JP2004303856A - Substrate manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a substrate by which a metallic conductive layer is formed selectively on a hole inner wall with a simple constitution. <P>SOLUTION: The manufacturing method for a substrate contains at least a process in which thermoplastic resin layers 4 are formed on both surfaces of the substrate for forming a circuit by using the substrate 10 for forming the circuit to which a hole 3 is formed, a process in which the resin layers in the opening section of the hole are removed and the thermoplastic resin layers are formed on both surfaces of the substrate with the exception of the opening section, a process in which the metallic conductive layers 2 are formed on the inner walls of the through-hole by a plating treatment, and a process in which the resin layers are removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a substrate for manufacturing a printed wiring board by a subtractive method, and in particular, to manufacturing a circuit forming substrate having a through hole and / or a non-through hole (hereinafter, collectively referred to as holes). It is about the method.
[0002]
[Prior art]
Manufacturing methods for printed wiring boards are broadly classified into two methods: a subtractive method and an additive method. The subtractive method is a method in which a resist image is formed on a circuit-forming substrate in which a metal conductive layer such as copper is provided on an insulating substrate, and the metal conductive layer not covered with the resist image is removed by etching. The additive method is a method of forming a metal conductive layer only on a wiring pattern portion on an insulating substrate by a metal plating process.
[0003]
In addition, with the recent miniaturization and multifunctionality of electronic devices, the density of printed wiring boards used inside the devices and the miniaturization of circuit patterns have been promoted. As means for achieving such conditions, And multilayered printed wiring boards. In the multilayer printed wiring board, in order to form a multilayer structure, conduction between layers is generally performed through holes such as through holes and non-through holes whose inner walls are covered with a metal conductive layer, which are generally called through holes and via holes.
[0004]
Generally, in order to form a hole in which the inner wall is covered with a metal conductive layer, an outer layer board (hereinafter referred to as a circuit forming board) in a manufacturing process of a copper-clad laminate or a multilayer printed wiring board having a metal conductive layer provided on both sides of an insulating substrate. After the hole is formed on the substrate using a drill or laser processing, both surfaces of the substrate including the inner wall of the hole are subjected to electroless plating, and then a metal conductive layer having a predetermined thickness is formed by electrolytic plating on the inner wall of the through hole. Formed.
[0005]
However, when the holes are formed as described above, a second metal conductive layer is further formed by electrolytic plating on the metal conductive layers on both surfaces of the circuit forming substrate, and a predetermined thickness is formed on the inner wall of the hole. If an attempt is made to form a metal conductive layer, the second metal conductive layer also has a corresponding thickness, which not only consumes the plating solution more than necessary, but also reduces unnecessary metal accompanying the subsequent circuit formation. The processing solution load in removing the conductive layer also increases.
[0006]
According to a method of forming a through hole in a circuit forming substrate, laminating a dry film-shaped plating resist, removing a dry film in a through hole portion including a portion covering a land, and then performing a metal plating process, In order to selectively remove the opening of the through hole including the portion covering the land, it is necessary to expose a photopolymer such as a photocurable resin or to perform processing such as laser processing that requires alignment. Similarly, a through hole is formed in a circuit forming substrate in which a metal conductive layer is formed on both surfaces of an insulating substrate, and a wiring pattern other than the through hole portion is formed by a general subtractive method. Laminating the plating resist and removing the dry film of the through hole including the part covering the land, and then selectively removing the opening of the through hole including the part covering the land also by the metal plating method In order to do this, not only is it necessary to expose a photopolymer such as a photocurable resin, or perform processing that requires alignment such as laser processing, but also the wiring pattern near the through-hole and the through-hole plating are not intended. In some cases, a short circuit occurred (see, for example, Patent Document 1).
[0007]
[Patent Document 1]
JP-A-7-17068 (pages 1-2)
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for manufacturing a substrate in which a metal conductive layer is selectively formed on the inner wall of a hole with a simple configuration.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, a thermoplastic resin layer is formed on both sides of a circuit forming substrate having a through hole and / or a non-through hole formed therein, and then the thermoplastic resin layer is formed only in the opening of the hole. It has been found that a method of manufacturing a substrate may be applied in which a metal conductive layer is formed on the inner wall of the hole, and then the thermoplastic resin layer is removed.
[0010]
Further, a metal conductive layer is formed on both sides of the circuit forming substrate including the inner wall surface of the through hole and / or the non-through hole in the circuit forming substrate having the through hole and / or the non-through hole, and then the circuit forming substrate is formed. A substrate on which a thermoplastic resin layer is formed on both sides of the substrate, and after removing the thermoplastic resin layer at the opening of the hole, a metal conductive layer is formed on the inner wall of the hole, and then the thermoplastic resin layer is removed. It has been found that the manufacturing method can be applied.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the method for manufacturing a substrate of the present invention will be described in detail.
[0012]
First, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a first embodiment of the present invention. A through hole 3 is formed in a circuit forming substrate 10 having a metal conductive layer 2 provided on both surfaces of an insulating substrate 1 (FIG. 1B). Next, after laminating a dry film composed of the thermoplastic resin layer 4 and the carrier film 5 (FIG. 1C), the carrier film 5 and the thermoplastic resin layer at the opening of the through hole are removed, and the opening is removed. A thermoplastic resin layer is formed on both sides of the circuit-forming substrate except for that shown in FIG. 1 (d). Next, an electroless copper plating layer 6 is provided on the inner wall of the hole which is a portion other than the thermoplastic resin layer by electroless copper plating (FIG. 1 (e)), and an electrolytic copper plating layer 7 is further formed thereon by electrolytic copper plating. It is formed to a predetermined thickness (FIG. 1F). Thereafter, the thermoplastic resin layer 4 is removed (FIG. 1 (g)). Further, a substrate having a through-hole is manufactured by polishing excess plating at the through-hole edge as necessary (FIG. 1 (h)).
[0013]
In the above description, the through-hole has been described as an example. However, even in the case of having a non-through-hole, if the thermoplastic resin layer at the opening of the non-through-hole is removed in the same manner as in the case of the through-hole, other steps are performed. The same process as in the case of having holes is performed. Further, in the first embodiment, the metal conductive layer on the inner wall of the hole is constituted by the electroless copper plating layer 6 and the electrolytic copper plating layer 7. However, if desired, only the electroless copper plating layer 6 may be used. As long as the metal conductive layer can be formed on the inner wall, it is not necessary to use the plating method at all.
[0014]
As a result, even if the metal conductive layer on the inner wall of the hole is formed by a plating method, it is not necessary to apply unnecessary plating to the surface of the circuit-forming substrate, and not only can unnecessary consumption of plating solution be suppressed, but also The processing liquid load in the removal of the unnecessary metal conductive layer on the circuit formation surface accompanying the circuit formation is greatly reduced.
[0015]
FIG. 2 is a cross-sectional view showing a second embodiment of the present invention. Similar to the first embodiment, description will be made using a substrate having only through holes. The metal conductive layer formed on the inner wall of the hole also conforms to the first embodiment. A through hole 3 is formed in a circuit forming substrate 10 in which a metal conductive layer 2 is provided on both surfaces of an insulating substrate 1 (FIG. 2B). Next, the surface of the substrate including the inner wall of the through hole 3 is subjected to an electroless copper plating treatment to form an electroless copper plating layer 6 (FIG. 2C), and a dry layer comprising the thermoplastic resin layer 4 and the carrier film 5. After laminating the film (FIG. 2D), the carrier film 5 and the thermoplastic resin layer at the opening of the through hole are removed, and the thermoplastic resin layers are formed on both surfaces of the circuit forming substrate except for the opening. (FIG. 2 (e)). Further, an electrolytic copper plating layer 7 is formed to a predetermined thickness by an electrolytic copper plating treatment (FIG. 2 (f)). Thereafter, the thermoplastic resin layer 4 is removed (FIG. 2 (g)), and if necessary, the excess plating at the edge of the through hole is polished to produce a substrate having a through hole.
[0016]
Next, various materials related to the substrate manufacturing method of the present invention will be described. The circuit-forming substrate having the through-holes and / or non-through-holes according to the present invention is basically a laminated board having a metal conductive layer provided on both sides of an insulating substrate, or a through-hole and a non-through-hole. Forming an outer layer board before forming a hole (laminate having a wiring pattern layer and a ground layer via an insulating layer in the inner layer) before manufacturing a multilayer printed wiring board having a step of forming a hole, and forming a non-through hole at the time of build-up It is obtained by forming holes, such as through holes and non-through holes, using a punch, a drill, a pulse laser, or the like on the inner layer plate or the like. For example, the above-mentioned multilayer printed wiring board that performs interlayer connection by through holes and non-through holes is described in "JPCA Standard, Build-up Wiring Board" (May 1998, published by Japan Printed Circuit Industries Association). Basic through-holes, buried via-holes, blind via-holes, and the like that can be basically applied by the subtractive method can be used.
[0017]
Examples of the laminated board having a metal conductive layer provided on both sides of the insulating substrate are described in, for example, "Printed Circuit Technology Handbook-Second Edition-" (edited by The Printed Circuit Society, published by Nikkan Kogyo Shimbun). You can use what is. Examples of the insulating substrate include a paper substrate or a glass substrate impregnated with an epoxy resin or a phenol resin, a polyester film, a polyimide film, and the like. Examples of the material of the metal conductive layer include copper, silver, aluminum, and the like.
[0018]
Examples of the metal plating method according to the method for manufacturing a substrate of the present invention include, for example, those described in “Surface Mounting Technology” (June 1993, published by Nikkan Kogyo Shimbun) when the plating conductive layer is copper. An electroless plating step, an electroless plating-electrolytic plating step, a direct electrolytic plating step, or the like can be applied.
[0019]
The thermoplastic resin layers formed on both sides of the circuit-forming substrate according to the present invention basically have a structure in which the thermoplastic resin does not enter the inside of the hole even at the opening of the hole, and the circuit formation includes the opening of the hole. What is necessary is just to form it with a substantially uniform thickness on the surface of a board | substrate. Examples of the method of forming the thermoplastic resin layer in this manner include a dry film laminating method, a roll coating method, a table coating method, a curtain coating method, and the like.In the roll coating method, the table coating method, and the curtain coating method, A dry film laminating method is preferably used because restrictions such as the viscosity of the coating liquid are increased. In any case, the thickness of the thermoplastic resin layer may be about 5 μm to 30 μm, and preferably 10 μm to 15 μm.
[0020]
The dry film used in the dry film laminating method only needs to be composed of at least two layers, a carrier film and a thermoplastic resin layer. The thermoplastic resin layer is formed by dissolving in a medium, coating and drying on the carrier film. As the carrier film, films of polytetrafluoroethylene, polyethylene terephthalate, aramid, Kapton, polymethylpentene, polyethylene, polypropylene, polyvinyl chloride and the like can be used.
[0021]
In addition, a film having no carrier film consisting of only a thermoplastic resin may be laminated or coated, or with or without a carrier film, having an adhesive layer on the thermoplastic resin layer, via an adhesive layer or the like. Alternatively, a thermoplastic resin layer may be provided on both sides of the circuit forming substrate. In some cases, a protective film such as polyethylene may be provided on the surface opposite to the carrier film with the thermoplastic resin layer or the like interposed between them in terms of stability against physical impact during storage and changes over time in the composition. Furthermore, in order to control the adhesiveness of the surface to which the thermoplastic resin layer is applied, it is also possible to use a film that has been subjected to a corona treatment or a primer treatment.
[0022]
The thermoplastic resin layer according to the present invention basically has resistance when forming a metal conductive layer on the inner wall of a hole such as a through hole and a non-through hole, and when the metal conductive layer is formed by plating. And a thermoplastic resin that is insoluble in the plating solution used for it. Specific examples thereof include styrene / maleic acid monoester copolymer, methacrylic acid / methacrylic acid ester copolymer, and styrene / methacrylic acid / methacrylic acid ester as resins having acid resistance to withstand at least acidic electrolytic plating solution. Copolymer, acrylic acid / methacrylic acid ester copolymer, styrene / acrylic acid / methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, acrylic acid ester / methacrylic acid ester copolymer Styrene, (meth) acrylate, vinyl acetate, and vinyl benzoate monomers such as polymers, vinyl acetate / crotonic acid copolymers, and vinyl acetate / crotonic acid / methacrylic acid ester copolymers; and (Meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, etc. A copolymer of two or more monomers selected from the carboxyl group-containing monomer of monoesters of maleic acid and fumaric acid, and phenol resins. When a resin that can withstand an alkaline electroless copper plating solution or the like is required, a copolymer resin may be obtained from a monomer having no acidic functional group. Further, the thermoplastic resin layer used for the thermoplastic resin layer according to the present invention may be a mixture of two or more thermoplastic resins.
[0023]
As a solvent used for preparing a coating solution when a thermoplastic resin solution is provided with a thermoplastic resin layer by various coating methods, any solvent that can uniformly dissolve the thermoplastic resin in the present invention may be used. Alcohols such as methanol, ethanol and 1-propanol, THF, 1,4-dioxane, 1,2-dimethoxyethane, ethylene glycol monomethyl ether, ethers such as 1-methoxy-2-propanol, methyl ethyl ketone, cyclohexanone, methyl isobutyl Ketones such as ketones, aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate, propyl acetate and isobutyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and the like Amides, dimethyl sulfoxide, etc. Is not limited to these, it can be selected and used singly or two or appropriate ones by a coating method and drying conditions. Regarding the solid content concentration of the coating liquid, an appropriate concentration can be selected depending on the coating method, drying conditions, and the like. If necessary, an additive such as an adhesion promoter may be added to the coating liquid in order to improve the physical properties of the thermoplastic resin layer, the viscosity of the coating liquid, and the like, in addition to the thermoplastic resin.
[0024]
Further, in the present invention, if necessary, between the thermoplastic resin layer and the circuit-forming substrate, for improving the adhesion to the circuit-forming substrate, etc., as necessary, casein, polyvinyl alcohol, hydroxyethyl cellulose, phenol resin Styrene / maleic anhydride copolymer, maleic acid / acrylic acid copolymer, acrylic acid / methacrylic acid copolymer, polyacrylic acid, and alkali metal salts and / or ammonium salts of these polymer electrolytes, ethanolamines And hydroxycarboxylic acids such as hydrochloride, oxalate, phosphate, citric acid, and tartaric acid, and salts thereof, amino acids such as glycine, alanine, and glutamic acid; aliphatic aminosulfonic acids such as sulfamic acid; and ethylenediamine. Such as tetraacetic acid, nitrilotriacetic acid, and triethylenetetramine hexaacetic acid ( (I) aminopolyacetic acid, aminotri (methylenephosphonic) acid, 1-hydroxyethylidene-1,1-diphosphonic acid, (poly) aminopoly (methylenephosphonic acid) such as ethylenediaminetetra (methylenephosphonic acid) and the like, and their compounds May be provided with an intermediate layer in which at least a part of the acid group is made of an alkali metal salt or an ammonium salt.
[0025]
The intermediate layer may further contain submicron fine particles such as titanium oxide, alumina, silica, zirconia, and antimony oxide. The thickness of the intermediate layer is not particularly limited, but may be at most about 5 μm irrespective of the circuit-forming substrate to be used if the purpose is to adhere the thermoplastic resin layer.
[0026]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.
[0027]
Example 1
As a thermoplastic resin, a copolymer resin composed of 60 parts of 2-ethylhexyl acrylate, 25 parts of methyl methacrylate, and 15 parts of phenoxyethyl methacrylate was dissolved in ethyl acetate to have a solid content of 25% by weight. On a corona-treated surface of a 16 μm-thick polyethylene terephthalate film (H500, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) having one surface subjected to a corona treatment, the thermoplastic resin layer after drying was 12 μm by using a curtain coat method. To obtain a dry film according to the present invention. Further, as a circuit forming substrate, a copper laminated board (EL170, manufactured by Mitsubishi Gas Chemical Co., Ltd., EL170) having a size of 200 × 200 × 0.4 mm was used, and a plurality of 0.3 μm through-holes were formed with a drill to form a vacuum laminator. Then, the dry film prepared above was laminated under the condition of preheating at 100 ° C. Thereafter, when the carrier film was peeled off at room temperature, the thermoplastic resin at the opening of the through hole was peeled off while being in close contact with the carrier film. Further, electroless copper plating-electrolytic copper plating treatment (Okuno Pharmaceutical Co., Ltd., OPC process M) is performed, a copper plating layer having a thickness of 10 μm is provided on the inner wall of the through hole, and then the circuit formation substrate is formed with 2-propanol. Then, the excess copper at the edge of the through hole was polished and removed by buffing to obtain a substrate having a through hole. When a pattern was formed on the obtained substrate and a heat cycle test was performed, no problem was observed up to 500 cycles.
[0028]
Example 2
As a thermoplastic resin, a copolymer resin composed of 55 parts of 2-ethylhexyl acrylate, 25 parts of methacrylic acid, and 20 parts of phenoxyethyl methacrylate was dissolved in ethyl acetate to have a solid content of 25 wt% to prepare a liquid. On a corona-treated surface of a 16 μm-thick polyethylene terephthalate film (H500, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) having one surface subjected to a corona treatment, the thermoplastic resin layer after drying was 12 μm by using a curtain coat method. To obtain a dry film according to the present invention. Further, a 200 × 200 × 0.4 mm copper-clad laminate (manufactured by Mitsubishi Gas Chemical Co., Ltd., EL170) was used as a circuit formation substrate, and a plurality of 0.3 μm through holes were formed with a drill. Plating was applied to the entire surface including the inner wall of the through hole. After laminating the dry film prepared above under 100 ° C. preheating condition using a vacuum laminator, and peeling the carrier film at room temperature, the thermoplastic resin in the opening of the through hole is peeled off while being in close contact with the carrier film. Was. Further, an electrolytic copper plating process is performed to provide a copper plating layer having a thickness of 10 μm on the inner wall of the through hole. Then, the thermoplastic resin layer on the circuit forming substrate is peeled off with a 2% aqueous sodium carbonate solution, and finally, buffing is performed. Excess copper at the edge of the through hole was removed by polishing to obtain a substrate having a through hole. When a pattern was formed on the obtained substrate and a heat cycle test was performed, no problem was observed up to 500 cycles.
[0029]
COMPARATIVE EXAMPLE As the thermoplastic resin, the same copolymer resin as that of Example 2 was used, and a negative type was prepared by using a coating solution in which 1% by weight of 2-methylanthraquinone and 25% by weight of pentaerythritol / trimethacrylate were added to the solid content. A photopolymer dry film was obtained. Further, a 200 × 200 × 0.4 mm copper-clad laminate (manufactured by Mitsubishi Gas Chemical Co., Ltd., EL170) was used as a circuit formation substrate, and a plurality of 0.3 μm through holes were formed with a drill. Plating was applied to the entire surface including the inner wall of the through hole. After laminating the dry film adjusted as described above under a preheating condition of 100 ° C. using a vacuum laminator, a portion other than the opening and the land of the through hole was exposed using a film mask corresponding to the through hole. Thereafter, when the carrier film was peeled off at room temperature, the resin layer in the opening of the through hole and the land portion was peeled off while being in close contact with the carrier film. Further, an electrolytic copper plating process is performed to provide a copper plating layer having a thickness of 10 μm on the inner wall of the through hole. Then, the thermoplastic resin layer on the circuit forming substrate is peeled off with a 2% aqueous sodium hydroxide solution, and finally buffed. The excess copper at the edge of the through hole was removed by polishing to obtain a substrate having a through hole. Observation of the obtained substrate in detail revealed that a plating defect was caused at the edge of the substrate due to an exposure pattern misalignment. When a pattern was formed and a heat cycle test was performed, the wire was broken in three cycles.
[0030]
【The invention's effect】
As described above, according to the method for manufacturing a substrate of the present invention, not only is it unnecessary to apply unnecessary plating to the surface of the circuit forming substrate, but also because there is no need for photopolymer or laser processing, the product has a high alignment accuracy with respect to the holes. The yield will not be affected.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a first embodiment of the present invention.
FIG. 2 is a sectional view showing a second embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Insulating substrate 2 Metal conductive layer 3 Through hole, hole 4 Thermoplastic resin layer 5 Carrier film 6 Electroless plating layer 7 Electrolytic plating layer 10 Circuit forming substrate

Claims (2)

A thermoplastic resin layer is formed on both sides of a circuit forming substrate having a through-hole and / or a non-through-hole formed therein, and then the thermoplastic resin layer is removed only at the opening of the hole. A method for manufacturing a substrate, comprising: removing a thermoplastic resin layer after forming a conductive layer. A metal conductive layer is formed on both sides of the circuit forming substrate including the inner wall surface of the through hole and / or the non-through hole in the circuit forming substrate having the through hole and / or the non-through hole, and then the circuit forming substrate is formed. Forming a thermoplastic resin layer on both sides of the hole, removing the thermoplastic resin layer at the opening of the hole, forming a metal conductive layer on the inner wall of the hole, and then removing the thermoplastic resin layer. Manufacturing method of a substrate.

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