Ntc thermistor element

Abstract

An NTC thermistor element includes a thermistor element body including a plurality of crystal grains and a plurality of electrodes. The plurality of electrodes includes a plurality of external electrodes disposed on the thermistor element body and a plurality of internal electrodes facing each other inside the thermistor element body. The plurality of internal electrodes includes an internal electrode connected to a corresponding external electrode. The thermistor element body has a first region between the internal electrodes adjacent to each other and separated from an outer surface of the thermistor element body, and a second region outside the first region and including the outer surface. The plurality of crystal grains includes a plurality of first crystal grains included in the first region and a plurality of second crystal grains included in the second region. A first average particle diameter of the plurality of first crystal grains is greater than a second average particle diameter of the plurality of second crystal grains.

Description

Technical Field

[0001] This invention relates to an NTC (Negative Temperature Coefficient) thermistor element. Background Technology

[0002] Known NTC thermistor elements include a thermistor element comprising multiple grains and multiple electrodes disposed on the thermistor element (e.g., refer to International Publication No. 2017 / 038189). The multiple electrodes may include, for example, multiple external electrodes disposed on the thermistor element and multiple internal electrodes disposed within the thermistor element. Summary of the Invention

[0003] One objective of this invention is to provide an NTC thermistor element with excellent thermal responsiveness.

[0004] The inventors investigated and studied NTC thermistor elements with excellent thermal responsiveness. As a result, the inventors gained the following new insights, which led to the invention of this invention.

[0005] A thermistor element includes a region located between adjacent internal electrodes among a plurality of internal electrodes. In NTC thermistor elements, the region located between the internal electrodes, for example, contributes to the characteristics of the element. Therefore, a structure that efficiently transfers heat to the region located between the internal electrodes improves the thermal response of the NTC thermistor element.

[0006] First, the inventors focused on the heat transfer path for the thermistor element. This transfer path includes not only a path where heat is directly transferred from the outside of the thermistor element to the thermistor element, but also a path where heat is transferred from the outside of the thermistor element to the thermistor element via electrodes. That is, the electrodes facilitate the transfer of heat to the thermistor element. In a structure where the electrodes include external and internal electrodes, for example, heat is transferred from the external electrodes to the internal electrodes, and from the internal electrodes to the region located between the internal electrodes. As described above, the region located between the internal electrodes contributes to the characteristics of the NTC thermistor element.

[0007] Next, the inventors focused on the diameter of the grains contained in the thermistor element. Larger diameter grains tend to improve heat transfer efficiency compared to smaller diameter grains. Therefore, a structure with larger diameter grains in the region between the internal electrodes exhibits improved thermal responsiveness compared to a structure with smaller diameter grains in the same region.

[0008] An NTC thermistor element according to one aspect of the present invention comprises a thermistor body including a plurality of grains and a plurality of electrodes disposed on the thermistor body. The plurality of electrodes have a plurality of external electrodes disposed on the thermistor body and a plurality of internal electrodes opposing each other within the thermistor body. The plurality of internal electrodes include internal electrodes connected to corresponding external electrodes among the plurality of external electrodes. The thermistor body has a first region and a second region. The first region is located between adjacent internal electrodes among the plurality of internal electrodes and is separated from the outer surface of the thermistor body. The second region is located outside the first region and includes the outer surface. The plurality of grains includes a plurality of first grains contained in the first region and a plurality of second grains contained in the second region. The first average grain size of the plurality of first grains is larger than the second average grain size of the plurality of second grains.

[0009] In one of the above methods, the first average particle size is larger than the second average particle size. The first region tends to increase heat transfer efficiency. Therefore, the above method exhibits excellent thermal responsiveness.

[0010] In one of the above methods, the first average particle size can also be less than twice the second average particle size.

[0011] Structures with a first average particle size greater than twice the second average particle size tend to increase the stress acting on the internal electrodes from the first region. This stress acting on the internal electrodes from the first region may cause deformation of the internal electrodes. This deformation may cause changes in the spacing between adjacent internal electrodes. Changes in the spacing between adjacent internal electrodes may degrade the characteristics of the NTC thermistor element. For example, changes in the spacing between adjacent internal electrodes may cause changes in the resistance value of the NTC thermistor element.

[0012] A structure where the first average particle size is less than twice the second average particle size makes it difficult to increase the stress acting on the internal electrode from the first region. Therefore, the internal electrode is less prone to deformation. As a result, this structure suppresses the degradation of the NTC thermistor element's characteristics.

[0013] In one of the above methods, the thickness of each of the multiple internal electrodes may be larger than the first average particle size.

[0014] A structure in which multiple internal electrodes each have a thickness less than a first average particle size tends to cause variations in the spacing between adjacent internal electrodes. Variations in the spacing between adjacent internal electrodes can potentially degrade the characteristics of the NTC thermistor element. For example, variations in the spacing between adjacent internal electrodes can cause variations in the resistance value of the NTC thermistor element.

[0015] The structure, in which the thickness of each of the multiple internal electrodes is greater than the first average particle size, makes it difficult to vary the spacing between adjacent internal electrodes. Therefore, this structure suppresses the degradation of the characteristics of the NTC thermistor element.

[0016] The invention will be more fully understood from the detailed description and accompanying drawings given below, which are given by way of illustration only and should not be construed as limiting the invention.

[0017] The further scope of the invention will become apparent from the detailed description given below. However, it should be understood that while embodiments of the invention have been described, the detailed description and specific examples are given by way of illustration only, as various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Attached Figure Description

[0018] Figure 1 This is a perspective view showing an NTC thermistor element according to one embodiment.

[0019] Figure 2 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in this embodiment.

[0020] Figure 3 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in this embodiment.

[0021] Figure 4 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in this embodiment.

[0022] Figure 5 This is a schematic diagram showing the structure of a thermistor element.

[0023] Figure 6 This is a schematic diagram showing the structure of a thermistor element.

[0024] Figure 7 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in a variation of this embodiment.

[0025] Figure 8 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in a variation of this embodiment.

[0026] Figure 9 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in a variation of this embodiment. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same elements or elements having the same function are represented by the same symbols, and repeated explanations are omitted.

[0028] Reference Figures 1-6The structure of the NTC thermistor element T1 involved in this embodiment will be described. Figure 1 This is a perspective view showing the NTC thermistor element involved in this embodiment. Figure 2 , Figure 3 and Figure 4 This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in this embodiment. Figure 5 and Figure 6 This is a schematic diagram showing the structure of a thermistor element. Figures 2-4 In order to clearly show the structure of the NTC thermistor element T1, the shading line has been omitted.

