JP2011192473A - Ceramic heater and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater which prevents the deterioration of a resistance heating material and suppresses the detachment of the electrode pad from a ceramic substrate without deteriorating adhesiveness between an electrode pad and a metal plating. <P>SOLUTION: The ceramic heater includes: a ceramic substrate 11 composed of ceramic; a heating portion which is arranged in the ceramic substrate 11 and in which the resistance heating material is buried; a drawing portion which is arranged in the ceramic substrate 11 and electrically connected to the heating portion; an electrode pad 18 which is arranged on a surface of the ceramic substrate 11 and connected to the drawing portion; and a metal plating 19 which is arranged on a surface of the electrode pad 18, in which a content of an oxide of Mg in the ceramic is 0.01-0.2 wt.% on an MgO basis; the electrode pad 18 is composed of ceramic; a content of the ceramic in the electrode pad 18 is 1-45 vol.%; and a thicknesses of the electrode pad 18 is 15 μm or larger. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ceramic heater and a method for manufacturing the ceramic heater.

  The ceramic heater includes a ceramic base made of ceramic, a heat generating part provided in the ceramic base and embedded with a resistance heating material, a lead part provided in the ceramic base and electrically connected to the heat generating part, An electrode pad provided on the surface of the ceramic substrate and electrically connected to the lead portion. Ceramic heaters are used in exhaust gas concentration detectors (oxygen sensors), soldering irons, heat sources for oil vaporizers such as oil fan heaters, industrial equipment such as hot water heaters, electronic components, and other general household equipment. .

  For example, Patent Document 1 discloses a ceramic heater using a sintered material based on alumina containing an oxide with a predetermined content.

Japanese Patent No. 3921327

  However, the conventional ceramic heater described in Patent Document 1 and the like may be insufficient in durability because the resistance heating material may deteriorate and the electrical resistance value may increase when used at a high temperature for a long time. It is a problem. The cause of the deterioration of the resistance heating material is that the components of the resistance heating material or the ceramic substrate cause an electrochemical diffusion phenomenon, so-called electromigration (hereinafter, simply referred to as “migration”) when energized at a high temperature. It is mentioned.

  For example, if the component of the resistance heating material diffuses and flows out into the ceramic substrate due to migration, the resistance heating material may be consumed at the outflow portion, resulting in excessive temperature rise or disconnection. Further, metal oxide components such as MgO and CaO added as a sintering aid component exist in the form of a glass phase in the ceramic substrate, but the metal ions or oxygen ions contained therein are also likely to cause migration. . For example, when the main component of the resistance heating material is W, it is oxidized by oxygen ions that move due to migration, which may cause problems such as an increase in resistance value and disconnection.

  The present inventors have found that the above problem can be solved by reducing the content of MgO in the ceramic substrate as compared with the conventional one. However, the present inventors have found that when the addition amount of MgO is decreased, the electrode pad is likely to be partially peeled from the ceramic substrate. Furthermore, the present inventors have found that peeling of the electrode pad from the ceramic substrate can be suppressed by containing the same ceramic as the ceramic substrate in the electrode pad. However, it has been found that when the same ceramic as the ceramic substrate is contained in the electrode pad, the adhesion between the metal plating formed on the electrode pad and the electrode pad is lowered. When the adhesion between the metal plating and the electrode pad is lowered, peeling occurs between the electrode pad and the metal lead through the metal plating, which causes a problem of electrical connection failure.

  Therefore, the present invention provides a ceramic heater capable of preventing the resistance heating material from deteriorating and suppressing the peeling of the electrode pad from the ceramic substrate without reducing the adhesion between the electrode pad and the metal plating. It aims at providing the manufacturing method of a ceramic heater.

