Conjugate

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

Technical Field

[0001] The present invention relates to a joined body.

Background Art

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

[0003] As such a diaphragm structure, for example, Patent Document 1 discloses a diaphragm structure in which molded bodies are integrally sintered from the viewpoints of reliability, heat resistance, and corrosion resistance, and the diaphragm portion is convex outward in the direction opposite to the window portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

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

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

[0007] The method for manufacturing the bonded body according to the present disclosure includes a step of arranging a frame body containing polycrystalline first ceramics mainly composed of aluminum oxide and a plate-like body containing polycrystalline second ceramics mainly composed of aluminum oxide and thinner than the frame body so as to face each other in the thickness direction; and a step of performing heat treatment while pressing the frame body and the plate-like body from the thickness direction.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] As described above, Patent Document 1 discloses a diaphragm structure in which molded bodies are integrally sintered from the viewpoints of reliability, heat resistance, and corrosion resistance, and the diaphragm portion is convex outward in a direction opposite to the window portion. However, when the diaphragm portion is repeatedly bent, the convex diaphragm portion has a significant increase in residual stress. As a result, there is a problem of early breakage. Therefore, there is a demand for a bonded body that is difficult to break over a long period even when repeatedly bent.

[0010] As described above, the joined body according to the present disclosure has a structure in which a structure made of ceramics and a plate-like body made of ceramics are diffusion-joined in the thickness direction. Therefore, both main surfaces of the plate-like body made of ceramics are planar. Accordingly, the joined body according to the present disclosure is less likely to be damaged over a long period even when repeatedly bent.

[0011] Furthermore, the method for manufacturing the joined body according to the present disclosure includes, as described above, a step of diffusion-joining a structure made of ceramics and a plate-like body made of ceramics in the thickness direction. Therefore, both main surfaces of the plate-like body made of ceramics are planar. Accordingly, according to the method for manufacturing the joined body according to the present disclosure, a joined body that is less likely to be damaged over a long period even when repeatedly bent can be provided.

[0012] The joined body of 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. The joined body 1 according to an embodiment has a structure in which the frame body 2 and the plate-like body 3 are diffusion-joined in the thickness direction, as shown in FIG. 2. By having a diffusion-joined structure, both main surfaces (the first main surface 31 and the second main surface 32) of the plate-like body 3 become planar. As a result, the joined body 1 according to an embodiment is less likely to be damaged over a long period even when repeatedly bent.

[0013] Hereinafter, of the two main surfaces of the plate-like body 3, the main surface located on the side opposite to the frame body 2 is defined as the first main surface 31, the main surface located on the side of the frame body 2 is defined as the second main surface 32, and of the two main surfaces of the frame body 2, the main surface located on the side opposite to the plate-like body 3 is defined as the first main surface 21 for explanation.

[0014] The first ceramic contained in the frame body 2 is composed of polycrystals and has aluminum oxide as a main component. In this specification, "having aluminum oxide as a main component" means that the content of aluminum oxide is 90% by mass or more in 100% by mass in total of the ceramics 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, unavoidable impurities are reduced, so the mechanical strength can be improved. The aluminum oxide content contained in the second ceramic is higher than the aluminum oxide content contained in the first ceramic. Therefore, when the aluminum oxide content of the first ceramic is 92% by mass or more, the aluminum oxide content contained in the second ceramic described below will also exceed 92% by mass. Accordingly, 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 selected from the group consisting of, for example, silicon, magnesium, and calcium. The content in terms of oxides of these elements (hereinafter, the content in terms of oxides is referred to as the oxide equivalent amount) may be, for example, 6.7% by mass or less in total. When the oxide equivalent amounts of these elements are within this range, the rigidity of the first ceramic can be improved. As a result, the frame body 2 can support the plate-like body 3 more stably. For example, the oxide equivalent amount of silicon contained in the first ceramic is 2% by mass or more and 7% by mass or less, the oxide equivalent amount of magnesium is 0.42% by mass or more and 1% by mass or less, and the oxide equivalent amount of calcium is 0.17% by mass or more and 1.1% by mass or less.

[0017] As shown in FIG. 1, the frame body 2 has a square shape in plan view. The shape of the frame body 2 is not limited to a square shape, and may be a circular shape, an elliptical shape, or a polygonal shape other than a square shape. In the case of a polygonal shape including a square shape, it may be a regular polygon or an irregular polygon.

[0018] The size of the frame body 2 is not limited and is appropriately set according to the use of the joining body 1. When the size of the frame body 2 is a polygonal shape such as a quadrangular shape, the length of one side on the outer periphery may be, for example, 15 mm or more and 30 mm or less. When the frame body 2 has a circular shape or an 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, both the major axis and the minor axis may be within such a range. As shown in FIG. 2, the thickness T1 of the frame body 2 is not limited and is appropriately set according to the use of the joining 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 ceramics contained in the plate-like body 3 is composed of polycrystals and has aluminum oxide as the main component. The definition of the main component is as described above. In addition to aluminum oxide, the second ceramics may also contain at least one selected from the group consisting of, for example, silicon, magnesium, and calcium. For example, the amount of silicon in terms of oxide contained in the second ceramics is 0.01% by mass or more and 0.04% by mass or less, the amount of magnesium in terms of oxide is 0.028% by mass or more and 0.049% by mass or less, and the amount of calcium in terms of oxide is 0.022% by mass or more and 0.039% by mass or less.

[0020] The amount of these elements in terms of oxide contained in the second ceramics may be less than the amount of these elements in terms of oxide contained in the first ceramics. When the amount of these elements in terms of oxide contained in the second ceramics is small, for example, when a sensor element or the like is mounted on the plate-like body 3, a chemical reaction 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, since the static elastic modulus of the plate-like body 3 is higher than that of the frame body 2, 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 be damaged. The difference between the oxide equivalent amounts of these elements contained in the second ceramic and the oxide equivalent amounts of these elements contained in the first ceramic is, for example, 3.5 mass% or more and 4 mass% or less.

[0022] Magnesium aluminate may be further contained in the first ceramic and the second ceramic. The content of magnesium aluminate is not limited. For example, the content of magnesium aluminate contained in the second ceramic may be less than the content of magnesium aluminate contained in the first ceramic. Since the thickness of the plate-like body 3 is smaller than the thickness of the frame body 2, the thermal shock resistance of the plate-like body 3 becomes poorer than the thermal shock resistance of the frame body 2. However, by reducing the content of magnesium aluminate that affects the thermal shock resistance in the plate-like body 3 compared to the frame body 2, it is possible to suppress a decrease in the thermal shock resistance of the plate-like body 3.

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

[0024] Each component contained in the first ceramic and the second ceramic may be identified using an X-ray diffractometer with CuKα radiation. The content of each element may be converted into the compound identified by the X-ray diffractometer using a fluorescent X-ray analyzer (XRF) or an inductively coupled plasma 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 square shape when viewed in plan. The shape of the plate-like body 3 is not limited to a square shape, similar to the frame body 2, and may be a circular shape, an elliptical shape, or a polygonal shape other than a square shape. In the case of a polygonal shape including a square shape, it may be a regular polygon or an irregular polygon. The shape and size of the plate-like body 3 are appropriately set according to the shape of the frame body 2.

[0026] In the joined body 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, since the plate-like body 3 has a higher content of aluminum oxide and a higher static elastic modulus than the frame body 2, 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 reduced. 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 body 2 shown in FIGS. 1 and 2 is a rectangular parallelepiped and has a rectangular parallelepiped-shaped internal space that penetrates in the thickness direction of the rectangular parallelepiped. However, it is not limited to a rectangular parallelepiped, and a structure having an internal space that penetrates in the thickness direction, such as a polyhedron, a frustum of a cone, or a cylinder, may also be used. In this case, the internal space is not limited to a rectangular parallelepiped shape, and may be a polyhedron, a frustum of a cone, a cylinder, or the like. The internal space does not necessarily have to penetrate. The first main surface 21 of the frame body 2 located on the opposite side of 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. When the first main surface 21 does not have an opening, at least one or more holes connecting the internal space and the external space may be formed in the first main surface 21.

[0028] The size of the aluminum oxide crystal particles contained in the first ceramic and the size of the aluminum oxide crystal particles contained in the second ceramic are not limited. For example, the aluminum oxide crystal particles contained in the second ceramic may have an average value of the equivalent circle diameter smaller than that of the aluminum oxide crystal particles 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 particle on the surface obtained by sequentially polishing and thermally etching the first ceramic and the second ceramic.

[0029] The procedure is first to polish the first main surface 31 of the plate-like body 3 on a copper disk using diamond abrasive grains with an average particle size D 50 of 3 μm. Thereafter, it is polished on a tin disk using diamond abrasive grains with an average particle size D 50 of 0.5 μm. The polished surface obtained by these polishings is thermally etched at, for example, 1480° C. until the crystal particles and the grain boundary layer can be distinguished, and used as the measurement target surface. The heat treatment is, for example, about 30 minutes. For the frame body 2 as well, first, the first main surface 21 of the frame body 2 is polished on a copper disk using diamond abrasive grains with an average particle size D 50 of 3 μm, and thereafter, a measurement target surface can be obtained by the same procedure as described above.

