JPH11354570A - Method and device for testing rewinding of bonding wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect obstructive hooking portion of bonding in short time without a manual operation and a material at a condition simulated to real wire bonding, and to evaluate the winding quality of a bonding wire. SOLUTION: When a spool 2 which is horizontally held is rotated, the bonding wire 1 is rewound, the bonding wire 1 which is continuously drooped laterally moves with the rotation of the spool 2 while tension force is given by gravity and the spraying of air, a sensor 3 detects it and the rotation of the spool 2 is stopped. When rotation is resumed, the degree of the hooking of the bonding wire 1 is identified and evaluated in accordance with whether the bonding wire 1 immediately and laterally moves and the sensor 3 detects it again or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the winding quality of a bonding wire wound on a spool while rewinding the bonding wire, and an apparatus therefor.

[0002]

2. Description of the Related Art A bonding wire used for connecting a semiconductor element to an external lead is supplied by being wound around a cylindrical spool. Therefore, when this bonding wire is used in a wire bonder, the bond wire pulled out by the wire bonder must be smoothly unwound from the spool.

In particular, in recent years, the length of a bonding wire wound around one spool has become longer, and the number of windings has increased in many cases. When the number of winding layers is increased as described above, unwinding is not performed smoothly due to biting or entanglement of the bonding wire, which tends to hinder wire bonding.

In order to solve this problem, when winding a bonding wire around a spool, a winding pitch, a tensile force, and the like are adjusted. However, since there is no method for evaluating the winding quality of the bonding wire wound around the spool, it has been difficult to determine appropriate winding conditions such as a winding pitch and a tensile force for each bonding wire having a different material and a different wire diameter.

[0005]

Conventionally, when evaluating the winding quality of a bonding wire, a bonding wire wound on a spool is provided to a wire bonder, and the wire is caught by rewinding while actually performing wire bonding. Alternatively, the only method was to suspend the spool so that the surface around which the bonding wire was wound was perpendicular to the ground, and to rewind by gravity while counting the number of hooks.

However, when a wire bonder is used, since bonding is actually performed, a bonding wire is consumed, and a large number of members such as a lead frame are required, which is extremely uneconomical.
In the method of unwinding the bonding wire by gravity, the conditions of actual wire bonding and unwinding are completely different, and the worker must always count the number of horizontal hooks and work to eliminate the hooks. Was.

The present invention has been made in view of such a conventional situation,
It is an object of the present invention to provide a method and an apparatus for evaluating the winding quality of a bonding wire in a short time under conditions similar to actual wire bonding without using any manpower or materials.

[0008]

In order to achieve the above object, a test method provided by the present invention is to hold a shaft of a spool around which a bonding wire is wound horizontally, and to rotate the spool to rewind the bonding wire. A method for unwinding a bonding wire that detects the lateral movement with a sensor when the downwardly moving bonding wire moves in the horizontal direction with the rotation of the spool due to catching when the downwardly moving bonding wire is caught. In the above, when the sensor detects the lateral movement of the bonding wire, the rotation of the spool is temporarily stopped, and when the spool is rotated again after a predetermined time to resume the rewinding, the lateral movement of the bonding wire is immediately detected again by the sensor. It is characterized in that the degree of snagging is identified by whether or not it is.

In this bonding wire rewind test method, in order to apply a tensile force to the unwound bonding wire, the bonding wire is suspended from the spool to a length of 200 to 1000 mm,
Preferably, air is blown laterally onto the bonding wire hanging from the spool.

[0010] A test apparatus provided by the present invention comprises: a spool rotation driving unit for rotating a spool around which a bonding wire is wound at a predetermined speed while holding a shaft horizontally;
At least one sensor disposed below the spool held by the rotation drive unit, wherein the bonding wire that is continuously unwound from the spool and hangs down and moves downward with the rotation of the spool due to catching When moved in the lateral direction, in a bonding wire rewinding test device that detects the lateral movement with a sensor, the rotation drive unit of the spool temporarily stops rotation of the spool when the sensor detects the lateral movement of the bonding wire, Having a mechanism to rotate the spool again after a predetermined time, when the spool is rotated again and rewinding is resumed, immediately identify the degree of catch by whether or not the lateral movement of the bonding wire is detected again by the sensor. It is characterized by.

[0011] The bonding wire rewinding test apparatus may be provided with an air outlet for blowing air laterally to the bonding wire hanging from the spool. Further, as a sensor for detecting the lateral movement of the bonding wire, an electric contact sensor having an electric contact, a proximity sensor, an optical sensor, or the like can be used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the winding quality is evaluated based on whether or not there is a hook while the bonding wire is unwound from the spool under conditions close to actual wire bonding. Therefore, as shown in FIG.
The bonding wire 1 is rewound from the spool 2 while rotating the spool 2 held by keeping the axis horizontal by a motor. The unwinding speed of the bonding wire 1 is preferably substantially the same as or similar to that of an actual wire bonder, for example, about 0.6 to 1 m / min.

At the same time, while applying a tensile force to the unwound bonding wire 1 in a manner similar to that of actual wire bonding, the sensor 3 detects the hooking of the bonding wire 1 that is almost stopped by the wire bonder during the unwinding. To detect. As a general means therefor, there is a method in which a continuously unwound bonding wire 1 is hung downward from a spool 2 so as to have a predetermined length, and a tensile force due to gravity is applied to the bonding wire 1.

When a tensile force is applied to the bonding wire by gravity, the length of the bonding wire hanging down from the spool, ie, the center of the axis of the spool and a receiving portion for depositing the unwound bonding wire or a winding portion for winding up. Is preferably adjusted in the range of 200 to 1000 mm. If the length or the interval is less than 200 mm, the gravity applied to the hanging bonding wire is too small, and even a very slight hook without any problem is detected. If the wire is suspended for more than 1000 mm, the gravitational force applied to the bonding wire is increased, and the problem of the actual wire bonding is eliminated. Conversely, there is a risk of digging into it.

As another method of applying a tensile force to the bonding wire, as shown in FIG. 2, air is blown from the lateral direction onto the unwound and hanging bonding wire 1 as shown in FIG. A tensile force can also be applied. In that case, the direction, flow rate, and flow rate of the air to be blown are kept constant, and the position of the receiving portion or take-up portion of the unwound bonding wire 1 is adjusted. The wire 1 is positioned within a predetermined range. By adjusting the position of the hanging portion of the bonding wire 1 in this manner, the tensile force applied to the hanging bonding wire 1 is also kept constant.

By unwinding the bonding wire 1 from the spool 2 while applying a tensile force in this way, a test can be performed under conditions similar to actual wire bonding, so that the bonding wire 1 wound on the spool 2 is practically used. If there is a problematic amount of snagging,
At that time, the bonding wire 1 moves in the lateral direction as the spool 2 rotates. The sensor 3 detects the laterally moved bonding wire 1 (shown by a dotted line in FIG. 1).

Various methods are conceivable for detecting the lateral movement of the bonding wire by the sensor. Usually, an electrical contact sensor having an electric contact is used, and the lateral movement of the bonding wire is detected by contact with the sensor. Further, a non-contact type sensor such as a proximity sensor or a light sensor can be used.

Regarding the evaluation of the winding quality of the bonding wire, when the sensor detects the lateral movement of the bonding wire as described above, the winding is evaluated as being caught and counted, and the winding quality is evaluated from the counted number in the entire length of the bonding wire. be able to. However,
For example, hooks that are resolved by the impact of the bonding wire touching the sensor or the impact of stopping the spool may not be an obstacle in actual wire bonding, so these hooks are considered as slight hooks , And can be evaluated separately.

In order to evaluate the winding quality by automatically identifying the degree of the above-mentioned catch, the rotation of the spool is temporarily stopped when the sensor detects the lateral movement of the bonding wire, and the predetermined time of about 1 to 30 seconds is set. After that, there is a method in which the spool is rotated again and the presence or absence of the catch immediately after the re-rotation is detected by a sensor. That is, when the rotation is stopped after the first detection and then the rotation is started again, the detection is not performed by the sensor if the catch is eliminated. On the other hand, when the catch is not eliminated, or when the catch is continued even if the catch is partially eliminated, the sensor is again detected immediately after the re-rotation.
Therefore, the former can be identified as lightly caught and the latter as severely caught, and can be evaluated separately. According to this method, it is possible to analyze the winding quality of the bonding wire in more detail while enabling continuous measurement.

In the case of the method of discriminating and evaluating the slight and heavy snagging, as shown in FIG. 3, a plurality of sensors 3a, 3b, 3c are installed along the direction in which the bonding wire 1 moves laterally. It is preferable to keep it. Especially when using an optical sensor or proximity sensor, the contact between the laterally moving bonding wire and the sensor does not eliminate the catch, so if one of the multiple sensors detects immediately when rotation resumes,
It is preferable to evaluate it by identifying it as severely caught.

