JP3488614B2 - Laminate material recess inspection device and laser processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recessed portion which is formed by irradiating a laminated material such as a laminated wiring board, which is a so-called printed board, with a laser beam to form blind via holes, grooves and the like. It is possible to know the state of the residual material that remains without being removed at the bottom of the concave part without performing a destructive inspection, and to check the thickness of the residual material. The present invention relates to a laminated material recessed portion inspection device that can perform detection and the like, and a laser processing apparatus including such a recessed portion inspection device.

[0002]

2. Description of the Related Art With the recent high performance of electronic equipment, there has been a demand for higher density wiring, and in order to meet this requirement, a multilayer printed circuit board and a small size are required. For that purpose, it is essential to form a fine blind hole for the interlayer conductive connection having a hole diameter of about 150 μm, which is called a blind via hole (hereinafter referred to as BVH). However, it is difficult to drill holes with a diameter of 0.2 mm or less in the current drilling process, and the insulating layer thickness is 100 μm for high-density printed circuit boards.
Since it is difficult to perform the depth control with this accuracy, it is impossible to form the fine BVH by drilling.

As a BVH forming method replacing the drilling, a method of applying a laser beam such as a carbon dioxide gas laser, a YAG laser or an excimer laser has attracted attention and has been partially put into practical use. Among these processing methods, the carbon dioxide laser processing method uses the difference in the absorption rate of the light energy of the carbon dioxide laser with respect to the resin or glass fiber which is the insulating base material constituting the printed circuit board and the copper which is the conductor layer. is there.

10 to 14 show a conventional BVH processing method for a printed circuit board. FIG. 10 is an explanatory view for explaining a process of processing a fine through hole portion, and FIG. 11 is a recess for forming a BVH. It is explanatory drawing explaining the processing method which processes a part. FIG. 12 is a block diagram of a laser processing apparatus equipped with an optical microscope, FIG. 13 is a block diagram of an optical microscope, and FIG. 14 is an explanatory diagram for explaining a reflection state of irradiated light.

For example, since copper almost reflects a carbon dioxide laser, the printed circuit board 2 as shown in FIG.
By forming a copper foil removing portion 36 by etching or the like so as to form a hole having a required diameter in the copper foil 24 on the surface of No. 1, and irradiating the copper foil removing portion 36 with a laser beam 20 which is a carbon dioxide gas laser, By selectively decomposing and removing the epoxy resin and the glass fiber forming the printed circuit board 21, as shown in FIG.
It is possible to form a fine processed hole portion 37 penetrating the printed board 21 as shown in 0 (b).

Further, as shown in FIG. 11, the printed circuit board 2
If a copper foil 24 as an inner layer is preliminarily laminated inside 1, the disassembly of the printed circuit board 21 when the laser beam 20 is irradiated
Since the removal stops at the inner copper foil 24, the inner copper foil 24
When it is surely stopped with, the blind hole processing portion 6 (hereinafter simply referred to as the hole processing portion 6) can be formed. However, when the hole processing portion 6 is processed by the carbon dioxide laser when the inner copper foil 24 is stopped in this way, the thickness is 1 μm even if the laser beam is sufficiently irradiated.
Copper foil 2 with inner layer of resin or glass fiber
4 above, that is, it remains on the bottom portion 6a of the hole processing portion 6.

Therefore, after laser processing, it is necessary to completely remove the residual resin by etching the residual resin with permanganate or the like. At this time, the hole diameter of the hole processing part 6 is 100μ.
When it is reduced to about m, it becomes difficult for the etching solution to reach the inside of the hole processing portion 6. For this reason, if the residual resin becomes thick due to defects such as laser processing conditions, the hole-processed portion 6 is likely to occur unless the residual resin can be completely removed by etching. When plating is performed in this state to form BVH, a part of the resin remains between the plating film and the inner layer copper foil 24.

[0008] Here, when stress is applied due to a heat cycle or the like, cracks are generated and propagate, and the plating film is peeled off. When the plating film is peeled off, the copper foil 24 of the inner layer is not electrically connected to the plating film, resulting in a defective product. Further, if the resin remains over the entire surface between the plated film and the copper foil 24 of the inner layer, the resin is not conductive from the beginning and becomes defective. For this reason, it is necessary to inspect the thickness of the residual resin after laser processing and, if the thickness is large, further perform laser processing to remove the residual resin.

Further, there is a processing method using a YAG laser or an excimer laser, and this processing method utilizes the fact that the removal depth per pulse is on the order of 1 μm. In these processing methods, since the removal amount of one pulse is small, the number of pulses required for processing increases, and the influence of disturbance such as energy fluctuation during processing is averaged. By utilizing this fact, the number of pulses is appropriately selected to uniformly form the drilled portion that stops near the inner copper foil 24.

However, when energy fluctuations occur over a long period even in the processing method using a YAG laser or an excimer laser, a resin having a thickness of 1 μm or less remains on the inner copper foil 24 as in the carbon dioxide laser. It may happen.

For this reason, the conventional laser processing apparatus for laminated materials is equipped with an optical microscope as shown in FIG. 12 to inspect the hole processing portion 6. However, Nikkei Science 199
In the conventional optical microscope as shown on page 45 of the October 0 issue, the bottom portion 6a of the hole machining portion 6 shown in FIG.
A processing defect in which the residual resin 22 of about μm or more remains can be detected, but it is impossible to detect the residual resin 22 of about several μm as described above. The printed circuit board 21
Has an epoxy resin 18 and a glass epoxy 19, and a copper foil 24 is provided therebetween.

For this reason, at present, after plating, the hole processing portion 6 is cut and polished by a destructive inspection, and then the residual resin thickness is inspected by observing a cross section, or instead of the destructive inspection, the hole processing portion 6 for inspection is used. Similarly, after separately cutting and polishing the hole processed portion, the residual resin thickness is inspected by observing the cross section. Therefore, the time required for the inspection was extremely long. Even with this other method, the residual resin could not be easily detected without destructing the substrate.

The reason why the residual resin cannot be detected by the conventional optical microscope will be described below. A conventional optical microscope is configured as shown in FIG. The white light 38 for illumination of the optical microscope emitted from the light source 1 is applied to the printed board 21 by the beam splitter 25 via the objective lens 5. The reflected light from the printed circuit board 21 forms an inverted real image 27 magnified by the objective lens 5 in front of the imaging lens 9 (see FIG. 1).
3) (to the right of 3) and make this real image CCD (solid-state image sensor)
It is detected by the camera 11.

Returning to FIG. 12, this image is processed by the image processing apparatus 1.
The analysis is performed according to 2, and the presence or absence of residual resin is determined. This determination result is transmitted to the control device 13 that controls the laser oscillator 13 and the processing table 17, and when the residual resin 22 is more than the predetermined thickness, the processing table 17 is moved to position the laser beam 20, Transfer mask 1
4, through the positioning mirror 15 and the transfer lens 16, the printed circuit board 21 is again irradiated with laser to the hole processing portion 6 to further remove the residual resin 22.

Here, as shown in FIG. 14, when the white light 38, which is the illumination light of the optical microscope, is applied to the surface of the residual resin 22, a part of it is reflected as reflected light 29 from the surface,
Others reach the bottom copper foil 24 after passing through the residual resin 22 and are almost reflected as reflected light 30. Therefore, the white light 3 is generated against the residual resin 22 having a small thickness on the copper foil 24.
When 8 is illuminated as illumination light, most of the reflected light is copper foil 2
Since it is the reflected light 30 returning from 4, the residual resin 2
I can't see 2.

[0016]

Since the optical microscope, which is the conventional apparatus for inspecting the recessed portion of the laminated material, is constructed as described above, there is a problem that it cannot be detected when the residual resin is thin. The present invention has been made in order to solve the above problems, and it is possible to easily detect the thickness of the material remaining without being removed at the bottom of the recessed portion of the laminated material in a nondestructive manner. An object of the present invention is to obtain a recessed portion inspection device that can be used, and a laser processing apparatus including such a recessed portion inspection device.

[0017]

In order to achieve the above object , the apparatus for inspecting a recess of a laminated material according to the present invention comprises:
A recessed portion formed on the second material by irradiating a laser beam on a laminated material formed by layering the first material and the second material with a laser beam irradiation device for processing to remove the first material Irradiation of the first illumination light whose absorption coefficient for the residual material, which is the first material remaining without being removed at the bottom of the, of the first material, and the second illumination light whose absorption coefficient for the residual material, is smaller than the predetermined value. Illuminating light irradiating device for determining the position of the surface of the residual material based on the first illuminating light reflected from the surface of the residual material, and passing through the residual material and reflecting from the surface of the second material. It is provided with a photodetector for determining the position of the surface of the second material based on the second illumination light and detecting the thickness of the residual material based on the positions of both surfaces.
The absorption coefficients of the first illuminating light and the second illuminating light with respect to the residual material are made different, and the wavelength of the first illuminating light is reflected on the surface of the residual material and is reflected on the surface of the second material. The position of the surface of the residual material can be detected by making it larger than the one, and the wavelength of another illumination light is reflected by the surface of the second material is reflected by the surface of the second material. It is possible to detect the position of the surface of the second material by making the thickness larger than that, and it is possible to detect the thickness of the residual material from the difference between the positions of the two surfaces.

Further, the first illumination light is ultraviolet light, and the second illumination light is white light. The residual material is generally an organic material, but since ultraviolet light has a large attenuation coefficient with respect to the organic material and white light has a small attenuation coefficient with respect to the organic material, it can be used as the first and second illumination lights.

The laser processing apparatus according to the present invention comprises one of the above-mentioned recessed portion inspection apparatuses for laminated materials. If such a recessed part inspection device for laminated material is provided, the state of the residual material can be immediately known without performing a destructive inspection after processing the recessed part, and a process for removing the residual material again if necessary. It can be performed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 shows a configuration of a laser processing apparatus including a concave portion inspection apparatus (hereinafter, sometimes simply referred to as an inspection apparatus). Figure,
FIG. 2 is an explanatory diagram for explaining the reflected light intensity when there is residual resin in the concave portion and when there is no residual resin.

In FIG. 1, a printed circuit board 21 which is a laminated material has an epoxy resin 18 and a glass epoxy 19 formed in layers. The laser processing apparatus uses a carbon dioxide gas laser as the laser oscillator 13. The processing laser beam 20 emitted from the laser oscillator 13 is applied to the printed board 21 through the transfer mask 14, the positioning mirror 15, and the transfer lens 16, and the epoxy resin 18 is removed to form a hole with a predetermined diameter. To form the hole processing portion 6. At this time, even though the laser beam 20 is applied as described above, the residual resin 2 is not removed by the bottom portion 6a of the hole processing portion 6
2 may remain.

In this embodiment, a mercury lamp is used as the light source 1 for generating the ultraviolet light that excites the residual resin as the illumination light. The excitation filter 3 mainly transmits the excitation light 7, which is the ultraviolet light in the vicinity of the wavelength that excites the residual resin 22, and has a transmission characteristic in the vicinity of 330 to 380 nm. 38 for dichroic mirror 4
A material having a property of reflecting light of 0 nm or less and transmitting light of 400 nm or more is used. In addition, the absorption filter 10 has 41
A filter that absorbs wavelengths below 0 nm was used.

The light emitted from the light source 1 passes through the excitation filter 3, the dichroic mirror 4 and the objective lens 5 and is applied to the bottom portion 6a of the processed hole processing portion 6. Since the excitation light 7 that has passed through the excitation filter 3 has a wavelength range in which the residual resin 22 on the bottom portion 6a of the hole processing portion 6 is excited to generate fluorescence, the luminescence 8 is generated when the residual resin 22 is present. Occur. The luminescence 8 forms an image on the CCD camera 11 by the objective lens 5 and the imaging lens 9 through the absorption filter 10 which transmits mainly wavelengths near the fluorescence wavelength. This image is analyzed by the image processing device 12 to determine the presence or absence of the residual resin 22.

The result of this determination is transmitted to the control device 23 which controls the laser oscillator 13 and the processing table 17, and when the residual resin 22 is thicker than a predetermined thickness, the processing table 17 is moved to move the laser beam. 20 is positioned, and the hole processing portion 6 is again irradiated with laser to further remove the residual resin 22.

In the present embodiment, as described above, a carbon dioxide laser is used as the laser oscillator 13, a mercury lamp is used as the light source 1 for generating the excitation light 7, and the copper foil of the bottom portion 6a of the hole processing portion 6 is used as the sample. Hole processing part 6 in which residual resin 22 of epoxy resin having a thickness of 1 μm or less remains partially on 24
Then, the printed circuit board 21 in which the epoxy resin was completely removed and the hole processing portion 6 in which the residual resin did not remain on the copper foil 24 was mixed was observed by the CCD camera 11.

As a result of observing the above sample, epoxy resin 2
The hole-processed portion 6 in which 2 remains is bright, and the hole-processed portion 6 in which the copper foil 24 is exposed has a dark image, and the residual resin 22 can be easily distinguished by visually observing the brightness of the image. . The observation may be performed by directly observing fluorescence from the residual material without using the CCD camera 11.

Further, the average X of the reflected light intensities x in a rectangular area 34, which is predetermined by the image processing device 12 in the circular image 33 of the hole-processed portion, is set in advance as shown in FIG. When the light intensity is higher than the reflected light intensity 35, a holed portion where the residual resin remains in excess of a predetermined thickness, and when the average Y of the reflected light intensity y is darker than the reflected light intensity 35, a holed portion where the epoxy remains less than the predetermined thickness. As a result of discriminating the hole-machined portion, it was possible to easily discriminate the hole-machined portion in which the epoxy remained more than the predetermined thickness. This determination was performed by the image processing device 12. It should be noted that it is possible to make a visual judgment without depending on the machine.

As Comparative Example 1, the printed board 21 of this sample was plated, the cross section was polished, and the presence or absence of residual resin between the plated layer and the copper foil was observed by an electron microscope. When this observation result is compared with the result determined by the image processing device 12 described in the present embodiment based on the lightness and darkness of the hole processing portion,
Both results corresponded well, and the validity of this inspection device was verified.

In addition, as a comparative example 2, in order to compare with the conventional method, the excitation light and the dichroic mirror as the visible light which does not excite the residual resin 22 of the epoxy resin in the first embodiment. When the same test was performed except for 4, no shade was generated between the drilled parts, and the magnitude of the residual resin amount or the presence or absence of residual resin could not be detected.

As described above, according to the present invention, it is possible to detect the residual resin 24 on the copper foil 24 easily and nondestructively. The residual resin 22 is not limited to the epoxy resin,
It may be a polyimide resin or other resin, and similarly emits fluorescence when irradiated with excitation light having an appropriate wavelength depending on the type of resin, so that it can be easily discriminated.

Further, the CCD camera 11 is intended for visible light, and for the purpose of protecting the eyes when visually recognizing whether the hole processing portion 6 is bright or dark, the absorption filter 10 which mainly passes only the fluorescence wavelength is used. Although the absorption filter 10 is used, the absorption filter 10 is not indispensable. For example, when a photodiode or the like is used, luminescence including ultraviolet rays can be detected, and therefore it is unnecessary.

Embodiment 2. FIG. 3 is a configuration diagram of an inspection apparatus and a laser processing apparatus showing another embodiment of the present invention. In FIG. 3, the second harmonic of a YAG laser having a wavelength of 473 nm is used as the laser oscillator 13. The laser oscillator 13 generates a laser beam 20 (see FIG. 1) for processing the hole processing part 6 and also generates excitation light 7 for exciting the residual resin 22 of the epoxy resin remaining on the bottom 6a of the hole processing part 6. . Specifically, the pumping light 7 is generated by narrowing the output of the laser oscillator 13.
Used as the light source 1 of FIG.

When forming the hole processing portion 6, the laser beam output from the laser oscillator 13 is passed through the objective lens 5 by the dichroic mirror 4 and the printed circuit board 2.
1 is irradiated to form a hole processing part 6. After that, the bottom portion 6a of the processed hole processing portion 6 is irradiated with the diaphragm excitation light 7 with an output of about 10%. When the excitation laser light is in a wavelength range in which the residual resin 22 in the hole processing portion 6 is excited to generate fluorescence, luminescence 8 is generated when the residual resin 22 is present. In addition, dichroic mirror 4
Has a property of reflecting 490 nm or less and transmitting 505 nm or more, and the absorption filter 10 uses a filter that absorbs a wavelength of 520 nm or less.

This luminescence 8 forms an image on the CCD camera 11 via the absorption filter 10 that transmits only wavelengths near the fluorescence wavelength by the objective lens 5 and the imaging lens 9. The brightness of this image is analyzed by the image processing device 12, and the presence or absence of the residual resin 22 and the degree of residual resin 22 are determined. This determination result is transmitted to the control device 23 which controls the laser oscillator 13 and the processing table 17, and when the residual resin 22 is more than the predetermined thickness, the laser intensity is increased and the hole processing portion 6 is irradiated with the laser again. Then, the residual resin 22 is further removed.

In the present embodiment, the second harmonic of the YAG laser having a wavelength of 473 nm is used as the laser oscillator 13 as described above. As a sample, a hole-processed portion 6 in which the epoxy resin having a thickness of 1 μm or less partially remained on the copper foil 24 and a hole-processed portion 6 in which the epoxy resin was completely removed and no epoxy resin remained were mixed. Using the printed circuit board 21,
The bottom portion 6a of the hole processing portion 6 was observed. As a result of observing the sample under test, a hole imaged portion 6 where the epoxy resin remains on the bottom portion 6a is bright, and a hole imaged portion 6 where the copper foil is exposed has a dark image, and the residual resin 22 is clearly shown. Could be detected.

If the average of the reflected light intensities in the predetermined area is brighter than the preset reflected light intensity as in the case of the image of the hole-processed portion shown in FIG. 2, the epoxy is more than the predetermined thickness. Remaining hole-processed part, and if it is dark, it is determined that the remaining hole of epoxy is less than the specified thickness.
As a result of determining the presence or absence and the degree of residual resin in the hole processing portion 6, it was possible to easily determine the hole processing portion in which the epoxy remained in excess of the predetermined thickness.

After plating the printed board of this sample, the cross section was polished and observed with an electron microscope to observe the state of residual resin between the plating layer and the copper foil. When this result was compared with the determination result by the inspection device described in the present embodiment, both results correspond well, and the validity of the determination by the inspection device was verified.

Embodiment 3. 4 to 7 show another embodiment of the present invention. FIG. 4 is a configuration diagram of an inspection device and a laser processing device, and FIG. 5 is an explanatory diagram for explaining a reflection state. FIG. 7 is a characteristic diagram showing the relationship between the residual film pressure of the residual material and the reflected light intensity,
FIG. 8 is an explanatory diagram for explaining the reflected light intensity when there is residual resin in the recessed portion and when there is no residual resin.

In these figures, the ultraviolet light 2 for illumination is sent from the light source 1, and is irradiated onto the printed board 21 from the beam splitter 25 via the objective lens 5. The reflected light 32 from the bottom of the hole-processed portion of the printed board 21 (not shown in FIG. 4) is a bandpass that transmits only the wavelength in the vicinity of the ultraviolet light 2 for illumination by the objective lens 5 and the imaging lens 9. An image 27 is formed on the image intensifier 26 mounted on the CCD camera 11 via the filter 31.

The image 27 is analyzed by the image processing device 12, the analysis result is displayed on the CRT 28, and the analysis result is sent to the control device 23. Here, the image intensifier 26 is a device that can increase the incident light intensity by tens of thousands of times. By adjusting the voltage applied to the image intensifier 26, the gain can be adjusted and the intensity of the incident light can be increased. It can be changed.

By the way, as shown in FIG. 5, when the surface of the residual resin 22 remaining at the bottom of the hole-formed portion of the printed board 21 is irradiated with the ultraviolet light 2 for illumination, a part of the resin surface is reflected from the surface. Objective lens 5 reflected as light 29 (FIG. 4)
And the others pass through the residual resin 22 while being absorbed by the residual resin 22 and reach the copper foil 24 at the bottom of the holed portion.

The ultraviolet light 2 that reaches the copper foil 24 is partially absorbed and the rest is reflected as reflected light 30 on the surface of the copper foil 24, and again passes through the residual resin 22 while being absorbed and passes through the residual resin 2.
It goes out of 2 and reaches the objective lens 5. Copper foil surface reflected light 30
Is significantly larger than the resin surface reflected light 29, it becomes difficult to detect the resin surface reflected light 29,
The resin surface cannot be detected. That is, the residual resin 22 cannot be detected, but only the copper foil 24 can be detected.

Therefore, in order to detect the residual resin 22, it is necessary to use light in which the residual resin reflected light 29 on the surface of the residual resin 22 is larger than the copper foil reflected light 30 on the surface of the copper foil 24. is there. Therefore, in this embodiment, the copper foil 2
Ultraviolet light having a low reflectance for 4 (reflectance: about 30%) was used as illumination light. The visible light has a reflectance of about 70 to 95% with respect to the copper foil 24, which is 30% of the ultraviolet light.
Much higher than.

Now, the absorption coefficient for the residual resin is α / cm.
It is assumed that the ultraviolet light 2 having the intensity K is incident on the residual resin 22. The absorption coefficient of the residual resin 22 for the ultraviolet light 2 is α / c
Therefore, the intensity J (z) of the ultraviolet light at the point of the depth z from the surface of the residual resin 22 is represented by J (z) = K · exp (−α · z) (1).

Assuming that the reflectance of the surface of the residual resin 22 with respect to the ultraviolet light 2 is about 10%, the intensity A of the resin surface reflected light 29 is as follows. A = 0.1K (2) Further, the intensity B of the incident light entering the residual resin 22 is B = 0.9K (3). Therefore, the intensity C of the ultraviolet light 2 that has passed through the residual resin 22 having a thickness d (cm) while being attenuated and has reached the surface of the copper foil 24 is C = 0.9K · exp (−α · d) (4 ).

The intensity D of the copper foil surface reflected light 30 on the surface of the copper foil 24 has a reflectance of 30% on the surface of the copper foil 24.
Since it is a degree, it becomes as follows. D = 0.9K ・ {e
xp (−α · d)} · 0.3 (5) This reflected light further passes through the residual resin 22 while being attenuated, and is reflected from the surface of the residual resin 22 by the copper foil surface reflected light 30.
It goes out. The intensity E of the reflected light 30 on the surface of the copper foil is more e than the value of the above formula (5) in the residual resin 22 having the thickness d.
It is attenuated by xp (−α · d) and becomes E = 0.9K · {exp (−2α · d)} · 0.3 (6).

Since the reflected light intensity R from the bottom of the hole-processed portion is the sum of the copper foil surface-reflected light 30 to the copper foil surface-reflected light 30 and the resin surface-reflected light 29, R = A + E (7). FIG. 6 shows the relationship between the residual film thickness t of the residual resin and the reflected light intensity R for some absorption coefficients α. The larger the slope of this curve, the greater the change in the brightness of the bottom of the hole-processed portion as the residual film thickness changes.

If the residual film thickness is about 0.2 μm, it can be removed by a chemical treatment, so that no defect occurs. If it exceeds about 0.6 μm, it cannot be removed by chemical treatment, and it often becomes defective. In order to mechanically detect the change in the reflected light intensity due to the difference in the film thickness, for example, in the CCD camera 11 and the image processing device 12, it is necessary to change the reflected light intensity R by about 20% or more. That is, the residual film thickness 0.2 μm
The difference between the reflected light intensity at the time of and the reflected light intensity at the residual film thickness of 0.6 μm is 0.2 (20%).
More necessary is an absorption coefficient α ≧ 5000 / cm. According to FIG. 6, when the absorption coefficient α = 5000 / cm, the reflected light intensity at a residual film thickness of 0.2 μm is about 0.32,
When the residual film thickness is 0.6 μm, the reflected light intensity is about 0.25, which is 0.25 / 0.32 = 0.78, which is a change of more than 20%.

Based on the above examination, in the present embodiment,
A nitrogen laser that emits ultraviolet light 2 having a wavelength of 337 nm is used as a light source 1 that emits illumination light, and a polyimide resin having a thickness of about 1 μm and about 0.4 μm remains on a copper foil 24 as a printed circuit board 21 of a sample. A printed circuit board with a hole-processed portion was used. Note that the wavelength 337 used in this embodiment is
Absorption coefficient of ultraviolet light of nm for polyimide resin is about 8
000 / cm. As the bandpass filter 31, a filter having a bandpass width of 10 nm near 337 nm was used.

As a result of inspecting the printed circuit board 21 using the inspection apparatus of the present embodiment, by adjusting the gain of the image intensifier 26, the holed portion where the polyimide remains about 1 μm is dark and A bright image was obtained in the hole-processed portion where 0.4 μm remained.

If the average U of the intensities of the reflected light u in the predetermined area 34 is brighter than the predetermined intensity level 35 of the predetermined reflected light, as shown in FIG. It is determined that the polyimide is a hole-processed portion in which about 0.4 μm remains, and when the average V of the intensities of the reflected light v is darker than the reflected light intensity level 35, it is determined that the polyimide is a hole-processed portion in which about 1 μm remains. , As a result of distinguishing the hole processing part,
It was possible to easily discriminate the hole-processed portion where the polyimide remained by 1 μm. This determination is performed by the image processing device 12 that analyzes the image of the intensifier 26.

After the printed circuit board was plated, the cross section was polished and observed with an electron microscope. As a result, a residual resin portion was observed between the plated layer and the copper foil. When this observation result and the result of the inspection device described in the present embodiment are compared, both results are 100% compatible, and the validity of the detection by the present inspection device was verified.

In addition, as Comparative Example 1, in order to compare with the conventional method, the light source 1 of FIG. 4 was used as visible light, and a similar test was performed except for the bandpass filter 31. Even if the gain was adjusted, the brightness of the bottom of the hole-processed portion did not change because the residual resin 22 was thick and thin, and the magnitude of the residual resin thickness could not be detected.

Further, as Comparative Example 2, in this embodiment, a nitrogen laser is not used, but a He-Cd laser which emits light having a wavelength of 442 nm having an absorption coefficient of about 4000 / cm for polyimide is used and a bandpass filter is used. When the same test was carried out by exchanging for this wavelength as well, it was possible to discriminate, but the agreement rate with the result of cross-section observation was 80.
It had fallen to%. That is, the absorption coefficient is about 4000
/ Cm, the accuracy of discrimination becomes low.

In the case of a resin other than polyimide, it is sufficient to select a light having a wavelength having an absorption coefficient of 5000 / cm or more depending on the resin. As described above, according to the present invention, it is possible to detect the residual thickness of the residual resin 22 on the copper foil 24 easily and nondestructively.

Fourth Embodiment 8 and 9 show another embodiment of the present invention. FIG. 8 is an explanatory diagram for explaining the operation of the inspection device and the laser processing device, and FIG. 9 shows a case where the focal position is deviated. It is explanatory drawing explaining the path | route of light. In FIG. 8, the light source 1
Is ultraviolet light 2 (FIG. 8A) and white light 3 as light for illumination.
8 (FIG. 8 (b)). First, in the case of the ultraviolet light 2, as shown in FIG. 8A, the ultraviolet light 2 emitted from the pinhole plate 39a placed in front of the light source 1 is passed through the objective lens 5 by the beam splitter 25 and the residual resin The surface of 22 is irradiated. At this time,
When the printed circuit board 21 is installed so as to be focused on the residual resin 22, the reflected light 32 from the surface of the residual resin 22
The objective lens 5 is focused on the position of the pinhole plate 39b installed in front of the photodetector 40 by the objective lens 5, passes through the pinhole plate 39b, and is detected by the photoelectric detector 40.

In the optical system using the ultraviolet light 2, the point light source generated by the pinhole plate 39a on the light source 1 side and the photoelectric detector 4 are used.
The 0-side pinhole plate 39b has a conjugate positional relationship with the objective lens 5. Such an optical system is called a confocal optical system. In the case of the confocal optical system, when the focus is deviated on the residual resin 22 which is the sample as shown in FIG. 9, the reflected light 32a is largely blurred in front of the pinhole plate 39b on the photoelectric detector 40 side, and the pinhole. It cannot pass through the plate 39b.

As described above, the photoelectric detector 40 has the residual resin 2
Since the reflected light 32a can be detected only when the light beam 2 is in focus, the focus position can be accurately detected. The focus position is adjusted by the processing table 17 on which the printed circuit board 21 is placed.
(See FIG. 1) is moved in the left-right direction in FIG.

Here, the reflected light 32a of the ultraviolet light 2 is as shown in FIG.
As shown in, the light reflected from the resin surface 29 and the light reflected from the copper foil surface 30
There are two types. In order to detect at least the resin surface with ultraviolet light, since the intensity A of the resin surface reflected light 29 is only 10% of the incident intensity, the intensity E of the copper foil surface reflected light 30 is equal to or less than the intensity A of the resin surface reflected light 29. And have to.
Therefore, in order to satisfy A ≧ E in the expressions (2) and (6) described in the third embodiment, the absorption coefficient α ≧ 5000 / cm is a necessary condition with the residual resin thickness d of 1 μm. Becomes

Next, in order to find the position of the copper foil 24, the illumination light is switched to the white light 38 to detect the focus position. At this time, the white light 38 has a remarkably smaller absorption coefficient with respect to the residual resin 22 than the ultraviolet light 2 and has a high reflectance with respect to the copper foil 24. Therefore, the intensity of the copper foil surface reflected light 30 of the copper foil 24 is high.
Therefore, the position of the copper foil 24 can be accurately detected by detecting the focal position of the surface of the copper foil 24 according to the principle of FIG. The focus position is adjusted by the processing table 17 on which the printed circuit board 21 is placed as in the case of the ultraviolet light 2.
(See FIG. 1) is moved in the left-right direction in FIG.

As a result, the difference d between the focal positions of the ultraviolet light 2 and the white light 38 (FIG. 8B) becomes the residual film thickness, and the residual film thickness can be measured nondestructively and easily. Then, when the residual film thickness is a predetermined value, for example, 0.15 μm or more, the hole processing portion 6 is irradiated again with the processing laser beam to remove the residual resin.

Based on the above examination, in this embodiment, a nitrogen laser having a wavelength of 337 nm is used as the ultraviolet light 2, and a white light 38 is emitted.
As the printed circuit board 21, a printed circuit board having a hole-processed portion 6 in which a polyimide resin having a thickness of about 1 μm remained as a residual resin 22 was used as the printed circuit board 21. Note that the wavelength 337 used in this embodiment is
The absorption coefficient of light of nm for polyimide resin is about 800.
It is 0 / cm.

As a result of measuring the residual film thickness of the residual resin 22 on the printed circuit board 21 using the inspection apparatus described in the present embodiment, it was confirmed that the residual polyimide thickness d was about 1 μm. It should be noted that although the ultraviolet light 2 and the white light 38 are used in the above-described embodiment, the invention is not limited to this, and instead of the white light 38, for example, ultraviolet light having an absorption coefficient smaller than that of the ultraviolet light 2 is used. You can also

In each of the above embodiments, the case of the copper foil 24 has been described, but the same effect can be obtained as long as the reflectance of the aluminum foil or the like with respect to the laser beam is a predetermined value or more. The wavelengths of the ultraviolet light 2 and the excitation light 7 are
It may be appropriately selected according to the material of the residual resin.

[0065]

Since the present invention is configured as described above, it has the following effects. That is, the first
The bottom of the recessed portion formed on the second material by irradiating the laminated material formed by layering the material and the second material with the laser beam by the processing laser beam irradiation device to remove the first material To the residual material that is the first material that remains without being removed by the first illumination light whose absorption coefficient for the residual material is a predetermined value or more and the second illumination light whose absorption coefficient for the residual material is smaller than the predetermined value. The position of the surface of the residual material is determined based on the illumination light irradiation device for irradiating and the first illumination light reflected from the surface of the residual material, and the position of the surface of the residual material is passed through the residual material and reflected from the surface of the second material. The second illumination light is used to determine the position of the surface of the second material and to detect the thickness of the residual material based on the positions of both surfaces. The absorption coefficient for the residual material with the second illumination light Normalize and detect the position of the surface of the residual material by making the wavelength of the first illumination light larger on the surface of the residual material than on the surface of the second material. Of the surface of the second material by allowing the wavelength of another illumination light to be greater on the surface of the second material than on the surface of the second material. The position can be detected, the thickness of the residual material can be known from the difference between the positions of the two surfaces, and appropriate measures can be taken if necessary.

Furthermore, since the first illumination light is ultraviolet light and the second illumination light is white light, the residual material is generally an organic material, but the ultraviolet light is an organic material. Has a large attenuation coefficient with respect to, and white light has a small attenuation coefficient with respect to an organic material, and thus can be used as the first and second illumination lights.

Further, since the laser processing apparatus according to the present invention is equipped with one of the above-mentioned recessed portion inspection apparatuses for laminated materials, the laser processing apparatus immediately remains without performing a destructive inspection after processing the recessed portions. It is possible to know the presence or absence of material, and it is possible to perform processing to remove residual material again if necessary,
Reliability and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a laser processing apparatus provided with an inspection apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating reflected light intensities when a residual resin is present in a recessed portion in the inspection apparatus of FIG. 1 and when it is not.

FIG. 3 is a configuration diagram of an inspection apparatus and a laser processing apparatus showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of an inspection apparatus and a laser processing apparatus showing another embodiment of the present invention.

5 is an explanatory diagram for explaining a reflection state in the inspection device of FIG.

6 is a characteristic diagram showing the relationship between the residual film pressure of the residual material and the reflected light intensity in the inspection device of FIG.

FIG. 7 is an explanatory diagram illustrating reflected light intensities when a residual resin is present in a recessed portion in the inspection apparatus of FIG. 4 and when it is not.

FIG. 8 is an explanatory diagram for explaining the operation of the inspection device and the laser processing device according to another embodiment of the present invention.

9 is an explanatory diagram illustrating a light path when the focus position is deviated in the detection device of FIG.

FIG. 10 is a diagram illustrating a conventional BVH processing method for a printed circuit board and is an explanatory diagram illustrating a step of processing a fine through hole portion.

FIG. 11 is a diagram illustrating a conventional BVH processing method for a printed circuit board, and is an explanatory diagram illustrating a processing method for processing a recessed portion for forming a BVH.

FIG. 12 is a configuration diagram of a conventional laser processing apparatus including an optical microscope.

13 is a configuration diagram of the optical microscope of FIG.

FIG. 14 is an explanatory diagram for explaining a state of reflection of irradiated light on a printed circuit board.

[Explanation of symbols]

1 light source, 2 ultraviolet light, 6 hole processing part, 6a bottom part, 7
Excitation light, 8 fluorescence, 11 CCD camera, 12 image processing device, 13 laser oscillator, 18 epoxy resin,
19 glass epoxy, 20 laser beam, 21 printed circuit board, 22 residual resin, 24 copper foil, 27 image,
29 resin surface reflected light, 30 copper foil surface reflected light, 32
a, 32b Reflected light from the bottom of the hole processed part, 33 Image of the hole processed part, 38 White light, 39a, 39b Pinhole plate.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-143401 (JP, A) JP-A-58-161808 (JP, A) JP-A-7-83841 (JP, A) JP-A-7- 128247 (JP, A) JP-A-4-236307 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 21/84-21/958 G01B 11/00-11/30

Claims (3)

(57) [Claims] 1. A first material and a second material are formed in layers.
Laminated laminated material with a laser beam irradiation device for processing.
Irradiate the beam to remove the first material and remove the second material.
Remains on the bottom of the recess formed on the material
The absorption coefficient for the residual material that is the first material
For the first illumination light above the specified value and the above residual material
The second illumination light whose absorption coefficient is smaller than the above specified value.
Illuminating light irradiating device and the surface of the residual material
A table of the residual material based on the first illumination light emitted.
Determine the position of the surface and pass through the above residual material
In the second illumination light reflected from the surface of the second material
Based on the position of the surface of the second material based on
A photodetector that detects the thickness of the residual material based on the position of
A device for inspecting a recessed portion of a laminated material, which is provided with a table. 2. The first illumination light is ultraviolet light,
The second illumination light is white light.
An apparatus for inspecting a recessed portion of a laminated material as set forth in . 3. The laminated material according to claim 1 or 2.
Laser processing device equipped with the recessed part inspection device.