Thermal Print Head and Method for Preparing the Same

Abstract

The present invention relates to the field of printing technology, and particularly to a thermal print head and a preparation method thereof. The preparation method includes: Step S1: Printing a layer of bottom glaze on a ceramic substrate by screen printing, and obtaining a glass bottom glaze substrate after sintering treatment; Step S2: Coating a pre-configured yellow thick film silver paste on the glass bottom glaze substrate to prepare a conductive circuit, and the thickness of the conductive circuit is 0.6 - 2.0 μm; Step S3: Printing a pre-configured yellow thick film resistor paste on the conductive circuit to prepare a resistor heating element; Step S4: Screen printing a thick film reinforcing silver paste at a preset position and performing sintering treatment to obtain an assembly; Step S5: Printing a layer of glass glaze on the surface of the assembly by screen printing, and successively performing sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal print head. By the above method, the present invention can solve the technical problems of high cost, low efficiency, and poor resistance consistency of the existing thermal print heads.

Description

Technical Field

[0001] The present invention relates to the field of printing technology, and particularly to a thermal print head and a preparation method thereof. Background Art

[0002] The technological process of preparing a thermal print head by the traditional thick film method includes the following steps: ① Through screen printing, a bottom glaze with a thickness of 50 - 80 μm is printed on an alumina ceramic substrate, and sintered at about 1250 °C to prepare a glass bottom glaze substrate with a smooth surface; ② A layer of organic gold paste is coated on the glass bottom glaze substrate through screen printing, roll coating, spin coating or other methods, and sintered at a high temperature of 850 °C to form a dense gold thin film. According to the thickness requirement, the above process is repeated to prepare a double-layer gold thin film with a thickness of about 0.6 μm; ③ A positive photoresist is spin-coated or roll-coated on the double-layer gold thin film, dried, exposed and developed to form a circuit pattern, etched with a gold etchant to form the circuit pattern, and the photoresist is removed with strong alkali; ④ A thick film resistance wire is screen-printed in the etched circuit pattern and sintered at 850 °C to form a resistance wire with good consistency; ⑤ Thick film reinforcing silver paste is screen-printed and sintered at the corresponding pad positions, GND positions, etc.; ⑥ A layer of glass glaze is screen-printed and sintered on the surface of the above combination; ⑦ After testing and adjusting the resistance value with a resistance trimming machine, it is encapsulated.

[0003] The above solution can achieve mass production, but has the following disadvantages:

[0004] 1. The circuit pattern is prepared from organic gold paste. The organic gold paste has a low gold content, and the single-layer thickness after sintering is only 0.3 μm, with a large resistance. In order to improve conductivity, two layers must be printed, resulting in low efficiency and high manufacturing cost;

[0005] 2. The raw materials contain organic gold paste, resulting in high costs;

[0006] 3. Organic gold requires a photoresist to prepare a pattern and then be etched. The etching solution needs to use strongly oxidizing iodine + strong acid (such as hydrochloric acid, nitric acid) or aqua regia, which is dangerous, has poor environmental protection and is inconvenient to operate;

[0007] 4. Using screen printing to prepare the resistance heating element has poor printing accuracy, and the resistance consistency after sintering is poor. Pulse voltage resistance trimming is required to adjust the resistance value, resulting in low efficiency, complex equipment and high cost.

[0008] In view of this, providing a new thermal print head and a preparation method thereof has become an urgent technical problem in this field. Summary of the Invention

[0009] Aiming at the defects in the prior art, the purpose of the present invention is to provide a thermal print head and a preparation method thereof, so as to solve the technical problems of high cost, low efficiency and poor resistance consistency in the existing preparation solutions of thermal print heads.

[0010] The object of the present invention can be achieved by the following technical solutions:

[0011] On the one hand, the present invention provides a method for preparing a thermal print head, and the preparation method includes the following steps:

[0012] Step S1: Print a layer of bottom glaze on a ceramic substrate by screen printing, and obtain a glass bottom glaze substrate after sintering treatment;

[0013] Step S2: Coat a layer of pre-prepared yellow light thick film silver paste on the glass bottom glaze substrate to prepare a conductive circuit, and the thickness of the conductive circuit is 0.6-2.0 μm;

[0014] Step S3: Print a layer of pre-prepared yellow light thick film resistor paste on the conductive circuit to prepare a resistor heating element;

[0015] Step S4: Screen print thick film reinforced silver paste at a preset position and perform sintering treatment to obtain a combination;

[0016] Step S5: Print a layer of glass glaze on the surface of the combination by screen printing, and sequentially perform sintering treatment, resistance adjustment treatment and chip packaging treatment to obtain the thermal print head.

[0017] According to an embodiment of the present invention, step S2 further includes:

[0018] Coat a layer of pre-prepared yellow light thick film silver paste on the glass bottom glaze substrate by screen printing, spin coating or roll coating, and the coating thickness of the yellow light thick film silver paste is 0.8-2.5 μm;

[0019] Bake the yellow light thick film silver paste to obtain a first film layer;

[0020] Perform alignment exposure treatment and development treatment on the first film layer to retain the electrode lines in the exposed area and form an electrode pattern;

[0021] Perform sintering treatment on the electrode pattern to obtain the conductive circuit, and the conductive circuit includes a plurality of independently arranged sub-circuits, first electrodes corresponding to each of the sub-circuits, second electrodes corresponding to each of the first electrodes, and a common circuit connected to the second electrodes.

[0022] According to an embodiment of the present invention, the baking temperature of the baking treatment is 80-110 °C, the baking time is 5-15 min; the energy of the alignment exposure treatment is 100-1000 mj; the developer for the development treatment is a 0.1%-0.3% sodium carbonate solution; the sintering temperature of the sintering treatment is 650-900 °C, and the sintering time is 5-20 min.

[0023] According to an embodiment of the present invention, the yellow thick film silver paste comprises the following components by mass percentage: 10%-20% of a first yellow organic carrier, 80-90% of silver powder, and 0.2-2.0% of glass powder. The first yellow organic carrier comprises a yellow resin, a UV prepolymer, a UV monomer, a solvent, a dispersant, a leveling agent, an antifoaming agent, a coupling agent, a film-forming aid, and a photoinitiator.

[0024] According to an embodiment of the present invention, step S3 further comprises:

[0025] Printing a layer of pre-configured yellow thick film resistor paste on the conductive circuit by means of screen printing or pad printing, and the printing thickness of the yellow thick film resistor paste is 6.5±0.4μm;

[0026] Performing a baking treatment on the yellow thick film resistor paste to obtain a second film layer;

[0027] Performing a alignment exposure treatment and a developing treatment on the second film layer to retain the resistor paste in the exposed area, and forming a resistor heating element pattern;

[0028] Performing a sintering treatment on the resistor heating element pattern to obtain the resistor heating element, and the resistor heating element is connected to the first electrode and the second electrode.

[0029] According to an embodiment of the present invention, the baking temperature of the baking treatment is 80-110°C, and the baking time is 5-15min; the energy of the alignment exposure treatment is 100-1000mj; the developer for the developing treatment is a 0.1%-0.3% sodium carbonate solution; the sintering temperature of the sintering treatment is 650-900°C, and the sintering time is 5-20min.

[0030] According to an embodiment of the present invention, the yellow thick film resistor paste comprises the following components by mass percentage: 20%-40% of a second yellow organic carrier, 60-80% of ruthenium oxide powder, and 0.2-10% of glass powder. The second yellow organic carrier is the same as the first yellow organic carrier.

[0031] According to an embodiment of the present invention, in the step of printing a layer of pre-configured yellow thick film resistor paste on the conductive circuit by means of screen printing or pad printing, a 500-mesh steel wire mesh is used as the screen plate for screen printing.

[0032] On the other hand, the present invention provides a thermal print head, which is prepared by using the preparation method of the thermal print head according to any one of claims 1-8.

[0033] According to an embodiment of the present invention, the thermal printhead includes a conductive circuit and a resistive heating element disposed in the conductive circuit, and the tolerance between the measured resistance value and the target resistance value of the resistive heating element is within 5%.

[0034] Beneficial effects: A conductive circuit is prepared by coating a pre-configured yellow thick film silver paste on a glass underglaze substrate, and the thickness of the conductive circuit is 0.6 μm - 2.0 μm; a resistive heating element is prepared by printing a pre-configured yellow thick film resistor paste on the conductive circuit; the pre-configured yellow thick film silver paste used has a lower raw material cost compared to traditional organic gold paste. To prepare the conductive circuit, only one printing and one sintering are required, with low process cost and high efficiency. The resistive heating element is prepared by the pre-configured yellow thick film resistor paste, and the resistance consistency is good, which can solve the technical problems of high cost, low efficiency, and poor resistance consistency in the existing preparation solutions for thermal printheads. Description of the Drawings

[0035] Figure 1 is a schematic flowchart of the method for preparing a thermal printhead according to an embodiment of the present invention;

[0036] Figure 2 is a schematic flowchart of step S2 in the method for preparing a thermal printhead according to an embodiment of the present invention;

[0037] Figure 3 is a schematic flowchart of step S3 in the method for preparing a thermal printhead according to an embodiment of the present invention;

[0038] Figure 4 is a schematic structural diagram of a conductive circuit according to an embodiment of the present invention;

[0039] Figure 5 is a schematic structural diagram of a circuit structure according to an embodiment of the present invention;

[0040] Figure 6 is a schematic partial structural diagram of a thermal printhead according to an embodiment of the present invention. Detailed Embodiments

[0041] The following specific embodiments are used to illustrate the technical solutions of the present invention.

