KR101133976B1 - Method and apparatus for 3-dimensional optical inspection - Google Patents

Abstract

A three-dimensional inspection method and a three-dimensional inspection apparatus using the same are disclosed. The three-dimensional inspection method includes the steps of inspecting a two-dimensional shape to grasp an end portion of a lead and a solder, inspecting a three-dimensional shape and grasping a contour of the solder from the end portion of the lead and the solder, And judging whether or not the solder has been found to be defective based on the outline of the solder. Therefore, it is possible to check whether the electronic element is well bonded to the pad of the printed circuit board by the solder paste.

Description

[0001] METHOD AND APPARATUS FOR 3-DIMENSIONAL OPTICAL INSPECTION [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional inspection method and a three-dimensional inspection apparatus using the same, more specifically, a three-dimensional inspection method for checking whether an electronic element is well bonded to a pad of a printed circuit board by solder paste, .

In general, many electronic products are formed by mounting various components on a printed circuit board (PCB). On the other hand, with miniaturization of electronic products, parts for forming electronic products have also been miniaturized. Accordingly, there is a possibility that defects may occur when mounting these components on a printed circuit board, Is being tested for defects.

That is, a surface mounting process (SMT) in which components are mounted on a printed circuit board includes a printing process for applying a solder paste onto a printed circuit board (PCB), a solder paste for inspecting the result of the printing process A solder paste inspection (SPI) process, a mounting process for disposing an electronic device on the solder paste applied, a pre-optical inspection process (BOI: Before Optical Inspection) for checking the result of the mounting process, A reflow process for attaching to the paste, and a post-optical inspection process (AOI: After Optical Inspection) for inspecting the result of the reflow process.

A printing process for applying a solder paste on a printed circuit board includes disposing a stencil on a printed circuit board, which is a mold plate having holes in a region corresponding to a pad region that is to be electrically contacted with the electronic device, After the paste is applied, the upper portion of the stencil is pressed by a blade and then moved, whereby a pad corresponding to the hole is formed.

Thereafter, through the solder paste inspecting process, for example, whether the solder paste is applied in the form of a pad (i.e., whether the solder paste has been applied over the entire planar shape of the hole), whether the volume of the solder paste is less than the volume of the pad (I.e., whether the solder paste has been applied to a thickness larger than the thickness of the stencil), or the like, or the like, if the volume of the solder paste is larger than the volume of the designed pad.

Thereafter, an electronic device is attached to the solder paste, a reflow process is performed, and a post-inspection process is performed to inspect the resulting product. In such post-optical inspection processes, research continues on a method for checking whether an electronic element is well bonded to a pad of a printed circuit board by solder paste.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a three dimensional inspection method for inspecting whether an electronic device is well bonded to a pad of a printed circuit board by solder paste .

Another object of the present invention is to provide a three-dimensional inspection apparatus using the inspection method.

A three-dimensional inspection method according to an exemplary embodiment of the present invention includes the steps of inspecting a two-dimensional shape to grasp an end of a lead and an end of the solder, Grasping the contour of the solder from the end of the solder, and determining whether the solder is defective with the outline of the solder.

For example, the step of determining whether the solder is defective may include: measuring a height of the solder attached to the side surface of the end of the lead from the outline of the solder; measuring a distance from the side surface of the lead to the end of the solder And determining that the ratio of the height to the distance is defective when the ratio is out of the predetermined range.

Alternatively, the step of determining whether the solder is bad may include determining a distance W from the solder end to the end side of the lead, and determining W / n (where n is a positive real number greater than one) from the end of the solder Measuring a solder height (h) at a spaced position, and determining that the ratio of the W / n and the height (h) is out of a predetermined range to be defective.

A three-dimensional inspection apparatus according to an exemplary embodiment of the present invention includes a measurement stage unit, at least one illumination unit, an image pickup unit, and a control unit. The measurement stage section supports the measurement object. The illumination unit includes a light source and a grating, and irradiates the measurement object with grating light. The image capturing unit captures a grid image reflected by the measurement object. The control unit controls the measurement stage unit, the illumination unit, and the image pickup unit, inspects the two-dimensional shape, grasps the ends of the leads and the solder, The contour of the solder is determined, and it is determined whether or not the solder is defective based on the outline of the solder.

For example, the three-dimensional inspection apparatus may further include a two-dimensional shape measurement light for irradiating the measurement object with white light to inspect the two-dimensional shape.

Such illumination for two-dimensional shape measurement can irradiate circular light around the image pickup section.

The controller calculates the height of the solder attached to the side surface of the end of the lead from the outline of the detected solder to calculate the distance from the side surface of the lead to the end of the solder, If the ratio of the height to the distance is out of the predetermined range, it can be determined as a failure.

Alternatively, the controller calculates a distance W from the end of the solder to the end side of the lead to determine whether the solder is defective, and the distance W / n (n is a positive real number greater than 1) The solder height h at the position where the solder is to be formed is calculated and if the ratio of the W / n and the height h is out of the predetermined range, it can be judged as defective.

According to the present invention, it is possible to check whether the electronic element is well bonded to the pad of the printed circuit board by the solder paste.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components 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. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms " comprising " or " comprising ", etc. are intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

In addition, a component describing a function may mean a combination of components performing the process for performing the function, and may also be represented as one component by combining the functions of the components.

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

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted as ideal or overly formal in meaning unless explicitly defined in the present 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 cross-sectional view showing a state where an electronic element is attached to a pad of a printed circuit board by solder paste. Fig. 2 is an enlarged view of part A of Fig. 1, and Fig. 3 is a plan view of Fig. 2. Fig.

1 to 3, an electronic element 1 is attached by a solder paste 40 on a printed circuit board 30 on which a pad 20 is formed. In more detail, the electronic device 1 includes a package 11 and a lid 12, and the lid 12 is attached by solder paste 40 so as to be electrically connected to the pad 20.

At this time, if the shape of the solder paste 40 is poor, the lead 12 may fall off from the pad 20. Therefore, it is necessary to measure the shape of the solder paste 40.

6 is a flowchart illustrating a three-dimensional inspection method according to an exemplary embodiment of the present invention.

Referring to FIG. 6, in the 3D inspection method according to an exemplary embodiment of the present invention, the 2D shape is first inspected to determine the ends of the leads and the solder (step S101) After determining the contour of the solder from the end of the lead and the solder (step S102), it is determined whether or not the solder is defective based on the outline of the solder (step S103).

As shown in Fig. 3, in order to grasp the end portion B of the lead and the end portion A of the solder (Step S101), a two-dimensional image is required. Since the height of the 3D inspection apparatus using the phase shift method is measured, it is not a problem when the end portion B of the lead and the end portion A of the solder can be clearly seen as in FIG. 4A, A problem may arise when the end portion B of the lead and the end portion A of the solder are not clearly distinguished. For this purpose, a two-dimensional image (e.g., a photograph) is used to clarify the end B of the lead and the end A of the solder.

Next, the contour of the solder is grasped from the end portion B of the lead and the end portion A of the solder, which are detected by checking the three-dimensional shape (Step S102).

The distance W between the end portion B of the lead and the end portion A of the solder 40 is measured and the height of the solder 40 at the end portion B of the lead H) is measured.

Thereafter, when the range of the ratio W and H, for example, the range of the value of the angle tan -1 (H / W) is within the preset value range, the solder 40 is judged to be good, The solder 40 can be grasped as defective.

On the other hand, if the H value deviates from the predetermined value range before or after the ratio of W and H is obtained, it can be grasped as a defect first. This is because, even when the range of the angle θ (tan -1 (H / W)) falls within the predetermined range, the contact between the lead 12 and the pad 20 may be poor if the H value is too small.

On the other hand, according to the solder paste, the outline of the solder 40 may have a concave case (a), a flat case (b) and a convex case (c) as shown in Fig. In this case, another criterion can be suggested.

Fig. 5 is another enlarged view of part A of Fig.

