Ultrasonic joint inspection method

Abstract

To provide an ultrasonic joint inspection method capable of non-destructively estimating joint strength between joint members.SOLUTION: An ultrasonic joint inspection method includes steps of: ST1 detecting an elastic wave to be transmitted from first and second joint members WC, WP with the use of an AE sensor 3 during ultrasonic joint of the first and second joint members WC, WP by applying an ultrasonic vibration UV to the first and second joint members WC, WP; ST2 acquiring a correction waveform PS1 by removing a component due to the ultrasonic vibration from a waveform RS1 of the elastic wave; and ST3 estimating joint strength between the first joint member WC and the second joint member WP based on a waveform area of the correction waveform PS1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasonic bond inspection method. [Background technology]

[0002] Patent Document 1 discloses a bond inspection device that inspects the bond quality between bonded members and a bonding member. During the bonding process between the bonded members and the bonding member, the bond inspection device uses an AE (acoustic emission) sensor to detect vibrations propagating through a jig or the housing of an ultrasonic bonding machine equipped with the jig, and outputs a detection signal. The bond inspection device also determines the bond condition between the bonded members and the bonding member based on the output detection signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 143410 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have discovered the following technical problems. There is a need to determine the bond strength between bonded members in a non-destructive manner, but such bond inspection devices have not been able to estimate the bond strength between bonded members in a non-destructive manner.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and provides an ultrasonic bond inspection method that can non-destructively estimate the bond strength between bonded members. [Means for solving the problem]

[0006] The ultrasonic bonding inspection method according to the present disclosure includes: detecting elastic waves transmitted from the first and second joining members using an AE sensor while ultrasonically joining the first and second joining members by applying ultrasonic vibrations to the first and second joining members; a step of removing a component due to the ultrasonic vibration from the waveform of the elastic wave to obtain a corrected waveform; and estimating the bonding strength between the first bonding member and the second bonding member based on the waveform area of ​​the corrected waveform. [Effects of the Invention]

[0007] According to the present disclosure, the bonding strength between bonding members can be estimated non-destructively. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an ultrasonic bonding inspection method. [Figure 2] 10A is a graph showing the output voltage versus time, and FIG. 10B is a graph showing the output voltage versus time from which the voltage component due to ultrasonic vibration has been removed. [Figure 3] 10 is a graph showing the relationship between bonding strength and corrugated area. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation.

[0010] <First Embodiment> A first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing an ultrasonic bond inspection method. Fig. 2(a) is a graph showing output voltage versus elapsed time. Fig. 2(b) is a graph showing output voltage with the voltage component corresponding to ultrasonic vibration removed versus elapsed time. Fig. 3 is a graph showing the relationship between bond strength and waveform area.

[0011] <Device> The ultrasonic bond inspection method according to this embodiment can utilize an ultrasonic bonding system 100 shown in FIG. 1. The ultrasonic bonding system 100 includes an ultrasonic bonding device 10 and a bond strength inspection device 20. In the ultrasonic bond inspection method according to this embodiment, a coil WC and a power line WP are ultrasonically bonded. The coil WC may be referred to as a first bonding member WC. The power line WP may be referred to as a second bonding member WP. The coil WC and the power line WP may, for example, constitute a stator of a motor (not shown). The coil WC may be made of copper or a copper alloy. The power line WP may be made of aluminum or an aluminum alloy.

[0012] The ultrasonic bonding device 10 includes a horn 1 and an anvil 2. The horn 1 and anvil 2 are positioned to sandwich the coil WC and the power line WP. The anvil 2 is fixed in a predetermined position, and the horn 1 is pressed against the coil WC and the power line WP to sandwich the coil WC and the power line WP between the horn 1 and the anvil 2. The ultrasonic bonding device 10 also includes an ultrasonic oscillator (not shown). The ultrasonic oscillator generates ultrasonic waves. The horn 1 efficiently transmits the generated ultrasonic waves to the coil WC and the power line WP. The coil WC and the power line WP vibrate due to the transmitted ultrasonic waves. This removes oxides and dirt from the interface between the coil WC and the power line WP, bonding the surfaces of the coil WC and the power line WP together. As a result, the coil WC and the power line WP are ultrasonically bonded.

