JP2019123910A - Formation method of front and rear surfaces of fine circuit pattern - Google Patents

Abstract

To provide a formation method of front and rear surfaces of a fine circuit pattern, the formation method being capable of executing a series of processes from a pretreatment of a transparent insulation substrate to an electroless plating using an existing facility in the atmosphere and in an inexpensive manner.SOLUTION: A formation method of front and rear surfaces of a fine circuit pattern in which a primer layer is formed on front and rear surfaces of a transparent substrate, and then a fine circuit pattern is formed by an electroless plating includes a process of preparing the transparent substrate with an impermeability for a deep ultra violet light with a wavelength of 300 nm or less, a process of forming a primer layer on front and rear surfaces of the transparent substrate, a process of radiating a deep ultraviolet light with a wavelength of 300 nm or less to the primer layer of the front and rear surfaces via a photo mask, and a process of electroless plating for a non-radiated region of the primer layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of forming front and back surfaces of a fine circuit pattern by electroless plating using a transparent substrate impermeable to deep ultraviolet light.

Forming fine circuits on the front and back sides using an electroless plating method in a working environment of visible light has been widely used so far for printed wiring boards and the like using negative / positive exposure films. For example, in the method for producing a printed circuit board disclosed in JP-A-49-132559, “A thermosetting adhesive is coated on a substrate to make it easy to form, an adhesive substrate is formed, and then a required circuit is required. A reverse pattern of the pattern is formed using a dry film for plating resistance, and then a sensitizing layer is formed with hydrochloric acid acid stannous chloride aqueous solution on the entire surface of the adhesive substrate containing the dry film for plating resistance, and then The reverse pattern of the adhesive circuit provisional circuit pattern having the above sensitizing layer is irradiated with ultraviolet light, and then an acid palladium chloride aqueous solution is applied to activate only the detouring pattern on the adhesive substrate including the above sensitizing layer with an aqueous acidic chloride chloride solution. Then, a conductive layer is formed only on the circuit pattern by chemical plating, and then the above-mentioned plating resistant dry film is removed, and further heating is performed to gradually remove the moisture contained in the thermosetting adhesive. Method for manufacturing a printed circuit board "is disclosed, wherein.

By applying the prior art of such a printed circuit board, after forming primer layers on the front and back of a transparent insulating substrate, fine conductor circuits can be formed on the front and back of the transparent insulating substrate by electroless plating. . However, when visible light is irradiated to front and back of a transparent insulating substrate through an exposure mask, the visible light which has passed through one exposure mask reaches the primer layer on the opposite side. For this reason, there is a problem that the inactive primer layer in the region covered with the exposure mask on the opposite side is activated by the transmitted light from the back surface. In particular, the boundary region of the conductor circuit is likely to be activated by scattered light, so that in this prior art it was not possible to form a fine conductor circuit due to the above problems.

Therefore, in order to form different conductor circuits on the front and back surfaces of a transparent insulating substrate, a catalyst may be applied one by one, electroless plating may be performed, or an opaque layer may be interposed between the transparent insulating substrates. It was However, with such a manufacturing method, the productivity is low and the cost is also high, so conventionally, it has been impossible to mass-produce fine circuit patterns with high accuracy.

On the other hand, in claim 1 of Japanese Patent Application Laid-Open No. 2007-16279 (Patent Document 1 described later), “Step of sensitizing treatment of the surface of the substrate with tin (II) chloride, ultraviolet light is applied to the substrate subjected to sensitization treatment A step of irradiating a pattern to suppress sensitization of the substrate in the exposed portion, and inactivating the tin adsorption layer of the exposed portion among the tin adsorption layers formed on the surface of the substrate by the sensitization treatment; The step of activating the tin adsorption layer in the non-exposed area remaining on the surface of the substrate with palladium (II) chloride, the step of reducing the activated substrate, and the catalyst nucleus of the metallic palladium subjected to the reduction treatment And B. forming an electroless plating film of metal on the tin adsorption layer having the above.

According to the same paragraph 0003, “When pattern irradiation is performed on a sensitized substrate with ultraviolet light ... In the exposed area, divalent tin compounds such as SnCl ₂ and SnO are oxidized and tetravalent tin such as SnCl ₄ and SnO ₂ As it becomes a compound, palladium ion is not reduced even if it is activated, and catalytic nuclei of metallic palladium are not generated.Thus, by immersing the substrate in the plating bath, selective only to the non-exposed area of ultraviolet light An electroless plated film of nickel can be deposited, and a desired fine pattern can be formed on the substrate.

However, this prior art pattern-irradiates only the surface with ultraviolet light, as shown in FIG. 1 of the same publication. Using the “disk-shaped substrate made of borosilicate glass having a smooth front and back surface” disclosed in the same paragraph 0020, the above-mentioned method for producing a printed circuit board (JP-A-49-132559) Similarly, it is presumed that there is a risk that transmitted ultraviolet rays reach the back side.

In addition, claim 1 of Japanese Patent Application Laid-Open No. 2007-131898 (Patent Document 2 described later) “A metal coating method for forming a metal layer on the surface of the open-cell molded article and the inner surface of the interconnected pores, A silicon-containing polymer layer is formed on the surface of the open-cell shaped molded article and on the inside of the interconnected pores, and the silicon-containing polymer layer excluding the portion to form a metal layer is irradiated with ultraviolet light, and then its counter anion is silicon A solution or suspension containing a transition metal salt capable of coordinating to a silicon atom of the contained polymer is brought into contact with the silicon-containing polymer layer, and the transition metal is selectively selected only in the portion of the silicon-containing polymer layer which is not irradiated. Disclosed is a metal coating method characterized by reducing precipitation of

In this metal coating method, in the same paragraph 0015, “the silicon-containing polymer layer excluding the portion to form the metal layer is irradiated with ultraviolet light, and then its counter anion can be coordinated to the silicon atom of the silicon-containing polymer And a solution or suspension containing a metal salt is brought into contact with the silicon-containing polymer layer to selectively reduce and deposit the transition metal only on the portion of the silicon-containing polymer layer which is not irradiated with ultraviolet light. Have been described.

However, this prior art is used for a porous foam that is metallized on the pore surface having communicating pores therein, and is not a transparent substrate. Further, in the paragraph 0031 of the same publication, in the portion (non-irradiated portion) where the ultraviolet light was not irradiated by the photo mask, the counter anion of the transition metal salt is coordinated to the silicon atom, so a metal layer is formed. In the invention that the surface to be activated is not activated, as described in the uninterrupted, in the irradiated part (irradiated part), no coordination of the anion to the silicon atom takes place and thus the metal layer is not formed. " is there. In such a processing technique, the interface between the irradiated part and the non-irradiated part tends to be unclear, and it is difficult to draw a fine circuit. The fact that light with a wavelength of more than 300 nm, such as a high pressure mercury lamp described in the same paragraph, can be used is also a proof.

Therefore, in the prior art so far, even if it is a transparent substrate, it was not possible to draw a fine circuit on the front and back in the working environment of electroless plating under the atmosphere. Therefore, when electroless plating is performed on a transparent insulating substrate that has been pretreated using conventional photolithography techniques, a scattering layer may be provided on the surface of the transparent insulating substrate to disperse incident light, or an opaque layer in the middle. To block incident light and pattern in a special working environment, and then electroless plating is performed by a normal plating process.

Japanese Patent Application Publication No. 2007-16279 JP 2007-131898 A

Furthermore, if the vapor phase process is performed in the special working environment as described above, the apparatus becomes large, and it takes time to pretreat the transparent insulating substrate, which is not suitable for mass production. In addition, the circuit pattern obtained has the disadvantage of being expensive. For this reason, even if it is a transparent insulating substrate, the cheap mass-production technology by the electroless plating process under the atmosphere which can form different fine circuits efficiently on the front and back is called for.

