JPH0210573B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to the work of connecting bonding wires to terminal electrodes of semiconductor devices such as ICs.
The present invention relates to a wire clamp disconnection detection device for a wire bonding device that detects wire abnormalities.

A wire bonding device that bonds a bonding wire made of gold wire to the terminal electrode of a semiconductor device such as an IC automatically supplies the wire and connects the tip of the wire with a torch rod. The wires are melted by electric discharge and are continuously connected between predetermined terminal portions of semiconductor devices that are continuously supplied and the frame. In this case, it is necessary to constantly monitor that the bonding wire is being supplied accurately and that the bonding operation is being carried out smoothly. It is also necessary to monitor the progress of this wire bonding work and supply signals from a control device such as a CPU that controls the entire system.

Figure 1 shows a configuration diagram illustrating a means for detecting wire abnormalities in a conventional wire bonding device. This is related. That is, a pulse-like high voltage signal for discharging is generated in the high voltage section 12 in response to a command from the switching section 11, and this high voltage signal is passed through the current limiting resistor 13 to the discharge gap section 14.
supply to.

Here, as shown in FIG. 2, the wire bonding part is made by holding and setting a wire 15 made of gold wire with a clamp 16, and arranging the tip of this wire 15 and a torch rod 17 oppositely at a small distance. An electric discharge is generated between the wire 15 and the torch rod 17, and a ball 18 is formed at the tip of the wire 15 by the electric discharge energy. In this case, for example, the wire 15
A negative polarity voltage is applied to the tip of the
Set the torch rod 17 to positive polarity and connect the current limiting resistor 13.
Apply a high voltage via.

In such a discharge gap section 14, a part of the discharge current is passed through the primary side diode of the photocoupler 19, the secondary side transistor is turned on to detect the discharge operation, and the detection signal is output.
The signal is supplied to the wire bond control section 20 including a CPU and the like. When the photocoupler 19 sends out the discharge detection signal, the control section 20 determines that the ball 18 has been formed normally and issues a command to continue the bonding operation. Also, switching 1
If the discharge detection signal is not obtained at the timing when the operation command for the high voltage section 12 is issued in step 1, the control section 20 determines that the ball 18 has not been formed and instructs the apparatus to stop.

Here, for example, as shown in FIG.
If the wire 15 comes off from the clamp 16 and the clamp 16 does not perform the action of pulling and cutting the wire 15, a wire abnormality occurs in which the wire 15 is doubly connected to the workpiece 21.

When such a wire abnormality occurs, the wire 15 comes into contact with the torch rod 17 at a point 22 while the torch rod 17 is in the dischargeable position. Therefore, when a high voltage is applied through the current limiting resistor 13 in this state, a short circuit current flows between the wire 15 and the torch bar 17. Since this short-circuit current has the same timing and magnitude as the discharge current, a current flows through the primary side diode of the photocoupler 19 and sends the same command signal to the control unit 20 as if a normal ball 18 had been formed. Start giving.

That is, even though the wire is in an abnormal state in which the ball 18 is not formed due to normal discharge, the control unit 20 determines that the wire is normal and continues the bonding work. Therefore, the wire is bonded with the wire abnormal, and the workpiece becomes defective.

This invention was made in view of the above points, and when a wire abnormality such as a wire coming off a clamp occurs, this is promptly detected and a device stop command is issued to the wire bond control section. It is an object of the present invention to provide a wire clamp disconnection detection device that enables the wire clamp to be released.

That is, the wire clamp disconnection detection device according to the present invention supplies a discharge detection signal between the wire and the torch bar to the wire bond control unit via the interface circuit, and also generates the signal at a timing faster than this discharge action. The interface circuit is controlled to detect a current caused by the contact between the wire and the torch rod, and to cut off the signal to the control unit in a time period specified in response to the detection of the current.

