KR101684244B1 - Board inspection method - Google Patents

Abstract

In order to inspect the substrate, first, a transparent layer having an opening is formed, and light is irradiated to a substrate on which an object to be measured is formed to obtain measurement data. Subsequently, the region of the measurement object is extracted from the measurement data, and the base region for the measurement object is extracted from the measurement data. Then, the height of the measurement object is obtained based on the measurement data of the area of the measurement object and the base area, and the height measurement offset by the transparent layer is obtained. Then, a height map of the measurement object is obtained based on the height measurement offset and the height of the measurement object. Accordingly, even when the transparent layer is formed, the measurement object can be measured more accurately, and it is possible to more accurately determine whether or not the substrate is defective.

Description

[0001] BOARD INSPECTION METHOD [

The present invention relates to a substrate inspection method, and more particularly, to a substrate inspection method capable of more accurately measuring a measurement object.

In general, at least one printed circuit board (PCB) is provided in an electronic device, and various circuit elements such as a circuit pattern, a connection pad portion, a driving chip electrically connected to the connection pad portion, Respectively.

In general, a shape measuring device is used to check whether various circuit elements as described above are properly formed or formed on the printed circuit board. In order to inspect whether the circuit elements can be properly formed on the printed circuit board, the shape measuring device can be used to check whether an appropriate amount of solder has been applied before the circuit elements are mounted on the printed circuit board.

Therefore, a substrate inspection method capable of accurately measuring the amount of solder is required.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a substrate inspection method capable of more accurately determining whether a substrate on which the measurement object is formed is more accurately measured even when a transparent layer is formed

In order to inspect a substrate according to an exemplary embodiment of the present invention, first, a transparent layer having an opening is formed, and measurement data is acquired by irradiating light onto a substrate on which the measurement object is formed. Then, the region of the measurement object is extracted from the measurement data. Next, a base region for the measurement object is extracted from the measurement data. Then, the height of the measurement object is acquired based on the measurement data of the area of the measurement object and the base area. Next, a height measurement offset by the transparent layer is obtained. Then, a height map of the measurement object is obtained based on the height measurement offset and the height of the measurement object.

According to the present invention, even when the transparent layer is formed around the measurement object, the height map of the measurement object can be obtained by measuring the offset by the transparent layer.

Further, even when the measurement object and the transparent layer are formed at the same height, the height map of the measurement object can be obtained.

In addition, the solder region on which the solder is formed on the substrate is extracted, and the base region adjacent to the solder region is extracted for each channel. In the case where the reference height of the extracted base region is different for each channel, And more accurately obtain the height map of the solder region.

As a result, the amount of solder can be more accurately measured, and it is possible to more accurately determine whether or not the printed circuit board is defective.

1 is a conceptual diagram showing a three-dimensional shape measuring apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a method of inspecting a substrate according to an embodiment of the present invention.
3 is a cross-sectional view showing an example of a substrate on which a measurement object to which the substrate inspection method of FIG. 2 is applied is formed.
4 is a plan view of the substrate of Fig.
FIG. 5 is a flowchart illustrating an embodiment of extracting a solder region in FIG. 2. FIG.
FIG. 6 is a flowchart illustrating an embodiment of extracting a base region in FIG.

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 "having ", and the like, 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, elements, parts, or combinations thereof.

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.

First, for understanding of the present invention, an example of a method of measuring a three-dimensional shape by a phase shift method using a moire pattern will be briefly described.

In a phase shift method using a moiré pattern, a grid pattern image is irradiated onto a measurement object, and a three-dimensional shape is measured by observing a lattice image reflected from the measurement object.

Assuming that each position of the surface of the substrate is an xy plane, the intensity of light corresponding to each x, y coordinate value can be expressed by the following equation (1).

I is the intensity of the measurement light, D is the DC light intensity (a function of the illumination light intensity and the reflectance of the object), and? Is the visibility (the reflectivity of the object and the function of the grating period). For example, for a 4-ary bucket algorithm, the subscripts may have 1, 2, 3, and 4, with 0 degrees (when the phase is unchanged), 90 degrees, 180 degrees, and 270 degrees It shows when to change.

From the implantation, equation (2) can be obtained.

On the other hand, the phase? And the height h are proportional to each other as shown in the following Equation (3).

Here,? Is a moire equivalent wavelength.

After the lattice pattern light is irradiated onto the object using the above described equations, a phase value (?) Corresponding to each x, y coordinate value is obtained, and the height corresponding to the x, y coordinate value (h) can be obtained, whereby a three-dimensional shape of the measurement object can be obtained.

1 is a conceptual diagram showing a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

1, the three-dimensional shape measuring apparatus used in the three-dimensional shape measuring method according to the present embodiment includes a measuring stage unit 100, an image capturing unit 200, first and second illuminating devices 300 and 400, A second illumination unit 450, an image acquisition unit 500, a module control unit 600, and a central control unit 700. The first illumination unit 450 includes a first illumination unit,

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 devices 300 and 400, the measurement object 10 ) Can be changed.

The image capturing unit 200 is disposed above 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 illuminating device 300 and the second illuminating device 400 and reflected by the measuring object 10, The plane image is photographed.

The image capturing unit 200 may include a camera 210, an image forming lens 220, a filter 230, and a circular lamp 240. The camera 210 receives the light reflected from the measurement object 10 and captures a plane image of the measurement object 10. For example, any one of a CCD camera and a CMOS camera may be employed. 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 circular lamp 240 may be 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.

The first illumination device 300 may be disposed at an oblique angle with respect to the stage 110 that supports the measurement object 10 on the right side of the image sensing unit 200, for example. The first illumination device 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 to transfer 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 Can be adopted. 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 device 400 may be disposed at an oblique angle with respect to the stage 110 supporting the measurement object 10 on the left side of the image sensing unit 200, for example. The second illumination device 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. Since the second illuminating device 400 is substantially the same as the first illuminating device 300 described above, detailed description will be omitted.

The first illumination device 300 irradiates N first grid pattern lights to 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 device 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 natural number, for example, 3 or 4.

In the present embodiment, only the first and second illuminating devices 300 and 400 are described as an illuminating device for generating the first and second lattice pattern lights, but the number of the illuminating devices 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 devices 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, and four When the illumination devices are arranged in a square shape around the image pickup part 200, four grid-shaped lights can be applied to the measurement object 10 in different directions. In addition, the first illuminating unit may include eight illuminating units. In this case, the first illuminating unit may illuminate the grating pattern light in eight directions to photograph the image.

The second illumination unit 450 irradiates the measurement object 10 with light for acquiring a two-dimensional image of the measurement object 10. In one embodiment, the second illumination portion 450 may include red illumination 452, green illumination 454, and blue illumination 456. For example, the red illumination 452, the green illumination 454, and the blue illumination 456 are arranged in a circular pattern on the upper side of the measurement object 10 to form red light, green light, Blue light may be irradiated, and they may be formed to have different heights as shown in FIG.

The image acquisition unit 500 is electrically connected to the camera 210 of the image capturing unit 200 and acquires and stores pattern images of the first illumination unit from the camera 210. [ In addition, the image acquisition unit 500 acquires and stores two-dimensional images by the second illumination unit 450 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 generates light by controlling the first and second illumination units 310 and 410, respectively, and the lattice controller controls the first and second grating transfer units 330 and 430, respectively, And moves the 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.

Hereinafter, a method of inspecting a predetermined element on a printed circuit board employed as the measurement object 10 using the above-described three-dimensional shape measuring apparatus will be described in more detail.

3 is a cross-sectional view showing an example of a substrate on which a measurement object to which the substrate inspection method of FIG. 2 is applied is formed, FIG. 4 is a cross-sectional view of the substrate inspection method of FIG. 3, Fig.

Referring to FIGS. 2 to 4, in order to inspect an object to be accurately measured according to an embodiment of the present invention, light is first irradiated onto a predetermined inspection area IA of a substrate on which a measurement object is formed, And acquires measurement data. 3, the measurement object may be a solder 950, and the substrate may be a printed circuit board (PCB) 900.

In one embodiment, grid data may be obtained by illuminating the substrate with grid pattern light for each of the M channels corresponding to the M directions and receiving the grid pattern light reflected from the substrate 900 (S110). Here, M is a natural number of 2 or more.

Alternatively, the second illumination unit 450 shown in FIG. 1 may be used to illuminate the substrate and receive light reflected from the substrate to obtain measurement data. At this time, the color and angle of the second illumination unit 450 may be differently irradiated to irradiate light.

In one embodiment, the printed circuit board 900 includes a base substrate 910, a conductive layer 920, a solder resist 930, and a transparent layer 940. The conductive layer 920, the solder resist 930, and the transparent layer 940 are sequentially stacked on the base substrate 910. The solder resist 930 and the transparent layer 940 are opened to expose at least a part of the conductive layer 920. Solder 950 is formed in the open space. The transparent layer 940 may be a mask for applying the solder 950, for example.

In one embodiment, the measurement data may be obtained by irradiating N grid patterns for each channel. At this time, N is a natural number of 2 or more, for example, N may be 4. Accordingly, the height data and the three-dimensional shape in the inspection area can be acquired for each channel by using, for example, N ?? Bucket algorithm with the obtained measurement data. The measurement data may be, for example, an image of the inspection area IA.

Subsequently, a solder region in which the solder 950 corresponding to the measurement object is formed is extracted from the measurement data (S120).

The solder region can be extracted from the measurement data by various methods. For example, the solder region can be extracted using at least one of a two-dimensional image, a three-dimensional image, and a measurement height.

FIG. 5 is a flowchart illustrating an embodiment of extracting a solder region in FIG. 2. FIG.

Referring to FIG. 5, in order to extract the solder region where the solder 950 is formed, an image obtained by measuring the inspection area IA is used.

First, a maximum value is extracted for each channel among N measurement data corresponding to the N grid pattern lights acquired for each channel (S122).

When the N number of grating light beams are reflected on the inspection area IA and are received by the camera, the intensity of the received light is different depending on the N times of the grating formed with the grating light. When using the maximum value of the intensity of light, all data that can be read out from the measured image can be utilized. That is, when generating an image in which a grid pattern is removed using N measurement data, for example, When a two-dimensional plane image is generated by averaging the measurement data, an area outside the usable effective gradation range may occur. However, when the maximum value of the light intensity is used, it is possible to utilize the data in the effective gradation range even in the area outside the effective gradation range as described above.

Then, the minimum value among the maximum values for each channel is extracted (S124).

The measurement data of each channel may generate noise such as a shadow area or a saturation area (saturation area) depending on an angle and direction of the illumination unit corresponding to each channel. When the maximum value is extracted for each channel among the N measurement data as described above, the saturation region in each channel may be different for each channel. Therefore, when extracting the minimum value among the maximum values for each channel, it is possible to remove the saturation region, which is different in each channel, with noise.

Specifically, when extracting the maximum value for each channel among the N measurement data as described above, the saturation region may be largely included as noise due to the selection of the maximum value. Since the saturation region may be formed differently for each channel, when the minimum value among the maximum values for each channel is extracted, such saturation region can be effectively removed.

Alternatively, the saturation region may be removed first as noise in each of the channel images, and an image may be synthesized by selecting an average or maximum value for each channel. In this case, as described above in step S122, it is possible to prevent the data of some areas out of the effective tone range from being discarded as noise. At this time, the process of removing the saturation region from the saturation region with noise may be performed, for example, in the step S122 of extracting the maximum value or the step of generating the averaged image per channel.

Next, the solder region is finally extracted in the inspection region using the minimum value (S126).

2 to 4, a base region for the solder 950 is extracted from the measurement data (S130).

The base region is a region located around the solder 950 and means an area separated from the solder region.

The base region may be extracted in various ways, for example, the remaining region of the inspection region IA except for the solder region.

Alternatively, the base region can be extracted by removing noise for accurate height measurement.

In one embodiment, the base region may be extracted differently for each channel, and the height of the base region may be obtained for each channel. Accordingly, it is possible to more accurately obtain the relative height of the solder region by using the height of each channel of the base region in the process described below.

FIG. 6 is a flowchart illustrating an embodiment of extracting a base region in FIG.

Referring to FIG. 6, the solder region is excluded from the measurement data for each channel (S132).

The solder area is the same as the solder area extracted in step S120 of extracting the preceding solder area.

In this embodiment, the operation of removing the solder region from the measurement data is performed independently for each channel.

Subsequently, the noise region is excluded from the measurement data for each channel (S134).

A noise region other than the solder region may be excluded for each channel in order to extract the base region which is a premise of obtaining the accurate height of the base region. In addition, the noise region may include an area that is recognized as abnormal in the measurement data, for example, a region photographed brighter than the surrounding area.

The operation of excluding the noise region from the measurement data is performed independently for each channel.

In this manner, the operation of excluding the noise region (S134) may be performed after the operation (S132) in which the solder region is excluded from the measurement data. Alternatively, the noise region may be first excluded from the measurement data, and then the solder region may be excluded later.

Next, a region excluding the solder region and the noise region for each channel is set as a base region for each channel (S136).

Accordingly, the height of the base region can be obtained relatively accurately for each channel.

2 to 4, the height of the solder is obtained based on the measurement data of the solder region and the base region (S140).

After the solder region and the base region are extracted, the height of the solder region relative to the base region may be obtained.

In one embodiment, the height of the solder may be obtained as follows.

First, the height of the solder region is calculated from the measurement data of the solder region, and the height of the base region is calculated from the measurement data of the base region.

At this time, the base region may be extracted for each channel.

In one embodiment, the height of the base region is calculated for each channel from measurement data for each channel corresponding to the base region extracted for each channel.

Since the base region is independently obtained for each channel, the height of the base region can be obtained by using measurement data of the base region for each channel. When the base area is independently set for each channel and the height of the base area is calculated for each channel as described above, the height of the base area can be relatively constant and accurately displayed.

Next, the height of the base region calculated for each channel is set as a reference height for each channel of the base region.

After the height of the base region is calculated, the relative height of the object to be measured with respect to the height of the base region is obtained.

In order to display the height of each channel obtained from the measurement data with reference to a predetermined reference, for example, the upper surface of the solder resist 930, . Accordingly, the height of the solder relative to the base region can be indicated.

Then, the relative heights of the obtained solder for each channel are merged.

Since the height of each channel is obtained by the number of the channels, the height obtained by combining the height of each channel is calculated. In one embodiment, when the number of channels is four, the merged height may be an average of the heights of the four channels. Alternatively, the merged heights may be obtained by averaging the heights of the two channels excluding the maximum value and the minimum value among the heights of the four channels.

Referring to FIGS. 2 to 4, a height measurement offset by the transparent layer is obtained (S150).

The height extracted from the measurement data may be shifted by a predetermined value according to the characteristics of the transparent layer 940. The transparent layer 940 is made of a transparent material having a predetermined transparency, and the measured height may be changed according to the reflection characteristic of the transparent material. That is, the measurement height may vary depending on the degree of transmission of light through the transparent layer 940 having transparency. Thus, it is possible to obtain the height measurement offset and subtract the height measurement offset from the height measured in the above process, thereby obtaining the height map of the solder described later. 3, the height measurement offset is represented by 'OS'. Next, a height map of the solder 950 is obtained based on the height measurement offset and the height of the solder 950 S160).

A height map of the solder 950 can be obtained by representing the height of the measured solder 950 by subtracting the height measurement offset with respect to each point of the solder region

As described above, since the transparent layer 940 has a predetermined transparency, a value smaller than the actual height of the transparent layer 940 is measured by transparency, not the actual height of the transparent layer 940, Since it is not transmitted, a value larger than 0 is measured. Therefore, in order to calculate the height when the transparent layer 940 is absent, the height variation measured by the transparency layer 940 may be compensated by subtracting the height value measured according to the transparency of the transparent layer 940 with an offset. The height measurement offset may be obtained by measurement in this step, but may be preset by experiment, calculation, or the like.

 For example, as shown in FIG. 3, the solder resist 930 and the transparent layer 940 may be formed with a stepped portion so that a part of the solder resist 930 is exposed. That is, the openings formed in the solder resist 930 and the openings formed in the transparent layer 940 do not coincide with each other, and a certain portion of the solder resist 930 may be exposed. Therefore, the height measurement offset can be determined by measuring the relative height of the solder resist 930 and the transparent layer 940 corresponding to the stepped portion. On the other hand, the transparent layer 940 may have a uniform thickness in the inspection area IA to more accurately determine the height measurement offset.

The height measurement offset may be determined by an offset determiner, and the offset determiner may include at least one of material and thickness of the transparent layer 940, for example.

Since the height measurement offset may vary depending on the material and the thickness of the transparent layer 940, the height of the base region where the transparent layer 940 is applied may be measured using reliable measurement data from which noises have been removed , It is possible to obtain a more accurate height of the solder 950.

Since the height of the solder region and the height of the base region are determined in advance by dividing the regions, the height of the base region and the height of the measured solder region are not different from each other, The height of the solder region can be determined by applying a measurement offset. That is, when the measurement is performed without setting the area division and height measurement offset, there is no height difference between the measured height of the base region and the solder region. However, when the height measurement offset is applied, Can be measured. At this time, the height of the solder region is equal to the height of the height measurement offset.

When the height map of the solder region is obtained in this way, the amount of solder can be calculated, and it is possible to determine whether the printed circuit board 900 is defective by checking whether the amount of the solder is within the permissible range.

According to the present invention, even when the transparent layer is formed around the measurement object, the height map of the measurement object can be obtained by measuring the offset by the transparent layer.

Further, even when the measurement object and the transparent layer are formed at the same height, the height map of the measurement object can be obtained.

In addition, the solder region on which the solder is formed on the substrate is extracted, and the base region adjacent to the solder region is extracted for each channel. In the case where the reference height of the extracted base region is different for each channel, And more accurately obtain the height map of the solder region.

As a result, the amount of solder can be more accurately measured, and it is possible to more accurately determine whether or not the printed circuit board is defective.

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.

100: measurement stage unit 200:
210: camera 300: first illuminator
400: Second illuminator 450: Second illuminator
500: image acquisition unit 600: module control unit
700: central control unit 900: printed circuit board
910: base substrate 920: conductive layer
930: solder resist 940: transparent layer
IA: Inspection area

Claims (11)

Forming a transparent layer having an opening, irradiating a substrate on which an object to be measured is formed with light to obtain measurement data;
Extracting an area of the measurement object from the measurement data;
Extracting a base region for the measurement object from the measurement data;
Obtaining a height of the measurement object based on measurement data of the area of the measurement object and the base area;
Obtaining a height measurement offset by the transparent layer; And
And obtaining a height map of the measurement object based on the height measurement offset and the height of the measurement object. The method according to claim 1,
Wherein the height measurement offset is determined by an offset determiner comprising at least one of a material and a thickness of the transparent layer. 2. The method of claim 1, wherein irradiating the substrate with light to obtain measurement data comprises:
Irradiating the substrate with at least two grid pattern light beams for each of at least one channel corresponding to at least one direction; And
And receiving the grid pattern light reflected from the substrate to obtain the measurement data. The method of claim 3,
Wherein the step of extracting the region of the measurement object from the measurement data comprises:
Extracting a maximum value for each channel among two or more measurement data corresponding to the two or more grid pattern lights obtained for each channel;
Extracting a minimum value among the maximum values for each channel; And
And extracting a region of the measurement object in the inspection region using the minimum value. The method of claim 3,
The step of extracting the base region for the measurement object from the measurement data includes:
Removing a region of the measurement object from the measurement data for each channel;
Removing a noise region from the measurement data for each channel;
And setting a region of the measurement object and a region excluding the noise region for each channel as a base region for each channel.

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