Sintering process for aluminum alloy plate of flat thick film heater

Abstract

The invention discloses a sintering process for an aluminum alloy plate of a flat thick film heater. An insulating glass medium is sintered to the surface of the aluminum alloy layer by layer through multiple times of printing and sintering, so that the final thickness of an insulating layer is larger than 200 microns, then the insulating standard indexes such as the withstand voltage of 4200 VDC and the like are achieved, the harsh requirement for ultrahigh high-voltage insulating safety is met, meanwhile, by means of a temperature control sintering furnace, an accurate temperature control curve is achieved, the temperature is slowly increased to 200-300 DEG C at the speed of 3-5 DEG C / min, and heat preservation is conducted; organic carriers can be fully and gently removed, and bubbles, pinholes or cracks caused by sudden volatilization are avoided.

Description

Technical Field

[0001] This invention relates to the field of material sintering, and in particular to a sintering process for aluminum alloy plates in a flat thick-film heater. Background Technology

[0002] The thick film heater for new energy vehicles is a core heating element used in the vehicle's thermal management system to replace the PTC heater. It adopts advanced thick film technology to print and sinter special heating materials onto a substrate to form a high-efficiency electrothermal conversion layer. Its core advantage lies in its rapid start-up, which can provide heat in a very short time and keep the battery warm in cold weather. It also has the advantages of compact structure and high power density.

[0003] In the prior art, the substrate carrier for thick film heating is stainless steel, with a material density of 7.9 g / cm³ and a thermal conductivity of 24 W / (m·K), while aluminum alloy has a material density of 2.7 g / cm³ and a thermal conductivity of 167 W / (m·K). Therefore, aluminum alloy has the advantages of being lightweight and having good thermal conductivity when used as a substrate. However, due to limitations in the process technology, issues such as the coefficient of thermal expansion (CTE), surface impurities, oxide layer, and uniform heating and heat dissipation lead to an excessive number of defective products. Summary of the Invention

[0004] The purpose of this invention is to provide a sintering process for aluminum alloy plates in a flat thick film heater, which has the advantage of good sintering effect.

[0005] The above-mentioned technical objective of this invention is achieved through the following technical solution: a sintering process for aluminum alloy plates in a flat thick-film heater, comprising the following steps.

[0006] Step 1: Pre-processing: Cut the aluminum alloy into a substrate according to the design dimensions, and process mounting holes and process holes.

[0007] Step 2, Substrate Surface Treatment: Grind the substrate surface to 850-900 mesh;

[0008] Step 3: Substrate surface cleaning: Use organic solvents to ultrasonically clean the substrate surface to remove surface processing debris, oil, and impurities;

[0009] Step 4: Chemical treatment of substrate surface: Micro-arc oxidation is performed on the substrate to form a ceramic oxide layer on the substrate surface;

[0010] Step 5: Drying the substrate;

[0011] Step 6, Adhesion of the underlying dry film: On the conveyor belt, the glass dielectric paste is printed onto the forming surface of the aluminum alloy substrate by pad printing or screen printing to form a dry film.

[0012] Step 7, substrate transfer: The conveyor belt transfers the substrate into the sintering furnace, where the bottom layer is sintered under the protection of protective gas. The sintering area of ​​the sintering furnace includes an interconnected and fully enclosed preheating zone, sintering zone, and cooling zone.

[0013] Step 8, Preheating Zone: Increase the temperature from room temperature at 3-5℃ / min to 200-300℃, hold for 10-15 minutes, and remove the organic carrier that entered in the previous stage;

[0014] Step 9, Sintering Zone: Increase the temperature to 450-500℃ at 2-3℃ / min and hold for 15-25 minutes to allow the components in the dry film to melt and flow, forming a dense insulating layer on the surface of the aluminum alloy substrate.

[0015] Step 10, Cooling Zone: Cool the furnace along with the substrate or reduce the furnace temperature to below 150°C at a rate of 2-4°C / min until the substrate is conveyed out of the furnace by the conveyor belt;

[0016] Step 11, Surface Quality Inspection: Inspect the sintered surface using a CCD camera, while ensuring the surface is clean;

[0017] Step 12, Multilayer Sintering: The conveyor belt carries the substrate back into the dry film attachment station, where glass dielectric paste is attached to the bottom insulating layer. Steps 6 to 11 are repeated to ensure that the final insulating layer thickness is greater than 200μm, or that it withstands a voltage of 4200VDC, has no breakdown, no arc, and leakage current of less than 3mA.

[0018] Step 13, Inspection: Use an optical microscope or electronic instrument to inspect the final sintered insulation layer for defects such as bubbles, cracks and pinholes, and test the insulation resistance, which should be greater than 100MΩ@1000VDC.

[0019] Step 14: Sintering of the conductor layer: Print the conductor layer on the surface of the insulating layer using a silver-palladium or silver-platinum conductive paste, and sinter the conductor layer at 450-500℃.

[0020] Step 15: Sintering of the heating resistance layer: A thick film resistive paste is printed on top of the insulating resistance layer and the conductor layer, and the heating resistance layer is sintered at 450-500℃.

[0021] Step 16: Low-temperature sintering of the surface insulation layer: Printing and sintering an insulating protective layer on top of the heating resistor layer and the conductor layer.

[0022] Preferably, the glass medium slurry is composed of 60%-80% lead-free microcrystalline glass powder, 1%-10% rare earth oxides and 19%-30% organic binder phase.

[0023] By adopting the above technical solutions, rare earth oxides reduce the sintering temperature of glass, improve dielectric properties and thermal stability, match the lower sintering temperature of aluminum substrates, and the 60%-80% glass powder content improves the density and insulation of the insulating dielectric layer after sintering; the 19%-30% organic binder phase improves the printability and leveling properties of the paste.

[0024] Preferably, the lead-free microcrystalline glass powder comprises, by weight, the following components:

[0025] SiO2: 50-60 parts

[0026] Bi2O3: 10-20 parts

[0027] B2O3: 1-3 parts

[0028] ZnO: 10-20 parts

[0029] K2O: 1-5 servings

[0030] SrO2: 5-10 parts

[0031] CaO: 5-10 parts.

[0032] By adopting the above technical solution, a material with low melting point and high insulation properties is formed. It fully melts at 450-500℃ to form a dense insulating layer. The SiO2, SrO2, and CaO are proportioned to adjust the average linear expansion coefficient of the glass powder to a range that matches that of the aluminum alloy. This effectively reduces the internal stress caused by thermal mismatch during sintering and cooling, preventing delamination and warping.

[0033] Preferably, the organic binder phase comprises, by weight, the following components:

[0034] 30-60 parts organic solvent,

[0035] 20-30 parts of polymeric thickener

[0036] 1-5 parts surfactant

[0037] 1-5 parts plasticizer

[0038] 1-5 parts dispersant

[0039] 1-5 parts defoamer

[0040] 1-5 parts thixotropic agent.

[0041] By adopting the above technical solutions, the advantages of improved printability, stability, and sintering effect are achieved.

[0042] Preferably, the rare earth oxide includes TiNi, with a content of 0.5%-1%.

[0043] By adopting the above technical solution, the reserves are large, and it also has a catalytic effect and improves the glass network structure, optimizes the dielectric constant and dielectric loss, and improves the overall electrical performance of the insulation layer. Significant effects can be produced by adding only 0.5%-1% of the product.

[0044] Preferably, the lead-free microcrystalline glass powder has a particle size of 1μm-3μm and an average coefficient of linear expansion of 1μm. .

[0045] By adopting the above technical solution, the fine particle size makes the glass powder more uniform on the surface during sintering, melts more fully, and flows more evenly, making it easier to form a dense insulating layer with a smooth surface and no internal pores, avoiding brittle cracking during cooling. At the same time, the average coefficient of linear expansion ensures that the insulating layer does not separate or crack from the aluminum substrate during thermal cycling, thus improving the thermal reliability of the product.

[0046] Preferably, the organic solvent includes one or more of terpineol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, and terpineol; the polymeric thickener includes one or more of ethyl cellulose, nitrocellulose, acrylic resin, and carboxypropyl methyl cellulose; the surfactant includes one or more of polyacrylamide, sodium polyacrylate, sorbitan trioleate, and polyethylene glycol PEG; the plasticizer includes one or more of dibutyl phthalate (DBP), dioctyl phthalate (DOP), and polyethylene glycol PEG; the dispersant includes one or more of phosphate ester dispersants and ammonium polyacrylates; the defoamer includes one or more of polydimethylsiloxane (silicone oil), polyether-modified polysiloxane, mineral oil-based defoamer, and acrylic polymers; and the thixotropic agent includes one or more of hydrogenated castor oil, fumed silica, organobentonite, and polyamide wax.

[0047] By adopting the above technical solution

[0048] Preferably, in step two, the substrate surface treatment, a shot peening process is used to treat the surface.

[0049] By adopting the above technical solution, shot peening can clean and roughen the substrate surface, removing oxide scale while forming tiny pits, increasing the contact area between the substrate and the subsequent micro-arc oxide layer and dielectric layer, further enhancing the mechanical interlocking effect, improving adhesion, and providing another surface treatment solution.

[0050] Preferably, the dry film thickness in step six is ​​20-40 μm each time.

[0051] By adopting the above technical solution, if the thickness is too thin, the production efficiency will be low and the number of sintering times will need to be increased. If the thickness is too thick, the organic matter will be difficult to handle during drying and sintering, and defects will easily occur. This thickness ensures that the single layer can be effectively thickened after sintering, while ensuring the quality of the layer.

[0052] Preferably, in steps seven to twelve, a ring-shaped chain conveyor belt is used for conveying. The chain conveyor belt is connected end to end in the horizontal direction. A segmented temperature-controlled precision sintering furnace is set on each side of the chain conveyor belt in the horizontal direction. Screen printing equipment or pad printing equipment is set at both ends of the chain conveyor belt in the length direction.

[0053] By adopting the above technical solution, the ring chain conveyor belt, combined with the segmented temperature-controlled sintering furnaces on both sides and the printing equipment at both ends, forms a closed-loop continuous production line, which improves production efficiency, reduces space occupation, and allows the substrate to return directly to the printing station for the next layer of printing without leaving the line after sintering and testing. This greatly reduces material handling, waiting and loading / unloading time, resulting in a fast production cycle, which is suitable for large-scale industrial production. The entire process is carried out in a closed and controllable system, reducing the impact of human intervention and environmental impurities on sintering quality, and ensuring consistency and high yield between product batches.

[0054] In summary, through multiple printing and sintering processes, the insulating glass dielectric is sintered layer by layer onto the aluminum alloy surface, resulting in a final insulation layer thickness greater than 200μm. This achieves insulation standards such as a withstand voltage of 4200VDC, meeting the stringent requirements for ultra-high voltage insulation safety. Simultaneously, the use of a temperature-controlled sintering furnace enables precise temperature control. A slow heating rate of 3-5℃ / min to 200-300℃ followed by holding at that temperature allows for the thorough and gradual removal of organic carriers, preventing bubbles, pinholes, or cracking caused by rapid volatilization. The peak sintering temperature of 450-500℃ is significantly lower than the melting point of the aluminum alloy, preventing substrate deformation and ensuring the glass powder melts and flows smoothly. Furthermore, a controlled cooling rate of 2-4℃ / min ensures optimal performance. This process avoids thermal stress cracking caused by excessively rapid cooling, ensuring the integrity of the insulation layer. The entire sintering process is carried out under a protective gas atmosphere in a fully enclosed preheating, sintering, and cooling zone, effectively preventing oxidation of the aluminum substrate and functional materials, and ensuring the stability of sintering quality and electrical performance. At the same time, grinding to 850-900 mesh makes the substrate surface rougher and more uniform, ensuring that the dry film of the dielectric slurry and the subsequent sintered film have physical contact anchor points, avoiding cooling delamination and brittleness. Micro-arc oxidation treatment generates a ceramic oxide layer on the surface of the aluminum substrate, enhancing the adhesion between the glass dielectric layer and the aluminum substrate, preventing internal oxidation of aluminum during high-temperature sintering, and improving the long-term stability and lifespan of the product. Attached Figure Description

[0055] Figure 1 This is a simplified top view of the production line in the embodiment;

[0056] Figure 2 These are images of the insulation layer peeling off in an embodiment;

[0057] Figure 3 This is an image of the black dots on the insulating layer in an embodiment;

[0058] Figure 4 This is a circled image of the insulating layer in an embodiment;

[0059] Figure 5 This is an orange peel image of the insulation layer after sintering, as shown in the embodiment.

[0060] Figure 6 These are images of black spots after the insulation layer of the embodiment has been sintered;

[0061] Figure 7 This is an image showing uneven coloring of the insulating layer after sintering, as described in the embodiment.

[0062] Figure 8 This is an image showing bubbles on the surface of the cover layer in this embodiment;

[0063] Figure 9 These are breakdown images from an embodiment;

[0064] Figure 10 These are images of the film bursting in an embodiment;

[0065] Figure 11 Image 1 shows an example where the insulation resistance is <100MΩ.

[0066] Figure 12 Image 2 shows an example where the insulation resistance is <100MΩ. Detailed Implementation

[0067] The present invention will be further described in detail below with reference to the accompanying drawings.

[0068] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0069] Example:

[0070] Aluminum alloy sheet of grade 6061 with a thermal conductivity of 160-200 W / m·K is selected. Lead-free glass dielectric paste is prepared according to the table below. The conductor layer paste, heating resistance layer paste and insulating protective layer paste are existing technologies and will not be described in detail here.

[0071] The glass dielectric slurry consists of 60%-80% lead-free microcrystalline glass powder, 1%-10% rare earth oxides, and 19%-30% organic binder phase. The lead-free microcrystalline glass powder, by weight, comprises SiO2: 50-60 parts, Bi2O3: 10-20 parts, B2O3: 1-3 parts, ZnO: 10-20 parts, K2O: 1-5 parts, SrO2: 5-10 parts, and CaO: 5-10 parts. The rare earth oxides include TiNi, with a content of 0.5%-1%. The particle size of the lead-free microcrystalline glass powder is 1μm-3μm; in the following examples, 3μm is used. The average linear expansion coefficient of the lead-free microcrystalline glass powder is... .

[0072] The organic solvent includes one or more of terpineol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, and terpineol; the polymeric thickener includes one or more of ethyl cellulose, nitrocellulose, acrylic resin, and carboxypropyl methyl cellulose; the surfactant includes one or more of polyacrylamide, sodium polyacrylate, sorbitan trioleate, and polyethylene glycol PEG; the plasticizer includes one or more of dibutyl phthalate (DBP), dioctyl phthalate (DOP), and polyethylene glycol PEG; the dispersant includes one or more of phosphate ester dispersants and ammonium polyacrylates; the defoamer includes one or more of polydimethylsiloxane (silicone oil), polyether-modified polysiloxane, mineral oil-based defoamer, and acrylic polymers; and the thixotropic agent includes one or more of hydrogenated castor oil, fumed silica, organobentonite, and polyamide wax.

[0073] The organic binder phases of Examples 1-10 were prepared by mixing the following components in parts by weight:

[0074] Organic solvent: 45 parts (a mixture of terpineol and diethylene glycol monobutyl ether in a 1:1 weight ratio), polymeric thickener: 25 parts (ethyl cellulose), surfactant: 3 parts (polyacrylamide), plasticizer: 3 parts (dibutyl phthalate DBP), dispersant: 3 parts (phosphate ester dispersant), defoamer: 3 parts (polydimethylsiloxane, i.e., silicone oil), thixotropic agent: 3 parts (hydrogenated castor oil).

[0075] A sintering process for aluminum alloy plates in a flat thick-film heater includes the following steps:

[0076] Step 1: Pre-processing: Cut the aluminum alloy into a substrate according to the design dimensions, and process mounting holes and process holes.

[0077] Step 2, Substrate Surface Treatment: Grind the substrate surface to 850-900 grit. The grinding process is carried out using a 600-800 grit belt sander. Alternatively, shot peening can be used to treat the surface and form a rough surface.

[0078] Step 3: Substrate surface cleaning: Use organic solvents to ultrasonically clean the substrate surface to remove surface processing debris, oil, and impurities;

[0079] Step 4: Chemical treatment of substrate surface: Micro-arc oxidation is performed on the substrate to form a ceramic oxide layer on the substrate surface;

[0080] Step 5: Drying the substrate, generally by air drying, negative ion drying, or natural air drying in a dust-free workshop;

[0081] Step 6, Adhesion of the bottom dry film: On the conveyor belt, the glass dielectric paste is printed onto the forming surface of the aluminum alloy substrate by pad printing or screen printing to form a dry film, with a dry film thickness of 20-40μm each time.

[0082] Step 7, substrate transfer: The conveyor belt transfers the substrate into the sintering furnace, where the bottom layer is sintered under the protection of protective gas. The sintering area of ​​the sintering furnace includes an interconnected and fully enclosed preheating zone, sintering zone, and cooling zone.

[0083] Step 8, Preheating Zone: Increase the temperature from room temperature at 3-5℃ / min to 200-300℃, hold for 10-15 minutes, and remove the organic carrier that entered in the previous stage;

[0084] Step 9, Sintering Zone: Increase the temperature to 450-500℃ at 2-3℃ / min and hold for 15-25 minutes to allow the components in the dry film to melt and flow, forming a dense insulating layer on the surface of the aluminum alloy substrate.

[0085] Step 10, Cooling Zone: Cool the furnace along with the substrate or reduce the furnace temperature to below 150°C at a rate of 2-4°C / min until the substrate is conveyed out of the furnace by the conveyor belt;

[0086] Step 11, Surface Quality Inspection: Inspect the sintered surface using a CCD camera, while ensuring the surface is clean;

[0087] Step 12, Multilayer Sintering: The conveyor belt carries the substrate back into the dry film attachment station, where glass dielectric paste is attached to the bottom insulating layer. Steps 6 to 11 are repeated to ensure that the final insulating layer thickness is greater than 200μm, or that it withstands a voltage of 4200VDC, has no breakdown, no arc, and leakage current of less than 3mA.

[0088] Step 13, Inspection: Use an optical microscope or electronic instrument to inspect the final sintered insulation layer for defects such as bubbles, cracks and pinholes, and test the insulation resistance, which should be greater than 100MΩ@1000VDC.

[0089] Step 14: Sintering of the conductor layer: Print the conductor layer on the surface of the insulating layer using a silver-palladium or silver-platinum conductive paste, and sinter the conductor layer at 450-500℃.

[0090] Step 15: Sintering of the heating resistance layer: A thick film resistive paste is printed on top of the insulating resistance layer and the conductor layer, and the heating resistance layer is sintered at 450-500℃.

[0091] Step 16: Low-temperature sintering of the surface insulation layer: Printing and sintering an insulating protective layer on top of the heating resistor layer and the conductor layer.

[0092] like Figure 1 As shown, the conveyor belts in steps six to twelve of the production process are circular chain conveyor belts, which are used to withstand the high-temperature sintering of the sintering box. The chain conveyor belts are connected end to end in the horizontal direction. Segmented temperature-controlled precision sintering furnaces are set on both sides of the chain conveyor belt in the horizontal direction. Screen printing equipment or pad printing equipment are set at both ends of the chain conveyor belt in the length direction.

[0093]

[0094] In Examples 1 to 10, the experiments were conducted according to the following parameters:

[0095] Step 8, Preheating Zone: The conveyor belt runs at a constant speed, causing the substrate to be heated from room temperature to 250°C at a rate of 4°C / min, and held at this temperature for 12 minutes, allowing the organic binder phase to fully and slowly volatilize and decompose.

[0096] Step Nine, Sintering Zone: Subsequently, the substrate enters the sintering zone, where it is heated to 480°C at a rate of 2.5°C / min and held at that temperature for 20 minutes. During this stage, the lead-free microcrystalline glass powder melts and flows, forming a dense insulating layer on the surface of the aluminum alloy substrate.

[0097] Step 10, Cooling Zone: After heat preservation, the substrate enters the cooling zone, where it is slowly cooled to below 150°C at a rate of 3°C / min under program control. It is then conveyed out of the sintering furnace. This process effectively releases thermal stress and prevents cracking of the insulation layer.

[0098] like Figure 2 As shown, due to the excessive smoothness of the substrate surface, the insulating layer may peel off.

[0099] like Figure 3As shown, due to impurities generated during the polishing process and the lack of a cleanroom in the workshop, black spots were generated in the insulation layer.

[0100] like Figure 4 As shown, during the substrate cleaning process, the drying residual liquid causes ring marks to form on the surface of the insulating layer.

[0101] like Figure 5 As shown, unreasonable screen printing machine parameter settings, marks on the product surface, mismatched paste viscosity, and screen surface texture result in irregular screen prints and orange peel-like surface after sintering.

[0102] like Figure 6 As shown, insufficient cleanliness of the substrate surface, incomplete surface treatment of the substrate, chemical reaction between the substrate material and the paste, and contamination during the substrate printing process can all lead to a large number of black spots in the color of the insulating layer after sintering.

[0103] like Figure 7 As shown, if an unsuitable slurry is used, the slurry reacts with the substrate surface and becomes contaminated, resulting in uneven color after the insulation layer is sintered.

[0104] like Figure 8 As shown, insufficient surface cleanliness of the printed layer, mismatched paste viscosity, excessively high sintering temperature, excessively short sintering time, and excessively rapid temperature rise during the sintering process all resulted in air bubbles on the surface of the cover layer.

[0105] like Figure 9 As shown, insufficient voltage withstand strength, insufficient sintering density, and excessive porosity of the insulation layer lead to breakdown.

[0106] like Figure 10 As shown, uneven cooling, excessively high applied voltage, and excessively long dry-burning load test time, exceeding the design temperature, led to the film bursting.

[0107] like Figure 11 and Figure 12 As shown, the dielectric density of the glass slurry after drying is insufficient, resulting in excessively low resistance.

Claims

1. A sintering process for aluminum alloy plates in a flat thick-film heater, characterized in that: Includes the following steps Step 1: Pre-processing: Cut the aluminum alloy into a substrate according to the design dimensions, and process mounting holes and process holes. Step 2, Substrate Surface Treatment: Grinding and polishing the substrate surface; Step 3: Substrate surface cleaning: Use organic solvents to ultrasonically clean the substrate surface to remove surface processing debris, oil, and impurities; Step 4: Chemical treatment of substrate surface: Micro-arc oxidation is performed on the substrate to form a ceramic oxide layer on the substrate surface; Step 5: Drying the substrate; Step 6, Adhesion of the underlying dry film: On the conveyor belt, the glass dielectric paste is printed onto the forming surface of the aluminum alloy substrate by pad printing or screen printing to form a dry film. Step 7, substrate transfer: The conveyor belt transfers the substrate into the sintering furnace, where the bottom layer is sintered under the protection of protective gas. The sintering area of ​​the sintering furnace includes an interconnected and fully enclosed preheating zone, sintering zone, and cooling zone. Step 8, Preheating Zone: Increase the temperature from room temperature at 3-5℃ / min to 200-300℃, hold for 10-15 minutes, and remove the organic carrier that entered in the previous stage; Step 9, Sintering Zone: Increase the temperature to 450-500℃ at 2-3℃ / min and hold for 15-25 minutes to allow the components in the dry film to melt and flow, forming a dense insulating layer on the surface of the aluminum alloy substrate. Step 10, Cooling Zone: Cool the furnace along with the substrate or reduce the furnace temperature to below 150°C at a rate of 2-4°C / min until the substrate is conveyed out of the furnace by the conveyor belt; Step 11, Surface Quality Inspection: Inspect the sintered surface using a CCD camera, while ensuring the surface is clean; Step 12, Multilayer Sintering: The conveyor belt carries the substrate back into the dry film attachment station, where glass dielectric paste is attached to the bottom insulating layer. Steps 6 to 11 are repeated to ensure that the final insulating layer thickness is greater than 200μm, or that it withstands a voltage of 4200VDC, has no breakdown, no arc, and leakage current of less than 3mA. Step 13, Inspection: Use an optical microscope or electronic instrument to inspect the final sintered insulation layer for defects such as bubbles, cracks and pinholes, and test the insulation resistance, which should be greater than 100MΩ@1000VDC. Step 14: Sintering of the conductor layer: Print the conductor layer on the surface of the insulating layer using a silver-palladium or silver-platinum conductive paste, and sinter the conductor layer at 450-500℃. Step 15: Sintering of the heating resistance layer: A thick film resistive paste is printed on top of the insulating resistance layer and the conductor layer, and the heating resistance layer is sintered at 450-500℃. Step 16: Low-temperature sintering of the surface insulation layer: Printing and sintering an insulating protective layer on top of the heating resistor layer and the conductor layer.

2. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 1, characterized in that: The glass medium slurry is composed of 60%-80% lead-free microcrystalline glass powder, 1%-10% rare earth oxides and 19%-30% organic binder phase.

3. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 2, characterized in that: The lead-free microcrystalline glass powder comprises, by weight, the following components. SiO2: 50-60 parts Bi2O3: 10-20 parts B2O3: 1-3 parts ZnO: 10-20 parts K2O: 1-5 servings SrO2: 5-10 parts CaO: 5-10 parts.

4. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 2, characterized in that: The organic binder phase comprises, by weight, the following components: 30-60 parts organic solvent, 20-30 parts of polymeric thickener 1-5 parts surfactant 1-5 parts plasticizer 1-5 parts dispersant 1-5 parts defoamer 1-5 parts thixotropic agent.

5. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 4, characterized in that: The rare earth oxides include TINI, with a content of 0.5%-1%.

6. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 2, characterized in that: The lead-free microcrystalline glass powder has a particle size of 1μm-3μm, and the average coefficient of linear expansion of the lead-free microcrystalline glass powder is [missing value]. .

7. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 2, characterized in that: The organic solvent includes one or more of terpineol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, and terpineol; the polymeric thickener includes one or more of ethyl cellulose, nitrocellulose, acrylic resin, and carboxypropyl methyl cellulose; the surfactant includes one or more of polyacrylamide, sodium polyacrylate, sorbitan trioleate, and polyethylene glycol PEG; the plasticizer includes one or more of dibutyl phthalate (DBP), dioctyl phthalate (DOP), and polyethylene glycol PEG; the dispersant includes one or more of phosphate ester dispersants and ammonium polyacrylates; the defoamer includes one or more of polydimethylsiloxane (silicone oil), polyether-modified polysiloxane, mineral oil-based defoamer, and acrylic polymers; and the thixotropic agent includes one or more of hydrogenated castor oil, fumed silica, organobentonite, and polyamide wax.

8. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 1, characterized in that: In step two, the substrate surface treatment, a shot peening process is used to treat the surface.

9. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 1, characterized in that: In step six, the dry film thickness is 20-40 μm each time.

10. The sintering process of aluminum alloy plates for flat thick-film heaters according to claim 1, characterized in that: In steps seven to twelve, a ring-shaped chain conveyor belt is used for conveying. The chain conveyor belt is connected end to end in the horizontal direction. A segmented temperature-controlled precision sintering furnace is set on each side of the chain conveyor belt in the horizontal direction. Screen printing equipment or pad printing equipment is set at both ends of the chain conveyor belt in the length direction.

Images