JPH02260552A - Bonding device - Google Patents

Abstract

PURPOSE:To enable immediate detection of wire bonding errors by detecting at least either of a dynamic load at collision of a horn during bonding or ultrasonic vibration of the horn during bonding based on output of a strain gage. CONSTITUTION:A strain gage 31 is applied to an ultrasonic horn 16 to monitor a dynamic load and ultrasonic vibration during wire bonding. As for the dynamic load, a signal whose ultrasonic vibration is cut is observed using a low path filter 33. When ultrasonic vibration is monitored, an element of dynamic load is eliminated using a high path filter 34 to observe it as a signal of ultrasonic vibration alone. Each of the dynamic load signal and the ultrasonic vibration signal is operated at a waveform operating section 36 and compared with a standard waveform from a standard waveform section 38. Troubles during wire bonding can be monitored in real time, thereby enabling prevention of including defective wire bonding in products and detection of deterioration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a wire bonding apparatus for manufacturing semiconductor devices.

(Prior Art) FIG. 3 shows a conventional wire bonding device. That is, a bonding head 2 is mounted on an xy table 1. A frame body 4 is attached to the bonding head 2 so as to be rotatable around a shaft 3. Frame 4
A pin 8 on a rotary plate 7 rotatable about a shaft 6 by a motor (not shown) is freely inserted between a pair of arms 5, 5 at the rear of the holder. The frame body 4 is rotated around the axis 3 by the rotation of the rotary plate 7. A support 11 is mounted within the frame 4 so as to be rotatable around the same axis 3 as described above. An end portion 11a of the support 11 is pressed against a stopper 13 by a tension coil spring 12. A linear motor 14 is provided below the end portion 11a of the support 11. The near motor 14 is connected to the end 11 of the support 11.
When a downward force is applied to a, the force with which the end portion 11a holds the horn 16 changes, and by controlling the linear motor 14, the force with which the horn 16 is held can be arbitrarily controlled. If the power of the linear motor 14 is lost,
The end portion 11a abuts against the stopper 13 by the force of the spring 12.

That is, the support 11 is supported by the balance of the forces of the linear motor 14 and the spring 12 and rotates around the shaft 3. A horn 16 is attached to the other end of the support 11.

An ultrasonic vibrator 17 for ultrasonic vibration is attached to the base of the horn 16, and an ultrasonic oscillator 18 is electrically connected to the vibrator 17. A capillary 21 through which a gold wire 22 is passed is attached to the tip of the horn 16. A sample stage 23 is provided below the capillary 21, and a chip 2 is mounted above this via a lead frame 24.
5 is supported.

Wire bonding using the wire bonding apparatus configured as described above is performed as follows.

That is, first, a gold wire 2 is heated by a torch mechanism (not shown).
A high voltage is applied to the capillary 21 to make the tip of the gold wire 22 protruding from the capillary 21 into a spherical shape. Next, the tip of the capillary 21 is moved to a predetermined bonding position by the XY table 1, and the rotating plate 7 is rotated. As a result, the frame body 4 and the support point 11 rotate counterclockwise around the shaft 3, the horn 16 descends downward, and the gold wire 22 is joined to the chip 25. After that, rotate the rotary plate 7 in the opposite direction and turn the horn 1.
6 is raised, and the gold wire 22 and the lead frame are joined by the same operation as above.

The bonding between the gold wire 22 and the chip 25 is achieved by using heat from a heater built into the sample stage 23 and by connecting the capillary 21 to the chip 2.
5 and the horn 1 by the ultrasonic oscillator 18.
This is carried out by an ultrasonic thermocompression bonding method in combination with ultrasonic vibration caused by vertical vibration of No. 6. And capillary 21
The force with which the tip 25 is pressed is determined by the descending speed of the horn 16 and the force holding the horn 16.
The dynamic load that collides with is shown in Figure 4. The force that holds the horn 16 is determined by the combined force of the spring 12 and linear motor 14.

Conventionally, the dynamic load shown in FIG. 4 is measured by placing a load sensor on the sample stage 23 instead of the chip 25 and lead frame 24, and measuring the dynamic load when the horn 16 collides with the load sensor. Ta.

The ultrasonic oscillator 18 excites the ultrasonic vibrator 17 to apply ultrasonic vibration to the horn 16 . The output from the ultrasonic oscillator 18 was as shown in FIG. 5, and the ultrasonic oscillation state was checked based on this waveform.

(Problem to be Solved by the Invention) Since the dynamic load is measured using a load sensor, it is only necessary to preliminarily measure and check before wire bonding. could not be monitored in real time.

In general, dynamic load is an important factor in crimping the gold wire 22, and in particular, the peak value of dynamic load A shown in FIG.
, B and time t1 are important factors. As shown in Figures 6a and b, the dynamic load is a factor that determines the collapse diameter C and the collapse thickness during crimping of the gold wire 21, and if the dynamic load varies, the collapse diameter C and the collapse thickness will also change. scattering,
Stable wire bonding cannot be performed.

Ultrasonic vibrations can be indirectly monitored by observing the output from the ultrasonic oscillator 18, but this is an oscillation output and does not directly measure the ultrasonic vibrations transmitted to the horn. In wire bonding, ultrasonic vibration is an important factor that determines the bonding force of the gold wire 21, and insufficient or uneven output of ultrasonic vibration leads to deterioration of the bondability of the gold wire.

The present invention has been made in view of the above, and its purpose is to:
To enable immediate detection of wire bonding errors by making it possible to monitor dynamic loads and ultrasonic vibrations in real time during wire bonding.

[Structure of the invention]

(Means for Solving the Problems) The wire bonding device of the present invention is a bonding device that performs bonding by pressing a bonding wire supported by an ultrasonic vibrating horn onto an object such as a chip or a lead frame. a pasted strain gauge; and a detection means for detecting at least one of a dynamic load at the time of a collision of the horn during bonding and an ultrasonic vibration of the horn during bonding, based on the output of the strain gauge; It is configured as a base with ,.

(Function) The dynamic load on the horn during bonding and the ultrasonic vibration of the horn are detected by the strain gauge.

Based on the output of the strain gauge, at least one of the dynamic load and the ultrasonic vibration is detected in real time. Based on these, it can be determined whether bonding was performed normally.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment according to the present invention. This embodiment differs from FIG. 3 in that a strain gauge 31 is attached to the ultrasonic horn 16 to monitor dynamic loads and ultrasonic vibrations during wire bonding. Third
Portions with the same reference numerals as those in the figures indicate the same parts as in FIG. 3.

Next, the present embodiment will be explained.

Dynamic strain amplifier 32 based on the output of strain gauge 31
In the signal outputted from the sensor, a signal component of dynamic load of 1)[]1z or less and a signal component of about 60K11z of ultrasonic vibration are combined. Therefore, regarding the dynamic load, a signal obtained by cutting ultrasonic vibrations using the low-pass filter 33 is observed. Furthermore, when monitoring ultrasonic vibrations, the dynamic load component is removed using the bypass filter 34, and only the ultrasonic vibrations are observed as a signal.

Each of the dynamic load signal and the ultrasonic vibration signal is calculated by a waveform calculation section 36 and compared with a reference waveform from a reference waveform section 38 . If the calculation unit 36 determines that the waveform during wire bonding due to dynamic load and ultrasonic vibration is different from the reference waveform, the wire bonding device is stopped as a bonding error or is recorded as a bonding error. It is then determined as a defective product.

If the waveform calculation unit 36 detects that there is a deviation between the reference waveform and the natural frequency, this indicates that an abnormality has appeared in the bonding head, such as loosening of the screw tightening the capillary 21. Abnormalities can be determined.

If the above waveform errors occur continuously, it can be treated as a device problem and the device setting data can be changed.

In addition, an FFT 35 is applied to the output signal from the dynamic distortion amplifier 32.
Dynamic loads and ultrasonic vibrations can also be obtained by applying fast Fourier transform to the frequency domain. The dynamic load is the bending vibration of the horn 16, and the ultrasonic vibration is the horn 1
This is the longitudinal vibration transmitted to horn 6, and the frequency of the waveform is
6 is the natural frequency of transverse vibration and longitudinal vibration.

FIG. 2 shows two displacements of the capillary 21 and a strain output waveform on the time axis. 2 displacement is the impact at the time of chip collision,
The tip is controlled to descend at a constant speed from the search height so that it remains constant even if the tip height varies.

The output waveform of the strain gauge 25 includes a low frequency of dynamic load and a high frequency of ultrasonic vibration. Waveforms filtered with a low-pass filter and a bypass filter are shown.

〔Effect of the invention〕

According to the present invention, troubles during wire bonding can be monitored in real time, and it is possible to prevent defective wire bonding products from being produced and to detect deterioration of wire bonding equipment.

[Brief explanation of drawings]

Figure 1 is an overall configuration diagram of an embodiment of the present invention, Figure 2 is a sequence diagram showing two displacements of the capillary, dynamic load, and ultrasonic vibration, Figure 3 is an overall configuration diagram of a conventional example, and Figure 4 is FIG. 5 is a diagram showing the dynamic load on the horn during bonding, FIG. 5 is a diagram showing the waveform of ultrasonic waves sent to the horn, and FIG. 6 is a plan view and a side view showing the gold ball in a crimped state. 16... Horn, 22... Gold wire, 24... Lead frame, 31... Strain gauge, 36... Waveform calculation section.

Claims (1)

[Claims] A bonding device that performs bonding by pressing a bonding wire supported by an ultrasonic vibrating horn onto an object such as a chip or a lead frame, comprising: a strain gauge affixed to the horn; and the strain gauge. Detecting means for detecting at least one of a dynamic load at the time of a collision of the horn during bonding and an ultrasonic vibration of the horn during bonding, based on the output of the bonding apparatus. .