JPH01269035A - Instrument for inspecting printed circuit board - Google Patents

Abstract

PURPOSE:To accurately inspect a printed circuit board with a small-capacity memory by providing a master data storing means, comparing means, etc. CONSTITUTION:Analog signals of picture signals are sent to an A/D converter 21 where the analog signals are converted into digital signals from a camera 20. Then binarized data are obtained from the digital signals at a binarization circuit 22 and stored in memory A 31 as master data. Then a printed circuit board is scanned by means of the camera 20 and the data of the visual field are supplied to a comparator circuit 40 as pattern data after the data are converted into digital signals by the converter 21 and binarized at the circuit 22. At the same time, the stored master data are read out from the memory A 31 and supplied to the circuit 40. When the master data are supplied to the circuit 40, master data related to the hole pattern are also sent to the circuit 40 from memory B 32. At the circuit 40, the pattern data from the object to be inspected is compared with the composite master data of the master data from the memories 31 and 32 and compared results are sent to a fault discrimination circuit 41, area-wise fault data collection circuit 42, and CPU 43.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a printed circuit board inspection device.

In particular, it concerns the data retention method that serves as the standard.

[Prior art]

As information equipment, measuring equipment, etc. become more sophisticated and smaller, printed wiring board patterns are becoming increasingly core-in and multi-layered. In manufacturing such highly accurate patterns, more accurate inspection is becoming necessary from the viewpoints of quality assurance, cost, etc.

However, various methods have been adopted for detecting defects in patterns of printed wiring boards.

Regarding the inspection after enching, an automatic inspection method using optical means is used. However, when inspecting substrates with special shapes such as a collection of small patterns or a chip-on-board substrate, it is not possible to obtain sufficient inspection results using conventional feature drawing methods or length measurement methods alone, and comparison A method is required.

For example, in Japanese Unexamined Patent Publication No. 1-263807.

A pattern defect inspection apparatus for printed wiring boards is shown. This inspection device includes a means for storing the entire pattern data of at least one printed wiring board, and a means for storing the entire pattern data of at least one printed wiring board, in order to inspect pattern defects by comparing pattern data of printed wiring boards of the same type. positional deviation detection means capable of detecting positional deviation between a printed wiring board to be mounted and a printed wiring board to be mounted later; and overall pattern data for the previous printed wiring board and overall pattern data for the subsequent printed wiring board. It is constructed by means of comparison, etc.

[Problem to be solved]

However, when the above comparison method is adopted, there is a problem with the storage method of the mask pattern (master data) used as a standard. In particular, the master data storage method is
Conventionally, compression methods such as run-length encoding and conversion to vector format data have been used to store data in a smaller storage capacity.

However, even when compression methods such as run-length encoding are used, the compression effect may not be obtained for dense patterns on printed wiring boards, and small circuit patterns may be re-manipulated on a single printed wiring board. For example,
100 circuit patterns of 10 columns x 10 columns), it is very difficult to prepare a mask pattern equivalent to one printed wiring board in actual work.

Conventionally, a mask pattern for an entire printed wiring board is stored and compared with the entire printed wiring board, which causes various problems as described above.

In view of the problems of the prior art, the present invention provides a printed circuit board inspection device that can accurately inspect a printed wiring board in which a large number of printed circuit boards with high-density patterns are repeatedly formed using a small memory capacity. This is what we are trying to provide.

[Means for solving problems]

The present invention is an apparatus that uses an imaging device to inspect defects in a circuit pattern of a printed wiring board in which a large number of printed circuit boards are repeatedly formed. master data storage means for storing, detection means for detecting pattern data on a printed wiring board of an object to be inspected that has entered the field of view of the imaging device, and readout control means for controlling reading of master data from the master data storage means. and a comparison means for comparing corresponding pixels of the master data and the pattern data under the control of the succession control means.

In the present invention, the pattern to be inspected is as follows.

This is a pattern of a portion that falls within the field of view of the imaging device during scanning. Patterns that fall within this field of view (see below).

As for the field of view pattern), the printed circuit board is
The case is arbitrary, such as the case of 2 pieces, the case of 2 or more pieces, the case of 1.2 pieces (see FIG. 2), or the case of 0.8 pieces.

These differ depending on the type of imaging device used, the size of the printed circuit board, etc.

The master data storage means stores master data serving as a standard for the visual field pattern. This master data is data read from a standard printed circuit board using an optical method, or data obtained using CAD (Computer Aided Design) when designing a printed circuit board.
ed Design) data etc. Further, as the standard printed circuit board, one arbitrary pattern in the printed wiring board to be inspected, for example, 10 rows x
It is also possible to use any one of the 10 rows of 100 printed circuit boards or the printed circuit boards above or below each row. Or, as mentioned above, 1. of the printed circuit board. A pattern for 5 pieces, 0.8 pieces, etc. can also be used as master data.

In addition to the above master data, as shown in the example,
It is preferable to use a memory that takes into consideration the through holes in the land portions of the printed circuit board (FIGS. 1 and 6).

Further, the detection means optically detects a pattern on a printed wiring board, which is an object to be inspected. In other words, it is a means for reading the pattern to be inspected. The object to be inspected is the visual field pattern as described above. The detection means includes an imaging device, an A/D converter, a binarization circuit, and the like.

As the imaging device, a CCD camera, a laser scan, etc. are used.

In the case of laser scanning, depending on the type of base material, it is possible to detect fluorescence emitted from a base material on which a pattern (copper) is not formed, so it is easy to read the pattern shape.

Further, the readout control means is means for reading master data from the master data storage means in order to compare corresponding pixels in the master data and pattern data.

The comparison means is means for comparing corresponding pixels between the stored master data and the pattern data detected by the imaging device on the printed wiring board to be inspected under the control of the readout control means. be.

However, the comparison results obtained by the above comparison means are as follows.

Judgment is made by a defect judgment circuit or the like, and a decision is made as to whether each printed circuit board to be tested passes or not.

Alternatively, a process such as marking a defective portion of the printed circuit board is performed.

[Operations and Effects] In the inspection apparatus of the present invention, first, the standard master data is transferred to the standard printed circuit board or CA
From the D data, store it in the master data storage means. Next, place the printed wiring board, which is the object to be inspected, on the examination table, and use the detection means using an imaging device such as a CCD camera.
The visual field pattern is read from the printed wiring board.

This read pattern data is sent to comparison means.

Meanwhile, the master data is read from the storage means.

This is sent to a comparing means, where both pixels of the pattern data and master data are compared. The comparison result is sent to a pass/fail judgment means or the like.

As described above, in the present invention, when inspecting a printed wiring board in which a large number of printed circuit boards having one set of patterns are repeatedly formed, master data and pattern data are compared using the visual field pattern as a unit. Therefore, the amount of information for both master data and pattern data can be extremely reduced compared to the conventional case where the entire printed wiring board is compared at once, in which a large number of printed circuit boards are repeatedly formed.

Therefore, there is no need to compress, store, and compare images of master data and pattern data, and the inspection device can have an extremely small memory capacity.

For this reason, the inspection device O memory capacity can also be spared, and fine patterns with line widths and line spacings of 80 μm or less can be easily inspected.

〔Example〕

First example The following is an inspection device according to an embodiment of the present invention.

This will be explained using FIGS. 1 to 7.

Fig. 1 is an explanatory diagram of the principle of a single inspection device. When an image obtained from a camera 20 serving as an imaging device is decomposed into pixels and data processing is performed, first, a standard printed circuit board is analyzed by the camera 20 to The analog signal is sent to an A/D converter 21, where it is converted into an m-bit digital signal.The digital signal is then converted into a zero-order digital signal by a binarization circuit 22, where black and white binary data is obtained from the digital signal. Then, this binarized data is stored in the memory A31 as master data.

Next, let's talk about the printed wiring board that will be tested.

Scanning is performed by the camera 20, and data of the field of view pattern is transmitted to the A/D converter 21 and the binarization circuit 22.

The binarized data of the subject is used as pattern data,
The signal is sent to the comparison circuit 40.

Also, at this time, the above-mentioned four-folded master data is read out from the memory A31 and sent to the comparator circuit 40. At this time, master data (FIG. 6) regarding the hole pattern, which will be described later, is also sent from the memory B32 to the comparison circuit 40. Then, the comparison circuit 40 compares the pattern data from the above-mentioned subject with the combined master data of the memory A31 and the memory B32.

The comparison result is sent to the defect determination circuit 41. Area-specific defect data aggregation circuit 42. The data is sent to the CPU 43 and then to a terminal 45 such as a printer 44 or a display.

In the above, the camera 20 has a 5000 element-dimensional C
An OD camera was used. Note that a two-dimensional image can be obtained by moving the printed wiring board l in synchronization with the scanning of the camera. In addition, the resolution of the camera is 7.5μ per pixel.
m, and one field of view is 35 temples.

The printed wiring board 1 is as shown in FIG.

40 printed circuit boards 11 (8 columns x 5 columns) are formed. The printed circuit board 11 is formed by a set of patterns 5, as shown in FIG. This pattern 5 has a cavity 50, a large number of lead parts 51, and a land part 52.

That is, the printed wiring board 1 has 40 repeated patterns 5. 1 pattern (printed circuit board 4
The width of Ii,) is 30ffiIl. Also, the pitch of each printed circuit board is formed with an accuracy of ±50 μm, but considering the expansion and contraction of the board, the pitch is ±100 μm.
It is thought that the degree of damage varies.

As for inspection using a camera, as shown in FIG. 3, the area in the X1 column on the left (diagonal M downward to the left) can be inspected in one scan.

The diagonal lattice portion of the X1 column is the storage range of the first master data pattern. Here, since the field of view of the camera (35 m) is larger than the width of the printed circuit board 11, the master data has a range larger than one printed circuit board 11.

That is, the width of the field of view pattern at the time of detection is larger than that of the printed circuit board, and therefore the field of view pattern of the mask pattern is also the same as the width of the field of view pattern at the time of detection.

Next, after the printed wiring board 1 finishes moving upward (in the Y direction) in the first row as described above.

To inspect the second row, the camera moves 35 degrees in the X direction, and the printed wiring board I moves downward. The inspection area in this second row is X! The diagonal lattice portion E of this X2 column is the pattern storage range of the master data in the second column.

In this way, after the printed wiring board 1 has been moved upward (first row), the camera is moved to the right by the field of view, and then the printed wiring board 1 is moved downward (second row). Then, one printed wiring board 1 is inspected by repeating the same operation of moving the camera to the right and further moving the printed wiring board 1 upward. At this time, the first camera field of view of each column such as the first column, second column, etc. (diagonal grid area or E in the figure) becomes the master data.

The master data in each Xl, Xz . . . column and the subsequent field of view pattern in that column are compared by a comparison circuit.

The above example applies when the field of view pattern is slightly larger than the printed circuit board (35m/30a*#1.
17 times).

Here, to simplify the explanation, a case where the width of the field of view pattern is the same as that of the printed circuit board will be described below.

That is, in the case of a board with 5 columns and 8 rows in the nine cases.

(Vertical, horizontal) - (1,1), (5,2), (1°3), (5,4), (1,5), (5,6).

The printed circuit boards 11 at (1, 7) and (5, 8) are stored as master data. Also, the pattern data in the detection means is (vertical, horizontal) - (1, 1) → (
2,1)→(3,l)→・・・(5,l)→(5,2)
→(4,2)→・・・(3,8)→(2,8)→(1,
8).

Therefore, the memory required for one master data (the diagonal lattice portion, E) is 6 Mbytes for pattern storage, which can store up to a pitch of 70 m. This master data storage means is the memory A31 shown in FIG. 1 above.

By the way, as shown in FIG. 6, the land portion 52 of the printed circuit board 9 usually has many through holes for inserting bottles. Therefore, binary images do not necessarily provide clear data, and there is a possibility that false alarms may appear around the through hole. Therefore, in order to mask the data in this through-hole portion, memory B32 shown in FIG. 1 is used. That is, the through hole 55 is provided in the land portion 52 of the actual printed circuit board. Since the through hole 55 is often formed in a process separate from pattern formation, it may not necessarily be formed at the center of the land portion. However, this through hole 5
5 is slightly in that position.

Even if they are formed out of alignment, there is no practical problem.

Therefore, in consideration of the allowable range, as shown in FIG. 6, data for a hole pattern 56 that is slightly larger than this through hole 55 is stored in the memory B32, and as shown in FIG. When comparing the pattern data of the object to be inspected and the master data, this memory B
The data of the hole pattern 56 is also sent from 32, and as shown in FIG. 6, the hole data and master data are combined to form a composite image 57, which is compared with the pattern data of the object to be inspected. This memory B32 has a capacity of 2 Mbytes.

Next, positioning is important when comparing patterns, but in this example, as shown in FIG. 4, using the frame pattern 12 of the printed wiring board 1, θ is being corrected. This includes X,
A table of Y and θ is used. Furthermore, when generating a repeated pattern of printed circuit boards, the pitch between each printed circuit board is not necessarily constant, so the pitch between each printed circuit board is measured in advance.

To describe the storage of master data including the above-mentioned positioning, first, points A1 and A2 for positioning in the Y direction (including θ) on the printed wiring board 1 are determined using a monitor camera, as shown in FIG. After determining the point, θ is corrected.

Next, two points A3 in the X direction. Decide on A4 in the same way.

0 Next, specify one printed circuit board whose position is to be stored, A5. After determining A6, the pitches P1 to P4 between printed circuit boards are automatically measured. After this is completed, master data is stored from the reference pattern. After storing the master data, the through holes in the pattern are selected, and the hole pattern 56 for the mask is stored in the storage memory B32 as described above (FIGS. 1 and 6). Storage of the master data (mask button) into the memory B32 is completed.

Therefore, when comparing the master data and pattern data, the x, y, and θ of the printed wiring board to be tested are corrected based on the points A1 to A4 determined above, and the comparison with the master data is performed. Note that the boundaries between each printed circuit board 11 are areas where there is usually a pattern for plating and are not part of the actual product, and this area is excluded from the inspection area.

Next, at the time of the above comparison, the CPU 33 as the readout control means reads from the printed circuit board pitch and the pattern start position as described above.

Read out the stored master data, i.e. (vertical,
The master data of (horizontal) = (1, 1) is transferred to the subject (2, 1)
→(3,1)→・・・Read for (5,L),
It is sent to comparison means together with the data of the mask hole pattern.

In the comparison circuit 40 as comparison means, the test object (2
, 1), the visual field pattern transmitted from the camera 20 and the master data are compared. In other words, it compares whether or not the same data (with or without pattern) in 3 x 3 pixels of the 9 master data exists in 7 x 7 pixels of the subject, and if it does not exist, a mismatch signal is output. However, at this stage, it is not determined whether there is a defect or not.Next, it moves one pixel to the right, performs the same comparison, and similarly issues a mismatch signal when there is no identical data.In this way, one print About circuit board 11 50
00 pixels are compared, and then the primary printed circuit board (3, 1) is similarly compared with the master data. In this way, 8 columns×5 columns=40 printed circuit boards are inspected. This inspection is performed while continuously moving the printed wiring board relative to the camera.

Therefore, when the mismatch signal appears all 12 times horizontally and 12 times vertically (144 times in terms of area) regarding one printed circuit board 11, the printed circuit board is determined to be defective. Note that the first printed circuit board to be used as master data, that is, the printed circuit board (1, 1) itself has a defect,
Subsequent printed circuit boards, namely (2,1) to (5,
If 1) is a good product, (2,1) to (5,1) appear to be good on the top and bottom, but 9 different re-inspections show that (1゜1) is a defective product, (2,1) ~(5,1) is considered to be an acceptable product.

As is known from the above, according to this example, the visual field range of the imaging device is used as master data, and the inspection is performed while comparing this with the visual field pattern (pattern data) on the printed circuit board at the time of inspection.

The capacity of the memory A31 can be made extremely small, and highly accurate inspection can be performed with a small capacity memory.

In one example, as shown in FIGS. 1 and 6.

Since the hole pattern of the land portion of the printed circuit board is stored in the memory A32 as a mask, inspection of the vicinity of the land portion is also accurate. Note that conventionally, as shown in Figure 8,
Since a large mask pattern M was provided around the land 52, the bridge defect 511 between lines could not be detected in this vicinity.

Second Embodiment In the inspection apparatus of the first embodiment, as master data,
It uses CAD data. This CAD data is data for manufacturing a pattern film for printed wiring boards (16MB), and is data for one field of view of a camera.In this example, one piece of data for one field of view of a camera is used for all printed circuit boards. It becomes master data.

According to this example, in addition to the effects shown in the first example, since there is little noise in the master data, strict comparison with the design pattern can be performed.

[Brief explanation of the drawing]

1 to 7 show an embodiment according to the present invention, FIG. 1 is a block circuit diagram of an inspection device, FIG. 2 is a layout diagram of a printed circuit board on a printed wiring board, and FIG. 3 is a pattern detection FIG. 4 is a pattern diagram showing a part of the printed circuit board, FIG. 5 is an illustration of positioning when storing master data, FIG. 6 is an explanatory diagram of the memory in the land portion of the printed circuit board, and FIG. FIG. 7 is a pattern diagram of a printed circuit board, and FIG. 8 is an explanatory diagram of a conventional land portion memory. 1...Printed wiring board. 11...Printed circuit board. 52... Land department. 55...Through hole. 56... Hole pattern. 57...Synthetic image.

Claims (3)

[Claims] (1) In a device that uses an imaging device to inspect defects in the circuit pattern of a printed wiring board formed by repeatedly forming a large number of printed circuit boards, master data that serves as a standard for patterns that fall within the field of view of the imaging device is stored. a detection means for detecting pattern data on a printed wiring board of an object to be inspected that has entered the field of view of the imaging device; and a readout control means for controlling readout of master data from the master data storage means. An inspection apparatus for a printed circuit board, comprising a comparison means for comparing corresponding pixels of the master data and the pattern data under the control of the readout control means. (2) A printed circuit board inspection apparatus according to claim 1, wherein the reference master data is read from a standard printed circuit board. (3) A printed circuit board inspection apparatus according to claim 1, wherein the reference master data is CAD data at the time of designing the printed circuit board.