Wiring circuit board and manufacturing method for the same

Abstract

To provide a wiring circuit board and a manufacturing method for the same that can suppress corrosion of wiring while suppressing a decrease in manufacturing efficiency.SOLUTION: A wiring circuit board 1 includes a first insulating layer 12, a conductor pattern 14, a second insulating layer 16, and a first nickel layer 15 positioned between wiring 143 and the second insulating layer 16, covering the wiring 143 but not covering a terminal 141. The first nickel layer 15 contains phosphorus, and the phosphorus content in the first nickel layer 15 is 6 mass% or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, a circuit board has been known that includes an insulating layer, a conductor circuit disposed on the insulating layer, a cover that covers the conductor circuit, and a thin metal film disposed between the conductor circuit and the cover. The thin metal film is made of nickel formed by electroless plating (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-233906 Summary of the Invention [Problem to be solved by the invention]

[0004] In the circuit board described in Patent Document 1, after a conductor circuit is formed, a thin metal film is formed on the entire surface of the conductor circuit, a cover is formed, and then unnecessary portions of the thin metal film are removed.

[0005] In this regard, if it takes an excessively long time to remove the metal thin film, there is a possibility that the manufacturing efficiency will decrease accordingly.

[0006] The present invention provides a wired circuit board that can suppress corrosion of wiring while suppressing a decrease in manufacturing efficiency, and a method for manufacturing the wired circuit board. [Means for solving the problem]

[0007] The present invention [1] includes a wired circuit board comprising: a first insulating layer; a conductor pattern disposed on the first insulating layer and having terminals and wiring; a second insulating layer disposed on the first insulating layer and covering the wiring but not the terminals; and a first nickel layer disposed between the wiring and the second insulating layer and covering the wiring but not the terminals, wherein the first nickel layer contains phosphorus, and the phosphorus content in the first nickel layer is 6 mass % or less.

[0008] According to this configuration, the first nickel layer is disposed between the wiring and the second insulating layer.

[0009] Therefore, the wiring can be protected from the second insulating layer, and corrosion of the wiring can be suppressed.

[0010] The phosphorus content of the first nickel layer is adjusted to 6 mass % or less.

[0011] Therefore, in manufacturing a wired circuit board, the first nickel layer is formed so as to cover the wires and terminals, and then the first nickel layer covering the terminals can be easily removed by etching.

[0012] Therefore, after the first nickel layer is formed, it is possible to prevent excessive time from being required to remove the first nickel layer that covers the terminals, and to prevent a decrease in manufacturing efficiency.

[0013] In summary, it is possible to suppress corrosion of wiring while suppressing a decrease in manufacturing efficiency.

[0014] The present invention [2] includes the wired circuit board of the above [1], further comprising a coating layer made of a metal different from that of the terminals and covering the terminals, the coating layer comprising a second nickel layer different from the first nickel layer.

[0015] With this configuration, the second nickel layer suitable for protecting the terminals can be selected independently of the first nickel layer that protects the wiring.

[0016] As a result, the degree of freedom in designing the printed circuit board can be ensured.

[0017] The present invention [3] includes the wired circuit board according to the above [2], wherein the second nickel layer contains phosphorus, and the phosphorus content in the second nickel layer is more than 6 mass %.

[0018] According to this configuration, the phosphorus content in the second nickel layer is adjusted to be greater than 6 mass %.

[0019] Therefore, when the terminal is made of copper and a surface layer made of gold is formed on the second nickel layer, it is possible to prevent the gold from diffusing into the terminal.

[0020] The present invention [4] includes the wired circuit board of any one of the above [1] to [3], wherein the thickness of the first nickel layer is 300 nm or less.

[0021] This configuration can prevent cracks from occurring in the wiring.

[0022] The present invention [5] includes the wired circuit board of any one of the above [1] to [4], wherein the first nickel layer is an electroless nickel-phosphorus plating layer.

[0023] The present invention [6] is a method for producing a wired circuit board according to any one of the above [1] to [5], comprising a conductor pattern forming step of forming the conductor pattern on the first insulating layer, a first nickel layer forming step of forming the first nickel layer covering the wiring and the terminals, a second insulating layer forming step of forming the second insulating layer on the first insulating layer, and a removal step of removing the first nickel layer covering the terminals by etching.

