CN116072434A - Sheet type high polymer tantalum fixed capacitor without humidity sensitivity grade and preparation method thereof - Google Patents
Sheet type high polymer tantalum fixed capacitor without humidity sensitivity grade and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 19
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/08—Housing; Encapsulation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/0029—Processes of manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/08—Housing; Encapsulation
- H01G9/10—Sealing, e.g. of lead-in wires
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/15—Solid electrolytic capacitors
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Abstract
A chip-type high-molecular tantalum fixed capacitor without humidity sensitivity level and a preparation method thereof are provided, wherein the chip-type high-molecular tantalum fixed capacitor comprises a tantalum core, a flexible insulating buffer layer, a plastic package shell, an anode lead and a cathode lead; the tantalum core comprises a tantalum block, a dielectric oxide layer, a cathode layer, a transition layer and a silver layer which are sequentially arranged from inside to outside, wherein the silver layer is formed by sintering a nano silver paste coated transition layer; the flexible insulating buffer layer is coated on the outer side of the silver layer; the plastic package shell is coated on the outer side of the flexible insulation buffer layer; one end of the positive electrode lead is connected with the tantalum block, and the other end of the positive electrode lead extends outwards to the outer side of the plastic package shell; one end of the negative electrode lead is connected with the silver layer, and the other end of the negative electrode lead extends outwards to the outer side of the plastic package shell; according to the method, the silver layer is formed on the transition layer through the cooperation of the insulating buffer layer coated on the outer side of the tantalum core and sintering, so that the humidity-sensitive grade of the prepared chip type high-polymer tantalum fixed capacitor can be reduced from 3 to 1, namely, the humidity-sensitive grade is not available, and the reliability, convenience and economical efficiency of use of customers are greatly improved.
Description
Technical Field
The invention belongs to the field of preparation of tantalum fixed capacitors, and particularly relates to a chip type high polymer tantalum fixed capacitor without humidity sensitivity level and a preparation method thereof.
Background
Tantalum capacitors are a basic component used in electronic circuits and are mainly used for filtering, coupling and power compensation of medium-low frequency circuits. Because the device has the characteristics of high volume capacity ratio, good temperature characteristic, excellent medium-low frequency characteristic, good storage resistance and the like, the method has wide application in the fields of aerospace, aviation, weapons, ships, electronics and the like. Along with the development of equipment construction and the domestic development requirement of basic components, tantalum capacitors are gradually developed towards the directions of sheet type, high frequency, super large capacity, high reliability and the like, and at the moment, sheet type polymer tantalum fixed capacitors are generated.
Chip polymer tantalum capacitor and conventional chip tantalum capacitor (MnO) 2 Cathode type) is mainly characterized by cathode material, when the traditional chip tantalum capacitor is used, the amount of the traditional chip tantalum capacitor must be greatly reduced, and when the switch circuit is used, the phenomena of short circuit and combustion explosion are easy to occur, in particular to the switch power supply circuit, and the traditional chip tantalum capacitor is characterized byThey were once classified as disabled or restricted in their ability to resist surge. The chip-type high-molecular tantalum capacitor adopts the conductive high-molecular material polythiophene as the cathode, so that the self impedance of the product is greatly reduced, a circuit with higher working frequency can be used, and the chip-type high-molecular tantalum capacitor is an irreplaceable product of a transient power supply of the novel active phased array radar T/R component. The filter is also very suitable for the technical requirements of miniaturization and high functionalization of the whole machine, especially for the filter circuits of electronic whole machines such as aviation, aerospace, missiles, satellites, microelectronics and the like, and can greatly improve the operation speed of the circuit and the functions of the whole machine and greatly reduce the volume, the weight and the production cost of the whole machine. When the high-power pulse charge-discharge circuit is used as a power supply, the volume and reliability of the high-power pulse charge-discharge circuit can meet higher requirements. When the filter circuit is used in various filter circuits, the insensitive phenomenon presented by the split Guan Langchong can ensure that the filter circuit can have higher safety without greatly derating, and the problem of startup failure of the switching power supply circuit is basically solved.
The disadvantage is that the conductive polymer material is easy to absorb moisture, so the chip-type polymer tantalum capacitor belongs to a humidity-sensitive device, the humidity-sensitive grade is generally 3, and the packaging, transportation, storage, installation and other aspects must be strictly operated according to the relevant regulations of the humidity-sensitive device. Even if the customer is strongly announced and reminded, quality accidents caused by improper moisture absorption or welding modes still occur endlessly in the using process, and failure modes are intensively reflected in cracking of the plastic package shell in the automatic patch welding process. The main mechanism is as follows: after the internal core absorbs water vapor in the surrounding environment, when reflow soldering is performed with the highest temperature reaching 230-260 ℃, the water vapor in the tantalum core rapidly expands and is released outwards to impact the plastic package shell, so that the plastic package shell of the capacitor is cracked, namely the so-called "popcorn phenomenon". For products with larger shell numbers, even if the products do not absorb moisture, the problem of package cracking often occurs when reflow soldering is performed, and the main reason is that the size of an internal core is large, and the plastic package shell is cracked due to the large expansion amount during soldering, so that the shell numbers above the Y shell number must be manually welded at present; and the current common method for reducing the humidity sensitivity level is to reduce the size of an internal core and improve the shock resistance of the plastic package shell by increasing the thickness of the plastic package shell. However, the method can only be used for a very small part of conservative specifications, has no improvement effect on the product performance, and does not meet the general requirements of the market on miniaturization, high capacity and high reliability of components.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a chip type polymer tantalum fixed capacitor without humidity sensitivity level, and also aims to provide a method for preparing the tantalum fixed capacitor.
The invention adopts the following technical scheme:
a chip-type high polymer tantalum fixed capacitor without humidity sensitivity level comprises a tantalum core, a flexible insulating buffer layer, a plastic package shell, an anode lead and a cathode lead;
the tantalum core comprises a tantalum block, a dielectric oxide layer, a cathode layer, a transition layer and a silver layer which are sequentially arranged from inside to outside, wherein the silver layer is formed by sintering a nano silver paste coated transition layer;
the flexible insulating buffer layer is coated on the outer side of the silver layer;
the plastic package shell is coated on the outer side of the flexible insulation buffer layer;
one end of the positive electrode lead is connected with the tantalum block, and the other end of the positive electrode lead extends outwards to the outer side of the plastic package shell;
and one end of the negative electrode lead is connected with the silver layer, and the other end of the negative electrode lead extends outwards to the outer side of the plastic package shell.
Further, the nano silver paste consists of resin, an organic solvent and silver powder, wherein the silver powder consists of 40-80% of nano silver particles and 20-60% of micro silver particles according to mass percent.
Further, the particle size of the nano-scale silver particles is 10-30nm, and the particle size of the micro-scale silver particles is 1-15um.
Further, the flexible insulating buffer layer is one of electronic three-proofing paint of acrylic acid, modified silicon, rubber elastomer, polyurethane and fluoropolymer.
Further, the front end of the tantalum block is provided with a connecting end connected with the positive electrode lead, and the flexible insulating buffer layer is provided with a yielding area connected with the negative electrode lead and the silver layer.
Further, the thickness of the flexible insulating buffer layer is 1-30um.
A preparation method of a chip type high polymer tantalum fixed capacitor without humidity sensitivity level comprises the following steps:
firstly, preparing a tantalum block, and sequentially forming a dielectric oxide layer, a cathode layer and a transition layer on the outer side of the tantalum block;
step two, dipping the tantalum block obtained in the step one into nano silver paste, then sending the tantalum block into an oven for pre-drying treatment, and sending the tantalum block into a high-temperature furnace for sintering for 5-10min at 200-260 ℃ to form a silver layer outside the transition layer, thus obtaining a tantalum core;
step three, connecting the positive electrode lead and the negative electrode lead with a tantalum block and a silver layer respectively, and then dipping a tantalum core assembled with the positive electrode lead and the negative electrode lead into an insulating buffer material to form a flexible insulating buffer layer on the surface of the tantalum core;
and step four, packaging the tantalum core with the flexible insulating buffer layer to form a plastic package shell outside the flexible insulating buffer layer, and then performing secondary curing to obtain the chip type high polymer tantalum fixed capacitor.
Further, in the second step, the pre-drying treatment is performed by: drying at 40-50deg.C for 30-60min, and drying at 80-100deg.C for 30-60min.
In the fourth step, the tantalum block packaged with the plastic package shell is firstly dried for 2-10 hours at 100-125 ℃ before secondary curing.
Further, in the fourth step, the packaging temperature is 160-180 ℃.
As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:
firstly, the silver layer formed on the transition layer by cladding the insulating buffer layer on the outer side of the tantalum core in a matched sintering manner can reduce the humidity-sensitive grade of the prepared sheet type high polymer tantalum fixed capacitor from 3 grade to 1 grade, namely no humidity-sensitive grade, moisture-proof packaging with higher cost is not needed after the preparation is finished, and the sheet type high polymer tantalum fixed capacitor can be put into use without any moisture absorption evaluation and drying treatment, so that the reliability, convenience and economy of use of customers are greatly improved; the obtained chip type high polymer tantalum fixed capacitor has simple integral structure and convenient manufacture, does not need to reduce the size of a tantalum core during design, and can fully utilize most of the existing preparation equipment and processes; meanwhile, the welding mode of automatic reflow soldering can be widened to larger shell numbers, such as Y shells, H shells and the like, which are required to be welded manually, so that more welding selectivity is provided for customers, and the welding compatibility of different components is improved;
secondly, by limiting the raw material composition of the silver paste to match with a sintering process, during high-temperature sintering, nano-scale silver particles in the silver paste are mutually sintered to form a layer of compact, high-strength and low-porosity silver layer with 5-10% on the surface of the tantalum core, and the silver layer has excellent conductivity and can greatly reduce the initial ESR value of the capacitor; the silver layer has strong mechanical impact resistance, can ensure the integrity of the silver layer and the complete package of the tantalum core, and improves the consistency of the product performance; the silver layer can ensure shrinkage matching with the transition layer and the cathode layer, and improve the temperature impact resistance of the capacitor; the silver layer has extremely low porosity, can slow down the erosion of water vapor to the internal tantalum core, and improves the moisture resistance of the capacitor; when the tantalum fixed capacitor is welded at a high temperature, water vapor absorbed by the tantalum core can only slowly leak outwards through tiny and rare pores on the silver layer, and the silver layer with high mechanical strength resists and disperses most of the impact of the water vapor, so that the impact of the water vapor on the plastic package shell is greatly slowed down. The flexible insulating buffer layer arranged on the outer side of the silver layer can slow down and disperse the impact of most of water vapor on the plastic package shell by virtue of micro deformation when the tantalum fixed capacitor is welded at high temperature, so that the use of the tantalum fixed capacitor is ensured;
thirdly, the plastic package shell is dried before secondary curing, so that a large amount of water vapor in the tantalum core is prevented from volatilizing to impact the plastic package shell which is not completely cured, the mechanical strength of the plastic package shell is improved, and the use of the tantalum fixed capacitor is ensured.
Drawings
FIG. 1 is a graph showing the morphology of silver layers in the tantalum fixed capacitors of comparative examples 1 and 5 with reference to FIG. 1;
fig. 2 is a graph of the morphology of the silver layer in the tantalum fixed capacitor of comparative example 4 and example 1 with reference to fig. 1;
FIG. 3 is a graph of the morphology of the silver layer in the tantalum fixed capacitor of comparative example 2 with reference to FIG. 3;
FIG. 4 is a graph of the morphology of the silver layer in the tantalum fixed capacitor of comparative example 3 with reference to FIG. 4;
FIG. 5 is a schematic diagram of a chip tantalum polymer fixed capacitor;
in the figure, a 1-tantalum block, a 2-dielectric oxide layer, a 3-cathode layer, a 4-transition layer, a 5-silver layer, a 6-flexible insulating buffer layer, a 7-plastic package shell, an 8-positive electrode lead, a 9-negative electrode lead, an 11-connecting end and a 61-yielding area.
Detailed Description
The invention is further described below by means of specific embodiments.
A chip-type high-molecular tantalum fixed capacitor without humidity sensitivity level comprises a tantalum core, a flexible insulating buffer layer 6, a plastic package shell 7, an anode lead 8 and a cathode lead 9.
The tantalum core comprises a tantalum block 1, a dielectric oxide layer 2, a cathode layer 3, a transition layer 4 and a silver layer 5 which are sequentially arranged from inside to outside.
The tantalum block 1 is formed by pressing and sintering tantalum powder and tantalum wires, and specifically, the front end of the tantalum block 1 is formed with a connecting end 11 connected with the positive electrode lead 8.
And the dielectric oxide layer 2 is coated on the outer side of the tantalum block 1 and is coated on the outer side of the tantalum block 1 by an electrochemical method.
And a cathode layer 3 coated on the outer side of the dielectric oxide layer 2, wherein the cathode layer 3 is specifically made of conductive polymer selected from one or more of polythiophene, polypyrrole or polyaniline.
The transition layer 4 is coated on the outer side of the cathode layer 3, and specifically, the transition layer 4 is composed of one or more of graphite, carbon black, carbon fiber or graphene.
The silver layer 5 is coated on the outer side of the transition layer 4, and specifically, the silver layer 5 is formed by sintering a nano silver paste coated transition layer 4, wherein the nano silver paste is formed by resin, an organic solvent and silver powder according to the mass ratio of 1:1:8; the silver powder consists of 40-80% of nano-scale spherical silver particles and 20-60% of micron-scale flaky silver particles according to mass percentage, wherein the particle size of the nano-scale spherical silver particles is 10-30nm, and the particle size of the micron-scale flaky silver particles is 1-15um; by limiting the composition and the forming method of the silver layer 5, the silver layer 5 is formed on the surface of the transition layer 4 in a high-temperature sintering mode, so that the initial ESR value of the capacitor is reduced, and the performance reliability of the capacitor is improved.
The flexible insulating buffer layer 6 is coated on the outer side of the silver layer 5, has the thickness of 1-30um and is selected from one of electronic three-proofing paint of acrylic acid, modified silicon, rubber elastomer, polyurethane and fluoropolymer; by adding the flexible insulating buffer layer 6 on the outer side of the silver layer 5, the flexible insulating buffer layer 6 can be subjected to micro deformation by itself to slow down and disperse the impact of most of water vapor on the plastic package shell when the obtained tantalum fixed capacitor is welded at high temperature; specifically, the flexible insulating buffer layer 6 may also be made of a flexible material with a dampproof function, so as to slow down the absorption of the tantalum core to water vapor; further, the thickness of the flexible insulating buffer layer 6 is preferably 1-10um.
The plastic package shell 7 is coated on the outer side of the flexible insulation buffer layer 6, and specifically, the plastic package shell 7 is formed by automatic injection molding of epoxy resin, wherein the plastic package temperature is 160-180 ℃; specifically, after the plastic package shell 7 is injection molded, secondary curing is needed to improve the strength of the plastic package shell 7, wherein the secondary curing temperature is 160-180 ℃ and the curing time is 2-4 hours; further, before secondary curing, the encapsulated tantalum core needs to be dried at 100-125 ℃ for 2-10 hours to prevent a large amount of vapor from volatilizing to impact the plastic package shell which is not completely cured yet.
One end of the positive electrode lead wire 8 is connected with the connecting end of the front end of the tantalum block 1, and the other end of the positive electrode lead wire extends outwards to the outer side of the plastic package shell 7;
a negative electrode lead 9, one end of which is connected with the silver layer 5 and the other end of which extends outwards to the outer side of the plastic package shell 7; specifically, the flexible insulating buffer layer 6 is provided with a relief region 61 to which the negative electrode lead 9 is connected to the silver layer 5.
The preparation method comprises the following steps:
firstly, preparing a tantalum block 1, and sequentially forming a dielectric oxide layer 2, a cathode layer 3 and a transition layer 4 on the outer side of the tantalum block;
step two, dipping the tantalum block 1 obtained in the step one into nano silver paste with the viscosity of 1000-2000cp, then sticking out excessive silver paste at the bottom, then sending the paste into an oven, firstly drying the paste for 30-60min at 40-50 ℃, then drying the paste for 30-60min at 80-100 ℃ to finish pre-drying treatment, and sending the paste into a high-temperature oven to sinter the paste for 5-10min at 200-260 ℃ to form a silver layer 5 at the outer side of the transition layer 4, thus obtaining a tantalum core;
step three, connecting the positive electrode lead 8 and the negative electrode lead 9 with the tantalum block 1 and the silver layer 5 respectively, then dipping the tantalum core assembled with the positive electrode lead 8 and the negative electrode lead 9 in an insulating buffer material for 1-15s, controlling the pulling speed to be 0.1-1.0cm/s, and airing at room temperature after dipping to form a flexible insulating buffer layer 6 on the surface of the tantalum core;
packaging the tantalum core with the flexible insulating buffer layer 6 at 160-180 ℃ to form a plastic package shell 7 outside the flexible insulating buffer layer 6, and then drying for 2-10h at 100-125 ℃; and then carrying out secondary curing for 2-4 hours at the temperature of 160-180 ℃ to obtain the chip type high polymer tantalum fixed capacitor.
Example 1
A chip-type high-molecular tantalum fixed capacitor without humidity sensitivity level comprises a tantalum core, a flexible insulating buffer layer 6, a plastic package shell 7, an anode lead 8 and a cathode lead 9.
The tantalum core comprises a tantalum block 1, a dielectric oxide layer 2, a cathode layer 3, a transition layer 4 and a silver layer 5 which are sequentially arranged from inside to outside.
The tantalum block 1 is formed by pressing and sintering tantalum powder and tantalum wires, and specifically, the front end of the tantalum block 1 is formed with a connecting end 11 connected with the positive electrode lead 8.
And the dielectric oxide layer 2 is coated on the outer side of the tantalum block 1 and is coated on the outer side of the tantalum block 1 by an electrochemical method.
And a cathode layer 3 coated on the outer side of the dielectric oxide layer 2, wherein the cathode layer 3 is specifically made of conductive polymer selected from one or more of polythiophene, polypyrrole or polyaniline.
The transition layer 4 is coated on the outer side of the cathode layer 3, and specifically, the transition layer 4 is composed of one or more of graphite, carbon black, carbon fiber or graphene.
The silver layer 5 is coated on the outer side of the transition layer 4, and specifically, the silver layer 5 is formed by sintering a transition layer coated by nano silver paste, and the nano silver paste is formed by resin, an organic solvent and silver powder according to the mass ratio of 1:1:8; the silver powder consists of 60% of nano-scale spherical silver particles and 40% of micro-scale flaky silver particles according to mass percentage, wherein the particle size of the nano-scale spherical silver particles is 10-30nm, and the particle size of the micro-scale flaky silver particles is 1-15um.
The flexible insulating buffer layer 6 is coated on the outer side of the silver layer 5, has the thickness of 1-10um and is selected from fluorine electron moisture-proof agents with the solid content of 5-10%.
The plastic package shell 7 is coated on the outer side of the flexible insulation buffer layer 6, the thickness is 150-200um, and specifically, the plastic package shell 7 is formed by automatic injection molding of epoxy resin.
One end of the positive electrode lead 8 is connected with the connecting end 11 at the front end of the tantalum block 1, and the other end of the positive electrode lead extends outwards to the outer side of the plastic package shell 7;
a negative electrode lead 9, one end of which is connected with the silver layer 5 and the other end of which extends outwards to the outer side of the plastic package shell 7; specifically, the flexible insulating buffer layer 6 is provided with a relief region 61 to which the negative electrode lead 9 is connected to the silver layer 5.
The preparation method comprises the following steps:
firstly, preparing tantalum blocks 1 with 5mm of 5.2mm of 3.4mm, and sequentially forming a dielectric oxide layer 2, a cathode layer 3 and a transition layer 4 on the outer side of the tantalum blocks;
immersing the tantalum block obtained in the step one into nano silver paste with the viscosity of 1500cp, then sticking out excessive silver paste at the bottom, then sending the nano silver paste into an oven, firstly drying the nano silver paste at 45 ℃ for 45min, then drying the nano silver paste at 90 ℃ for 45min to finish pre-drying treatment, and then sending the nano silver paste into a high-temperature furnace to sinter the nano silver paste at 230 ℃ for 8min to form a silver layer 5 with the porosity of 6-8% on the outer side of a transition layer 4, thus obtaining a tantalum core;
step three, connecting the positive electrode lead 8 and the negative electrode lead 9 with the tantalum block 1 and the silver layer 5 respectively, then immersing the tantalum core assembled with the positive electrode lead 8 and the negative electrode lead 9 in a fluorine electron moisture-proof agent with the solid content of 5-10% for 8s, controlling the pulling speed at 0.5cm/s, and airing at room temperature after immersing to form a flexible insulating buffer layer 6 on the surface of the tantalum core;
packaging the tantalum core with the flexible insulating buffer layer 6 at 170 ℃ to form a plastic package shell 7 outside the flexible insulating buffer layer 6, and then drying for 6 hours at 115 ℃; and then carrying out secondary curing for 3 hours at the temperature of 170 ℃ to obtain the chip type polymer tantalum fixed capacitor.
Comparative example 1
The structure and preparation method are basically the same as those of example 1, except that: the silver layer is formed by coating and drying silver paste, the drying and curing temperature is 165 ℃, and silver powder in the silver paste is common silver powder.
Comparative example 2
The structure and preparation method are basically the same as those of example 1, except that: the silver layer is formed by coating and drying nano silver paste, and the drying and curing temperature is 165 ℃.
Comparative example 3
The structure and preparation method are basically the same as those of example 1, except that: the silver powder in the silver paste is common silver paste.
Comparative example 4
The structure and preparation method are basically the same as those of example 1, except that: there is no flexible insulating buffer layer.
Comparative example 5
The structure and preparation method are basically the same as those of example 1, except that: the silver layer is formed by coating and drying silver paste, the drying and curing temperature is 165 ℃, and silver powder in the silver paste is common silver powder.
Comparative example 6
The structure and preparation method are basically the same as those of example 1, except that: the silver powder in the nano silver paste is 100% of nano spherical silver particles without a flexible insulating buffer layer.
Comparative example 7
The structure and preparation method are basically the same as those of example 1, except that: the silver powder in the nano silver paste is 100% of micron-sized flaky silver particles without a flexible insulating buffer layer.
The chip type high polymer tantalum fixed capacitor prepared in example 1 and comparative documents 1 to 7 was tested to obtain the following data: wherein, the comparative example 3 can not form a complete silver layer, the comparative example 6 extrudes the transition layer and the cathode layer due to the transition shrinkage of the silver layer, the initial electrical property of the capacitor is poor, and no grading is carried out;
in addition, the morphology of the silver layer in the tantalum fixed capacitor of comparative examples 1 and 5 is referred to fig. 1, the morphology of the silver layer in the tantalum fixed capacitor of comparative examples 4 and 1 is referred to fig. 2, the morphology of the silver layer in the tantalum fixed capacitor of comparative example 2 is referred to fig. 3, and the morphology of the silver layer in the tantalum fixed capacitor of comparative example 3 is referred to fig. 4;
table 1 test results table of each example
According to the table, in the embodiment 1, the insulating buffer layer is coated on the outer side of the tantalum core, and the silver layer is matched with the sintering molding on the transition layer, so that the shell of the prepared chip type high polymer tantalum fixed capacitor is not cracked and has qualified performance under the most severe temperature and humidity and reflow welding rod, and the humidity sensitivity level can be reduced from 3 level to 1 level, namely, the humidity sensitivity level is not generated;
referring to comparative example 1 and example 1, it can be seen that the performance and appearance of the silver layer (i.e., the conventional chip-type tantalum-polymer fixed capacitor) prepared by using the common silver paste in combination with the coating, drying and curing process can not meet the requirements of the moisture-free class defined in the application, but can not meet the requirements of the limited use.
Referring to comparative example 4, comparative example 5, comparative example 6, and comparative example 7 and example 1, it is known that the composition of nano silver paste and the arrangement of flexible insulating buffer layer are indispensable for preparing tantalum fixed capacitors to achieve a moisture-free rating.
As can be seen from comparative example 2, comparative example 3 and example 1, the prepared tantalum fixed capacitor is required to achieve the moisture-free grade, the silver layer formed by the nano silver paste is required to be realized by matching with a specific sintering process, and the moisture-free grade cannot be achieved by adopting a coating and drying process in the prior art.
In summary, according to the method, the insulating buffer layer is coated on the outer side of the tantalum core, and the silver layer is matched with the sintering molding on the transition layer, so that the humidity-sensitive grade of the prepared sheet type high polymer tantalum fixed capacitor can be reduced from 3 grade to 1 grade, namely, no humidity-sensitive grade is adopted, moisture-proof packaging with higher cost is not required after the preparation is finished, and the sheet type high polymer tantalum fixed capacitor can be put into use without any moisture absorption evaluation and drying treatment, so that the reliability, convenience and economy of use of customers are greatly improved; the obtained chip type high polymer tantalum fixed capacitor has simple integral structure and convenient manufacture, does not need to reduce the size of a tantalum core during design, and can fully utilize most of the existing preparation equipment and processes; meanwhile, the welding mode of automatic reflow soldering can be widened to larger shell numbers, such as Y shells, H shells and the like, which are required to be welded manually, so that more welding selectivity is provided for customers, and the welding compatibility of different components is improved.
The foregoing description is only illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention, i.e., the invention is not to be limited to the details of the claims and the description, but rather is to cover all modifications which are within the scope of the invention.
Claims (10)
1. A sheet type macromolecule tantalum fixed capacitor without humidity-sensitive grade is characterized in that: the device comprises a tantalum core, a flexible insulating buffer layer, a plastic package shell, a positive electrode lead and a negative electrode lead;
the tantalum core comprises a tantalum block, a dielectric oxide layer, a cathode layer, a transition layer and a silver layer which are sequentially arranged from inside to outside, wherein the silver layer is formed by sintering a nano silver paste coated transition layer;
the flexible insulating buffer layer is coated on the outer side of the silver layer;
the plastic package shell is coated on the outer side of the flexible insulation buffer layer;
one end of the positive electrode lead is connected with the tantalum block, and the other end of the positive electrode lead extends outwards to the outer side of the plastic package shell;
and one end of the negative electrode lead is connected with the silver layer, and the other end of the negative electrode lead extends outwards to the outer side of the plastic package shell.
2. The moisture-sensitive-free chip-type high molecular tantalum fixed capacitor of claim 1, wherein: the nano silver paste consists of resin, an organic solvent and silver powder, wherein the silver powder consists of 40-80% of nano silver particles and 20-60% of micro silver particles according to mass percentage.
3. A moisture-sensitive-free chip-type high molecular tantalum fixed capacitor according to claim 2, wherein: the particle size of the nano-scale silver particles is 10-30nm, and the particle size of the micro-scale silver particles is 1-15um.
4. The moisture-sensitive-free chip-type high molecular tantalum fixed capacitor of claim 1, wherein: the flexible insulating buffer layer is one of acrylic acid, modified silicon, rubber elastomer, polyurethane and fluoropolymer electronic three-proofing paint.
5. The moisture-sensitive-free chip-type high molecular tantalum fixed capacitor of claim 1, wherein: the front end of tantalum piece is formed with the link of being connected with the anodal lead wire, flexible insulating buffer layer sets up the district of stepping down of being connected with confession negative pole lead wire and silver layer.
6. The moisture-sensitive-free chip-type high molecular tantalum fixed capacitor of claim 1, wherein: the thickness of the flexible insulating buffer layer is 1-30um.
7. The method for manufacturing the chip-type high-molecular tantalum fixed capacitor without the humidity-sensitive grade according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
firstly, preparing a tantalum block, and sequentially forming a dielectric oxide layer, a cathode layer and a transition layer on the outer side of the tantalum block;
step two, dipping the tantalum block obtained in the step one into nano silver paste, then sending the tantalum block into an oven for pre-drying treatment, and sending the tantalum block into a high-temperature furnace for sintering for 5-10min at 200-260 ℃ to form a silver layer outside the transition layer, thus obtaining a tantalum core;
step three, connecting the positive electrode lead and the negative electrode lead with a tantalum block and a silver layer respectively, and then dipping a tantalum core assembled with the positive electrode lead and the negative electrode lead into an insulating buffer material to form a flexible insulating buffer layer on the surface of the tantalum core;
and step four, packaging the tantalum core with the flexible insulating buffer layer to form a plastic package shell outside the flexible insulating buffer layer, and then performing secondary curing to obtain the chip type high polymer tantalum fixed capacitor.
8. The method for manufacturing the chip-type high-molecular tantalum fixed capacitor without humidity sensitivity grade according to claim 7, wherein the method comprises the following steps: in the second step, the pre-drying treatment process is as follows: drying at 40-50deg.C for 30-60min, and drying at 80-100deg.C for 30-60min.
9. The method for manufacturing the chip-type high-molecular tantalum fixed capacitor without humidity sensitivity grade according to claim 7, wherein the method comprises the following steps: and step four, before secondary curing, the tantalum block packaged with the plastic package shell is firstly dried for 2-10h at 100-125 ℃.
10. The method for manufacturing the chip-type high-molecular tantalum fixed capacitor without humidity sensitivity grade according to claim 7, wherein the method comprises the following steps: in the fourth step, the packaging temperature is 160-180 ℃.
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