JP2002124534A - Rectilinear propagation estimating equipment and method of metal thin wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce irregularity of estimation in rectilinear propagation estimation of a metal thin wire by visual observation. SOLUTION: This rectilinear propagation estimating equipment is provided with an object material holding means which suspends vertically the metal thin wire by a prescribed length from the tip, an illumination device for lighting the object material (it is preferably that light sources are arranged on both the right and left sides of the front of the object material), an imaging device for imaging the object material, and an image processing means for data- processing an imaged object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for evaluating the straightness of a thin metal wire, and more particularly to the evaluation of the straightness of a thin metal wire used as a bonding wire for connecting an IC chip electrode to an external lead when mounting a semiconductor device. Apparatus and method.

[0002]

2. Description of the Related Art At present, with the miniaturization and thinning of semiconductor devices, the performance required for thin metal wires used for mounting semiconductor devices has been increased in order to cope with narrow pitch and long loop bonding methods. Among the required performances, straightness of the thin metal wire is an important performance, and improvement of this is required.

[0003] In order to improve the straightness of the thin metal wire, a method of measuring the straightness is required. Therefore, the applicant of the present invention firstly described an apparatus and method for measuring the straightness of a thin metal wire for evaluating the straightness. It was proposed in Japanese Unexamined Patent Publication No. Hei 11-190604. The outline of the proposal will be described with reference to FIG. 1 is a windshield container, 2 is a front door, 3 is a spool around which a thin metal wire is wound, 4 is a feeding motor, 5 is a controller, 6 is a plane mirror, 7 is a hanging thin metal wire, and 8 is a transparency scale.

When the motor 4 is driven using the controller 5 and the spool 3 is rotated, the thin metal wire 7 is fed out of the spool 3 and hangs downward. Referring to FIG. 2, an image 9 of a thin metal wire reflected on a plane mirror is visually observed from a position where the thin metal wire coincides with the thin metal wire 7, and the linearity of the thin metal wire is measured using the scale 8. As information for evaluating the straightness, a great deal of information such as twist, meandering width, meandering frequency, splash width, and loop bend can be obtained.

[0005]

The use of the above-described apparatus and method for measuring the straightness of a thin metal wire by visual observation makes it possible to obtain a great deal of information on wire bending, and to detect abnormalities in the manufacturing process and improve the quality. It is now possible to obtain a certain result when making a guarantee. However, there has been a problem that the dispersion of measured values is large while using the above-mentioned measuring method.

As the causes of the variation, firstly, the material to be measured is shaken during the measurement, and secondly, since the measurement is performed by visual observation, individual differences between persons can be caused. The swing of the first material occurs because the thin metal wire is too light. Incidentally, a diameter of 2 which is a thin metal wire often used for mounting a semiconductor device.
When a 5 μm gold wire is suspended by 30 cm, the weight is 3 mg, and it is considered that the wire is lightweight and is affected by a small amount of wind from the outside and a minute wind due to convection generated by heat generated by the motor.

On the other hand, in the bending information, for example, as in the meandering width measurement, it takes 1 to 2 minutes to obtain a measurement value from the setting of the scale, so that the fluctuation of the material increases the measurement error. The present invention has been made in view of the above-described circumstances, and an object of the present invention is to measure the straightness of a thin metal wire and, in the measurement of the straightness of a thin metal wire, to evaluate the linearity of a thin metal wire that can suppress the variation of the measured value. And a method.

[0008]

In view of the above-mentioned circumstances, the present inventors have made intensive studies and as a result, photographed a state in which a thin metal wire was extended and hung downward as a still image with a camera, and further used a computer. By performing image processing, it was considered that variation in measured values could be suppressed to a small value.

[0009] However, it has not always been easy to clearly image the entire required length of the target material. It was difficult to clearly photograph the entire length of about 30 cm of a 25 μm-diameter thin metal wire from one of the above-described thin metal wires. Therefore, as a result of further study by the present inventors, it was possible to perform image processing on the entire length of the fine metal wire having the above-mentioned small diameter and a predetermined length by installing a lighting device and further devising the lighting, thereby completing the present invention. I came to.

That is, the present invention provides the following. (1) A target material holding means for hanging a thin metal wire from a tip by a predetermined length, an illumination device for illuminating the target material, and an imaging device for imaging the target material, and an image of the target material from the imaging device And an image processing means for processing the image after inputting the information.