[0024] According to this method, the first nickel layer can be formed between the wiring and the second insulating layer.

[0025] Therefore, the wiring can be protected from the second insulating layer, and corrosion of the wiring can be suppressed.

[0026] The phosphorus content of the first nickel layer is adjusted to 6 mass % or less.

[0027] Therefore, in the first nickel layer forming step, the first nickel layer is formed so as to cover the wiring and the terminals, and then in the removing step, the first nickel layer covering the terminals can be easily removed by etching.

[0028] Therefore, the removal process can be prevented from taking an excessively long time, and a decrease in manufacturing efficiency can be prevented.

[0029] In summary, it is possible to suppress corrosion of wiring while suppressing a decrease in manufacturing efficiency.

[0030] The present invention [7] includes the method for producing a wired circuit board according to the above [6], wherein in the first nickel layer forming step, the first nickel layer is formed on the wiring and the terminals by electroless plating using a catalyst. [Effects of the Invention]

[0031] According to the wired circuit board and the method for manufacturing the wired circuit board of the present invention, it is possible to suppress corrosion of the wiring while suppressing a decrease in manufacturing efficiency. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a plan view of one embodiment of the wired circuit board of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the printed circuit board shown in FIG. 1 taken along the line AA. [Figure 3] Figure 3A shows the first insulating layer formation step in the manufacturing method of the wired circuit board shown in Figure 2, Figure 3B shows the step of forming a protective metal layer on the first insulating layer following Figure 3A, and Figure 3C shows the step of forming a metal thin film on the protective metal layer following Figure 3B. [Figure 4] Figure 4A shows the process of forming a conductive pattern on a metal thin film following Figure 3C, Figure 4B shows the process of forming a first nickel layer following Figure 4A, and Figure 4C shows the process of forming a second insulating layer following Figure 4B. [Figure 5] FIG. 5A shows a removal step subsequent to FIG. 4C, FIG. 5B shows a step of forming a second nickel layer on the terminal, and FIG. 5C shows a step of forming a surface layer on the second nickel layer. DETAILED DESCRIPTION OF THE INVENTION

[0033] 1. Wiring circuit board As shown in Fig. 1, the wired circuit board 1 extends in the length direction and width direction. In this embodiment, the wired circuit board 1 has a substantially rectangular shape. However, the shape of the wired circuit board 1 is not limited to this embodiment. The wired circuit board 1 may be a flexible wired circuit board or a circuit-equipped suspension board.

[0034] As shown in FIG. 2, the wired circuit board 1 includes a metal support layer 11, a first insulating layer 12, a protective metal layer 13, a conductive pattern 14, a first nickel layer 15, a second insulating layer 16, and a coating layer 17.

[0035] (1) Metal support layer The metal support layer 11 supports the first insulating layer 12, the conductive pattern 14, and the second insulating layer 16. Examples of materials for the metal support layer 11 include stainless steel and copper alloys.

[0036] The metal support layer 11 has a thickness of, for example, 10 μm to 1000 μm, or preferably 50 μm to 200 μm.

[0037] (2) First insulating layer The first insulating layer 12 is disposed on one side of the metal support layer 11 in the thickness direction of the metal support layer 11. The thickness direction is perpendicular to the length direction and width direction. The first insulating layer 12 is disposed on one surface of the metal support layer 11 in the thickness direction. The first insulating layer 12 is disposed between the metal support layer 11 and the conductive pattern 14 in the thickness direction. The first insulating layer 12 can insulate the metal support layer 11 from the conductive pattern 14. The first insulating layer 12 is made of a resin. Examples of resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. Preferably, the first insulating layer 12 is made of polyimide.

[0038] The thickness of the first insulating layer 12 is in the range of, for example, 3 μm to 50 μm, or preferably 5 μm to 20 μm.

