heater

Abstract

To provide a heater with excellent heat distribution. [Solution] A heater comprising a disc-shaped base and a plurality of wirings as a heating element disposed inside the base, wherein the plurality of wirings comprises a first wiring and a second wiring arranged at intervals in a first direction along the thickness of the base, the first wiring comprises a first high potential portion and a first low potential portion, the second wiring comprises a second high potential portion and a second low potential portion, and when the plurality of wirings are viewed in the first direction, there is an overlapping region where the first wiring and the second wiring overlap, the overlapping region comprises a first region and a second region, the first region is the region where the first high potential portion and the second high potential portion overlap, and the second region is the region where the first low potential portion and the second low potential portion overlap, and the average potential difference V between the first wiring and the second wiring in each of the first region and the second region is smaller than the value obtained by √{(α×ρ×L) / S1}.

Description

[Technical Field]

[0001] This disclosure relates to heaters. [Background technology]

[0002] Patent Document 1 discloses a heating heater equipped with a mounting base on which an object to be heated is placed. Multiple heating circuits are embedded inside the mounting base. The multiple heating circuits are arranged in layers with spacing along the thickness of the mounting base. Hereinafter, the mounting base will be referred to as the base body, and the heating circuits as wiring. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-174713 [Overview of the project] [Problems that the invention aims to solve]

[0004] When multiple wires are spaced apart along the thickness of the substrate, depending on the volume resistivity of the substrate and the circuit pattern of the multiple wires, current may leak between adjacent wires in a specific direction, potentially causing a localized rise in the substrate temperature.

[0005] One of the objectives of this disclosure is to provide a heater with excellent uniform heating properties. [Means for solving the problem]

[0006] The heater of this disclosure comprises a disc-shaped substrate and a plurality of wirings arranged inside the substrate as a heating element. The plurality of wirings comprises a first wiring and a second wiring arranged at intervals in a first direction along the thickness of the substrate. The first wiring comprises a first high-potential portion and a first low-potential portion. The second wiring comprises a second high-potential portion and a second low-potential portion. The heater of this disclosure has an overlapping region where the first wiring and the second wiring overlap when viewed in the first direction. The overlapping region comprises a first region and a second region. The first region is the region where the first high-potential portion and the second high-potential portion overlap. The second region is the region where the first low-potential portion and the second low-potential portion overlap. The average potential difference V between the first wiring and the second wiring in each of the first and second regions is smaller than the value obtained by √{(α×ρ×L) / S1}, where α is a predetermined allowable heat generation amount in W. ρ is the volume resistivity of the substrate, and its unit is Ω·m. L is the distance between the first and second wiring along the first direction, and its unit is mm. S1 is the area of ​​the first region and the second region when viewed in the first direction, and its unit is mm. 2 That is the case. [Effects of the Invention]

[0007] The heater of this disclosure has excellent uniform heating properties. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing the heater of Embodiment 1. [Figure 2] Figure 2 is a schematic diagram showing an example of the multiple wirings provided in the heater of Embodiment 1. [Figure 3] Figure 3 is a schematic diagram showing the first wiring shown in Figure 2. [Figure 4] Figure 4 is a schematic diagram showing the second wiring shown in Figure 2. [Figure 5] Figure 5 is a schematic cross-sectional view showing a portion of the overlapping area between the first and second wiring shown in Figure 2. [Figure 6]Figure 6 is a schematic diagram showing an example of the multiple wirings provided in the heater of Embodiment 2. [Figure 7] Figure 7 is a schematic diagram showing the second wiring shown in Figure 6. [Figure 8] Figure 8 is a graph showing the heat output of the heater and the degree of deterioration in heat distribution as measured in the test example. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] (1) A heater according to one aspect of the present disclosure comprises a disc-shaped base and a plurality of wirings as a heating element disposed inside the base. The plurality of wirings comprises a first wiring and a second wiring arranged at intervals in a first direction along the thickness of the base. The first wiring comprises a first high-potential portion and a first low-potential portion. The second wiring comprises a second high-potential portion and a second low-potential portion. The heater has an overlapping region where the first wiring and the second wiring overlap when viewed in the first direction. The overlapping region comprises a first region and a second region. The first region is the region where the first high-potential portion and the second high-potential portion overlap. The second region is the region where the first low-potential portion and the second low-potential portion overlap. The average potential difference V between the first wiring and the second wiring in each of the first and second regions is less than the value obtained by √{(α×ρ×L) / S1}, where α is a predetermined allowable heat generation amount, and its unit is W. ρ is the volume resistivity of the substrate, and its unit is Ω·m. L is the distance between the first and second wiring along the first direction, and its unit is mm. S1 is the area of ​​the first region and the second region when viewed in the first direction, and its unit is mm. 2 That is the case.

