JP2761930B2 - Position detection switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a position detection switch.

<Conventional technology> In recent years, various position detection switches have been used in connection with factory automation,
As an apparatus using such a position detection switch, there is, for example, a wire bonding apparatus used for manufacturing a semiconductor.

FIGS. 16 to 16 show a conventional example of this wire bonding apparatus.
This is shown in FIG. FIGS. 16 to 18 show the head end of the wire bonding apparatus, and a tool lifter 2 is swingably supported around a horizontal axis 1 provided on a main body (not shown). The tool lifter 2 is repeatedly rotated around a horizontal axis 1 within a predetermined angle range by a not-shown swing actuator.

A tool holder 3 is swingably supported around a horizontal axis 2a pivotally supported by the tool lifter 2. The tool holder 3 has arms 3a and 3b extending on both sides of the horizontal shaft 2a, and one arm 3a has a capillary 5 supported by the tip of an ultrasonic horn 4 and a gold wire. And a wire clamper 7 for clamping the tool lifter 6, and a contact forming a contact type position detection switch 8 for detecting the proximity of the tool lifter 2 to the other arm 3 b.
8a is provided on the upper surface, and a magnetic plate 9 for attracting the tool lifter 2 and the tool holder 3 to surround the contact 8a is provided.

The tool lifter 2 is provided with a rod 8b made of a magnetic material constituting a position detection switch 8 for detecting the close contact between the tool lifter 2 and the tool holder 3 by contacting the contact 8a in alignment with the contact 8a. Further, a holding electromagnet 10 used to attract the tool lifter 2 and the tool holder 3 around the rod 8b is provided.

Thus, when a current is supplied to the holding electromagnet 10,
The magnetic plate 9 of the tool holder 3 is attracted to the holding electromagnet 10 so that the tool lifter 2 and the tool holder 3 are attracted and integrated with each other. When the lifter 2 and the tool holder 3 are integrated, the rod 8b
The contact between the rod 8b and the contact 8a is established by the contact between the rod 8b and the contact 8a, and it is detected that the arm 3b of the tool holder 3 is in close contact with the tool lifter 2.

A tension spring 11 is stretched between the tip of the arm 3b of the tool holder 3 and the tool lifter 2.
The arm 3b is urged in a direction to approach the tool lifter 2.

In the wire bonding operation in such a wire bonding apparatus, the following control is performed when the gold ball 12 at the tip of the capillary 5 formed by melting the gold wire 6 is bonded to the bonding pad 13.

That is, before starting the bonding, a current is supplied to the holding electromagnet 10 so that the tool lifter 2 and the tool holder 3 are attracted and integrated. In this state, the tool holder 3 is lowered integrally by swinging the tool lifter 2 counterclockwise around the horizontal axis 1 in FIG. Here, when the tool holder 3 descends to a predetermined height position (search height), the current supply to the holding electromagnet 10 is stopped, the constraint of the tool holder 3 on the tool lifter 2 is released, and the tool holder 3 is further slightly moved. By lowering the gold ball 12 at the tip of the capillary 5
Is brought into contact with the bonding pad 13 (see FIG. 17).
In this state, the arm 3a side of the tool holder 3 is
The arm 3b of the tool holder 3 separates from the tool lifter 2 with the swing of the tool lifter 2 because the position is regulated by the contact between the rod 8b and the contact 8a. Non-contact is detected by the position detection switch 8.

In the state shown in FIG. 17, a force for swinging the tool holder 3 counterclockwise around the horizontal axis 2a is applied by the elastic return force of the tension spring 11, and this urging force is bonded to the gold ball 12. The gold ball 12 is pressed by the bonding pad 13 in addition to the contact portion with the pad 13.
With the pressing operation, the tool holder 3 swings clockwise around the horizontal axis 2a, and the separation of the arm 3b of the tool holder 3 from the tool lifter 2 is detected by the position detection switch 8 by contactless contact. , And tension spring 11
When the horizontal axis 2a is lowered by several tens of μm by an amount corresponding to the required bonding pressure with the urging force, the ball bonding operation is considered to be completed, and the horizontal axis 2a starts to rise. In the process, the contact of the position detection switch 8 contacts, the current is supplied to the holding electromagnet 10, and the tool holder 3 is attracted to the tool lifter 2, and the tool lifter 2 is rotated clockwise around the horizontal axis 1 in the figure. By swinging, the bonding head is raised, and the process proceeds to the next bonding operation.

