CN115483025A - Preparation process of mica sheet capacitor - Google Patents

Abstract

The invention relates to the technical field of production of mica sheet capacitors, and discloses a preparation process of a mica sheet capacitor, wherein the specific operation method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness; classifying the thickness of the mica sheets: and (4) classifying the thickness of the flake mica in the step by using a dial indicator. The silver paste is coated on the mica sheet, and after silver printing and sintering are carried out, the produced product is subjected to voltage resistance test, insulation resistance test, loss tangent value test, capacitor temperature coefficient test and capacity stability test, so that the reject ratio of the product can be effectively avoided, and meanwhile, the test is carried out step by step, so that the tested finished product is classified, the raw material waste caused by defective products is effectively reduced, and the large-scale production requirement of mica sheet color change production is met.

Description

Preparation process of mica sheet capacitor

Technical Field

The invention relates to the technical field of production of mica sheet capacitors, in particular to a preparation process of a mica sheet capacitor.

Background

The mica sheet is composed of multi-silicon muscovite, quartz, garnet, rutile and the like, albite, tetrahedrite, chlorite and the like can appear, garnet is rich in Fe and Mg, si in the multi-silicon muscovite can reach 3.369, and the high-pressure combination is also realized. The insulating and low-loss thermal resistance function is realized, and the black body is good; the natural mica sheet is a mica part with a certain thickness and a certain shape, which is prepared by peeling, thickening, cutting, drilling or punching thick mica sheets, and the product is suitable for televisions, power capacitors, thermal relays, monitoring displays, aerospace, aviation, communication, radars, heat-resistant framework sheets and the like as raw and auxiliary materials.

The mica capacitor is a capacitor taking natural mica as a medium in the middle of the capacitor, and the manufacturing method comprises the following steps: the metal foil or the mica sheet is sprayed with a silver layer to be used as an electrode plate, the electrode plate and the mica are laminated layer by layer and then are die-cast in bakelite powder or sealed in epoxy resin to prepare the mica sheet, wherein silver is coated to process the single-layer mica sheet, and then the whole assembly is realized in a series connection and parallel connection mode.

Monolithic mica sheet is exactly the capacitor assembly of a completion, the silver thick liquid silver content that present cover silver processing production adopted is unable to be guaranteed, the volume effect that the silver thick liquid of producing is again coated on the mica sheet surface can influence and is made, secondly, current cover silver adhesive force can't be guaranteed, when using to the mica sheet condenser after covering silver, lead to the silver layer to drop so that influence the use of condenser because of colliding with easily, when testing the finished product, the process is comparatively loaded down with trivial details, can't effectively avoid the product defective rate.

Therefore, a preparation process of the mica sheet capacitor is proposed.

Disclosure of Invention

The invention mainly aims to provide a preparation process of a mica sheet capacitor, which can effectively solve the problems that silver paste content adopted in the existing silver coating processing production cannot be guaranteed, the produced silver paste is coated on the surface of a mica sheet to influence the prepared capacity effect, the existing silver coating adhesive force cannot be guaranteed, when the mica sheet capacitor coated with silver is used, a silver layer is easy to fall off due to collision to influence the use of the capacitor, when a finished product is tested, the process is complicated, and the product reject ratio cannot be effectively avoided.

In order to achieve the purpose, the invention adopts the technical scheme that:

the preparation process of the mica sheet capacitor comprises the following steps:

the method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness;

step two: classifying the thickness of the mica sheets: classifying the thickness of the sheet mica in the above step by a dial indicator, wherein the allowable error of each specification is +/-1 μm;

step three: baking the mica sheet: heating a muffle furnace to 570 +/-10 ℃ and keeping the temperature constant, slightly placing mica sheets with the size specification of 14X14 and the thickness specification of 26-30 mu m in a metal mesh disc, uniformly placing the mica sheets in the furnace, closing a furnace door for baking for 3-8 minutes, clamping the metal mesh disc by using a long-handle forceps, placing the metal mesh disc on an operation table, and slightly clamping the metal mesh disc in a container by using the forceps;

step four: cleaning: putting the mica sheets baked in the above steps into boiling distilled water, adding about 1% ammonia water for rinsing, shaking the mesh screen during rinsing, then rinsing with distilled water for several times, taking out after water drops dry, and putting in a copper wire mesh disc; putting the cleaned mica sheets into an oven at the temperature of 160 +/-20 ℃ for drying until the mica sheets are completely dried, and taking out the mica sheets;

step five: silver paste preparation: preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight: 1400-1600 parts of silver mud, 500-700 parts of adhesive, 100-300 parts of terpineol, 30.5-32.5 parts of bismuth oxide, 20-28 parts of lead borate and 80-120 parts of ethylene glycol ethyl ether;

step six: preparing a screen:

s11, paving a polyester film on an insulating plate, and engraving the required silver coating size on the insulating plate by using a blade and a steel plate ruler, wherein the size of a screen printing frame is (16 +/-0.3) X (16 +/-0.3);

s12, fastening a nylon screen on the frame, and attaching the pre-engraved polyester film on the nylon screen by using silver paste;

step seven: silver printing:

s21, adding qualified silver paste sieved by a screen of 170-180 meshes into an enamel tray by a spoon, and adjusting the concentration of the silver paste by ethylene glycol ether to make the silver paste suitable for printing;

s22, turning on a power switch, and adjusting a hot plate voltage regulator until the temperature of the baking sheet plate is 90-100 ℃;

s23, the sheets are neatly and lightly placed into a printing hopper, and the small amount of sheets is placed each time, so that the mica sheets are prevented from being damaged;

s24, absorbing the mica sheet on a workbench, adhering a proper amount of silver paste on a vacuum rubber brush, pressing down the frame pasted with the printing screen, and flatly and uniformly scraping the frame on the screen with force;

s25, sucking the printed sheets on a sheet drying plate on an electric heating sheet, drying the printed sheets, pouring the dried sheets into a sheet storage tray, printing the reverse side of the printed sheets after all the printed sheets are printed, and paying attention to the fact that silver layers on the two sides are overlapped when the reverse side is printed, wherein the silver layers on the two sides of each batch of the printed sheets are printed by one sample plate;

step eight: and (3) sintering and infiltrating:

s31, checking whether the furnace temperature reaches the specified temperature of 280-300 ℃;

s32, scattering the rectangular sheets with the two printed surfaces on a metal mesh disc, putting the metal mesh disc into a sintering and infiltrating furnace for sintering and infiltrating, wherein the temperature is 300 ℃ at the first low temperature for 10 minutes;

s33, after low-temperature burning out, checking and sorting according to different models and thicknesses, carrying out high-temperature 570 +/-10 ℃ burning-out on qualified mica sheets after checking and sorting for 2-3 minutes, then dragging the mica sheets to a furnace mouth, stopping for 2 minutes, and taking out;

step nine: and (3) single-chip withstand voltage test: carrying out pressure resistance test on the sintered mica sheets one by using an automatic pressure resistance machine or manually, wherein the pressure resistance test range of the 14X14 specification size is 750-1250V, if pressure resistance breakdown and damage are eliminated in the pressure measurement process, yellowing or oxidation phenomena can occur after the sintered mica sheets are stored for a long time, and the sintered mica sheets can be used after being sintered by using a high-temperature furnace at the temperature of 450 ℃;

step ten: and (3) testing the insulation resistance: testing mica sheet capacitors with qualified test voltage one by using a high-resistance meter, wherein the voltage used for testing the resistors is 100-500V, the requirement on the insulation resistance is more than or equal to 2000 MOmega, the capacitors with qualified test are placed in an oven to avoid being affected with damp, and the capacitors are charged before the insulation resistance is tested and then placed in a container;

step eleven: measuring loss tangent: the tan delta values measured for finished capacitors using a loss angle measuring instrument of 10-100pF, 100-1000pF, measured individually for capacitors having loss tangent (tan delta) values of different nominal capacities should not be greater than the following specifications:

nominal capacity (PF): 20-24, tangent (tan δ value): 23.5X10 ^-4 ；

Nominal capacity (PF): 27, tangent (tan δ value): 21X10 ^-4 ；

Nominal capacity (PF): 30, tangent (tan δ value): 20X10 ^-4 ；

Nominal capacity (PF): 33, tangent (tan δ value): 18X10 ^-4 ；

Nominal capacity (PF): 36-39, tan delta value: 16X10 ^-4 ；

Nominal capacity (PF): 43-47, tangent (tan δ value): 15.5X10 ^-4 ；

Step twelve: measuring the temperature coefficient and the capacity stability of the mica sheet capacitor in a drawing mode;

s71: randomly selecting one mica sheet capacitor with the same specification as a standard, and numbering other tested mica sheet capacitors;

s72: measuring the capacity error of the numbered capacitor by using an error sorter, and recording the capacity error as a first measurement difference value;

s73: placing the mica sheet capacitor tested at room temperature in a drying oven at room temperature plus 50 ℃, heating for 30 minutes, taking out from the drying oven, immediately testing the capacity error, and recording the capacity error as a second difference value;

s74: cooling the capacitor subjected to the error test during temperature rise at room temperature, measuring the capacity error of the capacitor by using an error sorter after 1 hour, and recording the capacity error as a third difference value;

s75: the values measured above are calculated:

second difference measurement-first difference measurement = capacitance temperature coefficient;

third difference measurement-first difference measurement = stability;

s76: classifying the mica sheet capacitors in different intervals:

b type: the temperature coefficient of the capacitor is less than or equal to 200X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.5 percent;

class C: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 100X10 ^-6 (ii) a The volume stability is less than or equal to 0.2;

and D type: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 50X10 ^-6 (ii) a The volume stability is less than or equal to 0.1 percent;

through testing, the products which do not conform to the D group are allowed to be reworked, and the products which do not conform to the requirements of the D group are degraded after being reworked.

Further, in the step one, the mica sheets are classified into the following size and specification: 7X14, 12X12, 14X14, 16X16, 10X20, 19X25, 25X25, 20X30, 13X29, 17X34, 20X34, 30X40, 40X50; in the second step, the thickness of the mica sheets is graded as follows: the first grade is 14-16 μm, the second grade is 17-19 μm, the third grade is 20-22 μm, the fourth grade is 22-24 μm, the fifth grade is 26-30 μm, the sixth grade is 31-35 μm, the seventh grade is 36-40 μm, and the eighth grade is 41-45 μm.

Further, the invention also provides a silver paste preparation method which specifically comprises the following steps:

s41, preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight:

1400-1600 parts of silver mud,

the adhesive is used in the range of 500-700,

100-300 parts of terpineol,

30.5 to 32.5 portions of bismuth oxide,

20-28 parts of lead borate, namely lead borate,

80-120 parts of ethylene glycol ethyl ether;

s42, putting the silver paste raw material to be prepared into a porcelain bottle;

s43, tightly covering and sealing, then placing the ball mill for operation, and paying attention to prevent the ceramic balls from being broken during operation;

s44, controlling the ball milling time to be 100 +/-10 hours, and controlling the running speed of the ball mill to be 75 +/-5 revolutions per minute;

s45, filtering the normal small sample into a container by using a 170-180-mesh sieve, and storing the container in a clean and light-proof environment for later use;

the silver mud comprises the following components in percentage by weight: 850-1050 parts of silver carbonate, 4.5-5.0 parts of rosin, 3-8 parts of collodion, 1750-1850 parts of n-butyl alcohol and 75-80 parts of triethanolamine; wherein, the silver carbonate comprises the following components in percentage by weight: 10-15 parts of silver nitrate, 50-60 parts of ethanol, 4-8 parts of rosin, 30-50 parts of sodium carbonate and 150-200 parts of distilled water;

the adhesive comprises the following components in percentage by weight: 250-270 parts of terpineol, 35-50 parts of ethyl cellulose and 460-470 parts of ethylene glycol ethyl ether.

Further, the invention also provides a preparation method of the silver mud, which comprises the following steps:

s51, weighing 950-1000g of silver carbonate powder, pouring the silver carbonate powder into a stainless steel pot, pouring 1700-1800me n-butyl alcohol, heating and stirring;

s52, when the temperature is raised to 80-90 ℃, 4-5g of rosin powder and 4.5-6.5g of collodion are poured into the mixture and are continuously stirred;

s53, when the temperature reaches 90-95 ℃, dripping 78-79g of n-butanol and 78-79g of triethanolamine by using a separating funnel, stopping heating, keeping the temperature at 93 +/-1 ℃, dripping for 2-3 hours, and continuously keeping the temperature for 45-50 minutes, wherein the temperature is still 93 +/-1 ℃;

s54, taking out the silver mud, cooling for 10-12 hours, washing for 5-6 times by using absolute ethyl alcohol, removing impurities, then placing in a ventilation opening, naturally drying, and grinding and storing the dried silver mud;

s55, putting the milled silver mud in a dry, dark and clean place to prevent dust.

Further, the invention also provides a preparation method of the silver carbonate, which comprises the following steps:

s61, weighing 5-7g of rosin, grinding into powder, adding the powder into 50-58g of 99.5% ethanol, and dissolving into yellow brown liquid, namely 9% rosin water;

s62, adding 150-170me distilled water into 35-45g of sodium carbonate, heating to fully dissolve the sodium carbonate into a colorless and transparent sodium carbonate solution, and cooling for later use;

s63, adding 100-140g of silver nitrate into 250-300me of distilled water, stirring for 15-20 minutes, pouring 10-14me of rosin water, and continuously stirring for a plurality of minutes, wherein the rotating speed of a stirrer is 160-180 r/min;

s64, gradually dropping a sodium carbonate solution into a silver nitrate solution by using a separating funnel, stopping adding the sodium carbonate solution when the reactant is dropped into pink and alkaline by using 1% phenolphthalein solution after the reactant is dropped into the silver nitrate solution within 2-3 hours, and continuously stirring for a plurality of minutes;

s65, spreading filter paper in a porcelain funnel, pouring the filter paper into the prepared silver carbonate solution for filtering, washing with distilled water and performing suction filtration until a washing solution is not alkaline, and dripping 1% phenolphthalein solution into the discharged washing water until the washing water is not red;

s66, drying the washed silver carbonate powder in an oven at the temperature of 55-60 ℃ for 5-7 days until no moisture exists, so that the silver carbonate is light yellow powder.

Furthermore, the invention also provides a preparation method of the adhesive, which comprises the steps of weighing 250-270g of terpineol, 40-45g of ethyl cellulose and 450-470g of ethylene glycol ethyl ether, mixing and stirring until the ethyl cellulose is completely dissolved.

Further, in the step one, green, black, specks, impurities, bubbles, unequal utilization rate and low-grade mica sheets which account for more than 5 percent of the total area of the mica sheets are removed during the selection of the mica sheets, and severe burrs, cracks and uneven parts at the edges of the mica sheets are repaired; when the mica sheet is stripped, the uneven thickness and cracks of the edge of the mica are removed, and if bubbles and black spots are found, a small hole is pricked by using a pricker.

