Manufacturing a vacuum interrupter

Abstract

Method for producing a vacuum interrupter, wherein two components (203, 204) of the vacuum interrupter are connected to each other by - a nanostructure (200) comprising nanowires (205, 207, 208) is introduced between two metallic joining surfaces (201, 202) of the two components (203, 204) and - the two joining surfaces (201, 202) are then pressed together at a joining temperature with a joining force and thereby connected, wherein, for introducing the nanostructure (200) between the joining surfaces (201, 202), nanowires (205, 207) are applied to at least one of the two joining surfaces (201, 202), characterized in that the nanostructure (200) is designed such that at least one joining surface (201, 202) has regions (215) in which nanowires (205, 207) of a first length (L1) are applied to this joining surface (201, 202) and between which nanowires (205, 207) of a second length (L2) reduced compared to the first length (L1) are applied to this joining surface (201, 202).

Description

[0001] The invention relates to a method for producing a vacuum interrupter.

[0002] Vacuum interrupters are used primarily in vacuum switches. A vacuum interrupter is a circuit breaker whose switching contacts are located in a vacuum provided by a vacuum interrupter. Unlike a gas-insulated circuit breaker, a vacuum circuit breaker interrupts an arc that occurs when the switching contacts are separated in the vacuum interrupter. The use of a vacuum interrupter has the advantage of providing high insulation and arc extinguishing capacity while being small in size. Since no oxidation occurs in a vacuum, the switching contacts remain permanently clean, enabling consistent switching behavior. This makes vacuum interrupters virtually maintenance-free and extremely durable.

[0003] However, the manufacture of a vacuum interrupter is complex and expensive, because its tightness, in particular, places high demands on the vacuum interrupter. To ensure the tightness of the connections between components of a vacuum interrupter, solder foils containing active or passive solders are inserted between the components to be joined during the manufacture of the vacuum interrupter and melted in a furnace at high temperatures of up to 900°C. These processes and tools are also used in the prefabrication of assemblies, which entail a similar level of process engineering effort. Manufacturing a vacuum interrupter in this way requires long process times and process temperatures of up to 900°C. These high process temperatures cause high thermal stresses between the joining partners.For example, corrosion-resistant steel cannot be soldered directly to a metallized ceramic, so copper, for example, is inserted as a buffer layer between the components.

[0004] The use of solder foils to connect components during the manufacture of a vacuum interrupter is also disadvantageous for a number of other reasons. For example, the manufacture of a vacuum interrupter typically requires five to twenty solder foils. This results in a significant time expenditure. Furthermore, the solder foils vary in thickness and stiffness, making handling of the solder foils problematic in both manual and automated processes. Furthermore, solder foils are typically made of a copper-silver eutectic, an expensive material, which also increases the cost of manufacturing a vacuum interrupter. Furthermore, some solder foils contain toxic substances due to their required properties and therefore require special handling. One challenge in soldering processes can be insufficient capillary action, which prevents full flow of the solder and thus an adequate bond.A lack of solder can lead to insufficient bonding, which can result in insufficient vacuum and thus increases the risk of electrical breakdowns. On the other hand, an excess of solder can occur at junctions in the vacuum chamber, which is also critical for electrical breakdowns. In addition, solder foil technology requires special electroplating processes to design surface areas in such a way that they are reliably wetted by the solder.

[0005] The components of a vacuum interrupter are typically assembled vertically from bottom to top. As already mentioned, one challenge is handling the different sizes and thicknesses of solder foils that must be inserted between each pair of components to be joined for a subsequent material-to-material bond. Furthermore, the fixation and positional orientation (coaxiality) of the components are crucial to achieving the subsequent function of the vacuum interrupter. Currently, positional orientation in the manual assembly process is sometimes performed using additional centering devices, which increases the time required and costs, for example, for the manufacture of the centering devices. The use of such centering devices also complicates automated assembly and requires additional structures, which leads to higher costs and increased time requirements.

