JP2000098192A - Optical reception module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely fix an optical fiber while allowing the passage of light by filling a translucent resin adhesive only in the portion which is an optical path and fixing the optical fiber by a fixing resin adhesive. SOLUTION: Two stages of V-grooves 34, 35 are formed by developing a resist and by etching having anisotropy. The first V-groove 34 is broader and deeper and the second V-groove 35 is narrower and shallower. An inclining reflection surface 37 may be formed at the terminal of the second V-groove 35. Next, a spacing groove 36 is formed perpendicularly to the V-grooves 34, 35. The optical fiber is placed in the first V-groove 34 and is positioned in such a manner that the front end comes into contact with a front surface 38. The translucent resin is potted around the front end of the optical fiber, the spacing groove 36 and a PD chip. Further, the fixing resin having the excellent adhesiveness is applied near the optical fiber and the first V-groove 34, by which the optical fiber is fixed to an Si substrate. In such a case, the light emitted from the optical fiber is passed through the second V-groove 35 and is reflected by the inclining reflection surface 37 and is made incident on a photodetecting element chip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat mounting type receiving module used for optical communication. The term “planar mounting” is described. In a conventional optical receiving module, a PD is fixed to a stem, an optical fiber is supported above the PD so as to be perpendicular to the stem surface, and a lens is provided in the middle. The light from the optical fiber is focused by a condenser lens and vertically incident on the upper surface of the PD. The rays are perpendicular to the stem or PD plane.
Since there is a considerable spatial distance between the fiber and the PD and the light spreads, a lens is required to prevent this. It is a vertically long cylindrical shape and has an unwieldy shape in which the optical fiber protrudes from the top of the cylinder. When mounting on a printed circuit board, it is necessary to fix the module with pins and then lay it down. When many printed boards are stacked, the pitch is 9 mm, but the board thickness and the element thickness must be 9 mm or less. The conventional cylindrical vertically long light receiving module cannot meet such a demand.

[0002] Planar mount modules are the opposite concept of such bulky vertical modules. An optical fiber in which the incident direction of the optical fiber is parallel to the substrate surface and has no lens is called a planar mounting type. Since the optical fiber creeps on a plane, it is mounted on a plane. Since the optical fiber is parallel to the substrate surface, a cylindrical package is no longer necessary. Optical fiber or P on a flat substrate
D can be fixed to form a flat package. Further, since the optical fiber and the PD are brought close to each other so as not to propagate in free space, no lens is required. If a lens is not required, not only the material cost can be reduced, but also the alignment work can be omitted and the assembly cost can be reduced. This is convenient because it has a flat shape and does not take a height when mounted on a printed circuit board. Therefore, in order to further reduce the cost of the optical module, a planar mounting type is strongly desired.

In a surface mount module, a condenser lens is not used for optical coupling. Optical fiber and light emitting element (LD, L
ED) or a light receiving element (PD) is opposingly approached and directly optically coupled. For this reason, the dimensional accuracy of mounting becomes more severe. Several devices have been proposed for fixing the optical fiber and the light emitting element or the light receiving element with high accuracy. However, none of the proposals has been widely implemented.

[0004]

2. Description of the Related Art An optical receiving module often proposed as a planar mounting type optical module is one in which a structure is formed on a Si substrate to fix an optical fiber and a PD. A V-groove is formed in a Si substrate using anisotropic etching of a Si single crystal, an optical fiber is fixed here, and light emitted from an end face of the optical fiber is bent at a substantially right angle to be incident on a light receiving element mounted on the Si surface. Let it. Here, the etching anisotropy is {100}
The etching rate of the {111} plane differs from that of the {111} plane, and the former is significantly faster than the latter. An etchant exhibiting such anisotropy is known.

A resist is applied to the (100) plane Si single crystal, a stripe-shaped window is opened in the [011] direction, and anisotropic etching is performed with an appropriate etchant to obtain [011].
A V-groove consisting of the (1-11) plane and the (11-1) plane extending in the [1] direction is formed. Since the etching rate by the anisotropic etchant is high on the {100} plane and low on the {111} plane, such a V-groove is formed. A further advantage is that the (111) plane is exposed at the end of the V-groove. The angle between the surface (100) and the surfaces (1-11) and (11-1) of the V-groove is 126 °. The base angle of the V groove is 72 °.
Termination surface (111) and V groove both surfaces (1-11), (11-
The angle with 1) is 108 °. The angle between the terminal surface (111) and the surface is 126 °. Not 135 °.

Here, [...] indicates an individual direction, and <...> indicates a comprehensive direction. (...) indicates an individual plane, and ｛...｝ indicates a comprehensive plane. Although the above description is for the [011] stripe, a similar V-groove can be produced for a stripe having the [0 ± 1 ± 1] orientation. Since the Si substrate is electrically conductive as it is, the surface is oxidized to a thickness of about 1 μm to several μm to form SiO ₂ . Alternatively, an SiO ₂ film is deposited by sputtering. Most are single crystal Si, but the surface is insulating SiO ₂ . Therefore, the Si substrate is a SiO ₂ / Si substrate in detail. For simplicity, it is simply referred to as a Si substrate hereinafter.

When manufacturing a surface mount type module,
An optical fiber is fitted into this V-groove and fixed. PD fixed at the upper part by reflecting light at the (111) plane at the end of the groove
Light is incident on. As a result, a planar mounting type module that does not require a lens and has an optical fiber parallel to the surface can be obtained.

