JP7416425B2 - Plating pretreatment method for aluminum and aluminum alloys - Google Patents

Description

The present invention relates to a plating pretreatment method for performing electroless nickel plating on aluminum and aluminum alloys, particularly aluminum electrodes for semiconductors and aluminum alloy electrodes.

Conventionally, aluminum has been used for metal wiring of semiconductor devices from the viewpoints of electrical conductivity, heat resistance, cost, chemical stability, reactivity with silicon materials and silicon oxide materials, adhesiveness, etc. Aluminum has the property of easily moving into silicon materials and silicon oxide materials when electricity is applied due to the electromigration phenomenon. To prevent this, there are methods to create a laminated structure in which a layer of titanium-based material is interposed between aluminum and other materials, and a method in which aluminum contains silicon or copper in a range of 0.5 to 1.0% by weight. A method using an aluminum alloy is known. Furthermore, for the same reason, aluminum or an aluminum alloy such as an aluminum-silicon alloy, an aluminum-copper alloy, or an aluminum-silicon-copper alloy is used as a connecting electrode material for the outermost layer of a semiconductor device.

In order to improve the solder wettability of such electrodes made of aluminum or aluminum alloys, electroless nickel plating, displacement gold plating, etc. are applied to the electrodes made of aluminum or aluminum alloys. A double zincate method is known as a pretreatment process for applying electroless nickel plating to aluminum or aluminum alloys. Normally, in the double zincate method, degreasing treatment and acid or alkali etching treatment are performed, and then zinc replacement treatment is performed twice, consisting of first zinc replacement → nitric acid stripping → second zinc replacement, so-called double zincate treatment. to form a dense zinc-substituted film. Thereafter, a nickel film is formed on the zinc-substituted film by electroless nickel plating.

The surface condition of the electrode, which has been pretreated by this double zincate method and then subjected to electroless nickel plating, displacement gold plating, etc. to improve solder wettability, varies greatly depending on the surface condition of the aluminum alloy that makes up the electrode. It has been known. For example, it has been pointed out that in aluminum-silicon alloy electrodes, zinc substitution during zincate treatment is uneven, resulting in a rough plating film with many nodules, which improves the adhesion of the plating film and the solder wettability after plating. , there was a problem of lowering connection reliability.

Therefore, Patent Document 1 proposes a pretreatment method for etching aluminum and aluminum alloys as a pretreatment for zincate treatment. In this pretreatment method, aluminum or an aluminum alloy is degreased, washed with water, and then the aluminum or aluminum alloy is etched with an etching solution containing copper ions. Next, after washing with water, etching residues are removed from the aluminum alloy using a washing solution containing a copper dissolving agent. By performing such pre-treatment, the surface of aluminum or aluminum alloy has a finely uneven shape that allows the zincate treatment to be performed satisfactorily. It is also disclosed that the nickel plating film formed thereafter has good adhesion and film appearance without the generation of nodules.

However, the etching process of such a pretreatment method has the problem of "replacement omission" in which only etching progresses without replacing the added metal on a specific crystal orientation plane ((100) plane) of the aluminum material. It has also been known in recent years. Fine irregularities are not formed on the surface where substitution omissions occur during the etching process. On the surface where fine irregularities are not formed, zinc is not replaced in the subsequent zincate treatment, and the surface remains as a place where zinc has not been replaced. Even if nickel plating is applied to an aluminum material with such a surface, nickel will not precipitate in areas where zinc has not been replaced, resulting in insufficient adhesion of the nickel plating film or poor appearance of the nickel plating film. Occurs.

Therefore, Patent Document 2 discloses that aluminum or aluminum alloys are removed using a removing solution containing silver ions and/or copper ions and a solubilizing agent for the silver ions and/or copper ions and having a pH of 10 to 13.5. A method for treating the aluminum oxide film formed on the surface is proposed. It is said that this method makes it possible to quickly remove the oxide film, and also to uniformly etch even a specific crystal orientation plane ((100) plane) and replace the added metal. Furthermore, the removal liquid contains a quaternary ammonium hydroxide compound to suppress excessive etching of the surface of aluminum or aluminum alloy.

Japanese Patent Application Publication No. 2004-346405 Japanese Patent Application Publication No. 2012-26029

However, the removal liquid disclosed in Patent Document 2 has low bath stability because silver oxide precipitates during the etching process. Therefore, the pretreatment step for zincate treatment cannot be performed stably. Furthermore, since the removal liquid disclosed in Patent Document 2 has a high pH value of 10 to 13.5, the amount of corrosion of the aluminum material during pretreatment is as large as 1.0 μm or more. Therefore, when the aluminum material is a thin film, there is a problem in that the removal liquid cannot be used.

The present invention was made in view of the above circumstances, and is a method of zincate treatment to enable formation of a nickel film with good adhesion and film appearance on aluminum or aluminum alloy by electroless nickel plating. This is a plating pretreatment method. In other words, the present invention is a pretreatment method in which the added metal is substituted even on the crystal orientation plane ((100) plane) of the aluminum material, and the addition metal is not substituted or omitted from any crystal orientation plane. It is an object of the present invention to provide a plating pretreatment method that is highly stable and in which the amount of corrosion of an aluminum material during pretreatment is 0.1 μm or less.

In order to solve this problem, as a result of intensive research, we came up with the following invention.

The plating pretreatment method for zincate treatment and electroless nickel plating on aluminum and aluminum alloys according to the present invention is a plating pretreatment method for zincate treatment and electroless nickel plating on aluminum and aluminum alloys, comprising: etching the aluminum and aluminum alloy with an alkaline etching solution containing silver ions and a silver complexing agent and having a pH of 8 or more and 9.9 or less; and removing silver from the aluminum and aluminum alloy after the etching. Adopting a method for pre-treatment of plating aluminum and aluminum alloys, which comprises a step of removing the metal displaced and precipitated on the surfaces of the aluminum and aluminum alloys in the etching step using a cleaning solution that can dissolve the aluminum and aluminum alloys. did.

In the pre-plating method for aluminum and aluminum alloys according to the present invention, the additive metal is also substituted on the crystal orientation plane ((100) plane) of the aluminum material, and no substitution or omission of the additive metal occurs on any crystal orientation plane. and has high bath stability. In other words, by adopting the plating pretreatment method, the plating pretreatment step before the zincate treatment can be performed uniformly and stably on any crystal orientation surface, and the nickel plating formed afterwards can be performed uniformly and stably. The film does not generate nodules and has good adhesion and film appearance. Furthermore, in the plating pretreatment method, the amount of corrosion of the aluminum material is 0.1 μm or less. Therefore, even when the film thickness of the aluminum material to be treated is thin, the plating pretreatment method can be applied.

3 is a photograph of the appearance of a nickel plating film in Example 4. 3 is a photograph of the appearance of a nickel plating film in Comparative Example 2.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a method for plating pretreatment of aluminum and aluminum alloys according to the present invention will be described.

The plating pretreatment method for performing zincate treatment and electroless nickel plating on aluminum and aluminum alloys according to the present invention uses an alkaline etching solution containing silver ions and a silver complexing agent and having a pH of 8 or more and 10 or less. A process of etching aluminum and aluminum alloys, and removing metals precipitated by substitution on the surfaces of the aluminum and aluminum alloys in the etching process using a cleaning solution that can dissolve silver from the etched aluminum and aluminum alloys. It has a process.

Specifically, aluminum or an aluminum alloy is subjected to degreasing treatment, washed with water, and then subjected to the plating pretreatment according to the present invention. After performing the plating pretreatment, a nickel film can be formed on the surface of aluminum or aluminum alloy by double zincate treatment or electroless nickel plating. By performing the plating pre-treatment, the plating pre-treatment process can be performed uniformly and stably on any crystal orientation plane of the aluminum material, and the nickel plating film formed thereafter is free from the generation of nodules. The result is a film with good adhesion and film appearance. Furthermore, even if the aluminum material to be treated has a small film thickness, the plating pretreatment method can be applied.

