Printed wiring board

Abstract

To provide a printed wiring board that is improved in manufacturing yield.SOLUTION: A printed wiring board includes a first conductor layer, a resin insulation layer disposed on the first conductor layer and a second conductor layer disposed on the resin insulation layer. The resin insulation layer contains a thermosetting resin, inorganic particles having an average particle size of 0.1 μm or more and 3 μm or less and a fluorescent material having a quantum yield of 0.3 or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a printed wiring board. [Background technology]

[0002] Patent Document 1 discloses a printed wiring board including a substrate, a first conductor layer disposed on the substrate, a resin insulating layer having optical transparency and disposed on the first conductor layer, and a second conductor layer disposed on the resin insulating layer. In this printed wiring board, at least one of the first conductor layer and the second conductor layer is subjected to a surface treatment to make the reflectance in the visible light region of the first conductor layer and the second conductor layer different from each other, thereby increasing the optical S / N ratio and improving the inspection accuracy in the appearance inspection of the wiring pattern formed by the second conductor layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 088522 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] In recent printed wiring boards, there is a trend to reduce the thickness of the resin insulation layer. When the resin insulation layer is reduced in thickness, light passes through the resin insulation layer during visual inspection of the second conductor layer, and the first conductor layer is recognized together with the second conductor layer, which may reduce the inspection accuracy. [Means for solving the problem]

[0005] One aspect of the present disclosure is A first conductor layer; a resin insulating layer disposed on the first conductor layer; A second conductor layer disposed on the resin insulating layer; A printed wiring board comprising: The resin insulating layer contains a thermosetting resin, inorganic particles having an average particle size of 0.1 μm or more and 3 μm or less, and a fluorescent material having a quantum yield of 0.3 or more.

[0006] In one embodiment of the present disclosure, the resin insulating layer contains a thermosetting resin, inorganic particles having an average particle size of 0.1 μm or more and 3 μm or less, and a fluorescent material having a quantum yield of 0.3 or more. In the optical inspection (visual inspection) of the second conductor layer, for example, the fluorescent material is excited by the excitation light irradiated on the resin insulating layer, and the resin insulating layer emits light. On the other hand, the second conductor layer hardly reflects light to the excitation light (in other words, it reflects little light). Therefore, the contrast ratio between the resin insulating layer and the second conductor layer is increased, and the external shape of the second conductor layer can be obtained with high accuracy. In addition, the first conductor layer hardly reflects light to the excitation light, and instead, the resin insulating layer arranged on the first conductor layer emits light due to the excitation light, so that the first conductor layer is not recognized. Therefore, the recognition of the first conductor layer together with the second conductor layer is suppressed. In this way, in the optical inspection of the second conductor layer, the external shape of the second conductor layer can be obtained with high accuracy, so that a decrease in inspection accuracy can be suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a printed wiring board according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a state in which the printed wiring board of FIG. 1 is being inspected. [Diagram 3] FIG. 3 is a cross-sectional view that illustrates a printed wiring board according to another embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which the printed wiring board of FIG. 3 is being inspected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an example of an embodiment of the present disclosure will be described in detail with reference to the drawings. Components indicated by the same reference numerals in each drawing are the same or similar components. Note that duplicated descriptions and reference numerals in the embodiments described below may be omitted. In addition, all drawings used in the following description are schematic, and the dimensional relationships of each element, the ratios of each element, etc. shown in the drawings do not necessarily match the actual ones. In addition, the dimensional relationships of each element, the ratios of each element, etc. between multiple drawings do not necessarily match.

[0009] Fig. 1 is a cross-sectional view showing a printed wiring board 20 according to an embodiment. As shown in Fig. 1, printed wiring board 20 includes an insulating layer 22. Printed wiring board 20 also includes a first conductor layer 24, a resin insulating layer 26, and a second conductor layer 28.

[0010] The insulating layer 22 is formed using a resin. The insulating layer 22 may contain inorganic particles such as silica. The insulating layer 22 may contain a reinforcing material such as glass cloth. The insulating layer 22 has a first surface 22A (upper surface in the figure) and a second surface 22B (lower surface in the figure) opposite to the first surface 22A.

[0011] The first conductor layer 24 is disposed on the insulating layer 22. Specifically, the first conductor layer 24 is disposed on the first surface 22A of the insulating layer 22. The first conductor layer 24 forms a first wiring pattern (in other words, a first conductor circuit pattern) of the printed wiring board 20. The first conductor layer 24 is formed using a material having electrical conductivity. The material having electrical conductivity is, for example, a metal material. Examples of the metal material include copper, gold, silver, nickel, aluminum, and alloys using these materials.

[0012] Resin insulating layer 26 is disposed on first conductor layer 24. Specifically, resin insulating layer 26 is disposed on the upper surface of first conductor layer 24 and first surface 22A of insulating layer 22. Resin insulating layer 26 contains thermosetting resin 26A, a large number of inorganic particles 27, and a fluorescent material.

[0013] The thermosetting resin 26A may be, for example, an epoxy resin.

[0014] A large number of inorganic particles 27 are dispersed in the thermosetting resin 26A. The average particle diameter of the inorganic particles 27 is 0.1 μm or more and 3 μm or less. Examples of the inorganic particles 27 include silica and alumina.

[0015] The fluorescent material has a quantum yield of 0.3 or more. The fluorescent material may contain a coumarin derivative. When the thermosetting resin 26A is an epoxy resin, the coumarin derivative is preferably blended in an amount of 0.03 to 3 parts by weight per 100 parts by weight of the epoxy resin. Examples of the coumarin derivative include 7-hydroxycoumarin, 4-methyl-7-hydroxycoumarin, and esculin (6,7-dihydrocoumarin-6-glucoside), either alone or in combination.

[0016] The fluorescent material may also contain a fluorescent dye, such as perylene red.

[0017] The thickness of the resin insulating layer 26 is preferably 5 μm or more and 15 μm or less, and more preferably 6 μm or more and 12 μm or less.

[0018] The second conductor layer 28 is disposed on the resin insulating layer 26. Specifically, the second conductor layer 28 is disposed on the surface 26S of the resin insulating layer 26. The surface 26S of the resin insulating layer 26 is the surface of the resin insulating layer 26 opposite to the insulating layer 22. The second conductor layer 28 forms a second wiring pattern (in other words, a second conductor circuit pattern) of the printed wiring board 20. The second conductor layer 28 is formed using the same material as the first conductor layer 24. The second wiring pattern has a minimum line width W1 of 10 μm or less and a minimum line distance L1 of 10 μm or less. The second wiring pattern is electrically connected to the first wiring pattern, for example, by using a through conductor not shown.

[0019] The printed wiring board 20 can be manufactured by, for example, a semi-additive method or a full-additive method.

[0020] Next, a method for inspecting the wiring pattern formed on the surface of printed wiring board 20 will be described. Fig. 2 shows a method for inspecting a second wiring pattern formed on the surface of printed wiring board 20. The second wiring pattern is inspected by an optical inspection device (not shown). The optical inspection device is a conventionally known inspection device, and has a function of irradiating the surface of printed wiring board 20 with excitation light and inspecting the wiring pattern for abnormalities (defects) from the reflected light.

[0021] As shown in FIG. 2, when the surface of the printed wiring board 20 is irradiated with excitation light EL from the light source of the optical inspection device, the fluorescent material contained in the resin insulating layer 26 is excited, and the resin insulating layer 26 emits light. In other words, when the resin insulating layer 26 is irradiated with excitation light EL, it emits light (fluorescence or phosphorescence) FL. On the other hand, when the second conductor layer 28 is formed using a metal material, for example, copper, it hardly reflects light even when it is irradiated with excitation light EL (for example, ultraviolet light). In FIG. 2, the arrow of the reflected light is omitted to show that the second conductor layer 28 reflects little light. In this way, the resin insulating layer 26 emits light FL in response to the excitation light EL, and the second conductor layer 28 does not reflect light, so that the contrast ratio between the resin insulating layer 26 and the second conductor layer 28 is increased in an image of the surface of the printed wiring board 20. This makes it possible to obtain the external shape of the second wiring pattern with high accuracy by image analysis from the captured image. The external shape of the acquired second wiring pattern is compared with the external shape of a normal second wiring pattern stored in the optical inspection device, thereby inspecting whether or not there is an abnormality in the second wiring pattern.

[0022] Next, the operation of this embodiment will be described. In the printed wiring board 20 of this embodiment, when the surface of the printed wiring board 20 is irradiated with excitation light EL in the optical inspection of the second wiring pattern formed by the second conductor layer 28, the resin insulating layer 26 containing the fluorescent material emits light, and the second wiring pattern hardly reflects the light. Therefore, the contrast ratio between the resin insulating layer 26 and the second wiring pattern is increased, and the external shape of the second wiring pattern formed by the second conductor layer 28 can be obtained with high accuracy. In addition, the first wiring pattern formed by the first conductor layer 24 hardly reflects light to the excitation light, and instead, the resin insulating layer 26 arranged on the first conductor layer 24 emits light due to the excitation light, so that the first conductor layer 24 is not recognized. Therefore, recognition of the first wiring pattern formed by the first conductor layer 24 together with the second wiring pattern formed by the second conductor layer 28 is suppressed. In this way, the printed wiring board 20 is configured to be able to obtain the external shape of the second conductor layer 28 with high accuracy in the optical inspection of the second wiring pattern formed by the second conductor layer 28, and therefore deterioration of the inspection accuracy can be suppressed.

[0023] In addition, in the printed wiring board 20, since the resin insulating layer 26 contains a fluorescent material with a quantum yield of 0.3 or more, it is easy to increase the contrast ratio between the resin insulating layer 26 and the second wiring pattern. This makes it possible to obtain the external shape of the second wiring pattern formed by the second conductor layer 28 with higher accuracy.

[0024] Furthermore, in printed wiring board 20, inorganic particles 27 have an average particle size of 0.1 μm or more and 3 μm or less, so that resin insulating layer 26 has improved strength.

[0025] Furthermore, in printed wiring board 20, when the thickness of resin insulating layer 26 is set to be not less than 5 μm and not more than 15 μm, the wiring board can be made thin.

[0026] Furthermore, in the printed wiring board 20, when the fluorescent material contains a coumarin derivative, the luminescence intensity of the resin insulating layer 26 due to the excitation light EL is improved, making it easier to further increase the contrast ratio between the resin insulating layer 26 and the second wiring pattern.

[0027] In addition, in printed wiring board 20, when the minimum value of line width W1 in the second wiring pattern formed by second conductor layer 28 is 10 μm or less and the minimum value of line-to-line distance L1 is 10 μm or less, the external shape of the second wiring pattern can be obtained with high accuracy by image analysis.

[0028] (Other embodiments) In the printed wiring board 20 of the above embodiment, as shown in FIG. 1, the first conductor layer 24, the resin insulating layer 26, and the second conductor layer 28 are laminated on the insulating layer 22, but the present disclosure is not limited to this configuration. For example, a wiring layer and a resin insulating layer may be alternately laminated on the insulating layer 22. In the example (printed wiring board 21) shown in FIG. 3, the resin insulating layer 30 and the third conductor layer 32 are laminated on the second conductor layer 28. As shown in FIG. 3, the printed wiring board 21 includes the insulating layer 22, the first conductor layer 24, the resin insulating layer 26, the second conductor layer 28, the resin insulating layer 30, and the third conductor layer 32. The resin insulating layer 30 is formed using the same material as the resin insulating layer 26. In FIG. 3, the reference numeral 30A indicates a thermosetting resin contained in the resin insulating layer 30, and the reference numeral 33 indicates inorganic particles 33 contained in the resin insulating layer 30. The third conductor layer 32 is formed using the same material as the first conductor layer 24. The third wiring pattern formed by the third conductor layer 32 has a minimum line width W2 of 10 μm or less and a minimum line distance L2 of 10 μm or less. The third wiring pattern is electrically connected to the second wiring pattern, for example, by using a through conductor not shown. In the printed wiring board 21, after the second conductor layer 28 is formed on the surface 26S of the resin insulating layer 26, the second wiring pattern formed by the second conductor layer 28 may be inspected by an optical inspection device. Then, after the resin insulating layer 30 is disposed on the second conductor layer 28 and the third conductor layer 32 is formed on the surface 30S of the resin insulating layer 30, the third wiring pattern formed by the third conductor layer 32 may be inspected by an optical inspection device as shown in FIG. 4. In this way, in the manufacturing process of the printed wiring board, by inspecting the wiring pattern by the optical inspection device every time a conductor layer is formed, it is possible to provide a printed wiring board with improved manufacturing yield.

[0029] Furthermore, a fluorescent material with a quantum yield of 0.3 or more may be contained in the insulating layer 22 of the printed wiring board 20. In this case, the first wiring pattern formed by the first conductor layer 24 can also be optically inspected with high accuracy.

[0030] In the printed wiring board of the above embodiment, the first conductor layer 24 is disposed on the insulating layer 22 made of resin, but the present disclosure is not limited to this configuration. For example, the first conductor layer 24 may be disposed on a glass substrate. Also, the first conductor layer 24 may be disposed on a metal substrate whose surface has been subjected to an insulating treatment.

[0031] The printed wiring board of the present disclosure is not limited to the structures illustrated in the drawings, and the structures, shapes, and materials illustrated in this specification. [Explanation of symbols]

[0032] 20 Printed wiring board 21 Printed Wiring Board 22 Insulating layer 24 First conductor layer 26 Resin insulation layer 26A thermosetting resin 27 Inorganic particles 28 Second Conductor Layer 30 Resin insulation layer 30A thermosetting resin 32 Third conductor layer L1 Line distance L2 Line spacing W1 Line width W2 Line width

Claims

1. A first conductor layer; a resin insulating layer disposed on the first conductor layer; A second conductor layer disposed on the resin insulating layer; A printed wiring board comprising: The resin insulating layer contains a thermosetting resin, inorganic particles having an average particle size of 0.1 μm or more and 3 μm or less, and a fluorescent material having a quantum yield of 0.3 or more.

2. 2. The printed wiring board of claim 1, The resin insulating layer has a thickness of 5 μm or more and 15 μm or less.

3. 2. The printed wiring board of claim 1, The fluorescent material contains a coumarin derivative.

4. 2. The printed wiring board according to claim 1, In the wiring pattern formed by the second conductor layer, the minimum line width is 10 μm or less and the minimum line-to-line distance is 10 μm or less.

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