JP2630886B2 - Wire 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 process for assembling a semiconductor device by using a wire at a first bonding point, for example, an electrode on a semiconductor chip, and a second bonding point, for example, an external lead provided on a lead frame. And a wire bonding apparatus for connection.

[0002]

2. Description of the Related Art Conventionally, an apparatus for connecting an electrode on a semiconductor chip serving as a first bonding point and a lead serving as a second bonding point using a gold wire or a wire such as copper or aluminum is shown in FIG. A wire bonding apparatus having a circuit configuration as shown is known.

The device shown in FIG. 2 comprises a power supply circuit 1 for generating a high voltage, a constant current circuit 2 connected to the power supply circuit 1 for generating a constant current, a switching circuit 3, and a switching circuit 3 for a predetermined time. A timer circuit 4 for turning on / off,
It comprises a ballast 5 connected to the switching circuit 3, a discharge electrode 9, a clamper 6, a capillary 8, and a wire 7 inserted through the capillary 8. The ballast 5 has a large value resistor R for stabilizing spark discharge.
Is used.

In order to form a ball using the apparatus having the above configuration, the timer circuit 4 is triggered by an external trigger signal Tr to drive the switching circuit 3 to turn on the switch. When the switch is turned on, a constant current is supplied from the constant current circuit 2, and a high voltage, for example, −2500 V is applied to the discharge electrode 9 via the ballast 5. A discharge is caused, and the tip of the wire is melted by the discharge energy E to form a ball.

[0005]

Generally, in this type of device, the amount of energy E generated at the discharge electrode 9 is the product of the voltage V between the electrodes, the current I, and the time T. In the conventional device, when the distance S between the electrodes, that is, the distance between the tip of the wire 7 and the discharge electrode 9 changes, the voltage V between the electrodes changes.
Changes, the amount of energy E generated at the discharge electrode 9 changes, and the energy required for ball formation increases and decreases. Therefore, there is a disadvantage that the diameter of the ball formed thereby changes.

That is, when the interelectrode distance S changes, the interelectrode voltage V changes almost in proportion thereto. For example, when the interelectrode distance S increases, the interelectrode voltage V increases. When the current is constant, the energy amount E generated per unit time at the discharge electrode 9 increases. Conversely, when the interelectrode distance S decreases, the interelectrode voltage decreases. When the voltage V decreases and the current is constant, the amount of energy E generated at the discharge electrode 9 per unit time is obtained.
Becomes smaller. For this reason, the ball diameter changes, and variations occur.

Further, since a large value resistor R for stabilizing the spark discharge is used in the ballast 5, an appropriate current cannot be obtained due to a large voltage drop loss and a decrease in the spark discharge current for maintaining the discharge. Therefore, there is a problem that a good ball cannot be formed.

In view of the above, the present invention has been made in view of the above-mentioned drawbacks of the prior art, and has a variable leakage type step-up transformer in which a control winding is supplied with a current from a DC power supply. A high-frequency switching current is supplied to the primary winding, and a high-frequency voltage generated in the secondary winding of the variable leakage type step-up transformer is rectified and projected from the tip of the capillary through a ballast formed by an inductance element. Even if the distance between the electrodes changes by applying the voltage between the wire and the discharge electrode, the amount of energy E supplied to the discharge electrode per unit time is kept constant, and the diameter of the ball formed thereby is made uniform. It is an object of the present invention to provide a wire bonding apparatus capable of performing the above.

[0009]

According to the present invention, there is provided a wire bonding apparatus comprising: a switching control element which is switched by a high-frequency signal from a high-frequency oscillator; A variable leakage type boosting transformer, which is supplied to a line and a current from a DC power supply is supplied to a control winding, and an output voltage generated in a secondary winding of the variable leakage type boosting transformer is supplied from the tip of the capillary. It is configured to apply a voltage between the protruding wire and the discharge electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wire bonding apparatus according to the present invention will be described below.

FIG. 1 shows an example of a circuit configuration of a wire bonding apparatus according to the present invention. Components having the same functions and configurations as those of the conventional apparatus shown in FIG. 2 will be described using the same reference numerals. .

In FIG. 1, a timer circuit 11 is connected to a control circuit 10, and the timer circuit 11 operates intermittently by a trigger signal supplied from the control circuit 10.
A high-frequency oscillator 12 is connected to the timer circuit 11, and the high-frequency oscillator 12 performs an oscillating operation by a drive signal from the timer circuit 11.

The high frequency oscillator 12 is connected to the base electrodes of a pair of NPN type switching transistors Q1 and Q2 constituting a switching control element. A signal is supplied from each of the high-frequency oscillators 12. Further, the switching transistor Q
1, the emitter electrodes of Q2 are commonly connected, and the common emitter electrode is connected to the negative terminal of the DC power supply 13.

The switching transistors Q1, Q2
Are connected to both ends of a primary winding 15 of a variable leakage type step-up transformer 14, and a center tap of the primary winding 15 is connected to a positive terminal of the DC power supply 13.

The variable leakage type step-up transformer 14
Are two magnetic cores 17a via a magnetic gap 16,
17b, and the primary winding 15 is wound around a first magnetic core 17a.
The control winding 18 is wound around b. A DC current is supplied to both ends of the control winding 18 from the DC power supply 13 via a semi-fixed variable resistor R1.

