JPH08110305A - Method and device for inspecting appearance - Google Patents

Abstract

PURPOSE: To accurately judge a plurality of patterns with different widths by setting the line width allowable value of a pattern to be inspected, determining the line kind of pattern after each of measured values is compared with it and generating a radial code based on the result. CONSTITUTION: A storage circuit 14 stores a binarization data of reference pattern of a pattern to be inspected, and a measuring circuit 15 measures a measurement value based on this data, then a center detecting circuit 16 detects a central signal. A length measurement value and central signal are inputted in an allowable value determining circuit 17 and the maximum and minimum values of the allowable value for line width that is to be applied for the pattern to be inspected are obtained thereby. The circuits 16 and 17 expand the width to be judged as a center as far as possible according to the width of a reference line and the deviation between the reading positions of the pattern to be inspected that is piked up by a CCD camera 2 and the reference pattern from the circuit 14 is covered. When the deviation is large, it is corrected by a positioning circuit 19. When the correction cannot be made, a central signal comparing circuit 18 outputs an omission failure signal to an OK/NG judging circuit 11. Thus, a plurality of wiring patterns can be judged individually.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection apparatus used for pattern inspection of printed wiring boards. Printed wiring boards used for electronic devices in recent years have been highly multilayered and thinned. For this reason, visual inspection can no longer be performed to detect defects such as pattern defects, wire breaks, and short circuits on the printed wiring board, and therefore appearance inspection apparatuses have been used.

For appearance inspection, (1) a detection technique for optically reading a wiring pattern and converting it into an electric signal by a method such as binarization (2) discrimination for detecting a defect in the wiring pattern from the obtained inspection signal Technology exists.

The present invention relates to (2) a discrimination technique after the inspection signal is obtained.

[0004]

2. Description of the Related Art As a conventional appearance inspection apparatus, Japanese Patent Application No.
No. -10707407 (first example).

This conventional appearance inspection apparatus (first example) is designed so that the center of the pattern of the printed wiring board to be inspected is
The pattern lengths in a plurality of directions are measured by a radial length measuring sensor, and the measured values are coded (hereinafter referred to as "radial code"). Then, the quality of the pattern is determined by comparing this radial code with reference data (hereinafter referred to as “dictionary”) in which the quality of the radial code is stored in advance. The dictionary data stored in the dictionary has versatility that can be adapted to various patterns by creating a plurality of data corresponding to various patterns and replacing the plurality of data with the dictionary and storing the data.

Further, as a second example of the improvement of the above-mentioned conventional appearance inspection apparatus, there is an appearance inspection apparatus disclosed in Japanese Patent Laid-Open No. 5-264240. The second example of this conventional appearance inspection apparatus is the type of defect in the wiring pattern (for example, copper residue,
Set the type (hereinafter referred to as "category") for each protrusion (no need for protrusions, intervals, etc.), select a category stored in the dictionary based on the radial code obtained from the detected wiring pattern, and select the radial code as a category. Convert to code. Then, the converted category code and the category code stored in the dictionary are used to determine the quality of the wiring pattern and the type of the defect, so that a more accurate inspection according to the defect category of the wiring pattern is performed. Met.

In the conventional inspection logic (radial matching method), a judgment zone called an allowable value is provided at a position from the center of the pattern corresponding to the line width of the lead pattern, and the end portion of the lead pattern is within this allowable value. When present, the lead pattern was normal. At this time, assuming that the line width of the lead pattern is one, an allowable value of one kind of line width is set, and the quality of the pattern is judged by comparing with the pattern to be inspected in the binarized image obtained from the sample. I was making a decision.

FIG. 11 shows an example of an inspection method in the above-mentioned conventional appearance inspection apparatus. For example, in FIG.
Is the standard value of the line width of a normal pattern. When the inspection pattern image P ₁₀ as shown in FIG. 11 is obtained, the position d
_{At 1} the line width of the pattern to be inspected falls within the allowable value centered on a, but at position d ₂ the line width is b, which is smaller than the allowable value, so it is determined to be "thin". Further, at the position d ₃ , the line width is c, which is thicker than the allowable value, so that it is determined as “thick”.

As described above, in the conventional appearance inspection apparatus, when the reference pattern is one type, the quality of the pattern to be inspected can be reliably determined.

[0010]

However, the conventional visual inspection apparatus has a disadvantage of making an erroneous determination when a plurality of types of wiring patterns have different widths on the same substrate.

Problems of the conventional visual inspection apparatus will be described with reference to FIG. As shown in FIG. 12, the sample SP has patterns having a plurality of types of line widths. The pattern of the thickest straight line portion is called a straight line lead L ₃ , the pattern of the medium straight line portion is called a straight line lead L ₂ , and the pattern of the thinnest straight line portion is called a straight line lead L ₁ . In addition, lands R ₀ are scattered on the sample SP.

In the conventional appearance inspection apparatus, it is assumed that the line width of the pattern is only one kind. Therefore, for example, various values of the inspection apparatus are set so that the linear lead L ₂ in FIG. 12 is located at the center of the allowable value. Had set.

However, in this setting, the linear lead L ₁ having a line width narrower than the linear lead L ₂ and the linear lead L ₃ having a wide line width are naturally out of the allowable values set based on the standard value of the linear lead L _2. It often comes off. In other words, straight lead L
_{The 1} and the straight lead L ₃ are determined to be defective patterns even though there are no missing patterns or defects. This inconvenience cannot be substantially solved even if the reference value is changed to another linear lead.

Further, when the allowable value range is widened in order to include all the line widths within the allowable value, there is a possibility that a defective pattern which should originally be excluded as a defective product may be judged as a non-defective product. .

Therefore, it is an object of the present invention to provide an appearance inspection apparatus capable of making an accurate determination even if there are a plurality of patterns to be inspected having different widths.

[0016]

According to a first aspect of the present invention, a substantially center of a pattern is detected from a binarized image obtained by photographing a sample, and the pattern is detected in a plurality of directions from the detected substantially center. In the appearance detection method that converts each length measurement value of to a radial code and detects pattern defects based on the radial code, set the line width allowable value of the pattern to be inspected and set each length measurement value to the line width. The line type of the pattern is determined by comparing with the allowable value, and the radial code is generated based on the determined line type of the pattern.

According to a second aspect of the present invention, the substantially center of the pattern to be inspected is detected from the binarized image obtained by photographing the sample, and each of the pattern to be inspected in a plurality of directions from the detected substantially center. Convert the length measurement value to a radial code,
In the appearance detection method that detects defects in the pattern to be inspected based on the radial code, the line width allowable value is set based on the reference line width value obtained by measuring the reference pattern in advance, and each length measurement value is lined. The line type of the pattern to be inspected is determined by comparing the allowable width values, and a radial code is generated based on the determined line type of the pattern to be inspected.

According to a third aspect of the present invention, in the appearance inspection method according to the second aspect, the smallest line width value obtained by measuring the reference pattern is the reference line width value of the reference pattern. Then, the line width allowable value is set based on the reference line width value.

According to a fourth aspect of the present invention, in the appearance inspection method according to the second or third aspect, the maximum width and the minimum width of the reference line width are adjusted to predetermined values in advance, and the line width allowable value is set. To set.

According to a fifth aspect of the present invention, in the appearance inspection method according to the second to fourth aspects, the line width allowable value is set corresponding to each shape existing in the reference pattern, and the line width allowable value is set. The pattern shape of the reference pattern is determined based on, and the line width allowable value is corrected based on the pattern shape.

According to a sixth aspect of the present invention, an image pickup means for picking up the pattern to be inspected formed on the sample, an image binarizing means for binarizing the picked-up image, and a binary image Radial length measuring means for measuring the pattern portion length of the pattern portion in each pixel row extending in a plurality of directions from an arbitrary center pixel, and center detecting means for detecting the approximate center of the pattern to be inspected from the length measured values in the plurality of directions. An allowable value setting means for setting a line width allowable value for determining the line type of the pattern to be inspected, a line type of the pattern to be inspected based on the line width allowable value, and a plurality of directions based on the determination result. And a detecting means for detecting a defect in the pattern to be inspected based on the radial code.

According to a seventh aspect of the invention, in the appearance inspection apparatus according to the sixth aspect, the allowable value setting means and the reference pattern generating means for generating the binary image data of the reference pattern, and the binary image. Reference pattern length measuring means for measuring the pattern portion length of the pattern portion in each pixel row extending in a plurality of directions from an arbitrary center pixel above, and a reference for detecting the approximate center of the reference pattern from the length measurement values in a plurality of directions The pattern center detection means, the reference line width of the reference pattern is determined based on the length measurement value and the approximate center position of the reference pattern, and the line width allowable value for determining the line type of the pattern to be inspected based on the reference line width. And a permissible value determining means for setting.

The invention according to claim 8 is the appearance inspection apparatus according to claim 7, wherein the approximate center of the reference pattern and the approximate center of the inspected pattern are compared to detect a missing defect in the inspected pattern. It is configured to include defect detection means.

According to a ninth aspect of the present invention, in the appearance inspection apparatus according to the seventh aspect, the reference pattern center detecting means allows the line width of the area for detecting the substantially center of the reference pattern with the original center position as the center. It is constructed by expanding it to near the area.

According to a tenth aspect of the present invention, in the appearance inspection apparatus according to the seventh aspect, the allowable value determining means uses the smallest one of the line width values obtained by measuring the reference pattern as the reference. The reference line width value of the pattern is set, and the line width allowable value is set based on the reference line width value.

The invention according to claim 11 is the appearance inspection apparatus according to claim 7, wherein the allowable value determining means determines the line based on the maximum width and the minimum width of the reference line width adjusted to a predetermined value in advance. Set the width allowance.

According to a twelfth aspect of the present invention, in the appearance inspection apparatus according to the sixth or seventh aspect, the pattern portion length of the pattern to be inspected is interposed between the tolerance setting means and the coding means. The pattern shape in the vicinity of the center of the pattern to be inspected is specified on the basis of the above, and the line width allowable value is corrected based on the specified pattern shape.