[0013] The bond strength inspection device 20 includes an AE sensor 3 and a bond strength estimation device 4. The AE sensor 3 is provided on the anvil 2; specifically, the AE sensor 3 is preferably provided on the anvil 2 at a predetermined position spaced apart from the coil WC and the power line WP. The coil WC and the power line WP vibrate due to ultrasonic waves, generating elastic waves that are transmitted to the AE sensor 3 via the anvil 2. The AE sensor 3 detects the elastic waves transmitted via the anvil 2 and generates a detection signal. The AE sensor 3 is, for example, a piezoelectric element such as PZT (lead zirconate titanate).

[0014] The bond strength inspection device 20 may further include a preamplifier and a main amplifier. The preamplifier amplifies the detection signal generated by the AE sensor 3. The main amplifier further amplifies the detection signal amplified by the preamplifier. The detection signal is, for example, an analog voltage signal.

[0015] The bond strength estimation device 4 acquires a detection signal from the AE sensor 3 or the main amplifier. The bond strength estimation device 4 appropriately processes the acquired detection signal to generate an AE signal. This signal processing may be performed using an oscilloscope. The bond strength estimation device 4 uses the AE signal to remove components due to ultrasonic vibration from the elastic wave waveform to acquire a corrected waveform. The corrected waveform may also be acquired using commercially available data analysis software. The bond strength estimation device 4 estimates the bond strength between the coil WC and the power line WP based on the area of ​​the corrected waveform.

[0016] <Ultrasonic bonding inspection method> First, the AE sensor 3 detects elastic waves transmitted from the coil WC and the power line WP (step ST1). Specifically, ultrasonic vibrations are applied to the coil WC and the power line WP to ultrasonically bond the coil WC and the power line WP. During this ultrasonic bonding, the AE sensor 3 detects elastic waves transmitted through the anvil 2 and generates a detection signal.

[0017] The bond strength estimation device 4 also removes components due to ultrasonic vibration from the elastic wave waveform to obtain a corrected waveform (step ST2). Specifically, the bond strength estimation device 4 generates an AE signal by appropriately processing the detection signal of the elastic wave detected in step ST1. The bond strength estimation device 4 uses this AE signal to remove components due to ultrasonic vibration from the elastic wave waveform to obtain a corrected waveform. The elastic wave includes components due to ultrasonic vibration, components due to frictional behavior between the coil WC and the power line WP, and components due to strain vibration of each component. Compared to the elastic wave waveform, the corrected waveform includes more components due to frictional behavior between the coil WC and the power line WP and components due to strain vibration of each component.

[0018] For example, elastic wave waveforms RS1, RS2, and RS3 shown in Figure 2(a) are specific examples of elastic waves. The component due to ultrasonic vibration is removed from elastic wave waveform RS1 to obtain the corrected waveform PS1 shown in Figure 2(b). Similarly, the component due to ultrasonic vibration is removed from elastic wave waveform RS2 to obtain the corrected waveform PS2 shown in Figure 2(b). Similarly, the component due to ultrasonic vibration is removed from elastic wave waveform RS3 to obtain the corrected waveform PS3 shown in Figure 2(b).

[0019] Furthermore, the bond strength estimation device 4 estimates the bond strength between the coil WC and the power line WP based on the waveform area of ​​the corrected waveform (step ST3).

[0020] Specifically, the relationship between the waveform area and the bonding strength is determined in advance. FIG. 3 shows a specific example of the relationship between the waveform area A and the bonding strength S. In the specific example of the relationship between the waveform area A and the bonding strength S shown in FIG. 3, plots S1, S2, and S3 show specific values ​​of the waveform area A and the bonding strength S. Plots S1, S2, and S3 show specific values ​​of the waveform area A and the bonding strength S of the corrected waveforms PS1, PS2, and PS3 shown in FIG. 2(b). Plots S1, S2, and S3 show the waveform area A and the bonding strength S in increasing order.

[0021] The waveform area A of the corrected waveform PS1 is larger than the waveform area A of the corrected waveform PS2. The bond strength between the coil WC and the power line WP in the plot S1 is larger than the bond strength between the coil WC and the power line WP in the plot S2. In the ultrasonic bonding process in the plot S1, the coil WC and the power line WP were in close contact with each other before applying ultrasonic vibrations, and no foreign matter was sandwiched between them. Therefore, in the ultrasonic bonding process in the plot S1, applying ultrasonic vibrations to the coil WC and the power line WP ensured reliable ultrasonic bonding between the coil WC and the power line WP.

[0022] On the other hand, the waveform area A of the correction waveform PS3 is smaller than the waveform area A of the correction waveform PS2. The bond strength S between the coil WC and the power line WP for plot S3 is smaller than the bond strength S between the coil WC and the power line WP for plot S2. In the ultrasonic bonding process for plot S3, the slotted paper SP is sandwiched between the coil WC and the power line WP before ultrasonic vibration is applied. In this ultrasonic bonding process, the slotted paper SP is treated as a foreign object. Therefore, in the ultrasonic bonding process for plot S3, ultrasonic vibration is applied to the coil WC and the power line WP, but ultrasonic bonding between the coil WC and the power line WP is barely achieved.

[0023] By applying the least squares method to the plots S1, S2, S3, etc., the following relational expression (1) can be obtained: Correlation coefficient R 2 is 0.957, there is a strong positive correlation between the corrugation area A and the bonding strength S. A = 0.1708 × S + 232.33 … (1)

[0024] Using relational expression (1), a specific value of the corresponding bond strength S can be obtained from only a specific value of the waveform area A. This makes it possible to estimate the bond strength S between the coil WC and the power line WP based on the waveform area of ​​the corrected waveform. In addition, it is possible to estimate the degree to which foreign matter such as slot paper SP is trapped between the coil WC and the power line WP based on the waveform area of ​​the corrected waveform.

[0025] From the above, the joint strength between the coil WC and the power line WP can be estimated non-destructively.

[0026] Furthermore, according to the ultrasonic bond inspection method of this embodiment, the bond strength between the coil WC and the power line WP can be estimated based on a corrected waveform in which the component due to ultrasonic vibration has been removed, thereby suppressing the influence of the component due to ultrasonic vibration on the bond strength, and thus the bond strength between the coil WC and the power line WP can be estimated with high accuracy.

[0027] Furthermore, according to the ultrasonic bond inspection method of this embodiment, the tensile strength can be estimated using elastic waves detected when the coil WC and the power line WP are ultrasonically bonded together, which eliminates the need for an inspection process after ultrasonically bonding the coil WC and the power line WP. In other words, the bond strength between the coil WC and the power line WP can be estimated in-line.

[0028] The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit and scope of the present invention. Furthermore, the present invention may be implemented by appropriately combining the above-described embodiment and examples thereof. [Explanation of symbols]

[0029] 100 Ultrasonic Bonding System 10 Ultrasonic bonding equipment 1 Horn 2 Anvil 20 Bond strength inspection device 3 AE sensors 4 Joint strength estimation device WC coil (first joining member) WP Power line (second connecting member) SP Slot Paper UV ultrasonic vibration

Claims

[Claim 1] detecting elastic waves transmitted from the first and second joining members using an AE sensor while ultrasonically joining the first and second joining members by applying ultrasonic vibrations to the first and second joining members; a step of removing a component due to the ultrasonic vibration from the waveform of the elastic wave to obtain a corrected waveform; and estimating a bonding strength between the first bonding member and the second bonding member based on a waveform area of ​​the corrected waveform. Ultrasonic bond inspection method.

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