JP5234639B2 - Through-hole inspection equipment - Google Patents

Description

  The present invention relates to a through-hole inspection apparatus capable of inspecting the position of a through-hole formed in a pad of a printed circuit board.

  Generally, a through hole for mounting an electronic component is formed in a pad of a printed circuit board. By the way, since this through hole is formed in a processing step different from the formation of the pad, the position of the through hole may be shifted from the center of the pad. Accordingly, various inspection apparatuses that can accurately inspect the formation state of the through holes have been proposed (Patent Documents 1 to 4).

  For example, the following Patent Document 1 (Japanese Utility Model Laid-Open No. 2-105156) discloses a method of counting the number of through holes and inspecting whether or not the number matches the reference number. According to such a method, when the through hole is blocked, it can be detected as defective. Also, Patent Document 2 (Japanese Patent Laid-Open No. 5-60537) discloses an inspection device that can detect the clogging of a through hole as well as the diameter of the through hole.

  Further, in Patent Document 3 (Japanese Patent Publication No. 7-86468) below, as shown in FIG. 10, the image of the pad or the through hole can be thinned, and the end point can be found to detect the position shift of the through hole. Such a method is disclosed. According to such a method, for example, when the through hole protrudes from the pad, the edge of the pad is cut by the through hole, so that a plurality of end points are generated in the thinned line (see FIG. 10 is a cross mark in the lower figure), and thereby, the displacement of the through hole can be detected.

  Further, in the following Patent Document 4 (Japanese Patent Laid-Open No. 9-203620), an image of a pad or a through hole is binarized, and an edge is extracted by dividing the image in eight directions as shown in FIG. Thus, an inspection apparatus that can determine the formation state of a through hole is disclosed. According to such a method, even if an error occurs during the thinning process of Patent Document 3, it is possible to reliably detect the displacement of the through hole without generating the noise. Become.

Japanese Utility Model Publication No. 2-105156 JP-A-5-060537 Japanese Patent Publication No. 7-086468 JP-A-9-203620

  However, the method described in the above patent document causes the following problems.

  That is, since the method shown in Patent Document 1 and Patent Document 2 is for determining the number of through holes and the size of the hole diameter, even if the formation position of the through hole protrudes from the pad, If the number of holes and the hole diameter match, this cannot be judged as defective.

  Further, in the method of extracting and inspecting the edge as in Patent Document 3 and Patent Document 4, depending on the image acquisition state, the outline of the pad or the through hole becomes ambiguous, and an accurate edge can be extracted. Disappear. Especially when the resist is applied to the inside of the pad edge, "copper color (exposed metal color)" "resist color applied on copper" "resist color on the substrate" ”And the luminance value smoothly change, it is difficult to accurately extract an edge when an image is acquired using a gray scale. In addition, if the edge is strongly reflected or shaded depending on the light irradiation direction, it becomes more difficult to extract the edge. For this reason, in the method of thinning as in Patent Document 3 and the method of extracting edges in eight directions as shown in Patent Document 4, the image of the inspection area of the pad or through hole before the processing is ambiguous. Then, it becomes impossible to extract edges accurately.

  Accordingly, the present invention has been made paying attention to the above-described problem, and an object thereof is to provide a through-hole inspection apparatus capable of accurately inspecting through-hole misalignment without extracting an edge. And

  That is, in order to solve the above problems, the present invention provides an image acquisition means for acquiring a surface image of a printed circuit board in a through hole inspection apparatus for inspecting a formation state of a through hole provided in a pad of the printed circuit board, A region extraction unit that extracts an image of an inspection region including a pad from a surface image, a binarization processing unit that generates a binarization map from the extracted image, and a labeling process based on the binarization map And labeling means for counting the number of labeling areas other than the pads based on the information subjected to the labeling process, and determining means for determining that the position is shifted when the number of the labeling areas is equal to or less than a predetermined number. It is intended to be provided.

  In this way, when the through hole is formed beyond the edge of the pad, the through hole region and the labeling region other than the pad are connected to form one, thereby shifting the through hole. Can be detected. On the other hand, if the through hole is within the pad, there are two labeling areas for the through hole in the pad and two labeling areas outside the pad, so it is determined that the through hole is within the pad. Will be able to.

