JPS6375544A - Through hole inspection device - Google Patents

Abstract

PURPOSE:To improve defect detecting ability with a simple constitution by providing a lens with a shielding body which shields unnecessary light leaking from a gap formed at a part where the opening part of a through hole is shielded. CONSTITUTION:This inspection device is provided with a lens 1 for image formation, photodetectors 2 and 3 arranged on the image formation surface of the lens 1, and AND gate 5 and a light source which are connected from the detector 2 directly and from the detector 3 through a delay circuit 4, a mask 6 for shielding the through hole, etc. Further, the lens 1 is provided with the shielding body 11. This shielding body 11 is made beltlike in the same direction with the mask so as to prevent light from entering the lens 1 at a specific angle so that the light leaking from the gap between the through hole 8 and mask 6 does not reach the detector 2. Then the light leaking from the gap between the mask 6 and through hole 8 is shielded by the shielding body 11, so it never reaches the detector 2. Light leaking from a defect, on the other hand, tends to be intense in a slanting direction and almost all of components are image-formed on the detector 2 without being shielded by the shielding body 11.

Description

[Detailed Description of the Invention] [Summary] One opening of a through hole in a printed board is shielded, light is applied to the base material of the printed board, and the light leaking from the defective part of the through hole is blocked by a lens and a This is a through-hole inspection device that detects with an optical system consisting of a photodetector, and the lens includes a part of the lens to prevent unnecessary light leaking from the shielded opening of the through-hole from reaching the photodetector. By providing a shield to the surface, it is possible to improve the defect detection ability.

[Industrial application field]

The present invention relates to a through-hole inspection device for detecting defects in through-holes in printed circuit boards used in electronic devices such as communication devices and electronic computing devices.

A large number of through holes are formed in printed circuit boards used in various devices such as electronic computers, and the through holes are plated to provide conductive means. These platings are not necessarily formed in good condition, and it is necessary to inspect them.

There are two conventional inspection methods as follows.

One of them is manual visual inspection, but this is difficult because the diameter of the through hole has become extremely thin, around several hundred μm, or the thickness of the board has become 20 to 30 times the diameter of the through hole. If this happens, the inspection becomes difficult, which is an undesirable drawback in terms of inspection.

Another method is to apply electricity to the plated portion of the through hole to check its continuity. This method has the disadvantage that even if there is a defective part in a part of the plated part, the defect cannot be detected, and that it is time consuming and increases the cost of the apparatus. For this reason, a through-hole inspection device as described below has been developed.

[Conventional technology]

A conventional through-hole defect inspection device is shown in FIG. This includes an imaging lens l, photodetectors 2 and 3, a delay circuit 4, an AND gate 5, a printed board feeding device and a light source (not shown), and a roller-shaped mask 6. 2
and 3 are arranged at a certain distance on the imaging plane of the lens 1, and the output of the detector 2 is directly connected to the AND gate 5, and the output of the detector 3 is connected to the AND gate 5 via the delay circuit 4. ing. Note that when the printed board 7 is moved in the direction of the arrow, the photodetector 3 receives the light from the through hole 8 when it is at the position a shown by the dotted line, and the photodetector 2 receives the light from the through hole 8 at the position a shown by the solid line. It is designed to be able to receive light from a through hole. Also, delay circuit 4
The delay time is the same as the time it takes for the through hole to move from position a to position b.

When inspecting the through holes for defects, the printed board 7 is moved at a constant speed in the direction of the arrow while the light 9 is irradiated from below. Then, when the through hole 8 is at position a, the light passing through the through hole is received by the photodetector 3,
When the through hole 8 comes to position b, the mask 6 covers one opening of the through hole. Therefore, when there is no defect in the through hole, the photodetector 2 does not receive light and the AND gate 5
The output from is "L" indicating that there are no defects. If there is a defect in the through hole 8, the base material of the printed board 7 (epoxy resin or the like is transparent and scatters light internally)
The incident light leaks from the defect 10, and the light is transmitted to the photodetector 2.
is detected, and "H" is output from the AND gate 5, indicating that there is a defect.

[Problem that the invention seeks to solve]

The above-mentioned conventional through-hole inspection apparatus has a drawback that unnecessary light leaks from the gap created between the shielding mask 6 provided at the illumination side opening of the through-hole and the through-hole 8, and is mistakenly recognized as a defect.

The present invention was devised in view of these points, and an object of the present invention is to provide a through-hole inspection device with a simple configuration and improved defect detection ability.

[Means for solving problems]

Therefore, in the present invention, one opening of the through hole 8 of the printed board 7 is shielded, and the light 9 is applied to the base material of the printed board 7 to prevent the light leaking from the defective part 10 of the through hole 8. , in a device that performs defect inspection of through holes by detecting them with an optical system consisting of a lens 1 and a photodetector 2 placed on the imaging surface of the lens, from the gap that occurs in the part where the opening of the through hole 8 is shielded. The lens 1 is characterized in that a shielding body 11 is provided in a part of the lens 1 to block light entering the lens 1 from a specific angle so that leaked light does not reach the photodetector 2.

[For production]

By providing the lens 1 with a shielding body 11 that blocks unnecessary light leaking from the gap that occurs in the part where the opening of the through hole 8 is shielded, the photodetector 2 can prevent unnecessary light from leaking from other than the defective part of the through hole. Since no particles are incident, the S/N ratio becomes large, and defect detection ability can be improved.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention.

In this embodiment, an imaging lens 1, photodetectors 2 and 3 arranged on the imaging surface of the lens, and a photodetector 2 connected directly to the photodetector 3 and a delay circuit 4 connected to the photodetector 3 are connected. It is the same as the conventional example explained in FIG.
The reason is that the shielding body 11 is provided in the. In order to prevent light leaking from the gap between the through hole 8 and the mask 6 from reaching the photodetector 2, the shield 11 is fitted with a mask 6 as shown in the figure to prevent light from a specific angle from entering the lens 1. They are shaped like strips in the same direction. In FIG. 2, the specific angle is the angle θ between the lines connecting the longitudinal center of the through hole 8 and the edge of the opening.

This embodiment configured as described above can detect defects in the through ball 8 by the same effect as explained in the conventional example shown in FIG. The light leaking from the gap between the through hole 8 and the through hole 8 is blocked by the shielding body II, and therefore does not reach the photodetector 2. On the other hand, the light leaking from the defect has a property of being strongly emitted in a more inclined direction, and most of the components are imaged on the photodetector 2 without being blocked by the shielding body 11. Therefore, noise light is suppressed and the signal-to-noise ratio is increased, so that the defect detection ability is improved.

FIG. 3 is a diagram for explaining another embodiment of the present invention, in which the same parts as in FIG. 1 are denoted by the same reference numerals.

This embodiment differs from the previous embodiment in that the shape of the shield 11 is a disk whose diameter is the width W of the shield 11 of the previous embodiment.

According to this embodiment, by aligning the through hole 8 and the shielding body 11, leakage light (from defects) that spreads in the line direction can be detected without being blocked.
Furthermore, the S/N ratio becomes larger and the defect detection ability improves.

〔Effect of the invention〕

As described above, according to the present invention, a shielding body is provided in a part of the lens of the through-hole defect detection device L:t S /
By improving the N ratio, defect detection ability can be improved,
It is extremely useful in practical terms.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the operation of the embodiment of the present invention, Fig. 3 is a diagram showing another embodiment of the invention, and Fig. 4 is a diagram showing an embodiment of the present invention. FIG. 1 is a diagram showing a conventional through-hole inspection device. In Figures 1, 2 and 3, 1 is a lens, 2.3 is a photodetector, 4 is a delay circuit, 5 is an AND gate, 6 is a mask, 7... printed board, 8 is a through hole , 9 is a light, 10 is a through-hole defect, and 11 is a shield.

Claims (1)

[Claims] 1. One opening of the through hole (8) of the printed board (7) is blocked, and light (9) is applied to the base material (7) of the printed board to open the through hole. The through-hole defect is inspected by detecting the light leaking from the defective part (10) of (8) with an optical system consisting of a lens (1) and a photodetector (2) placed on the imaging plane of the lens. In the device, the light enters the lens (1) from a specific angle so that the light leaking from the gap created in the portion where the opening of the through hole (8) is shielded does not reach the photodetector (2). A through-hole inspection device characterized in that a shield (11) is provided as a part of a lens (1).