JP7569680B2 - Thermal printhead and method for manufacturing the same - Google Patents

Description

This disclosure relates to a thermal printhead and a method for manufacturing the same.

Patent document 1 discloses a thermal printhead having a substrate made of a material containing silicon. The substrate of the thermal printhead has a main surface and a convex portion extending in the main scanning direction and protruding from the main surface. As shown in FIG. 6 of Patent document 1, the multiple heat generating portions are arranged in the main scanning direction on the convex portion. With this configuration, the print medium can be accurately brought into contact with the convex portion on which the multiple heat generating portions are arranged, and therefore improvement in print quality can be expected. Furthermore, the substrate of the thermal printhead has the advantage that it has a relatively high thermal conductivity and is less expensive than a substrate made of a material containing aluminum nitride. However, in the manufacture of the thermal printhead, if a defect occurs on the periphery of the main surface of the substrate when the substrate is cut, the defect may spread to the main surface due to the influence of the crystal structure of the substrate. This may cause damage to the wiring layer formed on the main surface of the substrate.

JP 2019-166824 A

In view of the above circumstances, the present disclosure aims to provide a thermal printhead and a method for manufacturing the same that can prevent damage to the wiring layer caused by defects in the substrate that occur during manufacturing.

The thermal printhead provided by the first aspect of the present disclosure comprises a substrate having a main surface and a back surface facing opposite each other in the thickness direction and a first end surface connected to the main surface, a resistor layer including a plurality of heating portions arranged in the main scanning direction and at least a portion of which is formed on the main surface, and a wiring layer that is conductive to the plurality of heating portions and is formed in contact with the resistor layer, the first end surface overlapping the back surface when viewed along the thickness direction and inclined with respect to the main surface toward the side where the back surface is located in the thickness direction, and the first end surface is exposed from the resistor layer and the wiring layer.

A method for manufacturing a thermal printhead provided by a second aspect of the present disclosure includes the steps of forming a resistor layer including a plurality of heating elements arranged in a main scanning direction on a substrate having a main surface facing a thickness direction, forming a wiring layer in contact with the resistor layer and electrically connected to the plurality of heating elements, and cutting the substrate in the thickness direction, and further includes, between the steps of forming the wiring layer and cutting the substrate, a step of forming a groove portion in the substrate that is recessed from the main surface and extends along a direction perpendicular to the thickness direction, the groove portion being connected to the main surface and having an inclined surface inclined relative to the main surface, and in the step of cutting the substrate, a cutting line of the substrate passes through the groove portion.

The thermal printhead and manufacturing method thereof disclosed herein make it possible to prevent damage to the wiring layer caused by defects in the substrate that occur during manufacturing.

Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

1 is a plan view of a thermal printhead according to a first embodiment of the present disclosure, seen through a protective layer. FIG. 2 is a plan view of a main portion of the thermal printhead shown in FIG. 1 . FIG. 3 is a partially enlarged view of FIG. 2 . FIG. 2 is a cross-sectional view taken along line IV-IV in FIG. FIG. 2 is a cross-sectional view of a main part of the thermal printhead shown in FIG. FIG. 6 is a partially enlarged view of FIG. 5 . FIG. 6 is a partially enlarged view of FIG. 5 . 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are partially enlarged cross-sectional views illustrating a manufacturing process for a main part of the thermal printhead shown in FIG. 1 . 2A to 2C are partially enlarged cross-sectional views illustrating a manufacturing process for a main part of the thermal printhead shown in FIG. 1 . 2A to 2C are cross-sectional views illustrating a manufacturing process for the main part of the thermal printhead shown in FIG. 2A to 2C are partially enlarged cross-sectional views illustrating a manufacturing process for a main part of the thermal printhead shown in FIG. 1 . FIG. 2 is a partially enlarged cross-sectional view of a first modified example of the thermal printhead shown in FIG. FIG. 2 is a partially enlarged cross-sectional view of a second modified example of the thermal printhead shown in FIG. FIG. 2 is a partially enlarged cross-sectional view of a second modified example of the thermal printhead shown in FIG. FIG. 11 is a partially enlarged plan view of a main portion of a thermal printhead according to a second embodiment of the present disclosure, seen through a protective layer. A cross-sectional view taken along line XXV-XXV in Figure 24. A cross-sectional view taken along line XXVI-XXVI in Figure 24. A cross-sectional view taken along line XXVII-XXVII in Figure 24.

The form for implementing this disclosure will be described with reference to the attached drawings.

First Embodiment
A thermal printhead A10 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. The thermal printhead A10 constitutes a main part of a thermal printer B10 described later. The thermal printhead A10 is composed of a main part and an associated part. The main part of the thermal printhead A10 includes a substrate 1, an insulating layer 2, a resistor layer 3, a wiring layer 4, and a protective layer 5. The associated part of the thermal printhead A10 includes a wiring substrate 71, a heat dissipation member 72, a plurality of driving elements 73, a plurality of first wires 74, a plurality of second wires 75, a sealing resin 76, and a connector 77. Here, in FIG. 1, for ease of understanding, the protective layer 5 is shown through, and the first wires 74, the second wires 75, and the sealing resin 76 are omitted. In FIGS. 2 and 3, the protective layer 5 is shown through for ease of understanding.

For ease of explanation, the main scanning direction of the thermal printhead A10 is referred to as the "x direction". The sub-scanning direction of the thermal printhead A10 is referred to as the "y direction". The thickness direction of the substrate 1 is referred to as the "z direction". The z direction is perpendicular to both the x direction and the y direction. In the following explanation, "viewed along the z direction" refers to "viewed along the thickness direction".

As shown in FIG. 4, in the thermal printhead A10, the substrate 1, which is the main part of the thermal printhead A10, is joined to a heat dissipation member 72. Furthermore, the wiring board 71 is located next to the substrate 1 in the y direction. The wiring board 71 is fixed to the heat dissipation member 72, just like the substrate 1. On the substrate 1, a plurality of heat generating portions 31 (described in detail later) are formed, which form part of the resistor layer 3 and are arranged in the x direction. The plurality of heat generating portions 31 are selectively heated by a plurality of drive elements 73 mounted on the wiring board 71. The plurality of drive elements 73 are driven according to a print signal transmitted from the outside via a connector 77.

Furthermore, the thermal printer B10 according to the present disclosure includes a thermal printhead A10 and a platen roller 79, as shown in FIG. 4. In the thermal printer B10, the platen roller 79 is a roller-shaped mechanism that feeds a recording medium such as thermal paper. The platen roller 79 presses the recording medium against a plurality of heat generating parts 31, which then print on the recording medium. In the thermal printer B10, a mechanism that is not roller-shaped can be used instead of the platen roller 79. The mechanism has a flat surface. Here, the flat surface includes a curved surface having a small curvature. In the thermal printer B10, the roller-shaped mechanism such as the platen roller 79 and the mechanism are collectively called the "platen". Here, for convenience of explanation, the side of the supply source of the recording medium in FIG. 4 (the right side in FIG. 4) is called the "upstream side". In FIG. 4, the side of the destination of the recording medium (the left side in FIG. 4) is called the "downstream side".

As shown in FIG. 1, the substrate 1 has a rectangular shape extending in the x direction when viewed along the z direction. Therefore, the x direction corresponds to the long side direction of the substrate 1. The y direction corresponds to the short side direction of the substrate 1. The substrate 1 is made of a semiconductor material. The semiconductor material includes a single crystal material containing silicon (Si).

5, the substrate 1 has a main surface 11 and a back surface 12 that face in opposite directions in the z direction. The plane orientations of the main surface 11 and the back surface 12 based on the crystal structure of the substrate 1 are both (100) planes. As shown in FIG. 4, in the thermal printhead A10, the main surface 11 faces the platen roller 79, and the back surface 12 faces the wiring board 71. The main surface 11 includes a first edge 11A and a second edge 11B. The first edge 11A and the second edge 11B correspond to the periphery of the main surface 11. The first edge 11A extends in the x direction and is located closest to the resistor layer 3. The second edge 11B extends in the y direction. In the thermal printhead A10, the second edge 11B includes two sections that are connected to the first edge 11A and are located apart from each other in the x direction.

As shown in FIG. 5, the substrate 1 has a protrusion 19. The protrusion 19 protrudes from the main surface 11 in the z direction. As shown in FIGS. 1 and 2, the protrusion 19 extends in the x direction.

As shown in Figures 5 and 6, the protrusion 19 has a top surface 191 and a pair of inclined surfaces 192. The top surface 191 is located away from the main surface 11 in the z direction and is parallel to the main surface 11. The pair of inclined surfaces 192 are located away from each other in the y direction. The pair of inclined surfaces 192 are connected to the top surface 191 and the main surface 11. The pair of inclined surfaces 192 are inclined with respect to the main surface 11 so as to approach each other from the main surface 11 to the top surface 191. The inclination angles α of the pair of inclined surfaces 192 with respect to the main surface 11 are equal to each other.

2, 5 and 7, the substrate 1 has a first end surface 13, a second end surface 14 and an intermediate surface 15. The first end surface 13 is connected to the main surface 11. In the thermal printhead A10, the first end surface 13 is connected to a first edge 11A of the main surface 11. The first end surface 13 overlaps the back surface 12 when viewed along the z direction, and is inclined at an inclination angle β1 with respect to the main surface 11 in the z direction toward the side where the back surface 12 is located. The second end surface 14 is connected to the back surface 12. The second end surface 14 is located on the opposite side of the main surface 11 from the first end surface 13 in a direction perpendicular to the z direction (the y direction in the thermal printhead A10). The second end surface 14 is inclined at an inclination angle β2 with respect to the second end surface 14. The inclination angle β1 is smaller than the inclination angle β2. The intermediate surface 15 faces the z direction and is connected to the first end surface 13 and the second end surface 14. In the z direction, the intermediate surface 15 is located between the main surface 11 and the back surface 12. The first end surface 13, the second end surface 14, and the intermediate surface 15 are exposed from the resistor layer 3 and the wiring layer 4.

5 and 6, the insulating layer 2 covers the main surface 11 and the protrusions 19 of the substrate 1. The insulating layer 2 electrically insulates the substrate 1 from the resistor layer 3 and the wiring layer 4. The insulating layer 2 is made of silicon dioxide (SiO ₂ ) using tetraethyl orthosilicate (TEOS) as a raw material, for example. An example thickness of the insulating layer 2 is 1 μm or more and 15 μm or less.

As shown in Figures 5 and 6, the resistor layer 3 is formed on the main surface 11 and the protrusions 19 of the substrate 1. The resistor layer 3 is in contact with the insulating layer 2. As a result, in the thermal printhead A10, the insulating layer 2 is sandwiched between the substrate 1 and the resistor layer 3. The resistor layer 3 is made of, for example, tantalum nitride (TaN). An example thickness of the resistor layer 3 is 0.02 μm or more and 0.1 μm or less.

2, 3 and 6, the resistor layer 3 includes a plurality of heat generating portions 31. In the resistor layer 3, the plurality of heat generating portions 31 are exposed from the wiring layer 4. The plurality of heat generating portions 31 are selectively energized from the wiring layer 4, so that the plurality of heat generating portions 31 locally heat the recording medium. The plurality of heat generating portions 31 are arranged in the x direction. Among the plurality of heat generating portions 31, two adjacent heat generating portions 31 in the x direction are located apart from each other. The plurality of heat generating portions 31 are formed in contact with the insulating layer 2. In the thermal printhead A10, the plurality of heat generating portions 31 are formed on the top surface 191 of the convex portion 19 of the substrate 1. The plurality of heat generating portions 31 are located at the center of the top surface 191 in the y direction. As shown in FIG. 4, in the thermal printer B10, the plurality of heat generating portions 31 face the platen roller 79.

As shown in Figs. 5 and 6, the wiring layer 4 is formed in contact with the resistor layer 3. The wiring layer 4 forms a conductive path for passing electricity through the multiple heating parts 31 of the resistor layer 3. The electrical resistivity of the wiring layer 4 is smaller than that of the resistor layer 3. The wiring layer 4 is a metal layer made of, for example, copper (Cu). An example of the thickness of the wiring layer 4 is 0.3 μm or more and 2.0 μm or less. In addition, the wiring layer 4 may be configured to be made of two metal layers, a titanium (Ti) layer laminated on the resistor layer 3 and a copper layer laminated on the titanium layer. In this case, an example of the thickness of the titanium layer is 0.1 μm or more and 0.2 μm or less. As shown in Fig. 1, the wiring layer 4 is located away from the first edge 11A and the second edge 11B of the main surface 11 of the substrate 1.

