Heater and Method for Manufacturing the Same

Abstract

The present invention provides a heater and a method for manufacturing the same. The heater comprises a base film having a metal foil on its surface and a resistor element, wherein the metal foil forms a heater circuit portion that generates heat when energized, and the heater circuit portion is connected in series with the resistor element.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Japanese Patent Application No. 2020-085822 filed with the Japan Patent Office on May 15, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a heater and a method for manufacturing the same. Background Art

[0004] In the past, film heaters were used to heat the front windshield of a car, etc. In recent years, advanced driver assistance systems (ADAS) are being developed. In addition, the need for film heaters has increased to prevent fogging of the lens of a detection camera or the front windshield. In addition, the miniaturization of cameras is also advancing. Therefore, there is also a need for miniaturization of heaters. With this, there is a need to promote the thinning of the wiring used for the heater. As a result, it is difficult to keep the heating temperature fluctuations caused by the dimensional tolerance of the wiring within the allowable range.

[0005] In addition, conventional thin film heaters have problems such as the large number of manufacturing steps. Figure 10A 、 Figure 10B 、 Figure 11A 、 Figure 11B as well as Figure 11C A general thin film heater and a method for manufacturing the same will be described. Figure 10A 、 Figure 10B 、 Figure 11A 、 Figure 11B as well as Figure 11C This is a diagram showing the manufacturing process of a typical thin film heater.

[0006] First, a heating wire 510 is formed using a material that generates heat when electricity is applied (see Figure 10A ). Examples of materials used for the heating wire 510 include nickel-chromium alloy, SUS, aluminum, platinum, iron, nickel alloys, and pure metals. Next, a first insulating film 521 and a second insulating film 522 are provided on both sides of the heating wire 510. The first insulating film 521 and the second insulating film 522 sandwiching the heating wire 510 are bonded together by an adhesive layer 523 provided between these films (see Figure 10B ).also, Figure 10A A top view of the heater wire 510 is shown. Figure 10B A cross-sectional view schematically showing an intermediate product during the heater manufacturing process.

[0007] Next, the electronic component 530 is mounted on the surface of the first insulating film 521 so as to be electrically connected to the heating wire 510 (see Figure 11A). In the example shown in the figure, only one electronic component 530 is mounted on the insulating film. However, multiple electronic components can be mounted. In addition, as an example of the electronic component 530, a temperature fuse can be cited. Then, the wire harness 540 is electrically connected to the heating wire 510 by various methods such as riveting or welding (see Figure 11B ). In addition, the connector 550 is electrically connected to the end of the wire harness 540 by means of a crimping pin (not shown). The connector 550 is connected to a device having a power supply for energizing the heating wire 510 or a control device for temperature control. The heater 500 is obtained through the above manufacturing process. In addition, Figure 11A And 11B is a top view of an intermediate product in the process of manufacturing the heater. Figure 11C This is a top view of the finished product, heater 500. When heater 500 is obtained through the above manufacturing process, in addition to the process of mounting electronic components 530, it is necessary to mount wire harness 540 and connector 550. Therefore, multiple manufacturing processes are involved. Summary of the Invention

[0008] An object of the present invention is to provide a heater including a flexible printed wiring board and a method for manufacturing the heater, which can suppress fluctuations in heating temperature and reduce the number of manufacturing steps.

[0009] In the present invention, in order to solve the above-mentioned problems, the following means are adopted.

[0010] That is, the heater of the present invention comprises a base film having a metal foil on its surface and a resistance element. The metal foil forms a heater circuit portion that generates heat when energized, and the heater circuit portion and the resistance element are connected in series.

[0011] According to the present invention, the resistor element is connected in series with the heater circuit portion. Therefore, the voltage applied to the heater as a whole is divided by the heater circuit portion and the resistor element. As a result, voltages are applied to the heater circuit portion and the resistor element, respectively. Furthermore, when the size of the wiring constituting the heater circuit portion is thinner than the reference value within the dimensional tolerance, the voltage value applied to the heater circuit portion also increases by the amount by which the resistance value of the heater circuit portion is higher than the reference value. Thus, it is possible to suppress a reduction in current value due to wiring thinner than the reference value. In contrast, when the size of the wiring constituting the heater circuit portion is thicker than the reference value within the dimensional tolerance, the voltage value applied to the heater circuit portion also decreases by the amount by which the resistance value of the heater circuit portion is lower than the reference value. Thus, it is possible to suppress an increase in current value due to wiring thicker than the reference value.

[0012] In addition, the manufacturing method of the heater containing a flexible printed wiring board of the present invention includes an etching process, a lamination process and a reflow soldering process in sequence, the etching process includes etching a base film having a metal foil on the surface, and through the etching, a heater circuit part composed of a part of the metal foil that generates heat by being energized, and a power-on part that energizes the heater circuit part are formed. In the lamination process, a covering film covering the surface of the metal foil is provided. In the reflow soldering process, a resistance element connected in series with the heater circuit part and a connector electrically connected to the power-on part are provided through reflow soldering.

[0013] According to the present invention, the heater circuit and the current-carrying portion are formed through an etching process. This reduces the number of manufacturing steps. Furthermore, the resistor element and the connector can be mounted during the reflow process, further reducing the number of manufacturing steps.

[0014] As described above, according to this embodiment, it is possible to suppress heating temperature fluctuation and reduce the number of manufacturing steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A as well as Figure 1B 1 and 2 are circuit diagrams of the heater according to the present embodiment and a heater according to a reference example.

[0016] Figure 2A as well as Figure 2B Graphs showing temporal changes in voltage values in the heater of the present embodiment and the heater of the reference example.

[0017] Figure 3A as well as Figure 3B Graphs showing temporal changes in current values in the heater of the present embodiment and the heater of the reference example.

[0018] Figure 4A as well as Figure 4B Graphs showing changes in temperature over time in the heater of the present embodiment and the heater of the reference example.

[0019] Figure 5A as well as Figure 5B This is a diagram showing the manufacturing process of the heater including the flexible printed wiring board according to the present embodiment.

[0020] Figure 6A as well as Figure 6B This is a diagram showing a manufacturing process of a heater including a flexible printed wiring board according to the present embodiment.

[0021] Figure 7A as well as Figure 7B This is a diagram showing a manufacturing process of a heater including a flexible printed wiring board according to the present embodiment.

[0022] Figure 8 This is a diagram showing a manufacturing process of a heater including a flexible printed wiring board according to the present embodiment.

[0023] Figure 9A 、 Figure 9B as well as Figure 9C This is a diagram showing a manufacturing process of a heater including a flexible printed wiring board according to the present embodiment.

[0024] Figure 10A as well as Figure 10B This is a diagram showing the manufacturing process of a typical thin film heater.

[0025] Figure 11A as well as Figure 11B as well as Figure 11C This is a diagram showing the manufacturing process of a typical thin film heater. DETAILED DESCRIPTION

[0026] In the following detailed description, for purposes of illustration, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown for simplicity of drawing.

[0027] The embodiment will be described in detail below with reference to the accompanying drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment are not limited to those of this embodiment.

[0028] (Implementation Method)

[0029] Reference Figures 1A to 9C , a heater including a flexible printed wiring board and a method for manufacturing the same according to this embodiment will be described. Furthermore, the heater 10 according to this embodiment can be applied to heating the lens of a detection camera or the front windshield. Furthermore, the heater 10 according to this embodiment is not only used to heat various components constituting an automobile, but can also be applied to various devices other than automobiles. The heater 10 according to this embodiment is flexible. Therefore, the heater 10 can be bent in various directions. Therefore, even for a curved portion, the heater 10 can be attached and used along the curved surface.

[0030] (Heater)

[0031] Reference Figure 1A as well as Figure 1B , a schematic structure of a heater including a flexible printed wiring board according to this embodiment will be described. Figure 1A This is a circuit diagram schematically showing a heater including a flexible printed wiring board according to this embodiment connected to a power supply. Figure 1BThis is a circuit diagram schematically showing a heater including a flexible printed wiring board as a reference example connected to a power supply.

[0032] The heater 10 of this embodiment includes a heater circuit 121 that generates heat when energized, and a resistor (a chip resistor 310 in this embodiment) connected in series with the heater circuit 121. A voltage (constant voltage) is applied to the heater 10 thus configured by a power supply 400. Heater circuit 121 then generates heat. Figure 1B The reference example heater 10X shown also includes a heater circuit 121 that generates heat when energized. This reference example heater 10X differs from the heater of this embodiment only in that it does not include a resistor element. This reference example heater 10X also receives a voltage (constant voltage) from the power supply 400. Furthermore, the heater circuit 121 generates heat.

