Bonded body

Abstract

The bonded body according to the present disclosure comprises: a frame that contains a polycrystalline first ceramic for which aluminum oxide is the main component; and a plate-shaped body that is thinner than the frame and contains a polycrystalline second ceramic for which aluminum oxide is the main component. The bonded body according to the present disclosure has a structure in which the frame and the plate-shaped body are diffusion-bonded in the thickness direction. The content of the aluminum oxide contained in the second ceramic is greater than the content of the aluminum oxide contained in the first ceramic.

Description

zygote

[0001] The present invention relates to a conjugate.

[0002] Conventionally, diaphragm structures having a flexible film and a base having a window portion covered with this film have been used as components of various sensors. For example, when used as a component of a sensor, the diaphragm portion of the diaphragm structure is configured to detect, by an appropriate detection means, the bending displacement that the diaphragm portion of the diaphragm structure receives from an object to be measured. Furthermore, in recent years, diaphragm structures have also been used as components of piezoelectric / electrostrictive actuators. When used as a component of a piezoelectric / electrostrictive actuator, the diaphragm portion of the diaphragm structure is deformed by a piezoelectric / electrostrictive element, generating pressure in a pressure chamber formed inside the diaphragm structure.

[0003] As an example of such a diaphragm structure, Patent Document 1 discloses a diaphragm structure in which molded bodies are sintered together to achieve reliability, heat resistance, and corrosion resistance, and the diaphragm portion is formed into an outwardly convex shape opposite the window portion.

[0004] Japanese Patent Application Publication No. 8-51238

[0005] The joined body according to the present disclosure includes a frame containing a first polycrystalline ceramic primarily composed of aluminum oxide, and a plate-like body that contains a second polycrystalline ceramic primarily composed of aluminum oxide and is thinner than the frame. The joined body according to the present disclosure has a structure in which the frame and the plate-like body are diffusion-bonded in the thickness direction. The aluminum oxide content of the second ceramic is greater than the aluminum oxide content of the first ceramic.

[0006] A diaphragm structure according to the present disclosure includes the above-described bonded body. A pressure sensor according to the present disclosure includes the diaphragm structure and a sensor element or a thick-film resistor mounted on a first main surface of the plate-shaped body of the diaphragm structure.

[0007] The method for manufacturing a joined body according to the present disclosure includes the steps of: arranging a frame body containing a first polycrystalline ceramic primarily composed of aluminum oxide and a plate-like body that is thinner than the frame body and that contains a second polycrystalline ceramic primarily composed of aluminum oxide, so that they face each other in the thickness direction; and heat-treating the frame body and the plate-like body while pressing them in the thickness direction.

[0008] 1 is a plan view showing a bonded body according to an embodiment of the present disclosure. 2 is a cross-sectional view showing a cross section taken along line XX shown in FIG.

[0009] As described above, Patent Document 1 discloses a diaphragm structure in which molded bodies are integrally sintered together to provide reliability, heat resistance, and corrosion resistance, and the diaphragm portion is formed to have an outward convex shape opposite the window portion. However, when the diaphragm portion is repeatedly bent, the convex diaphragm portion experiences a significant increase in residual stress. As a result, there is a problem of early breakage. Therefore, there is a demand for a bonded structure that is resistant to breakage over a long period of time, even when repeatedly bent.

[0010] As described above, the bonded structure according to the present disclosure has a structure in which a ceramic structure and a ceramic plate are diffusion-bonded in the thickness direction. Therefore, both main surfaces of the ceramic plate are planar. Therefore, the bonded structure according to the present disclosure is less likely to break over a long period of time, even when repeatedly bent.

[0011] Furthermore, the manufacturing method of the bonded body according to the present disclosure includes a step of diffusion bonding the ceramic structure and the ceramic plate-like body in the thickness direction, as described above. Therefore, both main surfaces of the ceramic plate-like body are planar. Therefore, the manufacturing method of the bonded body according to the present disclosure can provide a bonded body that is resistant to breakage over a long period of time, even when repeatedly bent.

