JP2001015773A - Optical element carrier and its mounting structure - Google Patents

Abstract

(57) [Problem] To provide an optical element carrier suitable for mounting an optical element such as a surface light emitting / receiving element, excellent in mass productivity, miniaturizable, and excellent in high frequency characteristics, and a mounting structure thereof. An optical element carrier (C) having an optical element (2) disposed on a base (1), wherein the base (1) has an optical element arrangement surface (A1) on which the optical element (2) is disposed, and an optical element arrangement surface (1). A first inclined surface A which is an obtuse angle with respect to the installation surface A1 and is a lower surface side when the base 1 is erected.
2, a rear surface A4 opposed to the optical element mounting surface A1, a second inclined surface A3 which forms an obtuse angle with respect to the rear surface A4 and is a lower surface side when the base 1 is erected, and an optical element mounting surface. A1 and back A4
Between the optical element mounting surface A1 and the first inclined surface A2, and between the optical element mounting surface A1 and the through hole H. And a region extending to the second slope A3 through the back surface A4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element carrier used in an optical fiber communication system or a private optical communication system (optical LAN) and a mounting structure thereof, and more particularly to an optical element using a surface emitting element or a surface light receiving element as an optical element. About.

[0002]

2. Description of the Related Art In recent years, practical use of optical fiber communication has started in the field of CATV and public communication. 2. Description of the Related Art Hitherto, high-speed and high-reliability optical semiconductor modules have been realized in a module structure called a coaxial type or a dual-inline type, and these have already been put to practical use mainly in an area called a trunk system.

On the other hand, recently, Si (silicon)
On the substrate (also called Si platform)
2. Description of the Related Art Optical modules using technology for positioning and mounting an optical semiconductor element and a fiber with high accuracy only by mechanical accuracy have been actively developed. These are intended to be put to practical use mainly in an area called an access system, and are required to be reduced in size, height, cost, and the like.

Hereinafter, a conventional photodiode mounting structure will be described.

FIG. 6 shows a base 41 for mounting a photodiode. The base 41 has electrode pads 411 and 412 for an anode and a cathode of a photodiode formed at least on any two adjacent surfaces.
Each electrode pad is electrically connected at the boundary between the surfaces.

FIG. 7 shows a typical example in which a PIN type photodiode 2 is mounted on the submount 41. Although the photodiode 2 varies depending on the application, in this example, it is about 500 μm square, about 200 μm in thickness, and about 200 μm in light receiving diameter.
φ, and electrode pads 21 and 22 are formed on the light receiving surface and the opposite surface (back surface), respectively. The photodiode 2 is connected and fixed with AuSn solder or the like on the electrode pad 411 with the light receiving surface facing upward, and is electrically connected to the back electrode 22. Also, the electrode pad 412 and the light receiving surface electrode 21
Are electrically connected by wire bonds 31.

FIGS. 8 (a) to 8 (c) show that the base 41 has a PI.
An example in which the base 41 is mounted on the Si substrate S after mounting the N-type photodiode 2 is shown. The PIN photodiode 2 is connected so that its light receiving surface is perpendicular to the main surface of the Si substrate S. Thereby, the optical fiber (not shown) mounted in parallel with the main surface of the Si substrate S and the photodiode 2 are optically connected. Wiring for supplying power to the photodiode 2 is performed by wire bonding from the electrode pad on a surface different from the mounting surface of the photodiode 2 to the Si substrate S.

Here, the base 41 is generally formed by patterning electrode pads on each surface by printing using a paste containing filler on a ceramic body such as alumina.

A method of directly mounting a photodiode on a Si substrate without using the above-described base on the Si substrate has also been proposed (for example, see Japanese Patent Application Laid-Open No. 8-94887). In this proposal, a slope is formed in an optical fiber mounting groove on a Si substrate so as to face an optical fiber output end when mounting an optical fiber, and a photodiode is mounted on the slope. is there. Here, the electrode on the lower surface of the photodiode is brought into direct contact with the electrode formed on the slope, and the electrode on the upper surface of the photodiode is made by wiring.

Further, the photodiode is placed on a Si substrate with the light receiving surface of the photodiode facing down, and the 90 ° optical path is changed by a total reflection surface formed in a part of the optical path groove formed below the light receiving surface. A method has also been proposed in which light emitted from an optical fiber is guided to a light receiving surface (for example, see Japanese Patent Application Laid-Open No. 9-54228).

[0011]

However, in the above mounting structure, the accuracy of relative positioning of the two patterns depends on the mechanical accuracy of the outer shape in the formation of the electrode pads on the base. There was a problem. That is, the minimum line width of the electrode pad and the pad interval are each 70 μm.
m was the limit. For this reason, the parasitic capacitance of the electrode is increased, and there is a problem that the high-frequency characteristics are restricted and the entire base is increased in size.

In pattern formation on two or more surfaces, it is necessary to handle and align the bases one by one when forming the next pattern after pattern formation on the first surface is completed. There is a problem that productivity is remarkably poor, and that the smaller the size is, the more difficult it is to handle and the more the productivity is deteriorated.
Conventionally, the size limit is about 2 mm square,
Further miniaturization was difficult.

As described above, since there is a trade-off between size and cost, conventionally, there is a problem that the cost is extremely high due to the miniaturization and high performance of the base. There was a physical limit to high performance and high performance.

In the mounting structure, since the wiring surfaces are not on the same plane, the process becomes extremely complicated,
Since it is necessary to pattern the electrodes on the slope of the Si substrate, there is a problem that the process becomes complicated. Furthermore, the degree of freedom of the inclination angle of the slope is limited by the electrode fabrication process on the slope and the workability of wiring, and the light receiving sensitivity of the photodiode and the tolerance of the mounting alignment accuracy are received almost perpendicular to the optical path. There is also a problem that it becomes smaller than the case.

Also, depending on the mounting structure, as in the above-described mounting structure, it is inevitable that the process of forming an electrode in the groove becomes complicated and that the light receiving sensitivity is reduced.

Accordingly, the present invention has been proposed in view of the above-mentioned conventional problems, and is particularly suitable for mounting an optical element such as a surface light emitting / receiving element, and has excellent mass productivity, can be reduced in size, and has high frequency characteristics. An object is to provide an excellent optical element carrier and a mounting structure thereof.

[0017]

In order to achieve the above object, an optical element carrier according to the present invention is an optical element carrier having an optical element arranged on a base, wherein the base is an optical element carrier. An optical element disposition surface on which is disposed, a first inclined surface that forms an obtuse angle with respect to the optical element disposition surface and becomes a lower surface side when the base is erected,
A rear surface facing the optical element disposition surface, a second inclined surface that forms an obtuse angle with respect to the rear surface and becomes a lower surface side when the base is erected,
A through hole formed between the optical element mounting surface and the back surface, wherein a driving conductor of the optical element extends from the optical element mounting surface to the first inclined surface; It is characterized in that it is formed in a region extending from the back surface through the hole to the second slope.

The optical element carrier mounting structure of the present invention is an optical element carrier mounting structure in which the optical element carrier is fixed on a substrate on which two conductor patterns for driving the optical element are formed. A concave portion having two slopes each having a part of each of the two conductor patterns formed on the substrate, and aligning the first and second slopes of the optical element carrier with the two slopes of the concave portion; The driving conductor and the conductor pattern of the concave portion are connected to each other.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the optical element carrier and the mounting structure thereof according to the present invention will be described in detail with reference to the drawings.

In FIG. 1A, an optical fiber 5 as an optical waveguide and an optical element 2 such as a surface light emitting element or a surface light receiving element to be optically coupled thereto are provided on a substrate S made of silicon single crystal or the like. FIG. 1B is a plan view of an optical module M provided with an optical element carrier C, and FIG.
FIG. 4 is an enlarged view of a portion B of FIG.

Here, the first electrode pattern 3 and the second electrode pattern 4, which are two conductor patterns for driving the optical element 2, are formed on the substrate S. The concave portion 7 is provided on the substrate S in the mounting area Sa.
Slopes 7a and 7b are formed with high precision by anisotropic etching using an alkaline solution or the like (for example, if the substrate S is a silicon single crystal, the main surface is a (100) plane or the like) The slopes are (111) planes and the like.) On the two slopes 7a and 7b, a part of each of the first electrode pattern 3 and the second electrode pattern 4 is formed. In the recess 7, a driving conductor described later of the optical element 2 is connected to a conductor pattern of the recess 7, so that the optical element 2 can be driven.

As shown in FIG. 2 and FIG. 3, the optical element carrier C has a base 1 on which an optical element 2 is disposed and which forms a flat optical element mounting surface A1 and an optical element mounting surface A1. A first inclined surface A2 that forms an obtuse angle θ and is a lower surface side when the base 1 is erected.
A back surface A4 facing the optical element disposition surface A1, and a back surface A4
And a through hole H formed between the optical element disposing surface A1 and the back surface A4, the second inclined surface A3 being the lower surface side when the base 1 is erected at an obtuse angle θ with respect to The electrode pads 12 and 13 which are the driving conductors of the element 2 are disposed on the optical element arrangement surface
The electrode pad 11 is formed in a region extending from the first to the first inclined surface A2, and the electrode pad 11, 15, 14 extends from the optical element disposing surface A1 through the through hole H to the second inclined surface A3 via the back surface A4. Is formed. If the conductive pattern formed in the recessed portion 7 of the substrate S and the drive conductor of the optical element 2 can be conducted well, the drive conductor formed on the base 1 is not necessarily the first slope A2 and the second slope A2. It is not necessary to form the entire slope A3.

Here, the obtuse angle θ is set to 100 ° to 170 °. The reason for this is that if the angle is smaller than 100 °, the electrodes are formed solid, and good mechanical matching cannot be obtained. On the other hand, if it is larger than 170 °, it becomes difficult to form electrodes.

Specifically, electrode pads 11 and 12 are electrode pads for element connection, 13 and 14 are electrode pads for external lead-out, and 15 and 16 are electrode pads 11 for element connection and electrode pad 14 for external lead-out, respectively. Wiring patterns and through-hole conductors. Here, for convenience of explanation, 1
1, 16, 15, and 13 are called first electrode wirings, and 12, 13 are called second electrode wirings.

The optical element carrier C shown in FIG.
However, a light receiving element such as an avalanche photodiode can also be used. The optical element 2 is connected to the electrode pad 11 on the back electrode 22 side with the light receiving surface facing up. A for this connection
uSn solder or the like is used. The electrode 21 on the light receiving surface side of the optical element 2 and the electrode pad 12 are connected to the bonding wire 3.
1 connected.

Next, details of the characteristic shape, material, and dimensions of each part of the optical element carrier C will be described. The first electrode wiring is connected from the electrode pad 12 in the optical element mounting surface A1 to the electrode pad 13 on the first inclined surface A2 adjacent to this surface. On the other hand, the second electrode wiring is connected to the back surface A4 at a distance L5 from the electrode pad 11 in the optical element mounting surface A1.
Is connected through a through-hole conductor 16 to the electrode pad 14 on the second inclined surface A3 adjacent to the back surface A4. Electrode pads 13 and 1
4 are formed on the entire surfaces of the first inclined surface 2 and the second inclined surface A3 which form an obtuse angle θ with the optical element disposition surfaces A1 and the back surface A4, respectively, and their widths L2 and L3 are smaller than the distance L5. Opposed at a distance (L5> L2 · sin (π−θ)
+ L3 · sin (π-θ)). That is, the first inclined surface A
2. The second inclined surface A3 is included in one surface layer region of the optical element disposition surface A1 and the back surface A4, and can be regarded as a planar process region on each of these planes.

As a result, the fine pattern of the electrode can be formed on the opposing planes A1 and A4, so that the pattern can be formed using the high precision planar technology, as shown in FIGS. 5 (a) to 5 (g). As described above, it is possible to manufacture a very large amount from a single substrate with a small size.

Further, since the electrode pads 13 and 14 can be formed entirely on the inclined surface, there is no particular need for processing accuracy in pattern formation on the inclined surface. Since the electrode pads 12 and 13 and 14 and 15 are in contact at an obtuse angle, disconnection due to insufficient coverage of the electrode layer at the connection portion can be prevented.

Further, by eliminating the need for wiring for the electrical connection between the optical element carrier C and the substrate S, an increase or variation in the capacitance of the wiring can be suppressed as much as possible, whereby the light receiving sensitivity and reliability are excellent. An optical element carrier can be provided.

