Wired circuit boards and methods for manufacturing wired circuit boards.

Abstract

The invention relates to a wiring circuit board (XI) comprising a metal support (10); a first metal film (21); an insulating layer (22); a second metal film (23); and a conductive layer (24) in order oriented in one direction along the thickness direction. The metal support (10) comprises a metal support layer (11) and a surface metal layer (12). The surface metal layer (12) is arranged on a surface along the thickness direction of the metal support layer (11) and has higher conductivity than this metal support layer (11). The insulating layer (22) has a through hole (22a). The conductive layer (24) has a seam (24B). This seam (24B) is arranged in the through hole (22a) and is electrically connected to the metal support (10).

Description

Wired circuit board and method for manufacturing the same

[0001] The present invention relates to a wired circuit board and a method for manufacturing a wired circuit board.

[0002] A wired circuit board is known that includes a metal supporting substrate, an insulating layer on the supporting substrate, and a wiring pattern on the insulating layer. In this wired circuit board, for example, the supporting substrate has a multilayer structure to ensure good characteristics in the wiring pattern. Technology related to such a wired circuit board is described, for example, in Patent Document 1 listed below. The supporting substrate of the wired circuit board described in Patent Document 1 has a multilayer structure including a metal supporting substrate and a metal foil arranged on the wiring pattern side of the substrate.

[0003] Japanese Patent Application Laid-Open No. 2007-157836

[0004] The supporting substrate of the wired circuit board of Patent Document 1 has a metal thin film for forming the metal foil between the metal supporting board and the metal foil. The metal thin film is a plating seed layer for forming the metal foil. In one wired circuit board specifically described in Patent Document 1, the metal supporting board is made of stainless steel, the metal foil is made of copper, and the metal thin film is made of chromium.

[0005] However, in the manufacturing process of such a wired circuit board, the supporting substrate cannot be efficiently patterned by a single wet etching process (patterning of the supporting substrate is performed, for example, when processing the outer shape of the supporting substrate), because the etching solution for the stainless steel metal supporting substrate and copper metal foil contained in the supporting substrate is different from the etching solution for the chromium metal thin film.

[0006] On the other hand, in a wired circuit board, a via may be provided that penetrates an insulating layer in the thickness direction and connects the supporting substrate and the wiring pattern. The supporting substrate and the wiring pattern are electrically connected through the via. In such a wired circuit board, there is a demand for low resistance in the electrical connection between the supporting substrate and the wiring pattern.

[0007] The present invention provides a wired circuit board and a method for manufacturing a wired circuit board, which are suitable for realizing low-resistance electrical connection between a metal supporting board and a wiring layer formed on an insulating layer on the board, and are also suitable for efficiently patterning the metal supporting board.

[0008] The present invention [1] includes a wired circuit board comprising a metal supporting board, a first metal thin film, an insulating layer, a second metal thin film, and a conductor layer, in that order toward one side in a thickness direction, wherein the metal supporting board comprises a metal supporting layer and a surface metal layer that is arranged on one surface of the metal supporting layer in the thickness direction and has a higher conductivity than the metal supporting layer, the insulating layer has a through hole that penetrates the insulating layer in the thickness direction, and the conductor layer has a via part that is arranged in the through hole and is electrically connected to the metal supporting board.

[0009] The present invention [2] includes the wired circuit board according to the above [1], wherein the metal support layer includes at least one selected from the group consisting of stainless steel, copper alloy, aluminum, nickel, and titanium.

[0010] The present invention [3] includes the wired circuit board according to the above [1] or [2], wherein the surface metal layer contains at least one selected from the group consisting of gold, silver, and copper.

[0011] The present invention [4] includes the wired circuit board according to any one of the above [1] to [3], wherein the via portion is electrically connected to the metal supporting board via the first metal thin film and the second metal thin film.

[0012] The present invention [5] includes the wired circuit board according to any one of the above [1] to [3], wherein the first metal thin film has an opening that opens along the through hole, and the via portion is electrically connected to the metal supporting board via the second metal thin film.

