Manufacturing method for printed wiring board

Abstract

Provided is a manufacturing method for a printed wiring board, wherein sufficient curing of a photoresist layer in an exposure process, suppression of a short circuit, and improvement of communication accuracy can be achieved.　This manufacturing method for a printed wiring board comprises, in the following order, a step A for forming a seed layer on an insulating resin layer, a step B for forming an adhesive layer on the seed layer, a step C for forming a photoresist layer on the adhesive layer, a step D for exposing the photoresist layer in a patterned manner, a step E for patterning the photoresist layer and the adhesive layer through development to form a plated resist, a step F for forming a copper wiring on the exposed seed layer by using a plating method, a step G for stripping the plated resist and the adhesive layer by using a stripping solution, and a step H for removing the exposed seed layer through etching. The surface roughness Ra of the upper surface of the copper wiring is in the range of 0.05-0.15 μm, and the average absorption rate of the adhesive layer for ultraviolet light having a wavelength of 365 nm is in the range of 0.1-5.0%.

Description

Printed wiring board manufacturing method

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

[0002] A method for manufacturing a printed wiring board in which copper wiring is formed by a semi-additive process is known (see Patent Document 1). In the method for manufacturing a printed wiring board using the semi-additive process, a patterned plating resist is formed on a seed layer, and copper wiring is formed by plating in the areas where the plating resist is not formed. The plating resist is formed by curing a photoresist layer attached on the seed layer in an exposure process and patterning it in a development process.

[0003] Japanese Patent Application Laid-Open No. 2007-109902

[0004] With conventional technology, it was difficult to achieve the designed line width during the exposure process on the photoresist layer in response to the recent demand for higher density and thinner copper wiring. This led to a decrease in the yield of printed wiring boards, and improvements were needed. Specifically, the exposure light reflected by the seed layer during the exposure process was blurred, making it difficult to draw the plating resist to the specified width. Furthermore, with conventional technology, communication accuracy was insufficient due to noise generated on the surface of the copper wiring.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a printed wiring board that enables sufficient hardening of a photoresist layer in an exposure process, suppression of short circuits, and improvement of communication accuracy.

[0006] The above-mentioned problems of the present invention can be solved by the following means.

[0007] 1. A method for manufacturing a printed wiring board, comprising, in this order: Step A of forming a seed layer on an insulating resin layer; Step B of forming an adhesive layer on the seed layer; Step C of forming a photoresist layer on the adhesive layer; Step D of exposing the photoresist layer to light in a pattern; Step E of patterning the photoresist layer and the adhesive layer by development to form a plating resist; Step F of forming copper wiring on the exposed seed layer by a plating method; Step G of stripping the plating resist and the adhesive layer with a stripping solution; and Step H of removing the exposed seed layer by etching; wherein the surface roughness Ra of the upper surface of the copper wiring is within the range of 0.05 to 0.15 μm, and the average absorptance of the adhesive layer for ultraviolet light with a wavelength of 365 nm is within the range of 0.1 to 5.0%.

[0008] 2. The method for producing a printed wiring board according to Item 1, wherein the adhesive layer has an average thickness in the range of 2 to 10 nm.

[0009] 3. The method for producing a printed wiring board according to Item 1, wherein the minimum width of the upper surface of the plating resist is within the range of 10 to 30 μm.

[0010] 4. The method for producing a printed wiring board according to Item 1, wherein the adhesive layer contains a nitrogen-containing compound.

[0011] 5. The method for producing a printed wiring board according to Item 1, wherein the adhesive layer contains a compound A having the following structure:

[0012]

[0013] 6. The method for producing a printed wiring board according to Item 1, wherein the average angle formed between the side surface and the bottom surface of the plating resist is within a range of 45 to 135°.

[0014] 7. The method for producing a printed wiring board according to claim 1, wherein the seed layer contains Cu and / or Ni.

[0015] 8. The method for producing a printed wiring board according to Item 1, wherein the photoresist layer has an average thickness in the range of 20 to 50 μm.

[0016] According to the present invention, it is possible to sufficiently harden the photoresist layer in the exposure process, to prevent short circuits, and to improve communication accuracy.

[0017] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is presumed as follows.

[0018] 1 to 3 are schematic cross-sectional views illustrating the reflection of exposure light L on a seed layer 2 during the exposure step, and the appearance of hardened portions 4a and unhardened portions 4b of a photoresist layer 4. The explanation using Figures 1 to 3 takes as an example a case where the photoresist layer is made of a negative resist composition in which the bonds of polymers are strengthened (i.e., hardened) by exposure to light, thereby reducing the solubility in a developer.

[0019] As shown in Figure 1, if the reflection of exposure light L from the seed layer 2 is too weak due to factors such as the components of the adhesive layer 3, the lower part of the photoresist layer 4 will not be sufficiently cured, even within the desired curing range. As a result, the plating resist developed from the insufficiently cured portion may peel off before the plating process. Also, as shown in Figure 2, if the reflection of exposure light L from the seed layer 2 is too strong due to factors such as the absence of the adhesive layer 3, the lower part of the photoresist layer 4 will be cured up to the periphery of the desired curing range. This can result in the developed plating resist being thicker than expected. Therefore, with conventional technology, the plating resist could not be formed in the desired shape, and as a result, the copper wiring could not be drawn with the desired width. This made short circuits more likely to occur with conventional technology.

[0020] In contrast, the present invention includes a step of forming an adhesive layer 3 having an average absorptance of 0.1 to 5.0% for ultraviolet light with a wavelength of 365 nm between the photoresist layer 4 and the seed layer 2. As a result, as shown in Figure 3, in the present invention, the reflection intensity of the exposure light L at the seed layer 2 is controlled within an appropriate range, so that the lower part of the photoresist layer 4 is appropriately cured within the targeted curing range and short circuits are suppressed.

[0021] When the photoresist layer is composed of a positive resist composition in which the polymer bonds are weakened by exposure to light, increasing its solubility in the developer, the following occurs: If the reflection of the exposure light L from the seed layer 2 is too weak, the solubility of the lower part of the photoresist layer is not sufficiently increased, and the seed layer is not sufficiently exposed after the development process, making it difficult to form copper wiring with the desired width. If the reflection of the exposure light L from the seed layer 2 is too strong, the solubility of the photoresist layer surrounding the desired area is increased, resulting in the lower part of the copper wiring becoming thicker or becoming prone to short circuits. In contrast, in the present invention, the reflection intensity of the exposure light L from the seed layer 2 is controlled within an appropriate range, making it easier to form copper wiring with the desired width and suppressing short circuits.

[0022] Furthermore, in the present invention, the surface roughness Ra of the upper surface of the copper wiring is within the range of 0.05 to 0.15 μm, which suppresses noise and improves communication accuracy.

[0023] Schematic cross-sectional view illustrating the reflection of exposure light and the hardening of a photoresist layer (prior art) Schematic cross-sectional view illustrating the reflection of exposure light and the hardening of a photoresist layer (prior art) Schematic cross-sectional view illustrating the reflection of exposure light and the hardening of a photoresist layer (present invention) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process A) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process B) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process C) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process D) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process E) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process F) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process G) Schematic cross-sectional view showing a manufacturing process for a printed wiring board (Process H)

[0024] The following description describes embodiments of the present invention. The advantages and features of one or more embodiments of the present invention can be understood from the following detailed description and drawings. It should be noted that the following detailed description and drawings are provided for illustrative purposes only and do not limit the scope of the present invention.

[0025] The following description refers to the drawings and describes one or more embodiments of the invention, although the scope of the invention is not limited to the disclosed embodiments.

[0026] In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0027] The method for producing a printed wiring board of the present invention is classified as a semi-additive method, and comprises the following steps A to H in this order: Step A: forming a seed layer on an insulating resin layer; Step B: forming an adhesive layer on the seed layer; Step C: forming a photoresist layer on the adhesive layer; Step D: exposing the photoresist layer to light in a pattern; Step E: patterning the photoresist layer and adhesive layer by development to form a plating resist; Step F: forming copper wiring by plating on the exposed seed layer; Step G: stripping the plating resist and adhesive layer using a stripping solution; Step H: removing the exposed seed layer by etching.

[0028] Examples of each step will be described with reference to Figures 4 to 11, which are cross-sectional views of each component. The explanation using Figures 4 to 11 takes as an example a case where the photoresist layer is made of a negative resist composition.

[0029] 4, in step A, a seed layer 2 is formed on an insulating resin layer 1. The seed layer 2 can be formed by, for example, an electroless plating method, coating a metal fine particle dispersion liquid, and baking the coating.

[0030] Examples of components of the insulating resin layer 1 include flexible resins, rigid materials, and rigid-flexible materials. Examples of flexible resins include polyimide, liquid crystal polymer, fluororesin, polyethylene terephthalate, and polyethylene naphthalate. Examples of rigid materials include paper phenol, paper epoxy, glass composite, glass epoxy, polytetrafluoroethylene, and glass substrate. Rigid-flexible materials are, for example, a composite of hard and soft materials.

[0031] When the seed layer 2 is formed by electroless plating, examples of components of the seed layer 2 include nickel, copper, cobalt, gold, silver, tin, etc., or alloys thereof. The seed layer 2 preferably contains Cu and / or Ni, which improves conductivity and prevents oxidation.

[0032] The average thickness of the seed layer 2 is preferably within the range of 20 to 50 nm. This allows the overall thickness of the printed wiring board to be thinned while ensuring conductivity and durability, thereby reducing the weight of the printed wiring board. The average thickness is the average value of thicknesses measured at 10 or more locations randomly.

[0033] [Step B: Adhesion Layer Forming Step] In step B, as shown in FIG. 5, an adhesion layer 3 is formed on the seed layer 2 .

[0034] The adhesive layer 3 contains an adhesive component that bonds the seed layer 2 to the photoresist layer 4 described below. The adhesive component may be one type or two or more types. The adhesive component is not particularly limited, but from the viewpoints of adhesive strength and releasability in step G, it is preferably a nitrogen-containing compound, and more preferably a nitrogen-containing heterocyclic compound.

[0035] Examples of preferred nitrogen-containing heterocyclic compounds in the present invention include compound A having the following structure, a compound having a structure represented by the following general formula (1), and a compound having a structure represented by the following general formula (2). Of these, compound A is particularly preferred as the nitrogen-containing heterocyclic compound.

[0036]

[0037]

[0038] In the general formulas (1) and (2), Rn １ and Rn ２ represents an alkyl group. １ and Rn ２ is preferably an alkyl group having 1 to 6 carbon atoms. L represents a linking group. In general formula (1), W １ ~W ７represents a carbon atom or a nitrogen atom, at least two of which are nitrogen atoms, one of which is NH; W １ ~W ７ In general formula (2), Y １ ~Y ５ represents a carbon atom or a nitrogen atom, at least two of which are nitrogen atoms, one of which is NH; Y １ ~Y ５ In general formulas (1) and (2), m represents an integer of 1 or more. Preferably, m is an integer of 1 to 4.

[0039] The linking group represented by L is, for example, an atom or atomic group containing a carbon atom, a nitrogen atom, a sulfur atom, or an oxygen atom. Specific examples of the linking group represented by L include -O-, -S-, -N(R)-, -CO-, -SO2-, an alkylene group, an arylene group, and combinations thereof. R represents a hydrogen atom, an alkyl group, or a cycloalkyl group. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a 1,4-cyclohexylene group, a dodecylene group, a hexadecylene group, a 2-ethylhexylene group, and a 2-hexyldecalene group. Examples of the arylene group include a phenylene group, a naphthylene group, and the like.

[0040] The nitrogen-containing heterocyclic compound may have a structure represented by any one of the following general formulas (3) to (6).

[0041]

[0042] In the general formulas (3) to (6), Rn １ and Rn ２ represents an alkyl group, preferably an alkyl group having 1 to 6 carbon atoms. L represents a linking group. Examples of the linking group represented by L are the same as those described above. R １ represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group, and may further have a substituent. １ R preferably represents an aryl group which may have a substituent. １Examples of the substituent that R may have include an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carboxy group, an ester group, an amide group, a heteroaryl group, and a halogeno group (halogen atom). ２ R each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carboxy group, an ester group, an amide group, a heteroaryl group, or a halogeno group (a halogen atom). ２ preferably represents an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. Each n independently represents an integer of 0 to 4. Each m independently represents an integer of 1 or more. Preferably, m represents an integer of 1 to 4.

[0043] The nitrogen-containing heterocyclic compound may have a structure represented by the following general formula (7).

[0044]

[0045] In the general formula (7), Rn １ and Rn ２ represents an alkyl group, preferably an alkyl group having 1 to 6 carbon atoms. L represents a linking group. Examples of the linking group represented by L are the same as those described above. R ２ R each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carboxy group, an ester group, an amide group, a heteroaryl group, or a halogeno group (a halogen atom). ２ preferably represents an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. Each n independently represents an integer of 0 to 4. Each m independently represents an integer of 1 or more. Preferably, m represents an integer of 1 to 4.

[0046] Examples of nitrogen-containing heterocyclic compounds having a structure represented by at least one of general formulas (1) to (7) are listed below.

[0047]

[0048]

[0049]

[0050]

[0051] In addition to the above, the adhesive component may be a compound having a structure represented by any of the following structural formulas.

[0052]

[0053] The adhesive layer 3 can be formed, for example, by applying an adhesive layer-forming composition containing the adhesive component onto the seed layer 2 using a spray-type coating device or the like, and then drying it.

[0054] From the viewpoint of solubility, the adhesive layer-forming composition preferably contains at least water or an alcohol as a solvent. Examples of the alcohol include methanol, ethanol, and 2-propanol. The solvent may be a mixed solvent containing water and an alcohol. In this case, the mass ratio of water to alcohol in the mixed solvent is preferably within a range of 100:0 to 50:50, and more preferably within a range of 100:0 to 75:25.

[0055] The content of the adhesive component in the adhesive layer-forming composition is preferably in the range of 0.001 to 0.01% by mass, particularly preferably in the range of 0.001 to 0.005% by mass, from the viewpoint of film-forming properties.

[0056] The adhesive layer-forming composition may contain components other than those described above. Examples of the components other than those described above include surfactants, preservatives, stabilizers, acids, bases, pH adjusters, etc. It is preferable that the adhesive layer-forming composition does not contain a polymer, a polymerizable monomer, or an oligomer.

[0057] In the present invention, the average absorptance of the adhesive layer 3 for ultraviolet light with a wavelength of 365 nm is within the range of 0.1 to 5.0%. As a result, as described above, in the present invention, the reflection intensity of the exposure light L on the seed layer 2 in the exposure step (step D) is controlled within an appropriate range. Therefore, in the present invention, the lower part of the photoresist layer 4 is appropriately cured within the targeted curing range, and short-circuiting is also suppressed.

[0058] The average absorptance is more preferably in the range of 1.0 to 4.0%, and even more preferably in the range of 2.0 to 3.0%, which makes it easier to control the reflection intensity of the exposure light L at the seed layer 2 in the exposure step (step D) within an appropriate range.

[0059] The average absorptance can be measured using a spectrophotometer between step B and step C. As the spectrophotometer, for example, a V-670 spectrophotometer manufactured by JASCO Corporation can be used. The average absorptance is the average value of absorptance measured at 10 or more points randomly.

[0060] The average absorbency can be controlled by the type of adhesive component contained in the adhesive layer 3, the thickness of the adhesive layer 3, etc. The thickness of the adhesive layer 3 can be controlled by the amount of the adhesive layer-forming composition applied, the content of the adhesive component in the adhesive layer-forming composition, etc.

[0061] From the viewpoint of controlling the average absorption rate, the average thickness of the adhesive layer 3 is preferably within the range of 2 to 10 nm. The average thickness of the adhesive layer 3 can be measured using, for example, an analytical transmission electron microscope (FE-TEM / EDS, manufactured by ThermoScientific, Inc., Talos F200X). The average thickness is the average value of thicknesses measured at 10 or more random locations.

[0062] [Step C: Photoresist Layer Forming Step] In step C, as shown in FIG. 6, a photoresist layer 4 is formed on the adhesive layer 3 .

[0063] The photoresist layer 4 may be composed of either a negative resist composition or a positive resist composition. A negative resist composition is a composition in which the bonds of the polymer are strengthened (i.e., hardened) by exposure to light, thereby decreasing the solubility in a developer. A positive resist composition is a composition in which the bonds of the polymer are weakened by exposure to light, thereby increasing the solubility in a developer.

[0064] The photoresist layer 4 can be formed, for example, by coating and drying a liquid resist composition. Alternatively, the photoresist layer 4 can be formed by laminating a dry film resist that does not have fluidity at room temperature by thermocompression bonding.

[0065] By using a dry film resist as the photoresist layer 4, the thickness of the photoresist layer 4 can be made uniform and small, which makes it easier to make the plating resist 5 finer.

[0066] The average thickness of the photoresist layer 4 is preferably within the range of 20 to 50 μm. This makes it easier to control the reflection intensity of the exposure light L from the seed layer 2 within an appropriate range in the exposure step (step D). The average thickness of the photoresist layer 4 can be measured, for example, by observing the cross section using a scanning electron microscope (SEM). The average thickness is the average value of thicknesses measured at 10 or more random locations.

[0067] 7, in step D, the photoresist layer 4 is exposed to light in a pattern. Specifically, in step D, the photoresist layer 4 is selectively exposed to light L using a photomask or the like, thereby forming hardened portions 4a and unhardened portions 4b in the photoresist layer 4.

[0068] 8 , the photoresist layer 4 and the adhesive layer 3 are patterned by development to form a plating resist 5. Specifically, the photoresist layer 4 is patterned by partially washing away the portions 4b of the photoresist layer 4 that were not hardened in step D and the adhesive layer 3 thereunder using, for example, a developer. As a result, the portions 4a of the photoresist layer 4 that were hardened in step D become the plating resist 5.

[0069] An example of the developer is an aqueous sodium carbonate solution, etc. The concentration of sodium carbonate in the aqueous sodium carbonate solution is, for example, in the range of 0.5 to 2% by mass.

[0070] The average angle formed by the side and bottom surfaces of the plating resist 5 is preferably within the range of 45 to 135°, more preferably within the range of 60 to 120°, and even more preferably within the range of 75 to 105°. When the average angle is equal to or greater than the respective lower limits, the lower portion of the copper wiring 6 can be prevented from becoming too narrow. This ensures the cross-sectional area of ​​the copper wiring 6, thereby ensuring electrical conductivity. When the average angle is equal to or less than the respective upper limits, the lower portion of the copper wiring 6 can be prevented from becoming too wide. This prevents short circuits between the lower portions of the copper wiring 6. The average angle can be controlled by the average absorptivity of the adhesive layer 3 for ultraviolet light with a wavelength of 365 nm. When the photoresist layer 4 is composed of a negative resist composition, the lower portion of the plating resist 5 tends to be larger than the upper portion, and therefore the average angle is likely to be 90° or less. When the photoresist layer 4 is composed of a positive resist composition, the upper portion of the plating resist 5 tends to be larger than the lower portion, and therefore the average angle is likely to be 90° or more.

[0071] The average angle formed between the side and bottom surfaces of the plating resist 5 can be determined by the following procedure. First, a cross-sectional sample of the laminate after the development step (step E) is prepared. The cross-sectional sample can be prepared, for example, by a method (ion milling) in which a sample is irradiated with an ion beam using a cross-section polisher device to perform processing. Next, the cross-sectional sample is coated by carbon vapor deposition. Next, an SEM image of the cross-section of the sample is taken using a scanning electron microscope (SEM). Using the SEM image, the angle α (see FIG. 8 ) formed between the side and bottom surfaces of the plating resist 5 is measured at 10 or more randomly selected cross-sections. The average value of the measured angles α is taken as the average angle formed between the side and bottom surfaces of the plating resist 5.

[0072] The minimum width of the upper surface 51 of the plating resist 5 is preferably within a range of 10 to 30 μm, more preferably within a range of 15 to 25 μm, and even more preferably within a range of 18 to 23 μm. The minimum width of the upper surface 51 of the plating resist 5 is the width of the narrowest point of the upper surface 51 of the plating resist (the surface on the upper side in the stacking direction). When the minimum width is equal to or greater than the respective lower limit values, it is possible to prevent the average angle formed by the side and bottom surfaces of the plating resist 5 from becoming too small. When the minimum width is equal to or less than the respective upper limit values, it is possible to narrow the width of the space between each copper wiring 6, thereby enabling a high density of the copper wiring 6.

[0073] [Step F: Copper Wiring Formation Step] In step F, as shown in Fig. 9, copper wiring 6 is formed on the exposed seed layer 2 by plating. Specifically, for example, the laminate obtained in step E and an electrode opposing the laminate are placed in an electrolytic solution, and the negative electrode of a DC power supply is connected to the seed layer 2 and the positive electrode is connected to the opposing electrode, thereby depositing copper in the electrolytic solution on the surface of the exposed seed layer 2 to form copper wiring 6. The plating conditions are not particularly limited, and conventionally known conditions can be applied.

[0074] [Step G: Step of Stripping Plating Resist and Adhesive Layer] In step G, as shown in FIG. 10, the plating resist 5 and the adhesive layer 3 are stripped using a stripping solution.

[0075] The stripping solution is selected depending on the components of the plating resist 5. As the stripping solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution having a pH in the range of 11 to 13 can be used. The concentration of sodium hydroxide or potassium hydroxide in the stripping solution is, for example, in the range of 1 to 5 mass %.

[0076] [Step H: Seed Layer Etching Step] In step H, as shown in FIG. 11 , the exposed seed layer 2 is removed by etching. Specifically, the exposed seed layer 2 is dissolved and removed by, for example, wet etching using an etching solution. This electrically isolates the copper wirings 6 from each other. At this time, since the copper wirings 6 may also be removed by etching, it is preferable to select appropriate etching conditions so that only the surfaces of the copper wirings 6 are removed. The etching conditions are not particularly limited, and conventionally known conditions can be applied.

[0077] In the present invention, the surface roughness Ra of the upper surface 61 of the copper wiring 6 is within the range of 0.05 to 0.15 μm. This suppresses noise generated on the surface of the copper wiring 6, improving communication accuracy. Such copper wiring 6 is less likely to cause transmission loss even in short-wavelength radio wave communications, and is therefore suitable for use in 5G and 6G communication technologies.

[0078] The surface roughness Ra is the arithmetic mean roughness defined in JIS B 0601: 2013. The surface roughness Ra can be measured using, for example, a laser microscope (LASER MICROSCOPE VK-X100, manufactured by Keyence Corporation).

[0079] The above procedure produces the printed wiring board 100. The printed wiring board 100 produced in the present invention may be a multilayer printed wiring board constructed by alternately laminating copper wiring 6 and insulating resin layers 1 serving as build-up layers on an insulating resin layer 1 serving as a core layer reinforced with glass cloth or the like.

[0080] A printed circuit board can be manufactured by mounting electronic components on the printed wiring board 100 manufactured according to the present invention.

[0081] Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for purposes of illustration and example only and not limitation, and the scope of the present invention should be interpreted by the following claims.

[0082] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, operations were performed in a standard environment of 25°C and 50% RH. Furthermore, unless otherwise specified, "%", "ppm", and "parts" mean "% by mass", "ppm by mass", and "parts by mass", respectively.

[0083] The structures of the compounds used as adhesive components in the examples are as follows:

[0084]

[0085]

[0086] <Manufacturing Method 1> A printed wiring board was manufactured in the following manner.

[0087] [Step A: Step of forming seed layer] A seed layer was formed on an insulating resin layer by electroless plating. The material of the insulating resin layer was epoxy resin. The material of the seed layer was Cu. The average thickness of the seed layer was 30 nm. [Step B: Step of forming adhesive layer] An adhesive layer was formed on the seed layer by applying and drying an adhesive layer-forming composition. The adhesive layer-forming composition used was prepared by dissolving Compound A, an adhesive component, in water, a solvent, at 0.002 mass %. The amount of adhesive layer-forming composition applied was adjusted so that the adhesive layer would have an average thickness of 5 nm after drying.

[0088] The average absorptance of the formed adhesive layer to ultraviolet light with a wavelength of 365 nm was measured by the above-mentioned method and was found to be 2.5%.

[0089] [Step C: Photoresist Layer Formation Step] A photoresist layer was formed on the adhesive layer by thermocompression bonding a dry film resist containing a negative resist composition (manufactured by Asahi Kasei Corporation, product name: Sunfort, components: photocurable monomer, photosensitive material). The average thickness of the photoresist layer was 30 μm.

[0090] [Step D: Exposure Step] The photoresist layer was exposed to light in a pattern using a photomask. The wavelength of the exposure light was 365 nm. This cured the exposed portions of the photoresist layer.

[0091] [Step E: Development Step] The photoresist layer and the adhesive layer were patterned by development. A sodium carbonate aqueous solution (concentration: 1% by mass) was used as the developer for development. The development conditions were a temperature of 30°C and a development time of 3 minutes. As a result, a plating resist was formed in which the photoresist layer was patterned.

[0092] The minimum width of the upper surface of the plating resist (the surface opposite to the adhesive layer) was 1.5 μm.

[0093] The average angle formed by the side and bottom surfaces of the plating resist was 30° as measured by the above-mentioned method.

[0094] [Step F: Copper Wiring Formation Step] Copper wiring was formed on the exposed seed layer by plating. Specifically, the laminate obtained in Step E and an electrode facing the laminate were placed in an electrolytic solution, and the negative electrode of a DC power supply was connected to the seed layer 2 and the positive electrode was connected to the counter electrode, thereby depositing copper in the electrolytic solution on the surface of the exposed seed layer to form copper wiring.

[0095] [Step G: Step of Stripping Plating Resist and Adhesive Layer] The plating resist and adhesive layer were stripped using an aqueous sodium hydroxide solution (concentration: 3% by mass) as a stripping solution.

[0096] [Step H: Etching of Seed Layer] The exposed seed layer was removed by etching. Specifically, the exposed seed layer was dissolved and removed by wet etching using an aqueous hydrogen chloride solution (concentration: 2% by mass) and an aqueous ferric chloride solution (concentration: 2% by mass) as an etching solution. The etching conditions were a temperature of 30°C and a dipping time of 1 minute.

[0097] A printed wiring board was manufactured by the above procedure. The surface roughness Ra of the upper surface of the copper wiring in the manufactured printed wiring board was measured by the above method and was found to be 0.1 μm.

[0098] <Production Methods 2 to 12> Printed wiring boards were produced by Production Methods 2 to 12 in the same manner as Production Method 1, except that the type of adhesive component contained in the adhesive layer, the thickness of the adhesive layer, and the minimum width of the top surface of the plating resist were changed as shown in Table I.

[0099] The average absorptivity of the adhesive layer for ultraviolet light with a wavelength of 365 nm, the average angle formed by the side and bottom surfaces of the plating resist, and the surface roughness Ra of the top surface of the copper wiring for each manufacturing method were as shown in Table I.

[0100] <Evaluation of the degree of hardening of the photoresist layer> Between step D (exposure step) and step E (development step), a needle-shaped pin was inserted into the photoresist layer, and the depth of penetration of the pin was measured. Based on the penetration depth, the degree of hardening of the photoresist layer was evaluated according to the following criteria. The evaluation results are shown in Table II. A: The penetration depth was less than 1 μm. B: The penetration depth was 1 μm or more and less than 10 μm. C: The penetration depth was 10 μm or more, and hardening was insufficient.

[0101] <Short-Circuit Evaluation> A high-voltage insulation test was performed on the manufactured printed wiring boards to measure the leakage current value. Based on the leakage current value, short-circuiting was evaluated according to the following criteria. The evaluation results are shown in Table II. A: The leakage current value was 0 mA, and no short circuit occurred. B: The leakage current value was greater than 0 mA and not greater than 10 mA. C: The leakage current value was greater than 10 mA.

[0102] <Evaluation of communication accuracy> The transmission delay time was measured for the manufactured printed wiring boards. Based on the transmission delay time, the communication accuracy was evaluated according to the following criteria. The evaluation results are shown in Table II. A: The transmission delay time was 10 ms or less. B: The transmission delay time was more than 10 ms and less than 20 ms. C: The transmission delay time was more than 20 ms, and the communication accuracy was insufficient.

[0103]

[0104]

[0105] From the above results, it was confirmed that the method for manufacturing a printed wiring board of the present invention is capable of sufficiently hardening the photoresist layer in the exposure step, suppressing short circuits, and improving communication accuracy.

[0106] The present invention can be used in a method for manufacturing a printed wiring board.

[0107] REFERENCE SIGNS LIST 1 insulating resin layer 2 seed layer 3 adhesive layer 4 photoresist layer 4a hardened portion 4b unhardened portion 5 plating resist 6 copper wiring 100 printed wiring board L exposure light

Claims

1. A method for manufacturing a printed wiring board comprising, in this order: Step A: forming a seed layer on an insulating resin layer; Step B: forming an adhesive layer on the seed layer; Step C: forming a photoresist layer on the adhesive layer; Step D: exposing the photoresist layer to light in a pattern; Step E: patterning the photoresist layer and the adhesive layer by development to form a plating resist; Step F: forming copper wiring on the exposed seed layer by a plating method; Step G: stripping the plating resist and the adhesive layer using a stripping solution; and Step H: removing the exposed seed layer by etching; wherein the surface roughness Ra of the upper surface of the copper wiring is within the range of 0.05 to 0.15 μm, and the average absorptance of the adhesive layer for ultraviolet light with a wavelength of 365 nm is within the range of 0.1 to 5.0%.

2. The method for producing a printed wiring board according to claim 1, wherein the adhesive layer has an average thickness in the range of 2 to 10 nm.

3. The method for manufacturing a printed wiring board according to claim 1, wherein the minimum width of the upper surface of the plating resist is within the range of 10 to 30 μm.

4. The method for producing a printed wiring board according to claim 1, wherein the adhesive layer contains a nitrogen-containing compound.

5. The method for producing a printed wiring board according to claim 1, wherein the adhesive layer contains a compound A having the following structure:

6. The method for producing a printed wiring board according to claim 1, wherein the average angle formed by the side and bottom surfaces of the plating resist is within the range of 45 to 135 degrees.

7. The method for producing a printed wiring board according to claim 1, wherein the seed layer contains Cu and / or Ni.

8. The method for producing a printed wiring board according to claim 1, wherein the average thickness of the photoresist layer is within the range of 20 to 50 μm.

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