JP2018070911A - Heat treatment type method of forming electroconductive film over light metal that can easily be passivated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strengthen the adhesion of an electroconductive film of silver, copper, stannum or the like to a specific light metal selected from aluminum, magnesium, and titanium that can easily be passivated.SOLUTION: There is provided a method of forming an electroconductive film of silver, copper, stannum or the like over a light metal via an undercoat film which is a nickel-phosphorous film formed by using an electrolytic plating bath comprising a specified complexing agent, surfactant, brightener, and the like, and is subsequently subjected to a heat treatment alone or together with the electroconductive film under a condition including a low temperature range of 30°C or higher, whereby the adhesion of the undercoat film to the light metal is made stronger than in the case of no heat treatment, and the electroconductive film can be formed over the light metal with stronger adhesion.SELECTED DRAWING: None

Description

  The present invention relates to a method for forming a conductive film on a specific light metal such as aluminum or magnesium which is easily formed into a nonconductive state, by applying heat treatment to the light metal on which the formation of a plating film is difficult. Provided is one capable of forming a conductive film such as tin with a strong adhesion.

Certain light metals such as aluminum, magnesium, and titanium easily form a strong oxide film in the atmosphere and become non-conductive, so conductive films such as copper, silver, and tin are formed on the surface of these light metals. Even if it is going to be, the surface treatment by plating etc. is difficult, and even if it can form a plating film, it is difficult to ensure favorable adhesiveness with the said light metal.
Therefore, in the past, a conductive film was formed by electroplating after surface treatment of the light metal by the double zincate method, anodizing method, reverse electrolytic activation method, etc. Especially, the substitution reaction of zinc and aluminum In the double zincate method using the above, since the particles of the zinc film formed first are large, it is necessary to exfoliate it once and form a film with zinc particles again. There was a problem that the surface was relatively rough and it was difficult to form a smooth film by subsequent electroplating.

Therefore, when forming a conductive film on a light metal that easily forms a non-conductive state such as aluminum or magnesium, conventionally, the surface is subjected to alkali degreasing and the like to form a nickel-based film, or a predetermined amount of After surface treatment using a treatment liquid, forming a conductive film of copper, silver, tin or the like has been performed.
The conventional technology is as follows. However, Patent Document 6 below focuses on forming a nickel-based film on the light metal itself.
(1) Patent Document 1
Aluminum or aluminum alloy is subjected to AC electrolytic treatment in a treatment bath containing phosphoric acid and a prescribed nickel salt (nickel carbonate, nickel citrate, etc.) to form an oxide film with a fine concavo-convex structure and electroanalysis of particulate nickel It is a method for plating an aluminum material comprising a first step of simultaneously carrying out and a second step of performing electroless or electrolytic plating of copper, nickel or the like thereafter (claims 1, [0014] to [0015], [0044]).
In the first step, nickel metal enters the inside of the oxide film to form an anodic oxide film having a constant film thickness, and then the surface is uniformly coated with the particulate nickel film ([0014]).
In Example 5 ([0031]) of the treatment liquid in the first step, a nickel salt, phosphoric acid, and malonic acid (dicarboxylic acid) are included. In Example 8 ([0042]), nickel citrate and phosphoric acid are included. Is included.

(2) Patent Document 2
For the purpose of preventing cracks on the plating film ([0008]), the oxide film on the aluminum or aluminum alloy is removed acidic or alkaline ([0009] to [0026]), and then the first electroless nickel-phosphorous plating A surface treatment method of an aluminum material comprising a step of forming an electroless plating film with a liquid and a step of forming an electroless plating film with a second electroless nickel-phosphorous plating solution (claim 1, [0009]), Through this treatment, a conductive film is formed.
The first electroless nickel-phosphorous plating solution includes a nickel salt, hypophosphorous acid or a salt thereof, and a carboxylic acid other than aminocarboxylic acid (citric acid, acetic acid, succinic acid, malic acid, salts thereof, [0036] And the second electroless nickel-phosphorus plating solution contains a nickel salt, hypophosphorous acid or a salt thereof, and an aminocarboxylic acid (glycine, alanine, leucine, aspartic acid, glutamic acid) or a salt thereof, Does not contain carboxylic acids other than carboxylic acids.
In Example 1, a silicon plate coated with an aluminum layer was subjected to two-stage electroless nickel-phosphorus plating, and then a gold film was coated by electroless plating (Table 1).

(3) Patent Document 3
A pretreatment by cathode activation in a pretreatment liquid containing sulfuric acid and a nickel salt (or iron salt or cobalt salt) on at least one surface of an aluminum or aluminum alloy molded article, and a pretreated substrate A surface treatment method comprising a step of applying a metal layer (nickel, iron, cobalt, and alloys thereof) to each other by electroplating (Claims 1 and 2).
In the cathode activation treatment, a nickel nucleus is formed through a thin aluminum oxide film on the surface of the aluminum material. For example, when a nickel film is formed by subsequent electroplating, the nickel nucleus serves as an anchor point, and the surface of the aluminum material and the nickel film are formed. Plays the role of a thin tie layer ([0012]).
Moreover, boric acid is mentioned as a preferable example of the buffering agent contained about the pre-processing liquid used for the said cathode activation process (Claims 3-4, [0013]).

(4) Patent Document 4
Before forming a copper plating layer using electrolytic plating on a magnesium alloy, the surface of the magnesium alloy is treated with a pretreatment solution containing zinc sulfate, sodium pyrophosphate, potassium fluoride, and sodium carbonate to obtain a uniform current distribution. The electrolytic plating film to be provided is formed on the surface of the magnesium alloy (Claims 1 and 2), and the electroplating film formed on the surface of the magnesium alloy and the copper plating layer can be easily bonded by the method. Then, the copper electroplating layer 1 having good adhesion is formed ([0017], [0020] to [0021]).

(5) Patent Document 5
A surface treatment of Al or Al alloy (such as Al alloy) by cathodic electrolysis in a phosphoric acid solution, and electroplating the surface-treated Al alloy or the like to form a nickel film, nickel- Forming a plating film selected from a phosphorous film or a nickel-phosphorus-silicon carbide alloy film (claims 1 to 3).
Cathodic electrolytic treatment of Al alloy or the like in a phosphoric acid solution reduces or removes metal components such as magnesium, iron, and nickel other than Al and silicon, and etches the surface of Al alloy and the like to form fine irregularities. The plating film can be coated with good adhesion on the surface of an Al alloy or the like by the anchor effect ([0016] to [0017], [0029] to [0032]).

(6) Patent Document 6
In a developing roller such as a copying machine, an electro nickel plating layer is formed on an aluminum alloy sleeve constituting the developing roller, or an electro nickel plating layer is formed through an electroless nickel plating layer, and thereafter By performing the heat treatment, the adhesion strength of the plating layer to the aluminum alloy layer is improved (claims 1-4, [0010], [0018] to [0019]).
The conditions for the heat treatment are 100 to 150 ° C. and 30 minutes to 2 hours ([0015]).

JP-A-11-302854 JP 2008-190034 A Special table 2008-527178 JP 2009-019217 A JP2015-108169A JP 2001-125370 A

However, the treatment described in Patent Documents 1 to 5 or a treatment based on the treatment, a nickel-based undercoating is applied on a light metal such as aluminum or magnesium which easily forms a nonconductive state, or pretreatment. In the case of forming a conductive film of silver, copper, tin or the like by a method involving the use of, for example, even if a nickel-phosphorous film is formed by electroless plating in accordance with the above-mentioned Patent Document 2, it is electroless with respect to the light metal surface. The adhesion of the nickel-phosphorus film is weak (see comparative examples described later).
When a conductive film is formed on the light metal by electroplating through a nickel-based undercoat, for example, a special operation such as AC electrolytic treatment in Patent Document 1 and cathode activation process in Patent Document 3 is performed in parallel. Thus, even if improvement in adhesion can be expected as it is, a known nickel-based plating bath (including a known nickel-phosphorous plating bath) or the above-mentioned Patent Document 1 can be used without undergoing such a special operation. Even when electroplating using the nickel-based plating bath described in (3) to (3) is performed, the obtained nickel-based undercoat has poor adhesion (see Comparative Examples described later).

  This invention makes it a technical subject to strengthen the adhesive force of electroconductive films, such as silver, copper, and tin, with respect to the specific light metal chosen from aluminum, magnesium, and titanium which are easy to form a non-conductive state. .

When forming a conductive film on a specific light metal such as aluminum, magnesium, or titanium that easily forms a non-conductive state, the present inventors interpose a nickel base film between the light metal and the conductive film. When the nickel-phosphorus film is selected as the nickel-based film and the base film is formed with a specific electric nickel-phosphorous plating bath to which a predetermined complexing agent and a surfactant are added in combination, the base film is made of aluminum, It has been found that it can be satisfactorily adhered onto specific light metals such as magnesium and titanium, and has been proposed in Japanese Patent Application No. 2015-247207 (hereinafter referred to as the prior application invention).
The present invention is based on the above-mentioned prior application, and after forming a nickel-phosphorus undercoat on a light metal, the undercoat is heat-treated, or after forming a conductive film in the next step, When the conductive film is heat-treated, the adhesion of the ground film to the light metal can be further strengthened, so that the conductive film can be more firmly formed on the light metal, and the adhesion of the ground film can be increased by 30 ° C. It was found that the temperature conditions including the above low temperature range are sufficient, and the present invention was completed.

That is, the present invention 1 comprises (S1) a step of forming a base film composed of a nickel-phosphorus film on a non-conductive formable light metal selected from aluminum, magnesium, and titanium using an electric nickel-phosphorous plating bath;
(S2) In a conductive film forming method comprising a step of forming a conductive film on a heat-treated base film,
A step (S12) of heat-treating the base film at 30 ° C. or higher is interposed between the step (S1) and the step (S2), or
After adding the process (S3) which heat-processes a base film and an electroconductive film at 30 degreeC or more after the said process (S2),
The electric nickel-phosphorous plating bath is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) A method of forming a heat-treatable conductive film on a non-conductive formable light metal, comprising a brightener.

  Invention 2 is the same as Invention 1, wherein the compound (b) containing phosphorus in the electric nickel-phosphorous plating bath is phosphorous acid, hypophosphorous acid, pyrophosphoric acid, orthophosphoric acid, hydroxyethylenediamine diphosphonic acid, nitrilotris (methylene A method of forming a heat-treatable conductive film on a non-conductive light-forming metal, characterized in that it is at least one of phosphonic acid), ethylenediaminetetra (methylenephosphonic acid) or a salt thereof.

  The present invention 3 is the invention 1 or 2, wherein the complexing agent (c) of the electric nickel-phosphorus plating bath is citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid A method of forming a heat-treatable conductive film on a non-conductive non-forming light metal, characterized in that it is at least one of oxycarboxylic acid, polycarboxylic acid, aminocarboxylic acid or a salt thereof selected from diethylenetriaminepentaacetic acid is there.

  Invention 4 is the electro-nickel-phosphorous plating bath according to any one of Inventions 1 to 3, wherein the buffer (e) is at least one of boric acid, sodium carbonate, sodium bicarbonate, nickel acetate, ascorbic acid or a salt thereof. It is a method for forming a heat-treatable conductive film on a non-conductive-formable light metal.

  Invention 5 is the electro-nickel-phosphorous plating bath brightener (f) according to any one of Inventions 1 to 4, wherein the saccharin and its salt, benzenesulfonic acid or its salt, toluenesulfonic acid or its salt, naphthalenesulfonic acid Or at least one selected from salts thereof, allylsulfonic acid or salts thereof, butynediol, ethylene cyanohydrin, coumarin, propargyl alcohol, bis (3-sulfopropyl) disulfide, mercaptopropanesulfonic acid, and thiomalic acid. And a heat treatment type conductive film forming method on a non-conductive formable light metal.

  Invention 6 is the heat treatment formula on a non-conductive non-formable light metal according to any one of Inventions 1 to 5 above, wherein the pH of the electric nickel-phosphorous plating bath is 3.0 to 8.0. It is a conductive film forming method.

  Invention 7 is any one of Inventions 1 to 6, wherein the film thickness of the undercoat is 0.01 to 10.0 μm. This is a heat treatment type conductive film forming method on a non-conductive-forming light metal.

Present invention 8 is any one of the present invention 1 to 7, wherein the conductive film is formed by electroplating, electroless plating, sputtering or vapor deposition,
The conductive film is a film made of a metal selected from copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc, and chromium, or an alloy of these metals. This is a heat treatment type conductive film forming method on a non-conductive formable light metal.

In the above-mentioned prior application invention, when a conductive film such as copper, tin, silver or the like is formed on a non-conductive film-like light metal selected from aluminum, magnesium, and titanium, a predetermined complexing agent, a surfactant, After forming a base film consisting of a nickel-phosphorus film formed using an electric nickel-phosphorous plating bath containing a buffering agent on the light metal, and then forming a conductive film, the base film can be satisfactorily adhered onto the light metal. Thus, a conductive film can be formed on the light metal with good adhesion.
The present invention is an improvement of this prior invention, and based on the processing steps of the prior application invention, a base film formed on a light metal, or a temperature including a base film and a conductive film in a low temperature region of 30 ° C. or higher. By adding a heat treatment process under conditions, the adhesion of the base film on the light metal can be further enhanced, and the conductive film can be formed on the light metal with better adhesion.
About the said heat processing, the adhesive force of the base film on a light metal can fully be reinforce | strengthened also by simple heat processing in a low temperature range, such as bathing at 30-100 degreeC, for example. Moreover, if heat treatment is performed in a low temperature range, the energy to be dropped can be reduced and the productivity can be improved.

Incidentally, in Patent Document 6, it is disclosed that the adhesion of the plating layer to the aluminum alloy material is enhanced by covering the aluminum alloy base material with the electric nickel plating layer and then performing heat treatment. The document 6 relates to a developing roller for a copying machine or the like, and a nickel plating layer with a low phosphorus content is used for the plating layer covering the aluminum alloy material because it is necessary to reduce the electrical resistance (see [0019]). .
Accordingly, the plating layer covering the aluminum alloy material of Patent Document 6 is a nickel plating layer, which is different from the present invention in which the nickel-phosphorus film is selected as the undercoat, and in claim 4 of the same Document 6, Although it is disclosed that the adhesion of the nickel layer to the aluminum alloy material can be improved by heat treatment, this means that improvement by heat treatment is necessary to secure the adhesion sufficient to ensure reliability, or However, it is unclear whether this means that practical adhesion can be ensured without heat treatment, but the reliability of adhesion can be further enhanced by heating.
In addition, the specific composition of the electric nickel plating bath for forming the nickel layer is unknown.

In the present invention, a conductive film such as silver, copper, or tin is formed on a specific light metal that easily forms a non-conductive state selected from aluminum, magnesium, and titanium via a base film made of a nickel-phosphorus film. In this method, a base film is formed with a nickel-phosphorus film using an electroplating bath having a predetermined composition containing a specific complexing agent, a surfactant, a brightener, and the like. In this method, heat treatment is performed under conditions, or the base film and the conductive film are similarly heat-treated after the formation of the conductive film in the next step.
The above aluminum includes pure aluminum and aluminum alloys, the above magnesium includes pure magnesium and magnesium alloys, and the above titanium includes pure titanium and titanium alloys.

The present invention includes the following underlayer forming step (S1), conductive film forming step (S2), and a step of performing heat treatment after step (S1) or after step (S2) (see the present invention 1).
(S1) A step of forming a base film composed of a nickel-phosphorous film on a silicon substrate using an electric nickel-phosphorous plating bath (S2) a step of forming a conductive film on the base film. In the step (S1), The electric nickel-phosphorous plating bath used is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) Brightener is an essential component.

The soluble nickel salt (a) is only required to be able to supply nickel ions in the plating bath. Nickel sulfate, nickel chloride, nickel ammonium sulfate, nickel oxide, nickel acetate, nickel carbonate, nickel oxalate, nickel sulfamate, organic Examples thereof include nickel salts of sulfonic acid, and nickel sulfate, nickel sulfamate, nickel oxide and the like are preferable.
In addition, the phosphorus-containing compound (b) includes phosphorous acid, hypophosphorous acid, pyrophosphoric acid, orthophosphoric acid, hydroxyethylenediamine diphosphonic acid, nitrilotris (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) and These salts are mentioned.
The soluble nickel salt (a) can be used singly or in combination, and the content thereof relative to the plating bath is 0.01 to 3.0 mol / L, preferably 0.05 to 2.0 mol / L, more preferably 0.0. 1 to 1.5 mol / L.
The compound (b) containing phosphorus can be used singly or in combination, and its content with respect to the plating bath is 0.05 to 2.0 mol / L, preferably 0.1 to 1.0 mol / L, more preferably 0. 0.1 to 0.8 mol / L.

The complexing agent (c) contained in the electro-nickel-phosphorous plating bath is a compound that mainly forms a nickel complex in the plating bath, and the change in the cathode current density with respect to the change in the electrode potential is moderated. It functions to facilitate precipitation, and is selected from the group consisting of aminocarboxylic acids, oxycarboxylic acids, carbohydrates, amino alcohols, polycarboxylic acids, and polyamines.
The aminocarboxylic acids include ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), ethylenediaminetetrapropionic acid, nitrilotriacetic acid (NTA). , Iminodiacetic acid (IDA), iminodipropionic acid (IDP), metaphenylenediaminetetraacetic acid, 1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid, diaminopropionic acid and their salts. NTA and EDTA are preferable.
Examples of the oxycarboxylic acids include tartaric acid, citric acid, malic acid, gluconic acid, glycolic acid, lactic acid, glucoheptonic acid, and salts thereof, and citric acid, tartaric acid, gluconic acid, and salts thereof are preferable.
The sugars include glucose (glucose), fructose (fructose), lactose (lactose), maltose (maltose), isomaltulose (palatinose), xylose, sorbitol, xylitol, mannitol, maltitol, erythritol, reduced starch syrup, lactitol , Reduced isomaltulose, gluconolactone and the like, and sugar alcohols such as sorbitol, xylitol, mannitol, maltitol are preferred.
Examples of the amino alcohols include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, and tripropanolamine, with triethanolamine and tripropanolamine being preferred.
Examples of the polycarboxylic acids include succinic acid, oxalic acid, glutaric acid, adipic acid, malonic acid, and salts thereof, and succinic acid is preferable.
Examples of the polyamines include methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, and ethylenediamine is preferred.
As the complexing agent (c), oxycarboxylic acids, aminocarboxylic acids, and saccharides are preferable, and citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriamine-5 Acetic acid and salts thereof, sorbitol, mannitol, maltitol and the like are preferable.
The complexing agent (c) can be used singly or in combination, and its content with respect to the plating bath is 0.001 to 2 mol / L, preferably 0.05 to 0.8 mol / L, more preferably 0.0. 1 to 0.5 mol / L.

The surfactant (d) contained in the electric nickel-phosphorous plating bath is selected from nonionic surfactants and amphoteric surfactants, and promotes adhesion between the silicon substrate and the base film.
The nonionic surfactants are generally C1 to C20 alkanols, phenols, naphthols, bisphenols, (poly) C1 to C25 alkylphenols, (poly) arylalkylphenols, C1 to C25 alkylnaphthols, C1 to C25 alkoxylations. Phosphoric acid (salt), sorbitan ester, polyalkylene glycol, C1 to C22 aliphatic amine, C1 to C22 aliphatic amide and the like obtained by addition condensation of 2 to 300 moles of ethylene oxide (EO) and / or propylene oxide (PO) And C1-C25 alkoxylated phosphoric acid (salt). For example, polyoxyethylene cumin phenol ether, polyoxyethylene dodecyl phenyl ether, dibutyl-β-naphthol polyethoxylate, polyoxyethylene styrenated phenyl ether, ethylenediamine tetrapolyoxyethylene polyoxypropylene, polyethylene glycol, lauryl alcohol poly Ethoxylate is preferred.
Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, sulfobetaine, and aminocarboxylic acid. For example, lauryldimethylaminoacetic acid betaine, stearic acid amidopropyl betaine, lauric acid amidopropyldimethylamine oxide, and the like are suitable. In addition, sulfation of a condensation product of ethylene oxide and / or propylene oxide and an alkylamine or diamine, or a sulfonated adduct can also be used.
The surfactant (d) can be used alone or in combination, and the content thereof relative to the plating bath is 0.1 to 50 g / L, preferably 1 to 40 g / L, and more preferably 5 to 35 g / L.
As described above, in the nickel-phosphorous plating bath of the present invention, addition of nonionic and amphoteric surfactants is essential from the viewpoint of increasing adhesion, but in addition to these surfactants, other than the specific species It is not excluded to add a surfactant, that is, a cationic or anionic surfactant in combination.
However, without adding the predetermined surfactant of the present invention to the plating bath, the addition of a cationic or anionic surfactant alone does not contribute to the stability of the plating bath or the adhesion of the underlying film. This is as shown in a test example described later (see Comparative Example 7).

The buffer (e) contained in the electric nickel-phosphorous plating bath improves the adhesion of the base film to the silicon substrate and also acts as a stabilizer for the plating bath.
Examples of the buffer (e) include boric acid, sodium carbonate, sodium hydrogen carbonate, nickel acetate, succinic acid, ascorbic acid and the like, and boric acid and sodium carbonate are preferable.
The buffer (e) can be used singly or in combination, and its content with respect to the plating bath is 0.05 to 1.5 mol / L, preferably 0.05 to 1.0 mol / L, more preferably 0. 0.1 to 0.6 mol / L.

The brightener (f) contained in the electric nickel-phosphorous plating bath acts to improve the adhesion of the nickel-phosphorous film to the silicon substrate.
Examples of the brightener (f) include saccharin and its salt, benzenesulfonic acid and its salt, p-toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butynediol (specifically Are 2-butyne-1,4-diol), ethylene cyanohydrin, coumarin, propargyl alcohol, bis (3-sulfopropyl) disulfide, mercaptopropanesulfonic acid, thiomalic acid and the like.
The brightener (f) is effective even if the components are used alone, but it is suitable to combine the components, and in particular, benzenesulfonic acid or a salt thereof and saccharin, naphthalenesulfonic acid or a salt thereof and saccharin, butyne Diol and benzenesulfonic acid or salt thereof, butynediol and naphthalenesulfonic acid or salt thereof, allylsulfonic acid or salt thereof and saccharin, thiomalic acid and saccharin, bis (3-sulfopropyl) disulfide and saccharin, allylsulfonic acid or salt thereof It is preferable to use two or more in combination such as, propargyl alcohol, benzenesulfonic acid or a salt thereof, propargyl alcohol, naphthalenesulfonic acid or a salt thereof and propargyl alcohol.
As described above, the brightener (f) can be used singly or in combination, and its content with respect to the plating bath is 0.001 to 0.15 mol / L, preferably 0.005 to 0.07 mol / L. Preferably it is 0.01-0.05 mol / L.

The electric nickel-phosphorus plating bath of the present invention is intended to form a nickel-phosphorus coating on a silicon substrate, but the pH of the plating bath is suitably from 3.0 to 8.0, preferably 4.0. ~ 6.0.
In the base formation step (S1), the cathode current density at the time of electroplating is 0.01 to 5.0 A / dm 2, and preferably 0.05 to 2.0 A / dm 2.
In the undercoat film forming step (S1), the nickel-phosphorus film as the undercoat film is not required to be formed thick because it only needs to provide conductivity and adhesion sufficient to form a conductive film on the upper layer. Accordingly, the film thickness is 0.01 to 10.0 μm, preferably 0.01 to 8.0 μm, more preferably 0.01 to 5.0 μm.

In the above, the step (S1) of forming a nickel-phosphorus undercoat on a non-conductive light metal such as aluminum has been described in detail. Next, the nickel-phosphorus coating formed in the step (S1) is described. The process (S2) for forming a conductive film as the upper film will be described above.
The conductive film is not particularly limited as long as it is a known conductive film, but, for example, from copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc, chromium Examples include selected metals or alloys of these metals.
As the metal constituting the conductive metal, silver, copper, nickel, tin, palladium, gold, and bismuth are suitable. Examples of the metal alloy include nickel-tungsten alloy, nickel-molybdenum alloy, nickel-tin alloy, tin-silver alloy, tin-bismuth alloy, tin-copper alloy, tin-zinc alloy, and gold-tin alloy. Is preferred.
The conductive film can be formed by electroplating, electroless plating, sputtering, or vapor deposition. Among these, a plating method is preferable from the viewpoint of productivity, but sputtering or vapor deposition is not excluded.

The present invention is characterized in that a conductive film is formed on a non-conductive light-forming metal via a base film, but the conductive film may be formed as a single layer, but two layers, three layers, etc. It is also possible to form a multilayer.
As an example of a multi-layer conductive film, a metal selected from nickel, copper, cobalt, bismuth, zinc, chromium, iron, or an alloy of these metals is used as a lower layer (that is, the side facing the base film), A two-layered conductive film with tin, copper, gold, silver or the like as an upper layer can be exemplified.
Further, when the uppermost layer of the multi-layered conductive film is formed of tin, nickel, cobalt, chromium, silver, palladium, or an alloy thereof, a beautiful silver appearance can be imparted to the surface of the uppermost layer.

As described above, the present invention is characterized in that a heat treatment process is added as an essential constituent element to the base film forming process (S1) and the conductive film forming process (S2).
Therefore, this heat treatment step will be described in detail.
First, the first method of heat treatment is to interpose the heat treatment step (S12) between the base film formation step (S1) and the conductive film formation step (S2). Consists of.
(S1) A step of forming a base film made of a nickel-phosphorus film on a non-conductive formable light metal such as aluminum using an electric nickel-phosphorous plating bath (S12) a step of heat-treating the base film at 30 ° C. or higher (S2) ) The process of forming a conductive film on the base film After the base film is formed, if the base film is heat-treated at 30 ° C. or higher, the adhesion of the base film to a non-conductive light metal can be further improved. Thus, the conductive film can be formed more firmly on the non-conductive light metal.
30-300 degreeC is suitable as heat processing temperature, 30-250 degreeC is preferable, More preferably, it is 30-200 degreeC, More preferably, it is 30-150 degreeC (especially 30-100 degreeC is suitable).
Even if the heat treatment temperature is increased from 300 ° C., the effect of strengthening the adhesion is not changed so much. On the other hand, thermal distortion occurs in the undercoat, adversely affecting the adhesion, or there is a risk of oxidizing the undercoat. Productivity is also reduced by wasting energy. In view of this point, the upper limit of the heat treatment temperature is preferably about 200 ° C. In addition, as shown in the above-mentioned prior application invention, after the undercoat formation step (S1), practical adhesion of the undercoat to the non-conductive formable light metal can be ensured without performing heat treatment. The lower limit of the heat treatment was set to about 30 ° C., since further improvement in adhesion to this practical level can be expected even at about 30 ° C.
Next, the second method of heat treatment is a method in which a heat treatment step (S3) is added after the conductive film formation step (S2), and this subsequent heat treatment method includes the following three steps.
(S1) A step of forming a base film made of a nickel-phosphorous film on a non-conductive formable light metal such as aluminum using an electric nickel-phosphorous plating bath (S2) a step of forming a conductive film on the base film ( S3) Step of heat-treating the base film and the conductive film at 30 ° C. or higher The temperature condition of the heat treatment in the second method may be the same as in the first method.
About the said heat processing, although the heat processing system of an intermediate | middle and a back | latter stage is common, various aspects, such as oven heating, hot air heating with a dryer, immersion in warm water or an oil bath, can be selected. In addition, for example, when hot water treatment at 30 to 100 ° C (boiled water bathing in hot water) is selected, the heat treatment is performed in a low temperature range with hot water bath, so heat energy is reduced and processing is simplified, and productivity is improved. it can.

Hereinafter, an electric nickel-phosphorus plating bath for forming a base film (nickel-phosphorus film) on a non-conductive-formable light metal such as aluminum, a plating bath for forming a conductive film, and the light metal by a heat treatment method. An example of a method for forming a conductive film through the base film will be described above, and an evaluation test example of the adhesion of the nickel-phosphorus film to the light metal will be sequentially described.
The present invention is not limited to the following examples and test examples, and it is needless to say that arbitrary modifications can be made within the scope of the technical idea of the present invention.

<< Example of a method for forming a conductive film on a light metal that forms a nonconductive state by heat treatment >>
Of the following Examples 1 to 23, Examples 1 to 7 are nickel-phosphorus film (undercoat film) / tin film (conductive film), and Example 8 is nickel-phosphorus film (undercoat film) / copper film (conductive) Example 9 is a nickel-phosphorus film (undercoat) / nickel coat (conductive film), Examples 10 and 13 are a nickel-phosphorus film (undercoat) / silver film (conductive film), Example 11 is an example of nickel-phosphorus film (undercoat film) / palladium film (conductive film), and Example 12 is an example of nickel-phosphorus film (undercoat film) / tin-bismuth alloy film (conductive film). The conductive film (silver film) of Example 13 was formed by electroless plating, and the other examples were formed by electroplating.
Examples 1 to 7 are examples in which the composition of the nickel-phosphorous plating bath in step (S1) was changed.
In the timing conditions for performing the heat treatment, Examples 1 to 13 are examples of an intermediate heat treatment method in which heat treatment is interposed between the base film forming step (S1) and the conductive film forming step (S2). This is an example of a post-stage heat treatment method in which heat treatment is performed after the step (S2). In this post-stage heat treatment method, the processing conditions of Example 14 are based on Example 1 except for the timing conditions. Similarly, Example 15 is based on Example 3 and Example 16 is based on Example. Example 8 is based on Example 9, and Example 17 is based on Example 9, respectively.
In the additional conditions of heat treatment, Examples 1 to 17 are examples of hot water roasting at 70 ° C. for 5 minutes, Examples 18 to 20 are examples of hot water roasting under different conditions, Example 21 is an example of hot air heating, and Example 22 -23 are examples of oven heating.
The reference example is an example of the invention of the prior application described above. In other words, the example is based on Example 1 and directly moves to the step (S2) without the heat treatment after the step (S1).

On the other hand, the following Comparative Examples 1 to 9 are based on Example 1, and in Comparative Example 1, a conductive film was directly formed by electroplating without forming a base film on a light metal such as an aluminum alloy. It is a blank example (example without heat treatment).
Comparative Examples 2 to 3 were obtained by forming a conductive film on a light metal via a nickel base film instead of a nickel-phosphorus film, Comparative Example 2 was an example of heat treatment, and Comparative Example 3 was an example of no heat treatment. It is.
Comparative Examples 4 to 9 are examples in which the nickel-phosphorous plating bath in the undercoat film forming step (S1) of the present invention does not contain some of the essential components or are replaced with other components, and Comparative Example 4 is the plating. In this example, the bath does not contain the complexing agent (c).
Comparative Examples 5 to 6 do not contain the surfactant (d) of the present invention in the nickel-phosphorous plating bath, Comparative Example 5 is an example in which heat treatment was performed, and Comparative Example 6 is an example in which no heat treatment was performed.
In Comparative Example 7, the nickel-phosphorus plating bath was heat-treated using a cationic surfactant instead of the surfactant (d) of the present invention.
Comparative Examples 8-9 do not contain the brightener (f) of the present invention in the nickel-phosphorous plating bath, Comparative Example 8 is an example in which heat treatment was performed, and Comparative Example 9 is an example without heat treatment.

(1) Example 1
(S1) Step of forming undercoat As shown in the following (i) to (iv), three types of 5 cm × 5 cm square aluminum alloy plates and one type of 5 cm × 5 cm square magnesium alloy plates are prepared, Each sample of the non-conductive-forming light metal was used (the same applies to Examples 2 to 22 and Comparative Examples 1 to 9 below).
In particular, three types of aluminum alloys were selected because there are many types of such alloys, so the versatility of whether the undercoat of the present invention can be applied with good adhesion even if the type of aluminum alloy changes is verified. It is to do.
(I) Sample 1: Aluminum alloy / Al-Cu system (A2024P; JIS standard)
(Ii) Sample 2: Aluminum alloy / Al-Mg system (A5052P; JIS standard)
(Iii) Sample 3: Aluminum alloy / Al-Mg-Si system (A6061P; JIS standard)
(Iv) Sample 4: Magnesium alloy / Mg—Al—Zn system (AZ31; JIS standard)
First, each sample was alkali degreased with sodium hydroxide (3% by weight) at 25 ° C. for 3 minutes, and a base film was formed on the sample by the nickel-phosphorous plating bath and electroplating conditions of (A) below. Washed with water at 25 ° C. for about 30 seconds.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
The phosphorous acid is a phosphorus-containing compound, citric acid is a complexing agent, ethylenediamine alkylene oxide adduct is a nonionic surfactant, boric acid is a buffering agent, and saccharin and thiomalic acid are brightening agents.
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was bathed under the following conditions.
[Heat treatment conditions]
Hot water temperature: 70 ° C
Bathing time: 5 minutes (S2) Step of forming conductive film A conductive film was formed on each heat-treated sample by the following tin plating bath and electroplating conditions (B), washed with water, and then dried.
(B) Conductive film: tin An electric tin plating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn2 +) 0.5 mol / L
Methanesulfonic acid 1.0 mol / L
Polyoxyethylene cumylphenyl ether (EO10 mol) 10g / L
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 2A / dm2
Plating time: 5 minutes [Plating film]
Film thickness: 5μm

(2) Example 2
(S1) Base film forming step Based on Example 1, the nickel salt of the electric nickel-phosphorus plating bath was changed. The compound containing phosphorus and the complexing agent were also slightly changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfate hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium hydrogen phosphite 2.5 hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.3 μm
Phosphorus content: 6.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(3) Example 3
(S1) Base film forming step Based on Example 1, the phosphorus compound of the electric nickel-phosphorous plating bath was changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium hypophosphite 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 5.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.1 A / dm2
Plating time: 2 minutes [Plating film]
Film thickness: 0.01 μm
Phosphorus content: 4.5%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(4) Example 4
(S1) Base film forming step Based on Example 1, the complexing agent of the electric nickel-phosphorous plating bath was changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Sodium gluconate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 24% sodium hydroxide) 5.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(5) Example 5
(S1) Base film forming step Based on Example 1, the nonionic surfactant of the electric nickel-phosphorus plating bath was changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium hydrogen phosphite 2.5 hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Polyoxyethylene octylphenol ether (EO10 mol) 10g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 3.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(6) Example 6
(S1) Base film forming step Based on Example 1, the buffer for the electric nickel-phosphorous plating bath was changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Sodium carbonate 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(7) Example 7
(S1) Base film forming step Based on Example 1, the brightening agent for the electric nickel-phosphorous plating bath was changed.
(A) Composition of nickel-phosphorous plating bath and electroplating conditions An electric nickel-phosphorous plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Sodium carbonate 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
2-butyne-1,4-diol 0.02 mol / L
Benzenesulfonic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above. The conductive film is tin.

(8) Example 8
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a copper film.
(B) Conductive film: copper An electrolytic copper plating bath was constructed with the following composition.
Copper sulfate pentahydrate (as Cu2 +) 0.8 mol / L
Sulfuric acid 1.0 mol / L
Hydrochloric acid 0.1 mmol / L
Bis (3-sulfopropyl) disulfide 1.0 mg / L
Polyethylene glycol (molecular weight 4000) 1.0g / L
Polyethyleneimine 3.0mg / L
[Electroplating conditions]
Bath temperature: 25 ° C
Current density: 1A / dm2
Plating time: 5 minutes [Plating film]
Film thickness: 10μm

(9) Example 9
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a nickel film.
(B) Conductive film: nickel An electric nickel plating bath was constructed with the following composition.
Nickel sulfate hexahydrate (as Ni2 +) 0.15 mol / L
Nickel chloride (as Ni2 +) 0.5 mol / L
Boric acid 0.7 mol / L
pH (adjusted with 28% ammonia) 4.0
[Electroplating conditions]
Bath temperature: 60 ° C
Current density: 1A / dm2
Plating time: 5 minutes [Plating film]
Film thickness: 10μm

(10) Example 10
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a silver film.
(B) Conductive film: Silver An electrosilver plating bath was constructed with the following composition.
Silver methanesulfonate (as Ag +) 0.45 mol / L
Succinimide 1.5 mol / L
Sodium tetraborate 0.025 mol / L
[Electroplating conditions]
Bath temperature: 25 ° C
Current density: 1A / dm2
Plating time: 3 minutes [Plating film]
Film thickness: 2.0 μm

(11) Example 11
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a palladium film.
(B) Conductive film: Palladium An electric palladium plating bath was constructed with the following composition.
Palladium sulfate (as Pd2 +) 0.02 mol / L
Sulfuric acid 0.4 mol / L
Phosphoric acid 0.6 mol / L
Sulfurous acid 0.006 mol / L
[Electroplating conditions]
Bath temperature: 25 ° C
Current density: 0.6 A / dm2
Plating time: 20 minutes [Plating film]
Film thickness: 1.5μm

(12) Example 12
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a tin-bismuth alloy film.
(B) Conductive film: tin-bismuth alloy An electric tin-bismuth alloy plating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn2 +) 0.6 mol / L
Bismuth methanesulfonate (as Bi3 +) 0.02 mol / L
Methanesulfonic acid 1.0 mol / L
Polyoxyethylene cumylphenyl ether (EO10 mol) 10g / L
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 2A / dm2
Plating time: 5 minutes [Plating film]
Film thickness: 5.0 μm
Bismuth precipitation rate: 2%

(13) Example 13
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a silver film.
(B) Conductive film: silver An electroless silver plating bath was constructed with the following composition.
Silver nitrate (as Ag +) 0.01 mol / L
Succinimide 0.05 mol / L
Imidazole 0.05 mol / L
[Electroplating conditions]
Bath temperature: 50 ° C
Plating time: 60 minutes [Plating film]
Film thickness: 1.0μm

(14) Example 14
Based on Example 1, instead of performing heat treatment between Step (S1) and Step (S2), heat treatment was performed after Step (S2) (this is an example of post-stage heat treatment. the same).
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.
(S3) Heat treatment step The same as step (S12) in Example 1 above.

(15) Example 15
Based on Example 3, instead of performing heat treatment between step (S1) and step (S2), heat treatment was performed after step (S2).
(S1) Base film forming step The processing conditions are the same as in Example 3 above.
(S2) Step of forming conductive film The processing conditions are the same as in Example 3 above.
(S3) Heat treatment step The treatment conditions are the same as in step (S12) of Example 3 above.

(16) Example 16
Based on Example 8, instead of performing heat treatment between the step (S1) and the step (S2), heat treatment was performed after the step (S2).
(S1) Base film forming step The processing conditions are the same as in Example 8 above.
(S2) Step of forming conductive film The processing conditions are the same as in Example 8 above.
(S3) Heat treatment step The treatment conditions are the same as those in the step (S12) of Example 8.

(17) Example 17
Based on Example 9, heat treatment was performed after the step (S2) instead of heat treatment between the step (S1) and the step (S2).
(S1) Base film forming step The processing conditions are the same as in Example 9 above.
(S2) Step of forming conductive film The processing conditions are the same as in Example 9 above.
(S3) Heat treatment step The treatment conditions are the same as in step (S12) of Example 9 above.

(18) Example 18
Based on Example 1, the additional conditions for the heat treatment in the step (S12) were changed (hereinafter, Examples 19 to 23 are the same).
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was bathed under the following conditions.
[Heat treatment conditions]
Bath temperature: 35 ° C
Bathing time: 80 minutes (S2) Conductive film formation process The treatment conditions are the same as in Example 1 above.

(19) Example 19
Based on Example 1, the additional conditions for the heat treatment in step (S12) were changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was bathed under the following conditions.
[Heat treatment conditions]
Bath temperature: 50 ° C
Bathing time: 30 minutes (S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(20) Example 20
Based on Example 1, the additional conditions for the heat treatment in step (S12) were changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was bathed under the following conditions.
[Heat treatment conditions]
Hot water temperature: 90 ° C
Bathing time: 10 minutes (S2) Step of forming conductive film The treatment conditions are the same as in Example 1 above.

(21) Example 21
Based on Example 1, the additional conditions for the heat treatment in step (S12) were changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was heated with a dryer under the following conditions.
[Heat treatment conditions]
Hot air heating temperature: 150 ° C
Heating time: 5 minutes (S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(22) Example 22
Based on Example 1, the additional conditions for the heat treatment in step (S12) were changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was oven-heated under the following conditions.
[Heat treatment conditions]
Oven heating temperature: 150 ° C
Heating time: 10 minutes (S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(23) Example 23
Based on Example 1, the additional conditions for the heat treatment in step (S12) were changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step Next, each sample on which the nickel-phosphorus film was formed was oven-heated under the following conditions.
[Heat treatment conditions]
Oven heating temperature: 200 ° C
Heating time: 5 minutes (S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(24) Reference Example Based on the above-mentioned prior application, the step (S2) was carried out after the step (S1) without heat treatment on the basis of the above-mentioned Example 1.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(25) Comparative Example 1
Based on Example 1 described above, a conductive film was formed directly on each sample without forming a base film. Therefore, the base film forming step (S1) and the heat treatment step (S12) were not performed.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.
As a result, an attempt was made to form a conductive film (tin film) on the sample, but only a powdery precipitate was produced, and no tin plating film was formed.

(26) Comparative Example 2
This is an example in which a conductive film is formed by electroplating on a light metal material through a nickel base film instead of a nickel-phosphorus film on the basis of Example 1 (with heat treatment).
(S1) Formation process of base film (A) Composition of nickel plating bath and electroplating conditions An electronicking bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 1.0μm
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(27) Comparative Example 3
This is an example without heat treatment on the basis of the comparative example 2.
(S1) Base film forming step The processing conditions are the same as in Comparative Example 2 above.
(S2) Step of forming conductive film The processing conditions are the same as in Comparative Example 2 above.

(28) Comparative Example 4
This is an example in which the complexing agent (c) is not contained in the nickel-phosphorus plating bath in the base film forming step (S1) on the basis of Example 1 described above.
(S1) Base film forming step (A) Composition of nickel-phosphorus plating bath and electroplating conditions An electronicking bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes Since the plating bath was decomposed, the formation of the base film itself could not be performed, and the next heat treatment step (S12) was not achieved.

(29) Comparative Example 5
This is an example in which the surfactant (d) of the present invention is not contained in the nickel-phosphorus plating bath in the base film forming step (S1) based on the above Example 1 (with heat treatment).
(S1) Formation process of base film (A) Composition of nickel plating bath and electroplating conditions An electronicking bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(30) Comparative Example 6
This is an example without heat treatment based on the comparative example 5.
(S1) Base film forming step The processing conditions are the same as in Comparative Example 5 above.
(S2) Step of forming conductive film The processing conditions are the same as in Comparative Example 5 above.

(31) Comparative Example 7
On the basis of Example 1 described above, the nickel-phosphorous plating bath in the base film forming step (S1) includes a cationic surfactant instead of the surfactant (d) of the present invention (no heat treatment).
(S1) Formation process of base film (A) Composition of nickel plating bath and electroplating conditions An electronicking bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Lauryltrimethylammonium chloride 20g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(32) Comparative Example 8
This is an example in which the brightener (f) of the present invention is not included in the nickel-phosphorous plating bath in the base film forming step (S1) based on Example 1 (with heat treatment).
(S1) Formation process of base film (A) Composition of nickel plating bath and electroplating conditions An electronicking bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(33) Comparative Example 9
This is an example without heat treatment on the basis of the comparative example 8.
(S1) Base film forming step The processing conditions are the same as in Comparative Example 8 above.
(S2) Step of forming conductive film The processing conditions are the same as in Comparative Example 8 above.

<< Evaluation test example of adhesion of base coating to non-conductive forming light metal >>
As the adhesion of the undercoat to the non-conductive light metal plate increases, the adhesion of the upper conductive film to the light metal plate is improved. Evaluation was based on the superiority or inferiority of the adhesion of the underlying film (which was formed in close contact with one another).
In addition, although the test is evaluated by the adhesion strength of the ground film, except for some comparative examples, in each of the examples, the reference examples, and the comparative examples, the point that the conductive film is formed is also described above. It is as follows.

Therefore, according to JIS K5600 cross-cut method (25 squares), the above Examples 1 to 23, Reference Examples and Comparative Examples 1 to 9 applied to and formed on each sample made of a light metal plate (aluminum alloy plate, magnesium alloy plate). Then, as described above, paying attention to the boundary between the base metal film and the light metal plate formed in close contact with the conductive film, and observe whether the base film peels off the light metal plate starting from the boundary, The superiority or inferiority of the adhesion of the undercoat to the non-conductive formable light metal plate was evaluated based on the following criteria.
That is, out of 25 squares in which a cut was made in the base film, it was judged that the smaller the number of squares actually peeled when the peeling external force was applied, the better the adhesion, and the larger the number, the poorer the adhesion.
A: All of the 25 squares did not peel from the sample.
○: 1 to 3 cells were peeled out of 25 cells.
(Triangle | delta): 4-24 squares peeled among 25 squares.
X: All of 25 squares peeled.

The table below shows the test results.
However, since magnesium alloys are not as diverse as aluminum alloys, the magnesium alloy plate of sample 4 is evaluated only in Examples 1 and 2, and the evaluation of other examples is estimated based on the test results. (See "-" in the examples in the table below).
Further, in Comparative Examples 1 and 4, since the base film could not be formed on the light metal, “-” in the comparative examples in the table below indicates that the base film peeling test itself was not performed.
“Trial n” (n = 1 to 4) in the table below represents “Sample n”.
Trial 1 Trial 2 Trial 3 Trial 4 Trial 1 Trial 2 Trial 3 Trial 4
Example 1 ◎ ◎ ◎ ○ Example 18 ◎ ◎ ◎ −−
Example 2 ◎ ◎ ◎ ○ Example 19 ◎ ◎ ◎ −−
Example 3 ◎ ◎ ◎ −− Example 20 ◎ ◎ ◎ −−
Example 4 ◎ ◎ ◎ −− Example 21 ◎ ◎ ◎ −−
Example 5 ◎ ◎ ◎ −− Example 22 ◎ ◎ ◎ −−
Example 6 ◎ ◎ ◎ −− Example 23 ◎ ◎ ◎ −−
Example 7 ◎ ◎ ◎-Reference example ○ ○ ○ ○
Example 8 ◎ ◎ ◎ −−
Example 9 ◎ ◎ ◎ −− Comparative Example 1 −− −− −−
Example 10 ◎ ◎ ◎ −− Comparative Example 2 △ △ △
Example 11 ◎ ◎ ◎ −− Comparative Example 3 × × ×
Example 12 ◎ ◎ ◎ −− Comparative Example 4 −− −− −−
Example 13 ◎ ◎ ◎--Comparative Example 5 △ △ △
Example 14 ◎ ◎ ◎ −− Comparative Example 6 × × ×
Example 15 ◎ ◎ ◎ −− Comparative Example 7 △ △ △
Example 16 ◎ ◎ ◎--Comparative Example 8 △ △ △
Example 17 ◎ ◎ ◎ −− Comparative Example 9 × × ×

<< Evaluation of test results >>
According to the above table, in Comparative Example 1, an attempt was made to form a conductive film (tin film) directly on a light metal plate without forming a base film, but a tin film was not obtained, and a powdery precipitate was observed. It was only obtained.
On the other hand, in the reference example (without heat treatment) in which the conductive film is formed through the base film, the base film is well adhered to the light metal plate, and as described above, there are various types of aluminum alloys. However, it is judged that the nickel-phosphorus film formed by the electroplating bath of the present invention on the aluminum alloy is versatile, showing good adhesion for all three types of aluminum alloy samples 1 to 3. it can. Moreover, since the said base film shows favorable adhesiveness also to the magnesium alloy of the sample 4, it turns out that a conductive film can be formed with sufficient adhesiveness also through a base film also with respect to a magnesium alloy.
On the other hand, in Examples 1 to 23 in which heat treatment was applied to the undercoat, the adhesion of the undercoat onto the light metal was further improved as compared to the above reference example. It can be seen that the aluminum alloy plate is more firmly attached.
However, with respect to the magnesium alloy plate, the adhesion strength of Examples 1 to 23 was the same as that of the reference example, and was a good adhesion strength.

Next, in Comparative Example 3 above, the base film formed by electroplating on the light metal was changed from the nickel-phosphorus film to the nickel film, and the base film was not heat-treated, but for the light metal plate (aluminum alloy plate) Therefore, the adhesion of the nickel film is significantly inferior to that of the nickel-phosphorus film (it is evaluated as x), and therefore, it is not possible to form a conductive film (tin film) on the non-conductive light metal with good adhesion. It was.
In Comparative Example 2 in which the nickel undercoat was heat-treated, the adhesion was improved as compared with Comparative Example 3 without heat treatment, and the evaluation was Δ, but it still did not reach the reference example that was evaluated as ○. In Examples 1 to 23 in which heat treatment was applied to this reference example, the adhesion of the base film to the aluminum alloy plate was significantly improved, and the evaluation was ◎.
Comparing Comparative Examples 2 to 3 with Examples 1 to 23, when a nickel-based undercoat is formed on a non-conductive light-forming metal such as an aluminum alloy, the nickel electrodeposition coating is inferior in adhesion. In order to realize more practical and strong adhesion, it can be judged that it is important to select a nickel-phosphorus base coating instead of nickel and to heat-treat the base coating.

In Comparative Example 4, a nickel-phosphorus plating bath lacking the predetermined complexing agent of the present invention was intended to form an undercoat on a light metal. However, because the plating bath was unstable, precipitation occurred and electrodeposition was performed. A film could not be formed.
Therefore, when Comparative Example 4 is compared with Examples 1 to 23, in order to form a strong nickel-phosphorus undercoat on a light metal, a predetermined complexing agent is contained instead of a conventionally known nickel-phosphorous plating bath. The importance of selecting the nickel-phosphorous plating bath of the present invention has become apparent.

In Comparative Example 6 described above, a base film was formed on a light metal in a nickel-phosphorus plating bath lacking the predetermined surfactant of the present invention, and the base film was not heat-treated. The adhesion of the film was greatly inferior (it was evaluated as x), and therefore, the conductive film (tin film) could not be formed with good adhesion on the light non-conductive metal.
In Comparative Example 5 in which the base film of Comparative Example 6 was heat-treated, the adhesion was improved as compared with Comparative Example 6 without heat treatment, and the evaluation was Δ. In Examples 1 to 23 in which heat treatment was applied to the examples, the adhesion of the base film to the aluminum alloy plate was significantly improved and was evaluated as ◎.
Therefore, in comparison with Examples 1 to 23, when Comparative Examples 5 to 6 are inferior in adhesion of the undercoat when the nickel-phosphorus plating bath for forming the undercoat lacks a predetermined surfactant, the aluminum alloy plate On the other hand, in order to realize more practical and strong adhesion, it can be determined that it is important to heat-treat the undercoat while containing the surfactant specialized in the present invention in the plating bath.

In Comparative Example 7 described above, a base film was formed on a light metal with a nickel-phosphorus plating bath containing a cationic surfactant instead of the surfactant of the present invention (no heat treatment), but a light metal plate (aluminum alloy plate). The adhesion of the base film to the film was greatly inferior (it was evaluated as x), and therefore, a conductive film (tin film) could not be formed with good adhesion on a non-conductive light-forming metal.
Therefore, when this Comparative Example 7 is compared with Examples 1 to 23, in order to realize more practical and strong adhesion, a nickel-phosphorous plating bath is not a cationic surfactant but an interface specialized in the present invention. It can be judged that it contains an activator and it is important to heat-treat the undercoat.

In Comparative Example 9 described above, a base film was formed on a light metal in a nickel-phosphorous plating bath lacking the predetermined brightener of the present invention, and the base film was not heat-treated, but the base film on a light metal plate (aluminum alloy plate). Therefore, the conductive film (tin film) could not be formed with good adhesion on the non-conductive light metal.
In Comparative Example 8 in which the base film of Comparative Example 9 was heat-treated, the adhesion was improved as compared with Comparative Example 9 without heat treatment, and the evaluation was Δ. In Examples 1 to 23 in which heat treatment was applied to the examples, the adhesion of the base film to the aluminum alloy plate was significantly improved and was evaluated as ◎.
Therefore, when this Comparative Example 8-9 is compared with Examples 1-23, when the predetermined brightener is lacking in the nickel-phosphorus plating bath for forming the undercoat, the adhesiveness of the undercoat is inferior. On the other hand, in order to realize more practical and strong adhesion, it can be judged that it is important to contain the brightener specialized in the present invention in the plating bath and to heat treat the undercoat.

Therefore, Examples 1 to 23 will be described in detail focusing on heat treatment.
First, in Examples 1 to 7, the conductive film is a tin film, Example 8 is also a copper film, Example 9 is also a nickel film, Examples 10 and 13 are also silver films, and Example 11 is also a palladium film. Example 12 is also each example of a tin-bismuth film. By applying heat treatment to the reference example, the adhesion strength of the nickel-phosphorus undercoat on the light metal can be greatly enhanced. Thus, various conductive films can be formed more firmly on the light metal.
In this case, since the upper limit film thickness in Examples 1 to 7 is 0.3 μm, an extremely thin base film of 0.3 μm or less is required to firmly form the base film on the non-conductor-forming light metal by heat treatment. In particular, it can be seen from Example 3 that an extremely thin film such as 0.01 μm is sufficient. Examples 1 to 7 are examples in which the composition of the nickel-phosphorous plating bath in step (S1), that is, the type of complexing agent, surfactant, nickel salt, phosphorus compound, brightening agent, etc., was changed. When a base film is formed using a nickel-phosphorous plating bath with conditions suitable for the invention and this is heat-treated, even if the composition of the plating bath is different (as compared to the reference example) ) It can be seen that it can be greatly improved.

Next, focusing on the temporal conditions of this heat treatment, Examples 1 to 13 are intermediate heat treatment methods in which the heat treatment step (S12) is performed after the base film formation step (S1), and Examples 14 to 17 are conductive film formation steps. (S2) This is a post-stage heat treatment method in which the heat treatment step (S3) is performed later, but in any method, the adhesion of the undercoat can be greatly strengthened, and the conductive film is made stronger on the light metal than the reference example. Since adhesion can be formed, it can be determined that the strengthening of adhesion does not matter when the heat treatment is performed.
Further, focusing attention on the additional conditions for heat treatment, Examples 1 to 17 were roasted at 70 ° C. for 20 minutes, Example 18 was 35 ° C. for 80 minutes, Example 19 was 50 ° C. for 30 minutes, Example No. 20 was 90 ° C. and 10 minutes of hot water, respectively. The hot water bath, which is a relatively simple heating means, and heating in a low temperature range of 100 ° C. or lower (see Reference Example) Compared to). Moreover, as in Example 18, it was confirmed that the adhesion can be enhanced by continuing the heat treatment over a very low temperature range (35 ° C.).
If heat treatment in a relatively high temperature range such as dryer heating as in Example 21 or oven heating as in Examples 22 to 23 is selected instead of hot water bath, the heating time can be shortened.
In summary, if hot water bathing is selected as a heat treatment condition, the input of heat energy can be reduced and productivity can be improved.

That is, the present invention 1 comprises (S1) a step of forming a base film composed of a nickel-phosphorus film on a non-conductive formable light metal selected from aluminum, magnesium, and titanium using an electric nickel-phosphorous plating bath;
(S2) In a method for forming a conductive film comprising a step of forming a conductive film on a base film ,
A step (S12) of heat-treating the base film at 30 ° C. or higher is interposed between the step (S1) and the step (S2), or
After adding the process (S3) which heat-processes a base film and an electroconductive film at 30 degreeC or more after the said process (S2),
The electric nickel-phosphorous plating bath is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) A method of forming a heat-treatable conductive film on a non-conductive formable light metal, comprising a brightener.

The present invention relates to a method for forming a conductive film on a specific light metal selected from aluminum and magnesium that are easily formed into a nonconductive state. Provided are those capable of forming a conductive film such as silver or tin with a strong adhesion.

This invention makes it a technical subject to strengthen the adhesive force of electroconductive films, such as silver, copper, and tin, with respect to the specific light metal chosen from aluminum and magnesium which are easy to form a non-conductive state.

That is, the present invention 1 includes (S1) a step of forming a base film composed of a nickel-phosphorus film on a non-conductive formable light metal selected from aluminum and magnesium using an electric nickel-phosphorous plating bath;
(S2) In a method for forming a conductive film comprising a step of forming a conductive film on a base film,
A step (S12) of heat-treating the base film at 30 ° C. or higher is interposed between the step (S1) and the step (S2), or
After adding the process (S3) which heat-processes a base film and an electroconductive film at 30 degreeC or more after the said process (S2),
The electric nickel-phosphorous plating bath is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) A method of forming a heat-treatable conductive film on a non-conductive formable light metal, comprising a brightener.

The present invention 3 is the invention 1 or 2, wherein the complexing agent (c) of the electric nickel-phosphorus plating bath is citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid Onto a non-formable light metal characterized by being at least one of oxycarboxylic acid selected from diethylenetriaminepentaacetic acid, polycarboxylic acid, aminocarboxylic acid or salt thereof , amino alcohols, polyamines, and carbohydrates This is a heat treatment type conductive film forming method.

Invention 4 is that in any one of Inventions 1 to 3, the buffer (e) of the electro-nickel-phosphorous plating bath is at least one of boric acid, sodium carbonate, sodium bicarbonate, ascorbic acid or a salt thereof. This is a heat treatment type conductive film forming method on a non-conductive-formable light metal.

In the above-mentioned prior application invention, when a conductive film such as copper, tin, silver or the like is formed on a non-conductive film-like light metal selected from aluminum, magnesium, and titanium, a predetermined complexing agent, a surfactant, After forming a base film consisting of a nickel-phosphorus film formed using an electric nickel-phosphorous plating bath containing a buffering agent on the light metal, and then forming a conductive film, the base film can be satisfactorily adhered onto the light metal. Thus, a conductive film can be formed on the light metal with good adhesion.
The present invention is an improvement of this prior invention, and based on the treatment process of the prior application, an undercoat formed on a light metal selected from aluminum and magnesium , or an undercoat and a conductive film of 30 ° C. or higher. By adding the heat treatment step under the temperature condition including the low temperature region, the adhesion of the base film on the light metal can be further strengthened, and the conductive film can be formed on the light metal with better adhesion.
About the said heat processing, the adhesive force of the base film on a light metal can fully be reinforce | strengthened also by simple heat processing in a low temperature range, such as bathing at 30-100 degreeC, for example. Moreover, if heat treatment is performed in a low temperature range, the energy to be dropped can be reduced and the productivity can be improved.

The present invention is a method of forming a conductive film such as silver, copper, or tin on a specific light metal that easily forms a non-conductive state selected from aluminum and magnesium via a base film made of a nickel-phosphorus film. The undercoat is formed with a nickel-phosphorus film using an electroplating bath having a predetermined composition containing a specific complexing agent, a surfactant, a brightener, and the like. In this method, heat treatment is performed, or the base film and the conductive film are similarly heat-treated after the formation of the conductive film in the next step.
The above aluminum includes pure aluminum and aluminum alloys, and the above magnesium includes the concept of pure magnesium and magnesium alloys.

The present invention comprises the following undercoat film forming step (S1), conductive film forming step (S2), and a heat treatment step after step (S1) or after step (S2) (see the present invention 1). .
(S1) A step of forming a base film composed of a nickel-phosphorus film on a non-conductive- formable light metal selected from aluminum and magnesium using an electric nickel-phosphorous plating bath (S2) a conductive film on the base film In addition, the electric nickel-phosphorus plating bath used in the step (S1) is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) Brightener is an essential component.

The buffer (e) contained in the electric nickel-phosphorous plating bath improves the adhesion of the undercoat to a non-conductive light metal selected from aluminum and magnesium, and also acts as a plating bath stabilizer.
Examples of the buffer (e) include boric acid, sodium carbonate, sodium bicarbonate, ascorbic acid and the like, and boric acid and sodium carbonate are preferable.
The buffer (e) can be used singly or in combination, and its content with respect to the plating bath is 0.05 to 1.5 mol / L, preferably 0.05 to 1.0 mol / L, more preferably 0. 0.1 to 0.6 mol / L.

The brightening agent (f) contained in the electric nickel-phosphorus plating bath functions to improve the adhesion of the nickel-phosphorus film to a non-conductive light metal selected from aluminum and magnesium.
Examples of the brightener (f) include saccharin and its salt, benzenesulfonic acid and its salt, p-toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butynediol (specifically Are 2-butyne-1,4-diol), ethylene cyanohydrin, coumarin, propargyl alcohol, bis (3-sulfopropyl) disulfide, mercaptopropanesulfonic acid, thiomalic acid and the like.
The brightener (f) is effective even if the components are used alone, but it is suitable to combine the components, and in particular, benzenesulfonic acid or a salt thereof and saccharin, naphthalenesulfonic acid or a salt thereof and saccharin, butyne Diol and benzenesulfonic acid or salt thereof, butynediol and naphthalenesulfonic acid or salt thereof, allylsulfonic acid or salt thereof and saccharin, thiomalic acid and saccharin, bis (3-sulfopropyl) disulfide and saccharin, allylsulfonic acid or salt thereof It is preferable to use two or more in combination such as, propargyl alcohol, benzenesulfonic acid or a salt thereof, propargyl alcohol, naphthalenesulfonic acid or a salt thereof and propargyl alcohol.
As described above, the brightener (f) can be used singly or in combination, and its content with respect to the plating bath is 0.001 to 0.15 mol / L, preferably 0.005 to 0.07 mol / L. Preferably it is 0.01-0.05 mol / L.

The electric nickel-phosphorus plating bath of the present invention is intended to form a nickel-phosphorus film on a non-conducting light metal selected from aluminum and magnesium, but the pH of the plating bath is 3.0-8. 0.0 is suitable, preferably 4.0 to 6.0.
In the base formation step (S1), the cathode current density at the time of electroplating is 0.01 to 5.0 A / dm 2, and preferably 0.05 to 2.0 A / dm 2.
In the undercoat film forming step (S1), the nickel-phosphorus film as the undercoat film is not required to be formed thick because it only needs to provide conductivity and adhesion sufficient to form a conductive film on the upper layer. Accordingly, the film thickness is 0.01 to 10.0 μm, preferably 0.01 to 8.0 μm, more preferably 0.01 to 5.0 μm.

On the other hand, the following Comparative Examples 1 to 9 are based on Example 1, and in Comparative Example 1, a conductive film was directly formed by electroplating without forming a base film on a light metal such as an aluminum alloy. It is a blank example (example without heat treatment).
Comparative Examples 2 to 3 were obtained by forming a conductive film on a light metal via a nickel base film instead of a nickel-phosphorus film, Comparative Example 2 was an example of heat treatment, and Comparative Example 3 was an example of no heat treatment. It is.
Comparative Examples 4 to 9 are examples in which the nickel-phosphorous plating bath in the undercoat film forming step (S1) of the present invention does not contain some of the essential components or are replaced with other components, and Comparative Example 4 is the plating. In this example, the bath does not contain the complexing agent (c).
Comparative Examples 5 to 6 do not contain the surfactant (d) of the present invention in the nickel-phosphorous plating bath, Comparative Example 5 is an example in which heat treatment was performed, and Comparative Example 6 is an example in which no heat treatment was performed.
In Comparative Example 7, a cationic surfactant was used in the nickel-phosphorous plating bath instead of the surfactant (d) of the present invention, and no heat treatment was performed.
Comparative Examples 8-9 do not contain the brightener (f) of the present invention in the nickel-phosphorous plating bath, Comparative Example 8 is an example in which heat treatment was performed, and Comparative Example 9 is an example without heat treatment.

(13) Example 13
Based on Example 1 above, the conductive film was changed.
(S1) Base film forming step The processing conditions are the same as in Example 1 above.
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Formation process of conductive film Based on Example 1, the conductive film was changed to a silver film.
(B) Conductive film: silver An electroless silver plating bath was constructed with the following composition.
Silver nitrate (as Ag +) 0.01 mol / L
Succinimide 0.05 mol / L
Imidazole 0.05 mol / L
[ Electroless plating conditions]
Bath temperature: 50 ° C
Plating time: 60 minutes [Plating film]
Film thickness: 1.0μm

(28) Comparative Example 4
This is an example in which the complexing agent (c) is not contained in the nickel-phosphorus plating bath in the base film forming step (S1) on the basis of Example 1 described above.
(S1) primer film forming step (A) a nickel - phosphorus plating bath composition and electroplating conditions The following electric nickel composition - was bath preparation phosphorus plating bath.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes Since the plating bath was decomposed, the formation of the base film itself could not be performed, and the next heat treatment step (S12) was not achieved.

(29) Comparative Example 5
This is an example in which the surfactant (d) of the present invention is not contained in the nickel-phosphorus plating bath in the base film forming step (S1) based on the above Example 1 (with heat treatment).
(S1) primer film forming step (A) Electrical nickel composition and electroplating conditions The following composition of nickel plating bath - were bath preparation phosphorus plating bath.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(31) Comparative Example 7
On the basis of Example 1 described above, the nickel-phosphorous plating bath in the base film forming step (S1) includes a cationic surfactant instead of the surfactant (d) of the present invention (no heat treatment).
(S1) primer film forming step (A) Electrical nickel composition and electroplating conditions The following composition of nickel plating bath - were bath preparation phosphorus plating bath.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Saccharin 0.02 mol / L
Thiomalic acid 0.01 mol / L
Lauryltrimethylammonium chloride 20g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

(32) Comparative Example 8
This is an example in which the brightener (f) of the present invention is not included in the nickel-phosphorous plating bath in the base film forming step (S1) based on Example 1 (with heat treatment).
(S1) step of forming the primer film (A) Nickel - phosphorus plating bath composition and electroplating conditions The following electric nickel composition - was bath preparation phosphorus plating bath.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Trisodium citrate dihydrate 0.3 mol / L
Ethylenediaminetetrapolyoxyethylene (EO 40 mol)
-Polyoxypropylene (PO50 mol) 10g / L
pH (adjusted with 28% ammonia) 4.5
[Electroplating conditions]
Bath temperature: 35 ° C
Current density: 0.5 A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat treatment step The treatment conditions are the same as in the first embodiment.
(S2) Step of forming conductive film The processing conditions are the same as in Example 1 above.

The brightening agent (f) contained in the electric nickel-phosphorus plating bath functions to improve the adhesion of the nickel-phosphorus film to a non-conductive light metal selected from aluminum and magnesium .
Examples of the brightener (f) include saccharin and its salt, benzenesulfonic acid and its salt, p-toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butynediol (specifically Are 2-butyne-1,4-diol), ethylene cyanohydrin, coumarin, propargyl alcohol, bis (3-sulfopropyl) disulfide, mercaptopropanesulfonic acid, thiomalic acid and the like.
The brightener (f) is effective even if the components are used alone, but it is suitable to combine the components, and in particular, benzenesulfonic acid or a salt thereof and saccharin, naphthalenesulfonic acid or a salt thereof and saccharin, butyne Diol and benzenesulfonic acid or salt thereof, butynediol and naphthalenesulfonic acid or salt thereof, allylsulfonic acid or salt thereof and saccharin, thiomalic acid and saccharin, bis (3-sulfopropyl) disulfide and saccharin, allylsulfonic acid or salt thereof It is preferable to use two or more in combination such as, propargyl alcohol, benzenesulfonic acid or a salt thereof, propargyl alcohol, naphthalenesulfonic acid or a salt thereof and propargyl alcohol.
As described above, the brightener (f) can be used singly or in combination, and its content with respect to the plating bath is 0.001 to 0.15 mol / L, preferably 0.005 to 0.07 mol / L. Preferably it is 0.01-0.05 mol / L.

The electric nickel-phosphorus plating bath of the present invention is intended to form a nickel-phosphorus film on a non- conducting light metal selected from aluminum and magnesium, but the pH of the plating bath is 3.0-8. 0.0 is suitable, preferably 4.0 to 6.0.
In the base formation step (S1), the cathode current density at the time of electroplating is 0.01 to 5.0 A / dm 2, and preferably 0.05 to 2.0 A / dm 2.
In the undercoat film forming step (S1), the nickel-phosphorus film as the undercoat film is not required to be formed thick because it only needs to provide conductivity and adhesion sufficient to form a conductive film on the upper layer. Accordingly, the film thickness is 0.01 to 10.0 μm, preferably 0.01 to 8.0 μm, more preferably 0.01 to 5.0 μm.

Claims (8)

(S1) forming a base film made of a nickel-phosphorus film on a non-conductive formable light metal selected from aluminum, magnesium and titanium using an electric nickel-phosphorous plating bath;
(S2) In a conductive film forming method comprising a step of forming a conductive film on a heat-treated base film,
A step (S12) of heat-treating the base film at 30 ° C. or higher is interposed between the step (S1) and the step (S2), or
After adding the process (S3) which heat-processes a base film and an electroconductive film at 30 degreeC or more after the said process (S2),
The electric nickel-phosphorous plating bath is
(a) a soluble nickel salt;
(b) a compound containing phosphorus;
(c) a complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, carbohydrates, aminoalcohols, polycarboxylic acids, polyamines;
(d) a surfactant selected from nonionic surfactants and amphoteric surfactants;
(e) a buffering agent;
(f) A method of forming a heat-treatable conductive film on a non-conductive formable light metal, comprising a brightener.   Phosphorous acid, hypophosphorous acid, pyrophosphoric acid, orthophosphoric acid, hydroxyethylenediamine diphosphonic acid, nitrilotris (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) The method for forming a heat-treatable conductive film on a non-conductive-formable light metal according to claim 1, which is at least one of these salts.   The complexing agent (c) of the electric nickel-phosphorous plating bath is an oxycarboxylic acid selected from citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, poly The method for forming a heat-treatable conductive film on a nonconductive non-formable light metal according to claim 1 or 2, which is at least one of carboxylic acid, aminocarboxylic acid or a salt thereof.   The buffer (e) of the electric nickel-phosphorus plating bath is at least one of boric acid, sodium carbonate, sodium hydrogen carbonate, nickel acetate, ascorbic acid or a salt thereof. A method for forming a heat-treatable conductive film on the non-conductive formable light metal described in 1.   The brightener (f) of the electro-nickel-phosphorous plating bath is saccharin and its salt, benzenesulfonic acid and its salt, toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butynediol, ethylene cyanide The hydrin, coumarin, propargyl alcohol, bis (3-sulfopropyl) disulfide, mercaptopropane sulfonic acid, or thiomalic acid is at least one compound selected from any one of claims 1-4. A method for forming a heat-treatable conductive film on the non-conductive formable light metal described in 1.   6. A heat-treatable conductive film on a non-conductive non-forming light metal according to claim 1, wherein the pH of the electric nickel-phosphorous plating bath is 3.0 to 8.0. Forming method.   The film thickness of the undercoat is 0.01 to 10.0 µm, The heat-treatable conductive film formation on the non-conductive formable light metal according to any one of claims 1 to 6 Method. The conductive film is formed by electroplating, electroless plating, sputtering or vapor deposition,
The conductive film is a film made of a metal selected from copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc, and chromium, or an alloy of these metals. The method for forming a heat-treatable conductive film on the non-conductive formable light metal according to any one of claims 1 to 7.