Joined body of metal and insulator, use thereof, and method for producing joined body of metal and insulator

Abstract

This joined body has a metal member, an insulation member, and a joined member in which the metal member and the insulation member are joined. When a section of the surface of the metal member that is in contact with the joining member is defined as a joining section, the average crystal grain size in a surface layer of the metal member in the joining section is smaller than the average crystal grain size inside the metal member. The joined body is for use in an airtight terminal, or the like.

Description

Metal-insulator bonded body, its uses, and method for manufacturing a metal-insulator bonded body

[0001] The present disclosure relates to a bonded body of a metal and an insulator, uses of the bonded body such as a hermetic terminal, and a method for producing the bonded body of a metal and an insulator.

[0002] Airtight terminals, also known as hermetic seals, are used, for example, as inlets for signals and currents between the inside and outside of chambers, piping, and the like that require airtightness. Airtight terminals typically include a columnar conductive pin, an insulating member that is an insulator having a through-hole for inserting the conductive pin, and a cylindrical sleeve that surrounds the outer periphery of the insulating member. The conductive pin and sleeve are made of metal. Therefore, advanced joining technology between the insulating member and the metal member is required.

[0003] Patent Document 1 describes a feed-through terminal including a cylindrical member, a plate member (corresponding to the insulating member) made of a ceramic insulating material and airtightly joined to the inner periphery of the cylindrical member, and a pin made of a conductive material that penetrates the plate member. Patent Document 1 also describes that the cylindrical member is an alloy containing at least iron, nickel, and cobalt as components.

[0004] In order to maintain airtightness, the feedthrough terminal in Patent Document 1 is joined by a metal tube interposed between a plate member made of a ceramic insulating material and a pin made of a conductive material such as copper, etc. This allows the feedthrough terminal to maintain airtightness regardless of residual stress.

[0005] Japanese Patent Application Laid-Open No. 2003-323856

[0006] A bonded body of a metal and an insulator (hereinafter sometimes simply referred to as a "bonded body") according to the present disclosure includes a metal member, an insulating member, and a bonding material bonding the metal member and the insulating member together. When a portion of the surface of the metal member that contacts the bonding material is defined as a bonded portion, the average crystal grain size of the surface layer of the metal member at the bonded portion is smaller than the average crystal grain size inside the metal member.

[0007] The bonded body of the present disclosure is used for applications such as an electromagnetic wave transmission window member, a power supply terminal, and an airtight terminal.

[0008] The method for manufacturing a bonded body of the present disclosure includes a preparation step of preparing an insulating member, a metal member, and a bonding material containing metal or glass, a bonding step of bonding the insulating member and the metal member with the bonding material to produce a pre-bonded body, and a cooling step of cooling the pre-bonded body at a temperature of −100° C. or lower to obtain a bonded body.

[0009] 2 is a perspective view showing a joined body according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the joined body shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view of portion A in FIG. 2. FIG. 4 is an enlarged cross-sectional view showing another example of the joined portion in portion A in FIG. 2. FIG. 5 is an enlarged cross-sectional view showing yet another example of the joined portion in portion A in FIG. 2. FIG. 6 is an enlarged cross-sectional view showing an example that does not become a joined portion. FIG. 7 is an enlarged cross-sectional view showing another example that does not become a joined portion. FIG. 8 is an enlarged cross-sectional view of portion B in FIG. 2. FIG. 9 is an enlarged cross-sectional view showing another example of the joined portion in portion B in FIG. 2. FIG. 10 is an enlarged cross-sectional view showing yet another example of the joined portion in portion B in FIG. 2. FIG. 11 is a cross-sectional view of another hermetic terminal according to the present disclosure. FIG. 12 is an enlarged cross-sectional view showing another example of the joined portion in portion A in FIG. 2. FIG. 13 is an enlarged cross-sectional view showing another example of the joined portion in portion B in FIG. 2. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus distance (μm) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the crystal refinement rate (with the internal average crystal grain size set to 100%) versus depth ratio (%) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus distance (μm) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus depth ratio (%) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus depth ratio (%) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus distance (μm) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a graph showing the change in average crystal grain size versus depth ratio (%) from the surface of the first metal member, determined from FIGS. 15A and 15B. 15B is a microscope image (magnification: 1500x) of the crystal shape at the surface and inside of the joint of the second metal member, determined from the present disclosure, and tracing the crystal shape ... away from the joint of the second metal member, determined from the present disclosure, and tracing the crystal shape. FIG. 18B shows a trace of the crystal shape shown in FIG. 18A.19A and 19B.

[0033] FIG. 18B is a diagram showing a trace of the crystal shape shown in FIG. 18B.

[0034] FIG. 19A is a graph showing the change in average crystal grain size versus the distance (μm) from the surface of the second metal member, obtained from FIGS. 19A and 19B.

[0035] FIG. 19B is a graph showing the crystal refinement rate (with the internal average crystal grain size being 100%) versus the depth ratio (%) from the surface of the second metal member, obtained from FIGS. 19A and 19B.

[0036] FIG. 19A is a microscope image (magnification: 1500x) of the crystal shape of the surface and interior of a metal element that has been immersed in liquid nitrogen and cooled, and the crystal shape is traced.

[0037] FIG. 21A is a diagram showing a trace of the crystal shape shown in FIG. 21B.

[0038] FIG. 21B is a graph showing the change in average crystal grain size versus the distance (μm) from the surface of the metal element, obtained from FIGS. 21A and 21B. 21B. FIG. 21C is a graph showing the crystal refinement rate (with the internal average crystal grain size taken as 100%) versus the depth ratio (%) from the surface of the metal simple substance, obtained from FIGS. 21A and 21B.

[0010] A bonded structure according to an embodiment of the present disclosure will be described below with reference to the drawings. However, the drawings referred to below show simplified embodiments of the present disclosure for the sake of convenience. Therefore, the bonded structure disclosed below may include any components not shown in the drawings. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0011] The feed-through terminal described in Patent Document 1 has low mechanical strength, and therefore, when external stress is applied, cracks are likely to occur in the tubular member, tube, and pin made of a metal material near the brazed joint. In particular, when the feed-through terminal is used in a low-temperature environment or a high-pressure environment, large stress is applied to the metal material near the brazed joint, and cracks are likely to occur in the tubular member, tube, and pin. When cracks occur in the tubular member, tube, and pin, the airtightness of the feed-through terminal is reduced. Cracks are particularly likely to occur when repeated stress is applied.

[0012] Fig. 1 is a perspective view showing a bonded body 20 according to this embodiment, and Fig. 2 is a cross-sectional view thereof. The bonded body 20 shown in Figs. 1 and 2 can be used as, for example, an airtight terminal.

[0013] The joined body 20 has metal members including a first metal member 2 that is a cylindrical body and a second metal member 4 that is a columnar body, and is joined to an insulating member 6 that is an insulator. The insulating member 6 is located within the inner wall of the cylindrical body of the first metal member 2 and has a through hole 5. The second metal member is located so as to pass through the through hole 5.

[0014] The first metal member 2 and the second metal member 4 are joined to the insulating member 6 by a joining material 12. The insulating member 6 and the first metal member 2 and the second metal member 4 face each other via gaps 8a and 8b, respectively, and at least a portion of the joining material 12 is located within the gaps 8a and 8b. In another embodiment, the gaps 8a and 8b may not be provided at least partially, and the first metal member 2 and the second metal member 4 may abut against the insulating member 6, for example. Examples of the joining material 12 include metals such as brazing filler metals, glass, and the like.

[0015] Fig. 3 is an enlarged cross-sectional view of portion A in Fig. 2. As shown in Fig. 3, bonding material 12, which bonds first metal member 2 including a cylindrical body to insulating member 6, has first extending portion 12a1 and first filling portion 12a2 located in gap 8a. First extending portion 12a1 extends in a direction away from insulating member 6 and has a fillet shape that contacts part of the surface of first metal member 2 and part of the surface of insulating member 6.

[0016] The portion of the surface of the first metal member 2 that contacts the bonding material 12 is referred to as the first bonding portion 10a. In FIG. 3, the portion of the surface of the first metal member 2 that contacts the first extending portion 12a1 and the first filling portion 12a2 is referred to as the first bonding portion 10a. The portion A in FIG. 2 has a configuration as shown in FIGS. 4A and 4B in addition to FIG. 3. In FIG. 4A, the bonding material 12 has only the first filling portion 12a2. In FIG. 4B, the bonding material 12 has only the first extending portion 12a1. The first filling portion 12a2 requires that the bonding material 12 contact both the first metal member 2 and the insulating member 6 within the gap 8a. Contacting both means that the bonding material 12 is located on the line segment that connects the first metal member 2 and the insulating member 6 at the shortest distance within the gap 8a. However, it is assumed that there are no voids (closed gaps in the bonding material 12) on the line segment that do not contact the first metal member 2 or the insulating member 6. 5A and 5B , when the bonding material 12 is not in contact with at least one of the first metal member 2 and the insulating member 6 (portion D), it is not the first bonding portion 10a. Even when the bonding material 12 is in contact with both the first metal member 2 and the insulating member 6, the portion within the gap 8a where the bonding material 12 is not present on the line segment connecting the first metal member 2 and the insulating member 6 at the shortest distance, excluding voids, is not the first bonding portion 10a.

[0017] In this embodiment, the average crystal grain size of the first surface layer 2a1 of the first metal member 2 at the first bonding portion 10a is smaller than the average crystal grain size of the first interior portion 2b of the first metal member 2. For example, when the average crystal grain size of the first interior portion 2b of the first metal member 2 is Di (μm) and the average crystal grain size of the first surface layer 2a1 is Ds (μm), this can be expressed by the formula: Ds≦0.7Di. In other words, this means that the average crystal grain size Ds of the first surface layer 2a1 is 70% or less of the average crystal grain size Di of the first interior portion 2b. The formula: Ds≦0.6Di may also be satisfied.

[0018] Thus, the crystals in the first surface layer 2a1 of the first metal member 2 are finer, which improves the mechanical strength. Therefore, for example, when stress (mechanical stress, thermal stress, etc.) is applied to the first metal member 2 from the insulating member 6 via the first joint 10a, it is possible to reduce the occurrence of cracks in the first surface layer 2a1 of the inner wall of the cylindrical body that is the first metal member 2. Because the average crystal grain size of the first interior 2b of the first metal member 2 is relatively large, even if fine cracks are generated in the first surface layer 2a1 of the first metal member 2, it is possible to reduce the propagation of the cracks inward. Furthermore, because the rigidity of the first metal member 2 is high, fracture is less likely to occur even when stress is repeatedly applied to the joined body 20.

[0019] The first surface layer 2a1 of the first metal member 2 refers to a region extending from the surface (inner wall surface) of the first metal member 2 to a depth L of 5% of the thickness. For example, if the thickness of the cylindrical first metal member 2 is 0.75 mm, the first surface layer 2a1 refers to a region extending from the surface to a depth L of 0.0375 mm in the thickness direction.

