JPS59141215A - Method of producing laminated ceramic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic capacitor with improved adhesive strength of terminal electrodes and element strength.

Conventional Structure and Problems Multilayer ceramic capacitors having a parallel wiring structure of ceramic thin film dielectrics are well known for the purpose of achieving smaller size and larger capacity. The manufacturing method for this multilayer ceramic capacitor is generally the following two-page process. First, several types of additives are added to oxides such as barium titanate, calcium titanate, and magnesium titanate, and after mixing, an organic binder is added to form a highly viscous slurry. A 30 to 100 μmΩ sheet is produced by a sheet forming method. Thereafter, a paste prepared by dispersing palladium or an alloy powder of silver and palladium in an organic binder is printed on the sheet by screen printing, and the sheets are stacked on top of the paste for printing. Repeat this for 2 to 40
Create a stack of layers. This laminate is cut into a suitable size and fired in an electric furnace at 12 oO to 1400''C to obtain sintered chips.

A paste made of silver and palladium alloy or silver powder is attached to the end face of this chip as a terminal electrode, and
A multilayer ceramic capacitor is obtained by baking at 900°C.

In most cases, such multilayer ceramic capacitors are used by being directly soldered to a printed wiring board. Printed wiring boards are made of epoxy resin and tend to warp during use, so a tensile stress of more than 9 in 10 acts on the soldered multilayer ceramic capacitor terminals. Often, this stress could not be withstood, causing the terminal electrodes to come off or the element itself to crank, resulting in problems with its characteristics. To solve this problem, there is a method of attaching glass frit to the surface of the sintered ceramic capacitor and diffusing the glass component into the ceramic through heat treatment, but it is generally difficult to do so when the particle size of the glass frit is 10μ or more. Because of its roughness, it was difficult to apply it uniformly to the surface of multilayer ceramic capacitors, and even after treatment, the effect varied depending on the device.

OBJECTS OF THE INVENTION In view of the above facts, an object of the present invention is to provide a homogeneous multilayer ceramic capacitor that improves the adhesive strength of terminal electrodes and the element strength.

Structure of the Invention The present invention provides a sintered multilayer ceramic capacitor made of a glass-forming compound (eg, B, Pb, St, AN, etc.).

Organic and inorganic compounds such as B1! After immersing in the mixed solution of 10),
It is characterized in that a thin layer of the above compound is formed on the surface of the multilayer ceramic capacitor sintered body by drying, and then heat-treated to form glass and diffuse into the ceramic at the same time.

Description of Examples Calcium titanate (Ca T 103) to 100 parts by weight of barium titanate (B a T 103)
, 3 parts by weight of niobium oxide (Nb2Q5) and 0.2 part by weight of manganese dioxide (MnO2) are added and thoroughly mixed. Thereafter, it is made into a slurry with an organic binder, and a sheet with a thickness of 8 μm is produced by a blade construction method. Palladium paste is screen-printed on this sheet, and the sheet is stacked on top of it and the printing is repeated to create a stack. This laminate was cut and heated at 1300 to 1360°C.
Fired at. The shape of this sintered chip is 1.5 mm.
(Width) x3. omm (length) Xo, 55B (thickness).

5) Such a sintered body was immersed in an aqueous solution of tetraboric acid (H2BO3) and then dried at 100°C for 2 hours. Next, it is immersed in an acetone solution containing 6% silicone oil and 4% lead stearate, and air-dried in the air. The amount of glass component attached to this product was 0.7% of the sintered chip. This amount can be adjusted by changing the solution concentration. Seal this in an aluminum crucible and ta o o'C
heat treated with The compound decomposes into B2O3-8102-
It becomes PbO-based glass and diffuses into ceramic. The purpose of sealing the aluminum crucible is to prevent volatile components such as PbO from evaporating.

Silver electrodes were provided on the terminals of the chip thus obtained. However, 2 to 3% of glass frit having the same composition as above was mixed into the silver paste for silver electrodes.

The effect diagram of the invention is a diagram showing a multilayer ceramic capacitor obtained by the manufacturing method of the invention, in which 1 is a ceramic dielectric, 2 is a palladium electrode, 3 is a glass layer, and 6 pages 4 is a silver terminal electrode. Furthermore, Table 1 shows the conventional manufacturing method, that is, the method in which glass frit is not attached and diffused on the surface of the sintered chip, the method in which glass frit is attached and diffused on the surface of the sintered chip, and the method according to the present invention. This figure shows a comparison of the terminal electrode tensile strength, bending strength, and electrical properties of multilayer ceramic capacitors based on the manufacturing method. Note that the bending strength is the result of a three-point bending test with a span of 2 m.

As is clear from this table, the strength of the multilayer ceramic capacitor obtained by the manufacturing method of the present invention is significantly improved,
Moreover, it is recognized that the variation in strength is small. This allows the adhesion of the glass-forming compound to be uniformly spread over the element surface, and provides better results with less variation than in the case of no treatment or in comparison with conventional glass frit treatments.

Regarding the electrical characteristics of the capacitor, no abnormality was observed except for the capacitance being slightly small. It is thought that this effect is achieved because glass fills the pores unique to ceramics.

As mentioned above, the mechanical strength of the multilayer ceramic capacitor according to the manufacturing method of the present invention is extremely excellent, and even when soldered to a printed circuit board, the terminal electrodes will not come off due to the deflection of the board, and the elements will not be damaged. It is extremely effective in preventing cracks from forming, and its significance is great.

In the examples, boron is used as a glass-forming element.

Although a compound of silicon and lead is used, a compound of zinc or aluminum may also be included, or a combination of compounds mainly consisting of boron, silicon, and bismuth is also possible. In this case, the form of the compound must be changed depending on the element, and the solvent should be selected so that the components are compatible with each other as much as possible.

If it is difficult to dissolve them at the same time, it is possible to select a combination of solvents that do not dissolve each other and apply them in multiple batches, as in the example. Furthermore, although ceramic dielectrics made of barium titanate, calcium titanate, niobium oxide, and manganese dioxide were used in the examples, it goes without saying that any composition of ceramic dielectrics may be used.

Although silver was used as the terminal electrode in the embodiment, an alloy of silver and palladium may also be used.

[Brief explanation of the drawing]

The figure shows a multilayer ceramic capacitor based on the manufacturing method of the present invention. 1...Ceramic dielectric, 2...Palladium electrode, 3...Glass layer, 4-...Silver terminal electrode.

Claims (1)

[Claims] A laminate in which ceramic dielectric layers and metal electrode layers are alternately laminated is immersed in a glass-forming compound mixed solution, dried, and then heat-treated to decompose and vitrify the compound, which is then diffused onto the surface of the laminate. A method of manufacturing a multilayer ceramic capacitor characterized by: