Ceramic structure

Abstract

This ceramic structure comprises: a ceramic body that has a first surface; an electrode; and a metal lead. The electrode is positioned inside the ceramic body. The metal lead is connected to the electrode. The ceramic body has a metal lead fixing part that opens to the first surface. When a direction that is orthogonal to the axial direction of the metal lead and extends along the first surface is defined as the first direction, the fixing part has a first portion that is close to the center of the ceramic body, the first portion has a first opening part and a first bottom part, and the first opening part has a longer length in the first direction than the first bottom part.

Description

Ceramic Structure

[0001] SUMMARY OF THE INVENTION The disclosed embodiments relate to ceramic structures.

[0002] Patent Document 1 discloses a ceramic heater in which lead wires are firmly brazed to an exposed heating resistor, allowing the ceramic heater to function as a heating element for a long period of time.

[0003] Japanese Patent Application Publication No. 6-196253

[0004] A ceramic structure according to one aspect of the embodiment includes a ceramic body having a first surface, an electrode, and a metal lead. The electrode is located inside the ceramic body. The metal lead is connected to the electrode. The ceramic body has a fixing portion for the metal lead that opens in the first surface. When a direction perpendicular to the axial direction of the metal lead and along the first surface is defined as a first direction, the fixing portion has a first portion near the center of the ceramic body, the first portion having a first opening and a first bottom, and the first opening is longer in the first direction than the first bottom.

[0005] FIG. 1A is a plan view showing a ceramic structure according to a first embodiment. FIG. 1B is a perspective view showing an enlarged view of the periphery of one fixing portion according to the first embodiment. FIG. 1C is a cross-sectional view taken along the arrows A1-A1 shown in FIG. 1B. FIG. 1D is a cross-sectional view taken along the arrows B1-B1 shown in FIG. 1B. FIG. 1E is a cross-sectional view taken along the arrows C1-C1 shown in FIG. 1B. FIG. 1F is a diagram showing another example shown in a cross section similar to FIG. 1C. FIG. 2A is a perspective view showing an enlarged view of the periphery of one fixing portion according to a second embodiment. FIG. 2B is a cross-sectional view taken along the arrows C2-C2 shown in FIG. 2A. FIG. 3A is a perspective view showing an enlarged view of the periphery of one fixing portion according to a third embodiment. FIG. 3B is a cross-sectional view taken along the arrows D3-D3 shown in FIG. 3A. FIG. 4 is a plan view showing an enlarged view of the periphery of one fixing portion according to a fourth embodiment. FIG. 5A is a perspective view showing an enlarged view of the periphery of one fixing portion according to a fifth embodiment. FIG. 5B is a cross-sectional view taken along the arrows A4-A4 shown in FIG. 5A. FIG. 5C is a partially enlarged view of the ceramic body shown in FIG. 5B after firing. FIG. 5D is a plan view showing an enlarged view of the periphery of one fixing portion according to the fifth embodiment. FIG. 6A is a perspective view showing an enlarged view of the periphery of one fixing portion according to the sixth embodiment. FIG. 6B is a cross-sectional view taken along the arrows A5-A5 shown in FIG. 6A. FIG. 6C is a cross-sectional view taken along the arrows D5-D5 shown in FIG. 6A. FIG. 6D is a plan view showing an enlarged view of the periphery of one fixing portion according to the sixth embodiment. FIG. 7A is a cross-sectional view of one fixing portion according to the seventh embodiment. FIG. 7B is a cross-sectional view of one fixing portion according to the seventh embodiment. FIG. 8A is a cross-sectional view of one fixing portion according to the eighth embodiment. FIG. 8B is a cross-sectional view of one fixing portion according to the eighth embodiment. FIG. 9A is a cross-sectional view of one fixing portion according to the ninth embodiment. FIG. 9B is a cross-sectional view of one fixing portion according to the ninth embodiment.

[0006] Hereinafter, embodiments of the ceramic structure according to the present disclosure will be described with reference to the accompanying drawings. Note that the ceramic structure according to the present disclosure is not limited to these embodiments. Furthermore, the respective embodiments can be appropriately combined within a range that does not cause contradictions in the processing content. Furthermore, the same components in the respective embodiments are given the same reference numerals, and duplicated explanations may be omitted.

[0007] Furthermore, although expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used in each embodiment, these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in a strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc. Furthermore, the drawings referred to are schematic, and the dimensional relationships between elements, the ratios of elements, etc. may differ from reality.

[0008] In recent years, there has been a demand for ceramic structures such as heaters that are smaller and can operate at higher temperatures. Meanwhile, ceramic structures have electrodes, leads connected to the electrodes, and fixing portions to which the leads are fixed. Heat tends to accumulate in the fixing portions of the leads, and this heat can cause problems in the ceramic structure.

[0009] Therefore, there is a need for a ceramic structure that can solve the above-mentioned problems and eliminate the buildup of heat in the lead fixing portion, which will make it possible to eliminate the buildup of heat in the lead fixing portion.

[0010] [First Embodiment] The configuration of a ceramic structure according to a first embodiment will be described with reference to Figures 1A and 1B. Figure 1A is a plan view showing the ceramic structure according to the first embodiment.

