Thermal print head and thermal print head manufacturing method

Abstract

To provide a thermal print head which can suppress wire bonding failure.SOLUTION: A thermal print head comprises a substrate, an insulation layer, a wiring layer, a resistor layer, and a protective layer. The substrate has a first face, and a second face opposite to the first face. A bump, which projects toward an opposite side of the second face and extends along a first direction in a plan view, is formed on the first face. The insulation layer is located on the first face. The wiring layer is located on the insulation layer with the resistor layer interposed therebetween. The wiring layer has a bonding pad. A constituent material of the wiring layer is aluminum or aluminum alloy. The protective layer is located on the insulation layer so as to cover the wiring layer. An opening for exposing the bonding pad is formed in the protective layer. The width of the opening in the first direction is larger than the width of the bonding pad in the first direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a thermal printhead and a method for manufacturing a thermal printhead. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open No. 2022-165673 (Patent Document 1) describes a thermal printhead. The thermal printhead described in Patent Document 1 has a substrate, an insulating layer, a wiring layer, a resistor layer, a protective layer, and a plating layer.

[0003] The insulating layer is disposed on the substrate. The wiring layer is disposed on the insulating layer with a resistor layer interposed therebetween. The wiring layer is made of copper. The wiring layer has a bonding pad. The protective layer is disposed on the insulating layer so as to cover the wiring layer. The protective layer has an opening penetrating the protective layer. The bonding pad is partially exposed from the opening. The plating layer is disposed on the bonding pad exposed from the opening. Wire bonding is performed on the bonding pad via the plating layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-165673 A [Summary] In order to reduce manufacturing costs, it is possible to change the constituent material of the wiring layer from copper to aluminum (or an aluminum alloy). This eliminates the need to form a plating layer on the bonding pad. However, since the upper surface of the bonding pad is lower than the upper surface of the protective layer, the capillary may come into contact with the edge of the opening when performing wire bonding. Contact between the capillary and the edge of the opening causes wire bonding failure.

[0005] The thermal printhead of the present disclosure includes a substrate, an insulating layer, a wiring layer, a resistor layer, and a protective layer. The substrate has a first surface and a second surface opposite to the first surface. A protuberance is formed on the first surface, protruding toward the side opposite to the second surface and extending along a first direction in a plan view. The insulating layer is disposed on the first surface. The wiring layer is disposed on the insulating layer with the resistor layer interposed therebetween. The wiring layer has a bonding pad. The wiring layer is made of aluminum or an aluminum alloy. The protective layer is disposed on the insulating layer so as to cover the wiring layer. An opening is formed in the protective layer to expose the bonding pad. The width of the opening in the first direction is larger than the width of the bonding pad in the first direction. [Brief description of the drawings]

[0006] [Figure 1] FIG. 2 is a plan view of the thermal printhead 100. [Figure 2A] FIG. 2 is a cross-sectional view taken along line IIA-IIA in FIG. [Figure 2B] FIG. 2 is a cross-sectional view taken along line IIB-IIB in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 2 is a plan view of the thermal printhead 100 with bonding wires 60 bonded thereto. [Diagram 5] 1A to 1C are diagrams illustrating the manufacturing process of the thermal printhead 100. [Figure 6] FIG. 11 is a first cross-sectional view illustrating a protrusion forming step S2. [Figure 7] FIG. 11 is a second cross-sectional view illustrating the protrusion forming step S2. [Figure 8] FIG. 11 is a third cross-sectional view illustrating the protrusion forming step S2. [Figure 9] FIG. 11 is a cross-sectional view illustrating an insulating layer forming step S3. [Figure 10] FIG. 11 is a first cross-sectional view illustrating a wiring layer forming step S4. [Figure 11] FIG. 11 is a second cross-sectional view illustrating the wiring layer forming step S4. [Figure 12] FIG. 11 is a third cross-sectional view illustrating the wiring layer forming step S4. [Figure 13] FIG. 4 is a fourth cross-sectional view illustrating a wiring layer forming step S4. [Figure 14] FIG. 5 is a fifth cross-sectional view illustrating a wiring layer forming step S4. [Figure 15] 11 is a cross-sectional view illustrating a protective layer forming step S5. FIG. [Figure 16] FIG. 2 is a plan view of a thermal printhead 200. [Figure 17] FIG. 18 is a cross-sectional view taken along line XVII-XVII in FIG.

