PT82516B - PROCESS FOR THE MANUFACTURE OF MATERIALS FOR INTERNAL OXIDIZED AG-SNO SYSTEM LEAD ELECTRONIC CONTACTS AND MATERIALS PRODUCED BY THAT PROCESS - Google Patents

Description

farm its synthesis. The major differences are that the former, ie the previously oxidized Ag-Sn system alloys, are far superior to the latter with respect to structural density, while the latter have a more uniform dispersion of metal oxides first * The last iw. can be worn very quickly when the rapid changeover options are frequent. It is preferred that the particles dissolved in the alloys are precipitated in the alloys of the alloys and precipitated therein under the dispersion of the very small particles distributed in the silver matrix and the oxidized metallic precipitates are characterized by their characteristics The silver backing plates, when used, function as ms-ie for the welding of silver alloy contact materials. oxidized to support the base metal contacts.

It has been found in the literature that when Ag alloys of the aforementioned type are given interierments, the metal elements dissolved in the Ag alloys do not precipitate and distribute uniformly in their Ag matrices but tend to precipitate in the case of a precipitated concentration makes the outer areas directly exposed to oxygen. This precipitation of the metal exidents on the outer surfaces causes their segregation on the outer surfaces, particularly on the upper surfaces, and form by dewatering layers, with a thickness insignificant, which lie between the upper and lower surfaces of the Ag alloys, which are oxidized internally of their two sides. The high concentrations of metal oxides in the super fi ces of the electrically conductive materials make the exterior surfaces physically demolished and produce an electrically conductive, substantially contact-resistant resist- ance. at an initial stage of corrosion, and thereby cause excessive temperature to evaporate. In practice, such segregations on the exterior surfaces are often removed by obio from files or the like. It is also difficult to use the outer surfaces as they are contaminated by limes. In comparison with internally oxidized Ag-Sn system alloys, the internally oxidized Ag-Cd system alloys, which compete with the alloys of the Ag-á-system, exhibit a uniform Maya dispersion of the metal oxides. This is mainly due to the fact that the diffusion velocity of the Cri in a silver matrix is inherently balanced with the rate of diffusion of oxygen in the internal oxidation, which is not the case for internally oxidized Ag-3n system alloys. the materials for electrolytic contacting made with the oxidized Ag-Cd system are known, and the processes for preparing them can hardly constitute useful references for the preparation of the Ag-2n system alloys for their oxidation in #

In all cases, the segregation of the oxides on the outer surfaces causes them to become hard and very difficult to open on the surfaces. From the segregation or excessive concentration of the oxides of tin on the upper surfaces result in high silctric contact resistances, especially in an initial phase of the electrical contacts. Such segregation results in an undetermined increase in the temperature of the contacts. In order to avoid the production of such seals, some processes as described in the potent crsrisana AI5 have been discovered by the invention. ψΓ (f

if " . 4 457 787, in which the void is produced in the silver alloy in the matrix by absorption with hydrogen or the like and filling these voids in the course of internal oxidation with melt which precipitates as oxides in a large number of atomic numbers at the atomic scale, without extensive diffusion but rather as the neighboring voids are reached, and therefore without any segregation and depletion thereof, and in U.S. Patent No. 4,472,221, in which an high contact resistance caused by the high concentration or supersaturation of metal oxides, including tin oxides, at the contacting surface, submerging, reducing or extracting the dissolved metals at the contacting surface prior to their internal oxidation.

Said depletion layers in which the metal oxides d 1 are completely absent are extremely thin, they can hardly withstand severe switching operations since they have poor refractory properties. Therefore, when a contact material with a depletion layer between its outer contact surface and the lower surface is worn to the depletion layer, it reaches the end of its life. That is to say that while the lower half of the contact material beneath the depletion layer can be joined to the upper half above the depletion layer to disperse the heat generated in the switching operations and to provide a desired height of material, it can not be active as a contact surface. Often the existence of this lower half of the contact material has no meaning.

Accordingly, the object of the present invention is to provide electrical contact materials made from internally oxidized Ag-SnO System alloys, having contact surfaces with a moderate initial contact resistance

and having no depletion layer, and a manufacturing process of such excellent contacting materials, without using the processes described in the above-mentioned US patents, which are difficult to control suitably.

Brief description of the invention faith:

" V b IS :.

It has been found in accordance with the present invention that although the structures of the Ag-5n system alloys oxidized internally on their surface or surfaces with which the oxygen first comes in contact and from which it peaks in the alloy are rough, the deeper one goes into the alloy, the finer it becomes. In other words, the inwardly oxidized structures which have been produced in the forward region along a progressive direction of internal oxidation are fine and are free from segregation of the tin oxide. They are therefore more suitable for use as contact surfaces.

It has been found that, along the progressive direction of internal oxidation, the grain sizes of the tin oxides precipitated in the Ag 'matrices become larger and larger. Therefore, the contrast between the Ag matrices and the tin oxides becomes clearer or more noticeable in the progressive direction of the internal oxidation, which contrast may be expressed by the foregoing words which say that the oxx- / w structure given internally in the area more forward along the progressive direction in the internal oxidation is the finer. The larger the tin oxide precipitates, the greater the area that the Ag matrices can occupy so as to ensure low electrical contact resistances and undue contact temperature rises. Assuring that the concentration of Sn in the entire alloy is constant or from the most forward area to the rearward area of the internal oxidation of the alloy, 3 fc *;

In the fore and aft area, consisting of Ag matrices and (for example only) a grain of tin oxides having a certain percentage by weight of silver, larger, compared contact surfaces may be provided to the Ag matrices. with the rearward area consisting of (for example) ten grains of the same percentage by weight of the silver matrices · It should also be noted that the larger the tin oxide precipitates, the lower is the voltage produced on the oxides of tin by internal oxidation, so that the precipitates will reach a lesser degree, which will hardly give rise to cracks in the contact surfaces.

Relative to the expression " the most forward area along a progressive direction of internal oxidation " used in the specification and claims, it can be understood microscopically by those skilled in the art and can define the present invention.

Such structures of Ag-Sn alloys oxidized internally in the front or leading area of the internal oxidation appear, when the alloy is oxidized on both sides, centrally in the alloy, with a depletion zone between the two faces, when alloy is oxidized from only one face on a lower surface opposite a surface from which oxygen enters the alloy. Since the depletion zone, or zone where the tin oxides are scarce, is usually near the leading edge of the internal oxidation, said area which is used according to the present invention as the contact surface must be free of those areas.

The typical Ag-Sn constituents usable in the present invention are those formed by matrices with from 0.5 to 12% by weight Ag, from Sn and from 0.5 to 15% by weight of In, and those formed by matrices of Ag, 3 to 12% by weight, Sn and 0.01 to • M 5 **

less than 1.5 wt.% of Bi. Said constituents may contain one or more metal elements selected from 0.1 to 5 by weight, Cd, 0.1 to 2% by weight, Zn, 0.1 to 2% by weight, Sb and 0 , 01 to 2% by weight of Pb. In the case of the last-mentioned constituents, they may contain 0.1 to less than 2% by weight In addition, they may contain less than 0.5% by weight, of one or more elements of the iron family.

In one embodiment of the present invention, said Ag-alloy is prepared in the form of a plate or plate disc having a height that is at least equal to twice the desired final height and is increased by a height of a layer of which is assumed to be formed when the silver alloy is completely oxidized internally. Said Ag alloy is supported on both sides by pure Ag layers.

The silver alloy thus prepared is oxidized internally completely, in an oxygen atmosphere, at a set pressure and at an elevated temperature.

During the internal oxidation of the Ag-alloy, the fine Ag-pure support layers function as follows.

Since the partial pressure of oxygen, which has dissolved in the silver at elevated temperature, is comparatively low, and since the amount of oxygen diffusing through the silver is constant at a specified temperature, oxygen dioxide at the predetermined specific pressure, a quantity of oxygen is diffused into the metal alloy through the silver to oxidize therein, which amount of oxygen can be easily and freely contracted. In addition to this advantage, as plague oxygen diffuses in the metal alloy through silver, and therefore in a given direction of the oxygen paths, the oxidized and precipitated crystalline metal grains in the metal alloy are not disposed at random, but yes they can align themselves prismatically in the oxygen trajectories. Since these metal oxides are prismatically aligned, they are also parallel to the current paths passing through the internally oxidized Ag alloy contact material, the electrical resistance of the material is reduced. The fully oxidized Ag alloy flat plate or disk internally with a depletion layer which lies centrally and perpendicularly to the axis or the height of the plate or the disc is cut along said depletion layer by means of a superhard cutting device and the raised velocity, for example with a cutter having a width greater than the width of the dewatering layer. In contrast to the abrasive segregation of the metal oxides of the outer surfaces of the oxidized Ag alloys, said cutting operation does not produce any contamination of the surfaces of cut and a cut portion of the Ag alloy which includes a depletion layer.

The two parts so cut from a plate or disc respectively have a fully internally oxidized Ag alloy body with a fresh contact surface with a moderate hardness and a moderate initial strength and a silver backing layer pure at its lower surface, having no depletion layer.

Preferred Embodiments

Example 1 1) Ag-Sn 8% - In 4% 2) Ag-Sn 8% - In 4% - Cd 0.5% ...... r

3) Ag-Sn 7% - Bi 0.5% 4) Ag-Sn 7 - Bi 0.5% - Zn 0.3% ρ '1

Alloys of the above types (1) to (4) were melted in a high frequency melt furnace at about 1100 to 1200Â ° C and cast into molds to obtain ingots of about 5 kg each. Each of the ingots was cleaned on one of its faces. Then, each of the ingots was pressed against a plate of nickel by means of a hydraulic press and drawn so as to obtain a plate about 2.2 mm thick, nickel coating of about 1 mm.

Each plate was subjected to an oxygen atmosphere for 200 hours and at 650Â ° C, so that the plate was thoroughly oxidized internally. As the nickel coating is stainless, the internal oxidation has progressed from just the clean surface. Segregation of tin oxides on the cleaned surface was found. The internally oxidized structures produced in the plate in the leading area along the progressive direction of internal oxidation, ie in this case about 2 mm deep from the clean surface, were extra fine and completely free from segregation of metal oxides. A depletion zone, or a zone where the tin oxides are scarce, near said more dihedral area had a thickness of about 1 mm.

Each of the oxidized plates was placed internally in a hydrogen atmosphere and heated to 75Â ° C for ten minutes, so that the metal oxide on the cleaned surface was reduced and decomposed, so that the cleaned surface could be welded to a base of fixed or mobile contact. The nickel plate may be replaced by other non-oxidizable metals and the reduction or decomposition of the metal oxides on the clean surface may be done by heating the melt or by immersion in an acidic solution.

The plates were then cut horizontally by a plane 0.2 mm from the bottom; then the plates were cut to obtain square electrical contacts having a 5 mm side at a thickness of 1.9 mm, having as contact surfaces the front areas oxidized internally along their progressive direction, and cut surfaces, such as rear supports.

Instead of cutting the plates after internal oxidation, they may be cut or stamped to the desired configuration prior to internal oxidation.

In order to compare the prior electrical contacts made according to the present invention, sdguintest contacts were made 5) Ag-Sn 8% -In 4% 6) Ag-Sn 8% - Cd 0.5% Bi 0.5% Θ) Ag-Sn 7% - Zn 0.3%

In a manner analogous to the previous example, the above alloys 5) to 8) were prepared in ingots. Each ingot was then sandwiched on its clean surface to a pure silver plate by means of a hydraulic press, which was heated to about 440Â ° C and drawn to a plate having a thickness of about 2 mm, annealed about 600 ° C, at all stages of stretch rates of 30% in reduction.

Each of the plates was oxidized internally in an oxygen atmosphere for 200 hours at 650 ° C. Then

(1) 0.6 - 2.1 (2) C, is - 2.1 (3) 1.5 - 1.4 (4) / V " drying the present invention " 0.5 - 1.6 (5) 1.2 - 2.2 (b) 1.2 - 2.2 (7) 0.7 - 2.1 (8) " 1.7 In the foregoing tables, contact compositions made according to the present invention have a moderate hardness and a lower initial contact resistance compared to the corrosion resistant materials. A billet of the alloy Ag-Rn 8 V- - Ir. .. · · · · · · · · · · · as as as as as · as una una una una una una una una una una una una una una una una una una una The first 303 pound coins are then paid at the same rate as the first one in the first half of the year. , with a height of 1 mm, with a spreading rate of 33 per cent,

making it part of the 2.5mm iris.

the front of the cctect. .'.s. The inner surfaces of the surfaces of the surfaces may be subjected to the action of the prior art. that the sspiga is scalable to an account, as described in section 1,

Ds account acts or; In addition, the compositions of the present invention have had physical characteristics at the same time as the conventional conventional materials. It has been found that 3 3 U c. hardness of the shell of conventional shells. The initial deflection ratio was 5D, 1R. j Ag-Sr. Ag-3n SA-Cd n, 5) - 11) Ag-3n 7 - nnc ···, ** "wj" F * 5 ** 2i Zr. 0.3 g of the above gas 9 to 12) in a high-pressure melting furnace, the gasket was cast in molds to obtain ingots of 5 kg * The ingots were then quenched in both phases. Each of the ingots was then applied to its cleaned surfaces by silver plating of a hydraulic press which was heated to 4C C-9 were drawn to a plate having a diameter of 3.1, tended to be near the SCD-C during the stretching steps at 3 ° C reduction.

To each of its two faces, the plate had said 2.5 mm (S) alloys 12) bonded by a layer of pure silver with a thickness of C, 3 mm.

Each of the plates was oxidized to another inert gas, under an oxygen atmosphere, for 2 hours at 5Â ° C. The plate had a thickness of about Γ to Ι mm thick. The plates were then plucked in two sections by flashing with a C-5 aorta and the plates were plated to obtain electrical contacts with a 5-nm side of the ε-side with Thickness of 1 mm is applied by applying a thin silver layer of C3 mm thickness to one of its surfaces.

Instead of cutting the DSP plates from the internal oxidation, they may be cut or stamped to the desired configuration prior to the internal oxidation.

The prior art samples 9) to 12) according to the present invention, the prior art alloys (Example 1) are shown during their contact strength and the value of the initial contact strength, r.ss ccndiçccs ceçuir.tesi

Initial Contact Withdrawal

Contact Pretreatment - 4Γ2 g

Zorrsnts - continue S'J, IA TABLE 1

Samples

Hardness (HR ") 9 (10) (11) (12) " according to the present invention * 69 67 64 67 80 72 75 75 (5) (6) (7) (B) " prior art " 95 93 90 90 105 94 100 100 TABLE 2

Samples

Initial contact resistance (m) (9) (10) (11) (12) 0.60.6 1.5 0.5 2.02.0 1.3 1.4 " according to the present invention " (5) 1.2-2.2 (6) 1.2-2.2 (7) 0.7-2.1 (8) " of the previous technique " 1.7 - 2.2 1-ψ. - 15 -

Thus from the foregoing tables it may be concluded that the materials made in accordance with the present invention have a moderate hardness and a lower initial contact resistance than corresponding prior art contact materials.

While in the above examples Ag-Sn system alloys have been prepared by the melt process and then subjected to internal oxidation, they can be prepared by the processes of the metallurgy of the feet, preferably with subsequent forming, and then subjected to internal oxidation * t. It is evident that since the internal oxidation mechanisms in the case of the latter alloys act in exactly the same way as in the case of the first alloys, the present invention, as defined by the appended claims, also covers the latter alloys. It should also be understood that although the electrical contact materials 9) to 12) obtained in Example 3 according to the present invention, in which they are brought into contact with the oxygen not directly but indirectly by means of pure piata sieves, have structures of less rough oxidation on the surfaces immediately adjacent to said silver screens and therefore first in contact with the oxygen, compared to the oxidized structures internally around the cleaned surfaces of alloys 1) to 4) of Example 1, the its most forward areas along the progressive direction of internal oxidation have finer structures, to which they can be clearly distinguished by microscopic observation, as discussed above. - 16 -

19 -

A process for the manufacture of materials for internal elastomeric alloys of the internal oxidized Ag-SnO system, characterized in that it comprises. the preparation of an Ag alloy comprising 0.5 to 12 1 by weight Sn and O, 5 to 15 1 by weight In or 0.01 to less than 1.5% by weight Bi, and one or more metal elements selected from the following group consisting of 0.1 to 5% by weight of Cd, 0.1 to 2%, by weight of Zn, 0.1 to 2 by weight, of Sb, 0.01 to 2% by weight of Pb and 0.1 to less than 2% by weight of In; complete internal oxidation of the alloy; to the cutting of the alloy so that the foremost areas in the axial oxidation along its progressive direction in the alloy are exposed as contact surfaces thereof. - 29 -

A process for the manufacture of alloying elastomer materials of the Ag-SnO system, characterized in that it comprises; the preparation of an Ag-alloy having a desired thickness, comprising 0.5 to 12% by weight of Sn, and 0.5 to 15% by weight of 1 μm or 0.01 to less than 1 , 51, by weight of Bi, and one or more metal elements selected from the group

Claims (1)

consisting of 0.1 to 5% by weight of Cd, 0.1 to 2 by weight of Zn, 0.1 to 2% by weight of Sb, 0.01 to 2% by weight of Pb, and 0.1 to less than 2% by weight of In, with a thickness at least two times greater than the desired thickness mentioned above and with an expected thickness of a depletion layer to be produced in the alloy and sandwiched between the thin layers of pure silver; complete internal oxidation of the alloy; and cutting the alloy horizontally into two parts, while removing at the same time by said cut the depletion layer of the alloy. The process according to claim 2, wherein the alloy is cut to the desired configurations after The internal oxidation process according to claim 2, wherein the alloy is stamped or cut into the desired configurations prior to the internal oxidation of the alloy elastomer contacts of the internally oxidized Ag-5n0 System, produced by the process of according to the previous claims, made by complete internal oxidation of the alloy comprising 0.5 - 12% Sn and 0, 5 to 15% by weight In or 0.01 to less than 1.5%, in weight ratio of Jli, the alloy may be added one or more elements, v '18 of the group consisting of 0.1 to 5% by weight of Cd, 0.1 to 2% by weight of Zn, 0.1 to 2% by weight of Sb, 0.01 to 2% by weight of Pb and 0.1 to less than 2% by weight of In, characterized in that it has leading edge areas of internal oxidation along its progressive direction which are used as contact surfaces. The material for electrical contacts according to claim 1, characterized in that said leading areas have been exposed as contact surfaces by cutting or scraping the alloy at a point on its surface from which oxygen has diffused into the interior of the alloy for internal oxidation, so that the areas situated in the vicinity of said foremost areas and in which the metallic oxides are scarce are removed from the alloy, - Material for electrical contacts according to claim 6, characterized in that the surface from which the oxygen diffused into the internal oxidation has been subjected to a chemical removal so that the metal oxides therein are reduced or decomposed, thereby becoming said surface capable of being welded, 85 _ Material for electrical contacts of alloys of internally oxidized Ag-SnQ system, consisting of a portion of cont with a desired thickness made of Ag alloy comprising 0.5 to 12% by weight of Sn and 0.5 to 15% by weight of In or 0.01 to less than 1.5% by weight, weight ratio of Bi, , 4 / .W.-VV ^ Vv one said alloy is one of the metal elements selected from the group consisting of 0.1 to 5% by weight of Cd, 0.1 to 2%, by weight of Zn, 0.1 to 2 by weight , of In and said alloy having a thickness at least two times greater than the aforementioned desired thickness and additionally with an expected thickness of a depletion layer to be produced in the alloy which is completely oxidized internally after having been sandwiched enters two layers of pure silver, cut horizontally into two parts, said bed being withdrawn at the same time from the decontamination material according to claim 8, characterized in that the alloy sandwiched enters the layers of silver have been cut to a desired configuration after being internally oxidized. The material for electrical contacts according to claim 8, characterized in that the alloy sandwiched between the layers of pure silver has been printed or The applicant claims that the first applications of this patent were filed in the United States of America on 30 August 1985 and on 23 September 1985 under the numbers 771,341 and 779,066, respectively; • Lisbon, 6 May 1986. OFFICIAL AGENT OF THE PROPOSAL: 21 SUMMARY " PROCESS FOR THE MANUFACTURE OF MATERIALS FOR ELECTRICAL CONNECTION OF THE INTERNAL OXIDATED AG-5NO SYSTEM AND THE MATERIALS PRODUCED BY THAT PROCESS " The invention relates to materials for electrical contacts made from an internally oxidized silver alloy containing 0.5 to 12% by weight of tin. The oxidized structures internally produced in the bonds in the forwardmost zone along a progressive direction of internal oxidation, which are thin and free from the segregation of tin oxides. Another surface opposite the said contact surfaces can be solderable by subjecting it to a reduction or decomposition of metal oxides around said other surface. In one embodiment, the alloy is oxidized internally by sandwiching it between thin layers of pure silver and is drawn horizontally perpendicular to the axis in two parts, while simultaneously removing the depletion layer of the oxidized alloy internally *