  In view of the above circumstances, the present invention provides a ceramic base made of ceramics, a heat generating part provided in the ceramic base and having at least a resistance heating material embedded therein, and provided in the ceramic base and electrically connected to the heat generating part. A lead portion, an electrode pad provided on the surface of the ceramic base, and electrically connected to the lead portion; and a metal plating provided on the surface of the electrode pad, and the content of Mg oxide in the ceramic is , 0.01 to 0.2% by weight in terms of MgO, the electrode pad contains ceramic, the ceramic content in the electrode pad is 1 to 45% by volume, and the thickness of the electrode pad is 15 μm or more. Provide ceramic heater. In the present invention, the ceramic contained in the electrode pad may be the same as or different from the ceramic of the ceramic substrate.

  According to the ceramic heater according to the present invention, it is possible to suppress peeling of the electrode pad from the ceramic substrate without reducing the adhesion between the electrode pad and the metal plating.

  Moreover, in the said invention, deterioration of a resistance heat generating material is prevented because the content rate of Mg oxide in ceramics is 0.01 to 0.2 weight% in conversion of MgO.

  A method of manufacturing a ceramic heater according to the present invention includes a ceramic base precursor containing ceramic raw material powder, a precursor of a heat generating portion provided in the ceramic base precursor and having at least a resistance heating material embedded therein, and a ceramic base. The lead part precursor provided in the precursor body and connected to the heat generating part precursor, the electrode pad precursor provided on the surface of the ceramic base precursor, and a part of the ceramic base precursor A firing step of firing a conductor paste in contact with the precursor of the lead portion and the electrode pad filled in the through-hole penetrating, and a surface of the electrode pad formed from the precursor of the electrode pad in the firing step And a plating step of forming metal plating on the ceramic, and the content of Mg oxide in the ceramic raw material powder is 0.01-0. The electrode pad precursor contains ceramic raw material powder, and the total value of the volume of the metal contained in the electrode pad precursor and the volume of the ceramic raw material powder contained in the electrode pad precursor is The volume of the ceramic raw material powder contained in the electrode pad precursor is 1 to 45% by volume, and the thickness of the electrode pad precursor is 19 μm or more. In the present invention, the ceramic raw material powder contained in the electrode pad precursor may be the same as or different from the ceramic raw material powder contained in the ceramic substrate precursor.

  According to the method for manufacturing a ceramic heater according to the present invention, it is possible to prevent the resistance heating material from being deteriorated and to peel the electrode pad from the ceramic substrate without reducing the adhesion between the electrode pad and the metal plating. The ceramic heater of the present invention can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to prevent deterioration of a resistance heating material, the ceramic heater which can suppress peeling of the electrode pad from a ceramic base | substrate, without reducing the adhesiveness of an electrode pad and metal plating. And a method of manufacturing a ceramic heater can be provided.

It is the schematic of the rod-shaped ceramic heater which is one Embodiment of the ceramic hitter of this invention. It is a figure which shows the state of the ceramic base body before winding in FIG. FIG. 2 is a sectional view taken along the line zz in FIG. 1.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as occasion demands, but the present invention is not limited thereto.

(Ceramic heater)
The ceramic heater of this embodiment shown in FIGS. 1 to 3 includes a heat generating portion 14 in which a resistance heat generating material is embedded, and a ceramic base 11 made of ceramics and having the heat generating portion 14 built therein. The ceramic substrate 11 has a configuration in which a ceramic sheet 12 is wound around a ceramic shaft 13. A heating part 14 is provided on the ceramic sheet 12, and a drawer part 15 is connected to the heating part 14. The ceramic base 11 is provided with an electrode portion 16 for supplying power to the resistance heating material, and a metal lead 17 is brazed to the electrode portion 16.

  The structure of the ceramic heater of the present embodiment will be described in more detail with reference to FIGS. FIG. 2 is a diagram illustrating a state of the ceramic substrate 11 before winding. A heating part 14 is provided on the ceramic sheet 12, and a drawer part 15 is connected to the heating part 14. The lead portion 15 is connected to an electrode pad 18 (metallized) formed on the back surface of the ceramic sheet 12 by a conductor filled in the through hole 22. Then, the ceramic base 11 is formed by winding the ceramic sheet 12 around the ceramic shaft 13 with the heat generating portion 14 and the drawing portion 15 inside.

  As shown in FIG. 3, electrode pads 18 and metal plating (Ni plating 19) are laminated in this order on the surface of the ceramic substrate 11, and metal leads 17 are brazed by a brazing material 20 on the Ni plating 19. The electrode part 16 is formed. In order to prevent the electrode portion 16 from being deteriorated due to temperature, humidity, etc., another Ni plating 21 may be optionally formed so as to cover the brazing material 20 and the metal lead 17.

Hereinafter, each element of the ceramic heater will be described. The ceramics in the ceramic sheet 12 and the ceramic shaft 13 contain, for example, oxides of Al ₂ O ₃ , SiO ₂ , CaO and Mg. However, the composition of ceramics is not limited to this.

The content of Al ₂ O _{3 in} the ceramic is preferably 88 to 96% by weight, more preferably 89 to 94% by weight, and most preferably 90 to 92% by weight.

The content of SiO _{2 in} the ceramic is preferably 3 to 10% by weight, more preferably 4 to 8% by weight, and most preferably 5 to 7% by weight.

  The content of CaO in the ceramic is preferably 1 to 2% by weight, more preferably 1.4 to 1.9% by weight, and most preferably 1.6 to 1.8% by weight. preferable.

  The content of Mg oxide in the ceramic is 0.01 to 0.2% by weight in terms of MgO. When the content of the Mg oxide is in the above range, the segregation of MgO in the heat generating portion 14 can be sufficiently prevented, and the variation in resistance value due to the segregation can be suppressed to a low level. Therefore, even when used for a long time or intermittently and at a high temperature, the resistance heating material can be sufficiently prevented from being deteriorated, and the durability of the ceramic heater is improved. Further, the Mg oxide content is more preferably 0.02 to 0.20% by weight and 0.05 to 0.10% by weight from the viewpoint that segregation of MgO can be more highly prevented. Most preferred.

The weight ratio of SiO _{2 to} CaO in the ceramic is preferably 1.5 or more and less than 3.5, more preferably 2.5 or more and less than 3.45, and 3.0 or more and less than 3.4. Most preferably it is. When the weight ratio of SiO _{2 to} CaO is in the above range, the temperature at which a liquid phase composed of SiO ₂ and CaO is generated can be increased, and as a result, the firing temperature can be increased, and the sintering aid and grain growth can be increased. Even if the amount of Mg oxide as an inhibitor is reduced to the above range, sufficiently high dispersibility can be obtained, and thus sufficient performance can be obtained.

  The ceramics may further contain a base material such as high-temperature high-strength ceramics such as alumina-like ceramics such as mullite and spinel.

The ceramics may contain an auxiliary such as 0.01 to 3.0% by weight of ZrO ₂ .

  The ceramic is an oxide of at least one metal selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. And less than 0.1% by weight.

  As the metal contained in the resistance heating material embedded in the heat generating portion 14, the lead portion 15, and the electrode pad 18, a high melting point metal such as W, Mo, Re, or the like can be used.

The electrode pad 18 contains not only a refractory metal but also ceramics. The ceramic contained in the electrode pad 18 may be, for example, Al ₂ O ₃ , SiO ₂ , CaO, Ca ₂ CO ₃ and MgO, or a mixture thereof. The ceramic contained in the electrode pad 18 may be the same as or different from the ceramic of the ceramic substrate 11. The ceramic contained in the electrode pad 18 is preferably the same as the ceramic contained in the ceramic substrate 11. Thereby, the electrode pad 18 and the ceramic substrate 11 are easily sintered, and the effect of the present invention becomes remarkable.

  When the content of Mg oxide in the ceramic substrate 11 is 0.01 to 0.2% by weight in terms of MgO and is smaller than the conventional ceramic substrate, the resistance heating material is prevented from being deteriorated as described above. The Further, when the content of Mg oxide in the ceramic substrate 11 is small, it is considered that the amount of Mg oxide that oozes out from the ceramic substrate to the electrode pad in the ceramic heater manufacturing process is smaller than that of the conventional ceramic heater. . The more the oxide of Mg, which is a sintering aid, oozes out from the ceramic substrate to the electrode pad, the more the adhesion between the ceramic substrate and the electrode pad tends to be improved. If it is small, such a seepage cannot be expected.

  However, in this embodiment, since the electrode pad 18 contains ceramic, the ceramic in the electrode pad 18 functions as a co-material, and the adhesion between the ceramic substrate 11 and the electrode pad 18 is improved. Therefore, in this embodiment, peeling of the electrode pad 18 from the ceramic substrate 11 is suppressed.

  The ceramic content in the electrode pad 18 is 1 to 45% by volume. When the ceramic content is less than 1% by volume, the electrode pad 18 is easily peeled off from the ceramic substrate 11. When the ceramic content is higher than 45% by volume, the adhesion between the electrode pad 18 and the Ni plating 19 is lowered.

  The electrode pad 18 has a thickness of 15 μm or more. Thereby, the electrode pad 18 becomes difficult to peel from the ceramic substrate 11. When the metal lead 17 brazed to the electrode portion 16 is pulled and peeled off from the ceramic substrate 11, tensile stress concentrates on the periphery of the brazing material 20. However, if the thickness of the electrode pad 18 is 15 μm or more, it is considered that the concentrated stress is dispersed and transmitted to the ceramic substrate 11 side, so that the electrode pad 18 is difficult to peel off. The upper limit value of the thickness of the electrode pad 18 is not particularly limited, but is usually about 40 μm.

  As the brazing material 20, for example, a brazing material made of at least one of Ag, Au, Cu, Ni, and Pd can be used.

  The ceramic shaft 13 may be a cylindrical one or a tubular one having a hollow structure.

(Manufacturing method of ceramic heater)
A method for manufacturing the rod-shaped ceramic heater shown in FIG. 1 will be described below.

First, a ceramic raw material powder, a molding binder and an organic solvent are mixed by a wet method to obtain a ceramic composition. The ceramic raw material powder contains a base material and a sintering aid. The base material is a raw material corresponding to Al ₂ O ₃ , and the sintering aid is a raw material corresponding to oxides of SiO ₂ , CaO and Mg. The composition of the ceramic raw material powder may be adjusted so that the above ceramic composition is obtained after firing. The content of Mg oxide in the ceramic raw material powder is adjusted to 0.01 to 0.2% by weight in terms of MgO. As the base material and the sintering aid, oxides (Al ₂ O ₃ , SiO ₂ , CaO and Mg oxides) contained in ceramics themselves can be used as oxides in the firing process. Use it. For example, various salts such as carbonates corresponding to the above oxides, hydroxides, and composite oxides may be used.

  The ceramic raw material powder may be calcined at 700 to 1450 ° C. for 1 to 100 hours before firing. Further, the base material and the sintering aid may be calcined separately and then mixed. Furthermore, you may mix with a base and a sintering auxiliary agent after calcining at least 1 type of a sintering auxiliary agent component.

  Next, the ceramic composition described above is molded by a doctor blade method or the like to produce an unfired ceramic sheet 12. Further, the ceramic composition is extruded to produce an unfired ceramic shaft 13. On the obtained unfired ceramic sheet 12, a precursor (unfired heat generating part) of the heat generating part 14 is formed by screen printing or the like. Further, a precursor (unfired drawer portion) of the lead portion 15 connected to the precursor of the heat generating portion 14 is formed by screen printing or the like. A through hole that penetrates the unfired ceramic sheet 12 is formed in a portion of the unfired ceramic sheet 12 where the end of the precursor of the lead portion 15 is located, and a conductive paste is filled in the through hole.

  The unfired ceramic shaft 12 and the unfired ceramic sheet 12 are sandwiched between the unfired ceramic shaft 13 and the unfired ceramic sheet 12 so as to sandwich the precursor of the heating portion 14 and the precursor of the lead portion 15. Is formed to form a molded body (precursor of the ceramic substrate 11). A precursor of the electrode pad 18 (metallization) is formed so as to cover the through hole located on the surface of the molded body. The thickness of the electrode pad precursor is adjusted to 19 μm or more. Thereby, it becomes possible to make the thickness of the electrode pad obtained after a baking process into 15 micrometers or more. The upper limit of the thickness of the electrode pad precursor is not particularly limited, but is usually about 50 μm.

  Next, in the firing step, the molded body on which the precursor of the electrode pad 18 is formed is heated in a reducing atmosphere of about 1450 to 1650 ° C. After firing, the ceramic substrate 11 is obtained in which the heat generating part 14 and the lead part 15 are provided inside, and the electrode pad 18 connected to the lead part 15 through the through hole 22 is provided on the surface.

  The precursor of the electrode pad 18 contains ceramic raw material powder. For example, the precursor of the electrode pad 18 may contain a ceramic raw material powder similar to that contained in the unfired ceramic sheet 12 and the ceramic shaft 13. Moreover, the precursor of the electrode pad 18 may contain a ceramic raw material powder different from those contained in the unfired ceramic sheet 12 and the ceramic shaft 13. The precursor of the electrode pad 18 contains refractory metal particles such as W, Mo, and Re as main components. The melting point of these metals is higher than the sintering temperature of the ceramic raw material powder. Therefore, in the firing step, the ceramic raw material powder is sintered, but the metal particles contained in the precursor of the electrode pad 18 are not melted and are not sintered together. Therefore, if the precursor of the electrode pad 18 does not contain ceramic raw material powder, a gap is formed between the metal particles constituting the electrode pad 18 after the firing step. As a result, the electrode pad 18 is easily peeled from the ceramic substrate 11. However, in the present embodiment, in the firing step, the ceramic raw material powder contained in the precursor of the electrode pad 18 is sintered to fill the gaps between the metal particles to form a ceramic (alumina) network. The ceramic raw material powder contained in the molded body is also sintered. As a result, in the present embodiment, the adhesion between the ceramic base 11 and the electrode pad 18 is improved as compared with the case where the precursor of the electrode pad 18 does not contain ceramic raw material powder.

  The precursor of the electrode pad 18 includes a component that evaporates in the baking process, such as an organic binder or an organic solvent. The total volume of the ceramic raw material powder in the whole precursor of the electrode pad 18 containing these components is 1 to 36% by volume. Further, with respect to the total value (total volume of solid content) of the total volume of metal particles included in the precursor of the electrode pad 18 and the total volume of ceramic raw material powder included in the precursor of the electrode pad 18, The total volume of the ceramic raw material powder contained in the precursor is 1 to 45% by volume. Thereby, the content rate of the ceramic in the electrode pad 18 with which the ceramic heater after completion becomes 1 to 45 volume%. When the total volume of the ceramic raw material powder is less than 1% by volume, the molded body and the precursor of the electrode pad 18 are not sufficiently adhered in the firing step. When the total volume of the ceramic raw material powder is larger than 45% by volume, the adhesion between the electrode pad 18 and the Ni plating 19 after the firing step is lowered.

  In the plating step after the firing step, Ni plating 19 is applied to the surface of the electrode pad 18. The metal lead 17 is brazed onto the Ni plating 19 using a brazing material 20, whereby the electrode portion 16 is formed and the ceramic heater shown in FIG. 1 is obtained. In order to protect the brazing material 20 and the metal lead 17, Ni plating 21 may be applied.

  As the molding binder and the organic solvent, for example, a mixed solution of polyvinyl butyral, dibutyl phthalate, methyl ethyl ketone, and toluene can be used.

