JPH0548620B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a wire bonding device,
In particular, the present invention relates to improvements in a bonding surface position detection circuit for detecting the position of a bonding surface.

[Technical background of the invention]

Wire bonding equipment used for assembling integrated circuits generally attaches a capillary through which a wire is inserted to a bonding arm, and swings the bonding arm to move the capillary up and down to perform wire bonding on the object to be bonded. is configured to do so. FIG. 1 shows one line of the construction of the mechanical parts of this device. In the same figure, 1 is an XY table,
A swing bracket 3 is mounted on the XY table 1 so as to be swingable in the direction of the arrow by a support column 2. This swing bracket 3 has a substantially T-shape,
A bonding arm 5 holding a capillary 4 at its tip is arranged below the front arm 3a. The base end of this bonding arm 5 is fixed to an arm holder 6, and this arm holder 6 is fixed to the swing bracket 3 via a leaf spring 7. Further, the upper protruding piece 6a of the arm holder 6
A tension spring 8 is stretched between and the protruding piece 3b of the swing bracket 3. This tension spring 8
, together with the leaf spring 7, provide a load when pressing the capillary 4 against the bonding surface of the bonding object 10. In the figure, 9 is a stopper for setting the initial position of the bonding arm 5 with respect to the swing bracket 3, and 11 is a balance spring.

With this configuration, the capillary 4 is positioned above the bonding position of the bonding object 10 by horizontally moving the XY table 1,
When the swing bracket 3 is swung by a drive mechanism (not shown) in this state, the bonding arm 5 is swung accordingly.
descends and first comes into contact with the bonding surface of the bonding object 10. When the swing bracket 3 is further swung, the capillary 4 is pressed against the bonding surface with a predetermined pressure by the elastic force of the leaf spring 7 and the tension spring 8, thereby performing bonding.

By the way, it is extremely important to keep the pressing force of the capillary 4 constant in such a bonding operation in order to perform high-quality bonding. It is necessary to accurately detect the position of the bonding surface.

Conventionally, a sensor 20 for detecting a change in the distance between the swing bracket 3 and the bonding arm 5, that is, a change in the distance between the swing bracket 3 and the capillary 4, is attached to the tip 3a of the swing bracket 3, as shown in the figure. The output is led to the circuit shown in FIG. 2 to detect the position of the bonding surface. That is, in this detection circuit, the output from the sensor 20 is amplified by the image amplifier 21 and then introduced into the sample and hold circuit 22.The circuit 22 samples and holds the output at a constant period, and the outputs are sent to the A/D converter 2.
3, each is converted into a digital signal. Then, the digital signal for each hold is introduced into the control circuit 24, and this circuit 24 monitors the change in the hold output to detect the point at which the capillary 4 contacts the bonding surface, that is, the position of the bonding surface. ing.

[Problems with background technology]

However, in general, the descending speed of the capillary 4 is extremely high, and therefore, in the conventional circuit, the sampling and holding period of the detection output is made extremely short in order to cope with the above-mentioned speed, and the A/D
A high-speed converter 23 must be used. Therefore, the circuit was very expensive.

Furthermore, when the capillary 4 descends, it may cause minute vibrations due to the response characteristics of the swing drive motor and the mechanical response characteristics of each spring. When this minute vibration occurs, in the conventional circuit, the capillary 4
Even if the capillary 4 approaches the bonding surface and comes into contact with it temporarily due to the above vibration, the capillary 4 at this time
The position of the bonding surface may be detected as the position of the bonding surface, resulting in low detection accuracy.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding surface position detection circuit that can perform highly accurate position detection with a simple and inexpensive circuit configuration even when the capillary descends at a high speed or when vibration occurs. do.

[Summary of the invention]

In order to achieve the above object, the present invention uses the sensor output before the capillary comes into contact with the bonding surface as a reference level, and uses this reference level as a reference value to define a non-detection area larger than the vibration amplitude of the capillary. A comparator is provided, and the output of the sensor is inputted to the comparator to compare the level with the non-detection area, and a bonding surface position detection signal is generated when the sensor deviates from this area.

[Embodiments of the invention]

FIG. 3 is a block diagram of a bonding surface position detection circuit according to an embodiment of the present invention, in which the same parts as in FIG. 2 are given the same reference numerals.

