JPH04177152A - Observation of hole - Google Patents

Abstract

PURPOSE:To observe even a fine and long hole by using a fluorescent detection method with only an image guide part. CONSTITUTION:Only the image guide part 11 of a fiberscope is taken out to be inserted in a through-hole 12. The illumination light 15 from a light source 14 becomes light composed only of a violet component by a violet filter 16 and this light is reflected by a wavelength separating filter 17 to be incident on the detection end 11a of the guide part 11 by an objective lens 18 to irradiate the inner wall 12a of the hole 12 at the observation end 11b of the guide part 11. The image of the inner wall 12a is guided to the focal surface of the line 18 through the guide part 11 and only the fluorescent component therein passes through the filter 17 and a yellow filter 19 as detection light 15 to be capable of being observed by an eyepiece 20. Even when the same optical fiber is used in the guide of the illumination light 15 and the guide of the detection light 15a in fluorescent detection, the halation due to the illumination light 15 is not generated in the detection light 15a. Further, in the observation by fluores cence, a copper plating part is made dark and a void part (base material ex posed part) is made bright to obtain an image improved in contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for observing the condition of the inner wall of a through hole provided in a laminated board such as a printed circuit board.

[Prior art] The conventional wL observation method, as described in Japanese Utility Model Application Publication No. 126856/1983, involves inserting a shaft with an inclined reflective surface at the tip into the hole, and then transmitting an image of the inner wall of the hole to the inclined reflecting surface. The beam is reflected by the beam and guided outside the hole for observation. That is, in the conventional hole observation method, as shown in FIG. 3, illumination light 15 from a light source 14 is reflected by a half mirror 32,
The light is guided into the through hole 12 and is further reflected by the reflective surface 34a at the tip of the shaft 34 inserted into the through hole 12 to illuminate the inner wall 12a of the through hole 12. The image on the inner wall 12a of the through hole 12 is similarly reflected by the reflective surface 34a at the tip of the shaft 34 and guided to the outside of the through hole.The image that passes through the half mirror 32 is then transferred to the photoelectric conversion element 36 by the optical lens system 35. It was imaged and detected.

Another conventional observation method is to observe the inner wall of the hole using a small-diameter fiberscope 40 as shown in FIG. 4(a). This fiberscope 4o is structurally the same as a general one used for medical purposes. Illumination light from a light source (not shown) is guided by a light guide 41 to the inner wall 12 of the through hole 12.
irradiate a. The image on the inner wall 12a of the through hole 12 is guided to the eyepiece section by the image guide section 11 and observed.

If the fiberscope 4o is inserted into the through hole 12 (FIG. 4(b)), the inner wall 12a of the through hole 12 can be observed. In this case, the observed image is that the inner wall 12a of the through hole 12 has a concentric shape,
The result will be as shown in Figure 4(c). Mouth 12b of through hole 12
will be observed centrally. Note that the image guide section 11 has an imaging lens 42 attached to its tip.

Furthermore, as shown in Figure 5, another conventional observation method uses a through hole 1 with a smaller diameter than the fiberscope 4o.
2, only the image guide section 11 of the fiberscope 40 is inserted into the through hole 12 for observation. The illumination light 15 is a half mirror 32
The light is reflected by the optical lens system 35 and enters the detection end 11a of the image guide section 11, and illuminates the inner wall 12a of the through hole 12 from the observation end 11b. Through hole 12
The image of the inner wall 12a is transmitted through the image guide section 11, passes through the optical lens system 35, and is observed after passing through the half mirror 32.

[Problems to be Solved by the Invention] The conventional observation method disclosed in the above-mentioned Japanese Utility Model Application Publication No. 126856/1985 was considered for the through holes 12 that do not have a high aspect ratio. This is difficult when the aspect ratio is high and the diameter of the through hole 12 is small.

In other words, a thin and long through hole 1 as shown in No. 6 @
In No. 2, the shaft 34 must also be made thin and long according to the through hole 12, making it difficult to manufacture the reflective surface 34a at the tip. Further, some of the through holes 12 have an inclination, and it is difficult to move the shaft 34 in and out of the through hole 12 or rotate it without contacting the inner wall 12a of the through hole 12.

Bringing the shaft 34 into contact is problematic because it may damage the inner wall 12a of the through hole and change its condition, or it may damage the shaft 34 itself. Furthermore, a portion of the illumination light 15 and a portion of the detection light 61 are blocked by the end 12c of the through hole 12, making it impossible to obtain an observation image with sufficient brightness.

On the other hand, with the conventional observation method shown in FIG. 3, it is virtually impossible to observe the through-hole 12 having a diameter smaller than that of the fiberscope 40. (Currently, the amount is also thin fiber scope 4
The diameter of 0 is 0.55 mm. ) fiber scope 40
The general structure is that the light guide 41 and the image guide section 11 are combined into one set. The light guide 41 is necessary as a means for guiding illumination when observing an image in the image guide section 11, and if the light guide 41 is removed, the inner wall 12a of the through hole 12 cannot be observed.

Furthermore, in the conventional observation method shown in FIG.
By using the through hole 1 as a light guide, the hole diameter is smaller than that of the fiberscope 40.
2, but the illumination light 15 enters the detection light within the image guide 11 and causes halation, making it impossible to actually observe the image.

The illumination light 15 is passed through the image guide section 11 of the through hole 12.
Halation will also occur if the light is irradiated from the side that is not inserted.

An object of the present invention is to provide a hole inspection method that allows even thin and long holes to be observed without any inconvenience.

[Means for solving the problem] The above purpose is not to use a method using a mirror as shown in FIG. 3, but to use only an image guide section as shown in FIG. This can be achieved by providing the two functions of a light guide 41 like a scope 40 and an image guide section 11, and using a fluorescence detection method that prevents the image guide section 11 from being directly affected by the light from the light guide 41. .

[Function] In the present invention, since the hole observation method requires only the diameter of the fiber for the part that transmits the image, it is possible to insert even a hole with an inclination, and excitation light can be irradiated with a separately provided illumination. For example, it becomes possible to easily observe even holes that are thinner and longer than before.

[Examples] The present invention will be described in more detail below with reference to Examples shown in the attached drawings.

FIG. 1 shows a first embodiment of the present invention. As shown,
A fiberscope 40 with only the image guide part 11 assembled is inserted into a through hole 12 having a diameter smaller than that of the fiberscope. A fluorescence microscope 1It13 is arranged on the detection end 11a side of the image guide section 11. Illumination light 15 from light source 14 is passed through violet filter 16
As a result, only the violet component is generated, which is reflected by the wavelength separation filter 17, and is transmitted to the image guide section 1 by the objective lens 18.
The light enters the detection end 11a of No. 1 and illuminates the inner wall 12a of the through hole 12 from the observation end 11b. The image on the inner wall 12a of the through hole 12 is guided to the focal plane of the objective lens 18 of the microscope 13 through the image guide section 11.
Of the image a, only the fluorescent component passes through the wavelength separation filter 17 and yellow filter 19 as detection light 15a and can be observed through the eyepiece lens 20.

By applying fluorescence detection and making it possible to separate the illumination light 15 and the detection light 15a, even if the same optical fiber is used to guide the illumination light 15 and the detection light 15a, the illumination light 15a can be separated from the detection light 15a. There is no halation caused by light 15. In addition, when detecting [1] due to fluorescence, the copper plating area becomes darker and the void area (
Since the areas where the base material is exposed can be observed brightly, images with good contrast can be obtained, and the presence or absence of voids can be clearly seen.

The generation of fluorescence by printed board substrates is described in the document IEEE T
rans, PAMI Vol, IO, No, IP,
69 (1988).

FIG. 2 shows a second embodiment of the present invention. Similar to the first embodiment, an image guide section 11 and a fluorescence microscope [13] are used, but an illumination fiber 21 is separately used for illumination. The light emitted from the illumination fiber 21 becomes only a violet component by the violet filter 16 attached to the tip of the illumination fiber 21, and illuminates the inside of the through hole 12.

The illumination light itself is cut by the yellow filter 19,
As in the first embodiment, only the fluorescent component can be observed.

[Effects of the Invention] According to the present invention, it is possible to observe the inner wall of even a particularly narrow and long hole such as a through hole in a high-density laminated printed circuit board. Conventionally, in order to observe the inner wall, it was necessary to conduct a destructive inspection of the board, but with the present invention, it is no longer necessary to conduct a destructive inspection. In addition, when fluorescent light is used, the presence or absence of peeling defects (voids) on the inner wall plating can be directly detected! You will be able to understand.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the hole observation method according to the present invention, and FIGS. 3 to 6 are explanatory diagrams of the conventional hole observation method. Explanation of symbols 11: Image guide section. 13...Fluorescence microscope, 16...Purple filter, 17...Wavelength separation filter, 19...Yellow filter. /2Q Figure 2 30th 40th

Claims (3)

[Claims] 1. In order to observe the inner wall of a long and narrow hole, an optical fiber for image transmission with an imaging lens attached to the tip is pushed into the hole, and the optical fiber transmits an image of the inside of the hole to the outside of the hole. A hole observation method characterized by transmitting the image and observing the transmitted image using an externally provided magnifying optical system. 2. 2. The hole observation method according to claim 1, wherein light is incident on the inserted optical fiber, and the light emitted from the optical fiber is used as light for illuminating the inner wall of the hole. 3. In claim 2, when the material of the inner wall of the target hole is composed of a material that generates fluorescence and a material that does not generate fluorescence, the illumination light is either light with a wavelength in a band that excites fluorescence, or light with a wavelength in a band that excites fluorescent light, or By adding an optical filter that only allows light to pass through, light in a specific band can be used as illumination light, and
A hole observation method for observing an image of the inner wall of the hole caused by fluorescence by providing an optical filter that selects only light in the fluorescence band from among the light transmitted to the outside of the hole by the optical fiber.