[0008] The basic structure of the planar mounting type module is as described above. A number of proposals have been made for the planar mounting type. However, each has some difficulties and has not yet been widely implemented. Surface mount PD
Three structures will be described for the main known technologies relating to modules. [Conventional Structure 1: Fiber Insertion Structure Directly Below PD (FIGS. 1 to 4)] German Patent Publication DE 35 43 558 C2 (1)
Filed on December 10, 985) Inventors Hillary Bernd, Rohdemann Fred B. HILLERICH & A. GEYER, "SELF-ALIGNED FLAT-PACK
FIBER-PHOTODIODE COUPLING ", Electronics Lett. Vol.
24, No. 15, 1988, p918-919,

A V-groove is formed in a Si substrate by anisotropic etching. A light receiving element (PD) is mounted on the end of the V groove. The optical fiber is inserted just below the PD in the V groove, and the optical fiber is fixed with an adhesive having a refractive index substantially the same as that of the optical fiber. The feature is that the tip of the optical fiber enters just below the light receiving element. This structure will be described with reference to FIGS. 1 is a cross-sectional view of a completed state, FIG. 2 is a plan view of a V-groove portion, FIG. 3 is a plan view of a state where an optical fiber is attached to the V-groove, and FIG. 4 is a state where a PD chip and an optical fiber are fixed. It is a top view.

A resist is applied to the (100) plane Si substrate 1, a stripe window in the [011] direction is opened by exposure and development using a mask, and etching is performed using an anisotropic etchant. V consisting of (1-11) and (11-1) planes
Groove 2 is formed. An inclined reflecting surface 4 which is a (111) plane is generated at the end of the V groove 2. The PD chip 5 is positioned and fixed directly above the inclined reflecting surface 4. Wire the wires. The tip of the optical fiber 3 is inserted under the PD chip 5, and the tip is applied to the inclined reflecting surface 4. The optical fiber 3 is put in the V groove. An adhesive 7 is applied to the optical fiber 3 and the V groove 2. Once the adhesive has dried, it is ready.

The V-groove needs to be dug considerably deeply. This is because the optical fiber is completely buried. The depth of the V groove is W,
Assuming that a half of the base angle is φ and the diameter of the optical fiber is D, it is necessary that W> D (1 + cosec φ) / 2 (1). Since the base angle of the V groove is 72 °, W
> D (1 + cosec 36 °) /2=1.35D. For example, if D = 125 μm, W is 16
Deeper than 9 μm. If the V-groove is a perfect {111} plane,
A simple relationship between depth W and width B

B = 2 W tan φ = 2 W tan 36１ = 1.45 W (2) Therefore, the width B of this V groove is 245
μm or more. The lateral positioning of the optical fiber is naturally done by the V-groove. The axial positioning of the optical fiber is accurately performed by the inclined reflecting surface. That is, the optical fiber does not need to be aligned. This is an advantage. Since the distance from the tip of the optical fiber to the PD chip is extremely short, the beam does not spread. The PD chip 5 is stably fixed to the U-shaped portion on the upper surface of the V groove. The structure is simple. This is also an advantage. It is sufficient that the PD is accurately positioned.

However, this structure has two disadvantages.
One is that the tip of the optical fiber 3 is sunk under the PD 5 so that the tip cannot be seen. Therefore, it is not known whether the tip is in contact with the inclined reflecting surface 4. The wraparound state of the adhesive cannot be observed.

The other is that the adhesive 7 does not flow to the V groove portion under the PD. An optical fiber is inserted into a narrow hole formed by the PD and the V-groove, and then an adhesive is applied. For example, if W = 1.35D, the cross-sectional area of the hole surrounded by the V-groove and the PD is about 1.7 times the cross-sectional area of the optical fiber.
However, since the optical fiber is inserted, the effective area is only 0.7 times the cross-sectional area of the optical fiber. The adhesive is difficult to enter because of such a small width. If the adhesive does not cover the tip of the optical fiber, a void 8 is formed in the hole as shown in FIG.
The adhesive has the same refractive index as that of the optical fiber and also has a function of preventing light of the optical fiber from being reflected at the end face. If the air gap 8 is generated, there is a loss due to end face reflection. In air, the beam spreads out. The reflection loss on the back surface of the chip also increases. As shown in FIG. 1, if bubbles are formed in the adhesive even if there is no gap 8, scattering and reflection loss by the bubbles occur. Such losses can occur if the adhesive does not completely fill the holes. Because of the PD, the fiber tip cannot be seen, so it is not known whether the adhesive has filled the hole. [Conventional structure 2: Two-board bonding structure (FIGS. 5 and 6)]

This is a structure proposed in Japanese Patent Publication No. 63-22565. An optical fiber and a PD are attached to two substrates and cannot be mounted on a single substrate, and are attached to each other. This will be described with reference to FIGS. FIG.
FIG. 3 is a perspective view of a first Si substrate. First parallel V-shaped grooves 12, 13 extending in the [011] direction are provided on the (100) Si substrate 11 by anisotropic etching. At the same time, the transverse groove 14 is formed in the [0-11] direction orthogonal to the above. The bottom of the lateral groove 14 is deeper than the bottom of the two parallel V grooves 12 and 13.
At the same time, anisotropic etching is performed, but since the depth is too short, the (100) plane seems to remain on the bottom surface of the lateral groove 14. The facing surface of the lateral groove 14 is a (111) plane. This becomes the reflection surface 15. Optical fiber 1 in V-grooves 12 and 13
6 and 17 are inserted, and the tip is brought into contact with the inclined reflecting surface 15. In this state, the optical fiber is fixed with an adhesive. Light emitted from the optical fiber is reflected by the inclined reflecting surface 15 to become upward light beams 23 and 24.

