Ceramic sealing part and method of manufacturing the same

Abstract

The ceramic sealing part according to the embodiment is a ceramic sealing part in which a ceramic part and a nickel-plated metal part are bonded by a bonding layer comprising silver, copper, an active metal, and a low-melting point metal, wherein a compound of nickel and an active metal is formed in the bonding layer and the distance between the compound and the surface of the bonding layer is 10 μm or more. In addition, the method for manufacturing the ceramic sealing part according to the embodiment comprises a process of obtaining an active metal paste printed part by printing and drying an active metal paste containing at least copper, an active metal, and a low-melting point metal on a ceramic part, a process of obtaining a solder paste printed part by printing and drying a solder paste containing at least silver and copper on the surface of the active metal paste printed part, and a bonding process of installing a metal part on the solder paste printed part and heat treating it.

Description

Technology Field

[0001] An embodiment relates to a ceramic sealing part (hereinafter referred to as a ceramic sealing part) in which a ceramic part and a metal part used in power pipes, etc. are joined. Background Technology

[0002] As ceramic sealing components for magnetrons, power tubes, and electron tubes, ceramic sealing components are used in which a metallized layer, mainly composed of a high-melting-point metal such as molybdenum (Mo), is formed on a ceramic component such as alumina (aluminum oxide: Al2O3). By joining ceramics and metals to block external air and hermetically sealing the inside of the component, the ceramic sealing component can protect the interior from the external environment and provide electrical insulation through the ceramics. In the ceramic sealing component, a metallized layer mainly composed of molybdenum is formed on two ring-shaped bottom surfaces (first bottom surface and second bottom surface) that are the joints of a cylindrical ceramic component containing an alumina sintered body. On the surface of this metallized layer, a nickel (Ni) layer of a predetermined thickness is formed to improve the bonding strength with the cylindrical metal component to be joined to the ceramic sealing component and to perform the sealing. This nickel layer and the cylindrical metal part are joined by silver solder (e.g., BAg-8).

[0003] An electron tube having a vacuum sealing structure is disclosed in which a metal surface made of molybdenum is formed at the joint of a cylindrical ceramic as a ceramic sealing component, and a cylindrical iron metal is joined through a solder (Patent Document 1). According to Patent Document 1, a low-cost electron tube can be manufactured by changing the metal component joined to the ceramic from kovar to iron.

[0004] In addition, a vacuum switch exterior is disclosed in which a nickel-based alloy is bonded to ceramics by an active metal without using high-melting-point metals such as molybdenum (Patent Document 2). According to Patent Document 2, a vacuum switch exterior with high bonding strength can be manufactured without forming intermetallic compounds that cause instability in the bonding state. In addition, a bonded body using stainless steel that does not contain nickel is disclosed (Patent Document 3). According to Patent Document 3, since no compounds are formed between the active metal and nickel, airtightness and bonding strength can be maintained. Prior art literature

[0005] Japanese Patent Application No. Hei 1-46978 Publication Japanese Patent Publication No. 2001-220253 Publication International Publication No. 2023 / 063396 The problem to be solved

[0006] When metallizing the surface of ceramics using high-melting-point metals such as molybdenum, a furnace is required to heat to a high temperature of 1400°C or higher, and energy costs are incurred because the processing is performed at high temperatures. In addition, it is difficult to solder the formed metallized layer of the high-melting-point metal directly to metal parts, and the process is complex because it is necessary to perform plating treatment with nickel or the like on the surface.

[0007] In contrast, bonding using active metal solder has an advantage in terms of energy costs as the heating temperature is 1000°C or lower. However, when nickel plating is applied to metal parts to improve corrosion resistance and wettability, nickel and the active metal form a compound, which lowers the bonding strength and causes leakage defects.

[0008] The embodiment solves these problems and relates to a high-productivity ceramic sealing part and a method for manufacturing the same, which suppresses bonding defects or leakage defects when a ceramic part and a metal part are bonded with an active metal solder. means of solving the problem

[0009] The ceramic sealing part according to the embodiment is a ceramic sealing part in which a ceramic part and a nickel-plated metal part are bonded by a bonding layer comprising silver, copper, an active metal, and a low-melting point metal, wherein a compound of nickel and an active metal is formed in the bonding layer and the distance between the compound and the surface of the bonding layer is 10 μm or more. Brief explanation of the drawing

[0010] FIG. 1 is a perspective view illustrating an example of a ceramic sealing part according to an embodiment. FIG. 2 is a cross-sectional view illustrating an example of a ceramic sealing part according to an embodiment. FIG. 3 is a drawing illustrating an example of a cross-section of a joint of a ceramic sealing part according to an embodiment. FIG. 4 is a drawing illustrating an example of an enlarged cross-sectional view of a joint of a ceramic sealing part according to an embodiment. FIG. 5 is a drawing illustrating an example of the mass % of the cross-section of the joint of a ceramic sealing part according to an embodiment. FIG. 6 is a cross-sectional view illustrating an example of a manufacturing process for a ceramic sealing part according to an embodiment. FIG. 7 is a drawing illustrating an example of a heating profile of a ceramic sealing part according to an embodiment. Specific details for implementing the invention

[0011] The ceramic sealing part according to the embodiment is a ceramic sealing part in which a ceramic part and a nickel-plated metal part are bonded by a bonding layer comprising silver, copper, an active metal, and a low-melting point metal, wherein a compound of nickel and an active metal is formed in the bonding layer and the distance between the compound and the surface of the bonding layer is 10 μm or more.

[0012] FIG. 1 illustrates an example of a perspective view of a ceramic sealing part (1) according to an embodiment. Reference numeral 3 denotes a cylindrical ceramic part, and reference numeral 2 denotes a cylindrical metal part. The metal part (2) is joined through two ring-shaped bottom surfaces (first bottom surface and second bottom surface) that are joints of the ceramic part (3). FIG. 1 shows an example in which the metal part (2) is joined to the first bottom surface (e.g., upper end surface) and the second bottom surface (e.g., lower end surface) of the ceramic part (3). The embodiments are not limited to these forms, and may include a form in which a metal part is bonded to a ceramic part in the shape of a cylinder, a form in which a metal part is bonded only to a metal part on one bottom surface (e.g., lower bottom surface) without a metal part, or a form in which a metal part is bonded to a ceramic part having two or more openings on one bottom surface (e.g., upper bottom surface).

[0013] FIG. 2 shows an example of a cross-sectional view (a drawing showing a cross-section along a central axis perpendicular to the bottom surface) of a ceramic sealing part (1) according to an embodiment. The ceramic sealing part (1) according to an embodiment comprises, for example, a ceramic part (3) including a cylindrical alumina and a metal part (2) bonded thereto. In addition, for example, the metal part (2) is a metal part that has been nickel-plated on iron (Fe) or covar (Fe-Ni-Co). There is a bonding layer (4) (shown in FIG. 3) between the ceramic part (3) and the metal part (2), and the sealing (airtightness) between the inside and outside of the part is maintained.

[0014] The ceramic component (3) preferably comprises one of alumina, aluminum nitride, silicon nitride, or zirconia-added alumina (alzil). The alumina includes alumina-based ceramics in which other ceramics are added to the alumina. For example, zirconia-added alumina is a sintered body formed by mixing alumina and zirconium oxide. Additionally, a sintering aid other than zirconia may be added to the alumina. This is to densify the alumina sintered body by forming a grain boundary phase containing a glass phase with the added sintering aid. Examples of sintering aids include compounds such as manganese (Mn), silicon (Si), magnesium (Mg), and calcium (Ca), and it is preferable to add at least one of these in a total amount of 1 mass% or more and 15 mass% or less when converted to individual metal elements. Additionally, the ceramic component (3) is preferably alumina that offers good cost-effectiveness as an insulating sealing component.

[0015] The material of the metal part (2) joined to the ceramic part (3) is preferably iron (Fe) and iron alloy, iron-nickel alloy, copper (Cu) and copper alloy, tungsten (W), and molybdenum (Mo). The iron alloy is an alloy steel such as carbon steel, chrome steel, and stainless steel. Examples of iron-nickel alloys include 42 alloy (Ni 42 mass%, Mn 0.8 mass% or less, remainder Fe) and Covar (Ni 29 mass%, Co 17 mass%, remainder Fe). Iron and iron alloys have excellent cost-effectiveness, and iron-nickel alloys have excellent physical properties such as the coefficient of thermal expansion. Additionally, copper and copper alloys are prone to deformation to relieve stress caused by the difference in thermal expansion, and it is preferable to form the metal part using copper and copper alloys when the influence of heat is significant. Copper alloys include pure copper such as oxygen-free copper, tough pitch copper, and deoxidized copper, as well as copper alloys such as beryllium copper and titanium copper. For this reason, depending on the application, it is preferable to use iron and iron alloys, iron-nickel alloys, and copper and copper alloys as metal parts (2). In addition, it is possible to join two or more types of metal parts (2) to a ceramic part (3), such as making one metal part (2) of Covar and the other metal part (2) of copper. In addition, the metal part (2) is manufactured by processing it into a predetermined shape through press processing, cutting processing, and bending processing. After processing the metal part (2) into a part shape, nickel plating is performed to improve corrosion resistance and wettability. In addition, when a metal part (2) containing copper and a copper alloy and another metal part (2) that has been nickel-plated are simultaneously bonded to a ceramic part (3), the metal part (2) containing copper and a copper alloy is easily wetted with lead components even without nickel plating, so nickel plating is not required.

[0016] The thickness of the nickel plating applied to the metal part (2) is 0.5㎛ or more and 3.0㎛ or less. If the thickness of the nickel plating is less than 0.5㎛, wetting with the solder material is poor, and there is a possibility that areas where the solder is not wetted (solder breakage) may occur, which cause a decrease in bonding strength or leakage defects. Even if the thickness of the nickel plating exceeds 3.0㎛, further improvement in wettability cannot be obtained. In addition, this is because the nickel plating is too thick, causing excess nickel to form a compound with the active metal.

[0017] FIG. 3 shows an example of a cross-sectional view of a joint portion of a ceramic sealing part (1) according to an embodiment which is an enlarged view of part A of FIG. 2. Reference numeral 1 is a ceramic sealing part, reference numeral 2 is a metal part, reference numeral 3 is a ceramic part, and reference numeral 4 is a joint layer. The joint layer (4) on the side of the ceramic part (3) is formed of lead metals such as copper (Cu) and silver (Ag), active metals such as titanium (Ti), zirconium (Zr), and hafnium (Hf), and low-melting point metals such as indium (In), tin (Sn), bismuth (Bi), antimony (Sb), and zinc (Zn).

[0018] The bonding layer (4) is an active metal solder layer containing an active metal solder material, and includes a solder metal (silver and copper), an active metal, and a low-melting-point metal. Copper and silver, used as the solder metal of the bonding layer (4), have relatively low melting points as metals and are easy to melt at temperatures suitable for soldering. Furthermore, if copper and silver are alloyed, the melting point becomes even lower. Since the melting point of the alloyed copper and silver is lower than the melting point of the metal part (2) used for soldering, there is an advantage that the metal part (2) can be bonded without melting. In addition, copper and silver have excellent fluidity and permeability required for soldering and are easy to penetrate between parts using capillary action. Furthermore, copper and silver contribute to the strength and durability of the bonded part after soldering. Since copper and silver make it difficult for stress to occur between the ceramic part (3) and the metal part (2) when cooling after soldering, cracks or deformation are unlikely to occur in the bonded part. In addition, it has excellent thermal and electrical conductivity, and is unlikely to affect the functionality of the joint after soldering.

[0019] The active metal of the bonding layer (4) reacts with ceramics that have poor wettability with metals, thereby lowering the interfacial energy and improving wettability. When wettability improves, the solder material becomes easier to penetrate into the gaps of the parts, and the bonding strength is improved. In addition, the active metal forms metallic bonds between the atoms of the base material and the solder material, thereby creating a solid solution at the bonding interface, which contributes to the strength and durability of the bond. The active metal is prone to reacting with nickel to form a nickel-active metal compound. For this reason, the nickel contained in the metal part (2) or the nickel plating formed on the surface of the metal part (2) reacts with the active metal to form a nickel-active metal compound. Since this nickel-active metal compound is prone to becoming embrittled by reacting with an external atmosphere such as hydrogen, there is a possibility of causing a decrease in bonding strength or leakage failure.

[0020] The low-melting point metal of the bonding layer (4) has a lower melting point than other elements included in the bonding layer (4). The melting points of the low-melting point metals are indium (157°C), tin (232°C), bismuth (271°C), antimony (630°C), and zinc (419°C). Their melting points are lower than those of other metals included in the bonding layer, such as silver (961°C), copper (1085°C), titanium (1666°C), zirconium (1852°C), and hafnium (2233°C). For this reason, the low-melting point metal has the characteristic of diffusing faster than other metals when subjected to heat treatment. By diffusing faster than nickel or active metals, the added low-melting point metal reacts with copper or silver to form a bonding layer, preventing nickel-active metal compounds from precipitating up to the surface of the bonding layer. Additionally, the low-melting point metal is added to the active metal solder paste. This is because when added to a lead paste containing silver and copper, the melting point of the silver and copper alloy is lowered, causing it to melt and solidify first.

[0021] The proportion of low-melting point metal is 5 mass% or more and 15 mass% or less. If the amount of low-melting point metal is less than 5 mass%, diffusion into the solder layer is insufficient, and the effect of preventing nickel-active metal compounds from precipitating on the outermost surface of the bonding layer cannot be obtained. Conversely, if the proportion of low-melting point metal is greater than 15 mass%, the proportion of silver or copper, which are the main components of the solder, decreases, and there is a possibility that the function of the bonding layer, such as mechanical properties, may deteriorate.

[0022] FIG. 4 shows an example of a cross-sectional view of a joint portion of a ceramic sealing part (1) according to an embodiment which is an enlarged view of part B of FIG. 3. Reference numeral 5 is an active metal layer mainly composed of an active metal among the bonding layer (4). The active metal layer (5) exists on the surface of the ceramic part (3) and contributes to the bonding of the ceramic part (3) and the metal part (2). Reference numeral 6 is a solder layer (hereinafter referred to as the "solder layer") among the bonding layer (4) comprising a solder metal (silver and copper) and a low-melting point metal. The solder layer (6) exists between the active metal layer (5) and the metal part (2) near the end surface of the metal part (2) and contributes to the bonding of the active metal layer (5) and the metal part (2). In addition, the solder layer (6) forms a meniscus at a location on the side of the metal part (2) to improve bonding strength. For this reason, the solder layer (6) forming the meniscus forms an outermost surface (hereinafter referred to as the “solder layer outermost surface”) (61) that is in contact with the external atmosphere. The solder layer outermost surface (61) includes solder metal (silver and copper) and a low-melting point metal. This is because, as described in the manufacturing method below, the low-melting point metal contained in the active metal solder paste printed on the side of the ceramic part (3) is heat-treated and diffuses to the solder layer outermost surface (61). Reference numeral 7 is a nickel-active metal compound (three examples in FIG. 4) among the bonding layer (4). As described in the manufacturing method below, the active metal contained in the active metal solder paste printed on the side of the ceramic part (3) reacts with the nickel plating layer formed on the surface of the metal part (2) to form a nickel-active metal compound (hereinafter referred to as the “nickel-active metal compound”) with nickel and the active metal as main components. The nickel-active metal compound (7) contains at least 50 mass% of nickel and an active metal. The nickel-active metal compound (7) may contain lead metals (silver and copper) or low-melting point metals.As described above, since the diffusion rate of the added low-melting point metal is fast and it reaches the outermost surface (61) of the lead layer first, the nickel-active metal compound (7) is located inside the outermost surface (61) of the lead layer.

[0023] The distance L between the outermost surface (61) of the lead layer and the nickel-active metal compound (7) is 10 μm or more. If the distance L is less than 10 μm, the nickel-active metal compound (7) may react with an external atmosphere such as oxygen or hydrogen and become embrittled, which may reduce airtightness or bonding strength.

[0024] The method for measuring the distance L between the outermost surface of the lead layer (61) and the nickel-active metal compound (7) is obtained by observing the cross-section of the joint. Simply put, the distance is determined based on the distribution of elements. The cross-section of the joint portion, as shown in FIG. 4, is color-mapped for nickel and active metal using an energy-dispersive fluorescence X-ray analyzer (EDX). Since the overlapping portion of nickel and active metal can be considered as the nickel-active metal compound (7), the distance L between the outermost surface of the lead layer (61) and the nickel-active metal compound (7) can be measured.

[0025] If the boundary of the nickel-active metal compound (7) is unclear, it can be measured by performing mass analysis by X-ray across the boundary. FIG. 5(a) is a schematic diagram showing the mass percentage of constituent elements when measuring a distance L from the D1 direction with respect to part C of FIG. 4. The mass percentage is measured for the constituent elements by an energy dispersive fluorescence X-ray analyzer (EDX). It shows the distribution of the mass percentage of the lead metal (silver and copper), active metal, low-melting point metal, and nickel constituting the lead layer (6) from the outer side (part exposed to an atmosphere such as air or gas of the ceramic metal circuit component) to the inner side (inside the bonding layer). The minimum value (zero) of the mass percentage is the part where the observed element does not exist, and the mass percentage increases as the observed element is present. The location where any metal element exceeds 2 mass% is designated as the outermost surface position L1. FIG. 5(b) is an enlarged view of part D of FIG. 5(a). Additionally, position L2, which is the boundary between the lead layer (6) and the nickel-active metal compound (7), is a location where the nickel content is 20 mass% or more. Accordingly, the distance L is the distance between position L1 and position L2.

[0026] FIG. 6 shows a process diagram of a method for manufacturing a ceramic sealing part according to an embodiment. FIG. 6 (a) is a cross-sectional view of a ceramic part (3). In FIG. 6 (a), chamfers are formed on the outer and inner peripheries of the ceramic part (3). Although it is possible to obtain a ceramic sealing part (1) without chamfers, ceramics are prone to breakage due to external impacts, etc., so chamfering is effective for preventing breakage.

[0027] FIG. 6(b) shows the state of an active metal paste printed part in which an active metal solder paste (8) is printed and dried on a ceramic part (3). Since the paste is printed on the end surface of the flat ceramic part (3), the surface of the active metal solder paste (8) before bonding is approximately flat. In addition, while FIG. 6(b) shows the active metal solder paste (8) printed only on the flat end portion, it is also possible to print the active metal solder paste (8) up to the chamfered portion.

[0028] The active metal solder paste (8) is prepared by adding an organic binder and an organic solvent to a metal powder mixed with one or more types of solder metals such as copper and silver, one or more types of active metals such as titanium, zirconium, and hafnium, and one or more types of low-melting point metals such as indium, tin, bismuth, antimony, and zinc. The organic binder is not particularly limited as long as it is lost during the drying process or bonding process. A preferred example of an organic binder is ethyl cellulose. The organic solvent is not particularly limited as long as it is lost during the drying process or bonding process. A preferred example of an organic solvent is terpineol or butyl carbitol. The active metal solder paste (8) is prepared by mixing the active metal powder and the solder metal powder, and then mixing them with an organic binder and an organic solvent. In addition, the proportion of active metal included in the active metal lead component is 0.1 mass% or more and 15 mass% or less, preferably 0.5 mass% or more and 10 mass% or less.

[0029] It is preferable that the printing thickness of the active metal solder paste (8) be 10㎛ or more and 30㎛ or less. If the printing thickness is less than 10㎛, there will be a variation in the thickness of the active metal solder layer, which lowers the bonding strength. On the other hand, if it exceeds 30㎛, no further effect can be obtained. In addition, the paste is printed with a uniform thickness on the end surface of the ceramic part by a screen printing method, etc. If the printing thickness is uneven, the active metal solder will be excessive in the thicker parts, causing solder pooling and cracking due to thermal stress. In addition, leakage defects will occur in the thinner parts due to solder breakage. For this reason, it is preferable that the difference between the thicker and thinner parts of the printing thickness be 5㎛ or less.

[0030] FIG. 6(c) is the state of a dried solder paste printed part, in which a solder paste (9) is printed on the surface of the dried active metal solder paste (8) of FIG. 6(b). The solder paste (9) consists of a metal part (2), an active metal solder, and a metal with good wettability. Silver solder is a solder material widely used for joining ceramic parts (3) and metal parts (2). Silver solder consists mainly of silver and copper, but may also contain other metal components such as zinc or nickel. There is silver solder (BAg-8) composed of 72% silver and 28% copper, which is frequently used when joining ceramic parts (3) and metal parts (2). In BAg-8 according to "Silver Solder (JIS Z3261:1998)," silver (Ag) is 71% or more and 73% or less, copper (Cu) is 27% or more and 29% or less, and the total of other elements is 0.15% or less. The lead paste (9) is prepared by adding an organic binder and an organic solvent to a mixture of lead metal powder. The organic binder is not particularly limited as long as it is lost during the drying process or bonding process. Ethyl cellulose is a preferred example of an organic binder. The organic solvent is not particularly limited as long as it is lost during the drying process or bonding process. Terpineol or butyl carbitol is a preferred example of an organic solvent. The lead paste is prepared by, for example, crushing and mixing metal powder, and then mixing it with an organic binder and an organic solvent.

[0031] The printing thickness of the solder paste (9) is preferably 70㎛ or more and 300㎛ or less. If the printing thickness is less than 70㎛, there will be a variation in the thickness of the solder layer, which lowers the bonding strength. On the other hand, if it exceeds 300㎛, no further effect can be obtained. In addition, the paste is printed with a uniform thickness on the end surface of the ceramic part by a screen printing method or the like. If the printing thickness is uneven, the active metal solder will be excessive in the thicker parts, causing solder pooling and cracking due to thermal stress. In addition, leakage defects will occur in the thinner parts due to solder breakage. Therefore, it is preferable that the difference in printing thickness between the thicker parts and the thinner parts be 20㎛ or less.

[0032] Since the active metal solder paste (8) contains an active metal that reacts with nickel to form a compound that is prone to embrittlement, it is desirable that the solder paste (9) cover the entire surface of the active metal solder after bonding. When printing with the same printing pattern as the active metal solder paste (8), it is possible to spread and cover the entire surface during printing by making the viscosity of the solder paste (9) lower than that of the active metal solder paste (8). Additionally, it is possible to print to cover the entire surface of the active metal solder layer by making the printing pattern of the solder paste (9) larger (wider) than the printing pattern of the active metal solder paste (8). If the printing pattern is too large, the solder paste (9) does not react with the ceramic part (3) during heat treatment and accumulates on the active metal solder layer or metal part (2). At this time, if it exists as a lump around the active metal solder layer or metal part, it causes stress concentration. For this reason, when making the printing pattern of the solder paste (9) larger, it is preferable to make it larger in the range of 0.1 mm or less than the printing pattern of the active metal solder paste (8).

[0033] Figure 6 (d) shows a state in which a metal part (2) is installed on the surface of the printed and dried solder paste (9) of the solder paste printed part. When multiple metal parts (2) are joined as in Figure 2, multiple metal parts (2) are installed simultaneously. The metal parts (2) are joined by heat treatment in the installed state.

[0034] It is preferable to perform the heat treatment profile in two stages: a first heating temperature and a second heating temperature higher than the first heating temperature. FIG. 7 is a diagram illustrating an example of a heat treatment profile, where the vertical axis represents temperature and the horizontal axis represents time. The first heating temperature T1 is set to a temperature higher than the melting point of the low-melting-point metal because the low-melting-point metal needs to be melted. In addition, the holding time of the first heating temperature T1 is preferably 10 to 30 minutes so that the low-melting-point metal diffuses throughout the bonding layer. If the holding time is shorter than 10 minutes, the low-melting-point metal does not diffuse throughout, and the effect of preventing the nickel-active metal compound from precipitating on the outermost surface of the bonding layer is lost. Furthermore, even if the holding time is extended beyond 30 minutes, no further effect can be obtained.

[0035] In addition, the difference between the first heating temperature T1 and the second heating temperature T2 (T2-T1) is 120°C or less. Since the second heating temperature T2 is heated in a state where the low-melting point metal has diffused due to the first heating temperature T1, the melting temperature of the solder paste is lower than usual. For this reason, if the difference between the first heating temperature T1 and the second heating temperature T2 (T2-T1) is greater than 120°C and the second heating temperature T2 is high, the solder paste spreads on the surface of the metal part (2) and a meniscus is not formed, and if a meniscus is not formed, there is a possibility that the bonding strength of the metal part (2) will decrease. In addition, the holding time of the second heating temperature T2 is 1 to 10 minutes to melt the solder. If the holding time is shorter than 1 minute, sufficient heating to melt the solder cannot be obtained. In addition, if it is extended beyond 10 minutes, no further effect can be obtained.

[0036] Figure 6 (e) shows the state in which the metal part (2) is joined. The bonding layer (4) climbs up the side of the metal part (2) to form a strong bond. In this way, by the bonding layer (4) covering the side of the metal part (2), the bonding strength is increased, making it possible to achieve a seal without leakage inside or outside the part.

[0037] Next, a method for manufacturing a ceramic sealing part (1) according to an embodiment will be described. If the ceramic sealing part (1) has the configuration described above, the method of manufacturing it is not particularly limited, but the following may be cited as a method for obtaining it with a high yield.

[0038] An example of a ceramic part (3) according to the embodiment is a cylindrical shape, for example, with an outer diameter of 50 mm, an inner diameter of 38 mm, and a height of 50 mm. The ceramic part (3) is prone to defects or cracks occurring in the corners due to external impacts, etc. For this reason, it is desirable to perform chamfering on the outer and inner peripheries of the end surface. The shape of the chamfer is, for example, a C chamfer or an R chamfer, and the size of the chamfer is preferably 0.1 mm or more and 2 mm or less.

[0039] The material of the metal part (2) according to the embodiment may include iron and iron alloy, copper and copper alloy, iron-nickel alloy, tungsten, molybdenum, etc. An example of the shape of the metal part (2) according to the embodiment is approximately cylindrical. For example, in FIG. 2, the height is 20 mm, the outer diameter is 46 mm, and the inner diameter is 44 mm. These metal parts (2) are nickel-plated with a thickness of 0.5 μm or more and 3.0 μm or less to improve corrosion resistance and wettability.

[0040] Active metal solder is available in the form of a paste. Sheets or wires require a process to melt the active metal solder, process it into a sheet or wire shape, and then machine it to specific dimensions to match the product shape. In contrast, while the paste requires a manufacturing process, it offers superior handling, such as printing at required locations to match the product shape. Furthermore, since too little active metal solder can cause solder breaks at unbonded areas, and too much can lead to solder pooling and stress failure, it is possible to adjust the amount of paste used according to the bonding area.

[0041] The active metal solder paste (8) is prepared by adding an organic binder and an organic solvent to a mixture of active metal powder and solder metal powder. The organic binder is not particularly limited as long as it is lost during the drying process or bonding process. Ethyl cellulose can be cited as a preferred example of an organic binder. The organic solvent is not particularly limited as long as it is lost during the drying process or bonding process. Terpineol or butyl carbitol can be cited as preferred examples of organic solvents. The active metal solder paste is prepared, for example, by crushing and mixing the active metal powder and the solder metal powder, and then mixing them with an organic binder and an organic solvent. In addition, the proportion of the active metal included in the active metal solder component is 0.1 mass% or more and 15 mass% or less, preferably 0.5 mass% or more and 10 mass% or less.

[0042] It is preferable that the printing thickness of the active metal solder paste (8) be 10㎛ or more and 30㎛ or less. If the printing thickness is less than 10㎛, there will be a variation in the thickness of the active metal solder layer, which lowers the bonding strength. On the other hand, if it exceeds 30㎛, no further effect can be obtained. In addition, the paste is printed with a uniform thickness on the end surface of the ceramic part (3) by a screen printing method or the like. If the printing thickness is uneven, the active metal solder becomes excessive in the thicker parts, causing solder pooling and cracking due to thermal stress. In addition, in the thinner parts, leakage failure occurs due to the breakage of the active metal solder. Therefore, it is preferable that the difference in printing thickness between the thicker parts and the thinner parts be 5㎛ or less.

[0043] The paste printed on the ceramic part (3) is dried in the atmosphere, etc. If the drying temperature is low and the drying time is short, the solution components of the paste do not volatilize sufficiently, and there is a possibility that the remaining solution will volatilize during bonding and voids will occur. Conversely, if the drying temperature is high and the drying time is long, oxidation of the surface of the paste will proceed, and there is a possibility that the bonding temperature will change. For this reason, the drying temperature is 50°C or higher and 100°C or lower, preferably 60°C or higher and 80°C or lower. In addition, the drying time is 5 to 30 minutes, preferably 10 to 20 minutes.

[0044] The solder paste (9) consists of a metal part (2), an active metal solder, and a metal with good wettability. Silver solder is a solder widely used for joining ceramic parts (3) and metal parts (2). Silver solder consists mainly of silver and copper, but may also contain other metal components such as zinc or nickel. There is silver solder (BAg-8) composed of 72% silver and 28% copper that is frequently used when joining ceramic parts (3) and metal parts (2). In BAg-8 according to "Silver Solder (JIS Z3261:1998)," silver (Ag) is 71% or more and 73% or less, copper (Cu) is 27% or more and 29% or less, and the total of other elements is 0.15% or less. The solder paste (9) is made by adding an organic binder and an organic solvent to a mixture of solder metal powder. The organic binder is not particularly limited as long as it is lost during the drying or bonding process. A preferred example of an organic binder is ethyl cellulose. The organic solvent is not particularly limited as long as it is lost during the drying or bonding process. Preferred examples of organic solvents are terpineol or butyl carbitol. The solder paste is prepared, for example, by crushing and mixing metal powder, and then mixing it with an organic binder and an organic solvent.

[0045] It is preferable that the printing thickness of the solder paste (9) be 70㎛ or more and 300㎛ or less. If the printing thickness is less than 70㎛, there will be a variation in the thickness of the solder layer, which lowers the bonding strength. On the other hand, if it exceeds 300㎛, no further effect can be obtained. In addition, the paste is printed with a uniform thickness on the end surface of the ceramic part (3) by a screen printing method or the like. If the printing thickness is uneven, the solder will be excessive in the thicker parts, causing solder pooling and cracking due to thermal stress. In addition, in the thinner parts, leakage defects will occur due to the breakage of the active metal solder. Therefore, it is preferable that the difference in printing thickness between the thicker parts and the thinner parts be 20㎛ or less, and furthermore 15㎛ or less.

[0046] The solder paste (9) printed on the active metal solder layer by the active metal solder paste (8) is dried in the atmosphere, etc. If the drying temperature is low and the drying time is short, the solution components of the paste do not volatilize sufficiently, and there is a possibility that the remaining solution will volatilize during bonding and voids will occur. Conversely, if the drying temperature is high and the drying time is long, oxidation of the surface of the paste will proceed, and there is a possibility that the bonding temperature conditions will change. For this reason, the drying temperature is 50°C or higher and 100°C or lower, preferably 60°C or higher and 80°C or lower. In addition, the drying time is 5 to 30 minutes, preferably 10 to 20 minutes.

[0047] After drying the solder paste (9), a metal part (2) is placed on the dried surface of the paste and heat-treated to perform bonding. The heat treatment profile preferably has a two-stage heating process consisting of a first heating and a second heating at a higher temperature than the first heating. The first heating temperature T1 is 650°C or higher and 850°C or lower, preferably 700°C or higher and 800°C or lower. Additionally, the bonding time of the first heating is preferably in the range of 10 to 30 minutes after reaching the first heating temperature. Furthermore, at the second heating temperature T2 following the first heating, it is preferable that the difference (T2-T1) from the first heating temperature T1 is 120°C or lower. Additionally, the bonding time of the second heating is preferably between 1 and 10 minutes after reaching the second heating temperature T2. As shown in FIG. 6 (e), the bonding layer (4) melts and wets the surface of the metal part (2) to perform the bonding, so a bonding with sealing properties is performed. If the bonding temperature is low and the bonding time is short, the active metal solder may not melt sufficiently and the bonding may not be performed. Conversely, if the bonding temperature is high and the bonding time is long, the solder may melt too much and wet diffuse, causing solder breakage or voids to occur.

[0048] In addition, the bonding atmosphere is performed in a non-oxidizing atmosphere as needed. Examples of non-oxidizing atmospheres include a nitrogen atmosphere and a nitrogen-hydrogen atmosphere. By using a non-oxidizing atmosphere, oxidation of the bonding layer (4) can be suppressed. This improves the bonding strength. A continuous furnace or a batch furnace is used for the bonding process. A continuous furnace is superior in terms of mass production, while a batch furnace is easier to control in terms of temperature and atmosphere. Bonding is performed by heating the parts for a predetermined time in the above atmosphere.

[0049] It is preferable that the thickness of the bonding layer (4) that bonds the ceramic part (3) and the metal part (2) be 80 μm or more. As described above, this is because the bonding layer (4) is formed from an active metal solder paste (8) of 10 μm or more and a solder paste (9) of 70 μm or more. In addition, the thickness of the bonding layer (4) at this time represents the distance between the bonding surface of the metal part (2) and the ceramic part (3). For example, in FIG. 6 (e), the tip (end surface) of the metal part (2) is flat. In this case, the thickness of the bonding layer (4) represents the distance between the flat part of the metal part (2) approximately in the center and the flat part of the ceramic part (3) and the flat part of the metal part (2). In addition, if the tip of the metal part (2) is bent into a flange shape and bonded to the ceramic part (3), the thickness of the bonding layer (4) is the approximately center portion of the bent flange portion. In addition, if the tip of the metal part (2) is pointed, such as in a U-shape or V-shape, the distance between the pointed tip and the ceramic surface is the thickness of the bonding layer (4).

[0050] According to the above, in the method for manufacturing a ceramic sealing part (1) in an embodiment of the present invention, a ceramic sealing part with excellent cost-effectiveness can be obtained while maintaining airtightness performance as a sealing part.

[0051] (Examples 1 to 6, Comparative Examples 1 to 6)

[0052] A granulated powder having a composition of 92 mass% alumina was prepared by adding auxiliaries of manganese oxide (MnO2), silicon dioxide (silica: SiO2), and magnesium oxide (magnesia: MgO) to alumina. The granulated powder was molded using a die press and sintered in air at 1500°C to obtain a cylindrical ceramic part with an outer diameter of 50 mm, an inner diameter of 40 mm, a height of 50 mm, an outer diameter C chamfer of 0.5 mm, and an inner diameter C chamfer of 0.5 mm. Additionally, an aluminum nitride granulated powder was prepared by adding 3 mass% of yttria (yttrium oxide: Y2O3) to aluminum nitride (AlN). The granulated powder was molded using a die press and sintered in nitrogen at 1800°C to obtain a cylindrical ceramic part with the same dimensions as the alumina part.

[0053] The metal parts were obtained by press-forming iron, stainless steel (SUS304), and Covar into a cylindrical shape with an outer diameter of 46 mm, an inner diameter of 44 mm, and a height of 20 mm, as shown in Table 1. In addition, nickel plating with the thickness shown in Table 1 was applied to the surface of the processed metal parts.

[0054] Next, the metal powder mixture was composed of silver powder, copper powder, low-melting point metal powder, and active metal powder in mass% as shown in Fig. 1. In Example 1, the composition was 30 mass% copper powder, 10 mass% indium powder, 2 mass% titanium, and the remainder silver powder. Additionally, in Example 1, it was labeled as "Ag-30Cu-10In-2Ti" in Table 1, and similar labeling was applied to other examples and comparative examples. The combined metal powder was mixed with ethylcellulose and terpineol and formed into a paste using a kneader to produce an active metal solder paste. An active metal paste with a thickness of 30 μm was printed onto the upper and lower ends (ring portions) of a ceramic part by screen printing using a 100-mesh screen with an outer diameter of 48 mm × an inner diameter of 42 mm, and dried in the atmosphere at 100°C. The active metal solder paste was dried.

[0055] Next, silver powder and copper powder were combined in a mass ratio of 72:28 to produce a silver solder paste, which was then pasteurized using the same method as the active metal solder paste. A solder paste with a thickness of 100 μm was printed by screen printing using a 100-mesh screen with an outer diameter of 48 mm × an inner diameter of 42 mm onto the upper and lower ends (ring portions) of the ceramic part having formed an active metal solder layer, and then dried in air at 100°C. Next, the metal part, ceramic part, and metal part were set in a jig in that order, and then in a vacuum (1 × 10⁻⁶) in a vacuum furnace -2 A ceramic sealing part was fabricated by joining a metal part and a ceramic part by heating at a first heating temperature T1 listed in Table 2 for 20 minutes and at a second heating temperature for 5 minutes (below Pa).

[0056]

[0057]

[0058] As can be seen from Tables 1 and 2, in the examples, the values ​​of nickel plating thickness, active metal lead paste ratio, and heating temperature difference (T2-T1) were within the desirable range. On the other hand, in the comparative examples, they were outside the desirable range.

[0059] Next, the ceramic sealing part was cut at the central portion as shown in FIG. 2, and the bonding site was polished as shown in FIG. 3. Next, the surface analysis of the constituent elements was performed on the surrounding portion of the bonding site using an energy dispersive fluorescence X-ray analyzer (EDX). Based on the surface analysis, the position of D1 in FIG. 4 was determined, and mass % analysis was performed. From the mass % analysis value, the bonding distance L as shown in FIG. 5 was calculated. The obtained results are shown in Table 3.

[0060] Next, a hydrogen heating test was performed to check for brittleness from an external atmosphere. For the hydrogen heating test, the heating treatment was performed by heating the ceramic bonded part five times, with one heating treatment being at 400°C or higher for 10 minutes in a nitrogen-hydrogen atmosphere of 20% hydrogen in a belt heating furnace. By visually observing the bonded part after the heating treatment, a result with no change in surface color (discoloration) was passed (○), and a result with discoloration (including partial discoloration such as spots) was rejected (×).

[0061] Next, the bonding strength was determined by tensile testing the upper and lower metal parts of the ceramic bonded part after hydrogen heat treatment using an Instron tensile testing machine.

[0062] In addition, a helium leak test was performed by applying silicone to the upper part of the ceramic sealing part after hydrogen heat treatment using a circular jig made of Viton rubber, pressing it down, fixing the lower part to a helium leak detector, and suctioning it. The helium leak test was conducted in accordance with the vacuum spray method (spray method) of the "Helium Leak Test Method" (JIS Z2331:2006), and at a vacuum level of 1.3 μPa, 1 × 10⁻⁶ -9 It was determined that no leakage of Pa·㎥ / s or more passed (○), and that leakage failed (×).

[0063]

[0064] As can be seen from Table 3, regarding the bonding distance L, in the examples, it was a desirable range of 10 μm or more. This is because, under the bonding conditions of the examples, the nickel-active metal compound is prevented from precipitating on the surface of the bonding layer due to the diffusion of the low-melting-point metal, etc. On the other hand, in the comparative examples, it was outside the desirable range. This was because a barrier to prevent the precipitation of the nickel-active metal compound was not formed.

[0065] In addition, as can be seen in Table 3, regarding the hydrogen heating test, no discoloration was observed in the examples. This is because hydrogen embrittlement did not occur since a sufficient bonding distance L was obtained. On the other hand, discoloration was observed in the comparative examples. This is because hydrogen embrittlement occurred since a sufficient bonding distance L was not obtained.

[0066] In addition, as can be seen in Table 3, the bonding strength of the example was a good value of 40 MPa or higher. This is because, under the bonding conditions of the example, a strong bonding layer was formed, and it did not become embrittled even during the hydrogen heating test. In contrast, the comparative example was 25 MPa or lower. This is because embrittlement progressed during the hydrogen heating test, leading to a decrease in bonding strength.

[0067] Furthermore, the ceramic sealing component according to the embodiment did not exhibit leakage failure in the helium leakage test. This is because it did not undergo embrittlement even in the hydrogen heating test. In contrast, leakage failure occurred in the comparative example. This is because embrittlement progressed during the hydrogen heating test, which resulted in a decrease in bonding strength and an inability to maintain airtightness.

[0068] As is evident from the results shown above, the example was confirmed to have improved resistance to external atmosphere compared to the comparative example.

[0069] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments may be implemented in various other forms, and various omissions, substitutions, and modifications may be made without departing from the essence of the invention. These embodiments and variations thereof are included within the scope of the invention and the scope of the claims and the scope of equivalents thereof. Furthermore, each of the aforementioned embodiments may be implemented in combination with one another.

Claims

Claim 1 A ceramic sealing part comprising a ceramic part and a nickel-plated metal part joined by a bonding layer comprising silver, copper, an active metal, and a low-melting point metal, wherein a compound of nickel and the active metal is formed in the bonding layer, and the distance between the compound and the outermost surface of a solder layer in contact with an external atmosphere is 10 μm or more. Claim 2 A ceramic sealing part according to claim 1, characterized in that the active metal is one or more metals selected from titanium, zirconium, and hafnium, and the low melting point metal is one or more metals selected from indium, tin, bismuth, antimony, and zinc. Claim 3 A ceramic sealing part according to claim 1 or 2, characterized in that the metal part is one or more metal parts selected from iron, iron alloy, iron-nickel alloy, copper, and copper alloy. Claim 4 A ceramic sealing part according to claim 1 or 2, characterized in that the thickness of the nickel plating is 0.5 μm or more. Claim 5 A ceramic sealing part according to claim 1 or 2, characterized in that the ceramic part is alumina, aluminum nitride, silicon nitride, or zirconia-added alumina. Claim 6 A method for manufacturing a ceramic sealing part that joins a ceramic part and a nickel-plated metal part, comprising: a process of printing and drying an active metal paste containing at least copper, an active metal, and a low-melting point metal onto the ceramic part to obtain an active metal paste printed part; a process of printing and drying a solder paste containing at least silver and copper to cover the entire surface of the active metal paste printed part to obtain a solder paste printed part; and a bonding process in which the metal part is installed on the solder paste printed part and a heat treatment is performed such that the difference (T2-T1) between a first heating temperature T1 and a second heating temperature T2 which is higher than the first heating temperature is 120°C or less. Claim 7 A method for manufacturing a ceramic sealing part according to claim 6, characterized in that the printing thickness of the active metal paste is 30㎛ or less and the difference in printing thickness is 5㎛ or less, and the thickness of the solder paste is 70㎛ or more and the difference in printing thickness is 20㎛ or less. Claim 8 A method for manufacturing a ceramic sealing part according to claim 6 or 7, characterized in that the holding time of the first heating temperature is 10 minutes or more and 30 minutes or less, and the holding time of the second heating temperature is 1 minute or more and 10 minutes or less.

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