Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Wire contact – lead – or bond
Reexamination Certificate
2002-08-28
2004-06-22
Lebentritt, Michael S. (Department: 2824)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Wire contact, lead, or bond
C257S737000, C257S678000, C257S684000, C257S688000, C257S728000, C257S734000
Reexamination Certificate
active
06753615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical element module having a coil in a bias circuit for supplying power.
2. Description of the Related Art
FIG. 28
is a top view showing a structural example of a conventional optical element module. In
FIG. 28
, reference numerals
1
,
2
, and
3
respectively designate a light emitting element for converting an electric signal and an optical signal, a light emitting element carrier as a substrate for mounting this light emitting element
1
and manufactured by aluminum nitride, and a light receiving element for monitoring a rear face output from the light emitting element
1
. Reference numerals
4
,
5
, and
6
respectively designate a light receiving element carrier for mounting this light receiving element
3
, a filter, and a filter substrate for mounting this filter
5
. Reference numerals
9
,
11
, and
13
respectively designate a package for airtightly sealing the light emitting element
1
, etc., a feed-through having a coplanar or a microstrip line, etc. for electrically conducting the interior and the exterior of this package
9
, and an electrode for high frequency arranged in this feed-through
11
and supplying an RF signal to the light emitting element
1
. Reference numerals
15
, and
17
respectively designate an electrode for bias arranged in the feed-through
11
and supplying a bias electric current from an unillustrated power source to the light emitting element
1
, and an optical fiber for transmitting the optical signal.
FIG. 29
is a top view of a main portion of the conventional optical element module shown in FIG.
28
.
FIG. 30
is a side view of the main portion shown in FIG.
29
. In these figures, reference numerals
19
,
20
, and
5
a
respectively designate a base carrier for placing the light emitting element carrier
2
and the light receiving element carrier
4
, a pattern formed on the light emitting element carrier
2
, and an air-core coil as a central portion of the filter
5
. Reference numerals
21
a
and
21
b
designate connecting portions extending from one end and the other end of this air-core coil
5
a
. The filter
5
is constructed by this air-core coil
5
a
and the connecting portions
21
a
and
21
b
. Reference numerals
22
a
and
22
b
respectively designate solder joining portions for soldering and joining the connecting portions
21
a
and
21
b
to the filter substrate
6
. Reference numeral
23
a
designates a bonding wire for making an electrical connection between the electrode
15
for bias and the solder joining portion
22
a
. Reference numeral
23
b
designates a bonding wire for making an electrical connection between the solder joining portion
22
b
and the pattern
20
. Reference numeral
23
c
designates a bonding wire for making an electrical connection between the pattern
20
and the light emitting element
1
. Reference numeral
23
d
designates a bonding wire for making an electrical connection between the pattern
20
and the electrode for high frequency.
The conventional optical element module is constructed as mentioned above. An RF signal transmitted from an unillustrated driver IC is inputted to the light emitting element
1
via the electrode
13
for high frequency, the bonding wire
23
d
, the pattern
20
and the bonding wire
23
c
. A direct current (DC) for supplying the bias electric current from the power source to the light emitting element
1
is inputted to the light emitting element
1
via the electrode
15
for bias, the bonding wire
23
a
, the solder joining portion
22
a
, the connecting portion
21
a
, the air-core coil
5
a
, the connecting portion
21
b
, the solder joining portion
22
b
, the bonding wire
23
b
, the pattern
20
and the bonding wire
23
c.
Namely, a bias circuit for supplying power is generally arranged in the optical element module in addition to a circuit for supplying the RF signal. The air-core coil
5
a
is a noise countermeasure part used in this bias circuit, and functions as a filter for preventing the RF signal from being transmitted to the bias circuit. The air-core coil
5
a
is widely used as a part for the bias circuit for the following reasons, etc. Namely, (1) compactness can be realized by a precise winding technique, (2) the electric current flowing through the air-core coil
5
a
can be increased since the air-core coil
5
a
has low direct current resistance, and (3) the RF signal can be prevented in a wide band since parasitic capacity is small and self resonance frequency is high.
On the other hand, a high speed operation of the optical element module is required to cope with an increase in transmission capacity. Recently, the optical element module of 10 Gbps or more is required instead of the conventional optical element module of 2.5 Gbps.
Here, when the length of a line path (the total of lengths of the connecting portion
21
b
, the solder joining portion
22
b
, the bonding wire
23
b
, the pattern
20
and the bonding wire
23
c
) between the light emitting element
1
and the bias circuit (the air-core coil
5
a
in this case) is longer than ¼ of an upper limit frequency wavelength in a passing band, the resonance frequency of the line path itself between the light emitting element
1
and the bias circuit lies within this passing band. Therefore, the passing band is limited by this resonance. It is necessary to set the line path length between the light emitting element
1
and one end of the air-core coil
5
a
to about 1 mm or less so as to cope with the recent high speed of 10 Gbps or more.
In the conventional optical element module, as mentioned above, the filter substrate
6
mounting the air-core coil
5
a
thereto is mounted in the vicinity of the light emitting element
1
, and the light emitting element
1
and the air-core coil
5
a
are electrically connected to each other by the bonding wires
23
b
,
23
c
, etc. Therefore, a problem exists in that it is difficult to set the line path length between the light emitting element
1
and the air-core coil
5
a
to about 1 mm or less, and no preferable high frequency characteristics are obtained.
SUMMARY OF THE INVENTION
This invention is made to solve the above problem, and an object of this invention is to provide an optical element module able to obtain preferable high frequency characteristics by shortening the line path length between the light emitting element
1
and the air-core coil
5
a.
An optical element module in this invention comprises alight emitting element; and a filter portion used in one portion of a bias circuit for supplying a bias electric current from a power source to this light emitting element; wherein this filter portion has a coil portion and a first connecting portion extending from one end of this coil portion; and the first connecting portion directly connects the coil portion and the light emitting element without electrically joining the first connecting portion to any substrate on the way.
In the optical element module in this invention, the coil portion and the light emitting element are connected to each other by thermocompression-bonding a one-side end portion of the first connecting portion to the light emitting element.
In the optical element module in this invention, the light emitting element has a metallic electrode on its surface, and a one-side end portion of the first connecting portion is constructed by forming a metallic film on a lead wire, and the coil portion and the light emitting element are connected to each other by joining the one-side end portion having the metallic film to the metallic electrode.
In the optical element module in this invention, the light emitting element has a metallic electrode on its surface, and the coil portion and the light emitting element are connected to each other by fixing a one-side end portion of the first connecting portion to this metallic electrode by a bump.
In the optical element module in this invention, the one-side end portion of the first connecting portion is constructed by
Aruga Hiroshi
Takagi Shin-ichi
Burns Doane Swecker & Mathis L.L.P.
Lebentritt Michael S.
Menz Douglas
Mitsubishi Denki & Kabushiki Kaisha
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