Circuit Structure of Thermal Print Head, Thermal Print Head and Preparation Method Thereof

Abstract

The present invention relates to the field of printing technology, and particularly to a circuit structure of a thermal print head, a thermal print head and a preparation method thereof. The circuit structure includes a conductive circuit formed on a preset substrate and a resistance heating element formed on the preset substrate and connected to the conductive circuit; 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 spaced from the first electrode, and a common circuit connected to the second electrode, and the resistance heating element is arranged corresponding to each sub-circuit and connected to the first electrode and the second electrode. By the above method, the present invention can effectively reduce the size of the resistance heating element, thereby reducing the heating area and the contact area with the conductive circuit, and improving the printing accuracy of the thermal print head.

Description

Technical Field

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

[0002] The resistors and conductive circuits in a thermal print head are good conductors of heat, and heat is easily diffused, resulting in a decrease in printing accuracy. At present, due to the limitations of the printing process, the width of the resistor wire can only be made 120 microns, and the area of the heating point is relatively large, making it difficult to improve the printing accuracy.

[0003] The process flow 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 microns 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 by screen printing, roll coating, spin coating or other methods, and a dense gold thin film is formed after high-temperature sintering at 850 °C. 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, the circuit pattern is etched with a gold etchant, and the photoresist is removed with strong alkali; ④ A thick film resistor wire is screen-printed in the etched circuit pattern and sintered at 850 °C to form a resistor wire with good consistency; ⑤ Thick film reinforced silver paste is screen-printed and sintered at the corresponding pad positions, GND and other positions; ⑥ A layer of glass glaze is screen-printed on the surface of the above combination and sintered; ⑦ After testing and adjusting the resistance value with a resistance adjusting machine, it is encapsulated.

[0004] The above solution can achieve mass production, but has the following disadvantages:

[0005] 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;

[0006] 2. The raw materials contain organic gold paste, resulting in high costs;

[0007] 3. Organic gold needs to use photoresist to prepare patterns and then etch. The etching scheme requires the use of strongly oxidizing iodine + strong acid (such as hydrochloric acid, nitric acid) or aqua regia, which is dangerous, poor in environmental protection and inconvenient to operate;

[0008] 4. Using screen printing to prepare the resistor heating element has poor printing accuracy and poor resistance consistency after sintering. Pulse voltage resistance adjustment method needs to be used to adjust the resistance value, resulting in low efficiency, complex equipment and high cost.

[0009] In view of this, providing a new circuit structure of a thermal print head, a thermal print head and a preparation method thereof has become an urgent technical problem to be solved in the art. Summary of the Invention

[0010] Aiming at the defects in the prior art, the purpose of the present invention is to provide a circuit structure of a thermal print head, a thermal print head and a preparation method thereof, so as to solve the technical problems of high preparation cost, low efficiency and low printing accuracy of the existing thermal print head.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] On the one hand, the present invention provides a circuit structure of a thermal print head, and the circuit structure includes: a conductive circuit formed on a preset substrate and a resistive heating element formed on the preset substrate and connected to the conductive circuit;

[0013] The conductive circuit includes a plurality of independently arranged sub-circuits, a first electrode corresponding to each of the sub-circuits, a second electrode corresponding to each of the first electrodes and spaced apart from the first electrode, and a common circuit connected to the second electrode. The resistive heating element is arranged corresponding to each sub-circuit and connects the first electrode and the second electrode.

[0014] According to an embodiment of the present invention, the conductive circuit and the resistive heating element are made by a yellow light thick film process and / or a laser engraving process.

[0015] According to an embodiment of the present invention, in the yellow light thick film process, the conductive circuit is made of yellow light thick film silver paste, and the yellow light thick film silver paste includes the following components by mass percentage: 10%-20% of a first yellow light organic carrier, 80-90% of silver powder, and 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.

[0016] According to an embodiment of the present invention, the conductive circuit is formed by coating a pre-configured yellow light thick film silver paste on the preset substrate by screen printing, spin coating or roll coating. The coating thickness of the yellow light thick film silver paste is 0.8-2.5 μm, and the thickness of the conductive circuit is 0.6-2.0 μm.

