JPS63136640A - Ball formation device for wire bonding - Google Patents

Abstract

PURPOSE:To improve the discriminating accuracy of a ball diameter by providing ball diameter discriminating means for comparing the integrated value of an integrator with a good level when the set discharge command time of discharge condition setting means is elapsed to discriminate whether the ball diameter arrives at a predetermined value or not. CONSTITUTION:A discharge generator 12 contains a constantcurrent power source circuit to generate a discharge between the end 21A of a wire 21 and an electrode 22 on the basis of a discharge command to form a ball at the wire end 21A. A ball diameter discriminator 17 compares the integrated value of an integrator 15 with a good level L set in advance at a normal discharge state setter 16 when a discharge command time T set at a discharge condition setter 11 is elapsed to discriminate whether the ball diameter arrives at a predetermined value or not and to output a good signal G or a discrimination regulate to a bonding unit. When a discharge current detected by a discharge current detector 13 is binarized and integrated, the increasing rate of the integrated value becomes constant. This characteristic is utilized to judge whether the ball diameter arrives at a predetermined value or not.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ball forming device for wire bonding in semiconductor manufacturing equipment.

[Prior art] Is Fig. 5 wire bonding? FIG. 2 is a schematic diagram illustrating an L position, in which a wire L is bonded to a pellet 5 and a lead frame 6 placed on a heater 4 through a clamper 2 and a bonding tool 3. continue,
When the wire 1 is lifted up by the clamper 2, the wire 1 is cut at the portion where it is bonded to the lead frame 6, and its tip is returned to the position shown by the broken line. Further, on the side of the wire tip IA, an electrode 8 that forms an electric torch together with a discharge generator 7 containing a built-in power source is arranged.
By applying a high voltage between the wire tip IA and the electrode 8, a discharge is generated and a ball IB is formed at the wire tip IA. This ball IB is suitable for pounding the pellet 5, but as a premise, an appropriate ball diameter is required in accordance with changes in the area of the pounding pad of the pellet 5, changes in the diameter of the wire 1, etc.

Therefore, in the past, the ball diameter was optimized by adopting discharge generation methods such as applying a constant voltage between the wire l and the electrode 8, or adding a constant current circuit to control the current at the time of discharge. There is.

As mentioned above, even if improvements are made to the discharge generation method in order to optimize the ball diameter, it is necessary to confirm that a proper ball has been formed when bonding, that is, to judge whether the ball diameter is good or bad. , it is necessary to more reliably form a ball with an appropriate ball diameter.

The conventional method for determining whether the ball diameter is good or bad is to check whether current is flowing at a certain instant during discharge.

Alternatively, the discharge state is monitored by detecting whether the voltage applied across the discharge gap is abnormal, and if the discharge state is abnormal, it is determined that the ball diameter is also abnormal. However, in this method, the detection timing of the discharge state is limited to a certain instant during the discharge, and therefore the discharge state at other times is ignored, resulting in poor determination accuracy.

Therefore, as described in Japanese Patent Application Laid-Open No. 80-206145, a method has been proposed in which an infinite number of discharge state detection timings are set to improve the 1-judgment performance.

[Problems to be Solved by the Invention] However, when setting an infinite number of detection timings for the discharge state and detecting the discharge state 7g at each timing, it is necessary to generate an infinite number of detection timing signals, resulting in a complicated process. This requires a control circuit, making the device configuration extremely complicated.

An object of the present invention is to improve the accuracy of ball diameter determination with a simple device configuration.

[Means for Solving the Problems] A first aspect of the present invention is a ball forming device for wire bonding that generates a discharge between the tip of the wire and an electrode to form a ball at the tip of the wire. , a discharge condition setting means for setting a discharge current to be given to the wire and a discharge command time; a discharge generating means for causing the set discharge current set by the discharge condition setting means to flow through the wire for the set discharge command time; A current presence/absence detection means for detecting the presence or absence of a discharge current flowing in a discharge circuit and outputting the detection result as a binary signal, an integrator for integrating an output value of the current presence/absence detection means, and a ball having a constant diameter. A normal discharge state setting means which predetermines the integral value of the integrator under the condition to be formed as a good level, and a discharge finger of the discharge condition setting means sets the integral value of the integrator to the good level at the time when the current time has elapsed. The invention is characterized by comprising a ball diameter determining means for determining whether or not the ball diameter has reached a certain value.

