JP5063374B2 - Solid electrolytic capacitor - Google Patents

Description

The present invention, LC (leakage current) of the solid electrolytic capacitor relates the reduction of defects.

  As shown in FIGS. 2 and 3, the conventional capacitor is formed by winding the anode electrode foil 13 and the cathode electrode foil 14 connected to the lead tab terminal 101 as an electrical lead through a separator 15 to mix the monomer and the oxidizing agent. Capacitor element 100 in which a solid electrolyte layer (not shown because it is thin) is filled between anode electrode foil 13 and cathode electrode foil 14 is immersed in a working solution or a separate solution.

  Thereafter, the capacitor element 100 is put in the aluminum case 20 and sealed with rubber 21 or the like.

  Here, as shown in FIG. 3, the lead tab terminal 101 includes a round bar portion 8, a flat portion 9 formed by processing the round bar portion 8 into a flat shape, and a lead wire 10 connected to the round bar portion 8. The round bar portion 8 and the flat portion 9 are anodized, and the flat portion 9 is connected to the anode foil 13 and the cathode foil 14. The round bar portion 8 and the flat portion 9 are anodized to form an anodic oxide film, and occurrence of short circuits and reduction of LC defects have been performed.

In recent years, wound type solid electrolytic capacitors have a market demand for miniaturization and large capacity. For example, the number of windings is increased by using electrode foils (anode foil and cathode foil) of about 20 μm to 150 μm, and the electrode foils are increased. A high-density capacitor element is obtained by enlarging the effective surface area by performing high-density etching treatment on the electrode, or winding the electrode foil while applying high tensile stress.
JP 2001-284174 A

  Anodized films are formed by anodic oxidation on the round bar portion 8 and the flat portion 9 of the lead tab terminal 101. However, since the adhesion strength is not so strong, winding is performed while applying high tensile stress to the electrode foil as described above. As a result, cracks and peeling occurred in the anodic oxide film, and there were problems such as occurrence of short circuit and LC (leakage current) failure.

The present invention relates to a capacitor element lead tab terminal is turned respectively connected anode foil and winding a cathode foil, in the solid electrolytic capacitor impregnated with a solid electrolyte, lead tab terminal, the round bars unit anode foil or the cathode a flat portion connected to the foil, and a lead wire connected to the round rod portion, on the surface of the flat portion, and characterized that you have an aluminum oxide film or a titanium oxide film is formed by sputtering To do.

  Preferably, the sputtering is reactive sputtering.

  According to the present invention, the film is formed more firmly than the anodic oxide film formed by anodic oxidation, so that film peeling hardly occurs, and occurrence of short circuit and LC (leakage current) can be reduced.

  In addition, since it is an oxide film of at least one metal selected from the group consisting of IVa group, Va group, and VIa group, it has better wear resistance than aluminum, and its hardness is harder, so film peeling and the like hardly occur. Short circuit occurrence and LC (leakage current) can be reduced.

  Further, by forming the metal oxide film by reactive sputtering, a metal oxide film suitable for the application can be easily formed by appropriately changing the oxygen concentration without preparing a large number of sputtering targets.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.
Example 1
3A is a perspective view, FIG. 3B is a view seen from the direction of the arrow, FIG. 3C is an enlarged view of a flat portion, and FIGS. As shown in an enlarged view of a different flat part, a round bar part 8, a flat part 9 processed into a flat shape leaving a part of the round bar part 8, and a lead wire 10 connected to the round bar part 8, It consists of

Next, in order to form the aluminum oxide film on the flat portion 9, a vacuum film forming apparatus 1 having a magnetron sputtering cathode 6, a heater 5, a substrate rotating mechanism that rotates in the direction of the arrow as shown in FIG. (AIP-S40 multifunction machine manufactured by Kobe Steel, Ltd.) was used.
After mounting the aluminum metal target on the sputtering cathode 6, tab terminals (round bar portion 8 and flat portion 9) are attached to the planetary rotating jig 4 provided on the rotary table 3 in the vacuum film forming apparatus 1. (Substrate) is inserted and fixed, exhausted to a vacuum state, the inside of the vacuum layer is replaced with an atmosphere containing argon gas and oxygen gas, the discharge power applied to the sputtering cathode 6 is about 2 kW, argon The gas flow rate was fixed at 120 sccm, and the oxygen gas flow rate and discharge voltage were adjusted as appropriate. In other words, during film formation, the gas composition at a position of about 20 mm from the target surface where aluminum atoms evaporate was measured with plasma emission spectroscopy using the emission intensity of aluminum and oxygen as a guide, and the result was obtained. The discharge voltage was adjusted based on the pulse DC reaction sputtering method. The thickness of the aluminum oxide film on the flat portion 9 of the tab terminal was 5.3 μm by fluorescent X-ray analysis. In FIG. 3, the aluminum oxide film is not shown because it is thin.

  Here, even if sputtering was intermittently formed, a similar film could be produced. In this case, the film thickness and the film formation time per one time were adjusted by controlling the rotation speed and discharge power of the rotary table 3 and the planetary rotating jig 4.

  Here, although aluminum was used as a material which comprises the round bar part 8 and the flat part 10, another metal material may be used. The lead wire 10 can be an iron wire, a copper wire, or an iron wire coated with copper, and the surface thereof is solder-plated for easy soldering.

  Next, a perspective view of the capacitor element 100 is shown in FIG. FIG. 4 is a cross-sectional view of a solid electrolytic capacitor.

As shown in FIG. 2, after the aluminum foil to be the anode foil 13 is etched, it is subjected to an electrolytic conversion treatment with a phosphoric acid aqueous solution or an adipic acid aqueous solution of 0.01 to 2 wt% to form a dielectric film on the surface, Anode foil 13 was obtained. Here, the dielectric film is not shown because it is thin.
Next, the obtained anode foil 13 and the cathode foil 14 are opposed to each other, and wound between the anode foil 13 and the cathode foil 14 in a cylindrical shape via a separator 15 made of electrolytic paper mainly composed of Manila hemp, The capacitor element 100 was formed by stopping with the winding tape 16.
Here, the separator 15 may be a nonwoven fabric mainly composed of PET (polyethylene terephthalate), vinylon, or aramid fiber.

Next, the capacitor element 100 was impregnated with 3,4-ethylenedioxythiophene as a polymerizable monomer and 50 wt% p-toluenesulfonic acid ferric ethanol solution as an oxidant solution, and heated to 280 ° C. By polymerizing, a conductive polymer layer was formed between the anode and cathode electrodes of the capacitor element 100. Here, a conductive inorganic material such as manganese dioxide or a TCNQ complex salt exhibits the same effect, but more preferably, it is advantageous because the conductivity of the conductive polymer is large.
Next, as shown in FIG. 3, a sealing rubber 21 is inserted into the capacitor element 100, and is stored and fixed in an aluminum case 20 having a size φ8 × 11.5L, and then the opening of the aluminum case 20 is curled with a horizontal diaphragm. Then, sealing is performed, and then an aging process is performed.
Next, a plastic seat 22 is inserted into the curled surface of the capacitor, and the lead wires 18 (for anode) and 19 (for cathode) of the capacitor are pressed and bent as electrode terminals to complete a solid electrolytic capacitor. It was.
(Example 2)
In Example 2, in the formation of the lead tab terminal 100, a titanium metal target is mounted on the sputtering cathode 6 of the vacuum apparatus 1, the discharge power applied to the sputtering cathode 6 is about 3 kW, the argon gas flow rate is constant at 130 sccm, It was produced in the same manner as in Example 1 except that the oxygen gas flow rate and the discharge voltage were appropriately adjusted.

The thickness of the titanium oxide film in the flattened portion obtained as a result of the above was 4.2 μm by fluorescent X-ray analysis.
(Comparative Example 1)
In Comparative Example 1, the oxide film of the lead tab terminal was formed by immersing only the flat part 9 in a 2.0% ammonium adipate aqueous solution and increasing the voltage at a constant voltage of 400 V, followed by anodic oxidation for 2 hours. The film thickness of the aluminum oxide film on the flat portion 9 was 5.7 μm by fluorescent X-ray analysis.

  The lead tab terminal was manufactured in the same manner as in Example 1 except that the oxide film was formed by anodic oxidation.

Table 1 shows the lead tab terminal oxide film formation method, metal oxide film thickness, metal oxide film thickness, LC (leakage current), and LC (leakage current) yield of capacitors manufactured in Examples 1 and 2 and Comparative Example 1. . (The number of prototypes is 300, and the measured value is the average)
The prototype is rated voltage 2.5V, rated capacity 180pF (Φ6.3mm, length 6.0mm)
In the leakage current measurement, LC (leakage current) 60 seconds after applying 2.5 V was measured.
As the LC (leakage current) yield, a standard value of 300 μA or less was accepted.

  From the results of Table 1, in Examples 1 and 2, LC (leakage current) was suppressed to about 20% to 30% lower than that in Comparative Example 1.

  Further, regarding the film thickness of the metal oxide film, although the titanium oxide film is 4.2 μm and about 1 μm thinner than the aluminum oxide film 5.3 μm, it shows almost the same LC (leakage current) and yield. This is because the IVa, Va, and VIa groups have higher wear resistance, heat resistance, hardness and the like than Al.

  Moreover, it is reactive sputtering, and a further favorable film | membrane can be easily formed by changing gas concentration.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications without equivalent meaning and scope to the scope of claims for patent.

Schematic diagram of vacuum deposition system It is a capacitor element figure of a capacitor. It is (a) perspective view of the lead tab terminal concerning this invention, (b) The top view seen from the arrow direction, (c) The enlarged view of the flat shape of a flat part. It is sectional drawing of a solid electrolytic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum film-forming apparatus 2 Base material 3 Rotary table 4 Planetary rotating jig 5 Heater 6 Sputtering cathode 8 Round bar part 9 Flat part 10 Lead wire 100 Capacitor element 12 Capacitor element body 13 Anode foil 14 Cathode foil 15 Separator 16 Winding tape 18 Anode lead wire 19 Cathode lead wire

Claims (2)

In a solid electrolytic capacitor in which a solid electrolyte is impregnated in a capacitor element in which an anode foil and a cathode foil each having a lead tab terminal connected thereto are wound,
The lead tab terminal, e Bei a flat portion connected to the anode foil and the cathode foil and the round bar portion, and a lead wire connected to the round rod portion,
Wherein the surface of the flat portion, the solid electrolytic capacitor characterized that you have been aluminum oxide film or titanium oxide film formed by the sputtering. The sputtering is solid electrolytic capacitor according to claim 1, characterized in that the reactive sputtering.

Images