JP2007234820A - Ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic electronic component in which cracks hardly occur on solder even if thermal shock is applied in a state where it is soldered on a substrate, and which can easily manufactured and mounted. <P>SOLUTION: Terminal electrodes 15 are formed on respective end surfaces 12a of a ceramic base 12 of the ceramic electronic component 10a. The terminal electrodes are each covered with a conductive terminal cover 17. The terminal electrodes each have side portions 15b, 15c formed on opposite side faces 12b, 12c of the ceramic base. The terminal cover has a main body 17a connected to the terminal electrode, and extending portions 17b, 17c extending from the main body so as to cover the opposite side portions of each of the terminal electrodes. The extending portions are spaced from the side portions of the terminal electrodes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic component having a ceramic body.

  A ceramic electronic component in which terminal electrodes are provided at both ends of a ceramic body is known. A typical example of a ceramic electronic component is a multilayer ceramic capacitor. Ceramic electronic components are often mounted on a substrate by soldering. Usually, since there is a difference in thermal expansion coefficient between the substrate and the ceramic body, a stress is applied to the ceramic electronic component in a thermal shock that repeatedly increases and decreases in temperature, and the ceramic electronic component is likely to be broken.

  In order to solve this problem, Patent Document 1 below discloses a technique in which a terminal member made of a metal plate is soldered onto a terminal electrode of a ceramic electronic component, and the terminal member is soldered to a substrate. A bent portion extending in parallel with the side surface of the ceramic body is provided at the lower end of the terminal member, and this bent portion is soldered to the substrate. Even if the substrate expands or contracts due to a temperature change, the deformation or movement of the terminal member absorbs the stress of the substrate, so that the stress is not directly applied to the ceramic body. As a result, cracks are less likely to occur in the ceramic body.

Furthermore, in the same document, stress is generated in the terminal electrode due to thermal shock during soldering between the terminal electrode and the terminal member, and the portion of the terminal electrode that contacts the side surface of the element body compresses the side surface to the element body It points out the problems that cause cracks. In order to solve this problem, the ceramic electronic component disclosed in this document has a terminal electrode formed only on the end face of the ceramic body.
JP 2001-85262 A

  In recent years, in consideration of environmental problems, lead-free solder is often used for manufacturing and mounting of ceramic electronic components. However, according to the inventor's research, it is found that when a ceramic electronic component is soldered onto a substrate using lead-free solder and a thermal shock is applied, the solder is likely to crack rather than the ceramic body. It was. According to the inventor's research, the terminal member disclosed in Patent Document 1 is considered to be effective to some extent in preventing such solder cracks.

  However, the ceramic electronic component of Patent Document 1 requires a care so that the terminal electrode does not reach the side surface of the ceramic body during its manufacture, and thus has a disadvantage that it is difficult to manufacture. Further, when the ceramic electronic component is mounted on the substrate, the bent portion provided at one end of the terminal member must be joined to the electrode on the substrate. For this reason, it is necessary to pay attention to the orientation of the ceramic capacitor during mounting.

  Accordingly, an object of the present invention is to provide a ceramic electronic component that is less likely to cause cracks in solder even when subjected to thermal shock while being soldered to a substrate, and that is easy to manufacture and mount.

  A ceramic electronic component according to the present invention includes two end faces facing each other, a ceramic body having the first side face and the second side face facing each other, and on each end face of the ceramic body. And a conductive terminal cover that is electrically connected to each terminal electrode and covers each terminal electrode. Each terminal electrode is formed on a center portion formed on each end face of the ceramic body, a first side portion formed on the first side surface of the ceramic body, and a second side surface of the ceramic body. And a second side portion. Each terminal cover includes a main body connected to a central portion of each terminal electrode, a first extension extending from the main body so as to cover a first side portion of each terminal electrode, and a second side portion of each terminal electrode. And a second extension extending from the main body so as to cover. The first extension of each terminal cover is spaced from the first side of each terminal electrode, and the second extension of each terminal cover is spaced from the second side of each terminal electrode.

  In this ceramic electronic component, a space is formed between the first extension of the terminal cover and the first side part of the terminal electrode, and between the second extension of the terminal cover and the second side part of the terminal electrode. Yes. If either the first extension portion or the second extension portion of the terminal cover is soldered to the substrate, the stress applied to the solder when the substrate is bent due to thermal shock is alleviated by the space. Therefore, even if the ceramic electronic component of the present invention is subjected to thermal shock while being soldered to the substrate, it is difficult for cracks to occur in the solder. Since cracks can be suppressed even when the terminal electrode extends on the first and second side surfaces of the ceramic body, it is not necessary to form the terminal electrode only on the end surface of the ceramic body. Therefore, the ceramic electronic component of the present invention is easy to manufacture. Further, the first and second extension portions of the terminal cover are arranged on both sides of the ceramic body, and solder cracks can be suppressed regardless of which is soldered to the substrate, so that the ceramic electronic component of the present invention is applied to the substrate. Is easy to implement.

  The ceramic body may further include a third side surface and a fourth side surface that connect the two end surfaces and face each other. Each terminal electrode may further include a third side portion formed on the third side surface of the ceramic body and a fourth side portion formed on the fourth side surface of the ceramic body. . Each terminal cover further includes a third extension extending from the main body so as to cover the third side portion of each terminal electrode, and a fourth extension extending from the main body so as to cover the fourth side portion of each terminal electrode. You may have. The 3rd extension part of each terminal cover may be spaced apart from the 3rd side part of each terminal electrode. The 4th extension part of each terminal cover may be spaced apart from the 4th side part of each terminal electrode.

  According to this configuration, spaces are also generated between the third extension of the terminal cover and the third side portion of the terminal electrode, and between the fourth extension of the terminal cover and the fourth side portion of the terminal electrode. Therefore, if any one of the first to fourth extensions is soldered to the substrate, the stress applied to the solder when the substrate is bent due to thermal shock is alleviated by the above space, so that cracks are unlikely to occur in the solder. . Since cracks can be suppressed even if the terminal electrode extends on the first to fourth side surfaces of the ceramic body, it is not necessary to form the terminal electrode only on the end surface of the ceramic body. Therefore, the ceramic electronic component of the present invention is easy to manufacture. Further, the first to fourth extension portions of the terminal cover are arranged above the four side surfaces of the ceramic body, and any extension portion can be soldered to the substrate, so that cracking of the solder can be suppressed. Is easier to mount on the board.

  The ceramic electronic component according to the present invention may further include a conductive resin layer provided between the center portion of each terminal electrode and the main body of each terminal cover. According to this configuration, when the terminal cover of the ceramic electronic component is soldered to the substrate, the stress applied to the solder due to thermal shock is further relaxed by the conductive resin layer. As a result, solder cracks can be further suppressed.

  The ceramic electronic component according to the present invention is less likely to cause cracks in solder even when subjected to thermal shock while being soldered to a substrate, and is easy to manufacture and mount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

First Embodiment FIG. 1 is an exploded perspective view showing a ceramic electronic component according to a first embodiment, FIG. 2 is a sectional view taken along line 2--2 of FIG. 1, and FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1. The ceramic electronic component of this embodiment is a multilayer ceramic capacitor. The multilayer ceramic capacitor 10 a includes a rectangular parallelepiped ceramic body 12, a pair of terminal electrodes 15 formed at both ends of the ceramic body 12, and a conductive terminal cover 17 that covers each terminal electrode 15. Yes.

  As shown in FIGS. 2 and 3, both end faces 12 a of the ceramic body 12 are opposed to each other along the longitudinal direction of the ceramic body 12. These two end surfaces 12a are connected by a first side surface 12b, a second side surface 12c, a third side surface 12d, and a fourth side surface 12e. The first side surface 12b and the second side surface 12c, and the third side surface 12d and the fourth side surface 12e face each other.

  The ceramic body 12 has a structure in which a first internal electrode 23 and a second internal electrode 24 are embedded in a ceramic dielectric 22. These internal electrodes 23, 24 are both rectangular flat plates, and are alternately stacked via dielectrics 22. One end of the internal electrode 23 is exposed on one end face 12a of the ceramic body 12, and is connected to a terminal electrode 15 formed on the end face 12a. One end of the internal electrode 24 is exposed to the other end surface 12a of the ceramic body 12, and is connected to the terminal electrode 15 formed on the end surface 12a.

  Each terminal electrode 15 covers the entire end surface 12 a of the ceramic body 12, and a part thereof extends on the first to fourth side surfaces 12 b to 12 e of the ceramic body 12. Hereinafter, the portion 15a formed on the end surface 12a of the ceramic body 12 of the terminal electrode 15 is referred to as “center portion”, the portion 15b formed on the first side surface 12b is referred to as “first side portion”, and the second portion. The portion 15c formed on the side surface 12c is the "second side portion", the portion 15d formed on the third side surface 12d is the "third side portion", and the portion 15e formed on the fourth side surface 12e is This is called “fourth side”. The internal electrodes 23 and 24 in the ceramic body 12 are in contact with the central portion 15a.

  Each terminal cover 17 is bonded to the terminal electrode 15 by the conductive resin layer 16. Each terminal cover 17 is made of metal, and has a rectangular flat plate-like main body 17a, and a rectangular plate-like first extension portion 17b and a second extension extending perpendicularly to the main body 17a from a pair of opposing ends of the main body 17a. It has a portion 17c. The conductive resin layer 16 is interposed between the main body 17 a and the central portion 15 a of the terminal electrode 15, and electrically connects the terminal cover 17 to the terminal electrode 15. The first extension portion 17 b covers the first side portion 15 b of the terminal electrode 15, and the second extension portion 17 c covers the second side portion 15 c of the terminal electrode 15. The first extension portion 17b is separated from the first side portion 15b, and the second extension portion 17c is separated from the second side portion 15c. Therefore, a space 18 is formed between the first extension portion 17b and the first side portion 15b, and a space 19 is formed between the second extension portion 17c and the second side portion 15c. As will be described later, the terminal cover 17 prevents cracks in solder used for mounting the multilayer ceramic capacitor 10a, and also protects the terminal electrode 15 from moisture.

  Below, the manufacturing method of the multilayer ceramic capacitor 10a is demonstrated. First, an electrode pattern to be an internal electrode is formed on the surface of the ceramic green sheet, another ceramic green sheet is overlaid thereon, and an electrode pattern to be another internal electrode is formed on the surface. repeat. The ceramic green sheet laminate thus obtained is fired to form the ceramic body 12.

  Next, a conductive paste as a raw material for the terminal electrode 15 is applied to both ends of the ceramic body 12. This conductive paste is, for example, a metal paste containing glass. The conductive paste may be applied by immersing both end portions of the ceramic body 12 in the conductive paste. The conductive paste extends from the end surface 12a of the ceramic body 12 to the first to fourth side surfaces 12b to 12e. If the conductive paste is dried and then baked, the terminal electrode 15 is formed.

  Subsequently, a conductive resin paste is applied to the central portion 15 a of the terminal electrode 15. This conductive resin paste contains a metal and a thermosetting resin.

  Next, a terminal cover 17 is prepared, and the terminal cover 17 is placed on the terminal electrode 15 so that the main body 17a is in contact with the conductive resin paste. At this time, between the first extension portion 17b of the terminal cover 17 and the first side portion 15b of the terminal electrode 15, and between the second extension portion 17c of the terminal cover 17 and the second side portion 15c of the terminal electrode 15. The terminal cover 17 is positioned so that the spaces 18 and 19 are formed therebetween.

  Thereafter, the conductive resin paste is heated and cured to bond the terminal electrode 15 and the terminal cover 17 together. The cured conductive resin paste becomes the conductive resin layer 16 described above and remains between the terminal electrode 15 and the terminal cover 17. In this way, the multilayer ceramic capacitor 10a of this embodiment is obtained.

  Below, the effect of this embodiment is demonstrated, referring FIG. Here, FIG. 4 is a schematic cross-sectional view showing a state in which the multilayer ceramic capacitor 10 a is mounted on the substrate 26. At the time of mounting, the terminal electrode 15 is soldered to a conductive land (not shown) on the substrate 26 using solder 28.