That is, the tool holder 3 is controlled by the position detection switch 8.
Is detected to be separated from the tool lifter 2, the bonding operation is deemed to have been started, and the bonding head presses the gold ball with the required pressure. It has become.

<Problems to be Solved by the Invention> By the way, in the above-described wire bonding apparatus, since the minute position change of the tool holder 3 is detected as described above, the bonding operation is controlled. Although the position detection switch 8 is required to have high accuracy, a minute vibration is generated at the time of operation because a motor or the like for reciprocating the tool lifter 2 is provided.
In some cases, the position of the contact of the position detection switch 8 is erroneously detected due to the influence of the vibration.

That is, when the holding by the holding electromagnet 10 is released, the tool holder 3 can be swung with respect to the tool lifter 2, but normally, the contact is separated by swinging at the start of bonding. However, if the contact is separated due to the vibration before the tool holder 3 swings and the ball bonding is started by the bonding start operation, it cannot be determined whether or not this is a detection accompanying the normal operation. Assuming that the ball operation does not shift to a sufficient ball bonding operation, the operation is lowered by several tens of μm by the stroke required for pressing, and the operation immediately proceeds to the ascending operation, which may cause a bonding failure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is capable of responding to high-precision requests such as detecting the position of a tool holder in a wire bonding apparatus, and of course, avoiding erroneous detection in use in a microvibration environment. The purpose is to provide.

<Means for Solving the Problems> Therefore, in the present invention, a fixed-side core around which a coil is wound, and a movable-side core that forms a magnetic circuit together with the fixed-side core are provided, and the movable-side core with respect to the fixed-side core. By changing the magnetic resistance by changing the gap between the two cores according to the displacement,
A position detection switch for detecting a predetermined displacement position of a movable magnetic core with respect to a fixed magnetic core in an on / off manner by measuring an impedance change of a coil based on the magnetic resistance change, comprising: a rectangular wave generating circuit; A low-pass filter that removes the high-frequency component of the square wave oscillated from the generator to obtain a sine wave, and drives the coil with the sine wave obtained by the low-pass filter, while the coil is synchronized with the square wave A synchronous rectifier circuit that extracts only a DC component from the terminal voltage of the terminal, and a comparator that generates an on / off signal by comparing the DC voltage obtained through the synchronous rectifier circuit with a reference voltage. Configured the switch.

<Operation> According to the position detection switch having such a configuration, a change in the magnetic resistance due to a change in the gap between the magnetic cores is regarded as a change in the impedance of the coil. Are turned on and off, and a position corresponding to the predetermined value is detected on and off. That is, the ON / OFF signal is inverted and output by the expansion or contraction of the gap at the predetermined gap between the two magnetic cores, whereby the signal is inverted when the gap changes less than the predetermined gap. Without
Erroneous detection due to vibration of the device can be avoided.

Particularly, in the present invention, when measuring the impedance change of the coil, a high-frequency component of the rectangular wave oscillated from the rectangular wave generator is removed by a low-pass filter to obtain a sine wave, and the sine wave drives the coil. The synchronous rectifier circuit extracts only the DC component from the terminal voltage of the coil in synchronization with the rectangular wave, and the comparator compares the DC voltage obtained through the synchronous rectifier circuit with the reference voltage to turn on / off. It is configured to generate a signal.

<Examples> Examples of the present invention will be described below.

1 and 2 show an embodiment of the position detecting switch according to the present invention. Here, a coil 52 is wound around a fixed-side magnetic core 51 formed in a U-shape with a rectangular cross section, and a plate-shaped movable-side magnetic core 53 is arranged so as to face the U-shaped open end face of the fixed-side magnetic core 51. The fixed-side magnetic core 51 and the movable-side magnetic core 53 constitute a magnetic circuit. Here, the movable core 53 is displaced with respect to the fixed side core 51,
Varying both the gap (gap) l _A, the magnetic resistance R of the magnetic circuit changes according to the following equation.

In the above equation, l is the magnetic path between the magnetic cores (= 2 × l _A ), L is the magnetic path of the magnetic core part (= l _B + l _C ), and S is the cross-sectional area of the fixed core 51 (= 2a × b). ), and, μ ₀ is the vacuum permeability, is μ _S is the relative permeability of the magnetic core.