[0033] (Advantages of the Heater of This Embodiment)

[0034] Generally speaking, in various products, the dimensions of each part will deviate due to various influences including raw materials and manufacturing processes. Therefore, for the dimensions of each part, a dimensional tolerance is set based on the target design value. The heater including the heating wire made of an alloy described in the background art has a relatively large size. Therefore, the influence of the dimensional tolerance on the heating temperature is small. In contrast, the wiring of the heater including a flexible printed wiring board is made of metal foil such as copper foil. Therefore, the wiring constituting the heater circuit portion 121 can be made thinner. On the other hand, if the thinning is achieved, the influence of the dimensional tolerance on the heating temperature becomes larger. Therefore, in the heater 10 of the present embodiment, as described above, a structure including a resistance element (chip resistor 310) connected in series with the heater circuit portion 121 is adopted. As a result, fluctuations in the heating temperature caused by the dimensional tolerance of the wiring constituting the heater circuit portion 121 can be suppressed. The reason why fluctuations in the heating temperature can be suppressed is explained below.

[0035] When the voltage of the power supply 400 is E[V], the resistance value of the heater circuit part 121 is R1[Ω], and the resistance value of the resistance element (chip resistor 310) is R2[Ω], the voltage (voltage divider) V1 applied to the heater circuit part 121 and the voltage (voltage divider) V2 applied to the resistance element have the following relationship.

[0036] V1=(R1÷(R1+R2))×E[V]

[0037] V2=(R2÷(R1+R2))×E[V]

[0038] Among them, when the size of the wiring constituting the heater circuit portion 121 is thinner than the reference value within the dimensional tolerance, the voltage value V1 applied to the heater circuit portion 121 is also increased by the amount by which the resistance value R1 of the heater circuit portion 121 is higher than the reference value. Thus, the reduction in current value caused by the size of the wiring being thinner than the reference value can be suppressed. In contrast, when the size of the wiring constituting the heater circuit portion 121 is thicker than the reference value within the dimensional tolerance, the voltage value V1 applied to the heater circuit portion 121 is also reduced by the amount by which the resistance value R1 of the heater circuit portion 121 is lower than the reference value. Thus, the increase in current value caused by the size of the wiring being thicker than the reference value can be suppressed. Therefore, the fluctuation of the heating temperature caused by the dimensional tolerance of the wiring constituting the heater circuit portion 121 can be suppressed.

[0039] This point will be described in more detail with reference to FIG. 2 to FIG. 4 . Figure 2A as well as Figure 2B This is a graph showing how the voltage value of the heater circuit changes with time after voltage is applied to the heater. Figure 2A A case of a heater according to this embodiment is shown. Figure 2B The situation of the reference example is shown. Figure 3A as well as Figure 3B This is a graph showing how the current value of the heater circuit changes with time after voltage is applied to the heater. Figure 3A A case of a heater according to this embodiment is shown. Figure 3B The situation of the reference example is shown. Figure 4A as well as Figure 4B This is a graph showing how the temperature of the heater circuit section changes with time after voltage is applied to the heater. Figure 4A A case of a heater according to this embodiment is shown. Figure 4B The situation of the reference example is shown.

[0040] Figure 2A The curve Lvma in FIG. 1 shows a case where the wiring in the heater circuit portion 121 has a reference size. The curve Lvta shows a case where the wiring is thinnest within the size tolerance. The curve Lvha shows a case where the wiring is thickest within the size tolerance. Figure 2B The middle curve Lvmb represents the case where the wiring in the heater circuit portion 121 has a reference value size. The curve Lvtb represents the case where the wiring is the thinnest within the size tolerance. The curve Lvhb represents the case where the wiring is the thickest within the size tolerance.

[0041] As shown in the reference example, when no resistor is provided, the voltage of the power supply 400 is directly applied to the heater circuit 121. Therefore, the same voltage is applied regardless of the wiring size. In contrast, in the case of the heater 10 of this embodiment, by providing a resistor, the thinner the wiring in the heater circuit 121, the greater the voltage applied to the heater circuit 121.

[0042] Figure 3A The curve Lima in FIG. 1 shows a case where the wiring in the heater circuit section 121 has a reference size. The curve Lita shows a case where the wiring is thinnest within the size tolerance. The curve Liha shows a case where the wiring is thickest within the size tolerance. Figure 3B The middle curve Limb represents the case where the wiring in the heater circuit portion 121 has a reference value size. The curve Litb represents the case where the wiring is the thinnest within the size tolerance. The curve Lihb represents the case where the wiring is the thickest within the size tolerance.

[0043] In the case of the reference example, as described above, the voltage applied to the heater circuit portion 121 is the same regardless of the wiring size. Therefore, the thicker the wiring, the smaller the resistance value. As a result, the amount of current increases. In addition, the fluctuation in the current value caused by the difference in the thickness of the wiring also increases. In addition, due to the heat generated by the power supply, the resistance value increases as the temperature rises. Therefore, after the current value gradually decreases during a predetermined time from the start of power supply, the current value becomes constant. In the reference example, when the wiring is thick, the change in the current value is significant. In contrast, in the case of the heater 10 of this embodiment, the thicker the wiring, the larger the current value. However, the thinner the wiring, the larger the voltage applied. Therefore, the fluctuation in the current value caused by the difference in the thickness of the wiring is reduced. In addition, the change in the current value at the initial stage of power supply can also be suppressed.

[0044] Figure 4A The curve Ltma in FIG. 1 shows a case where the wiring in the heater circuit section 121 has a reference size. The curve Ltta shows a case where the wiring is thinnest within the size tolerance. The curve Ltha shows a case where the wiring is thickest within the size tolerance. Figure 4B The middle curve Ltmb represents the case where the wiring in the heater circuit portion 121 has a reference value size. The curve Lttb represents the case where the wiring is the thinnest within the dimensional tolerance. The curve Lthb represents the case where the wiring is the thickest within the dimensional tolerance.

[0045] In the case of the reference example, the voltage applied to the heater circuit portion 121 is the same regardless of the size of the wiring. Furthermore, the thicker the wiring, the greater the amount of current. Therefore, the temperature fluctuation of the heater circuit portion 121 caused by the dimensional tolerance of the wiring increases. In contrast, in the case of the heater 10 of this embodiment, the thinner the wiring, the greater the voltage applied to the heater circuit portion 121. Furthermore, the amount of current decreases. On the other hand, the thicker the wiring, the smaller the voltage applied to the heater circuit portion 121. Furthermore, the amount of current increases. Thus, as Figure 4A As shown, temperature fluctuations caused by dimensional tolerances of wiring can be reduced. As described above, according to the heater 10 of this embodiment, fluctuations in the heating temperature caused by dimensional tolerances of the wiring constituting the heater circuit portion 121 can be suppressed. Furthermore, in the case of the heater 10 of this embodiment, since the applied voltage is controlled differently according to the thickness of the wiring, it is possible to suppress a decrease in the heating temperature caused by an increase in resistance value associated with an increase in the temperature of the heater circuit portion 121.

[0046] (Method for Manufacturing Heater Including Flexible Printed Wiring Board According to the Present Embodiment)

[0047] Reference Figures 5A to 9B , a method for manufacturing a heater including a flexible printed wiring board is described in order of the manufacturing steps.

[0048]

raw materials

[0049] Figure 5A 5B shows a material 100 used to manufacture the heater 10 of this embodiment. Figure 5A It is a plan view showing a portion of the raw material 100 . Figure 5B 1 is a schematic cross-sectional view of the raw material 100 (sectional view taken along line AA in FIG1 ).

[0050] The raw material 100 is a commercially available material commonly known as a copper-clad laminate. It consists of a base film 110 with a metal foil 120 on its surface. The base film 110 is made of an insulating, flexible resin material (e.g., polyimide or polyethylene naphthalate). The metal foil 120 is made of copper foil. Because the raw material 100 is thus flexible, it can be bent in various directions.

[0051]

Etching process

[0052] A resist pattern (a portion that becomes a mask) is formed on one side of the raw material 100 using a method such as photolithography. Then, etching is performed. Thus, unnecessary copper foil is removed. In this way, the heater circuit portion 121 and the power-carrying portions 122 and 123 are formed. That is, the heater circuit portion 121 and the power-carrying portions 122 and 123 are formed from a portion of the metal foil 120. In addition, these heater circuit portions 121 and the power-carrying portions 122 and 123 are formed almost simultaneously by etching. Figure 6A 6B shows the first intermediate product 100X after the etching process. Figure 6A It is a top view of the first intermediate product 100X. Figure 6B is a cross-sectional view of the first intermediate product 100X ( Figure 6A BB cross-section in ).

[0053] In this embodiment, the line width of the heater line in the heater circuit portion 121 is set to be constant. In addition, the heater circuit portion 121 is provided with at least one area where the heater lines meander at equal intervals (see Figure 6A ). In addition, in this embodiment, four columns of serpentine regions are provided. However, it goes without saying that the pattern of the heater circuit portion 121 is not limited to the example shown in the figure. In addition, the method for forming the resist pattern is not limited to photolithography technology. Various known technologies can be used.

[0054]

Lamination process

[0055] After the etching process, a cover film 211 is provided to cover the surface of the metal foil 120 (heater circuit 121 and current-carrying portions 122 and 123). The cover film 211 is bonded to the base film 110 via an adhesive layer 212, sandwiching the heater circuit 121 and current-carrying portions 122 and 123. Like the base film 110, the cover film 211 is made of an insulating and flexible resin material. Furthermore, the cover film 211 has openings 211a and 211b.

[0056] Figure 7A as well as Figure 7B The second intermediate product 200 after the lamination step is shown. Figure 7A 2 is a top view of the second intermediate product 200 . Figure 7B is a cross-sectional view of the second intermediate product 200 ( Figure 7A (CC cross-sectional view in FIG. 2 ). As for the lamination method for providing the cover film 211, various known techniques may be employed. Therefore, the description thereof will be omitted. Furthermore, the second intermediate product 200 corresponds to a flexible printed wiring board.

[0057]

Reflow process (installation process)

[0058] After the lamination process, the chip resistor 310 and the connector 320 are installed on the second intermediate product 200, i.e., the flexible printed wiring board. First, the exposed portion of the metal foil 120 (equivalent to the conducting portion 122, 123) through the openings 211a, 211b is subjected to surface treatment such as gold plating or water-soluble pre-flux treatment. Then, soldering is performed in a reflow oven. In this way, various components are installed. That is, in this embodiment, the chip resistor 310 is connected to the conducting portion 122 through the opening 211a by reflow soldering. In addition, the connector 320 is connected to the conducting portion 122, 123 through the opening 211b (can be electrically connected). Therefore, in one process, the installation of the chip resistor 310 and the installation of the connector 320 are performed almost simultaneously. Figure 8 The second intermediate product 200 after the reflow process is shown. Figure 8 This is a top view of the intermediate product. Furthermore, in this embodiment, the chip resistor 310 and connector 320 are mounted during the reflow process as an example. However, other electronic components can also be mounted simultaneously. For example, a surface-mounted thermal fuse can be mounted on the heater circuit portion 121.

[0059]

Cutting process

[0060] After the reflow process, the shape is punched out by cutting, such as Figure 9A 、 Figure 9B as well as Figure 9C As shown, a finished heater 10 is obtained. In addition, a plurality of heaters 10 can be manufactured from one raw material 100. Figure 9A FIG. 1 is a top view of the finished heater 10 . Figure 9B yes Figure 9A Similarly, Figure 9C yes Figure 9A EE cross-section diagram in. Figure 1A The schematic structure of the heater of this embodiment has been described. Hereinafter, the structure of the heater 10 will be described in more detail.

[0061] In this embodiment, the heater 10 comprises a heating unit 250 for heating a heating target, an electrical wiring unit 260, a chip resistor 310, and a connector 320 provided at the end of the electrical wiring unit 260. The connector 320 is provided for connecting to a power supply 400 for energizing the heater circuit unit 121. Furthermore, the power supply 400 generally includes various control devices.

[0062] Next, the internal structure of the heating portion 250 and the electrical wiring portion 260 in the heater 10 will be described. The heater 10 of this embodiment includes a base film 110, a heater circuit portion 121 provided on one surface of the base film 110, and power supply portions 122 and 123 (see also FIG. Figure 6A The heater circuit unit 121 is energized by the power supply 400 connected to the connector 320 through the energizing units 122 and 123 to generate heat.

[0063] The heating portion 250 described above corresponds to a region where the heater circuit portion 121 is provided. The electric wiring portion 260 described above corresponds to a region where the current-carrying portions 122 and 123 are provided.

[0064] Thus, in the heater 10 of this embodiment, the heater circuit 121 that generates heat when electricity is applied is formed by the metal foil 120 provided on the surface of the base film 110. In addition, the heater 10 of this embodiment includes the chip resistor 310 as a resistance element connected in series with the heater circuit 121.

[0065] (Advantages of the Method for Manufacturing a Heater Including a Flexible Printed Wiring Board According to the Present Embodiment)

[0066] According to the heater 10 including the flexible printed wiring board of this embodiment and the manufacturing method thereof, the heater circuit portion 121 and the power supply portions 122 and 123 are formed through an etching process. As a result, the number of manufacturing processes can be reduced. Therefore, the conventional process of installing the wire harness is no longer necessary. Therefore, the number of parts is reduced. At the same time, the number of manufacturing processes can be reduced. In addition, the chip resistor 310 and the connector 320 can be installed during the reflow soldering process. Therefore, the number of manufacturing processes can be further reduced.

[0067] (other)

[0068] The heater described in the above embodiment includes a flexible printed wiring board having a metal foil 120 only on one side of the base film 110. However, in this embodiment, a flexible printed wiring board having a metal foil on both sides of the base film can also be used. In this case, a heater circuit portion can be provided on both sides. Alternatively, a heater circuit portion can be provided on only one side of them, while the other side has a different function. In addition, in the above embodiment, a chip resistor is mentioned as a resistance element. However, the resistance element in this embodiment is not limited to a chip resistor. Various resistors such as an axial resistor can be used.

[0069] The detailed description has been presented for purposes of illustration and description. Numerous variations and modifications are possible in light of the above teachings. The detailed description is not intended to be exhaustive or to limit the subject matter described herein. Although the subject matter has been described in terms of specific structural features and / or methodological procedures, it should be understood that the subject matter defined in the claims is not necessarily limited to the specific features or procedures described. Rather, the specific features and procedures described are described as examples of implementing the claims.

Claims

1. A heater, characterized in that: It consists of a base film with a metal foil surface, a cover film, a resistor element and a connector. The metal foil is provided with a heater circuit portion that generates heat when energized, and a first energizing portion and a second energizing portion that energize the heater circuit portion. The cover film is provided so as to cover the surface of the metal foil via an adhesive layer. The cover film and the adhesive layer have a first opening and a second opening that penetrate the cover film and the adhesive layer. The first opening is provided for the first conducting portion, and the second opening is provided for each of the first conducting portion and the second conducting portion, wherein the first opening, the second opening provided for the first conducting portion, and the second opening provided for the second conducting portion are separated from each other. The resistor is connected to the first conducting portion through the first opening so as to be connected in series with the heater circuit portion between the heater circuit portion and the connector. The connector is connected to the first conducting portion and the second conducting portion through the second opening.

2. A method for manufacturing a heater, characterized in that: It includes etching process, lamination process and reflow process in sequence. The etching step includes etching a base film having a metal foil on its surface, and forming a heater circuit portion that generates heat when energized, and a first energizing portion and a second energizing portion that energize the heater circuit portion, which are formed by a portion of the metal foil. In the lamination step, a cover film is provided to cover the surface of the metal foil via an adhesive layer, and a first opening and a second opening are provided on the cover film and the adhesive layer, penetrating the cover film and the adhesive layer. The first opening is provided for the first conducting portion, and the second opening is provided for each of the first conducting portion and the second conducting portion, wherein the first opening, the second opening provided for the first conducting portion, and the second opening provided for the second conducting portion are separated from each other. In the reflow soldering process, a resistance element and a connector that can be electrically connected to the first power-carrying part and the second power-carrying part are set through reflow soldering. The resistance element is connected to the first power-carrying part through the first opening part in a manner of being connected in series with the heater circuit part between the heater circuit part and the connector, and the connector is connected to the first power-carrying part and the second power-carrying part through the second opening part.

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