Active solid-state devices (e.g. – transistors – solid-state diode – Transmission line lead
Reexamination Certificate
2000-01-18
2002-04-02
Whitehead, Jr., Carl (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Transmission line lead
C257S728000, C257S699000, C257S708000, C257S698000, C257S678000, C257S730000, C257S731000
Reexamination Certificate
active
06365961
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency input/output feedthrough for a package for housing a high-frequency semiconductor element for the millimeter wave region or the like, and also to a package for housing a high-frequency semiconductor element and using the high-frequency input/output feedthrough.
2. Description of the Related Art
A package for housing a high-frequency semiconductor element houses a high-frequency semiconductor element using a high-frequency signal in the micrometer wave region, the millimeter wave region, or the like, in a hermetically sealed manner. A signal input/output portion of such a package employs a feedthrough structure to which a transmission line such as a microstrip line or a stripline is joined and which is hermetically sealed while a semiconductor element is housed in the package.
An example of the configuration of such an input/output feedthrough is shown in
FIGS. 19A
,
19
B, and
FIG. 19A
is a plane view and
FIG. 19B
is a sectional view taken along line I—I of
FIG. 19A
, in which lower dielectric substrate
1
is made of ceramics or the like. An upper dielectric substrate
2
is made of ceramics or the like and joined to the upper face of the lower dielectric substrate
1
, and serves as a part of a case wall of a package. A line conductor
3
is formed on the upper face of the lower dielectric substrate
1
. Side face ground layers
4
are formed on the side faces of the lower and upper dielectric substrates
1
and
2
. A bottom face ground layer
5
is formed on the bottom face of the lower dielectric substrate
1
. An upper-face ground layer
6
is formed on the upper face of the upper dielectric substrate
2
. The prior art of
FIG. 7
is the configuration of an input/output feedthrough used for so-called metal wall type packages.
According to this input/output feedthrough, the matching of the characteristic impedance of the line conductor
3
is attained by changing the line width of the portion sandwiched between the lower dielectric substrate
1
and the upper dielectric substrate
2
and corresponding to the stripline, with respect to that of the portions in front and in rear of the portion and corresponding to a microstrip line, thereby realizing low return and insertion losses. When an input/output feedthrough having the bottom face ground layer
5
and the side face ground layers
4
on the sides of the dielectric substrates
1
and
2
is embedded in a cutaway part formed in a metal substrate of the package, the isolation characteristics between the line conductor
3
and a line conductor of another input/output feedthrough which is juxtaposed to the line conductor
3
are improved.
In another input/output feedthrough, a ground pattern is disposed on both sides of a line conductor as shown in
FIGS. 20A and 20B
.
FIG. 20A
is a plane view, and
FIG. 20B
is a section view taken along line II—II. Referring to these figures, a lower dielectric substrate
7
, an upper dielectric substrate
8
, a line conductor
9
, a bottom face ground layer
10
, and an upper-face ground layer
11
are configured in the same manner as the lower dielectric substrate
1
, the upper dielectric substrate
2
, the line conductor
3
, the bottom face ground layer
5
, and the upper-face ground layer
6
of
FIG. 19
, respectively. Ground patterns
12
are formed on the lower dielectric substrate
7
so as to laterally sandwich the line conductor
9
. Through conductors
13
are through hole conductors or the like through which the ground patterns
12
are connected to the bottom face ground layer
10
. Through conductors
14
are through holes or the like through which the ground patterns
12
are connected to the upper-face ground layer
11
. The prior art of
FIG. 20
has the configuration of an input/output feedthrough used for the so-called ceramic wall type packages. According to this input/output feedthrough, in the same manner as the input/output feedthrough shown in
FIG. 19
, the matching of the characteristic impedance of the line conductor
9
is attained so as to realize low return and insertion losses. Furthermore, the isolation characteristics are improved by surrounding the line conductor
9
with the ground patterns
12
, the through conductors
13
and
14
, the bottom face ground layer
10
, and the upper-face ground layer
11
.
In each of the high-frequency input/output feedthroughs, the lower dielectric substrate
1
or
7
and the upper dielectric substrate
2
or
8
which constitute the stripline portion are usually made of the same dielectric material and configured as dielectric members having a substantially same thickness.
According to such a high-frequency input/output feedthrough of the prior art, in the region (the microwave region) wherein the frequency is relatively low among high frequencies, the transmission characteristics for a high-frequency signal are excellent because the characteristic impedance of the microstrip line portion is matched with that of the stripline portion.
However, for example, in a higher frequency region wherein the frequency is higher than 30 GHz (the millimeter wave region) there arises the following problem. In order to match the characteristic impedance of the line conductor
3
,
9
in the stripline portion with that in the microstrip line portion and further suppress a higher order modes, it is necessary to decrease the thickness of the lower dielectric substrate
1
,
7
and additionally, since a width d
1
of the line conductor in the stripline portion is very small and an unstable state is brought, it is necessary to set a length d
2
of the line conductor
3
,
9
in the stripline portion to 1/2n (n is a natural number) of the wavelength of a high-frequency signal to be transmitted via the input/output feedthrough, with the result that the length d
2
of the line conductor
3
,
9
in the stripline portion becomes very short. Consequently, the strength of the input/output feedthrough part is extremely lowered. Even when the length is designed to be 1/2n of the wavelength, the transmission mode in the stripline portion is substantially different from that in the microstrip line portions in front and in rear of the stripline portion because the input/output feedthrough part has a complex three-dimensional shape and the shape is dispersedly produced. This produces a further problem in that the return and insertion losses are increased and the transmission characteristics for a high-frequency signal are impaired.
The configuration shown in
FIG. 8
has further problems in that it is difficult to produce the input/output feedthrough because the small through conductors
13
,
14
must be formed in the dielectric substrates
7
and
8
, and that, because of the shield due to the through conductors, the return and insertion losses are larger as compared with the case of a planar shield.
SUMMARY OF THE INVENTION
The invention has been conducted in view of the above-discussed problems. It is an object of the invention to provide a high-frequency input/output feedthrough having excellent transmission characteristics in which the transmission mode for a high-frequency signal in a portion corresponding to a microstrip line is matched with that in a portion corresponding to a stripline portion to reduce the return and insertion losses.
It is another object of the invention to provide a package for housing a high-frequency semiconductor element having excellent transmission characteristics in which, in an input/output feedthrough part, the transmission mode for a high-frequency signal in a portion corresponding to a microstrip line is matched with that in a portion corresponding to a stripline, to reduce the return and insertion losses.
In a first aspect of the invention, a high-frequency input/output feedthrough comprises:
a) a first dielectric substrate
15
;
b) a high-frequency transmission line
19
of narrow width extending on one surface of the first dielectric substrate, the high-frequency transmission line having a first
Hogan & Hartson L.L.P.
Jr. Carl Whitehead
Kyocera Corporation
Mitchell James
LandOfFree
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