JP2799938B2 - Wire bonding apparatus and method - 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, such as an electrode on a semiconductor chip.
And an external lead provided on a lead frame, for example, using a wire.

[0002]

2. Description of the Related Art Conventionally, in a wire bonding 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, A high voltage is ignited between the tip of the wire protruding from the capillary as a bonding tool and the discharge electrode (electric torch) to cause a discharge, and the discharge energy melts the tip of the wire to form a tip on the tip of the capillary. A ball is formed. Then, while applying a predetermined bonding load to the bonding point, the ball formed at the tip of the capillary is overheated by using ultrasonic waves and other heating means, and the wire is connected to the first bonding point. It is done as follows.

[0003] Subsequently, the capillary is relatively moved according to a predetermined loop control while the wire is fed out from the tip of the capillary, and the capillary is positioned immediately above the second bonding point. Then, the capillary is crimped while applying a predetermined bonding load to the bonding point,
Heating is performed by using ultrasonic waves and other heating means together to connect a wire to the second bonding point.

In a conventional wire bonding apparatus in which bonding is performed in this manner, an electromechanical converter for applying a mechanical biasing force to a capillary in order to apply a bonding load to a bonding point is provided. Provided. The electromechanical conversion means includes, for example, a pressure coil and a magnetic core that is attracted to the pressure coil, and controls an electrical input supplied to the pressure coil, that is, a current value. It is made to adjust the bonding load applied to the point.

[0005] The electrical input supplied to the electromechanical conversion means is calculated based on, for example, a set load value input to a keyboard, and a current value is determined based on the calculated output.

[0006]

According to the above-described conventional wire bonding apparatus, the bonding load applied to the bonding point is set based on the set load value input to the keyboard, but is not set. A load according to the set load value is not always applied to the bonding point, and an error occurs between the set load value and an actually measured load value actually applied to the bonding point depending on conditions. Conventionally, in order to eliminate this error, potentiometers (not shown) for respectively adjusting the electric gain value G and the offset value S are provided, and these two potentiometers are adjusted. Therefore, it is necessary to perform a correction operation to adjust the error between the set load value and the actually measured load value so as to be minimized.

That is, in this correction work, first, a predetermined first set load value is input to the keyboard, and at this time, a first actually measured load value acting on the bonding point is measured. Next, input the second set load value to the keyboard,
At this time, a second measured load value acting on the bonding point is set. An electric gain value G and an offset value are set by the two potentiometers so that the relationship between the first and second measured load values with respect to the first and second set load values is always proportional. It is necessary to adjust S individually.

However, such adjustment (correction) work can only be performed by those who are familiar with the operation of the combination regarding the electrical gain value G and the offset value S. It is necessary to repeat the measuring operation and adjust the two potentiometers.

In view of the above, the present invention has been made in view of the above-mentioned conventional problems, and includes first and second set load values, and first and second actually measured load values acting on the bonding point at this time. Is input to a keyboard to calculate the optimum electrical gain value G and offset value S, respectively, and to provide a method therefor.

[0010]

According to the present invention, a first set load value to be added to a bonding point is inputted to a keyboard, and the input of the first set load value to the bonding point is performed in accordance with the input of the first set load value. First input means for inputting a first actually measured load value to be applied, and a second set load value to be added to a bonding point are input to a keyboard, and the input of the second set load value is performed. A second input means for inputting a second actually measured load value to be applied to the bonding point; first and second set load values input by the first input means and the second input means; First calculating means for calculating a proportional constant and a fixed constant indicating a relationship between the set value and the measured value from the first and second measured load values;
A storage means for calculating a gain value and an offset value for a set load value from the proportional constant and the fixed constant obtained by the first calculating means, and storing the calculated gain value and offset value in a memory; And a second calculating means for performing multiplication and addition processing on the newly input set load value based on the gain value and the offset value stored in the memory by the storage means. Further, according to the present invention, a first set load value to be applied to the bonding point is input to the keyboard, and a first actually measured load applied to the bonding point in accordance with the input of the first set load value is provided. First to enter a value
Input means and a second set load value to be applied to the bonding point to the keyboard, and a second actually measured load value applied to the bonding point with the input of the second set load value Second input means for inputting
Proportion indicating the relationship between the set value and the actually measured value from the first and second set load values input by the first input means and the second input means and the first and second actually measured load values Calculating a gain value and an offset value with respect to a set load value from a first calculating means for obtaining a constant and a fixed constant, and a proportional constant and a fixed constant obtained by the first calculating means; And storage means for storing the offset value in the memory, based on the gain value and the offset value stored in the memory by the storage means,
Multiplying and adding processing are performed on the set load value newly input by the second calculating means, and optimal electric input is performed on the electromechanical converting means.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a head unit portion in a wire bonding apparatus according to the present invention.