(2) The device for evaluating straightness of a thin metal wire according to (1), wherein the lighting device has a light source in front and left and right of the target material. (3) The straight metal linearity evaluation device according to (1) or (2), wherein the image processing means has a means for correcting an unclear image portion. (4) The thin metal wire is suspended from the tip by a predetermined length, the target material is illuminated, the suspended thin metal wire is imaged by an imaging device, and the straightness of the thin metal wire is obtained based on the obtained captured image of the thin metal wire. A method for evaluating the straightness of a thin metal wire, comprising:

(5) The method for evaluating straightness of a thin metal wire according to (4), wherein the straightness of the thin metal wire is evaluated by a data processor based on the photographed image. (6) The method for evaluating straightness of a thin metal wire according to (4) or (5), wherein a light source is disposed on both the left and right sides of the hanging thin metal wire to illuminate the thin metal wire. (7) The method for evaluating straightness of a thin metal wire according to any one of (4) to (6), wherein when there is an unclear image portion in the photographed image, the portion is corrected.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION (1) Fine metal wire The fine metal wire to be evaluated in the present invention is used by winding a wire having a diameter of 10 to 100 μm mainly used for mounting a semiconductor device on a spool in a unit of 500 to 5000 m. However, this tends to be longer. Those having a diameter of about 600 μm are also used for mounting semiconductor devices. The composition is Au, Al, C
u, Sn, Pb and the like and alloys containing these as main components are used.

An object of the present invention is to objectively and accurately evaluate the straightness of a thin metal wire wound on a spool. The metal thin wire to be evaluated in the present invention basically has a property of hanging down by its own weight and becoming a straight line when unwound from a spool. Therefore, it is intended to unwind the thin metal wire from the spool, measure the straightness in a predetermined range, and evaluate the straightness of the thin metal wire wound on the spool by averaging the measured values and comprehensive evaluation. (2) Evaluation apparatus An apparatus for evaluating the straightness of a thin metal wire according to the present invention will be described with reference to the drawings.

FIG. 3 shows an example of the apparatus. 1 is a windshield container, 2 is a front door, 3 is a spool wound with a thin metal wire,
4 is a feed motor, 5 is a controller, 15 is a black alumite plate, 7 is a hanging thin metal wire, 16 is a motor fixed base, 17 is a fixed base rotating shaft, 11 is an annular illumination, 12 is an imaging device, 13 is a controller, 14 Denotes an image processing device. Target Material Holding Means The spool 3 around which the thin metal wire 7 as the target material of the present invention is wound is rotatably mounted on a spool mounting portion (not shown). The spool mounting portion may be any medium that can rotate and can fix the spool. Preferably, the spool mounting portion is a motor-driven type, and simply, the spool 3 can be mounted directly on a rotating shaft (not shown) of the motor. Good.

When the motor 4 is driven by the controller 5 and the spool 3 is rotated, the thin metal wire 7 is drawn out of the spool 3 and is suspended for a predetermined length. As shown in FIG. 3, which is the target material of the present invention, the region including the hanging thin metal wire 7 is a windshield container 1 provided with an opening / closing door 2 on the front in order to prevent the influence of wind such as movement of a person or air conditioning. It is preferable to use it by covering it.

It is preferable to change the position of the thin metal wire 7 in the circumferential direction as viewed from the front so that the straightness of the thin metal wire 7 can be more accurately grasped. Therefore, the motor 4 is fixed to the motor fixing base 16 so that the motor 4 can be rotated at a predetermined angle by using the rotating shaft 17. The position shown in FIG.
It is preferable to measure at a position rotated by 90 degrees.
When the measurement is performed while changing the circumferential position of the thin metal wire 7, a material having good straightness tends to be more easily scattered than a material having poor straightness. For this reason, when conducting a further straightness improvement test by clarifying the difference in a relatively thin straight metal wire, a means for changing the circumferential position of the thin metal wire is included in the evaluation device. Is preferred. The lighting device 11 is a lighting device that illuminates the target material. FIG. 3 shows an annular illumination device. The target material used in the present invention has a length of a suspended metal fine wire of about 30 cm, a diameter of usually 10 to 100 μm, and is used as a very fine wire.
Therefore, it is a very fine line and the aspect ratio is 3 × 10 ⁴
It is as large as 3 × 10 ⁵ .

Since the target material of the present invention is a very fine line and has a large aspect ratio, it is necessary to use a lighting device. Even in a situation where an image having a size of about several centimeters can be imaged, an image can be obtained by directly illuminating the ultrafine line and imaging the reflected light with an imaging device in the case of the aforementioned ultrafine line.
The illumination device according to the present invention refers to a special illumination for photographing a thin metal wire, separately from the illumination of a normal room. By using this special lighting device, it is possible to make the photographing of the thin metal wire by the camera with no or almost no omission. This lighting device is desirably incorporated in the evaluation device, but may be prepared separately. Further, the lighting device of the present invention is different from ordinary room lighting in that the thin metal wire is illuminated from multiple directions, and the reflected light beams from each portion of the thin metal wire enter the imaging device evenly. For this reason, a planar, annular light source is preferred for the metal wires and the imaging device.

