JP3257776B2 - Optical module mounting structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of an optical module used for an optical information communication device or the like.

[0002]

2. Description of the Related Art For the development of high-speed and large-capacity information communication devices and massively parallel computers that perform parallel processing among a large number of processors, the development of parallel optical interconnection modules for high-speed and high-density communication in the devices has been active. Is being done. In such a parallel optical interconnection module, a multi-mode is adopted as a fiber interface for transmitting a relatively short distance of several hundred meters or less and reducing module cost by eliminating complicated optical coupling. . For this reason, a film formed from a polymer optical waveguide that can easily form a multimode is used as an optical wiring for connecting an optical device such as a VCSEL to an optical fiber (for example, YS Liu et. .Al.,
“High Density Optical Int
erconnects for Board and and
Backplane Applications
ing VCSELs and Polymer Wa
veguides "; Proc. 47th ECTC
pp. 391-398 (1997)). Since the optical module is not fixed between the optical device and the film optical wiring, even if the optical module is positioned at room temperature and is subjected to a temperature load during the operation of the optical module or during a reliability test, the film optical wiring is not fixed. Due to the difference in the coefficient of thermal expansion between the constituting polymer and the ceramic constituting the substrate (about 10 times the polymer is larger), the film optical wiring is displaced and the optical coupling loss increases, and the optical module characteristics May deteriorate. Therefore, there has been proposed a structure in which a flexible film optical wiring and an optical device are fixed with bumps made of solder or the like, and then the optical device is die-bonded onto a substrate (Japanese Patent Application No. 10-157328). This structure is shown in FIG.
Shown in In the figure, 10 is a bump, 11 is a film optical wiring,
12 is an optical waveguide core, 13 is a mirror surface, 14 is an optical device, 15 is an optical connector, 16 is an optical fiber, 17 is a substrate, 18 is an active part of the optical device 14, and 19 is a die bonding part. In this structure, the film optical wiring 11 and the optical device 14 are fixed by the bumps 10 made of solder or the like, and a flexible film optical wiring 11 is used. ,
When the film optical wiring 11 buckles, the fixed state between the optical device 14 and the film optical wiring 11 does not change, so that the displacement can be suppressed.

[0003]

However, in the optical module mounting structure shown in FIG.
There is a gap between the optical device 14 and the optical device 14, and there is a danger that the active portion 18 of the optical device 14 is exposed to dust, moisture, or the like. There is a problem that the connection strength between them may be insufficient.

The present invention has been made in view of the above circumstances, and the active portion of an optical device is exposed to dust and moisture by filling the gap between the film optical wiring and the optical device with an adhesive. In addition, an object of the present invention is to provide an optical module mounting structure in which the reliability is improved even when the number of bumps is small because the connection strength between the film optical wiring and the optical device is increased.

[0005]

In order to achieve the above object, an optical module mounting structure according to the present invention is characterized in that an optical waveguide core through which an optical signal propagates has an optical waveguide cladding layer having a smaller refractive index than the optical waveguide core. Are formed in the optical waveguide core, and further in the propagation direction of the optical signal propagating through the optical waveguide core,
A film optical wiring having an oblique surface formed at an arbitrary position at an angle at which the optical signal is totally reflected or at an angle of 45 degrees, and light receiving or transmitting the optical signal reflected or reflected at the oblique surface In the optical module mounting structure having at least a device, the optical device is configured to receive an optical signal emitted from the optical device at a position for receiving the propagation light of the optical waveguide core reflected on the oblique surface of the film optical wiring or the optical signal. The optical device and the film optical wiring, which are fixed to the film optical wiring surface using one or more bumps at positions where the light is reflected by the oblique surface and propagated to the optical waveguide core, and are formed via the bumps. gap between a refractive index 1
Characterized in that it is filled with an adhesive having a predetermined value ranging from the refractive index of the optical waveguide cladding layer to the refractive index of the optical waveguide cladding layer.

Further, according to the present invention, in the above optical module mounting structure, the adhesive filling the void formed between the film optical wiring and the optical device via the bump is provided in an active portion of the optical device, and The gap is filled so as to surround a space including a portion where the active portion is projected on the film optical wiring surface facing the active portion.

Further, the present invention is characterized in that in the optical module mounting structure, the film optical wiring is made of a polymer having flexibility.

Further, the present invention is characterized in that in the optical module mounting structure, the adhesive is made of an ultraviolet curable material.

According to the optical module mounting structure of the present invention, since the gap between the film optical wiring and the optical device is filled with the adhesive, the active portion of the optical device is not exposed to dust or moisture. Further, since the connection strength between the film optical wiring and the optical device is increased, there is an advantage that the reliability is improved even when the number of bumps is small.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view (xz plane) showing an embodiment of the present invention, and FIG. 2 is a sectional view (xy plane) taken along the line AA 'of FIG. In the figure, 10 is a bump, 11
Is a film optical wiring, 12 is an optical waveguide core, 13 is a mirror surface, 14 is an optical device, 15 is an optical connector, 16 is an optical fiber, 17 is a substrate, 18 is an active portion of the optical device 14,
20 is an adhesive.

In FIG. 1 and FIG.
1 is formed as follows. For example, a lower cladding layer made of, for example, fluorinated polyimide and having a thickness of 37.5 μm, a 50 μm square optical waveguide core 12 (for example, a relative refractive index difference) is formed on a Si wafer (not shown) by spin coating, curing, or reactive ion etching. 1.2%), and an upper clad layer having a thickness of 37.5 μm is formed in the same manner as the lower clad layer. Next, a circular pad made of Ti / Pt / Au having a diameter of 35 μm is formed on the surface of the fluorinated polyimide optical waveguide film by sputtering or etching, for example, so as to be positioned at each corner of a square.
Four linear markers having a width of, for example, 10 μm are formed at positions (not shown) at the same time on the optical waveguide core 12.
Is formed at right angles to the longitudinal direction. Next, the fluorinated polyimide optical waveguide film is formed by peeling off the Si substrate with, for example, hydrofluoric acid, and fixed to, for example, an adhesive sheet (not shown). Next, for the fluorinated polyimide optical waveguide film, from the surface on which the circular pad is not formed, a mirror surface 13 having a 45-degree angle is formed by, for example, dicing in the above-described straight line marker, and further, By cutting the end of the optical waveguide core 12 at 90 degrees and cutting it into a desired size, the film optical wiring 1
1 is completed.

Next, a diameter 40 made of, for example, Au / Sn
After aligning four optical devices 14 having four bumps 10 made of, for example, spherical solder at intervals of μm and 120 μm at each corner of a square, to four circular pads of the film optical wiring 11, the bumps 10 are formed. The optical device 14 and the film optical wiring 11 are connected via the. in this case,
Due to the self-alignment effect of the bumps 10 made of solder, the optical device 14 can be aligned and fixed with the film optical wiring 11 with an accuracy of 1 μm or less (within the xy plane).

Next, the back surface of the optical device 14 is
After die bonding with the substrate 17 made of N by, for example, Sn / Pb solder, the end of the optical waveguide core 12 cut at 90 degrees is fixed in the optical connector 15 fixed to the substrate 17, and a micro nozzle (not shown) Through
An adhesive 20 having a certain refractive index between 1 and the refractive index of the cladding of the film optical wiring 11 and having a loss of, for example, 20 dB / cm or less with respect to the wavelength of the transmission signal,
After filling the gap between the optical device 14 and the film optical wiring 11, it is cured by irradiating, for example, ultraviolet rays. Finally, the optical fiber 16 is inserted into the optical connector 15 to complete the first optical module mounting structure of the present invention as shown in FIG. FIG. 2 is an xy plane sectioned along the line AA 'in FIG.
This shows that the adhesive 20 is filled between the film optical wiring 11 and the optical device 14. The active part 18
Is covered with the adhesive 20.

FIG. 3 is a cross-sectional view (x-z plane) showing another embodiment of the present invention, and FIG. 4 is a cross-sectional view (xy plane) along the line BB 'in FIG. In the figure, 10 is a bump, 11
Is a film optical wiring, 12 is an optical waveguide core, 13 is a mirror surface, 14 is an optical device, 15 is an optical connector, 16 is an optical fiber, 17 is a substrate, 18 is an active portion of the optical device 14,
20 'is an adhesive.

In FIGS. 3 and 4, the film optical wiring 1 is shown.
1 is formed as follows. For example, a lower cladding layer made of, for example, fluorinated polyimide and having a thickness of 37.5 μm, a 50 μm square optical waveguide core 12 (for example, a relative refractive index difference) is formed on a Si wafer (not shown) by spin coating, curing, or reactive ion etching. 1.2%), and an upper clad layer having a thickness of 37.5 μm is formed in the same manner as the lower clad layer. Next, a circular pad made of Ti / Pt / Au having a diameter of 35 μm is formed on the surface of the fluorinated polyimide optical waveguide film by sputtering or etching, for example, so as to be positioned at each corner of a square.
Four linear markers having a width of, for example, 10 μm are formed at positions (not shown) at the same time on the optical waveguide core 12.
Is formed at right angles to the longitudinal direction. Next, the fluorinated polyimide optical waveguide film is formed by peeling off the Si substrate with, for example, hydrofluoric acid, and fixed to, for example, an adhesive sheet (not shown). Next, for the fluorinated polyimide optical waveguide film, from the surface on which the circular pad is not formed, a mirror surface 13 having a 45-degree angle is formed by, for example, dicing in the above-described straight line marker, and further, By cutting the end of the optical waveguide core 12 at 90 degrees and cutting it into a desired size, the film optical wiring 1
1 is completed.

Next, for example, a diameter 40 of Au / Sn
After aligning four optical devices 14 having four bumps 10 made of, for example, spherical solder at intervals of μm and 120 μm at each corner of a square, to four circular pads of the film optical wiring 11, the bumps 10 are formed. The optical device 14 and the film optical wiring 11 are connected via the. in this case,
Due to the self-alignment effect of the bumps 10 made of solder, the optical device 14 can be aligned and fixed with the film optical wiring 11 with an accuracy of 1 μm or less (within the xy plane).

Next, the back surface of the optical device 14 is
After die bonding with the substrate 17 made of N by, for example, Sn / Pb solder, the end of the optical waveguide core 12 cut at 90 degrees is fixed in the optical connector 15 fixed to the substrate 17, and a micro nozzle (not shown) Through
Adhesive 20 'having a certain refractive index between 1 and the refractive index of the cladding of film optical wiring 11 and having a loss of, for example, 20 dB / cm or less with respect to the wavelength of the transmission signal.
Is filled in the gap between the film optical wiring 11 and the optical device 14 while tracing the periphery on the optical device 14, and then cured by irradiating, for example, ultraviolet rays. At this time, it is desirable that the viscosity of the adhesive 20 'is higher. Finally, the optical fiber 16 is inserted into the optical connector 15 to complete the optical module mounting structure according to another embodiment of the present invention as shown in FIG. FIG. 4 is a sectional view taken along the line BB ′ in FIG.
(Face) shows that the adhesive 20 ′ is filled between the film optical wiring 11 and the optical device 14 except for the periphery of the active portion 18 of the optical device 14.

Although not shown in the figure, the bonding state of the film optical wiring 11 surface facing the optical device 14 is the same, except for the film optical wiring 11 surface on which the active portion 18 of the optical device 14 is projected. The adhesive 20 'is filled. With such a structure, when, for example, a VCSEL is used as the optical device 14, a gap is maintained between the active portion 18 and the surface of the film optical wiring 11 that projects the active portion 18, and therefore, the reflectance in the active portion 18 of the VCSEL is maintained. Does not change due to the refractive index of the adhesive 20 '.

In each of the above embodiments, the mirror surface is not limited to an angle of 45 degrees, but may be an angle at which an optical signal is totally reflected. The material of the film optical wiring 11 is not limited to fluorinated polyimide, but a flexible polymer material such as silicone resin or epoxy resin can be used. The curing of the adhesive is not limited to ultraviolet rays, and may be thermal curing or the like.
Although not limited to B / cm or less, a smaller one is desirable. In addition,
In the other embodiments shown in FIGS. 3 and 4, the refractive index and the loss of the adhesive are not particularly specified. further,
The adhesive, in addition to the gap between the film optical wiring and the optical device, may surround the optical device, that is, surround the periphery in the thickness direction of the optical device, and may even contact the substrate surface. . Also, the portion where the film optical wiring is connected to the optical connector is not limited to one end. For example, each side of the film optical wiring is fixed by the optical connector, and the mirror surface or the solder is placed at an arbitrary position in the film optical wiring surface. An optical device fixed by a bump may be arranged, and a gap between the film optical wiring and the optical device may be filled with an adhesive. The medium connected to the film optical wiring via the optical connector is not limited to an optical fiber, but may be another film optical wiring. The method of forming the film optical wiring is not limited to the above method. For example, the polymer sheet formed by casting may be irradiated with ultraviolet rays or the like to form the optical waveguide core. Further, the optical waveguide is not limited to the multimode, but may be a single mode. Further, the bump material is not limited to Au / Sn solder, but may be Sn / Pb solder, Sn / Ag solder, polymer beads made of, for example, polystyrene, or Au bumps, and the shape of the bump is not limited to a sphere but may be an ellipse. It goes without saying that a shape or a square shape does not depart from the invention.

[0021]

As described above in detail, when the optical module mounting structure of the present invention is used, the gap between the film optical wiring and the optical device is filled with the adhesive, so that the active portion of the optical device can be formed. No exposure to dust or moisture. Further, since the connection strength between the film optical wiring and the optical device increases, the reliability improves even when the number of bumps is small. Moreover, since the adhesive takes a certain value between 1 and the refractive index of the cladding of the film optical wiring,
The reflection between the optical device and the film optical wiring can be suppressed.
Further, in a structure in which the adhesive is filled except for the space created by the active portion of the optical device and the film optical wiring surface that projects the active portion, when a VCSEL is used as the optical device, for example, the reflectance in the active portion is reduced by the adhesive. Since there is no change due to the refractive index, there is also an advantage that it is not necessary to change the film configuration of the active portion according to the adhesive.

[Brief description of the drawings]

FIG. 1 is a sectional view (xz plane) showing an optical module mounting structure according to an embodiment of the present invention.

FIG. 2 is a sectional view (xy plane) taken along line AA ′ of FIG.

FIG. 3 is a sectional view (xz plane) showing an optical module mounting structure according to another embodiment of the present invention.

FIG. 4 is a sectional view (xy plane) taken along line BB ′ of FIG. 3;

FIG. 5 is a cross-sectional view illustrating a conventional optical module mounting structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bump 11 Film optical wiring 12 Optical waveguide core 13 Mirror surface 14 Optical device 15 Optical connector 16 Optical fiber 17 Substrate 18 Active part of optical device 19 Die bonding part 20 Adhesive 20 'Adhesive

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Suzuko Ishizawa 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-6-222230 (JP, A) JP-A-3-290606 (JP, A) JP-A-8-21930 (JP, A) JP-A-3-265804 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6 / 42 G02B 6/12

Claims (4)

(57) [Claims] An optical waveguide core through which an optical signal propagates is formed in an optical waveguide cladding layer having a smaller refractive index than the optical waveguide core, and further, the optical signal propagates through the optical waveguide core. A film optical wiring in which an oblique surface is formed at an arbitrary position at an angle at which the optical signal is totally reflected or at an angle of 45 degrees with respect to the direction, and the optical signal reflected or reflected by the oblique surface is An optical module mounting structure having at least a receiving or transmitting optical device, wherein the optical device emits light from the optical device at a position for receiving the propagation light of the optical waveguide core reflected on the oblique surface of the film optical wiring or from the optical device. The optical signal is reflected by the oblique surface,
A position between the optical device and the film optical wiring, which is fixed to the film optical wiring surface using one or more bumps at a position where the light propagates to the optical waveguide core, and is formed via the bumps. Wherein the gap is filled with an adhesive having a predetermined value between 1 and the refractive index of the cladding layer of the optical waveguide. 2. The optical module mounting structure according to claim 1, wherein the adhesive filling the gap formed between the film optical wiring and the optical device via the bump comprises: an active portion of the optical device; And an optical module mounting structure, wherein the space is filled so as to surround a space including a portion where the active portion is projected on the film optical wiring surface facing the active portion. 3. The optical module mounting structure according to claim 1, wherein said film optical wiring is made of a polymer having flexibility. 4. The optical module mounting structure according to claim 1, wherein the adhesive is made of an ultraviolet curing material.