JPH0699289A - Ultrasonic joining method - Google Patents

Abstract

PURPOSE:To detect a joined state with high accuracy not depending on face properties, etc., of the joined face by using amplitude of high frequency oscillation as the substitute property of the joined state in the ultrasonic joining method for stabilizing the joining quality. CONSTITUTION:Base material 1 and material 2 to be joined are aligned and set on an anvil tip 3. A welding tip 4 to press the material 2 to be joined with specified pressure is oscillated by high frequency of an ultrasonic region. The amplitude of oscillation of the welding tip 4 is detected by a fiber type displacement gage 6. The amplitude of the welding tip 4 is converted into a voltage signal by a voltmeter 7. A joined state discrimination circuit 8 detects the width of amplitude based on a crest value of the voltage signal of the voltmeter 7. When the amplitude is larger than a specified threshold, it is determined that joining strength is insufficient and when the amplitude is smaller than the specified threshold, it is determined that the sufficient joining strength is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic bonding method,
In particular, it relates to an ultrasonic bonding method for stabilizing the bonding quality.

[0002]

2. Description of the Related Art Ultrasonic bonding has been known as a kind of bonding method for resins and metals. This joining method is
It is carried out by utilizing friction and frictional heat generated by superposing a base material and an article to be bonded to the base material and sliding the bonding surfaces at a high frequency. That is, when the joint surfaces are slid at high frequency, the resin is melted by the friction and frictional heat, or oxides and other stains on the metal surface are removed,
A strong bonding strength is generated between resins or metals.

By the way, the bonding strength between the bonding surfaces bonded by the ultrasonic bonding method cannot be measured without a destructive test. For this reason, it is difficult to make a pass / fail judgment of the joining quality after joining, and it is required to build in the quality at the joining stage.

From such a demand, conventionally, it is necessary to measure the electric power required to vibrate the objects to be welded at the time of ultrasonic welding and determine whether or not the electric power value is a legal value. Has proposed a device for judging whether or not the joining quality is acceptable (Japanese Utility Model Laid-Open No. 56-79312).

The apparatus described in the above publication integrates the power consumed by the high-frequency oscillator that gives high-frequency vibrations to the objects to be bonded during the bonding time, and compares the value with a predetermined value to determine the bonding quality. The pass / fail judgment is performed. This is based on the fact that in ultrasonic bonding, the power consumed by the high-frequency oscillator has a close relationship with the sliding energy between the bonding surfaces, that is, the energy used for bonding.

[0006]

However, the above-mentioned conventional apparatus is premised on that the sliding energy of the joint surface and the energy used for ultrasonic welding have a certain relationship. Therefore, for example, when the surface condition such as the oxidation state or the degree of contamination of the objects to be joined, or the surface roughness changes, the mechanical impedance changes, so the energy required for sliding between the joining surfaces changes, The relationship between the electric power consumed by the vibrator and the energy used for joining changes.

Such a situation may occur even when the object to be welded is obliquely arranged on the base material or the dimensions of the object to be welded are changed, and it is determined when the object is to be used as mass production equipment. Had a difficulty in reliability.

The present invention has been made in view of the above points, and by using the amplitude of the high frequency vibration as a substitute characteristic of the bonding state on the bonding surface, it is possible to accurately measure regardless of the surface property of the bonding surface. An object of the present invention is to provide an ultrasonic bonding method capable of detecting a bonding state.

[0009]

The above object is to apply high frequency vibration to an object to be bonded to a base material so as to slide the bonding surface of the base material and the bonding surface of the object to be bonded with high frequency. In the ultrasonic joining method of joining both joining surfaces by moving, the joining surface of the base material and the joining surface of the article to be joined are slid at high frequency as shown in the principle diagram of FIG. Based on the first step M1, the second step M2 of monitoring the amplitude of the sliding, and the amplitude monitored in the second step, the bonding surface of the base material and the bonding surface of the object to be bonded are The ultrasonic bonding method including the third step M3 of judging the bonding state of.

[0010]

In the ultrasonic joining method according to the present invention, the first step M1 is to slide the joining surface of the base material and the joining surface of the article to be joined at a high frequency, and to gradually increase the distance between the joining surfaces. Acts to give a strong bonding strength to the.

The second step M2 detects a change in the amplitude of sliding between the joint surfaces. The amplitude between the joint surfaces of the base material and the article to be joined is large at the initial stage of sliding when the joint strength between them is small and becomes smaller as the joint strength increases. Further, if the sliding is continued after the joining surfaces are sufficiently joined, fatigue failure occurs in the joined portion, and the amplitude of sliding again increases.

In the third step, the characteristics of the sliding amplitude that fluctuates in this way is utilized to accurately determine the joining state between the joining surfaces from the amplitude monitored in the second step.

[0013]

FIG. 2 is a block diagram showing an example of an apparatus for carrying out an embodiment of the ultrasonic welding method according to the present invention.

In the figure, reference numerals 1 and 2 respectively denote a metallic base material and an article to be joined which are to be joined by ultrasonic joining. These are aligned with each other and set on the anvil tip 2 fixed on the processing table of the equipment.

Reference numeral 4 denotes a welding tip, which applies a high frequency drive signal supplied from the welding tip drive circuit 5 while pressurizing the base material 1 and the article to be welded 2 set on the anvil tip 3 with a predetermined pressure. Based on this, as shown by the arrow in FIG. The surface of the anvil tip 3 that faces the base material 1 and the surface of the welding tip 4 that presses the object 2 to be welded are subjected to anti-slip processing with fine irregularities, and the high frequency vibration of the welding tip 4 , Is efficiently converted into sliding between the base material 1 and the article 2 to be joined.

Further, in the figure, reference numeral 6 indicates a fiber type displacement gauge composed of a light emitting portion 6a, a fiber cable 6b and a main body 6c. This fiber type displacement meter 6 includes a light emitting unit 6
A non-contact type displacement meter that emits light from a toward the object to be measured and measures the distance to the object to be measured based on the amount of reflected light.
A voltage signal corresponding to the distance between the light emitting section 6a and the object to be measured appears at the output terminal of the main body 6c.

In the apparatus of this embodiment, the welding tip 4 is the object to be measured, and the light emitted from the light emitting portion 6a is applied to the side surface 4a of the welding tip 4. Therefore, when the welding tip 4 vibrates, the side surface 4a of the welding tip 4 and the light emitting portion 6
The distance from a changes and a voltage signal corresponding to the amplitude of the welding tip 4 appears at the output terminal of the fiber displacement meter 6. The fiber type displacement meter 6 used in the apparatus of this embodiment has a good frequency characteristic, and has a frequency characteristic capable of responding up to about 100 kHz.

The output terminal of the fiber type displacement meter 6 is
It is connected to the input terminal of the voltmeter 7. This voltmeter 7
Is a voltmeter that converts the amplitude of the voltage signal supplied from the fiber type displacement meter into a peak value. In other words, the output terminal of the voltmeter 7 receives the signal supplied from the fiber displacement meter 6,
That is, a high frequency voltage signal that vibrates in the vibration cycle of the welding tip 4 appears.

The output terminal of the voltmeter 7 is connected to the joining state determination circuit 8 which is the main part of the apparatus of this embodiment. The bonding state determination circuit 8 performs the process described below to detect the magnitude of the voltage supplied from the voltmeter 7, that is, the amplitude of the welding tip 4 between the base material 1 and the article 2 to be bonded. This is a circuit for judging the joining state, and starts the judgment when the measurement start signal is supplied from the programmable controller (PC) 9, and outputs the result to the PC 9.

The PC 9 is a controller that comprehensively controls the apparatus of this embodiment and exchanges signals with the joining state determination circuit 8 and also starts or stops driving of the welding tip drive circuit 5 described above. Supply a signal.

The operation of the apparatus having the above construction will be described below. Prior to that, the relationship between the amplitude of the welding tip during ultrasonic bonding and the bonding state will be described.

FIG. 3 is an ultrasonic wave oscillation when the base material 1 and the article 2 to be bonded, which have average surface properties such as the oxidation state of the bonding surface, the degree of dirt, and the surface roughness, are bonded by the apparatus having the above-mentioned configuration. The relationship between the time (the driving time of the welding tip 4) and the amplitude of the welding tip 4 is shown. Therefore, if the surface properties are different,
Will be shown in the vertical and horizontal directions.

Here, the welding tip 4 is always supplied with a constant electric power, and the effect of the above-mentioned anti-slip processing is exerted between the base material 1 and the anvil tip 3 and between the article 2 and the welding tip 4. Almost no slippage occurs. That is, the amplitude fluctuation of the welding tip 4 during bonding is caused by the fluctuation of the energy required to slide the article 2 to be bonded with respect to the base material 1.

Before the joining is started, an oxide is formed on the surface of the base material 1 and the surface of the article 2 to be joined, and dirt such as oil is attached. Therefore, naturally, no bonding strength will be generated by simply stacking them. Therefore, as shown in FIG. 3, immediately after the start of ultrasonic oscillation (after about 0.1 to 0.2 sec), the sliding amplitude between the base material 1 and the workpiece 2 is large, and at this stage, the welding tip 4 shows the maximum amplitude (about 10 μm).

When the oscillation is continued thereafter, oxides and dirt on the metal surface are removed, and when the metal surface is exposed, the bonding strength due to the metal bonding gradually occurs at the bonding interface. This joining strength increases the energy required to slide the base material 1 and the article 2 to be joined together, and reduces the sliding amplitude. Therefore, as shown in FIG. 3, the amplitude of the welding tip 4 gradually decreases after recording the maximum value (about 0.2 to 0.9 sec).

When the oscillation is further continued, the amplitude of the welding tip 4 starts to increase again after recording the minimum value (about 0.5 μm). This is because fatigue fracture begins to occur at the joining site between the base material 1 and the article 2 to be joined, and the joining strength begins to decrease.

That is, in the process of joining by ultrasonic joining, the amplitude of the welding tip 4 changes according to the joining state of the base material 1 and the object to be welded 2, and the smaller the amplitude, the better the joining. That is, the joining has a high joining strength.

The joining state judging circuit 8 of the apparatus of this embodiment judges the joining quality by utilizing the relation between the amplitude of the welding tip 4 and the joining state of the base material 1 and the object 2 to be welded. is there.

Next, the operation of the apparatus of this embodiment will be described with reference to the flowchart of the routine executed by the PC 9 shown in FIG.

When the above apparatus is started with the base material 1 and the object to be welded 2 set in predetermined positions, first, the PC 9
A drive start signal is transmitted from the welding tip drive circuit 5 to the welding tip drive circuit 5 (step 101). Welding tip drive circuit 5
When the drive start signal is received, the drive signal is transmitted to the welding tip 4, and the ultrasonic bonding corresponding to the first step is started.

Next, in the PC 9, it is checked whether the timer T, which started counting at the same time as the joining is started, reaches the joining state determination time T ₁ (step 102), and T ≧ T
If it is ₁ , a joining state determination signal is transmitted to the joining state determination circuit 8 (step 103). The determination time T ₁
Is set to a time slightly shorter than the welding tip driving time (bonding time) T ₂ set to a predetermined time.

FIGS. 5A and 5B show output waveforms of the fiber type displacement meter 6 and the voltmeter 7, respectively. As shown in (A) of the figure, the output signal of the fiber displacement sensor is
It is a high frequency voltage signal, the frequency of which is the same as the vibration frequency of the welding tip 4. The output signal of the voltmeter 7 is a voltage signal obtained by converting the amplitude of the output signal of the fiber type displacement meter 7 into a peak value, and represents the amplitude of the welding tip 4 at each time.

When the joining state determination circuit 8 receives the above-mentioned joining state determination signal after a lapse of time T ₁ from the start of the joining, as shown in FIG. 5B, as a second step, the voltmeter 7 at that time point Read the output signal. Then, as a third step, the voltage signal is compared with a predetermined threshold value,
Whether or not the joining quality is acceptable is determined, and the result is output to the PC 9.

After transmitting the joining state determination signal in step 103, the PC 9 proceeds to step 104 and checks whether the timer T has reached the welding tip drive time T ₂ . If T ≧ T _2, it is determined that the set joining time has elapsed, and a welding tip stop signal is transmitted to the welding tip drive circuit 5 (step 105). Then
After taking in the decision signal supplied from the joining state decision circuit 8 and performing processing such as displaying the pass / fail thereof (step 106), the processing is ended.

As described above, in the apparatus of this embodiment, it is possible to reliably determine whether or not good joining is obtained under the preset joining conditions, and it is possible to set the article to be joined 2 by mistake. It is possible to reliably prevent the outflow of defective products. Further, even when the surface properties of the base material 1 and the article 2 to be joined are changed, the abnormality can be detected quickly, and particularly in a mass production line, stable joining quality can be maintained as compared with the conventional apparatus. Becomes

Further, according to the apparatus of this embodiment, the inspection process such as the visual inspection, which has been conventionally required, can be eliminated, which greatly contributes to the labor saving and also the production cost reduction. be able to.

