JPH043062A - Photosensitive resin composition and formation of conductive pattern - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of plating without roughening by dissolving a photosensitive resin and a metal salt into a common solvent, thereby forming the above compsn. CONSTITUTION:The photosensitive resin compsn. is prepd. by dissolving the photosensitive resin and the metal salt into the common solvent. The photosensitive resin to be used is not limited in its kinds and types, insofar as this resin is soluble in the common solvent for the metal salt and has affinity to the metal salt. The inorg. metal salts which develop plating catalyst activity by being reduced to metal by the reducing agent and are soluble in the common solvent for the photosensitive resin are adequate as the metal salt to be used. The kinds of the photosensitive resin and metal salt to be used are properly selected in this way. The adhesive strength, hardness, plating catalyst activity, etc., of the primary coating film for plating obtd. in such a manner are adjusted according to purposes in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photosensitive resin composition for forming a conductive pattern and a method for forming a conductive pattern.

Conductive patterns are used as printed wiring boards, electrodes, heating elements, and the like.

Conventional technology Conventional methods for forming conductive patterns include (1) printing a conductive paste, and (2) a sub-travel method using a copper-clad laminate as a starting material and removing unnecessary portions by etching to leave a conductive pattern. Typical examples include the additive method, and (3) the additive method in which a plating resist (negative) is formed on the substrate and selective plating is applied to other parts.

However, method (1) has low conductivity, poor paste adhesion, low pattern accuracy, and high cost, and is not practical for conducting through holes in the field of printed circuit boards. , there are problems such as poor soldering heat resistance of the paste.

In addition, method (2) has problems such as a complicated process, being unsuitable for fine pattern formation, and poor plating adhesion at the through-hole area, and it seems that the process of rationalization has already reached its limit.

In addition, method (3) eliminates the need for etching away unnecessary parts, and responds to the demands for higher interconnect density and higher interconnect reliability; Because the resin layer is not patterned, its insulation properties are low.
Furthermore, it is difficult to obtain fine patterns, the substrate also contains a catalyst, which results in poor insulation properties, poor physical properties such as strength, high catalyst cost, low plating adhesion, and There were problems such as the need for roughening.

Problems to be Solved by the Invention The purpose of the present invention is to improve the additive method.
The purpose is to improve the adhesion of plating, simplify the process, and improve pattern accuracy without causing roughening.

Means for Solving the Problems The method for forming a conductive pattern of the present invention includes a photosensitive resin composition in which a photosensitive resin and a metal salt are dissolved in a common solvent, and this solution is applied to a base material of a desired shape, and after prebaking, When forming a desired pattern by sequentially performing exposure, development, and post-bake, the metal salt is treated with a reducing agent in the step after the pre-bake, and electroless plating is performed on the metal salt using the reduced metal as a catalyst. This is a method of forming a conductive pattern.

This will be explained in detail below.

The base material of the present invention is selected depending on the intended use and is not particularly limited. Examples include copper-clad laminates, metal plates, plastic plates, plastic films, and ceramic plates.

The photosensitive resin used in the present invention can be used regardless of its type and type (neutral type, positive type) as long as it is soluble in a common solvent with the metal salt and has an affinity for the metal salt. Examples of photosensitive resins that can be used include those commonly used as photosensitive resins, such as photosensitive polyimide, novola added with a photosensitizer, resin, cyclized natural rubber, cyclized synthetic rubber, polysilane late vinyl, polysilane, etc. Examples include methyl isopropenyl ketone, polyvinylphenol, polyvinyl-p-azidobenzoate, polymethacryloyloxybenzalacetophenone, and polyvinyl alcohol.

The gold metal used in the present invention exhibits plating catalytic activity by being reduced to metal by a reducing agent as described below, and is soluble in a common solvent with the photosensitive resin as described above. Organic or inorganic, especially inorganic metal salts are suitable. It is preferable that such metal salts are stable against the atmosphere or moisture. Examples include sulfates, nitrates, chlorides, and organic salts (eg, acetate group) of metals in Group Ib and Group III of the Periodic Table of the Elements, such as platinum and gold.

These metal salts can be used alone or in a mixture of two or more.

The ratio of these metal salts to the photosensitive resin can be varied over a wide range depending on the physical properties required for the plating base coating, the type of metal salt, etc.
5 to 100 parts by weight per 00 parts by weight is preferred.

Common solvents for both photosensitive resins and metal salts include, for example, chloroform, methylene chloride, trichloroethylene, tetrachloroethylene, benzene, toluene,
xylene, acetone, ethyl acetate, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, N
- A single or mixed solvent such as methylpyrrolidone is used. It is selected appropriately depending on the combination of photosensitive resin and metal salt used. The amount of solvent used for the photosensitive resin is selected so that it has appropriate viscosity and fluidity and is suitable for coating on molded articles.

A coating film containing a metal salt is formed by applying a solution consisting of a photosensitive resin, a metal salt, and a solvent to a base material (top) of an arbitrary shape. For application, a usual application method such as coating, spray painting, or dipping is selected depending on the shape of the substrate.

Further, the coating film is formed under conditions (temperature, 5 hours) that are determined depending on the type of photosensitive resin, strength, coating film thickness, etc. The coating is usually performed at a nonvolatile content concentration of 5 to 20% by weight.

A mask (negative or positive film) is placed in close contact with the coating film obtained in this way and light is irradiated.The amount of exposure at this time is determined based on the photosensitive resin composition used and the amount necessary for patterning. Based on the sufficient amount, the amount can be adjusted as appropriate depending on the purpose.

After exposure, the coating M is patterned by developing it using a special developer, but unnecessary parts (unexposed parts in the case of a negative type) do not necessarily need to be removed by dissolving the entire resin; A desired conductive pattern can also be formed by diffusing and removing only the oxide.

Reduction processing is usually performed after post-bake (cure), but
It may be performed after each step of blibeta, exposure, and development.
By treating with a reducing agent, the metal salt in the coating film is precipitated intensively on the surface, forming an integrated reduced metal (plating catalyst) layer that is partially embedded in the coating film. Since it is integrated into the coating film, the plating adhesion is extremely good, and since the metal is precipitated and protruding from the surface, there is no need to perform roughening as in the conventional additive method.

The reducing agent used in the present invention is one that can reduce metal salts to metals, such as FeSO4, sodium hypophosphite, sodium borohydride, aminoporan, dimethylamineporan, hydroxylamine sulfate, and hydrosulfide. These reducing agents are usually used as an aqueous solution, but there is no limitation as long as the solvent system can dissolve the reducing agent.The concentration of the reducing agent in the reducing agent solution can be changed as appropriate depending on the purpose of use, but o, About oi to 2o weight%, preferably 0.0
It is 5 to 10% by weight, more preferably 0.1 to 7% by weight.

This reduction can be easily carried out by immersing the base material having the coating film containing the metal salt in the reducing solution for an appropriate time, or by spraying the reducing solution.

The reduction temperature is preferably about room temperature to 80° C., and the contact time with the reducing agent solution is suitably about several tens of seconds to more than ten minutes. The coating film may be preheated before reduction.

The solvent in the coating film may be completely removed before reduction, or some portion may remain. In the case of a coating film from which the solvent has been completely removed, the temperature of the reducing solution may be raised slightly, or It is preferable to preheat the coating film before reduction.Preheating improves reduction efficiency.Reduction is usually carried out until at least the metal salts present in the surface layer are almost completely reduced, but it is not necessary. You may stop midway depending on your needs.

The plating-based pattern is transferred to an electroless plating process to become a desired metal conductive pattern. For electroless plating, a commonly used method may be selected depending on the purpose, and typical examples include Xi plating and Cu plating.

In the method of the present invention, patterning (
By changing operating conditions such as exposure, development) conditions, reducing agent treatment conditions, etc., the adhesion strength, hardness, plating catalyst activity, etc. of the resulting plating base coating film can be adjusted according to the purpose.

Next, the present invention will be specifically explained with reference to Examples.

Examples Example 1 Negative photosensitive polyimide “Lithocoat PI” manufactured by Ube Industries
-400J for 100 parts (all parts by weight),
CoCQ2 ・8H2024, 75 copies, PdC120,
25 parts were added and dissolved in N-methylpyrrolidone (NMP) solution to form a mixed solution (resin concentration 5 wt%).

This mixed solution was applied to the “SANE/<-B” formed on a glass plate.
After coating on a film of 410J (polyimide varnish made by Yasan Kagaku Kogyo), it was prebaked (dried) at 65°C for 2 hours. A stainless steel mask was placed in close contact with the prebaked coating (5IL) and exposed to a mercury lamp (ultraviolet light). (exposure amount '''cm2) Rinsing was performed for 1 minute each in an ethanol solution containing 5% methyl-2-pyrrolidone (second stage; ethanol).

The obtained pattern was heat treated at 160°C for 30 minutes and at 230°C for 30 minutes, then immersed in a 0.5% sodium borohydride aqueous solution for 5 minutes for reduction treatment, washed with water, and treated with Ni plating solution RS880J (50°C) manufactured by Nippon Kanigen. immersed in it for 5 minutes.

Nickel gradually began to precipitate about 300 seconds after immersion in the plating solution, and after 5 minutes, a conductive pattern with metallic luster was formed.

The surface resistance of the conductive part was 100Ω/mouth, and the mask part showed insulation. Adhesion and pattern accuracy were also good.

Example 2 A pattern (plating base) was obtained under the same conditions as in Example 1 except that the reduction treatment was performed after development and rinsing. This was similarly immersed in the Ni plating solution for 3 minutes. Nickel began to precipitate from the entire surface of the pattern at the same time about 5 seconds after immersion, and a similar conductive pattern was formed after 3 minutes. The surface resistance of the conductive part was 1097, and the mask part showed insulation. Adhesion and pattern accuracy were also good (If).

Example 3 The plating base pattern obtained in Example 2 was immersed in a copper plating solution (room temperature) manufactured by Meltex (Enplate cu-406J) for 3 minutes. Copper begins to precipitate about 5 seconds after immersion,
After 3 minutes, a conductive pattern with copper luster was obtained. The surface resistance of the conductive part was 1Ω/hole, and the mask part showed insulation. Adhesion and pattern accuracy were also good.

Example 4 A curved plate printing mask (
Negative film) was placed in close contact with the film, sandwiched between Pyrex glass plates, and exposed to light using a metal halide lamp (exposure amount: 2J).
/e+w2). After exposure, ultrasonic development was performed in a special developer for 3 minutes to obtain a pattern. Thereafter, the pattern was nickel plated under the same conditions as in Example 2. A pattern with a line width of 50 mm or more had a clear conductive pattern and good conductivity.

Example 5 N1CQ□Fist eH,o
25 PHR was added and dissolved in a dimethylformamide (DMF) solution to form a mixed solution. This mixed solution was applied onto a glass epoxy substrate and prebaked at 70° C. for 30 minutes to form a coating film.

A mask was tightly attached to this coating film, and it was exposed to light using a mercury lamp (exposure amount I J/cm2). After exposure, a dedicated developer rN-
It was developed in AsJ (alkaline aqueous solution system, 25° C.) for 3 minutes by the immersion rocking method.

After rinsing (washing with water) the obtained pattern, 120℃30
Post-baking was performed for 1 minute, followed by immersion in a 0.5% sodium borohydride aqueous solution for 3 minutes to reduce the metal salt and form a plating base. Thereafter, nickel plating was performed under the same conditions as in Example 1 to obtain a conductive pattern. Adhesion and pattern accuracy were also good.

Example 6 CoC22@8H2 was added to the novolac resin positive etching resist rPMERP-DF40SJ manufactured by Tokyo Ohka Co., Ltd.
0 was dissolved in a DMF solution to form a mixed solution. This mixed solution was applied on a glass plate and heated at 90°C3.
A coating film was formed by prebaking for 0 minutes. A mask was closely attached to this coating film, and it was exposed to light using a mercury lamp (exposure amount IJ/cm
2).

After exposure, development was carried out for 3 minutes in a dedicated developer r P-1sJ (alkaline aqueous solution system, 25° C.) using the immersion rocking method.

After rinsing the obtained pattern, +40”01
Post-baking was performed for 0 minutes, followed by immersion in a 0.5% sodium borohydride aqueous solution for 3 minutes to reduce the metal salt and form a plating base. Thereafter, copper plating was performed under the same conditions as in Example 3 to obtain a conductive pattern. Adhesion and pattern accuracy were also good.

Effects of the Invention The present invention makes it possible to obtain a conductive pattern by a simple method. The conductive (plating) layer uses a catalyst layer integrated with the photosensitive resin coating as the plating base, so it does not roughen the base material, but it peels off easily like conventional electroless plating layers. There is no need to worry; coating, development, reduction, and plating can be done by dipping, and there are no restrictions on the shape or size of the substrate to be processed. I can do something.

Further, since it is easy to adjust the adhesion strength, hardness, plating catalyst activity, etc. of the plating base coating film according to the purpose, various metal platings are possible. However, since plating and plating can be performed at relatively low temperatures (room temperature to 90°C), there is little risk of adverse effects on the original physical properties of the coating film.

Furthermore, in the case of a negative photosensitive resin (for example, photosensitive polyimide), if only the metal salt is removed from the unexposed areas before development, it can be used as is as an insulating coating. This is also effective in forming (ultra)fine patterns and maintaining coating film adhesion.

Representative Patent Attorney Masaaki Ii Procedural amendment September j9, 1990

Claims (5)

[Claims] (1) A photosensitive resin composition comprising a photosensitive resin and a metal salt dissolved in a common solvent. (2) A photosensitive resin composition in which a photosensitive resin and a metal salt are dissolved in a common solvent is (a) applied to a base material, (b) prebaked,
(c) Exposure, (d) Development, and (e) Post-bake are performed sequentially to form a desired pattern.
), (c), (d), and (e), a reduction treatment is performed, and then electroless plating is performed. The method according to claim (2), wherein (3) the reduction treatment is performed after the (d) development step, and is performed by immersion in an aqueous solution in which a reducing agent is dissolved. (4) The composition according to claim (1), wherein the metal salt is a salt of a metal selected from Group Ib and Group VIII of the Periodic Table of the Elements. (5) The method according to claim (2) or (3), wherein the metal salt is a salt of a metal selected from Group Ib and Group VIII of the Periodic Table of the Elements.