Since the ultrafine line of the object material of the present invention is bent in an arbitrary direction, it is ideal to irradiate the light from multiple directions so that any reflected light is directed to the imaging device.
In the lighting device, if the number of light sources is one, a portion where the entire length of the ultrafine line as the target material is not captured as a still image is generated in a plurality of places. The image of the unclear portion is completed as an estimated image by the correction described later, and is used for measurement.

However, as the number of unclear portions is smaller, it is not necessary to perform the correction, and the curve formula as a reference for the correction described later becomes more accurate. Most preferably, there are no unclear portions. In order to reduce such unclear portions, it is preferable that the lighting device has a light source in front and left of the target material. Since the ultrafine line of the target material of the present invention is bent in an arbitrary direction, it is preferable that irradiation is performed from multiple directions, and a situation in which any reflected light is directed to the imaging device occurs over the entire length of the target material.

The above-mentioned front and left and right light sources may each be a single point, but it is preferable that each of the right and left light sources is more than one. It is preferable to arrange a plurality of light sources so that the entire length of the target material can be irradiated. As a specific method of arranging a light source composed of a plurality of points on the left and right, it is simple and preferable to use a linear or curved light source. Alternatively, it is preferable to perform an annular, random arrangement on the surface, since irradiation to the target material can be performed from multiple directions, so that unclear portions are reduced. If a planar or annular light source with a cavity inside is arranged at a position outside the camera angle in front of the target material, it can be illuminated from multiple directions including the left and right of the target material, even though it is a simple lighting device. It is preferable because clear parts are reduced.

Illustrative examples of the linear lighting device include a linear fluorescent tube and a lighting device in which point light sources are arranged in a straight line. Illustrative examples of the planar lighting device include a linear fluorescent tube and a point light source arranged linearly and further arranged in parallel to form a planar illumination device. An example of the annular illuminating device is an illuminating device in which an annular fluorescent tube and a point light source are arranged in an annular shape. The ring may have any shape such as a circle, an ellipse, a square, and a triangle. Further, when a linear or curved light source is used, a continuous light source such as a fluorescent tube may be used, or point light sources may be continuously arranged in a target shape. When a linear, planar, or annular illumination device is formed using a point light source, there may be some gaps.

The position of the light source may be in front of the target material, that is, on the imaging device side, but is preferably behind the imaging device, that is, on the opposite side of the target material. It is preferable to make the back surface of the target material black, since the contrast becomes clear and the degree of imaging is improved. (3) Imaging device 12 is an imaging device. A commercially available camera can be used as the imaging device. A so-called photographic film camera may be used. If necessary, it can be read and image processed by a scanner. However, electronic cameras are preferred because they can directly process image data. A so-called CCD camera may be used. For example, “3D Digital Finescope VC4500” manufactured by OMRON Corporation, “Digital HD Microscope VH-7000” manufactured by Keyence Corporation, etc. are preferably used. (4) Image processing unit 14 is an image processing unit that performs image processing on a still image captured by the imaging device. Commercially available image processing software can be used as the image processing means.

Here, the image processing will be specifically described with reference to FIG. Here, "spring width"
"Kazu Yamazu" and "meandering width" will be described. Splash width Click the lower end P1 of the thin metal wire 7 suspended from the spool 3. An intersection P2 with the thin metal wire 7 located a predetermined length (50 mm in FIG. 5) above P1 is detected. The lateral length of the circumscribed rectangle of P1 and P2 is measured and defined as the splash width. Radius of predetermined length centering on P2
mm) and the intersection P3 between the thin metal wire 7 and the arc. P2
And a straight line connecting P3 to the image is counted. As an example of the counting method, a curve expression of a thin metal wire is made, and the number of times the differential value becomes 0, P2 and P3
A method of counting the number of intersections with a straight line connecting. "Wandering width" The maximum length of a perpendicular line from the curved point of the thin metal wire to the line connecting P2 and P3 is defined as the left-side meandering width or the right-side meandering width, and the adjacent total is defined as the meandering width.

Here, the image processing means completes the still image by correcting the curve equation of the adjacent curve when the still image is not sufficiently captured and an unclear portion occurs in a part of the curve (see FIG. 4). Has a function. In this case as well, it is preferable to perform sufficient illumination so that unclear portions do not occur.

