JP2004311433A - Ceramic heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that there is an increasing degree of requirements for improvement in a rapid temperature rising property to heighten exhaust gas detecting ability as is especially seen in an automobile oxygen sensor heating heater, vibration resistance accompanying downsizing of vehicles, a long lifetime through strength-proof and an extended warranty period, and durability by prevention of disconnection of a heat generating resistive element due to ionic migration of CaO, MgO and SiO<SB>2</SB>of matrix components in a ceramic with decreasing of wiring members by making high voltage 42V of an automobile power source. <P>SOLUTION: The ceramic heater, with a heat generating resistive element, an electrode pulling part connected to the heat generating resistive element and an electrode pad to conduct the electrode pulling part on a back surface facing the electrode pulling part printed by silk screening on a ceramic sheet surface has the ceramic sheet adhered to a circumference of a ceramic core material with the front surface inside. Each average pore diameter of the ceramic core material and the ceramic sheet is from 1 to 10μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to various heaters for industrial equipment such as a heater for heating an oxygen sensor for an automobile, a soldering iron, a heater for a vaporizer of an oil fan heater, a hot water heater, a general household, an electronic component, and an industrial equipment. The present invention relates to a ceramic heater used in a ceramic heater.

  2. Description of the Related Art Conventionally, as a ceramic heater, heaters having various shapes such as a flat plate, a rod, and a tube have been used in accordance with each application. Above all, the use of rod-shaped ceramic heaters used in automobile exhaust gas sensors tends to increase in conjunction with global environmental protection activities.

  FIGS. 1A to 1C are schematic diagrams of a rod-shaped ceramic heater 1 that is generally used. The ceramic heater 1 has a built-in heat generating resistor 4 and an electrode lead-out portion 5. An electrode pad 8 is formed on a surface 3 a of the ceramic heater 1, and a lead member 9 for supplying power to the internal heat generating resistor 4 is provided. It is brazed to the electrode pad 8.

  Further, the ceramic body 6 has a structure in which a ceramic sheet 3 in which a heating resistor 4 is screen-printed on a ceramic core material 2 is circumferentially adhered as shown in FIGS. 1B and 1C. An electrode pad 8 for connecting the heating resistor 4 and a lead member 9 made of metal is provided on the back surface of the ceramic sheet 3. The electrode pads 8 are electrically connected to each other by providing a through hole 7 filled with a conductor in the ceramic sheet 3 between the electrode pad 8 and the electrode lead portion 5.

  Further, the surface of the electrode pad 8 formed on the surface of the ceramic body 6 is subjected to plating 10 by any of electrolytic plating containing Ni as a main component, electroless boron-based plating, and electroless phosphorus-based plating, and the lead member 9 is formed. It is fixed by brazing with an Au-Cu-based, Ag-Cu-based, Ag-based, and Cu-based brazing material 11. Further, in order to prevent the lead member 9 and the electrode pad 8 from being deteriorated due to the temperature and humidity depending on the use environment of the ceramic heater 1, similarly to the plating 10, electrolytic plating containing Ni as a main component, electroless boron plating, In some cases, plating 12 is performed by any one of electroless phosphorous plating. The ceramic heater 1 includes a rod-shaped heater and a tubular heater in which the ceramic core material 2 is hollow.

The material of the ceramic core 2 and the ceramic sheet 3 of the ceramic heater 1 of the present _invention, Al ₂ O 3 88 to 95 wt%, _SiO 2 2 to 7 wt%, CaO0.5~3 wt%, MgO0.5~ 3 wt%, from consist ZrO 2 _{1 to 3} wt%, the heat generating resistor 4, W, as a main component at least one member selected from the group consisting of Re and Mo, an organic binder and optionally added ceramic component Become. Conventionally, when the ceramic heater 1 for automobiles is used, the average pore diameter is generally 10 to 30 μm, and the porosity is generally 5 to 8%.

  Many ceramic heaters 1 are used to heat an oxygen sensor for measuring the oxygen concentration in the exhaust gas of an automobile to an operating temperature, and the ceramic heater 1 used in such an application applies a DC voltage. And it is often used continuously at a high temperature of 600 to 800 ° C. For this reason, it is necessary to improve the durability under the condition of applying a DC voltage in order to extend the life of the ceramic heater 1.

  As shown in FIG. 4, under the condition of applying a DC voltage, migration occurs in which cations contained in the base material of the ceramic body 6 move from the anode side 4a to the cathode side 4b due to this voltage. Due to this migration, cations collect on the cathode side 4b with time, and conversely, the anode side 4a changes to a sparse state with time. Then, oxygen in the air starts to diffuse near the heating resistor 4 on the anode side 4a, and the heating resistor 4 is oxidized and disconnected.

  Here, as for the pore diameter of the general ceramic 2, for example, there is a proposal of a ceramic substrate for a semiconductor manufacturing / inspection apparatus in which the maximum pore diameter of the ceramic is 50 μm or less (see Patent Document 1).

Further, it has been proposed that it is effective to add a component which does not easily cause migration to the electrode lead-out portion 5 connected to the heating resistor 4 in order to make it difficult for migration which causes disconnection of the ceramic heater 1 to occur. (See Patent Document 2).
JP-A-2001-298074 JP-A-1997-245946

  Recent trends regarding the ceramic heater 1 include a rapid temperature rise property for enhancing exhaust gas detection capability, particularly in a heater for heating an oxygen sensor for an automobile, and an increase in vibration resistance, strength, and a warranty period associated with a compact vehicle. There is a strong demand for a long service life. Specifically, there is a trend to reduce the current flowing through the wiring by setting the vehicle power supply to 42 V, thereby reducing the wire diameter of the wiring member and reducing the number of parts, thereby reducing the weight.

  The adverse effect caused by this is ion migration caused by the electric field. When the shellac heater 1 is used at a high temperature, components such as Ca, Mg and Si in the ceramic body and alkali metals such as Na and K contained as impurities move by the electric field. In this ion movement, as the voltage applied to the ceramic heater 1 increases, the moving speed is accelerated and the moving amount increases. Accordingly, there is a problem that the resistance value of the heating resistor 4 is increased, durability of the heating resistor 4 is reduced, and the heating resistor 4 is disconnected.

  Here, Patent Literature 1 is a ceramic substrate for a semiconductor manufacturing / inspection apparatus which secures a withstand voltage by adding electrically conductive carbon to the ceramic substrate, and has a different field and problem from the present invention. It cannot be diverted.

  In addition, in Patent Document 2, it is effective to add a component that does not easily cause migration to the electrode lead-out portion 5 connected to the heating resistor 4 in order to make it difficult to cause migration which causes disconnection of the ceramic heater 1. Although it has been proposed. There was a problem that sinterability deteriorated.

  In view of the above, the present invention provides a heating resistor on the surface of a ceramic sheet and an electrode lead portion connected to the heating resistor, and an electrode pad for conducting with the electrode lead portion on a back surface opposite to the electrode lead portion. In a ceramic heater in which each of the ceramic sheets is screen-printed, and the ceramic sheet is circumferentially adhered to the ceramic core with the surface inside, the average pore diameter of the ceramic core and the ceramic sheet is 1 to 30 μm, and the porosity is 0.3 to 6%.

  Further, the porosity of the ceramic core material is not more than the porosity of the ceramic sheet.

  When the porosity of the ceramic core material is A and the porosity of the ceramic sheet is B, 0.3 ≦ A / B ≦ 0.95.

  Further, a heating resistor, an electrode lead portion and an electrode pad portion connected to the heating resistor are formed on the surface of the ceramic sheet, and another ceramic sheet is laminated on at least the heating resistor, and closely adhered, fired and integrated. The ceramic heater is characterized in that the ceramic heater has an average pore diameter of 1 to 30 μm and a porosity of 0.3 to 6%.

  As described above, according to the present invention, the heating resistor is provided on the surface of the ceramic sheet, the electrode lead portion connected to the heating resistor, and the electrode for conducting the electrode lead portion on the back surface opposite to the electrode lead portion. In a ceramic heater in which a pad is screen-printed and the ceramic sheet is circumferentially adhered to the ceramic core with the surface facing the inside, the average pore diameter of the ceramic core and the ceramic sheet is 1 to 30 μm, and the porosity is 6 %, A cation trapping volume can be secured, and a ceramic heater with improved durability against disconnection of the heating resistor due to migration of cations can be obtained.

  In view of the above, the present invention provides a heating resistor on the surface of a ceramic sheet and an electrode lead portion connected to the heating resistor, and an electrode pad for conducting with the electrode lead portion on a back surface opposite to the electrode lead portion. In a ceramic heater in which the ceramic sheet is screen-printed and the ceramic sheet is circumferentially adhered to the ceramic core with the surface inside, the average pore diameter of the ceramic core and the ceramic sheet is 1 to 30 μm, and the porosity is 0.3. The cation trapping volume can be ensured as ~ 6%.

  Here, the average pore diameter and the porosity indicate the average pore diameter and the porosity of the ceramic sheet and the ceramic core material in the sintered porcelain.

  When the porosity of the ceramic core material is equal to or less than the porosity of the ceramic sheet, more preferably, when the porosity of the ceramic core material is A and the porosity of the ceramic sheet is B, 0.3 ≦ A / B By setting ≦ 0.95, durability against disconnection of the heating resistor due to migration of cations was improved.

  Hereinafter, an embodiment of the ceramic heater of the present invention will be described with reference to FIG.

  1A is a partially cutaway perspective view of the ceramic heater 1, FIG. 1B is a developed view of the ceramic body 6 a, and FIG. 1C is a view near the electrode pad 8. It is sectional drawing.

  A heating resistor 4 and an electrode lead-out portion 5 are formed on the front surface 3a of the ceramic sheet 3, and furthermore, a structure is provided in which a through hole 7 is formed between the heating resistor 4 and an electrode pad 8 formed on the back surface thereof. The ceramic body 6 is formed by sintering the ceramic sheet 3 thus prepared on the surface 3a of the ceramic core material 2 so that the surface 3a is inside. Further, the lead member 9 is joined to the electrode pad 8 using a brazing material, whereby the ceramic heater 1 is obtained.

  In order to reduce the average pore diameter and porosity of the ceramic core material 2 and the ceramic sheet 3, the particle size of the raw material is reduced, the pressurized bulk density of the raw material is increased, and the particle size is blended so that the raw material can be finely packed. Such means may be taken.

  When the particle size of the raw material is reduced, the filling during molding becomes difficult, the firing shrinkage of the ceramic core 2 becomes larger than the firing shrinkage of the ceramic sheet 3, and the ceramic core 2 shrinks more. In this case, if the ceramic core material 2 is calcined first, contracted in a predetermined ratio in advance, and then the ceramic sheet 3 is wound around the surface of the ceramic core material 2 and fired, the firing of both materials is possible. The shrinkage can be adjusted.

  Further, in order to increase the pressurized bulk density of the raw material, it is preferable to process the raw material into a nearly spherical shape. If the raw material has an angular shape, the powder blocks each other when pressurized and prevents filling, so that the powder filling rate at the time of molding does not increase. For this reason, pores in the ceramic increase. Therefore, if the raw material is processed into a spherical shape during raw material production, or the raw material is ground by a method such as a ball mill to remove the angular portion of the raw material, the pressurized bulk density of the powder is increased, and the porosity is increased. Can be reduced. The fine raw material generated by this grinding is effective also in the particle size mixing for finely filling the raw material.

  Here, the pressurized bulk density is a density when a powder is filled in a metal mold and molded at a constant pressure.

  If the average pore diameter is less than 1 μm, when the cations are concentrated on the cathode side 4b due to the migration, the volume of pores for absorbing the cations is small, so that the ceramic body 6 is broken and disconnected.

  On the other hand, when the average pore diameter is larger than 30 μm, when migration occurs and cations move from the anode side 4a to the cathode side 4b, the density on the anode side 4a side becomes too low and durability is rapidly increased. It was found that a problem of deterioration occurred.

  The average pore diameter is more preferably set to 1 to 20 μm.

  When the porosity of the ceramic core material 2 is A and the porosity of the ceramic sheet 3 is B, the durability is reduced to about 1/2 when A / B is less than 0.3 and greater than 0.95. It turned out to be.

  Further, the porosity A and B are preferably 1 to 10%, respectively, because they are stable in production.

  Positive ion migration due to migration is greater in the ceramic core material 2 inside the heating resistor 4 than in the ceramic sheet 3. Therefore, by reducing the porosity of the ceramic core material 2, the density on the song side is prevented from becoming extremely low, and the durability is improved.

  Here, a method for evaluating the average pore diameter and the porosity will be described.

  First, the ceramic heater 1 is embedded in a resin to perform a cross section, and a 1000-fold photograph of the cross section is taken with a metallographic microscope. Then, the number and diameter of pores of 1 μm or more were measured using an image processing device (device name: LUZEX-FS manufactured by Nireco) in a range of 240 μm × 160 μm in one visual field = 240 μm × 160 μm for each of the ceramic core 2 and the ceramic sheet 3. The average pore diameter and the porosity A of the ceramic core material 2 and the porosity B of the ceramic sheet 3 are measured, and A / B is calculated.

  Next, a method for measuring durability will be described.

  A voltage was applied so that the highest heating portion (not shown) of the ceramic heater 1 as an evaluation sample became 1200 ° C., and the number of wires disconnected after 500 hours, and a voltage was applied so that the temperature became 1200 ° C., and all the samples were disconnected. The average time to reach was measured.

  Next, details of the ceramic heater 1 of the present invention will be described with reference to FIG.

The material of the ceramic core 2 and the ceramic sheet 3 of the ceramic heater 1 of the present _invention, Al ₂ O 3 88 to 95 wt%, _SiO 2 2 to 7 wt%, CaO0.5~3 wt%, MgO0.5~ 3 wt%, it is preferable to use a _ZrO 2 1 to 3 wt%.

If the Al ₂ O ₃ content is less than this, the glassiness increases, and the migration during energization increases, which is not preferable. Conversely, if the Al ₂ O ₃ content is increased more than this, the amount of glass diffused into the metal layer of the built-in heating resistor 4 decreases, and the durability of the ceramic heater 1 deteriorates, which is not preferable.

  The heating resistor 4 has at least one selected from the group consisting of W, Re, and Mo as a main component, and includes an organic binder and a ceramic component appropriately added. The material of the heating resistor 4 is appropriately selected depending on the use required of the ceramic heater 1.

  Further, the electrode pad 8 is subjected to a plating 10 of any one of electrolytic plating containing Ni as a main component, electroless boron-based plating, and electroless phosphorus-based plating after firing. The plating 10 is for improving the flow of the brazing material and increasing the brazing strength when the lead member 9 is brazed to the surface of the electrode pad 8, and usually forms the plating 10 having a thickness of 1 to 5 μm.

  As the brazing material 11 for fixing the lead member 9, Au, Cu, Au-Cu, Au-Ni, Ag, or Ag-Cu-based brazing material is used. Preferably, when the Au content is 25 to 95% by weight as the Au-Cu brazing and the Au content is 50 to 95% by weight as the Au-Ni brazing, the brazing temperature can be set to about 1000 ° C. This is because the residual stress after the attachment can be reduced. In addition, when used in an atmosphere with high humidity, it is preferable to use an Au-based or Cu-based brazing material because migration is less likely to occur.

  Further, the brazing material 11 is protected by forming a plating 12 from the viewpoint of corrosion such as oxidation.

  2, the dimensions of the ceramic heater 1 will be described.

  For example, the outer diameter d can be about 2 to 20 mm, and the length l can be about 40 to 200 mm. The ceramic heater 1 for heating the air-fuel ratio sensor of an automobile preferably has an outer diameter d of 2 to 4 mm and a length l of 40 to 65 mm.

  Further, when used as the ceramic heater 1 for an automobile, it is preferable that the heating length f of the heating resistor 4 be 3 to 15 mm. If the heat generation length f is shorter than 3 mm, the temperature rise during energization can be accelerated, but the durability of the ceramic heater 1 decreases. On the other hand, if the length is longer than 15 mm, the heating rate is reduced, and if the heating rate is increased, the power consumption of the ceramic heater 1 is increased.

  The heating length f indicates the length of the reciprocating pattern of the heating resistor 4 excluding the electrode lead-out portion 5, and the heating length f is variously selected depending on the application.

  Further, electrode lead portions 5 are formed at both ends of the heating resistor 4, and as shown in FIG. 1C, the electrode drawing portion 5 is energized to the heating resistor 4 via the through hole 7. Electrode pads 8 are formed.

  Further, a plating layer made of a high melting point metal having an average thickness of 20 μm or more is formed on the inner peripheral surface of the through hole 7, and a brazing material such as copper brazing, silver brazing or gold copper brazing, or a high melting point such as tungsten, molybdenum, rhenium or the like is used. A through-hole conductor made of metal is filled, and an electrode pad 8 is attached so as to be electrically connected to the electrode lead portion 5.

  FIG. 3 is a view showing an example of another embodiment of the present invention, and shows a ceramic heater 1 having a heating resistor 4 built in between a plurality of ceramic sheets 3.

  The electrode pad 8 is formed in a part of the ceramic sheet 3 so as to be exposed in the notch 16, and a lead member 9 is fixed to the electrode pad 8 by a brazing material 11.

  In the flat ceramic heater 1 produced by stacking a plurality of such ceramic sheets 3, the distribution of voids in the fired ceramic sheet 3 affects the durability.

