JP3707674B2 - Pattern inspection apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern inspection apparatus and method for optically inspecting a wiring pattern such as a printed circuit board, and more specifically, highly accurate pattern inspection by recognizing the position of a hole formed in a printed circuit board. The present invention relates to an apparatus and a method for enabling
[0002]
[Prior art]
As is well known, on the surface of a printed board on which electronic components and the like are mounted, conductor wiring necessary for constituting a predetermined circuit is formed by a pattern. Further, a hole (hereinafter referred to as a through hole) penetrating a printed board such as a through hole into which a lead of an electronic component is inserted is formed in the land portion of the pattern.
[0003]
Conventionally, the inspection of whether or not there is a defect in the pattern of a printed circuit board in which the above-described through holes are formed is performed, for example, as follows.
First, the printed circuit board is placed on a transparent glass plate with the surface on which the pattern to be inspected is formed facing upward. The mounted printed circuit board is fixed to the glass plate by the end portion being clamped by a clamp mechanism. Next, illumination light is irradiated on the upper surface of the printed circuit board from a light source for epi-illumination arranged above the printed circuit board on the glass plate. Moreover, illumination light is irradiated to the lower surface of a printed circuit board from the light source for transmitted illumination arrange | positioned under the glass plate through a glass plate.
An imaging camera is arranged above the printed circuit board placed on the glass plate. In this imaging camera, the reflected light image based on the light reflected from the upper surface of the printed circuit board and the light transmitted through the through hole of the printed circuit board among the transmitted light from the transmitted light source. Based on the transmitted light image. Next, an image in which the hole is embedded is generated by synthesizing the transmitted light image at a position corresponding to the through hole in the captured reflected light image. Then, processing based on a pattern matching method, a design rule check method, or the like is performed on the hole-filled image, and a pattern defect is detected.
[0004]
As described above, by performing the hole filling process of the image, it is possible to detect the defect more accurately than detecting the defect based only on the reflected light image. That is, when only the reflected light image is processed, the shape of the reflected light image (the size of the image of the through-hole portion) changes depending on the threshold value of the binarization process for obtaining the reflected light image. Due to such a change in shape, if the threshold value for the binarization process is not set correctly, a problem that the defect cannot be detected without the defect portion appearing on the reflected light image occurs. In order to solve this problem, the above-described hole filling process is performed to compensate for the instability caused by the binarization process.
[0005]
[Problems to be solved by the invention]
However, in the following cases, there is a problem that the inspection using the transmitted light image based on the transmitted light described above cannot be executed.
First, in a certain manufacturing process, a printed circuit board in which a through hole is filled with a specific substance such as a resin may be used. When inspecting such a board, illumination light from a light source for transmitted illumination is emitted. It is blocked by resin or the like and a transmitted light image cannot be obtained.
Second, in a multilayer printed circuit board, there are cases where holes such as via holes (hereinafter referred to as non-through holes) having a depth of several layers from the surface are formed without penetrating the printed circuit board. is there. For such a non-through hole, it is impossible to obtain a transmitted light image corresponding to that portion.
Thirdly, as described above, in the configuration in which the end portion is clamped and the printed board is fixed on the glass plate, the central portion of the fixed printed board may bend. This deflection causes a problem that the defect inspection cannot be performed accurately. Therefore, in order to solve this problem, a configuration that employs a suction table that holds the entire lower surface of the printed circuit board with a vacuum suction force instead of the clamp mechanism is conceivable. However, the suction table is made of metal and is opaque because of the structure that it is necessary to form a large number of suction holes on the mounting surface of the suction table and to form an exhaust passage for the sucked air inside. As a result, illumination light cannot be irradiated on the lower surface of the printed circuit board, and a transmitted light image cannot be obtained.
[0006]
Therefore, in view of the above points, the object of the present invention is formed on a printed circuit board even when a transmitted light image cannot be used due to the filling of through holes or the presence of non-through holes. It is an object of the present invention to provide a pattern inspection apparatus and method capable of accurately inspecting the presence or absence of defects on a pattern.