[0029] like Figure 1 As shown, the NTC thermistor element T1 includes a thermistor body 1. The thermistor body 1 is, for example, rectangular parallelepiped in shape. The thermistor body 1 has a pair of opposing main surfaces 1a and 1b, a pair of opposing end surfaces 1c and 1d, and a pair of opposing side surfaces 1e and 1f. The main surfaces 1a and 1b, the end surfaces 1c and 1d, and the side surfaces 1e and 1f constitute the outer surface of the thermistor body 1. The main surfaces 1a and 1b, the end surfaces 1c and 1d, and the side surfaces 1e and 1f are rectangular. In this specification, "rectangular parallelepiped shape" includes a rectangular parallelepiped shape with chamfered corners and edges, or a rectangular parallelepiped shape with rounded corners and edges. In this specification, "rectangular" includes, for example, a shape with chamfered corners or a shape with rounded corners.

[0030] Main surfaces 1a and 1b are opposite to each other in the first direction D1. Main surfaces 1a and 1b define the two ends of the thermistor element 1 in the first direction D1. End surfaces 1c and 1d are adjacent to main surfaces 1a and 1b and are opposite to each other in the second direction D2, which intersects the first direction D1. End surfaces 1c and 1d define the two ends of the thermistor element 1 in the second direction D2. Side surfaces 1e and 1f are adjacent to main surfaces 1a and 1b and end surfaces 1c and 1d, and are opposite to each other in the third direction D3. The third direction D3 intersects the first direction D1 and the second direction D2. Side surfaces 1e and 1f define the two ends of the thermistor element 1 in the third direction D3. In this embodiment, the first direction D1, the second direction D2, and the third direction D3 are orthogonal to each other.

[0031] Main faces 1a and 1b extend in the second direction D2, connecting end faces 1c and 1d. Main faces 1a and 1b extend in the third direction D3, connecting side faces 1e and 1f. End faces 1c and 1d extend in the first direction D1, connecting main faces 1a and 1b. End faces 1c and 1d extend in the third direction D3, connecting side faces 1e and 1f. Side faces 1e and 1f extend in the first direction D1, connecting main faces 1a and 1b. Side faces 1e and 1f extend in the second direction D2, connecting end faces 1c and 1d.

[0032] The NTC thermistor element T1 is soldered onto an electronic device, for example. The electronic device includes, for example, a circuit board or electronic components. In the NTC thermistor element T1, for example, the main surface 1a is opposite to the electronic device. Main surface 1a is a mounting surface. Main surface 1b can also be a mounting surface.

[0033] The thermistor body 1 is constructed by stacking multiple thermistor layers in a first direction D1. The stacking direction of the multiple thermistor layers is consistent with the first direction D1. The thermistor body 1 has multiple stacked thermistor layers. Each thermistor layer is, for example, composed of a sintered body of a ceramic green sheet. The sintered body of the ceramic green sheet contains an NTC thermistor material. The NTC thermistor material functions as an NTC thermistor and, for example, contains a semiconductor ceramic material. The NTC thermistor material contains, for example, a composite oxide having a spinel structure. This composite oxide contains, for example, two or more elements selected from transition metal elements including Mn, Ni, Co, and Fe. The composite oxide having a spinel structure is, for example, the main component of the NTC thermistor material. In this embodiment, the composite oxide contained in the NTC thermistor material contains, for example, Mn, Ni, and Co. In this case, the raw materials of the NTC thermistor material include Mn3O4 powder, NiO powder, and Co3O4 powder.

[0034] NTC thermistor materials may also contain secondary components that improve characteristics. These secondary components may be, for example, Cu, Al, or Zr. In this embodiment, at least Zr is a secondary component. The composition of the main and secondary components, and the content of each component, are determined according to the required characteristics of the NTC thermistor element T1. In the actual thermistor body 1, each thermistor layer is integrated to such an extent that the boundaries between the thermistor layers cannot be visually confirmed. The thermistor body 1 comprises multiple grains.

[0035] The NTC thermistor element T1 includes a cover layer 5. The cover layer 5 is formed on the outer surface of the thermistor body 1, namely the main surfaces 1a and 1b, the end surfaces 1c and 1d, and the side surfaces 1e and 1f. The cover layer 5 covers the outer surface of the thermistor body 1. In this embodiment, the cover layer 5 covers substantially the entire outer surface of the thermistor body 1. The cover layer 5 may contain, for example, a glass material. The thickness of the cover layer 5 is, for example, 0.01 to 2.0 μm. In this embodiment, the thickness of the cover layer 5 is 0.5 μm. The glass material may, for example, contain SiO2-Al2O3-LiO2 based crystalline glass. The glass material may also contain amorphous glass.

[0036] The NTC thermistor element T1 has, for example, the 0402 dimension shown in the JIS display. The 0402 dimension in the JIS display corresponds to the 01005 dimension shown in the EIA display. The length of the thermistor element 1 in the first direction D1 is, for example, approximately 0.2 mm. The length of the thermistor element 1 in the second direction D2 is approximately 0.4 mm. The length of the thermistor element 1 in the third direction D3 is approximately 0.2 mm.

[0037] like Figure 2 As shown, the NTC thermistor element T1 includes multiple electrodes 10, 20, 30, and 40. The multiple electrodes 10, 20, 30, and 40 have multiple external electrodes 10, 20 and multiple internal electrodes 30, 40. The multiple external electrodes 10, 20 are disposed on the thermistor element 1. The multiple internal electrodes 30, 40 are disposed within the thermistor element 1. The multiple internal electrodes 30, 40 are opposite to each other within the thermistor element 1.

[0038] In this embodiment, the NTC thermistor element T1 includes a pair of external electrodes 10 and 20. The external electrodes 10 and 20 are disposed on the thermistor element 1. The external electrodes 10 and 20 are disposed on the outer surface of the thermistor element 1. The external electrodes 10 and 20 are, for example, disposed at both ends of the thermistor element 1 in the second direction D2. The external electrodes 10 and 20 are opposite to each other in the second direction D2, separated by the thermistor element 1.

[0039] An external electrode 10 is disposed at one end of the thermistor element 1. In this embodiment, the external electrode 10 is disposed at one end such that it covers end face 1c. The external electrode 10 is disposed on end face 1c. The external electrode 10 is also disposed on a portion of the main faces 1a and 1b and a portion of the side faces 1e and 1f. The external electrode 10 is formed on five faces: end face 1c, main faces 1a and 1b, and side faces 1e and 1f. The external electrode 10 covers the corners formed by the four faces of end face 1c, main faces 1a and 1b, and side faces 1e and 1f, and the ridges connecting the corners. An external electrode 20 is disposed at the other end of the thermistor element 1. In this embodiment, the external electrode 20 is disposed at the other end such that it covers end face 1d. The external electrode 10 is disposed on end face 1d. The external electrode 20 is also disposed on a portion of the main faces 1a and 1b and a portion of the side faces 1e and 1f. External electrodes 20 are formed on five surfaces: end face 1d, main faces 1a and 1b, and side faces 1e and 1f. External electrodes 20 cover the corners formed by the four surfaces of end face 1d, main faces 1a and 1b, and side faces 1e and 1f, and the edge portions that connect the corners to each other.