The PD cannot be fixed because the lateral groove 14 extends laterally. Therefore, the second Si substrate 18 is used. This is a complicated Si substrate 18 having an L-shaped cross section. Two holes are made, and two PDs 19 and 20 are embedded in the holes. This PD is a p-electrode, n
The electrodes are both on the upper surface and are connected to a metallized pattern (not shown) by wire bonding. 2nd Si
The back surface 21 of the first Si substrate 11 is
Is applied to the inner surface of the horizontal piece 22 of the second Si substrate 18,
The substrates 11 and 18 are overlapped and bonded. Rays 23, 2
4 is incident on the PDs 19 and 20.

In the case of this structure, the depth W of the groove must be W> (D / 2) (cosec φ + 1) (3) since the optical fiber is sunk below the substrate surface. The lateral groove 14 is a groove deeper than this.

This does not plug the optical fiber under the PD. Work with the end of the optical fiber clearly visible. Axial alignment (applied to the inclined reflecting surface 15) and adhesion are easy. Further, the lateral groove 14 can be filled with an adhesive, and the tip of the optical fiber can be completely covered with the adhesive. There are no problems such as uneven adhesion of the adhesive and irregular reflection in the air gap. Further, it is convenient to attach a plurality of PDs and optical fibers. They are advantages.

However, the lateral groove 14 is wide and the PD cannot be supported on three sides. It is of course impossible to do such an unstable operation as supporting the PD in a cantilever manner. That is, the PD cannot be supported by the same substrate as the optical fiber.
The second substrate 18 is indispensable for supporting the PD.
Then, the alignment between the two substrates must be performed. Since one of the substrates is turned upside down and bonded, it is extremely difficult to perform positioning. P on the second Si substrate 18
The D position, the position of the lateral groove on the first substrate, and the like also cause errors. If these are out of order, it is not possible to find the optimum position only by the timely alignment between the two substrates.

The structure is more complicated than that. Since a PD and an optical fiber are attached to two Si substrates, respectively, and they are combined, the surface mounting can no longer be called. It is not practical because the production cost increases. [Conventional structure 3: Two-stage V-groove structure (FIGS. 7 to 9)]

A two-stage V-groove structure light receiving module is disclosed in
No. 54228. A light receiving module having a two-stage V-groove structure will be described with reference to FIGS. 7 is a longitudinal sectional view, FIG. 8 is a plan view, and FIG. 9 is a sectional view taken along a line crossing a V groove.

A large first V-groove 26 and a subsequent smaller second V-groove 27 are simultaneously formed in the (100) Si substrate 25 by anisotropic etching. In each case, the V-groove extending in the [011] direction has a common center line. The surface of the V groove is (1
-11) and (11-1) planes. Since the depth is different, an inclined surface 28 is formed in the middle. A small inclined reflecting surface 29 is formed at the end of the second V-shaped groove 27. This is also the (111) plane. The optical fiber 30 is fitted into the first V groove 26. It is fixed at a position where the tip hits the inclined surface 28. The PD chip 32 is fixed to a portion corresponding to the second V groove 27. Optical fiber 30
Light passing through the second V-groove 27 is reflected upward by the inclined reflecting surface 29. Then, the light enters the PD chip 32 from below.

The optical fiber 30 is partially exposed on the first V groove 26. The depth W of the first V groove is W <D (1 + cosec
φ) / 2 = D (1 + cosec 36 °) /2=1.35D
(4). For example, if D = 125 μm, W is shallower than 169 μm. But the beam is second
I have to go through the V-groove 27

W> (D / 2) cosec φ = (D / 2) cosec 36 ゜ = 0.85D (5) That is, the depth W of the first V-groove is (D / 2) cosec φ <W <(D / 2) (cosec φ + 1) (6), but when φ = 36 °, W is 0.85D to 1 .3
Between 5D. Since the tip of the optical fiber hits the inclined surface 28, the depth U of the second V-groove is

U <W− (D / 2) (cosec 36 ゜ −1) = W−0.35D (7) The beam emitted from the optical fiber is the second
To pass through the V groove,

U> W− (D / 2) cosec 36 ゜ = W−0.85D (8) In other words, the depth V of the second V-groove is W- (D / 2) cosec φ <U <W- (D / 2) (cosec φ-1) (9) In this case, U is W-0.85D ~ W-0.35
It is necessary to be between D.

The advantages of this structure will be described. First, the tip of the optical fiber 30 does not go under the PD 32. Since the tip is visible, the fixed state of the optical fiber can be observed. The optical fiber can be easily fixed. The space between the tip of the optical fiber and the lower part of the PD can be filled with the resin. There is no resin and no light is reflected or scattered. The two-step groove can be carved by a single anisotropic etching.

[0028]

However, all three structures introduced as prior art have drawbacks. In [Conventional structure 1 (fiber insertion structure directly under PD)], an optical fiber is inserted to a position below a light receiving element. There is a disadvantage that the resin does not sufficiently flow into the narrow hole below the light receiving element. If the adhesive does not completely cover the tip of the optical fiber, it will be reflected at the boundary between air, the optical fiber and the adhesive. If there are bubbles in the optical path, irregular reflection occurs, causing a loss of light quantity. Further, as pointed out as a disadvantage in Japanese Patent Application Laid-Open No. 9-54228, there is a problem that the tip of the optical fiber cannot be seen.
In the case of [Conventional structure 2 (two-substrate bonding structure)], the PD cannot be attached to the same substrate because the lateral groove extends laterally, resulting in two substrates. It is difficult to align the optical fiber side substrate and the PD side substrate. It becomes a thick structure instead of a flat type. The structure is complicated and difficult to manufacture. Increases cost. [Conventional structure 3 (two-stage V
Groove structure)] does not have sufficient consideration for the type of adhesive. The adhesive is primarily for fixing the optical fiber to the substrate. But that's not all. Since the adhesive fills the space between the optical fiber and the PD, it must be transparent. It is translucent. In addition, it is desirable that the optical fiber has a refractive index close to the refractive index (1.46) of the optical fiber. Otherwise, reflection occurs at the optical fiber-adhesive interface. Therefore, the two-step V-groove structure is used for fixing the optical fiber and filling the optical path by applying a light-transmitting adhesive to the entire surface of the optical fiber.
However, the translucent resin has low adhesive strength. Even after drying, the member is soft and can move slightly. To permanently fix the optical fiber and the substrate, it is desirable to use a stronger adhesive. However, the adhesive having strong adhesiveness is opaque and cannot be used between the optical fiber and the PD. Therefore, this proposal has a problem with the adhesive and cannot be used for many years.

As described above, in the conventional example, it is difficult to appropriately use two kinds of resins having different purposes.

A first object of the present invention is to provide a surface mount type light receiving module which can securely fix an optical fiber while passing light by using two kinds of resins having different properties.
Is the purpose. It is a second object of the present invention to provide a surface mount type optical receiving module which can be spatially separated so that two kinds of resins having different properties are not mixed. A third object is to provide an inexpensive resin-molded light receiving module.

[0031]

An optical receiving module according to the present invention comprises a substrate, a deeper first V-groove formed on the substrate, and a gap groove provided on the substrate perpendicular to the first V-groove. A second V-groove, which is formed on the substrate so as to be opposed to the first V-groove via a gap groove and has a common axis and is shallower than the first V-groove, an upwardly inclined reflecting surface formed at the end of the second V-groove A PD chip fixed on the upper end of the end of the second V groove;
An optical fiber inserted into the first V-groove, the end face of which contacts the front surface of the gap groove;
It consists of a translucent resin filling the lower surface of the D chip, a fixing resin for fixing most of the optical fibers to the substrate, and a resin mold package which is entirely covered and cured.

In the present invention, the optical fiber fixing V-groove (first V
Groove), a reflection mirror part (optical path conversion part: second V groove),
A trench (gap groove) for partitioning these is provided. One of the reason for interposing the gap groove is for positioning the optical fiber. Another role is to separate the two kinds of adhesives (light-transmitting resin and fixing resin) so as not to mix. The optical path is filled with the translucent resin using the gap groove. Further, a fixing resin is filled from above to serve also for fixing the optical fiber. By forming these three elements (the first V groove, the second V groove, and the gap groove) on one Si substrate, a high degree of positional accuracy is secured.

The resin will be described. As the translucent resin, a silicon-based soft transparent resin is suitable. Since it is soft, stress on the end face of the light receiving element or the optical fiber is small. In particular, the positional relationship between the light receiving element and the optical fiber is not greatly changed by expansion and contraction due to temperature change. This resin is
It is cured by ultraviolet light or temperature heating, but does not completely solidify, maintains a gelatinous state, and does not stress surrounding components. The silicon-based translucent resin also has a refractive index close to that of an optical fiber, plays a role as a matching oil, and has almost no absorption in the communication wavelength band of 1300 nm to 1600 nm. The prior arts which have been introduced so far emphasize translucency, so that a translucent resin is used for the entire surface.

However, translucent resin is not enough to fix the optical fiber in the V-groove. The curing may not be complete and the optical fiber may shift. The advantage of the translucent resin is a disadvantage for the purpose of fixing the optical fiber. Therefore, the present invention uses a completely cured resin which is not a translucent resin for fixing the optical fiber. The fixing resin is represented here.
As long as the fixing resin can support the optical fiber firmly,
Optical properties such as transparency and refractive index identity are not required. Since the main purpose is to fix firmly and securely, for example, an epoxy resin is used as the fixing resin.

The use of two kinds of resins is one of the novel features of the present invention. However, if only two types of resins are allowed to flow, the boundaries are not determined and are mixed with each other, and the fixed resin may block the optical path connecting the optical fiber and the PD. The present invention of course has provisions for such problems. This is the point that the gap groove is provided orthogonally between the two types of V-grooves.

The gap groove also has the function of stopping and positioning the tip of the optical fiber. In addition, it has the function of providing a clear space for potting the translucent adhesive. The gap groove of the present invention is different from the lateral groove of FIG. If it ends in a lateral groove, the PD chip cannot be fixed there. In the present invention, since the thinner second V-groove is cut, three surfaces (U-shaped surfaces) for supporting the PD chip can be secured. The PD can be fixed on the same substrate, as shown in FIGS.
No single substrate is required. 7 to 9 have a two-stage V-groove but no gap groove. Two types of resins cannot be spatially separated.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical receiving module according to the present invention will be described with reference to FIGS. FIG. 10 is a partial perspective view of only the optical fiber fixing portion. FIG. 11 is a cross-sectional view of the groove. FIG. 12 is a longitudinal sectional view of the groove.

An Si substrate 33 having an orientation (100) is used as a base material. Si is conductive as it is
An O ₂ film is formed on the surface. Si by sputtering
Attach an O ₂ film or make a film by oxidation. The film thickness is 1μ
m to several μm is sufficient. A photoresist is applied to the Si substrate 33 and exposed through a mask to form a stripe window in the [011] direction. The resist is developed and two steps of V-grooves 34 and 35 are formed in the [011] direction by anisotropic etching. The first V-groove 34 is wider and deeper, and the second V-groove is narrower and shallower. An inclined reflection surface 37 is formed at the end of the second V groove. The second V-groove 35 and the inclined reflecting surface 37 are collectively referred to as an optical path changing unit. The inclined reflecting surface 37 (mirror surface) is, for example, (11
This is the inclined surface of 1). Since the refractive index of Si is high, there is a certain degree of reflectance even with Si. However, it is even better to deposit a metal film to increase the reflectance to near 100%. 1st V
The groove 34, the second V-shaped groove 35, and the inclined reflecting surface 37 can be formed by one-time anisotropic etching.