An object of the present invention is to provide a method of forming front and back surfaces of a fine circuit pattern which can carry out a series of processes from the pretreatment of a transparent insulating substrate to the electroless plating under the environment of the atmosphere at low cost. It is In particular, a further object of the present invention is to provide a method of forming front and back surfaces of a fine circuit pattern capable of forming patterns of fine circuits having different front and back surfaces accurately and accurately by one irradiation of deep ultraviolet light. It is.

Another object of the present invention is to meet the above-mentioned problems, and to provide a method of forming front and back surfaces of a fine circuit pattern which can be manufactured by an ordinary electroless plating process using an inexpensive and compact commercial device. It is. In particular, the provision of the step of deactivating the active surface of the primer layer provides a method of forming front and back surfaces of a fine circuit pattern capable of performing electroless plating more reliably, more precisely, and more accurately. It is to be.

The present invention utilizes the property of an ordinary glass substrate or a plastic resin substrate, which is an insulating substrate transparent to visible light and which is opaque to deep ultraviolet light. The present invention is based on the new finding that the active primer layer is inactivated by deep ultraviolet light without being inactivated by visible light or ultraviolet light having a wavelength of more than 300 nm. The deep ultraviolet light of the present invention means monochromatic light having a wavelength of 300 nm or less or light in which a plurality of wavelengths are mixed. Visible light generally refers to monochromatic light having a wavelength of about 380 nm to about 700 nm or light in which a plurality of wavelengths are mixed.

One of the methods for forming the front and back surfaces of the fine circuit pattern of the present invention is a method of forming the front and back surfaces of the fine circuit pattern by electroless plating after forming primer layers on the front and back surfaces of the transparent substrate A step of preparing a transparent substrate impermeable to light, a step of forming a primer layer on the front and back of the transparent substrate, and a step of irradiating the primer layer on the front and back with deep ultraviolet light having a wavelength of 300 nm or less And a step of electrolessly plating a non-irradiated area of the primer layer.

Another method of forming the front and back surfaces of the fine circuit pattern of the present invention comprises forming primer layers on the front and back surfaces of the transparent substrate and then forming the front and back surfaces of the fine circuit pattern by electroless plating. A step of preparing a transparent substrate impervious to deep ultraviolet light, a step of forming a primer layer on front and back of the transparent substrate, deep ultraviolet light having a wavelength of 300 nm or less on the primer layer of the front and back via a photomask It is characterized by comprising a step of irradiating, a step of forming a catalyst layer in a non-irradiated region of the primer layer, and a step of electrolessly plating the non-irradiated region of the primer layer.

The embodiment terms of the present invention are as follows. That is, it is preferable that the shape of the area | region which irradiates a deep ultraviolet ray to the primer layer of the said front and back via a photomask differs in front and back. Moreover, it is preferable that the said transparent substrate is containing machine type | system | group ultraviolet-ray absorber resin. Furthermore, when providing the process of forming the said catalyst layer, it is preferable to provide a noble metal nanoparticle catalyst layer as pre-processing of the said electroless plating.

In the method of forming front and back surfaces of the fine circuit pattern according to the present invention, the reason why effective ultraviolet light is light having a wavelength of 300 nm or less is that general soda glass, polyethylene terephthalate resin (PET resin), etc. It is from. Raw materials of soda glass are composed of silica, soda ash, soda lime and the like. Besides PET resin, acrylonitrile-styrene resin (AS resin), polypropylene resin (PP resin), high density polyethylene resin (PE resin), melamine resin (MF resin), methacrylic resin (PMMA resin), and the like.

In the present invention, the activated primer layer may be partially removed by laser ablation upon deep ultraviolet light irradiation. Depending on the type of primer layer and transparent substrate, the surface etc. of the transparent substrate may be altered and electroless plating may occur up to the light transmitting part of the photomask, so long-time irradiation with a short wavelength ultraviolet laser is not preferable There is.

In the transparent substrate of the present invention, a glass substrate, a resin substrate, a laminate substrate of these, and a substrate using these in combination can be used as a transparent substrate. Moreover, a PET raw material, a glass raw material, etc. can be used as a flexible transparent substrate, and can also be laminated | stacked as a coating film or a coating agent. Moreover, when the imperviousness of deep-ultraviolet light is inadequate, the imperviousness of deep-ultraviolet light can be ensured by thickening the plate | board thickness (film thickness) of a transparent substrate.

The resin used for the transparent substrate of the present invention is exemplified in JP-A-2010-513721, paragraph 0040. Thus, "examples of thermoplastic polymers useful in the present disclosure include polyolefins, polyacrylates, polyamides, polyimides, polycarbonates, polyesters, and biphenol-based or naphthalene-based liquid crystal polymers. Additional useful thermoplastic resins" Examples include polyethylene, polypropylene, poly (methyl methacrylate), polycarbonate of bisphenol A, poly (vinyl chloride), polyethylene terephthalate, polyethylene naphthalate, and poly (vinylidene fluoride). Optics are particularly suitable for certain display and sensor applications that support patterned conductors (eg, EMI shielding films) that are polycarbonate and polyester in particular. Others of these polymers are also polyimides and liquid crystal polymers, in particular electrical circuit applications supporting patterned conductors (eg support and interconnection of electronic components) It has thermal and electrical properties which make it particularly suitable for

In the resin used for the transparent substrate of the present invention, fine particles of zinc oxide, titanium oxide, tungsten oxide, strontium titanate, etc. are kneaded into a resin material such as epoxy resin or polyester resin, or glass base material or resin It can be laminated on a substrate. The coating method in the case of laminating includes spin coating, dip coating, spray coating and the like.

In addition, ultraviolet shielding agents such as paraaminobenzoic acid (260 nm to 313 nm), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (280 nm to 320 nm), ethyl 4-aminobenzoate (308 nm to 311 nm) and the like are epoxy resins Or a transparent substrate such as polyester resin.

In general, organic ultraviolet absorbers such as benzotriazole type and triazine type or inorganic type ultraviolet absorbers such as zinc oxide and rare earth oxides are appropriately mixed with a transparent substrate of such resin or glass and ultraviolet rays appropriately. It has been marketed with absorbency.

As a light source for emitting deep ultraviolet light having a wavelength of 300 nm or less according to the present invention, a light source of ultraviolet light used in a semiconductor device can be used. For example, it can be deactivated on a mass production line of electroless plating by using an ultraviolet lamp or scan irradiation in the atmosphere with ultraviolet laser light having a linear irradiation range.

Ultraviolet lamps include low pressure mercury lamps and excimer lamps. The low pressure mercury lamp can emit ultraviolet light with wavelengths of 185 nm and 254 nm. The excimer lamps include Xe ₂ excimer lamp: wavelength 172 nm, KrBr excimer lamp: wavelength 206 nm, KrCl excimer lamp: wavelength 222 nm, KrF excimer lamp: wavelength 248 nm, and the like.

If the cost is neglected, the shorter the wavelength of the ultraviolet light, the shorter the activation surface of the primer layer tends to be surely deactivated in a short time. That is, when the wavelength of the ultraviolet light becomes short, the accuracy of the error of the circuit width is improved, and the circuit pattern can be drawn precisely, so that the circuit wall of the electroless plating becomes sharp. For example, the circuit width error is 0.35 nm to 0.18 nm for a deep ultraviolet light source having a wavelength of 248 nm, 0.18 μm to 0.13 μm for a 193 nm ArF excimer laser, and 0 for a 157 nm F ₂ laser. .10 μm or less.

The primer layer of the present invention has good adhesion to the transparent substrate, and is made of a composition capable of electroless plating on the surface of the primer layer. More preferably, the primer layer of the present invention includes an activation treatment step of activating the primer layer by pretreatment. The primer layer can also contain a resin component or metal as a catalyst.