[0040] External electrodes 10 and 20 have sintered metal layers. Each portion of the external electrodes 10 and 20 has a sintered metal layer. The sintered metal layer is formed by sintering a conductive paste applied to the outer surface of the thermistor body 1. The sintered metal layer is formed by sintering the metal components contained in the conductive paste. The metal components contained in the conductive paste may include, for example, metal powder. The sintered metal layer contains noble metals or noble metal alloys. Noble metals may include, for example, Ag, Pd, Au, or Pt. Noble metal alloys may include, for example, Ag-Pd alloys. The sintered metal layer may contain base metals or base metal alloys. Base metals may include, for example, Cu or Ni. The conductive paste may contain, for example, metal powders of the above types, glass components, organic binders, and organic solvents.

[0041] The external electrodes 10 and 20 may also have a plating layer. The plating layer is formed on a sintered metal layer, for example, by covering the sintered metal layer. The plating layer may have a two-layer structure. In a two-layer structure, the first layer may include, for example, a Ni plating layer, a Sn plating layer, a Cu plating layer, or an Au plating layer, and the second layer disposed on the first layer may include, for example, a Sn plating layer, a Sn-Ag alloy plating layer, a Sn-Bi alloy plating layer, or a Sn-Cu alloy plating layer. The plating layer may have a three- or more layer structure. The thickness of the external electrodes 10 and 20 is, for example, 5.0–30 μm.

[0042] like Figures 2-4As shown, in this embodiment, the NTC thermistor element T1 includes a pair of internal electrodes 30 and 40. The internal electrodes 30 and 40 are opposite to each other, for example, in the first direction D1. For example, internal electrode 30 faces the main surface 1a, and internal electrode 40 faces the main surface 1b. That is, compared to internal electrode 40, internal electrode 30 is closer to main surface 1a in the first direction D1, and internal electrode 40 is closer to main surface 1b in the first direction D1 compared to internal electrode 30. Internal electrode 30 is connected to external electrode 10, and internal electrode 40 is connected to external electrode 20. In other words, the plurality of internal electrodes 30 and 40 are connected to corresponding external electrodes among the plurality of external electrodes 10 and 20.

[0043] The internal electrode 30 has two opposing faces in the first direction D1. The internal electrode 30 is disposed within the thermistor element 1, for example, such that one face of the opposing face of the internal electrode 30 faces the main surface 1a. The other face of the opposing face of the internal electrode 30 faces the main surface 1b. One face of the internal electrode 30 is separated from the main surface 1a and is not exposed on the main surface 1a. The other face of the internal electrode 30 is separated from the main surface 1b and is not exposed on the main surface 1b. The internal electrode 30 has one end exposed at end face 1c. The internal electrode 30 is physically and electrically connected to the external electrode 10 at the end exposed at end face 1c. Except for the end exposed at end face 1c, the internal electrode 30 is located within the thermistor element 1.

[0044] The internal electrode 40 has two opposing faces in the first direction D1. The internal electrode 40 is disposed within the thermistor element 1, for example, such that one face of the opposing face of the internal electrode 40 faces the main surface 1a. The other face of the opposing face of the internal electrode 40 faces the main surface 1b. One face of the internal electrode 40 is separated from the main surface 1a and is not exposed on the main surface 1a. The other face of the internal electrode 40 is separated from the main surface 1b and is not exposed on the main surface 1b. The internal electrode 40 has one end exposed at end face 1d. The internal electrode 40 is physically and electrically connected to the external electrode 20 at the end exposed at end face 1d. Except for the end exposed at end face 1d, the internal electrode 40 is located within the thermistor element 1.

[0045] Viewed from the first direction D1, the internal electrodes 30 and 40 are, for example, rectangular in shape. In each of the internal electrodes 30 and 40, for example, the length in the second direction D2 is greater than the length in the third direction D3. The sizes of the internal electrodes 30 and 40 are, for example, approximately the same. The thickness of each of the internal electrodes 30 and 40 in the first direction D1 is, for example, 2.0 to 5.0 μm. In this embodiment, the thickness of each of the internal electrodes 30 and 40 in the first direction D1 is 3.0 μm.

[0046] The internal electrodes 30 and 40 are made of conductive materials. The conductive materials of the internal electrodes 30 and 40 include noble metals or noble metal alloys. Noble metals include, for example, Ag, Pd, Au, or Pt. Noble metal alloys include, for example, Ag-Pd alloys. The internal electrodes 30 and 40 may also contain base metals or base metal alloys. Base metals include, for example, Cu or Ni. The internal electrodes 30 and 40 are internal conductors disposed within the thermistor body 1, and may also contain conductive materials commonly used as internal conductors in multilayer electronic components. The internal electrodes 30 and 40 are configured as sintered bodies of conductive pastes containing the aforementioned types of conductive materials.

[0047] like Figures 2-4 As shown, the thermistor element 1 has regions R2 and R3. Region R3 is located inside the thermistor element 1 and is separated from the outer surface of the thermistor element 1. Region R2 is located outside region R3 and includes the outer surface of the thermistor element 1. Region R3 includes region R1. That is, the thermistor element 1 has region R1. Region R1 is located inside the thermistor element 1 and is separated from the outer surface of the thermistor element 1. Region R2 is located outside region R1. Region R1 is located between adjacent internal electrodes 30 and 40. Region R1 mainly contributes to the characteristics of the NTC thermistor element T1. For example, if region R2 constitutes a second region, region R3 constitutes a first region. For example, if region R2 constitutes a second region, region R1 constitutes a first region.