Here, l _A = 0, L = 30 mm, a = b = 5 mm, μ _S = 10 ⁴
Assuming that the number of turns of the coil 52 is about 30, the magnetic resistance R ₀ not including the gap (circuit resistance when the switch is set to A in the equivalent circuit of FIG. 3) is Further, when the gap l _{A is set} to 10 μm, the magnetic resistance R ₁ of the gap portion is Since the (circuit resistance when the switch B in the equivalent circuit shown in FIG. 3) is the total magnetic resistance R when the gap l _A and _{10μm, R = R 0 + R} 1 = 0.95 × 10 5 +0. since the ^{63 × 10 6 = 7.2 × 10} 5 AT / Wb, and when the gap l _a is zero, the gap l _a is
The magnetoresistance ratio α at 10 μm is And the total magnetic resistance R when the gap l _A is 10 μm is
It is about 7.5 times larger than when the gap l _A is zero.

In the present embodiment, utilizing the fact that a large magnetoresistance ratio α is obtained with such a small gap, the movable magnetic core 53 is fixed to the displacement member for detecting the position, while the fixed magnetic core 51 is fixed to the reference position side. The position of the displacement member is regarded as the displacement of the movable core 53 with respect to the fixed side core 51, and the position detection is turned on.
It is done off.

For the purpose of ON / OFF position detection, as shown in FIG. 4, a 50 KHz oscillator 61, for example, is connected to the coil 52 to supply a constant current, and the coil terminal voltage that changes with the change in the magnetoresistance is synchronized. A voltage detector 64 passes through a detector 62 and a low-pass filter (for example, a 6th-order Bessel low-pass filter) 63.
For example, when the gap l _A = 10 μm, the ON / OFF signal is output by comparing with the corresponding reference voltage Es. Thus, at initialization, if the gap adjustment so that the gap l _A is output ON or OFF signal when it is more than 10 [mu] m, OFF from ON when the actual gap is not less than 10 [mu] m or A position detection signal that switches from OFF to ON can be output.

For this reason, even if a mechanical vibration that changes the gap at less than 10 μm occurs, the position detection signal is not inverted and output at this time, and erroneous detection due to minute vibration is avoided. Further, as shown in FIG. 5, the change ratio of the terminal voltage of the coil 52 with respect to the change of the gap _1A becomes large in a minute area where the gap _1A is smaller than, for example, 10 μm. It is possible.

Next, a detailed example of the position detection circuit shown in FIG. 4 will be described with reference to FIG.

The circuit shown in FIG. 6 includes a + 5V power supply A, a rectangular wave generation circuit B, a low-pass filter C, an output amplifier D, a decoupling circuit E,
Consisting of constant current circuit F, detection coil (coil 52 wound around fixed core) G, amplifier H, inverting amplifier I, synchronous rectifier circuit J, low-pass filter K, comparator L, and output display unit M Have been.

Next, the function of each of the blocks A to M will be described. First, the +5 V power supply A generates +5 V serving as a power supply for an IC or the like from the +15 V power supply.

The rectangular wave generation circuit B is a circuit for generating high-frequency vibration for driving the detection coil G, generates a rectangular pulse having a period of 100 KHz by the free running multivibrator IC2, and is a flip-flop circuit.
The IC3 frequency-divides the pulse of 100 KHz into 50 KHz and outputs it. The 50KHz rectangular pulse signal output here is
It is also distributed and output to a synchronous rectifier circuit J described later, and the contacts are controlled to be opened and closed in synchronization with the rectangular pulse signal.

The low-pass filter C to which the rectangular pulse signal of 50 KHz is input from the rectangular wave generation circuit B removes the high-frequency component of the 50 KHz rectangular wave in order to supply a sine wave to the detection coil G.

That is, among the rectangular waves represented by A (sinωt + 1/3 sin3ωt + 1 / 5sin5ωt), only sinωt is passed, and sin
A sine wave is created by blocking the passage of 3ωt and sin5ωt and the like. Here, a third-order Chebyshev type low-pass filter with 2 dB ripple is used.

The output amplifier D is an amplifier for amplifying the output from the low-pass filter C into a 20 VPP sine wave signal and outputting the signal.

