KR101548949B1 - Ultrasonic bonding typed metal wire bonding apparatus - Google Patents

Abstract

An ultrasonic bonding type metal wire bonding apparatus for performing wire bonding with an ultrasonic bonding type and checking the quality of a wire bonding operation is disclosed. The disclosed metal wire bonding apparatus includes a bonding tool for pressing a bonding portion of a metal wire so as to be closely attached to a bonding pad, a bonding tool for bonding the bonding portion to the bonding pad, An ultrasonic vibration horn that is connected to the upper end of the bonding pad and vibrates in an ultrasonic wave frequency band, a wire clamp which is brought into close contact with the bonding pad and holds the metal wire when the bonding tool vibrates, A wire cutter for cutting a portion other than the bonding portion of the metal wire after bonding to the bonding pad to separate the electrically-connected metal wire from the non-electrically-connected metal wire; And a quality determiner for judging a bonding failure when the section deformation value is smaller than a predetermined section deformation reference value All.

Description

[0001] Ultrasonic bonding type metal wire bonding apparatus [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic bonding type metal wire bonding apparatus, and more particularly, to an ultrasonic bonding type metal wire bonding apparatus capable of simultaneously or simultaneously realizing good or bad bonding work.

The wire bonding method for connecting the semiconductor chip and the lead frame includes thermocompression bonding mainly using gold (Au) wire and ultrasonic bonding using mainly aluminum (Al) wire . The double ultrasonic bonding method is a method of applying ultrasonic vibration of 60 to 130 kHz in the horizontal direction together with the pressure in the vertical direction to bond the wires to the pad at room temperature, and aluminum (Al) or an alloy thereof is mainly used as a wire material However, a wire made of gold (Au) or copper (Cu) may be used.

FIG. 1 is a view for explaining a process of inspecting the quality of a wire bonding operation according to a conventional example. 1, a semiconductor chip 10 is mounted on the center of a lead frame 12, and one end 16 of an aluminum alloy wire 15 is connected to a semiconductor chip (not shown) And the other end 18 of the wire 15 is connected to a lead frame pad 13 provided at one side of the lead frame 12 ). A method of hanging a middle portion of the wire 15 with a hook 2 and pulling it with a predetermined force is used to check whether the bonding of the both ends 16 and 18 of the wire and the pads 11 and 13 is good . If one of the opposite end portions 16, 18 is pulled out by the pads 11, 13 when pulled by the hook 2, it is judged that the connection is defective.

However, the above-described wire bonding quality inspection method is performed by using a device separate from a device for performing a wire bonding operation after a wire bonding operation, thereby deteriorating the productivity of a semiconductor chip package. Even when the curved shape of the wire 15, that is, the loop, may be deformed or the wire 15 may be damaged and the quality is judged to be good when the wire 15 is pulled by the hook 2, , 18 and the pads 11, 13 can be weakened. Also, depending on the design, the hook 2 can not be inserted into the middle portion of the wire 15 due to the space constraint, so that quality inspection is sometimes impossible.

Korean Patent Publication No. 10-0139403 Korean Patent Publication No. 10-2005-0051805

The present invention provides an ultrasonic bonding type metal wire bonding apparatus that performs wire bonding with an ultrasonic bonding type and inspects the quality of a wire bonding operation.

The present invention also provides an ultrasonic bonding type metal wire bonding apparatus capable of inspecting the quality of a wire bonding operation without applying a physical force for quality inspection, such as pulling a wire.

The present invention relates to a bonding tool for pressing a bonding portion of a metal wire so as to be in close contact with a bonding pad so that the bonding portion vibrates so that the bonding portion is bonded to the bonding pad, An ultrasonic vibration horn which is connected to an upper end of the tool and vibrates in an ultrasonic wave frequency band; a wire clamp which hits the metal wire when the bonding part is in contact with the bonding pad and vibrates when the bonding tool vibrates; a wire cutter for cutting a portion of the metal wire other than the bonding portion after the bonding portion is bonded to the bonding pad and separating the electrically connected metal wire from the non-electrically connected metal wire, A deformation detector for detecting a deformation value of a section of the joint portion, and a deformation detector for detecting the deformation value of the deformation section, Surface provides a metal wire bonding apparatus having an quality estimation for determining a bonding failure.

