JPH02260691A - Formation of conductive circuit - Google Patents

Abstract

PURPOSE:To improve plating nucleuses in uniform dispersion after chemical reduction so as to enable the formation of a fine pattern by a method wherein an organic metal compound or an organic metal complex of a plating nucleus precursor is dispersed into a solution which contains prepolymer. CONSTITUTION:An organic metal compound or an organic metal complex, a photocuring prepolymer solution, and an organic solvent are mixed to form a photosensitive ink, it is applied onto an insulating board, and a photosensitive ink layer is exposed to light for the formation of a circuit pattern. Not only the non-exposed part of the ink layer is removed by dissolution with a developing solution but also the surface of the exposed part of the ink layer is roughened at the same time. Then, the roughened ink layer is processed with a reluctant to turn the organic metal compound or the organic metal complex dispersed in the ink into plating nucleuses, and a metal layer is formed on the ink layer by dipping the board into electroless plating bath. By this setup, plating nucleuses are high in uniform dispersion, so that a fine pattern can be formed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of forming a conductive circuit object such as a printed wiring board. In particular, the present invention relates to a method for producing a conductive circuit that can form fine patterns using an additive method and has excellent adhesion to a substrate regardless of the type of substrate. [Prior Art] Conventionally, there has been a subtractive method as a method for forming printed wiring boards. In this method, a resist pattern is formed on a copper-clad laminate, and unnecessary M4 foil portions in non-circuit areas are removed by etching. However, it has been pointed out that the subtractive method wastes copper resources and causes waste liquid pollution. moreover,
Currently used 35μm or 18μm thick W4
When etching foil, side etching occurs, so there is a limit to the processing of fine patterns. Therefore, the additive method was developed to solve these problems. The additive method is a method in which a conductor layer is formed by applying electroless plating to a Menki nucleus pattern on an insulating substrate. In the additive method currently in practical use, palladium particles are dispersed throughout the insulating substrate and the adhesive layer on the surface.
A negative circuit pattern is formed using a resist, and a conductor circuit layer is formed by electroless coating using palladium particles exposed on the surface of the circuit portion as plating nuclei.

[Problem to be solved by the invention]

However, in the above-mentioned additive method, expensive palladium particles are dispersed throughout the insulating substrate, so palladium particles on surfaces other than those used for plating are wasted. Further, it is difficult to uniformly disperse palladium particles in the insulating substrate and the adhesive layer, and there is a limit to making the palladium particles finer, making it difficult to obtain a fine plating pattern. Furthermore, in order to increase the adhesion between the plating layer and the insulating substrate, it is necessary to form an adhesive layer in a process separate from the circuit patterning. Moreover, it is necessary to use an insulating substrate into which palladium particles are kneaded, and commercially available insulating substrates cannot be used as they are. As described above, the conventional additive method for forming a conductive circuit is complicated and requires a large number of steps. Therefore, an object of the present invention is to provide a method for forming a conductive circuit that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the method for forming a conductive circuit of the present invention is to apply a photosensitive ink prepared by mixing an organometallic compound or an organometallic complex, a photocurable prepolymer solution, and an organic solvent to an insulating substrate. The photosensitive ink layer is exposed to the circuit pattern, the ink layer in the unexposed area is dissolved and removed by a developer, and at the same time the surface of the ink layer in the exposed area is roughened, and the roughened ink layer is treated with a reducing agent. The organic metal compound or organic metal complex dispersed in the ink was treated with the ink to convert it into plating nuclei, and the substrate was immersed in an electroless plating bath to form a metal layer on the surface of the ink layer. The other method for forming a conductive circuit is to coat an insulating substrate with a photosensitive ink that is a mixture of an organic metal compound or complex, a prepolymer solution that has both photocurability and thermosetting properties, and an organic solvent. , semi-curing the photosensitive ink layer by heating, exposing the photosensitive ink layer to a circuit pattern, dissolving and removing the ink layer in the unexposed area with a developer, and simultaneously roughening the surface of the ink layer in the exposed area, A process of treating the roughened ink layer with a reducing agent to transform the organometallic compound or organometallic complex dispersed in the ink into plating nuclei, and immersing the substrate in an electroless plating bath to reduce the surface of the ink layer. A metal layer is formed on the substrate, and the semi-cured ink layer is completely cured by heating the substrate. This invention will be explained in more detail. As organometallic compounds or organometallic complexes, at room temperature
Plating nuclei (plating catalysts) that are stable under normal pressure and are reduced with a reducing agent to liberate metals and become plating nuclei are currently commonly used in electroless coating.
are palladium particles, and in this invention, organic palladium compounds or organic palladium complexes are also preferred. Examples of organic palladium compounds or organic palladium complexes include palladium acetate, palladium (
■) Trifluoroacetate, dichloro [(L2゜5.
6. -η)-1,5-cyclooctadiene l palladium, (2,2”-bipyridine-N, N”) dimethyl palladium, bis(benzonitrile) dichloropalladium,
Bis(di-tert-butylphenylphosphine)palladium, bis(η2-L5-diphenyl-1,4-pentadien-3-onelpalladium, dichlorobis(triphenylphosphine)palladium, bis(2,4-pentanediona-)-0 ,0') palladium, bis(acetate-0)bis(triphenylphosphine)palladium, benzylchlorobis(triphenylphosphine)palladium, tris[(1,2-η)-1,5-diphenyl-1゜4- penkudien-2-one l palladium, tris 1η((1,2-η:4,5-η)-1,5-diphenyl-1,4-penkdien-3-one 11 di-palladium, di-μm chlorobis( η3-2-Chloro2-
propenyl) sibaradium, di-μm bromobis(η3
-2-propenyl)cybaradium, tetra-μmbromobis(η3-2-propenyl)tripalladium, di-μm
mchlorobis(η3-2-7”ropenyl)cybaradium, bis(η3-2-propenyl)palladium, bis[(
1,2,3-η)-2-butynyl 1 diη chlorosivaradium, di-μm chlorobis I(1,2,3-η)-
2-methyl-2-propenyl) cibaradium, dichlorobis[(L, 2.3-η)-2-methyl-2-butene-
1 yl 1 Sibaradium, di-μm chlorobis [(2,3
, 4-η)-3-penten-2-yl 1 cybaradium,
Di-μm chlorobis[(1,2,3-η)-2-cyclohebuten-1-yl)cybaradium, di-μmchlorobis[(1,5,6-η)-2゜5-cyclooctadiene- 1-yl 1 Sibaradium, di-μm chlorobis [(1
,2,3-η)-1-phenyl-2-propenyl 1 Sibaradium, di-μm chlorobis[(1,2,3η)-2
-Phenyl-2-propenyl 1 Sibaradium. The prepolymer solution is photocurable and consists of an oligomer, a photoinitiator, a reactive diluent, and the like. As the oligomer, for example, modified acrylates such as polyurethane acrylate, polyester acrylate, and epoxy acrylate can be used. As the photoinitiator, benzophenone, benzoin alkyl ether, benzoin, benzyl, xanthone, alkylanthraquinone, methylene blue, etc. can be used. If necessary, a reactive diluent such as a styrene monomer polyfunctional acrylate may be used. The photosensitive ink consists of an organometallic compound or an organometallic complex, a photocurable prepolymer solution, and an organic solvent. Further, if necessary, a pore forming agent, thickener, polymerization inhibitor, stabilizer, sensitizer, etc. are added to prepare a photosensitive ink, and this is applied to an insulating substrate. Insulating substrates used include glass-epoxy boards and phenol boards commonly used for printed wiring boards, as well as metal plates with an insulating layer formed on their surfaces. be able to. Furthermore, methods for applying photosensitive ink onto an insulating substrate include spin cording, dipping, roll coating, spray coating, and screen printing. The substrate coated with the photosensitive ink is pre-dried at room temperature or by heating at a low temperature, and then the photosensitive ink layer is exposed to light through a photomask that forms a necessary circuit pattern. After exposure, the ink layer in the non-circuit area, which is the unexposed area, is dissolved and removed by a developer. During the development process, the developer soft-etches the ink surface of the exposed area, so that surface roughening, which is convenient for improving the adhesion of the plating layer, can be performed at the same time. Subsequently, the ink layer formed in the shape of a circuit on the substrate is treated with a reducing agent to form plating nuclei. By reducing the organometallic compound or organometallic complex dispersed in the polymer matrix formed by photocuring with a reducing agent, the metal can be liberated and converted into plating nuclei. As the reducing agent, for example, glucose, formaldehyde, tartaric acid, sodium hypophosphite, etc. can be used. Finally, a metal layer is formed by performing electroless plating on the plating nuclei formed in the ink layer. A commercially available plating bath can be used as the plating bath.
For example, 0PC-700 (manufactured by Okuno Pharmaceutical Co., Ltd.) electroless copper plating bath can be used. A conductive circuit can be formed as described above. Further, as the prepolymer solution of the photosensitive ink, one having both photocurability and thermosetting properties can also be used. In this case, the photosensitive ink is prepared as described above and applied to the insulating substrate, and then heated to bring the photosensitive ink layer into a semi-cured (B-stage) state. Thereafter, the steps up to electroless plating are performed in the same manner as above, and finally the substrate is reheated to completely cure the ink layer. By doing so, a conductive circuit with extremely strong adhesion between the insulating substrate and the metal layer can be formed.

[Effect]

Uniform dispersion is possible in order to disperse an organometallic compound or an organometallic complex, which is a plating nucleus precursor, in a solution containing a prepolymer. Therefore, the uniform dispersion of plating nuclei after chemical reduction is very high (it is possible to form fine patterns, and the properties of the plating metal film are very good. Furthermore, after exposure, when developed with an organic solvent-based developer, Since the ink layer containing the organometallic compound or organometallic complex in the unexposed area dissolves extremely well in the organic solvent, no residue that can become plating nuclei remains in the unexposed area, and therefore there is no masking by resist. Also, bridging does not occur during electroless plating. Furthermore, by selecting a prepolymer solution, a conductive circuit with extremely high adhesion strength to any substrate can be obtained with fewer steps than conventional methods. Furthermore, If a prepolymer solution having both photocurability and thermosetting properties is used, a conductive circuit with extremely high adhesion strength can be obtained by complete thermosetting treatment after plating.

Example 1 A glass-epoxy substrate of 10 cI and 11 squares was washed and then coated with a photosensitive ink having a composition of 300 ml by digiping. Photosensitive ink Weight parts Palladium acetate 3 Epoxy acrylate 20 Chloroform
80 benzoin ethyl ether
After coating on a 0.1 substrate, it was dried at 60° C. for 30 minutes, and exposed for 30 seconds to an ultra-high pressure mercury lamp through a photomask. After developing with chloroform, it was dried at 70°C for 20 minutes. Next, chemical reduction was performed by immersing it in the following 70° C. reducing solution for 1 minute. Reducing liquid: Parts by weight Sodium hypophosphite 5 Water 100 After washing, it was dried and immersed in an electroless copper plating bath to obtain a metal layer. The adhesion strength of the obtained metal pattern was 1.0 kgf/ms
``That's all.'' 1 example - Photosensitive ink, using the following as reducing liquid, 1O
After coating on a steel square glass-epoxy substrate, it was dried at 60°C for 30 minutes and exposed to an ultra-high pressure mercury lamp through a photomask for 20 minutes. After developing with trichlene, it was dried at 70°C for 5 minutes, and then immersed in a reducing solution at room temperature for 2 minutes. After washing with water, it was immersed in an electroless copper plating bath to form a metal layer, and then heated at 150° C. for 30 minutes to completely cure the resin binder. The adhesion strength of the obtained metal pattern is 2.5k
gf/arm” or more. Photosensitive ink Part by weight Palladium acetylacetonate 1 Epoxy resin 5 Trichlene 94 ρ-Methyl dimethylaminobenzoate 0.05 Hensiphenone
0. O1 reducing liquid
Parts by weight Titanium trichloride solution (25%) 10
Water 89 Hydrochloric acid (35%) IX fatty charcoal photosensitive ink, using the following as reducing liquid, 10
After applying it to a cm square phenol substrate, it was dried at 60°C for 30 minutes, and exposed through a photomask to an ultra-high pressure mercury lamp for 20 minutes. After developing with trichlene, it was dried at 70°C for 5 minutes, and then immersed in a reducing solution at room temperature for 2 minutes. After washing with water, it was immersed in an electroless nickel plating bath to form a metal layer, and then heated at 180'C for 20 minutes to completely harden the resin binder. The adhesion strength of the obtained metal pattern was 2.0 kgf/a11" or more. Photosensitive ink Weight part dichloro [
(1,2,5,6,-η)-1,5cyclooctadiene]palladium 1 epoxy resin
5 Trikunun 74 Dimethylformamide 20 Methyl p-dimethylaminobenzoate 0.05 Thioxanthone 0
．． 01 Reducing liquid Part by weight Sodium hypophosphite 5 Water
95 [Effects of the Invention] The method for forming a conductive circuit of the present invention has good uniform dispersion of plating nuclei after chemical reduction, so it is possible to form fine patterns by electroless plating, and the characteristics of the plated metal film are very good. An excellent conductive circuit can be formed. In addition, because of its excellent development characteristics, bridging, where conduction occurs in areas other than the desired circuit pattern, is less likely to occur during plating. Furthermore, a commercially available substrate can be used, and the formed conductive circuit has extremely strong adhesion between the substrate and the conductive circuit. Patent applicant Nissha Printing Co., Ltd.

Claims (4)

[Claims] 1. a) A step of applying a photosensitive ink prepared by mixing an organometallic compound or an organometallic complex, a photocurable prepolymer solution, and an organic solvent onto an insulating substrate, and b) Forming the photosensitive ink layer into a circuit pattern. c) dissolving and removing the ink layer in the unexposed areas with a developer and simultaneously roughening the surface of the ink layer in the exposed areas; and d) treating the roughened ink layer with a reducing agent. and e) immersing the substrate in an electroless plating bath to form a metal layer on the surface of the ink layer. A method for forming a conductive circuit, characterized in that: 2. a) A step of applying a photosensitive ink prepared by mixing an organometallic compound or an organometallic complex, a prepolymer solution having both photocurability and thermosetting properties, and an organic solvent onto an insulating substrate, and b) heating. c) semi-curing the photosensitive ink layer;
a step of exposing the photosensitive ink layer to a circuit pattern; d) dissolving and removing the ink layer in the unexposed areas with a developer and simultaneously roughening the surface of the ink layer in the exposed areas; and e) roughening the surface of the ink layer in the exposed areas. a step of treating the ink layer with a reducing agent to convert the organometallic compound or organometallic complex dispersed in the ink into plating nuclei, and f) immersing the substrate in an electroless plating bath to coat the surface of the ink layer with metal. A method for forming a conductive circuit, comprising sequentially performing a step of forming a layer, and g) a step of completely curing the semi-cured ink layer by heating the substrate. 3. 3. The method for forming a conductive circuit according to claim 1, wherein the organometallic compound or organometallic complex is palladium-based. 4. 3. The method for forming a conductive circuit according to claim 1, wherein the prepolymer solution contains an epoxy compound.