As shown in FIG. 2, the wiring layer 4 includes a common wiring 41 and a plurality of individual wirings 42. The common wiring 41 is located on one side in the y direction of the plurality of heat generating portions 31 of the resistor layer 3. The plurality of individual wirings 42 are located on the other side in the y direction of the plurality of heat generating portions 31. As shown in FIG. 3, when viewed along the z direction, the plurality of regions of the resistor layer 3 sandwiched between the common wiring 41 and the plurality of individual wirings 42 are the plurality of heat generating portions 31.

2 and 3, the common wiring 41 has a base 411 and a plurality of extensions 412. In the y direction, the base 411 is located farthest from the plurality of heat generating parts 31 of the resistor layer 3. The base 411 is a strip extending in the x direction when viewed along the z direction. The plurality of extensions 412 are strips extending from an end of the base 411 facing the convex part 19 of the substrate 1 in the y direction toward the plurality of heat generating parts 31. The plurality of extensions 412 are arranged along the x direction. A portion of each of the plurality of extensions 412 is formed on the inclined surface 192 facing the base 411, of the pair of inclined surfaces 192 of the convex part 19. Therefore, a portion of the common wiring 41 is formed on one of the pair of inclined surfaces 192. In the common wiring 41, a current flows from the base 411 to the plurality of heat generating parts 31 through the plurality of extensions 412.

2 and 3, each of the multiple individual wirings 42 has a base 421 and an extension 422. In the y direction, the base 421 is located farthest from the multiple heat generating portions 31 of the resistor layer 3. The bases 421 of the multiple individual wirings 42 are arranged at equal intervals in a staggered arrangement in the x direction.

2 and 3, the extension 422 is a strip extending from an end of the base 421 facing the convex portion 19 of the substrate 1 in the y direction toward the heat generating portions 31. The extensions 422 of the individual wirings 42 are arranged along the x direction. The extensions 422 of the individual wirings 42 are formed on the inclined surface 192 facing the base 421 of the individual wirings 42, among the pair of inclined surfaces 192 of the substrate 1. Therefore, a part of each of the individual wirings 42 is formed on one of the pair of inclined surfaces 192. In each of the individual wirings 42, a current flows from one of the heat generating portions 31 to the base 421 through the extension 422. When viewed along the z direction, each of the heat generating portions 31 is sandwiched between one of the extensions 422 of the individual wirings 42 and one of the extensions 412 of the common wiring 41. The configurations of the wiring layer 4 and the multiple heat generating parts 31 shown in Figures 2 and 3 are examples. The configurations of the wiring layer 4 and the multiple heat generating parts 31 in this disclosure are not limited to the configurations shown in Figures 2 and 3.

As shown in FIG. 5, the protective layer 5 covers a part of the main surface 11 of the substrate 1, the plurality of heat generating parts 31 of the resistor layer 3, and the wiring layer 4. The protective layer 5 has electrical insulation properties. The protective layer 5 contains silicon in its composition. The protective layer 5 is made of, for example, silicon dioxide, silicon nitride ( _{Si3N4 )} , or silicon carbide (SiC). Alternatively, the protective layer 5 may be a laminate made of a plurality of types of these materials. An example of the thickness of the protective layer 5 is 1.0 μm or more and 10 μm or less. In the thermal printer B10, the recording medium is pressed against the area of the protective layer 5 that covers the plurality of heat generating parts 31 by the platen roller 79 shown in FIG. 4.

As shown in FIG. 5, the protective layer 5 has a wiring opening 51 and an end face 52. The wiring opening 51 penetrates the protective layer 5 in the z-direction. From the wiring opening 51, the bases 421 of the multiple individual wirings 42 and a portion of each of the extensions 422 of the multiple individual wirings 42 are exposed. As shown in FIG. 5 and FIG. 7, the end face 52 faces in the same direction as the first end face 13 of the substrate 1. The end face 52 is inclined with respect to the main surface 11 of the substrate 1. The inclination direction of the end face 52 with respect to the main surface 11 is equal to the inclination direction of the first end face 13 with respect to the main surface 11.

As shown in FIG. 4, the wiring board 71 is located next to the substrate 1 in the y direction. As shown in FIG. 1, when viewed along the z direction, the multiple individual wirings 42 are located between the multiple heating portions 31 of the resistor layer 3 and the wiring board 71 in the y direction. When viewed along the z direction, the area of the wiring board 71 is larger than the area of the substrate 1. Furthermore, when viewed along the z direction, the wiring board 71 is rectangular with the x direction as the longitudinal direction. The wiring board 71 is, for example, a PCB substrate. The wiring board 71 is equipped with multiple driving elements 73 and a connector 77.

As shown in FIG. 4, the heat dissipation member 72 faces the rear surface 12 of the substrate 1. The rear surface 12 is joined to the heat dissipation member 72. The wiring board 71 is fixed to the heat dissipation member 72 by a fastening member such as a screw. When the thermal printhead A10 is in use, a portion of the heat generated from the multiple heat generating portions 31 of the resistor layer 3 is conducted to the heat dissipation member 72 via the substrate 1. The heat conducted to the heat dissipation member 72 is dissipated to the outside. The heat dissipation member 72 is made of, for example, aluminum (Al).

1 and 4, the driving elements 73 are mounted on the wiring board 71 via an electrically insulating die bonding material (not shown). Each of the driving elements 73 is a semiconductor element in which various circuits are configured. Each of the driving elements 73 is joined to one end of each of the first wires 74 and one end of each of the second wires 75. The other ends of the first wires 74 are individually joined to the bases 421 of the individual wirings 42. The other ends of the second wires 75 are joined to wiring (not shown) provided on the wiring board 71 and conductive to the connector 77. As a result, the print signal, the control signal, and the voltage supplied to the heating parts 31 of the resistor layer 3 are input from the outside to the driving elements 73 via the connector 77. The driving elements 73 selectively apply voltage to the individual wirings 42 based on these electrical signals. As a result, the heating parts 31 selectively generate heat.

As shown in FIG. 4, the sealing resin 76 covers the multiple driving elements 73, the multiple first wires 74, and the multiple second wires 75, as well as parts of the substrate 1 and the wiring substrate 71. The sealing resin 76 has electrical insulation properties. The sealing resin 76 is, for example, a black, soft synthetic resin used for underfill. Alternatively, the sealing resin 76 may be a black, hard synthetic resin.

