JPH11219971A - Wire bonding electric torch device - Google Patents

Abstract

(57) [PROBLEMS] To prevent the diameter of a ball from being reduced when a wire coming out of a capillary is shortened in a wire bonding electric torch device. SOLUTION: The characteristic of a constant current circuit controller for increasing / decreasing a constant current value when a gap between an electric torch lot and a wire tip changes, a voltage applied between the electric torch lot and a wire exceeds a standard value. On the other hand, the gradient for lowering the constant current value is made gentler as the applied voltage increases. When the applied voltage exceeds the standard voltage, the diode CD ₁ is made conductive, and as the voltage increases, the constant voltage diode Z ₁ ,
Z ₂ is the gentle slope of sequential continuity and becomes divided voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of stabilizing a ball diameter in forming a ball at the tip of a wire by an electric torch of a wire bonding apparatus.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing the configuration of a conventional wire bonding electric torch device. One output terminal of the DC high-voltage power supply 2 is connected to an electric torch lot 9 via a constant current circuit 3 and a ballast 4, and the other output terminal is connected to a clamper 7. At the discharge timing, the clamper 7 is closed and is in electrical contact with the wire 10. In this way, when a high voltage is applied between the wire 10 and the electric torch lot 9, a spark discharge is generated, the tip of the wire 10 is melted by the discharge energy, and a ball is formed by surface tension. In order for bonding to be performed with high reliability, it is necessary that the ball is formed stably for each bonding. That is,
It is important that the diameter of the ball formed is the same for each bonding.

Conventionally, therefore, a constant current circuit 3 is provided so that the discharge current during and every discharge is constant even if the gap between the tip of the wire 10 and the electric torch lot 9 changes. However, if the gap between the tip of the wire 10 and the electric torch lot 9 becomes large for some reason, the discharge impedance naturally becomes high. This means that the voltage increases. If the current is constant and the voltage is increased, the energy at the time of discharge increases, the amount of melting at the tip of the wire 10 increases, and the resulting ball increases.

Conversely, if the gap between the tip of the wire 10 and the electric torch lot 9 becomes smaller for some reason, the discharge impedance naturally becomes smaller, so that the applied voltage becomes lower in order to maintain a constant current. In this case, the fact that the current is constant and the voltage is low means that the energy at the time of discharge is small, and there is a problem that the amount of melting at the tip of the wire 10 is small and the resulting ball is small.

Therefore, when the gap between the tip of the wire 10 and the electric torch lot 9 is a standard set interval, the constant high current value is centered on the standard high voltage value between the electric torch lot 9 and the wire 10. , Because the gap has changed,
When the high voltage between the electric torch lot 9 and the wire 10 fluctuates up and down, the constant current value changes with a constant linear gradient with respect to the change of the high voltage around the standard value of the constant current value when the high voltage rises. The constant current value increases as the voltage decreases and the high voltage decreases, so that the energy at the time of discharge becomes as similar as possible.

More specifically, since a high voltage between the electric torch lot 9 and the wire 10 is dangerous if it is used as it is, the partial pressure is detected by the partial pressure detector 5, while the voltage between the electric torch lot 9 and the end of the wire 10 is detected. A standard high voltage applied when the gap is at a standard setting interval is generated by a reference voltage generator 6 as a reference voltage V _S , with a voltage having a value equal to the voltage value detected by the partial pressure detector 5 as a divided voltage. , The detection voltage V _D and the reference voltage V _S are input to the linear constant current circuit controller 11. The linear constant current circuit controller 11 controls the constant current circuit 3 so that the constant current value I when the detection voltage V _D is just V _S becomes the standard current value I _S , and the detection voltage V _D is lower than V _S. In the range and the high range, as shown in FIG. 5, the constant current value I linearly decreases as the detection voltage increases.

Since the constant current value of the actual constant current circuit changes linearly with the change of the control voltage, the detection voltage V _D (this is the input voltage) of the linear constant current circuit controller versus the output voltage The characteristics are also linear characteristics similar to FIG. The ballast 4 is a circuit for stabilizing discharge.

[0008]

[SUMMARY OF THE INVENTION However, in the above prior art, including the reference voltage V _S, results that with respect to the change in the detected voltage V _D of the range there is a constant diameter of the ball was obtained However, there has been a problem that the diameter of the ball is reduced when the detection voltage is further increased.
The cause is considered as follows. An increase in the detection voltage V _D means that the electric torch lot 9 and the wire 10
Means that the gap between the capillary 8 and the electric torch lot 9 at the time of discharge is mechanically fixed with high precision, so that the wire 10 exits from the tip of the capillary 8 after all. Means that the length of the line has been shortened. As a result, a part of the heat energy for melting the tip of the wire 10 at the time of discharge escapes toward the capillary 8, so that the diameter of the formed ball is reduced.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a method in which the length of a wire 10 coming out of the tip of a capillary 8 becomes shorter than a standard setting.
An object of the present invention is to provide a wire bonding electric torch device in which the slope of the constant current value is controlled to be small so as to compensate for the thermal energy escaping to the ball, so that the ball diameter is not reduced.

[0010]

The present invention has the following arrangement to achieve the above object. That is, a DC high-voltage power supply, a constant current circuit connected in series to the current flowing from the DC high-voltage power supply, and a constant current circuit whose constant current value can be set and controlled by an external control voltage; A high voltage is applied between the bonding wire protruding from the tip of the bonding capillary and the electric torch lot, and a spark discharge is generated between the wire tip and the electric torch lot. A wire bonding electric torch device, comprising: a device for forming a bonding ball at the tip of the wire bonding device; (B) A partial pressure detector that detects the high voltage between the electric torch lot and the wire by dividing the voltage. (B) Divides the standard high voltage applied when the gap between the electric torch lot and the tip of the wire is the standard setting interval. A reference voltage generator that generates a voltage equal to the voltage value detected by the pressure detector as the reference voltage. (C) Receives the detection voltage from the partial pressure detector and the reference voltage from the reference voltage generator, and A control means for sending a control voltage to a current circuit, and outputs a control voltage in which a constant current value is set to a standard value when a detected voltage value is the same as a reference voltage value, and outputs a control voltage when the detected voltage value is smaller than the reference voltage value. Outputs a control voltage in which the constant current value increases linearly from the standard value with a preset gradient as the value decreases, and when the detected voltage value is greater than the reference voltage value, the control current increases from the standard value as the value increases. The preset Non-linear constant current circuit controller gradients from the gradient outputs a continuously or stepwise smaller becomes while decreasing control voltage

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is that a nonlinear constant current circuit controller is used instead of the linear constant current circuit controller 11 in the conventional configuration. The non-linear characteristic is that, when the voltage detected by the partial pressure detector becomes larger than the reference voltage of the reference voltage generator, conventionally, the constant current value drops linearly, that is, the constant current decreases. On the other hand, the characteristic is such that the gradient of the descent decreases continuously or stepwise.

By doing so, the degree of decrease in the constant current value decreases in the direction where the detection voltage is large, that is, in the case where the distance from the tip of the wire 10 to the capillary 8 is short, and the constant current value becomes larger than in the prior art. In order to compensate for the heat escaping toward 8, the ball diameter is not reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a wire bonding electric torch device of the present invention. The difference from the conventional configuration of FIG. 4 is that the linear constant current circuit controller 11 is replaced with the nonlinear constant current circuit controller 1. FIG.
It is an example of an implementation circuit of such a nonlinear constant current circuit controller 1. Since a negative high voltage is applied to the electric torch lot 9, both the detection voltage of the partial pressure detector 5 and the reference voltage of the reference voltage generator 6 are negative voltages. Accordingly, the input voltage to the detection voltage input terminal in FIG. 2 is also a negative voltage to the reference voltage input terminal. R _A, R _B, R _C is a resistor of the same resistance value, A ₁ is a differential amplifier. Therefore, the diode CD ₁ or CD
_{When 2} is conductive, the differential amplifier has a voltage gain of 1. The output of the differential amplifier A ₁ is 0 at the same time as the detection voltage is a reference voltage, when the detected voltage value is smaller than the reference voltage value, namely, the negative input terminal of the differential amplifier A ₁ is higher in potential than the positive input terminal , The difference value V appears at the output with a negative potential. The output of the differential amplifier A ₁ becomes a result diode CD ₂ conductive state appears at the point P _1,
It is sent to the synthesizer 12.

[0014] Conversely, when the detected voltage value is larger than the reference voltage value, that is, when the negative input terminal of the differential amplifier A ₁ is the potential from the positive input terminal becomes low at the output thereof difference value V is at positive potential . As a result, the diode CD ₁ becomes conductive, the output of the differential amplifier A ₁ appears at point P _2.
The output side of the resistor R ₀ which is connected to the point P ₂ resistors R ₁ and R ₂ are respectively grounded through a constant voltage diode Z ₁ and Z _2.

Now, assuming that the constant voltages of the constant voltage diodes Z ₁ and Z ₂ are V ₁ and V _2, and a relationship of V ₁ <V ₂ is established, the voltage V at the point P ₂ is 0 <V <V When it becomes _1, both of the constant voltage diodes Z ₁ and Z ₂ are in a non-conductive state, and are sent to the combiner 12 as they are. Synthesizer 1
2 has a high input impedance, the potential at point P ₂ appears at point P _{3 as} it is and is sent to combiner 12.

Next, when the voltage V is V ₁ <V <V ₂ , the constant voltage diode Z ₁ is turned on and the constant voltage diode Z ₂ is turned off. The voltage is divided by ₀ and R ₁ , and the gradient of the potential at the point P ₃ becomes smaller as expressed by Expression 1 as compared with 0 <V <V ₁ .

[0017]

(Equation 1)

Next, when the voltage V is V> V ₂ , both of the constant voltage diodes Z ₁ and Z ₂ become conductive.
Since the change in the voltage V is divided by the parallel value of the resistors R ₁ and R ₂ and the resistor R ₀ , the gradient of the potential at the point P ₃ is 0 <V <V ₁ In comparison, it becomes even smaller as represented by Equation 2.

[0019]

(Equation 2)

[0020] The above reference voltage elapsed - horizontal axis detection voltage, the vertical axis, the reference voltage - <take voltage at the point P ₁ to 0, the reference voltage - the detection voltage> detection voltage when the zero point to illustrate taking a voltage of P ₃ is as shown in Figure 3 (a). Then, combined into one output voltage and the voltage of the point P ₁ of the point P ₃ in the combiner 12, and then is shown in FIG. 3 Invert the polarity of the (b) in polarity inverter 13. This is the output voltage of the nonlinear constant current circuit controller 1 in this embodiment. That is, when the detected voltage value (absolute value) from the partial pressure detector 5 becomes smaller than the reference voltage value (absolute value), the output voltage increases with the same gradient, whereas the detected voltage value (absolute value) increases. absolute value) when the becomes larger than the reference voltage value (absolute value) is the gradient becomes smaller the difference value is at the V _1, gradient descends getting smaller so that further decreases at the V ₂ .

In this example, the gradient changes at two points. However, the gradient can be further subdivided by increasing the number of constant voltage diodes having different constant voltage values and selecting a resistance value connected in series to the constant voltage diodes. The gradient can be changed little by little in the divided section, and a gradient change closer to a curve can be realized.
Also, the gradient can be gradually reduced by using a nonlinear element.

When the output voltage of the non-linear constant current circuit controller 1 thus obtained is applied to the control voltage terminal of the constant current circuit 3, the set constant current value changes linearly with the change of the control voltage. The value changes substantially as shown in FIG. That is, when the detected voltage value becomes smaller than the reference voltage value, the set value of the constant current is increased almost linearly. Conversely, when the detected voltage value becomes larger than the reference voltage value, the constant current becomes constant. Although the set value of the current is reduced, the gradient of the decrease is made gentle to compensate for the escape of heat during discharge from the wire 10 to the capillary 8.

Thus, when the set value is reduced linearly as in the prior art, the problem that the ball diameter is reduced from a certain point is solved, and a ball having a substantially constant diameter is formed.

[0024]

As described above, in the wire bonding electric torch device of the present invention, when the distance between the electric torch lot and the tip of the wire becomes larger than the standard set value and the applied voltage increases. When lowering the constant current set value, the slope of the constant current set value drop with the increase in applied voltage was made gentle so as to compensate for the heat escaping from the wire tip toward the capillary, There is an advantage that the diameter of the ball does not decrease due to the escape of heat.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a wire bonding electric torch device of the present invention.

FIG. 2 is a diagram showing an embodiment of a circuit configuration of a nonlinear constant current circuit controller of the wire bonding electric torch device of the present invention.

FIG. 3 is a diagram illustrating input / output characteristics of the nonlinear constant current circuit controller of FIG. 2;

FIG. 4 is a block diagram showing a configuration of a conventional wire bonding electric torch device.

FIG. 5 is a diagram showing input / output characteristics of a linear constant current circuit controller of a conventional wire bonding electric torch device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nonlinear constant current circuit controller 2 DC high voltage power supply 3 Constant current circuit 4 Ballast 5 Voltage division detector 6 Reference voltage generator 7 Clamper 8 Capillary 9 Electric torch lot 10 Wire 11 Linear constant current circuit controller 12 Synthesizer 13 Polarity Inverter

Claims (1)

[Claims] 1. A DC high-voltage power supply, a constant current circuit connected in series to the current flowing from the DC high-voltage power supply, and a constant current circuit whose constant current value can be set and controlled by an external control voltage, and connected to its output side. A high voltage is applied between the bonding wire coming out of the tip of the bonding capillary and the electric torch lot to generate a spark discharge between the wire tip and the electric torch lot. A wire bonding electric torch device having the following configuration, which is a device for forming a bonding ball at the tip of a formed wire. (B) A partial pressure detector that detects the high voltage between the electric torch lot and the wire by dividing the voltage. (B) Divides the standard high voltage applied when the gap between the electric torch lot and the tip of the wire is the standard setting interval. A reference voltage generator that generates a voltage equal to the voltage value detected by the pressure detector as the reference voltage. (C) Receives the detection voltage from the partial pressure detector and the reference voltage from the reference voltage generator, and A control means for sending a control voltage to a current circuit, and outputs a control voltage in which a constant current value is set to a standard value when a detected voltage value is the same as a reference voltage value. Outputs a control voltage in which the constant current value increases linearly from the standard value with a preset gradient as the value decreases, and when the detected voltage value is greater than the reference voltage value, the control current increases from the standard value as the value increases. The preset Non-linear constant current circuit controller gradients from the gradient outputs a continuously or stepwise smaller becomes while decreasing control voltage