KR100548008B1 - A method for automatically forming a ball of wire bonding device - Google Patents

Abstract

The automatic ball forming method of a wire bonding device which automatically forms a ball when a second bonding error occurs in the wire bonding device according to the present invention includes the steps of (a) detecting whether a short tail error occurs; Fixing to avoid deviation, (c) calculating the length of the tail of the wire, (d) determining whether the length of the tail of the wire is sufficient for ball formation, and (e) performing an EFO discharge. It is characterized by. On the other hand, the automatic ball forming method of the present invention further comprises the step of pulling the wire tail by a predetermined length if it is determined in step (d) that the length of the wire tail is insufficient to form the ball.

 According to the wire bonding apparatus which concerns on this invention, there exist the following effects. First, in the wire bonding process, the ball forming process can be automatically performed when an error occurs in the secondary bonding, thereby improving work convenience and production efficiency. Second, in forming the ball automatically in the wire bonding process, there is no need for additional equipment, and existing wire bonding devices can be used, thereby reducing costs.

Description

A method for automatically forming a ball of wire bonding device}

1A to 1F are sequential schematic views of a ball forming method when a second bonding error occurs in a wire bonding device according to the related art.

Figure 2 is a schematic block diagram of a wire departure prevention apparatus according to the prior art.

3 is a schematic block diagram of an automatic ball forming apparatus of a wire bonding device used in the present invention.

4 is a flowchart illustrating an embodiment of an automatic ball forming method when a second bonding error occurs in the wire bonding device according to the present invention.

5A to 5F are schematic diagrams sequentially illustrating a step of extracting a wire tail by a predetermined length and an EFO discharge step in the automatic ball forming method when a second bonding error occurs in the wire bonding device according to the present invention.

Explanation of symbols on the main parts of the drawings

102: capillary 104: wire clamp

106: wire 210: bonding surface

220: stage and Z-axis control unit 230: wire clamp control unit

240: WBMS 250: ultrasonic generator

260 high voltage generator 270 host computer

The present invention relates to a method for automatically forming a ball of a wire bonding device, and more particularly, to a method for automatically forming a ball when an error occurs when performing a second bonding in a wire bonding device.

The wire bonding process is a process of joining and connecting a conductive medium, for example, a high purity gold wire, by capillary with ultrasonic waves and heat between a pad provided on an upper surface of a die and a lead of a lead frame.

In the wire bonding process, a ball is formed on a tail of a wire which is mounted on a wire bonding device and passes through a capillary to perform a first bonding on a chip pad which is a first bonding surface, and then after the first bonding capillary Move the wire to the secondary bonding position to form a loop, and then perform a secondary bonding in which the wire is in close contact with the lead as the second bonding surface by using the capillary, and after the second bonding, the capillary Lifting the li on the second bonding surface to form a wire tail of a predetermined length and then forming a ball for the next bonding by electric discharge.

At this time, when a so-called short tail error occurs in which the wire tail is shortly cut below a predetermined length after the second bonding, the tail is pulled back to a predetermined length through a procedure called a half cycle. In the related art, an operator manually performs such error elimination.

1A to 1F are schematic diagrams sequentially showing a half cycle for manually forming a ball in the case of an error during the second bonding during the wire bonding process, by hand.

FIG. 1A shows a state in which the end of the wire is placed inside the capillary 102 because the wire 106 is shortly cut to a predetermined length or less after the completion of the secondary bonding. Meanwhile, the wire clamp 104 disposed above the capillary is closed in order to prevent the wire from escaping from the capillary.

Referring to FIG. 1B, the wire clamp is temporarily opened so that an operator manually pulls out the wire to the exit end of the capillary, closes the wire clamp again, and then breaks the end of the wire to form the bent portion 108.

Referring to FIG. 1C, the stage is moved to a specific position where bonding of the lead frame 110 is possible while the wire having the bent portion 108 is mounted on the capillary 102.

Referring to FIG. 1D, the capillary assembly is lowered to bond the bent portion of the wire to the surface of the lead frame, and then the capillary assembly is raised to raise the bent portion 108 and the fusion portion (to the lead frame 110). Leaving 112, a wire tail of a predetermined length is formed outside the exit side of the capillary.

Referring to Figure 1e, the operator directly removes the bent end of the gold wire remaining in the bonding position.

Referring to FIG. 1F, an electro flame-off (EFO) discharge is generated on a wire tail of a predetermined length to form a ball 114 while the wire tail is melted.

Therefore, this conventional method, in which the operator manually executes the half cycle procedure, has to manually lower the wire and break the wire and remove the wire dregs. There has been a problem of reducing work convenience and production efficiency. Especially in the case of a large number of equipments to be managed, it was difficult for a limited number of workers to carry out individual manual work.

Therefore, the technical problem to be achieved by the present invention, when a short tail error occurs in the wire, automatic of the wire bonding device to automatically make the wire tail by a predetermined length to make the ball using the components of the existing wire bonding device To provide a ball forming method.

In the wire bonding device according to the present invention for achieving the above technical problem, the automatic ball forming method of the wire bonding device to automatically form a ball when the second bonding error occurs, (a) whether or not a short tail error occurs; Detecting, (b) securing the wire so that it does not escape, (c) calculating the length of the tail of the wire, (d) determining whether the length of the tail of the wire is sufficient for ball formation, (e) And performing an EFO discharge.

On the other hand, the automatic ball forming method of the present invention may further include the step of pulling the wire tail by a predetermined length if it is determined in the step (d) that the length of the wire tail is insufficient to form the ball.

Here, the step of extracting the wire tail by a predetermined length may include (f) moving the stage and moving the capillary assembly in the Z-axis direction, (g) generating ultrasonic waves, and (h) the wire tail is sticked. Determining whether or not the state, (i) it may include the step of moving to the Z side to the height of the EFO.

On the other hand, in the step (g), the vibration is generated in the wire by the ultrasonic wave so that the wire moves downward through the capillary.

Hereinafter, the configuration of the automatic ball forming method of the wire bonding device according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in detail as follows. Like reference numerals in the drawings denote components that perform the same function.

The general configuration of the wire bonding apparatus used in the wire bonding process to which the present invention is applied is already well known in the art. In this regard, in order to simply implement the method for forming a ball of the present invention, a technique for preventing the wire from falling out of the capillary must be preceded. If the wire is pulled out of the capillary, it is impossible to automatically form a wire tail to form a ball, which is necessary to prevent the wire breakout.

To this end, a device that implements a function of preventing the gold wire from breaking off is already known, and in the present invention, a device for preventing the wire from breaking off may adopt an existing wire leaving prevention device. .

FIG. 2 is a schematic diagram showing an example of such a conventional wire bonding device, in which a non-stick showing a state in which the wire tail is separated from the bonding surface in order to determine whether the length of the wire tail is appropriate to produce a ball. A device is shown in which a function is implemented that accurately measures the signal and prevents the wire from pulling up after the wire tail is broken.

Referring to FIG. 2, the WBMS 240 converts and outputs whether or not a wire is attached to the second bonding surface 110 into a non-stick signal, and outputs a load applied to the second bonding surface 110. Whether the wire tail is broken or not is converted into an electrical signal by converting the signal into a signal or measuring a current of the second bonding surface 110. The WBMS 240 also generates a start signal 208 the moment the capillary 102 rises after the second bonding.

The counter 204 is enabled with the start signal 208 and disabled with the nonstick signal 201 to perform a count operation from the start time until the nonstick signal 201 is generated.

Thereafter, after the time point at which the wire tail is broken, the wire clamp control unit 230 generates a counter read signal 205 to read the count data 207 from the counter. Using the read count data 207, the wire clamp control unit 230 calculates the length of the wire tail with respect to the ascending speed of the capillary 102.

In addition, when the non-stick signal 201 is generated, the wire clamp control unit 230 generates a wire clamp close signal 203 immediately. The wire clamp amplifier 206 closes the wire clamp 104 in response to the close signal 203.

As a result, the non-stick signal 201 is generated at the same time as the wire tail is disconnected, and the wire clamp 104 is closed at the same time as the non-stick signal is generated to prevent the wire from being separated.

However, despite the wire disconnection prevention function, a so-called 'short tail error' may occur, in which the tail of the wire is shortened, although the wire is not completely released after the wire is broken.

If such a short tail error occurs, the wire tail must be pulled out again below the exit side of the capillary to form a ball thereafter. To this end, the wire bonding device used in the automatic ball forming method of the wire bonding device of the present invention uses the components of the existing wire bonding device.

Referring to FIG. 3, the wire bonding apparatus to which the present invention is applied includes a capillary 102 on which the wire 106 is mounted and a wire clamp 104 that serves to fix the wire on the upper portion of the capillary. A stage and Z-axis control unit having a capillary assembly for controlling the XY axis movement of the stage with respect to the bonding surface and the height in the Z-axis direction, which is the vertical direction of the capillary, in order to set the exact position of the bonding surface. 220), the wire clamp control unit 230 for controlling the opening and closing of the wire clamp, the WBMS 240 for monitoring and monitoring whether the wire bonding state is a stick state or a non-stick state, an ultrasonic generator (Ultra Sonic) Generator, USG: 250), and a high voltage generator (Electro Flame-Off, EFO: 260), and a host computer 270 that controls these components via the VME BUS. In addition, the wire bonding device to which the present invention is applied includes a wire clamp amplifier, a counter, and the like with each control unit such as the component of FIG.

4 is a flowchart of a method for automatically forming a ball of a wire bonding apparatus according to an embodiment of the present invention, and not a flowchart of the entire series of wire bonding processes, but a process of automatically forming a ball after a short tail error occurs. Flowchart.

The automatic ball forming method of the wire bonding device according to the present invention includes the steps (a) of detecting whether or not a short tail error occurs when a short tail error occurs during the wire bonding process, and (b) fixing the wire not to be separated. Step 302, 304, (c) calculating the length of the tail of the wire (306), (d) determining whether the length of the tail of the wire is sufficient for ball formation (308), (e ) Performing 310 an EFO discharge.

In more detail, when the fact that the short tail error is generated is transmitted to the host computer, the wire bonding device performs the wire escape prevention operation as described in the above description of FIG. 2 to close the wire clamp (302) and A step 304 is performed in which the wire tension and air guide are closed.

The step of fixing the wire so that it does not escape is followed by the step 306 of measuring and calculating the length of the residual wire tail formed by the short tail error.

The details of step 306 are not described again because they use the method described above in the description of FIG. 2.

Once the step 306 of calculating the tail length is performed, a step 308 is made to determine if the tail length is sufficient for ball formation. Tail lengths sufficient for ball formation will have to be pre-populated into the system in advance.

If it is determined in step 308 that the ball is sufficient to form a ball despite the occurrence of a short tail error, the high voltage generator immediately performs the EFO discharge step 310 to form the ball and the next series of wires. The bonding process is performed.

However, as a result of the determination in step 308, if it is determined that the remaining wire tail is insufficient for ball formation, the EFO discharge step 310 is performed after the wire tail is pulled out by a predetermined length.

The drawing of the wire tail by a predetermined length may include (f) moving the stage and the capillary assembly in the Z-axis direction by the stage and the Z-axis control unit 220, and (g) the ultrasonic wave. Generating ultrasonic waves by the generator 250 (314), (h) determining whether the wire tails are sticky with respect to the bonding surface by detecting a change in impedance by the WBMS 240 (316), ( i) Z-side movement to the EFO height by the stage and Z-axis control unit 220.

In addition, in the step (g), the wire is moved downward through the capillary by the vibration generated by the ultrasonic wave.

If it is determined in step (h) that the wire tail is in a non-stick state rather than a stick state, the ultrasonic generator continues to operate so that the wire moves downward until it becomes a stick state.

In the following, the step of extracting the above-described wire tail by a predetermined length and the EFO discharge step will be described in more detail with reference to FIGS. 5A to 5F.

5A to 5F, an automatic ball forming method is sequentially performed when the length of the wire tail for forming the ball when the second bonding error occurs is not sufficient, using a wire bonding device basically provided with the configuration of FIG. 3. Is shown. Thus, each component of FIG. 3 is not shown separately in FIGS. 5A-5F, but only the behavior of the wire relative to the bonding portion according to the action of the respective component is shown.

5A shows a state in which a short tail error occurs and the end of the wire 106 is fixed by the wire clamp 104 in a state in which the end of the wire 106 is located inside without being exposed to the outside of the lower outlet side of the capillary 102. It is becoming. At this time, although not shown, the wire tension and the air guide are also closed to assist in preventing the wires from escaping.

According to FIG. 5B, the capillary assembly is positioned at a predetermined location designated by the operator by the stage and Z-axis control unit 220 (FIG. 3). That is, the capillary assembly is positioned on the bonding surface 210 with the wire 106 fixed.

Next, as shown in FIG. 5C, the wire clamp 104 is opened by the action of the wire clamp control unit so that the wire is released in a fixed state, and the ultrasonic generator 250 (FIG. 3) is connected to the host computer 270. In response to the command, vibration is generated using ultrasonic waves in the wire 106.

At this time, since the wire 106 vibrated by the ultrasonic generator 250 is not fixed by the wire clamp 104, the wire 106 naturally slides in the falling direction, which is the arrow direction of FIG. 5C. The end of the wire 106 is exposed to the outside of the outlet side of the capillary 102 during this process.

Referring to FIG. 5D, an end portion of the wire 106 moving in the downward direction comes into contact with the bonding surface 210 connected to the ground, thereby becoming a stick state. In this case, the change in the impedance occurs as compared with the impedance before contact by the stick state, and the WBMS 240 of FIG.

Therefore, in order to detect a change in impedance at a predetermined wire tail length, when setting the height in the Z-axis direction in FIG. 5B, the desired wire tail length is obtained when the wire contacts the bonding surface in consideration of the length of the predetermined wire tail. The stage and the Z-axis controller 220 (FIG. 3) should operate according to the previously input numerical value.

If the wire is pulled by the length of the predetermined wire tail by detecting the change in the impedance, as shown in FIG. 5E, the wire clamp 104 is closed by the wire clamp control unit (FIG. 3), and the wire is fixed. . In addition, the capillary assembly including the capillary 102 is moved by the stage and the Z-axis control unit (FIG. 3) in the upward direction in the direction of the arrow.

When the capillary 102 assembly moves up while the wire 106 is fixed by the wire clamp 104, the lifting movement is stopped when the capillary 102 assembly reaches a predetermined height to perform the EFO discharge. This process is performed in response to the signal response between the stage and Z-axis control unit 220 and the host computer 270 shown in FIG.

After the capillary assembly reaches a predetermined height at which to perform the EFO discharge, the high voltage generator 260 then exposes the wire exposed below the capillary outlet side to a predetermined length, as shown in FIG. 5F. In the tail of 106, a ball 214 is formed while the wire melts by an electric spark, and the ball maintains a round ball shape by chamfer discharge.

The ball 214 formed through this process is moved to the next primary contact surface for the wire bonding process to perform a series of wire bonding processes.

As described above, the automatic ball forming method of the wire bonding device according to the present invention has the following effects.

First, in the wire bonding process, the ball forming process can be automatically performed when an error occurs in the second bonding, which greatly reduces the labor and work time required for the wire bonding process, resulting in convenience and production efficiency (UPH, unit per). hour) is improved.

Second, in forming the ball automatically in the wire bonding process, there is no need for additional equipment, and existing wire bonding devices can be used, thereby reducing costs.                     

The best embodiments have been disclosed in the drawings and specification above. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (4)

In the automatic ball forming method of the wire bonding device to automatically form the ball when the second bonding error occurs in the wire bonding device, (a) detecting whether a short tail error has occurred; (b) securing the wires to prevent them from leaving; (c) calculating the length of the tail of the wire; (d) determining whether the length of the tail of the wire is sufficient for ball formation; And (e) a method for automatic ball forming of a wire bonding device, comprising performing an EFO discharge. The method of claim 1, further comprising: unplugging the wire tail by a predetermined length if it is determined that the length of the wire tail is insufficient for ball formation. Ball formation method. The method of claim 2, wherein the drawing of the wire tail by a predetermined length comprises: (f) moving the stage and moving the capillary assembly in the Z-axis direction; (g) generating an ultrasonic wave; (h) determining whether the wire tail is in a stick state; (i) Z-axis movement to the height of the EFO comprising the automatic ball forming method of the wire bonding device. The method of claim 3, wherein in step (g), vibration is generated in the wire by ultrasonic waves so that the wire moves downward through the capillary.

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