Thermal print head

Abstract

To provide a thermal print head that is able to prevent occurrence of ion migration.SOLUTION: A thermal print head 1 includes wiring (45), an external connection terminal 50, and an insulating protective layer 58. The external connection terminal 50 includes a first conductive layer 51 connected to the wiring and a second conductive layer 52 stacked on the first conductive layer 51. In a plan view, the entire portion (exposed from the insulating protective layer 58) of the outer peripheral edge of the first conductive layer 51 is located inside the second conductive layer 52. The first conductive layer 51 is a silver-particle sintered body layer. The second conductive layer 52 is a sintered body layer of silver particles and metal particles different from the silver particles. The metal particles are palladium particles or gold particles.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Japanese Patent Laid-Open Publication No. 2023-176504 (Patent Document 1) discloses a thermal printhead including a substrate, a glaze layer, a wiring layer, and a heating resistor. The wiring layer includes a common electrode, a plurality of individual electrodes, a plurality of signal wiring portions, and a plurality of pad portions. The wiring layer is a conductor primarily composed of silver. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-176504

[0004] [overview] An object of the present disclosure is to provide a thermal printhead that can suppress the occurrence of ion migration.

[0005] The thermal printhead of the present disclosure includes wiring, external connection terminals, and an insulating protective layer covering the wiring. The external connection terminals include a first conductive layer connected to the wiring and a second conductive layer laminated on the first conductive layer. In a plan view from the stacking direction of the first conductive layer and the second conductive layer, the entire portion of the outer edge of the first conductive layer exposed from the insulating protective layer is inside the second conductive layer. The first conductive layer is a silver particle sintered body layer. The second conductive layer is a sintered body layer of silver particles and metal particles other than the silver particles. The metal particles are palladium particles or gold particles. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic plan view of a thermal printhead according to a first and second embodiment. [Figure 2]FIG. 2 is a schematic, partially enlarged cross-sectional view of the thermal printhead of the first and second embodiments taken along the cross-sectional line II-II shown in FIG. [Figure 3] FIG. 3 is a schematic partial enlarged plan view of the thermal printhead of the first and second embodiments, showing the region III shown in FIG. [Figure 4] FIG. 4 is a circuit diagram of the thermal printhead according to the first and second embodiments. [Figure 5] FIG. 5 is a schematic partial enlarged plan view of the region V shown in FIG. 1 of the thermal printhead according to the first embodiment. [Figure 6] FIG. 6 is a schematic, partially enlarged cross-sectional view of the thermal printhead of the first embodiment taken along the cross-sectional line VI-VI shown in FIG. [Figure 7] 7 is a schematic, partially enlarged cross-sectional view of the thermal printhead of the first embodiment taken along the cross-sectional line VII-VII shown in FIG. [Figure 8] FIG. 8 is a flowchart showing the method of manufacturing the thermal printhead according to the first and second embodiments. [Figure 9] FIG. 9 is a schematic partial enlarged plan view of the region IX shown in FIG. 1 of the thermal printhead according to the second embodiment. [Figure 10] FIG. 10 is a schematic enlarged partial cross-sectional view of the thermal printhead of the second embodiment taken along the cross-sectional line XX shown in FIG. [Figure 11] FIG. 11 is a schematic enlarged partial cross-sectional view of the thermal printhead of the second embodiment taken along the cross-sectional line XI-XI shown in FIG.

[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) A thermal printhead 1 according to a first embodiment will be described with reference to Figures 1 to 7. The thermal printhead 1 of this embodiment includes an insulating substrate 10, a glaze 11, a planarizing layer 15, first wiring 20, a heating resistor 30, a protective layer 33, a driving IC 40, conductive wires 41, a sealing member 43, a plurality of second wirings 45, a plurality of external connection terminals 50, and an insulating protective layer 58. The thermal printhead 1 of this embodiment may further include a connector 61.

[0009] 1, 2, 6, and 7, insulating substrate 10 is a ceramic substrate such as an alumina substrate. Insulating substrate 10 has a main surface 10a. In a plan view of main surface 10a (hereinafter simply referred to as "plan view"), the longitudinal direction of insulating substrate 10 is main scanning direction X, the lateral direction of insulating substrate 10 is sub-scanning direction Y, and the thickness direction of insulating substrate 10 is plate thickness direction Z. Plate thickness direction Z is perpendicular to main scanning direction X and sub-scanning direction Y. In plan view, sub-scanning direction Y is the transport direction of a print medium (e.g., thermal recording paper).

[0010] 2, 3, and 5 to 7, glaze 11 is disposed on main surface 10a of insulating substrate 10. Glaze 11 is formed of a glass material such as amorphous glass. The thermal conductivity of glaze 11 may be lower than the thermal conductivity of insulating substrate 10. As shown in FIGS. 1 and 2, glaze 11 is provided on a portion of main surface 10a of insulating substrate 10. That is, glaze 11 is a so-called partial glaze. Glaze 11 includes heater glaze 12 and die bonding glaze 13.

[0011] The heater glaze 12 extends in the main scanning direction X in a plan view of the main surface 10a and has a band shape. 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 insulating substrate 10. The heater glaze 12 is a heat storage layer. The heater glaze 12 protrudes from a portion of the main surface 10a. The heater glaze 12 is provided to increase the height of the heating resistor 30 from the main surface 10a and press the heating resistor 30 against a print medium (e.g., thermal recording paper).

[0012] The die bonding glaze 13 is disposed upstream of and spaced apart from the heater glaze 12 in the sub-scanning direction Y. In a plan view of the main surface 10a, the die bonding glaze 13 extends in the main scanning direction X and has a band shape. The die bonding glaze 13 supports a part of the first wiring 20 and the driving IC 40.

[0013] 1 to 3, the planarization layer 15 is disposed on the principal surface 10a. The planarization layer 15 includes a first planarization layer 16 and a second planarization layer 17. In a planar view of the principal 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 downstream of the first planarization layer 16 in the sub-scanning direction Y. The second planarization layer 17 is disposed on the opposite side of the heater glaze 12 from the first planarization layer 16 in the sub-scanning direction Y. The thickness of the planarization layer 15 is smaller than the thickness of the glaze 11. The height of the top surface of the glaze 11 from the planarization layer 15 is smaller than the height of the top surface of the heater glaze 12 from the principal surface 10a. The height of the top surface of the glaze 11 from the planarization layer 15 is smaller than the height of the top surface of the die bonding glaze 13 from the principal surface 10a. The planarizing layer 15 can prevent breakage of the first wiring 20 due to roughness of the main surface 10a of the insulating substrate 10 and a step between the main surface 10a and the glaze 11. The planarizing layer 15 is formed of, for example, glass.

[0014] 1 to 4, the first wiring 20 is disposed on the glaze 11 and the planarizing layer 15. The first wiring 20 forms a conductive path for supplying electricity to the heating resistor 30. The first wiring 20 includes a common wiring 21 and a plurality of individual wirings 25.

[0015] The common wiring 21 is disposed on the heater glaze 12 and the second planarization layer 17. The common wiring 21 includes a plurality of strip-shaped portions 22, a connecting portion 23, and a detour portion 24.

[0016] The 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 in the sub-scanning direction Y. The plurality of strip-shaped portions 22 are arranged at equal pitches in the main scanning direction X. The plurality of strip-shaped portions 22 are, for example, gold (Au) wiring. The plurality of strip-shaped portions 22 are, for example, gold wiring. The plurality of strip-shaped portions 22 are, for example, formed of a gold particle sintered body.

[0017] The connecting portions 23 are disposed on the second planarizing layer 17. The connecting portions 23 extend in the main scanning direction X. The connecting portions 23 are connected to the plurality of strip-shaped portions 22, and connect the plurality of strip-shaped portions 22 together. The connecting portions 23 are, for example, silver (Ag) wiring. The connecting portions 23 are, for example, formed of a silver particle sintered body.

[0018] 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 main scanning direction X to the upstream side in the sub-scanning direction Y 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, for example, formed of a silver particle sintered body. Because the connecting portion 23 and the detour portion 24 contain silver (Ag) rather than gold (Au) as the main component, the cost of the thermal printhead 1 can be reduced.

[0019] 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 glaze 11 and the first planarizing layer 16. Each of the plurality of individual wires 25 includes a first individual wire portion 26 and a second individual wire portion 27.

[0020] 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.

[0021] 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 second individual wiring portion 27 contains silver (Ag) instead of gold (Au) as the main component, the cost of the thermal printhead 1 can be reduced.

[0022] 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 of, for example, a silver particle sintered body. The second layer 29 is formed of, for example, a frit glass containing silver particles.

[0023] 1 to 4, the heating resistor 30 is disposed on the heater glaze 12 (more specifically, on the top of the heater glaze 12). The heating resistor 30 extends in the main scanning direction X and has a band shape in a plan view. The heating resistor 30 protrudes from the glaze 11 on the side opposite to the insulating substrate 10.

[0024] The heating resistor 30 is connected to the first wiring 20. Specifically, the heating resistor 30 is connected to the plurality of strip-shaped portions 22 and the plurality of individual wirings 25 of the common wiring 21. In a plan view, the heating resistor 30 is arranged so as to intersect with the plurality of strip-shaped portions 22 and the plurality of individual wirings 25. The heating resistor 30 is formed so as to straddle the plurality of strip-shaped portions 22 and the plurality of individual wirings 25. Referring to FIG. 3 , the portions of the heating resistor 30 sandwiched between the strip-shaped portions 22 and the plurality of individual wirings 25 in the main scanning direction X are heating portions 31. The heating portions 31 are portions that generate heat when the heating resistor 30 is partially energized. The heat generated by the heating portions 31 prints on a print medium (e.g., thermal recording paper).

[0025] 2, the protective layer 33 protects the heating resistor 30. The protective layer 33 may further protect the common wiring 21 and the plurality of individual wirings 25. The protective layer 33 may be a laminate of a first protective layer 34 and a second protective layer 35.

[0026] 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 11 and a part of the planarizing 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 and is formed of, for example, amorphous glass.

[0027] 1, 2, and 4, the driving IC 40 selectively energizes the plurality of individual wirings 25. In this embodiment, the plurality of driving ICs 40 are arranged spaced apart from one another in the main scanning direction X. The driving IC 40 is arranged on the die bonding glaze 13. The driving IC 40 is electrically connected to the plurality of individual wirings 25 and the second wirings 45. For example, the driving IC 40 is electrically connected to the plurality of individual wirings 25 through conductive wires 41. The driving IC 40 is electrically connected to the second wirings 45 through conductive wires (not shown). The driving IC 40 includes, for example, a common electrode 40b, a power supply terminal 40c, a ground terminal 40d, a strobe signal terminal 40e, a data latch signal electrode terminal 50f, and a clock input signal electrode terminal 50g.

[0028] 2, the driving IC 40 is sealed with a sealing member 43. The sealing member 43 has electrical insulating properties and is made of an insulating resin material such as epoxy resin.

[0029] 1, 4, 5, and 7, the plurality of second wirings 45 are, for example, silver (Ag) wirings. The plurality of second wirings 45 are formed, for example, in the same manner as the second individual wiring portions 27. The plurality of second wirings 45 include, for example, a common wiring 45b, a power supply wiring 45c, a ground wiring 45d, a strobe wiring 45e, a data latch wiring 45f, and a clock wiring 45g.

[0030] 1 and 5 to 7, the plurality of external connection terminals 50 are terminals to which electric cables 60 are joined using a conductive joining member such as solder, or terminals to which connectors 61 to which the electric cables 60 are connected are attached. The plurality of external connection terminals 50 are arranged along the outer periphery of the insulating substrate 10 on the upstream side in the sub-scanning direction Y in a plan view of the main surface 10a. With reference to FIG. 4, the plurality of external connection terminals 50 include, for example, a first common electrode terminal 50a, a second common electrode terminal 50b, a power supply electrode terminal 50c, a ground electrode terminal 50d, a strobe signal electrode terminal 50e, a data latch signal electrode terminal 50f, and a clock input signal electrode terminal 50g.

[0031] 1 and 4, the first common electrode terminal 50a is electrically connected to the bypass portion 24 of the common wiring 21. As shown in FIG. 4, the second common electrode terminal 50b is electrically connected to the common electrode 40b of the driving IC 40 through a common wiring 45b. The power supply electrode terminal 50c is electrically connected to the power supply terminal 40c of the driving IC 40 through a power supply wiring 45c. The ground electrode terminal 50d is electrically connected to the ground terminal 40d of the driving IC 40 through a ground wiring 45d.

[0032] The strobe signal electrode terminal 50e is electrically connected to the strobe signal terminal 40e of the driving IC 40 through a strobe wiring 45e. The data latch signal electrode terminal 50f is electrically connected to the data latch signal terminal 40f of the driving IC 40 through a data latch wiring 45f. The clock input signal electrode terminal 50g is electrically connected to the clock input signal terminal 40g of the driving IC 40 through a clock wiring 45g.

[0033] 5 to 7, each of the plurality of external connection terminals 50 includes a first conductive layer 51 and a second conductive layer 52. Each of the plurality of external connection terminals 50 may further include a third conductive layer 53.

[0034] The first conductive layer 51 is connected to the second wiring 45. The first conductive layer 51 is disposed on the die bonding glaze 13. The first conductive layer 51 is a silver particle sintered body layer. In a plan view of the main surface 10a, a portion of the first conductive layer 51 is covered with an insulating protective layer 58, and the remaining portion of the first conductive layer 51 is exposed from the insulating protective layer 58. The first conductive layer 51 and the second wiring 45 may be formed together.

[0035] The second conductive layer 52 is stacked on the first conductive layer 51. As shown in FIG. 5 , in a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52 (i.e., in a plan view of the main surface 10a), the entire portion of the outer periphery of the first conductive layer 51 that is exposed from the insulating protective layer 58 is located inside the second conductive layer 52. In the above plan view, the entire portion of the outer periphery of the first conductive layer 51 that is exposed from the insulating protective layer 58 is covered with the second conductive layer 52. A second thickness t2 of the second conductive layer 52 is greater than a first thickness t1 of the first conductive layer 51.

[0036] The second conductive layer 52 is a sintered layer of silver particles and metal particles different from the silver particles. The metal particles are palladium (Pd) particles or gold (Au) particles. The weight ratio of the metal particles to the silver particles in the second conductive layer 52 is, for example, 15% or more and 35% or less. The first conductive layer 51 and the third conductive layer 53 do not contain the metal particles.

[0037] The third conductive layer 53 is laminated on the first conductive layer 51. In the present embodiment, the third conductive layer 53 is located between the first conductive layer 51 and the second conductive layer 52 in the lamination direction of the first conductive layer 51 and the second conductive layer 52 (the plate thickness direction Z of the insulating substrate 10 or the normal direction to the main surface 10a). That is, the third conductive layer 53 is formed on the first conductive layer 51, and the second conductive layer 52 is formed on the die bonding glaze 13, the first conductive layer 51, and the third conductive layer 53.

[0038] In a plan view, the third conductive layer 53 is disposed inside the second conductive layer 52. As shown in FIG. 5 , in a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52 (i.e., in a plan view of the main surface 10a), the entire portion of the outer periphery of the third conductive layer 53 that is exposed from the insulating protective layer 58 is located inside the second conductive layer 52. In the above plan view, the entire portion of the outer periphery of the third conductive layer 53 that is exposed from the insulating protective layer 58 is covered by the second conductive layer 52. In a plan view, the outer periphery of the third conductive layer 53 that is distal from the insulating protective layer 58 may be flush with the outer periphery of the first conductive layer 51 that is distal from the insulating protective layer 58. In a plan view, the other outer periphery of the third conductive layer 53 is disposed inside the second conductive layer 52.

[0039] The third thickness t3 of the third conductive layer 53 is greater than the first thickness t1 of the first conductive layer 51. The third conductive layer 53 is a silver particle sintered body layer.

[0040] The insulating protective layer 58 covers the second wiring 45 and a portion of the first conductive layer 51. The insulating protective layer 58 is formed of, for example, glass. The insulating protective layer 58 protects the second wiring 45 and a portion of the first conductive layer 51 from moisture in the surrounding environment. The insulating protective layer 58 may further cover a portion of the third conductive layer 53. The insulating protective layer 58 protects the portion of the third conductive layer 53 from moisture in the surrounding environment.

[0041] The connector 61 can receive the electric cable 60. Control signals and the like are supplied to the driving IC 40, the common wiring 21, and the like through the electric cable 60, the connector 61, and the plurality of external connection terminals 50. The connector 61 has connection terminals 62. The connection terminals 62 are, for example, clips. The clips of the connector 61 clamp each of the plurality of external connection terminals 50, thereby fixing the connector 61 to the plurality of external connection terminals 50. Note that if the electric cable 60 is joined to the plurality of external connection terminals 50 using a conductive joining member such as solder, the connector 61 may be omitted.

[0042] An example of a method for manufacturing the thermal printhead 1 of this embodiment will be described with reference to FIG.

[0043] A glaze 11 is formed on the main surface 10a of the insulating substrate 10 (step S1). For example, a glass paste is printed on the main surface 10a. The glass paste is fired. In this way, the glaze 11 is formed. The glaze 11 includes, for example, a heater glaze 12 and a die bonding glaze 13.

[0044] A planarization layer 15 is formed on the area of ​​the main surface 10a that is exposed from the glaze 11 (step S2). For example, a glass paste is printed on the area of ​​the main surface 10a that is exposed from the glaze 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.

[0045] Wiring (first wiring 20, second wiring 45) and a plurality of external connection terminals 50 are formed (step S3).

[0046] For example, a conductive paste containing gold (Au) particles is printed on the heater glaze 12 and the planarization layer 15. The conductive paste is patterned by photolithography and then fired. In this manner, the strip portion 22 of the common wiring 21 and the first individual wiring portions 26 of the plurality of individual wirings 25 are formed.

[0047] A resinate paste containing silver (Ag) particles is printed on the planarizing layer 15, heater glaze 12, and die bonding glaze 13. A glass paste containing silver (Ag) particles and glass frit is printed on a portion of the resinate paste. The resinate paste and glass paste are patterned by photolithography and then fired. In this manner, the connecting portion 23 and detour portion 24 of the common wiring 21, the first layer 28 and second layer 29 of the second individual wiring portion 27 of the multiple individual wirings 25, the second wiring 45, and the first conductive layer 51 of the multiple external connection terminals 50 are formed.

[0048] A conductive paste containing silver (Ag) particles is printed on the first conductive layer 51. The conductive paste is fired. In this way, the third conductive layer 53 is formed. A conductive paste containing silver (Ag) particles and metal particles other than the silver particles is printed on the die bonding glaze 13, the first conductive layer 51, and the third conductive layer 53. The metal particles are palladium (Pd) particles or gold (Au) particles. The conductive paste is fired. In this way, the second conductive layer 52 is formed.

[0049] The heating resistor 30 is formed (step S4). For example, a resistor paste is applied to the heater glaze 12, the strip portions 22 of the common wiring 21, and the first individual wiring portions 26 of the 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 way, the heating resistor 30 is formed.

[0050] The protective layer 33 and the insulating protective layer 58 are formed (step S5). Specifically, glass paste is printed on the glaze 11, the planarizing layer 15, the first wiring 20, and the heating resistor 30. The glass paste is fired. In this way, the protective layer 33 and the insulating protective layer 58 are formed.

[0051] The laminate including the insulating substrate 10, the glaze 11, the planarizing layer 15, the first wiring 20, the second wiring 45, the plurality of external connection terminals 50, the heating resistor 30, the protective layer 33, and the insulating protective layer 58 is divided (step S6). For example, a laser scribing method is used to form a cleaving groove in the insulating substrate 10. The laminate is then cleaved along the cleaving groove. In this way, the laminate is divided into individual pieces.

[0052] The driver IC 40 is mounted on the die bonding glaze 13 (step S7). For example, the driver IC 40 is fixed to the die bonding glaze 13 using a bonding material (not shown) such as a resin adhesive or solder.

[0053] Conductive wires are bonded (step S8). Conductive wires 41 are bonded to the driving IC 40 and the plurality of individual wires 25. Conductive wires (not shown) are bonded to the driving IC 40 and the plurality of second wires 45.

[0054] The driving IC 40 is sealed with the sealing member 43 (step S9). For example, a sealing resin material is potted on the driving IC 40. The sealing resin material is cured. In this way, the sealing member 43 is formed.

[0055] The connector 61 is attached to the plurality of external connection terminals 50 (step S10). For example, if the connection terminals 62 of the connector 61 are clips, the clips of the connector 61 clamp each of the plurality of external connection terminals 50, thereby fixing the connector 61 to the plurality of external connection terminals 50. Note that if the electric cable 60 is joined to the plurality of external connection terminals 50 using a conductive joining material such as solder, step S10 is omitted. In this manner, the thermal printhead 1 is obtained.

[0056] The operation of the thermal printhead 1 of this embodiment will be explained in comparison with a thermal printhead of a comparative example. The thermal printhead of the comparative example has the same configuration as the thermal printhead 1 of this embodiment, but does not include the second conductive layer 52.

[0057] The first conductive layer 51 is a silver particle sintered body layer. Silver is a metal material in which ion migration occurs more easily than with gold. In the comparative example, a portion of the first conductive layer 51 is exposed from the insulating protective layer 58 and is exposed to moisture in the surrounding environment. The multiple external connection terminals 50 are densely arranged, and the distance between two adjacent external connection terminals 50 among the multiple external connection terminals 50 is small. Therefore, in the comparative example, when a high voltage is applied to the multiple external connection terminals 50 (for example, the second common electrode terminal 50b), ion migration may occur between two adjacent external connection terminals 50 among the multiple external connection terminals 50.

[0058] In contrast, in the present embodiment, the external connection terminal 50 includes a second conductive layer 52. In a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52, the entire portion of the outer periphery of the first conductive layer 51 that is exposed from the insulating protective layer 58 is inside the second conductive layer 52. The entire first conductive layer 51 is covered by the insulating protective layer 58 and the second conductive layer 52. The second conductive layer 52 is a sintered layer of silver particles and metal particles other than the silver particles, and the metal particles are palladium (Pd) particles or gold (Au) particles. The second conductive layer 52 is less susceptible to ion migration than the first conductive layer 51. Therefore, in the present embodiment, it is possible to suppress ion migration between two adjacent external connection terminals 50 among the multiple external connection terminals 50.

[0059] The effects of the thermal printhead 1 of this embodiment will be described.

[0060] The thermal printhead 1 of this embodiment includes wiring (second wiring 45), external connection terminals 50, and an insulating protective layer 58 covering the wiring. The external connection terminals 50 include a first conductive layer 51 connected to the wiring and a second conductive layer 52 laminated on the first conductive layer 51. In a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52, the entire portion of the outer edge of the first conductive layer 51 exposed from the insulating protective layer 58 is located inside the second conductive layer 52. The first conductive layer 51 is a silver particle sintered body layer. The second conductive layer 52 is a sintered body layer of silver particles and metal particles other than the silver particles. The metal particles are palladium (Pd) particles or gold (Au) particles.

[0061] The entire first conductive layer 51 is covered with an insulating protective layer 58 and a second conductive layer 52. Ion migration is less likely to occur in the second conductive layer 52 than in the first conductive layer 51. Therefore, even if the first conductive layer 51 is formed of a silver particle sintered body layer, it is possible to suppress ion migration from occurring between two adjacent external connection terminals 50 among the plurality of external connection terminals 50.

[0062] In the thermal printhead 1 of this embodiment, the weight ratio of metal particles to silver particles in the second conductive layer 52 is 15% or more and 35% or less.

[0063] Ion migration is less likely to occur in the second conductive layer 52 than in the first conductive layer 51. Therefore, it is possible to prevent ion migration from occurring between two adjacent external connection terminals 50 among the plurality of external connection terminals 50.

[0064] In the thermal printhead 1 of this embodiment, the insulating protective layer 58 is made of glass.

[0065] The insulating protective layer 58 protects a part of the first conductive layer 51 from moisture in the surrounding environment, thereby making it possible to suppress ion migration between two adjacent external connection terminals 50 among the plurality of external connection terminals 50.

[0066] In the thermal printhead 1 of this embodiment, the second thickness t2 of the second conductive layer 52 is greater than the first thickness t1 of the first conductive layer 51.

[0067] This prevents the first conductive layer 51 and the second conductive layer 52 from being torn by mechanical or thermal shock when the electric cable 60 is attached to the thermal printhead 1 directly or using the connector 61. This more reliably prevents ion migration from occurring between two adjacent external connection terminals 50 among the plurality of external connection terminals 50. This also prevents an increase in connection resistance between the plurality of external connection terminals 50 and the electric cable 60.

[0068] In the thermal printhead 1 of this embodiment, the external connection terminal 50 includes a third conductive layer 53 laminated on the first conductive layer 51. The second conductive layer 52 and the third conductive layer 53 are laminated on the first conductive layer 51. The third conductive layer 53 is a silver particle sintered body layer, and is disposed inside the first conductive layer 51 and the second conductive layer 52 in a plan view.

[0069] The third conductive layer 53 is disposed inside the second conductive layer 52 in a plan view. Therefore, even if the third conductive layer 53 is formed of a silver particle sintered body, it is possible to suppress the occurrence of ion migration between two adjacent external connection terminals 50 among the plurality of external connection terminals 50.

[0070] In the thermal printhead 1 of this embodiment, the second thickness t2 of the second conductive layer 52 is greater than the first thickness t1 of the first conductive layer 51. The third thickness t3 of the third conductive layer 53 is greater than the first thickness t1 of the first conductive layer 51.

[0071] The second thickness t2 of the second conductive layer 52 and the third thickness t3 of the third conductive layer 53 are greater than the first thickness t1 of the first conductive layer 51. This prevents the first conductive layer 51, the second conductive layer 52, and the third conductive layer 53 from being torn by mechanical or thermal shock when the electric cable 60 is attached to the thermal printhead 1 directly or using the connector 61. This more reliably prevents ion migration from occurring between two adjacent external connection terminals 50 among the plurality of external connection terminals 50. This also prevents an increase in connection resistance between the plurality of external connection terminals 50 and the electric cable 60.

[0072] In the thermal printhead 1 of this embodiment, the third conductive layer 53 is located between the first conductive layer 51 and the second conductive layer 52 in the stacking direction of the first conductive layer 51 and the second conductive layer 52.

[0073] Therefore, the third conductive layer 53 can prevent the first conductive layer 51 from being broken due to mechanical or thermal shock when the electric cable 60 is fixed to the thermal printhead 1. An increase in connection resistance between the plurality of external connection terminals 50 and the electric cable 60 can be suppressed.

[0074] (Embodiment 2) A thermal printhead 1 of embodiment 2 will be described with reference to Figures 1 to 4 and 9 to 11. The thermal printhead 1 of this embodiment has a similar configuration to the thermal printhead 1 of embodiment 1, but differs from it mainly in the following respects.

[0075] In the thermal printhead 1 of this embodiment, in the stacking direction of the first conductive layer 51 and the second conductive layer 52, the second conductive layer 52 is located between the first conductive layer 51 and the third conductive layer 53. In other words, the second conductive layer 52 is formed on the die bonding glaze 13 and the first conductive layer 51, and the third conductive layer 53 is formed on the second conductive layer 52.

[0076] In a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52, the entire portion of the outer periphery of the first conductive layer 51 that is exposed from the insulating protective layer 58 and the entire portion of the outer periphery of the third conductive layer 53 that is exposed from the insulating protective layer 58 are located inside the second conductive layer 52. The entire first conductive layer 51 is covered by the insulating protective layer 58 and the second conductive layer 52. In a plan view from the stacking direction of the first conductive layer 51 and the second conductive layer 52, a portion of the third conductive layer 53 is covered by the insulating protective layer 58, and the remaining portion of the third conductive layer 53 is exposed from the insulating protective layer 58 and the second conductive layer 52.

[0077] In this embodiment, the connection terminals 62 of the connector 61 are, for example, pins. For example, the pins of the connector 61 are fixed to the external connection terminals 50 using a conductive joining member 65 such as solder. Note that if the electric cable 60 is joined to a plurality of external connection terminals 50 using a conductive joining member such as solder, the connector 61 is omitted.

[0078] An example of a method for manufacturing the thermal printhead 1 of this embodiment will be described with reference to Figure 8. The method for manufacturing the thermal printhead 1 of this embodiment includes similar steps to those of the method for manufacturing the thermal printhead 1 of embodiment 1, but differs from the method for manufacturing the thermal printhead 1 of embodiment 1 mainly in step S2, which is a step for forming the plurality of external connection terminals 50, and in step S9.

[0079] In step S2 of this embodiment, after forming the first conductive layer 51, a conductive paste containing silver (Ag) particles and metal particles is printed on the first conductive layer 51. The metal particles are palladium (Pd) particles or gold (Au) particles. The conductive paste is fired. In this manner, the second conductive layer 52 is formed. Then, a conductive paste containing silver (Ag) particles is printed on the first conductive layer 51 and the second conductive layer 52. The conductive paste is fired. In this manner, the third conductive layer 53 is formed.

[0080] In step S9 of the present embodiment, the pins of the connector 61 are fixed to the external connection terminals 50 using a conductive joining member 65 such as solder. Note that if the electric cable 60 is joined to a plurality of external connection terminals 50 using a conductive joining member such as solder, step S10 is omitted.

[0081] The thermal printhead 1 of this embodiment has the following advantages similar to those of the thermal printhead 1 of the first embodiment.

[0082] In the thermal printhead 1 of this embodiment, the second conductive layer 52 is located between the first conductive layer 51 and the third conductive layer 53 in the stacking direction of the first conductive layer 51 and the second conductive layer 52 .

[0083] Therefore, the third conductive layer 53 protects the second conductive layer 52 from mechanical or thermal shocks that may occur when the electric cable 60 is attached to the thermal printhead 1 directly or using the connector 61. This can prevent the second conductive layer 52 from being torn. This can also suppress ion migration from occurring between two adjacent external connection terminals 50 among the multiple external connection terminals 50.

[0084] In the thermal printhead 1 of this embodiment, the second thickness t2 of the second conductive layer 52 is greater than the first thickness t1 of the first conductive layer 51. The third thickness t3 of the third conductive layer 53 is greater than the first thickness t1 of the first conductive layer 51.

[0085] The second thickness t2 of the second conductive layer 52 and the third thickness t3 of the third conductive layer 53 are greater than the first thickness t1 of the first conductive layer 51. This prevents the first conductive layer 51, the second conductive layer 52, and the third conductive layer 53 from being torn by mechanical or thermal shock when the electric cable 60 is attached to the thermal printhead 1 directly or using the connector 61. This more reliably prevents ion migration from occurring between two adjacent external connection terminals 50 among the plurality of external connection terminals 50. This also prevents an increase in connection resistance between the plurality of external connection terminals 50 and the electric cable 60.

[0086] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) Wiring and An external connection terminal, an insulating protective layer covering the wiring; the external connection terminal includes a first conductive layer connected to the wiring and a second conductive layer stacked on the first conductive layer; when viewed from above in a stacking direction of the first conductive layer and the second conductive layer, an entire portion of an outer periphery of the first conductive layer that is exposed from the insulating protection layer is located inside the second conductive layer, the first conductive layer is a silver particle sintered body layer, the second conductive layer is a sintered layer of silver particles and metal particles different from the silver particles, A thermal printhead, wherein the metal particles are palladium particles or gold particles. (Appendix 2) 2. The thermal printhead of claim 1, wherein the weight ratio of the metal particles to the silver particles in the second conductive layer is 15% or more and 35% or less. (Appendix 3) 2. The thermal printhead of claim 1, wherein the insulating protective layer is formed of glass. (Appendix 4) 2. The thermal printhead of claim 1, wherein the second thickness of the second conductive layer is greater than the first thickness of the first conductive layer. (Appendix 5) the external connection terminal includes a third conductive layer laminated on the first conductive layer, the second conductive layer and the third conductive layer are stacked on the first conductive layer; A thermal printhead described in any one of Appendix 1 to Appendix 3, wherein the third conductive layer is a silver particle sintered body layer and is arranged inside the first conductive layer and the second conductive layer in the planar view. (Appendix 6) a second thickness of the second conductive layer that is greater than a first thickness of the first conductive layer; 6. A thermal printhead as described in Appendix 5, wherein a third thickness of the third conductive layer is greater than the first thickness of the first conductive layer. (Appendix 7) A thermal printhead as described in Appendix 6, wherein in the stacking direction, the third conductive layer is located between the first conductive layer and the second conductive layer. (Appendix 8) A thermal printhead as described in Appendix 6, wherein in the stacking direction, the second conductive layer is located between the first conductive layer and the third conductive layer.

[0087] The first and second 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 the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0088] 1 thermal print head, 10 insulating substrate, 10a main surface, 11 glaze, 12 heater glaze, 13 die bonding glaze, 15 planarization layer, 16 first planarization layer, 17 second planarization layer, 20 first wiring, 21 common wiring, 22 strip portion, 23 connecting portion, 24 detouring portion, 25 individual wiring, 26 first individual wiring portion, 27 second individual wiring portion, 28 first layer, 29 second layer, 30 heating resistor, 31 heating portion, 33 protective layer, 34 first protective layer, 35 second protective layer, 40 driving IC, 40b common electrode, 40c power supply terminal, 40d ground terminal, 40e strobe signal terminal, 40f data latch signal terminal, 40g clock input signal terminal, 41 conductive wire, 43 sealing member, 45 second wiring, 45b common wiring, 45c Power supply wiring, 45d ground wiring, 45e strobe wiring, 45f data latch wiring, 45g clock wiring, 50 external connection terminal, 50a first common electrode terminal, 50b second common electrode terminal, 50c power supply electrode terminal, 50d ground electrode terminal, 50e strobe signal electrode terminal, 50f data latch signal electrode terminal, 50g clock input signal electrode terminal, 51 first conductive layer, 52 second conductive layer, 53 third conductive layer, 58 insulating protection layer, 60 electric cable, 61 connector, 62 connection terminal, 65 conductive joining member.

Claims

1. Wiring and An external connection terminal, an insulating protective layer covering the wiring; the external connection terminal includes a first conductive layer connected to the wiring and a second conductive layer stacked on the first conductive layer; when viewed from above in a stacking direction of the first conductive layer and the second conductive layer, an entire portion of an outer periphery of the first conductive layer that is exposed from the insulating protection layer is located inside the second conductive layer, the first conductive layer is a silver particle sintered body layer, the second conductive layer is a sintered layer of silver particles and metal particles different from the silver particles, A thermal printhead, wherein the metal particles are palladium particles or gold particles.

2. 2. The thermal printhead according to claim 1, wherein the weight ratio of the metal particles to the silver particles in the second conductive layer is 15% or more and 35% or less.

3. The thermal printhead of claim 1 , wherein the insulating protective layer is made of glass.

4. The thermal printhead of claim 1 , wherein the second thickness of the second conductive layer is greater than the first thickness of the first conductive layer.

5. the external connection terminal includes a third conductive layer laminated on the first conductive layer, the second conductive layer and the third conductive layer are stacked on the first conductive layer, 4. The thermal printhead according to claim 1, wherein the third conductive layer is a silver particle sintered body layer and is arranged inside the first conductive layer and the second conductive layer in the planar view.

6. the second thickness of the second conductive layer is greater than the first thickness of the first conductive layer; The thermal printhead of claim 5 , wherein a third thickness of the third conductive layer is greater than the first thickness of the first conductive layer.

7. The thermal printhead of claim 6 , wherein the third conductive layer is located between the first conductive layer and the second conductive layer in the stacking direction.

8. The thermal printhead of claim 6 , wherein the second conductive layer is located between the first conductive layer and the third conductive layer in the stacking direction.

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