[0007] [Detailed Description] The details of the embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference characters, and redundant description will not be repeated. A thermal printhead according to the embodiment is referred to as a thermal printhead 100.

[0008] (Configuration of thermal print head 100) The configuration of the thermal printhead 100 will now be described.

[0009] FIG. 1 is a plan view of a thermal printhead 100. Note that in FIG. 1, the removed portions of the individual wiring 31 and the common wiring 32 are omitted. FIG. 2A is a cross-sectional view taken along line IIA-IIA in FIG. 1. FIG. 2B is a cross-sectional view taken along line IIB-IIB in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. As shown in FIGS. 1 to 3, the thermal printhead 100 has a substrate 10, an insulating layer 20, a wiring layer 30, a resistor layer 40, and a protective layer 50.

[0010] The constituent material of the substrate 10 is, for example, single crystal silicon. The substrate 10 has a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b are end surfaces in the thickness direction of the substrate 10. The second surface 10b is the surface opposite to the first surface 10a.

[0011] The first surface 10a is formed with a raised portion 11. The raised portion 11 protrudes from the first surface 10a to the opposite side to the second surface 10b. The raised portion 11 extends along a first direction DR1 in a plan view.

[0012] The insulating layer 20 includes, for example, a first insulating layer 21, a glaze layer 22, and a second insulating layer 23. The first insulating layer 21 is formed on the first surface 10a. The first insulating layer 21 is also disposed on the second surface 10b. The first insulating layer 21 is made of, for example, silicon oxide. The glaze layer 22 is disposed on the top surface of the protrusion 11 with the first insulating layer 21 interposed therebetween. The glaze layer 22 is made of, for example, glass. The second insulating layer 23 is disposed on the first insulating layer 21 so as to cover the glaze layer 22. The second insulating layer 23 is made of, for example, silicon oxide.

[0013] The wiring layer 30 is disposed on the insulating layer 20 with the resistor layer 40 interposed therebetween. The wiring layer 30 is made of, for example, aluminum or an aluminum alloy. The resistor layer 40 is made of, for example, tantalum nitride. An intermediate layer 41 may be interposed between the wiring layer 30 and the resistor layer 40. The intermediate layer 41 is made of, for example, titanium.

[0014] The wiring layer 30 includes a plurality of individual wirings 31 , a plurality of common wirings 32 , and a common electrode 33 .

[0015] The individual wirings 31 are arranged along a first direction DR1 in a plan view. One end of each of the individual wirings 31 in the second direction DR2 overlaps with the protruding portion 11 in a plan view. The individual wirings 31 have a bonding pad 31a at the other end in the second direction DR2. The second direction DR2 is perpendicular to the first direction DR1 in a plan view.

[0016] In a cross-sectional view perpendicular to the second direction DR2, the bonding pad 31a has a top surface, a bottom surface, and a side surface continuing to the top surface and the bottom surface. The width of the bottom surface of the bonding pad 31a in the first direction DR1 is preferably 1.1 times or more the width of the top surface of the bonding pad 31a in the first direction DR1. It is preferable that aluminum chloride is substantially absent on the side surface of the bonding pad 31a. From another perspective, it is preferable that the concentration of aluminum chloride on the side surface of the bonding pad 31a is not detected. The concentration of aluminum chloride on the side surface of the bonding pad 31a is measured by energy dispersive X-ray spectroscopy. The width of the bonding pad 31a in the first direction DR1 is preferably 100 μm or more.

[0017] The multiple common wirings 32 are arranged along the first direction DR1 in a plan view. The common wirings 32 are disposed between two adjacent individual wirings 31 in the first direction DR1. One end of the common wiring 32 in the second direction DR2 overlaps the protruding portion 11 in a plan view. One end of the common wiring 32 in the second direction DR2 is connected to one end of the individual wiring 31 in the second direction DR2. The other end of the common wiring 32 in the second direction DR2 is connected to a common electrode 33. The common electrode 33 extends along the first direction DR1 in a plan view. A common potential is supplied to the common electrode 33.

