JPH04360508A - Manufacture of solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve humidity resistance by using a lead frame provided with a belt type thermosetting resin layer at a part position which is positioned on a cathode lead leading-out part on which a capacitor element is not mounted, intersects the outward leading-out direction of the cathode lead leading-out part, and is coated with sheath resin. CONSTITUTION:Thermosetting resin 2 spread and cured at a part position which is on a cathode leading-out part 1b of a lead frame 1, intersects the outward leading-out direction of the cathode lead leading-out part, is coated with sheath resin, and is not connected with the conductor layer forming part of a laminate. That is, the thermosetting resin 2 18 spread between an A-A' part and a B-B' part. A conductor layer forming part 5 and an anode part 4 of a capacitor element 3 are mounted on and connected with a cathode leading-out part 1b and an anode leading-out part 1a of a lead frame 1, respectively. Seal molding is performed by transfer molding using sheath resin, so as to cover the thermosetting resin 2 which has already cured. An anode lead and a cathode lead are formed by cutting protruding parts of the lead frame 1 in the vicinity of the sheath 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 with good moisture resistance.

0002

[Prior Art] In conventional solid electrolytic capacitors, a part of a 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 remaining part is made up of a semiconductor layer and a conductive layer in sequence. This capacitor element is formed into a capacitor element, and then this capacitor element and a lead frame are connected as shown in FIG. FIG. 4(a) is a plan view showing the connection relationship between the capacitor element 3 and the lead frame 1;
b) is a sectional view thereof. The anode part 4 and the conductor layer forming part 5 of the capacitor element 3 are placed on the mutually facing convex parts 1a and 1b of the lead frame, and the former is welded and the latter is made of silver paste, etc. After electrically and mechanically connecting the protrusion, it is manufactured by sealing and molding with an exterior resin. On the other hand, the produced solid electrolytic capacitors are manufactured as products after passing various reliability tests such as moisture resistance tests.

0003

[Problems to be Solved by the Invention] However, when testing the moisture resistance of a solid electrolytic capacitor that uses a conventional lead frame as the cathode terminal and anode terminal and is sealed with an exterior resin, moisture enters over time and the capacitance increases. Shi,tan
This resulted in an increase in the δ value and LC value. This deterioration in performance is thought to be due to moisture entering the capacitor through the lead frame. To prevent this, the curing temperature of the outer resin should be raised to strengthen the bond with the lead frame. was considered. However, increasing the curing temperature of the exterior resin increases curing shrinkage of the resin, which causes stress to be applied to the solid electrolytic capacitor element within the seal, resulting in a disadvantage in that the tan δ value increases. In particular, the ta of solid electrolytic capacitors at high frequencies is
The increase in nδ value was large, making it difficult to improve both the moisture resistance and tanδ value described above. Therefore, an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor with good moisture resistance.

0004

[Means for Solving the Problems] The gist of the present invention is to use a part of an anode substrate having a valve action and a dielectric oxide film layer formed on the surface as an anode part, and a semiconductor layer on the remaining part, and a conductive layer on the anode part. The body layers are sequentially formed to form a capacitor element, and then the conductor layer forming part and the anode part of the capacitor element are connected to the cathode lead lead-out part and the anode lead lead-out part of the lead frame, respectively, and sealed with an exterior resin. When manufacturing a solid electrolytic capacitor, a band-shaped portion is placed on the cathode lead draw-out portion where the capacitor element is not placed, intersects with the external pull-out direction of the cathode lead draw-out portion, and is covered with the exterior resin. This manufacturing method is characterized by using a lead frame provided with a thermosetting resin layer.

[0005] As the anode substrate having a valve action used as an anode of a solid electrolytic capacitor in the present invention, any metal having a valve action can be used, such as aluminum, tantalum, and alloys using these as substrates. The shape of the anode substrate is aluminum foil,
Examples include plate-shaped or rod-shaped tantalum sintered bodies. The dielectric oxide film layer provided on the surface of the anode substrate may be an oxide layer of the valve metal itself provided on the surface of the valve metal, or an oxide layer of the valve metal itself provided on the surface of the valve metal. Although it may be a dielectric oxide layer, it is particularly desirable to be a layer made of an oxide of the valve metal itself. In either case, a conventionally known method such as an anodization method using an electrolytic solution can be used to provide the oxide layer.

A semiconductor layer is formed on the dielectric oxide film layer by selectively exposing a portion where an anode portion will be formed. There are no particular restrictions on the type of semiconductor layer, and conventionally known semiconductor layers can be used, but in particular, semiconductor layers made of lead dioxide or lead dioxide and lead sulfate (Japanese Patent Application Laid-Open No. 62-256423 Publication No. 63-5162
No. 1) is preferable because the produced solid electrolytic capacitor has good high frequency performance. In addition, a semiconductor layer formed of a conductive polymer compound such as polyaniline or polypyrrole by vapor phase polymerization using an oxidizing agent and an organic acid (Japanese Patent Laid-Open No. 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 (Japanese Unexamined Patent Publication No. 62-38715).

[0007] On this semiconductor layer, a conventionally known conductive paste such as carbon paste and/or silver paste is laminated to form a conductive layer to form a capacitor element.

[0008] It is important that the lead frame to which the above-mentioned capacitor element is connected be coated with a thermosetting resin in the form of a band at predetermined portions and hardened in advance. The portion where the thermosetting resin is applied and cured is shown in FIGS. 1(a) and 1(b). FIG. 1(a) shows a portion on the cathode lead-out portion 1b of the lead frame 1, which intersects with the external drawing direction of the cathode lead-out portion, is covered with an exterior resin, and is not connected to the conductor layer forming portion of the laminate, that is, A. -Lead frame 1 with thermosetting resin 2 applied and hardened between A' part and B-B' part
FIG. 3B is a plan view of FIG.

[0009] As the thermosetting resin used in the present invention,
Commercially available thermosetting resins can be used. Examples include epoxy resins, phenol resins, crosslinked butadiene resins, alkyd resins, urethane resins, imide resins, and amide-imide resins. Further, examples of the method for applying the thermosetting resin to a predetermined portion of the lead frame include a method using a dispenser and a method using screen printing.

[0010] Regarding the coating and curing temperature of the thermosetting resin used in the present invention, it is important that the resin be completely cured over a sufficient period of time at the curing temperature of each resin. For example, in the case of epoxy resin, it is preferable to cure it at 160° C. or higher for several hours.

As the material of the lead frame used in the present invention, commonly known metals for lead frames, such as bronze, copper, and iron-nickel alloys, are used. The surface of the lead frame may be plated with several μm of solder or tin.

The size of the cured portion of the thermosetting resin coated above may be within the range of the A-A' and B-B' sections, and the coating area, thickness, etc. should be determined depending on the lead frame. Since it varies depending on the conductor layer formation area of the capacitor element to be connected, the type of thermosetting resin, or the type of chemically formed foil, it is determined appropriately through preliminary experiments.

FIG. 2 is a cross-sectional view of a lead frame 1 having steps where a thermosetting resin 2 is applied and cured.

FIG. 3(a) shows the capacitor element 3 described above.
It is a plan view in which the conductor layer forming part 5 and the anode part 4 are placed on the cathode extension part 1b and the anode extension part 1a of the lead frame 1, respectively, and FIG. 2B is a cross-sectional view thereof. The aforementioned conductor layer forming portion 5 of the capacitor element 3 and the cathode lead-out portion 1b of the lead frame 1 are bonded by conductive paste or solder, and the anode portion 4 of the capacitor element 3 and the anode lead-out portion 1a of the lead frame 1 are Connections are made by welding, etc.

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

[0016]

[Operation] By applying a lead frame in which a sufficiently cured thermosetting resin is formed in a predetermined portion to the lead frame of a solid electrolytic capacitor, the curing temperature of the exterior resin of the solid electrolytic capacitor after sealing does not have to be high. It is also believed that this can prevent moisture from entering the lead frame during moisture resistance tests.

[0017]

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples. Example 1 A small piece of 5 x 3 mm of 45 μF/cm2 aluminum etching foil (hereinafter referred to as chemical foil) on which a dielectric oxide film layer was formed on the surface that had been chemically treated in an aqueous solution of phosphoric acid and ammonium phosphate was treated with lead acetate trihydrate. A 3 x 3 mm portion of the small piece was immersed in a mixed solution of a 2.4 mol/l aqueous solution of ammonium persulfate and a 4.0 mol/l aqueous solution of ammonium persulfate and left at 60°C for 20 minutes to form a semiconductor layer consisting of lead dioxide and lead sulfate. was formed. After repeating this operation three times, carbon paste and silver paste were sequentially laminated on the semiconductor layer to form a conductor layer, thereby producing a capacitor element. On the other hand, the width is 3.2mm
Prepare a lead frame with two opposing protrusions, made of iron-Ni alloy and 0.1 mm in thickness, and connect one of the protrusions to the conductive layer of the capacitor element described above.
Using a dispenser, apply epoxy resin 3.2 x 1 mm and 0.5 to 1.0 mm thick at 3 to 4 mm from the tip of the convex part, excluding the 3.2 mm part, and heat it at 175°C for 50 minutes.
It hardened over time. A capacitor element is mounted on this lead frame, and the connection with the conductor layer of the capacitor element is made with silver paste, and the connection with the anode part of the capacitor element (1 x 3 mm part of the part where the semiconductor layer is not formed) is made. After connecting by welding, the capacitors were covered with epoxy resin by transfer molding, and cured at 130° C. for 10 hours to produce a chip-shaped solid electrolytic capacitor.

Example 2 In Example 1, instead of using an epoxy resin as the thermosetting resin that was previously attached to the lead frame and curing it at 175°C for 5 hours, an alkyd resin was used and it was cured at 160°C for 3 hours.
A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1, except that the capacitor was cured over time.

Example 3 In Example 1, instead of using epoxy resin as the thermosetting resin that was previously attached to the lead frame and curing it at 175°C for 5 hours, a phenol resin was used and it was cured at 160°C for 3 hours.
A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1, except that the capacitor was cured over time.

Example 4 In Example 1, instead of using epoxy resin as the thermosetting resin to be attached to the lead frame in advance and curing it at 175°C for 5 hours, a urethane resin was used and curing at 160°C for 3 hours. Except for this, a chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1.

Example 5 Instead of the semiconductor layer used in Example 1, a chemically formed foil was immersed in a 2.0 mol/l aqueous solution of lead acetate trihydrate, and the semiconductor layer was immersed between it and a separately prepared platinum cathode. A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1, except that electrochemically formed lead dioxide was used.

Example 6 In Example 5, instead of using epoxy resin as the thermosetting resin that was previously attached to the lead frame and curing it at 175°C for 5 hours, an alkyd resin was used and it was cured at 160°C for 3 hours.
A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1, except that the capacitor was cured over time.

Example 7 In Example 5, instead of using epoxy resin as the thermosetting resin that was previously attached to the lead frame and curing it at 175°C for 5 hours, a phenol resin was used and it was cured at 160°C for 3 hours.
A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1, except that the capacitor was cured over time.

Example 8 In Example 5, instead of using epoxy resin as the thermosetting resin to be attached to the lead frame in advance and curing it at 175°C for 5 hours, a urethane resin was used and curing at 160°C for 3 hours. Except for this, a chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1.

Comparative Example 1 [0025] In place of the lead frame to which a thermosetting resin was applied in advance in Example 1, a lead frame to which a thermosetting resin was not applied and hardened was used. A chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1.

Comparative Example 2 A chip-shaped solid electrolyte was produced in the same manner as in Comparative Example 1, except that the curing conditions for the exterior resin were changed to 175° C. for 5 hours instead of 130° C. for 10 hours. A capacitor was created.

Performance of solid electrolytic capacitors of Examples 1 to 8 and Comparative Examples 1 to 2 prepared as described above and temperature at 85° C.
The tan δ values after the humidity test (500 hours) in 5% RH are summarized in Table 1. Note that all numerical values are the average value of n=20 points.

[0028]

[Table 1]

[0029]

[Effects of the Invention] According to the manufacturing method of a solid electrolytic capacitor of the present invention, by using a lead frame in which a thermosetting resin layer is provided in advance on the portion covered with the exterior resin, the manufactured solid electrolytic capacitor is tested during a moisture resistance test. The moisture resistance is extremely good.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a lead frame in which a thermosetting resin is applied and hardened to a predetermined portion of a cathode lead-out portion of the lead frame. (b) is a cross-sectional view of a lead frame in which a thermosetting resin is applied and hardened to a predetermined portion of the cathode lead-out portion of the lead frame.

FIG. 2 is a cross-sectional view of a lead frame in which a thermosetting resin is applied and hardened to a predetermined portion of a cathode lead-out portion of the lead frame having a step.

3(a) is a plan view showing a state in which a capacitor element is placed on the lead frame of FIG. 1; FIG. (b) is a sectional view showing a state in which a capacitor element is placed on the lead frame of FIG. 1. FIG.

FIG. 4 is a sectional view showing a conventional solid electrolytic capacitor element connected to a lead frame.

[Explanation of symbols]

1 Lead frame 1a Convex part of lead frame 1b Convex part of lead frame 2 Thermosetting resin 3 Capacitor element 4 Anode part 5 Conductor layer forming part

Claims (1)

[Claims] Claim 1: A capacitor element is formed by forming a part of the anode substrate having a valve action and having a dielectric oxide film layer formed on the surface as an anode part, a semiconductor layer in the remaining part, and a conductor layer thereon in sequence. Then, when manufacturing a solid electrolytic capacitor by connecting the conductor layer forming part and anode part of the capacitor element to the cathode lead lead-out part and the anode lead lead-out part of the lead frame, respectively, and sealing and molding with an exterior resin, A lead that is located on the cathode lead draw-out portion on which the capacitor element is not placed, and is provided with a band-shaped thermosetting resin layer at a portion that intersects with the external pull-out direction of the cathode lead draw-out portion and is covered with an exterior resin. A method for manufacturing a solid electrolytic capacitor, characterized by using a frame.