[0011] In the heater of (1) above, even if the first wiring and the second wiring overlap when the plurality of wirings are viewed along the first direction, the average potential difference V between the first wiring and the second wiring in the overlapping region is smaller than a specific value. Therefore, in the heater of (1) above, current hardly leaks between the first wiring and the second wiring. Since current hardly leaks between the first wiring and the second wiring, the temperature of the base is unlikely to rise locally. Therefore, the heater of (1) above is excellent in temperature uniformity.

[0012] (2) In the heater according to (1) above, the overlapping region may consist of two regions, the first region and the second region.

[0013] In the heater of (2) above, when the first wiring and the second wiring overlap when the plurality of wirings are viewed along the first direction, high potential portions overlap each other and low potential portions overlap each other. In other words, the high potential portion and the low potential portion do not overlap between the first wiring and the second wiring. Therefore, regardless of the volume resistivity of the base, current hardly leaks between the first wiring and the second wiring. With the heater of (2) above, the degree of freedom in selecting the material of the base is high.

[0014] (3) In the heater according to (1) above, the overlapping region may include at least one of a third region and a fourth region. The third region is a region where the first high potential portion and the second low potential portion overlap. The fourth region is a region where the first low potential portion and the second high potential portion overlap. The average potential difference V between the first wiring and the second wiring in each of the third region and the fourth region is smaller than the value obtained by √{(α×ρ×L) / S2}, where S2 is the area of each of the third region and the fourth region when viewed along the first direction, and the unit is mm 2 .

[0015] In the heater of (3) above, even if the high potential portion and the low potential portion overlap between the first wiring and the second wiring when the plurality of wirings are viewed along the first direction, the average potential difference V between the first wiring and the second wiring in the overlapping region is also smaller than a specific value. Therefore, in the heater of (3) above, current hardly leaks even between the high potential portion and the low potential portion adjacent in the first direction.

[0016] (4) In the heater according to any one of (1) to (3) above, α, which is the allowable calorific value, may be 5 W or less.

[0017] When the allowable calorific value is 5 W or less, for example, as shown in a test example described later, the degree of deterioration in temperature uniformity of the base can be 2°C or less.

[0018] (5) In the heater according to any one of (1) to (4) above, the first wiring may include a first circuit pattern arranged in a region including a center of the base. The second wiring may include: a second circuit pattern arranged in an annular region surrounding the first circuit pattern; and a first lead portion and a second lead portion arranged from the second circuit pattern toward the center of the base.

[0019] Since the first circuit pattern is arranged in the region including the center of the base, and the second circuit pattern is arranged in the annular region surrounding the first circuit pattern, the temperature uniformity of the heater can be improved by controlling the temperatures of the first wiring and the second wiring independently of each other. Since the first lead portion and the second lead portion are arranged from the second circuit pattern toward the center of the base, connection portions of the first wiring and the second wiring to terminals can be concentrated in the vicinity of the center of the base.

[0020] (6) In any of the heaters described in (1) to (4) above, the first wiring may include a first circuit pattern arranged in a region including the center of the base. The first circuit pattern may include a plurality of curved sections arranged along different circumferences concentric with the base, and a plurality of folded sections connecting adjacent curved sections so that the plurality of curved sections are connected in a series. The plurality of curved sections may include a plurality of first curved sections formed in the first high-potential section and a plurality of second curved sections formed in the first low-potential section. A portion of the plurality of first curved sections may include a first section arranged between adjacent second curved sections. A portion of the plurality of second curved sections may include a second section arranged between adjacent first curved sections. The second wiring may include a second circuit pattern arranged in an annular region surrounding the first circuit pattern, a first lead section formed in the second high-potential section, and a second lead section formed in the second low-potential section. The first lead portion may be positioned from the second circuit pattern toward the center of the base so as not to overlap the second portion when viewed in the first direction. The second lead portion may be positioned from the second circuit pattern toward the center of the base so as not to overlap the part when viewed in the first direction.

[0021] In the first circuit pattern, the uniformity of the heater can be improved by arranging the first curved section between adjacent second curved sections, and the second curved section between adjacent first curved sections. The first lead section is arranged so as not to overlap with the second section when viewed in the first direction, and the second lead section is arranged so as not to overlap with the first section, so that the high-potential section and the low-potential section do not overlap between the first wiring and the second wiring when viewed in the first direction. Therefore, in the heater of (6) above, current is less likely to leak between the first wiring and the second wiring, regardless of the volume resistivity of the substrate. The heater of (6) above has superior uniformity of heat because current is less likely to leak between the first wiring and the second wiring, and the uniformity of heat can be improved by the first circuit pattern and the second circuit pattern.

[0022] [Details of the embodiments of this disclosure] Specific examples of the heaters of this disclosure will be described with reference to the drawings. Identical reference numerals in the drawings indicate the same or corresponding parts. In each drawing, some parts of the configuration may be exaggerated or simplified for illustrative purposes. The dimensional ratios of parts in the drawings may also differ from those of the actual components. However, the present invention is not limited to these examples and is as defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended.

