JP4416427B2 - Ceramic heater and manufacturing method thereof - Google Patents

Description

【００５５】
表１より、ヤング率が７００ＭＰａよりも大きいグリーンシートを用いた場合、セラミック中の発熱体側端部からの開きの長さが５０μｍを越え、それによって試料Ｎｏ．７では破損率が急激に高いことがわかる。
【００５６】
また、ｗ／ｔが５よりも小さい試料Ｎｏ．１７では、セラミックの開きが大きくなり、耐久性が低下した。また、ｗ／ｔが４０を越える試料Ｎｏ．１６においても、セラミックの開きが大きくなり、耐久性が低下した。
【００５７】
これに対し、本発明品は、いずれも開きの長さが５μｍ以上、５０μｍ以下であり、破損率も６０％以下とすることができた。
【００５８】
【発明の効果】
以上詳述した通り、本発明によれば、白金を主成分とする発熱体パターンが印刷されたアルミナグリーンシートの表面にヤング率が７００ＭＰａ以下のアルミナグリーンシートを積層圧着して焼成してなる、アルミナを主成分とするセラミック絶縁層中に白金を主成分とする発熱体が埋設されたセラミックヒータであって、発熱体の断面における線幅ｗと最大厚みｔのｗ／ｔが５〜４０であり、発熱体の側端部における前記セラミック絶縁層を構成するセラミックの開きの長さを５μｍ以上、５０μｍ以下に小さくすることによって、高温度におけるヒータの耐久性や急速昇温の際の熱衝撃による破壊等の問題を解決し、ヒータ寿命を長期化した急速昇温が可能なセラミックヒータを提供することができる。
【図面の簡単な説明】
【図１】本発明のセラミックヒータの一例を説明するための概略断面図である。
【図２】本発明のセラミックヒータの製造方法を説明するための分解斜視図である。
【図３】本発明のセラミックヒータの応用例である酸素センサ素子の（ａ）概略斜視図、（ｂ）Ｘ１−Ｘ１断面図である。
【図４】図３の酸素センサ素子の製造方法を説明するための分解斜視図である。
【符号の説明】
１、２６ セラミック絶縁層
２，２７ａ 発熱体
３ セラミックの開き
２２ ・・・固体電解質基板
２２ａ ・・・大気導入孔
２３ａ ・・・基準電極
２４ａ ・・・測定電極
２５ ・・・セラミック多孔質層
２０ ・・・センサ部
２１ ・・・ヒータ部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic heater excellent in durability and suitably used for heating a heater for a semiconductor substrate, a petroleum fan heater, a gas sensor, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, a ceramic heater in which a heating element is embedded in an insulating substrate made of an insulating ceramic such as alumina is known (see Patent Document 1). In addition to a heater for a semiconductor substrate, a hot water heater or an oil fan heater is known. It is used as.
[0003]
On the other hand, in an internal combustion engine such as an automobile, by detecting the oxygen concentration in the exhaust gas and controlling the amount of air and fuel supplied to the internal combustion engine based on the detected value, harmful substances from the internal combustion engine, For example, a method of reducing CO, HC, and NOx is adopted.
[0004]
As this detection element, a solid electrolyte type oxygen sensor is used in which a pair of electrode layers are respectively formed on the outer surface and the inner surface of a solid electrolyte substrate mainly composed of zirconia having oxygen ion conductivity.
[0005]
A typical oxygen sensor includes a ceramic heater in which a reference electrode and a measurement electrode are provided on the outer surface and the inner surface of a flat solid electrolyte substrate, and a heating element made of platinum is embedded in a ceramic insulator. An integrated oxygen sensor has been proposed (for example, Patent Documents 2 and 3). The oxygen sensor integrated with this ceramic heater has the merit that the detection part is rapidly heated to a high temperature of 800 to 1000 ° C. by being directly heated by the ceramic heater.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 3-149971
[Patent Document 2]
Japanese Patent Laid-Open No. 2002-540399
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-236104
[Problems to be solved by the invention]
For these ceramic heaters as described in Patent Documents 1 to 3, performance can be achieved by shortening the so-called operation time or using them at high temperatures, which leads to the respective functions for the above applications. In order to stabilize the temperature of the ceramic heater itself, there has been an increasing demand for rapid temperature rise and a high heating temperature.
[0010]
However, when a ceramic heater is used for the above-mentioned application, when it is used in a high temperature environment exceeding 1000 ° C., or when the heater is heated rapidly, the heater is damaged or the resistance of the heating element is reduced. There was a problem that it increased rapidly. Therefore, these ceramic heaters are currently used at 1000 ° C. or lower, in many cases 700 ° C. or lower, and avoiding rapid rapid temperature rise.
[0011]
The present invention solves the above-mentioned problems such as the durability of the heater at a high temperature and the breakdown due to thermal shock at the time of rapid temperature rise, and a ceramic heater capable of rapid temperature rise with a prolonged heater life and its The object is to provide a manufacturing method.
[0012]
[Means for Solving the Problems]
As a result of studying the above problems, the inventor has improved the bonding between the ceramics at the end portions on the heating element side in the ceramic heater in which the platinum heating element is embedded, and the opening length from the end portion on the heating element side of the ceramic is predetermined. It has been found that the above problem can be solved by making the length or less.
[0013]
That is, the present invention is a surface Young's modulus of the alumina green sheet heating element patterns are printed mainly composed of platinum is formed by firing the laminate crimping the following alumina green sheet 700 MPa, mainly of alumina a ceramic heater heating element is embedded mainly composed of platinum on a ceramic insulating layer, the line width in the cross section of the heating element w and maximum thickness t of the w / t is 5-40, the heating side the ceramic of the length of the opening that constitutes the ceramic insulating layer is the heating side end portion from 5μm or more at the end, and wherein the at 50μm or less.
[0014]
At this time, the heating element mainly composed of platinum preferably contains 2 to 45% by volume of alumina in order to improve durability of the heating element at a high temperature.
[0015]
On the other hand, in order to improve thermal shock, it is desirable that the distance between the heating element mainly composed of platinum and the surface of the ceramic heater is 250 μm or more.
[0016]
Moreover, as a manufacturing method of a ceramic heater, the paste which has platinum as a main component on the surface of an alumina green sheet is satisfied, and the relationship of w / t of the line width w and thickness t in the cross section after baking satisfies 5-40. Thus, after printing and coating, an alumina green sheet having a Young's modulus of 700 MPa or less is laminated and pressure-bonded on the heating element pattern, and fired to form a ceramic insulating layer mainly composed of alumina at the end portion of the heating element. The opening length of the ceramic is 5 μm or more and 50 μm or less from the end portion on the heating element side . In addition, durability can be improved because the magnitude | size of the aggregated particle by the grind gauge measurement of the paste which has the said platinum as a main component is 20 micrometers or less.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Below, the basic structure of the ceramic heater of this invention is demonstrated, referring FIG. In the ceramic heater of the present invention, as shown in the cross-sectional view of FIG. 1A, a heating element 2 mainly composed of platinum is embedded in a ceramic insulating layer 1 mainly composed of alumina.
[0018]
At this time, in the present invention FIG. 1 (b) the length S of the ceramic opening 3 in the heat generating member 2 side end portions as shown in the heat generating element 2 is an enlarged sectional view of the heating body 2 side end portion in FIG. 1 It is important that the distance is 5 μm or more and 50 μm or less from the side end. When the length S of the ceramic opening 3 exceeds 50 μm, the ceramic heater is heated at a temperature rising rate of 80 ° C./sec or more in the atmosphere from room temperature to 400 ° C., or a high temperature exceeding 1000 ° C. When heated to a crack, cracks propagate laterally from the opening 3 due to the thermal stress caused by the difference in thermal expansion coefficient between the heating element 2 and the ceramic insulating layer 1, leading to destruction. The length S of the ceramic aperture 3 is particularly preferably 40 μm or less, and more preferably 30 μm or less.
[0019]
Further, according to the present invention, it is important that w / t of the line width w and the maximum thickness t in the cross section of the heating element 2 is 5 to 40. This is because when the w / t is smaller than 5, the ceramic opening 3 is increased, and crack elongation starting from the ceramic opening 3 is promoted to easily break. On the other hand, when w / t is larger than 40, the ceramic opening is similarly increased, and the elongation of cracks starting from the ceramic opening is promoted to easily cause breakage. As w / t, the range of 10 to 20 is particularly excellent. The above condition of w / t means that this condition is satisfied in any cross section of the heating element 2.
[0020]
Furthermore, the shortest distance L from the heating element 2 to the outer surface of the ceramic insulating layer 1 is preferably 250 μm or more, particularly 300 μm or more. When the shortest distance L from the heat generating element 2 to the outer surface of the ceramic insulating layer 1 is smaller than 250 μm, the heat generating element 2 side end is similarly caused by the thermal stress caused by the difference in thermal expansion coefficient between the heat generating element 2 and the ceramic insulating layer 1. The opening 3 is likely to exceed 50 μm.
[0021]
The alumina ceramic forming the ceramic insulating layer in the present invention contains 97% by mass or more of alumina. If necessary, a sintering aid such as SiO ₂ , MgO, CaO or the like is 3% by mass or less. The ceramic heater is increased in strength and durability by being composed of dense ceramics containing 5 to 1.5% by mass and having a relative density of 80% or more and an open porosity of 5% or less.
[0022]
Further, from the viewpoint of preventing migration of alkali metal such as Na to the negative electrode side and increase in resistance, the content of alkali metal (Na, K, Li) in the ceramic insulating layer 1 mainly composed of alumina is 50 ppm, respectively. In the following, it is particularly desirable that the content be 30 ppm or less.
[0023]
In the present invention, the heating element 2 contains platinum as a main component. Specifically, an alloy of platinum and one kind selected from the group of rhodium, palladium, and ruthenium is used in addition to platinum alone.
[0024]
Further, the heating element 2 preferably contains 2 to 45% by volume of alumina. If the content of alumina is less than 2% by volume, the heating element 2 is more likely to be disconnected by heating with a heater exceeding 1000 ° C. Conversely, if the content exceeds 45% by volume, the electrical resistance of the heating element 2 is reduced. It becomes high and cracks are likely to occur due to the rapid temperature rise or heating of the heater exceeding 1000 ° C. The alumina content of the heating element 2 is particularly preferably in the range of 10 to 30% by volume.
[0025]
The average crystal particle diameter of alumina in the heating element 2 is preferably 0.2 to 1.0 μm, particularly preferably 0.3 to 0.5 μm. As a result, the flatness of the heating element 2 can be improved, and variations in temperature in the heating element due to variations in the secondary particle diameter associated with the aggregation of Al ₂ O ₃ can be prevented.
[0026]
Next, the manufacturing method of the ceramic heater of this invention is demonstrated. As shown in FIG. 2, a paste for printing made of a mixed powder of a metal such as platinum and alumina is prepared, and the pattern 12 and the lead pattern 13 of the heating element 2 are printed on the surface of the green sheet 11 of alumina. After that, through holes are formed in the ceramic green sheet 16 and filled with platinum paste to form via conductors 14 and electrode pads 15 are printed and formed. Then, the ceramic green sheet 16 of alumina is formed on the heating element pattern 12. Alternatively, it is produced by laminating and pressing on the lead pattern 13 and firing in a oxidizing or neutral atmosphere at a temperature of 1200 to 1700 ° C.
[0027]
Here, the alumina green sheets 11 and 16 are made of alumina powder having an average particle diameter of 0.2 to 1.0 μm and 0 to 3 mass of a sintering aid such as SiO ₂ , MgO, and CaO as a sintering aid. %, And an organic binder is added and mixed to prepare a slurry. And this slurry is shape | molded by thickness of 50-500 micrometers by sheet forming methods, such as a doctor blade method. Of the alumina green sheets used here, it is important that the Young's modulus of the ceramic green sheet 16 laminated and pressure-bonded on the heating element pattern 12 is 700 Mpa, particularly 600 Mpa or less. That is, this Young's modulus indicates the ease of deformation of the green sheet. If this Young's modulus is greater than 700 MPa, the green sheet cannot be deformed with respect to the thickness of the heating element pattern, and the ceramic opening described above is not allowed. It gets bigger.
