JPH07106201A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance the humidity resistance by a method wherein thermorsetting resin layers are formed on specific positions of a lead frame whereon a capacitor element is mount-junctioned to be seal-molded with an exterior resin before or after the connection of an anode lead out part and a capacitor element anode. CONSTITUTION:Before and after the connection of an anode leading-out part 1a and an anode part of a capacitor element 3 by welding step, etc., the position covered with an exterior resin but not to be connected to the cathode part 5 of the capacitor element 3 on the cathode leading-out part 1b of a lead frame and the other position covered with the exterior resin on the rear surface of the cathode leading-out part 1b are coated with a thermosetting resin 2 to be set later. At this time, as for the exterior resin, a commercial thermosetting resin is applicable while the solid electrolytic capacitor element 3 connected to the lead frame is seal-molded out of the exterior resin e.g. an epoxy resin, etc., by transfer molding step, etc., as if covering the preset thermosetting resin 2 and then the protrusions 1a, 1b of the lead frame are cut off in the parts near the exterior resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a solid electrolytic capacitor having good moisture resistance.

[0002]

2. Description of the Related Art In a conventional solid electrolytic capacitor, a part of valve metal such as aluminum, tantalum or niobium having a dielectric oxide film layer on its surface is used as an anode part, and the rest is a semiconductor layer and a conductor layer sequentially. The cathode portion is laminated to form a capacitor element, which is then connected to the lead frame as shown in FIGS. 4 and 5. FIG. 4 is a plan view showing the connection relationship between the capacitor element 3 and the lead frame 1, and FIG. 5 is a sectional view thereof. The anode part 4 and the cathode part 5 of the capacitor element 3 are placed on the projecting parts 1a and 1b of the lead frame facing each other. The former is welding and the latter is silver paste, and the projecting parts of the lead frame 1 are mounted. It is manufactured by electrically and mechanically connecting and then sealing and molding with an exterior resin. On the other hand, the manufactured solid electrolytic capacitor is a product that has passed various reliability tests such as a moisture resistance test and passed.

[0003]

However, when a moisture resistance test is carried out after mounting a solid electrolytic capacitor, which is formed by molding a conventional lead frame as a cathode terminal and an anode terminal with an exterior resin and molded with an exterior resin, by soldering, the moisture content increases with time. And the capacity increased, leading to an increase in tan δ value and LC value.
It is considered that such deterioration of performance is caused by a gap at the interface between the lead frame and the exterior resin due to thermal stress during mounting with solder, and moisture is transmitted inside the capacitor through the lead frame. In order to prevent this, it has been considered to increase the curing temperature of the exterior resin to strengthen the bonding with the lead frame. However, by increasing the curing temperature of the exterior resin, the curing shrinkage of the resin increases, so that stress is applied to the solid electrolytic capacitor element in the encapsulation, and as a result, the tan δ value increases. Especially, tan δ at high frequency of solid electrolytic capacitor
The increase in the value was large, and it was difficult to improve both the above-mentioned moisture resistance and the tan δ value. An object of the present invention is to solve these problems and to provide a method of manufacturing a solid electrolytic capacitor having good moisture resistance.

[0004]

SUMMARY OF THE INVENTION The gist of the present invention is that a part of an anode substrate having a valve action and having a dielectric oxide film layer formed on its surface is used as an anode part, the rest is a semiconductor layer, and a conductive layer is formed thereon. A body part is sequentially laminated to form a cathode part to form a capacitor element,
Next, placing the cathode part and the anode part of the capacitor element on the cathode lead extraction part and the anode lead extraction part of the lead frame, respectively, and connecting the cathode lead extraction part and the cathode part of the capacitor element, and the anode Before or after the connection between the lead lead-out portion and the anode portion of the capacitor element, the capacitor lead-out portion is located at a position where it is in contact with the end face of the cathode portion of the capacitor element and the capacitor element is not mounted, and the cathode lead-out portion is pulled out to the outside. A part of the thermosetting resin layer that intersects with the exterior resin and that is located on the back surface of the cathode lead extraction portion on which the capacitor element is mounted and that is covered with the exterior resin is provided with a strip-shaped thermosetting resin layer; A method of manufacturing a solid electrolytic capacitor, which comprises a step of sealing and molding with an exterior resin while leaving a part of a lead frame.

As the anode substrate having a valve action which is used as the anode of the solid electrolytic capacitor in the present invention, any metal having a valve action such as aluminum, tantalum, and an alloy having these as a substrate can be used. And as the shape of the anode substrate, aluminum foil,
Examples include plate-shaped or rod-shaped sintered tantalum. The dielectric oxide film layer provided on the surface of the anode substrate may be an oxide layer of the valve action metal itself provided on the surface portion of the valve action metal, or another layer provided on the surface of the valve action metal. It may be a layer of a dielectric oxide, but is preferably a layer made of an oxide of the valve metal itself. In any case, as a method for providing the oxide layer, a conventionally known method such as an anodization method using an electrolytic solution can be used.

A semiconductor layer is formed on the dielectric oxide film layer by selectively exposing the portion forming the anode portion. The type of semiconductor layer is not particularly limited, and conventionally known semiconductor layers can be used. In particular, a semiconductor layer composed of lead dioxide or lead dioxide and lead sulfate according to the applicant of the present application (Japanese Patent Laid-Open No. 62-256423). Japanese Patent Laid-Open No. 63-5162
No. 1) is preferable because the produced solid electrolytic capacitor has good high-frequency performance. Further, a semiconductor layer in which a conductive polymer compound such as polyaniline or polypyrrole is formed by gas phase polymerization using an oxidizing agent and an organic acid (JP-A-62-4).
7109) and a semiconductor layer in which thallium oxide is chemically precipitated from a reaction mother liquor containing thallium ions and persulfate ions (JP-A-62-38715) are examples thereof. On this semiconductor layer, a cathode layer is formed by laminating a conductor layer with a conventionally known conductive paste such as carbon paste and / or silver paste to form a capacitor element. In the present invention, an insulating resin layer part may be formed in a spiral shape at the interface between the above-mentioned anode part and cathode part.

In the above-mentioned capacitor element, the cathode portion and the anode portion of the capacitor element are placed on the cathode lead lead portion and the anode lead lead portion of the lead frame, respectively, and the cathode lead lead portion and the capacitor element cathode portion are placed. Solder,
Connect with a conductive material such as silver paste. Then, before or after connecting the anode lead lead-out portion and the anode portion of the capacitor element by welding or the like, the capacitor element element is located at a position where it is in contact with the end face of the cathode element of the capacitor element and the capacitor element is not mounted. A band-shaped heat is applied to a portion that intersects with the external lead-out direction of the lead lead-out portion and is covered with the exterior resin and a portion that is located on the back surface of the cathode lead lead-out portion on which the capacitor element is mounted and that is covered with the exterior resin. A curable resin layer is provided. The portion where the thermosetting resin is applied and cured is shown in FIGS. 1, 2 and 3.

FIG. 1 shows a portion on the cathode lead-out portion 1b of the lead frame 1 which intersects with the external lead-out direction of the cathode lead-out portion and is covered with an exterior resin, to which the cathode portion 5 of the capacitor element 3 is not connected, that is, A -A 'part and BB'
FIG. 2 is a top view showing a state in which a thermosetting resin 2 is applied and cured between the parts. FIG. 2 is located on the back surface of the cathode lead lead-out part 1b on which the capacitor element 3 is mounted and is covered with an exterior resin. FIG. 4 is a bottom view showing a state where the thermosetting resin 2 is applied and cured between the portions, that is, the CC ′ portion and the DD ′ portion, and FIG. 3 is a sectional view thereof.

The thermosetting resin used in the present invention includes:
A commercially available thermosetting resin can be applied. For example, epoxy resin, phenol resin, cross-linking butadiene resin, alkyd resin, urethane resin, imide resin, amide imide resin and the like can be mentioned. Examples of the method of applying the thermosetting resin to a predetermined portion of the lead frame include a method using a dispenser and a method using screen printing.

As the material of the lead frame used in the present invention, generally known lead frame metals such as bronze, copper and iron-nickel alloy are used. The surface of the lead frame may be plated with solder or tin having a thickness of several μm. The size of the coated and cured portion of the thermosetting resin described above may be within the range of the AA ′ portion and the BB ′ portion described above and within the range of the CC ′ portion and the DD ′ portion. The coating area, the thickness, etc., vary depending on the area of the cathode portion of the capacitor element connected to the lead frame, the type of thermosetting resin, or the type of the chemical conversion foil, and are appropriately determined by preliminary experiments.

In the present invention, when the thermosetting resin is applied within the range of the AA 'portion and the BB' portion as described above, the cathode portion of the capacitor element is caused by the flow diffusion of the thermosetting resin. By flowing to the upper surface, a thermosetting resin thin film may be formed on the upper surface of the cathode portion after the thermosetting resin is cured.

The solid electrolytic capacitor element thus connected to the lead frame is sealed and molded by transfer molding or the like with an exterior resin such as epoxy resin so as to cover the thermosetting resin which has already been applied and cured. After that, the convex portion of the lead frame is cut near the exterior resin to form the anode lead and the cathode lead, and the solid electrolytic capacitor is obtained.

[0013]

[Function] Since the thermosetting resin layer is formed at a predetermined portion of the lead frame on which the capacitor element is mounted and joined,
It is considered that moisture can be prevented from entering from the lead frame at the time of the humidity resistance test without raising the curing temperature of the exterior resin of the solid electrolytic capacitor after sealing.

[0014]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 A small piece of a 45 μF / cm ² aluminum etching foil (hereinafter referred to as a chemical conversion foil) having a dielectric oxide film layer formed on the surface thereof subjected to chemical conversion treatment in phosphoric acid and an ammonium phosphate aqueous solution was cut into lead acetate 3 mm. A 3 mm × 3 mm portion of a small piece is dipped in a mixed solution of a hydrate of 2.4 mol / l and an ammonium persulfate solution of 4.0 mol / l, and the mixture is immersed at 60 ° C. for 20
After leaving for a minute, a semiconductor layer made of lead dioxide and lead sulfate was formed. After repeating such an operation three times, a carbon paste and a silver paste were sequentially laminated on the semiconductor layer to form a conductor layer, and a capacitor element was manufactured. On the other hand, width 3.
There are two 2 mm convex portions facing each other, and the anode part and the cathode part of the capacitor element are respectively placed on the two convex parts of the lead frame made of iron-Ni alloy and having a thickness of 0.1 mm. Was welded, and the cathode part was connected with silver paste. Next, at a position 3 to 4 mm from the tip of the lead frame to which the cathode part of the capacitor element was connected, 3.2 mm x 1 mm and a thickness of 0.
5 to 1.0 mm, 3.2 mm x 3 mm at a position 3 mm from the tip on the back side of the lead frame, and 0.5 to 1 mm in thickness
Apply epoxy resin with a dispenser and
Cured at 5 ° C. for 5 hours. Furthermore, except for a part of the projecting parts of the lead frame, it is packaged with epoxy resin by transfer molding, and then the projecting parts of the lead frame are cut in the vicinity of the packaging resin to form the anode lead and the cathode lead, and a solid electrolytic capacitor is created. did.

Examples 2 to 5 The epoxy resin was used as the thermosetting resin to be attached to the lead frame in Example 1, but the resin and curing temperature shown in Table 1 were used instead of curing at 175 ° C. for 5 hours. A solid electrolytic capacitor was produced in the same manner as in Example 1 except for the above.

Example 6 Instead of the semiconductor layer used in Example 1, the semiconductor layer was immersed in a 2.0 mol / l aqueous solution of lead acetate trihydrate, and the chemical conversion foil was immersed in the solution to form a platinum cathode separately prepared. A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the lead dioxide formed electrochemically was used.

Examples 7 to 10 In Example 6, instead of using the epoxy resin as the thermosetting resin to be attached to the lead frame and curing at 175 ° C. for 5 hours, the resin and curing temperature shown in Table 1 were used. Except I went
A solid electrolytic capacitor was produced in the same manner as in Example 1.

Comparative Example 1 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the lead frame was not coated with a thermosetting resin and cured.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the backside of the lead frame was not coated and cured when the lead frame was coated and cured with the thermosetting resin in Example 1. The performance of the solid electrolytic capacitors of Examples 1 to 10 and Comparative Examples 1 and 2 produced as described above and a humidity resistance test (250 hours) at 80 ° C. and 85% RH after being immersed in a solder bath at 240 ° C. for 10 seconds The subsequent performances are summarized in Table 2. All numerical values are average values of n = 30 points.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the method for producing a solid electrolytic capacitor of the present invention, the solid electrolytic capacitor produced by providing the thermosetting resin layer at a predetermined position of the lead frame on which the capacitor element is mounted and joined is soldered. Good moisture resistance afterwards.

[Brief description of drawings]

FIG. 1 is a top view showing a state in which a thermosetting resin is applied and cured on a predetermined portion of a cathode extraction portion of a lead frame on which a capacitor element is mounted.

FIG. 2 is a bottom view showing a state in which a thermosetting resin is applied and cured on a predetermined portion on the back surface of the cathode extraction portion of the lead frame on which the capacitor element is mounted.

FIG. 3 is a cross-sectional view showing a state in which a thermosetting resin is applied and cured on a predetermined portion of a cathode lead-out portion of a lead frame on which a capacitor element is mounted.

FIG. 4 is a plan view showing a state in which a conventional solid electrolytic capacitor element is connected to a lead frame.

FIG. 5 is a cross-sectional view showing a state in which a conventional solid electrolytic capacitor element is connected to a lead frame.

[Explanation of symbols]

 1 Lead Frame 1a Projection of Lead Frame 1b Projection of Lead Frame 2 Thermosetting Resin 3 Capacitor Element 4 Anode 5 Cathode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01G 9/05 F

Claims (1)

[Claims] 1. A part of an anode substrate having a valve action and having a dielectric oxide film layer formed on the surface thereof is used as an anode part, the rest is a semiconductor layer, and a conductor layer is sequentially laminated thereon to form a cathode part. To form a capacitor element, and then the cathode part and the anode part of the capacitor element are respectively placed on the cathode lead extraction part and the anode lead extraction part of the lead frame, and the cathode lead extraction part and the cathode part of the capacitor element are placed. Connection process,
Before or after the connection between the anode lead lead-out portion and the anode portion of the capacitor element, the cathode lead-out portion is in contact with the end face of the cathode portion of the capacitor element and where the capacitor element is not mounted. And a step of providing a strip-shaped thermosetting resin layer on a portion that intersects with the drawing direction and is covered with the exterior resin and on the back surface of the cathode lead extraction portion on which the capacitor element is mounted and that is covered with the exterior resin. A method for manufacturing a solid electrolytic capacitor, which comprises a step of sealing and molding with an exterior resin while leaving a part of the lead frame.