Heater

Abstract

A heater according to the present disclosure comprises: a ceramic substrate; a heating resistor; two lead parts; two surface electrodes; and a plurality of via conductors. The heating resistor is embedded in the ceramic substrate on one end side in the longitudinal direction thereof. The two lead parts are embedded in the ceramic substrate on the other end side in the longitudinal direction thereof, and are respectively connected to one end and the other end of the heating resistor. The two surface electrodes are respectively positioned on both principal surfaces of the ceramic substrate. The plurality of via conductors respectively connect one of the two lead parts and one of the two surface electrodes, and the other of the two lead parts and the other of the two surface electrodes. In the heater, the thickness of a portion of the lead parts that is connected with the via conductors is greater than the thickness of the other portions of the lead parts.

Description

heater

[0001] The present disclosure relates to a heater.

[0002] Conventionally, in order to realize a small and slim heater, surface electrodes have been provided on both main surfaces of the heater to ensure the surface electrode area (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2000-77171

[0004] A heater according to one aspect of the present disclosure includes a ceramic substrate, a heating resistor, two lead portions, two surface electrodes, and a plurality of via conductors. The heating resistor is embedded in one longitudinal end of the ceramic substrate. The two lead portions are embedded in the other longitudinal end of the ceramic substrate and are connected to one end and the other end of the heating resistor, respectively. The two surface electrodes are located on both main surfaces of the ceramic substrate. The plurality of via conductors connect one of the two lead portions to one of the two surface electrodes, and connect the other of the two lead portions to the other of the two surface electrodes, respectively. In the heater, the thickness of the connection portion between the via conductors in the lead portion is thicker than the thickness of other portions of the lead portion.

[0005] FIG. 1 is a perspective view showing an example of a heater according to the first embodiment. FIG. 2 is an exploded perspective view showing an example of a heater according to the first embodiment. FIG. 3 is a plan view showing an example of a heater according to the first embodiment. FIG. 4 is a bottom view showing an example of a heater according to the first embodiment. FIG. 5 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 6 is a cross-sectional view taken along line B-B in FIG. 1. FIG. 7 is a cross-sectional view taken along line C-C in FIG. 1. FIG. 8 is an enlarged view of region D in FIG. 5. FIG. 9 is a cross-sectional view showing another example of a heater according to the first embodiment. FIG. 10 is a cross-sectional view showing another example of a heater according to the first embodiment. FIG. 11 is an enlarged view showing another example of a heater according to the first embodiment. FIG. 12 is a perspective view showing an example of a heater according to a second embodiment. FIG. 13 is an exploded perspective view showing an example of a heater according to the second embodiment. FIG. 14 is a cross-sectional view taken along line E-E in FIG. 12. FIG. 15 is a cross-sectional view taken along line F-F in FIG. 12. FIG. 16 is a cross-sectional view taken along line G-G in FIG. 12. FIG. 17 is a cross-sectional view taken along line H-H in FIG. 12.

[0006] Hereinafter, a heater according to the present disclosure (hereinafter referred to as an "embodiment") will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments are given the same reference numerals, and redundant explanations will be omitted.

[0007] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0008] In addition, in the drawings referred to below, for ease of understanding, an orthogonal coordinate system may be shown in which the X-axis direction, Y-axis direction, and Z-axis direction, which are perpendicular to each other, are defined, and the positive Z-axis direction is the vertically upward direction.

[0009] In recent years, heaters have been required to be smaller and slimmer, and there is also an increasing demand for rapid heating. Here, the connection between the lead portion of the internal electrode and the via conductor is prone to become a heat spot, and repeated use of the heater can increase the electrical resistance of the connection, making it difficult for the heater to heat up. In such a situation, increasing the voltage applied to the heater to increase the heater temperature can place a heavy load on the heater, potentially reducing its durability.

[0010] Under these circumstances, there is a need for a technology that can improve the durability of heaters.

[0011] First Embodiment First, a heater according to a first embodiment will be described with reference to FIGS. 1 to 8. FIG. 1 is a perspective view showing an example of a heater according to the first embodiment. FIG. 2 is an exploded perspective view showing an example of a heater according to the first embodiment. FIG. 3 is a plan view showing an example of a heater according to the first embodiment. FIG. 4 is a bottom view showing an example of a heater according to the first embodiment. FIG. 5 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 6 is a cross-sectional view taken along line B-B in FIG. 1. FIG. 7 is a cross-sectional view taken along line C-C in FIG. 1. FIG. 8 is an enlarged view of region D in FIG. 5. Note that, although the lead layer 33 and the electrode layer 60 are actually integrated by firing, they are shown as separate bodies in FIGS. 2 and 5 to 7 for ease of explanation. FIG. 8 shows the lead layer 33 and the electrode layer 60 integrated together. The electrode layer 60 is omitted from FIG. 1.

[0012] As shown in FIGS. 1 to 4, the heater 1 according to the first embodiment includes a ceramic substrate 10, a heating resistor 20, lead portions 30, surface electrodes 40, and via conductors 50.

[0013] The ceramic substrate 10 is, for example, a flat plate-shaped member having a first main surface 10a, a second main surface 10b opposite the first main surface 10a, and four side surfaces 10c to 10f connecting the first main surface 10a and the second main surface 10b. The pair of side surfaces 10c and 10d are side surfaces along the longitudinal direction (X-axis direction) of the ceramic substrate 10. The pair of side surfaces 10e and 10f are side surfaces perpendicular to the longitudinal direction of the ceramic substrate 10, with the side surface 10e being located at one end of the ceramic substrate 10 in the longitudinal direction. The side surface 10f is located at the other end of the ceramic substrate 10 in the longitudinal direction.

[0014] The material of the ceramic substrate 10 is, for example, an insulating ceramic. This makes it possible to provide a heater 1 that is highly reliable during rapid temperature rise. The material of the ceramic substrate 10 can be, for example, oxide ceramics, nitride ceramics, or carbide ceramics. Specifically, alumina ceramics, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, etc. can be used.

[0015] The ceramic substrate 10 is formed, for example, by laminating a plurality of ceramic materials. The ceramic substrate 10 includes, for example, an upper ceramic substrate 11 and a lower ceramic substrate 12. The upper ceramic substrate 11 and the lower ceramic substrate 12 may be, for example, plate-like members having a predetermined shape. The upper ceramic substrate 11 and the lower ceramic substrate 12 may be bonded together with a bonding material, for example, or may be integrally molded by laminating them and then processing them, such as by firing.

[0016] 1 to 6, the heating resistor 20 and the lead portion 30 are located between the upper ceramic substrate 11 and the lower ceramic substrate 12. As a result, the heating resistor 20 and the lead portion 30 are embedded in the ceramic substrate 10.

[0017] The heating resistor 20 is embedded in one longitudinal end of the ceramic substrate 10, and the lead portion 30 is embedded in the other longitudinal end of the ceramic substrate 10. Here, the one longitudinal end may be, for example, one of two regions obtained by dividing the ceramic substrate 10 at a predetermined position in the longitudinal direction of the ceramic substrate 10, the region including the side surface 10e. Furthermore, the other longitudinal end may be, for example, one of two regions obtained by dividing the ceramic substrate 10 at a predetermined position in the longitudinal direction of the ceramic substrate 10, the region including the side surface 10f.

[0018] The heating resistor 20 is a member that generates heat when a current flows through it. The heating resistor 20 may be made mainly of tungsten, for example. The shape of the heating resistor 20 is not limited to the folded-over shape shown in FIGS. 1 and 2 , and can be changed as appropriate depending on the heating characteristics required of the heater 1, for example.

[0019] The lead portion 30 is electrically connected to the heating resistor 20. The lead portion 30 has a first lead portion 31 and a second lead portion 32. The first lead portion 31 is located closer to the side surface 10d than the second lead portion 32. The second lead portion 32 is located closer to the side surface 10c than the first lead portion 31. The first lead portion 31 extends in the longitudinal direction of the ceramic substrate 10 and is connected to one end of the heating resistor 20. The second lead portion 32 extends in the longitudinal direction of the ceramic substrate 10 and is connected to the other end of the heating resistor 20.

