Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For high frequency device
Reexamination Certificate
2002-07-30
2004-08-03
Cuneo, Kamand (Department: 2829)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For high frequency device
Reexamination Certificate
active
06770970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of molding resin on a substrate, and particularly relates to a method of molding resin on a thin-film resin substrate that works well for high-frequency characteristics and a high-frequency module.
2. Description of the Related Art
There is a rapid decrease in size, thickness and weight of electronic equipment such as portable mobile communication terminals. The portable mobile terminals are installed with high-frequency modules, such as power amplifiers and high-frequency circuit boards.
Thus, it is necessary to reduce size, thickness and weight of the high-frequency modules to further reduce the size, thickness and weight of such portable mobile terminals. For this purpose, it has been proposed to select a thin-film resin substrate that can achieve further reduction of size, thickness and weight and can improve the high-frequency characteristics.
However, due to its reduced thickness, the thin-film resin substrates are often deformed during a manufacturing process of the high-frequency module. Accordingly, there is a need for a resin molding method which can restrict the deformation of the thin-film resin substrate during the manufacturing process.
FIGS. 1A and 1B
are diagrams showing an example of a high-frequency module
1
of the related art.
FIG. 1A
is a plan view showing general structure of the high-frequency module
1
.
FIG. 1B
is a cross-sectional view showing general construction of the high-frequency module
1
. Such high-frequency module
1
may be used, for example, as a power amplifier of a portable mobile terminal. It is desirable to further reduce the size, thickness and weight of the high-frequency module
1
.
Generally, the high-frequency module
1
includes a high-frequency circuit board
2
, a high-frequency active chip
3
, chip components
4
, and a resin package
5
. The high-frequency circuit board
2
includes a base material
15
of ceramics, glass-ceramics, or glass-epoxy. On a first (upper) surface of the base material
15
, high-frequency circuit interconnections
6
and
7
, direct-current (DC) circuit interconnections
8
and
9
, and pad portions
12
to
14
are provided in a predetermined pattern. On a second (lower) surface of the base material
15
, a ground layer
18
and land portions
19
are provided.
The high-frequency circuit board
2
of the above structure is provided with an opening
16
formed at a predetermined position of the base material
15
. The high-frequency active chip
3
is mounted in the opening
16
. Also, the high-frequency active chip
3
and each of the interconnections
6
to
9
are electrically connected by wires
17
.
Also, a plurality of chip components
4
are mounted on the high-frequency circuit board
2
. Each chip component
4
is joined to the interconnections
6
to
9
by means of a conductive material. Further, the pad portions
12
to
14
are electrically connected to the ground layer
18
formed on the second (lower) surface of the base material by means of via holes
20
formed through the base material
15
.
A high-frequency input terminal RFIn, a high-frequency output terminal RFout and bias terminals
10
and
11
are provided at predetermined end portions of respective interconnections
6
to
9
. The terminals RFIn, RFout,
10
and
11
, respectively, are electrically connected to land portions
19
serving as external connection terminals by means of the via holes
20
formed through the base material
15
.
When the high-frequency module
1
is mounted on the mounting board, the land portions
19
will be electrically connected to the mounting board. Also, a first (upper) surface of the high-frequency circuit board
2
is sealed, for example, using a metal cap (not shown).
However, if the base material
15
of the high-frequency circuit board
2
is made of ceramics, the cost of the high-frequency module will be increased since a ceramics material is more expensive than a resin material. If the base material
15
of the high-frequency circuit board
2
is made of materials such as ceramics, glass-ceramics or glass-epoxy, it is difficult to reduce the thickness of the base material
15
below 100 &mgr;m. Thus, this is contrary to the aim of reducing the thickness of the high-frequency module
1
.
Also, it is difficult to implement a machining process on the prior art material used for the base material
15
with high accuracy. This is particularly problematic when forming the via holes
20
. With the high-frequency module
1
for processing high-frequency signals, it is preferable to reduce impedance. However, since it is difficult to optionally select the thickness of the base material
15
and the diameter of the via hole
20
, the impedance could not be reduced with the high-frequency module
1
of the related art. Accordingly, with the high-frequency module
1
of the related art, it is not possible to avoid any degradation of the characteristics due to the via holes
20
.
Also, with the high-frequency module
1
, it is desired to achieve a broader band with the same signal line width. In order to achieve broader band with the same signal line width, it is necessary to reduce the thickness of the base material
15
comprising the high-frequency circuit board
2
and to reduce the relative permittivity.
However, since the base material
1
has comparatively great thickness and relative permittivity, it is difficult to achieve broader band using the same signal line width. Therefore, with the circuit layout in a millimeter wave region using ceramics having high relative permittivity, the width of a 50&OHgr; signal line becomes extremely small and thus becomes difficult to form such signal line.
In order to solve the problems described above, the inventor has proposed a high-frequency module
30
A as shown in
FIGS. 2
to
6
(JP 11-310159 A1).
Generally, the high-frequency module
30
A includes a high-frequency circuit board
32
A, a high-frequency active chip
33
, chip components
34
, and a resin package
35
. The characteristic feature of the high-frequency circuit board
32
A is that it includes a base material
45
of polyimide.
On a first (upper) surface of the base material
45
, high-frequency circuit interconnections
36
A and
37
A (microstrip lines, coplanar lines etc.), direct-current (DC) circuit interconnections
38
A and
39
A, and pad portions
42
to
44
are formed in a predetermined pattern. The high-frequency circuit interconnections
36
A and
37
A are formed as so-called 50&OHgr; lines.
The interconnections
36
A to
38
A,
39
and the pad portions
42
to
44
, respectively, are made of a copper film or a gold film with a thickness of, for example, 35 microns. The predetermined regions of the high-frequency circuit interconnections
36
A,
37
A and the DC circuit interconnections
38
A and
39
constitute microstrip lines and a bias circuit of &lgr;/4. A second (lower) surface of the base material
45
is provided with a grounded ground layer
48
A and land portions
49
A to serve as external connection terminals.
A high-frequency active chip
33
is mounted on the high-frequency circuit board
32
A of the above structure. An opening
46
is formed in the base material
45
at a position at which the active chip
33
is to be mounted. Also, a bottom open end of the opening
46
is closed by the ground layer
48
A. Therefore, at a predetermined position of the high-frequency circuit board
32
A at which the high-frequency active chip
33
is to be mounted, a recessed portion is defined by the opening
46
and the ground layer
48
A.
The high-frequency active chip
33
is mounted in the opening
46
and is joined to the bottom ground layer
48
A by means of gold-tin alloy or conductive adhesive agent. With the base material
45
provided with the ground layer
48
A and the opening
46
and by mounting the high-frequency active chip
33
on the ground layer
48
A in the opening
46
, heat produced by the high-frequency active chip
33
can be dissipated in an
Cuneo Kamand
Geyer Scott B.
Staas & Halsey , LLP
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