  In recent years, in consideration of environmental problems, lead-free solder is often used as the solder 28. However, according to the research of the present inventor, when a ceramic electronic component is soldered onto a substrate using lead-free solder and a thermal shock is applied, the solder tends to crack rather than the ceramic body of the electronic component. I understood that.

  Even if the multilayer ceramic capacitor 10a of this embodiment is soldered to the substrate 26 by the lead-free solder 28, it is difficult for the solder 28 to generate cracks due to thermal shock. This is because spaces 18 and 19 are formed between the terminal electrode 15 and the terminal cover 17. When the substrate 26 and the multilayer ceramic capacitor 10a are subjected to thermal shock, the substrate 26 may be bent due to the difference in thermal expansion coefficient between the substrate 26 and the ceramic body 12. At this time, the spaces 18 and 19 function as cushions that relieve stress applied to the solder 28. This makes it difficult for cracks to occur in the solder 28.

  For example, let us consider a case where the space 18 does not exist and the first side portion 15b of the terminal electrode 15 and the first extension portion 17b of the terminal cover 17 are directly joined. In this case, if the board | substrate 26 curves, the 1st extension part 17b will apply a compressive stress or a tensile stress to the ceramic base body 12 via the 1st side part 15b. As a reaction of this stress, the solder 28 is also stressed. This causes a crack in the solder 28.

  On the other hand, in the present embodiment, since the space 18 is formed between the first side portion 15b and the first extension portion 17b, the first extension portion 17b is formed when the substrate 26 is bent by thermal shock. Therefore, stress is hardly applied to the ceramic body 12. As a result, the stress applied to the solder 28 is relaxed, and cracks are unlikely to occur in the solder 28. Similarly, the space 19 formed between the second side portion 15c and the first extension portion 17c also suppresses cracks in the solder 28 due to thermal shock. Further, since the first extension portion 17b is separated from the first side portion 15b, the first extension portion 17b can also be expected to function as a radiating fin that releases heat applied during soldering to the atmosphere. . Thereby, the thermal shock applied to the ceramic body 12 can be reduced.

  Forming the spaces 18 and 19 on both sides of the ceramic body 12 provides advantages in addition to suppressing solder cracks. That is, since the crack can be suppressed even if the terminal electrode 15 extends on the first side surface 12b and the second side surface 12c of the ceramic body 12, it is necessary to form the terminal electrode 15 only on the end surface 12a of the ceramic body 12. Absent. Therefore, the multilayer ceramic capacitor 10a is easy to manufacture.

  Furthermore, in FIG. 4, the second extension 17c of the terminal cover 17 is soldered to the substrate 26. However, even if the first extension 17b opposite to the second extension 17c is soldered to the substrate 26, Similarly, a crack suppressing effect can be obtained. Since the spaces 18 and 19 are arranged so as to face each other with the ceramic body 12 interposed therebetween, when mounting the multilayer ceramic capacitor 10 a on the substrate 26, either of the spaces 18 and 19 may be directed to the substrate 26. . Thus, the multilayer ceramic capacitor 10a has a high degree of freedom in the mounting direction, and therefore can be easily mounted on the substrate 26.

  Since the conductive resin layer 16 interposed between the terminal electrode 15 and the terminal cover 17 is flexible, the conductive resin layer 16 also relieves stress applied to the solder 28. Thereby, the crack of the solder 28 becomes harder to occur.

Second Embodiment FIG. 5 is an exploded perspective view showing a ceramic electronic component according to a second embodiment, FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5, and FIG. 5 is a cross-sectional view taken along line 7-7 of FIG. The ceramic electronic component of this embodiment is also a multilayer ceramic capacitor. The multilayer ceramic capacitor 10b has a configuration in which the terminal cover 17 is replaced with a terminal cover 27 in the multilayer ceramic capacitor 10a of the first embodiment. Other configurations are the same as those of the multilayer ceramic capacitor 10a.

  Each terminal cover 27 is bonded to each terminal electrode 15 with a conductive resin layer 16 so as to cover each terminal electrode 15. Each terminal cover 27 is made of metal and has a rectangular flat plate-shaped main body 27a. A pair of opposite ends of the main body 27a is provided with a first extension portion 27b and a second extension portion 27c that are rectangular flat plates extending perpendicularly to the main body 17a. Further, another pair of end portions of the main body 27a facing each other along a direction perpendicular to the direction in which the pair of end portions are arranged is a rectangular flat plate-like third extension portion extending perpendicularly to the main body 17a. 27d and a fourth extension 27e are provided. The conductive resin layer 16 is interposed between the main body 27 a and the central portion 15 a of the terminal electrode 15, and electrically connects the terminal cover 27 to the terminal electrode 15.

  The first to fourth extension portions 27b to 27e cover the first side portion 15b to the fourth side portion 15e of the terminal electrode 15, respectively. The first extension part 27b is from the first side part 15b, the second extension part 27c is from the second side part 15c, the third extension part 27d is from the third side part 15d, and the fourth extension part 27e is the fourth. The side portions 15e are spaced apart from each other. Accordingly, between the first extension portion 27b and the first side portion 15b, between the second extension portion 27c and the second side portion 15c, between the third extension portion 27d and the third side portion 15d, and fourth. A space 38 is formed between the extension portion 27e and the fourth side portion 15e.

  Similar to the spaces 18 and 19 in the first embodiment, this space 38 relaxes the stress applied to the solder due to thermal shock when the third extension 27d or the fourth extension 27e is soldered to the substrate. Suppresses cracks. Therefore, even if any of the first to fourth extension portions 27b to 27e is soldered to the substrate, cracks in the solder can be suppressed. As described above, the multilayer ceramic capacitor 10b has a higher degree of freedom in the mounting direction, and is thus easier to mount on the substrate 26.

  The inventor actually manufactured the multilayer ceramic capacitor 10a by the method described in the first embodiment as an example, and manufactured a multilayer ceramic capacitor having no space 18 as a comparative example, and applied thermal shock to both. And the presence or absence of cracks was examined.

  The conductive paste for the terminal electrode 15 used in the examples is mainly composed of Ag and glass frit. In addition, the conductive resin paste used in the examples has a concentration of 35 wt% of granular Ag powder having an average particle diameter of 1 μm, 35 wt% of flaky Ag powder having an average particle diameter of 10 μm, 12 wt% of epoxy resin, and 18 wt% of solvent. It includes in each. After the terminal cover 17 was put on the terminal electrode 15 through this conductive resin paste, the conductive resin paste was cured by heating at 200 ° C. for 60 minutes, and the terminal electrode 15 and the terminal cover 17 were bonded.

  On the other hand, when manufacturing a comparative example, after forming the terminal electrode 15 by the method similar to an Example, the conductive resin paste was apply | coated so that the whole surface of the center part 15a and the side parts 15b-15e might be covered. The same conductive resin paste as in the example was used. Next, after drying the conductive resin paste, it is heated at 200 ° C. for 60 minutes and cured to form a conductive resin layer. Next, an Ni plating film was formed on the surface of the conductive resin layer by an electrolytic plating method, and then an Sn plating film was formed on the surface of the Ni plating film by an electrolytic plating method. Thus, a multilayer ceramic capacitor of a comparative example was obtained.

この表において、「ｎ／５０」は５０個のサンプルのうちｎ個に半田クラックが生じたことを表す。表１に示されるように、２０００サイクル及び３０００サイクルの熱衝撃を加えたときに、比較例を使用したサンプルの一部に半田クラックが発生するが、実施例を使用したサンプルでは、３０００サイクルの熱衝撃を加えても半田クラックが一切発生しなかった。これは、端子電極１５と端子カバー１７との間に形成された空間１８、１９が半田クラックを防ぐ効果を示している。 The inventor manufactured 50 multilayer ceramic capacitors of Examples and Comparative Examples, and examined the thermal shock characteristics of each. Specifically, samples were prepared by reflow soldering each capacitor to a glass epoxy board using lead-free solder, and the thermal shock characteristics of each sample were examined. In one cycle of thermal shock, the sample is placed at a temperature of −55 ° C. for 30 minutes, then the temperature is increased to 125 ° C. and the sample is placed for an additional 30 minutes. In the next cycle, the temperature is lowered from 125 ° C. to −55 ° C., the sample is placed for 30 minutes, and then the temperature is raised to 125 ° C. for an additional 30 minutes. The inventor observed the cross section of each sample after 1000 cycles, 2000 cycles, and 3000 cycles, and examined whether or not solder cracks were generated. The results are shown in the following table.

In this table, “n / 50” indicates that solder cracks occurred in n out of 50 samples. As shown in Table 1, when a thermal shock of 2000 cycles and 3000 cycles was applied, a solder crack occurred in a part of the sample using the comparative example, but in the sample using the example, 3000 cycles No solder cracks occurred even when a thermal shock was applied. This shows the effect that the spaces 18 and 19 formed between the terminal electrode 15 and the terminal cover 17 prevent solder cracks.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  The ceramic electronic component of the present invention is not limited to the multilayer ceramic capacitor of the above embodiment, and may be any other electronic component. For example, the ceramic electronic component of the present invention may be an inductor having a ceramic body. This ceramic body has a ceramic magnetic body and a coil-shaped internal electrode embedded in the ceramic magnetic body. Terminal electrodes and terminal covers similar to those in the above embodiment are provided at both ends of the ceramic body.

  In the above embodiment, when the multilayer ceramic capacitor is viewed from above the extension along the direction perpendicular to each extension of the terminal cover, each side part of the terminal electrode is completely covered by the extension. . However, each extension part does not necessarily need to cover all of the side parts located below, and may cover only a part thereof.

It is a disassembled perspective view which shows 1st Embodiment. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1. It is sectional drawing which shows the laminated ceramic capacitor mounted on the board | substrate. It is a disassembled perspective view which shows 2nd Embodiment. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. FIG. 7 is a cross-sectional view taken along line 7-7 in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10a, 10b ... Multilayer ceramic capacitor, 12 ... Ceramic body, 15 ... Terminal electrode, 16 ... Conductive resin layer, 17 ... Terminal cover, 18, 19, and 38 ... Space, 22 ... Dielectric, 23 ... 1st internal electrode 24 ... second internal electrode, 26 ... substrate, 28 ... solder

Claims (3)

Two opposing end surfaces, and a ceramic element body connecting the two end surfaces and having first and second side surfaces facing each other;
Terminal electrodes provided on each of the end faces of the ceramic body,
A conductive terminal cover electrically connected to each of the terminal electrodes and covering each of the terminal electrodes;
A ceramic electronic component comprising:
Each of the terminal electrodes includes a central portion formed on each end face of the ceramic body, a first side portion formed on a first side surface of the ceramic body, and a second portion of the ceramic body. A second lateral portion formed on the side surface,
Each terminal cover includes a main body connected to a central portion of each terminal electrode, a first extension extending from the main body so as to cover a first lateral portion of each terminal electrode, and a first extension of each terminal electrode. A second extension extending from the main body so as to cover two side portions,
A first extension of each terminal cover is spaced apart from a first lateral portion of each terminal electrode;
A second extension of each terminal cover is spaced apart from a second lateral portion of each terminal electrode;
Ceramic electronic components. The ceramic body further includes a third side surface and a fourth side surface that connect the two end surfaces and face each other.
Each of the terminal electrodes further includes a third side portion formed on the third side surface of the ceramic body and a fourth side portion formed on the fourth side surface of the ceramic body. And
Each terminal cover includes a third extension extending from the main body so as to cover the third side portion of each terminal electrode, and a fourth extension extending from the main body so as to cover the fourth side portion of each terminal electrode. And further having an extension,
A third extension of each terminal cover is spaced apart from a third lateral portion of each terminal electrode;
The fourth extension of each terminal cover is spaced apart from the fourth side of each terminal electrode;
The ceramic electronic component according to claim 1.   3. The ceramic electronic component according to claim 1, further comprising a conductive resin layer provided between a central portion of each terminal electrode and a main body of each terminal cover.

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