Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2003-03-27
2004-10-19
Ngô, Ngân V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S459000, C257S532000
Reexamination Certificate
active
06806547
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a light-receiving module, in which an optical signal is converted to an electrical signal.
2. Related Prior Art
FIG. 7
is a plan view of a conventional light-receiving module. As shown in
FIG. 7
, the conventional module
101
has a semiconductor light-receiving device
131
, such as a photodiode, a base
111
for mounting the light-receiving device
131
, a plurality of lead terminals
121
to
124
, and a semiconductor electronic device
151
.
The base
111
is made of a conductive material and has a mounting surface
112
. The electrical isolation between the lead terminals and the base
111
are performed by an insulating glass material, which fixes and seals the lead terminals
121
to
124
to the base
111
.
The semiconductor light-receiving device
131
has a light-sensing area
132
on top of the device and has a first, a second, and a third electrode. The first electrode
133
is wire-bonded to the lead terminal
121
. The third electrode
135
outputs a current signal corresponding to the inputted optical signal to the electronic device
151
. Also, a resistor element
136
is integrated in the light-receiving device, which connects the first electrode
131
to the second electrode
132
.
The die capacitor
141
, a shape of which is a board-like, has one pad on a surface facing to the base
111
and two pads
142
,
143
on the other surface. The light-receiving device
131
is mounted on one of two pads
142
. The second electrode
134
of the light-receiving device
131
is wire-bonded to the pads
142
mounted the light-receiving device thereon. The other pad of the die capacitor is wire-bonded to the lead terminal
122
. The resistor element
136
in the light-receiving device
131
combined with the die capacitor
141
functions as a CR-filter, that is, it operates a de-coupling filter of a bias applied to the light-receiving device.
The semiconductor electronic device
51
converts the current signal from the light-receiving device
131
into a voltage signal and amplifies the voltage signal. The electronic device
151
has a plural electrode and a ground electrode wire-bonded directly to the base
111
. A first electrode
152
is wire-bonded to the pad
143
of the die capacitor
141
for supplying a bias voltage Vdd to the electronic device
151
. A second electrode
153
is connected to the third electrode of the light-receiving device
131
for inputting the current signal therefrom. A third electrode
154
and a fourth electrode
155
are wire-bonded to lead terminals
123
and
124
, respectively, for outputting amplified signals that are complementary to each other. A fifth electrode
156
is wire-bonded to a second die capacitor
161
mounted on the base
111
. A pad of a third die capacitor
162
is also connected to the lead terminal
122
.
The current optical communication using an optical module shown in FIG.
7
requires a transmission speed over 2.5 Gbps. In such high-speed application, the conventional optical module can not be applicable because a bonding wire, for example connecting the light-receiving device to the electronic device, behaves as an inductance. When the electrical signal transmits such bonding wires, a loss of the signal and reflection at points where the bonding wires are connected may occur. The higher the transmission speeds, the more serious the parasitic inductance problem. Moreover, a signal leak through a bias line influences an operation of the semiconductor electronic device. Occasionally, the instability of the signal leak causes a self-oscillation of the electronic device.
One solution for the above-mentioned problem is to lower the transmission impedance of the signal line and also the bias supply line. It is effective for lowering the transmission impedance to connect devices by plural wires or to surround the signal line by lines with low impedance such as a ground line.
However, a request for a small-sized and a lightweight module is growing more and more in the optical communication. Additional electronic parts for realizing the low impedance line are difficult to be installed in such small-sized optical module. Also, it is difficult to surround the signal line by plural lines with low impedance because only a restricted space for wiring is allowed in such module.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical module that realizes a low impedance signal line with a simple configuration.
According to a present invention, a light-receiving module comprises a base made of a conducting material, a semiconductor light-receiving device, a semiconductor electronic device and a die capacitor. The light-receiving device has a light-sensing portion and a signal-outputting electrode for outputting current signal corresponding to an optical signal entered into the light-sensing portion. The electronic device has a signal-inputting electrode and two ground electrodes located both sides of the signal-inputting electrode. The die capacitor has a primary pad and at least two auxiliary pads. The primary pad and two auxiliary pads are arranged in parallel so as to insert the primary pad therebetween. The light-receiving device is mounted on the primary pad and the outputting electrode is wire-bonded to the signal-inputting electrode of the electronic device. The electronic device is mounted on the base adjacent to the-die capacitor so as to face the signal-inputting electrode thereof to the signal-outputting electrode of the light-receiving device. The ground electrodes located both sides of the signal-inputting electrode are connected to the respective auxiliary pads of the die capacitor, and the respective auxiliary pads are wire-bonded to the base.
In the present module, the ground electrodes located both sides of the signal-inputting electrode of the electronic device are grounded to the base through the respective auxiliary pads of the die capacitor. This enable to shorten a total length of bonding wire form the ground electrode to the pad of the die capacitor and from the pad to the base as compared with the case that the ground electrode is directly connected to the base. Therefore, it is able to avoid the influence of the parasitic inductance of the bonding wire and to protect from the deformation of the bonding wire so that the bonding wire is hard to touch an undesirable portion. The present module realizes a configuration that the signal line from the light-receiving device to the electronic device is surrounded by plural ground line, which results in lowering the impedance of the signal line.
Moreover, the die capacitor preferably includes additional pad in the outer side of the auxiliary pad relative to the primary pad. The additional pad is preferably connected to a bias electrode of the electronic device. The die capacitor thus connected to the bias electrode operates as a de-coupling capacitor, which lower the impedance of the bias line.
Further aspect of the present invention, the electronic device preferably has a pair of outputting-electrode. The signals complementary to each other are output from outputting-electrodes to the respective lead terminals. The outputting electrodes faces the respective electrodes so as to shorten the bonding wire therebetween, thus suppressing the influence of the parasitic inductance of the bonding wire.
REFERENCES:
patent: 5841565 (1998-11-01), Kanai
patent: 6034424 (2000-03-01), Fujimura et al.
Ito Makoto
Kohmoto Kenichiro
Sekiguchi Takeshi
McDermott Will & Emery LLP
Ngo Ngan V.
Sumitomo Electric Industries Ltd.
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