The decoupling circuit E prevents the DC component from flowing to the detection coil G by the capacitor C14.
By not passing a DC component, no magnetic bias is applied to the detection coil G.

The constant current circuit F includes a resistor R14 connected in series to the detection coil G. The detection voltage E of the detection coil G is E = I × Z, where I is the current flowing through the coil G and Z is the impedance of the coil G. Here, the detection voltage E changes in proportion to the impedance Z. Thus, the current I is made constant.

Assuming that the output voltage of the output amplifier D is e ₀ , in a series connection circuit of the resistor R 14 and the coil G, I = e ₀ / (R 14 + Z)
Here, if R14 >> Z, then I ≒ e ₀ / R14, and the current I is constant regardless of the change in the impedance Z. Therefore, when a resistor having a large resistance value of about 10 KΩ is used as the resistor R14, Z = r + jωL ≒ jωL, and
If L = 2mH (gap l _A = 0), Z = 2π × 50 × 1
0 ³ × 2 × 10 ^-3 = 628Ω, which satisfies the condition of R14 >> Z, and the current I flowing through the detection coil G is substantially constant.

Here, the terminal voltage of the detection coil G (detection voltage) E _L is (Gap l _A = 0).

The amplifier H is for amplifying the terminal voltage of the detection coil G, and the amplification degree can be varied from 1.4 to 4 times by the volume VR2. Here, the volume VR2 is adjusted so that the output of the amplifier H becomes 5 VPP. I have.

The inverting amplifier I is provided for improving the efficiency of a synchronous rectifier circuit J described later, and inverts the 5VPP sine wave output from the amplifier H by -1 times (the seventh inversion).
See figure).

Synchronous rectification circuit J is a circuit for converting the detected voltage E _L of the detection coil G into a DC voltage, the rectangular wave generator B
As shown in FIG. 7, the output of the amplifier H is half-wave rectified and inverted by the inverting amplifier I by the gates 1 and 2, which are opened and closed based on the output signal of the flip-flop circuit. The signal is half-wave rectified, the output of the gate 1 and the output of the gate 2 are combined, and the AC terminal voltage of the detection coil G is converted into a DC voltage (see FIG. 7).

In such a synchronous rectifier circuit J, since the negative voltage is cut by opening and closing the gate 1 and the gate 2, it is possible to rectify even a minute input voltage and e = A
2 / 3cos2ω at (1 + 2 / 3cos2ωt−2 / 15cos4ωt)
Since the high-frequency components such as t, 2 / 15cos4ωt become the next and even-numbered high-frequency components twice and four times, the filter time constant for the subsequent averaging process can be shortened to improve the transient response. it can.

The low-pass filter K averages the output of the synchronous rectifier circuit J to obtain a high frequency component of 2 / 3cos2ωt, 2 / 15cos4ω.
The output voltage Edc = 2A / π is obtained by blocking t and the like. Here, if A = 2.5V, the output voltage Edc is 2 ×
2.5 / π = 1.59V. The rise time Tr is Tr = 2.2 × τ where τ is a time constant. In this case, since the frequency fc is 50 KHz, the rise time (transient response) T
r is Tr = 2.2 / 2πfc = 7 μs.

In this embodiment, a 6th-order Bessel type low-pass filter is used as the low-pass filter K in order to improve the transient response characteristics.

The comparator L is a circuit for binarizing (0 or 1) the analog signal obtained by the synchronous rectifier circuit J and the low-pass filter K, and is a threshold level (in the detection position) used for binarization. Equivalent voltage)
Can be set with volume VR3.

The display unit M is a circuit for outputting the output (ON / OFF signal) binarized by the comparator L to the outside, and includes a TTL level output (OUT PUT in FIG. 6) and an LED state. Display.

With the circuit having such a configuration, the magnetic resistance R of the magnetic circuit composed of the magnetic core changes due to the change in the gap l _A , thereby changing the impedance Z of the detection coil G (52). The voltage changes, and the terminal voltage is compared with a predetermined reference level voltage to thereby determine a gap corresponding to the predetermined reference level voltage.
l It can detect on / off whether it is closer or farther than _A.

Accordingly, the reference level voltage is binarized threshold level, setting the gap l _A corresponding voltage to be detected, ON detection signal as a boundary gap l _A to be detected
・ OFF can be inverted.

