Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Insulating material
Reexamination Certificate
1999-06-11
2001-06-19
Yu, David (Department: 2821)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Insulating material
C257S782000, C257S783000
Reexamination Certificate
active
06249049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ceramic package type electronic part. More particularly, the present invention relates to a ceramic package type electronic part which is high in connection strength to an electrode.
2. Description of the Related Art
IC devices and other electronic parts have been improved year by year. Operation of high accuracy is required of a high graded electronic device, for example, an IC device and an SAW (Surface Acoustic Wave Filter) resonator. Thus, in many cases, it is used in a condition that it is mounted in a hermetically sealed package. Such a package is required to protect the electronic device against the high density of a wiring circuit, the thermal generation thereof, the change of temperature and moisture, dust and other ambient environments. Such a hermetically sealed package has been developed more and more in recent years.
FIG. 1
shows a ceramic package type electronic part
190
created by hermetically mounting the electronic device in a so-called ceramic package, in such a hermetically sealed package. In
FIG. 1
, a cover
193
is illustrated at a top of
FIG. 1
, an electronic device (for example, a piezoelectric device, such as a quartz oscillator)
192
is illustrated thereunder, and a base
191
is further illustrated thereunder. In this ceramic package type electronic part
190
, an inner electrode
197
positioned on the base
191
and the quartz oscillator
192
are electrically connected to each other. The quartz oscillator
192
hermetically sealed by guiding a conductive line to an outer connection portion (outer electrode)
125
linked to the inner electrode
197
is adapted to serve as a part of an outer electronic circuit.
FIG. 2
is a side section view showing the ceramic package type electronic part
190
of FIG.
1
.
In the ceramic package type electronic part
190
, the quartz oscillator
192
is hermetically enclosed and positioned within a ceramic case
122
. At right and left ends of the quartz oscillator
192
, it is connected through conductive adhesives
124
to the inner electrode
197
. The inner electrode
197
is integrally extended up to the outer connection portion
125
, and connected through solder or the like to, for example, a wiring on a printed circuit board on which this ceramic package type electronic part
190
is mounted, outside the ceramic case
122
.
The side on which the quartz oscillator
192
of this ceramic package is positioned, namely, the portion between the base
191
and the hermetically enclosing cover
193
thereon is hermetically sealed and bonded with a glass
126
. The reason why the portion is hermetically sealed and adhered with the glass
126
is as follows. That is, a very precise operation is required of the piece of the quartz oscillator
192
. Thus, the change of the inner ambient of this ceramic case
122
has influence on the operation. Hence, the portion between the base
191
and the cover
193
is typically sealed with the glass
126
, from the viewpoint of the hermetic sealing, the reliability thereof and the like.
FIG. 3
is a side section view showing another ceramic package or another ceramic package type electronic part. As shown in
FIG. 3
, a quartz oscillator
202
is connected through a conductive substrate
205
to an inner electrode
207
located on a left side of a base
201
, and supported in a cantilever state. This inner electrode
207
is linked to an outer electrode
208
through a conductive line
206
wired on ceramic. Moreover, after the quartz oscillator
202
serving as the electronic device is fixed on the base
201
, an opening is enclosed by a cover
209
, and the quartz oscillator
202
is hermetically sealed. Usually, this cover
209
hermetically encloses the base
201
made of ceramic material by using glass and the like.
A method of typically manufacturing such a ceramic package or a ceramic package type electronic part will be described below. In general, such a ceramic package or a ceramic package type electronic part is manufactured by using a green sheet method. In the green sheet method, element on which conductor paste is printed is laminated on alumina green sheet created by a doctor blade method, and then the laminated element is collectively baked. The green sheet method is a method of manufacturing a circuit substrate having a high reliability for various type of electronic devices, quartz oscillators, piezoelectric actuators, SAW oscillators, ICs, LSIs and VLSIs or other devices with high reliability.
The ceramic body, such as a multiple-layer circuit substrate, a ceramic package or the like, made by this method has the following features.
Firstly, the easy lamination of a number of sheets each having hyperfine wiring enables the high density wiring.
Secondly, the operation of baking and forming an Insulation substrate and a conductor at the same time makes the integration thereof perfect and also makes the reliability thereof high.
A basic process of manufacturing the multiple-layer circuit substrate and the like, for example, the ceramic package by using the green sheet method will be described below with reference to
FIGS. 4A
to
4
I and
FIGS. 5A
to
5
E.
As shown in
FIG. 4A
, alumina of raw material powder, flux, binder, plasticizer and solvent are sufficiently mixed with each other in a ball mill and made into slurry. As shown in
FIGS. 4B and 4C
, element in which this slurry is extended and dried on a carrier tape by using a blade is referred to as a green sheet. This method is referred to as the doctor blade method, and this is typically used. This green sheet has a thickness between about 0.1 and 1.0 mm. The thickness can be adjusted as necessary (FIG.
4
D).
The conductive paste created in the state of metal powder having a high melting point on this green sheet is screen printed (FIG.
4
E). As a method of creating the multiple-layer in the green sheet method, there are three methods: a sheet lamination method; a print multiple-layer method and a method of jointly using both the methods. However, the frequently used method is the sheet lamination method.
According to the sheet lamination method, a hole is made in the green sheet by using a die or a micro drill. The conductive paste is filled into the hole. A plurality of sheets on which patterns are printed are laminated (FIG.
4
F). Then, they are baked in reduction ambience (FIG.
4
H). Accordingly, the ceramic body or the ceramic package body is manufactured (FIG.
4
I).
Then, such a ceramic body is machined to a form of case. An electronic device whose function is deteriorated by environment is mounted in the case. Then, it is hermetically sealed and put to practical use. In this case, a so-called box-shaped portion of this ceramic case is referred to as a base, and an element placed thereon is referred to as a cover.
The above-mentioned sheet lamination method is a very excellent method. The schematic specification is, for example, as follows.
Wiring material is tungsten system material, molybdenum system material or other materials. About 0.08 mm is possible as the minimum line width, about 0.1 mm is possible as the minimum line interval, about 0.1 mm is possible as the minimum through hole diameter, and about 0.25 mm is possible as the minimum through hole pitch. Also, alumina between about 90 and 94% is used as the material of the conventionally used raw material powder. Its thermal expansion coefficient is 75×10
−7
/°C., its dielectric constant is 8.5 and its specific resistance is about 10×10
14
&OHgr;/cm. The number of about 45 layers or more is possible as the maximum number of laminations of green sheets laminated as mentioned above.
Here, the above-mentioned wiring material connects the electric device mounted inside this ceramic case to the wiring positioned on, for example, a printed circuit board and the like mounted outside this ceramic case. There are an inner electrode and an outer connection portion in the wiring material. The inner electrode is a portion wired insid
Fukuhara Naoharu
Kamada Hiroshi
Katoh Hiroshi
Terai Katuya
Chen Shih-Chao
Hutchins, Wheeler & Dittmar
NEC Corporation
Yu David
LandOfFree
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