Wired circuit board and method for producing wired circuit board

Abstract

To provide a wiring circuit board which can be manufactured with simple facilities and processes and can reduce transmission loss, and to provide a method of manufacturing the wiring circuit board.SOLUTION: The wiring circuit board 1 sequentially includes a metal supporting board 2, a metal particle-containing layer 3 containing metal particles 31, an insulating layer 4, and a conductive pattern 5 toward one side in a thickness direction.SELECTED DRAWING: Figure 1

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-equipped suspension board (wired circuit board) has been known in which an insulating layer made of resin and a conductor pattern made of copper are formed in this order on a metal supporting substrate made of stainless steel. In such a circuit-equipped suspension board, the metal supporting substrate is made of stainless steel, which results in large transmission loss in the conductor pattern. In order to reduce transmission loss, it has been proposed to form a lower conductor made of copper or a copper alloy containing copper as a main component on the metal supporting substrate made of stainless steel, and then form an insulating layer, a recording-side conductor, and a reproducing-side conductor in this order on the lower conductor (see, for example, Patent Document 1).

[0003] It is also known that such a lower conductor is formed by electrolytic plating (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-11387 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-157836 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, by forming a lower conductor made of copper or a copper alloy containing copper as the main component on a metal supporting substrate made of stainless steel, it is possible to reduce transmission loss in the recording side conductor and the reproducing side conductor. However, when the lower conductor is formed by electrolytic plating as described in Patent Document 2, there are drawbacks in that equipment for electrolytic plating is required and the process becomes complicated.

[0006] The present invention provides a wired circuit board and a method for manufacturing the wired circuit board, which can be manufactured using simple equipment and steps and can reduce transmission loss. [Means for solving the problem]

[0007] The present invention [1] includes a wired circuit board including, in order toward one side in the thickness direction, a metal supporting board, a metal particle-containing layer containing metal particles, an insulating layer, and a conductor pattern.

[0008] The present invention [2] includes the wired circuit board according to the above [1], in which the electrical conductivity of the metal particles is greater than the electrical conductivity of the metal supporting board.

[0009] The present invention [3] includes the wired circuit board according to the above [1] or [2], in which the metal supporting board is made of stainless steel.

[0010] The present invention [4] includes the wired circuit board according to any one of the above [1] to [3], wherein the metal particles are at least one selected from the group consisting of copper particles and silver particles.

[0011] The present invention [5] includes the wired circuit board according to any one of the above [1] to [4], wherein the metal particle-containing layer is a layer made of the metal particles.

[0012] The present invention [6] includes the wired circuit board according to any one of the above [1] to [4], wherein the metal particle-containing layer is a layer made of the metal particles and a cured resin.

[0013] The present invention [7] includes the wired circuit board according to any one of the above [1] to [6], wherein the ratio of the average particle diameter of the metal particles to the thickness of the metal particle-containing layer is 0.1 or more and 1 or less.

[0014] The present invention [8] includes a method for manufacturing a wired circuit board, comprising the steps of: preparing a metal supporting board; forming a metal particle-containing layer containing metal particles on one thickness-wise side of the metal supporting board; forming an insulating layer on one thickness-wise side of the metal particle-containing layer; and forming a conductor pattern on one thickness-wise side of the insulating layer.

[0015] The present invention [9] includes the method for manufacturing a wired circuit board according to the above [8], in which the metal supporting board is made of stainless steel.

[0016] The present invention

[10] includes the method for producing a wired circuit board according to the above [8] or [9], wherein the metal particles are at least one selected from the group consisting of copper particles and silver particles.

[0017] The present invention

[11] includes the method for producing a wired circuit board according to any one of the above [8] to

[10] , wherein the step of forming the metal particle-containing layer comprises the steps of applying a metal particle-containing composition containing the metal particles to one surface of the metal supporting board in the thickness direction to form a coating film, and heat-treating the coating film.

[0018] The present invention

[12] includes the method for producing a wired circuit board according to the above

[11] , wherein the heat treatment step is a step of sintering the coating film.

[0019] The present invention

[13] includes the method for producing a wired circuit board according to the above

[11] , wherein the metal particle-containing composition further contains a thermosetting resin, and the heat treatment step is a step of curing the thermosetting resin. [Effects of the Invention]

[0020] The wired circuit board of the present invention includes a metal supporting board, a metal particle-containing layer containing metal particles, an insulating layer, and a conductor pattern, arranged in this order toward one side in the thickness direction, and therefore can be manufactured using simple equipment and processes, and transmission loss can be reduced.

[0021] The method for producing a wired circuit board of the present invention includes the steps of preparing a metal supporting board, forming a metal particle-containing layer containing metal particles on one thickness-wise side of the metal supporting board, forming an insulating layer on one thickness-wise side of the metal particle-containing layer, and forming a conductor pattern on one thickness-wise side of the insulating layer. Therefore, a wired circuit board that can reduce transmission loss can be produced using simple equipment and processes. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 shows a cross-sectional view of one embodiment of the wired circuit board of the present invention. [Figure 2] Fig. 2 shows a method for manufacturing the wired circuit board shown in Fig. 1. Fig. 2A shows a step of preparing a metal supporting board, Fig. 2B shows a step of forming a metal particle-containing layer on the metal supporting board, and Fig. 2C shows a step of forming an insulating layer and a conductor pattern on the metal particle-containing layer. [Figure 3] Fig. 3 shows details of the step of forming a metal particle-containing layer on a metal supporting board in the method for producing a wired circuit board shown in Fig. 2. Fig. 3 includes a first heat treatment step as a heat treatment step. Fig. 3A shows the step of forming a coating film of a metal particle-containing composition on a metal supporting board, and Fig. 3B shows the step of sintering the coating film (first heat treatment step). [Figure 4] Fig. 4 shows details of the step of forming a metal particle-containing layer on a metal supporting board in the method for producing a wired circuit board shown in Fig. 2. Fig. 4 includes a second heat treatment step as a heat treatment step. Fig. 4A shows the step of forming a coating film of a metal particle-containing composition on a metal supporting board, and Fig. 4B shows the step of thermally curing the thermosetting resin in the coating film (second heat treatment step). [Figure 5]Fig. 5 shows details of the step of forming an insulating layer and a conductor pattern on a metal particle-containing layer in the method for producing the wired circuit board shown in Fig. 2. Fig. 5 shows a first formation step in which an insulating layer and a conductor pattern are formed in that order. Fig. 5A shows the step of forming an insulating layer on a metal particle-containing layer, Fig. 5B shows the step of attaching a metal foil to the insulating layer, Fig. 5C shows the step of forming a resist on the metal foil and exposing it, Fig. 5D shows the step of removing the resist and metal foil from unexposed areas, and Fig. 5E shows the step of removing the resist from exposed areas. [Figure 6] Fig. 6 shows details of the step of forming an insulating layer and a conductor pattern on a metal particle-containing layer in the method for producing the wired circuit board shown in Fig. 2. Fig. 6 shows a second formation step using a metal-clad laminate including an insulating layer and metal foil. Fig. 6A shows the step of attaching a metal-clad laminate including an insulating layer and metal foil to a metal particle-containing layer, Fig. 6B shows the step of forming a resist on the metal foil and exposing it, Fig. 6C shows the step of removing the resist and metal foil from unexposed areas, and Fig. 6D shows the step of removing the resist from exposed areas. [Figure 7] FIG. 7 shows a cross-sectional view of a modified example of the printed circuit board shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] 1. Wiring circuit board An embodiment of the wired circuit board of the present invention will be described with reference to FIG.

[0024] 1, the wired circuit board 1 has a thickness. The wired circuit board 1 extends in a plane direction perpendicular to the thickness direction. The wired circuit board 1 has a sheet shape (film shape) or a plate shape.

[0025] The wired circuit board 1 includes, in order toward one side in the thickness direction, a metal supporting board 2, a metal particle-containing layer 3 containing metal particles 31, an insulating layer 4 (base insulating layer 4), and a conductor pattern 5. The wired circuit board 1 may further include an insulating cover layer 6.

[0026] 1.1.Metal Support Substrate The metal supporting board 2 is disposed on the other side of the wired circuit board 1 in the thickness direction. In other words, the metal supporting board 2 forms the other surface in the thickness direction of the wired circuit board 1. The metal supporting board 2 extends in the planar direction. The metal supporting board 2 has a sheet shape (film shape) or a plate shape.

[0027] Examples of materials for the metal supporting board 2 include iron, stainless steel, copper, and copper alloys. Stainless steel is preferred. That is, the metal supporting board 2 is preferably made of stainless steel.

[0028] The thickness of the metal supporting board 2 is, for example, 1 μm or more, or preferably 10 μm or more, and for example, 1000 μm or less, or preferably 500 μm or less.

[0029] The electrical conductivity of the metal supporting board 2 is preferably lower than the electrical conductivity of the metal particles 31 contained in the metal particle-containing layer 3, which will be described later. Note that the electrical conductivity of the metal supporting board 2 being lower than the electrical conductivity of the metal particles 31 contained in the metal particle-containing layer 3, which will be described later, means that the electrical conductivity of the metal supporting board 2 is lower than the electrical conductivity of the metal particles 31 contained in the metal particle-containing layer 3, which will be described later.

[0030] The conductivity of the metal supporting board 2 is, for example, 1.5% IACS or more, preferably 1.8% IACS or more, for example, 50% IACS or less, preferably 30% IACS.

[0031] The conductivity of the metal supporting board 2 can be measured, for example, according to JIS H0505 (1975).

