JP2001003194A - Heat resistant and corrosion resistant silver plating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase of contact resistance in the subject material even in the use for a long time in a high temp. environment and to improve its corrosion resistance by composing it of an intermediate layer of alloy plating contg. a specified amt. of P, and the balance Ni with inevitable impurities or contg. Ni and Co with inevitable impurities and an Ag or Ag alloy plating surface layer. SOLUTION: The content of P in the intermediate layer is controlled to 0.05 to 20 wt.%. P diffuses from the intermediate layer into the Ag plating and moreover into the Ag surface by heating to form a film of phosphorous oxide or phosphate. The film suppresses the corrosion of the plating caused by sulfide as a protection film without increasing the contact resistance of the plating surface and moreover suppresses the oxidation of the boundary between the plating and the intermediate layer. Ni or Co in the intermediate layer is a base metal for introducing P into the intermediate layer and moreover has the operation of preventing the phenomenon that Cu diffuses into the plating and is oxidized to increase the contact resistance. The thickness of the intermediate layer is preferably controlled to 0.5 to 3 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver-plated material used for a terminal, a connector, a material for an electronic component lead, and the like.
The present invention relates to a technique for producing a silver-plated material having a small increase in contact resistance and good corrosion resistance.

[0002]

2. Description of the Related Art Silver plated metal materials have low contact resistance and excellent electrical connection characteristics.
It is used as a contact material for terminals and connectors, as well as for lead materials for electronic components such as lead frames and lead wires. In addition, silver-plated materials are used for tableware, decorative parts, musical instruments and the like.

A silver plating material for an electric component is formed by directly forming silver or a silver alloy on the surface of a copper alloy strip such as copper or phosphor bronze by electroplating or hot-dip plating, or It is manufactured by forming a copper or nickel layer as an intermediate layer and then forming silver or a silver alloy. The silver-plated material is then turned into terminals, connectors, lead frames, etc. by pressing, punching, or the like. As another manufacturing method, there is a method in which a strip of copper or a copper alloy is first pressed, and then silver plating is performed.

[0004] The environment in which silver-plated terminals, connectors, and the like are used is not only a room temperature environment but also a relatively high temperature environment, for example, inside an electric device that generates heat or in an automobile engine room. In some cases. On the other hand, even when the ambient temperature is room temperature, the temperature of the plated material itself may rise to about 60 to 100 ° C. due to self-heating caused by energization. Thus, silver or silver-plated materials used for electronic components are often used at a temperature higher than room temperature.

[0005]

However, silver has low corrosion resistance to sulfides, and its surface may be corroded by, for example, sulfur oxides (SOx) or hydrogen sulfide contained in the atmosphere in trace amounts. When the silver surface is corroded by sulfide, the contact resistance of the connector made of silver-plated material increases and the solderability deteriorates. On the other hand, since silver has the property of easily transmitting oxygen, oxygen that has penetrated from the surface layer diffuses through the silver plating and reaches the base material or the intermediate layer, oxidizing the surface of the base material or the intermediate layer. The contact of the material may increase, the solderability may deteriorate, or the silver plating may peel off from the interface between the intermediate layer and the base material. The corrosion of silver plating by sulfides or the oxidation of silver plating by oxygen is more likely to occur at higher temperatures. Therefore, when using terminals and connectors made of silver plating in a high temperature environment, Needs attention.

The present invention has been made in view of the above-mentioned circumstances, and has a small increase in contact resistance even when used for a long time in a high-temperature environment, and has a good corrosion resistance for terminals and connectors. The purpose is to provide plating materials.

[0007]

Therefore, as a result of research for solving the above-mentioned problems, 0.05 to 20% by weight of phosphorus was contained in the base material of the metal material, and the balance was nickel and unavoidable impurities or nickel and cobalt. A heat-resistant silver-plated material characterized by having high heat resistance comprising an intermediate layer of alloy plating comprising unavoidable impurities and a surface layer of silver or silver alloy plating;

The intermediate layer contains 0.05 to 20% by weight of phosphorus and 10 to 60% by weight of one or more of Sn, Cu and Zn, with the balance being nickel and unavoidable impurities or nickel. A heat-resistant silver-plated material according to the above (1), characterized in that it is an alloy comprising cobalt and unavoidable impurities.

The intermediate layer is made of an alloy comprising 0.05 to 20 wt% of phosphorus, 0.05 to 20 wt% of boron, and the balance being nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities. Heat-resistant silver-plated material according to 1),

(4) The intermediate layer contains phosphorus in an amount of 0.05 to 20 watts.
t%, boron is 0.05 to 20 wt%, and Sn,
One or two or more of Cu and Zn
The heat-resistant silver-plated product according to the above (1), wherein the intermediate layer has a thickness of 0 to 60 wt% and the balance is an alloy composed of nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities. A heat-resistant silver-plated material according to any one of (1) to (4),

(6) The terminal and the connector having excellent heat resistance, wherein the contact is made of the heat-resistant silver-plated material as described in (1) to (5) above, for a long time in a high temperature environment. Even so, it was found that the increase in contact resistance can be suppressed to a small level.

[0012]

In the intermediate layer, nickel or cobalt is a base element for putting phosphorus, boron, copper, tin, and zinc into the intermediate layer, and alloy plating can be performed with any of these elements. The alloy ratio in the case of a nickel-cobalt alloy can be any ratio. In addition, the effect of nickel or cobalt has an effect of suppressing diffusion of copper into silver plating, that is, a function of preventing copper from being diffused and oxidized in silver plating to increase contact resistance. However, when only nickel or a nickel-cobalt alloy is used as the intermediate layer, it is impossible to prevent corrosion by sulfide of silver plating or oxidation inside the plating. In the present invention, if there is a nickel-containing alloy layer under the surface silver or silver alloy, there is no problem even if there is another plating layer under that, that is, between the base metal and the alloy layer. The present invention is also effective in this case.

On the other hand, when a nickel (or nickel-cobalt alloy) alloy containing one or both of phosphorus and boron is used as the intermediate layer, phosphorus or boron diffuses from the intermediate layer into the silver plating by heating. , And further diffuses to the silver surface to form a film of phosphorus oxide or boron oxide or a salt thereof. These coatings
Suppresses silver plating corrosion due to sulfide as a protective film without increasing the contact resistance of the silver plating surface. By the same mechanism, oxidation at the interface between the silver plating and the intermediate layer is also suppressed.

The content of phosphorus and boron in the intermediate layer may be determined according to the required heat resistance and corrosion resistance.
If the content is less than 0.5% by weight, no effect can be obtained.
It is desirably at least wt%. The upper limit of 20 wt% is an upper limit at which alloy plating with nickel (or a nickel-cobalt alloy) is possible, and it is difficult to further contain phosphorus and boron. Also,
If the content of phosphorus and boron exceeds 15% by weight, the plating film becomes hard, and cracks and burrs of the plating easily occur during pressing. Therefore, the content is more preferably 15% by weight or less.

Copper, zinc, and tin as elements added in addition to phosphorus and boron reduce the hardness of nickel-phosphorus, nickel-cobalt-phosphorus, nickel-boron, nickel-cobalt-boron plating films, It is added as needed to improve pressability. It contains 10 to 60% by weight of one or more of copper, zinc and tin. If the content of these elements is less than 10 wt%, the effects of the respective elements will not be sufficiently exhibited. On the other hand, if it exceeds 60% by weight, the diffusion of copper, which is an original effect of nickel or cobalt, cannot be suppressed.

If the thickness of the intermediate layer is less than 0.5 μm, the effect of heat resistance cannot be obtained.
Preferably, 1.0 or more is required. If the thickness is too large, the pressability is impaired, so the upper limit is 3 μm or less. On the other hand, it is also possible to form another plating layer, for example, chromium plating, between the intermediate layer and the base material to form a multilayer plating structure.

The thickness of the silver or silver alloy plating layer on the surface is
If the thickness is less than 0.1 μm, a low contact resistance cannot be maintained. On the other hand, if the thickness of the surface layer is too large, the manufacturing cost of plating increases, while the terminal insertion force increases. Therefore, the thickness of silver or silver alloy plating is preferably 5 μm or less. The surface plating layer is
It is also possible to select an alloy plating such as a silver alloy other than silver, for example, a silver-nickel alloy.

As the plating solution for the intermediate layer, the basic nickel-phosphorus alloy plating or nickel-cobalt-phosphorus alloy plating is performed using a known nickel sulfate-nickel chloride-phosphoric acid.
-Phosphorous acid or nickel sulfate-nickel chloride-cobalt sulfate-phosphoric acid-phosphorous acid. Here, phosphoric acid is a pH adjuster. Phosphorous acid controls phosphorus in the plating film by changing the amount of phosphorous acid added. However, in the present application, in any plating, the composition and conditions of the plating bath can be arbitrarily selected. Other alloying elements of phosphorus are boron, borane amine complex (a source for depositing boron in the plating film), copper is copper sulfate, etc., tin is tin sulfate, etc., and zinc is metal salt, such as zinc sulfate. Is alloyed by adding a small amount of When adding copper, a complexing agent is used because the natural potential of copper is higher than the others. Glycine added as a complexing agent is for co-depositing copper and nickel. It is necessary to select an optimum complexing agent depending on the pH of the plating bath. However, the effects of the present invention are not limited at all by setting these conditions.

Regarding silver or silver alloy plating on the surface layer,
Known cyanide baths and iodide baths can be used. The present invention is not limited to plating conditions, and is effective no matter what plating conditions are used. For the plating base material,
Metal materials such as copper, copper alloys, iron, iron alloys, stainless steel, and high nickel alloys can be used, and there is no restriction on the components of the base metal material.

The plated material of the present invention can be made into a contact of a connector, a semiconductor lead frame, or the like by pressing or etching.

[0021]

Next, the effects of the present invention will be specifically described based on examples. As the plating base material, a phosphor bronze (JIS C5210) having a thickness of 0.2 mm that had been degreased and pickled was used. The plating of the intermediate layer was evaluated for all the platings indicated in the claims. The surface plating was evaluated for silver plating and silver-nickel alloy plating.

The plating conditions of the nickel-phosphorous system and the system to which tin, copper and zinc are added are shown in Tables 1-4.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

The nickel-cobalt-phosphorus system is shown in Table 5.

[0028]

[Table 5]

Tables 6 to 9 show the plating conditions of the nickel-phosphorus-boron system and the system to which tin, copper and zinc are added.

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

[Table 8]

[0033]

[Table 9]

Tables 10 to 11 show the conditions of silver plating and silver-nickel alloy plating of the surface layer.

[0035]

[Table 10]

[0036]

[Table 11]

The composition of the intermediate layer, the thickness of the intermediate layer, the composition of the surface layer, and the thickness of the surface layer of these plated materials, and other comparative materials without the intermediate layer, those with copper plating as the intermediate layer,
A nickel-plated intermediate layer, a low-phosphorus concentration in the intermediate layer, a thin intermediate layer, and a thin surface silver plating were also prepared. Table 12 shows the plating compositions and thicknesses of these comparative materials.

[0038]

[Table 12]

The evaluation was conducted as a heat resistance test by measuring the contact resistance after heating at 155 ° C. for 16 hours in an air atmosphere. As a corrosion resistance test, a hydrogen sulfide concentration of 3 ppm, a temperature of 40 ° C. and a humidity of 50% R were used.
H, contact resistance after 6 hours of exposure time was measured. The contact resistance was measured using an electric contact simulator CRS-113-Au manufactured by Yamazaki Seiki Laboratory Co., Ltd. When the contact resistance after the heating and the corrosion resistance test was 10 mΩ or less, the evaluation material was judged to have good heat resistance and corrosion resistance. Also,
In order to confirm the effects of the present invention, pressability was also evaluated. The pressability was evaluated by pressing the evaluation material onto the terminal and observing the bent portion and the pressed end face. From this, it can be seen that in all cases, the working material is superior.

[0040]

As described above, according to the present invention, a silver-plated material having heat resistance can be supplied.

Continued on the front page F term (reference) 4K023 AA24 AB20 AB40 BA06 BA08 BA11 CA09 CB03 CB05 CB11 CB21 CB29 4K024 AA10 AA14 AA15 AA19 AA23 AA24 AB02 BA09 BB10 GA04 GA16

Claims (6)

[Claims] 1. The method according to claim 1, wherein the phosphorus is 0.05
Characterized in that it has a high heat resistance consisting of an intermediate layer of alloy plating consisting of nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities, and a silver or silver alloy plating surface layer, with the balance being 20% by weight. Silver plated material. 2. An intermediate layer containing 0.05 to 20% by weight of phosphorus,
And one or more of Sn, Cu, and Zn in a total content of 10 to 60 wt%, with the balance being an alloy comprising nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities. The heat-resistant and corrosion-resistant silver-plated material according to claim 1. 3. The intermediate layer contains 0.05 to 20% by weight of phosphorus,
The heat-resistant and corrosion-resistant silver-plated material according to claim 1, wherein the alloy is composed of 0.05 to 20% by weight of boron and the balance being nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities. 4. An intermediate layer containing 0.05 to 20 wt% of phosphorus,
Boron is 0.05 to 20 wt%, and one or more of Sn, Cu, and Zn is 10 to 6 in total.
The heat-resistant and corrosion-resistant silver-plated material according to claim 1, wherein the alloy is 0 wt%, and the balance is an alloy comprising nickel and unavoidable impurities or nickel, cobalt and unavoidable impurities. 5. The heat-resisting device according to claim 1, wherein the intermediate layer has a thickness of 0.3 μm to 3 μm.
Corrosion resistant silver plated material. 6. A terminal and a connector having excellent heat resistance and corrosion resistance, wherein the heat-resistant silver-plated material according to claim 1 is used as a contact.