[0007]
[Means for Solving the Problems and Effects of the Invention]
1st invention is a pattern inspection apparatus which inspects the pattern formed on the to-be-inspected object,
An illumination unit that irradiates illumination light onto the surface to be inspected;
An imaging unit that captures a reflected light image based on light reflected by the surface to be inspected by illumination light;
A binarization processing unit that binarizes the reflected light image and generates a pattern image corresponding to the pattern formed on the inspection object;
Predetermined hole position images representing the positions of the hole portions in the design pattern are arranged in the area corresponding to the hole portions of the pattern image, and the hole position images are expanded until reaching the pattern image surrounding the hole position image. An expansion processing unit for generating an expansion hole position image;
An inspection unit that inspects the pattern based on the inspection image obtained by combining the pattern image and the expansion hole position image is provided.
[0008]
As described above, according to the first invention, the pattern image obtained from the reflected light from the inspection object and the predetermined hole position image are used, and the hole position image is embedded in the portion corresponding to the hole of the pattern image. An inspection image is generated, and pattern inspection is performed using this image. Thereby, even when the transmitted light image cannot be used due to the filling of the through holes or the presence of the non-through holes, it is possible to accurately inspect for the presence or absence of defects on the pattern formed on the printed circuit board.
[0009]
The second invention is an invention subordinate to the first invention,
The predetermined hole position image is an image smaller than an actual hole size in the design pattern.
[0010]
As described above, according to the second invention, since the size of the hole position image is set smaller than the hole diameter of the design value, it is possible to process even if a certain amount of deviation occurs in the captured pattern image. It becomes.
[0011]
A third invention is an invention subordinate to the first and second inventions,
It further comprises a suction stand for sucking and holding the inspection object from the side opposite to the inspection surface of the inspection object.
[0012]
As described above, according to the third invention, since only reflected light is used, it is possible to employ a suction stand that holds the entire surface of the printed board opposite to the surface to be inspected by suction force. It can be avoided that the defect inspection becomes inaccurate due to the deflection.
[0013]
The fourth invention is an invention subordinate to the first to third inventions,
The expansion processing unit expands the pattern image by a predetermined amount, expands the arranged hole position image until reaching the expanded pattern image surrounding the pattern image, and further expands the expanded hole position image. The expansion hole position image is generated by being expanded by a predetermined amount.
[0014]
As described above, according to the fourth invention, after the pattern image is expanded by a predetermined amount in advance, the hole position image is expanded by expanding the hole position image. The phenomenon of expanding beyond the pattern image can be avoided.
[0015]
A fifth invention is a pattern inspection method for inspecting a pattern formed on an object to be inspected,
Illuminating illumination light onto the surface to be inspected of the inspection object, and imaging a reflected light image based on the light reflected by the surface of the inspection object;
Binarizing the reflected light image to generate a pattern image corresponding to the pattern formed on the inspection object;
Placing each predetermined hole position image representing the position of the hole in the design pattern in an area corresponding to the hole in the pattern image;
Generating an expanded hole position image in which each of the hole position images is expanded until a pattern image surrounding the hole position image is reached;
And a step of inspecting the pattern based on the inspection image obtained by combining the pattern image and the expanded hole position image.
[0016]
As described above, according to the fifth invention, the pattern image obtained from the reflected light from the object to be inspected and the predetermined hole position image are used, and the hole position image is embedded in the portion corresponding to the hole of the pattern image. An inspection image is generated, and pattern inspection is performed using this image. Thereby, even when the transmitted light image cannot be used due to the filling of the through holes or the presence of the non-through holes, it is possible to accurately inspect for the presence or absence of defects on the pattern formed on the printed circuit board.
[0017]
The sixth invention is an invention subordinate to the fifth invention,
The predetermined hole position image is an image smaller than an actual hole size in the design pattern.
[0018]
As described above, according to the sixth invention, since the size of the hole position image is set smaller than the hole diameter of the design value, it is possible to process even if a certain amount of deviation occurs in the captured pattern image. It becomes.
[0019]
A seventh invention is an invention subordinate to the fifth and sixth inventions,
The step of generating the expansion hole position image includes:
Inflating the pattern image by a predetermined amount;
Expanding each of the arranged hole position images until reaching an expanded pattern image surrounding it;
And expanding the expanded hole position image by a predetermined amount.
[0020]
As described above, according to the seventh invention, after the pattern image is expanded by a predetermined amount in advance, the hole position image is expanded by expanding the hole position image. The phenomenon of expanding beyond the pattern image can be avoided.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a pattern inspection apparatus according to an embodiment of the present invention. In FIG. 1, the pattern inspection apparatus according to the present embodiment includes an imaging unit 1 and an inspection unit 2. The imaging unit 1 includes an adsorption table 11, an illumination unit 12, and an imaging camera 13. The inspection unit 2 includes a binarization processing unit 21, a pattern image storage unit 22, a hole position image storage unit 23, an inspection image generation unit 24, an inspection unit 25, and an output unit 26.
First, the outline | summary of each structure of the imaging part 1 and the test | inspection part 2 is demonstrated below.
[0022]
In the imaging unit 1, the suction table 11 is a table on which the printed board 10 to be processed is placed, and has a function of fixing the placed printed board by a vacuum suction force. The illumination unit 12 is disposed above the placement surface of the suction table 11 and irradiates predetermined illumination light toward the printed circuit board 10 placed on the suction table 11. The imaging camera 13 is disposed above the mounting surface of the suction table 11 and captures a reflected light image based on light reflected from the surface of the printed board 10 (surface 10a to be inspected) by illumination light emitted from the illumination unit 12. To do. The captured reflected light image is output to the binarization processing unit 21 of the inspection unit 2.
In the inspection unit 2, the binarization processing unit 21 binarizes the reflected light image input from the imaging camera 13 on a pixel basis based on a predetermined reference. This binarized reflected light image is stored in the pattern image storage unit 22 as a pattern image. The hole position image storage unit 23 stores in advance a predetermined hole position image representing the position of the hole in the design pattern. The inspection image generation unit 24 uses the pattern image and the hole position image to generate an inspection image in which pixels obtained from the hole position image are embedded in a pixel portion that will correspond to the hole in the pattern image. To do. The inspection unit 25 performs a desired inspection using the inspection image generated by the inspection image generation unit 24. The output unit 26 is a display device such as a display, and outputs the result of the inspection performed by the inspection unit 25.
[0023]
Next, an inspection method performed by the pattern inspection apparatus of the present embodiment will be described with further reference to FIGS. FIG. 2 is a flowchart showing a processing procedure of an inspection method performed by the pattern inspection apparatus according to the embodiment of the present invention.
First, a printed circuit board to be processed is placed on the suction table 11 (step S110). A number of suction holes (not shown) are provided in the substrate mounting surface of the suction table 11, and by sucking air from these suction holes, the printed board is placed on the suction table 11 by a vacuum suction force. Adhere closely. Thereby, a printed circuit board can be mounted on the suction stand 11 without bending.
[0024]
Next, illumination light is irradiated from the illumination unit 12 toward the printed circuit board placed on the suction table 11, and a reflected light image is captured by light reflected by the printed circuit board in the imaging camera 13 (step S120). ). At this time, the pattern portion, the substrate material portion, and the hole portion (hole portion) have different light reflectivities depending on the material, surface treatment, and the like. It will be different in parts. Generally, since the pattern portion is formed of a conductive metal, the reflected light level of that portion is the highest. Here, the “hole portion” means a portion where a through hole such as a through hole is formed, a portion where a non-through hole such as a via hole is formed, or a through hole or a non-through hole is filled with a resin or the like. Say part.
[0025]
The binarization processing unit 21 inputs a reflected light image captured by the imaging camera 13, binarizes the reflected light image into a value of “0” or “1” in units of pixels based on a predetermined reference, A pattern image is generated (step S130). Here, as described above, when the reflected light level of the pattern portion is the highest in the reflected light image, the reflected light level is such that the pattern portion has the value “1” and the other portions have the value “0”. The threshold value may be set as a predetermined reference. Thereby, the pattern image which specified only the pattern part in the printed circuit board used as processing object can be generated. This pattern image is stored in the pattern image storage unit 22.
FIG. 3 illustrates a part of the pattern image P generated by the binarization process of the reflected light image. In the figure, the pixel value of the shaded portion is “1”.
[0026]
On the other hand, the hole position image storage unit 23 stores in advance a predetermined hole position image H representing the position of the hole in the design pattern. As shown in FIG. 4, the hole position image H has, for each hole portion designed on the printed circuit board, a pixel (a hatched area in the drawing) in a predetermined area smaller than the designed hole diameter. 1 ”and all the pixels in other areas are binary images. It should be noted that the size of the predetermined area set in each hole can be arbitrarily set by taking into account the later-described expansion process.
The hole position image H may be generated from CAD data for creating a design pattern, or a film in which a hole pattern is drawn based on a design value (design pattern) may be scanned in and captured. .
[0027]
Next, the inspection image generation unit 24 uses the pattern image P stored in the pattern image storage unit 22 and the hole position image H stored in the hole position image storage unit 23 as follows. An image is generated (step S140). A more detailed processing procedure of this step S140 is shown in FIG.
Referring to FIG. 5, the inspection image generation unit 24 first performs a process (expansion process A) for expanding the pattern image by a predetermined amount (step S141). This expansion (the same applies to the expansion described below) is performed on a pixel-by-pixel basis, and a 4-connected expansion and / or an 8-connected expansion known in the image processing field is used as the technique. Therefore, the predetermined amount referred to here is expressed by how many times the 4-connected expansion and / or the 8-connected expansion is performed. Note that the 4-connected expansion is a technique for expanding four pixels adjacent to a certain pixel in the vertical and horizontal directions, and the 8-connected expansion is a technique for expanding all eight pixels adjacent to a certain pixel. It is. For example, when the pattern image P and the hole position image H exist in the positional relationship shown in FIG. 6A, the pattern image P is expanded pixel Ea as shown in FIG. Inflates by the amount. In the example of FIG.6 (b), the case where 4 connection expansion is performed once is shown.
[0028]
In the expansion processing A, when there is a portion P1 (upper right portion) where the land pattern of the pattern image is drawn with a width of one pixel as shown in FIG. 6A, the expansion of the hole position image performed in step S142 described later. In the process B, it is performed to prevent the hole position image from expanding beyond a portion corresponding to the hole HP in the pattern image. Therefore, when the land pattern of the pattern image is drawn with a width of 2 pixels or more, such expansion does not occur, and the expansion process A can be omitted.
[0029]
Next, based on the pattern image PE expanded by the expansion process A, the inspection image generation unit 24 performs a process of expanding the hole position image H until reaching the pattern image PE (expansion process B) (step S142). . This expansion process B is performed in order to determine a portion that is considered to be a hole HP obtained from the pattern image PE as the hole HP. For example, by executing the expansion process B on the image shown in FIG. 6B, the hole position image reaches the pattern image, that is, the blank portion (the portion of the value “0” in the pattern image) in FIG. The pixel is expanded by the expansion pixel Eb until it disappears (FIG. 6C). In the expansion process B, control is performed so that the expansion of each pixel constituting the hole position image ends when the pattern image PE is reached.
Incidentally, when the expansion process B is executed based on the pattern image P that does not execute the expansion process A (FIG. 6A), the hole position image HEe exceeds the pattern image P as shown in FIG. It will expand. Such cross-border expansion becomes a problem because it is recognized as a defect in pattern inspection.
