JPH02310406A - Method for inspecting pattern of printed circuit board - Google Patents

Abstract

PURPOSE:To exactly decide an aperture angle by deciding the various size relations between the 1st and 2nd distances with plural positions, determining the pattern interruption range between wiring patterns and through-holes and deciding relative positional relations. CONSTITUTION:A printed circuit board 11 disposed on a stage 10 is sent in a transporting direction Y while the image thereof is read by a reader 20 in every line direction X. The image data read by the reader 20 is binarized by binarizing circuits 21a, 21b. The binary signals are inputted as a hole image original signal HIS0 and a pattern image original signal PIS0 to a through-hole inspecting circuit 30. The relative positional relations of the through-holes and wiring patterns are inspected in the circuit 30 and the results thereof are applied to a central processing unit (MPU) 50. A control system 51 is controlled by the MPU 50. The X-Y address for specifying the address of the data obtd. in the circuit 30 is formed in the control system 51. The X-Y address is applied to a stage driving system 52 as well, by which the transporting mechanism of the stage 10 is controlled. The results of the various computations are displayed 60.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for inspecting patterns of printed circuit boards, particularly wiring patterns and through holes (including mini-via holes).
This invention relates to an inspection method for determining the quality of relative positional deviation.

[Conventional technology]

As electronic components become smaller, lighter, and more sophisticated, printed circuit board circuit patterns are also becoming smaller and more dense.
There is a demand for thinner patterns and smaller diameter through holes. In particular, as a through hole for conduction in a multilayer board,
O', 5 which has been further reduced in diameter from the past 0.8mm diameter
Through holes called mini-via holes with diameters of mm to 0.1 mm are currently used.

As through-holes become smaller in diameter, new technologies are needed in various areas such as through-hole plating, drilling, and reliability testing.

Drilling is generally less precise than photoetching processes, and through holes often deviate from the pattern. For through holes with a diameter of about 0.8,
A sufficiently large land was provided around it, so even if the through hole was slightly misaligned, the effect on the electrical reliability of the board was minimal.

However, as the diameter of through-holes has become smaller, lands have also become smaller, and the accuracy of drilling holes for through-holes in lands can no longer be guaranteed.

Therefore, a decrease in the electrical reliability of the printed circuit board due to the misalignment of the holes becomes a problem, and the importance of inspecting the misalignment of the through-holes increases.

Inspecting hole misalignment requires approaches from both electrical inspection and visual inspection.

In visual inspection, inspection machines that detect light leaking from cracks in plating are known, but as boards become more multi-layered, various problems have been pointed out. Further, it cannot be applied to inspection of pattern breakage caused by relative positional deviation between a through hole and a pattern.

Figures 12A and 12B show land R and through hole H.
It is a figure showing the relative positional relationship with. In FIG. 12A, the center O of the through hole H coincides with the center of the land R, resulting in a good pattern. In FIG. 12B, the center of the land R and the center O of the through hole H are shifted from each other, and a portion of the through hole H protrudes to the outside of the land R. The size of this protruding portion is determined by the aperture angle θ. When the aperture angle θ is larger than a predetermined value, the pattern breakage is determined to be defective.

Figures 13A and 13B show the straight line portion PL of the wiring pattern.
3 is a diagram showing the relative positional relationship between the through hole H and the through hole H. FIG.

In FIG. 13A, the center O of the through hole is located on the center line CL of the straight portion PL, resulting in a good pattern. In Figure 13B, center line CL and center 0
is shifted, and a portion of the through hole H protrudes outside the straight portion PL. The size of this protruding portion is also determined by the aperture angle θ, and when the aperture angle θ is larger than a predetermined standard, the pattern breakage is determined to be defective.

As described above, the quality of pattern breakage can be determined by determining the aperture angle θ, but in many conventional inspections, this determination has been made by visual inspection using a magnifying lens or the like.

In addition, when aiming to automate the determination, it is necessary to accurately read the image of the through hole or wiring pattern, but the opening edge of the through hole H has uneven optical reflection characteristics, wobbles, etc. Because of the presence of slanted parts, it was difficult to accurately binarize images of through holes and lands.

[Problem to be solved by the invention]

As described above, the conventional printed circuit board pattern inspection method relies on human visual inspection, which has the problems of inconsistent judgment criteria depending on the subjectivity of the inspector and poor inspection efficiency.

Further, in the technology intended to automate inspection, there is a problem in that it is difficult to binarize the opening edge of a through hole, and it is difficult to accurately determine the opening angle.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and aims to provide a printed circuit board pattern inspection method that enables automation of printed circuit board pattern inspection and accurate aperture angle determination. purpose.

[Means to solve the problem]

A pattern inspection method for a printed circuit board having a first configuration according to the present invention photoelectrically scans the printed circuit board and detects the relative relationship between the wiring pattern and the through hole on the printed circuit board based on image data read for each pixel. A printed circuit board pattern inspection method for determining the positional relationship of
Based on the image data, a pattern image showing the wiring pattern and a hole image showing the through hole are determined and named.

Next, a first image regarding the through hole is obtained using the hole image itself or an image that has been slightly enlarged, and the pattern image itself or the pattern is A second image regarding the wiring pattern is obtained using the enlarged image.

Then, the center line of the first image is determined, and a first distance from the center line in a predetermined direction to the outer circumference of the first image, and a second distance from the center line in the predetermined direction to the inner circumference of the second image are determined. The distances are calculated from a plurality of positions on the center line.

Further, for each of the plurality of positions, determine the magnitude relationship between the first and second distances, and determine the pattern breakage range between the wiring pattern and the through hole in a predetermined direction based on the magnitude relationship, The relative positional relationship is determined based on the pattern cut range.

Further, in the method for inspecting a pattern of a printed circuit board having the second configuration according to the present invention, first, a first image is obtained using an enlarged hole image obtained by performing an enlargement process on the hole image, and a second image is obtained using the pattern image itself. Find an image of.

Then, the first image is divided into a first divided hole image and a second divided hole image by its center line, and first and second distances are determined for each of the first and second divided hole images. , the length of the pattern cut range is integrated for the first and second divided hole images to obtain the total pattern cut length.

Furthermore, the relative positional relationship between the wiring pattern and the through hole is determined based on the ratio between the length representing the entire circumference of the first image and the total pattern cut length.

[Effect]

The length of the pattern cutting range in this invention is defined as the first distance from the center line of the first image to the outer periphery of the first image, and the distance from the center line of the first image to the inner periphery of the second image. Since it is determined based on the magnitude relationship between the wiring pattern and the second distance, by comparing the total pattern cut length, which is the sum of the lengths of the pattern cut range, and the length indicating the entire circumference of the first image, the wiring pattern The relative positional relationship with the through hole is grasped.

〔Example〕

A. Overall configuration and general operation FIG. 2 is a block diagram showing the overall configuration of a pattern inspection apparatus to which an embodiment of the present invention is applied.

On the stage 10 is a printed circuit board 11 to be inspected.
is placed. The printed circuit board 11 is conveyed in the transport direction Y while its image is read by the reading device 20 in each line direction X. The reading device 20 has a plurality of CCDs each having several thousand elements arranged in series in the line direction X, and reads the pattern of the printed circuit board 11 pixel by pixel. The read image data is sent to the binarization circuit 21
a, 21b. The binarization circuit 21a generates a hole image original signal HISo, which will be described later.
1b generates a pattern image original signal PIS, which will be described later. Both signals HIS and PIS0 are input to the through-hole inspection circuit 30.

The through-hole inspection circuit 30 has a function to be described later, and inspects the relative positional relationship between the through-hole and the wiring pattern (including lands), and sends the result to the central processing unit (MPU).
Give 50.

The MPU 50 controls the entire device via a control system 51. The control system 51 generates an XY address and the like for specifying the address of data obtained in the through-hole inspection circuit 30. The XY address is also given to the stage drive system 52 to control the transport mechanism of the stage 10.

The CRT 60 receives instructions from the MPU 50 and displays various calculation results, such as a hole image. The keyboard 70 is used to input various commands to the MPU 50.