[0032] 1.2. Metal particle-containing layer The metal particle-containing layer 3 is disposed on one side in the thickness direction of the metal supporting board 2. Specifically, the other surface in the thickness direction of the metal particle-containing layer 3 contacts one surface in the thickness direction of the metal supporting board 2. In this embodiment, the metal particle-containing layer 3 contacts the entire one surface in the thickness direction of the metal supporting board 2. In other words, when projected in the thickness direction, the metal particle-containing layer 3 and the metal supporting board 2 have the same shape. The metal particle-containing layer 3 extends in the planar direction.

[0033] The metal particle-containing layer 3 contains metal particles 31. The metal particle-containing layer 3 may also contain a cured resin 32. The metal particle-containing layer 3 may also contain additives as necessary. The metal particle-containing layer 3 is preferably a layer made of metal particles 31, or a layer made of metal particles 31 and a cured resin 32.

[0034] Examples of materials for the metal particles 31 include copper, nickel, aluminum, gold, silver, and alloys thereof. Preferably, copper and silver are used. That is, the metal particles 31 are preferably at least one selected from the group consisting of copper particles and silver particles. Note that, as the metal particles 31, one type of particle may be used alone, or two or more types of particles may be used in combination.

[0035] The average particle size of the metal particles 31 is, for example, 0.1 μm or more, preferably 0.5 μm or more, more preferably 1.0 μm or more, and for example, 10.0 μm or less, preferably 8.0 μm or less, more preferably 6.0 μm or less. The metal particles 31 may be nanoparticles whose average particle size is less than 0.1 μm.

[0036] The electrical conductivity of the metal particles 31 is preferably higher than the electrical conductivity of the metal supporting board 2. Here, the expression "the electrical conductivity of the metal particles 31 is higher than the electrical conductivity of the metal supporting board 2" means that the electrical conductivity of the metal particles 31 is higher than the electrical conductivity of the metal supporting board 2.

[0037] The electrical conductivity of the metal particles 31 is, for example, 25% IACS or more, preferably 40% IACS or more, for example, 110% IACS or less.

[0038] The conductivity of the metal particles 31 can be measured, for example, according to JIS H0505 (1975).

[0039] Since the metal particles 31 contained in the metal particle-containing layer 3 have a relatively high electrical conductivity, the transmission loss of the electrical signal transmitted to the conductive pattern 5 described below can be reduced.

[0040] Examples of resins include thermosetting resins, ultraviolet curing resins, and room temperature curing resins. Preferably, thermosetting resins are used. Thermosetting resins are not particularly limited, and examples thereof include polycarbonate resins, polyimide resins, fluorinated polyimide resins, epoxy resins, phenolic resins, urea resins, melamine resins, diallyl phthalate resins, silicone resins, thermosetting urethane resins, and fluororesins. Thermosetting resins may be used alone or in combination of two or more. The cured resin 32 is a cured resin.

[0041] When the metal particle-containing layer 3 contains metal particles 31 and a cured resin material 32, the content of the metal particles 31 in the total amount of the metal particles 31 and the cured resin material 32 is, for example, 50 mass% or more, preferably 70 mass% or more, more preferably 80 mass% or more, and for example, 99 mass% or less, preferably 98 mass% or less, more preferably 97 mass% or less.

[0042] The additives are not particularly limited, and examples thereof include a curing accelerator and a dispersant. The curing accelerator is a catalyst (thermosetting catalyst) that accelerates the curing of a thermosetting resin by heating. Examples of the curing accelerator include an imidazole-based curing accelerator, a phosphorus-based curing accelerator, and a urea-based curing accelerator. The dispersant uniformly disperses the metal particles 31 in the metal particle-containing composition described below. Examples of the dispersant include an amine-based polymer dispersant (e.g., polyethyleneimine, polyvinylpyrrolidone) and a hydrocarbon-based polymer dispersant (e.g., polyacrylic acid, carboxymethyl cellulose).

[0043] The thickness of the metal particle-containing layer 3 is, for example, 0.5 μm or more, preferably 1 μm or more, more preferably 3 μm or more, and for example, 10 μm or less, preferably 8 μm or less, more preferably 6 μm or less.

[0044] The ratio of the average particle diameter of the metal particles 31 to the thickness of the metal particle-containing layer 3 is, for example, 0.1 or more, preferably 0.3 or more, and for example, 1 or less, preferably 0.8 or less.

[0045] The ratio of the electrical conductivity of the metal particle-containing layer 3 to the electrical conductivity of the metal supporting board 2 is, for example, 1.2 or more, or preferably 2 or more, and for example, 70 or less.

[0046] 1.3.Insulating layer (base insulating layer) The insulating layer 4 (base insulating layer 4) is disposed on one thickness-wise side of the metal particle-containing layer 3. The other thickness-wise surface of the base insulating layer 4 contacts one thickness-wise surface of the metal particle-containing layer 3. Specifically, the base insulating layer 4 contacts the entire one thickness-wise surface of the metal particle-containing layer 3. The base insulating layer 4 extends in the planar direction.

[0047] Examples of materials for the insulating base layer 4 include insulating resins. Examples of insulating resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. Preferably, polyimide is used.

[0048] The insulating base layer 4 has a thickness of, for example, 1 μm or more, or preferably 5 μm or more, and for example, 100 μm or less, or preferably 50 μm or less.

[0049] 1.4.Conductor Pattern The conductive pattern 5 is disposed on one side in the thickness direction of the insulating layer 4 (base insulating layer 4). The other surface in the thickness direction of the conductive pattern 5 is in contact with one surface of the base insulating layer 4 in the thickness direction.

[0050] The conductive pattern 5 is made of, for example, a metal. Examples of metals include copper, silver, gold, iron, aluminum, chromium, and alloys thereof. From the viewpoint of obtaining good electrical properties, copper is preferred.

[0051] The conductive pattern 5 is preferably a circuit pattern having a predetermined pattern shape, and includes, for example, a plurality of wires 51 and a plurality of terminals (not shown).

[0052] 1 is a wiring 51. The wiring 51 extends in one direction (first direction) in a plane direction perpendicular to the thickness direction. Although not shown, the first direction is the depth direction in the drawing.

[0053] The wiring 51 is provided as a pair of differential wirings. In this embodiment, as shown in Fig. 1, two sets of differential wirings (four wirings 51) are provided.

[0054] The thickness of the wiring 51 is, for example, 1 μm or more, or preferably 3 μm or more, and for example, 50 μm or less, or preferably 30 μm or less.

[0055] The width of the wiring 51 (the dimension in the second direction perpendicular to the first direction in the planar direction) is, for example, 5 μm or more, or preferably 8 μm or more, and for example, 100 μm or less, or preferably 50 μm or less.

[0056] The separation distance between adjacent wirings 51 (in the surface direction, in the second direction) is, for example, 5 μm or more, preferably 10 μm or more, and for example, 1000 μm or less, preferably 500 μm or less.

[0057] A terminal (not shown) is disposed at an end of the wiring 51. The terminal is electrically connected to the wiring 51. The terminal is not covered with the cover insulating layer 6 described below, and one surface of the terminal in the thickness direction is exposed.

[0058] The thickness of the terminal is, for example, 1 μm or more, preferably 3 μm or more, and for example, 50 μm or less, preferably 30 μm or less. The thickness of the terminal may be the same as or different from that of the wiring 51. The width of the terminal is preferably larger than that of the wiring 51.

[0059] 1.5.Cover insulating layer The cover insulating layer 6 is disposed on one thickness-wise side of the base insulating layer 4 so as to cover the wiring 51. The other thickness-wise surface of the cover insulating layer 6 contacts one thickness-wise surface of the base insulating layer 4 and one thickness-wise surface of the wiring 51. Although not shown, the cover insulating layer 6 does not cover the terminals. The cover insulating layer 6 extends in the planar direction.

[0060] Examples of materials for the insulating cover layer 6 include insulating resins. Examples of insulating resins include polyimide, maleimide, epoxy resin, polybenzoxazole, and polyester. Preferably, polyimide is used.

[0061] The thickness of the insulating cover layer 6 is, for example, 1 μm or more, or preferably 5 μm or more, and for example, 100 μm or less, or preferably 50 μm or less. The thickness of the insulating cover layer is the distance from one surface of the insulating base layer 4 to one surface of the insulating cover layer 6 in the thickness direction.

[0062] 2. Manufacturing method of printed circuit board Referring to FIG. 2, one embodiment of the method for producing a wired circuit board of the present invention will be described.

[0063] The method for manufacturing a wired circuit board includes the steps of preparing a metal supporting board 2, forming a metal particle-containing layer 3 containing metal particles 31 on one thickness-wise side of the metal supporting board 2, forming an insulating layer 4 on one thickness-wise side of the metal particle-containing layer 3, and forming a conductor pattern 5 on one thickness-wise side of the insulating layer 4.

[0064] As shown in FIG. 2A, first, a metal supporting board 2 is prepared.

[0065] Next, as shown in FIG. 2B, a metal particle-containing layer 3 containing metal particles 31 is formed on one side of the metal supporting board 2 in the thickness direction.

[0066] The process of forming the metal particle-containing layer 3 includes a process of applying a composition containing metal particles 31 (metal particle-containing composition) to one surface in the thickness direction of the metal supporting board 2 to form a coating film 30 of the metal particle-containing composition, drying it as necessary, and a process of heat-treating the coating film 30.

[0067] The metal particle-containing composition is, for example, a composition containing metal particles 31. The metal particle-containing composition optionally contains at least one selected from the group consisting of the above-mentioned resin, the above-mentioned additive, and a dispersion medium.

[0068] The dispersion medium is not particularly limited, and examples thereof include water and organic solvents, such as alcohols (e.g., methanol and ethanol) and ketones (e.g., acetone and methyl ethyl ketone).

[0069] The form of the metal particle-containing composition is not particularly limited as long as it can be applied to one surface in the thickness direction of the metal supporting board 2 to form a coating film 30, and examples thereof include paste and liquid forms.

[0070] Examples of the coating method include conventionally known coating methods, such as spin coating, spray coating, bar coating, die coating, slit coating, roll coating, and dip coating. Alternatively, the coating can be applied to a part of one surface in the thickness direction of the metal supporting board 2 by screen printing, a dispenser, or the like.

[0071] These coating methods allow the coating film 30 of the metal particle-containing composition to be formed using simple equipment and steps.

[0072] The drying temperature is, for example, 50° C. to 200° C. The drying time is, for example, 1 minute to 60 minutes.

[0073] When the metal particle-containing composition contains a dispersion medium, the dispersion medium is partially or entirely removed from the coating film 30 by drying. The coating film 30 is then heat-treated. The heat-treating step will be described in detail below, but the coating film 30 is heat-treated in either a first heat-treatment step or a second heat-treatment step. This forms the metal particle-containing layer 3.

[0074] 2C, an insulating layer 4 and a conductive pattern 5 are formed on the metal particle-containing layer 3. The process of forming the insulating layer 4 and the conductive pattern 5 on the metal particle-containing layer 3 will be described in detail later, but the insulating layer 4 and the conductive pattern 5 are formed in either the first formation process or the second formation process.

[0075] In this manner, the wired circuit board 1 is manufactured.

[0076] (First heat treatment step) The first heat treatment step will be described with reference to FIG.

[0077] The first heat treatment step is one embodiment of a step of heat treating the coating film 30. Specifically, the first heat treatment step is a step of sintering the coating film 30 applied to one surface of the metal supporting board 2 in the thickness direction.

[0078] 3A, a metal supporting board 2 having a coating film 30 formed on one surface in the thickness direction thereof is prepared. The coating film 30 is formed on one surface in the thickness direction of the metal supporting board 2 as described above.

[0079] Next, as shown in Fig. 3B, the coating film 30 is sintered. Specifically, the coating film 30 is heated (sintered) at a high temperature to volatilize and remove components other than the metal particles 31 in the coating film 30. Adjacent metal particles 31 in the coating film 30 bond together to form a sintered body. This forms the metal particle-containing layer 3. In this case, the metal particle-containing layer 3 is made of metal particles 31 (sintered body of metal particles 31).

[0080] 3B shows an example in which metal particles 31 and resin 32' are contained in coating film 30 (metal particle-containing composition). By heating (sintering) coating film 30 at a high temperature, components other than metal particles 31 in coating film 30 (including resin 32') are volatilized and removed. Resin 32' is shown in a state before it is completely cured.

[0081] When the coating film 30 is sintered, some of the metal particles 31 are oxidized. That is, some of the metal particles 31 become metal oxide particles. That is, the metal particles 31 may contain the metal oxide particles of their raw material as unavoidable impurities.

[0082] The sintering temperature is, for example, 150° C. to 500° C., or preferably 200° C. to 400° C. The sintering time is, for example, 10 minutes to 24 hours, or preferably 1 hour to 18 hours.

[0083] In this way, the metal particle-containing layer 3 made of the metal particles 31 is formed.

[0084] (Second heat treatment process) The second heat treatment step will be described with reference to FIG.

[0085] The second heat treatment step is one embodiment of a step of heat treating the coating film 30. Specifically, the second heat treatment step is a step of curing the thermosetting resin 32′ in the coating film 30 applied to one surface in the thickness direction of the metal supporting board 2. The second heat treatment step is applied when the metal particle-containing composition contains a thermosetting resin.

[0086] 4A, a metal supporting board 2 having a coating film 30 formed on one surface in the thickness direction thereof is prepared. The coating film 30 is formed on one surface in the thickness direction of the metal supporting board 2 as described above. Note that the thermosetting resin 32′ in the coating film 30 before the second heat treatment step is in a semi-cured state (B-stage state) before being completely cured.

[0087] Next, as shown in FIG. 4B, the semi-cured thermosetting resin 32' in the coating film 30 is cured. Specifically, the coating film 30 is heated to a temperature equal to or higher than the curing temperature of the thermosetting resin 32' to completely cure the thermosetting resin 32' (to a C-stage state). This forms the metal particle-containing layer 3. In this case, the metal particle-containing layer 3 is composed of metal particles 31 and a cured thermosetting resin 32.

[0088] The heating temperature is adjusted appropriately depending on the type of thermosetting resin, but is, for example, 100° C. to 250° C. The heating time is, for example, 10 minutes to 10 hours.

[0089] In this way, the metal particle-containing layer 3 made of the metal particles 31 and the cured thermosetting resin 32 is formed.

[0090] (1st formation step) 5, the process of forming the insulating layer 4 and the conductive pattern 5 on one surface in the thickness direction of the metal particle-containing layer 3 will be described in detail. Specifically, the first forming process of sequentially forming the insulating layer 4 and the conductive pattern 5 on one surface in the thickness direction of the metal particle-containing layer 3 will be described.

[0091] The first formation process includes a step of forming an insulating layer 4 on one thickness-wise surface of the metal particle-containing layer 3, a step of attaching a metal foil 50 to one thickness-wise surface of the insulating layer 4, a step of forming a resist 7 on one thickness-wise surface of the metal foil 50 and exposing it, a step of removing the resist 7 and the metal foil 50 from the unexposed areas, and a step of removing the resist 7 from the exposed areas.

[0092] As shown in FIG. 5A, an insulating layer 4 is formed on one surface of the metal particle-containing layer 3 in the thickness direction.

[0093] Specifically, a solution (varnish) of an insulating resin is applied to one surface in the thickness direction of the metal particle-containing layer 3 to form a coating film of the insulating resin. Then, this coating film is dried. After drying, it may be patterned as necessary. If the insulating resin is a photosensitive resin, the coating film of the insulating resin can be patterned by exposing it to light and developing it.

[0094] The insulating resin coating may be heated and cured after drying, or may be heated and cured after the metal foil 50 described below is attached.

[0095] Next, as shown in FIG. 5B, metal foil 50 is attached to one surface in the thickness direction of insulating layer 4 (insulating resin coating film).

[0096] Specifically, the metal foil 50 is attached to one surface in the thickness direction of the insulating layer 4 via an adhesive (not shown). Alternatively, the metal foil 50 is attached to one surface in the thickness direction of the insulating resin coating (before it is completely cured) without an adhesive, and then the insulating resin coating is heated to cure.

[0097] The metal foil 50 is a layer for forming the conductive pattern 5. The metal foil 50 is made of the same metal as the material of the above-mentioned conductive pattern 5. That is, the metal foil 50 is preferably a copper foil.

[0098] The thickness of the metal foil 50 is the same as the thickness of the conductive pattern 5 .

[0099] The adhesive is not particularly limited as long as it is one that is commonly used for wiring circuit boards, and examples thereof include adhesives containing resin. Examples of resins include thermosetting resins (e.g., epoxy resins, thermosetting polyimide resins, urethane resins) and thermoplastic resins (e.g., acrylic resins, thermoplastic polyimide resins). Furthermore, when patterning the adhesive, a photosensitive resin is used.

[0100] Next, as shown in FIG. 5C, a resist 7 (dry film resist) is formed on one surface in the thickness direction of the metal foil 50, and is irradiated with ultraviolet light through a photomask M (exposure).

[0101] The photomask M has openings Ma corresponding to the pattern shape of the conductor pattern 5, and the resist 7 has exposed portions (portions corresponding to the openings Ma) and unexposed portions (portions other than the portions corresponding to the openings Ma).

[0102] The wavelength of the irradiated ultraviolet light is, for example, 300 nm to 500 nm. The cumulative irradiation amount of the ultraviolet light is, for example, 100 mJ / cm 2 2 ~1000mJ / cm 2 is.

[0103] Next, as shown in FIG. 5D, the resist 7 in the unexposed area and the metal foil 50 in the corresponding area are removed.

[0104] Specifically, the unexposed portions of the resist 7 are dissolved and removed using a developer, and the metal foil 50 corresponding to the unexposed portions of the resist 7 is then removed using an etching solution.

[0105] The developer may be, for example, a basic developer, such as an inorganic alkaline solution or an organic alkaline solution.

[0106] Examples of the etching solution include acidic solutions such as ferric chloride, hydrogen peroxide / sulfuric acid mixture, ammonium persulfate, and sodium persulfate.

[0107] Examples of the developing method and etching method include a dipping method, a spray method, and a puddle method.

[0108] As a result, the conductive pattern 5 covered with the resist 7 (exposed portion) is formed.

[0109] 5E, the resist 7 (exposed portion) covering the conductive pattern 5 is removed. There are no particular limitations on the removal method, and known methods such as peeling can be used.

[0110] In this manner, the insulating layer 4 and the conductive pattern 5 are formed on one surface of the metal particle-containing layer 3 in the thickness direction.

[0111] (Second formation process) 6, the process of forming the insulating layer 4 and the conductive pattern 5 on one surface in the thickness direction of the metal particle-containing layer 3 will be described in detail. Specifically, the second forming process using a metal-clad laminate including the insulating layer 4 and the metal foil 50 will be described.

[0112] The second formation process includes a process of attaching a metal-clad laminate having an insulating layer 4 and a metal foil 50 to one thickness-wise surface of the metal particle-containing layer 3, a process of forming a resist 7 on one thickness-wise surface of the metal foil 50 and exposing it, a process of removing the resist 7 and the metal foil 50 from the unexposed areas, and a process of removing the resist 7 from the exposed areas.

[0113] As shown in Figure 6A, first, a metal-clad laminate including an insulating layer 4 and a metal foil 50 is prepared, and the surface of the metal-clad laminate where the insulating layer 4 is exposed (the other thickness-wise surface in Figure 6A) is attached to one thickness-wise surface of the metal particle-containing layer 3.

[0114] The metal-clad laminate includes, for example, an insulating layer 4 and a metal foil 50 in this order toward one side in the thickness direction. The metal-clad laminate is preferably a copper-clad laminate including an insulating layer 4 and a copper foil in this order toward one side in the thickness direction.

[0115] A protective film may be attached to the surface of the metal-clad laminate where the insulating layer 4 is exposed (the other surface in the thickness direction) until immediately before use.

[0116] The metal-clad laminate is attached to one surface of the metal particle-containing layer 3 in the thickness direction via an adhesive (not shown).

[0117] The steps shown in FIGS. 6B to 6D are the same as the steps shown in FIGS. 5C to 5E above.

[0118] In this manner, the insulating layer 4 and the conductive pattern 5 are formed on one surface of the metal particle-containing layer 3 in the thickness direction.

[0119] 3. Effects The wired circuit board 1 includes, in order toward one side in the thickness direction, a metal supporting board 2, a metal particle-containing layer 3 containing metal particles 31, an insulating layer 4, and a conductor pattern 5.

[0120] Such a wired circuit board 1 can be manufactured using simple equipment and steps because electrolytic plating is not used to form the metal particle-containing layer 3. Furthermore, the provision of the metal particle-containing layer 3 allows for reduced transmission loss.

[0121] The method for manufacturing the wired circuit board includes the steps of preparing a metal supporting board 2, forming a metal particle-containing layer 3 containing metal particles 31 on one thickness-wise side of the metal supporting board 2, forming an insulating layer 4 on one thickness-wise side of the metal particle-containing layer 3, and forming a conductor pattern 5 on one thickness-wise side of the insulating layer 4.

[0122] Such a method for producing a wired circuit board can be produced using simple equipment and steps because electrolytic plating is not used to form the metal particle-containing layer 3. Furthermore, the provision of the metal particle-containing layer 3 can reduce transmission loss.

[0123] 4. Modified Wired Circuit Board A description will be given of modified examples of the wired circuit board 1. In the modified examples of the wired circuit board 1, the same components as those in the above-described embodiment of the wired circuit board 1 are denoted by the same reference numerals, and the description thereof will be omitted.

[0124] In one embodiment of the wired circuit board 1 described above, the metal particle-containing layer 3 is in contact with the entire surface of one thickness direction of the metal supporting board 2, but the invention is not limited to this.

[0125] 7, the metal particle-containing layer 3 may be disposed on one surface in the thickness direction of the metal supporting board 2 so as to face at least the portion where the conductive pattern 5 is formed. That is, as long as the metal particle-containing layer 3 is contained in the metal supporting board 2 when projected in the thickness direction, the metal particle-containing layer 3 may be partially contained in the metal supporting board 2. Note that in FIG. 7, the metal particle-containing layer 3 is disposed only in the center so as to face the portion where the conductive pattern 5 is formed in the second direction, and is not disposed at both ends.

[0126] In addition, as shown in FIG. 7, in this modification, the insulating layer 4 is disposed so as to cover the metal particle-containing layer 3.

[0127] 5. Modified Example of the Method for Manufacturing a Wired Circuit Board A modified example of the method for manufacturing a wired circuit board will be described. In the modified example of the method for manufacturing a wired circuit board, the same components as those in the embodiment of the method for manufacturing a wired circuit board described above are denoted by the same reference numerals, and the description thereof will be omitted.

[0128] 5.1. First Modification of the Method for Manufacturing a Wired Circuit Board In one embodiment of the method for manufacturing the above-mentioned wired circuit board, as shown in FIG. 3, the first heat treatment step is shown in a case where the coating film 30 (metal particle-containing composition) contains metal particles 31 and resin 32′, but is not limited to this.

[0129] Specifically, although not shown, the metal particle-containing composition may be a metal particle-containing composition containing metal particles 31 and a dispersion medium. A metal particle-containing composition containing metal particles 31 and a dispersion medium is applied to one surface in the thickness direction of the metal supporting substrate 2 to form a coating film 30, which is then dried. The drying volatilizes part or all of the dispersion medium in the coating film 30. Then, the coating film 30 is heated (sintered) at a high temperature to volatilize and remove components other than the metal particles 31 in the coating film 30 (including any remaining dispersion medium), thereby forming a metal particle-containing layer 3 consisting of the metal particles 31.

[0130] 5.2. Second Modification of the Method for Manufacturing a Wired Circuit Board One embodiment of the method for producing the wired circuit board described above includes a step of heat treating the coating film 30 as shown in FIGS. 3 and 4, but is not limited to this.

