JPH04179109A - Method for manufacturing electrodes for chip-type solid electrolytic capacitors - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an electrode for a chip-type solid electrolytic capacitor, and particularly to a method of bonding an anode element and a lead of the electrolytic capacitor.

(Prior Art) A chip-type solid electrolytic capacitor has an anode element 1. As shown in the outline of its cross section in FIG. and one end of the ribbon-like REET 2 are joined, and this joined portion is coated with an insulating material 3. The other end of the lead 2 is joined to a lead frame 4. The surface of the anode element 1 is covered with an insulating film 5, and the outer surface of the anode element 1 is further covered with a cathode material 6 such as graphite. Reference numeral 7 denotes a cathode side lead frame, one end of which is joined to the cathode material 6 with a conductive material 8 such as silver paste.

These are then hardened with mold resin 9 to form a capacitor.

The anode element 1-, which is a component of the electrode, is made of a 1-base foil, that is, pure Aβ (99,99%) or an A1 alloy (for example, Al-Zr alloy, AA-Ti alloy, etc.),
Alternatively, it is made of a composite material of pure Aβ and A1 alloy, which is cut in advance to the desired anode element size, one end of the lead 2 is bonded, and then etched to make a rough surface and expand the surface area. Process. Further, a chemical conversion treatment is performed after this etching to form a dense oxide film (insulating film) such as β203 on the enlarged surface, thereby improving dielectric properties.

Conventionally, leads are bonded to elements that have been cut to predetermined dimensions in this way because the element surface, which has an oxide film formed through chemical formation, is difficult to connect to the leads due to the necessary electrical connections and This is because it becomes impossible to obtain sufficient bonding strength. The joined leads serve as a hanging device when the device is immersed in an electrolytic solution during etching or chemical conversion treatment.

(Problems to be Solved by the Invention) In such conventional methods, each cut piece is etched and chemically treated one by one, making the process complicated.
A problem has arisen that hinders productivity.

The present invention improves these conventional problems by etching and chemically treating the strip or large plate before cutting it into element shapes, thereby improving productivity and making it possible to cut the material after processing. An object of the present invention is to provide a method for manufacturing an electrode for a chip-type solid electrolytic capacitor in which bonding strength does not deteriorate by bonding the surface of the electrode to a lead.

(Means for Solving the Problems) In order to achieve the above object, the present invention involves etching an AI base foil to expand its surface area, and then chemically treating it to form an oxide film on the surface. A method for producing an electrode for a chip-type solid electrolytic capacitor, which comprises cutting an AA' base foil into a chip-type electrode of a desired size, and joining a lead to the center portion of the cut surface that has not undergone etching or chemical conversion treatment. The gist is:

The present invention will be explained in detail below.

The positive electrode material of the chip-type electrolytic capacitor in the present invention may be pure AI or A alloy as described above, or may be a composite (clad) foil of pure AI and A1 alloy.

In order to manufacture a large capacity capacitor, it is necessary to increase the surface area of the electrode material and to form a dense film with good insulating properties on the surface.

Conventionally used AI foil is oxidized to produce An
20. The dielectric constant of AA' 2 'Ch is approximately 7 to 10, which is higher than that of other metals, such as the oxide films of Ta and TI (Ta20. and TiO2), which are so-called valve metals. It's not that expensive. Therefore, attempts have been made to increase the surface area by mechanical means or electrochemical etching methods, while also improving the anodizing treatment to form an oxide film and increasing the capacitance.

On the other hand, by using an alloy of pure A and adding other alloying elements (valve metal) to increase the dielectric constant as the anode material, and manufacturing this alloy by a rapid solidification method, we have created an electrode material for large-capacity electrolytic capacitors. For example, JP-A-1-12
It is disclosed in Publication No. 4212. This includes T during AI
The present invention proposes an alloy foil electrode containing at least one type of valve metal such as i, Ta, Zr, Hf, and Nb, and in which an intermetallic compound of these valve metals and AI is finely dispersed and precipitated. Further, it is known from JP-A-1-29021 that a three-phase clad foil with such alloy foils on both sides and A[ as a core material in the middle is used for an electrolytic capacitor electrode.

The present invention is directed to all such AI-based materials that have already been proposed, but it is possible to create a foil in which pure AI exists even after etching, at least in the center, and this has a thickness suitable for bonding. It should be made of thick material.

That is, due to etching, pitting corrosion starts on the surface of the A [base material, and especially in the case of a clad material made of pure AA' as the core material and A1 alloy, such as A7-Zr alloy, bonded to the image side, etching occurs only on the I alloy. By performing irregular etching that exposes the intermetallic compound (Al3Zr) uniformly dispersed in the alloy, the surface area can be greatly expanded, and the center (core material) part contains pure AI that is easy to bond with the lead. It is possible to obtain a material (electrode material) in which

In the present invention, in addition to such etching, a chemical conversion treatment is subsequently performed to form an oxide film (A120° x Zr02) on the material whose surface area has been expanded by the etching, in the form of a strip or a large plate. This makes it possible to significantly improve processing efficiency.

