JPH09148359A - Bonding arm and wire bonding apparatus provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid causing an unstable oscillation mode near a resonance point of an ultrasonic horn by appropriately setting the selectivity Q of this horn. SOLUTION: An ultrasonic oscillator 1c of a binding arm 1 is composed of disk-like piezoelectric elements 41a-41d with electrode films 42a-42e, each formed on both side faces of each piezoelectric element so as to hold it between the adjacent films. Ultrasonic power is fed to every two electrode films from an ultrasonic power source 31. A mechanical-to-electrical converter element 1e composed of piezoelectric elements 51a-51b adjacent to the oscillator 1c is loaded by a resistance element 61. This constitution provides an appropriate damping action near on a resonance point of an ultrasonic horn to thereby appropriately set the selectivity Q of the horn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding apparatus adapted to apply ultrasonic vibration to a bonding arm and a capillary attached to the tip of the bonding arm.

[0002]

2. Description of the Related Art Conventionally, in order to perform bonding connection between a pad and a lead of an IC chip using this type of wire bonding apparatus, the wire is held by a capillary provided at the tip of a bonding arm, The surface of the pad or the lead to be formed is brought into contact with the surface of the pad or lead, and a part of the wire having the ball formed at the tip thereof is crushed using the capillary and thermocompression-bonded to be welded. At this time, at the same time, ultrasonic vibration can be applied to the tip of the wire.

FIG. 6 shows an example of a bonding arm in a conventional wire bonding apparatus.
The bonding arm 1 is mainly made of stainless steel or a titanium alloy, and has an ultrasonic horn 1a, a cylindrical flange portion 1b for attaching to a support mechanism that swingably supports the ultrasonic horn 1a, and the cylinder. Flange 1b
The ultrasonic transducer 1c is attached to the rear end portion of the rear end, and the capillary 7 is attached to the front end portion.

Ultrasonic power is supplied from the ultrasonic power source 31 to the ultrasonic transducer 1c, and ultrasonic power is received from the ultrasonic power source 31 to vibrate ultrasonically. The child 1c is excited, and ultrasonic vibration is applied to the capillary 7 via the ultrasonic horn 1a.

On the other hand, the IC chip 25, which is a semiconductor component that is wire-bonded by the bonding arm 1, is mounted on a bonding stage (not shown), and as shown in FIG. The wire 9 is sequentially connected between the pad 25a and a lead (not shown) located on the outer periphery of the pad 25a.

FIG. 8 shows the structure of a conventional ultrasonic transducer 1c attached to the bonding arm 1. In the figure, the same reference numerals as those in FIG. 6 indicate the same parts.

This ultrasonic transducer 1c is composed of a plurality of disc-shaped piezoelectric elements 41a to 41f, and electrode films 42a to 42g are formed on both side surfaces of the piezoelectric elements 41a to 41f so as to sandwich the piezoelectric elements 41a to 41f. ing. The lead wires 43a, 43 are alternately formed between every other adjacent electrode films.
b is connected, and ultrasonic power is supplied from the ultrasonic power source 31 to the pair of lead wires 43a and 43b.

With this configuration, ultrasonic power is applied in parallel to the respective electrode films 42a to 42g sandwiching the respective piezoelectric elements 41a to 41f, and the respective piezoelectric elements 41a to 4g.
The resonance frequency of the ultrasonic vibration excited by 1f is transmitted to the capillary 7 via the ultrasonic horn 1a in the bonding arm 1.

A process of performing wire bonding using the above wire bonding apparatus will be described with reference to FIG.

When attempting to wire-bond a pad on the IC chip 25 placed on the bonding stage 26, a ball 9 is attached to the tip by an electric discharge means (not shown).
After positioning the capillary 7 through which the wire 9 having the a formed therein is inserted by the movement of the XY table that is movable in the two-dimensional direction based on information from an imaging device (not shown) or the like, the capillary 7 is moved to the position shown in FIG. As shown, the ball is pressed down onto the pad and thermocompression bonding is performed.