As shown in Figures 1 and 4, the connector 77 is mounted on one end of the wiring board 71 in the y direction. The connector 77 is connected to the thermal printer B10. The connector 77 has a plurality of pins (not shown). Some of the plurality of pins are electrically connected to wiring (not shown) on the wiring board 71 to which the plurality of second wires 75 are joined. Furthermore, another portion of the plurality of pins are electrically connected to wiring (not shown) on the wiring board 71 that is electrically connected to the base 411 of the common wiring 41.

Next, an example of a method for manufacturing the thermal printhead A10 will be described with reference to Figures 8 to 20. Here, the cross-sectional positions of Figures 8 to 16 and Figure 19 are the same as the cross-sectional position of Figure 5, which shows the main part of the thermal printhead A10.

First, as shown in Figures 8 and 9, a protrusion 19 is formed on a substrate 81.

8, a first mask layer 891 that covers the substrate 81 and a second mask layer 892 that covers a part of the first mask layer 891 are formed. The substrate 81 is made of a semiconductor material. The semiconductor material includes a single crystal material composed of silicon. The substrate 81 is a silicon wafer. In a direction perpendicular to the z direction, a plurality of regions corresponding to the plurality of substrates 1 are connected together to form the substrate 81. The substrate 81 has a first surface 81A and a second surface 81B. The first surface 81A and the second surface 81B face in opposite directions in the z direction. The surface orientations of the first surface 81A and the second surface 81B based on the crystal structure of the substrate 81 are both (100) surfaces. The first mask layer 891 is formed so as to cover the first surface 81A and the second surface 81B. The first mask layer 891 is made of silicon dioxide. The second mask layer 892 is formed to cover the area of the first mask layer 891 that covers the first surface 81A. The second mask layer 892 is made of silicon nitride. A portion of the first surface 81A is exposed from the first mask layer 891 that covers the first surface 81A and the second mask layer 892 that covers the first mask layer 891.

When forming the first mask layer 891 and the second mask layer 892, first, a thin film of silicon dioxide is formed by thermal oxidation to cover the first surface 81A and the second surface 81B. Next, a thin film of silicon nitride is formed by thermal CVD (Chemical Vapor Deposition) to cover the region of the first mask layer 891 that covers the first surface 81A. Finally, a part of the region of the thin film of silicon dioxide that covers the first surface 81A and a part of the thin film of silicon nitride that covers the region are removed by lithography patterning and reactive ion etching (RIE). This forms the first mask layer 891 and the second mask layer 892.

9, the main surface 11 and the protrusions 19 are formed on the substrate 81. The main surface 11 and the protrusions 19 are formed by wet etching the area of the first surface 81A exposed from the first mask layer 891 and the second mask layer 892 shown in FIG. 8 using an aqueous potassium hydroxide (KOH) solution. The etching is anisotropic. Finally, the first mask layer 891 and the second mask layer 892 are removed by wet etching using hydrofluoric acid (HF). As a result, the main surface 11 and the protrusions 19 are formed on the substrate 81. Furthermore, the second surface 81B of the substrate 81 becomes the back surface 12. The protrusions 19 are connected to the main surface 11 and bulge from the main surface 11 in the z direction. The protrusions 19 bulge from the main surface 11 in the z direction and extend along the x direction. The protrusions 19 include the protrusions 19. The area of the first surface 81A that was covered by the first mask layer 891 and the second mask layer 892 becomes the top surface 191 of the protrusion 19. Furthermore, the inclination angle α of each of the pair of inclined surfaces 192 of the protrusion 19 relative to the main surface 11 is the same. This is because the protrusion 19 is formed by anisotropic etching.

In the process shown in FIG. 9, after the main surface 11 and the protrusions 19 are formed on the substrate 81, a thin film of silicon dioxide covering the main surface 11 may be formed by thermal oxidation. A metal layer may be laminated by plating on the bases 421 of the multiple individual wirings 42 to which the multiple first wires 74 are individually joined. The thin film of silicon dioxide has the effect of suppressing abnormal growth of the metal layer when the metal layer is laminated by plating.

Next, as shown in FIG. 10, an insulating layer 2 is formed to cover the main surface 11 and the protrusions 19 of the substrate 81. The insulating layer 2 is formed by laminating thin films of silicon dioxide formed by plasma CVD using tetraethyl orthosilicate (TEOS) as a raw material gas multiple times.

Next, as shown in Figures 11 to 13, the resistor layer 3 and the wiring layer 4 are formed. The resistor layer 3 includes a plurality of heat generating portions 31 arranged in the x direction. The wiring layer 4 is electrically connected to the plurality of heat generating portions 31. Furthermore, the process of forming the wiring layer 4 includes a process of forming a common wiring 41 and a plurality of individual wirings 42. In the substrate 81, the common wiring 41 is located on one side in the y direction relative to the plurality of heat generating portions 31 of the resistor layer 3 shown in Figure 13. In the substrate 81, the plurality of individual wirings 42 are located on the other side in the y direction relative to the plurality of heat generating portions 31 shown in Figure 13.

First, as shown in FIG. 11, a resistor film 82 is formed on the main surface 11 and the protrusions 19 of the substrate 81. The resistor film 82 is formed so as to cover the entire surface of the insulating layer 2. The resistor film 82 is formed by laminating a thin film of tantalum nitride on the insulating layer 2 by a sputtering method.

Next, as shown in FIG. 12, a conductive layer 83 is formed to cover the entire surface of the resistor film 82. The conductive layer 83 is formed by laminating a thin copper film on the resistor film 82 multiple times by a sputtering method. Alternatively, the conductive layer 83 may be formed by laminating a thin titanium film on the resistor film 82 by a sputtering method, and then laminating a thin copper film multiple times on the thin titanium film by a sputtering method.

13, the conductive layer 83 is lithographically patterned, and then a portion of the conductive layer 83 is removed. The removal is performed by wet etching using a mixed solution of sulfuric acid ( _{H2SO4 )} and hydrogen peroxide ( _H2O2 ). As a result, the common wiring 41 and a plurality of individual wirings 42 are formed in contact with the resistor film _82. In addition, the region of the resistor film 82 formed on the top surface 191 of the protrusion 19 of the substrate 81 is exposed from the wiring layer 4. Thereafter, the resistor film 82 and the wiring layer 4 are lithographically patterned, and then a portion of the resistor film 82 is removed. The removal is performed by reactive ion etching. As a result, the resistor layer 3 is formed on the main surface 11 and the protrusion 19 of the substrate 81. A plurality of heating portions 31 appear on the top surface 191 of the substrate 81.

Next, as shown in FIG. 14, a protective layer 5 is formed to cover a portion of the main surface 11 of the substrate 81, the multiple heating portions 31 of the resistor layer 3, and the wiring layer 4. The protective layer 5 is formed by laminating a thin film of silicon nitride by plasma CVD.

15, a wiring opening 51 penetrating in the z-direction is formed in the protective layer 5. The wiring opening 51 is formed by removing a part of the protective layer 5 after lithographic patterning of the protective layer 5. The removal is performed by reactive ion etching. As a result, a part of the multiple individual wirings 42 (the base 421 of the multiple individual wirings 42 shown in FIG. 5 and a part of each of the extensions 422 of the multiple individual wirings 42) is exposed from the wiring opening 51. The part of each of the multiple individual wirings 42 exposed from the wiring opening 51 forms the base 421 to which the multiple first wires 74 are individually bonded by, for example, wire bonding. A metal layer such as gold may be laminated by plating on each part of the multiple individual wirings 42 exposed from the wiring opening 51 (including the base 421).

Next, as shown in FIG. 16, a groove 811 is formed in the substrate 81, recessed from the main surface 11 and extending in a direction perpendicular to the z direction (x direction in the case of the thermal printhead A10). The groove 811 has a bottom surface 811A and a pair of inclined surfaces 811B. The bottom surface 811A is located between the main surface 11 and the back surface 12 in the z direction. The pair of inclined surfaces 811B are located apart from each other in the y direction in the thermal printhead A10, and are connected to the bottom surface 811A and the main surface 11. The pair of inclined surfaces 811B are inclined so as to approach each other in the z direction from the main surface 11 toward the bottom surface 811A.

As shown in FIG. 16, the groove 811 of the substrate 81 is formed using the first blade 87. As shown in FIG. 17, the first blade 87 has a base 871 and a cutting edge 872. The cutting edge 872 extends from the base 871 in the radial direction of the first blade 87 and surrounds the base 871 in the circumferential direction of the first blade 87. The groove 811 is formed in the substrate 81 by rotating the first blade 87 in the y direction and bringing the cutting edge 872 into contact with the substrate 81. The thickness t2 of the cutting edge 872 gradually decreases the farther away from the base 871 in the radial direction of the first blade 87. Thus, the cutting edge 872 is tapered.

As shown in FIG. 17, the cross-sectional shape of the cutting edge 872 in the circumferential direction of the first blade 87 is trapezoidal. Alternatively, as shown in FIG. 18, the cross-sectional shape of the cutting edge 872 may be triangular.

In the process of forming the groove portion 811 in the substrate 81 shown in FIG. 16, in addition to the method using the first blade 87, the groove portion 811 may be formed by removing a portion of the insulating layer 2 and the protective layer 5 and then performing anisotropic etching as shown in FIG. 9.

Next, as shown in FIG. 19, the substrate 81 is cut in the thickness direction along the x and y directions. The pieces thus obtained become the main parts of the thermal printhead A10 including the substrate 1. In this process, the substrate 81 is cut using the second blade 88. As shown in FIG. 20, the thickness t3 of the second blade 88 is smaller than the thickness t1 of the base 871 of the first blade 87 shown in FIG. 17 and FIG. 18. In this process, the cutting line CL of the substrate 81 is set to pass through the groove 811 as shown in FIG. 20. Furthermore, in the process of cutting the substrate 81 along the x direction, the second blade 88 is brought into contact with the bottom surface 811A of the groove 811 and is separated from the inclined surface 811B of the groove 811.

Next, a plurality of driving elements 73 and a connector 77 are mounted on the wiring board 71. Next, the rear surface 12 of the substrate 1 and the wiring board 71 are bonded to the heat dissipation member 72. Next, a plurality of first wires 74 and a plurality of second wires 75 are bonded to the wiring board 71. Finally, a sealing resin 76 is formed on the substrate 1 and the wiring board 71 to cover the driving elements 73, the plurality of first wires 74, and the plurality of second wires 75. Through the above steps, the thermal printhead A10 is obtained.

<First Modification>
Next, a thermal printhead A11, which is a modification of the thermal printhead A10, will be described with reference to Fig. 21. The cross-sectional position of Fig. 21 is the same as that of Fig. 7.

As shown in FIG. 21, in thermal printhead A11, the configuration of substrate 1 is different from that of thermal printhead A10. The second end surface 14 of substrate 1 is connected to the first end surface 13 of substrate 1. Therefore, substrate 1 of thermal printhead A11 does not have an intermediate surface 15. This configuration is obtained by setting thickness t3 of second blade 88 so that second blade 88 contacts bottom surface 811A and inclined surface 811B of groove portion 811 in the manufacturing process of thermal printhead A10 shown in FIG. 19.

<Second Modification>
Next, a thermal printhead A12, which is a modification of the thermal printhead A10, will be described with reference to Fig. 22. The cross-sectional position of Fig. 22 is the same as that of Fig. 7.

As shown in FIG. 22, in thermal printhead A12, the configuration of substrate 1 differs from that of thermal printhead A10. The first end surface 13 of substrate 1 is connected to the rear surface 12 of substrate 1. Therefore, substrate 1 of thermal printhead A12 does not have a second end surface 14 or an intermediate surface 15. This configuration is obtained by forming a groove portion 811 penetrating in the z direction in substrate 81 using a first blade 87 in the manufacturing process of thermal printhead A10 shown in FIG. 16.

<Third Modification>
Next, a thermal printhead A13, which is a modification of the thermal printhead A10, will be described with reference to Fig. 23. The cross-sectional position of Fig. 23 is the same as that of Fig. 7.

As shown in FIG. 23, in the thermal printhead A13, the configuration of the protective layer 5 differs from that of the thermal printhead A10. The end face 52 of the protective layer 5 is perpendicular to the main surface 11 of the substrate 1. When viewed along the z direction, the end face 52 is located closer to the side where the wiring layer 4 is located than the periphery of the insulating layer 2. This configuration is obtained in the manufacturing process of the thermal printhead A10 shown in FIG. 15 by forming an opening in the protective layer 5 that overlaps with the groove portion 811 of the base material 81 shown in FIG. 16 when viewed along the z direction. The opening is formed at the same time as the wiring opening 51.

