JP2012072440A - Electroless plating method - Google Patents

Abstract

In an electroless plating method, good adhesion between plating and an object to be plated can be secured without using noble metals such as palladium and without using harmful agents such as chromic acid, and plating. To provide an electroless plating method capable of repeatedly using a liquid.
A step (1) of coating a polymer containing an organic residue in a side chain having an ability to reduce metal ions of a plating metal on the surface of an object to be plated, and the polymer is coated. A step (2) of depositing a partially reduced metal oxide of the metal ion in a solution containing the metal ion and not containing a reducing agent capable of reducing the metal ion on the surface of the object to be plated; A step (3) of reducing the partially reduced metal oxide to a plating metal having autocatalytic properties in a solution containing a reducing agent capable of reducing metal, and plating in an electroless plating solution on the surface of the object to be plated And a step (4) of forming a metal film.
[Selection figure] None

Description

  The present invention relates to an electroless plating method. The electroless plating method is suitable as an electroless copper plating method for electronic circuits and decorations.

  The electroless plating technique is widely used as a method for forming a plating film on the surface of an object having no electrical conductivity such as plastics and ceramics. In the field of electronic materials, when performing multilayer wiring to a wiring board, it is an indispensable technique as a plating technique for imparting conductivity to through holes and via holes for connecting between layers. Further, for the purpose of shielding electromagnetic waves generated from electronic devices and the like, electroless plating is also used on the inner surface of the case of electronic devices molded of plastic or the like. Furthermore, if a material having excellent moldability such as plastic is plated, an appearance having a metallic luster can be imparted to a molded product having a complicated shape, and it is widely used for decorative purposes. Furthermore, in various industrial products such as automobiles, parts that previously used metal have been replaced with plastics for the purpose of reducing weight and cost, giving a metal-like appearance. Electroless plating is performed for the purpose of giving a high-class feeling.

  However, electroless plating technology that has been widely used in the past requires adsorption of noble metal fine particles such as palladium as a catalyst for accelerating the electroless plating reaction on the surface of an object for which a plating film is desired to be formed (to-be-plated object). It was. As the method, the object to be plated is immersed in a tin-palladium colloidal dispersion to adsorb the colloid, and then the tin is dissolved and removed so that the palladium fine particles adhere to the surface. A method of immersing in a containing solution and subsequently depositing palladium by a reduction treatment is performed. However, since palladium is difficult to be dissolved and removed by the etching solution used when manufacturing the circuit board, it tends to remain between the wirings. For this reason, if the wiring interval is narrowed in order to increase the density of the circuit, there is a problem that insulation failure occurs due to the remaining palladium. Furthermore, since palladium is a rare metal, there are concerns about cost problems and stable supply. Therefore, an electroless plating method that does not use a noble metal catalyst such as palladium has been desired.

  Also, when electroless plating is performed on the plastic surface, a process is required to roughen the surface of the plastic with an oxidizing liquid containing chromium and manganese to improve adhesion, and the waste liquid discharged in this process contains harmful metals. Therefore, there were problems in terms of work environment and waste disposal.

For these problems, in Patent Document 1, after immersing an object to be plated in a solution containing cupric chloride (CuCl ₂ ) and stannous chloride (SnCl ₂ ) instead of palladium, the substrate is immersed in a solution containing a reducing agent. Thus, a method of reducing copper to form a catalyst nucleus has been proposed. In this method, since copper is attached instead of palladium as a catalyst, the catalyst nucleus can be easily dissolved and removed when the wiring board is formed, and the insulation reliability is improved. Further, since no precious metal is used, the cost can be reduced.

  Examples of the electroless plating method that does not use palladium include the method disclosed in Patent Document 2 and the method disclosed in Patent Document 3 and Non-Patent Document 1. In these methods, instead of roughening the surface with an oxidizing liquid, a material having excellent adhesion to plating or an object to be plated is coated. In these methods, there is an advantage that it is not necessary to roughen the plastic surface with an oxidizing liquid containing chromium or manganese by selecting a coating material such as a polymer having excellent adhesion to the object to be plated.

  Among these, in the method of Patent Document 2, a composition containing a powder obtained by pulverizing a cation exchange resin mixed with an acrylic resin or the like is applied to an object to be plated, and then a solution containing metal ions such as copper ions. So that the sulfonic acid group in the cation exchange resin can be held as a cation, and then reduced with a reducing agent such as sodium borohydride or dimethylaminoborane to deposit metal copper as a catalyst nucleus. Through the process, finally, electroless plating is deposited using a normal electroless plating solution.

On the other hand, in Patent Document 3 and Non-Patent Document 1, the polymer applied to the object to be plated is a polymer mainly composed of dopamine having a catechol skeleton, as in the polymer used in the present invention. In Patent Document 3 and Non-Patent Document 1, paying attention to the fact that mussels and the like contain a large amount of dopamine in the adhesive protein used to fix the body to various objects in the sea, polymers containing dopamine are included in various substances. It is said that it is possible to perform coating with good adhesion. These documents disclose that electroless plating is possible on the surface of the coated polymer. The method is to deposit a plating by immersing the object to be plated coated with the polymer in a plating solution in which dimethylaminoborane, copper (II) chloride (CuCl ₂ ) and sodium hydroxide are dissolved.

JP 2008-214706 A JP 2005-248220 A International Publication No. 2008/049108 Pamphlet

Haeshin Lee, Shara M. Dellatore, William M. Miller, Phillip B. Messersmith, SCIENCE, 318, p426-430 (2007)

The method described in the above patent document includes several problems.
In the electroless plating method described in Patent Document 1, when electroless plating is performed on a plastic such as an ABS resin, it is necessary to roughen the plastic surface with an oxidizing liquid containing chromium or manganese.

  In the method of Patent Document 2, since a cation exchange resin is used, there is a problem that resistance to an electroless plating solution which is generally strongly basic is inferior. In addition, since it has a strongly acidic group such as sulfonic acid, there is a possibility that the insulation reliability is lowered in an electronic material having a fine wiring pattern.

  Further, in paragraph 0015 of Patent Document 2, since the particle diameter of the ion exchange resin powder determined as a preferable range is 5 to 10 μm, the thickness of the coating film is thick. For this reason, when the surface of a to-be-plated object is a fine shape, there exists a problem that the shape of a plating surface becomes difficult to reproduce the surface shape of a to-be-plated object. Further, since the coating film contains a large amount of powder, the transparency of the coating film is impaired, and after plating is deposited on a transparent object to be plated, an appearance with metallic luster cannot be seen from the back surface.

As disclosed in Patent Document 3 and Non-Patent Document 1, when dimethylaminoborane, which is a strong reducing agent, and copper ions are mixed in the plating solution, the stability as the plating solution is poor, and It is a fact well known to those skilled in the art that copper is reduced and deposited regardless of the presence or absence of so-called plating solution decomposition. When the present inventors tried electroless plating with a plating solution similar to Patent Document 3 or Non-Patent Document 1 using a test piece in which a polymer containing a dopamine residue was applied to one side of a PET film, the first Nothing happened for about 30 minutes, after that many bubbles were generated from the plating solution, and the solution turned black. Thereafter, when the test piece was taken out, copper plating was deposited on both surfaces of the PET film, and further, plating was deposited on the inner surface of the glass container in which the plating solution was put.
Thus, although the copper plating is deposited by the methods described in Patent Document 3 and Non-Patent Document 1, it is not possible to selectively deposit the plating only on the surface of the polymer containing the dopamine residue. Moreover, even if it tried plating using the same liquid after this, since the plating solution was decomposed | disassembled, it was not able to deposit plating repeatedly.

  Such a plating method can be used only once and has little industrial value. In addition, the polymer containing a dopamine residue is useful for ensuring adhesion to an object to be coated, but in the plating solution described in Patent Document 3 and Non-Patent Document 1, the polymer has a dopamine skeleton. Since the contained catechol group is less reducible than dimethylaminoborane, it cannot exhibit reducibility with respect to metal ions, and it can be said that catechol is not substantially involved in the plating reaction.

  In the electroless plating method, the present invention can ensure good adhesion between the plating and the object to be plated without using a noble metal such as palladium and without using a harmful agent such as chromic acid, and The present inventors have studied to provide an electroless plating method that can repeatedly use a plating solution.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means described in the following (1) and (9). They are listed together with (2) to (8) which are preferred embodiments.
(1) A step of coating a polymer containing an organic residue in a side chain having an ability to reduce metal ions of a plating metal on the surface of the plated object, and a plated object coated with the polymer. A step of precipitating a partially reduced metal oxide of the metal ion in a solution containing the metal ion and not containing a reducing agent capable of reducing the metal ion; and a reducing agent capable of reducing the metal ion. A step of reducing the partially reduced metal oxide to a plating metal having autocatalytic properties in a solution containing the step of forming a coating film of the plating metal on the surface of the object to be plated in an electroless plating solution; Including electroless plating method,
(2) The electroless plating method according to (1), wherein the organic residue is a hydroquinone residue, a catechol residue or a pyrogallol residue,
(3) The electroless plating method according to (1) or (2), wherein the polymer is crosslinked,
(4) The electroless plating method according to any one of (1) to (3), wherein the content of the phenolic hydroxyl group of the organic residue is 4 mmol / g polymer or more.
(5) The electroless plating method according to any one of (1) to (4), wherein the plating metal is copper or nickel,
(6) The electroless plating method according to any one of (1) to (5), which is a step (3) in which a plating metal having autocatalytic properties covers a surface of an object to be plated by 5% or more. ,
(7) The absence of copper according to any one of (1) to (6), wherein the plating metal is copper, and the partially reduced metal oxide in the step (2) is Cu ₂ O. Electrolytic plating method,
(8) The electroless plating method according to any one of (1) to (7), including a step of patterning the polymer and forming a pattern film of the plating metal.
(9) A plated product in which electroless plating is deposited by the electroless plating method according to any one of (1) to (8).

  Unlike the electroless plating method conventionally used industrially, the electroless plating method according to the present invention can perform good electroless plating without using palladium which is a noble metal. For this reason, future resource supply anxiety can be solved at low cost. Furthermore, the problem of palladium remaining after etching, which has been a problem in the field of electronic materials, can be eliminated, and the insulation reliability can be improved. In addition, since the adhesion of the plating film to the object to be plated is obtained without performing a roughening process using toxic metals such as chromium, the work safety is high, and soil and water pollution due to leakage of waste liquid is achieved. It can be eliminated. For these reasons, it is extremely useful as an electroless plating method.

It is a graph which shows the relationship between pH of a solution containing a various reducing agent, and oxidation-reduction potential. An example (crystal structure) of an atomic force microscope (AFM) photograph showing an example in which particles of partially reduced oxide of copper are formed on the surface of an object to be plated in the plating method of the present invention is shown.

The present invention will be described in detail below.
The electroless plating method of the present invention comprises a step (1) of coating a polymer containing an organic residue having a capability of reducing plating metal ions on the surface of an object to be plated; A step (2) of precipitating a partially reduced metal oxide of the metal ion on a surface of the object to be plated in a solution containing the metal ion and not containing a reducing agent capable of reducing the metal ion; A step (3) of reducing the partially reduced metal oxide to a plating metal having autocatalytic properties in a solution containing a reducing agent capable of reducing the metal ions, and electroless plating on the surface of the object to be plated And (4) forming a plating metal film in the liquid.
Hereinafter, it demonstrates in order of these processes.

The first step of the electroless plating method of the present invention is the step (1) of applying a polymer containing an organic residue in the side chain having the ability to reduce metal ions of the plating metal on the surface of the object to be plated. It is. Hereinafter, a polymer containing an organic residue having a capability of reducing metal ions of a plating metal in a side chain is also referred to as a “reducing polymer”.
The reducing polymer used in the present invention is a polymer containing in the side chain an organic residue having the ability to reduce the metal ion of the plating metal. The organic residue having reducibility preferably has two or more phenolic hydroxyl groups in the benzene ring, and at least two of them are positions corresponding to the ortho or para positions relative to each other, such as a catechol or hydroquinone structure. More preferably, it is bonded to. The reason is that when two hydroxyl groups are bonded to each other at the ortho or para position, the reducing power is further increased. When two hydroxyl groups are bonded to each other at the meta position, such as resorcinol, the reducing power is weaker than ortho or para and cannot be used preferably. However, when three or more hydroxyl groups are bonded, two of them are bonded. May have a hydroxyl group that is in a meta positional relationship with other combinations, and if there are three or more hydroxyl groups, the reducing power may become stronger and preferable.

In the present invention, the organic residue in the polymer is preferably a hydroquinone residue, a catechol residue or a pyrogallol residue, and more preferably a pyrogallol residue.
In addition, regardless of whether the polymer is a homopolymer or a copolymer, the content of the phenolic hydroxyl group of the organic residue in the polymer is preferably 4 mmol / g polymer or more, and it is preferably 4 to 18.2 mmol / g polymer. More preferably.

The reducing polymer used in the present invention is preferably mixed with a cross-linking agent and subjected to a cross-linking reaction after coating or molding in order to achieve an object such as enhancing durability against plating chemicals. The crosslinking method and the crosslinking agent used are not particularly limited. For example, an epoxy compound can be preferably used as the crosslinking agent. In this case, the epoxy group contained in the epoxy compound and the phenolic hydroxyl group in the polymer react and are chemically crosslinked by a treatment such as heating. At this time, attention must be paid to the amount of the epoxy resin added. That is, because the phenolic hydroxyl group having reducing properties is consumed by the epoxy group, if too much epoxy resin is added, electroless plating cannot be performed in the process of the present invention. As a guideline for blending the epoxy compound, it is assumed that the epoxy group and the phenolic hydroxyl group have reacted 1: 1, and the amount of the remaining phenolic hydroxyl group is 4 mmol / g or more per solid content of the coating composition. It is preferable to prepare at 7 mmol / g or more.
As already described, the reducing polymer formed on the object to be plated is preferably crosslinked so that it can be processed without being dissolved in the solution used in the processing after step (2).

  As other crosslinking agents, isocyanate compounds can also be preferably used. The isocyanate group reacts with the phenolic hydroxyl group, but more easily reacts with the alcoholic hydroxyl group, so that the crosslinking reaction can be quickly performed by copolymerizing the monomer containing the alcoholic hydroxyl group with the polymer. It can be preferably used when the object to be plated is deformed at a high temperature. A monomer containing such an alcoholic hydroxyl group is not particularly limited, but a monofunctional hydroxy acrylate such as 2-hydroxyethyl (meth) acrylate or 3-phenoxy-2-hydroxypropyl (meth) acrylate is copolymerized. Can be used.

  In the present invention, there are preferably two means for disposing the reducing polymer on the surface of the object to be plated. That is, a method in which a reducing polymer is blended with a crosslinking agent as necessary and a solution diluted with a solvent is applied to the object to be plated, and a method in which the reducing polymer itself is blended with a crosslinking agent as necessary and molded. is there.

  The means for applying the reducing polymer used in the present invention to the object to be plated is not particularly limited. If the object to be coated is a flat surface such as a film, a coater or the like can be used. When applying to a complicated shape, a method using a spray, a method using a brush, etc., or directly immersing the object to be plated in a polymer solution or dispersion. The method of taking out can also be used.

  The molded product of the reducing polymer that can be used in the present invention is a method in which the reducing polymer to be plated is melted and poured into a mold to mold the object to be plated, and the solution is poured into the mold and dried to be plated. Such as a method of forming a product, a method in which a crosslinkable functional group is chemically bonded in a polymer, or a method in which a reducing polymer is cured by a method of crosslinking by adding a crosslinking agent, suspension polymerization, emulsion polymerization, etc. It is an object to be plated that contains a reducing polymer at least on its surface, which can be obtained by a method such as molding into fine particles by a method.

  In the step (2) in the present invention, the metal ion is contained in a solution that contains the metal ion on the surface of the object to be plated and does not contain a reducing agent that can reduce the metal ion. In which the partially reduced metal oxide is deposited.

In the present invention, the metal on which the plating film is deposited preferably has an autocatalytic ability for the electroless plating reaction. Such metal has the ability to promote oxidation of the reducing agent used in the electroless plating solution used in step (4), and a combination of a metal and a reducing agent that can exhibit autocatalytic activity depending on the type of reducing agent used. It is preferable that For example, when the reducing agent is sodium hypophosphite, gold, nickel, cobalt, and the like are known, and when formaldehyde is used, copper, gold, silver, and the like are known. Among these, copper and nickel are preferable. Autocatalytic property means that when the metal is reduced to zero valence, when it comes into contact with a plating solution containing a metal ion and a reducing agent, the catalytic reaction promotes an oxidation reaction in which the reducing agent is oxidized. A metal that undergoes an electroless plating reaction due to a mechanism in which it is reduced by electrons released from the agent and deposited as a plating film on its surface, and is widely known in the industry that specializes in plating.
In the present invention, the plating metal is preferably copper or nickel, and more preferably copper.

  The metal ion-containing solution used in the step (2) includes additives such as the above-mentioned metal ions having a self-catalytic property, a pH adjuster, a surfactant, and a chelating agent. Not included. The reason is that the reducing functional group bonded to the reducing polymer generally has a reducing power weaker than that of a reducing agent used in electroless plating, and therefore the liquid contains such a reducing agent. This is because the reduction reaction in the liquid has priority over the polymer surface. In this case, a small amount of reducing agent that does not inhibit the reaction of the metal ions on the polymer surface as a partially reduced metal oxide may be contained.

  As the metal ion-containing solution used in the step (2), a solution that does not contain a reducing agent can be used with respect to a plating solution used in normal electroless plating. Copper sulfate, copper chloride, etc. can be used as the copper ion source. These liquids contain a strong base such as sodium hydroxide as a pH adjuster, ethylenediaminetetraacetic acid (EDTA), a chelating agent such as citric acid, a surfactant, etc. for stably presenting copper ions at high pH. be able to.

  The temperature of the metal ion-containing solution used in the step (2) is not particularly limited, and a temperature range from 0 ° C. to 100 ° C. can be used, preferably 5 ° C. to 60 ° C., more preferably 10 ° C. to 40 ° C. ° C. The reducing polymer used in the present invention has a polyfunctional phenol or the like as a reducing functional group. When reducing metal ions with these functional groups, a condition of pH 11 or higher is preferable. The liquid temperature is preferably lower in the sense of reducing damage to the reducing polymer and the object to be plated used in the present invention, and the lower temperature is also preferable in the sense of suppressing change in the liquid concentration due to water volatilization. . Furthermore, according to the experiments by the present inventors, in step (2), although the reaction is faster when the temperature is higher, the reaction is sufficiently performed even at a room temperature of about 20 ° C. Therefore, except when working in a special cold place. For example, heating and cooling are not necessarily required.

  In the step (2), the metal ions are deposited on the surface of the reducing agent-containing polymer in the form of an oxide or the like reduced to zero or partially. If it is reduced to zero valence in this step, the step (3) is not performed, and the process can proceed to the electroless plating reaction step using the electroless plating solution in the step (4).

  If the partially reduced metal oxide of the metal ion is deposited by the step (2) and is not reduced to zero valence, it cannot act as a catalyst for electroless plating as it is. It is necessary to reduce the partially reduced metal oxide to a plating metal having autocatalytic properties so as to act as a catalyst nucleus for electroless plating in the step (4).

  The liquid used in step (3) is a solution containing a reducing agent, preferably an aqueous solution. This liquid may contain a pH adjuster, a surfactant and the like. As the reducing agent, it is preferable to use a reducing agent having an ability to easily reduce metal ions to be plated even when a metal (zero valent) having an autocatalytic action does not exist. As such a reducing agent, dimethylaminoborane, sodium borohydride and the like can be used. On the other hand, since the step (3) is a step for reducing the partially reduced metal oxide that has not been reduced to zero valence to zero valence, a metal having self-catalysis such as formalin and hypophosphite (zero valence) If no exists, a reducing agent that cannot easily reduce metal ions to be plated cannot be used. Moreover, it adjusts and uses it for suitable pH using a base and an acid with the combination of the metal to precipitate and a reducing agent.

  The above-mentioned dimethylaminoborane and sodium borohydride have a strong reducing power and have the ability to reduce metal ions without using a catalyst such as a metal having autocatalytic properties. When combined with a solution containing metal ions, the metal ions are reduced to decompose the plating solution, making it impossible to repeatedly use the plating solution. For this reason, it is hardly used as a reducing agent for electroless copper plating or electroless nickel plating solution. In the step (3) according to the present invention, the metal is brought into the liquid of the step (3) in a state of being deposited as a solid like oxide fine particles on the surface of the object to be plated, so even if these reducing agents are used. It can be used repeatedly without liquid decomposition.

  The temperature of the liquid used in the step (3) is not particularly limited, but generally the higher the temperature, the faster the reduction reaction. Therefore, the temperature is adjusted according to the type, pH, concentration, etc. of the reducing agent. In the case of dimethylaminoborane, the temperature is preferably about 30 to 80 ° C. With sodium borohydride, sufficient reducibility can be obtained even at 10 to 60 ° C.

  In the present invention, it is preferable that the plated metal having autocatalytic properties deposited in the step (3) covers 5% or more of the surface of the object to be plated. If the coverage is smaller than this, plating deposition may be too slow or may not deposit at all. Further, when the coating is 15% or more, it is possible to perform plating in a short time, so that damage to the reducing polymer and the object to be plated by the plating solution is reduced, and the applicable range of materials that can be plated is widened.

  In the step (4), the object to be plated which is reduced to zero valence through the step (2) or the steps (2) and (3) and deposits a metal having autocatalytic property against the electroless plating is electroless. It is a step of bringing electroless plating into contact with a plating solution.

  As the electroless plating solution used in the step (4), the same plating solution as that used when electroless plating is usually carried out after depositing palladium as a catalyst can be used. As typical plating solutions, copper sulfate and copper chloride can be used as a source of copper ions in electroless copper plating, and examples of using formalin and hypophosphite as reducing agents are widely known. It has been. These solutions can be added with a strong base such as sodium hydroxide as a pH adjuster, a chelating agent such as EDTA for allowing copper ions to stably exist at a high pH, a surfactant, and the like.

  Although the temperature of the liquid used at a process (4) is not specifically limited, Generally the same conditions may be sufficient as the electroless plating which uses palladium as a catalyst. In the case of formalin and other reducing agents, which are typical reducing agents for electroless copper plating, 30 to 80 ° C is preferable, and 40 to 70 ° C is more preferable. Within this temperature range, an appropriate plating rate can be obtained, and the plating solution can also be used stably.

  Between steps (2) to (4), by preventing the solution or plating solution used in each step from being mixed with the solution or plating solution in the subsequent step, the quality of the plating film is stabilized and each solution or plating solution is used. For the purpose of maintaining the number of times of use, it is preferable to include a washing step with water and the like, and a step of removing the washing liquid as necessary.

  When the solution used in step (2) is mixed with the solution in step (3), the metal ions brought into the solution in step (2) are reduced and waste the reducing agent, and the solution is repeated. This is not preferable because the number of times it can be used is reduced. In addition, it is not preferable that a cleaning liquid such as water is mixed with the solution in step (3) because the concentration of the liquid decreases during repeated use and the number of times the solution can be used repeatedly decreases.

  When the solution used in step (3) is mixed with the plating solution in step (4), the reducing agent brought into the plating solution used in step (4) reduces the metal ions in the plating solution in step (4). , Metal is deposited. Since decomposition of the liquid is promoted by the autocatalytic action of the deposited metal, it is preferable to prevent this. In addition, it is not preferable that a cleaning liquid such as water is mixed with the solution in step (3) because the concentration of the liquid decreases during repeated use and the number of times the solution can be used repeatedly decreases.

  Water is usually used for the cleaning liquid between such adjacent steps, and the cleaning method is not particularly limited as long as the above-described purpose can be achieved. For example, spraying by spraying or immersion in water can be performed. it can.

  The specific method of removing the cleaning liquid is not particularly limited. For example, the cleaning liquid can be naturally dropped by hanging or standing, or air can be blown to shorten the time required for the process. It is possible to perform a method such as attaching or squeezing between two rolls.

The electroless plating method according to the present invention can be used for electroless plating using a metal having autocatalytic properties.
In the present invention, on the surface of the object to be plated, once and a step of precipitating the Cu ₂ O, the step of reducing to a metallic copper having autocatalytic, the electroless plating method of the copper can be preferably performed.

  The electroless plating method of the present invention can include a step of patterning the reducing polymer, and a step of forming a patterned film of the plated metal. A known technique can be adopted for the patterning step. A desired pattern can be formed on the sheet-shaped workpiece using a photoresist in the layer of the reducing polymer formed in the step (1). Further, the reducing polymer can be oxidatively decomposed by pressing a reverse pattern of the target pattern against the reducing polymer layer.

  The electroless plating method of the present invention is different from the conventional method in which palladium is adsorbed on the surface of the object to be plated, and a reducing polymer film is formed on the surface of the object to be plated, and then the self-plating on the surface of the polymer. A metal having catalytic properties is deposited and used as a catalyst for electroless plating. Since palladium, which is a noble metal, is not used, there are advantages such as cost reduction and stable supply of resources. Further, when used in an electronic circuit, there is no palladium remaining between the circuits by the etching process, so that the reliability is improved. In addition, in plating on plastics, the adhesiveness is good without roughening with a liquid containing a harmful metal, so the influence on the environment is mitigated. Furthermore, since palladium is not used or a roughening step is not required, if one side of a transparent resin is plated, the metallic luster can be seen from the back side, and the design is improved.

  Hereinafter, the present invention will be described by monomer synthesis, synthesis of a reducing polymer, and examples.

(Example of production of dopamine (meth) acrylate)
Sodium borate (50.3 g, 0.25 mol), sodium bicarbonate (21.0 g, 0.25 mol) were added to a 1 L four-necked flask equipped with a stirrer, thermometer, dropping funnel, pH meter, and nitrogen gas blowing tube. Was dissolved in distilled water (500 mL) and bubbled with nitrogen gas for 30 minutes or more while cooling in an ice bath. To this buffer solution was added dopamine hydrochloride (25 g, 0.13 mol) and dissolved. A solution of acrylic acid chloride (15.6 mL, 0.195 mol) in dehydrated THF (tetrahydrofuran) (125 mL) was added dropwise from a 200 mL dropping funnel over about 2 hours so that the internal temperature was maintained at 30 ° C. or lower. During the dropwise addition, an appropriate amount of 1N sodium hydroxide aqueous solution was added so that the pH would not become 8 or less while observing the pH meter. The ice bath was removed after completion | finish of dripping, and it stirred at room temperature for 1 day. Nitrogen bubbling continued until the end of the reaction.

  After completion of the reaction, the reaction solution was filtered through a glass filter and washed with a small amount of distilled water. The filtrate was transferred to a 2 L separatory funnel, washed with ethyl acetate (3 × 200 mL), and the aqueous layer was collected. The aqueous layer was cooled in an ice bath and acidified (pH 2) by adding an appropriate amount of concentrated hydrochloric acid. Transfer again to a 1 L separatory funnel and extract with ethyl acetate (3 × 200 mL). The organic layer was washed with distilled water (200 mL) and saturated brine (200 mL), dried over anhydrous sodium sulfate, filtered, evaporated under reduced pressure while blowing nitrogen, and concentrated to about 100 mL. While vigorously stirring, n-hexane (900 mL) was added to precipitate crystals. Stirring was continued for 1 hour on an ice bath. The crystals were filtered through a glass filter, washed with a small amount of hexane, and the obtained solid was dried under reduced pressure to obtain 19.9 g (yield 74%) of dopamine acrylate.

  The acrylic acid chloride of the above Example was changed to methacrylic anhydride (23.0 mL, 0.146 mol) to synthesize methacrylate by the same operation (yield 21.5 g (yield 75%)).

(Polymer synthesis example 1: polydopamine acrylamide)
30 g of dopamine acrylamide was dissolved in 60 g of dimethylformamide in a four-necked flask having a capacity of 200 mL equipped with a stirrer, a dropping funnel, a cooler, and a gas blowing tube, and stirred for 2 hours while blowing nitrogen gas. Thereafter, the temperature was raised to 70 ° C., and while continuing stirring and nitrogen blowing, 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., product) from a dropping funnel to 10 g of dimethylformamide (Name V65) A solution in which 0.1 g was mixed was dropped over 1 hour. After the addition, the mixture was further stirred for 10 hours, and the heating and stirring were stopped. As a result, the reaction solution was slightly brown and the viscosity was increased. A homopolymer solution of polydopamine acrylamide was obtained. The content of the phenolic hydroxyl group was 9.65 mmol / g per solid content of the homopolymer.
200 g of methanol was added to this solution to dilute the polymer concentration to 10% by weight and used for the coating composition formulation of the examples.

(Polymer synthesis example 2)
To a 2 L four-necked flask equipped with a stirrer, a dropping funnel, a cooler, and a gas blowing tube, 15 g of dopamine acrylamide and 3-phenoxy-2-hydroxypropyl acrylate (product name, Aronix M5700, manufactured by Toagosei Co., Ltd.) ) 15 g was dissolved in 60 g of dimethylformamide and stirred for 2 hours while blowing nitrogen gas. Thereafter, the temperature was raised to 70 ° C., and while continuing stirring and nitrogen blowing, 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., product) from a dropping funnel to 10 g of dimethylformamide (Name V65) A solution in which 0.1 g was mixed was dropped over 1 hour. After the addition, the mixture was further stirred for 10 hours, heated, and the stirring was stopped. As a result, the reaction solution was colored slightly brown and the viscosity increased. A copolymer solution of dopamine acrylamide was obtained. The content of phenolic hydroxyl group was 4.83 mmol / g per solid content of the copolymer.
200 g of methanol was added to this solution to dilute the polymer concentration to 10% by weight and used for the coating composition formulation of the examples.

(Polymer synthesis example 3)
Dissolve 27 g of dopamine acrylamide and 3 g of 2-hydroxyethyl acrylate in 60 g of dimethylformamide in a 2 L four-necked flask equipped with a stirrer, dropping funnel, cooler and gas blowing tube, and stir for 2 hours while blowing nitrogen gas. did. Thereafter, the temperature was raised to 70 ° C., and while continuing stirring and nitrogen blowing, 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., product) from a dropping funnel to 10 g of dimethylformamide (Name V65) A solution in which 0.1 g was mixed was dropped over 1 hour. After the addition, the mixture was further stirred for 10 hours, and the heating and stirring were stopped. As a result, the reaction solution was slightly brown and the viscosity was increased. A copolymer solution of 27 g of dopamine acrylamide and 2-hydroxyethyl acrylate was obtained. The content of phenolic hydroxyl group was 8.69 mmol / g per solid content of the copolymer.
To the obtained polydopamine acrylamide copolymer solution, 200 g of dimethylformamide was added to dilute the polymer concentration to 10% by weight and used for the coating composition formulation of the examples.

(Polymer synthesis example 4)
30 g of dopamine methacrylamide was dissolved in 60 g of dimethylformamide in a four-necked flask with a capacity of 200 mL equipped with a stirrer, a dropping funnel, a cooler, and a gas blowing tube, and stirred for 2 hours while blowing nitrogen gas. Thereafter, the temperature was raised to 70 ° C., and while continuing stirring and nitrogen blowing, 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., product) from a dropping funnel to 10 g of dimethylformamide (Name V65) A solution in which 0.1 g was mixed was dropped over 1 hour. After the addition, the mixture was further stirred for 10 hours, and the heating and stirring were stopped. As a result, the reaction solution was slightly brown and the viscosity was increased. To the obtained polydopamine methacrylamide solution, 200 g of methanol was added to dilute the polymer concentration to 10% by weight and used for the coating composition formulation of the examples.

Below, the compounding example of the solution used by process (2)-(4) is described.
(Formulation example 1)
(Formulation example 1 of solution used in step (2))
Copper sulfate pentahydrate 7.5 g, ethylenediaminetetraacetate tetrasodium salt tetrahydrate 91.2 g, polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name PEG2000) 0.1 g, 2,2′-bipyridyl 0 0.02 g was put into a beaker and water was added to make 1 L. To this, sodium hydroxide was dissolved until the pH reached 12.5.

(Formulation example 2)
(Formulation example 2 of solution used in step (2))
3 g of cupric chloride dihydrate and 91.2 g of ethylenediaminetetraacetate tetrasodium salt tetrahydrate were placed in a beaker, and water was added to make 1 L. To this, sodium hydroxide was dissolved until the pH reached 12.5.

(Formulation example 3)
(Formulation example 1 of solution used in step (3))
35.5 g of dimethylaminoborane was placed in a beaker, and water was added to make 1 L. To this, sodium hydroxide was dissolved until the pH reached 12.5.

(Formulation example 4)
(Formulation example 2 of solution used in step (3))
2 g of sodium borohydride was placed in a beaker, and water was added to 1 L. To this, sodium hydroxide was dissolved until the pH reached 10.

(Formulation example 5)
(Example of formulation of solution used in step (4))
7.5 g of copper sulfate pentahydrate, 91.2 g of ethylenediaminetetraacetate tetrasodium salt tetrahydrate, 0.1 g of polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name PEG2000), 2,2′-bipyridyl 0 0.02 g was put into a beaker and water was added to make 1 L. To this, 16 mL of 20% formalin was added, and finally, sodium hydroxide was dissolved until the pH reached 12.5.

Example 1
1.5 g of bisphenol A type epoxy resin (trade name JER828, manufactured by Japan Epoxy Resin Co., Ltd.) having an epoxy equivalent of about 190 g / eq was added to 2.0 g of the polymer solution having a concentration of 10% by weight obtained in Synthesis Example 1. 0.56 g of an epoxy resin solution consisting of 0.015 g of methylimidazole, 9 g of methanol and 4.5 g of dimethylformamide was added and mixed by stirring to prepare a coating solution. This solution was applied to a PET film having a thickness of 50 μm with a bar coater, placed in an oven blown with nitrogen, dried at 110 ° C. for 1 hour, and a crosslinking reaction of polydopamine acrylamide with an epoxy compound was advanced. In this case, assuming that the epoxy group and the phenolic hydroxyl group had undergone a crosslinking reaction, the concentration of the remaining phenolic hydroxyl group was calculated to be about 8.2 mmol / g based on the solid content of the coating composition.

When electroless plating was carried out under the following conditions using the prepared test piece for plating, glossy copper plating was deposited only on the surface to which a polymer having reducibility was applied. It was confirmed that these solutions could be plated in the same manner even when used several times.
In Tables 1 to 8, the evaluation of the plating deposition property is represented by “◯” when plating is deposited on the entire surface, “Δ” when precipitation is partially observed, and “x” when no plating is deposited.

  The photograph of the particle | grains observed by expanding and observing with the atomic force microscope (AFM) about the test piece after passing through a process (3) is shown in FIG. In the photograph of FIG. 2, it can be observed that particulate substances having a diameter of about 10 nm are concentrated.

(Example 2)
1.5 g of bisphenol A type epoxy resin (trade name JER828, manufactured by Japan Epoxy Resin Co., Ltd.) having an epoxy equivalent of about 190 g / eq was added to 2.0 g of the polymer solution having a concentration of 10% by weight obtained in Synthesis Example 2. 0.56 g of an epoxy resin solution consisting of 0.015 g of methylimidazole, 9 g of methanol and 4.5 g of dimethylformamide was added and mixed by stirring to prepare a coating solution. This solution was applied to a PET film having a thickness of 50 μm with a bar coater, placed in an oven blown with nitrogen, dried at 110 ° C. for 1 hour, and a crosslinking reaction of polydopamine acrylamide with an epoxy compound was advanced. In this case, assuming that the epoxy group and the phenolic hydroxyl group had undergone a crosslinking reaction, the concentration of the remaining phenolic hydroxyl group was calculated to be about 3.8 mmol / g based on the solid content of the coating composition.

When electroless plating was carried out under the following conditions using the prepared test specimen for plating, the temperature was set higher than in Example 1, and the polymer having reducibility was applied by setting the time longer. A shiny copper plating was deposited only on the finished surface. It was confirmed that even when these solutions were used repeatedly several times, they could be similarly plated. In the table, the evaluation of the plating depositability is as described above. In this example, the surface of the test piece after the step (3) was observed with an AFM and the AFM image was observed under conditions where the plating deposition property was Δ and ○, respectively. It turned out that the size and the number of the fine particle precipitates increased as the mark became.
Moreover, when the area ratio in the image of the fine particle precipitate produced | generated by the process (3) of condition number 4 and 5 was calculated with the image processing software, they were 5.7% and 19.0%, respectively. Therefore, it was found that the deposition area of the fine particles is preferably 5% or more and more preferably 15% or more in order to deposit the plating.

(Example 3)
1.5 g of bisphenol A type epoxy resin (trade name JER828, manufactured by Japan Epoxy Resin Co., Ltd.) having an epoxy equivalent of about 190 g / eq with respect to 2.0 g of the polymer solution having a concentration of 10% by weight obtained in Synthesis Example 2; 1.4 g of an epoxy resin solution consisting of 0.015 g of 2-methylimidazole, 9 g of methanol and 4.5 g of dimethylformamide was added and mixed by stirring to prepare a coating solution. This solution was applied to a PET film having a thickness of 50 μm with a bar coater, placed in an oven blown with nitrogen, dried at 110 ° C. for 1 hour, and a crosslinking reaction of polydopamine acrylamide with an epoxy compound was advanced. In this case, assuming that the epoxy group and the phenolic hydroxyl group had undergone a crosslinking reaction, the concentration of the remaining phenolic hydroxyl group was calculated to be about 2.8 mmol / g based on the solid content of the coating composition.

  When electroless plating was carried out under the following conditions using the prepared test specimen for plating, the temperature was set higher than in Example 2, and the polymer having reducibility was applied by setting the time longer. A shiny copper plating was deposited on a part of the finished surface. Furthermore, there is a possibility that the plating is deposited on the entire surface by taking time, but since it takes too much time industrially, the conditions were not examined any more. It was confirmed that even when these solutions were used repeatedly several times, they could be similarly plated.

Example 4
0.03 g of a solution having an isocyanate content of 13.2% and a solid content concentration of 75% (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 2.0 g of the polymer solution having a concentration of 10% by weight obtained in Synthesis Example 3. Then, 0.2 g of dimethylformamide was added and mixed by stirring to prepare a coating solution. This solution was applied to a PET film having a thickness of 50 μm by a bar coater, placed in an oven blown with nitrogen, dried at 80 ° C. for 1 hour, and a cross-linking reaction of polydopamine acrylamide with an isocyanate compound was advanced. In this case, assuming that the epoxy resin and the phenolic hydroxyl group had undergone a crosslinking reaction, the concentration of the remaining phenolic hydroxyl group was calculated to be about 8.2 mmol / g based on the solid content of the coating composition.

  When electroless plating was performed under the following conditions using the prepared test piece for plating, shiny copper plating was deposited on the surface coated with the reducing polymer under the same conditions as in Example 1. It was confirmed that even when these solutions were used repeatedly several times, they could be similarly plated. In the table, the evaluation of the plating deposition property is represented by ◯ when the entire surface is plated.

(Example 5)
1. A bisphenol A type epoxy resin having an epoxy equivalent of about 190 g / eq (2.0 brand name JER828, manufactured by Japan Epoxy Resin Co., Ltd.) in 2.0 g of a 10 wt% polydopamine methacrylamide solution obtained in Synthesis Example 4. An epoxy resin solution 0.56 g composed of 5 g, 2-methylimidazole 0.015 g, methanol 9 g, and dimethylformamide 4.5 g was added and mixed by stirring to prepare a coating solution. This solution was applied to a PET film having a thickness of 50 μm with a bar coater, placed in an oven blown with nitrogen, dried at 110 ° C. for 1 hour, and a crosslinking reaction of polydopamine acrylamide with an epoxy compound was advanced. In this case, assuming that the epoxy group and the phenolic hydroxyl group were cross-linked, the concentration of the remaining phenolic hydroxyl group was calculated to be about 7.6 mmol / g based on the solid content of the coating composition.

  When electroless plating was carried out under the following conditions using the prepared test piece for plating, glossy copper plating was deposited only on the surface to which a polymer having reducibility was applied. It was confirmed that even when these solutions were used repeatedly several times, they could be similarly plated.

Example 6 Pattern Formation Example Trimethylolpropane triacrylate (trade name Aronix M309, manufactured by Toagosei Co., Ltd.) as an ultraviolet curable resin was added to 2.0 g of the polymer solution having a concentration of 10% by weight obtained in Synthesis Example 1. .4 g, radical photopolymerization initiator (BASF, trade name Irgacure 907), epoxy equivalent of about 190 g / eq bisphenol A type epoxy resin (Japan Epoxy Resin, trade name JER828) 1.5 g, An epoxy resin solution 0.56 g composed of 0.015 g of 2-methylimidazole, 9 g of methanol and 4.5 g of dimethylformamide was added and mixed by stirring to prepare a coating solution. This solution was applied to a 50 μm thick PET film by a bar coater, put into an oven blown with nitrogen, dried at 60 ° C. for 1 hour, and taken out. A photomask in which circular black patterns with a diameter of 3 mm were arranged in a lattice pattern was brought into close contact therewith, and ultraviolet rays were irradiated from above the photomask at 400 mJ / cm ² . Subsequently, the photomask was removed, and the coating surface was washed with methanol. Furthermore, it was put into an oven in which nitrogen was blown, and a crosslinking reaction of polydopamine acrylamide with an epoxy compound was advanced at 110 ° C. for 1 hour. In this case, assuming that the epoxy group and the phenolic hydroxyl group had undergone a crosslinking reaction, the concentration of the remaining phenolic hydroxyl group was calculated to be about 5.9 mmol / g based on the solid content of the coating composition.

    When electroless plating was performed under the condition 5 of Example 2 using the prepared test piece for plating, copper plating was deposited on portions other than the portion corresponding to the black circular pattern of the photomask.

(Comparative Example 1)
About the test piece created in Example 1, when the process (4) was performed without performing the process (3) after the process (2), the plating did not precipitate even if the conditions were changed. When the sample after passing through the step (2) was observed by AFM, a surface shape in which fine particles having a diameter of several tens of nm were densely observed on the entire surface was observed.
When passing through the steps (2) and (3), a similar shape in which particles were densely observed on the object to be plated could be observed. It can be said that the fine particles deposited in the step (2) do not have autocatalytic properties, that is, are not zero-valent copper. From the result of the reference example described later, it is considered that the fine particle substance deposited on the surface after passing through the step (2) is cuprous oxide (Cu ₂ O).

(Comparative Example 2)
About the test piece created in Example 1, when the process (3) and the process (4) were performed without performing the process (2), plating did not precipitate even if the conditions were changed. As a result, there is no possibility that plating can be performed in the step (4) due to the attachment of the reducing agent in the step (3). From the results of Comparative Examples 1 and 2, in this case, it can be said that the plating was deposited in step (4) by going through both steps (2) and (3).

(Comparative Example 3)
About the test piece created in Example 1, when performing only the process (4) without performing any of the process (2) and the process (3), the plating did not precipitate even if the conditions were changed.

(Comparative Example 4)
Based on Patent Document 3, 8.5 g of copper (II) chloride dihydrate, 14.6 g of ethylenediaminetetraacetic acid, 6.2 g of boric acid, and 5.9 g of dimethylaminoborane were placed in a beaker, and ultrapure water was added to make 1 L. The pH was adjusted to 7 by adding sodium hydroxide while dissolving. When this liquid was kept at 30 ° C. and the test piece prepared in Example 1 was immersed, plating did not precipitate for about 40 minutes, and after 40 minutes, the liquid turned black and a black solid precipitated. When the test piece was taken out, plating was deposited on both sides of the coated surface of the reducing group-containing polymer and the uncoated surface, and a part of the plating was also deposited inside the beaker. This plating solution was blue-green before the test piece was introduced, but after the black solid precipitated, it became colorless and transparent and could not be used repeatedly for plating. The plating solution was in a state of being decomposed, which is well known to plating companies.

(Reference example)
In a four-necked flask with a capacity of 300 mL, various phenols and dimethylaminoborane are collected so that the phenolic hydroxyl group concentration is 0.2 mol / L, and in the case of dimethylaminoborane, the concentration is 0.2 mol / L. , Water was added to 200 mL. This beaker was immersed in a warm water bath to maintain the liquid temperature in the beaker at 60 ° C. ± 1 ° C. The pH was raised while sodium hydroxide was added little by little, and the oxidation-reduction potential was measured. The relationship between pH and redox potential is shown in FIG.
Further, prepare liquids with different pH values for the same liquid, add 1.5 g of copper (II) chloride to each, stir, cool to room temperature, filter the liquid, wash several times with ultrapure water, and filter paper Each was dried in a vacuum dryer. Precipitation occurred differently depending on the pH and the type of the reducing compound. In the aqueous solution to which catechol, hydroquinone and pyrogallol were added, a reddish brown precipitate was generated around pH 12, and no precipitate was formed below pH 10. In addition, precipitation did not occur from an aqueous solution of phenol and resorcinol. Phenol and resorcinol have higher redox potential near pH 12 than catechol and hydroquinone, and are considered to have no ability to reduce metal ions. Even if there is only one hydroxyl group or two hydroxyl groups, In the structure located at the meta position, the reducing power is insufficient. On the other hand, even if there are hydroxyl groups located at the meta positions, sufficient reducibility can be obtained if any combination is in the ortho or para position as in pyrogallol. A dark brown precipitate was obtained at pH 12 from the aqueous dimethylaminoborane solution used for comparison.

These precipitates were analyzed by X-ray diffractometer (XRD) by CuKα ray diffraction. As a result, the main components of reddish brown precipitates obtained from a solution containing catechol, hydroquinone and pyrogallol were found to have diffraction angles 2θ = 38.4 ° and 42 The .2 ° peak coincided with the sample, indicating that it was cuprous oxide (Cu ₂ O). The blackish brown precipitate obtained from the aqueous dimethylaminoborane solution was copper. Therefore, when the metal having an autocatalyst is copper, catechol, hydroquinone, and pyrogallol are not as reducing as dimethylaminoborane, as can be seen from the oxidation-reduction potential, but when the pH increases to around 12, It has the ability to reduce monovalent copper ions to monovalent, and the oxidation-reduction potential at that time needs to be −300 mV or less when the Ag / AgCl electrode is used as a reference.
From this result, it is considered that the particulate material precipitated in step (2) of the example is cuprous oxide (Cu ₂ O), and in step (3), it is reduced to Cu with a reducing agent such as dimethylaminoborane. It is thought that it came to function as a catalyst of the electroless copper plating in a process (4) by doing.

(Plating performance evaluation method)
For the electroless plating films deposited in Examples 1 to 3 and Comparative Example 4, in order to examine the adhesion, two cuts by a cutter knife were put on the plating so as to intersect at 30 degrees. A transparent tape was stretched and peeled off to observe the peeling of the plating. None of them peeled off and showed good adhesion.

Claims (9)

A step (1) of coating a polymer containing an organic residue in a side chain having an ability to reduce metal ions of a plating metal on the surface of an object to be plated;
A step of precipitating a partially reduced metal oxide of the metal ion in a solution containing the metal ion and not containing a reducing agent capable of reducing the metal ion on the surface of the object coated with the polymer ( 2) and
A step (3) of reducing the partially reduced metal oxide to a plating metal having autocatalytic properties in a solution containing a reducing agent capable of reducing the metal ions;
A step (4) of forming a plating metal film on the surface of an object to be plated in an electroless plating solution.   The electroless plating method according to claim 1, wherein the organic residue is a hydroquinone residue, a catechol residue, or a pyrogallol residue.   The electroless plating method according to claim 1, wherein the polymer is crosslinked.   The electroless plating method according to any one of claims 1 to 3, wherein a content of the phenolic hydroxyl group of the organic residue is 4 mmol / g polymer or more.   The electroless plating method according to claim 1, wherein the plating metal is copper or nickel.   The electroless plating method according to any one of claims 1 to 5, which is a step (3) in which a plating metal having self-catalytic properties covers a surface of an object to be plated by 5% or more. The electroless plating method for copper according to any one of claims 1 to 6, wherein the plating metal is copper, and the partially reduced metal oxide in the step (2) is Cu ₂ O.   The electroless plating method according to any one of claims 1 to 7, which includes a step of patterning the polymer and forming a patterned film of the plated metal.   A plated product in which electroless plating is deposited by the electroless plating method according to claim 1.

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