Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2002-03-27
2004-04-27
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S090000, C257S734000, C438S617000
Reexamination Certificate
active
06726376
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a lead frame, and a semiconductor integrated circuit using the lead frame, and an optical module and a producing method for the optical module.
2. Description of the Ralated Art
FIG. 7
is a cutaway perspective view showing the sectional structure of a semiconductor laser transmitter in the related art. A semiconductor laser
70
(LD: laser diode) and a monitor photodiode
71
(M-PD) for detecting a light intensity of the semiconductor laser
70
are mounted in a package. An optical signal outputted from the LD
70
is emitted into an optical fiber
73
via a lens
72
. Such an optical module is structurally called a coaxial type.
However, the structure of the coaxial type optical module is three-dimensional. Therefore, the three-dimensional structure of the coaxial type optical module makes difficult it to minimize the dimension of the structure and reduce the production process.
In order to solve this problem, a surf ace packaging technique has been developed such that LD and M-PD or a photodiode (PD) and a pre-amplifier (PRE-AMP) are packaged on a substrate. The steps of manufacturing the optical module by using the above-described surface packaging technique are described by reference to
FIGS. 8
to
10
.
FIG. 8
is a plan view of a lead frame in the related art.
FIG. 9
is a flowchart showing a process of manufacturing the optical module.
FIG. 10
is a diagram showing a method for manufacturing the optical module.
Here, a lead frame
80
is plated on a copper plate with Ni and Au. The copper plate is 200 &mgr;m thickness. As shown
FIG. 8
, the lead frame
80
is provided with frame
81
, die pad
82
, leads
83
, and connection leads
84
. The die pads
82
are coupled to the lead frame
80
via leads
83
, and each leads
83
are coupled by connection leads
84
.
An optical module using the lead frame
80
is manufactured through the steps as shown in
FIGS. 9 and 10
.
First, a Si platform
20
is formed with a V-shaped groove for securely holding an optical fiber
30
and an electrode pattern for soldering LD
21
and an M-PD
22
.
The LD
21
and the M-PD
22
are soldered to the Si platform
20
. And then, the optical fiber
30
is fixed with resin to the Si plat form. At this time, the optical fiber
30
is put in between a glass plate
40
and the Si platform
20
. This intermediate product in this condition is called a sub-module.
After the sub-module is fixed on the die pad
82
of the lead frame
80
, the sub-module is connected to the leads
83
by wire bonding and then the sub-module is encapsulated with resin
50
by using a transfer molding technique.
Further, the connection leads
84
and the frame
81
are cut away to electrically insulate leads
83
with one another. And then, portions of the leads
83
extended from the package are bent to form in a predetermined angle.
When the sub-module is processed as described-above, electricity can flow through the LD and the M-PD for a screening test of the sub-module. In the screening test of the sub-module, a current flows through the LD in a high-temperature environment or applying a reverse bias voltage to the sub-module. The quality of the LD depends on the changing rate of a threshold current sensitive to stress. Further, the quality of the M-PD depends on the rate of change of a leakage current. The sub-module is finally examined after the screening test.
Therefore, the Optical fiber, the glass plate, the resin for molding, and a cost of all process including the molding process are wasted in the related art, when the defective LD and M-PD of the sub-module are found by the screening test. Therefore, in the related art, the yield of the products depends on the yields of the LD and M-PD, so that a total cost of the products is increased. When the defective LD and M-PD is found by the screening test which is carried out after the molding process, the optical fiber with ferrule has to be discarded, thereby the cost of the products are increased owing to the discarded optical fiber with ferrule.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a lead frame structure, which permits screening test to be performed at a pre-processing step and a drastic cost reduction, and to provide an optical module using the lead frame structure or a producing method of the optical module.
In the invention, leads in the lead frame are electrically insulated with regard to one another. More specifically, a lead frame has a plurality of leads, a die pad, and a plurality of connection leads connecting the leads.
Further, the connection leads are formed of an insulating material, and the connection leads electrically insulate the leads with one another.
Heretofore, when the connection leads and the leads are formed of the same metallic material and the leads electrically conducts with one another, it is difficult to perform screening test that current flows through each LD and each M-PD prior to resin molding. According to the invention, when the connection leads are formed of insulating material to electrically insulate leads with regard to one another, the screening test can be carried out even before packaging or encapsulating by the resin molding.
Consequently, the waste of the component elements of the leads frame can be eliminated and the cost of the products can be reduced.
The material of the connection leads may not be restrictive as long as the material has insulating property and is excellent in producibility. The connection leads are preferably formed of thermoplastic resin since the thermoplastic which is excellent in producibility can be hardened in a short time. Particularly, the connection leads are preferably formed of liquid crystal polymer. The connection leads is removed at the post-processing stage, the liquid crystal polymer is suitably adaptable and easily removable.
Such lead frames can be utilize for semiconductor integrated circuits such as LSI and optical modules. In the semiconductor integrated circuit, a semiconductor chip is mounted on a die pad in a lead frame. In the optical module, an optical communication functional portion is mounted on a die pad.
The optical communication functional portion preferably includes an optical transmission member and at least one of a light receiving element and a light emitting element. The optical transmission member may be an optical fiber or an optical waveguide. As the optical communication functional portion, there may be enumerated a transmitter or a receiver or a transceiver for optical communication. For example, an optical transmitter having built-in LD and M-PD and an optical receiver having built-in PD and PRE-AMP are formed on one substrate by using the surface packaging technique.
When the surface packaging is performed, the optical communication functional portion is preferably formed on Si substrate or a ceramic substrate. The Si substrate can be used in the surface packaging of the invention because Si is easily etched to form a V-shaped groove. Further, the ceramic substrate can be used in the surface packaging of invention because ceramics such as alumina has great hardness to thereby perform the surface packaging in high precision.
The optical communication functional portion is sealed in a plastic package or by a transfer molding. When the optical communication functional portion is sealed in the plastic package, the optical communication functional portion is fitted into a preformed package. When the optical communication functional portion is sealed by the transfer molding, the optical communication functional portion is encapsulated with a resin. Further, the sealed optical communication functional portion by transfer molding may be sealed in the plastic packaging.
In the invention, a method for producing an optical module having a lead frame and optical communication functional portion, comprising:
performing a screening test of the optical functional portion;
mounting the optical functional portion on the die pad of the lead frame after the s
Kuhara Yoshiki
Nakanishi Hiromi
Smith , Gambrell & Russell, LLP
Sumitomo Electric Industries Ltd.
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