The second aspect of the present invention is a ball forming device for wire bonding that generates a discharge between the tip of the wire and the electrode to form a ball at the tip of the wire, and the discharge current and discharge command to be given to the wire. discharge condition setting means for setting a time; discharge generating means for allowing the set discharge current set by the discharge condition setting means to flow through the wire for the set discharge command time; and discharge current flowing in a discharge circuit including the wire during discharge. a current detection means for detecting the presence or absence of a radio wave and outputting the detection result as a binary signal; an integrator for integrating the output value of the radio wave presence detection means; It has a normal discharge state setting means that predetermines the integral value of the integrator as a good level, and a ball diameter determining means that compares the integral value of the integrator with the good level and determines whether the ball diameter has reached a certain value. The present invention is characterized in that the discharge by the discharge generating means is terminated on condition that the ball diameter determining means determines that the ball diameter has reached a certain value.

[Operation] The ball diameter is determined by the amount of charge given to the wire during discharge, ie, the product of the discharge time and the discharge time. Therefore, according to the first aspect of the present invention, when the amount of charge to be given to the wire in order to form a constant ball diameter is set in the discharge condition setting means as the discharge current and the discharge command time, the discharge generating means A discharge current is passed through the wire for the set discharge command time.

Furthermore, the current presence detection means detects the presence or absence of a discharge current flowing in the discharge circuit including the wire, and outputs a signal of logic level "1" while the discharge current is flowing, and the integrator outputs a signal of logic level "1". Integrate. As a result, even when the amount of charge to be applied to the wire is changed by changing the discharge current in response to a change in the diameter of the ball formed on the wire, the rate of increase in the integral value accumulated by the integrator remains constant. Become. Therefore, by comparing the integrated value of the integrator with the good level preset in the normal discharge state setting means at the time when the set discharge command time has elapsed, it can be determined whether the ball diameter has reached the initially determined diameter. This allows for a simple device configuration without the need for a complex control circuit, as well as the ability to produce balls of various sizes without the need for detailed adjustment of the ball diameter judgment criteria, that is, the ball diameter, according to the various ball diameters. The diameter can be determined easily and with high accuracy.

Furthermore, according to the second aspect of the present invention, compared to the first aspect of the present invention described above, the discharge by the discharge generating means is terminated on the condition that the ball diameter determining means determines that the ball diameter has reached a certain value. As a result, the bonding work can be started immediately after a proper ball is formed, and it is also possible to shorten the overall bonding speed.

[Embodiment] Fig. 1 is a block diagram showing a ball forming device according to a first embodiment of the present invention, Fig. 2 is a waveform diagram showing control waveforms used in the ball forming device, and Fig. 3 (A), ( B) is a schematic diagram illustrating the integration state of the charge amount equivalent value.

The ball forming device 10 includes a discharge condition setting section (discharge condition setting means) 11, a discharge generation device (discharge generation means) 12, a discharge current detection section 13. Current presence/absence detection section (current presence/absence detection means)
14, integrator 15, normal discharge state setting section (normal discharge state setting means) 1B, ball diameter determination section (ball diameter determination means)
It is equipped with 17. The ball forming device 10 also includes a discharge voltage detection section 18 and a voltage presence/absence detection section 19.

The discharge generator 12 has a built-in constant current power supply circuit,
Based on the discharge commands A1 to A3, the tip end 2 of the wire 21
1A and the electrode 22, the wire tip 2
Form a ball at 1A.

In this example, discharge command A! The discharge state according to the discharge command A2 is normal, the discharge state according to the discharge command A2 is a defective state (open) where the discharge gap does not widen, and the discharge state according to the discharge command A3 is a defective state (short) where the wire 21 contacts the pole 22. shall be.

Here, the discharge condition setting unit 11 sets the amount of charge that should be given to the wire 21 in order to form a constant ball diameter as the discharge current I and the discharge command time T, and
2, the set discharge current I set by the discharge condition setting unit 11 is caused to flow through the wire 21 for the set discharge command time T.
).

(B) is an example in which the amount of charge to be given to the wire 21 is changed according to changes in the discharge current, with the current discharge command time T being constant TI. For example, in the case of a small ball diameter, the discharge current is It, the ball diameter is In case of large discharge current, I2(>It
).

Of course, the discharge command time T can also be changed.

The current presence/absence detection unit 14 is given discharge currents +1 to i3 from the discharge current detection unit 13 in response to each of the discharge commands A1 to A3, and outputs the detection results as a binary signal. That is, the current presence/absence detection unit 14 outputs a signal of logic level "1" as a current cloth when the discharge state is normal and the discharge current i1 is flowing, and when the discharge state is open and the discharge current I2 is flowing. When there is no current cylinder, it functions as a logic level.”
Outputs a 0" signal.

The integrator 15 integrates the output value of the current presence/absence detection section 14, that is, accumulates a value equivalent to the amount of charge applied to the wire 21.

The normal discharge state setting unit 16 predetermines the integral value of the integrator 15 in a state in which a constant ball diameter is to be formed, that is, in a state in which the minimum amount of electric field required for the wire 21 is given, and sets it to a good level L. It is set as .

The setting method will be described later.

The ball diameter determination unit 17 compares the integral value of the integrator 15 with the good level L preset in the normal discharge state setting unit 16 at the time when the discharge command time T set in the discharge condition setting unit 11 has elapsed, and determines the ball diameter. It is determined whether the diameter has reached a certain value and outputs the determination result, such as outputting a good signal G, to the bonding device.

By the way, assuming that normal discharge is performed over the entire discharge command time T1, and if the discharge current detected by the discharge current detection section 13 is not binarized but is integrated by an integrator, the rate of increase in the integral value is As shown in FIG. 3(A), the ball diameter determination criterion changes every time the discharge current changes, and accordingly, the ball diameter determination criterion is 11, and as shown in FIG. 2, fine adjustment is required. On the other hand, when the discharge current detected by the discharge current detection unit 13 is binarized and integrated as in this embodiment, the rate of increase in the integral value is as shown in FIG. 3 regardless of the discharge current 11.12. It becomes constant as shown in (B). This characteristic is utilized in this embodiment to determine whether the ball diameter has reached a certain value.

Here, an example of how to set the discharge current and discharge command time set in the discharge condition setting section 11 and the good level L set in the normal discharge state setting section 16 will be explained.

First, at the initial setting stage, the operator experimentally causes a certain discharge current l to flow through the wire 21 and connects the wire 21 with the current 2.
2. Observe the ball that is formed while causing normal discharge. Then, determine whether the time it takes to form a ball with the minimum ball diameter currently required is appropriate, taking into account factors such as bonding speed, and adjust the discharge current i until it is determined to be appropriate. Adjust. Note that this work can be carried out extremely efficiently if data on the relationship between the wire diameter, the required ball diameter, and the discharge current are available in advance. In this way, the discharge current 11 is first determined, and assuming that a ball of the minimum diameter required now is formed at time Ta in FIG. 3(B), the good level L is determined here. .

The above description assumes that normal discharge occurs during the entire time period Ta, but it is conceivable that no discharge may occur temporarily for some reason during actual discharge.

Taking these into consideration, the discharge command time T1, which is longer than the previously determined time Ta, is determined. In determining this discharge command time TI, factors such as the bonding speed mentioned above are taken into consideration.

Also, when the diameter of the ball required for the primary is large.

It is necessary to increase the amount of charge applied to the wire. For this, discharge current! , and discharge command time T. In this embodiment, the discharge command time T! is the same as before. is used, the discharge current I
It is necessary to make it larger. For this reason, the operator increases the discharge current from the previous II, and sets the discharge condition to ■2, which is the current that will allow a ball with the minimum required ball diameter to be formed in time Ta under normal discharge conditions. This will be set in the setting section 11.

Next, a method for determining whether the ball diameter has reached a certain value in actual pounding work will be explained in detail.

First, when the discharge state is normal, the discharge current 11 flows during the entire generation period of the discharge command AI, and the discharge command time T1
Since the integral value S1 after the elapse of time exceeds the good level L, the good signal G is output, and the ball diameter length is determined.

In this case, as shown by the two-dot chain line in Fig. 3 CB), even if there is a non-discharge period during the discharge, if the integral value St' after the elapse of the discharge command time TI exceeds the good level L. , it is determined that the necessary amount of charge has been added to the wire 21, and the ball diameter is determined to be the same.