  Further, in such an invention, the pad RGB information corresponding to the pad area and the exclusion RGB information corresponding to the area other than the pad are set in advance, and the pad RGB information and the exclusion RGB information area are inflated and processed. An image of the inspection area is extracted from the image.

  In this way, when extracting a pad area and other areas from a color image, several pixels or RGB in a certain area can be selected without specifying all of the RGB values of the pad RGB and non-pad RGB. Only by setting, pixels close to the designated RGB can be extracted and excluded.

  Furthermore, in such an invention, when determining the formation state of the through hole from the labeled image, the labeling area other than the pad in contact with the outer boundary of the inspection area is removed, and then the number of labeling areas other than the pad is counted. If the number is equal to or less than the predetermined value, it is determined that the position is shifted.

  In this way, even when there are scratches or other wiring patterns in the inspection region, the labeling region divided by the scratches is removed to accurately inspect the positional deviation of the through holes. Will be able to.

  According to the inspection apparatus of the present invention, the image acquisition means for acquiring the surface image of the printed circuit board, the area extraction means for extracting the image of the inspection area including the pad from the surface image, and binarization from the extracted image A binarization processing unit that generates a map, a labeling unit that executes a labeling process based on the binarized map, and counts the number of labeling regions other than the pads based on the information that has been labeled, When the number of areas is equal to or less than the predetermined number, the determination means for determining that the position is shifted is provided. Therefore, when the through hole is formed beyond the edge of the pad, the through hole area and the pad The number of labeling regions other than is connected to be one, thereby detecting the displacement of the through hole. On the other hand, if the through hole is within the pad, there are two labeling areas for the through hole in the pad and two labeling areas outside the pad, so it is determined that the through hole is within the pad. Will be able to.

1 is a functional block diagram of an inspection apparatus according to an embodiment of the present invention. The pad RGB area | region acquired from the surface image of the printed circuit board in the same form, and the information of exclusion RGB excluded are shown. The positional relationship of the pad and through hole in the same form is shown. It is a figure which shows the state in which a crack etc. exist in the pad vicinity in the same form. 2 shows a binarized map subjected to binarization processing in the same form. The figure which shows the outline of a labeling process in the same form In the same embodiment, a labeled image and a determination process are shown. The flowchart which shows the setting process in the form is shown. The flowchart which shows the inspection process in the form is shown. The through-hole inspection method of a prior art example is shown. The through-hole inspection method of a prior art example is shown.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 3, the inspection apparatus 1 according to the present embodiment can inspect whether or not a through hole 84 is accurately contained in a pad 81 formed on a printed circuit board. The surface image is acquired from the substrate 8, and an image of the inspection region 9 at the position where the pad 81 is present is extracted. Then, as shown in FIGS. 4 and 5, binarization processing is performed on the area of the pad 81 and other areas in the inspection area 9 (the area of the pad 81 is “0” and the other area is “1”). Binarization processing), and it is possible to inspect whether or not the through hole 84 protrudes from the pad 81 based on the number of labeling regions other than the pad. Hereinafter, the configuration of the inspection apparatus 1 will be described in detail based on the functional block diagram in FIG.

  First, the image acquisition means 2 acquires the surface image from the printed circuit board 8 to be inspected. When acquiring a surface image from the printed circuit board 8, the surface image may be acquired by a gray scale. However, in the case of the gray scale, the area of the pad 81 where the metal is exposed as shown in FIG. ) The brightness of the region 81R (region between the broken line and solid line) where the resist 83 is applied on the pad 81 and the region 82R (region outside the solid line) where the resist 83 is applied directly on the substrate 82 The difference between the values is not clear, and the image of the pad 81 cannot be accurately extracted only with the luminance values of 256 gradations. For this reason, the surface image of the printed circuit board 8 is preferably acquired by a color image. When the surface image of the printed circuit board 8 is acquired by the image acquisition means 2, light is emitted from an illumination device arranged obliquely above the printed circuit board 8, and the reflected light is reflected on the line sensor or the Obtained by area sensor. The acquired surface image is composed of pixels having luminances of (RGB) = (0, 0, 0) to (255, 255, 255). Then, the surface image is stored in the image memory, and the image of the pad 81 and the through hole 84 that are the inspection area 9 is extracted from the surface image.

