Wiring circuit board

Abstract

To provide a wiring circuit board that can reduce heavy metals, which have a high environmental impact. [Solution] The wiring circuit board 1 comprises a first insulating layer 13, a conductor pattern 15 disposed on the first insulating layer 13, and a second protective layer 14 disposed between the first insulating layer 13 and the conductor pattern 15 to protect the conductor pattern 15. The second protective layer 14 is made of a metal oxide.

Description

Technical Field

[0001] The present invention relates to a wiring circuit board.

Background Art

[0002] Conventionally, a circuit board has been proposed that includes an insulating layer, a conductor circuit disposed on the insulating layer, a cover covering the conductor circuit, a chromium thin film and a copper thin film disposed between the insulating layer and the conductor circuit, and a metal thin film disposed between the cover and the conductor circuit (see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the circuit board described in Patent Document 1 above, there is a desire to reduce heavy metals with a high environmental load such as chromium.

[0005] The present invention provides a wiring circuit board capable of reducing heavy metals with a high environmental load.

Means for Solving the Problems

[0006] The present invention [1] includes a first insulating layer, a conductor pattern disposed on the first insulating layer, and a protective layer disposed between the first insulating layer and the conductor pattern and protecting the conductor pattern, wherein the protective layer is made of a metal oxide and includes a wiring circuit board.

[0007] The present invention [2] includes the wiring circuit board described in [1], wherein the wiring circuit board further comprises a second insulating layer disposed on the first insulating layer and covering the conductor pattern, and the protective layer is an insulator and is also disposed between the first insulating layer and the second insulating layer.

[0008] The present invention [3] includes the wiring circuit board described in [1] or [2], further comprising: a metal support layer disposed on the opposite side of the conductor pattern from the first insulating layer and supporting the first insulating layer and the conductor pattern; and a second protective layer disposed between the first insulating layer and the metal support layer and protecting the metal support layer.

[0009] The present invention [4] includes any one of the above [1] to [3] wiring circuit boards, wherein the protective layer contains aluminum.

[0010] The present invention [5] includes any one of the above [1] to [4] wiring circuit boards, wherein the protective layer contains aluminum oxide. [Effects of the Invention]

[0011] According to the wiring circuit board of the present invention, the protective layer disposed between the first insulating layer and the conductor pattern is made of a metal oxide.

[0012] Therefore, compared to cases where the protective layer is made of heavy metals such as chromium, it is possible to reduce the amount of heavy metals that have a high environmental impact.

[0013] Furthermore, it is possible to reduce not only the heavy metals contained in the wiring circuit board, but also the heavy metal waste liquid generated during the manufacturing process of the wiring circuit board. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a plan view of a wiring circuit board as one embodiment of the present invention. [Figure 2] Figure 2A is a cross-sectional view AA of the wiring circuit board shown in Figure 1. Figure 2B is a cross-sectional view BB of the wiring circuit board shown in Figure 1. [Figure 3] Figs. 3A to 3G are explanatory diagrams for explaining a method of manufacturing a wiring circuit board. Fig. 3A shows a step of preparing a support layer. Fig. 3B shows a step of forming a first protective layer on the support layer. Fig. 3C shows a step of forming a first insulating layer on the first protective layer and forming a second protective layer on the first insulating layer. Fig. 3D shows a step of removing the second protective layer in the via by etching. Fig. 3E shows a step of forming a conductor pattern on the second protective layer. Fig. 3F shows a step of forming a third protective layer on the conductor pattern. [Figure 4] Fig. 4 is an explanatory diagram for explaining a first modification example. [Figure 5] Fig. 5 is an explanatory diagram for explaining a second modification example. [Figure 6] Fig. 6 is an explanatory diagram for explaining a third modification example. [Figure 7] Fig. 7 is an explanatory diagram for explaining a fourth modification example.

Embodiments for Carrying Out the Invention

[0015] 1. Wiring Circuit Board As shown in Fig. 1, the wiring circuit board 1 extends in a first direction and a second direction. In the present embodiment, the wiring circuit board 1 has a substantially rectangular shape. Note that the shape of the wiring circuit board 1 is not limited.