[0021]

EXAMPLES Three types of bonding wires wound on a spool with different winding conditions were prepared, and the winding quality of the bonding wires was evaluated using the rewinding test apparatus of the present invention. That is, the spool around which the bonding wire is wound around the rotation drive unit of the test apparatus is held with the shaft being horizontal, the spool is driven to rotate, the bonding wire is rewound at a speed of 0.8 m / min, and the bonding wire is hung vertically. , And continuously received on a pan portion arranged 600 mm below the spool.

An electric contact sensor is disposed below the spool, and when a bonding wire hanging down from the spool moves laterally with rotation of the spool due to catching, the lateral movement is detected by the sensor. , The rotation of the spool was stopped, and the rotation was started again after 15 seconds. When this rotation is resumed, only if the sensor immediately re-detects the lateral movement of the bonding wire,
It was evaluated as a severe hook, and the number of times of the severe hook was counted.

According to the rewind test, the number of severe hooks, that is, the length of each bonding wire 100
The count of severe hooking per 0 m was 24 for the bonding wire under the winding condition A, 8 for the winding condition B, and 0 for the winding condition C.

Next, three bonding wires each having a length of 1000 m and wound on a spool under the same three kinds of winding conditions A to C as described above are prepared, and each of the three bonding wires is attached to an actual wire bonder. Was carried out. In this actual wire bonding, the number of stops of the wire bonder caused by the bonding failure detection function was measured.

As a result, the number of stops of the wire bonder is 47 for three bonding wires under the winding condition A.
Times, 56 times, 44 times, 32 times, 27 times, 35 times for three bonding wires of winding condition B, and 11, 13, 9 times for three bonding wires of winding condition C.

From the above, it can be seen that the evaluation of the winding quality of the bonding wire obtained by counting only the severe hooking in the rewind test of the present invention is well related to the actual number of stoppages of the wire bonder. understood.
In addition, if the evaluation of the slight hooking is also made, the reliability of the evaluation of the winding quality of the bonding wire can be further improved.

[0027]

According to the present invention, the winding quality of a bonding wire affecting wire bonding can be reduced economically in a short period of time without any manual work or material while rewinding under conditions close to actual wire bonding. Can be evaluated.

[Brief description of the drawings]

FIG. 1 is a schematic side view for explaining a basic unwinding test method of a bonding wire according to the present invention.

FIG. 2 is a schematic side view for explaining another unwinding test method of a bonding wire according to the present invention.

FIG. 3 is a schematic side view for explaining still another unwinding test method of a bonding wire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bonding wire 2 Spool 3, 3a, 3b, 3c Sensor

Claims (6)

[Claims] 1. A spool wire around which a bonding wire is wound is held horizontally, and the spool is rotated to rewind the bonding wire. The bonding wire is continuously hung down while applying a tensile force. Therefore, in the bonding wire rewind test method where the lateral movement is detected by a sensor when the lateral movement is caused by the rotation of the spool, the rotation of the spool is temporarily stopped when the sensor detects the lateral movement of the bonding wire. When the spool is rotated again after a predetermined time and rewinding is resumed, the extent of the hooking is immediately identified by whether or not the lateral movement of the bonding wire is detected again by the sensor. Test method. 2. The unwinding of the bonding wire according to claim 1, wherein a tensile force is applied to the bonding wire by dropping the bonding wire from the spool to a length of 200 to 1000 mm while rewinding the bonding wire. Test method. 3. The bonding wire according to claim 1, wherein a tensile force is applied to the bonding wire by blowing air from a lateral direction onto the bonding wire unwound from the spool and hung down. Rewind test method. 4. A spool rotation drive for rotating a spool around which a bonding wire is wound at a predetermined speed while keeping a shaft horizontal, and at least one spool disposed below the spool held by the rotation drive. A bonding wire that has a sensor and detects the lateral movement with a sensor when the bonding wire that is continuously rewound from the spool and moves downward by hanging is moved in the horizontal direction with the rotation of the spool due to catching. In the rewinding test apparatus, the rotation drive unit of the spool has a mechanism for temporarily stopping the rotation of the spool when the sensor detects the lateral movement of the bonding wire, rotating the spool again after a predetermined time, and rotating the spool again. When rewinding is resumed, the lateral movement of the bonding wire is immediately applied to the sensor. An unwinding test apparatus for a bonding wire, characterized in that the degree of snagging is identified based on whether or not re-detection is performed. 5. The apparatus according to claim 4, further comprising an air outlet for blowing air from a lateral direction to the bonding wire hanging from the spool. 6. The apparatus according to claim 4, wherein the sensor is an electrical contact sensor having an electrical contact, a proximity sensor, or an optical sensor.