  The area extraction unit 3 extracts an image of the inspection area 9 of the pad 81 that is the inspection area 9 from the acquired surface image of the printed circuit board 8. At this time, the coordinate position where the pad 81 exists is set in advance by the setting means 4. Also, pad RGB pixel information to be extracted from the image and excluded RGB pixel information to be positively excluded therefrom are set. Here, when setting the coordinate position of the pad 81, the coordinate position of the pad 81 is set based on the CAD data used at the time of designing the printed circuit board 8, and all the pads 81 are included around the coordinate position. A proper inspection area 9 is set. The shape of the inspection area 9 may be a rectangular shape such as a square or a rectangle, or may be a circular shape. Preferably, all pads 81 and through holes 84 to be inspected are included.

  On the other hand, the pad RGB information indicates RGB luminance information for extracting the pad 81 from the surface image, and is set based on the image acquired from the pad 81 of the reference printed circuit board 8. At this time, for example, when only the exposed metal portion of the pad 81 is extracted, a luminance value in the vicinity of (R, G, B) = (200, 60, 60) is set, and the outer peripheral portion of the pad 81 is registered. In the case where 83 overlap portions 81R are extracted as pad areas, luminance values in the vicinity of (R, G, B) = (120, 150, 80) are set. Since these luminance values change depending on the coating thickness of the resist 83 or polishing scratches on the metal surface, after setting the luminance values, the RGB luminance values are expanded by a certain width so as to include these luminance values. Specifically, one pixel or a rectangular area of the pad 81 is set with the mouse from the surface image of the reference printed circuit board 8, and then the luminance value of the designated pixel (if the rectangular area is set, the rectangle is set. For example, 120-α1 <R <200 + α2, 60-β1 <G <150 + β2, 60-γ1 <B <80 + γ2, etc. (see FIG. 2). Here, the values of α1 to γ2 are individually set and may be different from each other, or may be set to be the same as α1 = α2, β1 = β2, and γ1 = γ2.

  The excluded RGB information is a set of RGB luminance values that are to be positively excluded from the surface image. In this embodiment, the excluded RGB information is set to a base color close to the pad color, a resist color on the substrate 82, or the like. This excluded RGB information is also set based on the image acquired from the reference printed circuit board 8. For example, when only the color of the base material 82 itself is excluded, (R, G, B) = (60, 30 , 30) If a luminance value in the vicinity is set and the region 82R where the resist 83 is applied on the base material 82 is excluded, the vicinity of (R, G, B) = (80, 120, 50) Set to the brightness value of. Since these luminance values also change depending on the coating thickness of the resist 83, after the luminance values are designated, the RGB luminance values are expanded by a certain width so as to include these luminance values (see FIG. 2). That is, after setting one pixel or a rectangular area from the surface image of the printed circuit board 8 serving as a reference with the mouse, the luminance value of the designated pixel (if a rectangular area is set, all the pixels in the rectangular area are set). (Brightness value).

  When the pad RGB information and the excluded RGB information are inflated as described above, there is a possibility that the area 31 indicating the pad RGB information and the area 32 indicating the excluded RGB information overlap as shown in FIG. In such a case, the pixels included in the excluded RGB information area 32 are first removed from the inspection area 9, and then the pixels included in the pad RGB information area 31 are extracted. On the other hand, if the pixels included in the excluded RGB information are excluded after the pixels belonging to the pad RGB information are extracted, the extracted images are the same as a result.

  The binarization processing means 5 performs binarization processing based on the image of the inspection area 9 extracted in this way, and generates a binarization map as shown in FIG. 4 or FIG. In the binarization process, “0” is set for pixels extracted as pad RGB colors in the inspection area 9, and “1” is set for pixels excluded as removed RGB colors other than pads. At this time, for example, when the through hole 84 protrudes from the pad 81, and the through hole 84 is accommodated in the pad 81, as shown in FIG. There will be a total of two chunks inside and outside the pad, while there is only one chunk in the area other than the pad (ie, bit value “1”), as shown in FIG. 5B. .