[0023] <Embodiment 1> ≪Overview≫ The heater 1 of Embodiment 1 will be described with reference to Figures 1 to 5. As shown in Figure 1, the heater 1 comprises a base 2 and a plurality of wires 4 as heating elements. The plurality of wires 4 are arranged inside the base 2. The plurality of wires 4 comprises first wires 5 and second wires 6 that are spaced apart in a first direction D1 along the thickness of the base 2. As shown in Figures 2 and 3, the first wire 5 comprises a first high-potential portion 5H and a first low-potential portion 5L. As shown in Figures 2 and 4, the second wire 6 comprises a second high-potential portion 6H and a second low-potential portion 6L.

[0024] In Figure 2, the first wiring 5 is shown as a solid line, and the second wiring 6 is shown as a dashed line. In Figures 2 and 3, the first high-potential section 5H is hatched. In Figures 2 and 4, the second high-potential section 6H is hatched.

[0025] As shown in Figure 2, the heater 1 has an overlapping region 7 where the first wire 5 and the second wire 6 overlap when viewed in the first direction D1 with respect to the multiple wires 4. The overlapping region 7 comprises a first region 71 and a second region 72. The overlapping region 7 may further comprise at least one of a third region 73 and a fourth region 74. The first region 71 and the second region 72 are mandatory regions, while the third region 73 and the fourth region 74 are optional regions. In this example, the overlapping region 7 comprises the first region 71, the second region 72, the third region 73, and the fourth region 74, as shown in Figure 2.

[0026] One of the features of the heater 1 of Embodiment 1 is that the average potential difference V between the first wiring 5 and the second wiring 6 in each of the first region 71, second region 72, third region 73, and fourth region 74 is smaller than a specific value.

[0027] ≪Base≫ The base body 2 is a disk. As shown in Figure 1, the base body 2 has a first surface 21 and a second surface 22. The first surface 21 and the second surface 22 face each other. A heating object (not shown) is placed on the first surface 21. The heating object is, for example, a wafer such as a semiconductor. A support member 9 is attached to the second surface 22.

[0028] The material of the substrate 2 is, for example, ceramics. The ceramics are, for example, aluminum nitride, silicon nitride, silicon carbide, or aluminum oxide. The substrate 2 may also be formed from a composite material of the above ceramics and a metal. The metal is, for example, aluminum, copper, or an alloy thereof.

[0029] Wiring Wiring 4 is a heating element that heats an object placed on the first surface 21 of the base 2. Wiring 4 comprises a first wiring 5 and a second wiring 6. The first wiring 5 and the second wiring 6 are spaced apart in the first direction D1, as shown in Figure 1. The first wiring 5 and the second wiring 6 are arranged concentrically with the base 2, as shown in Figure 2. Concentricity means that when the heater 1 is viewed from above in the first direction D1, the envelope of the first wiring 5 and the envelope of the second wiring 6 have a common center, and the diameters of each envelope are different. The center of this envelope coincides with the center 20 of the base 2. The temperature of the first wiring 5 and the second wiring 6 are controlled independently of each other.

[0030] [First wiring] As shown in Figure 1, the first wiring 5 is located in a layer closer to the first surface 21 than the second wiring 6. As shown in Figure 2, the first wiring 5 is located in a region that includes the center 20 of the substrate 2.

[0031] As shown in Figure 3, the first wiring 5 comprises a first high-potential section 5H and a first low-potential section 5L. The first high-potential section 5H is a region where the potential is 1 / 2 or more of the applied voltage to the first wiring 5. The first low-potential section 5L is a region where the potential is less than 1 / 2 of the applied voltage to the first wiring 5. The first high-potential section 5H and the first low-potential section 5L are connected in series.

[0032] The first wiring 5 comprises a first circuit pattern 50 arranged in a region including the center 20 (Figure 2) of the base 2. In this example, the first circuit pattern 50 is arranged in a circular region including the center 20. The first circuit pattern 50 is formed, for example, by bending a strip-shaped portion formed by the first wiring 5. Bending of the strip-shaped portion includes bending in a spiral or meandering manner. The first circuit pattern 50 is appropriately selected according to the heating temperature and the desired temperature distribution.

[0033] The first circuit pattern 50 in this example comprises a plurality of curved sections 51 and a plurality of folded sections 52. The plurality of curved sections 51 are arranged along different circumferences concentric with the base 2. The plurality of folded sections 52 connect adjacent curved sections 51 so that the plurality of curved sections 51 are connected in a series.

[0034] Each of the multiple curved sections 51 comprises a plurality of first curved sections 51H and a plurality of second curved sections 51L. Each first curved section 51H is formed by a first high-potential section 5H. The plurality of first curved sections 51H are arranged in a line within the envelope of the first wiring 5, moving from the center of the envelope towards the outer edge. Adjacent first curved sections 51H are connected by folded sections 52 formed by the first high-potential section 5H. Each second curved section 51L is formed by a first low-potential section 5L. The plurality of second curved sections 51L are arranged in a line within the envelope of the first wiring 5, moving from the center of the envelope towards the outer edge. Adjacent second curved sections 51L are connected by folded sections 52 formed by the first low-potential section 5L. In this example, the boundary between the first curved section 51H and the second curved section 51L is on the outermost circumference of a different circle concentric with the base 2.