In the above circuit configuration, a synchronous rectifier circuit J is used for the AC / DC converter, and the AC output voltage of the detection coil G and the AC voltage obtained by inverting the AC output voltage are subjected to anti-wave rectification by opening and closing the gate to obtain a DC component. As a result, the input / output linearity of the rectifier circuit is good, and it is possible to rectify even a minute input voltage. Further, since it is necessary to output a square wave for use in opening and closing the gate and a sine wave for driving the detection coil G, the square wave oscillation is used as a source oscillation.
While the gate opening / closing control is performed by the rectangular wave, a sine wave is obtained by passing the rectangular wave through the low-pass filter C. Therefore, the oscillation source for opening and closing the gate and the oscillation source for driving the detection coil G are provided. Shared.

In the above embodiment, the detection voltage is binarized based on a fixed threshold level.
The amount of hysteresis as shown in the figure can be controlled by a circuit so that the level (gap) when turning from ON to OFF and the level (gap) when turning from OFF to ON can be different.

Next, a wire bonding apparatus to which the position detection switch as described above is applied will be described.

FIG. 9 is a perspective view showing the external appearance of a wire bonding apparatus 101. A magazine (not shown) in which a plurality of vertically arranged lead frames 103 in which a plurality of chips 102 such as semiconductors are arranged in a single row is a magazine rack. Chips 102 on a lead frame 103 which are stored in a plurality of layers vertically stacked in a magazine 104 and are pulled out from the lowest magazine in a magazine rack 104 are sequentially arranged in the center of the wire bonding head 1 at the center.
Wire bonding at 05, one lead frame 10
When all the upper chips 102 are wire-bonded, the lead frame 103 is inserted into a magazine rack 106 in which a plurality of empty magazines are stored in advance.

Lead frame 1 in the magazine on the magazine rack 104 side
When all of the magazines 03 are pulled out and the magazine is empty, the stopper at the lower end of the magazine rack 104 is opened and stored in the main body 107 side, while a predetermined number of lead frames 103 are stored in the lowest magazine on the magazine rack 106 side. Then, the magazine is also dropped and stored from the magazine rack 106 to the main body 107 side.

In FIG. 9, reference numeral 108 denotes a monitor, which displays a bonding state photographed by a camera unit provided in the wire bonding head 105, and displays set bonding conditions and the like.

FIG. 10 is a side view of the wire bonding head 105. The wire bonding head 105 is fixed on an XY table 109, and is moved in the X-axis and Y-axis directions by an X-axis driving motor and a Y-axis driving motor (not shown). Can be moved in a plane.

The wire bonding head 105 includes a main body 110,
A camera unit 111 and a tool unit 112 are provided. The main unit 110 includes a Z-axis drive motor 113 for moving the tool unit 112 in the Z-axis direction, and a driving force of the Z-axis drive motor 113. And a crank mechanism 114 for transmitting to the
The tool portion 112 supported to be swingable with respect to the main body portion 110 by the
A reciprocating swing motion is performed in a predetermined angle range in the axial direction.

The camera unit 111 arranges the photographing lens 115 downward toward the bonding execution unit at the tip of the tool unit 112, and bends the optical image signal by the photographing lens 115 by a mirror (not shown) to be provided on the base end side of the main body unit 110. CCD camera
The optical image signal is converted into an electric image signal to guide the image to an electrical image signal, and the image is captured. The image captured by the CCD camera 116 is displayed on the monitor 108.

Further, as shown in FIGS. 11 to 13, the tool part 112 supports a tool lifter 118 swingably around a horizontal axis 117 provided on the main body part 110 side. The Z-axis drive motor 113 repeatedly swings around the horizontal axis 117 within a predetermined angle range.

Also, a horizontal shaft 119 supported by the tool lifter 118 is provided.
A tool holder 120 is supported so as to swing around. The tool holder 120 includes arms 120a and 120b extending on both sides with the shaft 119 interposed therebetween.
In a, a capillary 122 supported on the tip of an ultrasonic horn 121 and a wire clamper 124 for clamping the gold wire 123 are provided.On the other arm 120b, the displacement position with respect to the tool lifter 118 is turned on. The movable core 53 (see FIGS. 1 and 2) constituting the position detection switch 125 having the above-described configuration for detecting the off state is provided on the upper surface, and faces the movable core 53. As described above, the fixed side magnetic core 51 is provided on the tool lifter 118 side. Thus, the position detection switch 125 outputs an ON / OFF signal depending on the interval between the tool holder 120 and the tool lifter 118.

The tool holder 120 (movable magnetic core 53) is used here.
The gap between the tool lifter 118 (fixed magnetic core 51) and the tool holder 120 and the tool lifter 118 is substantially zero when the tool holder 120 and the tool lifter 118 are attracted and integrated by a holding electromagnet 126 described later. Electromagnet for holding 126
The position detection switch 125 is set so as to generate an OFF signal from an ON signal when the gap between the two exceeds 10 μm even after the suction by the above is released.

A holding electromagnet 126 for adsorbing and integrating the tool holder 120 and the tool lifter 118 is provided on the tool lifter 118 side.
120b has a magnetic plate 127 attracted to the holding electromagnet 126
When the holding electromagnet 126 is energized, the magnetic plate 127 is attracted to the holding electromagnet 126 so that the tool holder 120 and the tool lifter 118 move integrally.

Further, a tension spring 128 is stretched between the tip of the arm portion 120b of the tool holder 120 and the tool lifter 118, and urges the arm portion 120b in a direction approaching the tool lifter 118.

Next, the bonding operation in the wire bonding head 105 having the above configuration will be briefly described with reference to FIGS. 14 and 15. First, a pad (about 100
μm □) Capillary 1 to make the first bond to 130
22 descends with the shaft 117 as the swing axis (see FIG. 11). At this time, the holding electromagnet 126 is energized, and the magnetic plate 127 is attracted to the holding electromagnet 126 so that the tool holder 12
The tool holder 120 is integrated with the tool lifter 118 so that vibration does not occur when the tool holder 120 swings around the shaft 117 even during high-speed operation.

While the tool holder 120 is descending, the holding electromagnet 126
Is stopped, the tool holder 120 can swing around the axis 119, and the gold ball 123a formed by an electric torch at the tip of the capillary 122 can be pressed by the urging force of the tension spring 128. . At this time, the tool holder 120 vibrates due to vibrations generated from various drive motors and various operating parts, and the vibration changes the gap between the fixed core 51 and the movable core 53 within 10 μm. If present, position detection switch
The 125 ON / OFF signal is not inverted due to the above-mentioned vibration.

That is, in the present embodiment, if the gap between the fixed-side magnetic core 51 and the movable-side magnetic core 53 is less than 10 μm, an ON signal is output and 10 μm is output.
m, the output signal is turned on even if the gap vibrates with less than 10 μm.
Is maintained. Therefore, according to the present embodiment, the OFF signal is output when the tool holder 120 is separated from the tool lifter 118 by 10 μm or more by the start of the true bonding operation without the influence of vibration.

As shown in FIG. 12, when the gold ball 123a rides on the pad 130, the gold ball 123a is pressurized by the urging force of the tension spring 128 while sliding by the ultrasonic vibration generated by the ultrasonic horn 121, where For the first time, the gap between the two magnetic cores in the position detection switch 125 becomes 10 μm or more, and an OFF signal is generated. Note that, by the above-described gold ball 123a rubbing operation, the oxide film on the surface of the pad 130 made of the aluminum material is peeled off to expose the aluminum background, thereby promoting the chemical reaction between the gold and the aluminum.

When the OFF signal is output from the position detection switch 125, the
As shown in FIG. 12, it is considered that the ball bonding on the pad 130 has started, and
When an ON signal is output from 5, it is considered that the gold ball 123 a has been pressed on the pad 130, the tool lifter 118 is raised, and the process proceeds to the next second bonding step.

Here, when the signal of the position detection switch 125 is turned off due to the vibration of the tool holder 120 having a size of less than 10 μm, the tool lifter 118 is raised before the bonding of the gold ball 123a is sufficiently performed as described above. The bond will be defective. However, in this embodiment,
Position detection switch 12 when the gap threshold is exceeded
5 switches ON / OFF signals and outputs them. By setting the threshold value to be equal to or greater than the vibration width, erroneous detection due to the influence of vibration is avoided, and ball bonding can be performed reliably.

