JPS621245B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a ceramic capacitor that exhibits little deterioration of capacitor characteristics during solder immersion and has good solderability and electrode adhesion. [Prior Art] Conventionally, porcelain capacitors are made by mixing silver oxide or metallic silver powder mixed with lead borosilicate glass powder (frit) and a solution such as a solvent or resin to form a silver paste, which is then made into a porcelain element. Electrodes were formed by coating and baking on the body surface. However, this method has the disadvantage that after solder immersion, the silver electrode diffuses into the solder and peels off, resulting in a decrease in electrode adhesion strength, a decrease in capacitance, and a deterioration in tan δ. Therefore, after applying silver paste to the surface of the porcelain body, a method is proposed in which a silver layer is formed by a plating method using, for example, a plating solution mixed with chloro or soda or a plating solution mixed with cyanide, or by reducing dimethylamine borane. A method has been proposed in which a silver layer is laminated using an electroless silver plating method. [Problem to be solved by the invention] However, in the former case, if chlorine or soda is mixed, the resulting capacitor may have insulation defects, and if cyanide is used, it may cause pollution. The reality is that this method is not implemented due to reasons such as the need for large-scale equipment and undesirability, as there is a risk of inducing In the latter case, part of the silver layer diffuses into the solder or peels off during solder immersion, oxidizing the underlying silver layer, resulting in a decrease in electrode adhesion strength, a decrease in capacitance, and a decrease in tan.
This was not desirable as it might lead to deterioration of δ. [Object of the Invention] It is an object of the present invention to provide a method for manufacturing a ceramic capacitor that eliminates these drawbacks, has excellent mass productivity, and can be produced at low cost. [Means for Solving the Problems] The method for manufacturing a ceramic capacitor according to the present invention includes applying a first conductive layer to the surface of the ceramic body by a silver baking method, and reducing dimethylamine borane onto the first conductive layer. In a method for manufacturing a ceramic capacitor, in which an electrode is formed by laminating a silver layer by an electroless silver plating method and applying a second conductive layer, dimethylamine borane is applied as a reducing agent on the first conductive layer. A nickel layer is laminated on the first conductive layer by a nickel plating method before a silver layer is laminated by an electroless silver plating method and a second conductive layer is applied. [Function of the invention] In the present invention, the second conductive layer is formed by laminating a nickel layer on the first conductive layer by an electroless plating method using dimethylamine borane as a reducing agent, and on this nickel layer, dimethyl Since the silver layer is laminated using an electroless silver plating method using amine borane as a reducing agent, the adhesion between the nickel layer and the silver layer is good, and some of the silver on the surface layer diffuses into the solder when immersed in solder. Even so, the surface of the underlying nickel layer is not oxidized, so the solderability is good. [Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings. In the figure, reference numeral 1 denotes a porcelain body having an arbitrary shape, and a first conductive layer a made by coating and baking a known silver paste on designated areas on the surface of the porcelain body 1.
has been granted. 2 is a nickel layer formed on this first conductive layer a by an electroless plating method using dimethylamine borane as a reducing agent, and 3 is a nickel layer formed on this nickel layer 2 by an electroless silver plating method using dimethylamine borane as a reducing agent. It is a silver layer formed by
The nickel layer 2 and the silver layer 3 constitute a second conductive layer b. Next, a method for manufacturing a ceramic capacitor according to the present invention will be explained. First, the first conductive layer a is applied by applying and baking a silver paste mixed with a lead borosilicate glass powder (frit), a resin, and a solvent onto the surface of the porcelain element 1. As this silver paste,
For example, a mixture of 75% metallic silver powder, 6% lead borosilicate glass frit, 19% cellulose resin binder and carbitol acetate is used, and selected on the required surface area of the porcelain body 1 by screen printing. Coat and then bake at 800℃. In this first conductive layer a, strong adhesion is achieved by reinforcing the bond between the porcelain body 1 and the first conductive layer a formed by baking silver with a lead borosilicate glass frit. After applying the first conductive layer a, dirt on the surface is removed using an emulsion degreaser. Furthermore, the surface was activated by immersing it in about 5% dilute sulfuric acid for 1 to 3 minutes, and after washing with water, it was soaked in palladium chloride 50 in a 5% ferrous chloride solution.
After immersing in a solution containing ppm at 20℃ for 1 to 2 minutes, washing with water, and then electroless plating using dimethylamine borane (DMAB) as a reducing agent at 50 to 55℃ for 1 hour. Perform metsuki. Nickel chloride (NiCl ₂ 6H ₂ O) is used as an electroless plating solution.
30g/, sodium citrate (Na ₃ C ₆ H ₅ O ₇ .
2H ₂ O) 60g/, ammonium chloride (NH ₄ Cl)
30g/dimethylamine borane [(CH ₃ ) ₂ NHBH ₃ ] 5g/adjusted to pH7.3 with sodium hydroxide was used. The provision of this nickel layer 2 provides the performance of a capacitor, but if it is left in the air, an oxide film will form on the nickel surface and the solderability will deteriorate, making it impractical. A silver layer 3 is applied onto the nickel layer 2 by boron-based electroless silver plating to improve solderability. In the electroless plating that provides the nickel layer 2, the precipitated nickel film is semi-photosensitive and the rate of passivation of the film is slow. and silver layer 3
can increase adhesion. After applying the nickel layer 2, it is thoroughly washed with water, and a silver layer 3 is applied at 50° C. for 15 minutes by electroless silver plating using dimethylamine borane as a reducing agent. As an electroless silver plating solution, 8.5g/of silver nitrate (AgNO ₃ ), 7.35g/of sodium cyanide (NaCN), and 0.35g/of sodium borohydride (NaBH ₄ ) are PH-treated with sodium hydroxide.
A solution adjusted to 13.0 was used. Thereafter, sufficient water washing is performed to form electrodes. Incidentally, the electroless plating of the nickel layer 2 and the silver layer 3 is not limited to the above ratio as long as it does not depart from the purpose of the present invention. Table 1 shows the characteristics of the ceramic capacitor according to the present invention after being immersed in molten solder at 300° C. for 1 minute (capacitance change rate with respect to the value before being immersed in solder and tensile strength between electrodes and elements after being immersed in solder).

