JP2007042615A - Ceramic heater, its manufacturing method and gas sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater having excellent durability even in rapid temperature rising and in a high-temperature environment; and to provide its manufacturing method. <P>SOLUTION: This ceramic heater includes, in a ceramic insulation layer 1, a heat generation part 2a, a lead part 2b for supplying a current to the heat generation part 2a and a joint part 2c for jointing the heat generation part 2a to the lead part 2b. The joint part 2c has a shape projecting to both sides in the thickness direction relative to the heat generation part 2a and the lead part 2b adjacent to both its ends. This manufacturing method of the ceramic heater comprises a process for forming a conductor pattern for the heat generation part and a conductor pattern for the lead part so as to superpose ends of the conductor patterns on each other in a layered product formed of a ceramic green sheet and at a position on the side of one-side principal surface of the layered product as compared with the center in the thickness direction of the layered product and for pressing the layered product with buffer layers arranged on the principal surfaces on both the sides of the layered product. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ceramic heater excellent in durability and suitably used for heating a semiconductor substrate heater, a petroleum fan heater, and a vehicle gas sensor, and a method for manufacturing the same.

  Conventionally, a ceramic heater in which a heat generating portion is embedded in an insulating substrate made of an insulating ceramic such as alumina has been 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.

  Recently, the rise time of the air-fuel ratio sensor has been shortened, and the operating temperature of various ceramic heaters tends to increase, so that the resistance value of the heating resistor (heat generating portion) tends to decrease. That is, attempts have been made to shorten the so-called operating time leading to the development of each function for the above applications, or to stabilize the performance when used at high temperatures. There has been an increasing demand for rapid temperature rise and higher heating temperature.

  In many cases, the same conductive paste material is used for the ceramic heater as the material of the heat generating part and the lead part, and by adjusting the width of both, the resistance ratio of the two is adjusted to prevent the heat generation of the lead part. . However, due to the recent reduction in resistance of the heat generating portion, the resistance ratio cannot be adjusted only by adjusting the width.

Therefore, the resistance ratio is increased by dividing the heat generating portion and the lead portion and using different materials for each (see Patent Document 2). When the heat generating part and the lead part are formed of such different materials, for example, they are joined by overlapping the end of the heat generating part and the end of the lead part.
JP-A-3-149971 JP 2000-58237 A

  However, in the ceramic heater manufactured by the above method, as shown in FIG. 11, a portion (step D) having a smaller thickness than the heat generating portion 2a and the lead portion 2b is formed at the joint portion between the heat generating portion 2a and the lead portion 2b. It was sometimes done. This is due to the fact that the thickness of the end portion of the print pattern tends to be thin. When the thin tip portions are overlapped with each other in this way, the step D as described above may be formed in the joint portion formed thereby. As a result, when the temperature is rapidly raised to a high temperature, stress concentrates on the step D, which is a factor that impairs durability such as disconnection.

  Furthermore, in recent years, ceramic heaters are sometimes used in high-temperature environments exceeding 1000 ° C., while demands for rapid temperature rise and higher heating temperature are increasing. There is a need for something superior. Further, when used at a high temperature that greatly exceeds the assumed temperature, there is a risk of cracks occurring in the ceramic body near the joint between the heat generating portion and the lead portion.

  An object of this invention is to provide the ceramic heater which has the outstanding durability at the time of rapid temperature rising, and a high temperature environment, and its manufacturing method.

  As a result of intensive research to solve the above-mentioned problems, the present inventor has achieved a durability that is excellent even at a rapid temperature rise or in a high-temperature environment by making the joint part where the heat generating part and the lead part are joined into a predetermined shape. The present inventors have found a new fact that a ceramic heater having properties can be obtained, and have completed the present invention.

  That is, the ceramic heater and the manufacturing method thereof according to the present invention have the following configurations.

  (1) In a ceramic heater having, in a ceramic body, a heat generating portion, a lead portion for supplying current to the heat generating portion, and a joint portion where the heat generating portion and the lead portion are joined, the joint portion is A ceramic heater having a shape projecting on both sides in the thickness direction from the heat generating part and the lead part adjacent to both end parts thereof.

  (2) The ceramic heater according to (1), wherein the thickness of the joint portion is greater than that of the heat generating portion and the lead portion in the entire region from one end to the other end in the length direction.

  (3) The ceramic heater according to (1) or (2), wherein an apex on one side and an apex on the other side in the thickness direction of the joint are formed at positions facing the thickness direction.

  (4) The ceramic heater according to any one of (1) to (3), wherein the lead portion is thicker than the heat generating portion and thinner than the joint portion.

  (5) The ceramic heater according to any one of (1) to (4), wherein a length of the joint portion is 100 to 1000 μm.

  (6) The ceramic heater according to any one of (1) to (5), wherein the heat generating part contains platinum as a main component and contains 30 to 55% by volume of alumina.

  (7) The ceramic heater according to any one of (1) to (6), wherein the lead portion contains platinum as a main component and contains 5 to 29% by volume of alumina.

  (8) The heating part and the lead part are mainly composed of platinum, and the platinum content in the lead part is larger than the platinum content in the heating part, according to any one of (1) to (7). Ceramic heater.

  (9) A method for producing a ceramic heater, comprising: a heat generating part in a ceramic body; a lead part for supplying a current to the heat generating part; and a joint part where the heat generating part and the lead part are joined. A conductive pattern for the heat generating portion and the lead portion in a laminated body composed of ceramic green sheets and at a position closer to one main surface of the laminated body than the center in the thickness direction of the laminated body. A conductor pattern is disposed so that ends of these conductor patterns overlap with each other, and a step of pressing the multilayer body in a state where buffer layers are disposed on both main surfaces of the multilayer body is provided. A method of manufacturing a ceramic heater.

  (10) The method for producing a ceramic heater according to (9), wherein the buffer layer has a Young's modulus of 200 to 1500 MPa.

  (11) A gas sensor element comprising the ceramic heater according to any one of (1) to (8).

  According to the ceramic heater described in the above (1), the joint portion protrudes on both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions thereof, so that it can be used at a rapid temperature rise or in a high temperature environment. Even in this case, cracks can be prevented from occurring in the ceramic body in the vicinity of the joint between the heat generating portion and the lead portion.

  The reason why such an effect can be obtained is considered as follows. That is, in the conventional ceramic heater as shown in FIG. 11, the shape of one side and the other side in the thickness direction of the joint portion are greatly different. Since the thermal expansion coefficients of the ceramic body and the heat generating portion and the lead portion are greatly different, if the shape of the joint portion adjacent to the ceramic body is greatly different on one side and the other side in the thickness direction as in the prior art, the ceramic body is adjacent to the joint portion. As a result, the behavior of thermal expansion and thermal contraction when using the heater is greatly different between one side and the other side in the thickness direction of the ceramic body. As described above, when the behavior of thermal expansion / contraction of the ceramic body adjacent through the joint portion becomes large, cracks are likely to occur in the ceramic body near the joint portion. Such a phenomenon becomes particularly prominent when used at a rapid temperature rise or in a high temperature environment. On the other hand, the joint portion protrudes on both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions thereof, so that the thermal expansion and thermal expansion of one side and the other side of the ceramic body adjacent in the thickness direction of the joint portion It is possible to suppress a difference in the behavior of heat shrinkage. Thereby, it can prevent that a crack generate | occur | produces in the ceramic body of the junction part vicinity. Therefore, according to the ceramic heater of the present invention, the occurrence of cracks can be prevented, so that it is possible to provide a ceramic heater excellent in durability capable of rapid temperature increase.

  Hereinafter, a ceramic heater according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an exploded perspective view showing a ceramic heater according to the present embodiment. FIG. 2 is a perspective view showing the ceramic heater according to the present embodiment.

  As shown in FIGS. 1 and 2, the ceramic heater of the present embodiment includes a heat generating portion 2a in a ceramic insulating layer (ceramic body) 1, and a lead portion 2b for supplying a current to the heat generating portion 2a. It has a heating part 2a and a joining part 2c in which the lead part 2b is joined. Here, in the present embodiment, the joining portion 2c refers to a portion where the heat generating portion 2a and the lead portion 2b overlap each other. Two electrode pads 4 are formed on the outer surface of the ceramic insulating layer 1 at positions corresponding to the end portions of the lead portions 2 b, and these electrode pads 4 and the lead portions 2 b are electrically connected by the through-hole conductors 5. Connected.

  3 is a cross-sectional view taken along the line Y1-Y1 of the ceramic heater shown in FIG. 2 (passing through substantially the center in the width direction of the heat generating portion 2a, passing through the joint portion 2c and the lead portion 2b, and of the heat generating portion 2a and the lead portion 2b). It is an example of a cross-sectional view when a ceramic heater is cut off in a plane substantially perpendicular to the upper surface. FIG. 4 is another example of a cross-sectional view taken along the line Y1-Y1.

  As shown in FIGS. 3 and 4, the ceramic heater according to the present embodiment has a joining portion 2 c that is disposed and joined so that the end portions of the heat generating portion 2 a and the lead portion 2 b overlap each other. The joint portion 2c has a convex shape that protrudes on both sides in the thickness direction from the heat generating portion 2a and the lead portion 2b adjacent to both ends thereof.

  Specifically, the joint portion 2c is formed between the one end in the thickness direction of the heat generating portion 2a at the boundary with the joint portion 2c (the upper end of the heat generating portion in FIGS. 3 and 4) and the lead portion 2b at the boundary with the joint portion 2c. Thickness of the heat generating portion 2a at the boundary with the joint portion 2c, having a convex shape protruding outward in one of the thickness direction from a straight line connecting one end in the thickness direction (the upper end of the lead portion in FIGS. 3 and 4). Than the straight line connecting the other end in the direction (the lower end of the heat generating part in FIGS. 3 and 4) and the other end in the thickness direction of the lead part 2b at the boundary with the joint 2c (the lower end of the lead part in FIGS. 3 and 4). It has a convex shape that protrudes to the other outer side in the thickness direction.

  According to such a ceramic heater of the present embodiment, the joint portion protrudes on both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions, so that it can be used at a rapid temperature rise or in a high temperature environment. Even in this case, cracks can be prevented from occurring in the ceramic body in the vicinity of the joined portion between the heat generating portion and the lead portion, and disconnection of the joined portion due to the crack can be prevented.

  The reason why such an effect can be obtained is considered as follows. That is, in the conventional ceramic heater as shown in FIG. 11, the shape of one side and the other side in the thickness direction of the joint portion are greatly different. Since the thermal expansion coefficients of the ceramic body and the heat generating portion and the lead portion are greatly different, if the shape of the joint portion adjacent to the ceramic body is greatly different on one side and the other side in the thickness direction as in the prior art, the ceramic body is adjacent to the joint portion. As a result, the behavior of thermal expansion and thermal contraction when using the heater is greatly different between one side and the other side in the thickness direction of the ceramic body. As described above, when the behavior of thermal expansion / contraction of the ceramic body adjacent through the joint portion becomes large, cracks are likely to occur in the ceramic body near the joint portion. Such a phenomenon becomes particularly prominent when used at a rapid temperature rise or in a high temperature environment. On the other hand, the joint portion protrudes on both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions thereof, so that the thermal expansion and thermal expansion of one side and the other side of the ceramic body adjacent in the thickness direction of the joint portion It is possible to suppress a difference in the behavior of heat shrinkage. Thereby, it can prevent that a crack generate | occur | produces in the ceramic body of the junction part vicinity. Therefore, according to the ceramic heater of the present invention, the occurrence of cracks can be prevented, so that it is possible to provide a ceramic heater excellent in durability capable of rapid temperature increase.

  In addition, if the ceramic body and the heat generating part and the lead part are used for a long period of time at a rapid temperature rise or in a high temperature environment, the thermal expansion coefficient differs greatly. May be more likely to occur. In the ceramic heater of the present invention, since the joint portion has a shape protruding on both sides in the thickness direction, this protruding portion exerts an anchor effect and peels between the ceramic body and the heat generating portion and the lead portion. Can be suppressed.

  Furthermore, since the joint portion protrudes on both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions, the joint portion is buffered when the heat of the heat generating portion is transferred to the ceramic body. The thermal stress generated at the time of rapid temperature rise can be reduced.

  Further, the joint portion is present in a substantially symmetrical shape on both sides in the thickness direction with respect to the heat generating portion and the lead portion adjacent to both end portions thereof. Since the stress generated by the thermal expansion difference between the heat generating part and the lead part and the ceramic body can be averaged by making the joint part symmetrical, the maximum stress can be reduced as a result. As a result, disconnection and cracks can be prevented. Moreover, the problem of the peeling of the porcelain generated from the joint at the time of rapid temperature increase under vibration in a practical environment can be prevented by dispersing the stress.

  Furthermore, when the heat generating part and the lead part are composed of materials having different volume specific resistance values, the pattern resistance value of the joint part connecting the high resistance part of the heat generating part and the low resistance part of the lead part changes in an inclined manner. It becomes possible to realize a broader temperature distribution. As a result, the occurrence of disconnection and cracks can be prevented more reliably, so that it is possible to provide a ceramic heater excellent in durability capable of rapid temperature increase.

  In the ceramic heater shown in FIG. 3, after the conductor pattern of the heat generating portion 2a is printed, the conductor pattern of the lead portion 2b is printed to form the joint portion 2c. On the other hand, in the ceramic heater shown in FIG. 4, after the conductor pattern of the lead portion 2b is printed first, the conductor pattern of the heat generating portion 2a is printed to form a joint portion, and the formation order thereof is particularly limited. It is not a thing.

  In the joint portion 2c, it is preferable that the apex on one side in the thickness direction and the apex on the other side have substantially the same position in the length direction of the joint portion 2c (position facing the thickness direction). Here, in this embodiment, the apex of the joint portion 2c is a portion located on the outermost side in the thickness direction on one side in the thickness direction of the joint portion 2c, and on the outermost side in the thickness direction on the other side in the thickness direction of the joint portion 2c. It refers to the location. Further, it is more preferable that the two apexes are located at the approximate center in the length direction of the joint portion 2c. Furthermore, it is more preferable that the joint portion 2c is substantially plane-symmetric with respect to a plane perpendicular to the thickness direction. As described above, when the two vertices are substantially at the same position, or the joint portion 2c is substantially plane-symmetric, thermal expansion / contraction of one side and the other side of the ceramic body adjacent to each other in the thickness direction of the joint portion. It can suppress more reliably that a difference arises in behavior of. Thereby, the effect which prevents that a crack generate | occur | produces in the ceramic body near a junction part can be heightened more. In addition, since the temperature gradient inside the ceramic insulating layer 1 during the temperature rising process becomes more gradual, the temperature distribution in the ceramic insulating layer 1 becomes more difficult to be attached, and as a result, the thermal stress is reduced. Occurrence can be prevented.

  Here, “the apex on the one side in the thickness direction and the apex on the other side in the thickness direction” are in the following state. That is, when a perpendicular line is dropped from the apex on one side in the thickness direction and the apex on the other side to the center line 7 in the joint portion, and the interval (displacement dimension in the length direction) of these perpendicular lines is ΔT, this ΔT and the joint portion The ratio (ΔT / n) to the length n is evaluated. At this time, when the ratio (ΔT / n) is 0.3 or less, it is assumed that the vertexes on one side and the other side face each other. This ratio (ΔT / n) is more preferably 0.2 or less, and further preferably 0.1 or less. Thereby, a breakage rate can be reduced remarkably.

  The thickness of the joining part 2c is set so as to be thicker than the heat generating part 2a and the lead part 2b. The lead portion 2b is preferably thicker than the heat generating portion 2a and thinner than the joint portion 2c. When the lead portion 2b is thicker than the heat generating portion 2a, the temperature gradient in the ceramic insulating layer 1 during the temperature rising process becomes gentler, so the thermal stress is reduced. This is because, as described above, the role of the bonding portion 2c as a buffer when the heat transfer from the heat generating portion 2a to the entire ceramic insulating layer 1 acts more effectively. As a result, since the thermal stress generated at the time of rapid temperature increase is reduced, the occurrence of disconnection and cracks can be prevented.

  When the heat generated from the heat generating portion 2a is transferred to the lead portion 2b and the ceramic insulating layer 1, it is transferred to the ceramic insulating layer 1 through a thick portion (joined portion 2c) formed of platinum or the like having good thermal conductivity. By conducting heat, the temperature gradient inside the ceramic insulating layer 1 during the temperature rising process becomes gentle. In other words, the bonding portion 2c serves as a buffer when heat is transferred from the heat generating portion 2a to the entire ceramic insulating layer 1. As a result, the thermal stress generated at the time of rapid temperature increase is reduced, so that disconnection and cracks can be prevented.

  Moreover, it is preferable that the thickness of the joining portion 2c is thicker than that of the heat generating portion 2a and the lead portion 2b in the entire region extending from one end to the other end in the length direction. As a result, even when the temperature is rapidly raised to a high temperature, it is possible to prevent stress from concentrating on a part and to prevent problems such as disconnection.

  In the present invention, as shown in FIG. 5, the apex on one side in the thickness direction and the apex on the other side in the joining portion 2d may be at different positions in the length direction of the joining portion. In order to make the temperature distribution inside the insulating layer 1 less likely to adhere, it is preferable that the two vertices are at substantially the same position as shown in FIGS.

  As shown in FIG. 12, when the thickness of the joining portion 2e is thinner than the thickness of the heating portion 2a and the lead portion 2b, or one of the thicknesses, the joining portion 2c is thicker than the lead portion 2b and the heating portion 2a. Since the buffer effect of the joint portion is not sufficiently obtained as compared with the above, the heat generated in the heat generating portion 2a is easily transferred directly to the ceramic insulating layer 1, so that the temperature gradient inside the ceramic insulating layer 1 during the temperature rising process Becomes abrupt and the thermal stress generated during rapid temperature increase increases. As a result, the probability of occurrence of disconnection or cracks increases, so that the durability of the ceramic heater decreases.

  As shown in FIG. 13 and FIG. 14, in the case where the joint portion 2 f protrudes only to one side in the thickness direction, the joint portion 2 f has an asymmetric shape in the thickness direction. Accordingly, a large temperature difference is likely to occur in the ceramic insulating layer 1 during the temperature rising process between the vicinity of the protruding joint portion 2f and the vicinity of the non-protruding joint portion 2f, and high thermal stress is generated. Since there is a possibility, durability will fall.

  The length (dimension in the longitudinal direction) n of the joint portions 2c and 2d is preferably in the range of 100 μm to 1000 μm. When the length n of the joint portions 2c and 2d is less than 100 μm, the thickness of the joint portion is thinner than the thickness of the heat generating portion 2a and the lead portion 2b or one of the thicknesses as shown in FIG. As described above, the durability is deteriorated. That is, the conductor pattern when forming the heat generating portion 2a and the lead portion 2b is likely to be thick near the end portion, and further thin near the tip. Therefore, by adjusting the length n of the joint portion 2c within the range of 100 μm to 1000 μm, the thick portion of the conductor pattern of the heat generating portion 2a and the thick portion of the conductor pattern of the lead portion 2b are overlapped at substantially the same position. Can be matched. Thereby, in the junction part 2c, the vertex in one convex shape and the vertex in the other convex shape can exist in the substantially the same position of the length direction of the junction part 2c.

  On the other hand, when the length n of the joint portion 2c is less than 100 μm, that is, when the heat generating portion 2a and the lead portion 2b overlap each other only in the vicinity of the most distal end, the thickness of the joint portion 2c is the heat generating portion 2a and the lead portion. It becomes thinner than 2b. Further, when the length n of the joint portion 2c exceeds 1000 μm, that is, the portion where the heat generating portion 2a and the lead portion 2b overlap with each other becomes longer and the position of the thick portion does not overlap with each other, as shown in FIG. Thus, the vertex in one convex shape and the vertex in the other convex shape exist in different positions in the length direction of the joint portion 2d.

  The material constituting the ceramic insulating layer 1 is not particularly limited, and examples thereof include a ceramic material mainly composed of alumina. Moreover, as a material which comprises the heat-emitting part 2a, and the material which comprises the lead part 2b, the thing which has platinum as a main component is mentioned, for example.

  In particular, it is preferable that the heat generating portion 2a and the lead portion 2b have platinum as a main component and the ceramic insulating layer 1 has alumina as a main component. Specifically, the heat generating part 2a is preferably composed mainly of platinum and contains 30 to 55% by volume of alumina. More preferably, it is desirable to contain 35 volume% to 50 volume% alumina. Thereby, the resistance of the heat generating portion 2a can be kept stable, the platinum particles can be prevented from growing during energization, and the rapid temperature rise of the ceramic heater can be enhanced. If the content of alumina is less than 30% by volume, the rate of temperature rise is slow, so there is a risk that the temperature will not rise rapidly. If the alumina content exceeds 55% by volume, the desired temperature may not be reached with respect to a predetermined applied voltage.

  The lead portion 2b is preferably composed mainly of platinum and contains 5 to 29% by volume of alumina, and more preferably contains 10% to 20% by volume of alumina. If the lead portion 2b contains 29% by volume or more of alumina, there is a risk that the temperature will not rise rapidly. When the alumina content of the lead portion 2b is 5% by volume or less, sintering proceeds excessively during firing, and disconnection is likely to occur. Further, the temperature raising rate may be increased more than necessary, and the durability may be deteriorated.

  It is preferable that the heat generating portion 2a and the lead portion 2b are mainly composed of platinum, and the platinum content in the lead portion 2b is larger than the platinum content in the heat generating portion 2a. FIG. 6 is a schematic diagram schematically showing an enlarged structure of an interface where the heat generating part 2a and the lead part 2b are in contact with each other in the joining part 2c before firing. FIG. 7 is a schematic view schematically showing an enlarged structure of an interface where the heat generating portion 2a and the lead portion 2b are in contact with each other in the bonded portion 2c after firing. As shown in FIG. 6, before firing, the boundary is clear at the interface 10 where the heat generating portion 2a and the lead portion 2b are in contact. During the firing, the composition of the lead part 2b is platinum-excessive with respect to the heat generating part 2a, thereby promoting the movement of the platinum particles 8 from the lead part 2b to the heat generating part 2a. The boundary is unclear at the interface 10 where 2a and the lead portion 2b contact. As a result, a tightly bonded structure is obtained, and disconnection during rapid temperature rise can be prevented. Since this disconnection preventing effect has a synergistic effect with the disconnection preventing effect due to the shape of the joint portion 2c of the present invention described above, a ceramic heater having extremely excellent durability can be obtained.

The alumina ceramic that forms the ceramic insulating layer 1 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, particularly 0%. You may make it contain 5-1.5 mass%. Further, by using a dense ceramic having a relative density of 80% or more and an open porosity of 5% or less, the strength of the ceramic heater can be increased and the durability can be enhanced.

  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 layers 1a and 1b mainly composed of alumina is low. It is desirable that each be 50 ppm or less, particularly 30 ppm or less.

  Further, according to the present invention, the heating element 2 is located on one side of the center line 7 of the ceramic insulating layer 1, and buffer layers having a Young's modulus of 200 to 1500 MPa are installed on the upper and lower surfaces of the ceramic insulating layer 1 and pressurized. By laminating, the outer surface of the ceramic insulating layer 1 on the side closer to the heating element 2 with respect to the center line 7 is deformed outward along the joint portion, so that it is possible to make a shape protruding vertically. That is, the conductor pattern and the lead portion for the heat generating part are located inside the laminated body composed of ceramic green sheets and at a position that is biased toward one main surface side of the laminated body from the center in the thickness direction of the laminated body. It is preferable to provide a step of pressing the laminated body in a state where the conductive patterns for the above are formed so that the ends of these conductive patterns overlap each other and the buffer layers are disposed on the main surfaces on both sides of the laminated body. . As a result, the outer surface of the ceramic insulating layer 1 is deformed outward along the joint as shown by the deformed portion 6 in FIGS. 3, 4, and 5. Thus, the ceramic heater of this invention can distinguish easily the position where a junction part exists because the deformation | transformation part 6 is formed. Thereby, even if it is a case where it inspects, for example by cutting out the cross section of a junction part, the position can be pinpointed easily. Moreover, since the position of a junction part can be specified nondestructively, when mounting the ceramic heater of this invention in a certain apparatus, positioning becomes easy. As the buffer layer, specifically, a material such as silicone or polyurethane may be used.

  When the buffer layer having a Young's modulus of less than 200 MPa is used, as shown in FIG. For this reason, there is a possibility that sufficient durability cannot be obtained as described above. On the other hand, if the Young's modulus is greater than 1500 MPa, it is necessary to apply a considerably high pressure to apply the specified pressure, which is not preferable because it is not economical. The thickness of the buffer layer is about 0.1 mm to 5 mm, preferably about 0.5 mm to 2 mm.

  In addition, as shown in FIG. 13, when the position of the heating element 2 is arranged at the center in the thickness direction of the ceramic insulating layer 1 (on the center line 7), it has a vertically asymmetrical shape that protrudes only in one of the upper and lower sides. As described above, the durability may be reduced. That is, as shown in FIG. 3 and the like, when the distance between the conductor pattern and the outer surface (the lower surface in FIG. 3) of the ceramic insulating layer 1 is short (when the thickness is thin), the ceramic insulating layer 1 below the joint portion 2c is If the distance between the conductor pattern and the outer surface of the ceramic insulating layer 1 (the lower surface in FIG. 13) is long (thick), as shown in FIG. 13, the ceramic insulating layer 1 below the joint is easily deformed. Is difficult to deform. The distance between the conductor pattern and the outer surface (lower surface) of the ceramic insulating layer 1 can be set by appropriately adjusting the thickness of the ceramic green sheet.

  Next, a method for manufacturing a ceramic heater comprising the platinum heat generating portion 2a and the lead portion 2b according to the present invention will be described with reference to FIG. First, pastes for printing the heat generating portion 2a and the lead portion 2b made of a mixed powder of a metal such as platinum and alumina are prepared. Then, using each paste, after the pattern of the heat generating portion 2a is printed with a predetermined width and thickness on the surface of the unfired ceramic insulating layer 1a (green sheet 1a), the pattern of the lead portion 2b is further formed with a predetermined width. In addition, printing is performed so that the end portions overlap each other with respect to the thickness (for the printing of the heat generating portion 2a and the lead portion 2b, after the lead portion 2b is printed first, the heat generating portion 2a may be printed so as to overlap with it. ). The ratio of platinum and alumina in the heat generating portion 2a and the lead portion 2b may be adjusted as appropriate according to the heater characteristics and dimensions of the ceramic heater. The heat generating part 2a preferably contains 30 to 55% by volume of alumina, and the lead part 2b preferably contains 5 to 29% by volume of alumina.

  Next, a through hole is formed in the unfired ceramic insulating layer 1b (green sheet 1b) and filled with a platinum paste to form the via conductor 5, and the electrode pad 4 is formed by printing using the platinum paste. The unfired ceramic insulating layer 1b is laminated and pressure-bonded on the pattern of the heat generating portion 2a and the lead 2b, and then fired at a temperature of 1200 to 1700 ° C. in an oxidizing or neutral atmosphere. A ceramic heater is produced.

The ceramic insulating layers 1a and 1b are, for example, 0 to 3% by mass, preferably 0.1%, of alumina powder having an average particle size of 0.2 to 1.0 μm and a sintering aid such as SiO ₂ , MgO, and CaO. A slurry prepared by adding and mixing ˜1 mass% and adding and mixing an organic binder thereto is molded to a thickness of 50 to 500 μm by a molding method such as a doctor blade method.

  The pressure at the time of laminating and pressing is preferably adjusted to a range of 30 to 50 MPa. Thereby, it can suppress that an opening generate | occur | produces in the junction part of the ceramic insulating layer 1. FIG. The Young's modulus of the ceramic insulating layers 1a and 1b is 5 to 20 parts by mass with respect to 100 parts by mass of the organic binder, and 50 to 100 parts by mass of the plasticizer with respect to 100 parts by mass of the raw material. It can be easily controlled by changing the mass range. Moreover, at the time of lamination | stacking crimping | compression-bonding, it is good to press in the state which has arrange | positioned the above-mentioned buffer layer to both the main surfaces of a laminated body.

  In addition, the conductive paste for printing the pattern of the heat generating portion 2a and the pattern of the lead portion 2b has been described above with an alumina powder having an average particle size of 0.1 to 1.0 μm, such as platinum powder having an average particle size of 1 to 3 μm. Each is added and mixed at a predetermined ratio, and an organic binder such as an acrylic resin, a plasticizer such as DBP and DOP, and an organic solvent such as toluene are added in an appropriate amount and mixed.

  In this conductor paste, it is important from the viewpoint of durability of the heat generating portion 2a that the size of the aggregated particles is controlled to 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 the agglomerated particles of the paste, and is a parameter representing the maximum agglomerated particle size. That is, when the grind gauge is larger than 20 μm, the surface of the heat generating portion 2a is uneven, and the reliability of the characteristics is reduced. The size of the aggregated particles can be controlled by adjusting the alumina particle size in the paste and the metal particle size of platinum.

  In the present invention, as shown in FIG. 1, the pattern of the heat generating portion 2a may be a structure that extends in the longitudinal direction of the ceramic heater and is folded at the longitudinal end portion, or an end portion in a direction orthogonal to the longitudinal direction. However, from the viewpoint of durability of the ceramic heater, a pattern folded at the end portion in the longitudinal direction as shown in FIG. 1 is desirable. At this time, the line width of the heating element 2 is preferably 0.15 mm or more, particularly preferably 0.2 mm or more in view of printing accuracy.

  Furthermore, the ceramic heater of the present invention is a ceramic heater structure integrated with other members in order to heat various elements such as oxygen sensors, NOx sensors, CO sensors, etc., in addition to heating means in various structural parts. Can be formed.

  A specific example in which the ceramic heater of the present invention is applied for heating the oxygen sensor element is shown in FIG. FIG. 9 is a schematic perspective view of FIG. 8, showing a cross section taken along line X2-X2.

  As shown in FIG. 9, the oxygen sensor element of this embodiment includes a sensor unit 20 and a ceramic heater 21. The sensor unit 20 includes a solid electrolyte substrate 22 made of zirconia and having oxygen ion conductivity, a reference electrode 23a that is in contact with air, and a measurement electrode 24a that is in contact with exhaust gas. And has a function of detecting a difference in oxygen concentration between the reference electrode 23a and the measurement electrode 24a.

  On the other hand, the heater 21 includes an insulating ceramic base 26 in which the heat generating portion 27a is embedded. Between the heater part 21 and the sensor part 20, the flat hollow with the front-end | tip sealed is formed. This hollow portion forms the air introduction hole 22a. Then, a reference electrode 23a that comes into contact with a reference gas such as air is deposited on the hollow inner wall, and measurement that comes into contact with a measured gas such as exhaust gas is performed on the outer surface of the solid electrolyte substrate 22 facing the reference electrode 23a. Electrode 24a is formed.

The solid electrolyte constituting the sensor unit 20 is made of a ceramic containing ZrO ₂ , and Y ₂ O ₃ and Yb ₂ O ₃ , Sc ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ , Dy are used as stabilizers. 1 to 30 mol% of rare earth oxides such as ₂ O ₃ in terms of the oxide, preferably can be used is partially stabilized ZrO ₂ or stabilized ZrO ₂ containing 3 to 15 mol%. Further, when ZrO ₂ in which 1 to 20 atomic% of Zr in ZrO ₂ is substituted with Ce is used, there is an effect that the ionic conductivity is increased and the responsiveness is further improved.

Furthermore, for the purpose of improving the sinterability, Al ₂ O ₃ and SiO ₂ can be added to ZrO ₂ , but if it is contained in a large amount, the creep properties at high temperatures deteriorate, The total amount of Al ₂ O ₃ and SiO ₂ added is preferably 5% by mass or less, particularly preferably 2% by mass or less.

  As the reference electrode 23a and the measurement electrode 24a deposited on the surface of the solid electrolyte substrate 22, platinum or an alloy of platinum and one selected from the group of rhodium, palladium, ruthenium and gold is used.

  In addition, for the purpose of preventing the growth of metal grains in the reference electrode 23a and the measurement electrode 24a during operation and increasing the contact at the so-called three-phase interface between platinum particles, solid electrolyte, and gas related to responsiveness, You may mix a ceramic solid electrolyte component in the said electrode in the ratio of 1-50 volume%, especially 10-30 volume%.

  The shapes of the reference electrode 23a and the measurement electrode 24a may be quadrangular or elliptical. The thicknesses of the measurement electrode 23a and the reference electrode 24a are preferably 3 to 20 μm, particularly preferably 5 to 10 μm.

  On the other hand, the heater portion 21 is the ceramic heater of the present invention in which the shape of the joint portion between the heat generating portion 2a and the lead portion 2b is formed as described above, similarly to the ceramic heater shown in FIGS.

  The ceramic insulating layer 26 in which the heat generating portion 27a is embedded is made of a dense ceramic made of alumina ceramics having a relative density of 80% or more and an open porosity of 5% or less, thereby increasing the strength of the gas sensor and making it durable. Can increase the sex.

  Although not shown in FIGS. 8 and 9, a ceramic porous layer is formed on the surface of the measurement electrode 24a from the viewpoint of preventing the measurement electrode from being poisoned by exhaust gas. The ceramic porous layer is preferably formed of at least one selected from the group consisting of zirconia, alumina, γ-alumina, spinel and titania having a thickness of 10 to 800 μm and a porosity of 10 to 50%.

  Next, a method for manufacturing the ceramic heater structure (gas sensor) of the present invention will be described with reference to the exploded perspective view of FIG.

  First, a solid electrolyte green sheet 41 is prepared. For example, the green sheet 41 may be formed by appropriately adding a molding organic binder to a ceramic solid electrolyte powder having oxygen ion conductivity of zirconia to form a doctor blade method, extrusion molding, or isostatic pressing (rubber press). It is produced by a known method such as press molding.

  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 unit 20 is produced by printing using a slurry dipping method, screen printing, pad printing, roll transfer, or the like.

  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.

  Next, a mixed powder of platinum having an average particle diameter of 1 to 3 μm and alumina having an average particle diameter of 0.2 to 1.0 μm and an organic material such as an acrylic resin is formed on the surface of the green sheet 47 made of an insulating ceramic substrate. A binder and an organic solvent such as toluene are added and mixed to prepare a paste for printing for forming the heat generating portion 2a and the lead portion 2b. Using this paste, the heat generating portion pattern 49, the lead pattern 50, the electrode pattern 51, and the through The holes 52 and the like are printed by screen printing, pad printing, and roll transfer, and are printed and formed to have predetermined thicknesses as described above.

  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; A laminated body for the heater unit 21 is manufactured by mechanically bonding.

  After that, the laminated body of the sensor unit 20 and the laminated body of the heater unit 21 are bonded 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. After integration, these are fired. The firing is performed in an atmosphere corresponding to firing of the heat generating portion 2a and the lead portion 2b, that is, in the air or in an inert gas atmosphere in the case of platinum, and in an inert gas or a reducing gas in the case of tungsten or molybdenum. Bake in the temperature range of 1700 ° C. for 1-10 hours.

  Thereafter, if necessary, the heater portion is integrated by forming at least one ceramic porous layer 25 selected from the group consisting of alumina, zirconia, spinel and titania on the measurement electrode 42a by plasma spraying or the like. The formed oxygen sensor element can be formed.

  In the above method, the heater portion 21 is formed by simultaneous firing with the sensor portion 21. However, after the sensor portion 20 and the heater portion 21 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.

To ceramic powder obtained by adding 0.5% by weight of SiO ₂ , MgO and CaO to commercially available alumina powder (containing 0.1% by mass of silica) having a purity of 99.9% and an average particle size of 0.5 μm, acrylic A slurry was prepared by adding the organic binder and toluene as a solvent, and an alumina green sheet having a sheet thickness of about 0.3 to 0.4 mm was prepared by a doctor blade method.

  As a conductor of the heat generating part 2a, a conductor paste containing platinum powder having an average particle diameter of 2 μm containing 25 to 60% by volume of alumina powder having an average particle diameter after firing of about 0.3 μm, and a conductor of the lead part 2b, Conductive pastes containing platinum powder having an average particle diameter of 2 μm and containing about 3 to 32% by volume of alumina powder having an average particle diameter of 0.3 μm were prepared. At this time, the maximum diameter of the aggregated particles measured with a grind gauge was 15 μm or less.

  Using these two types of conductor paste, first, the conductor pattern of the heat generating portion 2a is printed, and then the conductor pattern of the lead portion 2b is printed so that the ends of the conductor patterns overlap and are electrically connected. did. Further, the order of printing was changed. First, the conductor pattern of the lead portion 2b was printed, and then the conductor pattern of the heat generating portion 2a was printed so that the ends of the conductor patterns overlapped. At this time, it printed so that the thickness N of the junction part 2c of the heat generating part 2a and the lead part 2b might become 80-1200 micrometers after baking. The distance between adjacent lead portions 2b was set to 1.0 to 1.2 mm after firing.

  And the said alumina green sheet was laminated | stacked and crimped | bonded by the pressure of 10 Mpa at room temperature using the allyl type organic adhesive material on the upper surface of these conductor patterns, and the laminated body was produced. At this time, the laminate was pressure-bonded in a state where the buffer material having a Young's modulus of 200 to 1500 MPa was inserted above and below the laminate. This laminate was fired in the air at a temperature of 1500 ° C. for 1 hour. Note that the relative density of the ceramic insulating layer 1 under these conditions was 98% or more and the porosity was within 2%. The content of alkali metal in alumina was 50 ppm or less.

  Thereafter, the unevenness on the side surface of the ceramic heater was removed, and at the same time, the edge portion was chamfered with 0.2 mm.

(Characteristics and performance evaluation)
The characteristics shown in Table 1 were measured by the following method.

(1) The length and thickness of the joined portion between the heat generating portion 2a and the lead portion 2b For the manufactured ceramic heater, the cross section of the heat generating portion 2a and the lead portion 2b is mirrored as shown in FIG. An electron micrograph was taken, and the length n, thickness, etc. of the joint were measured from each photo. The width and thickness of the ceramic heater were measured with a micrometer. The sample quantity was measured for 20 samples of the following (4), and the average value was obtained.

(2) Resistance Value The resistance value was measured between the electrode pads 4 in a constant temperature room at 25 ° C. The values in Table 1 were similarly the average values of the 20 samples of (4), and the variation in resistance value was ± 5%.

(3) Rapid temperature rise property Rapid temperature rise property is the time required for the maximum surface temperature of the heater portion 21 shown in FIG. 9 to reach from 400 ° C. to 400 ° C. when a voltage of 12 V is applied to the above ceramic heater ( Seconds). This also shows the average value of 20 of (4).

(4) Element failure rate A voltage of about 25 V was applied to the above ceramic heater, the temperature was raised from room temperature to 1100 ° C. in about 20 seconds, and held at 1100 ° C. for 1 minute. The heater was air 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. The number of samples was 20 each.
Table 1 shows the measurement results. The “position of the joint” in Table 1 means that a perpendicular line is dropped from the vertex on one side in the thickness direction and the vertex on the other side to the center line 7 in the joint, and the interval between these perpendiculars (the length of deviation). Is the ratio (ΔT / n) between ΔT and the length n of the joint, where ΔT is ΔT. When this ratio (ΔT / n) is 0.3 or less, it is assumed that the apex on one side and the apex on the other side of the joint are opposed to each other.