[0026]

EXAMPLE A wire with a purity of 99.99% by weight of Au was drawn to a diameter of 25 μm, annealed so as to have an elongation of 4%, a lubricant was applied to the surface, and then wound 1000 m on an aluminum spool. A sample was prepared. In this process, feed A,
Two types of sample B were prepared and used as test materials.

First, the spool is set at the position 3 shown in FIG. 3, and the motor 4 is driven to rotate the spool so that the wire 7
As shown in the illustration, and the back is a black alumite plate 1
It was set to 5. Next, the lighting device 11 is connected to the Au wire 7 and the camera 1.
It was arranged between two and outside the camera angle. FIG. 3 shows an example in which an annular light source is used as a lighting device.

Next, the camera 12 as an imaging device was set, and the gold wire 7 was imaged. Next, the still image was operated by the controller 13 and taken into the personal computer 14 as an image processing means to display the image. When a non-imaging location occurred, correction was performed using the equations of the front and rear curves to complete a continuous image of gold lines. Here, an example of a non-imaging location is shown in FIG.
FIG. 4A shows a third embodiment using the sample A, and FIG.
(2) is the situation of the non-imaging location that occurred in Example 9 described below using sample B.

Using a continuous image of Au lines, “bounce width”, “kazu no mountain”, and “meandering width” as straightness evaluation were measured.
First, the "spring width" measurement is performed by firstly arranging the gold wire tips P1 and P1 in FIG.
From position 1, the position P2 of the Au line at a vertical length of 50 mm is detected. The lateral length of the circumscribed rectangle of P1 and P2 was measured and defined as the splash width. "Kazu Yamazu" detects the intersection P3 of the arc of 220 mm in radius centered on P2 and the gold wire 7 in FIG. A straight line connecting P2 and P3 was written in the image to create a curve equation of the left and right thin metal wires, and the number of times the differential value became 0 was counted. The meandering width is defined as the leftmost meandering width or the rightmost meandering width of the perpendicular from the point on the curve of the gold wire 7 in FIG. 5 to the line connecting P2 and P3, and the maximum value of the adjacent total is meandering. Width.

In the first and seventh embodiments, one point light source is provided at the center in the longitudinal direction of the target material, and one point light source is installed on the left side. In the second and eighth embodiments, the point light source is disposed in the longitudinal direction of the target material. In the third and ninth embodiments, a total of four point light sources are installed at each of the left and right sides at a height of the upper and lower quarters in the longitudinal direction of the target material. 4 and 10 install two linear light sources with a length exceeding the target material, one each on the left and right,
5 and 11 each install one annular light source as shown in FIG. 3 in front of the target material, that is, between the imaging device and the target material.
12 is a point light source at a random position in the length direction of the target material,
A total of 10 pieces were installed, 5 pieces each on the left and right. Samples A and B having different linearity were used.

First, the sample A was extended, the tip was cut so as to hang down by about 30 cm, and the lighting device was changed at the wire position as in Examples 1 to 6, and the “splash width” and “mountain” were changed.
The “meandering width” and the number of non-imaging portions were measured. The measurement was performed ten times under the same conditions, and the average and the measurement results of the variations are shown in Table 1 as Examples 1 to 6. Then, the measurements of Examples 7 to 12 were performed in correspondence with Examples 1 to 6 except that Sample B was used instead of Sample A, and the measurement results were similarly shown in Table 1.
It was shown to.

As a conventional method, using the apparatus shown in FIG. 1 and utilizing a transparent scale plate 8 installed on the front door 2, "spring width"
The measurement was carried out visually for “Kazu Yamazu” and “meandering width.” At this time, the gold wire image 9 and the gold wire 7 shown in the plane mirror shown in FIG.
Observed from the position where. Using the samples A and B, P1, P2, and P3 were set ten times under the same conditions as in the example, and the average value and the measurement results of the variation were shown in Table 1 as Comparative Examples 1 and 2. Indicated.

[0033]

[Table 1]

(Test Results) (1) The reliability of the measured values was statistically averaged ± 1.96σ.
/ (N ^1/2 ) (where σ is the standard deviation and n is the number of measurements). Considering that n = 2 to 3 is practically used, it is understood that it is necessary that the standard deviation of the measured value be small in order to improve the reliability. (2) A comparison of the standard deviation of the spring width by visual analysis and image analysis using the sample A reveals the following from comparison between Comparative Example 1 and Examples 1 to 6.

Comparative Example 1 where the standard deviation is a visual measurement
Is 0.95 mm, whereas in Examples 1 to 6 which are image analysis, the variation is as small as 0.11 to 0.47 mm. Among the image analysis, those of Examples 2 to 6 in which the illumination devices were installed on both sides of the sample had a standard deviation of 0.11 to 0.43.
It can be seen that the variation with mm is even smaller. (3) Comparing the standard deviation of the meandering width by visual analysis and image analysis using the sample A, the following is found from the comparison between the comparative example 1 and the examples 1 to 6.

