Thermal printhead, thermal printer, and method for producing thermal printhead

Abstract

This thermal printhead comprises a substrate, a wiring layer and a resistor layer, a protective layer, a driver IC, and a filling resin layer having a portion interposed between a main surface and the driver IC, wherein the wiring layer comprises Ag and has a plurality of first pads, the driver IC has a plurality of electrodes, the protective layer has openings where the plurality of electrodes are exposed, the plurality of electrodes are electrically connected to the plurality of first pads through the openings, and the filling resin layer fills all of the openings.

Description

Thermal printhead, thermal printer, and method for manufacturing thermal printhead

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

[0002] Thermal printheads have been used as devices that print by applying heat to thermal paper or thermal ink ribbons. For example, Patent Document 1 discloses a conventional thermal printhead. The thermal printhead described in Patent Document 1 includes a substrate, a wiring layer, a resistor layer, a protective layer, a driver IC, and a sealing resin. The resistor layer is electrically connected to the driver IC via the wiring layer. In this document, the wiring layer contains Ag.

[0003] Japanese Patent Application Laid-Open No. 2018-103608

[0004] When a voltage is applied to a wiring layer containing Ag, ion migration may occur. If parts of the wiring layer come into contact with each other due to ion migration, an electrical short circuit may occur.

[0005] An object of the present disclosure is to provide an improved thermal printhead, a thermal printer, and a method for manufacturing a thermal printhead. In particular, in view of the above-mentioned circumstances, an object of the present disclosure is to provide a thermal printhead, a thermal printer, and a method for manufacturing a thermal printhead that can suppress the occurrence of ion migration in the wiring layer.

[0006] A thermal printhead provided by a first aspect of the present disclosure includes a substrate having a main surface and a back surface facing opposite each other in a thickness direction, a wiring layer and a resistor layer supported on the main surface, a protective layer covering a portion of the wiring layer and at least a portion of the resistor layer, a driver IC disposed on the main surface and controlling the flow of current to the resistor layer, and a filled resin layer having a portion interposed between the main surface and the driver IC. The wiring layer contains Ag and has a plurality of pad portions. The driver IC has a plurality of electrodes. The protective layer has openings exposing the plurality of pad portions. The plurality of electrodes are conductively joined to the plurality of pad portions through the openings. The filled resin layer covers all of the openings.

[0007] A thermal printer provided by a second aspect of the present disclosure includes the thermal printhead provided by the first aspect of the present disclosure.

[0008] A third aspect of the present disclosure provides a method for manufacturing a thermal printhead, comprising the steps of: preparing a substrate having a main surface and a back surface facing opposite each other in a thickness direction; forming a wiring layer and a resistor layer supported on the main surface; forming a protective layer covering a portion of the wiring layer and at least a portion of the resistor layer; conductively joining a driver IC to the wiring layer; and forming a filled resin layer having a portion interposed between the main surface and the driver IC. The wiring layer contains Ag and has a plurality of pad portions. The driver IC has a plurality of electrodes. The protective layer has openings that expose the plurality of pad portions. In the step of conductively joining the driver IC to the wiring layer, the plurality of electrodes are conductively joined to the plurality of pad portions through the openings. The step of forming the filled resin layer includes the steps of forming a first portion interposed between the main surface and the driver IC and spaced from an edge of the opening, and forming a second portion that closes the area between the first portion and the edge of the opening.

[0009] According to the above configuration, it is possible to suppress the occurrence of ion migration in the wiring layer.

[0010] Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0011] FIG. 1 is a plan view showing a thermal printhead according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 , showing a printer according to the first embodiment of the present disclosure. FIG. 3 is an enlarged plan view of a thermal printhead according to the first embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is an enlarged plan view of a thermal printhead according to the first embodiment of the present disclosure. FIG. 6 is an enlarged cross-sectional view of a thermal printhead according to the first embodiment of the present disclosure. FIG. 7 is an enlarged cross-sectional view taken along line VII-VII in FIG. 5. FIG. 8 is a flowchart showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 9 is an enlarged cross-sectional view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 10 is an enlarged cross-sectional view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 11 is an enlarged cross-sectional view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 12 is an enlarged cross-sectional view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. Fig. 13 is an enlarged plan view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. Fig. 14 is an enlarged cross-sectional view of a main portion taken along line XIV-XIV in Fig. 13. Fig. 15 is an enlarged cross-sectional view of a main portion showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. Fig. 16 is an enlarged cross-sectional view of a main portion taken along line XVI-XVI in Fig. 15. Fig. 17 is an enlarged plan view of a main portion showing a thermal printhead according to a second embodiment of the present disclosure. Fig. 18 is an enlarged plan view of a main portion showing a thermal printhead according to the second embodiment of the present disclosure. Fig. 19 is an enlarged cross-sectional view of a main portion taken along line XIX-XIX in Fig. 17. Fig. 20 is an enlarged cross-sectional view of a main portion showing a thermal printhead according to a third embodiment of the present disclosure.

[0012] Preferred embodiments of the present disclosure will now be described in detail with reference to the drawings.

[0013] The terms "first," "second," "third," etc. in this disclosure are used for identification purposes only and are not intended to impose any ranking on their objects.

[0014] In this disclosure, unless otherwise specified, "a certain object A is formed on a certain object B" and "a certain object A is formed on a certain object B" include "a certain object A is formed directly on a certain object B" and "a certain object A is formed on a certain object B with another object interposed between the certain object A and the certain object B." Similarly, "a certain object A is disposed on a certain object B" and "a certain object A is disposed on a certain object B" include "a certain object A is disposed directly on a certain object B" and "a certain object A is disposed on a certain object B with another object interposed between the certain object A and the certain object B" unless otherwise specified. Similarly, "a certain object A is located on a certain object B" includes "a certain object A is located on a certain object B with a certain object A in contact with the certain object B" and "a certain object A is located on a certain object B with another object interposed between the certain object A and the certain object B." Furthermore, unless otherwise specified, the phrase "an object A overlaps an object B when viewed in a certain direction" includes "an object A overlaps the entire object B" and "an object A overlaps a part of an object B." Furthermore, in the present disclosure, "a surface A faces in (one side or the other side of) direction B" is not limited to the case where the angle of surface A with respect to direction B is 90°, but also includes the case where surface A is tilted with respect to direction B.

[0015] 1 to 7 show a thermal printhead A1 and a thermal printer P1 according to a first embodiment of the present disclosure. The thermal printhead A1 comprises a substrate 1, a protective layer 2, a wiring layer 3, a resistor layer 4, multiple driving ICs 7, a protective resin 78, a filling resin layer 8, and a heat dissipation member 9. The thermal printhead A1 is incorporated into a thermal printer P1 that prints on a print medium C1 (see FIG. 2).

[0016] The thermal printer P1 includes a thermal printhead A1 and a platen roller B1. The platen roller B1 faces the thermal printhead A1. A print medium C1 is sandwiched between the thermal printhead A1 and the platen roller B1 and transported in the sub-scanning direction y by the platen roller B1. Examples of such print media C1 include thermal paper for creating barcode sheets or receipts. A flat rubber platen may be used instead of the platen roller B1. This platen includes a cylindrical rubber portion with a large radius of curvature that is arch-shaped in cross section.

[0017] FIG. 1 is a plan view showing a thermal printhead A1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, showing a printer according to a first embodiment of the present disclosure. FIG. 3 is an enlarged plan view showing a main portion of the thermal printhead A1. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is an enlarged plan view showing a main portion of the thermal printhead A1. FIG. 6 is an enlarged cross-sectional view showing a main portion of the thermal printhead A1. FIG. 7 is an enlarged cross-sectional view taken along line VII-VII in FIG. 5. In FIG. 1, the protective layer 2 is omitted. In FIG. 3, the protective layer 2 is omitted, and the wiring layer 3 is hatched. In FIGS. 5 and 6, the protective resin 78 is omitted. In FIG. 5, the protective layer 2 and the filled resin layer 8 are hatched. In FIG. 6, the driving IC 7 and the filled resin layer 8 are indicated by imaginary lines.

[0018] In these figures, the thickness direction of the substrate 1 (base material 11 described below) is referred to as the thickness direction z. One side of the thickness direction z may be referred to as the z1 side, and the other side as the z2 side. The main scanning direction x and the sub-scanning direction y are both directions perpendicular to the thickness direction z. During printing, the printing medium C1 is fed from the y2 side to the y1 side of the sub-scanning direction y. In the sub-scanning direction y, the y1 side may be referred to as the downstream side, and the y2 side as the upstream side.

[0019] 1, the substrate 1 is a plate-like member extending in the primary scanning direction x. The substrate 1 is a support member that supports the protective layer 2, the wiring layer 3, the resistor layer 4, and the plurality of driving ICs 7. The substrate 1 has a base material 11 and a glaze layer 12.

[0020] The substrate 11 includes a ceramic such as AlN (aluminum nitride), Al2O3 (alumina), or zirconia, and has these ceramics as its main component. The substrate 11 has a thickness of 0.6 mm or more and 1.0 mm or less. As shown in FIG. 1 , the substrate 11 has a rectangular shape extending elongatedly in the primary scanning direction x in a plan view. The substrate 11 has a principal surface 11a and a first back surface 11b. The principal surface 11a and the first back surface 11b are spaced apart in the thickness direction z. The principal surface 11a faces the z1 side in the thickness direction z. The first back surface 11b faces the z2 side in the thickness direction z. The principal surface 11a is the principal surface of the present disclosure, and the first back surface 11b is the back surface of the present disclosure.

[0021] The glaze layer 12 is formed on the main surface 11a of the substrate 11. The glaze layer 12 covers the main surface 11a. The glaze layer 12 is made of a glass material such as amorphous glass. In this example, the glaze layer 12 includes a bulging portion 122 and a flat portion 121. Note that the glaze layer 12 may also include the flat portion 121 but not the bulging portion 122.

[0022] The bulging portion 122 extends elongatedly in the main scanning direction x. When viewed in the main scanning direction x, the bulging portion 122 bulges in the thickness direction z. As shown in FIG. 4 , the bulging portion 122 has an arc-shaped cross section (y-z cross section) taken along a plane perpendicular to the main scanning direction x. The bulging portion 122 is provided to make it easier to press the heat-generating portion of the resistor layer 4 (the heat-generating portion 41 described below) against the print medium C1. The bulging portion 122 is also provided as a heat storage layer that accumulates heat from the heat-generating portion 41. The dimension (maximum dimension) of the bulging portion 122 in the thickness direction z is larger than that of the flat portion 121.

[0023] The flat portion 121 is formed adjacent to the bulging portion 122, and has a flat surface on the z1 side in the thickness direction z. The thickness of the flat portion 121 is, for example, about 2.0 μm. The flat portion 121 covers the main surface 11 a of the base material 11, which is a relatively rough surface, to form a smooth surface suitable for forming the wiring layer 3.

[0024] There are no limitations on the softening point of the glaze layer 12. The softening point of the flat portion 121 and the softening point of the bulging portion 122 may be the same or different from each other. The softening points of the flat portion 121 and the bulging portion 122 are, for example, 800°C or higher and 850°C or lower, or, for example, approximately 680°C.

[0025] The substrate 1 of this embodiment is also provided with a plurality of terminals 19. The plurality of terminals 19 are arranged in the main scanning direction x, for example, along the edge of the substrate 1 on the y2 side in the sub-scanning direction y.

[0026] (Wiring Layer 3) The wiring layer 3 forms a conductive path for passing electricity through the resistor layer 4. The wiring layer 3 is made of a conductive material. The wiring layer 3 contains at least Ag (silver). Furthermore, another part of the wiring layer 3 may contain a material other than Ag (silver), such as Au (gold).

[0027] Examples of the wiring layer 3 containing Ag (silver) include those formed by printing and firing a paste containing an organic Ag compound or a paste containing Ag particles, glass frit, Pd (palladium), and resin. In this embodiment, the portions of the wiring layer 3 shown in, for example, FIGS. 5 to 7 are primarily composed of Ag (silver). Furthermore, the plurality of strip portions 32 and the plurality of strip portions 35 of the wiring layer 3 that contact the resistor layer 4 may be primarily composed of Au (gold). The thickness of the wiring layer 3 is not particularly limited and is, for example, 1 μm or more and 10 μm or less.

[0028] The wiring layer 3 is formed on the glaze layer 12 of the substrate 1. As shown in Figures 3 and 4, the wiring layer 3 has a common electrode 31 and a plurality of individual electrodes 34. Note that the shape and arrangement of each part of the wiring layer 3 are not limited to the examples shown in Figures 3 and 4, and various configurations are possible.

[0029] As shown in FIG. 3 , the common electrode 31 has a plurality of strip-shaped portions 32 and connecting portions 33. The connecting portions 33 are arranged near the edge of the substrate 1 on the y1 side in the sub-scanning direction y and are strip-shaped extending in the main scanning direction x. The plurality of strip-shaped portions 32 each extend from the connecting portion 33 to the y2 side in the sub-scanning direction y and are arranged at equal intervals in the main scanning direction x. In the example shown in FIG. 3 , an auxiliary layer 331 is laminated on the connecting portion 33 to reduce the resistance value of the connecting portion 33, but the auxiliary layer 331 does not have to be laminated. The auxiliary layer 331 is formed, for example, by printing and firing a paste containing an organic Ag (silver) compound or a paste containing Ag (silver) particles, glass frit, Pd (palladium), and a resin.

[0030] The plurality of individual electrodes 34 are used to partially apply electricity to the resistor layer 4. Each individual electrode 34 has an opposite polarity to the common electrode 31. Each individual electrode 34 extends from the resistor layer 4 toward the driving IC 7. The plurality of individual electrodes 34 are arranged in the main scanning direction x. The specific configuration of the resistor layer 4 is not limited in any way, and each of the plurality of individual electrodes 34 has a strip portion 35, a connecting portion 36, and a first pad portion 37.

[0031] 3, the strip portions 35 extend in the sub-scanning direction y and are strip-shaped when viewed in the thickness direction z. Each strip portion 35 is located between two adjacent strip portions 32 of the common electrode 31. The distance between the strip portions 35 of adjacent individual electrodes 34 and the strip portions 32 of the common electrode 31 is, for example, 50 μm or less.

[0032] 5 and 6, the plurality of first pad portions 37 are formed at the end portion on the y2 side in the sub-scanning direction y of the individual electrode 34. The shape of the first pad portion 37 is not limited in any way, and in the illustrated example, it is circular.

[0033] The arrangement of the multiple first pad portions 37 is not limited in any way. In this embodiment, the multiple first pad portions 37 include multiple first pad portions 37A and multiple first pad portions 37B. The multiple first pad portions 37A are arranged at equal intervals along the main scanning direction x. The first pad portions 37B are arranged on the y2 side of the first pad portions 37A in the sub-scanning direction y, and are arranged at equal intervals along the main scanning direction x. In other words, the multiple first pad portions 37 are arranged in a staggered pattern. The first pad portion 37B is connected to the straight portion 361 sandwiched between two adjacent first pad portions 37A.

[0034] As shown in FIGS. 3 , 5 , and 6 , the connecting portion 36 extends from the strip portion 35 toward the plurality of first pad portions 37. The connecting portion 36 includes a straight portion 361, an inclined portion 362, an intermediate portion 363, and a second pad portion 364. One end of the straight portion 361 is connected to the first pad portion 37 and extends along the sub-scanning direction y. The inclined portion 362 is connected to the end of the strip portion 35 on the y2 side in the sub-scanning direction y and is inclined with respect to the sub-scanning direction y. The intermediate portion 363 is interposed between the straight portion 361 and the inclined portion 362. The shape of the intermediate portion 363 is not limited in any way, and in the illustrated example, it is a curved strip-shaped portion. The second pad portion 364 is interposed between the first pad portion 37 and the heat generating portion 41 and is formed integrally with the intermediate portion 363 in the illustrated example. There are no limitations on the size or shape of the second pad portion 364, and in this embodiment, the second pad portion 364 is larger than the first pad portion 37. In the illustrated example, the second pad portion 364 has a substantially pentagonal shape.

[0035] The second pad portions 364 of the connecting portions 36 of the individual electrodes 34 constitute a plurality of second pad portions 364. The arrangement of the plurality of second pad portions 364 is not limited in any way. The plurality of second pad portions 364 includes a plurality of second pad portions 364A and a plurality of second pad portions 364B. The plurality of second pad portions 364A are arranged at equal intervals along the main scanning direction x. The plurality of second pad portions 364B are arranged at equal intervals along the main scanning direction x on the y2 side of the plurality of second pad portions 364A in the sub-scanning direction y. In other words, the plurality of second pad portions 364 are arranged in a staggered pattern. Between adjacent second pad portions 364A, an intermediate portion 363 formed integrally with the second pad portion 364B is arranged. Between adjacent second pad portions 364B, an intermediate portion 363 formed integrally with the second pad portion 364A is arranged. In the illustrated example, the second pad portion 364A and the second pad portion 364B are in a line-symmetric relationship with respect to an axis of symmetry extending in the primary scanning direction x.

[0036] 5 to 7 show a plurality of pad portions. In this embodiment, the plurality of pad portions include a plurality of pad portions 381 and a plurality of pad portions 382 in addition to the above-described plurality of first pad portions 37. Furthermore, the wiring layer 3 includes a wiring portion 391 and a plurality of wiring portions 392.

[0037] The pads 381 are arranged at equal intervals in the main scanning direction x. The pads 381 are arranged on the y2 side in the sub-scanning direction y relative to the first pads 37. The pads 381 are connected to a wiring portion 391. The wiring portion 391 is arranged on the y2 side in the sub-scanning direction y relative to the pads 381, and is rectangular in the illustrated example. The wiring portion 391 is, for example, part of a power supply line for enabling printing by the thermal printhead A1.

[0038] The pad portions 382 are arranged on both sides of the first pad portions 37 in the main scanning direction x. In the illustrated example, the pad portions 382 include those arranged in the main scanning direction x together with the first pad portions 37A, and those arranged in the main scanning direction x together with the pad portions 381. The pad portions 382 include those connected to the wiring portions 392.

[0039] (Resistor Layer 4) The resistor layer 4 is formed using a material with a higher resistivity than the material constituting the wiring layer 3. The resistor layer 4 includes, for example, ruthenium oxide. In this example, the resistor layer 4 is formed on the bulge portion 122 as shown in FIGS. 3 and 4 . The shape of the resistor layer 4 as viewed in the thickness direction z is not limited. In this embodiment, as shown in FIGS. 1 and 3 , the resistor layer 4 has a strip shape extending in the main scanning direction x. The resistor layer 4 intersects with each strip portion 32 (common electrode 31) and each strip portion 35 (individual electrode 34). In the thickness direction z, the resistor layer 4 is stacked on the z1 side of the multiple strip portions 32 and the multiple strip portions 35.

[0040] The portions of the resistor layer 4 sandwiched between the strip portions 32 and 35 are heat generating portions 41. The heat generating portions 41 generate heat when partially energized by the wiring layer 3. Print dots are formed by the heat generated by each heat generating portion 41. The heat generating portions 41 are arranged in the main scanning direction x. The greater the number of heat generating portions 41 arranged in the main scanning direction x per unit length (e.g., 1 mm) of the main scanning direction x of the substrate 1, the greater the dot density of the thermal printhead A1.

[0041] The thickness of the resistor layer 4 is, for example, 3 μm or more and 6 μm or less. In the example shown in FIG. 4 , the resistor layer 4 is formed on the top of the bulge portion 122, but it does not have to be formed on the top of the bulge portion 122.

[0042] (Protective Layer 2) The protective layer 2 is intended to protect the wiring layer 3, the resistor layer 4, and the like. The protective layer 2 may be composed of a single layer or a laminate of multiple layers. The material of the protective layer 2 is not limited in any way. One example of the protective layer 2 is primarily composed of amorphous glass. Another example of the protective layer 2 is a laminate of a first layer composed of amorphous glass and a second layer composed of SiAlON. SiAlON is a silicon nitride-based engineering ceramic obtained by combining SiN (silicon nitride) with AlO (alumina) and SiO (silica). The second layer is formed, for example, by sputtering. SiC (silicon carbide) may be used for the second layer instead of SiAlON.

[0043] 5 to 7 , the protective layer 2 has an opening 21. The opening 21 is configured as a through-hole that penetrates the protective layer 2 in the thickness direction z. The shape, size, and arrangement of the opening 21 are not limited in any way and are set appropriately depending on the configuration of the multiple driver ICs 7, the wiring layer 3, etc. For example, in this embodiment, the opening 21 is formed in a substantially rectangular shape.

[0044] The opening 21 exposes the plurality of first pad portions 37. That is, the plurality of first pad portions 37 are exposed from the protective layer 2 through the opening 21 and are contained within the opening 21 as viewed in the thickness direction z. In addition, in this embodiment, the plurality of second pad portions 364 are contained within the opening 21 as viewed in the thickness direction z. Furthermore, the plurality of pad portions 381 and the plurality of pad portions 382 are contained within the opening 21 as viewed in the thickness direction z.

[0045] An edge of the opening 21 on the y1 side in the sub-scanning direction y intersects with the plurality of individual electrodes 34. In this embodiment, the edge of the opening 21 on the y1 side in the sub-scanning direction y intersects with the inclined portion 362 or the intermediate portion 363. An edge of the opening 21 on the y2 side in the sub-scanning direction y intersects with the wiring portion 391. Both edge portions of the opening 21 in the main scanning direction x intersect with the plurality of wiring portions 392.

[0046] (Driver IC 7) A plurality of driver ICs 7 are mounted on the substrate 1. In this embodiment, the plurality of driver ICs 7 are used to individually energize the plurality of heat generating portions 41. Each driver IC 7 has a plurality of electrodes 71. As shown in FIG. 7 , the plurality of electrodes 71 are conductively joined to the wiring layer 3 by a bonding layer 79 through the openings 21. The bonding layer 79 is, for example, solder. This allows the plurality of driver ICs 7 to be electrically connected to the wiring layer 3 and the resistor layer 4. In the illustrated example, the plurality of electrodes 71 are conductively joined to the plurality of first pad portions 37, the plurality of pad portions 381, and the plurality of pad portions 382 through the openings 21 by the bonding layer 79. The arrangement of the driver ICs 7 is not limited in any way, and in this embodiment, the entire driver IC 7 is enclosed within the opening 21 when viewed in the thickness direction z.

[0047] The control of the energization of the heat generating elements 41 by the drive ICs 7 is in accordance with command signals input from outside the thermal printhead A1, for example, via the terminals 19. The drive ICs 7 are provided as needed according to the number of heat generating elements 41.

[0048] (Filled Resin Layer 8) As shown in FIG. 7 , the filled resin layer 8 includes a portion interposed between the substrate 1 (main surface 11 a) and the driving IC 7. In this embodiment, the filled resin layer 8 fills the flat portion 121 of the glaze layer 12 and the gap between the wiring layer 3 and the driving IC 7. Furthermore, the filled resin layer 8 completely covers the opening 21. As shown in FIGS. 5 and 6 , in this embodiment, the filled resin layer 8 extends from the driving IC 7 in the thickness direction z and reaches the edge of the opening 21. The filled resin layer 8 is, for example, what is called an underfill agent, and is formed by hardening a highly permeable insulating liquid (or paste, etc.). There are no particular limitations on the material of the filled resin layer 8, and any conventionally known resin may be used as appropriate.

[0049] 7, in the illustrated example, the filling resin layer 8 is in contact with part of the side surface of the driving IC 7. Also, as shown in FIGS. 5 to 7, the filling resin layer 8 has a portion located on the protective layer 2 (a portion covering part of the protective layer 2).

[0050] (Protective Resin 78) The protective resin 78 covers the multiple driver ICs 7, the filling resin layer 8, and part of the protective layer 2. The protective resin 78 is made of, for example, an insulating resin and is, for example, black. The protective resin 78 may also be configured with multiple layers made of different materials (resin, glass, etc.) stacked together. In FIG. 2, the cross-sectional shape of the protective resin 78 is shown as gently bulging toward the z1 side in the thickness direction z, but is not limited to this and may be configured in various other shapes. The protective resin 78 may also be configured to cover part of the filling resin layer 8.

[0051] (Heat Dissipation Member 9) As shown in Figures 1 and 2, the heat dissipation member 9 supports the substrate 1. The heat dissipation member 9 is intended to dissipate some of the heat generated by the multiple heat-generating portions 41 to the outside via the substrate 1. The heat dissipation member 9 is a block-shaped member made of a metal such as Al (aluminum). As shown in Figure 2, the heat dissipation member 9 has a support surface 91. The support surface 91 faces the z1 side in the thickness direction z. A first back surface 11b of the base material 11 is joined to the support surface 91.

[0052] Next, a method for manufacturing the thermal printhead A1 will be described below with reference to FIGS.

[0053] 8 is a flowchart showing a method for manufacturing the thermal printhead A1 according to this embodiment. The method for manufacturing the thermal printhead A1 includes the steps of preparing the substrate 1, forming the wiring layer 3 and the resistor layer 4, forming the wiring layer 3, electrically connecting the driver IC 7 to the wiring layer 3, and forming the filled resin layer 8.

[0054] First, a substrate 1 is prepared as shown in Fig. 9. For example, the substrate 1 is obtained by forming a glaze layer 12 on a main surface 11a of a base material 11.

[0055] Next, as shown in FIG. 10 , the wiring layer 3 and the resistor layer 4 are formed. However, the resistor layer 4 does not appear in the area shown in the figure. The wiring layer 3 is formed by printing, for example, a paste containing an organic Ag compound or a paste containing Ag particles, glass frit, Pd (palladium), and resin on the glaze layer 12 and firing it. This results in a conductive film containing Ag (silver). The wiring layer 3 is obtained by appropriately patterning this conductive film. Next, a paste containing, for example, ruthenium oxide is printed in the main scanning direction x across the multiple strip portions 32 and the multiple strip portions 35 and then firing it. This results in the resistor layer 4.

[0056] 11, the protective layer 2 is formed. The protective layer 2 can be formed, for example, by printing a glass paste and then firing it. The openings 21 can be formed, for example, by not printing the glass paste in the areas where the openings 21 should be formed.

[0057] 12 , the electrodes 71 of the driving IC 7 are conductively joined to the wiring layer 3 by the bonding layer 79. As a result, the electrodes 71 are conductively joined to the first pads 37, the pads 381, and the pads 381. As a result, the driving IC 7 is enclosed within the opening 21 when viewed in the thickness direction z.

[0058] Next, the filled resin layer 8 is formed. In this embodiment, the formation of the filled resin layer 8 begins with forming a first portion 81, as shown in FIGS. 13 and 14 . An underfill agent or the like is filled into the gap between the glaze layer 12 (main surface 11 a) and the wiring layer 3 and the driver IC 7 using a dispenser. In the illustrated example, the underfill agent adheres to a portion of the side surface of the driver IC 7. However, when viewed in the thickness direction z, the underfill agent remains immediately below or near the driver IC 7 and is separated from the edge of the opening 21. The underfill agent is appropriately cured, etc., to form the first portion 81.

[0059] Next, as shown in Figures 15 and 16, the second portion 82 is formed. An underfill agent or the like is applied to the region between the first portion 81 and the edge of the opening 21 when viewed in the thickness direction z. That is, it is applied to the portion of the opening 21 that is not blocked by the first portion 81. In this embodiment, the second portion 82 covers, for example, the plurality of second pad portions 364. Furthermore, in the illustrated example, the underfill agent is applied to a portion of the protective layer 2. The underfill agent is appropriately cured, etc., to form the second portion 82, and as a result, the filled resin layer 8 consisting of the first portion 81 and the second portion 82 is formed.

[0060] The filled resin layer 8 may be configured such that the first portion 81 and the second portion 82 are distinguishable from each other, or may be configured such that the first portion 81 and the second portion 82 are indistinguishable from each other. For example, if the first portion 81 and the second portion 82 are formed from underfill agents of different materials, or if the first portion 81 and the second portion 82 are cured at different times, the filled resin layer 8 may be configured such that the first portion 81 and the second portion 82 are distinguishable from each other.

[0061] After this, the thermal printhead A1 is obtained by forming the protective resin 78, attaching the substrate 1 to the heat dissipation member 9, and so on.

[0062] Next, the operation of the thermal printhead A1 and the thermal printer P1 will be described.

[0063] 5 to 7, in this embodiment, the driver IC 7 is electrically connected to the first pads 37 through the openings 21. All of the openings 21 are covered with the filled resin layer 8. This prevents unintended components contained in the outside air in the operating environment of the thermal printhead A1 from affecting the wiring layer 3. This prevents ion migration from occurring in the wiring layer 3.

[0064] The manufacturing method for the thermal printhead A1 involves forming a first portion 81 shown in Figures 13 and 14 and a second portion 82 shown in Figures 15 and 16. The formation of the first portion 81 allows sufficient filling of an underfill agent or the like into the gaps between the substrate 1, wiring layer 3, and driver IC 7. The formation of the second portion 82 also allows for more reliable coverage of the region of the opening 21 that extends far beyond the driver IC 7, i.e., the region not covered by the first portion 81. Therefore, even if the opening 21 becomes larger, ion migration in the wiring layer 3 can be suppressed.

[0065] In this embodiment, the plurality of second pad portions 364 are contained within the opening 21. This allows the plurality of second pad portions 364 to be used to measure the individual resistance values ​​of the plurality of heat generating portions 41 after completing the steps of forming the wiring layer 3 and resistor layer 4 shown in FIG. 10 and forming the protective layer 2 shown in FIG. 11 in the manufacturing method of the thermal printhead A1. Heat generating portions 41 with inappropriate resistance values ​​can be adjusted to appropriate values ​​by, for example, laser trimming. Furthermore, by covering the plurality of second pad portions 364 with the second portion 82, ion migration in the wiring layer 3 can be suppressed even when the opening 21 is large enough to contain the plurality of second pad portions 364.

[0066] 17 to 20 show modified examples and other embodiments of the present disclosure. In these figures, elements that are the same as or similar to those in the above-described embodiment are given the same reference numerals. Furthermore, the configurations of the various parts in each modified example and each embodiment can be combined with each other as appropriate within the scope of not causing technical contradictions.

[0067] 17 to 19 show a thermal printhead according to a second embodiment of the present disclosure. The thermal printhead A2 of this embodiment differs from the above-described embodiment mainly in the configurations of the protective layer 2, wiring layer 3, and filling resin layer 8.

[0068] In this embodiment, each of the connecting portions 36 of the plurality of individual electrodes 34 of the wiring layer 3 does not have the above-described intermediate portion 363 and second pad portion 364. In this embodiment, the straight portion 361 and the inclined portion 362 are connected to each other.

[0069] The edge of the opening 21 on the y1 side in the sub-scanning direction y intersects with the inclined portion 362 of the connecting portion 36 of the plurality of individual electrodes 34. The distance between the edge of the opening 21 on the y1 side in the sub-scanning direction y and the driving IC 7 is smaller than the distance in the thermal printhead A1, for example.

[0070] This embodiment also makes it possible to suppress the occurrence of ion migration in the wiring layer 3. Furthermore, since the connecting portion 36 does not have the intermediate portion 363 and the second pad portion 364, it is possible to reduce the size of the opening 21. This makes it possible to reduce the area of ​​the portion of the wiring layer 3 that is exposed from the opening 21, which is preferable for suppressing the occurrence of ion migration in the wiring layer 3. Note that, in this embodiment, the resistance values ​​of the above-mentioned plurality of heat generating portions 41 may be measured using, for example, the plurality of first pad portions 37.

[0071] 20 shows a thermal printhead according to a third embodiment of the present disclosure. The thermal printhead A3 of this embodiment differs from the above-described embodiments mainly in the configurations of the protective layer 2, the driving IC 7, and the filling resin layer 8.

[0072] In this embodiment, when viewed in the thickness direction z, at least a part of the edge of the opening 21 overlaps with the driving IC 7. In the example shown in the figure, when viewed in the thickness direction z, the entire edge of the opening 21 overlaps with the driving IC 7.

[0073] In this embodiment as well, the filled resin layer 8 closes all of the openings 21. In this embodiment, for example, the filled resin layer 8 may be configured by only the first portion 81 described above.

[0074] This embodiment also makes it possible to suppress the occurrence of ion migration in the wiring layer 3. As can be understood from this embodiment, the opening 21 only needs to be opened so as to appropriately electrically connect the driving IC 7 and the wiring layer 3. The opening 21 is not limited to a configuration that includes the entire driving IC 7, and may be a configuration that includes only a portion of the driving IC 7.

[0075] The thermal printhead, thermal printer, and method of manufacturing a thermal printhead according to the present disclosure are not limited to the above-described embodiments. The specific configurations of the thermal printhead, thermal printer, and method of manufacturing a thermal printhead according to the present disclosure can be freely modified in various ways. The present disclosure includes the embodiments described in the following appendices.

[0076] Appendix 1. A thermal printhead comprising: a substrate having a main surface and a back surface facing opposite each other in a thickness direction; a wiring layer and a resistor layer supported on the main surface; a protective layer covering part of the wiring layer and at least part of the resistor layer; a driver IC that controls the flow of current to the resistor layer and is arranged on the main surface; and a filled resin layer having a portion interposed between the main surface and the driver IC, wherein the wiring layer contains Ag and has a plurality of pad portions, the driver IC has a plurality of electrodes, the protective layer has openings exposing the plurality of pad portions, the plurality of electrodes are conductively joined to the plurality of pad portions through the openings, and the filled resin layer covers all of the openings. Appendix 2. The thermal printhead according to Appendix 1, further comprising a protective resin that covers the driver IC and at least a portion of the filled resin layer when viewed in the thickness direction. Appendix 3. The thermal printhead according to Appendix 2, wherein the protective resin covers the entire filled resin layer when viewed in the thickness direction. Appendix 4. A thermal printhead according to any one of Appendixes 1 to 3, wherein the entire driving IC is enclosed in the opening when viewed in the thickness direction. Appendix 5. A thermal printhead according to any one of Appendixes 1 to 4, wherein the resistor layer includes a plurality of heat generating portions arranged in the main scanning direction. Appendix 6. A thermal printhead according to Appendix 5, wherein the wiring layer includes a plurality of individual wires individually connected to the plurality of heat generating portions. Appendix 7. A thermal printhead according to Appendix 6, wherein each of the individual wires has a first pad portion, and the plurality of pad portions include the first pad portion of the plurality of individual wires. Appendix 8. A thermal printhead according to Appendix 7, wherein the first pad portions of the plurality of individual wires are arranged along the main scanning direction. Appendix 9. A thermal printhead according to Appendix 8, wherein each of the individual wires has a straight portion connected to the first pad portion and extending in the sub-scanning direction, and an inclined portion connected to the straight portion and inclined with respect to the sub-scanning direction. Appendix 10. 10. The thermal printhead of claim 9, wherein an edge of the opening intersects with the inclined portions of the plurality of individual wirings.Appendix 11. The thermal printhead according to any one of Appendixes 7 to 10, wherein each of the individual wirings has a second pad portion interposed between the respective heat generating portion and the first pad portion, and the second pad portion is contained in the opening when viewed in the thickness direction and is spaced apart from the driving IC. Appendix 12. The thermal printhead according to Appendix 11, wherein the second pad portion is larger than the first pad portion. Appendix 13. The thermal printhead according to Appendix 11 or 12, wherein the second pad portions of the plurality of individual wirings are arranged in a staggered pattern along the main scanning direction. Appendix 14. The thermal printhead according to Appendix 1, wherein at least a portion of an edge of the opening overlaps the driving IC when viewed in the thickness direction. Appendix 15. The thermal printhead according to any one of Appendixes 1 to 14, wherein the substrate includes a ceramic. Appendix 16. The thermal printhead according to any one of Appendixes 1 to 15, further comprising a glaze layer interposed between the substrate and the resistor layer and the wiring layer. Appendix 17. A thermal printer comprising the thermal printhead according to Appendix 1. Appendix 18. a step of forming a filled resin layer having a portion interposed between the main surface and the driving IC; wherein the wiring layer contains Ag and has a plurality of pad portions; the driving IC has a plurality of electrodes; and the protective layer has an opening exposing the plurality of pad portions. In the step of electrically connecting the driving IC to the wiring layer, the plurality of electrodes are electrically connected to the plurality of pad portions through the opening. The step of forming the filled resin layer includes the steps of: forming a first portion interposed between the main surface and the driving IC and spaced apart from an edge of the opening; and forming a second portion that closes an area between the first portion and the edge of the opening.

[0077] A1, A2, A3: thermal print head P1: thermal printer 1: substrate 2: protective layer 3: wiring layer 4: resistor layer 7: driving IC 8: filled resin layer 9: heat dissipation member 11: base material 11a: main surface 11b: first back surface 12: glaze layer 19: terminal 21: opening 31: common electrode 32: strip-shaped portion 33: connecting portion 34: individual electrode 35: strip-shaped portion 36: connecting portion 37, 37A, 37B: first pad portion 41: heat generating portion 71: electrode 78: protective resin 79: bonding layer 81: first portion 82: second portion 91: support surface 121: flat portion 122: bulging portion 331: auxiliary layer 361: straight portion 362: inclined portion 363: intermediate portion 364, 364A, 364B: Second pad portion 381, 382: Pad portion 391, 392: Wiring portion B1: Platen roller C1: Printing medium x: Main scanning direction y: Sub-scanning direction z: Thickness direction

Claims

1. A substrate having a main surface and a back surface facing opposite each other in a thickness direction; a wiring layer and a resistor layer supported on the main surface; a protective layer covering a portion of the wiring layer and at least a portion of the resistor layer; a driver IC that controls current flow to the resistor layer and is disposed on the main surface; a filled resin layer having a portion interposed between the main surface and the driving IC; the wiring layer contains Ag and has a plurality of pad portions; The driving IC has a plurality of electrodes, the protective layer has openings that expose the pad portions, the plurality of electrodes are conductively joined to the plurality of pad portions through the openings, The filled resin layer fills all of the openings.

2. The thermal printhead according to claim 1 , further comprising a protective resin that covers the driving IC and at least a portion of the filled resin layer when viewed in the thickness direction.

3. The thermal printhead according to claim 2 , wherein the protective resin covers the entire filled resin layer when viewed in the thickness direction.

4. 4. The thermal printhead according to claim 1, wherein the driver IC is entirely contained within the opening when viewed in the thickness direction.

5. 5. The thermal printhead according to claim 4, wherein the resistor layer includes a plurality of heat generating portions arranged in a main scanning direction.

6. The thermal printhead according to claim 5 , wherein the wiring layer includes a plurality of individual wirings each connected to one of the heat generating portions.

7. Each of the individual wirings has a first pad portion, The thermal printhead according to claim 6 , wherein the plurality of pad portions include the first pad portions of the plurality of individual wirings.

8. The thermal printhead according to claim 7 , wherein the first pad portions of the plurality of individual wirings are arranged in a main scanning direction.

9. 9. The thermal printhead according to claim 8, wherein each of the individual wirings has a straight portion connected to the first pad portion and extending in the sub-scanning direction, and an inclined portion connected to the straight portion and inclined with respect to the sub-scanning direction.

10. The thermal printhead of claim 9 , wherein an edge of the opening intersects with the inclined portions of the plurality of individual traces.

11. Each of the individual wirings has a second pad portion interposed between the heat generating portion and the first pad portion, The thermal printhead according to claim 7 , wherein the second pad portion is contained within the opening portion when viewed in the thickness direction, and is spaced apart from the driving IC.

12. The thermal printhead of claim 11 , wherein the second pad portion is larger than the first pad portion.

13. The thermal printhead according to claim 11 , wherein the second pad portions of the plurality of individual wirings are arranged in a staggered manner along the main scanning direction.

14. The thermal printhead according to claim 1 , wherein at least a portion of an edge of the opening overlaps with the driving IC when viewed in the thickness direction.

15. The thermal printhead of claim 1 , wherein the substrate comprises a ceramic.

16. The thermal printhead according to claim 1 , further comprising a glaze layer interposed between the substrate and the resistor layer and between the substrate and the wiring layer.

17. A thermal printer comprising the thermal printhead according to claim 1.

18. preparing a substrate having a main surface and a back surface facing opposite each other in a thickness direction; forming a wiring layer and a resistor layer supported on the main surface; forming a protective layer covering a portion of the wiring layer and at least a portion of the resistor layer; a step of conductively connecting a driving IC to the wiring layer; forming a filled resin layer having a portion interposed between the main surface and the driving IC; the wiring layer contains Ag and has a plurality of pad portions; The driving IC has a plurality of electrodes, the protective layer has openings that expose the pad portions, In the step of conductively connecting the driving IC to the wiring layer, the electrodes are conductively connected to the pad portions through the openings, A method for manufacturing a thermal printhead, wherein the process of forming the filled resin layer includes a process of forming a first portion interposed between the main surface and the driving IC and spaced apart from an edge of the opening, and a process of forming a second portion that fills an area between the first portion and the edge of the opening.