JPS6027747B2 - electrical contact materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrical contact materials, particularly Ag metal oxide composite contact materials.

As an Ag oxide-based contact material, a contact material of Ag-Cd○ is widely used.

Ag-Cd○ contact material not only shows excellent average performance in terms of properties such as contact resistance, welding resistance, and wear resistance required for contact materials, but also has sufficient machinability for practical use. Therefore, they are often used for load currents of several amperes or more, such as relays, no-fuse breakers, and power switches for household electronic equipment. However, in recent years, as safety regulations have become stricter for various power switches, contact materials have come to be required to have better properties than ever before. In particular, for household electrical equipment, switches are required to be easier to operate and more compact, and on the other hand, from a safety standpoint, there is a strong need to improve the performance of both welding, which can lead to inability to separate, and wear, which can lead to insulation deterioration. desired. In addition, in recent years, with the rapid rise in the cost of Ag materials, there has been a trend to reduce the size of contacts from an economic standpoint, and as a result, the switching load per unit area of contacts has been reduced. There is a need for materials that can be produced in large quantities. In view of the above points, the present invention provides a contact material that can replace the Ag-Cd○ saddle point material, and basically proposes improvements in the characteristics of the Ag-Bi203 contact material. be.

A contact material in which Bi203 is dispersed in an Ag matrix is a contact material with low contact resistance and excellent welding resistance, as disclosed in JP-A-52-13356Y, but it has drawbacks. It was observed that there was a large amount of wear and tear.

In order to improve this point, the inventors conducted various studies and developed A.
In the g matrix, Bi203 and Sn02 are dispersed and reacted to form a composite oxide of Bi and Sn (Bi2Sn
We found that a material converted to 207) significantly improved wear resistance and also showed an improvement effect in terms of welding resistance. However, as mentioned above, due to recent trends, the shape of the contact is made smaller and the switching load per unit area is increased. Start generating. The cross section of the contact at this time is shown in Fig. 1. In the figure, 1 and 1' are Tawara point springs, 2 and 2' are Ag monoxide contacts, and 3 and 3' are Ag-rich layers. As the number of openings and closings increases further, the Ag-rich layer grows proportionally, so that the area of the Ag-rich layer on the entire contact surface becomes proportional to the square of the opening and closing times. As a result, the proportion of true contact points on the contact surface in the Ag-rich layer is also proportional to the square of the contact surface. Naturally, since the Ag-rich layer has poor adhesion resistance, the number of occurrences of contact dropout begins to increase significantly. The tendency is shown in FIG. 2, where the cumulative number of occurrences of settling shows a roughly squared curve with respect to the number of openings and closings. The inventors added Bi-Sn oxide (B
Subsequently, improvements were made to the material in which i2S ratio 07) was dispersed, and as a method for preventing the formation of an Ag-rich layer,
It was found that adding small amounts of oxides such as ln, Cd, and Sb was effective.

Among these, Cd is not desirable because it is regulated as a polluting element, and Sb oxides have disadvantages in other properties, such as increasing consumption and making contact resistance more likely to fluctuate. It's easy to do. The oxide of ln was found to be an additive with relatively few drawbacks from this point of view, and was developed. Next, the material of the present invention will be explained in more detail.

The material of the present invention has a Bj-Sn oxide (Bi2S-07) dispersed as a main oxide in an Ag matrix, and furthermore, a Bi oxide (Bi2S-07) is dispersed in an Ag matrix depending on the composition ratio of Bi and Sn.
It is an Ag-oxide composite contact material containing a small amount of oxide of Sn (Sn02) or oxide of Sn (Sn02), and in addition, an oxide of ln (ln203) is dispersed, and the amount of the contained oxide is as follows: Bi 25% by weight in metal equivalent value, Sn is B
i, 4 to 8% by weight (excluding 4% by weight), lnl. 8 to 5% by weight (excluding 1.% by weight), with the remainder being Ag.

In this compositional ratio relationship, the desired performance can be determined and achieved, and a significant improvement in switching performance can be expected, especially when the switching current is large in a small contact as described above. Main oxide B contained in the material of the present invention
The oxide in i-S (Bi2S mountain 07) is the oxide of Bj (
Bi203) and Sn oxide (Sn02) in a molar ratio of 1
By heating at a temperature in the range of 700 to 900° C. at a ratio of 2:2, an oxide with a yellow-green right-lateral structure is produced.

Its melting point shows sublimation at 1200° C. or higher, and by dispersing it in an Ag matrix, it has a great effect of improving welding resistance and abrasion resistance. In the Ag matrix, the above Bi-
As a method for dispersing Sn oxide and ln oxide, a quaternary alloy of Ag-Bi-Sn-ln is heated in an oxidizing atmosphere and Bi, Sn, and ln are selectively oxidized using so-called internal oxidation. However, regarding Bi and Sn, when converted from the above molar ratio, Bi weight x and Sn weight y in the quaternary alloy are y/x〒0.57, then B
ibn207 can be generated.

However, since Bi is easily polarized in the alloy, it is difficult to reliably convert it into Bi-Sn oxide by internal oxidation treatment, and Bi oxide and Sn oxide exist alone. There is. Also, as a matter of course, if the value of y/x above becomes larger than 0.57, Bi
The chances of the oxide of Sn existing alone decreases, and the oxide content of Sn increases. The value of y/x above is 0.57
It is clear that as the size becomes smaller, the opposite trend will occur. However, in the case of small-sized devices with large switching currents, for which the material of the present invention is mainly used, the value of y/x is larger than 0.57, and the Sn oxide is different from the Bi-Sn oxide. There is little consumption when they coexist. However, l
When Sn oxide increases in the presence of n oxide, processability deteriorates significantly and contact resistance increases, so the amount of ln oxide can prevent the formation of the above-mentioned Ag-rich layer. It is desirable that the amount of Sn oxide be set to a minimum amount so that y/x can be adjusted to about 1 to 2. The composition of the material of the present invention was determined under the conditions described above, and the composition in terms of metal is at least 2 to 5% by weight of Bi, 4 to 8% by weight of Sn (excluding 4% by weight), and lnl. 8-5% by weight
(However, 1.% by weight of Tsuru is not included), and the balance consists of Ag. In relation to the above composition, if we summarize the functions of oxides dispersed in the Ag matrix, Bi oxides are effective in improving welding resistance, and Sn oxides are effective in improving welding resistance.
The oxide is effective in reducing arc consumption and improving the welding resistance through a synergistic effect with the Bi oxide. In addition, the ln oxide suppresses the formation of the Ag-rich layer around the contacts mentioned above in small contacts with large switching load currents for which the present invention material is used, and as a result improves welding resistance. It is also effective in reducing arc consumption. However, the ln oxide has a tendency to somewhat impede the settling resistance of the material body which is obtained by the Bi oxide, and in this respect it is necessary to increase the Bi oxide content. The content of each oxide can be selected depending on the application, but in the composition of the material of the present invention, the minimum amount is set as the lower limit that is recognized as having a practical effect for the purpose of the material of the present invention. It is something that
On the other hand, for each oxide, as its content increases, B
Regarding i-oxide, when dispersing it in an Ag matrix, when producing an alloy ingot as shown in the example below, if the solid solubility limit of the Bi content is exceeded, it becomes more likely to become unbalanced. As a result, Bi oxide is unevenly distributed alone in the Ag matrix, leading to an increase in consumption. Regarding Sn oxides, in the presence of ln oxides, as the amount added increases, the contact resistance tends to increase and the processing capacity also decreases.
In particular, ln oxide has a metal equivalent value of 1. Since the amount of Sn oxide is added in excess of the base weight %, adverse effects are likely to occur due to an increase in the amount of Sn oxide, so the amount added must be regulated in relation to the amount of Bi. Regarding the ln oxide, if the amount added increases in balance with the Sn oxide, the workability deteriorates and the contact resistance tends to increase. Its content should be considered before the amount of Sn oxide. However, there is a possibility that this may seriously deteriorate the welding resistance. From the above viewpoint, the upper limit of each component composition is set. In the material according to the present invention, Bj-
An oxide of Cn (for example, C ship i204) can be included.

Several types of Bi-Cn oxide structures are recognized, but all of them have low melting points, and the melting point of bismuth oxide (Bi203) is usually 8.
Lower than 25:00 ○. Most of them are 780-800
It's around 0○. The presence of this oxide significantly improves processability, but on the other hand increases arc wear and often leads to deterioration of contact properties. therefore,
It is undesirable to add an excessive amount, and the amount should be kept to the minimum necessary. When adding, the above Ag-
Further, metal Cu is added to the Bi-Sn-ln quaternary alloy and selectively oxidized to the C type by an internal oxidation method.
Furthermore, it reacts with Bi203 and converts it into forms such as C elbow i204. A desirable addition amount is 0.016 to 2% by weight in terms of metal Cu. 0.01% by weight of Cu corresponds to 0.02% by weight in terms of oxide (Cu0), which is the minimum amount in which an effect is recognized. The materials of the present invention explained above will be explained in more detail based on Examples.

According to the composition of the present invention, Ag, Bi, Sn, ln, and Cu were dissolved in a total amount of 20 M to produce an ingot containing Ag-Bi-Sn-ln as a main component.

An alumina crucible was used for the melting, and a high frequency furnace was used in an argon atmosphere. The molten metal is 15×30×
It was cast into the mold of 7 enemies 3. The ingot thus produced was immediately ground into scale-like chips with a thickness of about 1 skin using a rolling mill. This was heated in air at 700°C for 6 hours to selectively internally oxidize Bi, Sn, In, etc., and convert the Bi oxide into a composite oxide. Next, this is rolled again using a rolling machine to a thickness of 0.
．． The chip size was 2 legs or less. After the chips having a thickness of 0.2 mm or less were cleaned, they were loaded into a cylindrical mold with a diameter of 2 mm and molded at a pressure of 8 tons/ground. Next, this molded body was phosphorized in air at a temperature of 900° C. for 2 hours. This material was extruded at a temperature of 600 pm and processed into a wire rod with a diameter of 3 skins. After that, while repeating cold working and lump anchoring,
The wire was processed to have a length of 1.7 ribs, and was further processed into a contact rivet with a spherical head of willow with a diameter of 3.5 and a radius of curvature of 8, which was used as a sample for a contact opening/closing test. Contact characteristics were evaluated by tests conducted using the circuit shown in FIG.

That is, as the switch S, using an ASTM type testing machine, the opening/closing conditions were set as contact force of 30 mm, separation force of 40 mm, and opening/closing speed of 10 mm/sec, and the test load was a commercial power supply frequency of 6 mm.
0Hz, voltage 125V, diode protection resistor r21.
250, load R=12.50, and capacity C=1140 peak F. Therefore, the peak inrush current is 160A, and the steady state is 10A.
It is A. Switch S2 transfers the charge of capacitor C to switch S
, constitutes a circuit for discharging immediately before turning on. The evaluation of the contact characteristics was based on the number of welds when the contact was opened and closed 3×1 times under the above conditions, that is, the number of times a force exceeding 40 degrees was required to open the contact, and the number of welds after opening and closing 3×1 times. This was done based on the amount of points consumed. The number of tests was 6 pairs each, and the results are shown in the table as the maximum and maximum values for each characteristic. For reference, test results of Ag-Cd0 and Ag-Bi-Sn alloys produced using the same manufacturing method are also shown as comparative samples. As is clear from the results in the table, the contact material according to the present invention exhibits extremely superior values in all characteristics of wear and tear compared to the conventional Ag-Cd◯ contact.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a cross section of a contact during a switching test using a conventional electrical connection material. FIG. 2 is a curve diagram showing the relationship between the number of openings and closings and the cumulative number of landings in the conventional example. FIG. 3 shows an example of a typical usage of the electrical contact material according to the present invention, which is used as a test circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. The oxide dispersed in the Ag matrix is Bi-Sn.
oxide (Bi_2Sn_2O_7) and Sn oxide (Bi_2Sn_2O_7)
SnO_2) is an Ag monoxide-based electrical contact material whose metal synthesis components include 2 to 5% by weight of Bi and 4 to 8% by weight of Sn within a range not exceeding twice the amount of Bi.
(However, excluding 4% by weight), In1.8 to 5% by weight (
An electrical contact material characterized in that the proportion is 1.8% by weight (excluding 1.8% by weight), with the balance being Ag. 2 The main oxide dispersed in the Ag matrix is Bi
-Ag oxide-based electrical contact material that is an oxide of Sn (Bi_2Sn_2O_7) and an oxide of Sn (SnO_2), whose metal synthesis components are Bi2 to 5 in metal equivalent value.
Weight%, Sn not exceeding twice that of Bi, 4 to 8 weight% (excluding 4 weight%), In 1.8 to 5 weight%
An electrical contact material characterized by having a proportion of Cu (excluding 1.8% by weight), 0.06 to 2% by weight of Cu, and the balance being Ag.