CN111574218A - Voltage dependent resistor medium co-firing method - Google Patents
Voltage dependent resistor medium co-firing method Download PDFInfo
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- CN111574218A CN111574218A CN202010430239.8A CN202010430239A CN111574218A CN 111574218 A CN111574218 A CN 111574218A CN 202010430239 A CN202010430239 A CN 202010430239A CN 111574218 A CN111574218 A CN 111574218A
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- 238000010344 co-firing Methods 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000001419 dependent effect Effects 0.000 title claims abstract description 26
- 238000005245 sintering Methods 0.000 claims abstract description 226
- 239000002994 raw material Substances 0.000 claims abstract description 140
- 238000012360 testing method Methods 0.000 claims abstract description 73
- 238000004519 manufacturing process Methods 0.000 claims abstract description 66
- 238000012797 qualification Methods 0.000 claims abstract description 38
- 239000002270 dispersing agent Substances 0.000 claims description 41
- 239000000654 additive Substances 0.000 claims description 40
- 230000000996 additive effect Effects 0.000 claims description 35
- 238000000227 grinding Methods 0.000 claims description 34
- 239000002245 particle Substances 0.000 claims description 34
- 230000001105 regulatory effect Effects 0.000 claims description 18
- 238000001514 detection method Methods 0.000 claims description 15
- 239000006185 dispersion Substances 0.000 claims description 8
- 239000002699 waste material Substances 0.000 abstract description 8
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N SnO2 Inorganic materials O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 26
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 24
- WMWLMWRWZQELOS-UHFFFAOYSA-N bismuth(III) oxide Inorganic materials O=[Bi]O[Bi]=O WMWLMWRWZQELOS-UHFFFAOYSA-N 0.000 description 13
- 239000011787 zinc oxide Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 10
- 238000011160 research Methods 0.000 description 10
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 8
- 230000003247 decreasing effect Effects 0.000 description 8
- 238000002156 mixing Methods 0.000 description 8
- 229910052726 zirconium Inorganic materials 0.000 description 8
- UPWOEMHINGJHOB-UHFFFAOYSA-N cobalt(III) oxide Inorganic materials O=[Co]O[Co]=O UPWOEMHINGJHOB-UHFFFAOYSA-N 0.000 description 6
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Inorganic materials O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 6
- 238000003801 milling Methods 0.000 description 6
- 239000000843 powder Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 238000009472 formulation Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000003985 ceramic capacitor Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- JQJCSZOEVBFDKO-UHFFFAOYSA-N lead zinc Chemical compound [Zn].[Pb] JQJCSZOEVBFDKO-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
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- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/105—Varistor cores
- H01C7/108—Metal oxide
- H01C7/112—ZnO type
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Abstract
A co-firing method of a voltage dependent resistor medium comprises the following steps: (1) setting the sintering temperature and the sintering time of a sintering furnace, and simultaneously determining a qualified rate reference value; (2) manufacturing a test blank, and detecting the qualified rate after sintering; (3) if the qualification rate of the piezoresistor medium for the test obtained in the step (2) is equal to or greater than the qualification rate reference value, judging that the qualification rate is met, and recording the raw material formula and the manufacturing process parameters of the blank for the test; (4) preparing a blank according to the raw material formula and the manufacturing process parameters of the blank for the test recorded when the blank for the test is judged to meet the requirements in the step (3); and putting the various blanks into a sintering furnace together, and sintering at the set sintering temperature and the set sintering time. The method of the invention can reduce the equipment investment, improve the equipment utilization rate, and reduce the time waste and the raw material waste caused by the sintering temperature debugging, thereby reducing the overall cost of the product and being beneficial to ensuring the qualification rate of the product.
Description
Technical Field
The invention relates to preparation of a piezoresistor dielectric material, in particular to a piezoresistor dielectric co-firing method.
Background
The voltage dependent resistor is a resistor device with nonlinear volt-ampere characteristics, and is mainly used for clamping voltage when a circuit bears overvoltage and absorbing redundant current to protect a sensitive device.
Most of the currently used zinc oxide piezoresistors use zinc oxide as a main material (zinc oxide is in the form of white powder, the crystal structure is hexagonal, and lead-zinc ore type, the density of the lattice constant is 5.61g · cm-3, the melting point is 1975 ℃, and the zinc oxide is easy to sublimate at 1720 ℃ under normal pressure), and other components are added on the basis of the zinc oxide piezoresistor to improve the material performance (such as pulse endurance, material densification degree), reduce the sintering temperature and the like.
The method of making the piezoresistive medium generally comprises the steps of: (1) preparing raw materials in proportion, wherein the raw materials comprise a main component (such as ZnO) and various additive components; (2) adding the prepared additive raw materials into pure water, and adding a dispersing agent (such as an ammonium salt dispersing agent); then grinding (such as ball milling in a ball mill) is carried out, so that the raw materials of the additives and the dispersing agent are fully mixed to obtain additive slurry; (3) adding the main component raw materials into the additive slurry, stirring until the main component raw materials are uniformly mixed, then adding the binder, and uniformly mixing to obtain spray slurry; (4) spray-drying the spray slurry by adopting a centrifugal spray-drying tower to obtain powder; (5) forming the powder in a dry pressing mode, and pressing the powder into a green body; (6) and (3) sintering the blank for a certain time at a certain temperature after removing the adhesive (namely removing the adhesive) to obtain the piezoresistor medium.
The performance of the varistor medium is mainly determined by the raw material formula (including the types and proportions of the raw materials), and the sintering temperature has a remarkable influence on the qualification rate of the finally obtained varistor medium.
According to the magnitude of potential gradient, the varistor medium is generally divided into three types, namely a high-potential gradient varistor medium, a medium-potential gradient varistor medium and a low-potential gradient varistor medium, and under the condition of similar formula systems, the three types of varistor medium are generally different in suitable sintering temperature, for example, the high-potential gradient varistor medium is suitable for sintering at about 1180 ℃, the medium-potential gradient varistor medium is suitable for sintering at about 1210 ℃, and the low-potential gradient varistor medium is suitable for sintering at about 1240 ℃. In actual production, in order to ensure the consistency and the qualification rate of the varistor medium products, the best mode is to configure three sets of sintering furnaces for sintering the high potential gradient varistor medium, the medium potential gradient varistor medium and the low potential gradient varistor medium respectively, and after the sintering temperature of each sintering furnace is adjusted (in subsequent production, the sintering temperature is not generally adjusted), the three types of varistor media are placed into the respective sintering furnaces for sintering respectively.
However, for most of small and medium-sized enterprises, because the output of each type of varistor medium is small, or the output of a certain type of varistor medium is small, if a sintering furnace is configured for each type of varistor medium, the equipment cost is greatly increased, the equipment vacancy rate is high, and a large space is occupied, so that the overall cost of the product is greatly increased. If the same sintering furnace is adopted for sintering various types of varistor media, the sintering temperature of the sintering furnace needs to be frequently adjusted, the sintering temperature can meet the sintering requirement of the varistor media and needs to be repeatedly debugged due to the fact that one-time adjustment is difficult in actual production, a large amount of time needs to be spent in the whole debugging process, normal production is affected, a large amount of waste products are generated in the debugging process, and a large amount of raw materials are wasted. Therefore, when small and medium-sized enterprises produce various types of varistor media, the problems of increasing equipment or bearing time loss caused by debugging are faced.
Disclosure of Invention
The invention aims to provide a voltage-sensitive resistor medium co-firing method, which can realize the sintering of various voltage-sensitive resistor media in the same sintering furnace at the same sintering temperature and sintering time, thereby reducing the equipment investment and time waste caused by the debugging of the sintering temperature of the sintering furnace.
The applicant has found through research that the sintering temperature of the varistor medium is mainly related to the following factors: (1) the additive amount of the additive raw material for adjusting the sintering temperature in the raw material formula is large or small; (2) the dispersion degree of various raw materials (including main component raw materials and various additive raw materials) is high or low; (3) the grain sizes of various raw materials in the blank body. Moreover, the three factors are adjusted, and main performance parameters (such as potential gradient, pulse tolerance and the like) of the piezoresistor medium are not greatly influenced.
Based on the research results, the applicant proposes the following technical scheme:
a piezoresistor medium cofiring method is characterized by comprising the following steps:
(1) setting the sintering temperature and the sintering time of a sintering furnace as the co-firing temperature and the co-firing time of various voltage-sensitive resistor media; meanwhile, determining a product qualified rate target value as a qualified rate reference value;
(2) sintering test and detection
Obtaining a green body for a test according to a certain raw material formula of the piezoresistor medium and a manufacturing process of the piezoresistor medium, putting the green body for the test into the sintering furnace in the step (1) for sintering to obtain the piezoresistor medium for the test, and detecting the qualification rate of the piezoresistor medium for the test;
(3) if the qualification rate of the piezoresistor medium for the test obtained in the step (2) is equal to or greater than the qualification rate reference value, judging that the qualification rate is met, and recording the raw material formula and the manufacturing process parameters of the blank for the test;
if the qualification rate of the piezoresistor medium for testing obtained in the step (2) is less than the qualification rate reference value, judging that the piezoresistor medium does not meet the requirement, adjusting the raw material formula and/or the manufacturing process parameters of the piezoresistor medium, and performing the sintering test and detection in the step (2) again;
(4) mass production
(4-1) taking the recorded raw material formula and manufacturing process parameters of the green body for the test when the judgment in the step (3) is that the green body for the test meets the requirements as the raw material formula and manufacturing process parameters for manufacturing the corresponding piezoresistor medium in batches, and then manufacturing the green body according to the raw material formula and the manufacturing process parameters of the piezoresistor medium;
and (4-2) when sintering, putting various green bodies meeting the requirements of the step (4-1) into the sintering furnace of the step (1) together, and sintering at the set sintering temperature and sintering time to obtain corresponding various varistor media.
As described above, in order to adjust the sintering temperature without greatly affecting the main performance parameters of the varistor medium, the following three aspects can be mainly used: (1) changing the addition amount of sintering temperature adjusting additive raw materials (namely, additive raw materials for adjusting the sintering temperature) in the raw material formula; (2) the addition amount of the dispersing agent in the raw material mixing process is changed to adjust the dispersion degree of various raw materials; (3) and adjusting the grinding process to change the particle sizes of various raw materials in the blank. Correspondingly, when the raw material formula and/or the manufacturing process parameters of the voltage-sensitive resistor medium are adjusted after the step (3) is judged to be not satisfactory, any one of the following three adjusting means can be adopted, or a plurality of adjusting means can be combined for use: (1) the addition amount of the sintering temperature adjusting additive raw material in the raw material formula is changed; (2) the addition amount of the dispersing agent in the manufacturing process is changed to adjust the dispersion degree of various raw materials; (3) and adjusting the parameters of the grinding process in the manufacturing process to change the grain sizes of various raw materials in the blank. The addition amount of the dispersant and the parameters of the grinding process all belong to the manufacturing process parameters.