[0020] The lead portion 30 may be mainly composed of tungsten, for example, like the heating resistor 20. The lead portion 30 may be formed to be wider than the heating resistor 20. The lead portion 30 may be formed using a material different from that of the heating resistor 20.

[0021] The surface electrode 40 is connected to an external power supply and is electrically connected to the heating resistor 20 via the via conductors 50 and the lead portions 30. Power supplied from the external power supply is supplied to the heating resistor 20 via the surface electrode 40, the via conductors 50, and the lead portions 30. The surface electrode 40 has a first surface electrode 41 and a second surface electrode 42. The first surface electrode 41 is located on the first main surface 10a. The second surface electrode 42 is located on the second main surface 10b. One of the first surface electrode 41 and the second surface electrode 42 is an anode and the other is a cathode. Note that the first surface electrode 41 is omitted from FIG. 6 .

[0022] The surface electrode 40 may be, for example, a sintered body of tungsten plated with nickel, or a plate material containing a metal material such as nickel, iron, or a nickel-based heat-resistant alloy. The surface electrode 40 may be, for example, rectangular.

[0023] The via conductors 50 are located on the other longitudinal end side of the ceramic substrate 10. The via conductors 50 extend inward from the first main surface 10a or the second main surface 10b of the ceramic substrate 10 in the vertical direction (Z-axis direction) of the ceramic substrate 10 and are electrically connected to the heating resistor 20 via the lead portions 30. The via conductors 50 include a plurality (two in this example) of first via conductors 51 and a plurality (two in this example) of second via conductors 52. The first via conductors 51 are located between the first lead portion 31 and the first surface electrode 41, and electrically connect the first lead portion 31 and the first surface electrode 41. The second via conductors 52 are located between the second lead portion 32 and the second surface electrode 42, and electrically connect the second lead portion 32 and the second surface electrode 42. The heater 1 is required to include at least one first via conductor 51 and at least one second via conductor 52.

[0024] The via conductor 50 may be, for example, rod-shaped. The via conductor 50 may be integral with the lead portion 30. The via conductor 50 may be configured such that any portion of the via conductor 50 is connected to a thick portion P (see FIGS. 5 and 6 ) of the lead portion 30, which will be described later. The via conductor 50 may be made of a metal material containing, for example, tungsten.

[0025] The lead portion 30 may be configured to include a lead layer 33 and an electrode layer 60. Specifically, the first lead portion 31 may be configured to include a first lead layer 34 and a first electrode layer 61. Furthermore, the second lead portion 32 may be configured to include a second lead layer 35 and a second electrode layer 62.

[0026] The first lead layer 34 and the second lead layer 35 both extend along the longitudinal direction of the ceramic substrate 10 and are connected to the heating resistor 20. Specifically, the first lead layer 34 is connected to one end of the heating resistor 20, and the second lead layer 32 is connected to the other end of the heating resistor 20. The first lead layer 34 and the second lead layer 35 may have a constant thickness along the longitudinal direction.

[0027] The electrode layer 60 may be located at a connection portion of the lead layer 33 with the via conductors 50. Specifically, as shown in Fig. 5, the first electrode layer 61 may be located at a connection portion of the first lead layer 34 with the plurality of first via conductors 51. In other words, the first electrode layer 61 may be located in a region overlapping with the plurality of first via conductors 51 when the heater 1 is viewed in a plan view. The first electrode layer 61 may be in contact with the first lead layer 34 in the thickness direction of the ceramic substrate 10 (here, the Z-axis direction). The first electrode layer 61 may be located at a position facing the plurality of first via conductors 51 with the first lead layer 34 interposed therebetween.

[0028] 6 , the second electrode layer 62 may be located in a connection portion of the second lead layer 35 with the plurality of second via conductors 52. In other words, the second electrode layer 62 may be located in a region overlapping with the plurality of second via conductors 52 when the heater 1 is viewed in a plan view. The second electrode layer 62 may be in contact with the second lead layer 35 in the thickness direction of the ceramic substrate 10 (here, the Z-axis direction). For example, the second electrode layer 62 may be located between the second lead layer 35 and the plurality of second via conductors 52.

[0029] In this way, the thick portion P of the first lead portion 31 may be composed of a part of the first lead layer 34 and the first electrode layer 61. Furthermore, the thick portion P of the second lead portion 32 may be composed of a part of the second lead layer 35 and the second electrode layer 62.

[0030] The electrode layer 60 may be primarily composed of tungsten, as in the lead layer 33. In this case, the electrical resistance of the electrode layer 60 can be made smaller than that of the lead layer 33 by differentiating the additives contained in the electrode layer 60 from those in the lead layer 33. The electrical resistance of the electrode layer 60 can also be made smaller than that of the lead layer 33 by differentiating the particle size of tungsten. Alumina and a trace amount of calcium may be added to the electrode layer 60 and the lead layer 33 to increase the adhesive strength. The electrode layer 60 may be rectangular, for example. It is preferable that the area of ​​the electrode layer 60 be larger than the cross-sectional area of ​​the via conductor 50 in the horizontal direction (XY direction).

[0031] 5 to 8, in the heater 1 according to the first embodiment, an electrode layer 60 is located at the connection portion of the lead portion 30 with the via conductor 50. As a result, the connection portion of the lead portion 30 with the via conductor 50 becomes a portion P that is thicker than other portions of the lead portion 30. For example, the portion of the lead portion 30 where the electrode layer 60 is located has a thickness from the upper surface of the lead layer 33 to the lower surface of the electrode layer 60, which is thicker than other portions of the lead portion 30, i.e., portions formed only by the lead layer 33.

[0032] In this way, the thickness of the connection portion of the lead portion 30 with the via conductor 50 is made thicker than the thickness of other portions of the lead portion 30. This makes it possible to lower the electrical resistance of the connection portion of the lead portion 30 with the via conductor 50 compared to when the thickness of the connection portion of the lead portion 30 with the via conductor 50 is the same as the thickness of other portions of the lead portion 30. This suppresses a temperature rise in the connection portion of the lead portion 30 with the via conductor 50. By suppressing a temperature rise in the connection portion of the lead portion 30 with the via conductor 50, the electrical resistance of the connection portion of the lead portion 30 with the via conductor 50 is less likely to increase even with repeated use of the heater 1, and therefore a decrease in heater temperature is less likely to occur. Therefore, there is less need to increase the voltage applied to the heater 1 to increase the heater temperature, and the heater 1 is less likely to be subjected to a large load. This improves the durability of the heater 1.

[0033] The following methods can be used to make the thickness of the connection portion of the lead portion 30 with the via conductor 50 thicker than the thickness of other portions of the lead portion 30. For example, one method is to form the lead portion 30 using a dispenser or the like, thereby partially controlling the thickness in the process of forming one layer of the lead portion 30, or to form the lead portion 30 with a controlled thickness on a PET film in advance and then transfer it. Therefore, the thickness itself can have the above configuration whether it is a single layer or a multilayer.

[0034] Furthermore, the thick portion P of the lead portion 30 is composed of two layers: the lead layer 33 and the electrode layer 60. As a result, even if the connection portion between the lead portion 30 and the via conductor 50 suddenly thermally expands when an inrush voltage is applied, the heater 1 can disperse the stress caused by the thermal expansion by the thermal expansion of the lead layer 33 and the electrode layer 60. As a result, the durability of the heater 1 can be improved.

[0035] The electrode layer 60 may also have multiple layers. This allows the heater 1 to disperse stress due to thermal expansion even when the connection between the lead portion 30 and the via conductor 50 undergoes rapid thermal expansion when an inrush voltage is applied, as the multiple electrode layers 60 each thermally expand. As a result, the durability of the heater 1 can be improved. When the electrode layer 60 has multiple layers, for example, methods of varying the particle size of tungsten or adjusting the additives contained therein can be used.

[0036] Here, an example is shown in which the thick portion P of the lead portion 30 is composed of two layers, the lead layer 33 and the electrode layer 60, but the thick portion P of the lead portion 30 may be composed of three or more layers. Also, the thick portion P of the lead portion 30 may be a single layer.

