Piezoelectric resonance component

Details Piezoelectric resonance component Piezoelectric resonance component

2000-03-28

2002-04-09

Tamai, Karl (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S365000, C310S348000

Reexamination Certificate

active

06369487

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric resonance component for use in, for example, a chip-type piezoelectric oscillator. More particularly, the present invention relates to a piezoelectric resonance component including a piezoelectric resonance element housed in a package that includes a capacitor substrate.
2. Description of the Related Art
A piezoelectric resonance element is housed in a package so as to allow for free vibration of its piezoelectric vibrating portion.
For example, in the case of a piezoelectric oscillator circuit that includes a piezoelectric resonance element, a capacitor is electrically connected to the piezoelectric resonance element. When such a piezoelectric oscillator circuit is to be arranged in the form of a chip-type component, the capacitor is provided within a housing substrate so as to achieve compactness.
For example, Japanese Patent Application Laid-Open (kokai) No. 4-192709 discloses a chip-type piezoelectric resonance component
50
as shown in FIG.
10
. The chip-type piezoelectric resonance component
50
includes, as a housing substrate, a capacitor substrate
51
formed by monolithic-ceramic firing technology. A ceramic cap
52
opening downward is soldered to the capacitor substrate
51
via solder
53
. In order to improve solderability, a soldering layer
54
is formed with Ag and Pd on the lower surface of the ceramic cap
52
, whereas a soldering layer
55
is formed of NiCr and Au on the upper surface of the capacitor substrate
51
.
A piezoelectric resonance element
56
is housed in a package defined by the capacitor substrate
51
and the ceramic cap
52
. The piezoelectric resonance element
56
includes a piezoelectric substrate
57
and excitation electrodes
58
and
59
provided on the upper and lower surfaces, respectively, of the piezoelectric substrate
57
. A portion of the piezoelectric resonance element
56
where the excitation electrodes
58
and
59
overlap each other functions as a vibrating portion which utilizes an energy-trapping-type thickness-shear-vibration mode.
The piezoelectric resonance element
56
is soldered to electrodes
62
and
63
, respectively, provided on the upper surface of the housing substrate
51
.
A plurality of inner electrodes
64
to
68
are provided within the capacitor substrate
51
. The inner electrodes
64
and
65
are electrically connected to a via hole electrode
69
extending through the capacitor substrate
51
. A via hole electrode
70
is electrically connected to the lower surface of the inner electrode
66
. The inner electrodes
67
and
68
are electrically connected to a via hole electrode
71
extending through the capacitor substrate
51
. The via hole electrodes
69
and
71
are arranged such that the upper ends are electrically connected to the electrodes
62
and
63
, respectively, and such that the lower ends are electrically connected to terminal electrodes
72
and
73
, respectively, provided on the lower surface of the capacitor substrate
51
. The lower end of the via hole electrode
70
is electrically connected to a terminal electrode
74
provided on the lower surface of the capacitor substrate
51
.
Japanese Utility Model Application Laid-Open (kokal) No. 5-181205 discloses a piezoelectric resonance component
81
as shown in
FIG. 11. A
capacitor substrate
82
and a cap
83
define a package. Inner electrodes
84
and
85
are disposed within the capacitor substrate
82
. An electrode
86
a
is provided on the upper surface of the capacitor substrate
82
such that the electrode
86
a
and the inner electrode
85
overlap each other with a dielectric layer disposed therebetween. Similarly, an electrode
86
b
is provided on the lower surface of the capacitor substrate
82
such that the electrode
86
b
and the inner electrode
84
overlap each other with a dielectric layer disposed therebetween. The electrodes
86
a
and
86
b
are electrically connected together on unillustrated side surfaces of the capacitor substrate
82
.
The inner electrodes
84
and
85
are electrically connected to outer electrodes
87
a
and
87
b,
respectively, which are arranged so as to cover the corresponding end surfaces of the capacitor substrate
82
. The outer electrodes
87
a
and
87
b
extend so as to cover portions of the upper and lower surfaces of the capacitor substrate
82
. A piezoelectric resonator
90
is soldered to portions of the outer electrodes
87
a
and
87
b
which cover the corresponding portions of the upper surface of the capacitor substrate
82
. The piezoelectric resonator
90
is an energy-trapping type utilizing a thickness shear-vibration mode. The piezoelectric resonator
90
is enclosed within a space defined by the capacitor substrate
82
and the cap
83
.
The piezoelectric resonance component
50
shown in
FIG. 10
has the via hole electrodes
69
to
71
provided therein in order to establish an electrical connection between the piezoelectric resonance element
56
and the capacitor substrate
51
functioning as a capacitor and among the terminal electrodes
72
to
74
, the capacitor, and the piezoelectric resonance element
56
.
Accordingly, fabrication of the piezoelectric resonance component
50
must include a step of forming the via hole electrodes
69
to
71
, resulting in an increase in the number of steps required for manufacturing, as well as an increase in the degree of difficulty in processing. A relatively high manufacturing cost for the capacitor substrate
51
is also caused.
Since the via hole electrodes
69
to
71
must be provided in the capacitor substrate
51
, the internal electrodes cannot be extended such that the internal electrodes face each other at areas where the via hole electrodes
69
to
71
are located. In other words, the via hole electrodes
69
to
71
prevents an increase in the opposed area of inner electrodes, thus preventing a reduction in size and causing an increase in the required area for mounting.
The presence of the via hole electrodes
69
to
71
impairs the symmetry of the capacitor substrate
51
, potentially causing deformation of the capacitor substrate
51
during firing in the manufacturing process. For example, upper and lower portions of the via hole electrode
70
are not symmetrical relative to each other with respect to an imaginary plane that passes through the center of the capacitor substrate
51
and extends parallel to the upper and lower surfaces of the capacitor substrate
51
. Such impaired symmetry causes deformation of the capacitor substrate
51
, thereby causing poor soldering between the capacitor substrate
51
and the piezoelectric resonance element
56
, or formation of a gap between the capacitor substrate
51
and the cap
52
with a resultant impairment in sealing performance. Further, when the piezoelectric resonance component
50
is mounted on a printed circuit board, mounting accuracy may be impaired, or poor soldering may result.
In contrast, the piezoelectric resonance component
81
shown in
FIG. 11
does not have via hole electrodes formed in the capacitor substrate
82
. Thus, the above-mentioned problems associated with the presence of via hole electrodes do not occur.
When the piezoelectric resonance component
81
is mounted on a printed circuit board, electrical connection therebetween is established via the outer electrodes
87
a
and
87
b
and the outer electrodes (not shown) provided on the side surfaces of the capacitor substrate
82
and electrically connected to the electrodes
86
a
and
86
b.
The outer electrodes
87
a
and
87
b
are provided on the end surfaces of the capacitor substrate
82
, whereas the outer electrodes connected to the electrodes
86
a
and
86
b
are provided on the side surfaces of the capacitor substrate
82
. Accordingly, both end surfaces and both side surfaces of the capacitor substrate
82
must be soldered to the printed circuit board, thus making a mounting process very complicated.
In addition, since capacitance is established by

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