Method of manufacturing printed circuit board and method of inspecting printed circuit board

A printed circuit board is fabricated in a manufacturing process. In an inspection process, first and second light sources of an inspection device irradiate the printed circuit board with first and second light having first and second wavelength distributions. First and second imaging devices produce a monochromatic first image and a color second image of an inspection subject region of the printed circuit board based on the first and second light respectively reflected by the printed circuit board. Presence and absence of a defect is determined based on at least the first image by automatic optical inspection. Further, verification of the defect is performed by visual observation of at least the second image.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method of manufacturing a printed circuit board and a method of inspecting the printed circuit board.

Description of Related Art

Conventionally, during manufacture of a printed circuit board, automatic optical inspection (AOI) for detecting a defect of wiring traces is performed. After the AOI, verification of a result of inspection is performed by an operator.

Generally, in the automatic optical inspection, a monochromatic light source is used, and the printed circuit board is irradiated with light having a specific wavelength, and a monochromatic image of the printed circuit board is acquired by a monochromatic camera. A defect of the printed circuit board is determined based on the acquired monochromatic image. Thereafter, in a verification step, a color image of a portion, which is determined to be defective by the automatic optical inspection, is acquired by a color camera. The operator verifies the defect based on the color image (JP 2012-549756 A etc.)

BRIEF SUMMARY OF THE INVENTION

In the inspection by the conventional method of manufacturing the printed circuit board, it is necessary to acquire a monochromatic image during the AOI and acquire a color image in the verification step. Therefore, a time period required for the inspection is lengthened. In recent years, it is required to shorten a time period required for the inspection in order to reduce a manufacturing cost.

An object of the present invention is to provide a method of manufacturing a printed circuit board and a method of inspecting the printed circuit board capable of shortening a time period required for inspection.

(1) According to one aspect of the present invention, a method of manufacturing a printed circuit board includes the steps of fabricating the printed circuit board, producing an image of an inspection subject region of the printed circuit board as a first image by a first imaging device, and producing an image of the inspection subject region of the printed circuit board as a second image by a second imaging device, determining presence and absence of a defect of the printed circuit board based on at least the first image, and determining presence and absence of a defect of the printed circuit board based on at least the second image, wherein the first imaging device produces the first image by receiving first light having a first wavelength distribution, and the second imaging device produces the second image by receiving second light having a second wavelength distribution at least partially different from the first wavelength region.

In this manufacturing method, the first image is produced based on the first light having the first wavelength distribution, and the second image is produced based on the second light having the second wavelength distribution. Thus, the first and second images show states of portions different from each other in a thickness direction of the printed circuit board. The presence and absence of the defect is determined based on the first image, and the presence and absence of the defect is determined based on the second image. The first and second images of the inspection subject region of the printed circuit board are simultaneously produced by the first and second imaging devices. Therefore, a time period required for inspection of the printed circuit board can be shortened.

(2) The step of determining the presence and absence of the defect of the printed circuit board based on the at least the first image may include determining presence and absence of a defect of the printed circuit board by automatic optical inspection based on at least the first image, and the step of determining the presence and absence of the defect of the printed circuit board based on the at least the second image may include determining presence and absence of a defect of the printed circuit board by visual observation based on at least the second image.

In this case, the presence and absence of the defect is determined by the automatic optical inspection based on the first image, and the presence and absence of the defect is determined by visual observation of the second image. Thus, the defect detected by the automatic optical inspection can be visually verified.

(3) The step of determining the presence and absence of the defect based on the at least the first image may include determining presence and absence of the defect based on the first image and the second image.

In this case, the first and second images show the states of the portions different from each other in the thickness direction of the printed circuit board, so that the presence and absence of the defect of the printed circuit board can be determined based on the first and second images with high accuracy. Further, a defect that cannot be detected only from the first image can be detected.

(4) The step of determining the presence and absence of the defect of the printed circuit board based on the at least the second image may include determining presence and absence of the defect of the printed circuit board based on the first image and the second image.

In this case, the first and second images show the states of the portions different from each other in the thickness direction of the printed circuit board, so that the presence and absence of the defect of the printed circuit board can be determined based on the first and second images with high accuracy. Further, a defect that cannot be detected from only the second image can be detected.

(5) The first light may be monochromatic light having a peak wavelength in a specific wavelength region, and the second light may be white light, the first imaging device may produce a monochromatic image as the first image by receiving the first light, and the second imaging device may produce a color image as the second image by receiving the second light.

In this case, the monochromatic image mainly shows a state of the inside of the printed circuit board, and the color image mainly shows a state of the surface of the printed circuit board. Thus, presence and absence of a defect of the inside of the printed circuit board can be mainly determined. Further, the detected defect of the inside can be verified mainly based on the state of the surface of the printed circuit board. Further, a defect of the surface of the printed circuit board can be detected.

(6) The step of producing the first and second images may further include irradiating the inspection subject region with the first light generated by a first light source, and irradiating the inspection subject region with the second light generated by a second light source, and the first imaging device may be provided to receive the first light from the printed circuit board, and the second imaging device may be provided to receive the second light from the printed circuit board.

In this case, the first imaging device receives the first light from the inspection subject region, and the second imaging device receives the second light from the inspection subject region. Thus, light other than the first and second light is not incident on the respective first and second imaging devices. Therefore, flexibility of selection of types of the first and second imaging devices is large.

(7) The first imaging device may be provided to receive the first light reflected by the printed circuit board, and the second imaging device may be provided to receive the second light reflected by the printed circuit board.

In this case, the first imaging device and the first light source can be arranged on the same side with respect to the printed circuit board. Further, the second imaging device and the second light source can be arranged on the same side with respect to the printed circuit board. Therefore, it is possible to produce the first and second images without complicating an arrangement of the first and second imaging devices, and the first and second light sources.

(8) The step of producing the first and second images may further include relatively moving the first and second imaging devices and the printed circuit board in a first direction, the first imaging device may include a first line camera arranged to image a line region extending in a second direction that intersects with the first direction in the printed circuit board, and the second imaging device may include a second line camera arranged to image the line region extending in the second direction in the printed circuit board.

In this case, it is possible to respectively produce the first and second images of the large inspection subject region without increasing the size of each of the first and second imaging devices.

(9) The first and second line cameras may be provided in parallel to each other, and configured to simultaneously move in the first direction while imaging the line region extending in the second direction.

In this case, the first and second images of the same region of the printed circuit board can be acquired in a short period of time. Thus, a time period required for the inspection of the printed circuit board can be more sufficiently shortened.

(10) The first wavelength distribution may be defined such that the first image shows a state of inside of the printed circuit board, and the second wavelength distribution may be defined such that the second image shows a state of a surface of the printed circuit board.

In this case, presence and absence of a defect of the inside of the printed circuit board can be determined based on the first image. Further, the detected defect of the inside can be verified mainly based on the state of the surface of the printed circuit board. Further, the defect of the surface of the printed circuit board can be detected based on the second image.

(11) According to another aspect of the present invention, a method of inspecting a printed circuit board includes the steps of producing an image of an inspection subject region of the printed circuit board as a first image by a first imaging device, and producing an image of the inspection subject region of the printed circuit board as a second image by a second imaging device, determining presence and absence of a defect of the printed circuit board based on at least the first image, and determining presence and absence of a defect of the printed circuit board based on at least the second image, wherein the first imaging device produces the first image by receiving first light having a first wavelength distribution, and the second imaging device produces the second image by receiving second light having a second wavelength distribution at least partially different from the first wavelength region.

In the inspection method, the first image is produced based on the first light having the first wavelength distribution, and the second image is produced based on the second light having the second wavelength distribution. Thus, the first and second images show the states of portions different from each other in the thickness direction of the printed circuit board. The presence and absence of the defect is determined based on the first image, and the presence and absence of the defect is determined based on the second image. The first and second images of the inspection subject region of the printed circuit board are simultaneously produced by the first and second imaging devices by the above-mentioned method. Therefore, a time period required for the inspection of the printed circuit board can be shortened.

(12) The step of determining the presence and absence of the defect of the printed circuit board based on the at least the first image may include determining presence and absence of a defect of the printed circuit board by automatic optical inspection based on at least the first image, and the step of determining the presence and absence of the defect of the printed circuit board based on the at least the second image may include determining presence and absence of a defect of the printed circuit board by visual observation based on at least the second image.

In this case, the presence and absence of the defect is determined by the automatic optical inspection based on the first image, and the presence and absence of the defect is determined by visual observation of the second image. Thus, the defect detected by the automatic optical inspection can be visually verified.

Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of manufacturing a printed circuit board and a method of inspecting the printed circuit board according to embodiments of the present invention will be described below with reference to drawings. The method of manufacturing the printed circuit board includes steps of manufacturing the printed circuit board and steps of inspecting the printed circuit board. The printed circuit board is a suspension board having a circuit, for example.

(1) Manufacturing Process of Printed Circuit Board

FIGS. 1A to 1Dare cross sectional views showing one example of the manufacturing process of the printed circuit board according to the present embodiment. First, as shown inFIG. 1A, an elongated metal support substrate11made of stainless, for example, is prepared. While the manufacturing process of the one printed circuit board is shown inFIGS. 1A to 1D, the plurality of printed circuit boards are formed on the elongated metal support substrate11by a roll-to-roll system in the present embodiment. The thickness of the metal support substrate11is not less than 5 μm and not more than 50 μm, for example, and is preferably not less than 10 μm and not more than 30 μm.

Next, as shown inFIG. 1B, a base insulating layer12made of polyimide, for example, is formed on the metal support substrate11. The thickness of the base insulating layer12is not less than 1 μm and not more than 30 μm, for example, and is preferably not less than 3 μm and not more than 20 μm.

Then, as shown inFIG. 1C, a plurality of wiring traces13are formed on the base insulating layer12. In the present embodiment, each of wiring traces13is constituted by conductor traces14made of copper, for example, and metal cover layers15made of nickel, for example. The thickness of the wiring traces13is not less than 3 μm and not more than 30 μm, for example, and preferably not less than 5 μm and not more than 20 μm. Each wiring trace13includes a line wiring layer and terminal portions such as pads provided at both ends of the wiring layer, for example. The wiring trace13may be a grounding conductor layer. Each conductor trace14may be formed using a semi-additive method, for example, or may be formed using another method such as a subtractive method. The metal cover layer15is formed to cover a surface of the conductor trace14by electroless plating, for example. The thickness of the metal cover layers15is not more than 2 μm, for example, and is preferably not less than 0.1 μm and not more than 1 μm.

As shown inFIG. 1D, a cover insulating layer16made of polyimide, for example, is formed on the base insulating layer12to cover the plurality of wiring traces13. In this case, openings are provided at the cover insulating layer16such that each terminal portion of each wiring trace13is exposed. The thickness of the cover insulating layer16is not less than 3 μm and not more than 30 μm, for example, and is preferably not less than 5 μm and not more than 20 μm.

(2) Inspection Device for Printed Circuit Board

An elongated board assembly sheet having the plurality of printed circuit boards10is fabricated by the steps of the above-mentionedFIGS. 1A to 1D. Next, inspection of each printed circuit board10of the board assembly sheet is performed.

FIG. 2is a schematic diagram showing the inspection device for inspecting the printed circuit boards of the board assembly sheet transported by the roll-to-roll system.

As shown inFIG. 2, a feed roll20and a wind-up roll30are arranged at a distance to be rotatable in a direction of arrows. The board assembly sheet50fed from the feed roll20is transported in a direction of an arrow and is wound by the wind-up roll30.

The inspection device100includes a first light source111, a second light source112, a first imaging device121, a second imaging device122, a driving device130, a display device140and a control device150.

Hereinafter, a direction parallel to a surface of the transported board assembly sheet50is referred to as a first direction X, and a direction that is parallel to the surface of the board assembly sheet50and intersects with the first direction X is referred to as a second direction Y. In the present embodiment, the first direction X and the second direction Y are orthogonal to each other.

The driving device130is arranged above the transported board assembly sheet50. This driving device130includes a support member131and a guide member132. The guide member132is provided at the support member131to extend in the first direction X. The first imaging device121and the second imaging device122are provided in parallel to each other to be arranged in the first direction X by the guide member132. Further, the first light source111and the second light source112are arranged in parallel to each other to be arranged in the first direction X by the guide member132. The first light source111, the second light source112, the first imaging device121and the second imaging device122are configured to be integrally and simultaneously movable in the first direction X along the guide member132.

The first light source111emits first light having a first wavelength distribution. In the present embodiment, the first light source111is a monochromatic light source that generates monochromatic light. The first light has a peak wavelength in a wavelength region from 400 nm to 500 nm or a wavelength from 630 nm to 850 nm, for example. As the first light source111, a plurality of light-emitting diodes that emit violet light or blue light may be used, or a plurality of light-emitting diodes that emit red light or infrared-light may be used, for example. The second light source112emits second light having a second wavelength distribution. In the present embodiment, the second light source112is a white light source that generates white light, for example. The second light has a wavelength component ranging from 380 nm to 780 nm, for example. As the second light source112, a plurality of light-emitting diodes that emit white light are used. The first light source111and the second light source112are turned on when the first imaging device121and the second imaging device122are operated.

In the present embodiment, the first imaging device121is a monochromatic line camera that uses a monochromatic line sensor such as a one dimensional CCD (Charge-Coupled Device), and has a plurality of linearly arranged pixels. The number of pixels of the first imaging device121is 16,384 for example, and a pixel size is 5 μm×5 μm, for example. The first imaging device121is arranged such that the plurality of pixels are arranged in the second direction Y. Further, in the present embodiment, the second imaging device122is a color line camera using a color line sensor such as the one dimensional CCD, and has a plurality of pixels linearly arranged in four rows. The number of pixels of the second imaging device122is 4×16384, for example, and a pixel size is 5 μm×5 μm, for example. The second imaging device122is arranged such that the plurality of pixels in each row are arranged in the second direction Y.

The control device150is constituted by a CPU (Central Control Processing Unit) and a semiconductor memory, for example. This control device150controls operations of the feed roll20, the wind-up roll30, the first light source111, the second light source112, the first imaging device121, the second imaging device122, the driving device130and the display device140, and functions as a determinator that performs automatic optical inspection based on a first image and a second image, described below.

The first light source111emits the first light as incident light31itowards the board assembly sheet50. Thus, the incident light31iis incident on the surface of the board assembly sheet50. Reflected light31rfrom the board assembly sheet50is incident on the first imaging device121. The second light source112emits the second light as the incident light32itowards the board assembly sheet50. Thus, the incident light32iis incident on the surface of the board assembly sheet50. The reflected light32rfrom the board assembly sheet50is incident on the second imaging device122.

FIG. 3is a schematic plan view of the board assembly sheet50in the inspection process. In the inspection process, the board assembly sheet50is temporarily stopped. In this state, on the board assembly sheet50ofFIG. 3, a linear first imaging region51that can be imaged by the first imaging device121ofFIG. 2is set, and a linear second imaging region52that can be imaged by the second imaging device122is set. The first imaging region51and the second imaging region52extend in the second direction Y. The first imaging region51and the second imaging region52are close to each other in the first direction X. The first imaging region51is irradiated with the first light by the first light source111, and the second imaging region52is irradiated with the second light by the second light source112. The first light and the second light have linear cross sections that extend in the second direction Y. The first imaging device121receives reflected light from the first imaging region51, and the second imaging device122receives reflected light from the second imaging region52.

In this state, the first light source111, the second light source112, the first imaging device121and the second imaging device122are simultaneously moved in the first direction X by the driving device130. Thus, the first and second imaging regions51,52on the board assembly sheet50are moved in the first direction X by a constant distance. In this case, a rectangular region of the board assembly sheet50is scanned by the respective first and second light having linear cross sections, and imaged by the first and second imaging devices121,122. The rectangular region scanned by the first and second light is referred to as an inspection subject region (a region to be inspected)53. In the present embodiment, the inspection subject region53includes a plurality of printed circuit boards10.

As a result of the above-mentioned operation, a monochromatic image of the inspection subject region53of the board assembly sheet50is acquired by the first imaging device121, and a color image of the inspection subject region53of the board assembly sheet50is acquired by the second imaging device122. Hereinafter, the monochromatic image acquired by the first imaging device121is referred to as a first image, and the color image acquired by the second imaging device122is referred to as a second image.

In the present embodiment, the control device150controls the first light source111, the second light source112, the first imaging device121, the second imaging device122and the driving device130such that the first and second images of the same inspection subject region53of the board assembly sheet50are acquired.

The cover insulating layer16of the printed circuit board10ofFIGS. 1A to 1Dtransmits a large part of the first light, and the large part of the first light is reflected by the wiring traces13. Part of the first light is reflected by a surface of the cover insulating layer16on the wiring traces13. Therefore, in the first image, a state of the wring traces13in the printed circuit board10is mainly clearly shown, and a state of the surface of the printed circuit board10is lightly shown. On the one hand, a large part of the second light is reflected by the surface of the cover insulating layer16on the wiring traces13. The cover insulating layer16of the printed circuit board10transmits part of the second light, and the part of the second light is reflected by the wiring traces13. Therefore, in the second image, a state of the surface (an appearance) of the printed circuit board10is mainly clearly shown, and a state of the wiring traces13in the printed circuit board10is lightly shown.

FIGS. 4A and 4Bare diagrams showing one example of the first image and the second image respectively acquired by the first imaging device121and the second imaging device122.FIGS. 5A and 5Bare diagrams showing another example of the first image and the second image respectively acquired by the first imaging device121and the second imaging device122.FIGS. 4A and 4BandFIGS. 5A and 5Bshow part of the first and second images.

In the example of the first image ofFIG. 4A, the wiring traces13are clearly shown, and a defect D is also shown. In the example of the second image ofFIG. 4B, the wiring traces13are lightly shown, and the defect D is also shown.

In the example of the first image ofFIG. 5A, the wiring traces are clearly shown, and a pad18exposed on the surface of the printed circuit board10is also shown. In the example of the second image ofFIG. 5B, the pad18exposed on the surface of the printed circuit board10is clearly shown, and the wiring traces13are lightly shown.

In this manner, the first and second light respectively have first and second wavelength distributions different from each other, so that the first and second images show states of portions different from each other in a thickness direction of the printed circuit board10. In the present embodiment, the first image mainly shows a state of the inside of the wiring traces13of the printed circuit board10, and the second image mainly shows a state of the surface of the printed circuit board10.

(3) Inspecting Process of Printed Circuit Board

FIG. 6is a flow chart showing the inspecting process of the printed circuit board10according to the present embodiment.

First, the control device150ofFIG. 2temporarily stops the movement of the board assembly sheet50by stopping the rotation of each of the feed roll20and the wind-up roll30(step S1). In this state, the control device150turns on the first light source111and the second light source112(step S2). Further, the control device150controls the driving device130such that the first light source111, the second light source112, the first imaging device121and the second imaging device122are moved in the first direction X. At this time, the first imaging device121and the second imaging device122respectively produce the first image and the second image (step S3). As described above, in the present embodiment, a monochromatic image and a color image of the same inspection subject region53of the board assembly sheet50are acquired as the first and second images.

Next, the control device150determines presence and absence of a defect by the automatic optical inspection based on the first image and the second image (step S4). Thereafter, the control device150arranges and displays the first image and the second image on the screen of the display device140. An operator verifies a defect by visually observing the first and second images including the defect detected in the automatic optical inspection (step S5).

FIG. 7is a diagram showing an example of the first and second images shown on the screen. As shown inFIG. 7, the monochromatic first image V1and the color second image V2are arranged and displayed on the screen. In the example ofFIG. 7, the defect D is shown on both of the first image V1and the second image V2. In this case, it is considered that the defect D is caused by contamination.

When it is confirmed that a defect is present in the printed circuit board by the automatic optical inspection and visual observation, it is determined that the printed circuit board is defective. On the one hand, when it is confirmed that a defect is absent from the printed circuit board by the automatic optical inspection and the visual observation, it is determined that the printed circuit board is non-defective.

(4) Effects of Embodiment

In the manufacturing method according to the present embodiment, the first image showing the state of the inside of the printed circuit board10and the second image showing the state of the surface of the printed circuit board10are simultaneously acquired in the inspection process. Therefore, a time period required for the inspection of the printed circuit board10can be shortened.

Further, the automatic optical inspection can be performed based on the monochromatic first image showing the state of the inside of the printed circuit board10, and the color second image showing the state of the surface of the printed circuit board10, whereby the presence and absence of a defect of the printed circuit board10can be determined with high accuracy. Further, a defect that is not detected from only the first image can be detected.

Further, it is possible to verify the defect with high accuracy by visually observing the monochromatic first image showing the state of the inside of the printed circuit board10, and the color second image showing the state of the surface of the printed circuit board10. Further, the defect at the surface of the printed circuit board10can be visually detected.

Further, a monochromatic light source is used as the first light source111, and a white light source is used as the second light source112, so that monochromatic light is incident on the first imaging device121, and white light is incident on the second imaging device122. In this case, even when the color line camera is used as the first imaging device121, a monochromatic image can be acquired by the first imaging device121, for example. Therefore, flexibility of selection of types of the first imaging device121increases.

