JP6767147B2 - Metallic material for thin film plating - Google Patents

Description

The present invention is suitable as a contact material that is required to have excellent plating properties relates to the particularly thin plated metal materials that also require good corrosion resistance in the thickness.

In the metal material for contacts used in electronic devices, functional material plating is performed by utilizing the physical properties of the plating film itself such as electrical properties. For example, conductive spring materials such as terminals, connectors, switches, and relays are plated with nickel, copper, and tin for the purpose of improving contact resistance, solderability, and insertability, and the lead frame is wire. Silver plating and copper plating for bonding are applied.

On the other hand, for example, a copper alloy material that is often used as a contact material is manufactured by appropriately combining heat treatment, hot rolling, cold rolling, and buffing after casting in the manufacturing process, and as a result, it is produced on the surface layer. There is a layer different from the inside called a processed alteration layer.

Conventionally, it is known that the processed altered layer adversely affects the plating property, and the processed altered layer has been removed in advance before plating.

For example, in Patent No. 4629154 (Patent Document 1), since the processed alteration layer inhibits the adhesion between the plating film and the base material, the processed altered layer (30) on the surface is subjected to electrolytic etching treatment with an alkaline aqueous solution such as caustic soda water. It is described that nickel plating should be performed after removing (thickness of about 40 μm). Furthermore, it is described that the processed altered layer is prepared so as to satisfy a predetermined particle size and abundance ratio.

According to Japanese Patent Application Laid-Open No. 2006-2233 (Patent Document 2), it is possible to remove a work-altered layer for the purpose of providing an object to be plated having excellent moldability without cracking in the plating layer due to bending or the like. Are listed. Further, as a method for removing the processed altered layer, a dissolution method with an acid such as sulfuric acid, nitric acid, hydrochloric acid, hydrogen peroxide solution, hydrofluoric acid, an energization dissolution method in an electrolytic solution, a sputtering method, an etching method and the like are described. ing.

According to Japanese Patent Application Laid-Open No. 2007-39804 (Patent Document 3), a processed alteration layer (surface layer) is provided for the purpose of providing a copper alloy for electronic devices having excellent plating properties, which does not cause abnormal precipitation of plating or deterioration of oxide film adhesion. A copper alloy for electronic devices in which the thickness of (amorphous to a structure having a crystal particle size of less than 0.2 μm) is controlled to 0.2 μm or less is described. The thickness of the processed alteration layer here is the average of the measured values at five observation points by measuring the thickness at the position where the processed alteration layer is the thickest in the field of view of magnified observation. It is described that the work-altered layer is removed by a chemical dissolution treatment, an electrochemical dissolution treatment, a physical treatment such as sputtering, and in the embodiment, immersion in a mixed acid of sulfuric acid and hydrogen peroxide solution, It is described that the processed altered layer was removed by heat treatment in a heating furnace in a hydrogen-reducing atmosphere and electrolytic dissolution in an aqueous solution containing phosphoric acid.

Patent No. 4629154 JP 2006-2233 JP-A-2007-39804

Patent Documents 1 to 3 describe that the processed alteration layer is removed for the purpose of suppressing the adhesion between the plating film and the base material and the abnormal precipitation of the plating. However, in recent years, there is a need to reduce the thickness of the plating coating in the demand for cost reduction. Simply dissolving and removing the work-altered layer makes a difference in the corrosion resistance of the plating material when it is finished as a plated material even with the same plating film thickness. It turns out that it can be seen. In particular, the tendency is remarkable when the plating film is thinner than 1 μm, more preferably 0.5 μm or less. From these, it is an object of the present invention to provide a metal material which is a base (base material) suitable for a thin film plated product having excellent corrosion resistance even after being formed with a particularly thin plating thickness. Further, the present invention is to provide a plating with metallic materials subjected to plating a metal material which is the base material prior to such plating with another object.

As a result of diligent research to solve the above problems, the present inventor has found that the corrosion resistance is greatly improved by making the surface shape (steepness) of the metal material which is the base material before plating within a certain threshold value. It was. In particular, the tendency becomes more remarkable as the plating thickness becomes thinner, and shows a very large effect on a plated product to be thinned, for example, 1 μm or less, further 0.5 μm or less. The present invention has been completed based on this finding.

That is, according to the present invention, the following means are provided:
(1) A metal material for forming a plating layer on the upper layer , and the steepness measured by an atomic force microscope (AFM) at 25 μm × 25 μm on the surface of the metal material is 15.1 to 30 degrees . , A metal material having a thickness of the plating layer formed on the surface of 0.03 to 1 μm .
(2) The metal material according to item (1), wherein the metal material is copper, a copper alloy, iron, an iron alloy, aluminum or an aluminum alloy.
(3) A plated metal material having a plating layer having a thickness of 0.03 to 1 μm on the surface of the metal material according to item (1) or (2) , wherein the metal type of the plating layer is gold. A plated metal material that is at least one of a gold alloy, a silver, a silver alloy, a nickel, a nickel alloy, a palladium, a palladium alloy, a rhodium, a rhodium alloy, a ruthenium, a ruthenium alloy, a platinum or a platinum alloy.
(4 ) The plated metal material according to (3 ), which shows a rating number of 7 or more on the plated surface after the 8-hour test in the salt spray test according to JIS H 8502.

According to the present invention, by satisfying the smoothness (steepness) of a specific surface, it is possible to provide a metal material which is a base material before plating and has excellent corrosion resistance.

FIG. 1 is a diagram illustrating the smoothness of a specific surface defined by the present invention.

First, the smoothness of a specific surface defined by the present invention will be described.
That is, the smoothness of the surface of the metal material that is the base material before plating can be determined from the surface roughness obtained from the observation field of view of several tens of microns using an atomic force microscope (AFM) as follows. It is defined by an index of steepness calculated using the formula ((inclination of unevenness: Sy / interval of unevenness) (unit: rad). It is a parameter indicating the gradient of each unevenness). Here, the steepness is arctan (height difference between plots / average value of plot intervals). The specific surface smoothness defined in the present invention refers to the following minute irregularities on the surface. In the present invention, for example, using a Nanosurf Mobile (trade name) manufactured by Nanosurf AG of Swisserland, the measured values of 256 plots scanned at equal intervals in the direction perpendicular to the rolled streaks on the material surface within the measurement range are measured between the plots. It is the inclination angle of the unevenness calculated by taking the average value of the squares of each of the 255 values (inclinations) obtained by dividing the height difference by the plot interval and applying the average value to the following equation. (See Fig. 1)

In the present invention, when the steepness is measured in an area of 25 μm × 25 μm, the angle is 30 degrees or less, preferably 20 degrees or less, so that a plating film having excellent corrosion resistance can be obtained even with a thin coating thickness. The lower limit is not specified, but the feasibility is 0.01 degrees or more.

When the roughness of the rolling roll is Ra 0.12 μm or more, the unevenness of the surface of the material to be transferred becomes large, the current density distribution becomes uneven during plating, the pinholes of the plating film increase, and the corrosion resistance deteriorates remarkably.

When the plating thickness is thinner than 0.03 μm, the pinholes of the plating film increase and the corrosion resistance is significantly deteriorated.

The production method of the present embodiment preferably includes the following first to fourth steps. The drug names and other manufacturing conditions specifically listed below are typical examples for explanation. The present invention is not limited thereto.

First, as the first step (S1), a plate material as a raw material is produced. After rough rolling the ingot, for example, phosphor bronze alloy (C5210), the dough buffing treatment is performed, and the quality is separated by using, for example, a finish rolling roll having a roll roughness Ra = 0.03 μm. For example, finish rolling is performed so that the plate thickness becomes, for example, 0.15 mm at a processing rate of 30%, which becomes EH, and further, low temperature annealing is performed according to a conventional method to reduce distortion inside the material, and the plate material is manufactured. ..

As the second step (S2), the phosphor bronze alloy (for example, C5210) is cathodically electrolytically degreased in an alkaline solution such as caustic soda.

In the next third step (S3) (activation treatment), for example, the nonionic surfactant is 0 in a solution containing at least one of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and hydrofluoric acid. It is activated by pickling by immersing it in a mixed solution containing .0001 to 20%. Here, the solution of each system is a solution containing 10 to 50% sulfuric acid, 5 to 30% hydrochloric acid, 10 to 70% phosphoric acid, 5 to 30% nitric acid, and 0.0001 to 20% nonionic surfactant. Is.
Here, among various solutions, the phosphoric acid-based solution refers to a solution containing phosphoric acid as a main component, and the nitric acid-based solution refers to a solution containing nitric acid as a main component.

In the next fourth step (S4), for example, an electrolytic solution containing silver cyanide and potassium cyanide is electrolyzed at a cathode current density ( ^{2 to} 15 A / dm ² ) to form a plating layer by silver plating. To do.

By such treatments from the first step to the fourth step, a plated metal material can be produced.

Further, in the fourth step (S4) of forming the outermost layer, instead of the silver plating described above, antimonyl potassium tartrate is added to an electrolytic solution containing silver cyanide and potassium cyanide, and the cathode current density (2 to 5 A) is added. It may be electrolyzed with / dm ² ) and plated with a silver alloy (silver-antimony alloy).
Alternatively, after the activation treatment in the third step (S3), electrolysis is performed at a cathode current density (1 to 5 A / dm ² ) with an electrolytic solution containing silver cyanide and potassium cyanide, and then silver strike plating is performed. , The above-mentioned silver plating or silver alloy plating may be applied.

Hereinafter, the present invention will be described in more detail based on examples of the method for producing a metal material according to the above embodiment, but the present invention is not limited thereto.

As each sample of Examples, Comparative Examples, and Conventional Examples, any of C5210, SUS301, Al, or Al alloy is used as a material, and the manufacturing process is performed according to the first step (S1) to the fourth step (S4). In, the presence or absence of dough buffing, finish rolling roll roughness, quality, presence or absence of low temperature annealing (strain removal annealing, 150 to 600 ° C, 1 minute to 10 hours), plating metal type and / or plating thickness are various. Table 1 shows the samples prepared by changing. In the third step (S3) (activation treatment), various solutions shown in Table 1 (indicated as "pretreatment" in the table) were used.
Here, A6061 was used as the Al alloy (aluminum alloy).

AFM measurements were performed on these samples as described above (see FIG. 1). When the steepness is 18 degrees or less as "excellent" and "◎" is added in the table, and when it exceeds 18 degrees and 30 degrees or less is "good" and "○" is added in the table and exceeds 30 degrees. Is marked as "inferior" and "x" is added in the table.

Each sample shown in Table 1 was subjected to a salt spray test under the conditions of 35 ° C., 5% NaCl and pH 6.5 for 8 hours as specified in JIS H8502, and the rating number was measured to evaluate the corrosion resistance. did.
The degree of corrosion was determined from the results of the salt spray test. Samples with a rating of less than 7 and corrosion was visually indicated as "NG" in the table, and samples with a rating of 7 or higher with a slight or no corrosion were "excellent". "OK" is shown in the table.

From Table 1, all the samples of the invention examples showed a rating number of 7 or more. From this, it was confirmed that the corrosion resistance was good.

On the other hand, in Comparative Example 1 and Conventional Examples 1 and 2 shown in Table 1, the rating numbers were less than 7, and the corrosion resistance was not good.

Claims (4)

A metallic material for forming a plating layer on the upper layer, steepness was measured by an atomic force microscope (AFM) in 25 [mu] m × 25 [mu] m of the metal material surface is 15.1 to 30 degrees, to the surface A metal material having a thickness of the plating layer formed of 0.03 to 1 μm . The metal material according to claim 1, wherein the metal material is copper, a copper alloy, iron, an iron alloy, aluminum or an aluminum alloy. A plated metal material having a plating layer having a thickness of 0.03 to 1 μm on the surface of the metal material according to claim 1 or 2 , wherein the metal type of the plating layer is gold, a gold alloy, silver, or a silver alloy. , Nickel, nickel alloys, palladium, palladium alloys, rhodium, rhodium alloys, ruthenium, ruthenium alloys, platinum or at least one of platinum alloys, plated metal materials. The plated metal material according to claim 3 , wherein the rating number on the plated surface after the 8-hour test in the salt spray test according to JIS H 8502 is 7 or more.

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