JPH04178542A - Through hole checking device - Google Patents

Abstract

PURPOSE:To easily detect a defect of a through hole even in the case of a printed board having a layer for shielding light at the bottom by illuminating a printed board from above, and detecting the leakage of fluorescence generated in the base material portion in a through hole. CONSTITUTION:Figs. (a) and (b) show the relation of the detection pattern of CCD cameras 16, 17 for a normal through hole to the detection signal level. Figs. (c) and (d) show the relation of the detection pattern of the cameras 16, 17 for a through hole having a defect to the detection signal level. In case of the camera 16 of Figs. (a) and (c), with respect to the luminance level of the base material portion, a metal portion A of the periphery of a through hole is relatively bright and the interior B of the through hole is relatively dark. By this pattern detection, the position of the through hole can be decided. On the other hand, with the CCD camera 17, in case of a through hole having a defect, fluorescence leaks into the interior B of the through hole through the defective portion, so that a more bright pattern can be detected in the interior B of the through hole as compared with the metal portion A of the periphery of the through hole.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a technology for inspecting through-holes in printed circuit boards, particularly regarding the configuration of a device that uses optical means to inspect whether or not there are defects inside the through-holes. An apparatus for inspecting the presence or absence of defects in through-holes provided in a printed board having a light-shielding layer at the bottom, with the aim of making it applicable to printed boards having a light-shielding layer. Irradiating the printed board from above with light that does not contain fluorescence wavelength components generated from the base material of the printed board,
an optical system for forming an image of the irradiated area; a means for separating the imaged light into a reflected light component and a fluorescent component; means for generating first and second detection patterns based on the first detection pattern, determining the position of the through hole based on the first detection pattern, and corresponding to the position of the through hole based on the second detection pattern; and means for determining whether or not the through hole has a defect based on the brightness of the extracted pattern, thereby determining the position of the through hole determined to be defective. Configure to output information externally.

[Industrial Field of Application] The present invention relates to a technique for inspecting through holes in printed circuit boards, and particularly to the configuration of an apparatus that uses optical means to inspect whether or not there are defects inside the through holes.

[Prior art and problems to be solved by the invention]

FIG. 6 shows an example of the configuration of a conventional through-hole inspection device.

In the same figure (a), 30 is a printed board, 31 and 32 are through holes, 33 is a roller mask for shielding the through holes from light, and 34 is light passing through the through holes or light leaking from the through holes. Lenses 35 and 36 for forming images are through holes 31. and 36, respectively.
A charge-coupled device (CCD) 37 detects light from 32 and generates a signal corresponding to the intensity of the light. 38 is an AND gate that generates a signal indicating the presence or absence of a defect in response to the output of the delay circuit (through-hole position signal) and the output of the CCD 36 (light leakage signal).

Note that FIG. 3B is a diagram conceptually showing the positional relationship between each of the above-mentioned signals and the through holes.

In this form, the "
The following method is used to detect "interruptions".

First, the printed board 30 is irradiated with light from the bottom, and the CCD 35 detects the light passing through the through hole 31 and the light transmitted from the base material of the printed board, and compares the light intensity of the two to detect the light passing through the through hole 31. Determine the position (through-hole position signal). Next, the roller mask 33 is moved to block the position of the through hole 32 while the light is irradiated from the bottom of the printed board 30.

At this time, if the inside of the shielded through hole is properly plated (that is, if there is no defect inside the through hole), the amount of light leaking out from the through hole 32 is extremely small. On the other hand, if even a part of the plating inside the through hole is missing (in other words, there is a defect inside the through hole), a sufficient amount of light will pass from the base material through the "chipped" part and into the through hole. Leak. This leakage light is CCD
36 (light leakage signal). Therefore, by comparing the difference in intensity of light leakage in both cases, it is possible to detect whether or not there is a defect in the through hole.

However, in this method, the printed board 30 is illuminated from the bottom and the transmitted light is observed from the top, so the base material of the printed board 30 is required to have the property of transmitting light to the extent that the transmitted light can be detected. be done. Therefore, the conventional inspection method has the disadvantage that it cannot be applied to printed boards that have a layer that blocks light, such as a metal layer, on the bottom.

The present invention was created in view of the problems in the prior art, and an object of the present invention is to provide a through-hole inspection device that can be applied to printed boards that have a light-shielding layer on the bottom.

[Means to solve the problem]

In order to solve the above problems, in the present invention, a printed board is illuminated from above, and it is detected whether or not fluorescence generated in the base material part leaks into the through hole. In other words, if there is a defect in the through hole, the fluorescence to the defect
It uses "leakage".

Therefore, according to the present invention, there is provided an apparatus for inspecting the presence or absence of defects in a through-hole provided in a printed board having a light-shielding layer at the bottom, the apparatus comprising: a wavelength of fluorescence generated from a base material portion of the printed board; an optical system that irradiates the printed board with component-free light from above and forms an image of the irradiated area; a means for separating the imaged light into a reflected light component and a fluorescent component; means for detecting the separated reflected light component and fluorescent component to generate first and second detection patterns based on the light intensity, respectively; and determining the position of the through hole based on the first detection pattern; , means for extracting a pattern in an area corresponding to the position of the through hole based on the second detection pattern, and means for determining whether or not the through hole has a defect based on the brightness of the extracted pattern. Provided is a through-hole inspection device characterized in that the information on the position of the through-hole determined to be defective is outputted to the outside.

[Effect]

According to the above-described configuration, when fluorescence is detected from inside the through hole, it can be determined that there is an "interruption" (that is, a defect) in the plating portion inside the through hole. In other words, in the present invention, instead of detecting the presence or absence of a defect depending on the amount of light passing through the through hole as in the conventional type, the fluorescence generated from the base material of the printed board is detected inside the through hole. The presence or absence of a defect is determined by detecting whether or not it leaks into the surface.

Fluorescence is a phenomenon that occurs when certain materials (e.g., epoxy, polyimide, etc.) used in the base material of printed circuit boards are irradiated with short wavelength light such as ultraviolet light.
This refers to the visible light produced when the atoms that make up a substance are excited by the energy of the irradiated light and return to their original state.

In this way, since through-holes are inspected based on a principle different from conventional inspection methods, the present apparatus can also be applied to printed boards that have a layer that blocks light at the bottom.

Note that other structural features and details of the operation of the present invention will be explained using the embodiments described below with reference to the accompanying drawings.

[Embodiment] FIG. 1 schematically shows a part of the configuration of a through-hole inspection apparatus as an embodiment of the present invention.

In the figure, 1 is a printed board, 2 is a base material constituting the printed board, 3 is a through hole, and 4 is a metal layer (layer for blocking light) formed at the bottom of the printed board 1. Further, 10 is a high-pressure mercury lamp as a light source, 11 is a mirror in the form of a concave mirror for focusing the light from the light source 0 on a predetermined position, and 12 is for converting the light reflected by the mirror into parallel light. The lens 13 represents a color filter that transmits only light having a specific wavelength component among the light supplied through the lens.

As shown in FIG. 2(a), this color filter 13 is arranged so as not to transmit light having a fluorescence wavelength component (light in the fluorescence wavelength band) generated from the base material portion 2 of the printed board 10. , wavelength characteristics are set so that the light supplied through the lens 12, excluding the fluorescent component, is transmitted.

The high-pressure mercury lamp 10, the mirror 11, the lens 12, and the color filter 13 are arranged so that the printed board 1 is irradiated with light having the above-mentioned specific wavelength component from above. Further, 14 is a lens that forms an image of the irradiated area on the printed board 1 at a predetermined position, and 15 is a color filter that is disposed at the predetermined position and separates the imaged light into a reflected light component and a fluorescent component. shows.

As shown in FIGS. 2(b) and 2(C), this color filter 15 has wavelength characteristics set so as to transmit only components excluding the fluorescence wavelength band and reflect only components in the fluorescence wavelength band. ing.

16 is a CCD camera that detects the light component transmitted through the color filter 15 (reflected light from the printed board l) and generates a signal (detection pattern) corresponding to the intensity of the light; 17 is the light reflected by the color filter 15; (fluorescence generated from the base material 2 of the printed board 1) component is detected and a signal (
A CCD camera that generates a detection pattern) is shown. In addition,
Components 10 to 17 constitute an optical system in this device.

Further, 21 and 22 are image buffers for temporarily storing the patterns (image data) detected by the CCD cameras 16 and 17, respectively, and 23 is for determining the position of the through hole based on the data of the image buffer 21. Determining circuit, 2
4 is a circuit that extracts a pattern of an area corresponding to the position of the through hole based on the data of the image buffer 22;
Reference numeral 25 indicates a circuit that determines whether or not the through hole has a defect based on the brightness of the extracted pattern, and the information on the position of the through hole determined to be defective by the defect presence determination circuit 25 is as follows. It is output externally as defect information output. Note that components 21 to 25 constitute an image processing system in this apparatus.

FIG. 3 shows the relationship between the detection pattern (including the area near the through hole) detected by the CCD camera 16, 17 and the corresponding detection signal level.

In the figure, (a) and (b) respectively show the relationship between the detection pattern of the CCD camera 16 and 17 and the detection signal level for normal through holes, while (c) and (d)
shows the relationship between the detection pattern of the CCD cameras 16 and 17 and the detection signal level for each defective through hole.

Referring to FIGS. 3(a) and 3(c), in the CCD camera 16, the metal part (plated part ) A pattern is detected that is relatively bright at A and relatively dark at B inside the through hole.

By detecting this pattern, the position of the through hole can be determined.

On the other hand, in the case of a normal through hole (see FIG. 3(b)), the CCD camera 17 detects the fluorescence from the base member 2.
Since there is no "leakage", the fluorescence is not detected, but in the case of a defective through hole (see figure (d))
In this case, fluorescence leaks into the inside B of the through hole through the defective part, so a pattern that is brighter in the inside B of the through hole than in the metal part A around the through hole is detected.

Due to the difference in these two patterns, that is, the difference in brightness,
The presence or absence of defects can be detected.

In this way, in this embodiment, the presence or absence of a defect is not detected according to the amount of light passing through a through hole, as in the conventional type, but the presence or absence of a defect is detected from the base material portion 2 of the printed board 1. The presence or absence of a defect is determined by detecting whether or not fluorescence leaks into the through hole 3. Therefore, the present device can be applied to a printed board 1 having a light-shielding layer 4 at the bottom as in the present embodiment, and defects in through holes 3 can be easily extracted.

In the above-described embodiment, a case was described in which one color filter 15 was used as a means for separating reflected light and fluorescence, but other forms of separating means may be used instead. An example thereof is shown in FIG.

In the illustrated configuration example, the means for separating reflected light and fluorescence is
A beam splitter 18 separates the light imaged through the lens 14 into two directions, and a color filter 19 receives one of the separated lights, transmits only the reflected light component, and supplies it to the CCD camera 16. The color filter 20 receives the other light, transmits only the fluorescent component, and supplies it to the CCD camera 17.

In FIGS. 5(a) and 5(b), color filters 19 are shown.
．． Transmittance characteristics for 20 wavelengths are shown. As shown in the figure, the wavelength characteristics of the color filter 19 are set so as not to transmit light in the fluorescence wavelength band, that is, to transmit only the reflected light component imaged through the lens 14. In No. 20, the wavelength characteristics are set so that only components in the fluorescence wavelength band are transmitted.

[Effects of the Invention] As described above, according to the present invention, defects in through-holes can be easily extracted even in a printed board having a light-shielding layer at the bottom.

[Brief explanation of drawings]

FIG. 1 is a block diagram partially schematically showing the configuration of a through-hole inspection device as an embodiment of the present invention. FIGS. 3(a) to 3(d) are graphs showing the relationship between the detection pattern by the CCD camera in FIG. 1 and the corresponding detection signal level. FIG. Figures 5(a) and 5(b) are graphs showing the transmittance characteristics with respect to wavelength of the color filter in Figure 4; Figure 6 is a diagram partially schematically showing the configuration of an optical system in another embodiment; (a
) and (b) are perspective views showing the configuration of a through-hole inspection device as an example of a conventional type. (Explanation of symbols) 1... Printed board, 2... Base material part, 3... Through hole, 4... Light blocking layer, 10... Light source (high pressure mercury lamp), 11...・Mirror, 12... Lens, 1
3... Color filter, 14... Lens, 15... Color filter, 16.17... CCD camera, 18...
Beam splitter, 19.20... Color filter, 21
．． 22... Image buffer, 23... Through hole position determination circuit, 24... Pattern extraction circuit, 25...
Defect detection circuit. Position Position CCD camera (16) CCD camera (17) (a) (
b) Position Position CO
D camera (16) CCD camera (17) (c)
(d) Figure 3 Color filter (19) (b) Figure 5 Through holes as an example of conventional type No. 6 30...Printed board 31, 32...Through holes 33...Roller mask inspection Perspective diagram showing the configuration of the device 34... Lenses 35, 36... COD

Claims (3)

[Claims] 1. Printed board with a light-shielding layer (4) on the bottom (
1) is a device for inspecting the presence or absence of defects in the through hole (3) provided in the printed board, the device for inspecting the presence or absence of defects in the through-hole (3) provided in the printed board, which directs light that does not include wavelength components of fluorescence generated from the base material portion (2) of the printed board to the printed board. an optical system (10 to 14) that illuminates the irradiated area from above and forms an image of the irradiated area;
and means (15; 18 to 20) for separating the imaged light into a reflected light component and a fluorescent component; means (16, 17) for generating a second detection pattern; determining the position of the through hole based on the first detection pattern; and determining the position of the through hole based on the second detection pattern; Means for extracting the pattern of the corresponding area (23, 24
) and a means (25) for determining whether or not the through hole has a defect based on the brightness of the extracted pattern, and thereby transmitting information on the position of the through hole determined to be defective to the outside. A through-hole inspection device characterized by outputting. 2. 2. The means for separating the reflected light component and the fluorescent component comprises a color filter (15) having a property of transmitting the reflected light component and reflecting the fluorescent component, or vice versa. The through-hole inspection device described. 3. The means for separating the reflected light component and the fluorescent component includes a beam splitter (1) that separates the imaged light into two directions.
8), a color filter (19) that transmits only the reflected light component of one of the separated lights, and a color filter (20) that transmits only the fluorescent component of the other separated light.
The through-hole inspection device according to claim 1, comprising: a through-hole inspection device;