[0006] In addition, pre-assembled and pre-soldered subassemblies are provided for the assembly process. These subassemblies are already pre-assembled and pre-soldered and contain similar solder foils, or have been partially pre-fixed by mechanical (positive or non-positive) processes, for example, by caulking. With the help of complex centering devices, which add additional mass to the furnace, the assembled and aligned vacuum interrupters are evacuated and soldered in the vacuum furnace at temperatures ranging from approximately 700°C to 900°C. Process times vary depending on the size of the component, the pre-assembly, or the vacuum interrupter and can range from 8 hours to more than 24 hours. The fixing devices are then dismantled for the furnace run. Due to the considerable time required for a furnace run, several furnaces are usually required. These furnaces differ in type, shape, and dimensions and incur high acquisition and maintenance costs.

[0007] JP 2020 - 136 004 A1 discloses a manufacturing method for a vacuum interrupter in which nanoparticles are used in the solder material for soldering components of the vacuum interrupter.

[0008] DE 10 2020 107 513 A1 discloses a method for connecting contact surfaces that uses nanowires on the contact surfaces.

[0009] A method for connecting semiconductor chips is known from DE 10 2017 104 923 A1, wherein nanowires are used as connecting material between a semiconductor chip and the respective basic component.

[0010] The invention is based on the object of providing an improved method for producing a vacuum interrupter.

[0011] The object is achieved according to the invention by a method having the features of claim 1.

[0012] Advantageous embodiments of the invention are the subject of the subclaims.

[0013] In the method according to the invention for producing a vacuum interrupter, two components of the vacuum interrupter are connected to each other by - a nanostructure containing nanowires is inserted between two metallic joining surfaces of the two components and - the two joining surfaces are then pressed together at a joining temperature with a joining force and thus connected.

[0014] A nanowire is a very thin, elongated object with a diameter in the nanometer to micrometer range. The invention exploits the fact that nanowires can generate strong adhesion forces between metallic surfaces, thus connecting the surfaces. For this purpose, nanowires are inserted between the surfaces and pressed together at a joining temperature with a joining force. The joining temperature, joining force, and joining time depend on the materials used and the desired bond strength. The joining temperature is typically in the range of 100°C to 270°C, particularly in the range of 150°C to 200°C, and is significantly lower than, for example, when joining surfaces using solder foils.

[0015] The joining surfaces of the components joined in the process are metallic. However, this does not necessarily require the components to be metallic. For example, at least one of the components can have a base body made of a ceramic or plastic with a metallized surface section that forms the metallic joining surface. In general, a joining surface can be the surface of a buffer layer applied to a base body of a component, for example, to enable or improve the connection of nanowires to the joining surface.

[0016] The statement that two components are joined together in the method according to the invention should not be understood to mean that only two components are joined together according to the invention using a nanostructure. Rather, the statement should be understood to mean that at least two components are joined together according to the invention using a nanostructure. Accordingly, the statement that when two components are joined, two joining surfaces of these components are joined should be understood to mean that at least two joining surfaces of these components are joined.

[0017] Compared to a process for manufacturing a vacuum interrupter, which uses solder foils to connect components, the solder foils and their complex handling due to their varying thicknesses, stiffnesses, and shapes are eliminated. This also increases the automation potential and the degree of standardization of the process. Avoiding the use of toxic solder foils leads to improved and safer handling, as well as a reduction in risks with regard to occupational health and safety and environmental protection. Due to the elimination of solder foils, the electroplating process is less extensive. In particular, optimal flux properties for solder foils are no longer relevant.