Examples of the aluminum alloy to be subjected to the plating pretreatment of the present invention include aluminum alloys such as aluminum-silicon alloy, aluminum-copper alloy, aluminum-silicon-copper alloy, and aluminum-neodymium alloy.

[Alkaline etching solution]
The alkaline etching solution according to the present invention contains silver ions and a silver complexing agent. By containing silver ions in the alkaline etching solution, substitution and omission of silver, which is an added metal, does not occur in any crystal orientation plane of the aluminum material. Thereafter, the cleaning solution according to the present invention is used to remove silver deposited by displacement on the surfaces of aluminum and aluminum alloys, thereby bringing the surfaces of aluminum and aluminum alloys into a state where zincate treatment can be performed satisfactorily. Specifically, by etching with the alkaline etching solution, the oxide film on the surface of aluminum and aluminum alloy is completely dissolved, and silver is precipitated by substitution on the surface of aluminum and aluminum alloy. Then, by removing the silver deposited by displacement using the cleaning solution according to the present invention, the surface of the aluminum or aluminum alloy becomes finely uneven so that the zincate treatment can be performed well.

The pH of the alkaline etching solution is preferably 8 or more and 10 or less. This is because the aluminum material is not excessively etched. As a result, the alkaline etching solution according to the present invention does not require a compound to suppress etching, such as an alkaline compound such as a quaternary ammonium hydroxide compound. In consideration of not excessively etching the aluminum material, the upper limit of the pH value is more preferably 9.9.

Compounds that supply silver ions to the alkaline etching solution include silver nitrate, silver chloride, silver oxide, silver carbonate, silver methanesulfonate, silver bromide, silver iodide, silver vanadate, silver sulfate, silver thiocyanate, silver acetate, etc. can be mentioned. However, the present invention is not limited to the compounds listed here, and one type of these compounds may be used alone, or two or more types of these compounds may be used.

The concentration of the above-mentioned silver ions is preferably 0.1 mg/L or more and 1000 mg/L or less. If the concentration of silver ions is less than 0.1 mg/L or more than 1000 mg/L, the surface of aluminum or aluminum alloy after the plating pretreatment process will not have an appropriate unevenness, and nodules will occur on the formed nickel film. This is because the adhesion is reduced and the appearance of the film is deteriorated.

In addition, silver complexing agents include ethylenediaminetetraacetic acid (EDTA) or its salt, nitrilotriacetic acid, ethylenediamine, succinimide, hydantoin compounds, salicylic acid, nicotinic acid, triethylenetetramine, tetraethylenepentamine, barbituric acid. Examples include compounds such as imidazole, triazole, pyridine, aminopyridine, and pyridine carboxylic acids. In particular, it is preferably one or more selected from the group of ethylenediaminetetraacetic acid (EDTA) or its salts. By using one or more selected from the group of ethylenediaminetetraacetic acid (EDTA) or its salts as a silver complexing agent, the added metal can be substituted even in a specific crystal orientation plane ((100) plane) of the aluminum material. This is because the added metal will not be substituted or omitted from any crystal orientation plane, and the bath stability of the alkaline etching solution will be increased.

The concentration of the silver complexing agent described above is preferably 0.01 g/L or more and 10 g/L or less. If the concentration of the silver complexing agent is less than 0.01 g/L, silver oxide may precipitate and the bath may become unstable. This is because if it exceeds 10 g/L, there is a risk that the added metal will not be substituted onto the aluminum.

It is preferable that the alkaline etching solution contains one or more types selected from the group of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide as a pH adjuster. This is because the pH of the alkaline etching solution can be adjusted to 8 or more and 10 or less.

In addition, alkaline etching solutions can be used as pH buffers such as phosphates such as sodium bicarbonate and trisodium phosphate, polyphosphates such as sodium tripolyphosphate and sodium polyphosphate, carbonates such as sodium carbonate and calcium carbonate, and phosphates such as sodium bicarbonate and trisodium phosphate. It is preferable to contain one or more selected from the group of borates such as sodium borate and ammonium tetraborate. When an aluminum material is etched using an alkaline etching solution, hydroxide ions in the bath are consumed and the pH value decreases. This is because by adding the pH buffer to the alkaline etching solution, it is possible to suppress fluctuations in the pH value during the etching process, and the pH of the alkaline etching solution can be maintained at 8 or more and 10 or less. Note that any compound having a buffering property in the pH range of 8 or more and 10 or less can be used as a pH buffer without being limited to the above.

Furthermore, the alkaline etching solution may contain a surfactant in an amount of 0.1 mg/L or more and 1000 mg/L or less. This is because by imparting water wettability to the surfaces of aluminum and aluminum alloys, the surfaces of aluminum and aluminum alloys can be uniformly etched and the added metal can be replaced.

As surfactants, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, glycol fatty acid ester, glycerin fatty acid ester, alkyl glycoside, alkyl sulfate, polyoxyethylene alkyl ether sulfate, aliphatic Anionic surfactants such as monocarboxylate, dialkyl sulfosuccinate, alkanesulfonate, linear alkylbenzene sulfonate, naphthalene sulfonic acid-formamide condensate, alkylnaphthalene sulfonate, monoalkylamine salt, dialkyl Examples include cationic surfactants such as amine salts, trialkylamine salts, alkyltrimethylammonium chlorides, dialkyldimethylammonium chlorides, and alkylbenzalkonium chlorides. However, the compounds are not limited to those listed here, and one type thereof may be used alone or two or more types may be used.

[Cleaning solution]
The cleaning solution according to the present invention oxidizes and dissolves silver deposited on the surface of aluminum or aluminum alloy by substitution with an alkaline etching solution. By removing the silver deposited by substitution, the surface of the aluminum or aluminum alloy becomes finely uneven. Examples of the oxidizing agent contained in the cleaning solution include nitric acid, iron nitrate, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, and hydrogen peroxide. In particular, the silver oxidizing agent is preferably one or more selected from the group of nitric acid, iron nitrate, and persulfate. This is because in cleaning solutions using these oxidizing agents, aluminum forms a passive state on the surface and is not excessively corroded.

The concentration of the above-mentioned oxidizing agent is preferably 1 g/L or more and 500 g/L or less. If the concentration of the oxidizing agent is less than 1 g/L, nodules are observed in the formed nickel plating film, the adhesion is reduced, and the appearance of the film is deteriorated, which is not preferable. Further, even if the concentration of the oxidizing agent exceeds 500 g/L, it can be used as a cleaning solution, but it is not preferable because more oxidizing agent than necessary will be wasted.

[Plating pretreatment method]
The steps of the plating pretreatment method for aluminum and aluminum alloys according to the present invention will be explained. In this plating pretreatment step, aluminum or aluminum alloy is used, which has been degreased and then washed with water to wash off the chemicals used in the degreasing treatment. This aluminum or aluminum alloy is immersed in the above-mentioned alkaline etching solution. This is called an etching process in the present invention. At this time, the temperature of the alkaline etching solution is not particularly limited, but is preferably in the range of 20 to 80°C, for example. If the liquid temperature is less than 20°C, it may not be possible to dissolve the oxide film on the surface of aluminum or aluminum alloy, which is not preferable. If the liquid temperature exceeds 80°C, aluminum or aluminum alloy may be eluted, which is not preferable.

The immersion time in the alkaline etching solution is not particularly limited, and can be appropriately set based on the surface condition of the aluminum or aluminum alloy to be treated, such as the thickness of the aluminum oxide film. Usually, it is preferable that the time is 10 seconds or more and 300 seconds or less. If the immersion time is less than 10 seconds, it is not preferable because the oxide film on the surface of aluminum or aluminum alloy cannot be sufficiently dissolved. If the immersion time exceeds 300 seconds, aluminum or aluminum alloy may be eluted, which is not preferable.

After the etching process, water washing is performed to wash away the alkaline etching solution used in the etching process. Thereafter, the aluminum or aluminum alloy is immersed in the above-mentioned cleaning solution. This is called a conditioning step in the present invention. At this time, the temperature of the cleaning solution is not particularly limited, but is preferably, for example, 15° C. or higher and 80° C. or lower. If the liquid temperature is less than 15° C., silver deposited by displacement in the etching process may not be sufficiently dissolved, which is not preferable. If the liquid temperature exceeds 80° C., corrosive mist may be generated and it is not economical, which is not preferable.

The immersion time in the cleaning solution is not particularly limited and can be appropriately set based on the surface condition of the aluminum or aluminum alloy to be treated, such as the thickness of the substituted silver film deposited in the etching process. . Usually, it is preferable that the time is 5 seconds or more and 300 seconds or less. If the immersion time is less than 5 seconds, the substituted silver cannot be sufficiently dissolved, which is not preferable. Although there are no particular disadvantages due to an excessively long immersion time, in consideration of productivity, the shorter the immersion time is, the better, and the immersion time is preferably 300 seconds or less.

After the conditioning step, water is washed to remove the cleaning solution used in the conditioning step. After that, zincate treatment (double zincate treatment) and electroless nickel plating can be performed.

The embodiment of the present invention described above is one aspect of the present invention, and can be modified as appropriate without departing from the spirit of the present invention. Further, although the present invention will be described in more detail with reference to Examples below, the present invention is not limited to the following Examples.

In Example 1, an aluminum plate having a mixture of (100) and (111) crystal orientation planes was subjected to a degreasing process, an etching process, a conditioning process, a first zinc substitution process, a zinc peeling process, and a second zinc substitution process. , each step of the electroless nickel plating process was performed in order. Table 1 shows the composition or product name of the solution used in each step. Note that the alkaline etching solution used in the etching process of Example 1 was adjusted to pH=8.5 using a pH adjuster. Each process was then carried out at the bath temperature and treatment time shown in Table 1. In addition, a 1-minute water washing step was provided between each step.

The same process as in Example 1 was performed except that the pH value of the alkaline etching solution used in the etching process was adjusted to pH=9.0, and the aluminum plate was subjected to a degreasing process, an etching process, a conditioning process, a first zinc substitution process, Each process of a zinc stripping process, a second zinc replacement process, and an electroless nickel plating process was performed in order.

The same process as in Example 1 was performed except that the pH value of the alkaline etching solution used in the etching process was adjusted to pH = 9.5, and the aluminum plate was subjected to a degreasing process, an etching process, a conditioning process, a first zinc substitution process, Each process of a zinc stripping process, a second zinc substitution process, and an electroless nickel plating process was performed in order.

The same process as in Example 1 was performed except that the pH value of the alkaline etching solution used in the etching process was adjusted to pH=9.75, and the aluminum plate was subjected to a degreasing process, an etching process, a conditioning process, a first zinc substitution process, Each process of a zinc stripping process, a second zinc replacement process, and an electroless nickel plating process was performed in order.

Comparative example

[Comparative example 1]
In the alkaline etching solution used in the etching process, zinc sulfate heptahydrate was used instead of silver nitrate to supply silver ions so that the concentration was 30 mg/L in terms of zinc ions. Furthermore, tetrasodium ethylenediaminetetraacetate was not used. Then, the pH value of the alkaline etching solution was adjusted to pH=9.75. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in sequence.

[Comparative example 2]
In the alkaline etching solution used in the etching process, copper sulfate pentahydrate was used instead of silver nitrate to supply silver ions so that the concentration was 30 mg/L in terms of copper ions. Using. Furthermore, tetrasodium ethylenediaminetetraacetate was not used. Then, the pH value of the alkaline etching solution was adjusted to pH=9.75. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 3]
Tetrasodium ethylenediaminetetraacetate was not used in the alkaline etching solution used in the etching process. Then, the pH value of the alkaline etching solution was adjusted to pH=10.0. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 4]
Tetrasodium ethylenediaminetetraacetate was not used in the alkaline etching solution used in the etching process. Then, the pH value of the alkaline etching solution was adjusted to pH=10.5. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 5]
Tetrasodium ethylenediaminetetraacetate was not used in the alkaline etching solution used in the etching process. Then, the pH value of the alkaline etching solution was adjusted to pH=11.0. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 6]
In the alkaline etching solution used in the etching process, the complexing agent tetrasodium ethylenediaminetetraacetate was not used. Then, the pH value of the alkaline etching solution was adjusted to pH=9.75. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 7]
In the alkaline etching solution used in the etching process, 0.5 g/L of 5,5-dimethylhydantoin was used as a complexing agent instead of tetrasodium ethylenediaminetetraacetate. Then, the pH value of the alkaline etching solution was adjusted to pH=9.75. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in sequence.

[Comparative example 8]
In the alkaline etching solution used in the etching process, 0.5 g/L of succinimide was used as a complexing agent instead of tetrasodium ethylenediaminetetraacetate. Then, the pH value of the alkaline etching solution was adjusted to pH=9.75. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

[Comparative example 9]
In the alkaline etching solution used in the etching process, the concentration of silver nitrate that supplies silver ions was 10 mg/L, and sodium hydrogen carbonate was not used. As complexing agents, 10 g/L of nitrilotriacetic acid, 1 g/L of 5,5-dimethylhydantoin, and 1 g/L of polyoxyethylene ether were used instead of tetrasodium ethylenediaminetetraacetate. Further, the pH value of the alkaline etching solution was adjusted to pH=12.8 using a quaternary ammonium hydroxide compound (TMAH). The bath temperature in the etching step was 60° C., and the processing time was 60 seconds. Except for the above, the aluminum plate was subjected to each step of the degreasing process, etching process, conditioning process, first zinc replacement process, zinc peeling process, second zinc replacement process, and electroless nickel plating process in the same manner as in Example 1. were applied in order.

〔Evaluation results〕
For the aluminum plates subjected to each process of Examples 1 to 4 and Comparative Examples 1 to 9, the amount of aluminum etched in the etching process and the precipitation of added metal in the etching process were evaluated. The bath stability of the alkaline etching solution in the etching process was also evaluated.

The amount of aluminum etched was calculated from the difference in weight by measuring the weight of an aluminum plate having a mixture of (100) and (111) crystal orientation planes before and after immersion in an alkaline etching solution. The etching amount of the aluminum material of 0.1 μm or less was determined to be good. The precipitation of the additive metal was determined by observing the surface of the aluminum plate after electroless nickel plating. Specifically, the case where the nickel plating film is formed on the entire surface of the aluminum plate is considered as good, and the case where the nickel plating film is not formed (in other words, the substitution omission of silver, which is an additive metal in the alkaline etching solution) is considered as good. If the location (where the problem occurred) was confirmed, it was classified as bad. The bath stability was evaluated by immersing an aluminum plate into a beaker containing the alkaline etching solution of each Example and Comparative Example, and applying 1 dm ² /L (processing an area of 1 dm ² of the aluminum plate per 1 L of alkaline etching solution). It was treated at the loading amount for 5 minutes. If no precipitate was generated in the alkaline etching solution after the treatment, it was evaluated as good (Good), and if any precipitate was generated, it was evaluated as poor (Bad). The evaluation results are shown in Table 2. Based on the results of each evaluation item, the results of the overall judgment of quality are recorded in the judgment column.

From Table 2, the pre-treatment method for plating aluminum and aluminum alloys according to the present invention uses a compound for suppressing excessive etching, such as a quaternary ammonium hydroxide compound, by setting the pH to 8 or more and 10 or less. Even when not included in the alkaline etching solution, the amount of corrosion of the aluminum material was 0.1 μm or less. Therefore, it was confirmed that the plating pretreatment method can be applied even when the aluminum material to be treated has a thin film thickness.

Furthermore, from the results shown in Table 2, it is clear that the plating pretreatment method replaces the additive metal even on a specific crystal orientation plane ((100) plane) of the aluminum material, and eliminates the substitution of the additive metal on any crystal orientation plane. We confirmed that this does not occur. A photograph of the appearance of the nickel plating film in Example 4 is shown in FIG. In the nickel plating film treated using the alkaline etching solution of Example 4, no nodules were generated even on the (100) plane, and no replacement or omission of the added metal occurred on any crystal orientation plane. Ta. On the other hand, an external photograph of the nickel plating film in Comparative Example 2 is shown in FIG. In the nickel plating film treated using the alkaline etching solution of Comparative Example 2, the additive metal precipitated sparsely on the (100) plane, and the entire surface was not precipitated.

The results shown in Table 2 also revealed that the alkaline etching solution used in the plating pretreatment method had high bath stability. That is, by employing the plating pretreatment method, the plating pretreatment step before the zincate treatment can be performed uniformly and stably on any crystal orientation plane. Then, the nickel plating film formed through the zincate treatment is free of nodules and has good adhesion and film appearance.

In the method for plating pre-treatment of aluminum and aluminum alloys according to the present invention, the additive metal is substituted even on a specific crystal orientation plane ((100) plane) of the aluminum material, and the additive metal is not replaced on any crystal orientation plane. No generation occurs and bath stability is high. Therefore, the plating pretreatment step before the zincate treatment can be performed uniformly and stably. Therefore, the nickel plating film formed after the zincate treatment does not generate nodules and has good adhesion and film appearance. Furthermore, since the amount of corrosion of the aluminum material in this plating pretreatment method is 0.1 μm or less, the plating pretreatment method can be applied even when the film thickness of the aluminum material to be treated is thin. can. That is, the pre-treatment method for plating aluminum and aluminum alloys according to the present invention is a zincate treatment for performing electroless nickel plating, displacement gold plating, etc. on electrodes made of aluminum or aluminum alloys for connection of the outermost layer of semiconductor devices. Suitable for pretreatment.

Claims (8)

A plating pretreatment method for zincate treatment and electroless nickel plating on aluminum and aluminum alloys, the method comprising:
etching the aluminum and aluminum alloy with an alkaline etching solution containing silver ions and a silver complexing agent and having a pH of 8 or more and 9.9 or less;
The method further comprises a step of removing, from the aluminum and aluminum alloy after the etching, the metal displaced and precipitated on the surface of the aluminum and aluminum alloy in the etching step using a cleaning solution capable of dissolving silver. A pre-treatment method for plating aluminum and aluminum alloys. The method for plating pretreatment of aluminum and aluminum alloys according to claim 1, wherein the concentration of the silver ions is 0.1 mg/L or more and 1000 mg/L or less. 3. The method for plating pretreatment of aluminum and aluminum alloys according to claim 1 or 2, wherein the silver complexing agent contains one or more selected from the group of ethylenediaminetetraacetic acid (EDTA) or a salt thereof. The method for plating pretreatment of aluminum and aluminum alloys according to any one of claims 1 to 3, wherein the concentration of the silver complexing agent is 0.01 g/L or more and 10 g/L or less. Any one of claims 1 to 4, wherein the alkaline etching solution contains one or more selected from the group of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide as a pH adjuster. The method for plating pretreatment of aluminum and aluminum alloys according to item (1). The alkaline etching solution contains one or more selected from the group of phosphates, polyphosphates, carbonates, and borates as a pH buffering agent. The described method for pre-plating aluminum and aluminum alloys. The cleaning solution contains at least one selected from the group of nitric acid, iron nitrate, and persulfate as a silver oxidizing agent. Plating pretreatment method. The method for plating pretreatment of aluminum and aluminum alloys according to claim 7, wherein the concentration of the silver oxidizing agent is 1 g/L or more and 500 g/L or less.