Manufacturing method for laminated thermistor and laminated thermistor

Abstract

To provide a manufacturing method for a laminated thermistor, the method enabling easy formation of a dense high-resistance portion excellent in peeling resistance and crack resistance and enabling improvement of reliability such as moisture resistance.SOLUTION: A manufacturing method for a laminated thermistor comprises: a first step; a second step; a third step; and a fourth step. In the first step, a sintered body including manganese oxide and having at least one pair of internal electrodes inside the sintered body is prepared. In the second step, the sintered body is impregnated with solution containing silicon. In the third step, the sintered body after the second step is heat-treated to form a high-resistance portion in at least a part of the surface layer of the sintered body. In the fourth step, at least one pair of external electrodes electrically connected to at least one pair of internal electrodes are formed on a part of the surface of the sintered body after the third step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a laminated thermistor and a laminated thermistor, and more particularly to a method for manufacturing a laminated thermistor used in various electronic devices and a laminated thermistor. [Background technology]

[0002] Multilayer thermistors are used for temperature detection and temperature compensation in a variety of electronic devices, home appliances, and other devices. Multilayer thermistors are required to be durable enough to maintain performance even after long-term use, and are particularly required to have excellent moisture resistance under high humidity conditions and improved reliability in humidity tests.

[0003] Patent Document 1 discloses a ceramic electronic component in which electrodes are formed on the surface of an electronic component body containing ceramic impregnated with a glass component, the ceramic component having a relative density of 90% or less. In Patent Document 1, the low resistance and high withstand voltage of a PTC (Positive Temperature Coefficient) thermistor are improved by impregnating a glass component onto the surface of a semiconductor ceramic whose main component is barium titanate, whose relative density has been reduced by increasing the porosity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-217004 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, NTC (Negative Temperature Coefficient) thermistors have traditionally been coated using a glass diffusion process in which glass frit is attached to a sintered body and then heat-treated, but there is a need to further improve reliability. In addition, the method described in Patent Document 1 above is complicated, and it is difficult to obtain a dense protective layer (high resistance portion) formed on the surface of the sintered body, and there is a possibility of peeling or cracking.

[0006] An object of the present disclosure is to provide a method for manufacturing a multilayer thermistor that can easily form a high-resistance portion that is dense and has excellent peel resistance and crack resistance, and that can improve reliability such as moisture resistance, and to provide a multilayer thermistor. [Means for solving the problem]

[0007] A method for manufacturing a multilayer thermistor according to one embodiment of the present disclosure includes a first step, a second step, a third step, and a fourth step. In the first step, a sintered body containing manganese oxide and having at least one pair of internal electrodes therein is prepared. In the second step, the sintered body is impregnated with a solution containing silicon. In the third step, the sintered body after the second step is heat-treated to generate a high-resistance portion in at least a portion of a surface layer of the sintered body. In the fourth step, at least one pair of external electrodes electrically connected to each of the at least one pair of internal electrodes is formed on a portion of the surface of the sintered body after the third step.

[0008] A multilayer thermistor according to one embodiment of the present disclosure comprises a sintered body, at least one pair of internal electrodes, a high-resistance portion, and at least one pair of external electrodes. The sintered body contains manganese oxide. The internal electrodes are provided inside the sintered body. The high-resistance portion is provided on at least a portion of the surface of the sintered body. The external electrodes are provided on a portion of the surface of the sintered body and are electrically connected to each of the at least one pair of internal electrodes. The high-resistance portion contains Mn2SiO4. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a method for manufacturing a laminated thermistor that can easily form a high-resistance portion that is dense and has excellent peel resistance and crack resistance, and that can improve reliability such as moisture resistance, and a laminated thermistor. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multilayer thermistor according to this embodiment. [Figure 2] FIG. 2 is a schematic perspective view of the multilayer thermistor according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1. Overview Hereinafter, a method for manufacturing a multilayer thermistor and the multilayer thermistor according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios.

[0012] The method for manufacturing the multilayer thermistor 1 of this embodiment includes a first step, a second step, a third step, and a fourth step. In the first step, a sintered body 11 containing manganese oxide and having at least a pair of internal electrodes 12 therein is prepared. In the second step, the sintered body 11 is impregnated with a solution containing silicon. In the third step, the sintered body 11 after the second step is heat-treated to generate high-resistance portions 13 on at least a portion of the surface layer of the sintered body 11. In the fourth step, at least a pair of external electrodes 14 electrically connected to each of the at least a pair of internal electrodes 12 are formed on a portion of the surface of the sintered body 11 after the third step.

[0013] The inventors, through extensive research into methods for manufacturing multilayer thermistors, have discovered that in the manufacture of NTC thermistors using sintered bodies containing manganese oxide, by employing a method of impregnating the sintered body with a solution containing specific components, the density of the high resistance portions formed can be increased, as well as the peel resistance and crack resistance, thereby improving the reliability of the moisture resistance performance of the multilayer thermistor, and have completed the present disclosure.

[0014] As described above, the multilayer thermistor 1 obtained by the manufacturing method of this embodiment has improved high-resistance portions 13 in density, peeling resistance, and cracking resistance, resulting in improved reliability, such as moisture resistance. The reason why the manufacturing method of this embodiment provides the above-described effects is not entirely clear, but it can be speculated, for example, as follows. By impregnating a sintered body 11 containing manganese oxide with a silicon-containing solution and then performing a heat treatment, the manganese oxide contained in the sintered body 11 reacts with the silicon contained in the impregnated solution, forming dense high-resistance portions 13 containing Mn silicate on the surface layer of the sintered body 11. This high-resistance portion 13 is dense and has excellent adhesion to the sintered body 11, resulting in improved peeling resistance and cracking resistance. The high-resistance portions 13 with improved density, peeling resistance, and cracking resistance enable the multilayer thermistor 1 to effectively suppress moisture penetration, thereby improving reliability, such as moisture resistance. Moreover, according to the present manufacturing method, such an excellent high resistance portion 13 can be easily formed.

[0015] As shown in Fig. 1, the multilayer thermistor 1 of this embodiment includes a sintered body 11, at least one pair of internal electrodes 12, a high-resistance portion 13, and at least one pair of external electrodes 14. The sintered body 11 contains manganese oxide. The internal electrodes 12 are provided inside the sintered body 11. The high-resistance portion 13 is provided on at least a portion of the surface of the sintered body 11. The external electrodes 14 are provided on a portion of the surface of the sintered body 11 and are electrically connected to each of the at least one pair of internal electrodes 12. The high-resistance portion 13 contains Mn2SiO4.

[0016] In the multilayer thermistor 1 of this embodiment, the high resistance portion 13 containing Mn2SiO4 is dense and has excellent peeling resistance and crack resistance, and therefore reliability such as moisture resistance can be improved.

[0017] 2.Details <Manufacturing method for multilayer thermistors> The method for manufacturing the multilayer thermistor 1 of this embodiment includes steps 1, 2, 3, and 4. The manufacturing method of this embodiment may further include a step (hereinafter also referred to as step 5) of forming a plated electrode so as to cover at least a portion of the external electrode 14.

[0018] The multilayer thermistor 1 of this embodiment may be provided with at least one pair of internal electrodes 12. The multilayer thermistor 1 of FIG. 1 is provided with a pair of internal electrodes 12. That is, the internal electrodes 12 include a first internal electrode 12A and a second internal electrode 12B. The multilayer thermistor 1 may be provided with at least one pair of external electrodes 14. The multilayer thermistor 1 of FIG. 1 is provided with a pair of external electrodes 14. That is, the external electrodes 14 include a first external electrode 14A and a second external electrode 14B.

[0019] One external electrode 14 may be electrically connected to one or more internal electrodes 12. In the multilayer thermistor 1 of Fig. 1, the first external electrode 14A is electrically connected to the first internal electrode 12A, and the second external electrode 14B is electrically connected to the second internal electrode 12B.

[0020] Each step of the manufacturing method of this embodiment will be described below.

[0021] [1st step] In the first step, a sintered body 11 containing manganese oxide and having at least one pair of internal electrodes 12 therein is prepared.

[0022] The sintered body 11 having the internal electrodes 12 therein can be produced, for example, as follows. First, ceramic materials containing manganese oxide as the main raw material are mixed, and then an organic binder such as polyvinyl butyral resin, an organic solvent such as butyl acetate, and a plasticizer such as benzyl butyl phthalate are added and mixed to obtain a slurry. The ceramic material may also contain auxiliary raw materials such as cobalt oxide, nickel oxide, copper oxide, and zirconium oxide. Next, this slurry is transferred to a carrier film or the like to obtain a ceramic sheet of a predetermined thickness.

[0023] On the other hand, an internal electrode paste for forming the internal electrodes 12 is prepared by mixing a conductive metal powder such as Pd powder, Pd—Ag powder, or Pt powder with an organic binder such as polyvinyl butyral resin, an organic solvent such as butyl acetate, a plasticizer such as benzyl butyl phthalate, and the like, and then kneading the mixture using a roll mill or the like.

[0024] The internal electrode paste is printed onto a ceramic sheet to form a predetermined shape, and then laminated, pressed, and cut. After that, the binder is removed, fired, and chamfered to produce a sintered body 11 having an internal electrode 12 inside.

[0025] The firing temperature can be adjusted appropriately depending on the constituent composition of the resulting sintered body 11, and is, for example, 1050° C. or higher and 1350° C. or lower. Chamfering is usually performed after firing, but may be performed before firing.

[0026] In this way, a sintered body 11 having at least one pair of internal electrodes 12 therein can be obtained.

[0027] [Second process] In the second step, the sintered body 11 prepared in the first step is impregnated with a solution containing silicon. That is, the sintered body 11 having at least one pair of internal electrodes 12 therein is impregnated with a solution containing silicon.

[0028] In the second step, first, a silicon-containing solution is prepared. The term "silicon-containing solution" refers to a solution in which a silicon-containing substance is dissolved.

[0029] Examples of silicon-containing substances include silicates, silane coupling agents, polysiloxane compounds, polysilazane compounds, and silica (SiO2).

[0030] Examples of silicates include alkali metal silicates such as sodium silicate, potassium silicate, and lithium silicate; alkaline earth metal silicates such as calcium silicate and magnesium silicate; aluminum silicate, and copper silicate.

[0031] Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane and vinyltriethoxysilane. An example of the polysiloxane compound is dimethylpolysiloxane. Examples of the polysilazane compound include perhydropolysilazane and dimethylpolysilazane.

[0032] Examples of the solvent in the silicon-containing solution include water and organic solvents such as alcohols, etc. Among these, water is preferred.

[0033] The silicon-containing solution is preferably a silicate solution, more preferably an alkali metal silicate solution, further preferably a sodium silicate solution, and particularly preferably an aqueous sodium silicate solution.Silicate solutions, particularly sodium silicate solutions, are inexpensive, easy to obtain and handle, and are prone to react with manganese oxide to produce Mn silicate.

[0034] Sodium silicate is a substance expressed by the chemical formula Na2O·nSiO2, where n, which represents the molar ratio of SiO2 to Na2O (SiO2 / Na2O), is usually in the range of 1 or more and 40 or less.

[0035] The molar ratio of SiO to NaO in the sodium silicate solution is preferably 23 or more and 29 or less, more preferably 25 or more and 27 or less. By setting the SiO / NaO molar ratio within this range, the viscosity of the sodium silicate solution and the glass transition temperature of sodium silicate can be made more appropriate, resulting in improved density, peel resistance, and crack resistance of the high-resistance portion 13 formed. If the molar ratio of the sodium silicate solution is below the lower limit, the viscosity of the solution may become too high, which may result in insufficient penetration of the silicon-containing solution into the surface layer of the sintered body 11. If the molar ratio exceeds the upper limit, the glass transition temperature of sodium silicate may become high, which may result in the temperature of the heat treatment in the third step becoming too high, which may affect the internal electrode 12.

[0036] The viscosity of the silicon-containing solution is preferably 1 mPa·s or more and 20 mPa·s or less, and more preferably 3 mPa·s or more and 15 mPa·s or less, at 20°C. By setting the viscosity of the silicon-containing solution within this range, the density, peel resistance, and crack resistance of the high-resistance portion 13 formed can be further improved. The viscosity of a sodium silicate aqueous solution with an SiO2 / Na2O molar ratio of approximately 25 is approximately 10 mPa·s at 20°C.

[0037] Next, the sintered body 11 prepared in the first step is impregnated with the silicon-containing solution prepared above. By using the method of impregnating the sintered body 11 with the solution, it is possible to form the high-resistance portion 13 that is dense and has improved peel resistance and crack resistance in a simple manner.

[0038] This impregnation can be carried out by a known method, for example, by adding the sintered body 11 to a solution containing silicon, immersing it, and leaving it for a predetermined time while stirring, and then removing the solvent and drying it. If this impregnation is carried out by immersing the entire sintered body 11 in the solution, the high resistance portion 13 is formed on the entire surface layer of the sintered body 11. If the high resistance portion 13 is to be formed on a part of the surface layer of the sintered body 11, the impregnation can be carried out by immersing only that part of the sintered body 11 in the solution.

[0039] The impregnation method may be, depending on the conditions of pressure change during impregnation, impregnation under normal pressure (normal pressure impregnation method), impregnation under reduced pressure (reduced pressure impregnation method, vacuum impregnation method), impregnation under pressure (pressure impregnation method), etc. These impregnation methods may be performed repeatedly, or two or more may be performed in combination. The reduced pressure impregnation method refers to a method in which impregnation is performed under reduced pressure. The pressurized impregnation method refers to a method in which impregnation is performed under pressurized conditions.

[0040] Among these, the method of impregnation under reduced pressure is preferable. By performing impregnation under reduced pressure, air in voids near the surface of the sintered body 11 can be removed, and the solution can be reliably penetrated into the voids, etc., resulting in the formation of high-resistance portions 13 with greater thickness.

[0041] When impregnation is performed under reduced pressure, it is preferably performed under a reduced pressure of 0.1 kPa or more and 50 kPa or less (absolute pressure), and more preferably under a reduced pressure of 0.1 kPa or more and 10 kPa or less. By performing impregnation under a reduced pressure within the above range, the thickness of the high resistance portion 13 formed can be made larger.

[0042] In this way, a sintered body 11 can be obtained in which a silicon-containing substance is present in at least a part of the surface layer.

[0043] [3rd step] In the third step, the sintered body 11 after the second step is heat-treated to generate a high resistance portion 13 in at least a part of the surface layer of the sintered body 11. That is, the sintered body 11, which has a surface layer containing a silicon-containing substance, is heated to generate the high resistance portion 13. The "high resistance portion" is a region having a higher electrical resistance than the sintered body 11.

[0044] By subjecting the sintered body 11 obtained in the second step to heat treatment, manganese oxide in the surface layer of the sintered body 11 reacts with a silicon-containing substance in the surface layer to form a high-resistance portion 13 containing Mn silicate such as Mn2SiO4. The formed high-resistance portion 13 usually has a layer structure.

[0045] This heat treatment is preferably carried out under conditions where the oxygen partial pressure in the atmosphere is low. Under conditions where the oxygen partial pressure is low, the reaction between manganese oxide and the silicon-containing substance is promoted, making it possible to carry out the heat treatment at a relatively low temperature. The oxygen partial pressure is preferably 10 kPa or less, and more preferably 1 kPa or less. The heat treatment is particularly preferably carried out in an inert gas atmosphere. Examples of inert gas atmospheres include a nitrogen atmosphere and an argon atmosphere. The heat treatment temperature is preferably 800°C or more and 1050°C or less, and more preferably 850°C or more and 1000°C or less. By carrying out the heat treatment at a temperature within the above range, the density, peel resistance, and crack resistance of the high-resistance portion 13 formed can be further improved. The heat treatment time is preferably 10 minutes or more and 5 hours or less.

[0046] This heat treatment forms high-resistance portions 13 in the surface layer of the sintered body 11 into which the silicon-containing substance was infiltrated during the second impregnation step. The high-resistance portions 13 contain Mn2SiO4. When the entire surface of the sintered body 11 is impregnated, the high-resistance portions 13 are formed in the surface layer of the entire surface of the sintered body 11. That is, as shown in FIG. 2, the high-resistance portions 13 are formed in the surface layers of the main surface (stacking surface) (13a), side surface (13b), and end surface of the sintered body 11.

[0047] The thickness of the formed high resistance portion 13 is, for example, 0.1 μm or more and 20 μm or less, preferably 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less.

[0048] Because the high resistance portion 13 is formed by impregnating the sintered body 11 with a solution in the second step, the silicon-containing solution does not penetrate into the region inside the sintered body where at least one pair of internal electrodes 12 faces each other, and as a result, no high resistance portion 13 is present in the region inside the sintered body 11 where at least one pair of internal electrodes 12 faces each other. Therefore, the multilayer thermistor 1 can suppress fluctuations in its electrical characteristics compared to when high resistance portions 13 are present in the region where the internal electrodes 12 face each other.

[0049] [4th step] In the fourth step, at least one pair of external electrodes 14 electrically connected to at least one pair of internal electrodes 12 are formed on a part of the surface of the sintered body 11 after the third step.

[0050] The external electrode 14 can usually be formed by applying an external electrode paste so as to cover part of the surface of the high resistance portion formed in the third step and to come into contact with part of the internal electrode 12, or by immersing at least a part of the sintered body 11 in the external electrode paste and then baking it.

[0051] The external electrode paste may be, for example, a Cu paste, an Ag paste, etc. The external electrode paste may further contain a resin, a solvent, etc.

[0052] In this way, two external electrodes 14A and 14B can be formed so as to cover the two end faces of the sintered body 11, for example.

[0053] [5th ​​step] In the fifth step, the plating electrodes 15 are formed so as to cover at least a portion of the external electrodes 14.

[0054] The plating electrode 15 can be formed by, for example, electrolytic plating, by carrying out Ni plating and Sn plating in that order.

[0055] <Multilayer thermistor> The multilayer thermistor 1 of this embodiment can be manufactured by the above-described method for manufacturing the multilayer thermistor 1. The multilayer thermistor 1 includes a sintered body 11, at least one pair of internal electrodes 12, a high-resistance portion 13, and at least one pair of external electrodes 14. The multilayer thermistor 1 may further include at least one pair of plated electrodes 15. Each component will be described below.

[0056] [Sintered body] The sintered body 11 contains manganese oxide, preferably as a main component, and may contain, as a secondary component, for example, cobalt oxide, nickel oxide, copper oxide, zirconium oxide, or the like.

[0057] [Internal electrode] The internal electrodes 12 are provided inside the sintered body 11. In Fig. 1, the number of internal electrodes 12 is two (a pair), but this is not limited thereto and may be three or more, and a desired electrode structure can be formed.

[0058] The internal electrodes 12 are formed using an internal electrode paste containing, for example, Pd, Ag—Pd, Pt, or the like.

[0059] [High resistance part] The high resistance portion 13 is provided on at least a portion of the surface of the sintered body 11. The high resistance portion 13 has a higher electrical resistance than the sintered body 11. In the multilayer thermistor 1 of FIG. 1, the high resistance portion 13 has a layered structure. The multilayer thermistor 1 of FIG. 2 has, as the high resistance portion 13, a high resistance portion 13a covering the main surface of the sintered body 11, a high resistance portion 13b covering the side surface of the sintered body 11, and a high resistance portion 13c (not shown) covering the end surface of the sintered body 11.

[0060] The high resistance portion 13 contains Mn2SiO4. By including Mn2SiO4, the high resistance portion 13 has improved density, peel resistance, and crack resistance, thereby improving the reliability of the multilayer thermistor 1, such as its moisture resistance. The high resistance portion 13 may also contain Mn silicates other than Mn2SiO4.

[0061] It is preferable that no high resistance portion 13 is present in the region inside the sintered body 11 where at least one pair of internal electrodes 12 faces each other. In this case, fluctuations in the electrical characteristics of the multilayer thermistor 1 can be suppressed compared to when a high resistance portion 13 is present in the region where the internal electrodes 12 face each other. The "region where the internal electrodes face each other" refers to the region between the two internal electrodes 12 when there is a pair of internal electrodes 12, or the region between the two outermost internal electrodes 12 when there are three or more internal electrodes 12.

[0062] [External electrode] The external electrode 14 is provided on a part of the surface of the sintered body 11 and is electrically connected to the internal electrode 12 .

[0063] The external electrodes 14 are formed using an external electrode paste containing, for example, Cu, Ag, or the like.

[0064] [Plating electrode] The plated electrode 15 is provided so as to cover at least a part of the external electrode 14. The multilayer thermistor 1 of FIG. 2 includes two plated electrodes 15A and 15B provided so as to cover the external electrodes 14A and 14B provided so as to cover the two end faces of the sintered body 11.

[0065] The plating electrode 15 is formed by, for example, performing Ni plating and Sn plating in this order by electrolytic plating.

[0066] (summary) As is clear from the above-described embodiment, the method for manufacturing a multilayer thermistor according to the first aspect of the present disclosure includes a first step, a second step, a third step, and a fourth step. In the first step, a sintered body (11) containing manganese oxide and having at least one pair of internal electrodes (12) therein is prepared. In the second step, the sintered body (11) is impregnated with a solution containing silicon. In the third step, the sintered body (11) after the second step is heat-treated to form high-resistance portions (13) on at least a portion of the surface layer of the sintered body (11). In the fourth step, at least one pair of external electrodes (14) electrically connected to each of the at least one pair of internal electrodes (12) are formed on a portion of the surface of the sintered body (11) after the third step.

[0067] According to the first aspect, a high resistance portion (13) that is dense and has excellent peel resistance and crack resistance can be easily formed, and the reliability of the multilayer thermistor (1) can be improved in terms of moisture resistance, etc.

[0068] In the second embodiment of the present disclosure, in the first embodiment, the high resistance portion (13) contains Mn2SiO4.

[0069] According to the second aspect, the density, peel resistance, and crack resistance of the high resistance portion (13) to be formed can be further improved.

[0070] In a third or fourth aspect of the present disclosure, in the first or second aspect, the silicon-containing solution is a silicate solution.

[0071] According to the third and fourth aspects, by using a silicate solution that easily reacts with manganese oxide to form Mn2SiO4, the density, peel resistance, and crack resistance of the high resistance portion (13) formed can be further improved.

[0072] In a fifth aspect of the present disclosure, in the third or fourth aspect, the silicate solution is a sodium silicate solution.

[0073] According to the fifth aspect, by using a sodium silicate solution which is inexpensive, easy to obtain and handle, and which readily reacts with manganese oxide to produce Mn silicate, the reliability of the multilayer thermistor (1), such as its moisture resistance, can be improved more easily.

[0074] In a sixth aspect of the present disclosure, in the fifth aspect, the molar ratio of SiO2 to Na2O in the sodium silicate solution is 23 or more and 29 or less.

[0075] According to the sixth aspect, the viscosity of the sodium silicate solution and the glass transition temperature of the sodium silicate can be made more appropriate, and as a result, the density, peel resistance, and crack resistance of the high resistance portion (13) formed can be further improved.

[0076] In a seventh aspect of the present disclosure, in any one of the first to sixth aspects, the viscosity of the silicon-containing solution at 20°C is 1 mPa·s or more and 20 mPa·s or less.

[0077] According to the seventh aspect, the density, peel resistance, and crack resistance of the high resistance portion (13) to be formed can be further improved.

[0078] In an eighth aspect of the present disclosure, in any one of the first to seventh aspects, the second step is performed under reduced pressure.

[0079] According to the eighth aspect, by performing the impregnation under reduced pressure, the air in the voids near the surface of the sintered body (11) can be removed, and the solution can be reliably penetrated into the voids, etc., and as a result, a high resistance portion (13) having a greater thickness can be formed.

[0080] In a ninth aspect of the present disclosure, in the eighth aspect, in the second step, the impregnation is performed under a reduced pressure of 0.1 kPa or more and 50 kPa or less.

[0081] According to the ninth aspect, the thickness of the high resistance portion (13) formed can be increased.

[0082] In a tenth aspect of the present disclosure, in any one of the first to ninth aspects, the third step is heat-treated in an inert gas atmosphere.

[0083] According to the tenth aspect, the reaction between manganese oxide and the silicon-containing substance is promoted, so that the heat treatment can be carried out at a relatively low temperature.

[0084] In an eleventh aspect of the present disclosure, in any one of the first to tenth aspects, the third step is heat-treated at 800°C or higher and 1050°C or lower.

[0085] According to the eleventh aspect, the density, peel resistance, and crack resistance of the high resistance portion (13) to be formed can be further improved.

[0086] A multilayer thermistor (1) according to a twelfth aspect of the present disclosure includes a sintered body (11) containing manganese oxide, at least one pair of internal electrodes (12) provided inside the sintered body (11), a high-resistance portion (13) provided on at least a portion of the surface of the sintered body (11), and at least one pair of external electrodes (14) provided on a portion of the surface of the sintered body (11) and electrically connected to each of the at least one pair of internal electrodes (12). The high-resistance portion (13) contains Mn2SiO4.

[0087] According to the twelfth aspect, the high resistance portion (13) containing Mn2SiO4 is dense and has excellent peel resistance and crack resistance, thereby improving the reliability of the multilayer thermistor (1) in terms of moisture resistance and the like.

[0088] In a thirteenth aspect of the present disclosure, in the twelfth aspect, no high resistance portion (13) is present in the region inside the sintered body (11) where at least one pair of internal electrodes (12) faces each other.

[0089] According to the thirteenth aspect, fluctuations in the electrical characteristics of the multilayer thermistor (1) can be suppressed compared to when the high resistance portion (13) is present in the region where the internal electrodes (12) face each other. [Explanation of symbols]

[0090] 1 Multilayer thermistor 11 Sintered body 12 Internal electrode 12A 1st internal electrode 12B 2nd internal electrode 13 High resistance section 14 External electrode 14A 1st external electrode 14B 2nd external electrode 15 Plating electrode

Claims

1. A first step of preparing a sintered body containing manganese oxide and having at least one pair of internal electrodes therein; a second step of impregnating the sintered body with a solution containing silicon; a third step of heat-treating the sintered body after the second step to generate a high resistance portion in at least a part of a surface layer of the sintered body; a fourth step of forming at least one pair of external electrodes electrically connected to the at least one pair of internal electrodes on a part of the surface of the sintered body after the third step; A method for manufacturing a multilayer thermistor, comprising:

2. The high resistance portion is made of Mn ２ SiO ４ Including, A method for producing the multilayer thermistor according to claim 1.

3. The silicon-containing solution is a silicate solution; A method for producing the multilayer thermistor according to claim 1.

4. The silicon-containing solution is a silicate solution; A method for producing the laminated thermistor according to claim 2.

5. The silicate solution is a sodium silicate solution. A method for producing the laminated thermistor according to claim 3 or 4.

6. In the sodium silicate solution, Na ２ SiO to O ２ is greater than or equal to 23 and less than or equal to 29; A method for producing the laminated thermistor according to claim 5.

7. The viscosity of the silicon-containing solution is 1 mPa·s or more and 20 mPa·s or less at 20°C. A method for producing the laminated thermistor according to any one of claims 1 to 3.

8. In the second step, the impregnation is carried out under reduced pressure. A method for producing the laminated thermistor according to any one of claims 1 to 3.

9. In the second step, the impregnation is performed under a reduced pressure of 0.1 kPa or more and 50 kPa or less. A method for producing the multilayer thermistor according to claim 8.

10. In the third step, the heat treatment is performed in an inert gas atmosphere. A method for producing the laminated thermistor according to any one of claims 1 to 3.

11. In the third step, the heat treatment is performed at 800°C or more and 1050°C or less. A method for producing the laminated thermistor according to any one of claims 1 to 3.

12. a sintered body containing manganese oxide; At least one pair of internal electrodes provided inside the sintered body; a high resistance portion provided on at least a part of the surface of the sintered body; at least one pair of external electrodes provided on a part of the surface of the sintered body and electrically connected to the at least one pair of internal electrodes, respectively; Equipped with The high resistance portion is made of Mn ２ SiO ４ Including, Multilayer thermistor.

13. The high resistance portion is not present in a region inside the sintered body where the at least one pair of internal electrodes face each other. The multilayer thermistor according to claim 12.

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