The option section 80 includes a defect confirmation device 81. A defective product removing device 82, a defective position marking device 83, and the like are arranged. The defect confirmation device 81 is a device for enlarging and displaying a detected defect on, for example, a CRT. Moreover, the defective product removal device 82 removes the defective printed circuit board 1.
1 is detected, the device transports the printed circuit board 11 to a tray for defective products or the like. Further, the defect position marking device 83 is a device for directly marking a defective portion on the printed circuit board 11 or at a point on the sheet corresponding to the defective portion. These devices are installed as needed.

B. Reading optical system FIG. 3 shows the stage 10. shown in FIG. Printed circuit board 1
1 is a diagram illustrating an example of a reading optical system configured by a reading device 1, a reading device 20, and the like.

In FIG. 3, the light from the light source 22 is transmitted to the half mirror 2.
3 and is irradiated onto the printed circuit board 11 on the stage 10. On the printed circuit board 11, there are a base B serving as a base, a wiring pattern P, a through hole H, and a land R around it. The reflected light from the printed circuit board 11 passes through the half mirror 23, and further enters the CCD 24 provided in the reading device 20 via the lens 25. The CCD 24 is connected to the base B, the wiring pattern P, and the through hole H on the printed circuit board 11 that is sent in the transport direction Y.
, the reflected light from the land R etc. is read line-sequentially.b Fig. 4A is a graph showing the signal waveform read on line A-A' in Fig. 3, and Fig. 4B is a graph showing the signal waveform read from the line A-A' in Fig. 3. FIG. 3 is a diagram showing an example of a pattern obtained by combining signal waveforms near the line AA' read by.

As shown in FIG. 4A, there is relatively little reflected light at the base B, and a signal with a level between the threshold values THI and TH2 (THI<TH2) is generated. Since the land R is formed of metal such as copper, the reflected light at this portion is large (and a signal with a level equal to or higher than the threshold value TH2 is generated).

Note that a signal of the same level is generated in the wiring pattern P as well. Furthermore, in the through hole H, there is almost no reflected light, and a signal with a level below the threshold value THI is generated. Furthermore, between the through hole H and the land R, there is usually an edge (opening edge) E formed during drilling. There are wobbles and inclinations in this part, and the reflected light level in this part does not take a particularly constant value, but is approximately between the threshold value THI and the threshold value TH2.

FIG. 4B shows the A-A′ read as described above.
It is a figure which shows the pattern near a line. The signal from the reading device 20 is binarized in binarization circuits 21a and 21b using, for example, thresholds 1i1ffTH1 and TH2, respectively. The binarization circuit 21a generates a hole image H1 indicating the through hole H, and the binarization circuit 21b generates a pattern image PI indicating the land R and the wiring pattern P. These two images H1 and PI are used as signals necessary for processing to be described later. Base B and edge E are not particularly binarized, but edge E is recognized as an area between land R and through hole H, so land R
When grasping the relative positional relationship between the through hole H and the through hole H, it is important to treat the edge E, which is the gap area.

FIG. 5 is a diagram showing another example of the reading optical system.

The light from the light R22a is irradiated as reflected light onto the CCD 24 in the reading device 20 via the half mirror 23 and the lens 25, as in the example shown in FIG. In this example, a light [22b] is further provided on the back side of the stage 10, and the light that has passed through the through hole H is also transmitted to the CCD 22.
irradiated on top.

Therefore, in the through hole H, the signal level is the highest, in the land R1 wiring pattern P, the signal level is medium, and in the base B and edge E, the signal level is relatively low.

Furthermore, as another example, two or more rows of CCD24 are prepared,
The light source 22a may detect the land R and the wiring pattern P, the light source 22b may detect only the through hole H, and the data may be separately output to the subsequent binarization circuit.

C. Through-hole inspection circuit FIG. 1A is a block diagram showing the internal configuration of the through-hole inspection circuit 30 shown in FIG.
3 is a flowchart showing a processing procedure of a printed circuit board pattern inspection method performed using the circuit shown in the figure.

The hole image original signal HIS and pattern image original signal PISo generated by the binarization circuits 21a and 21b in FIG. Hole image signal HIS, pattern image signal PIS
becomes. This process and the binarization process described above correspond to step S11 in FIG. 1B.

The hole image signal HIS is provided to the hole image enlargement block 31. Hole image enlargement block 3
1, an enlarged hole image H1 is obtained by enlarging the original hole image H1 by 0 steps based on the hole image signal HIS.
generate. This enlarging process is performed, for example, by a spatial filter that uses one pixel in each of the upper, lower, right, left, and diagonal directions of the original enlarged portion as a new enlarged portion each time the image is enlarged by one step. This process corresponds to step S12 in FIG. 1B. Note that the number of expansion stages n can be set using software.

The signal indicating the enlarged hole image H1 is sent to the line memory 32.
a, the pattern image signal PIS is stored in the line memory 32.
b, and each two-dimensional image is reconstructed. FIG. 6 is a diagram showing the reconstructed enlarged hole image H as the first image and the pattern image PI as the second image superimposed on the same plane.

When the hole image H1 is enlarged, the edge E shown in FIG. 4B described above degenerates due to the enlargement process. When the number of enlarged steps n is set to a predetermined number of steps or more corresponding to the maximum width of the edge E, the edge E disappears as shown in FIG. 6, and the outer line of the enlarged hole image H1° enters the pattern image PI. The first distance of a vector (Yllo) that extends vertically upward from a point on the center line CL to the outer line of the enlarged hole image H1 (Yllo) extends vertically upward from the same point on the center line CL to the inner line of the pattern image PI. The length of the reaching vector (second distance) is larger than Y, and the relationship YIIU>YPU holds true. The relationship Yllo<YPU in the image before the enlargement process shown in FIG. 4B is reversed. Also.

From the same point on the center line CL downward and vertically to the outside line of the enlarged hole image H1 (first distance) Yllo of the vector vertically downward and reaching the outside line of the enlarged hole image H1 from the same point on the centerline CL downward and vertically inside the pattern image PI Similarly, the relationship YIID>YPD also holds true between Yl, which is the length of the vector that reaches Yl.

Moreover, the defective portion of the original hole image H1 is shaped by the enlargement process, and the enlarged hole image H1 has a regular shape.

FIG. 7A is a diagram showing the upper half of the enlarged hole image H shown in FIG. 6 and data corresponding thereto.
FIG. B is a diagram showing the upper half of the pattern image PI shown in FIG. 6 and data corresponding thereto.

In FIG. 7A, the inside of the enlarged hole image H1° corresponds to data "0" representing a black image, and the outside corresponds to data "1" representing a white image. Further, in FIG. 7B, data "0" representing a black image corresponds to the outside of pattern image P2, and data "1" representing its own image corresponds to the inside thereof. In Figures 7A and 7B,
Enlarged hole image HI on scanning line SL, respectively
data array D on 1 and scanning line SL on 1
The data array DPU regarding the pattern image PI of U is
It is shown. Data arrays D and D (not shown) regarding the lower half of the enlarged hole image H1 and the pattern image PI are similarly defined +10 PD .

Note that the correspondence between the inside and outside of the image and the data "0" and "1" can be arbitrarily defined by the reading optical system such as the illumination system and the data processing after reading, but the same processing as shown below can be used. Applicable.

The encoder 33a outputs a data array D11. is input, reads the number of data "0" representing the black image continuously held in the data array DI+LI from the center line CL, and outputs the length Yll of the corresponding vector shown in FIG. 6 mentioned above. .

Similarly, the encoder 33b is input with the data array D110 regarding the lower half of the enlarged hole image H1, and the sixth
Output the length YIID of the corresponding vector shown in the figure.

Similarly, encoders 33c and 33d use data arrays DD regarding the upper and lower halves of the pattern image PI.
, respectively, and output the vector lengths Y and Y corresponding to 1'tl'PI), respectively.
U PD Ru. Incidentally, such encoders 33a to 33d can be configured by, for example, FROM or the like.

The length "IILI" generated by the encoder 33a and the length YPU generated by the encoder 33c are determined by the aperture determiner 3.
4a, the length "+10" generated by the encoder 33b and the length YPD generated by the encoder 33d are respectively input to the aperture determination device 34b, and the following aperture determination is performed.

Figure 8 shows an enlarged hole image H1 when there is a positional shift.
It is a figure which shows the relative positional relationship of and pattern image PI. If the positional deviation is large, the pattern image PI is interrupted and the enlarged hole image H1 becomes the pattern image PI.
It protrudes outside. At the opening, the center line CL
There is no line inside the pattern image PI vertically upward from the line, and the length is greater than ``PU is length'' + 10.

As shown in FIG. 6 mentioned above, in the normal positional relationship, the relationship "Ill>YPU" is established, so an enlarged hole image If is formed, and the length (second distance) Ypu and the first By determining the magnitude relationship between distance) YIIIJ, the following formulas (Ia) and (lb)
Whether it is an opening (OP) or not (cS) can be determined as follows.

y nu < y pu op...
(ta) Y nu > Y pu CS...
(1b) As shown in Figure 8, at the opening, Yll
The relationships ol<Y and Y<Y hold true, Pu1l 1ILI2 Pt12, and the relationship YIIU3>Y holds true in the portions that are not openings. Note that the upper limit of the length YPUt13 is determined by the number of bits in the Y direction of the line memories 32a and 32b.

The aperture determiners 34a and 34b respectively perform aperture determination regarding the upper half and lower half for each scanning line SL, and convert the open/non-open (OP/CS) signal into an aperture determination signal AS.
Output as . Note that the above series of aperture determination processing is
This corresponds to step 313 in FIG. 1B.

The length "IIU" generated by the encoder 33a and the length "YllD" generated by the encoder 33b are input to the diameter calculator 35. The diameter calculator 35 calculates the lengths Y, Y
Add up each of them to get the enlarged hole +10 11
0 Calculate the area of the upper half) and the area of the lower half of the image HIn. Then, a center determination is performed to determine whether the center of the enlarged hole image HIn and the center of the line memory 32a match. When it is determined that the respective centers match, calculation of the length of the aperture and determination of aperture ratio tolerance, which will be described later, are performed.

In addition, the diameter calculator 35 holds the X coordinate when the scanning line SL touches the enlarged hole image HIn and starts calculating the length in the Y direction, and the X coordinate when the calculation of the length in the Y direction ends. Then, by simply averaging the two X coordinates, the center coordinates of the enlarged hole image HIn are calculated.

Furthermore, by composing the lengths Y and Y, the scanning line S
Y of enlarged hole image H1 sliced by L
The combined growth height "IIU+YIID" in the direction is calculated.Then, by sequentially selecting larger values of the combined growth height YIIU+YIID, the maximum value of the combined growth height YIIU+"IID is detected, and the diameter 2" of the enlarged hole image H1 is detected. The combined growth at the center coordinates is 1.
Find IEI+”+10, enlarged hole image H1,
The diameter may be 2r. Each piece of data obtained as described above is used as a center/diameter signal CR8 to calculate the length of the opening, which will be described later.

Next, the structural blocks related to calculation of the length of the opening will be explained.

The X-direction measuring device 36a determines the length of the upper half of the opening in the X direction based on the aperture determination signal AS from the aperture determining device 34a. The Y-direction measuring device 37a receives the aperture determination signal AS from the aperture determiner 34a and the encoder 33a.
The length of the upper half of the opening in the Y direction is determined based on the length YIIU. Similarly, the X direction measuring device 36
b determines the length of the lower half of the opening in the X direction based on the aperture determination signal AS from the aperture determination unit 34b.

The Y direction measuring device 37b receives the aperture determination signal AS from the aperture determiner 34b and the length YIID from the encoder 33b.
Based on this, the length of the lower half of the opening in the Y direction is determined.

FIG. 9 is a diagram showing an example of how the length of the opening is calculated. However, FIG. 9 is a diagram showing the calculation of the length of the opening in the enlarged hole image H1 and the pattern image PI in the upper half from the center line CL, and the opening is located at one point in the X-Y coordinate system. FIG. 6 is a diagram showing how calculation is performed in the case of existence within a quadrant.

In the section where the enlarged hole image H1° does not exist in the scanning line memory, the length YllU=0, and no particular calculation is performed. This section is section NC in Figure 9.
It is shown in

When the scanning line SL, the enlarged hole image H1, and the mouth come into contact, the length YIll becomes a finite value and the aperture determination described above begins. When the scanning line SL moves from right to left in FIG. 9, the scanning line SL touches the enlarged hole image H1° at the coordinate Xs, and the aperture determination starts. In the section from coordinate Xs to coordinate X1, YI
The relationship ll>YPU is established, and the aperture determination signal AS becomes non-aperture (cS).

When the scanning line SL reaches the coordinate X1, the opening PUI
The relationship IIUI was established, and the opening began.
>Y The interest rate setting signal AS becomes open (OP). The length at this time”
+101 is stored for use in calculating the length of the opening in the Y direction, which will be described later.

When the scanning line SL reaches the coordinate X2, the opening ends,
The aperture determination signal AS becomes non-aperture (cS) again. Coordinate X
The length YIIl, 12 at the X coordinate immediately before 2 is also stored for use in calculating the length of the opening in the Y direction, which will be described later.

The length of the opening in the X direction is determined based on the X coordinate of the starting point of the opening and the X coordinate of the ending point of the opening. In FIG. 9, the aperture determination signal AS is an aperture (OP) until the scanning line SL reaches the coordinate X2 from the coordinate X1.
The length DX in the X direction is determined by counting the system clock (not shown) during that period.

The length of the opening in the Y direction is determined as follows. In FIG. 9, the length Y at the starting point of the aperture and the length YIIU2 at a point +1 UI before the ending point of the aperture are read out. Then, it is decided to count the difference between length Y and length Y.
The length DY in the Y direction is determined from I II 02 . For example, length Y
-7, length Y -9, length in Y direction DY-
It becomes Y-Y-2. In addition, this II 02
Although the counting of +101 involves an error due to the enlargement process, the error becomes sufficiently small if the number of enlargement stages n is not too large. Further, as shown in FIG. 9, the length DY' may be the length in the Y direction.

The above-described processing is similarly performed when the opening exists within one quadrant in the lower half from the center line CL, and the processing results are added later.

FIG. 10 is a diagram showing another example of how the length of the opening is calculated. However, FIG. 10 is a diagram showing the calculation of the length of the opening in the enlarged hole image H1° and the pattern image PI regarding the upper half from the center line CL, and the opening is located between the two in the X-Y coordinate system. It is a figure which shows the state of calculation about the case where it exists continuously in a quadrant. Also, in this example, the center/diameter signal C from the diameter calculator 35
R3 is also used to calculate the length of the opening.

In a section where no enlarged hole image HIn exists on the scanning line SL, the length is "IIU"=O, and no particular calculation is performed. This section is the section NC as in Fig. 9.
It is shown in

When the scanning line SL and the enlarged hole image H1 come into contact, the length YIll becomes a finite value and the aperture determination described above begins. In the section from coordinate X8 to coordinate X3, Y
The relationship IIU>YPU is established, and the aperture determination signal AS
becomes non-opening (cS).

When the scanning line SL reaches the coordinate x3, the aperture begins and the relationship Y > Y is established, and the opening P U 3
II U 3 0 determiner number AS is open (OP). Length Y at this time
is stored for use in calculating the length of the opening in the Y direction, 1U3, which will be described later.

When the scanning line SL reaches the coordinate X4, the opening ends,
The aperture determination signal AS becomes non-aperture (cS) again. Coordinate X
The length YIIU4 at the X coordinate immediately before 4 is also stored for use in calculating the length of the opening in the Y direction, which will be described later.

The length DX of the opening in the X direction is determined by counting the system clock (not shown) in the section from the coordinate X3 to the coordinate X4 of the scanning line SL, as in FIG. 9. Moreover, since the center coordinate Xc included in the center/diameter signal CR3 exists between the coordinate X3 and the coordinate X4, it is recognized that the opening exists continuously in two quadrants.

The length of the opening in the Y direction is determined as follows. Similar to the example shown in FIG. 9, the pre-stored length Y at the starting point of the opening, the length Y at the point immediately before the end point of the opening 11[+30 parts, and 1U4 are read out. Furthermore, since the opening exists continuously in two quadrants, the diameter 2r of the enlarged hole image HI that receives the center/diameter signal CRS1:D is also read out. Then, by counting the difference between the radius and the length Y and the difference between the radius and the length Y, the lengths DY and DY2 in the 1U4 Y direction are found, and further the length DY
, DY2 are mutually added to obtain the length DY in the Y direction.
is required.

For example, length Y -6, length Y -7, radius II 0
3 II 04 r-10, the length in the Y direction DY-DYl+DY2
- (10-6)+ (10-7)-7.

Note that this counting involves an error due to the enlargement process, but the error becomes sufficiently small if the number of enlargement stages n is not too large.

The lengths DX and D obtained through the above series of processing
Y is applied to an adder 38, where addition is performed for all quadrants to generate an added value SL-ΣDX+ΣDY. Note that the above processing corresponds to step S14 in FIG. 1B.

The tolerance determiner 39 is given the diameter 2r from the diameter calculator 35, the added value SL from the adder 38, and a preset aperture ratio tolerance A, and makes an aperture ratio tolerance determination as shown below. conduct.

First, as shown in FIG. 11, the enlarged hole image HI
The total circumference π×2r is the total circumference 4×2r of the square SQ, and the length of the circular arc of the opening is the added value S1. and approximate each. Then, the ratio of the aperture angle θ to the total circumferential angle of 360 degrees is approximated as shown in equation (2) below.

θ/360QIS /4X2 r −(2) Furthermore, the error due to the above approximation is within 4 degrees when converted to the aperture angle θ, and is sufficiently practical. This approximation also simplifies the hardware configuration.

Furthermore, the preset aperture ratio tolerance A and the approximate aperture ratio S
By determining the magnitude relationship between L/(4X 2 r), it is possible to determine whether the opening is good (OK) or bad (NG) as shown in equations (3a) and (3b) below. can.

A > S L / (4X 2 r) O
K=・(3a) A<SL/(4×2r) NG
...(3b) For example, the user's criterion is the opening angle θ-
If it is 120 degrees or less, the aperture ratio tolerance is A-120/360-
The aperture ratio may be determined by setting the value to 0.33.

The acceptance determination unit 39 outputs a good/bad (OK/NG) signal as an aperture ratio acceptance determination signal AR3.

Note that the above processing corresponds to step S15 in FIG. 1B.

Through the series of processes described above, the relative positional relationship between the through hole and the pattern is determined.

Note that the above approximation process may not be performed, and the determination may be made by finding the ratio of the circular arc of the opening to the entire circumference πX2r of the enlarged hole image HI.

D. Modified Example In the example described above, the hole image HI was enlarged, but if at least one of the hole image H1 and the pattern image PI is enlarged, the length Y
The magnitude relationship between l and the length "I[U" is reversed, and the same aperture ratio acceptance determination process can be performed.

Also, using the coordinate values (X, Y) and (X, Y2) of the end points P and P of the opening shown in Fig. 9, find the distance between the two points P and P2, and compare this with the reference value. By doing so, the quality of the opening may be determined.

Furthermore, if the printed circuit board has a mounting hole other than a through hole, this mounting hole can be excluded from the inspection and not inspected, or even if it is inspected, it is not determined to be defective. To do this, data such as the position, shape, and size of the mounting hole may be input in advance.

〔Effect of the invention〕

As described above, according to the present invention, at least one of the hole image and the pattern image is enlarged, and the length of the pattern cutting range is determined from the center line of the first image (hole image or enlarged hole image). Based on the magnitude relationship between the first distance to the outer circumference of the first image and the second distance from the center line of the first image to the inner circumference of the second image (enlarged pattern image or pattern image) Therefore, it is possible to determine whether the relative positional deviation between the wiring pattern and the through hole is good or bad after eliminating the effects of wobbling or inclination at the opening edge of the through hole. In the second invention, the relative positional relationship between the wiring pattern and the through hole is determined by comparing the total pattern cut length, which is the sum of the lengths of the pattern cut range, and the length indicating the entire circumference of the first image. be understood.

Therefore, it is possible to obtain a printed circuit board pattern inspection method that enables automation of inspection of printed circuit board patterns and allows accurate aperture angle determination.

[Brief explanation of drawings]

ffllA is a block diagram of a through-hole inspection circuit according to an embodiment of the present invention, FIG. 1B is a flowchart showing the processing procedure of a printed circuit board pattern inspection method according to an embodiment of the present invention, and FIG. 2 is a block diagram of a through-hole inspection circuit according to an embodiment of the present invention. A block diagram showing the overall configuration of the inspection device according to the embodiment, FIG. 3 is a diagram showing an example of a reading optical system, FIG. 4A is a diagram showing a signal waveform obtained by the device shown in FIG. 3, and FIG. 4B is a diagram showing an example of a reading optical system. 4A is a diagram showing a pattern obtained by combining the signal waveforms; FIG. 5 is a diagram showing another example of the reading optical system; FIG. 6 is a diagram showing an enlarged hole image and a pattern image; 7A is a diagram showing the upper half of the enlarged hole image shown in FIG. 6 and data corresponding to it, FIG. 7B is a diagram showing the upper half of the pattern image shown in FIG. 6 and data corresponding to it, and FIG. The figure shows the positional relationship between the enlarged hole image and the pattern image when there is a positional shift. Figure 9 shows an example of how the length of the opening is calculated. Figure 10 shows the length of the opening. FIG. 11 is a diagram showing another example of how the aperture ratio is determined. FIG. 12 is a diagram showing how the aperture ratio is determined. A
The figure shows a good relative positional relationship between a land and a through hole. Figure 12B shows a bad relative positional relationship between a land and a through hole. Figure 13A shows a good relationship between a wiring pattern and a through hole. FIG. 13B is a diagram showing a poor relative positional relationship between a wiring pattern and a through hole. H...Hole, R...Land, P...
Wiring pattern, HI... hole image, PI...
・Pattern image (second image), Hl ・
...Enlarged hole image (first image) CL...
Center line, Y, Y...longest distance), 11U
110 "pu' Ypo...longer second distance), AS...
・Opening judgment signal, DX...Length in the X direction, DY...Length in the Y direction,
SL...Additional value, "...Radius A...Aperture ratio allowable value, AR3...Aperture ratio allowable judgment signal,

Claims (2)

[Claims] (1) A printed circuit board pattern inspection method in which the printed circuit board is photoelectrically scanned and the relative positional relationship between the wiring pattern and the through hole on the printed circuit board is determined based on image data read for each pixel. (a) obtaining a pattern image indicating the wiring pattern and a hole image indicating the through hole based on the image data; (b) enlarging the hole image itself or the hole image; (c) enlarging the pattern image itself or the pattern image so that it has an overlapping area with the first image; (d) determining a center line of the first image; (e) determining a second image of the wiring pattern from the center line in a predetermined direction; determining a first distance to the outer circumference of the image and a second distance from the center line to the inner circumference of the second image in the predetermined direction from a plurality of positions on the center line; f) Determine the magnitude relationship between the first and second distances for each of the plurality of positions, and determine the pattern break between the wiring pattern and the through hole in the predetermined direction based on the magnitude relationship. A method for inspecting a printed circuit board pattern, the method comprising: determining a range; and (g) determining the relative positional relationship based on the pattern breakage range. (2) The printed circuit board pattern inspection method according to claim 1, wherein step (b) comprises: (b-1) obtaining the first image using an enlarged hole image obtained by performing enlargement processing on the hole image. and the step (c) is a step of obtaining a second image using the (c-1) pattern image itself, and the step (d) is a step of (d-1) converting the first image into the first image. (e-1) determining first and second distances for each of the first and second divided hole images; (g-1) integrating the length of the pattern cut range for the first and second divided hole images to obtain the total pattern cut length; and (g-2) ) determining the relative positional relationship between the wiring pattern and the through hole based on the ratio of the length representing the entire circumference of the first image and the total pattern cut length;
A printed circuit board pattern inspection method including: