KR20120062662A - Image sensing method and system - Google Patents

Abstract

PURPOSE: A device and a method for inspecting a shape are provided to efficiently eliminate faults of a printed circuit board and to enhance the accuracy of an inspection by using brightness of a two-dimensional shape. CONSTITUTION: A method for inspecting a shape is as follows. Lattice images reflected from the measurement object containing a pad unit(121) for an electrical connection with external devices are obtained while moving a lattice as predetermined times. A confidence index with respect to the lattice images is obtained by using the lattice images. The obtained confidence index is used for inspecting scratches on a surface of the pad unit. If a range of the obtained confidence index is within a set range, the measurement object is fine. If the range of the obtained confidence index is out of the set range, the measurement object is faulty.

Description

Shape Inspection Method and Shape Inspection Device {Image Sensing Method and System}

The present invention relates to a shape inspection method and a shape inspection apparatus, and more particularly, to a shape inspection method and a shape inspection apparatus capable of simultaneously measuring two-dimensional and three-dimensional shape.

Electronic equipment has developed remarkably, and lightweight and miniaturization has been gradually progressed. Therefore, the possibility of an error occurring in the manufacturing process of these electronic equipment is increasing, and the equipment for detecting it is also being improved accordingly.

In recent years, three-dimensional shape measurement technology is not limited to the engineering field, but is expanding its application to various ranges. As a three-dimensional shape measurement technology that can satisfy the needs of these fields, in the past, there was a contact measurement method using a three-dimensional coordinate measuring machine (CMM), but active research on the non-contact three-dimensional shape measurement technology based on optical theory is in progress. It is becoming.

The three-dimensional shape measurement method using the moiré phenomenon, one of the representative non-contact measurement methods, was first proposed in 1970 by Meadows and Takasaki. Later, Yoshino proposed a projection moiré method that can enlarge the measurement area, and the limiting contact, the grating and the measuring object that the size of the grating used for the measurement, which was a disadvantage of the shadow moiré method, should be larger than the measurement object. The problem of limiting the distance between them has been solved. In addition, Kujawinska is a moiré pattern analysis method that includes three-dimensional shape information. By applying the phase shift method used for optical interference pattern analysis, the measurement resolution is remarkably improved and the measurement is not affected by the moire pattern shape. This became possible.

The three-dimensional shape measurement technology can be used for inspection of printed circuit boards, etc., various techniques have been developed to improve the accuracy of inspection.

Accordingly, the problem to be solved by the present invention is to provide a shape inspection apparatus that can measure a two-dimensional shape and a three-dimensional shape at the same time, and can improve the accuracy of the inspection.

In addition, another problem to be solved by the present invention is to provide a shape inspection method that can measure a two-dimensional shape and a three-dimensional shape at the same time, and can improve the accuracy of the inspection.

According to one or more exemplary embodiments, a shape inspection method may include: obtaining grid images reflected from a measurement object including a pad unit for moving the grid a predetermined number of times and electrically connecting the external device; Acquiring a confidence index for the grid images using the grid images, and checking the surface scratch of the pad part, and determining that the measurement object is good if the range of the obtained confidence index is within a set value range And determining that the measurement object is defective when the obtained range of the confidence index is out of a range of a set value.

In this case, the confidence index may be at least one of signal strength, visibility, and signal noise ratio.

The method may further include acquiring a two-dimensional image of the object to be measured, and even when the range of the confidence index of the pad is within a range of a set value, the luminance and the luminance of a specific area in the two-dimensional image are determined. When the difference in luminance of the peripheral portion is out of the range of the set value, the pad may be determined to be defective.

A shape inspection apparatus according to an exemplary embodiment of the present invention includes a work-stage, a projection unit, an image forming unit, and a controller. The work-stage fixes a base member including an object to be measured and an adhesive member attached to the device part and a pad part for electrical connection with an external device. The projection part includes a light source, a grating part for transmitting light emitted from the light source, and a projection lens part for forming grating image light of the grating part on a measurement target of the base member. The image forming unit receives the grating image light reflected by the measurement object of the base member. The control unit controls the work-stage, the projection unit and the imaging unit, calculates a confidence index calculated using the grid image received from the imaging unit and a phase value for the measurement object, and the measurement object is the In the case of the adhesive member, the measured object is inspected using the calculated phase value. When the object is the pad unit, the object is inspected using the confidence index.

In this case, the confidence index may be at least one of signal strength, visibility, or signal noise ratio.

According to the shape inspection apparatus according to the present invention, since the two-dimensional shape is measured by using the three-dimensional shape measurement data, wasteful elements such as the need to collect separate data for the two-dimensional shape measurement can be eliminated.

In addition, it is possible to remove defects such as a printed circuit board more efficiently by measuring data of two-dimensional and three-dimensional shapes at the same time.

In addition, the accuracy of the inspection can be further improved by using the luminance of the two-dimensional shape separately.

1 is a schematic schematic side view of a shape inspection apparatus according to an exemplary embodiment of the present invention.
Fig. 2 is a schematic plan view of a shape inspection apparatus according to another exemplary embodiment of the present invention.
3 is a plan view showing the base member shown in FIG.
4 is a schematic diagram for explaining the principle of measuring the three-dimensional image by the shape inspection apparatus according to the present invention.
5 is a view for explaining the principle of measuring the two-dimensional image by the shape inspection apparatus according to the present invention.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and that one or more other features It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art.

Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a schematic schematic side view of a shape inspection apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the shape inspection apparatus 100 according to an exemplary embodiment of the present invention may include a work stage 130, a projection unit 110, an image forming unit 150, and a controller 140. It includes. In addition, the shape inspection apparatus 100 may include a first auxiliary light source 160 and a second auxiliary light source 170.

The work-stage 130 fixes the base member 120 on which the measurement object A is formed. In addition, the work-stage 130 transfers the measurement object A in the x-axis or y-axis direction. After the work-stage 130 is controlled by the controller 140 to transfer and fix the measurement substrate 120, the first auxiliary light source 160 and the second auxiliary light source 170 may be the base member 120. The measurement object A is irradiated with light, and the entire measurement area of the base member 120 is set using the recognition mark displayed on the base member 120.

The projection unit 110 irradiates the grid image toward the measurement object (A). The plurality of projection units 110 may be installed, and the plurality of projection units 110 may be disposed to irradiate light at a predetermined angle with respect to the normal of the base member 120. In addition, the plurality of projections 110 may be arranged symmetrically with respect to the normal. Each of the projection parts 110 includes a light source 111, a grating part 112, and a projection lens part 113. For example, the projection units 110 may be symmetrical with respect to the measurement object A. FIG.

The light source 111 irradiates light toward the measurement object A.

The grid unit 112 generates a grid image by transmitting light emitted from the light source 111. The grating portion 112 includes a blocking portion (not shown) and a transmission portion (not shown). The blocking unit blocks the light irradiated from the light source 111, and the transmitting unit transmits the light. The grating portion 112 may be formed in various forms. For example, the grating part 112 may be formed by patterning a grating pattern having a blocking part and a transmitting part on a glass substrate, or may be formed using a liquid crystal display panel.

In the case of the lattice part 112 formed by patterning a lattice pattern having a blocking part and a transmission part on the glass substrate, the shape inspecting apparatus 100 includes an actuator (not shown) for finely moving the lattice part 112. Further, in the case of the grating portion 112 formed by using the liquid crystal display panel, since the shape of the grid pattern can be moved finely using the liquid crystal display panel, the shape inspection apparatus 100 requires an actuator. I never do that.

The projection lens 113 forms the grating image light of the grating part 112 on the measurement target A of the base member 120. The projection lens 113 may be formed of, for example, a plurality of lens combinations, and focuses a grid image formed through the grating part 112 to form an image on the measurement object A disposed on the base member 120. Let's do it.

The imaging unit 150 receives the grid image light reflected from the measurement target A of the base member 120. The imaging unit 150 includes, for example, a camera 151 and a light receiving lens unit 152. The grating image reflected by the measurement object A is captured by the camera 151 via the light receiving lens unit 152.

The controller 140 controls operations of the work-stage 130, the projection unit 110, and the image forming unit 150, and the confidence index and the measurement object for the grid image received from the image forming unit 150. The phase value for (A) is calculated, and the two-dimensional shape and the three-dimensional shape are measured by processing the grid image received by the imaging unit 150. The process of measuring the two-dimensional shape and the three-dimensional shape by the controller 140 will be described in detail later.

