Wiring for multilayer board and manufacturing method thereof

Abstract

The present invention is a multilayer substrate wiring (100) that includes copper wiring (101), a first resin layer (103), and a second resin layer (105), wherein the copper wiring (101) has a first surface (107) and a second surface (109), the first surface (107) is affixed to the surface of the first resin layer (103), the copper wiring (101) is embedded in the second resin layer (105), the second surface (109) has a layer that includes a copper oxide, and the multilayer substrate wiring has strong properties for bonding and adhesion to a resin substrate.

Description

[Technical Field]

[0001] The present invention relates to wiring for multilayer substrates and a method for manufacturing the same. [Background technology]

[0002] As electronic devices become smaller, printed wiring boards are becoming increasingly multilayered and have higher wiring density (Japanese Patent Application Laid-Open No. 2017-191894). In multilayer wiring, the top and side surfaces of the inner wiring are generally subjected to surface treatment to ensure adhesion with the resin. Conventional surface treatments include etching (JP 2019-060013 A) and blackening (JP 2004-140268 A). Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide wiring for a multilayer substrate that has high adhesion and bonding to a resin substrate, and a method for manufacturing the same. [Means for solving the problem]

[0004] As a result of extensive research, the inventors of the present application have succeeded in producing wiring for multilayer boards that has high adhesion and bonding to resin substrates by forming a copper oxide film with fine needle-like protrusions on the surface of the inner layer wiring.

[0005] One embodiment of the present invention is a wiring for a multilayer substrate, comprising a copper wiring, a first resin layer, and a second resin layer, wherein the copper wiring has a first surface and a second surface, the first surface being bonded to the surface of the first resin layer, the copper wiring being embedded in the second resin layer, and the second surface having a layer containing copper oxide. In a cross section of the copper wiring perpendicular to the first surface, there may be 1.5 or less bubbles per 10 μm between the first surface and the first resin layer, and between the second surface and the second resin layer. The minor and major axes of the bubbles are 10 nm to 500 nm. The bubbles having a minor axis of 10 nm or more present on the first surface may not be present more than 500 nm from either end of a line segment corresponding to the first surface in a cross section of the copper wiring perpendicular to the first surface and crossing the bubbles having a minor axis of 10 nm or more. The shape of the copper wiring may be linear with a substantially rectangular cross section, and the second surface may be composed of a third surface facing the first surface and two fourth surfaces connecting the first and second surfaces. The thickness of the layer containing copper oxide on the third surface and / or the fourth surface may be 0.05 μm or more and 0.4 μm or less. Protrusions may be present on part or all of the third surface and / or the fourth surface, and the height of the protrusions may be 0.05 μm or more and 0.7 μm or less. Another embodiment of the present invention is a multilayer substrate including any of the above-described wiring for a multilayer substrate. The substrate may include, on at least one side thereof, one outer layer including an outer layer wiring and one or more inner layers including any of the above-described wiring for a multilayer substrate as inner layer wiring. The distance between the closest portions of the copper wirings may be 3 μm or less. The height of the layer including copper oxide on the fourth surface may be one-third or less of the distance between the closest portions of the copper wirings. The distance between the closest portions of the copper wirings may be 3 μm or less. The thinning of the copper wiring may be 23% or less when the copper wiring is 3 μm to 10 μm, 7% or less when the copper wiring is 10 μm to 19 μm, 3.5% or less when the copper wiring is 20 μm to 49 μm, and 1.4% or less when the copper wiring is 50 μm. A further embodiment of the present invention is any of the above methods for manufacturing a wiring for a multilayer substrate, comprising a first step of forming the copper oxide-containing layer by oxidizing a wiring substrate, in which the copper wiring and the first resin layer are bonded to the first resin layer on a first side of the copper wiring, with an oxidizing agent containing a copper corrosion inhibitor and having a pH of 11.5 to 14. The method may also include a second step, performed before the first step, of treating the wiring for a multilayer substrate with an alkaline solution of pH 9 or higher. The method may also include a third step, performed after the first step, of treating the wiring for a multilayer substrate with a dissolving agent. The method may also include a fourth step, performed after the first step, of treating the wiring for a multilayer substrate with a reducing agent. The method may also include a fifth step, performed after the first step, of treating the wiring substrate with a coupling agent. The method may also include a sixth step, performed after the first step, of treating the wiring substrate with an anti-corrosion agent. The method may also include a seventh step, performed after the first step, of plating the wiring substrate.

[0006] ==Cross-reference to related literature== This application claims priority based on Japanese Patent Application No. 2020-183680, filed on November 2, 2020, and the basic application is incorporated herein by reference. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a wiring for a multilayer substrate according to an embodiment of the present invention; [Figure 2] 1 is a typical scanning electron microscope (SEM) photograph showing bubbles at the boundary between the copper wiring and the resin layer in an example and a comparative example of the present invention. [Figure 3] 10 is a SEM photograph showing a method for identifying the number of bubbles in a comparative example of the present invention. [Figure 4] 10 is a SEM photograph showing a method for measuring the maximum distance to a bubble at the wiring inner boundary in a comparative example of the present invention. [Figure 5] 1 is a SEM photograph showing a method for measuring the thickness of a copper oxide layer in Examples and Comparative Examples of the present invention. [Figure 6] 10 is a SEM photograph showing a method for measuring the height of a convex portion on the outer surface of a wiring in an example of the present invention and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] <Wiring for multilayer board> A wiring 100 for a multilayer substrate according to one embodiment of the present invention includes a copper wiring 101, a first resin layer 103, and a second resin layer 105. The copper wiring 101 has a first surface 107 and a second surface 109. The first surface 107 is bonded to the surface of the first resin layer 103. The copper wiring 101 is embedded in the second resin layer 105. The second surface 109 has a layer containing copper oxide. The copper wiring 100 may have a linear shape having a longitudinal direction throughout, perpendicular to the first surface 107, and a substantially rectangular cross section perpendicular to the longitudinal axis. The second surface 109 may include a third surface 111 facing the first surface 107 and two fourth surfaces 113 connecting the first surface 107 and the second surface 109. FIG. 1 shows a schematic cross-sectional view. The multilayer substrate wiring 100 will be described in detail below.

[0010] In this specification, a quadrangle means a polygon having four clear corners when observing an image with a resolution such that each side appears as a line, and each side may be straight or curved, or may have minute irregularities. The interior angle of each corner is preferably 30° to 120°, and more preferably 40° to 105°.

[0011] Furthermore, "perpendicular to a surface or line" refers to a cross section perpendicular to a straight line when an image with a resolution sufficient to make the surface or interface appear as a straight line is used.

[0012] In addition, in the multilayer board wiring 100 and the multilayer board, the surface side is referred to as the outside and the board side is referred to as the inside. Therefore, if there are wiring on both sides of the board, the inside and outside directions will be opposite on both sides.

[0013] (Embodiment 1) In the multilayer substrate wiring 100 of this embodiment, in a cross section perpendicular to the first surface 107 and perpendicular to the long axis direction, bubbles with a minor axis of 10 nm or more are present between the first surface 107 and the first resin layer 103, and between the second surface 109 and the second resin layer 105, at a density of 1.5 or less per 10 μm. The number of bubbles is preferably 1.5 or less per 10 μm, more preferably 1.0 or less, even more preferably 0.8 or less, and even more preferably 0.5 or less. Here, bubbles refer to bubbles with a minor axis of 10 nm or more, and the major axis of the bubbles is preferably 500 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. That is, the minor and major axes of the bubbles are 10 nm or more and 500 nm or less, 10 nm or more and 200 nm or less, or 10 nm or more and 100 nm or less. The major axis refers to the longest distance between two points on the boundary of a bubble in the cross section, and the minor axis refers to the longest distance between two points between a line perpendicular to the major axis and the boundary of the bubble. A small number of bubbles indicates that the first surface 107 and the first resin layer 103, and the second surface 109 and the second resin layer 105 are tightly adhered to each other. The presence of a large number of bubbles or large bubbles can reduce reliability.

[0014] Furthermore, the bubbles with a minor axis of 10 nm or more present on first surface 107 preferably do not exist within 500 nm, and preferably within 380 nm, from either end of a line segment corresponding to first surface 107 in a cross section perpendicular to first surface 107 and perpendicular to the major axis direction, which crosses the bubbles with a minor axis of 10 nm or more. A short distance indicates that first surface 107 and first resin layer 103 are formed in close contact with each other. Convex portions, particularly minute convex portions, may be present on part or all of third surface 111 and / or fourth surface 113. The height of the convex portions is not particularly limited, but is preferably 0.05 μm or more and 0.7 μm or less, and more preferably 0.39 μm or more and 0.68 μm or less. Here, the height of the convex portions is determined, for example, by measuring the length from the lowest point to the highest point of the convex portions within a width of 6.2 μm in a 30,000x SEM image of a cross section perpendicular to first surface 107 and perpendicular to the long axis direction, and calculating the average value of multiple images (e.g., three images). If this height is too high, transmission loss increases, and in the case of fine wiring, if the height of the convex portion is large, the wiring will thin partially from both sides of fourth surface 113, resulting in an uneven wiring shape and adversely affecting the transmission of electrical signals. Therefore, the wiring thinning is preferably 1.4% or less when the wiring width is 50 μm, 3.5% or less when it is 20 to 49 μm, 7% or less when it is 10 to 19 μm, and 23% or less when it is 3 to 9 μm. The wiring thinning rate can be calculated by convex portion height / wiring width * 100.

[0015] (Embodiment 2) A layer containing copper oxide may be present on the third surface 111 and / or the fourth surface 113. There are no particular limitations on the thickness of the layer, but it is preferably 0.05 μm or more and 0.4 μm or less, and more preferably 0.09 μm or more and 0.38 μm or less. This allows the second resin layer 105 to be formed in close contact with the second surface 109. If the amount of copper oxide attached is too small, the adhesion to the resin layer will be weak, and if the amount of copper oxide attached is too large, the resin will not be able to fill the gaps between the recesses and protrusions formed by the copper oxide, increasing the possibility of air bubbles forming.

[0016] Here, the thickness of the copper oxide-containing layer is measured by, for example, taking five points every 1.03 μm on a 30,000x SEM cross-sectional image, measuring the length from the base of the protrusion to the highest point of the protrusion in the vertical direction at each point, and calculating the average value for the five points.

[0017] In addition to this layer containing copper oxide, the wiring 100 for a multilayer substrate may be such that, as in the first embodiment, in a cross section perpendicular to the first surface 107 and perpendicular to the longitudinal direction, there are 1.5 or less bubbles per 10 μm between the first surface 107 and the first resin layer 103, and between the second surface 109 and the second resin layer 105.

[0018] <Multilayer board> In this specification, the outermost layer of the multilayer board that has no other layers stacked on top of it is referred to as the outer layer, the layer inside the multilayer board that is sandwiched between layers of wiring 100 for multilayer boards on the top and bottom is referred to as the inner layer, and the wiring present on each layer is referred to as the outer layer wiring and the inner layer wiring, respectively.

[0019] A multilayer substrate according to one embodiment of the present invention includes the above-described multilayer substrate wiring 100 as an inner layer wiring. When wiring is formed on one side of the substrate, the multilayer substrate comprises one outer layer including outer layer wiring and one or more layers including inner layer wiring. When wiring is formed on both sides of the substrate, each side comprises one outer layer including outer layer wiring and one or more inner layers including inner layer wiring, making the substrate as a whole one or two outer layers and one or more inner layers. The surface of the outer layer wiring is preferably covered with solder resist.

[0020] The distance between the inner layer wirings at their closest points is not particularly limited, but may be 7 μm or less, preferably 5 μm or less, and more preferably 3 μm or less, which allows the multilayer board wiring 100 of the present disclosure to be used more suitably.

[0021] In this multilayer substrate, the height of the layer containing copper oxide on fourth surface 113 is preferably ⅓ or less of the distance between the closest copper wirings, which makes it difficult for the copper oxide-containing protrusions on fourth surface 113 to come into contact with adjacent wirings.

[0022] <Method of manufacturing wiring for multilayer boards> A method for manufacturing wiring for a multilayer substrate according to one embodiment of the present invention includes a first step of forming a layer containing copper oxide by oxidizing a wiring substrate, in which a copper wiring and a first resin layer are bonded to the first resin layer on a first surface of the copper wiring, with an oxidizing agent having a pH of 11.5 to 14 and containing a copper corrosion inhibitor.

[0023] The method for manufacturing the copper wiring is not particularly limited, and wiring may be formed using, for example, a subtractive method, a semi-additive (SAP) method, or a modified semi-additive (MSAP) method.

[0024] In this step, the surface of the copper wiring is oxidized with an oxidizing agent to form a layer containing copper oxide and to form fine irregularities on the surface.

[0025] The oxidizing agent is not particularly limited, and examples thereof include sodium chlorite, potassium chlorite, sodium hypochlorite, potassium hypochlorite, sodium chlorate, potassium chlorate, sodium perchlorate, potassium perchlorate, etc. The oxidizing agent is preferably in the form of an aqueous solution.

[0026] 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. The oxidizing agent may be oxidized for 1 minute or more, and more preferably for 1 to 10 minutes. The pH of the oxidizing agent may be alkaline, and is preferably 11.5 or more, 12.0 or more, 12.5 or more, or 13 or more at 73°C, and is preferably 14.0 or less, or 13.5 or less. The preferred pH range depends on the measurement temperature, and can be determined by those skilled in the art through appropriate experiments.

[0027] The oxidizing agent preferably includes a copper corrosion inhibitor. A copper corrosion inhibitor refers to an inorganic or organic compound, its hydrolyzate, or a salt thereof (including acidic, basic, or normal salts) that, when added in small amounts to a corrosive environment, acts on either or both of the anodic reaction and the cathodic reaction, thereby significantly reducing copper corrosion. The corrosion inhibitor reacts with copper atoms, copper ions (I or II), copper hydroxide (I or II), or copper oxide (I or II) to form a bond, which acts directly on the copper surface to form a barrier film against the corrosive environment or forms a stable passive film on the copper, thereby inhibiting copper corrosion. However, the inhibitor may also form multiple types of films to function as barrier films against corrosion.

[0028] Copper corrosion inhibitors are classified as inorganic inhibitors or organic inhibitors, and further classified according to the type of film they form into oxide film type inhibitors, precipitate film type inhibitors, and adsorption film type inhibitors.

[0029] The copper corrosion inhibitor is preferably water-soluble. For example, in the case of polyglycerol polyglycidyl ether, the content at 73°C is preferably 0.20 g / L or more, 0.50 g / L or more, 0.75 g / L or more, 1.00 g / L or more, 1.50 g / L or more, 2.00 g / L or more, or 2.50 g / L or more, and preferably 5 g / L or less, 4 g / L or less, 3.5 g / L or less, or 3 g / L or less.

[0030] Oxide film type inhibitors can form an oxide film on the copper surface that acts as a barrier. Oxide film type inhibitors include chromates (e.g., cyclohexylammonium chromate (CH 11NH8)2·CrO4), nitrites (e.g., NaNO2), molybdates (e.g., Na2MoO4·2H2O), iron and iron ions that form an iron oxide film, etc.

[0031] Precipitated film-type inhibitors react with calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ) and metal ion-type inhibitors that can form an insoluble salt with copper ions to form a barrier film.

[0032] Ionic inhibitors in water include phosphates (polyphosphates, phosphonates, orthophosphates), silicates, metasilicates, etc. A specific compound is sodium silicate. Sodium silicate includes anhydrous sodium silicate (Na2O·nSiO2) and hydrated sodium silicate (Na2O·nSiO2·mH2O), where n is usually 0.5 to 4.0. Sodium silicate, also known as water glass or sodium silicate, may be added to the oxidizer.

[0033] Metal ion inhibitors include: (1) Benzotriazole (BTA) and its derivatives (e.g., tolutriazole (TTA); 2-mercaptobenzothiazole (MBT); 2,5-dimercaptothiazole (DMTDA); benzimidazole (BIA); benzimidazole thiol (BIT); benzoxazole thiol (BOT); mixtures of methylbenzothiazole and indole; mercaptothiazoline; and 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol (TT-LYK)); (2) Dithiocarbamic acid and its derivatives (e.g., dimethyldithiocarbamate; diethyldithiocarbamate; N-methyldithiocarbamate; ethylene-bisdithiocarbamate); (3) Thiourea, thioacetamide, thiosemicarbamide, thiophenol, p-thiocresol, thiobenzoic acid, ω-mercaptocarboxylic acid derivatives (RS(CH2) n sulfur compounds containing COOH (wherein n=1 or 2; R is a C1-5 alkyl group); (4) 6-substituted 1,3,5-triazine 2,4-dithiol (R-TDT); and salts thereof.

[0034] Adsorption film-type inhibitors can directly adsorb and / or bind to the copper surface to form a barrier film. (1) Water-soluble silane coupling agent; (2) Quinoline, amines (e.g., octadecylamine and dicyclohexylamine), amides, tetrazole and its derivatives (e.g., 3-amino-1,2,4-triazole), and their salts; (3) Water-soluble epoxy or glycidyl monomers (e.g., polyepoxy ethers and polyglycidyl ethers) having monofunctional or polyfunctional (di-, tri-, tetra-, or penta- or more) epoxy or glycidyl groups per molecule, and their salts.

[0035] Silane coupling agents are compounds that combine organic functional groups with alkoxysilyl groups (-Si(OR) n ( In the formula, OR is an alkoxy group including ethoxy and methoxy groups, and n=1, 2, or 3. )) or a compound having an organic functional group and a silanol group (-Si(OH) n ) and salts thereof. The organic functional group is preferably a functional group having a vinyl group, an epoxy group, a styryl group, a methacryl group, an acrylic group, an amino group, an isocyanurate group, a ureido group, a mercapto group, an isocyanate group, or an acid anhydride functional group (for example, a "functional group having an epoxy group" includes a glycidyl group). Silane coupling agents have the following properties depending on the type of organic functional group: 1) Silane coupling agents having a vinyl group (e.g., vinyltrimethoxysilane, vinylethoxysilane); 2) silane coupling agents having an epoxy group (for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane); 3) silane coupling agents having a styryl group (for example, p-styryltrimethoxysilane); 4) silane coupling agents having a methacryl group (for example, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane); 5) silane coupling agents having an acrylic group (e.g., 3-acryloxypropyltrimethoxysilane); 6) silane coupling agents having an amino group (for example, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane); 7) silane coupling agents having an isocyanurate group (e.g., tris-(trimethoxysilylpropyl)isocyanurate); 8) silane coupling agents having a ureido group (for example, 3-ureidopropyltrialkoxysilane); 9) silane coupling agents having a mercapto group (for example, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane); 10) silane coupling agents having an isocyanate group (for example, 3-isocyanatepropyltriethoxysilane); 11) Silane coupling agents having an acid anhydride functional group (for example, 3-trimethoxysilylpropylsuccinic anhydride having a succinic anhydride functional group); They are classified into the following categories.

[0036] The water-soluble silane coupling agent preferably has a solubility in water at 73° C. under alkaline conditions, for example, at pH 11.5 to 14, of 0.01 g / L or more, 0.1 g / L or more, 0.5 g / L or more, or 1 g / L or more.

[0037] Although not particularly limited, the water-soluble silane coupling agent may include: Vinyltrimethoxysilane, vinylethoxysilane; 3-Glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; p-Styryltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane; 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane; tris-(trimethoxysilylpropyl)isocyanurate; 3-ureidopropyltrialkoxysilane; 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane; 3-Trimethoxysilylpropylsuccinic anhydride; their hydrolysates; and These salts are included.

[0038] The water-soluble monofunctional or polyfunctional epoxy polymer or glycidyl polymer preferably has a solubility in water at 73°C under alkaline conditions, for example, at a pH of 11.5 to 14, of 0.01 g / L or more, 0.1 g / L or more, 0.2 g / L or more, or 1 g / L or more.

[0039] Water-soluble monofunctional or polyfunctional epoxy or glycidyl polymers include polyglycidyl ethers (e.g., glycerol polyepoxy ether, trimethylolpropane polyepoxy ether, pentaerythritol polyepoxy ether, polyglycerol polyepoxy ether, and sorbitol polyepoxy ether) and polyglycidyl ethers (e.g., glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether).

[0040] Copper corrosion inhibitors are -OH groups that can bond with copper atoms, copper ions (I or II), copper hydroxides (I or II), or copper oxides (I or II) in an oxidizing agent with a pH of 11.5 to 14. It may also be a compound having an ether group (—O—) or a N atom. The copper corrosion inhibitor preferably becomes a compound having a silanol group, an epoxy group, a glycidyl group, a trizole ring, or a thiazole ring in the oxidizing agent. Benzotriazole (BTA) and its derivatives are polymerized by the formation of coordinate bonds between the N atoms constituting the triazole ring, thiazole ring, etc. and copper ions. The water-soluble silane coupling agent has an alkoxysilyl group (-Si(OR)n ) is hydrolyzed in the presence of an oxidizing agent to form a silanol group (-Si(OH) n ), and the silanol groups react with copper to form Si-O-metal (M) bonds. In polyepoxy ethers and polyglycidyl ethers, the epoxy group or glycidyl group reacts with copper. Many copper corrosion inhibitors have these functional groups, which form conjugate molecules with copper atoms, copper ions, copper hydroxide, or copper oxide. Preferably, one molecule of a copper corrosion inhibitor contains one or more (2, 3, 4, 5, or 6 or more) of these functional groups or atoms.

[0041] The oxidizing agent may contain one of these copper corrosion inhibitors alone or a plurality of types thereof.

[0042] As long as the technical features of the present invention are not impaired, a second step may be carried out before the oxidation treatment, in which the wiring for multilayer boards is treated with an alkaline solution having a pH of 9 or higher. The method of alkaline treatment is not particularly limited, but it is sufficient to treat the wiring for multilayer boards using an alkaline aqueous solution of preferably 0.1 to 10 g / L, more preferably 1 to 2 g / L, such as an aqueous sodium hydroxide solution, at 30 to 50°C for about 0.5 to 2 minutes.

[0043] As long as the technical features of the present invention are not impaired, after the oxidation treatment, 1) a third step of partially dissolving the copper oxide-containing layer formed by the oxidation treatment with a dissolving agent (e.g., a chelating agent such as ethylenediaminetetraacetic acid, diethanolglycine, tetrasodium L-glutamic acid diacetate, ethylenediamine-N,N'-disuccinic acid, sodium 3-hydroxy-2,2'-iminodisuccinate, trisodium methylglycine diacetate, tetrasodium aspartic acid diacetate, disodium N-(2-hydroxyethyl)iminodiacetate, or sodium gluconate);

[0044] 2) a fourth step of partially reducing copper oxide contained in the copper oxide-containing layer formed by the oxidation treatment using a reducing agent (e.g., dimethylamine borane (DMAB), diborane, sodium borohydride, hydrazine, etc.);

[0045] 3) a fifth step of treating the copper oxide-containing layer formed by the oxidation treatment with a coupling agent (including a silane coupling agent, etc.) to form a coupling treatment layer, and a sixth step of treating the copper oxide-containing layer with a corrosion-resistant agent (including benzotriazoles, etc.) to form a corrosion-resistant layer;

[0046] 4) a seventh step of performing a plating treatment (including electroplating, electroless plating, vacuum deposition, chemical conversion treatment, etc.) to form a plated layer of a metal (e.g., Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, Pt, or an alloy thereof) on the copper oxide-containing layer formed by the oxidation treatment; Surface treatment such as the above may also be performed.

[0047] In this manner, wiring for a multilayer substrate according to one embodiment of the present invention can be manufactured. [Example]

[0048] 1. Formation of wiring for the board In Examples 1 to 11 and Comparative Examples 1 to 5, R5670KJ (Panasonic, thickness 100 μm) was heated to the matte side (matte side, rougher side compared to the opposite side) of electrolytic copper foil (FV-WS) manufactured by Furukawa Electric Co., Ltd. under a pressure of 0.49 MPa. When the temperature reached 110°C, the pressure was further increased to 2.94 MPa, the foil was heated to 210°C, and the temperature was maintained at 210°C for 120 minutes to thermocompression bond the foil to obtain a copper-clad substrate.

[0049] In Examples 1 to 10 and 12 and Comparative Examples 1 to 6, soft etching was used to bond the shiny side of the copper foil (the side that is flatter than the opposite side), which is the adhesive surface for the dry film resist on the copper-clad substrate, to the dry film photoresist (DFR). In Example 11, a plating process was performed after oxidation treatment. Soft etching was performed using a CPE900 Clean Etch (manufactured by Mitsubishi Gas Chemical Company) at 25°C for 43 seconds. The wiring for these substrates was then processed after exposure, development, and peeling of the dry film. The processing conditions are summarized in Table 1. In Example 11, it was confirmed that protrusions remained even after peeling of the DFR, and the substrate was used as is. In Examples 1 to 11 and Comparative Examples 1 to 5, copper wiring was formed using the subtractive method. In Example 12 and Comparative Example 6, copper wiring was formed using the SAP method.

[0050] 2. Formation of wiring for multilayer boards

[0051] (1) Pretreatment In Examples 1 to 12 and Comparative Example 5, the alkali treatment was carried out under the conditions shown in Table 1, followed by washing with water.

[0052] (2) Oxidation treatment In Examples 1 to 12 and Comparative Example 5, the oxidation treatment was carried out under the conditions shown in Table 1.

[0053] (3) Post-processing Under the conditions shown in Table 1, Example 7 was subjected to dissolution treatment, Example 8 to reduction treatment, Example 9 to coupling treatment, and Example 10 to corrosion resistance treatment.

[0054] (4) Wiring surface treatment of comparative example In Comparative Example 1, no treatment was performed after wiring. In Comparative Example 2, treatment was performed using Flat BOND GT (manufactured by MEC) at 30°C for 30 seconds, followed by treatment using Flat BOND GW (manufactured by MEC) at 30°C for 10 seconds. After rinsing with water, treatment was performed using Flat BOND GC (manufactured by MEC) at 30°C for 30 seconds, and drying was performed at 90°C for 30 seconds. In Comparative Example 3, treatment was performed using MB-150A (manufactured by MacDermid) at a concentration of 3.0 vol%, MB-150C (manufactured by MacDermid) at a concentration of 1.0 vol%, The steel was treated with a 4.0 vol% solution of 98% sulfuric acid and 15 g / L copper solution at 35° C. for 55 seconds. In Comparative Examples 4 and 6, blackening treatment was performed using an Enplate (manufactured by Meltex) at 80° C. for 6 minutes and 20 seconds.

[0055] Furthermore, R5670KJ (thickness: 100 μm) was laminated on the surface of the wiring to obtain an evaluation sample for wiring for multilayer boards. The lamination conditions were the same as those described above. [Table 1]

[0056] <Evaluation method for copper oxide layer> The copper oxide layer was confirmed using the continuous electrochemical reduction method. This method involves contacting the surface of an object with an electrolyte, passing a small current through the electrolyte, measuring the reduction potential specific to the materials that make up the object, and calculating the thickness and elemental content of each material using the time required for reduction. Surface elemental analysis was performed using a QC-100 (manufactured by ECI). The following electrolytes were used for the measurements. Electrolyte (pH=0.6~0.7) H4NO3 (ammonium nitrate) 200g / L H2NCSNH2 (thiourea) 15g / L NH4Cl (ammonium chloride) 5g / L HNO3 (nitric acid) 12ml / L :H2O Gasket diameter: 0.16 cm Current density: 90 μA / cm 2 When the above electrolyte was used, the potential range of -0.3 V to -0.6 V was determined to be a peak derived from cuprous oxide (CuO), and the potential range of -0.6 V to -0.85 V was determined to be a peak derived from copper oxide (CuO). The presence or absence of cuprous oxide and copper oxide was calculated using the following formula, and when the total thickness of cuprous oxide and copper oxide was 5 nm or more, it was determined that a copper oxide layer was present. Cu2O(nm)=0.0124×current density(μA / cm 2 ) × reduction time (sec) × 0.1 CuO(nm)=0.00639×current density(μA / cm 2) × reduction time (sec) × 0.1

[0057] 3. Evaluation method for wiring on multilayer boards The fabricated wiring for multilayer substrates was evaluated as follows, and the results are summarized in Table 2. Regarding the structure, SEM cross-sectional images were taken at 30,000x magnification for a cross section perpendicular to the surface of the copper wiring in contact with the resin layer and perpendicular to the long axis of the wiring for multilayer substrates, and evaluation was performed on these images. A representative example of the image is shown in Figure 2.

[0058] (1) Number of bubbles around the entire wiring The number of bubbles with a minor axis of 10 nm or more was counted around the entire circumference of the wiring in the SEM cross-sectional images, and the average value for three images was calculated. Figure 3 shows a typical example of a bubble image.

[0059] (2) Maximum distance to bubbles on the inner boundary of the wiring In an SEM cross-sectional image of a bubble with a minor axis of 10 nm or more present on the inner surface of the copper wiring in contact with the resin layer, the distance from both ends of a line segment corresponding to the surface of the copper wiring in the cross section of the copper wiring perpendicular to the first surface was measured. An example of the measurement method on the image is shown in Figure 4.

[0060] (3) Thickness of the copper oxide layer on the outer surface of the wiring Five points were taken every 1.03 μm on the SEM cross-sectional image, and the length from the base of the protrusion to the highest point of the protrusion was measured in the vertical direction at each point, and the average value for the five points was calculated to measure the thickness of the layer containing copper oxide on the outer surface of the copper wiring. An example of the measurement method on the image is shown in Figure 5.

[0061] (4) Height of the convex part on the outer surface of the wiring In the SEM image, the height of the convex part on the outer surface of the copper wiring was measured as the length from the lowest point to the highest point of the convex part within a width of 6.2 μm, and the average value of three images was calculated. An example of the measurement method on the image is shown in Figure 6.

[0062] (5) Moisture absorption reflow The fabricated wiring for multilayer boards was placed in a test tank at 120°C, 85% Rh, and 3 atmospheres for 48 hours, and then passed through a reflow furnace at 260°C for 20 seconds five times, and the presence or absence of swelling was visually checked.

[0063] (6) Thinning rate If the height of the convex portion is higher than the wiring, the actual wiring becomes thinner, which adversely affects electrical transmission. Therefore, the thinning rate was calculated using the following formula:

[0064] Thinning rate (%) = (height of the convex part on the outer surface of the wiring / wiring width) x 100

[0065] (7) High-frequency characteristics In Examples 1 to 11 and Comparative Examples 1 to 7, four sheets of NC0207 (Namics, thickness 25 μm) were laminated as an insulating adhesive film on the matte side (matte surface, rougher than the opposite side) of an electrolytic copper foil (FV-WS) manufactured by Furukawa Electric Co., Ltd., and thermocompression bonded to the outer surface of the wiring. A 100 mm long microstrip line was fabricated using a subtractive method on the shiny side of the copper foil (the side that is flat compared to the opposite side), which is the surface that adheres to the dry film resist of the substrate. In Examples 1 to 10 and 12 and Comparative Examples 1 to 6, soft etching was used for adhesion to the dry film photoresist (DFR), and in Example 11, plating was performed after oxidation treatment. Soft etching was performed using CPE900 Clean Etch (manufactured by Mitsubishi Gas Chemical Company) at 25°C for 43 seconds. These substrate wiring treatments were performed after exposure, development, and peeling of the dry film. The treatment for the substrate wiring was the same as described above. This microstrip line was used, with a circuit width of 270 μm and a characteristic impedance of 50 Ω. High-frequency signals up to 40 GHz were transmitted through this transmission line using a network analyzer, and the transmission loss was measured. The evaluation criteria for transmission loss at 40 GHz were as follows: ○: -0.94dB / Inch or more ×: Less than -0.94dB / Inch

[0066] (8) Peel strength The shiny side (the side that is flat compared to the other side) of Furukawa Electric Co., Ltd.'s electrodeposited copper foil (FV-WS) was subjected to the above-mentioned substrate application treatment, and NC0207 (Namics, thickness 25 μm) was used as the insulating adhesive film for the shiny side, and the foil was compressed at 1.0 MPa using a vacuum press. The copper foil was then adhered to the outer surface of the wiring by holding it at 200°C for 60 minutes. The peel strength was then measured when the copper foil was peeled off from the resin in a 90° direction at a rate of 50 mm / min. [Table 2]

[0067] 4. Summary In all of the Examples and Comparative Examples 4 to 6, the copper oxide layer was 5 nm or thicker. In all examples, the number of bubbles around the entire wiring was 1.5 or less per 10 μm, but in Comparative Example 1, in which no oxidation treatment was performed, and Comparative Examples 4 to 6, in which oxidation treatment was performed, the number was more than 1.5 per 10 μm. In all examples, the thickness of the copper oxide layer on the outer surface of the wiring was 0.09 to 0.38 μm, but in Comparative Examples 4 to 6, where oxidation treatment was performed, it was 0.50 μm or more. Without a copper oxide film layer, as in Comparative Example 1, adhesion to the substrate was not achieved, and if the thickness was too high, as in Comparative Examples 4 to 6, the resin did not penetrate deep into the oxide film. Therefore, many bubbles were present in both cases. The maximum distance to the bubbles on the inner boundary of the wiring was 0 to 113 nm in the examples, but in the comparative examples, it was 0 (Comparative Example 1) and 218 nm or more in all others. In particular, in Comparative Examples 2 and 3, the copper was etched to form irregularities, which is thought to have caused the copper to erode, resulting in a maximum distance to the bubbles on the inner boundary of the wiring of 1000 nm or more. Therefore, it is thought that the adhesion between the copper wiring and the resin in Comparative Examples 2 and 3 is quite low. The height of the convex portions on the outer surface of the wiring was 0.39 to 0.68 μm in the Examples. In Comparative Example 1, it was 0.43 μm, and the high-frequency characteristics were good, but the peel strength was low. In the other Comparative Examples, the peel strength was 0.74 kgf / cm, which was comparable to the 0.55 to 0.78 kgf / cm in the Examples, but the height of the convex portions was 0.78 μm or more, and the high-frequency characteristics were poor. In the Comparative Examples, there appears to be a trade-off between high-frequency characteristics and peel strength, but in the Examples, both were good. In the moisture absorption reflow test, no swelling occurred in any of the examples, but swelling occurred in all of the comparative examples. This is due to the large number of bubbles in the comparative examples and the poor adhesion between the copper wiring and the resin. Thus, the wiring for multilayer boards of the examples is excellent in both adhesion to the substrate and high frequency characteristics, whereas the wiring of the comparative examples is inferior in either performance. [Industrial Applicability]

[0068] The present invention makes it possible to provide wiring for multilayer substrates that has high adhesion and bonding to resin substrates, and a method for manufacturing the same. [Explanation of symbols]

[0069] 100...Multilayer board wiring 101... Copper wiring 103: First resin layer 105... Second resin layer 107 First Surface 109...Second Surface 111...Third Surface 113...Fourth Surface

Claims

1. A wiring for a multilayer substrate including a copper wiring, a first resin layer, and a second resin layer, the copper interconnect has a first surface and a second surface; The copper wiring has a linear shape, a cross section of the copper wiring perpendicular to the first surface and the long axis direction has a substantially rectangular shape; the second surface includes a third surface facing the first surface and two fourth surfaces connecting the first surface and the second surface; the first surface is adhered to a surface of the first resin layer; the copper wiring is embedded in a second resin layer, the second surface has a layer comprising copper oxide; the thickness of the copper oxide-containing layer on the third surface and / or the fourth surface is 0.05 μm or more and 0.4 μm or less; a protrusion is present on a part or the whole of the third surface and / or the fourth surface; the height of the convex portion is 0.05 μm or more and 0.7 μm or less, A wiring for a multilayer substrate, in which only a layer containing copper or copper oxide is formed on the third surface and / or the fourth surface.

2. 2. The wiring for a multilayer board according to claim 1, wherein in the cross section, there are 1.5 or fewer bubbles per 10 μm between the first surface and the first resin layer, and between the second surface and the second resin layer, or there are no bubbles at all.

3. 3. The wiring for a multilayer substrate according to claim 2, wherein the minor axis and major axis of the bubbles are 10 nm to 500 nm.

4. 4. A wiring for a multilayer substrate as described in claim 2 or 3, wherein the bubbles having a short diameter of 10 nm or more present on the first surface are not present more than 500 nm inside from both ends of a line segment corresponding to the first surface in a cross section of the copper wiring perpendicular to the first surface and crossing the bubbles having a short diameter of 10 nm or more.

5. 5. The wiring for a multilayer substrate according to claim 1, wherein the transmission loss at a frequency of 40 GHz is −0.94 dB / inch or more.

6. A multilayer board comprising the wiring for a multilayer board according to any one of claims 1 to 5.

7. The multilayer board of claim 6, comprising one outer layer including outer layer wiring and one or more inner layers including the wiring for a multilayer board according to any one of claims 1 to 5 as inner layer wiring, on at least one side of the board.

8. 7. The multilayer substrate according to claim 6, wherein the distance between the closest portions of the copper wirings is 3 [mu]m or less.

9. A multilayer substrate including the wiring for a multilayer substrate according to any one of claims 1 to 5, a height of the copper oxide-containing layer on the fourth surface that is one-third or less of a distance between portions of the copper wiring that are closest to each other;

10. 10. The multilayer substrate according to claim 9, wherein the distance between the closest portions of the copper wirings is 3 [mu]m or less.

11. The multilayer substrate according to any one of claims 6 to 10, When the copper wiring is 3 μm to 10 μm, the wiring thinning is 23% or less, When the copper wiring is 10 μm to 19 μm, the wiring thinning is 7% or less, When the copper wiring is 20 μm to 49 μm, the wiring thinning is 3.5% or less, A multilayer substrate in which the wiring thinning is 1.4% or less when the copper wiring is 50 μm wiring.

12. A method for manufacturing wiring for a multilayer substrate according to any one of claims 1 to 5, A method for manufacturing wiring for a multilayer substrate, comprising a first step of oxidizing a wiring substrate in which the copper wiring and the first resin layer are bonded to the first resin layer on a first surface of the copper wiring with an oxidizing agent containing a copper corrosion inhibitor and having a pH of 11.5 to 14, thereby forming the layer containing copper oxide.

13. 13. The method for manufacturing a wiring for a multilayer substrate according to claim 12, further comprising a second step, which is carried out before the first step, of treating the wiring for a multilayer substrate with an alkaline solution having a pH of 9 or more.

14. 14. The method for manufacturing a wiring for a multilayer substrate according to claim 12, further comprising a third step, which is carried out after the first step, of treating the wiring for a multilayer substrate with a dissolving agent.

15. 14. The method for manufacturing a wiring for a multilayer substrate according to claim 12, further comprising a fourth step, which is carried out after the first step, of treating the wiring for a multilayer substrate with a reducing agent.

16. 14. The method for manufacturing wiring for a multilayer board according to claim 12, further comprising a fifth step, which is carried out after the first step, of treating the wiring substrate with a coupling agent.

17. 14. The method for manufacturing wiring for a multilayer substrate according to claim 12, further comprising a sixth step, which is carried out after the first step, of treating the wiring substrate with an anti-corrosion agent.

18. 14. The method for manufacturing wiring for a multilayer board according to claim 12, further comprising a seventh step of plating the wiring substrate, which is carried out after the first step.

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