Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-01-28
2003-02-11
Enad, Elvin (Department: 2832)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S692000, C257S730000, C361S308200
Reexamination Certificate
active
06518632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ceramic electronic part, and more particularly to a ceramic electronic part having a structure in which an external terminal, for being mounted to, for example, a base, is disposed on a surface of a ceramic electronic part element so as to be in electrical conduction with an internal electrode disposed in ceramic.
2. Description of the Related Art
Some ceramic electronic parts include external terminals for being mounted to, for example, bases. An example of such ceramic electronic parts including external terminals are shown in
FIGS. 8A
,
8
B, and
8
C, wherein metallic external terminals
55
are bonded with a bonding material
56
, such as solder, an electrically conductive adhesive, or an electrically conductive paste, onto both end surfaces of a chip-type ceramic electronic part element
54
where external electrodes
53
are formed so as to be in electrical conduction with internal electrodes
52
disposed in ceramic
51
.
In another example shown in
FIG. 9
, metallic external terminals
55
are bonded through a bonding material
56
, such as solder, an electrically conductive adhesive, or an electrically conductive paste, onto a ceramic electronic part element
64
formed by stacking a plurality of chip-type electronic part elements
54
upon each other, where external electrodes
53
are formed so as to be in electrical conduction with internal electrodes
52
disposed in ceramic
51
.
In general, the external terminals
55
shown in
FIGS. 8A and 8C
, having widths WE approximately equal to width W of the ceramic electronic part element
54
(
64
), are often used.
The use of such external terminals does not become a serious problem when the ceramic electronic parts whose external terminals
55
are bonded to the ceramic electronic part element
54
(
64
) are small. However, when the ceramic electronic parts are large with, for example, a length L or a width W (see
FIGS. 8A
to
8
C and
FIG. 9
) equal to or greater than 10 mm, they are often used with a relatively high voltage and a large current, so that in order to make resistance values low the widths WE (see
FIG. 8A
) and thicknesses T (see
FIGS. 8B and 9
) of the external terminals
55
must be made large.
In such a case, a noticeable amount of stress is produced due to a difference between the linear expansion coefficients of the ceramic electronic part element
54
(
64
) and those of the external terminals
55
, so that a considerably large stress is exerted onto both end portions of the external terminals
55
. For this reason, during, for example, a heat cycle test of the ceramic electronic parts, cracks C are produced in the ceramic electronic part element
54
(
64
), particularly at the sides where the temperature is low, as shown in FIG.
10
.
SUMMARY OF THE INVENTION
To overcome the above-described problem, the present invention is able to provide a highly reliable ceramic electronic part with an external terminal, which eliminates the problem of cracks being produced in a ceramic electronic part element when the ceramic electronic part is large.
To this end, according to a first form of the present invention, there is provided a ceramic electronic part comprising:
a ceramic electronic part element constructed so that an internal electrode is disposed in ceramic, with a portion of the internal electrode being exposed from an end surface of the ceramic electronic part element; and
an external terminal being a metallic plate joined to the end surface of the ceramic electronic part element so as to be in electrical conduction with the internal electrode exposed from the end surface of the ceramic electronic part element;
wherein a width of a portion of the external terminal that is joined to the end surface of the ceramic electronic part element is equal to or less than a width of the internal electrode disposed in the ceramic electronic part element.
When the width of the portion of the external terminal that is joined to the ceramic electronic part element is equal to or less than the width of the internal electrode, and the ceramic electronic part element has a complex structure including the ceramic and the internal electrode (metal), an external electrode can be joined to a portion having a linear expansion coefficient closer to the linear expansion coefficient of the metal than the linear expansion coefficient of a portion including only the ceramic. Therefore, it is possible to reduce cracking as a result of reducing the amount of stress produced in a heat cycle test.
In the present invention, the phrase “joining an external terminal to an end surface of a ceramic electronic part element” is to be broadly interpreted as also meaning, for example, directly joining an external terminal to an end surface of a ceramic electronic part element, or joining an external terminal onto an end surface of a ceramic part element through, for example, a bonding material, such as solder, an electrically conductive adhesive, or an electrically conductive paste, and/or joining the external terminal to an external electrode formed on the end surface of the ceramic electronic part element in conductive connection with the internal electrode.
According to a second form of the present invention, the joining portion of the external terminal may be joined to the end surface of the ceramic electronic part element so as to be positioned within an area of the end surface of the ceramic electronic part element where the internal electrode is exposed when viewed in a plane.
When an external electrode is joined to an end surface of the ceramic electronic part element so that the joining portion of the external terminal is positioned within the area of the end surface of the ceramic electronic part element where the internal electrode is exposed when viewed in a plane, the external terminal can be reliably joined to a portion having a linear expansion coefficient closer to the linear expansion coefficient of a metal than the linear expansion coefficient of a portion including only ceramic. Therefore, the present invention can provide more satisfactory practical results.
According to a third form of the present invention, when a width of a portion of the external terminal that is joined to the end surface of the ceramic electronic part element is equal to or less than a width of the internal electrode disposed in the ceramic electronic part element, or when the joining portion of the external terminal is joined to the end surface of the ceramic electronic part element so as to be positioned within an area of the end surface of the ceramic electronic part element where the internal electrode is exposed when viewed in a plane, the ceramic electronic part element may be formed by stacking a plurality of ceramic electronic part elements upon each other.
Here, it is possible to use a type of ceramic electronic part known as a stacked-type ceramic electronic part formed by stacking a plurality of ceramic electronic part elements upon each other. Even in this case, it is possible to reduce the amount of stress generated in a heat cycle test in order to reduce cracking.
According to a fourth form of the present invention, when a width of a portion of the external terminal that is joined to the end surface of the ceramic electronic part element is equal to or less than a width of the internal electrode disposed in the ceramic electronic part element, or when the joining portion of the external terminal is joined to the end surface of the ceramic electronic part element so as to be positioned within an area of the end surface of the ceramic electronic part element where the internal electrode is exposed when viewed in a plane, or when the ceramic electronic part element is formed by stacking a plurality of ceramic electronic part elements upon each other, a width of at least a portion of the external terminal other than the joining portion that is joined to the ceramic electronic part element may be made larger than the width of the internal el
Kubota Yasuhiko
Moriwaki Nobushige
Yoshida Kazuhiro
Enad Elvin
Keating & Bennett LLP
Lee Kyung S.
Murata Manufacturing Co. Ltd.
LandOfFree
Ceramic electronic part does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ceramic electronic part, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ceramic electronic part will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3136984