JPH0670936B2 - Monolithic ceramic capacitors - Google Patents

Description

The present invention relates to a monolithic ceramic capacitor, and more particularly to an inexpensive and highly reliable monolithic ceramic capacitor.

[Prior Art] A monolithic ceramic capacitor is mainly composed of a ceramic dielectric, an internal electrode provided inside the ceramic dielectric, and an external electrode electrically connected to the internal electrode. Conventionally, the external electrodes of this monolithic ceramic capacitor are manufactured by kneading a mixture of noble metal powder and glass frit into an organic vehicle, applying this to a ceramic dielectric, and then firing at a temperature of about 600 to 800 ° C. On the surface of the external electrode manufactured in this way, Ni plating film, Sn plating film or Sn / Pb plating film is formed by electroplating method to improve solderability and heat resistance. Be used for.

[Problems to be Solved by the Invention] In the conventional monolithic ceramic capacitor in which the external electrodes are manufactured in this manner, high temperature firing is required, and thus the manufacturing cost is high.

Since the quality of the obtained monolithic ceramic capacitor and the adhesion strength with the plating film are affected by the firing conditions, the resistance of the glass frit to the plating solution, and other conditions such as the sintering state, it is necessary to obtain a highly reliable monolithic ceramic capacitor. Is difficult.

Since the external electrode has a high-hardness metal sintered structure, cracks may occur in the dielectric during temperature cycling.

There were problems such as.

An object of the present invention is to solve the above conventional problems and to provide a monolithic ceramic capacitor having high characteristics and high reliability, which can be manufactured at low cost.

[Means for Solving the Problems] The monolithic ceramic capacitor of the present invention is a monolithic ceramic capacitor having an internal electrode and an external electrode electrically connected to the internal electrode, the external electrode being made of a thermosetting resin containing a metal powder. In addition, the surface of the external electrode is plated.

The present invention will be described in detail below.

The metal powder forming the external electrode of the monolithic ceramic capacitor of the present invention is not particularly limited, and those used for the external electrode of the conventional monolithic ceramic capacitor can be preferably used. Specifically, a noble metal powder such as silver (Ag) powder or palladium (Pd) powder, a metal powder such as nickel (Ni) powder, or a mixed powder thereof can be used. The particle size of such metal powder is also not particularly limited, and those having a particle size conventionally used can be used.

As the thermosetting resin, those that cure at a temperature of 180 to 250 ° C. are preferable. Specific examples of the thermosetting resin include phenol resin, xylene resin and urethane resin.

Such a thermosetting resin can be easily formed into an external electrode by mixing it with a metal powder to form a paste, applying the paste to a dielectric having an internal electrode formed in advance, and then curing the paste by heating. In preparing the paste, if the viscosity of the paste is too high, an appropriate solvent such as butyl carbitol is mixed and used if necessary. In this case, the mixing ratio of the metal powder, the thermosetting resin and the solvent is not particularly limited, but in the usual case, the metal powder is 50 to 80% by weight, the thermosetting resin is 5 to 20% by weight, and the solvent is 5 to 30% by weight. It is appropriately determined within the range of%.

The multilayer ceramic capacitor of the present invention, when forming the external electrode, after applying a paste prepared by mixing a predetermined amount of metal powder, thermosetting resin and solvent if necessary,
It can be manufactured in the same manner as a conventional monolithic ceramic capacitor except that it is cured by heating. The heat curing is usually a curing temperature of the thermosetting resin used, for example,
Perform at 180-250 ℃ for about 30 minutes.

Examples of the method of plating the external electrode thus formed include electroplating and electroless plating. The material and thickness of plating may be the same as conventional ones, and generally, a Ni, Sn, or Sn / Pb plating film having a predetermined thickness is formed.

[Operation] The multilayer ceramic capacitor of the present invention does not require high temperature firing because the external electrodes are formed by molding and curing metal powder with a thermosetting resin. Therefore, the manufacturing cost is reduced. In addition, a plating film can be easily formed on the external electrodes of the monolithic ceramic capacitor of the present invention with high adhesive strength. Therefore, it is possible to provide solderability and heat resistance without deteriorating the electrical characteristics of the capacitor, and at the same time, it is possible to obtain a highly reliable multilayer ceramic capacitor with stable quality. In the monolithic ceramic capacitor having such external electrodes, cracking in the dielectric body due to thermal strain of the external electrodes is also prevented.

[Examples] The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 and Comparative Example 1 An Ag paste having the following composition was applied to a lead perovskite-based ceramic dielectric, which was then heated at 200 ° C. for 30 minutes to cure and then plated by the following electroplating method, A multilayer ceramic capacitor of the present invention was manufactured.

Ag paste formulation (% by weight) Ag powder (average particle size 2 μm): 75 Thermosetting resin: 6.2 Solvent: balance Electroplating method Ni sulfamic acid bath and Sn / Pb sulfonic acid bath were used for barrel plating.

Various characteristics of the obtained monolithic ceramic capacitor were examined according to the following methods and compared with a monolithic ceramic capacitor (Comparative Example 1) obtained by similarly plating a conventional firing type external electrode.

The results are shown in Table 1.

The test is performed on 30 samples (however, 20 for moisture resistance load test and 10 for external electrode tensile test), capacity, tan
Regarding δ and tensile strength, the maximum, minimum and average values were shown. Also, the insulation resistance showed the maximum and minimum values.

The capacity (nF) and tan δ (%) were measured at 1 KHz and 1 V.

Insulation resistance (Ω) 25V, after applying DC 5 seconds, shows the value 30 seconds later.

Temperature cycle durability The heat cycle of −25 ° C. (30 minutes) → normal temperature (3 minutes) → + 85 ° C. (30 minutes) was performed 100 times, and the number of samples in which the capacity decreased was shown.

Reliability (high temperature load test) + 125 ° C, DC32V was applied for 1000 hours to check for deterioration.

External electrode tensile test The tensile strength of the external electrode was measured.

Reliability (moisture resistance load test) + 85 ° C, 85% RH, DC16V was applied for 1000 hours to check for deterioration.

From Table 1, it is clear that the monolithic ceramic capacitor of the present invention is a monolithic ceramic capacitor having high characteristics and excellent quality stability as well as high adhesive strength of external electrodes, and extremely high reliability.

[Effects of the Invention] As described in detail above, according to the monolithic ceramic capacitor of the present invention, not only is it excellent in various characteristics and also in stability of quality, but also the adhesive strength of external electrodes is high, and the reliability is extremely high. Provided is a monolithic ceramic capacitor which can be manufactured at low cost.

Claims (1)

[Claims] 1. A monolithic ceramic capacitor having an internal electrode and an external electrode electrically connected to the internal electrode, wherein the external electrode is made of a thermosetting resin containing metal powder, and the surface of the external electrode is plated. A laminated ceramic capacitor characterized by being formed.