At this time, ultrasonic power is applied from the ultrasonic power source 31 to the ultrasonic vibrator 1c shown in FIGS. 6 and 8, and the bonding arm 1 is vibrated by a standing wave.
The vibration is transmitted to the capillary 7 and ultrasonic vibration is applied to the tip of the wire.

In this step, → moves the bonding tool downward at high speed, and → moves to low speed. At this time, the clamp 8a is open. Next, when the connection to the first bonding point is completed, the → clamp 8a
, The capillary 7 rises in the upward direction shown in FIG. 9, that is, in the Z direction, and the wire 8 is pulled out with the clamp 8a opened as shown in accordance with a predetermined loop control. It is connected to the lead 27 which becomes a point.

After this connection, the clamp 8a is closed while the wire 9 is pulled out from the tip of the capillary 7 by a predetermined feed amount f as shown by. In this state, the wire 9 is cut as shown in the process of further raising the capillary 7 to a predetermined height, a ball is again formed at the tip of the wire by using the electric discharge means, and the clamp 8a is opened. Return to the state of. Wire bonding is performed by such a series of steps.

[0014]

By the way, in the conventional wire bonding apparatus configured as described above, when ultrasonic power is applied to the ultrasonic vibrator, the capillary 7 serving as a bonding tool has the above-mentioned structure. It will be vibrated by the resonance frequency of the sonic horn.

In this case, the mechanical load fluctuates depending on whether the capillary 7 comes into contact with the pad or lead of the IC chip or not, and the resonance frequency also changes.

When the resonance frequency fluctuates in this way, a phase difference is generated between the driving voltage and the current of the ultrasonic horn. Therefore, the phase difference is detected and the ultrasonic power supplied to the ultrasonic vibrator is detected. Although the frequency is tracked, an unstable vibration mode may occur in the ultrasonic horn due to occasional interference or the like because the selectivity Q of the ultrasonic horn is high and the impedance change near the resonance point is large. .

The present invention has been made by paying attention to such a conventional problem, and by suppressing the selectivity Q of the ultrasonic horn to an appropriate degree, the unstable vibration of the ultrasonic horn is caused. SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding arm capable of preventing the occurrence of the above and always performing a stable bonding action, and a wire bonding apparatus equipped with the bonding arm.

[0018]

A bonding arm according to the present invention comprises a mechanical-electrical converting means for converting vibration of an ultrasonic horn into electric energy, and an electric impedance means for consuming electric energy obtained by the mechanical-electrical converting means. It is composed of and. A wire bonding apparatus according to the present invention includes a bonding stage on which a semiconductor component is placed, an ultrasonic horn that holds a capillary in which a wire is inserted, and an ultrasonic vibration that supplies ultrasonic vibration to the ultrasonic horn. A wire, a support mechanism that swingably supports the ultrasonic horn, and a wire bonding that applies ultrasonic vibration to the capillary by applying ultrasonic power to the ultrasonic vibrator. The device is configured so that mechanical-electrical conversion means for converting the vibration of the ultrasonic horn into electric energy and electric energy obtained by the mechanical-electrical conversion means are consumed by the electric impedance means. And preferably, the ultrasonic transducer and the electromechanical conversion means,
Both are composed of piezoelectric elements. In this case, the piezoelectric elements constituting the ultrasonic transducer and the electromechanical conversion means are attached to the ultrasonic horn with the electrodes sandwiched therebetween, and the ultrasonic element is interposed between the electrodes of the piezoelectric element constituting the ultrasonic transducer. When electric power is applied, a resistance element is connected between the electrodes of the piezoelectric element that constitutes the electromechanical conversion means. With such a configuration, the electrical output generated by the electromechanical conversion means is added to the resistance element and energy is consumed,
Due to such an action, the selectivity Q of the ultrasonic horn is appropriately suppressed. As a result, the change in impedance near the resonance point can be set small, and the occurrence of an unstable vibration mode in the ultrasonic horn due to interference or the like can be prevented.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a mechanical-electrical conversion element is arranged adjacent to an ultrasonic transducer for exciting an ultrasonic horn, and a resistor for consuming electric energy generated by the mechanical-electrical conversion element is used. An element is provided, and the selectivity Q is appropriately set in the vicinity of the resonance frequency of the ultrasonic horn by the resistance element. As a result, the ultrasonic horn suppresses the occurrence of abnormal vibration modes near the resonance frequency, and does not require a control means for strictly controlling the frequency of the ultrasonic power supplied to the ultrasonic vibrator, unlike the conventional one. You can also do it.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. 1 shows a main part of a wire bonding apparatus according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. It should be noted that components having the same configurations and functions as those of the conventional device will be described using the same reference numerals, and detailed description thereof will be omitted.

In this wire bonding apparatus, as shown in FIG. 1, a bonding arm 1 composed of a holding frame 1d and an ultrasonic horn 1a has a supporting shaft 3 together with a swing arm 2.
About the center of the axis. The bonding arm 1 is firmly fitted to the support shaft 3, and the swing arm 2 is swingably attached to the support shaft 3.

The support shaft 3 is mounted on an XY table or the like (not shown) that is movable in two dimensions. An ultrasonic transducer 1c for exciting the horn 1a is incorporated in the holding frame 1d.

The swing arm 2 and the holding frame 1d are respectively provided with a solenoid 4a and an electromagnetic attraction piece 4b as electromagnetic attraction means.
Are fixed to face each other, and when the bonding arm 1 is swung, an electric power is supplied to the solenoid 4a from a power source (not shown) to generate an attraction force between the solenoid 4a and the electromagnetic attraction piece 4b. As a result, the bonding arm 1 and the swing arm 2 can be fixed to each other by suction.

Further, the swing arm 2 and the holding frame 1d are
A magnet 5a and a coil 5b are respectively mounted at a position in front of the electromagnetic attraction means. The magnet 5a and the coil 5b constitute means for generating an attraction force for urging the portion holding the capillary 7 arranged at the tip of the bonding arm 1 at the time of bonding downward in FIG.

A clamp arm 8 is provided at the tip of the swing arm 2, and a wire 9 is gripped at the tip of the clamp arm 8 by an opening / closing mechanism (not shown) composed of a solenoid and a spring. A clamp 8a is provided as a clamping means for cutting. The wire 9 is wound around the spool 36 via the guide 12.

As shown in FIG. 2, a support shaft 15a is provided on the rear end side of the swing arm 2, and the arm side cam follower 15 and the swing base 16a rotate around the support shaft 15a. It is free. A bearing guide 16b is fixed to one end of the swing base 16a, and a preload arm 16d is rotatably attached to the other end of the bearing guide 16b via a support pin 16c.
A support shaft 17a is provided at a free end of the preload arm 16d, and a cam follower 17 is rotatably attached to the support shaft 17a.

A preload spring 16e, which is a tension spring, is laid between the tip of the preload arm 16d and the tip of the swing base 16a, and the arm side cam follower 15 is provided.
The cam follower 17 is pressed against a cam surface which is an outer peripheral surface of a cam 18 formed in a substantially heart shape. The two contact points of the arm side cam follower 15 and the cam follower 17 with respect to the cam surface 18 are located with the rotation center of the cam 18 interposed therebetween.

A frame structure is formed by the swing base 16a, the bearing guide 16b, and the preload arm 16d, which is generically referred to as the swing frame 16.

The bearing guide 16b, which is a component of the swing frame 16, has a cam shaft 1 to which a cam 18 is fitted.
9 is in contact with the outer ring of the radial bearing 20 attached to the radial bearing 20. The cam 18 is driven by the motor 21 and the cam shaft 19
Rotate forward and backward by the torque applied to. The height position of the capillary 7 is detected by a rotary encoder (not shown) connected to the support shaft 3.