  By setting the average pore diameter in the ceramic sheet 3 to 1 to 30 μm and the porosity to 0.3 to 6%, migration due to an electric field generated by applying a voltage to the heating resistor 4 during use of the ceramic heater 1. Can be mitigated and durability can be improved.

  When the average pore diameter is less than 0.3 μm, the porosity is reduced, and the effect on durability is reduced, which is not preferable. More preferably, the average pore diameter is preferably 1 to 20 μm, and the porosity is preferably 0.3 to 3%.

(Example 1)
Next, examples of the present invention will be described.

  Here, the average pore diameter and porosity of the pores 13 of the ceramic core material 2 and the ceramic sheet 3 and the durability of the ceramic heater 1 were investigated.

Al ₂ O ₃ as a main component, 92% by weight of Al ₂ O ₃ , 4.5% by weight of SiO ₂ , 1.5% by weight of CaO, 1.5% by weight of MgO, 0.5% by weight of ZrO _After adjusting to have the composition of No. ₂ and adding an organic solvent such as an organic binder to form a slurry, a ceramic sheet 3 was prepared by a doctor blade method.

  As shown in FIGS. 1 (a) to 1 (c), a heat generating portion 4 made of W-Re and an electrode lead portion 5 are printed on the front surface 3a, and W metallized on the rear surface to form an electrode pad 8. 9 was screen printed. Then, a through-hole 7 was formed at the end of the electrode lead-out portion 5, and a paste was injected into the through-hole 7 to establish conduction with the electrode pad 8.

  Next, after adjusting to the same material as the ceramic sheet 3 and forming a slurry to which an organic solvent such as a molding binder was added, a ceramic core material 2 was produced by extrusion molding and press molding. Next, after the ceramic sheet 3 is cut into a predetermined size, a step of setting the ceramic sheet 3 at a predetermined position by an automatic machine and a step of placing the ceramic core 2 thereon, and rolling the ceramic core 2 thereon. A ceramic sheet 3 is brought into close contact with its surface 3a, and a step of rotating the ceramic body 6 produced as described above between three rolls rotating in the same direction is performed. The sheet 3 was brought into close contact with the circuit. Note that an organic adhesive was screen-printed on the ceramic sheet 3 as an adhesive for bonding the ceramic core material 2 and the ceramic sheet 3.

In order to evaluate the average pore diameter and porosity of the pores 13 of the ceramic sheet 3 of the ceramic core material 2 and the durability of the ceramic heater 1 this time, the particle diameter of the raw material Al ₂ O ₃ and the matrix component ratio were changed. The sample was measured for each of ten levels of six levels.

  The sample had an outer diameter d of 3 mm and a length l of 60 mm.

  In the measurement and evaluation method of the average pore diameter and the porosity, first, the ceramic heater 1 is embedded in a resin to perform a cross section, and a 1000-fold photograph of the cross section is taken with a metal microscope or an electron microscope. Thereafter, the average pore diameter of the pores and the pores of the ceramic core material 2 are set in an image processing device (device name: LUZEX-FS manufactured by Nireco) in the range of 240 μm × 160 μm in each of eight places of the ceramic core material 2 and the ceramic sheet 3. The ratio A and the porosity B of the ceramic sheet 3 were measured and calculated to calculate A / B.

  Here, the diameter of the target pore was 0.1 μm or more.

  Regarding the method of measuring the durability, a voltage was applied so that the highest heat generating portion of the ceramic heater 1 as an evaluation sample reached 1200 ° C., and the number of disconnected wires 200 hours later was measured.

  Further, in Table 2, in a continuous conduction endurance test at 1200 ° C., the average of the time until all 10 pieces of each lot were disconnected was measured.

The results are shown in Tables 1 and 2.

  From Table 1, it can be said that the average pore diameter of the pores is 1 to 30 μm and the porosity is 0.3 to 6%.

  When the average pore diameter is 1 μm or less, when the cations are concentrated on the cathode side 4b due to the migration, the volume of the pores into which the cations enter is small, so that the ceramic body 6 may be broken and disconnected.

  On the other hand, if it exceeds 30 μm, it has been found that the anode side 4a becomes too sparse, causing a problem that durability is rapidly deteriorated.

In the case of an average pore diameter of 1 to 20 μm and a porosity of 1 to 3%, no disconnection occurred in a durability test at 1200 ° C. for 200 hours.

  From Table 2, in the relation A / B where the porosity of the ceramic core material 2 is A and the porosity of the ceramic sheet 3 is B, the durability of the ceramic heater 1 is 0.3 ≦ A / B ≦ 0.95. Was found to improve.

(Example 2)
Here, the average pore diameter and porosity of the pores 13 and the durability of the ceramic heater 1 in the ceramic heater 1 of the type in which the heating resistor 4 was formed between the two ceramic sheets 3 were investigated.

Al ₂ O ₃ as a main component, 92% by weight of Al ₂ O ₃ , 4.5% by weight of SiO ₂ , 1.5% by weight of CaO, 1.5% by weight of MgO, 0.5% by weight of ZrO _After adjusting to have the composition of No. ₂ and adding an organic solvent such as an organic binder to form a slurry, a ceramic sheet 3 was prepared by a doctor blade method. At this time, the porosity and the average pore diameter were adjusted by varying the particle size and grain shape of the raw material and the amount of the binder used for the ceramic sheet 3.

  Next, a heating resistor 4 made of W is formed on one main surface of the ceramic sheet 3 by printing with a thickness of 20 μm, and the ceramic sheet 3 is formed in order to reduce a step around the heating resistor 4 and prevent poor adhesion. After coating a coat layer (not shown) having the same composition, another ceramic sheet 3 is overlapped and adhered, processed into a predetermined shape, and fired in a reducing atmosphere at 1600 ° C., as shown in FIG. A plate-shaped ceramic heater 1 was obtained.

  A continuous energization endurance test at 1200 ° C. was conducted for 400 hours for each of the thus prepared ceramic heaters 20 in each lot, and the presence or absence of disconnection was evaluated. Separately, the porosity and the pore diameter of the cross section of the ceramic heater 1 of each lot were evaluated.

The results are shown in Table 3.

  As can be seen from Table 3, it can be said that the average pore diameter of the pores is 1 to 30 µm and the porosity is 0.3 to 6%.

  When the average pore diameter is 1 μm or less, when the cations are concentrated on the cathode side 4b due to the migration, the volume of the pores into which the cations enter is small, so that the ceramic body 6 may be broken and disconnected.

  On the other hand, if it exceeds 30 μm, it has been found that the anode side 4a becomes too sparse, causing a problem that durability is rapidly deteriorated.

  In the case of an average pore diameter of 1 to 20 μm and a porosity of 1 to 3%, no disconnection occurred in a durability test at 1200 ° C. for 200 hours.

  In addition, the particle size and the grain shape affect the pressurized bulk density of the raw material. The rate has increased.

  In addition, it was found that the raw material having an average particle size of 1 μm or less had a reduced bulk density under pressure, and thus tended to increase the porosity.

(A) is a perspective view of the ceramic heater of the present invention, (b) is a developed view thereof, and (c) is a cross-sectional view of the electrode pad portion. It is sectional drawing of the ceramic heater of this invention. 1A is a schematic top view of a ceramic heater of the present invention, FIG. 1A is a top view, and FIG. It is sectional drawing of the conventional ceramic heater.

Explanation of reference numerals

1: Ceramic heater 2: Ceramic core 3: Ceramic sheet 3a: Surface 4: Heating resistor 4a: Anode side 4b: Cathode side 5: Electrode lead-out section 6: Ceramic body 7: Through hole 8: Electrode pad 9: Lead member 10: Plating 11: Brazing material 12: Plating 13: Pores d: Ceramic heater outer diameter l: Ceramic heater full length f: Heating length

Claims (4)

A heating resistor is formed on the surface of the ceramic sheet, the heating resistor is formed inside, and the ceramic heating element is circumferentially adhered to the ceramic core with the surface on which the heating resistor is formed inside. A ceramic heater, wherein each ceramic sheet has an average pore diameter of 1 to 30 μm and a porosity of 0.3 to 6%. The ceramic heater according to claim 1, wherein a porosity of the ceramic core material is equal to or less than a porosity of the ceramic sheet. 3. The ceramic heater according to claim 2, wherein when the porosity of the ceramic core material is A and the porosity of the ceramic sheet is B, 0.3 ≦ A / B ≦ 0.95. 4. In a ceramic heater in which a heating resistor is formed on the surface of a ceramic sheet and at least another ceramic sheet is overlaid on and close to the heating resistor and integrally fired, the average pore diameter of the fired ceramic sheet is A ceramic heater having a thickness of 1 to 30 μm and a porosity of 0.3 to 6%.

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