【table】

〔Effect of the invention〕

Since the present invention is configured as described above, it has the following effects. Since the second conductive layer consisting of a nickel layer and a silver layer is provided on the first conductive layer, even if some of the silver on the surface layer diffuses into the solder during solder immersion, the surface layer of the lower nickel layer will remain intact. Since it is not oxidized, it has good solderability. Furthermore, even if the electrode is immersed in molten solder at 300° C. for one minute or more during the soldering process, there is almost no deterioration in the adhesion strength of the electrode, a decrease in capacitance, or a deterioration in tan δ. Furthermore, it is not necessary to roughen (etch) the surface of the porcelain element to obtain the adhesion strength between the electrode and the porcelain element, and centerless polishing or No complicated steps such as cutting are required, and known means such as screen printing can be used as is. In addition, since a boron-based electroless plating method is used to apply the second conductive layer, there is no problem with conductivity as with electroplating, making it suitable for mass production and highly useful in industry. It is.

[Brief explanation of the drawing]

The drawing is a side sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Porcelain element body, 2... Nickel layer, 3... Silver layer, a... First conductive layer, b... Second conductive layer.

Claims (1)

[Claims] 1 A first conductive layer is applied to the surface of the porcelain body by a silver baking method, and a second conductive layer is formed by laminating a silver layer on this first conductive layer by an electroless silver plating method using dimethylamine borane as a reducing agent. In a method of manufacturing a ceramic capacitor, in which an electrode is formed by depositing a silver layer on the first conductive layer by an electroless silver plating method using dimethylamine borane as a reducing agent, a second conductive layer is provided. 1. A method for manufacturing a ceramic capacitor, comprising: laminating a nickel layer on the first conductive layer by a nickel-metsuki method.