JP2003243243A - Ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a ceramic electronic component in which destruction hardly occurs in an interface between an elemental ceramic body and electrodes and, in addition, a resin encapsulating material of which is hardly broken. <P>SOLUTION: A ceramic capacitor 10 includes an elemental dielectric ceramic body 12 formed of a dielectric ceramic, and Ni electrodes 14 and 16 formed on the facing surfaces of the body 12. Solder 18 is adhered to the whole surfaces of the electrodes 14 and 16, and lead wires 20 and 22 are respectively connected to the electrodes 14 and 16. A resin encapsulating material 24 is formed to cover the dielectric body 12 and the solder 18 adhered to the whole surfaces of the electrodes 14 and 16. Solder free from Pb and Bi and mamly containing Sn and Cu is used as the solder 18. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic electronic component, and more particularly, to a method in which lead wires are soldered to electrodes formed on both surfaces of a ceramic body, for example. The present invention relates to a ceramic electronic component having a resin exterior material formed thereon. 2. Description of the Related Art FIG. 1 is a cross-sectional view showing an example of a ceramic capacitor as an electronic component serving as a background of the present invention, and FIG. 2 is a cross-sectional view showing the same as a side view. The ceramic capacitor 10 includes, for example, a disk-shaped dielectric ceramic body 12. The dielectric ceramic body 12 is made of, for example, BaTiO ₃ , SrTiO ₃ ,
It is formed of a ceramic dielectric such as TiO ₂ . The electrodes 1 are respectively provided on the opposing surfaces of the dielectric ceramic body 12.
4, 16 are formed. The electrodes 14 and 16 include, for example, Ag,
A baked electrode such as Cu or a wet-plated electrode such as Ni has been adopted. Here, in the case of a burn-in electrode, the electrodes 14 and 16 are formed by screen-printing and baking an electrode paste on the facing surface of the dielectric ceramic body 12. However, since the electrode paste is printed by screen printing, it is necessary to print the electrode paste up to the end of the facing surface of the dielectric ceramic body 12 so that the electrode paste does not adhere to the side peripheral surface of the dielectric ceramic body. Is difficult. Therefore, the dielectric ceramic body 1
A gap was formed between the edge of No. 2 and the electrode so that the electrode paste did not adhere to the side peripheral surface. However, the electric field concentrates at the edge of the electrode due to this gap, and a capacitor with a high withstand voltage cannot be obtained. Therefore, a Ni-plated electrode is formed on the entire surface of the dielectric ceramic body 12,
By grinding the electrode on the side peripheral surface of the
6 are formed. According to such a method, the electrodes 14 and 16 can be formed on the entire opposing surface of the dielectric ceramic body 12. When such electrodes 14 and 16 are formed, since there is no gap, the concentration of the electric field at the edge of the electrode is reduced, and the ceramic capacitor 10 with high withstand voltage can be obtained. Therefore, Ni-plated electrodes are used exclusively for high-voltage capacitors requiring high withstand voltage. [0005] Lead wires 20, 22 are connected to the electrodes 14, 16 by solder 18, respectively. The Ni electrode has a feature that solder erosion is less likely to occur than the Ag electrode and the Cu electrode. In addition, the Ni electrode has a feature that the diffusion of the Sn component of the solder is less likely to occur than the Ag electrode and the Cu electrode, and the Ni electrode has high reliability at a relatively high temperature. Further, the dielectric ceramic body 12 and the lead wires 20 and 2
2 to cover the periphery of the soldering portion,
4 are formed. The resin exterior material 24 is formed of, for example, an epoxy resin. [0006] Conventionally, as solder,
Since Sn-Pb-based solder was used, and the wet Ni-plated electrode had a relatively low Sn diffusion rate, there was no problem in reliability at a temperature of about 125 ° C. In recent years, compensation at a high temperature exceeding 125 ° C., for example, 150 ° C. has been required for automobiles and the like. However, at a high temperature of 150 ° C., Pb contained in the solder diffuses into the Ni electrode, and the adhesion strength between the Ni electrode and the dielectric ceramic body deteriorates.
A problem has been clarified that a break occurs at the interface between the dielectric ceramic body and the Ni electrode and the lead wire comes off. It has also been found that this problem is caused not only by Pb but also by Bi. [0007] Further, since the Ni electrode has poor solder wettability,
A method of soldering the entire surface has been adopted, but Sn-P
The b-type solder has a weak adhesive force with the epoxy resin, and when the ambient temperature is 150 ° C. or higher and there is a sudden change, stress is applied to the resin exterior material due to the creep phenomenon of the solder, and cracks are generated in the resin exterior material. The problem arose. Therefore, a main object of the present invention is to provide a ceramic electronic component in which destruction at an interface between a ceramic body and an electrode hardly occurs and a resin exterior material is hardly damaged. According to the present invention, a ceramic body, a Ni electrode formed on a facing surface of the ceramic body, and a Ni electrode are connected to the Ni electrode by solder attached to the entire surface of the Ni electrode. In a ceramic electronic component including a lead wire and a resin exterior material formed so as to cover the solder applied to the entire surface of the ceramic body and the Ni electrode, Pb and Bi are not included as components of the solder, Ceramic electronic components. By using a solder not containing Pb and Bi, the Ni electrode formed on the opposite surface of the dielectric ceramic body does not diffuse Pb, Bi, etc., and the Ni electrode and the dielectric ceramic body adhere to each other. Deterioration in strength can be suppressed, and destruction at the interface between the Ni electrode and the dielectric ceramic body is less likely to occur. Further, by using a solder containing no Pb, the adhesion between the solder and the resin exterior material is improved, and even if the ambient temperature changes, the occurrence of cracks in the resin exterior material due to the creep phenomenon of the solder can be suppressed. . The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the ceramic capacitor 10 shown in FIGS.
A plating electrode is formed. In addition, as a solder for connecting the lead wires 20 and 22 to the electrodes 14 and 16, a material that does not contain Pb or Bi, such as Sn—Cu, is used. In such a ceramic capacitor 10, by using Ni-plated electrodes as the electrodes 14 and 16, the electrodes 14 and 16 can be formed on the entire opposing surface of the dielectric ceramic body 12, and the concentration of the electric field can be improved. And a capacitor with high withstand voltage can be obtained. Further, as a material of the solder 18, Pb or B
By using a material that does not contain i, these metal components do not diffuse into the Ni electrodes 14 and 16 and breakage occurs at the interface between the dielectric ceramic body 12 and the electrodes 14 and 16 even at a high temperature. Hard to do. Therefore, lead wire 2
Problems such as the 0, 22 coming off hardly occur. The material of the solder 18 is Sn-Cu.
Is used, the adhesion between the solder 18 and the resin exterior material 24 is good, and even if the ambient temperature changes, the stress on the resin exterior material 24 due to the creep phenomenon of the solder 18 is small. The occurrence of cracks can be suppressed. EXAMPLE In order to produce the ceramic capacitor 10 shown in FIG. 1, a disk-shaped dielectric ceramic body 12 was prepared. After etching the dielectric ceramic body 12 with a strong acid, Ni electroless plating was performed to form a Ni film on the entire surface of the dielectric ceramic body 12. After that, the side surfaces of the dielectric ceramic body 12 were ground to form the electrodes 14 and 16. The thickness of the electrodes 14 and 16 is about 1 μm. The dielectric ceramic body 12 on which the electrodes 14 and 16 are formed is sandwiched between the lead wires 20 and 22, the entire dielectric ceramic body 12 is immersed in molten solder, and the lead wires 20 and 22 are joined. At the same time, the entire Ni electrode was covered with solder 18. As the solder 18, (1) 99.3Sn
-0.7Cu, (2) 96.5Sn-3.5Ag,
(3) 95.8Sn-3.5Ag-0.7Cu, (4)
63Sn-37Pb, (5) 96Sn-2.5Ag-1
Bi-0.5Cu was used. Further, the dielectric ceramic body 12 to which the lead wires 20 and 22 are connected is heated to 150 ° C., dipped and adhered to an epoxy powder resin, and heated at 150 ° C. for 30 minutes to cure the resin. A disk-shaped ceramic capacitor with leads was manufactured. After leaving the manufactured ceramic capacitor 10 with leads at a high temperature of 150 ° C. for 1000 hours, the mounting strength of the lead wires 20 and 22 was measured, and the measurement results shown in Table 1 were obtained. [Table 1] As can be seen from Table 1, at a high temperature of 150 ° C., the solder using no Pb or Bi maintains high strength even after standing for 1000 hours, and its effect is remarkable. The destruction was performed on the dielectric ceramic body 1
Occurs at the interface between the electrode 2 and the electrodes 20 and 22. At this interface, when using the solders (1), (2) and (3), Sn, Ag, Cu, etc. are not detected by the fluorescent X-ray analysis. However, when the solder (4) was used, Pb was detected, and when the solder (5) was used, Sn and Bi were detected. As described above, by using the solder containing no Pb or Bi, diffusion of Pb or Bi to the Ni electrodes 20 and 22 is eliminated, and deterioration of the strength of the electrodes 20 and 22 can be prevented. Next, the ceramic capacitor 10 is
After applying a temperature cycle at 0 ° C. for 30 minutes, at room temperature for 3 minutes, at 125 ° C. for 30 minutes, and at room temperature for 3 minutes, the resin exterior material 24 was examined for cracks. As a result, the results shown in Table 2 were obtained. [Table 2] As can be seen from Table 2, (1) and (2)
(3) In the case of using the solder of (5), no destruction occurred even if 200 temperature cycles were applied, but in the case of using the solder of (4), the lead wire was subjected to 50 temperature cycles, A crack occurred in the resin exterior material along the line. This is Pb
It is considered that the use of a solder that does not include a good adhesion between the solder and the resin exterior material results in less stress on the resin exterior material due to the creep phenomenon of the solder due to a temperature change. In the above embodiment, a ceramic capacitor is described as an example. However, the present invention is not limited to this. For example, an Ni electrode is formed on a ceramic body such as a thermistor or a varistor, and the lead wires are connected by soldering over the entire surface. Can be used for all parts. According to the present invention, the diffusion of Pb and Bi to the Ni electrode is achieved by applying a solder containing no Pb or Bi to the entire surface of the Ni electrode and connecting the Ni electrode and the lead wire. In addition, it is possible to prevent breakage of the electrode at the interface with the ceramic body and prevent the lead wire from coming off.
Further, it is possible to improve the adhesion between the solder and the resin exterior material, and it is possible to prevent the resin exterior material from cracking even when there is a temperature change.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative view showing one example of a ceramic capacitor as a background of the present invention; FIG. 2 is an illustrative view of the ceramic capacitor shown in FIG. 1 as viewed from a side. [Description of Signs] 10 Ceramic capacitor 12 Dielectric ceramic body 14, 16 Electrode 18 Solder 20, 22 Lead wire 24 Resin exterior material

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shuji Watanabe             Stock, 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto             Murata Manufacturing Co., Ltd. (72) Inventor Akihiro Fujii             Stock, 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto             Murata Manufacturing Co., Ltd. (72) Inventor Shinichi Kobayashi             Stock, 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto             Murata Manufacturing Co., Ltd. (72) Inventor Osamu Yamaoka             Stock, 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto             Murata Manufacturing Co., Ltd.

Claims (1)

Claims: 1. A ceramic body, a Ni electrode formed on an opposite surface of the ceramic body, a lead wire connected to the Ni electrode by solder attached to the entire surface of the Ni electrode, and A ceramic electronic component including a resin exterior material formed so as to cover the ceramic body and solder applied to the entire surface of the Ni electrode, wherein Pb and Bi are not included as components of the solder. parts.