U.S. patent application number 09/864317 was filed with the patent office on 2001-09-27 for photoelectronic device and method of manufacturing the same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Eguchi, Shuji, Miura, Toshimasa, Naka, Hiroshi, Takahashi, Shoichi.
Application Number | 20010024549 09/864317 |
Document ID | / |
Family ID | 26534083 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024549 |
Kind Code |
A1 |
Takahashi, Shoichi ; et
al. |
September 27, 2001 |
Photoelectronic device and method of manufacturing the same
Abstract
There is provided a method for manufacturing a photoelectronic
device comprising a silicon platform (support substrate) having a
groove for guiding an optical fiber, a semiconductor laser chip
secured on the substrate and an optical fiber fitted in the groove
at one end thereof to be secured on the support substrate wherein
the optical fiber fitted in the groove is secured on the support
substrate with a first bonding element constituted by an adhesive
injected to fill the groove under the optical fiber; one surface of
the support substrate is covered with silicone gel; the support
substrate is secured in a package made of plastic; and the package
is filled with the silicone gel which is a protective film
transparent to light transmitted by the optical fiber and resistant
to humidity. The method comprises the steps of applying an
ultraviolet-setting adhesive to a part of the groove on the support
substrate, fitting one end of the optical fiber in the groove on
the support substrate and adjusting optical coupling between the
photoelectric conversion element and optical fiber with the groove
under the optical fiber filled with the ultraviolet-setting
adhesive and securing the optical fiber on the support substrate by
irradiating the ultraviolet-setting adhesive with ultraviolet light
to set it.
Inventors: |
Takahashi, Shoichi;
(Saku-shi, JP) ; Naka, Hiroshi; (Komoro-shi,
JP) ; Miura, Toshimasa; (Fujisawa-shi, JP) ;
Eguchi, Shuji; (Naka-gun, JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR
104 East Hume Avenue
Alexandria
VA
22301
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
26534083 |
Appl. No.: |
09/864317 |
Filed: |
May 25, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09864317 |
May 25, 2001 |
|
|
|
09379468 |
Aug 24, 1999 |
|
|
|
Current U.S.
Class: |
385/49 ;
385/92 |
Current CPC
Class: |
H01L 2924/181 20130101;
G02B 6/423 20130101; G02B 6/4239 20130101; H01L 2224/48247
20130101; G02B 6/4253 20130101; G02B 6/4286 20130101; G02B 6/4243
20130101; H01L 2924/181 20130101; G02B 6/4273 20130101; G02B 6/4202
20130101; G02B 6/4257 20130101; G02B 6/4265 20130101; H01L
2924/00012 20130101 |
Class at
Publication: |
385/49 ;
385/92 |
International
Class: |
G02B 006/30; G02B
006/36 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 1998 |
JP |
10-239112 |
Sep 24, 1998 |
JP |
10-270339 |
Claims
1. A photoelectronic device comprising: a support substrate
constituted by a mounting portion for mounting a photoelectric
conversion element on one surface thereof and a support substrate
having a groove for guiding an optical fiber extending toward said
mounting portion; a photoelectric conversion element secured on
said mounting portion; and an optical fiber fitted in said groove
at one end thereof and secured on said support substrate at regions
excluding the utmost end thereof, wherein the optical fiber fitted
in said groove is secured with a first bonding element injected to
fill the groove under the optical fiber for securing said optical
fiber on said support substrate, and a protective element
transparent to light transmitted by said optical fiber covers a
region including said photoelectric conversion element on one
surface of said support substrate and one end of the optical
fiber.
2. A photoelectronic device comprising: a support substrate
constituted by a mounting portion for mounting a photoelectric
conversion element on one surface thereof and a support substrate
having a groove for guiding an optical fiber extending toward said
mounting portion; a photoelectric conversion element secured on
said mounting portion; and an optical fiber fitted in said groove
at one end thereof and secured on said support substrate at regions
excluding the utmost end thereof, wherein the optical fiber fitted
in said groove is secured with a first bonding element injected to
fill the groove under the optical fiber for preliminary securing
said optical fiber on said support substrate and a second bonding
element for finally securing the optical fiber on the support
substrate while covering a part of said optical fiber and said
support substrate, and a protective element transparent to light
transmitted by said optical fiber covers a region including said
photoelectric conversion element on one surface of said support
substrate and one end of the optical fiber.
3. A photoelectronic device according to claim 1, wherein said
support substrate is secured in a case made of plastic having a
guide for guiding said optical fiber; said case is filled with said
protective element to cover said support substrate, photoelectric
conversion element, and one end of the optical fiber and the like;
and said case is closed with a cap made of plastic and is secured
on said support substrate with an adhesive.
4. A photoelectronic device according to claim 1, wherein said
support substrate, said photoelectric conversion element and one
end of said optical fiber are covered by a package constituted by
insulating resin formed by molding resin, and said protective
element is provided in said package to block the path of moisture
that enters said photoelectric conversion element from the outside
of the package.
5. A photoelectronic device comprising: a support substrate
constituted by a mounting portion for mounting a photoelectric
conversion element on one surface thereof and a support substrate
having a groove for guiding an optical fiber extending toward said
mounting portion; a photoelectric conversion element secured on
said mounting portion; and an optical fiber fitted in said groove
at one end thereof and secured on said support substrate at regions
excluding the utmost end thereof, wherein said support substrate,
said photoelectric conversion element and one end of said optical
fiber are covered by a package made of insulating resin; in said
package, the optical fiber fitted in said groove is secured with a
first bonding element injected to fill the groove under the optical
fiber for securing said optical fiber on said support substrate;
and a protective element transparent to light transmitted by said
optical fiber and resistant to humidity covers a region including
said photoelectric conversion element on one surface of said
support substrate and one end of the optical fiber.
6. A photoelectronic device comprising: a support substrate
constituted by a mounting portion for mounting a photoelectric
conversion element on one surface thereof and a support substrate
having a groove for guiding an optical fiber extending toward said
mounting portion; a photoelectric conversion element secured on
said mounting portion; and an optical fiber fitted in said groove
at one end thereof and secured on said support substrate at regions
excluding the utmost end thereof, wherein said support substrate,
said photoelectric conversion element and one end of said optical
fiber are covered by a package made of insulating resin; in said
package, the optical fiber fitted in said groove is secured with a
first bonding element injected to fill the groove under the optical
fiber for securing said optical fiber on said support substrate; a
protective element transparent to light transmitted by said optical
fiber and resistant to humidity covers a region including said
photoelectric conversion element on one surface of said support
substrate and one end of the optical fiber; and bubbles having
diameters equal to or greater than one half of the distance between
the two points of said groove in contact with the circumferential
surface of said optical fiber are not present in the region defined
by said optical fiber and said groove and filled with said first
bonding element.
7. A photoelectronic device according to claim 1, wherein a bubble
generation preventing portion is provided in the form of a recess
or groove extending across said groove in a region between one end
of said optical fiber secured with said first bonding element and
said photoelectric conversion element.
8. A photoelectronic device according to claim 7, wherein the
utmost end of one end of said optical fiber is located above said
bubble preventing portion.
9. A photoelectronic device according to claim 8, wherein the
utmost end face of one end of said optical fiber is aligned with or
as close as several hundred .mu.m or less to an edge of said bubble
generation preventing portion.
10. A photoelectronic device according to claim 7, wherein one end
of said optical fiber extends beyond said bubble generation
preventing portion and its utmost end is supported by said
groove.
11. A photoelectronic device according to claim 7, wherein the
length of said bubble generation preventing portion is one hundred
and several tens .mu.m or more in the direction of said groove.
12. A photoelectronic device according to claim 2, wherein said
second bonding element covers all or a part of the region where
said first bonding element is present.
13. A photoelectronic device according to claim 1, wherein said
first bonding element is constituted by an ultraviolet-setting
adhesive or thermosetting resin.
14. A photoelectronic device according to claim 12, wherein said
first bonding element is constituted by an ultraviolet-setting
adhesive, and said second bonding element is constituted by
thermosetting resin.
15. A photoelectronic device according to claim 1, wherein said
protective element is constituted by any of silicone gel, silicone
rubber, low-stress epoxy resin, acrylic resin or urethane
resin.
16. A photoelectronic device according to claim 1, wherein said
support substrate is a silicon substrate, and said photoelectric
conversion element is a semiconductor laser chip.
17. A method for manufacturing a photoelectronic device comprising
the steps of: providing a support substrate having a photoelectric
conversion element mounted on one surface thereof and having a
groove for guiding an optical fiber extending toward said
photoelectric conversion element; applying an ultraviolet-setting
adhesive to a part of the groove on said support substrate, fitting
one end of the optical fiber in the groove on the support substrate
and adjusting optical coupling between said photoelectric
conversion element and optical fiber with the groove under the
optical fiber filled with said ultraviolet-setting adhesive; and
securing said optical fiber on said support substrate by
irradiating said ultraviolet-setting adhesive with ultraviolet
light to set it.
18. A method for manufacturing a photoelectronic device comprising:
a package constituted by a case made of plastic having a guide for
guiding an optical fiber and a cap made of plastic for closing said
case, attached to the case with an adhesive; a support substrate
secured in said case having a photoelectric conversion element
mounted on one surface thereof and having a groove for guiding an
optical fiber extending toward said photoelectric conversion
element and an optical fiber guided by said guide into and out of
the package, wherein one end of the optical fiber extending in said
package is fitted in the groove on said support substrate and is
secured on the support substrate through securing with an
ultraviolet-setting adhesive and securing with thermosetting resin,
the method comprising the steps of: applying the
ultraviolet-setting adhesive to a part of the groove on said
support substrate, fitting one end of the optical fiber in the
groove on the support substrate and adjusting optical coupling
between said photoelectric conversion element and optical fiber
with the groove under the optical fiber filled with said
ultraviolet-setting adhesive; securing said optical fiber on said
support substrate by irradiating said ultraviolet-setting adhesive
with ultraviolet light to set it; and filling said case with a
protective element transparent to light transmitted by said optical
fiber before mounting the cap and setting the same.
19. A method of manufacturing a photoelectronic device comprising:
a package made of insulating resin; a support portion located in
said package; a support substrate secured to said support portion
having a photoelectric conversion element mounted on one surface
thereof and having a groove for guiding an optical fiber extending
toward said photoelectric conversion element; a photoelectric
conversion element secured on said mounting portion; and an optical
fiber fitted in the groove on said support substrate and guided by
a guide or a ferrule having a sleeve with one end thereof in a
face-to-face relationship with said photoelectric conversion
element and the other end thereof located outside said package and
protected by a jacket, wherein one end of the optical fiber
extending in said package is fitted in the groove on said support
substrate and is secured on the support substrate through securing
with an ultraviolet-setting adhesive and securing with
thermosetting resin, the method comprising the steps of: providing
said support substrate on which a lead frame having said support
portion thereon and said photoelectric conversion element are
secured; securing said support substrate to the support portion on
said lead frame; applying the ultraviolet-setting adhesive to a
part of the groove on said support substrate, fitting one end of
the optical fiber protected by a jacket and guided by a guide or a
ferrule having a sleeve, in the groove on the support substrate,
and adjusting optical coupling between said photoelectric
conversion element and optical fiber with the groove under the
optical fiber filled with said ultraviolet-setting adhesive;
securing said optical fiber on said support substrate by
irradiating said ultraviolet-setting adhesive with ultraviolet
light to set it; connecting wiring on said support substrate and
leads on said lead frame with conductive wires before or after
securing said optical fiber on said support substrate; covering a
region including said photoelectric conversion element, one end of
said optical fiber, said wires and the region of the leads
connected to said wires, with a protective element transparent to
light transmitted by said optical fiber; molding a region including
said jacket or said sleeve halfway with insulating resin to form
said package; and cutting and removing an unnecessary part of the
lead frame protruding from said package.
20. A method for manufacturing a photoelectronic device comprising
an optical fiber, a support substrate having a photoelectric
conversion element mounted on one surface thereof and having a
groove for guiding said optical fiber extending toward said
photoelectric conversion element, and a protective film transparent
to light transmitted by said optical fiber and resistant to
humidity, provided in a package made of insulating resin, the
method comprising the steps of: applying a first adhesive to a part
of the groove on said support substrate; fitting one end of the
optical fiber in the groove on said support substrate and adjusting
optical coupling between said photoelectric conversion element and
optical fiber with the groove under the optical fiber filled with
said first adhesive; securing said optical fiber on said support
substrate; and forming a protective film transparent to light
transmitted by said optical fiber and resistant to humidity.
21. A method for manufacturing a photoelectronic device according
to claim 17, comprising the steps of: providing a support substrate
having a photoelectric conversion element mounted on one surface
thereof, a groove for guiding an optical fiber extending toward
said photoelectric conversion element, and a bubble generation
preventing portion in the form of a recess or a groove across said
groove provided closer to one end of the optical fiber than a
region of said optical fiber secured with a bonding element; and
thereafter adjusting optical coupling between said optical fiber
and said photoelectric conversion element and securing the optical
fiber to the region of said groove portion excluding said bubble
generation preventing portion with said ultraviolet-setting
adhesive.
22. A method for manufacturing a photoelectronic device according
to claim 17, wherein bubbles having diameters equal to or greater
than one half of the distance between the two points of said groove
in contact with the circumferential surface of said optical fiber
are not present in the region defined by said optical fiber and
said groove and filled with said first adhesive.
23. A method for manufacturing a photoelectronic device according
to claim 20, wherein said first adhesive is an ultraviolet-setting
adhesive which is irradiated with ultraviolet light to be set.
24. A method for manufacturing a photoelectronic device according
to claim 17, comprising the step of covering a part of said optical
fiber and said support substrate with thermosetting resin and
setting the thermosetting resin to secure the optical fiber on the
support substrate.
25. A method for manufacturing a photoelectronic device according
to claim 24, wherein securing is carried out by determining
positions for preliminary securing and/or final securing such that
all or a part of the portion secured with said ultraviolet-setting
adhesive is covered by the portion secured with said thermosetting
resin.
26. A method for manufacturing a photoelectronic device according
to claim 24, wherein securing is carried out such that a part of
the portion secured with said ultraviolet-setting adhesive is
covered by the portion secured with said thermosetting resin and
such that the portion secured with the thermosetting resin is
located on the side of the portion secured with said
ultraviolet-setting adhesive farther from said photoelectric
conversion element.
27. A method for manufacturing a photoelectronic device according
to claim 24, wherein the process of setting said thermosetting
resin is performed on a batch process basis.
28. A method for manufacturing a photoelectronic device according
to claim 18, wherein said protective element is formed using any of
silicone gel, silicone rubber, low-stress epoxy resin, acrylic
resin or urethane resin.
Description
[0001] The present invention relates to a photoelectronic device
(semiconductor optical module) and a method of manufacturing the
same and, more particularly, to a technique effective for bonding
and securing an optical fiber to a silicon substrate having a
groove on the surface thereof referred to as "silicon platform"
using a bonding element such as thermosetting resin or an
ultraviolet-setting adhesive.
BACKGROUND OF THE INVENTION
[0002] Photoelectronic device incorporating a semiconductor laser
(semiconductor laser chip) are used as light sources for
information processing apparatuses and light sources for optical
communication.
[0003] One well-known type of photoelectronic devices is
photoelectronic devices (semiconductor laser devices) having a
box-type package structure.
[0004] Referring to passive alignment mounting utilizing a silicon
platform, for example, passive alignment type optical modules are
known which has a structure in which a silicon platform is mounted
in a package having leads and a cover; a laser diode, a monitor
photodiode and a pig-tail optical fiber are mounted on the silicon
platform; and a presser plate is mounted.
SUMMARY OF THE INVENTION
[0005] The inventors are working on techniques for securing an
optical fiber on a silicon platform in a short period of time and
techniques to reduce the cost of packaging in optoelectonic
apparatuses incorporating a semiconductor laser (passive alignment
type optical module).
[0006] The inventors made the following studies of techniques for
securing an optical fiber on a silicon platform in a short period
of time.
[0007] In a conventional semiconductor optical module utilizing a
silicon platform (support substrate), an optical fiber embedded in
the silicon platform is secured after adjusting optical coupling
between the end of the optical fiber embedded in a groove on the
silicon platform so as to trail along it and a semiconductor laser
chip secured on the surface of the silicon platform. It is secured
using (1) a technique for securing it with thermosetting resin
(thermosetting epoxy resin) or an adhesive such as an
ultraviolet-setting adhesive and (2) a technique for securing the
optical fiber while pressing it against the silicon platform with a
presser plate.
[0008] When an optical fiber is secured with thermosetting resin, a
process of applying and setting the thermosetting resin must be
performed with the optical fiber pressed against the silicon
platform to remain static after adjustment of optical coupling.
[0009] However, this method reduces the efficiency of an operation
of securing optical fiber because the thermosetting resin takes a
long time to be set. For example, in the case of epoxy resin used
as thermosetting resin, the setting process takes about two minutes
even at a temperature of 150.degree. C. which is in the excess of
the guaranteed temperature for an optical fiber.
[0010] Since the adjustment of optical coupling is performed using
a fiber inserting apparatus, the long time spent for the adjustment
of optical coupling results in a reduction in the operating
efficiency of the fiber inserting apparatus. In addition, a fiber
inserting apparatus is expensive and consequently increases the
cost for the adjustment of optical coupling.
[0011] The method of setting thermosetting resin on a fiber
inserting apparatus after the adjustment of optical coupling has
had a problem in that the process of setting thermosetting resin
can not be performed on a batch process basis and this reduces the
operating efficiency of a fiber inserting apparatus further.
[0012] The efficiency of the conventional operation of securing an
optical fiber with thermosetting resin is thus reduced, which
hinders any reduction in the manufacturing cost of a
photoelectronic device (optical module).
[0013] The conventional technique for securing an optical fiber
with thermosetting resin results in a reduction of the yield of
optical axis alignment because the state of optical coupling can
change if the optical fiber is moved before the thermosetting resin
is reliably set.
[0014] Referring to the technique of securing an optical fiber on a
silicon platform by applying an ultraviolet-setting adhesive to a
part of the optical fiber and silicon platform and thereafter
irradiating the ultraviolet-setting adhesive with ultraviolet light
to set the ultraviolet-setting adhesive, it secures an optical
fiber with reduced reliability because regions which can not be
irradiated with ultraviolet light are not set, although the setting
process utilizing ultraviolet irradiation allows an optical fiber
to be secured in a short period of time.
[0015] A possible solution is a two-step processing mode which
involves setting by means of irradiation with ultraviolet beams and
heat setting using an ultraviolet-setting adhesive which can be set
by both ultraviolet beams and heat. In this case, the efficiency of
an operation of securing an optical fiber (turnaround time: TAT) is
reduced because the setting process using heat takes time. An
example of this type of ultraviolet-setting adhesives takes a
heating time as long as 60 minutes at 120.degree. C.
[0016] A heat setting process at a processing temperature as high
as 120.degree. C. and with a long processing time as described
above can result in deterioration of resin covering an optical
fiber (the region of a fiber cable).
[0017] In a structure in which a metalized layer is provided on the
surface of an optical fiber comprising a core and a clad (optical
fiber core) and in which the metalized layer is used to secure the
optical fiber to a silicon platform or a cylindrical fiber guide
for guiding the optical fiber with solder, when an optical fiber is
fitted in a groove on a silicon platform so as to trail along it,
variation of the thickness of the metalized layer can make it
difficult to adjust optical coupling between the core of the
optical fiber and a semiconductor laser chip.
[0018] Under such circumstances, the inventors are studying a
technique as described below for securing an optical fiber on a
silicon platform, although it is not a known technique.
Specifically, in a conventional method in which a silicon platform
(support substrate) having a groove on the surface thereof is
prepared; a photoelectric conversion element (semiconductor laser
chip) is thereafter secured on the surface of the support substrate
at one end of the groove; an optical fiber is fitted in the groove
so as to trail along it; and, thereafter, the state of transmission
and reception of light between the photoelectric conversion element
and the optical fiber is adjusted and the optical fiber is secured
on the support substrate with thermosetting resin, according to the
technique, the optical fiber is preliminaryly secured using
securing means in a securing time shorter than the setting time of
the thermosetting resin while it is pressed against the support
substrate, and is thereafter finally secured with thermosetting
resin with the pressing cancelled.
[0019] For example, an ultraviolet-setting adhesive is applied to a
part of the optical fiber and support substrate; the
ultraviolet-setting adhesive is set by irradiating it with
ultraviolet light to preliminary secure the optical fiber on the
support substrate; and a part of the optical fiber which is farther
from the semiconductor laser chip than the preliminary secured
position is covered with thermosetting resin.
[0020] According to this technique, since preliminary securing is
carried out using an ultraviolet-setting adhesive, a support
substrate and the like can be moved even after the application of
thermosetting resin and before the thermosetting resin is set. This
allows the support structure and the like to be removed from a
fiber inserting apparatus in a short period of time, and the
process of setting the thermosetting resin (final securing) can
therefore be carried out on a batch process basis. Such a batch
process makes it possible to reduce the time required for securing
an optical fiber on one support substrate. The reliability of
optical coupling is also improved.
[0021] In addition to the employment of this technique, the
inventors also studied techniques for reducing the cost of a
package. In order to achieve a reduction in the package cost, they
decided to make a package main body (case) and a cover element
(cap) forming a package from plastic and to adopt a structure in
which the case and cap are bonded with resin. Further, since
plastic is less resistant to humidity than ceramics, it was
conceived to improve humidity resistance by sealing the case with
silicone gel to cover the surface of components on the support
structure including a semiconductor laser chip.
[0022] Referring to this technique, however, it was revealed by the
inventors that such a silicone gel sealing structure reduces the
strength and reliability of the securing of an optical fiber and
also reduces humidity resistance. It was found that this is
attributable to bubbles generated in silicone gel.
[0023] Experiments and studies made on the mechanism of the
generation of bubbles revealed that the number of bubbles can
increase from the initial value depending on the temperature cycle,
i.e., the temperature of the environment of use.
[0024] FIG. 25 is a schematic view of a region in which an optical
fiber 3 is secured in a groove 2 on a silicon platform (support
substrate) 1 through preliminary securing with an
ultraviolet-setting adhesive 4 and final securing with
thermosetting resin 5 and in which the upper surface of the silicon
platform 1 is covered by silicone gel 6. The optical fiber 3 is
formed by a clad 3b and a core 3a located in the center of the
same. The two-dot chain line represents a semiconductor laser chip
6. As shown in FIG. 25, the generation of a bubble 10 is likely to
occur in the silicone gel in an enclosed region 9 defined by the
surface of the groove 2 of the silicon platform 1 and the optical
fiber.
[0025] The presence of the bubble reduces the strength and
reliability of the securing of the optical fiber 3 to the silicon
platform 1.
[0026] Humidity resistance is reduced not only by the presence of
the bubble 10 itself but also by the fact that the region of the
bubble acts as a nucleus to trap any invasive moisture to make it
difficult to release the moisture to the outside. A semiconductor
laser chip, light-receiving element and the like are provided ahead
of the end of the optical fiber and a wiring layer, wires and the
like are provided around the same. Therefore, any moisture trapped
by the bubble 10 can cause oxidation and corrosion of those parts
to reduce the humidity resistance of the optical module.
[0027] With moisture trapped at the region of a bubble, the
moisture can be frozen when the optical module is exposed to a
temperature below the freezing point, which can cause troubles
attributable to a resultant change in the volume.
[0028] As shown in FIGS. 26A, 26B, 27A and 27B, an experiment was
conducted in which a metal frame 16 was placed on the bottom of a
container 15; two capillaries 17 made of glass (having an inner
diameter of 0.13 mm) were arranged thereon in parallel and in
contact with each other; and the interior of the container 15 was
filled with silicone gel 6 to cover the surface and interior of the
capillaries 17 such that no bubble was involved. Thereafter, the
container 15 was kept under certain curing process conditions (a
processing temperature of 120.degree. C. and a processing time of
60 minutes). FIGS. 26A and 26B are schematic views showing the
distribution of bubbles 10 in the silicon gel set under the curing
process conditions. FIG. 26A is a plan view, and FIG. 26B is a
sectional view.
[0029] After the silicone gel was set, environmental tests such as
temperature cycles were conducted. Specifically, (1) 40 cycles of
about 35 minutes at a temperature in the range from -40 to
+85.degree. C., (2) 136 hours at a high temperature and humidity (a
temperature of 85.degree. C. and a relative humidity of 85%), (3)
high temperature baking (120.degree. C.) for 30 minutes and (4)
storage at a low temperature (-55.degree. C.) for 1.5 hours were
carried out in the order listed. FIGS. 27A and 27B are schematic
views showing the distribution of bubbles 10 generated in the
silicon gel during the environmental tests including temperature
cycles. FIG. 27A is a plan view, and FIG. 27B is a sectional
view.
[0030] The bubbles 10 in FIGS. 26A, 26B, 27A and 27B are
illustrations based on photographs which represent accurate
positions, although the shapes of the bubbles may be slightly
different from the real ones.
[0031] As shown in FIGS. 26A and 26B, the bubbles 10 are dispersed
across the inner diameter of the capillaries 17, but there is no
bubble at both ends of the capillaries 17. The reason is assumed to
be the fact that the silicone gel can freely move in and out the
capillary 17 at both ends thereof (open regions), and it is assumed
that cavities or bubbles 10 are generated at inner diameter regions
deep in the capillaries 17 because the movement of silicone gel in
such regions is not sufficient to compensate for a reduction of the
volume attributable to contraction.
[0032] Further, as shown in FIGS. 27A and 27B, since the
capillaries are repeatedly exposed to varying temperature and
humidity during the environmental tests, new cavities are generated
as the silicone gel moves to increase bubbles 10. It is assumed
that the shapes of bubbles 10 change as a result of integration or
separation of cavities adjacent to each other. Bubbles had greater
configurations and were subjected to great positional shifts at a
high temperature of 120.degree. C., and many small bubbles were
generated at a low temperature of -55.degree. C.
[0033] FIGS. 27A and 27B show that new bubbles 10 were generated in
a region where no bubble 10 had existed as shown in FIGS. 26A and
26B, specifically, the region surrounded by the metal frame 16 and
the two capillaries 17 (the enclosed region 9).
[0034] It was found that when the interior of the plastic case was
sealed with silicone gel to over the surface of components on the
support substrate 1 including the semiconductor laser chip 7,
bubbles 10 might be generated not only in the silicon gel 6 filled
in the groove 2 under the optical fiber 3 as shown in FIG. 28 but
also between the end face (front incidence surface) of the optical
fiber 1 and the semiconductor laser chip 7.
[0035] The reason is assumed to be the fact that the gap between
the end face of the optical fiber 3 and the front emission surface
of the semiconductor laser chip 7 does not act as an open region
because it is as small as 40 to 50 .mu.m and that the gap is likely
to generate bubbles when heated repeatedly. Specifically, while no
bubble 10 was observed at the gap between the end face of the
optical fiber 3 and the front emission surface of the semiconductor
laser chip 7 at an early stage when the silicone gel 6 had been
filled and set after assembly, the phenomenon of generation of
bubbles 10 at the gap between the end face of the optical fiber 3
and the front emission surface of the semiconductor laser chip 7
occasionally occurred after the heat cycle test.
[0036] When a bubble 10 is generated at the gap between the end
face of the optical fiber 3 and the semiconductor laser chip 7 to
come into the optical path of laser light 11 emitted from the
emission surface of the semiconductor laser chip 7 (see FIGS. 29
and 30), since the bubble 10 acts as an lens, the direction of the
laser light 11 emitted by the semiconductor laser chip 7 is changed
(eclipsed) to disallow optical coupling to the optical fiber 3 or
to reduce the efficiency of optical coupling. When the optical
fiber 3 is a single mode fiber whose core 3a has a diameter as
small as about 10 .mu.m, optical coupling is often disabled.
Reference number 31 in FIGS. 28 through 30 represents a
light-receiving element 31 for receiving the laser light 11 emitted
from the rear emission surface of the semiconductor laser chip 7.
In FIG. 30, the silicone gel 6 is present on the entire upper
surface of the support substrate 1.
[0037] It is an object of the invention to provide a
photoelectronic device with high optical coupling efficiency and a
method of manufacturing the same.
[0038] It is another object of the invention to provide a
photoelectronic device in which an optical fiber is secured with
high strength and reliability and a method of manufacturing the
same.
[0039] It is still another object of the invention to provide a
photoelectronic device having excellent humidity resistance and a
method of manufacturing the same.
[0040] It is still another object of the invention to provide a
photoelectronic device in which an optical fiber can be secured in
a shorter working time and a method of manufacturing the same.
[0041] It is still another object of the invention to provide a
photoelectronic device which can be manufactured at a reduced cost
and a method of manufacturing the same.
[0042] The above and other objects and novel features of the
invention will become apparent from the description of this
specification and the accompanying drawings.
[0043] Typical aspects of the invention disclosed here can be
briefly described as follows.
[0044] (1) There is provided a photoelectronic device comprising a
support substrate (silicon platform) constituted by a mounting
portion for mounting a photoelectric conversion element
(semiconductor laser chip) on one surface thereof and a silicon
substrate having a groove for guiding an optical fiber extending
toward the mounting portion, a photoelectric conversion element
secured on the mounting portion and an optical fiber fitted in the
groove at one end thereof and secured on the support substrate at
regions excluding the utmost end thereof, wherein the optical fiber
fitted in the groove is secured with a first bonding element
injected to fill the groove under the optical fiber for preliminary
securing the optical fiber on the support substrate and a second
bonding element for finally securing the optical fiber on the
support substrate while covering a part of the optical fiber and
support substrate and wherein a protective element transparent to
light transmitted by the optical fiber covers a region including
the photoelectric conversion element on one surface of the support
substrate and one end of the optical fiber. The second bonding
element covers all or a part of the region where the first bonding
element exists. The first bonding element is constituted by an
ultraviolet-setting adhesive, and the second bonding element is
constituted by thermosetting resin. The support substrate is
secured in a case made of plastic having a guide for guiding the
optical fiber. The case is filled with the protective element to
cover the support substrate, photoelectric conversion element,
optical fiber and the like. The case is closed with a cap made of
plastic and is secured on the support substrate with an adhesive.
The protective element is constituted by any of silicone gel,
silicone rubber, low-stress epoxy resin, acrylic resin or urethane
resin. For example, it is constituted by silicone gel. With this
configuration, bubbles in sizes equal to or greater than one half
of the distance between the two points of the groove in contact
with the circumferential surface of the optical fiber are not
present in the region defined by the optical fiber and groove and
the region between one end face of the optical fiber and the
semiconductor laser chip.
[0045] This configuration is characterized by the preliminary
securing and final securing referred to as "first securing" and
"second securing", respectively. In a certain limited aspect, it
may be stated that the optical fiber is secured on the support
substrate using first and second securing techniques (means) having
different securing speeds and that the securing speed of the first
securing means is higher than that of the second securing
means.
[0046] Such a photoelectronic device is manufactured according to
the following method.
[0047] The method comprises the steps of:
[0048] providing a support substrate having a photoelectric
conversion element mounted thereon and having a groove for guiding
an optical fiber extending toward the photoelectric conversion
element;
[0049] applying an ultraviolet-setting adhesive to a part of the
groove on the support substrate, fitting one end of the optical
fiber in the groove on the support substrate and adjusting optical
coupling between the photoelectric conversion element and optical
fiber with the groove under the optical fiber filled with the
ultraviolet-setting adhesive;
[0050] preliminary securing the optical fiber on the support
substrate by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it; and
[0051] covering a part of the optical fiber and support substrate
with thermosetting resin and setting the thermosetting resin to
finally secure the optical fiber on the support substrate.
[0052] Specifically, it is a method of manufacturing a
photoelectronic device comprising:
[0053] a package constituted by a case made of plastic having a
guide for guiding an optical fiber and a cap made of plastic for
closing the case, attached to the case with an adhesive;
[0054] a support substrate secured in the case having a
photoelectric conversion element mounted on one surface thereof and
having a groove for guiding an optical fiber extending toward the
photoelectric conversion element and an optical fiber guided by the
guide into and out of the package, wherein one end of the optical
fiber extending in the package is fitted in the groove on the
support substrate and is secured on the support substrate through
preliminary securing with an ultraviolet-setting adhesive and final
securing with thermosetting resin. The method comprises the steps
of:
[0055] applying the ultraviolet-setting adhesive to a part of the
groove on the support substrate, fitting one end of the optical
fiber in the groove on the support substrate and adjusting optical
coupling between the photoelectric conversion element and optical
fiber with the groove under the optical fiber filled with the
ultraviolet-setting adhesive;
[0056] preliminary securing the optical fiber on the support
substrate by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it;
[0057] covering a part of the optical fiber and support substrate
with thermosetting resin and setting the thermosetting resin to
finally secure the optical fiber on the support substrate; and
[0058] filling the case with a protective element transparent to
light transmitted by the optical fiber before mounting the case and
setting the same. The protective element is constituted by any of
silicone gel, silicone rubber, low-stress epoxy resin, acrylic
resin or urethane resin. For example, sillicon gel is used.
Securing is carried out by determining positions for the
preliminary securing and/or final securing such that all or a part
of the preliminary securing portion is covered by the final
securing portion. The process of setting the thermosetting resin at
the final securing is performed as a batch process.
[0059] A structure may be employed in which an optical fiber is
secured on a support substrate with only a first bonding element.
Specifically, there may be provided a photoelectronic device
comprising a support substrate constituted by a mounting portion
for mounting a photoelectric conversion element on one surface
thereof and a support substrate having a groove for guiding an
optical fiber extending toward the mounting portion, a
photoelectric conversion element secured on the mounting portion
and an optical fiber fitted in the groove and secured on the
support substrate at regions excluding the utmost end thereof, the
device having a structure wherein the optical fiber fitted in the
groove is secured with a first bonding element injected to fill the
groove under the optical fiber for securing the optical fiber on
the support substrate and wherein a protective element transparent
to light transmitted by the optical fiber covers a region including
the photoelectric conversion element on one surface of the support
substrate and one end of the optical fiber. In this case, the first
bonding element is constituted by an ultraviolet-setting adhesive
or thermosetting resin. Thus, after the ultraviolet-setting
adhesive is applied to the groove on the support substrate, optical
coupling between the photoelectric conversion element and optical
fiber is adjusted with the groove under the optical fiber filled
with the ultraviolet-setting resin.
[0060] (2) In the configuration described in the aspect (1), the
support substrate, photoelectric conversion element and the end of
the optical fiber are covered by a package constituted by
insulating resin formed by molding resin, and the protective
element is provided in the package to block the path of moisture
that enters the photoelectric conversion element from the outside
of the package.
[0061] According to the aspect (1), (a) while the package is formed
by a case and a cap made of plastic, humidity resistance can be
improved because the case is filled with silicone gel.
[0062] (b) When the optical fiber is fitted in the groove on the
silicon platform (support substrate), a space is defined by the
groove under the optical fiber. This space is filled with the
ultraviolet-setting adhesive. Therefore, the silicone gel does not
enter the region under the optical fiber associated with the
preliminary securing portion when the case is filled with the
silicone gel before sealing with the cap, and no bubble is caused
by the setting and contraction of the silicone gel. This makes it
possible to prevent any reduction in the strength and reliability
of the securing of the optical fiber 3 attributable to bubbles and
to prevent problems such as freezing of moisture trapped by
bubbles.
[0063] Specifically, even if moisture enters from the outside along
the optical fiber, since the gap between the optical fiber and
groove at the preliminary securing portion is filled with the
ultraviolet-setting adhesive for preliminary securing, the invasion
of moisture is prevented at the preliminary securing portion, and
there is no nucleus like a bubble in the silicone gel that can trap
moisture. This prevents trapping of moisture to improve humidity
resistance and eliminates the possibility of freezing of moisture
during use at a low temperature.
[0064] In the structure in which the optical fiber is secured on
the support substrate using only a first bonding element
constituted by an ultraviolet-setting adhesive or thermosetting
resin, since the groove under the optical fiber is filled with the
first bonding element, the silicone gel does not enter the groove
region under the optical fiber, and this also prevents the
generation of bubbles attributable to the setting and contraction
of the silicone gel.
[0065] Further, only a small amount of silicone gel enters the
groove under the end portion of the optical fiber because the end
portion protruding from the region secured using the first bonding
element is as short as several hundred .mu.m, and a region open to
the atmosphere exists ahead the end of the optical fiber. Thus, the
silicone gel moves when it sets and contracts, which suppresses the
generation of bubbles. This not only prevents the generation of
bubbles in the silicone gel at the end of the optical fiber and
under the same to eliminate nuclei to trap moisture but also
eliminates bubbles from the gap between the semiconductor laser
chip and optical fiber. This prevents eclipse of laser light
attributable to bubbles to allow optical coupling of the optical
fiber with high efficiency.
[0066] Even if bubbles are generated in the silicone gel in the
groove under the optical fiber, such bubbles have small
diameters.
[0067] (c) After the adjustment of optical coupling, the optical
fiber is preliminary secured to the region of the groove on the
silicon platform with the ultraviolet-setting adhesive and is
thereafter subjected to final securing with the thermosetting
resin. This improves the reliability of optical coupling.
[0068] (d) Since the thermosetting resin has high bonding strength,
the optical fiber is reliably secured to the silicon platform
through the final securing using the thermosetting resin, and the
optical fiber is thus secured with improved reliability. The
optical fiber is secured at the preliminary securing portion such
that the optical coupling between the optical fiber and the
semiconductor laser chip is not deteriorated, and the final
securing portion improves the securing strength of the optical
fiber.
[0069] (e) Since preliminary and final securing is carried out as
in (c) and (d) above, the optical fiber is secured on the silicon
platform with high optical coupling and high reliability of
coupling.
[0070] (f) When the optical fiber is secured in the groove on the
silicon platform, the optical fiber is pressed against the silicon
platform after optical coupling between the semiconductor laser
chip and optical fiber is adjusted, and the optical fiber is
preliminary secured in such a state by applying the
ultraviolet-setting adhesive and irradiating the
ultraviolet-setting adhesive with ultraviolet light to set it. This
makes it possible to reduce the time required for the preliminary
securing to several tens seconds.
[0071] (g) Since the preliminary securing using the
ultraviolet-setting adhesive provides high securing reliability in
a short term, the optical coupling between the optical fiber and
semiconductor laser chip is not deteriorated during the time
interval before the subsequent final securing. Therefore, when the
optical fiber is finally secured with the thermosetting resin
(epoxy resin) thereafter, the thermosetting process following the
application of the thermosetting resin can be carried out on a
batch process basis. This makes it possible to improve the
efficiency of the operation of securing the optical fiber, thereby
achieving a reduction in the manufacturing cost of the
photoelectronic device.
[0072] (h) The preliminary securing using the ultraviolet-setting
adhesive is carried out on a fiber inserting apparatus for aligning
the optical axes of the semiconductor laser chip and optical fiber.
Since the time for the preliminary securing of the optical fiber is
reduced (to several tens seconds), the operating efficiency of the
fiber inserting apparatus can be improved.
[0073] (i) Since a fiber inserting apparatus is expensive, improved
operating efficiency of a fiber inserting apparatus results in a
reduction of the manufacturing of the photoelectronic device.
[0074] In the aspect (2) described above, there is the following
effect in addition to the effects according to the aspect (1). In
this aspect, it is possible to achieve high productivity and to
reduce the manufacturing cost of a photoelectronic device because
the package is formed by molding insulating resin.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0075] FIG. 1 is an enlarged sectional view of the region of a
silicon platform in a photoelectronic device which is an embodiment
(first embodiment) of the invention.
[0076] FIG. 2 is a front view of the photoelectronic device of the
first embodiment.
[0077] FIG. 3 is a plan view of the photoelectronic device of the
first embodiment.
[0078] FIG. 4 is an enlarged sectional view of the photoelectronic
device of the first embodiment taken in the extending direction of
an optical fiber.
[0079] FIG. 5 is an enlarged sectional view of the photoelectronic
device of the first embodiment taken in the direction perpendicular
to the optical fiber.
[0080] FIG. 6 is an enlarged plan view of the photoelectronic
device of the first embodiment with the cap removed.
[0081] FIG. 7 is an enlarged plan view of the region of the silicon
platform in the photoelectronic device of the first embodiment.
[0082] FIG. 8 is an enlarged sectional view of the region of the
silicon platform in the photoelectronic device of the first
embodiment.
[0083] FIGS. 9A, 9B and 9C are schematic sectional views showing a
method for securing an optical fiber on the silicon platform during
the manufacture of the photoelectronic device of the first
embodiment.
[0084] FIG. 10 is a schematic perspective view showing the
application of an adhesive to a groove prior to the securing of the
optical fiber.
[0085] FIG. 11 is a schematic perspective view showing preliminary
securing of the optical fiber to the groove.
[0086] FIG. 12 is an enlarged sectional view showing a state in
which silicone gel is injected in the case during the manufacture
of the photoelectronic device of the first embodiment.
[0087] FIG. 13 is an enlarged plan view of the region of a silicon
platform in a photoelectronic device which is another embodiment
(second embodiment) of the invention.
[0088] FIG. 14 is an enlarged sectional view of the region of the
silicon platform of the photoelectronic device of the second
embodiment.
[0089] FIG. 15 is a schematic perspective view showing final
securing of an optical fiber in a groove on the silicon
platform.
[0090] FIG. 16 is a schematic enlarged sectional view of the region
of a silicon platform in a photoelectronic device which is another
embodiment (third embodiment) of the invention.
[0091] FIG. 17 is a schematic enlarged sectional view of the region
of a silicon platform in a photoelectronic device which is another
embodiment (fourth embodiment) of the invention.
[0092] FIG. 18 is a schematic enlarged plan view of the region of
the silicon platform in the photoelectronic device of the fourth
embodiment.
[0093] FIG. 19 is a schematic enlarged sectional view of the region
of a silicon platform in a photoelectronic device which is another
embodiment (fifth embodiment) of the invention.
[0094] FIG. 20 is a partially cut-away plan view of a
photoelectronic device which is another embodiment (sixth
embodiment) of the invention.
[0095] FIG. 21 is a sectional view of the photoelectronic device of
the sixth embodiment.
[0096] FIG. 22 is a plan view of a part of a lead frame showing the
state of the photoelectronic device of the sixth embodiment at one
step of manufacturing the same.
[0097] FIG. 23 is a partially cut-away plan view of a
photoelectronic device which is another embodiment (seventh
embodiment) of the invention.
[0098] FIG. 24 is a sectional view of the photoelectronic device of
the seventh embodiment.
[0099] FIG. 25 is a schematic enlarged sectional view showing
generation of a bubble in a space defined by an optical fiber and a
groove during securing of the optical fiber studied by the
inventor.
[0100] FIGS. 26A and 26B show data obtained from an experiment
carried out by the inventor in the form of schematic views showing
the distribution of bubbles generated at an early stage of setting
of silicone gel.
[0101] FIGS. 27A and 27B show data obtained from an experiment
carried out by the inventor in the form of schematic views showing
the distribution of bubbles generated in silicone gel as a result
of environmental tests such as temperature cycles.
[0102] FIG. 28 illustrates a phenomenon observed by the inventor in
the form of a schematic sectional view showing bubbles generated in
silicone gel in a groove under an optical fiber.
[0103] FIG. 29 illustrates a phenomenon observed by the inventor in
the form of a schematic sectional view showing bubbles generated in
silicone gel in a groove under an optical fiber and in the gap
between an end of the optical fiber and a semiconductor laser
chip.
[0104] FIG. 30 illustrates a phenomenon observed by the inventor in
the form of a schematic plan view showing bubbles generated in the
gap between an end of an optical fiber and a semiconductor laser
chip.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0105] Preferred embodiments of the invention will now be described
in detail with reference to the drawings. Throughout the drawings
presented here to describe the preferred embodiments of the
invention, parts having like functions are indicated by like
reference numbers, and repeated description will be omitted for
them.
[0106] A first embodiment of the invention will now be
described.
[0107] FIGS. 1 through 12 are drawings related to a photoelectronic
device which is the first embodiment of the invention and a method
of manufacturing the same.
[0108] As shown in FIGS. 2 and 3, a photoelectronic device
(semiconductor optical module) 20 of the first embodiment comprises
a plastic case 21 and a plastic cap 22 secured on the case 22 which
collectively form a package (sealing element) 23 when viewed
externally. The case 21 and cap 22 are respectively comprised of
rectangular main body portions 21a and 22a and elongate guide
portions 21b and 22b that protrude from the middle of ends of the
main body portions 21a and 22a.
[0109] An optical fiber cable 25 is guided by the guide portions
21b and 22b to protrude from the ends of the guide portions 21b and
22b. The region of the optical fiber 25 that protrudes from the
guide portions 21b and 22b is secured with an ultraviolet-setting
adhesive 26.
[0110] A plurality of leads 27 protrude from both sides of the case
21. In the present embodiment, the leads 27 are shaped in a dual
inline configuration. The case 21 and cap 22 are made of insulating
resin such as epoxy resin. Specifically, the package 23 is
constituted by a plastic package made of insulating resin.
[0111] FIG. 6 is an enlarged plan view of the semiconductor optical
module 20 with the cap 22 removed. FIG. 4 is an enlarged sectional
view of the semiconductor optical module 20 taken in the extending
direction of the optical fiber. FIG. 5 is an enlarged sectional
view of the semiconductor optical module 20 taken in the direction
perpendicular to the optical fiber. As shown in those figures, a
base plate 30 is provided on the inner bottom of the case 21. The
inner end of each lead 27 is located around the base plate 30. The
base plate 30 and leads 27 are incorporated in the case 21 when the
case 21 is molded.
[0112] While the optical fiber cable 25 is guided by the guide
portion 21b of the case 21, a silicon platform (support substrate
made of silicon single crystals) 1 is secured with a bonding
material 29, e.g., silver paste, on the base plate 30 which is
located on an imaginary line along which the optical fiber axis of
the optical fiber cable 25 extends.
[0113] The optical fiber cable 25 is covered by a jacket (fiber
jacket) as a protective tube made of, for example, nylon. While the
fiber jacket covers halfway the guide portion 21b of the case 21,
the fiber jacket is peeled off at the end of this portion to expose
an optical fiber 3 comprising a core and a clad. The region of the
optical fiber 3 is fitted in a groove 2 provided on the silicon
platform 1 so as to trail along it, In this structure, a
semiconductor laser chip 7 as a photoelectric conversion element
and a light-receiving element (photodiode) 31 are secured in series
on the silicon platform 1 that is located on an imaginary line
extending from the same.
[0114] Laser light emitted from a front emission surface of the
semiconductor laser chip 7 is taken into the optical fiber at an
end (one end) of the optical fiber 3, and the optical output
strength of laser light emitted from a rear emission surface is
monitored by the light-receiving element 31.
[0115] As shown in FIG. 7, the semiconductor laser chip 7 and
light-receiving element 31 are respectively secured to mounting
portions 32 and 33 constituted by a conductive metalized layer
provided on a surface of the silicon platform 1. Since both of the
semiconductor laser chip 7 and light-receiving element 31 have
electrodes on upper and lower surfaces thereof, the bonding
structure electrically connects the electrodes on the lower
surfaces to the mounting portions 32 and 33, respectively. A part
of the metalized layer continuous to the mounting portions 32 and
33 and the inner ends of predetermined leads 27 are connected by
conductive wires 34.
[0116] The electrodes on the upper surfaces of the semiconductor
laser chip 7 and light-receiving element 31 are secured to
respective independent metalized layers through the conductive
wires 34, and a part of the metalized layers is electrically
connected to the inner ends of predetermined leads 27 through the
wires 34.
[0117] A discharge groove 35 is provided such that it crosses the
groove 2 provided on one surface of the silicon platform 1. While
the optical fiber 3 extends beyond the discharge groove 35, it
protrudes beyond the groove only a small distance. For example, the
protruding length is about 100 .mu.m. The diameter of the optical
fiber 3 is, for example, about 125 .mu.m.
[0118] As shown in FIGS. 7 and 8, the optical fiber 3 is secured on
the silicon platform 1 in the vicinity of the discharge groove 35
using two types of adhesives at a preliminary securing portion 40
and a final securing portion 41. An ultraviolet-setting adhesive 4
is used at the preliminary securing portion 40, and thermosetting
resin 5 is used at the final securing portion 41. FIGS. 4 through 6
show only the final securing portion 41 which will be described in
detail with reference to other drawings.
[0119] One of the features of the invention is that the
ultraviolet-setting adhesive 4 that constitutes the preliminary
securing portion 40 is located below the optical fiber 3 (FIG. 7
shows the regions of the preliminary securing portion 40 and final
securing portion 41 and does not clearly show the vertical
positional relationship between them) and is filled in an enclosed
region 9 defined by the groove 2 on the silicon platform 1 and the
optical fiber 3 such that no gap is produced.
[0120] The final securing portion 41 is provided such that it
covers the preliminary securing portion 40 as a whole. However, the
final securing portion 41 is provided such that it does not exceed
the discharge groove 35 as a guide line to prevent it from invading
the space between the end of the optical fiber 3 and the
semiconductor laser chip 7. The purpose of this is to prevent the
final securing portion 41 from blocking the transmission and
reception of light.
[0121] At the preliminary securing portion 40, the
ultraviolet-setting adhesive 4 is used to perform securing in a
short period of time, and the thermosetting resin 5 is used at the
final securing portion 41 to improve securing strength. During the
manufacture, since the preliminary securing precedes the final
securing and the case 21 can be moved even after the preliminary
securing, the thermosetting resin 5 for the final securing is set
by a batch process after being applied. Thus, the case 21 is
removed from the fiber inserting apparatus in a short period of
time to improve the operating efficiency of the fiber inserting
apparatus, and the batch process improves the operability during
the setting of the thermosetting resin.
[0122] The optical fiber cable 25 and optical fiber 3 are secured
to various parts using an ultraviolet-setting adhesive,
thermosetting resin and the like. For example, the optical cable 25
is secured to the guide portion 21b with thermosetting resin 45.
When the optical fiber 3 is secured to the base plate 30 or the
like by means of soldering, techniques are employed including
provision of a metalized layer on the surface of the optical fiber
3.
[0123] The case 21 is filled with silicone gel 6 which is
transparent to light transmitted through the optical fiber 3 and
which serves as a protective body (protective film) resistant to
humidity. The silicone gel 6 covers the base plate 30, silicon
platform 1, optical fiber 3, semiconductor laser chip 7,
light-receiving element 31 and the like to improve humidity
resistance. The cap 22 is secured to the case 21 using an adhesive.
The adhesive is the thermosetting resin 45 for securing the optical
fiber cable 25 to the guide portions 21b and 22b. The protective
film 6 is not limited to silicone gel, and silicone rubber,
low-stress epoxy resin, acrylic resin or urethane resin may be
used.
[0124] A method of manufacturing a semiconductor optical module 20
will now be described.
[0125] First, there is provided a plastic case 21 having a guide
for guiding an optical fiber 3, a plastic cap 22 mounted so as to
close the case 21, and a silicon platform 1 having a semiconductor
laser chip 7 and a light-receiving element 31 mounted on one
surface thereof and having a groove 2 for guiding the optical fiber
3 extending toward the semiconductor laser chip 7. The case 21 and
cap 22 have structures as described above.
[0126] A metalized layer having a-predetermined pattern is formed
on one surface of the silicon platform 1, and a part of the same
constitute mounting portions 32 and 33. The semiconductor laser
chip 7 and light-receiving element 31 are secured to the mounting
portions 32 and 33. Both of the semiconductor laser chip 7 and
light-receiving element 31 have electrodes on upper and lower
surfaces, and the bonding structure therefore electrically connects
the electrodes on the lower surface to the mounting portions 32 and
33, respectively. A part of the mounting portions 32 and 33
constitutes pads connected to ends of wires which are connected to
inner ends of leads to be described later at other ends thereof.
The electrodes on the upper surfaces of the semiconductor laser
chip 7 and light-receiving element 31 are secured to respective
independent metalized layers through conductive wires 34. The
independent metalized layers also have pads connected to ends of
wires which are connected to inner ends of leads to be described
later at other ends thereof.
[0127] A discharge groove 35 is provided such that it crosses the
groove 2 provided on one surface of the silicon platform 1. The
discharge groove 35 has the function of guiding an adhesive that
flows into it when the optical fiber 3 is secured, to the outside,
to prevent the adhesive from flowing toward the semiconductor laser
chip 7.
[0128] Next, the silicon platform 1 is secured to a base plate 30
in the case 21 using a bonding material 29, e.g., silver paste.
[0129] Then, the pad portions of the metalized layer and inner ends
of leads 27 are connected with conductive wires 34 (see FIGS. 5 and
6).
[0130] Next, an optical fiber cable 25 from which an optical fiber
3 is exposed by removing a part of a jacket thereof a predetermined
distance from the end thereof is inserted into a guide portion 21b;
the semiconductor laser chip 7 is operated to emit laser light
which is taken into the optical fiber 3 from the end of the optical
fiber 3; optical coupling is adjusted while detecting optical
output; and thermosetting resin (e.g., epoxy resin) is applied to
the guide portion 21b to bond them together after the adjustment of
optical coupling is completed. The adjustment of optical coupling
is may be well-known passive alignment which involves no emission
of laser light.
[0131] Next, an ultraviolet-setting adhesive is applied to a part
of the groove 2 to perform preliminary securing of the optical
fiber 3. Specifically, as shown in FIGS. 9A and 10, an
ultraviolet-setting adhesive 4 is applied to the groove 2 of the
silicon platform 1, and the optical fiber 3 is thereafter pressed
against the ultraviolet-setting adhesive 4, which consequently
presses it against the bottom of the groove 2.
[0132] As shown in FIG. 9B, such a press is achieved by applying a
predetermined load to a pressing piece 50. For example, a load of
100 g is applied. The semiconductor laser chip 7 is operated to
emit laser light which is taken into the optical fiber 3 at the end
thereof, and optical coupling is adjusted while detecting optical
output.
[0133] At this point, as shown in FIG. 9B, the adjustment of
optical coupling is conducted in a state in which one end of the
optical fiber 3 is fitted in the groove 2 on the silicon platform 1
and the groove 2 under the optical fiber is filled with the
ultraviolet-setting adhesive 4.
[0134] Next, the ultraviolet-setting adhesive 4 on both sides of
the optical fiber 3 is irradiated with ultraviolet light using an
ultraviolet light radiation fibers 51 and 52 to set the
ultraviolet-setting adhesive 4. The ultraviolet-setting adhesive 4
thus set forms a preliminary securing portion 40 and, as shown in
FIG. 11, the optical fiber 3 becomes static and is secured to the
silicon platform 1. Then, an ultraviolet-setting adhesive 26 is
used to secure the region where the guide portion 21b and optical
fiber 3 contact each other and the region of the optical fiber
cable 25 that protrudes from the guide portion 21b.
[0135] Next, as shown in FIG. 9C, thermosetting resin 5 is applied
such that it extends from above the optical fiber 3 down to a
surface of the silicon platform 1 and is subjected to a
thermosetting process to form a final securing portion 41
constituted by the thermosetting resin 5 (see FIGS. 7 and 8). The
final securing portion 41 has a structure to cover the preliminary
securing portion 40 completely, thereby rigidly securing the
optical fiber 3 on the silicon platform 1.
[0136] As shown in FIGS. 7 and 8, the optical fiber 3 is thus
secured on the silicon platform 1 with the two types of adhesives
at the preliminary securing portion 40 and final securing portion
41 in the vicinity of the discharge groove 35. The preliminary
securing portion 40 is constituted by the ultraviolet-setting
adhesive 4, and the final securing portion 41 is constituted by the
thermosetting resin 5. FIGS. 4 through 6 show only the final
securing portion 41.
[0137] Next, as shown in FIG. 12, the case 21 is filled with
silicone gel 6 to cover the silicon platform 1, optical fiber 3,
semiconductor laser chip (not shown) and light-receiving element
(not shown). This is carried out in order to improve humidity
resistance. In doing so, in the region secured using the
ultraviolet-setting adhesive 4, the silicone gel 6 does not enter
the region of the groove 2 under the optical fiber 3 because this
region is filled with the ultraviolet-setting adhesive 4.
[0138] The cap 22 is then bonded to the case 21 using an adhesive
and is secured to the case 21 by baking the adhesive. The case 21
and cap 22 are secured together by filling the guide portions 21b
and 22b the case 21 and of the cap 22 with thermosetting resin 45
and by setting the thermosetting resin 45.
[0139] The optical fiber 3 may be secured to a predetermined
location using other bonding materials, although not described in
detail.
[0140] During the thermal process for securing the cap 22 to the
case 21, no bubble is generated in the silicone gel 6 because the
silicone gel 6 is not present under the optical fiber 3 in the
region secured using the ultraviolet-setting adhesive 4.
[0141] When the optical fiber 3 is fitted in the groove 2 on the
silicon platform 1, a space is defined by the groove 2 under the
optical fiber 3, and this space is filled with the
ultraviolet-setting adhesive 4 in the present embodiment.
Therefore, the silicone gel 6 does not enter the region under the
optical fiber 3 associated with the preliminary securing portion
when the case is filled with the silicone gel 6 before sealing with
the cap and, therefore, no bubble is caused by the setting and
contraction of the silicone gel 6. This makes it possible to
prevent any reduction in the strength and reliability of the
securing of the optical fiber 3 attributable to bubbles and to
prevent problems such as freezing of moisture trapped by
bubbles.
[0142] Specifically, even if moisture enters along the optical
fiber 3, since the gap between the optical fiber 3 and groove 2 at
the preliminary securing portion is filled with the
ultraviolet-setting adhesive 4 for preliminary securing, the
invasion of moisture is prevented at the preliminary securing
portion, and there is no nucleus like a bubble in the silicone gel
that can trap moisture. This prevents trapping of moisture to
improve humidity resistance and eliminates the possibility of
freezing moisture during use at a low temperature.
[0143] In a structure in which the optical fiber 3 is secured on
the support substrate 1 using only a first bonding element
constituted by an ultraviolet-setting adhesive or thermosetting
resin, since the groove 2 under the optical fiber 3 is filled with
the first bonding element 1, the silicone gel does not enter the
groove region under the optical fiber, and this also prevents the
generation of bubbles attributable to the setting and contraction
of the silicone gel.
[0144] Further, only a small amount of silicone gel 6 enters the
groove 2 under the end portion because the end portion of the
optical fiber 3 protruding from the region secured using the first
bonding element is as short as several hundred .mu.m, and a region
open to the atmosphere (open space) exists ahead the end of the
optical fiber 3. The silicone gel 6 moves when it sets and
contracts, which suppresses the generation of bubbles. This not
only prevents the generation of bubbles in the silicone gel at the
end of the optical fiber 3 and under the same to eliminate nuclei
to trap moisture but also eliminates bubbles from the gap between
the semiconductor laser chip 7 and optical fiber 3. This prevents
eclipse of laser light attributable to bubbles to allow optical
coupling of the optical fiber with high efficiency.
[0145] According to the present manufacturing method, even if
bubbles are generated in the silicone gel in the groove under the
optical fiber, such bubbles have small diameters. For example,
there will be no bubble that is equal to or greater than one half
of the distance between the two points of the groove in contact
with the circumferential surface of the optical fiber (the distance
is represented by "x" in FIG. 1 where x is about 102 .mu.m), and
bubbles will be smaller than the half of the distance between the
two points and will be unlikely to serve as nuclei to trap
moisture. Specifically, the inventor has found that even if the
silicon gel enters any cavity formed in the region of the
ultraviolet-setting adhesive 4 in the groove under the optical
fiber, any bubble generated in the silicon gel has a diameter .PHI.
equal to or smaller than x when the silicon gel has a diameter
.PHI. equal to or smaller than x (.PHI.<x/2) and is unlikely to
act as a nucleus to trap moisture. That is, no nucleus to trap
moisture is generated in the region of the ultraviolet-setting
adhesive 4 in the groove under the optical fiber where neither
bubbles nor silicon gel having a diameter greater than one half of
x exists in that region.
[0146] The first embodiment provides the following effects.
[0147] (1) The package 23 is formed by the case 21 and cap 22 made
of plastic, the case 21 is filled with the silicone gel 6 to cover
and protect the semiconductor laser chip 7, optical fiber 3,
light-receiving element 31, silicon platform 1 and the like. This
makes it possible to improve humidity resistance.
[0148] (2) After the adjustment of optical coupling, the optical
fiber 3 is preliminary secured to the region of the groove 2 on the
silicon platform 1 with the ultraviolet-setting adhesive 4 and is
thereafter subjected to final securing with the thermosetting resin
5, which improves the reliability of optical coupling.
[0149] (3) Since the thermosetting resin 5 has high bonding
strength, the optical fiber 3 is reliably secured to the silicon
platform 1 through the final securing using the thermosetting resin
5, and the optical fiber 3 is thus secured with improved
reliability. At the preliminary securing portion 40, the optical
fiber is secured so that the optical coupling between the optical
fiber 3 and the semiconductor laser chip 7 is not deteriorated, and
at the final securing portion 41, the strength of the securing of
the optical fiber 3 is improved.
[0150] (4) Since preliminary and final securing is carried out as
in (2) and (3) above, the optical fiber 3 is secured on the silicon
platform with high optical coupling and high reliability of
coupling.
[0151] (5) When the optical fiber 3 is secured in the groove 2 on
the silicon platform 1, the optical fiber 3 is pressed against the
silicon platform 1 after optical coupling between the semiconductor
laser chip 7 and optical fiber 3 is adjusted, and the optical fiber
3 is preliminary secured in such a state by applying the
ultraviolet-setting adhesive 4 and irradiating the
ultraviolet-setting adhesive 4 with ultraviolet light to set it.
This makes it possible to reduce the time required for the
preliminary securing to several tens seconds.
[0152] (6) Since the preliminary securing using the
ultraviolet-setting adhesive 4 provides high securing reliability
in a short term, the optical coupling between the optical fiber 3
and semiconductor laser chip 7 is not deteriorated during the time
interval before the subsequent final securing. Therefore, when the
optical fiber 3 is finally secured with the thermosetting resin 5
thereafter, the thermosetting process following the application of
the thermosetting resin 5 can be carried out on a batch process
basis. This makes it possible to improve the efficiency of the
operation of securing the optical fiber, thereby achieving a
reduction in the manufacturing cost of the semiconductor optical
module (photoelectronic device) 20.
[0153] (7) The preliminary securing using the ultraviolet-setting
adhesive 4 is carried out on a fiber inserting apparatus for
aligning the optical axes of the semiconductor laser chip 7 and
optical fiber 3. Since the time for the preliminary securing of the
optical fiber 3 is reduced to several tens seconds, the operating
efficiency of the fiber inserting apparatus can be improved.
[0154] (8) Since a fiber inserting apparatus is expensive, improved
operating efficiency of a fiber inserting apparatus results in a
reduction of the manufacturing of the semiconductor optical module
20.
[0155] A second embodiment of the invention will now be
described.
[0156] FIGS. 13 through 15 illustrate a semiconductor optical
module which is another embodiment (second embodiment) of the
invention. FIG. 13 is a schematic plan view of the region of the
silicon platform. FIG. 14 is a schematic sectional view of the
region of the silicon platform. FIG. 15 is a schematic perspective
view of an optical fiber secured on the silicon platform.
[0157] The second embodiment is different from the first embodiment
in that securing is performed such that the final securing portion
41 covers a part of the preliminary securing portion 40 and such
that the final securing portion 41 is located at the side of the
preliminary securing portion 40 which is farther from the
semiconductor laser chip 7 (photoelectric conversion element).
[0158] In such a structure wherein securing is performed such that
the final securing portion 41 covers a part of the preliminary
securing portion 40 and such that the final securing portion 41 is
located at the side of the preliminary securing portion 40 which is
farther from the semiconductor laser chip 7, even if the
thermosetting resin 5 for the final securing operation undesirably
flows during the application of the same, it does not flow toward
the semiconductor laser chip 7 beyond the edge of the
ultraviolet-setting adhesive 4 forming the preliminary securing
portion 40. Thus, the light path will not be blocked, and the
thermosetting resin 5 will not reduce light transmitted and
received between the optical fiber 3 and semiconductor laser chip
7.
[0159] The second embodiment provides the same effects as those of
the first embodiment.
[0160] A third embodiment of the invention will now be
described.
[0161] FIG. 16 is a schematic enlarged sectional view of the region
of the silicon platform of a photoelectronic device which is
another embodiment (third embodiment) of the invention, showing a
region where the semiconductor laser chip 7 and optical fiber 3 are
optically coupled.
[0162] In the present embodiment, a bubble generation preventing
portion 60 is provided in the form of a recess or groove extending
across the groove 2 in a region between one end of the optical
fiber 3 secured with a first bonding element (ultraviolet-setting
adhesive 4) and the photoelectric conversion element (semiconductor
laser chip) 7. The bubble generation preventing portion 60 has a
length as large as 50 .mu.m or more in the direction of the groove
2 (the extending direction of the optical fiber 3) and defines an
open region.
[0163] The utmost end of one end of the optical fiber 3 is located
above the bubble generation preventing portion 60.
[0164] The utmost end face of an end of the insulated optical fiber
3 is close to an edge of the bubble generation preventing portion
60. For example, the end face of the optical fiber 3 is located
above the bubble generation preventing portion 60 and protrudes
from the edge of the bubble generation preventing portion 60 a
distance of several hundred .mu.m or less.
[0165] Such a photoelectronic device is assembled using a method as
described below. There is provided the support substrate (silicon
platform 1) having the semiconductor laser chip 7 mounted on one
surface thereof, the groove 2 for guiding the optical fiber 3
extending toward the semiconductor laser chip 7, and the bubble
generation preventing portion 60 constituted by a recess or groove
extending across the groove 2, provided in a region close to an end
of the optical fiber 3 on a side of a securing portion utilizing a
bonding element (first bonding element) of the optical fiber 3.
[0166] Next, optical coupling between the optical fiber 3 and
semiconductor laser chip 7 is adjusted, and the optical fiber 3 is
preliminary secured to the groove 2 excluding the region of the
bubble generation preventing portion 60 using the
ultraviolet-setting adhesive 4.
[0167] The bubble generation preventing portion 60 is formed in
advance in a position such that the end face of the optical fiber 3
slightly protrudes above the bubble generation preventing portion
60 when optical coupling has been achieved.
[0168] According to the third embodiment of the invention, (1)
since the bubble generation preventing portion 60 in the form of a
recess or groove extending across the groove 2 is provided between
the region of the optical fiber 3 secured with the first bonding
element (ultraviolet-setting adhesive 4) at an end thereof and the
semiconductor laser chip 7, the bubble generation preventing
portion 60 which is an open region exists in the region of the
groove 2 directly under the optical fiber 3 on both sides of the
optical fiber 3. This results in movement of silicone gel 6 in the
groove 2 when it sets and contracts and thereby prevents the
generation of bubbles.
[0169] (2) Since the utmost end of one end of the optical fiber 3
is located above the bubble generation preventing portion 60 and
its utmost end face is as close as several hundred .mu.m to an edge
of the bubble generation preventing portion 60, no bubble is
generated directly under the optical fiber 3 and at the end of the
optical fiber. That is, the bubble generation preventing portion 60
serves as an open region that allows movement of the silicone gel 6
when the silicone gel 6 sets and contacts, to prevent the
generation of bubbles.
[0170] The present embodiment may have a configuration in which the
end face of the optical fiber 3 is aligned with the edge of the
bubble generation preventing portion 60. In this case, no bubble
will be generated because the ultraviolet-setting adhesive 4 is
present directly under the optical fiber 3.
[0171] According to the present embodiment, the effect of
suppressing bubbles can be achieved with a structure in which the
optical fiber 3 is secured on the silicon platform 1 with
thermosetting resin filled in the groove 2, i.e., a securing
structure utilizing one type of adhesive.
[0172] A fourth embodiment of the invention will now be
described.
[0173] FIG. 17 is a schematic enlarged sectional view of the region
of a silicon platform of a photoelectronic device which is another
embodiment (fourth embodiment) of the invention. FIG. 18 is a
schematic enlarged plan view of the region of the silicon
platform.
[0174] According to the present embodiment, one end of the optical
fiber 3 extends beyond the bubble generation preventing portion 60
and its utmost end is supported by the groove 2.
[0175] According to the present embodiment, since one end of the
optical fiber 3 extends beyond the bubble generation preventing
portion 60 and its utmost end is supported (guided) by the groove
2, the optical coupling factor between the optical fiber 3 and
semiconductor laser chip 7 is improved.
[0176] Although silicone gel 6 enters a region under the optical
fiber 3, the generation of bubbles is unlikely to occur in the
region because it has the bubble generation preventing portion 60
to serve as an open region. This makes it possible to suppress
trapping of moisture and to prevent eclipse of laser light 11
attributable to bubbles.
[0177] Since the bubble generation preventing portion 60 is a
recess and is not a groove whose ends are open at ends of silicon
platform 1, the silicone gel will not flow out. As a result, the
silicon gel is likely to move into the region directly under the
optical fiber 3 when the silicone gel sets and contracts, and this
makes it possible to prevent the generation of bubbles. However,
the bubble generation preventing portion 60 may be a groove as long
as it has a great width to contain the silicone gel in an amount
sufficient to prevent the generation of bubbles.
[0178] According to the present embodiment, the effect of
suppressing bubbles can be achieved with a structure in which the
optical fiber 3 is secured on the silicon platform 1 with
thermosetting resin filled in the groove 2, i.e., a securing
structure utilizing one type of adhesive.
[0179] A fifth embodiment of the invention will now be
described.
[0180] FIG. 19 is a schematic enlarged sectional view of the region
of a silicon platform of a photoelectronic device which is another
embodiment (fifth embodiment) of the invention.
[0181] The present embodiment is an example in which the bubble
generation preventing portion 60 is provided in a wide range
covering the securing portion utilizing the ultraviolet-setting
adhesive 4 and the region where the semiconductor laser chip 7 is
mounted. It employs a structure in which the end of the optical
fiber 3 is located above the bubble generation preventing portion
60.
[0182] According to the present embodiment, since the utmost end of
one end of the optical fiber 3 is located above the bubble
generation preventing portion 60, the bubble generation preventing
portion 60 as an open region exists in the region the groove 2
directly under the optical fiber 3 on both sides of the optical
fiber 3. This causes the silicone gel to move when it sets and
contracts, thereby preventing the generation of bubbles.
[0183] A sixth embodiment of the invention will now be
described.
[0184] FIGS. 20 through 22 illustrate a photoelectronic device
which is another embodiment (sixth embodiment) of the invention.
FIG. 20 is a partially cut away plan view of the photoelectronic
device. FIG. 21 is a sectional view of the photoelectronic device.
FIG. 22 is a plan view of a part of a lead frame showing the state
of the photoelectronic device at one step of manufacturing the
same.
[0185] In the present embodiment, a package 61 made of insulating
resin such as epoxy resin formed by means of resin molding covers
the support substrate (silicon platform) 1, semiconductor laser
chip 7, the ends of the leads 27, wires 34, one end of the optical
fiber 3 and the like.
[0186] The optical fiber 3 is coated with a jacket 62 which is
generally made of nylon or the like to form an optical cable 66. In
the present embodiment, the jacket 62 is peeled off at one end of
the optical cable 66 to expose the optical fiber 3 (optical fiber
core). The exposed optical fiber 3 and the end of the jacket 62 are
positioned and sealed in the package 62. The end of the jacket 62
is secured to a support portion 63 which is a downward step
provided on the silicon platform 1 with an adhesive 64.
[0187] The package 61 has a structure including a narrow optical
fiber guide for guiding the region of the jacket 62. The package 61
is formed by means of transfer molding, although this is not
limiting the invention.
[0188] The silicon platform 1 used in the present embodiment is
also in accordance with the above embodiments in the region of the
optical connection between the semiconductor laser chip 7 and
optical fiber 3. Specifically, a silicon platform 1 having the
structure according to the fourth embodiment shown in FIG. 17 is
used here.
[0189] As shown in FIGS. 20 and 21, in order to improve the
reliability (humidity resistance) of the photoelectronic device,
silicon gel 6 covers regions including the component mounting
surface of the silicon platform 1, wires 34, the inner ends of the
leads 27, and the inner end of the jacket 62.
[0190] The silicon platform 1 is secured on a flat support portion
(tab) 70 provided between the ends of some of the leads 27. The
package 61 has a structure in which the rear side of the tab 70 is
also sealed.
[0191] Such a photoelectronic device is manufactured using a method
as described below.
[0192] Specifically, it is a method of manufacturing a
photoelectronic device comprising:
[0193] a package 61 made of insulating resin;
[0194] a support portion 70 located in the package 61;
[0195] a support substrate (silicon platform) 1 secured to the
support portion 70 having a photoelectric conversion element
mounted on one surface thereof and having a groove 2 for guiding an
optical fiber 3 extending toward the photoelectric conversion
element (semiconductor laser chip 7);
[0196] a photoelectric conversion element mounted on the support
substrate; and
[0197] an optical fiber 3 fitted in the groove 2 on the support
substrate 1 to be guided thereby with one end thereof in a
face-to-face relationship with the photoelectric conversion element
and the other end thereof located outside the package and protected
by a jacket 62, wherein one end of the optical fiber 3 extending in
the package is fitted in the groove 2 on the support substrate 1
and is secured on the support substrate 1 through preliminary
securing with an ultraviolet-setting adhesive and final securing
with thermosetting resin, the method comprising the steps of:
[0198] providing the support substrate 1 on which a lead frame 71
having the support portion 70 thereon and the photoelectric
conversion element are secured;
[0199] securing the support substrate 1 to the support portion 70
on the lead frame 71;
[0200] applying the ultraviolet-setting adhesive to a part of the
groove 2 on the support substrate 1, fitting one end of the optical
fiber 3 guided under the protection of the jacket 62 in the groove
2 on the support substrate 1 and adjusting optical coupling between
the photoelectric conversion element and optical fiber 3 with the
groove 2 under the optical fiber 3 filled with the
ultraviolet-setting adhesive;
[0201] preliminary securing the optical fiber 3 on the support
substrate 1 by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it;
[0202] covering a part of the optical fiber 3 and support substrate
1 with the thermosetting resin and setting the thermosetting resin
to finally secure the optical fiber 3 on the support substrate
1;
[0203] connecting wiring on the support substrate 1 and leads 27 on
the lead frame with conductive wires 34 before or after securing
the optical fiber 3 on the support substrate 1;
[0204] covering a region including the photoelectric conversion
element, one end of the optical fiber 3, the wires 34 and the
region of the leads connected to the wires with a protective
element (silicone gel 6) transparent to light transmitted by the
optical fiber 3;
[0205] molding a region including the jacket 62 halfway with
insulating resin to form the package 61;
[0206] cutting and removing an unnecessary part of the lead frame
protruding from the package 61; and
[0207] shaping the leads 27 protruding from the package 61 into a
predetermined configuration.
[0208] The photoelectronic device according to the sixth embodiment
is manufactured using a lead frame 71 as shown in FIG. 21. The lead
frame 71 is in the form of a strip, and a plurality of
photoelectronic devices can be manufactured from one lead frame 71.
Specifically lead patterns 72 for manufacturing photoelectronic
devices are provided at constant intervals in the longitudinal
direction of a lead frame 71. FIG. 22 shows a single lead pattern
72.
[0209] FIG. 22 shows the formation of a package 61 by means of
transfer molding.
[0210] There are many possible operational procedures for
manufacturing the photoelectronic device, for example, the
semiconductor laser chip 7, light-receiving element 31 and the like
are secured on the silicon platform 1 with the groove 2, bubble
generation preventing portion 60, support portion (not shown) and
the like provided thereon, and the optical fiber 3 is thereafter
secured on the silicon platform 1 using the techniques described in
the above-described embodiments.
[0211] The silicon platform 1 is then secured on the tab 70 of the
lead frame 71.
[0212] Next, the silicone gel 6 is applied to a rectangular region
including the inner ends of the leads 27 and is thereafter
subjected to a thermal process at a predetermined temperature to be
set. In the present embodiment, when the silicon gel 6 sets, no
bubble is generated not only in the vicinity of the optical fiber 3
but also in other regions of the silicone gel 6 as described
above.
[0213] Next, the lead frame 71 is clamped by a molding die (not
shown) of a transfer molding apparatus and is molded to form the
package 61. FIG. 22 shows a subrunner 77 and a gate portion 78
through which melted resin flows.
[0214] After the molding, an unnecessary part of the lead frame is
cut and removed although not shown, and the leads 27 protruding
from the package 61 are shaped. They are shaped into a dual inline
configuration in the present embodiment.
[0215] The present embodiment makes it possible to achieve high
productivity and to reduce the manufacturing cost of a
photoelectronic device because the package 61 is formed by molding
insulating resin.
[0216] A seventh embodiment of the invention will now be
described.
[0217] FIG. 23 is a partially cut-away plan view of a
photoelectronic device which is another embodiment (seventh
embodiment) of the invention. FIG. 24 is a sectional view of the
photoelectronic device.
[0218] The present embodiment has a structure in which an optical
fiber 3 (optical fiber core) supported by a ferrule 81 with a
sleeve 80 is secured on the silicon platform 1. One end of the
sleeve 80 protrudes from the package 60, and an optical connector
is attached thereto.
[0219] The optical connector is secured to one end of the optical
fiber. In the present embodiment, the package 61 is provided with a
pair of latches 82 which elastically operate to lock the optical
connector fitted to the sleeve 80.
[0220] The present embodiment also makes it possible to achieve
high productivity and to reduce the manufacturing cost of a
photoelectonic device because the package 61 is formed by molding
insulating resin. Further, the optical connector can be simply
attached by a single action.
[0221] While the present invention has been specifically described
with reference to embodiments of the same, the invention is not
limited to the above-described embodiments and may obviously
modified in various ways without departing from the principle
behind the same. For example, a case and a cap made of materials
other than plastic may be similarly used with the same effects as
those of the above embodiments as long as a structure is employed
in which the case is filled with silicone gel.
[0222] While the embodiments have referred to structures for
optical coupling between an optical fiber fitted in a groove and a
semiconductor laser chip, the invention can be equally applied to
structures for optical coupling between an optical fiber fitted in
a groove and another photoelectric conversion element such as a
light-receiving element (photodiode) or light-emitting diode with
the same effects as those of the above-described embodiments.
[0223] The invention can be equally applied at least to structures
in which an optical fiber is secured in a groove such as a V-shaped
groove with an adhesive and in which the optical fiber and the like
is covered with a substance such as silicone gel that generates
bubbles therein when it thermally sets and contracts.
[0224] Typical aspects of the invention disclosed in the above
embodiments can be briefly described as follows.
[0225] (1) There is provided a photoelectronic device comprising a
support substrate (silicon platform) constituted by a mounting
portion for mounting a photoelectric conversion element
(semiconductor laser chip) on one surface thereof and a silicon
substrate having a groove for guiding an optical fiber extending
toward the mounting portion, a photoelectric conversion element
secured on the mounting portion and an optical fiber fitted in the
groove at one end thereof and secured on the support substrate at
regions excluding the utmost end thereof, wherein the optical fiber
fitted in the groove is secured with a first bonding element
injected to fill the groove under the optical fiber for preliminary
securing the optical fiber on the support substrate and a second
bonding element for finally securing the optical fiber on the
support substrate while covering a part of the optical fiber and
support substrate and wherein a protective element transparent to
light transmitted by the optical fiber covers a region including
the photoelectric conversion element on one surface of the support
substrate and one end of the optical fiber. The second bonding
element covers all or a part of the region where the first bonding
element exists. The first bonding element is constituted by an
ultraviolet-setting adhesive, and the second bonding element is
constituted by thermosetting resin. The support substrate is
secured in a case made of plastic having a guide for guiding the
optical fiber. The case is filled with the protective element to
cover the support substrate, photoelectric conversion element,
optical fiber and the like. The case is closed with a cap made of
plastic and is secured on the support substrate with an adhesive.
The protective element is constituted by any of silicone gel,
silicone rubber, low-stress epoxy resin, acrylic resin and urethane
resin. For example, it is constituted by silicone gel. With this
configuration, bubbles in sizes equal to or greater than one half
of the distance between the two points of the groove in contact
with the circumferential surface of the optical fiber are not
present in the region defined by the optical fiber and groove and
the region between one end face of the optical fiber and the
semiconductor laser chip.
[0226] This configuration is characterized by the preliminary
securing and final securing referred to as "first securing" and
"second securing", respectively. In a certain limited aspect, it
may be stated that the optical fiber is secured on the support
substrate using first and second securing techniques (means) having
different securing speeds and that the securing speed of the first
securing means is higher than that of the second securing
means.
[0227] Such a photoelectronic device is manufactured according to
the following method.
[0228] The method comprises the steps of:
[0229] providing a support substrate having a photoelectric
conversion element mounted thereon and having a groove for guiding
an optical fiber extending toward the photoelectric conversion
element;
[0230] applying an ultraviolet-setting adhesive to a part of the
groove on the support substrate, fitting one end of the optical
fiber in the groove on the support substrate and adjusting optical
coupling between the photoelectric conversion element and optical
fiber with the groove under the optical fiber filled with the
ultraviolet-setting adhesive;
[0231] preliminary securing the optical fiber on the support
substrate by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it; and
[0232] covering a part of the optical fiber and support substrate
with thermosetting resin and setting the thermosetting resin to
finally secure the optical fiber on the support substrate.
[0233] Specifically, it is a method of manufacturing a
photoelectronic device comprising:
[0234] a package constituted by a case made of plastic having a
guide for guiding an optical fiber and a cap made of plastic for
closing the case, attached to the case with an adhesive;
[0235] a support substrate secured in the case having a
photoelectric conversion element mounted on one surface thereof and
having a groove for guiding an optical fiber extending toward the
photoelectric conversion element and an optical fiber guided by the
guide into and out of the package, wherein one end of the optical
fiber extending in the package is fitted in the groove on the
support substrate and is secured on the support substrate through
preliminary securing with an ultraviolet-setting adhesive and final
securing with thermosetting resin. The method comprises the steps
of:
[0236] applying the ultraviolet-setting adhesive to a part of the
groove on the support substrate, fitting one end of the optical
fiber in the groove on the support substrate and adjusting optical
coupling between the photoelectric conversion element and optical
fiber with the groove under the optical fiber filled with the
ultraviolet-setting adhesive;
[0237] preliminary securing the optical fiber on the support
substrate by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it;
[0238] covering a part of the optical fiber and support substrate
with thermosetting resin and setting the thermosetting resin to
finally secure the optical fiber on the support substrate; and
[0239] filling the case with a protective element transparent to
light transmitted by the optical fiber before mounting the case,
and setting the same. The protective element is constituted by any
of silicone gel, silicone rubber, low-stress epoxy resin, acrylic
resin or urethane resin. For example, silicone gel is used.
Securing is carried out by determining positions for the
preliminary securing and/or final securing such that all or a part
of the preliminary securing portion is covered by the final
securing portion. The process of setting the thermosetting resin at
the final securing is performed as a batch process.
[0240] A structure may be employed in which an optical fiber is
secured on a support substrate with only a first bonding element.
Specifically, there may be provided a photoelectronic device
comprising a support substrate constituted by a mounting portion
for mounting a photoelectric conversion element on one surface
thereof and a silicon substrate having a groove for guiding an
optical fiber extending toward the mounting portion, a
photoelectric conversion element secured on the mounting portion
and an optical fiber fitted in the groove at one end thereof and
secured on the support substrate at regions excluding the utmost
end thereof, the device having a structure wherein the optical
fiber fitted in the groove is secured with a first bonding element
injected to fill the groove under the optical fiber for securing
the optical fiber on the support substrate and wherein a protective
element transparent to light transmitted by the optical fiber
covers a region including the photoelectric conversion element on
one surface of the support substrate and one end of the optical
fiber. In this case, the first bonding element is constituted by an
ultraviolet-setting adhesive or thermosetting resin.
[0241] (2) In the configuration described in the aspect (1), the
support substrate, photoelectric conversion element and one end of
the optical fiber are covered by a package constituted by
insulating resin formed by molding resin, and the protective
element is provided in the package to block the path of moisture
that enters the photoelectric conversion element from the outside
of the package.
[0242] Such a photoelectronic device is manufactured using the
following method.
[0243] It is a method for manufacturing a photoelectronic device
comprising:
[0244] a package made of insulating resin;
[0245] a support portion located in the package;
[0246] a support substrate secured to the support portion having a
photoelectric conversion element mounted on one surface thereof and
having a groove for guiding an optical fiber extending toward the
photoelectric conversion element;
[0247] a photoelectric conversion element mounted on the support
substrate; and
[0248] an optical fiber fitted in the groove on the support
substrate and guided by a guide or a ferrule having a sleeve with
one end thereof in a face-to-face relationship with the
photoelectric conversion element and the other end thereof located
outside the package and protected by a jacket, wherein one end of
the optical fiber extending in the package is fitted in the groove
on the support substrate and is secured on the support substrate
through preliminary securing with an ultraviolet-setting adhesive
and final securing with thermosetting resin, the method comprising
the steps of:
[0249] providing the support substrate on which a lead frame having
the support portion thereon and the photoelectric conversion
element are secured;
[0250] securing the support substrate to the support portion on the
lead frame;
[0251] applying the ultraviolet-setting adhesive to a part of the
groove on the support substrate, fitting one end of the optical
fiber protected by the jacket and guided by a guide or a ferrule
having a sleeve in the groove on the support substrate and
adjusting optical coupling between the photoelectric conversion
element and optical fiber with the groove under the optical fiber
filled with the ultraviolet-setting adhesive;
[0252] preliminary securing the optical fiber on the support
substrate by irradiating the ultraviolet-setting adhesive with
ultraviolet light to set it;
[0253] covering a part of the optical fiber and support substrate
with the thermosetting resin and setting the thermosetting resin to
finally secure the optical fiber on the support substrate;
[0254] connecting wiring on the support substrate and leads on the
lead frame with conductive wires before or after securing the
optical fiber on the support substrate;
[0255] covering a region including the photoelectric conversion
element, one end of the optical fiber, the wires and the region of
the leads connected to the wires with a protective element
transparent to light transmitted by the optical fiber;
[0256] molding a region including the jacket or the sleeve halfway
with insulating resin to form the package; and
[0257] cutting and removing an unnecessary part of the lead frame
protruding from the package.
[0258] (3) In the configuration according to the aspect (1) or (2),
securing is performed such that a part of the preliminary securing
portion is covered by the final securing portion and such that the
final securing portion is located at the side of the preliminary
securing portion farther from the photoelectric conversion
element.
[0259] (4) In the configuration according to any of the aspects (1)
through (3), a bubble generation preventing portion is provided in
the form of a recess or groove extending across the groove in a
region between one end of the optical fiber secured with the first
bonding element and the photoelectric conversion element. The
length of the bubble generation preventing portion is 50 .mu.m or
more in the direction of the groove.
[0260] The following method is used for such a photoelectronic
device. There is provided a support substrate having a
photoelectric conversion element mounted on one surface thereof, a
groove for guiding an optical fiber extending toward the
photoelectric conversion element, and a bubble generation
preventing portion constituted by a recess or groove extending
across the groove, provided in a region close to an end of the
optical fiber on a side of a securing portion utilizing a bonding
element. Thereafter, optical coupling between the optical fiber and
photoelectric conversion element is adjusted, and the optical fiber
is preliminary secured to the groove excluding the region of the
bubble generation preventing portion using an ultraviolet-setting
adhesive.
[0261] (5) In the configuration according to the aspect (4), the
utmost end of one end of the optical fiber is located above the
bubble generation preventing portion.
[0262] (6) In the configuration according to the aspect (5), the
utmost end face of one end of the optical fiber is as close as
several hundred .mu.m to an edge of the bubble generation
preventing portion.
[0263] (7) In the configuration according to the aspect (4), one
end of the optical fiber extends beyond the bubble generation
preventing portion and its utmost end is supported by the
groove.
[0264] According to the aspect (1), (a) while the package is formed
by a case and a cap made of plastic, humidity resistance can be
improved because the case is filled with silicone gel.
[0265] (b) When the optical fiber is fitted in the groove on the
silicon platform (support substrate), a space is defined by the
groove under the optical fiber. This space is filled with the
ultraviolet-setting adhesive in the present embodiment. Therefore,
the silicone gel does not enter the region under the optical fiber
associated with the preliminary securing portion when the case is
filled with the silicone gel before sealing with the cap, and no
bubble is caused by the setting and contraction of the silicone
gel. This makes it possible to prevent any reduction in the
strength and reliability of the securing of the optical fiber 3
attributable to bubbles and to prevent problems such as freezing of
moisture trapped by bubbles.
[0266] Specifically, even if moisture enters from the outside along
the optical fiber, since the gap between the optical fiber and
groove at the preliminary securing portion is filled with the
ultraviolet-setting adhesive for preliminary securing, the invasion
of moisture is prevented at the preliminary securing portion, and
there is no nucleus like a bubble in the silicone gel that can trap
moisture. This prevents trapping of moisture to improve humidity
resistance and eliminates the possibility of freezing of moisture
during use at a low temperature.
[0267] In the structure in which the optical fiber is secured on
the support substrate using only a first bonding element
constituted by an ultraviolet-setting adhesive or thermosetting
resin, since the groove under the optical fiber is filled with the
first bonding element, the silicone gel does not enter the groove
region under the optical fiber, and this also prevents the
generation of bubbles attributable to the setting and contraction
of the silicone gel.
[0268] Further, only a small amount of silicone gel enters the
groove under the end portion of the optical fiber because the end
portion protruding from the region secured using the first bonding
element is as short as several hundred .mu.m, and a region open to
the atmosphere exists ahead the end of the optical fiber. Thus, the
silicone gel moves when it sets and contracts, which suppresses the
generation of bubbles. This not only prevents the generation of
bubbles in the silicone gel at the end of the optical fiber and
under the same to eliminate nuclei to trap moisture but also
eliminates bubbles from the gap between the semiconductor laser
chip and optical fiber. This prevents eclipse of laser light
attributable to bubbles to allow optical coupling of the optical
fiber with high efficiency.
[0269] Even if bubbles are generated in the silicone gel in the
groove under the optical fiber, such bubbles have small
diameters.
[0270] (c) After the adjustment of optical coupling, the optical
fiber is preliminary secured to the region of the groove on the
silicon platform with the ultraviolet-setting adhesive and is
thereafter subjected to final securing with the thermosetting
resin. This improves the reliability of optical coupling.
[0271] (d) Since the thermosetting resin has high bonding strength,
the optical fiber is reliably secured to the silicon platform
through the final securing using the thermosetting resin, and the
optical fiber is thus secured with improved reliability. The
optical fiber is secured at the preliminary securing portion such
that the optical coupling between the optical fiber and the
semiconductor laser chip is not deteriorated, and the final
securing portion improves the securing strength of the optical
fiber.
[0272] (e) Since preliminary and final securing is carried out as
in (c) and (d) above, the optical fiber is secured on the silicon
platform with high optical coupling and high reliability of
coupling.
[0273] (f) When the optical fiber is secured in the groove on the
silicon platform, the optical fiber is pressed against the silicon
platform after optical coupling between the semiconductor laser
chip and optical fiber is adjusted, and the optical fiber is
preliminary secured in such a state by applying the
ultraviolet-setting adhesive and irradiating the
ultraviolet-setting adhesive with ultraviolet light to set it. This
makes it possible to reduce the time required for the preliminary
securing to several tens seconds.
[0274] (g) Since the preliminary securing using the
ultraviolet-setting adhesive provides high securing reliability in
a short term, the optical coupling between the optical fiber and
semiconductor laser chip is not deteriorated during the time
interval before the subsequent final securing. Therefore, when the
optical fiber is finally secured with the thermosetting resin
(epoxy resin) thereafter, the thermosetting process following the
application of the thermosetting resin can be carried out on a
batch process basis. This makes it possible to improve the
efficiency of the operation of securing the optical fiber, thereby
achieving a reduction in the manufacturing cost of the
photoelectronic device.
[0275] (h) The preliminary securing using the ultraviolet-setting
adhesive is carried out on a fiber inserting apparatus for aligning
the optical axes of the semiconductor laser chip and optical fiber.
Since the time for the preliminary securing of the optical fiber is
reduced (to several tens seconds), the operating efficiency of the
fiber inserting apparatus can be improved.
[0276] (i) Since a fiber inserting apparatus is expensive, improved
operating efficiency of a fiber inserting apparatus results in a
reduction of the manufacturing cost of the photoelectronic
device.
[0277] In the aspect (2) described above, there is the following
effect in addition to the effects according to the aspect (1). In
this aspect, it is possible to achieve high productivity and to
reduce the manufacturing cost of a photoelectronic device because
the package is formed by molding insulating resin.
[0278] In the aspect (3) described above, there is the following
effect in addition to the effects according to the aspects (1) and
(2). In this aspect, since securing is performed such that the
final securing portion covers a part of the preliminary securing
portion and such that the final securing portion is located at the
side of the preliminary securing portion which is farther from the
photoelectric conversion element, even if the thermosetting resin
for the final securing operation undesirably flows during the
application of the same, it does not flow toward the photoelectric
conversion element beyond the edge of the ultraviolet-setting
adhesive. Thus, the thermosetting resin will not reduce light
transmitted and received between the optical fiber and
photoelectric conversion element.
[0279] In the aspect (4) described above, since the bubble
generation preventing portion in the form of a recess or groove
extending across the groove is provided between the region of the
optical fiber unsecured with the first bonding element at one end
thereof and the photoelectric conversion element, the bubble
generation preventing portion which is an open region exists in the
region of the groove directly under the optical fiber on both sides
of the optical fiber. This results in movement of silicone gel in
the groove when it sets and contracts and thereby prevents the
generation of bubbles.
[0280] In the aspect (5) described above, since the utmost end of
one end of the optical fiber is located above the bubble generation
preventing portion, the bubble generation preventing portion which
is an open region exists in the region of the groove directly under
the optical fiber on both sides of the optical fiber. This results
in movement of silicone gel in the groove when it sets and
contracts and thereby prevents the generation of bubbles.
[0281] In the aspect (6) described above, since the utmost end of
one end of the optical fiber is located above the bubble generation
preventing portion and is aligned with or as close as several
hundred .mu.m to an edge of the bubble generation preventing
portion, no bubble is generated directly under the optical fiber
and at the end of the optical fiber.
[0282] In the aspect (7) described above, since one end of the
optical fiber extends beyond the bubble generation preventing
portion and its utmost end is supported by the groove, the optical
coupling factor between the optical fiber and semiconductor laser
chip is improved.
[0283] The effects achieved in typical aspects of the invention
disclosed here can be briefly summarized as follows.
[0284] (1) Since the package is formed by a case and a cap which
are both made of inexpensive plastic, the manufacturing cost of
semiconductor optical module (photoelectronic device) can be
reduced.
[0285] (2) Although the package is made of plastic, the case is
filled with silicone gel to cover and protect the semiconductor
laser chip, optical fiber, light-receiving element, silicon
platform and the like. It is therefore possible to improve humidity
resistance.
[0286] (3) Although a space is defined by the groove on the silicon
platform under the optical fiber when the optical fiber is fitted
in the groove, this space is filled by the ultraviolet-setting
adhesive forming the preliminary securing portion. Therefore,
silicone gel does not enter the region under the optical fiber
associated with the preliminary securing portion when the case is
filled with the silicone gel before sealing with the cap and,
therefore, no bubble is generated in silicone gel. This makes it
possible to prevent any reduction in the strength and reliability
of the securing of the optical fiber attributable to bubbles and to
prevent problems such as reduction of humidity resistance
attributable to bubbles and freezing of moisture trapped by
bubbles.
[0287] (4) After the adjustment of optical coupling, the optical
fiber is preliminary secured to the region of the groove on the
silicon platform with an ultraviolet-setting adhesive and is
thereafter subjected to final securing with thermosetting resin,
which improves the reliability of optical coupling.
[0288] (5) The optical fiber is secured using a fiber inserting
apparatus while adjusting optical coupling. Once the preliminary
securing with an ultraviolet-setting adhesive is completed, the
silicon platform may thereafter be removed from the fiber inserting
apparatus to allow the final securing with thermosetting resin to
be carried out in a different location. This makes it possible to
improve the operating efficiency of a fiber inserting
apparatus.
[0289] (6) The baking process that follows the final securing with
thermosetting resin can be carried out on a batch process basis
after the application of the thermosetting resin because
preliminary securing is completed. This improves operability and
consequently reduces the manufacturing cost of a photoelectronic
device.
[0290] (7) With a structure in which the package is formed by
molding insulating resin, productivity of the package can be
improved to allow a reduction in the manufacturing cost of a
photoelectronic device.
* * * * *