FIG. 6 shows a flowchart of another example of the processing executed by the bonding state determination circuit 8. The process shown in this example is performed by the bonding state determination circuit 8 in the process of ultrasonic bonding.
The welding state is continuously monitored with, and the oscillation of the welding tip 4 is continued until it is determined that the welding state is the best.

That is, in the joint state judging circuit 8,
When this process is activated, first, the PC 9 waits for a connection state determination signal to be transmitted (step 201). When the ultrasonic bonding which is the first step is started and the bonding state determination circuit 8 receives the bonding state determination signal, monitoring of the output signal of the voltmeter 7 is started (step 202). Then, when the value becomes higher than the set voltage V _H (see FIG. 7) obtained by the experiment, it is judged that the vibration of the welding tip 4 has started normally, and the peak voltage V is continuously measured. Perform (step 203).

Next, in step 204, the joining state is determined as a third step. If V <V _L is confirmed by comparing V with a predetermined threshold value V _L , an oscillation stop command signal is transmitted to the PC 9 (step 205). On the other hand, P
Upon receiving this signal, C9 immediately stops the oscillation of the welding tip 4 and therefore transmits a stop signal to the welding tip drive circuit 5.

The threshold value _VL used in the determination of the joining state in step 204 is based on the amplitude indicated by the welding tip 4 when the base material 1 and the article 2 are well joined. It is a value obtained experimentally.

As described above, according to the apparatus in which the processing of the present embodiment is executed, the welding conditions for ultrasonic welding are always set to the optimum welding conditions, and as shown in FIG. It becomes possible to maintain the bonding strength at a high level.

In the above process, step 2
At 04, the peak value V is set to a predetermined threshold value V _LAnd the configuration to compare with
But V_LReplace with the peak value measured from time to time
Then, it is configured to compare with the peak value V measured after that.
May be. In this case, the oscillation stop command signal is always the peak value.
The voltage will be sent after recording the lowest value,
It becomes possible to obtain a more stable bonding strength.

[0043]

As described above, according to the present invention, by using the sliding amplitude between the base material and the article to be joined as a substitute characteristic value of the joining strength generated between them, It is possible to detect the joining quality with high accuracy regardless of the surface quality of the. Therefore, when the method of the present invention is applied to mass production equipment, it is possible to always secure stable bonding strength, and it is possible to reliably prevent outflow of defective products.

[Brief description of drawings]

FIG. 1 is a principle diagram of an ultrasonic bonding method according to the present invention.

FIG. 2 is a configuration diagram of an example of an apparatus that executes an embodiment of the ultrasonic bonding method according to the present invention.

FIG. 3 is a diagram showing a relationship between an oscillation time and an amplitude of a welding tip in the apparatus of this embodiment.

FIG. 4 is a flowchart of an example of a routine executed by the programmable controller of the device of this embodiment.

FIG. 5 is an output voltage waveform of the fiber type displacement meter and the voltmeter of the device of the present embodiment.

FIG. 6 is a flowchart of an example of a routine executed by a bonding state determination circuit of the device of this embodiment.

FIG. 7 is a diagram for explaining a routine executed by a bonding state determination circuit of the device of this embodiment.

FIG. 8 is a diagram for explaining the effect of the device of this embodiment.

[Explanation of symbols]

 M1 1st process M2 2nd process M3 3rd process 1 Base material 2 Object to be bonded 3 Anvil tip 4 Welding tip 6 Fiber type displacement meter 8 Bonding state judgment circuit 9 Programmable controller (PC)

Claims (1)

[Claims] 1. A high-frequency vibration is applied to an article to be joined to a base material, and the joining surface of the base material and the joining surface of the article to be joined are slid at a high frequency so that both joining surfaces are joined. In the ultrasonic joining method of joining, a first step of sliding the joining surface of the base material and the joining surface of the article to be joined at a high frequency, a second step of monitoring the amplitude of the sliding, An ultrasonic bonding method comprising: a third step of determining a bonding state between the bonding surface of the base material and the bonding surface of the object to be bonded based on the amplitude monitored in the second step. .