[0013] The present invention [6] includes a method for manufacturing a wired circuit board, including: a first metal thin film forming step of forming a first metal thin film on one surface in the thickness direction of a metal supporting board having a metal support layer and a surface metal layer arranged on one surface in the thickness direction of the metal support layer and having a higher conductivity than the metal support layer; an insulating layer forming step of forming an insulating layer having a through hole on one surface in the thickness direction of the first metal thin film; a second metal thin film forming step of forming a second metal thin film on one surface in the thickness direction of the insulating layer and on a portion of the first metal thin film exposed at the through hole; and a conductor layer forming step of forming a conductor layer including a via portion arranged in the through hole on one surface in the thickness direction of the second metal thin film.

[0014] The present invention [7] includes a method for manufacturing a wired circuit board, including: a first metal thin film forming step of forming a first metal thin film on one surface in the thickness direction of a metal supporting board that includes a metal supporting layer and a surface metal layer that is arranged on one surface in the thickness direction of the metal supporting layer and has a higher conductivity than the metal supporting layer; an insulating layer forming step of forming an insulating layer having a through hole on one surface in the thickness direction of the first metal thin film; a removing step of removing a portion of the first metal thin film exposed in the through hole to expose the metal supporting board at the through hole; a second metal thin film forming step of forming a second metal thin film on one surface in the thickness direction of the insulating layer and on the portion of the metal supporting board exposed in the through hole; and a conductor layer forming step of forming a conductor layer that includes a via portion that is arranged in the through hole on one surface in the thickness direction of the second metal thin film.

[0015] In the wired circuit board of the present invention, as described above, the metal supporting board includes the metal supporting layer and the surface metal layer that is disposed on one surface of the metal supporting layer in the thickness direction and has higher conductivity than the metal supporting layer. Such a configuration is suitable for realizing low-resistance electrical connection between the metal supporting board and the conductor layer that is disposed on one side of the metal supporting board in the thickness direction.

[0016] In the wired circuit board of the present invention, as described above, the surface metal layer having a higher conductivity than the metal support layer is disposed on one surface of the metal support layer in the thickness direction. This configuration in which the metal support layer and the surface metal layer are in direct contact with each other without any other layer therebetween is suitable for efficiently patterning the metal supporting board by a single treatment (e.g., wet etching treatment) of the metal supporting board.

[0017] The method for producing a wired circuit board of the present invention is suitable for producing such a wired circuit board.

[0018] 4A is a partial cross-sectional view of one embodiment of the wired circuit board of the present invention; FIG. 4B is a partially enlarged cross-sectional view of the wired circuit board shown in FIG. 1; and FIG. 5 shows some steps in a method for manufacturing the wired circuit board shown in FIG. 1. FIG. 3A shows a preparation step, FIG. 3B shows a first metal thin film formation step, and FIG. 3C shows an insulating base layer formation step. These steps follow the step shown in FIG. 3C. FIG. 4A shows a second metal thin film formation step, FIG. 4B shows a conductor layer formation step, FIG. 4C shows an etching step, and FIG. 4D shows an insulating cover layer formation step. This is a partial cross-sectional view of another embodiment of the wired circuit board of the present invention; FIG. 5 is a partially enlarged cross-sectional view of the wired circuit board shown in FIG. 5; and FIG. 5 shows some steps in a method for manufacturing the wired circuit board shown in FIG. 5. FIG. 7A shows a removal step, FIG. 7B shows a second metal thin film formation step, and FIG. 7C shows a conductor layer formation step. These steps follow the step shown in FIG. 7C. FIG. 8A shows an etching step, and FIG. 8B shows an insulating cover layer formation step.

[0019] 1 and 2 , a wired circuit board X1 as one embodiment of the wired circuit board of the present invention includes, in order toward one side in the thickness direction, a metal supporting board 10, a first metal thin film 21, an insulating layer 22 as a base insulating layer, a second metal thin film 23, a conductor layer 24, and an insulating layer 25 as a cover insulating layer. The wired circuit board X1 extends in a direction (plane direction) perpendicular to the thickness direction and has a predetermined shape in a plan view.

[0020] The metal supporting board 10 includes a metal supporting layer 11 and a surface metal layer 12 .

