JPS61296618A - Making of modified contact material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing a highly reliable modified contact material with excellent electrical properties.

[Background technology]

Electrical contacts, which are widely used in switches for power, automatic control, and information transmission, are one of the few moving parts in an electrical circuit, and their electrical characteristics are strongly required to have high accuracy and reliability. In other words, many of the failures of electrical equipment occur in this part, and it is said that the quality of the contact material determines the lifespan of the equipment.

In general, the electrical properties of a contact material are influenced by its surface condition.For example, contacts such as relays are made of silver alloy with a gold plating or gold cladding layer provided on the surface to lower contact resistance. Many things are used. However,
Manufacturing methods such as plating or cladding (co-rolling) produce minute pinholes on the surface, which cannot be avoided. Contacts with such surface defects are susceptible to corrosion caused by chlorine-based gases, sulfur-based gases, etc. In an atmosphere containing toxic gases, a corrosion reaction with the underlying silver progresses through pinholes, producing silver chloride, silver sulfide, etc. on the surface.
This increases contact resistance and causes poor continuity. The use of such contacts impairs the reliability of the equipment and shortens its lifespan.

Therefore, there was still a strong demand for improvements in the contact area.

On the other hand, when the surface condition of the contact is microscopically observed, there are minute irregularities, and for this reason, the degree of adhesion of the contact in the contact state is about 1/1000 of the apparent surface of the contact. This poses a problem in that the electrical properties of the contact material cannot be fully demonstrated, resulting in insufficient high precision and high reliability. However, it is difficult to make the surface completely smooth, so metals with excellent electrical properties or alloys of these metals have been developed as contact materials, but all of them are made of expensive metals such as gold, silver, platinum, and rhodium. Mainly precious metals. Efforts are being made to reduce the use of precious metals in order to make them cheaper, but due to the trade-off with performance, sufficient materials have not yet been developed.On the other hand, high current contacts used in magnetic switches, etc. Although silver alloy materials are often used in the contacts, a portion of the contact material may start to melt due to the arc that occurs between the contacts during the opening/closing operation of the contacts, or due to the Joule heat generated at the contact points. As described above, conventional silver alloys still have the problem of being insufficient in terms of arc resistance and welding resistance.

[Purpose of the invention]

The object of the present invention is to improve the above-mentioned problems of the prior art and to provide a method for producing a modified contact material that has excellent electrical properties, is highly reliable, and is inexpensive.

[Disclosure of the invention]

As a result of extensive research, the inventors have found that all problems can be solved by using the ion implantation method. This invention was completed based on such knowledge.

Therefore, the first invention is a method of modifying a contact material by implanting ions into the contact material, which uses a contact material whose base surface is coated with a metal layer to improve its characteristics. The gist of the invention is a method for producing a modified contact material, which is characterized by implanting ions of an inert gas into the surface metal layer, and the second invention is a method for producing a modified contact material, which is characterized by implanting ions into the contact material. A method for producing a modified contact material, which uses an inexpensive conductive material as the contact material and implants ions of at least one of precious metals and alloys thereof into the material. As a summary, the third invention is a method for modifying a contact material by implanting ions therein, the method comprising implanting ions of a material having a higher melting point into the contact material. The gist is the manufacturing method of modified contact materials.

These three inventions will be explained in detail below.

In addition, noble metals are those with atomic number 44 to 47 (Ru, Rh
, Pd, Ag) and 76 to 79 (OS % I
r % P t % A u ).

FIG. 1 schematically shows an apparatus for ionizing and implanting a predetermined element into the surface of a contact material. A contact material 7 to be ion-implanted from six companies is placed in a sample chamber, and the inside of the ion implanter main body 1 is evacuated from an exhaust port 8 by a vacuum pump. When a predetermined vacuum (10' Torr or less) is reached, nitrogen is introduced from the gas inlet 9.

A fixed amount of inert gas such as argon is flowed in, and the ion generation power source 3 is turned on to cause the ion generation section 2 to generate ions. For solid elements, such as noble metal elements such as gold and silver, and high melting point metal elements such as tungsten and molybdenum,
For example, metal particles or compounds of these elements are inserted into the evaporation chamber 10, the metal is evaporated while being heated by a heater (resistance heater) 11, etc., the ion generation power source 3 is turned on, and the ion generation section 2 generates ions. to occur. Then, the ion accelerating power source 4 is turned on, and the ions are accelerated by the accelerator 5 and injected into the contact material 7.

Accelerating voltage is often used in the range of 50 to 500 keV.
Generally, when the acceleration voltage is increased, the depth of ion implantation becomes deeper, so it can be selected as appropriate depending on the purpose. In this case, it is desirable to select only predetermined ions from among the ions accelerated by the accelerator 5 by placing a mass separator midway, and to inject highly pure ions into the contact material. If the purity of the implanted ions can be expected to be higher than initially (such as when using a substance with high purity), the present invention is not limited to this.

Three specific examples of the invention will be described in detail below with reference to the drawings.

(First invention) Figure 2(a) shows the contact material before ion implantation.
b) shows the contact materials after ion implantation. Second
As shown in Figures (al and bl), the base 13 of the contact material on the base material 12 is made of silver alloy, and gold plating (or gold cladding) 14 is applied thereon to improve the electrical characteristics. However, there are unavoidable pinhole-like minute defects 15 in the gold plating layer 14. When ions are implanted into such a contact, an ion implantation layer 14' is formed, and the minute defects 15 on the surface of the contact material are formed. disappears.As shown,
In some cases, ions are implanted only in a portion of the surface side of the gold-plated layer 14, and in other cases, although not shown, ions are implanted over the entire gold-plated layer 14 to eliminate even minute defects inside.

The process by which such micro defects are repaired by ion implantation will be described below.

3(a) and 3(b) show the concept of changes in the gold plating layer (or gold cladding layer) 14 before and after ion implantation, and FIG. 3(C) shows the concept of changes in the gold plating layer 14 before and after ion implantation. The distribution curve of internally implanted ions is shown. Before implantation (a), it has a crystal structure in which gold atoms 16 are regularly arranged, and there are micro defects 1 between them.
Contains 5. This is followed by ions (for example, N ions,
When 17 (such as Ar ions) is implanted, collisions with atoms occur, resulting in a large number of so-called Frenkel defects consisting of interstitial atoms and vacancies. Of these, most of the vacancies recover and disappear at room temperature, but the interstitial atoms increase as the amount of ions to be implanted increases. Therefore, volumetric expansion occurs partially, and the micro defects 15 disappear. implanted ion 1
Since approximately 1,000 atoms of the metal layer (in this case, gold atoms 16) can be moved for each individual, the arrangement of atoms in the metal layer is disturbed and the metal layer becomes amorphous, forming an ion-implanted layer 14' on the surface. , and pinhole-like minute defect 1
5 disappears. In addition, the implanted ions 17 have an atom of 1
Colliding with 6 one after another, it eventually loses its energy,
Stop. Therefore, the ion-implanted plating layer 1
The distribution of ions within 4' is as shown in Figure 3 (C1).
Draws a bell-shaped concentration curve. The maximum penetration depth l of implanted ions depends on the atomic weight of the ions and the crystal structure of the plating layer into which the ions are implanted, but it is relatively easy to control because it is proportional to the magnitude of the accelerating voltage. .

Next, an example in which the inert gas is nitrogen gas will be shown.

The contact material 7 having the configuration shown in FIG. 2(a) is placed in the sample chamber 6 of the ion implanter 1 shown in FIG. 3, nitrogen ions are generated in the ion generating section 2, and the ion acceleration power source 4 is turned on to accelerate the ions at 100 keV. After confirming the predetermined ion implantation amount on the monitor on the main body of the device, the contact material is taken out. No minute defects such as pinholes were observed on the surface of this contact material.

The maximum penetration depth p of the implanted nitrogen ions into the gold-plated layer 14' was approximately 0.1 μm.

Therefore, even in an atmosphere containing corrosive gases such as chlorine-based gas and sulfur-based gas, the corrosion resistance of the contacts is improved and high reliability is achieved. In addition, the hardness has improved from HV70 before ion implantation to HV250 after ion implantation.
It has excellent wear resistance and reduces the amount of wear on the contacts. When nitrogen gas ions are implanted, the ion implanted layer becomes a hardened layer.

Next, an example in which the inert gas is argon gas will be shown.

FIG. 4(a) shows the contact material before ion implantation. In the figure, a base 13 of contact material on a substrate 12 is a silver alloy, on which a gold-plated or gold-clad layer 14 is provided to improve electrical properties. The state of the contact after ion implantation is as shown in FIG. 4(b). Fig. 4(a) and (bl) both schematically show the contact state of the contact material.The structure of the contact material may be without gold plating, gold cladding layer, etc.Gold cladding layer 1
When viewed microscopically, the surface of No. 4 has minute irregularities,
Both contacts share substantially only a few contact points. In the figure, pinhole-like minute defects that are thought to exist in the gold cladding layer are omitted.

Argon ions are implanted into the contact material shown in FIG. 4(a) using the ion implantation apparatus shown in FIG. 1 in the same manner as in the previous example except that argon gas is introduced from the gas inlet 9.

In this example, the ion-implanted layer 14' has a disordered atomic arrangement and is amorphous, compared to a crystalline layer.
Since the amorphous layer is highly elastic, when both contacts are brought into contact and pressed, their surfaces easily deform elastically as shown in Figure 4(b), and the actual contact area (adhesion area) increases dramatically. do. The contact area between both contacts before ion implantation was approximately 1/1000 of the apparent area, but after ion implantation, it increased to 1/2 to 1/3 of the apparent area.

In fact, the ion-implanted contact material exhibited extremely low contact resistance and good electrical properties.

When rare gas ions such as argon ions are implanted into the surface metal layer of the contact material in this way, a highly reliable contact with extremely low contact resistance can be obtained.

(Second invention) FIG. 5 shows a case where the contact material base 13 is copper, which is a conductive material cheaper than precious metals generally used as contact materials, and gold ions and/or silver ions are implanted into its surface. Indicates the status of

The implantation method is the same as the first invention, but in the ion implantation apparatus shown in FIG. 1, gold ions are generated by, for example, inserting a small amount of gold particles into the evaporation chamber 10 and heating them. This is done by generating all the steam and ionizing it in the ion generator 2. In addition, the generation of silver ions is
Similar to the generation of gold ions, for example, silver chloride vapor is generated.

The electrical properties of the contacts were similar to conventional contact materials made of gold-plated silver alloy. In this way, according to the ion implantation method, it is possible to use less precious metals, and a significant cost reduction can be achieved.

Similar attempts were made to implant gold ions and/or silver ions using aluminum as the base 13 of the contact material, but
Similar results were obtained when the base 13 of the contact material was made of copper.

In this way, when ions of at least one of noble metals and their alloys are implanted into inexpensive conductive materials,
High performance at low cost (high reliability and excellent electrical properties)
A contact point is obtained.

(Third invention) FIG. 6 shows a state in which the base 13 of the contact material is a silver alloy, and tungsten and/or molybdenum, which are so-called high melting point metals, are ionized and implanted into this. The implantation method is the same as the first invention, but in the ion implantation apparatus shown in FIG. 1, tungsten ions are generated by, for example, inserting a small amount of tungsten dioxide (WO3) into the evaporation chamber 10 and heating it. A mass separator is then used to inject only tungsten ions into the contact material. Furthermore, implantation of molybdenum ions can be similarly performed using a compound containing molybdenum. Of course, tungsten and molybdenum alone may also be used.

This contact has a high melting point on the contact surface layer, and the amount of evaporation caused by arcing or Joule heat is extremely small (hardly any welding is observed, and it has excellent arc resistance and welding resistance).

Even when the base 13 of the contact material is silver and tungsten ions and/or molybdenum ions are implanted into it, the amount of evaporation due to arc generation or Joule heat is extremely small, as is the case when the base is a silver alloy. Obtained.

Furthermore, even when the base 13 of the contact material was gold and tungsten ions and/or molybdenum ions were implanted into it, results were obtained in which the amount of evaporation due to arc generation, Joule heat, etc. was extremely small.

In this way, by implanting ions of a material with a higher melting point into the contact material, high reliability can be obtained and a contact with excellent electrical characteristics can be obtained.

Note that these three inventions are not limited to those described above.

〔Effect of the invention〕

As the first invention has been described above, even if there is a minute pinhole defect on the surface of the contact material, the defect can be repaired by implanted ions. Therefore, the corrosion resistance of the contact material is improved and high reliability can be obtained. Also,
When argon ions are implanted, the surface atoms become amorphous due to the interaction with the implanted ions, and the surface layer becomes a layer rich in elasticity, which is easily smoothed by pressure, so that there is substantial contact due to the minute irregularities existing on the surface. Even in cases where the area is reduced, the contact resistance on the contact surface can be significantly reduced.

The second invention, as seen above, is copper.

By implanting noble metal ions into the surface of an inexpensive conductive material such as aluminum, a highly reliable contact material with low manufacturing costs and excellent electrical properties can be obtained.

The third invention is that for contact materials that require arc resistance, high melting point metal ions such as tungsten are injected into the contact surface, resulting in less melting and evaporation when energized and high reliability (arc resistance). It is possible to obtain a contact material with good adhesive properties and welding resistance.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional plan view of the ion implanter, and Figure 2 (
a) is a side cross-sectional view showing a contact material with defects; FIG.
b) is a side sectional view showing the state after ion implantation according to an embodiment of the first invention using this contact material; FIG. 3(a)
, (b) is a cross-sectional conceptual diagram of the contact material surface before (a) and after ion implantation into the defective surface (bl) according to an embodiment of the first invention. , shows concentration curves of implanted ions in the depth direction from the material surface when ions are implanted, and FIGS. 4(a) and 4(b) show another embodiment of the first invention, and FIG. a), after (
Fig. 5 is a cross-sectional view showing the contact state of the contacts in b), and Fig. 5 is a side sectional view of the embodiment of the second invention, when noble metal ions are implanted into a normal conductive material. A side cross-sectional view when refractory metal ions are implanted into contact material. 1...Ion implanter main body 6...Sample chamber 7...
・Ion-implanted contact material 10... Evaporation chamber 13...
・Base of contact material 14...Coating N 14'
...Ion-implanted layer 15...Minute defects such as pinholes 17...Implanted ions

Claims (16)

[Claims] (1) A method of modifying the contact material by implanting ions into it, using a contact material whose base surface is coated with a metal layer to improve its characteristics. A method for producing a modified contact material characterized by implanting inert gas ions into a surface metal layer. (2) Claim 1 in which the inert gas is nitrogen gas
Manufacturing method of the modified contact material described in Section 1. (3) The method for producing a modified contact material according to claim 1, wherein the inert gas is argon gas. (4) The method for producing a modified contact material according to any one of claims 1 to 3, wherein the base material is a silver alloy. (5) The method for producing a modified contact material according to any one of claims 1 to 4, wherein the metal layer is gold. (6) The method for producing a modified contact material according to any one of claims 1 to 5, wherein the coating method is a plating method. (7) The method for producing a modified contact material according to any one of claims 1 to 5, wherein the coating method is a cladding method. (8) A method of modifying the contact material by implanting ions into it, in which an inexpensive conductive material is used as the contact material, and ions of at least one of precious metals and their alloys are added to the contact material. A method for producing a modified contact material characterized by injecting. (9) The method for producing a modified contact material according to claim 8, wherein the inexpensive conductive material is copper. (10) The method for producing a modified contact material according to claim 8, wherein the inexpensive conductive material is aluminum. (11) The method for producing a modified contact material according to any one of claims 8 to 10, wherein the noble metal is at least one of gold and silver. (12) A method for producing a modified contact material, which is a method for modifying a contact material by implanting ions into the contact material, the method comprising implanting ions of a material with a higher melting point into the contact material. . (13) The method for producing a modified contact material according to claim 12, wherein the contact material is silver. (14) Claim 12 in which the contact material is a silver alloy
Manufacturing method of the modified contact material described in Section 1. (15) The method for producing a modified contact material according to claim 12, wherein the contact material is gold. (16) The method for producing a modified contact material according to any one of claims 12 to 15, wherein the material having a high melting point is at least one of tungsten and molybdenum.