The reference value of the qualification rate set in the step (1) is optimally 100%; in consideration of the influence of various factors in actual production, it is difficult to achieve an ideal state in which no waste is generated at all, and therefore the yield reference value is usually not less than 95%, for example, 95%, 96%, 97%, 98%, 99%, or the like.
In order to improve the test efficiency, in a preferred scheme, in the step (2), for a certain voltage dependent resistor medium, a plurality of test blanks are manufactured according to different raw material formulas and manufacturing processes, the test blanks are put into the sintering furnace in the step (1) together for sintering, and then the qualification rate of each test voltage dependent resistor medium is detected respectively. In order to distinguish various test blanks, different saggars can be used for containing different test blanks, or the saggars can be marked.
In addition, the sintering of the green body for the test in the sintering test can be carried out simultaneously with the sintering of other green bodies of the piezoresistor media which are determined to be manufactured in batches, so that a sintering furnace does not need to be specially reserved for a specific period of time for the sintering test, and the test cost can be reduced.
Generally, in the case of similar raw material formulation systems, the suitable sintering temperature for the high potential gradient varistor media is lower, the suitable sintering temperature for the low potential gradient varistor media is higher, and the suitable sintering temperature for the medium potential gradient varistor media is intermediate, for example, the suitable sintering temperature for the high potential gradient varistor media is generally about 1180 ℃, the suitable sintering temperature for the medium potential gradient varistor media is generally about 1210 ℃, and the suitable sintering temperature for the low potential gradient varistor media is generally about 1240 ℃. Therefore, in order to easily realize that the high potential gradient varistor medium, the medium potential gradient varistor medium and the low potential gradient varistor medium are sintered together in the same sintering furnace at the same sintering temperature and sintering time, the sintering temperature and sintering time of the medium potential gradient varistor medium should be used as the co-firing temperature (e.g., 1210 ℃) and the co-firing time (e.g., 3 hours), and the suitable sintering temperature of the high potential gradient varistor medium is increased (eventually increased to the same temperature as the medium potential gradient varistor medium, e.g., 1210 ℃) by adjusting the raw material formulation and/or the manufacturing process parameters of the high potential gradient varistor medium, and the suitable sintering temperature of the low potential gradient varistor medium is decreased (eventually decreased to the same temperature as the medium potential gradient varistor medium, e.g., 1210 ℃), therefore, the suitable sintering temperatures of the high-potential gradient voltage-sensitive resistance medium, the medium-potential gradient voltage-sensitive resistance medium and the low-potential gradient voltage-sensitive resistance medium are unified, and after sintering is carried out in the same sintering furnace, the product qualification rate of various voltage-sensitive resistance media is equal to or greater than the qualification rate reference value. The suitable sintering temperature is that the product yield of the voltage dependent resistor medium is equal to or more than the yield reference value after sintering at the temperature.
The adjustment means (1) is to change the addition amount of the sintering temperature adjustment additive raw material in the raw material formula. In general, the proper sintering temperature of the varistor medium can be greatly reduced or increased by changing the addition amount of the sintering temperature adjusting additive in the raw material formula. It should be noted that the addition amount of the raw material of the sintering temperature adjustment additive is limited in practice, and the main performance parameters of the varistor medium may be affected when the addition amount is too large or too small, so that the addition amount of the raw material of the sintering temperature adjustment additive needs to be adjusted within a proper range. After the sintering test and detection in the step (2) are carried out, if the yield of the varistor medium is reduced, the operation of changing the addition amount of the sintering temperature regulating additive raw material is cancelled, and the addition amount of the sintering temperature regulating additive raw material is regulated again, or the regulating means (2) or the regulating means (3) is used. If the suitable sintering temperature of the varistor medium can be made to coincide with the set co-firing temperature by merely changing the addition amount of the sintering temperature adjusting additive material in the material formulation, the adjusting means (2) and the adjusting means (3) are not required.
Take a group of specific high potential gradient voltage dependent resistor medium, medium potential gradient voltage dependent resistor medium, low potential gradient voltage dependent resistor medium as an example:
the low-potential gradient voltage-sensitive resistor medium comprises the following raw materials in parts by weight: 100 parts of ZnO, Bi2O31.55 parts of SnO20.52 part of Co2O30.52 part, MnO20.52 part; the suitable sintering temperature of the low potential gradient voltage-sensitive resistance medium with the formula is 1240 ℃, and the sintering time is 3 hours.
The medium potential gradient piezoresistor medium comprises the following raw materials in parts by weight: 100 parts of ZnO, Bi2O33.21 parts of SnO21.60 parts of Co2O30.43 part, MnO20.21 part of CuO, 0.21 part of NiO; the medium potential gradient voltage-sensitive resistance medium of the formula is suitable for sintering at 1210 ℃ for 3 hours.
The original raw material formula of the high potential gradient voltage dependent resistor medium is as follows (by weight portion): 100 parts of ZnO, Bi2O39.15 parts of SnO23.43 parts of Co2O30.57 part, MnO20.34 portion of CuO, 0.34 portion of NiO, 0.23 portion of Al2O30.14 part; the moderate potential gradient piezoresistor medium in the formula is suitable for sintering at 1180 ℃ for 3 hours.
Through research and experiments, Bi in the raw materials is found2O3And SnO2The additive amount of (A) has a relatively obvious influence on the sintering temperature of the voltage dependent resistor medium, and belongs to a raw material of a sintering temperature regulating additive. Measured and calculated, Bi2O3Every 1 part of the increase, the suitable sintering temperature of the voltage dependent resistor medium is reduced by about 5 ℃; SnO2For every 0.1 part increase, the suitable sintering temperature for the varistor medium drops by approximately 2 ℃.
Based on the above situation, in order to realize that the high potential gradient varistor medium, the medium potential gradient varistor medium and the low potential gradient varistor medium are sintered together in the same sintering furnace at the same sintering temperature and sintering time, the sintering temperature and sintering time of the medium potential gradient varistor medium may be set to the co-firing temperatureThe raw material formula of the medium potential gradient voltage-sensitive resistor medium is kept unchanged at the temperature (1210 ℃) and the co-firing time (3 hours); by reducing Bi in high potential gradient varistor media2O3And/or SnO2The addition amount of (b) is increased to make the sintering temperature suitable to be increased (close to 1210 ℃); by increasing Bi in low potential gradient voltage dependent resistor medium2O3And/or SnO2The amount of (b) is so small that the suitable sintering temperature is lowered (closer to 1210 ℃). If only by changing Bi in the raw material formula2O3And/or SnO2The proper sintering temperature of the high-potential gradient varistor medium and the low-potential gradient varistor medium can be consistent with the set co-firing temperature, and the adjusting means (2) and the adjusting means (3) are not needed.
In actual practice, Bi is present immediately after the start of the adjustment2O3And SnO2Can be changed to a greater extent (e.g., Bi)2O3The addition amount of (A) is reduced or increased by 2 parts per adjustment, SnO2The addition amount of (b) is decreased or increased by 0.2 parts per adjustment); when the adjustment is close to the end sound (namely after a plurality of times of adjustment, the qualification rate of the piezoresistor medium for testing is close to a qualification rate reference value), Bi2O3And SnO2Can be changed to a small extent (e.g., Bi)2O3In each adjustment, the addition amount of (A) is reduced or increased by 0.5 part, SnO2The addition amount of (c) is decreased or increased by 0.05 parts per adjustment). When adjusted, Bi2O3And SnO2The addition amounts of the two are reduced or increased simultaneously; it is also possible to change only the amount of one of the additives while keeping the amount of the other additive constant.
The adjusting means (2) is to change the amount of the dispersing agent added in the raw material mixing step to adjust the degree of dispersion of each raw material. Generally, the amount of dispersant added is about 0.5 to 1.5% of the total weight of the various additive materials, and the amount of dispersant added can be adjusted within this interval without adversely affecting the performance of the varistor media. When adjusted, the amount of the dispersant added is preferably within the range of 0.5 to 1.5% by weight based on the total weight of the raw materials of the respective additives.
Research shows that the proper sintering temperature of the varistor medium is reduced by 3-5 ℃ every 0.1 percent (the percentage is the percentage of the total weight of the dispersant and various additive raw materials) of the dispersant; on the contrary, the suitable sintering temperature of the varistor medium increases by 3 to 5 ℃ for each 0.1% reduction of the dispersant.
Based on the above, in the case where the sintering temperature and sintering time of the medium potential gradient varistor medium are set to the co-firing temperature (i.e., 1210 ℃) and the co-firing time (i.e., 3 hours), the amount of the dispersant added in the manufacturing process of the medium potential gradient varistor medium remains unchanged; for the high potential gradient piezoresistor medium, the addition amount of the dispersing agent in the manufacturing process (namely the raw material mixing process) is reduced, so that the sintering temperature is increased (close to 1210 ℃); in the low potential gradient varistor medium, the amount of the dispersant added in the production process (i.e., the raw material mixing step) is increased to lower the suitable sintering temperature (closer to 1210 ℃).
After the addition amount of the dispersing agent is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the addition amount of the dispersing agent for the certain time is cancelled, and the addition amount of the dispersing agent is adjusted again, or the adjusting means (1) or the adjusting means (3) is used instead. If the suitable sintering temperature of the varistor medium can be adjusted to the set co-firing temperature by merely changing the amount of the dispersant added, the adjustment means (1) and the adjustment means (3) are not required.
The adjustment means (3) is to adjust the grinding process to change the particle size of each raw material in the green body. Research shows that the smaller the particle size of various raw materials after grinding is, the lower the suitable sintering temperature of the varistor medium is; the larger the particle size of the various raw materials after grinding, the higher the suitable sintering temperature for the varistor media. Generally, the particle size of the milled feedstock is expressed as the median particle diameter D50. Through research and measurement, the proper sintering temperature of the piezoresistor medium is reduced by 5-10 ℃ when the D50 of the ground raw material is reduced by 0.5 mu m; conversely, for every 0.5 μm increase in D50 of the milled material, the appropriate sintering temperature for the varistor media increases by 5-10 ℃. The milled particle size of the various raw materials should not generally exceed 4 μm, since too large a particle size of the raw materials after milling may result in deterioration of the performance of the varistor media. The median particle diameter D50 is preferably 0.5 to 2.5. mu.m.
The particle size of the raw materials after grinding depends on the grinding equipment, grinding media (such as zirconium balls), grinding time and other factors. For example, in the case of a ball mill using zirconium balls having a diameter of 5 to 10mm as a grinding medium, the correspondence between the grinding time and D50 is approximately 1 hour, 20 μm, 5 hours, 10 μm, 10 hours, 9 μm, 24 hours, 7 μm, 48 hours, 5 μm, 72 hours, or 4.8 μm. In the case of the stirring mill using zirconium balls having a diameter of 3 to 5mm as a milling medium, the correspondence between the milling time and D50 was approximately 1 hour, 5 μm, 5 hours, 2.2 μm, 10 hours, 2.0 μm, 24 hours, 1.8 μm, 48 hours, 1.7 μm, 72 hours, and 1.7 μm. In the case of the sand mill using zirconium balls having a diameter of 0.5 to 1mm as a grinding medium, the correspondence between the grinding time and D50 was approximately 1 hour, 3 μm, 5 hours, 1.0. mu.m, 10 hours, 0.8. mu.m, 24 hours, 0.6. mu.m, 48 hours, 0.6. mu.m, 72 hours, and 0.59. mu.m.
Based on the above, in the case where the sintering temperature and sintering time of the medium potential gradient varistor medium are set to the co-firing temperature (i.e., 1210 ℃) and the co-firing time (i.e., 3 hours), the particle size of the raw material after grinding in the manufacturing process of the medium potential gradient varistor medium remains unchanged; for the high potential gradient piezoresistor medium, the particle size of the ground raw material is increased, so that the suitable sintering temperature is increased (close to 1210 ℃); for low potential gradient varistor media, the particle size of the ground material is reduced to a suitable sintering temperature (closer to 1210 ℃).
After the particle size of the ground raw material is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the particle size of the ground raw material is cancelled, and the particle size of the ground raw material is adjusted again, or the adjustment means (1) or (2) is used. If the suitable sintering temperature of the varistor medium can be adjusted to the set co-firing temperature by merely changing the particle size of the ground raw material, the adjustment means (1) and the adjustment means (2) are not required.
The method can realize that various types of varistor media are sintered in the same sintering furnace at the same sintering temperature and the same sintering time, and after the sintering temperature of the sintering furnace is adjusted, the varistor media do not need to be adjusted again in subsequent production, thereby reducing the equipment investment, improving the equipment utilization rate, reducing the time waste and the raw material waste caused by the adjustment of the sintering temperature, further reducing the overall cost of products and being beneficial to ensuring the qualification rate of the products.
In addition, with reference to the method of the present invention, it is also possible to achieve sintering of a plurality of different ceramic capacitor media in the same sintering furnace at the same sintering temperature and sintering time, or to achieve sintering of a ceramic capacitor medium and a varistor medium in the same sintering furnace at the same sintering temperature and sintering time.
Detailed Description
In this embodiment, the co-firing method for the varistor dielectric includes the following steps:
(1) setting the sintering temperature and the sintering time of a sintering furnace as the co-firing temperature and the co-firing time of various voltage-sensitive resistor media; meanwhile, determining a product qualified rate target value as a qualified rate reference value;
(2) sintering test and detection
Obtaining a green body for a test according to a certain raw material formula of the piezoresistor medium and a manufacturing process of the piezoresistor medium, putting the green body for the test into the sintering furnace in the step (1) for sintering to obtain the piezoresistor medium for the test, and detecting the qualification rate of the piezoresistor medium for the test;
(3) if the qualification rate of the piezoresistor medium for the test obtained in the step (2) is equal to or greater than the qualification rate reference value, judging that the qualification rate is met, and recording the raw material formula and the manufacturing process parameters of the blank for the test;
if the qualification rate of the piezoresistor medium for testing obtained in the step (2) is less than the qualification rate reference value, judging that the piezoresistor medium does not meet the requirement, adjusting the raw material formula and/or the manufacturing process parameters of the piezoresistor medium, and performing the sintering test and detection in the step (2) again;
(4) mass production
(4-1) taking the recorded raw material formula and manufacturing process parameters of the green body for the test when the judgment in the step (3) is that the green body for the test meets the requirements as the raw material formula and manufacturing process parameters for manufacturing the corresponding piezoresistor medium in batches, and then manufacturing the green body according to the raw material formula and the manufacturing process parameters of the piezoresistor medium;
and (4-2) when sintering, putting various green bodies meeting the requirements of the step (4-1) into the sintering furnace of the step (1) together, and sintering at the set sintering temperature and sintering time to obtain corresponding various varistor media.
The qualification rate reference value set in the step (1) is 100% in the most ideal case; in consideration of the influence of various factors in actual production, it is difficult to achieve an ideal state in which no waste is generated at all, and therefore the yield reference value is usually not less than 95%, for example, 95%, 96%, 97%, 98%, 99%, or the like.
After the step (3) judges that the requirements are not met, when the raw material formula and/or the manufacturing process parameters of the voltage dependent resistor medium are adjusted, any one of the following three adjusting means is adopted, or a plurality of adjusting means are combined for use: (1) the addition amount of the sintering temperature adjusting additive raw material in the raw material formula is changed; (2) the addition amount of the dispersing agent in the manufacturing process is changed to adjust the dispersion degree of various raw materials; (3) and adjusting the parameters of the grinding process in the manufacturing process to change the grain sizes of various raw materials in the blank. The addition amount of the dispersing agent and the parameters of the grinding process belong to the manufacturing process parameters.
The following takes a specific group of varistor media (including high potential gradient varistor media, medium potential gradient varistor media, and low potential gradient varistor media) as an example to specifically describe the co-firing method of the varistor media:
the low-potential gradient voltage-sensitive resistor medium comprises the following raw materials in parts by weight: 100 parts of ZnO, Bi2O31.55 parts of SnO20.52 part of Co2O30.52 part, MnO20.52 part; the suitable sintering temperature of the low potential gradient voltage-sensitive resistance medium with the formula is 1240 ℃, and the sintering time is 3 hours.
The medium potential gradient piezoresistor medium comprises the following raw materials in parts by weight: 100 parts of ZnO, Bi2O33.21 parts of SnO21.60 parts of Co2O30.43 part, MnO20.21 part of CuO, 0.21 part of NiO; the medium potential gradient voltage-sensitive resistance medium of the formula is suitable for sintering at 1210 ℃ for 3 hours.
The original raw material formula of the high potential gradient voltage dependent resistor medium is as follows (by weight portion): 100 parts of ZnO, Bi2O39.15 parts of SnO23.43 parts of Co2O30.57 part, MnO20.34 portion of CuO, 0.34 portion of NiO, 0.23 portion of Al2O30.14 part; the moderate potential gradient piezoresistor medium in the formula is suitable for sintering at 1180 ℃ for 3 hours.
In order to easily realize that the high potential gradient varistor medium, the medium potential gradient varistor medium and the low potential gradient varistor medium are sintered together in the same sintering furnace at the same sintering temperature and sintering time, the sintering temperature and sintering time of the medium potential gradient varistor medium can be used as the co-firing temperature (e.g., 1210 ℃) and the co-firing time (e.g., 3 hours), and the suitable sintering temperature of the medium potential gradient varistor medium can be increased (finally increased to be the same as the medium potential gradient varistor medium, e.g., 1210 ℃) by adjusting the raw material formula and/or the manufacturing process parameters of the medium potential gradient varistor medium, and the suitable sintering temperature of the medium potential gradient varistor medium can be decreased (finally decreased to be the same as the medium potential gradient varistor medium, e.g., 1210 ℃), by adjusting the raw material formula and/or the manufacturing process parameters of the medium potential gradient varistor medium, The suitable sintering temperatures of the medium potential gradient voltage-sensitive resistance medium and the low potential gradient voltage-sensitive resistance medium are unified, and after sintering is carried out in the same sintering furnace, the product qualification rate of various voltage-sensitive resistance media is equal to or greater than a qualification rate reference value.
After the step (3) judges that the requirements are not met, when the raw material formula and/or the manufacturing process parameters of the voltage dependent resistor medium are adjusted, the adopted adjusting means comprises the following steps: (1) the addition amount of the sintering temperature adjusting additive raw material in the raw material formula is changed; (2) the addition amount of the dispersing agent in the manufacturing process is changed to adjust the dispersion degree of various raw materials; (3) and adjusting the parameters of the grinding process in the manufacturing process to change the grain sizes of various raw materials in the blank. The three adjusting means can be used independently, or multiple adjusting means can be used in combination (when multiple adjusting means are used in combination, the using sequence of the adjusting means is not limited).
Use of the regulating means of the first and second types (1)
The adjusting means (1) is to change the addition amount of the sintering temperature adjusting additive raw material in the raw material formula.
Through research and experiments, Bi in the raw materials is found2O3And SnO2The additive amount of (A) has a relatively obvious influence on the sintering temperature of the voltage dependent resistor medium, and belongs to a raw material of a sintering temperature regulating additive. Measured and calculated, Bi2O3Every 1 part of the increase, the suitable sintering temperature of the voltage dependent resistor medium is reduced by about 5 ℃; SnO2For every 0.1 part increase, the suitable sintering temperature for the varistor medium drops by approximately 2 ℃.
The sintering temperature and the sintering time of the medium potential gradient voltage-sensitive resistor medium can be set as the co-firing temperature (1210 ℃) and the co-firing time (3 hours), and the raw material formula of the medium potential gradient voltage-sensitive resistor medium is kept unchanged; by reducing Bi in high potential gradient varistor media2O3And/or SnO2The addition amount of (b) is increased to make the sintering temperature suitable to be increased (close to 1210 ℃); by increasing Bi in low potential gradient voltage dependent resistor medium2O3And/or SnO2The amount of (b) is so small that the suitable sintering temperature is lowered (closer to 1210 ℃).
In actual practice, at the very beginningWhen adjusted, Bi2O3And SnO2Can be changed to a greater extent (e.g., Bi)2O3The addition amount of (A) is reduced or increased by 2 parts per adjustment, SnO2The addition amount of (b) is decreased or increased by 0.2 parts per adjustment); when the adjustment is close to the end sound (namely after a plurality of times of adjustment, the qualification rate of the piezoresistor medium for testing is close to a qualification rate reference value), Bi2O3And SnO2Can be changed to a small extent (e.g., Bi)2O3In each adjustment, the addition amount of (A) is reduced or increased by 0.5 part, SnO2The addition amount of (c) is decreased or increased by 0.05 parts per adjustment). When adjusted, Bi2O3And SnO2The addition amounts of the two are reduced or increased simultaneously; it is also possible to change only the amount of one of the additives while keeping the amount of the other additive constant.
After the sintering test and detection in the step (2) are carried out, if the yield of the varistor medium is reduced, the operation of changing the addition amount of the sintering temperature regulating additive raw material is cancelled, and the addition amount of the sintering temperature regulating additive raw material is regulated again, or the regulating means (2) or the regulating means (3) is used.
If only by changing Bi in the raw material formula2O3And/or SnO2The proper sintering temperature of the high-potential gradient varistor medium and the low-potential gradient varistor medium can be consistent with the set co-firing temperature, and the adjusting means (2) and the adjusting means (3) are not needed.
Use of the second and (2) adjustment means
The adjustment means (2) is to change the amount of the dispersant added in the raw material mixing step to adjust the degree of dispersion of each raw material.
Research shows that the proper sintering temperature of the varistor medium is reduced by 3-5 ℃ every 0.1 percent (the percentage is the percentage of the total weight of the dispersant and various additive raw materials) of the dispersant; on the contrary, the suitable sintering temperature of the varistor medium increases by 3 to 5 ℃ for each 0.1% reduction of the dispersant.
The addition amount of the dispersing agent is about 0.5-1.5% of the total weight of various additive raw materials, and the addition amount of the dispersing agent can be adjusted in the interval, so that the performance of the voltage dependent resistor medium is not adversely affected. When adjusted, the amount of the dispersant added is preferably within the range of 0.5 to 1.5% by weight based on the total weight of the raw materials of the respective additives.
Under the condition that the sintering temperature and the sintering time of the medium potential gradient voltage sensitive resistor medium are set as the co-firing temperature (1210 ℃) and the co-firing time (3 hours), the adding amount of the dispersing agent in the manufacturing process of the medium potential gradient voltage sensitive resistor medium is kept unchanged; for the high potential gradient piezoresistor medium, the addition amount of the dispersing agent in the manufacturing process (namely the raw material mixing process) is reduced, so that the sintering temperature is increased (close to 1210 ℃); in the low potential gradient varistor medium, the amount of the dispersant added in the production process (i.e., the raw material mixing step) is increased to lower the suitable sintering temperature (closer to 1210 ℃).
After the addition amount of the dispersing agent is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the addition amount of the dispersing agent for the certain time is cancelled, and the addition amount of the dispersing agent is adjusted again, or the adjusting means (1) or the adjusting means (3) is used instead.
If the suitable sintering temperature of the varistor medium can be adjusted to the set co-firing temperature by merely changing the amount of the dispersant added, the adjustment means (1) and the adjustment means (3) are not required.
Use of the third and (3) adjustment means
The adjusting means (3) is to adjust the grinding process to change the particle size of each raw material in the blank.
Research shows that the smaller the particle size of various raw materials after grinding is, the lower the suitable sintering temperature of the varistor medium is; the larger the particle size of the various raw materials after grinding, the higher the suitable sintering temperature for the varistor media.
Through research and measurement, the proper sintering temperature of the piezoresistor medium is reduced by 5-10 ℃ when the D50 of the ground raw material is reduced by 0.5 mu m; conversely, for every 0.5 μm increase in D50 of the milled material, the appropriate sintering temperature for the varistor media increases by 5-10 ℃. The milled particle size of the various raw materials should not generally exceed 4 μm, since too large a particle size of the raw materials after milling may result in deterioration of the performance of the varistor media. The median particle diameter D50 is preferably 0.5 to 2.5. mu.m.
The particle size of the raw materials after grinding depends on the grinding equipment, grinding media (such as zirconium balls), grinding time and other factors. For example, in the case of a ball mill using zirconium balls having a diameter of 5 to 10mm as a grinding medium, the correspondence between the grinding time and D50 is approximately 1 hour, 20 μm, 5 hours, 10 μm, 10 hours, 9 μm, 24 hours, 7 μm, 48 hours, 5 μm, 72 hours, or 4.8 μm. In the case of the stirring mill using zirconium balls having a diameter of 3 to 5mm as a milling medium, the correspondence between the milling time and D50 was approximately 1 hour, 5 μm, 5 hours, 2.2 μm, 10 hours, 2.0 μm, 24 hours, 1.8 μm, 48 hours, 1.7 μm, 72 hours, and 1.7 μm. In the case of the sand mill using zirconium balls having a diameter of 0.5 to 1mm as a grinding medium, the correspondence between the grinding time and D50 was approximately 1 hour, 3 μm, 5 hours, 1.0. mu.m, 10 hours, 0.8. mu.m, 24 hours, 0.6. mu.m, 48 hours, 0.6. mu.m, 72 hours, and 0.59. mu.m.
Under the condition that the sintering temperature and the sintering time of the medium potential gradient voltage-sensitive resistor medium are set as the co-firing temperature (1210 ℃) and the co-firing time (3 hours), the granularity of the ground raw material of the medium potential gradient voltage-sensitive resistor medium in the manufacturing process is kept unchanged; for the high potential gradient piezoresistor medium, the particle size of the ground raw material is increased, so that the suitable sintering temperature is increased (close to 1210 ℃); for low potential gradient varistor media, the particle size of the ground material is reduced to a suitable sintering temperature (closer to 1210 ℃).
In actual operation, the particle size of the ground raw material can be controlled by adopting different grinding equipment, different grinding media and different grinding time.
After the particle size of the ground raw material is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the particle size of the ground raw material is cancelled, and the particle size of the ground raw material is adjusted again, or the adjustment means (1) or (2) is used.
If the suitable sintering temperature of the varistor medium can be adjusted to the set co-firing temperature by merely changing the particle size of the ground raw material, the adjustment means (1) and the adjustment means (2) are not required.
In order to improve the test efficiency, in the step (2), for a certain voltage dependent resistor medium, a plurality of test blanks are manufactured according to different raw material formulas and manufacturing processes, the test blanks are put into the sintering furnace in the step (1) together for sintering, and then the qualification rate of the voltage dependent resistor medium for various tests is detected respectively. In order to distinguish various test blanks, different saggars can be used for containing different test blanks, or the saggars can be marked.
Furthermore, the sintering of the test green bodies in the sintering test can be performed simultaneously with the sintering of other varistor medium green bodies already manufactured in series, so that the sintering furnace does not have to be specially left for a certain period of time for the sintering test.
Claims (8)
1. A piezoresistor medium cofiring method is characterized by comprising the following steps:
(1) setting the sintering temperature and the sintering time of a sintering furnace as the co-firing temperature and the co-firing time of various voltage-sensitive resistor media; meanwhile, determining a product qualified rate target value as a qualified rate reference value;
(2) sintering test and detection
Obtaining a green body for a test according to a certain raw material formula of the piezoresistor medium and a manufacturing process of the piezoresistor medium, putting the green body for the test into the sintering furnace in the step (1) for sintering to obtain the piezoresistor medium for the test, and detecting the qualification rate of the piezoresistor medium for the test;
(3) if the qualification rate of the piezoresistor medium for the test obtained in the step (2) is equal to or greater than the qualification rate reference value, judging that the qualification rate is met, and recording the raw material formula and the manufacturing process parameters of the blank for the test;
if the qualification rate of the piezoresistor medium for testing obtained in the step (2) is less than the qualification rate reference value, judging that the piezoresistor medium does not meet the requirement, adjusting the raw material formula and/or the manufacturing process parameters of the piezoresistor medium, and performing the sintering test and detection in the step (2) again;
(4) mass production
(4-1) taking the recorded raw material formula and manufacturing process parameters of the green body for the test when the judgment in the step (3) is that the green body for the test meets the requirements as the raw material formula and manufacturing process parameters for manufacturing the corresponding piezoresistor medium in batches, and then manufacturing the green body according to the raw material formula and the manufacturing process parameters of the piezoresistor medium;
and (4-2) when sintering, putting various green bodies meeting the requirements of the step (4-1) into the sintering furnace of the step (1) together, and sintering at the set sintering temperature and sintering time to obtain corresponding various varistor media.
2. The method of claim 1, wherein: after the step (3) judges that the requirements are not met, when the raw material formula and/or the manufacturing process parameters of the voltage dependent resistor medium are adjusted, any one of the following three adjusting means is adopted, or a plurality of adjusting means are combined for use: (1) the addition amount of the sintering temperature adjusting additive raw material in the raw material formula is changed; (2) the addition amount of the dispersing agent in the manufacturing process is changed to adjust the dispersion degree of various raw materials; (3) and adjusting the parameters of the grinding process in the manufacturing process to change the grain sizes of various raw materials in the blank.
3. A method of cofiring varistor media as in claim 1 or claim 2, wherein: the reference value of the qualified rate is more than or equal to 95 percent.
4. A method of cofiring varistor media as in claim 1 or claim 2, wherein: in the step (2), various test blanks are manufactured for a certain voltage dependent resistor medium according to different raw material formulas and manufacturing processes, the test blanks are put into the sintering furnace in the step (1) together for sintering, and then the qualification rate of the voltage dependent resistor medium for various tests is detected respectively.
5. A method of cofiring varistor media as in claim 1 or claim 2, wherein: the sintering of the green body for the test in the sintering test is carried out simultaneously with the sintering of other green bodies of the varistor media which are determined to be manufactured in batches.
6. The method of claim 2, wherein: after the sintering test and detection in the step (2) are carried out, if the yield of the varistor medium is reduced, the operation of changing the addition amount of the sintering temperature regulating additive raw material is cancelled, and the addition amount of the sintering temperature regulating additive raw material is regulated again, or the regulating means (2) or the regulating means (3) is used.
7. The method of claim 2, wherein: after the addition amount of the dispersing agent is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the addition amount of the dispersing agent for the certain time is cancelled, and the addition amount of the dispersing agent is adjusted again, or the adjusting means (1) or the adjusting means (3) is used instead.
8. The method of claim 2, wherein: after the particle size of the ground raw material is changed for a certain time, and after the sintering test and detection in the step (2), if the yield of the varistor medium is reduced, the operation of changing the particle size of the ground raw material is cancelled, and the particle size of the ground raw material is adjusted again, or the adjustment means (1) or (2) is used.
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