EP2747917A1

EP2747917A1 - Method for producing a semifinished product for electrical contacts and contact piece

Info

Publication number: EP2747917A1
Application number: EP12751331.5A
Authority: EP
Inventors: Andreas Schmidt; Werner Roth; Alexander Schade; Peter Seipel
Original assignee: Umicore AG and Co KG
Current assignee: Saxonia Technical Materials GmbH
Priority date: 2011-08-26
Filing date: 2012-08-24
Publication date: 2014-07-02
Also published as: US9779854B2; JP2014531700A; DE102011111300A1; CN103764319A; WO2013030123A1; US20140356646A1

Abstract

The present invention relates to a novel method for producing metallic semifinished products by extrusion, to the semifinished products thus obtained and to contact pieces that can be produced therefrom.

Description

Process for producing a semifinished product for electrical contacts and contact piece

Field of the invention

Composite materials based on silver with embedded oxide or carbon particles (so-called contact materials) are often difficult to weld and solder. In the production of

Semifinished for electrical contacts is therefore the bottom, i. the side facing away from the opposite contact, the

Contact material provided with a good solderable or weldable support layer, which often consists of silver or a silver alloy. Such support layers are often applied by plating a silver ribbon on contact materials. The disadvantage here is that the

Adhesive strength in this method does not always meet the requirements. It is also known a method for the production of

Single contacts, wherein applied to a layer of silver powder, a layer of contact material powder, both powder layers pressed together and sintered and so a semi-finished with a front of contact material and a back of solderable or weldable silver or silver-based is generated. Ribbon-shaped semi-finished product is not available.

It is also known, a contact material block with a

To coat silver tube and composite extrusion

reshape. By longitudinally dividing a composite strand produced in this way is a semi-finished with an upper side

Contact material and a silver underside available. However, producing a suitable silver tube and fitting or making a contact material block in the silver tube are cumbersome. It is also known to use a block of contact material

To coat silver powder, to press, to sinter and

extruding, dividing the strand. The disadvantage here is that a die with multiple openings must be used, which leads to shorter semi-finished lengths or a subsequent one-sided removal of the silver layer on the subsequent contact side is required.

Brief Description of the Invention The object of the invention is to provide a way, such as

a strand-shaped semifinished product for electrical contacts can be produced at low cost, which has a top intended for the electrical contact of a contact material based on silver and a bottom of a carrier material, in particular silver or a silver alloy.

This object is achieved by a method according to the following points:

1. A process for producing a strand-shaped, in particular band-shaped, semi-finished product for electrical contacts, wherein the semifinished product has a specific for the electrical contact top of a contact material based on silver, in which one or more metal oxides or carbon are embedded, and one

Contact material carrying a good solderable or weldable carrier layer with the following steps: - Producing a block of the contact material based on silver,

Partial encasing of the block of the contact material with the material of the carrier layer,

Pressing the jacketed block to compact the metal powder, to get a composite block,

Sintering the pressed composite block to obtain a sintered composite block;

- Forming the sintered composite block by extrusion. 2. The method according to item 1, characterized in that the block of the contact material with a metal powder, which consists of the material of the carrier layer, is sheathed.

3. The method according to any one of the preceding points, characterized in that the carrier layer consists of silver, copper, nickel, aluminum, iron and their base alloys.

4. The method according to any one of the preceding points, characterized in that the contact material is a silver-metal oxide composite material.

5. The method according to any one of the preceding points, characterized in that the contact material based on silver tin oxide and / or zinc oxide and / or indium oxide and / or cadmium oxide.

6. The method according to any one of the preceding points, characterized in that for wrapping the block from the

Contact material is a metallic powder mixture or sheets or films of silver, copper, nickel, aluminum, iron or their base alloys is used.

7. The method according to any one of the preceding points, characterized in that for wrapping the block from the

Silver based contact material Silver powder or silver based alloy powder is used. 8. Method according to one of the preceding points, characterized

in that the coated block is pressed isostatically, preferably cold isostatically. 9. Method according to one of the preceding points, characterized

characterized in that the extrusion is carried out at temperatures of 600 ° C to 950 ° C, in particular 700 ° C to 850 ° C.

10. The method according to any one of the preceding points, characterized in that the thickness of the strand produced by extrusion or a sub-strand is reduced by rolling.

11. The method according to any one of the preceding points, characterized in that the two flanks of the strand, which extend from the contact-giving upper side to the well-solderable and weldable underside of the strand formed by the carrier layer, are trimmed.

12. The method according to any one of the preceding points, characterized in that the trimming of the flanks of the strand is carried out by cutting or milling.

13. The method according to any one of the preceding points, characterized in that an approximately cylindrical sintered block is produced, whose lateral surface is turned off before the extrusion.

14. The method according to any one of the preceding points, characterized in that the block by the extrusion of a rectangular or cylindrical shape is converted into a shape with a rectangular cross-section.

15. The method according to any one of the preceding points, characterized in that the contact material is obtained by powder metallurgy.

16. Method according to one of the preceding points, characterized in that the three steps

Producing a block of the silver-based contact material,

- Partial wrapping of the block of the contact material with the material of the carrier layer, and

Pressing of the metal powder coated block for

Compressing the metal powder to obtain a composite block can be performed simultaneously.

17. The method according to any one of the preceding points, characterized in that the material of the carrier layer metal oxides, in particular the same metal oxides as used

Contact material, contains

18. The method according to any one of the preceding points, characterized in that the material of the carrier layer and the

Contact material are different from each other.

19. The method according to any one of the preceding points, characterized in that the wrap angle is less than 360 ° or 90 ° to 270 ° or 120 ° to 180 ° or 100 ° to 130 °. 20. Semi-finished product, produced by a method according to one of the preceding points, in particular band-shaped semi-finished product.

21. Electrical contact piece, made by cutting off the semifinished product according to item 20 and optionally forming the portion. Brief description of the drawings

Figure 1 shows a cylindrical (= circular cross-section) composite block 100, which consists of a contact material 101, which is partially covered by a substrate 102, wherein the wrap angle α indicates the shrouded circumference, which is spanned by two lines 104, with the center of the cross section 103 are connected.

FIG. 2 shows a cuboid (= rectangular cross section)

Composite block of contact material 201, which is partially enclosed by a carrier material 202, wherein the wrap angle in Figure 2a is 270 °, in 2b 180 ° and in Figure 2c 90 °.

Detailed description of the invention

In the method, a block is made of a silver-based contact material, the manufactured block is partially encased with silver powder or silver-based alloy powder and pressed to compact the powder clad.

In the method, a contact material which is a silver-metal oxide composite may be used. Tin oxides, zinc oxide, indium oxide, tellurium oxide, copper oxide, cadmium oxide, bismuth oxide, tungsten oxide, molybdenum oxide or combinations thereof may, in particular, be used as metal oxides. It is possible that the contact material used contains several metal oxides. Likewise it is possible that the contact material only a single metal oxide contains. The metal oxide component of the contact material preferably consists predominantly of tin oxide. As an alternative or in addition to metal oxides, the silver-based contact material used may also contain carbon, for example in the form of graphite or tungsten carbide. Other contact materials may, for example, be silver with tungsten carbide, silver with tungsten carbide and carbon, silver with tungsten.

These contact materials can be used in combination with a material as a carrier layer. Suitable materials for the carrier layer are silver, copper, nickel, aluminum, iron and their base alloys. Also suitable are silver-based alloys, such as silver-nickel alloys or silver-nickel alloys with 20%

Nickel content (AgNi20), but also alloys of copper with nickel, copper with silver or copper with tin, bronzes or brass. If base metals are used as the material of the carrier layer or if base metals are present, as for example in silver-nickel alloys, then further processing may take place under

Oxygen exclusion take place, which is e.g. can be achieved by working in a nitrogen atmosphere or powder metallurgical processing by using an organic coating of the powder particles as a sintering aid.

The block of contact material can be produced by powder metallurgy. Here, these steps of manufacturing the contact material block and the step of partially cladding with silver powder or silver base alloy powder and pressing may be both sequential and simultaneous.

If the production of the block of contact material and partial sheathing and pressing carried out sequentially, so can Making the block of contact material done, for example, by silver powder mixed with metal oxide powder, such as metal oxide powders of tellurium, indium, tin, zinc, copper, cadmium, bismuth, molybdenum, tungsten or combinations thereof, pressed and then sintered.

In another embodiment of the invention, silver powder is mixed with a base metal powder such as tellurium, indium, tin, zinc, copper, cadmium, bismuth, molybdenum, tungsten or combinations thereof, pressed and then oxidized

Sintered atmosphere, so by oxidation of the base

Metal particles Metal oxide particles are formed.