[0042] An embodiment of the present invention provides a method for preparing a thermal printhead. As Figure 1 shown, the preparation method includes the following steps:

[0043] Step S1: A layer of underglaze is printed on a ceramic substrate by screen printing and sintered to obtain a glass underglaze substrate.

[0044] In this step, the ceramic substrate can be an alumina ceramic substrate or an aluminum nitride ceramic substrate. In one embodiment, a layer of underglaze with a thickness of 50 - 80 μm is printed on the alumina ceramic substrate by screen printing, and after sintering treatment at 1250 °C, a glass underglaze substrate with a flat and smooth surface is obtained.

[0045] Step S2: Coat a layer of pre-prepared thick-film yellow light silver paste on the glass underglaze substrate to prepare a conductive circuit, and the thickness of the conductive circuit is 0.6 - 2.0 μm.

[0046] In this step, in this embodiment, the thickness of the conductive circuit is selected as the median value in the test results. In some embodiments, the thickness of the conductive circuit can be expressed as (0.6 ± 0.2 μm) - (2.0 ± 0.2 μm). By mass percentage, the thick-film yellow light silver paste includes the following components: 10% - 20% of the first yellow light organic carrier, 80 - 90% of silver powder, 0.2 - 2.0% of glass powder. The first yellow light organic carrier includes yellow light resin, UV prepolymer, UV monomer, solvent, dispersant, leveling agent, defoaming agent, coupling agent, film-forming aid, and photoinitiator.

[0047] Further, the yellow light resin includes resins containing groups such as carboxyl, C = C double bond, hydroxyl, isocyanate group, etc., with a molecular weight of 6000 - 50000 and an acid value of 30 - 300 mgKOH / g.

[0048] Further, the UV monomer includes one or more of methyl methacrylate, n-butyl methacrylate, lauryl methacrylate, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0049] Further, the UV prepolymer includes one or more of monofunctional polyurethane-modified acrylate monomers, difunctional polyurethane acrylates, polyfunctional polyurethane acrylates, monofunctional polyester-modified acrylate monomers, difunctional polyester acrylates, and polyfunctional polyester acrylates.

[0050] Further, the solvent includes one or more of diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol butyl ether, terpineol, ethylene glycol ethyl ether acetate, and ethylene glycol butyl ether acetate.

[0051] Further, the dispersant includes one or more of phosphate ester salt polymers, fatty acid ethylene oxide adducts, and polyethylene glycol type polyols.

[0052] Further, the leveling agent includes acrylate polymers and silicone leveling agents.

[0053] Further, the defoaming agent is a silicone defoaming agent.

[0054] Further, the coupling agent includes one or more of vinyltrimethoxysilane, vinyltri(β - methoxyethoxy)silane, vinyltriethoxysilane, 3 - mercaptopropyltriethoxysilane, and 3 - mercaptopropyltrimethoxysilane.

[0055] Further, the film - forming auxiliary agent includes one or more of alcohol ester 12, tributyl citrate, and tributyl acetylcitrate.

[0056] Further, the photo - initiator includes one or more of diphenyl - (2,4,6 - trimethylbenzoyl)phosphine oxide, 1 - hydroxycyclohexyl phenyl ketone, 2 - methyl - 1 - [4 - (methylthio)phenyl]-2 - (4 - morpholinyl)-1 - propanone, 2 - isopropylthioxanthone, η6 - isopropylbenzene ferrocene hexafluorophosphate, and 1 - [4 - (phenylthio)phenyl]-1,2 - octanedione 2 - (O - benzoyl oxime).

[0057] Further, the silver powder is spherical nano - silver powder or sub - micron - sized silver powder, and the particle size is 50nm - 1μm.

[0058] Further, the glass powder is glass powder with a softening point of 650 - 750°C, and the main components include silicon oxide, bismuth oxide, boron oxide, zinc oxide, sodium oxide, etc.

[0059] In an achievable embodiment, please refer to Figure 2 , step S2 further includes the following steps:

[0060] Step S21: Coating a layer of pre - configured yellow thick - film silver paste on the glass bottom - glaze substrate by means of screen printing, spin - coating or roll - coating.

[0061] In this step, the coating thickness of the yellow thick - film silver paste is 0.8 - 2.5μm.

[0062] Step S22: Baking the yellow thick - film silver paste to obtain the first film layer.

[0063] In this step, the baking temperature for the baking treatment is 80 - 110°C, preferably 90°C. The baking time is 5 - 15min, preferably 10min.

[0064] Step S23: Performing alignment exposure treatment and development treatment on the first film layer to retain the electrode lines in the exposed area and form an electrode pattern.

[0065] In this step, the energy for the alignment exposure treatment is 100 - 1000mj, preferably 500mj, and the exposure time is 20S; the developer for the development treatment is 0.1% - 0.3% sodium carbonate solution, and the time is 2min;

[0066] Step S24: Sinter the electrode pattern to obtain a conductive circuit, which includes a plurality of independently arranged sub-circuits, first electrodes corresponding to each sub-circuit, second electrodes corresponding to each first electrode, and a common circuit connected to the second electrodes.

[0067] In this step, the sintering temperature is 650 - 900 °C, preferably 850 °C. The sintering time is 5 - 20 min, preferably 10 min. As Figure 4 shown, the conductive circuit 10 includes a plurality of independently arranged sub-circuits 11, first electrodes 12 corresponding to each sub-circuit 11, second electrodes 13 corresponding to each first electrode 12, and a common circuit 14 connected to the second electrodes 13.

[0068] Step S3: Print a pre-configured yellow thick film resistor paste on the conductive circuit to prepare a resistive heating element.

[0069] In this step, the size of the resistive heating element can be represented by the median value in the test results. For example: the length of the resistive heating element is (60 ± 5 μm) - (60 ± 8 μm), the width of the resistive heating element is (60 ± 5 μm) - (60 ± 8 μm), and the height of the resistive heating element is (5.5 ± 0.5 μm) - (5.5 ± 0.9 μm). By mass percentage, the yellow thick film resistor paste includes the following components: 20% - 40% of the second yellow organic carrier, 60 - 80% of ruthenium oxide powder, 0.2 - 10% of glass powder. The second yellow organic carrier is the same as the first yellow organic carrier. Further, the yellow organic carrier is the carrier for yellow thick film silver paste. The ruthenium oxide powder is a customized high-purity ruthenium oxide powder, commercially available, with a particle size of 0.5 - 8 μm. The glass powder is a low-temperature glass powder with a softening point of 350 - 600 °C. The main components include copper oxide, bismuth oxide, sodium oxide, potassium oxide, zinc oxide, boron oxide, etc.

[0070] In an achievable embodiment, please refer to Figure 3 , step S3 further includes the following steps:

[0071] Step S31: Print a pre-configured yellow thick film resistor paste on the conductive circuit by means of screen printing or pad printing;

[0072] In this step, the printing thickness of the yellow thick film resistor paste is 6.5 ± 0.4 μm, and a 500-mesh steel wire mesh is used as the screen plate for screen printing.

[0073] Step S32: Bake the yellow thick film resistor paste to obtain a second film layer;

[0074] In this step, the baking temperature for the baking treatment is 80 - 110 °C, preferably 90 °C. The baking time is 5 - 15 min, preferably 10 min.

[0075] Step S33: Perform alignment exposure and development on the second film layer to retain the resist paste in the exposed area, forming a resist heating element pattern;

[0076] In this step, the energy of the alignment exposure is 100 - 1000 mj, preferably 500 mj, and the exposure time is 40S; the developer for the development is a 0.1% - 0.3% sodium carbonate solution, and the time is 2 min;

[0077] Step S34: Sinter the resist heating element pattern to obtain a resist heating element, and the resist heating element is connected to the first electrode and the second electrode.

[0078] In this step, the sintering temperature for the sintering process is 650 - 900 °C, preferably 850 °C. The sintering time is 5 - 20 min, preferably 10 min. As Figure 5 shown, the resist heating element 20 is correspondingly arranged with the sub - circuit 11, and the resist heating element 20 is connected between the first electrode 12 and the second electrode 13. In this embodiment, the resist heating element 20 is correspondingly arranged with the sub - circuit 11, one sub - circuit 11 is connected in series with one resist heating element 20, and the heating area is controlled by controlling the size of the resist heating element 20, so as to achieve precise temperature control of the thermal print head and improve the printing accuracy.

[0079] Step S4: Screen - print thick - film reinforced silver paste at a preset position and perform sintering treatment to obtain an assembly.

[0080] In this step, the preset position can be positions such as pad positions, GND, etc.

[0081] Step S5: Screen - print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal print head.

[0082] In this step, as Figure 6 shown, screen - print a layer of glass glaze on the surface of the assembly to form a protective layer 40, which plays a protective role for the conductive circuit 10.

[0083] The preparation method of the thermal print head according to the embodiment of the present invention prepares a conductive circuit by coating a pre - configured yellow - light thick - film silver paste on a glass bottom - glaze substrate, and the thickness of the conductive circuit is 0.6 μm - 2.0 μm; print a layer of pre - configured yellow - light thick - film resist paste on the conductive circuit to prepare a resist heating element; the used pre - configured yellow - light thick - film silver paste has a lower raw material cost compared with traditional organic gold paste. To prepare the conductive circuit, only one printing and one sintering are required, with low process cost and high efficiency. By using the pre - configured yellow - light thick - film resist paste to prepare the resist heating element, the resistance consistency is good, and it can solve the technical problems of high cost, low efficiency, and poor resistance consistency in the existing preparation schemes of thermal print heads.

[0084] An embodiment of the present invention further provides a thermal print head prepared by the above preparation method. As Figure 5 , Figure 6 shown, the thermal print head 200 includes: a preset substrate 30, a circuit structure 100 formed on the preset substrate 30, a protective layer 40 formed on the surface of the circuit structure 100, and a control chip (not shown in the figure) connected to the circuit structure 100. The circuit structure 100 at least includes a conductive circuit 10 and a resistive heating element 20 disposed in the conductive circuit. The conductive circuit 10 includes a plurality of independently provided sub-circuits 11, a first electrode 12 corresponding to each sub-circuit 11, a second electrode 13 corresponding to each first electrode 12, and a common circuit 14 connected to the second electrode 13. The resistive heating element 20 is correspondingly arranged with the sub-circuit 11, and one sub-circuit 11 is connected in series with one resistive heating element 20. The heating area is controlled by controlling the size of the resistive heating element 20, so as to realize precise temperature control of the thermal print head 200. The tolerance between the measured resistance value and the target resistance value of the resistive heating element 20 is within 5%, and the resistance value consistency is good, which can meet the product use requirements.

[0085] Example 1

[0086] Step S1: Print a layer of bottom glaze on a ceramic substrate by screen printing, and obtain a glass bottom glaze substrate after sintering treatment;

[0087] Step S2: Spin-coat a pre-prepared yellow thick film silver paste on the glass bottom glaze substrate at a rotation speed of 1500 rpm for a duration of 2 min, and the coating thickness is 2.5 μm; bake at 90 °C for 10 min to obtain a first film layer; perform alignment exposure treatment on the first film layer, with an energy of 500 mj and an exposure time of 20 S; develop with 0.1% sodium carbonate solution for 2 min, and retain the electrode lines in the exposed area to form an electrode pattern; sinter the electrode pattern at 850 °C for 10 min to obtain a conductive circuit, and the thickness of the conductive circuit is 1.8 ± 0.2 μm;

[0088] Step S3: Use a 500-mesh wire mesh as the screen plate, and brush a layer of pre-prepared yellow thick film resistor paste on the conductive circuit. The printing thickness is 6.5 ± 0.4 μm. Bake it at 90 °C for 10 min to obtain the second film layer. Perform alignment exposure on the second film layer with an energy of 500 mj and an exposure time of 40 S. Use a 0.1% sodium carbonate solution for development for 2 min, and retain the resistor paste in the exposed area to form a resistor heating element pattern. Sinter the resistor heating element pattern at 850 °C for 10 min to obtain a resistor heating element with a size of (60 ± 8 μm) * (60 ± 8 μm) * (5.5 ± 0.9 μm).

[0089] Step S4: Screen-print a thick film reinforcing silver paste at a preset position and perform sintering treatment to obtain an assembly.

[0090] Step S5: Screen-print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal print head.

[0091] Example 2

[0092] Step S1: Screen-print a layer of bottom glaze on the ceramic substrate and perform sintering treatment to obtain a glass bottom glaze substrate.

[0093] Step S2: Use the spin-coating method at a speed of 2500 rpm for a duration of 3 min to coat a layer of pre-prepared yellow thick film silver paste on the glass bottom glaze substrate. The coating thickness is 1.0 μm. Bake it at 90 °C for 10 min to obtain the first film layer. Perform alignment exposure on the first film layer with an energy of 500 mj and an exposure time of 20 S. Use a 0.1% sodium carbonate solution for development for 2 min, and retain the electrode lines in the exposed area to form an electrode pattern. Sinter the electrode pattern at 850 °C for 10 min to obtain a conductive circuit with a thickness of 0.8 ± 0.2 μm.

[0094] Step S3: Use a 500-mesh wire mesh as the screen plate, and brush a layer of pre-prepared yellow thick film resistor paste on the conductive circuit. The printing thickness is 6.5 ± 0.4 μm. Bake it at 90 °C for 10 min to obtain the second film layer. Perform alignment exposure on the second film layer with an energy of 500 mj and an exposure time of 40 S. Use a 0.1% sodium carbonate solution for development for 2 min, and retain the resistor paste in the exposed area to form a resistor heating element pattern. Sinter the resistor heating element pattern at 850 °C for 10 min to obtain a resistor heating element with a size of (60 ± 5 μm) * (60 ± 5 μm) * (5.5 ± 0.5 μm).

[0095] Step S4: Screen-print thick film reinforced silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0096] Step S5: Screen-print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal print head.

[0097] Example 3

[0098] Step S1: Screen-print a layer of bottom glaze on a ceramic substrate and perform sintering treatment to obtain a glass bottom glaze substrate;

[0099] Step S2: Spin-coat a pre-prepared yellow light thick film silver paste on the glass bottom glaze substrate at a speed of 2500 rpm for a duration of 3 min, and the coating thickness is 0.8 μm; bake at 90 °C for 10 min to obtain a first film layer; perform alignment exposure treatment on the first film layer, with an energy of 500 mj and an exposure time of 20 S; develop using 0.1% sodium carbonate solution for 2 min, and retain the electrode lines in the exposed area to form an electrode pattern; sinter the electrode pattern at 850 °C for 10 min to obtain a conductive circuit, and the thickness of the conductive circuit is 0.6 ± 0.2 μm;

[0100] Step S3: Use a 500-mesh steel wire mesh as a screen plate, and screen-print a pre-prepared yellow light thick film resistance paste on the conductive circuit, with a printing thickness of 6.5 ± 0.4 μm; bake at 90 °C for 10 min to obtain a second film layer; perform alignment exposure treatment on the second film layer, with an energy of 500 mj and an exposure time of 40 S; develop using 0.1% sodium carbonate solution for 2 min, and retain the resistance paste in the exposed area to form a resistance heating element pattern; sinter the resistance heating element pattern at 850 °C for 10 min to obtain a resistance heating element, and the size of the resistance heating element is (60 ± 5 μm) * (60 ± 5 μm) * (5.5 ± 0.5 μm);

[0101] Step S4: Screen-print thick film reinforced silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0102] Step S5: Screen-print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal print head.

[0103] Comparative Example

[0104] Step S1: Screen-print a layer of bottom glaze on a ceramic substrate and perform sintering treatment to obtain a glass bottom glaze substrate;

[0105] Step S2: Spin-coat a pre-prepared thick-film silver paste for yellow light on the glass bottom glaze substrate at a speed of 2500 rpm for 3 minutes, with a coating thickness of 1.0 μm; bake at 90 °C for 10 minutes to obtain the first film layer; perform alignment exposure on the first film layer with an energy of 500 mj and an exposure time of 20 S; develop using a 0.1% sodium carbonate solution for 2 minutes, retaining the electrode lines in the exposed area to form an electrode pattern; sinter the electrode pattern at 850 °C for 10 minutes to obtain a conductive circuit, and the thickness of the conductive circuit is 0.8 ± 0.2 μm;

[0106] Step S3: Use a 325-mesh steel wire mesh as a screen mask, screen-print a pre-prepared thick-film resistor paste for yellow light on the conductive circuit, with a printing thickness of 6.5 ± 1 μm; bake at 90 °C for 10 minutes to obtain the second film layer; perform alignment exposure on the second film layer with an energy of 500 mj and an exposure time of 40 S; develop using a 0.3% sodium carbonate solution for 2 minutes, retaining the resistor paste in the exposed area to form a resistor heating element pattern; sinter the resistor heating element pattern at 850 °C for 10 minutes to obtain a resistor heating element, and the size of the resistor heating element is (60 ± 8 μm) * (60 ± 8 μm) * (5.5 ± 1 μm);

[0107] Step S4: Screen-print a thick-film reinforcing silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0108] Step S5: Screen-print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain a thermal printer head.

[0109] In the embodiment of the present invention, the thickness of the conductive circuits prepared in Examples 1-3 and the comparative example is tested, the size of the resistor heating elements is tested, the resistance values of the resistor heating elements are tested and adjusted, and the test results are shown in the following table.

[0110] Thickness test: Use a step profiler and a 3D microscope, and select the multi-point measurement method.

[0111] Size test: Use a metallurgical microscope and a 3D microscope, and select the multi-point measurement method.

[0112] Resistance value test and adjustment: A pulse resistor trimming machine is used to measure the resistance value, and the multi-point measurement method is selected. Its principle is to correct the resistance value of the resistance heating element by using the pulse voltage trimming technology. The pulse voltage trimming technology applies a high-frequency and high-voltage electrical pulse to the electrodes at both ends of the resistance heating element of the thermal printer head. By using the high voltage to break down the very thin insulating layer in the resistor body, the conductive structure of the resistance heating element is changed to form a conductive path different from the original one, increasing the conduction path, thereby causing a change in the resistance value and realizing the correction of the resistance value.

[0113] Table 1: Resistance value test data of Example 1, unit is Ω.

[0114] 176 176 190 161 210 190 199 188 163 150 174 188 175 203 201 200 189 177 210 175 156 159 160 130 218 209 176 176 168 169 170 171 170 180 188 210 177 201 176 201 179 247 145 168 140 182 190 203 186 177

[0115] In Table 1, the minimum resistance value is 130 Ω, the maximum resistance value is 218 Ω, the target resistance value is 176 Ω, and the tolerance between the test resistance value and the target resistance value of 176 Ω reaches -26% to 23.8%, exceeding the ±10% usage range. However, after pulse voltage resistor trimming, the resistance value can be adjusted to within the range of 176 Ω ± 5%, meeting the usage requirements of some products.

[0116] Table 2: Resistance value test data of Example 2, unit is Ω.

[0117] 176 176 187 161 165 178 179 188 163 165 185 188 175 177 159 180 189 177 175 175 174 180 179 181 181 177 176 176 168 169 170 171 170 180 188 189 177 176 176 178 179 186 184 183 179 182 182 183 186 177

[0118] In Table 2, the minimum resistance value is 159 Ω, the maximum resistance value is 189 Ω, the target resistance value is 176 Ω, and the tolerance range between the test resistance value and the target resistance value of 176 Ω is between -9.6% and 7.4%, within the ±10% usage range, which can meet the usage requirements of some products without pulse voltage resistor trimming or laser resistor trimming, thus saving time cost, process cost, and hardware investment cost. However, after pulse voltage resistor trimming, the resistance value can be adjusted to within the range of 176 Ω ± 3%, meeting the usage requirements of all products.

[0119] Table 3: Resistance value test data of Example 3, unit is Ω.

[0120] 165 166 189 180 181 180 176 177 186 178 186 180 190 178 165 180 189 188 191 175 178 183 177 188 183 176 177 176 165 168 180 180 183 180 186 176 177 174 169 168 179 189 186 187 177 174 172 182 187 190

[0121] In Table 3, the minimum resistance value is 165 Ω, the maximum resistance value is 191 Ω, the target resistance value is 176 Ω, and the tolerance range between the test value and the target resistance value of 176 Ω is between -6.25% and 8.5%, within the ±10% usage range, which can meet the usage requirements of some products without pulse voltage resistor trimming or laser resistor trimming, thus saving time cost, process cost, and hardware investment cost. However, after pulse voltage resistor trimming, the resistance value can be adjusted to within the range of 176 Ω ± 3%, meeting the usage requirements of all products.

[0122] Table 4: Test data of the resistance values of the comparative examples, with the unit of Ω.

[0123] 205 178 173 232 168 178 179 188 163 265 256 188 175 277 159 180 189 177 175 120 234 180 189 167 181 177 176 176 154 131 136 171 126 180 154 189 177 176 176 126 178 245 232 253 145 256 156 167 154 277

[0124] In Table 4, the minimum resistance value is 120 Ω, the maximum resistance value is 277 Ω, the target resistance value is 176 Ω, and the tolerance range between the test value and the target resistance value of 176 Ω is between -32% and 57.4%, exceeding the usage requirement of ±10%. After adjusting the resistance with pulsed voltage, the resistance value can be adjusted to within the range of 176 Ω ± 15%, still unable to meet the product usage requirement.

[0125] Table 5: Relevant test results of Examples 1-3 and the comparative examples.

[0126]

[0127] As shown in Table 5, in Example 1, due to the relatively large coating thickness of the yellow light thick film silver paste, the thickness of the conductive circuit is relatively large, resulting in poor consistency of the screen printing thickness of the yellow light thick film resistance paste, thus leading to relatively large dimensional deviations of the resistance heating element, and the tolerance between the test resistance value and the target resistance value of the resistance heating element is relatively large. The thickness of the conductive circuits in Examples 2 and 3 is relatively thin, and the consistency of the thickness after screen printing of the yellow light thick film resistance paste is good, resulting in higher dimensional accuracy of the resistance heating element and better resistance value consistency, that is, the tolerance between the test resistance value and the target resistance value of the resistance heating element is relatively small. In the comparative example, the deviation of the printing thickness of the yellow light thick film resistance paste is large, and the dimensional accuracy of the resistance heating element is poor after exposure and development, resulting in poor resistance value consistency.

[0128] The above are only the implementation manners of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A method for preparing a thermal print head, characterized in that, The preparation method includes the following steps: Step S1: Print a layer of bottom glaze on a ceramic substrate by screen printing, and obtain a glass bottom glaze substrate after sintering treatment; Step S2: Coat a layer of pre-prepared yellow thick film silver paste on the glass bottom glaze substrate to prepare a conductive circuit, and the thickness of the conductive circuit is 0.6 - 2.0 μm; Step S2 further includes: coating a layer of pre-prepared yellow thick film silver paste on the glass bottom glaze substrate by screen printing, spin coating or roll coating, and the coating thickness of the yellow thick film silver paste is 0.8 - 2.5 μm; baking the yellow thick film silver paste to obtain a first film layer; performing alignment exposure treatment and development treatment on the first film layer to retain the electrode lines in the exposed area and form an electrode pattern; performing sintering treatment on the electrode pattern to obtain the conductive circuit, and the conductive circuit includes a plurality of independently arranged sub-circuits, a first electrode corresponding to each sub-circuit, a second electrode corresponding to each first electrode, and a common circuit connected to the second electrode; Step S3: Print a layer of pre-prepared yellow thick film resistor paste on the conductive circuit to prepare a resistor heating element; wherein, the yellow thick film silver paste includes the following components by mass percentage: 10% - 20% of a first yellow organic carrier, 80 - 90% of silver powder, 0.2 - 2.0% of glass powder, and the first yellow organic carrier includes yellow resin, UV prepolymer, UV monomer, solvent, dispersant, leveling agent, defoaming agent, coupling agent, film forming aid and photoinitiator; Specifically, Step S3 further includes: printing a layer of pre-prepared yellow thick film resistor paste on the conductive circuit by screen printing or pad printing, and using a 500-mesh steel wire screen as the screen plate for screen printing, and the printing thickness of the yellow thick film resistor paste is 6.5 ± 0.4 μm; baking the yellow thick film resistor paste to obtain a second film layer; performing alignment exposure treatment and development treatment on the second film layer to retain the resistor paste in the exposed area and form a resistor heating element pattern; performing sintering treatment on the resistor heating element pattern to obtain the resistor heating element, and the resistor heating element is connected to the first electrode and the second electrode; Step S4: Screen print a thick film reinforcing silver paste at a preset position and perform sintering treatment to obtain an assembly; Step S5: Screen print a layer of glass glaze on the surface of the assembly, and successively perform sintering treatment, resistance adjustment treatment and chip packaging treatment to obtain the thermal print head.

2. The preparation method of the thermal print head according to claim 1, characterized in that, The baking temperature for baking treatment is 80 - 110 °C, and the baking time is 5 - 15 min; the energy for alignment exposure treatment is 100 - 1000 mj; the developer for development treatment is a 0.1% - 0.3% sodium carbonate solution; the sintering temperature for sintering treatment is 650 - 900 °C, and the sintering time is 5 - 20 min.

3. The manufacturing method of the thermal print head according to claim 1, characterized in that, The yellow thick film resistor paste includes the following components by mass percentage: 20%-40% of a second yellow organic carrier, 60-80% of ruthenium oxide powder, and 0.2-10% of glass powder. The second yellow organic carrier is the same as the first yellow organic carrier.

4. A thermal print head, characterized in that, It is prepared by using the preparation method of the thermal print head according to any one of claims 1-3.

5. The thermal print head according to claim 4, wherein, The thermal print head includes a conductive circuit and a resistive heating element disposed in the conductive circuit. The tolerance between the measured resistance value and the target resistance value of the resistive heating element is within 5%.

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