Next, we will explain the effects of the thermal printhead A10.

The thermal printhead A10 includes a substrate 1 having a main surface 11 and a back surface 12 facing opposite sides in the z direction, and a first end surface 13 connected to the main surface 11. The first end surface 13 overlaps the back surface 12 when viewed along the z direction, and is inclined in the z direction with respect to the main surface 11 toward the side where the back surface 12 is located. The first end surface 13 is exposed from the resistor layer 3 and the wiring layer 4. As a result, in the step of cutting the substrate 81 (substrate 1) in the z direction (see FIG. 19) in the manufacturing process of the thermal printhead A10, the substrate 81 is cut at a position at least away from the main surface 11. Therefore, defects do not occur on the periphery of the main surface 11 (first edge 11A in the thermal printhead A10). Therefore, according to the thermal printhead A10, it is possible to prevent damage to the wiring layer 4 caused by defects in the substrate 1 that occur during the manufacturing of the thermal printhead A10.

In the manufacture of the thermal printhead A10, after the step of forming the grooves 811 in the substrate 81 shown in FIG. 16, the step of cutting the substrate 81 in the z direction shown in FIG. 19 is performed. The grooves 811 have an inclined surface 811B inclined with respect to the main surface 11. This reduces the external force in the z direction acting on the periphery of the main surface 11 when forming the grooves 811, so that the grooves 811 can be formed in the substrate 81 without causing defects. Furthermore, in the step of cutting the substrate 81 in the z direction, by setting the cutting line CL of the substrate 81 to pass through the grooves 811 as shown in FIG. 20, the substrate 81 can be cut without causing defects on the periphery of the main surface 11.

In the process of forming grooves 811 in substrate 81 (see FIG. 16) during the manufacturing process of thermal printhead A10, grooves 811 are formed using a first blade 87. First blade 87 has a base 871 and a cutting edge 872. The thickness t2 of cutting edge 872 gradually decreases the farther away from base 871 in the radial direction of first blade 87. This allows grooves 811 with inclined surfaces 811B to be formed in substrate 81.

In the process of cutting the substrate 81 in the z direction (see FIG. 19) during the manufacturing process of the thermal printhead A10, the substrate 81 is cut using a second blade 88. The thickness t3 of the second blade 88 is smaller than the thickness t1 of the base 871 of the first blade 87. This allows the substrate 81 to be cut without the second blade 88 coming into contact with the periphery of the main surface 11 of the substrate 81.

The substrate 1 has a second end surface 14 connected to the back surface 12. The second end surface 14 is located on the opposite side of the first end surface 13 to the main surface 11 in a direction perpendicular to the z direction. The second end surface 14 is exposed from the resistor layer 3 and the wiring layer 4. Furthermore, the inclination angle β1 of the first end surface 13 with respect to the main surface 11 is smaller than the inclination angle β2 of the second end surface 14 with respect to the back surface 12. This makes it possible to suppress the expansion of the dimensions of the substrate 1 having the first end surface 13.

The substrate 1 has an intermediate surface 15 that faces the z direction and is connected to the first end surface 13 and the second end surface 14. The intermediate surface 15 is exposed from the resistor layer 3 and the wiring layer 4. As a result, in the process of cutting the substrate 81 in the z direction (see FIG. 19) during the manufacturing process of the thermal printhead A10, the substrate 81 is cut at a position away from the main surface 11 and the first end surface 13. This makes it possible to more reliably prevent defects from occurring around the periphery of the main surface 11.

The substrate 1 is made of a semiconductor material. The semiconductor material includes a single crystal material composed of silicon. This allows the cost of the substrate 1 to be reduced while still providing a relatively high thermal conductivity (approximately 170 W/(m·K)). The substrate 1 having the first end surface 13 is particularly useful for preventing damage to the substrate 1 made of such a material.

The substrate 1 has a protrusion 19 that protrudes from the main surface 11 in the z direction. The multiple heat generating portions 31 of the resistor layer 3 are formed on the protrusions 19. This allows heat from the multiple heat generating portions 31 to be transferred to the recording medium 78 while minimizing the contact area of the recording medium 78 with the thermal print head A10 when printing on the recording medium 78 shown in FIG. 4. This improves the quality of printing on the recording medium 78.

The thermal printhead A10 further includes a protective layer 5 that covers the multiple heat generating portions 31 of the resistor layer 3 and the wiring layer 4. This allows the multiple heat generating portions 31 and the wiring layer 4 to be protected by the protective layer 5, and also allows the recording medium 78 to come into contact with the thermal printhead A10 more smoothly when the thermal printhead A10 is in use.

The thermal printhead A10 further includes a heat dissipation member 72. The rear surface 12 of the substrate 1 is joined to the heat dissipation member 72. This allows a portion of the heat generated by the multiple heat generating parts 31 to be quickly dissipated to the outside via the substrate 1 and the heat dissipation member 72 when the thermal printhead A10 is in use.

Second Embodiment
A thermal printhead A20 according to a second embodiment of the present disclosure will be described with reference to Figures 24 to 27. In these figures, elements that are the same as or similar to those of the thermal printhead A10 described above are given the same reference numerals, and duplicated explanations will be omitted. Here, for ease of understanding, Figure 24 shows the protective layer 5 through which the image is viewed.

In thermal printhead A20, the configuration of substrate 1 differs from that of thermal printhead A10 described above.

As shown in FIG. 24, the first end surface 13 of the substrate 1 includes a first region 131 and a second region 132. The first region 131 is connected to a first edge 11A of the main surface 11 of the substrate 1. The second region 132 is connected to a second edge 11B of the main surface 11 and to the first region 131. Furthermore, the second end surface 14 of the substrate 1 includes a third region 141 and a fourth region 142. The third region 141 extends in the x direction. The fourth region 142 extends in the y direction and is connected to the third region 141.

As shown in FIG. 24, the first region 131 is inclined at an inclination angle β1 with respect to the main surface 11. As shown in FIG. 25, the second region 132 is inclined at an inclination angle β1 with respect to the main surface 11. Therefore, in the thermal printhead A20, the inclination angle of the second region 132 with respect to the main surface 11 is equal to the inclination angle of the first region 131 with respect to the main surface 11. However, the inclination angle of the second region 132 with respect to the main surface 11 may be different from the inclination angle of the first region 131 with respect to the main surface 11.