[0017] According to an embodiment of the present invention, in the yellow light thick film process, the resistive heating element is made of yellow light thick film resistor paste, and the yellow light thick film resistor paste includes the following components by mass percentage: 20%-40% of a second yellow light organic carrier, 60-80% of ruthenium oxide powder, and 0.2-10% of glass powder.

[0018] According to an embodiment of the present invention, the resistive heating element is formed by screen printing or pad printing a layer of pre-configured yellow thick film resistor paste on the conductive circuit.

[0019] According to an embodiment of the present invention, the resistive heating element is a photoresistor.

[0020] On the other hand, the present invention provides a thermal print head, comprising:

[0021] A preset substrate, the preset substrate includes a substrate body and a bottom glaze layer formed on the substrate body;

[0022] The circuit structure is formed on the preset substrate;

[0023] A protective layer is formed on the surface of the circuit structure, and

[0024] A control chip, the control chip is connected to the circuit structure.

[0025] On the other hand, the present invention provides a method for manufacturing a thermal print head, the manufacturing method comprising the following steps:

[0026] Step S1: Screen print a layer of bottom glaze on the substrate body, and after sintering treatment, obtain the preset substrate;

[0027] Step S2: Coating a layer of pre-configured yellow thick film silver paste on the preset substrate by screen printing, spin coating or roll coating, the coating thickness is 0.8 - 2.5 μm, baking the yellow thick film silver paste, obtaining 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, forming an electrode pattern, and sintering the electrode pattern to obtain a conductive circuit with multiple independently arranged sub-circuits, the thickness of the conductive circuit is 0.6 - 2.0 μm;

[0028] Step S3: Screen print or pad print a layer of pre-configured yellow thick film resistor paste on the conductive circuit, bake the yellow thick film resistor paste, obtain a second film layer, perform alignment exposure treatment and development treatment on the second film layer to retain the resistor paste in the exposed area, form a resistive heating element pattern, and sinter the resistive heating element pattern to obtain a plurality of mutually independent resistive heating elements, each of the resistive heating elements is correspondingly connected to each of the sub-circuits;

[0029] Step S4: Screen print thick film reinforcing silver paste at a preset position and perform sintering treatment to obtain a combination;

[0030] Step S5: Print a layer of glass glaze on the surface of the assembly by screen printing, and successively perform sintering treatment, resistance adjustment treatment, and chip packaging treatment to obtain the thermal printing head.

[0031] According to an embodiment of the present invention, in the step S2 and the step S3, the baking temperature of the baking treatment is 80-110°C, and 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.

[0032] Beneficial effects: The circuit structure includes a conductive circuit formed on a preset substrate and a resistance heating element formed on the preset substrate and connected to the conductive circuit; 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 spaced from the first electrode, and a common circuit connected to the second electrode; the resistance heating element is arranged corresponding to each sub-circuit and connects the first electrode and the second electrode; it can effectively reduce the size of the resistance heating element, thereby reducing the heating area and the contact area with the conductive circuit, and improving the printing accuracy of the thermal printing head. Description of the Drawings

[0033] Figure 1 is a schematic diagram of the circuit structure of the thermal printing head according to an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of the partial structure of the thermal printing head according to an embodiment of the present invention;

[0035] Figure 3 is a schematic flow chart of the preparation method of the thermal printing head according to an embodiment of the present invention;

[0036] Figure 4 is a schematic diagram of the structure of the conductive circuit according to an embodiment of the present invention. Detailed Embodiments

[0037] The following illustrates the technical solutions of the present invention through specific embodiments.

[0038] Figure 1 is a schematic diagram of the circuit structure of the thermal printing head according to an embodiment of the present invention, as Figure 1As shown in the figure, the circuit structure 100 includes: a conductive circuit 10 formed on a preset substrate 30 and a resistive heating element 20 formed on the preset substrate 30 and connected to the conductive circuit 10; the conductive circuit 10 includes a plurality of independently arranged sub-circuits 11, a first electrode 12 corresponding to each sub-circuit 11, a second electrode 13 corresponding to each first electrode 12 and spaced apart from the first electrode 12, and a common circuit 14 connected to the second electrode 13. The resistive heating element 20 is arranged corresponding to each sub-circuit 11 and is connected to the first electrode 12 and the second electrode 13. Compared with the current circuit structure, this circuit structure 100 can effectively reduce the size of the resistive heating element 20, thereby reducing the heating area and the contact area with the conductive circuit 10, and improving the printing accuracy of the thermal printer head. In one embodiment, the resistive heating element 20 can be designed as small dots, greatly reducing the heating area and the contact area with the conductive circuit 10, thereby improving the printing accuracy of the thermal printer head.

[0039] As an achievable embodiment, the conductive circuit 10 and the resistive heating element 20 are made by a yellow light thick film process and / or a laser engraving process. The yellow light thick film process is defined as a thick film process that includes preparation steps such as printing, exposure, development, and sintering in a yellow light environment. For example, the conductive circuit 10 is made by the yellow light thick film process, and the resistive heating element 20 is made by the yellow light thick film process; or the conductive circuit 10 is made by the laser engraving process, and the resistive heating element 20 is made by the laser engraving process; or the conductive circuit 10 is made by the yellow light thick film process, and the resistive heating element 20 is made by the laser engraving process; or the conductive circuit 10 is made by the laser engraving process, and the resistive heating element 20 is made by the yellow light thick film process.

[0040] As an achievable embodiment, in the yellow light thick film process, the conductive circuit 10 is made of yellow light thick film silver paste, and the yellow light thick film silver paste includes the following components by mass percentage: 10%-20% of a first yellow light organic carrier, 80-90% of silver powder, and 0.2-2.0% of glass powder. The first yellow light organic carrier includes a yellow light 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.

[0041] Furthermore, the yellow light resin includes resins containing groups such as carboxyl, C=C double bond, hydroxyl, and isocyanate groups, with a molecular weight of 6000-50000 and an acid value of 30-300 mgKOH / g.

[0042] Furthermore, the UV monomer includes one or more of methyl methacrylate, n-butyl methacrylate, lauryl methacrylate, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0043] Furthermore, the UV prepolymer includes one or more of a monofunctional polyurethane-modified acrylate monomer, a bifunctional polyurethane acrylate, a polyfunctional polyurethane acrylate, a monofunctional polyester-modified acrylate monomer, a bifunctional polyester acrylate, and a polyfunctional polyester acrylate.

[0044] Furthermore, 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.

[0045] Furthermore, the dispersant includes one or more of a phosphate ester salt polymer, a fatty acid ethylene oxide adduct, and a polyethylene glycol type polyol.

[0046] Furthermore, the leveling agent includes an acrylate polymer and a silicone leveling agent.

[0047] Furthermore, the defoaming agent is a silicone defoaming agent.

[0048] Furthermore, the coupling agent includes one or more of vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0049] Furthermore, the film-forming aid includes one or more of alcohol ester twelve, tributyl citrate, and acetyl tributyl citrate.

[0050] Furthermore, the photoinitiator 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-benzoyloxime).

[0051] Furthermore, the silver powder is spherical nano silver powder or submicron silver powder, and the particle size is 50 nm - 1 μm.

[0052] Furthermore, the glass powder is a 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.

[0053] As an achievable embodiment, the conductive line 10 is formed by coating a pre-configured yellow thick film silver paste on the preset substrate 30 in a manner of screen printing, spin coating, or roll coating, and the coating thickness of the yellow thick film silver paste is 0.8 - 2.5 μm.

[0054] As an achievable embodiment, the thickness of the conductive line 10 is 0.6 - 2.0 μm. The thickness of the conductive line 10 is selected as the median value in the test results. In some embodiments, the thickness of the conductive line 10 can be expressed as (0.6 ± 0.2 μm) - (2.0 ± 0.2 μm).

[0055] As an achievable embodiment, in the yellow light thick film process, the resistive heating element 20 is made of a yellow light thick film resist paste, and the yellow light thick film resist paste includes the following components by mass percentage: 20% - 40% of the second yellow light organic carrier, 60 - 80% of ruthenium oxide powder, and 0.2 - 10% of glass powder.

[0056] Furthermore, the second yellow light organic carrier is the same as the first yellow light organic carrier. The yellow light organic carrier is a carrier for yellow light 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.

[0057] As an achievable embodiment, the resistive heating element 20 is formed by printing a pre-configured yellow light thick film resist paste on the conductive line 10 by screen printing or pad printing. The printing thickness of the yellow light thick film resist paste is 6.5 ± 0.4 μm, and a 500-mesh steel wire mesh is used as the screen plate for screen printing.

[0058] As an achievable embodiment, the resistive heating element 20 is a photosensitive resistor. In one embodiment, the resistive heating element 20 is sensitive to visible light and ultraviolet light. The resistive heating element 20 has high resolution and can achieve small-area heating, thereby improving the printing accuracy of the thermal print head.

[0059] Please refer to Figure 1 、 Figure 2 As shown in the figure, the embodiments of the present invention provide a thermal print head, and 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. Among them, the preset substrate 30 includes a substrate main body and an underglaze layer formed on the substrate main body. The thermal print head 200 can effectively reduce the size of the resistive heating element 20, thereby reducing the heating area and the contact area with the conductive line 10, and improving the printing accuracy of the thermal print head 200.

[0060] Please refer to Figure 3 As shown in the figure, the embodiments of the present invention provide a method for manufacturing a thermal print head, and the manufacturing method includes the following steps:

[0061] Step S1: Print a layer of base glaze on the substrate body by screen printing, and obtain a preset substrate after sintering treatment.

[0062] In this step, the substrate body can be a ceramic substrate, such as an alumina ceramic substrate or a aluminum nitride ceramic substrate. In one embodiment, a layer of base glaze with a thickness of 50 - 80 μm is printed on the alumina ceramic substrate by screen printing, and a glass base glaze substrate with a flat and smooth surface, that is, the preset substrate, is obtained after sintering treatment at 1250 °C.

[0063] Step S2: Coating a layer of pre - configured yellow thick - film silver paste on the preset substrate by screen printing, spin - coating or roll - coating, with a coating thickness of 0.8 - 2.5 μm. Bake the yellow thick - film silver paste to obtain a first film layer. Perform alignment exposure and development on the first film layer to retain the electrode lines in the exposed area, forming an electrode pattern. Sinter the electrode pattern to obtain a conductive circuit with multiple independently arranged sub - circuits, and the thickness of the conductive circuit is 0.6 - 2.0 μm.

[0064] In this step, the baking temperature for the baking treatment is 80 - 110 °C, and the baking time is 5 - 15 min; the energy for 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 for the sintering treatment is 650 - 900 °C, and the sintering time is 5 - 20 min. As Figure 4 shown, the conductive circuit 10 includes multiple 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 line 14 connected to the second electrode 13.

[0065] Step S3: Print a layer of pre - configured yellow thick - film resistor paste on the conductive circuit by screen printing or pad printing. Bake the yellow thick - film resistor paste to obtain a second film layer. Perform alignment exposure and development on the second film layer to retain the resistor paste in the exposed area, forming a resistor heating element pattern. Sinter the resistor heating element pattern to obtain multiple independent resistor heating elements, and each resistor heating element is correspondingly connected to each sub - circuit.

[0066] In this step, the baking temperature for the baking treatment is 80 - 110 °C, and the baking time is 5 - 15 min; the energy for the alignment exposure treatment is 100 - 1000 mj; the developer for the developing treatment is a 0.1% - 0.3% sodium carbonate solution; the sintering temperature for the sintering treatment is 650 - 900 °C, and the sintering time is 5 - 20 min. 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). As Figure 1 shown, the resistive heating element 20 is correspondingly arranged with the sub - circuit 11. The resistive heating element 20 is connected between the first electrode 12 and the second electrode 13. In this embodiment, the resistive heating element 20 is correspondingly arranged with the sub - circuit 11. One sub - circuit 11 is connected in series with one resistive heating element 20. By controlling the size of the resistive heating element 20, the heating area is controlled, so as to achieve precise temperature control of the thermal print head 100 and improve the printing accuracy.

[0067] Step S4: Screen - print a thick - film reinforced silver paste at a preset position and perform a sintering treatment to obtain a composite body.

[0068] In this step, the preset position can be a pad position, a GND position, etc.

[0069] Step S5: Screen - print a layer of glass glaze on the surface of the composite body, and sequentially perform a sintering treatment, a resistance - adjusting treatment, and a chip packaging treatment to obtain a thermal print head.

[0070] In this step, as Figure 2 shown, screen - print a layer of glass glaze on the surface of the composite body to form a protective layer 40, which plays a protective role for the conductive circuit 10.

[0071] 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 preset substrate. The thickness of the conductive circuit is 0.6 μm - 2.0 μm; print a layer of pre - configured yellow - light thick - film resistive paste on the conductive circuit to prepare a resistive heating element; the pre - configured yellow - light thick - film silver paste has a lower raw material cost compared with the 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 resistive paste to prepare the resistive heating element, the resistance consistency is good. The tolerance between the measured resistance value and the target resistance value of the resistive heating element prepared by this preparation method is within 5%, meeting the product use requirements, and can solve the technical problems of high cost, low efficiency, and poor resistance consistency in the existing preparation schemes of thermal print heads.

[0072] Example 1

[0073] Step S1: Print a layer of bottom glaze on the ceramic substrate by screen printing, and after sintering treatment, obtain a glass bottom glaze substrate;

[0074] Step S2: Adopt the spin coating method at a speed of 1500 rpm for a duration of 2 min to coat a pre-prepared yellow light thick film silver paste on the glass bottom glaze substrate, with a coating thickness of 2.5 μm; bake at 90 °C for 10 min to obtain the 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; use 0.1% sodium carbonate solution for development treatment for 2 min, 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;

[0075] Step S3: Use a 500-mesh steel wire mesh as the stencil, and brush a pre-prepared yellow light thick film resistor paste on the conductive circuit, with a printing thickness of 6.5 ± 0.4 μm; bake at 90 °C for 10 min to obtain the 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; use 0.1% sodium carbonate solution for development treatment for 2 min, 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, and the size of the resistor heating element is (60 ± 8 μm) * (60 ± 8 μm) * (5.5 ± 0.9 μm);

[0076] Step S4: Screen print a thick film reinforced silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0077] 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.

[0078] Example 2

[0079] Step S1: Print a layer of bottom glaze on the ceramic substrate by screen printing, and after sintering treatment, obtain a glass bottom glaze substrate;

[0080] Step S2: Spin-coat a layer of pre-prepared yellow thick film silver paste on the glass bottom glaze substrate at a speed of 2500 rpm for 3 minutes, with a coating thickness of 1.0 μm; bake it 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 it with 0.1% sodium carbonate solution for 2 minutes, and retain 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;

[0081] Step S3: Use a 500-mesh steel wire mesh as the screen plate, and screen-print a layer of pre-prepared yellow thick film resistor paste on the conductive circuit, with a printing thickness of 6.5 ± 0.4 μm; bake it 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 it with 0.1% sodium carbonate solution for 2 minutes, 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 minutes to obtain a resistor heating element, and the size of the resistor heating element is (60 ± 5 μm) * (60 ± 5 μm) * (5.5 ± 0.5 μm);

[0082] Step S4: Screen-print the thick film reinforcing silver paste at the preset position and perform sintering treatment to obtain an assembly;

[0083] 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.

[0084] Example 3

[0085] Step S1: Screen-print a layer of bottom glaze on the ceramic substrate and perform sintering treatment to obtain a glass bottom glaze substrate;

[0086] Step S2: Spin-coat a layer of pre-prepared yellow thick film silver paste on the glass bottom glaze substrate at a speed of 2500 rpm for 3 minutes, with a coating thickness of 0.8 μm; bake it 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 it with 0.1% sodium carbonate solution for 2 minutes, and retain 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 0.6 ± 0.2 μm;

[0087] Step S3: Use a 500-mesh steel 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 dimensions of (60 ± 5 μm) * (60 ± 5 μm) * (5.5 ± 0.5 μm);

[0088] Step S4: Screen-print a thick film reinforcing silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0089] 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.

[0090] Comparative example

[0091] Step S1: Screen-print a layer of bottom glaze on the ceramic substrate and, after sintering treatment, obtain a glass bottom glaze substrate;

[0092] Step S2: Use a spin-coating method at a speed of 2500 rpm for 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, and the thickness of the conductive circuit is 0.8 ± 0.2 μm;

[0093] Step S3: Use a 325-mesh steel 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 ± 1 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 0.3% 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 dimensions of (60 ± 8 μm) * (60 ± 8 μm) * (5.5 ± 1 μm);

[0094] Step S4: Screen-print thick film reinforced silver paste at a preset position and perform sintering treatment to obtain an assembly;

[0095] 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.

[0096] In the embodiments of the present invention, the thickness of the conductive lines prepared in Embodiments 1-3 and the comparative examples is tested, the size of the resistance heating element is tested, the resistance value of the resistance heating element is tested and adjusted, and the test results are shown in the following table.

[0097] Thickness test: Use a step profiler and a 3D microscope, and select the multi-point measurement method.

[0098] Size test: Use a metallurgical microscope and a 3D microscope, and select the multi-point measurement method.

[0099] Resistance value test and adjustment: Use a pulse resistance adjuster for resistance value, and select the multi-point measurement method. Its principle is to correct the resistance value of the resistance heating element by using pulse voltage fine-tuning technology. Pulse voltage fine-tuning technology is to apply a high-frequency high-voltage electrical pulse to the electrodes at both ends of the resistance heating element of the thermal print head, and use the high voltage to break down the very thin insulating layer in the resistor to change the conductive structure of the resistance heating element, so as to form a conductive path different from the original one, increase the conduction path, thereby causing a change in the resistance value, and then realizing the correction of the resistance value.

[0100] Table 1: Resistance value test data of Embodiment 1, unit is Ω.

[0101] 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

[0102] 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 usage range of ±10%. However, after pulse voltage resistance adjustment, the resistance value can be adjusted to within the range of 176 Ω ± 5%, meeting the usage requirements of some products.

[0103] Table 2: Resistance value test data of Embodiment 2, unit is Ω.

[0104] 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

[0105] 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 measured resistance value and the target resistance value of 176 Ω is between -9.6% and 7.4%. Within the usage range of ±10%, it can meet the usage requirements of some products without the need for pulse voltage resistance adjustment or laser resistance adjustment, thus saving time cost, process cost, and hardware investment cost. However, after pulse voltage resistance adjustment, the resistance value can be adjusted to within the range of 176 Ω ± 3%, meeting the usage requirements of all products.

[0106] Table 3: Resistance value test data of Example 3, unit is Ω.

[0107] 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

[0108] 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 measured value and the target resistance value of 176 Ω is between -6.25% and 8.5%. Within the usage range of ±10%, it can meet the usage requirements of some products without the need for pulse voltage resistance adjustment or laser resistance adjustment, thus saving time cost, process cost, and hardware investment cost. However, after pulse voltage resistance adjustment, the resistance value can be adjusted to within the range of 176 Ω ± 3%, meeting the usage requirements of all products.

[0109] Table 4: Resistance value test data of the comparative example, unit is Ω.

[0110] 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

[0111] 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 measured value and the target resistance value of 176 Ω is between -32% and 57.4%, exceeding the usage requirements of ±10%. After pulse voltage resistance adjustment, the resistance value can be adjusted to within the range of 176 Ω ± 15%, still unable to meet the product usage requirements.

[0112] Table 5: Related test results of Examples 1 - 3 and the comparative example.

[0113]

[0114] As shown in Table 5, in Example 1, due to the relatively large coating thickness of the yellow light thick film silver paste, the relatively large thickness of the conductive circuit leads to poor consistency in the screen printing thickness of the yellow light thick film resistor paste, resulting in a relatively large dimensional deviation of the resistor heating element. The tolerance between the measured resistance value and the target resistance value of the resistor heating element is relatively large. In Examples 2 and 3, the thickness of the conductive circuit is relatively thin, and the consistency of the thickness after screen printing of the yellow light thick film resistor paste is good, resulting in a relatively high dimensional accuracy of the resistor heating element and good resistance value consistency, that is, the tolerance between the measured resistance value and the target resistance value of the resistor heating element is relatively small. In the comparative example, the printing thickness deviation of the yellow light thick film resistor paste is large, and the dimensional accuracy of the resistor heating element after exposure and development is poor, resulting in poor resistance value consistency.

[0115] 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 circuit structure of a thermal print head, characterized in that, The circuit structure includes: a conductive circuit formed on a preset substrate and a resistive heating element formed on the preset substrate and connected to the conductive circuit; Among them, the conductive circuit and the resistive heating element are made by a yellow light thick film process and / or a laser engraving process; in the yellow light thick film process, the conductive circuit is made of yellow light thick film silver paste, and the yellow light thick film silver paste includes the following components by mass percentage: 10%-20% of a 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; the resistive heating element is made of yellow light thick film resistive paste, and the yellow light thick film resistive paste includes the following components by mass percentage: 20%-40% of a second yellow light organic carrier, 60-80% of ruthenium oxide powder, 0.2-10% of glass powder; the conductive circuit is formed by coating a pre-configured yellow light thick film silver paste on the preset 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, and the thickness of the conductive circuit is 0.6 -2.0 μm; 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 spaced apart from the first electrode, and a common circuit connected to the second electrode. The resistive heating element is arranged corresponding to each sub-circuit and connects the first electrode and the second electrode.

2. The circuit structure of the thermal print head according to claim 1, wherein, The resistive heating element is formed by printing a pre-configured yellow light thick film resistive paste on the conductive circuit by screen printing or pad printing.

3. The circuit structure of the thermal print head according to claim 1, wherein The resistive heating element is a photosensitive resistor.

4. A thermal print head, characterized in that, It includes: A preset substrate, which includes a substrate body and an underglaze layer formed on the substrate body; The circuit structure according to any one of claims 1-3, formed on the preset substrate; A protective layer, formed on the surface of the circuit structure, and A control chip, which is connected to the circuit structure.

5. A method for manufacturing a thermal print head, for implementing the thermal print head according to claim 4, characterized in that, The preparation method includes the following steps: Step S1: Print an underglaze on the substrate body by screen printing and obtain a preset substrate after sintering treatment; Step S2: Coat a pre-configured yellow light thick film silver paste on the preset substrate by screen printing, spin coating or roll coating, with a coating thickness of 0.8-2.5 μm, bake the yellow light thick film silver paste to obtain a first film layer, perform alignment exposure treatment and development treatment on the first film layer to retain the electrode lines in the exposed area to form an electrode pattern, and sinter the electrode pattern to obtain a conductive circuit with a plurality of independently arranged sub-circuits, and the thickness of the conductive circuit is 0.6 -2.0 μm; Step S3: Print a pre-configured yellow thick film resistor paste on the conductive circuit by means of screen printing or pad printing, bake the yellow thick film resistor paste to obtain a second film layer, perform alignment exposure and development on the second film layer to retain the resistor paste in the exposed area, form a resistor heating element pattern, and perform sintering treatment on the resistor heating element pattern to obtain a plurality of independent resistor heating elements, and each of the resistor heating elements is correspondingly connected to each of the sub-circuits; Step S4: Screen print a thick film reinforcing silver paste at a preset position and perform sintering treatment to obtain an assembly; Step S5: Print a layer of glass glaze on the surface of the assembly by means of screen printing, and successively perform sintering treatment, resistance adjustment treatment and chip packaging treatment to obtain the thermal print head.

6. The manufacturing method of the thermal print head according to claim 5, characterized in that, In the step S2 and the step S3, the baking temperature of the baking treatment is 80 - 110 °C, and 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.

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