TWI845164B - Method for manufacturing carbon-coated cathode foil for electrolytic capacitor, cathode foil and electrolytic capacitor - Google Patents

Abstract

The present invention provides a method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor, the cathode foil and the electrolytic capacitor. The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor comprises the following steps: step (a): immersing an aluminum foil body in a zinc replacement solution to plate a zinc replacement layer on the aluminum foil body; step (b): immersing the aluminum foil body with the zinc replacement layer in an electroless nickel plating solution to plate a nickel layer on the zinc replacement layer; and step (c): spraying slurry on the nickel layer to form a carbon layer on the nickel layer. The cathode foil is manufactured by the steps (a) to (c). The electrolytic capacitor comprises a casing; an anode foil; the cathode foil obtained by the steps (a) to (c); a dielectric between the anode foil and the cathode foil; and two lead terminals respectively connected to the anode foil and the cathode foil.

Description

Method for manufacturing carbon-coated cathode foil for electrolytic capacitor, cathode foil and electrolytic capacitor

The present invention provides an electrolytic capacitor and a method for manufacturing the same, and in particular, a method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor, the cathode foil and the electrolytic capacitor.

Electrolytic capacitors are made by winding anode aluminum foil, dielectric that has been chemically treated to form an oxide film on the anode aluminum foil, cathode aluminum foil, electrolytic paper, and lead terminals, impregnating them with electrolyte, placing them in an aluminum shell, and then sealing them with rubber.

Among them, although the cathode aluminum foil has not been chemically treated, it will still naturally oxidize during manufacturing or use, forming an oxide film on the surface of the cathode aluminum foil. That is, when the oxide film is formed on the cathode aluminum foil, it will form an unexpected capacitance with the dielectric on the surface of the anode aluminum foil, causing the electrolytic capacitor itself to form a capacitor series, which will reduce the overall capacitance value of the electrolytic capacitor component and fail to achieve the ideal expected electrical performance.

Therefore, if you want to obtain an ideal large capacitance, you must rely on increasing the electrode surface area, increasing the number of winding layers, or connecting more capacitors in parallel, which will increase the manufacturing cost on the one hand and occupy the circuit board area on the other hand, which is completely inconsistent with the design trend of electronic devices that are thin and short.

One purpose of the present invention is to provide a method for manufacturing a carbon-coated cathode foil for electrolytic capacitors, which prevents the formation of an additional oxide layer on the surface of the cathode aluminum foil by coating the carbon metal film, thereby solving the unexpected capacitor series effect and maintaining the excellent electrical performance of the electrolytic capacitor.

Another purpose of the present invention is to provide a method for manufacturing a carbon-coated cathode foil for electrolytic capacitors, thereby preventing the formation of an additional oxide layer on the surface of the cathode aluminum foil, thereby increasing the capacitance value of the overall capacitor by more than ten times.

Another purpose of the present invention is to provide an electrolytic capacitor with a carbon-coated cathode foil, which prevents the formation of an additional oxide layer on the surface of the cathode aluminum foil, thereby increasing the capacitance value of the overall capacitor by more than ten times.

Another object of the present invention is to provide an electrolytic capacitor with a carbon-coated cathode foil, which can significantly reduce the volume of capacitors with the same capacitance value and reduce the area occupied by the circuit board.

The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor disclosed in the present invention comprises the following steps: a) immersing an aluminum foil body in a zinc replacement solution to plate a zinc replacement layer on the aluminum foil body; b) immersing the aluminum foil body with the zinc replacement layer in a nickel plating solution to electrolessly plate a nickel layer on the zinc replacement layer; and c) spraying a slurry on the nickel layer to coat the nickel layer with a carbon film. The above-mentioned manufacturing method can produce a cathode foil with a carbon-coated metal film on the surface. On the one hand, it still has good conductivity, and on the other hand, the internal metal film is completely covered without being directly exposed to the air. In particular, the thickness of the coated carbon film can be easily controlled to an ideal thickness of several microns, and it can be produced quickly and economically to meet market demand.

According to one embodiment of the present invention, the step a) further includes: after the aluminum foil body is soaked in the zinc replacement solution, the aluminum foil body is soaked in pure water and alcohol in sequence, and then dried, thereby coating the aluminum foil body with the zinc replacement layer.

According to an embodiment of the present invention, the step b) further comprises: soaking the aluminum foil body having the zinc replacement layer in the nickel plating solution, and then soaking it in pure water and alcohol in sequence, and drying it.

According to one embodiment of the present invention, before step a), step d) is further included: the aluminum foil body is sequentially soaked in an acetone aqueous solution, a pure water, a sodium hydroxide aqueous solution and another pure water, and then dried for a cleaning step.

According to an embodiment of the present invention, the slurry contains a phenolic resin, an N-methylpyrrolidone and a carbon black.

According to one embodiment of the present invention, the step c) includes the following sub-steps: c1) spraying the slurry on the nickel layer and drying it; c2) spraying the slurry on the other side of the aluminum foil body opposite to the nickel layer and drying it; and c3) solidifying the slurry to form the carbon layer.

According to one embodiment of the present invention, the step c) further includes: before spraying the slurry onto the nickel layer, heating the aluminum foil body having the zinc replacement layer and the nickel layer (step c4).

The electrolytic capacitor comprises a shell; an anode foil; the cathode foil obtained by the above-mentioned manufacturing method; an electrolytic paper located between the anode foil and the cathode foil; and two lead terminals respectively connected to the anode foil and the cathode foil, wherein the anode foil, the cathode foil and the electrolytic paper are sealed in the shell in a coiled shape, and the two lead terminals extend outward from the shell.

Therefore, the present invention can achieve the effect of improving the adhesion between the aluminum foil body and the carbon layer and the structural stability and reliability of the cathode foil as a whole by sequentially forming a zinc replacement layer and a nickel layer between the aluminum foil body and the carbon layer.

1:Electrolytic capacitor

2. 2’: cathode foil

3: Anode foil

4: Electrolytic paper

5, 5’: Lead-out terminal

10: Shell

20, 20’: Aluminum foil body

22, 22’: Zinc replacement layer

24, 24’: Nickel layer

26, 26’: Carbon layer

110~140, 140’~148’: Steps

FIG1 is a schematic diagram showing the process of manufacturing a carbon-coated cathode foil for an electrolytic capacitor according to an embodiment of the present invention.

Figure 2 shows a schematic diagram of the structure of the cathode foil of an embodiment of the present invention.

FIG3 is a schematic diagram showing a partial process of manufacturing a carbon-coated cathode foil for an electrolytic capacitor according to another embodiment of the present invention, illustrating the spraying process.

FIG4 is a schematic diagram showing the structure of the cathode foil of the embodiment of FIG3.

Figure 5 shows a schematic diagram of the structure of the electrolytic capacitor of the present invention.

Figure 6 shows a schematic cross-sectional view of the electrolytic capacitor of the present invention.

The following is a specific example to illustrate the implementation of the present invention. People familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this manual.

The structures, proportions, sizes, etc. shown in the attached drawings of this manual are only used to match the contents disclosed in the manual for people familiar with this technology to understand and read. They are not used to limit the conditions under which the present invention can be implemented, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "one", "two", "upper", etc. quoted in this manual are only for the convenience of description, and are not used to limit the scope of the present invention. The changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

Please refer to FIG. 1 and FIG. 2 . The method for manufacturing the electrolytic capacitor carbon-coated cathode foil of the present invention mainly includes a pre-treatment process, a zinc replacement process, a nickel plating process and a spray coating process. In this example, an aluminum foil with a thickness of 25 to 50 microns is used as the cathode foil substrate. For the sake of convenience, it is referred to as an aluminum foil body 20. In the pre-treatment process, in step 110, a cathode foil with an area of 10 cm x 10 cm is firstly treated. The 20 cm aluminum foil body 20 is soaked in acetone, and then soaked in pure water for cleaning in step 112, and then soaked in a sodium hydroxide aqueous solution in step 114, and then cleaned with pure water in step 116, and finally dried in step 118, thereby cleaning the surfaces of the aluminum foil body 20.

The cleaned aluminum foil body 20 is then immersed in a zinc replacement aqueous solution in step 120 to plate a zinc replacement layer 22 on the aluminum foil body 20. Then, it is immersed in pure water again in step 122 and in alcohol in step 124 to remove impurities on the surface and zinc that has not been stably attached, and then dried again in step 126 to plate a zinc replacement layer 22 several microns thick on the surface of the aluminum foil body 20, hereinafter referred to as zinc-replaced aluminum foil.

Thereafter, in step 130, the aluminum foil body 20 having the zinc replacement layer 22 is immersed in a nickel plating aqueous solution for electroless chemical plating to plate a nickel layer 24 on the zinc replacement layer 22 of the zinc replacement aluminum foil. Similarly, after being immersed in pure water in step 132 and in alcohol in step 134, it is dried in step 136 to plate a nickel layer 24 with a thickness of several microns on the surface of the zinc replacement layer 22. For the convenience of explanation, it is hereinafter referred to as nickel-zinc-aluminum foil. Finally, in step 140, a slurry is sprayed on the nickel layer 24 to form a carbon layer 26 on the nickel layer 24, thereby isolating the contact and oxidation of the nickel-zinc-aluminum foil and oxygen, so that the cathode foil will not cause additional unexpected capacitance, and the electrical performance of the electrolytic capacitor can be ensured. The electrolytic capacitor manufactured by the present invention can easily increase the capacitance value of the electrolytic capacitor element, which is currently only about 100mF, by more than ten times without increasing the surface area of the anode and cathode, and achieve the effect of several farads.

The slurry is composed of phenolic acid, N-methylpyrrolidone and carbon black and is homogenized by ultrasonic vibration. A cathode foil 2 obtained by the above method includes, for example, an aluminum foil body 20 with a thickness of about 34 microns and a zinc replacement layer 22 with a thickness of about 2 microns, a nickel layer 24 with a thickness of about 3 microns and a carbon layer 26 with a thickness of about 4 microns formed on its upper surface in sequence.

Through the above steps, even if there is an aluminum oxide film originally formed on the surface of the aluminum foil body, it will be replaced by zinc and nickel, and a carbon layer is formed on the nickel layer by simply spraying and drying. Not only can the formation process of the carbon layer be very economical and rapid, but the thickness of the carbon layer can reach the ideal thickness of several microns. The layers have good adhesion and stability, and can also eliminate oxidation and degradation during use, effectively preventing unexpected equivalent series capacitance and increasing the capacitance value between the anode and cathode of the entire component.

Of course, as those skilled in the art can easily understand, when both sides of the dried nickel-zinc-aluminum foil need to be sprayed, as shown in FIG. 3 and FIG. 4 , the nickel-zinc-aluminum foil is first placed on a heating table to be heated to a preheating temperature in step 140 ′, and the slurry is sprayed on the nickel layer 24 ′ on one side of the nickel-zinc-aluminum foil, which is defined as the front side. In step 142', the slurry of the nickel layer 24' on the front side is dried, and then in step 144', the nickel-zinc-aluminum foil is turned over, and in step 146', the slurry is sprayed on the back side of the nickel-zinc-aluminum foil opposite to the front side and dried. Finally, in step 148', the nickel-zinc-aluminum foil with the slurry sprayed on both sides is placed in a temperature higher than the preheating temperature. The slurry is heated in an oven at a temperature of 1000°C to solidify, and a carbon layer 26' of several microns is formed on both sides of the nickel layer, so that a zinc replacement layer 22' and a nickel layer 24' are formed on both sides of the aluminum foil body 20' of the cathode foil 2', and a structure in which a carbon film is added to the surface of the nickel-zinc metal film on both sides of the nickel-zinc-aluminum foil is achieved. According to the above manufacturing method, a cathode foil for electrolytic capacitors that is not easily oxidized on the surface is manufactured.

Furthermore, an electrolytic capacitor 1 made of the cathode foil as shown in FIG5 and FIG6 comprises a shell 10; an anode foil 3; a cathode foil 2 made by the above method; an electrolytic paper 4 located between the anode foil 3 and the cathode foil 2; and two lead terminals 5, 5' respectively connected to the anode foil 3 and the cathode foil 2, wherein the anode foil 3, the cathode foil 2 and the electrolytic paper 4 are in a coiled shape and sealed in the shell 10 after being impregnated with an electrolyte, and the two lead terminals 5, 5' extend outwardly from the shell 10 in parallel, so as to facilitate the positive terminal of the power supply to be electrically connected to one of the lead terminals 5 and the negative terminal of the power supply to be electrically connected to the other lead terminal 5'. That is, the cathode foil 2 can achieve the reduction of the equivalent series capacitance value of the electrolytic capacitor 1 and increase the overall capacitance value of the electrolytic capacitor 1 by replacing the aluminum oxide originally formed on the aluminum foil body 20 with the zinc replacement layer 22.

In summary, the present invention can achieve the effect of improving the adhesion between the aluminum foil body 20 and the carbon layer 26 and the stability and reliability of the cathode foil 2 as a whole by forming the zinc replacement layer 22 and the nickel layer 24 between the aluminum foil body 20 and the carbon layer 26. Not only can the aluminum oxide originally formed on the aluminum foil body 20 be removed, but also it can be ensured that the cathode foil will not be accidentally oxidized during use, thereby reducing the equivalent series capacitance value of the electrolytic capacitor 1 and increasing its overall capacitance value. In particular, the manufacturing cost is quite economical, and the output efficiency and product yield are good, which can fully meet the trend of thin and short electronic components and reduce the area occupied on the circuit board.

The above embodiments are only for illustrative purposes to illustrate the principle and efficacy of the present invention, and are not intended to limit the present invention. Anyone familiar with this technology may modify the above embodiments without violating the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be as listed in the scope of the patent application described below.

S100: Method for manufacturing electrolytic capacitor carbon-coated metal film cathode foil

S110~S160: Steps (a1), (a)~(c)

Claims (9)

A method for preparing a carbon-coated cathode foil for an electrolytic capacitor comprises the following steps: a) immersing a cleaned aluminum foil body in a zinc replacement solution to plate a zinc replacement layer on the aluminum foil body; b) immersing the aluminum foil body with the zinc replacement layer in a nickel plating solution to electrolessly plate a nickel layer on the zinc replacement layer; and c) spraying a slurry on the nickel layer to coat the nickel layer with a carbon film. The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor as described in claim 1, wherein the step a) further comprises: after the aluminum foil body is immersed in the zinc replacement solution, the aluminum foil body is immersed in pure water and alcohol in sequence, and then dried, thereby coating the aluminum foil body with the zinc replacement layer. The method for manufacturing a carbon-coated cathode foil for electrolytic capacitors as described in claim 2, wherein the step b) further comprises: soaking the aluminum foil body having the zinc replacement layer in the nickel plating solution, then soaking it in pure water and alcohol in sequence, and drying it. The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor as described in claim 1 further includes a step d) before step a): soaking the aluminum foil body in an acetone aqueous solution, a pure water, a sodium hydroxide aqueous solution and another pure water in sequence, and then drying the aluminum foil body for cleaning. A method for preparing a carbon-coated cathode foil for an electrolytic capacitor as described in claim 1, wherein the slurry comprises a phenolic resin, an N-methylpyrrolidone and a carbon black. The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor as described in claim 1, wherein the step c) includes the following sub-steps: c1) spraying the slurry onto the nickel layer and drying it; c2) spraying the slurry onto the other side of the aluminum foil body opposite to the nickel layer and drying it; and c3) solidifying the slurry to form the carbon layer. The method for manufacturing a carbon-coated cathode foil for an electrolytic capacitor as described in claim 1, wherein the step c) further comprises: before spraying the slurry onto the nickel layer, heating the aluminum foil body having the zinc replacement layer and the nickel layer (step c4). A cathode foil for an electrolytic capacitor is made according to the method of claim 1, 2, 3, 4, 5, 6 or 7. An electrolytic capacitor comprises: a shell; an anode foil; a cathode foil as described in claim 8 above; an electrolytic paper located between the anode foil and the cathode foil; and two lead terminals respectively connected to the anode foil and the cathode foil, wherein the anode foil, the cathode foil and the electrolytic paper are sealed in the shell in a coiled shape, and the two lead terminals extend outward from the shell.

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