A secondary winding 19 is wound around the first magnetic core 17a of the variable leakage type step-up transformer 14, and a bridge type double wave rectifier is provided at both ends of the secondary winding 19. The circuit 20 is connected. This double-wave rectifier circuit 20
Is connected to the clamper 6. Further, a negative power supply line by the dual-wave rectifier circuit 20 is connected to the discharge electrode 9 via an inductance element constituting the ballast 21. The ballast 21 is formed of an inductance element. If, for example, the spark discharge current is reduced due to some influence during the discharge, a voltage corresponding to the reduced current is generated due to the self-induction action, and the stable discharge is performed. Keep state.

As described in the conventional example, the tip of the wire 7 clamped by the clamper 6 faces the discharge electrode 9 through the capillary 8.

In the above configuration, the trigger signal output from the control circuit 10 is applied to the timer circuit 11, and the timer circuit 11 supplies an intermittent drive signal to the high-frequency oscillator 12. The high-frequency oscillator 12 is driven by a driving signal supplied from the timer circuit 11, for example, from 10 kHz to 500 kHz.
A high frequency signal of about z is oscillated.

The oscillation output from the high-frequency oscillator 12 causes the pair of switching transistors Q1 and Q2 to alternately switch on. At this time, when the base electrode of the first switching transistor Q1 is shifted to a positive potential by the oscillation output of the high-frequency oscillator 12, the first switching transistor Q1 is turned on, and the voltage of about 20 V
From the positive terminal of the DC power supply 13 having an output voltage of about
Current is supplied to the five center taps. The current supplied to the center tap flows from the center tap of the transformer 14 through the primary winding to the transistor Q1 side,
It returns to the negative terminal of the DC power supply 13. In addition, the second
When the base electrode of the switching transistor Q2 is shifted to a positive potential by the output from the high-frequency oscillator 12, the second switching transistor Q2 is turned on, and similarly, the positive terminal of the DC power supply 13 Current is supplied to the center tap of the step-up transformer 14, flows from the center tap of the step-up transformer 14 through the primary winding to the transistor Q 2 side, and returns to the negative terminal of the DC power supply 13.

Here, a constant current is supplied from the DC power supply 13 to the control winding 18 of the variable leakage type step-up transformer 14 through the semi-fixed type variable resistor R1, as described above. The power supplied to the primary winding of the leakage type step-up transformer 14 is controlled to be constant by magnetic saturation.

The secondary winding 19 of the step-up transformer 14
The rectified boosted output is rectified by a double-wave rectifier circuit 20, its positive output is supplied to a wire 7 through a clamper 6, and the negative output rectified by the double-wave rectifier circuit 20 is passed through a ballast 21. The electric power is supplied to the discharge electrode 9, spark discharge occurs between the wire 7 and the discharge electrode 9, and a ball is formed at the tip of the wire 7.

In this embodiment, the power output from the variable leakage type step-up transformer 14 is determined by the DC current flowing into the control winding 18, and the output power on the secondary side of the step-up transformer 14 is substantially constant in units of time. Becomes Therefore, when the gap S between the wire 7 and the discharge electrode 9 increases and the discharge voltage V increases, the discharge current decreases. Conversely, when the gap S between the wire 7 and the discharge electrode 9 decreases and the discharge voltage V decreases, the discharge current increases. Therefore, even if the gap S changes, the energy amount E spent on the discharge phenomenon per unit time becomes constant, and the diameter of the ball formed at the tip of the wire can be made uniform.

[0023]

As is apparent from the above description, according to the wire bonding apparatus of the present invention, a constant control current is supplied to the control winding of the variable leakage type step-up transformer. The power in the unit of time outputted to the side is made constant. Therefore, even if the distance between the tip of the wire and the discharge electrode changes, the discharge energy required for ball formation can always be kept substantially constant, and the diameter of the ball formed at the tip of the wire can be made uniform. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a wire bonding apparatus according to the present invention.

FIG. 2 is a diagram showing a circuit configuration of a conventional wire bonding apparatus.

[Description of sign]

 Reference Signs List 6 clamper 7 wire 8 capillary 9 discharge electrode 10 control circuit 11 timer circuit 12 high-frequency oscillator 13 DC power supply 14 variable leakage type step-up transformer 15 primary winding 16 magnetic gap 17a, 17b magnetic core 18 control winding 19 secondary winding Line 20 Rectifier circuit 21 Ballast Q1, Q2 Switching transistor

Claims (1)

(57) [Claims] 1. A wire bonding in which a high voltage is applied between a tip of a wire protruding from a tip of a capillary and a discharge electrode to generate a discharge, and the discharge energy melts the tip of the wire to form a ball. In the device, a switching control element that is switched by a high-frequency signal from a high-frequency oscillator, a current from a DC power supply is supplied to a primary winding by switching of the switching control element, and a control winding is supplied to the control winding from the DC power supply. A variable leakage type step-up transformer to which a current is supplied, and an output voltage generated in a secondary winding of the variable leakage type step-up transformer is applied between a wire protruding from the capillary tip and a discharge electrode. A wire bonding apparatus, comprising: