Printed wiring board manufacturing method

Abstract

To provide a method for manufacturing a printed wiring board, a method for manufacturing a resin base material, and a method for forming a seed layer.SOLUTION: A method for manufacturing a printed wiring board includes the steps of: forming a projection containing a copper oxide on the surface of a copper foil; forming a protrusion on the surface of the copper foil where the projection is formed; treating the surface of the copper foil where the protrusion is formed with a dissolving agent; plating the surface of the copper foil where the protrusion is formed using a plating liquid; stacking a copper foil on a resin base material so as to bring the protrusion into contact therewith; applying a pressure to a part or all of the copper foil stacked on the resin base material under a predetermined condition including heating; peeling the copper foil to which the pressure is applied from the resin base material, and obtaining the resin base material where a seed layer is formed; and subjecting the surface of the seed layer to copper plating treatment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a printed wiring board. [Background technology]

[0002] Known circuit formation methods for printed wiring boards and semiconductor package substrates include subtractive methods and semi-additive methods such as SAP (Semi-Additive Process) and M-SAP (Modified Semi-Additive Process) (Patent Document 1).

[0003] In the subtractive method, a resist is formed on the necessary areas of a laminate consisting of copper foil laminated on a resin substrate, and the copper foil in the areas where there is no resist is etched and then removed to form copper wiring. In the SAP and MSAP methods, a resist is formed on the areas where wiring is not to be made on a resin substrate with a metal seed layer on its surface, and then a plating process is performed. After removing the resist, the remaining seed layer is etched to form fine circuits.

[0004] In the SAP method, a seed layer is formed on the surface of a resin substrate by electroless plating, while in the MSAP method, a resin substrate with copper foil is used as the seed layer. When manufacturing a resin substrate with copper foil, numerous fine protrusions are formed on the copper foil in advance, which is an effort to improve the adhesion between the copper foil and the resin substrate.

[0005] In contrast to these methods, a method has been disclosed in which copper foil having numerous fine protrusions is thermocompression bonded to a resin substrate, and then the copper foil is peeled off from the resin substrate to obtain a resin substrate to which numerous fine protrusions have been transferred; resist is formed on the surface of the resin substrate in areas where wiring will not be formed; plating is then performed; and the resist is removed to form a circuit (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-034216 [Patent Document 2] International Publication No. 2021 / 079952 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a novel method for manufacturing a printed wiring board. [Means for solving the problem]

[0008] One embodiment of the present invention is a method for transferring protrusions on a copper foil surface to a resin substrate to form a seed layer, the method comprising the steps of: forming protrusions containing copper oxide on the copper foil surface; forming convex portions on the copper foil surface on which the protrusions are formed; treating the copper foil surface on which the protrusions are formed with a solvent; plating the copper foil surface on which the protrusions are formed with a plating solution; laminating the copper foil on the resin substrate so that the convex portions contact the resin substrate; and applying pressure to part or all of the copper foil laminated on the resin substrate under predetermined conditions, including heating. The plating step may be performed after the solvent treatment step. The solvent treatment step and the plating step may be performed simultaneously by adding the solvent to the plating solution. The height of the protrusions may be 10 nm to 1000 μm. The predetermined conditions may include a temperature of 50°C to 400°C, a pressure of 0 to 20 MPa, and a time of 1 minute to 5 hours. The resin substrate may contain at least one insulating resin selected from the group consisting of polyphenylene ether (PPE), epoxy, polyphenylene oxide (PPO), polybenzoxazole (PBO), polytetrafluoroethylene (PTFE), liquid crystal polymer (LCP), thermoplastic polyimide (TPI), fluororesin, polyetherimide, polyetheretherketone, polycycloolefin, bismaleimide resin, low dielectric constant polyimide, and cyanate resin. The method may further include a step of peeling the copper foil, to which the pressure has been applied, from the resin substrate, so that a part or all of the protrusions present on the convex portions are transferred, thereby obtaining the resin substrate on which a seed layer has been formed.

[0009] Another embodiment of the present invention is a method for producing a resin substrate having copper oxide, comprising the steps of: oxidizing a copper foil surface with an oxidizing agent to form convex portions containing copper oxide on the copper foil surface; forming convex portions on the copper foil surface on which the protrusions are formed; treating the copper foil surface on which the protrusions are formed with a solvent; plating the copper foil surface on which the protrusions are formed using a plating solution; laminating the copper foil to the resin substrate so that the convex portions are in contact; applying pressure under predetermined conditions including heating to part or all of the copper foil laminated on the resin substrate; and peeling the copper foil to which the pressure has been applied from the resin substrate, transferring part or all of the protrusions present on the convex portions to obtain the resin substrate on which a seed layer is formed.

