JPS62212554A - Apparatus for inspecting through-hole - Google Patents

Abstract

PURPOSE:To prevent the erroneous judgement of the flaw of a through-hole, by optically detecting the position and flaw of the through-hole of a printed circuit board and judging the through-hole as one having no flaw when the position of the through-hole is present at an area other than a land area. CONSTITUTION:Each of through-holes 2 is provided to the land 3 of a substrate 1 and the position thereof is detected by a first optical detector 7a. The substrate 1 is moved in an A-direction and the through-hole 2 is blocked from light by a light blocking mask 8 to irradiate the through-hole 2 with direct light 5 and leaked light 6 due to a flaw 4 is detected by a second optical detector 7b. Next, the signals from the optical detectors 7a, 7b are passed through binarizing circuits 14a, 14b and a delay circuit 15 to be inputted to an AND circuit 9 to detect the position of the flaw. Subsequently, in a cutting control circuit 16, the pattern of the land 3 to the position of the flaw is cut off and a judge circuit 12 judges that the through-hole has no flaw when the position of the flaw is present out of the area of the land 3.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a defect inspection device for detecting defects in through holes formed on a printed circuit board, and includes a position detection means for detecting a through hole position pattern and light leakage from a through hole defect. A defect detection means is used to detect a defect, and the output of the rain detection means is compared to discriminate between a defect and a defect candidate, and the output is stored in a memory circuit to detect whether the defect is a true defect or a defect candidate. It provides a defect detection device,
Furthermore, when the thickness of the printed circuit board that is the object to be inspected increases and the aspect ratio, which is the ratio between the printed circuit board thick plate and the diameter of the through hole, reaches 15, it becomes difficult to detect defects in the plating in the through hole.

For this purpose, an electron tube is provided for multiplying the leakage image by electrons, and a function for correcting the image distortion of the electron tube is also provided.

[Industrial application field]

The present invention relates to a defect detection device, and more particularly to a defect detection device that stores defects or defect candidates, analyzes defect details, and detects only true defects.

A recent visual inspection device for automatically inspecting through-holes in a multilayer printed wiring board is one in which the diameter of the through-hole in the plating of the multilayer printed wiring board of the object to be inspected is approximately 0.2φ, and the thickness of the printed wiring board is 1. The thickness has increased from about .5 dragons to 3 dragons. Therefore, the aspect ratio is as large as 15, making visual inspection difficult. For this reason, since the plating of the through-hole is cylindrical, the applicant first covered one end of the hole to prevent light from entering the through-hole, and then irradiated the board surface with light, which caused the plating to become cylindrical. If there is a defect or there is a break, light enters the through hole and leaks from the top of the through hole.If there is no defect, the defect is detected using the fact that no light leaks, but the through hole position There is a technical problem in accurate automatic detection of , and there has been a demand for the development of a technical means that can solve this technical problem.

[Conventional technology]

In order to solve the above-mentioned requirements, the present applicant developed a self-strobe method and solved the problem.

This self-strobe method will be explained with reference to FIG.

FIG. 9 shows the object to be inspected. A sample such as a printed circuit board 1 is transported at a constant speed in the direction of the arrow.

The through hole 2 hangs onto the land 3, and when the through hole 2 reaches point a, the light 5 that directly passes through the through hole 2 enters the first photodetector 7a and is detected by the first photodetector 7a. The through hole position can be detected by determining the XY coordinate position of the board based on the output. Next, when the through hole 2 reaches point b, there is a light shielding mask 8 there.

Therefore, the direct light 5 is blocked. However, if there is a defect 4 in the through hole 2, the light leakage 6 scattered within the base material
The light leaks through the through hole 2 and enters the second photodetector 7b while reflecting off the through hole plated wall.

The outputs of the first and second photodetectors 7a are delayed by the delay circuit 15 by the time it takes for the through hole 2 to move from point a to point b, and the outputs of the photodetector 7b are A logical AND is performed to detect a defect in the output terminal.

That is, the outputs from both detectors are compared with each other to determine whether or not the light is leaking from a position where a through hole exists.

[Problem that the invention seeks to solve]

As mentioned above, when detecting and superimposing the leakage light from the through-hole position and the through-hole defect, if the two cannot be aligned accurately, light will emit from the land or from the board other than the wiring pattern when the board is irradiated with light. There was a risk that the light and the through-hole position signal would overlap, causing a normal through-hole to be mistakenly recognized as a defective through-hole.