In FIG. 1, a driving arm 1 and a bonding arm 2 are pivotally supported by a shaft 3 so as to be independently swingable. The bonding arm 2 holds, via a support member 5a, an ultrasonic horn 5 to which a capillary 4 for performing bonding connection is attached at the tip. An ultrasonic vibrator 6 for generating ultrasonic waves is provided at an end of the ultrasonic horn 5.
The ultrasonic wave generated by the ultrasonic transducer 6 is applied to the tip of the capillary 4 via the ultrasonic horn 5.

In the vicinity of the rear end face of the ultrasonic vibrator 6, the contacts 7 and 7 'are connected to the drive arm 1 and the bonding arm 2 respectively.
Are provided opposite to each other. The drive arm 1 and the bonding arm 2 have a pair of solenoid units 8.
When the solenoid units 8 and 8 ′ are excited by a command from a control circuit (not shown), they are attracted to each other, and the bonding arm 2 is supported on the shaft 3 in the direction of arrow ZZ ′ in FIG. To act on. However, since the contacts 7 and 7 'come into contact with each other and act as a stopper, the positional relationship between the drive arm 1 and the bonding arm 2 is fixedly held.

Between the contacts 7 and 7 'and the solenoid units 8 and 8', a pressing coil 9 and a magnetic core 9 'constituting electromechanical conversion means for applying a bonding load to a bonding point are driven. Detectors 10 and 1 which are provided to face the arm 1 and the bonding arm 2 and detect the displacement of the positional relationship between the drive arm 1 and the bonding arm 2 at the same time as the contacts 7 and 7 'are separated.
0 'is also provided opposite.

A vertical swing device for swinging the drive arm 1 up and down in the direction of arrow ZZ 'uses, for example, a cam mechanism (not shown). This vertical rocking device may be replaced with a cam mechanism having a configuration like a linear motor. When the drive arm 1 is oscillated in the direction of the arrow ZZ ′ by the vertical swing device, the bonding arm 2 is also configured to perform a swing motion in conjunction with the drive arm 1.

The operation of the head unit having the above configuration will be described below with reference to FIG. FIG. 2A shows a capillary 4 (101) for performing the first bonding.
The ball IB formed at the tip of the wire 102 is sufficiently pulled back to the capillary 4 (101) side by a tension load device (not shown), and the capillary 4 (101) moves at a constant circular motion. By I
The pad approaches the pad 104 provided on the C chip 103.

Thereafter, as shown in FIG.
Ball IB collides with the pad 104 and the ball IB is
Some deformation is caused by the kinetic energy of (101). At this time, the drive arm 1 continues the circular motion in the Z direction in FIG. 1 by a vertical swinging device (not shown), but the bonding arm 2 is connected to the capillary 4.
Since (101) and the upper surface of the pad 104 are in contact with each other via the ultrasonic horn 5 and are stopped, only the drive arm 1 continuously rotates in the Z direction in FIG. When separated, the positional relationship between the drive arm 1 and the bonding arm 2 is displaced.

The displacement is detected by the detector 10, and the detection output is used to stop the vertical rocking device in accordance with an instruction from a control circuit (not shown). After this stop, the pressure coil 9 as the pressure means is excited to generate a bonding load in the direction of arrow B shown in FIG. 2B. This load in the direction B is performed by using the application of the ultrasonic wave in the direction of arrow A, the pressurization in the direction of arrow B, and the heating means (not shown). As shown in ()), pressure bonding is performed until a predetermined pressure bonding diameter D and pressure bonding thickness WD are reached, and the bonding operation at the first bonding point is completed.

The bonding connection to the second bonding point is performed by the capillary 4 (1) as shown in FIG.
01) is moved in the horizontal direction to be positioned above the lead 105 serving as the second bonding point, and the capillary 101 is lowered as shown by the two-dot chain line to thereby remove the capillary 4 (10).
A bonding load is applied according to 1) to crush a portion of the wire 102 to form a flat portion. Here, ultrasonic waves are again applied to the tip of the capillary 4 (101) to connect the wire 102 to the lead 105.

As described above, when the capillary is pressed against the bonding point, a predetermined ultrasonic power is applied for a predetermined time and a predetermined bonding load is applied to the capillary.