In this invention, we focused on the point where the wire and the torch rod come into contact when the wire clamp comes loose, and we also focused on the phenomenon that this contact timing is faster than the original discharge timing. This phenomenon in which the contact timing is faster than the discharge timing can be understood from the movement of the torch bar 17. That is, the torch rod 17 is reciprocating at an angle of 15 degrees as shown in A in FIG.
Discharge occurs at the position shown. However, when the wire clamp comes loose, the wire 15 is connected to the workpiece 21 as shown in FIG. 3, so as shown in FIG. so that it comes into contact with the wire. That is, before the torch rod 17 swings through the angle of 15 degrees, it comes into contact with the wire at around 14 degrees, and there is an angle difference of about 1 degree from the normal case, and the contact occurs at a faster timing when the wire is abnormal.

The width of the discharge portion of the torch rod 17 is 1.2 mm, and during normal discharge, the discharge occurs near the center 23 of the width of the discharge portion. However, if the wire is abnormal, the torch bar 1
Contact with the wire at the front side surface part 24 of the discharge part 7,
Therefore, a timing difference occurs due to a movement of approximately 0.6 mm.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 5 shows its configuration. Similar to the case shown in FIG. 1, a pulsed high voltage signal is generated in the high voltage section 12 in response to a command from the switching section 11, is the current limiting resistor 13
The current is applied to the discharge gap section 14 through the discharge section, and the current flowing through the discharge section is detected by a photocoupler 19. Further, a wire abnormality detection control section 25 is further provided for such a circuit section,
The detection control section 25 includes a sensor section 26, a timer section 27, and an interface circuit 28, and the detection signal from the photocoupler 19 is supplied to the control section 20 via the interface circuit 28.

FIG. 6 shows the wire abnormality detection control section 25 in more detail. The sensor section 26 is composed of a silicon diode D, a resistor R1, and a capacitor C1, and receives a voltage signal pulled up to "+12V" during normal operation. It is given to the timer section 27 at the next stage. However, when the wire and torch rod are in contact,
"+12V" is diode D and current control resistor 1
3 to the ground line (GND), and it is detected that the current flows to the discharge section.

The timer section 27 includes a timer circuit 29 (for example, NE555) using an IC that is triggered and becomes operational when the input characteristic becomes 1/3 or less of the power supply voltage, for example.
, an integrating circuit consisting of a resistor R2, a capacitor C2, and a capacitor C3. The detection signal from the sensor section 26 is then supplied to a timer circuit 29.

Furthermore, the interface circuit 28 includes a photocoupler PC consisting of a primary side diode and a secondary side transistor, a transistor Tr connected to this by Darlington, and a resistor R3 for supplying power.
and a light emitting element LED.

That is, in the above-described wire abnormality detection control section 25, in a stationary state, the level of input pin No. 2 of the timer circuit 29 is pulled up to about 12 (V) by the resistor R1. As described above, this timer circuit 29 is triggered when the power supply voltage becomes 1/3 or less, so the timer does not operate in this state of 12 (V) (input power supply voltage). Therefore, at this time, the level of output pin No. 3 of the timer circuit 29 becomes low level, current flows through the primary side diode of the photocoupler PC, the light emitting element LED emits light, and the transistor Tr connected to Darlington is turned on. The state will be as follows. Therefore, a discharge detection signal from the photocoupler 19 that detects discharge is sent to the control section 20 via the interface circuit 28.
That is, a pulsed high voltage signal is generated as shown by A in FIG.
When discharge occurs between the two, a signal as shown in d in the figure is sent to the control section 20, indicating that bonding is being performed normally.

On the other hand, when the wire 15 is detached from the clamp 16, the wire 15 and the torch rod are connected to each other at a slightly faster timing as shown in FIG. 7b, compared to the normal discharge timing shown in FIG. 7a. 17 comes into contact. In this way, wire 15 and torch rod 1
7, the resistor R1 is grounded via the current limiting resistor 13 and the discharge gap 14, and the input voltage of 12V causes a voltage drop equal to the product of the resistor R1 and the flowing current, and the input pin of the timer circuit 29 The potential of No. 2 is less than 1/3 of the input voltage. Therefore, the timer circuit 29 is triggered, and the output pin No. 3 is activated within a certain period of time (for example, 330 m _s ) as shown in FIG. The level of is high level. Therefore, the current flowing through the primary side diode of the photocoupler PC is cut off, the light emitting element LED is turned off, the transistor Tr is turned off, and the circuit between the photocoupler 19 and the control section 20 is cut off.