[0048] In this embodiment, region R1 is located between adjacent internal electrodes 30 and 40 in a first direction D1, sandwiched between them. Viewed from the first direction D1, region R1 overlaps with both internal electrodes 30 and 40. Region R1 may, for example, contact the other face of internal electrode 30 and one face of internal electrode 40. Alternatively, region R1 may not contact either face of internal electrode 30 or the other face of internal electrode 40. Region R1 may, for example, be cuboid in shape. The height of region R1 is defined, for example, by the distance between internal electrodes 30 and 40 in the first direction D1, i.e., the distance between the other face of internal electrode 30 and one face of internal electrode 40 in the first direction D1. The edge of region R1, viewed from the first direction D1, is defined, for example, by the edge of internal electrode 30 and the edge of internal electrode 40. Viewed from the first direction D1, the edge of internal electrode 30 near side 1e and the edge of internal electrode 40 near side 1e have overlapping regions. Viewed from the first direction D1, the end edge of the internal electrode 30 near its side 1f overlaps with the end edge of the internal electrode 40 near its side 1f. For example... Figures 2-4As shown, when viewed from the first direction D1, the edge of the inner electrode 30 near its side 1e overlaps with the edge of the inner electrode 40 near its side 1e, and the edge of the inner electrode 30 near its side 1f overlaps with the edge of the inner electrode 40 near its side 1f. For example, when viewed from the first direction D1, the position of the edge of the inner electrode 30 near its side 1e in the third direction D3 may differ from the position of the edge of the inner electrode 40 near its side 1e in the third direction D3. Similarly, when viewed from the first direction D1, the position of the edge of the inner electrode 30 near its side 1f in the third direction D3 may differ from the position of the edge of the inner electrode 40 near its side 1f in the third direction D3.

[0049] Region R2 is exposed on the outer surface of the thermistor element 1. Region R2 may, for example, encompass the entire outer surface of the thermistor element 1. That is, region R2 may, for example, encompass the entirety of the main surfaces 1a and 1b, the end surfaces 1c and 1d, and the side surfaces 1e and 1f. Region R2 may, for example, be entirely exposed on the outer surface of the thermistor element 1. Region R2 may, for example, also encompass a portion of the outer surface of the thermistor element 1. Region R2 may, for example, cover the entirety of region R3.

[0050] Region R3 may, for example, encompass the entirety of region R1. Region R3 may also be identical to region R1. That is, region R3 may also contain only region R1. In a structure where region R3 contains only region R1, region R3 is located between adjacent internal electrodes 30 and 40 along a first direction D1, and is sandwiched between the internal electrodes 30 and 40 along the first direction D1. Region R3 may, for example, be cuboid in shape. Region R3 may also be in shapes other than cuboid. Region R3 may, for example, be spherical, ellipsoidal, prism-shaped, or frustum-shaped.

[0051] Figure 5 and Figure 6 This is a schematic diagram showing the structure of a thermistor element. Figure 5 An example representing the structure of regions R1 and R3. Figure 6 An example representing the structure of region R2. For example... Figure 5 As shown, regions R1 and R3 contain multiple grains CG1. Figure 6 As shown, region R2 contains a plurality of grains CG2. The plurality of grains CG1 are arranged, for example, continuously. The plurality of grains CG2 are arranged, for example, continuously. Regions R1 and R3 have grain boundaries formed by the plurality of grains CG1. Region R2 has grain boundaries formed by the plurality of grains CG2. In this specification, the continuous arrangement of the plurality of grains CG1 indicates a state in which adjacent grains of the plurality of grains CG1 are in direct contact. In this specification, the continuous arrangement of the plurality of grains CG2 indicates a state in which adjacent grains of the plurality of grains CG2 are in direct contact.

[0052] In this embodiment, the first average grain size of grain CG1 is larger than the second average grain size of grain CG2. In a cross-section along the first direction D1, the first average grain size is, for example, 1.5 to 2.0 μm. In this embodiment, the first average grain size is 2.0 μm. In this embodiment, the first average grain size is equal to or less than the thickness of the internal electrodes 30 and 40 along the first direction D1. That is, the thickness of each of the plurality of internal electrodes 30 and 40 is larger than the first average grain size.

[0053] In the cross-section along the first direction D1, the second average particle size is, for example, 1.0 to 1.5 μm. In this embodiment, the second average particle size is 1.5 μm. The second average particle size is equal to or less than the first average particle size. For example, the first average particle size is greater than the second average particle size. In this embodiment, the first average particle size is less than twice the second average particle size.

[0054] The first average particle size and the second average particle size are determined, for example, as described below.

[0055] Obtain cross-sectional photographs of the thermistor element 1 (NTC thermistor T1) at locations including regions R1 and R2. For example, a cross-sectional photograph is taken of the thermistor element 1 cut by a plane orthogonal to the main surface 1a. Therefore, a cross-sectional photograph is, for example, taken of the thermistor element 1 cut by a plane parallel to the sides 1e and 1f and located at equidistant from the sides 1e and 1f. Alternatively, a cross-sectional photograph can also be taken of the thermistor element 1 cut by a plane parallel to the main surfaces 1a and 1b and located between the internal electrode 30 and the main surface 1a, or between the internal electrode 30 and the internal electrode 40. The cross-sectional photograph can be an FE-SEM (Electrical Field Emission Scanning Electron Microscope) photograph. An FE-SEM photograph is, for example, a secondary electron image.

[0056] Software-based image processing is performed on the acquired cross-sectional photographs. This image processing identifies the boundaries of each grain CG1 and each grain CG2, and calculates the area of ​​each grain CG1 and CG2. Based on the calculated areas of grains CG1 and CG2, the grain size converted to the equivalent circle diameter is calculated. Alternatively, the grain size of all grains CG1 contained in region R1 can be calculated. The grain size of all grains CG2 contained in region R2 can also be calculated. Alternatively, the grain size of any number of grains CG1 contained in region R1 can be calculated. Alternatively, the grain size of any number of grains CG2 contained in region R2 can be calculated. For example, an arbitrary number could be 50. The average of the obtained grain sizes of grain CG1 is the first average grain size. The average of the obtained grain sizes of grain CG2 is the second average grain size.

[0057] The first and second average particle sizes are defined, for example, by the particle size at which the cumulative frequency in the particle size distribution reaches 50%, i.e., the d50 particle size. In this case, the first and second average particle sizes are calculated as follows.

[0058] For example, after calculating the grain size converted to the equivalent circle diameter, calculate the grain size of any number of grains CG1 and CG2, and determine the grain size distribution of these grains CG1 and CG2. The arbitrary number is, for example, 50. Based on the obtained grain size distribution, when grains CG1 and CG2 are divided into two groups with a certain grain size as the boundary, the grain size where the number of grains in the larger group and the number of grains in the smaller group are equal is called the d50 grain size.

[0059] The manufacturing method of NTC thermistor element T1 is explained.

[0060] First, in order to form the thermistor element 1, the starting materials are weighed in a prescribed manner. The starting materials may include, for example, Mn3O4 powder, NiO powder, and Co3O4 powder. The weighed starting materials are then mixed.