[0011] 1A, the ceramic structure 100 according to the first embodiment includes a ceramic body 1, an electrode 2, and a pair of metal leads 3. The ceramic body 1 is, for example, a rectangular plate-like member.

[0012] In the drawings referred to below, for ease of explanation, the direction parallel to the short side of the ceramic body 1 is defined as the X-axis direction, the direction parallel to the long side of the ceramic body 1 is defined as the Y-axis direction, and the vertical upward direction is defined as the Z-axis direction.

[0013] The ceramic body 1 is, for example, an insulating ceramic. Examples of materials that can be used for the ceramic body 1 include oxide ceramics, nitride ceramics, and carbide ceramics. Specifically, alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, and silicon carbide ceramics can be used.

[0014] 1B is an enlarged perspective view showing the periphery of one fixing portion 4 according to the first embodiment. As shown in FIG. 1B , the ceramic body 1 has a first surface 1a, a second surface 1b located opposite the first surface 1a, and a third surface 1c connected to the first surface 1a and the second surface 1b. For example, the first surface 1a is the front surface of the ceramic structure 100, the second surface 1b is the back surface of the ceramic structure 100, and the third surface 1c is a side surface of the ceramic structure 100.

[0015] 1B shows the ceramic body 1 according to this embodiment as a laminate of three ceramic layers (10, 11, 12) from top to bottom. This laminate has a structure in which ceramic green sheets that will become the ceramic layers (10, 11, 12) are stacked and integrated by sintering. However, the ceramic body 1 is not limited to this, and may be a single-layer ceramic plate, or may have a structure in which two or four or more layers of sheets are integrated.

[0016] The electrode 2 is located inside the ceramic body 1. In the example shown in FIG. 1B , the electrode 2 is embedded between the ceramic layers 11 and 12. The ceramic body 1 shields the electrode 2 from the atmosphere and prevents the electrode 2 from corroding due to moisture in the atmosphere, etc. As shown in FIG. 1A , the electrode 2 may have a meandering shape with a folded pattern. However, the electrode 2 is not limited to this and may have a pattern according to the characteristics required for the ceramic structure 100.

[0017] The ceramic structure 100 may function as a heater (heating element) or a sensor. For example, when the ceramic structure 100 functions as a heater, the electrode 2 may be a heating resistor and may include a high-resistance conductor containing, for example, tungsten, molybdenum, or the like. A current flows through the electrode 2 via the metal lead 3 when power is supplied from a power source (not shown). This causes the electrode 2 to generate Joule heat. In this way, the ceramic structure 100 can function as a heater. Note that the ceramic structure 100 may include a sensor between other ceramic layers in addition to the heater, and this sensor may or may not have the above-mentioned fixing portion structure.

[0018] For example, when the ceramic structure 100 functions as a temperature sensor, the electrode 2 may be a resistance temperature detector, and may be made of, for example, a metal such as platinum or a metal oxide, whose resistance value changes with a change in temperature. A current flows through the electrode 2 via a metal lead 3 when power is supplied from a power source (not shown). A measuring device (not shown) measures the voltage across the electrode 2. The ceramic structure 100 calculates the resistance value of the electrode 2 from the measured voltage. The ceramic structure 100 derives the temperature corresponding to the calculated resistance value based on correlation information between the resistance value and temperature obtained in advance. In this way, the ceramic structure 100 can function as a temperature sensor.

[0019] The metal leads 3 are made of a conductor such as nickel. The ceramic body 1 has fixing portions 4 for the metal leads 3. The fixing portions 4 are provided at two locations near both ends of the ceramic body 1 in the X direction in order to fix the pair of metal leads 3.

[0020] The fixing portion 4 has a first portion 41 and a second portion 42. The first portion 41 is located closer to the center of the ceramic body 1 than the second portion 42. In other words, the second portion 42 is located farther from the center of the ceramic body 1 than the first portion 41. The first portion 41 opens to the first surface 1a, and the second portion 42 opens to the first surface 1a and the third surface 1c.

[0021] A third portion 43, which is a portion that connects the electrode 2 and the metal lead 3, is located between the first portion 41 and the second portion 42. The third portion 43 is open to the first surface 1 a. The third portion 43 is also connected to both the first portion 41 and the second portion 42.

[0022] The first portion 41 has a first opening 41a and a first bottom 41b. The first opening 41a is an opening in the first portion 41, and the first bottom 41b is the bottom surface of the first portion 41. The electrode 2 extends from the first bottom 41b of the first portion 41 to the bottom of the third portion 43. Note that the electrode 2 extends from the first portion 41 to the third portion 43 but does not extend to the second portion 42. Each metal lead 3 is positioned at the first portion 41 and the second portion 42 of each fixing portion 4 and brazed to the electrode 2 at the third portion 43 with brazing material 6. This fixes the metal lead 3 to the fixing portion 4, and the electrode 2 and the metal lead 3 are electrically connected. The width of the electrode 2 at the third portion 43 is larger than the width of the electrode 2 at the folded pattern portion of the electrode 2 so that the portion connected to the metal lead 3 has low resistance. That is, the opening in the X direction of the third portion 43 is wider than the width in the X direction of the folded pattern portion of the electrode 2. Therefore, in the third portion 43, the metal lead 3 is brazed to the electrode 2 with a width wider than the line width of the folded pattern of the electrode 2. This results in a lower resistance in the portion connecting the electrode 2 to the metal lead 3.

[0023] 1B to 1E, the fixing portion 4 will be further described. Hereinafter, the direction perpendicular to the axis Ax direction of the metal lead 3 and along the first surface 1a will be referred to as the first direction, and the axis Ax direction of the metal lead 3 will be referred to as the second direction. The first direction coincides with the X direction, and the second direction coincides with the Y direction. The first direction and the second direction are perpendicular to each other.

[0024] 1C is a cross-sectional view taken along the arrows A1-A1 in FIG. 1B. As shown in FIGS. 1B and 1C, the first opening 41a is longer in the first direction than the first bottom 41b. Specifically, in the cross-section of the first portion 41 shown in FIG. 1C, the width of the first opening 41a in the first direction (hereinafter also referred to as the first opening width a) is longer than the width b of the first bottom 41b in the first direction. This promotes heat dissipation from the first opening 41a, making it less likely that heat will build up inside the first portion 41.

[0025] When the ceramic structure 100 functions as a heater, the ceramic structure 100 eliminates heat buildup in the first portion 41, thereby improving heat dissipation in the portion where the electrode 2 and the metal lead 3 are connected in the third portion 43. As a result, the ceramic structure 100 reduces oxidation and deterioration of the metal lead 3, thereby increasing the durability of the metal lead 3. Furthermore, because the width b in the first direction of the first bottom portion 41b is narrower than the first opening width a, the ceramic structure 100 can increase the accuracy of positioning the metal lead 3. As a result, the ceramic structure 100 can achieve both the fixation of the metal lead 3 and the durability of the metal lead 3.

[0026] When the ceramic structure 100 functions as a temperature sensor, if heat is trapped in the first portion 41, heat dissipation in the portion where the electrode 2 and the metal lead 3 are connected is impaired, causing the third portion 43 to heat up. Therefore, the resistance value measured by a measuring device (not shown) includes not only the resistance value of the electrode 2 in the folded pattern portion but also the resistance value of the portion where the electrode 2 and the metal lead 3 are connected, making it impossible to accurately measure the temperature. In contrast, the ceramic structure 100 according to this embodiment can improve heat dissipation in the portion where the electrode 2 and the metal lead 3 are connected by eliminating heat trapping in the first portion 41. This allows the ceramic structure 100 to accurately measure the resistance value of the electrode 2 using a measuring device. As a result, the ceramic structure 100 can accurately measure the temperature based on the measurement results of the resistance value.

[0027] The first portion 41 may further include a stepped portion 41c. The stepped portion 41c may be formed by exposing the upper surface of the ceramic layer 11 at the boundary between the ceramic layers 10 and 11 within the first portion 41. The first opening 41a is located closer to the first surface 1a than the stepped portion 41c. The stepped portion 41c widens the opening of the first opening 41a, thereby promoting heat dissipation from the first opening 41a. Furthermore, the metal lead 3 is more easily inserted from the wide opening of the first opening 41a to the first bottom portion 41b located below it. However, the first portion 41 does not necessarily have to include the stepped portion 41c. For example, opposing sidewalls of the first portion 41 in the first direction may be inclined so as to widen without a step from the first bottom portion 41b toward the first opening 41a. This also makes the first opening 41 a longer in the first direction than the first bottom 41 b in the ceramic structure 100 , thereby preventing heat from building up in the first portion 41 .

[0028] 1D is a cross-sectional view taken along the arrows B1-B1 in FIG. 1B. The third portion 43 may have a constant opening width c in the first direction. The third portion 43 is a portion where the electrode 2 and the metal lead 3 are brazed, and the opening width c in the first direction may be constant from the first surface 1a to the bottom of the third portion 43. This prevents the metal lead 3 from cooling excessively in the ceramic structure 100, thereby increasing the strength and reliability of the ceramic structure 100.

[0029] 1E is a cross-sectional view taken along the arrows C1-C1 in FIG. 1B. The second portion 42 may have a constant width in the first direction (hereinafter also referred to as the second opening width d) from the first surface 1a to the bottom of the second portion 42. This allows the ceramic structure 100 to easily position the metal lead 3 by the first portion 41 and the second portion 42.

[0030] As shown in FIG. 1C , the axis E of the metal lead 3 may be located farther from the first surface 1a than the step portion 41c. This allows the upper portion of the metal lead 3 to be more easily exposed to the outside air through the first opening 41a, which is a wider space than the first bottom portion 41b, making it less likely for heat to build up in the first portion 41. Furthermore, since the metal lead 3 is located in the space of the first bottom portion 41b, which is narrower than the first opening 41a, the metal lead 3 does not cool down too much. This makes it less likely for the brazed portion of the metal lead 3 in the third portion 43 to be damaged by so-called heat shock caused by the temperature difference between the metal lead 3 and the brazing material 6. If the step portion 41c is located above the maximum diameter of the metal lead 3, as shown in the example of FIG. 1C , the metal lead 3 is less likely to be damaged by heat shock.

[0031] 1F is another example showing a cross section similar to that of FIG. 1C. As shown in the example of FIG. 1F, the step portion 41c may be located below the maximum diameter of the metal lead 3 and above the axis E of the metal lead 3. This makes the step portion 41c less likely to be broken by heat shock than when it is located below the maximum diameter of the metal lead 3 but below the axis E of the metal lead 3.

[0032] [Second Embodiment] The configuration of a ceramic structure according to a second embodiment will be described with reference to Figures 2A and 2B. Figure 2A is an enlarged perspective view of the periphery of one fixing portion 4A according to the second embodiment. Figure 2B is a cross-sectional view taken along the arrows C2-C2 shown in Figure 2A.

[0033] The ceramic structure 100A according to the second embodiment has the same configuration as the ceramic structure 100 according to the first embodiment, except for the configuration of the second portion 42. Therefore, in the second embodiment, the configuration of the second portion 42 will be described, and descriptions of the other configurations will be omitted.

[0034] In the fixed portion 4A, the second portion 42 has a second opening 42a and a second bottom 42b. The second opening 42a is an opening in the second portion 42, and the second bottom 42b is a bottom surface of the second portion 42. As shown in FIG. 2B , the second opening 42a may be longer in the first direction than the second bottom 42b. Specifically, in the cross section of the second portion 42 shown in FIG. 2B , the second opening width d in the first direction of the second opening 42a is longer than the width e in the first direction of the first bottom 41b. This promotes heat dissipation from the second opening 42a, making it less likely that heat will build up inside the second portion 42.

[0035] Furthermore, the fixing portion 4A has a structure in which the two openings of the first portion 41 and the second portion 42 are continuously open from the center to the end of the ceramic structure 100A, from the position close to the folded pattern portion of the electrode 2 to the position far from it, and in which heat can be easily dissipated. This makes it even easier to eliminate heat buildup in the fixing portion 4A.

[0036] Furthermore, the second portion 42 is located closer to the end of the ceramic structure 100A than the first portion 41, and is in a position where the entire periphery of the metal lead 3 is exposed to the outside air. Therefore, the second portion 42 can further reduce the thermal shock generated in the ceramic structure 100A.

[0037] When ceramic structure 100A functions as a heater, heat accumulation in first portion 41 is eliminated, and heat accumulation in second portion 42 is also eliminated. As a result, ceramic structure 100 further improves heat dissipation in the portion of third portion 43 where electrode 2 is connected to metal lead 3. As a result, oxidation and deterioration of metal lead 3 are reduced, and durability of metal lead 3 is improved.

[0038] When the ceramic structure 100A functions as a temperature sensor, the heat accumulation in the first portion 41 is eliminated, and the heat accumulation in the second portion 42 is also eliminated, thereby improving heat dissipation in the portion where the electrode 2 is connected to the metal lead 3. This enables the ceramic structure 100 to more accurately measure the resistance value of the electrode 2. As a result, the ceramic structure 100A can perform temperature measurement with even greater accuracy based on the measurement result of the resistance value.

[0039] The second portion 42 may further include a stepped portion 42c. The stepped portion 42c may be formed by exposing the upper surface of the ceramic layer 11 at the boundary between the ceramic layers 10 and 11 within the second portion 42. The second opening 42a is located closer to the first surface 1a than the stepped portion 42c. The stepped portion 42c in the second portion 42 promotes heat dissipation from the second opening 42a. Furthermore, the metal lead 3 is easily inserted from the wide second opening 42a to the second bottom portion 42b located below it. However, the second portion 42 does not necessarily have to include the stepped portion 42c. For example, opposing sidewalls of the second portion 42 in the first direction may be inclined so as to widen without a step from the second bottom portion 42b toward the second opening 42a. This also makes the second opening 42a in the ceramic structure 100A longer in the first direction than the second bottom 42b, thereby preventing heat from building up in the second portion 42.

[0040] [Third Embodiment] The configuration of a ceramic structure according to a third embodiment will be described with reference to Figures 3A and 3B. Figure 3A is an enlarged perspective view of the periphery of one fixing portion 4B according to the third embodiment. Figure 3B is a cross-sectional view taken along the arrows D3-D3 shown in Figure 3A.

[0041] The ceramic structure 100B according to the third embodiment has the same configuration as the ceramic structure 100A according to the second embodiment, except for the configuration of the first portion 41. Therefore, in the third embodiment, the configuration of the first portion 41 will be described, and descriptions of the other configurations will be omitted.

[0042] 3A and 3B , in the fixing portion 4B, the first portion 41 has a first opening 41a, a first bottom 41b, and step portions 41c and 41d. As shown in Fig. 3A , in a cross section of the first portion 41, a first opening width a in the first direction of the first opening 41a is greater than a width b in the first direction of the first bottom 41b. Furthermore, as shown in Fig. 3B , in a cross section of the first portion 41, a width f in the second direction of the first opening 41a may be greater than a width g in the second direction of the first bottom 41b.

[0043] The first opening 41a is longer in the first direction and the second direction than the first bottom 41b, which further promotes heat dissipation from the first opening 41a and makes it even more difficult for heat to build up inside the first portion 41. This more efficiently prevents heat from building up inside the first opening 41a.

[0044] The first portion 41 may further include a stepped portion 41c. The stepped portion 41c may be formed by exposing the upper surface of the ceramic layer 11 at the boundary between the ceramic layers 10 and 11 in the first portion 41. The stepped portion 41c extends in the first direction on two surfaces on both sides of the first bottom portion 41b in a plan view so that a first opening width a, which is the length of the first opening 41a in the first direction, is longer than a width b, which is the length of the first bottom portion 41b in the first direction. In addition, the stepped portion 41d extends in the second direction on one surface toward the center of the ceramic body 1 so that a width f, which is the length of the first opening 41a in the second direction, is longer than a width g, which is the length of the first bottom portion 41b in the second direction. This allows thermal stress, which tends to concentrate in the corner portions of the first opening 41a, to be dispersed in the three directions of the stepped portion 41c and the stepped portion 41d. Therefore, even if the temperature of the third portion 43 repeatedly rises and falls, the buildup of heat in the first opening 41a is more efficiently eliminated.

[0045] As shown in the cross section of FIG. 3B , the step 41d makes the width f of the first opening 41a in the second direction longer than the width g of the first bottom 41b of the first portion 41 shown in region F. This prevents the brazing material 6 used to braze the metal lead 3 and the electrode 2 in the third portion 43 from flowing toward the corner of the first opening 41a in the second direction. However, the first portion 41 does not necessarily have to have the step 41d. For example, the sidewall from the first bottom 41b to the first opening 41a shown in FIG. 3B may be inclined. In the fixing portion 4B, the length of the step 41c in the first direction in the first portion 41 may be equal to the length of the step 41d in the second direction.

[0046] [Fourth Embodiment] In contrast to this, in the fourth embodiment, the length in the first direction of the step portion 41c of the first portion 41 is different from the length in the second direction of the step portion 41d. Since the other configurations of the ceramic structure according to the fourth embodiment are the same as those of the ceramic structure 100B according to the third embodiment, the following describes the configuration of the first portion 41 of the fixing portion 4C according to the fourth embodiment, and description of the other configurations will be omitted.

[0047] FIG. 4 is an enlarged plan view showing the periphery of one fixed portion 4C according to the fourth embodiment. For example, as shown in FIG. 4, the length w1 of the step portion 41c in the first direction may be longer than the length w2 of the step portion 41d in the second direction. Heat from the metal lead 3 dissipates along the axis Ax of the metal lead 3. This allows heat in the first portion 41 to easily dissipate from the step portion 41c to the first opening 41a along the axis Ax of the metal lead 3. This more efficiently eliminates heat buildup in the first portion 41. Note that, in the example of FIG. 4, the length w1 in the first direction is shown for one of the step portions 41c, but similarly, the length in the first direction of the other step portion 41c may be longer than the length w2 of the step portion 41d in the second direction.

[0048] [Fifth Embodiment] The configuration of a ceramic structure according to a fifth embodiment will be described with reference to Figures 5A to 5D. Figure 5A is an enlarged perspective view of the periphery of one fixing portion 4D according to the fifth embodiment. Figure 5B is a cross-sectional view taken along the arrows A4-A4 shown in Figure 5A. Figure 5C is an enlarged view of a portion of the ceramic body shown in Figure 5B after firing. Figure 5D is an enlarged plan view of the periphery of one fixing portion 4D according to the fifth embodiment.

[0049] The ceramic structure 100C according to the fifth embodiment has the same configuration as the ceramic structure 100A according to the second embodiment, except for the configuration of the first portion 41. Therefore, in the fifth embodiment, the configuration of the first portion 41 will be described, and descriptions of the other configurations will be omitted.

[0050] As shown in FIGS. 5A to 5D, in the fixing portion 4D of the metal lead 3, the step portion 41c and the sidewall of the first opening 41a may have a rounded or reversed rounded surface. As shown in FIG. 5B, the ceramic layers 10 and 11 are adhered to each other by an adhesive liquid. The ceramic layers 10 and 11 and the adhesive liquid may be made of the same material. For example, the ceramic layers 10 and 11 and the adhesive liquid may be made of the same material, such as alumina. The ceramic layers 10 and 11 and the adhesive liquid are integrated into the ceramic body 1 by firing, as illustrated in FIG. 5C. At this time, the adhesive liquid seeps out from between the ceramic layers 10 and 11, forming a reversed rounded surface 44a (shown in FIGS. 5A to 5D) between the ceramic layers 10 and 11 of the ceramic body 1. However, this is not limited to this, and a rounded surface (not shown) may also be formed between the step portion 41c and the sidewall of the first opening 41a. The reversed rounded surface 44a has a smoothly protruding surface, while the rounded surface has a smoothly recessed surface.

[0051] As a result, there is no corner between the step portion 41c and the sidewall of the first opening 41a, and a smooth curve is formed. This allows the first portion 41 to disperse thermal stress that tends to concentrate in corners. This allows the ceramic structure 100C to promote heat dissipation from the step portion 41c to the first opening 41a, and more efficiently eliminate heat buildup within the first opening 41a.

[0052] [Sixth Embodiment] The configuration of a ceramic structure according to a sixth embodiment will be described with reference to Figures 6A to 6D. Figure 6A is an enlarged perspective view of the periphery of one fixing portion 4E according to the sixth embodiment. Figure 6B is a cross-sectional view taken along the arrows A5-A5 shown in Figure 6A. Figure 6C is a cross-sectional view taken along the arrows D5-D5 shown in Figure 6A. Figure 6D is an enlarged plan view of the periphery of one fixing portion 4E according to the sixth embodiment.

[0053] The ceramic structure 100D according to the sixth embodiment has a new configuration in addition to the configuration of the first portion 41 in the ceramic structure 100C according to the fifth embodiment. Therefore, in the sixth embodiment, the new configuration of the first portion 41 will be described, and descriptions of the other configurations will be omitted.

[0054] In the ceramic structure 100D, the fixing portion 4E of the metal lead 3 may have a rounded or reversed rounded surface between the step portions 41c and 41d and the sidewall of the first opening 41a. As shown in FIGS. 6A to 6D , the ceramic layers 10 and 11 are adhered to each other by an adhesive liquid. The ceramic layers 10 and 11 and the adhesive liquid may be made of the same material. For example, the ceramic layers 10 and 11 and the adhesive liquid may be made of the same material, such as alumina. The ceramic layers 10 and 11 and the adhesive liquid are integrated into the ceramic body 1 by firing. During this process, the adhesive liquid seeps out from between the ceramic layers 10 and 11. As a result, the reversed rounded surface 44a and the reversed rounded surface 44b shown in FIGS. 6A to 6D are formed between the ceramic layers 10 and 11 of the ceramic body 1. However, this is not limited to this, and rounded surfaces (not shown) may also be formed between the step portions 41c and the sidewall of the first opening 41a, and between the step portions 41d and the sidewall of the first opening 41a.

[0055] As a result, there are no corners between the step portion 41c and the sidewall of the first opening 41a, and between the step portion 41d and the sidewall of the first opening 41a, and the curves are smooth. This allows the first portion 41 to disperse thermal stress that tends to concentrate in corners. This allows the ceramic structure 100D to promote heat dissipation from the step portion 41c and the step portion 41d to the first opening 41a, and more efficiently prevent heat from building up inside the first opening 41a.

[0056] [Seventh Embodiment] The configuration of a ceramic structure according to a seventh embodiment will be described with reference to Figures 7A and 7B. Figures 7A and 7B are cross-sectional views of one of the fixing portions according to the seventh embodiment. The fixing portion according to the seventh embodiment is an example of fixing portion 4B of ceramic structure 100B according to the third embodiment shown in Figure 3A.

[0057] 7A and 7B (A) are cross-sectional views taken along the arrows A3-A3 in FIG. 3A. 7A and 7B (B) are cross-sectional views taken along the arrows C3-C3 in FIG. 3A. As shown in FIGS. 7A (A) and 7B (B), the first opening width a of the first opening 41a may be shorter in the first direction than the second opening width d of the second opening 42a. This prevents heat dissipation from the metal leads 3, i.e., prevents the metal leads 3 from cooling excessively. As a result, for example, when the ceramic structure functions as a heater, the heating range can be widened, improving heater performance. Furthermore, the guiding function of the first opening 41a can be enhanced, preventing the metal leads 3 from coming loose.

[0058] 7B (A) and (B), the first opening width a of the first opening 41a may be longer in the first direction than the second opening width d of the second opening 42a. This makes it easier to attach the metal lead 3 to the third portion 43. In addition, the guiding function of the second opening 42a can be improved, and the metal lead 3 can be prevented from coming loose.

[0059] Eighth Embodiment The configuration of a ceramic structure according to an eighth embodiment will be described with reference to Figures 8A and 8B, which are cross-sectional views of one of the fixing portions according to the eighth embodiment.

[0060] In the fixing portion according to the eighth embodiment, the first portion 41 may have a sidewall that is inclined toward the first opening 41a. The inclination of the sidewall is confirmed by examining a cross section of the ceramic body 1 obtained by cutting the first portion 41 in the first direction, as shown in FIGS. 8A and 8B . By inclining the sidewall of the first portion 41 above the step portion 41c, heat can be more easily dissipated from the first opening 41a. This prevents heat from building up in the first portion 41 and suppresses the temperature of the third portion 43 from rising too high.

[0061] As shown in FIG. 8A , the opposing sidewalls of the first portion 41 may be inclined in the same direction toward the first opening 41a. Because the opposing sidewalls of the first opening 41a are inclined in the same direction, the first opening 41a does not expand excessively even when the ceramic structure is heated and thermally expands. This prevents the metal lead 3 and the brazing material 6 bonded to the metal lead 3 from cooling excessively. Therefore, the ceramic structure according to the eighth embodiment experiences less thermal shock even when the temperature of the third portion 43 repeatedly rises and falls, preventing the brazing portion connecting the metal lead 3 to the electrode 2 from peeling off, thereby improving the durability of the metal lead 3. Furthermore, the ceramic structure makes it easier to insert the metal lead 3 into the first opening 41a than when the opposing sidewalls of the first opening 41a are not inclined to the same angle. Additionally, the inclination of the opposing sidewalls of the first opening 41a improves the guiding function of the first opening 41a, preventing the metal lead 3 from coming loose.

[0062] As shown in FIG. 8B , the opposing sidewalls of the first portion 41 may be inclined in a direction that closes the first opening 41a. Because the opposing sidewalls of the first opening 41a are inclined in a direction that closes the opening of the first surface, the first opening 41a does not widen even when the ceramic structure is heated and thermally expanded. This prevents the metal lead 3 facing the first opening 41a and the brazing material 6 bonded to the metal lead 3 from cooling excessively. Therefore, even if the temperature of the third portion 43 repeatedly rises and falls, thermal shock is reduced, and the brazing portion connecting the metal lead 3 to the electrode 2 is prevented from peeling, thereby increasing the durability of the metal lead 3. Furthermore, the guiding function of the first opening 41a is enhanced, preventing the metal lead 3 from coming loose.

[0063] Ninth Embodiment The configuration of a ceramic structure according to the ninth embodiment will be described with reference to FIGS. 9A and 9B . FIGS. 9A and 9B are cross-sectional views of one of the fixing portions according to the ninth embodiment. In the fixing portion according to the ninth embodiment, as shown in FIG. 9A , opposing sidewalls in the first portion 41 may be inclined in the direction in which the first opening 41 a opens. Furthermore, as shown in FIG. 9B , opposing sidewalls in the second portion 42 may be inclined in the direction in which the second opening 42 a opens. The inclination of the sidewalls is confirmed by examining a cross section of the ceramic body 1 cut in the first direction through the first portion 41 and the second portion 42, as shown in FIGS. 9A and 9B . As a result, the opposing sidewalls in the first portion 41 are inclined in the direction in which the first opening 41 a opens, and the opposing sidewalls in the second portion 42 are inclined in the direction in which the second opening 42 a opens. This allows the metal lead 3 to be easily inserted into the first opening 41 a. The angle at which the opposing side walls in the first portion 41 tilt in the direction in which the first opening 41a opens and the angle at which the opposing side walls in the second portion 42 tilt in the direction in which the second opening 42a opens may be the same or different.

[0064] As described above, the ceramic structure according to each embodiment includes a ceramic body 1 having a first surface 1a, an electrode 2, and a metal lead 3. The electrode 2 is located inside the ceramic body 1. The metal lead 3 is connected to the electrode 2. The ceramic body 1 has a fixing portion 4 for the metal lead 3 that opens on the first surface 1a. When a first direction is defined as a direction perpendicular to the axial direction of the metal lead 3 and along the first surface 1a, the fixing portion 4 has a first portion 41 that is close to the center of the ceramic body 1. The first portion 41 has a first opening 41a and a first bottom 41b, and the first opening 41a is longer in the first direction than the first bottom 41b. This prevents heat buildup in the fixing portion for the metal lead 3. For example, when the ceramic structure functions as a heater, even if the temperature of the third portion 43 repeatedly rises and falls, oxidation and deterioration of the metal lead 3 are reduced, improving the durability of the metal lead 3. Furthermore, for example, when the ceramic structure functions as a sensor, the ceramic structure 100C can measure the resistance value of the resistance element of the electrode 2 more accurately, improving the detection ability of the sensor.

[0065] The number of fixing portions 4 provided on the ceramic body 1 is not limited to two in order to fix a pair of metal leads 3. Four or more fixing portions 4 may be provided on the ceramic body 1 in order to fix multiple pairs of metal leads 3. The first portions 41 of the four or more fixing portions 4 may or may not have the same shape. For example, of the four or more fixing portions 4, the first portions 41 of any two fixing portions 4 may have opposing side walls that incline to the right toward the first opening 41 a, and the first portions 41 of the remaining fixing portions 4 may have opposing side walls that incline to the left toward the first opening 41 a.

[0066] [Manufacturing Method of Ceramic Structure] An example of a manufacturing method of the ceramic structure 100 will be briefly described. First, a ceramic green sheet for forming the ceramic layer 12 is prepared. A heating element paste is printed thereon by screen printing to form a pattern of the electrode 2 on the ceramic green sheet for forming the ceramic layer 12. Ceramic green sheets for forming the ceramic layers 10 and 11 are then laminated on top of the ceramic green sheets. Thereafter, the ceramic green sheets for forming the ceramic layers 10 and 11 are each subjected to a punching process. As a result, a first portion 41, a second portion 42, and a third portion 43 that are opened on the first surface 1a are formed.

[0067] The ceramic green sheets thus stacked are fired at, for example, about 1600° C. to produce the ceramic body 1 in which the ceramic layers 10, 11, and 12 are integrated with the electrodes. Next, the metal lead 3 is positioned at the first portion 41 and the second portion 42, and the metal lead 3 is brazed to the electrode 2 at the third portion 43. This fixes the metal lead 3 to the ceramic body 1, completing the connection between the electrode 2 and the metal lead 3.

[0068] Further advantages and other aspects may readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0069] The present technology may have the following configurations. (1) A ceramic structure comprising: a ceramic body having a first surface; an electrode located inside the ceramic body; and a metal lead connected to the electrode, wherein the ceramic body has a fixing portion for the metal lead that opens in the first surface, and when a direction perpendicular to an axial direction of the metal lead and along the first surface is defined as a first direction, the fixing portion has a first portion close to a center of the ceramic body, the first portion having a first opening and a first bottom, and the first opening has a length in the first direction longer than the first bottom. (2) The ceramic structure according to (1), wherein the first portion has a step portion. (3) The ceramic structure according to (2), wherein an axis of the metal lead is located farther from the first surface than the step portion. (4) The ceramic structure according to any one of (1) to (3), wherein when the axial direction of the metal lead is defined as a second direction, the first opening has a length in the second direction longer than the first bottom. (5) The ceramic structure according to (2) or (3), wherein, when the axial direction of the metal lead is defined as a second direction, the step portion has a length in the first direction longer than a length in the second direction. (6) The ceramic structure according to any one of (1) to (5), wherein the fixing portion has a second portion farther from the center of the ceramic body than the first portion, the second portion having a second opening and a second bottom, and the second opening has a length in the first direction longer than the second bottom. (7) The ceramic structure according to (2), (3), or (5), wherein an R-surface or an inverted R-surface is formed between the step portion and a sidewall of the first opening. (8) The ceramic structure according to (6), wherein a first opening width of the first opening is longer in the first direction than a second opening width of the second opening. (9) The ceramic structure according to (6), wherein the first opening width of the first opening is shorter in the first direction than a second opening width of the second opening. (10) The ceramic structure according to any one of (1) to (9), wherein the first portion has a sidewall that is inclined toward the first opening.(11) The ceramic structure according to (10), wherein opposing side walls of the first portion are inclined in the same direction toward the first opening. (12) The ceramic structure according to (10), wherein opposing side walls of the first portion are inclined in a direction that closes the first opening. (13) The ceramic structure according to (10), wherein opposing side walls of the first portion are inclined in a direction that opens the first opening.

[0070] 100, 100A to 100D: Ceramic structure 1: Ceramic body 1a: First surface 1b: Second surface 1c: Third surface 2: Electrode 3: Metal lead 4, 4A to 4E: Fixing portion 41: First portion 41a: First opening 41b: First bottom portion 41c, 41d: Step portion 42: Second portion 42a: Second opening 42b: Second bottom portion 42c: Step portion 43: Third portion

Claims

1. A ceramic structure comprising: a ceramic body having a first surface; an electrode located inside the ceramic body; and a metal lead connected to the electrode; wherein the ceramic body has a fixing portion for the metal lead that opens into the first surface; and when a direction perpendicular to the axial direction of the metal lead and along the first surface is defined as a first direction, the fixing portion has a first portion near the center of the ceramic body, the first portion having a first opening and a first bottom, and the first opening is longer in the first direction than the first bottom.

2. The ceramic structure according to claim 1, wherein the first portion has a step portion.

3. The ceramic structure according to claim 2, wherein the axis of the metal lead is positioned farther from the first surface than the step portion.

4. A ceramic structure according to any one of claims 1 to 3, wherein, when the axial direction of the metal lead is defined as a second direction, the length of the first opening in the second direction is longer than that of the first bottom.

5. The ceramic structure according to claim 2 or 3, wherein, when the axial direction of the metal lead is defined as a second direction, the length of the step portion in the first direction is longer than the length of the step portion in the second direction.

6. The ceramic structure according to any one of claims 1 to 5, wherein the fixing portion has a second portion that is farther from the center of the ceramic body than the first portion, the second portion having a second opening and a second bottom, and the second opening has a length in the first direction that is longer than the second bottom.

7. The ceramic structure according to claim 2, 3 or 5, wherein the portion between the step portion and the side wall of the first opening is an R-surface or an inverse R-surface.

8. The ceramic structure according to claim 6, wherein a first opening width of the first opening is longer in the first direction than a second opening width of the second opening.

9. The ceramic structure according to claim 6, wherein a first opening width of the first opening is shorter in the first direction than a second opening width of the second opening.

10. A ceramic structure according to any one of claims 1 to 9, wherein the first portion has a sidewall that slopes toward the first opening.

11. The ceramic structure of claim 10, wherein opposing sidewalls of said first section are angled in the same direction toward said first opening.

12. The ceramic structure of claim 10, wherein the opposing side walls of the first portion are inclined in a direction that closes the first opening.

13. The ceramic structure of claim 10, wherein the opposing side walls of the first portion are inclined in a direction in which the first opening opens.

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