JPH04221747A - Method and device for inspecting through-hole - Google Patents

Abstract

PURPOSE:To inspect the breakage defect of a through-hole even when a translucent layer is laminated on an opaque base material. CONSTITUTION:A sample 10A, wherein a translucent layer 122 is laminated on an opaque base material 24 and a through-hole 14C in a metallic inner wall surface is formed on the translucent layer 122 is irradiated with illuminating light 21 at the inner wall surface. By detecting leak light 22A through the translucent layer 122 in the vicinity of the through-hole 14C, the breakage defect of the through-hole 14C is detected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for inspecting through holes in a sample in which a semitransparent layer is laminated on an opaque substrate and through holes are formed in the semitransparent layer.

0002

2. Description of the Related Art FIG. 4 shows a conventional through-hole inspection principle.

The sample 10 has a through hole 1 perpendicular to a semitransparent substrate 12 for connecting an interlayer wiring pattern 16.
4A and 14B are provided. Through hole 14A,
Conventionally, in order to detect defects such as holes formed in the wall surface of the sample 14B, a light shielding plate 18 is placed opposite the through holes 14A and 14B to be inspected, and illumination light 20 is directed upward perpendicularly to the sample 10. through holes 14A and 14B.
I was investigating whether leakage light 22 would come out from the. That is, if there is no defect like through hole 14A,
The illumination light 20 is blocked by the light shielding plate 18 and the through hole 14
Although no light enters the inside of the through hole 1, if there is a tear defect such as a hole as in the through hole 14B, the scattered light seeping into the semitransparent substrate 12 passes through this defect and enters the through hole 1.
4B, leaked light 22 is emitted upward from the through hole 14B and detected by a photodetector (not shown).

0004

[Problems to be Solved by the Invention] However, since through-hole defects have been detected using such a transmission method, if the semi-transparent substrate 12 is laminated on an opaque substrate such as ceramic, through-hole defects cannot be detected. It was not possible to inspect the hall.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a through-hole inspection method and apparatus that can inspect for tear defects in through-holes even when a translucent layer is laminated on an opaque base material. It's about doing.

[0006]

Means for Solving the Problems and Their Effects FIG. 1 shows the through-hole inspection principle according to the present invention.

Sample 10A has a through hole 14 in which a translucent layer 122 is laminated on an opaque base material 24, and the inner wall surface is metal.
C is formed on the semi-transparent layer 122. In this method invention, illumination light 21 is applied to the inner wall surface of such a sample 10A.
The through hole 1 is detected by irradiating the through hole 1 with
Detects tear defects of 4C.

If there is a tear or other defect in the inner wall of the through-hole 14C, light enters the semi-transparent layer 122 through this defect, diffuses within the semi-transparent layer 122, and causes the light to pass through the defect.
Light leakage 22A comes out from the surface of 22. Therefore, according to the present method invention, even if the translucent layer 122 is laminated on the opaque base material 24, it is possible to inspect tear defects in through holes.

Light leakage from defective part of through hole 14C 2
2A is weak light, but when the semitransparent layer 122 is made of fluorescent material, it blocks the reflected light of the illumination light 21 and the semitransparent layer 122
Through a filter 54 that transmits only fluorescence from
Detecting the light leakage 22A improves the signal-to-noise ratio and enables accurate detection of defects in the through-holes 14C.

Next, the present invention will be explained with reference to the drawings.

In the present device invention, as shown in FIG.
For example, a laser 28, a semi-transparent mirror 36 that divides the incident light beam from the light source 28 into a transmitted light beam and a reflected light beam, and an objective optical element such as an objective lens 34 that illuminates the inner wall surface of the sample 10A as described above. A photodetector, for example, a photomultiplier tube 42, and a photodetector 42 detecting light from the sample 10A reflected or transmitted by a semi-transparent mirror 36 through an objective optical element 34.
A condensing means, for example, an imaging lens 38, condenses the light onto the light receiving surface of the
Alternatively, it is placed in the optical path between the objective lens 34, the photodetector 42, and the semi-transparent mirror 36, and blocks the specularly reflected light from the sample 10A and allows the leaked light 22A from the semi-transparent layer 122 near the through hole 14C to pass through. A partial light shielding body, for example, a light shielding plate 40 is provided.

The operation of this device invention is the same as that of the method invention described above.

When the semi-transparent layer 122 is made of a fluorescent substance, it is placed in the optical path between the photodetector 42 and the semi-transparent mirror 36, as shown in FIG. A filter 54 can be used that blocks specularly reflected light from 10A and transmits leaked light (fluorescence) 22 from semi-transparent layer 122 near through hole 14C.

Furthermore, if both the partial light shield 40 and the filter 54 are used, even if stray light other than the leaked light 22A passes through the partial light shield 40, it will be blocked by the filter 54 and will not reach the photodetector 42. Therefore, the tear defect of the through hole 14C can be detected more accurately.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

(1) First embodiment FIG. 2 shows a through-hole inspection device according to the first embodiment.

Sample 10A is a multilayer printed wiring board, in which a first semitransparent layer 1 made of polyimide resin, epoxy resin, etc., which allows high-density wiring, is formed on an opaque base material 24 made of ceramic or the like.
21 and a second semi-transparent layer 122 are laminated. A diameter of 30
Through hole 1 with plated hole wall of ~100μm
4C is provided on the second semi-transparent layer 122. A ring-shaped through-hole land 15 continuous with the through-hole 14C is attached to the surface of the second semi-transparent layer 122.

The sample 10A is placed on a scanning X-Y stage 26 in order to inspect all of its through holes 14C.

An optical system of a through-hole inspection device is fixedly arranged above the sample 10A. That is, the laser 28, beam expander 30, partial light shielding plate 32, and objective lens 34 are arranged from above toward the sample 10A with their optical axes concentric and perpendicular to the sample 10A. A semi-transparent mirror 36 is arranged between the partial light-shielding plate 32 and the objective lens 34 so as to be inclined at 45 degrees with respect to the optical axis. On the side of the semi-transparent mirror 36, an imaging lens 38, a partial light shielding plate 40, and a photomultiplier tube 42 are arranged with their optical axes concentric.

The focal position of the objective lens 34 is the illumination light 21
is set above the sample 10A so that the cross-sectional diameter of the through-hole land 15 is equal to the inner diameter of the through-hole 14C. The partial light shielding plate 32 has a circular black light shielding portion formed in its center. Partial light shielding plate 3 is placed so that the entire bottom of through hole 14C (the portion of wiring pattern 16 surrounded by through hole 14C) is in the shadow.
A light shielding portion diameter of 2 is selected. In addition, the partial light shielding plate 4
0 is located at the focal position of the imaging lens 38. The partial light shielding plate 40 has a circular black light shielding portion formed in its center. In order to reliably block the strong specular reflection light from the wiring pattern 16 that occurs when the above conditions are not satisfied due to variations in the inner diameter and height of the through holes 14C, the diameter of the light shielding part of the partial light shielding plate 40 is set to the diameter of the light shielding part of the partial light shielding plate 40. It is selected to be equal to the diameter of the image of the through-hole land 15 on the through-hole land 40.

In the above configuration, when a laser beam is emitted from the laser 28, the diameter of the laser beam is expanded by the beam expander 30, and its central portion is blocked by the partial light shielding plate 32, resulting in a light beam having a donut-shaped cross section. This luminous flux is
The light passes through the objective lens 34, converges at a position above the sample 10A, and then diverges to illuminate the entire inner wall of the through hole 14C. Since the partial light shielding plate 32 is arranged, almost no light hits the bottom of the through hole 14C.

If there is a tear or other defect in the inner wall of the through hole 14C, light enters the second semi-transparent layer 122 through this defect, is diffused within the second semi-transparent layer 122, and is exposed to the second semi-transparent layer 122.
Light leakage 22A comes out from the surface of the semi-transparent layer 122. This leaked light 22A passes through the objective lens 34, is reflected by the semi-transparent mirror 36, passes through the imaging lens 38, and is condensed. Light leakage 22
Most of the light A is not collimated even though it passes through the objective lens 34, so most of the light focused by the imaging lens 38 is
The light leaves the light-shielding portion of the partial light-shielding plate 40, reaches the photomultiplier tube 42, and is detected.

On the other hand, when a part of the incident light hits the bottom surface of the through hole 14C, the specularly reflected light is reflected by the objective lens 3.
4, is parallelized by the semi-transparent mirror 36, and passes through the imaging lens 38, but does not reach the photomultiplier tube 42 because it is blocked by the light shielding part of the partial light shielding plate 40.

The output of the photomultiplier tube 42 is transmitted to the binarization circuit 4.
4 to one input terminal of the AND gate 46. On the other hand, the sample 1 is stored in the through-hole position memory 48.
The position of each through hole 14C based on the design data of 0A is stored. The through-hole position determination circuit 50 reads this through-hole position from the through-hole position memory 48, determines whether this position matches the position of the X-Y stage 26, and increases the output only when the position matches. level. Through-hole position determination circuit 50
The output of is supplied to the other input terminal of AND gate 46. Therefore, the output of AND gate 46 goes high only when a defect in through hole 14C is detected. When the output of the AND gate 46 becomes high level, the recorder 52 records the position of the XY stage 26 as a through-hole defect position.

Note that in the above configuration, a case has been described in which both the partial light shielding plate 32 and the partial light shielding plate 40 are used in order to improve the S/N ratio as much as possible, but in principle, the partial light shielding plate 32 is not essential. do not have. Further, the partial light shielding plate 40 may be arranged between the semi-transparent mirror 36 and the imaging lens 38. A laser 28, a beam expander 30, and a partial light shielding plate 32,
Imaging lens 38, partial light shielding plate 40, and photomultiplier tube 42
An optical arrangement may also be used in which the two are interchanged. Also,
A concave mirror or a Cassegrain mirror may be used instead of the objective lens 34, and a concave mirror may be used instead of the imaging lens 38. Furthermore, if the light beam incident on the objective lens 34 is a diverging light beam, the partial light shielding plate 40 can be used without using the imaging lens 38.
It can be imaged on top.

(2) Second Embodiment FIG. 3 shows a through-hole inspection method and apparatus according to a second embodiment.

Polyimide resin or epoxy resin is used as the material for the second semi-transparent layer 122. Both polyimide resin and epoxy resin have fluorescence, and when exposed to ultraviolet light with a wavelength of 300 to 400 nm. When irradiated, it emits orange fluorescence. On the other hand, since the light leakage 22A from the defective portion of the through hole 14C is weak light, it is necessary to improve the S/N ratio to accurately detect the defect in the through hole 14C.

Therefore, in the second embodiment, the partial light shielding plate 4
0 and the photomultiplier tube 42, an optical bandpass filter 54 such as an interference filter is disposed. The transmission center wavelength of the optical bandpass filter 54 matches the center wavelength of the leaked light 22A, and even if stray light other than the leaked light 22A passes through the partial light shielding plate 40, the optical bandpass filter 54
4, the light cannot reach the photomultiplier tube 42. Therefore, defects in the through hole 14C can be detected more accurately than in the first embodiment.

In the second embodiment, in order to improve the S/N ratio as much as possible, partial light shielding plates 32 and 40 are used in addition to the optical bandpass filter 54, but in principle, partial light shielding plates 32 and 40 are used. 40 is not required. Furthermore, an optical low-pass filter may be used instead of the optical band-pass filter 54.

[0030]

As explained above, in the through-hole inspection method and apparatus according to the present invention, illumination light is irradiated onto the inner wall surface of the through-hole of the sample and light leakage from the semi-transparent layer near the through-hole is detected. Even if a semi-transparent layer is laminated on an opaque base material, in other words, regardless of the presence or absence of an opaque base material, it has the excellent effect of being able to inspect tear defects in through-holes, contributing to the expansion of inspection targets. However, it is large.

The light leaking from the defective part of the through hole is weak light, but if the semi-transparent layer is made of fluorescent material, it passes through a filter that blocks the reflected light of the illumination light and transmits only the fluorescence from the semi-transparent layer. Detecting light leakage has the effect of improving the signal-to-noise ratio and making it possible to more accurately detect through-hole tear defects.

Furthermore, if both a partial light shield and a filter are used, even if stray light other than leaked light passes through the partial light shield,
Since the light is blocked by the filter and cannot reach the photodetector, it is possible to more accurately detect through-hole tear defects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the through-hole inspection principle according to the present invention.

FIG. 2 is a configuration diagram of a through-hole inspection device according to a first embodiment.

FIG. 3 is a configuration diagram of a through-hole inspection device according to a second embodiment.

FIG. 4 is an explanatory diagram of a conventional through-hole inspection principle.

[Explanation of symbols]

10, 10A Sample 121 First semi-transparent layer 122 Second semi-transparent layer 14A, 14B, 14C Through-hole 15 Through-hole land 16 Wiring pattern 18 Light-shielding plates 20, 21 Illumination light 22, 22A Light leakage 24 Opaque base material 32, 40 Part Light shielding plate 34 Objective lens 36 Semi-transparent mirror 38 Imaging lens 42 Photomultiplier tube 54 Optical bandpass filter

Claims (5)

[Claims] Claim 1: A translucent layer (1) on an opaque substrate (24).
22) are laminated, and the inner wall surface is a metal through hole (14).
For the sample (10A) in which C) was formed on the semi-transparent layer,
A through hole characterized in that a tear defect in the through hole is detected by irradiating the inner wall surface with illumination light (21) and detecting light leakage (22A) from the semitransparent layer near the through hole. Inspection method. 2. When the semi-transparent layer (122) is a fluorescent substance, a filter (54) blocks reflected light of the illumination light (21) and transmits only fluorescence from the semi-transparent layer.
The through-hole inspection method according to claim 1, characterized in that the leakage light (22A) is detected through the hole. 3. A light source (28), a semi-transparent mirror (36) that divides the incident light beam from the light source into a transmitted light beam and a reflected light beam; A translucent layer (122) is collected on the opaque substrate (24).
For a sample (10A) in which a through hole (14C) with a metal inner wall surface is formed in the translucent layer, an objective optical element (34) that illuminates the inner wall surface, and a photodetector (42) are used.
a condensing means (38) for condensing light from the sample reflected or transmitted by the semi-transparent mirror through the objective optical element onto a light-receiving surface of the photodetector; the photodetector and the semi-transparent mirror; is placed in the optical path between the sample and the specularly reflected light from the sample to block light leakage from the semi-transparent layer near the through hole (22A
) A through-hole inspection device characterized by having a partial light shielding member (40) that allows the light to pass through. 4. A light source (28), a semi-transparent mirror (36) that divides the incident light beam from the light source into a transmitted light beam and a reflected light beam; The light is collected to form a fluorescent semi-transparent layer (1) on an opaque substrate (24).
22) are laminated and the inner wall surface is metal through hole (14C
) is formed on the semitransparent layer, an objective optical element (34) that illuminates the inner wall surface, and a photodetector (
42), a condensing means (38) for condensing the light from the sample reflected or transmitted by the semi-transparent mirror through the objective optical element onto the light receiving surface of the photodetector; It is placed in the optical path between the semi-transparent mirror and blocks specularly reflected light from the sample and blocks light leakage from the semi-transparent layer near the through-hole (2
2A), a filter (54) that transmits fluorescence;
A through-hole inspection device characterized by having the following. 5. The photodetector (42) and the semi-transparent mirror (
36), a partial light shielding member that blocks specularly reflected light from the sample (10A) and allows leakage light (22A) from the semi-transparent layer (122) near the through hole (14C) to pass through. 5. The through-hole inspection device according to claim 4, further comprising: (40).