Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2000-02-09
2001-09-11
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S306300, C361S309000, C361S321200
Reexamination Certificate
active
06288887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ceramic electronic component, such as a multilayer ceramic capacitor; particularly, the invention relates to a terminal-mounted ceramic electronic component that has outer terminals for mounting a substrate on a ceramic electronic component element.
2. Description of the Related Art
Typical ceramic electronic components or multilayer ceramic capacitors include a type which has a structure such as that shown in FIG.
5
. The structure has multiple inner electrodes
52
opposing each other via a ceramic layer
51
, one end of each of the electrodes extends, in alternating fashion, to opposite end surfaces of a ceramic electronic component element
54
. The structure also has a pair of outer electrodes
53
arranged on opposite end surfaces so as to be electrically connected to exposed portions of the inner electrodes
52
. In addition, the structure has outer terminals
55
formed by bent metal plates connected to the outer electrodes
53
by a connecting material
56
, such as a solder, an electrically conductive adhesive, or an electrically conductive paste.
Another type of the typical multilayer ceramic capacitor has the structure as shown in FIG.
6
. In this structure, outer terminals
55
are connected to an electronic element
64
(stacked element) formed by stacking multiple ceramic electronic elements
54
. A connecting material
56
, similar to that used in the above type (such as a solder, an electrically conductive adhesive, or an electrically conductive paste) is used to connect the outer terminals
55
to the ceramic electronic elements
54
. Outer electrodes
53
are formed on the electronic component element
64
so as to be electrically connected to inner electrodes
52
arranged in a ceramic
51
.
The components described above, however, have certain drawbacks. For example, the terminal-mounted multilayer ceramic capacitor shown in
FIG. 5
exhibits insufficient strength to withstand certain levels of substrate deflection. A substrate-deflection testing was performed in accordance with requirements stipulated in Japanese Industrial Standards (JIS). The test was performed on the capacitor in a condition where the outer terminals
55
were connected to a printed circuit board
57
. During which test, depending on a thickness t of the outer terminal
5
, an elevation height H (distance in which each of the outer terminal
55
extends from a lower surface of the ceramic electronic element
54
), and a length L of the ceramic electronic element
54
, the strength of the structure is found to be insufficient to withstand a specified substrate deflection. At times, cracks C were created at portions near individual lower end surfaces of the end surfaces to which the outer terminals
55
are connected (force-exerted points).
The above problem is particularly problematic in large ceramic electronic components. In large components, since a distance L between the outer terminals (interterminal distance) is proportionally long, cracks are likely to occur, i.e., damage is likely to result. These problems can also arise with the stacked type of the ceramic electronic component shown in FIG.
6
.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the problems described above by providing a ceramic electronic component having a high strength against deflection of the substrate, thereby enjoying high reliability.
In order to solve the above described problems, the inventors carried out various experiments and studies. As a result, they learned that the relationship between the distance H
1
from the surface of the substrate to the point at which the outer terminals first contact the side surfaces of the electronic component and the length L of the electronic component element (as measured between the electrodes formed on its end surfaces) significantly affects the strength against deflection of the substrate of the ceramic electronic component. Based on this finding, the team further carried out experiments and studies, thereby making the present invention.
The ceramic electronic component of the present invention comprises:
a substantially rectangular ceramic electronic component having opposite side surfaces defined by respective outer electrodes which are substantially parallel to one another and are spaced apart by a length L, the electronic component also having a bottom surface extending between the side surfaces substantially perpendicularly thereto;
a pair of outer terminals connected to respective ones of the opposite end surfaces of the electronic component, each of the outer terminals extending below the bottom surface of the electronic component and terminating in surface mounting portions whose bottom surfaces extend in a common plane lying substantially parallel to the bottom surface of the electronic component, the distance from the common plane to the point at which the outer terminals first contact the side surfaces of the electronic component being H
1
, the distance from the common plane to the bottom surface of the electronic component being H
2
, each of the outer terminals having a thickness t,
the electronic component and outer terminals having the relationship:
H
1
≧0.03L and H
2
≧2t.
The force-exertion point (the point where a force is exerted from the outer terminal to the electronic component element) in the present invention is a concept signifying a point where the deflection stress caused by the substrate being stressed reaches the electronic component through the outer terminal. As a general rule, the force-exertion point will be the point at which the outer terminals as measured from the substrate first contacts the side surfaces of the electronic component element.
In the above, the outer terminals may be formed of a material selected from alloys containing a main component of at least one of Cu, Ni, Al, Ag, and Fe. With the outer terminals formed in this way, required mechanical strengths can be ensured, and concurrently, electrical-current capacitance can be ensured. This allows the present invention to be even more practically efficient.
Also, the length L of the electronic component element may be 3 to 50 mm, or more preferably, 10 to 50 mm. By applying the present invention to ceramic electronic components in which the distance between the outer terminals is arranged as described above, the strength against deflection of the substrate in large terminal-mounted ceramic electronic components which frequently cause problems of destruction due to deflection of their substrates can be improved. This allows the present invention to be even more practically efficient.
Also, in the ceramic electronic component described above, the pair of outer terminals may be soldered with the electronic component element. Generally, outer terminals are soldered with electronic component elements. The present invention also employs the soldering method, thereby allowing ceramic electronic components of various types to have an improved strength against deflection of their substrates. This also allows the invention to be even more practically efficient.
Furthermore, surfaces of the outer terminals may be plated or coated with at least one material selected from Au, Ni, Sn, and a solder. Generally, outer terminals are plated or coated with the aforementioned material to improve performance and soldering characteristics. Therefore, the present invention can be suitably to a wide range of ceramic electronic components with such outer terminals. This results in provision of a wide range of ceramic electronic components improved in the strength against deflection of their substrates.
REFERENCES:
patent: 6046902 (2000-04-01), Nakagawa et al.
patent: 6181544 (2001-01-01), Nakagawa et al.
patent: 2327631 (1999-02-01), None
patent: 11-40454 (1999-02-01), None
Kubota Yasuhiko
Moriwaki Nobushige
Yoshida Kazuhiro
Dinkins Anthony
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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