JPH0424934A - Wire bonding apparatus and method thereof - Google Patents

Abstract

PURPOSE:To obtain an ideal ball press-bonding shape by providing a bonding arm provided at an end with a capillary, a driving arm for vertically oscillating the arm, and pressurizing force varying means for varying pressurized force at the time of bonding, and varying the pressure to be applied to the end of the capillary. CONSTITUTION:A ball 43a formed at the end of a wire 43 is sufficiently absorbed by a capillary 8 by a tension loading unit to approach a pad 45 arranged on an IC chip 44. In this case, only a driving arm 1 is continuously rotated in a direction Z by a vertically oscillating device to separate contacts 4 and 4', and the positional relationship between the arm 1 and a bonding arm 2 is deviated. The deviation is detected by a detector 9, and the apparatus is transferred by the detection output. Thereafter, voice coil units 5, 5' of pressurizing means are excited to generate a pressurizing force. The pressurizing force in the direction (b) is obtained by applying an ultrasonic wave in the direction of an arrow (a), pressurizing force in the direction of an arrow (b) and overheating means.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to semiconductor integrated circuits (IC) and large-scale integrated circuits (L
The present invention relates to a semiconductor assembly apparatus for assembling semiconductor components (SI), and particularly relates to a wire bonding apparatus and method using an ultrasonic thermocompression method.

[Background Art] Conventionally, as this type of wire bonding apparatus, there is an apparatus shown in FIG. 5.

In FIG. 5, the ultrasonic transducer 3o is swingably supported via a bin 32 provided on a frame 31 on an XY table movable in the X and Y directions. A capillary 42 is attached to the tip of a bonding arm 33 attached to one end of the ultrasonic transducer 3o.

Further, a lever 34 is provided at the other end of the ultrasonic vibrator 3o, and a roller 35 is provided at the end of the lever 34. The roller 35 receives a counterclockwise moment from a spring 37 so as to come into contact with the cam surface of the cam 36, and the cam 36 is rotated by a driving means (not shown) such as a pulse motor, and the shape of the cam 36 is rotated. capillary 4
2 can be raised and lowered. Further, the wire 43 is wound around the liner 138, and the clamp 40 is used to grasp and cut the five-ear wire 43, and the wire 43 is used to grasp and cut the five-ear wire 43, and a half wire 43 is used to pull up the ball and bring it into contact with the lower end of the capillary 42. It's a clamp. It is also a torch for forming the 41G two-ball 43a, and is configured to be rotatable around a vertical axis.

The procedure for performing bonding work using the above device will be explained.

First, the frame 31 is moved in the X and Y directions, the secondary capillary 42 is positioned above the torch 41, the wire N43 is extended a predetermined length from the tip of the capillary 42, and the ball 43a is attached to the tip of the wire 43 using the torch 41. Form. Next, as shown in Figure 6(a), capillary 42 I
It is moved and positioned at a height directly above the pad 4S on the C chip (semiconductor) 44. Next, as shown in Section 6 (b), the capillary 42 is lowered by uniform circular movement to cause the ball 43a to collide with the pad 45, and bonding pressure is further applied to the predetermined position shown in FIG. 6 (C). The ball 43a is crushed until it has a thickness Z. At the same time as this crushing, ultrasonic vibration or superheating is applied. Thereafter, the capillary 42 is moved upward and horizontally as shown in FIG. A part of the wire 43 is crushed to form a flat part, which is fixed to the lead 46 by using ultrasonic waves or superheating.The wire 43 is pulled and cut from the end of the flat part, and then the capillary 42 is raised to form a flat part. Finish the bonding. Thereafter, a ball 43a is formed at the tip of the wire 43 by the torch 41, and the state shown in FIG. 6(a) is returned to perform the next bonding.

[Problems to be Solved by the Invention] However, in recent years, as the number of pins increases, the distance between adjacent pads is becoming smaller and the pads are becoming smaller, it is difficult to maintain a stable ball crimping shape or making the ball crimping shape uniform. desired. In addition, in order to improve quality and reliability, improvements have been made to reduce the impact force when the ball collides with the pad and to prevent the subsequent side change in order to prevent cracks (cracks, etc.) on the underside of the pad. Efforts are being made to improve quality and reliability by doing so. However, as a result of the reduction in impact force mentioned above, the amount of deformation of the ball at the time of collision is smaller than before, so in order to obtain the same ball crimping area and sufficient joint strength as before, it is necessary to It is necessary to add El sound waves.

Under the above background, in order to achieve stabilization and uniformity of ball crimping diameter by increasing the number of bins, conventional wire bonding equipment has the following drawbacks.

That is, firstly, the bonding strength between the ball 43a and the pad 45 is greatly influenced by the bonding area. Therefore, if an attempt is made to obtain the same bonding area as before, the crimping shape will be an ellipse that is longer in the direction of arrow A shown in FIG. There is a risk of destroying the 45° frame.

Second, in the case of the elliptical ball crimping square shape as described above, if positional deviation occurs due to the positioning accuracy of the bonding device itself, the pad 45 as shown in FIG. 7(b-2)
There is a fear that it will protrude from the top.

This problem is particularly likely to occur on small pads such as IC chips with a large number of pins.

Therefore, the present invention has been made in view of the deficiencies and limitations of the prior art, and provides a wire bonding device and method capable of obtaining the ideal ball pressure @ shape as shown in Section 7 (a-1). The purpose is to provide.

[Means for Solving the Problems] The present invention includes a bonding arm provided with a capillary at its tip, a drive arm that swings the bonding arm up and down, and a pressure force applied to the bonding arm during bonding. The pressurizing force varying means is configured to be able to vary the pressurizing force applied to the tip of the capillary during bonding by the pressurizing force varying means.

Further, in the present invention, the pressure applied to the capillary provided at the tip of the bonding arm is applied while being varied by the pressure varying means during bonding.

[Example] Next, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a diagram showing the configuration of a bonding head of a wire bonding apparatus according to the present invention. Note that devices having the same configuration and functions as conventional devices will be described using the same reference numerals.

[N In FIG. 1, the drive arm 1 and the bonding arm 2 are independently pivotably supported by a shaft 3. This bonding arm 2 has an ultrasonic horn 7 having a capillary 8 for bonding connection at its tip and a supporting member 7.
It is held through a. Contact points 4 and 4° are provided near the rear end surface of the ultrasonic horn 7 of the shaft 3 so as to face the drive arm 1 and the bonding arm 2. Also,
A pair of solenoid units 6 and 6' are provided facing each other on the drive arm 1 and bonding arm 2, and when the solenoid units 6 and 6 are energized by a command from a control circuit (not shown), they are attracted to each other, and the bonding arm 2, a force acts in the direction of the arrow 2 in FIG. 1 with the shaft 3 as a fulcrum.

However, since the contacts 4 and 4'' contact each other and act as a stopper, the driving arm 1 and the bonding arm 2
It is configured to maintain a fixed positional relationship with the Also,
Voice coil units 5 and 5°, which serve as pressurizing means, are located between the contacts 4 and 4′ and the solenoid units 6 and 6′.
and detectors 9 and 9' are provided opposite to the drive arm 1 and the bonding arm 2, and detect a displacement in the positional relationship between the drive arm 1 and the bonding arm 2 at the same time that the contacts 4 and 4° are separated. They are placed facing each other. The vertical swinging device for swinging the drive arm 1 up and down in the direction of arrow Zz° has the same function as the cam 36 shown in FIG. 5. This vertical swinging device may be constructed using a linear motor instead of the cam. The bonding arm 2 is configured to swing in conjunction with the drive arm 1 by swinging the drive arm 1 in the direction of the arrow ZZ° by this vertical swinging device.

[11] The operation of the device having the above configuration will be explained below.

A ball 43a formed at the tip of the gear 43 is connected to a tension loading device (not shown) (half clamp 39 in FIG. 5).
etc.), and is sufficiently attracted to the capillary 8, and approaches the pad 45 disposed on the IC chip 44 by the equicircular movement of the capillary 8. Thereafter, as shown in FIG. 6(b), the ball 43a collides with the pad 45, causing the ball 43a to collide with the pad 45.
3a is slightly deformed due to the kinetic energy possessed by the capillary 8. At this time, the drive arm 1 continues to move circularly in the directions of FIGS. Since the contacts are in a stopped state, only the drive arm 1 continues to rotate in the Z direction in FIG.
are separated, and the positional relationship between the drive arm 1 and the bonding arm 2 is displaced. The displacement is detected by the detector 9, and based on the detection output, the vertical swinging device is stopped by a command from a control circuit (not shown). After this stop, the voice coil units 5 and 5, which are pressurizing means, are excited to generate a pressurizing force in the direction of the arrow shown in FIG. 6(b). This pressurizing force in the direction of the mouth is performed using a combination of ultrasonic application in the direction of arrow A, pressurization in the direction of the arrow mouth, and heating means (not shown).
As a result, the pad 45 and the ball 43a are separated from each other in FIG.
), the first bonding is completed until the predetermined crimp diameter Y and thickness Z are achieved.

[I11] During the first bonding as described above,
In this embodiment, when applying pressure to the tip of the capillary 8 in combination with the application of ultrasonic waves of a predetermined frequency, the pressure itself is varied, thereby making it possible to
-2) (The latter is connected within the frame of the pad 45 even if the positional accuracy of the device is shifted by δ in the X and Y directions.)
As shown in the figure, the configuration is such that the spread of the ball crimping diameter in the direction of vibration of the ultrasonic wave is suppressed, and the spread of the ball crimping diameter in the direction orthogonal to the vibration direction of the ultrasonic wave is promoted.