FIG. 3 shows a predetermined ultrasonic power as described above.
FIG. 4 shows an example of a control circuit that generates a control signal related to an ultrasonic application time and a control signal related to a bonding load applied to a bonding point. That is, in FIG. 3, reference numeral 11 denotes a keyboard. In this keyboard 11, a set value relating to the ultrasonic power, a set load value when the capillary is crimped to the bonding point, and an actually measured load value at that time are input. When these data are input, the data is supplied to an arithmetic circuit 12 composed of a microprocessor unit (μpc).

The arithmetic circuit 12 receives the data related to the ultrasonic power, refers to the data table 13 connected to the arithmetic circuit 12, and generates a control signal p for generating the predetermined ultrasonic power, a predetermined ultrasonic application time. Is calculated with respect to the control signal t for controlling. The arithmetic circuit 12 receives a set load value when the capillary is pressed against the bonding point and data on the actually measured load value at that time, and calculates a control signal f regarding the bonding load.

The control signals p, t and f calculated by the arithmetic circuit 12 are an ultrasonic control circuit 14 for controlling the output power of the ultrasonic wave, and a switch circuit 1 for controlling the time.
5. The pressure is supplied to the pressure control circuit 16 for controlling the bonding load on the capillary. The ultrasonic control circuit 14 generates an ultrasonic drive signal in proportion to the control signal p supplied from the arithmetic circuit 12, and supplies this to the switch circuit 15. Further, the switch circuit 15 keeps the ON state for a predetermined time based on the control signal t supplied from the arithmetic circuit 12, during which the ultrasonic drive signal supplied from the ultrasonic control circuit 14 is supplied to the ultrasonic transducer 6. Supply. Further, the pressurization control circuit 16 includes the arithmetic circuit 1
An electric input based on the control signal f supplied from 2 is supplied to the pressure coil 9 to generate a bonding load at the bonding point.

Here, a method of controlling the bonding load performed by the arithmetic circuit 12 will be described with reference to FIG.

When the set load value x is input by the keyboard 11, the measured load value y acting on the bonding point based on the set load value x is x = as shown by the characteristic (1) shown by the solid line in FIG. y (1) That is, ideally, the set load value x = the actually measured load value y. If operated in accordance with this ideal characteristic, a load value y equal to the set load value x input to the keyboard 11 is given to the bonding point. However, an error occurs in the actual load value y applied to the bonding point due to an error of the electric component or an effect of a mechanical balance or the like. Now, assuming that the relationship between the measured load value y and the set load value x can be expressed as points A and B in FIG. 4, the measured load value y with respect to the set load value x
Is a characteristic (2) indicated by a broken line connecting the points A and B,
That is, y = ax + b (2). In order to correct the expression (2) as the expression (1), y = a · (1 / a) x + b (−b) (3) [where (1 / a) is a gain value G and (−b) are offset values S], so that the proportional constant a is multiplied by the gain value G, and the fixed constant b is offset value S.
May be added.

That is, at least a first set load value to be applied to the bonding point is input to the keyboard, and a first actually measured load value applied to the bonding point at this time is confirmed. If a second set load value to be added to the bonding point is input and the second actually measured load value applied to the bonding point can be confirmed at this time, the gain value G and the offset value S can be calculated and input to the keyboard. It is possible to automatically apply a load value according to the set load value to the bonding point.

FIG. 5 shows the flow of the correction method performed by the arithmetic circuit 12 comprising the microprocessor in accordance with the above considerations.

First, in step S1, the keyboard 1
The first set load value x1 to be added to the bonding point is input to the unit ₁ . If whether the first set load value x ₁ is input is determined in step S2, the first set load value x ₁ is determined to have been input, step S
In 3, the first input wait actual load value y ₁ applied to the bonding point with the first setting input of the load value x _1. In step S3, the applied to the bonding point with the first setting input of the load values x ₁ 1
The measured whether the load value y ₁ is inputted is determined in the step S4, if the first measured load value y ₁ is judged to have been input, at step S5, and the first set load value if the different second set becomes the waiting state of the input of the load values x _2, it is determined that the second set load value x ₂ is inputted at step S6, step S7 again
In, the second input wait actual load value y ₂ applied to the bonding point with the second input of the set load value x _2.

In step S8, the second measured load value y
_If it is determined that ₂ has been input, in step S9, the first and second set load values x ₁ and x ₂ input in steps S1 and S5, and input in steps S3 and S7. From the first and second measured load values y ₁ and y ₂ , a proportional constant a and a fixed constant b indicating the relationship between the set value and the measured value are obtained. This is because, in the arithmetic circuit 12, the points A and B shown in FIG.
From the characteristic connecting the points, it can be obtained by the equation of y = ax + b shown in equation (2).

