Stainless steel-based heating resistor paste and method for preparing the same

Abstract

The application belongs to the technical field of heating resistance paste, and relates to a stainless steel-based heating resistance paste and a preparation method thereof. The application provides a stainless steel-based heating resistance paste which is composed of an electrically conductive phase, a glass phase, an organic carrier and an additive. The additive is zirconium phosphate, boron carbide and layered double hydroxide. The additive provided by the application can effectively alleviate the damage of cold and hot cycles to the heating resistance, and can reduce the square resistance of the heating resistance to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of heating resistance paste technology, and relates to a stainless steel-based heating resistance paste and its preparation method. Background Technology

[0002] As a core material in electronic components, home appliance heating modules, and industrial temperature measuring elements, the performance of resistance heating paste directly determines the stability, lifespan, and energy efficiency of end products. Stainless steel substrates, due to their high strength, excellent corrosion resistance, good thermal conductivity, and cost advantages, have become the preferred substrate material for resistance heating devices, leading to the widespread research and application of stainless steel-based resistance heating pastes. However, existing stainless steel-based resistance heating pastes still present significant technical challenges in practical applications: Firstly, under cyclical heating and cooling conditions (such as alternating ambient temperatures and repeated heating-cooling switching), the difference in thermal expansion coefficients between the paste and the stainless steel substrate can easily lead to interface stress concentration, causing the paste layer to crack and peel off, resulting in a sharp drift in resistance value and even component failure, severely impacting the long-term reliability of the product. Secondly, to ensure conductivity stability, existing pastes typically employ a single or simple composite conductive phase system, resulting in high sheet resistance, which not only increases energy consumption but also limits their application in low-power, miniaturized devices. Furthermore, existing additives used to improve slurry performance are mostly single-component, only able to optimize wear resistance or bonding strength on one side, unable to simultaneously alleviate thermal cycling damage and reduce sheet resistance. Meanwhile, some slurries suffer from insufficient compatibility between the conductive and glassy phases, and poor dispersion of the organic carrier, further exacerbating poor resistance stability and low yield. This makes it difficult to meet current stringent requirements for high reliability and low energy consumption. Therefore, developing a stainless steel-based heating resistor slurry that can effectively resist thermal cycling damage, significantly reduce sheet resistance, has good component compatibility, and a stable preparation process has become a pressing technical challenge in this field. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a stainless steel-based heating resistor paste that effectively alleviates the damage to the heating resistor caused by thermal cycling and reduces the sheet resistance of the heating resistor to a certain extent.

[0004] On one hand, the present invention relates to a stainless steel-based heating resistance paste, which is composed of a conductive phase, a glass phase, an organic carrier and additives, wherein the additives are zirconium phosphate, boron carbide and layered double hydroxides;

[0005] The mass ratio of zirconium phosphate, boron carbide and layered double hydroxide is 10~14:4~8:1~3;

[0006] The additive is present in the stainless steel-based heating resistance paste at a mass percentage of 3-5%.

[0007] Furthermore, in the stainless steel-based heating resistor paste provided by the present invention, the stainless steel-based heating resistor paste is composed of 60-65% conductive phase, 2-4% glass phase, 3-5% of the additives and the balance organic carrier, by mass percentage.

[0008] Furthermore, in the stainless steel-based heating resistor slurry provided by the present invention, the layered double hydroxide is a copper-iron layered bimetallic hydroxide.

[0009] Furthermore, in the stainless steel-based heating resistor paste provided by the present invention, the conductive phase, by mass percentage, consists of 33-35% La2O3, 26-28% SrCO3, and the balance Co2O3.

[0010] Furthermore, in the stainless steel-based heating resistor paste provided by the present invention, the mass ratio of terpineol, ethyl cellulose and lauric acid in the organic carrier is 90~95:8~10:1~3.

[0011] On the other hand, the present invention relates to a method for preparing a stainless steel-based heating resistance paste, which includes the following steps:

[0012] S1. Weigh La2O3, SrCO3 and Co2O3 according to the proportion, mix, ball mill and dry, and pre-calcine at 850~950℃ for 3~5 hours to obtain pre-calcine powder; ball mill the pre-calcine powder again and sinter at 1200~1300℃ for 3~5 hours to obtain conductive phase powder.

[0013] S2. Weigh zirconium phosphate, boron carbide and the layered double hydroxide according to the proportion, mix them evenly, and obtain the additive mixed powder.

[0014] S3. Mix terpineol, ethyl cellulose and lauric acid in a certain proportion and stir at 80~90℃ until completely dissolved and transparent to obtain the organic carrier;

[0015] S4. The conductive phase powder obtained in step S1, the additive mixed powder obtained in step S2, and the glass phase powder are mixed in proportion to obtain a solid mixture; the solid mixture is mixed in proportion with the organic carrier obtained in step S3, and dispersed by three-roll rolling or stirring until uniform to obtain the stainless steel-based heating resistor slurry.

[0016] Furthermore, in the preparation method of the stainless steel-based heating resistor slurry provided by the present invention, the preparation method of the layered double hydroxide includes: mixing copper chloride and ferric chloride in deionized water at a mass ratio of 2 to 4:1, adjusting the pH to 6.5 to 7, and aging at 80 to 120°C for 24 to 75 hours to obtain the layered double hydroxide.

[0017] Furthermore, in the preparation method of stainless steel-based heating resistor slurry provided by the present invention, in step S1, the ball milling is carried out using anhydrous ethanol as the medium, and the ball milling time is 8~24h.

[0018] Furthermore, in the method for preparing stainless steel-based heating resistor slurry provided by the present invention, in step S4, the three-roll rolling is performed 3 to 5 times until the slurry fineness reaches below 20 μm.

[0019] On the other hand, the present invention relates to a stainless steel-based heating resistor, which is made using the aforementioned stainless steel-based heating resistor paste.

[0020] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0021] A composite additive system of zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide (specific mass ratio 10~14:4~8:1~3) synergistically alleviates interfacial stress concentration. After 10 thermal cycles, the resistivity change rate is as low as 1.8%~3.5%, far superior to the comparative example without zirconium phosphate (4.5%), effectively preventing slurry layer cracking and peeling. Through the adaptive design of the composite additive and conductive phase, the sheet resistance of the slurry is controlled at 55.75~65.48 Ω / sq, significantly lower than traditional slurries and the comparative example (94.64 Ω / sq), meeting the requirements of low-power devices. The yield rate after thermal cycling reaches 90%~100%, significantly higher than the comparative example (70%), and the preparation process parameters are clear and highly repeatable, suitable for industrial production, and can meet the stringent reliability requirements of electronic components, home appliance heating modules, and other fields. Detailed Implementation

[0022] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to mass percentages. Unless otherwise specified, all proportions in the following embodiments refer to mass ratios.

[0023] Example 1

[0024] This embodiment provides the preparation process of stainless steel-based heating resistor paste.

[0025] The conductive phase raw materials, La2O3, SrCO3 and Co2O3, all need to be dried at 105~110℃ for 4~6h to remove surface adsorbed water. After cooling, they are passed through a 200-mesh sieve to ensure uniform particle size and avoid impurities affecting conductivity.

[0026] Additive raw materials: zirconium phosphate, boron carbide, copper chloride (CuCl2·2H2O), and ferric chloride (FeCl3·6H2O). Zirconium phosphate and boron carbide need to be dried at 80~100℃ for 2~3 hours and passed through a 300-mesh sieve. Analytical grade reagents should be used for copper chloride and ferric chloride to avoid the introduction of impurities that may affect the synthesis of layered double hydroxides.

[0027] Glass phase raw materials: Low melting point glass powder suitable for stainless steel matrix is ​​selected, dried at 100℃ for 3 hours and then passed through a 200-mesh sieve for later use. The specific composition by mass percentage is 30% calcium oxide, 15% silicon oxide, 8% zirconium oxide, 8% tantalum oxide and boron oxide balance. The melting temperature is 1200℃ and the coefficient of thermal expansion is similar to that of stainless steel matrix.

[0028] Organic carrier raw materials: terpineol (industrial grade, purity ≥98%), ethyl cellulose (degree of polymerization 45~55), lauric acid (analytical grade). Terpineol needs to be dehydrated in advance (add an appropriate amount of anhydrous calcium chloride, stand for 24 hours, and then filter) to remove moisture and avoid affecting the dissolution effect.

[0029] Auxiliary materials: anhydrous ethanol (ball milling media, analytical grade), deionized water (for preparing layered double hydroxides), NaOH solution (for adjusting pH, concentration 0.5M).

[0030] Equipment: Planetary ball mill (equipped with zirconia grinding jar and zirconia balls to avoid metal contamination), high-speed disperser (adjustable speed from 0 to 3000 r / min), box-type atmosphere furnace, constant temperature magnetic stirrer, three-necked flask, reflux condenser, three-roll mill (roller surface accuracy Ra≤0.1μm, speed ratio adjustable), scraper fineness gauge (range 0~50μm), electronic balance (accuracy 0.0001g), pH meter (accuracy ±0.01), forced-air drying oven, vacuum drying oven, standard test sieve.

[0031] Step 1: Accurately weigh the dried copper chloride and ferric chloride at a mass ratio of 2~4:1, add them to deionized water at a ratio of 0.03g / mL, place them on a constant temperature magnetic stirrer, and stir at 50~60℃ for 30~40min until completely dissolved to form a homogeneous metal ion mixed solution.

[0032] Step 2: While maintaining stirring, slowly add NaOH solution dropwise to adjust the pH of the mixed solution to 6.5~7.0. Control the dropping rate to 1~2 drops / second to avoid uneven precipitation of metal hydroxides due to excessively high local pH.

[0033] Step 3: Transfer the pH-adjusted mixed solution to a high-pressure reactor and age it at a constant temperature of 80-120℃ for 24-75 hours; the higher the aging temperature, the shorter the required aging time (e.g., 24 hours at 120℃, 75 hours at 80℃). After aging, remove the reaction product, wash it repeatedly with deionized water until the washing solution is neutral, and then place it in a vacuum drying oven and dry it at 75℃ for 12 hours. After drying, grind the product in an agate mortar and pestle, and then pass it through a 300-mesh sieve to obtain copper-iron layered bimetallic hydroxide powder, which is then sealed and stored for later use.

[0034] Step 4: Weigh accurately the conductive phase, which consists of 33-35% La₂O₃, 26-28% SrCO₃, and the remainder Co₂O₃, by mass percentage, and place it in a planetary ball mill jar. Add anhydrous ethanol as the milling medium, controlling the ball-to-material ratio at 5:1. Adjust the ball mill speed to 300 r / min and mill for 12 hours. During the milling process, stop the mill every 4 hours to check and ensure uniform mixing. After milling, place the slurry in a forced-air drying oven and dry it at 80℃ for 8 hours to remove the anhydrous ethanol.

[0035] Step 5: Transfer the dried mixed powder to an alumina crucible, place it in a box-type atmosphere furnace, and heat it to 900°C at a rate of 5°C / min in an air atmosphere. Hold it at this temperature for 4 hours for pre-firing. After pre-firing, cool it to room temperature with the furnace.

[0036] Step 6: Place the pre-calcined powder back into a planetary ball mill jar, add anhydrous ethanol, and ball mill for a second time for 12 hours according to the above ball milling parameters to ensure uniform particle size. After the second ball milling, dry the powder and place it back into an alumina crucible. Place the crucible in a box-type atmosphere furnace and heat it to 1250°C at a heating rate of 5°C / min under air atmosphere. Hold the temperature for 4 hours. After sintering, cool the powder to room temperature with the furnace to obtain conductive phase powder. After passing it through a 200-mesh sieve, seal and store it.

[0037] Step 7: Accurately weigh zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide powders at a mass ratio of 10~14:4~8:1~3. Place the three powders in a planetary ball mill jar, add a small amount of anhydrous ethanol as a dispersion medium, maintain a ball-to-powder ratio of 3:1, and mill at 200 r / min for 3 hours to ensure uniform mixing. After milling, dry the powder and pass it through a 300-mesh sieve to obtain the additive mixture powder, which will then be sealed for later use.

[0038] Step 8: Accurately weigh the dehydrated terpineol, ethyl cellulose, and lauric acid at a mass ratio of 90~95:8~10:1~3 and place them in a three-necked flask equipped with a reflux condenser. Place the three-necked flask on a thermostatic magnetic stirrer, set the temperature to 85℃, turn on the stirring and reflux device, control the stirring speed at 400 r / min, and continue stirring for 2 hours until the ethyl cellulose and lauric acid are completely dissolved, the solution is transparent and homogeneous, and there are no obvious particles. Turn off the heating and stirring, allow the organic carrier to cool naturally to room temperature, filter through a 200-mesh sieve to remove undissolved impurities, and obtain a pure organic carrier. Seal and store in a dark place.

[0039] Step 9: Weigh the components according to the following mass percentages: 60-65% conductive phase, 2-4% glass phase, 3-5% additive powder mixture, and the balance organic carrier. After accurate weighing, place the conductive phase, glass phase, and additive powder mixture in a high-speed disperser and dry mix for 15 minutes to obtain a homogeneous solid mixture. Slowly add the dry-mixed solid mixture to the organic carrier while stirring with the high-speed disperser at a speed of 2000 r / min for 30 minutes to obtain a pre-dispersed slurry. Transfer the pre-dispersed slurry to a three-roll mill, adjust the roller speed ratio to 1:3:9, and roll it three times. After each rolling, use a scraper fineness gauge to check the fineness of the slurry until the fineness reaches below 20 μm. After passing the rolling test, place the slurry in a vacuum drying oven and degas it at 65℃ for 30 minutes to remove air bubbles. After degassing, filter it again through a 200-mesh sieve to obtain the final stainless steel-based heating resistor slurry.

[0040] Example 2

[0041] This embodiment provides a specific stainless steel-based heating resistor paste.

[0042] The preparation method is as described in Example 1. In step 1, the mass ratio of copper chloride to ferric chloride is 2:1. In step 4, the conductive phase is composed of 33% La2O3, 26% SrCO3, and the remainder Co2O3 by mass percentage. In step 7, zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide powder are accurately weighed at a mass ratio of 10:4:1. In step 8, dehydrated terpineol, ethyl cellulose, and lauric acid are accurately weighed at a mass ratio of 90:8:1. In step 9, the following components are weighed by mass percentage: 60% conductive phase, 2% glass phase, 3% additive mixed powder, and the remainder organic carrier.

[0043] Example 3

[0044] This embodiment provides a specific stainless steel-based heating resistor paste.

[0045] The preparation method is as described in Example 1. In step 1, the mass ratio of copper chloride to ferric chloride is 3:1. In step 4, the conductive phase is composed of 34% La2O3, 27% SrCO3, and the remainder Co2O3 by mass percentage. In step 7, zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide powder are accurately weighed in a mass ratio of 12:5:2. In step 8, dehydrated terpineol, ethyl cellulose, and lauric acid are accurately weighed in a mass ratio of 92:9:2. In step 9, the following components are weighed by mass percentage: 62% conductive phase, 3% glass phase, 4% additive mixed powder, and the remainder organic carrier.

[0046] Example 4

[0047] This embodiment provides a specific stainless steel-based heating resistor paste.

[0048] The preparation method is as described in Example 1. In step 1, the mass ratio of copper chloride to ferric chloride is 3:1. In step 4, the conductive phase is composed of 34% La2O3, 27% SrCO3, and the remainder Co2O3 by mass percentage. In step 7, zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide powder are accurately weighed in a mass ratio of 13:6:2. In step 8, dehydrated terpineol, ethyl cellulose, and lauric acid are accurately weighed in a mass ratio of 94:9:2. In step 9, the following components are weighed by mass percentage: 63% conductive phase, 3% glass phase, 4% additive mixed powder, and the remainder organic carrier.

[0049] Example 5

[0050] This embodiment provides a specific stainless steel-based heating resistor paste.

[0051] The preparation method is as described in Example 1. In step 1, the mass ratio of copper chloride to ferric chloride is 4:1. In step 4, the conductive phase is composed of 35% La2O3, 28% SrCO3, and the remainder Co2O3 by mass percentage. In step 7, zirconium phosphate, boron carbide, and copper-iron layered bimetallic hydroxide powder are accurately weighed in a mass ratio of 14:8:3. In step 8, dehydrated terpineol, ethyl cellulose, and lauric acid are accurately weighed in a mass ratio of 95:10:3. In step 9, the following components are weighed by mass percentage: 65% conductive phase, 4% glass phase, 5% additive mixed powder, and the remainder organic carrier.

[0052] Comparative Example 1

[0053] This comparative example is the same as Example 5, except that zirconium phosphate was not added.

[0054] The stainless steel-based heating resistor pastes provided in Examples 2-5 and Comparative Example 1 were sintered on a stainless steel substrate at 850°C, with the film thickness controlled to be 12-15 μm. The sheet resistance (at room temperature) was measured. The prepared stainless steel-based heating resistors were first placed in an environment of 80% humidity + 80°C for 24 hours, then in an environment of 80% humidity + 4°C for 24 hours. After 10 cycles, the resistance change rate of the products was measured. Products with a resistance change rate higher than 15% or showing cracks after 10 cycles were considered defective, and the yield rate (20 samples) was calculated. The experimental results are shown in Table 1.

[0055] Table 1: Properties of Stainless Steel-Based Resistance Heating Paste

[0056]

[0057] As shown in Table 1, the stainless steel-based heating resistor paste provided by the present invention has excellent sheet resistance and resistance reheating change rate, and the yield rate is well maintained after cold and hot cycling.

[0058] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A stainless steel-based heating resistor paste for mitigating damage to heating resistors caused by thermal cycling, wherein the raw materials of the stainless steel-based heating resistor paste are composed of a conductive phase, a glass phase, an organic carrier, and additives, characterized in that, The additives are zirconium phosphate, boron carbide, and layered double hydroxides; The mass ratio of zirconium phosphate, boron carbide and layered double hydroxide is 10~14:4~8:1~3; By mass percentage, the stainless steel-based heating resistance paste consists of 60-65% conductive phase, 2-4% glass phase, 3-5% additives, and the balance organic carrier; The layered double hydroxide is a copper-iron layered bimetallic hydroxide; The conductive phase, by mass percentage, consists of 33-35% La2O3, 26-28% SrCO3, and the balance Co2O3.

2. The stainless steel-based heating resistor paste for mitigating damage to the heating resistor caused by thermal cycling according to claim 1, characterized in that, The organic carrier is composed of terpineol, ethyl cellulose and lauric acid in a mass ratio of 90~95:8~10:1~3.

3. The method for preparing the stainless steel-based heating resistor paste for mitigating damage to the heating resistor caused by thermal cycling as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Weigh La2O3, SrCO3 and Co2O3 according to the proportion, mix, ball mill and dry, and pre-calcine at 850~950℃ for 3~5 hours to obtain pre-calcine powder; ball mill the pre-calcine powder again and sinter at 1200~1300℃ for 3~5 hours to obtain conductive phase powder. S2. Weigh zirconium phosphate, boron carbide and the layered double hydroxide according to the proportion, mix them evenly, and obtain the additive mixed powder. S3. Mix terpineol, ethyl cellulose and lauric acid in a certain proportion and stir at 80~90℃ until completely dissolved and transparent to obtain the organic carrier; S4. The conductive phase powder obtained in step S1, the additive mixed powder obtained in step S2, and the glass phase powder are mixed in proportion to obtain a solid mixture; the solid mixture is mixed in proportion with the organic carrier obtained in step S3, and dispersed by three-roll rolling or stirring until uniform to obtain the stainless steel-based heating resistor slurry.

4. The method for preparing stainless steel-based heating resistor paste for mitigating damage to heating resistors caused by thermal cycling according to claim 3, characterized in that, The preparation method of the layered double hydroxide includes: mixing copper chloride and ferric chloride in deionized water at a mass ratio of 2 to 4:1, adjusting the pH to 6.5 to 7, and aging at 80 to 120°C for 24 to 75 hours to obtain the layered double hydroxide.

5. The method for preparing stainless steel-based heating resistor paste for mitigating damage to heating resistors caused by thermal cycling according to claim 3, characterized in that, In step S1, the ball milling is performed using anhydrous ethanol as the medium, and the milling time is 8~24h.

6. In the method for preparing stainless steel-based heating resistor slurry to mitigate the damage of heating resistor to heating resistor by hot and cold cycles according to claim 3, in step S4, the three-roll rolling is performed 3 to 5 times until the fineness of the slurry reaches below 20 μm.

7. A stainless steel-based heating resistor, characterized in that, It is prepared using the stainless steel-based heating resistor paste described in any one of claims 1 to 2, which mitigates the damage to the heating resistor caused by thermal cycling.

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