[0061] Next, the mixed starting materials are pre-fired. The pre-fired temperature is, for example, 800–1300°C. The pre-fired starting materials are then coated, for example. The specific surface area of ​​the pre-fired starting materials is, for example, less than 10 m². 2 / g. In this case, the starting material is easily coated and easily printed and laminated. The specific surface area is obtained, for example, by the BET (Brunauer Emmett Teller) method. When the average particle size of the starting material is defined by the d50 particle size, the average particle size is, for example, less than 1.0 μm. In this embodiment, when the average particle size of the starting material is defined by the d50 particle size, the average particle size is 0.5 μm. For example, the pre-calcined material is coated and then pulverized. The pre-calcined material can also be pulverized when coating it. In this embodiment, an additive is mixed with the pulverized material to form a slurry. The additive includes, for example, an organic binder. The organic binder includes, for example, vinyl acetate or polyvinyl alcohol.

[0062] Next, a ceramic green sheet is formed, for example, from a slurry. The green sheet is formed, for example, by a doctor blade method. A portion of the green sheets is coated with a conductive paste for forming the internal electrodes 30, 40. This conductive paste contains, for example, Ag, Pd, Au, Pt, or an Ag-Pd alloy. In this embodiment, a laminate is formed by alternately stacking, for example, green sheets without conductive paste and ceramic green sheets coated with conductive paste.

[0063] Next, the laminate is fired in a firing furnace. The firing process of the laminate includes, for example, a heating process, a holding process, and a cooling process. When the firing process of the laminate includes heating, holding, and cooling, the temperature in the firing furnace during the holding process is, for example, 1000–1300°C. Through the firing process, the conductive paste is sintered to form internal electrodes 30 and 40.

[0064] Next, external electrodes 10 and 20 are formed. For example, a conductive paste for forming the external electrodes 10 and 20 is applied to the end faces 1c and 1d of the thermistor body 1. This conductive paste may contain, for example, Ag, Pd, Au, Pt, or an Ag-Pd alloy. The applied conductive paste is sintered to form the external electrodes 10 and 20. In this case, the sintering of the conductive paste forms the sintered metal layer of the external electrodes 10 and 20.

[0065] The NTC thermistor element T1 is obtained through the above manufacturing method. In this embodiment, the thermistor element 1 may also undergo annealing. However, this annealing process may not be performed.

[0066] The resulting NTC thermistor element T1 has, for example, the 0402 dimension shown in JIS. The resulting NTC thermistor element T1 may also have, for example, the 1005 dimension shown in JIS. The 1005 dimension shown in JIS corresponds to the 0402 dimension shown in EIA. The length of the thermistor element 1 in the first direction D1 is, for example, about 0.5 mm or less. The length of the thermistor element 1 in the second direction D2 is, for example, about 1.0 mm or less. The length of the thermistor element 1 in the third direction D3 is, for example, about 1.0 mm or less.

[0067] As described above, the NTC thermistor element T1 according to this embodiment includes: a thermistor body 1 comprising a plurality of grains CG1, CG2; and a plurality of electrodes 10, 20, 30, 40 disposed on the thermistor body 1. The plurality of electrodes 10, 20, 30, 40 have a plurality of external electrodes 10, 20 disposed on the thermistor body 1 and a plurality of internal electrodes 30, 40 opposing each other within the thermistor body 1. The internal electrodes 30 are connected to the external electrodes 10, and the internal electrodes 40 are connected to the external electrodes 20. The thermistor body 1 has a region R1 and a region R2. Region R1 is located between adjacent internal electrodes 30, 40 and is separated from the outer surface of the thermistor body 1. Region R2 is located outside region R1 and includes the outer surface of the thermistor body 1. The plurality of grains CG1, CG2 include the plurality of grains CG1 contained in region R1 and the plurality of grains CG2 contained in region R2. The first average grain size of multiple grains CG1 is greater than the second average grain size of multiple grains CG2.

[0068] In the NTC thermistor element T1, the first average particle size is larger than the second average particle size. Region R1 tends to increase heat transfer efficiency. Therefore, the NTC thermistor element T1 exhibits excellent thermal response.

[0069] The second average particle size is smaller than the first average particle size. Therefore, cracks are less likely to form in region R2 compared to region R1. The NTC thermistor element T1 has high flexural stress.

[0070] In the NTC thermistor element T1, the first average particle size is less than twice the second average particle size.

[0071] Structures with a first average particle size greater than twice the second average particle size tend to increase the stress acting on the internal electrodes 30 and 40 from region R1. The stress acting from region R1 may deform the internal electrodes 30 and 40. Deformation of the internal electrodes 30 and 40 may change the spacing between adjacent internal electrodes 30 and 40. Changes in the spacing between adjacent internal electrodes 30 and 40 may degrade the characteristics of the NTC thermistor element T1. For example, changes in the spacing between adjacent internal electrodes 30 and 40 may cause changes in the resistance value of the NTC thermistor element T1.

[0072] Structures with a first average particle size less than twice the second average particle size are unlikely to increase the stress acting on the internal electrodes 30 and 40 from region R1. Therefore, the internal electrodes 30 and 40 are difficult to deform. As a result, the suppression characteristics of the NTC thermistor element T1 deteriorate.

[0073] In the NTC thermistor element T1, the thickness of each of the multiple internal electrodes 30 and 40 is larger than the first average particle size.

[0074] The structure in which the thickness of each of the multiple internal electrodes 30, 40 is less than or equal to a first average particle size tends to vary the spacing between adjacent internal electrodes 30, 40. Variation in the spacing between adjacent internal electrodes 30, 40 may degrade the characteristics of the NTC thermistor element T1. As described above, variation in the spacing between adjacent internal electrodes 30, 40 may, for example, cause a change in the resistance value of the NTC thermistor element T1.

[0075] The structure in which the thickness of each of the multiple internal electrodes 30 and 40 is larger than the first average particle size makes it difficult to vary the spacing between adjacent internal electrodes 30 and 40. Therefore, the suppression characteristics of the NTC thermistor element T1 deteriorate.

[0076] Reference Figure 7 , Figure 8 as well as Figure 9 The NTC thermistor element T1 involved in the modified embodiment will be described. Figures 7-9This is a diagram showing the cross-sectional structure of the NTC thermistor element involved in a variation of this embodiment. Figures 7-9 In this example, the shaded lines are omitted to clearly show the structure of the NTC thermistor element T1. The NTC thermistor element T1 in this variation has the same structure as the NTC thermistor element T1 in the embodiment, except for the size of the thermistor body 1 and the structure of the internal electrodes. The thickness of the thermistor body 1 in the first direction D1 of this variation is, for example, less than 0.2 mm. The length of the thermistor body 1 in the second direction D2 is, for example, less than 0.4 mm. The length of the thermistor body 1 in the third direction D3 is, for example, less than 0.2 mm. The NTC thermistor element T1 in this variation is thin. The NTC thermistor element T1 in this variation may also have the 0402 dimension shown in JIS. Hereinafter, the differences between the above-described embodiment and this variation will be mainly explained.