[0131] Specifically, although not shown, the step of heat treating the coating film 30 may not be included.

[0132] For example, a metal particle-containing composition containing metal particles 31 and a room-temperature curable resin is applied to one surface in the thickness direction of the metal supporting board 2 to form a coating film 30, which is then dried. Then, by leaving it to stand at room temperature, the room-temperature curable resin in the coating film 30 is cured, and the metal particle-containing layer 3 can be formed.

[0133] Room-temperature curable resins are resins that can be cured at room temperature. Examples of room-temperature curable resins include resins that cure by reacting with oxygen in the air (e.g., alkyd resins), resins that cure using radicals generated from a polymerization initiator (e.g., unsaturated polyester-styrene resins), and room-temperature curable urethane resins.

[0134] Alternatively, for example, a metal particle-containing composition containing metal particles 31 and an ultraviolet-curable resin may be applied to one surface in the thickness direction of the metal supporting board 2 to form a coating film 30, which is then dried. Then, ultraviolet light may be irradiated to cure the ultraviolet-curable resin in the coating film 30, thereby forming the metal particle-containing layer 3.

[0135] The ultraviolet curable resin includes at least one selected from the group consisting of ultraviolet curable monomers, ultraviolet curable oligomers, and ultraviolet curable polymers. Examples of the ultraviolet curable resin include (meth)acrylic ultraviolet curable resins (acrylic ultraviolet curable resins and / or methacrylic ultraviolet curable resins).

[0136] 5.3. Third Modification of the Method for Manufacturing a Wired Circuit Board In one embodiment of the method for producing the wired circuit board described above, the coating film 30 is heat-treated before the insulating layer 4 is formed as shown in FIGS. 3 and 4, but the present invention is not limited to this.

[0137] Specifically, although not shown, the step of heat treating the coating film 30 may be carried out simultaneously with the formation of the insulating layer 4.

[0138] First, a metal particle-containing composition is applied to one surface in the thickness direction of the metal supporting board 2 to form a coating film 30, which is then dried. Then, an insulating resin solution (varnish) is applied to one surface in the thickness direction of the coating film 30 to form a coating film of the insulating resin, which is then dried.

[0139] Next, the coating film 30 (coating film 30 of the metal particle-containing composition) and the insulating resin coating film are heat-treated together. The heat-treatment step may be either the first heat-treatment step or the second heat-treatment step. This allows the metal particle-containing layer 3 and the insulating layer 4 to be formed simultaneously. [Explanation of symbols]

[0140] 1 Wiring circuit board 2 Metal Support Board 3 Metal particle containing layer 31 Metal particles 4. Insulation layer (base insulation layer) 5 Conductor pattern 6 Cover insulation layer

Claims

1. a metal supporting substrate; a metal particle-containing layer containing metal particles; an insulating layer; Conductor pattern and A wired circuit board having the above in order toward one side in the thickness direction.

2. The wired circuit board according to claim 1 , wherein the metal particles have a higher electrical conductivity than the metal supporting board.

3. The wired circuit board according to claim 1 , wherein the metal supporting board is made of stainless steel.

4. 4. The wired circuit board according to claim 1, wherein the metal particles are at least one selected from the group consisting of copper particles and silver particles.

5. The wired circuit board according to claim 4 , wherein the metal particle-containing layer is a layer made of the metal particles.

6. The wired circuit board according to claim 4 , wherein the metal particle-containing layer is a layer comprising the metal particles and a cured resin.

7. 5. The wired circuit board according to claim 4, wherein a ratio of an average particle diameter of the metal particles to a thickness of the metal particle-containing layer is 0.1 or more and 1 or less.

8. providing a metal supporting substrate; forming a metal particle-containing layer containing metal particles on one side in a thickness direction of the metal supporting board; forming an insulating layer on one side in a thickness direction of the metal particle-containing layer; forming a conductor pattern on one side of the insulating layer in a thickness direction; A method for manufacturing a wired circuit board, comprising:

9. The method for manufacturing a wired circuit board according to claim 8 , wherein the metal supporting board is made of stainless steel.

10. The method for producing a wired circuit board according to claim 8, wherein the metal particles are at least one selected from the group consisting of copper particles and silver particles.

11. The step of forming the metal particle-containing layer includes: a step of applying a metal particle-containing composition containing the metal particles to one surface of the metal supporting board in the thickness direction to form a coating film; a step of heat treating the coating film; The method for manufacturing a wired circuit board according to any one of claims 8 to 10, comprising:

12. The method for producing a wired circuit board according to claim 11, wherein the heat treatment step is a step of sintering the coating film.

13. the metal particle-containing composition further comprises a thermosetting resin; The method for producing a wired circuit board according to claim 11, wherein the heat treatment step is a step of curing the thermosetting resin.

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