That is, as shown in FIGS. 2 and 3, if the amplitude of the ultrasonic wave at the tip of the capillary 8 is a-b, the ball pressure diameter center O
When viewed from above, a and b are the maximum runout amounts. If the pressure used in conjunction with this ultrasonic vibration is varied between C and d at a frequency twice the frequency of the ultrasonic wave as shown in FIG. The pressure is the lowest and the highest at the ball crimp center 0. In other words, as shown in Fig. 3, when the pressure level is d, the set pressure α is applied, but this pressure level d is the lowest level (the value obtained by adding the predetermined pressure α). Therefore, at a and b where the ultrasonic waves have the maximum amplitude, the lowest level d is reached, and the ball pressure diameter center O
In this case, the maximum pressure level C is applied. Therefore, in a and b, the pressing force that pushes the ball 43a of the capillary 8 and tries to crush it can be controlled by adjusting the set value of d, and the ball 43a near the center of the crimp warp can be controlled.
The pressing force that attempts to crush the ball can also be controlled by adjusting the set value of C, so by controlling the ultrasonic amplitude ab as well, the ideal ball pressure as shown in Figure 7 (a-1) can be achieved. It becomes possible to obtain the shape.

The configuration of a circuit that applies ultrasonic waves of a predetermined frequency and varies the applied force as described above will be explained using the block diagram shown in FIG. 4.

In the figure, an oscillation circuit 10 generates ultrasonic vibrations of a predetermined frequency, and includes a reference clock generation circuit and the like. In the ultrasonic power data setting 12, the operator sets the ultrasonic output level, etc. using an operation means (not shown), and based on this setting, the ultrasonic control circuit 11 controls and drives the ultrasonic waves generated in the oscillation circuit 10. The signal is output to the circuit 13 to drive the ultrasonic horn 7. The clock of the oscillation circuit 10 is also sent to a multiplier circuit 14, and the multiplier circuit 14 sends the clock to the modulation circuit 18 when the switch in the switch circuit 15 is on. When the switch circuit 15 is off, the applied pressure does not fluctuate as shown in FIGS. 2 and 3.
This is a switching circuit for making bonding connections with constant pressure. Further, the pressurization data setting 16 is performed by the operator using an operation means (not shown) to set, for example, the value of the pressurization level d shown in FIG. controls the pressing force or not, and when the oscillation circuit 15 is on, the pressing force is varied at a predetermined frequency multiplied by the modulation circuit 18 and in synchronization with the ultrasonic wave, and is transmitted via the drive circuit 19. Drive voice coil unit 5.5°.

By configuring the circuit as described above, the circuit shown in FIG.
A ball crimped shape as shown in 1) is obtained.

Note that although this embodiment has been described using an example at the time of first bonding, a similar bonding connection can be performed using the configuration of this embodiment on the node side serving as a second bonding point. In addition, in this example, the frequency of the pressurization level is explained as twice the frequency, but the amplitude of the ultrasonic wave is 8.
As long as synchronization can be achieved at point 7, point b, and their midpoints as in this embodiment, the frequency need not be doubled; on the contrary, the frequency may be divided.

[Effects of the Invention] As explained above, according to the present invention, it is possible to control the variation of the pressing force in synchronization with ultrasonic vibration during bonding, and therefore, there is an effect that an ideal ball crimping shape can be formed. Therefore, it is possible to improve the quality and reliability of the product.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the configuration of the wire bonding apparatus according to the present invention, Fig. 2 is an explanatory diagram when ultrasonic vibration and pressure variation are used together, and Fig. 3 is an explanatory diagram showing the configuration of the wire bonding apparatus according to the present invention. 4 is a block diagram showing the configuration of the circuit of the present invention; FIG. 5 is a diagram showing the configuration of a conventional wire bonding device; FIG. 6 is a diagram explaining the wire bonding process; FIG. 7 is a diagram showing the crimped shape of the ball. 1... Drive arm, 2... Bonding arm, 3
...Axis, 4,4°...Contact, 5,5...Voice coil unit, 6,6°...Solenoid unit, 7...Ultrasonic horn, 8...Capillary, 9. 9
···Detector. Patent applicant Kaiyo Denki Co., Ltd. Agent Patent attorney Masaharu Hakiri (a-1) δ (a-2) (b-1) (b-2)

Claims (2)

[Claims] (1) Wire bonding using an ultrasonic thermocompression method, which includes a bonding arm with a capillary at its tip, a drive arm that swings the bonding arm up and down, and a varying pressure force during bonding of the bonding arm. 1. A wire bonding apparatus, comprising: a pressurizing force varying means, the pressurizing force varying means being configured to be able to vary the pressurizing force applied to the tip of the capillary during bonding. (2) Wire bonding using an ultrasonic thermocompression method, characterized in that the pressure applied to the capillary provided at the tip of the bonding arm is varied during bonding by a pressure variation means. Bonding method.