  As mentioned above, although one suitable embodiment of the present invention was described in detail, the present invention is not limited to the above-mentioned embodiment. For example, the ceramic heater according to the present invention may be a flat ceramic heater. The flat ceramic heater includes a flat ceramic base made of ceramics. The ceramic substrate is composed of a pair of stacked ceramic sheets. Between the pair of ceramic sheets, a heat generating portion in which the resistance heat generating material is embedded, and an anode side lead portion and a cathode side lead portion connected to the heat generating portion are sandwiched. The ceramic sheet is formed with a pair of through holes filled with a conductor. The anode side electrode pad formed on the outer surface of the ceramic substrate is connected to the anode side lead portion through the through hole. The cathode side electrode pad formed on the outer surface of the ceramic substrate is connected to the cathode side lead portion through another through hole. Metal plating is formed on the surface of each electrode pad. Even a flat ceramic heater having such a structure can exhibit the same effects as those of the above-described embodiments.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
Baking step after 91.2 wt% of _Al 2 _O 3, 5.9 wt% of _SiO 2, 1.7 wt% of CaO, contained 0.1% by weight of MgO and 1.1 wt% of ZrO ₂ In order to obtain ceramics, the base material and the sintering aid were weighed to prepare ceramic raw material powder. A ceramic raw material powder, a molding binder and an organic solvent were wet mixed to obtain a ceramic composition slurry. This slurry was molded by a doctor blade method to obtain a ceramic sheet. On the surface of this ceramic sheet, the precursor of the heat generating part containing W-Re and the precursor of the lead-out part containing W-Mo were screen printed.

  A through hole was formed in the ceramic sheet at a position where the end of the lead portion precursor was located, and the through paste was filled with the conductive paste.

  The same ceramic raw material powder, W powder, binder resin and organic solvent as those used for the ceramic sheet were kneaded by passing 3 times with a roll mill to form an electrode pad slurry.

  The total volume of the ceramic raw material powder contained in the electrode pad slurry is 10% by volume with respect to the total value of the total volume of the W powder contained in the electrode pad slurry and the total volume of the ceramic raw material powder contained in the electrode pad slurry. It was adjusted. In the following, the total volume of the ceramic raw material powder contained in the electrode pad slurry with respect to the total value of the total volume of the W powder contained in the electrode pad slurry and the total volume of the ceramic raw material powder contained in the electrode pad slurry, Abbreviated as “ceramics ratio”. The “ceramics ratio” is substantially equal to the ceramic content in the electrode pad provided in the completed ceramic heater.

  The electrode pad slurry was screen-printed on the back surface of the ceramic sheet so as to overlap the through-holes to form an electrode pad precursor. The thickness of the electrode pad precursor was adjusted to 31 μm.

  Next, a ceramic shaft was produced by extruding the slurry of the ceramic composition. Thereafter, the ceramic sheet is cut into a predetermined size, and an adhesive mainly composed of an organic solvent is formed on the surface of the cut ceramic sheet on the side where the precursor of the heat generating part and the precursor of the lead part are formed. Applied. The ceramic sheet was wound around the ceramic shaft so that the precursor of the heat generating portion and the precursor of the lead portion were sandwiched between the ceramic shaft and the ceramic sheet to obtain a molded body.

  The molded body was fired in a reducing atmosphere furnace at 1500 to 1600 ° C. to obtain a ceramic substrate having a heat generating portion, a lead portion, a through hole, and an electrode pad. The electrode pad formed on the surface of the ceramic substrate had a thickness of 25 μm. Thereafter, a base Ni plating was formed on the surface of the electrode pad after the firing step.

  After visual inspection of the base Ni plating, a metal lead was brazed to the base Ni plating using a solder made of Au—Cu, and the ceramic heater of Example 1 was obtained. A vacuum furnace was used for brazing.