[Means for solving problems]

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to store defects and defect candidates obtained by superimposing the outputs of the first and second photodetecting means in a storage circuit, and to store the defects and defect candidates in the storage circuit. The purpose of this is to obtain a defect inspection device that analyzes the defect contents and prevents false detection, and the means thereof is to connect the outputs of the first photodetector and the second photodetector to an AND circuit as shown in FIG. 9, the positions of defects and defect candidate through-holes, and the output of the through-hole light leakage pattern are stored in the storage circuit 11, and the reference dictionary pattern in the determination circuit 12 or the reference area cut out from the land area is used as a reference. If a through-hole position signal pattern appears outside the dictionary pattern or reference area, it is not regarded as a defect to prevent misjudgment.

[For production]

In the present invention, defects and defect candidate patterns obtained by the AND circuit of the first and second photodetectors are stored in a memory circuit, a reference land area is extracted, and the through-hole position signal is placed outside this land area. If a pattern appears, act so as not to treat it as a defect.

〔Example〕

An embodiment of the present invention is shown in FIGS. 2 and 3(a) below.

(b), (C1 will be described in detail.

Fig. 2 is a system diagram of the defect inspection device of the present invention, Fig. 3(a)
, (b) and (C) are through-hole pattern diagrams of land portions to be stored in the memory circuit, in which the substrate 1 is moved in the direction A and the first and second photodetectors are connected to each other. Direct light 5 and leakage light 6 incident on a and 7b pass through a lens 13 and become a through-hole position signal and a through-hole light leakage signal, which are then sent to a binarization circuit 14.
The analog values are digitized at a and 14b. The through-hole position signal component digitized by the binarization circuit 14a is applied to the delay circuit 15. The delay time of the delay circuit may be set equal to the time required for the substrate 1 to move in the A direction until the through hole position reaches the light shielding mask 8 position.

When the through hole 2 reaches the position of the light shielding mask 8, the leaked light 6 that leaks through the defect is binarized through the second photodetector 7b and directly sent to the AND circuit 9 without going through the delay circuit.
, and the delayed output of the first photodetector 7a is ANDed by the AND circuit 9 to form a through-hole position signal pattern 17 as shown in FIG. The presence of the hole light leakage signal pattern 18 is detected. FIG. 3 (81 is an enlarged view of the land 3 shown in FIG. 2 viewed from above. Normally, the light leakage signal pattern 18 is located approximately in the middle of the land 3 as shown by the broken line.

Here, if the through-hole position signals indicated by broken lines are taken as a logical product, it is determined that the through-hole is defective. However, if the through-hole position signal 17 shown by the solid line in Figure 3 (fl) is located at a position protruding from the land 3 and overlapped with the light leakage signal pattern, the board 1 will be detected even if the light leakage signal pattern 18 shown by the solid line is not present. The light 20 leaking from the base material portion is ANDed with the through hole position signal 17, and this portion is mistakenly judged to be a defective through hole.

The light irradiated onto the substrate 1 described above is close to 300,000 lux, and is sufficiently transmitted through the base material portion (excluding the land 3).

Furthermore, the diameter of the through-hole position signal pattern 17 is made larger than that of the through-hole light leakage pattern 18 in order to improve the overlay accuracy. Adjustment can be easily made by selecting a level greater than the level of the binarization circuit 14b.

In the present invention, the defect or defect candidate output from the AND circuit 9 is added to the cutting control circuit 16, and the cutting control circuit cuts out the area around the land 3 as shown in FIG. 3(b). Only the area is stored in the storage circuit 11. Next, the angle between the determination circuit 12 controlled by the extraction control circuit 16 and the storage circuit 11 is 0'', 45° as shown in FIG. 3 (bl).

Pattern edges 19a in the 90' and 135° directions ~
19d and each 0°, 45°, 90°, 1
The line segment of the 35° edge is extended, and the logical product of the through-hole position signal 17 and the light leakage signal is calculated inside the area 21 (land area 3) surrounded by the line segment to determine a defect. In other words, the through-hole position signal 17 that protrudes outside the area surrounded by the extracted line segment is a portion of the light 20 leaking from the base material portion, as shown in FIG. 3(C), and is conventionally treated as a defect. Since this is a misidentified part, this part is judged to be a defect when performing the logical product, and is eliminated.

An example of a method for extracting each of the edges 19a to 19d shown in FIG. 3(b) above will be explained with reference to FIG.

In Fig. 4, 22 indicates one memory cell, the shaded part indicates "1" with light, and the blank part indicates "0" with no light.
”, then if the conditions for the sensing elements a~ are as follows: a = “O”, b-r = all al”, and g- = all “O”, then it is defined as O° edge 19a, and 45° b for edge, 90° edge and 135° edge
Extraction may be performed by rotating the locations of -f and g-.

In the above embodiment, the determination circuit 12 cuts out and extracts a defect or a defect candidate, but this is stored in advance in a land area with a fixed shape as a dictionary, and the defect or defect candidate stored in the storage circuit 11 is compared with the dictionary to form a pattern. Matching may be performed, land areas may be recognized, and defect inspection may be performed.

In this case, even if the shape of the land area changes, it can be easily accommodated.

In the above-mentioned defect inspection apparatus, for example, when the thickness of the substrate 1 increases due to multilayering, the reflected light incident through the through-hole defect is attenuated and the amount of light leakage becomes minute.
If line sensors such as COD are used for a and 7b, CO
There was a problem in that the noise generated inside D made it impossible to detect light.

An embodiment for solving such problems will be described in detail with reference to FIGS. 5 to 8.

FIG. 5 is a schematic diagram showing another embodiment of the defect inspection device of the present invention and a system diagram showing its electrical system, FIG. 6 is a schematic diagram for imaging the reference pattern, and FIG. FIG. 8 is a pattern diagram showing the degree of deviation when the two photodetector output signals are superimposed, and FIG. 8 is a system diagram showing the delay amount adjustment circuit.

In FIG. 5, parts that are the same as those in FIG. 2 are given the same reference numerals and redundant explanations will be omitted. A secondary electron multiplier tube 25 such as a multi-channel play 1-tube and a lens 26 are arranged between a and 7b. The direct light 5 from below the substrate 1, which is imaged on the photosensitive surface 25a of the secondary electron multiplier 25, and the leaked light 6 reflected through the through holes are converted into hundreds to thousands of electrons by the multi-channel plate. The signal is multiplied twice and output to the fluorescent screen 25b.

By providing such a secondary electron multiplier, the analog data obtained by the first and second photodetectors 7a and 7b is digitized, and one system is delayed and added to the AND circuit 9. Even if the substrate 1 becomes thicker and the light emitted from the bottom of the substrate is attenuated in the through-holes and becomes weak,
It can be detected by CCD.

According to the above configuration, the following problems occur.

That is, the photosensitive surface 25a of the secondary electron multiplier 25 described above
The input image formed on the phosphor screen 25b and the output image projected onto the phosphor screen 25b are not completely similar, and image distortion occurs. As a result, the area of the group Fj,1 that should be inspected may be overlooked, or an area that should not be inspected may be inspected and mistakenly marked as a defect.

In order to eliminate this problem, in the present invention, as shown in FIG. 6, before the inspection, for example, the light leakage pattern in the case of a complete defect and the through-hole position signal pattern are superimposed on the reference pattern 3a, . . . -2 in a row
The first and second photodetectors 7a pass through the secondary electron multiplier 25.
, 7b, and the outputs of the first and second photodetectors are superimposed as shown in FIG. 7 by the computer 23 shown in FIG.

That is, in FIG. 7, 27a to 27d are the second photodetector output signal patterns, and 28a to 28d are the first photodetector output signal patterns. Displacement amount dx1 to dX4 and d
V+~d, 1a is measured by the computer 23, and this correction amount is written in the storage circuit 24. This correction (2) is a function of the delay time to be finely adjusted. Therefore, it is possible to adjust the delay time of the delay circuit 15 during board inspection and correct image distortion of the secondary electron multiplier in the optical system.

FIG. 8 shows a delay amount control circuit 29 for adjusting the above-mentioned delay time. 1. The delay circuit 15 described above is randomly accessible. It is composed of an α circuit 15a and a counter circuit 15d. Note 15b.

15c is an input/output terminal of the memory circuit 15a.

Numeral 15e is a multiplexer to which write/continue data is added from the read/write terminal 15f.

15g, 15h, and 15, 15f are subtraction circuits, and an average delay amount is added to the subtraction circuits 15g and 15h on the X and Y axes via an X delay foot terminal 15i and a Y delay amount terminal 15d. Further, the output of the counter circuit 15d is also added to the subtraction circuits 15g and 15h. Furthermore, the outputs of the subtraction circuits 15g and 15h are further added to another subtraction circuit 15, 15A, and a distortion correction value is added from the storage circuit 24 detailed in FIG. In the subtraction circuit 15, 15β
The output of is given to multiplexer 15e, and the output of multiplexer 15e is given to storage circuit 15a.

With the above configuration, the counter circuit 15d increments the count by 1 every time data is written, and when reading, the subtraction circuits 15g and 15h subtract a predetermined address from the counter value of the counter circuit 15d, and the multiplexer 15e switches the address. A delay circuit is configured by giving instructions and reading data, and a subtraction circuit 15 is also configured.
k.

151, the delay time is finely adjusted by adding or subtracting the distortion correction value from the storage circuit 24, and the delay time is obtained by adding or subtracting a minute time corresponding to the distortion correction amount to the average delay time.

By doing this, the delay time at each scanning position can be adjusted.

〔Effect of the invention〕

Since the present invention is constructed and operated as described above, it is possible to obtain a defect inspection device that does not judge a pattern as a defect even if the through-hole position of the substrate is deviated from the center of the land. It has the characteristics of being able to detect light leakage patterns even when it is as thick as 5 to 3 mm, and also being able to correct pattern distortion in multi-channel plates, etc.

[Brief explanation of drawings]

FIG. 1 is a principle system diagram of the defect inspection device of the present invention, FIG. 2 is a schematic diagram and system diagram showing an inspection method of an embodiment of the defect inspection device of the present invention, and FIG. An enlarged plan view of the land portion of the through hole provided in the substrate shown in the figure, Figure 3 (bl is an explanatory diagram for explaining the land cutting method used in the present invention, Figure 3 (C) is light leakage in the cut out land. An explanatory diagram of a state in which a pattern and a through-hole position signal are superimposed, FIG. 4 is a diagram for explaining the edge extraction method, and FIG. 5 is a plan view of the α cell. A schematic diagram and a system diagram showing the inspection method of the example. Figure 6 is a schematic diagram showing the method for imaging the reference pattern. Figure 7 is the position of the through-hole position signal pattern and the light leakage signal pattern at the scanning position. An explanatory diagram showing the deviation, Fig. 8 is a delay amount control circuit diagram used in the defect inspection device of the present invention, and Fig. 9 is a schematic diagram showing a conventional through-hole defect inspection method. 1... Multilayer printed circuit board, 2... Through hole, 3... Land, 7a, 7b... 1st and 2nd photodetector, 8... Light shielding mask, 9... AND circuit, 11... Memory circuit , 12... Judgment circuit, 15... Delay circuit, 16... Cutout control circuit, 24... Memory circuit, 25... Secondary electron multiplier tube. Patent applicant: Fujitsu Limited Figure 1 ：◇ 2nd illustration・LT 4th figure 6th figure 27a ~ 27d...2nd no ft) 4t5a:l5
-7A71 / Miya J) / <tar: /28a~2-...
・1st 9M Tokko Sake Kushito Ikuraro Padan d + a ~ dsc
a, dv+ ~dm ・-・7-h Quantity null hole m
Figure 7

Claims (6)

[Claims] (1) A first light detection means that optically detects the position of the through hole, and illuminates the base material of the printed circuit board by shielding one hole of the through hole from light, and detects light leaking from the defective part of the through hole. a second light detection means for detecting the first and second light detection means;
In an inspection apparatus that performs defect determination using a comparison means for comparing the outputs of the light detection means, the apparatus includes a storage means for cutting out and storing an output pattern of the comparison means, and a land pattern for extracting a land pattern from the cutout pattern to discriminate only true defects. A through-hole inspection device characterized by having a discriminating means configured as follows. (2) a first light detection means for irradiating light onto the printed circuit board and detecting the light passing through the through hole in order to detect the position of the through hole provided in the printed circuit board; A step of moving the board to move the through hole to a light shielding mask position to block the light, and detecting light leakage in which light incident from the base material of the printed circuit board enters the through hole through a defect in the through hole. In an inspection apparatus that performs defect determination using the second light detection means and the logical product means that performs defect determination by the logical product of the outputs of the first and second light detecting means, the through-hole position obtained by the logical product means is A storage means for cutting out and storing patterns and light leakage patterns; extracting a land pattern from the cut out pattern stored in the storage means; 2. The through-hole inspection device according to claim 1, further comprising determining means for prohibiting logical product. (3) The through-hole inspection device according to claim 2, wherein the land pattern extracted by the determining means is cut out. (4) The through-hole inspection device according to claim 2, wherein the land pattern extracted by the determining means is registered as a dictionary. (5) A first light detection means for optically detecting the position of the through hole, and irradiating the base material of the printed circuit board with one hole of the through hole shielded from light, and detecting the light leaking from the defective part of the through hole. a first light detection means for detecting
What is claimed is: 1. A through-hole inspection device for determining defects by means of comparison means for comparing the outputs of photodetection means, characterized in that a photoelectron multiplier is interposed between the through-hole and the photodetection means. (6) It has a first storage means for storing the light leakage and through hole position signals, and a second storage means for storing the image distortion amount of the photoelectron multiplier, and the second storage means stores the image distortion amount. 6. The through-hole inspection apparatus according to claim 5, wherein the distortion of the electron multiplier is compensated for by changing the readout address of the first memory circuit according to the amount of distortion.