Then, on the bonding stage 26,
The lead 27 is placed, and the IC chip 25 as a semiconductor component is mounted on the lead 27.

With the above-mentioned structure, the wire bonding process shown in FIG. 9 is realized.

Next, the ultrasonic transducer 1c in the bonding arm 1 is composed of a plurality of disc-shaped piezoelectric elements 41a to 41d as shown in FIG. 3, and the piezoelectric elements 41a to 41d are sandwiched therebetween. In addition, electrode films 42a to 42e are formed on both side surfaces thereof. The lead wires 43a, 4 are alternately arranged between every other adjacent electrode films.
3b is connected, and a pair of lead wires 43a and 43b
On the other hand, the ultrasonic power source 31 supplies ultrasonic power.

With such a configuration, each piezoelectric element 4
Ultrasonic power is applied in parallel to the electrode films 42a to 42e sandwiching the electrodes 1a to 41d, and the piezoelectric elements 41a
The resonance frequency of the ultrasonic vibrations excited by the to 41 d is transmitted to the capillary 7 via the ultrasonic horn 1 a in the bonding arm 1.

On the other hand, a mechanical-electrical conversion element 1e as a mechanical-electrical conversion means for converting the vibration of the ultrasonic horn 1a into electric energy is further provided adjacent to the ultrasonic vibrator 1c composed of the piezoelectric elements 41a to 41d. There is. The electromechanical conversion element 1e as the electromechanical conversion means is composed of disk-shaped piezoelectric elements 51a and 51b having the same shape as the piezoelectric element constituting the ultrasonic transducer 1c.

An electrode film 52a is arranged between the piezoelectric elements 51a and 51b, and an electrode film 52b is arranged on the end side of the piezoelectric element 51b.
And the electrode film 52b are connected by a lead wire 43b, and a resistance element 61 as an electric impedance means
Is connected to one end. Further, the electrode film 52a is connected to the other end of the resistance element 61 as an electric impedance means.

In the above structure, the electrode films 42 sandwiching the piezoelectric elements 41a to 41d constituting the ultrasonic vibrator 1c are provided.
When ultrasonic power is supplied to the a to 42e from the ultrasonic power source 31, the ultrasonic horn 1a is excited and transmitted to the capillary 7 as in the conventional one described above.

Here, the piezoelectric elements 51a and 51b constituting the electromechanical conversion element 1e as the electromechanical conversion means.
Receives the vibration of the ultrasonic horn 1a, and the electrode films 42e, 5e
Electric energy is induced between 2b and the electrode film 52a. The electric energy induced by the mechanical-electrical conversion element 1e is the resistance element 61 as an electric impedance means.
Is supplied to and is consumed by the resistance element 61 and converted into heat.

The electric energy level induced by the electromechanical conversion element 1e is approximately proportional to the vibration amplitude of the ultrasonic horn 1a. Therefore, when the ultrasonic horn 1a causes abnormal vibration, its induced signal is generated. The level also increases, and the consumption amount by the resistance element 61 also increases. That is,
The combination of the electromechanical conversion element 1e and the resistance element 61 has a damping effect on the vibration of the ultrasonic horn 1a.

FIGS. 4 and 5 show impedance characteristics near the resonance point of the ultrasonic horn.
Shows characteristics of the conventional bonding arm shown in FIG. 8, for example, which does not include a mechanical-electrical conversion element, and FIG. 5 shows characteristics of the embodiment of the present invention shown in FIG. 3 having a mechanical-electrical conversion element 1e. ing.

The horizontal axis represents frequency and the vertical axis represents impedance ratio. In each case, the measurement is performed in a state where the capillary is brought into contact with the aluminum block as a dummy of the semiconductor chip, and in the case of FIG. 5, the value of the resistance element connected to the electromechanical conversion element is It is 2K ohms.

Here, for convenience of display on the measuring machine, the vertical axis in FIGS. 4 and 5 is not shown in the same scale but is represented by the numerical ratio shown on the vertical axis.