Further, the first light source111, the second light source112, the first imaging device121, and the second imaging device122are arranged on the same side with respect to the printed circuit board10. Thus, it is possible to simultaneously acquire the first and second images without complicating the arrangement of the first light source111, the second light source112, the first imaging device121and the second imaging device122.

Further, the monochromatic line camera and the color line camera are respectively used as the first imaging device121and the second imaging device122, so that it is possible to acquire the first and second images of the large inspection subject region53without increasing the size of each of the first imaging device121and the second imaging device122.

Further, the first and second images are arranged and displayed, so that the operator can accurately verify the defect by comparing the first and second images to each other. Further, the operator can find a defect that is difficult to be detected by only one of the first and second images.

(5) Other Embodiments

While the first light source111, the second light source112, the first imaging device121and the second imaging device122are moved in order to acquire the first and second images in the above-mentioned embodiment, the board assembly sheet50may be moved with the first light source111, the second light source112, the first imaging device121and the second imaging device122being still.

While the line camera is used as each of the first imaging device121and the second imaging device122in the above-mentioned embodiment, an area camera using an area sensor such as a two-dimensional CCD may be used as each of the first imaging device121and the second imaging device122. In this case, it is possible to acquire the first and second images without moving the first light source111, the second light source112, the first imaging device121and the second imaging device122.

While the automatic optical inspection is performed based on the first and second images in the above-mentioned embodiment, the automatic optical inspection may be performed by only the first image. While verification of a defect is performed by visual observation of each of the first and second images in the above-mentioned embodiment, the defect may be verified by visual observation of only the second image.

While the first light is monochromatic light and the second light is white light in the above-mentioned embodiment, the first light and the second light may be monochromatic light having different wavelength distributions. For example, monochromatic light having a peak wavelength in a wavelength region from 400 nm to 500 nm may be used as the first light, and monochromatic light having a peak wavelength in a wavelength region from 630 nm to 850 nm may be used as the second light.

While a monochromatic light source that generates monochromatic light having a peak wavelength in the wavelength region from 400 nm to 500 nm or the wavelength region from 630 nm to 850 nm is used as the first light source111in the above-mentioned embodiment, the first light source111may selectively generate a plurality of types of light having peak wavelengths in different wavelength regions. For example, the first light source111may include a plurality of light emitting diodes that emit violet light or blue light and a plurality of light emitting diodes that emit red light or infrared light. In this case, the plurality of light-emitting diodes that emit violet light or blue light and the plurality of light-emitting diodes that emit red light or infrared light are selectively turned on according to a type of the printed circuit board10.

While the light-emitting diodes are used as each of the first light source111and the second light source112in the above-mentioned embodiment, other light-emitting devices such as laser diodes may be used as each of the first light source111and the second light source112.

The arrangement of the first and second light sources111,112and the first and second imaging devices121,122is not limited to the arrangement of the above-mentioned embodiment. The first and second light sources111,112may be arranged such that the first and second imaging regions51,52extend in the first direction X, and the first and second imaging devices121,122may be arranged to receive reflected light from the first and second imaging regions51,52extending in the first direction X. In this case, the first and second light sources111,112and the first and second imaging devices121,122are simultaneously moved in the second direction Y. Thus, the first and second imaging regions51,52on the board assembly sheet50are moved in the second direction Y by a constant distance.

As a material for the metal support substrate11, another metal or an alloy such as a42alloy, aluminum, copper-beryllium or phosphor bronze, or the like may be used instead of stainless. As a material for the base insulating layer12, another synthetic resin such as polyamide imide, acryl, polyethersulfone, polyethylene terephthalate (PET), polyethylenenaphthalate, polyvinyl chloride, or epoxy may be used instead of polyimide.

As a material for the conductor traces14, another metal such as gold (Au) or aluminum, or an alloy such as a copper alloy or an aluminum alloy may be used instead of copper. As a material for the metal cover layer15, another metal such as tin or an alloy may be used instead of nickel.

As a material for the cover insulating layer16, another synthetic resin such as polyamide imide, acryl, polyethersulfone, polyethylene terephthalate (PET), polyethylenenaphthalate, polyvinyl chloride, or epoxy may be used instead of polyimide.

The printed circuit board being a subject of the inspection is not limited to a suspension board having a circuit and may be another printed circuit board such as a flexible printed circuit board or a COF (Chip on Film) substrate.

INDUSTRIAL APPLICABILITY

The present invention can be utilized for manufacturing, inspecting or the like of printed circuit boards.