  The labeling means 6 executes a labeling process for each block of bit values “0” and “1” based on the binarization map that has been binarized in this way. Here, “labeling” means that a code is assigned to each block of binarized bit values. In this embodiment, an area other than the pad 81 (that is, an area to which “1” is assigned). A label is assigned to each lump.

  FIG. 6 shows an example of this labeling process. In FIG. 6, reference numeral 93 denotes a target pixel, and reference numeral 94 denotes a surrounding reference pixel. First, when assigning a label to the pixel of interest 93, if the bit value of the pixel of interest 93 is “1” and no reference has been assigned to the surrounding reference pixel 94, a new label is assigned. Assigned to the target pixel 93. On the other hand, if a label is already assigned to the reference pixel 94, the same label as that label is assigned to the target pixel 93. In FIG. 6, since the bit value of the target pixel 93 is “1” and the label “1” has already been assigned to the reference pixels 94 around the left side thereof, the label “1” is assigned to the target pixel 93. Assigned. Thereafter, a map labeled in the same manner from the upper left to the lower right of the inspection area 9 is generated. Although other methods may be adopted for this labeling processing method, depending on the labeling rules, there may be wrinkles caused by the rules, and the labeling area may be divided or integrated. is there. In particular, the boundary portion 91 of the inspection area 9 is relatively easy to generate noise as compared with the central portion. For example, as shown in FIG. 4, there is a scratch or a wiring pattern near the inspection area 9. As shown in FIG. 4B, there is a possibility that the region of the bit value “1” may be divided into the inner side and the outer side due to the scratch or the like.

  Therefore, the determination means 7 removes the labeling area 92 in contact with the boundary portion 91 of the inspection area 9 from the images thus labeled, and counts the number of labeling areas after the removal. That is, as shown in FIG. 5A, when the through hole 84 is formed inside the pad 81 without any other wiring pattern or scratch in the inspection area 9, the labeling area outside the pad 81 is formed. 92 and a labeling region 92 inside the pad 81 exist, and there are a total of two labeling regions (FIG. 7A). At this time, if the labeling region 92 in contact with the boundary portion 91 of the inspection region 9 is removed, only one labeling region 92 in the region of the pad 81 remains. That is, when the through hole 84 is formed in a normal state, the number of labeling regions after the boundary portion removal is only “1”. Further, as shown in FIG. 4A, when the resist region 82R on the base material 82 is divided by other wiring patterns or scratches of the inspection region 9, the number of labeling regions is “3”. However, since the labeling area outside the pad is in contact with the boundary portion 91 of the inspection area 9, the number of labeling areas is “1”.

  On the other hand, as shown in FIG. 5B, when the through hole 84 protrudes from the pad 81, the number of labeling regions 92 in the inspection region 9 becomes “0” when the labeling region 92 in contact with the outer boundary 91 is removed. (FIG. 7B). Therefore, the determination means 7 removes the labeling area 92 in contact with the boundary portion 91 of the inspection area 9 and counts the number of labeling areas thereafter, and if the number is “0”, it is “positional deviation”. judge.

  Next, the inspection flow of the inspection apparatus 1 configured as described above will be described with reference to the flowchart of FIG.

<Setting for image extraction of inspection area 9>
First, a preliminary operation for extracting the inspection region 9 including the pad 81 and the through hole 84 from the surface image will be described.

  First, when the inspection area 9 of the pad 81 is extracted from the printed circuit board 8 which is the inspection object, the reference printed circuit board 8 is prepared in advance and the surface image is acquired (step S1). At this time, as the printed circuit board 8 serving as a reference, another inspection device 1 or one determined to be non-defective by visual inspection is used, and the acquired surface image is displayed on the display (step S2). Then, setting of the coordinate position of the pad 81 is received from the operator by CAD data or a screen operation with the mouse (step S3), and the coordinate position and the size of the rectangular area including the pad 81 are stored (step S4).

  After setting the coordinate position and the size of the inspection area 9 in this way, this time, based on the image of the inspection area 9 displayed on the display, the metal exposed part of the pad 81 and the resist 83 application area on the pad 81 are displayed. The selection of a pixel is accepted, and the RGB information of the pixel is stored as pad RGB information (step S5). Similarly, selection is accepted for a pixel of a color to be positively excluded in a portion other than the pad 81, and the RGB information of the pixel is stored as excluded RGB information (step S6). At this time, a color that is easily mistaken for the pad color is set as the exclusion color. And after setting pad RGB information and exclusion RGB information in this way, each information is inflated and memorize | stored as pad RGB information and exclusion RGB information (step S7).

<Inspection processing of inspection object>
Next, a process for inspecting the printed circuit board 8 that is an inspection object after setting the coordinates of the inspection area 9, the pad RGB information, and the excluded RGB information will be described with reference to the flowchart of FIG.

  When inspecting the formation state of the printed circuit board 8 that is the inspection object, similarly, a surface image is acquired from the printed circuit board 8 that is the inspection object (step T1), and the image is stored in the image memory. Then, the inspection area 9 is extracted from the surface image based on the coordinate position of the pad 81 stored in advance (step T2), and the pixels included in the excluded RGB information subjected to the inflating process from the image of the inspection area 9 Is removed (step T3). At this time, pixels corresponding to the color of the substrate 82 itself, pixels corresponding to the color of the resist 83 applied on the substrate 82, and the like are removed. After removing the pixels included in the excluded RGB information in this way, the pixels belonging to the pad RGB information after the inflating process are extracted (step T4). For example, the metal color of the pad 81 or the resist on the pad 81 is extracted. Extract only the pixels included in the color. By performing such processing, only the image corresponding to the area of the pad 81 remains as the image of the inspection area 9, and the other images are removed.

  Next, the extracted image of the area of the pad 81 is binarized to generate a binarization map (step T5). In this binarization processing, the area other than the pad 81 is set to “1”, and the area of the pad 81 is set to “0”. As a result, as shown in FIGS. 4 and 5, the resist 83 region of the base material 82 and the through hole 84 portion are “1”, and the exposed metal portion of the pad 81 and the resist coating region 81R of the pad 81 are “0”. It becomes.

  In step T6, a labeling process is performed from the binarized map generated in this way. In this labeling process, a labeling process is executed for the area other than the pad 81, and a label is attached to each pixel cluster to which “1” is added in the binarization map. For example, when the through hole 84 is formed in the pad 81 by this process, as shown in FIG. 7, the label “1” portion of the through hole 84 portion and the label “ Two labeling regions 92 exist in the portion “2”. On the other hand, when the through hole 84 protrudes from the boundary portion of the pad 81, there is only one labeling region 92.

  In the determination process, the positional deviation of the through hole 84 is determined based on the map after the labeling process. In this determination processing, the labeling region 92 that is in contact with the boundary portion 91 of the inspection region 9 is removed (step T7), and the number of labeling regions 92 remaining there is counted. At this time, when the through hole 84 is formed in the pad 81, the number of the labeling areas after removing the labeling area 92 in contact with the boundary portion 91 of the inspection area 9 is “1” (through holes in the pad 81. On the other hand, when the through hole 84 protrudes from the pad 81, the through hole 84 and the outer region are integrated, and the number of labeling regions becomes “0”. Therefore, when the number of labeling areas is “0”, the determination means 7 determines that the position is misaligned (step T9). On the other hand, when the number of labeling areas is “1”, "None" is determined (step T10), and the result is output.

  As described above, according to the above embodiment, the image acquisition unit 2 that acquires the surface image of the printed circuit board 8 and the inspection region 9 including the pad 81 based on the coordinate position of the pad 81, the pad RGB information, the excluded RGB information, and the like. Area extraction means 3 for extracting the image of the image, binarization processing means 5 for generating a binarization map from the image of the inspection area 9, and labeling processing for areas other than the pad 81 based on the binarization map. Since the labeling means 6 to be executed is included and the number of labeling regions 92 other than the pad 81 is counted and the number is smaller than a predetermined value, it is determined that the position is misaligned. It can be determined whether or not the through hole 84 is formed beyond 81a.

  Further, when the inspection area 9 is extracted in this way, the image of the inspection area 9 is extracted by expanding the areas of the pad RGB information and the excluded RGB information, so that the inspection area 9 of the pad 81 is extracted with a color image. When extracting, it is not necessary to specify all the RGB brightness values of the pad 81 and RGB except for the pad 81, and by setting only a few pixels of RGB or RGB within a certain range, pixels in the vicinity of the specified RGB can be selected. It will be possible to extract and also exclude.

  Further, when the formation state of the through hole 84 is determined from the labeled image, the labeling region 92 in contact with the boundary portion 91 of the inspection region 9 is removed, and then the number of labeling regions other than the pad 81 is “0”. ”Is determined to be“ positional misalignment ”. Therefore, as shown in FIG. 4, even if there are scratches or other wiring patterns in the inspection area 9, it is divided by the scratches. It is possible to accurately inspect the displacement by removing the labeled region 92.

  In addition, this invention is not limited to the said embodiment, It can implement in a various aspect.

  For example, in the above-described embodiment, when the number of labeling areas is “0”, it is determined as “misalignment”, and when the number of labeling areas is “1”, it is determined as “not misalignment”. However, when the influence of scratches or the like can be ignored, the number of labeling regions is reduced by one when the through-hole 84 protrudes, and therefore when the number of labeling regions is smaller than the default value, “ You may make it judge that it is "position shift".

  Further, in the above embodiment, the positional deviation of the through hole 84 is detected by the number of labeling regions. However, when the through hole 84 is formed inside the pad 81, the area of the inner labeling region 92 is detected. Based on the above, the diameter of the through hole 84 may be inspected at the same time.

  Further, in the above embodiment, the excluded pixels are excluded first based on the excluded RGB information, and then the pixels corresponding to the pad 81 are extracted based on the pad RGB information. However, based on only the pad RGB information. Thus, pixels corresponding to the pad 81 may be extracted.

  The present invention can inspect misalignment of a through hole formed in a pad of a printed circuit board on which no electronic component is mounted.

DESCRIPTION OF SYMBOLS 1 ... Inspection apparatus 2 ... Image acquisition means 3 ... Area extraction means 4 ... Setting means 5 ... Binarization processing means 6 ... Labeling means 7 ... Determination means 31 ... -Pad RGB area 32 ... Excluded RGB area 8 ... Printed circuit board 81 ... Pad 81a ... Edge 82 ... Base material 83 ... Resist 82R ... Base material resist 81R ... Pad Upper resist 84 ... through hole 9 ... inspection area 91 ... boundary portion 92 ... labeling area

Claims (3)

In a through hole inspection device that inspects the formation state of a through hole provided in a pad of a printed circuit board,
Image acquisition means for acquiring a surface image of the printed circuit board;
Area extraction means for extracting an image of an inspection area including a pad from the surface image;
Binarization processing means for generating a binarization map from the extracted image;
Labeling means for executing a labeling process based on the binarized map;
A determination unit that counts the number of labeling areas other than the pads based on the information subjected to the labeling process, and determines that the position is shifted when the number of the labeling areas is equal to or less than a predetermined number;
A through-hole inspection device characterized by comprising: The area extracting means sets pad RGB information corresponding to the pad area and exclusion RGB information corresponding to the area other than the pad in advance, and inflates the areas of the pad RGB information and the exclusion RGB information to perform the inspection of the inspection area. The through-hole inspection apparatus according to claim 1, which extracts an image. When the determination means determines the formation state of the through hole from the labeled image, the labeling area other than the pad in contact with the outer boundary of the inspection area is removed, and then the number of labeling areas other than the pad is counted and 2. The through-hole inspection device according to claim 1, wherein when the number is equal to or less than a predetermined value, it is determined that the position is misaligned.

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