[0030]
Next, the inspection image generating unit 24 further expands a predetermined amount (expansion process) so that the expansion hole position image HE1 expanded by the expansion process B matches the hole HP of the actual pattern image. C) is performed (step S143). In this expansion process C, the pixel part (blank part HS in the hole part of FIG. 6E) where the pattern image is virtually expanded in the expansion process A is finally converted into the expansion hole position image HE2. In order to fill in, the process of expanding by the expansion pixel Ec is performed (FIG. 6F).
Here, the predetermined amount is determined as follows corresponding to the predetermined amount in the expansion process A. In the case where the expansion performed by the expansion process A has been completed by four-connection expansion, the expansion process C performs the same expansion as the expansion process A. In the case where the expansion performed by the expansion process A has been completed with eight connected expansions, the expansion process C performs the same expansion as the expansion process A, and then performs four connected expansions once.
If the expansion process A is not performed for the reason described above, the expansion process C need not be performed.
[0031]
When the expansion hole position image HE2 that matches the hole HP of the actual pattern image P is generated by the expansion processes A to C, the inspection image generation unit 24 generates the expansion hole position image HE2 and the pattern image P. Are combined to generate an inspection image (that is, the image shown in FIG. 6F), and if necessary, inspection prohibition information is generated (step S144). Here, the inspection prohibition information is information that gives an instruction to exclude this portion from the inspection target when there is a defect such as a portion where the land pattern is interrupted in the pattern image. The inspection prohibition information is generated based on an image HE3 obtained by expanding the corresponding hole position image portion by a predetermined amount (expansion process D).
In addition, when each process mentioned above is comprised by a functional block, it can represent as FIG. In FIG. 7, the phase adjustment is used to adjust the delay time generated by each expansion process when the pattern image P and the expansion hole position image HE2 subjected to the expansion process are combined. Note that P ′ in FIG. 7 indicates a pattern image after phase adjustment.
[0032]
Moreover, the specific structural example used for each expansion process AD which performs 4 connection expansion mentioned above and 8 connection expansion is shown in FIG. 8A is a configuration example of the expansion processes A, C, and D, and FIG. 8B is a configuration example of the expansion process B. In this configuration, eight pixel values (see FIG. 9) adjacent to the pixel (B1) to be expanded are extracted from the input image using the flip-flop (FF) and the line memory. In the expansion processes A, C, and D, the following logical processing is performed on each pixel value according to the number of connections, and images PE, HE2, and HE3 obtained by expansion are output. Note that EX in the following logical expression and FIG. 8 is an input for giving an instruction to inflate / not inflate, and is used to control how much to inflate in the case of multistage connection. Also, clocks necessary for operation are omitted.
4-connected expansion logic: Y = B1or (EXand (A1orB0orB2orC1))
8-connected expansion logic: Y = B1or (EXand (A0orA1orA2orB0orB2orC0orC1orC2))
On the other hand, in the expansion process B, an expansion prohibition image (= pattern image PE after the expansion process A is finished, P if the expansion process A is not performed) is added, and an attempt is made to expand the expansion process B. In the case where a pixel corresponds to an expansion prohibiting image (PE or P, represented by DP in the following logical expression), the pixel is not expanded.
4-connected expansion logic: Y = B1or (notDPandEXand (A1orB0orB2orC1))
8-connected expansion logic: Y = B1or (notDPandEXand (A0orA1orA2orB0orB2orC0orC1orC2))
A multi-stage expansion process can be realized by connecting these configurations in multiple stages in cascade.
[0033]
Referring to FIG. 2 again, the inspection unit 25 uses the inspection image generated by the inspection image generation unit 24 to execute a desired inspection based on a pattern matching method, a design rule check method, or the like (step S150). ), And outputs the inspection result via the output unit 26 (step S160).
[0034]
As described above, according to the pattern inspection apparatus and method according to one embodiment of the present invention, the pattern image obtained from the reflected light and the predetermined hole position image are used, and the hole position image corresponds to the hole portion of the pattern image. An inspection image embedded in a portion to be generated is generated, and pattern inspection is performed. Thereby, even if it is a printed circuit board which cannot utilize a transmitted light image due to the filling of a through hole or the existence of a non-through hole, it is possible to accurately inspect the presence or absence of a defect on a pattern formed on the printed circuit board.
In addition, since only reflected light is used, it is possible to employ a suction stand that holds the entire lower surface of the printed circuit board with a vacuum suction force, and avoids inaccurate defect inspection due to deflection of the printed circuit board. . An adsorption stand that holds the entire lower surface of the printed circuit board with an electrostatic adsorption force may be employed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a pattern inspection apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a processing procedure of an inspection method performed by the pattern inspection apparatus according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating a part of a pattern image P;
4 is a diagram illustrating a part of a hole position image H. FIG.
FIG. 5 is a flowchart showing a more detailed processing procedure of step S140 shown in FIG.
FIG. 6 is a diagram for explaining an expansion process performed on a pattern image and a hole position image.
FIG. 7 is a diagram illustrating each process illustrated in FIG. 5 as a functional block.
FIG. 8 is a block diagram showing a specific configuration for executing expansion processing A to D;
FIG. 9 is a diagram illustrating the concept of 4-connected expansion and 8-connected expansion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Imaging part 2 ... Inspection part 10 ... Printed circuit board 11 ... Suction stand 12 ... Illumination part 13 ... Imaging camera 21 ... Binarization processing part 22 ... Pattern image storage part 23 ... Hole position image storage part 24 ... Image generation for inspection Section 25 ... Inspection section 26 ... Output sections Ea, Eb, Ec ... Expansion pixel P ... Pattern image H ... Hole position image HE1, HE2 ... Expansion hole position image HP ... Hole

Claims (7)

A pattern inspection apparatus for inspecting a pattern formed on an inspection object,
An illumination unit that irradiates illumination light onto the surface to be inspected of the inspection object;
An imaging unit that captures a reflected light image based on the light reflected by the surface to be inspected by the illumination light;
A binarization processing unit that binarizes the reflected light image and generates a pattern image corresponding to a pattern formed on the inspection object;
Predetermined hole position images representing the positions of the holes in the design pattern are arranged in the area corresponding to the holes in the pattern image, and the hole position images are expanded until reaching the pattern image surrounding them. An expansion processing unit for generating an expansion hole position image,
A pattern inspection apparatus provided with the test | inspection part which test | inspects a pattern based on the image for a test | inspection which synthesize | combined the said pattern image and the said expansion hole position image. The pattern inspection apparatus according to claim 1, wherein the predetermined hole position image is an image smaller than an actual hole size in a design pattern. The pattern inspection apparatus according to claim 1, further comprising a suction stand for sucking and holding the inspection object from a surface opposite to the inspection surface of the inspection object. The expansion processing unit expands the pattern image by a predetermined amount, expands the arranged hole position image until reaching the expanded pattern image surrounding the pattern image, and expands the hole position. The pattern inspection apparatus according to claim 1, wherein the image is further expanded by a predetermined amount to generate an expansion hole position image. A pattern inspection method for inspecting a pattern formed on an inspection object,
Illuminating an inspection surface to be inspected of the inspection object with illumination light, and capturing a reflected light image based on the light reflected by the surface of the inspection object;
Binarizing the reflected light image to generate a pattern image corresponding to a pattern formed on the inspection object;
Placing each predetermined hole position image representing the position of the hole in the design pattern in an area corresponding to the hole in the pattern image;
Generating expanded hole position images, each expanded until the hole position image reaches the pattern image surrounding the hole position image;
A pattern inspection method comprising: inspecting a pattern based on an inspection image obtained by combining the pattern image and the expanded hole position image. The pattern inspection method according to claim 5, wherein the predetermined hole position image is an image smaller than an actual hole size in a design pattern. The step of generating the expansion hole position image includes:
Inflating the pattern image by a predetermined amount;
Expanding each of the arranged hole position images until reaching the expanded pattern image surrounding it;
The pattern inspection method according to claim 5, further comprising a step of expanding the expanded hole position image by a predetermined amount.

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