Usually, the anode electrode of a chip-type electrolytic capacitor is square in shape, and after the formation, it is cut into a size suitable for the anode electrode. In the present invention, a lead is joined to the newly cut surface. That is, since an etched/chemical layer is formed on the upper and lower surfaces of the electrode material, which makes it difficult to bond, the REET is bonded to the pure AI layer on the cut surface with good bondability in the center of the cross section.

The joining method of the present invention will be explained below based on illustrated examples.

In FIG. 1, 1 is a cross section of an anode material, the upper and lower surfaces are made up of an etching/chemical layer 5, the intermediate layer is a pure metal (Aβ) layer 9, and a lead 2 is attached to a cut surface 10 on the anode material. This is an example of using a laser for joining. That is, 11 is a laser oscillator, 12 is a condensing lens, and 13 is a laser beam oscillated from the laser oscillator.The laser beam is irradiated from the outer surface of the REET and pure A.
A part of the β layer 9 is melted and bonded. 14 indicates a welded portion.

FIG. 2 is an example of resistance welding, with spot welding electrode 1
5 is brought into contact with the lead 2, and electricity is applied from the power source 16 to resistance weld the lead 2 and the pure AI layer 9. 17 is Nugget, 1
8 is a ground electrode.

Figure 3 shows an example of TIG welding, in which a tungsten electrode 19
Welding is performed by supplying an arc 20 generated from a weld. In the figure, 21 is a welding part, and 22 is a welding power source.

As described above, the present invention uses a band-shaped or large plate electrode material that has been etched or chemically treated as an electrode (anode) of a predetermined size.
After the material is cut, the leads are welded together using the above-described means to obtain a welded part with high joint strength. Thereafter, a chip type solid electrolytic capacitor having a structure as shown in FIG. 4 is manufactured.

(Example) Examples of the present invention are shown below.

Example 1 [Production of electrode foil] A roll made of Cu with a diameter of 300 m + n and a width of 50 mm was rotated at a speed of 1300 rpm in an inert scum, and on its surface were Affl 97 at% and Zr3 at% housed in a container.
0.5 kg/cn of molten metal consisting of the following components:
It is ejected from the nozzle below the container with an ejection pressure of f, and has a width of 40 mm.
mm, thickness 100~], 2011[+1] alloy foil was obtained. Next, the obtained alloy foil 23 was placed on both sides of the AIIO2 of a 03-thick plate and rolled to form a rad foil as shown in FIG.

[Etching, chemical conversion treatment]

A DC 1
00ri-0:// After etching with CI[l,
20V chemical conversion was performed using a boric acid solution.

[Electrode foil cutting]

The electrode foil subjected to the above treatment was slit into pentavalent widths using a slitter to form a hoop shape, and then cut into 3.3 lengths using a shear.

[Leat joining]

The electrode foil after cutting and pure A with a thickness of 10 hm and a width of 2 mm [leads with a thickness of 100 mm on the cut surface of the electrode foil as shown in Figure 1]
μm, width 2nd generation pure A! The REET 2 was stacked and laser spot welding was performed at two locations in the arrangement shown in the same figure.

Welding was performed using a YAG pulse laser welding device with a rated output of 20 J under welding conditions of an output of 6 J/pulse and a pulse width of 2 ms.

As a result of shearing and tensile testing of the electrode foil and lead welded in this manner, the breaking load was 1.5 kg, and sufficient strength was obtained. Further, the time required to arrange the lead material on the end face of the electrode foil and to join it was 10 seconds.

Example 2 An electrode foil was produced, etched, chemically treated, and cut in the same manner as in Example 1. As shown in FIG. Resistance spot welding was performed by overlapping the two.

The electrode used for welding had a tip diameter of 1 mmφ and a welding current of 100
Welding was performed at two locations under the conditions of 0 A, a pressing force of 2 kg, and a current application time of 20 m5 ec.

A tensile test was conducted on the joint in the same manner as the actual probe, and sufficient strength was obtained with a breaking load of 1.3 kg. The time required for joining was 12 seconds.

(Effects of the Invention) As explained above, according to the method of the present invention, productivity is improved due to improved workability, and since the cut surface of the electrode material is joined to the lead, the electrode and lead joint portion is Its industrial value is extremely large, as it is strong and reliable, and the capacitor itself can be made smaller.

[Brief explanation of the drawing]

1, 2, and 3 are diagrams showing an embodiment of the method of joining the electrode material and the lead of the present invention, FIG. 4 is a diagram showing a cross section of the cladding foil of the present invention, and FIG. FIG. 2 is an explanatory diagram of a chip-type solid capacitor. 1: Anode element 2; Lead 3: Insulating coating 4: Lead frame 5; Insulating film (etching/chemical layer) 6; Cathode material 7; Lead frame 8: Mold resin 9. Pure AI layer 10; cut surface 11; laser oscillator 12:
Condensing lens 13; Laser beam 14; Welding part 15; Spot welding electrode.

Claims (1)

[Claims] Etching the Al base foil to expand its surface area, then chemical conversion treatment to form an oxide film on the surface, cutting the thus treated Al base foil into chip-type electrodes of a desired size, and etching the cut surface. , and a method for manufacturing an electrode for a chip-type solid electrolytic capacitor, characterized in that a lead is joined to a central portion that has not undergone chemical conversion treatment.