Compared with the prior art, the invention has the following beneficial effects:

the silver content can be effectively improved through the self-made silver carbonate, so that the silver content of the silver carbonate is kept between 74 and 78 percent, wherein during preparation of the silver carbonate, 99.5 percent ethanol and rosin are adopted, and the effects of preventing oxidation and improving the brightness of the silver carbonate can be effectively achieved; when the silver mud is prepared, the collodion can be added to effectively improve the toughness of the silver mud, the added triethanolamine can play a role of an emulsifier to realize thickening and maintain pH balance, an alkaline environment is provided to promote the hydrolysis of silver carbonate, the coating effect is good, the fine and bright white characteristics of the silver mud paste are effectively improved, the added n-butyl alcohol can be used as a solvent for preparing the silver mud to improve the reaction efficiency of the silver carbonate, rosin, collodion and triethanolamine, and the silver mud prepared by adopting the raw materials can effectively ensure that the silver content in the silver mud is maintained above 80%; the special adhesive is prepared and applied, the added ethyl cellulose is used as an organic carrier, the smoothness of the silver paste in use can be improved, and the added glycol ethyl ether is used as a diluent solvent, so that the dissolution of terpineol and ethyl cellulose can be effectively ensured; when the silver paste is prepared, the added silver mud is prepared from the silver carbonate prepared by the method, so that the silver content can be effectively ensured, meanwhile, the adhesive added when the silver paste is prepared can improve the lubrication degree of the silver paste in use, the added bismuth oxide has extremely high oxygen ion conductivity, and the added lead borate as a drier has a drying effect;

when the silver paste is coated on the surface of the mica sheet, the solvent can be quickly evaporated under the action of the collodion so that a layer of film is formed on the surface of the mica sheet;

the adhesive force is improved by adding the prepared adhesive, the silver paste and the mica sheet are easier to be co-melted during sintering and infiltration, a new uniform phase state is formed, the adhesive force of a silver layer is enhanced, and the adhesive effect of the mica sheet is effectively improved;

adopt when preparing silver paste be green pollution-free raw materials, low in production cost, with silver paste coating on the mica sheet through seal silver and burn the back that oozes, through carrying out withstand voltage test, insulation resistance test, survey loss tangent value, condenser temperature coefficient and capacity stability test to the product of production, can effectively avoid the defective rate of product, test step by step simultaneously, classify the finished product that tests out, effectively reduce the raw materials waste that the defective products caused, accord with the large-scale production demand of mica sheet discoloration production.

Drawings

FIG. 1 is a flow chart of the process for making a mica sheet capacitor of the present invention.

FIG. 2 is a diagram of a mica sheet subjected to a preparation process employing the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained by combining the specific embodiments.

Example 1

As shown in fig. 1, the specific operation method of the preparation process of the mica sheet capacitor comprises the following steps:

the method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness;

step two: classifying the thickness of the mica sheets: classifying the thickness of the flake mica in the step by using a dial indicator, wherein the allowable error of each grade of specification is +/-1 mu m;

step three: baking the mica sheet: heating a muffle furnace to 570 ℃ and keeping the temperature constant, slightly placing mica sheets with the size specification of 14X14 and the thickness specification of 26-30 μm in a metal mesh disc, uniformly placing the mica sheets in the furnace, closing a furnace door for roasting for 5 minutes, clamping the metal mesh disc by using long-handle tweezers, placing the metal mesh disc on an operation table, and slightly clamping the metal mesh disc in a container by using the tweezers;

step four: cleaning: putting the mica sheets baked in the above steps into boiling distilled water, adding about 1% ammonia water for rinsing, shaking a mesh screen during rinsing, then rinsing with distilled water for several times, taking out after water drops dry, and putting in a copper wire mesh tray; putting the cleaned mica sheets into an oven at the temperature of 160 ℃ for drying until the mica sheets are completely dried, and taking out the mica sheets;

step five: silver paste preparation:

s41, preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight:

the silver mud 1400 is mixed with the silver mud,

the adhesive (500) is applied to the substrate,

the terpineol content is 100 percent,

30.5 parts of bismuth oxide, namely,

a lead borate (20) in an amount of,

ethylene glycol ethyl ether 80;

s42, putting the silver paste raw material to be prepared into a porcelain bottle;

s43, after tightly covering and sealing, putting the ball mill to operate, and during operation, paying attention to prevent the ceramic balls from being cracked;

s44, controlling the ball milling time to be 100 hours, and controlling the running speed of the ball mill to be 75 r/m;

s45, filtering the normal small sample specimen by using a 170-mesh sieve, putting the filtered small sample specimen into a container, and storing the filtered small sample specimen in a clean and light-proof environment for later use;

the preparation method of the silver mud specifically comprises the following steps:

s51, weighing 950g of silver carbonate powder, pouring the silver carbonate powder into a stainless steel pot, pouring 1700me of n-butyl alcohol, heating and stirring;

s52, when the temperature rises to 80 ℃, 4g of rosin powder and 4.5g of collodion are added and stirred continuously;

s53, when the temperature reaches 90 ℃, dripping 78g of n-butanol and 78g of triethanolamine by using a separating funnel, stopping heating, keeping the temperature at 92 ℃, continuing to keep the temperature for 45 minutes after dripping for 2 hours, and keeping the temperature at 93 ℃;

s54, taking out the silver mud, cooling for 10 hours, washing for 5 times by using absolute ethyl alcohol, removing impurities, then placing the silver mud in a ventilation opening, naturally drying, grinding the dried silver mud and storing the ground silver mud;

s55, putting the milled silver mud in a dry, dark and clean place to prevent dust;

the preparation method of the silver carbonate specifically comprises the following steps:

s61, weighing 5g of rosin, grinding the rosin into powder, adding the powder into 50g of 99.5% ethanol, and dissolving the powder into yellow brown liquid, namely 9% rosin water;

s62, adding 150me of distilled water into 35g of sodium carbonate, heating to fully dissolve the sodium carbonate into a colorless and transparent sodium carbonate solution, and cooling for later use;

s63, adding 100g of silver nitrate into 250me of distilled water, stirring for 15 minutes, pouring 10me of rosin water, and continuously stirring for a plurality of minutes at the rotating speed of 160 rpm;

s64, gradually dropping a sodium carbonate solution into a silver nitrate solution by using a separating funnel, stopping adding the sodium carbonate solution when the reactant is dropped into pink and alkaline by using a 1% phenolphthalein solution after the reactant is dropped into the silver nitrate solution within 2 hours, and continuously stirring for a plurality of minutes;

s65, spreading filter paper in a porcelain funnel, pouring the filter paper into the prepared silver carbonate solution for filtering, washing with distilled water and performing suction filtration until a washing solution is not alkaline, and dripping 1% phenolphthalein solution into the discharged washing water until the washing water is not red;

s66, drying the washed silver carbonate powder in a drying oven at 55 ℃ for 5 days until no water exists, so that the silver carbonate is light yellow powder;

the preparation method of the adhesive comprises the steps of weighing 250g of terpineol, 40g of ethyl cellulose and 450g of ethylene glycol ethyl ether, mixing and stirring until the ethyl cellulose is completely dissolved;

step six: preparing a screen:

s11, paving a polyester film on an insulating plate, and carving the required silver coating size on the insulating plate by using a blade and a steel plate ruler, wherein the size of a screen printing frame is (16 +/-0.3) X (16 +/-0.3);

s12, fastening a nylon screen on the frame, and attaching the pre-engraved polyester film on the nylon screen by using silver paste;

step seven: silver printing:

s21, adding qualified silver paste sieved by a 170-mesh sieve into an enamel tray by a spoon, and adjusting the concentration of the silver paste by ethylene glycol ether to make the silver paste suitable for printing;

s22, turning on a power switch, and adjusting a hot plate voltage regulator until the temperature of the wafer baking plate is 90 ℃;

s23, the sheets are neatly and lightly placed into a printing hopper, and the small amount of sheets is placed each time, so that the mica sheets are prevented from being damaged;

s24, absorbing the mica sheets on a workbench, adhering a proper amount of silver paste on the vacuum rubber brush, pressing down the frame attached with the printing screen, and flatly and uniformly scraping on the screen with force;

s25, sucking the printed sheets on a sheet drying plate on an electric heating sheet, drying the sheets and pouring the sheets into a sheet storage tray, printing the reverse side of the printed sheets in a hopper after all the printed sheets are printed, paying attention to the fact that silver layers on the two sides are overlapped when the reverse side is printed, and printing the silver layers on the two sides of each batch of sheets by using a sample plate;

step eight: and (3) sintering and infiltrating:

s31, checking whether the furnace temperature reaches the regulated temperature of 280 ℃;

s32, scattering the rectangular sheets with the two sides printed on the metal mesh plate, putting the rectangular sheets into a sintering and infiltrating furnace for sintering and infiltrating, wherein the first sintering is carried out at the low temperature of 300 ℃ for 10 minutes;

s33, after low-temperature burning, sorting according to different models and thicknesses, carrying out high-temperature 570 ℃ sintering infiltration on qualified mica sheets after sorting for 2 minutes, then dragging the mica sheets to a furnace mouth for stopping for 2 minutes, and then taking out;

step nine: and (3) single-chip withstand voltage test: carrying out pressure resistance test on the sintered mica sheets one by using an automatic pressure resistance machine or manually, wherein the pressure resistance test range of the 14X14 specification size is 750-1250V, if pressure resistance breakdown and damage are eliminated in the pressure measurement process, and if the sintered mica sheets are stored for a long time, the sintered mica sheets can be used after yellowing or oxidation phenomena occur by adopting a high-temperature furnace with the temperature of 450 ℃;

step ten: and (3) testing the insulation resistance: testing mica sheet capacitors with qualified test voltage one by using a high-resistance meter, wherein the voltage used for testing the resistors is 100-500V, the insulation resistance requirement is more than or equal to 2000M omega, the capacitors with qualified test voltage are placed in an oven to avoid being damped, and the capacitors are charged before the insulation resistance is tested and then placed in a container;

step eleven: measuring loss tangent: the tan delta values of finished capacitors, measured individually using a loss angle measuring instrument of 10-100pF, 100-1000pF, measured for capacitors having a loss tangent (tan delta) of different nominal capacities, should not be greater than the following specifications:

nominal capacity (PF): 20-24, tangent (tan δ value): 23.5X10 ^-4 ；

Nominal capacity (PF): 27, tangent (tan δ value): 21X10 ^-4 ；

Nominal capacity (PF): 30, tangent (tan δ value): 20X10 ^-4 ；

Nominal capacity (PF): 33, tangent (tan δ value): 18X10 ^-4 ；

Nominal capacity (PF): 36-39, tangent (tan δ value): 16X10 ^-4 ；

Nominal capacity (PF): 43-47, tangent (tan δ value): 15.5X10 ^-4 ；

Step twelve: measuring the temperature coefficient and the capacity stability of the mica sheet capacitor by drawing;

s71: randomly selecting one mica sheet capacitor with the same specification as a standard, and numbering other tested mica sheet capacitors;

s72: measuring the capacity error of the numbered capacitor by using an error sorter, and recording the capacity error as a first measurement difference value;

s73: placing the mica sheet capacitor tested at room temperature in a drying oven at room temperature plus 50 ℃, heating for 30 minutes, taking out from the drying oven, immediately testing the capacity error, and recording the capacity error as a second difference value;

s74: cooling the capacitor subjected to the error test during temperature rise at room temperature, measuring the capacity error of the capacitor by using an error sorter after 1 hour, and recording the capacity error as a third difference value;

s75: calculating the measured values:

the second difference-the first difference = the temperature coefficient of the capacitor;

the third difference measurement-the first difference measurement = the stability;

s76: classifying the mica sheet capacitors in different intervals:

b type: the temperature coefficient of the capacitor is less than or equal to 200X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.5 percent;

class C: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 100X10 ^-6 (ii) a The volume stability is less than or equal to 0.2;

and D type: the temperature coefficient of the capacitor is less than or equal to 50X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.1 percent;

through testing, the products which do not conform to the D group are allowed to be reworked, and the products which do not conform to the requirements of the D group are degraded after being reworked.

Example 2

As shown in fig. 1, the specific operation method of the preparation process of the mica sheet capacitor comprises the following steps:

the method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness;

step two: classifying the thickness of the mica sheets: classifying the thickness of the sheet mica in the above step by a dial indicator, wherein the allowable error of each specification is +/-1 μm;

step three: baking a mica sheet: heating a muffle furnace to 570 ℃ and keeping the temperature constant, slightly placing mica sheets with the size specification of 14X14 and the thickness specification of 26-30 μm in a metal mesh disc, uniformly placing the mica sheets in the furnace, closing a furnace door for roasting for 5 minutes, clamping the metal mesh disc by using long-handle tweezers, placing the metal mesh disc on an operation table, and slightly clamping the metal mesh disc in a container by using the tweezers;

step four: cleaning: putting the mica sheets baked in the above steps into boiling distilled water, adding about 1% ammonia water for rinsing, shaking a mesh screen during rinsing, then rinsing with distilled water for several times, taking out after water drops dry, and putting in a copper wire mesh tray; putting the cleaned mica sheets into an oven at the temperature of 160 ℃ for drying until all the mica sheets are dried, and taking out the mica sheets;

step five: silver paste preparation:

s41, preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight:

the silver mud is 1500, and the silver mud is,

the adhesive (600) is applied to the substrate,

the terpineol is 200 parts by weight,

31.5 parts of bismuth oxide, namely,

the lead borate 24 is added to the mixture of lead borate and lead borate,

ethylene glycol ethyl ether 100;

s42, putting the silver paste raw material to be prepared into a porcelain bottle;

s43, after tightly covering and sealing, putting the ball mill to operate, and during operation, paying attention to prevent the ceramic balls from being cracked;

s44, controlling the ball milling time to be 100 hours, and controlling the running speed of the ball mill to be 75 revolutions per minute;

s45, filtering the normal small sample specimen by using a 170-mesh sieve, putting the filtered small sample specimen into a container, and storing the filtered small sample specimen in a clean and light-proof environment for later use;

the preparation method of the silver mud specifically comprises the following steps:

s51, weighing 975g of silver carbonate powder, pouring the silver carbonate powder into a stainless steel pot, pouring 1750me of n-butyl alcohol, heating and stirring;

s52, when the temperature is raised to 80 ℃,4.5g of rosin powder and 5.5g of collodion are poured into the mixture and continuously stirred;

s53, when the temperature reaches 90 ℃, dripping 78.5g of n-butanol and 78.5g of triethanolamine by using a separating funnel, stopping heating, keeping the temperature at 93 ℃, finishing dripping for 2 hours, and keeping the temperature for 45 minutes, wherein the temperature is still 93 ℃;

s54, taking out the silver mud, cooling for 10 hours, washing for 5 times by using absolute ethyl alcohol, removing impurities, then placing the silver mud in a ventilation opening, naturally drying, grinding the dried silver mud and storing the ground silver mud;

s55, placing the grinded silver mud in a dry, dark and clean place to prevent dust;

the preparation method of the silver carbonate specifically comprises the following steps:

s61, weighing 6g of rosin, grinding into powder, adding 54g of 99.5% ethanol, and dissolving into yellowish brown liquid, namely 9% rosin water;

s62, adding 160me distilled water into 40g of sodium carbonate, heating to fully dissolve the sodium carbonate into a colorless and transparent sodium carbonate solution, and cooling for later use;

s63, adding 120g of silver nitrate into 275me of distilled water, stirring for 15 minutes, pouring 12me of rosin water, and continuously stirring for a plurality of minutes at the rotation speed of 160 rpm of a stirrer;

s64, gradually dropping a sodium carbonate solution into a silver nitrate solution by using a separating funnel, stopping adding the sodium carbonate solution when the reactant is dripped into pink and alkaline by using a 1% phenolphthalein solution after the dripping is finished in 2 hours, and continuously stirring for a plurality of minutes;

s65, spreading filter paper in a porcelain funnel, pouring the filter paper into the prepared silver carbonate solution for filtering, washing with distilled water and performing suction filtration until a washing solution is not alkaline, and dripping 1% phenolphthalein solution into the discharged washing water until the washing water is not red;

s66, drying the washed silver carbonate powder in a drying oven at 55 ℃ for 5 days until no water exists, so that the silver carbonate is light yellow powder;

the preparation method of the adhesive comprises the steps of weighing 260g of terpineol, 42.5g of ethyl cellulose and 460g of ethylene glycol ethyl ether, mixing and stirring until the ethyl cellulose is completely dissolved;

step six: preparing a screen:

s11, paving a polyester film on an insulating plate, and engraving the required silver coating size on the insulating plate by using a blade and a steel plate ruler, wherein the size of a screen printing frame is (16 +/-0.3) X (16 +/-0.3);

s12, fastening a nylon screen on the frame, and attaching the pre-engraved polyester film on the nylon screen by using silver paste;

step seven: silver printing:

s21, adding qualified silver paste sieved by a 170-mesh sieve into an enamel tray by a spoon, and adjusting the concentration of the silver paste by ethylene glycol ether to make the silver paste suitable for printing;

s22, turning on a power switch, and adjusting the electric hot plate voltage regulator until the temperature of the baking sheet plate is 90 ℃;

s23, the sheets are neatly and lightly placed into a printing hopper, and the small amount of sheets is placed each time, so that the mica sheets are prevented from being damaged;

s24, absorbing the mica sheet on a workbench, adhering a proper amount of silver paste on a vacuum rubber brush, pressing down the frame pasted with the printing screen, and flatly and uniformly scraping the frame on the screen with force;

s25, sucking the printed sheets on a sheet drying plate on an electric heating sheet, drying the printed sheets, pouring the dried sheets into a sheet storage tray, printing the reverse side of the printed sheets after all the printed sheets are printed, and paying attention to the fact that silver layers on the two sides are overlapped when the reverse side is printed, wherein the silver layers on the two sides of each batch of the printed sheets are printed by one sample plate;

step eight: and (3) sintering and infiltrating:

s31, checking whether the furnace temperature reaches the specified 290 ℃;

s32, scattering the rectangular sheets with the two sides printed on the metal mesh plate, putting the rectangular sheets into a sintering and infiltrating furnace for sintering and infiltrating, wherein the first sintering is carried out at the low temperature of 300 ℃ for 10 minutes;

s33, after low-temperature burning out, checking and sorting according to different models and thicknesses, carrying out high-temperature 570-DEG C burning infiltration on qualified mica sheets after checking and sorting for 2-3 minutes, then dragging the mica sheets to a furnace mouth, stopping for 2 minutes, and taking out;

step nine: and (3) single-chip withstand voltage test: carrying out pressure resistance test on the sintered mica sheets one by using an automatic pressure resistance machine or manually, wherein the pressure resistance test range of the 14X14 specification size is 750-1250V, if pressure resistance breakdown and damage are eliminated in the pressure measurement process, and if the sintered mica sheets are stored for a long time, the sintered mica sheets can be used after yellowing or oxidation phenomena occur by adopting a high-temperature furnace with the temperature of 450 ℃;

step ten: and (3) testing the insulation resistance: testing mica sheet capacitors with qualified test voltage one by using a high-resistance meter, wherein the voltage used for testing the resistors is 100-500V, the insulation resistance requirement is more than or equal to 2000M omega, the capacitors with qualified test voltage are placed in an oven to avoid being damped, and the capacitors are charged before the insulation resistance is tested and then placed in a container;

step eleven: measuring loss tangent value: the tan delta values measured for finished capacitors using a loss angle measuring instrument of 10-100pF, 100-1000pF, measured individually for capacitors having loss tangent (tan delta) values of different nominal capacities should not be greater than the following specifications:

nominal capacity (PF): 20-24, tangent (tan δ value): 23.5X10 ^-4 ；

Nominal capacity (PF): 27, tangent (tan δ value): 21X10 ^-4 ；

Nominal capacity (PF): 30, tangent (tan δ value): 20X10 ^-4 ；

Nominal capacity (PF): 33, tangent (tan δ value): 18X10 ^-4 ；

Nominal capacity (PF): 36-39, tan delta value: 16X10 ^-4 ；

Nominal capacity (PF): 43-47, tangent (tan δ value): 15.5X10 ^-4 ；

Step twelve: measuring the temperature coefficient and the capacity stability of the mica sheet capacitor by drawing;

s71: randomly selecting one of the mica sheet capacitors with the same specification as a standard, and numbering other tested mica sheet capacitors;

s72: measuring the capacity error of the numbered capacitor by using an error sorter, and recording the capacity error as a first measurement difference value;

s73: placing the mica sheet capacitor tested at room temperature in a drying oven at room temperature plus 50 ℃, heating for 30 minutes, taking out from the drying oven, immediately testing the capacity error, and recording the capacity error as a second difference value;

s74: cooling the capacitor subjected to the error test during temperature rise at room temperature, measuring the capacity error of the capacitor by using an error sorter after 1 hour, and recording the capacity error as a third difference value;

s75: the values measured above are calculated:

second difference measurement-first difference measurement = capacitance temperature coefficient;

the third difference measurement-the first difference measurement = the stability;

s76: classifying the mica sheet capacitors in different intervals:

b type: the temperature coefficient of the capacitor is less than or equal to 200X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.5 percent;

class C: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 100X10 ^-6 (ii) a The volume stability is less than or equal to 0.2;

and D is: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 50X10 ^-6 (ii) a The volume stability is less than or equal to 0.1 percent;

through testing, the products which do not conform to the D group are allowed to be reworked, and the products which do not conform to the requirements of the D group are degraded after being reworked.

Example 3

As shown in fig. 1, the specific operation method of the preparation process of the mica sheet capacitor comprises the following steps:

the method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness;

step two: classifying the thickness of the mica sheets: classifying the thickness of the flake mica in the step by using a dial indicator, wherein the allowable error of each grade of specification is +/-1 mu m;

step three: baking the mica sheet: heating a muffle furnace to 570 ℃ and keeping the temperature constant, slightly placing mica sheets with the size specification of 14X14 and the thickness specification of 26-30 μm in a metal mesh disc, uniformly placing the mica sheets in the furnace, closing a furnace door for roasting for 5 minutes, clamping the metal mesh disc by using long-handle tweezers, placing the metal mesh disc on an operation table, and slightly clamping the metal mesh disc in a container by using the tweezers;

step four: cleaning: putting the mica sheets baked in the above steps into boiling distilled water, adding about 1% ammonia water for rinsing, shaking the mesh screen during rinsing, then rinsing with distilled water for several times, taking out after water drops dry, and putting in a copper wire mesh disc; putting the cleaned mica sheets into an oven at the temperature of 160 ℃ for drying until the mica sheets are completely dried, and taking out the mica sheets;

step five: silver paste preparation:

s41, preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight:

the silver mud (1600) is mixed with silver,

the adhesive (700) is applied to the substrate,

the terpineol content is 300, and the terpineol content is,

32.5 of bismuth oxide, and the bismuth oxide,

the lead (28) borate is added to the lead (II) borate,

ethylene glycol ethyl ether 100;

s42, putting the silver paste raw material to be prepared into a porcelain bottle;

s43, after tightly covering and sealing, putting the ball mill to operate, and during operation, paying attention to prevent the ceramic balls from being cracked;

s44, controlling the ball milling time to be 100 hours, and controlling the running speed of the ball mill to be 75 revolutions per minute;

s45, filtering the normal small sample specimen by using a 170-mesh sieve, putting the filtered small sample specimen into a container, and storing the filtered small sample specimen in a clean and light-proof environment for later use;

the preparation method of the silver mud specifically comprises the following steps:

s51, weighing 1000g of silver carbonate powder, pouring the silver carbonate powder into a stainless steel pot, pouring 1800me n-butyl alcohol, heating and stirring;

s52, when the temperature is raised to 80 ℃, 5g of rosin powder and 6.5g of collodion are poured into the mixture and continuously stirred;

s53, when the temperature reaches 90 ℃, dripping 79g of n-butanol and 79g of triethanolamine by using a separating funnel, stopping heating, keeping the temperature at 93 ℃, finishing dripping within 2 hours, and continuously preserving the temperature for 45 minutes, wherein the temperature is still 93 ℃;

s54, taking out the silver mud, cooling for 10 hours, washing for 5 times by using absolute ethyl alcohol, removing impurities, then placing the silver mud in a ventilation opening, naturally drying, grinding the dried silver mud and storing the ground silver mud;

s55, putting the milled silver mud in a dry, dark and clean place to prevent dust;

the preparation method of the silver carbonate specifically comprises the following steps:

s61, weighing 7g of rosin, grinding the rosin into powder, adding the powder into 58g of 99.5% ethanol, and dissolving the powder into yellowish-brown liquid, namely 9% rosin water;

s62, adding 170me distilled water into 45g of sodium carbonate, heating to fully dissolve the sodium carbonate into a colorless and transparent sodium carbonate solution, and cooling for later use;

s63, adding 140g of silver nitrate into 300me of distilled water, stirring for 15 minutes, pouring 14me of rosin water, and continuously stirring for a plurality of minutes at the rotating speed of 160 rpm of a stirrer;

s64, gradually dropping a sodium carbonate solution into a silver nitrate solution by using a separating funnel, stopping adding the sodium carbonate solution when the reactant is dripped into pink and alkaline by using a 1% phenolphthalein solution after the dripping is finished in 2 hours, and continuously stirring for a plurality of minutes;

s65, spreading filter paper in a porcelain funnel, pouring the filter paper into a prepared silver carbonate solution for filtering, washing with distilled water and performing suction filtration until a washing liquid is not alkaline, and dropping 1% phenolphthalein solution into the discharged washing water until the washing water is not red;

s66, drying the washed silver carbonate powder in an oven at 55 ℃ for 5 days until no moisture exists, so that the silver carbonate is light yellow powder;

the preparation method of the adhesive comprises the steps of weighing 270g of terpineol, 45g of ethyl cellulose and 470g of ethylene glycol ethyl ether, mixing and stirring until the ethyl cellulose is completely dissolved;

step six: preparing a screen:

s11, paving a polyester film on an insulating plate, and engraving the required silver coating size on the insulating plate by using a blade and a steel plate ruler, wherein the size of a screen printing frame is (16 +/-0.3) X (16 +/-0.3);

s12, fastening a nylon screen on the frame, and attaching the pre-engraved polyester film on the nylon screen by using silver paste;

step seven: silver printing:

s21, adding qualified silver paste sieved by a 170-mesh sieve into an enamel tray by a spoon, and adjusting the concentration of the silver paste by ethylene glycol ether to make the silver paste suitable for printing;

s22, turning on a power switch, and adjusting a hot plate voltage regulator until the temperature of the wafer baking plate is 90 ℃;

s23, the sheets are neatly and lightly placed into a printing hopper, and the small amount of sheets is placed each time, so that the mica sheets are prevented from being damaged;

s24, absorbing the mica sheet on a workbench, adhering a proper amount of silver paste on a vacuum rubber brush, pressing down the frame pasted with the printing screen, and flatly and uniformly scraping the frame on the screen with force;

s25, sucking the printed sheets on a sheet drying plate on an electric heating sheet, drying the sheets and pouring the sheets into a sheet storage tray, printing the reverse side of the printed sheets in a hopper after all the printed sheets are printed, paying attention to the fact that silver layers on the two sides are overlapped when the reverse side is printed, and printing the silver layers on the two sides of each batch of sheets by using a sample plate;

step eight: and (3) sintering and infiltrating:

s31, checking whether the furnace temperature reaches the specified 300 ℃;

s32, scattering the rectangular sheets with the two printed surfaces on a metal mesh disc, putting the metal mesh disc into a sintering and infiltrating furnace for sintering and infiltrating, wherein the temperature is 300 ℃ at the first low temperature for 10 minutes;

s33, after low-temperature burning, sorting according to different models and thicknesses, carrying out high-temperature 570 ℃ sintering infiltration on qualified mica sheets after sorting for 2 minutes, then dragging the mica sheets to a furnace mouth for stopping for 2 minutes, and then taking out;

step nine: and (3) single-chip voltage withstanding test: carrying out pressure resistance test on the sintered mica sheets one by using an automatic pressure resistance machine or manually, wherein the pressure resistance test range of the 14X14 specification size is 750-1250V, if pressure resistance breakdown and damage are eliminated in the pressure measurement process, yellowing or oxidation phenomena can occur after the sintered mica sheets are stored for a long time, and the sintered mica sheets can be used after being sintered by using a high-temperature furnace at the temperature of 450 ℃;

step ten: and (3) testing the insulation resistance: testing mica sheet capacitors with qualified test voltage one by using a high-resistance meter, wherein the voltage used for testing the resistors is 100-500V, the insulation resistance requirement is more than or equal to 2000M omega, the capacitors with qualified test voltage are placed in an oven to avoid being damped, and the capacitors are charged before the insulation resistance is tested and then placed in a container;

step eleven: measuring loss tangent value: the tan delta values measured for finished capacitors using a loss angle measuring instrument of 10-100pF, 100-1000pF, measured individually for capacitors having loss tangent (tan delta) values of different nominal capacities should not be greater than the following specifications:

nominal capacity (PF): 20-24, tan (tan δ value): 23.5X10 ^-4 ；

Nominal capacity (PF): 27, tangent (tan δ value): 21X10 ^-4 ；

Nominal capacity (PF): 30, tangent (tan δ value): 20X10 ^-4 ；

Nominal capacity (PF): 33, tangent (tan δ value): 18X10 ^-4 ；

Nominal capacity (PF): 36-39, tangent (tan δ value): 16X10 ^-4 ；

Nominal capacity (PF): 43-47, tangent (tan δ value): 15.5X10 ^-4 ；

Step twelve: measuring the temperature coefficient and the capacity stability of the mica sheet capacitor in a drawing mode;

s71: randomly selecting one of the mica sheet capacitors with the same specification as a standard, and numbering other tested mica sheet capacitors;

s72: measuring the capacity error of the numbered capacitor by using an error sorter, and recording the capacity error as a first measurement difference value;

s73: placing the mica sheet capacitor tested at room temperature in a drying oven at room temperature plus 50 ℃, heating for 30 minutes, taking out from the drying oven, immediately testing the capacity error, and recording the capacity error as a second difference value;

s74: cooling the capacitor subjected to the error test during temperature rise at room temperature, measuring the capacity error of the capacitor by using an error sorter after 1 hour, and recording the capacity error as a third difference value;

s75: the values measured above are calculated:

second difference measurement-first difference measurement = capacitance temperature coefficient;

third difference measurement-first difference measurement = stability;

s76: classifying the mica sheet capacitors in different intervals:

b type: the temperature coefficient of the capacitor is less than or equal to 200X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.5 percent;

class C: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 100X10 ^-6 (ii) a The volume stability is less than or equal to 0.2;

and D is: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 50X10 ^-6 (ii) a The volume stability is less than or equal to 0.1 percent;

through testing, the products which do not accord with the D group are allowed to be reworked, and the products which do not accord with the D group after reworking are degraded.

The mica sheet capacitors obtained in the above examples 1 to 3 were subjected to withstand voltage test, insulation resistance test, loss tangent test, capacitor temperature coefficient and capacity stability test, respectively, and the specific results are shown in table 1:

TABLE 1

The tests of examples 1-3 above show that: the product detection in three groups of embodiments prepared by the preparation process of the mica sheet capacitor disclosed by the invention shows that: the prepared products are all in a voltage withstanding test range, an insulation resistance requirement range and a loss tangent value specified range, and meanwhile, when the temperature coefficient and the capacity stability are measured, three groups of products can be divided into three groups through comparison of data, wherein the product prepared in the embodiment 1 belongs to a B-type product, the product prepared in the embodiment 2 belongs to a C-type product, and the product prepared in the embodiment 3 belongs to a D-type product.

The silver content can be effectively improved through the self-made silver carbonate, so that the silver content of the silver carbonate is kept between 74 and 78 percent, wherein during preparation of the silver carbonate, 99.5 percent ethanol and rosin are adopted, and the effects of preventing oxidation and improving the brightness of the silver carbonate can be effectively achieved; when the silver mud is prepared, the collodion is added to effectively improve the toughness of the silver mud, the added triethanolamine can play a role of an emulsifier to realize thickening and maintain pH balance, an alkaline environment is provided to promote the hydrolysis of silver carbonate, the coating effect is good, meanwhile, the fine and bright white characteristics of the silver mud paste are effectively improved, the added n-butyl alcohol can be used as a solvent for preparing the silver mud to improve the reaction efficiency of the silver carbonate, rosin, collodion and triethanolamine, and the silver mud prepared by adopting the raw materials can effectively ensure that the silver content in the silver mud is maintained above 80%; the special adhesive is prepared and applied, the added ethyl cellulose is used as an organic carrier, the smoothness of the silver paste in use can be improved, and the added glycol ethyl ether is used as a diluent solvent, so that the dissolution of terpineol and ethyl cellulose can be effectively ensured; when the silver paste is prepared, the added silver mud is prepared from the silver carbonate prepared by the method, so that the silver content can be effectively ensured, meanwhile, the adhesive added when the silver paste is prepared can improve the lubrication degree of the silver paste in use, the added bismuth oxide has extremely high oxygen ion conductivity, and the added lead borate as a drier has a drying effect;

when the silver paste is coated on the surface of the mica sheet, the solvent can be quickly evaporated under the action of the collodion, so that a layer of film is formed on the surface of the mica sheet;

the adhesive force is improved by adding the prepared adhesive, the silver paste and the mica sheet are easier to be co-melted during burning and infiltration, a new uniform phase state is formed, the adhesive force of the silver layer is enhanced, and the adhesive effect of the silver layer on the surface of the mica sheet is effectively improved; the damage of a surface silver layer caused by external influence when the single mica sheet capacitor is used is avoided, and on the other hand, the adhesion stability of the surface silver layer can be effectively improved when the mica sheet capacitor is assembled, so that the damage of the silver layer caused by external friction is avoided;

adopt when preparing silver paste be green pollution-free raw materials, low in production cost, with silver paste coating on the mica sheet through seal silver and burn the back that oozes, through carrying out withstand voltage test, insulation resistance test, survey loss tangent value, condenser temperature coefficient and capacity stability test to the product of production, can effectively avoid the defective rate of product, test step by step simultaneously, classify the finished product that tests out, effectively reduce the raw materials waste that the defective products caused, accord with the large-scale production demand of mica sheet discoloration production.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (7)

1. The preparation process of the mica sheet capacitor is characterized by comprising the following steps: the specific operation method comprises the following steps:

the method comprises the following steps: selecting and stripping mica sheets: selecting and trimming mica slabs, then stripping the selected mica slabs by using a stripping knife, and grading the stripped mica slabs according to the thickness;

step two: classifying the thickness of the mica sheets: classifying the thickness of the flake mica in the step by using a dial indicator, wherein the allowable error of each grade of specification is +/-1 mu m;

step three: baking a mica sheet: heating a muffle furnace to 570 +/-10 ℃, keeping constant temperature, slightly placing mica sheets with the size specification of 14X14 and the thickness specification of 26-30 mu m in a metal mesh disc, uniformly placing the mica sheets in the furnace, closing a furnace door for roasting for 3-8 minutes, clamping the metal mesh disc by using a long-handle forceps clamp, placing the metal mesh disc on an operation table, and slightly clamping the metal mesh disc in a container by using the forceps;

step four: cleaning: putting the mica sheets baked in the above steps into boiling distilled water, adding about 1% ammonia water for rinsing, shaking a mesh screen during rinsing, then rinsing with distilled water for several times, taking out after water drops dry, and putting in a copper wire mesh tray; putting the cleaned mica sheets into an oven at the temperature of 160 +/-20 ℃ for drying until the mica sheets are completely dried, and taking out the mica sheets;

step five: silver paste preparation: preparing silver paste for printing, weighing the following components in percentage by weight: 1400-1600 parts of silver mud, 500-700 parts of adhesive, 100-300 parts of terpineol, 30.5-32.5 parts of bismuth oxide, 20-28 parts of lead borate and 80-120 parts of ethylene glycol ethyl ether;

step six: preparing a screen:

s11, paving a polyester film on an insulating plate, and carving the required silver coating size on the insulating plate by using a blade and a steel plate ruler, wherein the size of a screen printing frame is (16 +/-0.3) X (16 +/-0.3);

s12, fastening a nylon screen on the frame, and attaching the pre-engraved polyester film on the nylon screen by using silver paste;

step seven: silver printing:

s21, adding qualified silver paste sieved by a 170-180-mesh sieve into an enamel tray by a spoon, and adjusting the concentration of the silver paste by ethylene glycol ether to make the silver paste suitable for printing;

s22, turning on a power switch, and adjusting a hot plate voltage regulator until the temperature of the baking sheet plate is 90-100 ℃;

s23, the sheets are neatly and lightly placed into a printing hopper, and the small amount of sheets is placed each time, so that the mica sheets are prevented from being damaged;

s24, absorbing the mica sheet on a workbench, adhering a proper amount of silver paste on a vacuum rubber brush, pressing down the frame pasted with the printing screen, and flatly and uniformly scraping the frame on the screen with force;

s25, sucking the printed sheets on a sheet drying plate on an electric heating sheet, drying the sheets and pouring the sheets into a sheet storage tray, printing the reverse side of the printed sheets in a hopper after all the printed sheets are printed, paying attention to the fact that silver layers on the two sides are overlapped when the reverse side is printed, and printing the silver layers on the two sides of each batch of sheets by using a sample plate;

step eight: and (3) sintering and infiltrating:

s31, checking whether the furnace temperature reaches the specified temperature of 280-300 ℃;

s32, scattering the rectangular sheets with the two printed surfaces on a metal mesh disc, putting the metal mesh disc into a sintering and infiltrating furnace for sintering and infiltrating, wherein the temperature is 300 ℃ at the first low temperature for 10 minutes;

s33, after low-temperature burning out, checking and sorting according to different models and thicknesses, carrying out high-temperature 570 +/-10 ℃ burning infiltration on qualified mica sheets after checking and sorting for 2-3 minutes, then dragging the mica sheets to a furnace mouth for stopping for 2 minutes, and taking out;

step nine: and (3) single-chip withstand voltage test: carrying out pressure resistance test on the sintered mica sheets one by using an automatic pressure resistance machine or manually, wherein the pressure resistance test range of the 14X14 specification size is 750-1250V, if pressure resistance breakdown and damage are eliminated in the pressure measurement process, yellowing or oxidation phenomena can occur after the sintered mica sheets are stored for a long time, and the sintered mica sheets can be used after being sintered by using a high-temperature furnace at the temperature of 450 ℃;

step ten: and (3) testing the insulation resistance: testing mica sheet capacitors with qualified test voltage one by using a high-resistance meter, wherein the voltage used for testing the resistors is 100-500V, the insulation resistance requirement is more than or equal to 2000M omega, the capacitors with qualified test voltage are placed in an oven to avoid being damped, and the capacitors are charged before the insulation resistance is tested and then placed in a container;

step eleven: measuring loss tangent: the tan delta values of finished capacitors, measured individually using a loss angle measuring instrument of 10-100pF, 100-1000pF, measured for capacitors having a loss tangent (tan delta) of different nominal capacities, should not be greater than the following specifications:

nominal capacity (PF): 20-24, tan (tan δ value): 23.5X10 ^-4 ；

Nominal capacity (PF): 27, tangent (tan δ value): 21X10 ^-4 ；

Nominal capacity (PF): 30, tangent (tan δ value): 20X10 ^-4 ；

Nominal capacity (PF): 33, tangent (tan δ value): 18X10 ^-4 ；

Nominal capacity (PF): 36-39, tan delta value: 16X10 ^-4 ；

Nominal capacity (PF): 43-47, tangent (tan δ value): 15.5X10 ^-4 ；

Step twelve: measuring the temperature coefficient and the capacity stability of the mica sheet capacitor in a drawing mode;

s71: randomly selecting one of the mica sheet capacitors with the same specification as a standard, and numbering other tested mica sheet capacitors;

s72: measuring the capacity error of the numbered capacitor by using an error sorter, and recording the capacity error as a first measurement difference value;

s73: placing the mica sheet capacitor tested at room temperature in a drying oven at room temperature plus 50 ℃, heating for 30 minutes, taking out from the drying oven, immediately testing the capacity error, and recording the capacity error as a second difference value;

s74: cooling the capacitor subjected to the error test during temperature rise at room temperature, measuring the capacity error of the capacitor by using an error sorter after 1 hour, and recording the capacity error as a third difference value;

s75: the values measured above are calculated:

second difference measurement-first difference measurement = capacitance temperature coefficient;

third difference measurement-first difference measurement = stability;

s76: classifying mica sheet capacitors in different intervals:

b type: the temperature coefficient of the capacitor is less than or equal to 200X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.5 percent;

class C: the temperature coefficient of the capacitor is 1/DEG C less than or equal to 100X10 ^-6 (ii) a The volume stability is less than or equal to 0.2;

and D type: the temperature coefficient of the capacitor is less than or equal to 50X10 at 1/DEG C ^-6 (ii) a The volume stability is less than or equal to 0.1 percent;

through testing, the products which do not conform to the D group are allowed to be reworked, and the products which do not conform to the requirements of the D group are degraded after being reworked.

2. The process for preparing a mica sheet capacitor as claimed in claim 1, wherein: in the first step, the size specification of the mica sheets is graded as follows: 7X14, 12X12, 14X14, 16X16, 10X20, 19X25, 25X25, 20X30, 13X29, 17X34, 20X34, 30X40, 40X50; in the second step, the thickness of the mica sheets is graded as follows: the first grade is 14-16 μm, the second grade is 17-19 μm, the third grade is 20-22 μm, the fourth grade is 22-24 μm, the fifth grade is 26-30 μm, the sixth grade is 31-35 μm, the seventh grade is 36-40 μm, and the eighth grade is 41-45 μm.

3. The process for preparing a mica sheet capacitor as claimed in claim 1, wherein: the silver paste preparation method in the fifth step comprises the following steps:

s41, preparing silver paste for printing, wherein the silver paste is prepared by weighing the following components in percentage by weight:

1400-1600 parts of silver mud,

the adhesive is used in the range of 500-700,

100-300 parts of terpineol,

30.5 to 32.5 portions of bismuth oxide,

20-28 parts of lead borate, namely lead borate,

80-120 parts of ethylene glycol ethyl ether;

s42, putting the silver paste raw material to be prepared into a porcelain bottle;

s43, tightly covering and sealing, then placing the ball mill for operation, and paying attention to prevent the ceramic balls from being broken during operation;

s44, controlling the ball milling time to be 100 +/-10 hours, and controlling the running speed of the ball mill to be 75 +/-5 revolutions per minute;

s45, filtering the normal small sample specimen by using a 170-180-mesh sieve, putting the filtered small sample specimen into a container, and storing the filtered small sample specimen in a clean and light-proof environment for later use;

the silver mud comprises the following components in percentage by weight: 850-1050 parts of silver carbonate, 4.5-5.0 parts of rosin, 3-8 parts of collodion, 1750-1850 parts of n-butyl alcohol and 75-80 parts of triethanolamine; wherein, the silver carbonate comprises the following components in percentage by weight: 10-15 parts of silver nitrate, 50-60 parts of ethanol, 4-8 parts of rosin, 30-50 parts of sodium carbonate and 150-200 parts of distilled water;

the adhesive comprises the following components in percentage by weight: 250-270 parts of terpineol, 35-50 parts of ethyl cellulose and 460-470 parts of ethylene glycol ethyl ether.

4. The process for preparing a mica sheet capacitor as claimed in claim 3, wherein: the preparation method of the silver mud specifically comprises the following steps:

s51, weighing 950-1000g of silver carbonate powder, pouring the silver carbonate powder into a stainless steel pot, pouring 1700-1800me n-butyl alcohol, heating and stirring;

s52, when the temperature is raised to 80-90 ℃, 4-5g of rosin powder and 4.5-6.5g of collodion are poured into the mixture and are continuously stirred;

s53, when the temperature reaches 90-95 ℃, dripping 78-79g of n-butanol and 78-79g of triethanolamine by using a separating funnel, stopping heating, keeping the temperature at 93 +/-1 ℃, finishing dripping within 2-3 hours, and continuously preserving the heat for 45-50 minutes, wherein the temperature is still 93 +/-1 ℃;

s54, taking out the silver mud, cooling for 10-12 hours, washing for 5-6 times by using absolute ethyl alcohol, removing impurities, then placing in a ventilation opening, naturally drying, and grinding and storing the dried silver mud;

s55, putting the milled silver mud in a dry, dark and clean place to prevent dust.

5. The process for preparing a mica sheet capacitor as claimed in claim 3, wherein: the preparation method of the silver carbonate specifically comprises the following steps:

s61, weighing 5-7g of rosin, grinding into powder, adding the powder into 50-58g of 99.5% ethanol, and dissolving into yellow brown liquid, namely 9% rosin water;

s62, adding 150-170me distilled water into 35-45g of sodium carbonate, heating to fully dissolve the sodium carbonate into a colorless and transparent sodium carbonate solution, and cooling for later use;

s63, adding 100-140g of silver nitrate into 250-300me of distilled water, stirring for 15-20 minutes, pouring 10-14me of rosin water, and continuously stirring for a plurality of minutes, wherein the rotating speed of a stirrer is 160-180 r/min;

s64, gradually dropping a sodium carbonate solution into a silver nitrate solution by using a separating funnel, stopping adding the sodium carbonate solution when the reactant is pink and alkaline after the reactant is dropped into the silver nitrate solution by using a 1% phenolphthalein solution, and continuously stirring for a plurality of minutes;

s65, spreading filter paper in a porcelain funnel, pouring the filter paper into a prepared silver carbonate solution for filtering, washing with distilled water and performing suction filtration until a washing liquid is not alkaline, and dropping 1% phenolphthalein solution into the discharged washing water until the washing water is not red;

s66, drying the washed silver carbonate powder in an oven at 55-60 ℃ for 5-7 days until no water exists, so that the silver carbonate is light yellow powder.

6. The process for preparing a mica sheet capacitor as claimed in claim 3, wherein: the preparation method of the adhesive comprises the steps of weighing 250-270g of terpineol, 40-45g of ethyl cellulose and 450-470g of ethylene glycol ethyl ether, mixing and stirring until the ethyl cellulose is completely dissolved.

7. The process for preparing a mica sheet capacitor as claimed in claim 1, wherein: during the selection of the mica sheets in the step one, green, black, specks, impurities, bubbles, uneven mica sheets with low utilization rate which account for more than 5 percent of the total area of the mica sheets are removed, and severe burrs, cracks and uneven parts at the edges of the mica sheets are repaired; when the mica sheet is stripped, the uneven thickness and cracks of the edge of the mica are removed, and if bubbles and black spots are found, a small hole is pricked by using a pricker.

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