JPH01257249A - Inspecting apparatus for through hole of printed board - Google Patents

Abstract

PURPOSE:To enable the precise detection of a defect even when a strong irradiation light is applied, by a construction wherein a light-intercepting means for intercepting light from a rotary body is disposed on the irradiation light side of the rotary body for intercepting light from a through hole, so as to avoid the application of the irradiation light onto the rotary body. CONSTITUTION:The opposite ends of a support shaft 7 of a rotary body 6 which is constructed of a roller-shaped light-intercepting body intercepting an irradiation light 24 from a plurality of through holes 23 simultaneously, are supported by an arm 8. To the fore end 8'a of an auxiliary arm 8a made integral with this arm 8, a light-intercepting body 25 of brass, for instance, which has substantially the same diameter and length as the rotary body 6 is fitted to a position whereat it intercepts light from the rotary body 6 when the rotary body 6 comes into close contact with a printed board 20. However strong the irradiation light 24 is, the rotary body 6 is prevented thereby from being deformed by heat absorption and complete blocking of openings of the through holes 23 is maintained. Irrespective of the intensity of the irradiation light 24, accordingly, the presence of a defect of the through hole 23 can be detected on the basis of whether a detector 10 detects a light signal in the through hole 23.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a through-hole inspection device for printed boards that inspects defects in through-holes in printed boards, and aims to accurately detect defects in through-holes even in thick printed boards. A roller-like rotating body positioned on one side of the printed board and rolling in close contact with the printed board masks only the through holes, and the area including the through holes is irradiated with light from above the rotating body, and the other side of the printed board is exposed to light. A through-hole inspection device for a printed circuit board that detects the presence or absence of diffused light from the printed board in the through-hole using a disposed photodetection system to detect the presence or absence of a defect in the through-hole, wherein the rotating body The device is configured to include means for shielding the body from irradiation light.

[Industrial application field]

The present invention relates to a printed board inspection apparatus, and more particularly to a printed board through-hole inspection apparatus for inspecting defects in through-holes in which a conductive layer is formed on the inner wall surface.

In general, double-sided printed boards and multilayer printed boards have through holes drilled in the inner wall using an electrical or chemical method for electrical connection between the front and back printed wiring formed on the board or between each layer of printed wiring. It is formed.

In this case, the plating layer mentioned above is not always in good condition and may have defects such as cuts and pinholes, but these defects impede the purpose of the connection and reduce the reliability of the printed board. Therefore, it is necessary to inspect for defects.

[Conventional technology]

One of the inspection methods for inspecting defects in through holes is to cover one end of the through hole in a translucent printed board with a flexible light shielding material to shield it from light, and then expose the area containing the through hole to light from above. irradiated, enters the printed board from the periphery of the through hole, diffuses, passes through the defective part of the inner wall plating layer, and leaks into the through hole; the light is detected by placing the light on the other side of the printed board; There is a method of determining the presence or absence of defects in the plating layer by detecting them using a system. (Japanese Patent Application No. 57-228376, filed December 27, 1982) FIG. 3 is a diagram showing an example of a conventional through-hole inspection device for printed circuit boards.

In the figures, (A) shows a side view and B) shows a perspective view of the rotated body part.

In Figures (A) and (B), 1 is the printed board to be inspected,
Reference numeral 2 denotes a light-transmissive substrate made of glass epoxy resin or the like constituting the printed board 1, and a through hole for electrically connecting the front and back conductors by forming a plating layer 3 on the inner wall surface of the through hole 2a of the base vi2. 4 is formed.

Further, 5 is irradiation light from an inspection light source (not shown).

Reference numeral 6 denotes a plurality of the above-mentioned through holes 4 lined up in the front-rear direction of the paper.
It is a rotary body made of a roller-shaped light shielding body having a length sufficient to simultaneously shield the irradiation light 5 from the irradiation light 5, and both ends of its support shaft 7 are supported by an arm 8 rotatably attached to a fixed part. A tension spring 9 is stretched between the arm 8 and the fixed part to bring the rotating body 6 into close contact with the light irradiation surface of the printed board 1.

Further, the printed board 1 is set on an X-Y table (not shown) and moved in the direction of arrow A, so that the rotary body 6 that rotates on its axis in close contact with the printed board 1 closes the plurality of through holes 4 and irradiates the irradiated light 5. is designed so that it does not enter into these through holes 4.

Reference numeral 10 denotes a photodetector disposed on the other side of the printed board 1 facing the rotating body 6, and is capable of detecting optical signals from the plurality of through holes 4 that are blocked by the rotating body 6. be.

Reference numeral 11 denotes a lens that focuses light leaking into the through hole due to a defect in the through hole 4 onto the photodetector 10.

In an inspection apparatus having such a configuration, when the printed board 1 is moved by a predetermined distance in the A direction on an does not enter through hole 4.

On the other hand, from around the through hole 4, the substrate 2 of the printed board 1 is
The irradiated light 5 that enters the substrate 2 is diffused within the substrate 2. At this time, if there is a defect 3a such as a cut or a pinhole in the plating N3 of the through hole 4, the diffused light passes through the defect 3a and enters the through hole 4. The light leaks inside and further passes through the lens 11 to the photodetector 10.
The light is focused on.

Furthermore, if there is no defect in the plating layer, the diffused light will not leak into the through hole 4, so the photodetector 10
doesn't work.

Therefore, the presence or absence of a defect in the through hole 4 can be detected depending on whether the photodetector 10 detects an optical signal within the through hole 4 or not.

However, since the light that propagates and diffuses through the printed board 1 is rapidly weakened as it progresses, the accuracy of detecting the defect decreases depending on the position of the defect in the plating layer 3.

In other words, there is a difference in the strength of the optical signal received by the photodetector 10 depending on whether the defect in the through hole 4 is located close to the irradiation surface of the irradiation light 5 or far from the irradiation surface. If there is a small defect in the position, it may not be detected.

Therefore, it is necessary to change the brightness of the irradiation light 5 depending on the thickness of the printed board 1, that is, the length of the through hole 4.

For example, if the thickness of the printed board is about 3 mm and the inner diameter of the through hole is about 0.2 mm, and the brightness of the irradiation light that can detect any defect is 1, then if the printed board is 7 mm
When the thickness of the through-hole is approximately 50 times higher, it requires about 50 times the brightness to detect a defect in a through-hole with the same inner diameter.

On the other hand, the demand for higher speed computing systems has led to increased multi-layer printed circuit boards and an increase in the thickness of printed circuit boards.

Therefore, it is necessary to make the irradiation light 5 brighter, but in this case, the roller-shaped rotating body 6 that shields the through hole 4 absorbs the heat of the strong irradiation light and is thermally deformed, so that the light shielding of the through hole 4 is incomplete. In some cases,

[Problem to be solved by the invention]

In conventional printed circuit board through-hole inspection equipment, as the thickness of the printed board increases, it is necessary to use powerful irradiation light, which deforms the roller-like rotating body and makes it impossible to shield the through holes from light. There was a problem in that the detection accuracy of through ball defects was lowered.

[Means to solve the problem]

The above problem can be solved by masking only the through holes with a roller-shaped rotating body located on one side of the printed board and rolling in close contact with the printed board, and irradiating the area containing the through holes with light from above the rotating body. A through-hole inspection device for a printed board, which detects the presence or absence of a defect in the through-hole by detecting the presence or absence of diffused light from the printed board in the through-hole using a photodetection system placed on the other side of the printed board, The problem is solved by a printed board through-hole inspection apparatus in which the rotating body is provided with means for shielding the rotating body from irradiation light.

[For production]

In order to enable accurate through-hole defect detection even when irradiated with powerful irradiation light, it is necessary to deform the rotating body that shields the through-hole by receiving light.

In the printed board through-hole inspection device according to the present invention,
Irradiation of the irradiation light onto the rotor is avoided by providing a light shielding means for shielding the rotor from light on the irradiation light side of the rotor that shields the through hole.

Therefore, even when inspecting through-holes in a thick printed circuit board by projecting powerful irradiation light, there is no deformation caused by the irradiation light from the rotating body, so it is possible to achieve highly accurate through-hole defect detection.

〔Example〕

FIG. 1 is a side view showing an example of a printed board through-hole inspection apparatus according to the present invention, and FIG. 2 is a diagram showing another embodiment.

In FIG. 1, reference numeral 20 indicates a printed board to be tested which is mounted on an X-Y table (not shown) and is movable in the front, back, left and right directions of the paper surface, and 21 is a light beam made of glass epoxy resin, etc. that constitutes the printed board 20. The printed board 20 is a transparent substrate, and in the case of the figure, three light-transmissive substrates 21 constitute a printed board 20. Further, a plating 122 is formed on the inner wall surface of the through hole 21a of the substrate 21 to form a through hole 23 for electrically connecting the front N conductor.

Further, a broken line 24 indicates irradiation light that is emitted from an inspection light source (not shown) and irradiates a region including a through hole to be inspected.

6 is a plurality of the above-mentioned through holes 2 lined up in the front and rear direction of the paper.
3 from the irradiation light 24 at the same time, it is a rotary body similar to that shown in FIG. As in the case of FIG. 3, the rotary body 6 is configured to be brought into close contact with the light irradiation surface of the printed board 20 by means of a tension spring 9 stretched between the rotation body 8 and the fixed portion.

Further, the tip portion 8a1 of the auxiliary arm 8a integrated with the arm 8 is provided at a position that is approximately parallel to the rotary body 6 and shields the rotary body 6 from the irradiation light 24 when the rotary body 6 comes into close contact with the printed board 20. A light shielding body 25 made of, for example, brass and having the same diameter and length is attached.

Reference numerals 10 and 11 denote a photodetector and a condenser lens similar to those shown in FIG. 3, which are placed on the other side of the printed board 20 facing the rotating body 6.

In the inspection apparatus having such a configuration, by moving the printed board 20 by a predetermined amount in the direction shown in the figure, for example,
The rotating body 6 that rotates on its axis in close contact with the printed board 20 closes the openings Q[- of the plurality of through holes 23 arranged in the longitudinal direction of the paper at a predetermined position on the printed board 20, so that the irradiated light 2
4 does not enter into these through holes 23, but at the same time, the irradiated light 24 is blocked by a light shielding body 25, so that it does not directly irradiate the rotating body 6.

Therefore, no matter how strong the irradiation light 24 is, the rotating body 6 will not be deformed due to heat absorption, and the opening of the through hole 23 will remain completely closed.

On the other hand, the irradiation light 24 that enters the light-transmitting substrate 21 of the printed board 20 from around the through-hole 23 is diffused within the substrate 21 as shown by the solid line 24'', but the through-hole 23
If there is a defect 23a such as a cut or a pinhole in the plating layer 22, a part of the diffused light passes through the defect 3a and leaks into the through ball 23, and then passes through the lens 11 and is focused on the photodetector 10. As described above, if there is no defect in the plating layer 22, the diffused light will not leak into the through hole 23, so the photodetector 10 will not operate.

Therefore, regardless of the intensity or brightness of the irradiated light 24, the presence or absence of a defect in the through-hole 23 can be detected based on whether the detector 10 detects an optical signal within the through-hole 23.

Figure 2, which shows an example of using line beam-shaped irradiation light to improve the usage efficiency of irradiation light, is an enlarged view of the part that shields the rotating body. (B) shows the case where an aluminum wedge with a mirror-finished surface is used, and (B) shows the case where an optical system is used as the rotating body light shielding means.

In Figure (A), as in Figure 1, 21 is a light-transmissive substrate constituting a printed board, 23 is a through-hole penetrating the light-transmissive substrate 21, 6 is an opening of the through-hole 23, and 7 is its opening. An arm whose supporting shafts 8 at both ends fit into the supporting shaft 7 to bring the rotating body 6 into close contact with the printed board.

8a is an auxiliary arm integrated with arm 8.

Further, 25 is an aluminum wedge formed of aluminum (A/) with an isosceles triangular cross section and a length approximately equal to that of the rotating body 6. The auxiliary arm 8a at both end surfaces
It is fixed so that its apex angle 25a faces the direction of the irradiation light. Furthermore, the two surfaces sandwiching the apex angle 25a are mirror-finished.

24a indicated by a broken line is a line beam-shaped irradiation light emitted from a light source for inspection (not shown) and long in the front-rear direction of the paper.

In this case, all of the line beam-shaped irradiation light 24a is reflected by the mirror surfaces on both sides of the aluminum wedge 25 that sandwich the apex angle 25a, and is incident on the printed board surface excluding the through hole 23 portion, and diffused light 24a is shown as a solid line. °.

Thereafter, the photodetector 10 detects the presence or absence of a defect in the through hole 23 using the diffused light 24a', as in the case of FIG.

Therefore, in this case, the efficiency of use as irradiation light is high, and since the rotating body 6 is not irradiated and the rotating body is not heated and deformed, through-hole defects can be detected with high accuracy.

In Figure (B), an optical prism 26 is used in place of the aluminum wedge 25 in Figure (A), and the other configurations are exactly the same as in Figure (A).

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a through-hole inspection device for a printed board that can detect through-hole defects with high accuracy even in a thick printed board with a large number of laminated layers.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an example of a printed board through-hole inspection device according to the present invention, Fig. 2 is a diagram showing another embodiment, and Fig. 3 is a side view of a conventional printed board through-hole inspection device. This is a diagram showing an example. In the figure, 6 is a rotating body, 7 is a support shaft, 8 is an arm, 8a is an auxiliary arm, 8a' is a tip, 9 is a spring, 10 is a photodetector, 11 is a condenser lens, 20 is a printed board, 21 21a is a transparent substrate, 21a is a through hole, 22 is a plating layer, 23 is a through hole, 23
a represents a defective portion, 24 represents irradiation light, 24a ## represents beam-like irradiation light, 25 represents a light shield, 26 represents an aluminum wedge, 26a represents an apex angle, and 27 represents an optical prism. Figure 1 A and Otsu σ and 9 and 213f row and F? Ko? 1 te
2 Figure 3m

Claims (1)

[Claims] A roller-shaped rotating body located on one side of a printed board and rolling in close contact with the printed board masks only the through-holes and irradiates the region including the through-holes with light from above the rotating body. , a through-hole inspection device for a printed board, which detects the presence or absence of diffused light from the printed board in the through-hole using a light detection system placed on the other side of the printed board to detect the presence or absence of a defect in the through-hole. . A through-hole inspection device for a printed board, characterized in that the rotating body is provided with means for shielding the rotating body from irradiation light.