[0037] The thick portion P of the first lead portion 31 may be configured in a rectangular shape that overlaps two first via conductors 51 in a planar view. Similarly, the thick portion P of the second lead portion 32 may be configured in a rectangular shape that overlaps two second via conductors 52 in a planar view. That is, when the heater 1 is configured such that multiple via conductors 50 are connected to one lead portion 30, the thick portion P of the lead portion 30 may be located in a region that includes the multiple via conductors 50 in a planar view. In this case, the thickness of the first lead portion 31 located between the two first via conductors 51 and the thickness of the second lead portion 32 located between the two second via conductors 52 are increased. This allows the areas between the two first via conductors 51 and the two second via conductors 52 to be low-resistance areas. This makes it less likely for heat to be trapped between the two first via conductors 51 and the two second via conductors 52, thereby further suppressing temperature increases at the connection portions of the lead portion 30 with the via conductors 50. Therefore, the durability of the heater 1 can be further improved.

[0038] 9 and 10 are also possible as another example of the heater 1 according to the first embodiment. FIGS. 9 and 10 are cross-sectional views showing another example of the heater 1 according to the first embodiment. Note that, in FIGS. 9 and 10 , the lead layer 33 and the electrode layer 60 are shown as separate entities, as in the above, for convenience of explanation. As shown in FIGS. 9 and 10 , the first electrode layer 61 may be positioned individually for each of the two first via conductors 51. The second electrode layer 62 may be positioned individually for each of the two second via conductors 52. In other words, in a configuration in which a plurality of via conductors 50 are connected to one lead portion 30, the thick portions P of the lead portion 30 may be formed individually for each of the plurality of via conductors 50.

[0039] The thick portion P of the first lead portion 31 according to the first embodiment will be described in detail below with further reference to Figures 1 to 8 and 11. Figure 11 is an enlarged view showing another example of the heater 1 according to the first embodiment. Note that in Figure 11, as with the above, the lead layer 33 and the electrode layer 60 are shown as separate entities for convenience of explanation.

[0040] For example, in the thick portion P of the lead portion 30, the end of the lead layer 33 and the end of the electrode layer 60 may not be aligned at the other longitudinal end of the ceramic substrate 10 (see FIGS. 5 and 6 ). For example, in the example shown in FIGS. 5 and 6 , the end of the first lead layer 34 is offset toward the positive X-axis direction relative to the end of the first electrode layer 61, and the end of the second lead layer 35 is offset toward the positive X-axis direction relative to the end of the second electrode layer 62. In this manner, the heater 1 may be configured so that multiple layers are offset. This allows the thickness of the ceramic substrate 10 to gradually decrease toward the end at the other longitudinal end (see FIG. 8 ). Therefore, even if the lead portion 30 is heated and thermally expanded, stress is less likely to concentrate at the end of the lead portion 30. As a result, the durability of the heater 1 can be improved.

[0041] Furthermore, in the heater 1, the thick portion P of the lead portion 30 may be contained within the region inside the surface electrode 40 in a plan view. This allows the heater 1 to easily dissipate heat from the connection portion between the lead portion 30 and the via conductor 50 from the surface electrode 40. As a result, the durability of the heater 1 can be improved.

[0042] Furthermore, as described above, the electrode layer 60 may have a lower electrical resistance than the lead layer 33. In such a configuration, when an inrush voltage is applied to the heater 1, current flows preferentially to the electrode layer 60, which has a lower electrical resistance, and therefore damage to the lead layer 33, which is directly connected to the heating resistor 20, can be reduced. This further improves the durability of the heater 1.

[0043] For example, the first surface electrode 41 may be connected to the positive electrode of an external power supply. The second surface electrode 42 may be connected to the negative electrode of the external power supply. That is, the two surface electrodes 40 may be composed of a positive surface electrode 40 and a negative surface electrode 40. The thick portions P of the lead portion 30 are located in the lead portion 30 (first lead portion 31) connected to the positive surface electrode 40 (first surface electrode 41) and in the lead portion 30 (second lead portion 32) connected to the negative surface electrode 40 (second surface electrode 42). By having the thick portions P located in both the first lead portion 31 and the second lead portion 32, the heater 1 can disperse inrush voltage. As a result, the durability of the heater 1 can be improved.

[0044] 11 , for example, the first lead portion 31 may be formed to be particularly thick directly below the first via conductor 51 (particularly near the center of the first via conductor 51). Similarly, although not shown, the second lead portion 32 may be formed to be particularly thick directly above the second via conductor 52 (particularly near the center of the second via conductor 52). That is, the heater 1 may be formed so that the thickness of the thick portion P of the lead portion 30 that overlaps with the via conductor 50 in a plan view is the thickest. This allows the heater 1 to further reduce inrush voltage. Furthermore, the heater 1 can also reduce thermal shock. As a result, the durability of the heater 1 can be improved.

[0045] Second Embodiment FIG. 12 is a perspective view showing an example of a heater according to a second embodiment. FIG. 13 is an exploded perspective view showing an example of a heater according to the second embodiment. FIG. 14 is a cross-sectional view taken along line E-E in FIG. 12. FIG. 15 is a cross-sectional view taken along line F-F in FIG. 12. FIG. 16 is a cross-sectional view taken along line G-G in FIG. 12. FIG. 17 is a cross-sectional view taken along line H-H in FIG. 12. As with the above, in FIGS. 13 to 17, the lead layer 33 and the electrode layer 60 are shown as separate entities for the sake of convenience. Also, the electrode layer 60 is omitted in FIG. 12. The second surface electrode 42 is omitted in FIG. 14. The first surface electrode 41 is omitted in FIG. 15.

[0046] 12 and 13 , the first lead layer 34 of the first lead portion 31 may be substantially L-shaped. Specifically, the first lead layer 34 may extend from one end of the heating resistor 20 in the longitudinal direction of the ceramic substrate 10, and then change direction at the other end of the ceramic substrate 10 to extend toward the side surface 10 c. The first electrode layer 61 may be located in a portion of the first lead layer 34 that extends toward the side surface 10 c. In other words, the thick portion P of the first lead portion 31 may be located in the portion of the first lead layer 34 that extends toward the side surface 10 c.

[0047] The second lead layer 35 of the second lead portion 32 may also be substantially L-shaped. Specifically, the second lead layer 35 extends from one end of the heating resistor 20 in the longitudinal direction of the ceramic substrate 10, changes direction just before the first lead layer 34, and extends toward the side surface 10d. The second electrode layer 62 may be located in a portion of the second lead layer 35 that extends toward the side surface 10d. In other words, the thick portion P of the second lead portion 32 may be located in a portion of the second lead layer 35 that extends toward the side surface 10d.

[0048] An imaginary line L connecting the thick portion P of the lead portion 30 connected to the positive surface electrode 40 and the thick portion P of the lead portion 30 connected to the negative surface electrode 40 may be parallel to the longitudinal direction of the ceramic substrate 10. In other words, the thick portion P of the lead portion 30 connected to the positive surface electrode 40 and the thick portion P of the lead portion 30 connected to the negative surface electrode 40 may be aligned in the longitudinal direction of the ceramic substrate 10. This allows the easily heated positions of the positive and negative surface electrodes 40 to be shifted in the longitudinal direction of the ceramic substrate 10, thereby further dispersing heat in the small and slim heater 1. As a result, the durability of the heater 1 can be improved.

[0049] For example, the first surface electrode 41 is connected to the positive electrode of an external power supply. The second surface electrode 42 is connected to the negative electrode of the external power supply. That is, the thicker portion P of the lead portion 30 connected to the positive surface electrode 40 is located closer to the other longitudinal end of the ceramic substrate 10 than the thicker portion P of the lead portion 30 connected to the negative surface electrode 40. Because the positive electrode of the heater 1 becomes hotter than the negative electrode, locating the positive electrode at the rear end of the heater 1, where the temperature is lowest, facilitates heat dissipation. Furthermore, the positive electrode can be separated from the heating region at one longitudinal end of the heater 1. As a result, the durability of the heater 1 can be improved.

[0050] Although the present disclosure has been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. are possible within the scope that does not deviate from the gist of the present disclosure.

[0051] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0052] The present technology can also be configured as follows: (1) A heater comprising: a ceramic substrate; a heating resistor embedded at one longitudinal end of the ceramic substrate; two lead portions embedded at the other longitudinal end of the ceramic substrate and connected to one end and the other end of the heating resistor, respectively; two surface electrodes located on both main surfaces of the ceramic substrate; and a plurality of via conductors connecting one of the two lead portions to one of the two surface electrodes, and connecting the other of the two lead portions to the other of the two surface electrodes, respectively, wherein a thickness of a connection portion of the lead portion with the via conductor is thicker than a thickness of other portions of the lead portion. (2) The heater according to (1), wherein a plurality of the via conductors are connected to one of the lead portions, and a thicker portion of the lead portion is located in a region including the plurality of via conductors in a plan view. (3) The heater according to (1) or (2), wherein the thick portion of the lead portion comprises: a lead layer connected to the heating resistor; and an electrode layer in contact with the lead layer in the thickness direction of the ceramic substrate. (4) The heater according to (3), wherein the electrical resistance of the electrode layer is smaller than the electrical resistance of the lead layer. (5) The heater according to any one of (1) to (4), wherein the thick portion of the lead portion is located in both the lead portion connected to one of the two surface electrodes and the lead portion connected to the other of the two surface electrodes. (6) The heater according to any one of (1) to (5), wherein the thickest portion of the lead portion is the portion that overlaps the via conductor in a plan view. (7) The heater according to any one of (1) to (6), wherein the two surface electrodes are composed of a positive surface electrode and a negative surface electrode, and an imaginary line connecting the thicker part of the lead portion connected to the positive surface electrode and the thicker part of the lead portion connected to the negative surface electrode is parallel to the longitudinal direction of the ceramic substrate.(8) The heater according to (7), wherein the thicker portion of the lead portion connected to the surface electrode of the positive electrode is located closer to the other longitudinal end of the ceramic substrate than the thicker portion of the lead portion connected to the surface electrode of the negative electrode.

[0053] REFERENCE SIGNS LIST 1 heater 10 ceramic substrate 10a first main surface 10b second main surface 20 heating resistor 30 lead portion 31 first lead portion 32 second lead portion 33 lead layer 34 first lead layer 35 second lead layer 40 surface electrode 41 first surface electrode 42 second surface electrode 50 via conductor 51 first via conductor 52 second via conductor 60 electrode layer 61 first electrode layer 62 second electrode layer L imaginary line P portion

Claims

1. A heater comprising: a ceramic substrate; a heating resistor embedded at one longitudinal end of the ceramic substrate; two lead portions embedded at the other longitudinal end of the ceramic substrate and connected to one end and the other end of the heating resistor, respectively; two surface electrodes located on both main surfaces of the ceramic substrate; and a plurality of via conductors connecting one of the two lead portions to one of the two surface electrodes, and connecting the other of the two lead portions to the other of the two surface electrodes, respectively; wherein the thickness of the connection portion between the via conductors in the lead portions is greater than the thickness of other portions of the lead portions.

2. The heater according to claim 1, wherein a plurality of the via conductors are connected to one of the lead portions, and the thicker portion of the lead portion is located in an area including the plurality of via conductors in a plan view.

3. A heater as described in claim 1 or claim 2, wherein the thick portion of the lead portion comprises a lead layer connected to the heating resistor, and an electrode layer in contact with the lead layer in the thickness direction of the ceramic substrate.

4. The heater according to claim 3, wherein the electrical resistance of said electrode layer is smaller than the electrical resistance of said lead layer.

5. A heater as described in any one of claims 1 to 4, wherein the thicker portions of the lead portion are located both in the lead portion connected to one of the two surface electrodes and in the lead portion connected to the other of the two surface electrodes.

6. A heater according to any one of claims 1 to 5, wherein, among the thicker portions of the lead portion, the portion overlapping the via conductor in a plan view is the thickest.

7. A heater as described in any one of claims 1 to 6, wherein the two surface electrodes are composed of a positive surface electrode and a negative surface electrode, and an imaginary line connecting the thicker part of the lead portion connected to the positive surface electrode and the thicker part of the lead portion connected to the negative surface electrode is parallel to the longitudinal direction of the ceramic substrate.

8. A heater as described in claim 7, wherein the thicker portion of the lead portion connected to the positive surface electrode is located closer to the other longitudinal end of the ceramic substrate than the thicker portion of the lead portion connected to the negative surface electrode.

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