WO2013129828A1

WO2013129828A1 - Substrate inspection method

Info

Publication number: WO2013129828A1
Application number: PCT/KR2013/001560
Authority: WO
Inventors: 유희욱
Original assignee: 주식회사 고영테크놀러지
Priority date: 2012-02-27
Filing date: 2013-02-27
Publication date: 2013-09-06

Abstract

The method for inspecting a substrate comprises: first setting a measurement region on a substrate; acquiring reference data for the measurement region; acquiring an infrared image, which is measured data for the measurement region, by irradiating the measurement region with infrared rays; extracting at least one feature object within the measurement region; acquiring the amount of distortion by comparing the measured data with reference data corresponding to the feature object; and setting an inspection region within the measurement region by compensating for the amount of distortion. Accordingly, an accurate inspection region in which distortion has been compensated for can be set.

Description

Board inspection method

The present invention relates to a substrate inspection method, and more particularly, to a substrate inspection method capable of setting an accurate inspection area.

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 part, and a driving chip electrically connected to the connection pad part are provided on the printed circuit board. Are mounted.

In general, a shape measuring device is used to confirm that the various circuit elements as described above are properly formed or disposed on the printed circuit board.

The conventional shape measuring apparatus sets a predetermined inspection area to check whether a predetermined circuit element is properly formed in the inspection area. In the conventional inspection area setting method, the area where a circuit element should exist is simply set as the inspection area in theory.

The inspection area must be set correctly at the desired location to measure the circuit elements that require measurement.However, the measurement object such as a printed circuit board may have distortion such as warp and distortion of the base substrate. Since it may occur, the conventional inspection area may not be accurately set at a desired position for measurement, and an image acquired by a camera of a photographing unit may theoretically have a certain difference from a position where a circuit element exists. Therefore, a need has been made for setting an inspection area that adequately compensates for the distortion of the measurement object as described above.

Conventionally, in order to set an inspection area that properly compensates for the distortion of a measurement object, an attempt has been made to set an accurate inspection area by obtaining and comparing and compensating reference data and measurement data for a measurement area set on a substrate. When measuring an object, the feature object as a reference may not be extracted correctly.

Therefore, there is a need for a substrate inspection method capable of accurately extracting feature objects.

Accordingly, the problem to be solved by the present invention is to obtain accurate measurement data when the feature objects are not extracted correctly, when using a figure pattern including a circular pattern as the feature object and when pattern recognition is difficult due to the color of the substrate It is possible to provide a substrate inspection method that can set the inspection area more accurately accordingly.

In order to inspect a substrate according to an exemplary embodiment of the present invention, a measurement area is first set on the substrate. Subsequently, reference data for the measurement area is obtained. Next, the infrared ray is irradiated to the measurement area to obtain an infrared image which is measurement data for the measurement area. Subsequently, at least one feature object is extracted in the measurement area. Next, the amount of distortion is obtained by comparing the measurement data with the reference data corresponding to the feature object. Subsequently, the inspection area in the measurement area is set by compensating for the distortion amount.

For example, the feature object may include at least one of a figure pattern including a curved pattern and a circular pattern.

In an embodiment, the feature object may be extracted in units of blocks to include a predetermined shape in the measurement area.

The predetermined shape included in the block may have a two-dimensional separator so that the possibility of mistaken by the surrounding shape is eliminated.

In one embodiment, the amount of distortion may be obtained by a quantified conversion formula between the reference data and the measurement data corresponding to the feature object, the quantified conversion formula, the reference data for the comparison block And may be defined using at least one of a position change, a tilt change, a size change, and a degree of deformation obtained by comparing the measurement data.

In one embodiment, the substrate may be a black printed circuit board.

In one embodiment, the measurement area may be set in plural, and whether infrared light for generating the infrared light is required before irradiating the infrared light to the measurement area to obtain an infrared image as measurement data for the measurement area. Can be determined. In this case, the infrared image may be acquired with respect to the measurement area determined to be necessary among the plurality of measurement areas.

The substrate inspection method may further include obtaining RGB images, which are measurement data of the measurement area, by irradiating RGB illumination to the measurement area.

In addition, the measurement area may be set in plural, and either one of the infrared image and the RGB image may be selectively acquired or all of each of the plurality of measurement areas.

In an embodiment, the extracting of the feature object may include: fitting a specific object in the measurement data; matching the fitted specific object with an object in the reference data; And extracting a matched object as the feature object according to the matching result.

According to the present invention, after obtaining the reference data and the measurement data for the measurement area set on the substrate to compare the reference data and the measurement data to obtain the amount of distortion to compensate for setting the inspection area, using infrared illumination By acquiring the measurement data, more accurate measurement data can be obtained, and accordingly, the inspection area can be set more accurately.

In addition, when a figure pattern including a circular pattern is used as a feature object and when pattern recognition is difficult due to the color of the substrate, measurement data can be obtained more accurately than in the prior art, and thus the inspection area can be set more accurately. .

1 is a flow chart showing a test method according to an embodiment of the present invention.

2 is a plan view illustrating an example of reference data in the inspection method of FIG. 1.

3 is a plan view illustrating an example of measurement data in the inspection method of FIG. 1.

4 is a cross-sectional view taken along line II ′ of FIG. 3.

FIG. 5 is a cross-sectional view taken along line II-II ′ of FIG. 3.

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.

Terms such as first and second 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 the second component, and similarly, the second component may also be referred to as the 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.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing an inspection method according to an embodiment of the present invention, Figure 2 is a plan view showing an example of the reference data in the inspection method of Figure 1, Figure 3 is one of the measurement data in the inspection method of FIG. It is a top view which showed the example.

1 to 3, in order to set an inspection area in which distortion is compensated according to an embodiment of the present invention, first, a measurement area FOV is set on a substrate (S110).

The measurement area (FOV) means a predetermined area set on the substrate for inspecting whether the substrate is defective, for example, a photographing range of a camera mounted on inspection equipment such as a three-dimensional shape measuring device. of view).

Subsequently, reference data RI for the measurement area FOV is obtained (S120).

The reference data RI may be a theoretical planar image of the substrate, for example, as shown in FIG. 2. In one embodiment, the reference data (RI) may be obtained from the CAD (CAD) information or the gerber information recording the shape of the substrate. The CAD information or Gerber information includes design reference information of the substrate, and generally includes layout information regarding the pad 10, the circuit pattern 30, the circular pattern 40, and the like.

In another embodiment, the reference data (RI) may be obtained from the learning information obtained by the learning mode. In the learning mode, for example, the board information is searched in a database, and if there is no board information as a result of the database search, the learning of the bare board is performed. Subsequently, the learning of the bare board is completed. If is calculated may be implemented in such a manner as to store the substrate information in the database. That is, the design reference information of the printed circuit board is obtained by learning a bare board of the printed circuit board in the learning mode, and the reference data (RI) may be obtained by obtaining the learning information through the learning mode.

Next, an infrared image is irradiated to the measurement area FOV to obtain an infrared image as measurement data for the measurement area FOV (S130).

As shown in FIG. 3, the measurement data PI is actually a component 20 mounted on a substrate, a terminal 22, a polarity display 24 formed on the component, a circuit pattern 30, and the like. This is a photographed image of a printed circuit board.

The measurement data PI illustrated in FIG. 3 is illustrated as having the same image as the reference data RI illustrated in FIG. 2 except that an additional configuration of the component 20 and the like appears. The substrate is distorted as compared with the reference data RI due to the warpage and the warpage of the substrate.

The measurement data PI may be obtained by irradiating light to the measurement area FOV using an illumination unit of the inspection equipment, and photographing a reflection image of the irradiated light by using a camera mounted to the inspection equipment. . At this time, the illumination unit of the inspection equipment employs infrared illumination, and thus the light irradiated to the measurement area (FOV) is infrared.

When the illumination unit of the inspection equipment employs infrared illumination, it may be advantageous when using a figure pattern including a circular pattern as a feature object and when pattern recognition is difficult due to the color of the substrate. Hereinafter, these cases will be described in more detail with reference to the drawings.

4 is a cross-sectional view taken along line II ′ of FIG. 3. FIG. 4 is a diagram for describing a captured image of a circular pattern in the measurement data of FIG. 3.

Referring to FIG. 4, when a solder resist SR is formed around the circular pattern 40, the solder resist SR may be formed to cover a portion of the circular pattern 40. . Accordingly, the circular pattern 40 may appear as an exposed pattern shape 40b differently from the actual pattern shape 40a. The actual pattern center CTa of the actual pattern shape 40a may be spaced apart from the exposure pattern center CTb of the exposed pattern shape 40b by a predetermined offset d.

When the measurement data PI is an RGB image obtained using conventional RGB illumination, the circular pattern 40 is represented by the exposure pattern shape 40b in the RGB image, and the center of the circle is the exposure pattern center ( CTb). However, when the measurement data PI is an infrared image obtained by using infrared light as in the present invention, the infrared rays generated from the infrared light pass through the solder resist SR, and thus the circular pattern ( 40 is represented by the actual pattern shape 40a and the center of the circle is represented by the actual pattern center CTa.

The circular pattern 40 and its center appearing in the reference data RI correspond to the actual pattern shape 40a and the actual pattern center CTa that appear in the measurement data PI, respectively. Therefore, the measurement data obtained by using the conventional RGB illumination does not exactly correspond to the reference data (RI), and the measurement data (PI) obtained by using the infrared illumination exactly corresponds to the reference data (RI). By using the measurement data PI obtained by using the infrared illumination when comparing the reference data and the measurement data, which will be described later, a more accurate amount of distortion can be obtained than in the related art.

In another embodiment, the same may be applied to a figure pattern other than the circular pattern 40. For example, even in the case of a rectangular pattern, each vertex or center of the quadratic object, which is a reference of the feature object, may be covered by a solder resist, so that an accurate value cannot be obtained when using RGB illumination. In the case of using infrared illumination, an accurate value can be obtained.

On the other hand, the substrate may be a black printed circuit board. When the substrate is a black printed circuit board, the feature object or the predetermined shape in the feature block is not distinguished from the surrounding black color properly. For example, the curved pattern 30 formed on the substrate is not well distinguished from the surrounding black color.

Even when the substrate is not a black printed circuit board, the pattern may be equally applied even when pattern recognition is difficult due to the color of the substrate.

FIG. 5 is a cross-sectional view taken along line II-II ′ of FIG. 3. FIG. 5 is a diagram for describing a photographed image when the substrate is a black printed circuit board.

Referring to FIG. 5, when the measurement data PI is an RGB image obtained using conventional RGB illumination, various patterns on the black printed circuit board may not appear exactly in the RGB image as described above. However, when the measurement data PI is an infrared image obtained by using infrared light as in the present invention, since the infrared rays generated from the infrared light pass through the solder resist SR, various patterns in the infrared image may be surrounded. Appears unaffected by the color of the.

In an embodiment, the curved pattern 30 appearing in the reference data RI corresponds exactly to the curved pattern 30 appearing in the measurement data PI. By using the measurement data PI obtained by using infrared illumination, more accurate distortion amount can be obtained than in the related art.

On the other hand, in this case, the illumination unit of the inspection equipment may further include conventional RGB illumination in addition to the infrared illumination, in this case may selectively apply both illumination to the acquisition of the measurement data (PI), both illumination You can also apply.

Accordingly, when acquiring measurement data for the measurement area (FOV), only infrared images may be obtained by irradiating infrared rays, or both infrared and RGB images may be obtained by irradiating infrared rays and RGB lights simultaneously or sequentially. have.

In one embodiment, the measurement area (FOV) may be set in plurality. Before this step (S130), it may be determined in advance whether the infrared illumination for generating the infrared light is required. In this case, the infrared image may be acquired with respect to the measurement area determined as necessary among the plurality of measurement areas (FOV).

If it is determined that the necessity, as described above, only the figure pattern including the circular pattern in the measurement area (FOV) may include the case that the qualified object, the black printed circuit board, and the like.

Alternatively, after the measurement area FOV is set, the method may further include preselecting one of the infrared light and the RGB light with respect to the measurement area FOV.

Subsequently, at least one feature object is extracted in the measurement area FOV (S140).

In order to obtain the amount of distortion by comparing the reference data RI and the measurement data PI, which will be described later, a comparison object is required, and the comparison object is defined as a feature object.

The feature object may be extracted, for example, in units of blocks so as to include a predetermined shape in the measurement area FOV. As shown in FIG. 3, the feature object may include first to sixth feature blocks FB1, FB2, FB3, FB4, FB5, and FB6.

The predetermined shape of the feature block in the block unit may have a two-dimensional separator capable of defining a two-dimensional plane so that the possibility of misunderstanding by the surrounding shape is eliminated. For example, the two-dimensional separator may include various lines, squares, circles, and combinations thereof, and the straight line cannot define the two-dimensional plane and thus cannot be the two-dimensional separator.

For example, the predetermined shape may include at least one of a curved pattern and a circular pattern. In particular, when the predetermined shape includes a circular pattern, as described above, more accurate results may be obtained by utilizing measurement data PI acquired using infrared illumination.

For example, when only the circular pattern exists in the shape having the two-dimensional separator so that the characteristic object can be used as the feature object in the measurement area (FOV), if the exact center of the circular pattern is not obtained, an accurate result is obtained. Can't.

The feature object may be extracted using a fitting with respect to a predetermined shape in the measurement area FOV. Specifically, after fitting to define the shape of a specific object in the measurement data PI, the matched specific object and the object in the reference data RI are matched with each other according to the matching result. An object may be extracted as the feature object.

The specific object may include, for example, a circle, a straight line, a curve, or the like, but may be somewhat different from a circle, a straight line, a curve, and the like in a mathematical sense. Accordingly, the specific object is defined as a circle, a straight line, a curve, or the like in a mathematical sense by fitting such a curve fitting, linear fitting, and the like, and the fitted object is defined in the reference data RI. By comparing with the object, the matched object can be extracted as the feature object. In this case, the matching may be performed by determining a match between the reference data RI and the measurement data PI based on an edge of the object.

Next, the amount of distortion is obtained by comparing the reference data corresponding to the feature object with the measured data (S150).

The distortion amount may be represented by a transformation relationship between the reference data (RI) and the measurement data (PI) corresponding to the feature object, and the transformation relationship is between the reference data (RI) and the measurement data (PI). It can include a quantified conversion formula of.

The measurement data PI is distorted as compared with the reference data RI corresponding to theoretical reference information due to warpage and warpage of the substrate. The conversion formula is a formula for converting the reference data (RI) and the measurement data (PI) to each other to represent the amount of distortion, that is, the amount of distortion. The quantified conversion formula may be set using at least one of a position change, a slope change, a size change, and a degree of deformation obtained by comparing the reference data (RI) with respect to the feature object and the measurement data (PI). have.

Meanwhile, as an example, the conversion formula may be obtained by using Equation 1.

Equation 1

In Equation 1, P _CAD is a coordinate of a target according to CAD information or Gerber information, that is, a coordinate in the reference data RI, and f (tm) is a transformation matrix as a transfer matrix. P _real is a coordinate of the target in the measurement data PI obtained by the camera. When the theoretical coordinate P _CAD in the reference data RI and the actual coordinate P _real in the measurement data PI are obtained, the transformation matrix can be known.

For example, the transformation matrix may include a coordinate transformation matrix according to an affine transformation or a perspective transformation in which a point correspondence relationship in an n-dimensional space is represented by a first-order equation. In order to define the coordinate transformation matrix, the number of feature objects may be appropriately set. For example, three or more feature objects may be set in the case of an affine transformation and four or more feature objects in the perspective transformation.

Subsequently, the inspection area within the measurement area is set by compensating for the distortion amount (S160).

Since the distortion amount represents the degree of distortion generated in the measurement data PI compared to the reference data RI, when compensated for, the inspection area may be closer to the shape of the actual substrate. The inspection area may be set for all or part of the measurement area FOV.

By setting the inspection area in the measurement data PI by compensating for the distortion amount, it is possible to more accurately inspect whether or not a component in the inspection area is defective. In this case, the inspection may use the measurement data PI acquired in the step S130 of obtaining measurement data PI for the measurement area FOV.

According to the present invention as described above, after obtaining the reference data and the measurement data for the measurement area set on the substrate to compare the reference data and the measurement data to obtain and compensate for the distortion amount to set the inspection area, By using the measurement data as an infrared image, more accurate measurement data can be obtained and accordingly, an inspection area can be set more accurately.

In the detailed description of the present invention described above with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary skill in the art will be described in the claims to be described later And various modifications and variations of the present invention without departing from the scope of the art. 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.

Claims

Setting a measurement area on the substrate;

Acquiring reference data for the measurement area;

Irradiating infrared rays to the measurement area to obtain an infrared image as measurement data of the measurement area;

Extracting at least one feature object in the measurement area;

Comparing the measurement data with reference data corresponding to the feature object to obtain a distortion amount;

Compensating the distortion amount to set the inspection area in the measurement area.
The method of claim 1,

The feature object may include at least one of a figure pattern including a curved pattern and a circular pattern.
The method of claim 1,

And the feature object is extracted in units of blocks so as to include a predetermined shape in the measurement area.
The method of claim 1,

The predetermined shape included in the block has a two-dimensional separator so that the possibility of misunderstanding by the surrounding shape is eliminated.
The method of claim 1,

The distortion amount is obtained by a quantified conversion formula between the reference data and the measurement data corresponding to the feature object,

The quantified transformation formula is defined using at least one of position change, slope change, size change, and degree of deformation obtained by comparing the reference data and the measurement data for the comparison block. method of inspection.
The method of claim 1,

And the substrate is a black printed circuit board.
The method of claim 1,

The measurement area is set to a plurality,

Before the step of irradiating the infrared ray to the measurement area to obtain an infrared image which is measurement data for the measurement area,

Determining whether an infrared light for generating the infrared light is needed;

And obtaining the infrared image of the measurement area determined to be necessary among the plurality of measurement areas.
The method of claim 1,

And irradiating RGB illumination to the measurement area to obtain an RGB image which is measurement data of the measurement area.
The method of claim 8,

The measurement area is set to a plurality,

And at least one of the infrared image and the RGB image is selectively acquired for each of the plurality of measurement regions.
The method of claim 1, wherein the extracting of the feature object comprises:

Fitting to a specific object in the measurement data;

Matching the fitted specific object with an object in the reference data; And

And extracting a matched object as the feature object according to the matching result.