In the second bonding step, the gold wire 123 is pressed against the gold-plated portion of the lead frame 131 and rubbed together by ultrasonic waves, so that both golds are integrated and bonded. When the wire bonding to the lead frame 131 is completed,
By raising the bonding head by clamping the gold wire 123 by the wire clamper 124, the gold wire 123 is cut, and a series of wire bonding operations is completed.

<Effect of the Invention> As described above, according to the position detection switch of the present invention, the magnetic resistance of the magnetic circuit is changed by changing the gap between the movable core and the fixed core in accordance with the displacement of the magnetic core. Since the position detection of the movable core is performed on / off by measuring the impedance change of the coil of the fixed core based on the resistance change, the on / off reversal is performed when the gap exceeds a predetermined value. Position can be detected, even if the gap changes less than the predetermined value due to the influence of equipment vibration, without erroneously detecting this,
The control accuracy of the device based on the position detection switch is improved. For example, if the position detection switch according to the present invention is applied to a wire bonding apparatus, the start / end of the bonding operation can be accurately detected, and it is possible to avoid occurrence of bonding failure due to pick-up of apparatus vibration by the switch.

Furthermore, the rectangular wave oscillated from the rectangular wave generator is passed through a low-pass filter to remove high-frequency components to obtain a sine wave, and the sine wave drives the coil of the fixed-side magnetic core while synchronizing with the square wave. By extracting only the DC component from the coil terminal voltage and comparing this DC voltage with the reference voltage to generate an on / off signal, it is possible to rectify even the minute input of the coil terminal voltage and rectify The input / output linearity of the circuit is improved, and a sine wave for driving the coil and a synchronous signal in the synchronous rectifier circuit can be obtained by the rectangular wave generator.

[Brief description of the drawings]

1 is a front view showing an embodiment of a position detecting switch according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is an equivalent circuit of a magnetic circuit constituting the switch shown in FIG. circuit diagram,
FIG. 4 is a block diagram showing a signal processing circuit of the switch shown in FIG. 1, FIG. 5 is a diagram showing output characteristics of the switch of the above embodiment, and FIG. 6 is a detailed example of the signal processing circuit shown in FIG. FIG. 7 is a time chart for explaining signal processing characteristics in the circuit shown in FIG. 6, and FIG. 8 is a line showing characteristics when hysteresis is given to the ON / OFF characteristics of the switch in the above embodiment. 9 is a perspective view showing the appearance of a wire bonding apparatus to which the position detection switch according to the present invention is applied. FIG. 10 is a side view showing a bonding head section in the wire bonding apparatus shown in FIG. 9, and FIGS. FIG. 13 is a side view of the tip of the bonding head for explaining the bonding operation, FIG. 14 is a schematic process diagram showing the bonding operation of the wire bonding apparatus in the same order, and FIG. Time chart showing the control characteristics of the upper wire bonding apparatus, FIG. 16-FIG. 18 is a side view of a wire bonding apparatus which is applied a conventional position detecting switch, respectively. 51: Fixed core, 52: Coil, 53: Movable core,
125 ... Position detection switch, A ... + 5V power supply, B ... Square wave generator, C ... Low pass filter, D ... Output amplifier circuit, E ... Decoupling circuit, F ... Constant current circuit, G ... ... Detection coil, H ... Amplifier, I ... Inverting amplifier, J ... Synchronous rectifier circuit, K ... Low-pass filter,
L: comparator, M: output display

Claims (1)

(57) [Claims] A fixed magnetic core on which a coil is wound and a movable magnetic core forming a magnetic circuit together with the fixed magnetic core;
The magnetic resistance is changed by a gap change between the movable core and the fixed core in accordance with the displacement of the movable core with respect to the fixed core, and a change in the impedance of the coil based on the change in the magnetic resistance is measured. A position detection switch for detecting a displacement position on / off, comprising: a rectangular wave generating circuit; and a low-pass filter for removing a high frequency component of a rectangular wave oscillated from the rectangular wave generating circuit to obtain a sine wave. A synchronous rectifier circuit configured to drive the coil with a sine wave obtained by the low-pass filter, and to extract only a DC component from a terminal voltage of the coil in synchronization with the rectangular wave; and And a comparator for generating an on / off signal by comparing the DC voltage obtained by the above with a reference voltage. Position detection switch.