JPH07286296A - Method for electroless nickel plating aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To provide an electroless nickel plating method capable of applying a lustrous nickel plating film having high adhesive strength and an extremely smooth surface on an aluminum or aluminum alloy. CONSTITUTION:An aluminum or aluminum alloy is anodized by using phosphoric acid or pyrophosphoric acid as the treating bath and using an AC current or a reversing current as the current to form an anodic oxide film having 0.05-0.20mum thickness measured by ESCA on the aluminum or aluminum alloy, then a catalyst nucleus is deposited on the film, and then electroless plating is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroless nickel plating of aluminum or aluminum alloy, which is 90 °
Provided is a novel electroless nickel plating method for aluminum or aluminum alloy, which has a adhesion strength that does not cause peeling even by a bending test (JIS H 8504), and has a very smooth surface and a bright nickel plating film. It is a thing.

[0002]

2. Description of the Related Art Conventionally, various pretreatments have been carried out in performing electroless plating using aluminum or an aluminum alloy as an object to be plated. It is well known that there is a pretreatment technology called "anodic oxide film formation / secondary electrolytic coloring method" in which an anodized film is formed and a metal serving as a catalytic nucleus of electroless plating is attached to the film. .
As a typical example of this pretreatment technique, aluminum or an aluminum alloy is anodized to form a porous anodic oxide film, and then a metal serving as a catalyst nucleus for electroless plating is formed in the fine pores of the porous film. Special fair 2 to let you turn electronically
The pretreatment technique described in JP-A-45704 (Japanese Patent Laid-Open No. 59-140398) can be used.

Further, Japanese Examined Patent Publication No. 2-50988 (Japanese Patent Laid-Open No. 61-194184) discloses "... Japanese Laid-Open Patent Publication No. 59-140398,"
A method has been proposed in which the metal to be projected into the pores in the anodized film is kept at the bottom of the pores, and then electroless plating is performed to obtain a plating film with higher adhesion. However, the present invention has solved the problem of the surface roughness of the plating film in the anodic oxide film formation / secondary electrolytic coloring method ... the aluminum film has a smoothness and adhesion strength. Or, it is formed on the alloy promptly and surely ... "Before the pretreatment as described in JP-B-2-45704, electrolytic etching is performed on aluminum or an aluminum alloy using a caustic soda bath. A pretreatment technique is described in which an electroless plating film having a smoother surface is obtained by applying treatment.

[0004]

The pretreatment techniques described in the above publications are all electroless plating having a stronger adhesion strength and a smoother surface by the anodic oxide film formation / secondary electrolytic coloring method. Although it has been proposed to obtain a coating as a technical problem, it is hard to say that the obtained plating coating has sufficient adhesion strength, smoothness, and gloss according to the results of additional tests by the present inventors. Also, since it takes a long time to form the anodized film and strict processing condition setting is required, it is difficult to say that it is sufficiently satisfactory in terms of efficiency and ease of implementation in industrial implementation. Was inherent.

Therefore, the present inventors have decided to form an anodized film.
As a technical problem to solve the above problems by further improving the secondary electrolytic coloring method, as a result of repeated research and experimentation, an anodized film, using a phosphoric acid or pyrophosphoric acid bath as a treatment bath, In addition, when the film is formed by anodizing treatment using an alternating current as an electric current, the anodized film should be as thin as possible (specifically, ESCA: the thickness measured by ESCA method is 0.05 μm). As a result, the inventors have obtained a remarkable new finding that an electroless plating film having satisfactory adhesion strength, smoothness, and gloss can be obtained, thereby completing the present invention.

Incidentally, in the pretreatment technique described in Japanese Patent Publication No. 2-45704, the process of forming an anodic oxide film is as follows: "The treatment bath for anodic oxidation treatment is an inorganic acid bath represented by a normal sulfuric acid bath, or oxalic acid. A representative organic acid bath or a mixed acid bath thereof may be used, and the current to be used may be a direct current, an alternating current, an alternating current (presumed to be a erroneous "direct") superposition, or the like ( It is presumed that "any of" is erroneously written), and the thickness of the anodized film formed is "2 to 8 µm" in "Example".
Those within the range of "m" are shown. Further, in the anodic oxide film forming step in the pretreatment technique described in Japanese Patent Publication No. 50988/1990, "... in the case of a phosphoric acid bath, when using DC electrolysis, sulfuric acid, silicic acid, and sulfamic acid baths, It is said that an oxide film having a large pore diameter as shown in FIG. 2 is formed by electrolysis by alternating current electrolysis or a waveform having a pole change, and the thickness of the anodized film formed is "... the minimum required thickness. 0.2 to 6 μm, preferably 0.
It is about 5 to 3 μm.