Subsequently, in step S10, the proportional constant a and the fixed constant b obtained in step S9 are determined.
, The gain value G (1 / a) and the offset value S (−b) for the set load value are calculated, and the calculated gain value G is calculated.
And the offset value S are stored in a memory (not shown) provided in the arithmetic circuit 12. With the gain value G and the offset value S stored in the memory as described above, when a new set load value is input to the keyboard 11 in step S11, the arithmetic circuit 12 calculates the proportional constant a of the new set load value. Is multiplied by the gain value G, and the offset value S is added to the fixed constant b.

In step S12, a control signal f based on the calculation result calculated in step S11 is generated, and a correction output based on the equation (3) is sent to the pressure control circuit 16 shown in FIG. The pressure is supplied to the pressure coil 9.

As a result, an attraction action occurs between the pressing coil 9 as the electromechanical conversion means and the magnetic core 9 ′, and a bonding load is applied to the capillary 4.

[0033]

As is apparent from the above description, according to the present invention, the first set weight value and the second set load value are input to the keyboard, and the first and second set weight values are inputted. A first measured load value and a second measured load value generated by inputting a load value are input. A proportional constant and a fixed constant are calculated based on these input values, and a gain value and an offset value are calculated based on the calculation results and stored in the storage unit. When a new set load value is input, multiplication by the gain value stored in the storage means and addition processing by the offset value are performed, and the electrical input given to the electromechanical conversion means is controlled. As a result,
It is possible to obtain a bonding load in which the set load value input to the keyboard and the actually measured load value applied to the bonding point by the capillary substantially match. Therefore, unlike the related art, it is not necessary to perform a correcting operation such as adjusting two potentiometers after familiarizing the operation of the combination regarding the electric gain value and the offset value. Also, the straightening operation can be easily achieved. Further, according to the present invention, since only keyboard input is sufficient, there is no need for a member such as a potentiometer as in the related art, so that there is an effect that the cost can be reduced and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a bonding head of a wire bonding apparatus according to the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating a wire bonding process.

FIG. 3 is a block diagram illustrating an example of a circuit configuration for generating a control signal applied to the bonding head illustrated in FIG. 1;

FIG. 4 is a characteristic diagram showing a relationship between a set load value and an actually measured load value.

FIG. 5 is a flowchart showing a flow of an arithmetic process performed by the arithmetic circuit of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive arm 2 Bonding arm 3 Axis 4 Capillary 5 Ultrasonic horn 6 Ultrasonic transducer 7, 7 'Contact 8, 8' Solenoid unit 9 Pressurizing coil 9 'Magnetic core 10, 10' Detector 11 Keyboard 12 Arithmetic circuit 13 Data table 14 Ultrasonic control circuit 15 Switch circuit 16 Pressurization control circuit

Claims (2)

(57) [Claims] 1. A wire bonding apparatus configured to bond a wire to a bonding point while applying a bonding load to the bonding point, wherein a first set load to be applied to the bonding point to a keyboard is provided. A first input means for inputting a first measured load value to be applied to the bonding point in response to the input of the first set load value, and an input to the keyboard for the bonding point. A second input means for inputting a second set load value and a second measured load value applied to the bonding point in accordance with the input of the second set load value; and the first input means The relationship between the set value and the actually measured value is shown from the first and second set load values input by the first and second input means and the first and second actually measured load values. Calculating a gain value and an offset value for a set load value from a first calculating means for obtaining a proportional constant and a fixed constant; and a proportional constant and a fixed constant obtained by the first calculating means. A storage unit for storing a value and an offset value in a memory; and performing a multiplication and addition process on a newly input set load value based on the gain value and the offset value stored in the memory by the storage unit. A wire bonding apparatus comprising: a second arithmetic unit for performing an optimal electrical input to the electromechanical conversion unit. 2. A first set load value to be applied to a bonding point is input to a keyboard, and a first actually measured load value applied to the bonding point in response to the input of the first set load value. Inputting a second set load value to be applied to the bonding point to the keyboard, and inputting a second set load value to be applied to the bonding point with the input of the second set load value to the keyboard. Second input means for inputting an actually measured load value of the second, first and second set load values inputted by the first input means and the second input means, and first and second actually measured values. A first calculating means for obtaining a proportional constant and a fixed constant indicating a relationship between the set value and the actually measured value from the load value; and a proportional constant and a fixed constant obtained by the first calculating means for the set load value. Gain value and A storage means for calculating an offset value and storing the calculated gain value and offset value in a memory; and a second calculating means based on the gain value and the offset value stored in the memory by the storage means. A wire bonding method, wherein a multiplication and addition process is performed on a newly input set load value, and an optimal electrical input is performed to an electromechanical converter.