Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For high frequency device
Reexamination Certificate
2000-08-31
2003-03-11
Abraham, Fetsum (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For high frequency device
C257S731000, C257S692000, C257S678000, C257S680000, C257S687000
Reexamination Certificate
active
06531775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to high-frequency modules, and more particularly to a high-frequency module suitable for a smaller, thinner, and lighter-weight electronic device.
2. Description of the Related Art
Smaller, thinner, and lighter-weight electronic devices such as portable mobile terminals have been developed at an increasing speed. The portable mobile terminals include high-frequency modules or high-frequency substrates represented by power amplifiers.
Therefore, it is also necessary to develop smaller, thinner, and lighter-weight high-frequency modules in order to obtain smaller, thinner, and lighter-weight portable mobile terminals.
FIGS. 1 and 2
are a schematic plan view and a schematic cross-sectional view of a conventional high-frequency module
1
, respectively.
The high-frequency module
1
includes a high-frequency substrate
2
, a high-frequency active chip
3
and a plurality of electronic components
4
. The high-frequency substrate
2
includes a base material
15
made of ceramics, glass-ceramics, a glass fabric based epoxy resin or the like. The base material
15
has high-frequency circuit wiring lines
6
and
7
, direct-current (DC) circuit wiring lines
8
and
9
, and pad portions
12
through
14
each formed in a predetermined pattern on its upper surface, and a ground film
18
and land portions
19
formed on its lower surface. Hereinafter, the high-frequency circuit wiring lines
6
and
7
and the DC circuit wiring lines
8
and
9
are referred to as wiring lines
6
,
7
,
8
and
9
, respectively.
An opening portion
16
is formed in a predetermined position in the base material
15
of the high-frequency substrate
2
having the above structure. Mounted in the opening portion
16
is the high-frequency active chip
3
, which is electrically bonded to the wiring lines
6
through
9
by bonding wires
17
.
The high-frequency substrate
2
has the electronic components
4
mounted thereon, which are joined to the respective wiring lines
6
through
9
by a conductive material such as a solder, a gold paste, or a silver paste. The pad portions
12
through
14
are electrically connected to the ground film
18
formed on the lower surface of the base material
15
by via holes (not shown) formed to penetrate the base material
15
.
On the other hand, a high-frequency input terminal
22
, a high-frequency output terminal
23
, and bias terminals
10
and
11
(hereinafter referred to as terminals
22
,
23
,
10
and
11
, respectively) are formed on the predetermined end portions of the wiring lines
6
through
9
, respectively. The terminals
22
,
23
,
10
, and
11
are electrically connected to the respective land portions
19
serving as terminals for external connection by via holes
20
formed to penetrate the base material
15
. The land portions
19
are electrically connected to a mounting board when the high-frequency module
1
is mounted thereon. The upper surface of the high-frequency substrate
2
is sealed by a metal cap (not shown) or the like.
For example, Japanese Laid-Open Patent Application No. 11-017063 discloses a package for accommodating a semiconductor chip on which a semiconductor chip compatible with high frequencies, which is different from a high-frequency module, alone is mounted.
Conventionally, however, when ceramics, which is more expensive than a resin material, is employed as the base material
15
of the high-frequency substrate
2
provided for the high-frequency module
1
, there arises a problem that the cost of the high-frequency module
1
rises.
Another problem with the conventional high-frequency module
1
is that when ceramics, glass-ceramics, a glass fabric based epoxy resin or the like is employed as the base material
15
of the high-frequency substrate
2
, difficulty in reducing the thickness of the base material 15 to 100 &mgr;m or less prevents the thickness of the high-frequency module
1
from being reduced.
Further, when ceramics or glass-ceramics is employed as the base material
15
, it is difficult to freely obtain the diameter of each of the via holes
20
in desired size considering the burning shrinkage of a green sheet. When a glass fabric based epoxy resin is employed as the base material
15
, it is also difficult to freely form the diameter of each of the via holes
20
in desired size, for there is a limit to the downsizing of the diameter of each of the via holes
20
because through holes to be formed into the via holes
20
are formed by machining.
As an electric circuit, each of the via holes
20
forms an equivalent circuit shown in
FIG. 3
including an inductance L, an electrostatic capacity C and a resistance R because the high-frequency module
1
processes a high-frequency signal.
In the high-frequency module
1
processing the high-frequency signal, the equivalent circuit causes the high-frequency characteristic of the high-frequency module
1
to be deteriorated. The impedance of the equivalent circuit increases as the diameter of each of the via holes
20
becomes smaller or the base material
15
becomes thicker.
It is desirable to reduce the impedance of the equivalent circuit as much as possible. According to the conventional high-frequency module
1
, however, such difficulties in freely obtaining the desired thickness of the base material
15
and the diameter of each of the via holes
20
in desired size prevent the impedance from being reduced, thus entailing the deterioration of the high-frequency characteristic of the high-frequency module
1
resulting from the via holes
20
.
Such measures as to design the circuit of the high-frequency module
1
in consideration of the characteristic of the via holes
20
can be taken in order to preclude the deterioration of the high-frequency characteristics of the high-frequency module
1
. However, it is difficult to securely remove the loss resulting from the via holes
20
because the characteristic of the equivalent circuit, as described above, varies depending on the diameter of each of the via holes
20
and the thickness of the base material
15
. As the frequency of a signal to be processed in the high-frequency module
1
becomes higher, the high-frequency characteristic thereof becomes more deteriorated, thus causing such a circuit design to be extremely difficult especially in case of a high frequency.
Further, it is desired of the high-frequency module
1
to expand a bandwidth without changing the width of a signal line, which requires the base material
15
to be thinner and a relative dielectric constant to be lower.
However, when a conventional material such as ceramics, glass-ceramics or a glass fabric based epoxy resin is employed as the base material
15
, the base material
15
becomes so thick and the dielectric constant becomes so high that it is difficult to expand the bandwidth without changing the width of the signal line. Therefore, when a circuit is designed in a millimeter wave region by employing ceramics, which has a high relative dielectric constant, as a base material, the width of a 50-&OHgr; signal line becomes so narrow as to be difficult to form.
Further, as a measure to radiate heat from a part to be mounted, or the high-frequency active chip
3
, thermal vias
21
can be formed in the base material
15
as shown in FIG.
2
. When the amount of heat radiated from the high-frequency active chip
3
is so large as to require the thermal resistance of the high-frequency substrate
2
to be reduced, it is possible to increase the number of the thermal vias
21
in order to radiate such amount of heat.
However, it is not desirable to increase the number of the thermal vias
21
in light of the strength of the high-frequency substrate
2
. In other words, a problem lies in that the strength of the high-frequency substrate
2
decreases as the heat radiation characteristic is enhanced, while the heat radiation characteristic is deteriorated as the strength thereof increases.
SUMMARY OF THE INVENTION
It is a general ob
Kobayashi Kazuhiko
Sano Yoshiaki
Abraham Fetsum
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
LandOfFree
High-frequency module does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-frequency module, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-frequency module will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3009607