Next, a gap groove 36 is formed at right angles to the V grooves 34 and 35. If the gap groove 36 has a wall perpendicular to the plane, it cannot be formed by the same anisotropic etching.
The gap groove can be formed by RIE (reactive ion etching) etching capable of obtaining a high aspect ratio. Further, the groove at the bottom of the box type can be cut out mechanically by a dicing saw. The depth of the gap groove is set to be deeper than the first V-groove 34 and the groove of the optical path changing portion (the second V-groove 35).

Although the gap groove has a vertical wall in terms of positioning of the optical fiber, the positioning of the optical fiber is possible even with an oblique wall. If the gap groove of the oblique wall is sufficient, the gap groove can be formed at the same time by the same anisotropic etching as the V groove. The gap groove has a function of accommodating the translucent resin and a function of positioning the optical fiber. The former is preferably a gap groove having a vertical wall, while the latter may be a sloped wall. However, the depth of the gap groove Q
Is desirably deeper than the depth W of the first V-groove 34 and the depth U of the second V-groove 35 (Q>W> U). As shown in FIG.
Optical fiber (core + clad; coating stripped) 40
Are fixed to the first V-groove 34, but a part thereof is exposed on the first V-groove. The optical fiber center is below the substrate surface. V
Assuming that the half of the bottom angle of the groove is φ and the diameter of the optical fiber is D, the depth W of the first V groove is

(D / 2) cosec φ <W <(D / 2) (1 + cosec φ) (10) The groove becomes shallower than the conventional structures 1 and 2. The gap groove 36 is a groove deeper than this. In the case of dicing, the width and depth of the gap groove are irrelevant. Therefore, even if the groove is deep, the width does not increase so much.

From the condition that the depth V of the second V-groove is below the optical fiber core (center) and the condition that it is shallower than the first V-groove, W- (D / 2) cosec φ <U <W (11 ). This is imposed in the range of the depth U of the second V groove.

When using anisotropic etching of the Si substrate, φ = 36 °. (111) plane 37 of the optical path conversion unit
Is 54 °. The slope of the V groove is (1-11),
(11-1) plane. The depth is Q>W> as shown in FIG.
U. The front surface 38 of the gap groove 36 is a portion where the tip of the optical fiber hits. The space between the rear surface 39 and the front surface 38 can be filled with a translucent adhesive. FIGS. 13 and 14 are plan views, in which an optical fiber is placed in the first V-groove 34 so that the front end 38
Position so that it contacts. The order is not as shown in FIG. After that, the optical fiber is attached.
Figures 10, 14 and the like are shown to show stopping at 8. A metal film is deposited on the inclined reflecting surface 37 and the second V-groove 35 near the inclined reflecting surface 37 to enhance the reflectance. The PD chip 42 is fixed immediately above the optical path changing unit. Therefore, a metallized surface is formed on a substrate. The back-illuminated type is suitable for the PD chip. In the case of the back-illuminated type, the n-electrode becomes a ring electrode, from which light enters. The n electrode is bonded to the metallized surface.

The PD chip is, for example, 450 μm square thickness 2
A 00 μm InGaAs PD chip is used. This is soldered to a predetermined position. As shown in FIG. 15, the optical fiber 40 is inserted into the first V-groove 34 and temporarily fixed by a holding jig. Since the tip contacts the gap groove surface 38, accurate positioning can be performed. A translucent resin 43 is potted around the tip of the optical fiber, the gap groove 36 and the PD chip 42.
An adhesive that is transparent and transmits light, and has a refractive index similar to that of an optical fiber. Adhesive strength is inferior but optical properties are prioritized, and a silicone resin adhesive is used. Since there is the gap groove 36, the light-transmitting transparent resin 43 can stay in the gap groove. A light-transmitting resin is required to prevent a gap from being formed in the optical path between the tip of the optical fiber and the PD chip.

However, strong adhesiveness cannot be realized only with the light-transmitting resin. Further, a fixing resin 44 having excellent adhesiveness is applied to the vicinity of the optical fiber and the first V-groove 34 to fix the optical fiber to the Si substrate. The fixing resin may have any optical properties and may be opaque. For example, an epoxy adhesive is used. The fixing resin 44 functions not only to fix the optical fiber but also to protect the translucent resin.
The two types of adhesives are used effectively to satisfy the requirements of adhesive strength and optical function. There was no such device in the prior art.

Referring to FIG. 15, the PD 42 looks unstable, but actually, as shown in FIGS.
Is stable because the bottom is supported by a U-shaped part.

FIG. 16 is an overall plan view of the Si substrate. A V-groove for accommodating the optical fiber is formed at the center in the vertical direction. There is a large V groove 47 at the end of the first V groove 34 described above. This is a groove for attaching a ferrule to an optical fiber and accommodating the ferrule. The optical fiber has a cladding diameter of 125 μm, but the ferrule is much thicker, so a large V groove 47 is required. That portion is a front lower surface 46. The inclined surface 45 is formed by V grooves 47, 3 by anisotropic etching.
This is because 4, 35 and the inclined surface 45 are formed at once. The middle surface 48 only has the first V-groove 34 in the vertical direction.

The rear surface 49 has an optical path changing portion (the second V groove 35,
In addition to the inclined reflecting surface 37), metallizations 50 to 53 are formed by printing or vapor deposition. On the rear surface, in addition to the PD, a metallized surface for extracting electrodes is provided so that an amplifier, a capacitor, and other electronic circuit elements can be attached. The surface of the Si substrate is an oxide film Si
The metallization is covered with O ₂ and is insulated from each other because it is on SiO ₂ . That is, Si is exposed in the portion where the groove is cut. However, since only the optical fiber comes into contact with the groove, there is no problem.

