JPS5866321A - 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 The present invention has a silicone coating and silver or silver-coated ends.
The present invention relates to a method for manufacturing a multilayer ceramic capacitor with good moisture resistance and having electrode parts made of palladium alloy, nickel, and tin-lead alloy.

2/, -... Multilayer ceramic capacitors have traditionally been made smaller and larger in capacity in conjunction with the miniaturization of electronic circuits, and are currently in demand as chip components for hybrid ICs and for direct mounting on printed circuit boards. is rapidly increasing.

Multilayer ceramic capacitors are generally based on a laminate obtained by alternately laminating a ceramic dielectric and thin film layers of palladium and/or platinum, and a parallel circuit is formed by sandwiching the dielectric between the internal metal thin films. It is configured to be connected to a silver or silver-palladium alloy electrode at the end so as to form a structure.

The thickness of the dielectric material used in this multilayer ceramic capacitor is approximately 16 to 10-0 μm, and electrodes are provided on the flat surface of such a thin dielectric material to form a folded surface structure.

Generally, the capacitance of a capacitor is c=tt mutual t I'm torn about it. Here, ε is the dielectric constant of vacuum, ε.

is the dielectric constant of the dielectric, S is the electrode area, and t is the electrode distance. Therefore, considering the capacity l per volume as s/knee=', it is inversely proportional to the square of the thickness. Therefore, when comparing the capacitance per volume of a single-plate ceramic capacitor and a multilayer ceramic capacitor, the thickness of a multilayer ceramic capacitor can be approximately 100 times smaller than that of a disk-type ceramic capacitor. The above capacity can be obtained with the same volume. (However, since it is impossible to reduce the thickness of disc-type ceramic capacitors in terms of strength, the current limit is around 500 μm.) In this way, multilayer ceramic capacitors are small and have large capacitance. It is suitable for the miniaturization of electronic circuits, and by applying tin and lead alloy plating to the electrodes, it has become easy to attach it directly to a printed circuit board.

However, such multilayer ceramic capacitors have several drawbacks, one of which is defects that occur due to the thinning of the dielectric material.

That is, the ceramic itself originally has pores because it is a polycrystalline material. Such pores are also not of uniform size, and large pores also exist. Making these pores small and uniformly distributed is one of the challenges, and although much research has been done, it cannot be said to be sufficient yet.

The effect of such pores is to weaken moisture resistance. Particularly, in processes using electrolytes such as nickel or tin-lead alloy plating, residual electrolyte may become a problem. If the electrolyte remains, the insulation resistance may decrease due to re-penetration of moisture. Such a situation significantly impairs the reliability of the product and often causes problems in the market. For this reason, special attention must be paid to multilayer ceramic capacitors provided with plated electrodes.

The present invention was achieved through various experiments in consideration of the above drawbacks.

Hereinafter, details of the present invention will be explained based on examples.

71.4 parts by weight of barium titanate, 20.4 parts by weight of barium zirconate, 7.4 parts by weight of calcium titanate, 0.2 parts by weight of zinc oxide, 0.16 parts by weight of manganese dioxide,
A slurry was prepared from a mixed powder consisting of 0.25 parts by weight of tungsten oxide and 0.25 parts by weight of aluminum oxide using a binder mainly composed of ethyl cellulose, and a sheet with a thickness of 40±2 μm was prepared using a doctor blade method. It was molded using

After punching out this sheet to a certain size, palladium electrodes were printed. After stacking and pressing the electrode-printed sheets so that the electrodes form a comb shape, 3.61111
×j, 8 NM X O, cut into a size of 45ff. This chip was fired at 1370°C ± 20°C for 2 hours, and silver paste was applied to both end faces of the obtained sintered body.
Baked at ℃. Silicone was applied to the entire surface of the laminate thus produced, and
After heat-treating for 6 hours to polymerize the silicone, the heat-treated laminate was put into a polypot with an inner diameter of 150111 and stirred for 30 minutes at a rotational speed of 96~1o067, -co, r, p, m. Then, the silicone on the silver electrodes at both ends was removed.Next, the silver electrodes at both ends from which the silicone had been removed were plated with two-layer plating to a thickness of 1 to 2 μm, and then tin and lead alloy plating was applied to a thickness of 1 to 2 μm on top of that. Where was it?

FIG. 1 shows the multilayer ceramic capacitor of the present invention thus obtained, in which 1 is a ceramic dielectric layer, 2 is a palladium electrode layer, 3 is a silver electrode, 4 is a nickel plating layer, and 5 is a nickel plating layer.
6 is a tin and lead alloy plating layer, and 6 is a silicone layer.

Figure 2 shows a multilayer ceramic capacitor based on the method of the present invention and a multilayer ceramic capacitor based on a conventional method without silicone treatment (same as the method of the present invention except for silicone treatment) at 40'C and relative humidity of 95. This figure shows the moisture resistance characteristics when SOV is applied in the room.

In FIG. 2, the tortoise indicates the characteristics of the product of the present invention, and b indicates the characteristics of the conventional product. As is clear from FIG. 2, it is clear that the moisture resistance of the multilayer ceramic capacitor based on the method of the present invention is extremely stable.

7.2 As described above, the method of the present invention is extremely significant in that it solves the problem of instability in moisture resistance, which is common in multilayer ceramic capacitors provided with plated electrodes.

Incidentally, in the above embodiment, a porcelain dielectric material mainly composed of barium titanate, barium zirconate, and calcium titanate was used, but it goes without saying that the present invention is also applicable to other dielectric materials. Furthermore, although a case has been described in which silver electrodes are provided on both end faces, silver-palladium alloy electrodes may also be used.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor based on the method of the present invention, and FIG. 2 is a comparison diagram of the moisture resistance characteristics of multilayer ceramic capacitors based on the method of the present invention and the conventional method. 1... Ceramic dielectric layer, 2... Electrode layer (
palladium electrode layer), 3...silver electrode, 4...
...Nickel plating layer, 6...Tin and lead alloy plating layer, 6...Fucone layer. Figure 1 Figure 2 → Wipe I # Mochiko (hrs)

Claims (1)

[Claims] having both ends kIl or silver-palladium alloy electrodes,
Metallic silicone is applied to the entire surface of the laminate consisting of porcelain dielectric layers and comb-shaped electrode layers alternately laminated, and the laminate with the silicone adhered is heat treated to polymerize the silicone, and then the steel poles at both ends are attached. A method for manufacturing a multilayer ceramic capacitor, in which silicone adhering to the capacitor is removed, then nickel plating is applied to the silver electrodes at both ends, and a portion of the nickel plating is coated with tin and lead alloy plating.