According to the method of forming front and back surfaces of the fine circuit pattern of the present invention, only the necessary portions on both sides of the active primer layer are mechanically mechanically irradiated by irradiating deep ultraviolet light having a wavelength of 300 nm or less through the photomask. Can be inactivated. It is said that ultraviolet light with a wavelength of 254 nm most efficiently generates active oxygen from the atmosphere for the deactivation of the active primer layer, and the reactive oxygen reacts with the active surface of the primer layer to deactivate the active surface. It is thought that

Since the light transmission part and the light shielding part are mixedly distributed in the photomask, if the light transmission part of the primer layer is irradiated with deep ultraviolet light to deactivate its active part, the primer layer active in the light shielding part Can be formed with high precision because the fineness of the circuit pattern is maintained. That is, since the deep ultraviolet light has a short wavelength of 300 nm or less, the boundary between the inactivated surface and the non-inactivated surface can be sharply defined on the primer layer, and even if thick plating is performed, the electroless plated layer There is no need to blur the outline. Moreover, even if the deep ultraviolet light of the previous transparent substrate leaks in the mass production process and the light transmitting part of the subsequent transparent substrate is irradiated, the subsequent deactivation of the transparent substrate is not affected.

In order to sharply divide the boundary on the primer layer by the light transmitting portion and the light shielding portion, the shorter the wavelength of the ultraviolet light, the better. On the other hand, the shorter the wavelength of the ultraviolet light, the more easily the surface of the primer layer is roughened by laser ablation and the surface of the transparent substrate is more likely to be reactivated. When the surface of the primer layer or the surface of the transparent substrate is roughened, the catalyst metal and the plating metal easily adhere. The wavelength, intensity, time and the like of the ultraviolet light used in the present invention can be appropriately determined depending on the resin material of the primer, the thickness and the like.

The material which comprises the primer layer in this invention can use a conventional well-known material.
For example, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane as a silane coupling agent having an amino group, mercapto group and isocyanurate group , 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3 -Mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, tris- (trimethoxysilylpropyl) isocyanurate and the like.

Further, a base resin having an amino group, a mercapto group and an isocyanurate group in the molecule can also be used as a primer layer. The base resin can be selected from epoxy resin, phenol resin, cyanate resin, isocyanate resin, benzoxazine resin, oxetane resin, polyester resin, allyl resin, dicyclopentadiene resin and the like.

Furthermore, an epoxy resin, a phenol resin, a cyanate resin, an isocyanate resin, a benzoxazine resin, an oxetane resin, a polyester resin, an allyl resin, a dicyclopentadiene resin or the like may be used as a base resin and the above-mentioned silane coupling agent may be mixed.

The method for applying the primer is not particularly limited, and for example, using a spray, screen printer, gravure printer, flexo printer, inkjet printer, offset printer, dipping, spin coater, roll coater, flow coater, etc. It can be printed or coated. The drying conditions are also not particularly limited, and may be performed at room temperature or heating conditions.

The thickness of the primer layer to be formed is preferably in the range of 2 nm to 1000 nm. If the thickness of the primer layer is too thin, it may be difficult to form the primer layer uniformly, so the lower limit thickness of the primer layer is preferably 2 nm or more. Moreover, even if the film thickness of the primer layer is increased, for example, if it exceeds 1000 nm, it becomes difficult to sharply divide the boundary between the inactivated surface and the non-inactivated surface on the primer layer. The upper limit thickness is preferably 1000 nm or less.

The lower limit thickness of the primer layer is more preferably 5 nm or more, and still more preferably 10 nm or more. The upper limit thickness of the primer layer is more preferably 800 nm or less, and still more preferably 500 nm or less.

Further, in the method for forming front and back surfaces of the fine circuit pattern of the present invention, a catalyst layer of noble metal colloid can be provided as a pretreatment for the electroless plating. In this case, since the noble metal catalyst layer on the primer layer exerts the anchor effect of electroless plating, it is possible to obtain the electroless plating deposit with stronger adhesion.

The catalyst solution is a solution containing a noble metal (catalyst metal) having catalytic activity for electroless plating, and examples of the catalyst metal include palladium (Pd), gold (Au), platinum (Pt), rhodium (Rh) and the like. Be These metals may be used alone or as a compound, but from the viewpoint of the stability of the solution containing the catalyst metal, noble metal nanoparticles having a uniform particle size are preferable.

In particular, a sugar alcohol solution containing noble metal nanoparticles is preferred. As a specific catalyst liquid, a 0.1% sugar alcohol aqueous solution (pH = 6.5) containing 0.5 mass g / L of precious metal nanoparticles having an average particle diameter of 2 nm to 100 nm can be mentioned. The treatment temperature is 20 ° C. to 70 ° C., preferably 30 ° C. to 60 ° C., and the treatment time is 0.1 minute to 20 minutes, preferably 1 minute to 10 minutes. By the above operation, the noble metal nanoparticles are immobilized on the active primer layer to form a catalyst layer.

If the particle size of the precious metal colloid is made uniform on a scale unit of an average particle size of 2 nm to 100 nm, the anchor effect of the catalyst layer is leveled. In particular, when a precious metal catalyst layer having a uniform particle size is formed with a sugar alcohol solution, so-called self-assembly phenomenon in which the precious metal catalyst particles are planarly assembled on the primer layer and mutually repel each other. As a result, even if the film thickness of the electroless plating is thin, a smooth plating film can be obtained.

The substrate treated above is immersed in an electroless plating solution for depositing a metal forming a circuit pattern. Thereby, an electroless plating film is formed. The electroless plating solution is preferably autocatalytic electroless plating. Once metal deposition starts, metal ions in the electroless plating solution are continuously reduced and progress. That is, metals that can be used for electroless plating include noble metals such as gold (Au), silver (Ag), platinum (Pt) and palladium (Pd), as well as copper (Cu), nickel (Ni), cobalt (Co) And other base metals can be applied, but inexpensive copper (Cu) is preferred.

Suitable reducing agents for electroless copper plating baths include formaldehyde, hydrazine, aminoborane, and hypophosphite. As a specific example of the electroless copper plating bath, for example, the treatment temperature is 40 ° C. to 70 ° C., preferably 50 ° C. to 60 ° C., and the treatment time is 1 minute to 30 minutes, preferably 5 minutes to 15 It is a minute.

According to the present invention, there is a mass production effect in which the step of irradiating deep ultraviolet light having a wavelength of 300 nm or less and the step of electroless plating can be performed in a series of flow operations under the atmosphere. In addition, by providing the step of deactivating the active primer layer according to the present invention, there is an effect that the electroless plating can be performed more surely, more precisely, and more accurately than ever before.

In particular, if a step of forming a catalyst layer in the non-irradiated region of the primer layer after irradiation with this deep ultraviolet light is provided, catalyst particles can be adsorbed only in the light shielding portion by this catalyst step, and the light transmitting portion and the light shielding portion It has the effect of making the border area of In addition, there is an effect that a strong deposit of electroless plating can be obtained by the anchor effect of the catalyst particles. As a result, it is possible to mass-produce transparent substrates in which fine conductor circuit patterns are formed thinner on the front and back surfaces. Furthermore, there is also an effect that it becomes easy to provide an expensive precious metal catalyst layer without waste as a pretreatment for electroless plating.

In addition, since formation of circuit patterns on the front and back surfaces can be continuously performed in one stage, there is an effect that high-mix small-quantity small amount electroless plating products can be efficiently manufactured. In addition, when a catalyst layer of noble metal nanoparticles with uniform particle diameter is provided, it is possible to form a more stable thickness and a stable electroless plating deposition layer.

It is an image figure which shows the Example of this invention.

EXAMPLES The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto.
Example 1
As a transparent substrate, immerse a PET film (Lumirror T60 manufactured by Toray Industries, film thickness 0.1 mm) in N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane solution (10% toluene solvent) and dry at 100 ° C. It dried with an oven and obtained the active primer layer with a film thickness of 20 nm on front and back.

As shown in FIG. 1, photomasks of different patterns were placed on both sides of the primer layer, and the PET film was irradiated with deep ultraviolet light of wavelength (λ) = 172 nm with a xenon (Xe ₂ ) excimer lamp in the atmosphere. The exposure dose was 1500 mJ / cm ² .

Next, this transparent substrate was immersed for 10 minutes in a 1% trisodium citrate aqueous solution (pH = 6.0) containing 0.2 mass g / L of palladium (Pd) nanoparticles having an average particle diameter of 10 nm. After that, it was immersed in an electroless copper plating bath using formalin as a reducing agent for 2 minutes to obtain a copper (Cu) plated film having a film thickness of 50 nm.

Circuit patterns different in front and back were formed on the above transparent substrate, and the minimum copper (Cu) line width was 10 μm. Further, no formation failure of the copper (Cu) circuit pattern was observed.
(Comparative example 1)

Electroless plating was performed in the same manner as in Example 1 except that irradiation with ultraviolet light of wavelength (λ) = 365 nm was performed using a high pressure mercury lamp. The active primer layer was hardly inactivated, a copper (Cu) film was formed on the entire surface, and a circuit pattern was not formed.
(Example 2)

A glass substrate (EAGLE-XG manufactured by Corning, plate thickness 0.7 mm) was prepared as a transparent substrate. The following compounds were mixed and then stirred to prepare a primer layer coating solution (a). The coating solution (a) was applied to a transparent substrate by a bar coating method so as to give a film thickness of 0.2 μm after drying, and dried at 100 ° C. for 10 minutes to form primer layers on both sides of the transparent substrate.

<Primer layer coating solution (a)>
Base resin: Thermoplastic saturated polyester resin: 90 parts by mass Silane coupling agent: HS- (CH ₂ ) ₁₁ -O-azobenzene (Prochimia company): 10 parts by mass Solvent: methyl ethyl ketone

As shown in FIG. 1, different predetermined patterns of photomasks were placed on the front and back surfaces of the transparent substrate coated with the primer layer, and deep ultraviolet light was irradiated with a low pressure mercury lamp with a central wavelength (λ) = 254 nm. The exposure dose was 500 mJ / cm ² .

Next, this transparent substrate was immersed for 10 minutes in a 1% aqueous solution of trisodium citrate (pH = 6.0) containing 0.2 mass g / L of gold (Au) nanoparticles having an average particle diameter of 10 nm. Thereafter, the resultant was immersed for 10 minutes in an electroless gold plating solution (PRECIOUS FABAC G 3000 WX, manufactured by Nippon Electroplating Engineering Co., Ltd.) kept at 65 ° C. to obtain a gold (Au) plated film having a thickness of 100 nm.

Circuit patterns different in front and back were formed on the above transparent substrate, and the minimum line width was 25 μm. In addition, formation defects of the gold (Au) circuit pattern were not observed.
(Comparative example 2)

Electroless gold plating was performed in the same manner as in Example 2 except that irradiation with ultraviolet light of wavelength (λ) = 365 nm was performed using a high pressure mercury lamp. The image of the circuit where the pattern of front and back was combined appeared on both sides of a transparent substrate, and it became a thing which can not be applied to a circuit pattern. It is presumed that the ultraviolet light transmitted through the transparent substrate deactivates even the primer layer of the light-shielding portion on the opposite side, resulting in a defective circuit image in which the patterns of the front and back surfaces overlap.
(Example 3)

A glass substrate (EAGLE-XG board thickness 0.7 mm manufactured by Corning) was prepared as a transparent substrate, and the following compounds were mixed and stirred to prepare a primer layer coating solution (b). The coating solution (b) was applied to the front and back of the transparent substrate by spin coating so as to give a film thickness of 0.1 μm after drying, and dried at 160 ° C. for 10 minutes to form a primer layer.

<Primer layer coating solution (b)>
Base resin: poly (bisphenol A co-epichlorohydrin) glycidyl endcapped (manufactured by Sigma Aldrich) 70 parts by mass amine crosslinker: aminoethylated acrylic resin (manufactured by Nippon Shokubai Co., Ltd., NK-350) 30 Parts by mass solvent: cyclohexanone

Photo masks of different predetermined patterns were placed on the front and back of this transparent substrate, and deep ultraviolet light was irradiated with a low pressure mercury lamp with a center wavelength (λ) = 185 nm as shown in FIG. The exposure dose was 700 mJ / cm ² .

Next, this transparent substrate was immersed in a 1% aqueous solution of trisodium citrate (pH = 8.0) containing 0.1 mass g / L of palladium (Pd) nanoparticles with an average particle diameter of 5 nm for 20 minutes. Thereafter, it was immersed for 15 minutes in an electroless nickel (Ni) plating solution (MICROFABELN 500, manufactured by Nippon Electroplating Engineering Co., Ltd.) kept at 80 ° C. to obtain a nickel (Ni) plating film having a thickness of 1.5 μm.

Circuit patterns different in front and back were formed on the above transparent substrate, and the minimum line width was 5 μm. Further, the variation in film thickness of the circuit pattern of the nickel (Ni) plating film was hardly observed, and there was no defective portion in pattern formation.
(Comparative example 3)

Electroless nickel plating was performed in the same manner as in Example 3 except that a synthetic quartz polishing plate (a plate thickness of 1.0 mm manufactured by As One Corporation) was used as a transparent substrate. As in Comparative Example 2, an image in which the patterns on the front and back surfaces were combined appeared on both surfaces, and was not applicable to the circuit pattern. Since the quartz substrate has deep ultraviolet light permeability, it is presumed that even the primer layer on the opposite side is inactivated, resulting in a defective circuit image in which the front and back patterns overlap.

As apparent from the above Examples and Comparative Examples, according to the method for forming front and back surfaces of the fine circuit pattern of the present invention, the electroless plating film can be obtained by irradiating visible light with a single deep ultraviolet light under the atmospheric working environment. Can be precisely and precisely formed on the required places on both sides of the transparent substrate. Further, according to the method of forming front and back surfaces of the fine circuit pattern of the present invention, deep ultraviolet light can be irradiated in a series of conventional electroless plating steps, and expensive precision-processed jigs and equipment are required. do not do. In particular, by providing the step of deactivating the active surface of the primer layer, it was possible to obtain electroless plating which is sharper, more accurate, and more accurate. Therefore, fine circuit patterns can be mass-produced on the front and back surfaces of the transparent substrate in a low cost electroless plating process.

The method for forming front and back surfaces of the fine circuit pattern of the present invention is particularly effective for electroless plating on a plastic resin whose pretreatment method differs depending on the material because the substrate itself is not roughened. In addition, the present invention can be advantageously applied to electroplating of a portable personal computer, a housing of a mobile phone or the like performed for the purpose of shielding electromagnetic waves. In addition, it is useful also for formation of the fine circuit in various fields, such as a printed wiring board and a three-dimensional circuit formation part.

Claims (5)

After forming a primer layer on front and back of a transparent substrate, in the method of forming front and back of a fine circuit pattern by electroless plating, a step of preparing a transparent substrate opaque to deep ultraviolet light having a wavelength of 300 nm or less From the step of forming a primer layer on the front and back of the step, the step of irradiating the primer layer on the front and back with deep ultraviolet light having a wavelength of 300 nm or less through a photomask, and the step of electrolessly plating the non-irradiated region of the primer layer A method of forming front and back surfaces of a fine circuit pattern, characterized in that After forming a primer layer on front and back of a transparent substrate, in the method of forming front and back of a fine circuit pattern by electroless plating, a step of preparing a transparent substrate opaque to deep ultraviolet light having a wavelength of 300 nm or less Forming a primer layer on the front and back surfaces of the substrate, irradiating deep ultraviolet light having a wavelength of 300 nm or less onto the primer layers on the front and back surfaces via a photomask, and forming a catalyst layer in a non-irradiated region of the primer layer A method of forming front and back surfaces of a fine circuit pattern, comprising the step of electrolessly plating a non-irradiated area of the primer layer. The method for forming front and back surfaces of a fine circuit pattern according to claim 1 or 2, wherein the shape of the region where deep ultraviolet light is irradiated to the primer layer on the front and back surfaces through a photomask is different between the front and back surfaces. The method for forming front and back surfaces of a fine circuit pattern according to claim 1 or 2, wherein the transparent substrate is a mechanical ultraviolet absorber resin. The method for forming front and back surfaces of a fine circuit pattern according to claim 2, wherein a noble metal nanoparticle catalyst layer is provided as a pretreatment of the electroless plating.