JP2976602B2 - Wire bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding method, and more particularly, to sample a voltage and a current applied to a transducer to obtain an output and an impedance of the transducer, and to judge the quality of the wire bonding based on the output and impedance. It is like that.

[0002]

2. Description of the Related Art After a semiconductor chip is mounted on a substrate such as a lead frame by a die bonder, electrodes of the semiconductor chip and electrodes of the substrate are connected by wires using a wire bonder. In this wire bonder, a wire is led out from the lower end of a capillary held by a transducer, high-frequency energy is applied to the transducer, and the transducer is ultrasonically (US) vibrated while the wire is wound on an electrode of a semiconductor chip or a substrate. And the semiconductor chip and the substrate are connected by wires.

[0003] The transducer is supplied with high-frequency energy from the US oscillation section and a load from a load device such as a linear motor. In order to perform good bonding, the substrate is firmly clamped by a clamper. The US oscillating unit and the load device must be controlled so as to appropriately apply high-frequency energy and load.

[0004]

A predetermined voltage is applied to the transducer as high-frequency energy from the US oscillating unit, and a current flows in accordance with the load of the transducer. If the values deviate, bonding failure occurs. Therefore, the present inventor made a correlation diagram of the magnitude of the output of the transducer and the impedance of the transducer based on the magnitude of the load applied to the transducer by the load device. It turned out that it can be clearly distinguished on the figure.

The present invention has been made in view of the above points, and has as its object to provide means for judging the quality of bonding based on the correlation between the output and impedance.

[0006]

According to the present invention, the output and impedance of the transducer are calculated by sampling the voltage and current applied to the transducer, and the correlation between the output and impedance of the transducer and the bonding quality is determined in advance. In addition, the quality of the bonding is determined by comparing the above calculation result with this correlation.

[0007]

In the above arrangement, the output and impedance of the transducer are calculated based on the sampled voltage and current. Then, the quality of the bonding is determined by comparing the calculated result with a previously obtained correlation. If the bonding is defective, the bonding operation is stopped.

[0008]

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

In FIG. 1, reference numeral 1 denotes a transducer. A piezoelectric element 3 is attached to a rear end of a bar-shaped horn 2, and a capillary 4 is held at a front end of the horn 2. 5 is a substrate such as a lead frame, 6
Is a semiconductor chip mounted on the upper surface. 7 is a wire such as a thin gold wire passed through the capillary 4,
The electrodes formed on the upper surface of the semiconductor chip 6 and the electrodes of the substrate 5 are connected by the wires 7. Reference numeral 9 denotes a clamper for clamping and positioning the substrate 5 from left and right.

Reference numeral 10 denotes a load device comprising a linear motor, 1
1 is a coil spring. When a current is applied to the coil portion 10a, the coil portion 10a protrudes and retracts against the spring force of the spring 11, and the horn 2 swings around the rotating shaft 8 in the direction of the arrow,
The lower end of the capillary 4 is pressed against the upper surface of the semiconductor chip 6 or the substrate 5. 19 is a touch sensor. This pressing force, that is, the load of the capillary 4 is reduced by the coil portion 10a.
Is controlled by the amount of power supplied to the

Reference numeral 20 denotes an input setting unit comprising an 8-bit digital / analog converter, which is connected to the US oscillation unit 21. 22 is an amplifier connected to the US oscillation unit 21;
23 is a transformer. The secondary side of the transformer 23 is connected to the piezoelectric element 3. On the secondary side of the transformer 23, a voltage extracting unit 24 and a current extracting unit 25 are provided, and the voltage VO and the current I
Remove O. The voltage VO and the current IO are applied to the effective value circuits 31 and 32 of the monitor unit 30. The monitor section 30 includes a multiplier 41 for multiplying the effective voltage value V extracted from the effective value circuits 31 and 32 by the effective current value I, a divider 42 for dividing, and an A / D for A / D converting the result. Converters 32 and 33, a recognition unit 35 connected to the A / D converters 32 and 33 via a multi-bus 34, a CPU 3
6, a memory 37, and a display 38 connected to the recognition unit 35. Reference numeral 40 denotes a switch unit.

FIG. 2 shows outputs V, RMS of effective value circuits 31, 32.
The waveform of I is shown. V ′ and I ′ are sampled effective values, and the sampling time is 0.2 ms. The memory 37 stores the sampled effective values V 'and I'. The multiplier 41 and the divider 42 calculate the output P = V × I and the impedance Z = V ÷ I of the transducer 1.

The recognition unit 35 creates a correlation diagram of two-dimensional coordinates indicating the correlation between the impedance Z and the output P and the quality of the bonding shown in FIG. 3 based on the calculation result, and the display 38 displays this. Display a plot on the monitor screen.

In FIG. 3, black dots indicate good bonding, and x indicates poor bonding. As described in the section of the problem to be solved by the invention, good bonding and poor bonding can be clearly distinguished. That is, FIG.
As is clear from the above, the one with good bonding exists in the elongated area B centered on the curve A, and the one with bad bonding exists outside the area B. This correlation diagram can be easily obtained experimentally.

Therefore, the above sampling is appropriately performed,
The calculated value is displayed in this figure. If this calculated value is present in the area B, for example, at points a and b, it can be determined that the bonding has been performed satisfactorily.
Also, if the points protrude from the area B as at points c, d, and e, the bonding can be determined to be defective. In this case, the operation of the apparatus is stopped, and information for determining whether the US output is large or the load is too large is provided. For example, in the case of the point c, the impedance and the output are respectively ΔZ
The set value of the input setting unit 20 is adjusted so as to increase by 1, P1 or more. In the case of the point d, the set value of the input setting unit 20 is adjusted so that the output increases by ΔP2 or more without changing the impedance. In the case of the point e, the output and the impedance may be adjusted so as to decrease by ΔP3 and ΔZ3 or more, respectively.

Since the impedance Z is proportional to the strength of the force for strongly pressing the capillary 4 against the substrate 5 or the semiconductor chip 6, the impedance Z can be adjusted by controlling the amount of power supplied to the linear motor 10.

[0017]

As described above, according to the present invention, the output and impedance of the transducer are calculated by sampling the voltage and current applied to the transducer, and the output and impedance of the transducer are plotted and displayed on a two-dimensional coordinate correlation diagram. For example, the quality of the bonding for each wire can be easily determined.

[Brief description of the drawings]

FIG. 1 is an overall view of a wire bonding means according to the present invention.

FIG. 2 is a waveform diagram of voltage and current according to the present invention.

FIG. 3 is a diagram showing the correlation between the voltage and current and the quality of bonding according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transducer 4 Capillary 5 Substrate 6 Semiconductor chip 7 Wire 20 Input setting part 21 US oscillation part

Claims (1)

(57) [Claims] 1. A capillary through which a wire is passed, a transducer for holding the capillary, a US oscillating section for applying high-frequency energy to the transducer, and an input setting section for controlling the US oscillating section.
A wire bonder in which a wire led out of a capillary is bonded to a semiconductor chip and a substrate while driving the oscillator to ultrasonically vibrate the transducer, and the semiconductor chip and the substrate are connected by a wire. The output voltage and current are sampled, and the output and impedance of the transducer are calculated from the voltage and current.On the other hand, the correlation between the output and impedance of the transducer and the quality of the bonding is determined in advance, and the above calculation result is used as the correlation. A wire bonding method, wherein the quality of bonding is determined in light of the above.