5, in order to detect defects in the concave (a), flat (b), and convex cases (c) as shown in Fig. 2, the outline of the solder 40, Measuring a distance W from the end of the solder to the end side of the lead and measuring a solder height h at a location spaced a distance W1 from the end W / n (where n is a positive real number greater than 1) , And when the ratio between the W / n and the height h is out of the predetermined range, it can be judged as defective.

7 is a block diagram of a three-dimensional inspection apparatus according to an exemplary embodiment of the present invention.

7, the three-dimensional inspection apparatus used in the three-dimensional inspection method according to the present exemplary embodiment includes a measurement stage unit 100, an image capturing unit 200, first and second illumination units 300 and 400, An image acquisition unit 500, and a control unit including a module control unit 600 and a central control unit 700.

The measurement stage unit 100 may include a stage 110 for supporting the measurement object 10 and a stage transfer unit 120 for transferring the stage 110. [ In this embodiment, as the measurement object 10 is moved by the stage 110 relative to the image capturing unit 200 and the first and second illumination units 300 and 400, the measurement object 10 10 can be changed.

The image capturing unit 200 is disposed at an upper portion of the stage 110 and receives light reflected from the measurement object 10 to measure an image of the measurement object 10. That is, the image capturing unit 200 receives the light emitted from the first and second illumination units 300 and 400 and reflected by the measurement object 10, and captures an image of the measurement object 10 do.

The image capturing unit 200 may include a camera 210, an image forming lens 220, a filter 230, and an illumination 240 for two-dimensional shape measurement. The camera 210 receives the light reflected from the measurement object 10 and captures a plane image of the measurement object 10. For example, either a CCD camera or a CMOS camera can be applied. The image-forming lens 220 is disposed below the camera 210 to image the light reflected from the measurement object 10 at the camera 210.

The filter 230 is disposed at a lower portion of the image forming lens 220 to filter the light reflected from the measurement object 10 and provide the image to the image forming lens 220. For example, And an intensity adjustment filter. The two-dimensional shape illumination light 240 is disposed below the filter 230 to provide light to the measurement object 10 in order to capture a specific image such as a two-dimensional shape of the measurement object 10 can do. Although it has been described that the two-dimensional shape measuring light 240 is a component of the image capturing unit 200 for convenience, it is natural that the two-dimensional shape measuring light 240 may be a component other than the component of the image capturing unit 200. [ This two-dimensional shape measuring light 240 is used for measuring the end portion B of the lead and the end portion A of the solder, as shown in Fig.

The illumination light 240 for two-dimensional shape measurement can illuminate a circular light around the camera 210 of the image pickup unit 200 to ensure symmetry of all directions. In the figure, the two-dimensional shape measuring illumination 240 is formed in one stage, but it may be formed of two or more stages having different diameters, and a circular lamp or a circularly arranged illumination may be used have.

The first illumination unit 300 may be disposed at an angle to the stage 110 supporting the measurement object 10 on the right side of the image sensing unit 200. The first illumination unit 300 may include a first illumination unit 310, a first grating unit 320, a first grating transfer unit 330, and a first condenser lens 340. The first illumination unit 310 is composed of an illumination source and at least one lens to generate light, and the first grating unit 320 is disposed below the first illumination unit 310, Unit 310 to the first lattice pattern light having a lattice pattern.

The first grating transfer unit 330 is connected to the first grating unit 320 and transfers the first grating unit 320. For example, the first grating transfer unit 330 may be a PZT (Piezoelectric) transfer unit or a fine linear transfer unit . The first condensing lens 340 is disposed below the first grating unit 320 to condense the first grating pattern light emitted from the first grating unit 320 into the measurement object 10.

The second illumination unit 400 may be disposed at an angle to the stage 110 supporting the measurement object 10 on the left side of the image sensing unit 200. The second illumination unit 400 may include a second illumination unit 410, a second grating unit 420, a second grating transfer unit 430, and a second condenser lens 440. Here, the second illuminating unit 400 is substantially the same as the first illuminating unit 300 described above, and thus a detailed description thereof will be omitted.

The first illumination unit 300 irradiates N first grid pattern lights with the measurement object 10 while the first grid transfer unit 330 sequentially moves the first grid unit 320 N times, The image capturing unit 200 may sequentially acquire N first pattern images by sequentially receiving the N first pattern light beams reflected from the measurement object 10. [

The second illuminating unit 400 may be configured such that the second grating transfer unit 430 sequentially moves the second grating unit 420 N times, The image capturing unit 200 may sequentially receive the N second grid pattern lights reflected from the measurement object 10 and take N second pattern images. Here, N is a positive real number, e.g., 3 or 4.

In the present embodiment, only the first and second illumination units 300 and 400 are described as an illumination device for generating the first and second grid-patterned lights, but the number of the illumination units may be three or more . That is, the grid pattern light irradiated to the measurement object 10 is irradiated in various directions, and various types of pattern images can be photographed.

For example, when three illumination units are arranged in an equilateral triangle shape around the image capturing unit 200, three grid pattern lights can be applied to the measurement object 10 in different directions, The four grid-patterned lights can be applied to the measurement object 10 in different directions when the image pickup unit 200 is arranged in a square shape with the center of the image pickup unit 200 as a center.

A grid pattern image is formed on the measurement object 10 when the grid pattern light emitted from any one of the plurality of illumination portions is irradiated onto the measurement object 10. [ At this time, the grid pattern image includes a plurality of grid patterns. In this embodiment, the interval between the grid patterns, that is, the grid pitch is defined as a measurement range (?).

Meanwhile, the measurement range (?) May have the same value regardless of the type of the grating light, but may have a different value depending on the type of the grating light. At this time, it is preferable that at least two or more of the measurement range (λ) are different from each other depending on the type of the grid pattern light. For example, the grid pattern image of the first grid pattern light generated in the first illumination unit 300 has a grid pattern of a first measurement range, and the grid pattern image of the second grid pattern light generated by the second illumination unit 400 The grid pattern image by the grid pattern light may have a grid pattern of a second measurement range different from the first measurement range.

When a grid pattern light emitted from any one of the plurality of illumination units is irradiated onto the measurement object 10, the image captured by the camera 210 has a relatively dark shadow area and a relatively bright A saturation area may be formed.

For example, when the grid pattern light is applied to the measurement object 10 in the right direction as shown in Fig. 3, generally, the saturation region is mainly formed in the right portion of the measurement object, As shown in FIG. On the other hand, as shown in FIG. 4, when the arbitrary light is applied to the measurement object 10 in the right direction from the grid pattern light in the left direction, the saturation region is generally formed mainly in the right portion of the measurement object, The region may be formed primarily in the left portion of the measurement object. Therefore, when the first illuminating unit 300 and the second illuminating unit 400 are formed at positions facing each other, such a shadow region can be removed.

The image acquisition unit 500 is electrically connected to the camera 210 of the image capturing unit 200 and acquires and stores the pattern images from the camera 210. For example, the image acquisition unit 500 includes an image system for receiving and storing the N first pattern images and the N second pattern images captured by the camera 210.

The module control unit 600 is electrically connected to the measurement stage unit 100, the image capturing unit 200, the first illuminating unit 300, and the second illuminating unit 400 to control the module. The module control unit 600 includes, for example, a lighting controller, a lattice controller, and a stage controller. The illumination controller controls the first and second illumination units 310 and 410 to generate light, and the lattice controller controls the first and second lattice transfer units 330 and 430, respectively, Thereby moving the first and second grating units 320 and 420. The stage controller may control the stage transfer unit 120 to move the stage 110 vertically and horizontally.

The central control unit 700 is electrically connected to the image acquisition unit 500 and the module control unit 600 to control the respective units. Specifically, the central control unit 700 receives the N first pattern images and the N second pattern images from the image system of the image obtaining unit 500, processes the received N first pattern images and the N second pattern images, The shape can be measured. In addition, the central control unit 700 may control the illumination controller, the lattice controller, and the stage controller of the module control unit 600, respectively. As such, the central control unit may include an image processing board, a control board, and an interface board.

Also, the control unit 500 determines whether or not it is defective by the method described above. That is, the controller 500 inspects the two-dimensional shape, grasps the ends of the leads and the solder, inspects the three-dimensional shape, grasps the contour of the solder from the edge of the lead and the solder, And determines whether or not the solder is defective based on the outline of the solder.

According to the present invention, it is possible to check whether the electronic element is well bonded to the pad of the printed circuit board by the solder paste.

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. Accordingly, the foregoing description and drawings are to be regarded as illustrative rather than limiting of the present invention.

1 is a cross-sectional view showing a state where an electronic element is attached to a pad of a printed circuit board by solder paste.

2 is an enlarged view of a portion A in Fig.

3 is a plan view of Fig.

Figs. 4A and 4B are schematic views of part A of Fig. 1 measured through a three-dimensional shape measuring apparatus. Fig.

Fig. 5 is another enlarged view of part A of Fig.

6 is a flowchart illustrating a three-dimensional inspection method according to an exemplary embodiment of the present invention.

7 is a block diagram of a three-dimensional inspection apparatus according to an exemplary embodiment of the present invention.

<Short description of main drawing number>

1: electronic device 11: package

12: lead 20: pad

30: printed circuit board 40: solder paste

10: Measurement object 100: Measurement stage

110: stage 120: stage transfer unit

200: image capturing unit 210: camera

220: image forming lens 230: filter

240: illumination for two-dimensional shape measurement 310: first illumination unit

320: first grating unit 330: first grating transfer unit

340: first condenser lens 300: first illumination unit

410: second illumination unit 420: second grating unit

430: second grating transfer unit 440: second condenser lens

400: second illuminating unit 500: image acquiring unit

600: module control unit 700: central control unit

Claims (8)

Inspecting the two-dimensional shape to grasp an end of the lead and an end of the solder; Inspecting the three-dimensional shape to grasp the edge of the lead and the contour of the solder from the edge of the solder; And And judging whether or not the solder is defective based on the detected outline of the solder, The method of claim 1, Measuring the height of the solder attached to the end side of the lead from the outline of the solder; Measuring a distance from an end side of the lead to an end of the solder; And And determining that the ratio of the height to the distance is defective when the ratio is out of the predetermined range, Wherein the step of determining whether or not the defect is determined comprises: Measuring a distance W from an end of the solder to an end side of the lead; Measuring a solder height (h) at a location spaced a distance W / n (where n is a positive real number greater than 1) from the end of the solder; And And determining that the ratio between the W / n and the height (h) is defective when the ratio is out of the predetermined range. delete delete A measurement stage for supporting a measurement object; At least one illumination unit including a light source and a grating, the illumination unit irradiating the measurement object with grating illumination; An image capturing unit for capturing a grid image reflected by the measurement object; And The shape of the lead and the end of the solder are determined by inspecting the measurement stage portion, the illumination portion, and the image capturing portion, inspecting the two-dimensional shape to determine the end portion of the lead and the end portion of the solder, And determining whether or not the solder is defective based on the outline of the detected solder, In order to determine whether or not there is a defect, Calculating the height of the solder attached to the side surface of the end of the lead from the outline of the detected solder and calculating the distance from the side surface of the end of the lead to the end of the solder, If it is judged to be defective, Calculating a distance W from an end of the solder to an end side of the lead and calculating a solder height h at a position spaced a distance W / n (n is a positive real number greater than 1) from the end of the solder, And judging that the ratio between the W / n and the height (h) is defective when the ratio is out of the predetermined range. The three-dimensional inspection apparatus according to claim 4, further comprising a two-dimensional shape measuring light for irradiating the measurement object with white light to inspect the two-dimensional shape. The three-dimensional inspection apparatus according to claim 5, wherein the illumination for two-dimensional shape measurement irradiates a circular light around the image pickup section. delete delete

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