The controller 140 also inspects the measurement object using the calculated phase value and the confidence index. In this case, the phase value may be used for the three-dimensional shape of the measurement target A, and the confidence index may be used to determine whether the measurement target is defective. The confidence index may be at least one of signal strength, visibility, and signal noise ratio. Here, the signal strength will be described in Equations 14 and 15 below, the visibility is described in Equations 16 or 17, and the signal-to-noise ratio receives images to which the N-bucket algorithm is applied in the imaging unit 150. The ratio or difference between the periodic function generated through the filtering process and the actual received signal.

If the confidence index value is out of the range of the set value, the controller 140 determines the measurement object A as defective.

For example, the controller 140 may determine that the difference between the visibility () of the specific region of the shape image and the visibility () of the periphery of the shape image calculated through Equation 16 or 17 is out of the set value range. The controller 140 determines that the measurement object is defective.

In addition, any one of the first auxiliary light source 160 and the second auxiliary light source 170 may be used for measuring a two-dimensional shape. More specifically, light is irradiated to the measurement target A of the base member 120 using any one of the first auxiliary light source 160 and the second auxiliary light source 170, and the reflected light is formed in the image forming unit ( It is captured by the camera 151 of 150 to obtain a two-dimensional shape image.

In addition, even when the confidence index value is within the range of the setting value, the control unit 140 measures the measurement object A when the luminance difference of the specific region and the luminance of the peripheral portion of the two-dimensional shape image are out of the range of the setting value. ) Can be determined to be defective, and when the luminance of some regions of the entire region of the measurement target A is out of the set value range, the measurement target A can be determined as defective.

For example, even when the visibility () of the specific region calculated by Equation 16 or 17 below and the visibility () of the peripheral area are within the set value range, the first auxiliary light source 160 or the second auxiliary light source. When the difference between the luminance (or intensity) of a specific region and the luminance (intensity) of the peripheral portion is out of a range of a setting value in the two-dimensional shape image detected by the light irradiated at 170, or a portion of the entire region is set When exceeding the range of values, the control unit 140 determines the measurement object as defective.

The controller 140 sequentially inspects two-dimensional and three-dimensional shapes of the inspection regions of the base member divided into a plurality of inspection regions FOV arranged in a matrix.

Fig. 2 is a schematic plan view of a shape inspection apparatus according to another exemplary embodiment of the present invention. The shape inspection apparatus according to the present embodiment is substantially the same except for the shape inspection apparatus 100 and the projection unit shown in FIG. 1. Therefore, the same components denote the same reference numerals, and redundant descriptions are omitted.

Referring to FIG. 2, the shape inspection apparatus according to the present embodiment includes a plurality of projections 110 including a grid portion 112, and the plurality of projections 110 are arranged at positions of vertices of regular polygons. do. In FIG. 2, the plurality of projections 110 are arranged at vertices of a square, for example, but may be arranged at vertices such as a regular hexagon and a regular octagon.

When the grid image is captured only from one side, since the measurement object A is a three-dimensional shape protruding, the other side of the measurement object A may not be irradiated so that an accurate three-dimensional shape may not be measured. Therefore, by measuring again on the opposite side, a more accurate three-dimensional shape can be measured.

For example, when the measurement object A is a quadrilateral, the control unit 140 may turn on the two projection units 110 in opposite directions, and the measurement object (as determined by the control unit 140) When A) is a complicated shape, the further projection part 110 can be turned on.

3 is a plan view showing the base member shown in FIG.

2, for example, a pad part 121 and an element part 122 are formed in a base member 120 such as a printed circuit board (PCT).

The pad part 121 is an area where pads for electrical connection with the outside are formed, and the device part 122 is an area to which various elements are attached.

An element is mounted on the element part 122 through an adhesive member such as solder paste. If the shape or amount of the solder paste is incorrectly adjusted, the element may be shorted to a neighboring element, thereby causing an error. Therefore, in order to detect this, the shape or height of the solder paste is measured to determine whether the quantification. Therefore, the three-dimensional shape of the solder paste is measured.

The pad part 121 also needs to check whether there is a short circuit with an adjacent pad part. In this case, it is possible to check whether the pad portions are short-circuited by measuring the two-dimensional shape by using Equation 14 or Equation 15 below.

In addition, the surface of the pad portion (or fan-out portion 121) should be formed flat. Since the pad part 121 is an electrical connection part with the outside, even if a minute scratch occurs on the surface of the pad part 121, serious defects may result, so the surface condition inspection of the pad part is important.

To check this, if the confidence index of the specific area is out of the range of the setting value by examining the confidence index of the pad unit 121, it is determined as an error. In addition, even when the confidence index of the specific region is within the range of the set value, it is measured by two-dimensional shape measurement illumination, that is, any one of the first auxiliary light source 160 and the second auxiliary light source 170 of FIG. If the luminance of the specific region of the two-dimensional shape is out of the range of the set value of the luminance difference of the peripheral portion, it is determined that a defect such as a scratch occurred in the pad.

Meanwhile, the pad part 121 is a flat metal surface, and the value received from the camera 151 of the imaging unit 150 of FIG. 1 is saturated due to the light reflected from the pad part 121. It may happen that the value itself is not measured. On the other hand, the confidence index can be measured, and in this case, using the confidence index, the pad 121 can be inspected. In addition, the confidence index for each projection unit 110 may be used as a weight value for the height value measured by each projection unit.

The shape inspection apparatus has been described above. In the shape inspection method according to the present invention, the inspection method by the shape inspection apparatus described above is applied as it is. That is, according to the shape inspection method according to the present invention, first, the grid is moved by a predetermined number of times, and grid images reflected from the measurement object are acquired. Subsequently, the confidence index for the grid images is obtained using the grid images, and when the obtained confidence index is within a range of a setting value, the measurement object is determined to be good, and the range of the confidence index obtained is If it is out of the range of the set value, it is determined that the measurement object is bad. In this case, the two-dimensional shape image of the measurement object is further obtained, and even when the range of the confidence index of the pad is within the range of the set value, the difference between the luminance of the specific area and the luminance of the peripheral part is set in the two-dimensional shape image. If out of the range of values, the pad can be determined as bad.

Figure 4 is a schematic diagram for explaining the principle of measuring the three-dimensional and two-dimensional image of the shape inspection apparatus according to the present invention.

The intensity I of the measurement light received from the imaging unit 150 by irradiating the grating image to the base member 120 of FIG. 1 is represented by the governing equation of the moire interference fringe as shown in Equation 1 below.

In this equation, I is the intensity of the measured light, D is the signal intensity of the signal pattern (i.e. function of DC light intensity (light intensity) and reflectance of the object), and visibility is a function of reflectance and lattice period of the object. , Is the moir equivalent wavelength (function of magnification, lattice period and).

Since the intensity I of the measurement light is a function of the height h in Equation 1, the height h can be known by using the intensity I of the measurement light.

When the phase shift is measured and the intensity of the measurement light is measured in the imaging unit 150 of FIG. 1, it is represented by Equation 2 below, which is the governing equation of the moire interference fringe.

In transplantation, k is the amount of phase shift.

In order to obtain the height h by applying Equation 2, at least three shifts are required.

That is, the height (h) is to be obtained when the three-bucket algorithm that applies three shifts. First, when I ₁ is obtained by substituting 0 radians (0 degrees) into ₁ of Equation 2, it is represented by Equation 3 below.

When I ₂ is obtained by substituting 2/3 radians (120 degrees) into 2 of Equation 2, Equation 4 below is expressed.

When I ₃ is obtained by substituting 4/3 radians (240 degrees) into 2 of Equation 2, Equation 5 below is expressed.

From Equations 3 to 5, Equation 6 below can be obtained.

When the height h is obtained from Equation 6, Equation 7 below is used.

On the other hand, in the case of applying the four-bucket algorithm applying the four shifts, the height (h) will be obtained. First, when I ₁ is obtained by substituting 0 radians (0 degrees) into 1 of Equation 2, Equation 8 is expressed below.

When I ₂ is obtained by substituting 2/2 radians (90 degrees) to 2 of Equation 2, Equation 9 is expressed below.

When I ₃ is obtained by substituting radians (180 degrees) in 3 of Equation 2, Equation 10 is expressed below.

When I ₄ is obtained by substituting 3/2 radians (270 degrees) into 4 of Equation 2, Equation 11 is expressed below.

From Equations 8 to 11, the following Equation 12 can be obtained.

When the height h is obtained from the above Equation 12, it is represented by the following Equation 13.

By using the above-described equation, the three-dimensional position value is obtained by overlapping the three-dimensional shape of the object on the striped grid, and by repeating this operation by moving the image several times, the three-dimensional overall shape is obtained. Can be.

5 is a view for explaining the principle of measuring the two-dimensional image by the shape inspection apparatus according to the present invention.

5 are graphs of I ₁ I ₂ , I _3, and I ₄ of Equations 8, 9, 10, and 11.

If the arithmetic mean value I _ave of I ₁ I ₂ , I ₃ and I ₄ is obtained, it is described by Equation 14 below.

Therefore, the effects of the lattice pattern cancel each other out so that the two-dimensional shape can be measured.

Even for the three-bucket algorithm, I ₁ I _{2 in} Equations 3, 4, and 5 And the arithmetic mean value I _ave of I ₃ are given by Equation 15 below.

On the other hand, the visibility in Equation 2 is expressed as Equation 16 below using Equations 3, 4, 5, and 15 in the case of the 3-bucket algorithm.

Also, in the case of the four-bucket algorithm, using Equations 8, 9, 10, 11, and 14 is expressed as Equation 17 below.

According to the present invention, since the two-dimensional shape is measured by using the three-dimensional shape measurement data, wasteful elements such as needing to collect separate data for the two-dimensional shape measurement can be removed.

In addition, it is possible to remove defects such as a printed circuit board more efficiently by measuring data of two-dimensional and three-dimensional shapes at the same time.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the above description and the drawings below should be construed as illustrating the present invention, not limiting the technical spirit of the present invention.

100: shape inspection device 110: projection unit
111: light source 112: grid portion
113: projection lens portion 120: base member
121: pad region 121: element region
130: work-stage 140: control unit
150: image forming unit 151: camera
152: light receiving lens unit 160: a first auxiliary light source
170: second auxiliary light source

Claims (7)

Moving the grating a predetermined number of times and obtaining grating images reflected from a measurement object including a pad unit for electrical connection with an external device;
Obtaining a confidence index for the grid images using the grid images; And
In order to inspect the surface scratches of the pad part, the measurement object is judged to be good when the obtained confidence index is in the range of the set value, and the measurement when the obtained confidence index is out of the range of the set value. Shape inspection method for the measurement object comprising the step of determining that the object is defective. The method of claim 1,
The confidence index is a shape inspection method, characterized in that at least one or more of the signal strength, visibility and signal noise ratio (Signal Noise Ratio). The method of claim 1,
Obtaining a two-dimensional shape image of the measurement object;
Even when the range of the confidence index of the pad is within the range of the setting value, when the difference between the luminance of the specific area and the luminance of the peripheral portion of the two-dimensional image is outside the range of the setting value, the pad is determined to be defective. Shape inspection method characterized by. A work stage for fixing a base member including an object to be measured and a measurement object provided with a pad part for electrical connection with an external device;
A projection unit including a light source, a grating part for transmitting light emitted from the light source, and a projection lens part for forming grating image light of the grating part on a measurement object of the base member;
An imaging unit configured to receive the grid image light reflected from the measurement target of the base member; And
The workpiece-stage, the projection unit, and the image forming unit are controlled, a confidence index calculated using the grid image received from the image forming unit and a phase value for the measurement object are calculated, and the measurement object is the adhesive member. And a control unit for inspecting the measured object using the calculated index value and inspecting the measured object using the confidence index when the measured object is the pad unit. The method of claim 4, wherein
And the confidence index is at least one of signal strength, visibility, or signal noise ratio. The method of claim 4, wherein
And when the confidence index for the pad is out of a range of a set value, the controller determines the pad as bad. The method of claim 4, wherein
Further comprising an auxiliary light source for measuring the two-dimensional shape of the measurement object of the base member,
Even when the confidence index of the pad is determined to be normal, when the difference between the luminance of the specific region and the luminance of the peripheral portion of the two-dimensional shape image detected by the light irradiated from the auxiliary light source is outside the range of the set value, the controller measures the measurement. An inspection apparatus characterized by determining that an object is defective.

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