JPH03180476A - Electroless nickel plating method - Google Patents

Abstract

PURPOSE:To enable the adsorption of an Sn-Pd activator on a substrate and to perform uniform electroless nickel plating on the substrate by previously adsorbing a quat. ammonium type surfactant on the surface of the substrate with a formed positive type photoresist layer having a prescribed pattern. CONSTITUTION:A positive type photoresist layer having a prescribed pattern is formed on the surface of a substrate and at least one kind of surfactant selected among quat. ammonium type, betaine type, amine oxide type, aminocarboxylate type and polyoxyethylene alkylamine type is adsorbed on the surface of the substrate by dipping in an aq. soln. contg. about 0.001-2% of the surfactant. The surface of the substrate can be activated with an Sn-Pd activator and uniform electroless nickel plating is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electroless nickel plating method, and particularly to a method for electroless nickel plating on a substrate on which a positive photoresist layer having a predetermined pattern is formed. Regarding the method of application.

[Summary of the invention]

In the present invention, the surface of a substrate on which a positive photoresist layer having a predetermined pattern has been formed is coated with quaternary ammonium-based, betaine-based, amine carboxylate-based, amine acetate-based, and polyoxyethylene alkyl amines. By adsorbing at least one type of surfactant selected from the tin-based photoresist layer, the catalyst of the tin-palladium-based activator can be adsorbed onto the surface of the positive photoresist layer, and electroless nickel plating on the surface of the substrate can be achieved. This makes it possible to

[Conventional technology]

Unlike electrolytic plating, which involves an electrochemical reduction reaction of the metal on the surface of the cathode, electroless plating produces an autocatalytic reaction on the surface of the object to be plated by reducing metal ions with a reducing agent contained in a solution. This is a plating method in which metals (or alloys) are deposited directly. Electroless plating method is ■
By adsorbing an appropriate catalyst, metal can also be deposited on the surface of the conductive object. ■Metal can be deposited to a uniform thickness on the surface of any shape of the object to be plated, as long as it is in contact with the plating solution. It has excellent features such as: ■ produces a highly hard plating film with few defects; and ■ simple equipment and equipment. It is useful for forming circuit patterns in printed circuits, through-hole plating, and hard disk Formation of a non-magnetic base film on an aluminum-based substrate for
It is used in many technical fields to provide electromagnetic shielding for computer cases, etc.

One such field of application is the creation of master discs (stambars) for manufacturing optical discs. In the general master production process for optical discs, a photoresist is first coated on a substrate made of a polished glass plate, etc., and a photoresist with predetermined patterns such as signal focus and guide grooves is formed by selective irradiation with laser light and development. A metal master is created by shaping the resist layer, making it conductive, and electroforming.

In recent years, this metal master has been directly inserted into an injection molding machine and used as a stand bar. The electroless plating method is applied to the above conductor treatment,
By forming a metal film on the surface of a non-conductive photoresist layer, it becomes conductive and electroforming becomes possible. Here, other methods such as the vacuum single-layer method and the sputtering method may be considered as methods for the above-mentioned conductor treatment, but these methods require special equipment and therefore increase costs;
This method has problems such as poor productivity and the need for advanced drying techniques to dry the photoresist layer in advance. On the other hand, electroless plating allows the formation of metal films with fewer defects using inexpensive equipment, and there is no need to dry the object to be plated beforehand, resulting in improved reliability and
It is extremely practical in terms of economy, productivity, etc.

Several types of metals are known that can be deposited by electroless plating, but silver, copper, and nickel are used for the purpose of conductive treatment in the optical disk master production process mentioned above. is possible. Of these, silver and copper are easily reduced, so pretreatment for electroless plating is relatively easy. However, the metal film formed lacks hardness, so a metal master with this on the surface can be directly used as a standbar. When used, there is a risk that the pattern of the metal coating may be deformed by the injection pressure. If such a stand bar is used to manufacture an optical disc, deformation of the focus will occur, which will cause a deterioration of the CN ratio of the reproduced signal. Therefore, it can be said that nickel is most suitable for the above-mentioned purpose since it provides a metal coating with few defects and high hardness.

By the way, in general, in order to form a nickel film by electroless plating, a metal catalyst is held on the surface of the object to be plated as a pretreatment (activation treatment), and nickel is deposited using this as a nucleus. be exposed. As the metal catalyst, it is common to adsorb palladium colloid.

Conventionally, as a method for adsorbing colloidal palladium, the object to be plated is immersed in stannous chloride to adsorb tin ions, and then immersed in a palladium chloride/8 solution to reduce the palladium ions and form a colloid. Precipitation methods have been widely adopted. However, in this method, stannous chloride is converted to stannic chloride by air oxidation during treatment, and colloidal precipitates are likely to be generated during washing with water. This colloidal precipitate grows to a size that is visible to the naked eye, so when it is applied to the above-mentioned optical disc master production process that requires the formation of fine patterns, it can cause defects in the manufactured optical disc. This is not desirable because it causes Therefore, an alternative activation processing method is desired.

(Problem to be solved by the invention) On the other hand, in the field of general electroless nickel plating,
In order to prevent the formation of colloidal precipitates as described above, in recent years, tin-palladium activators containing both tin ions and palladium ions, so-called catalysts, have been increasingly used. In the catalyst, palladium is thought to exist in a state coated with a protective colloid of tin ions.

However, when performing electroless plating of nickel for the purpose of conductive treatment in the optical disc master production process, even if you try to adsorb the precious metal catalyst to the surface of the plated object using the catalyst described above, it will not work as a positive type. There is a problem in that the photoresist layer repels the catalyst, making it impossible to perform electroless plating.

Therefore, an object of the present invention is to provide a method that enables electroless nickel plating by successfully performing activation treatment using a catalyst even on a substrate having a positive photoresist layer.

[Means to solve the problem]

The present inventors conducted intensive studies to achieve the above object, and found that by adsorbing a surfactant having a specific molecular structure on the surface of a positive photoresist layer,
It has been found that the surface of the positive photoresist layer can also be successfully activated with a tin-palladium activator, making electroless nickel plating possible.

The electroless nickel plating method according to the present invention is proposed based on this knowledge, and the electroless nickel plating method according to the present invention is based on this knowledge. system, amine oxide system.

After adsorbing at least one type of surfactant selected from amine carboxylate-based and polyoxyethylene alkylamine-based surfactants, the substrate is subjected to activation treatment with a tin-palladium-based activator and placed in a true electrolytic nickel plating bath. It is characterized by being immersed.

First, the positive photoresist layer is formed of, for example, a naphthoquinone diazide photoresist, which is a typical example of a positive photoresist material. The naphthoquinone diazide photoresist has a phenol resin and naphthoquinone diazide, which is a photodegradable compound, as main components, and various commercially available products can be used in the present invention. This positive photoresist material is applied onto a substrate such as glass according to a conventional method, and is selectively exposed and developed to become a positive photoresist layer having a predetermined pattern.

Since this positive photoresist layer as it is will repel the tin-palladium activator used in the activation process, in the present invention a surfactant is adsorbed onto this surface. Examples of this surfactant include quaternary ammonium type, betaine type,
Amine oxide type.

Compounds selected from amine carboxylate salts and polyoxyethylene alkyl amines are used, and one type of compound may be used alone or several types of compounds may be used in combination.When used, An aqueous solution containing the above surfactant at a concentration of about 0.001 to 2% is prepared, and the object to be plated is immersed in the aqueous solution. If the concentration of the surfactant is less than the above concentration range, it will not be possible to obtain a surface modification effect sufficient to enable uniform adsorption of the tin-palladium active agent, and if the concentration is too high, the surfactant will The desired effect may not be obtained due to the formation of calyx cells. The immersion time, the temperature of the aqueous solution, etc. are not particularly limited, and may be set as appropriate.

After being immersed in an aqueous solution containing a surfactant, the object to be plated is washed with water to remove excess surfactant, and then subjected to an activation treatment using a tin-palladium activator in accordance with a conventional method to form electroless nickel. Plating is applied. The compositions of the tin-palladium activator and electroless nickel plating bath are not particularly limited, and in addition to those having the composition applied to -a, various commercially available products can be used.

[Effect]

The surfactants used in the present invention are all surfactants that have a positive charge on a quaternary nitrogen atom, an amino nitrogen atom, or a nitrogen atom that is coordinately bonded to an oxygen atom in the molecule. be. These substances have the property of being strongly adsorbed onto the surface of substances that generally have a negative surface charge, such as fibers, metals, glass, plastics, FL materials, etc., with the nitrogen atom or the vicinity of the nitrogen atom directed. Therefore, such a surfactant is well adsorbed onto a substrate to be plated in the present invention, that is, a substrate on which a positive photoresist layer having a predetermined pattern has been formed in advance.

The surface of the substrate on which the surfactant is adsorbed in this way is tin-
The affinity for the palladium-based activator is increased, and the palladium coated with the protective colloid of tin ions can be retained. As a result, even if the protective colloid is finally removed by acid or alkali, palladium is stably retained on the substrate, and nickel can be deposited using this as a nucleus in the presence of an appropriate reducing agent. .

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental results.

First, Table 1 shows the names and structural formulas of the surfactants used in each of the following Examples.

Table 1 Note that the polyoxyethylene alkylamines in Table 1 are represented by general formulas, where m is usually an integer of 5 to 20 and n
is selected as an integer from 12 to 18. In the following experiment m=5
．． Polyoxyethylene laurylamine with n=12 was used.

Example 1 In this example, when applying the present invention to the production of a stamper for manufacturing optical disks, the results of the present invention were as follows: This is a study of the effects.

First, a positive photoresist (manufactured by Hoechst) was placed on a polished 36 cm diameter disk-shaped glass substrate.

After coating (trade name AZ-1350) and drying it, a positive photoresist layer having a predetermined pattern was formed by selective exposure and development.

Next, this substrate was treated with 0% of each surfactant shown in Table 1 above.
．． After immersion in a 25% aqueous solution for 30 seconds, excess surfactant molecules were removed by washing with running water. With this process,
The surfactant molecules were uniformly adsorbed on the surface of the substrate.

Next, the above substrate was mixed with a mixture of 1 part of a tin-palladium activator in the form of a concentrated solution (manufactured by Sibgy Co., Ltd., trade name Catalyst 9F) diluted with 1 part of concentrated hydrochloric acid and 5 parts of pure water, and immersed for 1 minute overnight. and washed with running water.

Furthermore, in order to remove the protective colloid of tin ions and adsorb only palladium on the substrate surface, add 1 part of an acid accelerator (manufactured by Sibley, trade name: Accelerator 19) to a mixed solution diluted with 5 parts of pure water. It was immersed for 1 minute and washed with running water. Here, the tin-palladium-based activator was not repelled by the positive photoresist layer and adhered uniformly to the substrate surface, and the subsequent acid promoter treatment resulted in a state in which palladium was uniformly adsorbed.

The substrate was immersed for 1 minute in a plating bath (bath temperature: 35 to 40°C) filled with electroless nickel plating 'a (manufactured by Shipley Co., Ltd., trade name Niboji 1-468). This results in
A nickel film with a thickness of 0.3 to 0.4 mm was uniformly deposited on the surface of the substrate including the surface of the positive photoresist layer. The nickel coating did not peel off even in the subsequent electroforming process.

In addition, in the above-mentioned process, a similar effect was observed when the concentration of the aqueous surfactant solution was changed to 0.025% or 0.0025%, and a uniform nickel film could be deposited in either case.

Furthermore, in order to investigate the effect of the type of electroless nickel plating solution, similar experiments were conducted using five types of commercially available electroless nickel plating solutions and an electroless nickel plating solution prepared by the inventors. Ta.

The commercial products used here were manufactured by Shipley Co., Ltd., trade name: Niriroy 22; manufactured by Sibley Co., Ltd., Niposit 68; manufactured by Nishilight Co., Ltd., trade name: Meiko Nirex; manufactured by Canning Co., Ltd., trade name: Knife Os 3000; manufactured by Nippon Kanigen Co., Ltd.

The product name is Schema-5680.

In addition, the electroless nickel plating solution prepared by the present inventors (
The composition of pH=7.5) is as follows.

Nickel chloride 20 g/j! Sodium hypophosphite 15g/j! glycine
20g/j! Sodium succinate 25 g/l
Using these electroless nickel plating solutions, the bath temperature is 35℃.
When electroless nickel plating was carried out in both cases, a uniform nickel film (more precisely, a nickel film containing phosphorus, etc. in the reducing agent) was formed, and there was no particular effect of the type of plating solution. I understand.

Example 2 Manufactured by Tokyo Ohka Co., Ltd. as a positive photoresist material.

Example 1 described above except that the product name 0FPR-77 was used.
The experiment was conducted in the same way. In both cases, good nickel coatings were obtained.

Example 3 Manufactured by Kodak as a positive photoresist material.

An experiment was conducted in the same manner as in Example 1 above, except that KMPR820 was used and polyoxymethylene laurylamine was used as a surfactant at a concentration of 0.2%, and a good nickel film was obtained.

However, the desired effect could not be obtained with the other five types of surfactants shown in Table 1. This is considered to be due to the difference in the molecular structure of the positive photoresist materials. That is, the above-mentioned KMPR820 is a compound in which naphthoquinonediazide, which is a photosensitive group, is added to a novolak resin, whereas the above-mentioned AZ-1350 and 0
FPR-77 is different in that it is a mixture of novolak resin and naphthoquinonediazide, and it is thought that this is reflected in the surface properties of the positive photoresist layer and changes its affinity for surfactants.

Comparative Example An experiment similar to Example 1 or Example 2 above was conducted without using any surfactant, but although a nickel film was formed on the exposed portion of the glass substrate, A Z-1
No nickel film was formed on the surface of the positive photoresist layer made of 350 or 0FPR-77.

Furthermore, the concentration of the tin-palladium activator (manufactured by Shipley, trade name Catalis 19F) was increased to twice that of Example 1 and 3 times as high.
When the concentration of concentrated hydrochloric acid is twice that of Example 1, and when the concentration of electroless nickel plating solution (manufactured by Shipley, trade name Niposit 468) is twice that of Example 1. Similar experiments were conducted in each case, but no nickel film was formed on the surface of the positive photoresist layer in any case.

Therefore, it is clear that treatment with a surfactant is essential in order to perform uniform electroless nickel plating on the surface of a substrate having a positive photoresist layer as described above.

Although the above examples and comparative examples have been explained based on the premise of creating a stamper for manufacturing optical disks, the present invention is not limited to this, and the present invention is not limited to this. This method can be widely applied as a method for electroless nickel plating.

〔Effect of the invention〕

As is clear from the above explanation, by applying the electroless nickel plating method of the present invention, uniform electroless nickel plating can be performed on a substrate having a positive photoresist layer formed in a predetermined pattern in advance. I can do it. Moreover,
The present invention can be implemented with high productivity and high reliability using inexpensive equipment.

For example, if the present invention is applied to the creation of a stamper for manufacturing optical discs, a highly reliable stamper with a pattern that faithfully reflects minute patterns such as signal pits can be created.
Can be created economically.

Claims (1)

[Claims] A quaternary ammonium based,
After adsorbing at least one type of surfactant selected from betaine type, amine oxide type, amine carboxylate type, and polyoxyethylene alkylamine type,
An electroless nickel plating method comprising immersing the substrate in an electroless nickel plating bath after undergoing activation treatment with a tin-palladium activator.