High-frequency low-ESR organic chip-style solid tantalum electrolytic capacitor

Abstract

The present invention relates to the technical field of tantalum capacitors and discloses a high-frequency low-ESR organic chip-style solid tantalum electrolytic capacitor, comprising: a tantalum block, where a tantalum wire lead is fixedly connected at the center of one end of the tantalum block; a tantalum pentoxide dielectric layer is formed on an outer wall of the tantalum block by means of anodization; a conductive polymer layer is provided outside the dielectric layer; a graphite layer and a silver powder paint layer are arranged outside the conductive polymer layer; the end of the silver powder paint layer away from the tantalum wire lead is connected to a cathode guide; the tantalum wire lead is connected to an anode guide; and the tantalum block is wholly covered with a modified epoxy resin protection layer. The modified epoxy resin protection layer of the present invention comprises an added DOPO derivative having dual DOPO groups; at the same ratio, the flame retardance thereof is improved, and thus the amount of flame retardant used can be reduced, causing the overall performance of the resin to improve.

Description

A high-frequency, low-ESR organic chip solid tantalum electrolytic capacitor Technical Field

[0001] The present invention belongs to the technical field of tantalum capacitors, and in particular relates to a high-frequency, low-ESR organic chip-type solid tantalum electrolytic capacitor. Background Art

[0002] In recent years, end-user systems have experienced rapid development, sharing a common theme: increasingly complex circuits require electronic components with higher energy density and greater integration. This trend shows little sign of slowing down. To meet the demands of rapidly evolving circuits, tantalum electrolytic capacitors have evolved from direct-insert (DIP) to surface-mount (SMT) designs. Chip-mount tantalum electrolytic capacitors have also seen significant growth, finding widespread application in automation, communications, power grids, transportation, portable devices, and other fields. However, the structural characteristics of existing SMT solid electrolyte tantalum capacitors have led to a capacity bottleneck. Traditional molded SMT tantalum capacitors no longer offer a significant advantage in energy density per unit volume.

[0003] During the processing of existing solid electrolyte tantalum capacitors, a layer of sealing material needs to be wrapped on the outside, which not only protects the core of the tantalum capacitor, but also improves the performance of the tantalum capacitor. There are currently two encapsulation methods for tantalum capacitors, powder encapsulation and liquid resin encapsulation. The powder encapsulation method mainly includes fluidization, encapsulation, corner cutting, leveling, curing, marking, and encapsulation. Not only is the process complicated and time-consuming, but it also consumes a lot of energy. The post-processing process can easily cause the lead wires to fall off, and the product qualification rate is low. The existing liquid resin encapsulation method usually uses epoxy resin for encapsulation. The limiting oxygen index of epoxy resin is about 20, which is extremely flammable. If local high-temperature spontaneous combustion occurs during the use of electronic components, the epoxy resin encapsulation layer will quickly ignite, causing the fire to spread.

[0004] Summary of the Invention

[0005] In order to address the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a high-frequency, low-ESR organic chip solid tantalum electrolytic capacitor, which is wrapped with a modified epoxy resin protective layer, wherein the modified epoxy resin protective layer is added with a DOPO derivative having a double DOPO group. At the same proportion, its flame retardant performance is improved, thereby reducing the amount of flame retardant used and improving the overall performance of the resin.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A high-frequency, low-ESR, organic chip-type solid tantalum electrolytic capacitor comprises a tantalum block, one end of the tantalum block having a fixed connection to a tantalum wire lead at its center, an outer wall of the tantalum block being anodic-oxidized to form a tantalum pentoxide dielectric layer, an outer surface of the dielectric layer being provided with a conductive polymer layer, an outer surface of the conductive polymer layer being provided with a graphite layer and a silver powder paint layer, an outer wall of the silver powder paint layer being away from one end of the tantalum wire lead being connected to a cathode conductor, the tantalum wire lead being connected to an anode conductor, and the entire tantalum block being wrapped with a modified epoxy resin protective layer.

[0008] Further preferably, the conductive polymer layer is phosphoric acid-doped poly (3,4-ethylenedioxythiophene).

[0009] Further preferably, the modified epoxy resin protective layer comprises the following raw materials in parts by weight: 30-40 parts of epoxy resin, 5-10 parts of DOPO derivative, 25-30 parts of curing agent, and 3-5 parts of synergistic flame retardant;

[0010] The preparation method of the modified epoxy resin protective layer comprises the following steps:

[0011] (1) Weighing epoxy resin, DOPO derivative, and synergistic flame retardant according to the ratio, putting the raw materials into a blender, stirring at 1000-2000 rpm for 20-30 minutes, adding a curing agent and continuing to stir for 3-5 minutes to obtain a modified epoxy resin slurry;

[0012] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 100-120°C for 1-2 hours to form a modified epoxy resin protective layer.

[0013] More preferably, the curing agent is one or more of imidazoles, imidazolines, trialkylphosphoniums, quaternary ammonium salts, quaternary phosphonium salts and organic ureas.

[0014] More preferably, the synergistic flame retardant is one or more of diammonium hydrogen phosphate, melamine cyanurate, sodium triphosphate, ammonium dihydrogen phosphate, magnesium hydroxide, aluminum hydroxide and aluminum oxalate.

[0015] More preferably, the structural formula of the DOPO derivative is as follows:

[0016] The preparation method of DOPO derivatives comprises the following steps:

[0017] S1. Dissolve 2-aminothiazole and 2,5-dihydroxyterephthalaldehyde separately with 1,4-dioxane, then slowly add the 2,5-dihydroxyterephthalaldehyde solution dropwise to the 2-aminothiazole solution, raise the temperature to 55-65°C, and react for 6-8 hours;

[0018] S2. Dissolve DOPO in 1,4-dioxane, then slowly add it to the above reaction system, raise the temperature to 75-85°C, and continue the reaction for 6-8 hours;

[0019] S3. After the reaction is completed, the product is subjected to rotary evaporation, and the obtained viscous solid is placed in a vacuum oven and dried at 60-70° C. for 8-10 h to obtain a DOPO derivative.

[0020] More preferably, the molar ratio of 2-aminothiazole, 2,5-dihydroxyterephthalaldehyde and DOPO is 2:1:2.

[0021] Beneficial effects of the present invention:

[0022] The solid tantalum electrolytic capacitor of the present invention is wrapped with a modified epoxy resin protective layer, wherein the modified epoxy resin protective layer is added with a DOPO derivative having a double DOPO group. Under the same proportion, its flame retardant performance is improved, thereby reducing the amount of flame retardant used and improving the overall performance of the resin. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] A high-frequency, low-ESR, organic chip-type solid tantalum electrolytic capacitor comprises a tantalum block, one end of the tantalum block having a fixed connection to a tantalum wire lead at its center, an outer wall of the tantalum block forming a tantalum pentoxide dielectric layer by anodic oxidation, an outer surface of the dielectric layer of which is provided a conductive polymer layer, the conductive polymer layer being phosphoric acid-doped poly-3,4-ethylenedioxythiophene, an outer surface of the conductive polymer layer of which is provided a graphite layer and a silver powder paint layer, an outer wall of the silver powder paint layer being connected to a cathode conductor away from one end of the tantalum wire lead, the tantalum wire lead being connected to an anode conductor, and the entire tantalum block being wrapped with a modified epoxy resin protective layer.

[0025] Example 1

[0026] The modified epoxy resin protective layer includes the following raw materials by weight: 30 parts epoxy resin, 10 parts DOPO derivative, 25 parts curing agent, and 5 parts synergistic flame retardant. The structural formula of the DOPO derivative is as follows:

[0027] The preparation method of DOPO derivatives comprises the following steps:

[0028] S1. Dissolve 4 g of 2-aminothiazole and 3.2 g of 2,5-dihydroxyterephthalaldehyde in 20 ml of 1,4-dioxane, then slowly add the 2,5-dihydroxyterephthalaldehyde solution dropwise to the 2-aminothiazole solution, heat to 55°C, and react for 8 hours.

[0029] S2. Dissolve 8.6 g of DOPO in 40 ml of 1,4-dioxane, then slowly add it to the above reaction system, raise the temperature to 75°C, and continue the reaction for 8 hours;

[0030] S3. After the reaction, the product was rotary evaporated, and the obtained viscous solid was placed in a vacuum oven and dried at 60° C. for 10 h to obtain a DOPO derivative;

[0031] The method for preparing the modified epoxy resin protective layer comprises the following steps:

[0032] (1) Weighing epoxy resin, DOPO derivative, and synergistic flame retardant according to the ratio, putting the raw materials into a blender, stirring at 1000 rpm for 30 minutes, adding a curing agent and continuing to stir for 3 minutes to obtain a modified epoxy resin slurry;

[0033] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 100°C for 2 hours to form a modified epoxy resin protective layer.

[0034] Example 2

[0035] The modified epoxy resin protective layer includes the following raw materials in parts by weight: 40 parts of epoxy resin, 5 parts of DOPO derivative, 30 parts of curing agent, and 3 parts of synergistic flame retardant;

[0036] The preparation method of DOPO derivatives comprises the following steps:

[0037] S1. Dissolve 2-aminothiazole and 2,5-dihydroxyterephthalaldehyde separately with 1,4-dioxane, then slowly add the 2,5-dihydroxyterephthalaldehyde solution dropwise to the 2-aminothiazole solution, raise the temperature to 65°C, and react for 6 hours;

[0038] S2. Dissolve DOPO in 1,4-dioxane and then slowly add it to the above reaction system, raise the temperature to 85°C, and continue the reaction for 6 hours;

[0039] S3. After the reaction, the product was rotary evaporated, and the obtained viscous solid was placed in a vacuum oven and dried at 70° C. for 8 h to obtain a DOPO derivative;

[0040] The method for preparing the modified epoxy resin protective layer comprises the following steps:

[0041] (1) Weighing epoxy resin, DOPO derivative, and synergistic flame retardant according to the ratio, putting the raw materials into a blender, stirring at 2000 rpm for 20 minutes, adding a curing agent and continuing to stir for 5 minutes to obtain a modified epoxy resin slurry;

[0042] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 120°C for 1 hour to form a modified epoxy resin protective layer.

[0043] Example 3

[0044] The modified epoxy resin protective layer includes the following raw materials in parts by weight: 35 parts of epoxy resin, 8 parts of DOPO derivative, 27 parts of curing agent, and 4 parts of synergistic flame retardant;

[0045] The preparation method of DOPO derivatives comprises the following steps:

[0046] S1. Dissolve 2-aminothiazole and 2,5-dihydroxyterephthalaldehyde separately with 1,4-dioxane, then slowly add the 2,5-dihydroxyterephthalaldehyde solution dropwise to the 2-aminothiazole solution, raise the temperature to 60°C, and react for 7 hours;

[0047] S2. Dissolve DOPO in 1,4-dioxane and then slowly add it to the above reaction system, raise the temperature to 80°C, and continue the reaction for 7 hours;

[0048] S3. After the reaction, the product was rotary evaporated, and the obtained viscous solid was placed in a vacuum oven and dried at 65° C. for 9 h to obtain a DOPO derivative;

[0049] The method for preparing the modified epoxy resin protective layer comprises the following steps:

[0050] (1) Weighing epoxy resin, DOPO derivative, and synergistic flame retardant according to the ratio, putting the raw materials into a blender, stirring at 1500 rpm for 25 minutes, adding a curing agent and continuing to stir for 4 minutes to obtain a modified epoxy resin slurry;

[0051] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 110°C for 1.5 hours to form a modified epoxy resin protective layer.

[0052] Comparative Example 1

[0053] The modified epoxy resin protective layer includes the following raw materials in parts by weight: 35 parts of epoxy resin, 8 parts of DOPO, 27 parts of curing agent, and 4 parts of synergistic flame retardant;

[0054] The method for preparing the modified epoxy resin protective layer comprises the following steps:

[0055] (1) Epoxy resin, DOPO, and synergistic flame retardant were weighed according to the ratio, and the raw materials were put into a blender and stirred at 1500 rpm for 25 min. A curing agent was added and stirred for another 4 min to obtain a modified epoxy resin slurry;

[0056] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 110°C for 1.5 hours to form a modified epoxy resin protective layer.

[0057] Comparative Example 2

[0058] The modified epoxy resin protective layer includes the following raw materials in parts by weight: 35 parts of epoxy resin, 27 parts of curing agent, and 4 parts of synergistic flame retardant;

[0059] The method for preparing the modified epoxy resin protective layer comprises the following steps:

[0060] (1) Weighing epoxy resin and synergistic flame retardant according to the ratio, putting the raw materials into a mixer, stirring at 1500 rpm for 25 minutes, adding curing agent and continuing stirring for 4 minutes to obtain modified epoxy resin slurry;

[0061] (2) Place the assembled capacitor into a mold, squeeze in the prepared modified epoxy resin slurry, and cure at 110°C for 1.5 hours to form a modified epoxy resin protective layer.

[0062] Performance testing

[0063] The modified epoxy resin protective layer of the high-frequency, low-ESR organic chip solid tantalum electrolytic capacitors in Examples 1 to 3 and Comparative Examples 1 to 2 was made into standard specimens with a size of 127×12.7×3.2 mm. The horizontal and vertical (UL-94) burning tests were performed according to ASTM D3801-1996. The oxygen index (LOI) test was also performed according to ASTM D2863-70. The data are shown in Table 1 below.

[0064] Table 1 Test results of flame retardant performance of sheath of high frequency low ESR organic chip solid tantalum electrolytic capacitor

[0065] As can be seen from the data in Table 1, at the same flame retardant ratio, the flame retardant performance of Comparative Example 1 is significantly lower than that of Example 3. Comparative Example 2, in which no DOPO derivative is added, has poor flame retardant performance, indicating that the DOPO derivative prepared by the present invention has stronger flame retardant performance. This is because DOPO is grafted onto 2-aminothiazole and 2,5-dihydroxyterephthalaldehyde after reaction, and the derivative molecule has a double DOPO group. At the same ratio, its flame retardant performance is improved, so the amount of flame retardant can be reduced, thereby improving the overall performance of the resin.

[0066] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A high frequency low ESR organic chip solid tantalum electrolytic capacitor, characterized in that: It comprises a tantalum block, wherein the center of one end of the tantalum block is fixedly connected to a tantalum wire lead, the outer wall of the tantalum block forms a tantalum pentoxide dielectric layer through anodization, a conductive polymer layer is arranged outside the dielectric layer, a graphite layer and a silver powder paint layer are arranged outside the conductive polymer layer, the outer wall of the silver powder paint layer is connected to a cathode guide block away from one end of the tantalum wire lead, the tantalum wire lead is connected to an anode guide block, and the tantalum block is entirely wrapped with a modified epoxy resin protective layer; The modified epoxy resin protective layer comprises the following raw materials in parts by weight: 30-40 parts of epoxy resin, 5-10 parts of DOPO derivative, 25-30 parts of curing agent, and 3-5 parts of synergistic flame retardant. The structural formula of the DOPO derivative is as follows: The preparation method of the DOPO derivative comprises the following steps: S1. Dissolve 2-aminothiazole and 2,5-dihydroxyterephthalaldehyde respectively with 1,4-dioxane, then slowly drop the 2,5-dihydroxyterephthalaldehyde solution into the 2-aminothiazole solution, raise the temperature to 55-65°C, and react for 6-8h; S2, dissolving DOPO with 1,4-dioxane, and then slowly adding it to the above reaction system, heating to 75-85°C, and continuing the reaction for 6-8h; S3. After the reaction is completed, the product is subjected to rotary evaporation, and the obtained viscous solid is placed in a vacuum oven and dried at 60-70° C. for 8-10 hours to obtain the DOPO derivative.

2. The high frequency low ESR organic chip solid tantalum electrolytic capacitor according to claim 1, characterized in that: The conductive polymer layer is phosphoric acid-doped poly 3,4-ethylenedioxythiophene.

3. The high frequency low ESR organic chip solid tantalum electrolytic capacitor according to claim 1, characterized in that: The method for preparing the modified epoxy resin protective layer comprises the following steps: (1) weighing epoxy resin, DOPO derivative, and synergistic flame retardant according to the ratio, putting the raw materials into a mixer, stirring at 1000-2000 rpm for 20-30 min, adding a curing agent and continuing to stir for 3-5 min to obtain a modified epoxy resin slurry; (2) The assembled capacitor is placed in a mold, and the prepared modified epoxy resin slurry is squeezed in, and cured at 100 to 120° C. for 1 to 2 hours to form a modified epoxy resin protective layer.

4. The high frequency low ESR organic chip solid tantalum electrolytic capacitor according to claim 1, characterized in that: The curing agent is one or more of imidazoles, imidazolines, trialkylphosphine, quaternary ammonium salts, quaternary phosphonium salts and organic ureas.

5. The high frequency low ESR organic chip solid tantalum electrolytic capacitor according to claim 1, characterized in that: The synergistic flame retardant is one or more of diammonium hydrogen phosphate, melamine cyanurate, sodium triphosphate, diammonium dihydrogen phosphate, magnesium hydroxide, aluminum hydroxide and aluminum oxalate.

6. The high frequency low ESR organic chip solid tantalum electrolytic capacitor according to claim 1, characterized in that: The molar ratio of the 2-aminothiazole, 2,5-dihydroxyterephthalaldehyde and DOPO is 2:1:2.

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