Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2000-11-01
2001-12-11
Ullah, Akm E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
Reexamination Certificate
active
06328485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical module comprising an optical fiber and a light-emitting element and/or light-receiving element used in an optical data transmission device, and a method for manufacturing same.
2. Description of Related Art
FIG.
6
and
FIG. 7
give general views of one example of a conventional optical module comprising optical fibers, a light-emitting element and/or a light-receiving element.
FIG. 6
is an oblique view of an optical module and
FIG. 7
shows the structure of a section cut along plane B in FIG.
6
.
An ‘optical module’ is a general term for an optical transmission module comprising an optical fiber and a light-emitting element, an optical reception module comprising an optical fiber and a light-receiving element, or an optical transmission and reception module comprising an optical fiber, light-emitting element and light-receiving element.
According to FIG.
6
and
FIG. 7
, the optical module
100
comprises an Si substrate
102
, an optical semiconductor element
104
and an optical fiber
106
. An LD chip forming the optical semiconductor element
104
is provided in a respective position on the upper face of the Si substrate
102
.
A V-shaped groove
102
x
is formed on top of the Si substrate
102
, and an optical fiber
106
is mounted in this V-shaped groove
102
x
in such a manner that it contacts both walls thereof. A fiber cover
108
is provided in such a fashion that it covers the optical fiber
106
. The fiber cover
108
and Si substrate
102
are bonded by means of an ultraviolet-setting adhesive. Thereby, the optical fiber
106
is secured under pressure between the fiber cover
108
and the Si substrate
102
. Moreover, an anode electrode
110
and a cathode electrode
112
are respectively provided in an electrically unconnected fashion on the upper face of the Si substrate
102
, at distant positions from the light input face
106
a
of the optical fiber
106
. These electrodes
110
and
112
are laminated films formed by successively layering Ti film, Pt film and Au film onto the Si substrate
102
. Moreover, an LD chip
104
is fixed by Au/Sn soldering onto the anode electrode
110
. A light output face
104
a
of the LD chip
104
opposes the light input face
106
a
of the optical fiber
106
. The LD chip
104
and optical fiber
106
are respectively positioned with very high accuracy by means of a dicing half-cut
101
formed in the Si substrate
102
, in such a manner that light output by the LD chip enters into the optical fiber
106
. Moreover, the upper face of the LD chip
104
and the cathode electrode
112
are connected by means of wire bonding
114
.
Furthermore, this optical module is sealed by means of a resin, in such a manner that the whole of the LD chip
104
and the portion of the optical fiber
106
on the light input face
106
a
side thereof are covered, as illustrated in FIG.
7
. In
FIG. 6
, this resin is omitted from the drawing in order to describe the internal composition of the module
100
. Hereinafter, the sealed portion of the module is called the sealing section
116
. Moreover, the resin in the sealing section
116
is called ‘potting resin’, for which an Si resin, which is a thermosetting resin, is used.
The manufacture of an optical module
100
of this kind is performed as described below, for example. Firstly, a V-shaped groove
102
x
is formed by an etching process in the region of the Si substrate
102
where an optical fiber is to be installed. Thereupon, a Ti film, Pt film and Au film are layered in that order onto the upper face of the Si substrate
102
, by means of sputtering. Consequently, a laminated film (Ti—Pt—Au film) is formed on the upper face of the Si substrate
102
. Thereupon, the laminated film is patterned by means of photolithography and subsequent etching processes, in such a manner that it forms a cathode electrode-shaped and anode electrode-shaped pattern. Next, an optical axis direction positioning groove (called a ‘dicing half cut’)
101
for an LD chip and optical fiber is formed in the Si substrate
102
. Thereupon, an LD chip
104
is located in position over the anode electrode-shaped pattern by a marker alignment process, whereupon it is fixed by means of Au/Sn solder. The upper face of the LD chip
104
and the cathode electrode-shaped pattern are connected by means of wire bonding
114
. Thereby, the anode electrode-shaped pattern forms an anode electrode
110
, and the cathode electrode-shaped pattern forms a cathode electrode
112
. Next, the optical fiber
106
is mounted in the V-shaped groove
102
x
, whilst positioning same in the optical axis direction with respect to the LD chip by means of the dicing half-cut
101
provided in the substrate
102
. Thereupon, a fiber cover
108
is provided in such a manner that it covers the optical fiber
106
, and the fiber cover
108
and Si substrate
102
are bonded together by means of an ultraviolet-setting adhesive.
Next, an Si resin forming the potting resin is applied on in such a manner that it covers the whole of the LD chip
104
and the portion of the optical fiber
106
on the light input side
106
a
thereof. Next, the resin is hardened by heating the assembly in an oven at a temperature of 130-150° C. Thereby, a sealing section
116
is formed.
However, in the process of forming the aforementioned sealing section
116
, during the hardening of the potting resin by means of the heating process, loosening of the resin may occur, due to physical causes such as decline in the viscosity of the resin below the viscosity immediately after the application thereof, or decline in the surface tension of the resin. Therefore, after heat treatment, the potting resin does not provide a satisfactory cover over the LD chip
104
and the optical coupling section
118
between the LD chip
104
and the optical fiber
106
(indicating the region between the light output face
104
a
of the LD
104
and the light input face
106
a
of the optical fiber
106
). When the optical coupling section
118
is exposed to the external atmosphere, the constituent components of the elements are oxidized by oxygen in the air, for example, and there is a risk that this may cause degradation of device reliability. Moreover, in order to prevent this degradation of device reliability, in other words, in order to obtain a sealing section
116
of sufficient thickness, the potting resin coating process and heating processing must be repeated a number of times in order to form a sealing section
116
(
116
a
,
116
b
,
116
c
) comprising a plurality of layers (FIG.
7
).
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an optical module having high reliability of the sealing of the optical fiber front end portion, the sealing of the optical semiconductor element itself, and the sealing of the optical coupling section between the optical fiber and the optical semiconductor element. Moreover, it is a further object of the present invention to provide a method for manufacturing an optical module whereby an optical module having a highly reliable sealing section can be fabricated readily.
In order to achieve these objects, the optical module according to the present invention has a composition comprising the following characteristic features. Namely, the optical module according to the present invention comprises: an optical semiconductor element: an optical fiber coupled optically with the optical semiconductor element; a substrate whereon the optical semiconductor element and the optical fiber are mounted; and a sealing section wherein the optical semiconductor element and a portion of the optical fiber containing the end face thereof adjacent to the optical semiconductor element are covered by a sealant. In this invention, a sealant retaining section is formed on the upper face of the substrate and the sealing section has a dome shape constituted by a single layer of sealant. Moreover, in this invention, the end portions o
Burdett James R.
Oki Electric Industry Co. Ltd.
Ullah Akm E.
Venable
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