[0016] As shown in Figs. 2A and 2B, the wiring circuit board 1 includes a support layer 11, a first protective layer 12, a first insulating layer 13, a second protective layer 14 as an example of a protective layer, a conductor pattern 15, a third protective layer 16, a second insulating layer 17, and a plating layer 18.

[0017] (1) Support Layer The support layer 11 supports the first protective layer 12, the first insulating layer 13, the second protective layer 14, the conductor pattern 15, the third protective layer 16, and the second insulating layer 17. In the present embodiment, the support layer 11 is made of metal. Examples of the metal include a stainless alloy and a copper alloy.

[0018] (2) First protective layer The first protective layer 12 is disposed on the support layer 11 in the thickness direction of the wiring circuit board 1. The thickness direction is orthogonal to the first direction and the second direction. The first protective layer 12 is disposed between the support layer 11 and the first insulating layer 13. The first protective layer 12 protects the support layer 11. The first protective layer 12 is made of metal. Examples of the metal include chromium, nickel, titanium, and alloys thereof.

[0019] (3) First insulating layer The first insulating layer 13 is disposed on the first protective layer 12 in the thickness direction. In other words, the first insulating layer 13 is disposed on the support layer 11 via the first protective layer 12 in the thickness direction. The first insulating layer 13 is disposed between the support layer 11 and the conductor pattern 15. The first insulating layer 13 insulates the first protective layer 12 and the conductor pattern 15. The first insulating layer 13 is made of resin. Examples of the resin include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. In the present embodiment, the first insulating layer 13 has via holes 13A.

[0020] (4) Second protective layer The second protective layer 14 is disposed on the first insulating layer 13 in the thickness direction. The second protective layer 14 is disposed between the conductor pattern 15 and the first insulating layer 13. The second protective layer 14 protects the conductor pattern 15. Specifically, the second protective layer 14 is disposed between the wiring pattern 15A and the first insulating layer 13, between the wiring pattern 15B and the first insulating layer 13, between the wiring pattern 15C and the first insulating layer 13, and between the ground pattern 15D and the first insulating layer 13. The wiring patterns 15A, 15B, 15C, and the ground pattern 15D will be described later. In the present embodiment, the second protective layer 14 is an insulator. When the second protective layer 14 is an insulator, the second protective layer 14 may also be disposed between the first insulating layer 13 and the second insulating layer 17.

[0021] The second protective layer 14 is made of a metal oxide. The second protective layer 14 is non-magnetic. Examples of metal oxides for the second protective layer 14 include aluminum oxide, zinc oxide, aluminum silicate, silicon dioxide, and magnesium oxide.

[0022] Furthermore, examples of metal oxides include metal oxides containing aluminum, silicon, zinc, and unavoidable impurities as metallic components.

[0023] The second protective layer 14 preferably contains aluminum. More preferably, the second protective layer 14 contains aluminum oxide. Preferred metal oxides include aluminum oxide and aluminum silicate.

[0024] The proportion of aluminum in the second protective layer 14 is, for example, 0.5% by mass or more, preferably 0.9% by mass or more. If the proportion of aluminum in the second protective layer 14 is above the lower limit, the second protective layer 14 can be easily etched in the manufacturing method of the wiring circuit board 1 described later. There is no upper limit to the proportion of aluminum in the second protective layer 14. For example, the proportion of aluminum in the second protective layer 14 is 60% by mass or less.

[0025] Furthermore, the proportion of aluminum oxide in the second protective layer 14 is, for example, 1% by mass or more, preferably 2% by mass or more. If the proportion of aluminum oxide in the second protective layer 14 is equal to or greater than the lower limit, the second protective layer 14 can be easily etched in the manufacturing method of the wiring circuit board 1 described later. Note that there is no upper limit to the proportion of aluminum oxide in the second protective layer 14. The proportion of aluminum oxide in the second protective layer 14 is, for example, 100% by mass or less.

[0026] The thickness of the second protective layer 14 is, for example, 1 nm or more, preferably 3 nm or more. If the thickness of the second protective layer 14 is greater than or equal to the lower limit, the wiring 153 can be reliably protected. The thickness of the second protective layer 14 is, for example, 100 nm or less, preferably 20 nm or less, and more preferably 10 nm or less. If the thickness of the second protective layer 14 is less than or equal to the upper limit, the second protective layer 14 can be easily etched in the manufacturing method of the wiring circuit board 1 described later.

[0027] (5) Conductor pattern The conductor pattern 15 is positioned on the second protective layer 14 in the thickness direction. In other words, the conductor pattern 15 is positioned on the first insulating layer 13 via the second protective layer 14 in the thickness direction. The conductor pattern 15 is positioned on the opposite side of the support layer 11 from the first insulating layer 13 in the thickness direction. The conductor pattern 15 is made of metal. Examples of metals include copper, silver, gold, iron, aluminum, chromium, and their alloys. From the viewpoint of obtaining good electrical properties, copper is preferred. The shape of the conductor pattern 15 is not limited.

[0028] In this embodiment, as shown in Figure 1, the conductor pattern 15 has a plurality of wiring patterns 15A, 15B, 15C and a ground pattern 15D. The wiring patterns 15A, 15B, 15C and the ground pattern 15D are arranged in a second direction with space between them.

[0029] (5-1) Wiring Pattern The wiring pattern 15A has terminal 151A, terminal 152A, and wiring 153A. The wiring pattern 15A electrically connects the electronic component connected to terminal 151A and the electronic component connected to terminal 152A.

[0030] Terminal 151A is located at one end of the wiring circuit board 1 in the first direction. Terminal 151A has a square land shape.

[0031] Terminal 152A is located at the other end of the wiring circuit board 1 in the first direction. Terminal 152A has a square land shape.

[0032] One end of wire 153A is connected to terminal 151A. The other end of wire 153A is connected to terminal 152A. Wire 153A electrically connects terminals 151A and 152A.

[0033] Wiring patterns 15B and 15C are described in the same way as wiring pattern 15A. Therefore, separate explanations for wiring patterns 15B and 15C are omitted.

[0034] (5-2) Ground Pattern The ground pattern 15D has a ground terminal 151D and a ground wire 152D. The ground pattern 15D connects the electronic component connected to the ground terminal 151D to the ground via the support layer 11.

[0035] The ground terminal 151D is located at one end of the wiring circuit board 1 in the first direction. The ground terminal 151D has a square land shape. Terminals 151A, 151B, 151C, 151D, and the ground terminal 151D are arranged in the second direction, spaced apart from each other.

[0036] One end of the ground wire 152D is connected to the ground terminal 151D. The other end of the ground wire 152D is connected to the first protective layer 12 through a via hole 13A (see Figure 2A) in the base insulating layer 13. As a result, the ground wire 152D is electrically connected to the support layer 11 via the first protective layer 12.

[0037] (6) Third protective layer As shown in Figures 2A and 2B, the third protective layer 16 covers the entire conductor pattern 15. The third protective layer 16 is positioned between the conductor pattern 15 and the second insulating layer 17. The third protective layer 16 protects the conductor pattern 15. The third protective layer 16 is made of a metal. Examples of metals include nickel and nickel-phosphorus alloys.

[0038] (7) Second insulating layer As shown in Figure 1, the second insulating layer 17 covers all the wirings 153A, 153B, 153C and the ground wiring 153D. In other words, the second insulating layer 17 covers the conductor pattern 15. The second insulating layer 17 is positioned on top of the first insulating layer 13 in the thickness direction. The second insulating layer 17 does not cover the terminals 151A, 151B, 151C, the ground terminal 151D, and the terminals 152A, 152B, 152C. The second insulating layer 17 is made of resin. Examples of resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester.

[0039] (8) Plating layer As shown in Figure 2B, the plating layer 18 covers terminals 151A, 151B, 151C, and the ground terminal 151D. Although not shown, the plating layer 18 also covers terminals 152A, 152B, and 152C. The plating layer 18 may have multiple layers. The plating layer 18 is made of metal. Gold is an example of the metal used for the plating layer 18.

[0040] 2. Manufacturing method of a wiring circuit board Next, the manufacturing method of the wiring circuit board 1 will be described.

[0041] In this embodiment, the wiring circuit board 1 is manufactured by an additive manufacturing method.

[0042] To manufacture the wiring circuit board 1, first, a support layer 11 is prepared, as shown in Figure 3A. In this embodiment, the support layer 11 is a metal foil drawn from a roll of metal foil.

[0043] Next, as shown in Figure 3B, a first protective layer 12 is formed on the support layer 11. The first protective layer 12 is formed, for example, by sputtering.

[0044] Next, as shown in Figure 3C, a first insulating layer 13 is formed on the first protective layer 12. To form the first insulating layer 13, first, a photosensitive resin solution (varnish) is applied to the first protective layer 12 and dried to form a photosensitive resin coating. Next, the photosensitive resin coating is exposed to light and developed. As a result, the first insulating layer 13 is formed on the first protective layer 12.

[0045] Next, a second protective layer 14 is formed on the first insulating layer 13. The second protective layer 14 is formed, for example, by sputtering. The second protective layer 14 is also formed on the inner surface of the via hole 13A.

[0046] Next, as shown in Figure 3D, the second protective layer 14 in the via hole 13A is removed by etching with an acidic or alkaline aqueous solution. Preferably, the second protective layer 14 is removed by etching with an acidic aqueous solution.

[0047] In more detail, an etching resist is bonded onto the second protective layer 14, and the etching resist is exposed while the via hole 13A is shielded from light.

[0048] Next, the exposed etching resist is developed. This removes the etching resist on top of the via hole 13A, exposing the second protective layer 14 inside the via hole 13A. The etching resist in the exposed areas, i.e., the areas that are not etched, remains.

[0049] Next, the second protective layer 14 inside the via hole 13A is etched with an acidic or alkaline aqueous solution. This removes the second protective layer 14 inside the via hole 13A. After etching is complete, the etching resist is peeled off.

[0050] The second protective layer 14 inside the via hole 13A may be removed by laser etching.

[0051] Next, as shown in Figure 3E, a conductor pattern 15 is formed on the second protective layer 14 by electroplating.

[0052] In more detail, a plating resist is bonded onto the second protective layer 14, and the plating resist is exposed to light while the area where the conductive pattern 15 is formed is shielded from light.

[0053] Next, the exposed plating resist is developed. This removes the plating resist from the light-shielded areas, exposing the second protective layer 14 in the areas where the conductor pattern 15 is formed. The plating resist remains in the exposed areas, i.e., the areas where the conductor pattern 15 is not formed.

[0054] Next, a conductor pattern 15 is formed on the exposed second protective layer 14 by electroplating. The conductor pattern 15 also fills the via holes 13A. After the electroplating is completed, the plating resist is peeled off.

[0055] Next, as shown in Figure 3F, a third protective layer 16 is formed on the surface of the conductor pattern 15 by electroless plating.

[0056] Next, as shown in Figure 2A, a second insulating layer 17 is formed on the first insulating layer 13 and the conductor pattern 15 in the same manner as the formation of the first insulating layer 13. As described above, the second insulating layer 17 covers all wirings 153A, 153B, 153C and the ground wiring 153D, but does not cover terminals 151A, 151B, 151C, the ground terminal 151D, and terminals 152A, 152B, 152C.

[0057] Next, as shown in Figure 2B, a plating layer 18 is formed on the surfaces of terminals 151A, 151B, 151C, the ground terminal 151D, and terminals 152A, 152B, 152C by electroless plating.

[0058] 3. Effects (1) According to the wiring circuit board 1, as shown in Figure 2A, the second protective layer 14, which is placed between the first insulating layer 13 and the conductor pattern 15, is made of a metal oxide.

[0059] Therefore, compared to cases where the second protective layer 14 is made of heavy metals such as chromium, it is possible to reduce the amount of heavy metals that have a high environmental impact.

[0060] Furthermore, it is possible to reduce not only the heavy metals contained in the wiring circuit board 1, but also the heavy metal waste liquid generated during the manufacturing process of the wiring circuit board 1.

[0061] (2) According to the wiring circuit board 1, as shown in Figure 2A, the second protective layer 14 is an insulator and is also placed between the first insulating layer 13 and the second insulating layer 17.

[0062] If the second protective layer 14 is a semiconductor or conductor, the second protective layer 14 between the first insulating layer 13 and the second insulating layer 17 must be removed to prevent short circuits in the wiring patterns 15A, 15B, 15C and the ground pattern 15D, respectively.

[0063] To remove the second protective layer 14 between the first insulating layer 13 and the second insulating layer 17, it is necessary to remove the second protective layer 14 between the first insulating layer 13 and the second insulating layer 17 after forming the conductor pattern 15 and before forming the second insulating layer 17.

[0064] In this regard, if the second protective layer 14 is an insulator, it is not necessary to remove the second protective layer 14 between the first insulating layer 13 and the second insulating layer 17, thereby simplifying the manufacturing process.

[0065] 4. Variations Next, a modified example will be described. In the modified example, the same reference numerals are used for components similar to those in the above-described embodiment, and their descriptions are omitted.

[0066] (1) As shown in Figure 4, the third protective layer 16 may also be formed from a metal oxide. In this case, the third protective layer 16 is formed on the conductor pattern 15 and the second protective layer 14, for example, by sputtering. After the second insulating layer 17 is formed, the third protective layer 16 that is not covered by the second insulating layer 17 is removed by etching with an acidic or alkaline aqueous solution.

[0067] (2) As shown in Figure 5, the first protective layer 12 may also be formed from a metal oxide. In this case, when etching the second protective layer 14 in the via hole 13A, the first protective layer 12 in the via hole 13A is also removed by etching.

[0068] (3) As shown in Figure 6, of the first protective layer 12, second protective layer 14, and third protective layer 16, only the first protective layer 12 may be formed from a metal oxide. In this case, the first protective layer 12 in the via hole 13A is removed by etching after the first insulating layer 13 is formed. Also, after the conductive pattern 15 is formed on the second protective layer 14, the second protective layer 14, which was covered with a plating resist, is etched with an acidic aqueous solution or an alkaline aqueous solution.

[0069] (4) As shown in Figure 7, the first protective layer 12, the second protective layer 14, and the third protective layer 16 may all be formed from metal oxides.

[0070] (5) The third protective layer 16 may be a semiconductor or a conductor. If the third protective layer 16 is a semiconductor or a conductor, it is not placed between the first insulating layer 13 and the second insulating layer 17. Examples of semiconductors or conductors include alumina-doped zinc oxide.

[0071] Alumina-doped zinc oxide contains aluminum oxide in an amount of, for example, 1% by mass or more, preferably 2% by mass or more, for example, 10% by mass or less, preferably 5% by mass or less.

[0072] Alumina-doped zinc oxide contains silicon dioxide in an amount of, for example, 10% by mass or more, preferably 15% by mass or more, for example, 30% by mass or less, preferably 25% by mass or less.

[0073] Alumina-doped zinc oxide contains zinc oxide in an amount of, for example, 40% by mass or more, preferably 60% by mass or more, for example, 90% by mass or less, preferably 80% by mass or less. [Explanation of Symbols]

[0074] 1 Wiring circuit board 13. First insulating layer 14 Second protective layer 15 Conductor Patterns 17. Second insulating layer

Claims

1. The first insulating layer and A conductor pattern disposed on the first insulating layer, A protective layer is disposed between the first insulating layer and the conductor pattern to protect the conductor pattern. Equipped with, The aforementioned protective layer is made of a metal oxide, and is a wiring circuit board.

2. The aforementioned wiring circuit board is The system further comprises a second insulating layer disposed on the first insulating layer and covering the conductor pattern, The wiring circuit board according to claim 1, wherein the protective layer is an insulator and is also disposed between the first insulating layer and the second insulating layer.

3. The aforementioned wiring circuit board is A metal support layer is provided, which is positioned on the opposite side of the conductor pattern from the first insulating layer and supports the first insulating layer and the conductor pattern. The wiring circuit board according to claim 1 or 2, further comprising a second protective layer disposed between the first insulating layer and the metal support layer for protecting the metal support layer.

4. The wiring circuit board according to any one of claims 1 to 3, wherein the protective layer contains aluminum.

5. The wiring circuit board according to any one of claims 1 to 4, wherein the protective layer contains aluminum oxide.

Images