Inspection equipment and inspection method

Abstract

This allows for detailed assessment of the condition of through-vias during inspection of substrates containing through-vias. [Solution] The inspection device includes a first light source provided on the side of the first surface of the substrate, a first lens that outputs first parallel light obtained by making the light rays from the first light source parallel, a light receiving unit provided on the side of the second surface of the substrate opposite to the first surface, which receives first transmitted light obtained when the first parallel light passes through the through hole and outputs image data corresponding to the intensity of the received first transmitted light, and an information output unit that outputs information indicating the state of the through hole based on the image data. The direction of propagation of the parallel light is parallel to the depth direction of the through hole.

Description

[Technical Field]

[0001] The disclosed technology relates to inspection equipment and inspection methods. [Background technology]

[0002] The following technologies are known for inspecting printed circuit boards. Patent Document 1 describes an inspection device for inspecting through-hole clogging in a printed circuit board having wiring patterns and through-holes. This inspection device includes: a reading means that reads an image of the printed circuit board to obtain a pattern image signal corresponding to an image of the wiring pattern and having binary information, and a hole image signal corresponding to an image of the through-hole and having binary information; a first calculation means that calculates the logical OR of the pattern image signal and the hole image signal to obtain a first image signal corresponding to the logical OR; an enlargement means that obtains an enlarged hole image signal by enlarging the hole image signal by a predetermined number of pixels; a second calculation means that calculates the logical AND of the inverted signal of the first image signal and the enlarged hole image signal to obtain a second image signal corresponding to the logical AND; and a determination means that compares the second image signal with an operator containing a predetermined number of pixels and outputs a determination signal indicating hole clogging when the image area represented by the second image signal encompasses the operator. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-322523 [Overview of the project] [Problems that the invention aims to solve]

[0004] Multilayer printed circuit boards having multiple wiring layers are equipped with through-vias for interlayer connections of the wiring. Through-vias are formed by creating through-holes in the substrate and forming a conductive film made of a metal such as Cu on the inner wall of the through-holes by a plating process.

[0005] If foreign matter remains inside through-vias, the acid used in the cleaning process may not be completely removed by subsequent pure water washing and may remain inside the through-vias, potentially corroding the conductor film inside the through-vias and causing electrical connection failures. For this reason, through-vias are often treated to prevent the retention of foreign matter inside them.

[0006] However, if the inner diameter of the through-via is very small (e.g., 0.2 mm or less), it becomes difficult to remove foreign matter from inside the through-via. For this reason, before acid cleaning, measures are sometimes taken to seal the through-via by some means to prevent the acid from entering the inside of the through-via. Solder resist, which is applied to the surface of the printed circuit board, can be used as the material to seal the through-via. By using solder resist, it becomes possible to fill the through-via with solder resist during the existing solder resist application process. This makes it possible to reduce manufacturing costs compared to sealing the through-via with other materials.

[0007] Insufficient filling of through-vias with solder resist can lead to the aforementioned problem of acid residue within the through-vias; therefore, it is necessary to inspect the solder resist filling state within the through-vias. While the technology described in Patent Document 1 can determine whether or not through-holes are clogged, it cannot determine the state in which the filling material within the through-vias is packed.

[0008] The disclosed technology was developed in view of the above points and aims to enable detailed understanding of the condition of through-vias in the inspection of substrates having through-vias. [Means for solving the problem]

[0009] An inspection apparatus according to the disclosed technique is an inspection apparatus for a substrate having a through hole, comprising: a first light source provided on a first surface side of the substrate; a first lens that outputs first parallel light obtained by collimating light rays from the first light source; a light receiving unit provided on a second surface side opposite to the first surface of the substrate, configured to receive first transmitted light obtained by transmitting the first parallel light through the through hole, and output image data corresponding to an intensity of the received first transmitted light; and an information output unit configured to output information indicating a state of the through hole based on the image data. A traveling direction of the parallel light is parallel to a depth direction of the through hole.

[0010] The information output unit may output information indicating a thickness of a substance filled inside the through hole based on the image data. The information output unit may derive the thickness of the substance filled inside the through hole based on data indicating a relationship between the image data and the thickness of the substance filled inside the through hole. The information output unit may output information indicating at least one of an area and a volume of an unfilled region in the through hole based on the image data.

[0011] The inspection apparatus may further comprise a moving mechanism that moves a relative position between the substrate and an optical system including the light source, the lens, and the light receiving unit. The first light source may be a laser light source that outputs light of a single wavelength.

[0012] The inspection device may include a second light source that outputs light of a single wavelength different from the wavelength of light output from the first light source, a second lens that outputs second parallel light obtained by making the light rays from the second light source parallel, and an optical element that aligns the optical axes of the first parallel light and the second parallel light incident from different directions and guides the first parallel light and the second parallel light to the substrate such that the aligned optical axes are parallel to the depth direction of the through hole. The light receiving unit may receive first transmitted light obtained when the first parallel light passes through the through hole and second transmitted light obtained when the second parallel light passes through the through hole, and output first image data corresponding to the intensity of the first transmitted light and second image data corresponding to the intensity of the second transmitted light. The information output unit may output information indicating the state of the through hole based on the comparison result of the first image data and the second image data.

[0013] The inspection method relating to the disclosed technology is an inspection method for a substrate having a through hole, comprising: irradiating the through hole with first parallel light whose direction of propagation is parallel to the depth direction of the through hole; acquiring image data corresponding to the intensity of first transmitted light obtained by the first parallel light passing through the through hole; and acquiring information indicating the state of the through hole based on the image data. [Effects of the Invention]

[0014] According to the inspection apparatus relating to the disclosed technology, it becomes possible to understand the detailed condition of through-vias when inspecting a substrate having through-vias. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows an example of the configuration of an inspection device according to an embodiment of the disclosed technology. [Figure 2] This figure shows an example of the configuration of an inspection apparatus according to another embodiment of the disclosed technology. [Figure 3] This is a map showing the thickness distribution of solder resist according to an embodiment of the disclosed technology. [Figure 4]This figure shows an example of the configuration of an inspection apparatus according to another embodiment of the disclosed technology. [Modes for carrying out the invention]

[0016] Hereinafter, an example of an embodiment of the disclosed technology will be described with reference to the drawings. In each drawing, identical or equivalent components and parts will be given the same reference numerals, and redundant descriptions will be omitted.

[0017] [First Embodiment] Figure 1 shows an example of the configuration of an inspection apparatus 10 according to an embodiment of the disclosed technology. The inspection apparatus 10 inspects a printed circuit board 30. The printed circuit board 30 has a plurality of wirings 32 and through vias 33 laminated in a substrate 31. Interlayer connections of the wirings 32 are made by the through vias 33. The through vias 33 are formed by forming through holes in the substrate 31 and forming a conductive film made of a metal such as Cu on the inner wall of the through holes by a plating process. Solder resist 34 is formed on both sides of the substrate 31. Solder resist 34 is filled inside the through vias 33. By sealing the openings of the through vias 33 with solder resist 34, it is possible to prevent acid from entering the through vias 33 during the cleaning process.

[0018] If the solder resist 34 is not sufficiently filled into the through via 33, the problem of acid residue within the through via 33 will occur. The inspection device 10 inspects the filling state of the solder resist 34 within the through via 33.

[0019] The inspection device 10 includes an optical system 20 comprising a light source 21, a lens 22, and a light receiving unit 23, a moving mechanism 24, and an information output unit 25. The light source 21 and lens 22 are provided on the side of the first surface S1 of the printed circuit board 30, and the light receiving unit 23 is provided on the side of the second surface S2 of the printed circuit board 30 opposite to the first surface S1.

[0020] The light source 21 is, for example, a laser light source, and outputs light of a single wavelength. The wavelength of the laser light is set based on the transmittance of the solder resist 34 and the spectral sensitivity of the light receiving unit 23. A white light source can also be used as the light source 21. The light source 21 is an example of the "first light source" in the disclosed technology.

[0021] The lens 22 is provided between the light source 21 and the printed circuit board 30. The lens 22 is a collimating lens, and outputs collimated light L obtained by collimating the light beam output from the light source 21 P1 . The lens 22 may be constituted by a combination of a plurality of lenses. The collimated light L output from the lens 22 P1 the light source 21 and the lens 22 are disposed such that the traveling direction of coincides with the depth direction of the through via 33 (the direction perpendicular to the printed circuit board 30). Further, the relative position between the inspection apparatus 10 and the printed circuit board 30 is determined by the moving mechanism 24 such that the irradiation range of the collimated light L P1 includes one or two or more through vias 33. FIG. 2 shows the collimated light L P1 is a diagram illustrating a case where a plurality of through vias 33 are included in the irradiation range of.

[0022] The collimated light L P1 is transmitted through the through via 33, and the transmitted light L obtained thereby t1 is received by the light receiving unit 23. The light receiving unit 23 has a plurality of pixels, and outputs image data D corresponding to the intensity of the transmitted light L t1 . The light receiving unit 23 outputs image data D representing the intensity of the transmitted light L t1 in, for example, 256 gradations. The light receiving unit 23 may be a line scan camera that outputs a one-dimensional image of the transmitted light L t1 , or may be an area scan camera that outputs a two-dimensional image of the transmitted light L t1 .[[$END]]

[0023] Light transmitted through the inside of the through via 33 is attenuated by the solder resist 34 filled inside the through via 33. The amount of attenuation increases as the thickness of the solder resist 34 filled inside the through via 33 increases, and the transmitted light L t1The intensity of the light decreases. Therefore, the image data D output from the light receiving unit 23 reflects the thickness of the solder resist 34 filled inside the through via 33. Furthermore, the distribution of the pixel values ​​in the image data D makes it possible to understand the thickness distribution of the solder resist 34 filled inside the through via 33. Note that when nothing is filled inside the through via 33 and there is no attenuation, the transmitted light L t1 It is preferable to adjust the light-receiving sensitivity of the light-receiving unit 23 so that the corresponding pixel value is, for example, 250 or more and 255 or less.

[0024] The moving mechanism 24 illuminates all through vias 33 provided on the printed circuit board 30 with parallel light L P1 The relative position of the optical system 20 and the printed circuit board 30 is moved so that it can scan. The moving mechanism 24 may move either the optical system 20 or the printed circuit board 30, or it may move both.

[0025] The information output unit 25 is composed of a computer including a CPU (Central Processing Unit) and memory, and outputs information indicating the state of the through-via 33 based on the image data D output from the light receiving unit 23. For example, the information output unit outputs information indicating the thickness of the solder resist 34 filled inside the through-via based on the image data D.

[0026] There is a correlation between the pixel values ​​of the image data D and the thickness of the solder resist 34 filling the through-via 33. Specifically, the thicker the solder resist 34 filling the through-via 33, the smaller the pixel values ​​of the image data D. The information output unit 25 has a conversion table 26 for converting the pixel values ​​of the image data D to the thickness of the solder resist 34, and derives the thickness of the solder resist 34 filling the through-via 33 by referring to the conversion table 26. Alternatively, a conversion formula can be used to convert the pixel values ​​of the image data D to the thickness of the solder resist 34 instead of the conversion table 26.

[0027] The information output unit 25 may output a map 40 showing the thickness distribution of the solder resist 34 filled inside the through via 33, as illustrated in Figure 3, based on the image data D. The map 40 may, for example, represent the thickness of the solder resist 34 for each part of the through via 33 in grayscale. The information output unit 25 may output statistical values ​​such as maximum value, minimum value, mean value, and standard deviation for the thickness of the solder resist 34 filled inside the through via 33, based on the image data D. The information output unit 25 may output a pass / fail judgment result for the thickness of the solder resist 34 derived based on the image data D. The information output unit 25 may output information showing at least one of the area and volume of the unfilled region of the through via 33, based on the image data D. In this case, for example, a region having a pixel value of 250 or more and 255 or less may be considered as the unfilled region of the through via 33.

[0028] As described above, the inspection apparatus 10 according to the embodiment of the disclosed technology is for inspecting a printed circuit board 30 having through vias 33, and includes a light source 21 provided on the first surface S1 side of the printed circuit board 30 and parallel light L formed by aligning the light rays from the light source 21. P1 A lens 22 that outputs light, and a parallel light source L are provided on the side of the second surface S2 opposite to the first surface S1 of the printed circuit board 30. P1 Transmitted light L obtained by passing through the through via 33 t1 The light is received, and the received transmitted light L t1 It has a light receiving unit 23 that outputs image data D corresponding to the intensity of the parallel light L, and an information output unit 25 that outputs information indicating the state of the through via 33 based on the image data D. P1 The direction of travel is parallel to the depth direction of the through via 33.

[0029] According to the inspection apparatus 10 according to an embodiment of the disclosed technology, the information output unit 25 outputs parallel light L P1 Transmitted light L obtained by passing through the through via 33 t1 Based on image data D corresponding to the intensity, information indicating the state of the through-via 33 is output, making it possible to understand the detailed state of the through-via 33.

[0030] Furthermore, parallel light L whose direction of travel is parallel to the depth direction of the through via 33 P1 By using this method, the transmitted light L is increased compared to when using diffused light. t1 This increases the intensity of the signal, allowing the amount of light received by the light-receiving unit 23 to be increased. As a result, it becomes possible to obtain image data D with high clarity, and the accuracy of the information indicating the state of the through-via 33 can be improved.

[0031] [Second Embodiment] Figure 4 shows an example of the configuration of an inspection apparatus 10A according to a second embodiment of the disclosed technology. The inspection apparatus 10A differs from the inspection apparatus 10 according to the first embodiment described above (see Figure 1) in that it further includes a light source 27, a lens 28, and an optical element 29.

[0032] Light source 27 is, for example, a laser light source, which outputs light of a single wavelength different from the wavelength of light output from light source 21. Light source 27 is an example of a “second light source” in the disclosed art. Lens 28 is a collimating lens, which parallelizes the light rays output from light source 27 to produce parallel light L P2 Output. Parallel light L output from lens 28. P2 The direction of travel is the parallel light L output from lens 22. P1 The light source 27 and lens 28 are positioned perpendicular to each other.

[0033] The optical element 29 emits parallel light L P1 and parallel light L P2 It is positioned at the intersection of the lines. The optical element 29 receives parallel light L incident from different directions. P1 and parallel light L P2 The optical axes are aligned, and the aligned optical axes are made parallel to the depth direction of the through via 33, so that parallel light L P1 and parallel light L P2 The light is guided to the printed circuit board 30. The optical element 29 may be, for example, a dichroic prism. The optical element 29 guides parallel light L P1 and parallel light L P2 Reflective surface S inclined with respect to both directions of travelr It has a parallel light L P1 is the reflective surface S r While light L is transmitted through, parallel light L P2 is the reflective surface S r By being reflected and having its direction of propagation bent, parallel light L P1 and parallel light L P2 The optical axes align.

[0034] The light receiving unit 23 receives parallel light L P1 Transmitted light L obtained by passing through the through via 33 t1 and parallel light L P2 Transmitted light L obtained by passing through the through via 33 t2 Each receives light. The light receiving unit 23 receives transmitted light L t1 Image data D1 and transmitted light L according to their intensity t2 Image data D2 corresponding to the intensity of the light is output. In other words, the light receiving unit 23 can detect the intensity of two lights with different wavelengths for each wavelength and generate image data for each wavelength. Therefore, it is possible to output light from light sources 21 and 27 simultaneously.

[0035] The information output unit 25 outputs information indicating the thickness of the solder resist 34 filling the inside of the through-via, based on the image data D1 and D2, similar to the first embodiment described above. The information output unit 25 in this embodiment outputs further information indicating the state of the through-via 33 based on the comparison result of image data D1 and image data D2.

[0036] If the solder resist 34 filling the through-via 33 contains air bubbles or cracks, light passing through the solder resist 34 will be refracted at the location of the air bubbles or cracks. Since the angle of refraction differs depending on the wavelength of light, if the solder resist 34 filling the through-via 33 contains air bubbles or cracks, the distribution of pixel values ​​in image data D1 and the distribution of pixel values ​​in image data D2 will be different. Therefore, by comparing image data D1 and image data D2, it is possible to determine whether or not the solder resist 34 filling the through-via 33 contains air bubbles or cracks.

[0037] For example, the information output unit 25 may determine that air bubbles are present in the solder resist 34 filling the through via 33 if the average value of pixel values ​​in image data D1 is greater than the average value of pixel values ​​in image data D2. The information output unit 25 may also determine that cracks are present in the solder resist 34 filling the through via 33 if the average value of pixel values ​​in image data D1 is less than the average value of pixel values ​​in image data D2. Furthermore, the information output unit 25 may determine that neither air bubbles nor cracks are present in the solder resist 34 filling the through via 33 if the difference between the average value of pixel values ​​in image data D1 and the average value of pixel values ​​in image data D2 is less than or equal to a threshold.

[0038] Furthermore, the information output unit 25 may determine whether or not the solder resist 34 filling the through via 33 contains air bubbles or cracks based on the differential image data, which is the difference between image data D1 and image data D2. In this case, the information output unit 25 may perform the above determination using a determination model learned by machine learning.

[0039] As described above, according to the inspection apparatus 10A of the second embodiment, since multiple lights with different wavelengths are used as the light transmitted through the through via 33, it becomes possible to obtain information about the state of the through via 33 that is difficult to obtain with a single wavelength. It is also possible to use three or more lights with different wavelengths.

[0040] In the above description, the example given is that the inspection devices 10 and 10A inspect a printed circuit board 30 having through-vias 33, but the disclosed technology can be applied to any substrate having through-holes. Furthermore, the material filling the inside of the through-holes only needs to be light-transmitting and is not limited to solder resist.

[0041] The following additional information is disclosed regarding the embodiments described above. (Note 1) An inspection apparatus for substrates having through holes, A first light source provided on the first surface side of the substrate, A first lens that outputs first parallel light by making the light rays from the first light source parallel, A light receiving unit is provided on the second surface of the substrate opposite to the first surface, which receives the first transmitted light obtained when the first parallel light passes through the through hole, and outputs image data corresponding to the intensity of the received first transmitted light. It has an information output unit that outputs information indicating the state of the through hole based on the image data, The direction of propagation of the parallel light is parallel to the depth direction of the through hole. Inspection device.

[0042] (Note 2) The information output unit outputs information indicating the thickness of the material filling the inside of the through hole, based on the image data. The inspection device described in Appendix 1.

[0043] (Note 3) The information output unit derives the thickness of the material filling the inside of the through hole based on the data showing the relationship between the image data and the thickness of the material filling the inside of the through hole. The inspection device described in Appendix 2.

[0044] (Note 4) The information output unit outputs information indicating at least one of the area and volume of the unfilled region of the through-hole, based on the image data. The inspection device described in any one of the appendices 1 to 3.

[0045] (Note 5) The optical system, which includes the light source, the lens, and the light-receiving unit, has a moving mechanism that moves the relative position between the optical system and the substrate. The inspection device described in any one of the appendices 1 through 4.

[0046] (Note 6) The first light source is a laser light source that outputs light of a single wavelength. The inspection device described in any one of the appendices 1 through 5.

[0047] (Note 7) A second light source that outputs light of a single wavelength different from the wavelength of light output from the first light source, A second lens that outputs a second parallel light beam formed by aligning the light rays from the second light source, An optical element that aligns the optical axes of the first parallel light and the second parallel light incident from different directions and guides the first parallel light and the second parallel light to the substrate such that the aligned optical axes are parallel to the depth direction of the through hole, It has, The light-receiving unit receives the first transmitted light obtained when the first parallel light passes through the through-hole and the second transmitted light obtained when the second parallel light passes through the through-hole, respectively, and outputs first image data corresponding to the intensity of the first transmitted light and second image data corresponding to the intensity of the second transmitted light. The information output unit outputs information indicating the state of the through hole based on the comparison result between the first image data and the second image data. The inspection device described in any one of the appendices 1 through 6.

[0048] (Note 8) A method for inspecting a substrate having through holes, A first parallel beam of light, whose direction of propagation is parallel to the depth direction of the through-hole, is shone into the through-hole. Image data corresponding to the intensity of the first transmitted light obtained when the first parallel light passes through the through hole is acquired. Based on the aforementioned image data, information indicating the state of the through-hole is acquired. Testing method. [Explanation of Symbols]

[0049] 10, 10A Inspection Device 20 Optical system 21, 27 light source 22, 28 lenses 23 Light receiving section 24 Moving mechanism 25 Information Output Unit 26 Conversion Table 29 Optical elements 30 Printed circuit boards 31 Base material 32 Wiring 33 Through vias 34 Solder Resist

Claims

1. An inspection apparatus for substrates having through holes, A first light source provided on the first surface side of the substrate, A first lens that outputs first parallel light by making the light rays from the first light source parallel, A light receiving unit is provided on the second surface of the substrate opposite to the first surface, which receives the first transmitted light obtained when the first parallel light passes through the through hole, and outputs image data corresponding to the intensity of the received first transmitted light. It has an information output unit that outputs information indicating the state of the through hole based on the image data, The direction of propagation of the parallel light is parallel to the depth direction of the through hole. Inspection device.

2. The information output unit outputs information indicating the thickness of the material filling the inside of the through hole, based on the image data. The inspection apparatus according to claim 1.

3. The information output unit derives the thickness of the material filling the inside of the through hole based on the data showing the relationship between the image data and the thickness of the material filling the inside of the through hole. The inspection apparatus according to claim 2.

4. The information output unit outputs information indicating at least one of the area and volume of the unfilled region of the through hole, based on the image data. The inspection apparatus according to claim 1.

5. The optical system, which includes the light source, the lens, and the light-receiving unit, has a moving mechanism that moves the relative position between the optical system and the substrate. The inspection apparatus according to claim 1.

6. The first light source is a laser light source that outputs light of a single wavelength. The inspection apparatus according to claim 1.

7. A second light source that outputs light of a single wavelength different from the wavelength of light output from the first light source, A second lens that outputs a second parallel light beam formed by aligning the light rays from the second light source, An optical element that aligns the optical axes of the first parallel light and the second parallel light incident from different directions and guides the first parallel light and the second parallel light to the substrate such that the aligned optical axes are parallel to the depth direction of the through hole, It has, The light receiving unit receives the first transmitted light obtained when the first parallel light passes through the through hole and the second transmitted light obtained when the second parallel light passes through the through hole, and outputs first image data corresponding to the intensity of the first transmitted light and second image data corresponding to the intensity of the second transmitted light. The information output unit outputs information indicating the state of the through hole based on the comparison result between the first image data and the second image data. The inspection apparatus according to claim 1.

8. A method for inspecting a substrate having through holes, A first parallel beam of light, whose direction of propagation is parallel to the depth direction of the through-hole, is shone into the through-hole. Image data corresponding to the intensity of the first transmitted light obtained when the first parallel light passes through the through hole is acquired. Based on the aforementioned image data, information indicating the state of the through-hole is acquired. Testing method.

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