That is, with a command from the switching section 11,
A discharge command signal as shown by a in Fig. 7 is generated,
Even if the photocoupler 19 detects a signal similar to that in the case of electric discharge through the wire 15 and the torch rod 17 that are in contact, the signal is determined to be an erroneous electric discharge signal and is not sent to the control unit 20. Become so.

In addition, the diode D cuts off the high voltage applied during discharge, the capacitors C1 and C2 function as noise absorbers, and the resistor R3 functions as a current limiting resistor.

The reason why the timer circuit 29 is also triggered by a voltage that is 1/3 or less of the power supply voltage of the input characteristic is as follows. That is, when switching is performed through the current limiting resistor 13, the voltage at the input pin of the timer circuit does not become zero, but a voltage of several (V) is generated. Therefore, ordinary discrete elements and ICs do not perform normal switching operations. Furthermore, if the timer circuit is connected directly to the discharge gap 14,
Malfunctions are likely to occur due to noise, and in order to satisfy these points, the input characteristics of the timer circuit 29 are configured with elements that are triggered by a voltage of 1/3 or less of the power supply voltage.

In the above embodiment, the photocoupler 19 blocks the erroneous discharge signal corresponding to the disconnection of the wire clamp.
This was realized by disconnecting the interface circuit 28 between the controller 20 and the controller 20. However, depending on the characteristics of the high-voltage part and the workpiece, it may be inconvenient if a short-circuit current flows through the discharge gap. In such a case, the transistor of the interface circuit 28
The switching unit 11 is set to the cut state by a signal from the Tr, or the switching unit 1 is set to the reset state by the interface circuit.
If a command signal is sent to the wire 15 and the command to the high voltage section 12 is cut off, the wire 15 and the torch rod 17
Even if they come into contact, no short-circuit current will flow there, and as a result, the erroneous discharge signal to the control unit 20 will be cut off, and the wire bonding device will be controlled to stop.

As described above, according to the present invention, the defective rate due to wire clamp coming off (this defective rate is not limited to missing clamps, but also includes defects caused by contact between the wire and the torch bar) is 0.5% or less compared to the conventional method. This can be very effective in controlling the wire bonding device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram explaining a conventional wire bonding device, FIGS. 2 and 3 are diagrams each explaining the state of the discharge section of the wire bond, and FIG. 4 shows the relationship between the torch rod and the wire in the discharge section. A diagram explaining the relationship,
FIG. 5 is a block diagram illustrating a wire bonding device according to an embodiment of the present invention, FIG. 6 is a circuit diagram showing a wire abnormality detection control section of the device, and FIG. 7 is a diagram illustrating the operation of the device. It is. 11... Switching section, 12... High pressure section, 13...
Current limiting resistor, 14...Discharge gap, 15...Wire, 16...Clamp, 17...Torch bar, 18...Ball, 19...Photocoupler, 20...Wire bond control section, 25...Wire abnormality detection control section, 26...Sensor section, 27...Timer section, 28...Interface circuit.

Claims (1)

[Claims] 1. In a device for detecting wire clamp disconnection in a wire bonding device, means for detecting a current flowing due to contact between a bonding wire and a torch bar when a wire comes off from a wire clamp portion during operation of the wire bonding device, and a means for detecting this current. means for controlling an interface circuit that supplies a discharge signal to the wire bond control section within a time range specified in accordance with the above, and preventing the discharge detection signal from being supplied to the wire bond control section. A wire clamp disconnection detection device characterized by: