JP2000137002A - Inspection method for via hole of printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect a via hole while processing it. SOLUTION: An insulating layer 2 covering the surface of a conductor is irradiated with a laser beam L, thereby a via hole 3 is processed so as to expose the conductor 1 at its bottom. At this time, the remaining state of the insulating layer 2 at the bottom of the via hole 3 is detected by measuring a change in the optical signal generated during the irradiation of the laser beam L. As a result, the via hole 3 can be inspected while processing it by applying the laser beam L thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a via hole inspection method for a printed circuit board in which a via hole is formed by laser beam irradiation.

[0002]

2. Description of the Related Art In a multilayer printed circuit board, an insulating layer made of a resin is provided between a conductor forming a lower layer circuit and a conductor forming an upper layer circuit. In order to establish conduction between the upper and lower conductors, a part of the insulating layer covering the lower conductor is removed, and a via hole in which the conductor is exposed is formed on the bottom surface. In processing such a via hole, if the insulating layer is not sufficiently removed and the resin remains at the bottom of the via hole, poor conduction may occur.

[0003] For this purpose, conventionally, after processing a via hole, a microscopic observation is performed to check whether or not resin remains at the bottom of the via hole. But,
This inspection method requires not only the skill of the inspector but also the possibility of overlooking a defective part due to the large number of inspection points.

To solve this problem, Japanese Patent Laid-Open No. 4-248448 discloses a technique as shown in FIG. 13 in which via hole inspection can be performed automatically. That is, in FIG. 13, 1 is a conductor forming a circuit of the printed circuit board 8, 2 is an insulating layer covering the surface of the conductor, 3 is a via hole formed in the insulating layer 2, and a light from the light source 15 is stopped. The light is irradiated on the bottom surface of the via hole 3 through the lens 16 and the lens 17, and the light reflected on the bottom surface of the via hole 3 is received by the light receiver 18 for measurement. If the processing of the via hole 3 is good and no resin remains at the bottom, light is reflected at a high reflectance on the surface of the conductor 1 formed of metal such as copper foil as shown in FIG. Poor processing of hole 3 and residual resin 1 at bottom
With 9, the light is reflected on the surface of the residual resin 19 with low reflectance as shown in FIG. Therefore, the quality of the processing of the via hole 3 can be determined based on the ratio between the amount of light emitted from the light source 15 and the amount of reflected light received by the light receiver 18.

[0005]

However, the above-mentioned Japanese Patent Laid-Open No.
In the method disclosed in Japanese Patent Application Laid-Open No. 248448/1990, inspection of the via hole 3 is performed after the via hole 3 is processed, and the inspection step is a separate step from the processing step of the via hole 3. There was a problem with productivity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a via hole inspection method for a printed circuit board, which can perform via hole inspection simultaneously with via hole processing. is there.

[0007]

According to a first aspect of the present invention, there is provided a method for inspecting a via hole in a printed circuit board, wherein an insulating layer covering the surface of the conductor is irradiated with a laser beam so that the bottom of the conductor is exposed. In processing the via hole 3 to be exposed into the insulating layer 2, the remaining state of the insulating layer 2 at the bottom of the via hole 3 is detected by measuring a change in an optical signal generated during the irradiation of the laser beam L. It is characterized by the following.

Further, the invention according to claim 2 is characterized in that the irradiation of the laser beam L for processing the via hole 3
The inspection light R _T having a wavelength of 00 nm is irradiated to the via hole 3, and the reflected light is measured.

[0009] According to another embodiment of the present invention 3 is characterized in that to measure the laser beam L optical R _P emitted from the plume 4 generated by irradiation of the insulating layer 2.

The invention according to claim 4 is that the via hole 3 is formed.
Reflected light R of laser beam L to be processed _LTo measure
It is a feature.

According to a fifth aspect of the present invention, the laser beam L is reflected by the half mirror 5 and is radiated to the insulating layer 2 to process the via hole 3 and is generated by irradiating the insulating layer 2 with the laser beam L. Half mirror 5 of the optical signal
Is characterized by measuring what transmits light.

According to a sixth aspect of the present invention, the laser beam L is reflected by the pinhole mirror 6 and is radiated to the insulating layer 2 to process the via hole 3 and is generated by irradiating the insulating layer 2 with the laser beam L. It is characterized in that the optical signal transmitted through the pinhole 7 of the pinhole mirror 6 is measured.

Further, according to a seventh aspect of the present invention, a via hole 3 is formed.
Reflected light R of laser beam L to be processed _LThe laser beam
The measurement is performed outside the optical path of L.

The invention of claim 8 is characterized in that the shape of the plume 4 generated by irradiating the insulating layer 2 with the laser beam L is measured.

[0015] According to a ninth aspect of the invention, measuring the laser beam irradiates the inspection laser beam L _T plume 4 generated by irradiation of the L, inspection laser beam L _T transmitted through the plume 4 in the insulating layer 2 It is characterized by doing.

[0016] According to another embodiment of the present invention 10, the inspection laser beam L _T irradiating the plume 4 generated by the irradiation of the laser beam L to the insulating layer 2, which is excited by irradiation of inspection laser beam L _T plume 4 is characterized in that the emission intensity of the particles in 4 is measured.

The invention according to claim 11 is characterized in that optical signals are measured from two or more places.

The invention of claim 12 provides the above-mentioned claim 2.
The method is characterized in that the measurement is performed by combining a plurality of methods selected from the above-described 10 methods.

[0019]

Embodiments of the present invention will be described below.

The printed circuit board 8 is made of a conductor 1 forming a circuit.
Is formed by laminating a plurality of layers through the insulating layer 2, and a part of the insulating layer 2 covering the conductor 1 is irradiated with a laser beam L to remove a part of the insulating layer 2. Then, the via hole 3 is processed to expose the conductor 1 on the bottom surface of the via hole 3. FIG. 2 shows an example of an apparatus for processing the via hole 3. A laser beam L such as a CO ₂ laser oscillated from a laser oscillator 21 passes through a mask 24, is reflected by galvanometer mirrors 22 and 23, and f− Irradiation is performed on the insulating layer 2 on the surface of the printed circuit board 8 through a lens 25 such as a θ lens. The galvanometer mirror 22 is rotated in the X-axis direction by an X-axis rotation device 26, and the galvanometer mirror 23 is rotated in the Y-axis direction by a Y-axis rotation device 27, along the surface of the printed circuit board 8. The laser beam L is scanned to perform high-speed processing. The printed circuit board 8 has a Y-axis table 28a which is moved in the Y-axis direction.
Consisting of an X-axis table 28b moved in the X-axis direction
-Set on the Y table 28,
Processing by the laser beam L can be performed while moving the printed board 8 in the XY directions.

According to the present invention, while processing the via hole 3 by irradiating the insulating layer 2 of the printed circuit board 1 with the laser beam L, the change of the optical signal generated during the irradiation of the laser beam L is measured. By doing so, the remaining state of the insulating layer 2 at the bottom of the via hole 3 is detected.

FIG. 1 shows an example of this, in which a laser beam L is applied to an insulating layer 2 to process a via hole 3 and, at the same time, a test light source 30
_T is applied to the bottom of the via hole 3, and the light _RL reflected at the bottom of the via hole 3 is received by the light receiver 31 as an optical signal. Inspection light source 3 as light receiver 31
A photosensor or the like which can detect light having a wavelength emitted from 0 can be used. Then, when the inspection light source 30 irradiates the inspection light _RT from the inspection light source 30 to the via hole 3 where the hole processing is good and the resin does not remain at the bottom, the optical signal of the reflected light _RL received by the light receiver 31 is measured in advance. If the range of the optical signal value when the via hole 3 is good is set in advance, the optical signal value received and measured by the light receiver 31 when the via hole 3 is processed is set to this set value. By comparing with the range, the quality of the via hole 3 can be determined. At this time, if a stop is provided so that an optical signal from around the via hole 3 is not measured and the optical signal is condensed, the accuracy of the measurement can be improved. In addition, the in-line inspection can be performed by using the light receiver 31 having the same or higher responsiveness to the processing by the laser beam L.

As described above, the inspection of the via hole 3 can be performed while processing the via hole 3 by irradiating the laser beam L.
This eliminates the need for an inspection step that is separate from the processing step described above, thereby improving productivity. And via hole 3
The inspection of the via hole 3 can be performed simultaneously with the progress of the processing, so that when a defect is detected, an additional pulse can be given to rework the via hole 3 with the laser beam L. is there.

In a general multilayer printed circuit board 8, a metal foil such as a copper foil is used as the conductor 1 and an epoxy resin is used as the insulating layer 2. The light absorptivity of the epoxy resin differs depending on the wavelength and also depends on the thickness of the resin. For example, when the copper foil is used as the conductor 1 and the epoxy resin is used as the insulating layer 2, the resin thickness is changed.
FIG. 3 is a graph showing the results of measuring the light reflectance of each type of sample. A indicates the reflectance when the resin thickness is small, B indicates the reflectance when the resin thickness is medium, and C indicates the reflectance when the resin thickness is large. As shown in FIG. When the wavelength is in the range of 500 to 700 nm, the change in the intensity of the reflected light with respect to the change in the resin thickness is greater than the light in other wavelength ranges.

Therefore, according to the second aspect of the present invention, as shown in FIG. 1, the inspection light source 30 irradiates the bottom of the via hole 3 with the inspection light R _T, and the intensity of the reflected light R _L is detected by the light receiver 3.
In the inspection of the via hole 3 by the measurement in step 1, the inspection light _RT having a wavelength in the range of 500 to 700 nm is used.
1, the thickness of the residual resin 19 remaining at the bottom of the via hole 3 can be detected with high accuracy from the intensity of the reflected light received at the bottom of the via hole 3.
9 is accurately determined so that the inspection of the via hole 3 can be performed with high accuracy. For example, a He-Ne laser with a wavelength of 633 nm, a wavelength of 53
A 2 nm SHG-YAG laser or the like has a wavelength of 500 to 7
Since it falls within the range of 00 nm, it is effective as inspection light _RT . Further, using the inspection light R _T including light of wavelength 500 to 700 nm, through a light reflected at the bottom of the via hole 3 to the filter, and only light of wavelength 500 to 700 nm to be received by the photodetector 31 Can also perform a highly accurate inspection.

As described above, in the general multilayer printed circuit board 8, a metal foil such as a copper foil is used as the conductor 1 and an epoxy resin or the like is used as the insulating layer 2. When the resin is removed by irradiating the insulating layer 2 with a laser beam L having a wavelength in the infrared region such as a CO ₂ laser, the resin of the insulating layer 2 which has received energy from the laser beam L is gradually removed from the surface side. When the thickness of the resin at the bottom of the via hole 3 is large, the laser beam L is absorbed by the resin, but when the thickness of the resin at the bottom of the via hole 3 is small, the laser beam L Is increased, and the laser beam L reaches the conductor 1 and is reflected.

[0027] Therefore the invention of claim 4 is, as shown in FIG. 4, the reflected light R _L of the laser beam L for processing the via hole 3 is irradiated to the insulating layer 2 and received by the photodetector 31, the reflectance The thickness of the residual resin 19 at the bottom of the via hole 3 is detected by measuring the thickness of the via hole 3 and the via hole 3 is inspected. By measuring the optical signal reflected at the bottom of the via hole 3 using the laser beam L itself for processing the via hole 3 in this way, the via hole can be formed at the same time as the processing without any need for a light source for inspection. The inspection of the hole 3 can be performed with high accuracy.

FIG. 5 shows an embodiment of the fifth aspect of the present invention.
It is shown. Fabricate via hole 3 as above
Of reflected laser beam L_LVia holes using
When the inspection of No. 3 is performed, the reflected light R_LIs the laser oscillator 21
To travel backward in the optical path of the laser beam L toward
Reflected light R on the optical path of laser beam L_LTo take out the optical system
Inspection can be performed easily by placing
You. That is, as shown in FIG. 5, the optical path of the laser beam L
The half mirror 5 is arranged on the upper side, and the laser beam L is
Reflected by the mirror 5 and collected by the F-θ lens 25.
The insulating layer 2 is irradiated with light. And ba
Reflected light R of laser beam L for processing earhole 3_Lof
Since a part goes straight through the half mirror 5, the laser
Arranged behind the half mirror 5 outside the optical path of the beam L
The reflected light R _LAnd its reflection
By measuring the rate and intensity (light intensity),
3 can be inspected. like this
And the reflected light R outside the optical path of the laser beam L_LThe light
It can be measured by receiving it as a signal,
Reflected light R of laser beam L for processing via hole 3_L
Inspection using the method becomes easy. Also half-mi
Outside the optical path of the laser beam L only by using the
Inspection equipment such as the light receiver 31 can be easily installed.
Later, it is possible to incorporate this test equipment into the system.
It will be easier. In the embodiment of FIG.
Reflected light R of the beam L_LThrough the half mirror 5
Is measured as an optical signal.
As shown in FIGS. 8, 10 and 11, the laser
From the plume 4 generated by irradiating the beam L
Of the generated light, the light transmitted through the half mirror 5
It can also be measured by receiving light as a signal with the light receiver 31.
Things.

FIG. 6 shows an embodiment of the invention according to claim 6. When performing the test of the via hole 3 with the reflected light R _L of the laser beam L for processing the via hole 3 as described above, the reflected light R _L is the laser oscillator 21
To travel backward in the optical path of the laser beam L toward
By arranging the optical system in the optical path of the laser beam L which transmits the wavelength range of the reflected light R _L, it is possible to easily perform the inspection. That is, as shown in FIG. 6, the pinhole mirror 6 is arranged on the optical path of the laser beam L, and the laser beam L is reflected by the pinhole mirror 6 and F-
The light is condensed by the θ lens 25 and irradiated on the insulating layer 2. And part of the reflected light R _L of the laser beam L for processing the via hole 3 to go straight through the pinhole 7 provided as minute through hole in the center portion of the pinhole mirror 6, the optical path outside of the laser beam L In this method, the via hole 3 can be inspected by receiving the reflected light _RL with a light receiver 31 arranged behind the half mirror 5 and measuring the reflectance and intensity (light quantity) thereof. It is. In this way, the reflected light _RL can be received as an optical signal and measured outside the optical path of the laser beam L, and the inspection using the reflected light of the laser beam L for processing the via hole 3 can be easily performed. It becomes. In addition, the inspection equipment such as the light receiver 31 can be easily installed outside the optical path of the laser beam L only by using the pinhole mirror 6, and the inspection equipment can be easily incorporated into the system later. is there. In the embodiment of Figure 6, but the one that passes through the pinhole mirror 6 of the reflected light R _L of the laser beam L is to be measured as an optical signal, as shown in FIGS. 8 and 11 below , Resin layer 2
Of the light generated from the plume 4 generated by irradiating the laser beam L onto the light source, the light transmitted through the pinhole mirror 6 can be received by the light receiver 31 as an optical signal and measured.

When inspecting the via hole 3 using the reflected light RL of the laser beam L for processing the via hole 3 as described above, the reflected light _RL of the laser beam _L is applied to the bottom of the via hole 3. A part is irregularly reflected out of the optical path of the laser beam L. Therefore, in the invention of claim 7, FIG.
As shown in (2), a light receiver 31 is arranged outside the optical path (off the optical axis) of the laser beam L, and the reflected light _RL reflected out of the optical path of the laser beam L at the bottom of the via hole 3 is reflected by the light receiver 31 as an optical signal The via hole 3 is inspected by measuring the intensity (light amount).
In FIG. 7, reference numeral 33 denotes a total reflection mirror. If the reflected light R _L of the laser beam L for processing in this manner the via hole 3 as measured by the outside of the optical path of the laser beam L, the inspection in which is possible without loss of working energy of the laser beam L . That is, when the reflected light _RL of the laser beam L is taken out of the optical path of the laser beam L by using the half mirror 5 as shown in FIG. 5 or using the pinhole mirror 6 as shown in FIG. A part of the laser beam L for processing the via hole 3 may also pass through the half mirror 5 and the pinhole mirror 6 and escape, and a part of the laser beam L required for the processing will be lost. However, in the configuration shown in FIG. 7, the laser beam L for processing is reflected by the total reflection mirror 33, so that no loss occurs in the laser beam L and the laser beam L can be used effectively for processing. At this time, by arranging a filter in front of the light receiver 31, the wavelength of the reflected light _RL to be detected can be selected, the degree of freedom of inspection is increased, and the via hole 3 with high accuracy suitable for the processing object is provided. Can be inspected.

FIG. 8 shows an embodiment of the third aspect of the present invention. Laser beam L such as CO ₂ laser
Irradiates the insulating layer 2 formed of an epoxy-based resin or the like with the laser beam L
When the resin of the insulating layer 2 is removed by the above, the resin that has received the energy from the laser beam L is excited and vaporized, and the molecules of the vaporized resin are ionized to be in a plasma state.
When the via hole 3 is processed by the laser beam L, high-luminance plasma called a plume 4 is generated above the via hole 3. The emission intensity of the plume 4 decreases as the amount of resin to be removed when processing the via hole 3 decreases, and when the resin to be removed runs out, the plume 4 also disappears and emits no light.

Therefore, as shown in FIG.
The light R _P generated from the light is received as an optical signal by the light receiver 31 and measured, and the intensity thereof is detected to detect the thickness of the residual resin 19 at the bottom of the via hole 3 and to accurately inspect the via hole 3. It can be done well. As described above, the inspection of the via hole 3 can be performed by using the plume 4 generated by the irradiation of the laser beam L for processing the via hole 3, so that the inspection light source is not particularly required, and the inspection can be performed simultaneously. The inspection of the via hole 3 can be performed with high accuracy.

As described above, when processing the via hole 3 with the laser beam L, a plume 4 of high brightness is generated above the via hole 3. The shape of the plume 4 depends on the energy input of the laser beam L. Depending on the state and the state of the resin of the insulating layer 2, if there is an abnormality in the input state of the energy of the laser beam L or the like and processing failure of the via hole 3 occurs, the shape of the plume 4 is also deformed.

[0034] Therefore, in the invention of claim 8, as shown in FIG. 9, so as to shoot the shape of the plume 4 camera 34 such as a CCD camera based on the light (optical signal) R _P generated from the plume 4 is there. At this time, the shape of the plume 4 generated at the time of processing the non-defective via hole 3 is photographed by the camera 34 in advance, image-processed, and compared with the actual shape of the plume 4 at the time of processing. The quality of the processing of No. 3 can be determined.
In this manner, the inspection of the via hole 3 can be performed with high accuracy at the same time as the processing, without particularly requiring the inspection light source.

As described above, when processing the via hole 3 with the laser beam L, a high-luminance plume 4 is generated above the via hole 3, and the intensity of the plume 4 is reduced when the via hole 3 is processed. As the amount of resin to be removed decreases, the size becomes smaller. When there is no more resin to be removed, the plume 4 also disappears. When the irradiation with the laser beam L _T for inspection to the plume 4, the laser beam L _T by the particles in the plume 4 is absorbed and diffused, although the laser beam L _T that transmits plume 4 decreases, the via hole 3 When the amount of processing to when the resin to be removed is reduced particles in the plume 4 with decreasing, reduction of the laser beam L _T that passes through the plume 4 transmittance is high is reduced, to be removed resin When the plume 4 disappears gone transmittance gone also decrease of the laser beam L _T becomes higher.

[0036] Therefore the invention of claim 9, as shown in FIG. 10, the inspection laser beam L _T from inspection laser oscillator 35 irradiates the plume 4, optical inspection laser beam L _T passing through the plume 4 The amount of the residual resin 19 remaining at the bottom of the via hole 3 can be detected by measuring the transmission intensity by receiving the signal as a signal with the light receiver 31 and measuring the transmission intensity thereof. Can be performed with high accuracy. As the inspection laser beam L _T, a dye laser, a wavelength of 633nm
He-Ne laser, 532 nm wavelength SHG-YAG
By using a laser or the like, a more accurate inspection can be performed. As described above, the inspection of the via hole 3 can be performed by using the plume 4 generated by the irradiation of the laser beam L for processing the via hole 3, so that the inspection of the via hole 3 with high reliability can be performed simultaneously with the processing. Can be done.

Further, as described above, when processing the via hole 3 with the laser beam L, a plume 4 of high luminance is generated above the via hole 3, and the intensity of the plume 4 is reduced when processing the via hole 3. As the amount of resin to be removed decreases, the size becomes smaller. When there is no more resin to be removed, the plume 4 also disappears. When the irradiation with the laser beam L _T for inspection plume 4, the particles in the plume 4 is resonantly excited by the laser beam L _T, emits light by excitation. Since the particles in the plume 4 is also reduced according to the amount of resin to be removed during processing of the via hole 3 is decreased, the laser beam L _T by excited light emitting intensity decreases, the resin to be removed When the plume 4 disappears due to the disappearance, the light emission due to the excitation also disappears.

[0038] Therefore the invention of claim 10 is, as shown in FIG. 11, the inspection laser beam L _T from inspection laser oscillator 35 irradiates the plume 4, the particles in the plume 4 by irradiation of the laser beam L _T Excited light R _E
Is received by the light receiver 31 as an optical signal and measured, and the emission intensity is measured to detect the particle density in the plume 4. Therefore, the amount of the residual resin 19 remaining at the bottom of the via hole 3 can be detected based on the detection result, and the inspection of the via hole 3 can be performed with high accuracy. In this method, FIG.
Unlike the method using no inspection light source as shown in FIG. 9 and FIG. 9, since the particles in the plume 4 are excited and emitted, the intensity of the optical signal increases, and the information of the plume 4 is detected more strongly than the noise component. As a result, the detection sensitivity is increased, and a highly accurate inspection can be performed. As the inspection laser beam L _T, a dye laser, wavelength 63
3nm He-Ne laser, 532nm wavelength SHG-
By using a YAG laser or the like, a more accurate inspection can be performed. As described above, the inspection of the via hole 3 can be performed by using the plume 4 generated by the irradiation of the laser beam L for processing the via hole 3, so that the inspection of the via hole 3 with high reliability can be performed simultaneously with the processing. Can be done.

In each of the above embodiments, the measurement for receiving the optical signal is performed at one location, but in the invention of claim 11, the optical signal is measured from two or more locations. By changing the measurement location to a plurality of locations as described above, it is possible to obtain information that cannot be detected from only one direction.
Can improve the reliability of the inspection.

FIG. 12 (a) shows an example of the embodiment of the present invention according to the eleventh aspect. As shown in FIG. 7, when processing the via hole 3 with the laser beam L, the bottom of the via hole 3 is formed. The reflected light R reflected out of the optical path of the laser beam L
_When light is received by the light receiver 31 and the via hole 3 is inspected, the light receivers 31 are arranged at a plurality of positions outside the optical path of the laser beam L. Therefore, in this case, the intensity (light amount) of the reflected light _RL can be measured at a plurality of locations, and high measurement accuracy can be obtained. _RL can also be received.

[0041] FIG. 12 (b) show another example of embodiment of the invention of claim 11, as shown in FIG. 11, the inspection laser beam L _T from inspection laser oscillator 35 to the plume 4 irradiated, light R _E the light receiver 3 particles in the plume 4 emits light by being excited by the irradiation of the laser beam L _T
When received by 1, irradiates the inspection laser beam L _T respectively from a plurality of inspection laser oscillator 35 arranged different wavelengths at a plurality of locations in the plume 4, each emitted light by being excited by the irradiation of the laser beam L _T a plurality of light receivers 31 where the light R _E are arranged in a plurality of locations are to be respectively received. By irradiating the inspection laser beam L _T of different wavelengths in the plume 4, different light R of the wavelength
Although _E is emitted, different light R _E of these wavelengths are those capable of receiving a plurality of each individual photodetector 31.

Incidentally, the invention of claim 11 is the same as that of FIG.
(A) It is not limited to the embodiment of (b),
The measurement is performed by disposing the light receivers 31 shown in FIGS. 1, 4, 5, 6, 8, and 10 at a plurality of positions, and the camera 3 shown in FIG.
Needless to say, the measurement can be performed by arranging the four at a plurality of locations.

According to a twelfth aspect of the present invention, the inspection of the via hole 3 is performed by combining a plurality of the methods of the above-described embodiments. For example, FIG. 1, FIGS. If the detection result of the residual resin 19 in the via hole 3 varies only by measuring the reflected light as shown in (a), the plume 4 shown in FIGS. 8 to 11 and FIG. By combining the used measurements, the inspection of the via hole 3 can be performed based on a lot of information, the inspection accuracy can be improved, and the reliability of the inspection can be increased.

[0044]

As described above, the method for inspecting via holes in a printed circuit board according to the first aspect of the present invention exposes the conductor to the bottom surface by irradiating the insulating layer covering the surface of the conductor with a laser beam. In processing the via hole into an insulating layer, the residual state of the insulating layer at the bottom of the via hole is detected by measuring the change in the optical signal generated during laser beam irradiation. While processing the via hole, the inspection of the via hole can be performed, eliminating the need for the inspection process of the via hole processing process and another process.
It can increase productivity.

The invention according to claim 2 is characterized in that the irradiation of the laser beam for processing the via hole is performed in a range of 500 to 700.
The inspection light having a wavelength of 500 nm is applied to the via hole, and the reflected light is measured.
The light of nm has a large change in the intensity of the reflected light with respect to the change in the thickness of the resin, and can accurately detect the remaining state of the insulating layer at the bottom of the via hole from the intensity of the reflected light.

According to the third aspect of the present invention, since the light emitted from the plume generated by irradiating the insulating layer with the laser beam is measured, the plume generated when processing the via hole with the laser beam is used. In this way, the inspection of the via hole can be performed, and the inspection of the via hole can be performed at the same time as the processing without specially requiring a light source for inspection.

According to the fourth aspect of the present invention, since the reflected light of the laser beam for processing the via hole is measured, the remaining state of the insulating layer at the bottom of the via hole is detected based on the intensity of the reflected light of the laser beam. Thus, the inspection of the via hole can be performed, and the inspection of the via hole can be performed without using a light source for inspection.

According to a fifth aspect of the present invention, a laser beam is reflected by a half mirror to irradiate an insulating layer to form a via hole, and a half mirror of an optical signal generated by irradiating the insulating layer with a laser beam. Since the laser beam that transmits the laser beam is measured, the optical signal generated by the laser beam irradiation can be measured outside the optical path of the laser beam, and the inspection using the laser beam for processing the via hole is easy. It becomes something.

According to a sixth aspect of the present invention, a laser beam is reflected by a pinhole mirror to irradiate an insulating layer to form a via hole, and a pin signal out of an optical signal generated by irradiating the insulating layer with the laser beam. Since the laser beam transmitted through the pinhole of the hole mirror is measured, an optical signal generated by laser beam irradiation can be measured outside the optical path of the laser beam. This facilitates the inspection that was used.

According to the seventh aspect of the present invention, since the reflected light of the laser beam for processing the via hole is measured outside the optical path of the laser beam, the reflected light can be measured outside the optical path of the laser beam. This facilitates inspection using reflected light of a laser beam for processing a via hole.

According to the invention of claim 8, since the shape of the plume generated by irradiating the insulating layer with the laser beam is measured, the plume generated when processing the via hole with the laser beam is utilized. The inspection of the via hole can be performed, and the inspection of the via hole can be performed at the same time as the processing without specially requiring a light source for inspection.

According to the ninth aspect of the present invention, the inspection laser beam is irradiated on the plume generated by irradiating the insulating layer with the laser beam, and the inspection laser beam transmitted through the plume is measured. Inspection of via holes can be performed using plumes generated when processing via holes at the same time. Via holes can be inspected at the same time as processing without specially requiring a light source for inspection. Can be done.

According to a tenth aspect of the present invention, a plume generated by irradiating the insulating layer with a laser beam is irradiated with an inspection laser beam, and the emission intensity of particles in the plume excited by the inspection laser beam irradiation is reduced. Since the measurement is performed, the via hole can be inspected by using the plume generated when processing the via hole with the laser beam, and the via hole can be inspected simultaneously with the processing. It is.

According to the eleventh aspect of the present invention, since optical signals are measured from two or more locations, it is possible to obtain information that cannot be measured from only one direction, to improve the accuracy of inspection, and to increase the accuracy of inspection. The reliability of the inspection of the hole can be improved.

The twelfth aspect of the present invention is the second aspect of the present invention.
Since the measurement is performed by combining a plurality of methods selected from among the above methods, it is possible to inspect the via hole based on a lot of information obtained from different methods, thereby improving the inspection accuracy. This can improve the reliability of the inspection.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the first embodiment.

FIG. 2 is a schematic view showing processing of a via hole.

FIG. 3 is a graph showing the relationship between the wavelength of light and the reflectance.

FIG. 4 is a schematic diagram showing an example of an embodiment according to claim 4;

FIG. 5 is a schematic diagram showing an example of the embodiment of claim 5;

FIG. 6 is a schematic diagram showing an example of the embodiment of claim 6;

FIG. 7 is a schematic diagram showing an example of the embodiment of claim 7;

FIG. 8 is a schematic diagram showing an example of the third embodiment.

FIG. 9 is a schematic diagram showing an example of the embodiment of claim 8;

FIG. 10 is a schematic diagram showing an example of the embodiment of claim 9;

FIG. 11 is a schematic view showing an example of the tenth embodiment.

FIGS. 12A and 12B show an example of the embodiment of claim 11, wherein FIGS. 12A and 12B are schematic diagrams.

FIG. 13 shows a conventional example, and (a) and (b) are schematic diagrams, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulating layer 3 Via hole 4 Plume 5 Half mirror 6 Pinhole mirror 7 Pinhole 8 Printed circuit board

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[Procedure amendment]

[Submission date] December 28, 1998 (1998.12.
28)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

Continued on the front page F term (reference) 2G051 AA61 AA65 AB14 AB20 BA10 CA02 CA03 CA04 CB01 CC07 DA07 EB01 EB02 5E346 AA43 BB01 GG15 GG33 HH33

Claims (12)

[Claims] 1. A laser beam is irradiated onto an insulating layer covering the surface of a conductor, whereby a via hole exposing the conductor on the bottom surface is processed into the insulating layer to change an optical signal generated during the laser beam irradiation. A method for inspecting a via hole in a printed circuit board, wherein the state of the insulating layer at the bottom of the via hole is detected by measuring the residual state of the via hole. 2. The method according to claim 1, wherein the inspection light having a wavelength of 500 to 700 nm is applied to the via hole in parallel with the irradiation of the laser beam for processing the via hole, and the reflected light is measured. Inspection method of via hole of printed circuit board as described. 3. The method according to claim 1, wherein light emitted from a plume generated by irradiating the insulating layer with a laser beam is measured. 4. The method for inspecting a via hole in a printed circuit board according to claim 1, wherein reflected light of a laser beam for processing the via hole is measured. 5. A via hole is formed by reflecting a laser beam on a half mirror and irradiating the insulating layer, and measuring an optical signal generated by irradiating the insulating layer with the laser beam that passes through the half mirror. 5. The method for inspecting a via hole in a printed circuit board according to claim 2, wherein: 6. A method of manufacturing a via hole by reflecting a laser beam to a pinhole mirror and irradiating the insulating layer with a laser beam, and extracting a pinhole of the pinhole mirror among optical signals generated by irradiating the insulating layer with the laser beam. 5. The method for inspecting a via hole in a printed circuit board according to claim 2, wherein the transmitted light is measured. 7. The method according to claim 4, wherein the reflected light of the laser beam for processing the via hole is measured outside the optical path of the laser beam. 8. The method according to claim 1, wherein a shape of a plume generated by irradiating the insulating layer with a laser beam is measured. 9. The inspection laser beam according to claim 1, wherein the inspection laser beam is irradiated on a plume generated by irradiating the insulating layer with the laser beam, and the inspection laser beam transmitted through the plume is measured. A method for inspecting a via hole in a printed circuit board according to any one of the above. 10. A method for irradiating an inspection laser beam to a plume generated by irradiating an insulating layer with a laser beam, and measuring emission intensity of particles in the plume excited by the irradiation of the inspection laser beam. Claim 1,
The method for inspecting a via hole in a printed circuit board according to any one of claims 5 and 6. 11. The method according to claim 1, wherein optical signals are measured from two or more locations. 12. A method of inspecting a via hole in a printed circuit board, wherein the measurement is performed by combining a plurality of methods selected from the methods of claim 2 to 10.