[0012] A joined body according to the present disclosure will be described with reference to FIGS. 1 and 2 . A joined body 1 according to an embodiment of the present disclosure shown in FIG. 1 includes a frame body 2 containing a first ceramic and a plate-like body 3 containing a second ceramic. As shown in FIG. 2 , the joined body 1 according to the embodiment has a structure in which the frame body 2 and the plate-like body 3 are diffusion-bonded in the thickness direction. The diffusion-bonded structure makes both main surfaces (first main surface 31 and second main surface 32) of the plate-like body 3 flat. As a result, the joined body 1 according to the embodiment is less likely to break over a long period of time, even when repeatedly bent.

[0013] In the following, of the two main surfaces of the plate-shaped body 3, the main surface located on the opposite side of the frame body 2 will be defined as the first main surface 31, the main surface located on the frame body 2 side will be defined as the second main surface 32, and of the two main surfaces of the frame body 2, the main surface located on the opposite side of the plate-shaped body 3 will be defined as the first main surface 21.

[0014] The first ceramic contained in the frame 2 is made of polycrystal and contains aluminum oxide as a main component. In this specification, "containing aluminum oxide as a main component" means that the content of aluminum oxide is 90 mass% or more in a total of 100 mass% of the ceramic of interest.

[0015] The first ceramic may have an aluminum oxide content of 92% by mass or more. When the aluminum oxide content of the first ceramic is 92% by mass or more, the amount of unavoidable impurities is reduced, thereby improving the mechanical strength. The aluminum oxide content of the second ceramic is greater than the aluminum oxide content of the first ceramic. Therefore, when the aluminum oxide content of the first ceramic is 92% by mass or more, the aluminum oxide content of the second ceramic (described later) also exceeds 92% by mass. Therefore, the mechanical strength of the second ceramic can also be improved.

[0016] In addition to aluminum oxide, the first ceramic may contain at least one element selected from the group consisting of silicon, magnesium, and calcium. The content of these elements in terms of oxide (hereinafter, the content in terms of oxide is referred to as the oxide equivalent amount) may be, for example, 6.7 mass% or less in total. When the oxide equivalent amount of these elements is within this range, the rigidity of the first ceramic can be improved. As a result, the frame 2 can more stably support the plate-shaped body 3. For example, the silicon oxide equivalent amount contained in the first ceramic is 2 mass% to 7 mass% inclusive, the magnesium oxide equivalent amount is 0.42 mass% to 1 mass% inclusive, and the calcium oxide equivalent amount is 0.17 mass% to 1.1 mass% inclusive.

[0017] As shown in Fig. 1, the frame 2 has a quadrilateral shape in plan view. The shape of the frame 2 is not limited to a quadrilateral shape, and may be a circle, an ellipse, or a polygonal shape other than a quadrilateral. In the case of a polygonal shape, including a quadrilateral shape, it may be a regular polygon or a scalene polygon.

[0018] The size of the frame body 2 is not limited and is set appropriately depending on the application of the bonded body 1. When the frame body 2 has a polygonal shape such as a square, the length of one side of the outer periphery may be, for example, 15 mm or more and 30 mm or less. When the frame body 2 has a circular or elliptical shape, the outer diameter may be, for example, 15 mm or more and 30 mm or less. In the case of an elliptical shape, it is sufficient that both the major axis and the minor axis are within such ranges. As shown in FIG. 2 , the thickness T1 of the frame body 2 is not limited and is set appropriately depending on the application of the bonded body 1. The thickness T1 of the frame body 2 may be, for example, 10 mm or more and 20 mm or less.

[0019] The second ceramic contained in the plate-shaped body 3 is polycrystalline and contains aluminum oxide as its main component. The definition of the main component is as described above. In addition to aluminum oxide, the second ceramic may also contain at least one element selected from the group consisting of silicon, magnesium, and calcium. For example, the silicon oxide-equivalent content of the second ceramic is 0.01% by mass to 0.04% by mass, the magnesium oxide-equivalent content of the second ceramic is 0.028% by mass to 0.049% by mass, and the calcium oxide-equivalent content of the second ceramic is 0.022% by mass to 0.039% by mass.

[0020] The amount of these elements contained in the second ceramic in terms of oxide may be smaller than the amount of these elements contained in the first ceramic in terms of oxide. If the amount of these elements contained in the second ceramic in terms of oxide is small, for example, when a sensor element or the like is mounted on the plate-shaped body 3, chemical reactions that may affect the sensor element or the like can be reduced.

