JPS6350856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonding apparatus used in manufacturing semiconductor devices and the like.

Generally, a wire bonding apparatus is used for wire bonding work in which a wire such as a gold wire is used to connect a bonding pad on a semiconductor pellet to a lead. An example of this wire bonding apparatus is shown in FIG.

FIG. 1 shows an elongated bonding arm 1 that is swingably supported by a support shaft 2 and has a cylindrical capillary 3 at its tip that supports a wire.
and an L disposed at the other end of the bonding arm 1 and swingably attached to the support shaft 9 at the center.
A wire bonding device is shown that includes a lever 5 in the shape of a letter 5 and a tension spring 6 for bonding load provided at the other end of the bonding arm 1. One end of the lever 5 is brought into contact with the other end of the bonding arm 1 via a roller 8 provided at its tip, and the other end is brought into contact with the cam 4 via a cam follower 7 provided at its tip.
It is designed so that it can be brought into contact with the According to such a device, by rotating the cam 4 in the direction of the arrow using a rotation mechanism (for example, a servo motor) not shown, the roller 8 portion of the lever 5 can be moved up and down, and the load is accordingly reduced. The bonding arm 1 is swung by the force of the spring 6, and the capillary 3 can be moved up and down. Therefore, if the shape of the cam 4 is appropriately set, the vertical movement of the capillary can be controlled by the rotation of the cam, as shown in FIG. That is, FIG. 2 shows the relationship between the rotation angle of the cam and the height of the capillary, and when the capillary is first lowered, the semiconductor pellet is bonded to the pad part.
A case is shown in which bonding to the lead portion is performed during the second lowering of the capillary. By using such a mechanism, bonding can be performed continuously just by rotating the cam.

By the way, although a servo motor is normally used as a driving means for the cam, in such a case there is a problem that the bondability of the first wire (hereinafter referred to as the first wire) is deteriorated during bonding. In other words, as shown in Figure 3, the correlation curve between motor rotational speed and time is determined over a certain period of time (t ₀ ~
Steady rotation is not reached until t ₁ ) has elapsed. The cam displacement curve shown in FIG. 2 above is obtained when the motor that drives the cam is in steady rotation; if the motor does not reach the steady position, the movement of the capillary becomes slow. When the movement of the capillary becomes slow in this way, the bonding load becomes less than a predetermined value. In other words, when the rotation speed of the cam 4 is constant, the other end of the arm 1 and the roller 8 are separated from each other, and then the other end of the arm 1 is raised by the tension spring 6. However, if the rotation speed of cam 4 is low, the other end of arm 1 will rise without separating from roller 8. In this case, all of the tension spring force is not used as bonding load. As a result, the bondability of the first wire deteriorates, resulting in peeling of the bonding portion, which is an undesirable result.

In addition, after bonding the pad part of the semiconductor pellet, the XY
Bonding is performed by moving the table to move the capillary onto the lead, but depending on the product, the distance between the pad part and the lead part is extremely long. Even in such a case, since the cam is made to rotate at a constant rate, when the bonding arm is moved to the lead portion, the capillary will already begin to descend on the lead surface while the bonding arm is in the middle of movement. At this time, vibrations of the table during movement remain, causing a situation in which the load during bonding changes (particularly, the load becomes insufficient). In such a case, the problem of poor bondability also arises.

The present invention has been made to solve the above problems, and its purpose is to provide a wire bonding device that can always apply an optimal bonding load no matter what the bonding state is. Another object of the present invention is to provide a wire bonding device that can improve bonding accuracy.

According to the present invention, there is provided a bonding device having a capillary for holding a wire at one end thereof, a bonding arm having the other end connected to a vertical movement mechanism, and a load supply means for applying a bonding load to the capillary. The supply means includes a solenoid coil and an iron core disposed in the solenoid coil, and changes the bonding load by supplying the solenoid coil with a current generated according to the point to be bonded. It is characterized by

The present invention will be explained below with reference to Examples.

FIG. 4 is a diagram including a block diagram showing a wire bonding apparatus previously invented by the present inventor.
In the following explanation, the same parts as in FIG. 1 will be explained using the same reference numerals.

The figure shows a bonding arm 1 swingably supported by a support shaft 2, a cylindrical capillary 3 provided at the tip of the bonding arm 1, and a tip abutting the other end of the bonding arm 1. L-shaped lever 5 arranged as follows, this lever 5
a cam 4 that moves up and down the bonding arm 1; a servo motor 15 disposed above the other end of the bonding arm 1; a wire 10 that is wound around the rotating shaft of the servo motor 15 and whose tip is attached to the other end of the bonding arm 1. , and drive means 23 for driving a servo motor 15. In one embodiment of the present invention, the bonding load is applied to the bonding arm 1 by rotating the servo motor 15. That is,
As the servo motor 15 rotates, the wire 10 attached to the rotating shaft is wound up and acts to pull up the other end of the bonding arm 1. Therefore, this wire 10 performs the same function as a conventional tension spring.

The driving means 23 includes a timing signal setting circuit 11 and an output of this timing signal setting circuit 11.
A program circuit 12 which receives T ₁ to _{T 3} and appropriately selects output lines l ₁ to _{l 3} based on a program prepared in advance, and output lines l ₁ to _{l 3} of the program circuit 12. Connected electromagnetic relays RY ₁ to RY ₃ , resistors R ₁ to R ₃ with different values connected to the electromagnetic relays RY ₁ to RY ₃ , and the above-mentioned resistors R ₁ to R ₃ connected to the inverting terminal (-). Connect in common,
It consists of an operational amplifier (op-amp) 13 whose non-inverting terminal (+) is grounded via a resistor _R0 , and a current amplifier 14 whose input is the output of this operational amplifier 13.

The timing signal setting circuit 11 sets the following timing signals.

First, the first timing signal _T1 is a start signal for the cam drive servo motor at the start of bonding. This timing signal _T1 is used for setting the bonding load for the first wire.

Next, the second timing signal T ₂ and the third timing signal T ₃ are formed using an apparatus as shown in FIG.

In the figure, numeral 4 is a cam which is a vertical movement mechanism of the capillary, and numeral 18 is a slit disk provided coaxially with a camshaft 22 of this cam 4, and has two slit holes 20 and 21. 19 is a photo sensor. The slit holes 20 and 21 are provided facing each other in the longitudinal direction of the cam 4. One of the long axes of this cam 4 is used for the downward movement when bonding the pad part, and the other side is used for the downward movement when bonding the lead part. Therefore, an electrical signal is obtained from the photo sensor 19 that is generated intermittently each time each slit hole 20, 21 passes.
The output of this photo sensor is input to the counter 24, and the counter 24 outputs a pulse signal every one count.
Let the timing signal T2 be _T2 . This timing signal _T2 is used for setting a load during steady bonding. Further, a comparator 25 is provided on the output side of the counter to compare the output signal of the counter 24 with a predetermined set value S, and when the two match, a match signal _T3 is generated from the comparator 25. Keep it. This coincidence signal _T3 is the third timing signal, and is used for setting the bonding load when the distance between the pad part and the lead part is long. Therefore, the above set value S can be set by observing the bonding object in advance, determining the number of parts where the distance between the pad part and the lead part is long, and setting the value corresponding to this number. .

The program circuit 12 selects the output lines _l1 to _l3 based on the timing signals _T1 to _T3 ,
A current is supplied thereto, and this selection is made according to a program created in advance. Such a program is set up as follows.

First, when the first timing signal T ₁ is input, the first output line l ₁ is selected and current is supplied to this selected line, and then the second timing signal T ₂ is input. When the second output line _l2 is selected and current is supplied to it, when the third timing signal _T3 is input, the third
Select the output line _L3 and supply current to it.
These selections are made alternatively, and only a single output line is always selected.
Such program control can be easily achieved using a program board or microcomputer.

The electromagnetic relays RY ₁ to RY ₃ are each composed of a pair of electromagnetic coils L ₁ to L ₃ and switches S ₁ to _{S 3} that turn on when current flows through the electromagnetic coils. It is designed to operate selectively based on the selection operation of the circuit 12.

Resistors R ₁ to _{R 3} having different values are connected in series to the electromagnetic relays RY ₁ to _{RY 3} , and a common connection point of these resistors is connected to the inverting input terminal (−) of the operational amplifier 13 . Therefore, the outputs D ₁ to D 3 of the selection circuit 12 select the electromagnetic relays RY 1 to RY ₁ to D ₃ .
If RY ₃ is turned on individually, operational amplifier 13
The input resistances R ₁ to _{R 3} will change. When the input resistance of the operational amplifier changes in this way, the input currents I ₁ to I ₃ change, and the output current changes accordingly. Here, the values of the resistors _R1 to _R3 are determined so that the relationship between the input currents _I1 to _I3 is _I1 > _I3 > _I2 .

If this current change is amplified by the current amplifier 14 and applied to the servo motor 15, the torque of this motor changes, and the wire 10 wound around the rotating shaft changes.
(i.e. bonding arm 1
(pulling force) changes. Since this tensile force is directly transmitted to the capillary 3, the bonding load can be changed. As a result, it becomes possible to programmatically control the bonding load according to the bonding state. Here, the bonding load is, for example, 130 g when the input current I ₁ of the operational amplifier 13 is I _{2 .}
We will set it so that it is 100g when , and 120g when I ₃ .

Here, it is desirable that the torque of the servo motor 15 is smaller than the torque of the drive motor of the cam 4. This is because either the torque of both is the same or the motor 15 that winds the wire 10
This is because if the torque is increased, the lever 5 cannot be moved up and down, and therefore the capillary 3 cannot be moved up and down. The motor 15 that winds the wire 10 in this way
When the cam 4 acts to lower the other end of the bonding arm 1 via the lever 5 by setting the torque of the drive motor of the cam 4 to be smaller than that of the drive motor of the wire 10, the motor for winding the wire 10 15 is forcibly rotated in the reverse direction, and the wire 10 is wound back to its original state.

