JP3537069B2 - Bonding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding apparatus for bonding a semiconductor component as a component to be bonded placed on a bonding stage, and in particular, when a bonding tool touches a semiconductor component. The present invention relates to a bonding apparatus that can quickly remove the micro-vibration generated in the substrate and obtain a reliable bonding action.

[0002]

2. Description of the Related Art In a wire bonding apparatus used in a semiconductor device assembly process, a pad (electrode) on a semiconductor chip serving as a first bonding point using a gold wire or a wire such as copper or aluminum, and a second bonding. It is made to connect with the lead which becomes a point.

Conventionally, in this type of wire bonding apparatus, prior to the above-described bonding, a high voltage is applied between the tip of a wire drawn out from a capillary as a bonding tool and a torch rod as a discharge electrode. A discharge is caused to occur, and the tip of the wire is melted by the heat energy accompanying the discharge to form a ball at the tip of the capillary.

After forming the ball in this way, the wire is held by the capillary, and the ball is crushed to the pad on the semiconductor chip to be the first bonding point, and thermocompression bonding is performed. At this time, the ultrasonic vibration is applied to the wire tip at the same time.

Subsequently, while pulling out the wire from the tip of the capillary, the capillary is pressed against the lead on the target semiconductor chip to connect the wire to the lead serving as the second bonding point. After connecting the wire to the second bonding point in this way, the wire is cut by the clamp in the process of raising the capillary to a predetermined height, and the series of bonding steps is completed.

[0006]

By the way, when bonding wires to the first bonding point and the second bonding point as described above, a motor for controlling the movement of the capillary relative to the semiconductor component is provided. The bonding arm including the capillary is driven by the motor.

This motor is constructed so as to perform position control by a so-called digital servo (feedback) circuit using the output of a rotary encoder connected to the drive shaft of the motor.

The sine wave obtained by this rotary encoder is converted into a pulse signal and position servo is applied by the pulse signal.

However, the converted pulse signal does not generate a signal between the pulses even though the motor drive shaft is slightly rotated. This means that there is no position information feedback temporarily, and servo control becomes unstable, and a phenomenon occurs in which vibration of about ± 1 bit (limit cycle) remains.

In this case, if a strong feedback is applied in order to improve the response of the digital servo, the vibration is more likely to occur.

In such a state, even when a ball formed at the tip of the wire is pressed against the first bonding point and an ultrasonic signal is applied, for example, the mechanical vibration may cause a defect in bonding. There is also a possibility that the reliability of bonding may be lacking due to the occurrence of the same phenomenon at the second bonding point.

The present invention has been made paying attention to such a conventional problem, and a signal for canceling the vibration of the motor as the driving means is forced to the digital servo circuit at the time of bonding. It is an object of the present invention to provide a bonding apparatus capable of improving the reliability of bonding by providing feedback.

[0013]

A wire bonding apparatus according to the present invention generates a position signal by detecting a position of a driving means for controlling movement of a bonding tool relative to a part to be bonded, and a position of the driving means. Based on position detection means, a servo circuit that superimposes the position signal from the position detection means on the drive circuit of the drive means as a first feedback signal, and a sine wave output indicating the position of the drive means obtained by the position detection means A position signal generating circuit for generating a position signal and a speed signal based on the position signal obtained from the position signal generating circuit when a work touch signal indicating that the bonding tool has contacted a part to be bonded is obtained. Switching means for supplying the servo circuit as a second feedback signal. That.

In this case, the position signal generating circuit includes an adder circuit for adding the first sine wave and the second sine wave having different phase relationships, and the first sine wave and the second sine wave. A subtracting circuit for extracting a difference, and first and second outputs for shifting the output at the zero cross points of the first sine wave and the second sine wave, respectively.
Comparator, a waveform selection circuit that generates an exclusive OR output of the first and second comparator outputs, and a waveform switching circuit that selects the output of the addition circuit or subtraction circuit based on the output of the waveform selection circuit Is done.

With the above configuration, the position signal generating circuit generates a position signal of the driving means, and the position signal is converted into a speed circuit in the speed signal generating circuit and fed back to the digital servo circuit of the driving means.

Therefore, it is possible to cancel the vibration due to the limit cycle generated in the digital servo circuit in which the drive circuit of the drive means is closed, and a stable bonding action can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. First, FIG. 1 shows a main part of a wire bonding apparatus according to the present invention, and FIG. 2 shows a cross-sectional view taken along line AA in FIG.

In this wire bonding apparatus, as shown in FIG. 1, a bonding arm 1 comprising a holding frame 1a and an ultrasonic horn 1b has a support shaft 3 and a swing arm 2.
It can be swung around the axis center. 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 (not shown) that can move in a two-dimensional direction. An ultrasonic vibrator (not shown) for exciting the horn 1b is incorporated in the holding frame 1a.

A solenoid 4a and an electromagnetic attracting piece 4b are fixed to the swing arm 2 and the holding frame 1a so as to face each other. When the bonding arm 1 is swung, the solenoid 4a is not shown. By energizing from an unillustrated power source and generating an attracting force between this and the electromagnetic attracting piece 4b, the bonding arm 1 and the swing arm 2 are fixedly coupled to each other. In order to prevent this, an adjustable stopper 6 fixed to the swing arm 2 with a screw or the like is provided. Further, a magnet 5a and a coil 5b are respectively attached to the swing arm 2 and the holding frame 1a at positions in front of the electromagnetic attracting means. The magnet 5a and the coil 5b constitute means for generating an attracting force for urging the tip of the bonding arm 1, that is, a portion holding the capillary 7 as a bonding tool, downward in FIG. .

A clamp arm 8 is provided at the tip of the swing arm 2, and a wire 9 is held 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 by a method described later. A torch rod 10 serving as an electric discharge means is disposed on the vertical axis (not shown) below the capillary 7 so as to be rotatable by the action of an actuator or the like, and rotates around the capillary 7 as the bonding arm 1 moves. It has a movable configuration.

The torch rod 10 forms a ball at the tip of the wire 9 by applying a predetermined high voltage. In addition, above the clamp 8a, a fixing instruction is given to a frame (not shown),
A tension clamp 11 is provided by applying a predetermined tension to the wire 9 so that the wire 9 is always kept straight up to the tip of the capillary 7 of the bonding arm 1 and can be opened and closed by an opening / closing mechanism (not shown). 9
Is wound by a spool 36 via a 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 the swing base 16a at one end, 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 the 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 stretched between the tip of the preload arm 16d and the tip of the swing base 16a.
The cam follower 17 is in pressure contact with 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 in between.

The swing base 16a, the bearing guide 16b, and the preload arm 16d form a frame structure, which is collectively referred to as the swing frame 16.

A bearing guide 16b as a constituent member of the swing frame 16 is provided on the cam shaft 1 on which a cam 18 is fitted.
9 is in contact with the outer ring of the radial bearing 20 attached to the bearing 9. The cam 18 is a motor 2 as driving means.
1 is rotated by the torque applied to the camshaft 19 from 1,
The capillary 7 as a bonding tool is configured to move and control with respect to the bonding point.

The height position of the capillary 7 is detected by a rotary encoder (not shown) as height position detecting means connected to the support shaft 3.

On the bonding stage 26,
A lead 27 as a component to be bonded is mounted, and a semiconductor component, that is, an IC chip 25 as a component to be bonded is mounted on the lead 27.

FIG. 3 shows a drive circuit of a motor 21 as drive means for controlling the movement of the capillary 7 as a bonding tool with respect to the bonding point.

A block 41 surrounded by a broken line shows a digital servo circuit of the motor 21. The motor 21 is connected to a rotary encoder 41a as a position detecting means with respect to the drive shaft of the motor 21. Yes.

Accordingly, a position signal by a sine wave can be obtained from the rotary encoder 41a as the drive shaft of the motor 21 rotates. The position signal by this sine wave is converted into a pulse signal by the pulse converter 41b,
It is supplied to the position command signal generator 41c. The position command signal generator 41c receives a command signal for driving the capillary 7 as a bonding tool as an input point 41.
Therefore, the output from the pulse converter 41b is added as a feedback signal (first feedback signal) at the input point 41e of the position command signal generator 41c.

The output of the position command signal generator 41c is
The speed signal supplied to the speed command signal generator 41f and obtained by the speed command signal generator 41f is supplied to the current command signal generator 4 through the feedback signal input point 41g.
1h, where the electric power is amplified and formed into a drive current of a motor 21 as a drive means.

The digital servo circuit is configured as described above.

Next, a block 42 surrounded by a broken line indicates a position signal generating circuit. This position signal generation circuit 42
Is for generating a position signal based on a sine wave output indicating the rotational position of the motor 21 obtained by the rotary encoder 41a.

That is, the rotary encoder 41a outputs A-phase and B-phase sine wave signals as shown in FIG. 4 in a phase relationship of 90 degrees depending on the position of the drive shaft of the motor. This sine wave signal is applied to the adder circuit 42c and the subtractor circuit 42d via the gain offset adjustment amplifiers 42a and 42b.

Therefore, the adder circuit 42c has a circuit shown in FIG.
The output of A + B shown in FIG. 5 is obtained, and the output of AB shown in FIG. The output of A + B and the output of AB are respectively output from the waveform switching circuit 42e.
It is comprised so that it may be supplied to.

On the other hand, the gain offset adjusting amplifier 4
The A-phase and B-phase outputs obtained from 2a and 42b are supplied to comparators 42f and 42g, respectively. The comparators 42f and 42g shift to the output “1” or “0” at the zero cross point of the sine wave signal, and are thus converted into signals indicated as P and Q in FIG.

The P and Q signals obtained by the comparators 42f and 42g are supplied to the waveform selection circuit 42h. The waveform selection circuit 42h constitutes an exclusive OR circuit, and the exclusive OR output of the P and Q signals is supplied to the waveform switching circuit 42e and input to the waveform switching circuit 42e. The output of A + B or the output of AB is selectively selected by the exclusive OR output of the P and Q signals. Therefore, the waveform switching circuit 42
A position signal is output from e.

A block 43 surrounded by a broken line indicates a speed signal generating circuit. This speed signal generation circuit 43
Is provided with a waveform shaping circuit 43a to which outputs of the A phase and the B phase obtained from the gain offset adjustment amplifiers 42a and 42b are input.

The waveform shaping circuit 43a has a function of adding an offset voltage to the position signal obtained from the waveform switching circuit 42e. That is, the waveform of the output of the waveform switching circuit 42e is disturbed because the sign of the output level is inverted by signal switching.

In order to prevent this, a positive (+) or negative (-) offset voltage is applied to the position signal output at the timing of switching, and a discontinuous signal with switching is formed into a continuous position signal. Is.

The position signal obtained in this way is supplied to the differentiation circuit 43b and converted into a speed signal by the differentiation circuit 43b.

The speed signal obtained by the differentiating circuit 43b is converted into a sample hold (S / H) amplifier 43c.
In addition, the S / H amplifier 43c removes noise at the time of signal switching, and noise is removed by an analog filter provided in the amplifier 43d.

The speed signal obtained by such a configuration is supplied to a switch circuit 44 as switching means.
The switch circuit 44 serving as the switching means is configured such that a control signal input point is obtained when a work touch signal indicating that the capillary 7 is in contact with the semiconductor component (contacts the first bonding point or the second bonding point) is obtained. It is turned on by a control signal supplied to 45, and the speed signal is supplied to the servo circuit 41 as a feedback signal (second feedback signal).

The control signal supplied to the switch circuit 44 has no change in the position of the capillary 7 based on information from a rotary encoder as a height position detecting means connected to the support shaft 3 shown in FIG. This state is generated by detecting the state by software.

Therefore, when the capillary 7 comes into contact with the first bonding point or the second bonding point, a speed signal is applied to the feedback signal input point 41g of the digital servo circuit 41 of the motor 21, and the digital servo circuit 41, that is, the rotary encoder. By forming the discontinuous signal by 41a or the like into a continuous position signal, the fine vibration due to the limit cycle is cancelled.

Therefore, when the capillary 7 is in contact with the first bonding point or the second bonding point,
Slight vibration is effectively suppressed, a reliable bonding action can be obtained, and the bonding reliability can be improved.

Although the present invention has been described based on a wire bonding apparatus, it can be appropriately adopted and used in a tape bonding apparatus or the like.

[0049]

As apparent from the above description, according to the bonding apparatus of the present invention, in the servo circuit in which the drive circuit of the drive means for controlling the movement of the bonding tool relative to the part to be bonded is a closed circuit. The position signal generating circuit generates a position signal based on the sine wave output indicating the position of the driving means obtained by the position detecting means, and a work touch signal indicating that the bonding tool has contacted the part to be bonded is obtained. Since the velocity signal based on the position signal obtained from the position signal generation circuit is supplied as a feedback signal to the servo circuit, the minute vibration due to the limit cycle generated in the drive means in the servo circuit is effective. Can be reduced.

Therefore, a reliable bonding action can be obtained with the bonding tool stationary, and the reliability of the bonding apparatus can be improved.

[Brief description of the drawings]

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

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

FIG. 3 is a block diagram showing a motor control circuit in the apparatus shown in FIG. 1;

FIG. 4 is a waveform diagram of main parts in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Bonding arm 2 Swing arm 3 Support shaft 7 Capillary (bonding tool) 8 Clamp arm 8a Clamp 9 Wire 10 Torch rod 16 Swing frame 18 Cam 21 Motor (driving means) 25 IC chip (semiconductor component) (part to be bonded) 25a pad (electrode) 26 bonding stage 27 lead (part to be bonded) 41 digital servo circuit 41a rotary encoder (position detection means) 41b pulse converter 41c position command signal generator 41d input point 41e feedback signal (first feedback signal) input Point 41f Speed command signal generator 41g Feedback signal (second feedback signal) input point 41h Current command signal generator 42 Position signal generator 42a Gain offset adjustment amplifier 42b Gain Offset adjustment amplifier 42c Addition circuit 42d Subtraction circuit 42e Waveform switching circuit 42f Comparator 42g Comparator 42h Waveform selection circuit (exclusive OR circuit) 43 Speed signal generation circuit 43a Waveform shaping circuit 43b Differentiation circuit 43c Sample hold amplifier 43d Amplifier 44 Switch circuit ( 45) Control signal input point

Claims (2)

(57) [Claims] 1. A driving means for controlling movement of a bonding tool relative to a part to be bonded, a position detecting means for detecting a position of the driving means and generating a position signal, and a position signal from the position detecting means A first feedback signal superimposed on the drive circuit of the drive means, a position signal generation circuit for generating a position signal based on a sine wave output indicating the position of the drive means obtained by the position detection means, When a work touch signal indicating that the bonding tool has contacted the part to be bonded is obtained,
A bonding apparatus comprising: switching means for supplying a speed signal based on the position signal obtained from the position signal generation circuit as a second feedback signal to the servo circuit. 2. The position signal generation circuit includes: an adder circuit that adds a first sine wave and a second sine wave having different phase relationships; and a difference between the first sine wave and the second sine wave. A first and second comparators for shifting the output at the zero-cross points of the first sine wave and the second sine wave, respectively, and exclusive logic of the first and second comparator outputs The bonding apparatus according to claim 1, comprising: a waveform selection circuit that generates a sum output; and a waveform switching circuit that selects an output of the addition circuit or subtraction circuit based on an output of the waveform selection circuit.