JPS61265557A - Apparatus for inspecting through-hole - Google Patents

Abstract

PURPOSE:To detect the flaw of a through-hole with high accuracy, by allowing light to be incident only on the circumference of the through-hole when leaking light leaked in the through-hole from the plating region of the through-hole is detected. CONSTITUTION:Light is incident on a mirror 3 from a light source 1. In said mirror 3, a light converging point comes to a light pervious region 32 and the other part comes to a reflective region 32. The reflected light from the reflective region 32 is incident on the through-hole 51 of a printed circuit board 5. At this time, the reflected light is not reflected because the center thereof is present in the light pervious region 31 of the mirror 3 and converged only to the circumference of the through-hole 51. When a flaw is present on the plating surface of the through-hole 51, light is leaked in the through-hole 51. The leaked light is reflected to the reverse direction and passed through the light pervious region 31 of the mirror 3 to be detected by a light detector 7. Because light is incident only on the circumference of the through-hole, the leaked light is detected without being mixed with external light and a flaw can be detected with high accuracy.

Description

[Detailed Description of the Invention] [Summary] The present invention is an improvement of a through-hole inspection device that uses light leakage, in which the incident light does not enter the through-hole itself to be inspected, but instead enters the through-hole to be inspected. Leakage light that is incident only on the surrounding area and leaks into the through hole from the plating defect area of the through hole, etc., is transmitted through a partial area in order to guide it alone to the photodetector (without mixing with outside light). A mirror having a light region or a region with low reflectance, or a mirror in which only a partial region is a mirror and the remaining region is a transparent region, and an optical system that focuses light on the above-mentioned partial region.

It is a combination.

The first method is to use a mirror with a light-transmitting area in the central area, reflect it only in the surrounding area, and direct this reflected light only around the through-hole to be inspected (without making it incident on the through-hole). irradiation, and only the leaked light is allowed to pass through the light-transmitting area of the mirror, while the disturbance light is blocked by the mirror.

The second means is to provide a light-transmitting object having a light-blocking area in an area corresponding to the above-mentioned light-transmitting area in front of the light source of the first means, and further, in front of the photodetector, providing a light-transmitting object having a light-blocking area corresponding to the above-mentioned light-transmitting area. The above-mentioned effect is further ensured by providing a light-shielding material having a light-transmitting region in the region where the light is transmitted.

The third method uses a mirror in which only the central area is a mirror and the remaining portion is a transparent area, and the incident light enters the back surface of this mirror and only the central area is blocked. Light is transmitted only in the surrounding area, and only this light is irradiated only around the through hole, and only the leaked light is reflected on the surface of the mirror above and enters the photodetector, but the disturbance light is transmitted through the mirror. The light passes through the area and does not enter the photodetector.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an improvement in a through-hole inspection device using light leakage. In particular, it relates to improvements that improve detection sensitivity.

[Conventional technology]

A printed circuit board on which electronic components and the like are mounted naturally requires means for connecting the electronic components and the like. One of the connection means is a through hole whose inner surface is coated with a conductive material by plating or the like. Although the diameter of a through hole is generally several hundred meters, the thickness of a printed circuit board is several meters thick, so it is not easy to plate the inner surface of the through hole uniformly, and it is often difficult to plate the inner surface of the through hole evenly. Area remains.

Therefore, it is necessary to inspect the plating condition of the inner surface of the through-hole, but as mentioned above, the diameter of the through-hole is generally several hundred grams, while the thickness of the printed circuit board is several hundred grams.
Since it is a seal, its inspection is not easy.

There are various through-hole inspection devices that have been used in the past, and one of them is a method that uses leaked light (Japanese Patent Application No. 57-131798). A photodetector is provided adjacent to the through hole and shielded from external light and placed so as to receive only the light coming out of the through hole. Light is irradiated from the bottom surface to leak light into the through hole from the well-metallic area on the inner surface of the through hole, and this leaked light is detected using the above photodetector to detect defects in the plating formed on the inner surface of the through hole. This is to determine whether or not there is.

[Problem that the invention seeks to solve]

The through-hole inspection device according to the prior art that can be written as
The stage on which the printed circuit board to be inspected must be placed must be translucent, making the device complicated, which is unavoidable, and it is difficult to improve sensitivity with the method in which the irradiation light is irradiated from the L side of the printed circuit board. It has the disadvantage of being

The purpose of the present invention is to eliminate these drawbacks,
It is an object of the present invention to provide a leakage light detection type through-hole inspection device with a relatively simple mechanism and excellent detection sensitivity.

[Means for solving problems]

A first means of the present invention, as shown in FIG. 1(a), uses a first optical system 2 to condense the light from l light sources 1 to one point, and A mirror 3 with a transparent area 31 is provided, and the reflection area 32 of this mirror 3 reflects the light beam, which is missing at the center and reflects only the surrounding light beam, which is inspected using the second optical system 4. The light is focused around the through hole 51 (light is irradiated only to the surrounding area without irradiating the eye of the through hole 51), and if there is a defect in the through hole 51, light will leak into the through hole 51. This leaked light passes through the second optical system 4 in the opposite direction and is focused on the light-transmitting region 31 of the mirror 3, and this light-transmitting region 31 is different from the incident light from the light source 1. The third optical system 6 is used to condense the light onto the photodetector 7 and detect it.

The second means of the present invention is an extension of the first means, and the first means (
b) As shown in the figure, between the light source 1 and the first university system 2, preferably just in front of the light source 1, there is a light-transmitting plate-like material having a non-transparent region 81 in a region corresponding to the center of the optical axis. A light-transmitting region 91 is provided between the photodetector 7 and the third optical system 6, preferably immediately in front of the photodetector 7, only in a region corresponding to the center of the optical axis. A light-shielding plate-like body 9 is provided. This prevents the irradiation light from reaching the vicinity of the through hole 51 to be inspected, and on the other hand, prevents light other than leaked light from reaching the detector 7, improving the detection accuracy of through hole defect areas. do.

In the above two means, the light-transmitting region 31 may utilize an opening 33 provided in the mirror 3, as shown in FIG. 1(C).

As a modification of the above three means, a configuration as shown in FIG. 1(d) is also possible. That is, the mirror 3 described above is made by providing semi-light-shielding reflective films 341, 342 such as metal thin films on both sides of a translucent plate-like body 34 such as glass, and one of the semi-light-shielding reflective films 341, 342. There is an opening in the bond castle 343. 34
4, and only the opening area thereof is made translucent, and the size of this translucent area is such that the side 343 that receives the light from the light source is larger than the side 344 that transmits leaked light. As a result, the light irradiated around the through hole 51 is irradiated only to an area quite far away from the through hole 51, while the leaked light is only the light at the center (only the original leaked light that does not include disturbance light). ) Since the light is incident on the photodetector 7, the detection accuracy of through-hole defect areas is improved.

The third means of the present invention is as shown in FIG. 1(e),
The first optical system 2 is used to condense the light from one light source 1 to one point, and the condensed point is a mirror 3 that is a non-transparent area 36 that forms the back surface of a reflective area 35. A light beam is provided to irradiate the through hole 51 to be inspected with a beam of light that is omitted at the center and only at the periphery, and this irradiated light is focused around the through hole 51 to be inspected using the second optical system 4. (The light is not irradiated onto the through hole 51 itself, but only around it.) If there is a defect in the through hole 51, leakage light will leak into the through hole, so this leakage light is transmitted to the second optical system. System 4
is passed in the opposite direction and focused on the surface of the mirror 3, reflected by the reflective area 35 of this mirror 3, and focused on the photodetector 7 using the third optical system 6 to collect the light. It is something to detect.

[Effect]

The present invention solves the above-mentioned drawbacks that were conventionally unavoidable in through-hole inspection devices that utilize leaked light. The surrounding area should be illuminated with strong light, and (b) the leaked light leaking from the plating defect area into the through hole could be guided to the photodetector without being mixed with ambient light. It is based on the idea that it is good.

〔Example〕

Hereinafter, embodiments of each means of the present invention will be further described with reference to the drawings.

Referring to FIG. 1(a), 1 is a light source, preferably a point light source, and 2 is an optical system that focuses light on a transparent area 31 of a mirror 3 according to the gist of the present invention. The mirror 3 has a reflective area 32 other than the transparent area 31, and its reflective surface faces the optical system 2. 4 is the second
This is an optical system that transmits only the light reflected by the reflective area 32 of the mirror 3 (the light goes straight and is not reflected in the central translucent area 31), and transmits only the light reflected by the reflective area 32 of the mirror 3 to the area around the through hole 51 of the printed circuit board 5 to be inspected. (the through hole 51 itself and its immediate area are not irradiated).

If there is a defect in the plating surface of the through hole 51 to be inspected, light will leak into the through hole 51. and,
This leaked light passes through the second optical system 4 in the opposite direction and is focused on the transparent area 31 of the mirror 3. At this time, the disturbance light is reflected by the reflection area 32 of the mirror 3 and does not proceed toward the photodetector 7. 6 is a third optical system, and only the leaked light that has passed through the light-transmitting area 31 of the mirror 3. is focused on the photodetector 7.

As described above, in this example, the through hole itself to be inspected and the area immediately adjacent to it are not irradiated;
The surrounding area is strongly irradiated, and the leaked light enters the photodetector without being mixed with disturbance light, so detection sensitivity can be improved with a relatively simple mechanism.

Refer to FIG. 1(b) In the above embodiment, strong light is irradiated around the through hole 51 except for the through hole 51 and its immediate area, and moreover, the leakage light is prevented from being mixed with external disturbance light. However, in order to further increase this effect (preventing light from entering the through hole and its immediate area, and preventing disturbance light from entering the photodetector), light source 1 and the first optical system 2, preferably immediately in front of the light source 1, a translucent plate-like body 8 having a non-transparent region 81 in a region corresponding to the optical axis is provided, and furthermore, a third optical system 6 and a photodetector 7 are provided. A light-shielding plate-like member 9 having a translucent region 91 in a region corresponding to the optical axis is provided between the photodetector 7 and preferably immediately in front of the photodetector 7 . The other configurations are the same as those of the above embodiment.

By adding these members 8.9, the incidence of light to the through hole 51 and its immediate area is reliably blocked, and furthermore,
Since the light incident on the photodetector 7 is limited to the light (leakage light) emitted from the through hole 51, detection accuracy is further improved.

Refer to FIG. 1(C) In any of the above embodiments, the light-transmitting region 31 provided in the mirror 3 can be an opening 33 provided in the mirror 3. The light transmittance is extremely good, and the effect of not having to choose the material of the substrate can be obtained.

Refer to FIG. 1(d) In each of the above embodiments, the mirror 3 is a translucent plate member 3.
4 by forming a light-shielding reflective film such as a metal film on both sides 341 and 342, and an opening is provided in a part of the light-shielding reflective film to form a light-transmitting region 31. As for the size of the aperture, if the aperture (343) on the light source side is made somewhat larger and the aperture (344) on the photodetector side is made somewhat smaller, the light blur that occurs in the boundary area can be reduced, and the detection accuracy can be further improved. can be improved.

Refer to Fig. 1 (e) In this embodiment, the traveling direction of light is reversed.
Reference numeral 1 is a light source, preferably a point light source, and 2 is an optical system that focuses light on the opaque area 3B of the mirror 3 according to the gist of the present invention. In the mirror 3, the back surface of the opaque area 36 is a reflective area (original mirror)
35, and the other areas are transparent areas 37. As a result, the light from light source 1 is blocked at the center,
Only the surrounding area is transparent. Reference numeral 4 denotes a second optical system, which applies only the light that has passed through the transparent area 37 of the mirror 3 to the area around the through hole 51 of the printed circuit board 5 to be inspected (the through hole 51 itself and its immediate area are irradiated). ), focused.

If there is a defect in the plating surface of the through hole 51 to be inspected, light will leak into the through hole 51. and,
This leaked light passes through the second optical system 4 in the opposite direction, is focused on the reflective area 35 of the mirror 3, is reflected there, passes through the third optical system 6, and enters the photodetector 7. do. Leakage light such as disturbance light Extraneous light passes through the transparent area 37 of the mirror 3 and travels straight, so it does not enter the photodetector 7. Therefore, only the leakage light enters the photodetector 7.

As described above, in this example, the through hole itself to be inspected and the area immediately adjacent to it are not irradiated;
The surrounding area is strongly irradiated, and on the other hand, the leaked light enters the photodetector without being mixed with disturbance light, so detection sensitivity can be improved with a relatively simple mechanism.

〔Effect of the invention〕

As explained above, in the present invention, a mirror having a transmissive area or a low reflectance area in a partial area, or a mirror in which only a partial area is a mirror (reflecting area) and the remaining area is a transparent area, and Since this system is combined with an optical system that focuses light on a partial area of the through-hole, no light enters the through-hole itself or its immediate area, and furthermore, any leakage light that leaks into the through-hole is eliminated. Since only the ambient light enters the photodetector without being mixed with the disturbance light, it is possible to provide a leakage light detection type through-hole inspection device with high sensitivity and commercial accuracy.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram of the first means of the present invention. FIG. 1(b) is a configuration diagram of the second means of the present invention. FIG. 1(C) is a configuration diagram of a mirror according to the gist of embodiment l applicable to the first and second means of the present invention. FIG. 1(d) is a configuration diagram of a mirror according to another embodiment applicable to the first and second means of the present invention. FIG. 1(e) is a block diagram of the third means of the present invention. 11. Light source, 2.--First optical system, 3. Mirror,
31. φ translucent area, 32. fist/reflection area, 33.
・Reference opening, 34- ・・Translucent plate-like body, 341,
342...Each surface of the translucent plate-like body, 343
... Incident light receiving area, 344@-φ leakage light transmitting area,
345.346・Φ・Light-shielding reflective film, 35...
Reflective area, 3B... Opaque area on the back side of the reflective area,
37 building/kai translucent area, 4... second optical system,
5...Printed circuit board to be inspected, 51.1111
Through hole, 6. Third optical system, 7φ fist, photodetector, 8. Translucent plate, 81. Non-transparent area, 9. 9. Light-shielding plate. 91-ψ・Translucent region.

Claims (1)

[Claims] [1] A first light source (1), and a first optical system (2) that focuses the light of the light source (1) to one point.
and a mirror (having a light transmitting region (31) at the point where the light is focused and having a reflective region (32) surrounding the light transmitting region (31)).
3), focusing only the light reflected in the reflection area (32) of the mirror (3) only around the through-hole (51) to be inspected, and focusing the light leaking into the through-hole (51) into the a second optical system (4) that focuses on the transparent area (31) of the mirror (3); and a third optical system that focuses only the leaked light that has passed through the transparent area (31) of the mirror (3). A through-hole inspection device comprising an optical system (6) and a photodetector (7) disposed at a point where the leaked light is focused. [2] A first light source (1) and a first optical system (2) that focuses the light of the light source (1) on one point.
and a translucent plate-like body (81) disposed between the first optical system (2) and the light source (1) and having a non-transparent region (81) in a partial region corresponding to the optical axis. 8); a mirror (3) having a transparent area (31) at the point where the light is focused and a reflective area (32) surrounding the transparent area (31); The light reflected in the reflective area (32) of the mirror (3) is focused only around the through hole (51) to be inspected, and the light leaked into the through hole (51) is focused on the transparent area of the mirror (3). (31); a third optical system (6) that focuses only the leaked light that has passed through the transparent region (31) of the mirror (3); a photodetector (7) disposed at a point where light is focused; and a photodetector (7) disposed between the photodetector (7) and the third optical system (6) and corresponding to the optical axis. A through-hole inspection device comprising: a light-shielding plate-like body (9) having a light-transmitting region (91) in a portion thereof. [3] The through-hole inspection device according to claim 1 or 2, wherein the light-transmitting area (31) is constituted by an opening (33) provided in the mirror (3). [4] The mirror (3) covers both sides (3) of the translucent plate (34).
41, 342), a semi-light-shielding reflective film (343, 344) having openings (343, 344) in a part of the light-transmitting region (31);
345, 346) are formed, and the openings (343, 346) are formed in the semi-light-shielding reflective film (345, 346).
44) is a through hole according to claim 1, 2, or 3, wherein the area (343) that receives light from the light source is larger than the area (344) that transmits the leaked light. Inspection equipment. [5] A first light source (1) and a first optical system (2) that focuses the light of the light source (1) on one point.
and a non-transparent region (36) forming the back surface of the reflective region (35) at the point where the light is focused, and a transparent region (37) surrounding the non-transparent region (36). The light that has passed through the mirror (3) and the light-transmitting area (37) of the mirror (3) is focused only around the through-hole (51) to be inspected, and leaks into the through-hole (51). Mirror the light (3)
a second optical system (4) focusing on said reflective region (35) of
a third optical system (6) that focuses only the leakage light reflected on the reflection area (35) of the mirror (3); and a photodetector () disposed at the point where the leakage light is focused. 7) A through-hole inspection device comprising: