JP2003270782A - Dry film photoresist and method of making printed-wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry film photoresist having a photosensitive resin layer which follows well the rugged parts, such as gouges and flaws, on a substrate for forming circuits and a method of making printed-wiring board having decreased defects by using such dry film photoresist. <P>SOLUTION: The dry film photoresist formed by disposing the photosensitive resin layer containing a gelatinizing agent in a photosensitive resin composition on a carrier film and the method of making the printed-wiring board using the same. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry film photoresist and a method of manufacturing a printed wiring board using the same, and more specifically, a photosensitive resin layer for uneven portions such as dents and scratches on a circuit forming substrate. The present invention relates to a method for manufacturing a printed wiring board, which has excellent followability and has very few defects.

[0002]

2. Description of the Related Art Generally, a printed wiring board is produced by forming a resist layer (photosensitive resin layer) made of a photosensitive resin composition on a circuit-forming substrate and obtaining a resist pattern by photolithography. As a material for forming the resist layer, a dry film photoresist for laminating a sheet-shaped photosensitive resin composition on a circuit-forming substrate in advance, and a liquid photosensitive composition are used as the substrate. There is a method using a photosensitive material of a liquid photoresist applied to the surface.

In the method of producing a printed wiring board using a liquid photoresist, first, a liquid photoresist is applied on a circuit-forming substrate, dried, and then a circuit pattern is exposed and alkali-developed to form a resist pattern portion. A printed wiring board is manufactured by etching away the metal conductive layers other than.

When the liquid photoresist is used as described above, the resist liquid enters the irregularities such as dents and scratches on the circuit-forming substrate at the time of coating, so that the photoresist layer following the irregularities can be formed. Adhesion failure defects are significantly less than when dry film photoresist is used.

However, since the surface of the photoresist layer is sticky, it is not possible to contaminate the phototool, and it is impossible to form a good resist film on the edge or inside of the throughhole. There is a problem of being corroded by the etching solution. Therefore, the use of the liquid photoresist is limited to the inner layer substrate having no through hole, or if a multilayer board having a through hole is handled, an additional process such as a hole filling process is unavoidable.

The structure of the dry film photoresist is usually a three-layer structure in which a photosensitive resin layer is sandwiched between a carrier film (polyethylene terephthalate etc.) and a protective film (polyethylene etc.). A two-layer structure without a protective film has been used in recent years. The method of manufacturing a printed wiring board with a dry film photoresist is as follows. First, the surface from which the protective film has been removed is laminated on the circuit-forming substrate, then the circuit pattern is exposed, the carrier film is removed, and alkali development is performed. A printed wiring board is manufactured by etching away the metal conductive layers other than.

As described above, in the method for producing a printed wiring board using the dry film photoresist, the handling and workability of the liquid found in the liquid photoresist is remarkably improved, and the problem of phototool contamination occurs. Absent.
Further, since the tenting is possible, the protection of the through hole is remarkably high, and the dry film photoresist is predominant at present.

However, as described above, as compared with the liquid photoresist, the followability of the photosensitive resin layer with respect to the irregularities such as dents and scratches on the circuit-forming substrate is poor, and etching of the photosensitive resin layer is difficult. At this time, there is a problem that the etching solution infiltrates from the poorly adhered portion, causing open defects such as disconnection and cracks. Therefore, in the dry film photoresist, development of a compound in which a softening agent or an adhesion promoter is compounded or the molecular weight of a monomer, an oligomer or a binder polymer is adjusted to a low level is under way. However, since it is essentially a solid film, the unevenness followability is not sufficiently satisfied.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a dry film photoresist having excellent followability of a photosensitive resin layer to uneven portions such as dents and scratches on a circuit forming substrate, and a dry film photoresist thereof. The present invention aims to provide a method for manufacturing a printed wiring board having very few defects by using the method.

[0010]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a dry film in which a photosensitive resin layer containing a gelling agent in a photosensitive resin composition is provided on a carrier film. It was found that the photoresist has excellent followability of the photosensitive resin layer with respect to the uneven portion of the circuit-forming substrate.

That is, by utilizing the gelling agent contained in the photosensitive resin composition, a property that a rapid change in state with respect to temperature is exhibited as compared with the conventional dry film photoresist was utilized. The dry film photoresist containing a gelling agent is a solid having a practical strength at room temperature and does not impair the handling property, cold flow, developing property, etching property, tenting property and the like. Then, since the state changes to a low-viscosity fluid liquid during heating during lamination, the liquid infiltrates into the uneven portion on the circuit-forming substrate. Then, after laminating, it is cooled to be solidified in its original state, and the photosensitive resin layer is satisfactorily formed on the circuit-forming substrate.

When this dry film photoresist is used as a resist material for forming a circuit by the subtractive method, the dry film photoresist heated above the temperature at which the photosensitive resin layer becomes a sol is formed on the circuit forming substrate. Laminate and cool to a gelling temperature to form a photosensitive resin layer on the circuit-forming substrate, then expose the circuit pattern, develop to form a resist pattern, and form the metal conductive layer other than the resist pattern portion. By removing by etching, a printed wiring board with few defects due to poor adhesion can be manufactured.

Also, when this dry film photoresist is used as a solder resist, the photosensitive resin layer follows the step of the circuit (about 10 to 40 μm) on the substrate surface based on the above-mentioned principle without any adhesion failure. . That is, the dry film photoresist can be laminated on the circuit-formed substrate, exposed and developed, and post-cured to be cured to form the solder resist without defective coating.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a dry film photoresist and a printed wiring board according to the present invention will be described in detail below.

The photosensitive resin composition according to the present invention is a generally used photosensitive resin composition for printed wiring boards, which is either a circuit forming or a solder mask photosensitive resin composition. And may be any of the photosensitive resin compositions used in the subtractive method, the semi-additive method, the full-additive method, and the plating method as long as it is for forming a circuit. It can be selected and used depending on the application of the photoresist. Further, it may be either of a negative type in which the light irradiation part is hardened and becomes insoluble in the developing solution, or a positive type in which the light irradiation part is decomposed and becomes soluble in the developing solution. Examples will be given below, but any photosensitive resin composition can be applied as long as it does not differ from the gist of the present invention. For example, a negative photosensitive resin composition comprising a binder polymer containing a carboxylic acid group, a photopolymerizable polyfunctional monomer, a photopolymerization initiator, a solvent, and other additives can be used. Their blending ratio is determined by how to balance the required properties such as sensitivity, resolution, hardness and tenting property. Examples of the positive photosensitive composition include a mixture of a novolak resin and a sulfoester compound of o-naphthoquinonediazide, a siloxane-based polymer and an acid generator (and a mixture of a cresol novolac resin, etc.) and the like. If it is for a solder mask, a binder polymer, a multi-functional monomer, an epoxy resin, a photopolymerization initiator, a sensitizer, an epoxy thermosetting agent,
A photosensitive resin composition containing a solvent, other additives and the like in a necessary balance can be used. Examples of these compositions are "Photopolymer Handbook" (edited by Photopolymer Forum,
Published in 1989, published by Kogyo Kenkyukai Co., Ltd. and “Photopolymer Technology” (edited by Ao Yamamoto, Gentaro Nagamatsu, 19).
Published in 1988, published by Nikkan Kogyo Shimbun), etc.,
A desired photosensitive resin composition can be used.

The gelling agent according to the present invention has the property of gelling the photosensitive resin composition at room temperature,
Any material may be used as long as it has a property that it can be made into a fluid liquid (sol) by heating the gelled solid matter, and that it can be given a thermoreversible property that returns to the original state when cooled. Common gelling agents can be used, for example, 12-
(Poly) hydroxystearic acid such as hydroxystearic acid, hydroxyalkyl alcohol, benzylidene sorbitols, benzylidene xylitols, N-acylamine acid derivatives, benzoyl gluconamide derivatives, 2,3-o-isopropylidene glyceraldehyde derivatives, L- Isoleucine derivative, L-valyl-L-valine derivative, diamide and diurea derivative synthesized from trans-1,2-cyclohexanediamine, double-headed amino acid derivative, L-lysine derivative, etc. are used, and a single compound or a plurality of compounds are combined. Used. Also,
A polymer gelling agent having an amide bond, a hydroxyl group, a carboxyl group or the like can also be used if it is thermoreversible. The gelation by these gelling agents is driven by weak bonds such as electrostatic interaction, hydrogen bond, van der Waals force, and π-π interaction, and therefore strongly depends on the polarity of the dissolving medium. Therefore, the gelling agent to be used is selected depending on the photosensitive resin composition used and the solvent contained therein.
The amount of these gelling agents used depends on the sensitivity of the photosensitive resin composition,
It is used to the extent that necessary properties such as resolution and tenting properties are not significantly reduced, and specifically, it is used in the range of 0.1 to 30 mass% with respect to the photosensitive resin composition.

The carrier film according to the present invention is
For the polymer film, for example, polyethylene terephthalate, polypropylene, polyethylene, polyester, polyvinyl alcohol, etc. can be used. Among the,
When polyethylene terephthalate film is used, it is advantageous for laminating suitability, peeling suitability, light transmittance, and refractive index, and is inexpensive, does not become brittle, has excellent solvent resistance, and has high tensile strength. Easy to use. The thickness is preferably 1 to 100 μm.

The photosensitive resin composition may be provided on the carrier film by a roll coater, a comma coater, a gravure coater, an air knife, a die coater, a bar coater or the like. When the photosensitive resin composition containing the gelling agent is liquid at room temperature, the mixture is applied at the same temperature as room temperature or slightly heated to apply the solution, and the solvent is dried to form the photosensitive resin layer as a carrier. Provided on the film. When the photosensitive composition containing the gelling agent is solid at room temperature, it is heated under stirring until it reaches a required viscosity, and in that state, it is applied by the above-mentioned application method or it is cast to form a film. Can be formed. If the photosensitive resin composition is solvent-free, the photosensitive resin layer is formed only by cooling. The thickness of the photosensitive resin layer is preferably about 1 to 100 μm.

The dry film photoresist of the present invention may be coated with a protective film, if necessary. The protective film is provided to prevent oxygen inhibition and blocking of the photosensitive resin layer, and is provided on the photosensitive resin layer opposite to the carrier film. As the protective film, one having a smaller adhesive force between the photosensitive resin layer and the protective film than the adhesive force between the photosensitive resin layer and the carrier film is preferable, and one having a small fish eye is preferable. Examples thereof include polyethylene film and polypropylene film.

The application of the dry film photoresist of the present invention depends on the photosensitive resin composition used, but it can be applied to both circuit formation and solder mask use. Further, as long as it is for forming a circuit, any of a subtractive method, a semi-additive method, a full-additive method, and a dry film used in a plating method may be used. Among them, especially for circuit formation, it can be usefully used in the subtractive method.

The temperature for forming a sol in the method for producing a printed wiring board of the present invention is a temperature at which the photosensitive resin composition becomes a liquid, and is a combination of the selected photosensitive resin composition and a gelling agent or The amount varies from 60 to 15
0 ° C is preferred. If the temperature is lower than 60 ° C, there is no resistance to a developing solution or an etching solution, and if the temperature is 150 ° C or higher, the laminating efficiency is poor and the carrier film, the circuit-forming substrate and the circuit-formed substrate are deteriorated.

The circuit-forming substrate in the method for producing a printed wiring board of the present invention is an electrically insulating substrate provided with a metal conductive layer, and a paper-based phenol resin or a glass-based epoxy resin is used as a metal. A typical example of the conductive layer is a copper foil or the like bonded together. Examples of these substrates are described in "Printed Circuit Technology Handbook" (edited by Japan Printed Circuit Industry Association, published in 1987, published by Nikkan Kogyo Shimbun), and desired substrates can be used. The thickness of the electrically insulating substrate is about 60 μm to 3.2 mm,
The material and thickness of the printed wiring board are selected depending on the final use form. Further, it may be a shield plate formed by stacking circuits. Various thicknesses can be used for the metal conductive layer, and generally 12 to 35 μm is used. Examples of the metal used for the metal conductive layer include copper, silver, aluminum, stainless steel, nichrome, and tungsten. Before laminating the dry film photoresist, pretreatment such as buffing, jet scrubbing, belt sander polishing, and pickling is performed.

The laminating method relating to the method for producing a printed wiring board of the present invention does not cause unevenness in the photosensitive resin layer and does not mix air or dust between the layers.
Any method may be used as long as the photosensitive resin layer can be provided without waviness. For example, a device that presses a rubber roll with pressure to perform lamination may be used. At this time, the rubber roll is heated to a temperature at which the photosensitive resin layer becomes a sol or higher, and the pressure, the conveyance speed, and the rubber roll temperature are adjusted.

The method for cooling to a gelling temperature in the method for producing a printed wiring board of the present invention may be stored at room temperature or may be used in combination with a roll device for cooling after laminating or a blower.

As a method of exposing a circuit pattern relating to the method for producing a printed wiring board of the present invention, a xenon lamp,
High-pressure mercury lamp, low-pressure mercury lamp, ultra-high-pressure mercury lamp, reflective image exposure using UV fluorescent lamp as a light source, one side using photo tool,
Examples include double-sided contact exposure, proximity method, projection method, and laser scanning exposure. When performing scanning exposure, a laser light source such as a He-Ne laser, a He-Cd laser, an argon laser, a krypton ion laser, a ruby laser, a YAG laser, a nitrogen laser, a dye laser and an excimer laser is used according to the emission wavelength. The exposure can be performed by wavelength conversion and scanning exposure, or by scanning exposure using a liquid crystal shutter or a micromirror array shutter.

The developing method relating to the method for producing a printed wiring board of the present invention uses a developer suitable for the photosensitive resin composition, removes unnecessary portions as a resist pattern, and forms a resist layer composed of the photosensitive resin layer. This is a step of forming a circuit pattern. As the developing solution, an aqueous alkali solution is usefully used and contains a water-soluble basic compound, and examples thereof include alkali metal silicates, alkali metal hydroxides, phosphoric acid and alkali metal carbonates, phosphoric acid and ammonium carbonate salts, and the like. Inorganic basic compounds, organic basic compounds such as ethanolamines, ethylenediamine, propanediamines, triethylenetetramine, and morpholine can be used. The above basic compounds can be used alone or as a mixture. Generally, a weak alkaline aqueous solution such as a sodium carbonate aqueous solution is used.

In the method for producing a printed wiring board of the present invention,
The exposed metal conductive layer other than the resist pattern portion is removed by etching. In the etching process, "Printed Circuit Technology Handbook" (edited by the Japan Printed Circuit Industry Association,
The method described in 1987, published by Nikkan Kogyo Shimbun) can be used. The etching liquid may be one that can dissolve and remove the metal conductive layer, and at least the photosensitive resin layer has resistance. Further, the liquid temperature needs to be lower than the temperature at which the sol is formed. Generally, when a copper layer is used for the metal conductive layer, an aqueous solution of ferric chloride, an aqueous solution of cupric chloride or the like can be used.

After the etching step, the resist pattern can be removed by treating it with a solution stronger than the developing solution used in the development. Generally, an aqueous solution of sodium hydroxide or the like is used, but similarly in the present invention, a solution suitable for the photoresist to be used is also used. Further, if necessary, methyl ethyl ketone, dioxane, methanol, ethanol, propanol and the like can be used.

[0029]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example A negative photosensitive resin composition was prepared according to Table 1. Then, as a gelling agent, 12-hydroxystearic acid, benzylidenesorbitol, N-laurolyl-L-
Glutamic acid- [alpha]. [Gamma] -di-n-butyramide was added to the photosensitive resin composition 100 at a mass ratio of 3, 3, and 3 and stirred to be dissolved. The solution thus obtained was applied onto a carrier film of polyethylene terephthalate (PET) having a thickness of 38 μm and dried to prepare a dry film photoresist having a photosensitive resin layer of 15 μm.

[0031]

[Table 1]

Next, a double-sided copper clad laminate (area: 340 mm × 5)
10 mm, copper foil thickness 18 μm, base material thickness 0.2 mm, Mitsubishi Gas Chemical Co., Ltd., CCL-E170) are uniformly observed with a microscope to find 20 dents or scratches, which can be distinguished even after etching. The coordinates were recorded like this. Next, the dry film photoresist prepared as described above was heated to 150 ° C. using a simple laminating device to laminate the dry film on the double-sided copper clad laminate and cooled to form a photosensitive resin layer.

Next, exposure was carried out by a contact UV exposure machine using a photo tool having a wiring pattern of 75 μm line width, the PET film was peeled off, and then a 1% by mass sodium carbonate aqueous solution (liquid temperature 35 ° C.) was used. By performing alkali development in (1), the photoresist layer other than the exposed portion was removed to form a resist pattern. Further, the substrate on which the resist pattern was formed was treated with a ferric chloride solution (40 ° C., spray pressure: 3.0 kg / cm ² ) to remove the copper layer in the portion not covered with the resist pattern. Then 4
It was treated with a 3.0% by mass sodium hydroxide solution at 0 ° C. and the remaining resist layer was removed to obtain a printed wiring board.

The printed wiring board thus obtained was inspected using AOI (PI-7800 manufactured by Dainippon Screen Mfg. Co., Ltd.), and the detected defects were observed with a microscope. The number of defects was about 1 / m ² .

Comparative Example Based on Table 1, a negative photosensitive resin composition was prepared. No gelling agent was added. This solution was applied onto a polyethylene terephthalate carrier film having a thickness of 38 μm and dried to prepare a dry film photoresist having a photosensitive resin layer of 15 μm.

Next, a double-sided copper clad laminate (area: 340 mm × 5)
10 mm, copper foil thickness 18 μm, base material thickness 0.2 mm, Mitsubishi Gas Chemical Co., Ltd., CCL-E170) was uniformly observed with a microscope in the same manner as in Example 1 to obtain 20 dents or scratches.
The spots were found and the coordinates were recorded so that they could be identified even after etching. Next, the dry film photoresist prepared as described above was heated to 150 ° C. using a simple laminating device to laminate the dry film on the double-sided copper clad laminate and cooled to form a photosensitive resin layer.

Next, exposure was carried out with a contact UV exposure machine using a photo tool having a wiring pattern of 75 μm line width, the PET film was peeled off, and then a 1% by mass sodium carbonate aqueous solution (liquid temperature 35 ° C.) was used. By performing alkali development in (1), the photoresist layer other than the exposed portion was removed to form a resist pattern. Further, the substrate on which the resist pattern was formed was treated with a ferric chloride solution (40 ° C., spray pressure: 3.0 kg / cm ² ) to remove the copper layer in the portion not covered with the resist pattern. Then 4
It was treated with a 3.0% by mass sodium hydroxide solution at 0 ° C. and the remaining resist layer was removed to obtain a printed wiring board.

The obtained printed wiring board was inspected using AOI (PI-7800 manufactured by Dainippon Screen Mfg. Co., Ltd.) and the detected defects were observed with a microscope. The number of defects was about 10 / m ² . Moreover, when it was confirmed whether the generated open defects corresponded to the dents or scratches whose coordinates were recorded at the first stage, it was found that about 90% or more were defects derived from the unevenness.

[0039]

As described above, the dry film photoresist of the present invention satisfactorily follows the dents and scratches on the circuit-forming substrate, thus providing a good printed wiring board with few defects. it can.

Claims (2)

[Claims] 1. A dry film photoresist in which a photosensitive resin layer containing a gelling agent is provided on a carrier film in a photosensitive resin composition. 2. A photosensitive resin layer is laminated on a circuit-forming substrate with a dry film photoresist heated to a temperature at which the photosensitive resin layer becomes a sol or higher, and the photosensitive resin layer is cooled to a temperature at which the photosensitive resin layer gels. A method for producing a printed wiring board, which comprises: forming a resist pattern on a circuit pattern by exposing the circuit pattern to light, developing the resist pattern, and etching away the metal conductive layer other than the resist pattern portion.