[Ni plating appearance inspection]
When an appearance inspection of the underlying Ni plating provided in the ceramic heater of Example 1 was performed, no abnormality was confirmed. That is, in Example 1, it was confirmed that there is no problem in the adhesion between the electrode pad and the underlying Ni plating.

[Tensile strength test]
In the tensile strength test, the ceramic base of the ceramic heater of Example 1 was fixed, and the metal lead was pulled in the diameter direction of the ceramic base (direction perpendicular to the long axis of the ceramic base). And the force (tensile strength) which acted on the metal lead when the metal lead was pulled and the ceramic heater was destroyed was measured. Moreover, the part destroyed in the ceramic heater was investigated. The test results are shown in Table 1. In Example 1, when the tensile strength was 115 N, the metal lead was cut, but the electrode pad did not peel from the ceramic substrate.

(Examples 2 to 4, Comparative Examples 1 and 2)
The ceramic heaters of Examples 2 to 4 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the ceramic ratio was adjusted to the values shown in Table 1. In the same manner as in Example 1, the appearance inspection of the underlying Ni plating was also performed in Examples 2 to 4 and Comparative Examples 1 and 2. Table 1 shows the results of the appearance inspection. In the same manner as in Example 1, Examples 2 to 4 and Comparative Examples 1 and 2 were subjected to a tensile strength test. The test results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4 and Comparative Example 1, it was confirmed that there was no abnormality in the appearance of the underlying Ni plating and that there was no problem in the adhesion between the electrode pad and the underlying Ni plating. In Comparative Example 2, since the ceramic contained in the electrode pad was too much, the base Ni plating was swollen. That is, in Comparative Example 2, it was confirmed that the adhesion between the electrode pad and the underlying Ni plating was lower than that of the example.

  In Examples 1 to 4 and Comparative Example 2, the metal lead was cut in the tensile strength test, but it was confirmed that the electrode pad did not peel from the ceramic substrate. In Comparative Example 1 in which the ceramic ratio was zero, part of the electrode pad was peeled from the ceramic substrate in the tensile strength test.

(Examples 5 and 6, Comparative Examples 3 and 4)
The ceramic heaters of Examples 5 and 6 and Comparative Examples 3 and 4 were produced in the same manner as in Example 2 except that the electrode pad precursor and the thickness of the electrode pad were adjusted to the values shown in Table 2. A tensile strength test was performed on Examples 5 and 6 and Comparative Examples 3 and 4 in the same manner as in Example 1. The test results are shown in Table 2.

  In Examples 5 and 6 in which the thickness of the electrode pad was 15 μm or more, the metal lead was cut in the tensile strength test, but it was confirmed that the electrode pad did not peel from the ceramic substrate. In Comparative Examples 3 and 4 in which the thickness of the electrode pad was less than 15 μm, part of the electrode pad peeled off from the ceramic substrate in the tensile strength test.

(Examples 7 to 9)
The ceramic heaters of Examples 7 to 9 were produced in the same manner as in Example 2 except that the composition of the ceramic contained in the electrode pad was adjusted to the values shown in Table 3. A tensile strength test was performed on Examples 7 to 9 in the same manner as in Example 1. The test results are shown in Table 3.

  In Examples 7 to 9, in the tensile strength test, the metal lead was cut, but it was confirmed that the electrode pad did not peel from the ceramic substrate.

(Examples 10-12, Comparative Examples 5-7)
The ceramic heaters of Examples 10 to 12 and Comparative Examples 5 to 7 were produced in the same manner as in Example 1 except that the composition of the ceramic substrate was changed to the composition shown in Table 4.

[Continuous current test]
The ceramic heaters of Examples 10 to 12 and Comparative Examples 5 to 7 were energized and heated to perform a continuous energization test so that the surface temperature of the heat generating portion was 1100 ° C. Table 5 shows the room temperature resistance before (initial) heating, the room temperature resistance after 1000 hours heating, the rate of change in resistance, and the presence or absence of disconnection after 3000 hours heating.

