.

[0059] The amplitude A at a specified location (e.g., a location where the amplitude is relatively large) of the horn tip 40 is optically measured by an amplitude sensor constituting the status sensor 24 (FIG. 3 / STEP 10). It is then determined whether the time derivative δA (= current amplitude A(k)−previous amplitude A(k−1)) of the amplitude A at the horn tip 40 is negative and whether the amplitude A is equal to or less than a reference amplitude A0 (FIG. 3 / STEP 12). 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.

[0060] If the determination result is negative (FIG. 3 / STEP 12...NO), ultrasonic vibrations are continuously generated in the vibration element (FIG. 3 / STEP 08). On the other hand, if the determination result is positive (FIG. 3 / STEP 12...YES), the generation of ultrasonic vibrations in the vibration element is stopped (FIG. 3 / STEP 14). For example, as shown in FIG. 4, after the amplitude of the horn tip 40 changes from increasing to decreasing and becomes equal to or less than the reference amplitude A0 at time t=t2, the ultrasonic power of the horn tip 40 is controlled to be 0 with a slight response delay.

[0061] (Effects) With the ultrasonic complex vibration device 1 configured as described above, the ratio (D1 / d1) of the axial length D1 of the rod portion 44 to the maximum distance d1 (the radius of the substantially circular cross-section) from the center of the cross-section having the largest cross-sectional area to the periphery of the cross-section in a direction perpendicular to the axial direction of the substantially cylindrical rod portion 44 is 40 or greater. The ratio (S1 / s1) of the maximum cross-sectional area S1 in a direction perpendicular to the axial direction of the base portion 42 to the maximum cross-sectional area s1 in a direction perpendicular to the axial direction of the rod portion 44 is 52.9 or less. Therefore, before and after completion of ultrasonic welding of the workpieces W1 and W2 that the horn tip 40 is in contact with, the sensitivity of the amplitude A of the ultrasonic vibration of the horn tip 40 to changes in the force acting on the horn tip 40 from one of the workpieces W1 is improved.

[0062] On the other hand, in a direction perpendicular to the axial direction of the substantially cylindrical rod portion 44, the ratio (D1 / d1) of the axial length D1 of the rod portion 44 to the maximum distance d1 from the center of a cross section having the largest cross section to the periphery of the cross section is 100 or less. Also, the ratio (S1 / s1) of the maximum cross-sectional area S1 in a direction perpendicular to the axial direction of the base portion 42 to the maximum cross-sectional area s1 in a direction perpendicular to the axial direction of the rod portion 44 is 6.2 or more. Therefore, the ultrasonic vibrations of the horn tip 40 are efficiently transmitted to one workpiece W1 and the other workpiece W2, thereby improving the joining efficiency of the one workpiece W1 and the other workpiece W2.

[0063] Therefore, whether the joining of the first workpiece W1 and the second workpiece W2 is complete can be accurately determined based on the change in the value of a specified parameter, such as the amplitude A of the ultrasonic vibration of the horn tip 40, which changes depending on the progress of the joining (see FIG. 3 / STEP 12 and the horn tip amplitude in FIG. 4). If the determination result indicates that the joining of the first workpiece W1 and the second workpiece W2 is complete, the ultrasonic vibration of the horn tip 40 can be stopped (see FIG. 3 / STEP 12...YES→STEP 14 and the ultrasonic vibration power after time t=t2 in FIG. 4). As a result, the period during which the horn tip 40 is ultrasonically vibrated can be appropriately controlled to improve the quality of the joining of the first workpiece W1 and the second workpiece W2.

[0064] (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. However, in another embodiment, 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.

[0065] As shown in FIG. 5 , a horn tip 40 according to another embodiment of the present invention has a single designated portion 440 located in the axially intermediate portion thereof, the diameter of which is locally reduced compared to the base end 441 and the tip end 442. The base end 441 is formed in a generally cylindrical shape. The tip end 442 is formed in a shape in which a generally cylindrical first portion having a smaller diameter than the base end 441 and a generally truncated cone-shaped second portion having a lower base surface of generally the same diameter as the first portion are combined coaxially and continuously. The designated portion 440 is formed in a generally cylindrical shape with a smaller diameter than the first portion of the tip end 442. As in the above embodiment, an attachment portion 41 may be provided on the base end side of the base end 441.

[0066] Designated portion 440 may be formed in a generally corrugated shape that gradually reduces in diameter from one end on the base end 441 side to the other end on the tip end 442 side (in the axial or longitudinal direction of horn tip 40), reaches a minimum diameter in an intermediate region, and then gradually expands in diameter, so that the diameter of designated portion 440 is at least the smallest in the intermediate region. In this case, designated portion 440 may have a diameter that is approximately the same as or smaller than that of base end 441 at one end, and may have a diameter that is approximately the same as or smaller than that of a first portion of tip end 442 at the other end. Designated portion 440 may also be defined as the area from the point where the second derivative (= 2(dr / dx)) of the diameter (= 2r) in the axial direction (x direction) of horn tip 40 changes from negative to positive to the point where it changes from positive to negative.