[0021] In the joined body 1 according to one embodiment, the content of aluminum oxide contained in the second ceramic is greater than the content of aluminum oxide contained in the first ceramic. That is, the plate-like body 3 has a higher static elastic modulus than the frame body 2, and therefore the plate-like body 3 has higher rigidity than the frame body 2. As a result, even if the thickness of the plate-like body 3 is reduced, the plate-like body 3 is less likely to break. The difference between the amount of these elements contained in the second ceramic in terms of oxide and the amount of these elements contained in the first ceramic in terms of oxide is, for example, 3.5% by mass or more and 4% by mass or less.

[0022] The first ceramic and the second ceramic may further contain magnesium aluminate. The content of magnesium aluminate is not limited, and for example, the magnesium aluminate contained in the second ceramic may be less than the magnesium aluminate contained in the first ceramic. Because the thickness of the plate-shaped body 3 is thinner than the thickness of the frame body 2, the thermal shock resistance of the plate-shaped body 3 is poorer than that of the frame body 2. However, by making the content of magnesium aluminate, which affects thermal shock resistance, lower in the plate-shaped body 3 than in the frame body 2, the deterioration of the thermal shock resistance of the plate-shaped body 3 can be suppressed.

[0023] The difference in magnesium aluminate content between the first ceramic and the second ceramic is preferably 0.5% by mass or more, and the magnesium aluminate content in the first ceramic is preferably 0.5% by mass or more and 3% by mass or less. The second ceramic may not contain magnesium aluminate. In this case, deterioration in the thermal shock resistance of the plate-shaped body 3 can be further suppressed.

[0024] The components contained in the first ceramic and the second ceramic may be identified using an X-ray diffractometer using CuKα radiation. The content of each element may be converted to the compound identified by the X-ray diffractometer using an X-ray fluorescence analyzer (XRF) or an ICP optical emission spectrometer (ICP). The content of magnesium aluminate may be determined using the Rietveld method.

[0025] As shown in Fig. 1, the plate-like body 3 has a quadrangular shape when viewed from above. Like the frame body 2, the shape of the plate-like body 3 is not limited to a quadrangular shape, and may be a circle, an ellipse, or a polygonal shape other than a quadrangular shape. In the case of a polygonal shape, including a quadrangular shape, it may be a regular polygon or an irregular polygon. The shape and size of the plate-like body 3 are set appropriately depending on the shape of the frame body 2.

[0026] In the bonded structure 1 according to one embodiment, as shown in FIG. 2 , the thickness T2 of the plate-like body 3 is not limited as long as it is thinner than the thickness T1 of the frame body 2. The thickness T2 of the plate-like body 3 may be, for example, 0.1 mm or more and 2 mm or less. As described above, the plate-like body 3 contains a larger amount of aluminum oxide than the frame body 2, and therefore has a higher static elastic modulus, and therefore the plate-like body 3 has higher rigidity than the frame body 2. As a result, the thickness of the plate-like body 3 can be made thinner. The thickness T2 of the plate-like body 3 is preferably 0.2 mm or more and 0.6 mm or less. The static elastic modulus of the plate-like body 3 is, for example, 360 GPa or more.

[0027] The frame 2 shown in Figures 1 and 2 is a rectangular parallelepiped having a rectangular parallelepiped-shaped internal space penetrating in the thickness direction of the rectangular parallelepiped. However, the frame 2 is not limited to a rectangular parallelepiped and may be a structure having an internal space penetrating in the thickness direction, such as a polyhedron, a frustum, or a cylinder. In this case, the internal space is not limited to a rectangular parallelepiped and may be a polyhedron, a frustum, a cylinder, or other shape. The internal space does not necessarily have to be penetrating, and the first main surface 21 of the frame 2 located opposite the plate-like body 3 may be a structure without an opening. In this case, the internal space is in contact with the second main surface 32 of the plate-like body 3. If the first main surface 21 does not have an opening, at least one hole connecting the internal space to the external space may be formed in the first main surface 21.

[0028] The sizes of the aluminum oxide crystal grains contained in the first ceramic and the second ceramic are not limited. For example, the aluminum oxide crystal grains contained in the second ceramic may have an average equivalent circle diameter smaller than that of the aluminum oxide crystal grains contained in the first ceramic. Here, the equivalent circle diameter is the diameter of a circle having the same area as the area of ​​each crystal grain on the surfaces of the first ceramic and the second ceramic that have been sequentially polished and thermally etched.

[0029] The procedure is as follows: first, the average particle size D 50 The first main surface 31 of the plate-shaped body 3 is polished on a copper plate using diamond abrasive grains with an average grain size D 50The surface is polished on a tin plate using diamond abrasive grains with a diameter of 0.5 μm. The polished surface obtained by these polishing steps is thermally etched at, for example, 1480° C. until the crystal grains and the grain boundary layer become distinguishable, and the surface is used as the measurement target surface. The heat treatment is performed for, for example, about 30 minutes. 50 The first main surface 21 of the frame 2 is polished with a copper plate using diamond abrasive grains of 3 μm in diameter, and the measurement surface can be obtained by the same procedure as described above.

[0030] The heat-treated surface is observed with an optical microscope and photographed at a magnification of, for example, 400 times. 2 The measurement range is a range of 1 / 3 μm. By analyzing this measurement range using image analysis software (e.g., Win ROOF, manufactured by Mitani Corporation), the equivalent circle diameter of each crystal particle can be obtained. In determining the equivalent circle diameter, the threshold value of the equivalent circle diameter is set to 0.21 μm, and equivalent circle diameters less than 0.21 μm are not included in the calculation of the average value.

[0031] A small average value of the equivalent circle diameter can improve the mechanical strength and rigidity of the ceramics. That is, the mechanical strength and rigidity of the second ceramic can be improved compared to the first ceramic. As a result, even if the thickness of the plate-shaped body 3 is reduced, the plate-shaped body 3 is less likely to break.

[0032] The equivalent circle diameter of the aluminum oxide crystal particles contained in the second ceramic is, for example, 1 μm or more and 5 μm or less. The equivalent circle diameter of the aluminum oxide crystal particles contained in the first ceramic is, for example, 4 μm or more and 10 μm or less. The difference between the equivalent circle diameter of the aluminum oxide crystal particles contained in the second ceramic and the equivalent circle diameter of the aluminum oxide crystal particles contained in the first ceramic is, for example, 1 μm or more, and particularly 2 μm or more.

[0033] The surface texture of the main surfaces of the plate-like body 3 is not particularly limited. For example, the first main surface 31 of the plate-like body 3 may have a larger average value of the cut level difference (Rδc), which is the difference between the cut level at a load length ratio of 25% on the roughness curve and the cut level at a load length ratio of 75% on the roughness curve, than the second main surface 32 of the plate-like body 3. When a sensor element or the like is mounted on the plate-like body 3 and fixed with an adhesive or the like, an appropriate anchor effect is exerted on the sensor element or the like. As a result, the sensor element or the like can be firmly fixed to the plate-like body 3.

[0034] The average value of the cut level difference (Rδc) of the first main surface 31 is, for example, 0.6 μm or more and 1.5 μm or less. The average value of the cut level difference (Rδc) of the second main surface 32 is, for example, 0.3 μm or more and 0.9 μm or less. The difference between the average value of the cut level difference (Rδc) of the first main surface 31 and the average value of the cut level difference (Rδc) of the second main surface 32 is, for example, 0.3 μm or more and 0.6 μm or less.

[0035] The cut level difference (Rδc) in the roughness curve is an index showing the difference in height between the cut levels C(Rrm1) and C(Rrm2) that correspond to the load length ratios Rmr1 and Rmr2, respectively, in the roughness curve specified in JIS B0601: 2001. A smaller value of the cut level difference (Rδc) in the roughness curve indicates a smoother surface with fewer irregularities.

[0036] The cut level difference (Rδc) can be measured in accordance with JIS B 0601:2001 using a laser microscope (Keyence Corporation, Ultra-Deep Color 3D Shape Measuring Microscope (VK-X1000 or its successor model)). Measurement conditions include a coaxial illumination method, no cutoff value λs, a cutoff value λc of 0.08 mm, no cutoff value λf, end effect correction, a measurement magnification of 240x, and a measurement range of 1428 μm × 1070 μm per location on the first principal surface 31 and the second principal surface 32 to be measured. Four lines to be measured are drawn along the longitudinal direction of each measurement range, and line roughness measurements are performed. Prior to line roughness measurement, a correction strength of 5 is used to perform surface shape correction by waviness removal. The length of each line to be measured is, for example, 1282 μm. Two measurement ranges are set on each of the first main surface 31 and the second main surface 32, and the cut level difference (Rδc) is measured from a total of eight lines, and the average value is calculated.

[0037] The method for manufacturing the bonded body 1 according to one embodiment is not limited. The bonded body 1 is manufactured, for example, by arranging the frame body 2 and the plate-like body 3 so as to face each other and performing heat treatment while pressing them in the thickness direction. Specifically, the bonded body 1 is manufactured by the following steps: Step (a): A step of arranging a frame body containing a first polycrystalline ceramic mainly composed of aluminum oxide and a plate-like body thinner than the frame body, which contains a second polycrystalline ceramic mainly composed of aluminum oxide, so as to face each other in the thickness direction; and Step (b): A step of heat treatment while pressing the frame body and the plate-like body in the thickness direction.

[0038] In step (a), first, a frame 2 and a plate 3 are prepared. The frame 2 and the plate 3 are as described above, and detailed description thereof will be omitted. The first ceramic and the second ceramic contained in the frame 2 and the plate 3 are obtained, for example, by the following procedure.

[0039] Powders of aluminum oxide (purity of 99.9% by mass or more), magnesium hydroxide, silicon oxide, and calcium carbonate are charged into a grinding mill together with a solvent (ion-exchanged water). 50After pulverizing the aluminum oxide powder to a particle size of 1.5 μm or less, an organic binder and a dispersant for dispersing the aluminum oxide powder are added and mixed to obtain a slurry. Examples of organic binders include acrylic emulsion, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide.

[0040] To obtain the first ceramic, for example, the content of magnesium hydroxide powder is 0.6% by mass to 1.5% by mass, the content of silicon oxide powder is 2% by mass to 7% by mass, the content of calcium carbonate powder is 0.3% by mass to 2% by mass, and the balance is aluminum oxide powder, based on a total of 100% by mass of the powders. The total content of unavoidable impurities is 0.25% by mass or less.

[0041] To obtain the second ceramic, for example, the content of magnesium hydroxide powder is 0.04% by mass to 0.07% by mass, the content of silicon oxide powder is 0.01% by mass to 0.04% by mass, the content of calcium carbonate powder is 0.04% by mass to 0.07% by mass, and the balance is aluminum oxide powder, based on a total of 100% by mass of the powders. The total content of inevitable impurities is 0.25% by mass or less.

[0042] After the slurry is spray-granulated to obtain granules, a uniaxial press molding device or a cold isostatic press molding device is used to apply a molding pressure of 78 MPa to 128 MPa to obtain molded bodies corresponding to the shapes of the final frame body 2 and plate-like body 3. These molded bodies are fired under conditions of 1500°C to 1700°C for 4 hours to 6 hours, thereby obtaining the frame body 2 containing the first ceramic and the plate-like body 3 containing the second ceramic.

[0043] The obtained frame body 2 and plate-like body 3 are arranged so as to face each other in the thickness direction. Specifically, the first region 2a of the frame body 2 facing the plate-like body 3 and the second region 3a of the plate-like body 3 facing the frame body 2 are arranged so as to face each other. Water may be applied to at least one of the first region 2a and the second region 3a, if necessary.

[0044] At least one of the first region 2 a and the second region 3 a may be subjected to at least one of grinding and polishing before the frame body 2 and the plate-like body 3 are arranged to face each other. If at least one of the first region 2 a and the second region 3 a is subjected to such processing, the suction force between the first region 2 a and the second region 3 a can be improved in the step (b) described below.

[0045] The grinding method and the polishing method are not limited. Grinding can be performed using, for example, a surface grinder. Polishing can be performed by, for example, supplying a diamond slurry having an average particle size of 0.5 μm or more and 3 μm or less to a lapping machine made of copper, tin, or tin-lead alloy at predetermined intervals.

[0046] Next, in step (b), the frame body 2 and the plate-like body 3, which are arranged so as to face each other, are subjected to heat treatment while being pressed from the thickness direction. Examples of a method of joining by performing heat treatment while pressing in this manner include diffusion bonding. Specifically, the frame body 2 and the plate-like body 3 are arranged so as to face each other, and pressed from the thickness direction, for example, by the weight of the plate-like body 3, and heat treatment is performed under conditions of 1000°C to 1800°C and 4 hours to 6 hours. If necessary, the frame body 2 and the plate-like body 3 may be pressed from the thickness direction with a force of, for example, 800 gf to 3 kgf, and heat treatment may be performed under the above conditions. By performing heat treatment in this manner, a bonded body 1 according to one embodiment can be obtained.

[0047] In step (b), the heat treatment is preferably performed, for example, with the plate-like body 3 facing downward. By performing the heat treatment with the plate-like body 3 facing downward, it becomes easier to control the flatness of both main surfaces (the first main surface 31 and the second main surface 32) of the plate-like body 3 compared to when the heat treatment is performed with the plate-like body 3 facing upward.

[0048] Furthermore, after step (b), at least one of the first main surface 21 of the frame 2 and the first main surface 31 of the plate-like body 3 may be subjected to at least one of grinding and polishing.

[0049] Before arranging the frame body 2 and the plate-like body 3 so that they face each other, the second region 3a of the plate-like body 3 facing the frame body 2 is ground, and after step (b), the first main surface 31 of the plate-like body 3 is ground, and the grinding stone used to grind the first main surface 31 should have a larger grit number than the grinding stone used to grind the second region 3a.

[0050] Before arranging the frame body 2 and the plate-like body 3 so that they face each other, the second region 3a of the plate-like body 3 facing the frame body 2 is polished, and after step (b), the first main surface 31 of the plate-like body 3 is polished. In this case, the abrasive grains used to polish the first main surface 31 may have a larger grit size number than the abrasive grains used to polish the second region 3a.

[0051] Before arranging the frame body 2 and the plate-like body 3 so that they face each other, the second region 3a of the plate-like body 3 facing the frame body 2 is polished, and after step (b), the first main surface 31 of the plate-like body 3 is ground, thereby making it possible to efficiently obtain a bonded body.

[0052] By carrying out such processing, it becomes easier to control the parallelism and flatness of the first main surface 31 of the plate-like body 3 relative to the first main surface 21 of the frame body 2. Grinding and polishing are as described above, and detailed description thereof will be omitted. The above-mentioned method has been described for the case where the frame body 2 is a rectangular parallelepiped and has a rectangular parallelepiped-shaped internal space penetrating in the thickness direction of the rectangular parallelepiped, but it is not limited to a rectangular parallelepiped, and the same applies to structures such as polyhedrons, frustums, and cylinders that have an internal space penetrating in the thickness direction.

[0053] The assembly 1 according to one embodiment is used, for example, as a diaphragm structure. A diaphragm is a film that undergoes displacement under the influence of pressure. A pressure sensor according to the present disclosure includes the diaphragm structure and a sensor element or thick-film resistor mounted on a first main surface (first main surface 31 of plate-shaped body 3) of a plate-shaped body of the diaphragm structure (corresponding to plate-shaped body 3 of the assembly 1 and acting as a diaphragm body).

[0054] Specifically, in the pressure sensor according to one embodiment, a sensor element is provided at the center of a first main surface of a plate-shaped body of a diaphragm structure, and the pressure sensor according to one embodiment detects, by the sensor element, deflection of the plate-shaped body (plate-shaped body 3) of the diaphragm structure caused by the pressure difference between the pressure inside the frame 2 and the pressure outside the frame 2, which is maintained at a specific pressure.

[0055] In the pressure sensor according to the other embodiment, a thick film resistor is provided on the first main surface of the plate-shaped body of the diaphragm structure instead of a sensor element. As with the pressure sensor according to the first embodiment, the pressure sensor according to the other embodiment also uses the thick film resistor to detect deflection of the plate-shaped body of the diaphragm structure (plate-shaped body 3) caused by the differential pressure between the pressure inside the frame 2 and the outside of the frame 2, which is maintained at a specific pressure.

[0056] The diaphragm structure of the present disclosure may be used not only in pressure sensors but also in various sensors such as vibration sensors, strain sensors, acoustic sensors, MEMS sensors, biosensors, and ultrasonic sensors.

[0057] Furthermore, the assembly of the present disclosure may be not only a diaphragm structure but also a housing (package) including a polyhedron (container) having an internal space and a plate-like body thinner than the polyhedron. A sphere for absorbing vibration may be housed in a movable state in the internal space of this housing, and when a sphere is housed, the assembly may be used as a ball sensor.

[0058] REFERENCE SIGNS LIST 1 Bonded body 2 Frame body 21 First main surface of frame body 2a First region 3 Plate-like body 31 First main surface of plate-like body 32 Second main surface of plate-like body 3a Second region

Claims

1. A frame containing a first ceramic material having aluminum oxide as a main component and being polycrystalline; a plate-like body containing a polycrystalline second ceramic mainly composed of aluminum oxide and being thinner than the frame body; Including, The frame body and the plate-like body have a structure in which they are diffusion-bonded in a thickness direction, The content of aluminum oxide contained in the second ceramic is greater than the content of aluminum oxide contained in the first ceramic. zygote.

2. The joined body according to claim 1 , wherein the content of aluminum oxide contained in the first ceramic is 92 mass % or more.

3. The first ceramic and the second ceramic further contain at least one selected from the group consisting of silicon, magnesium, and calcium, 2. The joined body according to claim 1, wherein the total content of these elements calculated as oxides of the second ceramic is smaller than that of the first ceramic.

4. 4. The joined body according to claim 3, wherein the total content of silicon, magnesium and calcium contained in the first ceramic calculated as oxide is 6.7 mass % or less.

5. 2. The joined body according to claim 1, wherein the second ceramic has a lower magnesium aluminate content than the first ceramic.

6. 2. The joined body according to claim 1, wherein the second ceramic has a smaller average equivalent circle diameter of aluminum oxide crystal grains than that of the first ceramic.

7. The first main surface of the plate-like body on the opposite side to the frame has a larger average value of a cut level difference (Rδc), which is the difference between the cut level at a load length ratio of 25% on the roughness curve and the cut level at a load length ratio of 75% on the roughness curve, than the second main surface of the plate-like body on the frame side. The bonded body according to claim 1.

8. A diaphragm structure comprising the joint body according to any one of claims 1 to 7.

9. The diaphragm structure according to claim 8 ; a sensor element mounted on the first main surface of the plate-shaped body of the diaphragm structure; 2. A pressure sensor comprising:

10. The diaphragm structure according to claim 8 ; a thick film resistor mounted on the first main surface of the plate-shaped body of the diaphragm structure; 2. A pressure sensor comprising:

11. a step of disposing a frame containing a first ceramic which is a polycrystalline material mainly composed of aluminum oxide and a plate-like body which contains a second ceramic which is a polycrystalline material mainly composed of aluminum oxide and is thinner than the frame, so as to face each other in a thickness direction; a step of heat treating the frame body and the plate-like body while pressing them from a thickness direction; A method for producing a joint body, comprising:

12. the first ceramic and the second ceramic contain silicon, magnesium and calcium; The total content of these elements calculated as oxides of the second ceramic is less than that of the first ceramic. The method for producing the bonded body according to claim 11 .

13. 13. The method for manufacturing a joint body according to claim 11 or 12, wherein, before arranging the frame body and the plate body so as to face each other, at least one of a first region of the frame body facing the plate body and a second region of the plate body facing the frame body is subjected to at least one of grinding and polishing.

14. A method for manufacturing a joint body as described in claim 11 or 12, wherein the heat treatment process is performed with the plate-like body facing down.

15. 13. The method for manufacturing a joined body according to claim 11 or 12, wherein at least one of a first main surface of the frame body opposite the plate-like body and a first main surface of the plate-like body opposite the frame body is subjected to at least one of grinding and polishing after the heat treatment step.