Stainless steel-based heating resistor paste and preparation method thereof

Abstract

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

Description

TECHNICAL FIELD

[0001] 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. BACKGROUND

[0002] As the core material in the fields of electronic components, household heating modules, industrial temperature measuring elements and the like, the performance of the heating resistance paste directly determines the stability, service life and energy efficiency of the terminal product. The stainless steel substrate is the preferred substrate material for the heating resistance due to its high strength, excellent corrosion resistance, good thermal conductivity and cost advantage, and the corresponding stainless steel-based heating resistance paste has also been widely researched and applied. However, the existing stainless steel-based heating resistance paste still has significant technical pain points in actual use. On the one hand, under the cold-heat cycle working condition (such as alternating environmental temperature and repeated switching of heating-cooling), the difference in the thermal expansion coefficient between the paste and the stainless steel substrate easily leads to stress concentration at the interface, causes the paste layer to crack and fall off, and further causes the resistance value to drift sharply, even causes the element to fail, and seriously affects the long-term reliability of the product. On the other hand, in order to ensure the stable conductivity, the existing paste usually adopts a single or simply compounded conductive phase system, which leads to high square resistance, increases the energy consumption, and limits the application in low-power and small-sized devices. In addition, the additives used in the existing technology to improve the performance of the paste are mostly single components, which can only optimize the wear resistance or the adhesion on one side, and cannot simultaneously relieve the cold-heat cycle damage and reduce the square resistance. At the same time, some pastes have the problems of insufficient compatibility between the conductive phase and the glass phase and poor dispersibility of the organic carrier, which further aggravates the poor resistance stability and low yield. It is difficult to meet the current strict requirements for high reliability and low energy consumption. Therefore, it is a technical problem to be solved in the field to develop a stainless steel-based heating resistance paste which can effectively resist the cold-heat cycle damage, significantly reduce the square resistance of the heating resistance, and has good compatibility of components and stable preparation process. SUMMARY

[0003] In view of the above problems, the purpose of the present application is to provide a stainless steel-based heating resistance paste which can effectively relieve the damage of the cold-heat cycle to the heating resistance and reduce the square resistance of the heating resistance to a certain extent.

[0004] On the one hand, the present application relates to a stainless steel-based heating resistance paste which is composed of a conductive phase, a glass phase, an organic carrier and an additive, and the additive is zirconium phosphate, boron carbide and layered double hydroxide. The mass ratio of zirconium phosphate, boron carbide and layered double hydroxide is 10-14:4-8:1-3. The mass percentage of the additive in the stainless steel-based heating resistance paste is 3-5%.

[0005] Further, in the stainless steel-based heating resistance paste provided by the present application, the stainless steel-based heating resistance paste is composed of 60-65% of the conductive phase, 2-4% of the glass phase, 3-5% of the additive, and the rest of the organic carrier, in terms of mass percentage.

[0006] Further, in the stainless steel-based heating resistance paste provided by the present application, the layered double hydroxide is copper-iron layered double metal hydroxide.

[0007] Further, in the stainless steel-based heating resistance paste provided by the present application, the conductive phase is composed of 33-35% of La2O3, 26-28% of SrCO3, and the rest of Co2O3, in terms of mass percentage.

[0008] Further, in the stainless steel-based heating resistance paste provided by the present application, the mass ratio of terpineol, ethyl cellulose, and lauric acid in the organic carrier is 90-95:8-10:1-3.

[0009] In another aspect, the present application relates to a preparation method of a stainless steel-based heating resistance paste, comprising the following steps: S1, La2O3, SrCO3, and Co2O3 are weighed in proportion, mixed, ball milled, and dried, and then pre-sintered at 850-950℃ for 3-5 hours to obtain a pre-sintered powder; the pre-sintered powder is ball milled again, and then sintered at 1200-1300℃ for 3-5 hours to obtain a conductive phase powder; S2, zirconium phosphate, boron carbide, and the layered double hydroxide are weighed in proportion and uniformly mixed to obtain an additive mixed powder; S3, terpineol, ethyl cellulose, and lauric acid are mixed in proportion, stirred 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 and the organic carrier obtained in step S3 are mixed in proportion, and then three-roll milled or stirred and dispersed until uniform to obtain the stainless steel-based heating resistance paste.

[0010] Further, in the preparation method of the stainless steel-based heating resistance paste provided by the present application, the preparation method of the layered double hydroxide comprises: uniformly mixing copper chloride and iron chloride in deionized water at a mass ratio of 2-4:1, adjusting the pH to 6.5-7, and aging at 80-120℃ for 24-75h to obtain the layered double hydroxide.

[0011] Further, in the preparation method of the stainless steel-based heating resistance paste provided by the present application, in step S1, the ball milling is performed in anhydrous ethanol as a medium, and the ball milling time is 8-24h. Further, in the preparation method of the stainless steel-based heating resistance paste provided by the present application, in step S1, the ball milling is performed in anhydrous ethanol as a medium, and the ball milling time is 8-24h.

[0012] Further, in the preparation method of the stainless steel-based heating resistance paste provided by the present application, in step S4, the number of three-roll rolling is 3-5 times, until the fineness of the paste reaches below 20 μm.

[0013] On the other hand, the present application relates to a stainless steel-based heating resistance prepared by using the stainless steel-based heating resistance paste.

[0014] Compared with the prior art, the technical scheme provided by the present application has at least the following beneficial effects or advantages: The composite additive system (specific mass ratio 10-14:4-8:1-3) of zirconium phosphate, boron carbide and copper-iron layered double metal hydroxide is used to synergistically relieve the interface stress concentration, and the resistance change rate is as low as 1.8%-3.5% after 10 cold and hot cycles, which is much better than the comparative example (4.5%) without zirconium phosphate. The paste sheet resistance is controlled to be 55.75-65.48 Ω / sq, which is greatly reduced compared with the traditional paste and the comparative example (94.64 Ω / sq), and meets the low-power device requirement. The good product rate after cold and hot cycles is 90%-100%, which is significantly higher than that of the comparative example (70%), and the preparation process parameters are clear and repeatable, which is suitable for industrial production and can meet the strict reliability requirements in the fields of electronic components and household heating modules. DETAILED DESCRIPTION

[0015] In the following, the technical scheme of the present application will be described in conjunction with examples, but the present application is not limited to the following examples. The experimental methods and detection methods described in the examples are conventional methods unless otherwise specified. The reagents and materials described are commercially available unless otherwise specified. In the following examples, % is mass percent unless otherwise specified. In the following examples, the ratio is mass ratio unless otherwise specified.

[0016] Example 1 The present example provides a preparation process of a stainless steel-based heating resistance paste.

[0017] 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, and then cooled and sieved through a 200 mesh sieve to ensure uniform particle size and avoid impurities affecting the conductive performance.

[0018] The additive raw materials: zirconium phosphate, boron carbide, copper chloride (CuCl2·2H2O) and iron chloride (FeCl3·6H2O), among which zirconium phosphate and boron carbide need to be dried at 80-100℃ for 2-3h and sieved through a 300 mesh sieve; copper chloride and iron chloride need to use analytical reagents to avoid the introduction of impurities affecting the synthesis of layered double hydroxide.

[0019] Glass phase raw material: low melting point glass powder suitable for stainless steel substrate is selected, dried at 100°C for 3h, and then sieved through a 200 mesh sieve for use. The specific composition is calcium oxide 30%, silicon oxide 15%, zirconium oxide 8%, tantalum oxide 8%, and the balance of boron oxide, by mass percent. The melting temperature is 1200°C, and the coefficient of thermal expansion is similar to that of the stainless steel substrate.

[0020] Organic carrier raw material: terpineol (industrial grade, purity ≥98%), ethyl cellulose (polymerization degree 45-55), lauric acid (analytical pure), terpineol needs to be dehydrated in advance (add an appropriate amount of anhydrous calcium chloride, stand for 24h, then filter), remove water to avoid affecting the dissolution effect.

[0021] Auxiliary materials: anhydrous ethanol (ball milling medium, analytical pure), deionized water (for preparing layered double hydroxide), NaOH solution (for adjusting pH, concentration 0.5M).

[0022] Equipment: planetary ball mill (equipped with zirconia ball mill tank and zirconia balls to avoid metal contamination), high-speed disperser (speed 0-3000r / min adjustable), box-type atmosphere furnace, constant temperature magnetic stirrer, three-necked flask, reflux condensing device, three-roll mill (roller surface precision Ra≤0.1μm, speed ratio adjustable), doctor blade fineness gauge (range 0-50μm), electronic balance (precision 0.0001g), pH meter (precision ±0.01), air blowing drying oven, vacuum drying oven, standard test sieve.

[0023] Step 1: accurately weigh the dried copper chloride and iron chloride in a mass ratio of 2-4:1, add deionized water at a ratio of 0.03g / mL, and place it in a constant temperature magnetic stirrer. Stir at 50-60°C for 30-40min until completely dissolved, forming a uniform mixture of metal ions.

[0024] Step 2: keep stirring, slowly add NaOH solution, adjust the pH of the mixture to 6.5-7.0, the drop speed is controlled at 1-2 drops / s, to avoid local high pH leading to uneven precipitation of metal hydroxide.

[0025] Step 3: transfer the mixed solution with adjusted pH to a high-pressure reaction kettle, and keep it at 80-120°C for 24-75h; the higher the aging temperature, the shorter the required aging time (e.g. 24h at 120°C, 75h at 80°C). After aging, take out the reaction product, wash repeatedly with deionized water until the washing liquid is neutral, then place it in a vacuum drying oven at 75°C for 12h. After drying, the product is ground with an agate mortar, then sieved through a 300 mesh sieve to obtain copper-iron layered double metal hydroxide powder, which is sealed and stored for future use.

[0026] Step 4: The conductive phase was composed of La2O3 33~35%, SrCO3 26~28% and Co2O3 balance, which was accurately weighed and placed in a planetary ball mill jar. Anhydrous ethanol was added as a ball milling medium, the ball-to-material ratio was controlled at 5:1, and the ball mill speed was adjusted to 300 r / min. The ball milling process was checked every 4 h to ensure uniform mixing. After ball milling for 12 h, the slurry was placed in a forced air drying oven and dried at 80℃ for 8 h to remove the anhydrous ethanol.

[0027] Step 5: The dried mixed powder was transferred to an alumina crucible and placed in a box-type atmosphere furnace. The temperature was raised to 900℃ at a rate of 5℃ / min under air atmosphere, and the pre-sintering was carried out for 4 h. After pre-sintering, the furnace was cooled to room temperature.

[0028] Step 6: The pre-sintered powder was again placed in a planetary ball mill jar and anhydrous ethanol was added. The powder was ball milled for 12 h according to the above ball milling parameters to ensure uniform particle size. After the second ball milling, the powder was dried and placed in an alumina crucible. The temperature was raised to 1250℃ at a rate of 5℃ / min under air atmosphere, and the sintering was carried out for 4 h. After sintering, the furnace was cooled to room temperature to obtain the conductive phase powder, which was sieved through a 200 mesh sieve and sealed for storage.

[0029] Step 7: Zirconium phosphate, boron carbide and copper-iron layered double hydroxide powders were accurately weighed according to the mass ratio of 10~14:4~8:1~3. The three powders were placed in a planetary ball mill jar and a small amount of anhydrous ethanol was added as a dispersing medium. The ball-to-material ratio was 3:1, the speed was 200 r / min, and the ball milling time was 3 h to ensure uniform mixing. After ball milling, the powder was dried and sieved through a 300 mesh sieve to obtain the additive mixed powder, which was sealed for later use.

[0030] Step 8: Dehydrated terpineol, ethyl cellulose and lauric acid were accurately weighed according to the mass ratio of 90~95:8~10:1~3 and placed in a three-necked flask equipped with a reflux condenser. The three-necked flask was placed on a constant temperature magnetic stirrer, the temperature was set to 85℃, the stirring and reflux devices were turned on, the stirring rate was controlled at 400 r / min, and the stirring was continued for 2 h until the ethyl cellulose and lauric acid were completely dissolved. The solution was transparent and uniform without obvious particles. The heating and stirring were turned off, and the organic carrier was naturally cooled to room temperature. It was filtered through a 200 mesh sieve to remove undissolved impurities, and a pure organic carrier was obtained, which was sealed and stored in the dark.

[0031] Step 9: Take each component by mass percentage: conductive phase 60-65%, glass phase 2-4%, additive mixed powder 3-5%, and organic carrier in the rest; after accurate weighing, first put the conductive phase, glass phase and additive mixed powder into a high-speed dispersion machine, dry mix for 15 min to obtain a uniform solid mixture. Slowly add the dry mixed solid mixture into the organic carrier, stirring with a high-speed dispersion machine at a stirring rate of 2000 r / min, stirring for 30 min to obtain a preliminarily dispersed slurry. Transfer the preliminarily dispersed slurry to a three-roll grinding machine, adjust the roller speed ratio to 1:3:9, and roll for 3 times; after each rolling, detect the fineness of the slurry with a doctor blade fineness gauge until the fineness of the slurry reaches below 20 μm. After passing the rolling, place the slurry in a vacuum drying box, vacuum degas at 65°C for 30 min to remove the bubbles in the slurry; after degassing, filter again through a 200-mesh sieve to obtain the final stainless steel-based heating resistance slurry.

[0032] Example 2 This example provides a specific stainless steel-based heating resistance slurry.

[0033] The preparation method refers to Example 1, the mass ratio of copper chloride and iron chloride in Step 1 is 2:1; in Step 4, the conductive phase is composed of La2O3 33%, SrCO3 26% and Co2O3 in the rest by mass percentage; in Step 7, accurately take zirconium phosphate, boron carbide and copper-iron layered double hydroxide powder by mass ratio 10:4:1; in Step 8, accurately take dehydrated terpineol, ethyl cellulose and lauric acid by mass ratio 90:8:1; in Step 9, take each component by mass percentage: conductive phase 60%, glass phase 2%, additive mixed powder 3%, and organic carrier in the rest.

[0034] Example 3 This example provides a specific stainless steel-based heating resistance slurry.

[0035] The preparation method refers to Example 1, the mass ratio of copper chloride and iron chloride in Step 1 is 3:1; in Step 4, the conductive phase is composed of La2O3 34%, SrCO3 27% and Co2O3 in the rest by mass percentage; in Step 7, accurately take zirconium phosphate, boron carbide and copper-iron layered double hydroxide powder by mass ratio 12:5:2; in Step 8, accurately take dehydrated terpineol, ethyl cellulose and lauric acid by mass ratio 92:9:2; in Step 9, take each component by mass percentage: conductive phase 62%, glass phase 3%, additive mixed powder 4%, and organic carrier in the rest.

[0036] Example 4 This example provides a specific stainless steel-based heating resistance slurry.

[0037] The preparation method refers to Example 1, the mass ratio of copper chloride and iron chloride in step 1 is 3:1; in step 4, the conductive phase is composed of La2O334%, SrCO327% and Co2O3 in mass percentage; in step 7, zirconium phosphate, boron carbide and copper-iron layered double hydroxide powder are accurately weighed according to the mass ratio of 13:6:2; in step 8, dehydrated terpineol, ethyl cellulose and lauric acid are accurately weighed according to the mass ratio of 94:9:2; in step 9, each component is weighed according to mass percentage: conductive phase 63%, glass phase 3%, additive mixed powder 4% and the rest is organic carrier.

[0038] Example 5 The present example provides a specific stainless steel-based heating resistance paste.

[0039] The preparation method refers to Example 1, the mass ratio of copper chloride and iron chloride in step 1 is 4:1; in step 4, the conductive phase is composed of La2O335%, SrCO328% and Co2O3 in mass percentage; in step 7, zirconium phosphate, boron carbide and copper-iron layered double hydroxide powder are accurately weighed according to the mass ratio of 14:8:3; in step 8, dehydrated terpineol, ethyl cellulose and lauric acid are accurately weighed according to the mass ratio of 95:10:3; in step 9, each component is weighed according to mass percentage: conductive phase 65%, glass phase 4%, additive mixed powder 5% and the rest is organic carrier.

[0040] Comparative Example 1 The present comparative example is the same as Example 5, except that zirconium phosphate is not added.

[0041] The stainless steel-based heating resistance paste provided by Examples 2-5 and Comparative Example 1 is sintered on a stainless steel substrate at 850°C, and the film thickness is controlled to be 12-15 μm. The sheet resistance (at room temperature) is measured. The stainless steel-based heating resistance is placed in an environment of 80% humidity + 80°C for 24 hours, and then placed in an environment of 80% humidity + 4°C for 24 hours, and the cycle is repeated for 10 times. After 10 cycles, the resistance change rate of the product is measured. If the resistance change rate is higher than 15% or cracks appear, the product is considered to be a defective product, and the yield rate (20 samples) is calculated. The experimental results are shown in Table 1.

[0042] Table 1: Performance of stainless steel-based heating resistance paste

[0043] As can be seen from Table 1, the stainless steel-based heating resistance paste provided by the present application has excellent sheet resistance and resistance change rate after re-sintering, and in particular, the yield rate is well maintained after cold and hot cycles.

[0044] The above-described embodiments are merely some of the embodiments of the present application, but not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but merely represents the preferred embodiments of the application. All other embodiments obtained by those of ordinary skill in the art based on the concept of the present application, without making creative labor, are within the scope of the present application.

Claims

1. A stainless steel-based heating resistance paste, comprising a conductive phase, a glassy 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; The additive is present in the stainless steel-based heating resistance paste at a mass percentage of 3-5%.

2. The stainless steel-based heating resistance paste according to claim 1, characterized in that, By weight percentage, the stainless steel-based heating resistor paste consists of 60-65% conductive phase, 2-4% glass phase, 3-5% of the additives and the balance organic carrier.

3. The stainless steel-based heating resistance paste according to claim 1, characterized in that, The layered double hydroxide is a copper-iron layered bimetallic hydroxide.

4. The stainless steel-based heating resistance paste according to claim 1, characterized in that, The conductive phase, by mass percentage, consists of 33-35% La2O3, 26-28% SrCO3, and the balance Co2O3.

5. The stainless steel-based heating resistance paste according to claim 1, characterized in that, The organic carrier contains terpineol, ethyl cellulose, and lauric acid in a mass ratio of 90-95:8-10:1-3.

6. A method for preparing a stainless steel-based heating resistance paste, characterized in that, The preparation of the stainless steel-based heating resistance paste according to any one of claims 1 to 5 comprises 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.

7. The method for preparing the stainless steel-based heating resistance paste according to claim 6, 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.

8. The method for preparing the stainless steel-based heating resistance paste according to claim 6, characterized in that, In step S1, the ball milling is performed using anhydrous ethanol as the medium, and the milling time is 8~24h.

9. The method for preparing the stainless steel-based heating resistance paste according to claim 6, characterized in that, In step S4, the three-roll rolling is performed 3 to 5 times until the fineness of the slurry reaches below 20 μm.

10. A stainless steel-based heating resistor, characterized in that, It is prepared using the stainless steel-based heating resistance paste according to any one of claims 1 to 5.

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