Thermal print head

Abstract

To provide a thermal print head capable of suppressing disconnection of a wiring layer.SOLUTION: A thermal print head 1 includes a substrate 10, a glaze layer 11, and a planarized layer 15. The substrate 10 includes a first surface 10a. The glaze layer 11 is provided on the first surface 10a. The flattening layer 15 is provided on the first surface 10a. The flattening layer 15 includes crystal portions 15b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to thermal printheads. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2022-52544 (Patent Document 1) discloses a thermal printhead including a substrate, a glaze layer, a wiring layer, and a heating resistor. The glaze layer includes a glass layer that forms a smooth surface on which the wiring layer is disposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-52544

[0004] [overview] An object of the present disclosure is to provide a thermal printhead in which disconnection of the wiring layer can be suppressed.

[0005] The thermal printhead of the present disclosure includes a substrate, a glaze layer, and a planarization layer. The substrate has a first surface. The glaze layer is provided on the first surface. The planarization layer is provided on the first surface. The planarization layer includes a crystalline portion. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic plan view of a thermal printhead according to a first embodiment. [Figure 2] FIG. 2 is a schematic enlarged partial cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a schematic partial enlarged plan view of region III in FIG. [Figure 4] FIG. 4 is an SEM image showing a cross section of the planarizing layer of the thermal printhead according to the first embodiment. [Figure 5]FIG. 5 is a flowchart of a method for manufacturing a thermal printhead according to the first embodiment. [Figure 6] FIG. 6 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 7] FIG. 7 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 8] FIG. 8 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 9] FIG. 9 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 10] FIG. 10 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 11] FIG. 11 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 12] FIG. 12 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 13] FIG. 13 is a schematic, partially enlarged cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment.

[0007] [Detailed explanation] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated. At least some of the configurations of the embodiments described below may be combined in any manner.

[0008] (Embodiment 1)

[0009] <Thermal printhead configuration> FIG. 1 is a schematic plan view of a thermal printhead 1 according to a first embodiment. FIG. 2 is a schematic, partially enlarged cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a schematic, partially enlarged plan view of region III in FIG. 1. As shown in FIGS. 1 and 2, the thermal printhead 1 according to the first embodiment includes a substrate 10, a glaze layer 11, a planarizing layer 15, wiring layers 20 and 45, a heating resistor 30, a protective layer 33, a drive circuit 40, conductive wires 41, a sealing member 43, and a plurality of external connection terminals 50. Note that the protective layer 33 is not shown in FIGS. 1 and 3.

[0010] The substrate 10 is, for example, a ceramic substrate such as an alumina substrate. As shown in FIG. 2, the substrate 10 has a first surface 10a. In a plan view of the first surface 10a (hereinafter simply referred to as "plan view"), the longitudinal direction of the substrate 10 is the x-direction. The x-direction is the main scanning direction. The lateral direction of the substrate 10 is the y-direction. The y-direction is the sub-scanning direction. The thickness direction of the substrate 10 is the z-direction. The z-direction is perpendicular to the x-direction (main scanning direction) and the y-direction (sub-scanning direction). In a plan view, the y-direction (sub-scanning direction) is the transport direction of a print medium (e.g., thermal recording paper).

[0011] 2, the glaze layer 11 is provided on the first surface 10a of the substrate 10. The glaze layer 11 includes an amorphous portion formed of, for example, amorphous glass. The thermal conductivity of the glaze layer 11 may be lower than that of the substrate 10.

[0012] 2, the glaze layer 11 is provided on a portion of the first surface 10a. That is, the glaze layer 11 is a so-called partial glaze. The glaze layer 11 includes a heater glaze 12 and a die bonding glaze 13.

[0013] The heater glaze 12 extends in the x-direction in a plan view of the first surface 10a. The heater glaze 12 is disposed below the heating resistor 30. The heater glaze 12 prevents heat from the heating resistor 30 from dissipating to the substrate 10. The heater glaze 12 is a heat storage layer. The heater glaze 12 protrudes from a portion of the first surface 10a. The heater glaze 12 increases the height of the heating resistor 30 from the first surface 10a. The heating resistor 30 is pressed against a print medium (e.g., thermal recording paper).

[0014] The die bonding glaze 13 is disposed at a distance in the y direction from the heater glaze 12. In a plan view of the first surface 10a, the die bonding glaze 13 extends in the x direction. The die bonding glaze 13 supports a part of the wiring layer 20 and the drive circuit 40.

[0015] As shown in FIG. 2, the planarization layer 15 is provided on the first surface 10a. The material constituting the planarization layer 15 includes glass. The material constituting the planarization layer 15 may also include alumina. Specifically, the planarization layer 15 includes, for example, an amorphous portion 15a formed of amorphous glass and a crystalline portion 15b formed of crystallized glass (see FIG. 4). The planarization layer 15 may also include a filler 15c formed of alumina.

[0016] The planarization layer 15 includes a first planarization layer 16 and a second planarization layer 17. In a planar view of the first surface 10a, the first planarization layer 16 is disposed between the heater glaze 12 and the die bonding glaze 13. The second planarization layer 17 is disposed away from the first planarization layer 16 in the y direction. The second planarization layer 17 is disposed opposite the first planarization layer 16 with respect to the heater glaze 12 in the y direction.

[0017] As shown in FIG. 2, the thickness of the planarization layer 15 in the z direction is smaller than the thickness of the glaze layer 11 in the z direction. Specifically, the thickness of the planarization layer 15 in the z direction is smaller than the thickness of the heater glaze 12 in the z direction. The thickness of the planarization layer 15 in the z direction is smaller than the thickness of the die bonding glaze 13 in the z direction. The surface roughness of the planarization layer 15 is smaller than the surface roughness of the first surface 10a. Therefore, by disposing the wiring layer 20 on the planarization layer 15, it is possible to suppress breaks in the wiring layer 20 due to the surface roughness of the first surface 10a.

[0018] 2, the wiring layer 20 is disposed on the glaze layer 11 and the planarization layer 15. The wiring layer 20 forms a conductive path for supplying electricity to the heating resistor 30. The wiring layer 20 includes a common wiring 21 and a plurality of individual wirings 25.

[0019] 1 to 3, the common wiring 21 is disposed on the heater glaze 12, the die bonding glaze 13, the first planarization layer 16, and the second planarization layer 17. The common wiring 21 includes a plurality of strip portions 22, a connecting portion 23, and a detour portion 24.

[0020] As shown in FIGS. 2 and 3, a plurality of strip-shaped portions 22 are disposed on the heater glaze 12 and the second planarizing layer 17. Each of the plurality of strip-shaped portions 22 extends along the -y direction. The plurality of strip-shaped portions 22 are arranged at equal intervals in the x direction. The plurality of strip-shaped portions 22 are, for example, gold (Au) wiring. The plurality of strip-shaped portions 22 are, for example, formed of a gold particle sintered body.

[0021] As shown in FIGS. 2 and 3, the connecting portion 23 is disposed on the second planarizing layer 17. The connecting portion 23 extends along the x direction. The connecting portion 23 is connected to the plurality of strip-shaped portions 22. The plurality of strip-shaped portions 22 are connected by the connecting portion 23. The connecting portion 23 is, for example, a silver (Ag) wiring. The connecting portion 23 is, for example, formed of a silver particle sintered body.

[0022] As shown in FIG. 1 , the detour portion 24 is connected to the connecting portion 23. The detour portion 24 extends from both ends of the connecting portion 23 in the x direction along the -y direction so as to detour around the multiple individual wirings 25. The detour portion 24 is disposed on the second planarization layer 17, the heater glaze 12, the first planarization layer 16, and the die bonding glaze 13. The detour portion 24 is, for example, a silver (Ag) wiring. The detour portion 24 is formed, for example, of a silver particle sintered body. Because the material constituting the connecting portion 23 and the detour portion 24 contains silver (Ag) instead of gold (Au), the manufacturing cost of the thermal printhead 1 can be reduced.

[0023] Each of the plurality of individual wires 25 partially conducts electricity to the heating resistor 30. The plurality of individual wires 25 are disposed on the heater glaze 12, the die bonding glaze 13, and the first planarization layer 16. As shown in FIG. 2 , each of the plurality of individual wires 25 includes a first individual wire portion 26 and a second individual wire portion 27.

[0024] The first individual wiring portions 26 are disposed on the heater glaze 12 and the first planarizing layer 16. The first individual wiring portions 26 are, for example, gold (Au) wiring. The first individual wiring portions 26 are, for example, formed of a gold particle sintered body.

[0025] The second individual wiring portion 27 is connected to the first individual wiring portion 26. The second individual wiring portion 27 is disposed on the die bonding glaze 13 and the first planarization layer 16. The second individual wiring portion 27 is, for example, a silver (Ag) wiring. The second individual wiring portion 27 is formed, for example, of a silver particle sintered body. Because the material constituting the second individual wiring portion 27 contains silver (Ag) instead of gold (Au), the manufacturing cost of the thermal printhead 1 can be reduced. The second individual wiring portion 27 may be a laminate of a first layer 28 and a second layer 29. The first layer 28 is formed, for example, of a silver particle sintered body. The second layer 29 is formed, for example, of frit glass containing silver particles.

[0026] As shown in FIG. 1, in plan view, each of the plurality of individual wirings 25 includes individual wiring regions 25a, 25b, and 25c.

[0027] As shown in FIG. 2, the individual wiring region 25a is a portion of the individual wiring 25 that is disposed on the first planarization layer 16. As shown in FIG. 3, the individual wiring region 25a extends in a direction inclined with respect to the y direction. As shown in FIG. 2, the individual wiring region 25a is formed from the second individual wiring portion 27. It is sufficient that the second individual wiring portion 27 is disposed in the individual wiring region 25a. In other words, the first individual wiring portion 26 may be disposed in the individual wiring region 25a. From a different perspective, the first individual wiring portion 26 and the second individual wiring portion 27 may be connected to the individual wiring region 25a. The individual wiring region 25a is longer than the individual wiring region 25b and also longer than the individual wiring region 25c. Note that the individual wiring region 25a may be shorter than the individual wiring regions 25b and 25c.

[0028] As shown in FIG. 2, the individual wiring region 25b is connected to one end of the individual wiring region 25a. The individual wiring region 25b is a portion of the individual wiring 25 that is disposed on the heater glaze 12, and is electrically connected to the heating resistor 30. As shown in FIG. 3, the individual wiring region 25b extends along the y direction. As shown in FIG. 2, the individual wiring region 25b is formed from a first individual wiring portion 26. A second individual wiring portion 27 may be disposed in the individual wiring region 25b. From a different perspective, the first individual wiring portion 26 and the second individual wiring portion 27 may be connected to the individual wiring region 25b.

[0029] As shown in Fig. 2, the individual wiring region 25c is connected to the other end of the individual wiring region 25a. The individual wiring region 25c is a portion of the individual wiring 25 that is disposed on the die bonding glaze 13, and is electrically connected to the drive circuit 40. The individual wiring region 25c extends along the y direction (not shown). As shown in Fig. 2, the individual wiring region 25c is formed from a second individual wiring portion 27.

[0030] 1 to 3, the heating resistor 30 is disposed on top of the heater glaze 12. The heating resistor 30 extends in the x-direction. In a plan view of the first surface 10a, the heating resistor 30 may have a strip-like shape, for example. The heating resistor 30 protrudes from the heater glaze 12 to the opposite side of the substrate 10 in the z-direction.

[0031] The heating resistor 30 is connected to the wiring layer 20. Specifically, as shown in FIG. 3, the heating resistor 30 is connected to the plurality of strip portions 22 of the common wiring 21 and the individual wiring areas 25b of the plurality of individual wirings 25. In a plan view, the heating resistor 30 is arranged so as to intersect with the plurality of strip portions 22 and the plurality of individual wiring areas 25b. The heating resistor 30 is formed so as to straddle the plurality of strip portions 22 and the individual wiring areas 25b. Heat generated by the heating resistor 30 causes printing on a print medium (e.g., thermal recording paper).

[0032] 2, the protective layer 33 protects the heating resistor 30. The protective layer 33 may protect the common wiring 21 and the individual wirings 25. The protective layer 33 may be a laminate of a first protective layer 34 and a second protective layer 35.

[0033] The first protective layer 34 is formed on the heating resistor 30 and covers the heating resistor 30. The first protective layer 34 is formed on the common wiring 21 and the plurality of individual wirings 25 and may cover the common wiring 21 and the plurality of individual wirings 25. The first protective layer 34 may be formed on a part of the glaze layer 11 and a part of the planarization layer 15. The first protective layer 34 is an insulating layer. The first protective layer 34 is formed of, for example, amorphous glass. The second protective layer 35 is formed on the first protective layer 34. The second protective layer 35 is formed of, for example, amorphous glass.

[0034] As shown in FIGS. 1 and 2, the drive circuit 40 selectively energizes the plurality of individual wirings 25. The drive circuit 40 is, for example, a drive IC. In the first embodiment, the plurality of drive circuits 40 are arranged spaced apart from one another in the x direction. The drive circuit 40 is arranged on the die bonding glaze 13. The drive circuit 40 is electrically connected to the individual wiring regions 25c of the plurality of individual wirings 25 and the wiring layer 45. For example, the drive circuit 40 is electrically connected to the plurality of individual wiring regions 25b via conductive wires 41. The drive circuit 40 is electrically connected to the wiring layer 45 via conductive wires (not shown).

[0035] 2, the sealing member 43 seals the drive circuit 40. The sealing member 43 has electrical insulating properties and is made of an insulating resin material such as epoxy resin.

[0036] 1, the wiring layer 45 electrically connects the drive circuit 40 and the plurality of external connection terminals 50. The wiring layer 45 is, for example, a silver (Ag) wiring. The wiring layer 45 is formed in the same manner as the second individual wiring portion 27, for example.

[0037] The plurality of external connection terminals 50 may be terminals to which an electric cable is joined using a conductive joining material such as solder, or may be terminals to which a connector is attached. The plurality of external connection terminals 50 are arranged along the outer periphery of the substrate 10 in the y direction in a plan view of the first surface 10a. The plurality of external connection terminals 50 are electrically connected to the wiring layer 45 and the detour portion 24 of the common wiring 21. The plurality of external connection terminals 50 are formed in the same manner as, for example, the second individual wiring portion 27.

[0038] The thermal printhead 1 according to the first embodiment is characterized in that the planarizing layer 15 includes a crystalline portion 15b formed of crystallized glass, as shown in Fig. 4. Fig. 4 is a scanning electron microscope (SEM) image showing a cross section of the planarizing layer 15 of the thermal printhead 1 according to the first embodiment.

[0039] As described above, to reduce the manufacturing cost of the thermal printhead 1, a silver layer is formed on the planarization layer 15 as silver wiring. If the planarization layer 15 does not include the crystalline portion 15b but includes the amorphous portion 15a, there is a risk of air bubbles forming in the planarization layer 15 when the silver layer is formed on the planarization layer 15. Furthermore, there is a risk of the planarization layer 15 softening and flowing when the silver layer is formed. Therefore, there is a risk of the wiring layer 20 provided on the planarization layer 15 being broken due to the air bubbles formed in the planarization layer 15 or the softening and flow.

[0040] In particular, the softening point of the planarizing layer 15 is lower than that of the glaze layer 11. Specifically, the softening point of the glaze layer 11 is 900°C or higher, and the softening point of the planarizing layer 15 is less than 800°C.

[0041] On the other hand, in the thermal printhead 1 according to the first embodiment, as shown in FIG. 4, the planarization layer 15 contains crystalline portions 15b. Therefore, the softening point of the planarization layer 15 is higher than that of a planarization layer that does not contain crystalline portions 15b. Specifically, the softening point of the planarization layer 15 according to the first embodiment is 800°C or higher and 870°C or lower. This suppresses the generation of bubbles in the planarization layer 15 and the softening and flow of the planarization layer 15 when the wiring layer 20 is formed. As a result, breakage of the wiring layer 20 can be suppressed.

[0042] As shown in FIG. 4, the majority of the planarization layer 15 is occupied by amorphous portions 15a. From a different perspective, the crystalline portions 15b are unevenly distributed within the amorphous portions 15a. That is, in the cross section of the planarization layer 15, multiple crystalline portions 15b are dispersed within the amorphous portions 15a serving as the base material. Specifically, in the cross section of the planarization layer 15, the crystalline portions 15b occupy 10% or more of the area of ​​the planarization layer 15. This increases the softening point of the planarization layer 15, thereby suppressing disconnections in the wiring layer 20. In the cross section of the planarization layer 15, the crystalline portions 15b may occupy 15% or more of the area of ​​the planarization layer 15.

[0043] In Fig. 4, the portions shown as white rectangular regions are crystalline portions 15b. As shown in Fig. 4, in the cross section of the planarizing layer 15, the shape of the crystalline portions 15b may be a line extending in one direction, a rectangle, a circle, or an ellipse. Filler 15c such as alumina may be disposed in the amorphous portions 15a.

[0044] Furthermore, for example, if the crystallization of the planarization layer 15 progresses and the crystalline portion 15b occupies more of the planarization layer 15, the softening point of the planarization layer 15 increases, but the surface roughness of the planarization layer 15 increases. This may cause disconnection of the wiring layer 20 formed on the planarization layer 15. Therefore, in the cross section of the planarization layer 15, the crystalline portion 15b may occupy 30 percent or less of the area of ​​the planarization layer 15. In the cross section of the planarization layer 15, the crystalline portion 15b may occupy 25 percent or less of the area of ​​the planarization layer 15.

[0045] The crystalline portion 15b can be confirmed by observing the cross section of the planarizing layer 15. Specifically, the thermal printhead 1 is first cross-section polished using a CP (Cross Section Polisher). The cross section is then viewed using a scanning electron microscope (SEM) manufactured by Hitachi High-Technologies Corporation (model number: SU-70), and a cross-sectional image such as that shown in FIG. 4 can be obtained. The crystalline portion 15b can be confirmed from the cross-sectional image.

[0046] <Thermal printhead manufacturing method>

[0047] A method for manufacturing the thermal printhead 1 according to the present embodiment 1 will now be described. Fig. 5 is a flowchart of the method for manufacturing the thermal printhead 1 according to the embodiment 1. Figs. 6 to 13 are partially enlarged cross-sectional views each showing a step in the method for manufacturing the thermal printhead according to the embodiment 1.

[0048] First, a step (S1) of preparing a substrate 10 is performed. In this step (S1), a substrate 10 having a first surface 10a is prepared as shown in Fig. 6. The substrate 10 is, for example, a ceramic substrate such as an alumina substrate.

[0049] Next, a step (S2) of forming a glaze layer 11 is performed. In this step (S2), as shown in FIG. 7, the glaze layer 11 is formed on the first surface 10a of the substrate 10. Specifically, a glass paste that will become the glaze layer 11 is printed on the first surface 10a of the substrate 10. The glass paste is fired. In this way, the glaze layer 11 is formed. The glaze layer 11 includes, for example, a heater glaze 12 and a die bonding glaze 13.

[0050] Next, a step (S3) of forming a planarization layer 15 is performed. In this step (S3), as shown in FIG. 8, the planarization layer 15 is formed on the region of the first surface 10a that is not covered by the glaze layer 11. For example, a glass paste that will become the planarization layer 15 is printed on the region of the first surface 10a that is not covered by the glaze layer 11. The glass paste is fired. In this way, the planarization layer 15 is formed. The planarization layer 15 includes, for example, a first planarization layer 16 and a second planarization layer 17.

[0051] By firing the glass paste at 800°C, crystallized glass can be precipitated on the planarization layer 15. As a result, the planarization layer 15 including the crystalline portion 15b can be formed. The glass paste that becomes the planarization layer 15 contains a nucleation material. Examples of the nucleation material include zirconia (ZrO2), titanium oxide (TiO2), and phosphorus oxide (P2O5). The inclusion of the nucleation material in the glass paste causes crystallized glass to be precipitated on the planarization layer 15. The formed planarization layer 15 may contain any of aluminum oxide (Al2O3), lithium oxide (Li2O), zinc oxide (ZnO), and magnesium oxide (MgO).

[0052] Next, a step (S4) of forming a wiring layer 20 is performed. In this step (S4), as shown in FIG. 9, the wiring layer 20 is formed on the glaze layer 11 and the planarization layer 15. First, a paste containing a conductive material, such as gold (Au) particles, is printed on the heater glaze 12 and the planarization layer 15. The paste is fired to form a first conductive layer. The first conductive layer is patterned by a photolithography process. The photolithography process includes a step of forming an etching mask by an exposure step and a development step, and a step of etching the first conductive layer using the etching mask. In this way, the strip portion 22 of the common wiring 21 and the individual wiring regions 25b (first individual wiring portions 26) of the multiple individual wirings 25 are formed.

[0053] Next, a resinate paste containing a conductive material such as silver (Ag) particles is printed on the planarizing layer 15, heater glaze 12, and die bonding glaze 13. A glass paste containing a conductive material such as silver (Ag) particles and glass frit is printed on a portion of the resinate paste. The resinate paste and glass paste are fired to form a second conductive layer. The second conductive layer is patterned by a photolithography process. The photolithography process includes a process of forming an etching mask by an exposure process and a development process, and a process of etching the second conductive layer using the etching mask.

[0054] In this manner, the connecting portion 23 of the common wiring 21, the detour portion 24, the individual wiring regions 25a and 25c of the multiple individual wirings 25 (the first layer 28 and the second layer 29 of the second individual wiring portion 27), the wiring layer 45, and the multiple external connection terminals 50 are formed. The softening point of the planarization layer 15 is 800°C or higher. Therefore, when the first layer 28 is formed on the planarization layer 15 as a silver wiring, no bubbles are generated in the planarization layer 15, and no softening or flow occurs. As a result, breaks in the wiring layer 20 are suppressed in the thermal printhead 1 according to the first embodiment. Note that the method for forming the wiring layer 20 is not limited to the above method.

[0055] Next, step (S5) of forming the heating resistor 30 is performed. In this step (S5), as shown in FIG. 10, for example, the heating resistor 30 is formed on the heater glaze 12, the plurality of strip portions 22 of the common wiring 21, and the individual wiring regions 25b of the plurality of individual wirings 25. First, a resistor paste is applied to the heater glaze 12, the plurality of strip portions 22 of the common wiring 21, and the individual wiring regions 25b of the plurality of individual wirings 25. The resistor paste contains a conductive material, such as ruthenium oxide, tantalum nitride, tantalum, or silver-vanadium, and glass. The resistor paste is then fired. In this manner, the heating resistor 30 is formed.

[0056] Next, a step (S6) of forming a protective layer 33 is performed. In this step (S6), as shown in FIG. 11 , the protective layer 33 is formed on the glaze layer 11, the planarization layer 15, the wiring layer 20, and the heating resistor 30. Specifically, a glass paste that will become the first protective layer 34 is printed on the glaze layer 11, the planarization layer 15, the wiring layer 20, and the heating resistor 30. The glass paste is fired. As a result, the first protective layer 34 is formed. Furthermore, a glass paste that will become the second protective layer 35 is printed on the first protective layer 34. The glass paste is fired. As a result, the second protective layer 35 is formed. In this manner, the protective layer 33 is formed.

[0057] Next, a singulation step (S7) is performed. In this step (S7), the laminate including the substrate 10, the glaze layer 11, the planarization layer 15, the wiring layers 20 and 45, the plurality of external connection terminals 50, the heating resistor 30, and the protective layer 33 is divided. For example, grooves are formed in the substrate 10 by a laser scribing method. The laminate is then cut along the grooves. In this manner, the laminate is singulated.

[0058] Next, a step (S8) of mounting the driving circuit 40 is performed. In this step (S8), the driving circuit 40 is mounted on the die bonding glaze 13, as shown in Fig. 12. For example, the driving circuit 40 is fixed to the die bonding glaze 13 using a bonding member (not shown) such as a resin adhesive or solder.

[0059] Next, a step (S9) of forming conductive wires 41 is performed. In this step (S9), the conductive wires 41 are bonded as shown in Fig. 13. The conductive wires 41 are bonded to the drive circuit 40 and the individual wiring regions 25c of the plurality of individual wires 25. The conductive wires (not shown) are bonded to the drive circuit 40 and the plurality of wiring layers 45.

[0060] Next, a step (S10) of forming a sealing member 43 is carried out. In this step (S10), the drive circuit 40 is sealed with the sealing member 43. For example, a sealing resin material is potted onto the drive circuit 40. The sealing resin material is then cured. In this manner, the sealing member 43 is formed. In this manner, the thermal printhead 1 according to the first embodiment, as shown in FIGS. 1 to 3, is manufactured. In the thermal printhead 1 according to the first embodiment, connectors may be attached to the plurality of external connection terminals 50.

[0061] <Action and effect>

[0062] A thermal printhead 1 according to the present disclosure includes a substrate 10, a glaze layer 11, and a planarization layer 15. The substrate 10 has a first surface 10a. The glaze layer 11 is provided on the first surface 10a. The planarization layer 15 is provided on the first surface 10a. The planarization layer 15 includes a crystalline portion 15b.

[0063] This can prevent bubbles from being formed in the planarizing layer 15 and prevent the planarizing layer 15 from softening and flowing, thereby preventing the wiring layer 20 from being broken.

[0064] In the thermal printhead 1, the crystalline portion 15b occupies 10% to 30% of the cross section of the planarizing layer 15.

[0065] This reduces the surface roughness of the planarization layer 15, while also suppressing the generation of bubbles and softening and flowing of the planarization layer 15. As a result, breaks in the wiring layer 20 can be suppressed.

[0066] The thermal printhead 1 includes a wiring layer 20 disposed on the planarization layer 15. The wiring layer 20 includes silver wiring.

[0067] In this way, the manufacturing cost of the thermal printhead 1 can be reduced.

[0068] In the thermal printhead 1, the planarizing layer 15 includes an amorphous portion 15a.

[0069] This reduces the surface roughness of the planarization layer 15, while also suppressing the generation of bubbles and softening and flowing of the planarization layer 15. As a result, breaks in the wiring layer 20 can be suppressed.

[0070] According to the thermal printhead 1, the material that forms the planarizing layer 15 includes glass.

[0071] In this way, the crystalline portion 15b can be precipitated when the planarizing layer 15 is formed. As a result, the softening point of the planarizing layer 15 increases, and the generation of bubbles and softening flow in the planarizing layer 15 are suppressed. In this way, breakage of the wiring layer 20 can be suppressed.

[0072] In the thermal printhead 1 , the softening point of the planarizing layer 15 is lower than the softening point of the glaze layer 11 .

[0073] In this way, after the glaze layer 11 is formed, the flattening layer 15 can be formed without softening the glaze layer 11.

[0074] According to the thermal printhead 1, the softening point of the planarizing layer 15 is 800°C or higher and 870°C or lower.

[0075] In this way, the crystalline portion 15b can be precipitated when the planarizing layer 15 is formed. As a result, the softening point of the planarizing layer 15 increases, and the generation of bubbles and softening flow in the planarizing layer 15 are suppressed. In this way, breakage of the wiring layer 20 can be suppressed.

[0076] In the thermal printhead 1, the glaze layer 11 includes a heater glaze 12 and a die bonding glaze 13. The die bonding glaze 13 is disposed apart from the heater glaze 12. The planarizing layer 15 (first planarizing layer 16) is disposed between the heater glaze 12 and the die bonding glaze 13.

[0077] In this way, the wiring layer 20 can be formed on the first planarizing layer 16 as a conductive path for supplying electricity to the heating resistor 30 .

[0078] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) a substrate having a first surface; a glaze layer provided on the first surface; a planarization layer provided on the first surface, A thermal printhead, wherein the planarization layer includes a crystalline portion. (Appendix 2) A thermal printhead as described in Appendix 1, wherein, in a cross section of the planarization layer, the crystalline portion occupies an area of ​​the planarization layer that is greater than or equal to 10 percent and less than or equal to 30 percent. (Appendix 3) a wiring layer disposed on the planarization layer; 3. The thermal printhead of claim 1, wherein the wiring layer includes silver wiring. (Appendix 4) 4. The thermal printhead of claim 1, wherein the planarization layer includes an amorphous portion. (Appendix 5) 5. The thermal printhead of claim 1, wherein the material constituting the planarization layer includes glass. (Appendix 6) 6. The thermal printhead of claim 1, wherein the softening point of the planarization layer is lower than the softening point of the glaze layer. (Appendix 7) 7. The thermal printhead according to claim 6, wherein the softening point of the planarization layer is 800°C or higher and 870°C or lower. (Appendix 8) the glaze layer includes a heater glaze and a die bonding glaze spaced apart from the heater glaze; 8. The thermal printhead of claim 1, wherein the planarization layer is disposed between the heater glaze and the die bonding glaze.

[0079] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0080] 1 thermal print head, 10 substrate, 10a first surface, 11 glaze layer, 12 heater glaze, 13 die bonding glaze, 15 planarization layer, 15a amorphous portion, 15b crystalline portion, 15c filler, 16 first planarization layer, 17 second planarization layer, 20 wiring layer, 21 common wiring, 22 strip portion, 23 connecting portion, 24 detour portion, 25 individual wiring, 25a individual wiring area, 25b individual wiring area, 25c individual wiring area, 26 first individual wiring portion, 27 second individual wiring portion, 28 first layer, 29 second layer, 30 heating resistor, 33 protective layer, 34 first protective layer, 35 second protective layer, 40 drive circuit, 41 conductive wire, 43 sealing member, 45 wiring layer, 50 external connection terminal.

Claims

1. a substrate having a first surface; a glaze layer provided on the first surface; a planarization layer provided on the first surface, A thermal printhead, wherein the planarization layer includes a crystalline portion.

2. 2. The thermal printhead of claim 1, wherein the crystalline portion occupies an area of ​​the planarization layer that is 10 percent to 30 percent of the cross section of the planarization layer.

3. a wiring layer disposed on the planarization layer; 3. The thermal printhead according to claim 1, wherein the wiring layer includes silver wiring.

4. 3. The thermal printhead according to claim 1, wherein the planarization layer includes an amorphous portion.

5. 3. The thermal printhead according to claim 1, wherein the material constituting the planarization layer includes glass.

6. 3. The thermal printhead according to claim 1, wherein the softening point of the planarizing layer is lower than the softening point of the glaze layer.

7. 7. The thermal printhead according to claim 6, wherein the softening point of the planarizing layer is 800°C or higher and 870°C or lower.

8. the glaze layer includes a heater glaze and a die bonding glaze spaced apart from the heater glaze; 3. The thermal printhead according to claim 1, wherein the planarization layer is disposed between the heater glaze and the die bonding glaze.

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