The cross-sectional deformation value may be a thickness reduction amount of the joining portion where the joining portion is pressed and deformed in a direction in which it is brought into close contact with the joining pad.

The deformation detector may include an encoder for measuring the amount of fine movement in the vertical direction of the bonding tool to detect a thickness reduction amount of the bonding portion.

The metal wire bonding apparatus includes a phase of an input signal for ultrasonic vibration of the ultrasonic vibration horn and a feedback signal of the ultrasonic vibration transmitted by the ultrasonic vibration horn, Further comprising a feedback gain detector for detecting a feedback gain value corresponding to the phase difference of the vibration, wherein the quality determiner can be configured to determine a poor connection if the feedback gain value is greater than a predetermined feedback gain reference value have.

According to another aspect of the present invention, there is provided a bonding tool including a bonding tool for pressing a bonding portion of a metal wire so as to be closely attached to a bonding pad, a bonding tool for bonding the bonding portion to the bonding pad, An ultrasonic vibration horn which is connected to an upper end of the tool and vibrates in an ultrasonic wave frequency band; a wire clamp which hits the metal wire when the bonding part is in contact with the bonding pad and vibrates when the bonding tool vibrates; a wire cutter for cutting a portion of the metal wire other than the bonding portion after the bonding portion is bonded to the bonding pad and separating the electrically connected metal wire from the non-electrically connected metal wire, A phase of an input signal for ultrasonic vibration of the ultrasonic vibration horn, A feedback gain detector for detecting a feedback gain value corresponding to a phase difference of a feedback vibration transmitted to the ultrasonic vibration horn when the feedback gain value is greater than a predetermined feedback gain reference value And judges that the bonding is defective if the bonding strength is larger than the bonding strength of the metal wire bonding apparatus.

The metal wire bonding apparatus of the present invention may be configured such that the feedback gain value is periodically detected and an input signal for ultrasonic vibration of the ultrasonic vibration horn is changed by reflecting the periodically detected feedback gain value.

The feedback gain value may be expressed by a power value.

The metal wire bonding apparatus of the present invention may be configured such that when the wire cutter is moved to cut the metal wire, the wire cutter is limited in movement so as not to contact the bond pad.

The metal wire bonding apparatus of the present invention can be configured such that, when the quality judging unit judges that the bonding defects are defective, the wire cutter or the bonding tool breaks the defective bonding defective product.

According to the metal wire bonding apparatus of the present invention, a factor that affects bonding quality during wire bonding of the ultrasonic bonding system is measured in real time, and whether the quality is good or bad can be known immediately after wire bonding is completed. Therefore, there is no need for a device separate from the time for the quality inspection, so that the productivity of the semiconductor chip package is improved and the cost is reduced.

In addition, as compared with the conventional inspection method of pulling a wire by a hook, damage of the wire and weakening of the bonding force do not occur, and the quality inspection can be performed on the wire bonding of all the ultrasonic bonding methods.

Also, the metal wire bonding apparatus according to the embodiment of the present invention improves the quality of the wire bonding by providing a configuration for correcting the input considering real-time feedback on the input causing the ultrasonic vibration.

FIG. 1 is a view for explaining a process of inspecting the quality of a wire bonding operation according to a conventional example.
2 is a perspective view of a lead frame in which a wire bonding operation is completed.
3 is a perspective view of a metal wire bonding apparatus according to an embodiment of the present invention.
4 is a side view illustrating a wire bonding operation performed by a metal wire bonding apparatus according to an embodiment of the present invention.
5 is a side view showing a state where the wire is cut by the wire cutter of FIG.
FIG. 6 is a block diagram illustrating a structure of a metal wire bonding apparatus according to an exemplary embodiment of the present invention.
7 is a cross-sectional view showing a cross-section deformation of a wire by a wire bonding operation.
8 is a graph showing the relationship between the feedback gain value and the wire bonding quality.

Hereinafter, an ultrasonic bonding type metal wire bonding apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The terminology used herein is a term used to properly express the preferred embodiment of the present invention, which may vary depending on the intention of the user or operator or the custom in the field to which the present invention belongs. Therefore, the definitions of these terms should be based on the contents throughout this specification.

First, an example of an object of a work performed by the metal wire bonding apparatus of the present invention will be described. Referring to FIG. 2, the semiconductor chip 10 is mounted on one side of the lead frame 12, and the chip pad 10 on the side of the semiconductor chip 10 11 and the lead frame pad 13 on the other side of the lead frame 12 are electrically connected by a metal wire 15. One side 16 of the metal wire 15 is bonded to the chip pad 11 and the other side 18 is bonded to the lead frame pad 13 in an ultrasonic manner. The material of the metal wire 15 may be aluminum (Al) or an aluminum alloy.

FIG. 3 is a perspective view of a metal wire bonding apparatus according to an embodiment of the present invention, and FIG. 4 is a side view illustrating a wire bonding operation performed by a metal wire bonding apparatus according to an embodiment of the present invention. 3 and 4, a metal wire bonding apparatus 30 according to an embodiment of the present invention includes a bonding head 40 and a bonding head 40 that supports the bonding head 40, A Z-theta driver 34 for driving the bonding head 40 in the vertical direction to rotate about the longitudinal direction of the head shaft 38, Z and an XY driver 31 for driving the -θ driver 34 in a direction parallel to the X axis and the Y axis, that is, in the horizontal direction. Wire bonding operation is performed when the lead frame 12 (see Fig. 2) is fed in a line in a direction parallel to the Y axis and stopped below the bonding head 40, and the finished lead frame 12 is moved to the Y axis Lt; RTI ID = 0.0 > direction. ≪ / RTI >

The bonding head 40 is provided with a bonding tool 50, an ultrasonic vibration horn 42, a wire clamp 70 and a wire cutter 60 do. The bonding tool 50 presses the bonding portion 19 of the metal wire 15 into close contact with the bonding pads 11 and 13 in a stick shape elongated in the vertical direction. The lower end of the bonding tool 50 is formed as a tapered wedge and is also called a wedge. The lower end of the bonding tool 50 is formed with a groove 52 so that the metal wire 15 can be held without being separated when the metal wire 15 is pressed against the bonding pads 11 and 13. For example, the groove 52 may be an inverted V-shaped groove.

The ultrasonic vibration horn 42 is connected to the upper end of the bonding tool 50 and vibrates in an ultrasonic frequency band (for example, 60 kHz). The vibration of the ultrasonic vibration horn 42 is applied to the bonding portion 19 of the metal wire 15 which is in close contact with the bonding pads 11 and 13 through the bonding tool 50 in the horizontal direction, The bonding portion 19 is bonded to the bonding pads 11 and 13 by vibrating. The ultrasonic vibration horn 42 is supported on the horn support bracket 45 and the horn support bracket 45 is finely elevably engaged with the head shaft 38. [ The minute lift amount of the horn support bracket 45 with respect to the head shaft 38 is measured by the encoder 47. The bonding tool 50 of the bonding head 40, the wire cutter 60 and the wire clamp 70 can be raised and lowered at the same time by driving the Z-theta drive 34 and the horn support bracket 45 is moved up and down The bonding tool 50 can be raised and lowered independently of the wire cutter 60 and the wire clamp 70.

The wire clamp 70 fixes the metal wire 15 when the bonding portion 19 is brought into close contact with the bonding pads 11 and 13 and the bonding tool 50 is ultrasonically vibrated. At this time, if the wire clamp 70 does not hold the metal wire 15, the bonding portion 19 is not firmly adhered to the bonding pads 11 and 13, and the probability of occurrence of the bonding failure of the wire 15 is increased.

The wire cutter 60 cuts the portion other than the bonding portion 19 of the metal wire 15 after the bonding portion 19 is bonded to the lead frame pad 13. The metal wire 15 having one end 16 and the other end 18 electrically connected to the chip pad 11 and the lead frame pad 13 is electrically connected to the metal wire 15 not electrically connected, . The metal wire 15 which is not electrically connected is wound on a reel mounted on the metal wire bonding device 30 and supplied to the bonding head 40 and is cut by the wire cutter 60 The end portion is attracted to the bonding head 40 and is next bonded to the chip pad 11 of the lead frame 12 (see FIG. 2).

5 is a side view showing a state where the wire is cut by the wire cutter of FIG. Referring to FIG. 5, the wire cutter 60 lowers the lower blade to cut the metal wire 15. At this time, the downward movement of the blade lower end portion 62 of the wire cutter 60 is limited so as not to contact the lead frame pad 13. Conversely, the bonding tool 50, which has pressed the metal wire 15, slightly rises apart from the downward movement of the wire cutter 60. As a result, the blade lower end portion 62 and the bonding tool lower end portion 54 are almost equal in height, and the metal wire 15 is cut by about 2/3 of the thickness by the blade lower end portion 62, do. When the bonding head 40 (see FIG. 3) is lifted with the wire clamp 70 holding the metal wire 15, about one third of the thickness of the remaining metal wire 15 is cut off and separated .

FIG. 6 is a block diagram showing a configuration for checking bonding quality provided in a metal wire bonding apparatus according to an embodiment of the present invention, FIG. 7 is a sectional view showing a section of a wire by a wire bonding operation, 8 is a graph showing the relationship between the feedback gain value and the wire bonding quality. 3, the metal wire bonding apparatus 30 (see FIG. 3) is configured to check the bonding quality of the metal wire 15, and includes a strain detector 92 and a quality plate (95).

The deformation detector 92 is configured to detect the deformation value of the cross section of the joint portion 19. In the embodiment of the present invention, the above-mentioned section deformation value is a reduction amount of the thickness H of the bonding portion 19 which is pressed and deformed in the direction in which the bonding portion 19 is in close contact with the bonding pads 11, 13 . When the bonding portion 19 of the metal wire is bonded to the bonding pads 11 and 13 by ultrasonic bonding and the deformation of the bonding portion 19 is relatively large, the bonding quality is superior to that when the deformation of the portion is relatively small . Therefore, the thickness reduction amount DH2 when the bonding quality is good is larger than the thickness reduction amount DH1 when the bonding quality is poor, and the bonding quality can be determined using the thickness reduction amount DH2. The strain detector 92 is provided with the encoder 47. The encoder 47 measures the amount of fine movement in the vertical direction of the bonding tool 50 which is finely descending as the wire bonding of the ultrasonic vibration type proceeds and measures the decrease amount of the thickness H of the bonding portion 19 do.

The quality determiner 95 determines the cross-sectional deformation value measured by the encoder 47 immediately after the ultrasonic vibration for a predetermined time for bonding the metal wire 15, that is, the thickness H of the joint portion 19, If the reduction amount is smaller than the predetermined section deformation reference value, it is determined that the joint failure is caused. The section deformation reference value may be determined by repeated tests.

Referring to FIGS. 4, 6 and 8, the metal wire bonding device 30 (see FIG. 3) is configured to check the bonding quality of the metal wire 15, and includes a feedback gain detector 90 ). In order to ultrasonically vibrate the ultrasonic vibration horn 42, an input signal of an ultrasonic wave frequency of 60 kHz, for example, is generated in the input signal generator 80 and inputted to the ultrasonic vibration horn 42. The vibration of the ultrasonic vibration horn 42 is transmitted to the metal wire bonding portion 19 through the bonding tool 50 and reflected back to the ultrasonic vibration horn 42 as feedback vibration. The feedback vibration detector 84 detects this feedback vibration. The phase comparator 82 compares the phase of the feedback oscillation received from the feedback oscillation detector 84 with the phase of the input signal received from the input signal determiner 87. The feedback gain detector 90 receives a signal corresponding to the phase difference between the phase of the input signal and the feedback oscillation from the phase comparator 82 and detects a feedback gain value. The feedback gain value may be expressed as a power value.

Since the phase characteristic of the input signal transmitted from the input signal determiner 87 to the phase comparator 82 is the same as the phase characteristic of the input signal transmitted from the input signal generator 80, Corresponds to the phase difference between the output vibration of the input shaft 42 and the feedback vibration. When the phase difference between the output vibration and the feedback vibration is 180 °, the feedback gain value expressed by the power value is 0V. At this time, the resonance energy is maximized and the quality of the ultrasonic type wire bonding is good. On the other hand, as the phase difference between the output vibration and the feedback vibration deviates from 180 degrees, the feedback gain value expressed by the power value becomes larger, the resonance energy becomes smaller, and the quality of the ultrasonic type wire bonding becomes poor.

Meanwhile, while the ultrasonic vibration for the metal wire bonding operation continues, the feedback gain value is periodically detected by the feedback gain detector 90, and the periodically detected feedback gain value is detected by the input signal generator 80 and the input signal determiner 87 So that the input signal for vibrating the ultrasonic vibration horn 42 is changed. That is, the feedback gain value is reflected, and the phase difference between the output oscillation and the feedback oscillation is 180 degrees next, and the phase characteristic of the input signal is changed in the direction in which the resonance energy becomes maximum. As described above, the metal wire bonding device 30 (see FIG. 3) is controlled so that the feedback gain value is reflected in the input signal in real time, thereby improving the quality of the metal wire bonding.

If the maximum value of the feedback gain values detected during the ultrasonic vibration time immediately after the ultrasonic vibration for a predetermined time for bonding the metal wires 15 is larger than the predetermined feedback gain reference value, . The feedback gain reference value may be determined by repeated testing.

Referring to the graph of FIG. 8, during 15 metal wire bonding tests, feedback gain voltage values in the first, third, fifth, eleventh, and eighth turn tests were detected in excess of the reference value of 1.2 V, All of which corresponded to poor wire bonding quality. In the test times other than the above-mentioned rotation, the feedback gain voltage value was much lower than the reference value, and a voltage value close to 0 V was detected. All of these values corresponded to the wire bonding quality.

In the metal wire bonding device 30 (see FIG. 3), the quality determining device 95 can determine the quality of the wire bonding by considering both the cross-sectional deformation value of the bonding portion 19 and the feedback gain value. That is, it is judged that the wire bonding quality is good only when a condition that a section deformation value is equal to or larger than a section deformation reference value and a case where the feedback gain value satisfies both conditions equal to or smaller than the feedback gain reference value.

On the other hand, if the quality judging device 95 judges that the wire bonding is a bonding failure, the wire cutter 60 or the bonding tool 50 can be set to break the product 12 (see Fig. Specifically, the wire cutter 60 may cut between one end 16 (see FIG. 2) and the other end 18 (see FIG. 2) of the wire 15 determined to be defective. Alternatively, the semiconductor chip 10 may be pressed by the bonding tool 50 to form an identifiable mark or cause a short.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

11: Semiconductor chip pad 13: Lead frame pad
15: metal wire 30: metal wire bonding device
40: bonding head 42: ultrasonic vibration horn
50: bonding tool 60: wire cutter
70: wire clamp 90: feedback gain detector
92: strain detector 95: quality judging device

Claims (9)

A bonding tool for pressing the joining portion of the metal wire so as to be in close contact with the joining pad;
An ultrasonic vibration horn connected to an upper end of the bonding tool to vibrate in an ultrasonic wave frequency band so that the bonding tool vibrates and the bonding part is bonded to the bonding pad;
A wire clamp for holding the metal wire when the bonding part is brought into close contact with the bonding pad and the bonding tool is vibrated;
A wire cutter for cutting a portion of the metal wire other than the bonding portion after the bonding portion is bonded to the bonding pad to separate the electrically-connected metal wire from the non-electrically-connected metal wire;
A phase of vibration for ultrasonic vibration of the ultrasonic vibration horn and a phase of vibration corresponding to a resonance energy value according to a phase difference of feedback vibration transmitted to the ultrasonic vibration horn by the ultrasonic vibration A feedback gain detector for detecting a feedback gain value; And
And judging that the bonding failure is judged if the feedback gain value is larger than a predetermined feedback gain reference value. The method according to claim 1,
A deformation detector for detecting a deformation value of a cross section of the joint portion; And
And judging that the bonding failure is judged if the section deformation value is smaller than a predetermined section deformation reference value,
Wherein the cross-sectional deformation value is a thickness reduction amount of a bonding portion where the bonding portion is pressed and deformed in a direction in which the bonding portion closely contacts the bonding pad. 3. The method of claim 2,
Wherein the deformation detector comprises an encoder for measuring a vertical movement amount of the bonding tool to detect a thickness reduction amount of the bonding portion. . delete delete The method according to claim 1,
The feedback gain value is periodically detected,
Wherein the input signal for ultrasonic vibration of the ultrasonic vibration horn is changed by reflecting the periodically detected feedback gain value. The method according to claim 1,
Wherein the feedback gain value is expressed as a power value. The method according to claim 1,
Wherein when the wire cutter moves to cut the metal wire, movement of the wire cutter is restricted so as not to contact the bonding pad. The method according to claim 1,
Wherein the wire cutter or the bonding tool is configured to break the product in which the bonding defect is determined when the quality judging unit judges that the bonding is defective.

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