Metal surface treatment method

Abstract

To provide a surface treatment method of a silver or silver-alloy plated metallic material that can suppress tarnish after high temperature heating in silver or silver-alloy plating, decrease or increase in reflectance, and increase in a contact electric resistance value.SOLUTION: A surface treatment method of a silver or silver-alloy plated metallic material includes a step of forming a film on a silver or silver-alloy plated surface by contacting a surface treatment solution in which pH is adjusted to 7.0 or less by dissolving or dispersing an organic compound having a mercapto group and a sulfonate group, an aluminum salt, a zirconium salt, a molybdate, or a vanadate, and an iodide into water, and the silver or silver-alloy plated metallic material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for treating the surface of a metal material, and more particularly to a method for treating the surface of a metal material plated with silver or a silver alloy. [Background technology]

[0002] Silver or silver alloy plating has excellent properties such as electrical conductivity, low contact resistance, solderability, and reflectivity, and is widely used in electrical and electronic components as coatings for various switches, contacts, terminals, connectors, lead frames, etc. These electrical and electronic components mainly use materials in which the surface of brass or phosphor bronze is underplated with copper, nickel, or palladium, and then plated with silver or silver alloy.

[0003] Silver or silver alloy plating is prone to discoloration due to reaction with sulfur components in the air, and when heated to high temperatures, its crystal state changes, causing various properties to deteriorate.

[0004] In response to such problems, Patent Document 1 discloses a surface treatment agent for forming a highly heat-resistant coating on a metal, which is characterized by dissolving or dispersing 0.01 to 0.15 g / L of one or more compounds selected from the group consisting of benzotriazole compounds represented by a specific formula, mercaptobenzothiazole compounds represented by a specific formula, and triazine compounds represented by a specific formula as inhibitors, and 0.1 to 20 g / L of iodide and / or bromide in water, and adjusting the pH to 4 to 7. It is also described that the surface treatment agent can provide a coating on a metal that is excellent in heat resistance, has a high discoloration prevention effect even when exposed to a heat treatment in the LED manufacturing process or a high-temperature environment during use, and has excellent wire bonding properties, and does not deteriorate in reflectance due to the surface treatment.

[0005] In Patent Document 2, a discoloration prevention treatment composition consisting of an aqueous solution containing zinc ions and nitrate ions is used, and a treatment target containing a silver-based material is used as the cathode at a liquid temperature of 55°C or less and a cathode current density of 0.01 to 2 mA / cm. 2 The publication discloses a method for preventing discoloration of a silver-based material, which is characterized by performing an electrolytic treatment under the following conditions: The publication also discloses that the method for preventing discoloration of a silver-based material makes it difficult for the treated silver-based material to deteriorate in appearance, such as reflectance and gloss, and also suppresses deterioration in various performances, such as wire bonding property and solderability.

[0006] Patent Document 3 discloses an appearance protecting agent that suppresses discoloration and / or corrosion of the outermost layer of a metal body having a silver plating film, a silver alloy plating film, a gold plating film, a gold alloy plating film, a palladium plating film, or a palladium alloy plating film as the outermost layer, and maintains the appearance of the metal body, the outermost layer being at least one metal selected from the group consisting of copper, copper alloy, nickel, nickel alloy, palladium, and palladium alloy as the base metal, and is characterized by containing a benzotriazole ring compound, and an amine compound represented by a specific formula and / or an ammonium compound having an ammonium cation represented by a specific formula. It is also disclosed that the appearance protecting agent can prevent discoloration and corrosion of silver plating film, silver alloy plating film, gold plating film, gold alloy plating film, palladium plating film, and palladium alloy plating film, maintain the appearance, and provide excellent heat resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5473135 [Patent Document 2] Patent No. 5888696 [Patent Document 3] JP 2019-2062 A Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, various characteristics are required for silver or silver alloy plating used as a surface coating for various electric and electronic components such as switches, contacts, terminals, connectors, lead frames, etc. Among these, suppression of discoloration after high-temperature heating, reduction or increase in reflectance, and increase in contact electrical resistance are very important characteristics for various applications. There is still room for improvement in silver or silver alloy plated metal materials that simultaneously satisfy all of these characteristics.

[0009] In view of these problems, the present invention aims to provide a surface treatment method for a metal material plated with silver or silver alloy, which is capable of suppressing discoloration, a decrease or increase in reflectance, and an increase in contact electrical resistance value after high-temperature heating in the silver or silver alloy plating. [Means for solving the problem]

[0010] As a result of extensive research, the inventors have found that the above-mentioned effects can be obtained by forming a coating on the surface of silver or silver alloy plating using a surface treatment solution containing an organic compound having a mercapto group and a sulfonic acid group, a specified metal salt, and an iodide.

[0011] In order to achieve the above object, the present invention is specified as follows. [1] A method for surface treatment of a metal material plated with silver or silver alloy, comprising the steps of: an organic compound having a mercapto group and a sulfonic acid group; an aluminum salt, a zirconium salt, a molybdate or a vanadate; Iodide, A surface treatment method for a metal material, comprising the steps of: contacting a metal material plated with silver or a silver alloy with a surface treatment solution prepared by dissolving or dispersing the above in water and adjusting the pH to 7.0 or less, thereby forming a coating on the surface of the silver or silver alloy plating. [2] The method for treating a surface of a metal material according to [1], wherein the aluminum salt is aluminum sulfate, aluminum chloride, or aluminum hydroxide, the zirconium salt is zirconium sulfate, zirconium oxychloride, zirconium oxynitrate, or zirconium acetate, the molybdate is sodium molybdate, ammonium molybdate, and the vanadate is sodium vanadate, potassium vanadate, or vanadium oxysulfate. [3] The method for treating a surface of a metal material according to [1] or [2], wherein the iodide is sodium iodide or potassium iodide. [4] The method for treating a surface of a metal material according to any one of [1] to [3], wherein the concentration of the organic compound having a mercapto group and a sulfonic acid group in the surface treatment liquid is 0.05 to 50.0 g / L. [5] The method for treating a surface of a metal material according to any one of [1] to [4], wherein the concentration of the aluminum salt, the zirconium salt, the molybdate or the vanadate in the surface treatment solution is 0.25 to 100.0 g / L. [6] The method for treating a surface of a metal material according to any one of [1] to [5], wherein a concentration of the iodide in the surface treatment solution is 0.005 to 2.0 g / L. [7] The metal material is (1) A metal substrate and a silver or silver alloy plating provided on the surface of the metal substrate, or (2) A metal substrate, a base plating formed on the surface of the metal substrate and made of copper, nickel, palladium, or an alloy thereof, and a silver or silver alloy plating formed on the surface of the base plating. The surface treatment method for a metal material according to any one of [1] to [6]. [8] The method for treating the surface of a metal material according to any one of [1] to [7], wherein the metal material is an electric or electronic part. Effect of the Invention

[0012] According to the present invention, a surface treatment method for a metal material plated with silver or silver alloy can be provided, which can suppress discoloration, a decrease or increase in reflectance, and an increase in contact electrical resistance value after high-temperature heating in silver or silver alloy plating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Metal materials> The metal material to be treated according to the embodiment of the present invention will be described below. The metal material may be a metal base material having a surface plated with silver or a silver alloy, or the metal base material may have an undercoat on its surface, and the undercoat may be plated with silver or a silver alloy.

[0014] The metal substrate is not particularly limited as long as it has electrical conductivity, and examples thereof include aluminum and aluminum alloys, iron and iron alloys, titanium and titanium alloys, stainless steel, copper and copper alloys, etc. Among these, it is preferable to use copper and copper alloys because they have excellent electrical conductivity, thermal conductivity, and ductility.

[0015] The silver or silver alloy plating may be pure silver plating, or may be alloy plating of silver and one or more metal elements selected from copper, tin, nickel, cobalt, selenium, antimony, tellurium, and bismuth.

[0016] The underplating is preferably made of copper, nickel, palladium, or an alloy thereof.

[0017] <Metal surface treatment method> Next, the method for treating the surface of a silver or silver alloy plated metal material according to an embodiment of the present invention will be described in detail. First, a surface treatment liquid is prepared by dissolving or dispersing an organic compound having a mercapto group and a sulfonic acid group, an aluminum salt, a zirconium salt, a molybdate salt or a vanadate salt, and an iodide in water.

[0018] The organic compounds contained in the surface treatment solution are mercapto groups (-SH) and sulfonic acid groups (-SO3 - ), and when it is contained as a coating component on the surface of the silver or silver alloy plating, the heat resistance of the silver or silver alloy plating is improved. In addition, it is possible to suppress changes in the crystal state of the silver or silver alloy plating after heating, and as a result, if the silver or silver alloy plating is a gloss plating, it is possible to suppress a decrease in gloss (a decrease in reflectance), and if the silver or silver alloy plating is a matte plating, it is possible to suppress an increase in gloss (an increase in reflectance), and further to suppress an increase in electrical resistance value. In addition, the organic compound having a mercapto group and a sulfonic acid group may be a hydrate.

[0019] Specific examples of organic compounds having a mercapto group and a sulfonic acid group include dimercaptopropanesulfonic acid, mercaptomethanesulfonic acid, 2-mercaptoethanesulfonic acid, sodium 3-mercapto-1-propanesulfonate, 4-mercapto-1-butanesulfonic acid, 5-mercaptopentane-1-sulfonic acid, 10-mercapto-1-decanesulfonic acid, 11-mercapto-1-undecanesulfonic acid, sodium 12-mercaptododecane-1-sulfonate, 15-mercapto-1-pentadecanesulfonic acid, 2-mercapto-1-pentanesulfonic acid, sodium 2-mercapto-5-benzimidazolesulfonate, 3-mercaptobenzenemethanesulfonic acid, 4-mercaptophenylmethanesulfonic acid, and 4-mercaptobenzenesulfonic acid.

[0020] The concentration of the organic compound having a mercapto group and a sulfonic acid group in the surface treatment solution is preferably 0.05 to 50.0 g / L. If the concentration of the organic compound having a mercapto group and a sulfonic acid group exceeds 50.0 g / L, uneven treatment is likely to occur. If the concentration of the organic compound having a mercapto group and a sulfonic acid group is less than 0.05 g / L, the effect of inhibiting discoloration after heating becomes insufficient. Furthermore, the concentration of the organic compound having a mercapto group and a sulfonic acid group is more preferably 0.1 to 10.0 g / L.

[0021] In addition, the heat resistance of the silver or silver alloy plating is improved by including aluminum salt, zirconium salt, molybdate, or vanadate as a coating component on the surface of the silver or silver alloy plating. In addition, the change in the crystal state of the silver or silver alloy plating after heating can be suppressed, and as a result, if the silver or silver alloy plating is a glossy plating, the decrease in gloss (decrease in reflectance) can be suppressed, and if the silver or silver alloy plating is a matte plating, the increase in gloss (increase in reflectance) can be suppressed, and further, the increase in the electrical resistance value can be suppressed. Examples of aluminum salts include aluminum sulfate, aluminum chloride, and aluminum hydroxide. Examples of zirconium salts include zirconium sulfate, zirconium oxychloride, zirconium oxynitrate, and zirconium acetate. Examples of molybdates include sodium molybdate and ammonium molybdate. Examples of vanadates include sodium vanadate, potassium vanadate, and vanadium oxysulfate.

[0022] The concentration of aluminum salt, zirconium salt, molybdate or vanadate in the surface treatment solution is preferably 0.25 to 100.0 g / L. If the concentration of aluminum salt, zirconium salt, molybdate or vanadate exceeds 100.0 g / L, uneven treatment is likely to occur and the solution stability is deteriorated. If the concentration of aluminum salt, zirconium salt, molybdate or vanadate is less than 0.25 g / L, the effect of inhibiting discoloration after heating becomes insufficient. Furthermore, the concentration of aluminum salt, zirconium salt, molybdate or vanadate is more preferably 0.5 to 20.0 g / L.

[0023] In addition, by including iodide as a coating component on the surface of silver or silver alloy plating, the heat resistance of the silver or silver alloy plating is improved. In addition, sulfurization of the surface after heating of the silver or silver alloy plating can be suppressed, and as a result, discoloration of the silver or silver alloy plating surface can be suppressed. Examples of iodide include sodium iodide and potassium iodide.

[0024] The concentration of iodide in the surface treatment solution is preferably 0.005 to 2.0 g / L. If the concentration of iodide exceeds 2.0 g / L, yellowing is likely to occur after treatment. If the concentration of iodide is less than 0.005 g / L, the effect of inhibiting sulfurization after heating decreases. Furthermore, the concentration of iodide is more preferably 0.01 to 1.0 g / L.

[0025] The method for dissolving or dispersing the organic compound having a mercapto group and a sulfonic acid group, the aluminum salt, the zirconium salt, the molybdate or the vanadate, and the iodide in water is not particularly limited, and a known method can be used. The water used is preferably pure water such as ion-exchanged water (deionized water) or distilled water.

[0026] The surface treatment liquid is adjusted to pH 7.0 or less, and a silver- or silver alloy-plated metal material is brought into contact with the surface treatment liquid to form a coating on the silver- or silver alloy-plated surface. Specifically, the silver- or silver alloy-plated metal material is immersed in the surface treatment liquid whose pH has been adjusted to 7.0 or less for a predetermined period of time to form a coating. Alternatively, the surface treatment liquid is sprayed onto the surface of the silver- or silver alloy-plated metal material for a predetermined period of time to form a coating. After the surface treatment liquid is brought into contact with the metal material to form a coating on the silver- or silver alloy-plated surface, the metal material is washed with water and dried.

[0027] Since the pH of the surface treatment liquid is 7.0 or less, the effect of inhibiting discoloration after heating and the stability of the surface treatment liquid are good.

[0028] The contact time between the surface treatment liquid and the metal material can be appropriately adjusted depending on the concentration of the surface treatment liquid, etc., but from the viewpoint of forming a good coating, it is preferably 10 seconds to 5 minutes, and more preferably 30 seconds to 3 minutes. The temperature of the surface treatment liquid is preferably 20 to 60°C. If the temperature of the surface treatment liquid exceeds 60°C, water is easily evaporated, making it difficult to control the concentration. Also, if the temperature of the surface treatment liquid is less than 20°C, the treatment time becomes long and productivity decreases.

[0029] As described above, according to the surface treatment method for metal materials according to the embodiment of the present invention, a desired coating can be formed on the surface of the silver or silver alloy plating by simply contacting the silver or silver alloy plated metal material to be treated with a surface treatment liquid (dipping in the surface treatment liquid, spraying the surface treatment liquid, etc.). This improves the efficiency of the manufacturing method. In addition, the surface treatment method for metal materials according to the embodiment of the present invention can suppress discoloration, reduction or increase in reflectance, and increase in contact electrical resistance value after high-temperature heating in the silver or silver alloy plating. Therefore, it is very useful as a surface treatment method for various electric and electronic parts such as various switches, contacts, terminals, connectors, and lead frames. EXAMPLES

[0030] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0031] <Surface treatment test for metal materials> 1. Test Specimen Preparation A copper plate (tough pitch copper plate: C1100P) with dimensions of length x width x thickness = 2.5 cm x 2.5 cm x 0.3 mm was plated with nickel to a thickness of 3 μm as a base plating by a known method, and then a gloss silver plating of 5 μm was formed on the surface of the nickel plating by a known method to produce a metal material. The surface of the metal material was washed with water.

[0032] (Test pieces of Examples 1 to 13) Next, surface treatment solutions having the components shown in Table 1 below were prepared. The surface treatment solutions were prepared by adding appropriate amounts of each component with a known concentration to pure water and mixing them. The pH of the surface treatment solutions was adjusted to 2.0 by adding hydrochloric acid. Next, the metal material was immersed in the surface treatment solutions for 1 minute at 40°C. The mercapto groups (-SH) and sulfonic acid groups (-SO3 - The organic compound having the formula (I) was sodium 3-mercapto-1-propanesulfonate or sodium 2-mercapto-5-benzimidazolesulfonate (dihydrate).

[0033] Next, the metal material was taken out of the surface treatment solution, washed with water, and dried to obtain test pieces according to Examples 1 to 13 in which a coating was formed on the silver-plated surface.

[0034] (Test piece of Comparative Example 1) The 6-anilino-1,3,5-triazine-2,4-dithiol solution was diluted with ultrapure water and adjusted to pH 6.0 using phosphoric acid to prepare a surface treatment liquid. The concentration of 6-anilino-1,3,5-triazine-2,4-dithiol in the surface treatment liquid was 0.07 g / L. The composition of the surface treatment liquid is shown in Table 2 below. Next, the metal material was immersed in the surface treatment solution at room temperature for 10 minutes, then taken out, washed with water and dried to obtain a test piece according to Comparative Example 1 in which a coating was formed on the silver-plated surface.

[0035] (Test piece of Comparative Example 2) The triazine-2,4,6-trithiol solution was diluted with ultrapure water, potassium iodide, a surfactant, and a dissolving aid were added, and the pH was adjusted to 5.5 using sodium hydrogen phosphate to prepare a surface treatment liquid. The triazine-2,4,6-trithiol concentration in the surface treatment liquid was 0.1 g / L, the potassium iodide concentration was 10 g / L, and the sodium hydrogen phosphate concentration was 0.1 g / L. The surfactant used was oleyl alcohol ethoxylate, with a concentration of 0.1 g / L. The dissolving aid used was butyl propylene glycol, with a concentration of 10 g / L. The composition of the surface treatment liquid is shown in Table 2 below. Next, the metal material was immersed in the surface treatment solution at 40°C for 40 seconds, then removed, washed with water and dried to obtain a test piece according to Comparative Example 2 in which a coating was formed on the silver-plated surface.

[0036] (Test pieces of Comparative Examples 3 and 4) Surface treatment solutions having the components shown in Table 2 below were prepared. The surface treatment solutions were prepared by adding appropriate amounts of each component with a known concentration to pure water and mixing them. The pH of the surface treatment solutions was adjusted to 2.0 by adding hydrochloric acid. Next, the metal material was immersed in the surface treatment solutions at 40°C for 1 minute. Next, the metal material was taken out of the surface treatment solution, washed with water and dried to obtain test pieces according to Comparative Examples 3 and 4, in which a coating was formed on the silver-plated surface.

[0037] 2.Evaluation Test (Appearance evaluation test after heat treatment) Using a high-power digital hot plate "HP-01SA" manufactured by AS ONE Corporation, the temperature of the plate was measured with a surface thermometer so that the temperature of the plate was 260°C, and the test piece was placed on the plate and heat-treated for 30 minutes. Subsequently, the discolored area of ​​the test piece after the heat treatment was visually observed and evaluated according to the following criteria. A: Discoloration area is less than 20% of the total area B: Discoloration area is 20% or more but less than 40% of the total area C: Discoloration area is 40% or more of the total area

[0038] (Reflectance evaluation test) The reflectance of the test piece surface before and after heat treatment was measured using a densitometer (reflection concentration meter) ND-11 manufactured by Nippon Denshoku Industries Co., Ltd. For the heat treatment, the high-power digital hot plate "HP-01SA" manufactured by AS ONE Corporation described above was used, the temperature of the plate part was measured with a surface thermometer so that the temperature of the plate part was 260°C, and the test piece was placed on the plate part and heat-treated for 10 minutes. The evaluation criteria for reflectance are as follows: Calculation formula: X = [(reflectance after heating) / (reflectance before heating)] x 100 (%) A:X is 80% or more B: X is 60% or more but less than 80% C:X is less than 60%

[0039] (Hydrogen sulfide evaluation test) Using the high-power digital hot plate "HP-01SA" manufactured by AS ONE Corporation mentioned above, the temperature of the plate was measured with a surface thermometer so that the temperature of the plate part was 260°C, and the test piece was placed on the plate part and heat-treated for 30 minutes. The test piece was then left in an atmosphere of 3 ppm hydrogen sulfide gas at 40° C. for 4 hours. Subsequently, the discolored area of ​​the test piece was visually observed and evaluated according to the following criteria. A: Discoloration area is less than 20% of the total area B: Discoloration area is 20% or more but less than 40% of the total area C: Discoloration area is 40% or more of the total area

[0040] (Contact Electrical Resistance Evaluation Test) The contact electrical resistance of the test piece after the above-mentioned hydrogen sulfide evaluation test was measured using an electrical contact simulator CRS-1 manufactured by Yamazaki Seiki Kenkyusho Co., Ltd. at a direct current of 10 mA and a load of 5 gf. The evaluation criteria for electrical contact resistance are as follows: A: Less than 0.002 Ω C: 0.002Ω or more The evaluation results are shown in Tables 1 and 2.

[0041] [Table 1]

[0042] [Table 2]

[0043] (Consideration) In all of Examples 1 to 13, the silver-plated metal material was treated with a surface treatment solution containing an organic compound having a mercapto group and a sulfonic acid group, an aluminum salt, a zirconium salt, a molybdate or a vanadate, and an iodide, so that discoloration, a decrease or increase in reflectance, and an increase in contact electrical resistance after high-temperature heating could be suppressed. On the other hand, in Comparative Examples 1 and 2, the organic compound in the surface treatment solution did not have a sulfonic acid group, and it was not possible to suppress discoloration, a decrease or increase in reflectance, and an increase in contact electrical resistance value after high-temperature heating. In Comparative Example 3, the surface treatment solution did not contain a specified metal salt, and the suppression of discoloration and the decrease or increase in reflectance after high-temperature heating was inferior to Examples 1-13. In Comparative Example 4, the surface treatment liquid did not contain an organic compound having a mercapto group and a sulfonic acid group, and the suppression of discoloration and the decrease or increase in reflectance after high-temperature heating was inferior to Examples 1 to 13.

[0044] Furthermore, tests were carried out in the same manner as in Examples 1 to 7, except that test pieces were prepared by forming a matte silver plating based on a known manufacturing method instead of the above-mentioned glossy silver plating, and all of the test pieces were evaluated as follows: A in the appearance evaluation test after heat treatment, A in the reflectance evaluation test, A in the hydrogen sulfide evaluation test, and A in the contact electrical resistance evaluation test. This demonstrates that the surface treatment method for metal material according to the present invention is effective for both glossy silver plating and matte silver plating.

Claims

1. A method for surface treatment of a metal material plated with silver or silver alloy, comprising the steps of: an organic compound having a mercapto group and a sulfonic acid group; an aluminum salt, a zirconium salt, a molybdate or a vanadate; Iodide, The present invention relates to a surface treatment method for a metal material, the method comprising the steps of: contacting a metal material plated with silver or a silver alloy with a surface treatment solution prepared by dissolving or dispersing the above-mentioned compound in water and adjusting the pH to 7.0 or less, thereby forming a coating on the surface of the silver or silver alloy plating.

2. the aluminum salt is aluminum sulfate, aluminum chloride, or aluminum hydroxide; the zirconium salt is zirconium sulfate, zirconium oxychloride, zirconium oxynitrate, or zirconium acetate; The molybdate is sodium molybdate or ammonium molybdate, 2. The method for treating a surface of a metal material according to claim 1, wherein the vanadate is sodium vanadate, potassium vanadate, or vanadium oxysulfate.

3. 3. The method for treating a surface of a metal material according to claim 1, wherein the iodide is sodium iodide or potassium iodide.

4. The method for treating a surface of a metal material according to any one of claims 1 to 3, wherein a concentration of the organic compound having a mercapto group and a sulfonic acid group in the surface treatment solution is 0.05 to 50.0 g / L.

5. 5. The method for treating a metal surface according to claim 1, wherein the concentration of the aluminum salt, the zirconium salt, the molybdate, or the vanadate in the surface treatment solution is 0.25 to 100.0 g / L.

6. The method for treating a surface of a metal material according to any one of claims 1 to 5, wherein a concentration of the iodide in the surface treatment solution is 0.005 to 2.0 g / L.

7. The metal material is (1) A metal substrate and a silver or silver alloy plating provided on the surface of the metal substrate, or (2) A metal substrate, a base plating formed on the surface of the metal substrate and made of copper, nickel, palladium, or an alloy thereof, and a silver or silver alloy plating formed on the surface of the base plating. The method for treating the surface of a metal material according to any one of claims 1 to 6.

8. The method for treating a surface of a metal material according to any one of claims 1 to 7, wherein the metal material is an electric or electronic part.

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