Ceramic component, ceramic sealing component, and method for manufacturing ceramic sealing component

Abstract

A ceramic component according to an embodiment of the present invention is a ceramic component having two bottom surfaces for joining metal components of different materials, wherein, when the arithmetic mean surface height of a first bottom surface of the two bottom surfaces is defined as S1 and the arithmetic mean surface height of the other second bottom surface is defined as S2, S1 / S2≥1.2. A method for manufacturing a ceramic sealing component according to an embodiment of the present invention is a method for joining metal components of different materials to two bottom surfaces of a ceramic component, and comprises a step for joining the ceramic component and the metal component via at least one active metal selected from titanium, zirconium, and hafnium.

Description

Ceramic parts, ceramic sealed parts, and manufacturing method of ceramic sealed parts

[0001] The embodiments generally relate to a ceramic part, a ceramic sealed part in which a ceramic part and a metal part are joined (hereinafter abbreviated as "ceramic sealed part"), and a method for manufacturing the ceramic sealed part.

[0002] As ceramic sealing parts for magnetrons, power tubes, and electron tubes, metallized layers mainly composed of high-melting point metals such as molybdenum (Mo) are coated with alumina (aluminum oxide: Al ２ O ３ Ceramic sealed components formed on ceramic components such as ceramics, ceramic alloys, and ceramic alloys are used. Ceramic sealed components bond ceramics to metals, blocking external air and hermetically sealing the interior of the component, thereby protecting the interior from the external environment and providing electrical insulation through the ceramics. The ceramic sealed component has a ring-shaped metallized layer primarily composed of molybdenum formed on two bottom surfaces (first and second bottom surfaces) that form the joining portion of a cylindrical ceramic component made of sintered alumina. A nickel (Ni) layer of a predetermined thickness is formed on the surface of this metallized layer to improve the bonding strength with a cylindrical metal component to be bonded to the ceramic sealed component and to perform sealing. This nickel layer and the cylindrical metal component are bonded using silver solder (e.g., BAg-8).

[0003] As a ceramics-sealed component, an electron tube having a vacuum airtight structure in which a metal surface made of molybdenum is formed at the joining portion of a cylindrical ceramic, and a cylindrical iron metal is joined via a brazing material has been disclosed (Patent Document 1). According to Patent Document 1, by replacing the metal component joined to the ceramic from Kovar with iron, it is possible to manufacture a low-cost electron tube.

[0004] Also, a vacuum switch outer tube has been disclosed in which a nickel-based alloy is bonded to ceramics using an active metal, without using a high-melting-point metal such as molybdenum (Patent Document 2). According to Patent Document 2, a vacuum switch outer tube with high bonding strength can be manufactured without forming intermetallic compounds that cause instability in the bonded state.

[0005] Japanese Patent Application No. 1-46978 Japanese Patent Application Laid-Open No. 2001-220253

[0006] The ceramics used in ceramic sealing parts are hard but brittle. One of the causes of this brittleness is the influence of the surface condition. If there are scratches or other defects on the surface of the ceramic, these defects can become the starting point for fractures. For this reason, polishing the surface of the ceramic to remove defects and reduce surface roughness improves the mechanical reliability of the ceramic. For example, ceramic balls for bearings have mechanical properties that allow them to withstand high speeds and rotations by reducing surface roughness through polishing.

[0007] However, when metallizing the surface of ceramics to join them to metals, a moderately rough ceramic surface increases the strength of the bond (metallization). This is because a rough surface allows for a larger bonding area through chemical reactions, and the metallization components penetrate into recesses, physically increasing the mechanical strength through an anchor effect. Therefore, there is a trade-off between the surface condition of ceramics: to increase the strength of the ceramics, it is better to reduce the surface roughness, and to increase the surface roughness, it is better to increase the bonding strength.

[0008] On the other hand, a strong bonding layer is required to ensure sealing (airtightness) when bonding ceramics and metal. However, since the thermal expansion coefficients of ceramics and metals are different (for example, the thermal expansion coefficient of alumina is 7.2 × 10 －６ / °C, copper 16.5 x 10 －６ / ℃, carbon steel 11.7 × 10 －６ / °C), differences in thermal expansion create stress, which can easily lead to cracks. When joining metals of the same type, there is no difference in the joining, but when joining multiple types of metals with different properties, differences in the joining are likely to occur, which can impair sealing.

[0009] In addition, one way to increase the bond strength between ceramics and metal without changing the state of the ceramics is to increase the amount of components that contribute to bonding during metallization and raise the bonding temperature. However, when increasing the bond strength of one metal among multiple metals with different properties, two types of pastes and two different bonding temperatures are required, which complicates the manufacturing process and results in poor cost performance. Furthermore, when increasing the bond strength of the bond between both metals, the bonding temperature also rises for metals that do not require increased bond strength, which creates further differences in thermal expansion and potentially impairs sealing.

[0010] The embodiments solve these problems and relate to a highly productive ceramic sealed component and a method for manufacturing the same, which suppresses poor bonding and leaks when a ceramic component is joined to multiple metal components with different characteristics.

[0011] The ceramic part according to the embodiment is a ceramic part for joining metal parts made of different materials to two bottom surfaces, and when the arithmetic mean surface height of one of the two bottom surfaces, the first bottom surface, is S1 and the arithmetic mean surface height of the other, the second bottom surface, is S2, S1 / S2≧1.2.

[0012] Fig. 1 is a perspective view showing an example of a ceramic seal component according to an embodiment. Fig. 2 is a longitudinal cross-sectional view showing an example of a ceramic component according to an embodiment. Fig. 3 is a longitudinal cross-sectional view showing an example of a ceramic seal component according to an embodiment. Fig. 4 is a cross-sectional view showing an example of a manufacturing process for the ceramic seal component according to an embodiment. Fig. 5 is a cross-sectional view showing an example of a manufacturing process for the ceramic seal component according to an embodiment. Embodiment

[0013] The ceramic part according to the embodiment is a ceramic part for joining metal parts made of different materials to two bottom surfaces, and when the arithmetic mean surface height of one of the two bottom surfaces, the first bottom surface, is S1 and the arithmetic mean surface height of the other, the second bottom surface, is S2, S1 / S2≧1.2.

[0014] FIG. 1 shows a perspective view of an example of a ceramic sealing component 1 according to an embodiment. Reference numeral 2 denotes a cylindrical ceramic component, and reference numerals 3 and 4 denote cylindrical metal components made of different materials. The metal components 3 and 4 are joined at two ring-shaped bottom surfaces (first and second bottom surfaces) that form the joining portion of the ceramic component 2. FIG. 1 illustrates an example in which the metal component 3 is joined to the first bottom surface (e.g., the upper end surface) of the ceramic component 2, and the metal component 4 is joined to the second bottom surface (e.g., the lower end surface). The embodiment is not limited to this form, and may include a configuration in which a metal component is joined to a rectangular cylindrical ceramic component, a configuration in which a metal component is not present on one bottom surface (e.g., the lower bottom surface) but is joined only to the other bottom surface (e.g., the upper end surface), or a configuration in which a metal component is joined to a ceramic component having openings in two or more locations on one bottom surface (e.g., the upper bottom surface).

[0015] 2 shows an example of a longitudinal cross-sectional view (a cross-section along a central axis perpendicular to the bottom surface) of a ceramic part according to an embodiment. The cylindrical ceramic part 2 has a first bottom surface 21 and a second bottom surface 22. When the arithmetic mean surface height of the first bottom surface 21 is S1 and the arithmetic mean surface height of the second bottom surface 22 is S2, S1 / S2≧1.2. In FIG. 2 and subsequent figures, the first bottom surface 21 is shown as a black layer for convenience in order to distinguish it from the second bottom surface 22.

[0016] FIG. 3 shows a longitudinal cross-sectional view of a ceramic sealed component 1 according to an embodiment. Reference numeral 3 denotes a metal A component (hereinafter abbreviated as "metal A component") made of metal A, and reference numeral 4 denotes a metal B component (hereinafter abbreviated as "metal B component") made of metal B. Here, the metal A component 3 and the metal B component 4 are made of different materials. For example, the metal A component 3 is a cylindrical metal component made of stainless steel, and the metal B component 4 is a cylindrical metal component made of copper (Cu). Here, the metal A component 3 is joined to a first bottom surface 21 having an arithmetic mean surface height S1 via a joining layer 5. Furthermore, the metal B component 4 is joined to a second bottom surface 22 having an arithmetic mean surface height S2 via a joining layer 5. For example, the ceramic component 2 is a cylindrical ceramic component made of aluminum oxide (alumina), and the joining layer 5 is joined with an active metal brazing material layer.

[0017] The ceramic component 2 is preferably made of one of alumina, zirconia-doped alumina (alzir), silicon nitride, and aluminum nitride. Alumina includes alumina-based ceramics in which other ceramics are added to alumina. For example, zirconia-doped alumina is a sintered body made by mixing alumina and zirconium oxide. Alumina may also contain sintering aids other than zirconia. This is because the added sintering aid forms a grain boundary phase consisting of a glass phase, thereby densifying the alumina sintered body. Examples of sintering aids include compounds of manganese (Mn), silicon (Si), magnesium (Mg), and calcium (Ca). It is preferable to add at least one of these sintering aids, Mn, Si, Mg, and Ca, in a total amount of 1 to 15 mass% in oxide equivalent. Sintering aids may also be added to silicon nitride and aluminum nitride for densification. Examples of sintering aids include oxides of rare earth elements, Mg, Ca, aluminum (Al), titanium (Ti), and hafnium (Hf). It is preferable to add at least one of these in an amount of 1 to 15 mass % or less in terms of oxide. Of the ceramic parts 2 manufactured by these methods, ceramic parts made of alumina are excellent in cost performance.

[0018] The ceramic part 2 has two bottom surfaces 21 and 22 that are bonded to the metal parts 3 and 4. One bottom surface of the ceramic part 2 is designated the first bottom surface 21, and the other bottom surface is designated the second bottom surface 22. When the arithmetic mean surface height of the first bottom surface 21 is S1 and the arithmetic mean surface height of the second bottom surface 22 is S2, S1 / S2 ≧ 1.2 is satisfied. To adjust the surface roughness of the ceramic part 2 to the range of S1 / S2 ≧ 1.2, there are two methods: conditioning the compact before sintering and conditioning the sintered body after sintering. For example, the method of conditioning the compact before sintering can mechanically roughen or refine one bottom surface of a pressed compact. To roughen the surface roughness of the compact, the surface of the compact can be polished with a rough buff or a material with a surface similar to a buff (e.g., resin or ceramic). The surface roughness of the compact can be adjusted by polishing the surface with a fine buff or a material with a surface similar to that of a buff. Also, in the production line, the surface roughness of the bottom surface of the compact can be made rougher by placing the compact on a setter with a rough surface and applying vibration.

[0019] In addition to the above-mentioned buffing method, the sintered body can be adjusted in a post-sintering process by honing (blasting) the surface to change its roughness. The surface roughness of the sintered body can also be adjusted by polishing with grindstones of different roughness.

[0020] The surface roughness of the bottom surfaces 21, 22 of the ceramic part 2 is defined as the arithmetic mean height (Sa) of the bottom surfaces 21, 22. The arithmetic mean height of the bottom surfaces 21, 22 is measured in accordance with "Geometric Properties of Products (GPS) - Surface Texture: Three-Dimensional - Part 6: Classification of Surface Texture Measurement Methods (JIS B0681-6:2014)." The measurement location and area are measured at approximately the center of the bottom surface (the joint), with a distance equal to half the width of the bottom surface as the diameter. For example, when joining the entire ring-shaped bottom surface formed on the cylindrical ceramic part 2, if the width of the bottom surface (the difference between the outer diameter and the inner diameter) is 10 mm, the measurement is performed at a diameter of 5 mm. Furthermore, if the inner and outer circumferences of the bottom surface are chamfered, the measurement is taken as half the width excluding the chamfered portions. In this case, if the width to be measured is not uniform, the largest (widest) point is measured. If the maximum width of the two bottom surfaces is different, the diameter of the measurement area of ​​the smaller bottom surface should be used. Measurements can be performed using a non-contact surface roughness meter and a laser microscope (such as the VK-X series manufactured by Keyence Corporation).

[0021] The material of the metal A component 3 bonded to the first bottom surface 21 of the ceramic component 2 is preferably iron (Fe), an iron alloy, or an iron-nickel alloy (hereinafter abbreviated as "iron and iron alloy, etc."). Iron alloys include carbon steels such as rolled steel, chromium steels, and stainless steel alloys. Examples of iron-nickel alloys include 42 alloy (42% Ni by mass, 0.8% or less Mn by mass, balance Fe) and Kovar (29% Ni by mass, 17% Co by mass, balance Fe). Iron and iron alloys offer excellent cost performance, while iron-nickel alloys offer excellent physical properties such as a thermal expansion coefficient. Furthermore, when using iron, iron alloys, or iron-nickel alloys, plating is preferred to improve wettability during bonding and to prevent rust. Nickel plating is preferred. This is because nickel plating has excellent heat resistance and prevents molecular diffusion between the plating and the base material.

[0022] The material of the metal B component 4 bonded to the second bottom surface 22 of the ceramic component 2 is preferably copper or a copper alloy. The copper alloy may be pure copper such as oxygen-free copper, tough pitch copper, or deoxidized copper, or a high-copper alloy such as beryllium copper or titanium copper. The metal components 3 and 4 are manufactured by processing into a predetermined shape by pressing, cutting, bending, or the like.

[0023] The ceramic part 2 and the metal parts 3 and 4 are joined by a joining layer 5. Typical methods for forming the joining layer 5 include the active metal method and the refractory metal method. The active metal method uses an active metal brazing filler metal containing one or more active metals selected from titanium (Ti), zirconium (Zr), and hafnium (Hf) and one or more brazing filler metals selected from copper and silver. For example, the active metal method uses an active metal such as titanium (Ti). Examples of active metals other than titanium include zirconium (Zr) and hafnium (Hf). An example of an active metal brazing filler metal is a mixture of titanium as the active metal and copper (Cu) as the brazing filler metal. For example, the titanium content is 0.1 to 10 mass %, with the remainder being copper. Another example of an active metal brazing filler metal is a mixture of titanium as the active metal and silver and copper as the brazing filler metals. The titanium content is 0.1 to 10 mass %, the copper content is 10 to 60 mass %, and the remainder being silver. Furthermore, to control the diffusion of the active metal brazing material during joining, 1 to 15 mass % of one or more elements selected from indium (In), tin (Sn), aluminum (Al), silicon (Si), carbon (C), and magnesium (Mg) may be added as needed. An active metal brazing material paste is printed on the surface of the ceramic part 2 and then dried. Metal parts 3 and 4 are then placed in contact with the printed and dried paste surface, and the ceramic part 2 and metal parts 3 and 4 are joined by heating at 780 to 820°C in a vacuum or in a non-oxidizing gas.

[0024] The refractory metal method involves printing a paste made of a powder of a refractory metal, such as molybdenum (Mo) or tungsten (W), on the surface of a ceramic and then heating it at high temperatures. A typical refractory metal method is the molybdenum-manganese (Mn) method. In this method, for example, 5 to 15 mass% manganese powder is added to molybdenum powder to form a paste. The refractory metal paste is printed on the bottom surfaces 21 and 22 and then dried. The paste is then heated at 1400 to 1500°C in a wet hydrogen nitrogen gas atmosphere to form a metallized layer 7 made of a refractory metal on the bottom surfaces 21 and 22. Because the refractory metal layer formed on the bottom surfaces 21 and 22 of the ceramic component 2 has poor wettability, the metallized layer 7 is plated with nickel (Ni) or the like to form a plating layer (e.g., a nickel plating layer) 8. A brazing material containing copper and silver (such as silver brazing foil) is formed between the plating layer 8 and the metal parts 3, 4 and heated to 780 to 820° C. to form a brazing material layer 9, thereby performing brazing and joining.

[0025] Both active metal joining and brazing joining after high melting point metal are performed by heating up to a joining temperature of approximately 800°C. Due to the thermal expansion coefficient and elongation (hardness), differences in the joining state occur between metal A part 3, which is iron or iron alloy, and metal B part 4, which is copper or copper alloy. The thermal expansion coefficients of iron and iron alloy, and copper and copper alloy, are greater than that of ceramics. Both expand when heated, and after joining with the ceramic, they contract when cooled. At this time, due to the difference in the thermal expansion coefficients of the metal and ceramic, the metal parts 3 and 4 contract more than the ceramic part 2, generating stress. For example, the thermal expansion coefficient of austenitic stainless steel SUS304 is 17.3 x 10 －６ / °C, and the thermal expansion coefficient of copper is 17.7 × 10 －６ / °C. However, the Vickers hardness of SUS304 is 150, which is harder than that of copper (50). Therefore, SUS304 is less likely to deform when cooled than copper. Thus, when joining to the ceramic part 2, stress is more likely to occur in the metal A part 3 (iron and iron alloys, etc.) than in the metal B part 4 (copper and copper alloys). Therefore, even if no fracture occurs when joining the ceramic part 2 to copper and copper alloys, fracture may occur when joining to iron and iron alloys, etc.

[0026] To increase the bonding strength on the side where greater stress occurs, it is possible to increase the proportion of reactive components in the paste or raise the bonding temperature, but doing so would also increase damage to the entire ceramic part 2, including the side where no stress is applied. In contrast, the ceramic part 2 according to the embodiment has a high surface roughness on the surface that is bonded to the metal part, which is subject to stress and prone to breakage. This makes it relatively easy to produce a ceramic part 2 that can be bonded to two or more types of metal parts 3, 4.

[0027] The bonding strength of the bonding layer 5 formed by the active metal method, the refractory metal method, or the like is greater when the surface roughness of the ceramic part 2 is greater. This is because the reactive area becomes larger as the surface roughness increases. Also, the bonding layer 5 penetrates into the ceramic part 2, and the anchor effect increases the physical bonding strength.

[0028] The above example is an example of a combination of a metal B part 4 (copper and copper alloy) and a metal A part 3 (iron and iron alloy, etc.), but combinations with metals having other linear expansion coefficients and hardnesses are also possible. Furthermore, even if the metals are the same type, it is possible to apply a combination of shapes that are easy to deform and shapes that are difficult to deform. For example, even if the metal parts are of the same type and have a cylindrical shape, thinner parts are more easily deformed, and thicker parts are more difficult to deform.

[0029] 4 shows a process diagram (longitudinal cross section) of a method for manufacturing a ceramic sealed component 1 using an active metal method according to an embodiment. The method for manufacturing a ceramic sealed component 1 according to an embodiment is a method for manufacturing a ceramic sealed component 1 having metal components 21, 22 made of different materials bonded to two bottom surfaces. First, a ceramic component 2 is prepared, in which S1 / S2 ≥ 1.2, where S1 is the arithmetic mean surface height of one first bottom surface 21 and S2 is the arithmetic mean surface height of the other second bottom surface 22. Next, the ceramic component 2 and metal components 3, 4 are bonded together using an active metal brazing filler metal containing one or more active metals selected from titanium, zirconium, and hafnium, and one or more brazing filler metals selected from copper and silver.

[0030] FIG. 4( a ) is a longitudinal cross-sectional view of the ceramic component 2. When the arithmetic mean surface height S21 of the first bottom surface 21 and the arithmetic mean surface height S22 of the second bottom surface 22 are defined as follows: S21 / S22≧1.2. FIG. 4( b ) shows the state in which an active metal brazing filler metal paste is printed and dried on the bottom surfaces 21 and 22 of the ceramic component 2, followed by heating in a vacuum or non-oxidizing gas to form an active metal brazing filler metal layer 6. Because the paste is printed on the flat bottom surfaces 21 and 22 of the ceramic component 2, the surface of the active metal brazing filler metal layer 6 is substantially flat before bonding. Although FIG. 4( b ) shows the active metal brazing filler metal paste printed only on the flat portions of the bottom surfaces 21 and 22, it is also possible to print the active metal brazing filler metal on the chamfered portions formed on the inner and outer peripheries. FIG. 4( c ) shows the state in which the metal components 3 and 4 are bonded to the ceramic component 2 by placing them on the surface of the active metal brazing filler metal layer 6 and heating them. Although it is possible to join the multiple metal components 3, 4 separately, it is preferable to place and join them simultaneously because stress from the previously joined metal component will be generated again. Note that instead of heating the active metal brazing material layer 6 once and then placing and heating the metal components 3, 4, it is also possible to join the ceramic component 2 and the metal components 3, 4 by placing the metal components 3, 4 on the surface of the printed and dried active metal brazing material and then heating them.

[0031] FIG. 5 shows a process diagram (cross-sectional view) of a method for manufacturing a ceramic seal component using a high-melting-point metal method according to an embodiment. The method for manufacturing a ceramic seal component according to an embodiment is a method for manufacturing a ceramic seal component 1 having two metal components 3 and 4 made of different materials bonded to bottom surfaces 21 and 22. First, a ceramic component is prepared in which S1 / S2 ≥ 1.2, where S1 is the arithmetic mean surface height of one bottom surface 21 and S2 is the arithmetic mean surface height of the other bottom surface 22. Next, a metallized layer 7 made of a high-melting-point metal is formed on the bottom surfaces 21 and 22 of the ceramic component 1. Next, a plating layer (e.g., a nickel plating layer) 8 is formed on the surface of the metallized layer 7. Next, the plating layer 8 and the metal components 3 and 4 are bonded using a brazing filler metal layer 9 containing copper and silver.

[0032] FIG. 5( a ) is a cross-sectional view of a ceramic part 2. When the arithmetic mean surface height S21 of the bottom surface 21 and the arithmetic mean surface height S22 of the bottom surface 22 are defined as follows: S21 / S22≧1.2. In FIG. 5( b ), a metallized layer 7 is formed on both bottom surfaces 21 and 22 of the ceramic part 2. The metallized layer 7 is formed by printing and drying a high-melting-point metal paste and then heating it at a high temperature. FIG. 5( c ) shows a plated layer 8 formed on the surface of the metallized layer 7. The plated layer 8 is formed by electrolytic plating or electroless plating. FIG. 5( d ) shows a brazing filler metal layer 9 formed between the plated layer 8 and the metal parts 3 and 4, joining the ceramic part 2 and the metal parts. The brazing filler metal layer 9 is formed by placing a brazing filler metal sheet or the like between the metal parts 3 and 4 and the surface of the plated layer 8 and heating it.

[0033] In the manufacturing method of the ceramic sealed component 1 according to the embodiment, a metal component 3 such as iron or an iron alloy is joined to a bottom surface 21 of a ceramic component 2, which has an arithmetic mean surface height S1, via a joining layer 5 (e.g., an active metal braze layer 6 or layers 7 to 9), and a metal component 4 of copper or a copper alloy is joined to a bottom surface 22, which has an arithmetic mean surface height S2, via a joining layer 5.

[0034] Next, a description will be given of a method for manufacturing the ceramic part 2 and the ceramic sealed part 1 according to the embodiment. As long as the ceramic part 2 and the ceramic sealed part 1 have the above-described configuration, the manufacturing method is not particularly limited. However, the following method can be mentioned as a method for obtaining the ceramic part 2 and the ceramic sealed part 1 with a high yield.

[0035] An example of the ceramic part 2 according to the embodiment has a cylindrical shape, for example, an outer diameter of 50 mm, an inner diameter of 38 mm, and a height of 50 mm. The ceramic part 2 is prone to chipping and cracking at its corners due to external impacts. For this reason, it is preferable that the outer and inner peripheries of the bottom surfaces 21 and 22 are chamfered. The chamfer shape can be a C-chamfer or an R-chamfer, and the chamfer size is preferably 0.1 to 2 mm.

[0036] Examples of materials for the metal components 3 and 4 according to the present embodiment include iron and iron alloys, copper and copper alloys, iron-nickel alloys such as 42 alloy and Kovar, tungsten, and molybdenum. Iron and iron alloys offer excellent cost performance, while copper and copper alloys are easily deformed to relieve stress caused by differences in thermal expansion. For this reason, it is preferable to form the metal components 3 and 4 from iron and iron alloys or copper and copper alloys.

[0037] An example of the shape of the metal parts 3, 4 is a substantially cylindrical shape. The joining ends of the metal parts 3, 4 may be straight so as to be joined perpendicularly to the bottom surfaces 21, 22 of the ceramic part 2, or they may be bent inward or outward at a substantially right angle so as to be joined horizontally to the bottom surfaces 21, 22 of the ceramic part 2. For example, the height may be 20 mm, and the straight shape may have an outer diameter of 46 mm and an inner diameter of 44 mm. In the bent shape, the outer diameter may be 48 mm, an inner diameter of 46 mm, and an inner diameter of 40 mm at the bent end. The joining with the straight-shaped metal parts 3, 4 is an edge seal, which is a line joining, so stress is less likely to be applied. The joining with the bent-shaped metal parts 3, 4 is a butt seal, which is a surface joining, so leak defects are less likely to occur. These metal parts can be plated with nickel or other metals to improve corrosion resistance and wettability.

[0038] The component form for joining using the active metal brazing material layer 6 (shown in FIG. 4( c)) is preferably a paste. The active metal brazing material paste is prepared by adding an organic binder and an organic solvent to a mixture of active metal powder and brazing material metal powder. The organic binder is not particularly limited as long as it is burned away during the drying process or the joining (heating) process. A preferred example is ethyl cellulose. The organic solvent is not particularly limited as long as it is burned away during the drying process or the sintering process. Preferred examples include terpineol and butyl carbitol. The active metal brazing material paste is prepared by crushing and mixing the active metal powder and brazing material metal powder, and then mixing them with the organic binder and the organic solvent. The active metal brazing material contains an active metal in an amount of 0.1 to 15% by mass, preferably 0.5 to 10% by mass.

[0039] The printing thickness of the active metal brazing paste is preferably 20 to 150 μm. If the printing thickness is less than 20 μm, the thickness of the active metal brazing layer will vary, reducing the bonding strength. On the other hand, if it exceeds 150 μm, no further effect will be obtained. The paste is printed to a uniform thickness on the bottom surfaces 21 and 22 of the ceramic component 2 using a screen printing method or the like. If the printing thickness is uneven, the active metal brazing material will be excessive in the thicker parts, causing brazing material pools and cracks due to thermal stress. Furthermore, in the thinner parts, leakage defects will occur due to the lack of active metal brazing material. For this reason, it is preferable that the difference in printing thickness between the thicker and thinner parts be 15 μm or less, and even 10 μm or less.

[0040] The paste printed on the bottom surfaces 21, 22 of the ceramic component 2 is dried in the air or other atmosphere. If the drying temperature is low and the drying time is short, the solution components of the paste will not volatilize sufficiently, which may result in voids during bonding. Conversely, if the drying temperature is high and the drying time is long, oxidation of the paste surface may progress, which may cause changes in the bonding temperature. For this reason, the drying temperature is 50 to 100°C, preferably 60 to 80°C. The drying time is 5 to 30 minutes, preferably 10 to 20 minutes.

[0041] After the paste has dried, the metal parts 3 and 4 are placed on the dried paste surface and heated to bond them. The bonding temperature is 600 to 850°C, preferably 700 to 800°C. The bonding time is preferably in the range of 5 to 60 minutes after the bonding temperature is reached. If the bonding temperature is low and the bonding time is short, the active metal brazing material may not melt sufficiently, resulting in no bonding. Conversely, if the bonding temperature is high and the bonding time is long, the active metal brazing material may melt too much, causing expansion and voids or brazing breaks. The active metal bonding atmosphere may be in a vacuum or a non-oxidizing atmosphere as needed. When performing in a vacuum, a 1×10 －２ Pa or less. Examples of non-oxidizing atmospheres include a nitrogen atmosphere and an argon atmosphere. By using a vacuum or a non-oxidizing atmosphere, oxidation of the active metal brazing material layer 6 can be suppressed, thereby improving the bonding strength. A continuous furnace or a batch furnace is used for brazing. A continuous furnace is superior in terms of mass productivity, while a batch furnace allows for easy control of the temperature and atmosphere. The active metal brazing material layer 6 is formed by heating for a predetermined time in the above-mentioned atmosphere.

[0042] On the other hand, metallization of high-melting-point metals is typically in the form of a paste. High-melting-point metal pastes are prepared by mixing powders of one or more high-melting-point metals selected from molybdenum and tungsten with additive powders, to which an organic binder and organic solvent are added. For example, a molybdenum-manganese paste is prepared by adding 10% by mass of manganese powder to molybdenum powder. The organic binder is not particularly limited as long as it is burned away during the drying and bonding (heating) processes. A preferred example is ethyl cellulose. The organic solvent is not particularly limited as long as it is burned away during the drying and sintering processes. Preferred examples include terpineol and butyl carbitol. The high-melting-point metal paste is prepared by crushing and mixing high-melting-point metal powders and additive powders, followed by mixing with an organic binder and organic solvent.

[0043] The printing thickness of the high-melting-point metal paste is preferably 10 to 30 μm. If the printing thickness is less than 10 μm, the thickness of the brazing material layer 9 will vary, reducing the bonding strength. On the other hand, if it exceeds 30 μm, no further effect will be obtained. The high-melting-point metal paste is printed in a uniform thickness on the bottom surfaces 21 and 22 of the ceramic component 2 using a method such as screen printing. If the printing thickness is uneven, a difference in bonding strength will occur between the thick and thin portions. For this reason, it is preferable that the difference in printing thickness between the thick and thin portions be 5 μm or less.

[0044] The high-melting-point metal paste printed on the ceramic part 2 is dried in the air or other atmosphere. If the drying temperature is low and the drying time is short, the solution components of the paste will not volatilize sufficiently, which may result in voids during bonding. Conversely, if the drying temperature is high and the drying time is long, oxidation of the surface of the high-melting-point metal paste will progress, which may cause changes in the bonding temperature. For this reason, the drying temperature is 50 to 100°C, preferably 60 to 80°C. The drying time is 5 to 30 minutes, preferably 10 to 20 minutes.

[0045] After drying the high-melting-point metal paste, the metallized layer 7 is formed by heating in a wet hydrogen nitrogen atmosphere. The heating temperature is 1350 to 1550°C. In the high-melting-point metal method, a glass phase diffuses from the ceramic part 2 to form a strong bonding layer. If the heating temperature is lower than 1350°C, the glass phase may not diffuse sufficiently, resulting in a decrease in bonding strength. Conversely, if the heating temperature is higher than 1550°C, the glass phase may reach the surface of the metallized layer, reducing the adhesion strength with the plating, which will be described later. A continuous furnace or batch furnace is used for heating. A continuous furnace is superior in terms of mass production.

[0046] The metallized layer 7 made of a high-melting-point metal is plated to form a plating layer (e.g., a nickel plating layer) 8 to improve bonding with the brazing filler metal. While nickel plating and gold plating are used, nickel plating offers excellent corrosion resistance and cost performance. Nickel plating is divided into electrolytic nickel plating, which is performed by passing an electric current, and electroless nickel plating, which does not require a current. Electrolytic nickel plating has lower chemical costs than electroless nickel plating and is therefore more cost-effective. It is preferable to perform electrolytic nickel plating to a thickness of 1 to 3 μm on the metallized layer 7. A thickness less than 1 μm may result in reduced wettability with the brazing filler metal, as described below. A thickness greater than 3 μm is too thick to ensure sufficient wettability with the brazing filler metal, and excessive thickness may result in blistering defects.

[0047] The formed plating layer 8 is bonded to the metal components 3, 4. A brazing filler metal is used for this bonding. Because the brazing filler metal wets easily with nickel plating, a silver brazing filler metal is preferred, as it provides a strong bond to the metal components 3, 4. Silver brazing filler metal (BAg-8), a 72% silver-28% copper alloy, is commonly used to bond ceramic components 2 and metal components 3, 4. According to "Silver Brazing Filler Metal (JIS Z3261:1998)," BAg-8 contains 71-73% silver (Ag), 27-29% copper (Cu), and a total of 0.15% or less of other elements. BAg-8 contains no evaporated metals, making it suitable for brazing electron tubes and vacuum tubes. Its high silver content provides excellent electrical conductivity and is suitable for use with components that have a high melting point and can withstand high temperatures. The silver brazing filler metal is processed into a sheet or wire ring shape and placed between the surface of the plating layer 8 and the metal components 3, 4, or printed as a paste on the surface of the plating layer 8 or the surface of the metal components 3, 4. The joining temperature for silver brazing is 650 to 900°C, preferably 750 to 820°C. If the joining temperature is too low, the silver brazing material may not melt sufficiently, resulting in no joining. Conversely, if the joining temperature is too high, the silver brazing material may melt too much, wetting and spreading, causing brazing failure and voids.

[0048] Furthermore, the silver brazing joining atmosphere is, if necessary, a non-oxidizing atmosphere. Examples of non-oxidizing atmospheres include a nitrogen atmosphere and a hydrogen nitrogen atmosphere. By using a non-oxidizing atmosphere, oxidation of the joining layer can be suppressed, improving the joining strength. Continuous furnaces and batch furnaces are used for silver brazing. Continuous furnaces are superior in terms of mass production, while batch furnaces allow for easy control of temperature and atmosphere. Silver brazing is performed by heating the parts in the above atmosphere for a specified period of time.

[0049] According to the method for manufacturing the ceramic seal component 1 in the embodiment of the present invention, it is possible to obtain a ceramic seal component 1 that is excellent in cost performance while maintaining the airtightness of the seal component.

[0050] (Examples 1 to 12, Comparative Examples 1 to 8) Alumina and manganese oxide (MnO ２ ), silicon dioxide (silica: SiO ２ Granulated powder having a composition of 92 mass% alumina was prepared by adding an auxiliary agent of magnesium oxide (magnesia: MgO). The granulated powder was molded using a mold press and sintered at 1500°C in air to obtain a cylindrical ceramic part having an outer diameter of 50 mm, an inner diameter of 38 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. Furthermore, Alsil (zirconia-added alumina) was prepared by adding zirconia to alumina to obtain 80 mass% alumina, which was molded in the same manner as alumina and sintered at 1500°C in air to obtain a cylindrical part with the same dimensions as the alumina part. Furthermore, silica (SiO ２ ) by 1 mass %, yttria (yttrium oxide: Y ２ O ３ Cylindrical silicon nitride parts with the same dimensions as the alumina parts were obtained by adding 3 mass% of yttria and 1 mass% of alumina as auxiliary agents, molding them in the same manner, and sintering them in nitrogen at 1800°C. Also, cylindrical aluminum nitride parts with the same dimensions as the alumina parts were obtained by adding 3 mass% of yttria as auxiliary agent to aluminum nitride (AlN), molding them in the same manner, and sintering them in nitrogen at 1800°C.

[0051] The ceramic parts obtained by sintering were barrel polished to remove dust and other impurities, and one of the bottom surfaces was roughened by blasting. The arithmetic mean surface height (Sa) of both bottom surfaces of the ceramic parts was then measured using a Keyence laser microscope (VK-X3000). Measurement conditions included measuring an area of ​​2.5 mm diameter centered at the midpoint of the ceramic part's width (44 mm diameter). Three measurements were performed, and the average value was calculated. The measurement results of the arithmetic mean surface heights of the surfaces are shown in Table 1. In the examples, the arithmetic mean surface height of the bottom surface with the larger arithmetic mean surface height was designated S1, and the arithmetic mean surface height of the unprocessed bottom surface was designated S2. In contrast, in Comparative Examples 1 and 6, neither bottom surface was processed by blasting. In the other comparative examples, the bottom surface with the larger arithmetic mean surface height in the examples was designated S2, and the unprocessed bottom surface in the examples was designated S1. In Table 1, ceramic parts processed in the same manner were constructed as the same lot. For example, Examples 1 to 6, 10 to 12 and Comparative Examples 3 and 8 are lots made up of ceramic parts that were manufactured and processed in the same manner and had their arithmetic mean surface heights measured. Also, in Table 1, aluminum nitride parts are represented as AlN.

[0052] Next, the joining method between the ceramic component and the metal component was selected from either the active metal joining method or the high-melting-point metal joining method. In the examples and comparative examples in which the active metal joining method was selected, copper powder, tin powder, and titanium hydride (TiH) powder were mixed in a metal powder blend ratio of 60:30:10 by mass, and ethyl cellulose and terpineol were added to form a paste using a kneader to prepare an active metal brazing paste. A 60 μm thick active metal paste was printed on the upper and lower ends (ring portions) of the ceramic component by screen printing using a 100-mesh screen with an outer diameter of 48 mm and an inner diameter of 40 mm, and then dried at 100 °C in air. Next, using the metal component described below, the metal component, ceramic component, and metal component were placed in a jig in this order and heated in a vacuum atmosphere at 820 °C or higher for 10 minutes to join the metal component and the ceramic component, thereby producing a ceramic sealed component.

[0053] In the examples and comparative examples using the high-melting-point metal method, molybdenum (Mo) powder and manganese (Mn) powder were mixed in a metal powder blend ratio of 90:10 by mass, and ethyl cellulose and terpineol were added. The mixture was then kneaded to form a paste to prepare a high-melting-point metal paste. A 25 μm-thick high-melting-point metal paste was printed on 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 and an inner diameter of 40 mm, and dried at 100°C in air. Next, a metallized layer of high-melting-point metal was formed on the surface of the ceramic part by heating at 1450°C or higher for 30 minutes in a wet hydrogen nitrogen atmosphere. Next, a 2 μm-thick nickel layer was formed on the surface of the metallized layer by electrolytic nickel plating. Next, using a 0.1 mm thick silver solder (BAg-8), the metal part, silver solder, ceramic part, silver solder, and metal part were set in a jig in this order, and heated in a hydrogen nitrogen atmosphere continuous furnace for 10 minutes at 820°C or higher to join the metal part and ceramic part, thereby producing a ceramic sealed part.

[0054]

[0055] In addition, a 10 mm × 100 mm × 0.5 mm copper plate was prepared instead of a metal part for measuring bonding strength. In the active metal method, the copper plate and the ceramic part printed with an active metal layer were placed in a jig in this order and heated to bond them together, producing a bonding strength test sample. In the high-melting-point metal method, the copper plate, silver solder, and the ceramic part with a plating layer formed on the surface of the metallized layer were placed in this order and heated to produce a bonding strength test sample. The ceramic part was fixed to a tensile strength tester, and the bonding strength (peel strength) was measured by pulling the vertically bent copper plate upward at 5 mm / min.

[0056] The peel strength measurement results are shown in Table 2. In Table 2, Examples 1 and 7 to 10 are shown as representatives of the same lot. The peel strengths of the S1 and S2 surfaces were measured using different ceramic parts from the same production lot, but for convenience they are listed in the same row in Table 2.

[0057]

[0058] As can be seen from Table 2, the peel strength of the surface with an increased arithmetic mean surface height (surface height S1) was greater than that of the surface without such an increase (surface height S2). This is because increasing the arithmetic mean surface height of the surface increases the bonding area and physical bonding occurs through an anchor effect, etc., resulting in increased bonding strength.

[0059] Table 3 shows the metal A parts and metal B parts used in the examples and comparative examples. The materials of the metal A parts include iron and iron alloys, such as pure iron (Fe), carbon steel (S45C), stainless steel (SUS304, SUS430), Kovar, and 42 alloy. The materials of the metal B parts include copper and copper alloys, such as oxygen-free copper and phosphorus-deoxidized copper. These metal parts were machined into cylindrical shapes with a height of 20 mm, an outer diameter of 48 mm, an inner diameter of 46 mm, and an inner diameter of 40 mm, with the tip of the joining side machined inward at a substantially right angle. The combinations of metal parts shown in Table 3 were used in the examples and comparative examples. The surfaces of the machined iron and iron alloy parts were plated with 2 μm of nickel.

[0060] Next, the upper part of the ceramic sealed part was coated with silicone and held down with a circular jig made of Viton rubber, and the lower part was fixed to a helium leak detector and sucked to perform a helium leak test. The helium leak test was performed in accordance with the vacuum spray method (spray method) of the "Helium Leak Test Method" (JIS Z2331:2006), and the helium leak rate was 1 × 10 at a vacuum of 1.3 μPa. －９ P.A.M. ３ The number of defectives was calculated based on the result of the test. If no leakage of 1 / s or more occurred, the test was considered to be pass, and if leakage occurred, the test was considered to be fail.

[0061] Furthermore, a thermal shock test (TST) was performed on the ceramic sealed components that passed the helium leak test. The test conditions were a low temperature condition of -40°C for 30 minutes, a high temperature condition of 125°C for 30 minutes, and 20 test cycles with a transfer time of 10 seconds or less. After the thermal shock test, a helium leak test was performed in the same manner as before the test. The number of defectives was calculated, with no leaks being considered as passing and leaks being considered as failing. The test results for the examples and comparative examples are shown in Table 3.

[0062]

[0063] The ceramic sealed components of the Example and Comparative Example 2 had a desirable number of leak defects in the helium leak test. This was because the bond strength obtained by combining the ceramic and metal components was appropriate, and the bond configuration was such that it would not break due to stress generated by the difference in thermal expansion during bonding. In contrast, the other Comparative Examples had a large number of leak defects. This was because the bond strength was not sufficiently high and the difference in thermal expansion between the ceramic and metal components damaged the bonded area, making it impossible to maintain airtightness.

[0064] Furthermore, the ceramic sealed components according to the examples did not experience any or only a small amount of leak failure in the helium leak test after the TST. This is because the bond strength obtained by combining the ceramic and metal components was appropriate, and the bond configuration was such that failure would not occur due to stress generated by the difference in thermal expansion under the TST test conditions. In contrast, the comparative examples experienced many helium leak failures after the TST. This was because the bond strength obtained by combining the ceramic and metal components was insufficient. Furthermore, even if the bond strength was sufficient, the increased surface roughness of the ceramic components caused significant damage, leading to the destruction of the ceramic components and the creation of many leak paths.

[0065] As is clear from the results shown above, the Examples showed improvements in leak characteristics and reliability in TST compared to the Comparative Examples.

[0066] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other.

Claims

1. A ceramic part for joining metal parts made of different materials to two bottom surfaces, wherein when the arithmetic mean surface height of the first bottom surface of one of the two bottom surfaces is S1 and the arithmetic mean surface height of the other second bottom surface is S2, the ceramic part satisfies S1 / S2≧1.

2.

2. A ceramic sealed component comprising: the ceramic part according to claim 1; iron or an iron alloy bonded to the first bottom surface of the ceramic part via a bonding layer; and copper or a copper alloy bonded to the second bottom surface of the ceramic part via a bonding layer.

3. A ceramic sealed part as described in claim 2, characterized in that the bonding layer comprises: a metallized layer formed on the surface of the ceramic part and made of one or more high melting point metals selected from tungsten and molybdenum; a nickel plating layer formed on the surface of the metallized layer; and a brazing material layer containing copper and silver formed on the surface of the nickel plating layer.

4. The ceramic sealing part according to claim 3, characterized in that the ceramic part is made of aluminum oxide.

5. The ceramic sealed part according to claim 2, characterized in that the bonding layer is made of an active metal brazing material layer containing one or more active metals selected from titanium, zirconium and hafnium, and one or more brazing material metals selected from copper and silver.

6. The ceramic sealed part according to claim 5, characterized in that the ceramic part is made of one material selected from the group consisting of aluminum oxide, silicon nitride and aluminum nitride.

7. A method for manufacturing a ceramic sealed part in which metal parts made of different materials are bonded to the two bottom surfaces of a ceramic part, the method comprising the steps of: bonding the ceramic part according to claim 1 and the metal part via an active metal brazing material containing one or more active metals selected from titanium, zirconium and hafnium, and one or more brazing metals selected from copper and silver.

8. A method for manufacturing a ceramic sealed part in which metal parts made of different materials are bonded to two bottom surfaces of a ceramic part, the method comprising the steps of: forming a metallized layer made of a high melting point metal on the two bottom surfaces of the ceramic part described in claim 1; forming a nickel plating layer on the surface of the metallized layer; and bonding the nickel plating layer and the metal parts via a brazing material layer containing copper and silver.

9. A method for manufacturing a ceramic sealed part as described in claim 7 or 8, characterized in that iron or an iron alloy is joined to the first bottom surface of the ceramic part via a joining layer, and copper or a copper alloy is joined to the second bottom surface via a joining layer.

10. The method for producing a ceramic sealed part according to claim 9, wherein the ceramic part is one selected from the group consisting of aluminum oxide, silicon nitride and aluminum nitride.

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