[0020] The first interior 2b of the first metal member 2 refers to a region having a depth of 20% to 80% of the thickness from the surface (inner wall surface) of the first metal member 2. For example, if the thickness of the first metal member 2 is 0.75 mm, the first interior 2b is a region having a depth of 0.15 mm to 0.6 mm from the surface in the thickness direction.

[0021] The average crystal grain size of the surface layer 2a2 of the first metal member 2 away from the first bonding portion 10a is preferably smaller than the average crystal grain size of the first interior portion 2b of the first metal member 2, and larger than the average crystal grain size of the first surface layer 2a1 of the first metal member 2 in contact with the first bonding portion 10a. This reduces the propagation of cracks into the first interior portion 2b, while also reducing the propagation of cracks into the surface layer 2a2 away from the first bonding portion 10a. This reduces the risk of fracture of the cylindrical first metal member 2 even when repeated stress is applied. A method for identifying the surface layer 2a2 away from the first bonding portion 10a will be described later.

[0022] Fig. 6 is an enlarged cross-sectional view of part B in Fig. 2. As shown in Fig. 6, bonding material 12 bonding second metal member 4 including a columnar body to insulating member 6 has second extending portion 12b1 having a fillet shape that contacts a part of the surface of second metal member 4 extending in a direction away from insulating member 6 and a part of the surface of insulating member 6, and second filling portion 12b2 located in gap 8b.

[0023] The portion of the surface of the second metal member 4 that comes into contact with the joining material 12 is referred to as the second joining portion 10b. In Fig. 6, the portion of the surface of the second metal member 4 that comes into contact with the second extending portion 12b1 and the second filling portion 12b2 is referred to as the second joining portion 10b.

[0024] In Fig. 7A, the bonding material 12 has only the second filling portion 12b2. In Fig. 7B, the bonding material 12 has only the second extending portion 12b1. The second bonding portion 10b in contact with the bonding material 12 includes not only the form shown in Fig. 6 but also the forms shown in Figs. 7A and 7B.

[0025] 6, 7A, and 7B , in the joint between the second metal member 4 including the columnar bodies and the insulating member 6, the average crystal grain size of the second surface layer 4a1 of the second metal member 4 at the second joint portion 10b is smaller than the average crystal grain size of the second inner portion 4b of the second metal member 4. For example, when the average crystal grain size of the second inner portion 4b of the second metal member 4 is Di (μm) and the average crystal grain size of the second surface layer 4a1 is Ds (μm), this can be expressed by the formula: Ds≦0.7Di. Alternatively, Ds≦0.6Di may be satisfied.

[0026] The second surface layer 4a1 of the second metal member 4 refers to a region having a depth L of 5% of the thickness (half the diameter in the case of a columnar body such as a solid pin) from the surface of the second metal member 4. For example, if the second metal member 4 has a diameter of 1.6 mm (radius of 0.8 mm), the second surface layer 4a1 is a region having a depth L of 0.04 mm in the radial direction from the surface.

[0027] The second interior 4b of the second metal member 4 refers to a region having a depth of 20% or more of the radial thickness from the surface of the second metal member 4 (half the diameter in the case of a columnar body such as a solid pin). For example, if the diameter of the second metal member 4 is 1.6 mm (radius 0.8 mm), the second interior 4b is a region that is deeper than 0.16 mm in the radial direction from the surface. The upper limit of the second interior 4b is the center C (axial center) of the second metal member 4.

[0028] In the second metal member 4, the average crystal grain size of the surface layer 4a2 away from the second joint 10b is smaller than the average crystal grain size of the second interior 4b of the second metal member 4, and is larger than the average crystal grain size of the second surface layer 4a1 of the second metal member 4 that is in contact with the second joint 10b.

[0029] The joined body 20 shown in Figure 2 is joined to the first metal member 2 and the second metal member 4 on one side (upper side) of the insulating member 6, but it may also be joined to the first metal member 2 and the second metal member 4 on both sides (upper and lower sides) of the insulating member 6, as in the joined body 21 shown in Figure 8.

[0030] 9A and 9B , the insulating member 6 may have a chamfered portion 14 on the outer peripheral surface facing the first metal member 2 and on the inner wall surface of the through hole 5 through which the second metal member 4 is inserted. The chamfered portion 14 may include at least one of a C-surface and an R-surface. Although the chamfered portion 14 is located on one side (upper side) of the insulating member 6 in FIGS. 9A and 9B , it may also be located on both sides (upper and lower) of the insulating member 6.

[0031] A method for identifying the first extending portion 12a1 and the second extending portion 12b1 will be described with reference to Fig. 10. Fig. 10 is a microscope image showing a cross section of the second bonding portion 10b and its surrounding area in the present disclosure. Fig. 10 uses the second extending portion 12b1 (second bonding portion 10b) as an example for description, but the first extending portion 12a1 (first bonding portion 10a) can also be identified using the same identification method.

[0032] (a) As shown in FIG. 10 , a first line L1 is drawn on the surface of the insulating member 6 and its extension. The first line L1 intersects with the second metal member 4. (b) A second line L2 is drawn on the contour of the outer circumferential surface of the second metal member 4. The second line L2 intersects with the first line L1. The intersection of the first line L1 and the second line L2 is defined as the origin P1. (c) A third line L3 is drawn starting from the origin P1 and at an angle of 1° from the second line L2 toward the second extension portion 12b1. (d) The first intersection point of the third line L3 with the contour of the second extension portion 12b1 is defined as point P2. (e) A fourth line L4 is drawn parallel to the first line L1 and passing through point P2. The second extension portion 12b1 is defined as the bonding material 12 located between the first line L1 and the fourth line L4. The second joint 10b in the second extension 12b1 is the surface of the second metal member 4 between the first line L1 and the fourth line L4. For reasons described below, the second joint 10b is illustrated as being between the first line L1 and the fifth line L5. In FIG. 10 , the second extension 12b1 is located on both sides of the second metal member 4, so it is preferable to identify the second joint 10b for each second extension 12b1. The angle between the second line L2 and the third line L3 is set to 1°, but may be appropriately selected within the range of 0.8° to 1.6°. If the angle is within the above range, the crystals in the second surface layer 4a1 of the second joint 10b are refined. The second extension 12b1 extends thinly through point P2 in a direction away from the insulating member 6, but is considered to be a thin film and therefore does not substantially contribute to the bonding. 10 is a schematic diagram for easy understanding of the method for identifying the second joint portion 10b, and in reality, point P2 is located near point P4. Note that if the second extending portion 12b1 (especially its terminal portion) has an irregular convex or bulging portion, it is best not to take such convex or bulging portion into consideration when identifying the second extending portion 12b1.

[0033] If it is difficult to identify the second bonding portion 10b using the above-described identification method, a portion of the extension having a thickness of 15 μm or more may be designated as the second extension portion 12b1. In Fig. 10, the portion of the extension above the fifth line L5 parallel to the first line L1 has a thickness of less than 15 μm and is therefore considered not to substantially contribute to the bonding.

[0034] If it is difficult to identify the second joint portion 10b using any of the above methods, the second joint portion 10b may be identified using the arc-shaped cross-sectional shape of the second extension portion 12b1. In the cross-sectional view shown in FIG. 10, an arc C1 is drawn so as to follow the contour of the second extension portion 12b1 as closely as possible. "Following the contour as closely as possible" means minimizing the difference between the arc C1 and the contour of the second extension portion 12b1. The difference between the arc C1 and the contour of the second extension portion 12b1 can be calculated, for example, as follows: A straight line is drawn from the center of the arc C1 toward the arc C1, and an intersection E between the line and the arc C1 and an intersection F between the line and the contour of the second extension portion 12b1 are identified. The direction from the center of the arc C1 toward the arc C1 is defined as the positive direction, and the length of the line from intersection E to intersection F is the difference between the arc C1 and the contour of the second extension portion 21b. For example, nine straight lines are drawn from the center of the arc C1, dividing the arc C1 into nine equal parts. The difference between the contours of the arc C1 and the second extension portion 12b1 is calculated for each line. The state where the sum of these differences is smallest is considered to be the smallest difference between the arc C1 and the second extension portion 12b1. The number of equal divisions of the arc C1 can be adjusted appropriately depending on the shape of the second extension portion 21b. The perimeter of the arc C1 is set to 1 / 4 of the circumference. The arc C1 has points P3 and P4 at both ends. Point P4 of the arc C1 is the point closest to the second metal member 4. A sixth straight line L6 is drawn that passes through point P4 of the arc C1 and is parallel to the first straight line L1 (in FIG. 10, it overlaps with the fifth straight line L5). In this case, the second joint portion 10b is the portion between the first straight line L1 and the sixth straight line L6. The first extension portion 12a1 is also identified using the same method.

[0035] A method for identifying the surface layer 4a2 away from the second bonding portion 10b will be described with reference to Figure 11. (1) The upper end of the second bonding portion 10b is set as the starting point (0 mm). The average crystal grain size of the surface layer and the second interior portion 4b of the second metal member 4 is measured at the starting point and at multiple portions along the surface of the second metal member 4 away from the starting point (for example, multiple portions spaced 0.25 mm apart as shown in Figure 11). (2) The crystal refinement rate (%) is calculated using the following formula: Refinement rate (%) = {(average crystal grain size of the surface layer) / (average crystal grain size of the interior)} x 100. The calculation results are shown in Table 1. The surface layer and interior are as described above. The measurement interval is not limited to 0.25 mm and can be changed as appropriate. (3) From Table 1 above, the region away from the starting point (0 mm), where the refinement rate (%) is greater than that of the starting point and where the refinement rate (%) value exceeds 80% (i.e., the region including the measurement positions 0.75 mm, 1.00 mm, and 1.25 mm) is defined as the surface layer 4a2 away from the second bonding portion 10b.

[0036] The surface layer 2a2 remote from the first bonding portion 10a can be identified by the same identification method as the surface layer 4a2 remote from the second bonding portion 10b.

[0037] A method for manufacturing the bonded body 20 shown in Figures 1 and 2 will be described. Figure 12 is a flowchart showing the manufacturing method, and Figure 13 is an exploded view showing the assembly method of each member. As shown in Figure 12, in manufacturing the bonded body of the present disclosure, an insulating member 6, which is an insulator as a raw material, a metal member (a first metal member 2 and a second metal member 4), and a bonding material 12 containing metal or glass are prepared (preparation step). The insulator is an insulating material having a volume resistivity of 10 at 20°C. １０ This refers to insulating materials with a resistance of Ω·m or more.

[0038] The insulating member 6 preferably contains, as its main component, one of alumina, zirconia, silicon nitride, silicon carbide, forsterite, cordierite, and sapphire. Among these insulating members 6, ceramic materials are inexpensive and have excellent mechanical strength, while sapphire has excellent optical transparency. The main component of an insulating member refers to a component that accounts for 60% by mass or more of the total 100% by mass of the components that make up the insulating member. In particular, the main component is preferably a component that accounts for 95% by mass or more of the total 100% by mass of the components that make up the insulating member. The components that make up the insulating member can be determined using an X-ray diffraction (XRD) analyzer. The content of each component can be determined by identifying the component, then using an X-ray fluorescence analyzer (XRF) or an ICP optical emission spectrometer to determine the content of the elements that make up the component, and converting the content into the identified component.

[0039] The first metal member 2 and the second metal member 4 preferably contain Fe, Ni, and Co, with the total content of Fe, Ni, and Co being 99% by mass or more, in order to reduce the thermal expansion coefficient and thereby reduce residual stress generated by bonding with the insulating member 6. This reduces cracking of the first metal member 2 and the second metal member 4. In this case, the insulating member 6 may be primarily composed of alumina, which has a thermal expansion coefficient similar to that of the first metal member 2 and the second metal member 4. The first metal member 2 and the second metal member 4 preferably contain Fe at least 40% by mass and no more than 56% by mass, Ni at least 25% by mass and no more than 40% by mass, and Co at least 10% by mass and no more than 30% by mass. Furthermore, the first metal member 2 and the second metal member 4 preferably contain Fe at least 50% by mass and no more than 56% by mass, Ni at least 26% by mass and no more than 33% by mass, and Co at least 14% by mass and no more than 20% by mass. Specifically, the first metal member 2 may be an Fe-Ni alloy such as Invar 36 (54% by mass Fe, 36% by mass Ni) or an Fe-Ni-Co alloy such as Kovar (53% by mass Fe, 29% by mass Ni, 17% by mass Co). The columnar second metal member 4 may be a metal having the same composition as the first metal member 2. The second metal member 4 may also be a metal different from that of the first metal member 2, such as Cu (copper) or an alloy containing Cu as a main component. The first metal member 2 may be Cu or an alloy containing Cu as a main component, and the second metal member 4 may be an alloy such as Kovar or Invar 36. The joining material 12 may preferably contain a metal such as a brazing filler metal or glass.

[0040] As an example of a combination in the present disclosure, at least one of the first metal member 2 and the second metal member 4 preferably contains a composition of 40% by mass or more and 56% by mass or less of Fe, 25% by mass or more and 40% by mass or less of Ni, and 10% by mass or more and 30% by mass or less of Co, the insulating member 6 contains alumina, and the joining material 12 contains Ag and Cu, and is a brazing material whose total content of Ag and Cu is 90% by mass or more.

[0041] 13 , the columnar second metal member 4 is inserted into the through hole 5 of the insulating member 6, and the insulating member 6 is inserted into the cylindrical first metal member 2. A bonding material 12 is disposed on either the opposing surface between the insulating member 6 and at least the first metal member 2 or at least one surface of the insulating member 6 near the opposing surface, and on either the opposing surface between the insulating member 6 and at least the second metal member 4 or at least one surface of the insulating member 6 near the opposing surface, to obtain an assembly (assembly process).

[0042] The assembly is heated in a vacuum or in an inert gas to melt the bonding material 12, and then cooled to 200°C or less to solidify the bonding material 12. This results in a pre-bonded body in which the insulating member 6 and the first metal member 2, and the insulating member 6 and the second metal member 4 are bonded together (bonding process).

[0043] A metallized layer may be formed on the insulating member 6 before the bonding material 12 is placed. Examples of the metallized layer include a Mo-Mn-based metallized layer. After the metallized layer is formed, a plating layer may be formed on the metallized layer. The plating layer may include Ni plating. Regardless of whether the metallized layer is formed or not, a plating layer may be formed on at least one of the inner wall surface of the first metal member 2 and the outer circumferential surface of the second metal member 4. The plating layer may include Ni plating.

[0044] The resulting pre-joined body is cooled at an ambient temperature of −100° C. or lower to obtain the joined body 20 (cooling step). Cooling the pre-joined body allows for finer crystals in the portions of the first metal member 2 and the second metal member 4 that abut the joints (i.e., the portions of the first surface layer 2a1 and the second surface layer 4a1). Finer metal crystals improve the mechanical strength of the finer portions, reducing the occurrence of cracks in the first joint portion 10a and the second joint portion 10b. This improves the mechanical strength of the joined body 20 of metal and ceramic, which is an insulator, and reduces fracture.

[0045] Cooling can be performed, for example, by immersion in a cooling liquid at −100°C or lower. Examples of cooling liquids include liquid oxygen (boiling point −183°C), liquid nitrogen (boiling point −196°C), liquid hydrogen (boiling point −253°C), and liquid helium (boiling point −269°C). The immersion time is at least 1 minute, and may be at least 10 minutes. The pre-joined body may be cooled to −100°C or lower in a gas atmosphere at an ambient temperature of −100°C or lower, rather than in a liquid. By extending the immersion time, the average crystal grain size of the first surface layer 2a1 and the second surface layer 4a1 can be reduced. The immersion time can be appropriately adjusted to achieve the desired average crystal grain size. In the joined body 20 of the present disclosure, the metal crystals of the first surface layer 2a1 and the second surface layer 4a1 of the first joining portion 10a and the second joining portion 10b are finer than those of other portions, rather than the entire metal. This is because residual stress occurs in first surface layer 2a1 and second surface layer 4a1 of first bonding portion 10a and second bonding portion 10b due to bonding.

[0046] The bonded structure of the present disclosure can be used as an electromagnetic wave-transmitting window member for introducing electromagnetic waves into semiconductor manufacturing equipment or outputting high-frequency waves from an accelerator. This window member has a cylindrical first metal member 2, and the outer surface of an insulating member 6 is bonded to the inner wall surface of this first metal member 2. The second metal member 4 including the columnar bodies described above is not necessarily required. The insulating member 6 used should preferably be primarily composed of alumina, zirconia, silicon nitride, silicon carbide, forsterite, cordierite, or sapphire. When the insulating member 6 is sapphire, the electromagnetic wave-transmitting window member can also be used as a peephole. Peepholes are used, for example, as windows for visually checking the inside of containers, piping, semiconductor manufacturing equipment, furnaces, and other equipment.

[0047] The assembly of the present disclosure can also be used as a power supply terminal. The power supply terminal is used, for example, as a power supply terminal for introducing a large current of 100 A or more into equipment. This power supply terminal has a second metal member 4 including a columnar body, and the insulating member 6 has a through hole 5 through which the second metal member 4 passes. The cylindrical first metal member 2 described above is not necessarily required.

[0048] The joined body of the present disclosure can also be used as an airtight power supply terminal that requires high airtightness. The airtight terminal is used, for example, as a power supply terminal that introduces current from the outside into a vacuum vessel, or as a signal terminal that transmits signals from a sensor installed inside a vessel, piping, equipment, or the like that requires airtightness. As shown in FIGS. 1 , 2 , and 8 , this airtight terminal includes an insulating member 6 located within the inner wall of a cylindrical first metal member 2 and a through hole 5 through which a columnar second metal member 4 passes. In the joined body 20, 21 used for the airtight terminal, the first metal member 2 and the second metal member 4 preferably contain 40% to 56% by mass of Fe, 25% to 40% by mass of Ni, and 10% to 30% by mass of Co, the insulating member 6 preferably contains alumina, and the joining material 12 preferably contains Ag and Cu, with the total Ag and Cu content being 90% by mass or more. This results in excellent airtightness between the cylindrical body of the first metal member 2 and the insulating member 6, and between the columnar body of the second metal member 4 and the insulating member 6, as well as excellent bonding strength between them. This is because the thermal expansion coefficients of the first metal member 2, the second metal member 4, and the insulating member 6 are similar, and the bonding material 12 has good wettability. Therefore, cracks are less likely to occur in the first metal member 2 and the second metal member 4 even when stress is applied. The airtight terminal maintains excellent airtightness even when used in an environment of -100°C or below, and can reduce cracks in the first metal member 2, the second metal member 4, and the insulating member 6 that constitute the airtight terminal.

[0049] Next, the crystal refinement will be described in detail with reference to examples.

[0050] Example 1: A bonded body 21 having the cross-sectional structure shown in FIG. 8 was fabricated, and the crystal size reduction in the first bonding portion 10a (see FIG. 9A ) of the cylindrical first metal member 2 was investigated. The components constituting the bonded body 21 were as follows: First metal member 2: A 0.75 mm-thick cylindrical body (sleeve) made of an Fe-Ni-Co alloy (Kovar containing 53% by mass of Fe, 29% by mass of Ni, and 17% by mass of Co). Second metal member 4: A 1.6 mm-diameter columnar body (pin) made of the same Fe-Ni-Co alloy as the first metal member 2. Insulating member 6: A sintered body containing 99.5% by mass of alumina, having two through holes 5 through which the second metal member 4 is inserted. Bonding material 12: A brazing filler metal containing Ag and Cu, with a total Ag and Cu content of 90% by mass or more. After assembly, the bonded body 21 was immersed in liquid nitrogen at −100°C or below for 10 minutes.

[0051] The bonded body 21 thus subjected to low-temperature treatment was embedded in resin and then cut using a diamond cutter. The cut surface was roughly polished using a diamond disk, buffed using diamond abrasive grains, and then buffed using silica abrasive grains. This resulted in a mirror-like polished surface. The polished surface was then moderately chemically polished using a 5% nitric acid-ethanol mixed solution or aqua regia (a liquid mixture of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 3:1). Instead of chemical polishing, moderate physical polishing using focused ion beam (FIB) processing or io-milling processing may also be used. This facilitates observation of the metal grain boundaries. The cross section of the sample thus treated was photographed using a microscope (Keyence VHX-5000, 1500x magnification).

[0052] 14A and 14B are microscope images of the crystal shape of the cross section of the cylindrical body that is the first metal member 2. FIG. 14A shows the crystal shape from the first surface layer 2a1 to the first interior 2b of the first metal member 2 at the first joint 10a, while FIG. 14B shows the crystal shape from the surface layer 2a2 to the interior of the first metal member 2 at a position (normal portion) away from the first joint 10a. In FIGS. 14A and 14B, the horizontal direction indicates the depth direction from the surface of the first metal member 2, and the vertical direction (i.e., the direction along the surface of the first metal member 2) indicates the measurement direction of the average crystal grain size. The normal portion is located 1 mm away from the surface of the insulating member 6 bonded to the first metal member 2. FIGS. 15A and 15B are microscope images of the crystal shape shown in FIGS. 14A and 14B, respectively. That is, Figures 15A and 15B were created by importing the electronic data of the microscope images shown in Figures 14A and 14B into PowerPoint (a trademark of Microsoft Corporation) and tracing the outline of the crystal using a drawing tool. Alternatively, the microscope image may be printed, a piece of tissue paper placed on top, and the outline of the crystal traced onto the tissue paper. Figures 16A and 16B are traces of the crystal shapes shown in Figures 15A and 15B, respectively.

[0053] The measurement positions of the average crystal grain size are indicated by the depth distance d (μm) from the surface and the percentage (%). The depth percentage (%) is calculated using the formula: (d / 0.75) × 100, with the thickness of the first metal member 2, 0.75 mm, being 100%. The measurement positions, expressed as the depth percentage (%), were arbitrarily set to 1.6%, 3.2%, 5.0%, 7.5%, 10%, 15%, 20%, 30%, 40%, 50%, and 65%. These measurement positions are indicated by vertical lines parallel to the measurement direction of the average crystal grain size on the traces in Figures 16A and 16B. At each measurement position on the traces in Figures 16A and 16B, a 150 μm line is drawn along the measurement direction of the average crystal grain size. The crystal count is calculated by subtracting 1 from the total number of points where this line intersects with the crystal grain boundary. The average crystal grain size is calculated by dividing the length of the line, 150 μm, by the crystal count. The measurement positions of the average crystal grain size will be described. FIG. 8 shows four first extension portions 12a1 that join the left and right first metal members 2 and the insulating member 6. Measurement locations were four locations in the first joints 10a that contact each first extension portion 12a1, and four locations in the normal portions away from each first joint 10a. The average crystal grain size was calculated as the average of the average crystal grain sizes at each measurement location. The results are shown in Table 2 and FIG. 17A. The graph in FIG. 17A shows the change in average crystal grain size versus distance (μm) from the surface, i.e., versus distance (μm) in the depth direction from the surface.

[0054] Table 3 shows the crystal refinement rate calculated from the average crystal grain size at each measurement position from the surface of the first metal member 2 to a depth of 15% and the average crystal grain size inside (a region from the surface to a depth of 20% to 65%), based on the measurement results in Table 2. The crystal refinement rate is calculated using the following formula: Refinement rate (%) = {(average crystal grain size at each measurement position) / (average crystal grain size inside)} × 100 The graph in Figure 17B shows the change in the crystal refinement rate versus the depth percentage (%) from the surface.

[0055] Table 4 shows the crystal refinement rate calculated from the average crystal grain size in the surface layer (region up to 5% depth from the surface) of the first metal member 2 and the average crystal grain size in the interior (region 20% to 65% depth from the surface) based on the measurement results in Table 2. The crystal refinement rate is calculated using the following formula: Refinement rate (%) = {(average crystal grain size in the surface) / (average crystal grain size in the interior)} x 100

[0056] As is clear from Table 4, the first surface layer 2a1 of the first bonding portion 10a has a smaller average crystal grain size than the first interior portion 2b. The surface layer of the normal portion also has a smaller average crystal grain size than the interior portion, but the average crystal grain size is larger than that of the first surface layer 2a1 of the first bonding portion 10a. The normal portion has a crystal refinement rate of 90%, which means that there is almost no refinement, while the first surface layer 2a1 of the first bonding portion 10a has a refinement rate of 69%.

[0057] Example 2: Using the bonded body 21 used in Example 1, we investigated the reduction of crystal size at the second bonding portion 10b (see FIG. 9B ) of the columnar second metal member 4 bonded to the insulating member 6. FIGS. 18A and 18B are microscope images of the cross-sectional crystal shape of a columnar body (pin) that is the second metal member 4. FIG. 18A shows the crystal shape from the second surface layer 4a1 to the second interior portion 4b of the second metal member 4 at the second bonding portion 10b, while FIG. 18B shows the crystal shape from the surface layer 4a2 to the interior of the second metal member 4 at a position (normal portion) away from the second bonding portion 10b. In these figures, the crystal shape is traced. FIGS. 19A and 19B are diagrams showing traces of the crystal shape shown in FIGS. 18A and 18B, respectively. The measurement locations for the average crystal grain size will be described. FIG. 8 shows eight second extension portions 12b1 that bond the left and right second metal members 4 to the insulating member 6. The measurement locations were four locations in the second joint 10b, which contacts the two second extensions 12b1 joining the left second metal member 4 and the upper surface of the insulating member 6, and the two second extensions 12b1 joining the right second metal member 4 and the lower surface of the insulating member 6, as well as four locations in the normal portion away from each second joint 10b. The average crystal grain size was calculated as the average of the average crystal grain sizes at the four measurement locations. The rest of the test was conducted in the same manner as in Example 1. The results are shown in Table 5. The average crystal grain size of the second joint 10b and the normal portion away from it in the joint that was not subjected to low-temperature treatment was also tested in the same manner. The results are shown in Table 6. The graph in Figure 20A shows the results of Tables 5 and 6, showing the change in average crystal grain size versus distance from the surface (μm).

[0058] Tables 7 and 8 show the crystal refinement rate calculated from the average crystal grain size at each measurement position from the surface of the second metal member 4 to a depth of 15% and the average crystal grain size inside (a region from the surface to 20% to 65% of the depth). The crystal refinement rate is calculated using the following formula: Refinement rate (%) = {(average crystal grain size at each measurement position) / (average crystal grain size inside)} x 100. The graph in Figure 20B shows the results of Tables 7 and 8, and indicates the change in average crystal grain size as a function of the depth percentage (%) from the surface.

[0059] Tables 9 and 10 show the crystal refinement rate calculated from the average crystal grain size in the surface layer (region up to 5% depth from the surface) of the second metal member 4 and the average crystal grain size in the interior (region 20% to 65% depth from the surface) based on the measurement results in Tables 7 and 8, respectively. The crystal refinement rate is calculated using the following formula: Refinement rate (%) = {(average crystal grain size in the surface) / (average crystal grain size in the interior)} x 100

[0060] As is clear from these test results, in the bonded body subjected to low-temperature treatment with liquid nitrogen, the crystals in the second surface layer 4a1 of the second bonded portion 10b were refined (crystal refinement rate: 61%), and when the average crystal grain size in the second interior portion 4b was taken as 100%, the refinement rate in the second surface layer 4a1 was 56 to 67%. On the other hand, in the normal portion, the refinement rate was 86%, and almost no crystal refinement was observed. Furthermore, in the bonded body not subjected to low-temperature treatment, the refinement rate in the bonded portion was 94%, and the refinement rate in the normal portion was about 96%, meaning that the crystals in the surface layer portion were not substantially refined.

[0061] (Reference Example) Using a columnar metal element made of the same material as the second metal member 4 used in Examples 1 and 2, a sample was subjected to low-temperature treatment by immersing it in liquid nitrogen at or below -100°C for 10 minutes to examine the crystal refinement of the sample. Measurements were performed at four randomly selected locations. For comparison, a sample that was not subjected to low-temperature treatment was also examined for crystal refinement. Figures 21A and 21B are microscope images of the cross-sectional crystal shapes of a low-temperature treated metal element and a non-low-temperature treated metal element, respectively. In these figures, the crystal shapes are traced. Figures 22A and 22B are diagrams showing traces of the crystal shapes shown in Figures 21A and 21B, respectively. The average crystal grain size and the calculation of the refinement rate were performed using the same method as in Example 1. The results are shown in Tables 11, 12, and 13 and Figures 23A and 23B. As shown in Tables 11, 12, and 13 and Figures 23A and 23B, no refinement of the crystal grains was observed in either the metal element that had been subjected to low-temperature treatment or the metal element that had not been subjected to low-temperature treatment.

[0062] Although the embodiments of the present disclosure have been described above, the bonded body of the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible.

[0063] 2 First metal member 2a1 First surface layer 2b First interior 2a2 Surface layer distant from first joint portion 4 Second metal member 4a1 Second surface layer 4b Second interior 4a2 Surface layer distant from second joint portion 5 Through hole 6 Insulating member 8a, 8b Gap portion 10a First joint portion 10b Second joint portion 12 Joining material 12a1 First extension portion 12a2 First filling portion 12b1 Second extension portion 12b2 Second filling portion 14 Chamfered portion 20 Joined body

Claims

1. A bonded body of metal and insulator comprising: a metal member; an insulating member; and a bonding material bonding the metal member and the insulating member together, wherein when a portion on the surface of the metal member that contacts the bonding material is defined as a bonding portion, the average crystal grain size of the surface layer of the metal member at the bonding portion is smaller than the average crystal grain size inside the metal member.

2. A joint between metal and insulator as claimed in claim 1, wherein the insulating member and the metal member face each other with a gap therebetween, and at least a portion of the joint material is located within the gap.

3. A joint between metal and insulator as described in claim 1, wherein the joint material extends along the surface of the metal member in a direction away from the insulating member and has a fillet shape in contact with a part of the surface of the metal member and a part of the surface of the insulating member.

4. A joint between metal and insulator as described in claim 2, wherein the joint material extends along the surface of the metal member in a direction away from the insulating member and has a fillet shape in contact with a portion of the surface of the metal member and a portion of the surface of the insulating member.

5. A joint between a metal and an insulator as described in any one of claims 1 to 4, wherein the average crystal grain size of the surface layer of the metal member away from the joint is smaller than the average crystal grain size inside the metal member, and is larger than the average crystal grain size of the surface layer of the metal member at the joint.

6. A joint between metal and insulator as described in any one of claims 1 to 4, wherein the metal member has a first metal member including a cylindrical body, and the insulating member is located within the inner wall of the cylindrical body of the first metal member.

7. A joint between a metal and an insulator according to any one of claims 1 to 4, wherein the metal member has a second metal member including a columnar body, the insulating member has a through hole, and the second metal member is positioned so as to pass through the through hole.

8. A joint between metal and insulator as described in any one of claims 1 to 4, wherein the metal members include a first metal member including a cylindrical body and a second metal member including a columnar body, the insulating member is located within the inner wall of the cylindrical body of the first metal member and has a through hole, and the second metal member is located passing through the through hole.

9. A joint between a metal and an insulator according to any one of claims 1 to 4, wherein the metal member contains Fe, Ni and Co, and the total content of the Fe, Ni and Co is 99 mass % or more.

10. A joint between a metal and an insulator according to any one of claims 1 to 4, wherein the insulating member is composed primarily of any one of alumina, zirconia, silicon nitride, silicon carbide, forsterite, cordierite and sapphire.

11. A joint between a metal and an insulator according to any one of claims 1 to 4, wherein the joint material comprises a metal or a glass.

12. A joint between metal and insulator as described in any one of claims 1 to 4, wherein the metal member contains 40% by mass or more and 56% by mass or less of Fe, 25% by mass or more and 40% by mass or less of Ni, and 10% by mass or more and 30% by mass or less of Co, the insulating member contains alumina, and the joining material includes a brazing material containing Ag and Cu, the total content of the Ag and the Cu being 90% by mass or more.

13. An electromagnetic wave transmitting window member using the bonded body according to claim 10.

14. A power supply terminal using the joint body according to claim 7.

15. An airtight terminal using the joint body according to claim 8.

16. An airtight terminal using the joint body according to claim 12.

17. The hermetic terminal according to claim 16, which is used in an environment of -100°C or less.

18. A method for manufacturing a bonded body of a metal and an insulator, comprising: a preparation step of preparing a metal member, an insulating member, and a bonding material containing metal or glass; a bonding step of bonding the insulating member and the metal member with the bonding material to produce a pre-bonded body; and a cooling step of cooling the pre-bonded body at an atmospheric temperature of -100°C or lower to obtain a bonded body.

19. The method for producing a joint between a metal and an insulator as set forth in claim 17, wherein the cooling is performed by immersing the pre-joined body in a liquid containing as a main component any one of liquid nitrogen, liquid oxygen, and liquid hydrogen.

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