[0018] The reduced joining temperature of less than 300°C compared to the brazing temperature in the range of 700°C to 900°C also has a number of advantages. It increases the energy efficiency and reduces the CO2 emissions of the process, as furnaces require less energy to generate the temperature. It also reduces the time required to generate the temperature in a furnace, thereby speeding up the process. The reduction in temperature also reduces the load on the furnaces used to generate the temperature and thus the effort and cost of maintaining and servicing the furnaces. Furthermore, the reduction in temperature enables the use of smaller and more cost-effective furnaces and materials such as plastics, aluminum, and certain glasses. Using such materials for the vacuum interrupter can also reduce the overall electroplating effort.Furthermore, the lower temperatures allow the components' residual mechanical stresses and cold-forming strength to be virtually preserved. This also makes it possible to minimize or eliminate run-in circuits during the process and optimize the components' settling behavior. The lower stress on the components due to lower temperatures can improve the testing process by reducing the scope of the required measurement procedures, resulting in shorter process times and lower costs.

[0019] To introduce the nanostructure, nanowires are applied between the joining surfaces on at least one of the two joining surfaces. For example, nanowires are applied to at least one joining surface by chemical, particularly electrochemical, deposition or spray coating. A joining surface to which nanowires are applied acts like an adhesive surface for connecting the components.

[0020] The nanostructure is designed such that at least one joining surface has regions in which nanowires of a first length are applied to this joining surface and between which nanowires of a second length reduced compared to the first length are applied to this joining surface.

[0021] It is particularly preferred that the vacuum interrupter is a vacuum interrupter for medium voltage, in particular for voltages between 1 kV and 52 kV.

[0022] In a further embodiment of the invention, the nanostructure is designed such that at least one joining surface has regions in which nanowires are applied to this joining surface and between which no nanowires are applied to this joining surface.

[0023] The purpose of the aforementioned embodiments of the invention is to create a nanostructure with at least one region that forms a gas outlet before the components are pressed together, through which gas (in particular air) can escape and which is closed when the components are pressed together. The gas outlet is formed by applying no nanowires or shorter nanowires compared to regions surrounding this region to a region of at least one joining surface. The gas outlet serves to dissipate gas through the nanostructure during manufacture of the vacuum interrupter in order to create a vacuum. Closing the gas outlet when the components are pressed together prevents gas from penetrating the nanostructure after the components have been connected and thus contributes to the vacuum-tightness of the vacuum interrupter.

[0024] In a further embodiment of the invention, at least one metal foil, to which nanowires are applied, is inserted between the joining surfaces to introduce the nanostructure. In this embodiment of the invention, the nanostructure is thus not created, or not only created, by applying nanowires to one or both joining surfaces, but alternatively or additionally by at least one metal foil, to which nanowires are applied, which is inserted between the joining surfaces. The metal foil is, for example, a thin copper foil. The metal foil acts like an adhesive tape, connecting the components.

[0025] In a further embodiment of the invention, several metal foils, to which nanowires are applied, are inserted at a distance from one another between the joining surfaces.

[0026] In a further embodiment of the invention, several metal foils are inserted between the joining surfaces, which differ from each other in the length of the nanowires applied to them.

[0027] In a further embodiment of the invention, a metal foil is introduced between the joining surfaces, which metal foil has regions on at least one side to which nanowires of a first length are applied and between which no nanowires or nanowires of a second length reduced compared to the first length are applied.

[0028] The three aforementioned embodiments of the invention in turn enable the formation of gas outlets in the nanostructure through which gas can escape through the nanostructure before the components are pressed together and which are closed by pressing the components together.

[0029] In a further embodiment of the invention, the joining surfaces are cleaned before the nanostructure is introduced. For example, the joining surfaces are cleaned before the nanostructure is introduced using a cleaning solution, a degreasing process, and / or an etching process, in particular by electroplating. Cleaning the joining surfaces can, in particular, remove contaminants and oxide layers from the joining surfaces that impair the adhesion of the nanowires to the joining surfaces.

[0030] In a further embodiment of the invention, the two joining surfaces are pressed together at the joining temperature using the joining force in a vacuum. For this purpose, the components are assembled before being joined, i.e., fixed in their relative position, and transferred to a vacuum furnace for joining. The vacuum furnace is then evacuated, whereby the pressure in the vacuum furnace is reduced to the vacuum level intended for the vacuum interrupter. The vacuum of the vacuum interrupter is thus created by joining the components in a vacuum of the desired vacuum level. Therefore, in addition to the vacuum, the vacuum tightness of the vacuum interrupter must also be realized when joining the components. This is achieved, among other things, by the aforementioned gas outlets of the nanostructure and their closure when the components are pressed together.

[0031] In a further embodiment of the invention, the nanowires have a diameter in the range of 30 nm to 4 µm and a length in the range of 500 nm to 50 µm. For example, the nanowires are made of copper, gold, nickel, silver, platinum, indium, or tin. Nanowires constructed in this way have proven particularly suitable for connecting components.

[0032] In a further embodiment of the invention, a joining temperature in the range of 100°C to 270°C, in particular in the range of 150°C to 200°C, is used. As already explained above, such a joining temperature has many advantages, particularly compared to temperatures required when using solder foils.

[0033] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. Fig. 1 a flow diagram of an embodiment of the method according to the invention for producing a vacuum interrupter, Fig. 2 a sectional view of a first example of a nanostructure between two joining surfaces, Fig. 3 a sectional view of a second example of a nanostructure between two joining surfaces, Fig. 4 a first sectional view of a third example of a nanostructure between two joining surfaces, Fig. 5 a second sectional view of the Fig. 4 shown nanostructure, Fig. 6 a sectional view of a fourth example of a nanostructure between two joining surfaces, Fig. 7 a sectional view of a fifth example of a nanostructure between two joining surfaces, Fig. 8 a first example of two connected components, Fig. 9 a second example of two connected components, Fig. 10 a third example of two connected components, Fig. 11 a fourth example of two connected components, Fig. 12 a fifth example of two connected components.

[0034] Corresponding parts are provided with the same reference numerals in the figures.

[0035] Fig. 1 ( Fig. 1) shows a flowchart 100 of an exemplary embodiment of the method according to the invention for producing a vacuum interrupter. In the method, two components of the vacuum interrupter are joined together by joining the metallic joining surfaces of the components.

[0036] In a first process step 101, the joining surfaces of the components are cleaned. For this purpose, cleaning solutions, degreasing processes, or etching processes, particularly electroplating, are used.

[0037] In a second process step 102, nanowires are applied to at least one of the two joining surfaces, which form a nanostructure between the joining surfaces during the subsequent joining of the components. The nanowires are applied to the joining surface, for example, by chemical, in particular electrochemical, deposition or spray coating.

[0038] The second method step 102 is omitted if the nanostructure between the joining surfaces is formed by a metal foil which has at least one side to which nanowires are applied and which is introduced between the joining surfaces before the components are connected.

[0039] In a third method step 103, the components with the nanostructures introduced between their joining surfaces are assembled in a clean room with a low particle concentration and low humidity. During assembly, the components of the vacuum interrupter are fixed relative to one another. Assembly is carried out in the clean room so that the nanostructures and the connection between the components are not compromised by dust or other particles. The clean room can contain a suitable gas that initiates chemical reactions that strengthen the connections between the nanowires and the joining surfaces. For example, a gas that reacts at specific temperatures in a controlled atmosphere is used to facilitate the formation of a bonding layer between the joining surfaces and the nanowires. Furthermore, a gas can be used that acts as a protective atmosphere to prevent oxidation of the nanostructures and / or the joining surfaces.

[0040] In a fourth method step 104, the assembled components are transferred to a vacuum furnace, and the vacuum furnace is subsequently evacuated, reducing the pressure in the vacuum furnace to the desired vacuum level of the vacuum interrupter. The individual components and / or the nanostructures are configured to have gas outlets such as channels that allow gas to escape during the evacuation of the vacuum furnace and are sealed during the subsequent joining of the components in a fifth method step 105.

[0041] In the fifth process step 105, the vacuum furnace is heated to a joining temperature, and the components are pressed together with a joining force, thereby bonding them together. The nanowires serve as the joining material. The specific parameters such as the joining temperature, joining force, and joining time depend on the materials used and the desired bond strength. The joining temperature ranges from 100°C to 270°C, particularly from 150°C to 200°C.

[0042] The Fig. 2 to 7 each show a nanostructure 200 between a metallic first joining surface 201 and a metallic second joining surface 202. The first joining surface 201 is a region of a surface of a first component 203 of a vacuum interrupter. The second joining surface 202 is a region of a surface of a second component 204 of the vacuum interrupter.

[0043] Fig. 2 ( Fig. 2) shows a sectional view of a nanostructure 200 formed by nanowires 205 applied to the first joining surface 201, while no nanowires are applied to the second joining surface 202.

[0044] Fig. 3 ( Fig. 3) shows a sectional view of a nanostructure 200 formed by nanowires 205 applied to the first joining surface 201 and nanowires 207 applied to the second joining surface 202.

[0045] Fig. 4 ( Fig. 4) and Fig. 5 ( Fig. 5) each show a sectional view of a nanostructure 200 formed by nanowires 205 applied to the first joining surface 201 and nanowires 207 applied to the second joining surface 202. Fig. 4 a sectional view in a first section plane analogous to the Fig. 2 and Fig. 3 and Fig. 5 shows a sectional view in a second sectional plane perpendicular to the first sectional plane. The nanostructure 200 is designed such that the first joining surface 201 has two regions 209 in which nanowires 205 are applied, and between which, in a region 211 of the first joining surface 201, no nanowires are applied. In contrast, nanowires 207 are uniformly applied to the second joining surface 202. Below the region 211 of the first joining surface 201, the nanostructure 200 thus forms a channel-like gas outlet 213 through which gas can escape during the evacuation of the vacuum furnace in the fourth method step 104 and which is closed in the fifth method step 105 when the joining surfaces 201, 202 are joined.

[0046] Fig. 6 ( Fig. 6) shows a sectional view of a nanostructure 200 formed by nanowires 205 applied to the first joining surface 201 and nanowires 207 applied to the second joining surface 202. Each joining surface 201, 202 has two regions 215 in which nanowires 205, 207 of a first length L1 are applied to this joining surface 201, 202, and between which, in a region 216, nanowires 205, 207 of a second length L2 reduced compared to the first length L1 are applied to this joining surface 201, 202. The regions 216 of the joining surfaces 201, 202 correspond to one another and are arranged one above the other. Between these regions 216, the nanostructure 200 forms a channel-like gas outlet 217 through which gas can escape during the evacuation of the vacuum furnace in the fourth process step 104 and which is closed in the fifth process step 105 when the joining surfaces 201, 202 are joined together.

[0047] Fig. 7 ( Fig. 7) shows a sectional view of a nanostructure 200 formed by nanowires 208 applied on both sides to a metal foil 219 inserted between the joining surfaces 201, 202.

[0048] The Fig. The nanostructure 200 shown in Figure 7 can also be modified to create a gas outlet. For example, for this purpose, a plurality of metal foils 219, each of which has nanowires 208 applied to it, are inserted at a distance from one another between the joining surfaces 201, 202. A gas outlet can be created by the distance between two metal foils 219. Alternatively or additionally, a plurality of metal foils 219 are inserted between the joining surfaces 201, 202, which differ from one another in the length of the nanowires 208 applied to them. Alternatively or additionally, a metal foil 219 is inserted between the joining surfaces 201, 202, which has regions on at least one side to which nanowires 208 of a first length L1 are applied and between which no nanowires or nanowires 208 of a second length L2 that is reduced compared to the first length L1 are applied.

[0049] The Fig. 8 to 12 each show two components 203, 204 which are connected by means of the method according to the invention.

[0050] Fig. 8 ( Fig. 8) shows two components 203, 204 with interconnected flat surface areas.

[0051] Fig. 9 ( Fig. 9) shows a first component 203 with a convex surface area which is connected to a flat surface area of ​​a second component 204.

[0052] Fig. 10 ( Fig. 10) shows two components 203, 204 with interconnected convex surface areas.

[0053] Fig. 11 ( Fig. 11) shows a first component 203 with a surface area formed by an edge, which is connected to a flat surface area of ​​a second component 204.

[0054] Fig. 12 ( Fig. 12) shows two components 203, 204 with interconnected stepped surface areas.

[0055] Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. List of reference symbols 100 Flowchart 101 to 105 process step 200 Nanostructure 201, 202 joining surface 203, 204 component 205, 207, 208 Nanowire 209, 211, 215, 216 Area of ​​a joining surface 213, 217 Gas outlet 219 Metal foil L1, L2 length

Claims

[1] Method for producing a vacuum interrupter, wherein two components (203, 204) of the vacuum interrupter are connected to each other by - a nanostructure (200) comprising nanowires (205, 207, 208) is introduced between two metallic joining surfaces (201, 202) of the two components (203, 204) and - the two joining surfaces (201, 202) are then pressed together at a joining temperature with a joining force and thereby connected, wherein, for introducing the nanostructure (200) between the joining surfaces (201, 202), nanowires (205, 207) are applied to at least one of the two joining surfaces (201, 202), characterized by , that the nanostructure (200) is designed such that at least one joining surface (201, 202) has regions (215) in which nanowires (205, 207) of a first length (L1) are applied to this joining surface (201, 202) and between which nanowires (205, 207) of a second length (L2) reduced compared to the first length (L1) are applied to this joining surface (201, 202). [2] Method according to claim 1, wherein the nanowires (205, 207) are applied to at least one joining surface (201, 202) by chemical, in particular electrochemical, deposition or spray coating. [3] Method according to claim 1 or 2, wherein the nanostructure (200) is designed such that at least one joining surface (201) has regions (209) in which the nanowires (205) are applied to this joining surface (201) and between which no nanowires are applied to this joining surface (201). [4] Method according to one of the preceding claims, wherein for introducing the nanostructure (200) between the joining surfaces (201, 202) at least one metal foil (219) is introduced, to which the nanowires (208) are applied. [5] Method according to claim 4, wherein a plurality of metal foils (219) onto which nanowires (208) are applied are inserted at a distance from one another between the joining surfaces (201, 202). [6] Method according to claim 4 or 5, wherein a plurality of metal foils (219) are introduced between the joining surfaces (201, 202), which differ from one another by the length of the nanowires (208) applied to them. [7] Method according to one of claims 4 to 6, wherein a metal foil (219) is introduced between the joining surfaces (201, 202), which metal foil has regions on at least one side to which nanowires (208) of a first length (L1) are applied and between which no nanowires or nanowires (208) of a second length (L2) reduced compared to the first length (L1) are applied. [8] Method according to one of the preceding claims, wherein the joining surfaces (201, 202) are cleaned before the introduction of the nanostructure (200). [9] Method according to claim 8, wherein the joining surfaces (201, 202) are cleaned by a cleaning solution, a degreasing process and / or an etching process, for example by means of electroplating, before the introduction of the nanostructure (200). [10] Method according to one of the preceding claims, wherein the two joining surfaces (201, 202) are pressed together at the joining temperature with the joining force in a vacuum. [11] Method according to one of the preceding claims, wherein the nanowires (205, 207, 208) have a diameter in the range of 30 nm to 4 µm and a length in the range of 500 nm to 50 µm. [12] Method according to one of the preceding claims, wherein the nanowires (205, 207, 208) are made of copper, gold, nickel, silver, platinum, indium or tin. [13] Method according to one of the preceding claims, wherein a joining temperature in the range of 100°C to 270°C, in particular in the range of 150°C to 200°C, is used.

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