Wave transmission lines and networks – Coupling networks – Electromechanical filter
Reexamination Certificate
2000-12-01
2002-11-19
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Electromechanical filter
C310S348000
Reexamination Certificate
active
06483401
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to substrates for mounting electronic components and more particularly to a substrate of a case for packaging chip-type electronic components. The present invention also relates to a piezoelectric resonance component including such a substrate.
2. Description of the Related Art
Conventionally, various chip-type piezoelectric resonance components including piezoelectric elements are known. Because the piezoelectric vibrating part in the piezoelectric resonator vibrates, the packaging of the piezoelectric resonator must be done in a manner that does not prevent or hinder the vibration.
FIG. 6
is an assembly view showing an example of a conventional chip-type piezoelectric resonance component.
This chip-type piezoelectric resonance component includes a substrate
51
made of an insulative ceramic such as alumina. On the upper surface of the substrate
51
, electrodes
52
to
54
for achieving external electrical connection are provided. Also on the upper surface of the substrate
51
, a rectangular-frame-shaped insulative glass layer
55
is disposed.
On the substrate
51
, a capacitor
57
is bonded via a conductive adhesive
56
. On the capacitor
57
, a piezoelectric resonator
58
, which vibrates in a thickness shear mode, is bonded by conductive adhesives (not shown).
A metal cap
59
is bonded on the upper surface of the substrate
51
by using an adhesive
60
so as to cover the layered structure including the capacitor
57
and the piezoelectric resonator
58
.
The rectangular-frame-shaped insulative glass layer
55
prevents a short-circuit between the metal cap
59
and the electrodes
52
to
54
.
FIG. 7
is an assembly view which shows another example of a conventional chip-type piezoelectric resonance component. This piezoelectric resonance component includes a substrate
61
having a dielectric body. The substrate
61
including the dielectric body has three capacitor electrodes, which constitute a three-terminal capacitor. Electrodes
62
and
63
are provided on the upper surface of the substrate
61
and an electrode
64
is disposed on the side surface of the substrate
61
. The three-terminal capacitor is defined by the electrodes
62
to
64
.
On the upper surface of the substrate
61
, a piezoelectric resonator
66
which vibrates in a thickness shear mode is fixed by a conductive adhesive
65
. A metal cap
67
is bonded on the upper surface of the base substrate
61
so as to cover the piezoelectric resonator
66
. In this example, in order to reliably prevent a short-circuit between the metal cap
67
and the electrodes
62
and
63
, an insulator
69
is applied to the metal cap
67
in advance. After hardening, the metal cap
67
is bonded to the substrate
61
via an insulative adhesive
68
.
As is apparent from the above, when the substrates
51
and
61
are bonded to the metal caps
59
and
67
, respectively, a very difficult and cumbersome process for securing the insulation between the metal cap
59
and the electrodes
52
to
54
provided on the substrate
51
, and for securing the insulation between the metal cap
67
and the electrodes
62
and
63
provided on the substrate
61
must be included in the manufacturing process of the conventional piezoelectric resonance components.
With respect to the chip-type piezoelectric resonance component shown in
FIG. 6
, when the electrodes
52
to
54
are formed by applying and baking a conductive paste after the substrate
51
made of alumina is baked, the baking process is repeated in order to bake the conductive paste, and, furthermore, in order to form the insulative glass layer
55
on the top thereof, insulative glass must be applied thereon and baked again. Because of these extremely cumbersome steps, the cost of the conventional piezoelectric resonance components is very high.
As for the chip-type piezoelectric resonance component shown in
FIG. 7
, an insulative resin
69
is applied to the metal cap
67
in advance and is hardened thereon. However, since the metal cap
67
is normally formed by deep-drawing a metal plate, the flatness at the opening edge thereof is not satisfactory. Consequently, it becomes extremely difficult to apply the insulative resin
69
on the opening edge of the metal cap
67
in an even manner. It also becomes difficult to obtain a seal between the substrate
61
and the metal cap
67
.
As is apparent from the above description, in the manufacture of the chip-type piezoelectric resonance components using metal caps, it is necessary to perform the steps of forming the insulative glass layer
55
on the substrate
51
and applying the insulative resin
69
.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a substrate on which electric components are mounted and a chip-type piezoelectric resonance component including such a substrate.
The substrate according to preferred embodiments of the present invention provides a simplified structure for preventing a short-circuit between the metal cap and the electrodes on the substrate, facilitates attachment of the metal cap to the substrate, and greatly improves the sealing performance of the space enclosed by the substrate and the metal cap.
A substrate according to a preferred embodiment of the present invention includes a substrate body layer, a plurality of electrodes disposed on the substrate body layer, and a first glass-ceramic layer arranged so as to cover a portion of the electrode disposed on the substrate body layer.
Preferably, the substrate further includes a second glass-ceramic layer disposed on the lower surface of the substrate body layer.
The first and second glass ceramic layers may include one of anorthite-type crystallized glass, forsterite-type crystallized glass, celsian-type crystallized glass, a composite including a ceramic powder and one the above crystallized glasses, and a composite including a ceramic powder and non-crystallized glass.
A piezoelectric resonance component according to another preferred embodiment of the present invention includes the substrate of the above-described preferred embodiment of the present invention, a piezoelectric resonator mounted on the substrate, and a conductive cap bonded to the first glass ceramic layer of the substrate, so as to cover the piezoelectric resonator.
Preferably, the substrate body layer of the substrate includes a dielectric body and a plurality of capacitor electrodes arranged to define a capacitor in the substrate body layer.
Preferably, the first glass-ceramic layer disposed on the upper surface of the substrate has a substantially rectangular-frame shaped configuration.
Preferably, the piezoelectric resonance component is a piezoelectric oscillator.
Because the first glass ceramic layer is disposed on the substrate main body so as to cover a portion of the electrodes, when the substrate body layer includes a dielectric ceramic or an insulative ceramic, the substrate body layer and the glass ceramic layer can be baked at the same time, thus reducing the manufacturing cost of the substrate.
Furthermore, because the upper surface of the glass ceramic layer has excellent flatness, when the metal cap is bonded thereon, the space enclosed by the metal cap and the substrate is tightly sealed.
When the second glass ceramic layer is disposed on the lower surface of the substrate body layer, mechanical strength of the substrate is greatly improved by the second glass ceramic layer. Thus, the reliability of the electronic components using the substrates of various preferred embodiments of the present invention is greatly improved.
When anorthite-type crystallized glass or forsterite-type crystallized is used in the first or second glass layers or both, these crystallized glasses have lower thermal expansion coefficients compared to alumina. Thus, when the metal cap is bonded thereon, the thermal expansion coefficient difference between the metal cap and the substrate is small, a
Amano Tsuneo
Yoshida Ryuhei
Keating & Bennett LLP
Pascal Robert
Takaoka Dean
LandOfFree
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