In another embodiment of the invention, an alloy of silver with one or more base metals, in particular tellurium, indium, tin, zinc, copper, cadmium, bismuth, molybdenum, tungsten or combinations thereof, is obtained by fusion metallurgy and subsequently heat-treated in an oxidizing atmosphere. so that metal oxide particles are formed by oxidation of the base metal particles. The block of contact material may optionally be subjected to a heat treatment to increase the ductility which causes coarsening of the oxides by Ostwald ripening and thereby

Improves ductility (see Sakairi et al., Holm Conference on Electrical Contacts - 1982, pp. 77-85).

After a block of one of the above ways

Contact material was obtained in a second step, the block of contact material with the material of the carrier layer is partially encased. For example, the block may be partially encased with a copper or silver powder, or powder of a silver-based alloy, and then pressed to compact the powder cladding. The pressing can be done isostatically, namely cold or hot isostatic. Suitable as the material of the carrier layer are silver, copper, nickel, aluminum, iron and their base alloys as described above. If an alloy is used as the material of

Carrier layer used, so alloy powder or mixtures of element powders can be used and are equally suitable.

However, the following step of partially enclosing may also be carried out so that a part of the surface of the block is removed from a contact material to the desired depth and then replenished with the material of the carrier layer.

This can be done by powder of the material of the carrier layer, ie of silver, copper, nickel, aluminum, iron and their base alloys, which either by thermal spraying

Flame spraying or cold gas spraying is applied or by filling with a powder of the material of the carrier layer with subsequent pressing and sintering. The powder of the material of the carrier layer (such as silver, copper, nickel, aluminum, iron) can also be mixed with other metal powder so as to powder metallurgical way a coat of a base alloy, ie an existing predominantly of this metal alloy produce. For example, a silver powder mixed with a base metal powder such as e.g. Nickel can be used as a

Material of the support layer, for example, to obtain a silver-based alloy such as AgNi20.

Likewise, the material of the carrier layer can be applied in the form of one or more correspondingly shaped sheets, which fill up the removed part again. Such sheets can be prepared by conventional methods such as sintering, optionally with powder backing, Welding, isostatic pressing, screws or the like are attached.

The above embodiments describe a sequential procedure. If the production of the block of contact material and partial sheathing and pressing carried out simultaneously, so may be a powder of a contact material or a mixture of

Silver powder can be used with metal oxide powder, such as mixtures with metal oxide powders of tellurium, indium, tin, zinc, copper, cadmium, bismuth, tungsten, molybdenum or their

Combinations, and be filled in a form provided with dividing plates. At the same time or in a subsequent step, the

Powder bed or the mixture of contact material or

Silver powder and metal oxide powder partially with a powder of the material of the support layer (such as silver powder or powder of a

Silver-based alloy) is partially encapsulated by filling the powder of the material of the carrier layer in the region separated by baffles from the powder for producing the contact material, removing the baffles, and then compacting the

Powder mantle is pressed to obtain a (pressed) composite block.

In another embodiment of the invention, the material of the carrier layer in the form of one or more appropriately shaped sheets or foils can be inserted into the mold and the powder for

Preparation of the contact material are filled. The pressing can then be done isostatically, cold or hot isostatic. "Partial sheathing" is to be understood in contrast to the sheathing so that a part of the block of contact material at the

Surface not with the material of the carrier layer such as the silver powder or powder of a silver-based alloy is coated, so that in the course of the process is always a part of the

Contact material of carrier material remains uncovered and exposed. The degree of coverage of the block of contact material is indicated by the wrap angle. This is explained in more detail in FIG. The composite block 100 consists of a part

Contact material 101 and a partial sheath off

Carrier material 102. Connecting the center 103 of the

Cross section of the composite block and the extreme ends of

Sheathing through straight lines, so stretch both straights the

Wrap angle α. When wrapping (ie a complete enclosure) of a block of contact material with the carrier material of the wrap angle is always 360 °, with a partial sheathing, it is therefore less than 360 °. In one embodiment of the invention, the wrap angle between 90 ° and 270 °, in a further embodiment of the invention between 120 ° and 180 ° and in another embodiment of the invention between 100 ° and 130 °. In Figure 2 are different angles of wrap of 270 °, 180 ° and 90 ° at one

Contact material block shown with rectangular cross-section, the cross-section can of course also be round.

The pressing of the powder can be at all above

Embodiments at pressures of 500 bar to 10,000 bar, or 500 bar to 2000 bar, or 800 bar to 1200 bar happen. As Pressv experienced can use isostatic pressing. Isostatic pressing can be performed at room temperature (cold isostatic) or at elevated temperatures (hot isostatic). In this way, a composite block is obtained. The (advantageously cold isostatically pressed) composite block is sintered in a further production step and then by

Formed extrusions. The sintering should be done in an atmosphere in which the base metal does not oxidize and the

Metal oxides can not be decomposed, such as in a vacuum or under

Nitrogen atmosphere. Since the contact material and the carrier material have different shrinkages during sintering or pressing, warping and cracking during sintering can easily occur. However, it may be advantageous for the method if the sintered composite block obtained by sintering is low-distortion and crack-free. This can be done by the pressed composite block is pressed high density, which can be done for example by hydraulic pressing at pressures of 1000 to 10000 bar, or 500 bar to 2000 bar and temperatures from room temperature, ie about 20 ° C, to 500 ° C. Alternatively, the shrinkage behavior during pressing and sintering by tuning the materials

controlled each other. Since the contact material is usually predetermined, the vote can often be made only on the substrate. The vote may be about the stoichiometry of the

Carrier material controls and, for example, a

Silver-based alloy can be used. For example, silver-nickel alloys such as silver-nickel alloys containing 20% nickel (AgNi20) are suitable. These can either be melted and atomized used as a powder, but can also be obtained via a metallic powder mixture of elemental powders of silver and nickel. Also suitable is silver with oxide additives, for example tin oxide. The oxide can be obtained via a powder mixture of the oxide with silver, wherein the oxide should be added in smaller amounts than in the contact material to the welding or Solderability does not deteriorate significantly. Another

The possibility of controlling the shrinkage behavior is the selection of the powder particle size. Here, a good effect by selecting a metal or alloy powder for the production of the

Carrier material having a particle size larger than the particle size of the metal powder for the production of the contact material can be achieved. In general, in this case, the metal or

Alloy powder for the preparation of the carrier material has a mean particle size D50 of> 50 μιτι and the metal powder for the

Production of the contact material have a mean particle size D50 of 1 - 20 μιτι have.

After sintering, the material of the carrier layer (silver or silver-based alloy) generally already adheres sufficiently strongly to the block, so that it is shaped and thus processed

precise fit can be done in an extrusion die. For example, by isostatic pressing and subsequent sintering as described above, an approximately cylindrical

Composite block to be produced, the lateral surface of which

Extruding can be turned off to clean the

Surface to achieve or if necessary to adapt to the inner dimensions of an extrusion die to effect. Then, the composite block by the extrusion of a

cylindrical shape into a shape with rectangular cross-section, the desired semi-finished, to be reshaped. This approach has certain advantages when using composite blocks with

Weights up to about 60 kg.

Alternatively, in an analog method, a

Composite block with rectangular cross-section produced and further processed. This procedure facilitates the Alignment of the part of the composite block with the material of the carrier layer with respect to the die of the extruder and has certain advantages when using composite blocks with weights up to about 10 kg.

The (sintered) composite block is in another

Process step formed by extrusion. For this purpose, the composite block is usually heated to temperatures of 600 ° C to 900 ° C or 700 ° C to 800 ° C and in one at 300 ° C to 600 ° C, usually 450 ° C to 550 ° C, such as about 500 ° C, preheated

Extruded container inserted. It can be used both direct and indirect composite extrusion, which can be achieved with the indirect composite extrusion presses good results, as by indirect composite extrusion in the

Hot forming over the length of a more uniform material flow and layer thickness ratio can be achieved. It is the

Inserted composite block in the tool of an extruder and aligned with the material of the carrier layer part of the composite block with respect to the die of the extruder so that the occupancy of the support layer on the desired side of the

Stranges is achieved. Subsequently, by extruding a strand with a top of contact material and a bottom of the material of the support layer, such as silver, copper, nickel,

Aluminum, iron and their base alloys, such as silver-nickel alloys or silver-nickel alloys with 20% nickel content (AgNi20), alloys of copper with nickel, copper with silver or copper with tin, bronze or brass.

The extrusion is preferably carried out at temperatures of 600 ° C to 950 ° C, in particular 700 ° C to 850 ° C. By extrusion can advantageously be achieved high compression, so that the strand has a relative density of 99.9% of the theoretically possible density.

The extrusion molding process can be achieved by further adjustments such as the die design (adjustment of lead-in angle and guide length) as well as the pressing parameters during extrusion (adjusting the

Press speed, block temperature, ratio of

Block diameter to block length) to the specific ones

Conditions and the desired products. In one embodiment, the two flanks of the strand, which extend from the contact-making upper side to the well-solderable and weldable underside of the strand, are trimmed,

especially by cutting or milling. The same effect can be achieved by dividing the strand by dividing the strand twice a few millimeters away from the side edges of the strand. In this way it can be ensured that in the further processing of the semifinished product or during subsequent use of an electrical contact made with the semifinished product no material of the carrier layer reaches the contact surface and impairs its function.

Subsequently, the thickness of the strand produced by extrusion can optionally be reduced by rolling, in particular by cold rolling. A reduction in thickness of at most 50% of the original thickness is recommended for cold rolling in order to avoid an excessive change in the mechanical properties of the semifinished product, such as an increase in hardness.

Optionally, the cold rolling is performed in multiple stages with less thickness reduction and heat treatments. In one embodiment of the invention, the thickness of the strand in the Rolls reduced by 30 to 50% of its original thickness. In another embodiment of the invention, the thickness of the strand is reduced to less than half by hot rolling and brought to final gauge by cold rolling. From the strip-shaped or band-shaped semifinished product obtained in this way, electrical contact pieces can be produced by methods known per se, such as by cutting or punching of the semifinished product, and optionally forming the section.

EXAMPLES

1. By mixing silver powder and tin oxide powder,

cold isostatic pressing and subsequent sintering is a

cylindrical block made of a contact material based on silver. For example, this block may become 8 through 14

Weight percent of metal oxide and otherwise consist of silver. One third of the lateral surface of the contact material block is with

Coated silver powder and then cold isostatically pressed. The isostatically pressed block is then sintered under air at 800 ° C to 900 ° C, for example for 2 to 5 hours. The sintered block is then turned off if necessary, so that it can be accurately used in an extruder. With appropriate

Process design is a twisting not necessary. The block is then extruded at a temperature of 750 ° C to 800 ° C from its cylindrical shape into a rectangular shape

Reshaped section.

The flanks of the strand thus produced are cut off. The band-shaped semi-finished product produced in this way has a carrier layer whose thickness accounts for about 10% to 30% of the thickness of the contact material layer and can be used for producing electrical contact pieces by rolling to the required final thickness, cut from the semifinished sections and according to the

Requirements of a specific application to be reshaped.

2. By mixing silver powder and with 8 to 14% by weight of tin oxide powder, a powder mixture is obtained. This is filled in a partitioned, cylindrical mold for cold isostatic pressing, wherein the separating plates separate a surface segment, which makes up about one third of the surface of the composite block to be obtained. In these through the dividers

clamped cavity is filled simultaneously a silver powder. Once the mold is filled, the dividers are through

Removed removed, cold isostatically pressed and sintered. The isostatically pressed block is then sintered under air at 800 ° C to 900 ° C, for example for 2 to 5 hours. One third of the

Contact material block is coated with silver powder. The block is then extruded at a temperature of 750 ° C to 800 ° C from its cylindrical shape into a rectangular shape

Reshaped cross-section and cut off the flanks of the strand. The band-shaped semi-finished product produced in this way has a carrier layer whose thickness is about 10% to 30% of the thickness of

Contact material layer makes up and can for the production

electrical contact pieces are used by the

Semi-finished sections are cut off and reshaped according to the requirements of a specific application.

Claims

claims

Pressing the jacketed block to densify the metal powder to obtain a composite block,

Sintering the pressed composite block to a sintered one

To obtain composite block;

- Forming the sintered composite block by extrusion.

2. The method according to claim 1, characterized in that for wrapping the block of the contact material, a metal powder, which consists of the material of the carrier layer, is used.

3. The method according to any one of the preceding claims, characterized in that the material of the carrier layer is selected from the group consisting of silver, copper, nickel, aluminum, iron and their base alloys.

4. The method according to any one of the preceding claims, characterized in that the contact material based on silver Zinnox and / or zinc oxide and / or indium oxide and / or cadmium oxide.

5. The method according to any one of the preceding claims, characterized in that for wrapping the block from the

Contact material is a metallic powder mixture or sheets or films of silver, copper, nickel, aluminum, iron or their

Base alloys is used.

6. The method according to any one of the preceding claims, characterized in that for wrapping the block from the

Silver based contact material Silver powder or silver based alloy powder is used.

7. The method according to any one of the preceding claims, characterized in that the coated block is isostatically pressed.

8. The method according to any one of the preceding claims, characterized in that the extrusion is carried out at temperatures of 600 ° C to 950 ° C.

9. Semi-finished product, produced by a method according to one of the preceding claims, in particular band-shaped semi-finished product.

10. Electrical contact piece, produced by cutting off the semifinished product according to claim 14 and forming the section.