[0035] In this example, a portion of the multiple first curved sections 51H includes a first section 55H positioned between adjacent second curved sections 51L. In this example, a portion of the multiple second curved sections 51L includes a second section 55L positioned between adjacent first curved sections 51H. In Figure 3, the first section 55H and the second section 55L are each enclosed by dashed lines. In the first circuit pattern 50, the uniform heating of the heater 1 can be improved by providing the first curved section 51H between adjacent second curved sections 51L, and providing the second curved section 51L between adjacent first curved sections 51H. The first section 55H and the second section 55L are positioned, for example, offset in the direction along the circumference of the envelope circle of the first wiring 5.

[0036] Terminals (not shown) are connected to the first end of the first curved section 51H and the first end of the second curved section 51L. The connection point 59H for the terminal in the first curved section 51H and the connection point 59L for the terminal in the second curved section 51L are located approximately at the center of the base body 2, separated from each other.

[0037] [Second wiring] As shown in Figure 1, the second wiring 6 is located in a layer further from the first surface 21 than the first wiring 5. As shown in Figure 2, the second wiring 6 is located over a wide area from the center 20 of the substrate 2 to near the outer edge.

[0038] As shown in Figure 4, the second wiring 6 comprises a second high-potential section 6H and a second low-potential section 6L. The second high-potential section 6H is a region where the potential is 1 / 2 or more of the applied voltage to the second wiring 6. The second low-potential section 6L is a region where the potential is less than 1 / 2 of the applied voltage to the second wiring 6. The second high-potential section 6H and the second low-potential section 6L are connected in series.

[0039] The second wiring 6 comprises a second circuit pattern 60 arranged in an annular region surrounding the first circuit pattern 50. In this example, the second circuit pattern 60 is arranged in an annular region surrounding the first circuit pattern 50. The second circuit pattern 60 is formed, for example, by bending a strip-shaped portion formed by the second wiring 6. Bending of the strip-shaped portion includes bending in a spiral or meandering shape. The shape of the second circuit pattern 60 is appropriately selected according to the heating temperature and the desired temperature distribution. By arranging the first circuit pattern 50 in a circular region including the center 20 of the base 2 and the second circuit pattern 60 in an annular region surrounding the first circuit pattern 50, the uniformity of heating of the heater 1 can be improved by independently controlling the temperature of the first wiring 5 and the second wiring 6.

[0040] The second circuit pattern 60 in this example comprises a plurality of curved sections 61 and a plurality of folded sections 62. The plurality of curved sections 61 are arranged along different circumferences concentric with the base 2. The plurality of folded sections 62 connect adjacent curved sections 61 so that the plurality of curved sections 61 are connected in a series.

[0041] Each of the multiple curved sections 61 comprises a plurality of third curved sections 61H and a plurality of fourth curved sections 61L. Each third curved section 61H is formed by a second high-potential section 6H. The plurality of third curved sections 61H are arranged in a line within the envelope of the second wiring 6, moving from the center of the envelope towards the outer edge. Adjacent third curved sections 61H are connected by folded sections 62 formed by the second high-potential section 6H. Each fourth curved section 61L is formed by a second low-potential section 6L. The plurality of fourth curved sections 61L are arranged in a line within the envelope of the second wiring 6, moving from the center of the envelope towards the outer edge. Adjacent fourth curved sections 61L are connected by folded sections 62 formed by the second low-potential section 6L. In this example, the boundary between the third curved section 61H and the fourth curved section 61L is on the outermost circumference of a different circle concentric with the base 2.

[0042] In this example, the third curved section 61H and the fourth curved section 61L are arranged symmetrically. That is, in this example, when viewed in the second direction perpendicular to the first direction D1, the fourth curved section 61L is not positioned between adjacent third curved sections 61H, and the third curved section 61H is not positioned between adjacent fourth curved sections 61L. When viewed in the second direction perpendicular to the first direction D1, the fourth curved section 61L may be positioned between adjacent third curved sections 61H, or the third curved section 61H may be positioned between adjacent fourth curved sections 61L.

[0043] The second wiring 6 comprises a first lead section 65H and a second lead section 65L. The first lead section 65H is formed by the second high-potential section 6H. The first lead section 65H is positioned from the second circuit pattern 60 toward the center of the base 2. A terminal (not shown) is positioned at the center of the base 2. The first lead section 65H connects the first end of the third curved section 61H to the terminal. The second lead section 65L is formed by the second low-potential section 6L. The second lead section 65L is positioned from the second circuit pattern 60 toward the center of the base 2. The second lead section 65L connects the first end of the fourth curved section 61L to the terminal. The connection point 69H between the first lead section 65H and the terminal in the second lead section 65L are positioned approximately at the center of the base 2, separated from each other. By arranging the first lead-out section 65H and the second lead-out section 65L from the second circuit pattern 60 toward the center 20 of the base 2, the connection points 69H and 69L with the terminals of the first wiring 5 and the second wiring 6 can be concentrated near the center 20 of the base 2.

[0044] The first lead section 65H and the second lead section 65L are formed to be wide in order to prevent overheating. The contours of the first lead section 65H and the second lead section 65L each correspond, for example, to roughly a semicircle of the envelope of the first wiring 5.

[0045] In this example, the second lead-out section 65L is provided with a notch 68. The notch 68 opens near the center of the base 2 in the semicircular contour of the second lead-out section 65L and is formed in a quarter-circular shape. When viewed in the first direction D1, a portion of the first high-potential section 5H is located within the notch 68 (Figure 2).

[0046] As shown in Figures 2 and 5, heater 1 has an overlapping region 7 where the first wiring 5 and the second wiring 6 overlap when viewed in the first direction D1. In this example, the overlapping region 7 comprises a first region 71, a second region 72, a third region 73, and a fourth region 74, as shown in Figure 2.

[0047] The first region 71 is the region where the first high-potential section 5H and the second high-potential section 6H overlap. The second region 72 is the region where the first low-potential section 5L and the second low-potential section 6L overlap. The third region 73 is the region where the first high-potential section 5H and the second low-potential section 6L overlap. The fourth region 74 is the region where the first low-potential section 5L and the second high-potential section 6H overlap. In Figure 5, the first region 71 is shown as a cross-section cut along the first direction D1. In the second region 72, the third region 73, and the fourth region 74, similar to the first region 71 shown in Figure 5, the first wiring 5 and the second wiring 6 overlap in the cross-section cut along the first direction D1.

[0048] In this example, the overlapping region 7, as shown in Figure 2, is the area where the first lead portion 65H (Figure 4) and the first high-potential portion 5H overlap when viewed in the first direction D1, and the area where the area of ​​the second lead portion 65L other than the notch 68 (Figure 4) overlaps with the first low-potential portion 5L. In this example, the overlapping region 7 corresponds to the strip-shaped portion formed by the first wiring 5.

[0049] The first lead portion 65H overlaps with the first high-potential portion 5H and the first low-potential portion 5L when viewed in the first direction D1. In this example, most of the first lead portion 65H overlaps with the first high-potential portion 5H. The first region 71 in this example is most of the first high-potential portion 5H that overlaps with the first lead portion 65H. The first lead portion 65H in this example overlaps with the second portion 55L (Figure 3), which is part of the first low-potential portion 5L. The fourth region 74 in this example is the portion of the second portion 55L that overlaps with the first lead portion 65H.

[0050] Viewed in the first direction D1, the portion of the second lead-out portion 65L other than the notch 68 overlaps with the first low-potential portion 5L and the first high-potential portion 5H. In this example, most of the second lead-out portion 65L overlaps with the first low-potential portion 5L. The second region 72 in this example is most of the first low-potential portion 5L that overlaps with the second lead-out portion 65L. The second lead-out portion 65L in this example overlaps with the first portion 55H (Figure 3), which is part of the first high-potential portion 5H. The third region 73 in this example is the portion of the first portion 55H that overlaps with the second lead-out portion 65L.

[0051] The average potential difference V between the first wiring 5 and the second wiring 6 in each of the first region 71, second region 72, third region 73, and fourth region 74 is less than the value obtained by √{(α × ρ × L) / S}. α is the predetermined allowable heat generation amount. The unit of α is W. ρ is the volume resistivity of the substrate 2. The unit of ρ is Ω·m. L is the distance between the first wiring 5 and the second wiring 6 along the first direction D1. The unit of L is mm. S is the area of ​​each of the first region 71, second region 72, third region 73, and fourth region 74 when viewed in the direction D1. The unit of S is mm. 2 That is the case.

[0052] In each of the first region 71, second region 72, third region 73, and fourth region 74, if each region 71, 72, 73, and 74 is divided into multiple regions along its longitudinal direction, the above formula can be obtained using the area S of each divided region. The number of divided regions in each region 71, 72, 73, and 74 depends on the shape of the first circuit pattern 50, the first lead section 65H, and the second lead section 65L. In this example, the number of divided regions depends on the shape of the first circuit pattern 50. The first region 71 shown in Figure 2 is divided into five regions. The second region shown in Figure 2 is also divided into five regions. The third region 73 shown in Figure 2 is not divided along its longitudinal direction and consists of one region. The fourth region 74 shown in Figure 2 is also not divided along its longitudinal direction and consists of one region.

[0053] The average potential difference V between the first wiring 5 and the second wiring 6 in each of the first region 71, second region 72, third region 73, and fourth region 74 is smaller than the value obtained by √{(α×ρ×L) / S}, making it difficult for current to leak between the first wiring 5 and the second wiring 6. Because it is difficult for current to leak between the first wiring 5 and the second wiring 6, the temperature of the substrate 2 does not rise locally.

[0054] The allowable heat output α is, for example, 5W or less. When the allowable heat output α is 5W or less, the degree of deterioration in the uniformity of the substrate 2 can be reduced to 2°C or less, as shown in the test example described later. The smaller the allowable heat output α, the better; 3W or less is acceptable. When the allowable heat output α is 3W or less, for example, the degree of deterioration in the uniformity of the substrate 2 can be reduced to 1°C or less.

[0055] The spacing L between the first wiring 5 and the second wiring 6 is, for example, 2 mm to 20 mm. The spacing L is the distance between the opposing faces of the layer on which the first wiring 5 is located and the layer on which the second wiring 6 is located. A spacing L of 2 mm or more makes it easy to electrically insulate the first wiring 5 and the second wiring 6. A spacing L of 20 mm or less prevents the substrate 2 from becoming too thick. The spacing L may also be 2 mm to 10 mm, or 2 mm to 6 mm. The thickness of the substrate 2 is, for example, 10 mm to 50 mm.

[0056] The material of the wiring 4 is not particularly limited as long as it is a material that can heat the object to be heated to the desired temperature. The material of the wiring 4 is a known metal suitable for resistance heating. Examples of metals include stainless steel, nickel, nickel alloys, silver, silver alloys, tungsten, tungsten alloys, molybdenum, molybdenum alloys, chromium, or chromium alloys.

[0057] Wiring 4 can be manufactured, for example, by combining screen printing and hot press bonding. In this example, it can be manufactured by the following procedure. Prepare three ceramic substrates and a screen mask capable of transferring the first wiring 5 and the second wiring 6. The screen mask used is capable of producing the first circuit pattern 50 of the first wiring 5, the second circuit pattern 60 of the second wiring 6, the first lead-out section 65H, and the second lead-out section 65L. Place the screen masks for the first circuit pattern 50, second circuit pattern 60, first lead-out section 65H, and second lead-out section 65L to be produced on each of the two ceramic substrates. Apply the paste that will become wiring 4 to the ceramic substrate on which the screen mask is placed. Transfer the wiring 4 to the ceramic substrate using a squeegee. After transferring the wiring 4, remove the screen mask. As a result, a first substrate with the first wiring 5 transferred and a second substrate with the second wiring 6 transferred are obtained. The first substrate, the second substrate, and the ceramic substrate without the wiring transferred are bonded together in order using a hot press. This connection produces a heater 1 in which the first wiring 5 and the second wiring 6 are arranged inside the base 2 with a gap in the first direction D1.

[0058] <Embodiment 2> The heater 1 of Embodiment 2 will be described with reference to Figures 6 and 7. In Embodiment 2, the shape of the first lead portion 65H and the second lead portion 65L in the second wiring 6 differs from that of Embodiment 1. The first wiring 5 of Embodiment 2 has the same configuration as that of Embodiment 1 shown in Figure 3. Similar to Embodiment 1, the first wiring 5 is located in a layer closer to the first surface 21 (Figure 1) than the second wiring 6.

[0059] The first extension section 65H is positioned so as not to overlap with the second section 55L (Figure 3) when viewed in the first direction D1. The second extension section 65L is positioned so as not to overlap with the first section 55H (Figure 3) when viewed in the first direction D1. In the heater 1 of Embodiment 2, the overlapping region 7 consists of only two regions: the first region 71 and the second region 72. In the heater 1 of Embodiment 2, the overlapping region 7 does not include the third region 73 and the fourth region 74 shown in Figure 2.

[0060] The first lead portion 65H is provided with an arc-shaped notch 66, as shown in Figure 7. The notch 66 opens in the middle of the chord that forms the semicircular contour of the first lead portion 65H and is formed in an arc shape over a 90° range. Looking toward the first direction D1, the second portion 55L is located within the notch 66 (Figure 6). Looking toward the first direction D1, the first high-potential portion 5H overlaps the portion of the first lead portion 65H other than the notch 66. The first region 71 is the majority of the first high-potential portion 5H that overlaps the portion of the first lead portion 65H other than the notch 66.

[0061] The second lead portion 65L is provided with two notches 67 and 68, as shown in Figure 7. Notch 67 opens in the middle of a chord that forms the semicircular contour of the second lead portion 65L and is formed in an arc shape over a 90° range. Notch 68 is the same as notch 68 in Embodiment 1. Looking toward the first direction D1, the first portion 55H is located within notch 67 (Figure 2). Looking toward the first direction D1, the first low-potential portion 5L overlaps the area of ​​the second lead portion 65L other than the notches 67 and 68. The second region 72 is the majority of the first low-potential portion 5L that overlaps the area of ​​the second lead portion 65L other than the notches 67 and 68.

[0062] If the first wiring 5 is provided with a first part 55H and a second part 55L, the uniform heating of the heater 1 can be improved, but when viewed in the first direction D1, the first high-potential part 5H and the second low-potential part 6L tend to overlap, and the first low-potential part 5L and the second high-potential part 6H tend to overlap. If the first lead-out part 65H is provided with a notch 66 and the second lead-out part 65L is provided with notches 67 and 68, when viewed in the first direction D1, the first high-potential part 5H and the second low-potential part 6L do not overlap, and the first low-potential part 5L and the second high-potential part 6H do not overlap. Therefore, regardless of the volume resistivity of the base 2, current is less likely to leak between the first wiring 5 and the second wiring 6. Because current is less likely to leak between the first wiring 5 and the second wiring 6, the temperature of the base 2 is less likely to rise locally.

[0063] [Example Test] In the test example, multiple heaters were fabricated in which the first and second wiring were spaced apart in the first direction along the thickness of the substrate, and the heat output of each heater and the degree of deterioration in uniform heating were investigated.

[0064] Seven test specimens were prepared, from test specimen A to test specimen G. Each test specimen has a first wiring 5 as shown in Figure 3 and a second wiring 6 as shown in Figure 4. In each test specimen, when viewed in the first direction D1, the first wiring 5 and the second wiring 6 overlap as shown in Figure 2. The first wiring 5 has a first high-potential section 5H and a first low-potential section 5L. The second wiring 6 has a second high-potential section 6H and a second low-potential section 6L. In each test specimen, when viewed in the first direction D1, the overlapping region 7 where the first wiring 5 and the second wiring 6 overlap includes a first region 71, a second region 72, a third region 73, and a fourth region 74.

[0065] <Heater heat output> For each test specimen's heater, the amount of heat generated was determined when connected to an AC power supply of the same phase. The amount of heat generated was (V 2 The formula used was (S) / (ρ×L). In each test specimen, the areas that can generate heat are the third region 73 and the fourth region 74 of the overlapping region 7. The first region 71 and the second region 72 do not generate heat easily because high-potential areas overlap with each other or low-potential areas overlap with each other. The third region 73 and the fourth region 74 generate heat easily because high-potential areas and low-potential areas overlap. The energizing conditions and area of ​​the third region 73 and the fourth region 74 are the same. Therefore, in this example, the amount of heat generated in the fourth region 74 was calculated. In the above formula, V is the average potential difference between the first wiring 5 and the second wiring 6 in the fourth region 74. S is the area of ​​the fourth region 74 when viewed in the first direction. ρ is the volume resistivity of the substrate 2. L is the distance between the first wiring 5 and the second wiring 6 along the first direction D1. The unit of heat generation is W.

[0066] The average potential difference V in the fourth region 74 of test specimens A, B, and C was 205V. The average potential difference V in the fourth region 74 of test specimens D, E, F, and G was 181V. The average potential difference V was determined as follows: In the fourth region 74 of test specimen A, the region of the first low potential section 5L between 0V and 10V and the region of the second high potential section 6H between 200V and 220V overlapped. In the fourth region 74, the average potential of the first low potential section 5L was 5V, and the average potential of the second high potential section 6H was 210V. Therefore, the average potential difference V in the fourth region 74 of test specimen A is 205V. The average potential difference V in the fourth region 74 of the other test specimens was determined in the same manner.

[0067] The area S of the fourth region 74 of test specimens A, B, and C is 101.7 mm². 2 The area S of the fourth region 74 of test specimen D was 99.9 mm². 2 The area S of the fourth region 74 of test specimens E, F, and G was 128.6 mm². 2 That was the case.

[0068] The volume resistivity ρ of base material 2 for test specimens A and E was 10,000 Ω·cm. The volume resistivity ρ of base material 2 for test specimens B and F was 50,000 Ω·cm. The volume resistivity ρ of base material 2 for test specimens C and G was 100,000 Ω·cm. The volume resistivity ρ of base material 2 for test specimen D was 5,000 Ω·cm.

[0069] In all test specimens, the distance L between the first wiring 5 and the second wiring 6 was 4 mm.

[0070] <Degree of deterioration in heater uniformity> For each test specimen's heater, the degree of deterioration in uniformity was measured using an infrared camera. The degree of deterioration in uniformity is the temperature variation on the surface of the substrate 2 of each test specimen, and is the difference between the minimum temperature and the maximum temperature. The unit of the degree of deterioration in uniformity is °C.

[0071] For the heater of each test specimen, the relationship between the calorific value and the degree of deterioration of temperature uniformity is shown in Figure 8. In the graph of Figure 8, the horizontal axis represents the calorific value, and the vertical axis represents the degree of deterioration of temperature uniformity. It can be seen from the graph of Figure 8 that the degree of deterioration of temperature uniformity and the calorific value satisfy the following relational expression. In the following relational expression, y represents the degree of deterioration of temperature uniformity, and x represents the calorific value. y=0.01194x 2 +0.3245x

[0072] In the graph of Figure 8, the above relational expression is shown by a solid line. In the above relational expression, regarding the performance of the heater, for example, if the calorific value is 5 W or less, the degree of deterioration of temperature uniformity can be 2°C or less. Further, if the calorific value is 3 W or less, the degree of deterioration of temperature uniformity can be 1°C or less.

[0073] As shown in Figure 8, Specimen B, Specimen C, Specimen F, and Specimen G satisfy the requirements that the calorific value is 5 W or less and the degree of deterioration of temperature uniformity is 2°C or less. All specimens satisfying that the calorific value is 5 W or less and the degree of deterioration of temperature uniformity is 2°C or less have an average potential difference V between the first wiring and the second wiring in the overlapping region that is smaller than the value obtained by √{(5×ρ×L) / S}. In other words, when the average potential difference V between the first wiring and the second wiring in the overlapping region is smaller than the value obtained by √{(5×ρ×L) / S}, the requirements that the calorific value is 5 W or less and the degree of deterioration of temperature uniformity is 2°C or less can be satisfied. Description of Reference Signs

[0074] 1 Heater 2 Base body 20 Center, 21 First surface, 22 Second surface 4 Wiring 5 First wiring 5H First high potential portion, 5L First low potential portion 50 First circuit pattern 51 Curved portion, 51H First curved portion, 51L Second curved portion, 52 Folded portion 55H First portion, 55L Second portion, 59H, 59L Connection site 6 Second wiring 6H Second high potential portion, 6L Second low potential portion 60 Second Circuit Pattern 61 Curved section, 61H Third curved section, 61L Fourth curved section, 62 Turning section 65H 1st drawer, 65L 2nd drawer, 66,67,68 notch 69H, 69L connection points 7 Overlapping area 71 First area, 72 Second area, 73 Third area, 74 Fourth area 9 Support members L spacing, S area D1 First direction

Claims

1. A disc-shaped base, The substrate comprises a plurality of wires that serve as heating elements, arranged inside the substrate, The plurality of wirings comprises a first wiring and a second wiring, which are spaced apart in a first direction along the thickness of the substrate. The first wiring comprises a first high-potential section and a first low-potential section. The second wiring comprises a second high-potential section and a second low-potential section. When the plurality of wirings are viewed in the first direction, they have an overlapping region where the first wiring and the second wiring overlap, The overlapping region comprises a first region and a second region, The first region is the region where the first high-potential portion and the second high-potential portion overlap. The second region is the region where the first low-potential region and the second low-potential region overlap. The average potential difference V between the first wiring and the second wiring in each of the first and second regions is less than the value obtained by √{(α × ρ × L) / S1}. heater. α is a predetermined allowable heat output, and its unit is W. ρ is the volume resistivity of the substrate, and its unit is Ω·m. L is the distance between the first wiring and the second wiring along the first direction, and its unit is mm. S1 is the area of ​​the first region and the second region when viewed in the first direction, and the unit is mm. ２ That is the case.

2. The heater according to claim 1, wherein the overlapping region consists of two regions: the first region and the second region.

3. The overlapping region comprises at least one of the third region and the fourth region, The third region is the region where the first high-potential region and the second low-potential region overlap. The fourth region is the region where the first low-potential region and the second high-potential region overlap. The heater according to claim 1, wherein the average potential difference V between the first wiring and the second wiring in each of the third and fourth regions is smaller than the value obtained by √{(α × ρ × L) / S²}. S2 is the area of ​​the third region and the fourth region when viewed in the first direction, and the unit is mm. ２ That is the case.

4. The heater according to claim 1 or claim 3, wherein the allowable heat generation amount α is 5W or less.

5. The first wiring comprises a first circuit pattern arranged in a region including the center of the substrate, The second wiring is, A second circuit pattern is arranged in a ring-shaped region surrounding the first circuit pattern, The heater according to claim 2 or claim 3, comprising a first lead portion and a second lead portion arranged toward the center of the base from the second circuit pattern.

6. The first wiring comprises a first circuit pattern arranged in a region including the center of the substrate, The first circuit pattern is, Multiple curved sections are arranged along different circumferences concentric with the base, It comprises a plurality of folded sections that connect adjacent curved sections so that the plurality of curved sections are connected in a series, The aforementioned multiple curved sections are, Multiple first curved sections formed in the first high-potential section, It comprises a plurality of second curved sections formed in the first low-potential section, A portion of the plurality of first curved sections comprises a first section positioned between adjacent second curved sections. A portion of the plurality of second curved sections comprises a second section positioned between adjacent first curved sections. The second wiring is, A second circuit pattern is arranged in a ring-shaped region surrounding the first circuit pattern, The first extraction portion formed in the second high-potential portion, The system comprises a second extraction portion formed in the second low-potential portion, The first lead-out section is positioned toward the center of the base body from the second circuit pattern so as not to overlap with the second section when viewed in the first direction. The heater according to claim 2 or 3, wherein the second lead portion is arranged toward the center of the base from the second circuit pattern such that it does not overlap with the part when viewed toward the first direction.

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