JPS6256658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire bonding apparatus applied to the manufacture of semiconductor devices.

FIG. 1 shows an outline of the wire bonding method.
In the figure, 1 is a capillary chip, 2 is an Au
3 is an Au ball formed at the tip of the Au wire 2, 4 is an Al vapor deposited pad, 5 is a Si chip provided with this pad 4, 6a is a chip mounting part of a lead frame, and 6b is a lead frame The lead portion 7 is an electric torch for forming the Au ball 3.

The capillary chip 1 is lowered from the position shown in FIG. 1A before the start of bonding, and the Au wire 2 is bonded onto the Al vapor deposited pad 4 (FIG. 1B). Padded 4
After bonding the wire 2 to the capillary chip 1, the capillary chip 1 moves toward the lead portion 6b (FIG. 2C), and the wire 2 is bonded to the lead portion 6b (FIG. 2D).

After joining the wire 2 to the lead part 6b,
The Au wire 2 is cut (FIG. 2E) and ball formation is performed again using the electric torch 7 (FIG. 2F).

Figure 2 shows the relationship between the bonding time and bonding strength when bonding the Au wire 2 to the Al vapor-deposited pad 4 on the Si chip 5, and the amount of descent of the capillary chip 1, that is, the progress of deformation of the Au ball 3, which was determined through experiments. Show the results. Briefly explaining the figure, as time passes, the capillary chip 1 descends, the deformation of the Au ball 3 progresses, and the bonding strength increases. After this, the deformation of the Au ball 3 stops and the bonding strength also saturates. There is a one-to-one relationship between the amount of descent of the capillary chip 1 and the bonding strength, and if the diameter of the Au ball 3 before bonding is kept constant, it becomes possible to evaluate the bonding strength based on the amount of descent of the capillary tip 1.

Conventionally, the Z-axis movement of the capillary chip 1 has been driven by a cam drive method, and the bonding time has been set to be quite long in consideration of variations in bonding time based on variations in the heights of the five surfaces of the Si chip. However, the time it takes to continue applying additional load and applying ultrasonic waves after the bonding strength reaches the acceptable strength shown in FIG. 2 is completely wasteful, and goes against the demand for speeding up the wire bonding process.

This invention determines whether the bonding strength has reached an acceptable level by the amount of descent of the capillary tip, and when the amount of descent reaches a set amount, raises the capillary tip, thereby shortening the bonding time and maintaining a good bonding condition. The present invention aims to provide a wire bonding device that can be obtained.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing an example of a wire bonding apparatus according to the present invention. 1 is a capillary chip, 8 is an ultrasonic horn in the capillary chip 1, and 9 is a reflection plate attached to the side of the ultrasonic horn 8. Reference numeral 10 denotes a non-contact displacement sensor, which together with a reflecting plate 9 constitutes means 11 for detecting the amount of descent of the capillary tip 1.

In this case, the amount of descent of the capillary tip 1 is determined by taking into consideration the variation in the diameter of the Au ball 3 shown in Figure 1 before bonding, selecting a value that will minimize the diameter of the Au ball 3 within the variation range, and setting it as the set value. This is the appropriate amount of descent.

13 is an actuator for raising and lowering the capillary chip 1, and a motor (Z-axis) is used. 1
4 is a comparator, which compares the set value of the setting device 12 and the output value from the sensor 10, that is, the measured fall amount. Reference numeral 15 denotes a control circuit that receives the determination output from the comparator 14 and controls the drive of the motor 13.

Next, the operation of the above configuration will be explained.

While the capillary tip 1 is being lowered by the motor 13, the amount of the lowering is successively detected. That is, by detecting the amount of light projected from the sensor 10 reflected from the reflector 9 and returned, the distance h between the reflector 9 and the sensor 10 is measured. In this case, the surface of the reflecting plate 9 needs to be a mirror surface, but the material may be used. When the output signal from the sensor 10 is input to the comparator 14, the comparator 14 sets the distance between the sensor 10 and the reflector 9, that is, the amount of descent of the capillary chip 1, to the setting device 1 in advance.
2, and determines the point in time when these amounts become equal, and applies a determination output to the control circuit 12. The control circuit 15 sends a signal to the chip drive motor 13 to raise the capillary chip 1.

As a result, the capillary tip 1 is raised as soon as the bonding strength reaches the acceptable strength.
Wasted bonding time is eliminated. At the same time, the reliability of the bonding is also ensured. FIG. 4 graphically shows the effects of the apparatus of the present invention. D _p represents the appropriate amount of descent, and T _p represents the appropriate bonding time.

In the above description, for the sake of convenience, we have described the case where the Au wire 3 is ball-bonded onto the Al vapor deposited pad 4, but it goes without saying that similar effects can be obtained with other wire materials or other pad materials. In addition, in the above embodiment, as a means for detecting the amount of descent of the capillary chip 1, an example was explained in which the amount of light projected by the sensor 10 is reflected from the reflector plate 9 and returned. It may also be a means for detecting the amount of decrease in the capacitance based on a change in capacitance.

As described above, according to the present invention, the point at which the bonding strength reaches a passing strength is determined from the amount of descent of the capillary tip, and when the amount of descent reaches a preset appropriate amount, the capillary tip is raised. The bonding time can be saved, the bonding time can be substantially shortened, and this has the effect of contributing to improving the productivity of semiconductor devices.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the wire bonding process;
FIG. 2 is a graph showing the relationship between bonding time, bonding strength, and amount of descent of the capillary chip, FIG. 3 is a block diagram showing an example of the wire bonding apparatus according to the present invention, and FIG. 4 is the bonding time using the apparatus of the present invention. 3 is a graph showing the relationship between the bonding strength and the appropriate amount of lowering of the capillary tip. 1...capillary chip, 11...detection means,
13... Actuator, 14... Comparator, 15
...control circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An actuator for driving the capillary tip up and down, a setting device for presetting the amount of descent of the capillary tip, a detection means for detecting the amount of descent of the capillary tip, and a detection means for detecting the amount of descent detected by the detection means and the setting amount of the setting device. a comparator that compares the lowering amount with the set amount and determines when the lowering amount matches the set amount; and a control that controls the drive of the actuator so that the capillary tip rises when receiving the determination output from the comparator. A wire bonding device equipped with a circuit.