Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2000-06-21
2002-10-01
Paladini, Albert W. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C029S025350, C361S772000
Reexamination Certificate
active
06459048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to surface-mount electronic components, and more particularly relates to a surface-mount electronic component having a terminal electrode film formed by a film-forming processing such as plating.
2. Description of the Related Art
FIG. 11
shows one example of a conventional surface-mount electronic component. A surface-mount electronic component
60
includes a rectangular main unit
11
having three terminal electrode films
12
to
14
provided on the surface thereof by electroless plating or electroplating. The terminal electrode films
12
and
14
are provided on the corresponding ends of the main unit
11
and function as an input terminal electrode film
12
is located between the terminal electrode films
12
and
14
and functions as a ground terminal.
The main unit
11
is formed by adhering a piezoelectric substrate
15
, an overlaid ceramic cover member
16
, and an underlaid ceramic cover member
17
. The major surfaces of the piezoelectric substrate
15
facing each other have corresponding vibrating electrodes
21
and
22
provided thereon, as shown in FIG.
12
. These vibrating electrodes
21
and
22
function as internal electrodes and constitute, along with the piezoelectric substrate
15
, a piezoelectric resonator
230
. As shown in
FIG. 11
, a lead-in terminal
21
a
of the vibrating electrode
21
extends to the right end portion of the piezoelectric substrate
15
and is exposed at the surface of the main unit
11
, including a right end surface
11
a.
A lead-in terminal
22
a
of the vibrating electrode
22
extends to the left end portion of the piezoelectric substrate
15
and is exposed at the surface of the main unit
11
, including a left end surface
11
b.
The terminal electrode film
12
is electrically connected to the lead-in terminal
21
a,
and the terminal electrode film
14
is electrically connected to the lead-in terminal
22
a.
Thus, the surface-mount electric component
60
is constructed as a three-terminal electronic component (an oscillator) having an equivalent circuit as shown in FIG.
13
. That is, the piezoelectric resonator
230
is connected between the terminal electrode film
12
(the input terminal) and the terminal electrode film
14
(the output terminal) capacitor C
1
is located between the terminal electrode films
12
and
13
(the ground terminal), and is coupled across the terminal electrode films
12
and
13
. A capacitor C
2
is located between the terminal electrode films
13
and
14
, and is coupled across the terminal electrode films
13
and
14
.
In the conventional surface-mount electronic component
60
, as shown in
FIGS. 11 and 12
, the lead-in terminals
21
a
and
22
a
are exposed at the end surfaces
11
a
and
11
b
of the main unit
11
, respectively. Accordingly, when the terminal electrodes
12
to
14
are formed by electroless plating or electroplating, a plated film
26
is formed on the surface of each of the exposed lead-in terminals
21
a
and
22
a.
However, since each of the lead-in terminals
21
a
and
22
a
is thin, the area for adhesion between the plated film
26
and the lead-in terminals
21
a
or
22
a
is very small. Therefore, the adhesion therebetween is weak, which causes the plated film
26
to be easily separated from the lead-in terminal
21
a
or
22
a.
For example, when some force or impact is applied to the plated film
26
in the course of forming the terminal electrodes
12
to
14
, or some tension is caused when molten solder is applied to the plated film
26
in the course of mounting of the printed substrate, the plated film
26
can easily separate from the plated film
26
. At this time, when the separated plated film
26
comes into contact with, for example, the terminal electrode film
12
or
13
, as shown in
FIG. 11
, short-circuiting occurs between the terminal electrode films
12
and
13
.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a highly reliable surface-mount electronic component which is constructed so as to prevent short-circuiting between terminal electrode films using films formed by various film-forming processes such as plating.
According to one preferred embodiment of the present invention, a surface-mount electronic component includes a terminal electrode film that is formed by film-forming processing on the surface of a main unit of the surface-mount electronic component, and a lead-in terminal conducted from an internal electrode disposed in the surface-mount electronic component and extending up to the surface of the main unit for establishing electrical connection between the internal electrode and the terminal electrode film. In the surface-mount electronic component, the lead-in terminal of the internal electrode is conducted up to at least one of the surfaces of the main unit, except a surface-mount surface of the main unit and the surface opposite to the surface-mount surface, and an exposed portion of the lead-in terminal is coated by at least one of the terminal electrode film and a protective film. In this context, the meaning of “coated” includes a case in which only a portion of an exposed part is coated.
A portion of the lead-in terminal exposed at the surface of the main unit is coated by the terminal electrode film and the protective film. When the terminal electrode film is formed by plating, the coating of the terminal electrode film or the protective film does not allow the plating to form on the exposed part of the lead-in terminal. Accordingly, easily separable and useless plated film is not formed.
In the surface-mount electronic component, alternatively, the surface-mount electronic component has at least two terminal electrode films, and the length of the exposed portion of each of the at least two terminal electrode films which is coated by none of the at least two terminal electrode films and the protective film, is shorter than the distance between the at least two terminal electrode films.
With the above-described setting, the length of the useless plated film, which is formed on each of the exposed parts of the lead-in terminals, and which is coated by none of the terminal electrode films and the protective film, is shorter than the distance between two adjacent terminal electrode films. Accordingly, even though the useless plated film is separated from the exposed part of the lead-in terminal, this separated plated film cannot cause short-circuiting to occur between the two adjacent terminal electrode films.
Other features, characteristics, elements and advantages of preferred embodiments of the present invention will be apparent from the detailed description of preferred embodiments of the present invention with reference to the attached drawings.
REFERENCES:
patent: 5357662 (1994-10-01), Takagi et al.
patent: 5896081 (1999-04-01), Tzeng et al.
patent: 5952898 (1999-09-01), Nakata et al.
patent: 6093996 (2000-07-01), Daidai et al.
patent: 6133637 (2000-10-01), Hikita et al.
Kotani Kenichi
Sakai Ken'ichi
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Paladini Albert W.
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