FIG. 17 is an enlarged sectional view of the optical path changing section of FIG. The optical fiber 40 includes a core 57 and a clad 56. The side surface of the second V-shaped groove 35 and the inclined reflecting surface 37 of the optical path changing portion are covered with a metal film. This is to increase the reflectance. In this figure, the tip of the optical fiber is above the bottom of the second V-groove 35, but is still positioned by the front face 38 of the gap groove. Since the V-groove has a base angle of 72 °, the tip of the optical fiber hits the side of the groove. Core 5
Light emitted from the center P of 7 spreads according to the aperture angle. The spread angle Θ is given by cos Θ = n ₁ / n ₀ . n
₁ is the cladding refractive index, and n ₀ is the core refractive index. The spread beams are PQ ₁ , PQ ₂ , and PQ ₃ . Inclined reflective surface 3
The beam is reflected at 7 and enters the back-illuminated type PD.

Since the inclination angle of the inclined reflecting surface 37 is 54 ° instead of 45 °, the beams Q ₁ R ₁ , Q ₂ R ₂ , Q ₃ R ₃
Is not perpendicular to the surface. A slightly backward beam.
These are incident on the PD 42 having a large refractive index, propagate to the upper light receiving section 58, and are sensed there. Since it is not vertically upward, the beam reflected by the PD surface does not return on the same path. If it returns, the optical fiber is reversed and returns to a laser (not shown) as a light source, which has a bad influence on laser oscillation. This is not the case in the present invention because a 54 ° inclined reflecting surface is used. In a conventional cylindrical optical receiving module, the tip of an optical fiber is polished at an angle of 8 ° to prevent reflected light from returning to the laser. This is not necessary in the present invention. Actually, here, the tip of the optical fiber 40 has the inclination (0 inclination).
゜) It is cut correctly.

When near-infrared light (1.55 μm or 1.3 μm) is used for communication light, a PD is placed on an InP substrate and an InG
A light-receiving layer of aAsP or InGaAs is epitaxially grown and a pn junction is created by Zn diffusion. Of course, Si-PDSi-APD can be used depending on the wavelength of the communication light.

FIG. 18 is a perspective view showing a state in which a chip or an optical fiber is attached to a structure such as a V-groove of the Si substrate 33. PD at the end of metallization 50 on the optical path conversion section
42 is soldered. Immediately before that, metallization 5
2, an amplifier IC 59 is soldered. Plate capacitors 61 and 62 are attached to the same metallization 52.
This is also called a die cap. It is inserted to lower the impedance of the power supply and cut off noise. The PD 42 has an n-electrode (cathode) facing downward, which is connected to the metallization 50. The upper p-electrode is connected to the input terminal of amplifier 59 by a wire. The output terminal and the power supply terminal of the amplifier are connected to other metallizations 53 and 51 by wires. The ground is taken from metallization 52. Since the photocurrent of the PD is amplified in the same package, it is hardly affected by external noise.

After the electronic components are soldered by the reflow furnace as described above, the short optical fiber 40 with the ferrule 60 is attached to the Si substrate. An optical fiber clad is placed in the first V-groove 34 and the ferrule 60 is connected to the large V-groove 47.
Put in and support. Thereafter, the optical fiber is fixed using an adhesive. First, a light-transmitting resin is dropped (potted) around the optical fiber tip, the gap groove, and the second V groove. Next, a fixing resin is applied to the ferrule 60 and the optical fiber 40.

FIG. 19 is a partial view of FIG. FIG.
(1) is a plan view of a part to which a PD is attached. The metallization 50 extending from the side of the substrate has a U-shape in the vicinity of the optical path changing portion so as to surround the second V-shaped groove 35.
An electrode pattern 66 is formed on the metallization 50 by vapor deposition, plating (for example, Au-Sn), or the like.
Outside the metallization 50, four alignment marks 67, 68, 69, 70 are provided. The four corner points of the PD 42 are attached so as to match these marks. FIG. 19 (2) shows an optical fiber butting portion.
The light emitted from the optical fiber spreads in the plane direction, but is reflected by the inclined reflection surface 37 and enters the PD. FIG. 19 (3) shows that the light of the optical fiber is reflected upward by the surface 37 and enters the PD. FIG. 19 (4) is a cross-sectional view of a portion crossing the optical fiber, and FIG. 19 (5) is a cross-sectional view of a portion of the second V groove.
Most of the optical fiber sinks into the first V-groove, but some of the upper part is exposed.

When the structure shown in FIG. 18 is completed, the structure is mounted on a lead frame obtained by punching a metal plate, and the pattern and the leads are connected by wires. Furthermore, it is poured into a mold and poured with a fluid resin to be solidified. Cut off the part that is outside the lead. That is, the package is made by resin molding. The conventional cylindrical optical receiving module is hermetically sealed in a metal package, which is costly. The present invention is housed in an inexpensive molded package. This can also reduce costs. One of the features of the present invention is that it is a mold.

FIG. 20 is a perspective view of the device of the present invention after resin molding. FIG. 21 is a cross-sectional view around an optical path changing unit,
FIG. 22 is a longitudinal sectional view, and FIG. 23 is a transverse sectional view around a ferrule portion. The light transmitting resin adhesive 43 covers the light path portion around the light path changing portion. Further, the optical fiber and the ferrule are covered with the fixing resin 44. Further, on the outside, an inexpensive resin 72 covers the whole. On both sides, leads 73, 74,..., 83,. The appearance is almost the same as a normal mold type IC. However, a ferrule 60 for connecting an optical fiber protrudes outside. This is a bit different from an electrical IC.

In the above description, one optical fiber was used. The present invention is also applicable to a plurality of optical receiving modules provided with a plurality of optical fibers and a plurality of PDs. FIG.
4 is a plan view of an Si substrate applied to a triple light receiving module. One common gap groove 87 is carved in the Si substrate 86. At right angles to the three first V-grooves 8
8, 89 and 90 are formed from the end face of the substrate to the middle. The second V-grooves 94 and 9 which are narrower than the gap groove 87
5, 96 are formed. The end is an inclined reflecting surface. That is the optical path conversion unit. As in the previous example, the V-groove can be formed by anisotropic etching. Only the gap grooves may be cut out with a dicing saw. The gap groove can also be formed by directional etching such as RIE. Of course, the V-groove can also be cut by mechanical means.

The PDs 97, 98, 10
0 is fixed. Electronic circuit elements 101, 102,..., 109, etc. are mounted further in front of the PD. These are optional such as an amplifier, a capacitor, and a waveform shaper.
Optical fibers 91, 92, and 93 are embedded in the first V-groove. The optical path conversion section is fixed with a translucent resin, and the entire optical fiber is fixed with a fixing resin. Not only three, but four
Any number of modules such as a series,... In this example, the ferrule does not protrude outside. This is for butt coupling with a tape optical fiber or the like. Of course, the structure may be such that three ferrules protrude as shown in FIG. The combination of ferrules can be freely changed depending on the shape of the optical fiber group to be coupled. Although this shows only the substrate portion, the whole is actually resin-molded as shown in FIG. 20 to obtain a finished product. Because the package is a resin mold, it is much cheaper than a metal can package or a ceramic package.

FIG. 25 shows a five-station embodiment. A gap groove 121 is carved in the Si substrate 120 in the lateral direction, and first V-grooves 122 to 126 are formed perpendicularly to the gap groove 121. As a continuation, the narrower second V-grooves 127 to 131 are inserted into the gap grooves 12.
1 is provided. The end of the second V groove is a (111) inclined reflection surface. A PD array 137 is fixed thereon. An array is used here instead of individually separated PDs. The PD array requires only one alignment. Behind the PD group, electronic circuit components 138, 139, 1
40 is attached. In this case as well, only the portion of the Si substrate is not shown, but the whole is actually molded with resin. At the open end of the optical fiber, a connector of five tape optical fibers 142 is also detachably attached by some means.

[0060]

According to the present invention, the first V-groove (fixing V-groove), the gap groove, and the second V-groove (optical path changing portion) are formed independently on the Si substrate. Since the gap groove is located between the two-step V-grooves, only the portion that becomes the optical path is filled with the translucent resin adhesive, and the optical fiber can be firmly and firmly fixed by the fixing resin adhesive. The gap groove allows spatial separation of the two adhesives. A combination of the translucent resin and the fixing resin can provide a receiving module with good performance. Such a thing does not exist in the conventional optical receiving module.

Since it is a planar mounting type and not a cylindrical package, it can be made 9 mm or less when mounted on a printed circuit board. Since it is a planar mounting type and is molded with resin, the cost is further reduced.

Not only one optical fiber but one PD,
The present invention can be applied to transmission of a plurality of optical fibers such as an optical parallel link connecting a plurality of optical fibers and PDs. As the number of optical fibers and PDs increases, the effect of alignment by V-grooves and fixation by resin are more effective. Production cost,
It is possible to provide a surface mounting type optical receiving module that can reduce both the component cost.

[Brief description of the drawings]

FIG. 1: German Patent DE 35 43 558 C2 and B. Hi
llerich & A. Geyer, "Self-aligned flat-pack fiber-ph
otodiode coupling ", ELECTRONICS LETTERS VOL.24, N
FIG. 2 is a central longitudinal sectional view of an optical receiving module proposed by O.15, P918 (1988).

FIG. 2 is a plan view of a part including a V-groove of the same optical receiving module.

FIG. 3 is a partial plan view of the same optical receiving module with an optical fiber inserted into a V-groove.

FIG. 4 is a partial plan view of the same optical receiving module with a PD attached and an optical fiber inserted into a V-groove.

FIG. 5 is a perspective view of a first substrate of the optical receiving module proposed in Japanese Patent Publication No. 63-22565.

FIG. 6 is a perspective view of a second substrate of the optical receiver module proposed in the same Japanese Patent Publication No. 63-22565.

FIG. 7 is a central longitudinal sectional view of an optical receiving module proposed in Japanese Patent Application Laid-Open No. 9-54228.

FIG. 8 is a partial plan view of an optical receiving module proposed in the same JP-A-9-54228.

FIG. 9 is a cross-sectional view of the same V-groove portion.

FIG. 10 is a perspective view of a portion including a V-groove of the optical receiving module of the present invention.

FIG. 11 is a cross-sectional view of a portion including a V-groove of the optical receiving module of the present invention.

FIG. 12 is a view showing V of a substrate part of the optical receiving module of the present invention.
Sectional drawing of a groove and a gap groove.

FIG. 13 is a partial plan view of the same.

FIG. 14 is a plan view of the same device in which an optical fiber is inserted into a V-groove.

FIG. 15 shows an optical path conversion unit, an optical fiber tip, and a light transmitting resin in the same optical receiving module, in which an optical fiber is attached.
Sectional drawing of the state which adhered the PD part, applied the adhesive of the fixing resin on it, and was hardened.

FIG. 16 is a plan view of a Si substrate of the optical receiving module according to the present invention.

FIG. 17 is an enlarged longitudinal sectional view of an optical path changing unit of the optical receiving module according to the present invention.

