JP4107294B2 - Laser inspection equipment - Google Patents

Description

  The present invention relates to a laser inspection apparatus, for example, detection of unremoved material remaining on the bottom surface of a blind via hole, thickness measurement, etc. during a blind via hole processing operation on a laminated wiring board called a printed circuit board. It has an inspection function.

  With recent high performance of electronic devices, higher wiring density is required. In order to satisfy this requirement, multilayer and miniaturization of printed circuit boards are progressing. As one of the techniques, it is essential to form a fine blind hole for interlayer conductive connection called a blind via hole (BVH) having a hole diameter of about 150 μm. However, drilling of φ0.2 mm or less and blind hole processing are difficult with current drilling, and in addition, the thickness of the insulating layer is 100 μm or less for high-density printed circuit boards. Since it is difficult to perform, it is impossible to form fine BVH by drilling.

  A method of applying a laser beam has attracted attention as a BVH forming method that replaces this drilling. This processing method uses the difference in the absorption rate of light energy between resin and glass fiber, which are insulating materials that form printed circuit boards, and copper, which is a conductor layer. Carbon dioxide laser is partly used as a laser light source. It has become. As shown in FIG. 11, if the interior copper foil 24 is laminated in advance inside the processed portion, the decomposition and removal of the insulating member stops at the inner layer copper foil 24, so the blind hole 6 that stops reliably at the inner layer copper foil 24 is formed. Can be formed. The hole processed in this way is called a direct image hole. In addition, in a substrate having a copper foil on the surface as shown in FIG. 12, a copper foil removal portion having a necessary hole diameter is formed by etching or the like, and laser beam 20 having a beam diameter larger than the removal portion is irradiated, The processed hole 6 can also be formed. The hole processed in this way is particularly called a conformal image hole.

  When the blind hole that stops at the copper foil is processed with a carbon dioxide laser as shown in FIGS. 11 and 12, even if the laser beam is sufficiently irradiated, the resin that is an insulating member having a thickness of 1 μm or less remains on the inner copper foil. End up. For this reason, it is necessary to completely remove the residual resin by etching the residual resin with permanganic acid after laser processing. At this time, if the blind hole is reduced to about 100 μm, the etching solution becomes difficult to reach the inside of the hole. Therefore, when the thickness of the residual resin exceeds 1 μm due to poor laser processing conditions or the like, there is a hole that cannot completely remove the residual resin. appear. When plating is performed in this state to form a BVH electrode, a part of the resin remains between the plating film and the inner layer copper foil. Here, when stress is applied due to a thermal cycle or the like, the plating film is peeled off starting from this. For this reason, after the laser processing, it is necessary to inspect the thickness of the residual resin.

  FIG. 13 shows the distribution of residual resin when the number of shots is changed. It has been found that the residual resin is small near the center of the hole and tends to remain near the hole wall. Even if there is little resin at the center position like a hole with 5 shots, there are cases where there are many resins around the center position, resulting in failure. Therefore, when inspecting the thickness of the residual resin, it is necessary to inspect a wide range from the center to the periphery.

  A conventional inspection apparatus inspects a processed part using an optical microscope as shown in FIG. Although the conventional optical microscope described on page 45 of the Nikkei Science October 1990 issue can detect when a resin of about 10 μm or more remains, the detection accuracy of the residual resin of about several μm as described above is poor. In mass production, it is difficult to apply, and the thickness of the residual resin must be inspected by observing the cross section after cutting / polishing the processed part after plating.

The reason why the conventional optical microscope cannot detect the resin as described above will be described.
A conventional optical microscope is configured as shown in FIG. The white light 38 for illumination is irradiated onto the printed circuit board 21 via the objective lens 5 by the beam splitter 25. The reflected light from the printed board 21 creates an inverted real image enlarged by the objective lens 5 in front of the imaging lens 9, and the real image is detected by the CCD camera 11.

  Here, as shown in FIG. 16, when the surface of the residual resin 22 is irradiated with white light 38, which is illumination light of the optical microscope, a part of the light is reflected, and the other passes through the residual resin 22 and reaches the copper foil 24 on the bottom surface. Reached and reflected. Accordingly, when the white light 38 is illuminated as illumination light with respect to the thin resin on the copper foil, most of the reflected light returns from the copper foil 24, and the residual resin 22 becomes invisible.