According to a thirteenth aspect of the present invention, in the appearance inspection apparatus according to the twelfth aspect, the correction means obtains the correction data of the line width allowable value corresponding to the pattern shape of the reference pattern based on the line width allowable value. The dictionary means for outputting is compared with the line width allowable value and the pattern shape stored in the dictionary means, and when the correction data of the pattern shape corresponding to the line width allowable value is stored in the dictionary means, the correction data is obtained from the dictionary means. And a calculation means for correcting the line width allowable value based on the correction data read from the dictionary means by the matching means.

[0029]

According to the first aspect of the invention, first, the sample is photographed and the approximate center of the pattern is detected from the obtained binarized image. Then, each measured value of the pattern in a plurality of directions from the detected substantially center is converted into a radial code, and a defect of the pattern is detected based on the radial code. Then, by setting the line width allowable value of the pattern to be inspected and comparing each measured value with the line width allowable value, a line indicating which line width the measured value has is a pattern. A species is determined and a radial code is generated based on the determined pattern line species.

Therefore, the generated radial code is generated for the correct line type without erroneously recognizing the line width.
According to the second aspect of the invention, the line width allowable value is set based on the reference line width value obtained by measuring the reference pattern in advance. The line type of the inspected pattern is determined by comparing each length measurement value obtained from the inspected pattern with the line width allowable value. A radial code is generated based on the determined line type of the pattern to be inspected.

According to the invention of claim 3, claim 2
In the appearance inspection method described in, the minimum line width value obtained by measuring the reference pattern is set as the reference line width value of the reference pattern, and the line width allowable value is set based on the reference line width value. To do.

According to the invention as set forth in claim 4, the maximum width and the minimum width of the reference line width are individually adjusted and set in advance to set the line width allowable value. As a result, an accurate inspection can be performed according to the characteristics of the pattern to be inspected.

According to the fifth aspect of the invention, a plurality of line width allowable values are set corresponding to the shape of the reference pattern. Then, the line width allowable value for the pattern shape near the center of the reference pattern is selected based on each length measurement value obtained from the inspected pattern.

According to the invention of claim 6, the image pickup means picks up an image of the pattern to be inspected formed on the sample,
The binarizing means binarizes the captured image. The radial length measuring means measures the pattern portion length of the pattern portion in each pixel row extending in a plurality of directions from an arbitrary central pixel on the binarized image. The center detecting means detects the approximate center of the pattern to be inspected from the measured values in a plurality of directions, and the tolerance setting means sets the line width tolerance for determining the line type of the pattern to be inspected. The coding means determines the line type of the pattern to be inspected based on the line width allowable value, and converts each length measurement value in a plurality of directions into a radial code based on the determination result. Then, the detecting means detects a defect in the pattern to be inspected based on the radial code.

According to the invention described in claim 7, in the allowable value setting means, the reference pattern generating means generates the binary image data of the reference pattern, and the reference pattern length measuring means on the binary image. The pattern portion length of the pattern portion in each pixel row extending in a plurality of directions from an arbitrary central pixel is measured. The reference pattern center detecting means detects the approximate center of the reference pattern from the measured values in a plurality of directions. The allowable value determining means determines the reference line width of the reference pattern based on the length measurement value and the substantially center position of the reference pattern, and the line width for determining the line type of the pattern to be inspected based on the reference line width. Set the allowable value.

According to the eighth aspect of the invention, the missing defect detecting means compares the approximate center of the reference pattern with the approximate center of the inspected pattern, and detects the missing defect in the inspected pattern. According to the invention as set forth in claim 9, the reference pattern center detecting means defines an area for detecting a substantially center of the reference pattern,
Since the original center position is widened to the vicinity of the line width allowable region as a center, the inspection can be sufficiently performed even if the center position is slightly deviated between the reference pattern and the pattern to be inspected.

According to the tenth aspect of the invention, the allowable value determining means sets the minimum of the line widths obtained by measuring the reference pattern as the reference line width of the reference pattern, and sets the reference line width. Since the line width allowance is set based on, the minimum line width is easily set as a line width.

According to the eleventh aspect of the present invention, the allowable value determining means sets the line width allowable value on the basis of the maximum width and the minimum width of the reference line width adjusted in advance, so that the maximum width and the minimum width are set. Can be changed appropriately according to the characteristics of the pattern to be inspected and can be inspected with optimum parameters.

According to the twelfth aspect of the invention, the correction means is interposed between the tolerance setting means and the coding means, and substantially correct the center of the pattern to be inspected based on the pattern portion length of the pattern to be inspected. The pattern shape in the vicinity is specified, and the line width allowable value is corrected based on the specified pattern shape.

According to the thirteenth aspect of the invention, in the correction means, the dictionary means outputs the correction data of the line width allowable value corresponding to the pattern shape of the reference pattern based on the line width allowable value. The matching means compares the line width allowable value with the pattern shape stored in the dictionary means, and reads the correction data from the dictionary means when the correction data of the pattern shape corresponding to the line width allowable value is stored in the dictionary means. put out. The calculation means corrects the line width allowable value based on the correction data read from the dictionary means by the matching means.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the appearance inspection method and apparatus of the present invention will be described with reference to the drawings. (I) First Embodiment A first embodiment of the present invention relates to a visual inspection method and apparatus to which the inventions of claims 1 to 4 and claims 6 to 11 are applied.

Description of Configuration FIG. 1 shows the configuration of a first embodiment of the present invention. As shown in FIG. 1, an appearance inspection apparatus 100 of the present invention inspects a sample SP which is an inspected object irradiated with illumination light for photographing by a light source 1. The sample is, for example, a printed wiring board or the like, and wiring patterns having a plurality of line widths are wired.

The CCD camera 2 captures the image of the sample SP and uses it as an analog image signal. The binarization circuit 3 binarizes this analog image signal by a known image processing technique.
The storage circuit 4 is a so-called image memory, and stores a binarized image signal.

The length measuring circuit 5 measures the pattern lengths in a plurality of directions (for example, 8 directions) at arbitrary points at the center of the pattern in the binarized signal by a length measuring sensor provided in a radial direction, and aligns the front and back directions. Measured value (eg 16 total
The center detection circuit 6 calculates the difference in the front-back direction among the length measurement values output from the length measurement circuit 5, and outputs a center signal (for example, "1") when the center is detected.

The radial encoding circuit 7 encodes the length measurement values of the pattern portion length in a plurality of directions based on the length measurement values to obtain a radial code. The category conversion circuit 8 is a radial encoding circuit 7 from a plurality of category code groups showing pattern shapes corresponding to various radial codes.
Select the category code that corresponds to the radial code encoded in.

The category map creating circuit 9 stores the category code as a distribution of the category code based on the inputted category. For example, by inputting some category codes, a category map of the approach point between the straight lead portion and the land is created.

The comparison circuit 10 determines whether there is a possibility of being applicable based on the category search method stored in the search method dictionary 12 _-2 and the search rule stored in the pass / fail judgment rule dictionary 12 _-1 . The higher category is judged and a defect signal is output.

The pass / fail result determination circuit 11 determines pass / fail of the pattern to be inspected based on the defect signal. The master data storage circuit 13 stores reference pattern data serving as a reference for comparison when inspecting a pattern to be inspected.

The memory circuit 14 reads out and stores the reference pattern data at a required position from the master data memory circuit 13. The length measuring circuit 15, like the length measuring circuit 5 for the pattern to be inspected, measures the width of the reference pattern and the like to obtain a radial code.

The center detection circuit 16 measures the center of the reference pattern based on the length measurement value measured by the length measurement circuit 15.
The allowable value determining circuit 17 determines the maximum and minimum allowable values of the line width to be applied to the pattern to be inspected, based on the center signal detected by the center detecting circuit 16 and the length measurement value.

The center signal comparison circuit 18 includes the center detection circuit 6
Center signal of the pattern to be inspected detected by the center detection circuit 1
6 is compared with the detected center signal of the reference pattern, and when a large deviation of the center is detected, a missing defect signal is output to the pass / fail result determination circuit 11.

The alignment circuit 19 corrects the overall positional deviation between the pattern position imaged by the CCD camera 2 and the pattern position read from the master data storage circuit 13.

Description of Operation Next, the operation will be described. i) Flow of image processing of pattern to be inspected The printed wiring board which is the sample SP has a land portion where through holes and the like are provided and a lead pattern portion which is a main body of wiring. There are a plurality of line width types in the lead pattern.

The pattern to be inspected on this sample SP is CC
The image is taken by the D camera 2 and binarized. In the binarized image of the pattern to be inspected, the length measuring circuit 5 counts the number of pixels from a certain point to the end of the pattern in a radial manner, and converts it into a length measured value.

The length measurement value is subjected to center detection by the center detection circuit 6 for the pattern to be inspected, and when it is at the center, a center signal of "1" is generated. The length measurement value is supplied to the radial coding circuit 7 together with the center signal.

The radial encoding circuit 7 encodes four sets of vertical, horizontal and diagonal of the measured values. The code includes a length code (2 bits), a balance code (1 bit), and a direction code (1 bit) for each of four sets of directions.

First, in the radial encoding circuit 7, the measured lengths are different by 180 ° (for example, 0 ° and 180 °).
The absolute value of the difference between the measured values of the radius (in the ° direction) is calculated to detect whether or not the measured values in both directions are balanced. Even if the balance is not balanced, the direction code indicating which is longer is output, and two bits of the balance code indicating the balance state and the direction code are generated.

At the same time, the sum of the bidirectional measurement values is calculated and compared with the coding threshold values V _th1 and V _th2 . The magnitude relationship is determined by comparing these threshold values, and when the measured value on one side is equal to or greater than the "OV threshold value", "O
V ”(overflow).

Here, the two threshold values V _th1 and V _th2 for detecting the line width of the lead pattern are the maximum and minimum of the allowable line width values supplied from the allowable value determination circuit 17 described later. It is a value. When the sum of the length measurement values is between the two threshold values, the pattern to be inspected for the input length measurement value can be determined as a lead pattern having a predetermined line width. Conventionally, this value is fixed, but in the present invention, this value changes. The determination code obtained here is a total of 2 bits including "OV" and a bit indicating the magnitude relationship.

By the above processing, a 4-bit code is obtained for one set of directions. The radial encoding circuit 7 is
This is obtained in four sets of directions and made into a 16-bit code. This code is the radial code. The radial code is output from the radial encoding circuit 7 when the center is detected by the center detecting circuit 6.

The pattern can be judged also by the distribution of the radial codes. However, when trying to determine the quality of a pattern based on the distribution of radial codes, there are too many combinations, so these radial codes are converted into category codes representing the shape of the corresponding pattern.

The category conversion circuit 8 is composed of a ROM-structured dictionary or the like, uses the code content of the radial code as an address, and reads and outputs the category code stored at the address. As a result, the pattern shape around an arbitrary point of the pattern to be inspected is coded and obtained.

Whether the pattern to be inspected is a normal pattern or an abnormal (defect) state is determined by the category map creation circuit 9, the pass / fail judgment rule dictionary 12 _-1 , and the search method dictionary 1.
2 _-2 , it is judged by the defect signal generated by the comparison circuit 10.

A method of searching for these defects will be described with reference to FIGS. 9 and 10. FIG. 9A is an example of a copper residual defect. As shown in FIG. 9A, the sample SP has a straight lead portion and a land portion, which are original pattern portions, and a copper residual portion which is unavoidably produced in manufacturing. In the figure, three kinds from the copper remaining 1 to the copper remaining 3 are shown.

These copper residues are considered to be defects when they occur between normal patterns and when they cause defects such as a short circuit during soldering of solder. In FIG. 9 (A),
Only remaining copper 3 is a problematic defect. As a method of determining this defective portion, the remaining copper portion is detected, and the intervals on both sides are inspected, and when both sides are too narrow, it is determined to be defective.
FIG. 10 is a diagram showing a flow of operations after the category conversion circuit.

In step S1, the category map creating circuit 9 creates a category map from a set of category codes obtained from a plurality of radial codes. From these category maps, for example, the category relating to “copper residue” is input to the comparison circuit 10 (hereinafter “input category”).
Say. ).

In step S2, the comparison circuit 10 determines that the category corresponding to the input category is the pass / fail judgment rule dictionary 1
It is compared whether it is stored in 2 _-1 . If there is no matching category (step S2: No), the quality determination result is output to the quality determination circuit 11 as a defect signal.

When a category matching the input category (for example, "copper remaining") is stored in the pass / fail judgment rule dictionary 12 _-1 (step S2: Yes), a specific search method most suitable for this category is searched. Method dictionary 12 _-2
Read from. For example, the search method of "two-sided search" is read as a search method suitable for "copper remaining" (step S3). This search method is a method of checking whether or not a designated category exists in a predetermined direction A and a direction B different by 180 ° from the predetermined direction with the target category as the center (FIG. 9 (B)). reference).

In step S4, the comparison circuit 10
The category in the category map created by the category map creating circuit 9 is searched according to the search method "two-sided search" read from the search method dictionary 12 _-2 , and the corresponding category to be searched (hereinafter referred to as "search category") is searched. To do.

In step S5, the comparison circuit 10
If the search category cannot be searched from the category map (step S5: No), none of the copper residues on the category map has a pattern in which both sides of the copper residue part are close to each other by an allowable value or more. It is judged as copper remaining.

On the other hand, when the search category can be found on the category map (step S5: Yes), it means that there is a copper remaining portion which is close to the allowable value or more in the "two-sided search". The defect signal shown is output to the pass / fail result determination circuit 11.

As described above, by converting the radial code into the category, it is possible to determine the quality in a global manner using the determination rule, and it is possible to output the quality result including the type of defect.

For example, regarding the three types of copper residue shown in FIG. 9A, when the copper residue 1 is on the category map, there is no category of defective spacing on both sides of the copper residue 1.
It can be judged as "normal copper remaining". In the case of copper remaining 2, since the category of defective spacing exists only on one side of the copper remaining 2, it can be determined as “normal copper remaining”. Further, in the case of the copper remaining 3, since the category of defective spacing exists on both sides of the copper remaining 3, it can be determined as “copper remaining defect”. ii) Flow to determination of allowable value The main object of the present invention relates to the process of determining the allowable value described below.

The master data storage circuit 13 stores, as reference data, binarized bit map data of a pattern to be ideally possessed by the pattern to be inspected. For example, FIG. 2 shows an example of the reference pattern MP to be stored in the master data storage circuit 13. The reference pattern MP shown in FIG. 2 has a lead pattern having three different line widths P _{1 to} P ₃ and a land R.

Based on the binarized data stored in the memory circuit 14, the length measurement circuit 15 measures the length measurement value in the same manner as the length measurement circuit 5 relating to the pattern to be inspected, and the center detecting circuit 16 causes the pattern to be inspected. The center signal is detected similarly to the center detection circuit 6 according to.

The center signal and the measured value are used as the allowable value determining circuit 1
7 is input. FIG. 3 shows the internal structure of the allowable value determination circuit 17. In FIG. 3, the minimum value selection block unit 22 is
With reference to the central signal, only the reference pattern satisfying the central condition is added with the measured values measured in the directions opposite to each other by 180 °, and the diameter in each direction is radially obtained from the central point (Fig. 2).
(See (1)).

Next, the minimum value is selected from the obtained four sets of diameter values (see FIG. 2 (2)). For example, FIG.
In (2), "d" is selected as the smallest diameter. Further, in order to provide a detection margin of the line width of the pattern to be detected with respect to the reference line width, an allowable minimum value and an allowable maximum value are set (see FIG. 2 (3)).

The allowable value determination block 24 inside the allowable value determination circuit 17 sets the minimum diameter value supplied from the minimum value determination block 22 as the reference line width, and the allowable minimum value and allowable maximum value corresponding to this reference line width. From the conversion table 26. If the conversion table 26 is constructed in a memory such as a ROM, it is possible to deal with the change of the allowable value accompanying the change of the board to be measured, which is preferable.

For example, according to the conversion table shown in FIG. 3, when the reference line width 300 [μm] is selected for the lead pattern P ₃ of the reference pattern MP, the allowable minimum value is 280 [μm] and the allowable maximum value is Can be set to 350 [μm].

The allowable minimum value and the allowable maximum value are supplied to the radial encoding circuit 7 as the above-mentioned encoding threshold value. As a result, different allowable values are set for different lead patterns such as P _{1 to} P ₃ , and it is possible to deal with lead patterns having a plurality of types of line widths.

In the radial encoding circuit 7,
For the conductor part of the reference pattern MP that does not satisfy the central condition, and the air space part where the pattern does not exist,
Since the allowable value to be referred cannot be set, the coding threshold value set as a fixed value in advance is supplied. This encoding threshold value may be provided inside the radial encoding circuit 7, or may be configured so that the allowable value determining circuit 17 determines and supplies the state of the pattern. iii) If the reference pattern of the inspection pattern is misaligned
When a positional deviation between the measured patterns to be actually measured with the reference pattern MP if, the appearance inspection apparatus 100 may not operate normally.

Therefore, the allowable value determination circuit 17 and the center detection circuit 16 expand the width determined as the "center" as much as possible according to the reference line width. FIG. 5 shows an example in which the center range of the pattern is enlarged and set.

As shown in FIG. 5, the lead pattern P is 1
When the reference line width is 0 pixel, for example, the range of 6 pixels is set to be the center C. If set in this way, the pattern to be inspected actually taken by the CCD camera 2 and the reference pattern M read from the master data storage circuit 13
Even if the read position with respect to P is slightly displaced, the center of the pattern to be inspected and the center of the reference pattern are not completely displaced.

Further, when the positional deviation is large and the central width is large, pattern matching of the image signal obtained in the alignment circuit 19 is performed. Then, the read position of the reference pattern MP is corrected, and the read position is adjusted so that the centers of the reference pattern and the pattern to be inspected substantially coincide with each other.

Further, the center signal comparison circuit 18 judges whether or not the missing defect signal is good when the pattern shift that cannot be corrected by the alignment circuit 19 or the pattern to be inspected read for some reason is different from the expected pattern. It is output to the result determination circuit 11.

For example, although the center detection circuit 16 detects the center of the reference pattern and outputs the center signal,
When the center detection circuit 6 does not detect the center from the pattern to be inspected and the center signal is not output, the center signal comparison circuit outputs the missing defect signal.

FIG. 4 shows a state of the allowable value data set for the reference pattern MP by the configuration of the above embodiment.
In FIG. 4, the permissible value is set in the darkly shown portion forming the central portion of the pattern. The center width C ₃ for the pattern P _3, the center width C ₂ for pattern P ₂ is the central width C ₁ is set for the pattern P _1. Further, with respect to the land R, the tolerance value data is set in the central portion C ₄ .

Effects of the Embodiments As described above, according to the first embodiment, it is possible to individually judge the pass / fail of a wiring pattern including a plurality of line types. Further, even if there is a positional deviation between the reference pattern and the pattern to be inspected, the positional deviation between both patterns can be sufficiently corrected by setting a large center width and using a positioning circuit together. (II) Second Embodiment The second embodiment of the present invention relates to a visual inspection apparatus to which the inventions of claims 5, 12 and 13 are applied. The visual inspection apparatus according to the second embodiment corrects the allowable value described in the first embodiment according to the pattern shape.

Even if the reference pattern MP is accurately created, the edge portion of the pattern to be inspected may expand due to the manufacturing process. For example, FIG. 7 shows the relationship between patterns and allowable value data.

As shown in FIG. 7 (A), the reference pattern is created so that even a bent portion of the pattern is bent at a right angle, and naturally, a pattern that is bent at a right angle in the range of the allowable value data is generated.

FIG. 7B shows data obtained when the pattern to be inspected is actually measured. As shown in FIG. 7 (B), in the captured image, the inner edge of the bent portion is rounded and the pattern is expanded. When the allowable value is created from this, a deviation occurs between the actual pattern to be inspected and the range of the allowable value data, and even a normal pattern to be inspected may be determined to be defective. Such a phenomenon occurs not only in the bent portion but also in a portion where the line width is suddenly changed and a joint portion between the lead pattern and the land.

Description of Configuration The configuration of the appearance inspection apparatus of the second embodiment is the same as that of the allowable value determination circuit 1 in the appearance inspection apparatus 100 of the first embodiment shown in FIG.
A correction circuit 30 is provided between the No. 7 and the radial encoding circuit 7.

FIG. 6 shows a detailed block configuration of the correction circuit 30. The matching circuit 32 reads the correction data to be added from the dictionary 32 based on the tolerance value data created by the tolerance value determining circuit 17.

The adder circuit 34 adds the correction data read from the dictionary 36 to the input allowable value data and outputs the corrected allowable value data to the radial encoding circuit 7.

The dictionary 36 stores correction data to be corrected for each pattern shape identified by the matching circuit 32. The correction data stores each of the plus direction and the minus direction.

The correction circuit 30 is provided in the latter stage as in the present embodiment of the allowance value determining circuit, and is also provided inside the allowance value determining circuit so that the allowance value data different depending on the pattern shape can be individually read. You may comprise.

Description of Operation Next, the operation will be described. The dictionary 36 is based on allowable value data that should be allowed for each pattern shape in which pattern expansion is likely to occur in the actual manufacturing process.
The correction data to be added to the standard allowable value data is stored.

For example, in the dictionary of FIG. 6, ₃ of D _{1 to} D 3
The correction data for one pattern shape is stored.
D ₁ is the pattern shape of the joint between the land and the lead pattern, and stores ± 20 [μm] as correction data.
D ₂ is a gently bent portion of the lead pattern, and ± 20 [μm] is stored as correction data. D ₃ is a strongly bent portion of the lead pattern, and is ± 2 as correction data.
Store 0 [μm]. These correction data may be changed and set according to the reference line width, the pattern shape, and the pattern thickness.

The matching circuit 32 of the correction circuit 30 inputs the allowable value data string and specifies what pattern shape the reference pattern corresponds to. For example, when the allowable value data corresponding to the joint between the lead and the land is input, the correction data corresponding to the pattern D ₁ is read from the dictionary 36.

The adder circuit 34 adds the correction data read from the dictionary 36, including plus and minus signs. That is, if the correction data is a positive value, the absolute value of the correction data is added to the original allowable value data, and if the correction data is a negative value, the absolute value of the correction data is subtracted from the original allowable value data. Is equivalent to

Effects of the Embodiment As described above, according to the correction circuit of the second embodiment, accurate correction can be made even if the expansion of the pattern occurs due to the change of the pattern shape. Appearance inspection can be performed without doing.

[0102]

According to the inventions of claim 1, claim 2, claim 6 and claim 7, since the line width allowable value of the pattern to be inspected can be set, a plurality of line widths are included. Even with a wiring pattern, an accurate visual inspection of the wiring pattern or the like can be performed without erroneous detection.

According to the third and tenth aspects of the present invention, the smallest line width value is used as the reference line width of the pattern, so that the reference line width can be easily and surely determined.
According to the inventions of claims 4 and 12, the line width allowable value is determined by previously determining the maximum value and the minimum value of the reference line width, so that the line width allowable value is determined by only two parameters. The determination can be made, and the comparison of the patterns to be inspected becomes easy.

According to the fifth, twelfth and thirteenth aspects of the present invention, the reference line width is corrected in accordance with the pattern shape. Appearance inspection can be performed without erroneous detection even if the pattern expansion occurs.

According to the eighth aspect of the invention, since the center of the reference pattern and the center of the pattern to be inspected are compared,
Defects can be detected for pattern shifts and large defects. According to the invention of claim 9, since the area for detecting the center of the reference pattern is expanded to the vicinity of the line width allowable value, even if the reference pattern and the pattern to be inspected are slightly displaced, the center position Therefore, it is possible to avoid the inconvenience of frequently interrupting the appearance inspection because

[Brief description of drawings]

FIG. 1 is a block diagram showing a visual inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of the appearance inspection apparatus of the first embodiment.

FIG. 3 is an operation explanatory diagram of an allowable value determination circuit.

FIG. 4 is an example of setting allowable value data.

FIG. 5 is an explanatory diagram showing a relationship with the center of a pattern.

FIG. 6 is a block diagram of a correction circuit in the visual inspection apparatus of the second embodiment.

FIG. 7 is an explanatory diagram showing a relationship between patterns and allowable value data, in which (A) is a reference pattern and (B) is a pattern to be inspected.

FIG. 8 is an explanatory diagram showing a relationship between allowable value data and correction.

FIG. 9 is an explanatory diagram of defect search.

FIG. 10 is a flowchart of operations after the category conversion circuit.

FIG. 11 is an explanatory diagram of an inspection method of a conventional appearance inspection device.

FIG. 12 is an explanatory diagram showing a problem of the conventional visual inspection apparatus.

[Explanation of symbols]

SP ... sample MP ... reference pattern _{P, P 1 ~P 3, P} 10 ... reference patterns D ₁ to D ₃ ... pattern R ... land C, C ₁ ~C ₄ ... central area D ₁ to D ₃ ... dictionary data A ₁ , A ₂ ... inspection area 1 ... light source 2 ... CCD camera 3 ... binarization circuit 4 ... storage circuit 5 ... length measurement circuit 6 ... center detection circuit 7 ... radial coding circuit 8 ... category conversion circuit 9 ... category map creation circuit 10 ... comparator circuit 11 ... quality result judgment circuit 12 _-1 ... quality determination rule dictionary _12-2 ... search method dictionary 13 ... master data storage circuit 14 ... memory circuit 15 ... measuring circuit 16 ... center detection circuit 17 ... tolerance Determination circuit 18 ... Center signal comparison circuit 19 ... Positioning circuit 22 ... Minimum value selection block 24 ... Allowable value determination block 26 ... Conversion table 30 ... Correction circuit 32 ... Matching circuit 34 ... Addition circuit