[0077] The modified NTC thermistor element T1 includes multiple electrodes 10, 20, 30, 40, and 50 disposed within the thermistor element 1. Each electrode 10, 20, 30, 40, and 50 has multiple internal electrodes 30, 40, and 50. These internal electrodes 30, 40, and 50 are disposed within the thermistor element 1. In this modified example, the multiple internal electrodes 30, 40, and 50 include two internal electrodes 30, two internal electrodes 40, and one internal electrode 50. The multiple internal electrodes 30, 40, and 50 are opposite to each other. For example, two internal electrodes 30 are opposite to each other in a first direction D1. For example, two internal electrodes 40 are opposite to each other in a first direction D1. An internal electrode 30 is connected to a corresponding external electrode 10 among the multiple external electrodes 10 and 20. An internal electrode 40 is connected to a corresponding external electrode 20 among the multiple external electrodes 10 and 20. The internal electrode 50 is not connected to any of the multiple external electrodes 10 or 20. That is, the internal electrode 50 is not directly connected to the plurality of external electrodes 10, 20. The internal electrode 50 is opposite to the internal electrodes 30, 40, for example, in the first direction D1. The internal electrode 50 and the internal electrode 30 are adjacent to each other, for example, in the first direction D1. The internal electrode 50 and the internal electrode 40 are adjacent to each other, for example, in the first direction D1.

[0078] Two internal electrodes 30 are disposed at different positions (layers) in the first direction D1. One internal electrode 30 is located closer to the main surface 1a in the first direction D1 than the other internal electrode 30. The other internal electrode 30 is located closer to the main surface 1b in the first direction D1 than the first internal electrode 30. Each internal electrode 30 has a pair of opposite faces in the first direction D1. For example, one internal electrode 30 is disposed within the thermistor element 1 such that one face of its opposite pair faces the main surface 1a. The other internal electrode 30 is disposed within the thermistor element 1 such that one face of its opposite pair faces the main surface 1b. The aforementioned face of one internal electrode 30 is separated from the main surface 1a and is not exposed on the main surface 1a. The aforementioned face of the other internal electrode 30 is separated from the main surface 1b and is not exposed on the main surface 1b. The other face of one pair of internal electrodes 30 faces the other face of the other pair of internal electrodes 30 in the first direction D1. Each internal electrode 30 has one end exposed on end face 1c. Each internal electrode 30 is physically and electrically connected to the external electrode 10 at the end exposed on end face 1c. Except for the end exposed on end face 1c, each internal electrode 30 is located inside the thermistor element 1.

[0079] Two internal electrodes 40 are disposed at different positions (layers) in the first direction D1. One internal electrode 40 is located closer to the main surface 1a in the first direction D1 than the other internal electrode 40. The other internal electrode 40 is located closer to the main surface 1b in the first direction D1 than the first internal electrode 40. Each internal electrode 40 has a pair of opposite faces in the first direction D1. For example, one internal electrode 40 is disposed within the thermistor element 1 such that one face of its opposite pair faces the main surface 1a. The other internal electrode 40 is disposed within the thermistor element 1 such that one face of its opposite pair faces the main surface 1b. The aforementioned face of one internal electrode 40 is separated from the main surface 1a and is not exposed on the main surface 1a. The aforementioned face of the other internal electrode 40 is separated from the main surface 1b and is not exposed on the main surface 1b. The other face of one pair of internal electrodes 40 faces the other face of the other pair of internal electrodes 40 in the first direction D1. Each internal electrode 40 has one end exposed at end face 1d. Each internal electrode 40 is physically and electrically connected to the external electrode 20 at the end exposed at end face 1d. Except for the end exposed at end face 1d, each internal electrode 40 is located within the thermistor element 1.

[0080] The internal electrode 50 is disposed at different positions (layers) from the internal electrodes 30 and 40 in the first direction D1. The internal electrode 50 is not exposed on the outer surface of the thermistor element 1. That is, the entire internal electrode 50 is not exposed on the outer surface of the thermistor element 1. The internal electrode 50 is not connected to the external electrodes 10 and 20. That is, the internal electrode 50 is not directly connected to the external electrodes 10 and 20. The internal electrode 50 is not physically connected to the external electrodes 10 and 20. The internal electrodes 50 and 30 and 40 are disposed relative to each other within the thermistor element 1 in a spaced-apart manner in the first direction D1. The internal electrode 50 is located in the layer containing one corresponding set of internal electrodes 30 and 40 and the layer containing another corresponding set of internal electrodes 30 and 40 in the first direction D1. In this modified example, in the first direction D1, the layer containing the internal electrode 50 is located approximately midway between the layer containing the aforementioned set of internal electrodes 30 and 40 and the layer containing the aforementioned other set of internal electrodes 30 and 40. One set of internal electrodes 30, 40 is located closer to the main surface 1a in the first direction D1 compared to another set of internal electrodes 30, 40. The other set of internal electrodes 30, 40 is located closer to the main surface 1b in the first direction D1 compared to the first set of internal electrodes 30, 40. For example, one set of internal electrodes 30, 40 is opposite to the main surface 1a, and the other set of internal electrodes 30, 40 is opposite to the main surface 1b. The internal electrode 50 includes a first portion opposite to the internal electrode 30, a second portion opposite to the internal electrode 40, and a third portion not opposite to the internal electrodes 30, 40. In the internal electrode 50, the third portion is located, for example, between the first and second portions in the second direction D2. In this modified example, the third portion is continuous with the first and second portions in the internal electrode 50.

[0081] Viewed from the first direction D1, the internal electrodes 30, 40, and 50 are, for example, rectangular in shape. In each of the internal electrodes 30, 40, and 50, for example, the length in the second direction D2 is greater than the length in the third direction D3. The sizes of the internal electrodes 30 and 40 are, for example, approximately the same. The thickness of the internal electrodes 30 and 40 in the first direction D1 is, for example, 2.0 to 5.0 μm. In this modified example, the thickness of the internal electrodes 30 and 40 in the first direction D1 is 3.0 μm. The thickness of the internal electrode 50 in the first direction D1 is, for example, 2.0 to 5.0 μm. In this modified example, the thickness of the internal electrode 50 in the first direction D1 is 3.0 μm. The internal electrodes 30, 40, and 50 involved in this modified example, for example, contain the same material as the internal electrodes 30 and 40 in the above-described embodiments.