[0028]
The pressure during the lamination bonding, by in the range of 30 to 50 m P a, it is possible to suppress the occurrence of the ceramic open. The Young's modulus of the green sheet is 5 to 20 parts by mass as the solid content with respect to 100 parts by mass of the organic binder, and the solvent amount is in the range of 50 to 100 parts by mass with respect to 100 parts by mass of the raw material. It can be easily controlled by changing the
[0029]
The conductive paste for printing the heating element pattern 12 and the lead pattern 13 is a platinum powder having an average particle diameter of 1 to 3 μm and an alumina powder having an average particle diameter of 0.2 to 1.0 μm in an amount of 2 to 45% by volume. It is prepared by adding and mixing at a ratio, adding an organic binder such as an acrylic resin and an organic solvent such as toluene and mixing them.
[0030]
In addition, it is desirable from the viewpoint of the durability of the heating element that this conductor paste is controlled to have a size of aggregated particles of 20 μm or less, particularly 15 μm or less as measured by a grind gauge. The grind gauge is a device for measuring the particle size of paste, and is a parameter representing the maximum particle size of aggregated particles and the like. That is, if the size of the aggregated particles by the grind gauge is larger than 20 μm, the heating element may be uneven, or the reliability of characteristics may be reduced. The grind gauge can be controlled by adjusting the alumina particle diameter and platinum particle diameter in the paste.
[0031]
In the present invention, the pattern of the heating element 2 may be a structure that extends in the longitudinal direction of the element and is folded at the end in the longitudinal direction, or a waveform (meander) structure that is folded at the end in the direction orthogonal to the longitudinal direction. But you can.
[0032]
Further, the ceramic heater of the present invention has no problem even if it has a cylindrical shape or a cylindrical shape in addition to the flat plate shape as shown in FIGS.
[0033]
Furthermore, the ceramic heater of the present invention is suitably used as a means for heating a sensor unit such as an oxygen sensor, a NOx sensor, or a CO sensor to a high temperature.
[0034]
As an application example of the present invention, FIG. 3 shows a case where the ceramic heater of the present invention is applied to heating of an oxygen sensor element. 3A is a schematic perspective view, and FIG. 3B is a sectional view taken along line X ₁ -X ₁ . This is generally called a theoretical air twist ratio sensor element. In the example of FIG. 3, the sensor unit 20 and the heater unit 21 are integrally formed.
[0035]
In the oxygen sensor element of FIG. 3, the solid electrolyte substrate 22 made of zirconia and having oxygen ion conductivity, and both surfaces of the solid electrolyte substrate 22 facing each other are made of platinum or platinum and rhodium, palladium, ruthenium and gold. A reference electrode 23a that is in contact with air made of an alloy selected from the group and a measurement electrode 24a that is in contact with exhaust gas are formed to form a sensor unit 20 having a function of detecting oxygen concentration. Further, from the viewpoint of preventing the electrode from being poisoned by exhaust gas, a zirconia ceramic porous layer 25 having a porosity of 10 to 50% is formed on the surface of the measurement electrode 24a as an electrode protective layer.
[0036]
On the other hand, the heater portion 21 composed of the insulating ceramic base 26 in which the heating element 27 is embedded is joined to the sensor portion 20 via a frame member 28 that forms an air introduction hole 22a made of zirconia solid electrolyte or alumina ceramic. Yes.
[0037]
In the heater unit 21 used in such an oxygen sensor, the ceramic insulating layer 26 in which the heating element 27 is embedded is composed of a dense ceramic made of alumina ceramics having a relative density of 80% or more and an open porosity of 5% or less. Therefore, the strength of the gas sensor can be increased and the durability can be increased.
[0038]
Further, this oxygen sensor has a rapid temperature increase of 0.8 to 1.5 mm, particularly 1.0 to 1.2 mm, and 45 to 55 mm, particularly 45 to 50 mm, as the total thickness of the element. It is preferable from the relationship between the characteristics and the mounting state of the element in the engine.
[0039]
Next, the method for manufacturing the ceramic heater of the present invention will be described based on the exploded perspective view of FIG.
[0040]
First, a solid electrolyte green sheet 41 is prepared. For example, the green sheet 41 may be formed by appropriately adding an organic binder for molding to a ceramic solid electrolyte powder having oxygen ion conductivity of zirconia, by a doctor blade method, extrusion molding, or isostatic pressing (rubber press). Or it produces by well-known methods, such as press formation.
[0041]
Next, on both surfaces of the green sheet 41, patterns 42a and 42c, lead patterns 42b and 42d, pads 43a, through-holes 43b, and the like, which become the measurement electrode 24 and the reference electrode 23, respectively, are conductive paste containing platinum, for example. The sensor part A is produced by printing by slurry dipping, screen printing, pad printing, or roll transfer.
[0042]
Furthermore, as the conductive paste containing platinum used at this time, platinum particles containing 1 to 50% by volume, particularly 10 to 30% by volume of zirconia composed of the ceramic solid electrolyte component described above are used. In addition, those containing an organic resin component such as ethyl cellulose are desirable.
[0043]
Next, a mixed powder of platinum having an average particle diameter of 0.5 to 2.0 μm and alumina having an average particle diameter of 0.1 to 1.2 μm on the surface of the green sheet 47 made of insulating ceramic such as alumina. The heating element pattern 49, the lead pattern 50, the electrode pattern 51, the through hole 52, and the like are printed and formed by screen printing, pad printing, and roll transfer. Further, green sheets 45 and 46 made of an insulating ceramic substrate having an air introduction hole 44 formed by applying an alumina green sheet with an adhesive such as an acrylic resin or an organic solvent, or applying pressure with a roller or the like; The laminated body B for the heater part 21 is produced by mechanically bonding. At this time, the size of the aggregated particles of the printing paste for the heating element is set to 20 μm or less, particularly 15 μm or less as measured by a grind gauge. In order to control the grind gauge within the above range, it may be adjusted by pulverizing platinum or alumina with a rotary mill, three rolls, or the like to obtain a particle size.
[0044]
Thereafter, the laminated body A of the sensor part and the laminated body B of the heater part are bonded together by interposing an adhesive such as an acrylic resin or an organic solvent, or by mechanically bonding the two while applying pressure with a roller or the like. These are fired. Firing is performed in the air or in an inert gas atmosphere at a temperature range of 1300 ° C. to 1700 ° C. for 1 to 10 hours.
[0045]
Thereafter, if necessary, the heater portion was integrated by forming at least one ceramic porous layer 25 selected from the group of alumina, zirconia, and spinel on the measurement electrode 42a by plasma spraying or the like. An oxygen sensor element can be formed.
[0046]
In the above method, the heater part 1 is formed by simultaneous firing with the sensor part 2. However, after the sensor part 1 and the heater part 2 are fired separately from each other, an appropriate inorganic material such as glass is used. It is also possible to integrate by bonding with a bonding material.
[0047]
【Example】
A slurry is prepared by adding a binder of acrylic resin and toluene as a solvent to alumina powder (containing 0.1% by mass of silica) having a commercial purity of 99.9% and an average particle size of 0.5 μm, and a doctor blade method Thus, an alumina green sheet having a sheet thickness of 0.3 mm was produced. At this time, the amount of organic binder and the amount of solvent were changed to produce alumina green sheets in which the Young's modulus of the green sheets was changed as shown in Table 1.
[0048]
To platinum powder having an average particle diameter of 0.2 μm containing 1 to 50% by volume of alumina powder,
A paste composed of an organic vehicle (organic binder + solvent) is mixed with three rolls using various platinum powders having an average particle diameter of 1 to 3 μm, and the maximum diameter of agglomerated particles by a grind gauge is 3, 20 or 30 μm. A seed paste was prepared, and a heating element pattern was printed by screen printing on the surface of the alumina green sheet by changing the printing thickness so that the resistance value after firing was about 8Ω at room temperature.
[0049]
In addition, after firing the thickness and the line width of the heating element, various ceramic heaters having different cross-sectional shapes were prepared by changing variously as shown in Table 1.
[0050]
And three alumina green sheets were laminated | stacked on the upper surface of these heat generating body patterns, and the laminated body of the heater was produced.
[0051]
Then, this laminated body was baked in air | atmosphere at 1500 degreeC for 2 hours. Thereafter, the outer periphery was processed so that the heater had a width of 4 mm and a length of 5 mm, and the edge portion was further chamfered with 0.2 mm.
[0052]
A voltage of about 25 V was applied to the manufactured heater, and the temperature was raised from room temperature to 1100 ° C. in about 20 seconds. After further holding at 1100 ° C. for 1 minute, the applied voltage was turned off and the heater was cooled to room temperature. This temperature cycle was defined as one cycle, and the failure rate of the heater when this was repeated 100,000 times was determined. At this time, 10 samples were used.
[0053]
Further, the length of the ceramic opening from the end portion on the heating element side is determined by mirroring the cross section of the central portion of the heater to determine the length of the ceramic opening for at least 10 heating elements from observation with a scanning electron microscope. The average value was measured. The Young's modulus of the sheet was obtained from a stress-strain curve obtained by conducting a tensile test on the sheet. The results are shown in Table 1.
[0054]
[Table 1]

[0055]
From Table 1, when a green sheet having a Young's modulus greater than 700 MPa was used, the length of the opening from the heating element side end in the ceramic exceeded 50 μm. 7 shows that the breakage rate is rapidly high.
[0056]
Sample No. w / t is smaller than 5. In No. 17, the opening of the ceramic became large and the durability decreased. Sample No. with w / t exceeding 40 is also shown. Also in No. 16, the opening of the ceramic became large and the durability decreased.
[0057]
In contrast, all of the products of the present invention had an opening length of 5 μm or more and 50 μm or less, and a breakage rate of 60% or less.
[0058]
【The invention's effect】
As described in detail above, according to the present invention, an alumina green sheet having a Young's modulus of 700 MPa or less is laminated and pressed on the surface of an alumina green sheet on which a heating element pattern mainly composed of platinum is printed. A ceramic heater in which a heating element mainly composed of platinum is embedded in a ceramic insulating layer mainly composed of alumina, wherein w / t of a line width w and a maximum thickness t in a section of the heating element is 5 to 40 Yes, by reducing the opening length of the ceramic constituting the ceramic insulating layer at the side edge of the heating element to 5 μm or more and 50 μm or less, the durability of the heater at high temperature and the thermal shock during rapid temperature rise Thus, it is possible to provide a ceramic heater capable of solving the problems such as breakage caused by the above and capable of rapid temperature increase with a prolonged heater life.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining an example of a ceramic heater of the present invention.
FIG. 2 is an exploded perspective view for explaining a method for producing a ceramic heater according to the present invention.
3A is a schematic perspective view of an oxygen sensor element that is an application example of the ceramic heater of the present invention, and FIG. 3B is a sectional view taken along line X1-X1.
4 is an exploded perspective view for explaining a method of manufacturing the oxygen sensor element of FIG. 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,26 Ceramic insulating layer 2,27a Heat generating body 3 Ceramic opening 22 ... Solid electrolyte substrate 22a ... Air introduction hole 23a ... Reference electrode 24a ... Measurement electrode 25 ... Ceramic porous layer 20 ... Sensor part 21 ... Heater part

Claims (5)

Platinum in a ceramic insulating layer mainly composed of alumina, which is obtained by laminating and firing an alumina green sheet having a Young's modulus of 700 MPa or less on the surface of an alumina green sheet on which a heating element pattern mainly composed of platinum is printed. Embedded in a ceramic heater, in which the width w and the maximum thickness t in the cross-section of the heating element are 5 to 40, and the ceramic insulation at the end of the heating element side ceramic heater, wherein the length of the ceramic opening constituting the layer is more than 5μm from the heating side end portion is 50μm or less. 2. The ceramic heater according to claim 1, wherein the heating element mainly composed of platinum contains 2 to 45% by volume of alumina. 3. The ceramic heater according to claim 1, wherein the shortest distance from the heating element mainly composed of platinum to the outer surface of the ceramic insulating layer is 250 μm or more. After applying and applying a paste containing platinum as a main component to the surface of the alumina green sheet so that w / t of the line width w and thickness t in the cross section after firing satisfies the relationship of 5 to 40, this An alumina green sheet having a Young's modulus of 700 MPa or less is laminated and pressure-bonded on the heating element pattern, and the firing length of the ceramic constituting the ceramic insulating layer containing alumina as a main component at the heating element side end is determined as the heat generation. A method for producing a ceramic heater, wherein the thickness is 5 μm or more and 50 μm or less from the body side end . 5. The method of manufacturing a ceramic heater according to claim 4, wherein the size of the aggregated particles measured by a grind gauge of the paste containing platinum as a main component is 20 [mu] m or less.

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