Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2000-05-15
2002-02-05
Dunn, Tom (Department: 1725)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S063000, C501S013000, C501S015000
Reexamination Certificate
active
06344424
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to low melting point glass, an insulating package, and a sealing member which are preferable for quartz oscillators, more specifically, low melting point glass, an insulating package, and a sealing member for secure sealing.
2. Description of the Related Art
In accordance with the recent tendency of compactness, weight reduction, and surface mounting of electronic parts, also in the quartz oscillators, the cylindrical metal package has been changed to a ceramic package. A typical type thereof shall be described below.
FIG.
1
A through
FIG. 1C
show a conventional surface mounting type quartz oscillator G, wherein
FIG. 1A
is a plan view partially cut and opened,
FIG. 1B
is a longitudinal section along the centerline in the length direction, and
FIG. 1C
is a lower view.
In the conventional surface mounting type oscillator G, bottom plate
101
and frame body
102
, which are made of ceramic, are formed and united to comprise insulating base
115
. The bottom plate
101
has the shape of a plate. The shape of the frame body
102
has the shape of a frame.
At the upper surface of one end in the length direction of the bottom plate
101
, as shown in
FIG. 1A
, an Ag/Pb paste is applied and sintered, whereby Ag/Pb electrodes
103
and
104
are formed. The Ag/Pb electrode
103
is led to the outside from one end in the length direction of the bottom plate
101
by passing between the bottom plate
101
and frame body
102
as shown in FIG.
1
B. The other Ag/Pb electrode
104
is, as shown in
FIG. 1B
, led to the outside from the other end of the bottom plate
101
by making a detour below the frame body
102
. Also, at both ends in the length direction of the lower surface of the bottom plate
101
, Ag/Pb terminals
105
and
106
are formed. The Ag/Pb electrodes
103
and
104
are connected to the Ag/Pb terminals
105
and
106
through the end face of the bottom plate
101
, respectively. On the Ag/Pb electrodes
103
and
104
and Ag/Pb terminals
105
and
106
, electroless Ni plating layer and/or electroless Au plating layer are formed although it is not shown.
On the Ag/Pb electrodes
103
and
104
, quartz oscillating piece
108
having electrodes (not shown) on both surfaces are adhered by an electric conductive adhesive, and the Ag/Pb electrodes
103
and
104
and quartz oscillating piece
108
are connected to each other.
Also, near the end portion of the opposite side of the Ag/Pb electrodes
103
and
104
at the upper surface of the bottom plate
101
, support
107
for supporting the quartz oscillating piece
108
in a horizontal condition is formed. The support
107
is called “pillow” in some cases.
On the frame body
102
, ceramic-made cap
110
is adhered via low melting point glass
109
. Thereby, the inside of the insulating package is sealed.
However, the surface mounting type quartz oscillator G has a serious problem in that, since the bottom plate
101
, frame body
102
, and cap
110
are formed from ceramic, due to a difference in the thermal expansion coefficient from quartz oscillating piece
108
, stresses are added to the quartz oscillating piece
108
, whereby the vibration characteristics are changed.
Also, if the cap
110
made of ceramic is used, in view of the mechanical strength, there is a limit to make the vibrator thinner. Therefore, there are also limits to making the entire quartz oscillator G smaller in height.
Therefore, the present applicant proposed that the insulating base was made of a glass ceramic compound, and in place of the ceramic-made cap, a metal cap made of stainless steel was used. FIG.
2
A through
FIG. 2C
show a conventional surface mounting type quartz oscillator H, wherein
FIG. 2A
is a plan view partially cut and opened,
FIG. 2B
is a longitudinal section along the centerline in the length direction, and
FIG. 2C
is a lower view.
In the conventional surface mounting type quartz oscillator H, bottom plate
121
and frame body
122
which are made of a glass ceramic compound are formed and united to comprise insulating base
135
. Also, on the frame body
122
, via low melting point glass
109
, metal cap
130
made of stainless steel is adhered. The other structure is the same as in that of the surface mounting type quartz oscillator G.
The glass ceramic compound is formed by dispersing fine powder of forsterite of 30 through 70 wt % in alkali glass, and its thermal expansion coefficient is 100×10
−7
through 150×10
−7
(/° C.). By using such glass ceramic, the difference in the thermal expansion coefficient between the quartz oscillating piece and metal cap is eliminated or remarkably reduced. Therefore, the change in characteristics of the quartz oscillating piece and separation of the metal cap due to the stress caused by the difference in the thermal expansion coefficient can be prevented.
However, when such a quartz oscillator was stored at a high temperature and in high humidity, a phenomenon in that separation occurred between the frame body and low melting point glass was shown.
SUMMARY OF THE INVENTION
The object of the invention is to provide low melting point glass, an insulating package, and a sealing member whereby secure sealing can be made between an insulating base and a cap.
According to one aspect of the present invention, low melting point glass contains at least one kind selected from a group consisting of Al, Ni, Ag, BaTiO
3
, NiCr, TiB, and TiO
2
.
The inventors thoroughly researched the cause for the abovementioned phenomenon, and as a result, they found that the alkali glass composing the glass ceramic caused elution of the phosphoric acid composing the low melting point glass, and the composition of the low melting point glass changed and its sealing performance was lost, whereby separation occurred. Also, they thoroughly researched a method for preventing such a phenomenon, and as a result, they found that, by adding certain kinds of additives to the low melting point glass, the phenomenon could be prevented.
The abovementioned low melting point glass has an action whereby elution of phosphoric acid from the low melting point glass due to the alkali glass ingredients in the glass ceramic is suppressed or prevented by the additive, and the low melting point glass can be directly sealed with the glass ceramic.
According to a second aspect of the present invention, a glass ceramic sealing member comprises a base member made of a glass ceramic compound, and low melting point glass to be used to seal the base member. The low melting point glass contains at least one kind of substance selected from a group consisting of Al, Ni, Ag, BaTiO
3
, NiCr, TiB, and TiO
2
.
In this aspect of the invention, elution of phosphoric acid in the low melting point glass due to the alkali glass ingredients in the glass ceramic is suppressed or prevented by the additive in the low melting point glass, whereby the glass ceramic sealing member can be increased in airtightness.
According to a third aspect of the present invention, a sealing member comprises a base member made of ceramic, low melting point glass to be used to seal the base member, and a buffer layer interposed between the base member and the low melting point glass.
In the aspect of the invention, by a buffer layer interposed between the ceramic and low melting point glass, mutual interference under storage at a high temperature and in high humidity is prevented, elution of phosphoric acid in the low melting point glass due to the alkali ingredients in the ceramic does not occur, and lowering in peel-strength at the sealing interfaces can be prevented, whereby separation does not occur.
According to a fourth aspect of the present invention, an insulating package comprises an insulating base having a bottom plate and frame body, electrodes led out from the inside to the outside of the insulating base, a metal cap which seals the frame body, and low melting point glass to adhere said metal cap to the frame body. The low melting point gla
Goto Yoshihiro
Kishi Eigo
Natsuhara Yoshinobu
Terai Katuya
Cooke Colleen P.
Dunn Tom
McGinn & Gibb PLLC
NEC Corporation
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