JPH0159617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a printed board pattern inspection method for automatically inspecting printed board patterns using digital image processing technology.

<Prior Art> Recently, attempts have been made to mechanize the inspection of wiring patterns on printed circuit boards, etc., which has conventionally been done visually, so that the inspection does not rely on manual labor.

In particular, due to the trend toward finer printed board patterns and demands for improved reliability and yield of printed board products, it is desired to improve the inspection quality and shorten the inspection time of printed board patterns.

Therefore, in order to meet such demands, it has become necessary to inspect printed board patterns at high speed and with high precision.

As shown in Figure 12, there are two conventional methods for inspecting printed board patterns: (a) an inspection method using a standard, and (b) an inspection method without using a standard.
Divided into two.

(a) The method of inspection using a standard uses a printed board with a normal pattern as an absolute reference, inputs the normal printed board pattern and the printed board pattern to be inspected, performs preprocessing, and generates a binary image signal. This method detects defective portions of the pattern by converting the pattern into a pattern, performing alignment, extracting features of corresponding portions, and comparing these with each other.

On the other hand, (b) method of performing pattern inspection without using a reference inputs the pattern to be inspected and performs binarization processing, and based on this binarized image signal and the shape, size, etc. of the pattern defined in advance. A comparison is made with the inspection logic (length measurement, feature extraction, etc.) that was created, and the portions that do not match are detected as pattern defective portions.

However, (a) method using standards requires high accuracy of the machine such as the alignment mechanism because accurate alignment of the normal printed board pattern and the printed board pattern to be inspected is required for each printed board to be inspected. However, there have been problems such as higher costs due to higher precision, difficulty in detecting minute defects, and a large amount of pattern data processing and long conversion processing time.

In addition, (b) methods that do not use standards cannot detect defects similar to normal patterns, such as missing patterns, and the inspection logic must be changed each time when inspecting printed board patterns with different design rules. Had to have a problem etc. that needed to be done.

<Problems to be Solved by the Invention> A technical problem to be solved by the present invention is to realize a method for accurately inspecting printed board patterns using digital image processing technology.
The purpose of the present invention is to provide a method that can constantly inspect printed board patterns at high speed and with high precision.

<Means for Solving the Problems> The printed board pattern inspection method of the present invention, which solves the above problems, has a land area added to a through-hole area of a printed board, and a through-hole area connected to the through-hole area. The method is as follows: As stated.

That is, an input unit that reads a printed board pattern and performs binary signal processing to convert it into image data with black pixels in the pattern portion, and an image memory that has at least one image memory plane and stores the image data. a main memory section that stores a printed board pattern inspection algorithm and its inspection results, an output section that outputs the inspection results to the outside, and a processor section that executes numerical calculations and the printed board pattern inspection algorithm. (a) a procedure for setting a two-dimensional matrix format table for storing printed board inspection information in the main memory; (b) inputting binary image data of the pattern to be inspected from the input unit into the image memory unit; (c) Label each through-hole area of the pattern to be inspected on this first image memory plane, and record the number of pixels and centroid coordinates of this through-hole area. (d) Detect a land area surrounding this through-hole area with the center of gravity coordinates of this through-hole area (label number I) as the center, fill in the land area and the pattern connected to it with white pixels, and then calculate the following: Steps for detecting whether the land area of the through-hole area of this label number (I+1) is filled from the label number (I+1) of (e) The through-hole area (label number J) whose land area is filled is When detected, the corresponding coordinate values (J, I) of the table set in the main memory section are set to "1" and these operations are repeated to establish connections between all through holes of the pattern to be inspected on the table. (f) A procedure for creating net list information that represents the relationship two-dimensionally in bit correspondence; (f) A procedure similar to the above (a This is a printed board pattern inspection method for detecting the presence or absence of defects in a printed board pattern by the steps of comparing through-hole net list information of a normal pattern created according to steps ) to (e).

Further, a second image memory of the image memory section
storing the binarized image data of the normal pattern in a plane and storing the binarized image data of the inspected pattern in a third image memory plane; Compare the net list information of the pattern to be inspected and the net list information of the normal pattern, and if they do not match, the land area surrounding the corresponding through-hole area in the pattern to be inspected and the normal pattern, and this land area. Detection of pattern defect positions is performed by: (b) outputting both the pattern to be inspected that has been filled out according to step (a) and the normal pattern; Let's do it.

<Example> The printed board pattern inspection method of the present invention is as follows:
As shown in the figure, this method belongs to the standard-based method, and focuses on the through holes that connect the patterns, and inputs the printed board pattern to be inspected using the through-hole net list information of the normal printed board pattern as the reference. Preprocessing is performed to obtain binary image information, through-hole net list information is created, and pattern defects are detected by comparing these two pieces of net list information.

The first typical pattern defect on printed circuit boards
As shown in FIG. 1, there are pinholes a, black spots b, protrusions c, chips d, breaks e, shorts f, etc. In addition, there are pattern omissions where part of the pattern is not drawn. Among these defects, the present invention targets disconnections, short circuits, and pattern omissions, which are particularly problematic in practical use.

Next, FIG. 2 shows an example of a digital image processing apparatus for realizing the printed board pattern inspection method of the present invention.

In this figure, 1 is an ITV that reads the printed board pattern, performs preprocessing such as sizing associated with photoelectric conversion and binarization processing, and converts the printed board pattern portion into image data with black pixels.
Input section for camera, semiconductor line/scanner, etc., 2
3 is a main memory section that stores printed board pattern inspection algorithms and their results; 4 is a processor 41 and a plurality of registers 42; A processor section 5 executes numerical calculations and pattern inspection algorithms, and 5 is an output section such as a CRT or printer that outputs pattern inspection results to the outside.These are connected to the system bus B and exchange data.

The process of the printed board pattern inspection method of the present invention is broadly divided into two steps: (a) pattern defect determination step (b) pattern defect position detection step, and the specific operation is shown in FIG. 1 (a). , (b) Explain in detail using a flowchart.

First, (1) define a two-dimensional matrix-format table A in the main memory section 3, and clear its contents. (2) Next, from the input section 1 to the pattern 2 to be inspected.
Valued image data is taken into memory plane A of the image memory section 2. (3) Raster scan the image data on memory plane A, assign numbers from 1 to N to all through-hole areas of the pattern to be inspected, and perform labeling processing. (4) Then, calculate the number of black pixels and the coordinates of the center of gravity of each labeled through-hole area, and calculate the through-hole number I (I=
1, 2,...N) and the corresponding number of pixels, center of gravity coordinates (X _I , Y _I ), status display flag FLI “0”
is stored in the main memory section 3 as through-hole area I information.

(5) Next, set the initial value "1" to register I in the register 42.

(6) Through-hole area I corresponding to label number I
Reads the flag FLI from main memory section 3, and
="0". (7) If FLI="0", (8) Read the number of white pixels and center of gravity coordinates (X _I , Y _I ) of the through hole area I from the through hole area I information in the main memory section 3, and Based on the information, the presence or absence of a land area I surrounding the through hole area I is investigated. This exploration method, for example, detects black and white pixels at exploration points that are located a certain distance l determined according to the number of pixels in one of four horizontal or vertical directions around the center of gravity coordinates of the through-hole area. If the pixel is a black pixel, the land area I is determined to be "present". At this time, when the through-hole area is large, the search distance l is made long, and when the through-hole area is small, the search distance l is made short.

(9) If there is a land area, (10) set any one point on the land area I (for example, the exploration point in step (8)) as a seed point, and use the land area I and patterns connected to this land area and other The land area is filled from black pixels to white pixels.

(11) Increment the contents of register I by 1, store the result in register J, and check the filling status of the land area of the through-hole area of the label number next to number I. (12) Read the flag FLJ of the through-hole area corresponding to the number J from the main memory section 3, (13) If the flag FLJ="0", (14) The presence or absence of the land area J as in step (8). explore. (15) If there is no land area J, it is determined that through-hole I and through-hole J are connected, and the flag FLJ of through-hole area J is set to "1" and stored in the main memory section 3. (17) Set bit "1" at bit position TA (J, I) corresponding to XY coordinates (J, I) of table A defined in main memory section 3. Then, (18) increment the value of register J by 1, and (19) if J>N, repeat the operation from step (12) to check the land area of the through-hole area (J+1).

Here, if the flag FLJ of the through-hole area J is "1" in step (13), or if there is a land area in the through-hole area J in step (15), the operation in step (18) is executed.

Then, (19) if J>N, that is, when the detection operation of the through-hole area and pattern connected to the through-hole area I is completed, the contents of register I are incremented by 1, and (21) if I>N,
From step (6), the same operation as described above is performed for the through hole area (I+1).

Here, if the flag of the through-hole area I is not "0" in step (7), or if there is no land area of the through-hole area I in step (9), the operation of step (20) is executed.

If the operation has been performed up to step (21) in this way, "1" will be set at several coordinates of table A in the main memory section 3, indicating the connection relationship of the through-hole areas of the pattern to be inspected. A net list table (information) A is created.
Then, in step (22), a net list of normal patterns predetermined on the main memory section 3 is created.
Compare table B with the created net list table A. (23) If the comparison results match, (24) there is “no pattern defect”, and (23)
If the comparison results do not match, (25) "Pattern defect present" is output as (26) inspection result.

The operations up to this point complete the process of determining whether or not there is a defective portion in the pattern to be inspected.

Next, the process of detecting the position of the defective portion of the pattern to be inspected will be explained.

(27) From the input unit 1, store the binary image data of the normal pattern in the memory plane B of the image memory unit 2 in advance, and store the binary image data of the pattern to be inspected in the memory plane C. Then (28)
Calculate the exclusive OR (EOR) of the contents of the net list table A of the inspected pattern obtained in the pattern defect discrimination process described above and the net list table B of the normal pattern set in advance. table A
net list table B), and a new net list table C is set in the main memory section 3.

At this time, in the coordinate values of the net list table C, a bit "1" is set at the location where the normal pattern (net list table B) and the pattern to be inspected (net list table A) differ.

(29) Set the initial value 1 to registers I and J.

(30) Increment the contents of register I by 1 and store it in register J.

and (31) of net list table C.
Bit TC (J,
I) are read out sequentially.

(32) When TC (J, I) = 1, (33) Read the number of pixels and centroid coordinates of the through-hole area I of the normal pattern from the main memory section 3, and in the image memory plane B, Performs fill-in processing for the pattern connected to the land area and other land areas, and (34) outputs the extraction results, such as the label number of the through-hole connected to the through-hole area I in the normal pattern, obtained by the fill-out process. It is output to the output unit 5 as B.

Next, in the same manner (35), the number of pixels and the barycentric coordinates of the through-hole area I of the pattern to be inspected are read from the main memory unit 3, and in the image memory plane C, the pattern connecting to the land area of the through-hole area I and other patterns are read out. (36) Through-hole area I in the pattern to be inspected obtained by the filling process.
The extraction result, such as the label number of the through hole connected to the , is outputted to the output section 5 as output C.

(37) The output unit 5 outputs the extraction results B and C to a CRT or printer, and confirms the position of the pattern by visually comparing the extraction results between the output normal pattern and the pattern to be inspected. Finally, the corresponding portion of the actual pattern to be inspected can be compared with the normal pattern, and the position of the pattern defect can be detected.

Note that (38) the contents of register I are incremented by 1, and (39) if I>N, the process returns to step (30) and repeats the above procedure.

Also, in step (32), if the coordinates TC (J, I) of net list table C is not 1, (40) the value of register J is incremented by 1, and (41) if J>N is not Returning to step (31), the bit reading operation of the XY coordinates (J, I) of the net list table C is started.
(41) If J>N, step (38) increment the contents of register I by 1.

In the manner described above, it is possible to determine whether there is a defect in the printed board pattern and to detect the position of the defect.

Next, specific operations will be explained according to the above-mentioned procedure.

First, in the main memory unit 3, as shown in FIG. 4, the vertical axis Y (Y=1, 2, . . . , I, . N) and coordinate values
A two-dimensional matrix format table A represented by TA (J, I) is defined. In this table A,
The connection relationship of the through holes of the printed board to be inspected is input.

Then, the binary image data of the printed board pattern to be inspected is stored in the memory plane A of the image memory unit 2 shown in FIG. At this time, N through-hole areas in the pattern to be inspected stored in memory plane A are (1, 2, ..., I, I+1,
..., N). At the same time, the center of gravity coordinates and number of pixels of each through-hole area are calculated, and the status display flag FL is set to "0", and these information are stored in the main memory section 3 as through-hole area information as shown in Figure 6. be memorized as .

Next, it is searched from the through-hole area number 1 to see if there is a land area to be added to this through-hole area, and if there is a land area, the land area, the pattern connected to this land area, and the through-hole Performs filling processing on the area. As shown in FIG. 7, the land exploration operation is performed using, for example, the already calculated barycenter coordinates (X _I , Y _I ) and the through hole area I for the through hole area I.
Based on the number of pixels (white pixel area), it is determined whether a pixel located at a certain distance l in the horizontal or vertical direction from the center of gravity is black or white. If a black pixel area is detected, it is determined that a land area exists, and a filling process is performed from black pixels to white pixels. fixed distance l
The value of is set in advance according to the number of pixels in the through-hole area I so that it can accommodate through-hole areas of various sizes.

When the filling process is completed, the flag value and the presence or absence of a land area are searched sequentially from the I+1th through-hole area to the through-hole area N, and if the flag is "0" in the J-th through-hole area, the land area is detected. If is "None", it is determined that this through-hole area is connected to through-hole area I, and the label I of this through-hole area and the through-hole J connected to it are displayed in the main memory as shown in FIG. Coordinates TA(J,
Set bit “1” in I).

At this time, if the flag of the J-th through-hole area is "0" and the land area is "present", this through-hole area J is considered not to be connected to the through-hole area I, and the flag is set to "1". In this case, it is assumed that this through-hole area J is already connected to another through-hole area, and table A is
The bit at the corresponding location remains “0”.

The net list table created in this way is shown in FIGS. 8a and 8b.

FIG. 8a shows a pattern to be inspected and its net list table, and FIG. 8b shows a normal pattern and its net list table. In this pattern to be inspected, compared to normal pattern b, through holes 2 and 3 are disconnected, through holes 4 and 5 and through holes 6 and 3 are disconnected.
7 is shorted.

(b) Normal pattern net list table B
is set in the main memory section 3 in advance (the process for creating this net list table B can be the same as the operation for creating the above net list table A), and looking at its contents, the coordinates are (2,
1), (3, 1), (5, 4), (7, 6) are set to bit "1", through hole 1, through hole 2 and through hole 3, through hole 4 and through hole 5, Through hole 6 and through hole 7
You can see that it is connected.

On the other hand, the net list table A of the pattern to be inspected has coordinate values (3, 1), (5, 4), (6, 4),
Bit “1” is set in (7, 4), through holes 1 and 3 are connected, through holes 4 and 5,
6 and 7 are connected. Then, the processor section 4 compares the net list table A and the net list table B,
The processor unit 4 determines that the two are different,
It can be determined that there is a defective portion in the pattern to be inspected.

Next, a process of detecting a pattern defect position will be explained.

First, binary image data of a normal pattern is stored in memory plane B, and binary image data of a pattern to be inspected is stored in memory plane C.

Through the calculations of the processor section 4, the net list table A of the pattern to be inspected created in the above steps and the preset net list table B
The exclusive OR of is calculated and a net list table C is created. This net list table C is shown in FIG. In the coordinate values of this net list table C, the locations where the bit "1" is set are the portions where the bit values of the net list table A and the net list table B are different.

Furthermore, in the initially set normal pattern on memory plane B and the pattern to be inspected on memory plane C, the J-th through hole at the coordinates (J, I) of bit "1" on net list table C is Performs filling processing on the land area of the area.

Then, this filling result is outputted by the output unit 5.
Output externally using CRT or printer, etc.

This output state is shown in FIG.

Fig. 10 shows the connection state between the pattern to be inspected and the normal pattern displayed on a CRT or the like, where a represents the disconnection state between through hole 2 and through hole 3, b and c represent the through hole 4, 5, This shows a short-circuited state of through holes 6 and 7.

By visually comparing the printed board pattern based on these output states, the position of the defective portion can be detected.

In the manner described above, the presence or absence of a defective portion of a printed board pattern and the position of the defective portion can be detected.

The printed board pattern inspection method according to the present invention includes:
This method uses a standard, but the difference from the conventional method using a standard is that the method of the present invention does not require accurate alignment of the normal pattern and the pattern to be inspected, and that the method of the present invention does not require accurate alignment between the normal pattern and the pattern to be inspected. - The advantage is that the list table does not need to be created every time the pattern to be inspected, but only needs to be created once at the beginning.

<Effects of the Invention> As described above, the printed board inspection method of the present invention provides the following effects.

As long as the alignment accuracy is sufficient to correctly create a net list table between the through-holes of the normal pattern and the pattern to be inspected, there is no need for accurate alignment of the normal pattern and the pattern to be inspected. A slight positional deviation does not pose a problem, and a certain degree of rotational deviation can be tolerated, thereby making it possible to shorten the alignment time and reduce the cost of the mechanical system.

Since the through-hole net list information of the pattern to be inspected is compared with the through-hole net list information of the inspected pattern based on the through-hole net information of the normal pattern obtained by performing the labeling process and the filling process, disconnections of the printed board pattern, The presence or absence of defects similar to short circuits and missing patterns can be detected at high speed and with high precision.

The through-hole net list information of the normal pattern only needs to be created once at the beginning, and does not need to be created every time the pattern to be inspected is inspected, thereby making it possible to shorten the inspection time.

The net information between through holes is 2 bits compatible.
Since the table is created in the dimensional matrix format, the memory capacity can be reduced compared to the table in the code information format.

If the through-hole net list information between the normal pattern and the tested pattern does not match, it is possible to extract image data that includes the mismatched part between the normal pattern and the tested pattern, and visually compare this information with the corresponding part. This makes it possible to easily detect the defect position.

[Brief explanation of drawings]

1A and 1B are flowcharts for explaining the printed board pattern inspection method according to the present invention, FIG. 2 is a circuit configuration block diagram for realizing the printed board inspection method according to the present invention, and FIG. 3 is a flowchart for explaining the printed board pattern inspection method according to the present invention. Figure 4 showing an overview of the printed board pattern inspection method of
The figure shows table A set in the main memory section 3, FIG. 5 shows the state of the pattern to be inspected on the image memory plane of the image memory section 2, and FIG. 6 shows the through hole in the main memory section A diagram showing area information, Figure 7 is a diagram showing how to search for a land area to be added to through-hole area I from the center of gravity coordinates (X _I , Y _I ) of through-hole area I, and Figures 8 a and b are views Figure 9 shows the tested pattern, normal pattern, and their net list tables A and B; Figure 9 shows the net list table C created from the net list tables A and B; Figure 10 a, b and c are diagrams showing examples of a normal pattern and a pattern to be inspected output from the output unit 5;
FIG. 1 is a diagram showing the types of pattern defects targeted by the present invention, and FIG. 12 is a diagram showing an outline of a conventional printed board inspection method. 1...Input section, 2...Image memory plane, 3
...Main memory section, 4...Processor section, 41...
Processor, 42...Register, 5...Output section.

Claims (1)

[Scope of Claims] 1. An input unit that reads a printed board pattern, performs binarized signal processing, and converts the pattern portion into image data with black pixels; and at least one image memory plane; an image memory section that stores a printed board pattern inspection algorithm and its inspection results; an output section that outputs the inspection results to the outside; and an output section that executes numerical calculations and the printed board pattern inspection algorithm. (a) a procedure for setting a two-dimensional matrix format table for storing printed board inspection information in the main memory section; (b) a procedure for inputting binary image data of a pattern to be inspected from the input section; (c) performing a labeling process on each through-hole area of the pattern to be inspected on this first image memory plane, and labeling the pixels of this through-hole area; (d) Detect a land area surrounding this through-hole area with the center of gravity coordinates of this through-hole area (label number I) as the center, and mark the land area and the pattern connected to it as white. Steps for detecting whether the land area of the through-hole area of this label number (I+1) is filled with pixels and from the next label number (I+1), (e) The through-hole area where the land area is filled ( When label number J) is detected, the corresponding coordinate values (J, I) of the table set in the main memory section are set to "1" and these operations are repeated to write all of the pattern to be inspected on the table. Steps for creating net list information that represents the connection relationships between through holes two-dimensionally in bit correspondence; A printed board pattern inspection method for detecting the presence or absence of a defect in a printed board pattern by a step of comparing with through-hole net list information of a normal pattern created according to similar steps (a) to (e). 2 storing the binarized image data of the normal pattern in a second image memory plane of the image memory unit, and storing the binarized image data of the inspected pattern in a third image memory plane; a) Compare the net list information of the pattern to be inspected and the net list information of the normal pattern set in the main memory section, and if there is a mismatch, compare the net list information of the pattern to be inspected and the net list information of the normal pattern. a step of filling out the land area surrounding the through-hole area and all patterns connected to this land area; (b) filling out both the pattern to be inspected that has been filled out in step (a) and the normal pattern; The printed board pattern inspection method according to claim 1, wherein a pattern defect position is detected by the step of outputting.