Claims (13)

[Claims] 1. A substantially center of a pattern is detected from a binarized image obtained by photographing a sample, and each measured value of the pattern in a plurality of directions from the detected substantially center is converted into a radial code, In the appearance detection method for detecting the defect of the pattern based on the radial code, by setting the line width allowable value of the pattern to be inspected and comparing each of the measured values with the line width allowable value, A visual inspection method, comprising determining a line type of a pattern and generating the radial code based on the determined line type of the pattern. 2. A substantially center of a pattern to be inspected is detected from a binarized image obtained by photographing a sample, and radial measurement values of respective length measurement values of the pattern to be inspected in a plurality of directions from the detected substantially center are detected. In the appearance detection method, in which the defect is detected in the pattern to be inspected based on the radial code, the allowable line width value is set based on the reference line width value obtained by measuring the reference pattern in advance. A line type of the inspected pattern is determined by comparing each of the measured values with the line width allowable value, and the radial code is generated based on the determined line type of the inspected pattern. Appearance inspection method. 3. The appearance inspection method according to claim 2, wherein the minimum of the line width values obtained by measuring the reference pattern is set as the reference line width value of the reference pattern, and the reference line width is set. An appearance inspection method characterized by setting a line width allowable value based on a value. 4. The appearance inspection method according to claim 2, wherein the line width allowable value is set by adjusting the maximum width and the minimum width of the reference line width to predetermined values in advance. Characteristic visual inspection method. 5. The appearance inspection method according to claim 2, wherein the line width allowable value is set corresponding to each shape existing in the reference pattern, and the line width allowable value is set based on the line width allowable value. An appearance inspection method comprising: determining a pattern shape of a reference pattern and correcting the line width allowable value based on the pattern shape. 6. An image pickup means for picking up an image of a pattern to be inspected formed on a sample, and an image 2 for binarizing the picked up image.
A binarizing unit, a radial length measuring unit that measures a pattern portion length of a pattern portion in each pixel row extending in a plurality of directions from an arbitrary central pixel on the binarized image, and a length measuring value in the plurality of directions. From the center detection means for detecting the substantially center of the pattern to be inspected, the allowable value setting means for setting the line width allowable value for determining the line type of the pattern to be inspected, and based on the line width allowable value A line type of the pattern to be inspected is determined, and coding means for converting each measurement value in the plurality of directions into a radial code based on the determination result, and detecting a defect in the pattern to be inspected based on the radial code. An appearance inspection apparatus comprising: a detection unit. 7. The appearance inspection apparatus according to claim 6, wherein the allowable value setting means is a reference pattern generating means for generating binarized image data of the reference pattern, and an arbitrary center on the binarized image. Reference pattern length measuring means for measuring a pattern portion length of a pattern portion in each pixel row extending in a plurality of directions from a pixel, and reference pattern center detection for detecting a substantially center of the reference pattern from the length measurement values in the plurality of directions And a line width for determining the reference line width of the reference pattern based on the length measurement value of the reference pattern and the substantially center position, and determining the line type of the inspection pattern based on the reference line width. An appearance inspection apparatus comprising: a tolerance determining means for setting a tolerance. 8. The appearance inspection apparatus according to claim 7, further comprising a missing defect detecting means for comparing a substantial center of the reference pattern and a substantially center of the inspected pattern to detect a missing defect of the inspected pattern. A visual inspection device characterized by being provided. 9. The appearance inspection apparatus according to claim 7, wherein the reference pattern center detection unit widens an area for detecting a substantially center of the reference pattern to a vicinity of a line width allowable area with an original center position as a center. Appearance inspection device characterized by being configured. 10. The appearance inspection apparatus according to claim 7, wherein the tolerance determining unit determines the minimum line width value obtained by measuring the reference pattern to be the reference line width of the reference pattern. And a line width allowable value is set based on the reference line width value. 11. The appearance inspection apparatus according to claim 7, wherein the allowable value determining unit sets the line width allowable value based on a maximum width and a minimum width of the reference line width adjusted to a predetermined value in advance. Appearance inspection device characterized by: 12. The appearance inspection apparatus according to claim 6 or 7, wherein the pattern to be inspected is interposed between the tolerance setting means and the coding means and is based on the line width tolerance. An appearance inspection apparatus comprising: a correction unit that specifies a pattern shape in the vicinity of substantially the center and corrects the line width allowable value based on the specified pattern shape. 13. The appearance inspection apparatus according to claim 12, wherein the correction unit outputs correction data of the line width allowable value corresponding to the pattern shape of the reference pattern based on the line width allowable value. And comparing the line width allowable value with the pattern shape stored in the dictionary means, and when the correction data of the pattern shape corresponding to the line width allowable value is stored in the dictionary means, corrects by the dictionary means. An appearance inspection apparatus comprising: matching means for reading data; and computing means for correcting the line width allowable value based on the correction data read by the matching means from the dictionary means.