  As shown in Table 1, Sample No. which is outside the scope of claims of the present invention. In No. 1, the thickness of the joined portion was thinner than the thickness of the heat generating portion 2a and the lead portion 2b, and the breakage rate of the ceramic heater was as high as 90%.

  On the other hand, sample no. As for 2-19, the favorable result was obtained. In particular, Sample Nos. 3, 4, 5, and 18 have the length n of the joint between the heat generating portion 2a and the lead portion 2b controlled to 500 to 800 μm, and one main surface from the center line 7 of the laminate. The conductor pattern was located on the side, and by setting the Young's modulus of the buffer material at the time of lamination to 200 to 1500 MPa, a convex shape protruding on both sides in the thickness direction was obtained, and the damage rate due to the temperature cycle became extremely small.

  Table 1 also shows that the alumina content of the heat generating part 2a is preferably 30 to 55% by volume, more preferably 35 to 50% by volume. On the other hand, the alumina content weight of the lead part 2b is preferably 5 to 29% by volume, more preferably 10 to 20% by volume.

  From the above results, it is apparent that the present invention is a ceramic heater excellent in durability in an environment such as rapid temperature rise and temperature cycle.

It is a disassembled perspective view which shows the ceramic heater concerning this embodiment. It is a perspective view which shows the ceramic heater concerning this embodiment. It is an example of the Y1-Y1 sectional view taken on the line of the ceramic heater shown in FIG. It is another example of the Y1-Y1 sectional view taken on the line of the ceramic heater shown in FIG. It is sectional drawing which shows the ceramic heater concerning other embodiment of this invention. It is the schematic which showed typically the expanded structure of the interface which the heat-emitting part and lead part of a junction part before baking contact | connect. It is the schematic which showed typically the expanded structure of the interface which the heat-emitting part and lead part of a junction part after baking contact | connect. It is a perspective view of the structure which applied the ceramic heater of this invention to the heating of the oxygen sensor element. It is the X2-X2 sectional view taken on the line of FIG. It is a disassembled perspective view for demonstrating the manufacturing method of the oxygen sensor element of this invention. In the conventional ceramic heater, it is the schematic for demonstrating the junction part of a heat-emitting part and a lead part. It is a schematic sectional drawing in case the thickness of the junction part of a heat generating part and a lead part is thinner than the thickness of a heat generating part and a lead part. It is a schematic sectional drawing in case the junction part of a heat-emitting part and a lead part protrudes only one side up and down. It is a schematic sectional drawing in case the junction part of a heat-emitting part and a lead part protrudes in a different place up and down. It is sectional drawing which shows the ceramic heater concerning other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Ceramic insulating layer 2 ... Heat generating body 2a ... Heat generating part 2b ... Lead part 4 ... Electrode pad 5 ... Via simple substance 6 ... Deformation part 7 ... Center line 8 ... Platinum 9 ... Alumina 10 ... Interface 42a where the heat-generating part and the lead part contact ... Measurement electrode pattern 42b ... Measurement electrode lead pattern 42c ... Reference electrode pattern 42d ... Reference electrode lead pattern 20 ... sensor unit 21 ... heater unit 22 ... solid electrolyte substrate 23, 23a ... reference electrode 24, 24a ... measurement electrode 26 ... ceramic insulating layer base 27a .. Heat generation part 41... Solid electrolyte green sheet 43a... Pad 43b .. through hole 44 .. air introduction hole 45... Green sheet 46. ... heating pattern 50 ... lead pattern 51 ... electrode pattern 52 ... via single

Claims (11)

In the ceramic body, in the ceramic heater having a heat generating portion, a lead portion for supplying current to the heat generating portion, and a joint portion where the heat generating portion and the lead portion are joined,
The ceramic heater according to claim 1, wherein the joining portion has a shape protruding to both sides in the thickness direction from the heat generating portion and the lead portion adjacent to both end portions thereof.   2. The ceramic heater according to claim 1, wherein the joining portion has a thickness greater than that of the heat generating portion and the lead portion in the entire region extending from one end to the other end in the length direction.   3. The ceramic heater according to claim 1, wherein an apex on one side and an apex on the other side in the thickness direction of the joint are formed at positions facing the thickness direction.   The ceramic heater according to any one of claims 1 to 3, wherein the lead portion is thicker than the heat generating portion and thinner than the joint portion.   The ceramic heater according to any one of claims 1 to 4, wherein a length of the joint portion is 100 to 1000 µm.   The ceramic heater according to any one of claims 1 to 5, wherein the heat generating part contains platinum as a main component and contains 30 to 55% by volume of alumina.   The ceramic heater according to any one of claims 1 to 6, wherein the lead portion contains platinum as a main component and contains 5 to 29% by volume of alumina.   The ceramic heater according to claim 1, wherein the heat generating part and the lead part are mainly composed of platinum, and the platinum content in the lead part is larger than the platinum content in the heat generating part. In the ceramic body, there is provided a method for manufacturing a ceramic heater having a heat generating part, a lead part for supplying a current to the heat generating part, and a joint part where the heat generating part and the lead part are joined,
The conductor pattern for the heat generating portion and the lead portion are disposed inside the laminated body composed of ceramic green sheets and at a position closer to one main surface of the laminated body than the center in the thickness direction of the laminated body. A step of pressing the laminate in a state where the conductor patterns are arranged so that ends of these conductor patterns overlap each other, and buffer layers are arranged on both main surfaces of the laminate. A method of manufacturing a ceramic heater.   The method for manufacturing a ceramic heater according to claim 9, wherein the buffer layer has a Young's modulus of 200 to 1500 MPa.   A gas sensor element comprising the ceramic heater according to claim 1.

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