  FIG. 17 shows an inspection apparatus described in an embodiment of Japanese Patent Laid-Open No. 7-83841. In the figure, 43 is an ultraviolet laser light source, 45 is a collimating lens, 44 is a mirror, 25 is a beam splitter, 46 is a rotating other-surface mirror, 21 is a printed circuit board to be inspected, 9 is a re-imaging lens, 48 is a pinhole, 47 is a photomultiplier (photomultiplier tube).

  Next, the operation of the conventional example will be described. The laser light generated by the ultraviolet laser light source 43 is expanded using the collimation lens 45. The enlarged laser beam is scanned using a rotating polygon mirror 46 and condensed on the printed circuit board 21 by the objective lens 5.

  The ultraviolet light generated from the printed circuit board 21 by the irradiation of the laser light traces back the incident path, is recursively returned, and is guided to the retroreflection detection system by the beam splitter 25 arranged in the optical path. This ultraviolet reflected light is imaged by the imaging lens 9. An image near the irradiation point of the laser beam on the printed circuit board to be inspected is observed on the imaging plane. Only the central portion is separated by the pinhole 48 placed on the image plane and detected by the photomultiplier 47.

Japanese Patent Laid-Open No. 7-83841

  Since the conventional detection device shown in FIGS. 15 and 16 is configured as described above, there is a problem that when the residual resin is thin as described above, the reflected light is strong and the residual resin cannot be detected. It was.

  In addition, although the inspection apparatus shown in FIG. 17 performs laser scanning with a rotary polygon mirror, the scanning line of the laser beam is shifted to the center line of the blind hole due to misalignment when the blind hole is processed or the accuracy of the scanning device deteriorates. May deviate from. For example, in the case of a blind hole with 5 pulses in the number of shots, when there is little residual resin near the center of the hole and it is a good product level, but the periphery is at a defective product level, there is a problem that a good product is erroneously determined as a defective product due to a scan line shift.

  In order to prevent this, it is necessary to make the interval between the scanning lines sufficiently smaller than the hole diameter and scan the entire surface of the hole bottom, but there is a problem that the inspection takes a long time.

  In addition, when a conformal substrate is inspected, since there is a copper foil on the surface of the substrate, fluorescence does not occur even when irradiated with laser light in addition to a blind hole, and thus there is a problem that it is erroneously determined as a good product.

  The present invention has been made to solve the above-described problems, and provides an inspection apparatus that can inspect the recesses reliably and at high speed.

  A laser inspection apparatus according to the present invention includes a light source that outputs laser light, an irradiation unit that irradiates a laser beam output from the light source to a desired position on a substrate having a recess, and the laser light is irradiated. Detection means for detecting fluorescence generated from the substrate and outputting a detection signal; and control means for controlling the irradiation means on the basis of the detection signal. The irradiation means has a predetermined vicinity in the vicinity of the recess. Laser light is scanned in the direction, and the detection means detects a change in the intensity of the fluorescence generated from the substrate by scanning the laser light and outputs a detection signal. The control means is based on the detection signal on the scanning line. The provisional center position of the recess is calculated, and then the irradiating means is controlled by the control means and scans the laser beam in the direction perpendicular to the scanning line through the calculated provisional center position. It is intended.

  Further, the control means discretizes the detection signal, rearranges the discretized data in the order of the level of the detection signal, and compares the data with the diameter of the concave portion stored in advance, so The center position is calculated.

  The irradiation means performs scanning in the same direction a plurality of times.

  In addition, it is provided with position detecting means for detecting the actual scanning position during laser scanning.

  A laser inspection apparatus according to the present invention includes a light source that outputs laser light, an irradiation unit that irradiates a laser beam output from the light source to a desired position on a substrate having a recess, and the laser light is irradiated. Detection means for detecting fluorescence generated from the substrate and outputting a detection signal; and control means for controlling the irradiation means on the basis of the detection signal. The irradiation means has a predetermined vicinity in the vicinity of the recess. Laser light is scanned in the direction, and the detection means detects a change in the intensity of the fluorescence generated from the substrate by scanning the laser light and outputs a detection signal. The control means is based on the detection signal on the scanning line. The provisional center position of the recess is calculated, and then the irradiating means is controlled by the control means and scans the laser beam in the direction perpendicular to the scanning line through the calculated provisional center position. Since, reliably scan line passing through the center of the recess, it is the inspection of the recess. In addition, since the inspection can be realized by two scans, high-speed inspection is possible.

  Further, the control means discretizes the detection signal, rearranges the discretized data in the order of the level of the detection signal, and compares the data with the diameter of the concave portion stored in advance, so Since the center position is calculated, even when the signal on the substrate surface is noisy, the center position of the recess is reliably detected and the center line of the recess is inspected, so that a highly reliable inspection can be realized.

  Further, since the irradiation means performs scanning in the same direction a plurality of times, a highly accurate inspection with little variation can be performed.

  Further, since the position detecting means for detecting the actual scanning position at the time of laser scanning is provided, it is possible to prevent the position detection accuracy of the concave portion due to the irradiation position from being deteriorated, and to increase the scanning speed.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an embodiment of the invention. In the figure, 13 is a laser oscillator, 4 is a dichroic mirror that reflects the laser beam emitted from the laser oscillator 13, 33 and 34 are galvanometer mirrors for scanning the laser beam in the X and Y directions, and 5 is a printed laser beam. An objective lens for condensing on the substrate 21, a filter for selecting the wavelength of fluorescence passing through the dichroic mirror 4 from the printed substrate 21 irradiated with laser light, and an imaging lens 9 for transferring the fluorescence. Reference numeral 2 denotes a detector for detecting fluorescence. The central processing chamber 31 instructs the galvanometer 26 to drive the scanning position and drives it. The signal from the fluorescence detector 2 is input to the central processing chamber 31 and determined.

  Next, the operation of the invention shown in FIG. 1 will be described. As in the conventional example, fluorescence is generated when the resin portion or the remaining resin portion of the blind hole is irradiated with laser light. Here, fluorescence has a longer wavelength (generally visible light) than laser light. The dichroic mirror 4 is configured to reflect the laser beam emitted from the laser device 13 but to pass other wavelengths. The filter 10 is used when selecting only the wavelength to be inspected as light entering the detector 2.

  In the present embodiment, the laser device 13 is a solid-state laser having a wavelength of 473 nm and 30 mW. Conventionally, for fluorescence observation, ultraviolet light has higher fluorescence intensity at the same power, so ultraviolet light is generally used, but ultraviolet light must be used without using a special optical system such as quartz glass. A laser beam having a wavelength of 473 nm was used because of its large absorption, large loss, and high cost of the optical system. The dichroic mirror 4 used was one that reflects 495 nm or less, and the filter 10 did not pass 520 nm or less. A carbon dioxide laser was used to process the blind holes on the printed circuit board.

  The light intensity of the fluorescence generated by the printed circuit board in the case of a mercury lamp and in the case of a solid-state laser beam of 30 mW by changing the number of shots of the carbon dioxide laser (the exposure time (seconds in FIG. 2) is described as the light intensity. 2 is a reciprocal of the numerical value). In this printed circuit board, no residual resin residue was observed by desmearing after processing 7 pulses of shots.

  It has been confirmed that if the residual resin at the bottom of the blind hole of the printed circuit board is about 0.2 μm to 0.6 μm, the residual resin can be removed by a desmear process in the subsequent process. According to FIG. 2, in the case of a mercury lamp, the intensity of fluorescence generated by both defective and non-defective products is almost the same. I understand that.

  As described in the conventional example, even if the processing with the carbon dioxide laser is completed normally, a resin residue of less than 1 μm is generated at the bottom of the blind hole. For this reason, in a lamp or the like that does not have the same phase, light passes through a very thin resin, fluorescence is not generated, and inspection cannot be performed. In addition, it was found that the determination was difficult because the intensity of the fluorescence itself was too low overall.

  On the other hand, a laser beam having a monochromatic property and a phase can be inspected because even a very thin resin having a wavelength is absorbed by the laser beam to generate fluorescence. Therefore, the resin residue of about 0.6μm at the bottom of the hole is not defective because it can be removed after desmear treatment, but if the resin residue is thicker than that, it cannot be removed by desmear treatment, so after processing with carbon dioxide laser, before desmear treatment In addition, it has been found that it is effective to use the laser beam in order to detect processing defects. In our experiment, a laser beam having a wavelength of 473 nm was used, so that a resin residue of substantially 0.5 μm or more can be sufficiently detected.

  In the configuration of the present invention, since the scanning optical system is configured by using two galvanometer mirrors, it can move from the beginning to the blind hole and only the periphery of the blind hole can be inspected, so the inspection is fast. On the other hand, for example, in the conventional observation apparatus described in JP-A-7-83841, a scanning method using a rotating polygon mirror is disclosed. However, since the entire surface of the printed circuit board must be scanned with a fine scanning line interval, take time.

  In the present embodiment, the position of the blind hole on the printed circuit board 21 is registered in the central processing chamber 32 in advance.

  Considering the positional deviation at the time of processing the blind hole and the accuracy of the scanning device, even if the blind hole is moved to the registered blind hole position, a deviation may occur between the laser irradiation position and the blind hole center position. FIG. 3 is a diagram for explaining a scanning method for detecting this shift and accurately irradiating a blind hole with laser light. After moving to the registered blind hole position (circle 1 in the figure), first, laser scanning is performed on the Y-direction scanning line segment 39 whose length is twice the hole diameter around the position (circle 2 in the figure) The temporary hole center position is detected from the signal detected by the fluorescence detector 2 (circle 3 in the figure). Since the true hole center position is on the X-direction line passing through the temporary hole center position and orthogonal to the Y scan line segment 39, if the X scan line segment 40 is laser-scanned, the fluorescence signal on the blind hole center line is detected. Can be detected (circle 4 in the figure), and the hole center position can be detected from the detection signal (circle 5 in the figure).

  Since the fluorescence intensity and the hole center position on the hole center line are detected by the above two scans, the residual resin level in a specific region on the center line can be inspected from the detected values (circle 6 in the figure). . In the present embodiment, the residual resin level is detected by integrating the fluorescence signal on the hole center line by the evaluation area around the hole center position. Even when inspecting blind holes where there is a difference between the center and the periphery of the residual resin, the deviation between the laser irradiation position and the blind hole position is detected, and the specific position of the blind hole bottom is inspected. Can do.

  Furthermore, in this embodiment, if the evaluation area is increased to about the hole diameter, the vicinity of the hole wall surface can be inspected. Even holes that are likely to become can be reliably inspected.

  Further, since the inspection can be realized by two scans, it is very fast. We confirmed that 90 holes could be inspected per second with our experimental device.

  If more precise inspection of the residual resin level is required, the laser scanning of the circles 4 to 6 in FIG. 3 and the residual resin detection may be performed a plurality of times, and the output may be averaged. Good. In general, it is known that with respect to random noise, the S / N ratio is improved in proportion to the square root of n by repeating n times.

  FIG. 4 is a diagram for explaining an example in which the hole center position is detected from the fluorescence signal in the circles 3 and 5. Since the surface of the direct image substrate is covered with a thick resin and there is little resin at the bottom of the blind hole, the fluorescence signal when the laser beam is scanned is a signal having a low level at the bottom of the hole. If this signal is binarized and the barycentric position of the lower level is calculated, the hole center position can be detected.

  In the present embodiment, the galvanometer mirror has been described as an example, but the same effect can be obtained by scanning using an AO (acoustic optical element), EO (electromagnetic optical element), or the like.

Embodiment 2. FIG.
The conformal substrate could not detect a blind hole because the surface was copper foil and no fluorescence was generated. FIG. 5 is a configuration diagram showing the second embodiment, and is a diagram for explaining an optical system for distinguishing between the copper foil on the surface and the copper foil on the bottom of the blind hole in the conformal substrate. The configuration is such that the photodetector 3 is attached to the laser inspection apparatus of FIG. The photodetector 3 is installed in an oblique direction with respect to the blind hole. The copper foil has fine irregularities, and when the laser beam 7 is irradiated, scattered reflected light is generated. Reference numeral 41 is reflected light that is scattered when the laser light is applied to the copper foil on the surface of the printed circuit board 21, and 42 is reflected light that is scattered when the laser light is applied to the bottom of the hole. The reflected light 41 on the copper foil on the substrate surface is detected by the detector 3, but the reflected light 42 on the hole bottom is blocked by the hole wall surface and is not detected by the detector 3. Accordingly, it is possible to distinguish whether the laser irradiation position is the copper foil on the substrate surface or the copper foil on the bottom of the hole based on the detection signal level of the detector 3. Even if the laser irradiation position and the blind hole position greatly deviate for some reason, if the reflected light level is larger than the threshold value, it can be determined that the hole is not the bottom, so that it is possible to eliminate erroneous determination as a non-defective product. Further, the blind hole can be detected by scanning the blind hole with a laser and binarizing the detection signal of the reflected light detector 3. In addition, since the fluorescence intensity and the reflected light intensity can be detected simultaneously, the inspection can be performed at high speed.

  Further, in the conformal substrate, in order to detect the deviation between the laser irradiation position and the blind hole position and to accurately irradiate the blind hole with the laser beam, the scanning method described in FIGS. 3 and 4 may be performed. . However, in detecting the hole center position in FIG. 4, a reflected light signal is used instead of the fluorescence signal. The reflected light signal at the time of conformal hole scanning has a low level at the bottom of the hole similarly to the fluorescence signal at the time of direct hole scanning, so that the hole position can be detected by the same method.

  Furthermore, if the mounting angle 49 of the reflected light photodetector 3 is set to be antan (a blind hole aspect ratio) or less, the reflected light 42 from the hole bottom is completely blocked by the hole wall surface, so that the hole bottom can be more reliably secured. Can be distinguished from the copper foil on the substrate surface.

  Further, if a plurality of the reflected light detectors 3 are arranged so as to surround the blind hole, the scanning direction of the detection signal is lost. In other words, the copper foil on the bottom of the hole and the copper foil on the surface of the substrate can be reliably distinguished in any direction.

  In addition, if an optical fiber is arranged around and the reflected light collected by the detector 3 is detected, the detection system is simple and inexpensive.

Embodiment 3 FIG.
In the third embodiment of FIG. 6, the ring light guide 23 is used for collecting the reflected light. Other configurations are the same as those of the second embodiment of FIG. The ring light guide 23 was originally developed for illumination, but the fibers are arranged in a ring shape and the mounting angle 49 can be easily reduced. And copper foil on the substrate surface can be distinguished.

  In addition to the direct hole and the conformal hole, the blind hole includes a special blind hole processed with a beam diameter smaller than the diameter etched on the copper foil on the substrate surface. In some cases, these holes are mixed in one printed board. FIG. 7 is a diagram for explaining a procedure for detecting a blind hole from a fluorescent signal and a reflected light signal for such a substrate. At the bottom of the hole, the level of the fluorescence signal and the reflected light signal is low in any type of blind hole. On the substrate surface, the level of the fluorescence signal is high in the case of resin, and the level of the reflected light signal is high in the case of copper foil. Therefore, the level of the signal obtained by combining (summing) the two detection signals is lower at the bottom of the hole than at the substrate surface in any type of hole. Therefore, if the synthesized signal is binarized with a certain threshold value, the hole bottom can be detected.

  As a result, even for printed boards with mixed direct holes and conformal holes, even if the laser irradiation position and the blind hole position greatly deviate for some reason, it can be determined that it is not the bottom of the hole, so it is possible to avoid misjudging it as a non-defective product. it can. Also, the hole center position can be detected by laser scanning over the blind hole, binarizing the combined signal, and calculating the center of gravity position of the lower level.

  Further, in the present embodiment, if the scanning described with reference to FIGS. 3 and 4 is performed, the center of the blind hole is detected and the laser is accurately detected with respect to the blind hole even on a printed circuit board in which direct holes and conformal holes are mixed. Inspection with light irradiation becomes possible. In detecting the hole center position in FIG. 4, a synthesized signal may be used instead of the fluorescence signal.

  8 and 9 are diagrams for explaining another hole center position detecting method in the present embodiment. FIG. 8 is a diagram for explaining a hole center position detection procedure by discretization / sort processing, and FIG. 9 is a diagram showing an example of a discretization circuit. In FIG. 9, 50 is a clock generator and 51 is a latch circuit.

  When the laser beam is irradiated on the substrate surface, strong fluorescence or reflected light is detected, but at the same time, a large noise component is also detected due to the output fluctuation of the laser oscillator and the influence of inclusions contained in the resin. Compared to this, since the fluorescence and reflected light are hardly detected from the copper foil at the bottom of the hole, the noise component is also small. Therefore, the hole center position can be reliably detected by using the hole bottom detection signal. Specifically, as shown in FIG. 8, first, the combined signal and the scanning position signal detected while scanning the laser beam at a constant speed are discretized by latching with the same clock. Next, the discretized data is rearranged in order from the lowest level of the synthesized signal. Then, the number of scanning position data corresponding to the hole bottom diameter from the top is averaged to detect the hole center position. In our experiments, it was confirmed that the blind hole center position can be detected more reliably than the binarization method when the detection signal is noisy. Of course, when inspecting a substrate having only a direct hole, a fluorescent signal may be used as a hole position detection signal instead of the synthesized signal.

Embodiment 4 FIG.
FIG. 10 is a block diagram showing the fourth embodiment. In the third embodiment, the scanning position signal detected by the position detector 28 of the galvano mirror is directly input to the central control room 31 and can be applied to the first and second embodiments. Needless to say. The galvanometer 26 that drives the galvanometer mirror has a servo system for controlling the scanning position. In general, in a position servo system, a tracking delay proportional to the scanning speed occurs. Therefore, particularly when the scanning speed is high, the scanning command position and the actual scanning position are shifted, and the hole position detection accuracy deteriorates. In the present embodiment, since the actual scanning position is detected by the position detector 28, it is possible to detect the hole position with high accuracy without deviation even if the scanning is performed at high speed, and it is possible to perform the residual resin inspection at high speed and with high reliability. .

1 is a configuration diagram showing a structure of a first embodiment. It is a figure which shows the comparison of fluorescence intensity. It is a figure explaining the inspection procedure of a residual resin. It is a figure explaining the method to detect a hole position from a fluorescence signal. 6 is a configuration diagram showing a structure of a second embodiment. FIG. FIG. 6 is a configuration diagram showing a structure of a third embodiment. It is a figure explaining the method to detect a hole position from a fluorescence signal and a reflected light signal. The figure explaining the detection procedure of the hole position by discretization and sort processing It is a figure explaining a discretization circuit. FIG. 10 is a configuration diagram showing a structure of a fourth embodiment. Schematic diagram showing laser processing of printed circuit board Schematic diagram showing laser processing of printed circuit board It is a schematic diagram which shows distribution of residual resin. It is a schematic diagram which shows the conventional inspection apparatus. It is a schematic diagram which shows the conventional inspection apparatus. It is the schematic which shows the irradiation condition to the resin part of white light. It is a schematic diagram which shows the conventional inspection apparatus.

Explanation of symbols

1 light source, 2 detector for fluorescence, 3 detector for reflected light,
4 dichroic mirror, 5 objective lens, 6 hole processing part,
7 excitation light, 8 reflected light, 9 imaging lens, 10 filter,
11 CCD camera, 12 image processing device, 13 laser oscillator,
14 transfer mask, 15 positioning mirror, 16 transfer lens,
17 processing table, 18 epoxy resin, 19 glass epoxy,
20 laser beam, 21 printed circuit board, 22 residual resin,
23 Ring light guide, 24 Copper foil, 25 Beam splitter,
26 Galvanometer, 27 Inverted real image, 28 Galvano position detector,
29 resin surface reflected light, 30 copper foil surface reflected light, 31 central processing chamber,
32 Reflected light from the bottom of the blind hole, 33 First galvanometer mirror,
34 second galvanometer mirror, 35 optical fiber bundle,
36 Copper foil removal part, 37 processing hole, 38 white light,
39 first scan line, 40 second scan line,
41 Scattered light from the copper foil on the substrate surface,
42 scattered light from the copper foil at the bottom of the blind hole, 43 ultraviolet laser light source,
44 mirrors, 45 collimating lenses, 46 rotating polygon mirrors,
47 Photomaru, 48 Pinhole,
49 Reflected light detector mounting angle, 50 clock generator,
51 Latch circuit.

Claims (3)

A light source that outputs laser light;
Irradiation means for irradiating a laser beam output from this light source to a desired position on the substrate on which the concave portion is formed by scanning in the XY directions;
Detecting means for detecting fluorescence generated from the substrate irradiated with the laser light and outputting a detection signal;
A temporary center point is calculated based on the detection signal when the irradiation means is scanned linearly at a predetermined interval with respect to the substrate, starting from the registered inspection position on the substrate, and the temporary center Control means for inspecting the inspection object based on the detection signal when the irradiation means is scanned in a direction perpendicular to the scanning direction through a point ;
The control means discretizes the detection signal, rearranges the discretized data in the order of the level of the detection signal, and compares the data with the diameter of the concave portion stored in advance, thereby obtaining a temporary center of the concave portion. A laser inspection apparatus characterized by calculating a position . The laser inspection apparatus according to claim 1, wherein the irradiation unit performs scanning in the same direction a plurality of times. The laser inspection apparatus according to any one of claims 1 to 2 comprising a position detection means for detecting an actual scanning position during laser scanning.

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