JPH08306256A - Electric contact point on the basis of nickel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise stability as good as gold while lowering contact resistance by providing a surface layer composed of an alloy of nickel with a glass-forming additive element. SOLUTION: A surface layer 22 is formed on an electrically conductive member 21, and this layer 22 is made of an alloy of nickel with at least one glass- forming additive element. A part 23 of the layer 22, when exposed to an oxidizing atmosphere, includes oxygen further. In this case, boron, silicon, germanium, phosphorus, arsenic, antimony, and bismuth are used as glass-forming additive elements, and the quantity of them in the contact layer is caused to fall within a range of 1 to 40 atomic % or a range of 2 to 10 atomic % with respect to the total quantity of nickel and the additive elements. With this, metallic conductivity of the contact layer in an oxidizing atmosphere is maintained, and along with this, formation of a semiconducting nickel oxide is inhibited, and/or a thermodynamically further stabilized compound can be formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD This invention relates to electrical contact surfaces and, more particularly, to nickel-based contact surface materials.

[0002]

BACKGROUND OF THE INVENTION Gold is typically used in making high quality electrical contacts. The low contact resistance and high chemical stability properties of gold are a major advantage in such applications. However, since the price of gold is still high, efforts are ongoing to find alternative materials for making contacts.

The major of such alternative materials are precious metals other than gold. Silver-palladium alloys, for example, have been found to be suitable for certain applications. While such alternative alloys are less expensive than gold, it is desirable to further reduce costs. Therefore, non-noble metal alloys such as copper-nickel alloys have been investigated in terms of contact resistance and long-term stability. S.M.Garte (S.M.
M. Garte) et al. "Contact characteristics of alloys containing nickel"
(“Contact Properties of Nickel-ContainingAlloy
s ”), electrical contacts ( Electrical Contac
t ) 1972, Iillinois Institu
te of Technology).

[0004]

SUMMARY OF THE INVENTION It has been found that certain nickel alloys have contact characteristics that are as stable and have low contact resistance as gold. The device according to the invention comprises nickel and at least one glass-forming additive element such as boron,
Includes contact surfaces that are surfaces of alloys containing silicon, germanium, phosphorus, arsenic, antimony or bismuth.
The presence of such glass-forming elements maintains the metal conductivity of the contact layer in an oxidizing atmosphere while inhibiting the formation of semiconducting nickel oxides and / or forming thermodynamically more stable compounds. It is thought that this will result in

The addition of one or several glass-forming elements results in a crystallographically disordered (dis) state, at least when the layer is exposed to oxidizing atmosphere.
ordered) structure occurs. This is in contrast to the formation of crystalline nickel oxide when the glass-forming element is not added. Alternatively, a crystallographically unordered structure is produced by ion irradiation. For this purpose, alpha particles are preferably used. Surface contact resistances of less than 100 mΩ are typically maintained after longer exposure to oxidative atmosphere.

[0006]

DETAILED DESCRIPTION The electrical connection device shown in FIG. 1 includes a housing 11 and contact pins 12. The housing 11 is made of an electrically insulating material and the contact pins 12 have contact surfaces according to the invention. Shown in cross-section in FIG. 2 is an electrically conductive member 21, on which a surface layer 22 is placed. In accordance with the present invention, surface layer 22 is made of an alloy of nickel and at least one glass-forming additive element.
Portion 23 of layer 22 further contains oxygen when exposed to oxidizing atmosphere.

Preferred glass-forming additive elements are boron, silicon, germanium, phosphorus, arsenic, antimony and bismuth, the amount of which in the contact layer is preferably 1 to 40 atoms relative to the total amount of nickel and additive element. %
Is more preferable, and the range of 2 to 10 atomic% is more preferable. A range of 25 to 35 atomic% is also preferred if thermodynamically stable stoichiometric compounds are formed.

In total, the nickel and glass forming additive elements make up at least 70 atomic percent of the contact layer material. From the viewpoint of improving electrical and mechanical contact characteristics, it is desirable to add cobalt, and it is desirable to limit the total of elements other than cobalt to less than 5 atomic% and preferably less than 1 atomic%. Particularly unsuitable is the presence of Group VI elements such as ions, selenium and tellurium, the total amount of which is preferably limited to less than 0.5 atom%.

In the case of non-stoichiometric aggregates, glass-forming additives to nickel are believed to inhibit the formation of semiconducting nickel oxide in oxidizing atmosphere. If a glass-forming additive is present, it is believed that instead of such a semiconductor nickel oxide, a surface layer of an assembly containing nickel, oxygen and a glass-forming additive will be formed over a sufficiently large area of the layer. To be Such an assembly inherently has metallic conducting properties. Based on experimental evidence, the thickness of the surface layer containing oxygen is estimated to be as large as 2.5 nm.

The crystallographically disordered structure in the layer containing nickel is also formed during ion irradiation, and in this case, the crystallographically disordered structure occurs even before the exposure to the oxidizing atmosphere. It is also believed that this is a disordered, quasi-amorphous glassy nature of the oxidized surface portion, which helps to achieve the desired low contact resistance of the contact layer used for oxidizing fumes. The crystallographically disordered nickel aggregate preferably comprises nickel in an amount of at least 50 atomic%. The following examples specify and describe the characteristics of the contacts of the present invention.

[0011]

Example 1 A layer consisting essentially of 95 atomic% nickel and 5 atomic% antimony was deposited by getter sputtering on a copper substrate to a thickness of about 3 μm. The surface contact resistance was measured using a standard four-point probe.
It was found to be in the range of mΩ. The deposited film was then tested for stability at elevated temperatures and humidity (temperature 75 ° C., 95% relative humidity for 65 hours), and contact resistance was found to be in the range of 15-20 mΩ.

[0012]

Example 2 An experiment similar to Example 1 was conducted on a layer consisting essentially of 95 atomic% nickel and 5 atomic% phosphorus. The contact resistance was 1.8 mΩ before the test and 4.4 to 5 mΩ after the test.

[0013]

Example 3 An experiment similar to Example 1 was performed on a layer consisting essentially of 95 atomic% nickel and 5 atomic% boron. The contact resistance was in the range of 2.9 to 3.5 mΩ before the test and in the range of 10 to 14 mΩ after the test.

[0014]

Example 4 An experiment similar to Example 1 was performed on a layer consisting essentially of 95 atomic% nickel and 5 atomic% silicon.
The contact resistance was in the range of 1.6 to 2.1 mΩ before the test and in the range of 4.5 to 6 mΩ after the test.

[0015]

Example 5 An experiment similar to Example 1 was performed on a layer consisting essentially of 95 atomic% nickel and 5 atomic% germanium. The contact resistance was in the range of 1.5 to 1.85 mΩ before the test and in the range of 10 to 14 mΩ after the test.

[0016]

[Example 6] 208 g / l of NiCl ₂ .6H ₂ O, 49
An aqueous solution containing 85% g / l H ₃ PO ₄ and 5 g / l H ₃ PO ₃ was prepared. This solution was used to electroplate on copper electrodes. The temperature of the plating bath was 75 ° C., the current density was 150 mA / cm ² , and the plating rate was about 3 μm / min. The thickness of the deposited layer was about 4.5 μm. The contact resistance of the deposited layer was less than 10 mΩ after exposure to test atmosphere.

[0017]

Example 7 An aqueous solution of 0.087 mol As ₂ O ₅ and 0.5 mol NiCl ₂ .6H ₂ O was prepared. The copper electrode is
This solution was plated with nickel and arsenic by pulse plating. Temperature is 75 ℃, current pulse is 200mA / cm
² was on for 1.5 seconds and off for 0.5 seconds. The thickness of the deposited layer was about 4.5 μm. The contact resistance of the deposited layer was less than 10 mΩ after exposure to test atmosphere.

[0018]

[Example 8] 5 g of GeO ₂ and 4 cc in 50 cc of water
Ammonium hydroxide and 0.5 mol of NiCl ₂
150 g / l ammonium citrate was added to the 6H ₂ O solution. The solution was filtered and ammonium hydroxide was added until the pH was 8.5. A nickel-germanium layer was plated from this solution onto a copper electrode.
The temperature was 75 ° C., the filtration density was 150 mA / cm ² , and the plating rate was about 2.5 μm / min. The thickness of the deposited layer was about 4.5 μm. The contact resistance of the deposited layer was less than 10 mΩ after exposure to test atmosphere.

[0019]

Example 9 A nickel layer about 350 nm thick was deposited on a polished copper foil. Part of the nickel layer is covered with aluminum foil, and the energy of the alpha particles is about 1.8 Me, which is the alpha particles implanted into the uncovered part of the nickel layer
It was V. The dose of alpha particles is about 1.6 × 10 ¹⁶ particles / c to obtain the minimum contact resistance (less than 10 mΩ) after exposure to humid air at the temperature described in Example 1.
It has been found that m ² is optimal or close to it. (This test is considered to be almost equivalent to exposure to normal atmospheric conditions for 5 years.) After the test, the driven part and the part covered with aluminum foil were compared. Upon visual inspection, the latter showed a dull brown color, while the former was bright and shiny.

[Brief description of drawings]

FIG. 1 is a perspective view of an electrical connection device according to the present invention.

FIG. 2 is a schematic cross-sectional view of a portion of a device according to the present invention.

[Explanation of symbols]

 11 housing 12 contact pins

Continued Front Page (72) Inventor Pleuze, John Travis United States 07928 New Jersey, Kazam, Woods Lane 8 (72) Inventor Robins Murray United States 07922 New Jersey, Berkeley Heights, Kent Drive 110

Claims (1)

[Claims] 1. A device comprising an electrical contact comprising a surface of a body of contact material, the contact material being crystallographically disordered and containing a substantial amount of nickel.