High-pressure vacuum tube

Abstract

The present invention relates to a high-pressure vacuum tube comprising: a vacuum tube housing comprising an interior; the anode assembly is arranged in the vacuum tube shell; and a cathode assembly disposed inside the vacuum tube enclosure, emitting a beam of electrodes to strike a target surface of the anode assembly and form electromagnetic radiation. The high pressure vacuum tube includes a brazed assembly including a first component and a second component connected together by a first brazed joint, the brazed joint including no more than 18.0 wt% in total of one or more noble metals selected from the group consisting of Au, Pd and Pt, where at least a portion of the brazed joint is exposed to an interior of the vacuum tube housing.

Description

TECHNICAL FIELD

[0001] The present invention relates to high-voltage vacuum tubes, in particular to X-ray tubes and to a process for manufacturing a brazed joint therein. BACKGROUND

[0002] A high-voltage vacuum tube comprises an anode and a cathode which are arranged opposite to each other in a vacuum interior space. The vacuum interior space is usually enclosed by a cylindrical metal housing, the anode and / or the cathode are electrically insulated by means of a ring-shaped insulator.

[0003] A high-voltage vacuum tube is a device for controlling the flow of electric current in a high vacuum between electrodes, both the filament (heater) and the electron bombardment anode generate a lot of heat. High-voltage applications of vacuum tubes include X-ray tubes, magnetrons, traveling wave tubes, excitron tubes and klystrons.

[0004] High-voltage vacuum tubes usually use a ceramic insulator to separate the high-voltage and low-voltage areas. For example, the anode under high voltage can be separated from the main body of the vacuum tube by a ceramic insulator. The main body of the vacuum tube is usually connected to the ceramic insulator. A metal sealing ring can be brazed to the outer surface of the ceramic insulator, thereby connecting the main body to the ceramic insulator. This connection forms a three-phase junction between the ceramic insulator, the sealing ring and the surrounding medium. The electric field at this three-phase junction can be relatively high, thereby generating electrons that can become a source of electric arc and / or perforation. US4126803 discloses a high-voltage structure in which the insulator is part of the vacuum chamber.

[0005] X-ray tubes are known for various applications, which apply a high-voltage direct or alternating voltage between anode and cathode, the applied voltage can amount to several hundred kilovolts depending on the required radiation intensity. In such X-ray tubes, the necessary insulation path is mainly arranged axially.

[0006] The choice of brazing material for X-ray tubes can be adapted to the required wettability and brazing flowability, for example a 50 / 50 Au / Cu mixture, an 81.5 / 16.5 Au / Cu mixture (Nicoro TM -80) and an 82 / 18 Au / Cu mixture (Nioro TM ).

[0007] Gold-copper brazing materials belong to the wider family of high-temperature brazing materials, which are based on noble metals (palladium, platinum, gold and silver) and are supplemented by nickel and copper. They have good mechanical properties and oxidation resistance at high temperatures. In vacuum brazing applications, Cu-Ge-based alloys are often used as an alternative to noble metal brazing alloys such as Au-Cu and Cu-Ag-based alloys.

[0008] Non-noble metal alloys, such as Cu-Ge alloys (trade name Gemco TMAlloys with a nominal composition of 87.75% Cu, 12% Ge, and 0.25% Ni have been used for vacuum brazing of copper, steel, and nickel-based metals. However, the wide range between the solidus and liquidus temperatures of these alloys, known as the solidification temperature range (STR), can lead to liquefaction problems in brazing applications. Liquefaction in brazing refers to the phenomenon where the lower-melting-point components of the brazing alloy separate from and flow away from the higher-melting-point components during heating. Liquefaction occurs when an alloy is slowly heated to its melting point range (e.g., in furnace brazing), manifesting as unmelted alloy lumps remaining at the brazing alloy coating. This typically leads to reduced joint strength due to the presence of brittle intermetallic compound phases in the brazed joint. Liquefaction is usually more pronounced in alloys with a large STR. Brazing operations performed in furnaces with large temperature fluctuations are also prone to liquefaction, especially when the brazing alloy has a large STR.

[0009] Another problem with brazing alloys with high STR (Stretch Strength) is that they cannot be used for step brazing when using cryogenic alloys for step brazing complex joints. During step brazing, the liquidus temperature of the cryogenic filler metal approaches the solidus temperature of the high-temperature filler metal (due to the latter's high STR), which can lead to changes in component dimensions.

[0010] A high-pressure vacuum tube is still needed, containing a material that can replace traditional brazing alloys / joints containing precious metals. However, compared to traditional non-precious metal brazing alloys, this brazed joint needs to have a sufficiently small STR (stretch mark) to avoid or reduce the risk of liquefaction. Furthermore, the brazing alloy needs to have sufficient formability to be machined into specific shapes so that it can be precisely placed near the X-ray tube components, allowing it to be drawn into the gaps between the components via capillary action during the brazing process. Summary of the Invention

[0011] In a first aspect of the invention, a high-pressure vacuum tube is provided, comprising:

[0012] Vacuum tube housing, including the interior;

[0013] The anode assembly, which is disposed inside the vacuum tube housing; and

[0014] The cathode assembly, disposed inside the vacuum tube housing, emits an electrode beam to strike the target surface of the anode assembly and generate electromagnetic radiation.

[0015] The high-pressure vacuum tube includes a brazing assembly comprising a first component and a second component connected together by a first brazing joint. The first brazing joint comprises a composition configured to include a solidification temperature range of no more than 90°C and a liquidus temperature range of 950°C to 1060°C. Relative to the total weight of the first brazing joint, the brazing joint comprises a total of no more than 18.0 wt% of one or more noble metals selected from Au, Pd, and Pt. At least a portion of the brazing joint is exposed inside the vacuum tube housing, and at least one of the first and second components forms part of one or more of the vacuum tube housing, the anode assembly, and the cathode assembly.

[0016] In a variation of the first aspect of this disclosure, an X-ray tube is provided, comprising:

[0017] X-ray tube housing, including the interior;

[0018] The anode assembly, which is disposed inside the X-ray tube housing; and

[0019] The cathode assembly, disposed inside the X-ray tube housing, emits an electrode beam to strike the target surface of the anode assembly and generate electromagnetic radiation.

[0020] The X-ray tube includes a brazing assembly comprising a first component and a second component connected together by a first brazing joint, the first brazing joint comprising a composition configured to include a solidification temperature range not exceeding 90°C and a liquidus temperature range of 950°C to 1060°C; the brazing joint comprises, relative to the total weight of the first brazing joint, one or more noble metals selected from Au, Pd, and Pt; at least a portion of the brazing joint is exposed inside the X-ray tube housing; and at least one of the first component and the second component forms part of one or more of the X-ray tube housing, the anode assembly, and the cathode assembly.

[0021] The anode assembly is a rotating anode assembly. Rotating anode assemblies are subjected to significant forces during operation, therefore the strength of the brazed joints is crucial.

[0022] In some embodiments, at least one of the first and second components forms part of the housing of an X-ray tube or vacuum tube. In some embodiments, at least one of the first and second components forms part of an anode or cathode assembly.

[0023] The high-voltage vacuum tube preferably includes a cathode and an anode capable of operating at at least 800°C. Examples of high-voltage vacuum tubes include power tubes, magnetrons, traveling wave tubes, exciton tubes, and klystrons, and the electromagnetic radiation emitted by the cathode assembly includes, but is not limited to, X-rays and microwaves. Attached Figure Description

[0024] The invention will now be described with reference to the accompanying drawings, which illustrate particularly preferred embodiments of the invention, wherein:

[0025] Figure 1 This is a schematic diagram of an X-ray tube according to the present invention.

[0026] Figure 2 It is a differential scanning calorimetry (DSC) scan of sample 4 according to the present invention.

[0027] Figure 3 This invention relates to the effect of boron content in the brazing alloy on the solidus-liquidus temperature range.

[0028] Figure 4 This is a photograph of the brazing fluidity test results between a copper and a 304 stainless steel substrate, which are bonded together by the brazing alloy composition of sample 14, in a hydrogen environment according to the present invention.

[0029] Figure 5 It is based on the present invention Figure 4 Microscopic image of the cross-section of the brazed joint.

[0030] Figures 6A to 6F are photographs illustrating the formability of samples 8 to 12 and C-6 respectively according to the present invention.

[0031] Figure 7 A is a photograph of two adjacent components before the brazing alloy wire of the present invention is used for brazing with the brazing alloy of sample 13.

[0032] Figure 7 B is based on the invention Figure 7 Photograph of brazed joint A after brazing.

[0033] Figure 7 C is according to the present invention Figure 7 SEM image of brazed joint A after brazing.

[0034] Figure 8 A is a current technology for brazing alloy wires using commercially available brazing alloy GEMCO. TM A photo of two adjacent components before brazing.

[0035] Figure 8 B is based on the invention Figure 8 Photograph of brazed joint A after brazing.

[0036] Figure 8 C is according to the present invention Figure 8 SEM image of brazed joint A after brazing.

[0037] Figure 9 This is a graph showing the solidification temperature range (STR) of the brazing alloy according to the present invention versus Au content.

[0038] Figure 10 The graph shows the liquidus and solidus temperatures of the brazing alloy according to the present invention as a function of Ge% wt. Detailed Implementation

[0039] High pressure vacuum tube components

[0040] It should be understood that, in the context of this specification and claims, the housing refers to a high-temperature, hermetically tight housing capable of operating at at least 500°C or at least 800°C, and capable of operating under a vacuum or containing gas, such that the brazed joint therein prevents gas from leaking into or out of the housing. Preferably, the hermetically tightness allows the brazed joint to pass through a hermetically tightness of 1x10 -6 Leakage test atm.cc / s or lower (ASTM F2391 using helium).

[0041] "Shell" refers to a container, tube, or shell that defines an enclosed space in which enclosed components, fluids, vacuum, or gases can reside. The shell separates or isolates the enclosed space from the space outside the shell.

[0042] As used herein, “airtight” and its variations refer to a sealed, airtight, and liquidtight brazed joint, container, tube, or housing relative to environmental conditions typically experienced by the enclosure or shell as described herein. Airtightness generally means that the brazed joint is able to isolate the external environment of the device from the interior of the same device. The enclosure can be part of an assembly, such as a high-pressure vacuum tube or a semiconductor process chamber assembly, in whole or in part.

[0043] Depending on their nature, the housing typically includes at least one brazed joint, one of which must be formed as a blind joint (i.e., the joint is not visible). That is, the joint, formed by drawing molten brazing alloy into the gap between two parts to be joined (e.g., 5µm to 500µm or 200µm) (e.g., via capillary action to avoid gas stagnation within the brazed joint), is usually formed after the sub-assembly components within the housing are in place. Therefore, the properties of the brazing alloy are crucial for first forming the brazed joint of the required size, which will be placed directly near the parts to be joined. Second, the brazed joint should have sufficient wettability and flowability to form a high-quality connection between the parts via capillary action (e.g., without liquefaction). Third, the brazed joint needs sufficient hermetical tightness, corrosion resistance, high-temperature resistance, and strength to ensure the long-term functional integrity of the housing. At least some brazed joints within the housing (or other brazed assemblies) should be blind-jointed.

[0044] Furthermore, many designs cannot be inspected after manufacturing. This is particularly important because brazed joints require a finite gap for proper brazing. If manufacturing tolerances are inconsistent, problems will arise regarding the required gap, as the final brazed gap will be unknown and too large. Therefore, it is essential to maintain the stress-bearing capacity, inspectability, and production consistency of brazed joints.

[0045] The average thickness of brazed joints typically ranges from 5µm to 500µm, or 8µm to 200µm, or 8µm to 100µm. The depth of brazed joints can range from 5µm to 50 mm, or 30µm to 10 mm, or 40µm to 5.0 mm. The flowability of the brazing filler metal is particularly important when forming blind joints, especially when the molten filler alloy needs to flow a greater distance to cover the required depth of the brazed joint.

[0046] Such components typically require operation at high temperatures and / or high precision, where highly conductive components such as copper are indispensable for their effective thermal management system. In vacuum tubes, the housing may also include a heat source enclosed therein, such as the cathode filament of an X-ray vacuum tube or the lamp head in a rapid thermal processing assembly within a semiconductor processing chamber. The heat source is preferably capable of heating at least a portion of the contents within the housing to at least 800°C, at least 900°C, or at least 1000°C. The maximum operating temperature of the housing is determined by the softening temperature and liquidus temperature of the materials used.

[0047] The first or second component may include copper or a copper alloy having excellent electrical conductivity. The first or second component may also include other metals, including but not limited to stainless steel, copper alloys, or other metals or metal alloys with a melting point greater than 1050°C or 1080°C. The housing may also include a cooling system to remove heat from the system.

[0048] The first or second component may also include ceramic or metallized ceramic (i.e., ceramic including a metallized coating).

[0049] The housing includes an anode and a cathode, which are arranged opposite each other in a vacuum interior space. The vacuum interior space may be surrounded by a cylindrical metal housing, and the anode and / or cathode are electrically insulated by an annular insulator (e.g., a ceramic or metallized ceramic component). A brazed joint can form a seal between the cylindrical metal housing and the annular insulator.

[0050] Brazing joints may include ceramic (or metal-coated ceramic) components and metal components, wherein the brazing joint connects the ceramic / metal-coated ceramic and metal components together.

[0051] Ceramic components may include metallization coatings, such as molybdenum-manganese coatings or nickel plating.

[0052] When available, wetting / bonding additives may be selected to improve the wettability and / or bonding of the alloy on the first and / or second components.

[0053] The vacuum tube of the present invention may include a brazed joint formed of a high-copper-content brazing alloy, the brazed joint having specific amounts of trace components that can be varied to adjust the desired solidus temperature while maintaining a relatively narrow liquidus-solidus temperature range. Furthermore, the brazed joint typically exhibits excellent wettability and flowability on a range of substrates, including copper, nickel and their alloys, stainless steel, nickel-cobalt-iron alloys, and molybdenum-manganese metallized substrates. These brazing alloy properties enable the formation of a wide variety of vacuum tubes using various brazing techniques and conditions.

[0054] Reference Figure 1 The diagram illustrates a bipolar rotating X-ray tube 10, which, in addition to serving as an intermediate component connecting the cathode 30 and the anode 40, includes a hermetically sealed housing 20 to maintain a high vacuum. For high-pressure vacuum tubes (e.g., 150 kV), the housing is typically made of stainless steel, heat-resistant steel, carbon structural steel, non-magnetic stainless steel, copper, or a nickel-copper alloy. The housing may include one or more welded seals W that provide a hermetically sealed seal.

[0055] Electrons are generated by heating the cathode filament 50. Under the influence of the accelerating electric field between the cathode 30 and the anode, the electrons bombard the target surface 60 at high speed, thereby generating X-rays. The target surface is a rotating disk made of tungsten, capable of withstanding the high temperatures generated by the impacting electrons. The induction motor 70 includes bearings 80 and a rotor rod 90, which is typically made of molybdenum. Its relatively low conductivity provides the motor with a degree of thermal insulation from the target surface 60. The stator (not shown) includes a series of magnets that can drive the rotation of the rotor 90 from outside the housing 20.

[0056] Electron bombardment on the target surface releases an X-ray stream, which can be selectively transmitted to the outside of the housing via emission window 100. High-voltage lines 110 and 120 are supplied to the cathode 30 and anode 40 via feedthroughs 130 and 140, respectively. The feedthroughs include conductors 110 and 120, which are insulated from the housing by metallized ceramic seals 150 and 160.

[0057] In this configuration, a brazing alloy capable of connecting various metal and / or ceramic components is required. For example, brazed joint B1 needs to hermetically seal the housing to the anode feed 140 and the conductor 120 within the ceramic seal 160. A similar arrangement is required at the cathode feed with brazed joint B2. Brazed joint B3 is also needed to hermetically seal the X-ray emission window 100 to the housing 20. Brazed joint B4 may also be needed to connect components of the rotating anode 40 or cathode (30).

[0058] Since only 1% of the total energy is used to generate X-rays, and the remaining 99% is converted into heat, X-ray vacuum tubes need to be composed of hermetically sealed components with different electrical conductivity and mechanical strength. These components must maintain good dimensional stability under extreme temperature changes during startup.

[0059] The housing assembly (not shown) may also include a cooling fluid (e.g., oil) that helps remove heat from the housing and maintain the temperature within the target operating range, typically up to 800°C, 900°C, 1000°C, or higher. Due to the high electrical conductivity of copper, many metal components of the vacuum tube and housing contain copper; therefore, using copper-based brazing alloys offers the advantage of similar coefficients of thermal expansion and allows operation at the required temperatures within the vacuum tube. Consequently, the brazing alloys of the present invention are advantageously used for brazing joints of B1, B2, B3, and B4 to join metals to metals, metals to metallized ceramics, and / or metals to ceramics.

[0060] Brazing alloys used in high-pressure vacuum tubes need to exhibit deformability (the alloy's ability to undergo plastic deformation without fracture), particularly ductility (under tensile stress), and be manufactured in various forms such as wire and foil. The production of brazing alloys begins with mixing all the elements in appropriate amounts and melting the mixture to a sufficiently high temperature, then casting it into a solid ingot or billet. The alloy's state can be changed from as-cast to forged by cold working or hot working (such as rolling, drawing, and stamping).

[0061] Rapid solidification methods (i.e., at extremely high cooling rates), such as melt spinning, can produce brazing alloys in the form of thin foils. Casting, ingot casting, or any other form of grinding or atomization techniques for brazing alloys can be used to manufacture alloys in powder form. Pre-shaped brazing alloys are manufactured by precisely cutting shaped and cold-forged wire into rings or stamped alloy strips or foils. Pre-forms provide precise volume for specific areas of a particular brazing joint. The pre-form is placed in the joining area and melts during brazing, then cools and solidifies to join with the substrate. In some embodiments, brazing is performed in a vacuum, hydrogen, or inert gas environment, and the brazing temperature is typically at least 20°C higher than the liquidus temperature of the brazing alloy.

[0062] The complexity of the device clearly demonstrates the critical importance of the brazing alloy's ability to be positioned and flow into a compact space to achieve the necessary mechanical and hermetic integrity for the brazed joint. Compared to brazing alloys with high STR values, the brazing process can employ a relatively lower temperature rise because the brazed joint of this invention is less prone to liquefaction.

[0063] Brazing alloy form

[0064] Brazing alloys preferably have sufficient ductility for standard alloy processing. They have sufficient machinability, meaning they can be easily deformed into the required size and shape via standard metal forming processes such as rolling, wire forming, drawing, and stamping.

[0065] In one embodiment, the brazing alloy can be fabricated into wires with diameters as low as 0.030 inches (760 µm) or as low as 0.015 inches (380 µm). In another embodiment, the brazing alloy can be fabricated into foils with thicknesses as low as at least 0.002 inches (50 µm) or less. Typically, foil thicknesses can be produced from 0.001 inches (25 µm) to 0.010 inches (250 µm) or greater.

[0066] Brazing alloy

[0067] Brazing alloys typically possess excellent wettability and flowability, enabling reliable hermetic seals at high temperatures. Brazing alloys are particularly suitable for applications in high-temperature environments, including vacuum tubes (such as X-ray tubes, waveguides, and klystron assemblies).

[0068] Brazing alloys require melting before operation. The melting behavior is determined by the solidus and liquidus temperatures, with the melting initiation temperature (solidus) and the melting range (the difference between the two points) being the most important for brazing. The solidus temperature of the brazing alloy should be higher than its highest operating temperature but lower than the solidus temperature of the lowest melting point base material.

[0069] The liquidus temperature of the brazing alloy composition is typically below about 1060°C, or typically below 1050°C. The liquidus temperature is typically at least 890°C, or at least 900°C, or at least 950°C. Therefore, brazing alloys are particularly suitable for brazing copper or copper alloy substrates. In one embodiment, the liquidus temperature of the brazing alloy is in the range of 950°C to 1060°C, or in the range of 970°C to 1050°C. The brazing alloy composition is preferably configured to achieve the above-mentioned liquidus temperature or range thereof.

[0070] Some brazing alloys have narrow melting ranges, while others have wider ones. The melting range is typically related to the flow rate, which can influence the choice, as well as the required heating rate. Brazing alloys with narrow melting ranges (smaller temperature range between the solidus and liquidus) can be used at rapid (e.g., greater than 30°C / min or 40°C / min from the solidus to the liquidus) or slow heating rates (e.g., in the range of 5°C / min or 10°C / min to 30°C / min from the solidus to the liquidus). For brazing alloys with wide melting ranges, slow heating rates, such as in-furnace brazing, can cause the solid and liquid phases to reach equilibrium and coexist for extended periods. This leads to liquefaction, where the initially formed liquid (with a specific composition different from the bulk) flows into the joint gap and physically separates from the solid residue. The resulting chemical inhomogeneity can be detrimental to the strength of the joint and is often aesthetically unappealing.

[0071] In some brazing applications, the filler metal (i.e., brazing alloy) may need to flow to enter the joint gap, but even with pre-placement, flow characteristics remain important for ensuring all joint gaps are filled. Alloys with better flowability can penetrate smaller capillary gaps, but if the alloy flows too freely in larger gaps, it may not remain in the joint, leading to porosity and reduced strength. The flow of an alloy is primarily determined by the relative amounts of solids and liquids present at the brazing temperature. If an alloy melts at a single point (e.g., a eutectic composition or a pure metal), it will be completely liquid at the brazing temperature and flow easily. Alloys brazed within their melting range will contain a certain amount of solids and liquids; if it is mostly molten, it will flow well; if the solids fraction is large, the flow will be slower.

[0072] Brazed joint composition

[0073] The brazed joint composition is configured to include a solidification temperature range not exceeding 90°C and a liquidus temperature range of 950°C to 1060°C, while the total amount of one or more noble metals selected from Au, Pd, and Pt contained therein does not exceed 18.0 wt% relative to the total weight of the first brazed joint. The brazed joint composition may contain at least 0.1 wt%, at least 0.3 wt%, at least 0.5 wt%, at least 0.8 wt%, at least 1.0 wt%, or at least 1.2 wt% of one or more of Pt, Pd, and Au. In some embodiments, the brazed joint composition contains Au.

[0074] The target solidification temperature range (e.g., not exceeding 90°C) can be obtained using a brazing alloy containing copper, preferably at least 70 wt% Cu, or at least 75 wt% Cu, or at least 80 wt% Cu, or at least 85 wt% Cu.

[0075] Germanium has been found to lower the liquidus temperature of copper-based alloys without significantly increasing the solidification temperature range (STR). Brazed joints typically contain no more than 9.0 wt% or 8.0 wt% Ge, as levels above this can make the brazed alloy too brittle to form wires, foils, or preforms for manufacturing X-ray tubes. A Ge level of at least 0.5 wt%, at least 1.0 wt%, at least 2.0 wt%, or at least 2.5 wt% may be required to adequately lower the liquidus temperature.

[0076] Brazing alloys may also include other liquidus point inhibitors, including Au, Pt, Pd, B, Cr, In, Sn, Si, and Al. Au, Pt, and Pd are particularly advantageously added to brazed joints to adjust the STR value while improving the joint strength and wettability of the brazing alloy during manufacturing.

[0077] The content of B, Cr, In, Sn, Si, and Al in brazed joints may need to be limited to a total amount not exceeding 5.0 wt%, or 4.0 wt%, or 3.0 wt%, or 2.5 wt%, or 2.0 wt%, because, as with germanium, the use of these components can adversely affect the formability of the brazing alloy composition.

[0078] In some embodiments, the brazing alloy composition does not contain one or both of boron and tin.

[0079] Brazed joints may also include one or more elements selected from the group consisting of transition metals and rare earth metals, which are not yet defined.

[0080] In one embodiment, the brazed joint comprises Cu, Ge, and one or more of Pt, Pd, Au, and boron. The brazed joint may comprise at least 0.5 wt% of the sum of Cu, Ge, and one or more of Au + Pd + Pt, and the sum of Cu, Ge, and (Pt + Pd + Au) is greater than 90 wt%, or 95 wt%, or 98 wt%, or 99 wt% of the total weight of the brazed joint.

[0081] In one embodiment, the weight percentages of the brazed joint are

[0082] In one embodiment, the brazed joint comprises, in wt%:

[0083] 60 ≤ Cu ≤ 95;

[0084] 0.5 ≤ Ge ≤ 9.5;

[0085] 0 ≤ sum of one or more of Cr, In, Sn, Si, Al ≤ 5.0;

[0086] 0 ≤ B ≤ 1.25;

[0087] 0 ≤ sum of one or more of Au, Pd, and Pt < 18.0; and

[0088] Incidental impurities.

[0089] In one embodiment, the brazed joint comprises, in wt%:

[0090] 60 ≤ Cu ≤ 95;

[0091] 0.5 ≤ Ge ≤ 9.5;

[0092] 0 ≤ sum of one or more of Cr, In, Sn, Si, Al ≤ 5.0;

[0093] 0 < B ≤ 1.25 and 0 < sum of one or more of Au, Pd, and Pt < 18.0; and

[0094] Incidental impurities.

[0095] In some embodiments, the brazed joint contains at least 0.02 wt% of B. In some embodiments, the brazed joint contains at least 0.5 wt% of Au.

[0096] In some embodiments, the remainder of the brazed joint comprises transition metals or rare earth metals.

[0097] In some embodiments, the amount of Sn in the brazed joint is limited to no more than 0.4 wt%. This Sn limitation is particularly preferred when the brazed joint composition contains B, as the combination of these elements has been found to be brittle.

[0098] In another embodiment, the brazed joint composition includes (or is substantially composed of) the following in wt% terms:

[0099] 2.0 ≤ Ge ≤ 9.5;

[0100] 0.02 < B ≤ 1.25;

[0101] Additives ranging from 0 to 5.0;

[0102] Containing impurities; and

[0103] The balance is Cu.

[0104] The additives and impurities mentioned herein do not contain Sn exceeding 0.4 wt% of the total weight of the brazing alloy components.

[0105] Additives may include or consist of one or more additives selected from the group consisting of transition metals and rare earth metals.

[0106] The brazing alloy composition is preferably suitable for vacuum tubes and has the desired properties, including low vapor pressure and low magnetism.

[0107] In another embodiment, the brazed joint composition, in wt%, includes:

[0108] 54 ≤ Cu ≤ 95.5;

[0109] 0.5≤Ge≤10.0, optionally 0 to 5.0 of the sum of Al, Sn, In, Si and B;

[0110] 0.5 ≤ the sum of Au, Pd, and Pt ≤ 30.0; and

[0111] Impurities less than 1.0.

[0112] In another embodiment, the brazed joint composition, in wt%, includes:

[0113] 66 ≤ Cu ≤ 95.5;

[0114] 0.5 ≤ Ge ≤ 10.0, optionally 0 to 5.0 of the sum of Al, Sn, In, Si and B;

[0115] 0.5 ≤ the sum of Au, Pd, and Pt ≤ 18.0; and

[0116] Impurities less than 1.0.

[0117] In another embodiment, the brazed joint composition, in wt%, includes:

[0118] 0.5 ≤ Ge ≤ 10.0, optionally 0 to 5.0 of the sum of Al, Sn, In, Si and B;

[0119] 0.5 ≤ the sum of Au, Pd and Pt ≤ 30.0;

[0120] Additives ranging from 0 to 5.0 are selected from the group consisting of transition metals and rare earth metals, excluding Cu, Au, Pt, Pd and Ni;

[0121] Accompanying impurities less than 1.0; and

[0122] The balance is Cu.

[0123] The brazing alloy for forming brazed joints within high-pressure vacuum tubes offers a non-noble metal or low-noble metal content (e.g., <18.0 wt%) as an alternative to high-temperature brazing, particularly in vacuum environments. The applicant has found that low-noble metal brazed joints can be configured with an ideal liquidus temperature; solidification temperature range (STR), exhibit good formability, and can form hermetically tight seals in low-pressure environments.

[0124] For the purposes of this disclosure, good formability means that the brazing alloy has at least 38% formability, as determined by the formability tests described herein, and / or the brazing alloy can be drawn into wires with diameters as low as 0.030 inches (0.76 mm), preferably as low as at least 0.015 inches (0.38 mm). Typically, wires with diameters up to 0.10 inches can be used, but larger diameter wires can also be manufactured as needed.

[0125] As disclosed herein, when the content of an element, compound, or other ingredient is specified as falling within a range of numbers including 0 or without a lower limit, the content of that element or compound may be zero. In other words, such an element, compound, or other ingredient may be absent and is therefore optional.

[0126] Germanium and optional liquidus temperature depressant

[0127] Germanium and optional liquidus temperature inhibitors: The amounts of aluminum, tin, indium, silicon, chromium and boron help to lower the liquidus temperature of the brazing alloy while maintaining a relatively small solidification temperature range (STR).

[0128] In some embodiments, the germanium content is less than 9.0 wt%, or less than 8.0 wt%, or less than 7.5 wt%, or less than 7.0 wt%, or less than 6.8 wt% of the total weight of the brazing alloy. The brazing alloy composition may contain at least 0.5 wt%, or at least 1.0 wt%, or at least 1.5 wt%, or at least 2.0 wt%, or at least 2.2 wt%, or at least 2.5 wt%, or at least 2.7 wt%, or at least 3.0 wt%, or at least 3.5 wt%, or at least 4.0 wt%, or at least 4.5 wt% of germanium.

[0129] In some embodiments, the germanium content is in the range of 2.5 to 8.0 wt%, or 3.0 to 7.5 wt%, or 3.5 to 7.0 wt%. It has been found that this range of germanium content, within a wide range of Pt, Pd, and Au contents, can yield the target liquidus temperature and STR.

[0130] In some embodiments, it has been found that for germanium contents of 2.0 wt% or less, or 2.1 wt% or less, or 2.2 wt% or less, or 2.3 wt% or less, or 2.4 wt% or less, or 2.5 wt% or less, or 3.0 wt% or less, or 3.5 wt% or less, or 4.0 wt% or less, the liquidus temperature is typically outside the desired target range (e.g., less than 1060 °C) unless the sum of Au, Pd, and Pt is greater than 10.0 wt%, preferably greater than 11.0 wt%, or greater than 12.0 wt% or greater than 13.0 wt%.

[0131] The liquidus temperature can be further reduced by adding liquidus temperature inhibitors such as aluminum, tin, indium, silicon, chromium, and boron. When present (e.g., >0.0 wt%), the boron content may not exceed 1.5 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.4 wt%, or not exceed 0.2 wt%, or not exceed 0.1 wt%. When present (e.g., >0.0 wt%), the chromium content may not exceed 1.5 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.4 wt%, or not exceed 0.2 wt%, or not exceed 0.1 wt%. When present, the aluminum content may not exceed 3.0 wt%, or not exceed 2.0 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.5 wt%, or not exceed 0.4 wt%. When present, the tin content may not exceed 1.5 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.4 wt%, or not exceed 0.2 wt%, or not exceed 0.1 wt%. When present, the silicon content may not exceed 3.0 wt%, or not exceed 2.0 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.5 wt%, or not exceed 0.4 wt%. When present, the indium content may not exceed 3.0 wt%, or not exceed 2.0 wt%, or not exceed 1.0 wt%, or not exceed 0.8 wt%, or not exceed 0.6 wt%, or not exceed 0.5 wt%, or not exceed 0.4 wt%. When present, the total amount of Al+Sn+In+Cr+Si+B may not exceed 4.0 wt%, or not exceed 3.0 wt%, or not exceed 2.0 wt%, or not exceed 1.0 wt%, or not exceed 0.5 wt%. Higher levels of these components may adversely affect one or both of the resulting brazing alloy composition's STR and machinability.

[0132] Gold, palladium and platinum

[0133] Relatively small amounts of gold, palladium, and platinum help maintain the ductility of the brazing alloy while keeping the STR (stretch mark) low.

[0134] When present, the gold, palladium, or platinum content is preferably no more than 17 wt%, or no more than 16 wt%, or no more than 15 wt%, or no more than 14 wt%, or no more than 13 wt%, or no more than 12 wt%, or no more than 11 wt%, or no more than 10 wt%, or no more than 9.0 wt%, or no more than 8.0 wt%, or no more than 7.0 wt%, or no more than 6.0 wt%. The gold, palladium, or platinum content may be at least 0.2 wt%, or at least 0.4 wt%, or at least 0.5 wt%, or at least 0.8 wt%, or at least 1.0 wt%, or at least 1.2 wt%, or at least 1.5 wt%, or at least 1.8 wt%, or at least 2.0 wt%.

[0135] The total amount of Au, Pd, and Pt is preferably no more than 17 wt%, or no more than 16 wt%, or no more than 15 wt%, or no more than 14 wt%, or no more than 13 wt%. Lower amounts of Au, Pd, and Pt may result in poorer machinability / ductility of the brazing alloy. The brazing alloy preferably contains at least 0.8 wt%, or at least 1.0 wt%, or at least 1.5 wt%, or at least 2.0 wt%, or at least 2.5 wt%, or at least 3.0 wt% of Au, Pd, and Pt. In some embodiments, the brazing alloy contains Au and optionally one or both of Pt and Pd. Pt and Pd can each be in the range of >0 to 10 wt%. In some embodiments, one or both of Pt and Pd are in the range of >0 to 8.0 wt%, or 0.1 wt% to 6.0 wt%, or 0.2 wt% to 4.0 wt%.

[0136] In one embodiment, the brazing alloy comprises 0.5 to 18.0 wt% Au and optionally >1.0 to 12.0 wt%, and one or both of Pd and Pt in the range of 0 to 10.0 wt%, or up to 8.0 wt%, or up to 6.0 wt%, or up to 4.0 wt%.

[0137] In other embodiments, the brazing alloy composition does not contain Au or one or both of Pd and Pt.

[0138] Due to their properties, including low vapor pressure and low magnetism, brazed joint compositions are preferably suitable for vacuum tubes and similar applications. The requirement for low magnetism precludes the use of excessive amounts of Ni, Co, and Fe. In some embodiments, the combined amount of Ni, Co, and Fe is no greater than 4.0 wt%, or no greater than 3.0 wt%, or no greater than 2.0 wt%, or no greater than 1.0 wt%.

[0139] Boron content

[0140] Adding elemental boron (e.g., boron >0.02 wt% or >0.05 wt% or >0.1 wt%) has been shown to reduce STR values, while boron content above 1.25 wt% results in insufficient formability of the brazing alloy, thus hindering the manufacture of the desired form of brazing alloy (e.g., in the form of wire or sheet / foil).

[0141] In some embodiments, the boron content is greater than 0.15 wt%, or greater than 0.20 wt%, or greater than 0.23 wt%, or greater than 0.25 wt%, or greater than 0.26 wt%, or greater than 0.27 wt%, or greater than 0.28 wt%, or greater than 0.29 wt%, or greater than 0.30 wt%, or greater than 0.31 wt%, or greater than 0.32 wt%, or greater than 0.33 wt%, or greater than 0.34 wt%, or greater than 0.35 wt%, or greater than 0.37 wt%, or greater than 0.39 wt%. In some embodiments, the boron content is no more than 1.2 wt%, or no more than 1.1 wt%, or no more than 1.0 wt%, or no more than 0.90 wt%, or no more than 0.80 wt%, or no more than 0.75 wt%, or no more than 0.70 wt%, or no more than 0.65 wt%, or no more than 0.60 wt%, or no more than 0.55 wt%, or no more than 0.50 wt%.

[0142] In a preferred embodiment, the boron content is in the range of greater than 0.27 wt% and not greater than 0.80 wt%. Within this range, the brazing alloy exhibits good formability and a low STR value.

[0143] Nickel content

[0144] When present, the Ni content may be less than 14 wt%, or less than 12 wt%, or less than 10 wt%, or less than 8.0 wt%, or less than 6.0 wt%, or less than 4.0 wt%, or less than 2.0 wt%, or less than 1.0 wt%. For some applications, the amount of nickel may depend on the requirement for low magnetic properties.

[0145] Additives

[0146] The additives do not include elements that are already defined components (e.g., Cu, Ge, Sn, Al, Si, in, Ni, Au, Pt, Pd and B in some embodiments).

[0147] A range of elemental additives (preferably metals) can be added to the alloy composition to aid in wettability and flowability during brazing and / or the mechanical strength of the resulting brazed joint. The selection of additives should not have a significant adverse effect on the STR (stretch mark), liquidus temperature; machinability and / or vapor pressure of the brazing alloy; or the mechanical integrity or sealing of the resulting joint.

[0148] Those skilled in the art will understand that small amounts of additives can be added to brazing alloy compositions that enhance or at least do not impair the function of the brazing alloy composition in a given system or application. The determination of the type and amount of additive will be within the capabilities of those skilled in the art and will not require excessive experimentation. The scope of this disclosure covers the addition of such additives.

[0149] In some embodiments, the presence of additives greater than 0.0 wt% (>0.0 wt%) requires the alloy composition to include at least some of these additives. For example, in some embodiments, the composition includes additives greater than 0 to 5.0 wt%. In some embodiments, the additives are selected from the group consisting of transition metals and rare earth metals, excluding Cu, Ni, Au, Pd, and Pt. The upper limits of the total additive composition and individual additive compositions will be limited by their ability to maintain the functional properties of the brazing alloy, while the lower limits will be limited by the amount required to provide functional benefits to the brazing alloy.

[0150] Transition metals and rare earth metals may include scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, silver, cadmium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, mercury, actinium, and so on. , , , , 、鿏、 , , , cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

[0151] In some embodiments, the additive contains >0 to 5 wt% of a transition metal, preferably at least 0.25 wt% or at least 0.5 wt%.

[0152] In some embodiments, the additive may include a wetting additive selected from the group consisting of Nb, Mo, W, Co and Fe.

[0153] In some embodiments, the additive may include Ag or Zn to further improve the machinability of the brazing alloy.

[0154] Ti, V and / or Zr can also be added to help the brazing alloy bond to the ceramic surface.

[0155] In one embodiment, the additive includes one or more of Nb, Mo, W, Co, Cr, Fe, Ti, V, Zr, Au, Ag, and Zn.

[0156] In some embodiments, the additive comprises 0 or >0 to 3 wt% of rare earth metals. The amount of rare earth metals may not exceed 2.0 wt%, or not exceed 1.0 wt%, or not exceed 0.5 wt%, or not exceed 0.1 wt%, or not exceed 0.05 wt%.

[0157] Rare earth metals, such as Nd, Y, Yb and Ce, can be added to further improve strength and / or airtightness through grain refinement.

[0158] In one embodiment, the additive includes one or more of Nb, Mo, W, Co, Cr, Fe, Ti, V, Zr, Au, Ag, Zn, Y, Yb, Nd, and Ce.

[0159] Additives may contain metals with liquidus temperatures of at least 500°C, 800°C, 900°C, or 1000°C. High liquidus temperature additives are preferred due to the need for low vapor pressure and high-temperature performance.

[0160] In some embodiments, additives are present in amounts of ≤4.0 wt%, ≤3.0 wt%, ≤2.0 wt%, ≤1.0 wt%, or ≤0.5 wt%. In other embodiments, when present, the additive content may be ≥0.05 wt%, ≥0.10 wt%, ≥0.15 wt%, or ≥0.20 wt%. Additive levels below these amounts may be insufficient to provide the desired functional effects, such as improved wettability or improved brazed joint strength. In some embodiments, the additives include or consist of metal wetting additives, which, when present, can be selected to improve the wettability of the brazing alloy on the substrate surface to be joined (e.g., Nb, Co, and / or Fe). The wettability of the brazing alloy to the substrate is crucial for ensuring robust mechanical and hermetic joints. Because brazing alloys require low vapor pressures in some applications, additives such as Cd and Zn are preferably not used.

[0161] In one embodiment, the vapor pressure of each additive at 700°C does not exceed 1.0 x 10⁻⁶. 7 mm Hg (1.33 x 10) -5 Pa), preferably not exceeding 5 x 10⁻⁵ at 700°C. 8 mm Hg (6.65 x 10) -6 Pa), or not exceeding 1.0 x 10⁻⁶ at 700°C. 8 mm Hg (1.33 x 10) -6In another embodiment, the addition of additives (including wetting additives) does not cause the vapor pressure to exceed 1.0 x 10⁻⁶ at 700°C. 7 mm Hg (1.33 x 10) -5 Pa), or more than 5 x 10⁻⁵ at 700°C. 8 mm Hg (6.65 x 10) -6 Pa) or more than 1.0 x 10⁻ 8 mm Hg (1.33 x 10) -6 These undesirable synthetic vapor pressures are typically higher than the vapor pressure of brazing alloys without additives. Brazing alloys preferably contain no more than 0.5 wt%, or no more than 0.4 wt%, or no more than 0.3 wt%, or no more than 0.2 wt%, or no more than 0.1 wt%, or no more than 0.05 wt% of additives that do not meet this requirement.

[0162] It should be understood that the composition of a brazed joint can be derived from the composition of the brazing alloy and the composition of the substrate to be joined (including its coating). At least some (if not all) of the additives in the brazed joint composition can be derived from the diffusion of components in the substrate to which the brazed joint is joined.

[0163] Inherent impurities

[0164] The incidental impurities used in this article refer to unavoidable elemental traces (including their oxidized or reduced forms) during the production of brazing alloys.

[0165] Unless otherwise specified, collateral contaminants may include any element or compound not yet specified in the brazing alloy composition. A typical list of collateral contaminants tested includes Al, P, Pb, Cd, and Zn. For the repeat analysis of Example 14 (Table 1), the measurements of all collateral contaminants were below the detection limits (%wt), i.e., Al < 0.001; P < 0.002; Pb < 0.001; Cd < 0.001; and Zn < 0.001. Although cadmium and zinc are transition metals, they are considered collateral contaminants for applications of brazing alloys (such as X-ray tubes). The applicant's use of ultrapure raw materials does not reflect typical collateral contaminant levels for these selected components.

[0166] The upper limit for the total amount of impurities may be 1.0 wt%, preferably 0.5 wt%, more preferably 0.15 wt%. These small amounts of elements generally do not affect or change the practical use and / or performance of the brazing alloy. In one embodiment, the incidental impurities comprise any one impurity element (e.g., C or P) in amounts not exceeding 0.5 wt%, or not exceeding 0.2 wt%, or not exceeding 0.15 wt%, or not exceeding 0.1 wt%, or not exceeding 0.05 wt%.

[0167] While contaminant impurities (also known as unavoidable impurities) may vary depending on the purity of the raw materials used, typical levels of contaminant impurities are less than 0.8 wt%, or 0.5 wt%, or 0.2 wt%, or 0.1 wt%, or 0.05 wt% of the total weight of the brazing alloy composition. Some applications require more stringent limits. For example, the limits for each of Zn, Cd, Pb, and C can be less than 0.1 wt%, or less than 0.05 wt%, or less than 0.01 wt%, or less than 0.005 wt%, or less than 0.01 wt% of the total weight of the brazing alloy composition. In one embodiment, Zn and Cd are limited to less than 0.002 wt%, or less than 0.001 wt%. The content of Pb and P can be less than 0.01 wt% or less than 0.002 wt%. C can be limited to less than 0.05 wt%, or less than 0.01 wt% of the total weight of the brazing alloy composition. The vapor pressure at 500°C is higher than 10. -7 mm Hg (1.33 x 10) -5 All other metallic impurities (Pa) are preferably limited to 0.1 wt%, or less than 0.01 wt% or less; or each less than 0.005 wt%, or less than 0.002 wt% or less. The vapor pressure at 500°C is less than 10. -7 The impurities in mm Hg are preferably limited to no more than 0.2 wt%, 0.1 wt%, or 0.075 wt% of the total weight of the brazing alloy composition.

[0168] Substrate

[0169] The high-pressure tube of the present invention may include various substrates suitable for connection and / or sealing using previously defined low-noble metal brazing alloys. The high-pressure vacuum tube may include brazing assemblies comprising substrates, including but not limited to copper or copper alloys, Kovar alloys (Ni-Co-Fe alloys), metallized ceramic components (e.g., molybdenum-manganese metallization or nickel or copper plating); steel, including stainless steel; copper, nickel, and nickel alloys (including nickel superalloys); and other refractory metals (e.g., molybdenum and its alloys) whose liquidus temperature is preferably at least 20°C, at least 35°C, or at least 50°C higher than the liquidus temperature of the brazing alloy.

[0170] Solidus temperature range

[0171] To avoid liquefaction in the brazed joint of the high-pressure vacuum tube and to promote good brazing coverage on the joint, the brazing alloy used to produce the brazed joint preferably has a narrow temperature difference (i.e., a low STR value) between the solidus temperature and the liquidus temperature. In some embodiments, the brazed joint composition is configured to obtain a temperature difference between the solidus temperature and the liquidus temperature of the brazing alloy that does not exceed 90°C, or 88°C, or 85°C, or 82°C, or 80°C, or 75°C, or 70°C, or 65°C, or 60°C, or 55°C, or 50°C, or 45°C, or 40°C, or 35°C, or 30°C, or 25°C, or 20°C. The above-mentioned STR range is considered a low STR value.

[0172] In a third aspect of the invention, a high-pressure vacuum tube brazing assembly is provided, comprising a first joint and a second joint, wherein at least one joint comprises a component of the brazing joint component portion as described above.

[0173] In one embodiment, the component includes two joints, each joint comprising a component according to the first aspect of the invention. Each brazing alloy may be different. The first joint may include a component whose liquidus temperature is lower than the solidus temperature of the component of the second brazing joint.

[0174] In one embodiment, the first and second brazed joints comprise components according to the first aspect of the invention. Preferably, the difference between the solidus temperature of the first joint and the liquidus temperature of the second joint is at least +15°C or at least +20°C. The first joint may contain a brazing alloy component with a solidus temperature of at least 950°C or at least 990°C, and the liquidus temperature of the second joint does not exceed 980°C.

[0175] This type of component is well-suited for stepped brazing processes, in which a higher-temperature brazed joint is assembled and cooled before assembling a second brazed joint at a lower temperature. Since the solidus temperature of the first brazed joint is higher than the liquidus temperature of the second brazed joint, the integrity of the first brazed joint should not be compromised if the brazing temperature of the second brazed joint remains below the solidus temperature of the brazing alloy of the first brazed joint.

[0176] While the present invention includes stepped brazing using two brazing alloy compositions, the present invention also includes additional stepped brazing in which only one brazed joint comprises a brazing alloy according to the first aspect of the present invention.

[0177] In some embodiments, the brazing process may cause boron to migrate from the brazed joint. The reduction in boron content in the first brazed joint compared to the original brazing alloy composition may result in an increase in both the solidus and liquidus temperatures, allowing the same brazing alloy composition to be used for stepped brazing operations. The increased liquidus temperature allows the same original brazing alloy to be subsequently used to braze adjacent components (second brazed joints) at temperatures lower than the solidus temperature of the first brazed joint.

[0178] The brazed joint may also include compositional variations compared to the brazing alloy composition used to form the brazed joint. In some embodiments, the brazed joint may be derived from the brazing alloy composition of the first aspect of the invention. The derived brazed joint may have a lower boron content compared to the brazing alloy composition of the derived brazed joint. Prior to forming the brazed joint, adjacent materials / components of the brazed joint may also have an assessed boron level relative to the material / component.

[0179] As used herein, brazing refers to the joining process of two (or more) materials together using a brazing alloy, which mixes with the materials to be joined upon melting. The melting temperature of the brazing alloy is lower than that of the materials to be joined. The liquefied / molten brazing alloy interacts with the materials to be joined and forms a brazed joint during cooling. The interaction between the brazing alloy and the materials to be joined can be described by the diffusion and formation processes of intermetallic phases and other compounds. Brazing can be performed in a vacuum, reducing, or protective environment (e.g., a mixture of hydrogen and nitrogen). Flux can be used during brazing to remove oxides from the brazing surfaces of the materials to be joined and to prevent oxide formation during brazing, thus allowing the liquefied / molten brazing alloy to thoroughly wet the surfaces of the materials to be joined. However, fluxless brazing is preferred.

[0180] A high-voltage vacuum tube consists of an anode and a cathode, which are positioned opposite each other within a vacuum interior space. This vacuum interior space is typically surrounded by a cylindrical metal casing, and the anode and / or cathode are electrically insulated by a ring-shaped insulator. High-voltage vacuum tubes can operate at temperatures exceeding 800°C, 900°C, 950°C, or 1000°C.

[0181] Process

[0182] In a third aspect of the invention, a process for producing a high-pressure vacuum tube according to the first aspect of the invention is provided, wherein a brazing assembly is formed from a first component; the second component and the brazing alloy composition comprise one or more noble metals selected from Au, Pd, and Pt in total, and configured to include a solidification temperature range of no more than 90°C and a liquidus temperature of 950°C to 1060°C, wherein the brazing assembly is formed by the following steps:

[0183] a. Optionally, the brazing assembly may be held at a temperature between 10°C and 400°C below the liquidus temperature of the brazing alloy composition for at least 10 minutes;

[0184] b. Heating the brazing assembly to a brazing temperature higher than the liquidus temperature of the brazing alloy composition; and

[0185] c. Cool the brazing assembly to below the solidus temperature of the brazing alloy composition to form a brazed joint that connects the first component and the second component together.

[0186] The process involves raising the brazing temperature between the solidus and liquidus temperatures at a rate of 1°C / min to 30°C / min. The rate of temperature rise may be less than 28°C / min, or less than 26°C / min, or less than 24°C / min, or less than 22°C / min, or less than 20°C / min, or less than 18°C / min, or less than 16°C / min, or less than 14°C / min, or less than 12°C / min. Compared to brazing alloys with high STR, the brazing alloy of the present invention can be brazed at a lower heating rate without incurring the same risk of liquefaction, thus avoiding poor joint performance. Using a lower heating rate also avoids other disadvantages associated with faster heating rates, such as component deformation, spalling, and excessive outgassing. This allows the brazing alloy to be used effectively in a wider range of brazing environments, including the brazing of components with low electrical conductivity (e.g., ceramics) and / or large thermal mass, making rapid heating rates difficult to achieve.

[0187] In some embodiments, the brazing cycle further includes, at the brazing temperature, maintaining the brazed joint and associated substrate at a temperature between 10°C and 400°C below the solidus temperature for 10 to 30 minutes before brazing the brazed joint, typically 15°C to 60°C above the liquidus temperature of the brazing alloy.

[0188] In other embodiments, double brazing is used, wherein the brazed joint is cooled by about 100°C (to below the solidus temperature) between brazing cycles.

[0189] Brazed joints can be formed in brazing furnaces that include vacuum, reduction (e.g., H2), or protective (e.g., N2 or argon) furnaces. Blind joints are particularly well-suited for brazing in furnaces or ovens because the temperature and atmospheric conditions can be reliably controlled. Vacuum furnaces can achieve vacuum levels less than 8 x 10⁻⁶. -4 mm Hg (1.17 x 10) -3 Pa), preferably less than 5 x 10 -4 mm Hg (6.65 x 10) -2Pa). The required levels of temperature and environmental control may also be achieved using laser brazing in controlled environments.

[0190] In some embodiments, a two-step stepped brazing process is employed, comprising heating a first brazing alloy component to a first brazing temperature and allowing cooling to form a first brazed joint, and then cooling a second brazing alloy component to a second brazing temperature and allowing cooling to form a second brazed joint, wherein the solidus temperature of the first brazed joint is higher than the liquidus temperature of the second brazed joint, and wherein the second brazing temperature is maintained below the solidus temperature of the first brazed joint (e.g., at least 10°C, at least 15°C, or at least 20°C).

[0191] In one embodiment, a brazed joint is formed by placing brazing alloy components in the form of wire, powder, slurry, or foil near the two components to be joined, heating the brazing components above their liquidus temperature, and allowing the molten brazing alloy to flow between the two components via capillary action.

[0192] Brazed joint properties

[0193] The brazing alloy and derived joint of the present invention are preferably airtight, and have good mechanical strength and low vapor pressure.

[0194] The brazed joint of the present invention preferably has airtightness, and the maximum permissible leakage rate of the sealed vacuum assembly is 1x10⁻⁶. -6 atm.cc / s or lower, 1x10 -7 atm.cc / s / or lower, or 1x10 -8 atm. cc / s or lower (ASTM F2391 for helium). In some applications, such as RTP assemblies, lower seal integrity may be sufficient, although the integrity of the brazed joint should ensure that the process gas is contained within the process chamber and does not leak through the brazed joint.

[0195] The brazed joints of the present invention preferably have a tensile strength of at least 900 MPa, or at least 950 MPa, or at least 1000 MPa. The brazed joints of the present invention preferably have a shear strength of at least 5.0 or at least 7.0 MPa. Tensile and shear strengths are measured according to the AWS C.3.2M / C3.2:2019 standard method for evaluating the strength of brazed joints. The reference substrate used for testing is 304 stainless steel bonded to 100% copper.

[0196] The brazing alloy of the present invention preferably has a content of less than 1 x 10⁻⁶ at 500°C. -11 mm Hg (1.33 x 10) -9 A vapor pressure of Pa, or having a vapor pressure of less than 1 x 10 at 500°C.-12 mm Hg (1.33 x 10) -10 A vapor pressure of Pa, or having a vapor pressure of less than 1 x 10 at 500°C. -13 mm Hg (1.33 x 10) -11 A vapor pressure of Pa, or having a vapor pressure of less than 1 x 10 at 500°C. -14 mm Hg (1.33x10 -12 A vapor pressure of Pa, or having a vapor pressure of less than 1 x 10 at 500°C. -15 mm Hg (1.33 x 10) -13 The vapor pressure (Pa) of the brazing alloy is preferably less than 1 x 10⁻⁶ at 700°C. -8 mm Hg (1.33 x 10) -6 Pa), or less than 1 x 10 -9 mmHg (1.33 x 10) -7 Pa), or less than 5 x 10 -10 mm Hg (1.33 x 10) -8 Pa), or less than 1 x 10 -11 mm Hg (1.33 x 10) -9 Pa).

[0197] The solidus temperature is the highest temperature of a metal, or the temperature at which an alloy becomes completely solid. The liquidus temperature is the lowest temperature at which a metal or alloy becomes completely liquid.

[0198] For the purposes of this invention, high voltage means a voltage of at least 1 kV, at least 10 kV, or at least 100 kV. The benefits of the brazing alloy of this invention can also be determined by applications with a sufficiently high voltage / distance (V / d) ratio, such as at least 0.5 kV / mm, at least 1 kV / mm, or at least 10 kV / mm.

[0199] Vacuum brazing is typically performed at approximately 1 x 10⁻⁶. -5 mm Hg (1.33 x 10) -3 It is carried out under a pressure of (Pa).

[0200] Machinability and formability are interchangeable terms.

[0201] The statement “the remainder is Cu” indicates that copper accounts for the remaining portion of the brazing alloy composition, up to 100.00 wt% (i.e., the weight % of copper = 100.00 wt% - the weight % of all other components in the brazing alloy).

[0202] The sum of all components in the brazing alloy composition must not exceed 100 wt%. The theoretical sum of component combinations exceeding 100 wt% should be disregarded.

[0203] Unless otherwise stated, references to %wt are based on the total weight of the brazing alloy composition.

[0204] For the purposes of this invention, precious metals refer to gold, silver, palladium, and platinum.

[0205] When referring to components, we mean those in elemental form (i.e., oxidation number = 0). Impurities can be in any permissible oxidation state, but preferably have an oxidation number of zero.

[0206] Examples

[0207] Brazing alloy samples with the various compositions listed in Table 1 were prepared by heating a mixture of elemental components to approximately 1080°C to form a homogeneous melt. The molten alloy was then cast into ingots, followed by cold working and annealing to produce alloys in the form of wire and / or foil.

[0208] Methodology

[0209] Solidus liquidus temperature

[0210] Differential scanning calorimetry (DSC) was used to characterize the melting behavior of these alloys. Liquidus and solidus temperatures were measured by DSC using small samples of approximately 20 mg mass placed in a covered alumina crucible. After loading the samples, the chamber was evacuated and backfilled with argon. Melting was performed at 20 K mins in the temperature range of 298 K to 1373 K. -1 The heating rate is analyzed. The output of the analysis is a curve showing the change in heat flux with temperature.

[0211] refer to Figure 2 DSC measures the physical and chemical changes within a material in response to temperature. It provides information about endothermic (absorbing heat), exothermic (releasing heat), and changes in heat capacity.

[0212] The DSC experiment (measured using a Netzch DSC instrument, model Jupiter STA 449 F3) consisted of two phases: heating and cooling, followed by a second identical cycle (a second heating and cooling cycle). Figure 2 These are the DSC curves for the second heating-cooling cycle of sample 4. For better visibility, the (continuous) DSC curves are separated, with the bottom curve representing the heating curve (from left to right) and the top curve representing the cooling curve (from right to left). The solidus temperature of 1032.4 °C was determined at the point on the heating curve before the heat flux increased, indicating the beginning of liquid phase formation. The liquidus temperature of 1039.3 °C was determined at the point on the cooling curve before the heat flux decreased, indicating the beginning of solid phase formation.

[0213] Formability

[0214] The alloy composition was prepared by melting 5 ± 1 grams (0.25 inches high) of the alloy in a water-cooled copper furnace under argon atmosphere using tungsten electrodes to produce hemispherical alloy ingots (cast ingots). Ingots of different compositions were cold-rolled using a twin-roll mill to test their ability to plastically deform into sheet-like shapes.

[0215] The formability of each component was determined by measuring the deformation (visually observed) required to cause fracture when passing through rolls at room temperature. In each step, the roll gap was adjusted to correspond to a 10% reduction in ingot thickness. Alloys capable of withstanding cold rolling to 0.002-inch (approximately 50 µm) thick sheets were considered to have formability close to ductility. Formability testing defined a reduction from 0.25 inches to 0.002 inches as 100% formability and a reduction to 0.125 inches as 50% formability.

[0216] If early fracture occurs before reaching the target thickness of approximately 50 µm, these components are considered to be somewhat brittle in nature. This methodology is used to evaluate the ability of various compositions of this alloy to fabricate braze filler wires or preforms. Early fracture refers to the appearance of fracture visible to the naked eye in the sample, such as… Figure 6d As shown in 6e (60% formability), 38% formability, and 20% formability, compared to... Figure 6a-6c In contrast, when the sample is processed to a thickness of 50µm (100% formability), Figure 6a-6c There were no obvious signs of breakage.

[0217] A formability percentage of at least 38% is considered suitable for manufacturing brazing alloy preforms, although at least 45%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or 100% formability is preferred. Therefore, the boron content of the brazing alloy composition can be configured to obtain the aforementioned formability values ​​or ranges.

[0218] Shear strength

[0219] Shear strength was measured according to the AWS C.3.2M / C3.2:2019 standard method for assessing the strength of brazed joints. Shear strength was measured between 304 stainless steel and pure copper substrates. It was observed that for each shear strength test, the failure point of the copper substrate indicated that the reported increase in shear strength was likely due to the diffusion of the brazed joint element of the present invention into the copper substrate, thereby strengthening the copper substrate.

[0220] Hermeticity

[0221] The airtightness of brazed joints was tested using helium according to ASTM F2391. Airtightness testing was performed on all samples that underwent shear strength testing, and all samples within the scope of this invention passed the test, achieving a shear strength of 1x10⁻⁶. -8 The allowable He leakage rate is atm.cc / s or lower.

[0222] Experimental results

[0223] A series of experiments were conducted to evaluate the properties of the brazing alloy in terms of solidus (S) and liquidus (L) temperatures and formability.

[0224] The vapor pressure of the brazing alloy of the present invention was found to be less than 1 x 10⁻⁶ in Table 1. -11 mm Hg (1.33 x 10) -9 The vapor pressure of each alloy was estimated using the individual vapor pressure contribution of each element: Pa.

[0225] (Formula 1)

[0226] in, It is activity. It is the equilibrium vapor pressure at the liquidus temperature +50°C.

[0227] The preferential evaporation of different alloying elements is a function of the element's volatility and its activity in the alloy. The partial contribution of each alloying element to the total equilibrium vapor pressure is a function of the equilibrium vapor pressure of the pure element and its activity in the alloy, as described in Equation (1).

[0228] We refer to Figure 3 The effect of boron on brazing alloys containing 2.5 wt% germanium (Line A) and 4.8 wt% germanium (Line B) indicates that each alloy has an optimal boron content that produces the minimum STR value. For 2.5 wt% germanium content (samples 1, 2, 3, C-1), 4.2 wt% (sample 4), and 4.8 wt% (samples C-2, C-3, 5, 6, 7), the optimal boron content ranges from approximately 0.5 to 1.25 wt% boron. Although a similar decrease in STR was observed at germanium contents of 7.2 wt% (the minimum STR recorded at 0.55 wt% boron) and 10 wt% (the minimum STR recorded at 0.80 wt% boron), the absolute minimum STR values ​​are not low compared to brazing alloys with lower germanium contents.

[0229] However, the limitation of low Ge content lies in their elevated liquidus temperature, which can be detrimental to applications involving brazing copper or copper alloy components. The brazing alloys of the present invention, with a Ge content of about 4.2 wt% to 4.8 wt%, have been found to possess an excellent combination of low STR values; liquidus temperatures within the target range for brazing copper / copper alloy components; and good formability. The brazing alloy compositions of the present invention provide a wide range of liquidus temperatures, favorable STR ranges, and acceptable formability to meet the functional requirements of many end-use applications, all without requiring the use of any significant amounts of precious metals.

[0230] For example, the melting curve of sample 4 is similar to that of the noble metal brazing alloy 35Au-65Cu (WESGO). TM Similar to the latter, which has a liquidus temperature of 1010 °C and an STR of 20 °C (Table 2). While other samples may have higher STRs than noble metal brazing alloy alternatives, they still offer better performance compared to existing non-noble metal alternatives. For example, 50Au-50Cu (WESGO) TM The liquidus temperature of sample 15 is 970℃, and the STR is 15℃ (Table 2). Samples 15 and 16 have similar liquidus temperatures, but their STRs are 68-69℃. This is for non-precious metal brazing alloys (WESGO). TM GEMCO TM This represents a significant improvement, with the liquidus temperature of the alloy being 975°C, while that of STR is 95°C (Table 2).

[0231] While brazing alloys with higher Ge content (e.g., 7.2 wt% or more) may have relatively higher STR levels and lower liquidus temperatures (compared to brazing alloys with lower Ge content), these brazing alloy properties are still acceptable in some applications.

[0232] As shown in Table 1, the formability of the brazing alloy tends to decrease with increasing boron content, and the formability decreases significantly when the boron content increases to above 1.0 wt%. Ge content appears to have a smaller effect on formability; at a constant boron content of 1.25 wt%, the formability decreases from 43 to 40 to 38 as the Ge content increases from 2.5 wt% to 4.8 wt% to 7.2 wt%. Figures 6A to 6F show the foils formed in samples 8 to 12; samples 11, 12, and C-6 show obvious signs of breakage as formability decreases.

[0233] The effects of adding Au, Pd, and Pt

[0234] As shown in samples 22, 24 to 41, the addition of Au, Pd, and Pt provides a brazing alloy composition with ideally low STR and a liquidus temperature within the target range, suitable for brazing the inner surfaces of X-ray tubes exposed to high temperatures, vacuum, and, in some cases, high stress. Compared to conventional brazing alloys (such as 50 Au 50 Cu) with a shear strength of 1279 PSI, brazed joints containing Au exhibit improved shear strength, making them particularly advantageous for use in rotating anode assemblies within X-ray tubes.

[0235] Table 1

[0236]

[0237] Table 1 (continued)

[0238]

[0239] like Figure 9 As shown, adding a relatively small amount of Au to a Cu-Ge alloy containing approximately 6 wt% (5.3 to 6.5 wt%) Ge results in a significant decrease in the STR (Structurally Absorbable) composition of the resulting brazing alloy. When the Au content is 5.3 wt%, an almost eutectic composition is obtained, and further increases in Au content subsequently lead to a gradual increase in STR. When interpolated... Figure 9 When estimating the STR using data from the study, Example 41, containing 4 wt% Pd and Pt (combined 8 wt%) and 6 wt% Ge, had a STR of 15 °C. This is consistent with the STR value of an equivalent composition containing 8 wt% Au (instead of 4 wt% each of Pd and Pt). This result supports the assertion that Pd and Pt have a similar effect on STR as Au, and that they can unexpectedly provide high-quality brazed joints when the contents of Au, Pt, and Pd are relatively low.

[0240] refer to Figure 10 At a fixed Au concentration of 10 wt%, the changes in liquidus and solidus temperatures with Ge concentration are prominent. The optimal Ge concentration at this Au concentration is between about 2.5 wt% and about 7.0 wt%, and the STR values ​​are particularly low between about 3.5 wt% and about 6.0 wt%.

[0241] Effects of Additives

[0242] Most examples contain 0.25 wt% Ni, which is added as a wetting aid to help the brazing alloy wet the stainless steel substrate. The brazing alloy composition tolerates Ni levels up to 4.8 wt% while still maintaining acceptable STR values, but additive levels above 5.0 wt% are expected to have adverse effects on STR or liquidus temperature, as shown in Comparative Example 10 (C-10) containing 5.25 wt% additive. Higher levels of Ni and Ag (C-9, C-11) further confirm this negative trend.

[0243] The effect of adding Sn was investigated by adding 1.0 wt% Sn to the composition of Example 5, which had a low STR (strength) of 12°C. The resulting composition (C-6) showed a deterioration in STR value to 173°C. Other Sn-containing compositions, C-7 and C-8, also exhibited high STR values ​​of 116°C and 185°C, respectively. The effect of Sn also significantly worsened the formability (100% formability) of Example 5, with the addition of 1.0 wt% Sn causing a sharp decrease in formability to 20% ( Figure 6f Similarly, after adding 1.0 wt% Sn, the formability of sample 17 decreased from 100% to 30% (sample C-7).

[0244] Brazed joint properties

[0245] refer to Figure 4 and Figure 5 It was found that the brazing components (sample 13) could flow between copper 410, 510 and 304 stainless steel 420, 520 blind joints 430, 530. Figure 4 The arrows in the image indicate the flow direction. (See cross-sectional images of the microstructure.) Figure 5 As shown in the diagram, copper 510 and 304 stainless steel substrate 520 are joined together by brazed joints 530 with an average thickness of approximately 10µm. Figure 5 As shown, the brazed joint provides a continuous and clean interface between the substrates. No significant liquefaction was observed. Testing confirmed that the brazed joint meets the 1x10 standard requirements for high-vacuum components. -8 The maximum permissible leakage rate of a closed vacuum assembly is atm.cc / s or lower.

[0246] Similar performance was obtained when 304 stainless steel strip was brazed onto copper strip in a “T” configuration (not shown) using a brazing alloy, and no liquefaction was observed.

[0247] Figure 7 A shows a copper plate 700 on a 304 stainless steel substrate 710, with brazed alloy wire (0.030 inches in diameter) 720 close to the two substrates. Figure 7B shows that after brazing (1048°C, 15 minutes under vacuum), the brazing alloy formed visible brazing fillets 730 on all four edges of the square blind joint specimen, indicating good brazing fluidity. Combined with EDS analysis of a portion of the brazed joint at (x30) magnification, the brazed joint 730 adjacent to the near end 740 and far end 750 of the copper plate 700 has a uniform and smooth appearance (i.e., no signs of liquefaction). EDS spectroscopy confirmed the uniform concentration of brazing elements, and the EDS spectrum also confirmed the presence of 304 stainless steel 760.

[0248] Table 2

[0249]

[0250] Figure 8 A shows a copper plate 800 on a 304 stainless steel substrate 810, using the commercial brazing alloy GEMCO. TM The wire (0.030 inch in diameter) 820 is adjacent to two substrates. Figure 8 B shows that after brazing (1000℃, vacuum for 15 minutes), the brazing alloy forms a visible brazing fillet at the edge where the brazed wire is placed, indicating limited brazing fluidity. Figure 7 Compared to the brazed joint of type B, this is a lower quality blind joint. Furthermore, combined with EDS analysis of a portion of brazed joint 830 at magnification (x30), it is shown that in portions of brazed joint 840 and 850 of the copper plate 800, the portion farther from the copper plate 850 exhibits a rough appearance (i.e., evidence of liquefaction), and the EDS spectrum also confirms the variation in the elemental concentration of the brazing element in this portion. Due to the variation in the brazed joint composition, the function of the brazed joint is expected to be impaired.

[0251] It should be understood that modifications and variations may be made without departing from the spirit and scope of the novel concept of this invention.

Claims

1. An X-ray tube comprising: X-ray tube housing, including the interior; An anode assembly is disposed inside the X-ray tube housing; as well as The cathode assembly, disposed inside the X-ray tube housing, emits an electrode beam to strike the target surface of the anode assembly and generate electromagnetic radiation. The X-ray tube includes a brazing assembly comprising a first component and a second component connected together by a first brazing joint, the first brazing joint comprising a composition configured to include a solidification temperature range not exceeding 90°C and a liquidus temperature range of 950°C to 1060°C; the brazing joint comprises, relative to the total weight of the first brazing joint, one or more noble metals selected from Au, Pd, and Pt; at least a portion of the brazing joint is exposed inside the X-ray tube housing; and at least one of the first component and the second component forms part of one or more of the X-ray tube housing, the anode assembly, and the cathode assembly.

2. A high-pressure vacuum tube, comprising: Vacuum tube housing, including the interior; An anode assembly is disposed inside the housing of the vacuum tube; as well as The cathode assembly, disposed inside the vacuum tube housing, emits an electrode beam to strike the target surface of the anode assembly and generate electromagnetic radiation. The high-pressure vacuum tube includes a brazing assembly comprising a first component and a second component connected together by a first brazing joint. The first brazing joint comprises a composition configured to include a solidification temperature range of no more than 90°C and a liquidus temperature range of 950°C to 1060°C. Relative to the total weight of the first brazing joint, the brazing joint comprises a total of no more than 18.0 wt% of one or more noble metals selected from Au, Pd, and Pt. At least a portion of the brazing joint is exposed inside the vacuum tube housing, and at least one of the first and second components forms part of one or more of the vacuum tube housing, the anode assembly, and the cathode assembly.

3. The high-voltage vacuum tube according to claim 2, comprising a voltage of at least 1.0 kV.

4. The high-pressure vacuum tube according to claim 2, wherein, The high-voltage vacuum tube is part of a power tube, magnetron, traveling wave tube, exciton tube, or klystron.

5. The high-pressure vacuum tube according to claim 2, wherein, The electromagnetic radiation is in the form of X-rays or microwaves.

6. The high-pressure vacuum tube according to claim 2, wherein, The anode assembly is a rotating anode assembly.

7. The high-pressure vacuum tube according to claim 2, wherein, At least one of the first component and the second component forms part of the vacuum tube housing.

8. The high-pressure vacuum tube according to claim 2, wherein, At least one of the first component and the second component forms part of the anode assembly or cathode assembly.

9. The high-pressure vacuum tube according to claim 2, wherein, The first component or the second component comprises ceramic or metallized ceramic.

10. The high-pressure vacuum tube according to claim 2, wherein, One or both of the first component and the second component include stainless steel, copper, copper alloy, nickel alloy or Ni-Co-Fe alloy.

11. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint includes Au.

12. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint comprises copper and no more than 8.0 wt% germanium.

13. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint further includes one or more elements selected from the group consisting of transition metals and rare earth metals.

14. The high-pressure vacuum tube according to claim 2, further comprising one or more of Pt, Pd, Au and B.

15. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint comprises Cu, Ge, and at least 0.5 wt% Au+Pd+Pt.

16. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint comprises, by weight (wt%) relative to the total weight of the brazed joint: 60 ≤ Cu ≤ 95; 0.5 ≤ Ge ≤ 9.5; 0 ≤ the sum of one or more of Cr, In, Sn, Si, and Al ≤ 5.0; 0 ≤ B ≤1.25； 0 ≤ the sum of one or more of Au, Pd, and Pt < 18.0; and Impurities are present.

17. The high-pressure vacuum tube according to claim 2, wherein, The brazed joint composition includes B and no more than 0.4 wt% Sn.

18. The high-pressure vacuum tube according to claim 2, wherein, The distance between the first and second components of the brazed joint is no more than 150µm, so that the brazed joint can be formed by capillary action.

19. The high-pressure vacuum tube according to claim 2, further comprising a second brazing joint, wherein, The difference between the solidus temperature of the first brazed joint and the liquidus temperature of the second brazed joint is at least +15°C.

20. The high-pressure vacuum tube according to claim 19, wherein, The first brazed joint includes a brazing alloy composition configured to achieve a solidus temperature of at least 950°C, and the second brazed joint composition is configured to achieve a liquidus temperature of no more than 1017°C.

21. The high-pressure vacuum tube according to claim 2, wherein, The first brazed joint includes components configured to include a solidification temperature range not exceeding 50°C.

22. A method for producing the high-pressure vacuum tube according to claim 2, wherein, The brazing assembly is formed from the first component; the second component and the brazing alloy composition, comprising a total of no more than 18.0 wt% of one or more noble metals selected from Au, Pd, and Pt, and configured to include a solidification temperature range of no more than 90°C and a liquidus temperature of 950°C to 1060°C, wherein the brazing assembly is formed by the following steps: a. Optionally, the brazed assembly may be held at a temperature between 10°C and 400°C below the liquidus temperature of the brazing alloy composition for at least 10 minutes; b. Heating the brazing assembly to a brazing temperature higher than the liquidus temperature of the brazing alloy composition; and c. Cool the brazing assembly below the solidus temperature of the brazing alloy composition to form a brazed joint that connects the first component and the second component together.

23. The method of claim 22, further comprising increasing the brazing temperature between the solidus and liquidus temperatures at a rate of 1°C / min to 30°C / min between the solidus and liquidus temperatures of the brazing alloy.

24. The method of claim 22, further comprising a distance between the first component and the second component, the distance being in the range of 10 µm to no more than 150 µm, such that the brazed joint can be formed by capillary action.

25. The method according to claim 22, wherein, The brazing assembly is heated inside a brazing furnace.

26. The method of claim 22, further comprising heating a first brazing alloy component to a first brazing temperature and allowing cooling to form a first brazed joint, and then heating a second brazing alloy component to a second brazing temperature and allowing cooling to form a second brazed joint, wherein, The first brazing alloy composition and the second brazing alloy composition are configured such that the solidus temperature of the first brazed joint is higher than the liquidus temperature of the second brazed joint, wherein the second brazing temperature is maintained below the solidus temperature of the first brazed joint.

27. The method according to claim 26, wherein, The second brazing temperature is maintained at at least 10°C below the solidus temperature of the first brazed joint.

28. The method according to claim 22, wherein, The brazing joint is formed by placing the brazing alloy component in the form of wire, powder, slurry, or foil near the first and second components to be joined, heating the brazing alloy component to above its liquidus temperature, and allowing the molten brazing alloy to flow between the first and second components via capillary action.

29. The method according to claim 22, wherein, The solidification temperature range of the brazing alloy composition does not exceed 50°C.

30. The method according to claim 22, wherein, The vapor pressure of the brazing alloy composition at 500°C is less than 1 x 10⁻⁶. -11 mm Hg (1.33 x 10) -9 Pa).

31. The method according to claim 22, wherein, The first component is the vacuum tube housing, and the second component is part of the anode assembly or the cathode assembly.

32. The method according to claim 22, wherein, The second component is part of the rotating anode assembly.

33. The method according to claim 22, wherein, The brazing alloy composition includes at least 80 wt% copper.

34. The method according to claim 22, wherein, The brazing alloy composition includes copper and no more than 8.0 wt% germanium.

35. The method according to claim 34, wherein, The brazing alloy composition also includes one or more elements selected from the group consisting of transition metals and rare earth metals.

36. The method according to claim 34, wherein, The brazing alloy composition also includes one or more of Pt, Pd, Au, and boron.

37. The method according to claim 22, wherein, The brazing alloy composition includes Au.

38. The method according to claim 22, wherein, The brazing alloy does not contain B.

39. The method according to claim 22, wherein, The sum of Cu, Ge, and Au in the brazing alloy composition is greater than 99 wt% of the total brazing alloy composition.

40. The method according to claim 22, wherein, The brazing alloy composition includes Cu, Ge and at least 0.5 wt% Au+Pd+Pt, and the sum of Cu, Ge and (Pt+Pd+Au) is greater than 90 wt% of the total weight of the brazed joint.

41. The method according to claim 22, wherein, The brazing alloy composition comprises, in wt% relative to the total weight of the brazed joint, the following: 60 ≤ Cu ≤ 95; 0.5 ≤ Ge ≤ 9.5; 0 ≤ the sum of one or more of Cr, In, Sn, Si, and Al ≤ 5.0; 0 ≤ B ≤ 1.25； 0 ≤ the sum of one or more of Au, Pd, and Pt < 18.0; and Impurities are present.

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