[0082] The thermistor element 1 has regions R2 and R3. Region R3 is located inside the thermistor element 1 and is separated from the outer surface of the thermistor element 1. Region R2 is located outside region R3 and includes the outer surface of the thermistor element 1. Region R3 includes region R1. That is, the thermistor element 1 has region R1. Region R1 is located inside the thermistor element 1 and is separated from the outer surface of the thermistor element 1. Region R2 is located outside region R1. Region R1 is located, for example, between adjacent internal electrodes 30 and 50, and is sandwiched between internal electrodes 30 and 50 in the first direction D1. Region R1 mainly contributes to the characteristics of the NTC thermistor element T1. For example, if region R2 constitutes a second region, region R3 constitutes a first region. For example, if region R2 constitutes a second region, region R1 constitutes a first region.

[0083] In this modified example, the thermistor element 1 has multiple regions R1. Figures 7-9 In the example shown, the thermistor element 1 has four regions R1. Two of the four regions R1 are located near end face 1c. The remaining two of the four regions R1 are located near end face 1d.

[0084] The two regions R1 near end face 1c include one region R1 and another region R1. One region R1 is located between an adjacent internal electrode 30 and an internal electrode 50, and is sandwiched between the two internal electrodes in the first direction D1. The other region R1 is located between another adjacent internal electrode 30 and an internal electrode 50, and is sandwiched between the two internal electrodes in the first direction D1. Viewed from the first direction D1, the two regions R1 near end face 1c overlap with the adjacent internal electrodes 30 and 50, respectively. The two regions R1 near end face 1c are, for example, rectangular parallelepipeds. The height of each of the two regions R1 near end face 1c is defined, for example, by the spacing between the internal electrodes 30 and 50 in the first direction D1. The end edges of each of the two regions R1 near end face 1c, as viewed from the first direction D1, are defined, for example, by the end edges of the internal electrodes 30 and 50.

[0085] The remaining two regions R1 near end face 1d include two additional regions R1. The additional regions R1 are located between one adjacent internal electrode 40 and internal electrode 50, and are sandwiched between one internal electrode 40 and internal electrode 50 in the first direction D1. The additional regions R1 are located between another adjacent internal electrode 40 and internal electrode 50, and are sandwiched between another internal electrode 40 and internal electrode 50 in the first direction D1. Viewed from the first direction D1, the remaining two regions R1 near end face 1d overlap with the adjacent internal electrodes 40 and 50, respectively. The remaining two regions R1 near end face 1d are, for example, cuboid in shape. The height of each of the remaining two regions R1 near end face 1d is defined, for example, by the spacing between the internal electrodes 40 and 50 in the first direction D1. The end edges of each of the remaining two regions R1 near end face 1d, viewed from the first direction D1, are defined, for example, by the end edges of the internal electrodes 40 and 50.

[0086] Region R2 is the same as in the embodiment described above, exposed on the outer surface of the thermistor element 1. Region R2, for example, encompasses the entire outer surface of the thermistor element 1. That is, region R2, for example, includes all of the main surfaces 1a, 1b, end surfaces 1c, 1d, and side surfaces 1e, 1f. Region R2, for example, exposes the entire outer surface of the thermistor element 1. Region R2 may also, for example, include a portion of the outer surface of the thermistor element 1. Region R2, for example, covers the entire region R3.

[0087] Region R3 may, for example, encompass the entirety of region R1. Region R3 may also be identical to region R1. That is, region R3 may also contain only region R1. In a structure where region R3 contains only region R1, region R3 may, for example, include a region located between and sandwiched between a pair of internal electrodes 30 and 50, and a region located between and sandwiched between a pair of internal electrodes 40 and 50. Region R3 may, for example, be cuboid in shape. Region R3 may also be in shapes other than cuboid. Region R3 may, for example, be spherical, ellipsoidal, prism-shaped, or frustum-shaped.

[0088] In this variation, region R1 contains a plurality of grains CG1. Region R2 contains a plurality of grains CG2. The first average grain size of grains CG1 is larger than the second average grain size of grains CG2. The first and second average grain sizes involved in this variation are, for example, the same as those involved in the embodiment. In this variation, the first average grain size is also less than twice the second average grain size, and the thickness of each of the internal electrodes 30, 40, and 50 is larger than the first average grain size.

[0089] As explained above, the modified NTC thermistor element T1 includes: a thermistor body 1 comprising multiple grains CG1, CG2; and multiple electrodes 10, 20, 30, 40, 50 disposed on the thermistor body 1. The multiple electrodes 10, 20, 30, 40, 50 have multiple external electrodes 10, 20 disposed on the thermistor body 1 and multiple internal electrodes 30, 40, 50 opposing each other within the thermistor body 1. Internal electrodes 30 are connected to external electrodes 10, and internal electrodes 40 are connected to external electrodes 20. Internal electrodes 50 are not connected to any of the external electrodes 10, 20. The thermistor body 1 has regions R1 and R2. Region R1 is located between adjacent internal electrodes of the multiple internal electrodes 30, 40, 50 and is separated from the outer surface of the thermistor body 1. For example, region R1 is located between adjacent internal electrodes 30, 50. Region R2 is located outside region R1 and includes the outer surface of the thermistor element 1. Multiple grains CG1 and CG2 comprise multiple grains CG1 contained in region R1 and multiple grains CG2 contained in region R2. The first average grain size of the multiple grains CG1 is larger than the second average grain size of the multiple grains CG2.

[0090] In the modified NTC thermistor element T1, the first average particle size is larger than the second average particle size. Region R1 tends to increase heat transfer efficiency. Therefore, the NTC thermistor element T1 exhibits excellent thermal responsiveness.

[0091] The second average particle size is smaller than the first average particle size. Therefore, cracks are less likely to form in region R2 compared to region R1. The NTC thermistor element T1 involved in the modified example has high flexural stress.

[0092] In the modified example, the NTC thermistor element T1 has a first average particle size that is less than twice the second average particle size.

[0093] Structures with a first average particle size greater than twice the second average particle size tend to increase the stress exerted on the internal electrodes 30, 40, and 50 from region R1. The stress exerted on the internal electrodes 30, 40, and 50 from region R1 may cause deformation of the internal electrodes 30, 40, and 50. Deformation of the internal electrodes 30, 40, and 50 may change the spacing between adjacent internal electrodes 30, 40, and 50. Changes in the spacing between adjacent internal electrodes 30, 40, and 50 may degrade the characteristics of the NTC thermistor element T1. For example, changes in the spacing between adjacent internal electrodes 30, 40, and 50 may cause changes in the resistance value of the NTC thermistor element T1.