However, when the discharge state becomes open, even if the discharge current 12 flows only during the period when the discharge command A2 does not reach the open state, the integral value S
No. 2 cannot reach the good level L, and it is determined that the ball diameter is defective.

By the way, when the discharge state becomes short-circuited, since the discharge generating device 12 uses a constant current power supply circuit, the discharge current (3) at almost the same level flows during the entire period in which the discharge command A3 is generated. Therefore, in this case, the discharge voltage detection section 18. Due to the presence of the voltage detection section 19, the output signal of the current detection section 14 after the occurrence of a sheet is not accumulated in the integrator 15. That is, the discharge voltages v1 to v3 detected by the discharge voltage detection section 18 are v3, which is smaller than the predetermined short level h. Therefore, when the discharge voltage is higher than the short level h, the voltage presence/absence detection unit 19 determines that the voltage is present and the logic level is "l".
”, and when the discharge voltage is lower than the short level h, it outputs a signal of logic level “0” as no voltage. The output signals of the current detection unit 14 can be accumulated only when there is no short-circuit condition (voltage is present).

As a result, the integral value s3 by the integrator 15 when a short circuit occurs cannot reach the good level L, and it can be determined that the ball diameter is defective.

Hereinafter, the operation of the above embodiment will be explained.

First, when the discharge current II, the discharge command time, and TI are set in the discharge condition setting section 11 as described above, the discharge generator 12 sets the discharge current to the wire 2 for the set discharge command time.
Further, the current presence/absence detection section 14 detects the presence or absence of a discharge current flowing through the wire 21, and outputs a signal of logic level "l" while the discharge current is flowing, and the integrator 15 ” is integrated. Thereby, even when the discharge current applied to the wire 21 is changed to X2 in response to a change in the diameter of the ball formed on the wire 21.

The rate of increase of the integral value accumulated by the integrator 15 is constant, and the good level L used for determining the ball diameter can be made the same regardless of the magnitude of the discharge current. therefore,
By comparing the integrated value of the integrator 15 after the elapse of the set discharge command time preset in the discharge condition setting section 11 with the good level L, it can be determined whether the ball diameter is at the initially determined constant value. As a result, according to the above-mentioned embodiment, the device configuration is simple without requiring a complicated control circuit, and without the need for fine adjustment of the ball diameter determination criteria according to various ball diameters. Ball diameters of various sizes can be determined easily and with high precision.

Next, other embodiments of the present invention will be described.

Since the configuration is almost the same as the previous example, the first
This will be explained using figures. In this example, the discharge generating device 12 is a discharge condition setting section! The point remains that the discharge current I set at 1 can be easily passed through the wire 21 for the set command discharge time T, but the ball diameter determination unit 17 determines that the ball diameter has reached a certain value. The difference is that the discharge is terminated on the condition that the determination is made. Therefore, in Figure 1, the dotted line 2
As shown in 5, the determination signal from the ball diameter determining section 17 is input to the discharge generating device 12 as a discharge end signal. As for when to end the discharge on the condition that the ball diameter determination unit 17 determines that the ball diameter has reached a certain value, first, as shown in FIG. It is conceivable that the ball diameter determination section 17 determines that the ball diameter has reached a certain value, that is, immediately after the ball diameter reaches the good level L. Second, as shown in FIG. 4(B), a certain period of time (
ΔT) later. In any case, in the case of the previous embodiment, at least the discharge command time T set in the discharge condition setting section 11 was required to form the ball, whereas in the present embodiment, the ball diameter reaches a certain value. Since the discharge is terminated on the condition that the
It also has the effect that the pounding work can be performed immediately after that, and the overall pounding speed can be greatly improved.

In addition, in the two embodiments described above, the discharge generator 12
may have a built-in circuit that applies a constant voltage between the wire 21 and the electrode 22. At this time, if the discharge state is short-circuited, the occurrence of a defective ball diameter is determined by the following method. .