A sensor 20 consisting of, for example, an electric micrometer
The detection output is amplified by an amplifier 21 and then sent to a sample hold circuit 41 and a window comparator 4.
2 is supplied. Sample hold circuit 41
In accordance with a sample and hold signal from the control circuit 44, the detection output of the sensor 20 is sampled and held before the capillary 4 contacts the bonding surface and at a timing immediately before the contact. This sample-and-hold output is then supplied to the window comparator 42 as a reference value _VB . Note that the sample hold timing is set in advance by the control circuit 44 based on the descending speed of the capillary 4 and the approximate position of the bonding surface.

On the other hand, the window comparator 42 sets a non-detection level region of a predetermined width with the reference value V _B outputted from the sample hold circuit 41 as the center value, and compares the level of this non-detection level region with the detection output of the sensor 20. When the detection output is out of the non-detection level area, the detection signal becomes “H” level.
It is something that generates OT. Note that the non-detection level region is set by the region specifying voltage V _W output from the variable resistance circuit 43.

FIG. 4 is a circuit diagram of the window comparator 42, which is composed of an addition circuit 45 and a subtraction circuit 46 for setting a non-detection level region, and a comparison circuit 47. First, the adder circuit 45 adds the area specified voltage V _W to the reference value V _B , and sets the added output to the upper limit value of the non-detection level area.
It is supplied to the comparator circuit 47 as Vref ₁ . Further, the subtraction circuit 46 subtracts the region specifying voltage V _W from the reference value V _B and supplies the output to the comparison circuit 47 as the lower limit value Vref ₂ of the non-detection level region.
On the other hand, the comparison circuit 47 includes a pair of comparators 48
a, 48b, and an OR circuit 49 that performs logical OR processing on the outputs thereof. Then, when Vref ₁ < Vi, the comparator 48a generates an "H" level detection signal, and when Vref ₂ > Vi, the comparator 48b generates an "H" level detection signal, and these detection signals are ORed. circuit 4
9 to the control circuit 44.

The control circuit 44 receives a capillary descent start signal ST from the wire bonding apparatus main body (not shown).
A sample and hold signal SH is emitted a predetermined time after receiving the signal SH, and the bonding surface position is recognized based on the detection signal OT from the window comparator 42.

With this configuration, when the capillary 4 starts descending and reaches the position just before the bonding surface, the control circuit 44 outputs a sample hold signal.
When SH is generated, the detection output of the sensor 20 is sampled and held in the sample and hold circuit 41. As a result, a reference value V _B is obtained when the output Vi of the sensor 20 is compared in level with the window comparator 42. When this reference value V _B is input, the window comparator 42 outputs the reference value V _B
The area designated voltage set by the variable resistance circuit 43 in
By adding and subtracting _VW , first, the upper limit value Vref ₁ and lower limit value Vref ₂ of the non-detection level region are respectively determined. Then, these upper limit value Vref ₁ and lower limit value Vref ₂ and the detection output Vi emitted from the sensor 20 from now on are connected to comparators 48a and 48.
Compare the levels in b.

In this state, when the swing bracket 3 swings until the capillary 4 reaches the bonding surface and makes sure contact, the sensor 20 detects the bonding arm 5.
The distance between the sensor 20 and the sensor 20 is shortened, and the detection output level Vi of the sensor 20 is reduced. And this detection output level
For example, when Vi decreases below the lower limit value Vref ₂ of the non _- detection level region _○ a shown in FIG.
The level detection signal OT is output, and the control circuit 44
supplied to As a result, the control circuit 44 determines that the capillary 4 has definitely contacted the bonding surface, recognizes the position of the capillary 4 at this time as the position of the bonding surface, and in this state, moves the swing bracket 3 further by a predetermined amount. Drive signal for rocking
Emits MS. Then, the capillary 4 is pressed against the bonding surface with a pressing force corresponding to the amount of rocking, and as a result, wire bonding is performed. Thus, bonding is always performed with a constant pressing force.

On the other hand, if mechanical vibrations caused by the springs 7 and 8 or electrical vibrations caused by the characteristics of the swing drive motor occur while the capillary 4 is lowering, the capillary 4 will cause minute vibrations, which will cause the ribboning arm 5 to
The distance between the capillary 4 and the sensor 20 changes depending on the vibration of the capillary 4, and as a result, the detection output of the sensor 20 changes. However, in the circuit of this embodiment, even if the detection output Vi of the sensor 20 changes as shown in _FIG . ,
No detection output (“H” level) OT is generated from each comparator 48a, 48b. Therefore, the problem of erroneously determining that a change in the output of the sensor 20 due to the vibration of the capillary 4 is due to the capillary 4 coming into contact with the bonding surface is eliminated.