FIG. 18 is a perspective view showing a state where a PD chip and an optical fiber are fixed to the optical receiving module of the present invention.

FIG. 19 is a detailed view of each part of the same module. (1) is a plan view of an optical path conversion unit. FIG. 2B is a plan view showing a state where the optical fiber is fixed to the optical path conversion unit. (3) is a longitudinal sectional view of the same. (4) is a cross-sectional view of an optical fiber portion. (5) Second
FIG. 4 is a cross-sectional view of a V-groove portion.

FIG. 20 is a perspective view of an electronic component or an optical fiber mounted on a Si substrate and molded as a whole.

FIG. 21 is a cross-sectional view of a portion including a PD chip of the same optical receiving module.

FIG. 22 is a central longitudinal sectional view of the same optical receiving module.

FIG. 23 is a cross-sectional view of a portion including an optical fiber of the same optical receiving module.

FIG. 24 is a plan view of the Si substrate portion of the optical receiving module of the present invention applied to a case where three optical fibers are provided.

FIG. 25 is a plan view of a Si substrate portion of the optical receiving module of the present invention applied to a case where five optical fibers are connected.

[Explanation of symbols]

 Reference Signs List 1 Si substrate 2 V groove 3 optical fiber 4 inclined reflection surface 5 PD chip 6 light beam 7 adhesive 8 void 11 Si substrate 12, 13 V groove 14 lateral groove 15 inclined reflection surface 16 optical fiber 17 optical fiber 18 cover plate 19 PD chip 20 PD chip 21 Si substrate back surface 22 Side piece 23 reflected light 24 reflected light 25 Si substrate 26 1st V groove 27 2nd V groove 28 inclined surface 29 inclined reflection surface 30 optical fiber 32 PD chip 33 Si substrate 34 first V groove 35 second V groove 36 gap groove 37 inclined reflection surface 38 groove front surface 39 groove rear surface 40 optical fiber 42 PD chip 43 translucent resin 44 fixing resin 45 inclined surface 46 front low surface 47 large V groove 48 middle surface 49 rear surface 50-53 metallized 54 reflective coating 55 reflective coating 56 clad 57 core 58 light receiving part 59 amplifier 60 optical fiber 61 flat plate capacitor 62 flat plate Capacitor 63 steps 64 wires 65 wires 66 AuSn plating pattern 67 to 70 alignment mark 72 mold 73 to 77 lead pin 83 to 85 lead pin 78 bottom plate 79 to 80 wire 86 Si substrate 87 gap groove 88 to 90 first V groove 91 to 93 optical fiber 94 to 96 second V groove 97-98 PD chip 100 PD chip 101-109 electronic circuit component 120Si substrate 121 gap groove 122-126 first V groove 127-131 second V groove 132-136 optical fiber 137PD array 138-140 electronic circuit component 142 tape fiber

Claims (11)

[Claims] 1. A substrate which is entirely made of an insulator or whose surface is covered with an insulating film, a first V-groove formed on the substrate for fixing an optical fiber, and a first V-groove formed on the substrate. A first and a second groove, which is orthogonal and deeper,
The first substrate is formed on the substrate so as to face the V groove and be on the same axis.
A second V-groove shallower than the V-groove, an inclined reflection surface formed at the end of the second V-groove, a light-receiving element chip fixed to the substrate above the second V-groove and the inclined reflection surface without involving the gap groove,
An optical fiber inserted and fixed in the first V-groove so that the tip is in contact with the gap groove, a light-transmitting resin adhesive applied to the tip of the optical fiber, the gap groove, the light receiving element chip, and the remaining portion of the optical fiber And a fixing resin adhesive for adhering the optical fiber to the substrate.
An optical receiving module, wherein the light is reflected by an inclined reflecting surface through a groove and is incident on a light receiving element chip. 2. The method according to claim 1, wherein the substrate is a (100) plane Si substrate,
The optical receiving module according to claim 1, wherein the first V-groove, the second V-groove, and the inclined reflecting surface are formed by anisotropic etching in which the etching rate of the {111} plane is lower than that of the {100} plane. . 3. The method according to claim 1, wherein the gap groove is formed by machining the substrate by dicing or the like.
Or the optical receiving module according to 2. 4. The optical receiving module according to claim 2, wherein the gap groove is formed by etching the Si substrate. 5. The optical receiving module according to claim 1, wherein the light receiving element chip is a back illuminated light receiving element. 6. The optical receiving module according to claim 5, wherein a metal film or a dielectric film is coated on the inclined reflecting surface. 7. The optical receiving module according to claim 1, wherein electronic circuit components for processing an electric signal from the light receiving element are integrated on the same substrate. 8. A gap groove from an optical fiber to a light receiving element,
The optical receiving module according to claim 1, wherein a space between the second V-groove and the inclined reflecting surface is filled with a translucent resin. 9. The optical receiving module according to claim 1, wherein the entire module is molded with resin. 10. The optical fiber is a silica-based single mode fiber, and the light receiving element is InGaAs or InGaAs.
The light receiving module according to claim 1, wherein the light receiving module is a back-illuminated light receiving element having a GaAsP light receiving layer. 11. An optical fiber comprising a plurality of optical fibers arranged in parallel at regular intervals, a plurality of first V-grooves corresponding to the optical fibers being provided in parallel on the substrate at the same regular interval, One gap groove is provided at right angles to all the first V grooves,
A plurality of second V-grooves are provided in parallel at the same interval as the first V-groove, and an inclined reflecting surface is provided at each end of the first V-groove, and a plurality of light receiving elements are provided above the inclined reflecting surface at equal intervals. The optical receiving module according to claim 1, wherein: