Preparation process of thermistor sintered electrode with high thermal stability

Abstract

The invention relates to a preparation process of a thermistor sintered electrode with high thermal stability, and belongs to the technical field of electronic components. According to the invention, manganese oxide, nickel oxide, aluminum oxide, cobalt oxide, a sintering aid, a binder, a heat-resistant agent and a self-made conductive enhancer are used as raw materials to prepare a thermistor sintered electrode with high thermal stability; the preparation method comprises the following steps: firstly, adding manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and a sintering aid into a ball mill for ball milling and mixing, then carrying out preheating and high-temperature sintering to obtain a thermistor block, then dissolving the thermistor block, a binder, a heat-resistant agent and a conductive enhancer with an organic solvent, carrying out high-speed stirring and mixing, then carrying out tape casting into a sheet, and drying to obtain the thermistor. Finally, the thermistor is attached to a working electrode and bonded through epoxy resin, and the thermistor sintered electrode with the high thermal stability is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic components, and in particular relates to a process for preparing a thermistor sintered electrode with high thermal stability. Background Art

[0002] Thermistor is a sensitive element based on temperature change. It can change its own resistance as the temperature changes, thereby changing the electrical signal to achieve temperature measurement and control. According to its temperature coefficient, thermistors can be divided into two categories: positive temperature coefficient (PTC) and negative temperature coefficient (NTC). The resistance value of PTC thermistor gradually increases when the temperature rises; while the opposite is true for NTC thermistor. As the temperature rises, the resistance value gradually decreases, thanks to the unique performance of thermistor. In the field of temperature measurement, thermistors can accurately sense temperature changes and provide accurate temperature data for various devices. Therefore, thermistors are widely used in automobile manufacturing and smart home fields.

[0003] The main disadvantage of thermistors at this stage is heat resistance. Under high temperature conditions, the resistance value of the thermistor will change rapidly, which will cause irreversible changes in the resistance value of the thermistor or even damage it. In addition, since the binder used in the preparation process of thermistors is not conductive, the volume of the thermistor material changes during the cycle, causing changes in resistance and affecting the accuracy of the thermistor. Summary of the invention

[0004] The object of the present invention is to provide a process for preparing a thermistor sintered electrode with high thermal stability, so as to solve the problems mentioned in the above background technology.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A process for preparing a thermistor sintered electrode with high thermal stability comprises the following steps:

[0007] Step 1: Mix 2-amino-4-hydroxythiophene, 2-(trifluoromethyl)propylene, imidazole hydrochloride and xylene in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 110-130° C. for 6-8 hours. After the reaction is completed, rotary evaporation is performed to obtain intermediate 1;

[0008] Step 2: Mix the intermediate 2, 2-chloroethyl isocyanate and acetonitrile in a three-necked flask, install a condenser and a thermometer, turn on the magnetic stirring, react at a temperature of 60-80°C for 12-16h, and after the reaction is completed, rotate to obtain the intermediate 2;

[0009] Step 3: Mix the intermediate 2, dibutyltin dilaurate and N,N-dimethylformamide in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, raise the system temperature to 60-80°C, add benzoyl peroxide to the three-necked flask, and react at a temperature of 60-80°C for 4-6h. After the reaction is completed, add deionized water to the three-necked flask for washing, separate the organic layer with a separatory funnel, and then rotate to obtain a conductive enhancer;

[0010] Step 4: Add manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and sintering aid into a ball mill for ball milling and mixing;

[0011] Step 5: pre-sintering the mixture obtained in the first step and then sintering at high temperature to obtain a thermistor block;

[0012] Step 6: Dissolve the binder, heat-resistant agent, and conductive enhancer obtained in the third step in an organic solvent, add the thermistor block obtained in the fifth step, mix with high-speed stirring, cast into a sheet, and dry at high temperature to constant weight to obtain a thermistor with high thermal stability;

[0013] Step 7: Lay the thermistor on the working electrode and bond it with epoxy resin to obtain a thermistor sintered electrode with high thermal stability.

[0014] Furthermore, the sintering aid is cerium oxide.

[0015] Furthermore, the binder is polyvinyl alcohol.

[0016] Furthermore, the heat-resistant agent is N-phenylmaleimide.

[0017] Furthermore, the amount ratio of 2-amino-4-hydroxythiophene, 2-(trifluoromethyl)propylene, imidazole hydrochloride and xylene used in the first step is 0.1 mol: 0.2 mol: 0.01-0.03 mol: 60-80 mL.

[0018] Furthermore, the usage ratio of the intermediate 2, 2-chloroethyl isocyanate, and acetonitrile used in the second step is 0.06 mol: 0.06-0.08 mol: 40-60 mL.

[0019] Furthermore, the usage ratio of the intermediate 2, dibutyltin dilaurate, N,N-dimethylformamide and benzoyl peroxide used in the third step is 0.05 mol: 0.003-0.01 g: 40-60 mL: 0.02 g.

[0020] Furthermore, in the fourth step, the ball milling medium used is industrial ethanol, the ball milling speed is 300-350 r / min, and the ball milling time is 4-6 h.

[0021] Furthermore, in the fifth step, the preheating temperature condition is 900-950° C., and the preheating time condition is 2-3 h.

[0022] Furthermore, in the fifth step, the temperature condition of high temperature sintering is 1200-1400° C., and the time condition of high temperature sintering is 3-4 hours.

[0023] Furthermore, in the sixth step, the rotation speed condition of high-speed stirring is 400-600 r / min, and the stirring time condition is 60-90 min.

[0024] Furthermore, the drying temperature in the sixth step is 100°C.

[0025] Beneficial effects of the present invention:

[0026] 1) The present invention uses 2-amino-4-hydroxythiophene and 2-(trifluoromethyl)propylene as raw materials, utilizes the amino group of 2-amino-4-hydroxythiophene and the double bond of 2-(trifluoromethyl)propylene to undergo Michael addition reaction under the catalysis of imidazole hydrochloride to obtain intermediate 1, then uses 2-chloroethyl isocyanate as a quaternization agent to undergo quaternary ammonium salt reaction on the tertiary amine structure of intermediate 1 to obtain intermediate 2, and finally makes the isocyanate group and hydroxyl group of intermediate 2 self-polymerize under the conditions of dibutyltin dilaurate as a catalyst and benzoyl peroxide as an initiator to obtain a conductivity enhancer; the conductivity enhancer of the present invention contains a large amount of carbon-fluorine bonds, the carbon-fluorine bonds have high bond energy and are not easy to break, so the conductivity enhancer of the present invention has good chemical stability and thermal stability; in addition, the conductivity enhancer of the present invention also has continuous quaternary ammonium salt structures, these quaternary ammonium salt structures can form stable conductive paths in the polymer, and assist the π electron cloud conjugated system of the thiophene structure in the conductivity enhancer to transmit electrons, so the conductivity enhancer of the present invention has good conductivity.

[0027] 2) The present invention uses manganese oxide, nickel oxide, aluminum oxide, cobalt oxide, sintering aid, binder, heat-resistant agent, and self-made conductive enhancer as raw materials to prepare a thermistor sintered electrode with high thermal stability; the present invention first adds manganese oxide, nickel oxide, aluminum oxide, cobalt oxide, and sintering aid together in a ball mill for ball milling and mixing, then preheats and sinters at high temperature to obtain a thermistor block, then dissolves the thermistor block, binder, heat-resistant agent, and conductive enhancer in an organic solvent, mixes them with high-speed stirring, casts them into sheets, and dries them to obtain a thermistor, and finally bonds the thermistor to a working electrode and coats them with epoxy resin. A thermistor sintered electrode with high thermal stability is obtained by resin bonding; in the preparation method of the present invention, N-phenylmaleimide is added as a heat-resistant agent and a self-made conductive enhancer with good heat resistance, which can effectively improve the thermal stability of the resistor obtained. In addition, the added conductive enhancer can also improve the problem of resistance change caused by volume change when the thermistor is powered on for a long time. In addition, in the preparation method of the present invention, cerium oxide is added as a sintering aid, which can form a solid solution activation lattice with the sintering raw materials, thereby reducing the sintering temperature and increasing the sintering speed, greatly reducing the energy consumption during sintering.

[0028] 3) The preparation process of the thermistor sintered electrode with high thermal stability of the present invention is energy-saving and environmentally friendly. The prepared resistor has strong thermal stability and stable resistance value. The electrode prepared with the resistor has good performance and can be widely used in the field of electrical components. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A conductive enhancer comprises the following preparation steps:

[0032] Step 1: 0.1 mol 2-amino-4-hydroxythiophene, 0.2 mol 2-(trifluoromethyl)propylene, 0.01 mol imidazole hydrochloride and 60 mL xylene were mixed in a container, stirred evenly, and reacted at 110°C for 8 h. After the reaction was completed, the intermediate 1 was obtained by rotary evaporation;

[0033] Step 2: 0.06 mol of intermediate 2, 0.06 mol of 2-chloroethyl isocyanate and 40 mL of acetonitrile were mixed in a container, stirred evenly, and reacted at 60°C for 16 h. After the reaction was completed, the intermediate 2 was obtained by rotation;

[0034] Step 3: Mix 0.05 mol of intermediate 2, 0.003 g of dibutyltin dilaurate, and 40 mL of N,N-dimethylformamide in a container, stir evenly, raise the system temperature to 60°C, then add 0.2 g of benzoyl peroxide to the container, and react at 60°C for 6 hours. After the reaction, add deionized water to the container for washing, separate the organic layer with a separatory funnel, and then rotate to obtain a conductive enhancer.

[0035] Example 2

[0036] A conductive enhancer comprises the following preparation steps:

[0037] Step 1: 0.1 mol 2-amino-4-hydroxythiophene, 0.2 mol 2-(trifluoromethyl)propylene, 0.02 mol imidazole hydrochloride, and 70 mL xylene were mixed in a container, stirred evenly, and reacted at 120°C for 7 h. After the reaction was completed, the intermediate 1 was obtained by rotary evaporation;

[0038] Step 2: 0.06 mol of intermediate 2, 0.07 mol of 2-chloroethyl isocyanate and 50 mL of acetonitrile were mixed in a container, stirred evenly, and reacted at 70°C for 14 h. After the reaction was completed, the intermediate 2 was obtained by rotation;

[0039] Step 3: Mix 0.05 mol of intermediate 2, 0.007 g of dibutyltin dilaurate, and 50 mL of N,N-dimethylformamide in a container, stir evenly, raise the system temperature to 70°C, then add 0.2 g of benzoyl peroxide to the container, and react at 70°C for 5 hours. After the reaction is completed, add deionized water to the container for washing, separate the organic layer with a separatory funnel, and then rotate to obtain a conductive enhancer.

[0040] Example 3

[0041] A conductive enhancer comprises the following preparation steps:

[0042] Step 1: 0.1 mol 2-amino-4-hydroxythiophene, 0.2 mol 2-(trifluoromethyl)propylene, 0.03 mol imidazole hydrochloride and 80 mL xylene were mixed in a container, stirred evenly, and reacted at 130°C for 6 h. After the reaction was completed, the intermediate 1 was obtained by rotary evaporation;

[0043] Step 2: 0.06 mol of intermediate 2, 0.08 mol of 2-chloroethyl isocyanate and 60 mL of acetonitrile were mixed in a container, stirred evenly, and reacted at 80°C for 12 h. After the reaction was completed, the intermediate 2 was obtained by rotation;

[0044] Step 3: Mix 0.05 mol of intermediate 2, 0.01 g of dibutyltin dilaurate and 60 mL of N,N-dimethylformamide in a container, stir evenly, raise the system temperature to 60-80°C, then add 0.2 g of benzoyl peroxide to the container, and react at 80°C for 4 hours. After the reaction, add deionized water to the container for washing, separate the organic layer with a separatory funnel, and then rotate to obtain a conductive enhancer.

[0045] Example 4

[0046] A process for preparing a thermistor sintered electrode with high thermal stability comprises the following steps:

[0047] Step 1: Add manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and sintering aid into a ball mill, use industrial ethanol as the ball milling medium, and mix them at a speed of 300 r / min for 6 hours;

[0048] Step 2: preheat the mixture obtained in the first step at 900°C for 2 hours and then calcine at 1200°C for 3 hours to obtain a thermistor block;

[0049] Step 3: polyvinyl alcohol, N-phenylmaleimide, and the conductive enhancer obtained in Example 1 are dissolved in acetonitrile, and the thermistor block obtained in the second step is added thereto, stirred at a speed of 400 r / min for 90 minutes, and then cast into a sheet, and dried at a temperature of 100° C. to a constant weight to obtain a thermistor with high thermal stability;

[0050] Step 4: Lay the thermistor on the working electrode and bond it with epoxy resin to obtain a thermistor sintered electrode with high thermal stability.

[0051] Example 5

[0052] A process for preparing a thermistor sintered electrode with high thermal stability comprises the following steps:

[0053] Step 1: Add manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and sintering aid into a ball mill, use industrial ethanol as the ball milling medium, and mix them at a speed of 325 r / min for 5 hours;

[0054] Step 2: preheat the mixture obtained in the first step at 925°C for 2.5 hours and then calcine at 1300°C for 3.5 hours to obtain a thermistor block;

[0055] Step 3: polyvinyl alcohol, N-phenylmaleimide, and the conductive enhancer obtained in Example 2 are dissolved in acetonitrile, and the thermistor block obtained in the second step is added thereto, stirred at a speed of 500 r / min for 75 minutes, and then cast into a sheet, and dried at a temperature of 100° C. to a constant weight to obtain a thermistor with high thermal stability;

[0056] Step 4: Lay the thermistor on the working electrode and bond it with epoxy resin to obtain a thermistor sintered electrode with high thermal stability.

[0057] Example 6

[0058] A process for preparing a thermistor sintered electrode with high thermal stability comprises the following steps:

[0059] Step 1: Add manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and sintering aid into a ball mill, use industrial ethanol as the ball milling medium, and mix them at a speed of 350 r / min for 4 hours;

[0060] Step 2: preheating the mixture obtained in the first step at 950°C for 3 hours and then calcining at 1400°C for 4 hours to obtain a thermistor block;

[0061] Step 3: polyvinyl alcohol, N-phenylmaleimide, and the conductive enhancer obtained in Example 3 are dissolved in acetonitrile, and the thermistor block obtained in the second step is added thereto, and the mixture is stirred at a speed of 600 r / min for 60 minutes and then cast into a sheet, and dried at a temperature of 100° C. to a constant weight to obtain a thermistor with high thermal stability;

[0062] Step 4: Lay the thermistor on the working electrode and bond it with epoxy resin to obtain a thermistor sintered electrode with high thermal stability.

[0063] Comparative Example 1

[0064] The "conductive enhancer obtained in Example 3" used in Example 6 was replaced with an equal amount of polyvinyl alcohol, and the other preparation steps remained unchanged.

[0065] Comparative Example 2

[0066] This comparative example is an NTC thermistor sold by Shiheng Electronics Co., Ltd.

[0067] The NTC thermistor assembled with electrodes sold by Heng Electronics Co., Ltd. in Comparative Example 2 and the high thermal stability thermistor sintered electrodes in Examples 4-6 and Comparative Example 1 were subjected to heat resistance test and stability test respectively. The heat resistance test was to place the electrode in a constant temperature box at a temperature of 150°C for 100 hours to test the change in resistance of the electrode. The stability test was to test the change in resistance of the electrode after normal operation at a temperature of 50°C for 100 hours. The test results are shown in Table 1:

[0068] Table 1

[0069] project △R at 150℃ △R at 50℃ for 100h normal operation Example 4 0.36％ 0.53％ Example 5 0.41％ 0.71％ Example 6 0.28％ 0.44％ Comparative Example 1 0.97％ 5.79％ Comparative Example 2 4.11％ 4.96％

[0070] It can be seen from Table 1 that the resistors prepared by the process for preparing a thermistor sintered electrode with high thermal stability of the present invention in Examples 4-6 are superior to the commercially available NTC thermistors in terms of heat resistance and stability, while the comparative example 1 without adding the conductivity enhancer of the present invention is still superior to the commercially available NTC thermistor in terms of heat resistance, but its stability under long-term operation is significantly reduced, indicating that adding the conductivity enhancer of the present invention can effectively improve the heat resistance of the resistor and the stability of the prepared electrode, and can be widely used in the field of electrical components.

[0071] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A process for preparing a thermistor sintered electrode with high thermal stability, characterized in that: The following steps are involved: Step 1: Mix 2-amino-4-hydroxythiophene, 2-(trifluoromethyl)propylene, imidazole hydrochloride and xylene in a container, stir evenly, and react at a temperature of 110-130° C. for 6-8 hours to obtain intermediate 1; Step 2: Mix the intermediate 2, 2-chloroethyl isocyanate and acetonitrile in a container, stir evenly, and react at a temperature of 60-80° C. for 12-16 hours to obtain the intermediate 2; Step 3: Mix the intermediate 2, dibutyltin dilaurate and N,N-dimethylformamide in a container, stir evenly, raise the system temperature to 60-80°C, add benzoyl peroxide to the three-necked flask, and then react at 60-80°C for 4-6h to obtain a conductivity enhancer; Step 4: Add manganese oxide, nickel oxide, aluminum oxide, cobalt oxide and sintering aid into a ball mill for ball milling and mixing; Step 5: pre-sintering the mixture obtained in the first step and then sintering at high temperature to obtain a thermistor block; Step 6: Dissolve the binder, heat-resistant agent, and conductive enhancer obtained in the third step in an organic solvent, add the thermistor block obtained in the fifth step, mix with high-speed stirring, cast into a sheet, and dry at high temperature to constant weight to obtain a thermistor with high thermal stability; Step 7: Lay the thermistor on the working electrode and bond it with epoxy resin to obtain a thermistor sintered electrode with high thermal stability.

2. A process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: The sintering aid is cerium oxide, the binder is polyvinyl alcohol, and the heat-resistant agent is N-phenylmaleimide.

3. A process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: The amount ratio of 2-amino-4-hydroxythiophene, 2-(trifluoromethyl)propylene, imidazole hydrochloride and xylene used in the first step is 0.1 mol: 0.2 mol: 0.01-0.03 mol: 60-80 mL.

4. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: The amount ratio of the intermediate 2, 2-chloroethyl isocyanate and acetonitrile used in the second step is 0.06 mol: 0.06-0.08 mol: 40-60 mL.

5. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: The usage ratio of the intermediate 2, dibutyltin dilaurate, N,N-dimethylformamide and benzoyl peroxide used in the third step is 0.05 mol: 0.003-0.01 g: 40-60 mL: 0.02 g.

6. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: In the fourth step, the ball milling medium used is industrial ethanol, the ball milling speed is 300-350r / min, and the ball milling time is 4-6h.

7. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: In the fifth step, the preheating temperature condition is 900-950°C, and the preheating time condition is 2-3h.

8. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: In the fifth step, the temperature condition of high temperature sintering is 1200-1400°C, and the time condition of high temperature sintering is 3-4h.

9. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: In the sixth step, the speed condition of high-speed stirring is 400-600r / min, and the time condition of stirring is 60-90min.

10. The process for preparing a thermistor sintered electrode with high thermal stability according to claim 1, characterized in that: The drying temperature in the sixth step is 100°C.