The impedance change near the resonance point of the present invention shown in FIG. 5 is much smaller than that of the conventional one shown in FIG. 4, and an unstable vibration mode due to interference or the like is suppressed. Can understand.

[0043]

As is apparent from the above description, according to the bonding arm and the wire bonding apparatus having the same according to the present invention, the mechanical-electrical conversion that receives the vibration of the ultrasonic horn of the bonding arm and converts it into electric energy. Since the electric energy obtained by the electromechanical conversion means is consumed by the electric impedance means, the selectivity Q in the vicinity of the resonance frequency of the ultrasonic horn can be appropriately set. Therefore, the ultrasonic horn suppresses the occurrence of the abnormal vibration mode near the resonance frequency, and does not require a control means for strictly controlling the frequency of the ultrasonic power supplied to the ultrasonic vibrator unlike the conventional one. You can also do it. Moreover, it is not necessary to use a complicated control means for tracking the frequency of the ultrasonic power by detecting the phase difference generated between the driving voltage and the current of the ultrasonic horn as in the conventional case, and the configuration is simple and inexpensive. You can Further, according to the present invention, it is possible to provide a device with higher accuracy when used in combination with the device using the above control means.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of a main part of an embodiment of a wire bonding apparatus according to the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a diagram showing a detailed configuration of the bonding arm shown in FIG.

FIG. 4 is a diagram showing frequency vs. impedance characteristics of a conventional bonding arm.

FIG. 5 is a diagram showing frequency vs. impedance characteristics of the bonding arm in the example of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional bonding arm.

FIG. 7 is a diagram showing a state in which wire bonding is performed on an IC chip.

FIG. 8 is a diagram illustrating a configuration of an ultrasonic transducer portion of the bonding arm shown in FIG.

FIG. 9 is an explanatory diagram showing a bonding process by a wire bonding device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bonding arm 1a Ultrasonic horn 1c Ultrasonic vibrator 1e Mechanical-electrical conversion element (mechanical-electrical conversion means) 2 Oscillating arm 3 Support shaft 7 Capillary 8 Clamp arm 8a Clamp 9 Wire 16 Oscillating frame 18 Cam 21 Motor 25 IC chip 25a Pad 26 Bonding stage 27 Lead 31 Ultrasonic power source 41a-41d Piezoelectric element 42a-42e Electrode film 51a, 51b Piezoelectric element 52a, 52b Electrode film 61 Resistance element (electrical impedance means)

Claims (5)

[Claims] 1. A bonding arm comprising: a mechanical-electrical converting means for converting vibration of an ultrasonic horn into electric energy; and an electric impedance means for consuming electric energy obtained by the mechanical-electrical converting means. 2. A bonding stage on which a semiconductor component is mounted, an ultrasonic horn that holds a capillary in which a wire is inserted, an ultrasonic vibrator that supplies ultrasonic vibration to the ultrasonic horn, and A supporting mechanism for swingably supporting an ultrasonic horn, and a wire bonding device for applying ultrasonic vibration to the capillary by applying ultrasonic power to the ultrasonic vibrator. A wire-bonding device, characterized in that a mechanical-electrical converting means for converting vibration of the ultrasonic horn into electric energy and electric energy obtained by the mechanical-electrical converting means are consumed by an electric impedance means. 3. The wire bonding apparatus according to claim 2, wherein the ultrasonic transducer and the electromechanical conversion means are both piezoelectric elements. 4. The piezoelectric element forming the ultrasonic transducer and the electromechanical converting means is attached to a bonding arm with electrodes sandwiched therebetween, and an ultrasonic wave is interposed between electrodes of the piezoelectric element forming the ultrasonic transducer. As sonic power is applied,
The wire bonding apparatus according to claim 3, wherein a resistance element is connected between the electrodes of the piezoelectric element forming the electromechanical conversion means. 5. The wire bonding apparatus according to claim 1, wherein the electrical impedance unit is a resistance element.