JPS6132807B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a chip-shaped solid electrolytic capacitor. Conventionally, chip-shaped solid electrolytic capacitors that are face-bonded and attached to printed circuit boards, etc. have been covered with resin by transfer molding, but these have been large in size and expensive. In addition, there was a bare type that was not transfer molded and had a solderable metal terminal welded to the lead drawn out from the anode body of the capacitor element, but the dimensional accuracy was poor, the mechanical strength was low, and it was difficult to attach to the printed circuit board. It was difficult to automate the installation. In addition, all of the above-mentioned products require a step of welding a metal terminal to the lead-out lead, which has the disadvantage that the structure is complicated and it is difficult to miniaturize. The present invention eliminates the above-mentioned drawbacks and provides a method for manufacturing a chip-shaped solid electrolytic capacitor that is small, easy to manufacture, and can be manufactured at low cost. The present invention will be explained below with reference to embodiments shown in FIGS. 1 to 4. First, as shown in FIG. 1, the lead-out leads 1 of a plurality of prismatic, cylindrical, etc. anode bodies 2 made of valve metal such as tantalum or aluminum and having lead-out leads 1 are welded and connected to the power supply bar 3. , a dielectric film 4 is formed on the surface of the anode body 2, and a semiconductor solid electrolyte layer 5 such as manganese dioxide is formed on the film;
Cathode conductive layer 6 such as carbon and silver paste
are formed sequentially. Next, a reinforcing resin 7 such as epoxy is applied to the lead-out portion of the lead-out lead 1 and cured.
A resin layer 8 is formed by applying an epoxy resin to cover the anode body 2, leaving the ends of the anode and cathode extraction electrode parts selectively. Note that if the resin layer covers the end of the anode electrode part, that part may be removed by air blasting, sandblasting, or the like. Furthermore, alumina powder is sprayed onto the resin layer 8 and foreign matter adhering to the lead-out lead 1, and the deposits are removed by a so-called sandblasting method, and the dielectric oxide film 4 on the surface of the lead-out lead 1 is also removed. Irregularities 1a are formed on the surface. However, if the dielectric oxide film 4 is not formed on the portion of the lead-out lead 1 to be subjected to electroless plating, the unevenness 1a may not be formed by sandblasting. Next, a cathode conductive layer 9 made of silver paste or the like is applied and hardened to the cathode side electrode portion selectively left without forming the resin layer 8 at the bottom of the anode body 2, and on top of that, iron is further added to the silver paste or the like. Then, a conductive layer containing a different metal such as copper is applied to the cathode conductive layer 6 and cured. At this time, the conductive layer 10 is also applied to the anode side and hardened. Commercially available silver paste for solid electrolytic capacitors usually contains 40 to 60% by weight of metal components such as silver, but in this case, the content of metal components such as silver does not impair the electrical characteristics of the capacitor. as long as
The amount is preferably 30% by weight or more, and a metal of the same type or a different type of metal that can be electrolessly plated with the cathode conductive layer 6 such as silver is mixed together with a solvent such as butyl cellosolve, coated, and cured, then the conductive layer is formed. When the component ratio of the same kind of metal or different kind of metal is in the range of 55% to 90% by weight, the plating property and heat resistance are excellent.
The dissimilar metals may include a mixture of one or more metals including iron, nickel, copper, tin, zinc, and lead, as well as noble metals such as gold, silver, and palladium. Next, a notch is made in the lead-out lead 1 by the power supply bar 3 in order to separate the lead-out lead wire 1. Then, an electroless plating process is performed on solderable nickel, copper, or the like to form an unresolved plating layer 11 on the conductive layer 10 and the lead-out lead 1, which do not have a dielectric oxide film. Thereafter, a solder layer 12 is formed by contacting with molten solder, and after aging treatment, the lead-out lead 1 is bent from the notch and separated from the power supply bar 3 to complete the process. The method for manufacturing a chip-shaped solid electrolytic capacitor of the present invention is carried out as described above. Therefore, the external electrode does not require a welding process, and has a conductive layer such as silver, an electroless plating layer that can be soldered, and an electrolytic layer such as a solder layer, so it is less expensive than conventional electrode layers such as silver and solder layers. However, it prevents the migration of silver into the solder at high temperatures, that is, solder bulging, and the conductive layer constituting the electrode part contains at least one kind of similar metal or a dissimilar metal that can be electrolessly plated. This has the effect that electroless plating can be formed evenly and extremely uniformly. The table shows a chip-shaped solid electrolytic capacitor with a rating of 315 V and 100 μF. The conductive layer 9 is formed using conventional silver paste, and the metal components of the conductive layer 10 containing the same or different metals are varied to improve plating performance and heat resistance. In the table, sample numbers 4 to 11 are the products of the present invention, sample numbers 1, 2, 3,
12 and 13 are samples for comparison. The conductive layer was prepared by mixing a resin-curing conductive material containing 50% by weight of silver with silver as a similar metal, or iron powder and a solvent as dissimilar metals, and varying the mixing ratio.

[Table] Items marked with an x in the plating properties and heat resistance in the table have almost no plating adhesion, and electrode cracking occurs in the soldering heat resistance test at 260°C for 1 minute (according to JIS C 5102). Those marked with △ lacked plating adhesion stability, and electrode cracking was observed in the soldering heat resistance test. For those marked with ○, the plating adhesion was stabilized by selecting the plating liquid, and the soldering heat resistance test was within the practically acceptable range. Those marked with ◎ had uniform plating thickness, good plating adhesion stability, and no electrode cracks were observed in the soldering heat resistance test. Furthermore, in terms of workability in the table, those marked with ○ indicate those for which the conductive layer material can be coated, those marked with △ indicate those that are difficult to coat, and those marked with x indicate those that cannot be coated. As is clear from the table, a range of 55 to 90% by weight of the metal component of the conductive layer containing the same or different metals is effective.If it is less than 55% by weight, the adhesion of electroless plating will be poor, and if it exceeds 90% by weight. The conductivity deteriorates and the equivalent series resistance of the capacitor also increases. In addition, the metal components of the different metals in the conductive layer mentioned above were 50% by weight of silver and 20% by weight of iron, and 40% by weight of silver in sample number 7.
% by weight and 30% by weight of iron, similar results are obtained when the metal component is 70% by weight, and similar effects are obtained for other sample numbers when the total amount of metal components is the same. This was confirmed. Furthermore, by forming the conductive layer 9 into two layers in the above-described embodiment, pinholes caused by evaporation of moisture stored in the capacitor element can be prevented, and plating liquid can also be prevented from entering the inside of the capacitor element through the pinholes. It has been confirmed that this can be prevented. In the above embodiment, the electrode layer was constructed by applying silver paste, and the case was described in which the dissimilar metal contained iron, but the inclusion of nickel, copper, tin, precious metals, etc. has a similar effect; Instead of paste, an organic solvent paste such as copper or tin may be used, or the conductive layer may be formed by sputtering or the like. As mentioned above, the chip-shaped solid electrolytic capacitor formed by the manufacturing method of the present invention is small and has extremely strong electrodes, and is extremely advantageous in terms of electrical characteristics and productivity, and has industrial and practical value. It is a great thing.

[Brief explanation of the drawing]

1 to 4 are explanatory diagrams of the manufacturing process of a chip-shaped solid electrolytic capacitor according to an embodiment of the present invention. 1: Derivation lead, 2: Anode body, 4: Dielectric oxide film, 5: Solid electrolyte layer, 6, 9: Cathode part conductive layer, 8: Resin layer, 10: Anode part and cathode part conductive layer, 11: None Electrolytic plating layer, 12: solder layer.

Claims (1)

[Claims] 1. A dielectric oxide film 4 is formed on the surface of an anode body 2 made of a valve metal having a lead-out lead 1, and a solid electrolyte layer 5 and a cathode conductive layer 6 are formed on the film,
A resin layer 8 is formed to selectively leave the ends of the anode and cathode extraction electrode parts and cover other parts of the anode body, and the anode conductive layer and the cathode are formed on the selectively left parts. At least one cathode conductive layer 9 , 10 containing the same or different metal is formed with respect to the conductive layer 6 , and an electroless plating layer 1 is formed on the conductive layer 9 , 10 and on the metal of the lead-out lead 1 .
1. A method for manufacturing a chip-shaped solid electrolytic capacitor, the method comprising forming a chip-shaped solid electrolytic capacitor and soldering the capacitor.