Under constant voltage control, when the discharge state becomes short-circuited, the discharge current i3 becomes i3z and the discharge voltage v3 becomes v in Fig. 2.
It becomes 3z. Therefore, a short-circuit determination section is provided that determines the occurrence of a short circuit by detecting an abnormal rise in which the current i3 detected by the discharge current detection section 13 becomes the current t3z, and based on the determination result of this short-circuit determination section, the integrator 15 calculates the This enables the ball diameter determining section 16 to determine whether a defective ball diameter has occurred.

In addition, in the two embodiments, the discharge command time T is constant T1 regardless of the required ball diameter, and the discharge current is varied. If the diameter is extremely large, it becomes necessary to lengthen the discharge command time T as well. This is 1. For example, the diameter of the wire 21 is from dl to d2 (di+Δd
l) It is possible to obtain the required balls within the same discharge command time in a group within the range of
In the group where the diameter of the wire 21 is in the range of d2 to d3 (d2 + Δd2), the discharge command time T must be longer than that of the former group. Therefore, the diameter of the wire 21 is dl
to the good level L1. corresponding to d2. By setting the good level L2 corresponding to d2 to d3 separately, at least the good level L within the group can be set separately.
The ball diameter can be determined by keeping constant.

[Effects of the Invention] According to the present invention, ball diameter determination accuracy can be improved with a simple device configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a ball forming device according to the first embodiment of the present invention, FIG. 2 is a waveform diagram showing control waveforms used in the ball forming device, and FIG. 3 is a waveform diagram showing the integral state of the electric charge equivalent value. FIG. 5 is a schematic diagram showing a wire bonding apparatus. DESCRIPTION OF SYMBOLS 10... Ball forming device, 11... Discharge condition setting part (discharge condition setting means), 12... Discharge generating device (discharge generating means), 13... Discharge current detection part, 14... Current Presence/absence detection section (current presence/absence detection means), 15... Integrator, 16... Normal discharge state setting section, 17... Ball diameter determination? s (ball diameter determination means), 2nd work...wire. 22...electrode. Agent - Dai Patent Attorney Shuji Shiokawa Figure 3 (A) η Time Figure 3 (B) T = -1・Time Figure 4 (A) Time - 4th (B) Time - Figure 5

Claims (4)

[Claims] (1) Setting the discharge current and discharge command time to be applied to the wire in a ball forming device for wire bonding that generates a discharge between the tip of the wire and the electrode to form a ball at the tip of the wire. discharge condition setting means;
A discharge generating means causes the set discharge current set by the discharge condition setting means to flow through the wire for the set discharge command time, and a discharge generating means detects the presence or absence of a discharge current flowing in the discharge circuit including the wire at the time of discharge, and converts the detection result into a binary value. a current detection means that outputs a current detection signal as a signal; an integrator that integrates the output value of the current presence detection means; and a normal state in which the integrated value of the integrator under a condition in which a constant ball diameter is to be formed is predetermined as a good level. A ball diameter determination unit that compares the integral value of an integrator with the good level at the time when the discharge command time set by the discharge condition setting means and the discharge condition setting means has elapsed, and determines whether the ball diameter has reached a certain value. 1. A ball forming device for wire bonding, comprising: means. (2) Setting the discharge current and discharge command time to be applied to the wire in a ball forming device for wire bonding that generates a discharge between the tip of the wire and the electrode to form a ball at the tip of the wire. discharge condition setting means;
A discharge generating means that allows the set discharge current set by the discharge condition setting means to flow through the wire for the set discharge command time, and a discharge generating means that detects the presence or absence of a discharge current flowing in a discharge circuit including the wire at the time of discharge, and detects the detection result. A current detection means outputs a binary signal, an integrator integrates the output value of the current presence detection means, and the integrated value of the integrator under a condition in which a constant ball diameter is to be formed is set as a good level in advance. The ball diameter determining means compares the integral value of the integrator with a good level and determines whether the ball diameter has reached a certain value. A ball forming apparatus for wire bonding, characterized in that the discharge by the discharge generating means is terminated on condition that the ball diameter determining means determines that the ball diameter has been formed. (3) The ball forming device for wire bonding according to claim 2, wherein the discharge generating means terminates the discharge immediately when the ball diameter determining means determines that the ball diameter has reached a certain value. (4) In claim 2, the discharge generating means is a ball forming device for wire bonding that terminates the discharge after a certain period of time after the ball diameter determining means determines that the ball diameter has reached a certain value. .