[0067] The shapes of the base end 441, the designated portion 440, and the tip end 442 may be changed in various ways. For example, the base end 441, the designated portion 440, and the tip end 442 may each be a substantially cylindrical shape, a substantially rectangular prism shape, a substantially truncated cone shape, a substantially truncated pyramid shape, or a combination thereof. The base end 441, the designated portion 440, and the tip end 442 may each be formed so that the cross-sectional shape in the axial direction changes in various orders along the axial direction into various shapes, such as a substantially circular shape, a substantially elliptical shape, a substantially rectangular shape (such as a square shape or a parallelogram shape), or a substantially polygonal shape (for example, a regular M-gon (e.g., M = 8 to 16), or a substantially star-shaped M-gon (e.g., M = 4 to 16)).

[0068] The ratio (D2 / d2) of the axial length D2 of the horn tip 40 to the axial length d2 of the single designated portion 440 is within the range of 1.5 to 3.5 (preferably, 1.8 to 3.0, 2.0 to 3.0, or 2.2 to 2.8). The ratio (S2 / s2) of the maximum cross-sectional area S2 of the horn tip 40 to the minimum cross-sectional area s2 of the designated portion 440 in a cross section perpendicular to the axial direction is within the range of 2 to 7 (preferably, 2.5 to 6.2, 3.2 to 5.5, or 3.8 to 4.6). In this embodiment, the designated portion 440 is approximately cylindrical, and therefore the minimum cross-sectional area s2 is expressed as πq2 using its radius q. In this embodiment, the cross-sectional area of ​​the horn tip 40 is greatest at the cross section of the approximately cylindrical base end 441, and therefore the maximum cross-sectional area S2 of the horn tip 40 is expressed as πQ2 using the radius Q of the base end 441. Therefore, the ratio (S2 / s2) = (Q2 / q2) of the maximum cross-sectional area S2 of the horn tip 40 to the minimum cross-sectional area s2 of the designated portion 440 is in the range of 2 to 7 ((Q / q) is in the range of 1.14 to 2.65).

[0069] With the horn tip 40 having this configuration, (D2 / d2) is 3.5 or less, and (S2 / s2) is 2 or more. Therefore, before and after completion of ultrasonic welding of one workpiece W1 and the other workpiece W2 that the horn tip 40 is in contact with, the sensitivity of the horn tip 40 to changes in the amplitude of ultrasonic vibration in response to changes in the force acting on the horn tip 40 from the one workpiece W1 is improved. Meanwhile, (D2 / d2) is 1.5 or more, and (S2 / s2) is 7 or less. Therefore, the ultrasonic vibration of the horn tip 40 is efficiently transmitted to the one workpiece W1, thereby improving the welding efficiency between the one workpiece W1 and the other workpiece W2.

[0070] Therefore, whether the joining of the first workpiece W1 and the second workpiece W2 is complete can be accurately determined based on the change in the value of a specified parameter, such as the amplitude A of the ultrasonic vibration of the horn tip 40, which changes depending on the progress of the joining (see FIG. 3 / STEP 12 and the horn tip amplitude in FIG. 4). If the determination result indicates that the joining of the first workpiece W1 and the second workpiece W2 is complete, the ultrasonic vibration of the horn tip 40 can be stopped (see FIG. 3 / STEP 12...YES→STEP 14 and the ultrasonic vibration power after time t=t2 in FIG. 4). As a result, the period during which the horn tip 40 is ultrasonically vibrated can be appropriately controlled to improve the quality of the joining of the first workpiece W1 and the second workpiece W2.

[0071] As shown in FIG. 2 , the outer shape of the horn tip 40 has a step at the junction between the base portion 42 and the rod portion 44 due to a difference in diameter or cross-sectional area. If this step, and therefore the change in cross-sectional area of ​​the horn tip 40, is excessively large, the amplitude (amount of displacement in a direction perpendicular to the axial direction) at the junction between the rod portion 44 and the base portion 42 may become excessively large. This not only increases the possibility of breakage at this junction of the horn tip 40, but also may cause the vibration state to become unstable. For this reason, it is preferable to form the horn tip 40 as an integral part and design the outer shape so that the change in cross-sectional area at the junction between the base portion 42 and the rod portion 44 is reduced, but this increases the manufacturing cost of the horn tip.

[0072] In order to reduce manufacturing costs, the horn tip 40 is composed of a separately formed base portion 42 and rod portion 44. The rear end of the rod portion 44 is press-fitted into a hole formed in the tip portion of the rod portion 42, or the male thread formed in the rear end of the rod portion 44 is screwed into the female thread formed in the hole in the tip portion of the rod portion 42.

[0073] To solve this problem, it is preferable to use different materials for the base 42 and the rod 44 so that the sound velocity cs44 in the rod 44 is greater than the sound velocity cs42 in the base 42. Since the sound velocity cs (the speed of longitudinal vibration of a rod-shaped member) is defined by (E / ρ)1 / 2 (E: Young's modulus, ρ: specific gravity), it is preferable to select materials (e.g., metal materials such as stainless steel) such that the Young's modulus E42 and specific gravity ρ42 of the material for the base 42 and the Young's modulus E44 and specific gravity ρ44 of the material for the rod 44 satisfy the magnitude relationship (E42 / ρ42)1 / 2 < (E44 / ρ44)1 / 2. For example, it is preferable to use stainless steel as the material for the base 42 and an alloy such as a tungsten alloy as the material for the rod 44.

[0074] In Figure 6, the solid line shows the amplitude (displacement perpendicular to the axial direction) of the rod portion 44 when the materials constituting the base 42 and the rod portion 44 are differentiated so that the sound velocity in the rod portion 44, cs44, is greater than cs42. The dashed line shows the amplitude of the rod portion 44 when the materials constituting the base 42 and the rod portion 44 are the same (when cs42 = cs44). It can be seen that the rate of increase in the axial displacement at the rear end of the rod portion 44 is smaller in the former case than in the latter case, thereby reducing the possibility of damage to the horn tip 40. Because materials with a high sound velocity typically also have a high Young's modulus E, the amplitude of the rod portion 44 is also reduced, allowing the vibration to maintain a stable vibration state without deviating from the central axis.

[0075] 1. Ultrasonic complex vibration device 10. Intermediate vibration element 100. Intermediate flange 11. First vibration element 112. Piezoelectric body 12. Second vibration element 120. Frequency adjustment element 121. Cylindrical portion 122. Cylindrical portion 124. Slit 126. Tip portion 128. Hole 18. Anvil 20. Control device 21. High frequency power supply device 22. Pressure device 24. Stroke sensor 26. Interface device 40. Horn tip (tip for ultrasonic welding) 41. Mounting portion 42. Base portion 44. Rod portion 440. Designated portion 441. Base end portion 442. Tip portion W1. One workpiece W2. Other workpiece.

Claims

1. An ultrasonic bonding tip having a base and a rod portion extending continuously in the axial direction from the base, wherein the ratio (D1 / d1) of the axial length D1 of the rod portion to the maximum distance d1 from the center of a cross section having the maximum cross-sectional area to the periphery of the cross section in a direction perpendicular to the axial direction of the rod portion is within the range of 30 to 120.

2. An ultrasonic bonding chip as described in claim 1, wherein the ratio (S1 / s1) of the maximum cross-sectional area S1 in a direction perpendicular to the axial direction of the base portion to the maximum cross-sectional area s1 in a direction perpendicular to the axial direction of the rod portion is within the range of 6.2 to 52.

9.

3. The ultrasonic bonding tip according to claim 1, wherein when the ultrasonic bonding tip is not in contact with the one of the workpieces, the ratio f2 / f1 of the resonant frequency f2 of the ultrasonic bonding tip alone to the resonant frequency f1 of the entire vibration system including the ultrasonic bonding tip is within the range of 1.005 to 1.

07.

4. An ultrasonic bonding chip as claimed in any one of claims 1 to 3, wherein the cross-sectional area of ​​the base in a direction perpendicular to the axial direction or the maximum distance to the periphery of the cross-section becomes smaller as it approaches the rod portion.

5. An ultrasonic bonding chip according to any one of claims 1 to 3, wherein the base and the rod are made of different materials, so that the speed of sound in the rod is faster than the speed of sound in the base.

6. An ultrasonic bonding tip formed to extend in an axial direction, wherein in a cross section perpendicular to the axial direction of the ultrasonic bonding tip, the ultrasonic bonding tip has a single designated portion which is locally tapered in the middle in the axial direction, a ratio (D2 / d2) of a length D2 in the axial direction of the ultrasonic bonding tip to a length d2 in the axial direction of the single designated portion is within a range of 1.5 to 3.5, and a ratio (S2 / s2) of a maximum cross-sectional area S2 of the ultrasonic bonding tip to a minimum cross-sectional area s2 of the single designated portion in a cross section perpendicular to the axial direction is within a range of 2 to 7.

7. An ultrasonic bonding device comprising a vibration element which induces a composite vibration by combining longitudinal vibration and torsional vibration, an ultrasonic bonding tip, and a control device which controls the composite vibration of the vibration element, the ultrasonic bonding tip being provided with a designated sensor which outputs a signal corresponding to a value of a designated parameter which changes according to the progress of bonding of one workpiece to another workpiece when the ultrasonic bonding tip is in contact with the one workpiece, the ultrasonic bonding tip having a base which is fixed to the vibration element or detachably attached thereto, and a rod portion which extends continuously in the axial direction from the base, the rod portion being formed such that a ratio (D1 / d1) of an axial length D1 of the rod portion to a maximum distance d1 from the center of a cross section having a maximum cross-sectional area to the periphery of the cross section in a direction perpendicular to the axial direction is within a range of 30 to 120, the control device determining whether or not bonding of the one workpiece to the other workpiece has been completed based on an output signal from the designated sensor, and stopping the composite vibration of the vibration element when it is determined that bonding of the one workpiece to the other workpiece has been completed. Ultrasonic bonding equipment.

8. An ultrasonic bonding device comprising: a vibration element which induces a composite vibration by combining longitudinal vibration and torsional vibration; an ultrasonic bonding tip which is fixed to the vibration element or detachably attached; and a control device which controls the composite vibration of the vibration element, the ultrasonic bonding tip being provided with a designated sensor which outputs a signal corresponding to a designated parameter value which changes according to the progress of bonding of one workpiece to another workpiece when the ultrasonic bonding tip is in contact with the one workpiece; the ultrasonic bonding tip having a single designated portion which is locally tapered in the middle portion in the axial direction in a cross section perpendicular to the axial direction of the ultrasonic bonding tip; a ratio (D2 / d2) of the axial length D2 of the ultrasonic bonding tip to the axial length d2 of the single designated portion being within a range of 1.5 to 3.5; and a ratio (S2 / s2) of the maximum cross-sectional area S2 of the ultrasonic bonding tip to the minimum cross-sectional area s2 of the single designated portion being within a range of 2 to 7 in a cross section perpendicular to the axial direction. The control device determines whether or not the joining of the one workpiece and the other workpiece has been completed based on the output signal of the designated sensor, and stops the composite vibration of the vibration element when it determines that the joining of the one workpiece and the other workpiece has been completed.

9. An ultrasonic bonding method for bonding a workpiece and another workpiece using an ultrasonic bonding device including a vibration element that induces a composite vibration by combining longitudinal vibration and torsional vibration, and an ultrasonic bonding tip that is fixed to the vibration element or detachably attached thereto, the ultrasonic bonding tip having a designated sensor that outputs a signal corresponding to a value of a designated parameter that changes according to the progress of bonding of the one workpiece to the other workpiece when the ultrasonic bonding tip is in contact with the workpiece to be bonded, the ultrasonic bonding tip having a base that is fixed to the vibration element or detachably attached thereto, and a rod portion that extends continuously in the axial direction from the base, the ultrasonic bonding tip being formed such that the ratio (D1 / d1) of the axial length D1 of the rod portion to the maximum distance d1 from the center of a cross section having a maximum cross-sectional area to the periphery of the cross section in a direction perpendicular to the axial direction of the rod portion is 40≦(D1 / d1)≦100, An ultrasonic joining method comprising: a step of determining whether or not joining of the one workpiece to the other workpiece has been completed, based on a signal corresponding to a value of a specified parameter that changes according to 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 a step of stopping the composite vibration of the vibration element when it is determined that joining of the one workpiece to the other workpiece has been completed.

10. An ultrasonic bonding method for bonding a workpiece and another workpiece using an ultrasonic bonding device equipped with a vibration element that induces a composite vibration by combining longitudinal vibration and torsional vibration, and an ultrasonic bonding tip that is fixed to the vibration element or detachably attached thereto, wherein the ultrasonic bonding tip has a single designated portion that is locally tapered in the middle in the axial direction in a cross section perpendicular to the axial direction, the ratio (D2 / d2) of the axial length D2 of the ultrasonic bonding tip to the axial length d2 of the single designated portion is within a range of 1.5 to 3.5, and the ratio (S2 / s2) of the maximum cross-sectional area S2 of the ultrasonic bonding tip to the minimum cross-sectional area s2 of the single designated portion in a cross section perpendicular to the axial direction is within a range of 2 to 7, An ultrasonic joining method comprising: a step of determining whether or not joining of the one workpiece to the other workpiece has been completed, based on a signal corresponding to a value of a specified parameter that changes according to 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 a step of stopping the composite vibration of the vibration element when it is determined that joining of the one workpiece to the other workpiece has been completed.

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