Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2002-07-18
2004-02-17
Prenty, Mark V. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S671000, C438S027000
Reexamination Certificate
active
06693304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lead frame, and an optical communication module using the lead frame and a method for manufacturing the optical communication module.
2. Description of the Related Art
FIG. 10
is a cut-away perspective view showing a sectional structure of a semiconductor laser transmitter that is employed in related art. In a package, a semiconductor laser
10
(LD) and a monitor photodiode
15
(M-PD) for sensing its light intensity are disposed. A light signal output from the LD
10
is incident upon an optical fiber
61
via a lens
16
. Such an optical communication module is called a coaxial type from such the structure.
However, the optical communication module of the coaxial type has a three-dimensional structure, and is limited in reducing the size and shortening the manufacturing process.
To solve this problem, a surface mounting technique for mounting the LD, the M-PD, the photodiode (PD) or a preamplifier (PRE-AMP) like a plane on the substrate has been developed. Referring to
FIGS. 11
to
13
, a manufacturing process of the optical communication module using this surface mounting technique will be described below.
FIG. 11
is a plan view of the related-art lead frame,
FIG. 12
is a flowchart showing a manufacturing process of the optical communication module, and
FIG. 13
is an explanatory view for explaining a manufacturing method for the optical communication module.
A lead frame
120
is formed by plating Ni and Au plated successively on a copper plate having a thickness of 200 &mgr;m. The lead frame
120
comprises a frame
121
like a framework, a die pad
122
connected via a lead
123
to the frame
121
, and each lead
123
connected to a tie bar
124
, as shown in FIG.
11
.
The optical communication module using the lead frame
120
is manufactured through the manufacturing process as shown in
FIGS. 12 and 13
.
First of all, a Si platform having a V-groove for fixing an optical fiber
61
inserted into a ferrule
62
and an electrode pattern for soldering a LD
10
or M-PD
15
is prepared.
The LD
10
and the M-PD
15
are soldered onto the Si platform
30
, and then the optical fiber
61
is fixed to the Si platform
30
by the resin. An intermediate product in this state is called a sub-module. At fixing the optical fiber
61
, the optical fiber
61
is sandwiched between a glass plate
130
and the Si platform
30
.
The sub-module is fixed onto the die pad of the lead frame
120
, wire bonded and sealed with a resin
140
by transfer molding technique.
Next, the tie bar
124
and the frame
121
of the lead frame
120
are cut, each lead
123
is electrically isolated, and the lead
123
exposed from the package is bent at a predetermined angle.
After the lead frame is completed up to this state, an electric current can be firstly passed through the LD and the M-PD. A so-called screening is made by passing electric current through the LD under high temperature environment or applying an inverse bias to the M-PD. The LD is determined good or defective, for embodiment, depending on a variation of threshold current that is especially sensitive to the stress. The M-PD is determined good or defective, depending on a change rate of leak current. The final check of product is made after screening.
In this way, the optical communication module using the surface mounting technique is enabled to lower the costs and reduce the size, and expected to contribute to a further progress of the optical communication.
However, the related-art technique had the following problems.
In the optical communication module using a standard one-layer lead frame, the number of leads is limited, so that the optical communication function to be implemented is limited. For example, in a case where the LD and the LD driver IC are built into the transmitter, the PD and the PRE-AMP are built into the receiver, or both of them are integrated, the number of components to be mounted is increased, requiring a greater number of leads.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a laminated lead frame capable of packaging at high density.
It is another object of the invention to provide an optical communication module of small size and low costs, which is allowed to package the optical communication functions at high density, and prevent the leakage of resin in resin molding.
Moreover, it is another object of the invention to provide a method for manufacturing an optical communication module capable of packaging the optical communication functions at high density.
A laminated lead frame of the present invention comprises a plurality of lead frames and a tie bar made of an insulating material for holding the plurality of lead frames like a laminate.
The laminated lead frame at high packaging density can be provided by integrating the plurality of lead frames that are laminated by the tie bar (insulating tie bar) made of insulating material. In particular, there is no shortage in the number of leads even if a number of components are mounted to implement the satisfactory optical communication functions.
Also, an optical communication module of the present invention comprises a laminated lead frame having a plurality of lead frames and a tie bar made of an insulating material for holding the plurality of lead frames like a laminate, and an optical communication functional unit that is disposed on at least one layer of the lead frame.
A great number of components can be mounted, employing the laminated lead frame, and the optical communication module can have the full optical communication functions.
In related art, since the tie bar was made of the same metal material as each lead, with each lead being electrically in conduction, the screening was not enabled by passing a current through the LD and the M-PD individually before resin molding. In the present invention, the tie bar is made of an insulating material, the leads in each layer are electrically isolated, whereby the screening is enabled at the former stage before packaging. Therefore, it is possible to eliminate the waste in rejection that causes the increased costs, and reduce the costs of the product.
Herein, the optical communication functional unit has the functions of a transmitter or receiver for use in the optical communication, or a composite transmitter/receiver. For instance, the optical communication functional unit preferably comprises at least one of a light emitting element and a light receiving element and an optical transmission medium. The optical transmitting module may employ the LD as the light emitting element and a driver IC for the LD as the electric circuit component. Furthermore, the optical transmitting module may employ the M-PD for sensing the light intensity of the LD. The optical receiving module may employ the PD as the receiving element and an amplifier for amplifying a PD signal as the electric circuit component. The optical transmitting/receiving module may comprise at least one pair of light emitting element and driver IC, and at least one pair of light receiving element and amplifier. The optical transmission medium may be the optical fiber or optical waveguide.
The material for the tie bar is not specifically limited so far as it has an insulating property and an excellent productivity. The thermoplastic resin that is cured in short time and excellent in productivity is preferable. In particular, the tie bar is preferably composed of the liquid crystal polymer.
The optical communication functional unit is preferably mounted on a Si substrate or a ceramic substrate. Si allows the V-groove to be easily formed by etching, or the ceramic such as alumina, which has insulating property and high hardness, can be worked at high precision.
The optical communication functional unit is desirably accommodated within a resin molded portion. The optical communication functional unit can be protected by resin molding. A specific method for forming the resin molded portion is preferably the
Kuhara Yoshiki
Nakanishi Hiromi
Okada Takeshi
Prenty Mark V.
Smith , Gambrell & Russell, LLP
Sumitomo Electric Industries Ltd.
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