JP2016156648A - Pattern inspection device and pattern inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect neck breakage.SOLUTION: In pattern inspection, coordinates of the center C2 of a target pore region 63 indicating one target pore are acquired in an inspection image obtained by imaging a printed circuit board formed with a wiring pattern including a land and a line and the pores, a line direction A4 being the direction where the target line connected to the target land formed with the target pore extends with the target land as a starting point is specified on the basis of the reference pattern data indicating the wiring pattern, a point on an object edge the closest to the position where the line extending in the line direction from the center of the target pore region and the edge of the target pore region intersect with each other is acquired as a determination point P2a with a portion being the edge of the target pore region and included in the wiring pattern region 60 indicating the wiring pattern as the object edge 631 in the inspection image, and neck breakage by the target pore is easily detected by determining whether or not the determination point is located outside the target land region 61 indicating the target land.SELECTED DRAWING: Figure 17A

Description

  The present invention relates to a printed circuit board pattern inspection apparatus and a pattern inspection method.

  Conventionally, various techniques have been proposed for inspecting a wiring pattern and a hole (for example, a via or a through hole) formed on a printed circuit board. For example, in Patent Document 1, the image of the inspection area is binarized, labeling processing is executed for an area other than the pad, and whether or not there is a displacement of the through hole is determined according to the number of labeling areas. In Patent Document 2, the edge of a wiring pattern is decomposed and extracted as edge image data for each predetermined direction component using an edge extraction filter in image data of a region including a land. Subsequently, while performing blurring processing and thinning-out processing, a plurality of edge image data are integrated by a hierarchical product-sum filter, and an output value indicating a degree approximating a shape corresponding to a line break is calculated, thereby generating a neck break. Presence / absence is determined.

  In Patent Document 3, a binarized image of a wiring pattern is separated into a land image corresponding to a land and a line image corresponding to a line. A hole image, which is a binarized image of the hole, is also acquired, and the presence or absence of neck breakage is determined based on the size of the overlapping portion between the enlarged hole image and the line image obtained by enlarging the hole image. The In Patent Document 4, a pattern image showing a wiring pattern and a hole image showing a through hole are obtained based on image data showing a printed circuit board, and a thinning pattern image is obtained by thinning the pattern image. . Then, the neck break of the wiring pattern is detected from the number of end points of the thinned pattern image in the window including the hole image.

JP 2010-175483 A JP-A-9-203620 JP-A-4-355352 JP-A-4-184244

  By the way, in Patent Documents 1 to 4, since processing (labeling processing, expansion processing, etc.) based on the luminance value is performed on the entire pixels of the image showing the vicinity of the land, the amount of calculation increases. Actually, an expensive circuit capable of parallel operation such as a field-programmable gate array (FPGA) is required, and the cost for inspecting the printed circuit board increases. Also, in the wiring pattern, not only the neck break that completely separates the land and the line by the hole, but also the defect in which the land and the line are partially separated by the hole (hereinafter referred to as such defect and neck break). Are collectively referred to as “missing neck”).

  The present invention has been made in view of the above problems, and an object thereof is to easily detect a neck defect.

  The invention according to claim 1 is a pattern inspection apparatus for a printed circuit board, wherein an inspection hole obtained by imaging a wiring pattern including lands and lines, and a printed circuit board in which holes are formed, has a single hole of interest. Based on the hole information acquisition unit that acquires the coordinates of the center of the indicated hole region and the reference pattern data that indicates the wiring pattern, or the inspection image, the region is connected to the land of interest where the hole of interest is formed. In the inspection image, the line of interest specifying the line direction that is a direction extending from the target land as a starting point, and the edge of the target hole area in the inspection image, the wiring pattern area indicating the wiring pattern With the included portion as a target edge, a line extending in the line direction from the center of the target hole region and the edge of the target hole region are A determination point acquisition unit that acquires, as a determination point, a point on the target edge that is closest to the difference position; and when the determination point is located outside the target land area indicating the target land, or the target line A neck missing detection unit that detects a neck missing due to the hole of interest when located in the attention line region shown.

  Invention of Claim 2 is a pattern inspection apparatus of Claim 1, Comprising: The said hole information acquisition part is a fixed angle space | interval on the said test | inspection image on the basis of the said center of the said attention hole part area | region. By setting a plurality of angular directions at, a plurality of candidate points, each of which is a point on the target edge in one angular direction, is obtained, and the discrimination point acquisition unit is one of the plurality of candidate points. Are obtained as the discrimination points.

  A third aspect of the present invention is the pattern inspection apparatus according to the second aspect, wherein the reference data including the reference pattern data and reference hole data indicating coordinates of the center of the hole is stored. The center of the land of interest with the center of the hole of interest indicated by the reference hole data as the center of the land of interest in the wiring pattern indicated by the reference pattern data. To acquire the distance from each of the plurality of angular directions to the edge of the wiring pattern, thereby specifying the line direction and the radius of the land area of interest.

  According to a fourth aspect of the present invention, in the pattern inspection apparatus according to the third aspect of the present invention, the neck missing detection unit is configured such that the center of the target hole region indicated by the reference hole data is the center of the target land region. As described above, the lack of the neck is detected by comparing the distance between the center of the land area of interest and the discrimination point with the radius of the land area of interest.

  Invention of Claim 5 is a pattern inspection apparatus in any one of Claim 2 thru | or 4, Comprising: The angle from which the said hole information acquisition part cannot obtain a candidate point by the absence of the said object edge When there is a no-candidate direction group that is a set of a predetermined number or more of no-candidate directions continuous in the circumferential direction with the direction as the no-candidate direction, a break due to the hole of interest is detected.

  The invention according to claim 6 is the pattern inspection apparatus according to claim 5, wherein the two no-candidates in which the discrimination points in the hole of interest where the neck defect is detected are discontinuous in the circumferential direction. The apparatus further includes a neck break detection unit that detects a neck break due to the hole of interest when an angle between the direction groups and a representative direction of the two no-candidate direction groups is equal to or smaller than a predetermined angle.

  A seventh aspect of the present invention is the pattern inspection apparatus according to any one of the first to sixth aspects, wherein, in the inspection image, the direction from the center of the target land area toward the center of the target hole area. When the angle formed with the line direction is equal to or greater than a predetermined angle, the discrimination point acquisition unit does not acquire the discrimination point for the hole of interest.

  The invention according to claim 8 is a method for inspecting a pattern of a printed circuit board, wherein: a) a wiring pattern including lands and lines, and an inspection image obtained by imaging a printed circuit board in which holes are formed, Obtaining the coordinates of the center of the target hole area indicating the portion; b) connecting to the target land where the target hole is formed based on the reference pattern data indicating the wiring pattern or the inspection image. A step of specifying a line direction in which the target line extends from the target land as a starting point; and c) an edge of the target hole region in the inspection image and included in the wiring pattern region indicating the wiring pattern A line extending from the center of the target hole region to the line direction and the edge of the target hole region A step of acquiring a point on the target edge closest to the point of interest as a discrimination point, and d) a case where the discrimination point is located outside the target land region indicating the target land, or a target line region indicating the target line And a step of detecting a lack of neck due to the hole of interest when located inside.

  The invention according to claim 9 is the pattern inspection method according to claim 8, wherein e) after the step a), the inspection image has a constant angle with respect to the center of the hole region of interest as a reference. The method further includes the step of obtaining a plurality of candidate points, each of which is a point on the target edge in one angular direction by setting a plurality of angular directions at intervals, and in the step c), the plurality of candidate points One candidate point is obtained as the discrimination point.

  The invention according to claim 10 is the pattern inspection method according to claim 9, wherein reference data including the reference pattern data and reference hole data indicating coordinates of the center of the hole is prepared in advance. In the step b), in the wiring pattern indicated by the reference pattern data, the center of the hole of interest indicated by the reference hole data is defined as the center of the land of interest, and the plurality of points from the center of the land of interest. By acquiring the distance to the edge of the wiring pattern in each of the angle directions, the line direction and the radius of the land area of interest are specified.

  The invention described in claim 11 is the pattern inspection method according to claim 10, wherein in the step d), the center of the target hole indicated by the reference hole data is set as the center of the target land area. The neck defect is detected by comparing the distance between the center of the land of interest and the discrimination point with the radius of the land of interest.

  The invention according to claim 12 is the pattern inspection method according to any one of claims 9 to 11, wherein in the step e), an angular direction in which no candidate point is obtained due to the absence of the target edge is determined. When there is a no-candidate direction group that is a set of a predetermined number or more of no-candidate directions continuous in the circumferential direction as the no-candidate direction, a break due to the hole of interest is detected.

  A thirteenth aspect of the present invention is the pattern inspection method according to the twelfth aspect of the present invention, in which the two no-candidates in which the discrimination points in the hole of interest where the neck defect is detected are discontinuous in the circumferential direction. The method further includes the step of detecting neck breakage due to the hole of interest when the angle between the direction groups and the representative direction of the two no-candidate direction groups is a predetermined angle or less.

  The invention according to claim 14 is the pattern inspection method according to any one of claims 8 to 13, wherein, in the inspection image, a direction from the center of the target land area toward the center of the target hole area. When the angle formed by the line direction is equal to or greater than a predetermined angle, in the step c), the determination point for the target hole is not acquired.

  According to the present invention, it is possible to easily detect a neck defect.

It is a figure which shows the structure of a pattern inspection apparatus. It is a figure which shows the structure of a computer. It is a block diagram which shows the function structure in a pattern inspection apparatus. It is a figure which shows a reference image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows the flow of the process which a pattern inspection apparatus inspects a printed circuit board. It is a figure which shows the flow of the process which a pattern inspection apparatus inspects a printed circuit board. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a reference image. It is a figure which shows a reference image. It is a figure which shows a reference image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image. It is a figure which shows a test | inspection image.

  FIG. 1 is a diagram showing a configuration of a pattern inspection apparatus 1 according to an embodiment of the present invention. For example, the pattern inspection apparatus 1 inspects the appearance of a printed circuit board 9 (also referred to as a printed wiring board) before electronic components are mounted. On the printed board 9, wiring patterns including lands and lines and holes (for example, through holes and vias) are formed. In the present embodiment, a multilayer substrate obtained by superimposing a plurality of substrates on which wiring patterns are formed is used as a printed circuit board 9 to be inspected. May be.

  The pattern inspection apparatus 1 includes an apparatus main body 2 that captures an image of the printed circuit board 9 and a computer 5 that controls the overall operation of the pattern inspection apparatus 1 and implements a calculation unit and the like described later. The apparatus main body 2 captures the printed circuit board 9 to acquire a multi-gradation image (data), a stage 22 that holds the printed circuit board 9, and the stage 22 relative to the imaging unit 21. The stage drive unit 23 moves to the position. The imaging unit 21 includes an illumination unit 211 that emits illumination light, an optical system 212 that guides the illumination light to the printed circuit board 9 and receives light from the printed circuit board 9, and an image of the printed circuit board 9 imaged by the optical system 212. An imaging device 213 that converts an image into an electrical signal is included.

  The stage drive unit 23 includes a ball screw, a guide rail, a motor, and the like. The computer 5 controls the stage driving unit 23 and the imaging unit 21 so that a predetermined area on the printed circuit board 9 is imaged. Instead of the stage driving unit 23, another mechanism for moving the imaging unit 21 relative to the printed circuit board 9 may be provided.

  FIG. 2 is a diagram illustrating the configuration of the computer 5. The computer 5 has a general computer system configuration including a CPU 51 that performs various arithmetic processes, a ROM 52 that stores basic programs, and a RAM 53 that stores various information. The computer 5 includes a fixed disk 54 for storing information, a display 55 for displaying various information such as images, a keyboard 56a and a mouse 56b (hereinafter collectively referred to as “input unit 56”) for receiving input from an operator, and the like. A reading device 57 that reads information from a computer-readable recording medium 8 such as an optical disk, a magnetic disk, a magneto-optical disk, and a communication unit 58 that transmits and receives signals to and from other components of the pattern inspection device 1 Including.

  In the computer 5, the program 80 is read from the recording medium 8 via the reading device 57 in advance and stored in the fixed disk 54. The CPU 51 executes arithmetic processing according to the program 80 while using the RAM 53 and the fixed disk 54.

  FIG. 3 is a block diagram showing a functional configuration in the pattern inspection apparatus 1. In FIG. 3, the functional configuration realized by the CPU 51, ROM 52, RAM 53, fixed disk 54, and the like of the computer 5 is surrounded by a broken-line rectangle denoted by reference numeral 5. The computer 5 includes a calculation unit 41 and a storage unit 49. The calculation unit 41 includes a hole information acquisition unit 411, a line direction identification unit 412, a discrimination point acquisition unit 413, a neck missing detection unit 414, and a neck break detection unit 415. Although not shown, an overall control unit that controls the operation of each functional configuration is also realized by the calculation unit 41. Details of functions realized by these configurations will be described later. In addition, these functions may be constructed by a dedicated electric circuit, or a dedicated electric circuit may be partially used.

  The storage unit 49 stores reference data 491 prepared in advance. The reference data 491 includes reference image data 492 and reference hole data 493. The reference image data 492 indicates a binary reference image generated from design data (CAD data) described later. The reference image indicates an area of an ideal wiring pattern to be formed on the printed circuit board 9 (for example, a mask pattern used for forming a wiring pattern, hereinafter referred to as “reference wiring pattern”). The reference hole data 493 indicates the coordinates and diameter of the center of each hole to be formed in the printed board 9 (ideal hole, hereinafter referred to as “reference hole”).

  FIG. 4 is a diagram illustrating a part of the reference image. In FIG. 4, the reference hole 73 is superimposed on the reference image and indicated by a two-dot chain line. The reference wiring pattern 70 includes a large number of lands 71 and lines 72 connected to the lands 71. In FIG. 4, only one land 71 and one line 72 are shown. Typically, the land 71 is circular, and the line 72 is a line having a constant width. The end of the line 72 is connected to the land 71. The reference hole 73 is disposed at the center of the land 71. The diameter of the reference hole 73 is smaller than the diameter of the land 71. In FIG. 4, the center of the reference hole 73 is indicated by a point denoted by C <b> 1, and the diameter of the reference hole 73 is denoted by an arrow denoted by D <b> 1.

  In the present embodiment, reference data 491 is generated from design data. The design data includes vector data indicating the edge (contour) of the reference wiring pattern 70 and reference hole data 493, and does not include information for individually specifying the land 71 and the line 72. Therefore, the coordinates and diameter of the center of the land 71 are unknown. On the other hand, as described above, the reference hole 73 is disposed at the center of the land 71, and the coordinates of the center C1 of the reference hole 73 are known. Therefore, it can be understood that the coordinates of the center of the land 71 are the same as the coordinates of the center C1 of the reference hole 73.

  Here, the type of defect caused by the positional deviation of the hole portion with respect to each land of the printed circuit board 9 will be described. 5 to 8 are diagrams showing a part of the inspection image acquired by the imaging unit 21, and show holes and lands in the printed circuit board 9. 5 to 8, a part of the edge of the land area 61 indicating the circular land and a part of the edge of the line area 62 indicating the line are indicated by a two-dot chain line. In the following description, it is assumed that a part of the land area 61 and a part of the line area 62 overlap. In the line area 62, the edge of the end overlapping the land area 61 is linear.

  In the example of FIG. 5, a hole region 63 indicating a hole is formed in the center of the land region 61. That is, there is no positional deviation of the hole with respect to the land, and FIG. 5 shows a normal state. In the example of FIGS. 6 to 8, the hole region 63 is formed at a position shifted from the center of the land region 61. Specifically, the hole region 63 overlaps the edge of the land region 61, and FIGS. 6 to 8 strictly show a state in which a part of the land has been removed by the formation of the hole, but in the following description, the land area 61 and the line area 62 have no holes. It is also assumed that the region removed (presumed to be) by the formation of.

  In the example of FIGS. 7 and 8, at the edge of the land region 61, a portion overlapping the line region 62 is used as a neck, and a part or all of the neck overlaps with the hole region 63. 8 shows a state of lack of a neck. In particular, FIG. 8 in which the hole area 63 overlaps the entire neck is shown in FIG. 8 in which the actual land on the printed circuit board 9 (the part of the land area 61 excluding the hole area 63) and the line (the hole area 63 in the line area 62). The part of the neck which is separated from (excluding the part) is shown. In the inspection process described below, the presence of a break in the land on the printed circuit board 9, a lack of a neck, and a neck break are detected.

  FIG. 9A and FIG. 9B are diagrams showing a flow of processing in which the pattern inspection apparatus 1 inspects the printed circuit board 9. In the pattern inspection, first, the printed circuit board 9 is placed on the stage 22 (see FIG. 1), and the wiring pattern on the printed circuit board 9 is placed in the imaging region by the imaging unit 21 by the stage driving unit 23. And the multi-tone image which shows a wiring pattern is acquired by the imaging part 21 as a test | inspection image, and is output to the calculating part 41 (step S11). The inspection image is aligned with the reference image indicated by the reference image data 492 by the calculation unit 41 (step S12). For example, the alignment between the inspection image and the reference image is performed by known pattern matching.

  In the hole information acquisition unit 411, by referring to the reference hole data 493, one of the holes to be inspected is specified as the target hole, and the center of the target hole indicated by the reference hole data 493 is specified. Based on these coordinates, a region including the hole of interest in the inspection image is specified (step S13). In the following description, a land on which a hole of interest is to be formed is referred to as a “land of interest”, and a line connected to the land of interest is referred to as a “line of interest”.

  FIG. 10 is a diagram illustrating a region including a hole of interest in an inspection image. In the inspection image, the hole information acquisition unit 411 indicates the center C1 of the target hole indicated by the reference hole data 493 (that is, the center of the reference hole that is the target hole, hereinafter referred to as “reference center C1”). The length measurement process for one angular direction is performed starting from the pixel at (1). In the length measurement process, the difference between the luminance value of the target pixel and the luminance value of the adjacent pixel adjacent to the target pixel in the angle direction (in this embodiment, the absolute value of the difference; The process of obtaining the “luminance difference between” is repeated while changing the adjacent pixel to the next target pixel. A position where the luminance difference between adjacent pixels is equal to or greater than a predetermined threshold is specified as an edge point P1 indicating the edge of the hole region 63 of the hole of interest (hereinafter referred to as “the hole of interest region 63”). . When the edge point P1 is specified, the luminance difference for the next target pixel is not calculated. Note that the coordinates of the edge point P1 may be obtained in units smaller than the pitch between pixels by interpolating the luminance value between adjacent pixels (the same applies to other length measurement processes).

  In the present embodiment, the average luminance of the land area 61 of the target land (hereinafter referred to as “target land area 61”) and the line area 62 of the target line (hereinafter referred to as “target line area 62”) are: It is higher than the average brightness of the background area, which is an area excluding the target land area 61, the target line area 62, and the target hole area 63, and the average brightness of the target hole area 63. Further, the difference between the average luminance of the background area and the average luminance of the target hole area 63 is slight. Therefore, the edge point P1 is specified in a portion (hereinafter, referred to as “target edge 631”) included in the wiring pattern region 60 indicating the wiring pattern among the edges of the target hole region 63. The wiring pattern region 60 is a set of a target land region 61 and a target line region 62. In FIG. 10, the target edge 631 is indicated by a thick solid line (the same applies to other drawings that refer to the target edge 631). In the wiring pattern forming step (photolithography) on the printed circuit board 9, it is possible to accurately form a wiring pattern with respect to design data. As described above, the coordinates of the center of the target land are referred to. It can be understood that the coordinates are the same as the coordinates of the center C1. Therefore, the reference center C1 can be regarded as the center of the target land area 61.

  In addition, when the edge point P1 is not specified even if the length measurement processing is performed from the pixel of the reference center C1 to a pixel separated by a distance corresponding to the diameter of the target hole indicated by the reference hole data 493, for example, The length measurement process in the angular direction ends. In this case, the edge point P1 in the angular direction that is the length measurement direction does not exist. In FIG. 10, the angle direction in which the edge point P1 cannot be obtained is indicated by a dashed arrow A1.

  When the length measurement process for one angular direction is completed, a direction rotated by a predetermined set angle with respect to the angular direction around the reference center C1 is set as the next angular direction. And the said length measurement process is performed with respect to the said angle direction, and the edge point P1 is searched. In this way, by setting a plurality of angular directions over the entire circumference at a fixed angular interval with the reference center C1 as a reference, as shown in FIG. 10, each on the target edge 631 in one angular direction. A plurality of edge points P1 are obtained (step S14).

  In the example of FIG. 10, the pixel of the reference center C <b> 1 is included in the target hole region 63, but if there is a possibility that the pixel of the reference center C <b> 1 is not included in the target hole region 63, The edge point P1 may be obtained based on a different point. For example, eight directions set at an angular interval of 45 ° are defined with reference to the reference center C1, and a predetermined distance (for example, a fraction of the diameter of the hole of interest) from the reference center C1 in each direction. The brightness value of the pixel separated by a) is confirmed. Subsequently, a pixel having a relatively low luminance value (within the range considered as the luminance of the target hole region 63) is specified as a specific pixel, and a representative position (for example, an average position) representing all the specific pixels is acquired. The Then, by setting a plurality of angular directions at a constant set angle interval with the representative position as a reference, a plurality of edge points P1, which are points on the target edge 631 in one angular direction, are obtained.

  When a plurality of edge points P1 indicating points on the target edge 631 of the target hole region 63 are obtained, the center of the virtual circle indicating the edge of the target hole region 63 is determined based on the coordinates of the plurality of edge points P1. The coordinates and radius are obtained (step S15). In FIG. 11, the center of the virtual circle is indicated by a point denoted by reference symbol C2, and the radius of the virtual circle is indicated by an arrow denoted by reference symbol R2. In the following description, the center C2 of the virtual circle is treated as the center of the target hole region 63 and is referred to as “target hole center C2”. The process of step S15 is a process of acquiring the center coordinates and radius of the target hole area 63.

  In the hole information acquisition unit 411, as in step S14, the length measurement process for one angular direction is performed starting from the pixel at the target hole center C2. Then, as shown in FIGS. 12 and 13, a position where the luminance difference between adjacent pixels is equal to or greater than a predetermined threshold is specified as an edge point P <b> 2 on the target edge 631 of the target hole area 63. As will be described later, the edge point P2 is a candidate for a discriminating point used for discriminating the presence or absence of a neck defect, and is hereinafter referred to as “candidate point P2”. The coordinates of the candidate point P2 are stored in the calculation unit 41.

  Even if the length measurement process is performed from the pixel at the center of the target hole C2 to a pixel separated by a distance obtained by adding an arbitrary length to the radius R2 of the imaginary circle (hereinafter referred to as a “measurement upper limit distance”), a candidate is used. If the point P2 is not specified, the length measurement process in the angular direction ends. In this case, the candidate point P2 in the angular direction is treated as nonexistent, and the angular direction is stored as a no-candidate direction. The no-candidate direction is an angular direction in which a candidate point cannot be obtained due to the absence of the target edge 631. In FIG. 13, the position of the length measurement upper limit distance with respect to the target hole center C2 is indicated by a broken-line circle denoted by reference symbol U2. An angle direction in which the candidate point P2 is not obtained, that is, a no-candidate direction is indicated by a broken-line arrow A2.

  When the length measurement process for one angular direction is completed, a direction rotated by a predetermined set angle with respect to the angular direction with respect to the target hole center C2 is set as the next angular direction. And the said length measurement process is performed with respect to the said angle direction, and candidate point P2 is searched. In this way, by setting a plurality of angular directions over the entire circumference at a constant set angle interval with the target hole center C2 as a reference, a plurality of points that are points on the target edge 631 in one angular direction. Candidate point P2 is obtained (step S16). The set angle interval may be arbitrarily determined. For example, on the circumference of the virtual circle, among the plurality of points located in the plurality of angular directions with the target hole center C2 as a reference, the circumferential angle is set. The distance between two adjacent points is determined in advance so as to be several pixels.

  In step S16, when the distance between the target hole center C2 and the candidate point P2 is equal to or less than the distance obtained by subtracting an arbitrary length from the radius R2 of the virtual circle, the candidate point P2 is It is preferred that use is prohibited in processing. Further, as described above, the luminance difference between the adjacent pixels is not calculated for the pixel that is separated from the pixel at the target hole center C2 by the length measurement upper limit distance. Thus, only the candidate point P2 whose distance from the target hole center C2 is larger than the distance obtained by subtracting an arbitrary length from the radius R2 of the virtual circle and not more than the length measurement upper limit distance is processed thereafter. By using as a target of use, it becomes possible to ignore a portion having a distorted shape at the target edge 631 of the target hole region 63.

  In the hole information acquisition unit 411, when a predetermined number or more (for example, 2 or more) of no-candidate directions that are set in advance in the circumferential direction centered on the hole center C2 of interest continue, The set is specified as a no-candidate direction group. In FIG. 13, a set of four no-candidate directions A2 continuous in the circumferential direction is a no-candidate direction group A0. In the example of FIG. 13 in which the no-candidate direction group A0 exists, it is determined that the target hole region 63 is in a cut-off state where the target hole region 63 overlaps the edge of the target land region 61, and the cut-off due to the target hole portion is detected (step S17 ). If a break due to the hole of interest is detected, the process proceeds to step S18 described later.

  The example of FIG. 12 in which the no-candidate direction group A0 does not exist is determined not to be in a sitting state (step S17). If there is a hole to be inspected next in the inspection image (step S24), the process returns to step S13 to specify the next hole of interest. When there is no hole to be inspected next in the inspection image (step S24), the processing in the pattern inspection apparatus 1 is completed.

  The direction in which the attention line connected to the attention land in which the attention hole is formed is extended from the attention land as a starting point in the line direction specifying unit 412 when the break due to the attention hole is detected. The line direction is identified (step S18). Specifically, in the reference image shown in FIG. 14A, the same plurality of angular directions (plural angular directions over the entire circumference) as in step S16 are set with reference to the reference center C1 of the hole of interest. Then, the luminance values of the pixels arranged along the respective angular directions are sequentially acquired from the pixel at the reference center C1. As described above, the reference image is a binary image, and the luminance value of the pixel included in the reference wiring pattern 70 (hereinafter referred to as “pattern luminance value”) and the luminance of the pixel not included in the reference wiring pattern 70. The value (that is, the luminance value of the background pixel, hereinafter referred to as “background luminance value”) is different. Therefore, when the luminance value of the pixel acquired in the angular direction is the background luminance value, the pixel is specified as an edge point indicating the edge of the reference wiring pattern 70 in the angular direction. 14A includes a target land 71 and a target line 72.

  In a preferable process in the line direction specifying unit 412, the luminance value is acquired from a pixel that is separated from the reference center C <b> 1 by a predetermined distance (for example, half the diameter of the reference hole 73 that is the target hole) in each angular direction. Be started. As a result, the processing time until the edge point is specified can be shortened. In a more preferable process, the confirmation process of sequentially confirming the luminance values of pixels that are separated by the same distance from the reference center C1 in a plurality of (all) set angular directions is repeated while increasing the distance by one pixel. At this time, the angular direction in which the edge point is specified is excluded from the next confirmation process. When an edge point is specified for an angular direction that is half or more of the number of angular directions (all angular directions) initially set in the line direction specifying unit 412, the subsequent confirmation processing is performed in the remaining angular directions. On the other hand, it is repeated a predetermined number of times. For example, when the set number of times is set to 5, the maximum number of 5 in each remaining angle direction from the pixel when the edge point is specified for the angle direction that is half or more of the number in all the angle directions. Confirmation processing is performed up to pixels separated by pixels. Then, an angle direction in which an edge point is not specified even by repeating the set number of confirmation processes is determined as a line candidate direction.

  In FIG. 14A, the line candidate direction is indicated by a thick solid arrow A3. When the number of line candidate directions A3 is one as in the example of FIG. 14A, the line candidate direction A3 is specified as the line direction. Also, as in the example shown in FIG. 14B, a plurality of line candidate directions A3 that are continuous in the circumferential direction around the reference center C1 (hereinafter, a set of these line candidate directions A3 is referred to as a “line candidate direction group”). Is acquired, one line candidate direction A3 is specified as the line direction among the plurality of line candidate directions A3 included in the line candidate direction group. When the number of line candidate directions A3 included in the line candidate direction group is an odd number, it is preferable that the center line candidate direction A3 is determined as the line direction among the line candidate directions A3. When the number of line candidate directions A3 included in the line candidate direction group is an even number, one of the two line candidate directions A3 in the vicinity of the center among the line candidate directions A3 may be determined as the line direction. preferable.

  Furthermore, as in the example illustrated in FIG. 14C, when a plurality of line candidate directions A3 that are discontinuous in the circumferential direction are acquired, each line candidate direction A3 is specified as a line direction. Of course, when there are a plurality of line candidate direction groups discontinuous in the circumferential direction, one line candidate direction A3 included in each line candidate direction group is determined as the line direction.

  The line direction specifying unit 412 stores the distance from the pixel at the reference center C1 to the edge point in each of a plurality of (all) angular directions for which the edge points have been obtained. The median value of the distance is specified as the radius of the land 71. As described above, in the wiring pattern forming process (photolithography) on the printed circuit board 9, it is possible to form a wiring pattern with high accuracy with respect to design data. Therefore, the radius of the land 71 required in the reference image is It can be considered as the radius of the land area 61 of interest in the inspection image. As described above, in the reference direction pattern 412 indicated by the reference image data 492, the line direction identification unit 412 sets the center C1 of the target hole indicated by the reference hole data 493 as the center of the target land, and a plurality of points from the center of the target land. By acquiring the distance to the edge of the reference wiring pattern 70 in each of the angular directions, the radius of the land area 61 of interest is specified together with the line direction (step S19).

  When the line direction and the radius of the target land area 61 are specified, as shown in FIG. 15A, the target hole area that is the center of the target hole area 63 from the reference center C1 that is the center of the target land area 61 in the inspection image. An angle θ1 formed by the direction A5 toward the center C2 and the line direction A4 is obtained. At this time, the angle θ1 is obtained with the reference center C1 as a reference and the clockwise direction from the line direction A4 as the positive direction and the counterclockwise direction as the negative direction. And when the magnitude | size (absolute value) of the said angle (theta) 1 is 90 degrees or more, for example, it determines with there is no possibility that the neck lack by the attention hole part has generate | occur | produced (step S20).

  In the example shown in FIGS. 15A and 15B, since the magnitude of the angle θ1 is 90 ° or more, it is determined that no neck defect has occurred. If there is a hole to be inspected next in the inspection image (step S24), the process returns to step S13 to specify the next hole of interest. When there is no hole to be inspected next in the inspection image (step S24), the processing in the pattern inspection apparatus 1 is completed.

  On the other hand, in the example shown in FIG. 16A to FIG. 16D in which the magnitude of the angle θ1 is less than 90 °, it is determined that there is a possibility of a missing neck (step S20), and the process proceeds to step S21 described later. . In FIG. 16B, the angle formed by the direction A5 from the reference center C1 toward the target hole center C2 and the line direction A4 is 0 °.

  In the discrimination point acquisition unit 413, as shown in FIG. 17A, when the candidate point P2a exists in the same angular direction as the line direction A4 with respect to the hole center C2 of interest in the inspection image, the candidate point P2a is determined as the discrimination point. (Step S21). The same applies to the examples shown in FIGS. 17B and 17C. The discrimination point P2a can be regarded as a candidate point located closest to the target line region 62 in the target edge 631 of the target hole region 63. When there are a plurality of line directions A4, a discrimination point P2a is acquired for each line direction A4.

  On the other hand, when the candidate point P2 does not exist in the same angular direction as the line direction A4, the existence of the candidate point P2 in the angular direction adjacent to the line direction A4 in the circumferential direction is confirmed. For example, when the angle θ1 obtained in step S20 is positive, the presence / absence of the candidate point P2 in the angular direction adjacent to the negative direction (counterclockwise with respect to the reference center C1) with respect to the line direction A4 Is confirmed. And when the candidate point P2 exists in the said angle direction, the said candidate point P2 is determined as a discrimination | determination point. When the candidate point P2 does not exist in the angular direction, the presence / absence of the candidate point P2 in the angular direction adjacent to the negative direction with respect to the angular direction is confirmed. The above process is repeated until a discrimination point is determined. Thereby, in the example shown in FIG. 17D, the candidate point P2a in the angular direction located in the negative direction with respect to the line direction A4 is determined as the discrimination point. When the angle θ1 obtained in step S20 is negative, the presence / absence of the candidate point P2 in the angular direction adjacent to the positive direction (clockwise with reference to the reference center C1) with respect to the line direction A4. It is confirmed.

  The above processing in the discrimination point acquisition unit 413 is performed by selecting a candidate point on the target edge 631 closest to the position where the line extending in the line direction A4 from the hole center C2 and the edge of the hole region 63 intersects. Is acquired as

  As shown in FIG. 18A, the missing neck detection unit 414 obtains a distance D2 between the reference center C1 and the determination point P2a, and the distance D2 is the radius R1 of the land area 61 of interest acquired in step S19. Compared with When it is confirmed that the distance D2 is larger than the radius R1, it is determined that the example of FIG. 18A is in a state of lack of neck (step S22), and the process proceeds to step S23 described later. The same applies to the examples shown in FIGS. 18B and 18C.

  On the other hand, as shown in FIG. 19, when the distance D2 is equal to or less than the radius R1, it is determined that no neck defect has occurred (step S22). If there is a hole to be inspected next in the inspection image (step S24), the process returns to step S13 to specify the next hole of interest. When there is no hole to be inspected next in the inspection image (step S24), the processing in the pattern inspection apparatus 1 is completed.

  The above-described process in the neck defect detection unit 414 is a process for detecting a neck defect due to the target hole when the discrimination point P2a is located outside the target land area 61. Note that the greater the distance D2 and the smaller the aforementioned angle θ1 (see FIG. 16A), the greater the degree of neck loss. Therefore, the degree of neck loss is classified based on the distance D2 and the angle θ1. Also good.

  In the neck breakage detection unit 415, the presence / absence of the no-candidate direction group A0 in each of the positive direction and the negative direction is confirmed with respect to the angular direction of the discrimination point P2a in the target hole where the neck missing is detected. As shown in FIG. 20, when two no-candidate direction groups A0 exist in the positive direction and the negative direction with respect to the angular direction of the discrimination point P2a with the target hole center C2 as a reference, The representative direction in each of the two no-candidate direction groups A0 is specified. The representative direction in each no-candidate direction group A0 is, for example, an average direction in a plurality of angular directions included in the no-candidate direction group A0. In FIG. 20, the representative direction is indicated by an arrow with a reference sign B1. .

  When the angle θ2 formed by the representative direction B1 of the two no-candidate direction groups A0 (however, the angle θ2 is an angle range including the angular direction of the determination point P2a) is, for example, 180 ° or less. In addition, it is determined that FIG. 20 is in a neck-out state (step S23). On the other hand, when no candidate direction group A0 exists in one of the positive direction and the negative direction with respect to the angular direction of the determination point P2a as in the example illustrated in FIGS. It is determined that it is not. Even when two no-candidate direction groups A0 exist in the positive direction and the negative direction, respectively, the angle θ2 formed by the representative direction B1 of the two no-candidate direction groups A0 is larger than 180 °. Is determined not to be out of neck.

  As described above, in the neck break detection unit 415, the determination point P2a is sandwiched between two no-candidate direction groups A0 that are discontinuous in the circumferential direction, and the representative direction B1 of the two no-candidate direction groups A0 is When the formed angle θ2 is equal to or smaller than a predetermined angle, a neck break due to the hole of interest is detected. The inspection for the target hole is completed by determining whether or not the neck is broken. If there is a hole to be inspected next in the inspection image (step S24), the process returns to step S13 to specify the next hole of interest. When there is no hole to be inspected next in the inspection image (step S24), the processing in the pattern inspection apparatus 1 is completed.

  As described above, in the pattern inspection apparatus 1, in the inspection image, the coordinates of the center C2 of the target hole region 63 indicating one target hole are acquired, and the target line extends from the target land as a starting point. A line direction A4 which is a direction is specified. Subsequently, in the inspection image, the point on the target edge 631 that is closest to the position where the line extending in the line direction A4 from the center C2 of the target hole region 63 and the edge of the target hole region 63 intersects is set as the determination point P2a. To be acquired. When the discrimination point P2a is located outside the target land area 61, a neck defect due to the target hole is detected. Thereby, it is possible to easily detect a neck defect. Also, the amount of calculation can be reduced in the pattern inspection process compared to the pattern inspection of the comparative example in which the process based on the luminance value is performed on the entire pixels of the image showing the vicinity of the land. As a result, the lack of a neck can be detected without using an expensive circuit, and the cost for inspecting the printed circuit board 9 can be reduced.

  Further, in the inspection image, by setting a plurality of angular directions at a constant angular interval with reference to the center C2 of the target hole region 63, a plurality of points each of which is a point on the target edge 631 in one angular direction. Candidate point P2 is obtained, and one candidate point among a plurality of candidate points P2 is acquired as discrimination point P2a. Thereby, the discrimination point P2a can be easily acquired.

  Further, with the center of the target hole area indicated by the reference hole data 493 as the center C1 of the target land area 61, the distance D2 between the center C1 of the target land area 61 and the discrimination point P2a, and the radius R1 of the target land area 61 Are compared. This makes it possible to more easily detect a neck defect.

  In the line direction identification unit 412, in the reference wiring pattern 70 indicated by the reference image data 492, the center C 1 of the target hole 71 indicated by the reference hole data 493 is set as the center C 1 of the target land 71. The distance to the edge of the reference wiring pattern 70 in each angular direction is acquired. Accordingly, it is possible to easily specify the radius of the line direction A4 and the land of interest 71 (the land of interest land 61).

  The hole information acquisition unit 411 confirms the existence of a no-candidate direction group A0 that is a set of a predetermined number or more of no-candidate directions A2 that are continuous in the circumferential direction. Thereby, it is possible to easily detect a break due to the hole of interest.

  In the neck break detection unit 415, the discrimination point P2a in the target hole where the neck missing is detected is sandwiched between two no-candidate direction groups A0 that are discontinuous in the circumferential direction, and the two no-candidate direction groups A0 It is confirmed whether or not the angle formed by the representative direction B1 is equal to or smaller than a predetermined angle. Thereby, it is possible to easily detect a neck break due to the hole of interest.

  In the pattern inspection apparatus 1, in the inspection image, when the angle θ1 formed by the direction from the center C1 of the target land region 61 to the center C2 of the target hole region 63 and the line direction A4 is equal to or larger than a predetermined angle, attention is paid. The discrimination point P2a for the hole is not acquired. Thereby, the process concerning acquisition of the discriminant point P2a for the hole of interest that is not lacking in the neck can be omitted, and the pattern inspection in the pattern inspection apparatus 1 can be completed in a short time.

  The pattern inspection apparatus 1 can be variously modified.

  In the embodiment described above, the reference image data 492 is prepared as reference pattern data indicating a reference wiring pattern, but vector data indicating a reference wiring pattern may be used as reference pattern data.

  In the above-described embodiment, the line direction can be easily specified by using the reference pattern data that indicates the reference wiring pattern and does not indicate the hole portion. Depending on the accuracy and the like, the line direction may be specified based on the inspection image.

  The neck defect detection unit 414 may detect a neck defect due to a hole of interest when the determination point P2a is located within the attention line region 62 indicating the attention line. In this case, a straight edge (see FIGS. 6 to 8) at the end overlapping the target land region 61 in the target line region 62 is regarded as a neck. For example, when the reference image data includes data that individually indicates a land and a line as reference pattern data, such as image data that indicates a land and image data that indicates a line. It is possible to easily determine whether or not P2a is located outside the attention land area 61 or whether or not it is located within the attention line area 62.

  Depending on the design of the pattern inspection apparatus 1, the determination point may be acquired without setting a plurality of angular directions with reference to the center C2 of the target hole region 63 (without acquiring a plurality of candidate points). .

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Pattern inspection apparatus 9 Printed circuit board 49 Memory | storage part 60 Wiring pattern area | region 61 Attention land area 62 Attention line area 63 Attention hole area 70 Reference wiring pattern 71 Attention land 72 Attention line 73 Reference hole part 411 Hole information acquisition part 412 Line direction Specific part 413 Discrimination point acquisition part 414 Neck missing detection part 415 Neck breakage detection part 491 Reference data 492 Reference image data 493 Reference hole data 631 Target edge A0 No candidate direction group A2 No candidate direction A4 Line direction B1 (No candidate direction group Representative direction C1 reference center C2 target hole center P2 candidate point P2a discrimination point S11-S24 steps

Claims (14)

A printed circuit board pattern inspection apparatus,
In the inspection image obtained by imaging the printed circuit board on which the wiring pattern including the land and the line and the hole is formed, the hole information acquisition unit that acquires the coordinates of the center of the hole region of interest indicating the one hole of interest;
Based on the reference pattern data indicating the wiring pattern or the inspection image, a line direction that is a direction in which the line of interest connected to the land of interest in which the hole of interest is formed extends from the land of interest is specified. A line direction identification unit;
In the inspection image, a line extending in the line direction from the center of the hole area of interest, with a portion included in the wiring pattern area indicating the wiring pattern being an edge of the hole area of interest, and the line direction A determination point acquisition unit that acquires, as a determination point, a point on the target edge that is closest to a position where the edge of the target hole region intersects;
When the determination point is located outside the target land area indicating the target land, or when the determination point is positioned within the target line area indicating the target line, a neck defect detection unit that detects a neck defect due to the target hole. When,
A pattern inspection apparatus comprising: The pattern inspection apparatus according to claim 1,
In the inspection image, the hole information acquisition unit sets a plurality of angular directions at a constant angular interval with reference to the center of the target hole region, and each of the target edges in one angular direction Find multiple candidate points that are the top points,
The pattern inspection apparatus, wherein the discrimination point acquisition unit acquires one candidate point of the plurality of candidate points as the discrimination point. The pattern inspection apparatus according to claim 2,
A storage unit for storing reference data including the reference pattern data and reference hole data indicating coordinates of the center of the hole;
In the wiring pattern indicated by the reference pattern data, the line direction specifying portion has the plurality of angles from the center of the attention land with the center of the attention hole indicated by the reference hole data as the center of the attention land. A pattern inspection apparatus, wherein the line direction and the radius of the land area of interest are specified by acquiring the distance to the edge of the wiring pattern in each direction. The pattern inspection apparatus according to claim 3,
The neck missing detection unit has the center of the target hole region indicated by the reference hole data as the center of the target land region, and the distance between the center of the target land region and the determination point, and the target point The pattern inspection apparatus, wherein the neck defect is detected by comparing the radius of the land area. The pattern inspection apparatus according to any one of claims 2 to 4,
A no-candidate direction group in which the hole information acquisition unit is a set of a predetermined number or more of no-candidate directions continuous in the circumferential direction, with an angular direction in which no candidate point is obtained due to the absence of the target edge as a no-candidate direction A pattern inspection apparatus that detects a break due to the hole of interest when a hole exists. The pattern inspection apparatus according to claim 5,
The determination point in the target hole where the neck defect is detected is sandwiched between two no-candidate direction groups that are discontinuous in the circumferential direction, and an angle formed by the representative directions of the two no-candidate direction groups is A pattern inspection apparatus, further comprising a neck breakage detection unit that detects neck breakage due to the hole of interest when the angle is equal to or less than a predetermined angle. The pattern inspection apparatus according to any one of claims 1 to 6,
In the inspection image, when the angle formed between the direction from the center of the target land region to the center of the target hole region and the line direction is a predetermined angle or more, the determination point acquisition unit A pattern inspection apparatus that does not acquire the discrimination point for a hole of interest. A pattern inspection method for a printed circuit board,
a) a step of acquiring a center coordinate of a hole region of interest indicating one hole of interest in an inspection image obtained by imaging a printed circuit board on which a wiring pattern including lands and lines and a hole is formed;
b) Based on reference pattern data indicating the wiring pattern or the inspection image, a line direction that is a direction in which the line of interest connected to the land of interest in which the hole of interest is formed extends from the land of interest is defined as a line direction. Identifying process;
c) a line extending in the line direction from the center of the hole region of interest with an edge of the hole region of interest in the inspection image included in the wiring pattern region indicating the wiring pattern as a target edge Obtaining a point on the target edge closest to a position where the edge of the hole area of interest intersects the edge as a discrimination point;
d) a step of detecting a neck defect due to the hole of interest when the discrimination point is located outside the land area of interest indicating the land of interest or within the area of attention line indicating the line of interest; ,
A pattern inspection method comprising: The pattern inspection method according to claim 8,
e) After the step a), in the inspection image, by setting a plurality of angular directions at a constant angular interval with reference to the center of the target hole region, each of the objects in one angular direction A step of obtaining a plurality of candidate points that are points on the edge;
In the step c), one candidate point of the plurality of candidate points is acquired as the discrimination point. The pattern inspection method according to claim 9,
Reference data including the reference pattern data and reference hole data indicating coordinates of the center of the hole is prepared in advance,
In the step b), in the wiring pattern indicated by the reference pattern data, with the center of the target hole indicated by the reference hole data as the center of the target land, the plurality of angular directions from the center of the target land. The pattern inspection method is characterized in that the line direction and the radius of the land area of interest are specified by acquiring the distance to the edge of the wiring pattern in each of the patterns. The pattern inspection method according to claim 10,
In the step d), with the center of the target hole indicated by the reference hole data as the center of the target land area, the distance between the center of the target land area and the discrimination point, and the target land The pattern inspection method, wherein the neck defect is detected by comparing with the radius of the region. The pattern inspection method according to any one of claims 9 to 11,
In step e), there is a no-candidate direction group that is a set of a predetermined number or more of no-candidate directions continuous in the circumferential direction, with an angular direction in which no candidate point is obtained due to the absence of the target edge as a no-candidate direction. In this case, the pattern inspection method is characterized in that a break due to the hole of interest is detected. The pattern inspection method according to claim 12,
The determination point in the target hole where the neck defect is detected is sandwiched between two no-candidate direction groups that are discontinuous in the circumferential direction, and an angle formed by the representative directions of the two no-candidate direction groups is A pattern inspection method, further comprising a step of detecting a neck break due to the hole of interest when the angle is equal to or less than a predetermined angle. The pattern inspection method according to any one of claims 8 to 13,
In the inspection image, when the angle formed by the direction from the center of the target land region toward the center of the target hole region and the line direction is equal to or larger than a predetermined angle, in the step c), the target A pattern inspection method, wherein the discrimination point is not acquired for a hole.

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