[0007]

The above technical problems can be achieved by the present invention as follows. That is, the present invention is an aluminum for performing electroless nickel plating after performing a pretreatment of forming an anodized film on aluminum or an aluminum alloy to be plated and depositing a metal serving as a catalyst nucleus of electroless plating on the film. Or in the electroless nickel plating method of aluminum alloy, the anodized film,
A phosphoric acid or pyrophosphoric acid bath is used as a treatment bath, and an anodic oxidation treatment using an alternating current or a current reversal as an electric current exceeds a value measured by the esca method of 0.05 μm and exceeds 0.20 μm.
It is an electroless nickel plating method of aluminum or aluminum alloy, which is characterized in that it is formed to a thickness of less than m 2.

The structure of the present invention will be described in more detail as follows. The most important point in the present invention is that the anodic oxide film formation is carried out by using a phosphoric acid or pyrophosphoric acid bath as a treatment bath, and alternating current or current reversal is used as a current. Well-known or well-known various technical means (for example, various technical means described in the above-mentioned respective publications) adopted when performing electroless plating using an alloy as an object to be plated are used. Therefore, first, various conditions for forming the anodized film in the present invention will be described.

The present inventors have found from the results of many experiments that the JIS 1100Al plate material and the JIS currently in practical use are used.
3003Al plate, JIS 5052Al plate, JI
S6061Al plate material, JIS 7003Al plate material and aluminum or aluminum alloy such as ADC-12 are anodized by using phosphoric acid or pyrophosphoric acid bath as a treatment bath and alternating current as an electric current to form an anodized film. In this case, it has been confirmed that an ultra-thin film showing a measured value by the Escal method of more than 0.05 μm and less than 0.20 μm can be formed with good reproducibility without setting strict processing conditions.

That is, in the present invention, the concentration of the phosphoric acid or pyrophosphoric acid bath is 2 to 40% by volume, preferably 5 to 2%.
The ultrathin anodic oxide film can be formed within the range of 5% by volume.

In the present invention, the AC current density is 0.4 to 8.0 A / dm ² , preferably 0.8 to 6.0 A.
The ultrathin anodic oxide film can be formed within the range of / dm ² .

In the present invention, the temperature of the phosphoric acid or pyrophosphoric acid bath is 5 ° C to 40 ° C, preferably 10 ° C to 3 ° C.
The ultrathin anodic oxide film can be formed at a temperature of 0 ° C, more preferably 15 ° C to 20 ° C.

In the present invention, the processing time is 60 seconds to 6 seconds.
The ultrathin anodic oxide film can be formed within a range of 00 seconds, preferably 120 seconds to 400 seconds.

As the counter electrode, an insoluble counter electrode such as platinum, stainless steel or lead may be used.

Prior to forming an anodized film under the conditions as described above, the aluminum or aluminum alloy to be treated may be subjected to pretreatments such as polishing, degreasing and acid treatment according to a conventional method. desirable.

Next, after forming the anodic oxide film, as described above, a process of attaching a metal serving as a catalyst nucleus of electroless plating to the film is performed by using various well-known or publicly known technical means. Alternatively, electroless nickel plating may be performed. In this case, the metal serving as the catalytic nucleus of electroless plating is optimally Ni, and the deposition treatment is optimally by electrodeposition.
The desirable conditions are as follows.

Ni bath: NiSO ₄ · 6H ₂ O when NiSO ₄ alone
Is about 20 g / l or more, and when NiSO ₄ and H ₃ BO ₃ are used, NiSO ₄ .6H ₂ O is about 3 g / l or more and H ₃ BO ₃ is 20 to 30 g / l. The voltage is 5V ~ 15
V. The bath temperature is 15 ° C to 50 ° C. Processing time is 3
It is 0 to 240 seconds. The pH value is in the range of 4-7. Note that the Ni bath, according to a conventional method, (NH _{4) 2} SO ₄
Etc. are added.

When Ni was electrodeposited under the above conditions, the anodized film was formed in the film even though it was an ultrathin film.
Ni is sufficiently adhered, and as shown in the examples described later, electroless nickel plating can be performed by a conventional method to form an electroless plating film having excellent adhesion strength.

The electroless nickel plating may be carried out by a conventional method using a commercially available electroless nickel plating solution. In this case, as the electroless nickel plating solution, for example, Top Nicolon N-47 (trade name: Okuno Pharmaceutical Co., Ltd.)
Manufactured by Top Nicolon BL (trade name: manufactured by Okuno Chemical Industries Co., Ltd.) are preferable, and desirable conditions are: bath temperature: 8
The temperature is 5 ° C to 95 ° C, the treatment time is 10 minutes or more, and the pH value is 4 to 5.

[0020]

In the present invention, an ultra-thin anodic oxide film having a value measured by the Eska method of more than 0.05 μm and less than 0.20 μm is formed within the above-mentioned conditions without setting strict treatment conditions. It can be presumed that the reason is that when the anodic oxide film is formed, its surface is dissolved one after another in phosphoric acid or pyrophosphoric acid, so that it is difficult to increase the film thickness beyond a certain thickness. .

Further, in the present invention, Ni, which serves as a catalyst nucleus of electroless nickel plating, is sufficiently adhered to the anodized film of the ultrathin film because the film is the above-mentioned ultrathin film over the entire surface thereof. The presence of fine and uniform irregularities can be confirmed by an electron microscope, and it can be inferred that the deposited Ni adheres to the irregularities of the irregularities.

Further, in the present invention, the electroless nickel plating film excellent in all of the adhesion strength, smoothness and luster as shown in the following examples can be obtained because the surface of the anodic oxide film at the time of electroless nickel plating is obtained. When the metal (same as above) attached to the concave and convex portions of the above and the electroless nickel plating solution react, the anodic oxide film is destroyed because it is the above-mentioned ultra thin film, and electroless nickel plating is performed. Can be estimated to be a factor. Although it is impossible to visually observe the above-mentioned destruction phenomenon of the anodic oxide film at the time of electroless nickel plating, the present inventors have conducted experiments to determine that the thickness of the anodized film is 0.
It has been confirmed that when an anodic oxide film having a thickness of more than 2 μm is formed, the smoothness and luster shown in the later-described examples cannot be obtained. From this fact, according to the present invention, the anode is used during electroless nickel plating. Since it cannot help thinking that the oxide film was destroyed, it estimated as above.

[0023]

EXAMPLES The constitution, action and effect of the present invention will be described below with reference to examples and comparative examples. The thickness of the anodic oxide film is measured by the ESCA method (XSAM-800: Shimadzu-Craitos, Inc.
Manufactured by the company), metal microscope and electron microscope, the nickel plating film thickness is measured by a micrometer, and the adhesion strength is 90 ° C bending test (JIS.
H 8504) was not peeled off, and the peeled off is indicated by X. The surface roughness was measured by a stylus type surface roughness meter (Model No. 554A: manufactured by Tokyo Seimitsu Co., Ltd.). The gloss was measured visually, and the one with strong gloss was indicated by a circle, the one with a weak gloss was indicated by a triangle, and the one without gloss was indicated by a cross.

Example 1 The surface of JIS 1100 Al plate material was polished by a conventional method to obtain R.
The object to be plated had a surface roughness of max 0.5 μm. Concentration of phosphoric acid bath: 20% by volume phosphoric acid, liquid temperature of the phosphoric acid bath: 25 ° C., alternating current density: 2 A / dm ² , counter electrode: platinum, and electrolytic treatment time: 300 seconds. An anodized film was formed on the surface. The thickness of this anodic oxide film was 0.10 μm according to the Escal method. Then, an electroless Ni bath composition and _{Concentration: NiSO 4 · 6H 2 O 100g} / l, H 3 BO
₃ 30g / l, liquid temperature of the Ni bath: 25 ° C, pH value of the Ni bath: pH
4. Under the conditions of AC voltage: 10 V, counter electrode: Ni, and treatment time: 60 seconds, Ni serving as catalyst nuclei was adhered to the object to be plated on which the anodic oxide film was formed according to a conventional method. Finally, a commercially available electroless nickel plating solution (Top Nicolon N-4
7: above), liquid temperature: 92 ° C., pH value of bath: pH 4.
5 and treatment time: 45 minutes, according to a conventional method, electroless nickel plating was performed on the object to be plated on which the catalyst nucleus Ni was attached. The thickness of this nickel plating film is 10 μm
Met. The nickel plating film thus obtained had an adhesion strength of ◯, a smoothness (surface roughness) of Rmax of 1.01 μm, and a gloss of ◯.

As the object to be plated, JIS 300
3Al plate material, JIS 5052Al plate material and JIS 606
The 1Al plate material was subjected to anodizing treatment, catalytic nucleation treatment and electroless nickel plating under the same conditions as above, and the results were the same as in the case of the JIS1100Al plate material.

Example 2 The surface of JIS 7003 Al plate material was polished by a conventional method to obtain R.
The object to be plated had a surface roughness of max 0.5 μm. Concentration of phosphoric acid bath: 5% by volume phosphoric acid, liquid temperature of the phosphoric acid bath: 20 ° C., alternating current density: 1.5 A / dm ² , counter electrode: platinum, and electrolytic treatment time: 600 seconds. An anodized film was formed on the surface of the plated product. The thickness of this anodized film was 0.15 μm according to the Escal method. next,
The composition and density of the electrolytic Ni _{bath: Ni (NH 2 SO 3)} 2 · 4H 2 O 200
g / l, liquid temperature of the Ni bath: 20 ° C., pH value of the Ni bath: pH 4.
5. Under the conditions of AC voltage: 15 V and treatment time: 30 seconds, Ni serving as catalyst nuclei was adhered to the object to be plated on which the anodic oxide film was formed according to a conventional method. Finally, under the same conditions as in Example 1, electroless nickel plating was performed on the object to be plated on which the catalyst nucleus Ni had been attached. The thickness of this nickel plating film was 10 μm. The nickel plating film thus obtained had an adhesion strength of ◯, a smoothness (surface roughness) of Rmax 0.96 μm, and a gloss of ◯.

JIS 1100 is used as the object to be plated.
Using an Al plate material and an ADC-12 plate material, anodization treatment, catalyst nucleus attachment treatment and electroless nickel plating were performed under the same conditions as above, and the results are the above JIS 70.
It was similar to the case of 03Al plate material.

Example 3 When forming the anodic oxide film, the "phosphoric acid bath" was changed to a 10% by volume pyrophosphoric acid bath, and the "treatment time: 300 seconds" was changed to a treatment time: 600.
An anodic oxide film was formed under the same conditions as in Example 1 except that the time was changed to seconds. The thickness of this anodized film was 0.08 μm according to the Escal method. Next, catalyst nucleation and electroless nickel plating were performed on the object to be plated on which the anodic oxide film was formed, in the same manner as in Example 1. The adhesion strength of the nickel-plated film obtained here was ◯, the smoothness (surface roughness) was Rmax 0.98 μm, and the gloss was ◯.

Example 4 An anodic oxide film was formed under the same conditions as in Example 2 except that the "phosphoric acid bath" used for forming the anodic oxide film was changed to a 5% by volume pyrophosphoric acid bath. The thickness of this anodized film was 0.08 μm according to the Escal method. Next, catalyst nuclei deposition and electroless nickel plating were performed on the object to be plated on which the anodized film was formed, in the same manner as in Example 2. The adhesion strength of the nickel plating film obtained here was ◯, the smoothness (surface roughness) was Rmax 1.05 μm, and the gloss was ◯.

Example 5 Example 1 except that the "commercial electroless nickel plating solution (Top Nicolon N-47: described above)" at the time of electroless nickel plating was changed to (Top Nicoron BF: described above). A nickel plating film was formed in exactly the same manner as in. The nickel plating film obtained here had an adhesion strength of ◯, a smoothness (surface roughness) of Rmax of 1.00 μm, and a gloss of ◯.

Example 6 Example 1 was repeated except that the “AC current density: 2 A / dm ² ” at the time of forming the anodic oxide film was changed to the current reversal current density: 2 A / dm ^2.
A nickel plating film was formed under the same conditions as above. In this case, the thickness of the anodic oxide film is 0.12 μm according to the Escal method.
The adhesion strength of the nickel plating film was ◯, the smoothness (surface roughness) was Rmax 0.96 μm, and the gloss was ◯.

Comparative Example 1 Anodizing treatment was carried out in the same manner as in Example 1 except that "AC current density: 2 A / dm ² " at the time of forming an anodized film was changed to DC current density: 0.5 A / dm ^2. , Catalytic nucleation treatment and electroless nickel plating were performed. The thickness of the anodized film in this case was 0.5 μm according to the Esca method. Further, the adhesion strength of the nickel plating film obtained here is ○,
The smoothness (surface roughness) was Rmax of 1.92 μm, and the gloss was Δ.

Comparative Example 2 A "phosphoric acid bath" used for forming an anodic oxide film had a concentration of H ₂ SO ₄ 15
Anodizing treatment, catalyst nucleus attachment treatment, and electroless nickel plating were performed in the same manner as in Example 1 except that the sulfuric acid bath was changed to 0 g / l. In this case, the thickness of the anodic oxide film was 1.8 μm according to a metallographic microscope and an electron microscope. Further, the adhesion strength of the nickel plating film obtained here is ○,
The smoothness (surface roughness) was Rmax 2.42 μm, and the gloss was x.

Examples 7 to 11 and Comparative Examples 3 to 5 The surface of JIS 1100 Al plate was polished by a conventional method to obtain R.
Each of the objects to be plated having a surface roughness of max 0.5 μm was subjected to anodizing treatment under the conditions shown in Table 1, and then subjected to catalytic nucleation treatment and electroless nickel plating under the same conditions as in Example 1. The results of the treatment are shown in Table 2.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

EFFECTS OF THE INVENTION According to the present invention, as shown in the examples, it is possible to apply a nickel plating film having excellent adhesion strength and having a very smooth surface and gloss to aluminum or aluminum alloy. You can Further, in the present invention, an ultrathin anodic oxide film can be easily formed with good reproducibility without setting strict treatment conditions. Further, in the present invention, the anodic oxide film can be formed in a short time. Further, in the present invention, since the ultra-thin anodic oxide film is formed, the jig residue does not remain even if the contact is changed during the anodic oxidation treatment, so that so-called "hand-over" in the plating technique can be performed. Therefore, it can be said that the industrial applicability of the present invention is extremely high.

Claims (5)

[Claims] 1. An aluminum or aluminum alloy to be plated, which is subjected to a pretreatment of forming an anodized film on an aluminum or aluminum alloy and depositing a metal serving as a catalytic nucleus of the electroless plating on the film, followed by electroless nickel plating. In the electroless nickel plating method for an aluminum alloy, the anodized film is used as a treatment bath using a phosphoric acid or pyrophosphoric acid bath, and an anodic oxidation treatment using an alternating current or a current reversal as a current gives a measured value of 0.05 by the esca method.
A method for electroless nickel plating of aluminum or aluminum alloy, which is characterized in that it is formed to a thickness of more than μm and less than 0.20 μm. 2. The concentration of phosphoric acid or pyrophosphoric acid bath is 2 to 4.
The electroless nickel plating method for aluminum or aluminum alloy according to claim 1, wherein the anodic oxide film is formed within the range of 0% by volume. 3. The electroless nickel plating method for aluminum or aluminum alloy according to claim 1, wherein the anodic oxide film is formed with an alternating current in the range of 0.4 to 8.0 A / dm ² . 4. The temperature of the phosphoric acid or pyrophosphoric acid bath is 5 ° C.
The electroless nickel plating method for aluminum or aluminum alloy according to claim 1, wherein an anodic oxide film is formed within a range of 40 ° C. 5. The electroless nickel plating method of aluminum or aluminum alloy according to claim 1, wherein the anodic oxide film is formed with a treatment time within a range of 60 seconds to 600 seconds.