[0039] (3) Protective metal layer The protective metal layer 13 is disposed between the first insulating layer 12 and the conductive pattern 14 in the thickness direction. The protective metal layer 13 is disposed on one surface of the first insulating layer 12 in the thickness direction. The protective metal layer 13 protects the conductive pattern 14 from the first insulating layer 12. The protective metal layer 13 is made of a metal different from that of the conductive pattern 14. Examples of materials for the protective metal layer 13 include chromium, nickel, titanium, and alloys thereof. Chromium is a preferred material for the protective metal layer 13.

[0040] (4) Conductor pattern The conductor pattern 14 is disposed on one side of the first insulating layer 12 in the thickness direction. The conductor pattern 14 is disposed on the protective metal layer 13 in the thickness direction. In other words, the conductor pattern 14 is disposed on one surface of the first insulating layer 12 in the thickness direction, with the protective metal layer 13 interposed therebetween. The conductor pattern 14 is disposed on the opposite side of the metal support layer 11 from the first insulating layer 12 in the thickness direction. The conductor pattern 14 is made of a metal. Examples of metals include copper, silver, gold, iron, aluminum, and alloys thereof. The conductor pattern 14 is preferably made of copper.

[0041] The thickness of the conductive pattern 14 is in the range of, for example, 3 μm to 70 μm, or preferably 5 μm to 30 μm.

[0042] 1, the conductive pattern 14 has a terminal 141, a terminal 142, and a wiring 143. The number of terminals and the number of wirings are not limited.

[0043] The terminal 141 is disposed at one end in the length direction of the wired circuit board 1. The terminal 141 has, for example, a square land shape.

[0044] The terminal 142 is disposed at the other end in the length direction of the wired circuit board 1. The terminal 142 has, for example, a square land shape.

[0045] One end of the wiring 143 is connected to the terminal 141. The other end of the wiring 143 is connected to the terminal 142. The wiring 143 electrically connects the terminal 141 and the terminal 142 together.

[0046] The width of the wiring 143 is narrower than the width of the terminals 141 and 142. The width of the wiring 143 is, for example, 5 μm to 100 μm, or preferably 8 μm to 50 μm.

[0047] (4) First nickel layer As shown in FIG. 2, the first nickel layer 15 is disposed between the wiring 143 and the second insulating layer 16. The first nickel layer 15 covers the wiring 143. The first nickel layer 15 covers the entire portion of the wiring 143 that is covered by the second insulating layer 16. More specifically, the first nickel layer 15 covers one surface of the wiring 143 in the thickness direction and all of both side surfaces of the wiring 143 in the width direction. The first nickel layer 15 protects the wiring 143 from the second insulating layer 16. The first nickel layer 15 does not cover the terminals 141, 142.

[0048] The first nickel layer 15 contains phosphorus. Specifically, the first nickel layer 15 is made of a nickel-phosphorus alloy. The first nickel layer 15 is preferably an electroless nickel-phosphorus plating layer.

[0049] The phosphorus content in the first nickel layer 15 is 6 mass % or less, preferably 4 mass % or less, and for example, more than 0 mass %, preferably 1 mass % or more.

[0050] When the content of phosphorus in the first nickel layer 15 is equal to or less than the upper limit, the first nickel layer 15 on the terminals 141, 142 can be efficiently removed by etching in the removal step of the method for producing the wired circuit board described below.

[0051] When the content of phosphorus in the first nickel layer 15 is equal to or greater than the lower limit, corrosion of the wiring 143 can be suppressed.

[0052] The first nickel layer 15 has a thickness T1 of, for example, 500 nm or less, preferably 300 nm or less, and for example, 1 nm or more, preferably 50 nm or more.

[0053] When the thickness T1 of the first nickel layer 15 is equal to or less than the upper limit, the occurrence of cracks in the wiring 143 can be suppressed.

[0054] When the thickness T1 of the first nickel layer 15 is equal to or greater than the above lower limit, corrosion of the wiring 143 can be suppressed.

[0055] (5) Second insulating layer 1 and 2, the second insulating layer 16 is disposed on the first insulating layer 12 in the thickness direction. The second insulating layer 16 covers the wiring 143. The second insulating layer 16 does not cover the terminals 141, 142. The second insulating layer 16 is made of a resin. Examples of the resin include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester.

[0056] (6) Covering layer The coating layer 17 covers the terminal 141. Specifically, the coating layer 17 covers one side of the terminal 141 in the thickness direction and both side surfaces of the terminal 141 in the width direction. The coating layer 17 is made of a metal different from that of the terminal 141. The coating layer 17 may be a single layer or multiple layers. The coating layer 17 is preferably multiple layers, and has a second nickel layer 171 and a surface layer 172.

[0057] The second nickel layer 171 covers the terminal 141. Specifically, the second nickel layer 171 covers one surface of the terminal 141 in the thickness direction and both side surfaces of the terminal 141 in the width direction. The second nickel layer 171 is disposed between the terminal 141 and the surface layer 172. The second nickel layer 171 contains phosphorus. Specifically, the second nickel layer 171 is made of, for example, a nickel-phosphorus alloy. The second nickel layer 171 is preferably an electroless nickel-phosphorus plated layer. The second nickel layer 171 is different from the first nickel layer 15. Specifically, the phosphorus content in the second nickel layer 171 is different from the phosphorus content in the first nickel layer 15.

[0058] The phosphorus content in the second nickel layer 171 is higher than the phosphorus content in the first nickel layer 15. Specifically, the phosphorus content in the second nickel layer 171 is, for example, higher than 6 mass %, preferably 7 mass % or more, and more preferably 9 mass % or more.

[0059] If the content of phosphorus in second nickel layer 171 is higher than the lower limit, when surface layer 172 is made of gold, the gold in surface layer 172 can be prevented from diffusing into terminal 141.

[0060] The thickness T2 of the second nickel layer 171 is thicker than the thickness T1 of the first nickel layer 15. The thickness T2 of the second nickel layer 171 is, for example, more than 50 nm, preferably 100 nm or more, and for example, 1000 nm or less, preferably 600 nm or less.

[0061] If the thickness of second nickel layer 171 is greater than the above lower limit, when surface layer 172 is made of gold, the gold of surface layer 172 can be prevented from diffusing into terminal 141.

[0062] Surface layer 172 covers second nickel layer 171. Surface layer 172 is made of a metal different from that of conductive pattern 14 and second nickel layer 171. Surface layer 172 is made of gold, for example. Surface layer 172 is preferably an electroless gold plating layer.

[0063] The above-mentioned coating layer 17 is also provided on the terminal 142 (see FIG. 1).

[0064] 2. Manufacturing method of printed circuit board A method for manufacturing the wired circuit board 1 will be described below with reference to FIGS. 3A to 5C.

[0065] The method for manufacturing the wired circuit board 1 includes a first insulating layer forming step (see FIG. 3A), a conductor pattern forming step (see FIGS. 3B to 4A), a first nickel layer forming step (see FIG. 4B), a second insulating layer forming step (see FIG. 4C), a removal step (see FIG. 5A), and a coating layer forming step (see FIGS. 5B and 5C).

[0066] (1) First insulating layer formation process As shown in FIG. 3A, in the first insulating layer forming step, first insulating layer 12 is formed on one surface of metal support layer 11.

[0067] Specifically, in the first insulating layer forming step, a photosensitive resin solution (varnish) is first applied onto the metal support layer 11 and dried to form a photosensitive resin coating. Next, the photosensitive resin coating is exposed to light and developed. This results in the first insulating layer 12.

[0068] (2) Conductor pattern formation process Next, in the conductive pattern forming step, a protective metal layer 13 and a conductive pattern 14 are formed on the first insulating layer 12.

[0069] More specifically, as shown in Figures 3B and 3C, first, a seed layer is formed on one surface of the first insulating layer 12 and one surface of the metal support layer 11 in the thickness direction. In this embodiment, the seed layer has a protective metal layer 13 and a conductive thin film M. The protective metal layer 13 is disposed on one surface of the first insulating layer 12 and one surface of the metal support layer 11. The conductive thin film M is disposed on one surface of the protective metal layer 13. The protective metal layer 13 and the conductive thin film M are formed by sputtering. That is, the protective metal layer 13 and the conductive thin film M are formed in this order on the first insulating layer and the metal support layer by sputtering. The conductive thin film M is made of the same material as the conductive pattern 14. The conductive thin film M constitutes a part of the conductive pattern 14.

[0070] Next, a plating resist is attached to one surface of the conductive thin film M in the thickness direction. The conductive thin film M is covered with the plating resist.

[0071] Next, the plating resist is exposed to light and developed, whereby the plating resist is removed from the areas where the conductive patterns 14 are to be formed, exposing the conductive thin film M in the areas where the conductive patterns 14 are to be formed. On the other hand, the plating resist remains in the areas where the conductive patterns 14 are not to be formed.

[0072] Next, a conductive pattern 14 is formed by electrolytic plating on the exposed conductive thin film M. After the electrolytic plating is completed, the plating resist is peeled off, and the seed layer (the conductive thin film M and the protective metal layer 13) exposed by the peeling of the plating resist is removed by etching.

[0073] As a result, a protective metal layer 13 and a conductive pattern 14 are formed on the first insulating layer 12, as shown in FIG. 4A.

[0074] (3) First nickel layer formation process Next, as shown in Fig. 4B, in the first nickel layer forming step, the first nickel layer 15 is formed. In the first nickel layer forming step, the first nickel layer is formed by electroless plating on the entire surface of the conductive pattern 14. In other words, in the first nickel layer forming step, the first nickel layer 15 is formed by electroless plating on the wiring 143 and the terminals 141, 142.

[0075] The plating solution (first plating solution) used in the first nickel layer forming step contains a nickel salt and a phosphinate as a reducing agent. Examples of nickel salts include nickel sulfate. Examples of phosphinate include sodium phosphinate. The first plating solution may contain a buffer. The buffer is not limited as long as it can stabilize the pH of the first plating solution.

[0076] The mixing ratio of the nickel salt in the first plating solution is, for example, 0.1 to 2.0 mass %, or preferably 0.5 to 1.5 mass %.

[0077] The mixing ratio of the reducing agent in the first plating liquid is, for example, 0.1% by mass to 2.0% by mass, or preferably 0.5% by mass to 1.5% by mass.

[0078] In the first nickel layer forming step, a catalyst is added to the first plating solution to promote the growth of the first nickel layer 15. That is, in the first nickel layer forming step, electroless plating is performed using a catalyst.

[0079] When the reducing agent is a phosphinate, catalysts include, for example, palladium, iron, nickel, and zinc.

[0080] The temperature of the first plating solution is, for example, 20°C to 80°C, preferably 30°C to 65°C, and more preferably 50°C to 60°C.

[0081] By performing electroless plating using the first plating solution having the above composition within the above temperature range of the first plating solution, the phosphorus content in the first nickel layer 15 can be adjusted to 6 mass % or less. Furthermore, by increasing the temperature of the first plating solution, the phosphorus content in the first nickel layer 15 can be reduced.

[0082] The first nickel layer 15 obtained in the first nickel layer forming step covers the wiring 143 and the terminals 141 and 142.

[0083] (4) Second insulating layer formation process Next, as shown in FIG. 4C, in the second insulating layer forming step, second insulating layer 16 is formed on first insulating layer 12.

[0084] More specifically, in the second insulating layer forming step, first, a photosensitive resin solution (varnish) is applied onto the first nickel layer 15 and the first insulating layer 12 and dried to form a photosensitive resin coating.

[0085] Next, the photosensitive resin coating is exposed to light and developed, thereby forming a second insulating layer 16 on the first insulating layer 12 to cover the first nickel layer 15.

[0086] (5) Removal process Next, as shown in FIG. 5A, in the removal step, the first nickel layer 15 covering the terminals 141 and 142 is removed.

[0087] To remove the first nickel layer 15, for example, the first nickel layer 15 is etched with an acid. Examples of the acid include nitric acid.

[0088] At this time, since the content of phosphorus in the first nickel layer 15 is adjusted to 6 mass % or less, the first nickel layer 15 can be efficiently removed by the acid.

[0089] (6) Covering layer formation process Next, in the coating layer forming step, the coating layer 17 is formed on the surfaces of the terminals 141 and 142.

[0090] More specifically, as shown in FIG. 5B, in the coating layer forming step, second nickel layers 171 are formed on the surfaces of terminals 141 and 142 by electroless plating.

[0091] The plating solution (second plating solution) used in forming the second nickel layer 171 also contains a nickel salt and a phosphinate as a reducing agent, similar to the first plating solution used in the first nickel layer forming step. Examples of nickel salts include nickel sulfate. Examples of phosphinates include sodium phosphinate. The second plating solution may contain a buffer. The buffer is not limited as long as it can stabilize the pH of the second plating solution.

[0092] The mixing ratio of the nickel salt in the second plating liquid is, for example, 3% by mass to 7% by mass, or preferably 4% by mass to 6% by mass.

[0093] The mixing ratio of the reducing agent in the second plating liquid is, for example, 1% by mass to 5% by mass, or preferably 1% by mass to 3% by mass.

[0094] In the step of forming the second nickel layer, as in the step of forming the first nickel layer, the growth of the second nickel layer 171 is promoted by adding the above-mentioned catalyst to the second plating solution.

[0095] The temperature of the second plating liquid is, for example, 80°C to 90°C.

[0096] By performing electroless plating using the second plating solution having the above composition within the above temperature range of the second plating solution, the phosphorus content in the second nickel layer 171 can be made greater than 6 mass %.

[0097] Next, as shown in FIG. 5C, a surface layer 172 is formed on the second nickel layer 171 by electroless gold plating.

[0098] In this way, the wired circuit board 1 can be obtained.

[0099] 3. Effects (1) According to the wired circuit board 1, the first nickel layer 15 is disposed between the wire 143 and the second insulating layer 16, as shown in FIG.

[0100] Therefore, the wiring 143 can be protected from the second insulating layer 16, and corrosion of the wiring 143 can be suppressed.

[0101] The phosphorus content of the first nickel layer 15 is adjusted to 6 mass % or less.

[0102] Therefore, as shown in Figure 4B, in the first nickel layer formation process, the first nickel layer 15 is formed to cover the wiring 143 and the terminals 141, 142, and then, as shown in Figure 5A, in the removal process, the first nickel layer 15 covering the terminals 141, 142 can be easily removed by etching.

[0103] Therefore, the removal process can be prevented from taking an excessively long time, and a decrease in manufacturing efficiency can be prevented.

[0104] In summary, it is possible to suppress corrosion of the wiring 143 while suppressing a decrease in manufacturing efficiency.

[0105] (2) According to the wired circuit board 1, the covering layer 17 covering the terminals 141 and 142 has the second nickel layer 171 different from the first nickel layer 15, as shown in FIG.

[0106] Therefore, the second nickel layer 171 suitable for protecting the terminals 141 and 142 can be selected independently of the first nickel layer 15 that protects the wiring 143 .

[0107] As a result, the degree of freedom in designing the wired circuit board 1 can be ensured.

[0108] (3) According to the wired circuit board 1, the phosphorus content in the second nickel layer 171 is adjusted to be greater than 6 mass %.

[0109] Therefore, when the terminals 141 and 142 are made of copper and the surface layer 172 made of gold is formed on the second nickel layer 171 , the diffusion of gold into the terminals 141 and 142 can be suppressed.

[0110] (4) According to the wired circuit board 1, the thickness T1 of the first nickel layer 15 is 300 nm or less.

[0111] Therefore, cracks in the wiring 143 can be suppressed.

[0112] 4. Variations In the modified example, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0113] (1) The wired circuit board 1 does not necessarily have to have the covering layer 17 .

[0114] (2) The method for forming the first nickel layer 15 is not limited to electroless plating, as long as a nickel-phosphorus alloy can be formed.

[0115] (3) The wired circuit board 1 does not necessarily have to have the metal support layer 11. [Example]

[0116] The present invention will be described in more detail below with reference to examples and comparative examples. It should be noted that the present invention is not limited to these examples and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be substituted with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Description of the Invention" above.

[0117] 1. Manufacturing of printed circuit boards (1) Example 1 First, a photosensitive polyimide (photosensitive resin) solution (varnish) was applied to a metal support layer made of a copper alloy and dried to form a photosensitive polyimide coating. Next, the photosensitive polyimide coating was exposed to light and developed. This resulted in the formation of a first insulating layer made of polyimide on the metal support layer (first insulating layer formation step, see Figure 3A).

[0118] Next, a seed layer was formed on the first insulating layer and the metal support layer. Specifically, a protective metal layer made of chromium and a conductive thin film made of copper were formed in this order on the first insulating layer and the metal support layer by sputtering (see Figures 3B and 3C). The seed layer consisted of a protective metal layer and a conductive thin film.

[0119] Next, a plating resist was attached to one side of the conductive thin film, and the plating resist was exposed and developed, whereby the plating resist was removed from the area where the conductive pattern was to be formed, exposing the conductive thin film in the area where the conductive pattern was to be formed.

[0120] Next, a copper conductor pattern was formed on the exposed conductor thin film by electrolytic plating (see Figure 4A). After electrolytic plating was completed, the plating resist was stripped off, and the seed layer (conductor thin film and protective metal layer) exposed by the stripping of the plating resist was removed by etching. This resulted in the formation of a protective metal layer and conductor pattern on the first insulating layer (conductor pattern formation process).

[0121] Next, a first nickel layer was formed on the entire surface of the conductive pattern by electroless nickel-phosphorus plating (first nickel layer forming step, see FIG. 4B).

[0122] Next, a photosensitive polyimide solution (varnish) was applied to the first nickel layer and the first insulating layer and dried to form a photosensitive polyimide coating. Next, the photosensitive polyimide coating was exposed to light and developed to form a second insulating layer on the first insulating layer, covering the first nickel layer (second insulating layer formation step, see Figure 4C).

[0123] Next, the first nickel layer covering the terminals was removed by etching with acid (nitric acid) at 30° C. (removal step, see FIG. 5A).

[0124] Next, a second nickel layer was formed on the surface of the terminal by electroless nickel-phosphorus plating (see FIG. 5B). Next, a gold surface layer was formed on the second nickel layer by electroless gold plating (see FIG. 5C).

[0125] In this way, a wired circuit board was obtained.

[0126] Table 1 shows the composition of the plating solution (first plating solution) used to form the first nickel layer, the temperature of the first plating solution, the thickness of the formed first nickel layer, the phosphorus content in the formed first nickel layer, the etchability of the first nickel layer in the removal step, the composition of the plating solution (second plating solution) used to form the second nickel layer, the temperature of the second plating solution, the thickness of the formed second nickel layer, and the phosphorus content in the formed second nickel layer.

[0127] The etching property of the first nickel layer in the removal step was evaluated according to the following evaluation criteria.

[0128] <Evaluation criteria for etching properties> A: The first nickel layer was completely removed.

[0129] B: The first nickel layer remained.

[0130] The phosphorus content was measured by X-ray fluorescence analysis using a standard sample with a known phosphorus content as a reference.

[0131] (2) Examples 2 and 3 A wired circuit board was produced in the same manner as in Example 1, except that the temperature of the first plating solution was changed to the temperature shown in Table 1. The results are shown in Table 1.

[0132] (3) Examples 4 to 6 A wired circuit board was produced in the same manner as in Example 1, except that the composition and temperature of the second plating solution were changed to those shown in Table 2. The results are shown in Table 2.

[0133] (4) Example 7 Except for forming the second nickel layer by electrolytic plating, a wired circuit board was produced in the same manner as in Example 1. The results are shown in Table 2.

[0134] (5) Example 8 Except for changing the thickness of the first nickel layer to 600 nm, a wired circuit board was produced in the same manner as in Example 1. The results are shown in Table 2.

[0135] (6) Comparative Example 1 Except for not forming the first nickel layer, a wired circuit board was produced in the same manner as in Example 1. The results are shown in Table 3.

[0136] (7) Comparative Example 2 Except for forming the first nickel layer by electrolytic plating, a wired circuit board was produced in the same manner as in Example 1. The results are shown in Table 3.

[0137] (8) Comparative Example 3 Except for forming the first nickel layer by electroless nickel-boron plating (reducing agent: dimethylamine borane), a wired circuit board was produced in the same manner as in Example 1. The results are shown in Table 3.

[0138] (9) Comparative Examples 4 and 5 A wired circuit board was produced in the same manner as in Example 1, except that the composition and temperature of the first plating solution were changed to those shown in Table 3. The results are shown in Table 3.

[0139] 2.Inspection of wiring circuit boards (1) Corrosion resistance of wiring Random vibration test specified in JIS Z0232:2020, test conditions: acceleration power spectrum density: 0.33g 2 The test was carried out under the following conditions: / Hz, frequency: 5 to 500 Hz, and test time: 2000 minutes.

[0140] Thereafter, the wiring was observed with a camera (CCD camera), and the corrosion resistance of the wiring was evaluated based on the following evaluation criteria. The results are shown in Tables 1 to 3.

[0141] <Evaluation criteria> A: There is no discoloration on the wiring.

[0142] B: The wiring is discolored.

[0143] (2) Wiring reliability test The reliability of the wiring was evaluated based on the following evaluation criteria, with the resistance values ​​of the wiring measured before and after the random vibration test. The results are shown in Tables 1 to 3.

[0144] <Evaluation criteria> A: The change in resistance value before and after the vibration test is less than 20%.

[0145] B: The rate of change in resistance value before and after the vibration test is 20% or more and less than 100%.

[0146] C: The rate of change in resistance value before and after the vibration test is 100% or more.

[0147] (3) Adhesion of the second insulating layer to the first nickel layer The second insulating layer was subjected to a cross-cut test according to JIS K5600-5-6: 1999 to evaluate the adhesion of the second insulating layer to the first nickel layer. The results are shown in Tables 1 to 3.

[0148] <Evaluation criteria> A: The second insulating layer did not peel off.

[0149] B: The second insulating layer peeled off.

[0150] (4) Diffusion of the gold plating layer (surface layer of the coating layer) of the terminal The diffusion of the gold-plated layer (surface layer of the coating layer) was evaluated by placing solder on the terminal and conducting a lateral shear strength (shear strength) test as specified in JIS C62137-1-2: 2010. The results are shown in Tables 1 to 3.

[0151] <Evaluation criteria> A: The shear strength is 1200gf or more.

[0152] B: The shear strength is 1000 gf or more and less than 1200 gf.

[0153] C: The shear strength is less than 1000 gf.

[0154] [Table 1]

[0155] [Table 2]

[0156] [Table 3] [Explanation of symbols]

[0157] 1 Wiring circuit board 12 First insulating layer 14 Conductor pattern 141 terminals 143 Wiring 15 First nickel layer 16 Second insulating layer 17 Covering layer 171 Second nickel layer 172 Surface layer

Claims

1. a first insulating layer; a conductor pattern disposed on the first insulating layer and having terminals and wiring; a second insulating layer disposed on the first insulating layer, covering the wiring but not the terminal; a first nickel layer disposed between the wiring and the second insulating layer, covering the wiring but not the terminal; Equipped with the first nickel layer contains phosphorus; The wired circuit board, wherein the phosphorus content in the first nickel layer is 6 mass % or less.

2. The terminal further includes a coating layer made of a metal different from that of the terminal, the coating layer covering the terminal, The printed circuit board according to claim 1 , wherein the coating layer has a second nickel layer different from the first nickel layer.

3. the second nickel layer contains phosphorus; The printed circuit board according to claim 2 , wherein the second nickel layer has a phosphorus content of more than 6 mass %.

4. The printed circuit board according to claim 1 , wherein the first nickel layer has a thickness of 300 nm or less.

5. 2. The printed circuit board according to claim 1, wherein the first nickel layer is an electroless nickel-phosphorus plating layer.

6. A method for producing the wired circuit board according to any one of claims 1 to 5, a conductor pattern forming step of forming the conductor pattern on the first insulating layer; a first nickel layer forming step of forming the first nickel layer to cover the wiring and the terminal; a second insulating layer forming step of forming the second insulating layer on the first insulating layer; a removing step of removing the first nickel layer covering the terminal by etching; A method for manufacturing a wired circuit board, comprising:

7. 7. The method for producing a wired circuit board according to claim 6, wherein in the first nickel layer forming step, the first nickel layer is formed on the wiring and the terminals by electroless plating using a catalyst.

Images