In this way, in this embodiment, the detection output Vi of the sensor 20 is determined using the window comparator 42.
Since the system continuously monitors the
The high-speed sample-and-hold operation and A/D converter as shown in Figure 1) can be eliminated, and as a result, the circuit configuration can be simplified. In addition, a non-detection level area ○a which is larger than the variation width of the detection output Vi of the sensor 20 corresponding to the vibration amplitude of the capillary is set in the window comparator 42, and this area and the detection output Vi of the sensor 20 are compared in level. detection signal
Since OT is generated, even if capillary 4 causes vibration, sensor 2 due to this vibration
0 output change can be prevented from being mistakenly recognized as contact of the capillary 4 with the bonding surface, and as a result, the timing of the contact of the capillary 4 with the bonding surface can be accurately detected, and the position of the bonding surface can be detected with high precision. can be done. Furthermore, according to this embodiment, since the non-detection level area ○a is set as an area with a predetermined width _VW in both the plus and minus directions around the reference value, after the capillary 4 comes into contact with the bonding surface, There is an advantage that both a type of sensor whose output level decreases and a type of sensor whose output level increases depending on the amount of pressing can be used in the same way. In other words, any sensor whose output changes depending on the gap amount can be used regardless of the direction of the change.

Note that the present invention is not limited to the above embodiments. For example, in the embodiment described above, the sample and hold circuit 41 is used to set the output of the sensor 10 immediately before the capillary 4 contacts the bonding surface as the reference value, thereby making the reference value as close as possible to the conditions at the time of contact. If the change in the output level of the sensor before contact is small, the reference value may be fixed in advance and input to the window comparator together with the area specifying voltage _VW . The configuration of the vertical comparator, the control contents of the control circuit, etc. can be modified in various ways without departing from the gist of the present invention.

〔Effect of the invention〕

As detailed above, the present invention uses the output of the sensor before the capillary comes into contact with the bonding surface as the reference level, and uses this reference level as the reference value to define a non-detection area larger than the vibration width of the capillary. A comparator is provided, and the output of the sensor is inputted to the comparator to compare the level with the non-detection area, and a bonding surface position detection signal is generated when the sensor deviates from this area.

As detailed above, according to the present invention, the bonding surface position can be detected with high accuracy using a simple and inexpensive circuit configuration even when the capillary descends at a high speed or when vibration occurs. A detection circuit can be provided.

[Brief explanation of drawings]

FIG. 1 is a side view showing the structure of a mechanical part of a wire bonding apparatus, FIG. 2 is a circuit block diagram of a conventional bonding surface position detection circuit, and FIG. 3 is a circuit diagram of a bonding surface position detection circuit according to an embodiment of the present invention. FIG. 4 is a circuit block diagram of a window comparator of the detection circuit, and FIG. 5 is a diagram used to explain the operation of the detection circuit shown in FIG. 3. 3... Swing bracket, 4... Capillary, 5
... bonding arm, 10 ... bonding object, 20 ... sensor, 21 ... amplifier, 41
... Sample hold circuit, 42 ... Wind comparator, 43 ... Variable resistance circuit, 44 ... Control circuit, 45 ... Addition circuit, 46 ... Subtraction circuit,
47... Comparison circuit, 48a, 48b... Comparator, 49... OR circuit.

Claims (1)

[Claims] 1. In a bonding surface position detection circuit of a wire bonding apparatus that performs bonding on a bonding surface by driving a bonding arm with a capillary attached to the tip and moving the capillary up and down, the bonding surface position detection circuit monitors the vertical movement of the capillary and performs bonding. A sensor that generates a detection output at a constant level before contact with a bonding surface and a detection output that changes depending on the amount of pressing of the capillary after contact; and a sensor that generates a detection output from the sensor before the capillary contacts the bonding surface. The detection output of the sensor is set as a reference level, and a comparator is provided in which a non-detection level region is set in advance using this reference level as a reference level and is larger than the amplitude of the minute vertical vibration of the capillary. 1. A bonding surface position detection circuit characterized in that the bonding surface position detection circuit is configured to input a signal and compare the level with the non-detection level region, and generate a bonding surface position detection signal when the signal deviates from the non-detection level region.