[Intermittent test]
The ceramic heaters of Examples 10 to 12 and Comparative Examples 5 to 7 are energized and heated so that the surface temperature of the heat generating part becomes 1100 ° C., held for 5 minutes, then de-energized and left at room temperature for 2 minutes. Was subjected to an intermittent energization test. Table 5 shows the room temperature resistance after 5000 cycles, the rate of change in resistance, and the presence or absence of disconnection after 20000 cycles.

  As shown in Table 5, according to the ceramic heaters of Examples 10 to 12, even when the energization test for 1000 hours was performed, the resistance change rate was suppressed to 5% or less, and the energization test for 3000 hours was performed. It was confirmed that no disconnection occurred even when the test was performed. Furthermore, according to the ceramic heaters of Examples 10 to 12, even when a 5000 cycle intermittent energization test is performed, the resistance change rate is suppressed to 8% or less, and when a 20000 cycle intermittent energization test is performed. It was confirmed that no disconnection occurred. That is, in Examples 10-12, it was confirmed that deterioration of the resistance heating material was prevented. Moreover, the continuous electricity test and the intermittent electricity test were implemented with respect to Examples 1-9 mentioned above similarly to Examples 10-12. As a result, in Examples 1 to 9, it was confirmed that the deterioration of the resistance heating material was prevented as in Examples 10 to 12. On the other hand, in Comparative Examples 5 to 7, it was confirmed that the resistance heating material was deteriorated.

  With respect to the ceramic heaters of Examples 10 to 12, the appearance inspection and the tensile strength test of the underlying Ni plating were performed in the same manner as in Example 1. As a result, in Examples 10 to 12, there was no abnormality in the appearance of the underlying Ni plating, and the electrode pad did not peel from the ceramic substrate.

  DESCRIPTION OF SYMBOLS 11 ... Ceramic base | substrate, 14 ... Heat generating part, 15 ... Lead-out part, 12 ... Ceramic sheet, 13 ... Ceramic shaft, 15 ... Lead-out part, 16 ... Electrode part, 17 ... Metal leads, 18 ... Electrode pads (metallized), 19, 21 ... Plating, 20 ... Brazing material, 22 ... Through holes.

Claims (2)

A ceramic substrate made of ceramics;
A heat generating portion provided in the ceramic substrate and having at least a resistance heating material embedded therein;
A lead portion provided in the ceramic base and electrically connected to the heat generating portion;
An electrode pad provided on the surface of the ceramic substrate and electrically connected to the lead portion;
Metal plating provided on the surface of the electrode pad;
With
The content of Mg oxide in the ceramic is 0.01 to 0.2% by weight in terms of MgO,
The electrode pad contains ceramics;
The ceramic content in the electrode pad is 1 to 45% by volume,
The electrode pad has a thickness of 15 μm or more;
Ceramic heater. A ceramic substrate precursor containing ceramic powder,
A precursor of a heat generating portion provided in the precursor of the ceramic base, and at least a resistance heating material embedded therein;
A lead portion precursor provided in the ceramic base precursor and connected to the heat generating portion precursor;
An electrode pad precursor provided on the surface of the ceramic substrate precursor;
A conductive paste filled in a through hole penetrating a part of the precursor of the ceramic substrate, and contacting the precursor of the lead portion and the precursor of the electrode pad;
Firing step of firing,
A plating step of forming metal plating on the surface of the electrode pad formed by firing the precursor of the electrode pad, and
The content of the oxide of Mg in the ceramic raw material powder is 0.01 to 0.2% by weight in terms of MgO,
The electrode pad precursor contains ceramic raw material powder,
The volume of the ceramic raw material powder included in the electrode pad precursor is 1 with respect to the total value of the volume of the metal included in the electrode pad precursor and the volume of the ceramic raw material powder included in the electrode pad precursor. ~ 45% by volume,
The electrode pad precursor has a thickness of 19 μm or more,
Manufacturing method of ceramic heater.

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