[0021] The metal support layer 11 is a base material for ensuring the strength of the wired circuit board X1. Examples of materials for the metal support layer 11 include stainless steel, copper, copper alloy, aluminum, nickel, titanium, and 42 alloy. Examples of stainless steel include SUS304, which is based on the AISI (American Iron and Steel Institute) standard. From the perspective of strength, the metal support layer 11 preferably includes at least one material selected from the group consisting of stainless steel, copper alloy, aluminum, nickel, and titanium, and more preferably at least one material selected from the group consisting of stainless steel, copper alloy, aluminum, nickel, and titanium. From the perspective of achieving both strength and conductivity, the metal support layer 11 is preferably made of a copper alloy. The thickness of the metal support layer 11 is, for example, 15 μm or more. The thickness of the metal support layer 11 is, for example, 500 μm or less, preferably 250 μm or less.

[0022] The surface metal layer 12 is disposed on one surface in the thickness direction of the metal support layer 11 (the surface metal layer 12 is in contact with the metal support layer 11). In this embodiment, the surface metal layer 12 is disposed on the entire surface of one side in the thickness direction of the metal support layer 11. Examples of the surface metal layer 12 include a film formed by a sputtering method (sputtered film), a film formed by a plating method (plated film), and a film formed by a vacuum deposition method (vacuum deposition film).

[0023] The surface metal layer 12 has a higher conductivity than the metal support layer 11. From the viewpoint of the conductivity of the surface metal layer 12, the surface metal layer 12 preferably contains at least one selected from the group consisting of gold, silver, and copper, and more preferably consists of at least one selected from the group consisting of gold, silver, and copper. From the viewpoint of the film-forming properties of the surface metal layer 12 when the metal support layer 11 is made of a copper alloy, the surface metal layer 12 is preferably made of copper.

[0024] The thickness of the surface metal layer 12 is preferably 0.5 μm or more, and more preferably 3 μm or more.

[0025] The first metal thin film 21 is disposed on one surface in the thickness direction of the metal supporting board 10. In this embodiment, the first metal thin film 21 is disposed over the entire surface of one side of the metal supporting board 10 in the thickness direction.

[0026] The first metal thin film 21 is a layer for ensuring the adhesion of the insulating layer 22 to the metal supporting board 10. Examples of the first metal thin film 21 include a film formed by a sputtering method (sputtered film), a film formed by a plating method (plated film), and a film formed by a vacuum deposition method (vacuum deposition film).

[0027] Examples of materials for the first metal thin film 21 include chromium, nickel, and titanium. The material for the first metal thin film 21 may be an alloy containing two or more metals selected from the group consisting of chromium, nickel, and titanium. Chromium is preferably used as the material for the first metal thin film 21.

[0028] The thickness of the first metal thin film 21 is, for example, 1 nm or more, preferably 10 nm or more, more preferably 20 nm or more. The thickness of the first metal thin film 21 is, for example, 10,000 nm or less, preferably 1,000 nm or less, more preferably 500 nm or less.

[0029] The insulating layer 22 is disposed on one surface of the first metal thin film 21 in the thickness direction. Examples of materials for the insulating layer 22 include resin materials such as polyimide, polyethernitrile, polyethersulfone, polyethylene terephthalate, polyethylene naphthalate, and polyvinyl chloride (similar resin materials can also be used for the insulating layer 25 described below). The thickness of the insulating layer 22 is, for example, 1 μm or more, preferably 3 μm or more. The thickness of the insulating layer 22 is, for example, 35 μm or less.

[0030] The insulating layer 22 has a through hole 22a penetrating the insulating layer 22 in the thickness direction. The through hole 22a has, for example, a substantially circular shape in a plan view. In this embodiment, the through hole 22a has an inclined inner wall surface 22b. The inner wall surface 22b is inclined so that the portion closer to the metal supporting board 10 is disposed more inward. In other words, the inner wall surface 22b is inclined so that the opening cross-sectional area of ​​the through hole 22a becomes smaller the portion closer to the metal supporting board 10. The first metal thin film 21 has a portion 21a facing the through hole 22a.

[0031] In this embodiment, the second metal thin film 23 is continuously disposed on one thickness direction surface of the insulating layer 22, on the inner wall surface 22b of the through hole 22a, and on the portion 21a of the first metal thin film 21 facing the through hole 22a. The second metal thin film 23 includes a second metal thin film 23A disposed outside the through hole 22a and a second metal thin film 23B disposed inside the through hole 22a. The second metal thin film 23B has a concave shape in the longitudinal cross section shown in FIG. 2, for example. On the insulating layer 22, the second metal thin film 23A has a predetermined pattern shape. In the through hole 22a, the second metal thin film 23B is connected to the first metal thin film 21. The second metal thin film 23A and the second metal thin film 23B are connected to each other.

[0032] The second metal thin film 23 is a seed layer for forming the conductor layer 24. Examples of the second metal thin film 23 include a sputtered film, a plated film, and a vacuum-deposited film.

[0033] Examples of materials for the second metal thin film 23 include chromium, copper, nickel, and titanium. The material for the second metal thin film 23 may also be an alloy containing two or more metals selected from the group consisting of chromium, copper, nickel, and titanium. Chromium is preferably used as the material for the second metal thin film 23. The second metal thin film 23 may have a single-layer structure or a multi-layer structure of two or more layers. When the second metal thin film 23 has a multi-layer structure, the second metal thin film 23 is composed of, for example, a chromium layer as a lower layer and a copper layer on the chromium layer.

[0034] The thickness of the second metal thin film 23 is, for example, 1 nm or more, preferably 10 nm or more, and is, for example, 500 nm or less, preferably 200 nm or less.

[0035] The conductor layer 24 is disposed on one surface in the thickness direction of the second metal thin film 23. The conductor layer 24 includes a wiring portion 24A disposed outside the through hole 22a and a via portion 24B disposed inside the through hole 22a. The wiring portion 24A and the via portion 24B are connected. The wiring portion 24A has a predetermined pattern shape. The via portion 24B has a concave shape in the longitudinal cross section shown in FIG. 2, for example. The via portion 24B has an inclined peripheral side surface 24b. The peripheral side surface 24b is inclined so that the portion closer to the metal supporting board 10 is disposed more inward. In other words, the peripheral side surface 24b is inclined so that the cross-sectional area of ​​the via portion 24B becomes smaller the portion closer to the metal supporting board 10.

[0036] Examples of materials for the conductor layer 24 include copper, nickel, and gold. The material for the conductor layer 24 may also be an alloy containing two or more metals selected from the group consisting of copper, nickel, and gold. Copper is preferably used as the material for the conductor layer 24.

[0037] On the insulating layer 22, the second metal thin film 23A and a wiring portion 24A on the second metal thin film 23A form a wiring layer 31 having a predetermined pattern shape. In the through hole 22a, the portion 21a of the first metal thin film 21, the second metal thin film 23B, and a via portion 24B on the second metal thin film 23B form a via 32. The via 32 is connected to the surface metal layer 12, which has a higher conductivity than the metal supporting layer 11, in the metal supporting board 10. The metal supporting board 10 and the wiring layer 31 are electrically connected via the via 32. The wiring layer 31 can be connected to ground via the via 32 and the metal supporting board 10.

[0038] The thickness of the wiring layer 31 is, for example, 3 μm or more, preferably 5 μm or more. The thickness of the wiring layer 31 is, for example, 50 μm or less, preferably 30 μm or less. The width of the wiring layer 31 (the dimension in the direction perpendicular to the extension direction of the wiring layer 31) is, for example, 5 μm or more, preferably 8 μm or more. The width of the wiring layer 31 is, for example, 100 μm or less, preferably 50 μm or less.

[0039] The insulating layer 25 is disposed on one thickness-wise side of the insulating layer 22 so as to cover the wiring layer 31 and the vias 32. The insulating layer 25 may have openings that partially expose the wiring layer 31 and / or the vias 32. That is, the insulating layer 25 may have openings through which the wiring layer 31 and / or the vias 32 are exposed. The portions of the wiring layer 31 and / or the vias 32 exposed through the openings can function as terminal portions of the wired circuit board X1, for example. The thickness of such an insulating layer 25 is, for example, 4 μm or more, preferably 6 μm or more. The thickness of the insulating layer is, for example, 60 μm or less, preferably 40 μm or less.

[0040] 3A to 3C and 4A to 4D show a method for manufacturing a wired circuit board X1 as one embodiment of the method for manufacturing a wired circuit board of the present invention. 3A to 3C and 4A to 4D show this manufacturing method as changes in the cross section corresponding to FIG.

[0041] In this manufacturing method, first, as shown in Fig. 3A, a metal supporting board 10 is prepared (preparation step). The metal supporting board 10 can be prepared by forming a surface metal layer 12 on a metal supporting layer 11 as a base material. Examples of methods for forming the surface metal layer 12 include a sputtering method, a plating method, and a vacuum deposition method. The surface metal layer 12 is preferably formed by a plating method.

[0042] 3B , a first metal thin film 21 is formed on the metal supporting board 10 (first metal thin film forming step). Examples of methods for forming the first metal thin film 21 include sputtering, vacuum deposition, and plating. Examples of plating methods include electrolytic plating and electroless plating. The first metal thin film 21 is preferably formed by sputtering.

[0043] Next, as shown in FIG. 3C , an insulating layer 22 is formed on one surface in the thickness direction of the first metal thin film 21 (base insulating layer formation process). In this process, the insulating layer 22 is formed, for example, as follows. First, a photosensitive resin solution (varnish) is applied to the first metal thin film 21 to form a coating film. Next, this coating film is dried by heating. Next, the coating film is subjected to an exposure process through a predetermined mask, a subsequent development process, and then a baking process as necessary. For example, in the above manner, an insulating layer 22 having a through hole 22 a can be formed on the first metal thin film 21. A portion 21 a of the first metal thin film 21 is exposed in the through hole 22 a.

[0044] Next, as shown in FIG. 4A , a second metal thin film 23 is formed (second metal thin film formation process). In this process, the second metal thin film 23 is continuously formed on one thickness-wise surface of the insulating layer 22, on the inner wall surface 22b of the through-hole 22a, and on the portion 21a of the first metal thin film 21 exposed in the through-hole 22a (the second metal thin film 23 includes the second metal thin film 23A outside the through-hole 22a and the second metal thin film 23B inside the through-hole 22a). Examples of methods for forming the second metal thin film 23 include sputtering, vacuum deposition, and plating. Examples of plating methods include electrolytic plating and electroless plating. The second metal thin film 23 is preferably formed by sputtering.

[0045] 4B, a conductor layer 24 is formed on one surface of the second metal thin film 23 in the thickness direction (conductor layer forming step).

[0046] First, a resist pattern is formed on the second metal thin film 23. The resist pattern has openings corresponding to the pattern shape of the conductor layer 24. To form the resist pattern, a photosensitive resist film is first attached to the second metal thin film 23 to form a resist film. Next, the resist film is subjected to an exposure process through a predetermined mask, a subsequent development process, and then a baking process, if necessary. To form the conductor layer 24, the above-mentioned metal is then grown on the second metal thin film 23 in the openings of the resist pattern by, for example, electroplating. Next, the resist pattern is removed. For example, in the above manner, a conductor layer 24 having a predetermined pattern can be formed on one surface in the thickness direction of the second metal thin film 23 (the conductor layer 24 includes wiring portions 24A on the second metal thin film 23A and via portions 24B on the second metal thin film 23B).

[0047] 4C , in this manufacturing method, the portion of the second metal thin film 23 that is not covered with the conductor layer 24 is then removed by etching (etching step). This forms the wiring layer 31 (wiring portion 24A, second metal thin film 23A) and the via 32 (via portion 24B, second metal thin film 23B, portion 21a). After this step, a nickel coating may be formed on the surface of the wiring layer 31 by, for example, electroless plating or electrolytic plating.

[0048] Next, as shown in FIG. 4D , an insulating layer 25 is formed on the insulating layer 22 so as to cover the wiring layer 31 and the vias 32 (cover insulating layer formation process). In this process, the insulating layer 25 is formed, for example, as follows. First, a photosensitive resin solution (varnish) is applied to the insulating layer 22, the wiring layer 31, and the vias 32 to form a coating film. Next, this coating film is dried. Next, the coating film is subjected to an exposure process through a predetermined mask, a subsequent development process, and then a baking process as necessary. For example, the insulating layer 25 as a cover insulating layer can be formed in the manner described above.

[0049] In this embodiment, the metal supporting board 10 is then patterned by etching the metal supporting board 10. This patterning includes, for example, processing to form the outer shape (outer shape in plan view) of the metal supporting board 10 and processing to form, for example, an island portion that is separated from the surrounding area on the metal supporting board 10. For example, after this step, a gold plating film may be formed on the exposed surface of the metal supporting board 10 by electrolytic plating or electroless plating. The exposed surface of the metal supporting board 10 specifically includes a surface that is not covered by the insulating layer 25 on one surface (surface metal layer 12) of the metal supporting board 10 in the thickness direction, the side surface of the metal supporting board 10, and the other surface (bottom surface in the drawing) of the metal supporting board 10 in the thickness direction.

[0050] In this manner, the wired circuit board X1 can be manufactured.

[0051] In the wired circuit board X1, as described above, the metal supporting board 10 includes the metal supporting layer 11 and the surface metal layer 12 that is disposed on one surface of the metal supporting layer 11 in the thickness direction and has a higher conductivity than the metal supporting layer 11. The via 32 is connected to the surface metal layer 12 that has a higher conductivity than the metal supporting layer 11 in the metal supporting board 10. Therefore, the wired circuit board X1 is suitable for realizing a low-resistance electrical connection between the metal supporting board 10 and the wiring layer 31 that is disposed on one side of the metal supporting board 10 in the thickness direction.

[0052] Furthermore, in the wired circuit board X1, as described above, the surface metal layer 12 having a higher conductivity than the metal support layer 11 is disposed on one surface in the thickness direction of the metal support layer 11. This configuration in which the metal support layer 11 and the surface metal layer 12 are in direct contact with each other without any other layer such as a Cr layer serving as a plating seed layer therebetween is suitable for efficiently patterning the metal supporting board 10 by a single treatment of the metal supporting board 10.

[0053] As described above, the wired circuit board X1 is suitable for realizing a low-resistance electrical connection between the metal supporting board 10 and the wiring layer 31 formed on the insulating layer 22 on the metal supporting board 10, and is also suitable for efficiently patterning the metal supporting board 10.

[0054] 5 and 6 show a wired circuit board X2 as another embodiment of the wired circuit board of the present invention. The wired circuit board X2 includes, in order toward one side in the thickness direction, a metal supporting board 10, a first metal thin film 21, an insulating layer 22 as a base insulating layer, a second metal thin film 23, a conductor layer 24, and an insulating layer 25 as a cover insulating layer. In the wired circuit board X2, the first metal thin film 21 has an opening 21b, and the second metal thin film 23 is connected to the first metal thin film 21 in the opening 21b. Other than this, the wired circuit board X2 has the same configuration as the wired circuit board X1.

[0055] In the wired circuit board X2, the opening 21b of the first metal thin film 21 penetrates the first metal thin film 21 in the thickness direction. The opening 21b has, for example, a substantially circular shape in a plan view. The opening 21b opens along the through hole 22a of the insulating layer 22. That is, the through hole 22a and the opening 21b overlap in a plan view. The through hole 22a and the opening 21b form a through hole H.

[0056] In the wired circuit board X2, the second metal thin film 23 is disposed continuously on one surface in the thickness direction of the insulating layer 22 and on a portion 10a of the metal supporting board 10 facing the through hole H (the second metal thin film 23 includes a second metal thin film 23A outside the through hole H and a second metal thin film 23B inside the through hole H). In the opening H, the second metal thin film 23B is directly connected to the metal supporting board 10.

[0057] In this embodiment, in the through hole H, the second metal thin film 23B and the via portion 24B on the second metal thin film 23B form a via 32. The via 32 is connected to the surface metal layer 12, which has a higher conductivity than the metal supporting layer 11, in the metal supporting board 10. The metal supporting board 10 and the wiring layer 31 are electrically connected via the via 32. The wiring layer 31 can be connected to ground via the via 32 and the metal supporting board 10.