[0030] Observe the heat-treated surface with an optical microscope and photograph it, for example, at a magnification of 400 times. Among the photographed images, set the measurement range to the range with an area of 4.8747×10 2 m. By analyzing this measurement range using image analysis software (for example, Win ROOF manufactured by Mitani Shoji Co., Ltd.), the equivalent circle diameter of each crystal particle can be obtained. When obtaining the equivalent circle diameter, the threshold value of the equivalent circle diameter is set to 0.21 μm, and the equivalent circle diameter less than 0.21 μm is not subject to the calculation of the average value.

[0031] When the average value of the equivalent circle diameter is small, the mechanical strength and rigidity of the ceramics can be improved. 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-like body 3 is reduced, the plate-like 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 preferably 2 μm or more.

[0033] The surface properties on the main surface of the plate-like body 3 are not particularly limited. For example, the first main surface 31 of the plate-like body 3 may have a large average value of the cutting level difference (Rδc), which is the difference between the cutting level at the 25% load length rate and the cutting level at the 75% load length rate in the roughness curve, compared to 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 cutting level difference (Rδc) of the first major surface 31 is, for example, 0.6 μm or more and 1.5 μm or less. The average value of the cutting level difference (Rδc) of the second major surface 32 is, for example, 0.3 μm or more and 0.9 μm or less. The difference between the average value of the cutting level difference (Rδc) of the first major surface 31 and the average value of the cutting level difference (Rδc) of the second major surface 32 is, for example, 0.3 μm or more and 0.6 μm or less.

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

[0036] The cutting level difference (Rδc) complies with JIS B 0601:2001 and can be measured using a laser microscope (manufactured by Keyence Corporation, ultra-depth color 3D shape measurement microscope (VK-X1000 or its successor models)). As the measurement conditions, the illumination method is the coaxial epi-illumination method, the cut-off value λs is none, the cut-off value λc is 0.08 mm, the cut-off value λf is none, there is correction for the end effect, the measurement magnification is 240 times, the measurement range per point from the first major surface 31 and the second major surface 32 to be measured is 1428 μm × 1070 μm, and for each measurement range, four lines to be measured are drawn along the longitudinal direction of the measurement range, and line roughness measurement can be performed. Before measuring the line roughness, surface shape correction by waviness removal is performed with the correction strength set to 5. The length per line to be measured is, for example, 1282 μm. Two measurement ranges are set from each of the first major surface 31 and the second major surface 32, and the cutting level difference (Rδc) is measured from a total of eight lines, and the average value can be calculated.

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

[0038] Regarding step (a), first, the frame body 2 and the plate-like body 3 are prepared. The frame body 2 and the plate-like body 3 are as described above, and detailed descriptions thereof are omitted. The first ceramic and the second ceramic contained in the frame body 2 and the plate-like body 3 are obtained, for example, by the following procedure.

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

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

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

[0042] After spray granulating the slurry to obtain granules, by using a uniaxial press molding device or a cold isostatic press molding device and applying pressure with a molding pressure of 78 MPa or more and 128 MPa or less, a molded body corresponding to the shape of the finally obtained frame body 2 and plate-like body 3 is obtained. By firing these molded bodies under the conditions of 1500 °C or more and 1700 °C or less and 4 hours or more and 6 hours or less, a frame body 2 containing the first ceramic and a plate-like body 3 containing the second ceramic are obtained.

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

[0044] Before arranging the frame body 2 and the plate-like body 3 so as to face each other, at least one of the first region 2a and the second region 3a may be subjected to at least one of grinding and polishing. When at least one of the first region 2a and the second region 3a is subjected to such processing, the adsorption force between the first region 2a and the second region 3a can be improved in the step (b) described later.

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

[0046] Next, in step (b), the frame body 2 and the plate-like body 3 arranged to face each other are heat-treated while being pressed from the thickness direction. As a method of performing heat treatment while pressing and joining in this way, diffusion bonding can be mentioned. Specifically, the frame body 2 and the plate-like body 3 are arranged to face each other, and are pressed from the thickness direction, for example, by the own weight of the plate-like body 3, and heat-treated under the conditions of 1000°C or higher and 1800°C or lower and 4 hours or longer and 6 hours or shorter. If necessary, it may be pressed from the thickness direction with a force of, for example, 800 gf or more and 3 kgf or less and heat-treated under the above conditions. By performing heat treatment in this way, the joined body 1 according to one embodiment is obtained.

[0047] In step (b), the heat treatment is preferably performed, for example, with the plate-like body 3 on the lower side. By performing the heat treatment with the plate-like body 3 on the lower side, 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 the case where the heat treatment is performed with the plate-like body 3 on the upper side.

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

[0049] Before arranging the frame body 2 and the plate-like body 3 to face each other, if the second region 3a of the plate-like body 3 facing the frame body 2 is ground and the first main surface 31 of the plate-like body 3 is ground after step (b), a grindstone having a larger grit number than the grindstone used for grinding the second region 3a may be used for grinding the first main surface 31.

[0050] Before arranging the frame body 2 and the plate-like body 3 to face each other, if the second region 3a of the plate-like body 3 facing the frame body 2 is polished and the first main surface 31 of the plate-like body 3 is polished after step (b), abrasive grains having a larger grit number than the abrasive grains used for polishing the second region 3a may be used for polishing the first main surface 31.

[0051] Before arranging the frame body 2 and the plate-like body 3 to face each other, if the second region 3a of the plate-like body 3 facing the frame body 2 is polished and the first main surface 31 of the plate-like body 3 is ground after the step (b), a bonded body can be obtained efficiently.

[0052] By performing such processing, it becomes easy to control the parallelism and flatness of the first main surface 31 of the plate-like body 3 with respect to the first main surface 21 of the frame body 2. Grinding and polishing are as described above, and detailed descriptions are omitted. The method described above 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 is not limited to the rectangular parallelepiped, and the same applies to structures having an internal space penetrating in the thickness direction such as polyhedrons, truncated cones, and cylinders.

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

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

[0055] In the pressure sensor according to another embodiment, a thick film resistor is provided on the first main surface of the plate-like body of the diaphragm structure instead of the sensor element. Similar to the pressure sensor according to one embodiment, the pressure sensor according to another embodiment also detects the deflection of the plate-like body (plate-like body 3) of the diaphragm structure caused by the differential pressure between the pressure inside the frame body 2 and the outside of the frame body 2 maintained at a specific pressure, by the thick film resistor.

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

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

Explanation of Signs

[0058] 1 Joined body 2 Frame body 21 First main surface of the frame body 2a First region 3 Plate-like body 31 First main surface of the plate-like body 32 Second main surface of the plate-like body 3a Second region

Claims

1. A frame body containing polycrystalline first ceramics mainly composed of aluminum oxide, and a plate-like body containing polycrystalline second ceramics mainly composed of aluminum oxide and thinner than the frame body, comprising: the frame body and the plate-like body having a structure in which they are diffusion-bonded in the thickness direction, the plate-like body having a first main surface located on the side opposite to the frame body and a second main surface located on the frame body side, the content of aluminum oxide contained in the second ceramics being more than the content of aluminum oxide contained in the first ceramics, the first ceramics and the second ceramics containing magnesium aluminate, and the second ceramics having a lower content of magnesium aluminate than the first ceramics, a joined body.

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

3. The first ceramics and the second ceramics further contain at least one selected from the group consisting of silicon, magnesium, and calcium, and the total content of these elements in terms of oxides is less in the second ceramics than in the first ceramics. The joined body according to claim 1.

4. The joined body according to claim 3, wherein the total content of silicon, magnesium, and calcium contained in the first ceramics in terms of oxides is 6.7% by mass or less.

5. The joined body according to claim 1, wherein the second ceramics have a smaller average value of the equivalent circle diameter of the crystal grains of aluminum oxide than the first ceramics.

6. The joined body according to claim 1, wherein the first main surface has a larger average value of the cutting level difference (Rδc), which is the difference between the cutting level at a 25% load length ratio and the cutting level at a 75% load length ratio in the roughness curve, than the second main surface.

7. A diaphragm structure body including the joined body according to any one of claims 1 to 6.

8. The diaphragm structure body according to claim 7, and a sensor element mounted on the first main surface of the plate-like body of the diaphragm structure body, comprising a pressure sensor.

9. The diaphragm structure body according to claim 7, and a thick film resistor mounted on the first main surface of the plate-like body of the diaphragm structure body, comprising a pressure sensor.

10. A step of arranging a frame body containing a polycrystalline first ceramic mainly composed of aluminum oxide and a plate-like body containing a polycrystalline second ceramic mainly composed of aluminum oxide and thinner than the frame body so as to face each other in the thickness direction; A step of heat-treating while pressing the frame body and the plate-like body from the thickness direction; including The first ceramic and the second ceramic contain magnesium aluminate, and the second ceramic contains less magnesium aluminate than the first ceramic. A method for manufacturing a joined body.

11. The first ceramic and the second ceramic contain silicon, magnesium and calcium, and the total content of these elements converted to oxides is less in the second ceramic than in the first ceramic. The method for manufacturing a joined body according to claim 10.

12. Before arranging the frame body and the plate-like body to face each other, at least one of a first region of the frame body facing the plate-like body and a second region of the plate-like body facing the frame body is subjected to at least one of grinding and polishing. The method for manufacturing a joined body according to claim 10 or 11.

13. The step of heat treatment is performed with the plate-like body on the lower side. The method for manufacturing a joined body according to claim 10 or 11.

14. At least one of a first main surface of the frame body on the side opposite to the plate-like body and a first main surface of the plate-like body on the side opposite to the frame body is subjected to at least one of grinding and polishing after the step of heat treatment. The method for manufacturing a joined body according to claim 10 or 11.

Images