Further, by setting L1 <L4, the rolling direction of the optical element carrier C is restricted, and the planes A1 to A
Since the rotation is suppressed only in the direction in which the ground 4 is grounded, workability during mounting is extremely good.

As the material of the base 1, ceramics such as alumina, glass and aluminum nitride, sapphire, quartz and the like are preferable. Since these materials have a small dielectric loss tangent, loss at high frequencies is small and is preferable. Among them, ceramics are excellent in workability of through holes and can be said to be suitable for the present invention. In particular, glass ceramic is the most suitable since it has the lowest dielectric constant and can reduce the capacitance of the entire optical element carrier.

The material of the conductor such as an electrode is preferably tungsten or copper, and the thickness of the electrode is about 10 μm.

Hereinafter, an example of a method for manufacturing the optical element carrier will be described.

First, alumina, glass, a binder, a solvent, and others are mixed in a ball mill to form a raw material mixture called raw. Next, it is processed into a sheet by passing it through a narrow gap called a doctor blade on the conveyor belt, and immediately thereafter, it is subjected to infrared drying to obtain a raw tape as shown in FIG. The substrate material 20 before sintering, called “sintering”, is produced.

Next, as shown in FIG. 5B, a through hole 20a for positioning is formed in the raw tape by punching, and as shown in FIG. 5C, the through hole 20a is aligned with the through hole 20a.
A large number of U-shaped grooves 22 are formed using a rotary blade.

Thereafter, as shown in FIG.
Tungsten metallized paste is printed in a desired pattern on the region including the mold-shaped groove 22, and as shown in FIG. 5E, a large number of through holes 24 are formed with the U-shaped groove 22 interposed therebetween. As shown in FIG. 5F, metallization of the through hole 24 is performed.

Finally, as shown in FIG. 5 (g), the raw tape is punched into a desired shape, sintered, and the electrodes are plated to complete the optical element carrier base.

Although it depends on the width of the tape, about 10,000 optical element carrier bases can be manufactured in one process.

Instead of punching out the final shape before sintering, the final shape can be cut out after sintering. In this case, one PIN-type photodiode is mounted on a chip on each of the optical element carriers on the ceramic substrate and wiring is performed at one location, and each step is repeated a plurality of times, and a plurality of photodiodes are mounted. The formed substrate is formed. As a result, the productivity of mounting an optical element on an optical element carrier can be significantly improved.

Thereafter, the substrate on which the photodiodes are mounted is cut, a plurality of optical element carriers on which the photodiodes are mounted are taken out, and a mounter capable of rotating the elements by 90 ° so that the light receiving surface is perpendicular to the ground. And mounted on the substrate S.

[0041]

Next, more specific examples will be described.

First, the base 1 was made of alumina ceramic having a dielectric constant of 9.0. The outer shape of the base is as shown in FIG. 2, where L1 = 0.6 mm, L2 = 0.14 mm, L3 =
0.14 mm, L4 = 0.9 mm, L5 = 0.6 mm,
The depth (L1 + L2) was designed to be about 0.7 mm.

The size of the electrode pad 11 on which the optical element is mounted is 0.5 mm square, which is almost the same as the size of the PIN photodiode 2. The electrode pad 12 is the electrode pad 11
, And the electrode width was 0.15 mm. The diameter of the through-hole conductor 16 was 0.2 mmφ. Also,
The electrode layer is made of an Au metallized film having a total thickness of about 2 μm and a part of the electrode pad 11 is made of Au having a total thickness of 2 μm.
Sn solder was used.

An optical element carrier is manufactured by transferring an electrode pattern and a through-hole electrode to a ceramic powder formed into a sheet with a binder and sintering at a high temperature to form an electrode pattern on both surfaces. About 10,000 optical element carrier bases were formed in a 10 cm square ceramic substrate.

Next, one PIN-type photodiode is mounted on each of the optical element carrier bases on the ceramic substrate, and wiring is performed at one location, and each step is repeated a plurality of times by the number of times. A substrate on which a plurality of photodiodes were mounted was formed. As a result, the productivity of mounting the optical element on the optical element carrier base has been significantly improved.

Thereafter, the substrate on which the photodiode was mounted was cut from the groove for braking, and a plurality of optical element carriers on which the photodiode was mounted were taken out. Then, the elements were aligned using a mounter capable of rotating the elements by 90 ° so that the light receiving surface was perpendicular to the ground, and mounted on the substrate S.

Since the substrate S was manufactured by the ceramic injection mold, the relative positional relationship between the optical fiber and the groove for mounting each of the optical element carriers could be set to an accuracy within 30 μm. Thereby, good optical coupling between the optical fiber and the optical element was obtained.

Further, a photodiode preamplifier was mounted on the substrate S. As a result, the wiring length to the optical element carrier can be shortened to about 1 mm, and the wiring capacitance to the photodiode (the capacitance between the electrode pads 11 and 12) is reduced to 0.05 pF by using a small optical element carrier.
It could be suppressed below.

[0049]

According to the optical element carrier and its mounting structure of the present invention, the following remarkable effects can be obtained.

The optical element carrier can be mass-produced from one flat substrate, and the mass productivity is extremely good.

It can be performed in a batch process, and there is no complicated operation such as handling during the manufacturing process.

The optical element can be mounted in the state of the substrate or in the aligned state after the end of the process (braking), and the workability of the mounting is improved. The downsizing is easy, and the downsizing is easy. Since the whole capacity is reduced, it is suitable for high-speed operation.

Since there is no need for wiring from the optical element carrier, there is an effect of greatly reducing the electric capacity, and it is suitable for high-speed operation and the mounting efficiency is improved.

In the inclined arrangement of the light receiving surface used for suppressing the reflection on the light receiving surface of the optical element, the inclination angle can be designed to have a high degree of freedom, so that it is possible to achieve low reflection and good light receiving sensitivity. .

With the above-described effects, it is possible to provide an optical element carrier having a low cost, a small size, an excellent high-frequency characteristic and a remarkably improved mass productivity, and a mounting structure thereof.

[Brief description of the drawings]

FIG. 1 is a view for explaining a mounting structure (optical module) of an optical element carrier according to the present invention, wherein (a) is a plan view,
(B) is a sectional view taken along line AA in (a).

FIG. 2 is a perspective view showing an optical element carrier base according to the present invention.

FIG. 3 is a perspective view showing an optical element carrier according to the present invention.

FIG. 4 is an enlarged view of a portion B in FIG. 1 (b).

FIGS. 5A to 5G are diagrams illustrating a method for manufacturing an optical element carrier according to the present invention, wherein FIGS.

FIG. 6 is a perspective view showing a conventional optical element carrier base.

FIG. 7 is a perspective view showing a conventional optical element carrier.

8A and 8B are diagrams illustrating an example in which a conventional optical element carrier is mounted on a substrate, wherein FIG.
(B) is a plan view, and (c) is a partial cross-sectional view on a side surface.

[Explanation of symbols]

 1: base 2: optical element (photodiode) 3: first electrode pattern (first conductor pattern) 4: second electrode pattern (second conductor pattern) 5: optical fiber (optical waveguide) 11 to 15: electrode Pad (driving conductor) 16: Through-hole conductor 21: Light receiving surface side electrode 22: Back surface electrode A1: Optical element mounting surface A2: First inclined surface A3: Second inclined surface A4: Back surface C: Optical element carrier H: Through Hall M: Optical module S: Substrate

Claims (2)

[Claims] 1. An optical element carrier comprising an optical element provided on a base, wherein the base has an optical element mounting surface on which the optical element is mounted, and an optical element mounting surface provided on the optical element mounting surface. A first inclined surface that forms an obtuse angle and becomes a lower surface side when the base is erected, a back surface facing the optical element disposition surface, and an obtuse angle with respect to the back surface, and the base is erected. A second inclined surface which is a lower surface side in the case of
An optical element having a through hole formed between the optical element mounting surface and the rear surface, wherein a driving conductor of the optical element extends from the optical element mounting surface to the first inclined surface; From the element mounting surface through the through hole to the second
An optical element carrier formed in a region reaching a slope. 2. The mounting structure of an optical element carrier according to claim 1, wherein the optical element carrier according to claim 1 is fixed on a substrate on which two conductor patterns for driving an optical element are formed. A concave portion having two inclined surfaces on which a part of each of the two conductor patterns is formed, and
A mounting structure for an optical element carrier, wherein the first and second slopes of the optical element carrier are aligned with two slopes, and the driving conductor of the optical element is connected to the conductor pattern of the recess.