As shown in FIG. 24, the substrate 1 has a ridge 16. The ridge 16 forms a boundary between a first region 131 and a second region 132. As shown in FIG. 27, the ridge 16 is inclined at an inclination angle γ with respect to the main surface 11. The inclination angle γ is smaller than the inclination angle β1 of the first end surface 13 with respect to the main surface 11 shown in FIG. 25 and FIG. 26.

Thermal printhead A20 may have a configuration in which the substrate 1 does not have an intermediate surface 15 (see FIG. 21), similar to the thermal printhead A11 described above. Thermal printhead A20 may have a configuration in which the substrate 1 does not have a second end surface 14 and an intermediate surface 15 (see FIG. 22), similar to the thermal printhead A12 described above. Furthermore, thermal printhead A20 may have an end surface 52 of the protective layer 5 similar to the thermal printhead A13 described above (see FIG. 23).

Next, we will explain the effects of the thermal printhead A20.

The thermal printhead A20 includes a substrate 1 having a main surface 11 and a back surface 12 facing opposite each other in the z direction, and a first end surface 13 connected to the main surface 11. The first end surface 13 overlaps the back surface 12 when viewed along the z direction, and is inclined relative to the main surface 11 in the z direction toward the side where the back surface 12 is located. The first end surface 13 is exposed from the resistor layer 3 and the wiring layer 4. Therefore, the thermal printhead A20 also makes it possible to prevent damage to the wiring layer 4 caused by defects in the substrate 1 that occur during the manufacture of the thermal printhead A20.

The main surface 11 of the substrate 1 includes a first edge 11A that extends in the x direction and is located closest to the resistor layer 3, and a second edge 11B that extends in the y direction. In the thermal printhead A20, the first end face 13 of the substrate 1 includes a first region 131 that is connected to the first edge 11A, and a second region 132 that is connected to the second edge 11B. This makes it possible to prevent defects from occurring on both the first edge 11A that extends in the x direction and the second edge 11B that extends in the y direction in the process of cutting the base material 81 (substrate 1) in the z direction (see FIG. 19) during the manufacturing process of the thermal printhead A20.

The substrate 1 has a ridge 16 that forms the boundary between the first region 131 and the second region 132. The ridge 16 is inclined with respect to the main surface 11 of the substrate 1. This makes it possible to prevent defects from occurring on the periphery located at the corners of the main surface 11. In this case, the inclination angle γ of the ridge 16 with respect to the main surface 11 is smaller than the inclination angle β1 of the first end face 13 with respect to the main surface 11, which makes it possible to more effectively prevent the occurrence of such defects. Therefore, this configuration is most suitable for preventing defects from occurring in the substrate 1.

This disclosure is not limited to the above-described embodiment. The specific configuration of each part of this disclosure can be freely designed in various ways.

The technical configurations of the thermal printhead and the manufacturing method thereof provided by the present disclosure are described below.
[Appendix 1]
a substrate having a main surface and a back surface facing in opposite directions in a thickness direction, and a first end surface connected to the main surface;
a resistor layer including a plurality of heat generating portions arranged in a main scanning direction and at least a portion of which is formed on the main surface;
a wiring layer that is electrically connected to the plurality of heat generating portions and is formed in contact with the resistor layer,
the first end surface overlaps the back surface when viewed along the thickness direction and is inclined with respect to the main surface toward a side where the back surface is located in the thickness direction,
the first end surface is exposed from the resistor layer and the wiring layer.
[Appendix 2]
the main surface includes a first edge extending in the main scanning direction and located closest to the resistor layer, and a second edge extending in a sub-scanning direction;
The first end surface has a first region connected to the first edge and a second region connected to the second edge,
2. The thermal printhead of claim 1, comprising:
[Appendix 3]
the substrate has a ridge that defines a boundary between the first region and the second region;
3. The thermal printhead of claim 2, wherein the ridge line is inclined with respect to the main surface.
[Appendix 4]
4. The thermal printhead of claim 3, wherein an inclination angle of the ridge line relative to the main surface is smaller than an inclination angle of the first end surface relative to the main surface.
[Appendix 5]
the substrate has a second end surface connected to the back surface,
the second end surface is located on an opposite side of the first end surface from the main surface in a direction perpendicular to the thickness direction,
5. The thermal printhead according to claim 1, wherein the second end surface is exposed from the resistor layer and the wiring layer.
[Appendix 6]
6. The thermal printhead of claim 5, wherein an inclination angle of the first end surface with respect to the main surface is smaller than an inclination angle of the second end surface with respect to the back surface.
[Appendix 7]
the substrate has an intermediate surface that faces the thickness direction and is connected to the first end surface and the second end surface;
7. The thermal printhead of claim 6, wherein the intermediate surface is exposed from the resistor layer and the wiring layer.
[Appendix 8]
7. The thermal printhead of claim 6, wherein the second end surface is connected to the first end surface.
[Appendix 9]
the substrate is made of a semiconductor material;
A thermal printhead as described in any one of appendix 1 to 8, wherein the semiconductor material includes a single crystal material composed of silicon.
[Appendix 10]
the substrate has a protrusion protruding from the main surface in the thickness direction,
10. The thermal printhead of claim 9, wherein the plurality of heat generating portions are formed on the convex portion.
[Appendix 11]
Further comprising an insulating layer covering the main surface,
the insulating layer is located between the substrate and the resistor layer;
11. The thermal printhead of claim 9, wherein the first end surface is exposed from the insulating layer.
[Appendix 12]
the wiring layer includes a common wiring and a plurality of individual wirings;
the common wiring is electrically connected to the plurality of heat generating portions,
12. The thermal printhead according to claim 1, wherein the individual wirings are individually connected to the heat generating portions.
[Appendix 13]
a protective layer covering the plurality of heat generating portions and the wiring layer;
13. The thermal printhead according to claim 1, wherein the first end surface is exposed from the protective layer.
[Appendix 14]
Further comprising a heat dissipation member,
14. The thermal printhead according to claim 1, wherein the rear surface is joined to the heat dissipation member.
[Appendix 15]
A step of forming a resistor layer including a plurality of heating portions arranged in a main scanning direction on a substrate having a main surface facing a thickness direction;
forming a wiring layer that is electrically connected to the plurality of heat generating portions in contact with the resistor layer;
cutting the base material in the thickness direction;
Between the step of forming the wiring layer and the step of cutting the base material,
The method further includes a step of forming a groove portion in the base material, the groove portion being recessed from the main surface and extending along a direction perpendicular to the thickness direction,
the groove portion has an inclined surface that is connected to the main surface and is inclined with respect to the main surface,
In the step of cutting the substrate, a cutting line of the substrate passes through the groove.
[Appendix 16]
In the step of forming the groove portion, the groove portion is formed using a first blade,
The first blade has a base portion and a cutting edge portion extending from the base portion in a radial direction of the first blade and surrounding the base portion in a circumferential direction of the first blade,
16. The method for manufacturing a thermal printhead according to claim 15, wherein the thickness of the cutting edge portion gradually decreases as the cutting edge portion moves away from the base portion in the radial direction.
[Appendix 17]
In the step of cutting the base material, the base material is cut using a second blade,
17. The method of claim 16, wherein the thickness of the second blade is less than the thickness of the base.

A10, A20, A30: Thermal print head B10: Thermal printer 1: Substrate 11: Main surface 11A: First edge 11B: Second edge 12: Back surface 13: First end surface 131: First region 132: Second region 14: Second end surface 141: Third region 142: Fourth region 15: Intermediate surface 16: Ridge line 19: Convex portion 191: Top surface 192: Inclined surface 2: Insulating layer 3: Resistor layer 31: Heat generating portion 4: Wiring layer 41: Common wiring 411: Base 412: Extension portion 42: Individual wiring 421: Base 422: Extension portion 5: Protective layer 51: Wiring opening 52: End surface 71: Wiring substrate 72: Heat dissipation member 73: Driving element 74: First wire 75: Second wire 76: Sealing resin 77: Connector 79: Platen roller 81: Base material 81A: First surface 81B: Second surface 811: Groove portion 811A: Bottom surface 811B: Inclined surface 82: Resistor film 83: Conductive layer 87: First blade 871: Base portion 872: Blade tip portion 88: Second blade 891: First mask layer 892: Second mask layer α, β1, β2, γ: Inclined angles t1, t2, t3: Thickness

Claims (12)

a substrate having a main surface and a back surface facing in opposite directions in a thickness direction, a first end surface connected to the main surface, and a second end surface connected to the back surface ;
a resistor layer including a plurality of heat generating portions arranged in a main scanning direction and at least a portion of which is formed on the main surface;
a wiring layer that is electrically connected to the plurality of heat generating portions and is formed in contact with the resistor layer,
each of the first end surface and the second end surface is located between the main surface and the back surface in the thickness direction;
The first end surface overlaps the back surface when viewed in the thickness direction,
the second end surface is located on an opposite side of the first end surface from the main surface in a direction perpendicular to the thickness direction,
the first end surface is inclined with respect to the main surface toward a side on which the second end surface is located in a direction perpendicular to the thickness direction ,
an inclination angle of the first end surface with respect to the main surface is smaller than an inclination angle of the second end surface with respect to the back surface;
the substrate has an intermediate surface that faces the thickness direction and is connected to the first end surface and the second end surface;
A thermal printhead, wherein, when viewed in the thickness direction, each of the first end surface, the second end surface and the intermediate surface is spaced apart from the resistor layer and the wiring layer . the main surface includes a first edge extending in the main scanning direction and located closest to the resistor layer, and a second edge extending in a sub-scanning direction;
The thermal printhead of claim 1 , wherein the first end surface includes a first region connected to the first edge and a second region connected to the second edge. the substrate has a ridge that defines a boundary between the first region and the second region;
The thermal printhead of claim 2 , wherein the ridge is inclined with respect to the main surface. The thermal printhead of claim 3, wherein the inclination angle of the ridge line relative to the main surface is smaller than the inclination angle of the first end surface relative to the main surface. the substrate is made of a semiconductor material;
5. A thermal printhead according to claim 1 , wherein the semiconductor material comprises a single crystal material having a composition of silicon . the substrate has a protrusion protruding from the main surface in the thickness direction,
The thermal printhead according to claim 5 , wherein the plurality of heat generating portions are formed on the convex portion . Further comprising an insulating layer covering the main surface,
the insulating layer is located between the substrate and the resistor layer;
The thermal printhead according to claim 5 , wherein the insulating layer entirely overlaps the main surface when viewed in the thickness direction . the wiring layer includes a common wiring and a plurality of individual wirings;
the common wiring is electrically connected to the plurality of heat generating portions,
The thermal printhead according to claim 7 , wherein the plurality of individual wirings are individually connected to the plurality of heat generating portions . a protective layer covering the plurality of heat generating portions and the wiring layer;
The thermal printhead according to claim 7 , wherein the entire protective layer overlaps the main surface when viewed in the thickness direction . the protective layer has an end surface facing a direction perpendicular to the thickness direction,
The thermal printhead according to claim 9 , wherein, when viewed in the thickness direction, the end face is spaced from a periphery of the insulating layer toward a side where the wiring layer is located . Further comprising a heat dissipation member,
11. The thermal printhead according to claim 1 , wherein the rear surface is joined to the heat dissipation member . A step of forming a resistor layer including a plurality of heating portions arranged in a main scanning direction on a substrate having a main surface facing one side in a thickness direction;
forming a wiring layer that is electrically connected to the plurality of heat generating portions in contact with the resistor layer;
forming a groove in the base material, the groove being recessed from the main surface, extending along a direction perpendicular to the thickness direction, and spaced apart from the resistor layer and the wiring layer;
cutting the base material in the thickness direction;
the groove portion has an inclined surface connected to the main surface and inclined with respect to the main surface, and a bottom surface facing the same side as the main surface in the thickness direction and located on the opposite side to the main surface with respect to the inclined surface in a direction perpendicular to the thickness direction,
In the step of forming the groove portion, the groove portion is formed using a first blade,
The first blade has a base portion and a cutting edge portion extending from the base portion in a radial direction of the first blade and surrounding the base portion in a circumferential direction of the first blade,
The thickness of the cutting edge portion decreases as it moves away from the base portion in the radial direction,
The cutting edge portion has an end surface facing the radial direction,
In the step of cutting the base material, the base material is cut using a second blade,
a thickness of the second blade is smaller than a dimension of the end surface in a direction perpendicular to the radial direction;
In the step of cutting the base material, the second blade is brought into contact with the bottom surface while moving the second blade away from the inclined surface.

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