JPS62238393A - Method for electroplating aluminum material - Google Patents

Abstract

PURPOSE:To enable the electroplating of an Al material even in case where the Al material is Al foil which is hardly electroplated by a conventional method, by pretreating the Al material by AC electrolysis in an acidic nickel salt bath of a specified pH. CONSTITUTION:An Al material is pretreated by AC electrolysis in an aqueous soln. of 2-3.5pH contg. a water soluble nickel salt and an inorg. acid and/or an org. acid forming a porous oxide film together with the nickel salt to form an underlayer. Cathodic electrolysis is then carried out in a conventional electrolytic bath in a single stage or plural stages.

Description

[Detailed description of the invention] East! The present invention is a method of electroplating aluminum or aluminum alloy materials (hereinafter collectively referred to as "aluminum materials"), and in particular applies a novel method to the formation of a base layer as a pretreatment. The present invention relates to an electroplating method.

Conventional technology When electroplating is applied to aluminum materials, the adhesion of the resulting film is poor and it easily peels off when electroplated directly, so it is recommended to form a base layer of zinc or tin and then electroplate the desired metal. It has been widely used. Furthermore, a method has long been known in which an anodic oxide film is formed on an aluminum material using a phosphoric acid bath and then electroplated.

However, when using the conventional method, the aluminum material is consumed a lot, and therefore, when applied to thin materials such as aluminum foil base materials, the aluminum foil may melt and disappear.For example, when manufacturing aluminum materials for printed circuit boards, It was difficult to apply.

Problem 8 to be Solved by the Invention In view of the above-mentioned problems of the conventional method, the present invention reduces dissolution and consumption of the material to be treated when forming the base layer, and also improves the adhesion of the electroplated layer. This paper proposes a method.

As a result, it is possible to provide a highly versatile means that can be applied not only to thick-walled materials that have conventionally been commonly processed, but also to thin-walled materials such as foil base materials used for printed circuit boards and other uses.

Means for Solving the Problems The present invention pre-treats the aluminum material by containing a water-soluble nickel salt and an inorganic acid and/or an organic acid that coexists with the water-soluble nickel salt to form a porous oxide film.

An aluminum material characterized by forming a base layer by performing alternating current electrolysis treatment in an aqueous solution with a pH value of 2.0 to 3.5, and then performing one or more stages of cathodic electrolysis in a conventional electroplating bath. This is an electroplating method.

As the water-soluble nickel salt, nickel sulfate, nickel chloride, nickel acetate, etc. can be used, but the concentration is Log/j
Nickel sulfate (NtSO, 6H, 0
), 10 g/l to 250 g, Q' is desirable.

To the nickel salt aqueous solution at this concentration, an inorganic acid, an organic acid, and a mixed acid thereof that coexist with the nickel salt to form a porous oxide film are added to adjust the pH value of the aqueous solution to 2.0.
Adjust to ~3.5.

As this kind of inorganic acid, sulfuric acid is most suitable, but chloric acid, hydrochloric acid, nitric acid, etc. can also be used.As organic acids, acetic acid, tartaric acid, citric acid, sulfamic acid, etc. Maleic acid, malic acid, etc. can be used, and when used as a mixed acid, a combination of inorganic acids, organic acids, or a combination of an inorganic acid and an organic acid may be used.

The aluminum material was immersed in the acidic nickel bath prepared above, and the bath temperature was 1o~60'C1 electrolytic density was 0.
．． AC electrolytic treatment is performed for 5 to 60 minutes at an electrolytic voltage of 4 to 1.0 A/dm" and an electrolytic voltage of 4 to 1.OV. The AC is commonly used as ordinary commercial AC, but PR waves may also be used.

Through such surface treatment, a thin porous oxide film of around 1μ is formed with a small amount of aluminum eluted, and a base layer with a structure in which metallic nickel is precipitated in the bores is formed. These precipitated nickel particles serve as active sites for depositing conductive metal during electroplating.

In such AC electrolytic treatment, the pH value of the bath and the electrolytic voltage value are important for forming the desired underlayer as described above. That is, when the pH value of the bath becomes strongly acidic (below 2.0), the hydrogen gas generation reaction becomes more dominant than the electrodeposition of nickel ions, and although an oxide film is formed, nickel precipitation does not occur. Desired base layer cannot be obtained. On the other hand, if the pH value becomes weakly acidic (4.0 or higher), nickel ions will be deposited, but a porous oxide film will be difficult to form, which is undesirable. It is appropriate that

Furthermore, even if the pH value of the bath is in the range of 2.0 to 3.5, the formation of an oxide film and the precipitation of nickel are difficult to occur when the electrolytic voltage is 4V or less; This is not preferable because the barrier layer in the oxide film becomes too thick and nickel ions are no longer deposited.

In addition, when adjusting the pH value, when preparing with an inorganic acid alone, it is preferable to set the lower limit pH value to about 2.5, and when using an organic acid alone or a mixed acid, the chelating effect of the organic acid is also exhibited. Therefore, the effect is expressed even at pH 2.0.

Aluminum materials to be subjected to such AC electrolytic treatment include (a) aluminum materials prepared through normal pretreatment such as degreasing and etching, and (b) aluminum materials that are used, for example, in the manufacture of printed circuit boards. If it is desired to form an electroplated layer in a certain pattern or pattern, an aluminum material may be used in which the non-electroplating areas have been previously treated with a non-conductive film. In that case, the non-conductive film can be a synthetic resin coating, a thick barrier type anodic oxide coating, or the like.

Although the bath was made of nickel salt, Ag and Sn were used as the bath.

It is possible to do the same with Cu salt, but Ag and Sn baths cause severe deterioration and are unsuitable for large-scale processing, and Cu baths lack reliability in film adhesion, so nickel salts, which can facilitate stable operation, are used. limited to.

After AC electrolysis treatment, electroplating treatment is performed next, but metallic nickel is precipitated in the oxide film during AC electrolysis treatment, and it can be used as a conductive base layer to form the desired metal plating layer on top. . Therefore, as an electroplating method, plating layers of various metals can be applied using an appropriate electroplating method. For example, electroplating of commonly used nickel, tin, copper, zinc, chromium, silver, etc. It can be selected as appropriate depending on the purpose. In addition, as an electroplating method, a treatment method of forming a plating layer consisting of a single layer as a single-stage or multi-step treatment, or a treatment method of forming a plating layer consisting of multiple layers of different metals, etc. can be applied as appropriate by conventional methods. .

The case where nickel plating is performed subsequent to AC electrolytic treatment will be described below as a typical example.

In the case of nickel plating, there are two methods: when the acidic nickel bath has a sufficient nickel concentration for electroplating, direct current cathodic electrolysis is subsequently carried out in the same bath, and there is a method known as a normal Watt bath. It is also possible to adopt a method in which the electroplating is carried out in a dedicated electroplating bath with a different composition.

The former method may have the advantage of not requiring a water washing process, but for example, nickel sulfate of 10 to 25
After adding sulfuric acid, halonic acid, tartaric acid, citric acid, etc. to 0 g/l and carrying out a specified AC electrolytic treatment in an aqueous solution with a pH of 2.0 to 3.5 and a bath temperature of 30 to 60°C, the electrolytic voltage was set to 2. ~10
v, 5 to 5 under the condition of current density 1.5 to 2.5 A/dm"
Direct current cathode electrolysis is performed for 60 minutes to form a 0.1-10 μm nickel plating layer. In this case, chromium plating or copper plating can be applied subsequently in a separate bath.

In the latter case, a Watt bath, a sulfamic acid bath, a Weissberb bath, an ordinary bath, a mixed bath, etc., which are known as general nickel plating baths, are appropriately selected and applied depending on the use of the material to be treated.

For example, in the case of a Watt bath, an aluminum material subjected to AC electrolysis treatment is immersed in a bath (pl, 5 to 5.5) whose main components are 240 g/l of nickel sulfate, 45 g/l of nickel chloride, and 30 g of halonic acid. Bath temperature 45-70℃, current density 2-8A
Direct current electrolysis is performed for 1 ( ) to 60 minutes at an electrolytic voltage of 2 to 5 V to form a nickel plating layer.

Similarly, even in the case of other metals, appropriate methods described in the Metal Surface Technology Handbook (Nikkan Kogyo Shimbunsha Series), Surface Treatment Handbook (Sangyo Toshosha Publishing Co., Ltd.), etc. can be applied. are shown in the table below.

In the electroplating process described below, the electroplating layer is formed on a portion of the material to be processed, as seen when plating is applied to a portion of the material to be processed, such as in the manufacture of printed circuit boards. It may be a pattern, a pattern, or an entire surface.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

<Example 1> After degreasing an aluminum foil with a purity of 99.9% and a thickness of 100 μm with acetone, it was degreased with nickel sulfate (N15On・6HzO
) 250 g/l, oxalic acid 25 g/l, sulfuric acid 5 g
AC electrolytic treatment was performed for 10 minutes using a bath temperature of 60° C., bath voltage of 6 V, and 50 Hz alternating current in a pH 3.0 bath consisting of / (!), followed by washing with water.

At this time, the aluminum foil was colored green and did not discolor even when rubbed with a finger, indicating that the precipitated nickel was in the bores in the AC coating.

Next, as nickel electroplating treatment, nickel sulfate (N15Oa・6HzO) 300g/β and nickel chloride (N1Cj!z) 45g/j? , 30g/
l! Direct current cathodic electrolysis was carried out for 10 minutes using a nickel anode at a bath temperature of 50°C and a current density of 5A/dm2 in a pH 5.0 bath consisting of the following.

A repeated bending test was performed on the aluminum foil on which the nickel plating film (5 μm) was formed, but no peeling occurred, and it was confirmed that a plating film with good adhesion was formed.

<Example 2> JIS6063 aluminum extruded tube was subjected to caustic soda etching treatment, and after washing with water, nickel sulfate (
NtSOn・68tO) 250g1l, tartaric acid 50g
/i I) AC electrolytic treatment was carried out in a H3,0(7) bath for 30 minutes using a commercial alternating current of 50 Hz at a bath temperature of 40° C. and a bath voltage of 8 μ.

Next, DC cathode electrolysis was performed in the same bath at a bath temperature of 40°C and a current density of 6 A/dm for 5 minutes using a nickel electrode as an anode. It was comparable.

Next, it was immersed in a bath consisting of 250 g of chromic anhydride, 5 g/l of sodium fluoride, and 1.5 g/l of sulfuric acid, and DC cathode electrolysis was performed for 10 minutes at a bath temperature of 55°C and a current density of 40 A/dm2 to remove nickel. Although a chromium layer was formed on top of the chromium layer, stable plating could be performed in the same manner as in the conventional method.

<Example 3> After degreasing an aluminum plate (0.3 times thick) with a purity of 99.0% using toluene, only the lower half of the plate was placed in a bath of 50 g/l ammonium tartrate aqueous solution at a bath temperature of 25°C and a bath voltage of 50 V. Direct current anodic oxidation treatment was performed for 2 minutes to form a barrier type oxide film.

Next, the sheet metal body was made of nickel sulfate (NiSO4.6H,0).
250g/11 citric acid 70g/l, pH 2.5, bath temperature 50°C, bath voltage 7v, using 50Hz alternating current,
When AC electrolytic treatment was performed for 15 minutes, only the upper half of the board was colored.

Next, 300g/j of sulfurized nickel? , hydric acid 3
The entire surface of the plate was immersed in a 0 g/l bath, and DC cathode electrolysis was performed for 25 minutes at a bath temperature of 50°C and a current density of 10 A/dm2.
After washing, the bottom half of the board was sealed by immersing it in boiling water.

Through these treatments, a partially plated material was obtained in which a nickel plating layer was formed on the upper half of the plate and an insulating layer of oxide film was formed on the lower half of the plate.

In addition, the present invention is capable of forming a base film consisting of a thin oxide film in which metallic nickel is precipitated in the bore in one step by performing AC electrolytic treatment in an acidic nickel salt bath with a pH of 2.0 to 3.5. This can be achieved with extremely small amounts of aluminum being eluted. As a result, conventionally,
Electroplating on foil base materials, which has been difficult, can also be performed using the present invention.

Further, following AC electrolysis, electroplating is repeated once or multiple times in an electroplating bath containing metal salts depending on the desired plating film, but the plating layer is integrated with the nickel contained in the bore. is formed, so the adhesion is superior to that obtained by surface treatment such as the substitution method.

Claims (1)

[Claims] After aluminum material is subjected to AC electrolytic treatment in an aqueous solution containing a water-soluble nickel salt and an inorganic acid and/or an organic acid that coexists with this to form a porous oxide film and has a pH value of 2.0 to 3.5. , a method for electroplating aluminum materials, characterized by carrying out one or more stages of cathodic electrolysis in an electroplating bath.