[0010] A further embodiment of the present invention is a method for manufacturing a printed wiring board, comprising the steps of: oxidizing a copper foil surface with an oxidizing agent to form protrusions containing copper oxide on the copper foil surface; forming convex portions on the copper foil surface on which the protrusions are formed; treating the copper foil surface on which the convex portions are formed with a solvent; plating the copper foil surface on which the convex portions are formed using the electrolytic plating solution; laminating the copper foil on the resin substrate so that the convex portions are in contact; applying pressure under predetermined conditions including heating to part or all of the copper foil laminated on the resin substrate; peeling the copper foil to which the pressure has been applied from the resin substrate, transferring part or all of the protrusions present on the convex portions to obtain the resin substrate on which a seed layer is formed; and performing a copper plating process on the surface of the seed layer. [Effects of the Invention]

[0011] The present invention provides a novel method for producing a printed wiring board. [Brief explanation of the drawings]

[0012] [Figure 1]This is a schematic diagram of a seed layer in one embodiment of the present invention. The gray portion represents the resin substrate, and the black portion represents the copper foil portion transferred to the resin substrate. When the copper foil is peeled off from the resin substrate, (A) an example of the case where the copper foil is peeled off just at the surface of the resin substrate, and (B) an example of the case where the copper foil is peeled off away from the surface of the resin substrate, inside the body foil, from the copper foil protrusion. The two straight lines correspond to the position of the peeled copper foil surface and the surface configured to include the bottom of the hole formed in the resin substrate by the copper foil protrusion, respectively. The portion sandwiched between these two straight lines is the seed layer, and the distance between the two straight lines represented by arrows is the thickness of the seed layer. [Figure 2] 1A and 1B are diagrams showing the appearance of a copper foil that has been surface-treated in an example of the present invention, where A shows the result of an example in which drawing was performed before plating, and B shows the result of a comparative example in which drawing was performed after plating. [Figure 3] 1A and 1B are diagrams showing the adhesive surfaces of the copper foil and the resin when the copper foil thermocompression-bonded to the resin is peeled off in an example of the present invention, where A shows the result of an example in which drawing was performed before plating, and B shows the result of a comparative example in which drawing was performed after plating. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not necessarily limited thereto. The objects, features, advantages, and concepts of the present invention will be apparent to those skilled in the art from the description in this specification, and those skilled in the art will be able to easily reproduce the present invention from the description in this specification. The embodiments and specific examples of the invention described below show preferred embodiments of the present invention and are presented for illustrative or explanatory purposes, and are not intended to limit the present invention thereto. It will be apparent to those skilled in the art that various changes and modifications can be made based on the description in this specification within the spirit and scope of the present invention disclosed herein.

[0014] ==How to form a seed layer== The method disclosed in this specification is a method for transferring protrusions on a copper foil surface to a resin substrate to form a seed layer, and includes the steps of forming protrusions containing copper oxide on the copper foil surface, forming convex portions on the copper foil surface on which the protrusions have been formed, treating the copper foil surface on which the convex portions have been formed with a solvent, plating the copper foil surface on which the convex portions have been formed with a plating solution, laminating the copper foil on the resin substrate so that the convex portions are in contact with the resin substrate, and applying pressure to part or all of the copper foil laminated on the resin substrate under predetermined conditions, including heating. Details of this method are described below.

[0015] (1) Preparing the copper foil The copper foil used in this method is preferably made of pure copper with a purity of 95% by mass or more, 99% by mass or more, or 99.9% by mass or more, more preferably made of tough pitch copper, deoxidized copper, or oxygen-free copper, and even more preferably made of oxygen-free copper with an oxygen content of 0.001% to 0.0005% by mass. There are no particular limitations on its thickness, but it is preferably 0.1 μm to 100 μm, more preferably 0.5 μm to 50 μm.

[0016] (2) Oxidation treatment process First, the copper foil surface is subjected to an oxidation treatment to form protrusions containing copper oxide on the copper foil surface, which roughens the copper material surface and increases its adhesiveness to resin.

[0017] Before this oxidation treatment, a surface roughening treatment such as soft etching or etching may be performed. Furthermore, before the oxidation treatment, degreasing treatment, acid washing to remove natural oxide films and make the surface uniform, or alkali treatment to prevent acid from being carried over into the oxidation step after acid washing may be performed. The alkali treatment method is not particularly limited, but it is preferable to treat with a 0.1 to 10 g / L, more preferably a 1 to 2 g / L, aqueous alkali solution, such as a sodium hydroxide solution, at 30 to 50°C for about 0.5 to 2 minutes.

[0018] The oxidation treatment method is not particularly limited, and the protrusions may be formed by heat treatment or anodic oxidation, but it is preferable to form the protrusions using an oxidizing agent.

[0019] The oxidizing agent is not particularly limited, and examples thereof include aqueous solutions of sodium chlorite, sodium hypochlorite, potassium chlorate, and potassium perchlorate. Various additives (e.g., phosphates such as trisodium phosphate dodecahydrate) and surface-active molecules may be added to the oxidizing agent. Examples of surface-active molecules include porphyrin, porphyrin macrocycle, expanded porphyrin, ring-contracted porphyrin, linear porphyrin polymer, porphyrin sandwich coordination complex, porphyrin array, silane, tetraorgano-silane, aminoethyl-aminopropyltrimethoxysilane, (3-aminopropyl)trimethoxysilane, (1-[3-(trimethoxysilyl)propyl]urea), (3-aminopropyl)triethoxysilane, ((3-glycidyloxypropyl)trimethoxysilane), and (3-chloropropyl)trimethoate. Examples include oxysilane, (3-glycidyloxypropyl)trimethoxysilane, dimethyldichlorosilane, 3-(trimethoxysilyl)propyl methacrylate, ethyltriacetoxysilane, triethoxy(isobutyl)silane, triethoxy(octyl)silane, tris(2-methoxyethoxy)(vinyl)silane, chlorotrimethylsilane, methyltrichlorosilane, silicon tetrachloride, tetraethoxysilane, phenyltrimethoxysilane, chlorotriethoxysilane, ethylene-trimethoxysilane, amines, and sugars.

[0020] The oxidation reaction conditions are not particularly limited, but the liquid temperature of the oxidizing agent is preferably 40 to 95°C, more preferably 45 to 80°C. The reaction time is preferably 0.5 to 30 minutes, more preferably 1 to 10 minutes. The concentration of the oxidizing agent is not particularly limited, but is preferably 5 to 300 g / L, more preferably 10 to 250 g / L.

[0021] The surface of this copper oxide layer may be reduced with a reducing agent, in which case cuprous oxide may be formed on the surface of the copper oxide-containing layer. Examples of reducing agents used in this reduction step include dimethylamine borane (DMAB), diborane, sodium borohydride, and hydrazine.

[0022] Furthermore, a chelating agent, particularly a biodegradable chelating agent, may be used with the copper oxide layer to adjust the size, thickness, height, and length of the copper oxide-containing protrusions. The chelating agent is not particularly limited, but examples include ethylenediaminetetraacetic acid, diethanolglycine, tetrasodium L-glutamate diacetate, ethylenediamine-N,N'-disuccinic acid, sodium 3-hydroxy-2,2'-iminodisuccinate, trisodium methylglycine diacetate, tetrasodium aspartate diacetate, disodium N-(2-hydroxyethyl)iminodiacetate, sodium gluconate, and nickel chloride. The pH of the chelating agent solution is not particularly limited, but is preferably alkaline, more preferably between 8 and 10.5, even more preferably between 9.0 and 10.5, and even more preferably between 9.8 and 10.2.

[0023] The resistivity of pure copper is 1.7 x 10 -8 (Ωm), whereas copper oxide is 1 to 10 (Ωm) and cuprous oxide is 1×10 6 ~1×10 7 (Ωm), the layer containing copper oxide has low conductivity, and even if the amount of the layer containing copper oxide transferred to the resin substrate is large, transmission loss due to the skin effect is unlikely to occur when forming a circuit for a printed wiring board or a semiconductor package substrate using the copper foil according to the present invention.

[0024] (3) Convex portion forming process The height of the convex portions to be formed is not particularly limited, but is preferably 10 nm to 1000 μm. The convex portions can be formed by applying pressure from the back surface of a copper foil having protrusions formed on one side thereof for transfer to a resin substrate, thereby causing the surface on which the protrusions are formed to protrude. The region in which the convex portions are to be formed is not particularly limited, and the convex portions may be formed in the area where transfer is desired, taking into consideration that the convex portions are preferentially transferred to the resin substrate.

[0025] The formation of the convex portions may be carried out before the dissolution treatment step, and may be carried out before or after the oxidation treatment step (2). Alternatively, a member on which convex portions have been formed in advance may be used.

[0026] (4) Dissolution process The copper foil surface on which the protrusions have been formed is subjected to a step of treating with a solvent to facilitate breaking off the surface layer portion including the protrusions from the copper foil. This step may be performed simultaneously with the plating step described below by adding the solvent to the plating solution.

[0027] The dissolving agent may contain a component that dissolves copper oxide, and may be selected from chlorides (nickel chloride, potassium chloride, zinc chloride, iron chloride, chromium chloride, tin(II) chloride, etc.), ammonium salts (ammonium citrate, ammonium chloride, ammonium sulfate, nickel ammonium sulfate, etc.), chelating agents (ethylenediaminetetraacetic acid, diethanolglycine, tetrasodium L-glutamate diacetate, ethylenediamine-N,N'-disuccinic acid, sodium 3-hydroxy-2,2'-iminodisuccinate, trisodium methylglycine diacetate, tetrasodium aspartate diacetate, disodium N-(2-hydroxyethyl)iminodiacetate, sodium gluconate, etc.), and citric acid.

[0028] For example, when treating with nickel chloride, it is preferable to immerse the copper foil on which the protrusions have been formed in a nickel chloride solution (concentration 45 g / L or higher) at room temperature or a temperature higher than room temperature for 5 seconds or more. Furthermore, when performing this treatment simultaneously with plating, it is preferable to add nickel chloride to the plating solution, immerse the foil in the plating solution for 5, 10, 15, 20, 30 seconds, 1 minute, or 2 minutes, and then perform plating. The immersion time may be changed as appropriate depending on the oxide film thickness.

[0029] This dissolution treatment step needs to be carried out after the formation of the convex portions, as shown in the examples. Although we do not intend to be bound by the following theory, it is thought that if treatment with a solvent is carried out after the formation of the convex portions, the convex portions are raised, so that the solvent is more likely to come into contact with the convex portions, or the flow of the solvent is faster near the convex portions, making it easier for the reaction caused by the solvent to proceed, and therefore the protrusions at the convex portions are further weakened, making it easier for transfer to proceed after resin bonding.

[0030] (5) Plating process In this step, the copper foil surface on which the protrusions have been formed is plated using a plating solution. The plating method is not particularly limited, and plating can be performed by electrolytic plating, electroless plating, vacuum deposition, chemical conversion treatment, etc., but electrolytic plating is preferred because it is preferable to form a uniform plating layer.

[0031] In the case of electrolytic plating, nickel plating and nickel alloy plating are preferred. Examples of metals formed by nickel plating and nickel alloy plating include pure nickel, Ni-Cu alloy, Ni-Cr alloy, Ni-Co alloy, Ni-Zn alloy, Ni-Mn alloy, Ni-Pb alloy, and Ni-P alloy.

[0032] Examples of metal salts used for nickel plating include nickel sulfate, nickel sulfamate, nickel chloride, nickel bromide, zinc oxide, zinc chloride, diamminedichloropalladium, iron sulfate, iron chloride, chromic anhydride, chromium chloride, sodium chromium sulfate, copper sulfate, copper pyrophosphate, cobalt sulfate, and manganese sulfate.

[0033] In nickel plating, the plating solution preferably contains, for example, nickel sulfate (e.g., 100 g / L or more and 350 g / L or less), nickel sulfamate (e.g., 100 g / L or more and 600 g / L or less), nickel chloride (e.g., more than 0 g / L and 300 g / L or less), or a mixture thereof, but may also contain additives such as sodium citrate (e.g., more than 0 g / L and 100 g / L or less) or boric acid (e.g., more than 0 g / L and 60 g / L or less).

[0034] When electroplating is performed on the surface of copper foil that has been oxidized, the copper oxide on the surface is first reduced to cuprous oxide or pure copper, and an electric charge is used to reduce it, resulting in a time lag before plating begins. After that, the metal that forms the metal layer begins to deposit. The amount of electric charge varies depending on the type of plating solution and the amount of copper oxide. For example, when applying Ni plating to copper foil, the area of ​​the copper foil to be electroplated, dm 2 It is preferable to apply a charge of 10 C or more and 90 C or less, and more preferable to apply a charge of 20 C or more and 65 C or less per charge.

[0035] The current density is not particularly limited, but is preferably 0.2 A / dm 2 ~10A / dm 2 The current may be changed depending on the time until the oxide contained in the protrusions on the surface of the copper foil is partially reduced and the time during which the plating is being coated.

[0036] The amount of metal deposited on the surface of the copper foil by plating is not particularly limited, but is preferably 0.8 to 6.0 mg / dm 2 The amount of metal attached can be calculated by, for example, dissolving the structure in an acidic solution, measuring the amount of metal by ICP analysis, and dividing the amount by the plan view area of ​​the structure.

[0037] (6) The process of thermocompression bonding the copper foil to the resin substrate In this step, first, a copper foil is laminated on a resin substrate so that the copper foil surface including the convex portions is in contact with the resin substrate.

[0038] The resin substrate used is not particularly limited, but preferably contains or is made of at least one insulating resin selected from the group consisting of polyphenylene ether (PPE), epoxy, polyphenylene oxide (PPO), polybenzoxazole (PBO), polytetrafluoroethylene (PTFE), liquid crystal polymer (LCP), thermoplastic polyimide (TPI), fluororesin, polyetherimide, polyetheretherketone, polycycloolefin, bismaleimide resin, low-dielectric-constant polyimide, and cyanate resin. The resin substrate may further contain inorganic filler or glass fiber. The relative dielectric constant of the resin substrate used is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.8 or less.

[0039] When the surface of the copper foil on which the protrusions are formed is laminated to a resin substrate, the surface profile including the copper foil protrusions is transferred to the resin substrate, with the protrusions present in the convex portions being preferentially transferred. Therefore, holes complementary to the protrusions present in the convex portions on the copper foil surface are formed on the surface of the resin substrate. The average depth of the holes is not particularly limited, but is sufficient as long as it is 2.50 μm or less, more preferably 2.00 μm or less, and even more preferably 1.70 μm or less. It is also preferable that it is 0.01 μm or more, more preferably 0.10 μm or more, and even more preferably 0.36 μm or more. If the depth is less than 0.01 μm, adhesion to the resin substrate decreases. If it exceeds 2.50 μm, wiring formability deteriorates. The average depth of the holes can be measured, for example, using SEM images.

[0040] The method for bonding the surface of the copper foil to the resin substrate involves applying pressure to part or all of the copper foil under specified conditions, including heating. The specified conditions (e.g., temperature, pressure, time, etc.) may be those recommended by each substrate manufacturer. Examples of the specified conditions include the following:

[0041] 1) When the resin substrate contains or is made of an epoxy resin, it is preferable to thermocompression bond the copper foil to the resin substrate by applying a pressure of 0 to 20 MPa at a temperature of 50°C to 300°C for 1 minute to 5 hours.

[0042] for example, 1-1) If the resin substrate is R-1551 (manufactured by Panasonic), Heat under a pressure of 1 MPa, and after reaching 100°C, hold at that temperature for 5 to 10 minutes; The material is then further heated under a pressure of 3.3 MPa, and once it reaches 170-180°C, it is held at that temperature for 50 minutes to achieve thermocompression bonding. 1-2) If the resin base material is R-1410A (manufactured by Panasonic), Heating is performed under a pressure of 1 MPa, and after the temperature reaches 130°C, the material is held at that temperature for 10 minutes; then, heating is performed further under a pressure of 2.9 MPa, and after the temperature reaches 200°C, the material is held at that temperature for 70 minutes to achieve thermocompression bonding.

[0043] 1-3) If the resin substrate is EM-285 (manufactured by EMC), Heating is performed under a pressure of 0.4 MPa, and after the temperature reaches 100°C, the pressure is increased to 2.4 to 2.9 MPa and heating is continued. After the temperature reaches 195°C, the material is held at that temperature for 50 minutes to achieve thermocompression bonding.

[0044] 1-4) If the resin substrate is GX13 (manufactured by Ajinomoto Fine-Techno), it can be thermocompression bonded by heating it while applying pressure at 1.0 MPa and holding it at 180°C for 60 minutes.

[0045] 2) When the resin substrate contains or consists of a PPE resin, it is preferable to thermocompress the copper foil to the resin substrate by applying a pressure of 0 to 20 MPa at a temperature of 50°C to 350°C for 1 minute to 5 hours.

[0046] for example, 2-1) If the resin substrate is R5620 (manufactured by Panasonic), After heating and pressing the material under a pressure of 0.5 MPa until the temperature reaches 100°C, the material can be further pressed by increasing the temperature and pressure to 2.0 to 3.0 MPa and 200 to 210°C for 120 minutes.

[0047] 2-2) If the resin substrate is R5670 (manufactured by Panasonic), After the thermocompression bonding is performed by heating under a pressure of 0.49 MPa until the temperature reaches 110°C, the temperature and pressure are increased and the temperature and pressure are maintained at 2.94 MPa and 210°C for 120 minutes, completing the thermocompression bonding.

[0048] 2-3) If the resin substrate is R5680 (manufactured by Panasonic), thermocompression bonding can be achieved by heating to 110°C under a pressure of 0.5 MPa, then increasing the temperature and pressure to 3.0 to 4.0 MPa and 195°C, and holding for 75 minutes.

[0049] 2-4) If the resin substrate is N-22 (manufactured by Nelco), it can be thermocompression bonded by heating it under pressure of 1.6 to 2.3 MPa, holding it at 177°C for 30 minutes, and then further heating it and holding it at 216°C for 60 minutes.

[0050] 3) When the resin substrate contains or is made of PTFE resin, it is preferable to thermocompress the copper foil to the resin substrate by applying a pressure of 0 to 20 MPa at a temperature of 50°C to 400°C for 1 minute to 5 hours.

[0051] for example, 3-1) If the resin substrate is NX9255 (manufactured by Park Electrochemical), it can be thermocompression bonded by heating it to 260°C while applying a pressure of 0.69 MPa, then increasing the pressure to 1.03 to 1.72 MPa and heating it to 385°C, and holding it at 385°C for 10 minutes.

[0052] 3-2) If the resin substrate is RO3003 (manufactured by Rogers), thermocompression bonding can be achieved by applying a pressure of 2.4 MPa 50 minutes after the start of pressing (approximately 220°C) and holding the temperature at 371°C for 30 to 60 minutes.

[0053] 4) When the resin substrate contains or consists of a liquid crystal polymer (LCP), it is preferable to thermocompression bond the copper foil to the resin substrate by applying a pressure of 0 to 20 MPa for 1 minute to 5 hours at a temperature of 50 to 400° C. For example, when the resin substrate is CT-Z (manufactured by Kuraray), thermocompression bonding can be achieved by heating under a pressure of 0 MPa, holding at 260° C. for 15 minutes, then further heating while applying a pressure of 4 MPa, and holding at 300° C. for 10 minutes.

[0054] (7) Copper foil peeling process In this process, the copper foil is peeled off from the resin substrate to which it has been thermocompression-bonded under specified conditions, resulting in the transfer of some or all of the protrusions present on the convex portions to the resin substrate, thereby obtaining a resin substrate on which a seed layer has been formed. In this specification, the term "seed layer" refers to the layer formed between the surface of the peeled copper foil and a surface configured to include the bottom of the holes formed in the resin substrate by the copper foil protrusions (Figure 1). Therefore, the holes and the metal derived from the copper foil transferred to the holes are contained within this layer. The bottom of the holes refers to the bottom of the multiple holes that is farthest from the peeled copper foil surface, and the surface configured to include the bottom of the holes is parallel to the peeled copper foil surface.

[0055] The method for peeling the copper foil from the resin substrate is not particularly limited, but may be performed based on a 90° peel test (Japanese Industrial Standard (JIS) C5016 "Test Methods for Flexible Printed Wiring Boards"; corresponding international standards IEC249-1:1982, IEC326-2:1990). In this case, the angle of the copper foil peeling direction is maintained at 90±5° relative to the surface on which pressure was applied for adhesion. Alternatively, the copper foil may be peeled manually, in which case it is peeled at an angle of 80 to 180° relative to the surface on which pressure was applied.

[0056] The metal contained in the protrusions present on the convex portions of the copper foil is preferably transferred to the resin substrate so as to fill 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, or 99.9% or more of the pores in the transferred surface profile. On the other hand, the metal contained in the protrusions present in portions other than the convex portions of the copper foil is preferably transferred to the resin substrate at a rate of 30% or less, 20% or less, 10% or less, 5% or less, 1% or less, or 0.1% or less.

[0057] (8) Plating process In this process, the surface of the resin substrate on which the seed layer has been formed is plated. At this time, the metal derived from the copper foil exposed on the surface of the resin substrate is plated, but the resin substrate itself is not plated, so that the plated metal can be used as wiring for the printed wiring board.

[0058] The plating method is not particularly limited, and may be electrolytic plating or electroless plating. The metal is also not particularly limited, and for example, one metal selected from Ni, Sn, Al, Cr, Co, and Cu may be used, but it is preferable to use copper and plate it by electroless plating. The plating thickness is not particularly limited, and may be about 0.02 to 2 μm.

[0059] (9) Manufacturing method for printed wiring board First, a copper foil is prepared by performing the surface treatment according to the above (1) to (5). In this case, in (3), protrusions are formed so as to have the same shape as the circuit of the desired copper wiring.

[0060] Next, a laminate of the resin substrate and the copper foil is produced according to (6) to (7). After that, if necessary, metal originating from the copper foil that has been transferred to areas other than the circuit shape on the surface of the resin substrate may be removed by etching.

[0061] Finally, by plating the resin substrate in accordance with (8), copper wiring can be formed on the seed layer formed on the resin substrate.

[0062] By manufacturing a printed wiring board in this manner, an etching step using a resist, which is required in the conventional subtractive method, SAP method, MSAP method, etc., is not necessary. [Example]

[0063] (1) Copper foil treatment The shiny side (the glossy side, which is flat compared to the opposite side) of copper foil (DR-WS, thickness: 18 μm) manufactured by Furukawa Electric Co., Ltd. was used as the copper material, and the following treatment was carried out.

[0064] (1-1) Pretreatment The copper foil was degreased by immersing it in a 5 g / L aqueous solution of potassium hydroxide at a liquid temperature of 25° C. for 1 minute to remove dirt from the copper surface, and then washed with water.

[0065] (1-2) Oxidation treatment After pretreatment, the shiny side of the copper foil was immersed in an oxidizing agent (sodium chlorite 227.5 g / L; potassium hydroxide 18 g / L) at a temperature of 50°C for 1 minute to perform an oxidation treatment, forming fine protrusions on the surface of the copper foil.

[0066] (1-3) Formation of convex parts Lines and letters were drawn with a ballpoint pen on the matte side (non-glossy side, opposite to the shiny side) of the oxidized copper foil, forming protruding convex portions on the shiny side.

[0067] (1-4) Electroplating The copper foil on which the pattern was applied was immersed for 30 seconds in a Ni electroplating solution (nickel sulfate 255 g / L; trisodium citrate 20 g / L) containing a dissolving agent (nickel chloride 49 g / L), and then the plating solution was heated at 45°C and a current density of 0.5 A / dm 2 , 45 seconds (i.e., 22.5C / dm 2 Electrolytic plating was performed under the condition of (1-1) copper foil area. As a comparative example, after electrolytic plating, convex portions protruding from the shiny side were formed on the matte side of the same copper foil in the same manner as in (1-3). The appearance of the copper foil after these treatments is shown in Figure 2.

[0068] (1-5)Result As shown in FIG. 2, similar convex portions were formed whether the drawing was performed before the plating treatment (Example) or after the plating treatment (Comparative Example).

[0069] (2) Transfer of convex parts (2-1) Method

[0070] After the convex portions were formed, R5680NJ (manufactured by Panasonic) was laminated onto the copper foil as a prepreg, and the copper foil was heated to 110°C in a vacuum using a vacuum high-pressure press while applying a pressure of 0.5 MPa.The pressure was then increased to 3.5 MPa, and the copper foil was held at 195°C for 75 minutes, thereby thermocompression bonding the copper foil to the resin.

[0071] The copper foil that had been thermocompressed onto the resin was manually peeled off, and the bonded surfaces of the copper foil and resin were observed. The results are shown in Figure 3.

[0072] (2-2) Results In the example shown in FIG. 3A, the traces of the letters and figures appear as white marks on the copper foil adhesive surface, while the letters and figures appear as black marks on the resin adhesive surface. This means that the metal on the copper foil surface was transferred to the resin only in the convex areas created by the ballpoint pen.

[0073] However, in the comparative example, as shown in Figure 3B, the letters and figures on the copper foil adhesive surface were the same color as the copper foil, and the letters and figures on the resin adhesive surface were not discolored and were the same color as the resin. Thus, in the comparative example, the metal on the copper foil surface was not transferred to the resin surface.

[0074] In this example, the dissolving agent treatment is carried out simultaneously with the plating treatment. However, as described above, it has been shown that in order for the metal transfer, including the protrusions on the copper foil surface, to occur, the formation of the convex portions must be carried out before the dissolving agent treatment.

[0075] (3) Summary As described above, by the treatment of this example, metals containing copper oxides present on the convex portions of the copper foil are preferentially transferred from the copper foil to the resin.

Claims

1. A method for transferring protrusions on a copper foil surface to a resin substrate to form a seed layer, comprising: forming protrusions containing copper oxide on the surface of the copper foil; forming a convex portion on the copper foil surface on which the protrusions have been formed; a step of treating the copper foil surface on which the protrusions are formed with a solvent; a step of plating the copper foil surface on which the protrusions are formed using a plating solution; laminating the copper foil on the resin base material so that the protrusions are in contact with the resin base material; a step of applying pressure to a part or all of the copper foil laminated on the resin base material under predetermined conditions including heating; Including, The convex portion is formed by applying pressure from the back surface of a copper foil having the protrusions formed on one side thereof to be transferred to the resin base material, thereby causing the surface on which the protrusions are formed to protrude. method.

2. 2. The method of claim 1, wherein the step of treating with the dissolving agent is followed by a step of plating.

3. 2. The method according to claim 1, wherein the step of treating with the dissolving agent and the step of plating are carried out simultaneously by adding the dissolving agent to the plating solution.

4. The method according to any one of claims 1 to 3, wherein the height of the convex portions is 10 nm to 1000 µm.

5. The method of any one of claims 1 to 4, wherein the predetermined conditions include a temperature of 50°C to 400°C, a pressure of 0 to 20 MPa, and a time of 1 minute to 5 hours.

6. The method according to any one of claims 1 to 5, wherein the resin substrate contains at least one insulating resin selected from the group consisting of polyphenylene ether (PPE), epoxy, polyphenylene oxide (PPO), polybenzoxazole (PBO), polytetrafluoroethylene (PTFE), liquid crystal polymer (LCP), thermoplastic polyimide (TPI), fluororesin, polyetherimide, polyetheretherketone, polycycloolefin, bismaleimide resin, low dielectric constant polyimide, and cyanate resin.

7. The method according to any one of claims 1 to 6, further comprising the step of peeling off the copper foil to which the pressure has been applied from the resin substrate, thereby transferring part or all of the protrusions present on the convex portions and obtaining the resin substrate on which a seed layer has been formed.

8. A method for producing a resin substrate containing copper oxide, comprising: a step of oxidizing a copper foil surface with an oxidizing agent to form protrusions containing copper oxide on the copper foil surface; forming a convex portion on the copper foil surface on which the protrusions have been formed; a step of treating the copper foil surface on which the protrusions are formed with a solvent; a step of plating the copper foil surface on which the protrusions are formed using a plating solution; laminating the copper foil on the resin base material so that the protrusions are in contact with the copper foil; a step of applying pressure to a part or all of the copper foil laminated on the resin base material under predetermined conditions including heating; peeling the copper foil to which the pressure has been applied from the resin base material, so that a part or all of the protrusions present on the convex portions are transferred to obtain the resin base material on which a seed layer has been formed; Including, The convex portion is formed by applying pressure from the back surface of a copper foil having the protrusions formed on one side thereof to be transferred to the resin base material, thereby causing the surface on which the protrusions are formed to protrude. Manufacturing method.

9. A method for manufacturing a printed wiring board, a step of oxidizing a copper foil surface with an oxidizing agent to form protrusions containing copper oxide on the copper foil surface; forming a convex portion on the copper foil surface on which the protrusions have been formed; a step of treating the copper foil surface on which the protrusions are formed with a solvent; a step of plating the copper foil surface on which the protrusions are formed using a plating solution; laminating the copper foil on a resin substrate so that the protrusions are in contact with the resin substrate; a step of applying pressure to a part or all of the copper foil laminated on the resin base material under predetermined conditions including heating; peeling the copper foil to which the pressure has been applied from the resin base material, so that a part or all of the protrusions present on the convex portions are transferred to obtain the resin base material on which a seed layer has been formed; a step of performing copper plating on the surface of the seed layer; Including, The convex portion is formed by applying pressure from the back surface of a copper foil having the protrusions formed on one side thereof to be transferred to the resin base material, thereby causing the surface on which the protrusions are formed to protrude. Manufacturing method.

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