According to the embodiment apparatus described above, bonding can be performed in the following manner.

First, an XY table (not shown) is moved so that the capillary 3 faces the upper surface of the first pad part, and a motor (not shown) that drives the cam 4 is activated. At this time, a timing signal _T1 is generated, and in the program circuit 12, an output line _l1 is generated based on this timing signal. Therefore, the electromagnetic relay RY ₁ operates and transfers the current I ₁ to the operational amplifier 13.
applied to the input of Therefore, the motor 15 rotates, winds up the wire 10, and applies a tensile force, but the load based on this tensile force is e.g.
Bonding of the first wire is performed using 130 g. In this way, the bonding load of the first wire is the load during steady bonding (for example, 100
g), so even if cam 4
Sufficient bonding can be carried out even when the drive motor does not reach a steady speed.

At the stage where bonding of the first wire is completed and bonding to the next first lead is performed, the first timing signal _T1 is canceled and the second timing signal _T2 is applied to the program circuit 12,
The second output line _l2 is selected. Based on this, the electromagnetic relay RY ₂ operates, and the current I ₂ is input to the operational amplifier 13. Since the servo motor 15 is driven by a signal based on this current I ₂ , the tensile force on the wire 10 becomes weaker than when the above-mentioned current I ₁ is supplied, and a load of, for example, 100 g is applied to the capillary 3. It's becoming like that.

Furthermore, when the distance between the pad part and the lead part becomes long, the timing signal _T3 is inputted to the program circuit 12, and the third output line _I3 is selected based on this. Therefore, a current _I3 is applied to the input of the operational amplifier 13, and the servo motor 15 is driven by a signal based on this current _I3 . Therefore, the tensile force of the wire 10 is set to approximately the intermediate strength when the above-mentioned currents I ₁ and I ₂ are supplied, and a load of, for example, 120 g is applied to the capillary 3. Since this load is larger than the load (100 g) during steady bonding, for example, even if some vibration or the like remains in the bonding arm 1 during movement, it will not impede the bonding work.

As is clear from the above, according to the wire bonding apparatus described above, the bonding load can be changed depending on the bonding state, and optimal bonding work can always be performed.

The present invention provides another example of a load supply means for achieving this function, and in particular, as shown in FIG.
and iron core 16 and wire 1 connected to this iron core 16
0. Even in such a case, the same objective can be achieved by simply supplying the output of the current amplifier 14 in the embodiment of FIG. 4 to the solenoid coil 17. Alternatively, the conventional tension spring may be left attached, and this load may coexist with the tension wire 10 according to the present invention.

According to the present invention, since the bonding load can be controlled by controlling the current of the solenoid coil, a relatively simple configuration can be achieved.

The invention is not limited to the above embodiments. for example,
In the above embodiment, a case has been described in which three types of bonding loads are controlled, but the bonding state may be further analyzed and changes may be made arbitrarily so that four or more types of control can be performed.

Further, the circuit configuration of the driving means 23 is not limited to the above embodiment, and may be of any type.

According to the present invention, an optimal bonding load can always be applied regardless of the bonding state, and the accuracy of wire bonding can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a conventional wire bonding device, FIG. 2 is a displacement curve showing the amount of displacement of the cam used in the wire bonding device, and FIG. 3 is a diagram showing the displacement amount of the cam used in the wire bonding device. FIG. 4 is an explanatory diagram including a block diagram showing an example of the wire bonding device invented by the present inventor, and FIG. 5 is a diagram showing the timing signal generating device used in the device of the present invention. An explanatory diagram showing an example, FIG. 6 is an explanatory diagram of a main part showing the present invention. 1... Bonding arm, 2... Support shaft, 3... Capillary, 4... Cam, 5... Lever, 6... Spring, 7...
Cam follower, 8... Roller, 9... Support shaft, 10... Wire, 11... Timing signal setting circuit, 12... Program circuit, 13... Operational amplifier, 14... Current amplifier, 15... Servo motor, 16... Iron core, 17...
Solenoid coil, 18...Slit disk, 19...
Photo sensor, 20, 21...slit hole, 22...
Camshaft, 23... Drive means, 24... Counter, 25... Comparator, RY ₁ to RY ₃ ... Electromagnetic relay,
_R0 to _R3 ...Resistance, _L1 to _L3 ...Coil, _S1 to _S3 ...Switch.

Claims (1)

[Claims] 1. A bonding device that has a capillary that holds a wire at one end, a bonding arm that is connected to a vertical movement mechanism at the other end, and a load supply means that applies a bonding load to the capillary, wherein the load supply means is a solenoid coil. and an iron core disposed in the solenoid coil, and the bonding load is changed by supplying a current generated depending on the point to be bonded to the solenoid coil. Wire bonding equipment.