[0018] The individual wiring 31 is partially removed at a position overlapping with the raised portion 11 in a planar view. The intermediate layer 41 and resistor layer 40 are exposed from the removed portion of the individual wiring 31. The intermediate layer 41 exposed from the removed portion of the individual wiring 31 is partially removed, and the resistor layer 40 is exposed from the removed portion of the intermediate layer 41. Similarly, the common wiring 32 is partially removed at a position overlapping with the raised portion 11 in a planar view. The intermediate layer 41 and resistor layer 40 are exposed from the removed portion of the common wiring 32. The intermediate layer 41 exposed from the removed portion of the common wiring 32 is partially removed, and the resistor layer 40 is exposed from the removed portion of the intermediate layer 41.

[0019] The protective layer 50 is made of, for example, silicon nitride. The protective layer 50 is disposed on the insulating layer 20 so as to cover the wiring layer 30. Note that in the removed portions of the individual wiring 31 and the removed portions of the common wiring 32, the protective layer 50 is also disposed on the resistor layer 40 and the intermediate layer 41.

[0020] An opening 51 is formed in the protective layer 50. The opening 51 penetrates the protective layer 50 in the thickness direction. In a plan view, the width of the opening 51 in the second direction DR2 is, for example, larger than the width of the opening 51 in the first direction DR1. In a plan view, the width of the opening 51 in the first direction DR1 is larger than the width of the bonding pad 31a in the first direction DR1. From another perspective, both ends of the bonding pad 31a in the first direction DR1 are exposed from the opening 51.

[0021] Fig. 4 is a plan view of the thermal printhead 100 with the bonding wire 60 bonded thereto. As shown in Fig. 4, one end of the bonding wire 60 is bonded to the bonding pad 31a. Although not shown, the other end of the bonding wire 60 is bonded to a bonding pad of a driver IC (Integrated Circuit). In this way, the thermal printhead 100 is electrically connected to the driver IC.

[0022] The driver IC individually supplies a potential to each of the multiple individual wirings 31 via the bonding wires 60. As a result, a current flows through the individual wiring 31 to which the potential is supplied and the common wiring 32 connected to the individual wiring 31. A current flows through the resistor layer 40 in the removed portion of the individual wiring 31 and the removed portion of the common wiring 32. As a result, the resistor layer 40 exposed from the removed portion of the individual wiring 31 to which the potential is supplied and the resistor layer 40 exposed from the removed portion of the common wiring 32 connected to the individual wiring 31 individually generate heat, and the heat is transferred to the paper, thereby printing on the paper.

[0023] (Method of manufacturing the thermal printhead 100) A method for manufacturing a thermal printhead will now be described.

[0024] Fig. 5 is a manufacturing process diagram of the thermal printhead 100. As shown in Fig. 5, the manufacturing method of the thermal printhead 100 includes a preparation step S1, a protrusion forming step S2, an insulating layer forming step S3, a wiring layer forming step S4, a protective layer forming step S5, and a singulation step S6. In the preparation step S1, a substrate 10 is prepared. After the preparation step S1, a protrusion forming step S2 is performed.

[0025] In the protuberance forming step S2, the protuberance 11 is formed on the first surface 10a. FIG. 6 is a first cross-sectional view illustrating the protuberance forming step S2. As shown in FIG. 6, in the protuberance forming step S2, first, a hard mask HM is formed on the surface of the substrate 10. The hard mask HM is made of, for example, silicon nitride. The hard mask HM is formed by, for example, a low-pressure CVD (Chemical Vapor Deposition) method. FIG. 7 is a second cross-sectional view illustrating the protuberance forming step S2. As shown in FIG. 7, in the protuberance forming step S2, second, the hard mask HM on the first surface 10a is partially removed by RIE (Reactive Ion Etching) using a resist pattern formed by photolithography as a mask. As a result, the hard mask HM remains on the first surface 10a only at positions corresponding to the top surfaces of the protuberances 11. FIG. 8 is a third cross-sectional view illustrating the protuberance forming step S2. 8, in the protuberance forming step S2, thirdly, wet etching is performed on the first surface 10a using a potassium hydroxide aqueous solution with the hard mask HM as a mask. Although not shown, after this wet etching, the hard mask HM is removed with hydrofluoric acid. After the protuberance forming step S2, an insulating layer forming step S3 is performed.

[0026] FIG. 9 is a cross-sectional view for explaining the insulating layer forming step S3. As shown in FIG. 9, in the insulating layer forming step S3, an insulating layer 20 is formed. In the insulating layer forming step S3, first, a first insulating layer 21 is formed on the surface of the substrate 10 by thermal oxidation. Second, a glaze layer 22 is formed on the top surface of the protuberance 11 with the first insulating layer 21 interposed therebetween. The glaze layer 22 is formed by applying a paste containing glass on the top surface of the protuberance 11 with the first insulating layer 21 interposed therebetween, and firing the applied paste. Third, a second insulating layer 23 is formed on the first insulating layer 21 on the first surface 10a so as to cover the glaze layer 22. The second insulating layer 23 is formed by a plasma CVD method using, for example, TEOS (Tetra Eth Oxy Silane). After the insulating layer forming step S3, a wiring layer forming step S4 is performed.

[0027] Fig. 10 is a first cross-sectional view illustrating the wiring layer formation step S4. As shown in Fig. 10, in the wiring layer formation step S4, first, a constituent material of the resistor layer 40, a constituent material of the intermediate layer 41, and a constituent material of the wiring layer 30 are sequentially formed on the insulating layer 20. This film formation is performed by, for example, sputtering.

[0028] 11 is a second cross-sectional view illustrating the wiring layer forming step S4. As shown in FIG. 11, in the wiring layer forming step S4, secondly, the constituent material of the formed wiring layer 30 is patterned by wet etching using a resist pattern formed by photolithography as a mask. As a result, the individual wiring 31, the common wiring 32, and the common electrode 33 are formed. At this stage, the individual wiring 31 and the common wiring 32 are not partially removed. Since the patterning of the wiring layer 30 is performed by wet etching, the width of the bottom surface of the bonding pad 31a in the first direction DR1 is 1.1 times or more the width of the top surface of the bonding pad 31a in the first direction DR1, and substantially no aluminum chloride is present on the side surface of the bonding pad 31a.

[0029] FIG. 12 is a third cross-sectional view explaining the wiring layer forming step S4. As shown in FIG. 12, in the wiring layer forming step S4, third, the constituent material of the formed intermediate layer 41 is patterned by wet etching using the individual wiring 31, the common wiring 32, and the common electrode 33 as a mask. This forms the intermediate layer 41. FIG. 13 is a fourth cross-sectional view explaining the wiring layer forming step S4. As shown in FIG. 13, in the wiring layer forming step S4, fourth, the individual wiring 31 and the common wiring 32 that are located at a position overlapping with the protrusion 11 in a plan view are partially removed by wet etching using a resist pattern formed by, for example, photolithography as a mask. In addition, with this etching, the intermediate layer 41 exposed from the removed portion of the individual wiring 31 and the removed portion of the common wiring 32 is also partially removed.

[0030] Fig. 14 is a fifth cross-sectional view illustrating the wiring layer forming step S4. As shown in Fig. 14, in the wiring layer forming step S4, the constituent material of the formed resistor layer 40 is patterned by RIE using a resist pattern formed by photolithography as a mask. At this time, the constituent material of the formed resistor layer 40 is not removed in the removed portions of the individual wirings 31 and the removed portions of the common wirings 32. After the wiring layer forming step S4, a protective layer forming step S5 is performed.

[0031] Fig. 15 is a cross-sectional view illustrating the protective layer forming step S5. As shown in Fig. 15, in the protective layer forming step S5, a protective layer 50 is formed. In the protective layer forming step S5, first, the protective layer 50 is formed by, for example, a CVD method. Second, an opening 51 is formed by, for example, RIE using a resist pattern formed by photolithography as a mask so as to expose the bonding pad 31a. After the protective layer forming step S5, a singulation step S6 is performed.

[0032] In the singulation step S6, the substrate 10 is cut to form the structures of the thermal printheads 100 shown in FIGS.

[0033] The thermal printhead 100 is subjected to a wire bonding process S7. The wire bonding process S7 is performed using a capillary. The bonding wire 60 is held in the capillary. The diameter of the capillary is preferably larger than the width of the bonding pad 31a in the first direction DR1. The difference between the width of the bonding pad 31a in the first direction DR1 and the diameter of the capillary is preferably 20 μm or more.

[0034] (Modification) In the thermal printhead 100, the top surface of the raised portion 11 may be formed by a plurality of flat surfaces. Also, in the thermal printhead 100, the insulating layer 20 may not have the glaze layer 22. In this case, in the raised portion forming step S2, wet etching is performed on the substrate 10 using an aqueous potassium hydroxide solution, followed by wet etching using TMAH (tetramethylammonium hydroxyl). As a result, the top surface of the raised portion 11 is composed of a plurality of flat surfaces.

[0035] (Effects of Thermal Print Head 100) The effects of the thermal printhead 100 will be described below in comparison with a comparative example. The thermal printhead according to the comparative example is referred to as a thermal printhead 200.

[0036] Fig. 16 is a plan view of the thermal printhead 200. Fig. 17 is a cross-sectional view taken along line XVII-XVII in Fig. 17. As shown in Fig. 16 and Fig. 17, in the thermal printhead 200, the width of the opening 51 in the first direction DR1 is smaller than the width of the bonding pad 31a in the first direction DR1. That is, in the thermal printhead 200, both ends of the bonding pad 31a in the first direction DR1 are covered with the protective layer 50, and the bonding pad 31a is not completely exposed from the opening 51.

[0037] In the thermal printhead 200, the width of the bottom surface of the bonding pad 31a in the first direction DR1 is less than 1.1 times the width of the top surface of the bonding pad 31a in the first direction DR1, and aluminum chloride remains on the side surface of the bonding pad 31a. That is, the patterning of the wiring layer 30 is formed by dry etching using a chlorine-based gas. In these respects, the configuration of the thermal printhead 200 differs from the configuration of the thermal printhead 100.

[0038] In the thermal printhead 200, the upper surface of the bonding pad 31a is lower than the upper surface of the protective layer 50, and the width of the opening 51 in the first direction DR1 is smaller than the width of the bonding pad 31a in the first direction DR1. Therefore, when wire bonding is performed in the thermal printhead 200, the capillary may come into contact with the edge of the opening 51, resulting in poor bonding between the bonding wire 60 and the bonding pad 31a.

[0039] In the thermal printhead 100, the upper surface of the bonding pad 31a is also lower than the upper surface of the protective layer 50. However, in the thermal printhead 100, the width of the opening 51 in the first direction DR1 is larger than the width of the bonding pad 31a in the first direction DR1, so that the capillary is unlikely to come into contact with the edge of the opening 51 when wire bonding is performed. In this way, the thermal printhead 100 makes it possible to suppress wire bonding defects.

[0040] In the thermal printhead 200, since aluminum chloride remains on the side surface of the bonding pad 31a, the width of the opening 51 in the first direction DR1 cannot be made larger than the width of the bonding pad 31a in the first direction DR1. If the width of the opening 51 in the first direction DR1 in the thermal printhead 200 is made larger than the width of the bonding pad 31a in the first direction DR1 (if the side surface of the bonding pad 31a is exposed from the protective layer 50), corrosion of the bonding pad 31a will progress due to the influence of the aluminum chloride remaining on the side surface.

[0041] (Additional Note) The present disclosure includes the following configurations.

[0042] <Appendix 1> A substrate; An insulating layer; A wiring layer; A resistor layer; A protective layer. the substrate has a first surface and a second surface opposite the first surface; a protrusion is formed on the first surface, the protrusion protruding toward a side opposite to the second surface and extending along a first direction in a plan view; the insulating layer is disposed on the first surface; the wiring layer is disposed on the insulating layer with the resistor layer therebetween, the wiring layer has a bonding pad; the wiring layer is made of aluminum or an aluminum alloy; the protective layer is disposed on the insulating layer so as to cover the wiring layer; an opening for exposing the bonding pad is formed in the protective layer; A thermal printhead, wherein a width of the opening in the first direction is greater than a width of the bonding pad in the first direction.

[0043] <Appendix 2> the bonding pad has a top surface and a bottom surface opposite the top surface; The width of the bottom surface in the second direction is 1.1 times or more the width of the top surface in the second direction, 2. The thermal printhead of claim 1, wherein the second direction is perpendicular to the first direction in a plan view.

[0044] <Appendix 3> In a cross-sectional view perpendicular to the second direction, the bonding pad has a top surface, a bottom surface opposite the top surface, and a side surface connected to the top surface and the bottom surface; In the above aspect, aluminum chloride is not detected, 3. The thermal printhead according to claim 1, wherein the second direction is perpendicular to the first direction in a plan view.

[0045] <Appendix 4> 4. The thermal printhead of claim 1, wherein the width of the opening in the first direction is 100 μm or more.

[0046] <Appendix 5> providing a substrate having a first surface and a second surface opposite the first surface; forming a protrusion on the first surface that protrudes toward an opposite side to the second surface and extends along a first direction in a plan view; forming an insulating layer on the first surface; forming a wiring layer on the insulating layer with a resistor layer interposed therebetween; forming a protective layer on the insulating layer so as to cover the wiring layer; the wiring layer is made of aluminum or an aluminum alloy; the wiring layer has a bonding pad; an opening for exposing the bonding pad is formed in the protective layer; A method for manufacturing a thermal printhead, wherein a width of the opening in the first direction is greater than a width of the bonding pad in the first direction.

[0047] <Appendix 6> The method for manufacturing a thermal printhead described in Appendix 5, wherein the step of forming the wiring layer includes a step of depositing a constituent material of the wiring layer, and a step of patterning the deposited constituent material of the wiring layer by wet etching using a resist pattern as a mask.

[0048] <Appendix 7> The method further includes a step of performing wire bonding on the bonding pad using a capillary. 7. The method for manufacturing a thermal printhead according to claim 5, wherein a width of the opening in the first direction is larger than a diameter of the capillary.

[0049] Although the embodiment of the present disclosure has been described above, the above-mentioned embodiment can be modified in various ways. The scope of the present invention is not limited to the above-mentioned embodiment. The scope of the present invention is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0050] 10 substrate, 10a first surface, 10b second surface, 11 raised portion, 20 insulating layer, 21 first insulating layer, 22 glaze layer, 23 second insulating layer, 30 wiring layer, 31 individual wiring, 31a bonding pad, 32 common wiring, 33 common electrode, 40 resistor layer, 41 intermediate layer, 50 protective layer, 51 opening, 60 bonding wire, 100, 200 thermal print head, DR1 first direction, DR2 second direction, HM hard mask, S1 preparation process, S2 raised portion formation process, S3 insulating layer formation process, S4 wiring layer formation process, S5 protective layer formation process, S6 singulation process, S7 wire bonding process.

Claims

1. A substrate; An insulating layer; A wiring layer; A resistor layer; A protective layer. The substrate has a first surface and a second surface opposite the first surface, a protruding portion is formed on the first surface, the protruding portion protruding toward an opposite side to the second surface and extending along a first direction in a plan view; the insulating layer is disposed on the first surface; the wiring layer is disposed on the insulating layer with the resistor layer therebetween, the wiring layer has a bonding pad; the wiring layer is made of aluminum or an aluminum alloy; the protective layer is disposed on the insulating layer so as to cover the wiring layer; an opening for exposing the bonding pad is formed in the protective layer; A thermal printhead, wherein a width of the opening in the first direction is greater than a width of the bonding pad in the first direction.

2. the bonding pad has a top surface and a bottom surface opposite the top surface; The width of the bottom surface in the second direction is 1.1 times or more the width of the top surface in the second direction, The thermal printhead according to claim 1 , wherein the second direction is perpendicular to the first direction in a plan view.

3. In a cross-sectional view perpendicular to the second direction, the bonding pad has a top surface, a bottom surface opposite the top surface, and a side surface connected to the top surface and the bottom surface; In the above aspect, the concentration of aluminum chloride is undetectable; The thermal printhead according to claim 1 , wherein the second direction is perpendicular to the first direction in a plan view.

4. The thermal printhead of claim 1 , wherein the width of the opening in the first direction is 100 μm or more.

5. providing a substrate having a first surface and a second surface opposite the first surface; forming a protrusion on the first surface, the protrusion protruding toward an opposite side to the second surface and extending along a first direction in a plan view; forming an insulating layer on the first surface; forming a wiring layer on the insulating layer with a resistor layer interposed therebetween; forming a protective layer on the insulating layer so as to cover the wiring layer; the wiring layer is made of aluminum or an aluminum alloy; the wiring layer has a bonding pad; an opening for exposing the bonding pad is formed in the protective layer; A method for manufacturing a thermal printhead, wherein a width of the opening in the first direction is greater than a width of the bonding pad in the first direction.

6. 6. The method for manufacturing a thermal printhead according to claim 5, wherein the step of forming the wiring layer includes the steps of: depositing a material for the wiring layer; and patterning the deposited material for the wiring layer by wet etching using a resist pattern as a mask.

7. The method further includes a step of performing wire bonding on the bonding pad using a capillary. The method for manufacturing a thermal printhead according to claim 5 or 6, wherein a width of the opening in the first direction is larger than a diameter of the capillary.

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