Comparative Example 1 is a standard deviation by visual measurement.
Is 0.88 mm, whereas in the case of Examples 1 to 6 which are image analysis, the variation is as small as 0.07 to 0.42 mm. Among the image analyses, those of Examples 2 to 6 in which the illumination devices were installed on both sides of the sample had a standard deviation of 0.07 to 0.39.
It can be seen that the variation with mm is even smaller. (4) A comparison of the standard deviation of the bounce width by visual analysis and image analysis using the sample B shows that Comparative Example 2 and Examples 7 to 12 were compared.
The following can be seen from the comparison of

The standard deviation is a visual measurement, Comparative Example 2
Is 0.64 mm, whereas in Examples 1 to 6 which are image analysis, the variation is small to 0.09 to 0.13 mm. In the image analysis, it can be seen that in Examples 3 to 6 in which the illuminating devices were installed at a plurality of positions on both sides of the sample, the standard deviation was 0.09 mm and the variation was further reduced. (5) Comparison of the standard deviation of the meandering width by visual analysis using sample B and image analysis shows that Comparative Example 2 and Examples 7 to 12 were compared.
The following can be seen from the comparison of

The standard deviation is a comparative example 2 which is a visual measurement.
Is 0.53 mm, whereas in the case of Examples 7 to 12, which are image analysis, the variation is as small as 0.06 to 0.13 mm. In the image analysis, in the case of Examples 9 to 12 in which the illuminating devices were installed so as to provide light sources at a plurality of locations on both sides of the sample, the standard deviation was 0.06 to 0.09 mm, and the variation was further reduced. I understand. (6) The following can be said from the above measurement results. Variations in the rectilinearity measured values such as the spring width and meandering width can be significantly suppressed by image analysis rather than by visual observation.

Among the image analysis methods, the dispersion of the straightness measurement value can be further suppressed as the illumination is made more reliable and the number of the non-imaging portions is reduced as compared with the method in which the non-imaging portions are corrected and measured.

[Brief description of the drawings]

FIG. 1 is a conventional thin metal wire straightness evaluation device.

FIG. 2 shows a visual image of a thin metal wire by the apparatus of FIG.

FIG. 3 is an example of an apparatus for evaluating the straightness of a thin metal wire according to the present invention.

FIG. 4 is an explanatory diagram of a missing portion in a captured image of a thin metal wire.

FIG. 5 is a diagram illustrating evaluation of straightness of a thin metal wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Windshield container 2 ... Front door 3 ... Spool 4 ... Feeding motor 5 ... Controller 7 ... Hanging thin metal wire 11 ... Illumination device 12 ... Imaging device 13 ... Controller 14 ... Image processing device 15 ... Black anodized plate 16 ... Motor fixed Table 17: Fixed table rotation axis

Continuation of the front page F term (reference) 2F065 AA47 BB12 DD06 DD11 FF04 GG15 GG16 GG17 HH14 JJ03 JJ26 PP11 QQ00 QQ17 QQ41 5B057 AA01 BA02 CF05 DA03 DA13 DB02 DC07 DC36 5F044 FF00

Claims (7)

[Claims] An object material holding means for suspending a thin metal wire from a tip by a predetermined length, an illuminating device for illuminating the object material, and an imaging device for imaging the object material, wherein the object material An image processing means for processing the image after the image has been input. 2. The apparatus for evaluating the straightness of a thin metal wire according to claim 1, wherein the illuminating apparatus is an illuminating apparatus having a light source in front and left and right of a target material. 3. The apparatus for evaluating straightness of a thin metal wire according to claim 1, wherein the image processing means has a means for correcting an unclear image portion. 4. A thin metal wire is suspended from a tip to a predetermined length, a target material is illuminated, an image of the suspended metal thin wire is taken by an imaging device, and the thin metal wire is straightened based on the obtained image of the thin metal wire. A method for evaluating the straightness of thin metal wires, comprising evaluating the straightness. 5. The method for evaluating the straightness of a thin metal wire according to claim 4, wherein the straightness of the thin metal wire is evaluated by a data processor based on the photographed image. 6. The method for evaluating the straightness of a thin metal wire according to claim 4, wherein a light source is disposed on both the left and right sides of the hanging thin metal wire for illumination. 7. The method for evaluating the straightness of a thin metal wire according to claim 4, wherein when there is an unclear portion in the photographed image, the portion is corrected.