Wiring circuit board

Abstract

This invention provides a wiring circuit board that can improve the accuracy of reading the shape of conductor patterns using image recognition. [Solution] The wiring circuit board 1 comprises a metal support layer 2, a metal layer 3, a first insulating layer 4, and a conductor pattern 5. The conductor pattern 5 has a first surface S11 that contacts one side surface S3 of the first insulating layer 4, and a second surface S12 that is positioned on the opposite side of the first insulating layer 4 from the first surface S11. The brightness L of one side surface S3 of the metal layer 3 * The value is 89.0 or less, and the brightness of the second surface S12 of the conductor pattern 5 is 155.0 or more.

Description

[Technical Field]

[0001] This invention relates to a wiring circuit board. [Background technology]

[0002] Conventionally, a wiring circuit board is known that comprises an insulating layer, a conductive layer disposed on one surface of the insulating layer, a metal support disposed on the other side of the insulating layer, and a metal thin film disposed between the insulating layer and the metal support (see, for example, Patent Document 1 below). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-8277 [Overview of the project] [Problems that the invention aims to solve]

[0004] In a wiring circuit board as described in Patent Document 1, if the shape of the conductor layer is to be inspected by image recognition, the accuracy of reading the shape of the conductor layer may decrease due to reflected light from the metal thin film.

[0005] This invention provides a wiring circuit board that can improve the accuracy of reading the shape of a conductor pattern using image recognition. [Means for solving the problem]

[0006] The present invention [1] comprises a metal support layer, a metal layer disposed on one side surface of the metal support layer in the thickness direction, an insulating layer disposed on one side surface of the metal layer in the thickness direction, and a conductor pattern disposed on one side surface of the insulating layer in the thickness direction, the conductor pattern having a first surface in contact with the one side surface of the insulating layer and a second surface disposed on the opposite side of the insulating layer to the first surface in the thickness direction, wherein the brightness L of the one side surface of the metal layer in the thickness direction * The wiring circuit board includes a circuit board in which the luminance of the second surface of the conductor pattern is 155.0 or higher, and the luminance of the second surface of the conductor pattern is 89.0 or lower.

[0007] With this configuration, the brightness L of one side surface of the metal layer * The value is 89.0 or less, and the brightness of the second surface of the conductor pattern is 155.0 or more.

[0008] Therefore, in image recognition, it is possible to ensure contrast between the metal layer and the conductive pattern.

[0009] As a result, it becomes possible to improve the accuracy of reading the shape of conductor patterns using image recognition.

[0010] The present invention [2] includes the wiring circuit board of [1], wherein the arithmetic mean roughness Ra of the second surface of the conductor pattern is 6.4 nm or less.

[0011] This configuration makes it possible to suppress the scattering of the illumination light from the inspection system on the second surface.

[0012] As a result, a better contrast can be ensured between the metal layer and the conductive pattern in image recognition.

[0013] The present invention [3] includes the wiring circuit board of the above [1] or [2], wherein the conductor pattern comprises a conductor layer and a covering metal layer covering the conductor layer, and the covering metal layer has the second surface.

[0014] The present invention [4] includes the wiring circuit board of [3] above, wherein the coated metal layer is a nickel plating layer.

[0015] The present invention [5] includes the wiring circuit board of [4] above, wherein the thickness of the coated metal layer is 45.0 nm or more.

[0016] The present invention [6] includes the wiring circuit board of any one of [1] to [5] above, wherein the metal layer is made of copper.

[0017] The present invention [7] includes the wiring circuit board of any one of [1] to [6] above, wherein the thickness of the insulating layer is 50 μm or less.

Advantages of the Invention

[0018] According to the wiring circuit board of the present invention, it is possible to improve the reading accuracy of the shape of the conductor pattern by image recognition.

Brief Description of the Drawings

[0019] <​​​​​​​​​​​​​​​​​​​​​​ As shown in Figure 1, the wiring circuit board 1 comprises a metal support layer 2, a metal layer 3, a first insulating layer 4 as an example of an insulating layer, a conductor pattern 5, and a second insulating layer 6.

[0021] (1) Metal support layer The metal support layer 2 supports the metal layer 3, the first insulating layer 4, the conductor pattern 5, and the second insulating layer 6. The entirety of the metal support layer 2 overlaps with the first insulating layer 4 in the thickness direction. The metal support layer 2 is made of a different metal from the metal layer 3 and the conductor pattern 5. Examples of materials for the metal support layer 2 include stainless steel and copper alloys. Preferably, the metal support layer 2 is made of a copper alloy.

[0022] (2) Metal layer The metal layer 3 is positioned on one side of the metal support layer 2 in the thickness direction. The metal layer 3 is positioned on one side surface S1 of the metal support layer 2 in the thickness direction. The metal layer 3 is positioned between the metal support layer 2 and the first insulating layer 4 in the thickness direction.

[0023] Brightness L of one side surface S2 of the metal layer 3 in the thickness direction * (JIS Z 8781-4) is 89.0 or less, preferably 82.0 or less, more preferably 81.0 or less, and more preferably 80.0 or less. Brightness L of one side surface S2 of the metal layer 3 in the thickness direction. * If the value is below the above upper limit, it is easier to ensure contrast between the metal layer 3 and the conductor pattern 5.

[0024] Brightness L of one side surface S2 of the metal layer 3 in the thickness direction * For example, it is 51.0 or higher. Brightness L of one side surface S2 of the metal layer 3 in the thickness direction. * It may be 65.0 or higher, or 70.0 or higher.

[0025] The metal layer 3 may have a conductive layer 31 and a protective metal layer 32. The metal layer 3 may also consist only of the conductive layer 31 without the protective metal layer 32. When the metal layer 3 consists only of the conductive layer 31 without the protective metal layer 32, the brightness L of one side surface S2 of the metal layer 3 in the thickness direction. * For example, it may be higher than 82.0, or 85.0 or higher.

[0026] The conductor layer 31 is positioned on one side surface S1 of the metal support layer 2 in the thickness direction. The conductor layer 31 is positioned between the metal support layer 2 and the protective metal layer 32 in the thickness direction. The conductor layer 31 is made of metal. Examples of metals include copper, silver, gold, iron, aluminum, chromium, and their alloys. The conductor layer 31 is preferably made of copper. If the metal layer 3 does not have a protective metal layer 32 and consists only of the conductor layer 31, the metal layer 3 is preferably made of copper. The conductor layer 31 is, for example, a plating layer.

[0027] The thickness of the conductive layer 31 is, for example, 1.0 μm to 15.0 μm, preferably 1.5 μm to 10.0 μm.

[0028] The protective metal layer 32 is disposed on one side surface of the conductor layer 31 in the thickness direction. The protective metal layer 32 covers the conductor layer 31. The protective metal layer 32 is disposed between the conductor layer 31 and the first insulating layer 4. The protective metal layer 32 protects the conductor layer 31. Examples of materials for the protective metal layer 32 include chromium, nickel, titanium, and alloys thereof. The protective metal layer 32 is preferably made of chromium. The protective metal layer 32 is, for example, a sputtering layer.

[0029] The thickness of the protective metal layer 32 is, for example, 30 nm to 100 nm, preferably 50 nm to 80 nm.

[0030] (4) First insulating layer The first insulating layer 4 is positioned on one side of the metal layer 3 in the thickness direction. The first insulating layer 4 is positioned on one side surface S2 of the metal layer 3 in the thickness direction. The first insulating layer 4 is positioned between the metal layer 3 and the conductor pattern 5 in the thickness direction. The first insulating layer 4 insulates the metal layer 3 from the conductor pattern 5. The first insulating layer 4 is made of a resin. Examples of resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. The first insulating layer 4 is preferably made of polyimide.

[0031] The thickness of the first insulating layer 4 is, for example, 50 μm or less, preferably 20 μm or less. When the thickness of the first insulating layer 4 is less than or equal to the above upper limit, the illumination light of the inspection system enters from one side of the first insulating layer 4, passes through the first insulating layer 4, and reaches the one-sided surface S2 of the metal layer 3. The illumination light that reaches the one-sided surface S2 of the metal layer 3 is reflected by the one-sided surface S2 of the metal layer 3. Here, when the thickness of the first insulating layer 4 is less than or equal to the above upper limit, the illumination light (incident light) that enters the first insulating layer 4 and the light reflected from the one-sided surface S2 of the metal layer 3 (reflected light) are less likely to be absorbed and less likely to be diffused within the first insulating layer 4. Therefore, the reflected light from the one-sided surface S2 of the metal layer 3 is less likely to be absorbed or diffused within the first insulating layer 4 and is more likely to reach the inspection system. Therefore, it is difficult to ensure contrast between the metal layer 3 and the conductor pattern 5.

[0032] If the metal layer 3 can be insulated from the conductor pattern 5, the lower limit of the thickness of the first insulating layer 4 is not limited. The thickness of the first insulating layer 4 is, for example, 5 μm or more.

[0033] (5) Conductor pattern The conductor pattern 5 is positioned on one side of the first insulating layer 4 in the thickness direction. The conductor pattern 5 is positioned on one side surface S3 of the first insulating layer 4 in the thickness direction. The conductor pattern 5 is positioned on the opposite side of the metal layer 3 to the first insulating layer 4 in the thickness direction. The conductor pattern 5 has a first surface S11 and a second surface S12. The first surface S11 is the other side surface of the conductor pattern 5 in the thickness direction. The first surface S11 is in contact with one side surface S3 of the first insulating layer 4. The second surface S12 is the one side surface of the conductor pattern 5 in the thickness direction. The second surface S12 is positioned on the opposite side of the first insulating layer 4 to the first surface S11 in the thickness direction.

[0034] The brightness of the second surface S12 of the conductor pattern 5 is 155.0 or higher, preferably 157.0 or higher. The brightness L of one side surface S1 of the metal layer 3. * If the value is 89.0 or less, and the brightness of the second surface S12 of the conductor pattern 5 is 155.0 or more, then even if the thickness of the first insulating layer 4 is less than or equal to the above upper limit, the contrast between the metal layer 3 and the conductor pattern 5 can be ensured. The brightness of the second surface S12 of the conductor pattern 5 is, for example, 200.0 or less.

[0035] The brightness of the second surface S12 of the conductor pattern 5 is measured by the method described in the embodiment later.

[0036] The arithmetic mean roughness Ra of the second surface S12 of the conductor pattern 5 is, for example, 6.4 nm or less, preferably 5.9 nm or less. When the arithmetic mean roughness Ra of the second surface S12 of the conductor pattern 5 is below the above upper limit, scattering of the illumination light of the inspection system on the second surface S12 can be suppressed. As a result, the contrast between the metal layer and the conductor pattern can be better ensured in image recognition. The arithmetic mean roughness Ra of the second surface S12 of the conductor pattern 5 is, for example, 5.0 nm or more.

[0037] The conductor pattern 5 may have a protective metal layer 51, a conductor layer 52, and a covering metal layer 53.

[0038] The protective metal layer 51 is disposed on one side surface S3 of the first insulating layer 4 in the thickness direction. The protective metal layer 51 is positioned between the first insulating layer 4 and the conductor layer 52. The protective metal layer 51 protects the conductor layer 52. Examples of materials for the protective metal layer 51 include chromium, nickel, titanium, and alloys thereof. The protective metal layer 51 is preferably made of chromium. The protective metal layer 51 is, for example, a sputtering layer.

[0039] The thickness of the protective metal layer 51 is, for example, 30 nm to 100 nm, preferably 50 nm to 80 nm.

[0040] The conductive layer 52 is arranged on one side surface of the protective metal layer 51 in the thickness direction. The conductive layer 52 is made of metal. Examples of metals include copper, silver, gold, iron, aluminum, chromium, and alloys thereof. The conductive layer 52 is preferably made of copper.

[0041] The thickness of the conductive layer 52 is, for example, 10 μm to 60 μm.

[0042] The covering metal layer 53 covers the conductor layer 52. More specifically, the covering metal layer 53 covers one side surface of the conductor layer 52 in the thickness direction and the side surface of the conductor layer 52. The covering metal layer 53 protects the conductor layer 52. The covering metal layer 53 is positioned between the conductor layer 52 and the second insulating layer 6. The covering metal layer 53 has a second surface S12 of the conductor pattern 5. Examples of materials for the covering metal layer 53 include nickel, tin, silver, palladium, and their alloys. Nickel is preferably used as the material for the covering metal layer 53. The covering metal layer 53 is preferably a nickel-plated layer.

[0043] The thickness of the coating metal layer 53 is, for example, 45.0 nm or more, preferably 50.0 nm or more. If the thickness of the coating metal layer 53 is greater than or equal to the above upper limit, the brightness of the coating metal layer 53 can be ensured. The thickness of the coating metal layer 53 is not limited as long as the conductor layer 52 is protected. The thickness of the coating metal layer 53 may be, for example, 100.0 nm or less, or 80.0 nm or less.

[0044] (6) Second insulating layer The second insulating layer 6 is positioned on one side of the first insulating layer 4 in the thickness direction. The second insulating layer 6 is positioned on one surface of the first insulating layer 4 in the thickness direction. The second insulating layer 6 is made of a resin. Examples of resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. The second insulating layer 6 is preferably made of polyimide. The second insulating layer 6 covers the conductor pattern 5.

[0045] The thickness of the second insulating layer 6 is, for example, 1 μm to 50 μm, preferably 4 μm to 20 μm.

[0046] 2. Manufacturing method of a wiring circuit board The manufacturing method for the wiring circuit board 1 includes a metal layer formation step (see Figure 2A), a first insulating layer formation step (see Figure 2B), a conductor pattern formation step (see Figures 3A to 3C), a second insulating layer formation step (see Figure 1), and an inspection step (see Figure 4).

[0047] (1) Metal layer formation process As shown in Figure 2A, in the conductor layer formation process, a metal layer 3 is formed on one side surface S1 of the metal support layer 2.

[0048] To form the metal layer 3, first, a conductive layer 31 is formed on one side surface S1 of the metal support layer 2, for example, by electroplating.

[0049] Next, a protective metal layer 32 is formed on the conductive layer 31, for example, by sputtering. This completes the formation of the metal layer 3.

[0050] (2) First insulating layer formation process Next, as shown in Figure 2B, in the first insulating layer formation step, the first insulating layer 4 is formed on one side surface S2 of the metal layer 3.

[0051] More specifically, in the first insulating layer formation step, a photosensitive resin solution (varnish) is first applied to the metal layer 3 and dried. This forms a photosensitive resin coating on the metal layer 3.

[0052] Next, the photosensitive resin coating is exposed to light, and then the exposed coating is developed. This completes the formation of the first insulating layer 4.

[0053] (3) Conductor pattern formation process Next, in the conductor pattern formation process, a conductor pattern 5 is formed on one side surface S3 of the first insulating layer 4 in the thickness direction.

[0054] In more detail, first, as shown in Figure 3A, a protective metal layer 51 is formed on one side surface S3 of the first insulating layer 4 in the thickness direction, for example by sputtering.

[0055] Next, as shown in Figure 3B, a conductive layer 52 is formed on one side surface of the protective metal layer 51 in the thickness direction, for example by electroplating.

[0056] To form the conductive layer 52, first, the protective metal layer 51 is covered with a plating resist R.

[0057] Next, the plating resist R is exposed, and then the exposed plating resist R is developed. As a result, the plating resist R in the areas where the conductive layer 52 is formed is removed, and the protective metal layer 51 is exposed in those areas. On the other hand, the plating resist R in the areas where the conductive layer 52 is not formed remains.

[0058] Next, a conductive layer 52 is formed on the exposed protective metal layer 51 by electroplating. After the electroplating is completed, the plating resist R is peeled off, and the protective metal layer 51 exposed by the peeling off of the plating resist R is removed by etching.

[0059] Next, as shown in Figure 3C, a coating metal layer 53 is formed on the surface of the conductor layer 52, for example, by electroless plating.

[0060] As described above, the conductor pattern 5 is formed.

[0061] (4) Second insulating layer forming step Next, as shown in FIG. 1, in the second insulating layer forming step, a second insulating layer 6 is formed on one surface S3 of the first insulating layer 4 in the thickness direction.

[0062] Specifically, in the second insulating layer forming step, first, a solution (varnish) of a photosensitive resin is applied onto the first insulating layer 4 and the conductor pattern 5 and dried to form a coating film of the photosensitive resin.

[0063] Next, the coating film of the photosensitive resin is exposed, and then the exposed coating film is developed. Thereby, the second insulating layer 6 is formed.

[0064] (5) Inspection step Next, in the inspection step, the shape of the conductor pattern 5 is inspected by image recognition using an inspection system (specifically, the inspection system described in the examples below).

[0065] Specifically, in the inspection step, as shown in FIG. 4, first, an image of the wiring circuit board 1 is acquired (S21). To acquire an image of the conductor pattern 5, as shown in FIG. 5, while illuminating one surface of the wiring circuit board 1 with illumination 10 of the inspection system (more specifically, the epi-LED of the inspection microscope described in the examples below), it is photographed.

[0066] At this time, the brightness L of one surface S2 of the metal layer 3 * is 89.0 or less, and the luminance of the second surface S12 of the conductor pattern 5 is 155.0 or more. Therefore, the contrast between the metal layer 3 and the conductor pattern 5 can be ensured.

[0067] The inspection system generates a contour model of the conductor pattern 5 with a predetermined luminance as a threshold value.

[0068] Next, as shown in Figure 4, the inspection system compares the contour model of the generated conductor pattern 5 with the shape of the conductor pattern 5 in the CAM data to detect defective areas (S22).

[0069] At this time, since contrast is ensured between the metal layer 3 and the conductor pattern 5, a decrease in the accuracy of the generated contour model can be suppressed. Therefore, an increase in false detection of defects (mistakenly detecting areas without defects as defective areas) can be suppressed. In other words, the accuracy of reading the shape of the conductor pattern 5 by image recognition can be improved.

[0070] Next, the workers make a judgment on whether the defective parts detected by the inspection system are good or bad (S23).

[0071] In this case, the increase in false detections of defective parts is suppressed, allowing workers to efficiently perform quality control checks.

[0072] 3. Effects (1) According to the wiring circuit board 1, the brightness L of one side surface S2 of the metal layer 3 * The value is 89.0 or less, and the brightness of the second surface S12 of the conductor pattern 5 is 155.0 or more.

[0073] Therefore, in image recognition, it is possible to ensure contrast between the metal layer 3 and the conductor pattern 5.

[0074] As a result, the accuracy of reading the shape of the conductor pattern 5 using image recognition can be improved.

[0075] (2) According to the wiring circuit board 1, the arithmetic mean roughness Ra of the second surface S12 of the conductor pattern 5 is 6.4 nm or less.

[0076] Therefore, scattering of the illumination light from the inspection system on the second surface S12 can be suppressed.

[0077] As a result, a better contrast can be ensured between the metal layer 3 and the conductive pattern 5 in image recognition. [Examples]

[0078] The present invention will be further described below with reference to examples and comparative examples. However, the present invention is not limited in any way to the examples and comparative examples. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical properties, and parameters used in the following description may be replaced with the upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than or equal to") of the corresponding blending ratios (content ratios), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0079] 1. Manufacturing of wiring circuit boards First, a conductive layer made of copper was formed on one side surface of a metal support layer made of a copper alloy by electroplating.

[0080] Next, a protective metal layer made of chromium was formed on the conductive layer by sputtering. Thus, a metal layer consisting of the conductive layer and the protective metal layer was formed on one side surface of the metal support layer (metal layer formation process).

[0081] Brightness L of one side surface of the metal layer * The color difference was measured using a colorimeter (CR-10 Plus, manufactured by Konica Minolta). The results are shown in Table 1.

[0082] Next, a photosensitive polyimide solution (varnish) was applied to one side surface of the metal layer and dried. This formed a photosensitive polyimide coating on one side surface of the metal layer.

[0083] Next, the photosensitive polyimide coating was exposed to light, and then the exposed coating was developed. This formed a first insulating layer made of polyimide on one side surface of the metal layer (first insulating layer formation step).

[0084] Next, a protective metal layer made of chromium was formed on the first insulating layer by sputtering.

[0085] Next, a plating resist was applied to the first insulating layer, and the plating resist was exposed to light and developed. As a result, the plating resist was removed from the areas where the conductive layer of the conductive pattern was to be formed, and the protective metal layer was exposed in those areas.

[0086] Next, a conductive layer made of copper was formed on the exposed protective metal layer by electroplating. The surface roughness (arithmetic mean roughness Ra) of one side surface of the conductive layer was measured using an atomic force microscope. The results are shown in Table 1. Note that surface roughness (arithmetic mean roughness Ra) can also be measured using a laser microscope.

[0087] After the electroplating was completed, the plating resist was stripped off, and the protective metal layer exposed by the stripping of the plating resist was removed by etching.

[0088] Next, a nickel coating metal layer was formed on the surface of the conductor layer by electroless plating. The thickness of the coating metal layer is shown in Table 1.

[0089] As a result, a conductor pattern is formed on the first insulating layer (conductor pattern formation step).

[0090] Next, a photosensitive polyimide solution (varnish) was applied to the first insulating layer and the conductor pattern and dried to form a photosensitive polyimide coating.

[0091] Next, the photosensitive polyimide coating was exposed to light, and then the exposed coating was developed. This formed a second insulating layer on the first insulating layer (second insulating layer formation step).

[0092] Based on the above, a wiring circuit board was obtained.

[0093] 2. Evaluation (1) Detection of defective parts Defects in the conductor patterns of the wiring circuit boards of each example and comparative example were detected using an image inspection system.

[0094] More specifically, the image inspection system comprises an inspection microscope (MX63L, manufactured by EVIDENT) and a digital camera for the microscope (DP22, manufactured by EVIDENT). The image inspection system captures an image of the wiring circuit board magnified by the inspection microscope using the digital camera for the microscope, and detects defective areas using image analysis software (Stream Basic, manufactured by OLYMPUS).

[0095] The shooting conditions can be controlled using image analysis software. The shooting conditions are shown below.

[0096] <Conditions for digital cameras used with microscopes> Exposure; 40ms Sensitivity; ISO 200 Contrast: 0.00 Sharpness: 1 White balance: R:1.6, B:2 <Inspection Microscope Conditions> Mirror unit; BF Incident LED brightness: 47 Aperture diaphragm; 50% Table 1 shows the brightness of the conductor patterns in the images captured under the above shooting conditions, and the number of images (number of detections) in which the inspection system detected defects.

[0097] (2) Method for measuring the surface roughness of the coated metal layer After detecting the defective areas, the second insulating layer was peeled off the wiring circuit boards of each example and comparative example, and the surface roughness (arithmetic mean roughness Ra) of one side surface (second surface) of the covering metal layer of the conductor pattern exposed by the peeling off of the second insulating layer was measured using an atomic force microscope. The results are shown in Table 1.

[0098] [Table 1] [Explanation of symbols]

[0099] 1 Wiring circuit board 2 Metal support layer 3 metal layer 31 Conductor layer 32 Protective metal layer 4. First insulating layer (an example of an insulating layer) 5 Conductor Patterns 51 Protective metal layer 52 Conductor layer 53 Coating metal layer 6. Second insulating layer S1 One side surface of the metal support layer S2 One side surface of the metal layer S3 One side surface of the first insulating layer S11 Conductor pattern, first surface S12 Conductor pattern, second side

Claims

1. Metal support layer, A metal layer disposed on one side surface of the metal support layer in the thickness direction, An insulating layer disposed on one side surface of the metal layer in the thickness direction, A conductor pattern disposed on one side surface of the insulating layer in the thickness direction, the conductor pattern having a first surface in contact with the one side surface of the insulating layer and a second surface disposed on the opposite side of the insulating layer from the first surface in the thickness direction. Equipped with, Brightness L of the one side surface of the metal layer in the thickness direction ＊ It is 89.0 or less, A wiring circuit board in which the brightness of the second surface of the conductor pattern is 155.0 or higher.

2. The wiring circuit board according to claim 1, wherein the arithmetic mean roughness Ra of the second surface of the conductor pattern is 6.4 nm or less.

3. The conductor pattern comprises a conductor layer and a covering metal layer that covers the conductor layer. The wiring circuit board according to claim 1, wherein the covering metal layer has the second surface.

4. The wiring circuit board according to claim 3, wherein the covering metal layer is a nickel-plated layer.

5. The wiring circuit board according to claim 4, wherein the thickness of the coating metal layer is 45.0 nm or more.

6. The wiring circuit board according to claim 1, wherein the metal layer is made of copper.

7. The wiring circuit board according to claim 1, wherein the thickness of the insulating layer is 50 μm or less.

Images