JP3433478B2 - Solid electrolytic capacitors - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor having good heat resistance. 2. Description of the Related Art A conventional solid electrolytic capacitor has, as an anode, a portion of a valve metal such as aluminum, tantalum or niobium having a dielectric oxide film layer on the surface, and a semiconductor layer and a conductor as the remainder. The layers are sequentially formed to form a cathode portion, and an insulating resin layer portion is formed at the interface between the anode portion and the cathode portion to form a capacitor element. Then, this capacitor element and a lead frame are connected as shown in FIGS. I have. FIG. 3 is a plan view showing a connection relationship between the capacitor element 2 and the lead frame 1, and FIG. 4 is a sectional view thereof. The anode section 3 and the cathode section 4 of the capacitor element 2 are mounted on the facing projections 1a and 1b of the lead frame, respectively. The former is welded or the like and the latter is made of silver paste or the like. Electrical,
After mechanical connection, it is manufactured by performing encapsulation 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 solder heat resistance test and passed. [0005] However, when a solid electrolytic capacitor sealed and molded with an exterior resin using a conventional lead frame for a cathode terminal and an anode terminal is subjected to a solder heat resistance test, it is found that the solder temperature is high. , The LC value increased. Such deterioration in performance is considered to be caused by destruction of the capacitor element due to thermal stress. To prevent this, it has been considered that the stress is relaxed by covering the capacitor element with an elastic resin or the like. However, since the curing shrinkage during curing of the elastic resin or the like becomes large, another stress is applied to the capacitor element, and as a result, the tan δ value increases. In particular, the rise of the tan δ value at high frequencies of the solid electrolytic capacitor is large, and it has been difficult to improve both the heat resistance and the tan δ value described above. An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor which solves these problems and has good heat resistance performance. The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the cause of the destruction of the capacitor element due to thermal stress during the soldering heat test is that the lead frame cathode is The present inventors have found that the tip of the lead portion exerts a stress on the cathode portion of the capacitor element, and have completed the present invention. [0005] That is, 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, a semiconductor layer is formed on the remaining part, and a conductor layer is formed thereon. Formed as a cathode part, an insulating resin layer part is formed at the interface between the anode part and the cathode part to form a capacitor element, and then the cathode part of the lead element and the anode lead part of the lead frame are respectively connected to the cathode part of the capacitor element. A solid electrolytic capacitor in which an anode portion is connected and sealed with an exterior resin, wherein a tip of the cathode lead lead-out portion is located in the insulating resin layer portion. As the anode substrate having a valve action used as the anode of the solid electrolytic capacitor in the present invention, any metal having a valve action such as aluminum, tantalum, and alloys using these as a substrate can be used. And as the shape of the anode substrate, aluminum foil,
A plate-like or rod-like sintered tantalum body is exemplified. 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 portion of the valve metal, or may be another oxide layer provided on the surface of the valve metal. It may be a dielectric oxide layer, 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 anodizing method using an electrolytic solution can be used. A portion for forming an anode portion is selectively exposed on the dielectric oxide film layer, and an insulating resin layer portion is formed in contact with the anode portion. Examples of the type of insulating resin used for the insulating resin layer include conventionally known resins such as a fluororesin, an acrylic resin, an alkyd resin, a cellulose resin, a phenol resin, a silicone resin, a butadiene resin, and an epoxy resin. The size of the insulating resin layer portion is usually 0.1 to 5 mm in width, and the above-mentioned anode portion and the later-described cathode portion are separated by forming a headband shape on the anode substrate.
In FIGS. 1 to 4, the insulating resin layer portion 5 is shown larger in order to facilitate understanding. In the cathode portion, a semiconductor layer and a conductor layer thereon are sequentially formed. The type of the semiconductor layer is not particularly limited, and a conventionally known semiconductor layer can be used. In particular, a semiconductor layer composed of lead dioxide or lead dioxide and lead sulfate (Japanese Patent Application Laid-Open No.
JP-A-256423 and JP-A-63-51621) are preferable because the high frequency performance of the manufactured solid electrolytic capacitor is good. 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 (Japanese Patent Application Laid-Open No. 62-4710)
No. 9) 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 also examples. This semiconductor layer is provided with a cathode portion by laminating a conventionally known conductive paste such as a carbon paste and / or a silver paste to form a conductor layer. As shown in FIGS. 1 and 2, the lead frame for connecting the above-described capacitor element
It is important that the tip of the cathode lead-out portion 1b is located in the insulating resin layer portion 5 of the capacitor element 2. FIG. 1 is a plan view in which the cathode part 4 and the anode part 3 of the above-described capacitor element 2 are mounted on the cathode lead part 1b and the anode lead part 1a of the lead frame 1, respectively, and FIG. 2 is a sectional view thereof. The connection between the cathode portion 4 of the capacitor element 2 and the cathode lead portion 1b of the lead frame 1 is made of a conductive paste or solder, and the connection between the anode portion 3 of the capacitor element 2 and the anode lead portion 1a of the lead frame 1 is welding. And so on. As the material of the lead frame used in the present invention, for example, a commonly known lead frame metal such as bronze, copper, iron-nickel alloy and the like is used. The surface of the lead frame may be subjected to solder plating or tin plating of several μm. The solid electrolytic capacitor element connected to the lead frame in this way is sealed with transfer molding or the like using an exterior resin such as an epoxy resin, and then the convex portion of the lead frame is cut near the exterior resin to form an anode. A lead and a cathode lead are formed to form a solid electrolytic capacitor. It is considered that the deterioration of the capacitor due to the thermal stress at the time of the soldering heat test can be reduced by providing the tip of the cathode lead portion of the lead frame on the insulating resin layer portion of the capacitor element. The present invention will be described below in more detail with reference to examples and comparative examples. Examples 1 to 5 A small 5 mm × 3 mm 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 a surface subjected to a chemical conversion treatment in an aqueous solution of phosphoric acid and ammonium phosphate was prepared. A 1 mm × 3 mm portion from the end was used as an anode portion, and an insulating resin layer portion was formed with an insulating resin shown in Table 1 on a 1 mm × 3 mm portion in contact with the anode portion. The remaining 3 mm × 3 mm portion of the small piece was immersed in a mixed solution of an aqueous solution of lead acetate trihydrate 2.4 mol / l and an aqueous solution of ammonium persulfate 4.0 mol / l, and allowed to stand at 60 ° C. for 20 minutes. A semiconductor layer made of lead was formed. After such an operation was repeated three times, a carbon paste and a silver paste were sequentially laminated on the semiconductor layer to form a cathode portion, thereby producing a capacitor element. On the other hand, a lead frame having a width of 3.2 mm opposed to two places, and a material having an interval of 0.5 mm between the projections of 0.5 mm, made of an iron-Ni alloy and having a thickness of 0.1 mm, is prepared. Is placed at the center of the insulating resin layer part of the capacitor element, the other end is placed at the inner end of the anode part of the capacitor element, the connection with the cathode part of the capacitor element is made of silver paste, and the connection with the anode part of the capacitor element is made. After being connected by welding, the package was formed by transfer molding with an epoxy resin to form a solid electrolytic capacitor. Comparative Examples 1 and 2 In Examples 1 and 2, a lead frame having a protrusion interval of 1.5 mm was prepared. One end of the protrusion was the cathode of the capacitor element and the other end was the capacitor element. A solid electrolytic capacitor was prepared in the same manner as in Examples 1 and 2, except that the capacitor was mounted on the inner end of the anode. Table 2 summarizes the performance of the solid electrolytic capacitors of Examples 1 to 5 and Comparative Examples 1 and 2 and the tan δ value and LC value after the heat resistance test immersed in a 240 ° C. solder bath for 30 seconds. Indicated. Note that all numerical values are average values of n = 30 points. [Table 1] [Table 2] The solid electrolytic capacitor of the present invention has very good heat resistance since the tip of the cathode lead lead-out portion of the lead frame is located in the insulating resin layer portion of the capacitor element.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a state where a capacitor element is mounted on a lead frame. FIG. 2 is a cross-sectional view showing a state where a capacitor element is mounted on a lead frame. FIG. 3 is a plan view showing a state where a conventional capacitor element is connected to a lead frame. FIG. 4 is a cross-sectional view showing a state where a conventional capacitor element is connected to a lead frame. [Description of Signs] 1 Lead frame 1a Projection 1b of lead frame Projection 2 of lead frame 2 Capacitor element 3 Anode 4 Cathode 5 Insulating resin layer

Claims (1)

(57) [Claims 1] A part of an anode substrate having a valve action and having a dielectric oxide film layer formed on a surface is used as an anode part, the remainder is a semiconductor layer, and a conductor is provided thereon. The layers are sequentially formed to form a cathode portion, an insulating resin layer portion is formed at the interface between the anode portion and the cathode portion to form a capacitor element, and then the capacitor elements are formed on a cathode lead extraction portion and an anode lead extraction portion of a lead frame, respectively. A solid electrolytic capacitor obtained by connecting a cathode part and an anode part and sealingly molding with an exterior resin, wherein a tip end of the cathode lead lead-out part is located in the insulating resin layer part.