[0094] Structures with a first average particle size less than twice the second average particle size are unlikely to increase the stress acting on the internal electrodes 30, 40, and 50 from region R1. Therefore, the internal electrodes 30, 40, and 50 are difficult to deform. As a result, the suppression characteristics of the NTC thermistor element T1 involved in this modified example deteriorate.

[0095] In the modified example of the NTC thermistor element T1, the thickness of each of the plurality of electrodes 30, 40, and 50 is larger than the first average particle size.

[0096] The structure in which the thickness of each of the multiple internal electrodes 30, 40, and 50 is less than or equal to a first average particle size tends to vary the spacing between adjacent internal electrodes 30, 40, and 50. Variation in the spacing between adjacent internal electrodes 30, 40, and 50 may degrade the characteristics of the NTC thermistor element T1. As described above, variation in the spacing between adjacent internal electrodes 30, 40, and 50 may, for example, cause a change in the resistance value of the NTC thermistor element T1.

[0097] The structure in which the thickness of each of the multiple internal electrodes 30, 40, and 50 is larger than the first average particle size makes it difficult to vary the spacing between adjacent internal electrodes 30, 40, and 50. Therefore, the suppression characteristics of the NTC thermistor element T1 involved in this modified example deteriorate.

[0098] The embodiments and variations also disclose an NTC thermistor element T1 having the following structure.

[0099] The NTC thermistor element T1 includes: a thermistor body 1 comprising multiple grains CG1 and CG2; and multiple electrodes disposed on the thermistor body 1. The multiple electrodes may include, for example, multiple electrodes 10, 20, 30, 40 or multiple electrodes 10, 20, 30, 40, 50. The thermistor body 1 has regions R3 and R2. Region R3 is located inside the thermistor body 1 and is separated from the outer surface of the thermistor body 1. Region R2 is located outside region R3 and includes the outer surface of the thermistor body 1. The multiple grains CG1 and CG2 include the multiple grains CG1 contained in region R3 and the multiple grains CG2 contained in region R2. The average grain size of the multiple grains CG1 is larger than the average grain size of the multiple grains CG2. The outer surface of the thermistor body 1 includes, for example, main surfaces 1a and 1b, end surfaces 1c and 1d, and side surfaces 1e and 1f.

[0100] In the NTC thermistor element T1, region R3 tends to improve the thermistor's characteristics compared to region R2. The first average grain size of the plurality of grains CG1 contained in region R3 is larger than the second average grain size of the plurality of grains CG2 contained in region R2. Therefore, region R3, which tends to improve the thermistor's characteristics, tends to increase heat transfer efficiency.

[0101] In the NTC thermistor element T1, the first average particle size is less than twice the second average particle size.

[0102] Structures with a first average particle size greater than twice the second average particle size tend to increase the stress acting on the internal electrodes from region R3. The internal electrodes include, for example, internal electrodes 30, 40, or internal electrodes 30, 40, 50. The stress acting from region R3 may deform the internal electrodes. Deformation of the internal electrodes may change the spacing between adjacent internal electrodes. Changes in the spacing between adjacent internal electrodes may degrade the characteristics of the NTC thermistor element T1. For example, changes in the spacing between adjacent internal electrodes may cause changes in the resistance value of the NTC thermistor element T1.

[0103] A structure where the first average particle size is less than twice the second average particle size makes it difficult to increase the stress acting on the internal electrode from region R3. Therefore, the internal electrode is less prone to deformation. As a result, this structure suppresses the degradation of the characteristics of the NTC thermistor element T1.

[0104] The embodiments and variations of the present invention have been described above, but the present invention is not necessarily limited to the embodiments and variations described above, and various changes can be made without departing from its spirit.

[0105] In the NTC thermistor element T1, the thickness of each of the multiple internal electrodes 30, 40, and 50 can also be less than or equal to the first average particle size. As described above, the structure in which the thickness of each of the multiple internal electrodes 30, 40, and 50 is greater than the first average particle size makes it difficult to change the spacing between adjacent internal electrodes 30, 40, and 50. Therefore, this structure suppresses the degradation of the characteristics of the NTC thermistor element T1.

Claims

1. An NTC thermistor element, wherein, have: Thermistor element containing multiple grains; and Multiple electrodes disposed on the thermistor element, The plurality of electrodes have a plurality of external electrodes disposed on the thermistor element and a plurality of internal electrodes facing each other within the thermistor element. The plurality of internal electrodes includes internal electrodes connected to corresponding external electrodes among the plurality of external electrodes. The thermistor element has: A first region located between adjacent internal electrodes of the plurality of internal electrodes and separated from the outer surface of the thermistor element; and A second region located outside the first region and including the outer surface. The plurality of grains includes a plurality of first grains contained in the first region and a plurality of second grains contained in the second region. The first average grain size of the plurality of first grains is greater than the second average grain size of the plurality of second grains. In a cross section along the direction in which the plurality of internal electrodes are opposite to each other, the first average particle size is 1.5 to 2.0 μm, and the second average particle size is 1.0 to 1.5 μm.

2. The NTC thermistor element according to claim 1, wherein, The first average particle size is less than twice the second average particle size.

3. The NTC thermistor element according to claim 1, wherein, The thickness of each of the plurality of internal electrodes is greater than the first average particle size.

4. The NTC thermistor element according to claim 2, wherein, The thickness of each of the plurality of internal electrodes is greater than the first average particle size.

5. The NTC thermistor element according to any one of claims 1 to 4, wherein, The plurality of internal electrodes includes two internal electrodes that are respectively connected to the corresponding external electrode among the plurality of external electrodes. The first region is located between the two internal electrodes.

6. The NTC thermistor element according to any one of claims 1 to 4, wherein, The plurality of internal electrodes also includes an internal electrode that is opposite to the internal electrode connected to the corresponding external electrode and is not directly connected to the plurality of external electrodes. The first region is located between the internal electrode connected to the corresponding external electrode and the internal electrode that is not directly connected to the plurality of external electrodes.

7. An NTC thermistor element, wherein, have: Thermistor element containing multiple grains; and Multiple electrodes disposed on the thermistor element, The thermistor element has: A first region located inside the thermistor element and separated from the outer surface of the thermistor element; and A second region located outside the first region and including the outer surface. The plurality of grains includes a plurality of first grains contained in the first region and a plurality of second grains contained in the second region. The first average grain size of the plurality of first grains is greater than the second average grain size of the plurality of second grains. In a cross section along a direction in which a pair of main faces of the thermistor element are opposite to each other, the first average particle size is 1.5~2.0 μm and the second average particle size is 1.0~1.5 μm.

8. The NTC thermistor element according to claim 7, wherein, The first average particle size is less than twice the second average particle size.

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