[0058] 7A to 7C and 8A to 8B show some steps in a method for manufacturing a wired circuit board X2 as one embodiment of the method for manufacturing a wired circuit board of the present invention. 7A to 7C and 8A to 8B show this manufacturing method as changes in the cross section corresponding to FIG. 5.

[0059] In this manufacturing method, first, the preparation step, the first metal thin film formation step, and the insulating base layer formation step are carried out in the same manner as described above with reference to FIGS. 3A to 3C.

[0060] Next, the portion 21a of the first metal thin film 21 exposed at the through hole 22a of the insulating layer 22 is removed. As a result, a part (portion 10a) of the metal supporting board 10 is exposed at the through hole 22a, as shown in Fig. 7A (removal step). In this step, an opening 21b is formed in the first metal thin film 21 by removing the portion 21a (the opening 21b opens along the through hole 22a, and the through hole 22a and the opening 21b form an opening H).

[0061] The removal method in this step includes wet etching and dry etching, with wet etching being preferred. Examples of the etching solution for wet etching include ceric ammonium nitrate solution, caustic soda solution, potassium permanganate solution, and sodium metasilicate solution, with ceric ammonium nitrate solution being preferred. The temperature of the etching solution in wet etching is, for example, 20°C or higher, preferably 30°C or higher. The temperature of the etching solution is, for example, 80°C or lower, preferably 65°C or lower. The etching time (immersion time) in wet etching is, for example, 1 minute or longer. The etching time is, for example, 15 minutes or shorter, preferably 10 minutes or shorter.

[0062] 7B , the second metal thin film 23 is formed (second metal thin film forming step). In this step, the second metal thin film 23 is continuously formed on one surface in the thickness direction of the insulating layer 22 and on the portion 10a of the metal supporting board 10 exposed at the through hole H (the second metal thin film 23 includes the second metal thin film 23A outside the through hole 22a and the second metal thin film 23B inside the through hole 22a). Examples of methods for forming the second metal thin film 23 include sputtering, vacuum deposition, and plating. Examples of plating methods include electrolytic plating and electroless plating. The second metal thin film 23 is preferably formed by sputtering.

[0063] Next, as shown in Fig. 7C, a conductor layer 24 is formed on one surface in the thickness direction of the second metal thin film 23 (conductor layer forming step). Specifically, this is the same as the conductor forming step described above with reference to Fig. 4B.

[0064] 8A , the portions of the second metal thin film 23 that are not covered with the conductor layer 24 are removed by etching (etching step), thereby forming the wiring layer 31 (wiring portion 24A, second metal thin film 23A) and the via 32 (via portion 24B, second metal thin film 23B).

[0065] Next, as shown in Fig. 8B, an insulating layer 25 is formed on the insulating layer 22 so as to cover the wiring layer 31 and the vias 32 (cover insulating layer forming step). Specifically, this is the same as the cover insulating layer forming step described above with reference to Fig. 4D.

[0066] In this embodiment, next, the metal supporting board 10 is patterned by etching the metal supporting board 10. This patterning includes, for example, processing to form the outer shape (outer shape in plan view) of the metal supporting board 10, and processing to form, for example, an island portion that is separated from the surrounding area in the metal supporting board 10.

[0067] In this manner, the wired circuit board X2 can be manufactured.

[0068] In this manufacturing method, a removing step (shown in FIG. 7A ) is performed after the insulating base layer forming step (shown in FIG. 3C ). In the removing step, the portion 21 a of the first metal thin film 21 is removed, and the metal supporting board 10 is exposed at the through hole 22 a. In such a removing step, even if the surface of the portion 21 a (shown in FIG. 3C ) of the first metal thin film 21 facing the through hole 22 a is oxidized, the portion 21 a with the oxide film can be removed. In the subsequent second metal thin film forming step (shown in FIG. 7B ), a second metal thin film 23B is formed on the portion 10 a of the metal supporting board 10 facing the through hole 22 a. Then, in the conductor layer forming step (shown in FIG. 7C ), a via portion 24B is formed on the second metal thin film 23B. As a result, a via 32 (the second metal thin film 23B, the via portion 24B) is formed in the through hole 22 a.

[0069] In this way, according to the present manufacturing method, the via 32 is formed, which is connected to the metal supporting board 10 without going through the first metal thin film 21. Therefore, the present manufacturing method is suitable for realizing low-resistance electrical connection between the metal supporting board 10 and the wiring layer 31.

[0070] In the wired circuit board X2, similarly to the wired circuit board X1, the metal supporting board 10 includes a surface metal layer 12 that is disposed on one surface in the thickness direction of the metal supporting layer 11 and has a higher conductivity than the metal supporting layer 11. Furthermore, the via 32 is connected to the surface metal layer 12, which has a higher conductivity than the metal supporting layer 11, in the metal supporting board 10. Therefore, similarly to the wired circuit board X1, the wired circuit board X2 is suitable for realizing a low-resistance electrical connection between the metal supporting board 10 and the wiring layer 31, and is suitable for efficiently patterning the metal supporting board 10.

[0071] The above-described embodiments are merely examples of the present invention, and the present invention should not be construed as being limited by these embodiments. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims.

[0072] The wired circuit board of the present invention can be applied to a wired circuit board having a metal supporting board as a supporting substrate.

[0073] X1, X2 Wired circuit board 10 Metal supporting board 11 Metal supporting layer 12 Surface metal layer 21 First metal thin film 21b Opening 22 Insulating layer 22a, H Through hole 22b Inner wall surface 23, 23A, 23B Second metal thin film 24 Conductor layer 24A Wiring portion 24B Via portion 24b Peripheral side surface 25 Insulating layer 31 Wiring layer 32 Via

Claims

1. A wired circuit board comprising, in order toward one side in the thickness direction, a metal supporting board, a first metal thin film, an insulating layer, a second metal thin film, and a conductor layer, wherein the metal supporting board comprises a metal supporting layer and a surface metal layer that is disposed on one surface of the metal supporting layer in the thickness direction and has a higher conductivity than the metal supporting layer, the insulating layer has a through hole that penetrates the insulating layer in the thickness direction, and the conductor layer has a via part that is disposed in the through hole and is electrically connected to the metal supporting board.

2. The printed circuit board according to claim 1, wherein said metal support layer comprises at least one selected from the group consisting of stainless steel, copper alloy, aluminum, nickel, and titanium.

3. The printed circuit board according to claim 1, wherein said surface metal layer contains at least one selected from the group consisting of gold, silver, and copper.

4. The wired circuit board according to claim 1, wherein the via portion is electrically connected to the metal supporting board through the first metal thin film and the second metal thin film.

5. The wired circuit board according to claim 1, wherein the first metal thin film has an opening that opens along the through hole, and the via portion is electrically connected to the metal supporting board through the second metal thin film.

6. A method for manufacturing a wired circuit board, comprising: a first metal thin film forming step of forming a first metal thin film on one surface in the thickness direction of a metal supporting board, the metal supporting board having a metal supporting layer and a surface metal layer disposed on one surface in the thickness direction of the metal supporting layer and having a higher conductivity than the metal supporting layer; an insulating layer forming step of forming an insulating layer having a through hole on one surface in the thickness direction of the first metal thin film; a second metal thin film forming step of forming a second metal thin film on one surface in the thickness direction of the insulating layer and on a portion of the first metal thin film exposed at the through hole; and a conductor layer forming step of forming a conductor layer including a via portion disposed in the through hole on one surface in the thickness direction of the second metal thin film.

7. A method for manufacturing a wired circuit board, comprising: a first metal thin film forming step of forming a first metal thin film on one surface in the thickness direction of a metal supporting board, the metal supporting board having a metal supporting layer and a surface metal layer arranged on one surface in the thickness direction of the metal supporting layer and having a higher conductivity than the metal supporting layer; an insulating layer forming step of forming an insulating layer having a through hole on one surface in the thickness direction of the first metal thin film; a removing step of removing a portion of the first metal thin film exposed in the through hole to expose the metal supporting board at the through hole; a second metal thin film forming step of forming a second metal thin film on one surface in the thickness direction of the insulating layer and on the portion of the metal supporting board exposed in the through hole; and a conductor layer forming step of forming a conductor layer including a via portion arranged in the through hole on one surface in the thickness direction of the second metal thin film.

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