JP2016070795A - Measurement method and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement method and measurement device that can accurately implement stable measurement without faulty measurements of a target object positioned below a non-target object.SOLUTION: A measurement method implements a measurement of a target object present on a reference surface 13 when a non-target object blocking a part or an entire portion of the target object in a plan view exists above the target object. The measurement method is configured to: capture a plurality of images having different focuses in height direction; generate a distance image indicative of depth information of captured objects by means of an in-focus point method from the captured images and estimate a height position of the reference surface 13; generate a measurement image in which the non-target object is not present by means of a non-focus point method from an image which is focused within a height range including at least an uppermost part from the reference surface 13 of the captured images but not including the non-target object; and measure the target object on the basis of the measurement image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a measurement method and a measurement apparatus for measuring a measurement object based on depth information reconstructed by a focusing method.

  For example, there is an apparatus for measuring a ball diameter, a ball position, and the like of a press-bonded ball when a wire is ball bonded between a semiconductor chip and a lead frame (Patent Document 1). The thing of patent document 1 changes the opening diameter of an optical means, and makes the depth of field deep or makes it shallow. In this apparatus, after setting a predetermined depth of field, the optical means is moved up and down to focus on the surface of the semiconductor chip and measure the pressure-bonded ball. This method can measure a press-bonded ball two-dimensionally, but cannot measure three-dimensionally. In other words, it cannot be measured at the height of the press-bonded ball.

  Therefore, as a method for measuring the press-bonded ball three-dimensionally, there is a method using a focusing method. In the focal method, the distance between the imaging system and the object is continuously changed (the imaging system is scanned in the z direction), and a plurality of images with different focal points are captured, and the depth information image (distance image) and the omnifocal image are captured. Generate an image. The distance image is an image expressed by brightness according to the distance from the imaging means to the imaging object, storing relative distance information at the time when the maximum focus evaluation value is detected for each pixel simultaneously with imaging. The omnifocal image is an omnifocal image obtained by acquiring a focus degree evaluation value for each local region and reconstructing a combination of focused local images. When capturing an image that is the basis of these images, it is necessary to ensure a sufficiently high vertical scanning range in consideration of variations in the thickness and posture of the bonded lead frame and the like.

  With the distance image created in this way, the height information of the imaged object can be obtained, and the omnifocal image is in focus at all the pixels. Using these distance images and omnifocal images, it is possible to perform optical measurements that cannot be performed with a normal two-dimensional image.

Japanese Patent No. 2981941

  As described above, since the focus information method reconstructs depth information based on an image captured from above, an image focused on a wire is used for reconstruction of depth information. That is, the omnifocal image is an image as shown in FIG. 4A, and the wire portion 12 extending upward from the press-bonded ball portion 11 blocks the observation view of the press-bonded ball portion 11. In this case, the depth information is a range from the chip surface 13 to the upper part of the wire portion 12 as shown in FIG. In particular, when the position of the wire portion 12 is an extremely low loop or a case where the diameter of the press-bonded ball portion 11 is small, the ball press-bonded portion 11 is connected to the wire portion 12 at a considerable area. Blocked. Further, in a case where high density bonding represented by multi-row bonding is performed, the field of view is also blocked by an adjacent wire loop.

  For this reason, the image information of the wire part 12 becomes noise for the measurement of the press-bonded ball part 11, and the effective part area for measuring the press-bonded ball height, diameter, position, etc. is minimized, and the measurement of the press-bonded ball part 11 is performed. Cannot be made with high accuracy. In some cases, erroneous measurement is performed, and inaccurate information may be output, leading to the outflow of defective products. In order to solve this, if a plurality of mechanical reciprocating operations are repeated, time is required for measurement. There is also a problem that the mechanism life is shortened.

  Therefore, in view of such circumstances, the present invention intends to provide a measurement method and a measurement apparatus that can stably measure with high accuracy without erroneously measuring a measurement object positioned below a non-measurement object. To do.

  The measurement method of the present invention measures the measurement object when there is a non-measurement object that blocks a part or all of the measurement object in plan view above the measurement object existing on the reference plane. In the measurement method to be performed, a plurality of images with different focal points in the height direction are captured, and a distance image indicating depth information of the captured object is generated from the captured images by a focusing method to estimate the position of the reference plane. Of the captured images, at least from the reference plane to the uppermost part of the measurement object, and not focused by an in-focus method from an image focused in a height range not including the non-measurement object A measurement image without an object is generated, and the measurement object is measured based on the measurement image.

  According to the measurement method of the present invention, a distance image is created from a plurality of images having different focal points in the height direction, the height position of the reference plane is extracted first, and a very small height range (reference The measurement image is created from the focused image in this height range and limited to the range from the surface to the top of the measurement object and not including the non-measurement object. Rebuild. That is, an image focused on a non-measurement object is excluded without being used for reconstruction of depth information. Thereby, a measurement image turns into an image which excluded the influence of the non-measurement target object above a measurement target object, and can extract a measurement target object. Moreover, when creating a measurement image, it is not necessary to capture the image, and the image information used in creating the distance image can be reused, and the measurement image can be created in a short processing time. it can.

  The said structure WHEREIN: The said measurement image can be made into the distance image which shows the depth information of a reference plane and a measurement target object. The measurement image may be an omnifocal image focused on the reference plane and the measurement object. Furthermore, the measurement image may be both a distance image and an omnifocal image.

  In the above-mentioned configuration, the measurement object may be a crimped ball part bonded by wire bonding, and the non-measurement object may be a wire part. Thereby, in the press-bonded ball portion, a portion blocked by the wire portion can be extracted, and the press-bonded ball portion can be measured with high accuracy.

  The said structure WHEREIN: The height from the said reference plane to the uppermost part of the said crimping | compression-bonding ball part, the diameter of the said crimping | compression-bonding ball part, and the position of the said crimping | compression-bonding ball part can be measured.

  The measurement apparatus of the present invention measures the measurement object when there is a non-measurement object that blocks a part or all of the measurement object in plan view above the measurement object on the reference plane. In the measurement device to be performed, an imaging unit that captures a plurality of images having different focal points in the height direction, and a first image generation unit that generates a distance image indicating depth information of the captured object from the captured images by a focusing method Including an estimation unit that estimates the position of the reference plane based on the distance image, and includes at least the reference plane to the top of the measurement object among the captured images, and includes the non-measurement object A second image generating means for generating a measurement image in which no non-measurement object exists by an in-focus method from an image focused in a range of heights, and measurement for measuring the measurement object based on the measurement image Means and equipment Those were.

  The said structure WHEREIN: The said 2nd image production | generation means shall produce | generate the distance image which shows the depth information of a reference plane and a measurement target object as said measurement image. In addition, the second image generation unit may generate an omnifocal image focused on the reference plane and the measurement object as the measurement image.

  In the above configuration, the measurement object may be a wire bonding bonded ball part, the non-measurement object may be a wire part, and the measuring unit may be an uppermost part of the pressure bonding ball part from the reference surface. Height, the diameter of the press-bonded ball portion, and the position of the press-bonded ball portion can be measured.

  In the present invention, the depth information excluding the influence of the non-measuring object can be acquired, and the measurement object can be extracted based on the acquired depth information. Without measuring, it is possible to stably measure with high accuracy.

It is a block diagram which shows the measuring device of this invention. It is a side view which shows the state by which the wire was ball-bonded to the chip | tip surface. (A) is a 2nd omnifocal image produced | generated by the 2nd image production | generation means of the measuring apparatus of this invention, (b) is a figure which shows depth information. (A) is a 1st omnifocal image produced | generated by the 1st image production | generation means of the measuring device of this invention, (b) is a figure which shows depth information.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  The measurement apparatus of the present invention measures a measurement object when there is a non-measurement object that blocks part or all of the measurement object in plan view above the measurement object on the reference plane. Is. In this embodiment, a case where a wire is ball bonded to a chip will be described as an example. In this case, as shown in FIG. 2, the reference surface is the chip surface 13, the measurement target is a press-bonded ball portion 11 that is press-bonded to the chip surface 13, and the non-measurement target extends from the press-bonded ball portion 11. This is a wire portion 12. The measuring device in the present embodiment measures the pressure ball height H, the diameter D of the pressure ball portion 11 (see FIG. 3), and the position of the pressure ball portion 11.

  Ball bonding is a method in which a wire (FAB) is formed by discharging to the tip of a wire to melt a metal, and then the wire is bonded by applying heat, ultrasonic waves, or pressure to the ball. For example, when a chip is fixed to a lead frame via an adhesive, and a wire is bonded on the chip, the FAB at the wire end protrudes from the capillary tip while being held by the chamfer in the capillary. . The capillary descends to the bonding position on the chip, and an impact load is applied at the bonding position, and the FAB is deformed. At this time, ultrasonic energy, load, and temperature are applied, and the FAB is further deformed according to the shape of the chamfer. At this time, the pressure ball height H is set in advance before bonding, and the ultrasonic energy, load, and temperature are determined so that the pressure ball height H after bonding becomes the set height.

  In this way, as shown in FIG. 2, the wire portion 12 is bonded to the chip surface 13 via the press-bonded ball portion 11 and the chamfer corresponding portion 14. The chamfer corresponding portion 14 is a portion of the FAB that is held by the chamfer during bonding, and has a shape corresponding to the inner diameter surface of the chamfer. The press-bonded ball portion 11 is a portion of the FAB that protrudes from the tip of the capillary during bonding, and extends in a circular shape. The height of the press-bonded ball portion 11 is from the chip surface 13 to the uppermost portion of the press-bonded ball portion 11 (that is, the boundary between the press-bonded ball portion 11 and the chamfer corresponding portion 14).

As shown in FIG. 1, the measurement apparatus of the present invention includes an imaging unit 1, a first image generation unit 2, an estimation unit 3, a second image generation unit 4, and a measurement unit 5. The imaging means 1 is composed of a CCD camera or the like. The imaging means 1 can move in the z direction (up and down direction), and continuously change the distance from the press-bonded ball portion 11 and the wire portion 12 to acquire images having different focal points in the height direction.

  The first image generating means 2, the estimating means 3, the second image generating means 4, and the measuring means 5 are provided in a computer not shown. Further, the computer includes a memory 6 for storing image data picked up by the image pickup means 1.

  The first image generating means 2 generates a distance image indicating depth information of the imaged object from the image data stored in the memory 6 by a focusing method. Here, the distance image stores relative distance information at the time when the maximum focus evaluation value is detected for each pixel at the same time as imaging, and is expressed by luminance according to the distance from the imaging means to the imaging object. It is an image and shows the depth information of the imaged object. Moreover, the 1st image generation means 2 can also produce | generate an omnifocal image as shown to Fig.4 (a) with the production | generation of a distance image. An omnifocal image is obtained by continuously changing the distance between the imaging system and the object (scanning the camera in the z direction), capturing a plurality of images with different focal points, and evaluating the degree of focus for each local region. And is reconstructed by combining local images that are in focus, and all the pixels are in focus.

  The estimation means 3 estimates the height position of the chip surface 13 based on the depth information acquired from the distance image.

  The second image generation means 4 generates a measurement image from a part of the image data stored in the memory 6. In the present embodiment, the measurement image is a distance image and an omnifocal image. That is, the second image generation means 4 generates a distance image and an omnifocal image as shown in FIG.

Based on the depth information based on the distance image generated by the second image generating unit and the omnifocal image, the measuring unit 5 measures the height H of the press-bonded ball, the diameter D of the press-bonded ball portion 11, and the size of the press-bonded ball portion 11. Measure the position.

  The measuring method of the press-bonded ball portion 11 using the measuring device of the present invention is as follows. First, the imaging unit 1 captures an image from above so that at least the press-bonded ball portion 11 that is a measurement target is in the imaging range. At this time, the image pickup means 1 is moved up and down to pick up a plurality of (for example, 100) images having different focal points in the height direction as shown in the range A of FIG. The range A extends from a position lower than the chip surface 13 to a position slightly higher than the upper portion of the wire portion 12, and 100 images with different focal points are obtained in the range A. The plurality of pieces of image data are stored in the memory 6.

  Next, the first image generating means 2 generates a distance image from the image data stored in the memory 6 by a focusing method to acquire depth information as shown in FIG. An omnifocal image as shown in (a) is generated. As shown in FIG. 4A, the all-focus image is in focus on all of the chip surface 13, the press-bonded ball portion 11, and the wire portion 12, and a part of the press-bonded ball portion 11 is a wire. It is blocked by the part 12. Further, the depth information extends from the chip surface 13 to the upper part of the wire portion 12 as shown in FIG.

  Based on the depth information of the distance image, the estimation means 3 extracts the chip surface 13 serving as a reference surface, and estimates the height position of the chip 13 surface.

  Thereafter, the second image generating means 4 includes a very small range in the height direction (from the surface of the chip 13 to the uppermost part of the press-bonded ball portion 11 and the wire portion 12 from the image data stored in the memory 6. The measurement image is created from the focused image in the height range B, limited to the range B) in FIG. 2, and the depth information is reconstructed again. That is, a distance image is generated by a focusing method using an image (for example, 10 images) in focus in a range B from about 10 μm below the chip surface 13 to the chamfer corresponding portion 14 as shown in FIG. Depth information as shown in FIG. Further, the second image generating means 4 generates an omnifocal image as shown in FIG. In the present embodiment, the range B is twice the height of the press-bonded ball set in advance before bonding.

  In the omnifocal image generated in this way, as shown in FIG. 3A, the wire portion 12 does not exist and the entire outer edge of the press-bonded ball portion 11 appears. Further, as shown in FIG. 3B, the depth information is only a part of the chamfer corresponding portion 14 from the chip surface 13.

  In this way, the image focused on the wire portion 12 is eliminated without being used for reconstruction of depth information. Thereby, the measurement image (distance image and omnifocal image) excluding the influence of the wire part 12 above the press-bonded ball part 11 can be acquired, and the press-bonded ball part 11 can be extracted. In addition, when creating a measurement image, it is not necessary to capture an image, and the image information used when creating the distance image by the first image generating means can be reused, and measurement can be performed in a short processing time. Images can be created.

  When the measurement image is generated, the measuring unit 5 determines the pressure ball height H of the pressure-bonded ball portion 11, the diameter D of the pressure-bonded ball portion 11, and the pressure-bonded ball portion 11 based on the measurement image (omnifocal image and depth information). Measure the position of.

  Since the measurement apparatus and measurement method of the present invention can acquire depth information and an omnifocal image excluding the influence of the wire portion 12 and can extract the crimp ball portion 11 based on this, the wire Without being erroneously measured, the press-bonded ball portion 11 positioned below the portion 12 can be stably measured with high accuracy.

  In the said embodiment, since the 1st image production | generation means 2 should just produce | generate a distance image at least, it may produce | generate only a distance image and may not produce | generate an omnifocal image.

  In the embodiment, the measurement image is both the distance image and the omnifocal image. However, the measurement image may be only the distance image or only the omnifocal image. That is, the second image generation unit 4 may generate only a distance image and not an omnifocal image. The second image generation unit 4 desirably generates at least a distance image, but may generate only an omnifocal image.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the measurement target is not limited to the press-bonded ball portion, and the non-measurement target. Is not limited to the wire portion. The present invention can be applied if there is a non-measurement object that blocks the measurement object above the measurement object. In this case, the non-measurement object may block a part of the measurement object or may block all of the measurement object. When the measurement object is a press-bonded ball portion, the reference surface is not limited to the chip surface, and may be a lead frame, a pad stacked on the chip, or the like. The height range for generating the measurement image is not limited to twice the height of the press-bonded ball portion set before bonding. The imaging means is not limited to a CCD camera, and various types such as a CMOS camera can be employed.

DESCRIPTION OF SYMBOLS 1 Imaging means 2 1st image generation means 3 Estimation means 4 2nd image generation means 5 Measurement means 11 Crimp ball part 12 Wire part 13 Chip surface B Range D Diameter H Crimp ball height

Claims (10)

In the measurement method for measuring the measurement object when there is a non-measurement object that blocks a part or all of the measurement object in plan view above the measurement object existing on the reference plane,
Take multiple images with different focal points in the height direction,
From the captured image, a focus image is used to generate a distance image indicating the depth information of the imaged object and estimate the position of the reference plane,
Among the captured images, a non-measurement target by an in-focus method from an image that includes at least the reference plane to the top of the measurement target and is focused in a height range that does not include the non-measurement target Generate a measurement image that does not exist,
A measurement method comprising measuring the measurement object based on the measurement image.   The measurement method according to claim 1, wherein the measurement image is a distance image indicating depth information of a reference plane and a measurement object.   The measurement method according to claim 1, wherein the measurement image is an omnifocal image focused on a reference plane and a measurement object.   The measurement method according to any one of claims 1 to 3, wherein the measurement object is a press-bonded ball part bonded by wire bonding, and the non-measurement object is a wire part.   The measuring method according to claim 4, wherein the height of the press-bonded ball from the reference surface to the uppermost portion of the press-bonded ball portion, the diameter of the press-bonded ball portion, and the position of the press-bonded ball portion are measured. In the measurement apparatus that measures the measurement object when there is a non-measurement object that blocks a part or all of the measurement object in plan view above the measurement object that exists on the reference plane,
Imaging means for imaging a plurality of images with different focal points in the height direction;
First image generation means for generating a distance image indicating depth information of the imaged object from the captured image by a focusing method;
Inference means for estimating the position of the reference surface based on the distance image;
Among the captured images, a non-measurement target by an in-focus method from an image that includes at least the reference plane to the top of the measurement target and is focused in a height range that does not include the non-measurement target Second image generation means for generating a measurement image in which no object exists;
A measurement apparatus comprising: a measurement unit that measures the measurement object based on the measurement image.   The measurement apparatus according to claim 6, wherein the second image generation unit generates a distance image indicating depth information of a reference plane and a measurement object as the measurement image.   The measurement apparatus according to claim 6, wherein the second image generation unit generates an omnifocal image focused on a reference plane and a measurement object as the measurement image.   The measurement apparatus according to claim 6, wherein the measurement object is a crimped ball part bonded by wire bonding, and the non-measurement object is a wire part.   10. The measurement according to claim 9, wherein the measuring unit measures a height from the reference surface to an uppermost portion of the press-bonded ball portion, a diameter of the press-bonded ball portion, and a position of the press-bonded ball portion. apparatus.

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